A numerical radiative transfer model for a spherical planetary atmosphere:combined differential-integral approach involving the Picard iterative approximation

A new radiative transfer model suitable to calculate the radiation field in a spherical planetary atmosphere has been developed. The suggested approac h involves the Picard iterative approximation to solve the radiative transf er equation in its integral form. The radiation field calculated by solving the integrodifferential radiative transfer equation in a pseudo-spherical atmosphere is used as an initial guess for the iterative scheme. The approa ch has the same advantages as the Monte-Carlo method, but is much more comp utationally efficient. The comparisons between the spherical model presente d in this paper and a Monte-Carlo radiative transfer model for radiances at the top of the atmosphere show differences less than 1% for most situation s. The accuracy of the recently developed CDI approach, which was intended to perform fast and accurate radiance computations for non-limb viewing geo metry, has been estimated for limb viewing geometry. (C) 2001 Elsevier Scie nce Ltd. All rights reserved.