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Titel |
Equatorial Atlantic forcing of the El Niño Southern Oscillation |
VerfasserIn |
Hui Ding, Noel Keenlyside, Mojib Latif |
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 |
250040733
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Zusammenfassung |
Observations indicate a significant influence of the Atlantic zonal mode
on the El Niño Southern Oscillation (ENSO), with variations in the
Atlantic leading by around six months. Detailed analysis of observations
and reanalysis show that a warm phase of the zonal mode during boreal
summer favors the development of a La Niña event during the boreal
winter. A warm SST anomaly in the Atlantic affects the Walker
circulation with anomalous rising and subsiding motions in the tropical
Atlantic and eastern tropical Pacific, respectively. This exerts an
easterly anomaly to the west of subsiding region that is amplified by
Bjerknes positive feedback, favoring the development of a La Niña event.
Here we reproduce the observed relationships, in terms of both strength
and phase, using a complex Coupled General Circulation Model
(ECHAM5/MPIOM). A five ensemble member simulation is performed with
observed sea surface temperature (SST) specified in the tropical
Atlantic and full coupling elsewhere. The simulations cover the period
1950 to 2005. The ensemble mean of the simulations reproduces the
results from observations and reanalysis very well, and supports the
mechanism outlined above. The impact of Atlantic on the mean state and
statistics of the variability will also be discussed. The potential
implication for ENSO prediction is investigated in seasonal hindcast
experiments with the model. |
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