A parametric radiative transfer model for sky radiance distribution

Abstract

A parametric model of sky radiance distribution is developed using radiative transfer theory. The radiation field is divided into four components: single-scattering; double-scattering; quasi-multiple-scattering; and surface related component. The first three components are associated with zero surface reflectance. The single-scattering and double-scattering radiance are exactly calculated, and quasi-multiple scattering is fitted statistically from the numerical code DISORT based on the discrete-ordinate algorithm. Surface bidirectional reflectance is incorporated into the last component. Comparisons of this simple model with a numerical code DISORT as well as another parametric sky radiance model are made under different conditions of aerosol optical depth, asymmetry parameter in the phase function and surface reflectance. Results indicate that the present model is very accurate and computationally efficient.