EOS Validation Program

Institution: University of Maryland Baltimore County
Phone: (301) 286-3836
E-mail: platnick@climate.gsfc.nasa.gov

Robert Pincus, University of Maryland Baltimore County

Final Report, March 2003

We propose to use model calculations along with analysis of MODIS and MAS data to assess the validity and accuracy of the MODIS Cloud Product retrievals of cloud optical thickness and effective radius. Specifically, we intend to: (1) Assess errors which arise in the computation of the reflectance libraries used in the retrieval scheme due to such factors as wavelength integration, the shape of the assumed drop size distribution, and the complex index of refraction of water. (2) Examine the uncertainty produced by imperfect knowledge of the environment in which the retrievals are performed. (3) Explore the effects of vertical stratification in droplet size on retrieved optical properties, paying special attention to understanding discrepancies between effective radii retrieved from reflection measurements at different wavelengths. (4) Determine tie uncertainties and potential biases in retrieved quantities due to horizontal inhomogeneity in cloud optical properties, and develop a theoretical framework for using information from regions of an image to estimate the uncertainty on the pixel level.We will acertain the dependence of the uncertainty to viewing and illumination geometry, optical depth, effective radius, and the parameters controlling the vertical an/or horizontal distribution of cloud optical properties.