Periodicity disruption of a model quasi-biennial oscillation

Antoine Renaud (1) , Louis-Philippe Nadeau (2) , Antoine Venaille (1)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 ISMER - Institut des Sciences de la MER de Rimouski

The quasi-biennial oscillation (QBO) of equatorial winds on Earth is the clearest example of the spontaneous emergence of a periodic phenomenon in geophysical fluids.In recent years, observations have revealed intriguing disruptions of this regular behaviour, and different QBO-like regimes have been reported in a variety of systems. Here we show that part of the variability in mean flow reversals can be attributed to the intrinsic dynamics of wave-mean flow interactions in stratified fluids. Using a constant-in-time monochromatic wave forcing, bifurcation diagrams are mapped for a hierarchy of simplified models of the QBO, ranging from a quasilinear model to fully nonlinear simulations. The existence of new bifurcations associated with faster and shallower flow reversals, as well as a quasiperiodic route to chaos are reported in these models. The possibility for periodicity disruptions is investigated by probing the resilience of regular wind reversals to external perturbations.

Domaines: Physique Générale [physics.gen-ph]; Géophysique [physics.geo-ph]; Planétologie et astrophysique de la terre [astro-ph.EP]; Dynamique Chaotique [nlin.CD]

Antoine Renaud, Louis-Philippe Nadeau, Antoine Venaille. Periodicity disruption of a model quasi-biennial oscillation. 2019. ⟨hal-01982926⟩