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| Titel |
The influence of chemical composition and mixing state of Los Angeles urban aerosol on CCN number and cloud properties |
| VerfasserIn |
M. J. Cubison, B. Ervens, G. Feingold, K. S. Docherty, I. M. Ulbrich, L. Shields, K. Prather, S. Hering, J. L. Jimenez |
| 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. 18 ; Nr. 8, no. 18 (2008-09-26), S.5649-5667 |
| Datensatznummer |
250006391
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| Publikation (Nr.) |
 copernicus.org/acp-8-5649-2008.pdf |
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| Zusammenfassung |
| The relationship between cloud condensation nuclei (CCN) number and the
physical and chemical properties of the atmospheric aerosol distribution is
explored for a polluted urban data set from the Study of Organic Aerosols at
Riverside I (SOAR-1) campaign conducted at Riverside, California, USA during
summer 2005. The mixing state and, to a lesser degree, the average chemical
composition are shown to be important parameters in determining the
activation properties of those particles around the critical activation
diameters for atmospherically-realistic supersaturation values. Closure
between predictions and measurements of CCN number at several
supersaturations is attempted by modeling a number of aerosol chemical
composition and mixing state cases of increasing complexity. It is shown
that a realistic treatment of the state of mixing of the urban aerosol
distribution is critical in order to eliminate model bias. Fresh emissions
such as elemental carbon and small organic particles must be treated as
non-activating and explicitly accounted for in the model. The relative
number concentration of these particles compared to inorganics and
oxygenated organic compounds of limited hygroscopicity plays an important
role in determining the CCN number. Furthermore, expanding the different
composition/mixing state cases to predictions of cloud droplet number
concentration in a cloud parcel model highlights the dependence of cloud
optical properties on the state of mixing and hygroscopic properties of the
different aerosol modes, but shows that the relative differences between the
different cases are reduced compared to those from the CCN model. |
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