Articles | Volume 16, issue 9
https://doi.org/10.5194/acp-16-5705-2016
https://doi.org/10.5194/acp-16-5705-2016
Research article
 | 
10 May 2016
Research article |  | 10 May 2016

Validation of ash optical depth and layer height retrieved from passive satellite sensors using EARLINET and airborne lidar data: the case of the Eyjafjallajökull eruption

Dimitris Balis, Maria-Elissavet Koukouli, Nikolaos Siomos, Spyridon Dimopoulos, Lucia Mona, Gelsomina Pappalardo, Franco Marenco, Lieven Clarisse, Lucy J. Ventress, Elisa Carboni, Roy G. Grainger, Ping Wang, Gijsbert Tilstra, Ronald van der A, Nicolas Theys, and Claus Zehner

Abstract. The vulnerability of the European airspace to volcanic eruptions was brought to the attention of the public and the scientific community by the 2010 eruptions of the Icelandic volcano Eyjafjallajökull. As a consequence of this event, ash concentration thresholds replaced the “zero tolerance to ash” rule, drastically changing the requirements on satellite ash retrievals. In response to that, the ESA funded several projects aiming at creating an optimal end-to-end system for volcanic ash plume monitoring and prediction. Two of them, namely the SACS-2 and SMASH projects, developed and improved dedicated satellite-derived ash plume and sulfur dioxide level assessments. The validation of volcanic ash levels and height extracted from the GOME-2 and IASI instruments on board the MetOp-A satellite is presented in this work. EARLINET lidar measurements are compared to different satellite retrievals for two eruptive episodes in April and May 2010. Comparisons were also made between satellite retrievals and aircraft lidar data obtained with the UK's BAe-146-301 Atmospheric Research Aircraft (managed by the Facility for Airborne Atmospheric Measurements, FAAM) over the United Kingdom and the surrounding regions. The validation results are promising for most satellite products and are within the estimated uncertainties of each of the comparative data sets, but more collocation scenes would be desirable to perform a comprehensive statistical analysis. The satellite estimates and the validation data sets are better correlated for high ash optical depth values, with correlation coefficients greater than 0.8. The IASI retrievals show a better agreement concerning the ash optical depth and ash layer height when compared with the ground-based and airborne lidar data.

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Short summary
The ESA-funded SACS-2 and SMASH projects developed and improved dedicated satellite-derived ash plume and sulfur dioxide level assessments. These estimates were validated using ground-based and aircraft lidar measurements. The validation results are promising for most satellite products and are within the estimated uncertainties of each of the comparative data sets. The IASI data show a better consistency concerning the ash optical depth and ash layer height.
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