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Communication incl. Poster: BibTeX citation key:  RodriguezFonsecaa
Rodriguez de Fonseca, M. B., Mohino, E., Losada Doval, T., Janicot, S. & Gervois, S. 2009. Understanding a global tropical mode influencing the WAM variability. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: Devic 2009-10-09 08:58:55    Last Edited by: roussot 2009-10-16 16:37:19
Categories: General
Keywords: Climate, Interannual variability
Creators: Gervois, Janicot, Losada Doval, Mohino, Rodriguez de Fonseca
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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Recent studies have pointed out that, from recent decades, the Equatorial Atlantic mode (EM) or Atlantic Niño is strongly correlated with opposite phase of its Pacific counterpart. In this way, the tropical convection associated with the EM produces stronger alterations in the tropical circulation and induces development of next-winter Pacific Niñas.
In the frame of the AMMA-EU project both observational and multimodel ensemble approaches show important changes, in the regional SST patterns associated with the summer WA rainfall, when considering the 1979-98 period or the 1957-78 one.
The results show that Pacific dominates alone when considering the decades before the 70’s and, when we focus after 1979 we see the same response for the Indian, Pacific and Atlantic modes, which in turn resembles the ENSO atmospheric response. Moreover, the presence or absence of the WA rainfall dipole observed in the anomalous rainfall patterns in both periods seems to be related to this tropical mode.
In the present study, we define a global tropical time-varying SST mode in relation to the summer anomalous WA rainfall; analyzing its associated atmospheric response. In this way, for positive phases of this mode (warm Atlantic and cold Pacific and Indian regions), the preonset and onset of the monsoon is dominated by the Atlantic Niño and there is a significant increase of rainfall over the Guinea region. As the Atlantic Niño decays, the Pacific influence dominates and the rainfall start to increase over the Sahel.
The results support other works pointing to a the fact that the ENSO phenomenon can be interpreted, during the last decades of the XX century, as a global scale pattern in which all the tropical basins seems to operate together.
Last Edited by: roussot