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Abstract: It has been 10 years since the ash cloud from the eruption of Eyjafjallajökull caused unprecedented disruption to air traffic across Europe. During this event, the London Volcanic Ash Advisory Centre (VAAC), hosted by the UK Met Office, provided advice and guidance on the expected location of volcanic ash in the atmosphere using observations and the atmospheric dispersion model NAME (Numerical Atmospheric-Dispersion Modelling Environment). Rapid changes in regulatory response and procedures during the eruption introduced the requirement to also provide forecasts of ash concentrations, representing a step-change in the level of interrogation of the dispersion model output. Although disruptive, the longevity of the event afforded the scientific community the opportunity to observe and extensively study the transport and dispersion of a volcanic ash cloud. I will discuss what we learnt from that event and the developments we have made to NAME in the decade since the eruption of Eyjafjallajökull. Much of the focus has been on improving the representation of the eruption source parameters which are subject to considerable uncertainty. This has included the application of Bayesian methods to reconstructing the source from satellite data and the use of integral plume models to determine the mass emission rate and other properties of the eruption column. Since the downwind spread of ash is sensitive to the distribution of ash particle size and density, considerable effort has also been made to improve their representation in NAME including secondary effects such as aggregation and particle shape. I will illustrate the effect of these and other changes to NAME.
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