Detailed microphysical structure and statistical characteristics of warm-based convection over southwest England

The COnvective Precipitation Experiment (COPE) took place in southwest England in July-August 2013 to observe convection using airborne and ground-based instrumentation, with a goal of evaluating the microphysical processes that lead to heavy rainfall. The primary data set used here is from the National Centre for Atmospheric Science (NCAS) X-band dual-polarization radar, which was operated during fifteen intensive operation periods in COPE. The NCAS radar measurements were supplemented in all but two of these cases with measurements made by the University of Wyoming King Air research aircraft.

The range of synoptic environments occurring during COPE allowed the observation of convective rainfall produced by both warm rain and ice processes, as indicated by polarimetric radar signatures and airborne measurements of hydrometeor characteristics and bulk cloud properties. Reflectivity values above 55 dBZ were observed in some cases even in shallow convective cells developing below the 0°C level. Deeper convection occurred in other cases, producing reflectivity values near 60 dBZ, with some cells developing columns of positive ZDR values extending several km above the freezing level. Airborne measurements confirmed the presence of supercooled drops within these ZDR columns in multiple cases, with drops up to ~8 mm in diameter observed at -9°C in one cell.

The extensive data sets obtained during COPE provide the opportunity to document the characteristics of a large number of convective cells. The structural features of individual cells will first be described briefly using the NCAS radar observations, with corresponding King Air measurements used to provide more direct verification of these characteristics. Next, statistical analyses of the convection's polarimetric characteristics will be presented for the full NCAS radar data set. These will be used to describe the inferred microphysical processes leading to rain production, in the context of the range of environments sampled during COPE.