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<br />0IAPl'ER 2: GmERAL OlARAC'1'ERISTla:> OF OOJ IN THE MILES CITY AREA <br /> <br />A representative survey of the characteristics of the CuOg clouds <br /> <br /> <br />studied in 1978 was presented in the 1978 annual report (Cooper et al., <br /> <br />1982a) . Since flights in subsequent years all had more specific <br /> <br /> <br />objectives and generally sought particular cloud types, especially <br /> <br /> <br />those of the HIPLEX-l experiment, 1978 was probably the most unbiased <br /> <br />year in our data set, and therefore will be emphasized in this chapter. <br /> <br /> <br />1978 was also the year with the greatest frequency of suitable clouds, <br /> <br /> <br />and it was the year with the most May-July rainfall (Hartzell and <br /> <br /> <br />Jameson, 1981), so the sample may be biased by nature rather than by <br /> <br /> <br />our selection. <br /> <br /> <br />2.1 Cloud base t:alperature. The cloud base temperature is an <br /> <br /> <br />important cloud characteristic, for it is the primary detenninant of <br /> <br /> <br />the "adiabatic" liquid water content possible at any height. Wann cloud <br /> <br /> <br />base temperatures provide the potential for high liquid water contents, <br /> <br />favoring such processes as coalescence developnent of rain or ice <br /> <br /> <br />mul tiplication via the Hallett and Mossop process; Hallett et al. <br /> <br /> <br />(1980) argued that the dominant precipitation process in an area is a <br /> <br />strong function of cloud base temperature. Thus the representative <br /> <br /> <br />temperature of the area is a key feature enabling comparisons to other <br /> <br /> <br />research areas, and we have therefore compiled a careful climatology of <br /> <br />cloud base conditions. <br /> <br />3 <br />