Effects of Reflection by Natural Surfaces on the Radiation Emerging from the Top of the Earth's Atmosphere

Abstract

The radiation emerging from the top of the earth's atmosphere is affected by the reflection characteristics of the underlying surface. Laboratory-gathered bidirectional reflectance data were used to characterize the reflection matrix for three different types of natural surfaces. The radiation emerging from the top of a pure molecular and an aerosol-laden plane parallel atmosphere was calculated for these three diverse types of surfaces and their Lambert model equivalents. The calculations indicate that the radiation emerging from the top of the atmospheres is significantly different for a real surface compared to a Lambert model. For the molecular atmosphere the difference is most pronounced at a wavelength of 0.6 ?m; this is mainly due to the light directly transmitted downward through the atmosphere, reflected, and then directly transmitted outward through the top of the atmosphere. For a turbid atmosphere the difference also is due to light with a history of diffuse transmission because the strong forward scattering of the aerosols partially offsets the smoothing effect of the diffuse multiple scattering. The calculations indicate that the polarization of the light emerging from the top of the atmosphere strongly mirrors the polarization reflected from the underlying surface. Thus, satellite-measured polarization would be an excellent parameter for distinguishing ground features with similar reflectance but different polarization characteristics.