Comprehensive analysis of marine heatwaves and ocean thermal structure impact on typhoon intensification in the East China Sea

Abstract

This study utilizes satellite observations and high-resolution reanalysis data to investigate the potential mechanisms of typhoon intensification in the East China Sea (ECS) from 1993 to 2022. Oceanic and atmospheric conditions within the wind radii of 30 and 50 knots surrounding typhoons were analyzed. During the study period, 30 out of 91 typhoons traversing the ECS intensified. The results show that intensified typhoons typically experienced relatively warmer sea surface temperatures and higher average ocean heat content (OHC) than non-intensified typhoons. Intensified typhoons exhibited lower vertical wind shear and slightly higher relative humidity, which helped maintain storm structure organization and enhanced upper atmospheric moisture. However, variability among individual typhoons was significant. The analysis also indicates that these favorable thermal structures, characterized by high OHC, enhance typhoon intensity with only about 40 % probability. The mixed layer depth in the ECS is generally shallow, averaging less than 25 m, with minimal variation between intensified and non-intensified typhoons, making it challenging to use ocean stratification as a determinant for typhoon intensification. Furthermore, marine heatwave (MHW) events do not significantly alter the upper ocean thermal conditions during typhoon passage, indicating that typhoon intensification due to MHWs might be exceptional, with some typhoons potentially weakening as they encounter these conditions. This study underscores the difficulties of predicting typhoon intensity changes in the ECS's complex marine environment, posing ongoing challenges for coastal disaster management.