EOS Validation Program

Institution: University of Maryland Baltimore County
Phone: (301) 286-4769
E-mail: marshak@climate.gsfc.nasa.gov

Anthony B. Davis, Los Alamos National Laboratory
Robert F. Cahalan, NASA/GSFC
Warren J. Wiscombe, NASA/GSFC

August 2001
Final Report, January 2003

We propose to thoroughly study a method which we have invented called Nonlocal Independent Pixel Approximation (NIPA). NIPA retains the simplicity of one-dimensional schemes while still incorporating information from neighboring pixels, and goes partway toward correcting the deficiencies of a pure "Independent Pixel Approximation" (IPA) retrieval, according to our preliminary calculations. In effect, NIPA sharpens the radiatively smoothed field of retrieved optical depths by generating small-scale structure which is consistent with the scaling properties of the large-scale structure. It is based on some recent discoveries by our group concerning the radiative smoothing process in marine stratocumulus clouds. However, much more needs to be done to extend NIPA to other types of clouds and, in particular, to more broken cloud fields. Since NIPA will generate a more realistic optical depth distribution than the IPA methods that MODIS will use at-launch, the use of NIPA on selected samples of MODIS data especially the 250-m pixel data, should contribute substantively to understanding errors in the IPA retrievals. This approach should provide important information on how accurate operational cloud retrievals are, and help set error bounds on them. To validate NIPA, microwave radiometer data at two ARM (Atmospheric Radiation Measurements) sites (Oklahoma and Western Pacific) will be used.