Articles | Volume 15, issue 4
Atmos. Chem. Phys., 15, 1621–1632, 2015

Special issue: Interactions between climate change and the Cryosphere: SVALI,...

Atmos. Chem. Phys., 15, 1621–1632, 2015

Research article 16 Feb 2015

Research article | 16 Feb 2015

Deposition-mode ice nucleation reexamined at temperatures below 200 K

E. S. Thomson1, X. Kong1, P. Papagiannakopoulos1,2, and J. B. C. Pettersson1 E. S. Thomson et al.
  • 1Department of Chemistry and Molecular Biology, Atmospheric Science, University of Gothenburg, 412 96, Gothenburg, Sweden
  • 2Laboratory of Photochemistry and Kinetics, Department of Chemistry, University of Crete, 71003 Heraklion, Crete, Greece

Abstract. The environmental chamber of a molecular beam apparatus is used to study deposition nucleation of ice on graphite, alcohols and acetic and nitric acids at temperatures between 155 and 200 K. The critical supersaturations necessary to spontaneously nucleate water ice on six different substrate materials are observed to occur at higher supersaturations than are theoretically predicted. This contradictory result motivates more careful examination of the experimental conditions and the underlying basis of the current theories. An analysis based on classical nucleation theory supports the view that at these temperatures nucleation is primarily controlled by the rarification of the vapor and the strength of water's interaction with the substrate surface. The technique enables a careful probing of the underlying processes of ice nucleation and the substrate materials of study. The findings are relevant to atmospheric nucleation processes that are intrinsically linked to cold cloud formation and lifetime.

Short summary
We present new observations of ice nucleation on substrate surfaces that affirm the ``puzzle'' of very high supersaturations required for nucleation from the vapor phase. To explain the observations, the kinetics and thermodynamics of nucleation theory are explored. The results explicitly connect the nucleation to the substrate material's surface binding energy and demonstrate that an improved fundamental understanding must include a strict understanding of the relevant microphysics.
Final-revised paper