Enhancing Rainfall Prediction Affected by the Northeast China Cold Vortex Using FY-4B GIIRS Radiance Data in CMA-MESO

The Northeast China Cold Vortex (NCCV) is a common cut-off low-pressure system in Northeast China, frequently causing localized heavy rainfall, strong winds, and thunderstorms during the early summer. In this study, clear-sky radiance of forty-eight longwave channels from the FY-4B Geostationary Interferometric Infrared Sounder (GIIRS) is assimilated into the China Meteorological Administration mesoscale model (CMA-MESO) to evaluate its impact on the development of NCCV and its effects on rainfall forecasting. The results show that after assimilating the GIIRS radiance data, the warm center at 200 hPa and the cold center at 850 hPa of the NCCV are strengthened, and the dry intrusion at 850 hPa becomes more pronounced. This leads to a stronger NCCV intensity in the following 24 hours and brings the precipitation intensity and area closer to the observation, resulting in significant improvements compared to the experiments that do not assimilate GIIRS radiance data. Furthermore, it is found that the enhancement of precipitation forecast is associated with the strengthening of cold air in the middle and lower troposphere, which intensifies the uplift of the warm, moist airflow. These results highlight the potential value of GIIRS data assimilation in enhancing early warnings and forecasts of extreme weather events influenced by the NCCV.