Impacts of the all-sky assimilation of FY-3D and FY-3E MWHS-2 radiances on analyses and forecasts of Typhoon Muifa (2022)

The newly launched Fengyun-3E (FY-3E) satellite in the early morning contributes to forming a complete threeorbit observation system, comprehensively improving the spatial coverage of satellite data. This study highlights the importance of applying the Microwave Humidity Sounder-II (MWHS-2) data from the FY-3E satellite by exploring the impact of jointly assimilating FY-3D and FY-3E MWHS-2 data under all-sky conditions on regional typhoon forecasting. Firstly, the impact of the different observation error statistics is studied based on FY-3D allsky MWHS-2 radiance data assimilation for Typhoon Muifa (2022). The results show that the features of adaptive observation error statistics are rather consistent based on observational and meteorological information samples over different periods. Appropriate observation errors have the potential to improve typhoon track and intensity predictions, especially for rainfall forecasts. Consistent positive benefits of the typhoon intensity forecasts are obtained with the assimilation of the cloud-affected radiances from FY-3D MWHS-2. Moreover, joint assimilation experiments using FY-3D and FY-3E MWHS-2 radiances are conducted to compare the relative impact of each sensor for both clear-sky and all-sky. Results indicate improvements in the analyses of 500 hPa geopotential height and humidity with the introduction of cloud-affected radiance in joint assimilation experiments. The forecast performance of the joint assimilation method is significantly better than that with only FY-3E MWHS-2 observations in terms of the typhoon track, intensity, and precipitation. This superiority is particularly obvious in all-sky data assimilation experiments compared to clear-sky conditions.