Editorial Type:
Article
Article Type:
Research Article

Does the South American Monsoon Influence African Rainfall?

Alice M. Grimm Department of Physics, Federal University of Parana, Curitiba, Brazil

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Chris J. C. Reason Department of Oceanography, University of Cape Town, Cape Town, South Africa

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Print Publication:
15 Feb 2011
DOI:
https://doi.org/10.1175/2010JCLI3722.1
Page(s):
1226–1238
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Abstract

Teleconnections between the South American monsoon and southern African rainfall are investigated for years with Benguela Niño or Niña events in the South Atlantic. During these events, it is found that substantial rainfall anomalies also occur over South America in addition to those previously known for southern Africa. The appearance of large rainfall anomalies in the South American monsoon region prior to the onset of the Benguela Niño proper suggests that anomalous convection over South America may influence the evolution of both the SST anomalies and the African rainfall anomalies associated with Benguela Niño events. This teleconnection between South America and southern African rainfall may occur directly, via atmospheric circulation anomalies induced by convection over South America, or indirectly, via the effect of induced circulation anomalies on regional SST.

To investigate these teleconnections, a vorticity equation model, which is linearized about a realistic basic state and which includes the divergence in this state and the advection of vorticity by the divergent wind, is applied to the events. The model is forced with anomalous divergence patterns observed during the events, and the steady-state solutions show that anomalies of convection during the South American monsoon produce the main circulation anomalies observed during the Benguela Niño events and hence influence rainfall and circulation patterns over Angola and other southern African countries. An influence function analysis confirms this result, indicating that South America is the most efficient source region to produce the observed anomalies, and also shows that there is no influence of convection over Africa on the South American monsoon. Based on these linear model and observational results, it is concluded that the South American monsoon can influence the evolution of Benguela Niños and associated rainfall anomalies in southern Africa.

Corresponding author address: Alice M. Grimm, Department of Physics, Federal University of Paraná, Caixa Postal 19044, 81531-990 Curitiba, PR, Brazil. Email: grimm@fisica.ufpr.br

Abstract

Teleconnections between the South American monsoon and southern African rainfall are investigated for years with Benguela Niño or Niña events in the South Atlantic. During these events, it is found that substantial rainfall anomalies also occur over South America in addition to those previously known for southern Africa. The appearance of large rainfall anomalies in the South American monsoon region prior to the onset of the Benguela Niño proper suggests that anomalous convection over South America may influence the evolution of both the SST anomalies and the African rainfall anomalies associated with Benguela Niño events. This teleconnection between South America and southern African rainfall may occur directly, via atmospheric circulation anomalies induced by convection over South America, or indirectly, via the effect of induced circulation anomalies on regional SST.

To investigate these teleconnections, a vorticity equation model, which is linearized about a realistic basic state and which includes the divergence in this state and the advection of vorticity by the divergent wind, is applied to the events. The model is forced with anomalous divergence patterns observed during the events, and the steady-state solutions show that anomalies of convection during the South American monsoon produce the main circulation anomalies observed during the Benguela Niño events and hence influence rainfall and circulation patterns over Angola and other southern African countries. An influence function analysis confirms this result, indicating that South America is the most efficient source region to produce the observed anomalies, and also shows that there is no influence of convection over Africa on the South American monsoon. Based on these linear model and observational results, it is concluded that the South American monsoon can influence the evolution of Benguela Niños and associated rainfall anomalies in southern Africa.

Corresponding author address: Alice M. Grimm, Department of Physics, Federal University of Paraná, Caixa Postal 19044, 81531-990 Curitiba, PR, Brazil. Email: grimm@fisica.ufpr.br

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  • Cook, C., C. J. C. Reason, and B. C. Hewitson, 2004: Wet and dry spells within particular wet and dry summers in the South African summer rainfall region. Climate Res., 26 , 17–31.

    • Search Google Scholar
    • Export Citation

  • Cook, K. H., J.-S. Hsieh, and S. M. Hagos, 2004: The Africa–South America intercontinental teleconnection. J. Climate, 17 , 2851–2865.

    • Search Google Scholar
    • Export Citation

  • Florenchie, P., J. R. E. Lutjeharms, C. J. C. Reason, S. Masson, and M. Rouault, 2003: The source of Benguela Ninos in the South Atlantic Ocean. Geophys. Res. Lett., 30 , 1505. doi:10.1029/2003GL017172.

    • Search Google Scholar
    • Export Citation

  • Florenchie, P., C. J. C. Reason, J. R. E. Lutjeharms, M. Rouault, C. Roy, and S. Masson, 2004: Evolution of interannual warm and cold events in the southeast Atlantic Ocean. J. Climate, 17 , 2318–2334.

    • Search Google Scholar
    • Export Citation

  • Gill, A. E., 1980: Some simple solutions for heat-induced tropical circulations. Quart. J. Roy. Meteor. Soc., 106 , 447–462.

  • Grimm, A. M., and P. L. Silva Dias, 1995a: Use of barotropic models in the study of the extratropical response to tropical heat sources. J. Meteor. Soc. Japan, 73 , 765–780.

    • Search Google Scholar
    • Export Citation

  • Grimm, A. M., and P. L. Silva Dias, 1995b: Analysis of tropical–extratropical interactions with influence functions of a barotropic model. J. Atmos. Sci., 52 , 3538–3555.

    • Search Google Scholar
    • Export Citation

  • Grimm, A. M., and M. T. Zilli, 2009: Interannual variability and seasonal evolution of summer monsoon rainfall in South America. J. Climate, 22 , 2257–2275.

    • Search Google Scholar
    • Export Citation

  • Hansingo, K., and C. J. C. Reason, 2009: Modelling the atmospheric response over southern Africa to SST forcing in the southeast tropical Atlantic and southwest subtropical Indian Oceans. Int. J. Climatol., 29 , 1001–1012.

    • Search Google Scholar
    • Export Citation

  • Hirst, A. C., and S. Hastenrath, 1983: Atmosphere–ocean mechanisms of climate anomalies in the Angola–tropical Atlantic sector. J. Phys. Oceanogr., 13 , 1146–1157.

    • Search Google Scholar
    • Export Citation

  • Hulme, M., T. J. Osborn, and T. C. Johns, 1998: Precipitation sensitivity to global warming: Comparison of observations with HadCM2 simulations. Geophys. Res. Lett., 25 , 3379–3382.

    • Search Google Scholar
    • Export Citation

  • Jin, F., and B. J. Hoskins, 1995: The direct response to tropical heating in a baroclinic atmosphere. J. Atmos. Sci., 52 , 307–319.

  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalysis Project. Bull. Amer. Meteor. Soc., 77 , 437–471.

  • Legates, D. R., and C. J. Willmott, 1990: Mean seasonal and spatial variability in gauge-corrected, global precipitation. Int. J. Climatol., 10 , 111–127.

    • Search Google Scholar
    • Export Citation

  • Nicholson, S. E., and D. Entekhabi, 1987: Rainfall variability in equatorial and southern Africa: Relationships with sea surface temperatures along the southwestern coast of Africa. J. Climate Appl. Meteor., 26 , 561–578.

    • Search Google Scholar
    • Export Citation

  • Nobre, P., J. A. Marengo, I. F. A. Cavalcanti, G. Obregon, V. Barros, I. Camilloni, N. Campos, and A. G. Ferreira, 2006: Seasonal-to-decadal predictability and prediction of South American climate. J. Climate, 19 , 5988–6004.

    • Search Google Scholar
    • Export Citation

  • Rayner, N. A., D. E. Parker, E. B. Horton, C. K. Folland, L. V. Alexander, D. P. Rowell, E. C. Kent, and A. Kaplan, 2003: Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century. J. Geophys. Res., 108 , 4407. doi:10.1029/2002JD002670.

    • Search Google Scholar
    • Export Citation

  • Reason, C. J. C., W. Landman, and W. Tennant, 2006: Seasonal to decadal prediction of southern African climate and its links with variability of the Atlantic Ocean. Bull. Amer. Meteor. Soc., 87 , 941–955.

    • Search Google Scholar
    • Export Citation

  • Rouault, M., P. Florenchie, N. Fauchereau, and C. J. C. Reason, 2003: South east tropical Atlantic warm events and southern African rainfall. Geophys. Res. Lett., 30 , 8009. doi:10.1029/2002GL014840.

    • Search Google Scholar
    • Export Citation

  • Rouault, M., J. Servain, C. J. C. Reason, B. Bourles, M. J. Rouault, and N. Fauchereau, 2009: Extension of PIRATA in the tropical south-east Atlantic: An initial one-year experiment. Afr. J. Mar. Sci., 31 , 63–71.

    • Search Google Scholar
    • Export Citation

  • Schneider, U., T. Fuchs, A. Meyer-Christoffer, and B. Rudolf, cited. 2008: Global precipitation analysis products of the GPCC. Global Precipitation Climatology Centre (GPCC), Deutscher Wetterdienst. [Available online at ftp://ftp-anon.dwd.de/pub/data/gpcc/PDF/GPCC_intro_products_2008.pdf].

    • Search Google Scholar
    • Export Citation

  • Shannon, L. V., A. J. Boyd, G. B. Brundrit, and J. Taunton-Clark, 1986: On the existence of an El Niño-type phenomenon in the Benguela system. J. Mar. Res., 44 , 495–520.

    • Search Google Scholar
    • Export Citation
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