HR: 1340h
AN: A23B-1256    [Abstracts]
TI: A comparison of water uptake by aerosols using the thermodynamic models of Metzger and Jacobson
AU: * Xu, L
EM: lixum@umich.edu
AF: Department of Atmospheric, Oceanic and Space Science, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109, United States
AU: Penner, J E
EM: penner@umich.edu
AF: Department of Atmospheric, Oceanic and Space Science, University of Michigan, 2455 Hayward Street, Ann Arbor, MI 48109, United States
AU: Metzger, S
EM: metzger@mpch-mainz.mpg.de
AF: Max Planck Insititute for Chemistry, Department of Atmospheric Chemistry, J. J. Becherweg 27, Mainz, D-55128, Germany
AB: The water uptake by hygroscopic aerosols can significantly alter aerosol size, optical properties and direct radiative forcing. Two methods to determine the uptake of water by aerosols are investigated here. Thermodynamic aerosol models determine aerosol water uptake by accounting for a mixing rule, also known as the Zdanovskii-Stokes-Robsin (ZSR) relationship, which is usually solved iteratively for a given equilibrium condition. The Metzger method (Metzger and Lelieveld, ACP, 2007) determines water uptake analytically (without any iteration). This yields a significant reduction of computing time. They assume the water activity to equal the ambient relative humidity at equilibrium, and hence only use relative-humidity-dependent activity coefficients for volatile aerosol compounds. Here, we examine this new method of uptake of water by aerosols by comparing the results with those of the thermodynamic model currently used in our global chemical transport model (Feng and Penner, JGR, 2007) under typical ambient conditions.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting