Weather modification : programs, problems, policy, and potential

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Weather modification : programs, problems, policy, and potential
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xxxii, 746 p. : ill. ; 24 cm.
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English
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United States -- Congress. -- Senate. -- Committee on Commerce, Science, and Transportation
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Weather control -- United States   ( lcsh )
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federal government publication   ( marcgt )
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Bibliography:
Bibliography: p. 641-645.
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May 1978.
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At head of title: 95th Congress, 2d session. Committee print.
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prepared at the request of Howard W. Cannon, chairman, Committee on Commerce, Science, and Transportation, United States Senate ; by the Congressional Research Service.

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University of Florida
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95th Congress o COMTTEE PRINT
2d Sessions






WEATHER MODIFICATION:

PROGRAMS, PROBLEMS, POLICY, AND
POTENTIAL





PREPARED AT THIEREQUEST OF

H-ON. HOWARD W. CANNON, Chairman

COMMITTEE ON COMMERCE,

SCIENCE, AND TRANSPORTATION

UNITED STATES SENATE











MAY 1978





Printed for the use of the
Committee on Commerce, Science, and Transportation


U.S. GOVERNMENT PRINTING OFFICE 34-857 WASHINGTON : 1978




































COMMITTEE ON COMMERCE, SCIENCE, AND TRANSPORTATION

HOWARD W. CANNON, Nevada, Chairman WARREN G. MAGNUSON, Washington JAMES B. PEARSON, Kansas
RUSSELL B. LONG, Louisiana ROBERT P. GRIFFIN, Michigan
ERNEST F. HOLLINGS, South Carolina TED STEVENS, Alaska DANIEL K. INOUYE, Hawaii BARRY GOLDWATER, Arizona
ADLAI E. STEVENSON, Illinois BOB PACKWOOD, Oregon
WENDELL H. FORD, Kentucky HARRISON H. SCH"MITT, New Mxc
JOHN A. DURKIN, New Hampshire JOHN C. DANFORTH, Missouri
EDWARD ZORINSKY, Nebraska
DONALD W. RIEGLE, JR., Michigan
AuBREY L. SARVIS, Staff Director and Chief Counsel EDWIN K. HALL, General Counsel
MALCOLM M. B. STERRETT, Minority Staff Director

(31)












LETTER OF TRANSMITTAL


U.S. SENATE,
COMMITTEE ON COMMERCE, SCIENCE, AND TRANSIrORTATEON,
November 15,1978.
To the members oJ the Committee on Commerce, Science, and
Transportation, U.S. Senate:
Ii am pleased to transmit herewith for your information and use the following report on "Weather Modification: Programs, Problems, Policy, and Potential."
The report was prepared at my request by the Congressional Research Service under the direction of Dr. Robert Morrison, Specialist in Earth Sciences, Science Policy Research Division. We thank Dr. Morrison and the others involved in the study for their extremely thorough and scholarly report. Substantial material on almost all areas of weather modification are included and the report will provide the committee with an excellent reference source for future deliberations on the subject.
The completion of the report is particularly timely due to the upcomning recommendations expected from the Weather Modification Advisory Board and the Department of Commerce (as directed by Public Law 94-490) on the future Federal role in weather modification.
JAMVES B. PEARSON,
Ranking minority member.














LETTER REQUESTING STUDY


U.S. SENATE
COMMITTEE ON COMMERCE SCIENCE ANI)TRANSPORTATION,
WASHINGTON, D.C., July 30,1976.
Dr. NORMANA. BECKMAN,
Acting Director, Congressional Research Service, Library of Congress, Washington, D.C.
DEAR DR. BECKMAN: Weather modification, although a relatively young science, has over the years stimulated great interest within the scientific, commercial, governmental, and agricultural communities. Such responses are readily understandable. Weather-related disasters and hazards affect virtually all Americans and annually cause untold human suffering and loss of life and result in billions of dollars of economic loss to crops and other property. While weather modification projects have been operational for nearly 25 years and have been shown to have significant potential for preventing, diverting, moderating, or ameliorating the adverse effects of such weather related disasters and hazards, I am greatly concerned regarding the lack of a coordinated Federal weather modification policy and a coordinated and comprehensive program for weather modification research and development. This fact is all the more disturbing in view of the manifest needs, and benefits, social and economic, that can be associated with weather modification activities. These deficiencies in our Federal organizational structure have resulted in a less than optimal return on our investments in weather modification activities and a failure, with few exceptions, to recognize that much additional research and development needs to be carried out before weather modification becomes a truly operational tool.
Reports and studies conducted by such diverse organizations as the National Academy of Sciences, the National Advisory Committee on Oceans and Atmosphere, the General Accounting Office, and the Domestic Council have highlighted the lack of a comprehensive Federal weather modification policy and research and development program. Hearings -that I chaired in February of this year reinforced my concerns regarding the wisdom of our continued failure to implement a national policy on this very important issue.
I am there ore requesting the Congressional Research Service to prepare a comprehensive report on weather modification. This report should include a review of the history and existing status of weather modification knowledge and technology; the legislative history of existing and proposed domestic legislation concerning weather modification; socio-economic and legal problems presented by weather modification activities; a review and analysis of the existing local, State, Federal, and international weather modification organizational
(V)





VI

structure: international implications of -weather modification activities: and a review and discussion of alternative LU.S. and international weather modification policies and research and development programs.
If you have any questions with respect to this request, please contact Mr. Gerry J. Kovach, Minority Staff Counsel of the Senate Commerce Committee. He has discussed this, study with Mr. Robert E. Morrison and Mr. John Justus of the Science Policy Division, Congressional Research Service.
Very truly yours,
JAMES B. PEARSON,
U.S. Senator.










LETTER OF SUBMITTAL


THE LIBRARY OF CONGRESS,
CONGRESSIONAL RESEARCH SERVICE,
Vashington, D.C., June 19, 1978.
Hon. JAXES B. PEARSON,
Cormnittee on Commerce, Science, and Transportation, U.S. Senate, Vashington, D.C.
DEAR SENATOR PEARSON: The enclosed report, entitled "Weather Modification: Programs, Problems, Policy, and Potential," has been prepared by the Congressional Research Service in response to your request.
The study reviews the history, technology, activities, and a number of special aspects of the field of weather modification. Activities discussed are those of the Federal, State, and local governments, of private organizations, and of foreign nations. Consideration is given to international, legal, economic, and ecological aspects. There are also an introductory chapter which includes a summary of issues, a chapter discussing inadvertent weather and climate modification, and a chapter summarizing recommendations from major Federal policy studies.
The study has been coordinated by Dr. Robert E. Morrison, Specialist in Earth Sciences, Science Policy Research Division, who also prepared chapters 1, 2, 3, 5, 7, 8, and 9 as well as the Summary and Conclusions. Mr. John R. Justus, Analyst in Earth Sciences, and Dr. James E. Mielke, Analyst in Marine and Earth Sciences, both of the Science Policy Research Division, contributed chapters 4 and 6, respectively. Chapter 10 was prepared by Mrs. Lois B. McHugh, Foreign Affairs Analyst, Foreign Affairs and National Defense Division. Chapter 11 was written jointly by Mrs. Nancy Lee Jones, Le-islative Attorney, and Mr. Daniel Hill Zafren, Specialist in American Public Law, both of the American Law Division. Dr. Warren Viessman, Jr., Senior Specialist in Engineering and Public Works, contributed chapter 12; and Mr. William C. Jolly, Analyst in Environmental Policy, Environment and Natural Resources Division, was responsible for chapter 13. In addition, appendixes C, F, Q, and R were assembled by Mrs. McHugh; appendixes D and S were prepared by Mrs. Jones; and information in the remaining appendixes was collected by Dr. Morrison.
I trust that this report will serve the needs of the Committee on Commerce, Science, and Transportation as well as those of other committees and individual Members of Congress who are concerned with weather modification. On behalf of the Congressional Research Service, I wish to express my appreciation for the opportunity to undertake this timely and worthwhile assignment.
Sincerely, GILBERT GUDE,
Director.
(VII)



















Digitized by the Internet Archive

in 2013














http://archive.org/details/weatificat00u nit










CONTENTS

Page
Letter of transmittal ----------------------------------------------- 11T
Letter requesting study v
Letter of Vil
Summary and conclusions ------------------------------------------ xIX

CHAPTER I
Introduction and summary of I

3
Timeliness ------------------------------------------------ 5
Definitions and scope of report ------------------------------ 7
Summary of issues in planned weather modification ---------------- 9
Technological problems and issues --------------------------- 9
Governmental issues --------------------------------------- 12
The role of the Federal Government --------------------- 12
Roles of State and local governments-------------------- 14
Legal 15
Private rights in the 15
Liability for weather 16
Interstate legal issues ---------------------------------- 17
International legal 17
Economic 18
Issues complicating economic analyses of weather modifica18
Weather modification and conflicting interests ------------- 19
Social 19
Social 20
Need for public education on weather modification --------- 21 Decisionmaking --------------------------------------- 22
International 23
Ecological issues ------------------------------------------- 24
CHAPTER 2
History of weather 25
Introduction -------------------------------------------------- 25
History of weather modification prior to 26
Prescientific 26
Early scientific period -------------------------------------- 27
Development of scientific 32
Early cloud-seeding experiments ----------------------------- 34
Weather modification since 35
35
L'angmuir, Schaefer, and 37
Research projects since 1947 -------------------------------- 39
Project 39
The Weather Bureau cloud physics project --------------- 41
The U.S. experiments of 42
Arizona Mountain cumulus experiments------------------ 44
Project Whitetop -------------------------------------- 44
Climax 45
Lightning suppression experiments 46
Fog dispersal research ---------------------------------- 46
Hurricane 46
Hall suppression --------------------------------------- 46
Foreign weather modification 47
Commercial 48
History of Federal activities, committees, policy studies, and
53
(IX)






X

CHAPTER 3
Page
Technology of planned weather modification---55
Introduction -------------------------------------------------- 55
Assessment of the status of weather modification technology-..... 56 Classification of weather modification technologies -------------- 61
Principles and status of weather modification technologies- 62
Precipitation augmentation--64
Cumulus clouds--66 Cumulus modification experiments----------------------- 67
Effectiveness of precipitation enhancement research and
operations_--69
Results achieved through cumulus modification-__ 70
Recent advances in cumulus cloud modification ------------ 71
Orographic clouds and precipitation---------------------- 71
Orographic precipitation modification ---------------------75
Orographic seeding experiments and seedability criteria----- 77 Operational orographic seeding projects------------------ 81
Results achieved through orographic precipitation modification- -82
Hail suppression--- -84
The hail problem- ----- 84
Modification of hail-- -86
Hail seeding technologies-- --87
Evaluation of hail suppression technology ....- 88
Surveys of hail suppression effectiveness------------------ 89
Conclusions from the TASH study ------------------------91
Dissipation of fog and stratus clouds ------------------------- 92
Cold fog modification--93 Warm fog modification-----------------93
Lightning suppression-- -96
Lightning modification-98 Evaluation of lightning suppression technology------------ 99
Modification of severe storms--101
Hurricanes--101 Generation and characteristics of hurricanes-------------- 104
Modification of hurricanes ------------------------------108
Tornadoes --------------------------------------------112
Modification of tornadoes--113
Technical problem areas in planned weather modification ----------- 115
Seeding technology--115 Evaluation of weather modification projects----------------- 118
Extended area effects of weather modification----------------- 124
Approaches to weather modification other than seeding ----------129
Research needs for the development of planned weather modification- 131
General considerations-131
Recommendations from the 1973 National Academy of Sciences
study--134
Recommendations of the Advanced Planning Group of NOAA__. 136 Summary of Federal research needs expressed by State officials- 138
Research recommendations of the AMS Committee on Weather
Modification---139
Research recommendations related to extended area and time
effects-- -- -- -143
CHAPTER 4
Inadvertent weather and climate modification-..145
Introduction -------------------------------------------------- 145
Terminology ----------------------------------------------145
Climate- -145 Climatic fluctuation and climatic change-.......-146 Weather---....146
Weather inodification--146 Climate modification -----------------------------------146
Planned climate modification--147 Inadvertent climate modification-148







Page

Background -------------------------------------------------- 149
Historical 149
Understanding the causes of climatic change and variability ---- 151
The concept of climatic change and variability ------------ 152
When and how do climatic changes occur ----------------- 154
The facts about inadvertent weather and climate modification ------- 156
Airborne particulate matter and atmospheric turbidity 156
Do more particles mean a warming or cooling? 157
Sources of atmospheric particulates: Natural vs. manmade-_ 158 Atmospheric processes affected by particulates 159
The La Porte weather anomaly: Urban climate modification- 162
Carbon dioxide and water 164
Increases in atmospheric carbon dioxide concentration:
What the record 164
Predicting future atmospheric carbon dioxide levels 166
Sources and sinks for carbon dioxide --------------------- 168
Atmospheric effects of increased carbon dioxide levels - - - 169
Implications of increasing atmospheric carbon dioxide concentrations- 169
Implications of a climatic warming- 170
Carbon dioxide and future climate: The real climate vs.
"model 171
Ozone 172
Concerns regarding ozone destruction 172
Action by the Government on the regulation of fluorocarbons ----------------------------------------------- 175
Climatic effects of ozone depletion ----------------------- 176
Waste 177
The urban "Heat 177
Albedo --------------------------------------------------- 179
Large-scale 180
181
Issues in inadvertent weather and climate modification------------- 184
Climatic barriers to long-term energy growth ------------------ 184
Thoughts and reflections-Can we contemplate a fossil-fuel-free
world?- 185
Research needs and 186

CHAPTER 5
Federal activities in weather modification ----------------------------- 193
Overview of Federal activities ---------------------------------- 193
Legislative and congressional activities 194
Federal legislation on weather modification------------------- 194
Summary --------------------------------------------- 194
The Advisory Committee on Weather Control------------- 195
Direction to the National Science Foundation ------------- 196
Reporting of weather modification activities to the Federal
Government ---------------------------------------- 197
The National Weather Modification Policy Act of 1976 ------ 198 Congressional direction to the Bureau of Reclamation ------- 201
Proposed Federal legislation on weather modification ------------ 203
Summary --------------------------------------------- 203
Legislation proposed in the 94th Congress and the 95th
Congress, 1st sessions -------------------------------- 205
Other congressional activities ------------------------------- 207
Resolutions on weather modification --------------------- 207
Hearings --------------------------------------------- 208
Studies and reports by congressional support agencies- - -_ -_ 209
Activities of the executive branch ------------------------------- 209
Introduction ---------------------------------------------- 209
Institutional structure of the Federal weather modification
program ------------------------------------------------ 210
Current status of Federal organization for weather modification ------------------------------------------------ 210





XlI

Page
Federal structure; 1946-57-- 214
Federal structure; 1958-68-- -----..-215
Federal structure; 1968-77 ------------------------------ 216
Future Federal organization for weather modification --------216
Coordination and advisory mechanisms for Federal weather
modification programs -----------------------------------221
Introduction ------------------------------------------ 221
The Interdepartmental Committee for Atmospheric Sciences
(ICAS) ---------------------------------------------222
The National Academy of Sciences/Committee on Atmospheric Sciences (NAS!CAS)__-226
The National Advisory Committee on Oceans and Atmosphere (NACOA)-227
Other coordination and advisory mechanisms ------------- 228
Weather Modification Advisory Board --------------------231
Weather modification activities reporting program ------------- 232
Background and regulations-232 Reporting of Federal activities-233 Summary reports on U.S. weather modification activities .. 233
Federal studies and reports on weather modification ------------- 234
Introduction_ ....234 Studies of the early 1950's- 235
Advisory Committee on Weather Control -----------------236
National Academy of Sciences studies --------------------237
Studies by the Interdepartmental Committee for Atmospheric Sciences (ICAS) -------------------------------238
Domestic Council study-239 Policy and planning reports produced by Federal agencies 239 Federal programs in weather modification -------------------------241
Introduction and funding summaries -------------------------241
Department of the Interior ---------------------------------246
Introduction ------------------------------------------246
Project Skywater; general discussion--------------------- 247
The Colorado River Basin Pilot Project (CRBPP)-------- 254 The High Plains Cooperative Program (HIPLEX) 258
The Sierra Cooperative Pilot Project (SCPP) --------------263
Drought mitigation assistance---266
National Science Foundation-- 267
Introduction and general -------------------------------267
Weather hazard mitigation_-274 Weather modification technology development- 282
Inadvertent weather modification-....- 283
Societal utilization activities--287 Agricultural weather modification--288
Department of Commerce--290
Introduction and general discussion---290 The Florida Area Cumulus Experiment (FACE)----------- 292
Project Stormfury_-296 Research Facilities Center (RFC)-300 Global Monitoring for Climatic Change (GMCC) ----------301 Lightning suppression---302 Modification of extratropical severe storms_302
Department of 0efense- 303
Introduction_ 303
Air Force fog dispersal operations--303 Army research and development-_-304 Navv research and development-_ 304
Air 'orce research and development-305 Overseas operations--307
Department of Transportation ------------------------------308
Department of Agriculture_-309 DeI)artment of Energy_-310






xin

CHAPTER 6
Review of recommendations for a national program in weather modifica- Page 313
313
Summaries of major weather modification 314
1A
Final report of the Advisory Committee on Weather Control 34 -x
Weather and climate modification: Report of the Special Commission on Weather 315
Weather and climate modification: Problems and prospects 17
A recommended national program in weather modification 318
A national program for accelerating progress in weather modifica320
'"'eather and climate modification: Problems and progress ------ 321 Annual reports to the President and Congress by NACOA ------ 323 Need for a national weather modification research program------ 324 The Federal role in weather modification --------------------- 325
Trendsand 326
CHAPTER 7
State and local activities in weather modification ---------------------- 331.
Overview of State weather modification activities------------------ 331
Introduction ---------------------------------------------- 331
North American Interstate Weather Modification Council------ 333
Survey and summary of State interests and activities in weather
340
State contacts for information on weather modification activities- 343 Non-Federal U.S. weather modification activities -------------- 343
Analysis of calendar year 1975 projects 344
Preliminary analysis of projects for calendar years 1976-77- 347
General discussion of local and regional weather modification policy
activities- 348
Weather modification activities within particular States-----------_ 3 5 1
California- 352
State weather modification law and regulations ------------ 352
Weather modification projects --------------------------- 353
State-sponsored emergency 356
Illinois --------------------------------------------------- 358
Illinois weather modification law and its administration - - 358 Operational projects ----------------------------------- 359
Research activities ------------------------------------- 36 0
M I
Kansas Weather Modification Act ----------------------- 361
Research 362
Operational 364
Emergency Drought Act of 364
North Dakota----- 365
Weather modification law and administration of regulations 0365 Authority and organization for local projects -------------- 370
North Dakota operational projects in 1975 and 1976 ------- 371
South 376
Utah ----------------------------------------------------- 381
Washington ----------------------------------------------- 382
CHAPTER 8
Private activities in weather modification ----------------------------- 385
385
Commercial weather 38(1
Scope and significance of contract activities ------------------- 38G
Summary of contract 38(i
Evaluation and research by commercial firms 388
Participation in Federal research programs- 389
Weather modificLition organizations ------------------------------ 389
Professional 389
Weather Niodification 390
American Meteorological 395






XIV


Page
Opposition to weather modification ---------------------------399
General dicsin------------------399
Opposition to the seeding project above Hungry Horse Dam-. 399 Tri-State Natural Weather Association--------------------400
Citizens for the Preservation of Natural Resources-----------402

CHAPTER 9
Foreign-activities in weather mdfcto---------------405
Introduction -------------------------------------------------- 405
World Meteorological Organization register of weather modification 40

Description of weather modification activities in some foreign nations. 412
The Union of Soviet Socialist Republics -----------------------412
Overview of projects in the U.S.S.R-------------412
Summary of weather modification and related atmospheric
research in the U.S.S.R -------------------------------413
Israel---------------------------415
Australia ------------------------------------------------- 416
Canada------------------------------------------------ 418
Mexico --------------------------------------------------- 419
People's Republic of Chn-----------------420
Kenya.---------------------------421
Republic of South Arc------------------422
Rhodsia-------------------------------------423
Indi----------------------------------------423
The Swiss hail exeiet-----------------424

CHAPTER 10
International aspects of weather modification---------------427
Introduction_-------------------------427
Convention on the prohibition of military or any other hostile use of
environmental modification techniques --------------------------429
Development of the treaty ---------------------------------- 429
Criticism of the cneto-----------------431
Activities since the United Nations approval of the convention-- 432
Activities of the World Meteorological Organization in weather
modification ------------------------------------------------ 433
Precipitation enhancement program (E)----------434 Other WMO activities in weather modification ------------------436
Registration and reporting of weather modification projects-. 436 WMO conferences on weather modification-----------------436
Typhoon and serious storm modification------------------ 437
Globaml atmospheric research porme---------437 Legal aspects of weather modification ----------------------437
United Nations Conference on the Human Environment-------------438
Declaration of the United Nations Conference on the Human
Envionmnt---------------------------------438
Action Plan for the Human Environment ----------------------438
Earthwatch Program -------------------------------------- 439
Study of Man's Impact on Ciae-------------439
Other internationalciviis------------------4
United Sta 1tes/ Canadian, a greement ---------------------------440
North American Interstate Weather Modification Council--------440
Congressional aciiis--------------------441
WNTeather modification as a weapon of wa-----------441
Senate Resoluition 7 1, pr-ohibiting environmental modification
as am weapon of war-------------------441
Congressional activities related to hostile use of weather
modification, 1974-76-------------------------------- 442
Other Congressional actions relating to weather modification..--.-- 443
Senate Concuirrent Rlesolution 67-U.S. participation in the
world weather pgrm---------------443
National Wcther Modification Policy Act of 1976 -----------444
Senate Resolution 49-----------------444






V

page
U.S. foreign 444
Various executive branch 445
National Advisory Committee on Oceans and Atmosphere------ 447 Activities in 1977 ------------------------------------------ 448
CHAPTER 11
Legal aspects of weather modification -------------------------------- 449
Domestic ----------------------------------------------------- 449
Private rights in the clouds --------------------------------- 449
Liability for weather modification---------------- ___ ------- 453
Defenses which may be raised against claims of liability -------- 456 Interstate allocation of atmospheric water- 457
Methods of controlling weather modification---------------,--- 459
Congressional authority under the Constitution to regulate, or
license weather modification activities ---------------------- 461
461
The commerce clause ---------------------------------- 461
The commerce clause generally ---------------------- 462
The commerce clause and the regulation of navigable
463
Limitations on the commerce power ------------------ 464
Fiscal 465
War powers ------------------------------------------- 466
Property 466
Treaty power---------------, -------------------------- 467
467
468
Certain hostile uses of weather modification are prohibited------ 471
Nations are responsible for environmental conduct which causes
injury or damage in or to other nations -------------------- 471
Nations are liable for injuries sustained by aliens within their
territory caused by tortuous conduct in violation of international law -------------------------------------------- 472
Nations or their citizens may be liable for injury and damage
they caused to citizens of another nation occurring in that
nation -------------------------------------------------- 472
CHAPTER 12
Economic aspects of weather modification- 475
Introduction -------------------------------------------------- 475
Economic setting ------------------------------------------- I --- 476
Economic aspects of weather modification procedures -------------- 477
Fog dispersal ---------------------------------------------- 477
Precipitation augmentation --------------------------------- 478
Orographic cloud seeding ------------------------------- 478
Convective cloud seeding ------------------------------- 478
Precipitation augmentation and energy considerations-- _ -_ 479
Hail suppression ------------------------------------------- 480
Lightning suppression and reduction in storm damage ---------- 480
Analytic methods for economic 481
Case studies of the economics of weather modification -------------- 482
Hungry Horse Area, 482
Connecticut River basin- 483
State of 483
Nine-countv Southeastern Crop Reporting District, South Dakota- 483
-Colorado 484
Conclusions -------------------------- ------------------------- 486
CHAPTER 13
Ecological effects of weather modification ----------------------------- 487
Introduction -------------------------------------------------- 487
Modification of weather and climate ------------------------- 487
Ecology and ecological systems ------------------------------ 487
Knowledge of ecological implications of applied weather modification technologies --------------------------------------- 488






xv'

Page
Important variables -------------------------------------------- 490
Temporal considerations ------------------------------------ 491
Season of modification efot--------------491
Duration of effort: Short- v. long-term --------------------491
Regularity of modification efr-------------491
Ecosystem type----------------------------------------- 492
Aquatic v. terrestrial sses-------------492
Cultivated v. natural systems ------------------------- 492
Arid v. humid svstems------------------------------ 492
Cumulative and synergistic effects--------------------------- 492
Effects of silver iodide ----------------------------------------- 493
Deliberate weather modification--------------------------------- 496
Precipitation enacmn-------------------496
Increased rainfall ------------------------------------------ 496
Snowpack augmentation ------------------------------------ 497
Severe storm abatement ------------------------------------- 498
-Fog dispersal-------------------------------------------------- 499
Hail suppression ----------------------------------------------- 499
Alteration or arrest of lightning discharges --------------------- 499
Inadvertent weather modification ------------------------------------ 499
Extra-area effects ---------------------------------------------- 499
Long-term, climatic, and global implications -----------------------500
Summary and cnlsos---------------------501

APPENDIXES
A. Statement on weather modification in Congressional Record of
June 17, 1975, by Congressman Gilb-ert Gude, containing White
House statement on Federal weather modification policy--------503
B. Department of Defense statement on position on weather modification. 509
C. Text of United Nations Convention on the prohibition of military
or any other hostile use of environmental m odification techniques- 510
D. State statutes concerning weather modification----------------------5 14
Arizona --------------------------------------------------- 515
California ------------------------------------------------- 5161
Coloado-------------------------------------520
Connecticut ----------------------------------------------- 528
Florida --------------------------------------------------- 529
Hawaii ---------------------------------------------------3531
Idaho ------------------------------------------------- 531
Illinois---------------------------------------------------- 533
Iowa ----------------------------------------------------- 541
Kansas --------------------------------------------------- 543
Louisiana ---------------------------------------------- 549
Minnesota-------------------------5.50
Montana-------------------------------------------------- 554
Nebraska---------------------------------------------- 557
Nevada --------------------------------------------------- 565
New Hampshire ---------------------------------------- 511
New Mexico ----------------------------------------------- 571
New Xr------------------------573
North Dakota ------------------------------------------ 573
Oklahoma------------------------------------------------- 584
Oregn---------------------------------------591
Pennsylvania ---------------------------------------------- 599
Soujth Dakota --------------------------------------------- 604
Texa-----------------------------------------O0
I-tah-------------------------------------------------- 612
Wahngtn---------------------------------- 613
West Vrii-------------------- -- 618
XX ieonin-------------------------------------622
NV 'volig----------------------------------------------- 622
E. List of Sltte contlvts for further information onvweathier modification
a'-tivities within the Stite------------------------------------- 625
F. Agree emenit on exchange oif informantion. on wea,,ther modification
between the 1miitc(I Statecs of America and Canaa----------------627






XVII

G. Weather modification activities in the United States during calendar PaRe
year 1975 --------------------------------------------------- 630
H. Selected bibliography of publications in weather modification--------- 641 1. Public laws dealing specifically with weather modification 646
J. Summary of language in congressional documents supporting public
works appropriations for the Bureau of Reclamation's atmospheric
water resources 655
K Membership and charter of the U.S. Department of Commerce
Weather Modification Advisory 660
L. Rules and regulations and required forms for submitting information
on weather modification activities to the National Oceanic and Atmospheric Administration, U.S. Department of Commerce, in
accordance with requirements of Public Law 92-205 --------------- 662
M. Selected State rules and regulations for the administration of State
weather modification 676
676
683
North Dakota --------------------------------------------- 691
707
Washington ----------------------------------------------- 712
N. Documents of the Weather Modification Association- 717
0. Policy statement of the American Meteorological Society on purposeful
and inadvertent modification of weather and climate --------------- 722
P. Reporting agencies of member countries and questionnaire circulated
to receive weather modification information from members of the
World Meteorological Organization ----------------------------- 724
Q. Report of the World Meteorological Organization/ United Nations
Environment programme informal meeting on legal aspects of
weather modification ----------------------------------------- 727
R. Text of Senate Resolution 71; considered, amended, and agreed to
July 11, 1973--- 734
S. Reported cases on 740
T. Glossary of selected terms in weather modification 741






























34-857-79-2














SUMMARY AND CONCLUSIONS
Weather modification is generally considered to be the deliberate
-effort to improve atmospheric conditions for beneficial human purposes-to augment water supplies through enhanced precipitation or to reduce economic losses, property damages, and deaths through mitigation of adverse effects of hail, lightning, fog, and severe storms. Not all weather modification activities, however,, have been or can be designed to benefit everyone, and some intentional operations have been used, or are perceived to have been used, as a weapon of war to impede the mobility or tactical readiness of an enemy. Furthermore, environmental change is also effected unintentionally and without any purpose at all, as man inadvertently modifies the weather and climate, whether for better or worse scientists are not certain, through activities such as clearing large tracts of land, building urban areas, and combustion of fossil fuels.
Historically, there -have been attempts, often nonscientific or pseudoscientific at best to change the weather for man's benefit. Until the 20th century, however, the scientific basis for such activities was meager, with most of our current understanding of cloud physics and precipitation processes beginning to unfold during the 1930's. The modern period in weather modification is about three decades old, datingr from events in 1946, when Schaefer and Langmuir of the General Electric Co. demonstrated that a cloud of supercooled water droplets could be transformed into ice crystals when seeded with dry ice. Soon afterward it was discovered that fine particles of pure silver iodide, with crystal structure similar to that of ice, were effective artificial ice nuclei, and that seeding clouds with such particles could produce ice crystals at temperatures just below freezing. Silver iodide remains the most often used material in modern "cloud seedi*ng."
By the 1950's, many experimental and operational weather modification projects were underway; however, these early attempts to augment precipitation or to alter severe storm effects were often inconclusive or ineffective, owing to improper experimental design, lack of evaluation schemes, and the primitive state of the technology. Through research programs over the past two decades, including laboratory studies and field experiments, understanding of atmospheric processes essential to improved weather modification technology has been advanced. Sophisticated evaluation schemes have been developed, using elaborate statistical tools; there has also been improvement in measuring instruments and weather radar systems; and simulation -of weather processes rising numerical models and high speed computers has provided further insights. Meanwhile, commercial weather modifiers, whose number decreased ;dramatically along with the total area of. the United States covered by their operations after the initial surge of the 1950 era, have grown in respectability and competence, and th ir operations haveincorprated improvements as they benefited from their accumulated experience and from the re(XIX)





XX

sults of research projects. Since such operations are designed for practical results, such as increased precipitation or reduced hail, however, the sophisticated evaluation procedures now used in most research projects are most often not used, so that the effectiveness of the operations is frequently difficult to assess.
Weather modification is at best an emerging technology. Progress in development of the technology over the past 30 years has been slow, although there has been an increased awareness of the complex nature of atmospheric processes and a steady improvement in basic understanding of those processes which underlie attempts at deliberate modification of weather phenomena. Though most cloud-seeding practices are based on a common theory and form the basis for a number of seeding objectives, there are really a series of weather modification technologies, each tailored to altering a particular atmospheric phenomenon and each having reached a different state of development and operational usefulness. For example, cold fog clearing is now considered to be operational, while, at the other extreme, the abatement of severe storms such as hurricanes remains in the initial research phase. Development progress for each of these technologies appears to be much less a function of research effort expended than a dependence on the fundamental atmospheric processes and the ease by which they can be altered. There continues to be obvious need for further research and development to refine those few techniques for which there has been some success and to advance technology where progress has been slow or at a virtual standstill.
The following summary provides a reasonably accurate assessment of the current status of weather modification technology:
1. The only routine operational projects are for clearing cold fog. Research on warm fog has yielded some useful knowledge and good models, but the resulting technologies are so costly that they are usable mainly for military purposes and very busy airports.
2. Several longrunning efforts to increase winter snowpack by seeding clouds in the mountains suggest that precipitation can be increased by some 15 percent over what would have happened "naturally."
3. A decade and a half of experience with seeding winter clouds on the U.S. west coast and in Israel, and summer clouds in Florida, also suggest a 10- to 15-percent increase over "natural" rainfall. Hypothess and techniques from the work in one area are not directly transferable to other areas, but will be helpful in designing comparable experiments with broadly similar cloud systems.
4. Numerous efforts to increase rain by seeding summer clouds in the central and western parts of the United States have left many questions unanswered. A major experiment to try to answer them-for the High Plains area-is now in its early stages.
5. It is scientifically possible to open holes in wintertime cloud layers by seeding them. Increasing sunshine and decreasing energy consmption may he especially relevant in the northeastern quadrant of the United States.
;. Some $10 million is spent by private and local public sponsors for elolld-seedingr efforts, but these projects are not desi" ied as scientific experiments and it is difficult to say for sure that operational cloud sed dirn causes the claimed results.





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7. Knowledge about hurricanes is improving with good models of their behavior. But the experience in modifying that behavior is primitive so far. It is inherently difficult to find enough test cases, especially since experimentation on, typhoons in the Western Paicific has been blocked for the time being by international political objections.
8. Although the Soviets and some U.S. private operators claim some success in suppressing hail by seeding clouds, our understanding of the physical processes that crea te hail is still weak. The one major U.S. field experiment increased our understanding of severe storms, but otherwise proved mostly the dimensions of what we do not yet know.
9. There have been many efforts to suppress lightning by seeding thunderstorms. Our knowledge of the processes involved is fair, but the techinology is still far from demonstrated, and the U.S. Forest Service has, recently abandoned further lightning experiments.'
Modification processes may also be initiated or triggered inadvertently rather than purposefully, and the possibility exists that society may be chang-ing the climate through its own actions by pushing on retain leverage points. Inadvertently, man is already causing measurable variations on the local scale. Artificial climatic effects have been ,observed and documented on local and regional scales, particularly in and downwind of heavily populated industrial areas where waste heat, particulate pollution and altered ground surface characteristics are primarily responsible for the perceived climate modification. The climte in and near large cities, for example, is warmer, the daily range ,of temperattnr3 is less, and annual precipitation is greater than if the cities had never been built. Although not verifiable at present, the time miay not be far off when human activities will result in measurable large-scale changes in weather and climate of more than passing significance. It is import-ant to appreciate the fact that the role of man at this global level is still controversial, and existing models of the gen~eral circulation are not yet capable of testing the effects in a conclusive manner.
N evertheless, a growing fraction of current evidence does point to the possibility of unprecedented impact on the global climate by human activities, albeit the effects may be occurring below the threshold where they could be statistically detected relative to the record of natuiral fluctuations and, therefore, could be almost imperceptible amid the ubiquitous variability of climate. But while the degree of influence On world climate may as yet be too small to detect against the back'ound of natural variations and although mathematical models of climatic change are still imperfect, significant global effects in the future are inferred if the rates of growth of industry and population Persist.
For over 30 years both legislative and executive branches of the Federal Government have been involved in a number of aspects of weather modification. Since 1947 about 110 weather modification bills pertaining to research support, operations, grants, policy studies, regulations, liabilities, activity reporting. etbiheto aesadcm
-mittees, and international concerns have been introduced -in the Con1Weather Modification Advisory Board. "A U.S. Policy to Enhance the Atmospheric Environment," Oct. 21, 1977. In testimony by Harlan Cleveland, Weather modification. Bearing before the Subcommittee on the Environment and the Atmosphere, Committee on Science and Technology, U.S. House of Representatives, 95th Cong., 1st sess., Oct. -26, 1977, Washington, U.S. Government Printing Office, 1977. pp. 28-30.





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gress. Resolutions, mostly concerned with using weather modification
as a weapon and promotion of a United Nations treaty banning such activities, have also been introduced in both houses of the Congress; one such resolution was passed by the Senate.
Six public laws specifically dealing with weather modification have been enacted since 1953, and others have included provisions which are in some way relevant to weather modification. Federal weather modification legislation has dealt primarily with three aspects-research program authorization and direction, collection and reporting of information on weather modification activities, and the commissioning of major policy studies. In addition to direction through authorizing legislation, the Congress initiated one major Federal research program through a write-in to an appropriations bill; this program regularly receives support through additional appropriations beyond recommended OMB funding levels.
There are two Federal laws currently in effect which are specifically concerned with weather modification. Public Law 92-205, of December 18, 1971, and its amendments requires the reporting of all nonFederal activities to the Secretary of Commerce and publication "from time to time" of summaries of such activities by the Secretary of Commerce.2 The National Weather Modification Policy Act of 1976 (Public Law 94-490), enacted October 13, 1976, directed the Secretary of Conmerce to conduct a major study on weather modification and tosubmit a report containing a recommended Federal policy and Federal research program on weather modification. The Secretary appointed a non-Government Weather Modification Advisory Board to conduct the mandated study, the report on which is to be submitted to the Secretary for her review and comment and subsequent transmittal to the President and the Congress during 1978. It is expected that, following receipt of the (aforementioned report, the Congress will consider legislation on Federal weather modification policy, presumably during the 96th Congress.
Congressional interest in weather modification has also been manifested in a number of hearings on various bills, in oversight hearings on pertinent ongoing Federal agency programs, in consideration of some 22 resolutions having to do with weather modification, and in commissioning studies on the subject by congressional support agencies.
The principal involvement in weather modification of the Federal Government has been through the research and development programs of the several Federal departments and agencies. Although Federal research programs can be traced from at least the period of World WTar II, the programs of most agencies other than the Defense Department were not begun until the 1950's and 1960's. These research and development programs have been sponsored at various times by at least eight departments and independent agencies-including the Departments of Agriculture, Commerce, defense Energy, Interior, and Transportation, the National Aeronautics and Space Administration (NASA), and the National Science F oundation (NSF). In fiscal year
2 Although FederalI ngencles were excinled from the requirements of this act. upon mtul: agreement. the afgeneies also submit information on their weather modification pro ects to the Seere-tairy of Commerce, so tha!t there is a single repository for information on ;Il weather mo ificattion activities conducted within the United States.





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1978 six agency programs were reported', those of Transportation an 'd NASA having been phased out, while that of 'Agriculture was severely curtailed.
Total funding 'for Federal Weather modification research in fiscal year 1978 is Iestimated at about $17 million, a decline from the highest funding level of $20 million reached in fiscal year 1976. The largest programs are'those, of the Departments of Interior 'and Coimmerce and of the NSF. The NSF has supported Iweather, modification research over a broad. spectrum for two'decades, although its fiscal year 1978 funding was reduced by more than 50 percent, land it is not clear that more than the very basic atmospheric science supportive of weather modification will be sponsored hereafter by the Foundation.
The present structure of Federal organization for weather modification research activities is characterized essentially by the missionoriented approach, whereby each of the agencies conducts its own program in accordance with broad agency goals or under specific directions 'from the Congress or the Executive. Programs have been loosely coordinated through various independent arrangements and/or advisory panels and particularly through the interdepartmental Committee for Atmospheric Sciences (ICAS). The ICAS, established in 1959 by the former Federal Council for Science and Technology, provides advice on matters related to atmospheric science in general and has also been the principal coordinating mechanism for Federal research in weather modification.
In 1958 the National Science Foundation was designated lead agency for Federal weather modification research by Public Law 85-510, a role which it maintained until 1968, when Public Law 90-407 removed this responsibility from NSF. No further action was taken to name a lead agency, although, there have been numerous recommendations to designate such a lead agency, and several bills introduced in the Congress wo uld have named either the Department of the Interior or the Department of Commerce in that role. During the 10-year period from 1958 to 19,68 the NSF promoted a vigorous research program through grants to various research organizations, established an Advisory Panel for Weath er Modification, and published a series of 10 annual reports on weather modification activities in the United States. Since 1968 there has been a lapse in Federal weather modification policy and in the' Federal structure for research programs, although, after a hiatus of over 3 years, the responsibility for collecting and disseminating information on weather modification activities was assigned to the Commerce Department in 1971. An important consideration -of any future weather modification legislation will probably -be the organizational structure of the Federal research program and that for administration of other related functions which may be the responsibility of the Federal Govern 'ment. Options include a continuation of the present mission-oriented approach with coordination through the WCAS or a similar interagency body, redesignation of a lead agency with some autonomy remaining with the several agencies, or creation of a single agency with control of all funding and all research responsibilities. The latter could be an independent agency or part of a larger department; it would presumably also administer other aspects of Federal weather modification responsibilities, such as reporting of activities,





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regulation and licensing, and monitoring and evaluation of operations, if any or all of these functions should become or continue to be services performed at the Federal level.
In addition to specific research programs sponsored by Federal agencies, there are other functions related to weather modification which are performed in several places in the executive branch. Various Federal advisory panels and committees and their staffs--established to conduct in-depth studies and prepare comprehensive reports, to provide advice and recommendations, or to coordinate Federal weather modification programs-have been housed and supported within executive departments. agencies, or offices. The program whereby Federal and non-Federal U.S. weather modification activities are reported to the Government is administered by the National Oceanic and Atmosuheric Administration (NOAA) within the Commerce Department. The State Department negotiates agreements with other nations which might be affected by U.S. experiments and has arranged for Federal agencies and other U.S. investigators to participate in international meteorological projects, including those, in weather modification. In the United Nations, the United States has been active in promoting the adoption of a treaty banning weather modification as a military weapon.
In accordance with the mandates of several public laws or self-initiated by the agencies or interagency committees, the executive branch of the Federal Government has undertaken a number of major weather modification policy studies over the past 25 years. Each of the completed major studies was followed by a report which included findings and recommendations. The most recent study is the one noted earlier that is being conducted by the Weather Modification Advisory Board on behalf of the Secretarv of Commerce, pursuant to requirements of the. National Weather Modification Policy Act of 1976. Nearly all previous studies emphasized the needs for designation of a lead agency, increased basic meteorological research, increased funding, improvement of support and cooperation from agencies, and consideration of ]eoral. socioeconomic, environmental, and international aspects. Other recommendations have included improvement of program evaluation, stnudv of inadvertent effects, increased regulation of activities, and a number of specific research projects. Although some of the recommended activities have been undertaken., many have not resulted in SIVcific actions to date. Almost invariably it was pointed out in the Studies that considerable progress would result from increased fundimi Although funding for weather modification research has increased over the past 20 years, most funding recommendations have been for eoniderablv higher levels than those provided. Since fiscal year 1976, the total Federal research funding for weather modification research I in fact. decreased.
Most States in the. Nation have some official interest in weather modification: 29 of them have some form of law which relates to such activities, usually concerned with various facets of regulation or control of operations within the State and sometimes pertaining to authorization for funding research and/or operations at the State or local level. A State's weather modification law usually reflects its general policy toward weather modification; some State' laws tend to en-





XXV

courage development and use of the technology, while others discourage such activities.
The current legal regime regulating weather modification has been developed by the States rather than the Federal Government, except in the areas of research support, commissioning studies, and requiring reporting of activities. The various -regulatory and management functions which the States perform include: (1) issuance, renewal, suspension, and revocation of licenses and permits; (2) monitoring and collecting of information on activities through requirements to maintain reco rds, submission of periodic activity reports, and inspection Of premises and equipment; (3) funding and managing of State or locally organized operational and/or research programs; (4) evaluation and advisory services to locally organized public and private operational programs within the State; and (5) miscellaneous administrative activities, including the organization and operation of State agencies and boards which are charged with carrying out statutory responsibilities. Administration of the regulatory and managerial responsibilities pertaining to weather modification within the States is accomplished through an assortment of institutional structures, including departments of water or natural resources, commissions, and special governing or advisory groups. Often there is a combination of two or -more of these agencies or groups in a State, separating functions of pure administration from those of appeals, permitting, or advisory services.
Involvement in weather modification operational and research programs varies from State to State. Some support research only, while others fund and operate both research and operational programs. In some cases funding only is provided to localities, usually at the county level, where -operational programs have been established. The recent 1976-77 drought led some Western States to initiate emergency cloudseeding progr .ams as one means of augmenting diminishing water supplies. Research conducted by atmospheric and other scientists at State universities 'or oth er research agencies may be supported in part with State funds but is often funded by one of the major Federal weather modification programs, such as that of the Bureau of Reclamation or the National Science Foundation. In a few cases, States contribute funds to a Federal research project which is conducted jointly with the States and partly within their borders.
In 1975, 1976, and 1977, respectively, there were 58, 61, and 88 nonfederally, supported weather modification projects, nearly all operational,' conducted throughout the United States. These projects were sponsored by community associations, airlines, utilities, private interests, municipal districts, cities, and States. Eighty-five percent of all projects in the United States during 1975 were carried out west of Kansas City, with the largest number in California. In that State there were 11 proiects in each of thie years 1975 and 1976, and 20 projects during 1977. The majority of these operational projects were designed to increase precipitation; others were intended' for suppression of hail or dispersal of fogs, the latter principally at airports.
In most instances, the principal beneficiaries of weather modification are the local or regional -users, who include farmers and ranchers,, weather-related industries, municipalities, airports, and utilities-





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those individuals and groups whose economic well-being and whose lives and property are directly subject to adverse consequences of drought or other severe weather. It is at the local level where the need to engage in weather modification is most keenly perceived and also where possible negative effects from such activities are most apparent to some sectors of the population. It follows that both the greatest support and the strongest opposition to weather modification projects are focussed at the local level. The popularity of a particular project and the degree of controversy surrounding it are frequently determined by the extent to which local citizens and local organizations have had a voice in the control or funding of the project. At the local level, deci' sions to implement or to withdraw from a project can most often be plade with minimum social stress. Indeed, studies have shown that most people are of the opinion that local residents or local government officials should make decisions on whether or not to use weather modification technology in a given situation.
Many of the operational weather modification services provided for private groups and governmental bodies within the States are carried out under contract by commercial firms who have developed expertise in a broad range of capabilities or who specialize in particular services essential to both operational or research projects. Contracts may cover only one season of the year, but a number of them are renewed annually, with target areas ranging from a few hundred to a few thousand square miles. In 1976, 6 of the 10 major companies having substantial numbers of contracts received about $2.7 million for operations in the United States, and a few of these companies also had contracts overseas. Owing to increased demand for emergency programs during the recent drought, it is estimated that 1977 contracts totaled about $3.5 million.
The initial role of the private weather modification operators was to sustain activities during the early years, when there was often heated scientific controversy with other meteorologists over the efficacy of cloud seeding. Later, their operations provided a valuable data base which permitted the early evaluation of seeding efforts and estimates of potential prospects for the technology, meanwhile growing in competence and public respect. Today, more often than not, they work hand in hand with researchers and, in fact, they often participate in research projects, contributing much of their knowhow acquired through their unique experiences.
Important among private institutions concerned with weather modification are the professional organizations of which research and operational weather modifiers and other interested meteorologists are members. These include the American Meteorological Society, the Weather Modification Association, and the Irrigation and Drainage Division of the American Society of Civil Engineers. Through the meetings and publications of these organizations the scientific, technical, and legal problems and findings on weather modification are aired and discussed. Tlse groups also address other matters such as statements of weather modification policy, opinions on pending legislation, social implications, and professional standards and certification. In ad(lition, the North American Interstate Weather Modification Council is ar organization whose membership consists of govern-





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ments of U.S. States and Canadian Provinces and the Government of Mexico, which serves as a forum for interstate coordination and exchange of information. on weather modification.
Weather modification is often controversial, and both formal and informal opposition groups have been organized in various sections of the country. Reasons for such opposition are varied (and are based on Ixth real and perceived adverse consequences from weather modification. Sometimes with little or no rational basis there are charges by these groups that otherwise unexplained and usually unpleasant weather-related events are linked to, cloud seeding. There are also cases where some farmers are economically disadvantaged through receiving m-ore, or less than optimum rainfall for their particular crops, when artificial inducement of such conditions may have indeed been planned to benefit those growing different crops with different moisture requirements. Opposition groups are often formed to protect 'the legitimate rights of farmers under such circumstances.
While the United States 'is the -apparent leader in weather modification research 'and 'operations, other -countries have also been active. Information on foreign weather modification activities is not uniformly documented and is not always available. In an 'attempt to assemble uniform weather modification 'activities information of its member nations, the World Meteorological Organization (WMO) in 1975h instigated a system of reporting'and of maintaining a register on such adivities. Under this 'arrangement -25 nations reported weather modification projects during 1976, and 16 countries provided similar information in 1975. The largest weather modification effort outside the United States is in the Soviet Union, where there are both a continuing research program and an expanding operational program. The latter is primarily a program designed to reduce crop damage from hail, the largest such effort in the world, covering about 5 million hectares (15 million acres) in 1976. Other countries with weather modification programs of some note include Canada, Israel, Mexico, 'and ,the People's Republic o'f China. Projects in Rhodesia and the Republic of South Africa are not reported through the WMO register since, these countries are not WMO member nations.
Recent years have seen increas 'ed international awareness of the potential benefits and possible risks of weather modification teclrnology and increased international efforts to control such activities. The major 'efforts of the international community in this area are to encourage
and maintain the high level of cooperation which currently exists in weather prediction and research and to insure that man's new abilities
will be used for peaceful pur-poses. There has been exchange of ideas on weather modification through international conferences and through more informal exchanges of scientists and research documents.
As with many scientific disciplines, however, the problems arising from -use of and experiments with weather modification are not just scientific in nature, but are political problems as well. .In addition to the problems of potential damage to countries through
commercial or experimental weather modification activities, another growing area of concern is that weather modification will be used for hostile purpose s and that the future will bring weather warfare between nations. The United States has already been involved in one





I XXVIII

such instance during the Vietnam war when attempts were maide to impede traffic by increasing rainfall during the monsoon season. In the future, even the perception that weather modification techniques are available or in use could lead to an increase in international tensions. Natural drought in a region, or any other natural disaster will be suspect or blamed on an enemy.
In light of these problems the international community has made scattered attempts both to further the study of weather and its modification and to insure the peaceful use of this new technology. One such attempt was the development of the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques., which was adopted by the General Assembly of the United Nations and opened for signature on May 18. 1977, at which time it was signed by the United States and 33 other nations (though it has not yet been submitted to the U.S. Senate for ratification). Another example of promotion of peaceful use of weather modification is the Precipitation Enhancement Program, sponsored by the WMO, whose aim is to plan, set up, and carry out an international, scientifically controlled precipitation experiment in a semiarid region of the world under conditions where the chances are optimal for increasing precipitation in sufficient amounts to produce economic benefits.
The United Nations Conference on the Human Environment, held in June 1972 in Stockholm, has been the pivotal point in much recent international environmental activity. It too has been an important catalyst in international activities relating to weather modification through portions of its "Declaration," its "Action Plan for the Human Environment," its "Earthwatch Program," and its "Study of Man's Impact on Climate."
Legal issues in weather modification are complex and unsettled. They can be considered in at least four broad categories: private rights in the clouds, liability for weather modification, interstate legal issues, and international legal issues. Since the body of law on weather modification is slight, existing case law offers few guidelines to determine these issues. Regarding the issue of private rights in the clouds, there is no general statutory determination of ownership of atmospheric water, so it is often necessary to use analogies to some general common law doctrines pertaining to water distribution, although each such doctrine has its own disadvantages when applied to weather modification. Some State laws reserve ownership or right to use atmospheric water to the State.
Issues of liability for damage may arise when drought, flooding, or other severe weather phenomena occur following attempts to modify y the weather. Such issues include causation, nuisance, strict liability, trespass, negligence, and charges of pollution of the air and water through introdiiction of artificial nucleants. Statutes of 10 States discuss weather modification liability; however, there is much variation among the specific provisions of the laws in those States. Before a case can be made for liability based on causation, it must be proven that the adverse weather conditions were indeed induced by the weather modifier: but, in fact, no one has ever been able to establish causation of ainages through such activities in view of the scientific uncertainties of weather modification.





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Significant issues may arise when weather modification activities conducted in one State affect another State as well. There may be, for example, the claim that seeding in one State has removed from the clouds water that should have fallen in an adjacent State or that excessive flooding resulted from cloud seeding in a State upwind. Operation of cloud-seeding equipment near the border of one State may also violate local or State regulations or prohibitions of such operations in that State. There have been some attempts to resolve these and other issues through specific legislation in some States and through informal bilateral agreements. While no formal compacts currently exist, some compacts allocating waters in interstate streams may be applicable.
Because atmospheric processes operate independent of national borders, weather modification is inherently of international concern, and. international legal issues have similarities to domestic interstate activities and dangers. Whereas domestic weather modification law is confused and unsettled, international law in this area is barely in the formative stage. In time, ramifications of weather modification may lead to major international controversy.
Whereas the potential for long-term economic gains through weather modification cannot be denied, current economic analyses are tenuous in view of present uncertainty of the technology and the complex nature of attendant legal and economic problems. Economic evaluation of weather modification activities has therefore been limited to special, localized cases. such as the dispersal of cold fog at airports, where benefit-cost ratios greater than 5 to I have been realized through savings in delayed or diverted traffic. It has also been estimated, on the basis of a 15-percent increase in snowpack through seeding orographic clouds, that about 2 million additional acre-feet of water per year could be produced in the Colorado River Basin, at a cost of about $1.50 per acre-foot.
Costs of most weather modification operations are generally small in relation to other costs in agriculture, for example, and are normally believed to be only a fraction of the benefits which could be achieved from successful operations. However, if all the benefits and all the costs are considered, benefit-cost ratios may be diminished. While direct costs and benefits from weather modification are reasonably apparent, indirect costs and benefits are elusive and require further study of sociological, legal, and ecological implications.
There are numerous cases of both real and perceived economic losses which one or more sectors of the public may suffer while another group is seeking economic advantage through some form of weather modification. Overall benefits from weather modification are accordingly reduced when net gains are determined from such instances of mixed economic advantages and disadvantages. In fact, when mechanisms are established for compensating those who have suffered losses resulting from weather modification, benefits to those groups seeking economic gain through such projects will probably be accordingly reduced.
Economically significant weather modification activities will have an eventual ecological effect, though appearance of that effect may be hidden or delayed by system resilience and/or confused by system





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complexity. Prediction of ecological effects may never be possible with any precision; however, the greater the precision with which the weather modifier can predict results of his activities, the more precisely can the ecologist predict ecological effects. Such effects will rarely be sudden or catastrophic, but will result from moderate weather-related shifts in rates of reproduction, growth, and mortalityof plants and animals. Adjustments of plant and animal communities will thus occur more slowly in regions of highly variable weather than in those with more uniform conditions which are slowly changing with some regularity over time. Deliberate weather modification, such as: precipitation augmentation, is likely to have a greater ecological impact in semi-arid regions than in humid ones.
Widespread cloud seeding, using silver iodide, could result in estimated local, temporary increases in silver concentrations in precipitation approaching those in natural waters, but exchange rates would be ain order of magnitude lower than the natural exchange r-ates. Exchange rates will likely be many orders of magnitude less than those rates at which plants and soils are adversely affected. Conclusiovs
1. Weather modification is an emerging technology; there is a wide spectrum of capabilities to modify various weather phenomena, ranging from the operational readiness of cold fog dispersal to little pr'ogress beyond initial research in the case of modifying severe storms such as hurricanes.
2. Along with cold fog dispersal, the only other weather modification capability showing near readiness for application is the augmentation of winter snowpack through seedingr mountain cloud systems. A probable increase of about 15 percent is indicated by a number of experiments and longrunning operational seeding projects in the western United States.
3. Most scientists and weather modification operators agree that there is continued need for a wide range of research and development activity both to refine weather modification techniques where there has been some success and to advance capabilities in modifying other weather phenomena where there has been much less or little progress.
4. Current Federal policy. for weather modification research and development follows the mission-oriented approach, where each agency charged with responsibility for dealing with a particular national problem is given latitude to seek the best approach or solution to the problem; this approach or solution may involve weather modification.
5. The structure of Federal organization for weather modification reflects the mission -oriented approach which is characteristic of the current Federal policy, ti e programs loosely coordinated through advisory groups and the Interdepartmental Committee for Atmospheric Sciences.
6. The interest of the Congress in weather modification has been shown by the introduction of 110 bills related to the subject since 1947-6 of* which have become public law-and the consideration of 212 resolutions on weather modification, one of which was passed by the Senate.
7. A number of major weather modification policy studies have been directed by public law or initiated within the executive branch w'-er





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the past 25 years; most of these studies recommended designation of a lead- 'agency, increased basic meteorological research, increased funding, improvement of support and cooperation from agencies, and consideration of legal, socioeconomic, environmental, and international aspects. Although some, recommended actions have been undertaken, others have not seen specific action to date.
8. While major policy studies have recommended increased fundingZ75 .for Federal weather modification, research and development and funding has generally increased over the past 20 years, recommended levels have been consistently higher than those provided, and funding has actually decreased since fiscal year 1976.
9. With enactment of the National Weather Modification PolicN7 Act of 19716 and completion of the major policy study mandated bV that act, there is a fresh opportunity for the Congress to assess tl e potential usefulness and problems in application of weather modification technology and to establish a new Federal policy for weather modification research and operations.
10. The principal role in regulating weather modification and in supporting operational programs has been taken by the States, while the role of the Federal Government has been support of research and development programs.
11. The majority of the States (29) have some form of law which relates to weather modification, and the general policy of a State toward -weather modification is usually reflected in the weather i-aodification law of that State; laws of some States tend to encourage development and use of the technology, while others discourage suCh activities.
12. The majority of operational weather modification projects in the United States (58 of a total of 72, or 80 percent in calendar year 1975) are conclucted*West of Kansas City, and the largest number of projects has been in California (20 during 1977) ; most operational project's are intended to increase precipitation, while others are designed to suppress hail or disperse fog.
13. Both the greatest support and the strongest opposition to weather modification projects are focused at the local level, where the economic and personal interests of local organizations and individuals are most directly affected; it follows that there is also the least social stress when decisions to apply or withhold weather modification are made at the local level.
14. Commercial weather modification operators have substaiiicd activities since the early days, after which some operations fell into disrepute, providing a valuable data base for evaluation of long-term projects and developing expertise over a broad range of capabilities: most have incorporated improvements into their te chnologo as they have benefited from accumulated experience and from research results.
15. While the United States is the apparent leader in overall researeli and operational weather modification activities, there have been approximately 20 foreign countries in which activities are conducted annually (25 countries reported such projects for 1976 through the r sister of the World Meteorological Organization); the largest foreign program is that of the Soviet Union, whose operational hail suppression program covered about 15 million acres in 1976, the largest such effort in the world.





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16. The international community has attempted to further the study of weather modification and insure its peaceful use through the recent development of a Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Techniques (adopted by the
L.General Assembly and opened for signature in May 1977) and through sponsorship by the World Meteorological Organization of an international precipitation enhancement program.
17. Legal issues in weather modification are complex and unsettled; they include resolution of problems of ownership of atmospheric water, i siiCS of liability, conflicting statutes and regulations of respective S tat-e laws, and the need to develop a regime of relevant international l aw.
18. Although the long-term potential for economic gains through welither modification cannot be denied, attempts to quantify benefits
-and costs from such activities will in most cases be difficult to undertake oii a practical basis until the technology is more highly developed and control systems are perfected to permit reliable predictions of out comes.
19. Economically sign-ificant weather modification will always have an eventual ecological effect, though appearance of the effect may be delayed or hidden by system resilience and '/or confounded by systeni complexity; the more precisely the weather modifier can specify effects he0 Will produce, the more precise can be the ecologist's prediction of ltkeiy ecological effects.
20. Modification processes may also be initiated or triggered inatdvertently rather than purposefully; man is already causing measurable variations unintentionally on the local scale, and artificial climate effects have been observed on local and regional scales. Although not verifiable at present, the time may not be remote when human activities will result in measurable large- scale changes in weather and climate o f AmIore than passing significance.











CHAPTER 1

INTRODUCTION AND SUMMARY OF ISSUES
(By Robert E. Mforrison, Specialist in Earth Sciences, Science Policy Research
Division, Congressional Research Service)
PERSPECTIVE
"It is entirely, possible, were he wise enough, that man could produce favorable effects, perhaps of enormous practical significance, transforming his environment to render it more salutary for hi's purposes. This is certainly a matter which should be studied assiduously and explored vigorously. The first steps are clear. In order to control meteorological matters at all we need to understand them, better than we 'now do. IWhen we understand fully we can at least predict weather with assurance for reasonable intervals in the future.
"With modern analytical devices, with a team of soundl back ground and high skills, it is possible today to do a piece of work in this field which will render immediate benefits, and carry us far to ward a more thorough undlerstancling of ultimate possibilities. L'y all means let us get at it."
-Vannevar Bush ~
SITUATION
Two decades* after completion of a major study and report oil weather modification by the Advisory Committee on Weather Control and after the assertions quoted above, many would agree that, some of the more fundamental questions about understanding and using weather modification remain unsolved. There is a great difference of opinion, however, on the state of technology in this field. According to Grant, "Some believe that weather modification is now ready for widespread application. In strong contrast, others hold that application of the technology may never be possible or practical on any substantial scale."1 2 It has been demonstrated thatiat least some atmnospheric phenomena- can be modified with some degree of predictable success, as a consequence of seeding supercooled clouds with artificial ice nuclei, and there is some promise that the present technology will be expanded to include a greater scope of weather modification capabilities. Nevertheless, a systematic approach and reasonable progress in development of weather modification technology have been impeded by a number of problems.
.Changnon asserts that a continuing and overriding problem rest ricting progress has been the attempt to apply an ill-defined technology to increase rain or suppress hail without an adequate scientific under' From statement of Dec. 2, 1957, quoted in final report of the Advisory Committee on Weather Control, Washington, D.C., U.S. Government Printing Office. 1958. Vol. L. P. 1. 2 Grant, Lewis 0., "Scientific and Other Uncertainties of Weather Modification." In William A. Thomas (editor), Legal and Scientific Uncertainties of Weather Modification, Proceedings of a symposium convened at Duke University. Mar. 11-12, 1976. by the National Conference of Lawyers and Scientists, Durham, N.C., Duke University Press, 1977, p. 7.
34-857-M9 3





2

standing and predictable outcome.3 Experimentation has been poorly conducted, intermittent, or too short; and "results have not been integrated with those of other projects so as to develop a continuing thread of improving knowledge." 4
In response to the query as to why progress in weather modification has been so slow, Fleagle identifies three broad, general impediments. "First, the physical processes associated with clouds have turned out to be especially complex and difficult * *. A second possibility may be that the atmosphere is inherently stable, so that within broad limits, no matter what we do to increase precipitation, the results are likely to be small and roughly the same * *. A third reason * is that progress has been hamstrung by fragmentation of resources, by submarginal funding, ineffective planning and coordination, and a general lack of administrative toughness and fiscal stability." 5
Droessler points out the need to "formulate a comprehensive national weather modification policy which has the broad support of the scien'tific community, the general public, private industry, and the Government," contending that "the greatest deterrent in getting on with the. task of preparing a satisfactory national policy is the lack of a consensus about the national goals for weather modification." 6
Although operational readiness varies from one form of weather
modification to another, as a result of the degree of understanding and the complexity of decisionmaking in given situations, the prospects for successful weather modification are sufficiently promising that attempts to develop effective applications will continue. This was one of the major areas of consensus at a recent syniposium on the uncertainties of weather modification:
There will be increased attempts to modify weather, both because people tend to do what is technically possible and because the anticipated benefits of precipitation augmentation, hail or lightning suppression, hurricane diversion, and other activities often exceed the associated costs.7
With the inevitable increases in weather modification capabilities and the increasing application of these capabilities, the development of a t echnology that is socially useful must be insured through a careful analysis of attendant benefits and disbenefits. According to Fleagle, et al.. deliberate efforts to modify the weather have thus far had only marginal societal ilnpacts; however, as future activities expand, "they will p)o)ably be accompanied by secondary effects which in many instances cannot be anticipated in detail * *." Consequently, "rational policy decisions are urgently needed to insure that activities are directed toward socially useful goals." 8 The lack of a capability to deal with impending societal problems C 'ha ugnon. Stanley A.. Jr., "The Federal Role In Weather Modification." background paper prepared for use by the U.S. Department of Commerce Weather Modification Advisory Board, 'Mar. 9. 1977, p. 5.
4 Ibid., pp. 5-6.
Fleagle. Robert G.. "An Analysis of Federal Policies in Weather Modification." bac'kground lipair jlriiared for use by the U.S. Department of Commerce Weather Modification Adv ,s ry Board, Mar. 1977. pp. 17-18.
(I3)ro.,s'l,,r. Earl G.. "Weather Modification" (Federal Policies. Funding From All Sources. I nt,,ragency Coordination), background paper prepared for use of the U.S. DepartIiL ,,)f '11111r1411 C Wntmivhr Moditication Advisory Board, Mar. 1, 1977, p. 10. STlionms. Williaml A. (editor). legall and Scientific Uncertainties of Weather MAodfiesthi," procedlings of a symiposiuni convened at Duke University, Mar. 11-12. 1976, by the N!'"onal Conferen.e of Lawyers and Scientists, Durham, N.C., Duke University Press, 1077, p. vi.
l,'wa~i. Robedrt G.. J:mes A. Crutetfleld. Ralph W. Johnson. and Mohamod F. Ahdo, "W,: tor Mo' Iffleation In tie Pubhlic Interest." Seattle, American Meteorological Society a ii the Uiiversity of Washington Press, 1978. p. 3, 31-32.






3


and emerging niageuieit issues in weather modification has been aphoristically summed up in the following statement by Crutchfield:
weather modification is in the throes of a serious schizoid process. The slow and sober business of piecing together the scientific knowledge of weather processes, developing the capacity to model the complex systems involved, and assessing systematically the results of modification efforts has led to responsible optimism about the future of these new technologies. On the other hand, the "social technology" of evaluation, choice, and execution has lagged badly. The present dCcisionmaking apparatus appears woefully inadequate to, the extraordinarily difficult task of fitting weather modification into man's pattern of life in optimal fashion. There are too many game plans, too many coaches. and a dlisconcerting-, proclivity for running hard before deciding which goal line to aim f or-or, indeed, which field to play on.
Mounting evidence indicates that weather modification of several types is, or may soon become technically feasible. That some groups will derive economic or other social benefits from such technology is a spur to action. But a whole thunderhead of critical questions looms on the horizon waiting to be resolved before any valid decisions can be made about the scale, composition, location, and management of possible operations."
ADXTA NTAGES
In a study for the Interdeportmental Committee for Atmospheric Sciences, Homer E. Newell highlighted the potential benefits of intentional weather modificatio-o :
The Earth's weather has a profound influence on agriculture, forestry, water resources-, industry, commerce, transportation, construction, field operation,, commercial fishing, and many other human activities. Adverse effects of weather on man's activities and the Earth's resources are extremely costly, amounting to billions of dollars per year, sometimes causing irreparable damage as when human lives are lost in severe storms. There is, therefore, great motivation to develop effective countermeasures against the destructive effects of weather, and, conversely, to enhance the beneficial aspects. The financial and other benefits to human welfare of being able to modify weather to augment water supplies, reduce lightning, suppress hail, mitigate tornadoes, and inhibit the full development of hurricanes would be very great.0
More recently, Louis J. Battan gave the following two reasons, with graphic examlnpes, for wanting to change tile weather:
First, violent weather kills a great many people and does enormous property. damage. A single hurricane that struck East Pakistan in November 1970 killed more than 250,000 people in a single day. Hurricane Camille hit the United States in 1969 and did approximately $1.5 billion worth of damage. An outbreak of tornadoes in the Chicago area on Palm Sunday of 1965 killed about 250 people. and the tornadoes of April 1974 did likewise. Storms kill people and damage Property, and it is reasonable to ask whether it is necessary for us to accept this type of geophysical destruction. I say, "No, it is not-it should be possible to do something."
.Second, weather modification involves, and in some respects might control, the production of those elements we need to survive. Water and food are currently in 'short supply in many areas, and these shortages almost certainly will be more severe in the future. We can develop new strains of wheat and rye and corn and soybeans and rice, but All is for naught if the weather fails to cooperate. If the monsoons do not deliver on schedule in India, residents of that country starve in large numbers. And if the drought that people have been Predicting for the last several years does spread over the Great Plains, there will be starvation around the world on a scale never before experienced.
Weather is the one uncontrollable factor in the whole business of agriculture. 144ail, strong winds, And floods aire the scourges of agriculture, and we should not have to continue to remain helpless in the face of them. It may be impossible
SCrivtehfield, Jamnes, A.. "Social CI'oice and Weather Modification: Concepts and MeasiireWent of Impact." In W. R. Derrick Sewell (editor). Modifying tihe Weather: a Social Aszessnient, Victoria, British Columbia, Uiniversity of Victoria, 1973, p. 187., 10 Newell, Homer K. "A Recommended National Program in Weather Modification." Federal Council for Science and Technology, Interdepartmental Committee for Atmospherkc Sciences, ICAS report No. 10a', Washington, D.C., Niovember 1966, p. 1L.







4

for us to develop the kind of technology we would like to have for modification of weather, but to assume failure in such an important endeavor is a course not to be followed by wise men.11

Specific statistics on annual losses of life and economic losses from property damages resulting from weather-related disasters in the United States are shown in table 1, which was developed in a recent study by the Domestic Council.2 In the table, for comparison, are the fiscal year 1975 expenditures by the Federal Government in weather modification research, according to the several categories of weather phenomena to be modified. Although it is clear that weather disasters can be mitigated only partially through weather modification, even if the technology were fully developed, the potential value, economic and otherwise, should be obvious. The following quotation from a Federal report written over a decade ago summarizes the full potential of benefits to mankind which might be realized through use of this technology:
With advances in his civilization, man has learned how to increase the fruit of the natural environment to insure a livelihood. * it is fortunate that growing knowledge of the natural world has given him an increasing awareness of the changes that are occurring in his environment and also hopefully some means for deliberate modification of these trends. An appraisal of the prospects for deliberate weather and climate modification can be directed toward the ultimate goal of bringing use of the environment into closer harmony with its capacities and with the purposes of man-whether this be for food production, relief from floods, assuring the continuance of biologic species, stopping pollution, or for purely esthetic reasons.
TABLE 1.-ANNUAL PROPERTY DAMAGE AND LOSS OF LIFE FROM WEATHER-RELATED DISASTERS AND HAZARDS IN THE UNITED STATES AND FISCAL YEAR 1975 FEDERAL WEATHER MODIFICATION RESEARCH FUNDING (FROM DOMESTIC COUNCIL REPORT, 1975)

Property Modification
damage I research
Weather hazard Loss of life I (billions) (millions)

Hurricanes--- 2 30 2 $0.8 3 $0.8
Tornadoes ----------------------------------------------- 2 140 2.4 4 1.0
Hail ----------------.--------------------------------------------------------- s.8 3.9
Lightning ------------6 110 .1 .4
Fog ------------------------------------------------------------- 1,000 7.5 1.3
Floods ----------------------------------------------------------- 8 240 82.3
Frost (agriculture) ---------------------------------------------------- 1.1
Drought- -- 7 7 93.4
Total ---------------------------------------------- 1,520 6.7 10.8

Sources: "Assessment of Research on Natural Hazards," Gilbert F. White and J. Eugene Haas, the MIT Press, Cambridge, Mass., 1975, pp 68, 286, 305, 374; "The Federal Plan for Meteorological Services and Supporting Research, Fiscal Year 1976," U.S. Department of Commerce, National Oceanic and Atmospheric Administration (NOAA), Washington, D.C., April 1975, p 9; "Weatherwise," February 1971, 1972, 1973, 1974, 1975, American Meteorological Society, Boston, Mass.; "Summary Report on Weather Modification, Fiscal Years 1969, 1970, 1971," U.S. Department of Commerce, NOAA, Washington, D.C., May 1973, pp 72, 81; "Estimating Crop Losses Due to Hail-Working Data for County Estimates," U.S. Department of Agriculture, Economic Research Ssrvice, September 1974; "Natural Disasters: Some Empirical and Economic Considerations," G. Thomas Sav, National Bureau of Standards, Washington, D.C., February 1974, p 19; Traffic Safety magazine, National Safety Counci, February 1974.
2 1970-74 average.
3 These funds do not include capital investment in research aircraft and instrumentation primarily for hurricane modification, which in fiscal year 1975 amounted to $9,200,000.
4 ihese funds support theoretical research on modification of extratropical cloud systems and their attendant severe storms such as thunderstorms and tornadoes.
51973.
6 1950-72 average.
7 Average.
4 1965-69 average.
g These funds support precipitation augmentation research, much of which may not have direct application to drought alleviation.
11 Battan, Louis J., "The Scientific Uncertainties: a Scientist Responds." In William A. Thomas editorr), "Iegal and Scientific Uncertainties of Weather Modification," proceediIgs of a symposimn convened at Duke University. Mar. 11-12, 1976. by tle Nattonll Coilference of Lawyers and Scientists, 1)urhami. N.C., )uke University Press, 1977, p. 26.
12 U., )omestif Council. Environmental Resources Committee, Subcommittee on Climate Change. "The Federal Role in Weather Modification," I)ecember 1975, t). 2.
'3 Special Commission on Weather Modification. "Weather and Climate Modflcat ,li,' National Science Foundation. NSF 66-3, Washington, D.C., Dec. 20, 1965, p. 7.






5

TIMELINESS

Theomodern period in weather modification is about three decades old, dating from events in 1946, when Schaefer and Langmuir demonstrated that a cloud of supercooled water droplets could be transformed into ice crystals when seeded with dry ice. Activities and interests among scientists, the commercial cloud seeders, and Government sponsors and policynakers have exhibited a nearly 10-year cyclic behavior over the ensuing years. Each of the three decades since the late 1940's has seen an initial burst of enthusiasm and activity in weather modification experiments and/or operations; a midcourse period of controversy, reservations, and retrenchment; and a final period of capability assessment and policy examination, with the issuance of major Federal reports with comprehensive recommendations on a future course.
The first such period ended with the publication of the final report of the Advisory Committee on Weather Control in 1957.4 In 1959, Dr. Robert Brode, then Associate Director of the National Science Foundation, summarized the significance of that study in a 1959 congressional hearing:
For 4 years the Advisory Committee studied and evaluated public and private cloud-seeding experiments and encouraged programs aimed at developing both physical and statistical evaluation methods. The final report of the committee * for the first time placed before the American public a body of available facts and a variety of views on the status of the science of cloud physics and the techniques and practices of cloud seeding and weather modification.5
The year 1966 was replete with Government weather modification studies, major ones conducted by the National Academy of Sciences, the Special Commission on Weather Modification of the National Science Foundation, the Interdepartmental Committee for Atmospheric Sciences, and the Legislative Reference Service of the Library of Congress. During that year, or thereabouts, planning reports were also produced by most of the Federal agencies with major weather modification programs. The significance of that year of reevaluation and the timeliness for congressional policy action were expressed by Hartman in his report to the Congress:
It is especially important that a comprehensive review of weather modification be undertaken by the Congress at this time, for a combination of circumstances prevails that may not be duplicated for many years. For the first time since 1957 there now exists, in two reports prepared concurrently by the National Academy of Sciences and a Special Commission on Weather Modification, created by the National Science Foundation, a definitive appraisal of the entire scope of this subject, the broad sweep of unsolved problems that are included, and critical areas of public policy that require attention. There are currently before the Congress several bills which address, for the first time since enactment of Public Law 85-510. the question of the formal assignment of Federal authority to undertake weather modification programs. And there is increasing demand throughout the country for the benefits that weather modification may bring.
U4 T.tablishment of the Advisory Committee on Weather Control by the Congress and its acti--ites are discussed in followin- chapters on the history of weather modification and on Federal activities, chs. 2 and 5, respectively. Recommendations of the final report are summarized in ch. 6. Other reports mentioned in the following paragraphs in this section are also discussed and referenced in chs. 5 and 6.
15U.S. Congress, House of Representatives. Committee on Science ,rd Astronautics. "Weather Modification." Hearing. 86th Cong., 1st sess., Feb. 16, 1959, Washington, D.C., U.S. e-overnment Printing Office. 1959. p. 1.
16 Hartman, Lawton M. "Weather Modification and Control." Library of Conaress, Legislative Reference Service. Apr. 27. 1966. Issued as a committee print by the Senate Committee on Commerce. 89th Cone., 2d sess., Senate Rept. No. 1139, Washington, D.C., U.S. Government Printing Office, 1966, p. 1.





6

Toward the close of the third decade, a number of policy studies and reports appeared, starting in 1973 with a second major study by the National Academy of Sciences, and including others by the U.S. General Accounting Office and by the U.S. Domestic Council. The major study of this period was commissioned by the Congress when it enacted Public Law 94-490, the National Weather Modification Policy Act of 1976, in October of 1976. By that law the Secretary of Commerce was directed to conduct a study and to recommend the Federal policy and a Federal research program in weather modification. That study was conducted on behalf of the Secretary of Commerce by a Weather Modification Advisory Board, appointed by the Secretary, and the required report will be transmitted to the Congress during 1978. The importance of that act and its mandated study was assessed by Dr. Robert M. White, former Administrator of the National Oceanic and Atmospheric Administration (NOAA), the Commerce Department agency with administrative responsibilities and research programs in weather modification:
The National Weather Modification Policy Act of 1976 * will influence NOAA to some degree during the next year, and its effect may have a large impact on the agency and the Nation in future years. The comprehensive study of and report on weather modification that will result from our implementation of this a(t will provide guidance and recommendations to the President and the Congress in the areas of policy, research, and utilization of this technology. We look to this study and report as an opportunity to help set the future course of a controversial science and technology with enormous potential for benefit to the Nation.
Thus, conditions once more are ripe and the stage has been set, as in
1957 and again in 1966, for the Congress to act in establishing a definitive Federal weather modification policy, one appropriate at least for the next decade and perhaps even longer. Among other considerations, such a policy would define the total role of the Federal Government, including its management structure, its responsibilities for research and development and for support operations, its authorities for regulation and licensing, its obligation to develop international cooperation in research and peaceful applications, and its function in the general promotion of purposeful weather modification as an economically viable and socially accepted technology. Oin the other hand, other factors, such as constr saints arising from public concern over spending, may inhibit the development of such policy.
While some would argue that there exists no Federal policy, at least one White House official, in response to a letter to the President, made a statement of weather modification policy in 1975:
A considerable amount of careful thought and study has been devoted to the subject of weather modification and what the Federal role and, in particular, the role of various agencies should be in this area. As a result of this study, we have developed a general strategy for addressing weather modification efforts which we believe provides for an appropriate level of coordination. We believe that the agency which is charged with the responsibility for dealing with a particular national problem should be given the latitude to seek the best ;lilioach or solution to the problem. In some instances this may involve a form of wea ther inodification, while in other instances other ai)proaches may be more appropriate.
While we would certainly agree that some level of coordination of weather imoificatioti research efforts is logical, we do not believe that a program under
17 .. Cores. hIouse of Representatives. Committee on Science and Technology. Subenm1i thftov wn tho En vir(,nmII~elt and the Atmosphore. Briefing (in th Nat tlonnll Ocwnie -Ind Atmospiherie Administration." Hearings. 95th Cong., 1st sess., May 17, 18, 1977. Washingti. U.S. Government Printing Office, 1977, p. 4-5.





7

the direction of any one single agency's leadership is either necessary or desirable. We have found from our study that the types of scientific research conducted by .agencies are substantially different in approach, techniques, and type of equipmnent employed, depending on the particular weather phenomena being addressed. Each type of weather modification requires a different form of program managemnent and there are few common threads which run along all programs."
Presumably, there will be a resurgence of congressional interest in weather modification policy during the first session of the 96th Congress, when the aforementioned report from the Secretary of Commerce has been reviewed and considered. In view of the recommendations in numerous recent studies and the opinions of the Weather Modification Advisory Board (the group of experts preparing the report for the Secretary of Commerce), it seems unlikely that any action by the Congress would perpetuate the policy expounded in the White 'House letter quoted above.
It is expected that this present report, intended as an overall review ,of the subject of weather modification, will be valuable and timely during the anticipated congressional deliberations.
DEFINITIONS AND SCOPE OF REPORT
In the broadest sense, weather modification refers to changes in weather phenomena brought on purposefully or accidentally through human activity. Weather effects stimulated unintentionally-such as urban influences on rainfall or fogs produced by industrial cornplexes-constit ute what is usually termed inadvertent weather inodifiCation. On the other hand, alterations to the weather which are induced consciously or intentionally are called planned or advertent weather modification. Such activities are intended to influence single weather events and to occur over relatively short time spans, ranging from a few hours in the case of clearing airport fog or seeding a thunderstorm fo perhaps a few days when attempts are made to redumce the severity of hurricane winds. Weather modification experimi-ents or operations can be, initiated or stopped rather promptly, and changes resulting from such activities are transient and generally reversible within a. matter of hours.
Climate modification, by contrast, encompasses changes of long-time climatic variables, usually affecting larger areas and with some degree of permanence, at least. in the short term. Climatic changes are also brought about by human intervention, and they miight result from either unintentional or planned activities. There are. numerous examiples of possible inadvertent climate modification; however, attempts to alter climate purposefully are only speculative. The concepts of inadvertent weather and climate modification are, defined .more extensively and discussed fully in chapter 4 of this report.
The primary emphasis of this report is on intentionalc or planned modification o'f weather events in the short, term for the general benefit of people, usually in a restricted locality and for a specific time. Such benefit may accrue through increased agricultural product iv18 Ross, Norman E., Jr., letter of June 5, 1975, to Congressman Gilbert Gude. This letter was the official White House response to a letter of April 25S. 1975, from Congressmen Gude and Donald M. Fraser and Senator Claiborne Pell, addressed to the President. urging that P. coordinated Federal program be initiated in the peaceful uses of weather modification. The letter to the President, the reply from Mr. Ross, and comments by Congressman Gude appeared -in the Congressional Record for June 17, 1975, pp. 19201-19203. (This statement from the Congressional Record, appears i~n app. A.)




8

ity or other advantages accompanying augmentation of precipitation or they may result from mitigation of effects of severe weather with attendant decreases in losses of life or property. There are broader implications as well, such as the general improvement of weather for the betterment of man's physical environment for aesthetic and cultural reasons as well as economic ones. The following recent definition sums up succinctly all of these purposes:
Weather modification is the deliberate and mindful effort by men and women to enhance the atmospheric environment, to aim the weather at human purposes."is
The specific kinds of planned weather modification usually considered, and those which are discussed, in turn, in some detail in chapter 3, are the following:
Precipitation enhancement.
Hail suppression.
Fog dissipation.
Lightning suppression.
Mitigation of effects of severe storms.
Planned weather modification is usually considered in the context of its net benefits to society at large. Nevertheless, it should be recognized that, in particular instances, benefits to some segment of the population may be accompanied by unintended injuries and costs, which may be real or perceived, to other segments. There is yet another aspect of advertent weather modification, which has engendered much controversy, both in the United States and internationally, not designed for the benefit of those directly affected-the use of weather modification for hostile purposes such as a weapon of war. This aspect is not a major consideration in this report, although there is some discussion in chapters 5 and 10 of congressional concern about such use of the technology, and in chapter 10 there is also a review of recent efforts by the United Nations to develop a treaty barring hostile use of weather modification.2o
Following this introductory chapter, with its summary of issues, the second chapter sets the historical perspective for weather modification, concentrating primarily on activities in the United States to about the year 1970. The third chapter attempts to review the scientific background, the status of technology, and selected technical problems areas in planned weather modification; while chapter 4 contains a discussion of weather and climate changes induced inadvertently by Ima s activities or by natural phlienomena.
The weather modification activities of the Federal Governmentthose of the Congress and the administrative and program activities of the executive branch agencies-are encompassed in chapter 5; and the findings and recoinmmiendations of major policy studies, conducted by or on behalf of the Federal government are sunnmmarized in chapter 6. The seventh, eighth, and ninth chapters are concerned with weather modification activities at the level of State and local govern111ens, bv private organizations, and in foreign countries, respectively.
SWeat!ter Modification Advisory Board, "A U.S. Policy to Enhance the Atmospheric Environment," Oct. 21. 1977. A discussion paper, included with testimony of Harlarn Cleveland. Chairman of the Advisory Board, in a congressional hearing: U.S. Congress. House of Representatives, Committee on Science and Technology. Subcommittee on the Environment nid the Atmosphere. Weather Modification, 95th Cong., 1st sess., Oct. 26, 1977, Washington. D.C., U.S. Government Printing Office, 1977, p. 25.
'~" ('opies of the current official position of the U.S. Department of Defense on weather modification and of the draft U.N. convention prohibiting hostile use of environmental modification, respectively, are found in apps. B and C.





9

The increasingly important international problems related to weather modification 'are addressed in chapter 10, while both domestic and international legal aspects are discussed in chapter 11. Chapters 12 and 13, respectively, contain discussions on economic and ecological ,aspects of this emerging technology.
The 20 appendixes to the report provide materials that are both supplementary to textual discussions in the 13 chapters and intended to be valuable sources of reference data. In particular, attention is called to appendix D, which contains excerpts dealing with weather modification from the statutes of the 29 States in which such activities are in some way addressed by State law, and to appendix E, which provides the names and -affiliations of individuals within the 50 States who are cog-nizant of weather modification activities and interests within the respective States. The reader is referred to the table of contents for the subjects of the remaining appendixes.

SUMMARY OF ISSUES IN PLANNED WEATIIER MODIFICATION
"The issues we now face in weather modification have roots in the science and- technology of the subject, but no less importantly in the politics of Government agencies and congressional committees and in~ public attitudes which grow out of a variety of historical, economic, and sociological factors."2 In this section there will be an identification of cirtical issues which have limited development of weather modification and which influence the ability to direct weather modification in a socially responsible manner. The categories of issues (10 not necessarily correspond with the subjects of succeeding chapters dealing with various aspects of weather modification; rather, they are organized to focus on those specific areas of the subject where there hias been and there are likely to be problems and controversies which impede the dev~eopment and application of this technology.
The following sections examine technological, governmental, legal, economic, social, international, and ecological issues. Since the primary concern Of this report is with the intentional, planned use of weather modification for beneficial purposes, the issues summarized are those involved with the development and use of this advertenft technology. Issues and recommendations for further research in the area of inadvertent weather modification are included in chapter 4, in which that general subject is fully discussed.

TECHNOLOGICAL PROBLEMS AND ISSUES
In a recent discussion paper, the Weather Modificati 'on Advisory Board summarized the state of weather modification by concluding that "nio one knows how to modify the weather very well, or on a very large scale, or in many atmospheric conditions at all. The first requiremnent of a national policy is to learn more about the atmosphere itself."1 22 Representative of the state of weather modification science
21Fleagie, Crutchfield, Johnson, and Abdo, "Weather Modification in the Public Interest," 1973, p. 15.
22 Weather Modification Advisory Board. "A U.S. Policy To Enhance the Atmospheric Environment.," Oct. 21, 1977. This discussion paper was included with the testimonY of Mr. Harlan Cleveland, Chairman of the'Advisory Board, in a recent congressional hearing: U.S. Congress, House of Representatives, Committee on Science and Technology, Subcommittee on the Environment and the Atmosphere. "Weather Modification." 95th Cong., 1st sess. Oct. 26, 1977, Washington, D.C., U.S. Govt. Print. Off., 1977, p. 25.





10

and technology is the following commentary on the state of understanding in the case of precipitation enhancement, or rainmaking as it is popularly called:
Today, despite the fact that modern techniques aimed at artificial stimulation of rain rest upon sound physical principles, progress is still fairly slow. The application of these principles is complicated by the overwhelming complexity of atmosleric phenomena. It is the same dilemna that meteorologists face when they attempt to predict weather. In both cases, predicting the evolution of atmospheric processes is limited by insufficient knowledge of the effects produced by the fairly well-known interactive mechanisms governing atmospheric phenomena. Moreover, the temporal and spatial variability of atmospheric phenomena presents an additional difficulty. Since any effects that are produced by artificial intervention are always imposed upon already active natural processes, assessment of the consequences becomes even more difficult.23
Grant recognizes the current progress and the magnitude of remaining problems when he says that:
Important-and steady advances have been made in developing technology for applied weather modification, but complexity of the problems and lack of adequate research resources and commitment retard progress. Advances have been made in training the needed specialists, in describing the natural and treated cloud systems, and in developing methodology and tools for the necessary research. Nevertheless, further efforts are required.24
Though it can be argued that progress in the development of weather modification has been retarded by lack of commitment, ineffective planning, and inadequate funding, there are specific scientific and technical problems and issues needing resolution which can be identified beyond these management problems and the basic scientific problem quoted above with respect to working with the atmosphere. Particular technical problems and issues at various levels which continue to affect both research and operational activities are listed below:
1. There is substantial diversity of opinion, even among informed scientists, on the present state of technologyT for specific types of weather modification and their readiness for application and with regard to weather modification in general.25
2. There are many who view weather modification only as a droughtrelief measure, expecting water deficits to be quickly replenished through its emergency use; however, during such periods weather modification is limited by less frequent opportunities; it should, insteadl, be developed and promoted for its year-round use along with other water management too0ls..23. The design and analysis of weather modification experiments is intimately related to the meteorological prediction problem, which needs further research, since the evaluation of any attempt to modify the atmosphere depends on a comparison between some weather parameter and an estiiiiate of what would have happened naturally.
4. Many of the problems which restrict understanding and prediction of weather nlodification phenomena stem from imprecise knowledge of fundamental cloud processes; the level of research in fundaI3 Dennis, Arnett S., and A. GegIn. "Recommendations for Future Research in Weather Modifi-ation," U.S. Department of Commerce, National Oceanic and Atmospheric .Administration. Environmental Research Laboratories, Bouhler, Colo.. November 1977, p. 12.
2' Grant. "Scientific and Other Uncertainties of Weather Modification," 1977, p. 17.
-'!f table 2. el. 3. p. 59.
2 Silverman, Bernard A., "What Do We Need in Weather Modification?" In preprints of the Sixth Conference on Planned and Inadvertent Weather Modification, Oct. 10-13, 1977, (hmnmnpaign, Ill., Boston, American Meteorological Society, 1977, p. 308.







mental cloud physics and cloud modeling has not kept pace with: weather modification activity.27
5. Progress in the area of weather modification evaluation methodology has been slow, owing to the complexity of verification problems and to inadequate understanding of cloud physics and dynamics.
6. Most operational weather modification projects, usually for the sake of economy or in the anticipation of achieving results faster and in greater abundance, fail to include a satisfactory means for project evaluation.
7. There are difficulties inherent in the design and evaluation of any experiment or operation which is established to test the efficacy of any weather modification technique, and such design requires the inclusion of proper statistical methods.
8. In view of the highly varying background of natural weather phenomena, statistical evaluation of seeding requires a sufficiently long experimental period; lnanv research projects just barely fail to achieve significance and credibility because of early termination; thus, there is a need for longer commitment for such projects, perhaps
5 to 10 years, to insure that meaningful results can be obtained.2s
9. There is a need to develop an ability to predict possible adverse weather effects which might accompany modification of specific weather phenomena; for example, the extent to which hail suppression or diminishing hurricane winds might also reduce beneficial precipitation, or the possibility of increasing hailfall or incidence of lightning from efforts to stimulate rainfall from cumulus clouds.29
10. The translation of cloud-seeding technologies demonstrated in one area to another geographical area has been less than satisfactory; this has been especially so in the case of convective cloud systems, whose differences are complex and subtle and whose classification is complicated and sometimes inconsistent.
11. There is increasing evidence that attempts to modify clouds in a prescribed target area have also induced changes outside the target area, resulting in the so-called downwind or extended area effect; reasons for this phenomenon and means for reducing negative results need investigation.
12. There is the possibility that cloud seeding in a given area and during a given time period has led to residual or extended time effects on weather phenomena in the target area beyond those planned from the initial seeding.
13. The conduct of independent cloud-seeding operations in adjacent locations or in the neighborhood of weather modification experiments may cause contamination of the atmosphere so that experimental results or estimates of operational success are biased.
14. There have been and continue to be conflicting claims as to the reliability with which one can conduct cloud-seeding operations so that the seeding agent is transported properly from the dispensing device to the clouds or portions of the clouds one seeks to modify.
"7Hosler, C. L.. "Overt Weather Modification." Reviews of Geophysics and Space Physle;. vol. 12, No. 3, August 1974, p. 526.
28 Simpson, Joanne, "What Weather Modification Needs." In preprints of the Sixth Conference on Planned and Inadvertent Weather Modification, Oct. 10-13, 1977, Champaign. Ill.. Boston. American Meteorological Society. 1977, p. 306.
2 Hosler, "Overt Weather Modification," 1974, p. 525.





1 12

15. There is need to develop, improve, and evaluate new and currently used cloud-seeding materials and to improve systems for delivery of these materials into the clouds.
16. There is need to improve the capability to measure concentrations of background freezing nuclei and their increase through seeding; there is poor agreement between measurements made with various ice nucleus counters, and there is uncertainty that cloud chamber measurements are applicable to real clouds.30
17. In order to estimate amounts of fallen precipitation in weather modification events, a combination of weather radar and raingage network are often used; results from such measurement systems have often been unsatisfactory owing to the quality of the radar and its calibration, and to uncertainties of the radar-raingage intercalibration.
18. There is continuing need for research in establishing seedability criteria; that is, definition of physical cloud conditions when seeding will be ete"rtive in increasing precipitation or in bringing about some other desired weather change.
19. Mathematical models used to describe cloud processes or account for interaction of cloud systems and larger scale weather systems greatly oversimplify the real atmosphere; therefore, model research must be coupled with field research.31
GOVERNMENTAL ISSUES
The basic problem which encompasses all governmental weather modification issues revolves about the question of the respective roles, if any, of the Federal, State, and local governments. Resolution of this fundamental question puts into perspective the specific issues of where in the several governmental levels, and to what extent, should goals be set, police established, research and/or operations supported, activities regulated, and disputes settled. Part of this basic question includes the role of the international community, considered in another section on international issues :32 the transnational character of weather modification may one day dictate the principal role to international organizations.
Role of the Federal Gorernment
Because weather modification cannot be restricted by State boundaries and because the Federal Government has responsibilities for resource development and for reduction of losses from natural hazards, few would argue that the Federal Government ought not to have some interest and some purpose in development and possible use of weather modification technology. The following broad and specific issues on the role of the Federal Government in weather modification are among those which may be considered in developing a Federal policy:
1. Should a maior policy analysis be conducted in an atteml)t to relate weather modification to the Nation's broad coals; that is, improvine hlman health and the quality of life, maintaining national security, providin'r sufficient energy supplies. enhancing environmental Oni.alitv, and the production of food and fiber? Barbara Farhar suggests that such a study has not been, but ought to be, undertaken.33
Ihid.
31 T',:1 je et al.. "Wenther Modftfl tlon T) the Public Interest." 1973. i. 57.
t ,~ C1", 4 )
SFOrbar. Barbarn C.. "The Societal TImTlieations of Weather fMoifiention a Review of Tasnow Townrd a National Polley." BUnek'uin paper uproired for the U.S. Department of Commerce Weather Modification Advisory Board, Mar. 1, 1977. p. 2.






13

2. Should the Federal Government commit itself to planned weather modification as one of several priority national goals? It can be argued that such commitment is important since Federal program support and political attitudes have an important overall influence on the development and the eventual acceptance and application of this technology.
3. Is there a need to reexamine, define, and facilitate a well-balanced, coordinated, and adequately funded Federal research and development program in weather modification? Many argue that the current. Federal research program is fragmented and that the level of funding is subcritical.
4. Is there a suitable Federal role in weather modification activities beyond that of research and development-su. as project evaluation and demonstration and operational programs? If such programs are advisable, how can they be identified, justified, and established?
5. Should the practice of providing Federal grants or operational services by Federal agencies to States for weather modification in times of emergency be reexamined, and should procedures for providing such grants and services be formalized? It has been sug-gested that such assistance in the past has been haphazard and has been provided after it was too late to be of any practical benefit.
6. Should the organizational structure of the Federal Government for weather modification be reexamined and reorganized? If so, what is the optimum agency structure for conducting the Federal research program and other functions deemed to be appropriate for the Federal Government?
7. Whlat is the role of the Federal Government., if any, in regulation of weather modification activities, including licensing, permitting, notification, inspection, and reporting? If such a role, is to be modified or expanded, how should existing Federal laws and/or regulations be modified?
8. If all or any of the regulatory functions are deemed to be more appropriate for the States than for the Federal Government, should the Federal Government consider mandating minimum standards and some uniformity among State laws and regulations?
9. Should the Federal Government attempt to develop a means adequate for governing the issues of atmospheric water rights between States, on Federal lands, and between the United States and neighboring countries?
10. Where federally sponsored research or possible operational weather modification projects occupy the same locale as local or State projects, with the possibility of interproject contamination, should a policy on project priorities be examined and established? 11. Should the Federal Government develop a policy with regard to the military use of weather modification and the active pursuit of international agreements -for the peaceful uses of weather modification? This has been identified as perhaps one of the most import ant areas of Federal concern.3
.12. Is there a need to examine and define the Federal responsibility for disseminating information about the current state of weather modication technology and about Federal policy, including the cap~ability for providing technical assistance to the States and to others?
24 Farhar, Barb~ara C'.. "What Does Weatier M~odfcation Need"- In preprints of the Sixth Conference on Planned and Inadvertent Weather Modification, Oct. 10-13, 1977, Champaign. Ill., Boston, American Meteorological Society, 1977, p. 299.






14
13. Should there be a continuing review of weather modification technology capabilities so that Federal policy can be informed regarding the readiess of technologies for export to foreign nations., with provision of technical assistance where and when it seems feasible ? 35
14. How does the principle of cooperative federalism apply to weather modification research projects and possible operations carried out within the States? Should planning of projects with field activities in particular States be done in consultation with the States, and should cooperation with the States through joint funding and research efforts be encouraged?
15. What should be the role of the single Federal agency whose activities are most likely to be affected significantly by weather modification technology and whose organization is best able to provide advisory services to the States-the U.S. Department of Agriculture? Among tha several agencies involved in weather modification, the ej)atntment of Agriculture has demonstrated least official interest and has not provided appreciable support to development of the technology."
Roles of State avai local governments
State and local 37 governments are in many ways closer to the public than the Federal Government-often as a result of more direct contact and personal acquaintance with officials and through greater actual or perceived control by the voters. Consequently, a number of weather modification functions, for both reasons of practical efficiency and social acceptance, may be better reserved for State and/or local implementation. Since weather phenomena and weather mrodification operations cannot be restricted by State boundaries or by boundaries within States. however, many functions cannot be carried out in isolation. Moreover, because of the economy in conducting research ind development on a common basis-and perhaps performing other functions as well-through a single governmental entity, such as an agency or agencies of the Federal Government. it may be neither feasible nor wise for State governments (even less for local jurisdictions) to carry out all activities.
Thus, there are activities which might best be reserved for the States (and possibly for local jurisdictions within States), and those which more properly belong to the Federal Government. In the previous list of issues on the role of the Federal Government, there was allusion to a number of functions which might, wholly or in part, be the reSl)Osibility of either Federal or State governments; most of these will not be repeated here. Issues and problems concerned primarily with State and local government functions are listed below:
1. State weather modification laws, where they exist, are nonuniform in their requirements and specifications for licensing, permitting, inspection, reporting, liabilities, and penalties for viol at ions. Moreover, some State laws and policies favor weather modification, while others oppose the technology.
2. Authorities for funding operational and research projects within States and local juris(lictions within States, through public funds
'ha ngnon, "The Federal Role in Weather Modtifiction." p. 11.
wa I 'o er r sfe. 1'roadllv to any Jiu-rtsdithn below the State level: it eould include (|t ies. I owJIShiTPs, Coullt IrO, grV)lllV of conties, wUater districts, or any other organized area operating under piullic authority.







or through special tax assessments, vary widely and, except in a few States, do not exist.
3. Decisionmaking procedures for public officials appear to be often lacking; these could be established and clarified, especially as the possibility of more widespread application of weather modification technology approaches.
4. Many public officials, usually not trained in scientific and engineering skills, often do not understand weather modification technology, its benefits, and its potential negative consequences. Some training of such officials could contribute to their making wise decisions on the use of the technology, even without complete informnation on which to base such decisions.
5. Many weather modification decisions have had strono- political overtones, with some legislators and other public officials expressing their views or casting their votes allegedly on the basis of political expediency rather than on the basis of present or potential societal benefits.
6. State and local authorities may need to provide for the education of the general public on the rudiments of weather modification, on its economic benefits and disbenefits, and on other societal aspects.
7. To keep communication channels open, mechanisms such as public hearings could be established to receive comments, criticisms, and general public sentiments on weather modification projects from individual citizens and from various interest groups.
8. Criteria and mechanisms have not been established for compensating those individuals or groups within States who might be economically injured from weather modification operations.
9. Questions of water rights within States, as well as between States, have not been addressed and/or resolved in a uniform manner.
LEGAL ISSUES
Legal issues in weather modification are complex and unsettled. They can be discussed in at least four broad categories:
1. Private rights in the clouds;
2. Liability for weather modification;
3. Interstate legal issues; and 4. International legal issues.38
The body of law on weather modification is slight, and existing case law offers few guidelines to determine these issues. It is often necessary, therefore, to analogize weather modification issues to more settled areas of law such as those pertaining to water distribution. Private rights in the clouds
The following issues regarding private rights in the clouds may be asked:
Are there any private rights in the clouds or in the water which
may be acquired from them?
Does a landowner have any particular rights in atmospheric
water?
Does a weather modifier have rights in atmospheric water?
:s Questions on regulation or control of weather modification activities through licensing and permitting, while of a basic legal nature, are related to important administrative functions and are dealt with under issues concerned with Federal and State activities.





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Some State statutes reserve the ownership or right to use atmospheric water to the State.39
There is no general statutory determination of ownership of atmospheric water and there is no well-developed body of case law. Consequently, analogies to the following general common law doctrines, may be helpful, but each has its own disadvantages when applied to weather modification:
1. The doctrine of natural rights, basically a protection of the landowner's right to use his land in its natural condition (i.e., precipitation is essential to use of the land as are air, sunlight, and the soil itself).
2. The ad coelum doctrine which states that whoever owns the land ought also to own all the space above it to an indefinite extent.
3. The doctrine of riparian rights, by which the one owning land which abuts a watercourse may make reasonable use of the water, subject to similar rights of others whose lands abut the watercourse.
4. The doctrine of appropriation, which gives priority of right based on actual use of the water.
5. The two main doctrines of ownership in the case of oil and gas (considered, like water, to be "fugitive and migratory" substances) that is, (a) the non-ownership theory, by which no one owns the oil and gas until it is produced and anyone may capture them if able to do so; and (b) the ownership-in-place theory, by which the landowner has the same interest in oil and gas as in solid minerals contained in his land.
6. The concept of "developed water," that is, water that would not be available or would be lost were it not for man's improvements.
7. The concept of "imported water," that is, water brought from one watershed to another.
Liability for weather modification
Issues of liability for damage may arise when drought, flooding, or other severe weather phenomena occur following attempts to modify the weather. Such issues include causation as well as nuisance, strict liability, trespass, and negligence. Other issues which could arise relate to pollution of the air or water through introduction of artificial nucleants such as silver iodide, into the environment. While statutes of 10 States discuss weather modification liability, there is much variation among the specific provisions of the laws in those States .4
Before any case can be made for weather modification liability based upon causation it must be proven that the adverse weather conditions were indeed brought about by the weather modifier, a very heavy burden of proof for the plaintiff. In fact, the scientific uncertainties of weather 1iodification are such that no one has ever been able to establish causation of damage through these activities. As weather nmodification technology is improved, however, the specter of a host of liability issues is expected to emerge as evidence for causation becomes more plausible.
While the general defense of the weather modifier against liability charges is that causation has not been estal)lished, lie may also use as further defensee the arguments based upon immunity, privilege, cosent, and waste.
J See p. 450, ch. 11, and app. 1).
40 See discussion p. 453 in ch. 11 and app. D.





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Interstate legal issues
I When, weather modification activities conducted in one State affect
another State as well, significant issues may arise. The following problem categories are examples of some generally unresolved interstate issues in weather modification:
1. There may be the claim that cloud seeding in one State has removed from the clouds water which should have fallen in a second State or that excessive flooding in a neighboring State has resulted from seeding in a State upwind.
2. Operation of cloud-seeding equipment near the border in one State may violate local or State ordinances which restrict or prohibit weather modification in an adjacent State, or such operations may conflict with regulations for licensing or permitting of activities within the bordering State.
Some States have attempted to resolve these issues through specific legislation and through informal bilateral agreements." ,Xiiotlier approach would be through interstate compact, though such compacts require the consent of Congress. No compacts specifically concerned with weather modification currently exist, though some existing compacts allocating waters in interstate streams may be applicable to weather modification.
International legal issue
Because atmospheric processes operate independent of national borders, weather notification is inherently of international concern. International legal issues have shnilarities to domestic interstate activities wad dangers. The following serious international questions, wbich have arisen in conj unction with a developing capability to, modify the weaker, have been identified by Orfield : 42
Do countries have the right to take unilateral action in all
-weather modification activities?
What liability might a country incur for its weather modification operations which [might] destroy life and property in a
foreign Stiate?
On what theory could and should that State base its claim?
The primary international legal issue regarding weather modification is that of liability for transnational injury or damage, which could conceivably result from any of the following situations:
(1) injury or damage in another nation caused by weather
modification activities executed within the United States;
(2) 'injury or damage in another nation caused by weather
modification activities executed in that nation or a third nation by
the United States or a citizen of the United States;
(3) injury or damage in another nation caused by weather
modification activities executed in an area not subject to the jurisdiction of any nation (e.g., over the high seas), by the United
States or a citizen thereof ; and
(4) injury or damage to an alien or an alien's property within
the United States caused by weather modification activities executed within the United States.
41 See discussion p. 457 in ch. 11 and app. D.
420rfield, Michael B., "Weather Genesis and Weather Neutralization, a New Approach to Weather Modification," California Western International Law Journal, vol. 6, no. 2, spring 1976, p. 414.
34-857-79





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Whereas domestic weather modification law is confused and unsetfled, international law in this area is barely in the formative stage. In time, ramifications of weather modification may lead to major internationl controversy.4
ECONOMIC ISSUES
The potential for long-term economic gains through weather modification cannot be denied; however, current economic analyses are tenuoHs in view of present uncertainty of the technology and the complex nature of attendant leczal and economic problems. Meaningful economic evaluation of weather modification activities is thus limited to special, localize(l casv, such as the dispersal of cold fog at airports, where benetit-cost ratios greaterr than 5 to 1 have been realized through savings in deliaY1d or diverted trafc. Various estimated costs for increased precipitation throu1i cloud( seeding range from $1.50 to $2.50 per acrefoot in the western United States. Is.-' eis cu.omplicatiqg economic an a(y?/ses of weather modiflceation
('osts of most weather modification operations are usually relatively siall and are normally believed to be only a fraction of the benefits obtained through such operations. However, if all the benefits and all tlIe coats are considered, )enefit-cost ratios may be diminished. While direct costs and I)enefits from weather modification are reasonably ol)\viious., in(lirect costs and benefits are elusive and require further study of sociological, legal, andl ecological implications.
In analyzin g benefit-cost ratios, some of the following considerations need to be examined:
Weather modification benefits must be considered in terms of
the costs for ahelieving the same objectives as increased precipitation, e.g., through importation of water, modified use of agricultural chemicals, or introduction of improved plant strains.
Costs for weather modification operations are so low in comparison with other agricultural investments that farmers may gamble in spending the 5 to 20 cents per acre for operations designed to increase rainfall or suppress hail in order to increase yield per acre. even though the results of the weather modification operations mavy ,e (oubtf Iful.
Atmosplieric conditions associated with prolonged droughts are
not conducive to success in increasing precipitation; however, under these conditions, it is likely that increased expenditures may be made for operations which offer little hope of economic
ret T'n.
Increased precipitation, obtained through a weather modification program sponsored and funded by a group of farmers. can also benefit other farmers who have not, shared in the costs; thus, the benefit-cost ratio to those participating in the program is
higher than it need be if all share in its costs.
As weather modlfication technology develops and programs become m1ore sophisticated. increased costs for equipment and labor will increase direct costs to clients: indirect costs resulting from increased State license and permit fees and liability insurance for
operators will probably also be passed on to the customer.
Ro chi. 10 on international aspects and p. 4(;~. ch. 11. on international legal aspects of weather modification.





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The sophistication of future programs will, likely incur additional costs for design, evaluation, and program information activities, along with supporting meteorological prediction services; these costs will be paid from public funds or by private clients, in
either case reducing the overall benefit-cost ratios.
Ultimate costs for compensation to those incurring disbenefits
from weather modification ope rations will offset ovyerail benefits
and thus reduce benefit-cost ratios.
IWea ther modificat ion and conflicting interest ts
There are numerous cases of both real and perceived economic losses which one or more sectors of the public may suffer while another group is seeking economic advantage through some form of weather modlificat ion. Ove rail ben efits from weather modification are accordingly reduced when net gains are computed from such instances of mixed economic advanitagwes and disadvantages. Benefits to the parties seeking economic gain through weather modification will be directly reduced at such time When mechanisms are established for compensating those who have s uffervd lossos. The fol~lowving are some examples of such conflicting situations:
Successful suppression of hail may be valuable in reducing crop
damage for orchardists while other agricultural crops may suffer
f rom decrease of rain concomitant with the hail decrease.
Additional rainy days may be of considerable value to farmers
during their growing season but may be detrimental to the financial success of outdoor recreational enterprises.
Increased snowpack from orographic cloud seeding maybe
beneficial to agricultural and hydroelectric power interests but increases the costs for maintaining f ree passage over highways
and railroads in mountainous areas.
Successful abatement of winds from severe storms, such as those
of hurricanes, may result in decreased precipitation necessary for agriculture in nearby coastal regions or may redistribute the adverse storm effects, so that one coastal area is benefitted at the expense of others.
SOCIAL ISSUES
It has been said that "weather modification is a means toward socially desired ends, not an end in itself. It is one potential tool in a set of possible societal adjustments to the vagaries of the weather. Identifying when, where, and how to use this tool, once it is scientifically established, is the primary need in weather modification."" 4 It is likely that, in the final analysis, the ultimate decisions on whether weather modification should and will be used in any given instance, or-will be adopted more generally as national or State programs depends on social acceptance of this tool, no matter how well the tool itself has been perfected. That this is increasingly the case has been suimyested by numerous examples in recent years. Recently Silverman said:
Weather modification, whether it be research or operations, will not prog0ress4 wisely, or perhaps at all, unless it is considered in a context that includes everyone 1 14Farhar. Barbara C. "What Does Weather MNodification Need ?*' In preprints of the Sixth Conference on Planned and Inadvertent Weather Modifi cation. October 10-i3, 19T7, Chainpaign, Ill. Boston, American Meteorological Society, 1977. p. 296.






20

that may be affected. We must develop and provide a new image of weather modification.5
Regardless of net economic benefits, a program is hard to justify when it produces obvious social losses as well as gains.
Research in the social science of weather modification has not kept pace with the development of the technology, slow as that has been. In time, this failure may be a serious constraint on further development and on its ultimate application. In the past, organized opposition has been very effective in retarding research experiments and in curtailing operational cloud-seeding programs. Thus, there is need for an expanded effort in understanding public behavior toward weather modification and for developing educational programs and effective decisionmaking processes to insure intelligent public involvement in eventual application of the technology.
Social issues discussed in this section are those which relate to public behavior and public response to weather modification, while societal issues are generally considered to include economic, legal, and other nontechnical issues as Ivell as the social ones. These other aspects of societal issues were discussed in preceding sections. In the subsections to follow there are summaries of social implications of weather modification, the need for public education, and the problem of decisionmaking.
Social factors
It has been said that social factors are perhaps the most elusive and difficult weather modification externalities to evaluate since such ftctors impinge on the vast and complex area of human values and attitudes.46 Fleagle, et al., identified the following important social implications of weather modification, which would presumably be taken into account in formulation of policies: 47
1. The individuals and groups to be affected, positively or negatively, by the project must be defined. An operation beneficial to one party may actually harn another. Or an aggrieved party may hold the operation responsible for damage * which might occur at the same time or following the modification.
2. The impact of a contemplated weather modification effort on the general well-being of society and the environment as a whole Inust be evaluated. Consideration should be given to conservationists, outdoor societies, and other citizens and groups representing various interests who presently tend to question any policies aimed at changes in the physical environment. It is reasonable and prudent to assume that, as weather modification operations expand, questioning and opposition by the public will become more vocal.
3. Consideration must be given to the general mode of human behavior in response to innovation. There are cases where local residents, perceiving a cause and effect relationship between economic losses from severe weather and nearby weather modification operations, have continued to protest, and even to threaten violence, after all operations have been suspended.
4. The uniqueness and complexity of certain weather modification operation' must be acknowledged, and special attention should be given to their social and legA inplications. The (ases of hurricanes and tornadoes are especially pertinent. Alteration of a few degrees in the path of a hurricane may result in its missing a certain area * and ravaging * instead, a different one. The decision on whether such an opIration is justified can reasonably be made only at the highest level, and would need to be based on the substantial scientific finding that the anticipated dn(mages would be less than those originally predicted had the hurricane been alloVed to follow its course.
C, Sillernini. Bernard A. "What Do We Need in Weather Modification?" In preprints of th,, Sixth (onferene on Planned and Inadvertent Weather Modification, October 10-13, 1977. Chalin pign, Ill., Boston, American Meteorological Society, 1977. p. 310.
lFhe; g]. (,rutchfleld, Johnson, and Abdo. "Weather Modification In the Public Interest." 1974, p. :7-38.
47 Ibid., p. 38-40.





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5. Attention must be given to alternatives in. considering a given weather modification proposal. The public may prefer some other solution to an attempt at weather tampering which may be regarded as predictable and risky. Furthermore, alternative policies may tend to be comfortable extensions of existing policies, or improvements on them, thus avoiding the public suspicion of innovation. In an area such as weather modification, where so many uncertainties exist, and where the determination or assigning of liability and responsibility are far from having been perfected, public opposition will surely be aroused. Any alternative plan or combination of plans will have its own social effects, however, and it is the overall impact of an alternative plan and the adverse effects of not carrying out such a plan which, in the final analysis, should guide decisions on alternative action.
.6. Finally, it is important to recognize that the benefits from a weather modification program may depend upon the ability and readiness of individuals to'change their modes of activity. The history of agricultural extension work in the United States suggests that this can be done successfully, but only with some time lag, and at a substantial cost. Social research studies suggest that !public perception of flood, earthquake, and storm hazards is astonishingly casual. Need for pu.~blic education on weather modification
The previous listing of social implications of weather modification was significantly replete with issues derived from basic human attitudes. To a large extent these attitudes have their origin in lack of information, -misconceptions, and even concerted efforts to misinform by organized groups which are antagonistic to weather modification. As capabilities to modify weather exp and and applications are more widespread, it would seem probable that this information gap would also widen if there are no explicit attempts to remedy the situation. "At the very least," according to F leagle, et al., "a large-scale continuing pro,gram of education (and perhaps some compulsion) will be required if the potential social gains from weather modification are to be realized 'in fact."1 48 Whether such educational. programs are mounted by the States or by some agency of the Federal Government is an issue of jurisdiction and would likely depend on whether the Federal Governmient or the States has eventual responsibility for management of operational weather modification programs. Information might also be provided privately by consumer groups, professional organizations, the weather modification industry, or the media.
It is likely that educational programs would be most effective if a variety of practical approaches are employed, including use of the news media, publication of pamphlets at a semitechinical level, seminars and hearings, and even formal, classes. Probably the latter categories would be most appropriate for civic groups, 'G'overnment officials, businessmen, or other interests who are likely to be directly 'affected by contemplated operations.
The following list of situations are examples of public lack of undlerstanding which could, at least in part, be remedied through proper educational approaches:
There is much apprehension over claims of potential danger of a
long-lasting nature on climate, which could supposedly result from both inadvertent and planned modification of the weather, with little insight to distinguish between the causes and the scales
of the effects.
There have been extravagant claims, propagated through ignorance or by deliberate di .stortion by antagonistic groups, about
4s Ibid., p. 40.






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the damaging effects of cloud seeding on ecological systems, human
health, and air and water quality.
The controversies between opposing groups of scientists on the
efficacy of weather modification technologies and between scientists and commercial operators on the readiness of these technologies for application has engendered a mood of skepticism and even mistrust of weather modification on the part of a public
which is largely uninformed on technical matters.
The public has often been misinformed by popular news media,
whose reporters seek to exploit the spectacular in popular weather modification "stories" and who, themselves usually uninformed in technical aspects of the subject, tend to oversimplify and distort the facts associated with a rather complex science and technology.
There has been an organized effort on the part of groups opposed
to weather modification to mount an educational program which runs counter to the objectives of informing the public about the potential benefits of a socially acceptable technology of weather
modification.
Portions of the public have acquired a negative impression that
meteorologists and Government officials concerned with weather modification are irresponsible as a result of past use. or perceived
present and future use. of the technology as a weapon of war.
Lack of information to the public has sometimes resulted in
citizen anger when it is discovered that a seeding project has been going on in their area for some time without their having been
informed of it.
Decisionmaking
"The nature of weather processes and the current knowledge about them require that most lmian decisions as to weather modification must be, made in the face of uncertainty. This imposes special restraints on ublic agencies and it increases the difficulty of predictin how individual farmers. manufacturers, and others whlo are directly affected )v weather would respond to changes in weather charactersi ics. t Th)e situation since 19 5 when this statement was made has chlianged little with reward to predic(ta)ilitv of weather processes ia l their modification. There Ihas also been little proffroqs toward developing decisionmaking processes which can be applied, should the need arise, on whether or not weather modification should be employved.
A number of studies on social attitudes indicated that the preference of most citizens is that decisionmaking in such areas as use or restraint from use of weather wodifical ion should be at the local level. owino to the feeling that citizens' rights and property are best protected vwhen decisions are made by officials over whom thlev have the most direct control. Farhar says that evidence suggests that one important condition for Ihlic eac eptance of weather modification technolour is public involvement in the decision process. especially in civic decisions.o Procedures must then be developed for enabling looal
4 Speial ('ornmmsion on Weather Modification. "Weather and Climate Modifleation. NS 6(:63. 19f;5. 1. 96.
I, Fvrlar. BTrrh n (. "The Pulie DooldeR About Weather Modification." Environmeint and Blehavior. vol. 9. No. 3. September 1977, p. 307.






23

officials, probably not technically trained, to make such decisions. intelligently. Such decisions must be based both on information received from Federal or State teclnical advisers and on the opinions, of local citizens and interest groups.
INTERNATIONAL ISSUES
International agreements regarding weather modification expe ri-. ments and operations have been very limited. There exists a United States-Canada agreement, which requires consultation and notification of the other country when there is the possibility that weather modification activities of one country could affect areas across the border.51 Earlier understandings were reached between the United States and Canada. concerning experiments over the Great Lakes and with the United Kingdom in connection with hurricane modification research in the Atlantic. 52 Recent attempts to reach agreement with the Governments of -Japan and the Pepl' Republic of China for U.S. experiments in the Far East on modification of typhoons were unsuccessful, though such research was encouraged by the Philippines. There is current intention to reach an agreement with Mexico, on hurricane research in the eastern Pacific off that nation's coast.
During 1976, 25- nations reported to the World Meteorological O rgani zat ion that they had conducted weather modification acivities. 3 There have been two principal international activities, dealing with somewhat different aspects of weather modification, in recent years. One of these is the preparation and design of a cooperative experiment under the auspices of the World Meteorological Organization, called the Precipitation Enhancement Experiment (PEP); while the other is the development of a convention by the United Nations on the prohibition .of hostile use of environmental modification.
The following international considerations on research and operational weather modification activities can be identified:
1. There is a common perception of a need to insure that the, current high level of cooperation which exists in the international comma unity with regard to more general meteorological researcliandl weather reporting will be extended to development and peaceful uses of planned Weather modification. ie-vNli h ,inb ap ) dt
2. There is now no body of international law ic cnb ppidt
the potentially serious international questions of weather modification, such as liability or ownership of atmospheric water resources.5
3. Past use by the United States, and speculated cur-rent or future use by various countries, of weather modification as a weapon have raised suspicions as to the possible intent in developing advertent weather modification technology.
4. There have been charges that weather modification research activities were used to divert severe weather conditions away from the
5The United States-Canada agreement on weather modification is reprodneed in app. F. 152Ta-ubenfeld, Howard J., "National Weather Modification Policy Act of 1976; International Agreements." Background paper for use of the U.S. Department of Commlerce Weather -Modification Advisory Board, March 1977, p. 13.
SSee table 1, chi. 9, p. 409.
MThese activities and other International aspects of weather modification are discussed' in chi. 10.
SSee previous section on legal issues, p. 17.





1 24

United States at the expense of other countries or that such activities have resulted in damage to the environment in those countries.56
5. As in domestic research projects, there are allegations of insufficient funding over periods of time too short to achieve significant results in the case of internationally sponsored experiments; in particular, many scientists feel that a means should be devised to insure that the planned Precipitation Enhancement Project (PEP) receives adequate continuous support.
6. Other nations should be consulted with regard to any planned weather modification activities by the United States which might conceivably affect, or be perceived to affect, those countries.

ECOLOGICAL ISSUES
The body of research on ecological effects of weather modification is limited but significantly greater than it was a decade ago. It is still true that much remains unknown about ecological effects of changes to weather and climate.
Economically significant weather modification will always have an eventual ecological effect, although appearance of that effect may be hidden or delayed by system resilience and/or confused by system complexity. It may never be possible to predict well the ecological effects of weather modification; however, the more precisely the weather modifier can specify the effects his activities will produce in terms of average percentage change in precipitation (or other variables), expected seasonal distribution of the induced change, expected year-to-year distribution of the change, and changes in relative form of precipitation, the more precise can be the ecologist's prediction of possible ecological effects.
Ecological effects will result from moderate weather-related shifts in rates of reproduction, growth, and mortality of plants and animals; they will rarely be sudden or catastrophic. Accordingly, weather modifications which occur with regularly over time are the ones to which biological communities will react. Adjustments of plant and animal communities will usually occur more slowly in regions of highly variable weather thaii in those with more uniform conditions. )eliberate weather modification is likely to have greater ecological impact in semiarid systems and less impact in humid ones. Since precipitation augmentation, for example, would have the greatest potential for economic value and iS., therefore, likely to have its greatest potential application in such areas, the ecological impacts in transition areas will be of particular concern.
Although widespread cloud seeding could result in local, temporary increases in concentrations of silver (from the most commonly used seeding agent, silver iodide), approaching the natural quantities in surface waters, the exchange rates would probably be an order of magn itude lower than the natural rates. Even in localized areas of precipitation management, it appears that exchange rates will be many orders of magnitude smaller than those adversely affecting plants and soils. Further research is required, however, especially as other pot'ential seeding agents are introduced.
:: For example. there were charges that attempts to mitigate severe effects of Hurricane Fifi in 197T5 caused devastationn to llonduras. a charge which the United States officially (denied. since no hurricanes had been seeded under Project Stormfury since 1971.












CHAPTER 2

HISTORY OF WEATHER MODIFICATION
(By Robert, E. Morrison, Specialist in Earth Sciences, Scie~nce Policy Research
Division, C2ongressional Research Service)
INTRODUCTION
The history of the desire to control the weather can be traced to antiquity. Throughout the ages man has sought to alleviate droughts or to allay other severe weather conditions which have adversely affected him by means of magic, supplication, pseudoscientific procedures such ,as c reating noises, and the more on less scientifically based techniques of recent times.
The expansion in research and operational weather modification projects has increased dramatically since World War 11; nevertheless, activities predating this period are of interest aiid have also provided the roots for many of the developments of the "modern" period. In a 1966 reprt for the Congress on weather modification, Lawton Hartman stated three reasons why a review of the, history of the subject can be valuable: (1) Weather modification is considerably older thanl is 'commonly recognized, and failure to consider this fact can lead to a distorted view of current problems and progress. (2) Weather modification has not developed as an isolated and independent field of research, but fof'over a century has been parallel to and related to progress in understanding weather processes generally. (3) Earlier experiences in weather modification may not have been very different from contemporary experiences in such matters as experimen tal deSign evaluation of results, partially successful projects, and efforts to base experiments on established scientific principles.'
Hartman found that the history of weather modification can be conveniently divided into five partially overlapping periods .2 He refers, to these as (1) a prescientific period (prior to about 1839) ; (2) an early scientific period .(extending approximately from 1839 through 1891) ; (3) a period during which elements of the. scientific framework were established (from about 1875 to 1933) ; (4) the period of the early cloud-seeding experiments (1921 to 1946) ; and (5) the modern period, beginning with the work of Langmuiir, Schaefer, and Vonnegut (since 1946). This same organization is adopted in discussions below; however, the four earlier periods are collected into one section, while the more significant history of the extensive activities of the post- 1946 period are treated separaely.

I Hartman, Lawton M., "History of Weather Modification." in U.S. Congress. Senate Committee on Commerce. "Weather Modification and Control." Washington. D.C.. U.S. Government Printing OYffice, 1966 (89th Cong., 2d sess., Senate Rept. No. 11i39, prepared byv the Legisiative Reference Service, the Library of Congress, at the request of Warren G. Maeunnvon), p. 11.
2 Ibid.
I (25)





26

HISTORY OF WEATIIER MkODIFICATION PRIOR TO 1946
1RESCIENTIFIC PERIOD
From ancient times through the early 19th century, and even since, there have been reported observations which led many to believe that rainfall could be induced from such phenomena as great noises and extensive fires. Plutarch is reported to have stated, "It is a matter of current observation that extraordinary rains pretty generally fall after great battles." 3 Following the invention of gunpowder, the frequency of such claims and the conviction of those espousing this hypothesis increased greatly. Many cases were cited where rain fell shortly after large battles. A practical use of this phenomenon was reported to have occurred in the memoirs of Benvenuto Cellini when, in 1539 on the occasion of a procession in Rome, he averted an impending rainstorm by firing artillery in the direction of the clouds, "which had already begun to drop their moisture." 4
William Iiumphreys posed a plausible explanation for the apparently high correlation between such weather events and preceding battles. He noted that plans were usually made and battles fought in good weather, so that after the battle in the temperate regions of Europe or North America, rain will often occur in accordance with the natural 3- to 5-day periodicity for such events.5 Even in modern times there was the conviction that local and global weather had been adversely affected after the explosion of the first nuclear weapons and the various subsequent tests in the Pacific and elsewhere. Despite statements of the U.S. Weather Bureau and others pointing out the fallacious reasoning, such notions became widespread and persistent.'
In addition to these somewhat rational though unscientific observations, many of which were accompanied by testimony of reliable witnesses, there had been, and there still exist in some primitive cultureq, superstitions and magical practices that accompany weather phenomena and attempts to induce changes to the weather. Daniel ITa]acy relates a number of such superstitiouslike procedures which have been invoked in attempts to bring rain to crops during a drought or to change the weather in some other way so as to be of particular benefit to man:8
Primitive rainmakers would often use various intuitive gestures, such as sprinkling water on the soil that they wanted the heavens to douse, blowing mouthfuls of water into the air like rain or mist, hammering on drums to imitate thunder, or throwing firebrands into the air to simulate lightning.
Women woull carry water at night to the field and pour it out to coax the skies to do likewise.
American Indians blew water from special pipes in imitation of the rainfall.
It was believed that frogs came down in the rain because many were seen following rain : therefore, frogs were hung from trees so that the heavens would pour down rain upon them.
Svmetilnes children were buried up to their necks in the parched ground and then cried for rain, their tears providing the imitative magic.
Ward. R. De C., "Artificial Rain: a Rpview of the Subject to the Close of 1889." Americoi i Met oorologica I Journal, vol. 8, May 1891-April 1892, p. 484.
4 Ibd. p. 49:1:Iumphreys. William J.. "Rain Making and Other Weather Vagaries." Baltimore, The Willi.ms and Wilkin Co.. 1926, p. 31.
SByrs, IIorace It., "History of Weather Modification." In Wilnot N. Hess (editor), "Wpat hber and Cliit.' Modification,"' New York, Wiley, 1974, p. 4.
tialaey, Daniel S., Jr., "The Weather Changers," New York. Harper & Row. 1968. pt. 52- :8.






27

In China, huge paper dragons were part of'religious festivals to bring rain; If, drought persisted, the dragon was angrily torn to bits.
North American. Indians roasted young. women from enemy tribes over a slow fire, then killed them with arrows before eating their hearts and burying their remains in the fields they wanted irrigated with rainfall.
tScottish witches conjured up the wind by beating a stone three times with a rag dipped in water, among intonations like those of characters in a Shakespearean play.
New Guinea natives used wind stones upon which they tapped with a stick, the force of the blow bringing anything from a zephyr to a hurricane.
Pregnant women in Greenland were thought to be able to go outdoors, take a breath, and exhale it indoors to calm a storm.
In Scandinavian countries witches sold knotted bits of string and cloth which, supposedly, contained the wind; untying one kniot at sea would produce a moderate wind, two a gale. and three a violent storm.
Australian bushmen thought that they could delay the Sun by putting a clod of dirt in the fork of a tree at just the height of the Sun, or hasten its departure by blowing sand after it.
Bells have been thought to prevent hail, lightning, and windstorms, and sometimes they are still rung todayv for this purpose.

EARLY SCIENTIFIC PERIOD

James P. Espy was a 19th century American meteorologist known especially for his development of a theory of storms based on convection. Recog-nizing that a necessary condition for rainfall is the formation Iof clouds by condensation of water vapor fromn rising air, Espy considered that rain could well be induced artificially when air is forced to -rise as a result of great fires, reviving a belief of the prescientific era but using~ scientific rationale. In the National Gazette in, Philadelphia of April 5, 1839, hie said:
From principles here established by experiment, and afterward confirmed by observation, it follows, that if a large body of air is made to ascend in a column, a large cloud will 'be generated and that that cloud will contain in itself a selfsustaining power, *vhich may move from the place over which it was formed, and cause the air over which it passes, to rise up into it, aiid thus form more cloud and rain, until the rain may become more general.'
If these principles are just, when the air is in a favorable state, the bursting, out of a volcano ought to produce rain; and such is known to be the fact; and I have abundant documents in my possession to prove it.
So, under very favorable conditions, the bursting out of great fires ought to produce rain ; and I have many facts in my possession rendering it highly probable, if not certain, that great rains have sometimes been produced by great fires."0
Later in the same article Espy stated that:
From these remarkable facts above, I think it will-be acknowledged that there is some connection between great fires and rains other than mere coincidence. But now, when it is demonstrated by the most decisive evidence, the evidence of experiment, that air, ini ascending into the atmosphere in a column, as it must (1o over a great fire, will cool by diminished pressure, so much that it will begin to condense its vapor into cloud.'
Espy postulated three mechanisms which could prevent great fires f rom, providing rain at all times when they occur: (1) If there is a current of air at some height, it sweeps away the up rushing current of air; (2) the dewpoint miay be too low to produce rain at all: and
(3) there may be an upper stratum of air so light that the rising

SEspy. JTanmes P.. "Artificial Rains," National Gazette. Philadelphia, Apr. 5, i19. Reprinted In James P. Espy, "Philosophy of Storms," Boston. Little & Brown. 1841. vP.
-493-494.
10 ibid., p. 494.
:L1 Ibid., p. 496.




1 28

column may not be able to rise far enough into it to cause rain.12 He proposed an experiment in which he would set fire to a "large mass of combustibles," which would be ready for the right circumstances and at a time of drought. He added: "Soon after the fire commences, I will expect to see clouds begin to form * *. I will expect to see this cloud rapidly increase in size, if its top is not swept off by a current of air at a considerable distance above the Earth, until it becomes so lofty as to rain." 3
For over a decade Espy served as an adviser to the Congress on meteorological problems. He proposed in 1850 what is perhaps the first Federal project for large-scale weather modification. His plan included amassing large quantities of timber in the Western States along a 600- to 700-mile north-south line, to be set on fire simultaneously at regular 7-day intervals. He believed that this fire could have started a "rain of great length" traveling toward the East, not breaking up until reaching "far over the Atlantic Ocean; that it will rain over the whole country east-of the place of beginning." The cost of this experiment would "not amount to half a cent, a year to each individual in the United States." 14 Congress did not endorse the proposal for reasons which are unknown; however. Fleagle speculates that perhaps this failure was due to the fact that Congress had not yet accustomed itself to appropriating funds for scientific enterprises.15
There was continuing controversy over whether or not fire could cause increased rainfall. In an article which appeared in Nature in 1871, J. K. Laughton stated that, "The idea that large fires do, in some way, bring on rain, is very old; but it was, I believe, for the first time stated as a fact and explained on scientific grounds by the late Professor Espy." 16 Laughton cited instances where burning brush in hot, dry weather did not result in any rainfall, and he concluded that: Large fires, explosions, battles, and earthquakes do tend to cause atmospheric disturbance, and especially to induce a fall of rain; but that for the tendency to produce effect, it is necessary that other conditions should be suitable. With regard to storms said to have been caused by some of these agencies, the evidence is still more unsatisfactory; and, in our present ignorance of the cause of storms generally, is quite insufficient to compel us to attribute any one particular gale. extending probably over a wide area, to some very limited and comparatively insignificant disturbance.7
The 1871 Chicago fire also aroused interest, many believing that the fire was stopped by the rainfall which it had initiated. Ward cites a telerral of the time sent to London which read:
This fire was chiefly checked on the third or fourth day by the heavy and continuous downpour of rain, which it is conjectured is partly due to the great atmospheric disturbances which such an extensive fire would cause, especially when we are told that the season just previous to the outbreak of the fire had been particularly dry.u'
12 Ibid.
1 I1d., p. 499.
4 Espy. Janmes P.. "Second Report on Meteorology to the Secretary of the Navy." U.S. Senate. Executive D)ocumients. No. 39, vol. 11, 31st ('ong., 1st sess. WashIngton, Wmin. M. Belt 1850 )20.
'= Fleogle. Robert G., "Background and Present Status of Weather Modifiection." In Robert G. Floagle (editor). "Weather Modlifincation : Science and Public Policy." University of WV- 4hifton P1re ., Seattle 196R., 1p. 7,
"' Laughton, J. K., "(Can Weather Be Influenced by Artificial Means?" Nature, Feb. 16, 1,471 1.. ?r;
17 Ibhid.. p. .307.
lo ertd in Ward, "Artificial Rain ; a Review of the Subject to the Close of 1889," 1892. pp, 4S !-4 0.





29

On the other hand, Prof. 1. A. Lapham, speaking of the Chicago fire, contradicted the previous account, saying:
During all this time-24 hours of conflagration-no rain was seen to fall, nor did any rain fall until 4 o'clock the next morning; and this was not a very considerable downpour, but only a gentle rain, that extended over a large district of country, differing i no respect from the usual rains. It was not until 4 days afterward that anything like a heavy rain occurred. It is, therefore, quite certain that this case cannot be referred to as an example of the production of rain by a great fire."
Lapham. goes on to say that, "The case neither confirms nor disproves the Espian theory, and we m~ay still believe the well-authenticated cases where, under favorable circumstances of ver most air and absence of wind, rain has been produced by very large fires."11 20
Prof. John Trowbridge of Harvard reported in 1872 on his experiments in which he investigated the influence of flares on atmospheric electricity. Noting that the normal atmospheric state is positive and that clearing weather is often preceded by a change from negative to positive charge, he suggested that perhaps large fires may influence the production of rain by changing the electrical state of the atmosphere, since, in his tests, his flame tended "to reduce the positive charge of electricity which generally characterizes the air of fine weather." 21He concluded by saying: "The state of our knowledge, however, in regard to the part that electricity plays in atmospheric changes is very meager. The question of the truth of the popular belief that great fires are foblowed by rain still remains unanswered."1 22 .Meanwhile, H. C. Russel, president of the Royal Society of South Wales and government astronomer, attempted to dispel the ideas that both cannonading and great fires could be used to produce rain. He hypothesized that, if fire were to have such an effect, rain should arrive within 48 hours-following the fire. Reviewing the records of 42 large fires (including two explosions) covering a 21-year period, Russel concluded that there was not one instance in which rain followed within 48 hours as an evident consequence of the fire. He further calciflated that to get increased rainfall of 60 percent over a land surface of 52,000 square feet at Sidney would require 9 million tons of coal per day, in an effort to show what magnitude of energy expenditure was necessary and how futile such an attempt would be.23
Toward the latter part of the 19th century there were a number of ideas and devices invented for producing rain artificially. In 1880 David Ruggles of Virginia patented what he said was "a new and useful mode of producing rain or precipitating rainfalls from rainclouds, for the purpose of sustaining vegetation and for sanitary purposes." His plan included a scheme by which balloons carrying explosives were sent up into the air, the explosives to be detonated in the upper air "by electric currents."1 24

1Lanham, L. A.. "The Great Fires of 1871 in the Northwest." The Journal of the Franklin Institute, Vol. 64, No. 1. July 1872, pp. 46-47. 20 Ibid., p. 47.
21 Trowbrige, John, "Great Fire's and Rain-storms." The Popular Science Monthly, vol. 2, December 1872, p. 211.
22 Ibid.
23 Report of an address by H. C. Russel was given in Science, vol. 3, No. 55, Feb. 22, 1884, pp. 229-230.
2 "New Method of Precipitating Rain Fails," Scientific American, vol. 43, Aug. 14. 1880, p. 106.






30

G. H. Bell suggested a rainmaking device, consisting of a hollow tower 1,500 feet high, through which air was to be blown into the atmosphere, the volume of the up-rushing air to be increased through use of a system of tubes around the tower. The inventer consider that the same system could be used to prevent rain, by reversing the blower so that the descending air might "annihilate" the clouds.25
Still other schemes and contrivances were proposed and patented. J. B. Atwater was granted a patent in 1887 for a scheme to dissipate tornadoes by detonating an explosive charge in their centers, and another was granted to Louis Gathman in 1891 for seeding clouds for rain by exploding a shell containing "liquid carbonic acid gas" at cloud. height,26 the latter concept antedating by over 50 years the more recent carbon dioxide seeding projects.
There continued to be adherents to the idea that explosions could cause rainfall. This belief was reinforced by "evidence" of such a con-nection in a book by Edward Powers, called "War and the Weather," published in 1871 and 1890 editions, in which the author recounted the instances in which rain followed battles, mostly from North America and Europe during the 19th century.27
Powers was convinced that:
The idea that rain can be produced by human agency, though sufficiently startling, is not one which, in this age of progress, ought to be considered as impossible of practical realization. Aside from its connection with the superstitions of certain savage tribes, it is an opinion of comparatively recent origin, and is one which cannot be regarded as belonging, in any degree, to a certain class of notions which prevail among the unthinking; * on the contrary, it is one which is coifined principally to those who are accustomied to draw coiiclsimoas only from adequate premises, and * founded on facts which have come under their own observation.8
In tones somewhat reminding us of those urging a greater Federal research effort in recent years, Powers proposed that experiments be undertaken for economic benefit:
Judging from the letters which I have received since commencing in 1870 an attempt to bring forward the subject of rains produced by cannon firing, I believe that the country would regard with interest some experiments in the matter, and would not begrudge the expense, even if they should prove unsuccessful in leading. to a practical use of the principle under discussion. In soine inatters connected with science, the Government has justly considered that an expenditure of public funds was calculated to be of public benefit: but where, in anything of the kind it has ever undertaken, has there been so promising a field for such actions as here? '
Powers, upon examining the records of many battles, said:
Let us proceed to facts-facts not one of which, perhaps, would be of any significance if it stood alone and unsupported by the others; but which, taken in the aggregate, furnish the strongest evidence that heavy artillery firing has an influence on the weather and tends to bring rain."'
Perhaps influenced by the arguments of Powers and others, in 1890 the U.S. Congress had become so much interested in and gained

"Another Rain Controller." Scientific American. vol. 4:. Aug. 21. 1 880. ) 11 :1.
26 Harrington, Mark Y.. "Weather-making. Ancient and Modern," Smithsonian Institu, lion ANwlai Rejort, to Jul 1 ,1 94. pp. 249-270.
2' Iowers. Edward. "War and the Weather," l)elavan. Wis., E. Powers,. 1890, revised edition, 202 pp. (An earlier edition was publi shed in Chicago in 1971. Incidentally. the plates for the first edition were destroyed in the Chicago fire, and Powers did not have an opport unity to complete his revision until 1890.) s Ibid. p. 35.
Ibid., lo. 143.
'It ldh., p. 11.





31

such faith in the possibility of weather modification that funds were appropriated to support experiments to be carried out under the auspices of the Forestry Division of the U.S. Department of Agriculture. The initial $2,000 appropriated was increased first to $7,000, and finally to $10,000, in the first federally sponsored weather modification project. Of the total appropriated, $9,.000 was to be spent on field experiments. Gen. Robert St. George Dyrenforth was selected by the Department of Agriculture to direct these tests, haying earlier conducted tests near Utica, N.Y., and Washington, D.C., using balloons and rockets carrying explosives. The principal experinents were executed near Midland, Tex., using a variety of explosive devices, detonated singly and in volleys, both on the ground and in the air.3'
According to an interesting account by Samuel Hopkins Adanis. Dyrenforth arrived in Texas on a hot day in August 1891 with a company of 80 workers, including "* * chemists, weather observers. balloon operators, electricians, kitefliers, gunners, ninelayers, sappeers, engineers, and laborers * together with some disinterested scientists, who were to serve as reporters." Adams discusses the apparatus which Dyrenforth took with him:
The expedition's equipment was impressive. There were 68 balloons of from 10 to 12 feet in diameter, and one of 20 feet-all to be filled with an explosive mixture of hydrogen and oxygen. There were also sixty 6-inch mortars, made of pipe, and several tons of rackarock (a terrifying blend of potassium chlorate and nitroenzol that was the general's favorite *'explodent"), dynamite, and blasting powder. Finally, there were the makings of a hundred kites, to be assembled on the scene, and sent up with sticks of dynamite lashed to them. The congressional $9,000 fell considerably short of sufficing for so elaborate an outfit, but expectant Texans chipped in with liberal contributions and the railroads helped out by supplying free transpo'rtation.Y3
Dyrenforth carried out five series of trials during 1891 and 1892: one period of sustained cannonading coincided with a heavy downpour, and the apparent connection provided support to the credibility of many people, who accepted the hypotheses as confirmed. Dyrenforth gave optimistic and promising reports of his results; however, meterologists and other scientists were critical of his work. It does not appear that the Forestry Division was fervently adVocating the research program for which it had responsibility. In
1891, Bernhard E. Fernow, Chief of the Division of Forestry, reported to the Secretary of Agriculture his sentiments regarding the experiments which were to be conducted in the coming summer, with a caution reminiscent of the concerns of many meterologists of the 1970's:
The theories in regard to the causes of storms, and especially their local and temporal distribution, are still incomplete and unsatisfactory. It can by no means be claimed that we know all the causes, much less their precise action in precipitation. It would, therefore, be presumptuous to deny any possible effects of explosions; but so far as we now understand the forces and methods in precipitating rain, there seems to be no reasonable ground for the expectation that they will be effective. We may say, then, that at this stage of meteorological knowledge we are not justified in expecting any results from trials as proposed for the production of artificial rainfall, and that it were better to increase this knowledge first
Fleagle, "Background and Present Status of Weather Modification," 1968, pp. 7-8.
Adams, Samuel Hopkins, The New Yorker, Oct. 9, 1952, pp. 93-100.
1 bid., 1,. 94.





32

by simple laboratory investigations and experiments preliminary to experiment on a larger scale."
In 1893, the Secretary of Agriculture asked for no more public funds for support of this project.5
Fleagle tells about the use of 36 "hail cannons" by Albert Stiger, a town burgomaster, on the hills surrounding his district in Austria in 1896:
The hail cannon consisted of a vertically pointing three-centimeter mortar above which was suspended the smokestack of a steam locomotive. This device not only produced an appalling sound, but also created a smoke ring a meter or more in diameter which ascended at about one hundred feet per second and produced a singing note lasting about ten seconds. Initial successes were impressive, and the hail cannon was widely and rapidly copied throughout central Europe. Accidental injuries and deaths were numerous, and in 1902 an inter uational conference was called by the Austrian government to assess the effects of the hail cannon. The conference proposed two tests, one in Austria and one in Italy, the results of which thoroughly discredited the device."
Though unsuccessful, the work of Dyrenforth and others had inspired belief in the possibilities of drought alleviation such that a number of unscrupulous rainmakerss" were able to capitalize on the situation. Halacy gives an account of a famous rainmaker of the early 20th century, Charles Warren Hatfield, who operated for about 10 years in the western United States. With a 25-foot platform and a secret device for dispensing chemicals, he claimed to create rain over extensive areas. In 1916. Hatfield contracted with the city of San Diego to alleviate drought conditions and was to be paid $1,000 for each inch of rain produced. When 20 inches of rain coincidentally fell nearby, the resulting floods destroyed a dam, killed 17 people, and produced millions of dollars damage. Hatfield, faced with a choice of assuming financial responsibility for the lawsuits or leaving the city without pay, chose the latter.37
One of Hatfield's accomplices was a colorful racetrack reporter from New York, who met and joined Hatfield in California in 1912, named James Stuart Aloysius MacDonald, alias Colonel Stingo, "the Honest Rainmaker." Over his half-century career as a writer, mostly for various horseracing journals, MacDonald reportedly involved himself in various schemes for quick profit, including weather changing projects on both the west and east coasts. Contracts with clients were drawn up with terms for remuneration that resembled very much the language of success or failure at the racetrack. By his own admission, MacDonald based his odds for success on past weather data for a given area, which he obtained from records of the U.S. Weather Bureau or the New York Public Library3 MacDonald, or Colonel Stingo, was
the inspiration for a Broadway play called "The Rainmaker" which opened in 1954.
DEVEIJOP3ENT OF SCIENTIFIC FUNDAMENTALS
Espy's 1839 proposal for an experiment on the production of convection currents and water vapor condensation at high altitudes was :A F'rnow, Bernhard E., in report to Jeremiah McClain Rusk. Secretary of Agriculture, 1891, as reported in Ward, "Artificial Rain ; a Review of the Subject to the Close of 1889." 1S92 P. 492.
Hvers. historyy of Weather Modification," 1974, p. 5. ." Fleagle. "Background and Present Status of Weather Modification," 1968. p. 9.
3 nlacy, "The Weather Changers." 1968, pI 68 69. '18 Ucling, A. J., "Profiles," The New Yorker, Sept. 20, 1952, pp. 45-71.






33

based onl sound 'Physical principles. Since knowledge of atmospheric processes was expanding and unfolding rapidly at the time, Hartman reminds us that the limited usefulness of Espy's weather modification concepts should not be ascribed to faulty logic, but rather to the primitiv-e understanding at the time of the complex processes in precipitation, many of which are still not understood satisfactorily. IThe understanding which meteorologists have today about precipitation has been learned slowly and sometimes painfully, and, while many of the discoveries have resulted f rom, 20th century research, some important findings of the latter part of the 19th century are fundamental to these processes. Important results were discovered in 1875 by Coulier in France on foreign contaminant particles in the normal atmosphere, and quantitative measurements of the concent ra tions of these particles were achieved by Aitken in 1879. These events established a basis for explaining the fundamental possibility for occurrence of 'precipitation. Earlier, it had been learned that high supersaturations were required for the formation of water droplets.40 Aitken was the first to imply that there are two types of nuclei, those with an affinity for water vapor (hygroscopic particles) and nuclei that require some degree of supersaturation in order to serve as condensation centers. The Swedish chemist-meteorologists of the 19201s developed a theory of condensation on hygroscopic nuclei and showed the importance of sea-salt particles. In the 1930's in Germany and the
-United Kingdom, a series of measurements were conducted on the numbers anld sizes of condensation nuclei by Landsberg, Judge, and Wright. Data from measurements near Frankfurt, augmented subsequently by results from other parts of the world, have been adopted as the standard' of reference for condensation nuclei worldwide. 41
At the. beginning of the 1930's important aspects of cloud phys* were not yet understood. In particular, the importance of the ic,- phia, to precipitation was not yet clarified, though, ever since the turn of the century meteorologists were aware that water droplets were abundantly present in clouds whose temperatures were well below the freezing point. Little was known about the microphysics of nucleation of ice crystals in clouds; however, it had been noted that rains fell only after visible glaciation of the upper parts of the clouds. Understanding of these processes was essential before scientific seeding of clouds for weather modification could be pursued rationally. In 1933 Tor Bergoeron presented and promulgated his now famous theory on the initiation of precipitaion in clouds containing a mixture of liquid and ice. WV. Findeisen expanded on Bergeron's ideas and published a clearer statement of the theory in 1938; consequently, the concept is generally known as the Bergeron-Findeisen theory.4 In his. investigation of the formation of ice crystals, Findeisen was of the opinion that they crystalizedi directly from the vapor (that is, by sublimation) ra,-the-r thenm freezing from droplets. Hle also conjectured that quartz crystals might be the nuclei responsible for this process and even foresaw that the mechanism might be initiated artificially by introducing suitable nUelei.43

-3 Hartmnan, "Weather Modification and Control," 1966, P. 13.
40 Ibid.
41 Byers, "History of Weather Modification," 1974, P. 7.
42 Ibid., p. 8.
43 Ibid., pp. 8-9.
34-857-79-5




34

Findeisen stated emphatically that rain of any importance must originate in the form of snow or hail, though Bergeron had admitted the occurrence of warm rain in the tropics. Though many meteorologists doubted that the ice crystal process was an absolute requirement for rain, they had been unable to collect evidence from aircraft observations. In Germany aerological evidence was obtained on the growth of rain drops by the collision-coalescence process in "warm" clouds, but the papers on this work were published in 1940, and World War II restricted communication of the results to meteorologists worldwide. Meanwhile in the United States, papers were published on the theory of the warm rain process. In 1938, Houghton showed that precipitation could be started by either the Bergeron process or by the collision-coalescence process. Ie noted that drops could be formed by condensation on "giant" hygroscopic nuclei present in the air and that growth of droplets to raindrop size was possible through collision. G. C. Simpson elucidated further on condensation and precipitation processes in 1941, disagreeing with Findeisen's rejection of "warm" rain formation by the collision-coalescence process."

EARLY CLOUD-SEEDING EXPERIMENTS
Starting about 1920 and continuing for about two decades until the outlbireak of World War II, there were a number of experiments and operations intended to produce rain or modify the weather in some other way. Although some of these activities were pusued in a scientific manner, others were less so and were directed at producing immediate results: all of these projects lacked the benefit of the fundamental knowledge of precipitation processes that was to be gained later during this same period, the discoveriess of which are discussed in the preceding subsection. Various schemes during this period included the dispensing of materials such as dust, electrified sand, dry ice. liUnid air, and various chemicals, and even tihe old idea that explosions can bring rain. Field tests were conducted in the U nited States, Germ'any, the Netherlands, and the Soviet U nion.
Byers tells about the experimental work of Dr. E. Leon Chaffee, professor of plhysics at IHarvard. who became interested in the possibility of making cloud particles coalesce by sprinkling- electrically charged sand over the clouds:
Dr. Chaffee became enthusiastic about the idea and developed in his laboratory a iiozzle or charging sand and(I dispersing it from an airplane. The nozzle could deliver sand grains having surface radients of the order of 1.000 V/cm. Flight experiments were carried out in Aug.ust and September of 1924 at Aberdeen, Md.. with a irplane scattering the sand particles in the clear air above clouds having tops at 5,{000 to 10.000 f et. D)r. Chaffee reported "success" in the reverse sense. in that several cloumds were observed to dissipate after treatment. The tests were well publicized inii newspapers and scientific news journals, and this author, then a freshman at the University of California. recalls that his physics professors were enthusiastic about the idea. Chaffee's results probably would not endlre th, tyne of statistical scrutiny to which experiments of this kind are subject today.?
('Lafie, considered se veral trials successful, since clouds were dissipated after being sprayed with the charged sand. It has been pointed
44 lhid f .
4 T bid., p. 5.




35

out, however, in view of the much greater experience in recent years, that scientist's must be extremely cautious in ascribing success in such experiments, when the evidence is based largely on visual observations.46
In the Netherlands, August Veraart successfully produced rain by seeding clouds with dry ice from a small aircraft in 1930. This was 16 years before the work at General Electric in the United States, when clouds were also seeded with dry ice, initiating the modern period in the history of weather modification. Since Veraart probably did not understand the mechanism involved in the precipitation process which he triggered, he did not realize that the dry ice was effective in development of ice crystals by cooling supercooled clouds, and his success was likely only a coincidence. Byers observes that. Veraart's vague concepts on changing the thermal structure of clouds, modifying tenperature inversions, and creating electrical effects were not accepted, however, by the scientific community He claimed to be a true rainmaker and made wide, sweeping claims of his successes. He died in 1932, a year before Bergeron's theory appeared, not aware of the theoretical basis for his work.48
Partly successful experiments on the dissipation of fog were conducted by the Massachusetts Institute of Technology in the 1930's. unt er the direction of Henry G. Houghton. At an airfield near Round Hill, Mass., fog was cleared using sprays of water-absorbing solutions, particularly calcium chloride, as well as fine particles of dry hygroscopic material. Results of these experiments, which predated some of the present-day fog dispersal attempts by some 30 years, were reported in 1938.49
WEATHER MODIFICATION' SINCE 1946

CHRONOLOGY
The following chronology of "critical events" relating to weather modification policy, compiled by Fleagle, unfolds only some of the major events and activity periods which have occurred since the historic discoveries of 1946: 50
1946: Schaefer demonstrated seeding with dry ice.
1947: Vonnegut demonstrated seeding with silver iodide.
1947-55: Irving Langmuir advertised weather modificaton widely and aggressively.
1947-53: General Electric field experiments ("Cirrus") extended evidence that clouds can be deliberately modified, but failed to demonstrate large effects.
1948-50: Weather Bureau Cloud Physics Project on cumulus and stratiform clouds resulted in conservative estimate of effects.
1948-52: Commercial operations grew to cover 10 percent of United States.
1950: Report of Panel on Meteorology of Defense Department's Research and Development Board (Haurwitz, Chairman) was adverse to Langmuir's claims.
1953: Public Law 83-256 established President's Advisory Committee on Weather Control.
4 McDonald, James E., "An Historical Note on an Early Cloud-Iodification Experiment." Bulletin of the American Meteorological Society. vol. 42. No. 3, March 1961, p. 195.
47 Byers, "History of Weather Modification," 1947. p. 6.
48 Hartman, "Weather Modification and Control." 1966. P. 15.
4 Houghton, Henry G.. and W. H. Radford, "On the Local Dissipation of Natural Fog." Papers in Physical Oceanography and Meteorology. Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, vol. 6, No. 3. Cambridge and Woods Hole, Mass., October 1938, 63 pp.
-5Fleagle, Robert G.. "An Analysis of Federal Policies in Weather Modification." Background paper prepared for use by the U.S. Department of Commerce Weather Modification Advisory Board. Seattle, Wash., March 1977, pp. 3-5.






36

1953-54: Petterssen" Advisory Committee organized field tests on storm systems, convective clouds, and cold and warm fog (supported by the Office of Naval Research, the Air Force, the Army Signal Corps, and the Weather Bureau). These statistically controlled experiments yielded results which have been substantially unchanged in subsequent tests.
1957: Report of Advisory Committee (Orville, Chairman) concluded that tests showed 15 percent increase in orographic winter precipitation.
1957: Major cut in research support across the board by Defense Department sends major perturbation through research structure.
1958: Public Law 85-510 assigned lead agency responsibility to the National Science Foundation (NSF).
1959: Commercial operations had diminished to cover about one percent of the United States.
1961: First hurricane seeding under Project Stormfury.
1961: Bureau of Reclamation authorized by Congress to conduct research in weather modification.
1961: RAND report on weather modification emphasized complexity of atmosphieric processes and interrelation of modification and prediction.
1962-70: Randomized field experiments established magnitude of orographic effects. ,
1964: Preliminary report of National Academy of Sciences/Committee on Atmospheric Sciences (NAS/CAS) roused anger of private operators and stimulated the evaluation of operational data.
1964-pre-sent: Department of the Interior pushed the case for operational seeding to augment water supplies.
1966: NAS/CAS report 1850 laid the basis for expanded Federal programs.
1966: Report of NSF Special Commission on Weather Modification and an NSF symposium called attention to social, economic, and legal aspects.
1966: Interdepartmental Committee for Atmospheric Sciences (ICAS) report (Newell, Chairman) proposed expanded Federal support to $90 million by 1970.
1966-68: Efforts of the Departments of Commerce and Interior to gain lead agency status were unsuccessful.
1967: ICAS recommended that Commerce be designated as lead agency.
1967: S. 2916, assigning lead agency responsibility to the Department of Comnterce; )asszed the Senate but did not become law.
1967-72: Military operational programs conducted in Vietnam.
1968: Public Law 90-407 removed the NSF mandate as lead agency.
1968: Detrimental effects of acid rain reported from Sweden.
1969: Public Law 91-190 (National Environmental Policy Act) required imI)a,'t statements.
1970: Massachusetts Institute of Technology Study of Critical Environmental Problems called attention to inadvertent effects on climate.
1970: Stratospheric contamination by SST's suggested.
1971: Departments of Commerce and Interior carried out operational programs in Oklahoma and Florida.
1971: Public Law 92-205 required filing of reports of non-Federal weather modification activities with the Department of Commerce.
1971 : International Study of Man's Impact on Climate raised this issue to international level.
1971: NAS/CAS report on priorities for the 1970's emphasized need for attention to management and policy problems of weather modification.
1971: Federal Council for Science and Technology approved seven national projects under various lead agencies.
1971-72: First technological assessments of weather modification projects are favorable to operational programs.
1971-74: Climate impact assessment program (ClAP) of Department of Transportation indicates potentially serious consequences of large SST fleet but suggests ways to ameliorate the problem.
1972: Failure of Soviet wheat crop and drought in Sahel emphasized critical need for understanding climate and the value of effective weather modification.
1973: Weather modification budget reduced by impoundment from $25.4 million to $20.2 million.
1973: Five national projects deferred or terminated. 1973: NAS/CAS report on weather and climate modification confirmed earlier conclusions and recommended lead agency status for NOAA.





37

1974: Stratospheric contamination by freon reported.
1974: Dbmestic Council organized panels in climate change and weather modification.
1974: General Accounting Office report on weather modification criticized weather modification program and pointed to need for lead agency.
1974: Defense Department released information on operations in Vietnam.
1974: The United States and the U.S.S.R. agreed to a joint statement intended "to overcome the dangers of the use of environmental modification techniques for military purposes."
1975: World Meteorological Organization Executive Committee proposed cumulus experiment perhaps in Africa or Iran.
1975: Department of Transportation CIAP report indicated that a fleet of 500 SST's would deplete ozone significantly, but suggested that cleaner engines could be developed.
1976: Chinese disapproval resulted in abandoning plans for Stormfury in the western Pacific.
1976: Hearings held on three weather modification bills by Senate Commerce Committee.
1976: The National Weather Modification Policy Act of 1976 (Public Law 94859) enacted requiring study of weather modification.
1977: Exceptionally dry winter in the west stimulates State operational programs intended to increase mountain snowpack.
Since the completion of Fleagle's list above in March 1977, at least three other activities of equivalent significance ought to be noted:
1977: The U.S. Department of Commerce Weather Modification Advisory Board established in April 1977 and initiated a major study on a recommended national policy and Federal program of research in weather modification, in accordance with requirements to be fulfilled by the Secretary of Commerce under Public Law 94-490, the National Weather Modification Policy Act of 1976. .1977: The United Nations General Assembly approved a treaty banning environmental modification activities for hostile purposes on May 18, 1977; and the treaty opened for signature by the member nations.
1978: The Report of the Commerce Department's Weather Modification Advisory Board transmitted through the Secretary of Commerce to the Congress.
The history of the modern period of weather modification which follows is essentially that of the two decades following the monumental discoveries of 1946. An excellent account of the history of weather modification, which emphasizes this period, has been prepared by Byers.,5' This work has been very helpful in some of the material to follow and is referenced frequently. The late 1960's and the 1970's aire so recent that events during this period are discussed in various sections of the report as ongoing activities or events leading to current activities in weather modification research programs, operations, and policy decisions rather than in this chapter as an integral part of an updated history of the subject.

LANG31UIR, SCHIAEFER. AND VONNEGUT

The modern era of scientific weather modification began in 1946, when a group of scientists at the General Electric Co. demonstrated that, through "seeding," a cloud of supercooled water droplets could be transformed into ice crystals and precipitation could be induced. These were not traditional meteorologists, though their leader, ]Dr. Irving Langmuir, was -a famous physicist and Nobel hi iireate.- He and his assistant, Vincent J. Schae-fer, -had been working for 8) years on cloud physics research, however, in which they were studying p~article sizes, precipitation static, and icing. Their field research was carrIiedl on

5Byers', "History of Weather Modification," 1974, pp. 3-44.





38

at the sununit of Mt. Washington. N.11.. where they observed supercooled clouds which often turned into snowstorims 2
In an attempt to simulate field conditions. Schaefer contrived a lal)oratory setup using a home freezer lined with black velvet, with a light mounted so as to illuminate ice crystals that might happen to form in the box. Breathing into the box, whose temperature was about
-230 C. produced fog but no ice (crystals. even when various substances-including sand, volcanic dust, sulfur, graphite. tale. and salt-were dropl)ed in as possible sublimation nuclei3 On July 12. 19416, Schaefer wanted to lower the freezer temperature somewhat. so he inserted a large piece of dry ice, and, in an instant, the air was full of millions of ice crystals. He discovered that even the tiniest piece of dry ice produced the same effect. In fact, dry ice had no direct effect on the supercooled cloud: producing an air temperature below -390 C was critical."
In his paper on the laboratory experiments, published in the November 15, 1946. issues of"'Science" Sc(haefer stated:
It is planned to attempt in the near future a large-scale conversion of supercooled clouds in the atmosphere to ice crystal clouds, by scattering small fragnments of dry ice into the cloud from a plane. It is believed that such an operalion is practical and economically feasible and that extensive cloud systems can be modified in this way.
Two days before the paper appeared, on November 13, 1946, Schaefer made his historic flight, accomplishing man's first scientific seeding of a supercooled cloud, as he scattered three pounds of dry ice along a 3-mile line over a cloud to the east of Schenectady, N.Y. At 14.000 feet the cloud temperature was 20 C,. and in about 5 minutes after seeding the entire cloud turned into snow. which fell 2,000 feet before evaporating.56
)Dr. Bernard Vonnegut had also worked on aircraft icing research and in 1946 at General Electric was pursuing a variety of nucleation problems: but, after Schaefe.rs laboratory experiments, he again turned his attention to ice nucleation research. le discovered that silver iodide and lead iodide had crystal structures close to that of ice and were also insoluble in water, and after repeated initial failures, owing to impurities in the material, Vonnegut was able to produce ice crystals, using very pure silver iodide powder, at temperatures only a few degrees below freezing. Soon means were developed for generating silver iodide smokes, and man's first successful attempt at artificial nucleation of supercooled clouds was accoml)lished.7
Langmnuir explained that dry ice could inake ice crystals formn by lowering the temperature to that required for natural nucleation on whatever might be present as nuclei. or even in the absence of all nuclei: however, the silver iodide provided a nucleus that was much more efficient than those occurring naturally.58

5 TIbid., pp. 9-10.
Halacy. "The Weather Changers," 1968. pp. 82-83.
SLangmuir, Irving. "The Growth of Particles in Smoke, and Clouds and the Prodluction of Snow from Supercooled Clouds." Proceedings of the American Philosophical Society. vol. 92. no. 3, July 1948, p. 182.
Schaefer. Vincent J.. "The Production of lee Crystnis in a Cloud of Supercooled Water I)roplets." Science. vol. 104, No. 2707. Nov. 15. 194G. p. 459.
1*Byers. "History of Weather Modification," 1974, p. 12.
hIbid.. p. 13.
LT.aIngmuir. Irvlnim. "Cloud Seoeding by Means of Dry lee, Silver Iodide, and Sodium Chloride." Transactions of the New York Academy of Sciences, ser. II, vol. 14, November 1951. p. 40.





39
Following Schaefer's successful flight of November 13, 1946, and in the months and immediate years thereafter, Langmuir was quoted in the popular press as being very optimistic in his predicted benefits from weather modification. In a 1948 paper lie said that "* * it becomes apparent that important changes in the whole weather map can be brought about by events which are not at present being considered by meteorologists." 59 His publications and informal statements of this character touched off years of arguments with professional meteorologists, by whom refutation was difficult in view of Lang-muir's standing in the scientific community. His enthusiasm for discussing the potential extreme effects from weather control was unrestrained until his death in 1957.60

RESEARCH PROJECTS SINCE 19 4 7
Project Cirrus
Although the business of the General Electric Co. had not been in meteorology, it supported the earl research of Langmuir and his associates because of the obvious importance of their discoveries. Realizing that weather modification research was more properly a concern of the Federal Government, the company welcomed the interest of, and contract support from, the U.S. Army Signal Corps in February 1947. Subsequently, contract support was augmented by the Office of Naval Research, the U.S. Air Force provided flight support, and the U.S. Weather Bureau participated in a consultative role. The entire program which followed, through 1951, under this arrangement, including the field activities by Government agencies and the laboratory work and general guidance by General Electric, was designated "Project Cirrus." 61 According to Byers: The most pronounced effect produced by Project Cirrus and subsequently substantiated by a number of tests by others, was the clearing of paths through supercooled stratus cloud layers by means of seeding from an airplane with dry ice or with silver iodide. When such clouds were not too thick, the snow that was artificially nucleated swept all the visible particles out of the cloud. * In one of the first flights, * the supercooled particles in stratus clouds were removed using only 12 pounds of dry ice distributed along a 14-mile line. In later flights even more spectacular results were achieved, documented by good photography.2
Initial Project Cirrus studies were made during the summer of 1947 on cumulus clouds near Schenectady, but the important seeding experiments were conducted the following year in New Mexico. Also during 1947, there was an attempt on October 13 to modify a hurricane east of Jacksonville, Fla., through seeding with dry ice.3 Visual observations, reported by flight personnel, seemed to indicate a pronounced change in the cloud deck after seeding, and, shortly thereafter, the hurricane changed its course and headed directly westward, striking:the coasts of Georgia and South Carolina. Even though there was precedent for such erratic behavior of hurricanes, there was speculation about the effect of seeding on the storm path, and the possibility of legal responsibility for damages which might be caused by
59 Langmuir. Irving. "The Production of Rain by a Chain Reaction in Cumulus Clouds at Temperatures Above Freezing," Journal of Meteorology. vol. 5. No. 5. October 194S, p. 192. 6q Rvers. "History of Weather Modification," 1974, pp. 13-14. 61 Thi.. p. 14.
62 Ibid.
63 See discussion of ProJect Stormfury in ch. 5. p. 296 ff.





40

such experiments in the future provided reason to avoid seeding thereafter any storms with the potential of reaching land. The legal counsel of the General Electric Co. admonished Langnmir not to relate the course of the hurricane to the seeding; however, throughout the remainder of his career he spoke of the great benefit to mankind of weather control and of the potential ability to abolish evil effects of hurricanes. As a result, it was expected that the U.S. Weather Bureau would undertake massive efforts in weather control. Meteorologists within and without of the Bureau were in a defensive position, with many other scientists, impressed by Langmuir's arguments, opposing their position. Thus great controversies which developed between Langmuir and the Weather Bureau and much of the meteorological community followed these and other claims, and often resulted from the fact that Langmuir did not seem to fully comprehend the magnitude and the mechanisms of atmospheric phenomena. 4
Langmuir wanted to work where he thought storms originated rather than in upstate New York. He chose New Mexico as operations area for Project Cirrus, also taking advantage of the opportunity to collaborate there with Dr. E. J. Workman at the New Mexico Institute of Mining and Technology, whose thunderstorm research included radar observations and laboratory experiments on the effects of ice on storm electrification. After cloud-seeding flights there in October 1948, Langmuir reported that, as a result of the seeding, rainfall had been produced over an area greater than 40,000 square miles (about one-fourth the area of the State of New Mexico)."'
The Project Cirrus group returned to New Mexico in July 1949, and 10 additional seeding flights were conducted. When Langmuir learned that Vonnegut was dispensing silver iodide from a ground generator in the same area and had, in fact, also been doing so during the flights of the previous October., he concluded that both the July 1949 results and the widespread effects of October 1948 were caused by the silver iodide rather than the dry ice seeding as he had theorized previously. Spectacular results continued to be reported by him, spurred on by meteorologists' challenges to his statistical methods and conclusions. Noting that Vonnegut had operated the ground generator only on certain days., Langmuir observed that rainfall responses corresponded to generator "on" times, leading him to his controversial "periodic seeding experiment," to which the remainder of his life was devoted.66
In the periodic seeding experiment, the silver iodide generators were operated in an attempt to effect a 7-day periodicity in the behavior of various weather properties. Langmuir was convinced that unusual weekly weather periodicities in early 1950 resulted from periodic seedings begun in New Mexico in December 1949, concluding that the effects were more widespread than he felt earlier and that temperatures and pressures thousands of miles away were also affected. Meteorologists obseired that, while these correlations were the most striking seen, yet such periodicities were not uncommon.67 The Weather Bureau undertook a study of records from 1919 to 1951 to see if such weather perio6h Ibid., pp. 14-16.
1111hd., P. 18R.
Ibid.. p, 19.
11b1d., pp. 19-20.






41

dicities had occurred in the past. Glenn W. Brier, author of the report on this study, indicated that a 7-day component in the harmonic analysis of the data appeared frequently, though seldom as marked as during the periodic seeding experiment.68 Byers' opinion is that the evidence appeared just as reliable for occurrence of a natural periodicity as for one controlled artificially. He contends that the most important discoveries in cloud physics and weather modification were made in the General Electric Research Laboratory before Project Cirrus was organized, that tie effect of clearing stratus decks was shown soon after the project was underway, and that the seeding experiments thereafter became more of a "program of advocacy than of objective proof." The project * failed to demonstrate that seeding of cumulus clouds increased rainfall, that seeding initiates self-propagating storms, that the atmosphere responds periodically to periodic seeding, or that a hurricane could be deflected in its path by seeding." 69
Seeding under Project Cirrus ended in 1951 and the final report appeared in 1953. After the close of the project, Langmuir continued his analyses and wrote two more papers before his death in 1957. The final paper was titled "Freedom-the Opportunity To Profit From the Unexpected," a report that Byers feels provided a fitting philosophical close to his career.70 The Defense Department sponsored another series of experiments, called the Artificial Cloud Nucleation Project, from 1951 to 1953.
The Weather Bureau Cloud Physics project
Amid increasing publicity and spectacular claims of results from cloud seeding in Project Cirrus, the U.S. Weather Bureau initiated in 1948 a project to test cloud seeding, with the cooperation of the National Advisory Committee for Aeronautics, the Navy, and the Air Force. The Cloud Physics Project. the first systematic series of seeding experiments in stratiform and cumuliform clouds, continued for 2 years, with flight operations in Ohio, California, and the Gulf States. Findings of Project Cirrus were substantiated in that striking visual cloud modifications occurred; however, there was no evidence to show spectacular precipitation effects. and the experiments led to a conservative assessment of the economic importance of seeding.7'1 Cloud dissipation rather than new cloud development seemed to be the general result from seeding, the only precipitation extractable from clouds was that contained in the clouds themselves, and cloud seeding methods did not seem to be promising for the relief of drought.72
Results of the cloud physics experiment had almost no effect on the prevalent enthusiasm at the time for rainmaking through cloud seeding, excei)t in the "hard core" of the meteorology community."73 As a result of these experiments and the interpretation of the results. the Weather Bureau and its successor organizations in the Commerce De~Pa,,rtment. the Environmental Science Services Administration and the National Oceanic and Atmospheric Administration, have been
Brier.. Glen W.. "Seven-Day Periodicities in May 1952." Bulletin of the American Metenrological Society. vol. 35. No. 3. March 1954. pp. 11R-121. SBvers, "History of Weather Modification." 1974. pp. 20-21.
0 Thid.. p. 20.
'Floagle, Robert G.. "Background and Present Status of Weather Modification." 19 pp 9-10.
2 Rers. "iTstory of Weather Modification." 1974. P. 18-17.
7 Thi.. p. 17.






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regarded by some critics as unimaginative and overconservative on weather modification.74
The U.S. experiments of 1953-54
In 1951 the Weather Bureau, the Army, the Navy, and the Air Force appointed an advisory group, chaired by Dr. Sverre Petterssen of the University of Chicago, under whose advice and guidance the following six weather modification projects were initiated: 5
1. Seeding of extratropical cyclones, sponsored by the Office of Naval Research and conducted by New York University.
2. Seeding of migratory cloud systems associated with fronts and cyclones, conducted by the Weather Bureau.
3. Treatment of convective clouds, supported by the Air Force and conducted by the University of Chicago.
4. Research on the'-dissipation of cold stratus and fog, conducted by the Army Signal Corps.
5. Studies of the physics of ice fogs, sponsored by the Air Force and conducted by the Stanford Research Institute.
6. Investigation of a special warm stratus and fog treatment system, sponsored by the Army and conducted by Arthur D. Little, Inc.
Field experiments on these projects were carried out in 1953 and 1954, and reports were published under the auspices of the American Meteorological Society in 1957.76
The purpose of the extratropical cyclone seeding project. called Project Scud, was to "* * ascertain whether or not it would be possible to modify the development and behavior of extratropical cyclones by artificial nucleation. * *" 7 Analysis obtained in Sctud from Florida to Long Island showed that "* * the seeding in this experiment failed to produce any effects which were large enough to be detected against the background of natural meteorological variance." 7S
The Weather Bureau project on migratory cloud systems was conducted in western Washington on cloud systems that enter the area from the Pacific during the rainy winter months. This project was criticized by ('ol ercial seeders since it was conducted in the West. which was considered "their territory," and by those who accused the WNfeatler Buarau of seeking a negative result to sulport their conservative view toward weather modification. Byvers feels that there was an attempt to avoid this negative impression by giving a more Positive interpretation to the results than the data possibly justified.7" In sumImlarizin results, HIall stated:
Considering the results as a whole there is no strong evidence to support a conclusion that the seeding produced measurable changes in rainfall. * the evalnations do not necessarily furnish information on what the effect might have been with more or less intense seeding activity, rate of release of dry ice, etc. Also it
Sfleagle. "Background iand Present Status of Weather Modification," 1968, p. 10.
Byers. "History of Weather Modification." 1974. p. 2'5.
Petterssen. Sverre. Jerome Spar, Ferguson Hall. Roscoe R. Braham. Jr.. Lois J Battn,. Tloraee R. Byers, H. J. aufm Kamoe. J. J. Kelly. and H. K. WeiekImann. "cloud an,
Weather Modification : a Group of Field Experiments." Meteorological Monographs, vol. 2. No 11 Atmerican Moteoro'odieal Soelety. Boston. 1957. 111 pp.
77Pet terssen, 'Sverre. "Reports on Experiments with Artificial Cloud Nucleation: Introfnlotorv Note" In Petterson oet al.. "Cloud anil Weather Modification: a Group or Field E xperrinats," 1oteorologican Monographs. vol. 2. No. 11. American Meteorological Society, BoUntn. 1957. p. "
-: SHr. .Terome "Proteet Send." In Potterssen oet al1.. "Cloud and Weather Molftciton a G(roan of 1F1d Er.erinents." Motoorologeical Monographs, vol. 2. No. 11. Amertean Meteorololen Soooet v. Io,' on. 197 p 22.
79 Tyers. "History of Weuthor Modifileation." 1974. p. 2C).






43

might be speculated that the seeding increased rainfall on some occasions and decreased it on others.8
The aim of the University of Chicago Cloud Physics project was as follows. 81
The formulation of a consistent and immediately applicable picture of the processes of formation of cumulus clouds, charged centers, and precipitation with a view toward testing the possibility that one can modify these processes and influence the natural behavior of clouds.
So that as many cumulus clouds as possible could be tested, work was conducted in the Middle West in the summer and in the Caribbean in the winter, realizing that the warm trade-wind cumulus clouds in the latter region might be amenable to seeding with large hygroscopic nuclei or water spray, and that the ice-crystal process would operate to initiate precipitation in the colder clouds of the Middle West.s" Of the numerous conclusions from this project 83 a few will serve to indicate the value of the project to the understanding of cloud phenomena and weather modification. In the Caribbean tests, water spray from an aircraft was seen to increase rainfall as determined by radar echoes; analysis showed that the treatment doubled the probability of occurrence of a radar echo in a cloud. From tests on dry ice seeding in the Middle West it was found that in the majority of cases treated clouds showed an echo, while untreated ones did not, although the sample was considered too small to be significant. In all cases clouds were considered in pairs, one treated by seeding and the other untreated, and only those clouds showing no echo initially were chosen for study.84
The seeding experiments with supercooled stratus clouds by the Army Signal Corps essentially substantiated the results of Project Cirrus; however, from these carefully conducted tests a number of new relationships were observed with regard to seeding rates, spread of glaciating effect, cloud thickness, overseeding, and cloud formation after seeding.,S5 The report on this project carefully summarized these relationships and conclusions for both dry ice and silver iodide seeding.86
The Air Force project on the physics of ice fogs, conducted by Stanford Research Institute, was intended to learn the relationship to such fogs of synoptic situations, local sources of water, and pollution. Investigations in Alaska at air bases showed that most fogs developed from local sources of water and pollution. In the Arthur 1). Little investigation for the Army attempts were made to construct generators which were capable of producing space charges, associated with aerosols, that could bring about precipitation of the water droplets in warm fogs and stratus.s8,
so Hall, Ferguson, "The Weather Bureau ACN Project." In Petterssen et al., "Cloud and Weather Modification; a Group of Field Experiments," Meteorological Monographs, vol. 2. No. II. American Meteorological Society. Boston. 1957, pp. 45-46.
8 Braham, Roscoe R., Jr.. Louis J. Battan. and Horace R. Byers, "Artificial Nucleation of Cumulus Clouds." In Petterssen et al., "Cloud and Weather Modification ; a Group of Field Experiments," 1957, p. 47.
82 Byers, "History of Weather Modification," 1974, pp. 26-27. 83 Conclusions are precisely spelled out in somewhat technical terms in: Braliam. Battan. and Byers. "Artificial Nucleation of Cumulus Clouds," 1957, pp. 82-$3. 84 Byers, "History of Weather Modification," 1974, p. 27. 85 Ibid.
m aufm Kampe, H. J., J. .T. Kelly, and H. K. Weickmann, "Seeding Experiments in Subcooled Stratus Clouds." In Petterssen et al., "Cloud and Weather Modification: a Group of Field Experiments." Meteorological Monographs, vol. 2, No. 11. American Meteorological Society, Boston, 1957, p. 93.
87 Petterssen, "Reports on Experiments With Artificial Cloud Nucleation: Introductory Note," 1957, p. 4.






44

Byers, in retrospect, wonders why the results of this series of six experiments, which were carefully controlled statistically, did not receive more attention than was accorded them. He attributes some of this lack of visibility to the publication in the somewhat obscure monograph of the American Meteorological Society 88 and to the delay in publishing the results, since the Petterssen committee held the manuscripts until all were completed, so that they could be submitted for publication together."
Arizona mountain cumulus expe iments
After 1954, the University of Chicago group joined with the Institute of Atmospheric Physics at the University of Arizona in seeding tests in the Santa Catalina Mountains in southern Arizona. These experiments were conducted in two phases, from 1957 through 1960 and from 19(61 through 1964, seeding mostly summer cumulus clouds, but some winter storms, with silver iodide from aircraft. In the first phase, analysis of precipitation data from the first 2 years revealed more rainfall during seeded than on nonseeded days; however, during the latter 2 years, considerably more rainfall was achieved on nonseeded days. Combining all data for the 4 years of the first phase yielded overall results with more rain on unseeded (lays than on seeded days; hence, the experiments were modified and the second phase undertaken. Of the 3 years in the second phase, only one showed more rain on seeded days than on nonseeded ones. None of the analyses attempted could support the hypothesis that airborne silver iodide seeding increased precipitation or influenced its area extent. Byers suggests that the failure to increase rainfall may have been due to the fact that precipitation initiation resulted from the coalescence process rather than the ice-crystal process.90 Project Whitetop
According to Byers, perhaps the most extensive and most sophistie4ated weather modification experiment (at least up to the time of Byers' historical review in 1973) was a 5-year program of summer convec.tive cloud seeding in south-central Missouri, called Project Whitetop. Conducted from 1960 through 1964 by a group from the University of Chicago, led by Dr. Roscoe R. Braham, the purpose of Whitetop was to settle with finality the question of whether or not summer convective clouds of the Midwest could be seeded with silver iodide to enhance or initiate precil)itation. Experimental days were divided into seed(ling and no seeding days, chosen randomly from operational (lays suitable for seeding, based on certain moisture critria. Another fe.Ature of the project was the attempt to determine the extent of spreading of silver iodide smoke plumes from the seeding line. IPrecipiitation effects were evaluated by radar and by a rain-gage network.91
Final analysis of all of the Project Whitetop data showed. that the overall effect wa1s that, in the presence of silver iodide nuclei, the rainfall was less than in the unsee(lded areas. Byers attributes these negative
8 Petterssen et al., "Cloud and Weather Modification; a Group of Field Experiments," 1957.
1 BIyers. "History of Weather Modification," 1974, p. 28.
9 Ibid., p. 29.
ex Ibid., pp. 29-30.






45

results to the physical data obtained from cloud-physics aircraft. "Most of the Missouri clouds produced raindrops by the coalescence process below the freezing line, and these drops were carried in the updrafts and frozen as ice pellets at surprisingly high subfreezing temperatures (-50 C to -100 C) .1 He further points out that the measured concentrations of ice particles, for the range of sizes present, were already in the natural unseeded conditions equivalent to those hoped for with seeding; consequently, the silver iodide only had the effect of overseeding.92
Climat experiments
Following the initial General Electric experiments, it was concluded by Bergeron 93 that the best possibility for causing considerable rainfall increase by artifical means might be found in seeding orographic 9 cloud systems. Consequently, there were almost immediate efforts to increase orographic precipitation, the greatest concentration of such work being in the Western United States. Commercial groups such as power companies -and irrigation concerns took the early initiative in attempts to augment snowfall from orographic, cloud systems in order to increase streamfiow from the subsequent snowmelt.
Colorado State University (CSU) began a randomized seeding experiment in the high Rocky Mountains of Colorado in 1960, under the direction of Lewis 0. Grant, t~o investigate snow augmentation from orographic clouds. The project was designed specifically to
(1) evaluate the potential, (2) define seedability criteria, and (3) develop a technology for seeding orographic clouds in central Colorado.95 It followed the 1957 report of the President's Advisory Committee for Weather Control, in which it had been concluded that seeding of orographic clouds could increase precipitation by 10 to 15 percent, basing this judgment, however, on data from a large number of seeding programs that had not been conducted on a random basis. 96
The first group of the CSU seeding experiments took place from 1960 to 1965' in the vicinity of Climax, Colo., and has been designated Climax I. A second set of tests in the same area from 1965 to 1970 has been referred to as Climax II. The Climax experiments are important in the history of weather modification because they were the first intensive projects of their kind and also because positive results were reported. 97 The precipitation for all seeded cases was greater than for all of the unseeded cases by 9, 13, and 39 percent, respectively, for Climax I, Climax II, and Climax JIB. The latter set of data are a subsample of those from Climax II, from which possibly contaminated cases due to upwind seeding by other groups were eliminated.
92 Ibid., p. 30.
93 Bergeron, Tor, "The Problem of an Artificial Control of Rainfall on the Globe; General Effects of Ice Nuclei In Clouds." Tellus, vol. 1, No. 1, February 1949, p. 42.
94 A definition of orographic clouds, a discussion of their formation, and a summary of attempts to modify them are found in ch. 3, p. 71 ff.
0' Grant, Lewis 0., and Archie M. Kahan, "Weather Modification for Augmenting Orographic Precipitation."~ In Wilmot N. Hess (editor), "Weather and Climate Modification," New York, Wiley, 1974, p. 295.
96 Advisory Committee on Weather Control. Final Report of the Advisory Committee on Weather Control, Washington, D.C., U.S. Government Printing Office, Dec. 31, 1957, vol. L, P. vi. (The establishment of the Advisory Committee and its activities leading to publication of its final report are discussed in ch. 5, under activities of the Congress and of the executive branch of the Federal Government. see pp. 195. 214, and 236.) 97 Byers, "History of Weather Modification," 1974, pp. 30-31. 98 Grant and Kahttn, "Weather Modification for Augmenting Orographic Precipitation," 1974, p. 298.






46

Lightning suppression experiments
From 1947 until the close of Project Cirrus, interspersed with his other activities, Vincent Schaefer visited U.S. Forest Service installations in the northern Rockies in order to assist in attempts to suppress lightning by cloud seeding. As early as 1949 an attempt was made to seed thunderstorm clouds with dry ice, dumping it from the open door of a twin-engine aircraft flying at 25,000 feet.99 This stimulated curiosity among those involved, but also showed that lightning-prevention research would require a long and carefully planned effort. These early activities led to the formal establishment of Project Skyfire in 1953, aimed at lightning suppression, as part of the overall research program of the Forest Service. Throughout the history of the project, research benefited from the cooperation and support of many agencies -and scientific groups, including the National Science Foundation, the Weather Bureau, Munitalp Foundation, the Advisory Committee on Weather Control, the National Park Service, General Electric Research Laboratories, Meteorology, Inc., and several universities. The project was phased out by the Forest Service in the 1970's, since results of years of tests were inconclusive, although there had been some reports of success. Skyfire was the longest continuing Federal weather modification research project, enduring for about 20 years.'
Fog dispersal research
Experiments were conducted on clearing supercooled fog from runways at Orly Airport in Paris since 1962, using sprays of liquid propane. Soon after these successful tests, the method became operational and has already succeeded in various U.S. Air Force installations. The dissipation of cold fog is now operational also at many locations, including some in North America and in the Soviet Union. Warn fogs, however, are more common over the inhabited globe, and efforts to dissipate them had not advanced very far, even by 1970.2 Hurricane modification
In an earlier discussion of the work of Langmuir and his associates under Project Cirrus, ani attempt at hurricane modification was mentioited.3 The historical unfolding of hurricane research in the United States thereafter will not be reported here since it is discussed in detail in chapter 5, under Project Stormfury, now a major weather modification research program of the National Oceanic and Atmospheric Administration of the U.S. Department of Commerce. Hail suppression
The principal lead in research to suppress hail during the 1950's and 1960's was not in the United States, but mainly elsewhere particularly in Switzerland,France, Ital V, the I.S.S.R., Argentina, Bulgaria, Yugoslavia, Kenya, and Canada. Hail suppression is based on the
,111 Barrows, 1. J., "Preventing Fire from the Sky." In U.S. Department of Agriculture, "Tie Yearbook of Agriculture, 1968: Science for Better Living." Washington, D.C., U.S. Government Printing Office. 1968, p. 219.
For a more detailed discussion of Project Skyf0re, see p. t09, under the weather moditicatio l prograin of the D)epa rt mentf of AgriciilIt ure in ch. 5.
2 Byers, "History of Weather Modification," 1974, p. 33.
See p. 3',(.
SSee p). 296.






47

hypothesis that, if a cloud is supplied with a superabundance of ice nuclei, the available water will be used to form a great number of snow crystals, thus depriving the hailstones of sufficient water to grow to damaging size. Most of the early foreign attempts to suppress hail using explosive rockets or ground-based silver iodide generators proved disappointing.5
In the Soviet Union, the Caucasus hail suppression experiments of the mid-1960's were of great interest to cloud physicists. Using radar to locate the zone of greatest water content in convective clouds and rockets with explosive warheads to deliver lead iodide with precision into this zone, the Russians claimed success in suppressing hailstorms, based on statistical reduction in crop damages. Operational hail suppression activity is now conducted on a large scale in the Soviet Union."' 7 Most hail suppression efforts in the United States in the 1960's were commercial operations which did not produce data of any significant value for further analysis. Foreign weather modification researcht
While the Russians and some other countries have concentrated on hail suppression research, Australia, like the United States, has been principally concerned with augmenting precipitation. Very shortly after Schaefer first seeded a natural cloud with dry ice, Krauss and squires of the Australian Weather Bureau seeded stratonimbus clouds in February 1947 near Sidney. The Commonwealth Scientific and Industrial Research Organization (CSIRO) subsequently organized, under Dr. E. G. Bowen, what might then have been the world's outstanding group of cloud physics and weather modification scientists. Byers feels that *Probably * no other group) contributed more to practical cloud physics during the period approximately from 1950 to 1965.*" 8
The Snowy Mountain project in Australia, whose object was to produce a significant precipitation increase over the mountains by silver iodide seeding, has attracted most attention. For a 5-year period from 1955 through 1959, this experiment was conducted during the colder part of the Southern Hemisphere year, using silver iodide dispensed from aircraft. Although initial experimental reports indicated successful increases in precipitation over the target, the final 1963 report after complete analysis stated that results were encouraging but inconclusive.9
Interesting experiments were carried out in Israel during the 1960's, using airborne silver iodide seeding of mostly cumulus clouds. Statistical analysis of data from the first. 51/2 years of tests revealed an increase of 18 percent in rainfall.'0
A project called Grossversuch III was conducted on the southern slopes of the Alps in Switzerland. Although initiated as a randomized hail suppression experiment, using ground-based silver iodide generators, the analysis indicated that hail frequency was greater on
5 Byers. "H1istry of Weather Modification," pp. 31-32.
6 Ibid., p. 32.
7The hail suppression efforts of the U.S.S.R. are discussed in more detail under the status of hail suppression technology in ch. 3, p. 88, and under foreign programs in ch. 9, 412.
8 Byers, "History of Weather Modification," 1974, p. 23.
9 Ibid., pp. 23-24.
10 Ibid., p. 31.






48

seeded than on nonseeded days, but that the average rainfall on seeded days was 21 percent greater than on nonseeded days."
COMMERCIAL OPERATIONS
In the weeks and months following Schaefer's first cloud seeding experiment public interest grew, and Langmuir and Schaefer spoke before and consulted with groups of water users, farmers and ranchers, city officials, Federal program directors, and scientific societies. As a result there was a burgeoning of new cloud-seeding efforts initiated by commercial operators, industrial organizations, water districts, and groups of farmers. Some used ground generators for dispensing silver iodide obviating the need for airplanes and their attendant high costs, so that many such operations became quite profitable. Many rainmakers were incompetent and some were unscrupulous, but their activities flourished for a whiile, as the experiments of Shaefer and Langmuir were poorly imitated. Some of the more reliable companies are still in business today, and their operations have provided data valuable to the development of weather modification technology.'2
Byers relates a few instances, of early commercial operations of particular interest.'13 In 1949-50 the city of New York hired Dr. Wallace E. Howell, a former associate of Langmuir, to augment its water supply by cloud seeding. New York's citizenry became interested and involved in discussions Over Howell's activities as the news media made them known. This project was also the first case where legal action was taken against cloud seeding by persons -whose businesses could be adversely affected by the increased rain. Although rains did come and the city reservoirs were filled, Howell could not prove that he was responsible for ending the drought.'14 Howell subsequently seeded in Quebec in August 1953 in an attempt to put out a forest fire and in Cuba to increase rainfall for a sugar plantation owner.'5
The Santa Barbara project in California., 'also a commercial. operation designed to increase water supply, received a great deal of attention. In this period water was increased through augmenting rain and snow in the mountains north and northeast of the city. The project was evaluated by the California State Water Resources Board and was unique among commercial contract operations, inasmuch as the clients permitted randomization (that is, random selection of only some storms for seeding) in order to allow adequate evaluation."6
In the West the earliest~ commercial operations were developed under Dr. Irving P. Krick, formerly head of the Department of Meteorology at~ the California institute of Technology. Asked to monitor aerial dry ice seeding over Mt. San Jacinto in 1947, Krick became interested in weather modification, left Caltech, and formed his Own company. Seeding projects were carried out during 1948 and 1949 for ranchers in San Diego County, Calif., in Mexico, and in Arizona. In 1950 be moved to Denver and foi'med a new company, which began seeding activity over the Great Plains, elsewhere in the West, and in
U1 Ibid.
12 Ibid., pp. 17, 21, 22.
"1 Ibid., pp. 22-23.
14L Ibid.. p. 22.
Is Imlacy. "The Weather changers," 1968, pp. 96-97.
16 Ibid., pp, 22-23.






49

other countries. A number of former students of Krick joined him or formed other cloud seeding companies, mostly in the West during the 19501S.17 By 1953 Krick had operated 150 projects in 18 States and 6
foreign countries and amassed over 200,000 hours of seeding time. For three winters-1949, 1950, and 1951-his company claimed that they had increased the snowpack in the Rockies around Denver from 175 to 288 percent over the average of the previous 10 years. After 6 months of seeding in Texas in 1953, the water in a drainage basin near Dallas had increased to 363 percent of the January 1 level, while in nearby nonseeded basins water ranged from a 22-percent deficit to an 'increase of 19 percent.18 V.
At the start of extensive seeding in the early 1950's there was a sharp increase in commercial operations, accompanied by great publicity as drought began in the Great Plains. During the middle and latter 1950's, however, seeding diminished as did the drought. The some 30 annual seeding projects in the United States during the mid and latter 1950's and the 1960's (excluding fog clearing projects) were conducted for the most part by about five firms, on whose staffs there were skilled meteorologists, cloud physicists, and engineers for installing and maintaining ground and air systems. Most of these projects were in the categories of enhancing rain or snowfall, with a distribution in a typical year as follows: About a dozen in the west coast States, half a dozen in the Rocky Mountains-Great Basin area, half a dozen in the Great Plains, and the remainder in the rest of the United States. Of the projects in the West, six t6 nine have been watershed projects sponsored by utility companies. Most of these projects endured for long periods of years and many are still underway.'9
Fleagle notes that by the early 1950's, 10 percent of the land area of the United States was under commercial seeding operations and $3 million to $5 million was being expended annually by ranchers, towns, orchardists, public utilities, and resort operators. The extent of such commercial operations receded sharply, and by the late 1950's business was only about one-tenth or less than it had been a decade earlier. As noted above, public utilities were among those who continued to sponsor projects throughout this period.2
Figure 1 shows the purposes of weather modification operations for various sections of the United States for the period July 1950 through June 1956. For each geographical section the column graphs represent the percentage of the total U.S. seeding for each of five purposes' that
was performed in that section. The bar graph in the inset shows the percentage of total U.S. cloud-seeding effort that is undertaken for each of these five purposes. Figure 2 shows the total area coverage and the percent of U.S. territory covered by cloud seeding for each year from July 1950 through June 1956. Both figures are from the final report of the President's Advisory Committee on Weather Control.'
17 Elliott, Robert D., "Experience of the Private Sector," 1974, p. 47. I's Halacy, "The Weather Changers," 1968, p. 96. 19 Elliott, "Experience of the Private Sector," 1974, p. 46-48. 20 Fleagle, "Background and Present Status of Weather Modification," 1968, P. 11. 21 AdioyCommittee on Weather Control, Final Report, 1958, vol. HI. Figures facing p. 242 and 243.







50












41 /
.1"- .- -o




-~ Q" ,.''















E :











~~U (Z1 "





gegr'hia setoso h ntdSaeuy15 hog ue1. (Fo Fial Rer of th dvsr Com.itte on Wahe Conto 1958 .) Z O


FIUR L-up so eahrmdfctonoeain odutdi aiu
gegahclscin fteUie tts uy15 hog ue15. Fo
Fina Reoto h disor Comte onWahrCnto,15.







51


CLOUD SEEPING IN TtE UNiTED STATES

300
t5%


250



200 "
-10%


W 150- Z
w
U 0J


0
_J 100-5




50


10.2% 14.1% 10.1% 8.6%] 10.5% 7.0%
0 -0.~ -- ...... ~
1950- 1951- 1952- 1953- 1954- 19551951 1952 1953 1954 1955 1956


FIGURE 2.-Total area coverage and percent of area coverage for the 48 coterminous States of the United States by weather modification operations for each year, July 1950 through June 1956. (From Final Report of the Advisory
Committee on Weather Control, 1958.)

Table 1 is a si mmary of weather modification operations for fiscal years 1966, 1967, and 1968, compiled by the National Science Foundation from field operators' reports which the Foundation required to be filed. Figure 3 shows the locations in the continental United States for both operational and research weather modification projects during fiscal year 1968. In September 1968, as provided by Public Law 90-407, the National Science Foundation was no longer authorized to require the submission of reports on operational weather modification projeets.2 Weather modification activities are now reported to the Department of Commerce, under provisions of Public Law 92-205, and summary reports of these activities are published from time to time.23

22 See discussions of this law and of the activities of the National Science Foundation as lead weather modification agency through September 1968. pp 196 and 215 in ch. 5.
See discussions of Public Law 92-205 and of the weather modification activities reporting program in ch. 5, 197 and 232. The activities summarized in the latest available Department of Commerce report are discussed in ch. 7 and listed in app. G.







52

TABLE 1.-SUMMARY OF WEATHER MODIFICATION ACTIVITIES FROM FIELD OPERATORS, REPORTS, FISCAL YEARS
1966, 1967, AND 1968 1 (FROM NSF TENTH ANNUAL REPORT OF WEATHER MODIFICATION, 1968)

Area treated Number of Number of Number of
(square miles) projects States 2 operators 2
Purpose 1966 1967 1968 1966 1967 1968 1966 1967 1968 1966 1967 1968

Rain augmentation and snowpack increase ------------ 61, 429 62, 021 53, 369 35 41 37 21 20 21 22 25 23
Hail suppression ----------- 20, 566 20, 556 13, 510 3 4 4 3 3 5 3 4 4
Fog dissipation,------------- 100 118 145 22 15 15 15 13 9 17 15 10
Cloud modification---------- 19, 345 28, 300 18, 600 9 18 8 8 12 7 8 14 6
Lightning suppression ---------314 314 314 1 1 1 1 1 1 1 1 1
Totals------------- 101,744 111,383 85,938 70 79 65 30 23 25 46 44 37

1Data for fiscal year 1968 include reports received to Sept. 1, 1968.
2 Totals are not the sum of the items since many States and operators are involved in more than one type of activity.

An early commercial hail suppression project was begun in Colorado in 1958. Eventually it involved 5 seeding aircraft and about 125 ground-based genierators,'making it the largest single cloud-seeding project up to that time. Results of the project were examined at Colorado State University and presented at the International Hail Conference in Verona, Italy, in 1960. This project stimulated the interest of scientists and provided historical roots for what later was established as the National Hail Research Experiment in the same area over a decade later by the National Science Foundlation.,5
During the 1960's, clearing of cold airport fog through cloud seeding became an operational procedure. Since the techniques used can only be applied to cold fog, they were used at the more northerly or high-altitude airports of the United States, where about 15 such projects were conducted, and are still underway, each winter.20

24 Elliott, "Experience of the Private Sector," 1974, p. 48.
25 The National Hail Research Experimient is discussed in detail under the weather modification protroin of thie National SMcience Foundation in ch. 5 -,se p. 274ff.
26 Elliott, "Experience of the Private Sector," 1974. pp. 48-49.





53





CANADA


cj, I





Ov,,,o? ,onai Seedn
Rtearch Seedng
toca~rh o++ a+ pp~o. ,'o'# i




FIGURE 3.-Weather modification projects in the United States during fiscal year
1968. (From NSF Tenth Annual Report on weather modification, 1968.)

HIISTORY OF FEDERAL ACTIVITIES, COMMITTEES, POLICY STUDIES, AND REPORTS
In the various discussions under activities of the Congress and the executive branch- of the Federal Government in chapter 5, there are historical accounts of legislative actions pertinent to weather modification, of the establishment and functioning of special committees in accordance with public laws or as directed by the executive agencies, and of the policy and planning studies and reports produced by the special committees or by the agencies. Inclusion of a separate historical account of these Federal activities at this point would be largely repetitive, and the reader is referred to the various sections of chapter 5. in which historical developments of various Federal activities are unfolded as part of the discussions of those activities.














CHAPTER 3

TECHNOLOGY OF PLANNED WEATHER MODIFICATION
(By Robert E. Morrison, Specialist in Earth Sciences, Science Policy Research
Division, Congressional Research Service)
INTRODUMON
Although the theoretical basis for weather modification was laid to a large extent during the 1930's, the laboratory and field experiments which ushered in the "modern era" occurred in 1946 and in the years immediately thereafter. By 1950, commercial cloud seeding had become widespread, covering an estimated total U.S. land area of a bout 10 percent.' By the mid-1950's, however, it was apparent that the fundamental atmospheric processes which come into play in weather modification are very complex and were far from being understood. A period of retrenchment and reevaluation began, the number of commercial operators had decreased dramatically, and weather modification had fallen into some disrepute among many meteorologists and much of the public. A period of carefully designed experiments was initiated about two decades ago, supported by increased cloud physics research and increasingly more sophisticated mathematical models and statistical evaluation schemes.
Meanwhile, a small group of commercial operators, generally more reliable and mox,e responsible than the typical cloud seeder of the 1950 era, has continued to provide operational weather modification services to both public and private sponsors. These operators have attempted to integrate useful research results into their techniques and have provided a bank of operational data useful to the research community. The operational and research projects have continued over the past two decades, often in a spirit of cooperation, not always characteristic of the attitudes of scientists and private operators in earlier years. Often the commercial cloud seeders have contracted for important roles in major field experiments. where their unique experiences have been valuable assets. I
Through the operational experiences and research activities of the past 30 years, a kind of weather modification technology has been emerging. Actually, though some practices are based on comIon theory and constitute the basic techniques for meeting a number of seeding objectives, there are really a series of weather modification technologies, each tailored to altering a particular atmospheric phenomenon and each having reached a different state of development and operational. usefulness. At one end of this spectrum is cold fog clearing, considered to be operational now, while the abatement of severe storms, at
Fleagle. Robert G., "Background and Present Status of Weather Modifiention." In "Weather Modification: Science and Public Policy," Seattle, University of Washington Press, 1968, p. 11.
(55)





56

the other extreme, remains in the initial research phase. Progress to date in development of these technologies has not been nearly so much a function of research effort expended as it has depended on the fundamental atmospheric processes and the ease by which they can be altered. There is obvious need for further research and development to refine techniques in those areas where there has been some success and to advance technology were progress has been slow or at a virtual standstill.
ASSESSMENT OF THE STATUS OF WEATHER MODIFICATION TECHNOLOGY
Recently, the following summary of the current status of weather modification technology was prepared by the Weather Modification Advisory Board:
1. The only routine operational projects are for clearing cold fog. Research on warm fog has yielded some useful knowledge and good models, but the resulting 4chnologies are so costly that they are usable mainly for military purposes and very busy airports.
2. Several long-riunning efforts to increase winter snowpack by seeding clouds in the mountains suggest that precipitation can be increased by some 15 percent over what would have happened "naturally."
3. A decade and a half of experience with seeding winter clouds on the U.S. west coast and in Israel, and summer clouds in Florida, also suggest a 10- to 15-percent increase over "natural" rainfall. Hypotheses and techniques from the work in one area are not directly transferable to other areas, but will be helpful in designing comparable experiments with broadly similar cloud systems.
4. Numerous efforts to increase rain by seeding summer clouds in the central and western parts of the United States have left many questions unanswered. A major experiment to try to answer them-for the High Plains area-is now in its early stages.
5. It is scientifically possible to open holes in wintertime cloud layers by seeding them. Increasing sunshine and decreasing energy consumption may be especially relevant to the northeastern quadrant of the United States.
6. Some $10 million is spent by private and local public sponsors for cloud-seeding efforts, but these projects are not designed as scientific experiments and it is difficult to say for sure that operational cloud seeding causes the claimed results.
7. Knowledge about hurricanes is in-,PVOvinc with trood models of their behavior. But the experience in modifying that behavior is primitive so far. It is inherently difficult to find enough test cases, especially since experimentation on typhoons in the Western Pacific has been blocked for the time being by international political objections.
8. Although the Soviets and some U.S. private operators claim some success in suppressing hail by seeding clo,,ds, our understanding of the plhvsical processes that create bail is still weak. The one major U.S. field experiment increased our understanding of severe storms" but otherwise proved mostly the dimensions of what we do not vet know.
9. There have been many efforts to suppress lightning by seeding thmderstorms. Our knowledge of the processes involved is fair, but







57

the technology is still far from demonstrated, and the U.S. Forest Service has recently abandoned further lightning experiments.2
Lewis 0. Grant recently summarized the state of general disagreement on the status of weather modification technology and its readiness for application.
There is a wide diversity of opinion on weather modification. Some believe that weather modification is now ready for widespread application. In strong contrast, others hold that application of the technology may never be possible or practical on any substantial scale.'
He concludes thatImportant and steady advances have been made in developing technology for applied weather modification, but complexity of the problems and lack of adequate research resources and commitment retard progress.4
In 1975, David Atlas, then president of the American Meteorological Society, expressed the following pessimistic opinion on the status of weather modification technology:
Almost no one doubts the economic and social importance of rainfall augmentation, hail suppression, fog dissipation, and severe storm abatement. But great controversy continues about just what beneficial modification effects have been demonstrated or are possible. Claims and counterclaims abound. After three decades of intense research and operational weather modification activities, only a handful of experiments have demonstrated beneficial effects to the general satisfaction of the scientific community.
To describe weather modification as a "technology" is to encourage misunderstanding of the state of the weather modification art. The word "technology" .implies that the major substantive scientific foundations of the field have been established and, therefore, that all that is required is to develop and apply techniques. But one of the conclusions of the special AMS study on cloud physics was that "the major bottleneck impeding developments of useful deliberate weather modification techniques is the lack of an adequate scientific base." 5
At a 1975 workshop on the present and future role of weather modification in agriculture, a panel of 10 meteorologists assessed the capabilities for mnodifyi ng various weather and weather-related phenomena, both for the present and for the period 10 to '20 years in the future. Conclusions from this assessment are summarized in table 1. The table shows estimated capabilities for both enhancement and dissipation, and includes percentages of change and areas affected, where appropriate, 6
A recent study by Barbara Farhar and Jack Clark surveyed the opinions of 551 scientists, all involved in some aspect of weather modification, on the current status of various weather modification tecimol2 Weather Modification Advisory Board. "A U.S. Policy to Enhance the Atmosnheric Environment." Oct. 21, 1977. In testimony by Harlan Cleveland. "Weather Modification." heqrIng before the Subcommittee on the Environment arid the Atmosphere. Comm' tep on Science and Technology. U.S. House of Representatives. 95th Cong.. 1st sess.., Oct. 26, 197. Washin~rton. D C.. U.S. Government Printwnr Office. 1077, pp. 28.-30.
3 Grant. Lewis 0., "Scientific and Other Uncertainties of Weather 'Modification." in Wil11am A. Thomas (editor). "Legal and Scientific Uncertainties of Weather Modification." Proceedings of a symposium convened at Duke University. Mar. 11-12, 1976, by the National Conference of Lawyers and Scientists. Durham. N.C., Duke University Press, 1977. p. 7.,
4 Ibid.. p. 17.
5 Atlas. David. "Selling Atmospheric Science. The President's Page." Bulletin of the American Meteorological Society. vol. 56. No. 7. JTuly 1975. p. 688.
6 Grant. Lewis 0. and John D. Reid (compilers). "Workshop for an Assessment of the Present and Potential Role of Weather Modification In Agricultural Producetion." Colorado State University, Fort Collins, Colo., July 15-1S. 1975, August 1975. PB-245-633, pp. 34-44.







1 58


ogies.7 Table 2 is a summary of the assessments of the level of development for each of 12 such technologies included in the questionaire to
which the scientists responded, and table 3 shows the estimates of effectiveness for 7 technologies where such estimates are pertinent. Results of this study were stratified in accordance with respondents' affiliation, specific education, level of education, age, and responsibility
or interest in weather modification, and tabulated summaries of
opinions on weather modification in accordance with these variables appear in the report by Farhar and Clark.8

TABLE I.-ASSESSMENT OF THE CAPABILITIES FOR MODIFYING VARIOUS WEATHER AND WEATHER-RELATED
NATURAL PHENOMENA, BASED ON THE OPINIONS OF 10 METEOROLOGISTS

[From Grant and Reid, 19751

Enhancement Dissipation
Amount Amount
change Area change Area
(per- (square (per- (square
Modified variable Now 10 to 2.) yr cent) miles) Now 10 to 20 yr cent) miles)

I. Clouds:
1. Cold stratus ------No (8) Yes (7) --------1-1000 Yes (10) Yes (10) --------1-1000
2. Warm stratus ------ No (10) No (5) ------------------- No (8) Yes (9) --------------------3. Fog, cold Yes (10) Yes (10) --------1-10 Yes (10) Yes (10) -------- 1-1000
4. Fog, warm Yes (10) Yes (10) --------1-100 Yes (10) Yes (10) -------.1-1
5. Fog, artifical (for
temperature control) ----------- Yes (10) Yes (10) --------1-10 N'A N/A ............
6. Contrails ---------- Yes (10) Yes (10) --------100-1000 No (10) No (10) ............
7. Cirrus---------- Yes (5) Yes (10) --------100-1000 No (10) No (8) .......
8. Carbon black ------- No (10) No (6) ------------------- NiA N/A --------------------9. Aerosol ----------- Yes (7) Yes (10) ----------------- N/A N/A --------------------II. Convective precipitation:
1. Isolated small ----- Yes (7) Yes (10) 100 10-100 Yes (5) Yes (8) 100 10-100 2. Isolated large ------ No (6) Yes (7) 15 100-1000 Yes (5) Yes (8) 15 10-1000
3. Squall lines -------- Yes (5) Yes (S) 20 100-10,000 No (8) Yes (5) 20 100-10,000
4. Nocturnal ---------- Yes (5) Yes (6) 100 100-1000 No (8) Yes (5) 100 100-1000
5. Imbedded cyclonic Yes (9) Yes (10) 30 300-6000 Yes (8) Yes (10) <5 300-6000
6. Imbedded Orographic --------Yes (9) Yes (10) 20 300-6000 Yes (8) Yes (10) 20 300-6000 ill. Stratoform precipitation:
1. Orographic -------Yes (10) Yes (10) 10 100-3000 Yes (10) Yes (10) 10 100-3000
2. Cyclonic ---------- No (10) No (6) ------------------- No (10) No (6) --------------------3. Cloud water collection -----------Yes (10) Yes (10) ------------------- N/A NIA --------------------IV. Hazards:
1. Hail ----- Yes (5) Yes (7) (1) 100-60,000 Yes Yes 30 100-60,000
2. Lightning --------- Yes (7) Yes (9) (1) 40,000 Yes (7) Yes (9) 40 40,000
3. Erosion-wind
gradient -------- No (10) No (10) ----------------No (10) No (10) --------------------4. Erosion-water
drop size --------- Yes (5) Yes (7) (1) 10,000 Yes (5) Yes (7) -------- 10,000
5. Wind-hurricane-- No (5) Yes (6) ------------------- No (6) Yes (6) --------------------6. Tornado ---------- No (10) Yes (5) ------------------ No (10) Yes (5) --------------------7. Blowdown --------- No (5) Yes (5) ------------------ No (9) Yes (5) --------------------8. Floods-symoptic ___ No (10) No (10) ------------------ No (10) No (3) --------------------9. Floods-mesoscale.. No (9) Yes (6) ------------------- No (9) Yes (6) --------------------10. Drought ----------- No (10) No (10) ------------------- Yes (5) Yes (6) --------------------V. Other:
1. Albedo ----------- Yes (5) Yes (10) ----------------- Yes(5) Yes (10) ------------------2. Surface roughness.. No (6) Yes (6) ------------------- No (6) Yes (6) --------------------3. Topography changes. No (6) Yes (5) ------------------- No (6) Yes (5) -------- 10-100

Uncertain.


7 Farhar. Barinra C. and Jack A. Clark. "Can We Modify the Weather? a Survey of
Scientists" Final report, vol. 3 (draft). Institute of Behavioral Science. University of Colorado, Boulder. Colo.. January 1978. (Based on research suT)ported by the National Science Fouindatiou inder grants No. ENV741S613 A3. G1-35452, GI-440S7. and ERT74-1;613, ;i part of "A Comnp:i rative Analysis of Public Support of and Resistance to Weather Modij:l T igon Projects. 59 pp.
I btd.






59

TABLE 2.-ASSESSMENT OF THE LEVEL OF DEVELOPMENT OF TWELVE WEATHER MODIFICATION TECHNOLOGIES BASED UPON A SURVEY OF 551 WEATHER MODIFICATION SCIENTISTS
[From Farhar and Clark, 19781

Operations I Research 2 Neither Don't know Other
Per- Per- Per- Per- Per- Tota I
Weather modification technology cent No. cent No. cent No. cent No. cent No. No.

Cold fog dispersal ------------------------- 78 406 8 42 0 1 14 72 0 0 521
Precipitation enhancement, winter orographic, continental --------------------- 68 357 20 104 1 6 11 57 0 1 525
Precipitation enhancement, winter orographic, maritime ------------------------ 64 337 22 113 1 5 13 70 0 1 526
Hail suppression -------------------------- 46 244 49 256 1 4 4 23 0 1 528
Precipitation enhancement, summer convecti e, continental ------------------------- 43 227 49 258 2 10 6 31 0 1 527
Precipitation enhancement, summer convective, maritime -------------------------- 42 220 46 244 1 5 11 56 0 2 529
Warm fog dispersal ------------------------ 33 170 48 253 1 3 18 92 0 0 518
Precipitation enhancement with hail suppression ------------------------------- 30 156 56 288 2 12 12 62 0 1 519
Precipitation enhancement, general storms-_ 25 128 58 300 5 28 12 64 0 2 522
Lightning suppression --------------------- 8 42 65 332 4 22 23 119 0 0 515
Hurricane suppression --------------------- 4 19 75 388 4 23 17 88 0 2 520
Severe storm mitigation -------------------- 3 13 68 353 9 47 20 101 0 1 515

1 This category is a 'combination of two responses: "The technology is ready for operational application" and "The technology can be effectively applied; research should continue."
2 This; category is a combination of two responses: "The technology is ready for field research only" and "The technology should remain at the level of laboratory research."










60



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61

CLASSIFICATION OF WEATHER MODIFICATION TECHNOLOGIES
In a previous review of weather modification for the Congress, three possible classifications of activities were identified-these classifications were in accordance with (1) the nature of the atmospheric processes to be modified, (2) the agent or mechanism used to trigger or bring about the modification, or (3) the scale or dimensions of the region in which the modification is attempted.9 The third classification was chosen in that study, where the three scales considered were the microscale (horizontal distances, generally less than 15 kilometers), the mesoscale (horizontal distances generally between 15 and 200 kilometers), and the macroscale (horizontal distances generally greater than 200 kilometers).10 Examples of modification of processes on each of these three scales are listed in table 4, data in which are from Hartman.1 Activities listed in the table are illustrative only, and there is no intent to indicate that these technologies have been developed, or even attempted in the case of the listed macroscale processes.
TABLE 4.-WEATHER AND CLIMATE MODIFICATION ACTIVITIES CLASSIFIED ACCORDING TO THE SCALE OR
DIMENSIONS OF THE REGION IN WHICH THE MODIFICATION IS ATTEMPTED [Information from Hartman, 19661
Scale Horizontal dimensions Examples of modification processes
Microscale --------------- Less than 15 km -----------Modification of human microclimates.
Modification of plant microclimates.
Evaporation suppression.
Fog dissipation.
Cloud dissipation.
Hail prevention.
Precipitation through individual cloud modification.
Mesoscale -------------- 15 to 200 km --------------- Precipitation from cloud systems.
Hurricane modification.
Modification of tornado systems.
Macroscale ------------- Greater than 200 km --------Changes to global atmospheric circulation patterns.
Melting the Arctic icecap.
Diverting ocean currents.

In this chapter the characteristics and status of weather modification activities will be classified and discussed according to the nature of the processes to be modified. This seems appropriate since such a breakdown is more consonant with the manner the subject has been popularly discussed and debated, and it is consistent with the directions in which various operational and research activities have moved. Classification by the second criterion above, that is, by triggering agent or mechlanism, focuses on technical details of weather modification, not of chief interest to the public or the policymaker, although these details will be noted from time to time in connection with discussion of the various weather modification activities.
In the following major section, then, discussion of the principles and the status of planned weather modification will be divided accord9 Hartman. Lawton M.. "Characteristics and Scope of Weather Modification." In U.S. Congress, Senate Committee on Commerce, "Weather Modification and Control," Washington. D.C., U.S. Government Printing Office. 1966. (89th Cong.. 2d sess., Senate Rept. No.
1139. prepared by the Legislative Reference Service, Library of Congress), p. 20. 10 Ibid.
Ibid.. pp. 21-31.



34-857 0 79 7






1 62

ing to the major broad categories of phenomena to be modified; these will include:
Precipitation augmentation.
Hail suppression.
Fog dissipation.
Lightning suppression.
Severe storm mitigation.
In subsequent major sections of this chapter there are reviews of some of the specific technical problem areas common to most weather modification act ivities and a summary of recommended research activities.
In addition to the intentional changes to atmospheric phenomena discussed in this chapter, it is clear that weather and climate have also been modified inadvertently as the result of man's activities and that modification can also be brought about through a number of naturally occurring processes. These unintentional aspects of weather and climate modification will be addressed in the following chapter of this report.12

PRINCIPLES AND STATUS OF WEATHER MODIFICATION TECHNOLOGIES

Before discussing the status and technologies for modification of precipitation, hail, fog, lightning, and hurricanes, it may be useful to consider briefly the basic concepts of cloud modification. The two major principles involved are (1) colloidal instability and (2) dynamic effects. Stanley Changnon describes how each of these principles can be effective in bringing about desired changes to the atmosphere: 13
Altering colloidal stability.-The physical basis for most weather modification operations has been the belief that seeding with certain elements would produce colloidal instability in clouds, either prematurely, to a greater degree, or with greater efficiency than in nature. Most cloud seeding presumes that at least a portion of the treated cloud is supercooled, that nature is not producing any or enough ice at that temperature of the cloud, and that treatment with chemical agents of refrigerants will change a proportion of the cloud to ice. The resultant mixture of water and ice is unstable and there is a rapid deposition of water vapor upon the ice and a simultaneous evaporation of water from the supercooled droplets in the cold part of the cloud. The ice crystals so formed become sufficiently large to fall relative to remaining droplets, and growth by collection enhances the probability that particles of ice or water will grow to be large enough to fall from the cloud and become precipitation.
This process of precipitation enhancement using ice nucleants has been demonstrated for the stratiform type cloud, and generally for those which are orographically-produced and supercooled. Cumulus clouds in a few regions of the United States have also been examined for the potential of colloidal instability in their supercooled portions. This has been founded on beliefs that precipitation
(1) can be initiated earlier than by natural causes, or (2) can be produced from a cloud which was too small to produce precipitation naturally.
Seeding in the warm portion of the cloud, or in "warm clouds" (below the freezing level), has also been attempted so as to alter their colloidal instability. Warm-cloud seeding has primarily attempted to provide the large droplets necessary to initiate the coalescence mechanism, and is of value in clouds where insuffi(lent Large drops exist. In general alteration of the coalescence process primarily precipitates out the liquid water naturally present in a cloud, whereas the icecrystal seeding process also causes a release of latent energy that conceivably results in an intensification of the storm, greater cloud growth, and additional pr ipitation.
Altering cloud dynamics.-The effects to alter the colloidal instability of clouds. or their microphysical processes, have been based on the concept of rain
12 Seep 1), 141.
1 (h1inunon. Stanlev A., Jr. "Prezent and Future of Weather Modlfientfnn: Regional Isues." The Journal of Weather Modification, vol. 7. No. 1. April 1975, pp. 154-156.







63

increase through increasing the precipitation efficiency of the cloud. Simpson and Dennis (1972) showed that alterations of cloud size and duration by "dynamic modification" could produce much more total rainfall than just altering the precipitation efficiency of the single cloud. In relation to cumulus clouds, "dynamic seeding" simply represents alteration one step beyond that sought in the principle of changing the colloidal stability. In most dynamic seeding effort, the same agents are introduced into the storm but often with a greater concentration, and in the conversion of water to ice, enormous amounts of latent heat are hopefully released producing a more vigorous cloud which will attain a greater height with accompanying stronger updrafts, a longer life, and more precipitation. Seeding to produce dynamic effects in cloud growth, whether stratiform or cumuliform types, is relatively recent at least in its serious investigation, but it may become the most important technique. If through controlled cloud seeding additional uplift can be produced, the productivity in terms of rainfall will be higher whether the actual precipitation mechanism involved is natural or artificial.
It has been proposed that the selective seeding of cumulus clouds also can either (a) bring upon a merger of two or more adjacent clouds and a much greater rainfall production through a longer-lived, larger cloud * or (b) produce eventually an organized line of clouds (through selective seeding of randamized cumulus). The latter could allegedly be accomplished by minimizing and organizing the energy into a few vigorous systems rather than a larger number of isolated clouds.' 0
Essentially, then, dynamic seeding is a label addressed to processes involved in altering cloud microphysics in a selective and preferential way to bring upon more rainfall through an alteration of the dynamical properties of the cloud system leading to the development of stronger clouds and mesoscale systems. Actually, dynamic effects might be produced in other ways such as alteration s of the surface characteristics to release heat, by the insertion of chemical materials into dry layers of the atmosphere to form clouds, or by re'distribution of precipitation through microphysical interactions in cloud processes.
The various seeding materials that have been used for cloud modification are intended, at least initially, to change the microphysical cloud structure. Minute amounts of these materials are used with the hope that selected concentrations delivered to specific portions of the cloud will trigger the desired modifications, through a series of rapid multiplicative reactions. Seeding materials most often used are classified as (1) ice nuclei, intended to enhance nucleation in the supercooled part of the cloud, or (2) hygroscopic materials, designed to alter the coalescence process. 14
Glaciation of the supercooled portions of clouds has been induced by seeding with various materials. Dry ice injected into the subfreezing part of a cloud or of a supercooled fog produces enormous numbers of ice crystals. Artificial ice nuclei, with a crystal structure closely resembling that of ice, usually silver iodide smoke particles, can also produce glaciation in clouds and supercooled fogs. The organic fertilizer, urea, can also induce artificial glaciation, even at temperatures slightly warmer than freezing. Urea might also enhance coalescence in warm clouds and warm fogs. Water spray and fine particles of sodium chloride have also been used in hygroscopic seeding intended to alter the coalescence process. There have been attempts to produce coalescence in clouds or fog using artificial electrification, either with chemicals that increase droplet combination by electrical forces, or with surface arrays of charged wires whose discharges Droduce ions which, attached to dust particles, may be transported to the clouds. 11 Problems of cloud seeding technology and details of seeding delivery methods are discussed in a later section of this chapter as are 141bid., p. 156.
15 Ibid., pp. 156-157.






64

some proposed techniques for atmospheric modification that go beyond cloud seeding.'6
PRECIPITATION AUGMENTATION
The seeding of clouds to increase precipitation, either rainfall or snowfall, is the best known and the most actively pursued weather modification activity. Changes in clouds and precipitation in the viciniity of cloud seeding operations have shown unquestionably that it is possible to modify precipitation. There is evidence, however, that such modification attempts do not always increase precipitation, but that under some conditions precipitation may actually be decreased, or at best no net change may be effected over an area. Nevertheless, continued observations of clouds and precipitation, from both seeded and nonseeded regions and from both experiments and commercial operations, are beginning to provide valuable information which will be useful for distinguishing those conditions for which seeding increases, decreases, or has no apparent effect on precipitation. These uncertainties were summarized in one of the conclusions in a recent study on weather modification by the National Academy of Scienes: 17
The Panel now concludes on the basis of statistical analysis of well-designed field experiments that ice-nuclei seeding can sometimes lead to more precipitation, can sometimes lead to less precipitation, and at other times the nuclei have no effect, depending on the meteorological conditions. Recent evidence has suggested that it is possible to specify those microphysical and mesophysical properties of some cloud systems that determine their behavior following artificial nucleation.
Precipitation enhancement has been attempted mostly for two general types of cloud forms, both of which naturally provide precipitation under somewhat different conditions. Convective or cumulus clouds are those which are formed by rising, unstable air, brought about by heating from below or cooling in the upper layers. Under natural conditions cumulus clouds may develop into cumulo-nimbus or "thunderheads," capable of producing heavy precipitation. Cumulus clouds and convective systems produce a significant portion of the rain in the United States, especially during critical growing seasons. Attempts to augment this rainfall f rom cumulus clouds under a variety of conditions have been underway for some years with generally uncertain success. The other type of precipitationp)roducing clouds of interest to weather modifie'rs are the orographic clouds, those which are formed when horizontally moving moistureladen air is forced to rise over a mountain. As a result of the cooling as the air rises, clouds form and precipitation often falls on the xwin dwx-ard side of the mountain. Through seeding operat ions, there have been attempts to augm~ent. precipitation through acceleration of this process, particularly in winter, in order to increase mountain snowpack.
Figures 1 and 2 show regions of the coterminous United States which are conducive to precipitation management through seeding of spring and summer convective clouds and through seeding orographic cilouid system s, respectively. The principles of precipitation
10 See pp. 115 a nd 129.
17 National A\cad(emy of Sciences, National Research Council, Committee on Atmospheric Sciences, "xWeather and Climate Modification: Problems and Progress," Washington, D.C., 1973, p. 4.






65
enhancement for both cumulus and orographic clouds, and the present state of knowledge and technology for such modification, are discussed in the following sections.


?~~~ U "T I ULAR OCCASIONAL APPLICATIO
APPLICATION APPLICATION OR SPECIAL SITUATIONS



"...... .. . ..............
.... ..._. .

---- -- .. .....
............ :....
......." ..... .. .....
.... ...... o ......
riafo srgn m .o .e.
...........

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FIGRE.-Regions where precipitation management may be applied to enhance




























snowfall from winter orographic weather systems, thus augmenting spring and summer runoff from mountain snowpacks.





66

Cumulus clouds
If air containing moisture is cooled sufficiently and if condensation nuclei such as dust particles are present, precipitation may be produced. This process occurs when air is forced to rise by convection, so that the water vapor condenses into clouds. Cumulus clouds are the woolly vertical clouds with a flat base and somewhat rounded top, whose origin can always be traced to the convection process. They can most often be observed during the summer and in latitudes of high temperature. When updrafts become strong under the proper conditions, cumulus clouds often develop into cumulonimbnl)us clouds, the principal producer of precipitation. About three-fourths of the rain in the tropics and subtropics and a significant portion of that falling on the United States is provided from cumulus clouds and convective systems.
The science of cloud study, begun in the 1930's and greatly expanded following World War II, includes two principal aspects-cloud microphysics and cloud dynamics. Though once approached separately by different groups of scientists, these studies are now merging into a single discipline. In cloud physics or microphysics the cloud particles-such as condensation and freezing nuclei, water droplets, and ice crystals-are studied along with their origin, growth, and behavior. Cloud dynamics is concerned with forces and motions in clouds, the prediction of cloud structure, and the life cycle of updrafts and downdrafts.18
For cloud modification purposes, present theories of microphysical processes provide an ample basis for field seeding experiments; however, further work is still needed on laboratory experiments. improved instrumentation, and research on assumptions. On the other hand, the processes in cloud dynamics are not completely understood and require continued research.9
Most cumulus clouds evaporate before they have had opportunity to produce precipitation at the Earth's surface. In fact many clouds begin to dissipate at about the same time that rain emerges from their bases, leading to the impression that they are destroyed by the formation of precipitation within them. This phenomenon is not yet fully understood. Cumulus clouds have a life cycle; they are born, mature, and eventually age and die. Small cumuli of the trade regions live only about 5 to 10 minutes, while medium-sized ones exist for about 30 minutes. On the other hand, a giant cumulonimbus cloud in a hurricane or squall line may be active for one to several hours. In its lifetime it may exchange over 50 million tons of water. producing heavy rain, lightning, and possibly hail. At all times, however, a cumulus cloud struggles to exist ; there is a precarious balance between the forces aiding its growth and its destruction.
TIhe increasing capability to simulate cloud processes on the compuiter has been a major advance toward understanding cloud modification. The ways in which cloud microphysics influences convective
Ssini ps on. Joanne and Arnott S. Diennis. "Ciumulus Clouds and Their Modification." In Wilmot N. Hess (ed.), "Weather and Clinmate Moditication," New York, John Wiley & Sons,
1 '.74. p. 283.
1 M sch ndreas, I)emetrios .1 and Irving Leichter. "Present Capabilities to Modif3 mulIus ('luds."l, Geonmet. Inc. report No. EF 463. Final report for U.S. Navy Environmental Predietion Rese arch FIaeilit, Mar. 30. 1976, ) p. 209.
SSim1son and Dennis, "Cumulus Clouds and Their Modification," 1947, pp. 234-235.