An investigation of surface current patterns related to upwelling in Monterey Bay, using high frequency radar

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Enriquez, Andres E.
Paduan, Jeffrey
Date of Issue
Monterey, California. Naval Postgraduate School
High Frequency (HF) radar backscatter instruments are under development and testing in the marine science and defense science communities for their abilities to remotely sense surface parameters in the coastal ocean over large areas. In the Navy context, the systems provide real-time mapping of ocean surface currents and waves critical to characterization and forecasting of the battlespace environment. In this study, HF radar, aircraft and satellite information were used to investigate and describe surface current in Monterey Bay, California, for a period of ten months, from June 01st, 2003 to March 31st, 2004. A network of five CODAR-type HF radar instruments measured hourly surface currents over the bay. The measurements were averaged over one-hour intervals and total surface velocities were mapped on a grid in the Monterey Bay. From the M1 Buoy located in the middle of the bay, an uninterrupted time series of wind intensity and direction was obtained for the whole period. Major upwelling events were observed during the period of June 14 to June 27, July 4 to July 19, August 8 to August 18 and other upwelling events were observed until late October. These periods of upwelling favorable winds are common during summer with durations of 10 to 20 days. Often they are interrupted by periods of relaxation state of just a few days as the winds veer to the northwest or northeast. Cyclonic circulation cells are developed on shore during upwelling conditions and an anticyclonic circulation in the middle of the bay is observed when the wind shifts to the southwest producing a strong flow out of the bay close to the coastline off Point Piǫs. Downwelling conditions are much common less than upwelling, with occurrences during winter and early fall storms with events lasting between two to five days. When the wind blows to the northeast with an intensity of 4 m/s or more for more than 12 hours, a well developed anticyclonic gyre forms in the middle of the bay. This is associated with a strong current, 35 to 40 cm/s, which flushes out in the southern part of the bay close to the coast off Point Piǫs. This flow reverses when the winds veer to the southwest and enter into the Bay with less intensity.
Series/Report No
Physical Oceanography
Other Units
NPS Report Number
xvi, 83 p. : ill. (some col.)
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Approved for public release; distribution is unlimited.
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