Radar backscattering over agricultural bare soils

Agricultural surfaces are complex non-isotropic surfaces presenting a main direction due to the rows in combination with various smaller spatial scales (the clods). The applicability of two recent electromagnetic models, able to take account of these anisotropic surfaces, was tested under a variety of roughness encountered on an agricultural watershed (ploughing and sowing) by comparison with radar measurements made over fields with known surface parameters (soil moisture and soil roughness). The data set was collected during the "Orgeval 1989" campaign in France. Radar copolarized signatures were provided from the French helicopter-borne scatterometer ERASME in C and X bands. The Shin and Kong's model (1984) is in the frame of the Kirchoff approximation. The Integral Equation Model (Fung et al. 1992) overlaps the gap between Physical Optics and Small Perturbation models where are located in C band most of the Orgeval sowing fields, but it fails to be applicable in X band, except for ploughed field. For s...