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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 Kahan, "Weather Modification for Augmenting Orographic Precipitation,

1974, p. 298.


Lightning suppression experiments

From 1947 until the close of Project Cirrus, interspersed with his

other activities, Vincent Schaefer visited U.S. Forest Service instal-

lations in the northern Rockies in order to assist in attempts to sup-

press 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." This

stimulated curiosity among those involved, but also showed that light-

ning-prevention research w T ould require a long and carefully planned

effort. These early activities led to the formal establishment of Proj-

ect Skyfire in 1953, aimed at lightning suppression, as part of the

overall research program of the Forest Service. Throughout the his-

tory of the project, research benefited from the cooperation and sup-

port 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 sev-

eral 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 con-

tinuing Federal weather modification research project, enduring for

about 20 years. 1

Fog dispersal research

Experiments were conducted on clearing supercooled fog from run-

ways at Orly Airport in Paris since 1962, using sprays of liquid pro-

pane. 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. Warm 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, an attempt at hurricane modification was men-

tioned. 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 modifica-

tion research program of the National Oceanic and Atmospheric Ad-

ministration of the U.S. Department of Commerce. 4

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, Italy, tho U.S.S.R., Argentina, Bulgaria,

Yugoslavia, Kenya, and Canada. Hail suppression is based on the

86 Barrows J S. "Preventing Fire from the Sky." In U.S. Department of Agriculture,

"The Yearbook of Agriculture, 1968: Science for Better Living." Washington. D.C., U.S.

Government Printing Office, 1968, p. 219.

1 For a more detailed discussion of Project Skyfire, see p. 309, under the weather modi-

fication program of the Department of Agriculture in ch. r>.

2 Byers, "History of Weather Modification," 1974, p. 33.

3 See p. 39.

* See p. 296.


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 sup-

pression activity is now conducted on a large scale in the Soviet

Union. 6 - 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 research

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 out-

standing 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 pro-

duce 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 suc-

cessful increases in precipitation over the target, the final 1963 re-

port 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. Statis-

tical analysis of data from the first 5% years of tests revealed an in-

crease of 18 percent in rainfall. 10

A project called Gross versuch 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 gen-

erators, the analysis indicated that hail frequency was greater on

5 Byers, "Histry of Weather Modification," pp. 31-32.

6 Ibid., p. 32.

7 The 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.

" Ibid., p. 31.


seeded than on nonseeded days, but that the average rainfall on seeded

days was 21 percent greater than on nonseeded days. 11


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 opepations became quite profitable. Many rain-

makers were incompetent and some were unscrupulous, but their activi-

ties flourished for a while, as the experiments of Shaefer and Lang-

muir were poorly imitated. Some of the more reliable companies are

still in business today, and their operations have provided data valu-

able to the development of weather modification technology. 12

Byers relates a few instances of early commercial operations of

particular interest. 13 In 1949-50 the city of New York hired Dr. Wal-

lace 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 re-

sponsible 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. 15

The Santa Barbara project in California, also a commercial opera-

tion designed to increase water supply, received a great deal of atten-

tion. 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. 16

In the West the earliest commercial operations were developed

under Dr. Irving P. Krick, formerly head of the Department of Mete-

orology 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

1050 lie moved to Denver and formed a new company, which began

seeding activity over the Great Plains, elsewhere in the West, and in

" Ibid.

12 Ibid., pp. 17, 21. 22.

" Ibid., pp. 22-23.

w Ibid., p. 22.

15 Hnlacv. "The Weather Chancers, " 1968, pp. 96-97.

"Ibid., pp. 22-23.


other countries. A number of former students of Krick joined him or

formed other cloud seeding companies, mostly in the West during the

1950's. 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

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 main-

taining 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 to nine have been watershed projects

sponsored by utility companies. Most of these projects endured for

long periods of years and many are still underway. 19

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 con-

tinued to sponsor projects throughout this period. 20

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. 21

17 Elliott, Robert D., "Experience of the Private Sector," 1974, p. 47.

18 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 Advisory Committee on Weather Control, Final Report, 1958, vol. II. Figures lacing

p. 242 and 243.

Figure 1 — Purposes of weather modification operations conducted in various

geographical sections of the United States, July 1950 through June 1956. (From

Final Report of the Advisory Committee on Weather Control, 1958.)




1950- 1951- 1952- 1953- (954- 1935-

1951 1952 1953 1954 1955 1936

Figure 2. — Total area coverage and percent of area coverage for the 48 cotermi-

' nous 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 summary of weather modification operations for fiscal

years 1966, 1967, and 1968, compiled by the National Science Founda-

tion 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 proj-

ects. 22 Weather modification activities are now reported to the Depart-

ment of Commerce, under provisions of Public Law 92-205, and sum-

mary 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 acency through September 1968. pp 196 and 215 in ch. 5.

23 See discussions of Public Law 92-205 and of the weather modification activities report-

ing 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.




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 snow-

pack 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

1 Data 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 generators "making it the largest single cloud-seeding

project up to that time. Results of the project were examined at Colo-

rado State University and presented at the International Hail Con-

ference in Verona, Italy, in 1960. This project stimulated the interest

of scientists and provided historical roots for what later was estab-

lished as the National Hail Research Experiment in the same area over

a decade later by the National Science Foundation. 2 ' 4 ' 25

During the 1960's, clearing of cold airport fog through cloud seed-

ing 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. 2,6

2 * Elliott, "Experience of the Private Sector," 1974, p. 48.

23 The National Hail Research Experiment is discussed in detail under the weather modi-

fier lion program ol" the Xationa' Science Foundation in ch. 5 ; se p. 274ff.

28 Elliott, "Experience of the Private Sector," 1974. pp. 48-49.


Figure 3. — Weather modification projects in the United States during fiscal year

1968. (From NSF Tenth Annual Report on weather modification, 1968.)



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 modifica-

tion, 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 repeti-

tive, and the reader is referred to the various sections of chapter 5, in

which historical developments of various Federal activities are un-

folded as part of the discussions of those activities.




(By Robert E. Morrison, Specialist in Earth Sciences, Science Policy Research

Division, Congressional Research Service)


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 about 10 per-

cent. 1 By the mid-1950's, however, it was apparent that the funda-

mental 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 com-

mercial operators had decreased dramatically, and weather modifica-

tion 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 more 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 pro-

vided 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.

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 common theory

and constitute the basic techniques for meeting a number of seeding

objectives, there are really a series of weather modification technol-

ogies, each tailored to altering a particular atmospheric phenomenon

and each having reached a different state of development and opera-

tional usefulness. At one end of this spectrum is cold fog clearing, con-

sidered to be operational now, while the abatement of severe storms, at

1 Fleagle. Robert G., "Background and Present Status of Weather Modification." In

"Weather Modification : Science and Public Policy," Seattle, University of Washington

Press, 1968, p. 11.



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 funda-

mental 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

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