CHIMERE

The text on this page is taken from an equivalent page of the IEHIAS-project.

The CHIMERE multi-scale model is primarily designed to produce daily forecasts of ozone, aerosols and other pollutants and make long-term simulations for emission control scenarios. CHIMERE runs over a range of spatial scales from the regional scale (several thousand kilometers) to the urban scale (100-200 Km) with resolutions from 1-2 Km to 100 Km.

Model description

Purpose

The CHIMERE multi-scale model is primarily designed to produce daily forecasts of ozone, aerosols and other pollutants and make long-term simulations for emission control scenarios. CHIMERE runs over a range of spatial scales from the regional scale (several thousand kilometers) to the urban scale (100-200 Km) with resolutions from 1-2 Km to 100 Km. CHIMERE proposes many different options for simulations which make it also a powerful research tool for testing parameterizations, hypotheses. Its use is relatively simple so long as input data is correctly provided. It can run with several vertical resolutions, and with a wide range of complexity. It can run with several chemical mechanisms, simplified or more complete, with or without aerosols.CHIMERE is a portable model which has been adapted to various types of input data. It requires meteorological data, boundary conditions, land-use information, emissions.

Boundaries

Chimere is mainly computing representative results over meso-scale domain (with horizontal resolution around 1km to 100 km). It's an offline model not producing its meteorology, so needs to be fed by high resolution meteorological data.

The chemical sheme is designed to focus on the photochemical activities of the lower troposphere.

The output fields are about outdoor concentrations of a set of reglementary pollutants (O3,NO2, PMs) and others (many COVs, Dust, heavy metals ...)

The model can be used for short-term simulations as well as for long term simulations (for climate and air quality interaction assessments).

Input

Meteorology: Meteo data is not provided on the server, but a CHIMERE interface for the MM5 mesoscale model is proposed. MM5 (free software1) can be used combined with AVN/NCEP (as forcing) public weather forecasts.

Boundary conditions: A set of boundary conditions from the MOZART and/or LMDz-INCA models is proposed as a default solution. Data are kindly provided by Max-Planck Institut, Hamburg, thanks to M. Schultz, G. Brasseur, C. Granier and D. Niehl, and IPSL/LSCE, thanks to Sophie Szopa and Didier Hauglustaine. This allows tropospheric simulations below 200 hPa. For aerosols, a set of boundary conditions is proposed based on GOCART global simulations, thanks to Mian Chin (NASA).

Land-use: CHIMERE needs input landuse information, as well as biogenic emission potentials, based on land cover. The default proposed land use is the GLCF data base2. The data for deriving biogenic emission potentials only cover Europe. It needs to be completed for other continents.

Emissions: Emissions are usually coming from local, nonpublic databases, such as EMEP.

Output

Results are timely (typical output timestep is 1h) produced over the horizontal domain in netcdf files.

Description of processes modelled and of technical details

The physics and numerics in short

• The chemical mechanism (MELCHIOR) is adapted from the original EMEP mechanism.
• Photolytic rates are attenuated using liquid water or relative humidity
• Boundary layer turbulence is represented as a diffusion (Troen and Mahrt, 1986, BLM)
• Vertical wind is diagnosed through a bottom-up mass balance scheme.
• Dry deposition is as in Wesely (1989). Wet deposition is included.
• Six aerosol sizes represented as "bins" in the model.
• Aerosol thermodynamic equilibrium is achieved using the ISORROPIA model.
• Several aqueous-phase reactions considered
• Secondary organic aerosols formation considered
• Advection is performed either by a first upwind scheme, the Van Leer scheme or by the PPM (Piecewise Parabolic Method) 3d order scheme for slow species.
• The numerical time solver is the TWOSTEP method.

The model (written in Fortran) has only been tested on PCs under GNU/Linux. It should also easily work on SUN and other UNIX systems with minor changes. Most changes should be due to the unformatted binary data interfaces. Please report to us all problems. A typical time for simulation on a single-processor PC, using the European version with a 65x33x8 grid, is 5 minutes for one simulated day with the gas-phase version, and 30 minutes with the aerosol version. It can then easily simulate entire seasons or years. A minimal setting of 1 Gb RAM is necessary. Software required is a Fortran 95 compiler (g95 is really great and free!) or ifort, and an MPI-1 compatible library. Simple graphical interfaces are available using either the GMT 3 or the GrADS 4 free software (to be installed).

References

• [Troen and Mahrt, 1986] Troen, I. and Mahrt, L. (1986). A simple model of the atmospheric boundary layer:
• Sensitivity to surface evaporation. Bound.-Layer Meteorol., 37:129–148.
• [Wesely, 1989] Wesely, M. (1989). Parameterization of surface resistances to gaseous dry deposition in regionalscale numerical models. Atmos. Environ., (23):1293–1304.

See also

• Worked example : Evolution of ozone and particulate matter concentrations in Europe under climate change with the CHIMERE model