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<br />')
<br />
<br />5. DISCUSSION
<br />
<br />.,.
<br />
<br />The results obtained in the preceding two sections are in line with those from previous studies of
<br />the Western Kansas Weather Modification Project and other programs in the central United States.
<br />
<br />The absence of any significant effect on seasonal rainfall is in agreement with a study of the
<br />Kansas project by Hsu and Chen [1], using data through 1979. The result is not in conflict with
<br />the fmding by Huff et al. [2] that seeding may have caused small rainfall increases on days when
<br />seeding was conducted primarily to stimulate rainfall rather than to suppress hail. The natural
<br />variability of rainfall from large storms, some of which were seeded for hail suppression, could
<br />easily mask changes in rainfall from smaller storms seeded to stimulate rainfall.
<br />
<br />There are no generally accepted results indicating that seeding large thunderstorms in the central
<br />United States would lead to a net rainfall increase. The best known seeding experiment on such
<br />storms, Project Whitetop, found evidence that seeding tall storms in Missouri may have led to
<br />decreases rather than increases in rainfall [12]. Fortunately, there is no significant evidence that the
<br />seeding in western Kansas caused rainfall decreases.
<br />
<br />The suggestion that seeding may have led to decreases in hail damage in the eastern part of the
<br />target area of a much as 50 percent is in line with Hsu and Chen [1] and with analyses of several
<br />other hail supppression programs in the Great Plains (e.g., Henderson and Changnon [13] and
<br />Rose et al. [14]). As the area of apparently favorable response in the eastem part of the target area
<br />merges with an area to the northeast that apparently was naturally favored during the seed years,
<br />one cannot be sure how far downwind the seeding effect extended.
<br />
<br />Assuming that there is a hail suppression effect, the analysis suggests that seeding operations
<br />would have to be extended farther to the west to provide much protection to the counties next to the
<br />Colorado border. Administrative restrictions on seeding inside Colorado have posed some
<br />problems to the project's operators. However, examination of figures 2.3 and 2.4 shows that the
<br />main concentration of seeding agents could be shifted westward some 20 to 30 km (say, 10 to 20
<br />miles) under the existing restrictions. It would also appear desirable to distribute the seeding
<br />material somewhat more widely so as to improve coverage in the southwest and southeast parts of
<br />the target area. The authors recognize, however, that the project has operated with quite limited
<br />resources and that wider distribution of seeding agents, as opposed to a simple shift westward,
<br />might require some additional aircraft.
<br />
<br />.
<br />
<br />6. REFERENCES
<br />
<br />[I] Hsu, C-F and J. Chen, "Statistical Evaluation of a Rain-Hail Operational Project in
<br />Southwestern Kansas." Preprints, Eighth Conference on Inadvertent and Planned Weather
<br />Modification, Reno, Nevada, pp 124-125, Amer. Meteor. Soc., Boston MA, October 5-7,
<br />1981,
<br />
<br />".
<br />
<br />[2] Huff, F.A., S.A. Changnon, Jr., C-F Hsu, and R.W. Scott, "A Statistical-Meteorological
<br />Evaluation of Two Operational Seeding Projects," J. Clim. & Appl. Meteor., vo124, pp.
<br />452-462, 1985.
<br />
<br />[3] Smith, C., Final Report, Western Kansas Weather Modification, April 15,1985 - September
<br />15, 1985, Western Kansas Groundwater Management District No.1, Scott City, KS, 31 pp. +
<br />appendixes, 1985.
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