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| Titel |
Commentary on "Homogeneous nucleation of NAD and NAT in liquid stratospheric aerosols: insufficient to explain denitrification" by Knopf et al. |
| VerfasserIn |
A. Tabazadeh |
| 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 ; 3, no. 3 ; Nr. 3, no. 3 (2003-06-24), S.863-865 |
| Datensatznummer |
250001053
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| Publikation (Nr.) |
 copernicus.org/acp-3-863-2003.pdf |
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| Zusammenfassung |
| In a recent published paper Knopf et a1. (2002) have suggested that the
homogeneous freezing behavior of stratospheric aerosols, under polar winter conditions,
can be simulated experimentally in large bulk phase-sized droplet samples
(0.12-0.27 cm in diameter). Their hypothesis is based on the fact that a nucleus, which freezes the
supercooled phase, forms within the bulk volume of a given sample, and therefore, if
large bulk volumes don't freeze in the laboratory, then small volumes in particles most
certainly remain unfrozen in the stratosphere. The important question to ask here is
whether their initial hypothesis, which they have used to analyze their data, is even
correct to begin with. For example, does a nucleus, which turns over the phase, forms
within the bulk volume or on the surface of the supercooled phase? Some recent studies
provide both experimental (Tabazadeh et al., 2002a, b) and theoretical (Djikaev et al.,
2002, 2003) support for the formation of the nucleus at the surface of a supercooled
droplet. If the homogeneous nucleation process initiates at the droplet surface, then the
approach taken by Knopf. et al. to study this crystallization process may not be directly
applicable to the stratospheric situation. |
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