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| Titel |
Ice nucleation by surrogates for atmospheric mineral dust and mineral dust/sulfate particles at cirrus temperatures |
| VerfasserIn |
C. M. Archuleta, P. J. DeMott, 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 ; 5, no. 10 ; Nr. 5, no. 10 (2005-10-04), S.2617-2634 |
| Datensatznummer |
250003097
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| Publikation (Nr.) |
 copernicus.org/acp-5-2617-2005.pdf |
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| Zusammenfassung |
| This study examines the potential role of some types of
mineral dust and mineral dust with sulfuric acid coatings as heterogeneous
ice nuclei at cirrus temperatures. Commercially-available nanoscale powder
samples of aluminum oxide, alumina-silicate and iron oxide were used as
surrogates for atmospheric mineral dust particles, with and without
multilayer coverage of sulfuric acid. A sample of Asian dust aerosol
particles was also studied. Measurements of ice nucleation were made using a
continuous-flow ice-thermal diffusion chamber (CFDC) operated to expose
size-selected aerosol particles to temperatures between -45 and -60°C
and a range of relative humidity above ice-saturated conditions. Pure metal
oxide particles supported heterogeneous ice nucleation at lower relative
humidities than those required to homogeneously freeze sulfuric acid
solution particles at sizes larger than about 50 nm. The ice nucleation
behavior of the same metal oxides coated with sulfuric acid indicate
heterogeneous freezing at lower relative humidities than those calculated
for homogeneous freezing of the diluted particle coatings. The effect of
soluble coatings on the ice activation relative humidity varied with the
respective uncoated core particle types, but for all types the heterogeneous
freezing rates increased with particle size for the same thermodynamic
conditions. For a selected size of 200 nm, the natural mineral dust
particles were the most effective ice nuclei tested, supporting
heterogeneous ice formation at an ice relative humidity of approximately
135%, irrespective of temperature. Modified homogeneous freezing
parameterizations and theoretical formulations are shown to have application
to the description of heterogeneous freezing of mineral dust-like particles
with soluble coatings. |
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