Observations of near-surface ocean currents at varying depths usinga new multifrequency HF radar

摘要

A new multifrequency (4-25 MHz) HF radar was installed at the LongMarine Lab. (University of California at Santa Cruz) on the north coastof Monterey Bay CA in July, 1996. This radar is capable of observingnear-surface currents at varying depths in the top two meters of theocean. Observations were made over a ten day period in March, 1997during which there was a strong land-sea breeze circulation overMonterey Bay. Radial current measurements corresponding to depths ofabout 0.3, 0.5, 1.0 and 1.4 m were made during this period using HFradar data from four operating frequencies. Fourier analysis of thesedata shows that very near the surface the strongest periodic componentis a diurnal one corresponding to the diurnally varying surface stressfrom the land-sea breeze. At deeper depths the diurnal componentremains, but a semi-diurnal component grows in strength with increasingdepth of the current measurement. Thus, multifrequency HF radar combinedwith deeper current measurements from buoys and moorings are able toinvestigate the upper layer of the coastal ocean where wind and tidallydriven currents struggle for dominance