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GEOPHYSICAL RESEARCH LETTERS,
VOL. 32,
L20814,
doi:10.1029/2005GL024175,
2005
Evaporation freezing by contact nucleation inside-out
Adam J. Durant
Department of Geological Engineering and Sciences, Michigan Technological University, Houghton, Michigan, USA Department of Physics, Michigan Technological University, Houghton, Michigan, USA
Raymond A. Shaw
Department of Physics, Michigan Technological University, Houghton, Michigan, USA
Abstract
Ice formation in atmospheric clouds is crucial to our understanding of precipitation and cloud radiative properties. In recent
work it was shown that heterogeneous ice nucleation rates can be strongly enhanced by a form of surface crystallization (Shaw
et al., 2005). Here we present new laboratory data and consider the implications for contact nucleation and its relevance
to ice nucleation in atmospheric clouds. Our observations contradict three leading hypotheses for contact nucleation and suggest,
instead, that the notion of contact nucleation should be generalized to include surface crystallization from particles contacting
a supercooled drop from the inside out, as well as from the outside in. Our findings lead to the hypothesis that the freezing
temperature of an evaporating drop will suddenly become higher once the drop surface contacts an immersed ice nucleus. This
mechanism for evaporation freezing is therefore a plausible explanation for the abundant observations of high ice concentrations
associated with cloud dilution and droplet evaporation.
Received 22
July
2005;
accepted 20
September
2005;
published 27
October
2005.
Index Terms: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801, 4906); 0320 Atmospheric Composition and Structure: Cloud physics and chemistry; 3311 Atmospheric Processes: Clouds and aerosols.
Read Full Article (file size: 128326 bytes) Cited by
Citation: Durant, A. J., and R. A. Shaw
(2005),
Evaporation freezing by contact nucleation inside-out,
Geophys. Res. Lett.,
32,
L20814,
doi:10.1029/2005GL024175.
Copyright 2005 by the American Geophysical Union.
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