Quality Assessments of Chinese FengYun-3B Microwave Temperature Sounder (MWTS) Measurements

Following the successful launch of the first polar-orbiting morning-configured satellite, FY-3A, on May 27, 2008, in a new Fengyun three (FY-3) series, the second afternoon-configured polar-orbiting satellite (FY-3B) was launched on November 5, 2010. The four-channel Microwave Temperature Sounder (MWTS) was onboard both FY-3A/B satellites, with designed channel frequency similar to channels 3, 5, 7, and 9 of the Advanced Microwave Sounding Unit-A (AMSU-A). This study assesses the quality of the brightness temperature measurements from FY-3B MWTS by comparing them with numerical weather prediction (NWP) model simulations and NOAA-18 AMSU-A measurements with the same frequencies. A strong latitudinal-dependent bias is found for both MWTS channel 3 and AMSU-A channel 7. At channel 4, the brightness temperatures are contaminated within a small latitudinal zone ( ~ 30^°-40^°N) of the Northern Hemisphere. It is also found that the MWTS channel 4 bias is strongly asymmetric across the scan and the fourth field of view (FOV4) of channel 4 is globally and systematically warmer than its neighboring FOVs. These anomalous biases may arise from sidelobe effect and interferences of the signal transmitted from some unknown sources. A quality control algorithm is developed to remove the anomalous data at MWTS channel 4 for its applications in NWP.