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| Titel |
Mixing of dust and NH3 observed globally over anthropogenic dust sources |
| VerfasserIn |
P. Ginoux, L. Clarisse, C. Clerbaux, P.-F. Coheur, O. Dubovik, N. C. Hsu, M. Damme |
| 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 ; 12, no. 16 ; Nr. 12, no. 16 (2012-08-16), S.7351-7363 |
| Datensatznummer |
250011388
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| Publikation (Nr.) |
 copernicus.org/acp-12-7351-2012.pdf |
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| Zusammenfassung |
| The global distribution of dust column burden derived from MODIS Deep Blue
aerosol products is compared to NH3 column burden retrieved from IASI
infrared spectra. We found similarities in their spatial distributions, in
particular their hot spots are often collocated over croplands and to a
lesser extent pastures. Globally, we found 22% of dust burden
collocated with NH3, with only 1% difference between land-use
databases. This confirms the importance of anthropogenic dust from
agriculture. Regionally, the Indian subcontinent has the highest amount of
dust mixed with NH3 (26%), mostly over cropland and during the
pre-monsoon season. North Africa represents 50% of total dust burden but
accounts for only 4% of mixed dust, which is found over croplands and
pastures in Sahel and the coastal region of the Mediterranean. In order to
evaluate the radiative effect of this mixing on dust optical properties, we
derive the mass extinction efficiency for various mixtures of dust and
NH3, using AERONET sunphotometers data. We found that for dusty days
the coarse mode mass extinction efficiency decreases from 0.62 to
0.48 m2 g−1 as NH3 burden increases from 0 to 40 mg m−2.
The fine mode extinction efficiency, ranging from 4 to 16 m2 g−1,
does not appear to depend on NH3 concentration or relative humidity but
rather on mineralogical composition and mixing with other aerosols. Our
results imply that a significant amount of dust is already mixed with
ammonium salt before its long range transport. This in turn will affect dust
lifetime, and its interactions with radiation and cloud properties. |
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