Multifrequency HF radar observations of the vertical structure of near-surface currents during COPE-3

An HF Multifrequency Coastal Radar (MCR) operating between 4.8 and 21.8 MHz was used as part of the third Chesapeake Outflow Plume Experiment (COPE-3) during October and November, 1997. The radar system surveyed the open ocean east of the coast near Chesapeake Bay, Virginia, from two sites separated by about 20 km. Measurements were taken once an hour, and the eastward and northward components of ocean currents were estimated at four depths ranging from about 0.5 m to 2 m below the surface for each location on a 2 km by 2 km grid. The radar measurements were compared to currents measured by several moored acoustic Doppler current profilers (ADCPs) with range bins 2-14 m below the water surface. Vertical current shear was estimated from the radar measurements by comparing currents measured at different radar wavelengths, and the radar shear estimates were compared to wind measurements from a nearby light tower. The radar and ADCP currents were highly correlated, and there was some correlation between radar current shear and wind speed