Simulation Of Typhoon Fung-wong By Air-Sea Coupled Model COAWST

Typhoon has a great influence on China every year,and in order to improve the simulation of typhoon processes,the interaction between air and ocean should be considered.Now more and more air-sea coupling models have been used in the study of interaction of cyclone and ocean.The COAWST(The fully coupled Atmosphere-Wave-Ocean model)air-sea two-way coupled model,the WRF(The Advanced Research Weather Research and Forecasting)and the ROMS(Regional Ocean Modeling System)one-way coupled model are utilized to simulate the atmosphere and ocean processes during transit of typhoon Fung-wong,which is the No.8 cyclone in 2008.The results show,for the simulation of typhoon track,the results from coupled and uncoupled model are similar,indicating that the cyclone track is mainly controlled by the large-scale air circulation field,rather than the local process"solved"by the interaction between atmosphere and ocean.The intensity of the cyclone debilitated after adding the feedback of sea surface temperature cooling into atmosphere model.According to the statistics of correlation and root mean square error,the coupled model is superior to the uncoupled model In the simulation of ocean,the coupled model accurately simulates the change of sea surface temperature during the cyclone transit,which is consistent with the MER SST data,and the results are obviously better than the uncoupled model.By studying the response of Fung-wong to ocean,we found that typhoon could barely intensify rapidly on the ocean,which with low TCHP(tropical cyclone heat potential),shallow 26 ? isotherm and mixing layer depth.Different sea surface temperature inferior cyclone mainly affects the distribution of wet enthalpy in the inner core of typhoon,especially at the maximum wind speed radius.Sea surface temperature decreased 1 ? and the enthalpy flux decreased 36%-43%.The higher sea surface temperature is,the greater is moist static energy of bottom atmosphere;The higher difference in moist static energy between cyclone center and periphery is,the stronger is intensity of the cyclone.The correlation between thermodynamic variables in the upper ocean and the intensity(strength)of cyclone shows that there is the best correlation between typhoon intensity and mixing layer depth within 50?200 km from the center of cyclone,followed by upper 100m ocean temperature,26 ? isotherm depth and SST within 100?200 km around the cyclone center.The most obvious response of marine to cyclone transit is the decrease of sea surface temperature,and the areas where the Fung-wong has caused significant cooling in the open ocean and inshore have been studied separately.The results show that the temperature drop in open ocean is mainly caused by vertical entrainment and the decrease of net heat flux(vertical diffusion term)in upper 50m,and below 50m,the drop is mainly caused by the cold water brought by vertical convection.Horizontal convection has little contribution to the cooling in this area.In the near-shore area,there is a significant temperature drop over 8 ? in the northeast of Taiwan Island,which is caused by the continuous easterly wind during the passage of cyclone,which"induced"the cold water to surface.