The Weather Research and Forecasting (WRF) model is being used to model the dispersion of ash from a volcanic plume. A thermal perturbation (or a surface heat flux) at the surface, coupled with the release of a co-located tracer, allows the model to track the spread of ash.

This has been completed for near-source regions (where the formation of shallow ash layers are thought to be important) to the far-field, the latter giving the dispersion of ash on a continental scale. Tests have been completed which show that the volcanic plumes simulated by WRF follow theoretical predictions with regard to the vertical extent and horizontal spread of the plume.

Refinements to the model include adding settling velocities to the tracer, simulating the effect of sedimentation. At present the model is constructed so that the motion of the atmosphere affects the spread of ash, but not vice-versa. Future work will focus on developing a full "multiphase" version of WRF where the ash can affect the atmosphere.

The modelling results can be compared to observations of the Eyjafjallajökull ash cloud by lidars at UK ground sites and on the FAAM aircraft.

Staff involved in this activity are:

Dr Ralph Burton, Dr Alan Gadian and Prof. Stephen Mobbs (University of Leeds)