# Periodicity disruption of a model quasi-biennial oscillation

## TL;DR

This paper investigates how wave-mean flow interactions in stratified fluids can cause disruptions in the regular periodicity of the quasi-biennial oscillation, revealing new bifurcations and routes to chaos through simplified models.

## Contribution

It demonstrates that intrinsic wave-mean flow dynamics can lead to QBO disruptions, identifying new bifurcations and complex behaviors in simplified models of the phenomenon.

## Key findings

- Identification of new bifurcations leading to faster flow reversals
- Discovery of quasiperiodic routes to chaos in QBO models
- Demonstration of the resilience of wind reversals to external perturbations

## Abstract

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.