Investigation of the complex dynamics and structure of the 2010 Eyjafjallajökull volcanic ash cloud using multispectral images and numerical simulations

摘要

We investigated the structure and evolution of the 2010 Eyjafjallajökull volcanic cloudand its dispersal over Iceland and Europe integrating satellite multispectral images and numerical simulations. Data acquired by Medium Resolution Imaging Spectrometer (MERIS)and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) have been analyzed to quantify the cloud extent and composition. The VOL-CALPUFF dispersal codewas applied to reconstruct the transient and 3-D evolution of the cloud. Source parameters estimated on the base of available a posteriori volcanological data sets have been used. Quantitative comparisons between satellite retrievals and modeling results were performed for two selected instants of time during the first and third eruptive phases on a regional scale. Sensitivity of the model to initial volcanological conditions has been analyzed at continental scale. Several complex non intuitive features of cloud dynamics have been highlighted andstrengths and limitations of the adopted methods identified. The main findings are: the level ofquantitative agreement between satellite observations and numerical results depends on ashcloud composition (particle sizes and concentration) with better agreement for smallerparticles and higher concentrations; the agreement between observations and modelingoutcomes also depends on the temporal stability of volcanological conditions and thecomplexity of the meteorological wind field; the irregular dispersion of ash, as reconstructedfrom satellite data and numerical modeling, can be well explained by the different response ofparticle sizes to strong vertical wind-shear, and by resuspension processes acting at ground level; eruptive source conditions are the main source of uncertainty in modeling, especially during an ongoing crisis and at long-range scales.