Hotstuff Seminar - Sara Osman and Lucy Rudd - University of Bristol. Title: Understanding particle size distributions to improve phreatomagmatic ash dispersal modelling and The Effect of Topographic Resolution on Ash Resuspension Modeling
Sara Osman and Lucy Rudd, University of Bristol
Room G8, School of Earth Sciences, Wills Memorial Building
Sara Osman: Understanding particle size distributions to improve phreatomagmatic ash dispersal modelling
Particle size distribution (PSD) is a key source parameter for modelling volcanic ash dispersal because particles are sorted by size during transport. Phreatomagmatic eruptions (where water interacts with magma) can produce PSDs that are finer and remain relatively constant with distance from the source, compared to magmatic eruptions. The Met Office, as the Volcanic Ash Advisory Centre, uses the NAME model to forecast ash dispersal over northern Europe. Currently model runs for operational forecasts are initialised using one default PSD, based on a magmatic eruption. However, because many Icelandic volcanoes lie under ice, modelling phreatomagmatic ash dispersal is important. Using data from published literature I am investigating PSDs for a range of phreatomagmatic eruptions with the aim of recommending default values for modelling ash dispersal from these eruptions. I will highlight my findings so far.
Lucy Rudd: The Effect of Topographic Resolution on Ash Resuspension Modeling
Resuspension of volcanic ash can be widespread and long-lasting, significantly prolonging volcanic hazard to years after an eruption. Resuspension events can pose long term health risks to people and animals and can have similar impacts to aviation and farming as eruptions. The resuspension of an ash deposit depends on meteorological conditions such as wind velocity, precipitation and soil moisture. Therefore, it is important to correctly characterise the effects of the meteorological conditions when modeling resuspension events. Since topography can affect wind velocity, for example by channelling winds through valleys, the resolution of topographic and meteorological data used in a model can affect the model output. The UK Met office uses an atmospheric dispersion model called NAME to produce daily resuspension forecasts for Iceland. They are in the process of changing the spatial resolution used in these forecasts from 4 km to 10 km to match the resolution they use for most of the world. The effect of this change on the forecasts will be assessed in this project.
All staff and students welcome.
For further information, please contact Damaris Butters.