Improving the Treatment of Ice Clouds for Climate Models


Scientists in DOE’s Atmospheric Radiation Measurement (ARM) program used ARM measurements to show that the shapes of ice crystal vary considerably between recently formed ice clouds and aged ice clouds.  This is important because the shape of ice crystals determines how sunlight is reflected by clouds.  Accurate representations of how clouds affect sunlight are needed for climate models to determine how clouds might enhance or reduce the warming associated with increases in greenhouse gases.  This study used unique high-resolution images of ice crystals measured near Darwin, Australia during the ARM-sponsored Tropical Warm Pool International Cloud Experiment.  These scientists also developed new models, which differ significantly from those currently used in climate models, to show how the observed aggregate crystals affect sunlight.  Application of these results in climate models will enable more accurate representations of the interactions of ice clouds and sunlight.


Um, J., and G.M. McFarquhar (2009), Single-scattering properties of aggregates of plates, Quart. J. Roy. Meteor. Soc., 135, 291-304.