• Behera, S. K., and T. Yamagata, 2001: Subtropical SST dipole events in the southern Indian Ocean. Geophys. Res. Lett., 28, 327330.

  • Behera, S. K., P. S. Salvekar, and T. Yamagata, 2000: Simulation of interannual SST variability in the tropical Indian Ocean. J. Climate, 13, 34873499.

    • Search Google Scholar
    • Export Citation
  • Blanke, B., and P. Delecluse, 1993: Variability of the tropical Atlantic Ocean simulated by a general circulation model with two different mixed-layer physics. J. Phys. Oceanogr., 23, 13631388.

    • Search Google Scholar
    • Export Citation
  • Chiodi, A. M., and D. E. Harrison, 2007: Mechanisms of summertime subtropical southern Indian Ocean sea surface temperature variability: On the importance of humidity anomalies and the meridional advection of water vapor. J. Climate, 20, 48354852.

    • Search Google Scholar
    • Export Citation
  • Colberg, F., and C. J. C. Reason, 2007: Ocean model diagnosis of low-frequency climate variability in the South Atlantic region. J. Climate, 20, 10161034.

    • Search Google Scholar
    • Export Citation
  • Colberg, F., C. J. C. Reason, and K. Rodgers, 2004: South Atlantic response to El Niño-Southern Oscillation induced climate variability in an ocean general circulation model. J. Geophys. Res., 109, C12015, doi:10.1029/2004JC002301.

    • Search Google Scholar
    • Export Citation
  • Cook, K. H., 2000: The South Indian Ocean convergence zone and interannual rainfall variability over southern Africa. J. Climate, 13, 37893804.

    • Search Google Scholar
    • Export Citation
  • Davis, R. E., R. de Szoeke, and P. Niiler, 1981: Variability in the upper ocean during MILE. Part II: Modeling the mixed layer response. Deep-Sea Res., 28, 14531475.

    • Search Google Scholar
    • Export Citation
  • Fauchereau, N., S. Trzaska, Y. Richard, P. Roucou, and P. Camberlin, 2003: Sea-surface temperature co-variability in the southern Atlantic and Indian Oceans and its connections with the atmospheric circulation in the Southern Hemisphere. Int. J. Climatol., 23, 663677, doi:10.1002/joc.905.

    • Search Google Scholar
    • Export Citation
  • Fauchereau, N., B. Pohl, C. J. C. Reason, M. Rouault, and Y. Richard, 2009: Recurrent daily OLR patterns in the Southern Africa/Southwest Indian Ocean region, implications for South African rainfall and teleconnections. Climate Dyn., 32, 575591.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., and J. C. McWilliams, 1990: Isopycnal mixing in ocean circulation models. J. Phys. Oceanogr., 20, 150155.

  • Gualdi, S., A. Navarra, E. Guilyardi, and P. Delecluse, 2003: Assessment of the tropical Indo-Pacific climate in the SINTEX CGCM. Ann. Geophys., 46, 126.

    • Search Google Scholar
    • Export Citation
  • Guilyardi, E., P. Delecluse, S. Gualdi, and A. Navarra, 2003: Mechanisms for ENSO phase change in a coupled GCM. J. Climate, 16, 11411158.

    • Search Google Scholar
    • Export Citation
  • Harrison, M. S. J., 1984: A generalized classification of South African summer rain-bearing synoptic systems. J. Climatol., 4, 547560.

    • Search Google Scholar
    • Export Citation
  • Hermes, J. C., and C. J. C. Reason, 2005: Ocean model diagnosis of interannual coevolving SST variability in the South Indian and South Atlantic Oceans. J. Climate, 18, 28642882.

    • Search Google Scholar
    • Export Citation
  • Hoskins, B. J., and D. J. Karoly, 1981: The steady linear response of a spherical atmosphere to thermal and orographic forcing. J. Atmos. Sci., 38, 11791196.

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

  • Kataoka, T., T. Tozuka, Y. Masumoto, and T. Yamagata, 2012: The Indian Ocean subtropical dipole mode simulated in the CMIP3 models. Climate Dyn., doi:10.1007/s00382-011-1271-2, in press.

    • Search Google Scholar
    • Export Citation
  • Kraus, E. B., and J. S. Turner, 1967: A one-dimensional model of the seasonal thermocline: II. The general theory and its consequences. Tellus, 19, 98106.

    • Search Google Scholar
    • Export Citation
  • Legates, D. R., and C. J. Willmott, 1990: Mean seasonal and spatial variability in gauge-corrected, global precipitation. Int. J. Climatol., 10, 111127.

    • Search Google Scholar
    • Export Citation
  • Lindesay, J. A., 1988: Southern African rainfall, the Southern Oscillation and a Southern Hemisphere semi-annual cycle. J. Climatol., 8, 1730.

    • Search Google Scholar
    • Export Citation
  • Locarnini, R. A., A. V. Mishonov, J. I. Antonov, T. P. Boyer, H. E. Garcia, O. K. Baranova, M. M. Zweng, and D. R. Johnson, 2010: Temperature. Vol. 1, World Ocean Atlas 2009, NOAA Atlas NESDIS 68, 184 pp.

  • Louis, J. F., 1979: A parametric model of vertical eddy fluxes in the atmosphere. Bound.-Layer Meteor., 17, 187202.

  • Luo, J. J., S. Masson, S. Behera, P. Delecluse, S. Gualdi, A. Navarra, and T. Yamagata, 2003: South Pacific origin of the decadal ENSO-like variation as simulated by a coupled GCM. Geophys. Res. Lett., 30, 2250, doi:10.1029/2003GL018649.

    • Search Google Scholar
    • Export Citation
  • Luo, J. J., S. Masson, E. Roeckner, G. Madec, and T. Yamagata, 2005: Reducing climatology bias in an ocean–atmosphere CGCM with improved coupling physics. J. Climate, 18, 23442360.

    • Search Google Scholar
    • Export Citation
  • Madec, G., P. Delecluse, M. Imbard, and C. Levy, 1998: OPA 8.1 ocean general circulation model reference manual. Tech. Note 11, LODYC/IPSL, 91 pp.

  • Mason, S. J., 1995: Sea-surface temperature—South African rainfall associations, 1910-1989. Int. J. Climatol., 15, 119135.

  • Moisan, J. R., and P. P. Niiler, 1998: The seasonal heat budget of the North Pacific: Net heat flux and heat storage rates (1950–1990). J. Phys. Oceanogr., 28, 401421.

    • Search Google Scholar
    • Export Citation
  • Morioka, Y., T. Tozuka, and T. Yamagata, 2010: Climate variability in the southern Indian Ocean as revealed by self-organizing maps. Climate Dyn., 35, 10591072.

    • Search Google Scholar
    • Export Citation
  • Morioka, Y., T. Tozuka, and T. Yamagata, 2011: On the growth and decay of the subtropical dipole mode in the South Atlantic. J. Climate, 24, 55385554.

    • Search Google Scholar
    • Export Citation
  • Nakamura, H., and A. Shimpo, 2004: Seasonal variations in the Southern Hemisphere storm tracks and jet streams as revealed in a reanalysis dataset. J. Climate, 17, 18281844.

    • Search Google Scholar
    • Export Citation
  • North, G. R., T. L. Bell, R. F. Cahalan, and F. J. Moeng, 1982: Sampling errors in the estimation of empirical orthogonal functions. Mon. Wea. Rev., 110, 699706.

    • Search Google Scholar
    • Export Citation
  • Paulson, C. A., and J. J. Simpson, 1977: Irradiance measurements in the upper ocean. J. Phys. Oceanogr., 7, 952956.

  • Qiu, B., and K. A. Kelly, 1993: Upper-ocean heat balance in the Kuroshio Extension region. J. Phys. Oceanogr., 23, 20272041.

  • 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., 1998: Warm and cold events in the southeast Atlantic/southwest Indian Ocean region and potential impacts on circulation and rainfall over southern Africa. Meteor. Atmos. Phys., 69, 4965.

    • Search Google Scholar
    • Export Citation
  • Reason, C. J. C., 2001: Subtropical Indian Ocean SST dipole events and southern African rainfall. Geophys. Res. Lett., 28, 22252227.

  • Reason, C. J. C., 2002: Sensitivity of the southern African circulation to dipole sea-surface temperature patterns in the South Indian Ocean. Int. J. Climatol., 22, 377393, doi:10.1002/joc.744.

    • Search Google Scholar
    • Export Citation
  • Reason, C. J. C., and H. Mulenga, 1999: Relationships between South African rainfall and SST anomalies in the southwest Indian Ocean. Int. J. Climatol., 19, 16511673.

    • Search Google Scholar
    • Export Citation
  • Reason, C. J. C., R. J. Allan, J. A. Lindesay, and T. J. Ansell, 2000: ENSO and climatic signals across the Indian Ocean basin in the global context: Part I, interannual composite patterns. Int. J. Climatol., 20, 12851327.

    • 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, 941955.

    • Search Google Scholar
    • Export Citation
  • Richard, Y., S. Trzaska, P. Roucou, and M. Rouault, 2000: Modification of the southern African rainfall variability/ENSO relationship since the late 1960s. Climate Dyn., 16, 883895.

    • Search Google Scholar
    • Export Citation
  • Roeckner, E., and Coauthors, 1996: The atmospheric general circulation model ECHAM-4: Model description and simulation of present-day climate. Max-Planck-Institut für Meteorologie Rep. 218, 90 pp.

  • Ropelewski, C., and M. S. Halpert, 1987: Global and regional scale precipitation patterns associated with the El Niño/Southern Oscillation. Mon. Wea. Rev., 115, 16061626.

    • Search Google Scholar
    • Export Citation
  • Sampe, T., H. Nakamura, A. Goto, and W. Ohfuchi, 2010: Significance of a midlatitude SST frontal zone in the formation of a storm track and an eddy-driven westerly jet. J. Climate, 23, 17931814.

    • Search Google Scholar
    • Export Citation
  • Sterl, A., and W. Hazeleger, 2003: Coupled variability and air-sea interaction in the South Atlantic Ocean. Climate Dyn., 21, 559571.

    • Search Google Scholar
    • Export Citation
  • Suzuki, R., S. K. Behera, S. Iizuka, and T. Yamagata, 2004: Indian Ocean subtropical dipole simulated using a coupled general circulation model. J. Geophys. Res., 109, C09001, doi:10.1029/2003JC001974.

    • Search Google Scholar
    • Export Citation
  • Terray, P., 2011: Southern Hemisphere extra-tropical forcing: A new paradigm for El Niño-Southern Oscillation. Climate Dyn., 36, 21712199.

    • Search Google Scholar
    • Export Citation
  • Tiedtke, M., 1989: A comprehensive mass flux scheme for cumulus parameterization in large-scale models. Mon. Wea. Rev., 117, 17791800.

    • Search Google Scholar
    • Export Citation
  • Valcke, S., L. Terray, and A. Piacentini, 2000: The OASIS coupler user’s guide version 2.4. Tech. Rep. TR/CMGC/00-10, CERFACS, 85 pp.

  • Venegas, S. A., L. A. Mysak, and D. N. Straub, 1997: Atmosphere–ocean coupled variability in the South Atlantic. J. Climate, 10, 29042920.

    • Search Google Scholar
    • Export Citation
  • Vigaud, N., Y. Richard, M. Rouault, and N. Fauchereau, 2009: Moisture transport between the South Atlantic Ocean and southern Africa: Relationships with summer rainfall and associated dynamics. Climate Dyn., 32, 113123.

    • Search Google Scholar
    • Export Citation
  • Walker, N. D., 1990: Links between South African summer rainfall and temperature variability of the Agulhas and Benguela current systems. J. Geophys. Res., 95, 32973319.

    • Search Google Scholar
    • Export Citation
  • Wang, F., 2010a: Thermodynamic coupled modes in the tropical atmosphere–ocean: An analytical solution. J. Atmos. Sci., 67, 16671677.

    • Search Google Scholar
    • Export Citation
  • Wang, F., 2010b: Subtropical dipole mode in the Southern Hemisphere: A global view. Geophys. Res. Lett., 37, L10702, doi:10.1029/2010GL042750.

    • Search Google Scholar
    • Export Citation
  • Yasuda, I., T. Tozuka, M. Noto, and S. Kouketsu, 2000: Heat balance and regime shifts of the mixed layer in the Kuroshio Extension. Prog. Oceanogr., 47, 257278.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 192 116 4
PDF Downloads 172 130 3

Subtropical Dipole Modes Simulated in a Coupled General Circulation Model

View More View Less
  • 1 Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
  • | 2 LOCEAN/IPSL, Université Pierre et Marie Curie, Paris, France
  • | 3 Research Institute for Global Change, JAMSTEC, Yokohama, Japan
  • | 4 Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, Tokyo, Japan
Restricted access

Abstract

The growth and decay mechanisms of subtropical dipole modes in the southern Indian and South Atlantic Oceans and their impacts on southern African rainfall are investigated using results from a coupled general circulation model originally developed for predicting tropical climate variations. The second (most) dominant mode of interannual sea surface temperature (SST) variations in the southern Indian (South Atlantic) Ocean represents a northeast–southwest oriented dipole, now called subtropical dipole mode. The positive (negative) SST interannual anomaly pole starts to grow in austral spring and reaches its peak in February. In austral late spring, the suppressed (enhanced) latent heat flux loss associated with the variations in the subtropical high causes a thinner (thicker) than normal mixed layer thickness that, in turn, enhances (reduces) the warming of the mixed layer by the climatological shortwave radiation. The positive (negative) pole gradually decays in austral fall because the mixed layer cooling by the entrainment is enhanced (reduced), mostly owing to the larger (smaller) temperature difference between the mixed layer and the entrained water. The increased (decreased) latent heat loss due to the warmer (colder) SST also contributes to the decay of the positive (negative) pole. Although further verification using longer observational data is required, the present coupled model suggests that the South Atlantic subtropical dipole may play a more important role in rainfall variations over the southern African region than the Indian Ocean subtropical dipole.

Corresponding author address: Toshio Yamagata, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. E-mail: yamagata@eps.s.u-tokyo.ac.jp

Abstract

The growth and decay mechanisms of subtropical dipole modes in the southern Indian and South Atlantic Oceans and their impacts on southern African rainfall are investigated using results from a coupled general circulation model originally developed for predicting tropical climate variations. The second (most) dominant mode of interannual sea surface temperature (SST) variations in the southern Indian (South Atlantic) Ocean represents a northeast–southwest oriented dipole, now called subtropical dipole mode. The positive (negative) SST interannual anomaly pole starts to grow in austral spring and reaches its peak in February. In austral late spring, the suppressed (enhanced) latent heat flux loss associated with the variations in the subtropical high causes a thinner (thicker) than normal mixed layer thickness that, in turn, enhances (reduces) the warming of the mixed layer by the climatological shortwave radiation. The positive (negative) pole gradually decays in austral fall because the mixed layer cooling by the entrainment is enhanced (reduced), mostly owing to the larger (smaller) temperature difference between the mixed layer and the entrained water. The increased (decreased) latent heat loss due to the warmer (colder) SST also contributes to the decay of the positive (negative) pole. Although further verification using longer observational data is required, the present coupled model suggests that the South Atlantic subtropical dipole may play a more important role in rainfall variations over the southern African region than the Indian Ocean subtropical dipole.

Corresponding author address: Toshio Yamagata, Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. E-mail: yamagata@eps.s.u-tokyo.ac.jp
Save