Climate Dynamics

, Volume 42, Issue 1–2, pp 189–201 | Cite as

Oceanic influence on the sub-seasonal to interannual timing and frequency of extreme dry spells over the West African Sahel

  • Seyni Salack
  • Alessandra Giannini
  • Moussa Diakhaté
  • Amadou. T. Gaye
  • Bertrand Muller


Intra-seasonal drought episodes (extreme dry spells) are strongly linked to crop yield loss in the West African Sahel, especially when they occur at crop critical stages such as juvenile or flowering stage. This paper seeks to expose potentially predictable features in the sub-seasonal to inter-annual occurrence of “extreme dry spells” (extDS) through their links to sea surface temperature anomalies (SSTAs). We consider two kinds of extreme dry spells: more than 2 weeks of consecutive dry days following a rain event (often found at the beginning of the rainy season, after the first rain events) and more than a week (observed towards the end of the rainy season, before the last rain events). We extract dry spells from daily rainfall data at 43 stations (31 stations in Senegal over 1950–2010 and 12 stations in Niger over 1960–2000) to identify the intra-seasonal distribution of extDS and their significant correlation with local rainfall deficits. Seasonality of distribution and high spatial coherence are found in the timing and the frequency of occurrence of extDS in different rainfall regions over Niger and Senegal. The correlation between the regional occurrence index (ROI), necessary to capture the spatial extent of extDS, and observed global sea surface temperature anomalies (SSTAs) sheds light on the influence of the external factors on the decadal, interannual and sub-seasonal variability of extDS over the West African Sahel. When the global tropics and the Atlantic are warmer than normal, more coherent and delayed June–July extDS are observed after onset of rainy season, as well as early cessation type in August–September. When the Indo-Pacific is cooler and the equatorial south Atlantic is warmer than normal little to no extDS are found in the onset sub-period of the monsoon season. Mostly late types of extDS occur in October as a result of late cessation. These results show potential predictability of extreme dry spells after onset and before cessation of monsoonal rain based on global patterns of sea surface temperature anomalies.


Extreme dry spells Seasonality Spatial coherence Regional Occurrence Index SST anomaly Niger and Senegal West African Sahel 



This research was supported by the 2012 START Partnership Enhancement Award. Special thanks to Charles S. Kauffman. The first author acknowledges the German Academic Exchange Service (DAAD) for the In-Regions Scholarship through CERAAS (#A/09/04677). SST data set recommendations were provided by Alexey Kaplan, at Lamont-Doherty Earth Observatory. Important suggestions were taken from Alban Lazar (LOCEAN). The efforts of the two anonymous reviewers to improve the quality of this paper are also acknowledged.


  1. Agrhymet (1996) Méthodologie de suivi des zones à risque. AGRHYMET FLASH, Bulletin de Suivi de la Campagne Agricole au Sahel. Centre Régional Agrhymet, B.P. 11011, Niamey, vol 2, No 0/96, p 2Google Scholar
  2. Agrhymet (2010) Le Sahel face aux changements climatiques: Enjeux pour le développement. Bulletin Mensuel, Centre Régional Agrhymet, B.P. 11011, Niamey, Niger. Numero specialGoogle Scholar
  3. Ali A, Lebel T (2009) The Sahelian standardized rainfall index revisited. Int J Climatol 29(12):1705–1714. doi: 10.1002/joc.1832 CrossRefGoogle Scholar
  4. Ati OF, Stigter CJ, Oladipo EO (2002) A comparison of methods to determine the onset of the growing season in northern Nigeria. Int J Climatol 22:731–742CrossRefGoogle Scholar
  5. Barron J, Rockström J, Gichuki F, Hatibu N (2003) Dry spell analysis and maize yields for two semi-arid locations in East Africa. Agric For Meteor 117:23–37CrossRefGoogle Scholar
  6. Bell MA, Lamb PJ (2006) Integration of weather system variability to multidecadal regional climate change: the West African Sudan–Sahel Zone, 1951–98. J Climat 19:5343–5365CrossRefGoogle Scholar
  7. Chiang JCH, Sobel AH (2002) Tropical tropospheric temperature variations caused by ENSO and their influence on the remote tropical climate. J Clim 15:2616–2631CrossRefGoogle Scholar
  8. Couvreux F, Guichard F, Bock O, Campistron B, Lafore J-P, Redelsperger J-L (2010) Synoptic variability of the monsoon flux over West Africa prior to the onset. Q J R Meteorol Soc 136(1):159–173CrossRefGoogle Scholar
  9. Denise MS, Jemain AA, Ibrahim K (2009) The best probability models for dry and wet spells in peninsular Malaysia during monsoon seasons. Int J Clim. doi: 10.1002/joc.1972 Google Scholar
  10. Dieng O, Roucou P, Louvet S (2008) Variabilité intra saisonnière des précipitations au Sénégal (1951–1996). Sécheresse 19(2):87–93Google Scholar
  11. Folland CK, Palmer TN, Parker DE (1986) Sahel rainfall and worldwide sea temperatures, 1901–85. Nature 320:602–607. doi: 10.1038/320602a0 CrossRefGoogle Scholar
  12. Fontaine B, Trazaska S, Janicot S (1998) Evolution of the relationship between near global and Atlantic SST modes and the rainy season in West Africa: Statistical analyses and sensitivity experiments. Clim Dyn 14:353–368Google Scholar
  13. Frappart F, Hiernaux P, Guichard F et al (2009) Rainfall regime across the Sahel band in the Gourma region, Mali. J Hydrol. doi: 10.1016/j.jhydrol.2009.03.007 Google Scholar
  14. Giannini A, Saravanan R, Chang P (2003) Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science 302:1027–1030CrossRefGoogle Scholar
  15. Giannini A, Biasutti M, Held I, Sobel AH (2008) A global perspective on African climate. Clim Change 90:359–383. doi: 10.1007/s10584-008-9396-y CrossRefGoogle Scholar
  16. Giannini A, Salack S, Loudon T, Ali A, Ndiaye O (2012) A reinterpretation of climate change in the Sahel linking intra-seasonal, inter-annual and longer time scales. Sci Mag (Under review)Google Scholar
  17. Hoerling MP, Hurrell JW, Eischeid J, Phillips AS (2006) Detection and attribution of 20th century Northern and Southern African monsoon change. J Clim 19:3989–4008. doi: 10.1175/JCLI3842.1 Google Scholar
  18. IPCC (2012) Managing the risks of extreme events and disasters to advance climate change adaptation. A special report of working groups I and II of the intergovernmental panel on climate change. In: CB Field, V Barros, TF Stocker, D Qin, DJ Dokken, KL Ebi, MD Mastrandrea, KJ Mach, G-K Plattner, SK Allen, M Tignor, P.M. Midgley (eds.). Cambridge University Press, CambridgeGoogle Scholar
  19. Janicot S, Trzaska S, Poccard I (2001) Summer Sahel-ENSO teleconnection and decadal time scale SST variations. Clim Dyn 18:303–320CrossRefGoogle Scholar
  20. Janicot S, Thorncroft CD, Ali A (2008) Large-scale overview of the summer monsoon over West Africa during the AMMA field experiment in 2006. Ann Geophy 26:2569–2595Google Scholar
  21. Lanà X, Martinez MD, Burgueno A, Serra C, Martin-Vide J, Gomez L (2008) Spatial and temporal patterns of dry spell lengths in the Iberian Peninsula for the second half of the twentieth century. Theor Appl Climatol 91:99–116CrossRefGoogle Scholar
  22. Le Barbé L, Lebel T, Tapsoba D (2002) Rainfall variability in West Africa during the years 1950–90. J Clim 15(2):187–202CrossRefGoogle Scholar
  23. Lebel T, Ali A (2009) Recent trends in the Central and Western Sahel rainfall regime (1990–2007). J Hydrol. doi: 10.1016/j.jhydrol.2008.11.030 Google Scholar
  24. Lebel T, Parker DJ, Flamant C et al (2010) The AMMA field campaigns : multiscale and multidisciplinary observations in the West African region. Q J R Meteorol Soc. doi: 10.1002/qj.486 Google Scholar
  25. Lyon B (2004) The strength of El Nino and the spatial extent of tropical drought. Geo Phy Res Lett 31:L21204. doi: 10.1029/2004GL020901 CrossRefGoogle Scholar
  26. Marteau R (2011) Cohérence spatiale et prévisibilité potentielle des descripteurs intra-saisonniers de la saison des pluies en Afrique soudano-sahélienne : application à la culture du mil dans la région de Niamey. PhDthesis. University of BourgogneGoogle Scholar
  27. Martin-Vide J, Garcia CCL (1993) Analyse par la Chaine de Markov de la Sécheresse dans le Sud-Est de l’Espagne. Note méthodologique. Sécheresse 4:123–129Google Scholar
  28. Mohino E, Rodriguez-Fonseca B, Mechoso CR, Gervois S, Ruti P, Chauvin F (2011) Impacts of the Tropical Pacific/Indian Oceans on the seasonal cycle of the West African Monsoon. J Clim 24:3878–3891CrossRefGoogle Scholar
  29. Moron V, Robertson AW, Ward MN (2006) Seasonal Predictability and spatial coherence of rainfall characteristics in the tropical setting of Senegal. Mon Wea Rev 134:3248–3262CrossRefGoogle Scholar
  30. Neelin JD, Chou C, Su H (2003) Tropical drought regions in global warming and El Nino teleconnections. Geo Phy Res Lett 30(24):2275. doi: 10.1029/2003GL018625 CrossRefGoogle Scholar
  31. Nicholson SE (2005) On the question of the “recovery” of the rains in the West African Sahel. J Arid Env 63:615–641CrossRefGoogle Scholar
  32. Nicholson SE (2009) On the factors modulating the intensity of the tropical rainbelt over West Africa. Int J Climatol 29:673–689CrossRefGoogle Scholar
  33. Ozer P, Erpicum M, Demarée G, Vandiepenbeeck M (2003) The Sahelian drought may have ended during the 1990s. Hydro Sci J 48:489–492CrossRefGoogle Scholar
  34. PRESAO_SG (2011) Seasonal climate outlook valid for July–August–September 2011 in West Africa, Chad and Cameroon. African Centre for Meteorological Applications for Development (ACMAD)Google Scholar
  35. Rayner NA, Parker DE, Horton EB, Folland CK, Alexander LV, Rowell DP, Kaplan A (2003) Globally complete analyses of SST, sea ice, and night marine air temperature, 1871–2000. J Geophys Res 108. doi: 10.1029/2002JD002670
  36. Redelsperger J-L, Thorncroft C, Diedhiou A, Lebel T, Parker D, Polcher J (2006) African monsoon, multidisciplinary analysis (AMMA): an International research project and _eld campaign. Bull Am Meteor Soc 87(12):1739–1746CrossRefGoogle Scholar
  37. Salack S, Muller B, Gaye AT (2011) Rain-based factors of high agricultural impacts over Senegal. Part I. Integration of local to sub-regional trends and variability. Theo App Clim 10:1–22. doi: 10.1007/s00704-011-0414-z CrossRefGoogle Scholar
  38. Salack S, Muller B, Gaye AT, Hourdin F, Cisse N (2012) Analyses multi-echelles des pauses pluviométriques au Niger et au Sénégal. Sécheresse 23:3–13. doi: 10.1684/sec.2012.0335 Google Scholar
  39. Sane T, Diop M, Sagna P (2008) Etude de la variabilité de la saison pluvieuse au Sud en Haute-Casamance (Sud-Sénégal). Sécheresse 19(1):23–28Google Scholar
  40. Segele ZT, Lamb PJ (2005) Characterization and variability of Kiremt rainy season over Ethiopia. Meteor Atmos Phy 89:153–180CrossRefGoogle Scholar
  41. Sivakumar MVK (1988) Predicting rainy season potential from the onset of rains in Southern Sahelian and Sudanian climatic zones of West Africa. Agric For Meteor 42:295–305CrossRefGoogle Scholar
  42. Sivakumar MVK (1992) Empirical analysis of dry-spells for agricultural applications in West Africa. J Clim 5:532–539CrossRefGoogle Scholar
  43. Sultan B, Janicot S (2003) The West African monsoon dynamics. Part II: the preonset and onset of the summer monsoon. J Clim 16:3407–3427CrossRefGoogle Scholar
  44. Sultan B, Baron C, Dingkhun M, Sarr B, Janicot S (2005) Agricultural impacts of large-scale variability of the West African monsoon. Agric For Meteor 128(1–2):93–110CrossRefGoogle Scholar
  45. Vizy E, Cook K (2002) Development and application of a mesoscale climate model for the tropics: influence of sea surface temperature anomalies on the West African monsoon. J Geophys Res 107(D3):4023. doi: 10.1029/2001JD000686 CrossRefGoogle Scholar
  46. von Storch H, Zwiers WF (2003) Statistical analysis in climate research. Cambridge University press, CambridgeGoogle Scholar
  47. Winkel T, Do F (1992) Caractéristiques morphologiques et physiologiques de résistance du mil (P. glaucum) à la Sécheresse. Agro Trop 46(4):339–351Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Seyni Salack
    • 1
    • 2
  • Alessandra Giannini
    • 3
  • Moussa Diakhaté
    • 1
  • Amadou. T. Gaye
    • 1
  • Bertrand Muller
    • 4
    • 5
  1. 1.Laboratoire de Physique de l’Atmosphère et de l’Océan–Siméon Fongang, Ecole Supérieure PolytechniqueUniversité Cheikh Anta DiopDakar-Fann, DakarSenegal
  2. 2.Centre d’Etude Régional pour l’Amélioration de l’Adaptation à la Sécheresse (CERAAS)Thiès Escale, ThièsSenegal
  3. 3.International Research Institute for Climate and Society, The Earth InstituteColumbia UniversityNew YorkUSA
  4. 4.Centre International de Recherche Agronomique pour le Développement (CIRAD), UMR, AGAPMontpellierFrance
  5. 5.Africa Rice CenterAfricaRice, Sahel Regional StationSaint-LouisSenegal

Personalised recommendations