NI: Pyroclastic Density Current Partnership (PDCP): A global partnership to align numerical models and experimental techniques.

Ten percent of the world's population (i.e. 100s of millions) live within 100 km of an active volcano. Furthermore, this number is set to rise with the increasing global population. During all explosive volcanic eruptions pyroclastic density currents (PDCs) can form - high temperature mixtures of rock and gas that rapidly flow away from the volcanic vent. These phenomena are the most lethal of all volcanic hazards and are responsible for more than a third of volcanic related fatalities. Furthermore, the accompanying ash clouds have the potential to cause global disruption and significant economic loss due to air-space closure.

However, despite the lethal nature of PDCs we currently lack accurate models to forecast these flows and thus any hazard maps and mitigation strategies are inherently limited. To improve our numerical models we need to understand the complex internal flow dynamics within these 'opaque' and hazardous flows. Direct internal observation is not possible, but controlled laboratory experiments (PI's lab focus) offer a way to rigorously study these otherwise hidden phenomena. This seedcorn fund will partner a complimentary team of global PDC experts with the PI's experimental laboratory to align future experimental efforts with numerical PDC models.

The members of this partnership have been strategically selected to ensure that, in combination with the PI's lab, a full research programme can be delivered - from unravelling the fundamental physics and incorporation into PDC flow models to direct real-world impact. Specifically members include unique, internationally renowned, numerical modelers who have all developed PDC models to forecast flow run-out and, in some cases, directly inform hazard maps for a range of volcanoes worldwide. Scientists from the government agencies and volcano observatory networks involved (e.g. the Italian National Institute of Geophysics and Volcanology; the British Geological Survey) will formally communicate advances in volcanic hazard and risk to domestic and international governments, thereby providing a clear pathway to impact from this new partnership. Academics who have experience working on the field deposits and characteristics of PDC ash, including their adverse health effects, will incorporate the partnership outcomes into their work. Finally, the Met Office, home to the London Volcanic Ash Advisory Centre (VAAC), are partners who provide advice, forecasts and guidance to the aviation authorities on the presence of volcanic ash in the atmosphere.

This seedcorn fund will support a series of workshops and laboratory exchange visits where members will: (1) outline the known and prioritise the missing physical parameters relevant for PDC models; (2) co-design pilot experiments to fill these knowledge gaps and (3) produce proof-of-concept data that will be used as a basis for future, longer term grant applications.

The final outcome will be a long-lasting partnership that is equipped to tackle timely research questions surrounding deadly, pyroclastic flows using state-of-the-art multidisciplinary methods. Subsequent research led by this team will, for example, forecast the spatial extent of deadly pyroclastic flows and the subsequent atmospheric dispersal of PDC produced, volcanic ash. Ultimately this will minimise the human and economic cost of explosive volcanic eruptions around the world and is an outcome only achievable through complimentary, global partnership.