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Analyse de la variabilité atmosphérique à l'échelle intrasaisonnière et de sa prévisibilité au dessus de la côte guinéenne et de l'Afrique Centrale

Abstract : In this study we document the intraseasonal variability of the tropical convection and its predictability during the rainy season over the Central Africa and the Gulf of Guinea. Here, our study mainly focuses on seasons of the year for which the ITCZ is north of the equator. Based separate studies carried out on March to June and September to November seasons, we are able to identify three main modes of variability that modulate tropical convection and rainfall in West and Central Africa. During these two seasons, while individual rain-producing systems move westward, their activity is highly modulated by eastward propagating subregional and regional scale systems. Results of detailed analysis indicate the coupling between tropical convection and equatorial Kelvin wave in the region. The phases of these eastward propagating signals play an important role by regulating the organization of convective systems. Moreover, the role played by westward propagating signals (Rossby wave in particular) and Mediterranean air intrusion needs to be taken into account. These systems by interacting with Kelvin wave, may modulate the phases of convective activity in the region. Therefore, external forcing associated with these systems can be useful to the predictability of the intraseasonal modes the region. A multi model diagnostic study is performed using data available from the TIGGE project in order to evaluate the predictability of each of the main modes of variability. For a typical phase of these modes, there seems to be a statistically significant skill associated with predictability of beyond 10 days, especially for predictions initiated from active main sources.
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https://tel.archives-ouvertes.fr/tel-01756970
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Submitted on : Tuesday, April 3, 2018 - 11:35:20 AM
Last modification on : Wednesday, January 13, 2021 - 11:12:05 AM

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  • HAL Id : tel-01756970, version 1

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Pierre Honoré Kamsu Tamo. Analyse de la variabilité atmosphérique à l'échelle intrasaisonnière et de sa prévisibilité au dessus de la côte guinéenne et de l'Afrique Centrale. Océan, Atmosphère. Université Pierre et Marie Curie - Paris VI; Université de Douala, 2017. Français. ⟨NNT : 2017PA066401⟩. ⟨tel-01756970⟩

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