An Assessment of the FY-3A Microwave Temperature Sounder Using the NCEP Numerical Weather Prediction Model

The MicroWave Temperature Sounder (MWTS) on FY-3A has four channels with designed band central frequencies of 50.3, 53.6, 54.9, and 57.3 GHz, respectively. Lu et al. found that the central frequency for three upper level sounding channels shifted after the satellite launch into orbit. This study confirms the findings Lu et al. using a different numerical weather prediction (NWP) model and a different radiative transfer model. Furthermore, it is shown that the strong temperature dependence of MWTS O - B^DF biases found in our earlier work is mostly induced by these frequency shifts, where O represents MWTS observations and B^DF is model simulations. The mean difference of brightness temperature simulations with (B^SF) and without (B^SF) incorporating the frequency shifts into the radiative transfer model resembles the O - B^SF biases. For NWP applications of FY-3A MWTS data, it is sufficient to generate new fast radiative transfer model coefficients that incorporate the new passband parameters, and the resulting MWTS O - B^shifted biases become constant as those of MetOp-A/NOAA-18 AMSU-A data. For climate applications, the FY-3A MWTS brightness temperatures adjusted by subtracting B^SF - B^DF match quite well with the MetOp-A/NOAA-18 AMSU-A data at the simultaneous nadir overpass locations in both the Arctic and Antarctic.