风云三号卫星微波大气温度探测仪资料偏差订正方法研究

A RADIANCE-BIAS CORRECTION SCHEME FOR FENGYUN 3A MICROWAVE TEMPERATURE SOUNDING FOR RADIANCE ASSIMILATION

为推动中国风云三号卫星（FY-3A／B）资料在区域数值天气预报中的同化研究，重点研究FY-3A的大气温度垂直探测仪（MWTS）资料的偏差订正问题。在欧洲中期天气预报中心（ECMWF）原全球TOVS辐射偏差订正方案的基础上，结合MWTS资料特征，建立适用于FY-3A卫星MWTS辐射率资料的偏差订正系统，并评价MWTS的偏差订正效果。结果表明：（1）同纬度带和扫描位置的扫描偏差不同，各通道表现出不同的偏差特征，通道1扫描偏差较大（0～5K），通道2、3、4较小（0～0．6K）；（2）扫描偏差订正和气团偏差订正后的观测残差基本符合均值为零的正态分布；（3）偏差订正后的观测残差标准方差有所降低，这将提高卫星资料对分析场的调整。证明了FY-3A MWTS资料质量较好，具有同化应用的潜力，开发的偏差订正系统可为FY-3A MWTS资料在区域模式中的同化应用提供条件。

This research focuses on the methodology for radiance bias correction of Fengyun 3A Microwave Temperature Sounding （MWTS） sensor. A radiance bias correction software system was developed using a classical scheme from European Centre for Medium-Range Weather Forecasts for radiance bias correction, combined with the characteristics of MWTS. The system was used to calculate radiance bias of MWTS and its outputs were applied to analyze the characteristics of MWTS radiance bias. In addition, some coefficients were calculated, which could be employed to correct MWTS radiance bias. Some results are found. （1） MWTS radiances bias at various scan positions and zones are different, and the bias ofMWTS band 1 （0-5 k） is higher than band 2, 3 or 4 （0-0.6 k）. （2） The residual error after the whole bias correction procedure fits a normal distribution （mean=0）. （3） The variance of the residual error decreases after bias correction, which enhances the effect of MWTS observation on the analysis. This research shows that the MWTS radiance data possess good quality and have the potential for data assimilation. The system can be used to pre-process MWTS radiance data.