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| Titel |
On modulation instability in a system of jets, waves and eddies off California |
| VerfasserIn |
L. M. Ivanov, C. A. Collins, T. Margolina |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
2198-5634
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics Discussions ; 1, no. 1 ; Nr. 1, no. 1 (2014-02-20), S.97-129 |
| Datensatznummer |
250115073
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| Publikation (Nr.) |
 copernicus.org/npgd-1-97-2014.pdf |
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| Zusammenfassung |
| SSH altimetry observations for 1992 to 2009 off Central and Southern
California are used to show that observed quasi-zonal jets were likely
driven by near-resonance interactions between different scales of the flow.
Quartet (modulational) instability dominated and caused non-local transfer
of energy from waves and eddies to bi-annual oscillations and quasi-zonal
jets. The total number of quartets induced off California was approximately
10 times larger than the number of existing triads, and quartet amplitudes
in general were larger than triad amplitudes. The spectral centroid
regularly shifted into the domain of low-order modes. Local "negative"
viscosity probably did not generate a classical inverse cascade because the
spectrum of SSHs did not demonstrate power behavior. Two types of quartets
were identified: (a) quasi-zonal jets, annual and semi-annual Rossby waves
and eddies, and (b) bi-annual oscillations, semi-annual Rossby waves and
eddies. For a case with bottom friction, quartet instability required the
existence of a certain level of dissipativity in the flow. |
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