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, the clear-sky radiance of 48 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 NCCV development 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 the 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.

东北冷涡（Northeast China Cold Vortex, NCCV）是我国东北地区常见的切断低压系统，在初夏时节常引发局地强降雨、大风及雷暴天气。本研究将风云四号B星静止轨道干涉式红外探测仪（Geostationary Interferometric Infrared Sounder, GIIRS）的48个长波通道晴空辐射亮度资料，同化至中国气象局中尺度数值模式（CMA-MESO）中，以评估其对东北冷涡发展的影响及其在降水预报中的作用。结果表明，同化GIIRS辐射亮度资料后，东北冷涡在200百帕高度层的暖中心与850百帕高度层的冷中心均得到增强，850百帕高度层的干侵入现象更为显著。这使得后续24小时内东北冷涡强度更强，且降水强度与落区更贴近观测实况，相较未同化GIIRS辐射亮度资料的对照试验，预报效果得到显著提升。进一步研究发现，降水预报效果的提升与对流层中低层冷空气活动增强密切相关，后者加剧了暖湿气流的抬升运动。上述结果凸显了GIIRS资料同化在提升受东北冷涡影响的极端天气事件预警与预报能力方面的潜在应用价值。