Mapping surface currents and waves in Monterey Bay with HF Radar

Jeffrey D. Paduan, Ph.D.
Naval Postgraduate School
Monterey, California

Wednesday, February 4, 1998
3:30 p.m.—Pacific Forum

High-frequency (HF) radar technology offers unique capabilities to map coastal ocean currents and wave heights out to distances of about 50 km from shore. These instruments work by observing energy backscattered from surface waves. Estimates of the currents derive from Doppler shifts of the spectral peaks, while wave heights and directions are related to the overall shape of the backscatter spectrum. The theory behind HF radar measurements has been described for several decades, but practical applications have lagged behind. Recent measurements from Monterey Bay, including Coastal Ocean Dynamics Applications Radar (CODAR) measurements collected at MBARI, have led to much broader acceptance within the oceanographic community.

This talk will overview the simple concepts behind HF radar, including the different designs used by existing systems such as CODAR and Ocean Surface Current Radar (OSCR). It will also present results from Monterey Bay, which have led to new understanding of the circulation. Currents, particularly during the summer months, are now known to be driven in nearly equal proportions by eddies and upwelling filaments, sea breeze winds, and tidal fluctuations. The two-dimensional current maps available from the HF radar network make it possible to observe and separate the effects of these multiple driving forces.

Future uses of HF radar are certain to influence coastal oceanography as well as public safety functions such as search and rescue, wave height predictions, and hazardous-spill tracking and containment. Some of the remaining problems with HF radar will be outlined with an eye toward the day when these real-time uses are commonplace.

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