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<br />-. <br /> <br />. <br /> <br />. <br /> <br />c <br /> <br />A Statistical Re3.nalysis of the :1.a?lic.:!tcd Cli;"ax ! and II <br />~inte~ti~e Orographic Cloud Seeding Experiments <br /> <br />Paul W. Mielke, Jr.1, Clenn W. Brier2. Le~is O. GrantZ, <br /> <br />Gerald J. Mulvey2.3. and Paul N. Rosenzweig2 <br /> <br />Colorado State University, Fort Collins, CO 80523 <br /> <br />Abstract <br /> <br />A reanalysis of the Climax I and II experiments is described. The <br /> <br />concern prompting this reanalysis is a suggestio~ arising from Colorado <br /> <br />State University analyses of extended area effects. Those analyses suggested <br /> <br />a region-wide pattern of precipitation that, by chance. may have favored the <br /> <br />randomly selected seeding days for some of the important meteorological <br /> <br />partitions used in earlier analyses. In order to address this concern, this <br /> <br />reanalysis employs excellent covariate relationships developed before the <br /> <br />initiation of C11.r.lax II and which aCCOunt for over half of the target <br /> <br />variability for most meteorological partitions of major interes~ (e.g., <br /> <br />ware SOO-mb temperatures and southwest 700-mb wind directions). The <br /> <br />statistical evidence of seeding induced increases associated with this <br /> <br />reanalysis is generally much stronger than the previous analysis ~hich did <br /> <br />not utilize the covariate data. For example. the joint one-sided Wilcoxon <br /> <br />test statistic P-value for testing the null hypothesis that seeding did not <br /> <br />induce a precipitation increase during ~arm SOO-mb temperatures of the <br /> <br />Climax I and II experiments is now 0.0013 compared to 0.0550 ~ith the <br /> <br />previous analysis ~hich did not utilize the covariate data. However, the <br /> <br />reanalysis also indicates that previous estilJl.1.tes of increases attributed <br /> <br />to seeding based strictly on ratios of seeded to non-seeded precipitation <br /> <br />amount means are apparently too large. For example, the esti~ted <br /> <br />precipit3tion increase of the combined Clim~x 1 and II data for the varm <br /> <br />SOO-mb teQperature partition is reduced from L1 percent to 25 percent when <br /> <br />usin; the full 5et of d~t~ as ~~plov~d in :his re~nal;sis. <br /> <br />/ <br /> <br />~ <br /> <br />A-1l-3 <br />