Aerosol optical thickness and classification: use of METEOSAT, GOME and modelled data

Satellite measurements at high spectral resolution and span that avoid gas absorption bands and determine aerosol spectral optical properties are necessary for obtaining aerosol optical thickness values at the reference wavelength of 550 nm thereinafter AOT). GOME (Global Ozone Monitoring Experiment on board the ERS-2 spacecraft) measurements fit such requirements, with a suitable spectral resolution over the region between UV and near IR while presenting a low spatial (320x40 Km(2)) and temporal resolution. The present new method overcomes these limitations by combining aerosol optical characteristics retrieved from GOME with METEOSAT visible data; the latter allow for monitoring aerosol events with adequate temporal resolution over wide cloud-free oceanic areas. The AOT results from fitting the measured broad-band visible METEOSAT radiance with the simulated radiance from radiative transfer calculations; aerosol properties estimated from GOME data are the essential input parameters. Several parameterisations of aerosol microphysical quantities have been tested to improve the AOT retrievals.