| 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{dollar}spcirc{dollar} sector from 61{dollar}spcirc{dollar} to 181{dollar}spcirc{dollar} (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 aximuthal and range increments of approximately 4{dollar}spcirc{dollar} 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.; An algorithm is also presented to estimate the tangential current components assuming the current is uniform about the location of the drifter velocity estimate. (Abstract shortened by UMI.)... |
