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| Titel |
Complex refractive indices of Saharan dust samples at visible and near UV wavelengths: a laboratory study |
| VerfasserIn |
R. Wagner, T. Ajtai, K. Kandler, K. Lieke, C. Linke, T. Müller, M. Schnaiter, M. Vragel |
| 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. 5 ; Nr. 12, no. 5 (2012-03-05), S.2491-2512 |
| Datensatznummer |
250010858
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| Publikation (Nr.) |
 copernicus.org/acp-12-2491-2012.pdf |
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| Zusammenfassung |
| We have retrieved the wavelength-dependent imaginary parts of the complex
refractive index for five different Saharan dust aerosol particles of
variable mineralogical composition at wavelengths between 305 and 955 nm.
The dust particles were generated by dispersing soil samples into a
laboratory aerosol chamber, typically yielding particle sizes with mean
diameters ranging from 0.3 to 0.4 μm and maximum diameters from
2 to 4 μm. The extinction and absorption coefficients as well as the number
size distribution of the dust particles were simultaneously measured by
various established techniques. An inversion scheme based on a spheroidal
dust model was employed to deduce the refractive indices. The retrieved
imaginary parts of the complex refractive index were in the range from 0.003
to 0.005, 0.005 to 0.011, and 0.016 to 0.050 at the wavelengths 955, 505,
and 305 nm. The hematite content of the dust particles was determined by
electron-microscopical single particle analysis. Hematite volume fractions
in the range from 1.1 to 2.7% were found for the different dusts, a range
typical for atmospheric mineral dust. We have performed a sensitivity study
to assess how accurately the retrieved imaginary refractive indices could be
reproduced by calculations with mixing rule approximations using the
experimentally determined hematite contents as input. |
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