Laboratory investigations of the hydrodynamics and radar backscattering properties of breaking waves

An experiment was conducted in a 110 m/spl times/7.6 m/spl times/4 m deep Marine Hydrodynamics facility to study the hydrodynamics of intermediate scale breaking waves and how they effect radar backscatter. An energetic spilling breaking wave, characterized by considerable whitecapping, was chosen for analysis. To characterize the wave, an array of seven capacitance wave probes were placed throughout the test basin. The waveprobes observed the temporal evolution of the breaking waves at multiple spatial locations, and were used to determine the spectral content of the pre and post-breaking small scale roughness. Wave probe data showed that the breaking wave reached its greatest amplitude at breaking and then decreased rapidly thereafter. Spectral analysis of the waveprobe data showed that prior to wave breaking, the spectral wave energy was confined to the low frequency wave components of the generated wave group. After breaking, some energy was transferred to high frequency waves, and some energy was dissipated. The energy transferred to the high frequency waves appeared as small scale roughness and was found to influence the radar backscatter.