用数值天气预报模式评估风云三号A星微波温度计资料的质量

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

搭载在风云三号A星上的微波温度计（MWTS）有4个通道。通道1～4的中心频率分别为50.3，53.6，54.9和57.3GHz。Lu等[1]指出风云三号A星成功进入轨道后，3个高层通道（通道2～4）的中心频率发生了漂移。Zou等[2]指出通道2～4的资料偏差随温度变化而变化。本文指出风云三号A星微波温度计资料偏差对温度的依赖性是由频率漂移引起的，并提出了解决这些资料在数值预报和气候研究应用中的相应措施。对于数值预报而言，只要在快速辐射传输模式中采用逐线积分模式和漂移后的频率产生一套新系数，就可以使用该快速辐射传输模式做资料同化。为了要把风云三号A星微波温度计资料接到NOAA系列和欧洲卫星相应仪器资料，可以用快速辐射传输模式估计由频率漂移引起的偏差，并将此偏差从观测中减去。本文利用2010年一年MetOp-A/NOAA-18微波温度计（AMSU-A）与风云三号A星微波温度计在南北两极的星下点同时过境处（SNO）资料，证明了该方法的可行性。

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.[1]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 BDFbiases found in our earlier work is mostly induced by these frequency shifts,where O represents MWTS observations and BDFis model simulations.The mean difference of brightness temperature simulations with(BSF) and without(BSF) incorporating the frequency shifts into the radiative transfer model resembles the O BSFbiases.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 Bshiftedbiases become constant as those of MetOp-A/NOAA-18 AMSU-A data.For climate applications,the FY-3A MWTS brightness temperatures adjusted by subtracting BSF BDFmatch quite well with the MetOp-A/NOAA-18 AMSU-A data at the simultaneous nadir overpass locations in both the Arctic and Antarctic.