Scattering from a Vegetation Layer

Abstract
A plane layer of vegetation separating air and soil is assumed to model dense crops such as alfalfa and soybeans. Backscattering from such a layer is computed by first determining the coherent fields existing in the layer by solving the Dyson equation under bilocal approximation. Then the scattered field is found using the first-order renormalization method. The scatter model is evaluated for different depths to correspond to the changes in height of the crop during its growth period. The behaviors of the scatter model versus moisture content and volume ratio of vegetation and soil permittivity are also illustrated. It was found that while ground effects are, in general, more significant near normal incidence than at large incidence angles, a reversal of this trend is possible for a thin vegetation layer. This offers a possible explanation for the relatively flat angular response observed in some of the measured scattering coefficients around 60-70°, since leaf density is not really uniform in practice. It was also found that any significant peaking of the backscattering coefficient near vertical incidence cannot be explained by volume scattering due to the propagation of the ground reflected field. It is believed that irregular ground is the contributing factor to large returns near vertical incidence.