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| Titel |
Multi-scale analysis of teleconnection indices: climate noise and nonlinear trend analysis |
| VerfasserIn |
C. Franzke |
| 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 ; 16, no. 1 ; Nr. 16, no. 1 (2009-02-06), S.65-76 |
| Datensatznummer |
250013088
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| Publikation (Nr.) |
 copernicus.org/npg-16-65-2009.pdf |
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| Zusammenfassung |
The multi-scale nature and climate noise properties of teleconnection indices
are examined by using the Empirical Mode Decomposition (EMD) procedure. The
EMD procedure allows for the analysis of non-stationary time series to extract
physically meaningful intrinsic mode functions (IMF) and nonlinear trends. The
climatologically relevant monthly mean teleconnection indices of the North
Atlantic Oscillation (NAO), the North Pacific index (NP) and the Southern
Annular Mode (SAM) are analyzed.
The significance of IMFs and trends are tested against the null hypothesis of
climate noise. The analysis of surrogate monthly mean time series from a red
noise process shows that the EMD procedure is effectively a dyadic filter bank
and the IMFs (except the first IMF) are nearly Gaussian distributed. The
distribution of the variance contained in IMFs of an ensemble of AR(1)
simulations is nearly χ2 distributed. To test the statistical
significance of the IMFs of the teleconnection indices and their nonlinear
trends we utilize an ensemble of corresponding monthly averaged AR(1)
processes, which we refer to as climate noise. Our results indicate that most
of the interannual and decadal variability of the analysed teleconnection
indices cannot be distinguished from climate noise. The NP and SAM indices
have significant nonlinear trends, while the NAO has no significant trend when
tested against a climate noise hypothesis. |
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