GOME aerosol optical depth retrieval over ocean: Correcting for the effects of residual cloud contamination

Aerosol optical depths (AODs) retrieved from GOME reflectances using a clear sky algorithm have been compared to AODs from ground-based sunphotometers. A systematic overestimation of GOME AOD was found, mainly due to the presence of clouds within the GOME field-of-view. In order to take the influence of clouds into account, a model which assumes a linear dependence of AOD on cloud fraction has been tested. This model was validated using independent measurements from different AERONET sites. The monthly averaged maps of corrected AOD show similar spatial behaviour to AVHRR and TOMS maps. The method proposed here produces monthly maps of AOD from GOME data. It is applicable on a statistical analysis (monthly) and is proved to be effective in regions with high AOD, but relatively large uncertainties remain for background marine conditions.