Experimental study and theoretical model of high-resolution radar backscatter from the sea

The temporal characteristics of radar backscatter from the sea depend on the pulse width for surface resolutions less than about 20 m. While low-resolution backscatter appears continuously noiselike, as the resolution is increased, the backscatter is punctuated by substantially quieter periods. This results in a noticeably ‘spikey’ characteristic. Measurements at 3 cm using several different pulse widths have been made near grazing incidence together with synchronized television views of the radar-illuminated surface. These observations confirm that the largest backscatter is due to whitecaps. However, even the quieter periods disclose spikes, although they are about 3 orders of magnitude lower in power. A simple model of the salient scattering regions consists of a random collection of effective scattering centers which change in number with whitecap growth or decay. By comparing modeled surface realization with radar data it is concluded that the decorrelation time of the surface and scatterers within the surface are each about 10^−-2 s at X band.