PM10 excedances and ceilometer observations due to a prolonged Saharan dust episode over the Eastern Alps

In April 2016, a Saharan dust cloud reached Central Europe, leading to enhanced PM10 concentrations and reduced visibility. Particle matter concentrations significantly increased at the Austrian mountain stations Hoher Sonnblick (3106 m a.s.l.), Dobratsch (2166 m a.s.l.) and Feuerkogel (1592 m a.s.l.) between April 3 and April 6, 2016. On April 5, 2016, daily concentrations exceeded 50 μgm-3 PM10 at most air quality stations in the Eastern Alpine area. The emission and transport of the Saharan dust cloud towards Central Europe is forecasted as well as analysed with the online coupled model WRF-Chem. The evolution of the atmospheric boundary layer (ABL) at the Eastern Alpine ridge is observed by a network of ceilometers; from the vertical backscatter profiles of these instruments, the aerosol load (qualitatively) and the mixing height are deduced. These data are especially valuable to distinguish whether PM10 concentrations are mainly influenced by long-range transport or by advection of aerosols from the ABL. Lagrangian particle dispersion modelling (FLEXPART) in backward mode is used to identify major source regions. The measurements and model results deliver a detailed picture of the onset, course, peaks and decay of this dust event over the Eastern Alpine region.