Critical Issues in Weather Modification Research (2003) / Chapter Skim
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1 Introduction
1 Introduction
Pages 9-22
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From page 9... ...
History is replete with examples of local and regional conflicts over water. Meeting the pressing need for clean, sustainable, and adequate water supplies will require comprehensive resource management strategies that include water conservation and efficiency measures, but there could also be tremendous societal benefits Tom taking actions to increase water supplies in select areas.
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. 1950 1955 1960 1965 1970 1975 Year _ Ground Water Surface Water Total Water Population .
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. 1 ABLE 1.1 Summary of Natural Hazard Statistics Lloyd 2001 in tile United States Property Crop Damage Weather Event Fatalities Injuries (Millions of $)
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From page 12... ...
Whether or not methods for weather modification ultimately prove effective in providing significant benefits, these expanding, societal stresses and threats will continue to make periodic reassessment of the science and technology underlying weather modification a national need. Searching for ways to enhance precipitation and mitigate hazardous weather is one of the most important challenges that could be tackled by science.
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From page 13... ...
Weather modification does not appear as a line item in the budget of any federal agency—although closely related topics such as cloud physics, water management, and climate change are being pursued and no work is being done on the complex social and economic implications of attempts to modify weather (see Box 1 14. Yet people in drought-prone areas willingly spend significant resources in support of cloud seeding to increase rain, and commercial operations for increasing mountain snowpack have been supported continuously far many years (Plate 21.
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From page 14... ...
For the purposes of this report, and at the rislc of oversimplification, it is useful to group these mechanisms into those that involve the formation of ice particles and those that do not. The so-called coalescence mechanism or warm-cloud precipitation mechanism is an all-liquid process wherein raindrops Tom by the merging of the cloud droplets (Bower, 1950; Ludlam, 1951; Young, ]
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From page 15... ...
Further growth through riming with cloud drops produces high-density graupel and small hail These particles then melt into raindrops upon descending below the 0°C-level This mechanistic appears to be very important ill convective clouds having bases warmer than about +1 5°C arid Title low s~b-cloud CCN concentrations. under certain cloud conditions the process of rinsing Nay result in the creation of small ice particles (so-called secondary ice particles, SIP)
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From page 16... ...
Between 1951 and 1953, Congressional hearings on several bills dealing with cloud seeding revealed that farmers, ranchers, electric utilities, municipalities and other water users were paying 2 cents to 20 cents per acre, and annually were spending between $3 million and $5 million on weather modification activities covering approximately l0 per cent of the land area of the nation....As a result of this lengthy consideration, the Advisory Committee on Weather Control was established by an Act of 13 August 1953. Findings of this committee are considered below.
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From page 17... ...
THE PIONEERING EXPERIMENTS In the early 1940s most meteorologists had little background in the physics and chemistry of cloud particles' but some of those who entered the field from other physical and engineering sciences during the wartime training programs saw the possibility that cloud seeding might prove useful as a tool for probing the inner workings of clouds. Recognition of the great potential benefits that might accrue from proven weather modification techniques prompted the Weather Bureau and scientific research units in the U.S Army, Navy, and Air Force to consider experiments to clari: the potential for cloud seeding.
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From page 18... ...
In an effort to put cloud seeding on a more rigorous foundation, several university and government groups launched major studies of clouds and their reaction to seeding. Some of the most productive studies during this petiod included randomized seeding trials with accompanying physical measurements using the most modern tools available at the time Measurements were made in both seeded and non-seeded clouds Some of these experiments were "double blind," such that the group conducting the seeding did not collect and analyze the rainfall data, while those involved in the analysis had no knowledge of Allen and where seeding had taken place (em, the Missouri Project Whitetop)
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From page 19... ...
It also sponsored two independent evaluations of a small number of commercial seeding operations Concerning their reanalysis of 14 short-duration, groulld-genel-ator operations in the eastern United States, they found indications of a positive seeding effect. However, "results of these fourteen projects...cannot by themselves be regarded as conclusive evidence of the efficacy of seeding; yet taken together they seem to us to be a new indication of positive effect, warranting optimism." The panel also sponsored an analysis using seasonal runoff data as the test variate in four west-coast winter-season orographic
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have no effect....lt is concluded that the r ecent demonstration of both positive and negative effects fit om seeding convective clouds emphasizes the complexity of the processes involved.A..A more careful search must be made to determine the seedability criteria that apply to the convective clouds over various climatic regions....The Panel concludes that there is a pressing need for furthet analyses of the areal extent of seeding effects under a variety of meteorological and topographical situations and for investigations into the physical mechanisms that ale responsible for any such effects. Concerning hail reduction and mitigation of severe weather hazards, the panel noted the need for further research (NRC.
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From page 21... ...
35.] Several assessments of individual seeding projects, or groups of projects, have been made by individual scientists familiar with cloud physics and cloud seeding but not directly involved with flee projects they assess.
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