Calibration and Validation of Feng Yun-3-D Microwave Humidity Sounder II

Abstract

On November 15, 2017, the fourth satellite, Feng Yun-3D (FY-3D), of the new generation of Chinese polar orbit meteorological satellites was successfully launched into orbit. As one of the key payloads, the second-generation Microwave Humidity Sounder (MWHS II) has 15 channels for observing atmospheric temperature and moisture. In the ground data processing system, the calibration is completed for every scanning period, and then, brightness temperature (TB) data are obtained with calibration coefficients. In order to analyze the performance of MWHS II, one year of in-orbit data are used to monitor the trend of internal blackbody target temperature, instrument temperature, calibration counts, and automatic gain control (AGC), and the results indicate whether the instrument is working well. The instrument noise equivalent differential temperature (NEDT) is calculated, and the value satisfies the design requirements. Two methods are used to validate FY-3D MWHS II measurements. One is the simultaneous nadir overpass (SNO) approach: in this method, ATMS is chosen as the reference sensor, and the standard deviations for five humidity sounding channels are all less than 1.3 K. In the alternate approach, a comparison of the observed and simulated TB of MWHS II is carried out between FY-3C and FY-3D. The results also demonstrate a consistent performance between the two instruments.