Evaluation and improvement of the ERA5 wind field in typhoon storm surge simulations

Based on ERA5 reanalysis data and an established global storm surge model, storm surge numerical simulations and wind speed analyses of eight historical typhoon events were carried out. The storm surge forcing from the ERA5 wind field was found to be systematically smaller than observed, and an analysis showed that large ERA5 wind speeds are significantly smaller than the observations, with the deviation rising with increasing wind speed. To solve this problem, we improved ERA5 by superimposing the Holland typhoon model wind field onto ERA5 to create a hybrid wind field, and two numerical simulation experiments of storm surges were carried out. The simulation results show that the average relative error of the maximum surge height decreased from 33.4% to 7.9% and from 25.0% to 10.0%. This method can significantly improve the wind speed and storm surge simulation accuracy in the ERA5 wind field near the typhoon center.