A Microphysical Analysis of Elevated Convection in the Comma Head Region of Continental Winter Cyclones

An analysis of the microphysical structure of elevated convection within the comma head region of two winter cyclones over the midwestern United States is presented using data from the Wyoming Cloud Radar (WCR) and microphysical probes on the NSF/NCAR C-130 aircraft during the Profiling of Winter Storms campaign. The aircraft penetrated 36 elevated convective cells at various temperatures T and distances below cloud top z(d). The statistical properties of ice water content (IWC), liquid water content (LWC), ice particle concentration with diameter > 500 mu m N->500, and median mass diameter D-mm, as well as particle habits within these cells were determined as functions of z(d) and T for active updrafts and residual stratiform regions originating from convective towers that ascended through unsaturated air. Insufficient data were available for analysis within downdrafts. For updrafts stratified by z(d), distributions of IWC, N->500, and D-mm for all z(d) between 1000 and 4000m proved to be statistically indistinct. These results imply that turbulence and mixing within the updrafts effectively distributed particles throughout their depths. A decrease in IWC and N->500 in the layer closest to cloud top was likely related to cloud-top entrainment. Within residual stratiform regions, decreases in IWC and N->500 and increases in D-mm were observed with depth below cloud top. These trends are consistent with particles falling and aggregating while entrainment and subsequent sublimation was occurring.