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| Titel |
Effects of aerosol organics on cloud condensation nucleus (CCN) concentration and first indirect aerosol effect |
| VerfasserIn |
J. Wang, Y.-N. Lee, P. H. Daum, J. Jayne, M. L. Alexander |
| 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 ; 8, no. 21 ; Nr. 8, no. 21 (2008-11-03), S.6325-6339 |
| Datensatznummer |
250006431
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| Publikation (Nr.) |
 copernicus.org/acp-8-6325-2008.pdf |
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| Zusammenfassung |
| Aerosol microphysics, chemical composition, and CCN properties were measured
on the Department of Energy Gulfstream-1 aircraft during the Marine
Stratus/Stratocumulus Experiment (MASE) conducted over the coastal waters
between Point Reyes National Seashore and Monterey Bay, California, in July
2005. Aerosols measured during MASE included free tropospheric aerosols,
marine boundary layer aerosols, and aerosols with high organic concentration
within a thin layer above the cloud. Closure analysis was carried out for
all three types of aerosols by comparing the measured CCN concentrations at
~0.2% supersaturation to those predicted based on size distribution
and chemical composition using Köhler theory. The effect of aerosol
organic species on predicted CCN concentration was examined using a single
hygroscopicity parameterization. For aerosols with organics volume fraction
up to 70%, such as the marine boundary layer and free troposphere
aerosols, CCN concentration and the corresponding first indirect aerosol
effect are insensitive to the properties of organics, and can be accurately
predicted with a constant hygroscopicity for all organic species. This
simplification can facilitate the prediction of indirect aerosol effects
using physically-based parameterizations in large scale models. However, for
the aerosols within the thin layers above clouds, organics contributed up to
90% of the total aerosol volume, and an accurate knowledge of the overall
organic hygroscopicity is required to accurately predict CCN concentrations.
Derivations of organic properties in future closure studies, when aerosols
are dominated by organic species, would help constrain the descriptions of
organics and aerosol-cloud parameterizations in large scale models. |
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