Dual polarized RCS grazing angle characteristics of internal gravity waves

Grazing angle dependencies of radar cross section (RCS) are shown to differ for horizontally (HH) and vertically (VV) polarized X-band marine radar sea scatter from internal gravity wave (IGW) spatial modulations. For these internal gravity waves, observed off the coast of North Carolina, an IGW crest-to-trough modulation of 30-dB is observed at HH at 1°, but only 10 dB at VV. The HH RCS decreases with increasing grazing angle, roughly to the minus one power, whereas VV RCS increases as for the composite model, but only to the first power. The HH/VV RCS ratio is 10 dB at 1°, again opposite that expected from the two scale model, and decreases to -10 dB at 10° grazing. The two scale model with wave-current modulation of short waves by wave-current interaction predicts a decrease in modulation as grazing is approached, opposite the results presented. The authors suggest an influence of wave breaking radar scatter sources to explain these internal wave results, similar to arguments made for breaking wave scatter occurring near fronts