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<br />t: <br />~, <br /> <br />Microphysical data collected with the aircraft near the top of the lower <br /> <br />stratiform cloud (-11 C) over the Atlas mountains shows the presence of low <br /> <br />concentrations of aggregates (<1 per liter) consisting of dendritic crystals in regions of <br />liquid water up to 0.3 gm-3 (Fig. 5). Since dendrites typically form at temperatures close <br /> <br />to -15 C and under conditions of water supersaturation, the source region for these <br /> <br />aggregates of dendrites was likely the upper level cloud deck, which had cloud top <br />temperature close to -16 C. The relatively high value of liquid water present at -11 C <br /> <br />suggests that these aggregates were not of high enough concentrations to efficiently <br /> <br />deplete the available liquid water, at least at this location of the storm. Aircraft <br /> <br />penetrations were also made near the tops of these stratiform clouds at a location 25 km <br /> <br />south-southwest of Beni Mellal over a lower ponion of the Atlas mountains. The data <br /> <br />collected there (Fig. 6) during repeated penetrations of the cloud show the persistence of <br />a liquid water region (>0.2 gm-3) for over 10 minutes, suggesting the absence of an <br /> <br />efficient depletion process at this location as well. <br /> <br />In the early afternoon of this day, convection developed over the plains 60 km <br /> <br />east of the coast. Six successive aircraft penetrations ~hrf)ugh a developing cumulus tower <br />(Fig. 7) shows sustained liquid water contents of up to 3 gm-3, which is near the <br />adiabatic value for the sounding on this day (recall that the estimated cloud base <br /> <br />temperature was about 7 C). Drops as large as 500 microns diameter were evident at the - <br />8 C level near cloud top without any significant ice concentration or evidence of frozen <br />drops. The high liquid water content lasted for more: than 10 minutes despite the <br />depletion of the liquid water by the large drops. The moderate updrafts (3-4 m/s) and <br /> <br />high liquid water are consistent with an active coalescence process. In order to quantify <br /> <br />this result, we performed a series of particle growth calculations using the model <br /> <br />described by Rasmussen and Heymsfield (1988). This model calculates the growth and <br />evolution of a single panicle by diffusion, coalescence. riming. melting, and evaporation <br />for specified environmental conditions. The environmental conditions for the current <br />