Impacts Of The Symmetrical And Asymmetrical Typhoons On The Storm Surge Simulation In The East China And The South China Seas

An unstructured grid model FVCOM was used to simulate the storm surges in the regions of the Changjiang Estuary, the Hangzhou Bay, the Fujian coast, the Pearl River Estuary and the South China Sea. Two kinds of typhoon model, i.e. the unsymmetrical typhoon provided by the WRF model and the symmetrical typhoon calculated by using the Fujita formula, and their impacts on the storm surge in different regions were compared. In this paper three grids were built in the same simulation domain and refined locally in three concerned regions.The model results of storm surge simulation showed that the topography has slight effect on typhoon structure in the regions of the Changjiang Estuary, the Hangzhou Bay and the Pearl River Estuary, and the typhoons there are in symmetrical feature. The validations of wind, storm surge and total water level at the tidal gauge stations indicated that both of two kinds of typhoon can simulate the storm surge well around these regions, with the unsymmetrical typhoon producing the results slightly better. For typhoons crossing the Taiwan Island and then landing along the Fujian coast, the Taiwan Island has significant effect on their structure, and those typhoons are unsymmetrical obviously. Typhoon feature from symmetrical typhoon model is quite different from the unsymmetrical typhoon, because topographic factor is excluded in the former. The verifications indicated that the unsymmetrical typhoon by WRF can simulate storm surge better than the symmetrical typhoon model, and has a good coincidence with the measured value. WRF model can provide more real typhoon datas for improving storm surge simulation. Symmetrical typhoon model is not suitable to simulate typhoons landing in the Fujian coast.The influences of two kinds of unsymmetrical typhoon on storm surge by GRAPES model and WRF model were also compared via some cases, respectively. The simulated results from GRAPES were provided by the Shanghai Typhoon Institute. The results showed that GRAPES gives a better performance in typhoon track simulation than WRF, but it simulates typhoon stronger than WRF and causes storm surge more severely than observation. WRF can simulate asymmetrical typhoon better, though a little deviation in typhoon track simulation. On the whole, the unsymmetrical typhoon simulated by WRF model is more accurate than that simulated by GRAPES model.