Evaluating aerosol optical properties observed by ground-based and satellite remote sensing over the Mediterranean and the Middle East in 2006

Abstract

This study evaluates the spatial and temporal variation of the aerosol optical depth (AOD), the particle size characteristics (Ångström coefficients) and single scattering albedos during selected episodes over the Mediterranean area in 2006, based on independent observational datasets. We compare the satellite data of MODIS and MISR with those of the ground-based AERONET and in situ measurements. In general the yearly mean MODIS and MISR AODs as well as their temporal variation are in good agreement with AERONET. The highest AODs are caused by mineral dust outbreaks and the accumulation of anthropogenic aerosols during stagnant meteorological conditions. The comparison of MODIS with MISR aerosol optical properties for June corroborates that the AODs, Ångström coefficients and single scattering albedos agree well, and indicates the presence of high dust loads over the Mediterranean. Later in summer, however, MISR AOD is generally lower than MODIS, which is consistent with previous studies that show that MISR tends to underestimate and MODIS tends to overestimate AOD over land when compared to AERONET observations. Comparing MODIS Aqua Deep Blue with MISR for June over the Saharan desert reveals some differences in the location and the maxima of the AODs. Over the eastern Mediterranean highest dust loads occur during spring and autumn. Biomass burning activities around the Black Sea during July and August cause high AODs (e.g. by agricultural waste burning), and the particulate pollution is transported to the eastern Mediterranean and the Middle East by the prevailing northerly Etesian winds.