In terms of methods, WP3 involves various modelling techniques (from along-trajectory Lagrangian and mesoscale chemistry-transport through global chemistry-climate modeling to inverse modeling and assimilation methods, and radiative transfer modelling) and a large array of complementary observations described in WP1 and WP2.
Here follow gaps to be filled in terms of methodology:
(i) satellite observations, ranging from the ultraviolet to the infrared spectral regions, are today extensively used to quantify the abundance of various volcanic gases and to detect and characterise physico-chemical properties of volcanic aerosols. However, gas retrievals from remote sensing techniques may be significantly affected by the co-existence within the volcanic plume of aerosols (including ash), liquid water droplets and ice crystals. Achieving a rigorous budget of volcanic gas emissions will consequently require new refined retrieval techniques involving more sophisticated in-plume radiative transfer modelling for taking into account the concurrent interaction of gases and particles with atmospheric radiation. New inversion techniques aimed at the detection and detailed chemical and microphysical characterization of volcanic sulphate aerosols at the regional scale have been recently developed (see, e.g. Sellitto and Legras, 2016; Sellitto et al., 2017c) but need to be further consolidated.
(ii) in terms of modelling, the difficulty specific to volcanic plumes is the necessity to accurately describe both long-range and local processes. In the near future, efforts will have to focus on the development of sub-grid scale parameterizations for different chemical (link to WP1) and physical processes (link to WP2). Intercomparisons of different models (Meso-NH, CHIMERE, MOCAGE, WRF-CHEM, WACCM-CARMA, LMDz-Chemistry-Aerosol) capability to simulate volcanic plume processes are also a target of this WP. Such intercomparison will also include the present state-of-the art operational emission modules used by Toulouse VAAC in MOCAGE, in order to identify key processes that should be added or improved.
(iii) Improve tools for in-situ sample collection both at the ground level and within the plume because one of the main questions for the volcanology community is what remains in the plume and how can this be measured and sampled, and how to restore the physical and chemical conditions at the vent (links to WP1 and WP2) from measurements and modelling at a far-distance.