Jc. West et al., LOW-GRAZING SCATTERING FROM BREAKING WATER-WAVES USING AN IMPEDANCE BOUNDARY MM GTD APPROACH/, IEEE transactions on antennas and propagation, 46(1), 1998, pp. 93-100
The radar backscattering from water waves of various degrees of breaki
ng is numerically examined, A hybrid moment method geometrical theory
of diffraction (MM/GTD) technique previously used for small-grazing sc
attering from perfectly conducting surfaces is reformulated using impe
dance boundary conditions, allowing the treatment of large (but finite
) conductivity scattering media such as sea water. This hybrid MM/GTD
approach avoids the artificial edge effects that limit the standard mo
ment method when applied to rough surfaces, allowing the calculation o
f the scattering at arbitrarily small grazing angles, Sample surfaces
are obtained through the edge detection of video stills of breaking wa
ves generated in a wave tank, The numerical calculations show that the
strength of the backscatter is closely associated with the size of th
e plume on the breaking wave, Strong interference appears in the both
horizontal (HH) and vertical (VV) backscatter when the surfaces are tr
eated as perfectly conducting, The VV interference is dramatically red
uced when a sea water surface is used, but the HH interference is unaf
fected. The interference leads to HH/VV ratios of up to 10 dB, The beh
avior of the scattering is consistent with the multipath theory of sea
-spike scattering.