Articles | Volume 7, issue 14
Atmos. Chem. Phys., 7, 3771–3781, 2007
Atmos. Chem. Phys., 7, 3771–3781, 2007

  23 Jul 2007

23 Jul 2007

Physical controls on orographic cirrus inhomogeneity

J. E. Kay1, M. Baker2, and D. Hegg2 J. E. Kay et al.
  • 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.

Final-revised paper