Abstract:To evaluate the accuracy and operational applicability of FY-4A/4B GIIRS-retrieved temperature and humidity profiles in Guizhou, the FY-4A temperature profile and FY-4B temperature and humidity profiles are verified against sounding observations at Guiyang and Weining stations and ERA5 reanalysis data. The results indicate that, in practical operations, it is considered that only the unusable data can be eliminated, while the data with the best and better quality can be retained so as to maximize the integrity of the temperature and humidity profiles. Clouds significantly degrade GIIRS retrieval performance. Under cloudy conditions, the root mean square error of FY-4A temperature increases by 1.19℃ (clear sky) and 0.96℃ (cloud edge), FY-4B temperature increases by 1.52℃ （clear sky） and 1.21℃ (cloud edge), and specific humidity increases by 1.28 g·kg-1 (clear sky) and 0.95 g·kg-1 (cloud edge), respectively. Moreover, cloud cover also amplifies vertical data dispersion. Seasonal comparisons between sounding and satellite profiles demonstrate that FY-4A/4B captures terrain-induced differences in atmospheric stratification between Guiyang and Weining. For three regional hail events in 2023, GIIRS products agree well with sounding observations. The high-resolution profiles reveal pre-hail instability, which is “upper dry and lower wet”, offering valuable forecast indicators. However, the near-surface layer retrieval errors lead to the underestimation of convective available potential energy (CAPE) and distort low-level sounding structures. After the surface 2 m temperature and dew point temperature corrections, a large CAPE and a sounding structure conducive to the occurrence of thunderstorms and strong winds are displayed. This is a good support for the short-time forecasting and nowcasting of severe convections.