Aerosol Particle Property Comparisons Between MISR and AERONET Retrieved Values

As a further 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 has been made against the Aerosol Robotic Network (AERONET). Angstrom exponent, single scattering albedo, and size distribution characteristic values and variance envelopes for individual sites and aggregates are compared, stratified by expected aerosol air mass type, optical depth magnitude and season. Specific examples illustrating strengths and weaknesses of this approach will be shown. More than seven years of data from about 52 geographically diverse sites having good long-term measurement records are first stratified by expected aerosol air mass types: maritime, biomass burning, desert dust, urban pollution, continental and mixed dust+smoke aerosols. Having observations in at least three of the four seasons is an additional constraint on the selection of sites. The number of actual coincident measurements is limited by requiring AERONET direct sun aerosol optical thickness (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. 3605 coincident observations are included in the data set. Both AERONET sun and sky data are averaged over the measurements obtained within these windows and are then interpolated to the MISR wavelengths to facilitate comparison. All AERONET measurements are Level 1.5, Version 2 data. A previous, systematic comparison of MISR and AERONET AOT data [Kahn, Gaitley et al., JGR 110, 2005] was used to suggest improvements to the MISR Standard Aerosol retrieval algorithms. The MISR aerosol products have been almost completely reprocessed with the upgraded algorithms. This new, uniformly processed database, that is used in the current study, which is aimed at further refining the MISR aerosol products, especially the particle property results. This work is performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration and at the NASA Goddard Space Flight Center.