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Synthetic aperture radar images of ocean waves were obtained in conjunction with reference wave data near Marineland, Florida, December 14, 1975. Each of the various types of measurements were processed into a form that allowed direct comparisons with the others. Maxima of radar spectra occurred at the same frequencies as the maxima of reference wave height spectra. In a comparison of a radar spectrum with observed spectra of wave height, wave orbital velocity, and surface slope the high-frequency portion of the radar spectrum lay near and between the wave height and the orbital velocity spectra but differed significantly from the surface slope spectrum. The radar-derived mean directions and model-fitted directional spreads of wave energy were close to the values from a directional wave buoy and indicated the accuracy of radar measurements o! wave direction. However, a directional plot of a radar spectrum near shore at the frequency of the maximum showed a sharper peak than such a plot of a fitted spectrum derived from reference data. The high directional resolution of the radar, in addition to its making observations at different locations, allowed radar images to provide information about ocean waves not available from the other instruments. As a swell propagated across the continental shelf, it was scattered in direction, apparently by the irregularities of the bottom, and very little of its energy reached shore. The shorter sea waves had a narrow directional distribution when first observed offshore that may have been sharpened by interaction with the Gulf Stream. Radar images showed effects of bottom refraction on the sea waves as they moved into progressively shallower water. the USSR [Bondarenko et al., 1972] since the early 1970's. Airborne synthetic aperture radar has been used to observe waves generated by hurricanes at L band [Ross et al., 1974], while X band systems have observed features of the Gulf Stream [ Wright et al., 1976]. The Seasat A satellite was the first attempt to obtain wave imagery from space. Preliminary results from its data [Gonzalez et al., 1979; Teleki et al., 1979] show that useful imagery can be obtained.concerned with wavelength and direction information. The results are encouraging, but it must be noted that the majority of waves imaged appear to have been swell and the limitations of the synthetic aperture approach in imaging local sea is not known.According to the theory of synthetic aperture systems, as discussed by Brown and Porcello [1969], the location of a reflecting element on the earth's surface is determined by tracking the Doppler phase history of the returned signal. For a fixed surface, there is a unique Doppler relationship for the received radar signal from a given earth location. If the surface is in motion, however, as in the case of ocean waves, the

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The maximum amplitude of shear stress in the bottom boundary layer of water waves was evaluated with a Preston probe inclined on a 1 12 5 slope beach Near bottom velocity profiles were obtained in laminar and developing turbulent flow conditions from which the experimental boundary layer thicknesses were evaluated Agreement between experimental bottom velocities and those calculated from Airy theory deteriorate with decreasing depth on the beach resulting m lower shear stress values than predicted by linear theory The measured boundary layer thickness on the slope exceeds the predicted for horizontal bottom, increasing shoreward to some critical depth outside the breaker zone from where it decreases shoreward The influence of roughness on the shear stress distribution is considerable m the "offshore" region, but becomes negligible near the breaker zone On a smooth bottom the coefficient of friction agrees with Kajiura's expression.

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