Cluster analysis of an impact of air back-trajectories on aerosol optical properties at Hornsund, Spitsbergen

摘要

Abstract. In this paper spectra of aerosol optical thickness from AERONET (AErosol RObotic NETwork) station at Hornsund in the southern part of Spitsbergen were employed to study the impact of air mass history on aerosol optical thickness (AOT(500)) and Angstrom coefficient. Backward trajectories computed by means of NOAA HYSPLIT model were used to trace air history. It was found that in spring changes in AOT values over the Hornsund station were influenced by the at least 8-day trajectories of air, which was advected both in free troposphere and in the boundary layer. However, the free tropospheric advection was dominating. In summer the AOT variability was created mainly by local conditions, local direction and speed of advection (1-day trajectories). During the ASTAR 2007 campaign aerosols near Hornsund showed low AOT values ranging from 0.06 to 0.09, which is lower than the mean AOT(500) for spring seasons from 2005 to 2007 (0.110±0.007; mean ± standard deviation of mean). The 9 April 2007 with AOT(500)=0.147 was an exception. Back-trajectories belonged to the clusters of low and average cluster mean AOT value. Beside the maximum AOT of the 9 April 2007, the observed AOT values were close to the means for the clusters to which they belonged or were lower than the means.