Diagnosing the angular momentum fluxes that drive the quasi-biennial oscillation
Date
2023
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Abstract
The quasi-biennial oscillation (QBO) is a descending pattern of alternating easterly and westerly equatorial stratospheric winds that is produced by the upward transport of momentum in multiple types of atmospheric waves. The discovery of the QBO and its role in the global circulation are discussed. The angular momentum budget of the QBO is analyzed using ERA-Interim isentropic analyses. We explain the benefits of isentropic coordinates and angular momentum as tools for analyzing atmospheric motion. We diagnose vertical motion utilizing continuity, allowing direct computation of the angular momentum fluxes due to vertical motion. The angular momentum fluxes due to unresolved convectively generated gravity waves are computed as a residual. These results are discussed with the goal of improving the representation of sub-grid scale motions in numerical models. We also discuss these results within the context of the reliability of reanalysis datasets and the downsides to treating reanalysis data as observations. We also revisit and discuss the seasonal dependence of the QBO transition.
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Subject
quasi-biennial oscillation
stratosphere
reanalysis
gravity waves