Remotely sensed surface currents in monterey bay from shore-based HF radar (Coastal Ocean Dynamics Application Radar)

Near-surface currents in Monterey Bay derived from a network of shore-based HF radars are presented for August-December 1994 and compared with those from April to September 1992. Focus is placed on the low-frequency (2- to 30-day period) motions in the remotely sensed data and on comparison of radar-derived currents with moored current and wind observations, ship-based acoustic Doppler current profiler observations, satellite-based surface temperature imagery, and surface drifter velocities. The radar-derived picture of the late summer mean flow is very similar in the two realizations and is consistent with historical data. Flow is equatorward in the outer part of the bay, poleward in a narrow band nearshore, and very sluggish in the middle of the bay. Low-pass-filtered time series of radar-derived currents are highly correlated with moored current observations and with winds in the outer part of the bay. The vector time series are also coherent across a broad frequency band with currents typically in phase between 1- and 9-m depths and with l-m currents typically 40 degrees-60 degrees to the right of the wind. Overall, these results confirm the utility of Coastal Ocean Dynamics Applications Radar (CODAR)-type HF radars for the study of coastal surface currents out to ranges similar to 50 km from shore, particularly for highly averaged fields. Data variability and comparison with in situ observations for high-frequency (1- to 48-hour period) motions point to the need to better characterize and minimize sources of error in the radar observations.