Contrasting microphysics and environmental drivers of weak and intense convection-induced extreme precipitation: Insights from GPM DPR observations

Abstract

Under global warming, extreme precipitation events (EPEs) have become frequent worldwide, with unclear microphysical differences in convective clouds. The weak and intense convection-induced EPEs (WeEPEs and InEPEs, respectively) over South China are identified with 10-year spaceborne dual-frequency precipitation radar observations. Results suggest that most EPEs occur in morning and nighttime. The distribution of WeEPEs (land-prevalent) and InEPEs (ocean-prevalent) is regulated by ocean thermal gradients, moisture transport, and orographic lifting. Weak sea surface temperature (SST) gradients and southerly moisture transport generate offshore moisture centers. The humid environment in the ocean may help the formation of WeEPEs. Conversely, strong SST gradients, coupled with stronger southerly moisture transport form inland moisture centers, with orographic forcing enhancing upward motion for strong convection. Weak convection generates extreme precipitation through synergistic increase in particle size and concentration below the 0 °C level, with high concentration being more critical. For oceanic events, InEPEs show a slightly larger particle diameter increase (0.11 mm) below the 0 °C level. However, WeEPEs have a much greater concentration increase (4.34 dB), resulting in a larger reflectivity factor increase (7.58 dBZ). For the most extreme precipitation, even if one of the warm-rain process and the ice-phase process dominates, the other still plays a significant role. Across eventsof different regions, continental WeEPEs reach peak rates through ice-particle melting (16.1 mm/h) and warm-rain coalescence to enhance particle size (70.6 mm/h); marine InEPEs (102.02 mm/h) rely on high liquid water path and efficient coalescence for maximum rates (warm-rain contribution: 43.3 mm/h).