A Brief History of Weather Modification Since 1946 1

VOL. 44, No. 7, JULY 1963 425 A Brief History of Weather Modification Since 1946 1 RALPH E. HUSCHKE The RAND Corporation, Santa Monica, Calif. 1. Analysis of the literature 1951, representing a public-awareness explosion as The written record of weather modification is to the potential of rainmaking on a commercial allowed to speak for itself. This formidable quan- basis; note that the "productive" peak occurs five tity of world literature was recently collected, years later, corresponding to the maximum serious organized, abstracted, and published for the Na- effort to evaluate cloud seeding as a rainmaking tional Science Foundation as a special "Bibliogra- technique. phy on Weather Modification" by the American A remark is in order concerning the relative Meteorological Society's Meteorological and Geo- volumes of commercial cloud-seeding literature astro physical Abstracts (Vol. 11, No. 12, Pt. 3, (groups 7 and 11 in Fig. 1) and non-commercial I960). The RAND Corporation has further ana- cloud-seeding literature (groups 6 and 10). A lyzed the literature to provide, it is hoped, a cursory comparison of reported cloud-seeding meaningful, quantitative chronology of activity in projects versus the literature generated thereby weather modification since 1946. indicates that commercial projects place in the Fig. 1 displays the gross results of the literature open literature only about one-tenth as much infor- analysis; it was derived as follows: mation as that generated by comparable non-commercial projects. This is not to say that complete a) Approximately 1,300 references were broken documentation may not reside in the files of com- down and grouped according to kind of informa- mercial operators and their clients. Also, there is tion disclosed. (Those references which disclose great variation in reporting philosophy among the more than one kind of information comprise, in private cloud seeders; some have been regular this analysis, more than one "item." Thus, the contributors to the productive literature. number of items totals over 1,700.) b) It was seen that the literature covered the 2. World distribution of cloud-modification spectrum of scientific worth and that the groups activity could be categorized accordingly. Thus, in Fig. 1, the tabulated chronology is presented as the sum If the literature items concerned with actual of "productive" items above the axis, "non-produc- cloud seeding (groups 4-11 of Fig. 1) are summed tive" items below the axis, with "marginally pro- by nation, they reveal a relative national distribu- ductive" items about the axis. The material tion of cloud seeding around the world, as pre- analyzed does not include any physical research sented in Fig. 2. The quantitative dominance of not consciously directed to problems of weather the U. S. would appear even greater if commercial modification. seeding produced its "share" of documentation. Other regions with greater seeding activity than Only crude patterns emerge from the kind of indicated by this literature survey, for reasons of agglomeration represented by Fig. 1, but as back- significant commercial operations, are Canada, ground, some are interesting and pertinent. For Spain, and South and Central America. example, note that the volumes of "non-produc- A word about the character of activity of some tive" and "productive" literature are about equal. of the principal nations involved: The experi- Note the rate of diminution of both since 1956, mental basis of French activity has probably been but especially that of the "non-productive" items. the broadest of any nation, covering nearly the full Note that the "non-productive'' peak occurs in selection of seeding agents and convection-stimula- 1 This study was supported by the National Science tion methods, and using many dispensing tech- Foundation Program on Atmospheric Sciences under niques. Work in Italy and Switzerland has con- Contract NSF-C252. This publication does not neces- sarily reflect the views of the National Science Founda- centrated almost entirely on the problem of hail tion. suppression. Japanese experiments are character- Unauthenticated | Downloaded 09/30/21 11:22 PM UTC 426 BULLETIN AMERICAN METEOROLOGICAL SOCIETY FIG. 1. Anatomy of 15 years' literature on weather modification. ized by scientific analysis, having contributed sig- have been more in the nature of scientific experi- nificantly to knowledge of the diffusion and physi- mentation in basic cloud physics than an attempt cochemical nature of seeding agents. Most of the to produce measureable modification. experimentation in Africa has been conducted by In the net, although it is derived from the total the British and French, taking advantage of the available literature, Fig. 1 can be taken as a fair desert and tropic climates and the sparsity of representation of the United States weather-modi- population. In the Soviet Union, seeding seems to fication history since 1946. Unauthenticated | Downloaded 09/30/21 11:22 PM UTC VOL. 44, No. 7, JULY 1963 427 3. Four eras of cloud modification importance of the breaking-drop chain-reaction process of warm precipitation. Project Cirrus 1946-50: Experimental era. Immediately fol- produced a flow of substantive "effects" upon lowing their own key laboratory and field discov- clouds of all types; and, despite the Project's own eries in 1946-47, investigators at the General concern with the need for more basic understand- Electric Research Laboratories received support ing, its enthusiastic reports and preliminary prac- from the three armed services for a very broad tical extrapolations served as the springboard for theoretical, laboratory, and field program (Proj- the next era. ect Cirrus) to explore cloud modification possibil- ities. In the course of its five years, Project That the "experimental era" generated a general Cirrus had extended and refined the practical (in particular, commercial) optimism about cloud status of seeding clouds with dry ice, Agl, and seeding was no fault of the joint Weather Bu- water to the limits of the hypotheses that the reau, Air Force, NACA Cloud Physics Project, project, concurrently, had advanced. Some of which was conducted from 1948-51 because: "In these hypotheses will be recognized as untested or view of the divergent claims made by both qualified disputed or both, even today; e.g., wide-scale and unqualified experimenters in the rain-making weather periodicities induced by periodic point field, the requirements for a long series of well seeding; the consequences of artificially produced controlled objective tests became obvious." 2 Us- ice-crystal "reservoirs" in broad, shallow layers in ing dry ice only, the Cloud Physics Project seeded the atmosphere; the concept of cloud self-propaga- a few types of supercooled stratiform and cumuli- tion due to release of latent heat of fusion; the concept of "overseeding," that is, the belief that the 2 Coons, R. D., and R. Gunn, 1951: Relation of artificial cloud-modification to the production of precipitation, reaction of a cloud may be reversed by regulating Compendium of meteorology, T. F. Malone (ed.), Amer. the amount and location of seeding; and the Meteor. Soc., Boston, Mass., pp. 235-241. FIG. 2. World distribution of reported cloud modification experiments (1946-1960). Unauthenticated | Downloaded 09/30/21 11:22 PM UTC 428 BULLETIN AMERICAN METEOROLOGICAL SOCIETY form clouds in Ohio, Alabama, and California, and making results, non-commercial projects were be- concluded that ". the artificial modification coming increasingly mired in the statistical no- of cumuliform clouds is of doubtful economic im- man's-land of inconclusiveness. portance for the production of rain." Their results 1952-57: Evaluation era. Actually, the question in dissipating supercooled stratus clouds were of rain-making evaluation was raised from the first generally positive (in accord with Project Cirrus claims of success. Evaluation became the domi- findings), but the significance thereof was nant factor in weather modification, however, only minimized. as a consequence of the work of the U. S. Advisory Both the Cloud Physics Project and Project Committee on Weather Control, established in Cirrus agreed on the pressing need for further 1953. Under the aegis of this committee, the non- research, for improvements in research techniques, commercial (and a small segment of the commer- and on the fact that, regardless of economic im- cial) branch of weather modification turned almost portance, cloud seeding should be adopted as an exclusively to the task of designing experiments exciting new tool for atmospheric research. to facilitate their evaluation by physical and statis- Reaction outside the United States was equally tical means. Because of their direct bearing upon quick to the 1946 announcements. By the end of matters of immediate public interest, the statistical 1947, cloud-seeding programs had begun in Aus- projects of the Advisory Committee received tralia, France, and South Africa, and renewed greater notoriety than the physical studies. The scientific attention was being paid to the "hail Committee's statistical conclusions were, in the shooting" that had been the practice in Alpine net, favorable to limited rainmaking; but they have Europe since the mid 'thirties. In 1948, the num- been attacked from both sides. ber of nations experimenting with cloud seeding The physical analysis of cloud seeding was was at least 12, increasing, by the end of 1950, to greatly encouraged by the Advisory Committee. about 30 nations and representing every continent. Projects Overseed, Skyfire, Seabreeze, Sailplane, 1949-54: Bandwagon era. There is probably at and some aspects of the Santa Barbara Project least one good technological reason why the growth started a favorable trend back to investigating the of cloud-seeding activity was not measurably de- scientific bases of weather modification. terred by the negative conclusions of the Cloud The grand and diversified attempt to evaluate Physics Project: silver iodide had been committed weather modification brought meteorologists to to general use as "the" seeding agent before the recognize, as they never had before, the extent to CPP's dry-ice tests were completed.

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