HR: 1340h
AN: A23D-1565    [Abstracts]
TI: Aerosol Processing in Mixed-Phase Clouds in ECHAM5-HAM: Comparison of Single-Column Model Simulations to Observations
AU: * Hoose, C
EM: corinna.hoose@env.ethz.ch
AF: ETH Zurich, Institute for Atmospheric and Climate Science, Universitaetsstrasse 16, Zurich, 8092, Switzerland
AU: Lohmann, U
EM: ulrike.lohmann@env.ethz.ch
AF: ETH Zurich, Institute for Atmospheric and Climate Science, Universitaetsstrasse 16, Zurich, 8092, Switzerland
AU: Stier, P
EM: philip.stier@caltech.edu
AF: California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 - 78, United States
AU: Verheggen, B
EM: bart.verheggen@env.ethz.ch
AF: ETH Zurich, Institute for Atmospheric and Climate Science, Universitaetsstrasse 16, Zurich, 8092, Switzerland
AU: Weingartner, E
EM: ernest.weingartner@psi.ch
AF: Paul Scherrer Institut, Labor fuer Atmosphaerenchemie, Villingen, 5232, Switzerland
AU: Herich, H
EM: hanna.herich@env.ethz.ch
AF: ETH Zurich, Institute for Atmospheric and Climate Science, Universitaetsstrasse 16, Zurich, 8092, Switzerland
AB: The global aerosol-climate model ECHAM5-HAM (Stier et al., 2005) has been extended by an explicit treatment of cloud-borne particles. Two additional modes for in-droplet and in-crystal particles are introduced, which are coupled to the number of cloud droplet and ice crystal concentrations simulated by the ECHAM5 double-moment cloud microphysics scheme (Lohmann et al., 2007). Transfer, production and removal of cloud-borne aerosol number and mass by cloud droplet activation, collision scavenging, aqueous-phase sulfate production, freezing, melting, evaporation, sublimation and precipitation formation are taken into account. The model performance is demonstrated and validated with observations of the evolution of total and interstitial aerosol concentrations and size distributions during three different mixed-phase cloud events at the alpine high-altitude research station Jungfraujoch (Switzerland) (Verheggen et al, 2007). Although the single-column simulations can not be compared one-to-one with the observations, the governing processes in the evolution of the cloud and aerosol parameters are captured qualitatively well. High scavenged fractions are found during the presence of liquid water, while the release of particles during the Bergeron-Findeisen process results in low scavenged fractions after cloud glaciation. The observed coexistence of liquid and ice, which might be related to cloud heterogeneity at subgrid scales, can only be simulated in the model when forcing non-equilibrium conditions. References: U. Lohmann et al., Cloud microphysics and aerosol indirect effects in the global climate model ECHAM5-HAM, Atmos. Chem. Phys. 7, 3425-3446 (2007) P. Stier et al., The aerosol-climate model ECHAM5-HAM, Atmos. Chem. Phys. 5, 1125-1156 (2005) B. Verheggen et al., Aerosol partitioning between the interstitial and the condensed phase in mixed-phase clouds, Accepted for publication in J. Geophys. Res. (2007)
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 3311 Clouds and aerosols
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting