Cl. Rino et Hd. Ngo, APPLICATION OF BEAM SIMULATION TO SCATTERING AT LOW GRAZING ANGLES .2. OCEANLIKE SURFACES, Radio science, 29(6), 1994, pp. 1381-1391
The beam simulation method developed by Maystre and Saillard is applie
d to one-dimensional power law surfaces with the same dielectric prope
rties and average spatial wave number content as wind-driven ocean wav
es. In the beam simulation method the scattering from overlapping surf
ace subsegments is first computed and then coherently combined to obta
in the scattered field. The beam simulation method is generally more e
fficient than the method of moments, but it is not an exact numerical
method. Thus we have developed a measure of the minimum subbeam size t
hat can be used for improved efficiency. This measure can be interpret
ed as the maximum distance on the surface over which local structures
interact. We find that the maximum interaction distance at 80 degrees
incidence can be as large as 200 lambda, and it increases with increas
ing incidence angle. As large-scale surface waves begin to dominate th
e surface structure, significant departures from the behavior predicte
d by first-order perturbation theory are observed within the accurate
computation range of low grazing angle backscatter. The results are di
scussed in light of ocean scattering data that evidently cannot be exp
lained by existing theories.