A modeling study of cloud physical properties of extreme and non-extreme precipitation in landfalling typhoons over China

Abstract

Extreme rainfall associated with landfalling tropical cyclones (ERLTC) can bring severe disaster losses. Revealing the typical characteristics and formation mechanisms of ERLTC has important scientific significance and potential application value. In this study, cloud microphysical properties of extreme and non-extreme rainfall in three landfalling TCs over China under the similar climatic backgrounds are comparatively investigated based on the cloud resolving simulations with a novel quantitative separating method of cold (warm) rain from the total precipitation. Results show that the warm (cold) rain may shape (modulate) the area (intensity) of TC precipitation. During the extreme precipitation period of the strongest TC Lekima (2019), the amount of cold rain accounts for >3/4 of the total precipitation, which plays a leading role in the precipitation rapid enhancement. With the increase of precipitation intensity, the proportion of cold (warm) rain to total precipitation tends to increase (decrease). The area near eyewall is commonly dominated by warm rain due to the weak radar echoes there. During the extreme precipitation process induced by Lekima (2019), the hydrometeor contents (mainly rain water and snow) increase rapidly and maintain for a long time. The processes of water vapor condensation, accretion of cloud water by rain water and melting of snow are the most active. In addition, the comparison with Hagupit (2020) and Yagi (2018) reveals that the processes of raindrop collecting graupel then melting, and the weak evaporation of raindrop make considerable contributions to the formation of extreme precipitation caused by Lekima (2019).