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| Titel |
Methods to describe barotropic vortices by global fields and vortex characteristics |
| VerfasserIn |
W.-G. Früh |
| 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 ; 9, no. 3/4 ; Nr. 9, no. 3/4, S.189-200 |
| Datensatznummer |
250006536
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| Publikation (Nr.) |
 copernicus.org/npg-9-189-2002.pdf |
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| Zusammenfassung |
Results from an
experimental study of vortices in a rotating shear layer are presented.
The data are in the form of maps of the instantaneous horizontal velocity
field obtained by a particle tracking technique. Two fundamentally
different methods to analyse time series of these velocity fields are
presented and compared. One technique is the empirical orthogonal function
(EOF) analysis, and the other method describes the flow field in terms of
a few individual localised vortices.
The flows discussed here are time-dependent two-vortex
flows, which could either be described as a global mode 2 or as a
collection of four unequal vortices. The results show that, while EOF
analysis is a very powerful tool to detect fairly regular travelling modes
or stationary features, it cannot detect local dynamics. The vortex
identification technique is very good at detecting local structures and
events but cannot put them into the context of a global flow structure.
The comparison of the techniques shows indications that the
time-dependence found in the system for low mode numbers could arise from
an interaction of the large scale, global-mode flow with a local mechanism
of vortex generation and shedding at a solid boundary. |
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