Study On The Effect Of Air-sea Interaction On The Intensity And Boundary Layer Process Of Typhoon Dujuan

As one of the most critical physical processes in the occurrence and development of tropical cyclones,air-sea interaction can affect the intensity and structure of tropical cyclones through a series of thermodynamic and dynamic factors,which are mainly realized through the boundary layer process.However,the current understanding of the mechanism and mechanism of the interaction between tropical cyclone and ocean is not enough,which has become one of the main reasons to restrict the promotion and development of tropical cyclone forecast and warning.In order to improve the understanding of the influence of air-sea interaction on the intensity and structure of typhoons,this study adopted the atmospheric and ocean coupling model and selected typhoon "Dujuan" in the northwest Pacific Ocean to carry out a high-resolution numerical test,so as to better simulate the strength evolution process and the characteristics of ocean cold wake.Based on the results,the influence mechanism of air-sea interaction on tropical cyclone intensity,overall structure and boundary layer process is analyzed.The main conclusions are as follows:(1)The cold wake can weaken the overall strength of the typhoon and reduce the wind speed in the boundary layer.Through calculation,it is found that although both the vertical diffusion coefficient and the inertial stability will decrease,the ratio between them,namely the scale parameter of the boundary layer height,will also decrease,thus leading to the reduction of the symmetrical height of the dynamic boundary layer.(2)A relatively cold wake with a relatively low sea surface temperature often appears behind the typhoon in the right direction of movement,resulting in asymmetric distribution of heat flux on the sea surface.The low value zone of sensible heat flux has a certain correspondence with the stratified stable zone,so it is easier to form stable boundary layer and stable near-stratum above the cold wake,and the near-stratum stable zone has a larger range than the boundary layer stable zone.(3)Through the potential temperature and moisture budget analysis of the boundary layer,it can be concluded that the air-sea interaction have a certain influence on the heat and water vapor cycling process in the typhoon boundary layer.The ocean cold wake can improve the proportion of water vapor obtained by ocean evaporation in the total water vapor content in the boundary layer effect,while weakening the overall strength of typhoons.Thereby it can affect the change of potential temperature and moisture budget.