• Allan, R., , and T. Ansell, 2006: A new globally complete monthly historical gridded mean sea level pressure dataset (HadSLP2): 1850–2004. J. Climate, 19, 58165842.

    • Search Google Scholar
    • Export Citation
  • Arblaster, J. M., , and G. A. Meehl, 2006: Contributions of external forcings to southern annular mode trends. J. Climate, 19, 28962905.

    • Search Google Scholar
    • Export Citation
  • Arblaster, J. M., , G. A. Meehl, , and D. J. Karoly, 2011: Future climate change in the Southern Hemisphere: Competing effects of ozone and greenhouse gases. Geophys. Res. Lett., 38, L02701, doi:10.1029/2010GL045384.

    • Search Google Scholar
    • Export Citation
  • Boé, J., , and L. Terray, 2008: Weather regimes and downscaling. Houille Blanche, 2, 4551.

  • Carvalho, L. M. V., , C. Jones, , and T. Ambrizzi, 2005: Opposite phases of the Antarctic Oscillation and relationships with intraseasonal to interannual activity in the tropics during the austral summer. J. Climate, 18, 702718.

    • Search Google Scholar
    • Export Citation
  • Cash, B. A., , P. J. Kushner, , and G. K. Vallis, 2002: The structure and composition of the annular modes in an aquaplanet general circulation model. J. Atmos. Sci., 59, 33993414.

    • Search Google Scholar
    • Export Citation
  • Cassou, C., 2008: Intraseasonal interaction between the Madden–Julian oscillation and the North Atlantic Oscillation. Nature, 455, 523527, doi:10.1038/nature07286.

    • Search Google Scholar
    • Export Citation
  • Cassou, C., , L. Terray, , and A. D. Phillips, 2005: Tropical Atlantic influence on European heat waves. J. Climate, 18, 28052811.

  • Cheng, X., , and J. M. Wallace, 1993: Regime analysis of the Northern Hemisphere wintertime 500-hPa height field: Spatial patterns. J. Atmos. Sci., 50, 26742696.

    • Search Google Scholar
    • Export Citation
  • Christiansen, B., 2007: Atmospheric circulation regimes: Can cluster analysis provide the number? J. Climate, 20, 22292250.

  • Compo, G. P., and Coauthors, 2011: The Twentieth Century Reanalysis project. Quart. J. Roy. Meteor. Soc., 137, 128.

  • Gille, S. T., 2002: Warming of the Southern Ocean since the 1950s. Science, 295, 1275.

  • Gille, S. T., 2008: Decadal-scale temperature trends in the Southern Hemisphere ocean. J. Climate, 21, 47494765.

  • Gillett, N. P., , T. D. Kell, , and P. D. Jones, 2006: Regional climate impacts of the southern annular mode. Geophys. Res. Lett., 33, L23704, doi:10.1029/2006GL027721.

    • Search Google Scholar
    • Export Citation
  • Gillett, N. P., , D. A. Stone, , P. A. Stott, , T. Nozawa, , A. Y. Karpechko, , G. C. Hegeri, , M. F. Wehner, , and P. D. Jones, 2008: Attribution of polar warming to human influence. Nat. Geosci., 1, 750754.

    • Search Google Scholar
    • Export Citation
  • Gong, D., , and S. Wang, 1999: Definition of Antarctic Oscillation index. Geophys. Res. Lett., 26, 459462.

  • Hendon, H. H., , D. W. Thompson, , and M. C. Wheeler, 2007: Australian rainfall and surface temperature variations associated with the Southern Hemisphere annular mode. J. Climate, 20, 24522467.

    • Search Google Scholar
    • Export Citation
  • Hines, K. M., , D. H. Bromwich, , and G. J. Marshall, 2000: Artificial surface pressure trends in the NCEP–NCAR reanalysis over the Southern Ocean and Antarctica. J. Climate, 13, 39403952.

    • Search Google Scholar
    • Export Citation
  • Huth, R., 1996: An intercomparison of computer-assisted circulation classification methods. Int. J. Climatol., 16, 893922.

  • Kageyama, M., , F. D’Andrea, , G. Ramstein, , P. J. Valdes, , and R. Vautard, 1999: Weather regimes in past climate atmospheric general circulation model simulations. Climate Dyn., 15, 773793.

    • Search Google Scholar
    • Export Citation
  • Kalnay, E., and Coauthors, 1996: The NCEP/NCAR 40-Year Reanalyses Project. Bull. Amer. Meteor. Soc., 77, 437471.

  • Kanamitsu, M., , W. Ebisuzaki, , J. Woollen, , S.-K. Yang, , J. J. Hnilo, , M. Fiorino, , and G. L. Potter, 2002: NCEP–DOE AMIP II Reanalysis (R-2). Bull. Amer. Meteor. Soc., 83, 16311643.

    • Search Google Scholar
    • Export Citation
  • Kushner, P. J., , and G. Lee, 2007: Resolving the regional signature of the annular modes. J. Climate, 20, 28402852.

  • L’Heureux, M. L., , and D. W. J. Thompson, 2006: Observed relationships between the El Niño–Southern Oscillation and the extratropical zonal-mean circulation. J. Climate, 19, 276287.

    • Search Google Scholar
    • Export Citation
  • Marshall, G. J., 2003: Trends in the southern annular mode from observations and reanalyses. J. Climate, 16, 41344143.

  • Meneghini, B., , I. Simmonds, , and I. N. Smith, 2006: Association between seasonal Australian rainfall and the southern annular mode. Proc. Eighth Int. Conf. on Southern Hemisphere Meteorology and Oceanography, Foz de Iguaçú, Brazil, INPE, 311–313.

  • Michelangeli, P.-A., , R. Vautard, , and B. Legras, 1995: Weather regime occurrence and quasi stationarity. J. Atmos. Sci., 52, 12371256.

    • Search Google Scholar
    • Export Citation
  • Mo, K. C., , and R. W. Higgins, 1998: The Pacific–South American modes and tropical convection during the Southern Hemisphere winter. Mon. Wea. Rev., 126, 15811596.

    • Search Google Scholar
    • Export Citation
  • Mo, K. C., , and J. N. Paegle, 2001: The Pacific–South American modes and their downstream effects. Int. J. Climatol., 21, 12111229.

  • Monaghan, A., , and D. Bromwich, 2008: Climate science: Global warming at the poles. Nat. Geosci., 1, 728729.

  • Monahan, A. H., , J. C. Fyfe, , and G. M. Flato, 2000: A regime view of Northern Hemisphere atmospheric variability and change under global warming. Geophys. Res. Lett., 27, 11391142.

    • Search Google Scholar
    • Export Citation
  • Monahan, A. H., , L. Pandolfo, , and J. C. Fyfe, 2001: The preferred structure of variability of the Northern Hemisphere atmospheric circulation. Geophys. Res. Lett., 28, 10191022.

    • Search Google Scholar
    • Export Citation
  • Moron, V., , and G. Plaut, 2003: The impact of El Niño-Southern Oscillation upon weather regimes over Europe and the North Atlantic during boreal winter. Int. J. Climatol., 23, 363379.

    • Search Google Scholar
    • Export Citation
  • Perlwitz, J., 2011: Atmospheric science: Tug of war on the jet stream. Nat. Climate Change, 1, 2931, doi:10.1038/nclimate1065.

  • Pohl, B., , N. Fauchereau, , C. J. C. Reason, , and M. Rouault, 2010: Relationships between the Antarctic Oscillation, the Madden–Julian oscillation, and ENSO, and consequences for rainfall analysis. J. Climate, 23, 238254.

    • Search Google Scholar
    • Export Citation
  • Polvani, L. M., , D. W. Waugh, , G. J. P. Correa, , and S.-W. Son, 2011: Stratospheric ozone depletion: The main driver of twentieth-century atmospheric circulation changes in the Southern Hemisphere. J. Climate, 24, 795812.

    • Search Google Scholar
    • Export Citation
  • Qu, X., , A. Hall, , and J. Boé, 2012: Why does the Antarctic Peninsula warm in climate simulations? Climate Dyn., 38, 913–927, doi:10.1007/s00382-011-1092-3.

    • Search Google Scholar
    • Export Citation
  • Reason, C. J. C., , and M. Rouault, 2005: Links between the Antarctic Oscillation and winter rainfall over western South Africa. Geophys. Res. Lett., 32, L07705, doi:10.1029/2005GL022419.

    • Search Google Scholar
    • Export Citation
  • Renwick, J. A., 2004: Trends in the Southern Hemisphere polar vortex in NCEP and ECMWF reanalyses. Geophys. Res. Lett., 31, L07209, doi:10.1029/2003GL019302.

    • Search Google Scholar
    • Export Citation
  • Rogers, J. C., , and H. van Loon, 1982: Spatial variability of sea level pressure and 500-mb height anomalies over the Southern Hemisphere. Mon. Wea. Rev., 110, 13751392.

    • Search Google Scholar
    • Export Citation
  • Sallée, J. B., , K. G. Speer, , and S. R. Rintoul, 2010: Zonally asymmetric response of the Southern Ocean mixed-layer depth to the southern annular mode. Nat. Geosci., 3, 273279.

    • Search Google Scholar
    • Export Citation
  • Schneider, D. P., , C. Deser, , and Y. Okumura, 2011: An assessment and interpretation of the observed warming of West Antarctica in the austral spring. Climate Dyn., 38, 323347, doi:10.1007/s00382-010-0985-x.

    • Search Google Scholar
    • Export Citation
  • Sen Gupta, A., , and M. H. England, 2006: Coupled ocean–atmosphere–ice response to variations in the southern annular mode. J. Climate, 19, 44574486.

    • Search Google Scholar
    • Export Citation
  • Shindell, D. T., , and G. A. Schmidt, 2004: Southern Hemisphere climate response to ozone changes and greenhouse gas increases. Geophys. Res. Lett., 31, L18209, doi:10.1029/2004GL020724.

    • Search Google Scholar
    • Export Citation
  • Solomon, S., , D. Qin, , M. Manning, , M. Marquis, , K. Averyt, , M. M. B. Tignor, , H. L. Miller Jr., , and Z. Chen, Eds., 2007: Climate Change 2007: The Physical Science Basis. Cambridge University Press, 996 pp.

  • Son, S.-W., and Coauthors, 2008: The impact of stratospheric ozone recovery on the Southern Hemisphere westerly jet. Science, 320, 14861489, doi:10.1126/science.1155939.

    • Search Google Scholar
    • Export Citation
  • Son, S.-W., and Coauthors, 2010: Impact of stratospheric ozone on Southern Hemisphere circulation change: A multimodel assessment. J. Geophys. Res., 115, D00M07, doi:10.1029/2010JD014271.

    • Search Google Scholar
    • Export Citation
  • Steig, E. J., , D. P. Schneider, , S. D. Rutherford, , M. E. Mann, , J. C. Comiso, , and D. T. Shindell, 2009: Warming of the Antarctic ice-sheet surface since the 1957 International Geophysical Year. Nature, 457, 459463.

    • Search Google Scholar
    • Export Citation
  • Stephenson, D. B., , A. Hannachi, , and A. O’Neill, 2004: On the existence of multiple climate regimes. Quart. J. Roy. Meteor. Soc., 130, 583606.

    • Search Google Scholar
    • Export Citation
  • Straus, D., , S. Corti, , and F. Molteni, 2007: Circulation regimes: Chaotic variability versus SST-forced predictability. J. Climate, 20, 22512272.

    • Search Google Scholar
    • Export Citation
  • Thompson, D. W., , and J. M. Wallace, 2000: Annular modes in the extratropical circulation. Part I: Month-to-month variability. J. Climate, 13, 10001016.

    • Search Google Scholar
    • Export Citation
  • Thompson, D. W., , and S. Solomon, 2002: Interpretation of recent Southern Hemisphere climate change. Science, 296, 895899.

  • Visbeck, M., 2009: A station-based southern annular mode index from 1884 to 2005. J. Climate, 22, 940950.

  • Yuan, X., , and C. Li, 2008: Climate modes in southern high latitudes and their impacts on Antarctic sea ice. J. Geophys. Res., 113, C06S91, doi:10.1029/2006JC004067.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 55 55 13
PDF Downloads 39 39 9

The Southern Annular Mode Seen through Weather Regimes

View More View Less
  • 1 Centre de Recherches de Climatologie, UMR6282 Biogéosciences, CNRS/Université de Bourgogne, Dijon, France
  • 2 Council for Scientific and Industrial Research, Stellenbosh, and Department of Oceanography, University of Cape Town, Cape Town, South Africa
© Get Permissions
Restricted access

Abstract

This article investigates the prominent features of the Southern Hemisphere (south of 20°S) atmospheric circulation when extracted using EOF analysis and a k-means clustering algorithm. The focus is on the southern annular mode (SAM), the nature of its recent trend, and the zonal symmetry of associated spatial patterns. The study uses the NCEP–Department of Energy Atmospheric Model Intercomparison Project II Reanalysis (NCEP-2) (period 1979–2009) to obtain robust patterns over the recent years and the Twentieth Century Reanalysis Project (period 1871–2008) to document decadal changes. Also presented is a comparison of these signals against a station-based reconstruction of the SAM index and a gridded interpolated dataset [Hadley Centre Sea Level Pressure dataset version 2 (HadSLP2)].

Over their common period, both reanalyses are in fair agreement, both in terms of spatial patterns and temporal variability. In particular, both datasets show weather regimes that can be interpreted as the opposite phases of the SAM. At the decadal time scale, the study shows that the trend toward the positive SAM phase (as inferred from the usual EOF-based index) is related more to an increase in the frequency of clusters corresponding to the positive phase, with little changes in the frequency of the negative SAM events. Similarly, the long-term tropospheric warming trend already discussed in the literature is shown to be related more to a decrease in the number of abnormally cold days, with little changes in the number of abnormally warm days. The cluster analysis therefore allows for complement descriptions based on simple indexes or EOF decompositions, highlighting the nonlinear nature of the decadal changes in the Southern Hemisphere atmospheric circulation and temperature.

Current affiliation: National Institute for Water and Atmospheric Research, Auckland, New Zealand.

Corresponding author address: Dr. Benjamin Pohl, Centre de Recherches de Climatologie, 6 Boulevard Gabriel, 21000 Dijon, France. E-mail: benjamin.pohl@u-bourgogne.fr

Abstract

This article investigates the prominent features of the Southern Hemisphere (south of 20°S) atmospheric circulation when extracted using EOF analysis and a k-means clustering algorithm. The focus is on the southern annular mode (SAM), the nature of its recent trend, and the zonal symmetry of associated spatial patterns. The study uses the NCEP–Department of Energy Atmospheric Model Intercomparison Project II Reanalysis (NCEP-2) (period 1979–2009) to obtain robust patterns over the recent years and the Twentieth Century Reanalysis Project (period 1871–2008) to document decadal changes. Also presented is a comparison of these signals against a station-based reconstruction of the SAM index and a gridded interpolated dataset [Hadley Centre Sea Level Pressure dataset version 2 (HadSLP2)].

Over their common period, both reanalyses are in fair agreement, both in terms of spatial patterns and temporal variability. In particular, both datasets show weather regimes that can be interpreted as the opposite phases of the SAM. At the decadal time scale, the study shows that the trend toward the positive SAM phase (as inferred from the usual EOF-based index) is related more to an increase in the frequency of clusters corresponding to the positive phase, with little changes in the frequency of the negative SAM events. Similarly, the long-term tropospheric warming trend already discussed in the literature is shown to be related more to a decrease in the number of abnormally cold days, with little changes in the number of abnormally warm days. The cluster analysis therefore allows for complement descriptions based on simple indexes or EOF decompositions, highlighting the nonlinear nature of the decadal changes in the Southern Hemisphere atmospheric circulation and temperature.

Current affiliation: National Institute for Water and Atmospheric Research, Auckland, New Zealand.

Corresponding author address: Dr. Benjamin Pohl, Centre de Recherches de Climatologie, 6 Boulevard Gabriel, 21000 Dijon, France. E-mail: benjamin.pohl@u-bourgogne.fr
Save