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| Titel |
A single parameter representation of hygroscopic growth and cloud condensation nucleus activity |
| VerfasserIn |
M. D. Petters, S. M. Kreidenweis |
| 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. 8 ; Nr. 7, no. 8 (2007-04-18), S.1961-1971 |
| Datensatznummer |
250004910
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| Publikation (Nr.) |
 copernicus.org/acp-7-1961-2007.pdf |
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| Zusammenfassung |
| We present a method to describe the relationship between particle dry
diameter and cloud condensation nuclei (CCN) activity using a single
hygroscopicity parameter κ. Values of the hygroscopicity parameter are between
0.5 and 1.4 for highly-CCN-active salts such as sodium chloride, between
0.01 and 0.5 for slightly to very hygroscopic organic species, and 0 for
nonhygroscopic components. Observations indicate that atmospheric
particulate matter is typically characterized by 0.1<κ<0.9. If
compositional data are available and if the hygroscopicity parameter of each
component is known, a multicomponent hygroscopicity parameter can be
computed by weighting component hygroscopicity parameters by their volume
fractions in the mixture. In the absence of information on chemical
composition, experimental data for complex, multicomponent particles can be
fitted to obtain the hygroscopicity parameter. The hygroscopicity parameter
can thus also be used to conveniently model the CCN activity of atmospheric
particles, including those containing insoluble components. We confirm the
applicability of the hygroscopicity parameter and its mixing
rule by applying it to published hygroscopic diameter growth factor and
CCN-activation data for single- and multi-component particles containing
varying amounts of inorganic, organic and surface active compounds. We
suggest that κ may be fit to CCN data assuming σs/a=0.072 J m−2 and
present a table of κ derived for this value and T=298.15 K. The predicted
hygroscopicities for mixtures that contain the surfactant fulvic acid agree
within uncertainties with the measured values. It thus appears that this
approach is adequate for predicting CCN activity of mixed particles
containing surface active materials, but the generality of this assumption
requires further verification. |
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