Application of a Combined Rough Surface And Volume Scattering Theory to Sea Ice And Snow Backscatter

Abstract

A radiative transfer theory which combines rough surface and volume scattering effects is applied to interpret backscatter measurements from snow and sea ice. The surface scattering effect is accounted for by the Kirchhoff model evaluated either with or without the deep phase modulation assumption. Hence, the major restriction on the surface model is that the horizontal roughness scale must be large enough to satisfy the large radius of curvature requirement. The inhomogeneous layer for simulating snow or sea ice is modeled by either the Rayleigh phase matrix or a continuous random medium with a cylindrically symmetric correlation function for its permittivity function. It is assumed that for the continuous random medium the Born approximation is applicable for computing the scattering phase functions of this inhomogeneous medium. For simplicity only the top boundary of the inhomogeneous layer is assumed rough. Its bottom interface is a plane separating the layer from a homogeneous semiinfinite medium. Comparisons with snow measurements using Polder and Van Santen's mixing formula for the permittivity model show satisfactory agreements at 7.6, 13, and 17 GHz and for sea ice at 9 and 13 GHz. For the cases considered for sea ice, it appears that the Rayleigh phase matrix is an adequate description for volume scattering.