EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Periodicity disruption of a model quasi-biennial oscillation of equatorial winds

Antoine Renaud1,2, Louis-Philippe Nadeau3, and Antoine Venaille1
Antoine Renaud et al.
  • 1ENS de Lyon CNRS, Laboratoire de Physique, Lyon, France (
  • 2School of Mathematics and Maxwell Institute for Mathematical Sciences, University of Edinburgh, King's Buildings, Edinburgh EH9 3FD, United Kingdom
  • 3Institut des Sciences de la Mer de Rimouski, Université du Québec à Rimouski. Rimouski, Québec, Canada

In the Earth's atmosphere, fast propagating equatorial waves generate slow reversals of the large scale stratospheric winds with a  period of about 28 months. This quasi-biennial oscillation is a spectacular manifestation of wave-mean flow interactions in stratified fluids, with analogues in other planetary atmospheres and laboratory experiments. Recent observations of a disruption of this periodic behavior have been attributed to external perturbations, but the mechanism explaining the disrupted response has remained elusive. We show the existence of secondary bifurcations and a quasiperiodic route to chaos in simplified models of the equatorial atmosphere ranging from the classical Holton-Lindzen-Plumb model to fully nonlinear simulations of stratified fluids. Perturbations of the slow oscillations are widely amplified in the proximity of the secondary bifurcation point. This suggests that intrinsic dynamics may be equally influential as external variability in explaining disruptions of regular wind reversals  [1].

[1] Renaud, A., Nadeau, L. P., & Venaille, A. (2019). Periodicity Disruption of a Model Quasibiennial Oscillation of Equatorial Winds. Physical Review Letters, 122(21), 214504.

How to cite: Renaud, A., Nadeau, L.-P., and Venaille, A.: Periodicity disruption of a model quasi-biennial oscillation of equatorial winds, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9362,, 2020