1. Aerosol Pattern over Southeastern Europe Rudolf B. Husar and Janja D. Husar CAPITA, Washington University, St. Louis, MO Conference on Visibility, Aerosols, and Atmospheric Optics Vienna, September 11-15, 2000 http://capita.wustl.edu/capita/capitareports/SEEuropeAerosol/SEEuropeAerosolVienna/

2. Aerosols over Southeastern Europe Southeastern Europe is a poorly documented, aerosol-rich region with multiple aerosol types Southeastern Europe has several topographically confined air basins including the Po River Valley, Pannonia and the Lower Danube River basin. The Eastern Mediterranean is surrounded by these basins as well as North Africa.

3. Sulfur and Dust Emission Regions The S emission density is moderately high over the Po River, Pannonia and Lower Danube basins. TOMS data for the summer season show a gradient of Sahara dust over the the Mediterranean.

4. Seasonal Fire Locations over Europe (IONIA) Biomass fires are most prevalent in Southern Europe during the summer season.

5. Seasonal Light Extinction Coefficient ( Visibility ) The winter season has the highest Bext The Po River Basin is always hazy

6. Satellite detection of haze (SeaWiFS) Satellite images (RBG truecolor, left; 0.4 um, right) show qualitative features of haze, quantitative detection over land is yet available Note the haze in the low-lying basins, Po River, Pannonia and L. Danube. In the winter the mountains extrude from the shallow haze layers.

7. Long-term Pattern of Dry Bext Long-term data (1982-97) shows trends and year-to-year variability The fraction of data with precipitation peaks in the fall/winter season (> 60% of the time) In the Fall and Winter, satellite aerosol detection is possible < 10% of time Since 1982 at Budapest, there is slight decrease of Bext (in the absence of precipitation)

8. Seasonal Pattern of Dry and Wet Bext Seasonal pattern illustrates the role of weather (precipitation, fog) The ‘wet’ Bext using all data has a strong (factor of 8) fall/winter peak The ‘dry’ Bext in the absence of precipitation has a ( x 3) fall/winter peak

9. Diurnal Pattern of Dry and Wet Bext Diurnal pattern is most influenced by humidity and aerosol sources The ‘wet’ Bext peaks in late night due to high RH The ‘dry’ Bext peaks in the early morning hours

10. Long-term, Seasonal and Diurnal Bext at Vienna The precipitation is most frequent (>50%) during the fall/winter There is a slight decline of dry Bext decline 1982 The strong Bext seasonality is mostly due to precipitation The diurnal cycle of Bext is also due to precipitation and RH

11. Seasonal Pattern Aerosol Index, PAI (POLDER Satellite) The lowest PAI is observed in the winter (note the absence of winter data) In Highest PAI values are the spring (Po River, Pannonia, L. Danube, Poland) Over the E. Mediterranean, highest values are in he summer

12. Aerosol Optical Depth and Angstrom Exp. ( POLDER ) The oceanic AOT is Low in December and higher in June, particularly over the central Mediterranean The Angstorm exponent is high over the Black Sea and North Sea and lower over the Mediterranean.

13. Dust and Smoke over the Mediterranean (SeaWiFS, TOMS) SeaWiFS data for August 25, 2000 show that the Eastern Mediterranean was covered by Sahara dust (W. of Barcelona, Sardinia) and smoke from forest fires (Corsica, Adriatic, Algiers). The elevated dust was also detected by the TOMS satellite but the low-level forest fire smoke was not.

14. Smoke over the Adriatic, August, 2000 a. During the convective hours the smoke is well mixed up to 1-2 km. b. In the evening, the elevated smoke layer is decoupled from the boundary layer a. Occasionally, the smoke has reduced the visibility to below 2 km. b. Sunset observations indicate that most of the smoke was in the BL, with some elevated layers.

15. Vertical Dispersion of Smoke During the convective hours (5 pm) the smoke is well mixed up to about 2 km. As the solar heating diminishes (7 pm), a distinct smoke layer appears. By the evening (8 pm), the smoke layer is decoupled from the boundary layer and rises to 2-3 km.

16. Extreme Visibility Variation Following the gail-strength ‘bora’ winds, the visual range exceeds 120 km. During smoke events, the mid-day visibility is frequently below 2 km.

17. Sunset Observations of Haze Depth Sunset observations indicate that on August 17, 2000, most of the haze (smoke ?) was in the BL, with some in elevated layers. On other days, the haze layer was much deeper.

18. SE Europe: Sulfate in the winter, dust and smoke in the summer In the winter, the high Bext is due to industrial sulfur and related emissions In the summer, the higher Bext in SE Europe is mostly due to due to biomass smoke and dust Confirmation of the above through speciated chemical data would be highly desirable

19. Summary Southeastern Europe is a poorly documented, aerosol-rich region with multiple aerosol types –The region is naturally delineated by the Alps and the Carpathian Mountains Data are available from a diverse set of surface and satellite observations –Visibility (Seasonal maps, trends, seasonal and diurnal pattern, WebCams) –POLDER satellite (‘Climatological’ Aerosol Index, AOT, Angtsrom Exponent) –Dynamic SeaWiFS, TOMS –Emissions (SOx, Dust, Fires) Winter aerosol pattern –highest aerosol over inland sulfur emission areas –strong role of wet meteorology –aerosol is confined to lower layers and basins –satellite detection not possible due to cloudiness Summer aerosol pattern –highest aerosol over southern Europe; Sahara dust and biomass smoke dominate the Mediteran –atmosphere is dry, humidity not a major factor –aerosol is layered, up to 4 km – smoke usually in lower, dust in higher layers –satellite detection is useful The above conclusions are based on semi-quantitative data. Speciated and size segregated aerosol data would allow a firm source apportionment over over Southeastern Europe