An Approximation to Multiple Scattering in the Earth's Atmosphere: Almucantar Radiance Formulation

Abstract

The retrieval of aerosol size distributions from solar aureole measurements, in the past, have been made tractable by assuming the single-scattering approximation, since the inclusion of multiple scattering by solving the complete radiative transfer equation would make such retrievals prohibitively expensive. Recently, ways have been sought to improve the accuracy of such retrievals without increasing the computational effort afforded by the single-scattering approximation. This has led to the development of a perturbation approximation, which makes allowance for molecular multiple scattering; aerosol multiple-scattering events are largely ignored. In this paper, the derivation of an empirical expression to account for this molecular multiple scattering is discussed, and the accuracy of this approximation is illustrated by some examples of the direct problem for the solar aureole.