Intercalibration of FY-3D MWHS-II Water Vapor Absorption Channels Against S-NPP ATMS Channels Using The Double Difference Method

This paper addresses the intercalibration of Fengyun 3D (FY-3D) Microwave Humidity Sounder II (MWHS-II) water vapor absorption channels against the Suomi National Polar-orbiting Partnership (S-NPP) Advanced Technology Microwave Sounder (ATMS) channels using the double difference method. First, a radiometric calibration transfer method is developed. Then, the matching samples in June of 2022 between the MWHS-II and ATMS observations are collected over both sea and land surfaces. Next, the brightness temperatures at top of atmosphere in the MWHS-II and ATMS channels are simulated, and the double differences are calculated. Finally, the radiometric calibration of the ATMS channels is transferred to the MWHS-II channels. The results show that radiometric calibration biases in the FY-3D MWHS-II channels 10, 11, 12, 13, 14 and 15 are -3.89±1.40 K, -2.80±1.00 K, -1.03±0.97 K, -0.42±1.11 K, 1.53±0.82 K, and -0.87±1.31 K, respectively.