Numerical modeling

Numerical modeling:

Development of models of the emissions chemistry and physics (from 0D to 3D, high-temperature to low-temperature) provide a framework to understand observations of the near-source plume in terms of their underlying processes, and to develop approaches to include these in larger scale atmospheric models e.g. MOCAGE or CHIMERE (see WP3). A key goal is to develop a plume-in-grid approach for the high temperature chemistry processes and a reduced chemical mechanism for the plume chemistry. The plume-in-grid approach will allow developing a plume chemistry parameterization near the vent following for instance Grellier et al. (2014) or the methodology used in Cariolle et al. (2009) for aircraft NOx emissions and in Gressent et al. (2016) for lightning NOx emissions. The reduced chemical mechanism developed in WP1 will be associated to the parameterization for convection and injection height that will be developed in WP2, in order to represent both the plume chemistry and the mixing of the chemical species produced inside the plume with the environment. Box models of plume chemistry provide a first step towards this goal, to elucidate processes at high-temperature (e.g. formation of radicals, sulfate precursors) and low-temperature (e.g. reactive halogens). These can also be coupled ‘off-line’ to plume-rise models. The ChemKin model provides a kinetics-based approach to simulate high-temperature chemistry processes (cf. thermodynamic models), and elucidate (and simplify) the underlying chemical mechanisms. This box model will help to determine the effective reaction rate constant needed to compute the formation of the secondary species within the plume near the source that will be used to develop a plume-in-grid approach. Towards advancing further models of low-temperature chemistry in the near-source plume, the PlumeChem box scheme includes reactive halogen chemistry. PlumeChem simulations will facilitate developing reduced chemical mechanism including the plume chemistry for Meso-NH, MOCAGE or CHIMERE models (see WP3). Meso-NH is a useful tool to bridge from local to regional scales and to study the complex heterogenous chemistry and the transport-dispersion over complex topography. However, due to computing cost, this research model is restricted to case study applications. The parameterization of plume chemistry could be assessed with MesoNH by comparison of LES simulations computing the nonlinear chemistry inside the plume to less horizontally resolved simulations including the plume chemistry parameterization performed by WP2.