Impact of Targeted Sounding Observations From FY-4B GIIRS on Two Super Typhoon Forecasts in 2024

Hyperspectral infrared (IR) sounders on board geostationary (GEO) satellite, represented by the GEO interferometric IR sounder (GIIRS), can provide unprecedented and valuable observations with high-temporal resolution for disaster prevention, mitigation, and meteorological support services. FengYun-4B (FY-4B) GIIRS has carried out targeted sounding observations with a temporal resolution of 15 min for two super typhoons in 2024 (Typhoon Gaemi and Typhoon Yagi). In this study, an operational parallel experiment system was established to assimilate the FY-4B GIIRS targeted radiances in real time, and the diagnosis and analysis of typhoon forecast were carried out after the typhoon dissipated. The results indicate that assimilating FY-4B GIIRS can improve the track forecast of the two super typhoons in real-time operational environment, and the improvement is more significant after 60-h forecast. The average track forecast was increased by 22.5% in Typhoon Gaemi and by 6.3% in Typhoon Yagi, although the impact on typhoon intensity forecast was not significant. Additionally, the difference in the number of clear sky points assimilated in the two case experiments shows the importance of cloud sky assimilation in the future. This study reveals the potential and value of FY-4B GIIRS quantitative assimilation application to improve numerical weather prediction (NWP) skills, especially high-impact weather (HIW) events.