Hon. GEORGE E. BROWN, CONGRESS OF THE UNITED STATES, Chairman, Subcommittee on the Environment and the Atmosphere, Washington, D.C. DEAR GEORGE: Enclosed is a brief statement in favor of H.R. 10039 and S. 3383, weather modification legislation, which I would like included in the record of your hearings scheduled for next week. While I likely will not be able to appear in person due to heavy involvement with food stamps legislation, I do want to be heard on this important legislation. I note that S. 3383 specifically refers to agricultural implications of weather modification activities. This is indeed desirable. Although these activities obviously affect us in many ways beyond the production of food and fiber and although both bills under consideration are appropriately couched in terms of the broader effects on our economy and our lives, the potential impact on agricultural production at home and in other countries is so great that it should be specifically cited in this legislation. I urge that H.R. 10039 be modified to spell out the special agricultural interests and implications, as S. 3383 now does. With kindest personal regards, Sincerely yours, BOB BERGLAND. STATEMENT OF THE HONORABLE BOB BERGLAND Mr. Chairman: I am very pleased to be here today to speak in support of S. 3383 and H.R. 10039, which I consider to be badly needed legislation to provide the development of a coordinated national weather modification policy and a program through which the policy can be implemented. This topic could hardly be more timely or of higher priority to my home District in Minnesota and, indeed, to other important agricultural areas. Drought has been a problem for Minnesota farmers during all of this growing season and is rampant in most of Minnesota even as I speak. Nor is the problem limited to the current seasonit is a persistently recurring problem of tremendous economic consequence. I have studied the legislation which we have under discussion here today and, against this background of need which I have briefly described, I feel very strongly the need for prompt passage and implementation. The need for this legislation is great. Weather-related disasters and hazardsdrought to which I've already alluded, hurricanes, tornadoes, hail, floods, frost, etc.-result every year in substantial human suffering and loss of life, billions of dollars in economic loss to producers of agricultural crops and property owners, and substantial direct and indirect losses to the Federal Treasury. The interstate nature of these weather-related problems complicates our ability to deliver satisfactory solutions and, in my judgement, calls for a truly coordinated Federal effort. States are now and must continue to be directly involved. However, weather problems transcend State boundaries and our modification solutions to them have many interstate consequences-involving serious legal, economic, environmental, and social questions. I strongly favor a Federally coordinated effort to develop a policy and program through which we can seek out solutions to these complicated, costly problems-as called for in S. 3383 and H.R. 10039. In the Subcommittee on Conservation and Credit, which I chair, we recently discussed legislation which would provide Federal cost-sharing of cloud-seeding operations in areas suffering drought conditions. A cold, hard fact confronting us in those discussions was that we simply do not know much about the effectiveness of these techniques, their optimal application, or, just as importantly, their consequences both inside and outside the treated area. I am convinced that weather modification projects have significant potential for preventing, diverting, (383) or at least moderating adverse effects of weather. Furthermore, the potential benefits far outweigh the kinds of costs which we are contemplating in the proposed legislation. But I do feel that we need the efforts embodied in the proposed legislation under discussion here today to develop that potential before we can do much with our practical applications. More specifically, but briefly, I believe S. 3383 and H.R. 10039 would provide us with the following, all of which are sorely needed at present: 1. Determine if and how existing technology can be used to modify destructive weather in a reasonable, safe manner. 2. Discover and develop improved technology designed to modify weather patterns in a safe, economical manner. 3. Assess the economic, social, environmental, and legal impacts of an operational program of weather modification. 4. Develop a realistic overall weather modification policy. 5. Develop a program or plan of action to implement the policy. Finally, I note that S. 3383 specifically refers to agricultural implications of weather modification activities. This is indeed desirable. Although these activities obviously affect us in many ways beyond the production of food and fiber and although both bills under consideration are appropriately couched in terms of the broader effects on our economy and our lives, the potential impact on agricultural production at home and in other countries is so great that it should be specifically cited in this legislation. I urge that H.R. 10039 be modified to spell out the special agricultural interests and implications, as S. 3383 now does. Again, I commend the efforts of the subcommittee and urge favorable treatment of this legislation to improve our ability to confront Mother Nature's weather patterns in a scientific, economical way. STATEMENT OF C. L. HOSLER, DEAN, COLLEGE OF EARTH AND MINERAL SCIENCES, THE PENNSYLVANIA STATE UNIVERSITY, PRESIDENT, AMERICAN METEOROLOGICAL SOCIETY I regret not being able to present testimony in person, however, I am indebted to the Committee for the privilege of submitting my thoughts in writing. The 9,000 members of the American Meteorological Society embrace a wide variety of views on the controversial topic of weather modification. Dr. Harold Orville, past Chairman of the Weather Modification Committee of the Society will present his views on the topic and a statement approved by the Council of the Society. The views which follow are my own and result from 25 years of association with weather modification research. If one separates the topic of weather modification into parts, some convergence of views is possible. There is no disagreement that supercooled fog and stratus can be dissipated under prescribed atmospheric conditions. There is general agreement that under the right conditions orographic precipitation can be augmented. When we discuss hail prevention, hurricane modification, modification of convective clouds or large storm systems, the divergence of views becomes great as to the degree of confidence in a known outcome justified by our present state of knowledge. This clearly points to the need for expanded and intensified research efforts and a national plan for weather modification research. Some of the furor over the ecological or international consequences of weather modification stems from an exaggerated idea of our present capabilities, nevertheless it is clear that in social, legal and political terms, what is perceived is equal in importance to what is reality. It is therefore necessary that legislation be considered to regulate weather modification activities and make it clear that what is done is in the open and a matter of choice for those affected or at least in the interest of the public at large. Lack of comprehensive reporting and notification in the past had led to a great deal of misunderstanding, apprehension and downright hostility on the part of those who felt that things were happening over which they had no control or knowledge. At the same time, care must be taken to protect research efforts from undue harassment and regulation. Otherwise we may never learn the true potential of either overt or inadvertent weather modification. It is important also to separate relatively innocuous experiments or operations, such as dissipation of a fog over an airport or alteration of a single cloud, from experiments or operations such as one designed to modify a hurricane which could affect many people. The expense and time consumed in complying with reporting and licensing regulations may eliminate many cheap but valuable small-scale experiments if this differentiation is not made. From this point of view legislation such as S. 3383 may be preferable to H.R. 10039 at this time because it would provide for further study of this problem. The recent report on weather modification by the subcommittee of the Domestic Council provides a ready-made point of departure for a study such as called for in S. 3383. I would like to request that a paper titled, "Overt Weather Modification" be entered as part of the record. This paper may be of use in putting the state of knowledge in several areas of weather modification in perspective. Thank you very much for your consideration. [From Reviews of Geophysics and Space Physics, vol. 12, No. 3, August 1974] OVERT WEATHER MODIFICATION (By C. L. Hosler, College of Earth and Mineral Sciences, Pennsylvania State University, University Park, Pa.) This review presents a short summary of the most often examined ideas about small-scale overt weather modification and a subjective assessment of the progress that has been made. In addition, suggestions are made as to where the most fruitful avenues of investigation may lie in the future. Global weather modification and climatic change are not discussed, since the techniques employed thus far in overt weather modification present us with no physical reason for supposing that they affect anything on a grid larger than a few hundred kilometers. Nor is inadvertent modification discussed, even though it is the author's opinion that man's impact upon weather and climate is at the present time principally through this channel. If one examines the literature on weather modification in the late forties or early fifties, i.e., Houghton [1951], M. Neiburger (unpublished data, 1955), or the testimony on weather modification before the hearings held in the spring by the U.S. Congress [1951], which reviewed the subject, one must conclude that most of the statements made at that time can still be made today. Supercooled water is frequently encountered in natural clouds. This water can be converted to ice by man. Changes in cloud structure can be brought about by cloud seeding but with final outcomes often in doubt owing to large gaps in our understanding of basic microphysical processes in clouds and their impact upon cloud dynamics and precipitation formation. The physical basis for cloud seeding varies with what is to be accomplished. Most clouds are a stable colloidal suspension of water droplets of diameters from 2 to 40 μ and produce no precipitation. In order for rain to form, millions of these droplets must coalesce. The possibility of achieving colloidal instability and rain development is a complex function of internal motions or cloud dynamics, the initial mass of water, number of droplets per unit volume, duration of the clouds, and particularly the drop size distribution. In general, a broad spectrum of drop sizes promotes growth by collision due to the varying fall speeds of the drops. In clouds that are at temperatures between 0° and -20° C. most of the cloud water remains in the liquid form. If artificial freezing nuclei are introduced to turn a few of the water droplets to ice, the ice crystals will grow rapidly owing to their lower vapor pressure. They can then fall in relation to the smaller drops and collect them. In this way, snow or rain can form in a cloud that may have remained a stable colloidal suspension if it had been left to its own devices. This has been the primary cloud seeding technique. In clouds warmer than 0° C. hygroscopic salts can achieve a similar result. Alternatively, where lifting of air to produce clouds has been insufficient in magnitude or rate to give rise to large clouds, which condense much water, there are occasions where the cloud temperature is so related to the environmental temperature that if an entire cloud or a region of a large cloud system is turned to ice, the heat of fusion that is released will provide sufficient buoyancy to give rise to significant upward motion. This technique may enable a cumulus cloud to penetrate an inversion and grow to very large size, or it may promote internal lifting in a large cloud system. Either way, additional water is condensed triggering the release not only of the heat of fusion but additional latent heat of condensation to perpetuate the buoyancy and upward motion. Although laboratory and theoretical work has proceeded at a modest pace, the last 20 years of weather modification research, at least in terms of resources applied, can best be characterized as a period of field experiments with varying degrees of statistical design and statistical control and subsequent analysis. This approach apparently reflected a hope that much of the complex cloud physics and dynamics could be overlooked and that either the effect of seeding clouds would be so large and unidirectional as to override the variations between individual cloud systems or else nature would produce clouds in a given location that are very uniform in their physical and dynamic characteristics. Orographic clouds in the western United States apparently have truly met these specifications, for the degree of confidence that precipitation can be increased from orographic clouds has increased through this period of statistically controlled experiments. The assurance of what outcomes could reliably be predicted when clouds are seeded in other situations has not increased correspondingly. In spite of very early recognition of the complexity of the processes leading to precipitation, including hail, and to phenomena such as lightning, our experiments in weather modification have been relatively crude, and only in a very few cases did they contribute to increased insight into what needed to be done to improve them except perhaps in the area of statistical design. Considering the wide variation in clouds seeded it is fortunate that any positive results have been found at all. Only in the straightforward orographic case do statistics seem to yield uniform results from cloud seeding as being positive. And only in the orographic case does the physical hypothesis tend to predict that this behavior would usually be the case and also lend itself to verification by routine seeding in target and control areas and subsequent statistical analysis. The only major departure from seeding of supercooled clouds to enhance colloidal instability and to hasten the formation of precipitation has been the relatively recent in-depth examination of hypotheses by both numerical and field experiments that involve stimulating growth of cumulus clouds in marginally unstable atmospheres. This too involves seeding to produce ice, but in this case the attempt is to produce as much ice as possible to release the heat of fusion. Enhanced growth of either individual clouds or cloud groups through this energy release would presumably enhance local rainfall. Even this idea is not really new; the effect was observed by Kraus and Squires [1947] and implied in the observations of Douglas et al. [1956]. Progress in modeling by investigators, such as Steiner [1973], Orville and Sloan [1970], and Weinstein [1968] to mention only a few, and field experiments by a number of groups, most notably Simpson et al. [1971] have developed this technique to the point where it appears it may have great promise. The seeding attempts do yield results that give good agreement between cloud growth observed and growth predicted by the models: A selected summary of modification techniques thus far employed with some degree of success follows: 1. Supercooled fog and stratus, as was demononstrated in the very beginning by Schaefer [1949], can be caused to precipitate as ice crystals, and thus visibility is increased. The clearing of fog from airports by this technique is operational in cold climates around the world [Silverman and Weinstein, 1973]. There is no argument about the effectiveness of this technique. It is based upon the fact that fog and clouds frequently remain supercooled in the natural state at temperatures down to -25° to -40° C and that a small proportion of the fog water can be turned to ice by seeding with solid carbon dioxide or other refrigerants or by seeding with silver iodide or other solids that nucleate the ice phase at higher temperatures than would be the case naturally. Some nucleating agents such as silver iodide can produce ice at temperatures as high as -4° C. The vapor pressure difference between water and ice leads to rapid growth of the proportion of the particles that turn to ice and evaporation of the remaining water drops. The ice crystals then fall out, and visibility is improved. 2. Under low-wind conditions, warm fogs can be dissipated by the direct application of heat from below or by the dropping of hygroscopic salts through the fog to absorb the water and form large drops that in time will sweep out small drops [Houghton and Radford, 1938; Silverman and Weinstein, 1973]. Helicopters hovering over shallow fogs can also dissipate small areas by mixing in unsaturated air from above. None of these three techniques is widely used or accepted for a variety of reasons, although in individual locations they are being applied. General application of these techniques will probably await some breakthrough in the general area of utilizing hygroscopic salts, but up until now, spreading suitably subdivided uniform size particles at the right time at the right place, which will not cause corrosion or other detrimental effects on the ground, has often proved to be impractical. Increased costs of diverting modern large aircraft have made direct heat application look more attractive and may hasten its development [Silverman and Weinstein, 1973]. 3. The efficiency of formation of precipitation in orographic clouds in which a state of continued uplift persists for many hours can be increased over long periods of time, and significant increases in precipitation have been achieved. One of the most thorough and latest tests is reported by Grant et al. [1971]. These increases are due primarily to more rapidly achieved and more efficiently achieved colloidal instability due to the introduction of ice. In some cases, secondary dynamic effects induced by latent heat of fusion released may contribute to more vigorous lifting and locally increased precipitation [Elliott et al., 1971]. 4. The seeding of cumulus clouds under suitable ambient conditions of stability in the atmosphere to produce dynamic growth and more rigorous lifting through release of the latent heat of fusion, which in turn leads to the release of additional latent heat of condensation, is an established technique of cloud modification with both theoretical and experimental evidence to support it. A delicate balance often exists between a cumulus cloud and its surroundings. The dependence of this balance upon the amount, type, and altitude of the liquid water or ice in the cloud and the variability of mixing rates of cloud air with the drier and cooler environment make the outcome of such seedings' releasing heat and at the same time affecting the precipitation growth processes difficult to predict. For this reason the exact consequence of the seeding and effects upon the amount of rainfall that reaches the ground vary. Increased rainfall is certain in some cases, but in others it may be diminished. There is also a good likelihood that increased lifting produced in one region may induce subsidence and decrease cumulus growth in adjacent regions. Promotion of growth of cloud groups or bands may overcome this by greatly enhancing total rainfall. The preponderant amount of natural precipitation falls from such organized systems, and physical considerations indicate that overt weather modification may be most productive in promoting such organization. Numerical modeling has played an important role in dynamic cloud seeding, and before operational seeding becomes very important, better predictive models are necessary along with detailed real time data on cloud and environmental properties and structure. 5. The seeding of cumulus clouds can result in the more rapid achievement of colloidal instability in either warm clouds or supercooled clouds if suitable hygroscopic nuclei or freezing nuclei are used. This technique can result in the hastening of precipitation formation. The degree to which this is effective in promoting rainfall is not as yet established, and this is by no means an operational technique. The timing, delivery in the proper place, and getting particles of prescribed sizes into the cloud pose operational problems. Also the effect of redistributing hydrometeor water influences cloud dynamics in an as yet unpredictable manner calling again for improved modeling. 6. The prevention of hail by firing cannons and rockets into thunderstorms has been practiced in Europe for more than 100 years. Recently, rockets and projectiles bearing silver iodide have been introduced. The most spectacular claims to success in preventing hail have probably come from the Soviet Union [Fedorov, 1967]. These claims, together with a hypothesis that if enough ice were provided in the cloud, hailstones produced would be small owing to competition for a fixed amount of supercooled water and would either melt or reach the ground as very small ice particles, helped to promote a U.S. national hail research experiment in 1971, which is still in progress. The results of this experiment are not yet available, but preliminary indications give some encouragement. 7. Seeding with silver iodide to prevent lightning has been carried out by the U.S. Forest Service in Montana [Fuquay, 1969] with mixed results, and most certainly no widespread agreement exists as to the efficacy of such a procedure. The physical hypothesis has assumed that since charging mechanisms involve formation of ice and interactions between ice crystals, radically changing the temperature at which ice forms would alter the natural charging rate or location of charge centers. Again, we must conclude that the microphysical and dynamic consequences of seeding are so complex and varied that with the models available and the state of knowledge of charge and discharge mechanisms one would be hard pressed to predict the electrical history of a given cloud system either as a consequence of natural events or with the introduction of seeding. We have a long way to go both in obtaining observations of the state of the cloud and in perfecting physical models. |