Advertisement

Climate Dynamics

, Volume 31, Issue 5, pp 587–598 | Cite as

On the origin of equatorial Atlantic biases in coupled general circulation models

  • Ingo RichterEmail author
  • Shang-Ping Xie
Article

Abstract

Many coupled ocean–atmosphere general circulation models (GCMs) suffer serious biases in the tropical Atlantic including a southward shift of the intertropical convergence zone (ITCZ) in the annual mean, a westerly bias in equatorial surface winds, and a failure to reproduce the eastern equatorial cold tongue in boreal summer. The present study examines an ensemble of coupled GCMs and their uncoupled atmospheric component to identify common sources of error. It is found that the westerly wind bias also exists in the atmospheric GCMs forced with observed sea surface temperature, but only in boreal spring. During this time sea-level pressure is anomalously high (low) in the western (eastern) equatorial Atlantic, which appears to be related to deficient (excessive) precipitation over tropical South America (Africa). In coupled simulations, this westerly bias leads to a deepening of the thermocline in the east, which prevents the equatorial cold tongue from developing in boreal summer. Thus reducing atmospheric model errors during boreal spring may lead to improved coupled simulations of tropical Atlantic climate.

Keywords

CMIP Model Cold Tongue West African Monsoon Atmospheric Model Intercomparison Project Wind Bias 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Notes

Acknowledgments

This study was supported by the NOAA CLIVAR Program and the Japan Agency for Marine-Earth Science and Technology through its sponsorship of the International Pacific Research Center. All the model output was downloaded from The IPCC Data Archive at Lawrence Livermore National Laboratory, which is supported by the Office of Science, U.S. Department of Energy. The authors would like to thank Justin Small and two anonymous reviewers for their helpful suggestions. IPRC publication #498.

References

  1. Biasutti M, Sobel AH, Kushnir Y (2006) AGCM precipitation biases in the tropical Atlantic. J Clim 19:935–958CrossRefGoogle Scholar
  2. Breugem W-P, Hazeleger W, Haarsma RJ (2006) Multimodel study of tropical Atlantic variability and change. Geophys Res Lett 33. doi: 10.1029/2006GL027831
  3. Chang P, Coauthors (2006) Climate fluctuations of tropical coupled system—the role of ocean dynamics. J Clim 19:5122–5174Google Scholar
  4. Chang CY, Carton JA, Grodsky SA, Nigam S (2007), Seasonal climate of the tropical Atlantic sector in the NCAR community climate system model 3: error structure and probable causes of errors. J Clim 20:1053–1070CrossRefGoogle Scholar
  5. Cohen JC, Silva Dias MA, Nobre CA (1995) Environmental conditions associated with Amazonian squall lines: a case study. Mon Weather Rev 123:3163–3174CrossRefGoogle Scholar
  6. Conkright ME, Locarnini R, Garcia H, O’Brien T, Boyer TP, Stephens C, Antonov J (2002) World Ocean Atlas 2001, objective analyses, data statistics and figures, CD-ROM documentation, National Oceanographic Data Center. Silver Spring, MDGoogle Scholar
  7. Davey MK, Coauthors (2002) STOIC: a study of coupled model climatology and variability in tropical ocean regions. Clim Dyn 18:403–420Google Scholar
  8. Deser C, Capotondi A, Saravanan R, Phillips AS (2006) Tropical Pacific and Atlantic climate variability in CCSM3. J Clim 19:2451–2481CrossRefGoogle Scholar
  9. de Szoeke SP, Xie S-P (2008) The tropical eastern Pacific seasonal cycle: assessment of errors and mechanisms in IPCC AR4 coupled ocean–atmosphere general circulation models. J Clim (in press)Google Scholar
  10. DeWitt DG (2005) Diagnosis of the tropical Atlantic near-equatorial SST bias in a directly coupled atmosphere-ocean general circulation model. Geophys Res Lett 32:L01703. doi: 10.1029/2004GL021707 CrossRefGoogle Scholar
  11. Dirmeyer PA, Koster RD, Guo Z (2006) Do global models properly represent the feedback between land and atmosphere? J Hydrometeor 7:1177–1198CrossRefGoogle Scholar
  12. Hagos SM, Cook KH (2005) Influence of Surface Processes over Africa on the Atlantic Marine ITCZ and South American Precipitation. J Clim 18:4993–5010CrossRefGoogle Scholar
  13. Hazeledger W, Haarsma RJ (2005) Sensitivity of tropical Atlantic climate to mixing in a coupled ocean–atmosphere model. Clim Dyn 25:387–399CrossRefGoogle Scholar
  14. Helber RW, Weisberg RH, Bonjean F, Johnson ES, Lagerloef GSE (2007) Satellite-derived surface current divergence in relation to tropical Atlantic SST and wind. J Phys Oceanogr 37:1357–1375CrossRefGoogle Scholar
  15. Huang B, Schopf PS, Shukla J (2004) Intrinsic ocean–atmosphere variability of the tropical Atlantic Ocean. J Clim 17:2058–2077CrossRefGoogle Scholar
  16. Huang B, Hu Z-Z, Jha B (2007) Evolution of model systematic errors in the tropical Atlantic basin from coupled climate hindcasts. Clim Dyn 28:661–682CrossRefGoogle Scholar
  17. Kalnay E, Coauthors (1996) The NCEP/NCAR 40-year reanalysis project. Bull Am Meteor Soc 77:437–471Google Scholar
  18. Keenlyside NS, Latif M (2007) Understanding equatorial Atlantic interannual variability. J Clim 20:131–142CrossRefGoogle Scholar
  19. Klein SA, Hartmann DL (1993) The seasonal cycle of low stratiform clouds. J Clim 6:1587–1606CrossRefGoogle Scholar
  20. Kousky VE (1980) Diurnal rainfall variation in northeast Brazil. Mon Weather Rev 108:488–498CrossRefGoogle Scholar
  21. Large WG, Danabasoglu G (2006) Attribution and impacts of upper-ocean biases in CCSM3. J Clim 19:2325–2346CrossRefGoogle Scholar
  22. Ma CC, Mechoso CR, Robertson AW, Arakawa A (1996) Peruvian stratus clouds and the tropical pacific circulation: a coupled ocean—atmosphere GCM study. J Clim 9:1635–1645CrossRefGoogle Scholar
  23. Mechoso CR, Roberston AW Coauthors (1995) The seasonal cycle over the tropical Pacific in general circulation models. Mon Weather Rev 123:2825–2835Google Scholar
  24. Meehl GA, Covey C, McAvaney B, Latif M, Stouffer RJ (2005) Overview of the coupled model intercomparison project. Bull Am Meteor Soc 86:89–93CrossRefGoogle Scholar
  25. Mesinger F, Janjić ZI, Ničković S, Gavrilov D, Deaven DG (1988) The step-mountain coordinate: model description and performance for cases of Alpine lee cyclogenesis and for a case of an Appalachian redevelopment. Mon Weather Rev 116:1493–1518CrossRefGoogle Scholar
  26. Mitchell TP, Wallace JM (1992) The annual cycle in equatorial convection and sea surface temperature. J Clim 5:1140–1156CrossRefGoogle Scholar
  27. Okumura Y, Xie S-P (2004) Interaction of the Atlantic equatorial cold tongue and African monsoon. J Clim 17:3588–3601CrossRefGoogle Scholar
  28. Okumura Y, Xie S-P (2006) Some overlooked features of tropical Atlantic climate leading to a new Nino-like phenomenon. J Clim 19:5859–5874CrossRefGoogle Scholar
  29. Repelli CA, Nobre P (2004) Statistical prediction of sea surface temperature over the tropical Atlantic. Int J Climatol 24:45–55CrossRefGoogle Scholar
  30. Richter I, Mechoso CR, Robertson AW (2008) What determines the position and intensity of the South Atlantic anticyclone in austral winter?—an AGCM study. J Clim 21:214–229Google Scholar
  31. Rickenbach TM (2004) Nocturnal cloud systems and the diurnal variation of clouds and rainfall in southwestern Amazonia. Mon Weather Rev 132:1201–1219CrossRefGoogle Scholar
  32. Rossow WB, Schiffer RA (1999) Advances in understanding clouds from ISCCP. Bull Am Meteor Soc 80:2261–2287CrossRefGoogle Scholar
  33. Rouault M, Florenchie P, Fauchereau N, Reason CJC (2003) South East tropical Atlantic warm events and southern African rainfall. Geophys Res Lett 30. doi: 10.1029/2002GL014840
  34. Shannon LV, Boyd AJ, Brundrit GB, Taunton-Clark J (1986) On the existence of an El Niño type phenomenon in the Benguela system. J Mar Res 44:495–520CrossRefGoogle Scholar
  35. Stockdale TN, Balmaseda MA, Vidard A (2006) Tropical Atlantic SST prediction with coupled ocean–atmosphere GCMs. J Clim 19:6047–6061CrossRefGoogle Scholar
  36. Wang H, Fu R (2007) The influence of Amazon rainfall on the Atlantic ITCZ through convectively coupled Kelvin waves. J Clim 20:1188–1201CrossRefGoogle Scholar
  37. Worley SJ, Woodruff SD, Reynolds RW, Lubker SJ, Lott N (2005) ICOADS Release 2.1 data and products. Int J Climatol 25:823–842CrossRefGoogle Scholar
  38. Xie S-P (1996) Westward propagation of latitudinal asymmetry in a coupled ocean–atmosphere model. J Atmos Sci 53:3236–3250CrossRefGoogle Scholar
  39. Xie P, Arkin PA (1997) Global precipitation: a 17-year monthly analysis based on gauge observations, satellite estimates, and numerical model outputs. Bull Am Meteor Soc 78:2539–2558CrossRefGoogle Scholar
  40. Xie S-P, Carton JA (2004) Tropical Atlantic variability: patterns, mechanisms, and impacts. In: Earth climate: the ocean–atmosphere interaction. Geophys Monograph, vol 147. AGU, Washington DC, pp 121–142Google Scholar

Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.International Pacific Research CenterUniversity of Hawaii at ManoaHonoluluUSA
  2. 2.Department of MeteorologyUniversity of Hawaii at ManoaHonoluluUSA

Personalised recommendations