HR: 0800h
AN: A51E-0843    [Abstracts]
TI: Heterogeneous Ice Nucleation on Soot
AU: * Dymarska, M
EM: mdymarsk@chem.ubc.ca
AF: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1 Canada
AU: Murray, B J
EM: bmurray@chem.ubc.ca
AF: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1 Canada
AU: Knopf, D A
EM: knopf@chem.ubc.ca
AF: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1 Canada
AU: Bertram, A K
EM: bertram@chem.ubc.ca
AF: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1 Canada
AB: The indirect aerosol effect of soot on Earth's climate is poorly understood partially because it is not clear if soot is an effective ice nucleus. Using an optical microscope coupled to a flow cell we determined the ice nucleating properties of soot. These particles were deposited on the bottom hydrophobic surface of the flow cell and the relative humidity was controlled by holding the vapour pressure constant while decreasing the temperature at a steady rate. As the temperature of the cell was reduced, the onset of ice formation was observed with digital optical microscopy. The ice nucleating properties of n-hexane soots and lamp black were studied between 258 to 238K. Also, lamp black was oxidized by ozone, and the ice nucleating properties of this soot were investigated. In all cases soot was found to be a poor ice nucleus. These results suggest that soot found in the troposphere is not an important ice nucleus at temperatures above 238K. Work is underway to establish if soot is a better ice nucleus at temperatures lower than 238K.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0340 Middle atmosphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting