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| Titel |
On realistic size equivalence and shape of spheroidal Saharan mineral dust particles applied in solar and thermal radiative transfer calculations |
| VerfasserIn |
S. Otto, T. Trautmann, M. Wendisch |
| 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. 9 ; Nr. 11, no. 9 (2011-05-12), S.4469-4490 |
| Datensatznummer |
250009714
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| Publikation (Nr.) |
 copernicus.org/acp-11-4469-2011.pdf |
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| Zusammenfassung |
| Realistic size equivalence and shape of Saharan mineral dust particles are
derived from in-situ particle, lidar and sun photometer measurements
during SAMUM-1 in Morocco (19 May 2006), dealing with measured size- and
altitude-resolved axis ratio distributions of assumed spheroidal model
particles. The data were applied in optical property, radiative effect,
forcing and heating effect simulations to quantify
the realistic impact of particle non-sphericity. It turned out that
volume-to-surface equivalent spheroids with prolate shape are most realistic:
particle non-sphericity only slightly affects single scattering albedo and
asymmetry parameter but may enhance extinction coefficient by up to 10 %.
At the bottom of the atmosphere (BOA) the Saharan mineral dust
always leads to a loss of solar radiation, while the sign of the forcing at
the top of the atmosphere (TOA) depends on surface albedo: solar
cooling/warming over a mean ocean/land surface. In the thermal spectral range
the dust inhibits the emission of radiation to space and warms the BOA. The most
realistic case of particle non-sphericity causes changes of total (solar plus thermal)
forcing by 55/5 % at the TOA over ocean/land and 15 % at the BOA over both land
and ocean and enhances total radiative heating within the dust plume by up to
20 %. Large dust particles significantly contribute to all the radiative
effects reported. They strongly enhance the absorbing properties and forward scattering
in the solar and increase predominantly, e.g., the total TOA forcing of the dust over land. |
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