HR: 15:25h
AN: A42E-08    [PDF]
TI: Mass and Composition Modification of (NH4)2SO4 Aerosols by Dicarboxylic Acid Formation in Clouds: Implications on Cloud Physics
AU: Ervens, B
EM: barbara.ervens@noaa.gov
AF: Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO 80523 United States
AU: * Feingold, G
EM: graham.feingold@noaa.gov
AF: NOAA/ ETL, 325 Broadway, Boulder, CO 80305 United States
AU: Kreidenweis, S M
EM: sonia@atmos.colostate.edu
AF: Department of Atmospheric Sciences, Colorado State University, Fort Collins, CO 80523 United States
AU: Clegg, S L
EM: s.clegg@uea.ac.uk
AF: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ United Kingdom
AB: We present a chemical mechanism focused on the in-cloud production of sulfate and small dicarboxylic acids ($<$ C6), which are a major part of organic aerosol fractions. The mechanism is applied to a size resolved aerosol model that calculates production rates for sulfate and organic aerosol mass. It is found that cloud processing of aerosol leads to (1) a modified aerosol mass distribution and (2) a modification of the hygroscopic behavior across the aerosol size spectrum due to the formation of different organic fractions in each aerosol size class. We present analysis of the conditions under which these modifications are significant for particle activation and cloud drop number concentration. We also evaluate the relative importance of the sulfate/organic mass fraction (i.e., composition) and variables such as updraft velocity and aerosol size distribution parameters in determining drop concentrations. The results show that, in general, the main fraction of organic aerosol mass produced by cloud chemistry consists of glutaric and oxalic acid. These acids are relatively soluble and do not change the water uptake of the particles significantly compared to pure ammonium sulfate. However, we find that high fractions of less soluble organics (e.g., adipic acid) can change the hygroscopic behavior of the aerosol population.
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0320 Cloud physics and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting