Rough Surface Effects in Backscatter Returns from Forests

Electromagnetic backscattering from hemlock trees in Howland forest, Maine, is studied. The forest is assumed to be a sparsely distributed medium with discrete dielectric scatterers, namely; leaves, branches and trunks. The earth beneath is a moderately rough surface. Backscattering is computed as a sum of direct, direct-reflected and surface backscattering coefficients. The trunk-ground contribution can be represented as a component reflected from the average surface and a contribution for the surface fluctuations. Previously, Kirchhoff's Method (Lang 2004) had been used to represent the scattering from the rough surface. The Integral Equation Method (IEM) which incorporates the Kirchhoff's approach will be used here. Comparisons of the results for the Kirchhoff and IEM approaches will be made. Both approaches show that when the surface is very rough, the backscatter from the trunk rough surface fluctuation component is dominant. These model results will then be compared to backscatter measurements made by Air SAR overflights in 1990.