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| Titel |
Temporal and vertical variations of aerosol physical and chemical properties over West Africa: AMMA aircraft campaign in summer 2006 |
| VerfasserIn |
A. Matsuki, B. Quennehen, A. Schwarzenboeck, S. Crumeyrolle, H. Venzac, P. Laj, L. Gomes |
| 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 ; 10, no. 17 ; Nr. 10, no. 17 (2010-09-07), S.8437-8451 |
| Datensatznummer |
250008758
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| Publikation (Nr.) |
 copernicus.org/acp-10-8437-2010.pdf |
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| Zusammenfassung |
While the Sahelian belt in West Africa stretches in the border between the
global hot-spots of mineral dust and biomass burning aerosols, the presence
of West African Monsoon is expected to create significant vertical and
temporal variations in the regional aerosol properties through transport and
mixing of particles from various sources (mineral dust, biomass burning,
sulfates, sea salt). In order to improve our understanding of the evolution
of the aerosol-cloud system over such region across the onset of the summer
monsoon, the French ATR-42 research aircraft was deployed in Niamey, Niger
(13°30' N, 02°05' E) in summer 2006, during the three special
observation periods (SOPs) of the African Monsoon Multidisciplinary Analysis
(AMMA) project. These three SOPs covered both dry and wet periods before and
after the onset of the Western African Monsoon.
State of the art physico-chemical aerosol measurements on the ATR-42 showed
a notable seasonal transition in averaged number size distributions where
(i) the Aitken mode is dominating over the accumulation mode during the dry
season preceding the monsoon arrival and (ii) the accumulation mode
increasingly gained importance after the onset of the West African monsoon
and even dominated the Aitken mode after the monsoon had fully developed.
The parameters for the mean log-normal distributions observed in respective
layers characterized by the different wind regimes (monsoon layer, SAL, free
troposphere) are presented, together with the major particle compositions
found in the accumulation mode particles. Thereby, results of this study
should facilitate radiative transfer calculations, validation of satellite
remote sensors, and detailed transport modeling by partners within and
outside the AMMA community.
Extended analysis of the chemical composition of single aerosol particles by
a transmission electron microscope (TEM) coupled to an energy dispersive
X-ray spectrometer (EDX) revealed dominance of mineral dust
(aluminosilicate) even in the submicron particle size range during the dry
period, gradually replaced by prevailing biomass burning and sulfate
particles, after the onset of the monsoon period. The spatial and temporal
evolution from SOP1 to SOP2a1 and SOP2a2 of the particle physical and
chemical properties and associated aerosol hygroscopic properties are
remarkably consistent. |
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