Cloud microphysical properties of convective clouds sampled during the Convective Precipitation Experiment (COPE) experiment.

Abstract:

The COnvective Precipitation Experiment (COPE), occurring in the southwest UK during Summer 2013, was motivated to improve quantitative precipitation forecasting, in part, with the aim to increase understanding of the warm and cold precipitation processes that can produce heavy convective rainfall in the southwest UK. In particular, we examine the creation of graupel embryos, the Hallett-Mossop process, and the effect of entrainment on these processes. To characterize the evolution of cloud microphysical properties of maturing thunderstorms, the University of Wyoming King Air sampled the tops of fresh turrets between -15 and 0. Data sampled by the Cloud Droplet Probe, Cloud Imaging grayscale Probe (CIP-Grey) and 2D Precipitation Probe during four missions are examined. Here we characterize the variability of the cloud liquid and ice particle size distributions and liquid water contents (LWC) inside updraft cores, as a function of temperature, T, and vertical velocity, w.

On one of the days, the number concentration of particles with maximum dimension D > 300 µm, N_>300, was less than 1 L^-1, with very few ice hydrometeors observed. However, on the other missions, N_>300 ranged from 1 L^-1 to 250 L^-1. The CIP-Grey detected liquid drops at T > -5 and a mixture of graupel and rimed columns at T < -5 for these missions, consistent with the warm rain process providing the frozen drops necessary to form graupel embryos that initiate secondary production. In general, LWC relative to adiabatic decreased from 0.75 to 0.2 with height and was lowest when N_>300 > 1 L^-1, consistent with precipitation growth by collision-coalescence and accretion. Finally, ice precipitation was primarily present at w < 7 m s^-1 and greatest when w < 3 m s^-1, suggesting that w influences the number of ice particles generated in the updraft cores sampled during COPE-MED.