SCOUT aerosol campaign: Temporal and spatial variations of aerosols at Thessaloniki, Greece

Aerosol spatial and temporal variability was investigated during a 10-day measurement campaign. The campaign took place at an environment with high aerosol load (Thessaloniki, Greece) in July 2006. Measurements of aerosol optical depth and Angstrom coefficients at the city center were compared with values measured at a site located 20 Km outside the city limits. For most of the cases the aerosol optical depth was similar even for days with high aerosol variability. During the 10-day period of the campaign aerosol optical depth at 340nm varied from 0.2 to 1.0. Lidar observations confirmed that for the first 5 days of the campaign aerosol layers from 1.5 to 2.5 Km contributed up to 50% to the total column aerosol load. The effect of the aerosol presence on solar UV irradiance was quantified. Comparing two cloudless days (23 rd and 25 th of July, 2006) we found that the UV irradiance difference at 340 nm between the two days was up to 30% depending on the aerosol optical depth difference and the solar zenith angle. Similar comparisons with a cloudless sky, aerosol free scenario using a radiative transfer model showed attenuation up to 20% for local noon UV irradiance.