Approximate model of clear sky radiance distribution

摘要

Sky radiance distribution is very important in theoretical study and application of the remote sensing. In this paper, an approximate sky radiance model is developed based on radiation transfer equation. The radiatiance observed from a point at the earth surface is divided into three parts, which is from single scattering, multiple scattering and related part with the earth surface. The single scattering and double scattering radiance is exactly calculated. All orders of multi-scattering beyond double scattering transfer were derived by a ratio of successive terms. Because of decreasing of sky radiance with increasing order, evaluating the sky radiance will stop when the effect on sky radiance of a given order multiple scattering is 5% less than the 1th multi-scattering magnitude. The interaction between the earth surface and scattering radiance is incorporated also. Comparisons of this model with a numerical code discrete coordinate method (DISORT) are made.