Refraction and shoaling of surface waves by currents and topography as observed by HF radars

Phased-array Doppler radars were deployed immediately south of the mouth of the Chesapeake Bay during the COPE-3 experiment in the fall of 1997. The radars collected the Doppler spectra and extracted surface current vectors for a period of 45 days. Significant wave height and peak period estimates were obtained from the Doppler spectra using the method originally developed by Barrick (1977). The study region was strongly impacted by the outflow from the Chesapeake Bay. The buoyant plume that emanated from the bay during ebb tides was observed in the surface current maps produced by the HF radars. Significant surface current shear existed at the boundary where the buoyant plume overrode denser shelf water, resulting in a convergence frontal zone. The refraction and shoaling of the surface waves was observed as they propagated over these regions. The current-induced shoaling of incident waves was isolated from the effects of local topography. The location of significant wave height growth and dissipation was found to be dependent upon the tidal stage and the wind and wave direction. Regional remote sensing of both waves and currents was necessary to identify these high energy regions which are of considerable interest for studies of mixing at the estuarine front as well as for the safe maritime operations.