Aerosol physical and optical properties in the Eastern Mediterranean Basin, Crete, from Aerosol Robotic Network Data

A. Fotiadi (1, 2) , E. Drakakis (2, 3) , N. Hatzianastassiou (2, 4) , C. Matsoukas (2, 5) , K. G. Pavlakis (1, 2, 6) , D. Hatzidimitriou (1, 2) , E. Gerasopoulos (7, 8) , N. Mihalopoulos (7) , I. Vardavas (1, 2)

1 Department of Physics
2 Foundation for Research and Technology-Hellas
3 Department of Electrical Engineering
4 Laboratory of Meteorology [Ioannina]
5 Department of Environment [Mytilene]
6 Department of General Applied Science
7 ECPL - Environmental Chemical Processes Laboratory [Heraklion]
8 Institute for Environmental Science and Sustainable Development

In this study, we investigate the aerosol optical properties, namely aerosol optical thickness (AOT), Angström parameter (?_440?870 and size distribution parameters over the Eastern Mediterranean Basin, using spectral measurements from the recently established FORTH (Foundation for Research and Technology-Hellas) AERONET station in Crete, for the two-year period 2003?2004. The location of the FORTH-AERONET station offers a unique opportunity to monitor aerosols from different sources. The AOT is maximum during spring, because of the high dust load transported mainly from African deserts, and minimum in winter. There are secondary maxima in AOT at 870 and 1020 nm in October, attributed to dust transport events occurring in autumn. Large values of AOT at 340 and 500 nm persisting during summer are associated with transport of fine aerosols of urban/industrial and biomass burning origin. The dust events are characterised by a drastic increase in AOT at all wavelengths accompanied by a drastic decrease in Angström parameter to values below 0.3. The mean annual values of AOT₃₄₀, AOT₅₀₀, AOT₈₇₀ and ?_440?870, are equal to 0.34±0.14, 0.21±0.11, 0.11±0.09 and 1.17±0.53 respectively. The scatterplots of Angström parameter versus aerosol optical thickness indicate a great variety of aerosol types over the study region including dust, urban-industrial/biomass burning, maritime, as well as mixed aerosol types. This is supported by back-trajectory analyses, and agrees with the measurements of experimental campaigns that took place in Crete during summer. The aerosol volume-size distributions are bimodal over all seasons, with a fine and a coarse mode having effective mean radius of 0.13 ?m and 2.12 ?m, respectively, and columnar volume concentrations of about 0.038 and 0.061 ?m³/?m². There is a general dominance of coarse to fine mode in terms of aerosol volume, in agreement with other maritime locations persisting through the year except for summer. Our analysis shows that the highest values of AOT are related to wind directions from the east, southeast and south, as well as from northwest. Northwestern winds are associated with maximum fine aerosol loads from industrial areas, while eastern, southeastern and southern winds are related to maximum coarse aerosol loads, namely sea salt and desert dust.

Domaines: Océan, Atmosphère

A. Fotiadi, E. Drakakis, N. Hatzianastassiou, C. Matsoukas, K. G. Pavlakis, et al.. Aerosol physical and optical properties in the Eastern Mediterranean Basin, Crete, from Aerosol Robotic Network Data. Atmospheric Chemistry and Physics Discussions, 2006, 6 (4), pp.7791-7834. ⟨hal-00302062⟩