Influence of compleX sOurce and wiNd conditions on Eruptive Plume Height (PHOENIX)

Explosive volcanic eruptions emit plumes of ash and gas with significant environmental and societal impacts. Volcanic plumes can reach heights of tens of kilometres into the atmosphere and form ash clouds that disperse over hundreds to thousands of kilometres, but they also sometimes collapse and form highly destructive pyroclastic density currents. In the air, ash and gas pose hazards to aviation on the ground, even small amounts of ash can cause health issues and infrastructure damage. One of the key gases emitted by volcanic eruptions, sulfur, can also cool the climate globally, temporarily mitigating global warming driven by anthropogenic activities. The UK is not immune to volcanic hazards, with plumes from Icelandic eruptions having affected UK airspace several times since 2015, and the 2010 Eyjafjallajökull eruption alone having cost over £2,000,000,000. One of the most important parameters governing volcanic impacts is the volcanic plume height, which determines where ash and gas will be transported and how long they will be suspended in the atmosphere. While the mechanisms controlling the height of simple plumes are well understood, current computer models used for rapid volcanic response fail to accurately simulate the heights of complex real-world eruptive plumes. This results in a limited understanding of volcanic hazards and their climate impacts. Our project will deliver important improvements in two critical areas to transform our capabilities for managing volcanic impacts: We poorly understand how the source geometry of a plume impacts the plume height. In particular, the height of plumes lofting from pyroclastic density currents (termed co-PDC plumes) up to tens of kilometres away from the volcanic crater, differs from that of volcanic plumes that rise directly above a volcanic crater. This particular dynamic is key to managing associated hazards. Atmospheric winds bend over volcanic plumes, reducing their height. However, most numerical models were developed assuming that wind speed is constant with altitude, a highly inaccurate approximation for the Earth’s atmosphere. Understanding how enhanced turbulence associated with vertically varying wind speed could affect rising plumes is thus critical. To drive transformative advances in these three challenges, we will leverage a newly established database of volcanological observations. This data will be enriched with additional information obtained from field investigations of co-PDC plume deposits. We will also create new small-scale laboratory experiments reproducing plumes analogous to volcanic ones, but controlling and measuring plume properties precisely which is challenging in the real world, and implementing the effect of varying wind fields for the first time. Last, we will take advantage of a new generation of complex 3-dimensional model of volcanic plumes. Using the observational, experimental and complex model data gathered, we will develop volcanic plume models that are: i) able to capture the complex dynamics associated with co-PDC plumes and vertically varying atmospheric winds; ii) sufficiently simple and fast to be applied in all research and operational contexts. We will quantify how our new plume models affect operational ash forecasts and climate projections issued by the UK Met Office. To ensure the successful implementation of our results, we will closely collaborate with international scientific partners, local volcano observatories in Italy, Guatemala, and the USA, along with global organisations such as the World Meteorological Organization. This cooperative effort will help us incorporate our findings into volcanic response protocols to manage volcanic hazards and environmental impacts worldwide.