• Adler, R. F., and Coauthors, 2003: The version 2 Global Precipitation Climatology Project (GPCP) monthly precipitation analysis (1979–present). J. Hydrometeor., 4, 11471167.

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

  • Ashok, K., , Z. Guan, , and T. Yamagata, 2003: Influence of the Indian Ocean dipole on the Australian winter rainfall. Geophys. Res. Lett., 30, 1821, doi:10.1029/2003GL017926.

    • Search Google Scholar
    • Export Citation
  • Black, E., , J. Slingo, , and K. R. Sperber, 2003: An observational study of the relationship between excessively strong short rains in coastal East Africa and Indian Ocean SST. Mon. Wea. Rev., 131, 7494.

    • Search Google Scholar
    • Export Citation
  • Bonjean, F., , and G. S. E. Lagerloef, 2002: Diagnostic model and analysis of the surface currents in the tropical Pacific Ocean. J. Phys. Oceanogr., 32, 29382954.

    • Search Google Scholar
    • Export Citation
  • Bosc, C., , T. Delcroix, , and C. Maes, 2009: Barrier layer variability in the western Pacific warm pool from 2000 to 2007. J. Geophys. Res., 114, C06023, doi:10.1029/2008JC005187.

    • Search Google Scholar
    • Export Citation
  • Cai, W., , H. H. Hendon, , and G. A. Meyers, 2005: Indian Ocean dipolelike variability in the CSIRO Mark 3 coupled climate model. J. Climate, 18, 14491468.

    • Search Google Scholar
    • Export Citation
  • Cai, W., , T. Cowan, , and M. Raupach, 2009a: Positive Indian Ocean dipole events precondition southeast Australia bushfires. Geophys. Res. Lett., 36, L19710, doi:10.1029/2009GL039902.

    • Search Google Scholar
    • Export Citation
  • Cai, W., , T. Cowan, , and A. Sullivan, 2009b: Recent unprecedented skewness towards positive Indian Ocean dipole occurrences and its impact on Australian rainfall. Geophys. Res. Lett., 36, L11705, doi:10.1029/2009GL037604.

    • Search Google Scholar
    • Export Citation
  • Cai, W., , A. Pan, , D. Roemmich, , T. Cowan, , and X. Guo, 2009c: Argo profiles a rare occurrence of three consecutive positive Indian Ocean dipole events, 2006–2008. Geophys. Res. Lett., 36, L08701, doi:10.1029/2008GL037038.

    • Search Google Scholar
    • Export Citation
  • Cai, W., , P. van Rensch, , T. Cowan, , and H. H. Hendon, 2011: Teleconnection pathways of ENSO and the IOD and the mechanisms for impacts on Australian rainfall. J. Climate, 24, 39103923.

    • Search Google Scholar
    • Export Citation
  • Cai, W., , P. van Rensch, , T. Cowan, , and H. H. Hendon, 2012: An asymmetry in the IOD and ENSO teleconnection pathway and its impact on Australian climate. J. Climate, 25, 63186329.

    • Search Google Scholar
    • Export Citation
  • Hong, C.-C., , and T. Li, 2010: Independence of SST skewness from thermocline feedback in the eastern equatorial Indian Ocean. Geophys. Res. Lett., 37, L11702, doi:10.1029/2010GL043380.

    • Search Google Scholar
    • Export Citation
  • Hong, C.-C., , T. Li, , H. Lin, , and J. S. Kug, 2008: Asymmetry of the Indian Ocean dipole. Part I: Observational analysis. J. Climate, 21, 48344848.

    • 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
  • Huffman, G. J., and Coauthors, 2007: The TRMM Multisatellite Precipitation Analysis (TMPA): Quasi-global, multiyear, combined-sensor precipitation estimates at fine scale. J. Hydrometeor., 8, 3855.

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

    • Search Google Scholar
    • Export Citation
  • Lareef, Z., , S. A. Rao, , and T. Yamagata, 2003: Modulation of Sri Lankan Maha rainfall by the Indian Ocean dipole. Geophys. Res. Lett., 30, 1063, doi:10.1029/2002GL015639.

    • Search Google Scholar
    • Export Citation
  • Li, T., , T. F. Hogan, , and C. P. Chang, 2000: Dynamic and thermodynamic regulation of ocean warming. J. Atmos. Sci., 57, 33533365.

  • Li, T., , B. Wang, , C.-P. Chang, , and Y. Zhang, 2003: A theory for the Indian Ocean dipole zonal mode. J. Atmos. Sci., 60, 21192135.

  • Liu, W. T., , X. Xie, , P. S. Polito, , S. P. Xie, , and H. Hashizume, 2000: Atmospheric manifestation of tropical instability waves observed by QuikSCAT and tropical rain measuring mission. Geophys. Res. Lett., 27, 25452548.

    • Search Google Scholar
    • Export Citation
  • Lukas, R., , and E. Lindstrom, 1991: The mixed-layer of the western equatorial Pacific Ocean. J. Geophys. Res., 96, 33433357.

  • Luo, J.-J., , S. Behera, , Y. Masumoto, , H. Sakuma, , and T. Yamagata, 2008: Successful prediction of the consecutive IOD in 2006 and 2007. Geophys. Res. Lett., 35, L14S02, doi:10.1029/2007GL032793.

    • Search Google Scholar
    • Export Citation
  • Masson, S., , J.-P. Boulanger, , C. Menkes, , P. Delecluse, , and T. Yamagata, 2004: Impact of salinity on the 1997 Indian Ocean dipole event in a numerical experiment. J. Geophys. Res., 109, C02002, doi:10.1029/2003JC001807.

    • Search Google Scholar
    • Export Citation
  • Ogata, T., , S.-P. Xie, , J. Lan, , and X. Zheng, 2013: Importance of ocean dynamics for the skewness of the Indian Ocean dipole mode. J. Climate, 26, 21452159.

    • Search Google Scholar
    • Export Citation
  • Oliver, M. A., , and R. Webster, 1990: Kriging: A method of interpolation for geographical information system. Int. J. Geogr. Inform. Syst., 4, 313332, doi:10.1080/02693799008941549.

    • Search Google Scholar
    • Export Citation
  • Qiu, Y., , W. Cai, , L. Li, , and X. Guo, 2012: Argo profiles variability of barrier layer in the tropical Indian Ocean and its relationship with the Indian Ocean dipole. Geophys. Res. Lett., 39, L08605, doi:10.1029/2012GL051441.

    • Search Google Scholar
    • Export Citation
  • Ramanathan, V., , and W. Collins, 1991: Thermodynamic regulation of ocean warming by cirrus clouds deduced from observations of the 1987 El Niño. Nature, 351, 2732.

    • Search Google Scholar
    • Export Citation
  • Roemmich, D., , and J. Gilson, 2009: The 2004–2008 mean and annual cycle of temperature, salinity and steric height in the global ocean from Argo Program. Prog. Oceanogr., 82, 81100, doi:10.1016/j.pocean.2009.03.004.

    • Search Google Scholar
    • Export Citation
  • Saji, N. H., , B. N. Goswami, , P. N. Vinayachandran, , and T. Yamagata, 1999: A dipole mode in the tropical Indian Ocean. Nature, 401, 360363.

    • Search Google Scholar
    • Export Citation
  • Ummenhofer, C. C., , M. H. England, , P. C. McIntosh, , G. A. Meyers, , M. J. Pook, , J. S. Risbey, , A. S. Gupta, , and A. S. Taschetto, 2009: What causes southeast Australia’s worst droughts? Geophys. Res. Lett., 36, L04706, doi:10.1029/2008GL036801.

    • Search Google Scholar
    • Export Citation
  • Wyrtki, K., 1971: Oceanographic Atlas of the International Indian Ocean Expedition. National Science Foundation, 531 pp.

  • Yu, L. S., , and R. A. Weller, 2007: Objectively analyzed air–sea heat fluxes for the global ice-free ocean (1981–2005). Bull. Amer. Meteor. Soc., 88, 527539.

    • Search Google Scholar
    • Export Citation
  • Zheng, X. T., , S. P. Xie, , G. A. Vecchi, , Q. Liu, , and J. Hafner, 2010: Indian Ocean dipole response to global warming: Analysis of ocean–atmospheric feedbacks in a coupled model. J. Climate, 23, 12401253.

    • Search Google Scholar
    • Export Citation
All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 34 34 5
PDF Downloads 19 19 3

An Observation-Based Assessment of Nonlinear Feedback Processes Associated with the Indian Ocean Dipole

View More View Less
  • 1 CSIRO Wealth from Oceans Flagship, CSIRO Water for a Healthy Country Flagship, and CSIRO Marine and Atmospheric Research, Aspendale, Victoria, Australia
  • | 2 Third Institute of Oceanography, State Oceanic Administration, Xiamen, China
© Get Permissions
Restricted access

Abstract

A well-known feature of the Indian Ocean dipole (IOD) is its positive skewness, with cold sea surface temperature (SST) anomalies over the east pole (IODE) exhibiting a larger amplitude than warm SST anomalies. Several mechanisms have been proposed for this asymmetry, but because of a lack of observations the role of various processes remains contentious. Using Argo profiles and other newly available data, the authors provide an observation-based assessment of the IOD skewness. First, the role of a nonlinear dynamical heating process is reaffirmed, which reinforces IODE cold anomalies but damps IODE warm anomalies. This reinforcing effect is greater than the damping effect, further contributing to the skewness. Second, the existence of a thermocline–temperature feedback asymmetry, whereby IODE cold anomalies induced by a shoaling thermocline are greater than warm anomalies associated with a deepening thermocline, is the primary forcing of the IOD skewness. This thermocline–temperature feedback asymmetry is a part of the nonlinear Bjerknes-like positive feedback loop involving winds, SST, and the thermocline, all displaying a consistent asymmetry with a stronger response when IODE SST is anomalously cold. The asymmetry is enhanced by a nonlinear barrier layer response, with a greater thinning associated with IODE cold anomalies than a thickening associated with IODE warm anomalies. Finally, in response to IODE cool anomalies, rainfall and evaporative heat loss diminish and incoming shortwave radiation increases, which results in damping the cool SST anomalies. The damping increases with IODE cold anomalies. Thus, the IOD skewness is generated in spite of a greater damping effect of the SST–cloud–radiation feedback process.

Corresponding author address: W. Cai, CSIRO Marine and Atmospheric Research, PMB1, Aspendale, VIC 3195, Australia. E-mail: wenju.cai@csiro.au

Abstract

A well-known feature of the Indian Ocean dipole (IOD) is its positive skewness, with cold sea surface temperature (SST) anomalies over the east pole (IODE) exhibiting a larger amplitude than warm SST anomalies. Several mechanisms have been proposed for this asymmetry, but because of a lack of observations the role of various processes remains contentious. Using Argo profiles and other newly available data, the authors provide an observation-based assessment of the IOD skewness. First, the role of a nonlinear dynamical heating process is reaffirmed, which reinforces IODE cold anomalies but damps IODE warm anomalies. This reinforcing effect is greater than the damping effect, further contributing to the skewness. Second, the existence of a thermocline–temperature feedback asymmetry, whereby IODE cold anomalies induced by a shoaling thermocline are greater than warm anomalies associated with a deepening thermocline, is the primary forcing of the IOD skewness. This thermocline–temperature feedback asymmetry is a part of the nonlinear Bjerknes-like positive feedback loop involving winds, SST, and the thermocline, all displaying a consistent asymmetry with a stronger response when IODE SST is anomalously cold. The asymmetry is enhanced by a nonlinear barrier layer response, with a greater thinning associated with IODE cold anomalies than a thickening associated with IODE warm anomalies. Finally, in response to IODE cool anomalies, rainfall and evaporative heat loss diminish and incoming shortwave radiation increases, which results in damping the cool SST anomalies. The damping increases with IODE cold anomalies. Thus, the IOD skewness is generated in spite of a greater damping effect of the SST–cloud–radiation feedback process.

Corresponding author address: W. Cai, CSIRO Marine and Atmospheric Research, PMB1, Aspendale, VIC 3195, Australia. E-mail: wenju.cai@csiro.au
Save