Mapping the U.S. West Coast surface circulation: A multiyear analysis of high-frequency radar observations
Article first published online: 5 MAR 2011
Copyright 2011 by the American Geophysical Union.
Journal of Geophysical Research: Oceans (1978–2012)
Volume 116, Issue C3, March 2011
How to Cite
2011), Mapping the U.S. West Coast surface circulation: A multiyear analysis of high-frequency radar observations, J. Geophys. Res., 116, C03011, doi:10.1029/2010JC006669., et al. (
- Issue published online: 5 MAR 2011
- Article first published online: 5 MAR 2011
- Manuscript Accepted: 8 DEC 2010
- Manuscript Revised: 22 NOV 2010
- Manuscript Received: 21 SEP 2010
- surface currents;
- high-frequency radar;
- wave number spectra
 The nearly completed U.S. West Coast (USWC) high-frequency radar (HFR) network provides an unprecedented capability to monitor and understand coastal ocean dynamics and phenomenology through hourly surface current measurements at up to 1 km resolution. The dynamics of the surface currents off the USWC are governed by tides, winds, Coriolis force, low-frequency pressure gradients (less than 0.4 cycles per day (cpd)), and nonlinear interactions of those forces. Alongshore surface currents show poleward propagating signals with phase speeds of O(10) and O(100 to 300) km day−1 and time scales of 2 to 3 weeks. The signals with slow phase speed are only observed in southern California. It is hypothesized that they are scattered and reflected by shoreline curvature and bathymetry change and do not penetrate north of Point Conception. The seasonal transition of alongshore surface circulation forced by upwelling-favorable winds and their relaxation is captured in fine detail. Submesoscale eddies, identified using flow geometry, have Rossby numbers of 0.1 to 3, diameters in the range of 10 to 60 km, and persistence for 2 to 12 days. The HFR surface currents resolve coastal surface ocean variability continuously across scales from submesoscale to mesoscale (O(1) km to O(1000) km). Their spectra decay with k−2 at high wave number (less than 100 km) in agreement with theoretical submesoscale spectra below the observational limits of present-day satellite altimeters.