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<br />HIPLEX-l clouds at levels above about -SoC. <br /> <br /> <br />In summary, the data indicate that classical lateral entrainment <br /> <br />played a minimal role in HIPLEX-l clouds. Entrained air which <br /> <br /> <br />originated near cloud top was found near the -80C level in HIPLEX <br /> <br /> <br />clouds, and very rapid rates of dilution were observed. Typically, <br /> <br />there was a large potential for the fonnation of negatively buoyant <br /> <br /> <br />downdrafts near the top of HIPLEX-l clouds. However, the methods of <br /> <br /> <br />Paluch (1979) and Boatman (1981) did not always yield a definitive <br /> <br />indication of the sources of entrained air, and not all HIPLEX-type <br /> <br /> <br />clouds could be shown to be daninated by entrainment from upper levels. <br /> <br /> <br />Since the study of entrainment was not a major thrust of this . <br /> <br /> <br />contract, many suggestions from the data have not yet been pursued, <br /> <br />and continued study of entrainment in these clouds is warranted. <br /> <br /> <br />2.8: Ice concentrations. Cerni (1982b,c), Cooper et al. (1982b), and <br /> <br /> <br />Cerni and Cooper (1980) have discussed the measurements of ice crystal <br /> <br /> <br />concentrations observed near the tops of growing cumulus clouds in the <br /> <br /> <br />Miles City HIPLEX area. Fig. 2.16 shows the measured ice crystal <br /> <br /> <br />concentrations as a function of cloud top temperature. Only cloud <br /> <br /> <br />passes which were made wi thin 500 m of the cloud top were used, and <br /> <br /> <br />only growing isolated clouds were considered; a total of 85 clouds were <br /> <br /> <br />used to compile this figure. <br /> <br /> <br />No ice was observed in clouds wi th cloud top temperatures wanner <br /> <br /> <br />than -lOoC. Some surprisingly high ice concentrations were observed at <br /> <br />temperatures just wanner than -lOoC, but there is some suspicion that <br /> <br /> <br />large water drops may have been misinterpreted as ice crystals. In <br /> <br /> <br />general, the concentrations all fell below lOlL for all temperatures <br /> <br />25 <br />