VIRR/FY-3A分裂窗波段与AIRS/AQUA和IASI/METOP-A数据的交叉辐射定标

实际应用显示搭载在风云三号A星(FY-3A)上的可见光红外扫描辐射计(VIRR)的两个分裂窗波段(IR4,~10.8μm;IR5,~12.0μm)存在定标偏差。本文选择高光谱卷积法,用AQUA卫星搭载的大气红外探空仪(AIRS/AQUA)和METOP-A卫星搭载的干涉式红外大气探测仪(IASI/METOP-A)的观测数据对VIRR/FY-3A的两个分裂窗波段进行交叉辐射定标。根据卫星轨道特点,选择北极地区(60°N~90°N,180°W~180°E)作为研究区域,并选择2010年6月、9月、12月以及2011年3月作为研究时间段。首先,分别将AIRS/AQUA和IASI/METOP-A数据与VIRR/FY-3A的第4波段和第5波段的光谱响应函数进行卷积;对观测数据进行重采样,并基于普朗克黑体辐射公式实现辐射值和亮度温度之间的转换。然后,使用两个相关的匹配条件提取VIRR/FY-3A分别与AIRS/AQUA、IASI/METOP-A在第4波段和第5波段的匹配观测点对。最后,对匹配观测点对进行回归分析,得到交叉辐射定标偏差订正方程的系数。结果表明AIRS/AQUA和IASI/METOP-A的在轨辐射定标非常一致。以AIRS/AQUA和IASI/METOP-A波段的辐射定标为标准,VIRR/FY-3A第4波段的平均定标偏差分别为2.39K和2.06K,第5波段的平均定标偏差分别为0.59K和0.44K。实验指出定标偏差与亮度温度有关。

Cross-calibration of VIRR/FY-3A split-window channels with AIRS/AQUA and IASI/METOP-A data

Some practical applications indicate that there is calibration deviation in the on-orbit radiometric calibration of the two split-window channels(IR4,~10.8 μm;IR5,~12.0 μm) on the Visible and Infrared Radiometer(VIRR) mounted in FY-3A. Therefore, this paper applies high-spectral convolution method to implementation of the cross radiometric calibration for the two spilt-window channels of VIRR/FY-3A based on the observation data from the Infrared Atmospheric Sounding Interferometer/METOP-A(IASI/METOP-A)and the Atmospheric Infrared Sounder/AQUA(AIRS/AQUA). According to the characteristics of the satellite orbit, the Arctic region (60°N-90°N,180°W-180°E) was chosen as the research area, and June, September, December 2010 and March 2011 were selected as the research satellite orbit spectral response functions of the 4th and 5th channels of VIRR/FY-3A. Then, the Planck blackbody radiation formula was used to achieve the conversion between radiation value and brightness temperature. On the basis on the corresponding matching conditions, the matching observation points between the 4th and 5th channesl of VIRR/FY-3A and AIRS/AQUA, the 4th and 5th channels of VIRR/FY-3A and IASI/METOP-A were extracted, respectively. Finally, the regression of matching observation point pairs was analyzed to obtain the cross radiometric calibration coefficients. The experimental results show that the proposed high-spectral convolution method with IASI/METOP-A and AIRS/AQUA for the cross calibration has the same calibration results. By using IASI/METOP-A and AIRS/AQUA as the standard, the brightness temperature biases for the 4th channel of VIRR/FY-3A are 2.39 K and 2.06 K; and those for the 5th channel of VIRR/FY-3A are 0.59 K and 0.44 K. This work indicates that calibration deviation is related to the brightness temperature.