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| Titel |
Efficiency of cloud condensation nuclei formation from ultrafine particles |
| VerfasserIn |
J. R. Pierce, 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. 5 ; Nr. 7, no. 5 (2007-02-27), S.1367-1379 |
| Datensatznummer |
250004749
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| Publikation (Nr.) |
 copernicus.org/acp-7-1367-2007.pdf |
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| Zusammenfassung |
| Atmospheric cloud condensation nuclei (CCN) concentrations are a key
uncertainty in the assessment of the effect of anthropogenic aerosol on
clouds and climate. The ability of new ultrafine particles to grow to become
CCN varies throughout the atmosphere and must be understood in order to
understand CCN formation. We have developed the Probability of Ultrafine
particle Growth (PUG) model to answer questions regarding which growth and
sink mechanisms control this growth, how the growth varies between different
parts of the atmosphere and how uncertainties with respect to the magnitude
and size distribution of ultrafine emissions translates into uncertainty in
CCN generation. The inputs to the PUG model are the concentrations of
condensable gases, the size distribution of ambient aerosol, particle deposition
timescales and physical properties of the particles and condensable gases.
It was found in most cases that condensation is the dominant
growth mechanism and coagulation with larger particles is the dominant sink
mechanism for ultrafine particles. In this work we found that the
probability of a new ultrafine particle generating a CCN varies from
<0.1% to ~90% in different parts of the atmosphere, though in the
boundary layer a large fraction of ultrafine particles have a probability
between 1% and 40%. Some regions, such as the tropical free
troposphere, are areas with high probabilities; however, variability within
regions makes it difficult to predict which regions of the atmosphere are
most efficient for generating CCN from ultrafine particles. For a given mass
of primary ultrafine aerosol, an uncertainty of a factor of two in the modal
diameter can lead to an uncertainty in the number of CCN generated as high
as a factor for eight. It was found that no single moment of the primary
aerosol size distribution, such as total mass or number, is a robust
predictor of the number of CCN ultimately generated. Therefore, a complete
description of the emissions size distribution is generally required for global
aerosol microphysics models. |
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