Upwelling and relaxation events inferred from high-frequency radar measurements of coastal ocean surface currents

High-frequency radar offers oceanographers a powerful yet convenient means of measuring coastal ocean currents and other air/sea interaction variables from land-based sites. The paper addresses the potential such a system offers for detecting the physically significant coastal circulation events known as coastal upwelling and relaxation. A high-frequency radar was in operation from April, 1990 until September, 1992 on the California Coast (USA) overlooking the Pacific Ocean near Monterey. Periods of months of uninterrupted radar operation have allowed the production of an unparalleled data set which includes radial ocean surface currents measured at five angles and eight range bins. Correlation of low-pass-filtered current measurements with shore-based measurements of sea surface temperature and buoy-measured wind speeds shows evidence of coastal upwelling and relaxation events