Earlinet observations of the Eyjafjallajökull ash plume over Greece

Abstract

The arrival of the volcanic ash plume of the Eyjafjallajökull eruption was observed over Greece almost one week after its major eruption (on April 14, 2010) with two multi-wavelength Raman lidar systems, members of the EARLINET network. Intensive lidar measurements were performed throughout the event over Thessaloniki and Athens to derive the optical properties of the ash aerosols in the troposphere. During April 21, 2010 two layers of volcanic ash were present over Thessaloniki, one around 2.5 and one around 5 km height after circulating over central Europe. The first layer was persistent but with variable thickness, while the thin layer observed at 5 km height disappeared after some hours. Later on and at higher altitudes thin layers of ash were observed between 5 and 8 km, directly associated with the volcanic eruption. The observed layer at around and 3 km was persistently observed till April 28. The volcanic ash was observed over Athens, after passing over Southern Italy, during April and May 2010, in two height regions: between 6-10 km height and between 4 km and the ground level. We found that this was directly linked to the maximum height of the emitted volcanic ash. The most intensive period for ash presence over Athens was between April 21 and 23. In most cases, ash layers were very well stratified in the form of filaments starting around 3-4 km down to 1.5 km height. Mixing of ash with locally produced aerosols was frequently observed during the measuring period resulting to enhanced PM 10 concentrations at ground level. Volcanic ash was also observed during May 10-11 and 17-19, 2010, after being transported over Spain and Northern Italy. Both over Athens and Thessaloniki Saharan dust particles were mixed with volcanic ones on certain days of May 2010, which resulted to more complicated structures of the aerosol layers observed over Greece.