Analysis of Sea Surface Temperature Cooling in Typhoon Events Passing the Kuroshio Current

The aim of this study is to investigate the sea surface temperature (SST) cooling as typhoons pass the Kuroshio Current. A numerical circulation model, denoted as the Stony Brook Parallel Ocean Model (sbPOM), was used to simulate the SST, which includes four wave-induced effect terms ( i.e. , radiation stress, nonbreaking waves, Stokes drift, and breaking waves) simulated using the third-generation wave model, called WAVEWATCH-III (WW3). The significant wave height (SWH) measurements from the Jason-2 altimeter were used to validate the WW3-simulated results, yielding a root mean square error (RMSE) of less than 0.50 m and a correlation coefficient (COR) of approximately 0.93. The water temperature measured from the Advanced Research and Global Observation Satellite was applied to validate the model simulation. Accordingly, the RMSE of the SST is 0.92°C with a COR of approximately 0.99. As revealed in the sbPOM-simulated SST fields, a reduction in the SST at the Kuroshio Current region was observed as a typhoon passed, although the water temperature of the Kuroshio Current is relatively high. The variation of the SST is consistent with that of the current, whereas the maximum SST lagged behind the occurrence of the peak SWH. Moreover, the Stokes drift plays an important role in the SST cooling after analyzing four wave-induced terms in the background of the Kuroshio Current. The sensitivity experiment also showed that the accuracy of the water temperature was significantly reduced when including breaking waves, which play a negative role in the inside part of the ocean. The variation in the mean mixing layer depth (MLD) showed that a typhoon could enhance the mean MLD in the Kuroshio Current area in September and October, whereas a typhoon has little influence on the mean MLD in the Kuroshio Current area in May. Moreover, the mean MLD rapidly decreased with the weakening of the strong wind force and wave-induced effects when a typhoon crossed the Kuroshio Current.