Abstract. An Ultra-Violet Rayleigh-Mie lidar has been integrated aboard the French research aircraft Falcon20 in order to monitor the ash plume emitted by the Eyjafjallajökul volcano in April-May 2010. Three operational flights were carried out on 21 April, 12 and 16 May 2010 inside French, Spanish and British air spaces, respectively. The original purpose of the flights was to provide the French civil aviation authorities with objective information on the presence and location of the ash plume. The present paper presents the results of detailed analyses elaborated after the volcano crisis. They bear on the structure of the ash clouds and their optical properties such as the extinction coefficient and the lidar ratio. Lidar ratios were measured in the range of 43 to 50 sr, in good agreement with the ratios derived from groundbased lidar near Paris (France) in April 2010 (∼ 48 sr). The ash signature in terms of particulate depolarization was consistent during all flights (between 34 ± 3 % and 38 ± 3 %). Such a value seems to be a good identification parameter for volcanic ash. Using specific cross-sections between 0.19 and 1.1 m 2 g −1 , the minimum (maximal) mass concentrations in the ash plumes derived for the flights on 12 and 16 May were 140 (2300) and 250 (1500) µg m −3 , respectively. It may be rather less than, or of the order of the critical level of damage (2 mg m −3 ) for the aircraft engines, but well above the 200 µg m −3 warning level.
International audienceFollowing the eruption of the Icelandic volcano Eyjafjallajökull on the 14 April 2010, ground-based N2-Raman lidar (GBL) measurements were used to trace the temporal evolution of the ash plume from 16 to 20 April 2010 above the southwestern suburb of Paris. The nighttime overpass of the Cloud-Aerosol LIdar with Orthogonal Polarization onboard Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation satellite (CALIPSO/CALIOP) on 17 April 2010 was an opportunity to complement GBL observations. The plume shape retrieved from GBL has been used to assess the size range of the particles size. The lidar-derived aerosol mass concentrations (PM) have been compared with model-derived PM concentrations held in the Eulerian model Polair3D transport model, driven by a source term inferred from the SEVIRI sensor onboard Meteosat satellite. The consistency between model and ground-based wind lidar and CALIOP observations has been checked. The spatial and temporal structures of the ash plume as estimated by each instrument and by the Polair3D simulations are in agreement. The ash plume was associated with a mean aerosol optical thickness of 0.1{plus minus}0.06 and 0.055{plus minus}0.053 for GBL (355 nm) and CALIOP (532 nm), respectively. Such values correspond to ash mass concentrations of ~400{plus minus}160 and ~720{plus minus}670 µg m-3, respectively, within the ash plume, which was lower than 0.5 km in width. The relative uncertainty is ~75% and mainly due to the assessment of the specific cross-section assuming an aerosol density of 2.6 g cm-3. The simulated ash plume is smoother leading to integrated mass of the same order of magnitude (between 50 and 250 mg m-2
Abstract. An Ultra-Violet Rayleigh-Mie lidar has been integrated aboard the French research aircraft Falcon 20 in order to monitor the ash plume emitted by the Eyjafjallajökul volcano in April–May 2010. Three operational flights were carried out on 21 April, 12 and 16 May 2010 inside French, Spanish and British air spaces, respectively. The original purpose of the flights was to provide the French civil aviation authorities with objective information on the presence and location of the ash plume. The present paper presents the results of detailed analyses elaborated after the volcano crisis. They bear on the structure of the ash clouds and their optical properties such as ash extinction coefficient and lidar ratio. Lidar ratios were measured in the range of 33 to 48 sr, in good agreement with the ratios derived from ground-based lidar measurements performed near Paris (France) in April 2010 (∼47 sr). The ash signature in terms of particulate depolarization was consistent around 45 ± 7% during all flights. Such a value seems to be a good identification parameter for ash. Using specific cross-sections between 0.29 and 1.1 m2 g−1, the minimum (maximal) mass concentrations in the ash plumes are derived for the flights on 12 and 16 May. They were 190 (2300) and 270 (1600) μg m−3, respectively. It may be rather less than, or of the order of the critical level of damage (2 mg m−3) for the aircraft engines, but well above the 200 μg m−3 warning level.
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