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Permanent Meanders in the California Current System
L. R. Centurioni, J. C. Ohlmann, P. P. Niiler
Scripps Institution of Oceanography
cohlmann@ucsd.edu(Abstract received 04/29/2005 for session A)
ABSTRACT
SVP drifter data from 1992-2004, AVISO sea level anomalies and NCEP reanalysis winds, are used to assemble a time mean distribution of 15 m velocity in the California Current System (CCS) seaward of 50 km from the coast. Ekman currents are subtracted from the drifter measurements and the resulting geostrophic velocities from drifters and AVISO are used to form an unbiased mean geostrophic circulation. The CCS flows southward with four permanent meanders that can have seaward extensions more than 3000 km offshore. The observed time mean circulation and its associated eddy energy are compared to those produces by various high resolution OGCS solutions (HYCOM, NLOM, POP, and ROMS). Simulations in closest agreement with observations come from ROMS, which produces four meanders and eddy energy within 50% of observed values. The time mean ageostropic velocity in ROMS is strongest within the cyclonic part of the meanders and appears similar to the ageostrophic velocity produced by non-linear interaction of Ekman currents with the near surface vorticity field. Because ROMS shows the near surface velocity within 50km of the coast is neither in Ekman nor in geostrophic balance, Lagrangian observations on the continental shelf of the CCS are necessary.
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2005 LAPCOD Meeting, Lerici, Italy, June 13-17, 2005