Assessing FY-3E HIRAS-II Radiance Accuracy Using AHI and MERSI-LL

The FY-3E/HIRAS-II (Hyperspectral Infrared Atmospheric Sounder-II), as an infrared hyperspectral instrument onboard the world’s first early morning polar-orbiting satellite, plays a major role in improving accuracy and timeliness of global numerical weather predictions. In order to assess its observation quality, geometrically, temporally, spatially matched scene homogeneous HIRAS-II observations were convolved channels corresponding Himawari-8/AHI (Advanced Himawari Imager) FY-3E/MERSI-LL (Medium-Resolution Spectral imagers from 15 March 21 April 2022, their brightness temperature deviation characteristics statistically calculated this paper. results show that in-orbit observed temperatures are slightly warmer than AHI all (long wave channel 8 16) with mean bias less 0.65 K. atmospheric absorption is larger window channel. A standard 0.31 K correlation coefficient higher 0.98 means quality satisfactory. thresholds chosen for colocation approximation factors (e.g., geometry angle, uniformity, azimuth, time) matching contribute little negligible uncertainty assessment, so difference between two radiations considered be mainly systematic two-instrument measurement. Compared MERSI-LL 5, both instruments very close, 0.002 (HIRAS-II minus MERSI-LL) water vapor 4 0.66 0.22 6 7 0.63 (the 0.36 K) 0.5 0.3 K), respectively. biases significantly positively correlated target temperature, U-shaped change increase smallest (close 0 when 250 280 statistical HIRAS-II–MERSI-LL vary minimally almost constantly over period time, indicating performance stable.