Ocean surface current estimation using a long-range, single-station, high-frequency ground wave radar

Estimation of ocean surface currents from a long-range, single-station, narrow-beam, high frequency (HF) ground wave radar (GWR) system is presented. This system, located at Cape Race, Newfoundland, is a frequency modulated interrupted continuous wave radar that operates in the lower HF band between 5 and 8 Mhz. It has a nominal range capability of 200 km over a 120° sector from 61° to 181° (True). Even though its primary purpose is for offshore target surveillance, it can be easily configured for the monitoring of oceanic surface conditions such as currents and waves. -- An experiment was performed during the fall of 1992 to test the current measuring capability of this experimental system. This HF GWR can monitor projections of the surface current field in azimuthal and range increments of approximately 4° and 400 m, respectively. These projections or radial surface current components are extracted from the first-order contributions of the radar Doppler spectra and compared with the estimates derived from the positional tracks of three Accurate Surface Tracker drifters. The comparison demonstrates the ability of the radar to estimate radial currents to within one standard deviation of both current measuring techniques. This has been demonstrated with simulated as well as actual data. -- An algorithm is also presented to estimate the tangential current components assuming the current is uniform about the location of the drifter velocity estimate. This algorithm was tested with simulated radar data and the analysis suggests the error of the tangential component to be within one standard deviation of the radar and drifter error estimates. However, in the comparison using the real radar data these errors were more than 2 standard deviations larger than the errors estimated by the simulations. These deviations have been attributed to a number of factors such as possible beamforming errors or non-stationary currents over the radar beam dwell periods. However, since the simulations strongly demonstrate the potential for mapping the vector current field without the need of a second site, the results from this thesis are very encouraging for further development in this area