Ocean temperature responses to Typhoon Mstsa in the East China Sea

The MASNUM wave-tide-circulation coupled model, with 21 layers in the vertical and (1/8)°horizontal resolution, was employed to investigate the oceanic responses to Typhoon Mstsa which traversed the East China Sea (ECS) during the period of 4~6 August, 2005. Numerical experiment results are analyzed and compared with observation. The responses of the sea surface temperature (SST), in a focused area of (27°~29°N, 121°~124°E), include heating and cooling stages. The heating is mainly due to warm Kuroshio water transportation and downwelling due to the water accumulation. In the cooling stage, the amplitude of the simulated cold wake (~3℃), located on the right side of this typhoon track, is compared quite well with that of the satellite observed SST data. The wave-induced mixing(Bv) plays a key role for the SST cooling. Bv still plays a leading role, which accounts for 36%, for the ocean temperature drop in the upper ocean of 0~40 m, while the upwelling is responsible for 84% of the cooling for the lower layer of 40~70 m. The mixed layer depth (MLD) increased quickly from 28 to 50 m in the typhoon period. However, the simulated MLD without the wave-induced vertical mixing, evolution from 13 to 32 m, was seriously underestimated. The surface wave is too important to be ignored for the ocean responses to a typhoon.