Contact freezing: a review of experimental studies L. A. Ladino Moreno1,*, O. Stetzer1, and U. Lohmann1 1Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, 8092, Zurich, Switzerland *now at: the 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 conducted using the cold plate technique
indicate that it can initiate ice formation at warmer temperatures than
immersion freezing. Additionally, a qualitative 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 contact nucleation in the laboratory and in the
field are needed to identify the conditions at which contact nucleation could
occur in the atmosphere. Important questions concerning contact freezing and
its potential role for ice cloud formation and climate are also summarized.
Citation: Ladino Moreno, L. A., Stetzer, O., and Lohmann, U.: Contact freezing: a review of experimental studies, Atmos. Chem. Phys., 13, 9745-9769, doi:10.5194/acp-13-9745-2013, 2013.