Laserfiche WebLink
R y <br /> Precipitation augmentation programs are unlikely to achieve higher scientific credibility until more complete <br /> understanding of the physical processes responsible for any modification effect is established and linked by <br /> direct observation to the specific methodology employed. Continued research emphasizing in situ <br /> measurements, atmospheric tracers, a variety of remote sensing techniques, and multidimensional numerical <br /> cloud models that employ sophisticated microphysics offer improved prospects that this can be accomplished. <br /> c. Hail suppression <br /> The efficacy of projects intended to mitigate the severity of hailstorms remains indeterminate. Statistical <br /> assessments of certain operational projects indicate successful reduction of crop hail damage,but scientific <br /> establishment of cause and effect are incomplete. Results of various operational and experimental projects <br /> provide a range of outcomes. Some suggest decreases in hailfall,but others have produced inconclusive results, <br /> and some suggest increases. Given the diversity of conceptual models,cloud seeding criteria, seeding agents, <br /> delivery techniques, assessment methods,and the storms themselves,this is not unexpected. It is a direct <br /> reflection of storm complexity as well as the spatial and temporal variability of hail. <br /> Statistical evaluations using hail characteristics (i.e.,kinetic energy, hailstone size, and area of hailfall)have <br /> often yielded inconclusive or inconsistent results. Historic trends in crop hail damage have been used to <br /> evaluate many operational programs,but these data can be unreliable and so must be used cautiously. <br /> Our understanding of hailstorms is not yet sufficient to allow confident prediction of the effects of seeding <br /> individual storms, and the most appropriate seeding methodology has not been determined. The possibility of <br /> increasing or decreasing both hail and rain in some circumstances is recognized,but numerical cloud models <br /> have recently affirmed that the desirable outcome,that is, a decrease in hail and an increase in rain, is possible. <br /> Hail results in significant economic losses worldwide; thus, research on hail suppression continues. As with <br /> precipitation augmentation efforts, increased in situ observations,remote sensing(e.g., multiparameter radar), <br /> and numerical cloud modeling capabilities continue to improve our understanding of hailstorms as a foundation <br /> for more effective scientific endeavors to suppress hail. <br /> d. Severe storms mitigation <br /> There is no generally accepted conceptual model for modifying tropical disturbances. Hurricane modification <br /> experiments of the 1950s and 1960s were inconclusive. Although strong interest continued into the 1970s,no <br /> organized research effort was undertaken, and few studies have been devoted to this subject for the past 20 <br /> years. <br /> No sound physical hypotheses exist for the modification of tornadoes, or of damaging winds in general, and no <br /> scientific experimentation has been conducted. Experiments have been carried out to suppress lightning but <br /> have not yet yielded methods sufficiently developed for application. <br /> Top of DocumenLi <br /> 3. Status of inadvertent weather modification <br /> There is ample evidence that agricultural and industrial activities modify local and sometimes regional weather <br /> conditions.Urbanization also results in localized weather modification. Air quality,visibility, surface and low- <br /> level winds,humidities and temperatures, and cloud and precipitation processes are all affected by large urban <br /> areas. <br /> 4 <br />