Temporal trend in anthropogenic sulfur aerosol transport from central and eastern Europe to Israel

Decrease of sulfur emissions in central and eastern Europe over the past 3 decades is well documented and linked to changes in economic activity, use of different fuels, addition of pollution controls, etc. These changes result in a decreasing trend of sulfate aerosol and aerosol, forcing over the source region, but also at a receptor site located in southern, Israel, thousands of kilometers downwind of the original source. A combination of several independent observations, namely, satellite and ground-based remote sensing, in situ aerosol sampling, and backward trajectory analysis, was implemented to show significant downward trends in fine particle aerosol optical. thickness (AOT), in general, and sulfur aerosol, in particular, between 1995 and 2007. For the study years, MODIS-Terra observations over central and eastern Europe show 38% reduction of fine AOT. At the reception site in southern Israel, 43% reduction of fine AOT was observed by a ground-based sun/sky photometer and 25% reduction of sampled fine aerosols was obtained. During the corresponding observation periods, the coarse mode AOT has remained constant. The majority of the backward trajectories, where meaningful sulfur events were observed at the receptor site, are originated from eastern and central. Europe. The aerosol radiative effect at top of the atmosphere has become less negative during the past decade, decreasing by 30% in Europe and 67% in Israel. The decrease in negative cloud-free aerosol forcing is consistent with observations of "global brightening" reported since 1990.