Analysis of the Causes of Typhoon"Chaba"Heavy Precipitation Under Strong Southwest Monsoon Background

XIAO Ting; CHENG Zhengquan; LIU Zijie; JIAO Yang; SHEN Xiaodian

doi:10.16032/j.issn.1004-4965.2025.034

Abstract：Based on the best tropical cyclone track data provided by China Meteorological Administration,rainfall observations data and ERA5 reanalysis data,the causes of large-scale sustained heavy rainfall caused by Typhoon 2203 Chaba in South China were analyzed.The results show that:(1)Chaba is connected with the strongest Southwest monsoon in 2022 for a long time,and obtains continuous water vapor and unstable energy supply in the process of interacting with the monsoon.(2)The abnormally strengthened upper level outflow superimposed on the abnormally strengthened lower level southwest jet,forming a strong coupling and suction effect,resulting in strong convergence and upward movement at the lower level.(3)The low-level southwest jet passes through the continental warm air mass and is heated,transporting strong warm advection to Guangdong;The strong upward movement transported the convective instability from the lower layer to the upper layer,which resulted in the thickening of the convective instability layer,and the weakening of the pseudo equivalent temperature advection with height also resulted in the strengthening of the local convective instability,which together led to the long-term maintenance of the atmospheric instability stratification in Guangdong.(4)After the landfall of Chaba,the low-level air flow was guided and blocked by mountains,and the secondary circulation generated was conducive to the local vorticity growth and the occurrence of heavy rain.In addition,the small environmental vertical wind shear makes the high-level warm core structure still not disappear after the landfall of Chaba,forming a divergence flow field in the upper air,which is also conducive to the occurrence of heavy precipitation.