Application Of Satellite Microwave Observation Brightness Temperature And Full Sky Brightness Temperature Simulation In Typhoon Positionin

The microwave humidity sounder carried on the polar-orbiting meteorological satellites can observe the water vapor information in the middle and low troposphere,which clearly reflects the structural distributions of water vapor,cloud and rainband around tropical cyclones.The observation data of microwave humidity sounder can not only be used to analyze the threedimensional structures of clouds and rainbands of tropical cyclones,but also to locate the center of tropical cyclones.As the output product of the global model,the atmospheric reanalysis data is widely used in the study of tropical cyclones because of the advantages of long-time scale and wide spatial coverage.However,the content of cloud hydrometeors calculated by parameterization scheme in global models is very uncertain,which is not conducive to the study of tropical cyclones accompanied by heavy precipitation.Microwave humidity sounder observations which are heavily influenced by cloud ice has been able to be assimilated under all-sky conditions thanks to the development of scatt module in the fast radiative transfer model.Therefore,the comparison of distribution of TB observation and all-sky TB simulation from global atmospheric reanalysis data near tropical cyclones is not only of great significance for all-sky assimilation,but also has important reference value for updating the global model assimilation scheme that produces atmospheric reanalysis data.In this paper,ERA5 reanalysis from the European Centre for Medium-Range Weather Forecasts(ECMWF)and GFS analysis from the National Centers for Environmental Prediction(NCEP)are used to simulate the TB of a variety of microwave humidity sounders.Taking Hurricanes Sandy and Isaac and Typhoon Infa as examples,the satellite observed and simulated center positions are obtained by the azimuth spectrum hurricane center positioning method and compared.The results show that:(1)The average difference between the center position of Hurricane Sandy(Isaac)and the best track is 35.8 km(32.9 km)based on TB observations from the ATMS carried by the afternoon satellite S-NPP and the MHS carried by the morning satellite MetOp-A,but as large as 73.3 km(82.1km)based on the ERA5 all-sky simulations.If grouped into tropical storm and hurricane intensity categories,the average distance from the best track determined by of satellite observations and ERA5 simulations is 36.5 km and 105.9 km,respectively,for tropical storm;25.8 km and 56.4 km,respectively,for hurricanes.If ATMS is replaced by FY-3B MWHS,similar results are obtained.(2)The average difference between the center position of Typhoon Infa and the best track is 107.2 km(55.1 km)based on ERA5(GFS)TB simulations from the ATMS carried by the satellite NOAA-20,the MHS carried by the satellite MetOp-B and the MWHS-2 carried by the satellite FY-3D.If grouped into tropical storm and hurricane intensity categories,the average distance from the best track determined by of ERA5 and GFS simulations is 154.8 km and 68.3km,respectively,for tropical storm;71.1 km and 31.8 km,respectively,for hurricanes.(3)The all-sky TB simulation is very similar to the distribution structure of ice water path because the TB of microwave humidity sounder is greatly affected by cloud ice water.