• Alexander, M. A., 1992: Midlatitude atmosphere–ocean interaction during El Niño. Part I: The North Pacific Ocean. J. Climate, 5, 944958, https://doi.org/10.1175/1520-0442(1992)005<0944:MAIDEN>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Alexander, M. A., D. J. Vimont, P. Chang, and J. D. Scott, 2010: The impact of extratropical atmospheric variability on ENSO: Testing the seasonal footprinting mechanism using coupled model experiments. J. Climate, 23, 28852901, https://doi.org/10.1175/2010JCLI3205.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Amaya, D. J., 2019: The Pacific meridional mode and ENSO: A review. Curr. Climate Change Rep., 5, 296307, https://doi.org/10.1007/s40641-019-00142-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, B. T., 2003: Tropical Pacific sea-surface temperatures and preceding sea-level pressure anomalies in the subtropical North Pacific. J. Geophys. Res., 108, 4732, https://doi.org/10.1029/2003JD003805.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, B. T., 2004: Investigation of a large-scale mode of ocean-atmosphere variability and its relation to tropical Pacific sea surface temperature anomalies. J. Climate, 17, 40894098, https://doi.org/10.1175/1520-0442(2004)017<4089:IOALMO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, B. T., 2007: Intraseasonal atmospheric variability in the extratropics and its relation to the onset of tropical Pacific sea surface temperature anomalies. J. Climate, 20, 926936, https://doi.org/10.1175/JCLI4036.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, B. T., and E. Maloney, 2006: Interannual tropical Pacific sea surface temperatures and their relation to preceding sea level pressures in the NCAR CCSM2. J. Climate, 19, 9981012, https://doi.org/10.1175/JCLI3674.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, B. T., and R. C. Perez, 2015: ENSO and non-ENSO induced charging and discharging of the equatorial Pacific. Climate Dyn., 45, 23092327, https://doi.org/10.1007/s00382-015-2472-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, B. T., E. Maloney, R. Perez, and A. Karspeck, 2013: Triggering of El Niño onset through the trade wind induced charging of the equatorial Pacific. Geophys. Res. Lett., 40, 12121216, https://doi.org/10.1002/grl.50200.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Anderson, B. T., P. Hassanzadeh, and R. Caballero, 2017: Persistent anomalies of the extratropical Northern Hemisphere wintertime circulation as an initiator of El Niño/Southern Oscillation events. Sci. Rep., 7, 10145, https://doi.org/10.1038/s41598-017-09580-9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Barnston, A. G., M. K. Tippett, M. L. L’Heureux, S. Li, and D. G. DeWitt, 2012: Skill of real-time seasonal ENSO model predictions during 2002–11: Is our capability increasing? Bull. Amer. Meteor. Soc., 93, 631651, https://doi.org/10.1175/BAMS-D-11-00111.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bjerknes, J., 1969: Atmospheric teleconnections from the equatorial Pacific. Mon. Wea. Rev., 97, 163172, https://doi.org/10.1175/1520-0493(1969)097<0163:ATFTEP>2.3.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Bretherton, C. S., C. Smith, and J. M. Wallace, 1992: An intercomparison of methods for finding coupled patterns in climate data. J. Climate, 5, 541560, https://doi.org/10.1175/1520-0442(1992)005<0541:AIOMFF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Carton, J. A., and B. S. Giese, 2008: A reanalysis of ocean climate using Simple Ocean Data Assimilation (SODA). Mon. Wea. Rev., 136, 29993017, https://doi.org/10.1175/2007MWR1978.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chakravorty, S., J. S. Chowdary, and C. Gnanaseelan, 2013: Spring asymmetric mode in the tropical Indian Ocean: Role of El Niño and IOD. Climate Dyn., 40, 14671481, https://doi.org/10.1007/s00382-012-1340-1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chakravorty, S., C. Gnanaseelan, and P. A. Pillai, 2016: Combined influence of remote and local SST forcing on Indian summer monsoon rainfall variability. Climate Dyn., 47, 28172831, https://doi.org/10.1007/s00382-016-2999-5.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chang, P., L. Zhang, R. Saravanan, D. J. Vimont, J. C. H. Chiang, L. Ji, H. Seidel, and M. K. Tippett, 2007: Pacific meridional mode and El Niño–Southern Oscillation. Geophys. Res. Lett., 34, L16608, https://doi.org/10.1029/2007GL030302.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chen, Z., B. Gan, L. Wu, and F. Jia, 2018: Pacific–North American teleconnection and North Pacific Oscillation: Historical simulation and future projection in CMIP5 models. Climate Dyn., 50, 43794403, https://doi.org/10.1007/s00382-017-3881-9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Chiang, J. C. H., and D. J. Vimont, 2004: Analogous Pacific and Atlantic meridional modes of tropical atmosphere–ocean variability. J. Climate, 17, 41434158, https://doi.org/10.1175/JCLI4953.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Clarke, A. J., S. V. Gorder, and G. Colantuono, 2007: Wind stress curl and ENSO discharge/recharge in the equatorial Pacific. J. Phys. Oceanogr., 37, 10771091, https://doi.org/10.1175/JPO3035.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Danabasoglu, G., S. C. Bates, B. P. Briegleb, S. R. Jayne, M. Jochum, W. G. Large, S. Peacock, and S. G. Yeager, 2012: The CCSM4 ocean component. J. Climate, 25, 13611389, https://doi.org/10.1175/JCLI-D-11-00091.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • DiNezio, P. N., C. Deser, Y. Okumura, and A. Karspeck, 2017: Predictability of 2-year La Niña events in a coupled general circulation model. Climate Dyn., 49, 42374261, https://doi.org/10.1007/s00382-017-3575-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Fedorov, A. V., S. Hu, M. Lengaigne, and E. Guilyardi, 2015: The impact of westerly wind bursts and ocean initial state on the development, and diversity of El Niño events. Climate Dyn., 44, 13811401, https://doi.org/10.1007/s00382-014-2126-4.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Gettelman, A., and et al. , 2010: Global simulations of ice nucleation and ice supersaturation with an improved cloud scheme in the Community Atmosphere Model. J. Geophys. Res., 115, D18216, https://doi.org/10.1029/2009JD013797.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Giese, B. S., and S. Ray, 2011: El Niño variability in Simple Ocean Data Assimilation (SODA), 1871–2008. J. Geophys. Res., 116, C02024, https://doi.org/10.1029/2010JC006695.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Giese, B. S., H. F. Seidel, G. P. Compo, and P. D. Sardeshmukh, 2016: An ensemble of ocean reanalyses for 1815–2013 with sparse observational input. J. Geophys. Res. Oceans, 121, 68916910, https://doi.org/10.1002/2016JC012079.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Graham, N. E., J. Michaelsen, and T. P. Barnett, 1987: An investigation of the El Niño–Southern Oscillation cycle with statistical models: 1. Predictor field characteristics. J. Geophys. Res., 92, 14 25114 270, https://doi.org/10.1029/JC092iC13p14251.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Guilyardi, E., P. Braconnot, F.-F. Jin, S. T. Kim, M. Kolasinski, T. Li, and I. Musat, 2009: Atmosphere feedbacks during ENSO in a coupled GCM with a modified atmospheric convection scheme. J. Climate, 22, 56985718, https://doi.org/10.1175/2009JCLI2815.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hu, S., and A. V. Fedorov, 2016: Exceptionally strong easterly wind burst stalling El Niño of 2014. Proc. Natl. Acad. Sci. USA, 113, 20052010, https://doi.org/10.1073/pnas.1514182113.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hu, S., and A. V. Fedorov, 2017: The extreme El Niño of 2015–2016: The role of westerly and easterly wind bursts, and preconditioning by the failed 2014 event. Climate Dyn., 52, 73397357, https://doi.org/10.1007/s00382-017-3531-2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Hurrell, J. W., and et al. , 2013: The Community Earth System Model: A framework for collaborative research. Bull. Amer. Meteor. Soc., 94, 13391360, https://doi.org/10.1175/BAMS-D-12-00121.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Izumo, T., M. Lengaigne, J. Vialard, I. Suresh, and Y. Planton, 2018: On the physical interpretation of the lead relation between warm water volume and the El Niño Southern Oscillation. Climate Dyn., 52, 29232942, https://doi.org/10.1007/s00382-018-4313-1.

    • Crossref
    • 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, https://doi.org/10.1175/1520-0469(1997)054<0811:AEORPF>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Large, W. G., and S. G. Yeager, 2009: The global climatology of an interannually varying air–sea flux data set. Climate Dyn., 33, 341364, https://doi.org/10.1007/s00382-008-0441-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larson, S., and B. Kirtman, 2013: The Pacific meridional mode as a trigger for ENSO in a high-resolution coupled model. Geophys. Res. Lett., 40, 31893194, https://doi.org/10.1002/grl.50571.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larson, S., and B. Kirtman, 2014: The Pacific meridional mode as an ENSO precursor and predictor in the North American multimodel ensemble. J. Climate, 27, 70187032, https://doi.org/10.1175/JCLI-D-14-00055.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larson, S., and B. P. Kirtman, 2015: Revisiting ENSO coupled instability theory and SST error growth in a fully coupled model. J. Climate, 28, 47244742, https://doi.org/10.1175/JCLI-D-14-00731.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larson, S., and B. P. Kirtman, 2017: Drivers of coupled model ENSO error dynamics and the spring predictability barrier. Climate Dyn., 48, 36313644, https://doi.org/10.1007/s00382-016-3290-5.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larson, S., and B. P. Kirtman, 2019: Linking preconditioning to extreme ENSO events and reduced ensemble spread. Climate Dyn., 52, 74177433, https://doi.org/10.1007/s00382-017-3791-x.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larson, S., K. V. Pegion, and B. P. Kirtman, 2018a: The South Pacific meridional mode as a thermally driven source of ENSO amplitude modulation and uncertainty. J. Climate, 31, 51275145, https://doi.org/10.1175/JCLI-D-17-0722.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Larson, S., D. J. Vimont, A. C. Clement, and B. P. Kirtman, 2018b: How momentum coupling affects SST variance and large-scale Pacific climate variability in CESM. J. Climate, 31, 29272944, https://doi.org/10.1175/JCLI-D-17-0645.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Lau, N.-C., and M. J. Nath, 1996: The role of the atmospheric bridge in linking tropical Pacific ENSO events to extratropical SST anomalies. J. Climate, 9, 20362057, https://doi.org/10.1175/1520-0442(1996)009<2036:TROTBI>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Levine, A. F. Z., and M. J. McPhaden, 2016: How the July 2014 easterly wind burst gave the 2015–2016 El Niño a head start. Geophys. Res. Lett., 43, 65036510, https://doi.org/10.1002/2016GL069204.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Li, T., 1997: Phase transition of the El Niño–Southern Oscillation: A stationary SST mode. J. Atmos. Sci., 54, 28722887, https://doi.org/10.1175/1520-0469(1997)054<2872:PTOTEN>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Linkin, M. E., and S. Nigam, 2008: The North Pacific Oscillation–west Pacific teleconnection pattern: Mature-phase structure and winter impacts. J. Climate, 21, 19791997, https://doi.org/10.1175/2007JCLI2048.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Liu, Z., and S. Xie, 1994: Equatorward propagation of coupled air–sea disturbances with application to the annual cycle of the eastern tropical Pacific. J. Atmos. Sci., 51, 38073822, https://doi.org/10.1175/1520-0469(1994)051<3807:EPOCAD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McPhaden, M. J., and et al. , 1998: The Tropical Ocean–Global Atmosphere observing system: A decade of progress. J. Geophys. Res., 103, 14 16914 240, https://doi.org/10.1029/97JC02906.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • McPhaden, M. J., S. E. Zebiak, and M. H. Glantz, 2006: ENSO as an integrating concept in Earth science. Science, 314, 17401745, https://doi.org/10.1126/science.1132588.

    • Crossref
    • 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, https://doi.org/10.1175/1520-0442(2000)013<3551:OOWWVC>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Min, Q., J. Su, R. Zhang, and X. Rong, 2015: What hindered the El Niño pattern in 2014? Geophys. Res. Lett., 42, 67626770, https://doi.org/10.1002/2015GL064899.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Neale, R. B., and et al. , 2012: Description of the NCAR Community Atmosphere Model (CAM 5.0). NCAR Tech. Note NCAR/TN-486+STR, 274 pp., www.cesm.ucar.edu/models/cesm1.0/cam/docs/description/cam5_desc.pdf.

  • Philander, S. G., 1983: El Niño Southern Oscillation phenomena. Nature, 302, 295301, https://doi.org/10.1038/302295a0.

  • Philander, S. G., 1990: El Niño and La Niña, and the Southern Oscillation. Academic Press, 289 pp.

  • Pierce, D., T. Barnett, and M. Latif, 2000: Connections between the Pacific Ocean tropics and midlatitudes on decadal timescales. J. Climate, 13, 11731194, https://doi.org/10.1175/1520-0442(2000)013%3C1173:CBTPOT%3E2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Puy, M., and et al. , 2017: Influence of westerly wind events stochasticity on El Niño amplitude: The case of 2014 vs. 2015. Climate Dyn., 52, 74357454, https://doi.org/10.1007/s00382-017-3938-9.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rasmusson, E. M., and T. H. Carpenter, 1982: Variations in tropical sea surface temperature and surface wind fields associated with the Southern Oscillation/El Niño. Mon. Wea. Rev., 110, 354384, https://doi.org/10.1175/1520-0493(1982)110<0354:VITSST>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Ray, S., and B. S. Giese, 2012: Historical changes in El Niño and La Niña characteristics in an ocean reanalysis. J. Geophys. Res., 117, C11007, https://doi.org/10.1029/2012JC008031.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Rogers, J. C., 1981: The North Pacific Oscillation. J. Climatol., 1, 3957, https://doi.org/10.1002/joc.3370010106.

  • Smith, R. D., and et al. , 2010: The Parallel Ocean Program (POP) reference manual: Ocean component of the Community Climate System Model (CCSM) and Community Earth System Model (CESM). Los Alamos National Laboratory Tech. Rep. LAUR-10-01853, 141 pp., http://www.cesm.ucar.edu/models/cesm1.0/pop2/doc/sci/POPRefManual.pdf.

  • Thomas, E. E., and D. J. Vimont, 2016: Modeling the mechanisms of linear and nonlinear ENSO responses to the Pacific meridional mode. J. Climate, 29, 87458761, https://doi.org/10.1175/JCLI-D-16-0090.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Tippett, M. K., A. G. Barnston, and S. Li, 2012: Performance of recent multimodel ENSO forecasts. J. Appl. Meteor. Climatol., 51, 637654, https://doi.org/10.1175/JAMC-D-11-093.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Trenberth, K. E., 1997: The definition of El Niño. Bull. Amer. Meteor. Soc., 78, 27712777, https://doi.org/10.1175/1520-0477(1997)078<2771:TDOENO>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vimont, D. J., 2010: Transient growth of thermodynamically coupled variations in the tropics under an equatorially symmetric mean state. J. Climate, 23, 57715789, https://doi.org/10.1175/2010JCLI3532.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vimont, D. J., D. S. Battisti, and A. C. Hirst, 2001: Footprinting: A seasonal connection between the tropics and mid-latitudes. Geophys. Res. Lett., 28, 39233926, https://doi.org/10.1029/2001GL013435.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vimont, D. J., D. S. Battisti, and A. C. Hirst, 2003a: The seasonal footprinting mechanism in the CSIRO general circulation models. J. Climate, 16, 26532667, https://doi.org/10.1175/1520-0442(2003)016<2653:TSFMIT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vimont, D. J., J. M. Wallace, and D. S. Battisti, 2003b: The seasonal footprinting mechanism in the Pacific: Implications for ENSO. J. Climate, 16, 26682675, https://doi.org/10.1175/1520-0442(2003)016<2668:TSFMIT>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Vimont, D. J., M. Alexander, and A. Fontaine, 2009: Midlatitude excitation of tropical variability in the Pacific: The role of thermodynamic coupling and seasonality. J. Climate, 22, 518534, https://doi.org/10.1175/2008JCLI2220.1.

    • Crossref
    • 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, https://doi.org/10.1175/1520-0442(2000)013<1517:PEATHD>2.0.CO;2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wang, F., 2010: Thermodynamic coupled modes in the tropical atmosphere–ocean: An analytical solution. J. Atmos. Sci., 67, 16671677, https://doi.org/10.1175/2009JAS3262.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wen, C., A. Kumar, Y. Xue, and M. J. McPhaden, 2014: Changes in tropical Pacific thermocline depth and their relationship to ENSO after 1999. J. Climate, 27, 72307249, https://doi.org/10.1175/JCLI-D-13-00518.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wieners, C. E., H. A. Dijkstra, and W. P. M. de Ruijter, 2019: The interaction between the western Indian Ocean and ENSO in CESM. Climate Dyn., 52, 51535172, https://doi.org/10.1007/s00382-018-4438-2.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Wyrtki, K., 1985: Water displacements in the Pacific and the genesis of El Niño cycle. J. Geophys. Res., 90, 71297132, https://doi.org/10.1029/JC090iC04p07129.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Xie, S.-P., and S. G. H. Philander, 1994: A coupled ocean–atmosphere model of relevance to the ITCZ in the eastern Pacific. Tellus, 46A, 340350, https://doi.org/10.3402/tellusa.v46i4.15484.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yeh, S.-W., J.-S. Kug, and S.-I. An, 2014: Recent progresses on two types of El Niño: Observations, dynamics, and future changes. Asia-Pac. J. Atmos. Sci., 50, 6981, https://doi.org/10.1007/S13143-014-0028-3.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • You, Y., and J. C. Furtado, 2017: The role of South Pacific atmospheric variability in the development of different types of ENSO. Geophys. Res. Lett., 44, 74387446, https://doi.org/10.1002/2017GL073475.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Yuan, X., 2004: ENSO-related impacts on Antarctic sea ice: A synthesis of phenomenon and mechanisms. Antarct. Sci., 16, 415425, https://doi.org/10.1017/S0954102004002238.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhang, T., X. Shao, and S. Li, 2017: Impacts of atmospheric processes on ENSO asymmetry: A comparison between CESM1 and CCSM4. J. Climate, 30, 97439762, https://doi.org/10.1175/JCLI-D-17-0360.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
  • Zhou, Z.-Q., S.-P. Xie, X.-T. Zheng, Q. Liu, and H. Wang, 2014: Global warming–induced changes in El Niño teleconnections over the North Pacific and North America. J. Climate, 27, 90509064, https://doi.org/10.1175/JCLI-D-14-00254.1.

    • Crossref
    • Search Google Scholar
    • Export Citation
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Testing the Trade Wind Charging Mechanism and Its Influence on ENSO Variability

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  • 1 Cooperative Institute of Marine and Atmospheric Studies, University of Miami, Miami, Florida
  • | 2 NOAA Atlantic Oceanographic and Meteorological Laboratory, Miami, Florida
  • | 3 Department of Earth and Environment, Boston University, Boston, Massachusetts
  • | 4 Department of Oceanography, Texas A&M University, College Station, Texas
  • | 5 Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, North Carolina
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Abstract

During the positive phase of the North Pacific Oscillation, westerly wind anomalies over the subtropical North Pacific substantially increase subsurface heat content along the equator by “trade wind charging” (TWC). TWC provides a direct pathway between extratropical atmospheric circulation and El Niño–Southern Oscillation (ENSO) initiation. Previous model studies of this mechanism lacked the ocean–atmospheric coupling needed for ENSO growth, so it is crucial to examine whether TWC-induced heat content anomalies develop into ENSO events in a coupled model. Here, coupled model experiments, forced with TWC favorable (+TWC) or unfavorable (−TWC) wind stress, are used to examine the ENSO response to TWC. The forcing is imposed on the ocean component of the model through the first winter and then the model evolves in a fully coupled configuration through the following winter. The +TWC (−TWC) forcing consistently charges (discharges) the equatorial Pacific in spring and generates positive (negative) subsurface temperature anomalies. These subsurface temperature anomalies advect eastward and upward along the equatorial thermocline and emerge as like-signed sea surface temperature (SST) anomalies in the eastern Pacific, creating favorable conditions upon which coupled air–sea feedback can act. During the fully coupled stage, warm SST anomalies in +TWC forced simulations are amplified by coupled feedbacks and lead to El Niño events. However, while −TWC forcing results in cool SST anomalies, pre-existing warm SST anomalies in the far eastern equatorial Pacific persist and induce local westerly wind anomalies that prevent consistent development of La Niña conditions. While the TWC mechanism provides adequate equatorial heat content to fuel ENSO development, other factors also play a role in determining whether an ENSO event develops.

Corresponding author: Soumi Chakravorty, soumi.chakravorty@noaa.gov

Abstract

During the positive phase of the North Pacific Oscillation, westerly wind anomalies over the subtropical North Pacific substantially increase subsurface heat content along the equator by “trade wind charging” (TWC). TWC provides a direct pathway between extratropical atmospheric circulation and El Niño–Southern Oscillation (ENSO) initiation. Previous model studies of this mechanism lacked the ocean–atmospheric coupling needed for ENSO growth, so it is crucial to examine whether TWC-induced heat content anomalies develop into ENSO events in a coupled model. Here, coupled model experiments, forced with TWC favorable (+TWC) or unfavorable (−TWC) wind stress, are used to examine the ENSO response to TWC. The forcing is imposed on the ocean component of the model through the first winter and then the model evolves in a fully coupled configuration through the following winter. The +TWC (−TWC) forcing consistently charges (discharges) the equatorial Pacific in spring and generates positive (negative) subsurface temperature anomalies. These subsurface temperature anomalies advect eastward and upward along the equatorial thermocline and emerge as like-signed sea surface temperature (SST) anomalies in the eastern Pacific, creating favorable conditions upon which coupled air–sea feedback can act. During the fully coupled stage, warm SST anomalies in +TWC forced simulations are amplified by coupled feedbacks and lead to El Niño events. However, while −TWC forcing results in cool SST anomalies, pre-existing warm SST anomalies in the far eastern equatorial Pacific persist and induce local westerly wind anomalies that prevent consistent development of La Niña conditions. While the TWC mechanism provides adequate equatorial heat content to fuel ENSO development, other factors also play a role in determining whether an ENSO event develops.

Corresponding author: Soumi Chakravorty, soumi.chakravorty@noaa.gov
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