A Theoretical Framework for Examining Geographical Variability in the Microphysical Mechanisms of Precipitation Development.
Final rept. 15 Jan 82-14 Jan 85,
ILLINOIS STATE WATER SURVEY DIV URBANA
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The overall goal of this study was to identify and evaluate the environmental or microphysical parameters that control the efficiency of the various mechanisms of precipitation development. Such evaluations can then be used as the basis for studying, or even predicting the effect of geographical or climatological differences between regions on the microphysical mechanisms of precipitation development. This study included work on warm rain initiation and development, ice multiplication, snowflake aggregation, and the growth of graupel by collection of supercooled water droplets. During the first year of the study, work concentrated on the warm-cloud studies and began on the investigation of snowflake aggregation. With the extension of the study into a third year, additional investigations were made on snowflake aggregation and preliminary investigations were begun to extend these studies into mixed-phase riming precipitation. The studies of riming and graupel development were quite successful and indicated that the studies of warm rain initiation and development could be extended to include mixed-phase precipitation development. In general, the study identified a number of key parameters that control the microphysical development of precipitation. The two primary parameters that need to be measured on a climatological basis are cloud base temperature and cloud droplet concentration. Other key parameters include the degree of entrainment and stability of the environment.