Variability in aerosol optical properties at Hornsund, Spitsbergen

Spectra of the aerosol optical thickness from the AERONET station at Hornsund in 2005-2008 were employed to study the interseasonal and intraseasonal variability in aerosol optical thickness for λ=500 nm (AOT(500)) and the Angström exponent in the southern part of Spitsbergen in spring and summer. The dependences of aerosol optical properties on long-range transport and local meteorological conditions, i.e. wind direction and speed and humidity, were analysed. Backward trajectories computed by means of NOAA HYSPLIT model (Draxler & Rolph 2003) were used to trace the air mass history. The mean values of AOT(500) for spring and summer were 0.110 ± 0.007 (mean and standard deviation of the mean) and 0.048 ± 0.003 respectively. The average values of the Angström exponent do not differ and take respective values of 1.44 ± 0.03 and 1.45 ± 0.03. In both seasons, the highest AOT(500) cases (the highest 20% of AOT values) can be explained by long-range transport from Europe, Asia (spring and summer) and North America (summer). In summer, the impact of distant sources on AOT is strongly modified by cleansing processes en route to Hornsund. Local meteorological conditions at the station are of secondary importance as regards the intraseasonal variability of aerosol optical properties in the southern part of Spitsbergen.