Climate Dynamics

, Volume 35, Issue 1, pp 75–94 | Cite as

Twentieth century Sahel rainfall variability as simulated by the ARPEGE AGCM, and future changes

  • C. Caminade
  • L. Terray


The ability of the ARPEGE AGCM in reproducing the twentieth century Sahelian drought when only forced by observed SST time evolution has been characterized. Atmospheric internal variability is shown to have a strong contribution in driving the simulated precipitation variability over the Sahel at decadal to multi-decadal time scales. The simulated drought is associated with a southward shift of the continental rainbelt over central and eastern Sahel, associated with an inter-hemispheric SST mode (the southern hemisphere oceans warming faster than the northern ones after 1970). The analysis of idealized experiments further highlights the importance of the Pacific basin. The related increase of the tropospheric temperature (TT) over the tropics is then suggested to dry the margin of convection zones over Africa, in agreement with the so-called “upped-ante” mechanism. A simple metric is then defined to determine the ability of the CMIP3 coupled models in reproducing both the observed Sahel drying and these mechanisms, in order to determine the reliability of the twenty-first century scenarios. Only one model reproduces both the observed drought over the Sahel and consistent SST/TT relationships over the second half of the twentieth century. This model predicts enhanced dry conditions over the Sahel at the end of the twenty-first century. However, as the mechanisms highlighted here for the recent period are not stationary during the twenty-first century when considering the trends, similarities between observed and simulated features of the West African monsoon for the twentieth century are a necessary but insufficient condition for a trustworthy prediction of the future.


West African monsoon SST and anthropogenic forcing Climate scenarios Decadal to multi-decadal variability Teleconnection 



This work was supported by the African Monsoon Multidisciplinary Analysis (AMMA) project and by the European Community via the sixth framework ENSEMBLE project under Contract GOCE-CT-2003-505539. The authors are grateful to all IPCC4 participants and to PCMDI for the build up of the database.


  1. Bader J, Latif M (2003) The impact of decadal-scale Indian Ocean sea surface temperature anomalies on Sahelian rainfall and the north Atlantic oscillation. Geophys Res Lett 30(22):2169. doi: 10.1029/2003GL018426 CrossRefGoogle Scholar
  2. Biasutti M, Giannini A (2006) Robust Sahel drying in response to late twentieth century forcings. Geophys Res Lett 33. doi: 10.1029/2006GLO26067
  3. Biasutti M, Held IM, Giannini A, Sobel AH (2008) SST forcings and Sahel rainfall variability of the twentieth and twenty-first centuries. J Clim (submitted).
  4. Bougeault P (1985) A simple parametrization of the large scale effects of deep cumulus convection. Mon Weather Rev 113:2108–2121. doi: 10.1175/1520-0493(1985)113<2108:ASPOTL>2.0.CO;2 CrossRefGoogle Scholar
  5. Camberlin P, Janicot S, Poccard I (2001) Seasonality and atmospheric dynamics of the teleconnections between Africa and tropical Ocean surface temperature: Atlantic versus ENSO. Int J Clim 21:973–1005. doi: 10.1002/joc.673 CrossRefGoogle Scholar
  6. Caminade C, Terray L (2006) Influence of increased greenhouse gases and sulphate aerosols concentration upon diurnal temperature range over Africa at the end of the twentieth century. Geophys Res Lett 33:L15703. doi: 10.1029/2006GL026381 CrossRefGoogle Scholar
  7. Charney JG, Quirk WJ, Show SH, Kornfield J (1977) A comparative study of the effects of albedo change on drought in semiarid regions. J Atmos Sci 34:1366–1385. doi: 10.1175/1520-0469(1977)034<1366:ACSOTE>2.0.CO;2 CrossRefGoogle Scholar
  8. Chiang J, Sobel A (2002) Tropical tropospheric temperature variations caused by ENSO and their influence on the remote tropical climate. J Clim 15:2616–2631. doi: 10.1175/1520-0442(2002)015<2616:TTTVCB>2.0.CO;2 CrossRefGoogle Scholar
  9. Chou C, Neelin JD (2004) Mechanisms of global warming impacts on regional tropical precipitation. J Clim 17(13):2688–2701. doi: 10.1175/1520-0442(2004)017<2688:MOGWIO>2.0.CO;2 CrossRefGoogle Scholar
  10. Déqué M (1999) Documentation ARPEGE-CLIMAT. Tech report Centre National de Recherche Météorologiques, Météo-France, Toulouse, FranceGoogle Scholar
  11. Déqué M, Dreveton C, Braun A, Cariolle D (1994) The climate version of the ARPEGE-IFS: a contribution of the French community climate modeling. Clim Dyn 10:249–266. doi: 10.1007/BF00208992 CrossRefGoogle Scholar
  12. Douville H (2003) Assesing the influence of soil moisture on seasonal climate variability with AGCMs. J Clim 14:1044–1066Google Scholar
  13. Douville H, Salas Mélia D, Tytéca S (2006) On the tropical origin of uncertainties in the global land precipitation response to global warming. Clim Dyn 26:367–385. doi: 10.1007/s00382-005-0088-2 CrossRefGoogle Scholar
  14. Folland CK, Palmer TN, Parker DE (1986) Sahel rainfall and worldwide sea surface temperature 1901–1985. Nature 320:602–607. doi: 10.1038/320602a0 CrossRefGoogle Scholar
  15. Fontaine B, Janicot S (1992) Wind field coherence and its variations over West Africa. J Clim 5:512–524. doi: 10.1175/1520-0442(1992)005<0512:WFCAIV>2.0.CO;2 CrossRefGoogle Scholar
  16. Giannini A, Saravanan R, Chang P (2003) Oceanic forcing of Sahel rainfall on interannual to interdecadal time scales. Science 302:1027–1030. doi: 10.1126/science.1089357 CrossRefGoogle Scholar
  17. Grist JP, Nicholson SE (2001) A study of dynamics factor influencing the rainfall variability in the West African Sahel. J Clim 14:1337–1359. doi: 10.1175/1520-0442(2001)014<1337:ASOTDF>2.0.CO;2 CrossRefGoogle Scholar
  18. Haarsma RJ, Selten FM, Weber SL, Kliphuis M (2005) Sahel rainfall and response to greenhouse warming. Geophys Res Lett 32. doi: 10.1029/2005GLO23232
  19. Hastenrath S (1990) Decadal-scale changes of the circulation in the tropical Atlantic sector associated with Sahel drought. Int J Clim 10:459–472. doi: 10.1002/joc.3370100504 CrossRefGoogle Scholar
  20. Held IM, Delworth TL, Lu J, Findell KL, Knutson TR (2005) Simulation of Sahel drought in the twentieth and twenty-first centuries. Proc Nat Acad Sci USA 102:17891–17896. doi: 10.1073/pnas.0509057102 CrossRefGoogle Scholar
  21. Herceg D, Sobel A, Sun L (2007) Regional modelling of decadal rainfall variability over the Sahel. Clim Dyn 29:88–99. doi: 10.1007/s00382-006-0218-5 CrossRefGoogle Scholar
  22. Hoerling MP, Hurrel JW, Eischeid J (2006) Detection and attribution of twentieth century northern and southern Africa monsoon change. J Clim 19:3989–4008. doi: 10.1175/JCLI3842.1 CrossRefGoogle Scholar
  23. Janicot S, Trzaska S, Poccard I (2001) Summer Sahel-ENSO teleconnection and decadal time scale SST variations. Clim Dyn 18:303–320. doi: 10.1007/s003820100172 CrossRefGoogle Scholar
  24. Joly M, Voldoire A, Douville H, Terray P, Royer JF (2007) African monsoon teleconnections with tropical SSTs: validation and evolution in a set of IPCC4 simulations. Clim Dyn. doi:0.1007/s00382-006-0215-8
  25. Kinter J, Fennessy M, Krishnamurphy V, Marx L (2004) An evaluation of the apparent interdecadal shift in the tropical divergent circulation in the NCEP–NCAR reanalysis. J Clim 17:349–361. doi: 10.1175/1520-0442(2004)017<0349:AEOTAI>2.0.CO;2 CrossRefGoogle Scholar
  26. Lamb PJ (1978) Large scale tropical surface circulation patterns associated with sub-Saharan weather anomalies. Tellus 30:240–251CrossRefGoogle Scholar
  27. Lau KM, Shen SSP, Kim KM, Wang (2006) A multimodel study of the twentieth century simulations of Sahel drought from the 1970s to 1990s. J Geophys Res 11:DO7111. doi: 10.1029/2005JD006821
  28. Louis JF, Tiedtke M, Geleyn JF (1981) A short history of the operational PBL-parameterization at ECMWF. In: ECMWF workshop planetary boundary layer parameterization, 25–27 Nov 1981, ECMWF, Reading, UK, pp 59–80Google Scholar
  29. Lu J, Delworth T (2005) Oceanic forcing of the late twentieth century Sahel drought. Geophys Res Lett 32. doi: 10.1029/2005GLO23316
  30. Mahfouf JF, Manzi AO, Noilhan J, Giordani H, Déqué M (1995) The land surface scheme ISBA within the Météo France climate model ARPEGE. Part I: implementation and preliminary results. J Clim 8:2039–2057. doi: 10.1175/1520-0442(1995)008<2039:TLSSIW>2.0.CO;2 CrossRefGoogle Scholar
  31. Mehta VM, Suarez MJ, Manganello JV, Delworth TL (2000) Oceanic influence on the north Atlantic oscillation and associated northern Hemisphere climate variations: 1959–1993. Geophys Res Lett 27(1):121–124. doi: 10.1029/1999GL002381 CrossRefGoogle Scholar
  32. Mitchell T, Jones P (2005) An improved method of constructing a database of monthly climate observations and associated high resolution grids. Int J Clim 25:693–712. doi: 10.1002/joc.1181 CrossRefGoogle Scholar
  33. Morcrette JJ (1990) Impact of changes to radiation transfer parametrizations plus cloud optical properties in the ECMWF model. Mon Weather Rev 118:847–873. doi: 10.1175/1520-0493(1990)118<0847:IOCTTR>2.0.CO;2 CrossRefGoogle Scholar
  34. Neelin JD, Chou C, Su H (2003) Tropical drought regions in global warming and El Niño teleconnections. Geophys Res Lett 30(24):2275. doi: 10.1029/2003GL018625 CrossRefGoogle Scholar
  35. Noilhan J, Planton S (1989) A simple parameterization of land surface processes for meteorological models. Mon Weather Rev 117:536–549. doi: 10.1175/1520-0493(1989)117<0536:ASPOLS>2.0.CO;2 CrossRefGoogle Scholar
  36. Palmer TN (1986) Influence of the Atlantic, Pacific and Indian oceans on Sahel rainfall. Nature 322:251–253. doi: 10.1038/322251a0 CrossRefGoogle Scholar
  37. Poccard I, Janicot S, Camberlin P (2000) Comparison of rainfall structures between NCEP and NCAR reanalysis and observed data over Africa. Clim Dyn 16:897–915. doi: 10.1007/s003820000087 CrossRefGoogle Scholar
  38. Ricard JL, Royer JF (1993) A statistical cloud scheme for use in AGCM. Ann Geophys 11:1095–1115Google Scholar
  39. Rowell DP (2001) Teleconnections between the tropical Pacific and the Sahel. Q J R Meteorol Soc 127:1683–1706. doi: 10.1002/qj.49712757512 CrossRefGoogle Scholar
  40. Rowell DP, Zwiers FW (1999) The global distribution of sources of atmospheric decadal variability and mechanisms over the tropical Pacific and southern North America. Clim Dyn 15:751–772. doi: 10.1007/s003820050314 CrossRefGoogle Scholar
  41. Smith T, Reynolds R (2004) Improved extended reconstruction of SST (1854–1997). J Clim 17:2466–2477. doi: 10.1175/1520-0442(2004)017<2466:IEROS>2.0.CO;2 CrossRefGoogle Scholar
  42. Su H, Neelin J, Meyerson J (2005) Mechanism for lagged atmospheric response to ENSO SST forcing. J Clim 18:4195–4215. doi: 10.1175/JCLI3514.1 CrossRefGoogle Scholar
  43. Yulaeva E, Wallace J (1994) The signature of ENSO in global temperature and precipitation fields derived from the microwave sounding unit. J Clim 7:1719–1736. doi: 10.1175/1520-0442(1994)007<1719:TSOEIG>2.0.CO;2 CrossRefGoogle Scholar
  44. Zhang R, Delworth TL (2006) Impact of Atlantic multidecadal oscillations on India/Sahel rainfall and Atlantic hurricanes. Geophys Res Lett 33:L17712. doi: 10.1029/2006GL026267 CrossRefGoogle Scholar
  45. Zwiers F (1996) Interannual variability and predictability in an ensemble of AMIP climate simulations conducted with the CCC GCM2. Clim Dyn 12:825–848. doi: 10.1007/s003820050146 CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  1. 1.CERFACSToulouse-CedexFrance

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