| In this paper,using the HWRF-V4.0a model and the adaptive observation sensitivity method,from the perspective of the internal parameterization process of the model and the improvement of the initial value of the model,Numerical simulation sensitivity experiments are carried out on the prediction of typhoon intensity and track to explore the influence of physical process parameterization scheme and horizontal diffusion and initial model value on typhoon simulation.This article selects the 15 th typhoon Lingling in the Western Pacific in2019.By changing the horizontal diffusion coefficient(h?diff)and the planetary boundary layer parameterization scheme,six sets of idealization and four sets of sensitivity experiments are designed.Selecting the super typhoon Mangkhut in 2018 and the typhoon Higos in 2020,the adaptive observation sensitivity method is used to estimate the observation sensitive area of typhoon forecast,and a series of assimilation sensitivity experiments of the observation sensitive region are designed.The numerical simulation experiment results of the horizontal diffusion and parameterization scheme show that in an ideal experiment,the horizontal diffusion coefficient is very sensitive to the intensity of the typhoon during the explosive growth period.When the horizontal diffusion coefficient is increased,during the explosive growth period of the typhoon,the vertical slope of the typhoon eye area increases,and the convergence wind speed of the typhoon boundary layer increases,which leads to the increase of the intensity of the typhoon.In real experiments,the choice of boundary layer parameter schemes also has a more important influence on the intensity of the typhoon.The calculation of the QNSE(Quasi-Normal Scale Elimination)boundary layer parameterization scheme in the boundary layer static stability function depends on different surface roughness,and its TKE fitting effect on the typhoon boundary layer is much higher than that of the GFDL scheme,therefore,the deviation of this scheme for typhoon intensity simulation is smaller than that of the GFDL(Geophysical Fluid Dynamics Laboratory)boundary layer parameterization scheme.when the horizontal diffusion coefficient is increased,the angular momentum of the boundary layer has greater convergence,which causes the vortex to rotate faster and further increases the intensity of the typhoon.By calculating the horizontal and vertical vortex diffusion of the typhoon boundary layer,it can be seen that when the horizontal diffusion coefficient is increased,the corresponding horizontal and vertical vortex diffusion will also increase.Therefore,from the perspective of the internal parameterization of the model,the horizontal diffusion coefficient has a very important influence on the typhoon forecast.The numerical model results for the improvement of the initial value of the typhoon show that for weak typhoons,the ensemble forecast provided by the European Center estimates that the sensitive areas are more concentrated,and the results are better than the results of the US NECP.The ensemble forecast estimated by the European center is more concentrated in the typhoon center,while the NCEP ensemble forecast estimated by the United States lags behind the typhoon.For strong typhoons,the sensitive areas estimated by the two ensemble forecasts are not much different.After the estimation of the sensitive area,the 18 hours before the typhoon landfall is selected as the assimilation time,and the basic amount of upper atmosphere assimilation provided by ERA5 is used to make artificially encrypted observations of the sensitive area.Then,enter the GSI assimilation system,and compare the results of the re-forecast with the results before the assimilation.It can be seen that when the upper atmosphere sounding data in the sensitive area is effectively increased,both the forecast of typhoon intensity and path will be significantly improved. |
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