Measurement of ocean surface currents using a long-range, high-frequency ground wave radar

High-frequency (HF) ground wave radar (GWR) is emerging as a significant tool for monitoring ocean surface conditions at ranges well beyond the line-of-sight horizon that limits conventional systems. An experimental GWR system at Cape Race, Newfoundland, Canada that has been operational since 1991, has the ability to performing routine surveillance of oceanic surface parameters and surface target detection. Operating in the frequency range between 5 and 8 MHz, the frequency modulated interrupted continuous wave (FMICW) radar has a nominal range capability of 200 km. An experiment was performed during the period of October 20-November 21, 1992 to test the surface current measuring capability of the Cape Race system. Here, near real-time radial surface current information is extracted from the Doppler spectra of the radar time series data and a comparison is performed to the Lagrangian velocities derived from the position-time tracks of Accurate Surface Tracker (AST) drifters. A wide range of oceanic conditions were experienced during the experimental period, and favorable results were obtained from the comparison regardless of the sea state conditions. The analysis shows the standard deviation in the radar radial velocity component to be approximately 5 cm/s