Aerosol Particle Property Comparisons Between MISR and AERONET Retrieved Values

As the final step in validating the NASA Earth Observing System Terra satellite's Multi-angle Imaging SpectroRadiometer (MISR) aerosol products, an extensive comparison of particle micro-physical properties is being made against the Aerosol Robotic Network (AERONET). Angstrom exponent, single scattering albedo, and size distribution mean values and variance envelopes for individual sites and aggregates will be compared, stratified by expected aerosol air mass type, optical depth magnitude and season. Specific examples showing strengths and weaknesses of this approach will be shown. Six years of data from about 40 selected sites having good long-term measurement records are first stratified by expected air mass types: maritime, biomass burning, desert dust, pollution and continental aerosols. The number of actual coincident measurements is limited by requiring AERONET direct sun aerosol optical depth (AOT) data be obtained from a two-hour window centered on the MISR overpass time and AERONET sky scans, which provide particle micro-physical properties and are taken only once an hour, obtained from a four- hour window also centered on the overpass. Both AERONET sun and sky data are averaged over the measurements obtained within these windows and are then interpolated to MISR wavelengths to facilitate comparison. A previous, systematic comparison from MISR and AERONET AOT data [Kahn, Gaitley et al., JGR 110, 2005] was used to improve MISR Standard Aerosol retrieval algorithms. The MISR aerosol products have been almost completely reprocessed with the upgraded algorithms. It is this new, uniform database that is used in the current study, which is aimed at further refining the MISR aerosol products. This work is performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration