Atmos. Chem. Phys. Discuss., 13, 7811-7869, 2013
www.atmos-chem-phys-discuss.net/13/7811/2013/
doi:10.5194/acpd-13-7811-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
Review Status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Contact freezing: a review
L. A. Ladino1,*, O. Stetzer1, and U. Lohmann1
1Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092 Zurich, Switzerland
*now at: Department of Chemistry, University of Toronto, Toronto, Ontario, Canada

Abstract. This manuscript compiles both theoretical and experimental information on contact freezing with the aim to better understand this potentially important but still not well quantified heterogeneous freezing mode. There is no complete theory that describes contact freezing and how the energy barrier has to be overcome to nucleate an ice crystal by contact freezing. Experiments on contact freezing indicate that it can initiate ice formation at the highest temperatures. A difference in the freezing temperatures between contact and immersion freezing has been found using different instrumentation and different ice nuclei. There is a lack of data on collision rates in most of the reported data, which inhibits a quantitative calculation of the freezing efficiencies. Thus, new or modified instrumentation to study this heterogeneous freezing mode in the laboratory and in the field are needed. Important questions concerning contact freezing and its potential role for ice cloud formation and climate are also summarized.

Citation: Ladino, L. A., Stetzer, O., and Lohmann, U.: Contact freezing: a review, Atmos. Chem. Phys. Discuss., 13, 7811-7869, doi:10.5194/acpd-13-7811-2013, 2013.
 
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