Climate Dynamics

, Volume 47, Issue 3–4, pp 697–717 | Cite as

The Congo Basin Walker circulation: dynamics and connections to precipitation

  • Kerry H. CookEmail author
  • Edward K. Vizy


The existence, seasonality, and variability of a Congo Basin Walker circulation are investigated in reanalyses, and connections with rainfall are explored. A zonal overturning circulation along the equator connects rising motion in the Congo Basin and sinking in the eastern Atlantic during June through October. This timing is out of phase with precipitation over equatorial Africa, which greatest during spring and fall, and does not correlate with the seasonality of land temperatures. Rather, the zonally-overturning circulation only occurs when the Atlantic cold tongue has formed. Although the cold tongue formation is essential for setting up the Congo Basin Walker circulation, variations in equatorial eastern Atlantic sea surface temperatures are not associated with interannual variability in the strength of the circulation. When cold tongue SSTs are anomalously cool (warm), evaporation from the ocean surface is reduced (enhanced) and the westerly flow advects less (more) moisture into the base of the Congo Basin Walker circulation. This reduces (increases) the release of latent heat in the upbranch and weakens (strengthens) the Walker circulation. This process dominates the pure dry dynamical response to enhanced land/sea temperature differences, which has an opposite sign. A positive correlation connects low-level vertical velocity in the Congo basin with low-level vertical velocity and precipitation over West Africa. A wave response to anomalous vertical velocity in the Congo Basin in several reanalyses suggests a teleconnection into West Africa such that an anomalously strong (weak) upbranch is associated with anomalously strong (weak) rainfall over the Guinean coast and southern Sahel.


Walker circulation Congo Basin Atlantic cold tongue African precipitation Sahel precipitation Equatorial Atlantic 



This research was supported by award ATM-1036604 from the National Science Foundation Climate and Large-Scale Dynamics program, and by award NNX13AQ76G from NASA’s Physical Oceanography Program.


  1. Adler RF, Huffman GJ, Chang A, Ferraro R, Xie P, Janowiak J, Rudolf B, Schneider U, Curtis S, Bolvin D, Gruber A, Susskind J, Arkin P (2003) The version 2 global precipitation climatology project (GPCP) monthly precipitation analysis (1979-present). J Hydrometeorl 4:1147–1167CrossRefGoogle Scholar
  2. Asefi-Najafabady S, Saatch S (2013) Response of African humid tropical forests to recent rainfall anomalies. Phil Trans R Soc B 268:20120306CrossRefGoogle Scholar
  3. Ashouri H, Hsu K-L, Sorooshian S, Braithwaite DK, Knapp KR, Cecil LD, Nelson BR, Prat OP (2015) PERSIANN-CDR: daily precipitation climate data record from multi-satellite observations for hydrological and climate studies. Bull Am Meteorol Soc 96:69–83. doi: 10.1175/BAMS-D-13-00068.1 CrossRefGoogle Scholar
  4. Cadet D, Nnoli N (1987) Water vapour transport over Africa and the Atlantic during the summer of 1979. Q J R Meteorol Soc 113:581–602CrossRefGoogle Scholar
  5. Carton JA, Cao X, Giese BS, da Silva AM (1996) Decadal and interannual SST variability in the tropical Atlantic Ocean. J Phys Oceanogr 26:1165–1175CrossRefGoogle Scholar
  6. Cook KH, Vizy EK (2006) Coupled model simulations of the West African monsoon system: Twentieth- and twenty-first century simulations. J Clim 19:3681–3703CrossRefGoogle Scholar
  7. Dee DP, Uppla SM, Simmons AJ, Berrisford P, Poli P, Kobayashi S et al (2011) The ERA-Interim reanalysis: configuration and performance of the data assimilation system. Q J R Meteorol Soc 137:553–597. doi: 10.1002/qj.828 CrossRefGoogle Scholar
  8. Dezfuli AK, Nicholson SE (2013) The relationship of rainfall variability in western Equatorial Africa to the tropical oceans and atmospheric circulation. Part II: the boreal autumn. J Clim 26:66–84CrossRefGoogle Scholar
  9. Dezfuli AK, Zaitchik BF, Gnanadesikan A (2015) Regional atmospheric circulation and rainfall variability in south equatorial Africa. J Clim 28:809–818CrossRefGoogle Scholar
  10. Flohn H (1971) Tropical circulation patterns. Bonner Meteorologische Abhandlungen 15:1–55Google Scholar
  11. Folland CK, Palmer TN, Parker DE (1986) Sahel rainfall and worldwide sea temperatures. Nature 320:602–607CrossRefGoogle Scholar
  12. Fontan JA, Druilhet B, Benech B, Lyra R (1992) The DECAFE experiments: overview and meteorology. J Geophys Res 97:6123–6136CrossRefGoogle Scholar
  13. Gill AE (1980) Some simple solutions for heat-induced tropical circulation. Q J R Meteorol Soc 106:447–462CrossRefGoogle Scholar
  14. Hagos S, Zhang C (2010) Diabatic heating, divergent circulation and moisture transport in the African monsoon system. Q J R Meteorol Soc 136:411–425CrossRefGoogle Scholar
  15. Harris I, Jones PD, Osborn TJ, Lister DH (2014) Updated high resolution grids of monthly climatic observations and the CRU TS3.10 dataset. Int J Climatol 34:623–642CrossRefGoogle Scholar
  16. Hermann SM, Mohr KI (2011) A continental-scale classification of rainfall seasonality regimes in Africa based on gridded precipitation and land surface temperature products. J Appl Meteorol Climatol 50:2504–2513CrossRefGoogle Scholar
  17. Hirst AC, Hastenrath SL (1983) Atmosphere-ocean mechanisms of climate anomalies in the Angola-tropical Atlantic sector. J Phys Oceanogr 13:1146–1157CrossRefGoogle Scholar
  18. Holton J (2004) An introduction to dynamic meteorology, 4th edn. Academic Press, New York, p 535Google Scholar
  19. James R, Washington R, Rowell DP (2013) Implications of global warming for the climate of African rainforests. Phil Trans R Soc B Biol Sci 368:20120298CrossRefGoogle Scholar
  20. Janicot S (1992) Spatiotemporal variability of West African rainfall Part II: associated surface and airmass characteristics. J Clim 5:499–511CrossRefGoogle Scholar
  21. Kanamitsu M, Ebisuzaki W, Woollen J, Yang S-K, Hnilo JJ, Fiorino M, Potter GL (2002) NCEP-DOE AMIP-II reanalysis (R-2). Bull Am Meteorol Soc 83:1631–1643CrossRefGoogle Scholar
  22. Kobayashi S, Ota Y, Harada Y, Ebita A, Moriya M, Onoda H, Onogi K, Kamahori H, Kobayashi C, Endo H, Miyaoka K, Takahashi K (2015) The JRA-55 reanalysis: general specifications and basic characteristics. J Meteorol Soc Jpn 93:5. doi: 10.2151/jmsj.2015-001 CrossRefGoogle Scholar
  23. Lamb PJ (1978) Case studies of tropical Atlantic surface circulation patterns during recent sub-Saharan weather anomalies: 1967 and 1968. Mon Weather Rev 106:482–491CrossRefGoogle Scholar
  24. Leduc-Leballeur M, de Coëtlogon G, Eymard L (2013) Air-sea interaction in the Gulf of Guinea at intraseasonal time-scales: wind bursts and coastal precipitation in boreal spring. Q J R Meteorol Soc 139:387–400. doi: 10.1002/qj.1981 CrossRefGoogle Scholar
  25. Malhi Y, Wright J (2004) Spatial patterns and recent trends in the climate of tropical rainforest regions. Phil Trans R Soc Lond B 359:311–329CrossRefGoogle Scholar
  26. Matsuno T (1966) Quasigeostrophic motions in the equatorial area. J Meteorol Soc Jpn 44:25–43Google Scholar
  27. Newell RE (1979) Climate and ocean. Am Sci 67:405–416Google Scholar
  28. Newell RE, Kidson IW (1984) African mean wind changes between Sahelian wet and dry periods. Int J Clim 4:27–33CrossRefGoogle Scholar
  29. Nicholson SE, Dezfuli AK (2013) The relationship of rainfall variability in western Equatorial Africa to the tropical oceans and atmospheric circulation. Part I: the boreal spring. J Clim 26:45–65CrossRefGoogle Scholar
  30. Nicholson SE, Grist JP (2003) The seasonal evolution of the atmospheric circulation over West Africa and equatorial Africa. J Clim 16:1013–1030CrossRefGoogle Scholar
  31. Novella NS, Thiaw WM (2013) African rainfall climatology version 2 for famine early warning systems. J Appl Meteorol Climatol 52:588–606CrossRefGoogle Scholar
  32. Pokam WM, Djiotang LAT, Mkankam FK (2012) Atmospheric water vapor transport and recycling in equatorial central Africa through NCEP/NCAR reanalysis data. Clim Dyn 38:1715–1729CrossRefGoogle Scholar
  33. Pokam MW, Bain CL, Chadwick RS, Graham R, Sonwa DJ, Kamga FM (2014) Identification of processes driving low-level westerlies in West Equatorial Africa. J Clim 27:4245–4262CrossRefGoogle Scholar
  34. Schwendike JP, Govekar P, Reeder MJ, Wardle R, Berry GJ, Jakob C (2014) Local partitioning of the overturning circulation in the tropics and the connection to the Hadley and Walker circulations. J Geophys Res Atmos 119:1322–1339. doi: 10.1002/2013JD020742 CrossRefGoogle Scholar
  35. Uppala S, Kallberg P, Simmons AJ, Andrae U, Bechtold VDC, Fiorino M, Gibson JK, Haseler J, Hernandez A, Kelly GA, Li X, Onogi K, Saarinen S, Sokka N, Allan RP, Andersson E, Arpe K, Balmaseda MA, Beljaars ACM, van de Berg L, Bidlot J, Bormann N, Caires S, Chevallier F, Dethof A, Dragosavac M, Fisher M, Fuentes M, Hagemann S, Holm E, Hoskins BJ, Isaksen L, Janssen PAEM, Jenne R, McNally AP, Mahfouf JF, Morcrette JJ, Rayner NA, Saunders RW, Simon P, Sterl A, Trenberth KE, Untch A, Vasiljevic D, Viterbo P, Woollen J (2005) The ERA-40 re-analysis. Q J R Meteorol Soc 131:2961–3012CrossRefGoogle Scholar
  36. Vizy EK, Cook KH (2001) Mechanisms by which Gulf of Guinea and eastern North Atlantic sea surface temperature anomalies can influence African rainfall. J Clim 14:795–821CrossRefGoogle Scholar
  37. Vizy EK, Cook KH (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 107:4023. doi: 10.1029/2001JD000686 CrossRefGoogle Scholar
  38. Wang C (2002) Atmospheric circulation cells associated with the El-Niño-Southern Oscillation. J Clim 15:399–419CrossRefGoogle Scholar
  39. Ward MN (1998) Diagnosis and short-lead time prediction of summer rainfall in tropical North Africa at interannual and multi-decadal timescales. J Clim 11:3167–3191CrossRefGoogle Scholar
  40. Washington R, James R, Pearce H, Pokam WM, Moufouma-Okia W (2013) Congo Basin rainfall climatology: Can we believe the climate models? Phil Trans R Soc S Biol Sci 368:20120296CrossRefGoogle Scholar
  41. Xie S-P, Carton JA (2004) Tropical Atlantic variability: patterns, mechanisms, and impacts. In: Wang C, Xie, S-P, Carton JA (ed) Earth climate: the ocean-atmosphere interaction. Geophysical Monograph, 147, AGU, Washington, DC, pp 121–142Google Scholar
  42. Zhou L, Tian Y, Myneni R, Ciais P, Saatch S et al (2014) Widespread decline of Congo rainforest greenness in the past decade. Nature 509:86–90CrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2015

Authors and Affiliations

  1. 1.Department of Geological Sciences, Jackson School of GeosciencesThe University of Texas at AustinAustinUSA

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