Do polluted clouds have sharper cloud edges?
Authors
J.-Y. Christine Chiu — Colorado State University
Julian Mann — University of Reading
Robin J. Hogan — University of Reading
Alexander Marshak — NASA - Goddard Space Flight Center
Graham Feingold — NOAA- Earth System Research Laboratory
Allison C. McComiskey — Brookhaven National Laboratory
Warren J. Wiscombe — Brookhaven National Laboratory
Category
Aerosol-Cloud-Radiation Interactions
Description
The transition zone between cloudy and clear air is a region of strong aerosol-cloud interactions. A number of large eddy simulations have found that clouds in more polluted air have sharper edges than those in cleaner air, due to faster evaporation of the smaller cloud droplets produced by pollution near cloud edges. If this finding is valid, cloud edge sharpness, to the extent it can be quantified from observations, can be a valuable parameter to evaluate the fidelity of aerosol-cloud microphysical parameterizations used in models. However, cloud edges are difficult to measure in reality, especially because of their tortured, fractal character, and thus this model finding has not been extensively tested from observations. In this paper, we will use high-temporal resolution zenith radiance measurements to test this model finding and to test whether aerosols modulate cloud edge sharpness in a similar degree between models and observations. We will also show how this aerosol effect varies with cloud type in environments with radically different degrees of pollution, using data collected from the ARM Mobile Facility field campaigns in China, the Azores, and Black Forest, Germany.
