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| Titel |
Formation and growth of nucleated particles into cloud condensation nuclei: model–measurement comparison |
| VerfasserIn |
D. M. Westervelt, J. R. Pierce, I. Riipinen, W. Trivitayanurak, A. Hamed, M. Kulmala  , A. Laaksonen, S. Decesari, 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 ; 13, no. 15 ; Nr. 13, no. 15 (2013-08-08), S.7645-7663 |
| Datensatznummer |
250085615
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| Publikation (Nr.) |
 copernicus.org/acp-13-7645-2013.pdf |
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| Zusammenfassung |
| Aerosol nucleation occurs frequently in the atmosphere and is an important
source of particle number. Observations suggest that nucleated particles are
capable of growing to sufficiently large sizes that they act as cloud
condensation nuclei (CCN), but some global models have reported that CCN
concentrations are only modestly sensitive to large changes in nucleation
rates. Here we present a novel approach for using long-term size distribution
observations to evaluate a global aerosol model's ability to predict
formation rates of CCN from nucleation and growth events. We derive from
observations at five locations nucleation-relevant metrics such as nucleation
rate of particles at diameter of 3 nm (J3), diameter growth rate (GR),
particle survival probability (SP), condensation and coagulation sinks, and
CCN formation rate (J100). These quantities are also derived for a
global microphysical model, GEOS-Chem-TOMAS, and compared to the observations
on a daily basis. Using GEOS-Chem-TOMAS, we simulate nucleation events
predicted by ternary (with a 10−5 tuning factor) or activation
nucleation over one year and find that the model slightly understates the
observed annual-average CCN formation mostly due to bias in the nucleation
rate predictions, but by no more than 50% in the ternary simulations. At
the two locations expected to be most impacted by large-scale regional
nucleation, Hyytiälä and San Pietro Capofiume, predicted
annual-average CCN formation rates are within 34 and 2% of the
observations, respectively. Model-predicted annual-average growth rates are
within 25% across all sites but also show a slight tendency to
underestimate the observations, at least in the ternary nucleation
simulations. On days that the growing nucleation mode reaches 100 nm, median
single-day survival probabilities to 100 nm for the model and measurements
range from less than 1–6% across the five locations we considered;
however, this does not include particles that may eventually grow to 100 nm
after the first day. This detailed exploration of new particle formation and
growth dynamics adds support to the use of global models as tools for
assessing the contribution of microphysical processes such as nucleation to
the total number and CCN budget. |
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