Multi-modal excitation to model the Quasi-Biennial Oscillation

P Léard (1) , D Lecoanet (2) , M. Le Bars (1)

1 IRPHE - Institut de Recherche sur les Phénomènes Hors Equilibre
2 Northwestern University [Evanston]

The quasibiennial oscillation (QBO) of stratospheric winds is the most striking example of mean-flow generation and reversal by the nonlinear 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. Multimodal wave forcing is thus essential for understanding wave–mean-flow interactions in nature.

Keywords: Astrophysical fluid dynamics; Atmospheric fluid dynamics; Stratified geophysical flows

Domains: Physics [physics]

P Léard, D Lecoanet, M. Le Bars. Multi-modal excitation to model the Quasi-Biennial Oscillation. Physical Review Letters, 2020, 125, pp.234501. ⟨10.1103/PhysRevLett.125.234501⟩. ⟨hal-03099186⟩