1National Technical University of Athens, Physics Department, Laser Remote Sensing Laboratory, 15780, Zografou, Greece
2Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Athens, Greece
3Department of Civil Engineering and Geomatics, Cyprus University of Technology, Lemessos, Cyprus
4Physics Instrumentation Center of General Physics Institute, Troitsk, Moscow 142190, Russia
5Norwegian Institute for Air Research, Kjeller, Norway
6Consiglio Nazionale delle Ricerche – Istituto di Metodologie per l'Analisi Ambientale, C. da S. Loja, 85050 Tito Scalo, Potenza, Italy
Abstract. Vertical profiles of the optical (extinction and backscatter coefficients, lidar ratio and Ångström exponent), microphysical (mean effective radius, mean refractive index, mean number concentration) and geometrical properties, as well as of the mass concentration of volcanic particles from the Eyjafjallajökull eruption were retrieved at selected heights over Athens, Greece using a multi-wavelength Raman lidar system and inversion models, during 21–24 April 2010. Additionally, Aerosol Robotic Network (AERONET) particulate columnar measurements indicated the presence of volcanic particles over our area. Simulations of the volcanic partilcles dispersion, done by the FLEXPART model, confirmed the presence of these particles over Athens. Our lidar data showed volcanic particles layers, in the form of filaments after 7-day transport from the source (approximately 4000 km away from our site) between from ground levels up to nearly 10 km. Over Athens the volcanic particles layers were found to be mixed with locally produced aerosols, inside the Planetary Boundary Layer (PBL). Mean hourly-averaged lidar signals indicated that the layer thickness of volcanic particles, ranged between 1.5 and 2.2 km. The corresponding aerosol optical depth (AOD) found to vary from 0.014 to 0.184 at 355 nm and from 0.017 up to 0.174 at 532 nm. Furthermore, the corresponding lidar ratios (LR) ranged between 59.7–79.6 sr (at 355 nm) and 43.9–88.3 sr (at 532 nm). Additionally, we calculated that the mean effective radius of the volcanic particles was 0.13–0.38 μm, while their refractive index ranged from 1.39+0.009i to 1.48+0.006i. Finally, our data also allowed us to quantitatively compare, for the first time, the volcanic ash concentrations simulated by FLEXPART with those calculated by the inversion code LIRIC, using data sets derived from coincident lidar-AERONET measurements. In general, good agreement was found between simulations and observations, concerning not only the geometrical properties of the volcanic particles layers, but also the particles mass concentration, with a correlation coefficient of the order of 0.75.