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| Titel |
The representation of the South Tropical Atlantic teleconnection to the Indian Ocean in the AR4 coupled models |
| VerfasserIn |
Rondrotiana Barimalala, Annalisa Bracco, Fred Kucharski |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250049686
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| Zusammenfassung |
| A series of recent papers showed that sea surface temperature
(SST) anomalies in the south equatorial tropical Atlantic
modulate the internannual variability of the African and
Indian monsoon rainfall. Physically such a teleconnection
can be explained by a simple Gill-Matsuno mechanism.
In this work, the output from five different models chosen
within theCMIP3 (Coupled Model Intercomparison Project
version 3) ensemble of coupled general circulation models
(CGCMs) are analyzed toinvestigate how state-of-the-art CGCMs
represent the impact of the South Tropical Atlantic (STA) SSTs
on the Indian and African region.
Using a correlation-regression technique, it is found that
four out of the five models display a teleconnection between
STA and Indian region which is in agreement with the observations
in the rainfall field. This teleconnection is also noticed in
the ensemble mean of the five models. Over Africa, however, the
significant changes in rainfall displayed in the observation are
properly caught by only one of the CGCMs. Additionally, none of the
model reproduces the symmetric upper-level wind response around the
Equator seen over the Indian Ocean in the observations. All models
have significant biases also in the surface pressure field response
to the tropical Atlantic SSTs. Nonetheless the overall response
found over the southern hemisphere in this study is indicative of
the Gill-Matsuno-type mechanism identified in previous studies
using idealized experiments with atmospheric GCMs and observational
data.
Overall the amplitude of the coupled model responses to the south
tropical Atlantic anomalies is weaker than in the observations. It
is shown that the difference in amplitude is not only due to the
strong bias of the CGCMs over the tropical Atlantic but it is also
caused by the different physical parameterizations used in models . |
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