Coherent microwave marine radars for deterministic wave profile mapping, decameter-scale coastal current mapping and ocean wave spectra measurements

Two different approaches in development of a coherent marine radar for ocean remote sensing applications have been designed, assembled, and tested: a fully coherent radar (COHrad) and a coherent-on-receive radar (CORrad). These radars operate similar to standard marine radars, with rotation revisit rates of either 0.4 or 0.8 Hz, suitable for measuring ocean wave frequencies of half these values. They allow repetitive maps of radial velocity, primarily orbital wave velocity of ocean waves, and thus can provide a map of ocean wave height directly, without the need for a modulation transfer function as is used with non-coherent radars. When averaging of a large set of consecutive images, slower time scale phenomena can be mapped, such as mean area currents and localized rip current features. Two radars illuminating a common area could thus provide the vector current field for all such processes in that area. A string of such radars along a coast with overlapping coverage could provide continuous coastal maps of ocean currents. A description of both radars is provided, the signal processing involved, and some preliminary examples of displays that are available for data from these systems.