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Cambridge NERC Doctoral Training Partnerships

Graduate Research Opportunities

Lead Supervisor: Michael Herzog, Geography

Co-Supervisors: Clive Oppenheimer, Geography & Benjamin Devenish, UK Met Office

CASE Partner: UK Met Office

Brief summary: 
This project will improve prediction of volcanic ash in collaboration with the UK Met Office.
Importance of the area of research concerned: 
The eruption of Eyjafjallajökull volcano in 2010 demonstrated the widespread disruption that even a relatively modest-scale eruption can cause. The management of the crisis highlighted the need for developments in computational models for ash transport and yet, nearly ten years on, many outstanding issues remain. These include the challenge of accurately characterising eruptive conditions at the vent, and our limited understanding of the processes that control the atmospheric dispersion and sedimentation of ash. One particular issue is the separation of different parts of an eruptive plume. This has now been widely observed but is exemplified by the 2011 eruption of Grímsvötn. At the time, models computed ash transport to areas where little or no ash was subsequently observed. This was because the ash had separated from the gaseous component of the volcanic plume due to wind shear and had been advected in an entirely different direction. This project will examine this case in detail as an entry point to a systematic study of how such phase separation occurs.
Project summary : 
A complex numerical plume model will be used to characterize and quantify the fate of volcanic gases and particles in volcanic eruption plumes. The key process of the separation of volcanic gases and ash particles can be explained in several ways: the multiphase nature of the plume with different phases (ash and gas) travelling at different speeds; differential sedimentation of ash particles of different sizes and, ash aggregation. The overall aim of the project is to improve and extend existing one-dimensional volcanic plume models to better capture the multiphase nature of such plumes by including critical processes such as sedimentation. Simple integral plume models already play an important role in initialising atmospheric dispersion models for operational forecasting of volcanic ash clouds, and this project will have clear practical benefits for future volcanic risk management.
What will the student do?: 
This project will make use of a model specifically designed for 3D simulation of volcanic plumes, the Active Tracer High-resolution Atmospheric Model (ATHAM; Oberhuber et al., 1998; Herzog et al., 2003). Unique features of ATHAM are its dynamically and thermodynamically active tracers, and its representation of strongly divergent flows with large vertical accelerations. Active tracers differ in their vertical velocity relative to the mixture so that particle sedimentation and gas particle separation are described by the model. ATHAM contains a cloud microphysical module (Herzog et al., 1998), which has been extended to study ash aggregation (Textor et al., 2006). The first part of the project will involve development of the ash aggregation module to incorporate the effects of electrically-charged ash particles. This will then enable novel studies of the effects of sedimentation and aggregation. Findings will be used to improve models used at the Met Office for operational ash cloud forecasting. The Met Office supports the project via an industrial CASE partnership and will host the student on multiple research visits.
References - references should provide further reading about the project: 
Van Eaton, A.R., Mastin, L.G., Herzog, M., Schwaiger, H.F., Schneider, D.J., Wallace, K.L. and Clarke, A.B., 2015. Hail formation triggers rapid ash aggregation in volcanic plumes. Nature Communications, v. 6, p.1-7. doi:10.1038/ncomms8860.
Cooke, M.C., Francis, P.N., Millington, S., Saunders, R. and Witham, C., 2014. Detection of the Grímsvötn 2011 volcanic eruption plumes using infrared satellite measurements. Atmospheric Science Letters, v. 15, pp 321-327.
Textor, C., Graf, H.F., Herzog, M., Oberhuber, J.M., Rose, W.I. and Ernst, G.G.J., 2006. Volcanic particle aggregation in explosive eruption columns. Part I: Parameterization of the microphysics of hydrometeors and ash. Journal of Volcanology and Geothermal Research, v. 150, pp 359-377.
You can find out about applying for this project on the Department of Geography page.
Dr Michael Herzog
Department of Geography Graduate Administrator
Professor Clive Oppenheimer