Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 7, 3771-3781, 2007
© Author(s) 2007. This work is licensed under the
Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
23 Jul 2007
Physical controls on orographic cirrus inhomogeneity
J. E. Kay1, M. Baker2, and D. Hegg2 1National Center for Atmospheric Research, Boulder, CO, USA
2Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
Abstract. Optical depth distributions (P(σ)) are a useful measure of radiatively important cirrus (Ci) inhomogeneity. Yet, the relationship between P(σ) and underlying cloud physical processes remains unclear. In this study, we investigate the influence of homogeneous and heterogeneous freezing processes, ice particle growth and fallout, and mesoscale vertical velocity fluctuations on P(σ) shape during an orographic Ci event. We evaluate Lagrangian Ci evolution along kinematic trajectories from a mesoscale weather model (MM5) using an adiabatic parcel model with binned ice microphysics. Although the presence of ice nuclei increased model cloud cover, our results highlight the importance of homogeneous freezing and mesoscale vertical velocity variability in controlling Ci P(σ) shape along realistic upper tropospheric trajectories.

Citation: Kay, J. E., Baker, M., and Hegg, D.: Physical controls on orographic cirrus inhomogeneity, Atmos. Chem. Phys., 7, 3771-3781, doi:10.5194/acp-7-3771-2007, 2007.
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