Thermal microwave emission from a halfspace containing scatterers

Abstract

The microwave brightness of heterogeneous materials is decreased by internal scattering. This study, based upon radiative transfer theory, shows that for low loss media darkening can be many tens of degrees, that the effect is greater for materials of lower dielectric constant, that darkening depends upon the dominance of scattering over absorption, that volume scattering tends to mask a temperature gradient, that darkening is slightly greater for V‐ than for H‐polarized radiation, and that darkening increases slightly with view angle. For isotropic scattering, the analysis yields the brightness temperature as a function of the scattering albedo, the complex dielectric constant, thermal temperature, and the temperature gradient.