Abstract: Surface broadband albedo is calculated from Enhanced Thematic Mapper Plus (ETM+) data using 6S (Second Simulation of Satellite Signal in the Solar Spectrum) simulations. First, land cover of study area is classified into three classes as vegetation, bare soil and water as to surface features so that it is possible to simulate the spectral data not available from ETM+ sensor as well as to reduce both the adjacency and angular effects. Then, The whole shortwave region(0 3 4 μm)is divided into 13 spectral bands following by the bandwidth of ETM+. ETM+ data has only six bands could be used to calculate broadband albedo. To remedy the spectral deficiency, the radiances in the wavelengths not included in ETM+ sensor are simulated by 6S using field measured reflectance and ASTER spectral library. Next, illuminated and reflected spectral irradiances at the surface are calculated for per band to estimate the spectral albedo and band weights. The spectral albedos are calculated as the ratio of spectral reflected to incident irradiance. Finally, broadband albedos in 0.3 - 0.7, 0.7 - 4, 0.3 - 4 μm ranges are estimated and validated using isochronous field measurement data obtained in Shunyi District of Beijing. Comparisons of satellite estimated and field observed albedos demonstrat high accordance with maximum relative error of 17.9%.

Key words: 6S, atmospheric correction, broadband albedo, radiative simulation

摘要： 利用增强的专题制图仪＋(Enhanced Thematic Mapper Plus, ETM+)数据，先针对各种下垫面反射率特征不同，对地物类型进行分类，以便减少邻近效应和模拟传感器未包含的谱段数据。借助卫星同步观测的气象数据，通过6S(Second Simulation of Satellite Signal in the Solar Spectrum)模型对ETM＋可见光、近红外6个波段数据进行了大气纠正。以ETM+可见光和近红外波段波谱范围为单位谱段，将整个短波波段(0 3～4 μm)分为13个光谱域，利用ASTER光谱数据库和实测地表反射率数据，6S模拟获取各ETM＋观测波段和未观测波段地表入射光通量密度和反射光通量密度，计算每一个光谱域入射能量占整个短波入射能量中的权重，并反演地表窄波段反照率。然后，各波段能量权重作为转换参数，实现窄波段反照率向宽波段反照率的转换。结果表明，模型反演和卫星同步观测的实测地表反照率之间最大相对误差17.9％，作者提出的方法可行。

关键词: 6S模型, 大气纠正, 反照率, 辐射模拟