HR: 17:00h
AN: A34B-05    [Abstracts]
TI: Possible Roles of Ice Nucleation Mode and Ice Nuclei Depletion in the Extended Lifetime of Arctic Mixed-Phase Clouds
AU: * Morrison, H
EM: morrison@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 United States
AU: Pinto, J O
EM: pinto@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 United States
AU: Curry, J A
EM: curryja@eas.gatech.edu
AF: Georgia Institute of Technology, 311 Ferst Dr., Atlanta, GA 30332 United States
AB: The sensitivity of Arctic mixed-phase clouds to the mode of ice particle nucleation is examined using a 1-D cloud model. The lifetime of the simulated low-level mixed-phase stratus is highly sensitive to the number concentration of depostion/condensation-freezing ice nuclei, and much less sensitive to the concentration of contact nuclei. Simulations with prognostic ice nuclei concentrations exhibit rapid depletion of deposition/condensation-freezing nuclei due to nucleatin scavenging, which significantly extends the mixed-phase cloud lifetime. Scavenging has much less impact on contact nuclei, so that when both modes are simultaneously considered, contact nucleation dominates in the cloud layer. The dominance of contact nucleation in mixed-phase clouds is consistent with a number of in situ observations and remote retrievals gathered in the Arctic. Based on these results, a conceptual model of long-lived mixed-phase clouds is developed, and implications for the prediction of mixed-phase clouds in cliamte and weather models are described.
DE: 3310 Clouds and cloud feedbacks
DE: 3311 Clouds and aerosols
DE: 3329 Mesoscale meteorology
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005