A. Mahmoud and M. , Le haut Gourma Central. 2nd, revised edition, R. Le Floc, 1992.

M. Balme, S. Galle, and T. Lebel, Démarrage de la saison des pluies au Sahel: variabilité aux échelles hydrologique et agronomique, pp.15-22, 2005.

M. Balme, T. Lebel, and A. Amani, Années sèches et années humides au Sahel: quo vadimus? Hydological Sci, J, vol.51, issue.2, pp.254-271, 2006.

M. A. Bell and P. J. Lamb, Integration of Weather System Variability to Multidecadal Regional Climate Change: The West African Sudan???Sahel Zone, 1951???98, Journal of Climate, vol.19, issue.20, pp.5343-5365, 2006.
DOI : 10.1175/JCLI4020.1

A. Dai, P. J. Lamb, K. E. Trenberth, M. Hulme, P. D. Jones et al., The recent Sahel drought is real, International Journal of Climatology, vol.24, issue.11, pp.1323-13331, 2004.
DOI : 10.1002/joc.1083

D. Amato, N. Lebel, and T. , On the characteristics of the rainfall events in the Sahel with a view to the analysis of climatic variability, International Journal of Climatology, vol.245, issue.189, pp.955-974, 1998.
DOI : 10.1002/(SICI)1097-0088(199807)18:9<955::AID-JOC236>3.0.CO;2-6

R. A. Houze and . Jr, Stratiform Precipitation in Regions of Convection: A Meteorological Paradox?, Bulletin of the American Meteorological Society, vol.78, issue.10, pp.2179-2196, 1997.
DOI : 10.1175/1520-0477(1997)078<2179:SPIROC>2.0.CO;2

M. Hulme, Rainfall changes in Africa: 1931???1960 to 1961???1990, International Journal of Climatology, vol.92, issue.7, pp.685-699, 1992.
DOI : 10.1002/joc.3370120703

M. Hulme, Climatic perspectives on Sahelian desiccation: 1973???1998, Global Environmental Change, vol.11, issue.1, pp.19-29, 2001.
DOI : 10.1016/S0959-3780(00)00042-X

URL : http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.502.5319

S. Janicot, Spatiotemporal Variability of West African Rainfall. Part I: Regionalizations and Typings, Journal of Climate, vol.5, issue.5, pp.489-497, 1992.
DOI : 10.1175/1520-0442(1992)005<0489:SVOWAR>2.0.CO;2

P. J. Lamb, Persistence of Subsaharan drought, Nature, vol.185, issue.5878, pp.46-47, 1982.
DOI : 10.1038/299046a0

K. Lau and H. Wu, Detecting trends in tropical rainfall characteristics, 1979.

H. Laurent, N. Amato, and T. Lebel, How important is the contribution of the mesoscale convective complexes to the Sahelian rainfall?, Physics and Chemistry of the Earth, vol.23, issue.5-6, pp.629-633, 1998.
DOI : 10.1016/S0079-1946(98)00099-8

L. Barbé, L. Lebel, and T. , Rainfall climatology during the years 1950-90, J. Hydrol, pp.188-189, 1997.

L. Barbé, L. Lebel, T. Tapsoba, and D. , Rainfall Variability in West Africa during the Years 1950???90, Journal of Climate, vol.15, issue.2, pp.187-202, 2002.
DOI : 10.1175/1520-0442(2002)015<0187:RVIWAD>2.0.CO;2

T. Lebel, J. D. Taupin, D. Amato, and N. , Rainfall monitoring during HAPEX-Sahel. 1. General rainfall conditions and climatology, Journal of Hydrology, vol.188, issue.189, pp.188-189, 1997.
DOI : 10.1016/S0022-1694(96)03155-1

T. Lebel, A. Diedhiou, and H. Laurent, Seasonal cycle and interannual variability of the Sahelian rainfall at hydrological scales, Journal of Geophysical Research, vol.11, issue.2, pp.10-1029, 2003.
DOI : 10.1029/2001JD001580

T. Lebel and A. Ali, Recent trends in the Central and Western rainfall regime, J. Hydro, 1990.
URL : https://hal.archives-ouvertes.fr/insu-00412630

L. 'hôte, Y. Mahé, G. Somé, B. Triboulet, and J. P. , Analysis of a Sahelian annual rainfall index from 1896 to 2000; the drought continues, Hydrological Sciences Journal, vol.325, issue.4, pp.563-572, 2002.
DOI : 10.2307/2346729

L. 'hôte, Y. Mahé, G. Somé, and B. , The 1990s rainfall in the Sahel: the third driest decade since the beginning of the century, Hydrological Sciences Journal, vol.11, issue.3, pp.493-496, 2003.
DOI : 10.2307/2346729

V. Mathon, H. Laurent, and T. Lebel, Mesoscale Convective System Rainfall in the Sahel, Journal of Applied Meteorology, vol.41, issue.11, pp.1081-1092, 2002.
DOI : 10.1175/1520-0450(2002)041<1081:MCSRIT>2.0.CO;2

K. I. Mohr, Interannual, Monthly, and Regional Variability in the Wet Season Diurnal Cycle of Precipitation in Sub-Saharan Africa, Journal of Climate, vol.17, issue.12, pp.2441-2453, 2004.
DOI : 10.1175/1520-0442(2004)017<2441:IMARVI>2.0.CO;2

R. Morel, Atlas agroclimatique des pays de la zone du CILSS, Comité Permanent de Lutte contre la Sècheresse dans le Sahel (CILSS), Programme Agrhymet, 1992.

V. Moron, Guinean and sahelian rainfall anomaly indices at annual and monthly scales (1933???1990), International Journal of Climatology, vol.11, issue.3, pp.325-341, 1994.
DOI : 10.1002/joc.3370140306

M. J. Mortimore and W. M. Adams, Farmer adaptation, change and ???crisis??? in the Sahel, Global Environmental Change, vol.11, issue.1, pp.49-57, 2001.
DOI : 10.1016/S0959-3780(00)00044-3

E. Mougin, The AMMA Gourma observatory site: an overview of research activities, J. Hydro, 2009.

J. E. Nachamkin, R. L. Mcanelly, and W. R. Cotton, An Observational Analysis of a Developing Mesoscale Convective Complex, Monthly Weather Review, vol.122, issue.6, pp.1168-1188, 1994.
DOI : 10.1175/1520-0493(1994)122<1168:AOAOAD>2.0.CO;2

M. New, B. Hewitson, D. B. Stephenson, A. Tsiga, A. Kruger et al., Evidence of trends in daily climate extremes over southern and west Africa, Journal of Geophysical Research, vol.16, issue.23, p.1410210, 1029.
DOI : 10.1029/2005JD006289

S. Nicholson, The Nature of Rainfall Fluctuations in Subtropical West Africa, Monthly Weather Review, vol.108, issue.4, pp.2191-2208, 1980.
DOI : 10.1175/1520-0493(1980)108<0473:TNORFI>2.0.CO;2

S. E. Nicholson, The Historical Climatology of Africa Climate and History, pp.249-270, 1981.

S. E. Nicholson, Long term changes in African rainfall. Weather, pp.46-56, 1989.

S. Nicholson, On the question of the ???recovery??? of the rains in the West African Sahel, Journal of Arid Environments, vol.63, issue.3, pp.615-641, 2005.
DOI : 10.1016/j.jaridenv.2005.03.004

S. Nicholson and I. Palao, A re-evaluation of rainfall variability in the sahel. Part I. Characteristics of rainfall fluctuations, International Journal of Climatology, vol.2, issue.4, pp.371-389, 1993.
DOI : 10.1002/joc.3370130403

J. Pedersen and T. A. Benjaminsen, One Leg or Two? Food Security and Pastoralism in the Northern Sahel, Human Ecology, vol.11, issue.1, pp.43-57, 2008.
DOI : 10.1007/s10745-007-9136-3

M. Shinoda, T. Okatani, and M. Saloum, Diurnal variations of rainfall over Niger in the West African Sahel: a comparison between wet and drought years, International Journal of Climatology, vol.73, issue.189, pp.81-94, 1999.
DOI : 10.1002/(SICI)1097-0088(199901)19:1<81::AID-JOC350>3.0.CO;2-F

M. V. Sivakumar, Agroclimatic aspects of rainfed agriculture in the Soudano? Sahelian zone, Proc. of the International Workshop on Soil, Crop and Water Management Systems for Rainfed Agriculture in the Soudano?Sahelian Zone, pp.7-11, 1987.

M. V. Sivakumar, Empirical Analysis of Dry Spells for Agricultural Applications in West Africa, Journal of Climate, vol.5, issue.5, pp.532-539, 1992.
DOI : 10.1175/1520-0442(1992)005<0532:EAODSF>2.0.CO;2

R. D. Stern, M. D. Dennet, and D. J. Garbutt, The start of the rains in West Africa, Journal of Climatology, vol.10, issue.1, pp.59-68, 1981.
DOI : 10.1002/joc.3370010107

A. Tarhule and P. J. Lamb, Climate Research and Seasonal Forecasting for West Africans: Perceptions, Dissemination, and Use?, Bulletin of the American Meteorological Society, vol.84, issue.12, pp.1741-1759, 2003.
DOI : 10.1175/BAMS-84-12-1741

A. V. Todorov, Sahel: The Changing Rainfall Regime and the ???Normals??? Used for its Assessment, Journal of Climate and Applied Meteorology, vol.24, issue.2, pp.97-107, 1985.
DOI : 10.1175/1520-0450(1985)024<0097:STCRRA>2.0.CO;2

J. M. Wallace, Diurnal Variations in Precipitation and Thunderstorm Frequency over the Conterminous United States, Monthly Weather Review, vol.103, issue.5, pp.406-419, 1975.
DOI : 10.1175/1520-0493(1975)103<0406:DVIPAT>2.0.CO;2

M. Wild, J. Grieser, and C. Schär, Combined surface solar brightening and increasing greenhouse effect support recent intensification of the global land-based hydrological cycle, Geophysical Research Letters, vol.448, issue.10, pp.10-1029, 2008.
DOI : 10.1029/2008GL034842

G. Y. Yang and J. Slingo, The Diurnal Cycle in the Tropics, Monthly Weather Review, vol.129, issue.4, pp.784-801, 2001.
DOI : 10.1175/1520-0493(2001)129<0784:TDCITT>2.0.CO;2