1Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Thessaloniki, Greece
2Consiglio Nazionale delle Ricerche, Istituto di Metodologie per l'Analisi Ambientale (CNR-IMAA), Tito Scalo, Potenza, Italy
3Met Office, Exeter, UK
4Université Libre de Bruxelles, Brussels, Belgium
5National Centre for Earth Observation, Atmospheric, Oceanic and Planetary Physics, University of
Oxford, Oxford, UK
6COMET, Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford, UK
7Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands
8Belgian Institute for Space Aeronomy (IASB-BIRA), Brussels, Belgium
9European Space Agency, ESRIN, Frascati, Italy
Received: 22 Dec 2015 – Discussion started: 19 Jan 2016
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.
Revised: 26 Apr 2016 – Accepted: 27 Apr 2016 – Published: 10 May 2016
Balis, D., Koukouli, M.-E., Siomos, N., Dimopoulos, S., Mona, L., Pappalardo, G., Marenco, F., Clarisse, L., Ventress, L. J., Carboni, E., Grainger, R. G., Wang, P., Tilstra, G., van der A, R., Theys, N., and Zehner, C.: 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, Atmos. Chem. Phys., 16, 5705-5720, doi:10.5194/acp-16-5705-2016, 2016.