Quoted from: CHIMERE, Chemistry-transport model v2020r1 Documentation. https://www.lmd.polytechnique.fr/chimere/docs/CHIMEREdoc_v2020r1.pdf 

      CHIMERE is a Eulerian chemistry-transport model (CTM). External forcings are required to run a simulation: meteorological fields, primary pollutant emissions and chemical boundary conditions. Using these input data, CHIMERE calculates and provides the atmospheric concentrations of hundreds of gas-phase and aerosol species over local to continental domains (from 1 km to few degrees resolution). The key processes affecting the chemical concentrations and represented in CHIMERE are emissions, transport (advection and mixing), chemistry and deposition, as presented in Figure 1.1 . The model can be used in offline or online mode. In offline mode, meteorological fields for the period and geographical region of the simulation are pre-calculated by a meteorological model. They are interpolated in space and time on the CHIMERE temporal and spatial grids. Any meteorological model can be used provided that all mandatory variables for the CHIMERE simulation are given in the appropriate format. Interfaces for WRF and ECMWF models are provided with the CHIMERE code. For online simulations, the meteorological model runs at the same time as CHIMERE and fields are exchanged between models during the simulation allowing for interactions to take place. The model is currently set up to use the WRF 3.7.1 regional model which is provided with the CHIMERE code.

      Figure 1.1: General principle of a chemistry-transport model such as CHIMERE. In the box ’Meteorology’, u* stands for the friction velocity, Q0 the surface sensible heat flux, L the Monin-Obukhov length and BLH the boundary layer height. cmod and cobs are for the chemical concentrations fields for the model and the observations, respectively.

      CHIMERE is designed to be used for several applications: analysis of pollution events, ensemble modelling, long-term simulations or forecast. The model is able to run with nested domains. For each process, several schemes are implemented and can be easily changed using the parameter file. The user can easily change some parameterizations, input databases of horizontal or vertical resolution. Several chemical mechanism are provided, simplified or more complete, with or without aerosols.

      Currently, the model is used for research on transport and mixing, turbulence, gas and aerosol chemistry, anthropogenic, biogenic, natural (mineral dust, fires, volcanos and marine) emissions and dry and wet deposition. It is also used for oerational forecast: for example by regional air quality networks (France, Italy, Spain, Netherlands, Portugal etc.), national (PREV’AIR) or continental scale (CAMS).

      The main parameterizations implemented in CHIMERE are described in Table 1.1.