Circulation in the Peruvian Upwelling system near 15/sup 0/S
During the March--May 1977 phase of the Coastal Upwelling Ecosystems Analysis Joint II experiment, an intensive array of current meters, tide gauges, and meteorological sensors was deployed over the Peruvian continental shelf and slope near 15/sup 0/S. The low-pass-filtered (frequency<0.51 cpd) local winds were equatorward (upwelling favorable) throughout the study period, and conditions in the upper 100 m over the shelf indicated an active upwelling circulation. Upwelling events (with time scales 2--10 days) showed clearly in the onshore velocity and temperature records but poorly in the alongshore velocity. Baroclinic, quasi-geostrophic free coastal trapped waves dominated the alongshore velocity records, and their dynamics are investigated with the help of empirical orthogonal functions and other techniques. The offshore Ekmann flux computed from the mean alongshore wind stress of 0.76 dyne cm/sup -2/ near the coast was more than twice as large as that computed from near-surface current measurements at midshelf but 27% smaller than the observed mean onshore flow at the same location. The fluctuating mass and omentum balances were also strongly three dimensional. The alongshore velocity component tended to be geostrophically balanced. Turbulent effects were important both near the surface and near the bottom over the shelf, where estimated eddy viscosities in the boundary layers were typically in the range of 40--60 cm/sup 2/ s/sup -1/. The three dimensionality of the circulation probably reflects the complexity of the local wind driving and of the bottom topography.
- Research Organization:
- School of Oceanography, Oregon State University, Corvallis, Oregon 97331
- OSTI ID:
- 5161301
- Journal Information:
- J. Geophys. Res.; (United States), Vol. 85:C7
- Country of Publication:
- United States
- Language:
- English
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