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| Titel |
What controls the recent changes in African mineral dust aerosol across the Atlantic? |
| VerfasserIn |
D. A. Ridley, C. L. Heald, J. M. Prospero |
| 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. 11 ; Nr. 14, no. 11 (2014-06-10), S.5735-5747 |
| Datensatznummer |
250118783
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| Publikation (Nr.) |
 copernicus.org/acp-14-5735-2014.pdf |
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| Zusammenfassung |
| Dust from Africa strongly perturbs the radiative balance over the Atlantic,
with emissions that are highly variable from year to year. We show that the
aerosol optical depth (AOD) of dust over the mid-Atlantic observed by the
AVHRR satellite has decreased by approximately 10% per decade from
1982 to 2008. This downward trend persists through both winter and summer close
to source and is also observed in dust surface concentration measurements
downwind in Barbados during summer. The GEOS-Chem model, driven with MERRA
re-analysis meteorology and using a new dust source activation scheme,
reproduces the observed trend and is used to quantify the factors
contributing to this trend and the observed variability from 1982 to 2008. We
find that changes in dustiness over the east mid-Atlantic are almost entirely
mediated by a reduction in surface winds over dust source regions in Africa
and are not directly linked with changes in land use or vegetation cover. The
global mean all-sky direct radiative effect (DRE) of African dust is
−0.18 Wm−2 at top of atmosphere, accounting for 46% of the
global dust total, with a regional DRE of −7.4 ± 1.5 Wm−2 at
the surface of the mid-Atlantic, varying by over 6.0 Wm−2 from year to
year, with a trend of +1.3 Wm−2 per decade. These large interannual
changes and the downward trend highlight the importance of climate feedbacks
on natural aerosol abundance. Our analysis of the CMIP5 models suggests that
the decreases in the indirect anthropogenic aerosol forcing over the North
Atlantic in recent decades may be responsible for the observed
climate response in African dust, indicating a potential amplification of
anthropogenic aerosol radiative impacts in the Atlantic via natural mineral
dust aerosol. |
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