Analysis of Brightness Temperature Measurement Biases and Their Contributing Factors for FY-4A and FY-4B Satellites

Dual-satellite observations of FY-4A and FY-4B exhibit continuity and complementarity, but differences in the satellites’ positions and observation paths may make their actual detection results inconsistent. This study, which is based on the AGRI full-disk Level 1 data and cloud top height products from dual-satellite imagers during June–August 2022, conducted parallax correction on the dual-satellite data and analyzed differences in thermal infrared channel brightness temperatures (BTs) under various cloud height scenarios and underlying surface conditions. The results showed that within the common observation area, the BT differences between FY-4A and FY-4B gradually turned positive to negative from west to east. In the equatorial region, the BT differences reached 8 K. As cloud height increases, the root mean square error of the BT differences increases from 1.63 K to 3.06 K. The differences were larger over land than over the ocean. Additionally, this study investigated the theoretical effects of satellite zenith angle on dual-satellite BT differences using the RTTOV fast radiative transfer model. Simulated BT difference trends between the satellites show broad consistency with observed empirical trends. Therefore, future research can perform physical correction on the dual-satellite observations according to these patterns, enabling joint applications of the dual-satellite data.