On the Extreme Precipitation Events With and Without Lightning Over Eastern and Southern China

Abstract

Extreme precipitation events (EPEs) without severe convective weather signatures such as frequent lightning may be more difficult to forecast and potentially more dangerous. This study investigates the differences in the macro- and micro-structures between EPEs with and without lightning over eastern and southern China, as well as their underlying environmental conditions. EPEs are defined as convective features with maximum hourly rain rate reaching the gauge-based climatological extreme precipitation threshold (99.9%). Results show that EPEs with lightning (EPE_LIG) account for 51%, and the other 49% EPEs have no lightning (EPE_NoLIG), whose fractional maxima are located along the coast. Most EPE_NoLIGs are embedded in large organized precipitation systems, although their convective cores are smaller than EPE_LIGs. The parent systems of both EPE types are multicellular in nature, but those of EPE_NoLIGs are more likely to produce multiple extreme precipitation centers. EPE_LIGs have the most intense convection, which is stronger than regular thunderstorms (NonEPEs with lightning), while the convective intensity of EPE_NoLIGs is just close to NonEPEs. Microphysical processes of the two types of EPEs differ significantly. The downward increasing radar reflectivity profiles and drop size distribution analyses suggest that warm-rain processes highly dominate (94.1%) in the formation of extreme precipitation in EPE_NoLIGs. Even for EPEs with very active ice-based processes (EPE_LIGs), warm-rain processes still contribute significantly (83.31%). The large-scale environments of EPE_NoLIGs are featured by a relatively convectively stable but deep moist troposphere and enhanced low-level southwesterly winds, highlighting the importance of excessive moisture transport and convergence in these events.