Influence of Ocean Salinity on Tropical Cyclone Intensification in the Western North Pacific

Tropical cyclone (TC) intensification is strongly regulated by air–sea interactions and the thermal–salinity structure of the upper ocean. While salinity stratification influences vertical mixing and mixed-layer stability, its role in modulating rapid intensification (RI) remains insufficiently quantified in fully coupled modeling systems. Here we investigate multiscale air–sea coupling during Super Typhoon DOKSURI using a high-resolution Unified Wave Interface–Coupled Model (UWIN-CM). The UWIN-CM couples the Weather Research and Forecasting (WRF) Model, the University of Miami Wave Model (UMWM), and the Hybrid Coordinate Ocean Model (HYCOM) in a single framework that explicitly resolves momentum, heat, and freshwater exchanges among the atmosphere, surface waves, and ocean. Model simulations show that salinity-stratified barrier layers and subsurface warm layers suppress vertical entrainment beneath the storm core, thereby limiting storm-induced sea surface cooling and preserving near-surface ocean thermal energy during the intensification phase. The reduced surface cooling sustains stronger air–sea enthalpy fluxes and maintains elevated boundary-layer moist static energy, reinforcing the thermodynamic support for continued RI. Comparative experiments further demonstrate that salinity-controlled modulation of upper-ocean mixing governs the surface thermal response, whereas the associated enhancement of sea surface temperature and latent heat flux acts mainly as a positive feedback that reinforces storm convection.