使用偏差原则和正则化方法反演晴空地表双向反射分布函数BRDF、方向一半球反射率DHR和双半球反射率BHR。利用6S辐射传输模型计算出天空散射光,并以此为权重将DHR和BHR进行线性组合得到地物光谱反照率。最后,通过窄波段反照率向宽波段转换,计算了0.25—2.5μm的短波反照率。使用POLDER-3/PARASOL多角度数据进行验证,并将所得结果与MODISAMBRALS算法进行比较。结果表明该算法和MODIS反演算法精度相当。
Based on discrepancy principle and regularization techniques, a regularizing inversion method is employed for the retrieval of clear-sky land surface bidirectional reflectance distribution function (BRDF), directional-hemispherical reflectance (DHR) and bi-hemispherical reflectance (BHR). The fraction of diffuse skylight is computed by using the 6S radiative transfer code. Therefore, by interpolating between DHR and BHR, the actual instantaneous spectral albedos can be computed. Accordingly, the calculation of shortwave (0.25-2.5μm) albedos can be implemented by the conversion of narrowband spectral albedos to broadband albedos. Validation of the presented algorithm is implemented with the POLDER-3/PARASOL BRDF data sets. Comparison of results retrieved by the presented algorithm with that by MODIS AMBRALS algorithm indicates that the accuracy of regularizing retrieval algorithm is equivalent to that of the MODIS algorithm.