HR: 1340h
AN: A23C-0972    [Abstracts]
TI: Can Contact Nuclei Explain the Persistence of Ice in Multi-Phase Arctic Boundary Layer Clouds?
AU: * Fridlind, A M
EM: ann.fridlind@nasa.gov
AF: NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 United States
AU: Ackerman, A S
EM: andrew.ackerman@nasa.gov
AF: NASA Goddard Institute for Space Studies, 2880 Broadway, New York, NY 10025 United States
AB: During the Department of Energy Atmospheric Radiation Measurement Program's Multi-Phase Arctic Cloud Experiment in October 2004, ice number concentrations measured in persistent multi-phase boundary layer clouds were often several times higher than the number concentrations of deposition and condensation ice nuclei measured in the surrounding clear air. Using a large-eddy simulation with a size-resolved microphysics treatment, with the peak ice nuclei measurements as an estimate of the total number of deposition, condensation, and immersion nuclei, we find that Hallett-Mossop multiplication processes are not sufficient to explain the difference. Here we investigate the hypothesis that contact nuclei are responsible for most ice nucleation, as has been suggested in the literature. We add phoretic forces to our aerosol-liquid coagulation kernel and initialize the model with local aerosol observations in order to rigorously test this hypothesis in terms of the rate of entrainment of possible nuclei and their likely ability to provide persistent ice. We also compare modeled liquid and ice fields with observations in terms of vertical profiles and horizontal variability, in addition to investigating the possibility of greater-than-expected uncertainty in the ice nuclei concentration measurements.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005