Theory for thermal microwave emission from a bounded medium containing spherical scatterers

Abstract

The theory of thermal microwave emission from a bounded medium containing spherical scatterers is developed with a radiative transfer approach using Mie‐scattering functions. Since the boundary of the bounded medium predetermines a preferred direction, the scattering phase functions that are more general than those commonly used have to be developed. Brightness temperatures are calculated and compared with Rayleigh results. Resonance phenomena that are characteristics of Mie scattering are revealed. Results computed from an iterative approach which accounts for single scattering are compared with that obtained from a numerical approach which accounts for multiple scattering. The multiple‐scattering results display less oscillatory behavior and are also more accurate. The brightness temperatures as functions of observation angles and frequencies are also examined for the vertical and horizontal polarizations and for particle size distributions.