Abstract
Coincident observations made over the Moroccan desert during the Sahara mineral dust experiment (SAMUM) 2006 field campaign are used both to validate aerosol amount and type retrieved from multi-angle imaging spectroradiometer (MISR) observations, and to place the suborbital aerosol measurements into the satellite’s larger regional context. On three moderately dusty days during which coincident observations were made, MISR mid-visible aerosol optical thickness (AOT) agrees with field measurements point-by-point to within 0.05–0.1. This is about as well as can be expected given spatial sampling differences; the space-based observations capture AOT trends and variability over an extended region. The field data also validate MISR’s ability to distinguish and to map aerosol air masses, from the combination of retrieved constraints on particle size, shape and single-scattering albedo. For the three study days, the satellite observations (1) highlight regional gradients in the mix of dust and background spherical particles, (2) identify a dust plume most likely part of a density flow and (3) show an aerosol air mass containing a higher proportion of small, spherical particles than the surroundings, that appears to be aerosol pollution transported from several thousand kilometres away.
Highlights
Satellite instruments such as the multi-angle imaging spectroradiometer (MISR) routinely produce global maps reporting aerosol amount and type
The MISR team participated actively in Sahara mineral dust experiment (SAMUM) field operations; this paper provides a summary of our initial scientific results
We begin with a brief review of the aerosol amount and property constraints produced by MISR over the study region, comparing values and trends with near-simultaneous field data acquired during SAMUM
Summary
Satellite instruments such as the multi-angle imaging spectroradiometer (MISR) routinely produce global maps reporting aerosol amount and type. The multi-angle imaging spectroradiometer makes nearsimultaneous measurements at nine view-angles spread out in the forward and aft directions along the flight path, at ±70.5 ̊, ±60.0 ̊, ±45.6 ̊, ±26.1 ̊, and nadir, in each of four spectral bands centred at 446, 558, 672 and 866 nm (Diner et al, 1998) With these observations, the instrument systematically covers a range of air mass factors (slant paths through the atmosphere). The maps provide context for the more detailed but less extensive measurements made by the aircraft and ground-based platforms We present here both initial validation results and regional maps for three Golden Days, days during which aircraft and surface data were acquired coincident with the MISR overpasses: 19 May, 28 May and 4 June 2006.
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