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Quantitative Volcanic Ash (QVA) -- A new operating requirement for Volcanic Ash Advisory Centres (VAACs)

Frances Beckett , Charlie Bates, Ben Evans, Matthew Hort, Andrew Jones, Nina Kristiansen, Violet Sherratt, Olivia Smedley, Nicola Stebbing, Tomasz Trzeciak, Charlie Tucker

Abstract

A global network of Volcanic Ash Advisory Centres (VAACs) provides advice and guidance to the aviation industry on the presence of volcanic ash in the atmosphere, to support decision-making on flight safety. Traditionally, forecasts have indicated the expected location of the ash cloud, in the form of a simple polygon, up to 18 hours ahead, referred to as a Volcanic Ash Graphic (VAG).    A new service has now been defined by the International Civil Aviation Organisation (ICAO) which stipulates that all VAACs move towards providing quantitative forecasts in the form of 4D gridded datasets of ash concentrations, probabilities of exceeding prescribed thresholds, and new sophisticated polygons in IWXXM format. This new capability is being referred to as Quantitative Volcanic Ash (QVA).    We will present the scientific and technical development of the operational modelling system used by the London VAAC to deliver QVA compliant forecasts. We will focus on the requirement to generate probabilistic forecasts for the first time, outlining their development, known limitations and further research and development requirements.