Two-scale analysis of LGA scattering from a 3-D spilling breaker crest

Scattering from the crests of intermediate-scale breaking waves with wavelengths on the order of a meter has been suggested as a significant contributor to sea-surface microwave backscattering at low grazing angle (LGA) illumination. Recently, West and Ja (Radio Sci., vol.37, no.4, p. 7-1-7-12, 2002) used the two-scale scattering model (TSM) to examine the scattering from the 2D measurements of the crest of a low energy spilling breaker wave-tank wave. The roughness was divided into large-scale and small-scale components using a moving average filter, and the deterministic TSM field equations of Guissard and Sobieski were used to find the field directly. These were compared with reference scattering found using a 2D computational EM technique. In this work, a 3D crest profile (rough in 2D) is synthesized from the 2D wave tank measurements. TSM is again applied, and the is field compared with reference scattering found using the multilevel fast multipole algorithm (MLFMA).