On a two-scatterer theory of sea echo

What are the mechanisms for non‐Bragg scattering from water wave surfaces?

“…His observation, reported in volume 13 of the MIT Radiation Laboratory Series, is probably the earliest documentation of superevents observed in microwave backscatter. From the mid-1960s to the mid-1970s, Pidgeon [1968] documented the separation of VV and HH Doppler peaks; Mel'nichuk and Chernikov [1971] noted the failure of the Bragg scattering mechanism to explain small grazing angle backscatter; Long [1974] correlated return spikes with wave breaking; Leykin et al [1975] noted that at small grazing angles, the horizontal polarization returns are mainly due to backscatter from the crest region of larger waves and stated that breaking wave crests contributed significantly to the horizontal returns; and Kalmykov and Pustovoytenko [1976] documented the observation of spiking and superevents. In 1991, Jessup et al [1991] observed superevents but tentatively attributed the signals to wedge scattering, "random fluctuations in the measurements or the effects also the dominant non-Bragg scattering mechanism for fast scatterers at small grazing angles.…”

Observations of sea clutter using an S‐band weather radar

“…Comparisons with experimental data have met with encouraging agreement. At small incident angles (less than 30°) some of the predictions of this theory relating to backscattered energy polarisation are contradicted by experiment (Long, 1974;Keller et al, 1989), and more work is still needed to clarify the mechanism responsible for sea clutter under these circumstances.…”

“…Theories of sea clutter for large incident angles (greater than 30°) have been proposed (Wright, 1968;Wu & Fung, 1972;Chan & Fung, 1973, 1977Long, 1974;Donelon & Pierson, 1987;Monahon & O'Muircheartaigh, 1986), which consider a two-scale roughness model of the sea surface. Small-scale waves are assumed to satisfy small perturbation theory, and large-scale waves to satisfy physical optics approximations.…”

Non-Rayleigh Sea Clutter: Properties and Detection of Targets

“…Long [21] has also noted the relationship between sea spikes and large wave structure. He reached the following conclusions.…”

“…is repeated in Appendix A) that is not. Rather, because of the presence of dorni:ant scatterers, which can be related to scattering from breaking and very peak-crested waves [20,21], p(xlao) is a Ricean density. This is difficult to show because a 0 changes so rapidly (in airborne systems) that there are too few samples to obtain a good estimate of p(xlao) before a 0 changes.…”