Optical properties of long-range transported volcanic ash over Romania and Poland during Eyjafjallajokull eruption in 2010

After Eyjafjallajokull volcano eruption on 14 April 2010, due to a complex air mass circulation, Romania was exposed to volcanic ash and its mixture with continental aerosols. Ash particles with an average ngstrom (UV-VIS) exponent of 1.4 +/- 0.2 and (VIS-IR) of 1.2 +/- 0.3, a color ratio (VIS-UV) of 0.54 and (IR-VIS) of 0.49, an average particle depolarization value similar to 9.4%, and a lidar ratio of 50 sr were retrieved on 18 April from multiwavelength Raman lidar measurements in Bucharest. Mixed volcanic ash with mineral dust particles advected from Sahara, depolarization similar to 12%, ngstrom (UV-VIS) exponent of 1.25 +/- 0.25 and (VIS-IR) of 1.45 +/- 0.25, an increased color ratio (VIS-UV) of 0.61, (IRVIS) of 0.39 and lidar ratio of 53 sr were identified on 28 April. From observations in Poland conducted by an elastic lidar at 532 nm and a ceilometer at 1064 nm we retrieved an average backscatter related ngstrom (VIS-IR) exponent of 1.25 +/- 0.35, and a color ratio (IR-VIS) of 0.53 in the layer at about 5.5 km during the night of 16/17 April, indicating fresh ash over Warsaw.