. . . Some Cloud Physics

. . . A few idealized cloud model runs were made using the Colorado State University RAMS mesoscale model (Pielke, et al., 1992). Results show that deeper LES clouds, with stronger updrafts (3 m/s for the test conducted), produce mostly graupel in the vicinity of the storm's updraft. In the layer at and near cloud top, the model finds large concentrations of supercooled water which, after 2-3 hr, become mixed with ice crystals.

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For shallow clouds, with weak updrafts (0.6 m/s), the model produces very little graupel. There is about one-third the amount of liquid water found near cloud top, and particulates are almost entirely crystal aggregates. These tentative results also help explain why the mature portion of intense LES bands over lakes often develop a water-mixed-with-ice signature at cloud top (on the 3.9/10.7 um dual-channel imagery), but within a few km over land (where buoyancy is less) tops typically seem to convert primarily to ice.

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