Study of the air-sea interaction during Typhoon Kaemi (2006)

The high-resolution Weather Research and Forecasting (WRF) model is coupled to the Princeton Ocean Model (POM) to investigate the effect of air-sea interaction during Typhoon Kaemi that formed in the Northwest Pacific at 0000 UTC 19 July 2006. The coupled model can reasonably reproduce the major features of ocean response to the moving tropical cyclone (TC) forcing, including the deepening of ocean mixed layer (ML), cooling of sea surface temperature (SST), and decaying of typhoon. Due to the appearance of maximum SST cooling to the left of the simulated typhoon track, two points respectively located to the left (16.25A degrees N, 130.1A degrees E, named as A, the maximum SST cooling region) and right (17.79A degrees N, 130.43A degrees E, named as B) of the typhoon track are taken as the sampling points to study the mechanisms of SST cooling. The low temperature at point A has a good correlation with the 10-m winds but does not persist for a long time, which illustrates that the temperature dropping produced by upwelling is a quick process. Although the wind-current resonance causes oscillations to the left of typhoon track at point A, the fluctuation is not so strong as that at point B. The thin ML and upwelling produced by the Ekman pumping from strong 10-m winds are the main reason of maximum SST cooling appearing to the left of the typhoon track. Due to weaker 10-m winds and thicker and warmer ML at point B, the colder water under the thermocline is surpressed and the temperature dropping is not dramatic when the strongest 10-m winds occur. Afterwards, the temperature gradually decreases, which is found to be caused by the inertial oscillations of the wind-current system.