Drop-Size Distribution Observations from PECAN in Mesoscale Convective System Stratiform Regions

A critical goal of the Plains Elevated Convection At Night (PECAN) experiment is to improve scientific understanding of nocturnal mesoscale convective systems (MCSs). Microphysical processes in MCSs remain poorly understood in part due to the limited number of observational analyses of MCS drop-size distributions (DSDs), and that those analyses focused on a single subset of MCS types (mature leading line, trailing stratiform or LLTS MCSs). DSD characteristics need to be examined across a spectrum of different MCS archetypes, lifecycles, and environmental characteristics to obtain an improved understanding of MCS microphysical properties. To address this need, DSD data were collected during PECAN using three Parsivel disdrometers and over 30 hours of DSD data were obtained from 10 MCS cases encompassing different MCS archetypes and lifecycle stages across a wide geographic region.

PECAN cases with stratiform rain observations from different MCS archetypes and lifecycle stages are presented. During the 25 July 2015 Iowa case, an MCS produced both leading stratiform (LS) and trailing stratiform (TS) regions. Since LS and TS DSDs result from different ice crystal trajectories through different MCS regions (e.g., pre- and post-convective line environments), similarities and differences between LS and TS DSDs will be analyzed. The 26 July 2015 LLTS MCS was observed during the developing stages of the transition zone (TZ) and TS region. These observations will be compared to a mature LLTS MCS TSR on 15 July 2015. These three MCS cases also included TZs with notable similarities and differences in DSDs, including both archetypal and non-archetypal configurations of the TZ relative to the convective line.