Numerical study on the influence of internal tides on tropical-cyclone-induced sea surface temperature cooling in the South China Sea

Sea surface temperature (SST) cooling is a typical ocean response to tropical cyclones (TCs). Previous studies have shown that TC-induced SST cooling is influenced by the TC characteristics, ocean stratification, and background vorticity. However, whether internal tides (ITs) affect TC-induced SST cooling remains unclear. Based on a series of numerical simulations in the South China Sea, the influence of ITs on TC-induced SST cooling is explored in this study. Results indicate that ITs can enhance TC-induced SST cooling by 0.2 - 0.4 degrees C in the Luzon Strait. Temperature budget analysis shows that ITs modulate the SST cooling mainly through changing the vertical mixing and advection. In the Luzon Strait, ITs enhance the vertical mixing but suppress the vertical advection. Because the contribution of vertical mixing to SST cooling is one order of magnitude higher than that of vertical advection, ITs enhance TC-induced SST cooling in the Luzon Strait mainly through enhancing the vertical mixing. Moreover, the enhancements of vertical mixing and SST cooling induced by ITs are found to be related to the TC characteristics. One reason is that in addition to ITs, the high-frequency waves generated by the interaction between TC-induced near-inertial waves and ITs also contribute to the shear and hence the turbulent mixing.