FY-3A微波湿度计资料的扫描偏差特征分析

Analysis of FY-3A Micro Wave Humidity Sounder(MWHS) data scanning bias characteristics

卫星辐射资料在数值天气预报系统中的直接同化中会受到系统偏差的影响。文章使用2010年1月20日06:00UTC FY-3A搭载的微波辐射计(MWHS)探测资料L1C格式产品,分析了亮度温度观测增量O-B随扫描角的分布特征,为FY-3A MWHS资料的偏差订正及直接同化提供参考。文章分析MWHS的5个通道观测亮度温度、模拟亮度温度、观测增量O-B亮度温度的全球分布图发现:所有通道中误差高值区都集中在中高纬地区,低纬地区偏差较小;窗区通道1、2的误差分布随空间变化增大,误差较大,不适合进行偏差订正,通道3、4、5的误差相对较小,适合进行偏差订正;通道3、4、5观测增量O-B与星下点偏差随扫描角的分布沿着星下点两端均不对称,其中,通道3和通道4的偏差较小,主要集中在±0.5 K范围内,分布在0轴附近;通道5的偏差较大,并扫描角分布变化较大,出现了双峰不对称的形状。

The direct assimilation of satellite radiation data in the numerical weather prediction system can be af-fected by system biases.In this paper,using L1C format product data detected by the Microwave Humidity Sounders(MWHS)onboard the Fengyun-3A at 06:00 Jan.20th,2010 UTC,the characteristics of the distribution of brightness temperature observation increment O-B with scanning-angle was analyzed,which can be used as a reference in the deviation correction and direct assimilation of FY-3A MWHS data in China.By comparing and analyzing the global distribution maps of observed brightness temperature,simulated brightness temperature,and observation increment O-B brightness temperature measured by 5-channel of MWHS,it was found that high value of error of all channels are located in the middle-and high-latitude areas in the map,and low-latitude ar-eas showed relatively lower value of error.And the distribution of error of channels 1 and 2 within the window ar-ea varies greatly with the space,and it is therefore not suitable for deviation correction.However,the errors of channels 3,4,and 5 are relatively small,and therefore it is suitable for deviation correction.The variation of de-viations of the sub-satellite points and the observation increment O-B of channels 3,4,and 5 with the scanningangle are not symmetrically distributed along both ends of the sub-satellite points,and the deviations of chan-nels 3 and 4,which are in the range of±0.5 K and are distributed around the 0 axis,are relatively small.Howev-er,the deviation of channel 5 is relatively large,and the distribution varies greatly with the scanning-angle,re-sulting in the appearance of a bimodal asymmetry.