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| Titel |
Linear interference effects on tropical-extratropical teleconnections |
| VerfasserIn |
Christopher G. Fletcher, Paul J. Kushner |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036902
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| Zusammenfassung |
| In the northern extratropics, seasonal prediction depends mainly on finding teleconnections linking modes of daily atmospheric variability with persistent sea-surface temperature (SST) anomalies in the Tropics. These links can be maintained for weeks, months or even years by, for example, El Nino/Southern Oscillation (ENSO) episodes or secular warming trends in the tropical Indian Ocean. In this study we provide new insight into the underlying dynamics of wintertime tropical-extratropical teleconnections using a series of atmospheric GCM experiments forced with prescribed (i) warm ENSO and (ii) warm Indian Ocean SST anomalies. The resulting extratropical zonal mean responses have opposite sign: Indian Ocean warming produces a positive Northern Annular Mode (NAM) response, while ENSO warming produces a negative NAM response. Most of this difference can be explained using recently developed linear wave interference arguments. The two forcings are separated by approximately 180-degrees of longitude and their associated Rossby wave responses have opposing projections onto the background stationary waves. Finally, using an idealized `perturbed topography' experiment, we show that changing the model's climatological stationary waves can significantly alter the extratropical response to tropical forcing. |
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