OCEAN SURFACE-WAVE MEASUREMENT USING A STEERABLE HIGH-FREQUENCY NARROW-BEAM GROUND WAVE RADAR

Ground wave radar is emerging as an important tool for routine monitor ing of ocean surface conditions and for ship and sea-ice surveillance at ranges well beyond the line-of-sight horizon that limits convention al systems. A major Canadian advance in this field is the recent devel opment of a long-range ground wave radar facility at Cape Race, Newfou ndland. Owned and operated by the Northern Radar Systems Limited, this shore-based radar system can monitor ocean surface conditions over a 120 degrees sector out to a range of 200 km for sea state and to a ran ge of 300 km for ocean surface currents. The near-real-time surface wa ve parameters are extracted from the Doppler spectra of the frequency- modulated interrupted continuous wave ground wave radar system. This p aper presents a brief overview of the radar system and discusses the p rocess of extracting the one-dimensional wave spectrum and significant wave height from the Doppler spectra. The latter involves both the di rect inversion of the HF (high frequency) radar cross section of the o cean surface as well as the least square fitting of modeled HF spectra . The ground wave radar facility at Cape Race was used in the measurem ent of wave parameters during the SAR(synthetic aperture radar) wave s pectra validation experiments, offshore Newfoundland during November 1 991. The SAR is one of the sensors aboard the European Space Agency's Remote Sensing Satellite (ERS-1) launched in June 1991. The wave param eters deduced by the ground wave radar were evaluated against buoy mea surements as well as against hindcast values from the operational wave model, Canadian Spectral Ocean Wave Model. The radar-deduced wave hei ghts were also evaluated against wave height charts prepared routinely by the Meteorology and Oceanography Centre at Halifax, Nova Scotia. O verall, a very good agreement was obtained. The utility of the radar f or nearshore wave analysis and nowcasting, as well as for offshore sur veillance, is discussed.