Wednesday, 9 July 2014
Daytime cloud optical and microphysical properties are often retrieved from passive satellite data using both visible and infrared radiances. Cloud optical depth is typically determined using visible channel reflectances, however, this is complicated over highly reflective surfaces because a cloud-free scene may have a reflectance equal to or greater than a cloudy scene. Additionally, it is difficult to model the clear-sky reflectance of snow-covered surfaces because surface texture and snow microphysics significantly affect surface bidirectional reflectance. Using infrared channels to retrieve cloud properties may help circumvent these difficulties. This paper details the progress being made to quantify cloud phase, optical depth, and effective particle size for clouds that occur over snow covered surfaces, using an infrared-only heritage algorithm developed at NASA Langley for the Clouds and the Earth's Radiant Energy System (CERES) program. This algorithm is applied to Advanced Very High Resolution Radiometer (AVHRR) data from NOAA-18. The results are analyzed for spatial continuity between snow-free and snow-covered surfaces and then compared to CALIPSO to determine accuracy.
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