MISR abstract

Gaitley, B., Kahn, R., and Holben, B., (2003). MISR-AERONET Aerosol Comparisons. Eos Trans. AGU, 84(46), Fall Meet. Suppl. 2003, Abstract # A11E-0025

MISR (Multi-angle Imaging SpectroRadiometer) aboard the Terra spacecraft has been collecting data for over three years. MISR views Earth using nine cameras, positioned at angles ranging from 70 degrees forward, through nadir, to 70 degrees aft. As the instrument flies overhead, each piece of Earth's surface below is successively imaged by all nine cameras, in each of four wavelengths (blue, green, red, and near-infrared). The additional information contained in these multi-angle, multi-spectral data make it possible to set limits on aerosol properties over both ocean and land. Aerosol abundance, as described by optical depth, is the first of these properties to be studied in detail, by comparing MISR results with the AERONET (AErosol RObotic NETwork) database. AERONET is a world-wide network of automated instruments that provide spectral aerosol optical thickness (AOT), inversion products and precipitable water in geographically diverse regimes. The network has standardized procedures for all of its instruments, calibration and data processing. In this study we systematically compare all AOT determinations, over a two-year period, between 30 AERONET sites and coincident MISR AOT retrievals. The sites were chosen for having good long-term measurement records, and for capturing each of four broad classes of aerosol airmass types: maritime, biomass burning, desert dust, and continental aerosols. Available AERONET AOT for two-hour windows around MISR overpass times were interpolated to MISR wavelengths and averaged. MISR AOT over the 17.6 km standard retrieval regions that include the AERONET sites are preferentially used for the comparison. The MISR AOTs are averages of over all "successful" aerosol type models in the MISR retrieval, where success is measured by the degree to which multi-angle, multi-spectral top-of-atmosphere radiances match modeled radiances, using several chi-squared criteria. When there is no center-region MISR retrieval, the average of all available AOT retrievals in the eight surrounding regions is used. Comparisons for individual sites and aggregates by expected aerosol airmass types are presented, along with variance envelopes.

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