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[1] 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.

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Dust/sand storms are common events, and one of the most important manifestations of desertification to occur in the arid and semi-arid regions of Middle Asia. Middle Asian deserts are characterized by strong winds, scarcity of vegetation cover, a continental and Mediterranean type of climate with long dry summers, lack of soil moisture and relatively low air moisture, frequent repetition of soil and atmospheric droughts, susceptibility of soils to erosion. Systematic studies of dust storms in the middle Asian region started in the 1930s when "black" and "white" storms increased in frequency. Most of the scientific observations of natural phenomena, including dust storms, in the region ended after the collapse of the USSR, during the 1990s.The main objectives of this study are to monitor and assess the spatial and temporal distribution and activity of dust events over the Middle Asian region. The frequency and spatial distribution of dust storms for three periods of time: 1936-1960, 1936-1980, and 1970-2000 will be shown using meteorological data from almost 500 ground stations and Geographic Information System, (GIS) software. Dust storm activities during these three periods show significant decrease in frequency and considerable changes in the source areas.Temperature and rainfall trends also show significant changes across the region as well as remarkable changes in the annual and inter-annual trends. For the 1936-2000, temperature and rainfall annual trends show three periods of decreases and increases -periods, which correspond to the different atmospheric circulation epochs. This is a future challenge which will be studied in detail. An important goal is to reveal the correlation between the atmospheric circulation patterns (meridional, zonal), synoptic processes and dust storms.