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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />A review of frequency tables for each wi ntelr season for 500 mb temperatures <br />obtained from the 1200 Z and 0000 Z soundin!~s from Winslow indicated a <br />small shift in the distribution (temperaturl~) to colder temperatures in wet <br />as compared to dry periods. Otherwise, thete were no discernable differen- <br />ces. Given in table 1 are the 500 mb temperature ranges by winter season. <br />The temperatures range from a warm -4 oC to a rather cold -43 aC. The 500 <br />mb temperatures are of particular interest since previous project eva- <br />luations have indicated this parameter to be useful as an index of seedabi- <br />lity (Mielke, et al., 1971; Grant and Elliott, 1974). <br /> <br />Meaningful infonnation on cloud treatment potential is obtained from the <br />study of distributions of parameters such as the 500 mb temperature (since <br />they index seedability) where only those cases with precipitation are con- <br />sidered. Since primary cloud seeding benefits likely lie in the enhan- <br />cement of a precipitation event rather than its initiation, analyses for <br />this study were concentrated on cases where precipitation occurred. <br /> <br />4.3 Precipitation event analyses <br /> <br />Daily precipitation measured at 1800 local time was obtained for most <br />available reporting stations in Arizona for the historical record period <br />ending with 1983. The data is published by the National Climatic Data <br />Center located in Asheville, North Carolina. Given in table 2 and figure 14 <br />are 17 stations selected for in-depth analyses. These were chosen based on <br />location with respect to potential cloud seeding target areas, site eleva- <br />tion, and expected positive response to moist air mass sources (storm <br />tracks). Stations were selected from the southern mountains as well as the <br />Mogollon Rim. <br /> <br />As indicated in table 2, stations were grouped in a manner to represent <br />3 areas of the Mogollon Rim (the northern, central and southeastern <br />regions). This was done, in part, to measure precipitation providing <br />runoff to the Verde River, central tributaries to the Salt River and the <br />White and Black Rivers which feed the Salt River from the east. <br />Additionally, the groupings enabled the development of the more stable <br /> <br />28 <br />