Surface Crystallization of Supercooled Water in Clouds

The process by which liquid cloud droplets homogeneously crystallize into ice is still not well understood. The ice nucleation process based on the standard and classical theory of homogeneous freezing initiates within the interior volume of a cloud droplet. Current experimental data on homogeneous...

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Bibliographic Details
Published inProceedings of the National Academy of Sciences - PNAS Vol. 99; no. 25; pp. 15873 - 15878
Main Authors Tabazadeh, A., Djikaev, Y.S., Reiss, H.
Format Journal Article
LanguageEnglish
Published United States National Academy of Sciences 10.12.2002
National Acad Sciences
Subjects
Clouds
Crystallization
Crystallography
Crystals
Data lines
Freezing
Ice
Ice nuclei
Interfacial tension
Liquids
Nucleation
Physical Sciences
Physics
Water
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Summary:The process by which liquid cloud droplets homogeneously crystallize into ice is still not well understood. The ice nucleation process based on the standard and classical theory of homogeneous freezing initiates within the interior volume of a cloud droplet. Current experimental data on homogeneous freezing rates of ice in droplets of supercooled water, both in air and emulsion oil samples, show considerable scatter. For example, at -33°C, the reported volume-based freezing rates of ice in supercooled water vary by as many as 5 orders of magnitude, which is well outside the range of measurement uncertainties. Here, we show that the process of ice nucleus formation at the air (or oil)-liquid water interface may help to explain why experimental results on ice nucleation rates yield different results in different ambient phases. Our results also suggest that surface crystallization of ice in cloud droplets can explain why low amounts of supercooled water have been observed in the atmosphere near -40°C.
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Contributed by H. Reiss
To whom correspondence should be addressed. E-mail: atabazadeh@mail.arc.nasa.gov.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.252640699