SCIAMACHY TOA reflectance correction effects on Aerosol Optical Depth retrieval
Walter Di Nicolantonio(1), Alessandra Cacciari(1), Stefano Scarpanti(1), Giovanni Ballista(1), Enrico Morisi(1) and Rodolfo Guzzi(2)
(1) Carlo Gavazzi Space c/o ISAC-CNR, via Gobetti, 101, 40129 Bologna, Italy
(2) Italian Space Agency, viale Liegi, 26, 00198 Roma, Italy
Aerosol retrieval from SCIAMACHY data processing at ISAC-CNR has been carried-out to retrieve Aerosol Optical Depth (AOD) at 500 nm wavelength together with a parameter (class) which defines a set of chemico-physical properties pertaining to suspended particles. SCIAMACHY level 1B data from nadir measurements both over ocean and land are used as input for this processor. SCIAMACHY, onboard ENVISAT, is a remote sensing spectrometer measuring sunlight scattered, transmitted and reflected by the Earth's surface-atmosphere system. Its wavelength range spans from about 240 nm to about 2440 nm, with a spectral resolution varying from 0.24 nm in the UV to 1.56 nm in the NIR.
In this aerosol retrieval algorithm, working wavelengths are selected in the UV-VIS range characterized by negligible gases absorption, i.e. lower than 1%.
At these wavelengths, the measured TOA reflectances are corrected taking into account that SCIAMACHY underestimates the reflectance in the ultraviolet and visible range by 10 to 25% and by 10 to 20%, respectively.
Once reflectances, presenting values of cloud coverage fraction lower than 0.05, are properly corrected, they are fitted with modelled reflectances. The couple formed by AOD and class which minimizes the merit function represent the retrieved aerosols parameters for the spectrum being analysed.
SCIAMACHY data relative to 2003 and 2004 and in spatio-temporal coincidence with AERONET measurements have been considered.
The effect on the aerosol retrieval of the applied reflectance correction factors will be critically discussed and quantified.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,