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| Titel |
A conceptual ENSO model under realistic noise forcing |
| VerfasserIn |
J. Saynisch, J. Kurths, D. Maraun |
| 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 ; 13, no. 3 ; Nr. 13, no. 3 (2006-07-13), S.275-285 |
| Datensatznummer |
250011771
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| Publikation (Nr.) |
 copernicus.org/npg-13-275-2006.pdf |
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| Zusammenfassung |
| We investigated the influence of atmospheric noise on the generation
of interannual El Niño variability. Therefore, we perturbed a
conceptual ENSO delay model with surrogate windstress data generated
from tropical windspeed measurements. The effect of the additional
stochastic forcing was studied for various parameter sets including
periodic and chaotic regimes. The evaluation was based on a spectrum
and amplitude-period relation comparison between model and measured
sea surface temperature data. The additional forcing turned out to
increase the variability of the model output in general. The
noise-free model was unable to reproduce the observed spectral
bandwidth for any choice of parameters. On the contrary, the
stochastically forced model is capable of producing a realistic
spectrum. The weakly nonlinear regimes of the model exhibit a
proportional relation between amplitude and period matching the
relation derived from measurement data. The chaotic regime, however,
shows an inversely proportional relation. A stability analysis of
the different regimes revealed that the spectra of the weakly
nonlinear regimes are robust against slight parameter changes
representing disregarded physical mechanisms, whereas the chaotic
regime exhibits a very unstable realistic spectrum. We conclude
that the model including stochastic forcing in a parameter range of
moderate nonlinearity best matches the real conditions. This
suggests that atmospheric noise plays an important role in the
coupled tropical pacific ocean-atmosphere system. |
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