改进BRDF先验知识耦合策略的Landsat30米地表反照率模型研究与验证

地表反照率是地气系统能量平衡的关键参数，随地表类型、结构和状态不同呈现高度异质性。被人类活动不断改变的地表覆被可给气候变化带来不容忽视的影响。准确理解这些变化所诱发的地表能量重新分割，则需精细尺度反照率遥感数据产品的支撑。申请人的30米Landsat反照率估算方法虽已被美国地质调查局和宇航局采纳并用于生产数据产品，但在融合BRDF先验知识方面仍有待提高。为进一步完善模型，项目从“组分-冠层-样方-像元”多层面开展研究，先分析升尺度过程中典型景观结构和端元方向反射特性，建立先验知识景合成前向模型；再利用多组像元BRDF及其端元占比方程反向求解降尺度参数，耦合Landsat方向观测，改造地表反照率估算模型；最后，开发Beta版系统，并与有效地面观测和原有算法等同类遥感数据产品对比验证，检验新模型性能。研究可提高我们对地表异质性尺度效应的认识和为我国自主研发类似卫星遥感数据产品积累经验。

Surface albedo as the recognized essential parameter of energy balance in the Earth-atmosphere system varies temporally and spatially with the type, structure, and state of underlying surface. The land cover changes caused by anthropogenic activities is significant, and induce unnegligible effects on the regional or global climate change. Thus, the fine resolution satellite-based products are required to support a further understanding on the re-partition of surface energy altered by the land cover changes. Though the Landsat “MODIS-concurrent” 30m surface albedo approach developed by the PI has been adopted by USGS and NASA of United States to generate the continuous surface albedo products over the North America region, further efforts are still needed on the fusion of BRDF aprior-knowledge. To upgrade this approach, this project proposes the coordinated investigation on “component-canopy-quadrat-pixel” multi-scale anisotropy for the understanding of scale-effect over typical BRDF shapes. This study will analyze the 3-D scene structures and the variation of directional reflect features of endmembers over typical land cover scenes in the scaling-up, construct the anisotropy apriori scene-combined forward model, inverse the coarse BRDF shape parameters from a series of pixel-based BRDF and their percentage of endmembers in fine resolution, couple the Landsat directional observations, upgrade the initial Landsat surface albedo model, code the system in Beta version to generate the test dataset, and validate with the available ground measurement followed by the cross-comparison with the initial approach and other similar satellite-based products to examine the performance of the upgraded model. This effort is expected to help improve our understanding of the scale effect on the surface anisotropy and also can help accumulate experience and methods in self-developing our national basis satellite albedo products.