Multi-modal excitation to model the Quasi-Biennial Oscillation

TL;DR

This paper investigates the Quasi-Biennial Oscillation by applying a realistic multi-modal wave spectrum, revealing that a broad frequency range of wave energy results in more regular oscillations and that different spectra can produce similar QBO patterns.

Contribution

It introduces the use of a continuous wave spectrum for modeling the QBO, showing that multi-modal forcing is crucial for realistic wave-mean flow interaction simulations.

Findings

Broader wave spectra lead to more regular QBO oscillations.

Different forcing spectra can produce similar QBO behavior.

Multi-modal forcing is essential for realistic modeling of the QBO.

Abstract

The Quasi-Biennial Oscillation (QBO) of stratospheric winds is the most striking example of mean-flow generation and reversal by the non-linear interactions of internal waves. Previous studies have used an idealized monochromatic forcing to investigate the QBO. Here we instead force a more realistic continuous wave spectrum. Unexpectedly, spreading the wave energy across a wide frequency range leads to more regular oscillations. We also find that different forcing spectra can yield the same QBO. Multi-modal wave forcing is thus essential for understanding wave/mean-flow interactions in nature.