Numerical estimation of extreme waves and surges over the northwest Pacific Ocean

A coupled modelling framework, consisting of the FVCOM circulation model and FVCOM-SWAVE wave model, was used to numerically estimate extreme waves and surges over the northwest Pacific Ocean. The ECMWF ERA-Interim atmospheric reanalysis data with modification by a parametric typhoon model were used as surface forcing to simulate waves and surges for a 35-year period. The extreme waves and surges with a 100-year return period were then estimated with the Gumbel distribution. The results showed that the extreme wave heights generally decreased northward and shoreward, varying from 23 m in deepwater areas to less than 7 m in nearshore areas. The extreme wave heights in the east and southeast directions were found to be larger than those in other directions; and the extreme waves in summer and autumn were found to be larger than those in other seasons. The extreme surge levels were relatively large in the radial sandy ridge area of the Jiangsu coast, Hangzhou Bay and north of the Qiongzhou Strait. This study demonstrated an effective approach to improve the representation of typhoon in the numerical estimation of extreme events. The results provide insights into the temporal and spatial distributions of extreme waves and surges over the northwest Pacific Ocean.