HR: 1340h
AN: A53D-1448    [Abstracts]
TI: Evaluation of a New Mixed-Phase Cloud Microphysics Parameterization with a Single Column Model, CAPT Forecasts and M-PACE Observations
AU: * Liu, X
EM: xiaohong.liu@pnl.gov
AF: Pacific Northwest National Laboratory, 3200 Q Ave., MSIN K9-24, Richland, WA 99352, United States
AU: Xie, S
EM: xie2@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, United States
AU: Boyle, J
EM: boyle5@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, United States
AU: Klein, S
EM: klein21@llnl.gov
AF: Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550, United States
AU: Ghan, S
EM: steve.ghan@pnl.gov
AF: Pacific Northwest National Laboratory, 3200 Q Ave., MSIN K9-24, Richland, WA 99352, United States
AB: Most global climate models generally prescribe the partitioning of condensed water into liquid droplets and ice crystals in mixed-phase clouds according to a temperature-dependent function, which affects modeled cloud phase, cloud lifetime and radiative properties. In this study we evaluate a new mixed-phase cloud microphysics parameterization (for ice nucleation and water vapor deposition) against the Atmospheric Radiation Measurement (ARM) Mixed-phase Arctic Cloud Experiment (M-PACE) observations using the NCAR Community Atmospheric Model Version 3 (CAM3) running in the single column mode (SCAM) and in the CCPP-ARM Parameterization Testbed (CAPT) forecasts. It is found that SCAM with the new physically-based cloud microphysical scheme produces a more realistic simulation of the cloud phase structure and the partitioning of condensed water into liquid droplets against observations during the M-PACE than the standard CAM with an oversimplified cloud microphysics. CAM3 in the CAPT forecasts significantly underestimates the observed boundary layer mixed- phase cloud fraction. The simulation of the boundary layer mixed-phase clouds and their microphysical properties is considerably improved in CAM3 when the new scheme is used. The new scheme also leads to an improved simulation of the surface and top of the atmosphere longwave radiative fluxes. Both SCAM simulations and CAPT forecasts suggest that the ice number concentration could play an important role in the simulated mixed-phase cloud microphysics, and thereby needs to be realistically represented in global climate models.
DE: 0321 Cloud/radiation interaction
DE: 3310 Clouds and cloud feedbacks
DE: 3311 Clouds and aerosols
DE: 3337 Global climate models (1626, 4928)
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting