The Effect of ENSO Events on the Tropical Pacific Mean Climate: Insights from an Analytical Model

Jin Liang Institute for Climate and Global Change Research, School of Atmospheric Sciences, Nanjing University, Nanjing, China, and Cooperative Institute for Research in Environmental Sciences, University of Colorado and NOAA/Earth System Research Laboratory/Physical Science Division, Boulder, Colorado

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Xiu-Qun Yang Institute for Climate and Global Change Research, School of Atmospheric Sciences, Nanjing University, Nanjing, China

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De-Zheng Sun Cooperative Institute for Research in Environmental Sciences, University of Colorado and NOAA/Earth System Research Laboratory/Physical Science Division, Boulder, Colorado

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Abstract

To better understand the causes of climate change in the tropical Pacific on decadal and longer time scales, the authors delineate the rectification effect of ENSO events into the mean state by contrasting the time-mean state of a low-order model for the Pacific with its equilibrium state. The model encapsulates the essential physics of the ENSO system, but remains simple enough to allow for the obtaining of its equilibrium state. The model has an oscillatory regime that resembles the observations. In this oscillatory regime, the time-mean SST in the eastern equatorial Pacific is found to be significantly different from the corresponding equilibrium SST, with the former being warmer than the latter. The difference is found to be proportional to the amplitude of ENSO. In addition, the zonal SST contrast of the time-mean state is found to be less sensitive to increases in external forcing than that of the equilibrium state, due to warming effect of ENSO events on the eastern Pacific. It is further shown that this rectification effect of ENSO events results from the nonlinear advection term in the heat budget equation. The study elucidates the role of ENSO events in shaping the tropical mean climate state and suggests that decadal warming in the recent decades in the eastern tropical Pacific may be more a consequence than a cause of the elevated ENSO activity during the same period. The results also provide a simple explanation for why it is difficult to detect an anthropogenically forced trend in the zonal SST contrast in the observations.

Corresponding author address: Dr. De-Zheng Sun, Cooperative Institute for Research in Environmental Sciences, University of Colorado and NOAA/Earth System Research Laboratory/Physical Science Division, Boulder, CO 80304. E-mail: dezheng.sun@noaa.gov

Abstract

To better understand the causes of climate change in the tropical Pacific on decadal and longer time scales, the authors delineate the rectification effect of ENSO events into the mean state by contrasting the time-mean state of a low-order model for the Pacific with its equilibrium state. The model encapsulates the essential physics of the ENSO system, but remains simple enough to allow for the obtaining of its equilibrium state. The model has an oscillatory regime that resembles the observations. In this oscillatory regime, the time-mean SST in the eastern equatorial Pacific is found to be significantly different from the corresponding equilibrium SST, with the former being warmer than the latter. The difference is found to be proportional to the amplitude of ENSO. In addition, the zonal SST contrast of the time-mean state is found to be less sensitive to increases in external forcing than that of the equilibrium state, due to warming effect of ENSO events on the eastern Pacific. It is further shown that this rectification effect of ENSO events results from the nonlinear advection term in the heat budget equation. The study elucidates the role of ENSO events in shaping the tropical mean climate state and suggests that decadal warming in the recent decades in the eastern tropical Pacific may be more a consequence than a cause of the elevated ENSO activity during the same period. The results also provide a simple explanation for why it is difficult to detect an anthropogenically forced trend in the zonal SST contrast in the observations.

Corresponding author address: Dr. De-Zheng Sun, Cooperative Institute for Research in Environmental Sciences, University of Colorado and NOAA/Earth System Research Laboratory/Physical Science Division, Boulder, CO 80304. E-mail: dezheng.sun@noaa.gov
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  • An, S.-I., and F.-F. Jin, 2001: Collective role of thermocline and zonal advective feedbacks in the ENSO mode. J. Climate, 14, 34213432.

    • Search Google Scholar
    • Export Citation
  • An, S.-I., and F.-F. Jin, 2004: Nonlinearity and asymmetry of ENSO. J. Climate, 17, 23992412.

  • An, S.-I., Y.-G. Ham, J.-S. Kug, F.-F. Jin, and I.-S. Kang, 2005: El Niño–La Niña asymmetry in the Coupled Model Intercomparison Project simulations. J. Climate, 18, 26172627.

    • Search Google Scholar
    • Export Citation
  • Burgers, G., and D. B. Stephenson, 1999: The “normality” of El Niño. Geophys. Res. Lett., 26, 10271030, doi:10.1029/1999GL900161.

    • Search Google Scholar
    • Export Citation
  • Cane, M. A., A. C. Clement, A. Kaplan, Y. Kushnir, D. Pozdnyakov, R. Seager, S. E. Zebiak, and R. Murtugudde, 1997: Twentieth-century sea surface temperature trends. Science, 275, 957960.

    • Search Google Scholar
    • Export Citation
  • Clement, A. C., R. Seager, M. A. Cane, and S. E. Zebiak, 1996: An ocean dynamical thermostat. J. Climate, 9, 21902196.

  • Collins, M., and Coauthors, 2010: The impact of global warming on the tropical Pacific Ocean and El Niño. Nat. Geosci., 3, 391397.

  • Deng, L., X.-Q. Yang, and Q. Xie, 2010: ENSO frequency change in coupled climate models as response to the increasing CO2 concentration. Chin. Sci. Bull., 55, 744751.

    • Search Google Scholar
    • Export Citation
  • Fedorov, A. V., and S. G. Philander, 2000: Is El Niño changing? Science, 288, 19972002.

  • Fedorov, A. V., and S. G. Philander, 2001: A stability analysis of tropical ocean–atmosphere interactions: Bridging measurements and theory for El Niño. J. Climate, 14, 30863101.

    • Search Google Scholar
    • Export Citation
  • Flugel, M., P. Chang, and C. Penland, 2004: Identification of dynamical regimes in an intermediate coupled ocean–atmosphere model. J. Climate, 13, 21052115.

    • Search Google Scholar
    • Export Citation
  • Gent, P. R., and M. A. Cane, 1989: A reduced gravity, primitive equation model of the upper equatorial ocean. J. Comput. Phys., 81, 444480.

    • Search Google Scholar
    • Export Citation
  • Guilyardi, E., A. Wittenberg, A. Fedorov, M. Collins, C. Wang, A. Capotondi, G. J. van Oldenborgh, and T. Stockdale, 2009: Understanding El Niño in ocean–atmosphere general circulation models. Bull. Amer. Meteor. Soc., 90, 325340.

    • Search Google Scholar
    • Export Citation
  • Guilyardi, E., W. J. Cai, M. Collins, A. Fedorov, F.-F. Jin, A. Kumar, D.-Z. Sun, and A. Wittenberg, 2012: New strategies for evaluating ENSO processes in climate models. Bull. Amer. Meteor. Soc., 93, 235238.

    • Search Google Scholar
    • Export Citation
  • Jin, F.-F., 1996: Tropical ocean–atmosphere interaction, Pacific cold tongue, and El Niño–Southern Oscillation. Science, 274, 7678.

    • Search Google Scholar
    • Export Citation
  • Jin, F.-F., 1997: An equatorial ocean recharge paradigm for ENSO. Part I: Conceptual model. J. Atmos. Sci., 54, 811829.

  • Jin, F.-F., S.-I. An, A. Timmermann, and J. X. Zhao, 2003: Strong El Niño events and nonlinear dynamical heating. Geophys. Res. Lett., 30, 1120, doi:10.1029/2002GL016356.

    • Search Google Scholar
    • Export Citation
  • Kleeman, R., 2008: Stochastic theories for the irregularity of ENSO. Philos. Trans. Roy. Soc., 366A, 25092524.

  • Manabe, S., and R. F. Möller, 1961: On the radiative equilibrium and the heat balance of the atmosphere. Mon. Wea. Rev., 89, 503532.

    • Search Google Scholar
    • Export Citation
  • Manabe, S., and R. F. Strickler, 1964: Thermal equilibrium of the atmosphere with convective adjustment. J. Atmos. Sci., 21, 361385.

  • Manabe, S., and R. T. Wetherald, 1967: Thermal equilibrium of the atmosphere with a given distribution of relative humidity. J. Atmos. Sci., 24, 241259.

    • Search Google Scholar
    • Export Citation
  • Meehl, G. A., A. Hu, and C. Tebaldi, 2010: Decadal prediction in the Pacific region. J. Climate, 23, 29592973.

  • Moore, A., and R. Kleeman, 1999: Stochastic forcing of ENSO by the intraseasonal oscillation. J. Climate, 12, 11991220.

  • Penland, C., 1996: A stochastic model of Indo-Pacific sea surface temperature anomalies. Physica D, 98, 534558.

  • Penland, C., and P. D. Sardeshmukh, 1995: The optimal growth of tropical sea surface temperature anomalies. J. Climate, 8, 19992024.

  • Philander, S. G., 1990: El Niño, La Niña, and the Southern Oscillation. Academic Press, 293 pp.

  • Picaut, J., F. Masia, and Y. du Penhoat, 1997: An advective-reflective conceptual model for the oscillatory nature of the ENSO. Science, 277, 663666.

    • Search Google Scholar
    • Export Citation
  • Rayner, N. A., E. B. Horton, D. E. Parker, C. K. Folland, and R. B. Hackett, 1996: Version 2.2 of the Global Sea-Ice and Sea Surface Temperature data set, 1993–1994. Hadley Centre Climate Research Tech. Note 74 (CRTN74), 46 pp. [Available online at http://www.metoffice.gov.uk/hadobs/gisst/crtn74.pdf.]

  • Rodgers, K. B., P. Friederichs, and M. Latif, 2004: Tropical Pacific decadal variability and its relation to decadal modulations of ENSO. J. Climate, 17, 37613774.

    • Search Google Scholar
    • Export Citation
  • Schopf, P. S., and R. J. Burgman, 2006: A simple mechanism for ENSO residuals and asymmetry. J. Climate, 19, 31673179.

  • Strogatz, S., 2001: Nonlinear Dynamics and Chaos: With Applications to Physics, Biology, Chemistry and Engineering. Westview Press, 528 pp.

  • Sun, D.-Z., 1997: El Niño: A coupled response to radiative heating? Geophys. Res. Lett., 24, 20312034.

  • Sun, D.-Z., 2000: Global climate change and ENSO: A theoretical framework. El Niño: Historical and Paleoclimatic Aspects of the Southern Oscillation, Multiscale Variability, and Global and Regional Impacts, H. F. Diaz and V. Markgraf, Eds., Cambridge University Press, 443–463.

  • Sun, D.-Z., 2003: A possible effect of an increase in the warm-pool SST on the magnitude of El Niño warming. J. Climate, 16, 185205.

    • Search Google Scholar
    • Export Citation
  • Sun, D.-Z., 2010: The diabatic and nonlinear aspects of El Niño–Southern Oscillation: Implications for its past and future behavior. Climate Dynamics: Why Does Climate Vary? Geophys. Monogr., Vol. 189, Amer. Geophys. Union, 79–104.

  • Sun, D.-Z., and Z. Liu, 1996: Dynamic ocean–atmosphere coupling: A thermostat for the tropics. Science, 272, 11481150.

  • Sun, D.-Z., and T. Zhang, 2006: A regulatory effect of ENSO on the time-mean thermal stratification of the equatorial upper ocean. Geophys. Res. Lett., 33, L07710, doi:10.1029/2005GL025296.

    • Search Google Scholar
    • Export Citation
  • Sun, D.-Z., and Coauthors, 2006: Radiative and dynamical feedbacks over the equatorial cold tongue: Results from nine atmospheric GCMs. J. Climate, 19, 40594074.

    • Search Google Scholar
    • Export Citation
  • Sun, F., and J.-Y. Yu, 2009: A 10–15-yr modulation cycle of ENSO intensity. J. Climate, 22, 17181735.

  • Timmermann, A., and F.-F. Jin, 2002: A nonlinear mechanism for decadal El Niño amplitude changes. Geophys. Res. Lett., 29, 1003, doi:10.1029/2001GL013369.

    • Search Google Scholar
    • Export Citation
  • Vecchi, G. A., A. Clement, and B. J. Soden, 2008: Examining the tropical Pacific’s response to global warming. Eos, Trans. Amer. Geophys. Union, 89, 81, doi:10.1029/2008EO090002.

    • Search Google Scholar
    • Export Citation
  • Wang, B., and S.-I. An, 2001: Why the properties of El Niño changed during the late 1970s. Geophys. Res. Lett., 28, 37093712.

  • Wang, X. L., and C.-F. Ropelewski, 1995: An assessment of ENSO-scale secular variability. J. Climate, 8, 15841599.

  • Wittenberg, A. T., 2009: Are historical records sufficient to constrain ENSO simulations? Geophys. Res. Lett., 36, L12702, doi:10.1029/2009GL038710.

    • Search Google Scholar
    • Export Citation
  • Xu, K.-M., and K. A. Emanuel, 1989: Is the tropical atmosphere conditionally unstable? Mon. Wea. Rev., 117, 14711479.

  • Zebiak, S. E., and M. A. Cane, 1987: A model El Niño–Southern Oscillation. Mon. Wea. Rev., 115, 22622278.

  • Zhang, T., D.-Z. Sun, R. Neale, and P. J. Rasch, 2009: An evaluation of ENSO asymmetry in the Community Climate System Models: A view from the subsurface. J. Climate, 22, 59335961.

    • Search Google Scholar
    • Export Citation
  • Zhang, Y., J. M. Wallace, and D. S. Battisti, 1997: ENSO-like interdecadal variability: 1900–93. J. Climate, 10, 10041020.

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