| The imager boarding on the polar-orbiting satellite can be used to improve the surface observe and obtain different water phase observations.Moreover,the geostationary satellite imager commonly has high temporal resolution.It can gain continuous satellite imagery for the evolution of synoptic system.It is important to improve their utilizations.In order to applicate radiance data from the new microwave imager---AMSR2(Advanced Microwave Scanning Radiometer 2)on Japanese polar-orbiting satellite GCOM-W1(Global Change Observation Mission-Waterl)into regional data assimilation system,this study firstly established the AMSR2 clear-sky assimilation module based on WRF(Weather Research and Forecasting model)data assimilation system(WRFDA).The Typhoon Son-tinh on Pacific was chosen to eastimate the impact of AMSR2 clear-sky radiance data assimilaton.Compared with the benchmark experiment with no AMSR2 assimilation,AMSR2 clear-ksy radiance data assimilation significantly improved the typhoon structure,the intensity and track forecasts of Son-tinh.Moreover,based on the clear-sky assimilaton mouldue,the symmetric observation error model was added in the module to realize the all-sky assimilation.The Hurricane Sandy on Atlantic was chosen to evaluate not only the impact of AMSR2 clear-sky assimilation for different cases but also the impact of all-sky assimilation on real cases analysis and forecast with 3D-Var(Three-Dimensional Variational).This study also discussed the sensitive of thinning mesh and channel selection.From the results,we can see that AMSR2 radiance data can catch the patterns of Hurricane on Atlantic as the Typhoon on Pacific.Both clear-sky and all-sky assimilation of AMSR2 data significantly improved the analysis of cyclone structure,environment variables,the forecast of cyclone track/intensity and the rainfall after landfall.Furthermore,the all-sky assimilation obtained better results than the clear-sky assimilation.Removing the low-frequency channels and choosing right thinning mesh can obtain better results.Compared with the imager boarded on the polar-orbit satellite,the imagers on geostationary satellites have the advantage of high spatial and temporal resolution.In this paper,it is also the first attempt to develop the GOES-Imager(Geostationary Operational Environmental Satellites-Imager)assimilation module in WRFDA system.The rapid refresh system and hybrid assimilation method were selected to evaluate the impact of GOES-Imager assimilation on the convective process analysis and forecast in Mexico.Compared with the benchmark experiment with no GOES-Imager radiance,the results showed that GOES-Imager assimilation has the positive effect for the temperature and humidity analysis.The water vapor in upper troposphere and rainfall forecast were also significantly improved after GOES-Imager assimilation.In the appendix of this paper,this study discussed the Kalman gain matrix of Kalman filter.From the comparison of the ideal test,it is found that the modified scheme can improve the analysis result and achieve a positive effect. |
