Abstract:

 Ice-phase microphysical processes are crucial to precipitation formation, especially in deep convection and its organized form of Mesoscale Convective Systems (MCSs). Many details of these processes remain unresolved partly due to the difficulties of in-situ observations, especially in the strong convective regions where mixed-phase microphysics dominate. Our study analyzes data from space-borne Dual-frequency Precipitation Radar (DPR) onboard the NASA Global Precipitation Measurement (GPM) satellite to decipher ice-phase particles’ bulk density and its spatial variations within the MCSs.

We use a 3-year compilation of GPM observed MCSs during the summer months in West Africa Monsoon region. We take advantage of the high vertical resolution of the GPM/DPR observations to study vertical profiles of ice-phase particle sizes and densities along their falling paths. The GPM/DPR statistics indicate that microphysical processes, inferred from the vertical evolution of particle densities and sizes, are much more closely related to storm dynamics than locations within the MCS as seen by the conventional convective/stratiform separation using radar observations. High-density particles associated with the riming process are present only inside the active updraft cores in the DPR algorithm labeled convective region. The rest of the convective region shows remarkably similar characteristics compared with the stratiform region in DPR data. This is likely due to the low vertical velocity outside the active convective core which cannot support supercooled liquid droplets and associated riming process. The implications of the dynamic separation of the convective/stratiform region instead of a morphological one as currently used in radar meteorology will also be discussed.