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On the magnitude and sensitivity of the quasi-biennial oscillation response to a tropical volcanic eruption

Brown, Flossie; Marshall, Lauren; Haynes, Peter H.; Garcia, Rolando R.; Birner, Thomas; Schmidt, Anja

On the magnitude and sensitivity of the quasi-biennial oscillation response to a tropical volcanic eruption Thumbnail


Authors

Flossie Brown

Peter H. Haynes

Rolando R. Garcia

Thomas Birner

Anja Schmidt



Abstract

Volcanic eruptions that inject sulfur dioxide into the stratosphere have the potential to alter large-scale circulation patterns, such as the quasi-biennial oscillation (QBO), which can affect weather and transport of chemical species. Here, we conduct simulations of tropical volcanic eruptions using the UM-UKCA aerosol-climate model with an explicit representation of the QBO. Eruptions emitting 60 Tg of SO2 (i.e. the magnitude of the 1815 Mt. Tambora eruption) and 15 Tg of SO2 (i.e. the magnitude of the 1991 Mt. Pinatubo eruption) were initiated at the Equator during two different QBO states. We show that tropical eruptions delay the progression of the QBO phases, with the magnitude of the delay dependent on the initial wind shear in the lower stratosphere and a much longer delay when the shear is easterly than when it is westerly. The QBO response in our model is driven by vertical advection of momentum by the stronger tropical upwelling caused by heating due to the increased volcanic sulfate aerosol loading. Direct aerosol-induced warming with subsequent thermal wind adjustment, as proposed by previous studies, is found to only play a secondary role. This interpretation of the response is supported by comparison with a simple dynamical model. The dependence of the magnitude of the response on the initial QBO state results from differences in the QBO secondary circulation. In the easterly shear zone of the QBO, the vertical component of the secondary circulation is upward and reinforces the anomalous upwelling driven by volcanic aerosol heating, whereas in the westerly shear zone the vertical component is downward and opposes the aerosol-induced upwelling. We also find a change in the latitudinal structure of the QBO, with the westerly phase of the QBO strengthening in the hemisphere with the lowest sulfate aerosol burden. Overall, our study suggests that tropical eruptions of Pinatubo magnitude or larger could force changes to the progression of the QBO, with particularly disruptive outcomes for the QBO if the eruption occurs during the easterly QBO shear.

Citation

Brown, F., Marshall, L., Haynes, P. H., Garcia, R. R., Birner, T., & Schmidt, A. (2023). On the magnitude and sensitivity of the quasi-biennial oscillation response to a tropical volcanic eruption. Atmospheric Chemistry and Physics, 23(9), 5335-5353. https://doi.org/10.5194/acp-23-5335-2023

Journal Article Type Article
Acceptance Date Apr 6, 2023
Online Publication Date May 12, 2023
Publication Date May 12, 2023
Deposit Date Oct 18, 2023
Publicly Available Date Oct 18, 2023
Journal Atmospheric Chemistry and Physics
Print ISSN 1680-7316
Electronic ISSN 1680-7324
Publisher European Geosciences Union
Peer Reviewed Peer Reviewed
Volume 23
Issue 9
Pages 5335-5353
DOI https://doi.org/10.5194/acp-23-5335-2023
Keywords Atmospheric Science
Public URL https://durham-repository.worktribe.com/output/1805931

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