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| Titel |
A coupled observation – modeling approach for studying activation kinetics from measurements of CCN activity |
| VerfasserIn |
T. Raatikainen, R. H. Moore, T. L. Lathem, A. Nenes |
| 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 ; 12, no. 9 ; Nr. 12, no. 9 (2012-05-11), S.4227-4243 |
| Datensatznummer |
250011131
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| Publikation (Nr.) |
 copernicus.org/acp-12-4227-2012.pdf |
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| Zusammenfassung |
| This paper presents an approach to study droplet activation kinetics from
measurements of CCN activity by the Continuous Flow Streamwise Thermal
Gradient CCN Chamber (CFSTGC) and a comprehensive model of the instrument and
droplet growth. The model, which can be downloaded from
http://nenes.eas.gatech.edu/Experiments/CFSTGC.html
, is evaluated against a series of experiments with
ammonium sulfate calibration aerosol. Observed and modeled droplet
sizes are in excellent agreement for a water vapor uptake coefficient
~0.2, which is consistent with theoretical expectations. The model
calculations can be considerably accelerated without significant loss of
accuracy by assuming simplified instrument geometry and constant parabolic
flow velocity profiles. With these assumptions, the model can be applied to
large experimental data sets to infer kinetic growth parameters while fully
accounting for water vapor depletion effects and changes in instrument
operation parameters such as the column temperature, flow rates, sheath and
sample flow relative humidities, and pressure. When the effects of instrument
operation parameters, water vapor depletion and equilibrium dry particle
properties on droplet size are accounted for, the remaining variations in
droplet size are most likely due to non-equilibrium processes such as those
caused by organic surface films, slow solute dissociation and glassy or
highly viscous particle states. As an example of model application, data
collected during a research flight in the ARCTAS 2008 campaign are analyzed.
The model shows that water vapor depletion effects can explain changes in the
observed average droplet size. |
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