A two-way nested coupled tide-surge model for the Taiwan Strait

A two-way nested coupled tide-surge prediction model was established and applied in the Taiwan Strait and adjacent sea area in this study. This two-dimensional (2D) model had a fine horizontal resolution and took into account the interaction between storm surges and astronomical tides, which made it suitable for depicting the complicated physical properties of storm surges in the Taiwan Strait. A two-way nesting technique and an open boundary condition developed from Flather's radiation condition and Røed and Smedstad's local mode idea, were successfully implemented in the model. A simulation experiment showed that the open boundary condition could be used in the coupled tide-surge model and that the performance of the two-way nested model was slightly superior in accuracy to that of the one-way nested one.The fluctuations of storm surge residuals with tidal period at Sansha and Pingtan tide stations during the period of typhoon Dan in 1999 were well reproduced by the model, with the coupling effect between storm surges and tides indicating that the effect of astronomical tides upon typhoon surges should be considered in a storm-surge prediction model for the Taiwan Strait. The forecast experiment during typhoon Talim in 2005 showed that the storm surge prediction outputs by the model were better in the early 20 h of the forecast period of each model run than those in the later period due to the prediction accuracy of the typhoon track, maximum winds, and central air pressures.