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

Abstract

[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.

Analysis of linear long-term trend of aerosol optical thickness derived from SeaWiFS using BAER over Europe and South China

“…Figure 10 shows the seasonal distributions of BAER AOTs (443 nm), which are good at examining the seasonal variation of AOT in the regions. Over European regions (BeNeLux, Po Valley, Eastern Europe, and Eastern Mediterranean), aerosols have a strong seasonal variation because industrial pollution composed of sulphur is enhanced during summer, when the solar radiation at the surface maximizes (Marmer et al, 2007;Karnieli et al, 2009). Furthermore, forest fires in Southern Europe, occurring mostly in summer, may well contribute to seasonal variation (Pace et al, 2006;Tafuro et al, 2008) and significant dust loads coming from northern African deserts are frequently observed over Mediterranean in spring and summer (Hatzianastassiou et al, 2009).…”

“…Even though this linear model may not be the real, it allows a simple approximation of direction and magnitude of the changes in the data for many practical purposes (Weatherhead et al, 1998). Many previous studies also have adopted the simple model for AOT trend analysis Zhao et al, 2008;Papadimas et al, 2008;Yu et al, 2009;Xie and Xia, 2008;Kishcha et al, 2009;Karnieli et al, 2009;de Meij et al, 2010;Kaskaoutis et al, 2011). This study used the simple linear model for AOT trend comparisons.…”

“…However, aerosol layer height and subpixel cloud contamination have a serious influence on the retrieval accuracy of aerosol using the near ultraviolet channel of TOMS Torres et al, 1998Torres et al, , 2002. Karnieli et al (2009) provided temporal trends of anthropogenic sulphur aerosol transported from central and Eastern Europe to Israel with independent data sets such as MODISTerra, CIMEL sun/sky photometer, and PM 10 Stacked Filter Unit sampler. For each research period between 1995 to 2007, MODIS-Terra (2000 observed 38 % reduction of fine AOT over central and Eastern Europe, a groundbased sun/sky photometer (1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007) showed 43 % reduction in southern Israel, and the aerosol sampler (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004) obtained 25 % reduction of fine aerosols mass.…”

Atmospheric pollution over the eastern Mediterranean during summer – a review

“…This decline is attributed to the decrease of S emissions in central and eastern Europe over the past 3 decades. Indeed, the majority (60 %) of the calculated air mass back trajectories related to extreme events (during which the fine fraction S concentration at Sde Boker exceeded a threshold of 3 µg m −3 ) originated from Russia, Ukraine, and the northern Black Sea region (Karnieli et al, 2009). …”

Three-year ground based measurements of aerosol optical depth over the Eastern Mediterranean: the urban environment of Athens

“…Formenti et al, 2001;Andreae et al, 2002;Gerasopoulos et al, 2003;Fotiadi et al, 2006;Kazadzis et al, 2007) and satellite based studies (e.g. Barnaba and Gobbi, 2004;Papadimas et al, 2008;Hatzianastassiou et al, 2009;Karnieli et al, 2009;Koukouli et al, Published by Copernicus Publications on behalf of the European Geosciences Union. E. Gerasopoulos et al: Three-year ground based measurements of aerosol optical depth 2010).…”