Impacts of nonbreaking wave-stirring-induced mixing on the upper ocean thermal structure and typhoon intensity in the South China Sea

To investigate the effect of nonbreaking wave-induced mixing caused by surface wave stirring on the upper ocean thermal structure (UOTS) and the typhoon intensity, a simple nonbreaking wave-stirring-induced mixing parameterization (WMP) scheme is incorporated into a regional coupled atmosphere-ocean model for the South China Sea (SCS), which couples the Princeton Ocean Model (POM) to the Weather Research and Forecasting (WRF) model using the OASIS3 coupler. The results of simulating two selected typhoon cases indicate that the nonbreaking wave-stirring-induced mixing has significant impacts on UOTS and the typhoon intensity, and the incorporation of the simple WMP scheme in the coupled model helps to improve the simulation of UOTS and thus the typhoon intensity. In the case that the typhoon intensity is underestimated by the atmosphere model alone, the improvement of initial UOTS by the ocean model with the WMP included can deepen the initial thermocline depth, reduce the effect of SST cooling, and prevent the typhoon intensity from undesired weakening. In the case that the typhoon intensity is overestimated (with strong winds), including the WMP in the ocean model significantly enhances the total vertical mixing rate in the upper ocean, which in turn enhances the SST cooling and thus reduces the typhoon intensity as desired. The results obtained in this study make a contribution to the ongoing efforts of improving the typhoon intensity forecast using a regional atmosphere-ocean coupled model by worldwide researchers and forecasters, especially for the typhoons in the SCS regions.