Scanning electron microscopy and molecular dynamics of surfaces of growing and ablating hexagonal ice crystals University of Puget Sound, Tacoma, Washington, 98416, USA
Received: 10 Aug 2009 – Published in Atmos. Chem. Phys. Discuss.: 01 Oct 2009Abstract. We present the first clearly resolved observations of
surfaces of growing and ablating hexagonal ice crystals using
variable-pressure scanning electron microscopy. The ice surface develops
trans-prismatic strands, separated from one another by distances of 5–10 μm.
The strands are present at a wide range of supersaturations, but
are most pronounced at temperatures near the frost point. Pyramidal facets
consistent with Miller-Bravais indices of 1011, and possibly also 2021,
are associated with ice growth under these conditions. A
molecular-dynamics model of a free-standing ice Ih nanocolumn containing
8400 water molecules does not develop trans-prismatic strands, suggesting
these features originate at larger spatial or temporal scales. The possible
relevance of these surface features to cirrus ice is discussed.
Revised: 19 Mar 2010 – Accepted: 23 Mar 2010 – Published: 29 Mar 2010
Citation: Pfalzgraff, W. C., Hulscher, R. M., and Neshyba, S. P.: Scanning electron microscopy and molecular dynamics of surfaces of growing and ablating hexagonal ice crystals, Atmos. Chem. Phys., 10, 2927-2935, doi:10.5194/acp-10-2927-2010, 2010.