Improving the monitoring of Etna's volcanic ash plumes using a new scanning Lidar

Since 2011 several lava fountains episodes have occurred at Etna. The volcanic activity produces eruption columns that may reach up to 10 km a.s.l. and eject to the atmosphere large amounts of volcanic ash. Volcanic ash particles dispersed in the atmosphere are dangerous to aviation operations and should be continuously monitored. In particular, the spatial distribution of volcanic ash and the estimation of the mass concentration in air are an essential information to forecast the volcanic ash plume evolution. For this reason, a new lidar with scanning capability has been recently realized by CNISM (Consorzio Nazionale Interuniversitario per le Scienze fisiche e della Materia) and funded by the VAMOS SEGURO project (www.ct.ingc.it/vamosseguro). The lidar laser transmitter works at 355 nm, the laser power is 0.6 W, the laser beam divergence is 0.3 mrad, the pulse width is 1 ns, and the laser repetition rate is 1 kHz. The lidar may also be easily transported to three different locations: Montedoro (CL), Serra La Nave Observatory, only 7 km away from the Etna summit craters, and to INAF - Catania Astrophysical Observatory, about 7 km from the International airport Fontanarossa. Zenithal Lidar measurements have been routinely carried out during days without eruptive activity. When lava fountain events occurred the Lidar beam was directed toward the volcanic plume with the aim to investigate physical properties of volcanic aerosols. In this work, preliminary results of data collected during the first months of 2013 are investigated. Reported measurements show how a scanning Lidar used near an active volcano is useful for analyzing both the background of atmospheric aerosols and some features of volcanic ash dispersion.