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| Titel |
The nonlinear evolution of unstable coupled equatorial ocean-atmosphere modes |
| VerfasserIn |
P. C. F. Vaart, H. A. Dijkstra |
| 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 ; 5, no. 1 ; Nr. 5, no. 1, S.39-52 |
| Datensatznummer |
250002183
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| Publikation (Nr.) |
 copernicus.org/npg-5-39-1998.pdf |
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| Zusammenfassung |
| In this paper we investigate whether observed intraseasonal
variability in the equatorial Pacific can be attributed to finite amplitude waves
resulting from unstable air-sea interactions. Within a Zebiak - Cane type model of the
coupled equatorial ocean - atmosphere, the nonlinear equilibration of instabilities of a
simple basic state is considered with periodic conditions on the ocean boundaries. Three
mechanisms exist which can induce a finite amplitude equilibration on a time scale
ε2t. Here t is the characteristic time scale of growth of
the disturbance and ε the relative distance from the instability threshold. For each
equilibration mechanism, the finite amplitude and period of the equilibrium state are
computed as a function of ε and substantial amplitude can be reached for a reasonable
degree of supercriticality. Thereafter the analysis is extended to include time-dependent
external forcing. It is shown that interannual variability may result through the
interaction of the response of a weak annual external forcing and the finite amplitude
development of the intraseasonal instabilities. |
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