Seasonal variations in precipitation microphysics over East China based on GPM DPR observations

Abstract

The disdrometer-observed raindrop size distribution (DSD) in East China has been shown to vary across seasons and rainfall types. In this study, as an extensive research, the seasonal variations of vertical structures and associated microphysical processes of precipitation were investigated using nine-year measurements of dual-frequency precipitation radar on board the Global Precipitation Measurement satellite. The spatial distribution and vertical profiles of the reflectivity factor (Ze), mass-weighted mean diameter (Dm), and generalized intercept parameter (Nw) showed different magnitudes of variability among seasons (and rain types). Generally, the collisional-coalescence process was dominant for sufficient raindrop growth in convective precipitation, followed by the breakup of melted large ice particles. Summer convective precipitation exhibited typical monsoonal features with the largest Ze and Dm values, whereas extremely weak winter convective precipitation exhibited stratiform-like characteristics. For stratiform precipitation, the major microphysical processes were competitive between the breakup and coalescence processes during different seasons. In contrast, collisional coalescence was predominant in the shallow convective precipitation throughout the year. The distribution of rainfall and DSD parameters with respect to storm top height also varied. Specifically, the storm (convective core) top converged around the upper (middle) troposphere during extreme rainfall, indicating moderate convection where Dm reached its maximum with moderate log10Nw. Warm-rain processes also play an important role in raindrop growth. Moreover, the discrepancies between the extreme rainfall and the highest echo top suggest a weak linkage between the heaviest rainfall and tallest storms. This study provides a comprehensive picture of the seasonal variability in precipitation microphysics in East China.