New measurements of high supersaturations to shape understanding of ice cloud nucleation

COLL 271

Melissa G. Trainer, trainer@lasp.colorado.edu, LASP and CIRES, Univeristy of Colorado at Boulder, Boulder, CO 80309-0216, Eric J. Jensen, NASA Ames Research Center, Moffett Field, CA, Owen B. Toon, Laboratory for Atmsopheric and Space Physics and Dept. of Atmospheric and Oceanic Sciences, University of Colorado at Boulder, Boulder, CO 80309, and Margaret A Tolbert, tolbert@spot.colorado.edu, Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO CO 80309.
We have performed a study of the heterogeneous depositional nucleation of ice on a solid Si substrate at temperatures from 150 – 180 K. Our results show there is a significant temperature dependence for the critical saturation ratios (Scrit) required for the onset of nucleation, larger than that predicted by classical heterogeneous nucleation theory when assuming a constant contact angle. The critical supersaturations measured below 175 K are also greater than the vapor saturation for supercooled liquid water. A derived relationship for Scrit values is given to relate our results to conditions observed in the atmosphere. Here we will discuss the implications of our results, with relevance for recent measurements of high supersaturations in the tropical tropopause layer. In addition, the low temperature data is discussed in terms of the nucleation of water ice in noctilucent clouds observed in the summer polar mesosphere.
 

The Physical Chemistry of Environmental Interfaces
6:00 PM-8:00 PM, Monday, April 7, 2008 Morial Convention Center -- Rm. 244/245, Poster

Division of Colloid & Surface Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008