The Outer‐Core Wind Structure Effects of Doksuri (2023) on the Heavy Rainfall Event in North China

Abstract

While considerable attention has been paid to factors that determine the inner‐core and remote structure of tropical cyclone (TC) rainfall, less attention has been paid to what modulates TC rainfall distribution at intermediate distances. This study investigates the sensitivity of TC rainfall post‐landfall to variations in the structure of the outer‐core wind, with a focus on the impact of these outer‐core wind variations on rainfall distributions at intermediate distances from the TC center, using TC Doksuri (2023) as a case study. Two sensitivity experiments are performed, where outer‐core wind speeds at landfall are increased by 25% (EXP1) and 50% (EXP2). Results have shown that stronger TC outer‐core wind has competing effects on the precipitation amounts both when the landfalling system retains its TC structure as well as after it has become a vortex remnant. Stronger outer‐core winds in EXP2 intensify water vapor transport during the TC stage, increasing precipitation amount. In the early remnant stage, the stronger outer‐core wind in EXP2 enhances low‐level water vapor flux and orographic uplift. However, the vortex exhibits a decoupling of the cyclonic circulation from the surface later in the remnant stage in EXP2, contracting the low‐level wind field. This contracts both the water vapor transport channel and strongest orographic uplift area, contributing to reduced precipitation amounts. In addition, the decoupling leads to an earlier dissipation, which reduces the precipitation amount at the end of the remnant stage. EXP1, by contrast, produces the most rainfall through a combination of stronger orographic uplift and remnants that persist throughout the time period. These results show the complex relationship between outer‐core wind and accumulated rainfall, highlighting the importance of predicting the evolution of the TC wind structure post‐landfall for improved rainfall prediction.