FY-3C/可见光红外扫描辐射计中红外通道太阳污染的识别和修正

基于风云-3C/可见光红外扫描辐射计(FY-3/CVIRR)的中红外通道(3.7μm)的太阳污染现象和发生规律,分析了太阳污染出现的时空特征,提出了初步判识并修正北半球太阳污染数据的方法,并就太阳污染对定标系数和黑体亮温的影响做了定量的评估。结果表明,对于FY-3C/VIRR的中红外通道,太阳光线照射到定标黑体时所形成的北半球高纬度太阳污染主要出现在太阳天顶角在85°~118°之间的位置时;由太阳污染导致的该区域地球观测亮温日平均偏差为4.5K左右,最大偏差达到15K左右。通过对逐日太阳污染数据进行识别,并采用污染前后定标系数进行线性求差值,可以初步修正太阳污染对定标系数带来的异常影响。

Discrimination and correction for solar contamination on mid-infrared band of FY-3C/VIRR

On the basis of solar contamination phenomenon and occurrence rules of the mid-infrared channel (3.7 μm) in the Fengyun-3C/Visible and Infrared Radiometer(FY-3C/VIRR), temporal and spatial characteristics of the solar contamination were analyzed. The method to discriminate initially and correct the solar contamination data in the northern hemisphere was proposed and the effect of solar contamination on calibration coefficients and blackbody brightness temperature was evaluated quantitatively. The results show that for the mid-infrared channel (3.7 μm) in the FY-3C/VIRR, the solar contamination in the northern hemisphere caused by the sun irradiation on calibrated blackbody will appear at the solar zenith angle between 85°-118°. The daily mean absolute error of blackbody temperature is up to 4.5 K, and the maximum absolute error in a day is up to 15 K. By discrimination of the solar contamination data day by day and calculating the linear difference of calibration coefficients before and after contaminations, the effect of solar contamination on calibration coefficients can be corrected initially.