Improved summer daily and sub-daily precipitation over Eastern China in convection-permitting simulations

Based on the long-term (1998-2007) regional climate simulations using the Weather Research and Forecasting (WRF) model with three different horizontal resolutions (36 km, 12 km and 4 km), this work examines the improvement of convection-permitting regional climate model (CP RCM) in simulating the daily and sub-daily precipitation over eastern China. CP RCM produces more reliable mean precipitation and more realistic wet day frequency as well as better low-level wind and moisture than those in the convection-parameterized counterpart. Due to the more realistic surface heterogeneities, CP RCM distinctly improves the representation of hourly precipitation by increasing the occurrence of high-intensity precipitation compared to the 36-km and 12-km simulations, especially over areas with complex topography. Moreover, the improvement of diurnal variation of low-level wind direction and moisture convergence also coincides with the more reasonable diurnal amplitude and nocturnal precipitation in CP RCM as compared to the 12-km and 36-km simulations. Because of the better depiction of convection and its interaction with large-scale motions, CP RCM has a clear advantage in reproducing low-level wind and moisture, which lead to the better reproduced sub-daily precipitation. This study provides greater confidence in the projection of future climate change using CP RCM.

Automated summary

This study investigates the improvement of convection-permitting regional climate model (CP RCM) in simulating daily and sub-daily precipitation over eastern China using long-term regional climate simulations. The results show that CP RCM produces more reliable mean precipitation, realistic wet day frequency, and better low-level wind and moisture compared to the convection-parameterized counterpart. The more realistic surface heterogeneities in CP RCM also lead to better representation of hourly precipitation, especially in areas with complex topography. Furthermore, CP RCM exhibits a better depiction of diurnal variation of low-level wind direction and moisture convergence, resulting in more reasonable diurnal amplitude and nocturnal precipitation. The improved representation of convection and its interaction with large-scale motions in CP RCM gives it an advantage in reproducing low-level wind and moisture, leading to better sub-daily precipitation. This study provides greater confidence in using CP RCM for future climate change projection.