Spatial distribution and temporal evolution of sea surface hydrodynamics estimated through a Coherent X-band Marine Radar

We deployed a newly-developed coherent X-band marine radar system during the ONR-funded Data Assimilation & Remote Sensing for Littoral Applications (DARLA) experiment at New River Inlet, NC (April-May 2012). The main objective was to collect observations of the spatial distribution and temporal evolution of the high-frequency hydrodynamics at the ocean surface within a complex littoral environment. The coherent radar (developed by Imaging Science Research, Inc.) relies on the Doppler shift of the backscattered signal to derive the radial component of velocity at the ocean surface. Within the 1.5-km radius of the imaged footprint, preliminary results show maximum instantaneous velocities ranging from -3.2 to 3.3 m s^-1 (negative values correspond to targets moving away from the radar; positive, toward). These velocities represent the combined contribution of wind-, wave- and tide-driven flows. Radial velocities averaged over 20-minute intervals were dominantly positive over most of the experiment, ranging from 0.2-1.1 m s^-1 with the higher values being located over the southern ebb-shoal. Most likely dominated by the contribution of breaking waves in the direction of the radar, these values are well in agreement with theoretical wave-orbital velocities estimated using NDBC 41109, located approximately 6 km SE of the New River Inlet. Additional analyses are being performed to assess the ability of the system to provide wave height H from the velocity measurements.