Transport Reversal Due to Typhoon Krosa in the Taiwan Strait

Abstract

A comprehensive hydrodynamic model, COMCOT-S, has been aimed at transport reversal in the Taiwan Strait during the period of Typhoon KROSA in 2007. The numerical model is originally based on COMCOT, and a parametric wind model with atmospheric sub-model is imbedded in COMCOT-S for simulating the typhoon-induced currents. The transport characteristics through the Taiwan Strait under the influence of Typhoon KROSA were analyzed using both field observations and numerical simulations during the period from 05 October to 08 October 2007 (GMT+8). The re- sults show that typhoon-induced currents did not fully response to the cease of the northward winds after the flow rever- sal, representing the influence of other dynamical forces on the flow orientation in the Taiwan Strait. Typhoon-induced wind shear stress and the water level gradient are found to be the direct driving forces of the southward transport events, whereas the atmospheric pressure gradient is dominant after the southward transport peak. By comparing with six numeri- cal experiments, the result of finer grid resolution is in good agreement with the observed current data at THL1 station near Mailiao Harbor. According to the transport simulation of numerical experiments, the Coriolis force is found to play a dominant role in the transport reversal as well, especially in the north Taiwan Strait. Besides, it is more relevant in the Penghu Channel than in the Taiwan Banks that the Coriolis force makes a negative contribution to the southward transport events. Finally, it's verified that the generation of an anticyclonic eddy near the Changyun Rise would not be reached without the contribution of the Coriolis force to the northward transport in the Penghu Channel.