期刊名称：Science et changements planétaires / Sécheresse
印刷版ISSN：1147-7806
电子版ISSN：1777-5922
出版年度：2004
卷号：15
期号：4
页码：321-330
出版社：John Libbey Eurotext
摘要：Figures See all figures Authors Benjamin Sultan , Serge Janicot Institut de recherche pour le développement (IRD), Laboratoire d’océanographie dynamique et de climat (LODYC), UMR 7617 (CNRS/IRD/P6/MNHN), Université Pierre et Marie Curie, Case 100, 4, place Jussieu, 75252 Paris cedex 05, France Key words: Hydrology, Climatology, Rainfall, Monsoon, West Africa Page(s) : 321-30 Published in: 2004 By using daily gridded rainfall data and NCEP/NCAR (National Center for Environmental Prediction / National Center for Atmospheric Research) reanalyses over the period 1968-1990, we have documented two main aspects of the West African monsoon dynamics: the onset of the summer monsoon and the intra-seasonal modulation of convection. It is shown that the onset stage of the summer monsoon over West Africa is linked to an abrupt latitudinal shift in late June of the Inter-Tropical Convergence Zone (ITCZ) from a quasi-stationary location at 5° N in May-June to a second quasi-stationary latitude at 10° N in July-August. In the second part of this study, we show the evidence of large and coherent fluctuations in the rainfall fields in two different spectral windows: between 10 and 25 days, and between 30 and 40 days. A composite analysis based on a filtered regional rainfall index suggests the existence of enhanced and weakened monsoon phases belonging to a quasi-periodic signal of about 15 days. These wet and dry sequences are characterized by a westward propagation of large convection anomalies over the Sahel.
关键词：Hydrology; Climatology; Rainfall; Monsoon; West Africa
