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| Titel |
Dimming over the Oceans: Transient Anthropogenic Aerosol Plumes in the 20th Century |
| VerfasserIn |
Tanja Dallafior, Doris Folini, Reto Knutti, Martin Wild |
| 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 |
250108881
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| Publikation (Nr.) |
 EGU/EGU2015-8717.pdf |
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| Zusammenfassung |
| Anthropogenic aerosols reduce incoming surface solar radiation (SSR), but the magnitude of
this effect for reducing sea surface temperature (SST) is still debated. Using simulations from
the global climate model ECHAM5 with the Hamburg Aerosol Module (HAM) and
prescribed SSTs, we quantify anthropogenic aerosol dimming over sea surfaces by
comparing ensembles, which only differ in anthropogenic aerosol emissions. We isolate
the anthropogenic aerosol effect on SSR with sufficiently large ensemble sizes to
provide statistically significant results. The following simulation results are obtained:
Dimming plumes extend from their source regions with clear seasonality. The latter is
predominantly shaped by atmospheric circulation, while interdecadal changes follow the
gradual increase in anthropogenic aerosol emissions. Comparing the 1990s with
the 1870s, on average, 9.4% (clearsky SSR) or 15.4% (allsky SSR) of the entire
ocean surface was affected by anthropogenic aerosol dimming larger than -4 W m-2
(annual mean). Comparing the same time periods, global average anthropogenic
dimming over oceans is -2.3 W m-2and -3.4 W m-2 for clearsky and allsky SSR,
respectively. Surface dimming is hemispherically asymmetrical with stronger Northern
Hemispheric dimming by 2.3 W m-2 and 4.5 W m-2 for clearsky and allsky SSR,
respectively. Zonal average clearsky dimming reaches its maximum (5.5 W m-2 ) near the
Equator. Allsky dimming peaks at 40Ë N (-8 W m-2 ) and is regionally larger
than clearsky dimming. Regionally, surface dimming can go beyond -20 W m-2
(clearsky) and -40 W m-2 (allsky). Results are a contribution towards better quantifying
spatially heterogeneous and time-dependent anthropogenic dimming effects on SSTs. |
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