Title Laboratory studies of ice formation pathways from ammonium sulfate particles
Author Wise, M.E.; Baustian, K.J.; Tolbert, M.A.
Author Affil Wise, M.E., University of Colorado, Department of Chemistry and Biochemistry, Boulder, CO
Source Atmospheric Chemistry and Physics, 9(5), p.1639-1646, . Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1680- 7316
Publication Date 2009
Notes In English. Published in Atmospheric Chemistry and Physics Discussions: 11 August 2008, http://www.atmos-chem-phys- discuss.net/8/15101/2008/acpd-8-15101-2008.ht ml; abstract: doi:10.5194/acp-9-1639-2009. 19 refs. GeoRef Acc. No: 310589
Index Terms clouds (meteorology); crystals; experimentation; freezing; ice; ice crystals; nucleation; particles; spectra; water; ammonium; ammonium sulfate; aqueous solutions; clouds; experimental studies; FTIR spectra; infrared spectra; laboratory studies; saturation; sulfates
Abstract Cirrus clouds are composed of ice particles and their formation pathways have been studied extensively in the laboratory. The ability of ammonium sulfate particles to act as nuclei for cirrus clouds has been of particular importance because of their ubiquitous presence in the upper troposphere. The results of past laboratory experiments of homogeneous ice nucleation from ammonium sulfate particles show a wide range of freezing conditions. In the present study, a flow tube apparatus equipped with Fourier transform infrared spectroscopy was used to reexamine these discrepancies. It was found that when ammonium sulfate particles were preconditioned at 100% relative humidity (RH) prior to experimentation, the particles began to freeze at conditions predicted by the homogeneous ice nucleation model developed by Koop et al. (2000). If the particles were not preconditioned at 100% RH, some froze at warmer temperatures and lower ice saturation ratios than predicted by Koop et al. (2000). It is hypothesized that a population of effloresced particles affected freezing conditions for particles that were not preconditioned at 100% RH.
URL http://www.atmos-chem-phys.net/9/1639/2009/acp-9-1639-2009.pdf
Publication Type journal article
Record ID 65007012