22 Dec 2023
 | 22 Dec 2023

Technical note: Exploring parameter and meteorological uncertainty via emulation in volcanic ash atmospheric dispersion modelling

James M. Salter, Helen N. Webster, and Cameron Saint

Abstract. Consideration of uncertainty in volcanic ash cloud forecasts is increasingly of interest, with an industry goal to provide probabilistic forecasts alongside deterministic forecasts. Simulations of volcanic clouds via dispersion modelling are subject to a number of uncertainties, relating to the eruption itself (mass of ash emitted, and when), parametrisations of physical processes, and the meteorological conditions. To fully explore these uncertainties through atmospheric dispersion model simulations alone may be expensive, and instead an emulator can be used to increase understanding of uncertainties in the model inputs and outputs, going beyond combinations of source, physical and meteorological inputs that were simulated by the dispersion model. We emulate the NAME dispersion model for simulations of the Raikoke 2019 eruption, and use these emulators to compare simulated ash clouds to observations derived from satellites, constraining NAME source and internal parameters via history matching. We demonstrate that the effect of varying both meteorological scenarios and model parameters can be captured in this way, with accurate emulation using only a small number of runs per meteorological scenario. We show that accounting for meteorological uncertainty simultaneously with other uncertainties may lead to the identification of different sensitive model parameters, and may lead to less constrained source and internal NAME parameters, however through idealised experiments we argue that this is a reasonable result and is properly accounting for all sources of uncertainty in the model inputs.

James M. Salter, Helen N. Webster, and Cameron Saint

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2870', Anonymous Referee #1, 09 Jan 2024
  • RC2: 'Comment on egusphere-2023-2870', Anonymous Referee #2, 15 Jan 2024
James M. Salter, Helen N. Webster, and Cameron Saint
James M. Salter, Helen N. Webster, and Cameron Saint


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Short summary
Models are used to make forecasts of volcanic ash dispersion during eruptions. These models have unknown inputs relating to the eruption itself, physical processes, and meteorological conditions. We use statistical models to predict the output of the expensive physical model and show we can account for the effects of the different inputs. We compare the model to real-world observations and show that accounting for all sources of uncertainty may lead to different conclusions about the inputs.