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

[摘要] In this study, we investigate the aerosol optical properties, namely aerosolextinction optical thickness (AOT), Angström parameter and sizedistribution over the Eastern Mediterranean Basin, using spectralmeasurements from the recently established FORTH (Foundation for Researchand Technology-Hellas) AERONET station in Crete, for the two-year period2003–2004. The location of the FORTH-AERONET station offers a uniqueopportunity to monitor aerosols from different sources. Maximum values ofAOT are found primarily in spring, which together with small values of theAngström parameter indicate dust transported from African deserts,whereas the minimum values of AOT occur in winter. In autumn, large AOTvalues observed at near-infrared wavelengths arise also from dust transport.In summer, large AOT values at ultraviolet (340 nm) and visible wavelengths(500 nm), together with large values of the Angström parameter, areassociated with transport of fine aerosols of urban/industrial and biomassburning origin. The Angström parameter values vary on a daily basiswithin the range 0.05–2.20, and on a monthly basis within the range 0.68–1.9.This behaviour, together with broad frequency distributions andback-trajectory analyses, indicates a great variety of aerosol types overthe study region including dust, urban-industrial and biomass-burningpollution, and maritime, as well as mixed aerosol types. Large temporalvariability is observed in AOT, Angström parameter, aerosol content andsize. The fine and coarse aerosol modes persist throughout the year, withthe coarse mode dominant except in summer. The highest values of AOT arerelated primarily to southeasterly winds, associated with coarse aerosols,and to a less extent to northwesterly winds associated with fine aerosols.The results of this study show that the FORTH AERONET station in Crete iswell suited for studying the transport and mixing of different types ofaerosols from a variety of sources, especially those associated with majordust events from the Sahara.

[学科分类] 大气科学