• An, S-I., , and I-S. Kang, 2000: A further investigation of the recharge oscillator paradigm for ENSO using a simple coupled model with the zonal mean and eddy separated. J. Climate, 13 , 19871993.

    • 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
  • Annamalai, H., , S-P. Xie, , J. P. McCreary, , and R. Murtugudde, 2005: Impact of Indian Ocean sea surface temperature on developing El Niño. J. Climate, 18 , 302319.

    • Search Google Scholar
    • Export Citation
  • Boulanger, J-P., , S. Cravatte, , and C. Menkes, 2003: Reflected and locally wind-forced interannual equatorial Kelvin waves in the western Pacific Ocean. J. Geophys. Res., 108 .3311, doi:10.1029/2002JC001760.

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

  • Carton, J. A., , G. Chepurin, , and X. Cao, 2000: A simple ocean data assimilation analysis of the global upper ocean 1950–95. Part II: Results. J. Phys. Oceanogr., 30 , 311326.

    • Search Google Scholar
    • Export Citation
  • Chao, Y., , and S. G. H. Philander, 1993: On the structure of the Southern Oscillation. J. Climate, 6 , 450469.

  • Galanti, E., , E. Tziperman, , M. Harrison, , A. Rosati, , R. Giering, , and Z. Sirkes, 2002: The equatorial thermocline outcropping—A seasonal control on the tropical Pacific ocean–atmosphere instability strength. J. Climate, 15 , 27212739.

    • Search Google Scholar
    • Export Citation
  • Graham, N. E., , and T. P. Barnett, 1987: Sea surface temperature, surface wind divergence, and convection over tropical oceans. Science, 238 , 657659.

    • 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, D. E., , and G. A. Vecchi, 1999: On the termination of El Niño. Geophys. Res. Lett., 26 , 15931596.

  • Hasegawa, T., , T. Horii, , and K. Hanawa, 2006: Two different features of discharge of equatorial upper ocean heat content related to El Niño events. Geophys. Res. Lett., 33 .L02609, doi:10.1029/2005GL024832.

    • Search Google Scholar
    • Export Citation
  • Hoerling, M. P., , and A. Kumar, 2003: The perfect ocean for drought. Science, 299 , 691694.

  • Hoerling, M. P., , A. Kumar, , and M. Zhong, 1997: El Niño, La Niña, and the nonlinearity of their teleconnections. J. Climate, 10 , 17691786.

    • Search Google Scholar
    • Export Citation
  • Hoerling, M. P., , A. Kumar, , and T-Y. Xu, 2001: Robustness of the nonlinear atmospheric response to opposite phases of ENSO. J. Climate, 14 , 12771293.

    • Search Google Scholar
    • Export Citation
  • Horii, T., , and K. Hanawa, 2004: A relationship between timing of El Niño onset and subsequent evolution. Geophys. Res. Lett., 31 .L06304, doi:10.1029/2003GL019239.

    • 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., , J-S. Kug, , S-I. An, , and I-S. Kang, 2003: A near-annual coupled ocean-atmosphere mode in the equatorial Pacific Ocean. Geophys. Res. Lett., 30 .1080, doi:10.1029/2002GL015983.

    • Search Google Scholar
    • Export Citation
  • Kang, I-S., , and J-S. Kug, 2002: El Niño and La Niña sea surface temperature anomalies: Asymmetry characteristics associated with their wind stress anomalies. J. Geophys. Res., 107 .4372, doi:10.1029/2001JD000393.

    • Search Google Scholar
    • Export Citation
  • Kessler, W. S., 2002: Is ENSO a cycle or a series of events? Geophys. Res. Lett., 29 .2125, doi:10.1029/2002GL015924.

  • Kug, J-S., , and I-S. Kang, 2006: Interactive feedback between the Indian Ocean and ENSO. J. Climate, 19 , 17841801.

  • Luo, J. J., , and T. Yamagata, 2001: Long-term El Niño-Southern Oscillation (ENSO)-like variation with special emphasis on the South Pacific. J. Geophys. Res., 106 , 2221122227.

    • Search Google Scholar
    • Export Citation
  • Meinen, C. S., , and M. J. McPhaden, 2000: Observations of warm water volume changes in the equatorial Pacific and their relationship to El Niño and La Niña. J. Climate, 13 , 35513559.

    • Search Google Scholar
    • Export Citation
  • Minobe, S., , and F-F. Jin, 2004: Generation of interannual and interdecadal climate oscillations through nonlinear subharmonic resonance in delayed oscillators. Geophys. Res. Lett., 31 .L16206, doi:10.1029/2004GL019776.

    • Search Google Scholar
    • Export Citation
  • Monahan, A. H., , and A. Dai, 2004: The spatial and temporal structure of ENSO nonlinearity. J. Climate, 17 , 30263036.

  • Ohba, M., , and H. Ueda, 2007: An impact of SST anomalies in the Indian Ocean in acceleration of the El Niño to La Niña transition. J. Meteor. Soc. Japan, 85 , 335348.

    • Search Google Scholar
    • Export Citation
  • Schopf, P. S., , and M. J. Suarez, 1988: Vacillations in a coupled ocean-atmosphere model. J. Atmos. Sci., 45 , 549566.

  • Shibata, K., , H. Yoshimura, , M. Ohizumi, , M. Hosaka, , and M. Sugi, 1999: A simulation of troposphere, stratosphere and mesosphere with an MRI/JMA98 GCM. Pap. Meteor. Geophys., 50 , 1553.

    • Search Google Scholar
    • Export Citation
  • Simmons, A. J., , and J. K. Gibson, 2000: The ERA-40 project plan. ERA-40 Project Report Series No. 1, ECMWF, 63 pp.

  • Smith, T. M., , and R. W. Reynolds, 2004: Improved Extended Reconstruction of SST (1854–1997). J. Climate, 17 , 24662477.

  • Tomita, T., , and T. Yasunari, 1993: On the two types of ENSO. J. Meteor. Soc. Japan, 71 , 273284.

  • Ueda, H., , and R. Kawamura, 2004: Summertime anomalous warming over the midlatitude western North Pacific and its relationships to the modulation of the Asian monsoon. Int. J. Climatol., 24 , 11091120.

    • Search Google Scholar
    • Export Citation
  • Vecchi, G. A., 2006: The termination of the 1997–98 El Niño. Part II: Mechanisms of atmospheric change. J. Climate, 19 , 26472664.

  • Vecchi, G. A., , and D. E. Harrison, 2003: On the termination of the 2002-03 El Niño event. Geophys. Res. Lett., 30 .1964, doi:10.1029/2003GL017564.

    • Search Google Scholar
    • Export Citation
  • Vecchi, G. A., , and D. E. Harrison, 2006: The termination of the 1997–98 El Niño. Part I: Mechanisms of oceanic change. J. Climate, 19 , 26332646.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , and Q. Zhang, 2002: Pacific–East Asian teleconnection. Part II: How the Philippine Sea anomalous anticyclone is established during El Niño development. J. Climate, 15 , 32523265.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , R. Wu, , and X. Fu, 2000: Pacific–East Asian teleconnection: How does ENSO affect East Asian climate? J. Climate, 13 , 15171536.

    • Search Google Scholar
    • Export Citation
  • Wang, B., , R. Wu, , R. Lukas, , and S. I. An, 2001: A possible mechanism for ENSO turnabout. Dynamics of Atmospheric General Circulation and Climate, IAP/Academia Sinica, Ed., China Meteorology Press, 552–578.

    • Search Google Scholar
    • Export Citation
  • Wang, C., , R. H. Weisberg, , and J. I. Virmani, 1999: Western Pacific interannual variability associated with the El Niño-Southern Oscillation. J. Geophys. Res., 104 , 51315149.

    • Search Google Scholar
    • Export Citation
  • Watanabe, M., , and F-F. Jin, 2002: Role of Indian Ocean warming in the development of Philippine Sea anticyclone during ENSO. Geophys. Res. Lett., 29 .1478, doi:10.1029/2001GL014318.

    • Search Google Scholar
    • Export Citation
  • Weisberg, R. H., , and C. Wang, 1997: Slow variability in the equatorial west-central Pacific in relation to ENSO. J. Climate, 10 , 19982017.

    • Search Google Scholar
    • Export Citation
  • Wu, R., , and B. P. Kirtman, 2005: Near-annual SST variability in the equatorial Pacific in a coupled general circulation model. J. Climate, 18 , 44544473.

    • Search Google Scholar
    • Export Citation
  • Yan, B., , and R. Wu, 2007: Relative roles of different components of the basic state in the phase locking of El Niño mature phases. J. Climate, 20 , 42674277.

    • Search Google Scholar
    • Export Citation
  • Yanai, M., , S. Esbensen, , and J-H. Chu, 1973: Determination of bulk properties of tropical cloud clusters from large-scale heat and moisture budgets. J. Atmos. Sci., 30 , 611627.

    • Search Google Scholar
    • Export Citation
  • Yukimoto, S., and Coauthors, 2001: The new Meteorological Research Institute coupled GCM (MRI-CGCM2)—Model climate and variability. Pap. Meteor. Geophys., 51 , 4788.

    • Search Google Scholar
    • Export Citation
  • Yukimoto, S., and Coauthors, 2006: Present-day climate and climate sensitivity in the Meteorological Research Institute coupled GCM version 2.3 (MRI-CGCM2.3). J. Meteor. Soc. Japan, 84 , 333363.

    • Search Google Scholar
    • Export Citation
  • Xie, S-P., 1995: Interaction between annual and interannual variations in the equatorial Pacific. J. Phys. Oceanogr., 25 , 19301941.

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

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 90 91 20
PDF Downloads 62 62 11

Role of Nonlinear Atmospheric Response to SST on the Asymmetric Transition Process of ENSO

View More View Less
  • 1 Terrestrial Environment Research Center, University of Tsukuba, Tsukuba, Japan
  • | 2 Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
© Get Permissions
Restricted access

Abstract

Physical processes that are responsible for the asymmetric transition processes between El Niño and La Niña events are investigated by using observational data and physical models to examine the nonlinear atmospheric response to SST. The air–sea coupled system of ENSO is able to remain in a weak, cold event for up to 2 yr, while the system of a relatively warm event turns into a cold phase. Through analysis of the oceanic observational data, it is found that there is a strong difference in thermocline variations in relation to surface zonal wind anomalies in the equatorial Pacific (EP) during the mature-to-decaying phase of ENSO. The atmospheric response for the warm phase of ENSO causes a rapid reduction of the EP westerlies in boreal winter, which play a role in hastening the following ENSO transition through the generation of upwelling oceanic Kelvin waves. However, the anomalous EP easterlies in the cold phase persist to the subsequent spring, which tends to counteract the turnabout from the cold to warm phase of ENSO.

A suite of idealized atmospheric general circulation model (AGCM) experiments are performed by imposing two different ENSO-related SST anomalies, which have equal amplitudes but opposite signs. The nonlinear climate response in the AGCM is found at the mature-to-decaying phase of ENSO that closely resembles the observations, including a zonal and meridional shift in the equatorial positions of the atmospheric wind. By using a simple ocean model, it is determined that the asymmetric responses of the equatorial zonal wind result in different recovery times of the thermocline in the eastern Pacific. Thus, the differences in transition processes between the warm and cold ENSO event are fundamentally due to the nonlinear atmospheric response to SST, which originates from the distribution of climatological SST and its seasonal changes. By including the asymmetric wind responses the intermediate air–sea coupled model herein demonstrates that the essential elements of the redevelopment of La Niña arise from the nonlinear atmospheric response to SST anomalies.

Corresponding author address: Masamichi Ohba, Terrestrial Environment Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan. Email: ooba@suiri.tsukuba.ac.jp

Abstract

Physical processes that are responsible for the asymmetric transition processes between El Niño and La Niña events are investigated by using observational data and physical models to examine the nonlinear atmospheric response to SST. The air–sea coupled system of ENSO is able to remain in a weak, cold event for up to 2 yr, while the system of a relatively warm event turns into a cold phase. Through analysis of the oceanic observational data, it is found that there is a strong difference in thermocline variations in relation to surface zonal wind anomalies in the equatorial Pacific (EP) during the mature-to-decaying phase of ENSO. The atmospheric response for the warm phase of ENSO causes a rapid reduction of the EP westerlies in boreal winter, which play a role in hastening the following ENSO transition through the generation of upwelling oceanic Kelvin waves. However, the anomalous EP easterlies in the cold phase persist to the subsequent spring, which tends to counteract the turnabout from the cold to warm phase of ENSO.

A suite of idealized atmospheric general circulation model (AGCM) experiments are performed by imposing two different ENSO-related SST anomalies, which have equal amplitudes but opposite signs. The nonlinear climate response in the AGCM is found at the mature-to-decaying phase of ENSO that closely resembles the observations, including a zonal and meridional shift in the equatorial positions of the atmospheric wind. By using a simple ocean model, it is determined that the asymmetric responses of the equatorial zonal wind result in different recovery times of the thermocline in the eastern Pacific. Thus, the differences in transition processes between the warm and cold ENSO event are fundamentally due to the nonlinear atmospheric response to SST, which originates from the distribution of climatological SST and its seasonal changes. By including the asymmetric wind responses the intermediate air–sea coupled model herein demonstrates that the essential elements of the redevelopment of La Niña arise from the nonlinear atmospheric response to SST anomalies.

Corresponding author address: Masamichi Ohba, Terrestrial Environment Research Center, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan. Email: ooba@suiri.tsukuba.ac.jp

Save