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Modulation of equatorial Pacific westerly/easterly wind events by the Madden–Julian oscillation and convectively-coupled Rossby waves

Abstract

Synoptic wind events in the equatorial Pacific strongly influence the El Niño/Southern Oscillation (ENSO) evolution. This paper characterizes the spatio-temporal distribution of Easterly (EWEs) and Westerly Wind Events (WWEs) and quantifies their relationship with intraseasonal and interannual large-scale climate variability. We unambiguously demonstrate that the Madden–Julian Oscillation (MJO) and Convectively-coupled Rossby Waves (CRW) modulate both WWEs and EWEs occurrence probability. 86 % of WWEs occur within convective MJO and/or CRW phases and 83 % of EWEs occur within the suppressed phase of MJO and/or CRW. 41 % of WWEs and 26 % of EWEs are in particular associated with the combined occurrence of a CRW/MJO, far more than what would be expected from a random distribution (3 %). Wind events embedded within MJO phases also have a stronger impact on the ocean, due to a tendency to have a larger amplitude, zonal extent and longer duration. These findings are robust irrespective of the wind events and MJO/CRW detection methods. While WWEs and EWEs behave rather symmetrically with respect to MJO/CRW activity, the impact of ENSO on wind events is asymmetrical. The WWEs occurrence probability indeed increases when the warm pool is displaced eastward during El Niño events, an increase that can partly be related to interannual modulation of the MJO/CRW activity in the western Pacific. On the other hand, the EWEs modulation by ENSO is less robust, and strongly depends on the wind event detection method. The consequences of these results for ENSO predictability are discussed.

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Acknowledgments

We acknowledge fruitful discussions with Andy Chiodi and Ed Harrison. This work was partially funded by the Agence Nationale pour la Recherche ANR-10-Blanc-616 METRO project. We also thank the reviewers for their comments that helped clarifying this manuscript. Martin Puy is funded by a Ministère de l’Enseignement Supérieur et de la Recherche (MESR) PhD grant. Jérôme Vialard and Matthieu Lengaigne are funded by Institut de Recherche pour le Développement (IRD). Eric Guilyardi is funded by the Centre National de la Recherche Scientifique (CNRS, France) and by the National Centre for Atmospheric Science (UK).

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Correspondence to Martin Puy.

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Puy, M., Vialard, J., Lengaigne, M. et al. Modulation of equatorial Pacific westerly/easterly wind events by the Madden–Julian oscillation and convectively-coupled Rossby waves. Clim Dyn 46, 2155–2178 (2016). https://doi.org/10.1007/s00382-015-2695-x

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  • DOI: https://doi.org/10.1007/s00382-015-2695-x

Keywords

  • Westerly wind events
  • Easterly wind events
  • ENSO
  • Madden–Julian Oscillation
  • Convectively-coupled Rossby waves