Abstract: Twenty historical typhoons which had a great impact on the Zhoushan sea area, were selected to perform analyses and inductions of the measured tidal level data at Dinghai station. It was found that in these twenty typhoons, the maximum storm surge was 207.1 cm under the Typhoon 5612, and the maximum storm high tidal level was 283.7 cm under the Typhoon 9711. Further, a 3D baroclinic hydrodynamics model, SELFE, was used to establish an unstructured triangular grid astronomical tide-storm surge coupled model, through adding the typhoon pressure field and wind field modules. The numerical results show that the baroclinic effect is more obvious while the nonlinear coupling is relatively weaker. But the two-tides-coupled storm surge data are still better than the single-factor data and closer to the measured data. On this basis, in the north and south of the original path of the Typhoon 5612, two parallel paths at certain intervals were designed respectively. The corresponding results show that the supposed typhoon which adopts the parameters of the Typhoon 5612 and moves along the S1 parallel path in the south of the original typhoon path at a distance interval of a maximum wind radius, can induce the probable maximum storm surge of approximately 243.9 cm. Finally, supposing that the probable maximum storm surge separately encounters the astronomical high, middle or low tidal level, it is found that there appears a probable maximum storm high tidal level of about 400 cm when encountering the astronomical high tide.

Key words: storm surge, baroclinic, nonlinear coupling, probable maximum storm surge, numerical model, Zhoushan Island