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| Titel |
Lagrangian characteristics of continental shelf flows forced by periodic wind stress |
| VerfasserIn |
B. T. Kuebel Cervantes, J. S. Allen, R. M. Samelson |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 11, no. 1 ; Nr. 11, no. 1 (2004-02-25), S.3-16 |
| Datensatznummer |
250009020
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| Publikation (Nr.) |
 copernicus.org/npg-11-3-2004.pdf |
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| Zusammenfassung |
The coastal ocean may experience periods of fluctuating along-shelf wind direction,
causing shifts between upwelling and downwelling conditions with responses that are
not symmetric. We seek to understand these asymmetries and their implications on the
Eulerian and Lagrangian flows. We use a two-dimensional (variations across-shelf and
with depth; uniformity along-shelf) primitive equation numerical model to study shelf
flows in the presence of periodic, zero-mean wind stress forcing. The model
bathymetry and initial stratification is typical of the broad, shallow shelf off Duck,
NC during summer. After an initial transient adjustment, the response of the
Eulerian fields is nearly periodic. Despite the symmetric wind stress forcing, there
exist both mean Eulerian and Lagrangian flows. The mean Lagrangian displacement
of parcels on the shelf depends both on their initial location and on the initial
phase of the forcing. Eulerian mean velocities, in contrast, have almost no
dependence on initial phase. In an experiment with sinusoidal wind stress forcing
of maximum amplitude 0.1Nm and period of 6 days, the mean Lagrangian
across-shelf displacements are largest in the surface and bottom boundary layers.
Parcels that originate near the coast in the top 15m experience complicated
across-shelf and vertical motion that does not display a clear pattern. Offshore
of this region in the top 10m a rotating cell feature exists with offshore
displacement near the surface and onshore displacement below. A mapping technique
is used to help identify the qualitative characteristics of the Lagrangian motion
and to clarify the long time nature of the parcel displacements. The complexity
of the Lagrangian motion in a region near the coast and the existence of a clear
boundary separating this region from a more regular surface cell feature offshore
are quantified by a calculation from the map of the largest Lyapunov exponent. |
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