Trans-disciplinary collaboration to investigate volcano plumes risks – STRAP

STRAP is a project for trans-disciplinary collaboration to investigate volcano plumes risks. It involves volcanologists and atmospheric scientists of four “Observatoires des Sciences de l’Univers INSU-CNRS” (OSU-R, OPGC, IPGP and OMP). All volcanic plumes can cause environmental, economic and societal hazards, but lack of knowledge on their physics and time evolution make prediction and forecast difficult. Improving our ability to quantify and model of the genesis, spread and impact of a volcanic plume is thus a key challenge for scientists and societal stakeholders. Mitigation of such volcanic crises relies on efficient, and effective, communication and interaction between key scientific actors in geology, physics, chemistry and remote sensing. The ultimate goal is to fully constrain on the volcanic source terms needed by physical and chemical modellers to predict the ascent, dispersion and the impact of volcanic ash and gas in the atmosphere. Within this context, this project aims apply an integrated approach to investigate, analyse and model the processes of formation and maturation of volcanic plumes during their transport from their source to their most distal points. The main scientific objective is to reduce the large uncertainties in characterisation of the key volcanic source terms, i.e. mass discharge rate and composition of the gas and particles mixture erupted from the vent. It needs to be convolved with fundamental atmospheric parameters, such as formation of particles in the upper atmosphere, plus direct and indirect radiative forcing due to the presence of volcanic particles. A first task will be to parameterize the process of volcanic convection in an atmospheric mesoscale model, with three main lines of enquiry: i) field-based studies of pyroclastic deposits, ii) study of dilute volcanic plumes, iii) study of dense ash and gas volcanic plumes. The second task will be to analyse the physicochemical evolution of plume optical properties and their variation over local scale and regional scales. This analysis involves tri-phase processes with the partition of the mixture between gas, particles and atmospheric plus volcanic- and atmospheric-origin water. The highly variable concentrations between the source and distal areas, as well as competition between different mechanisms (homogeneous and heterogeneous nucleation, condensation, coagulation, and activation) have to be considered. The final task will be to combine the two precedent tasks, accurately accounting for complex other external heat sources (e.g., atmospheric convection to concurrent lava flows beneath a dispersing plume). The principal aim is to integrate all of these processes in a tri-dimensional atmospheric mesoscale model. One of the deliverables of this final objective relates to a better analysis of environmental and human health risks related to population exposure to high concentrations of gas and particle charged air. Etna (or Stromboli -as an alternative) volcanoes in Italy, as well as Piton de la Fournaise volcano (La Réunion, France) will be used as test beds for deployment of new instrumentation. Kilauea (Hawai’i, USA) will constitute an alternative target to Piton de la Fournaise given the on-going collaboration with Hawaiian Volcano Observatory. These test beds will provide well-documented case data-sets for input into modelling activities. With regard to observations, the strategy will be to implement observing systems near the vents (for gas and particles thermodynamic observations) and around the convective plumes (for gas concentrations, particle size distributions, cloud optical properties, condensation nuclei properties, and aerosol chemistry). Physical modelling will focus on a 1-D model for volcanic plumes propagation at local scale and incorporating detailed parameterization of air entrainment, to scale up to a 3-D non-hydrostatic model at a regional scale.