The surface albedo retrieval of mountainous forest area from satellite MSS data

Abstract

The reflected near infrared radiance of rugged terrain as measured from space includes strong atmospheric and topographic effects. The removal of such effects from satellite image data is very important in retrieving the surface albedo distribution of remote mountainous forest areas. However, the radiative transfer process is much more complex for rugged terrain than for flat terrain because the complicated local topography such as elevation, slope, and aspect must be taken into account. In this study we proposed a new analytical radiometric correction method for rugged terrain image data which allows the use of more general Minnaert's law for the bidirectional reflection at the ground surface. Since the proposed radiometric correction method gives the surface albedo of mountainous area from satellite data, we can use it as a surface albedo retrieval method. In our albedo retrieval method single reflection by a target slope and up to double reflections by the mean background as well as diffuse reflection by the atmosphere were taken into account. By applying the proposed method to the Landsat MSS data, we found that the reflection by rugged terrain vegetation (mostly deciduous forest) follows Minnaert's law, rather than Lambert's law. The appropriate values of the Minnaert constant k and mean ground albedo A of the deciduous forest within our study site were retrieved by minimizing the standard deviation of ground albedo value. We found k = 0.61 and A = 0.33 ± 0.05 in band 6 and k = 0.62 and A = 0.55 ± 0.07 in band 7 from the Landsat MSS data.