Conducting Multi-Agency Volcanic Ash Cloud Exercises: Practicing forecast evaluation procedures and the pull-through of scientific advice to the London VAAC

Practising and testing emergency procedures are fundamental for ensuring an effective operational response to a crisis. In this presentation we will introduce a new series of exercises which have been developed to test the multi-agency response needed to produce volcanic ash forecasts at the London Volcanic Ash Advisory Centre (VAAC). Our exercises have been specifically designed to practice our ability to interpret and evaluate model simulations and observations, the pull through of international scientific expertise into the London VAAC, and decision-making procedures under uncertainty. In this presentation we will describe our exercise methodology, this includes the development of simulated observations for exercise conditions, and a framework for comparing transport and dispersion simulations generated using different model setups (multi-model ensemble). We will also discuss how we practice the necessary interactions between scientists supporting the London VAAC and external collaborators, which may include experts at volcano observatories, national/state geological or geophysical institutions, and volcano research institutions. We will present case-studies of exercises for hypothetical events in Iceland and outline the lessons learnt. Our Exercises have not only improved our ability to respond to a volcanic ash cloud event but have also driven scientific and technical improvement of the forecasts, and strengthened the relationships between collaborators and responders, with the aim of providing the best possible advice to the London VAAC.