关键词: 6S模型, 大气纠正, 反照率, 辐射模拟

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