World Meteorological Organization

GRASP (Generalized Retrieval of Aerosol and Surface Properties) retrieves both properties of aerosol and surface reflectance from PARASOL/POLDER observations. GRASP performs atmospheric radiation calculation on line. The retrieval is implemented as statistically optimized fitting and retrieves extended set of aerosol parameters including size distribution, complex refractive index, and fraction of non-spherical fraction. GRASP uses multi-pixel retrieval approach when retrieval is performed simultaneously for a group of observed satellite pixels. This principle allows for improving robustness of the retrieval by using additional constraint on temporal and spatial variability of retrieved parameters.

Example result

Satellite PARASOL (CNES)
Instrument(s) POLDER
Instrument / Algorithm PI Oleg Dubovik, Universite Lille-1
Contact Details oleg.dubovik[at]

Spectral AOD, spectral SSA, fraction  of spherical particles, aerosol fraction

Aerosol algorithm

GRASP (Generalized Retrieval of Aerosol and Surface Properties)

Cloud screening PARASOL operational
Aerosol model no precalculated models, solution in continues space
Retrieval assumptions 1 radiative transfer model, BRDF for surface reflectance, aerosol is modelled as polydisperse mixture of spheres and randomly oriented    homogeneous spheroids with complex refractive index independent on size
Retrieval limitations relatively long time of calculation
Spatial, temporal coverage 2008 / Africa + further selected regions
Spatial, temporal resolution

5.2 x 6.2 km / swath width: 1600 km / polar : global coverage in 2 days

Operations status experimental
Validation status major characteristics
Quality control fitting residual
last algorithm version 01/GRASP (03/2015)
last validation



Algorithm description Product format description
Version explanation Validation summary


Product data access
Image / quicklook data access