Do regions outside the tropical Pacific influence ENSO through atmospheric teleconnections?
- 572 Downloads
This paper aims at identifying oceanic regions outside the tropical Pacific, which may influence the El Niño Southern Oscillation (ENSO) through interannual modulation of equatorial Pacific winds. An Atmospheric General Circulation Model (AGCM) 7-members ensemble experiment forced by climatological sea surface temperature (hereafter, SST) in the tropical Pacific Ocean and observed interannually varying SST elsewhere produces ensemble-mean equatorial zonal wind stress interannual anomalies (ZWSA) over the equatorial Pacific. These ZWSA are largest during boreal winter in the western Pacific, and induce a ~0.5 °C response in the central Pacific during the following spring in a simple ocean model, that weakly but significantly correlates with the following ENSO peak amplitude. When correlated with global SST, the residual western equatorial Pacific ZWSA yield SST patterns that are reminiscent of ENSO teleconnections in the Indian, North and South Pacific, and Atlantic Oceans. We further design 20-members ensemble sensitivity experiments forced by typical SST patterns of the main climate modes for each of these regions, in order to identify regions that influence equatorial Pacific ZWSA most. In our experiments, only the Indian Ocean Basin-wide SST warming in late boreal winter produces a statistically significant ZWSA in the western equatorial Pacific, resulting in a weak but significant ~0.35 °C SST response in the central Pacific (i.e. ~35 % of the observed standard deviation) during the following spring, the season when the Bjerkness coupled feedback is particularly efficient. This paper hence agrees with previous studies, which suggest that ENSO-induced basin-wide SST signals in the Indian Ocean may contribute to the phase transition of ENSO. Our results suggest that studies exploring external influences on ENSO should adopt a global approach rather than focus on a specific region. Designing coupled model simulations would also allow investigating air–sea interactions-mediated teleconnection mechanisms, which we can’t reproduce in our forced AGCM framework.
KeywordsEl Niño Southern Oscillation External forcing Atmospheric teleconnections Indian Ocean
Hugo Dayan is funded by a PhD grant of Ministère de l’Enseignement Supérieur et de la Recherche and by the Institut National des Sciences de l’Univers (INSU) LEFE program. Jérôme Vialard, Takeshi Izumo and Matthieu Lengaigne are funded by Institut de Recherche pour le Développement (IRD). Sébastien Masson is funded by the Conseil National des Astronomes et Physiciens (CNAP). GPCP data are provided by the NOAA/OAR/ESRL PSD.
- Alexander M, Vimont D (2010) The impact of extratropical atmospheric variability on ENSO: testing the seasonal footprinting mechanism using coupled model experiments. J Clim 2885–2901. doi: 10.1175/2010JCLI3205.1
- Federov AV, Brown JN (2009) Equatorial waves. In: Steele J (ed) Encyclopedia of ocean sciences, 2nd edn. Academic Press, New York, pp 3679–3695Google Scholar
- Fouquart Y, Bonnel B (1980) Computations of solar heating of the Earth’s atmosphere: a new parameterization. Beitr Phys Atm 53:35–62Google Scholar
- Glantz MH (2001) Currents of change: El Niño’s impact on climate and society. Cambridge University Press, CambridgeGoogle Scholar
- Niiler PP, Kraus EB (1977) One-dimensional models of the upper ocean. In: Kraus EB (ed) Modeling and prediction of the upper layers of the ocean. Pergamon Press, New York, pp 143–172Google Scholar
- Nordeng TE (1994) Extended versions of the convective parameterization scheme at ECMWF and their impact on the mean and transient activity of the model in the tropics. ECMWF Tech Memo 206, 41 ppGoogle Scholar
- Roeckner E et al (2003) The atmospheric general circulation model ECHAM5. Part I: model description. Max Planck Institute for Meteorology Rep. 349, 127 ppGoogle Scholar
- Roeckner E, Brokopf R, Esch M, Giorgetta M, Hagemann S, Kornblueh L, Manzini E, Schlese U, Schulzweida U (2004) The atmospheric general circulation model ECHAM 5. PART II: sensitivity of simulated climate to horizontal and vertical resolution. MPI Report No. 354, Max Planck Institute for Meteorology, HamburgGoogle Scholar
- Saji NH, Goswami BN, Viayachandran PN, Yamagata T (1999) A dipole mode in the tropical Indian Ocean. Nature 401:360–363Google Scholar
- Spencer H, Slingo JM, Davey MK (2004) Seasonal predictability of ENSO teleconnections: the role of the remote ocean response. Clim Dyn 22:511–526 Google Scholar
- Watanabe M, Jin F-F (2002) Role of Indian Ocean warming in the development of the Philippine Sea anticyclone during El Nino. Geophys Res Lett 29. doi: 10.1029/2001GL014318
- Zhang H, Clement A, Di Nezio P (2014) The South Pacific Meridional Mode: a mechanism for ENSO-like variability. J Clim 27:769–783. doi: 10.1175/JCLI-D-13-00082.1