A Comparative Study on the Formation Mechanisms of Persistent and Short-Duration Extreme Heavy Rainfall Events in South China

Based on the hourly gridded precipitation product merged from the ERA5 reanalysis data, Chinese automatic weather stations, and the CMORPH (Climate Prediction Center Morphing Technique) product, this study analyzes the precipitation characteristics and formation mechanisms of the extreme persistent heavy precipitation event on June 29, 2011, and the extreme short-term heavy precipitation event on April 25, 2013, in the coastal area of South China. Through the comparative analysis of the differences in the weather circulation backgrounds, water vapor transportation, and vorticity budget of the two events, the results show that the extreme persistent heavy precipitation event on June 29, 2011, is accompanied by a stable low-pressure weather system, dominated by an upper-level vortex and a stable low-level water vapor transport. While the extreme short-term heavy precipitation event on April 25, 2013, did not have a stable weather system. The low-level water vapor transport is weak, but the hourly precipitation is large due to the presence of the short-duration strong water vapor convergence. In addition, from the vorticity budget equation, the extreme persistent precipitation event on June 29, 2011, has a greater positive vorticity gain, with the low-level jet being the key contributor to the low-level vorticity gain, while the generation and intensification of mid-level vortex is crucial for mid-level vorticity gain. The positive feedback from the above two processes is important in sustaining the precipitation.