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| Titel |
A sensitivity study on the effects of particle chemistry, asphericity and size on the mass extinction efficiency of mineral dust in the earth's atmosphere: from the near to thermal IR |
| VerfasserIn |
R. A. Jr. Hansell, J. S. Reid, S. C. Tsay, T. L. Roush, O. V. Kalashnikova |
| 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 ; 11, no. 4 ; Nr. 11, no. 4 (2011-02-17), S.1527-1547 |
| Datensatznummer |
250009362
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| Publikation (Nr.) |
 copernicus.org/acp-11-1527-2011.pdf |
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| Zusammenfassung |
| To determine a plausible range of mass extinction efficiencies (MEE) of
terrestrial atmospheric dust from the near to thermal IR, sensitivity
analyses are performed over an extended range of dust microphysical and
chemistry perturbations. The IR values are subsequently compared to those in
the near-IR, to evaluate spectral relationships in their optical properties.
Synthesized size distributions consistent with measurements, model particle
size, while composition is defined by the refractive indices of minerals
routinely observed in dust, including the widely used OPAC/Hess
parameterization. Single-scattering properties of representative dust
particle shapes are calculated using the T-matrix, Discrete Dipole
Approximation and Lorenz-Mie light-scattering codes. For the
parameterizations examined, MEE ranges from nearly zero to 1.2 m2 g−1, with the higher values associated with non-spheres composed of
quartz and gypsum. At near-IR wavelengths, MEE for non-spheres generally
exceeds those for spheres, while in the thermal IR, shape-induced changes in
MEE strongly depend on volume median diameter (VMD) and wavelength,
particularly for MEE evaluated at the mineral resonant frequencies. MEE
spectral distributions appear to follow particle geometry and are evidence
for shape dependency in the optical properties. It is also shown that
non-spheres best reproduce the positions of prominent absorption peaks found
in silicates. Generally, angular particles exhibit wider and more symmetric
MEE spectral distribution patterns from 8–10 μm than those with smooth
surfaces, likely due to their edge-effects. Lastly, MEE ratios allow for
inferring dust optical properties across the visible-IR spectrum. We
conclude the MEE of dust aerosol are significant for the parameter space
investigated, and are a key component for remote sensing applications and
the study of direct aerosol radiative effects. |
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