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| Titel |
Aerosol activation and cloud processing in the global aerosol-climate model ECHAM5-HAM |
| VerfasserIn |
G. J. Roelofs, P. Stier, J. Feichter, E. Vignati, J. Wilson |
| 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 ; 6, no. 9 ; Nr. 6, no. 9 (2006-06-29), S.2389-2399 |
| Datensatznummer |
250003966
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| Publikation (Nr.) |
 copernicus.org/acp-6-2389-2006.pdf |
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| Zusammenfassung |
| A parameterization for cloud processing is presented that calculates
activation of aerosol particles to cloud drops, cloud drop size, and
pH-dependent aqueous phase sulfur chemistry. The parameterization is
implemented in the global aerosol-climate model ECHAM5-HAM. The cloud
processing parameterization uses updraft speed, temperature, and aerosol
size and chemical parameters simulated by ECHAM5-HAM to estimate the maximum
supersaturation at the cloud base, and subsequently the cloud drop number
concentration (CDNC) due to activation. In-cloud sulfate production occurs
through oxidation of dissolved SO2 by ozone and hydrogen peroxide. The
model simulates realistic distributions for annually averaged CDNC although
it is underestimated especially in remote marine regions. On average, CDNC
is dominated by cloud droplets growing on particles from the accumulation
mode, with smaller contributions from the Aitken and coarse modes. The
simulations indicate that in-cloud sulfate production is a potentially
important source of accumulation mode sized cloud condensation nuclei, due
to chemical growth of activated Aitken particles and to enhanced coalescence
of processed particles. The strength of this source depends on the
distribution of produced sulfate over the activated modes. This distribution
is affected by uncertainties in many parameters that play a direct role in
particle activation, such as the updraft velocity, the aerosol chemical
composition and the organic solubility, and the simulated CDNC is found to
be relatively sensitive to these uncertainties. |
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