HR: 0800h
AN: A51E-0841    [Abstracts]
TI: Heterogeneous Nucleation of Ice by Long Chain Alcohols: Perspectives on the Structure of Water and Theories of Nucleation
AU: * Ochshorn, E K
EM: ekochsho@mtu.edu
AF: Department of Physics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AU: Cantrell, W H
EM: cantrell@mtu.edu
AF: Department of Physics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931 United States
AB: At temperatures greater than about -30 degrees C, ice cloud formation is only possible due to the microphysical effects that aerosol particles have on the water or solution droplets with which they are in contact. Though modeling studies have indicated that ice formed in this fashion is sufficiently prevalent as to have a significant impact on the radiative properties of cirrus clouds, the link between aerosol particles and the specific subset which catalyze freezing transitions is tenuous. The most frequently used model is classical nucleation theory, which predicts freezing efficacy for various substances based on knowledge of some basic physical properties of the substances (i.e. lattice match to bulk ice). As recent work has implied that there are likely some limits to the classical theory, we have used infrared spectroscopy to probe thin films of water covered with monolayers of long chain alcohols as the water undergoes a freezing transition. Long chain alcohols were chosen because of their suspected role in atmospheric ice production and their previously observed anomalous nucleating behavior. Interestingly, the spectra show a continuous transition from a spectrum characteristic of supercooled water to that of ice. We interpret our results in light of predictions from classical nucleation theory and in light of structural theories of water. The relevance of nonclassical nucleation theories is also discussed.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting