Multimode Radiative Transfer in Finite Optical Media. II: Solutions

Abstract

This paper extends the theoretical developments of Part I to illustrate the power of the method in solving multiple scattering problems with sources that result from i) the single scatter of a collimated beam of solar radiation that is directly transmitted to a given point in the medium and ii) thermal emission. These source terms are derived in the multimode context and solutions are presented to illustrate the effects of sun angle and infrared emission on the radiance and irradiance fields that emerge from hypothetical box shaped clouds. The results reiterate the earlier findings that the sides of clouds play an important role in the exchange of radiative energy between the cloud and its environment. The total infrared emission by cuboidal clouds, for example, is shown to be substantially larger than the emission from plane parallel clouds as a result of this additional exchange of radiant energy. The results presented in the paper, including the comparisons with available Monte Carlo calculations show the multimode approach to be a viable, accurate and computationally efficient method of solving the general problem of anisotropic scattering in horizontally finite optical media.