Added Benefit of the Early-Morning-Orbit Satellite Fengyun-3E on the Global Microwave Sounding of the Three-Orbit Constellation

The three-orbit constellation can comprehensively increase the spatial coverage of polar-orbiting satellites, but the polar-orbiting satellites currently in operation are only mid-morning-orbit and afternoon-orbit satellites. Fengyun-3E (FY-3E) was launched successfully on 5 July 2021 in China. As an early-morning-orbit satellite, FY-3E can help form a complete three-orbit observation system together with the mid-morning and afternoon satellites in the current mainstream operational system. In this study, we investigate the added benefit of FY-3E microwave sounding observations to the mid-morning-orbit Meteorological Operational satellite-B (MetOp-B) and afternoon-orbit Fengyun-3D (FY-3D) microwave observations in the Chinese Meteorological Administration global forecast system (CMA-GFS). The results show that the additional FY-3E microwave temperature sounder-3 (MWTS-3) and microwave humidity sounder-2 (MWHS-2) data can increase the global coverage of microwave temperature and humidity sounding data by 14.8