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| Titel |
A new temperature- and humidity-dependent surface site density approach for deposition ice nucleation |
| VerfasserIn |
I. Steinke, C. Hoose, O. Möhler, P. Connolly, T. Leisner |
| 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 ; 15, no. 7 ; Nr. 15, no. 7 (2015-04-02), S.3703-3717 |
| Datensatznummer |
250119614
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| Publikation (Nr.) |
 copernicus.org/acp-15-3703-2015.pdf |
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| Zusammenfassung |
Deposition nucleation experiments with Arizona Test Dust (ATD) as
a surrogate for mineral dusts were conducted at the AIDA cloud
chamber at temperatures between 220 and 250 K. The influence
of the aerosol size distribution and the cooling rate on the ice
nucleation efficiencies was investigated. Ice nucleation active
surface site (INAS) densities were calculated to quantify the ice
nucleation efficiency as a function of temperature, humidity and the
aerosol surface area concentration. Additionally, a contact angle
parameterization according to classical nucleation theory was fitted
to the experimental data in order to relate the ice nucleation
efficiencies to contact angle distributions. From this study it can
be concluded that the INAS density formulation is a very useful tool
to describe the temperature- and humidity-dependent ice nucleation
efficiency of ATD particles.
Deposition nucleation on ATD particles can be described by
a temperature- and relative-humidity-dependent INAS density function
ns(T, Sice) with
ns(xtherm) = 1.88 ×105 · exp(0.2659 · xtherm) [m−2] , (1)
where the temperature- and saturation-dependent function xtherm is defined as
xtherm = −(T−273.2)+(Sice−1) ×100, (2)
with the saturation ratio with respect to ice Sice >1 and within a temperature range between 226 and
250 K. For lower temperatures, xtherm deviates
from a linear behavior with temperature and relative humidity over
ice.
Also, two different approaches for describing the time dependence of
deposition nucleation initiated by ATD particles are proposed. Box
model estimates suggest that the time-dependent contribution is only
relevant for small cooling rates and low number fractions of
ice-active particles. |
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