Simulations of the 2010 Eyjafjallajökull volcanic ash dispersal over Europe using COSMO–MUSCAT

The ash plume of the Icelandic volcano Eyjafjallajökull covering Europe in April and May 2010 has notably attracted the interest of atmospheric researchers. Emission, transport, and deposition of the volcanic ash are simulated with the regional chemistry-transport model COSMO–MUSCAT. Key input parameters for transport models are the ash injection height, which controls the ash layer height during long-range transport, and the initial particle size distribution, which influences the sedimentation velocity. For each model layer, relative release rates are parameterised using stereo-derived plume heights from NASA’s space-borne Multi-angle Imaging SpectroRadiometer (MISR) observations near the source. With this model setup the ash is emitted at several levels beneath the maximum plume heights reported by the Volcanic Ash Advisory Centre (VAAC) London. The initial particle size distribution used in COSMO–MUSCAT is derived from airborne in-situ measurements. In addition, the impact of different injection heights on the vertical distribution of the volcanic ash plume over Europe is shown. Ash emissions at specific control levels allow to assess the relative contribution of each layer to the spatial distribution after transport. The model results are compared to aerosol optical depths from European Sun photometer sites, lidar profiles measured over Leipzig/Germany, and ground-based microphysical measurements from several German air quality stations. In particular the good agreement between modelled vertical profiles of volcanic ash and lidar observations indicates that using the MISR stereo-height retrievals to characterize atmospheric ash input provide an alternative to injection height models in case of lacking information on eruption dynamics.