Coherent Marine Radar Measurements of Ocean Waves, Near Surface Mean Currents and Rip Current Features

We have been developed a radar for radial Doppler velocity measurements: a standard marine radar modified to coherent-on-receive capability (CORrad). It measures the intensity and the radial velocity component of the radar echo. The latter can be used to generate orbital wave velocity spatial maps of ocean waves, as well as the mean radial ocean surface velocity when sequences of map images are summed, allowing mapping of mean current features such as rip currents in the surf zone. The radar allows direct measurement of the ocean wave spectrum by means of 3D-FFT processing of a sequence of radial velocity images of orbital wave spatial patterns (U.S. Patent #8305257). We present results of radar measurements of RMS wave height for a CORrad, using both horizontally and vertically polarized antennas. Vertical polarization is found to mitigate against errors in rms wave height retrieval for high wave conditions, when accelerating breaking features generate errors for horizontal polarization. Results of an experiment to measure rip currents off Daytona Beach are also reported.