Determination of time- and height-resolved volcanic ash emissions and their use for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption

The April-May, 2010 volcanic eruptions of Ey- jafjallaj ¨ okull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the avia- tion industry. Here we demonstrate for the first time that large improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the out- put of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of al- titude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3±4.2 Tg for particles in the size range of 2.8-28 µm diameter. We evaluate the results of our model results with a posteriori ash emissions using in- dependent ground-based, airborne and space-borne measure- ments both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the avia- tion industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the at- mosphere exceeded the limits for the "Normal" flying zone in up to 14 % (6-16 %), 2 % (1-3 %) and 7 % (4-11 %), respec- tively, of the European area. For a limit of 2 mg m 3 only two episodes with fractions of 1.5 % (0.2-2.8 %) and 0.9 % (0.1-1.6 %) occurred, while the current "No-Fly" zone crite- rion of 4 mg m 3 was rarely exceeded. Our results have im- portant ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.