PNNL

Abstract

Clouds are of tremendous importance to climate because of their direct radiative effects and because of their role in atmospheric dynamics and the hydrological cycle. The value of satellite imagery in monitoring cloud properties on a global basis can hardly be understated. One cloud property that satellites are in an advantageous position to monitor is cloud top height. Cloud top height retrievals are especially important for MISR because the derived height field is used to co-register the measured radiances. In this presentation we show the results of an ongoing comparison between ground-based millimeter-wave cloud radar and lidar measurements of cloud top and MISR stereo-derived cloud top height. This comparison is based on data from three radar systems located in the U.S Southern Great Plains (Lamont, Oklahoma), the Tropical Western Pacific (Nauru Island) and the North Slope of Alaska (Barrow, Alaska). These radars are operated as part of the U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program. The MISR stereo height algorithm is performing largely as expected for most optically thick clouds. As with many satellite retrievals, the stereo-height retrieval has difficulty with optically thin clouds or ice clouds with little optical contrast near cloud top.