A study of surface currents in the coastal ocean outside Chesapeake Bay using HF radar

Surface circulation in the coastal ocean outside of the Chesapeake Bay was studied using high frequency radar. Radar data were collected and analyzed from three long range HF radar sites operating at 5 MHz: 1) LISL located at Little Island Park in Virginia Beach 2) CEDR on Cedar Island, a barrier island offshore of Wachapreague, Virginia and 3) DUCK located in Duck, NC. These sites are long-term monitoring stations, part of a regional ocean observing system funded under the Mid-Atlantic Regional Association Coastal Ocean Observing System (MARACOOS). This study reports on surface current data collected from mid-August to mid-September 2011. Radial data were compared with ADCP current data measured at NOAA National Data Buoy Center station 44014. R² correlation values ranged from 0.61 to 0.76 and rms differences ranged from 12 to 14 cm/s. Total velocity data were also compared with the ADCP data. A complex correlation analysis of the ADCP data compared with radar total vector currents yielded a correlation amplitude of 0.6 and a correlation angle of 8 degrees. Circulation patterns during the study period, before the passage of Hurricane Irene, are illustrated with particle trajectories. Subtidal circulation has been described in terms of principal direction of flow. Locally averaged coastal surface subtidal currents were correlated with winds measured at the NDBC CHLV2 station (Chesapeake Light Tower). East-west (across-shelf) subtidal currents in the area offshore of the Bay are highly correlated with north-south winds (R² = 0.85).