The small slope approximation reflection coefficient for scattering from a "Pierson-Moskowitz" sea surface

Firstand second-order reflection coefficients are presented for the small slope approximation. The first-order reflection coefficient is identical to the Kirchhoff, or physical optics, result, and the secondorder reflection coefficient reduces to those of perturbation theory and the Kirchhoff approximation in the appropriate limits. Numerical results are obtained for acoustic or TE-polarized electromagnetic scattering from one-dimensional, “Pierson-Moskowitz” sea surfaces at low grazing angles. Comparison with exact integral equation results shows that the secondorder small slope approximation is extremely accurate and better than both the perturbation and Kirchhoff methods.