Examination of the two-flux model for radiative transfer in particular systems

An attempt is made to assess the predictive capability of the two-flux model without relying on any empirical or adjustable constants. Predictions of the two-flux model are compared with those of exact radiative transfer theory to determine the influence of optical depth and particle size parameter on the accuracy of the two-flux model. It is shown that acute single scattering anisotropy is the prime cause of inaccuracy. Although the combination of large optical thickness with strong forward scattering is the worst case, for quasi-isotropic phase functions the predictions of the two-flux model agree quite well with exact theory even at large optical depths. The results of similar past studies are reviewed.