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| Titel |
Contribution of primary carbonaceous aerosol to cloud condensation nuclei: processes and uncertainties evaluated with a global aerosol microphysics model |
| VerfasserIn |
J. R. Pierce, K. Chen, P. J. Adams |
| 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. 20 ; Nr. 7, no. 20 (2007-10-19), S.5447-5466 |
| Datensatznummer |
250005237
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| Publikation (Nr.) |
 copernicus.org/acp-7-5447-2007.pdf |
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| Zusammenfassung |
| This paper explores the impacts of primary carbonaceous aerosol on cloud
condensation nuclei (CCN) concentrations in a global climate model with
size-resolved aerosol microphysics. Organic matter (OM) and elemental carbon
(EC) from two emissions inventories were incorporated into a preexisting
model with sulfate and sea-salt aerosol. The addition of primary carbonaceous
aerosol increased CCN(0.2%) concentrations by 65–90% in the globally
averaged surface layer depending on the carbonaceous emissions inventory
used. Sensitivity studies were performed to determine the relative
importance of organic solubility/hygroscopicity in predicting CCN.
In a sensitivity study where carbonaceous aerosol was assumed to be completely insoluble, concentrations
of CCN(0.2%) still increased by 40–50% globally over the no
carbonaceous simulation because primary carbonaceous emissions were able to
become CCN via condensation of sulfuric acid. This shows that approximately
half of the contribution of primary carbonaceous particles to CCN in our model
comes from the addition of new particles (seeding effect) and half from the contribution of
organic solute (solute effect). The solute effect
tends to dominate more in areas where there is less inorganic aerosol than
organic aerosol and the seeding effect tends to dominate in areas where there is
more inorganic aerosol than organic aerosol. It was found that an accurate
simulation of the number size distribution is necessary to predict the CCN
concentration but assuming an average chemical composition will generally
give a CCN concentration within a factor of 2. If a "typical" size
distribution is assumed for each species when calculating CCN, such as is
done in bulk aerosol models, the mean error relative to a simulation with
size resolved microphysics is on the order of 35%. Predicted values of
carbonaceous aerosol mass and aerosol number were compared to observations
and the model showed average errors of a factor of 3 for carbonaceous mass
and a factor of 4 for total aerosol number; however, errors in the accumulation
mode concentrations were found to be lower in comparisons with European and
marine observations.. The errors in CN and carbonaceous mass may be reduced by
improving the emission size distributions of both primary sulfate and
primary carbonaceous aerosol. |
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