HR: 16:00h
AN: A54B-01 INVITED     [Abstracts]
TI: Hygroscopicity of organic-containing particles and implications for warm and cold cloud formation
AU: * Kreidenweis, S M
EM: sonia@chem.atmos.colostate.edu
AF: Colorado State University, Department of Atmospheric Science, Ft. Collins, CO 80523 United States
AB: The hygroscopic growth of ambient and laboratory-generated aerosols exposed to varying relative humidities has been commonly investigated using the Humidified Tandem Differential Mobility Analyzer (HTDMA). A methodology is presented that uses particle growth factors, obtained from HTDMA data, to derive solution water activities as functions of composition. The method is applied to HTDMA data for selected inorganic and organic species. Water activities derived in this manner generally compare well with previously-published data obtained by other techniques, although discrepancies were found for some of the investigated dicarboxylic acids. The derived water activity data are then used to predict critical supersaturations for drop formation and initiation of homogeneous freezing, and compared with published experimental data. Except for malonic acid, predicted critical supersaturations for drop formation are well within experimental uncertainities. Relative humidities required for initiation of homogeneous freezing at cirrus temperatures are not as well represented; possible reasons for observed differences, including experimental limitations, are discussed.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
DE: 0394 Instruments and techniques
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting