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| Titel |
Scavenging of black carbon in mixed phase clouds at the high alpine site Jungfraujoch |
| VerfasserIn |
J. Cozic, B. Verheggen, S. Mertes, P. Connolly, K. Bower, A. Petzold, U. Baltensperger, E. Weingärtner |
| 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 ; 7, no. 7 ; Nr. 7, no. 7 (2007-04-11), S.1797-1807 |
| Datensatznummer |
250004881
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| Publikation (Nr.) |
 copernicus.org/acp-7-1797-2007.pdf |
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| Zusammenfassung |
| The scavenging of black carbon (BC) in liquid and mixed phase clouds was
investigated during intensive experiments in winter 2004, summer 2004 and
winter 2005 at the high alpine research station Jungfraujoch (3580 m a.s.l.,
Switzerland). Aerosol residuals were sampled behind two well characterized
inlets; a total inlet which collected cloud particles (droplets and ice
particles) as well as interstitial (unactivated) aerosol particles; an
interstitial inlet which collected only interstitial aerosol particles. BC
concentrations were measured behind each of these inlets along with the
submicrometer aerosol number size distribution, from which a volume
concentration was derived. These measurements were complemented by in-situ
measurements of cloud microphysical parameters. BC was found to be scavenged
into the condensed phase to the same extent as the bulk aerosol, which
suggests that BC was covered with soluble material through aging processes,
rendering it more hygroscopic. The scavenged fraction of BC
(FScav,BC), defined as the fraction of BC that is incorporated into
cloud droplets and ice crystals, decreases with increasing cloud ice mass
fraction (IMF) from FScav,BC=60% in liquid phase clouds to
FScav,BC~5–10% in mixed-phase clouds with IMF>0.2. This
can be explained by the evaporation of liquid droplets in the presence of
ice crystals (Wegener-Bergeron-Findeisen process), releasing BC containing
cloud condensation nuclei back into the interstitial phase. In liquid
clouds, the scavenged BC fraction is found to decrease with decreasing cloud
liquid water content. The scavenged BC fraction is also found to decrease
with increasing BC mass concentration since there is an increased
competition for the available water vapour. |
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