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：2008
卷号：19
期号：2
页码：87-93
DOI：10.1684/sec.2008.0130
出版社：John Libbey Eurotext
摘要：Figures See all figures Authors Ousmane Dieng , Pascal Roucou , Samuel Louvet Centre de recherche de climatologie, 6, boulevard Gabriel, 21000 Dijon France Key words: climatology, monsoon, rainfall, Senegal, West Africa DOI : 10.1684/sec.2008.0130 Page(s) : 87-93 Published in: 2008 The onset of the West African monsoon is characterized by a succession of active and inactive phases (pauses), during which the rainfall increases and decreases. The calendar of the phases is very regular from year to year. The main goals of this paper are to specify the calendar of the pauses and to study their variability throughout the 1951-1996 period. First, the data of each rainfall station are aggregated in pentads (5 day means). Then, the time-series are filtered with a low-pass filter to eliminate the shortest meteorological fluctuations. To summarize the data we compute two rainfall indices using a hierarchical cluster analysis. A simple detection criterion of the pauses is then applied to the indices for each of the 46 seasons (April to August). The results show that the active and inactive phases are similar to those detected over West Africa. The first pause takes place in the South between June 19 and 23, on an average. The second pause is found across the whole country and takes place between July 29 and August 2 and between August 3 and 7, in the South and in the North, respectively. These mean dates remained unchanged from the pre-1970 wet period to the post-1970 dry period. At intra-seasonal time-scales, in the northern part of the country we observe that an earlier (later) pause is associated with upper (lower) seasonal rainfall amounts in July-August-September. There is no such relationship in the South. Understanding the pauses and forecasting them may thus offer interesting applications in agronomy, particularly in the North.
关键词：climatology; monsoon; rainfall; Senegal; West Africa
