 |
| Titel |
Ice nucleation in sulfuric acid/organic aerosols: implications for cirrus cloud formation |
| VerfasserIn |
M. R. Beaver, M. J. Elrod, R. M. Garland, M. A. Tolbert |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 11 ; Nr. 6, no. 11 (2006-08-04), S.3231-3242 |
| Datensatznummer |
250004050
|
| Publikation (Nr.) |
 copernicus.org/acp-6-3231-2006.pdf |
|
|
|
|
|
| Zusammenfassung |
| Using an aerosol flow tube apparatus, we have studied the effects of
aliphatic aldehydes (C3 to C10) and ketones (C3 and C9)
on ice nucleation in sulfuric acid aerosols. Mixed aerosols were prepared by
combining an organic vapor flow with a flow of sulfuric acid aerosols over a
small mixing time (~60 s) at room temperature. No acid-catalyzed
reactions were observed under these conditions, and physical uptake was
responsible for the organic content of the sulfuric acid aerosols. In these
experiments, aerosol organic content, determined by a Mie scattering
analysis, was found to vary with the partial pressure of organic, the flow
tube temperature, and the identity of the organic compound. The physical
properties of the organic compounds (primarily the solubility and melting
point) were found to play a dominant role in determining the inferred mode
of nucleation (homogenous or heterogeneous) and the specific freezing
temperatures observed. Overall, very soluble, low-melting organics, such as
acetone and propanal, caused a decrease in aerosol ice nucleation
temperatures when compared with aqueous sulfuric acid aerosol. In contrast,
sulfuric acid particles exposed to organic compounds of eight carbons and
greater, of much lower solubility and higher melting temperatures, nucleate
ice at temperatures above aqueous sulfuric acid aerosols. Organic compounds
of intermediate carbon chain length, C4-C7, (of intermediate
solubility and melting temperatures) nucleated ice at the same temperature
as aqueous sulfuric acid aerosols. Interpretations and implications of these
results for cirrus cloud formation are discussed. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|