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<br />the total rainfall within each type of event. Furthermore, the most <br /> <br />intense echo of a given day produced from 34 to 88% of the total rain <br /> <br />volume from the 30 to 50 echoes typically observed each day. Estimates <br /> <br />of mesoscale precipitation efficiency increased from ~2% in isolated <br /> <br />cell events to 80% in mesosynoptic events. A wide range of efficiency <br />was found in eaCh type of event. This further illustrates the critical <br /> <br />importance of careful mesoscale stratification of cases in the evalua- <br /> <br />tion of weather modification programs. <br /> <br />Line and mesosynoptic events accounted for 91% of the total rain <br /> <br />volume observed in this study. Isolated cells and clusters occurred in <br />conditions of large conditional instability with low values of Qe at <br />500 mb which indicate the potential for deep penetrative downdrafts. <br /> <br />Hence, these events may provide future opportunities to develop and test <br /> <br />dynamic seeding hypotheses that initiate and enhance meso-~ downdrafts; <br />thereby increasing precipitation efficiency over larger regions. <br /> <br />Combinations of thermodynamic, kinematic and cloud model predic- <br /> <br />tions based on mesoscale rawinsonde observations provide excellent <br /> <br />discrimination among types of events. This makes it possible to <br /> <br />stratify precipitation cases into more homogeneous samples having <br />similar mesoscale forcing, thereby reducing the larger uncertainty <br /> <br />associated with natural variability in weather modification programs. <br /> <br />David Aaron Matthews <br />Department of Atmospheric Sciences <br />Colorado State University <br />Fort Collins, Colorado 80523 <br />August 1983 <br /> <br />v <br />