Typhoon Process Simulation Based On A Coupled Atmosphere–Ocean–Wave Model

The ocean and atmosphere interact with each other during the process of tropical cyclones.The wind stress induces ocean current,sea surface temperature cooling and a change of sea surface roughness.In turn,the changes of the upper ocean affect the evolution of tropical cyclones.The interaction of atmosphere,ocean and wave should be involved in the numerical simulation,which is helpful to improve their forecast and hindcast accuracy during tropical cyclones.Using the Model Coupling Toolkit,based on the atmosphere model WRF,the third-generation wave model SWAN and the unstructured-grid ocean model FVCOM,an online coupled modeling system has been developed.The coupled model is improved and applied in the simulation of typhoon process in the present study.The main contents and conclusions are summarized as follows.1.To improve the coupled model,the long wave radiation,short wave radiation,sensible heat flux,latent heat flux,precipitation,evaporation,and sea surface pressure are exchanged between FVCOM and WRF model.The influences of different cumulus parameterization schemes,microphysics schemes,longwave and shortwave radiation schemes on the typhoon track and intensity are analyzed.2.With proper WRF parameters the coupled model is used to simulate the typhoon process of Rammasun and Kalmaegi in 2014.The averaged deviations of simulated track during Rammasun and Kalmaegi are 50 km and 35 km,respectively.The simulated change trend of the typhoon intensity,which increases at the beginning and then decreases,agrees with JMA best track datasets.3.The sea surface temperatures cooling,and the rotation and rightward bias of ocean current and wave height enhancement are also reasonably described by the coupled model.When the typhoon center was moving in the deep ocean the maximum SST cooling reaches 4°C during Rammasun,and it is about 1.4°C during Kalmaegi;the current velocity near Rammasun moving track reaches 2m/s,and it is 1.25m/s during Kalmaegi.The maximum significant wave height during Rammasun is 14.8m,and it is 13.4m during Kalmaegi.