Preliminary investigation of FengYun-3C Microwave Temperature Sounder (MWTS) measurements

Abstract

The third FengYun satellite (FY-3C) was successfully launched into morning-configured orbit on 23 September 2013. The cross-tracking scanning instrument microwave temperature sounder (MWTS) on board FY-3C provides 13 channels, many more than the four MWTS channels on board FY-3A/B, at frequencies ranging from 50 to 60 GHz, which allow for probing the atmospheric temperature under all conditions except heavy precipitation. This study investigates and assesses the quality of the brightness temperature measurements from MWTS using the rapid radiative transfer model. Overall, MWTS observations (labelled ‘O’) compare favourably with simulations (labelled ‘B’) for troposphere and stratosphere channels except for surface-sensitive channels, the measurements of which provide more detail of thermal structures in the lower troposphere, especially for storm conditions such as tropical cyclones. Moreover, measurements from channels 1 and 4 can be used to derive the cloud liquid water path index (LWPindex) for cloud detection. However, this study also finds that (1) the brightness temperature differences (labelled ‘O-B’) between observations and model simulations exhibit a clear striping pattern for upper level channels; (2) the geolocation result has a systematic bias towards the real geolocation; and (3) the calibrated cold space view is contaminated by light reflected from the moon.