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| Titel |
Potential impact of the May Southern Hemisphere annular mode on the Indian summer monsoon rainfall |
| VerfasserIn |
Juan Dou, Zhiwei Wu, Yefan Zhou |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250137426
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| Publikation (Nr.) |
 EGU/EGU2017-126.pdf |
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| Zusammenfassung |
| El Niño-Southern Oscillation (ENSO) is probably a most important external forcing to Indian
summer monsoon (ISM) rainfall (ISMR), yet the observed ENSO-ISMR relationship has
become weak in recent years. It’s essential to explore other predominant modes of variability
which can contribute to the ISMR. As the leading mode of the variability in Southern
Hemisphere (SH) extratropical atmospheric circulation, the SH annular mode (SAM) has
potential influence both on the northern and southern hemispheric climate. The present study
investigates the relationship between the SAM and ISMR. It is found that the May SAM
exhibits a significant positive correlation with the monsoon precipitation over the Indian
sub-continent and the adjacent areas in JunetJuly (JJ). Observational and numerical evidences
indicate that the May SAM anomaly can trigger a South Indian Ocean dipole (SIOD) sea
surface temperature anomaly (SSTA) through air-sea interactions. The SIOD SSTA
persisting into the following months of JJ excites abnormal meridional circulation
and modulates the low-level cross-equatorial flow. Accordingly, the ascending (or
descending) motion and water vapor transportation are enhanced (or suppressed),
which favors more (or less) precipitation over the Indian sub-continent and the
adjacent areas. In fact, the SIOD SSTA plays an “ocean bridge” role to “prolong” the
influence of the May SAM to the subsequent season and in turn impacts on the ISMR.
Moreover, an empirical model is established to forecast the JJ ISMR strength based on
the ENSO, Indian Ocean Dipole (IOD) and May SAM. The hindcast is carried
out for the period 1979–2014, and performs better than the multimodel ensemble
mean (MME) obtained from the Development of a European MME system for
seasonal to interannual prediction (DEMETER) project. Since all these predictors can
be monitored in real time before the early boreal summer, the empirical model
might provide a practical real-time forecast tool for predicting ISMR variations. |
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