Volume transport through the Taiwan Strait and the effect of synoptic events

Volume transport through the Taiwan Strait during 2005–2008 was simulated using a shallow water model forced by high spatio-temporal resolution meteorological data. On average, simulated monthly mean transports ranged from a southward maximum of 0.38 Sv in December to a northward maximum of 2.02 Sv in June, with an annual mean northward transport of 0.78 Sv. These estimates are in agreement with the published results based on bottom-mounted ADCP observations. Several sensitivity experiments were conducted to separately examine possible influence of ignoring air pressure or applying time-averaged wind forcing on the transport estimate. We found that excluding the air pressure component in the model gave rise to an insignificant difference (0.01 Sv) in the mean transport estimate. Using multi-year-averaged monthly mean wind, however, provided markedly different results; it brought about a magnitude change of up to 0.65 Sv for the monthly mean transport and 0.34 Sv for the annual mean transport. The nonlinear parameterization of wind stress was mainly responsible for the distortion. In addition, we found that typhoons, as one kind of synoptic events, had an accumulative influence not only on the monthly mean transport during the typhoon season but also on the annual mean transport. The effect of typhoons reduced the monthly mean transport by up to 0.45 Sv and the annual mean transport by 0.09 Sv (more than 10%). Therefore, high temporal resolution wind data with synoptic scale variability are required to accurately estimate the monthly mean and annual mean transports when using a model.