Investigating typhoon-induced storm surge and waves in the coast of Taiwan using an integrally-coupled tide-surge-wave model

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The coupled tide-surge and wave model was established for the coast of Taiwan and applied to simulate the storm surge during typhoon events. To prove the capability and availability of the coupled model, the model was calibrated and validated with measured water levels, atmospheric pressures, wind speeds, wave heights, and wave periods at different gauge stations under different historical typhoon events. Based on the statistical metrics including the mean absolute error, root mean square error, and skill, the simulated tide-surge, wave height, and wave period using coupled tide-surge-wave model reasonably reproduced the observational data. The parametric typhoon model provided reasonably simulated results compared to the observed atmospheric pressure and wind speed. The validated model was then utilized to explore the impact of waves on the storm surge and the influences of typhoon track, wind stress, and atmospheric pressure on the surge height around the Taiwan coast. The results showed that comparing the simulated water levels using the tide-surge-wave model and the tide-surge model, the averaged differences at Taipei Tamsui, Taichung Harbor, Kaohsiung Harbor, and Hualien Harbor are 0.24 m, 0.23 m, 0.22 m, and 0.22 m, respectively. The wave setup contributes between 6% and 35% to the total storm surge on Taiwan's coast. Furthermore, the typhoon track significantly affects the location of low pressure and the wind direction, subsequently causing the increase/decrease in surge height. The intensity of wind stress and the atmospheric pressure play crucial roles in affecting the water level and dominating the surge height along the coast of Taiwan.