Statistics of low grazing angle radar sea scatter for moderate and fully developed ocean waves

Results are reported of two deep ocean radar sea scatter experiments using calibrated marine navigation radars. The first experiment featured a continuous wind direction over a four-day period, satisfying time and fetch requirements for a fully developed sea. The second experiment experienced changing winds, which was expected to produce random seas. Radar cross section samples from a 60 degrees sector centered about the maximum clutter direction were assembled into cumulative distributions for several range bins, corresponding to different grazing angles between 1 degrees and 8 degrees . These distributions are bimodal for moderate to strong winds and were fitted by two Weibull distributions. The Weibull fit to the highest amplitudes was associated with discrete scatters, while that fitting the lower amplitudes was identified with distributed roughness. Models for scattering mechanisms are inferred from the results.<>