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| Titel |
The impact of volcanic aerosol on the Northern Hemisphere stratospheric polar vortex: mechanisms and sensitivity to forcing structure |
| VerfasserIn |
M. Toohey, K. Krüger, M. Bittner, C. Timmreck, H. Schmidt |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 14, no. 23 ; Nr. 14, no. 23 (2014-12-09), S.13063-13079 |
| Datensatznummer |
250119225
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| Publikation (Nr.) |
 copernicus.org/acp-14-13063-2014.pdf |
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| Zusammenfassung |
| Observations and simple theoretical arguments suggest that the Northern
Hemisphere (NH) stratospheric polar vortex is stronger in winters following
major volcanic eruptions. However, recent studies show that climate models
forced by prescribed volcanic aerosol fields fail to reproduce this effect.
We investigate the impact of volcanic aerosol forcing on stratospheric
dynamics, including the strength of the NH polar vortex, in ensemble
simulations with the Max Planck Institute Earth System Model. The model is
forced by four different prescribed forcing sets representing the radiative
properties of stratospheric aerosol following the 1991 eruption of Mt. Pinatubo: two forcing sets are based on observations, and are commonly used
in climate model simulations, and two forcing sets are constructed based on
coupled aerosol–climate model simulations. For all forcings, we find that simulated
temperature and zonal wind anomalies in the NH high latitudes are not
directly impacted by anomalous volcanic aerosol heating. Instead, high-latitude effects result from enhancements in stratospheric residual
circulation, which in turn result, at least in part, from enhanced
stratospheric wave activity. High-latitude effects are therefore much less
robust than would be expected if they were the direct result of aerosol
heating. Both observation-based forcing sets result in insignificant changes
in vortex strength. For the model-based forcing sets, the vortex response is
found to be sensitive to the structure of the forcing, with one forcing set
leading to significant strengthening of the polar vortex in rough agreement
with observation-based expectations. Differences in the dynamical response
to the forcing sets imply that reproducing the polar vortex responses to
past eruptions, or predicting the response to future eruptions, depends on
accurate representation of the space–time structure of the volcanic aerosol
forcing. |
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