| Long-term, high-frequency (HF) radar measurements of coastal ocean surface currents allow observation of large-scale coastal circulation events with a temporal and spatial resolution not readily available with conventional instrumentation. Additionally, HF radar is capable of measuring the directional distribution of ocean waves at a "resonant" frequency. These and other measurements using inversion techniques provide information useful for estimating a variety of wave and wind information. HF radar is thus a useful remote sensing tool for coastal oceanography.;HF radar measurements gathered during extended portions of the period from April, 1990 until July, 1992 on the California coast, about 15 miles south of Monterey, exhibit features of tidal and wind-driven ocean circulation. The effects of the tidal current ellipse are apparent in these radial measurements of the coastal currents. Additionally, correlation of the radar measurements with local sea surface temperature and winds indicates that the important features of coastal upwelling and relaxation are also evident within the radar data. The long period of observation has allowed a glimpse at seasonal and interannual variability in the coastal currents.;By comparing radar measurements of radially approaching and radially receding ocean waves, we see evidence of the effect of the wind on the phase speed of ocean waves. Until now, this was an unexplored effect partly due to the difficulty of its measurement.;Measurements of surface currents at two frequencies in the HF band make possible an estimate of the vector current shear (or the variation of the current speed and direction as a function of depth) in the uppermost layer of the ocean. We observed a clockwise rotation in current direction and a decrease in current magnitude with depth.;Finally, we compared HF radar measurements of ocean surface currents to surface motion measured with interferometric synthetic aperture radar and deeper currents measured with ship-mounted acoustic Doppler current profilers.;This study demonstrates many of the applications that HF radar offers to the examination of coastal oceanographic processes as well as of general physical processes within the surface layer of the ocean. |
