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| Titel |
Quantifying the effect of aerosols on the Southern Annular Mode: do aerosols tip the balance? |
| VerfasserIn |
Hamish Steptoe, Laura J. Wilcox, Ellie J. Highwood |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101296
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| Publikation (Nr.) |
 EGU/EGU2015-2055.pdf |
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| Zusammenfassung |
| Global increases in greenhouse gasses (GHGs) and the recovery of stratospheric ozone (sO3)
are known to have opposing effects on the position of the Southern Hemisphere (SH) jet
stream. These two forcings are the principal drivers of atmospheric variability in this
hemisphere, particularly in the Austral summer. To date, GHG and sO3 forcings have driven a
poleward jet shift, but in recent decades the recovery of sO3 is expected to counteract this
poleward trend. Recently, mechanisms have been proposed by which primarily Northern
Hemisphere aerosol may also affect SH circulation. In light of the opposing trends of GHGs
and sO3, the influence of anthropogenic aerosols (AAs) is expected to become more
important.
Using the Southern Annular Mode (SAM) as a diagnostic of SH atmospheric
variability across high and low frequency time scales, we use ensemble empirical mode
decomposition (EEMD) to extract non-linear non-stationary trends from a subset
of CMIP5 models under a range of historical forcings. We quantify the influence
and statistical significance of historical AA, GHG and all forcing trends on the
SAM over the last c.150 years. We present detailed trend analysis of single forcings
experiments, discuss individual model trends in the context of the wider implications of
accurately accounting for aerosol processes in climate models, and examine the
implications of assuming a linear paradigm for combined single forcings. We conclude by
assessing the capability of AAs in tipping the balance between a GHG-sO3 jet-shift
stalemate. |
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