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标题：Evolution of agro-climatic risks related to the recent trends of the rainfall regime over the Sudano-Sahelian region of West Africa
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作者：Agali Alhassane ; Seyni Salack ; Mohamed Ly 等
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：2013
卷号：24
期号：4
页码：282-293
DOI：10.1684/sec.2013.0400
出版社：John Libbey Eurotext
摘要：Figures See all figures Authors Agali Alhassane , Seyni Salack , Mohamed Ly , Issaka Lona , Seydou B Traoré , Benoît Sarr Centre régional Agrhymet BP 11011 Boulevard de l’Université Niamey Niger Key words: agroclimatic risks, rainfall regime, space-time evolution, Sudano-Sahelian climate, West Africa DOI : 10.1684/sec.2013.0400 Page(s) : 282-93 Published in: 2013 In the present context of climate change, agro-hydro-meteorological monitoring needs to be improved and strengthened. The objective of this study is to use station data to assess the space-time evolution of some agro-climatic risks related to the main trends observed in the rainfall regime of the Sudano-Sahelian region extending to the Northern parts of some humid countries (Benin, Togo and Nigeria) of West Africa. Over the 1950-2010 period, the rainfall regime evolved in three different phases, with respect to the 1961-1990 averages, which are quasi-identical on annual total rainfall (Cum), the cumulated rainfall over three consecutive days (Px3), and the length of the cropping seasons (LSC) : i) a period of above normal Cum and Px3 with longer LSC (1950-1969) ; ii) a period of Cum and Px3 deficits with shorter LSC (1970-1990) ; and iii) the recent period in which Cum, Px3 et LSC are much variable (1991-2010). However, onset dates of the cropping season show a quasi-stationary trend from 1970 to 2010. The agro-climatic risks of re-sowing seeds, post-flowering water stress and the occurrence of false starts/early cessation of the cropping period are commonly shared by the recent two decades and the historical drought periods. The occurrence of false starts/early cessations reduces the usefulness of the rainy season to farmers and is correlated to annual rainfall deficits. Beyond the statistical significance of their characteristics, these results lead to two major hypotheses : i) the agro-climatic risks of the recent 1991-2010 period are still the same as those in the historical drought period of 1970-1990 ; ii) the humid years are embedded with events of false starts in the first ten days of June or earlier. Whenever these false start (early cessation) events occur after the first ten days of June (before end-of-September), the season is likely to have below normal rainfall with respect to the 1961-1990 and 1981-2010 averages. These hypotheses can be used to strengthen the techniques of seasonal rainfall forecast and agro-climatic projections in the region.
关键词：agroclimatic risks; rainfall regime; space-time evolution; Sudano-Sahelian climate; West Africa