The Modulation of Tropical Cyclone Intensity by Subsurface Salinity Stratification: An Idealized Study Using Coupled General Circulation Model

Abstract

Tropical cyclone (TC) intensification is strongly influenced by the oceanic thermal structure, shaped by both temperature and salinity stratification. However, the mechanisms by which salinity stratification modulates TC intensity remain insufficiently quantified, particularly regarding the relative contributions of different oceanic dynamical processes. Based on simplified modeling frameworks, previous studies have primarily identified vertical mixing as the main factor controlling ocean response. Here we conducted idealized experiments using a fully coupled atmosphere–ocean model to systematically examine the role of salinity stratification in TC evolution. Heat budget analysis shows that, under varying salinity stratifications, total advection dominates the differences in sea surface temperature (SST) and TC intensity, while vertical mixing only plays a secondary role. Further decomposition of the total advection term reveals that these differences are primarily associated with variations in vertical advection. Specifically, for a fast‐moving TC, an intact barrier layer (BL) enhances vertical advection by intensifying vertical velocity gradients. When the TC moves sufficiently slowly, the BL is fully eroded, the inversion layer vanishes, and the influence of salinity stratification on TC intensity is substantially diminished. Overall, this study highlights the key role of total advection in mediating the impact of salinity stratification on TC intensity, providing a process‐based understanding of air–sea interaction and a physical basis for improving TC intensity prediction.