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.¹found that the central frequency for three upper level sounding channels shifted after the satellite launch into orbit. This study confirms the fi ndings 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^DFbiases found in our earlier work is mostly induced by these frequency shifts, where O represents MWTS observations and B^DFis 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^SFbiases. 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^shiftedbiases 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^DFmatch quite well with the MetOp-A/NOAA-18 AMSU-A data at the simultaneous nadir overpass locations in both the Arctic and Antarctic.