基于深对流云目标的风云二号可见光通道辐射定标

Study on Orbit Radiometric Calibration for FY-2 Visible Band based on Deep Convective Cloud

介绍了一种采用深对流云目标对风云二号(FY-2)扫描辐射计可见光通道进行辐射定标的方法。以深对流云作为辐射定标参考载体,以AQUA/MODIS获得的深对流云反射率作为辐射基准参考,以GOME-2和辐射模式模拟的DCC光谱进行了光谱响应函数的修正,评估FY-2系列卫星的可见光通道辐射定标精度及其长序列衰减趋势。结果表明:(1)FY-2可见光通道存在不同程度的衰减,FY-2D,FY-2E和FY-2F的年衰减率分别约为1.67%,1.69%和0.81%;(2)与国际推荐的参考仪器AQUA/MODIS的DCC反射率基准相比,风云二号可见光通道业务定标结果与之存在显著差异,其相对偏差了分别达到了39.9%,29%和19.2%。(3)FY-2卫星在轨期间,可见光通道存在一定程度的周期性的波动和跳跃现象。借助深对流云目标很好地实现了FY-2系列气象卫星的可见光辐射定标,获取的辐射定标结果已经作为业务定标更新的重要依据。

A radiometric calibration method is described in this paper by using the deep convective clouds（Deep Convective Cloud,DCC） target for FY-2 visible channel.The deep convective cloud can be used as the radiometric calibration transfer object The on-operational FY-2 radiometric calibration bias and the long-term degradation trend are evaluated according to the AQUA/MODIS instrument as the baseline of radiometric reference and DCC.The results show that：（1） There are different degrees of degradation for FY-2D,FY-2E and FY-2F,among which FY-2D has the biggest degradation due to the longest period.The annual rates of degradation for FY-2D and FY-2E are quite similar,1.67%and 1.69%respectively,whereas the rate for FY-2F is lower with 0.81%;（2） During the period of satellite eclipse,the instruments are not stable and this phenomenon could be detected by the DCC method;（3） There are bias in the the operational radiometric calibration between FY-2 and AQUA/MODIS,which is treated as the the radiometric reference usually.The radiometric calibration method based on DCC could work well in the radiometric calibration for FY-2.The results will help us to understand the degradation of instrument and for quantitative application usage.