The transport of aerosol in the troposphere during the 2002 eruption of Mount Etna was investigated integrating lidar observations and numerical simulations. The case study concentrates on the period 30 October to 2 November. The lidar observations performed in Potenza, Italy, reveal the presence of aerosol layers made up of young sulfate particles and a low soot content, characteristic of the volcano's emission. Downward large-scale motion was measured, with a velocity larger than that due to gravitational sedimentation. Forward trajectories from the volcano simulated from 27 October to 4 November show that particles released at the beginning of the period reached Potenza after traveling over the southern and western Mediterranean basin (partially including the Sahara region); direct northward transport occurred on 31 October and 1 November. The main result of this study is to highlight how the integrated use of observations and model simulations leads to understanding the main features of transport in this case study. Furthermore, some specific points are outlined. There is fair agreement between the simulated and observed presence of particles over Potenza. The vertical structure of the aerosol layers and the downward motion are also well evidenced. Time variations of the particle concentration deduced from measurements and approximately estimated from the numerical simulations also show qualitative agreement. Copyright 2006 by the American Geophysical Union.

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