Cluster analysis of back trajectories was combined with aerosol optical properties.
Clusters differ with respect to the speed of air mass flow and advection direction.
Clusters differ with respect to cluster means of AOT(500) and α(440,870).
Cluster mean AOT well correlates with frequency of occurrence of high sulphate AOT.
Mean α well correlates with occurrence of wind > 8 m s− 1 and high sulphate AOT.