Impact Of Boundary Layer Parameterization Schemes On The Simulation Of Typhoon�Lekima�

Based on the six optional parameterization schemes of the atmospheric boundary layer physical process provided by the mesoscale numerical model WRF(BouLac,MYJ,UW,YSU,ACM2,and SH),the simulation results of Typhoon "Lekima" were compared and analyzed in this paper.The results show that different boundary layer schemes have little effect on the simulation results of the track of "Lekima",but have a significant impact on the simulation results of its intensity and structural evolution.The simulation results of the local closure scheme UW are the strongest,followed by the local closure BouLac,while the simulation intensities of the local closure MYJ and the three non-local schemes YSU,ACM2,and SH are weaker.Among them,the typhoon track simulated by YSU is the closest to the real situation,and the lowest air pressure simulated by BouLac is the closest to the real situation.Through comparing the results from the different boundary layer schemes,it is found that,the difference in typhoon intensity is affected by both thermal and dynamic forces,the larger the surface latent heat flux and turbulent diffusion coefficient in the boundary layer are simulated,the larger the radial winds and low-level convergence will be generated,and thus the stronger the simulated typhoon,and vise versa.As the interaction between sea and air is one of the important physical processes in the boundary layer,typhoon interacts with the ocean surface through the low-level wind field,which leads to it can obtain a lot of heat and water vapor from the ocean surface and reduce the sea surface temperature.Meanwhile,it will transport momentum to the ocean in the form of ocean current.The dynamic roughness can mainly regulate the momentum exchange between sea and air,and has a partial influence on the ocean response caused by typhoon wind field.The heat and water vapor exchange between sea and air is mainly affected by the thermal roughness.Therefore,this paper also compares and analyzes the effects of four roughness schemes in the boundary layer process on the simulation of Typhoon Lekima.Among them,Opt3 is a newly added test scheme,while Opt0,1 and 2are the original roughness schemes in the WRF model.It can be found from the simulation results that the typhoon is very sensitive to the roughness length,and the typhoon intensity simulated by the four schemes has a great difference,which also reflects that the sea-air interaction has a great impact on the typhoon intensity.