Incoherent bistatic scattering from the sea surface at L-band

A bistatic electromagnetic wave scattering model for the sea surface is dev eloped to examine its wind dependence property over a wide range of inciden t angles along the specular direction. This is done by combining an existin g scattering model with a sea spectrum recently reported in the literature. In general, electromagnetic wave scattering from a rough surface is depend ent on the Fourier transform of the nth power of its height correlation fun ction which can be computed numerically from the surface spectrum. This tra nsform relation indicates that scattering is sensitive not only to the surf ace spectrum but also to its convoluted properties. Generally, surface scat tering is sensitive only to a portion of the surface correlation measured f rom the origin. The size of this portion is a function of three variables ( the incident angle, the surface height standard deviation, and the explorin g wavelength) and the rate of decay of the correlation function. The decay rate near the origin of the sea surface correlation is very small, so much so that at L-band this portion is too wide for a two-term approximation of the correlation function,This is true in spite of the fact that the sea sur face has a very large rms height. Thus, a scattering model based on geometr ic optics is generally not applicable at L-band especially at large angles of incidence. An additional finding is that in specular scattering wind dep endence is stronger at larger angles of incidence for incident angles betwe en 0 and 70 degrees over the wind speed range of 4 m/s-20 m/s.