R4AsH is a NERC-funded project that aims to deliver a fundamental advance in forecasting volcanic ash hazard. The R4AsH team comprises five UK universities, directly linked with national and international partners to ensure that findings reach operational users.

Dispersing volcanic eruption plumes can be modelled over 1000s km but forecasts are highly sensitive to the ‘source term’ parameters that describe the initial characteristics of the volcanic ash in the atmosphere. Source term uncertainties are poorly defined and we will develop a new model-inversion-based approach to determine their time-varying parameters, constrained by state-of-the-art satellite ash retrievals. To enable measurements closer to volcanoes, we will draw on recent advances in meteorology to derive a new multi-frequency radar inversion algorithm, benchmarked for volcanic plumes by novel laboratory experiments. Such radar observations aim to provide the capability for near-real-time retrieval of the key parameters that describe the particle content of plumes: particle concentration (mass loading) and size distribution.