Effects of Mid- and Upper-Level Dry Layers on Microphysics of Simulated Supercell Storms

Conceptual differences are presented among supercell storms simulated with midlevel and deep dry layers of varying magnitude. Initial patterns are identified which should be studied more comprehensively using observed or simulated data. These initial results indicate that mixing ratios of small ice particles are most sensitive to the depth of a dry layer rather than to its magnitude, with fewer particles in simulations containing a deep dry layer. Hail from frozen drops may be most abundant when a deep layer is dried, and bursts of hail species reaching low levels may be followed 15–20 min later by an increase in low-level vertical vorticity associated with the mesocyclone. Warm rain occurs repeatedly on the upshear side of the echo appendage, is especially variable in quantity, and is disfavored in simulations with a dry layer at midlevels. Increases in warm rain mixing ratio may be followed 10–20 min later by an increase in low-level vertical vorticity, though this association is sensitive to location of the warm rain and concurrent microphysical and dynamical processes. In simulations with substantial dry layers, vertical vorticity was concentrated more rapidly in association with the mesocyclone at low levels. Storms in simulations with deep dry layers produced larger areas of updraft \u3e10 m s–1 at 1000 m AGL, and produced strong updraft more quickly than moister soundings. These results may be applicable when storms move into areas with different moisture characteristics from where they form, and should be supplemented by additional microphysical observations