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Multimodal Excitation to Model the Quasibiennial Oscillation
P Léard1, D Lecoanet2, M Le Bars1
1Aix Marseille Université, CNRS, Centrale Marseille, IRPHE, Marseille 13013, France.
Physical Review Letters
|December 18, 2020
Summary
Using a continuous wave spectrum for atmospheric modeling, scientists found that spreading wave energy creates more regular quasibiennial oscillations (QBO). This multimodal forcing is key to understanding natural wave-mean-flow interactions.
Area of Science:
- Atmospheric Science
- Geophysics
- Fluid Dynamics
Background:
- The quasibiennial oscillation (QBO) in stratospheric winds demonstrates mean-flow generation and reversal.
- This phenomenon is driven by nonlinear interactions of internal waves.
- Previous research often used simplified, monochromatic wave forcing.
Purpose of the Study:
- To investigate the impact of a continuous wave spectrum on QBO dynamics.
- To compare results from continuous wave forcing with idealized monochromatic forcing.
- To understand the role of multimodal wave forcing in wave-mean-flow interactions.
Main Methods:
- Simulating the QBO using a more realistic continuous wave spectrum instead of monochromatic forcing.
- Analyzing the regularity and characteristics of oscillations under different spectral forcings.
- Comparing outcomes from various forcing spectra to identify common QBO patterns.
Main Results:
- Spreading wave energy across a wide frequency range unexpectedly resulted in more regular QBO.
- Different continuous forcing spectra were found to produce identical QBO patterns.
- The study highlights the sensitivity of QBO to the spectral distribution of wave energy.
Conclusions:
- Continuous, multimodal wave forcing is crucial for accurately modeling the QBO.
- Understanding wave-mean-flow interactions in nature requires considering realistic, continuous wave spectra.
- The findings challenge previous assumptions based on idealized monochromatic forcing.
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