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Journal Article: ID no. (ISBN etc.):  0894-8755 BibTeX citation key:  Joly2009a
Joly, M. & Voldoire, A. (2009) Influence of ENSO on the West African monsoon: Temporal aspects and atmospheric processes. IN Journal of Climate, 22. 3193–3210.
Added by: Mathieu Joly 2009-01-22 09:23:19    Last Edited by: Fanny Lefebvre 2011-01-17 17:29:23
Categories: Ocean-atmosphere interactions
Keywords: Climate
Creators: Joly, Voldoire
Collection: Journal of Climate
Bibliographies: cnrm, Prior150410

Peer reviewed
Number of views:  1105
Popularity index:  58.34%
Maturity index:  accepted

A significant part of the West African Monsoon (WAM) interannual variability can be explained by the remote influence of El Niño-Southern Oscillation (ENSO). Whereas the WAM occurs in the boreal summer, ENSO events generally peak in late autumn. Statistics show that in the observations, the WAM is influenced either during the developing phase of ENSO, or during the decay of some long-lasting La Niña events. The timing of ENSO seems thus essential to the teleconnection process. Composite maps for the developing ENSO illustrate the large-scale mechanisms of the teleconnection. The most robust features are a modulation of the Walker circulation and a Kelvin wave response in the high-troposphere.
In the CNRM-CM3 coupled model, the teleconnection occurs unrealistically at the end of ENSO events. An original sensitivity experiment is presented, in which the ocean component is forced with a reanalyzed wind-stress over the tropical Pacific. This allows the reproduction of the observed ENSO chronology in the coupled simulation. In CNRM-CM3, the atmospheric response to ENSO is slower than in reanalysis data, so that the influence on the WAM is delayed by a year.
The two principal features of the teleconnection are the timing of ENSO onsets and the time-lag of the atmospheric response. Both are assessed separately in sixteen of the CMIP3 20C3M coupled simulations. The temporal aspects of the ENSO teleconnection are reproduced with difficulty in state-of-the-art coupled models. Only four models simulate an impact of ENSO on the WAM during the developing phase.
Added by: Mathieu Joly    Last Edited by: Fanny Lefebvre