Model name


Full model name




All data required for a simulation are delivered in a example package, including meteorology, surface emissions, and boundary-conditions for test cases.

The last version of the model described here is in F90, with NetCDF input/output data format and is parallelized (LAM/MPI software is needed).

Intended field of application

Air quality modeling and forecasting

Model type and dimension

Regional air quality model, 1km to 100 km grid cell size, over domains 50km to 5000 km wide typically

Model description summary

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 scale from the regional scale (several thousand kilometers) to the urban scale (100-200 Km) with resolutions from 1-2 Km to 100 Km. On this server, documentation and source codes are proposed for the complete multi-scale model. However most data are valid only for Europe and should be revisited for applications on other continents.

CHIMERE proposes many different options for simulations which make it also a powerful research tool for testing parameterizations 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 by the PPM (Piecewise Parabolic Method) 3d order scheme for slow species.

The numerical time solver is the TWOSTEP method. zations, hypotheses. Its use is relatively simple provided 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.

Model limitations/approximations

Lower tropospheric description.

No global version.


Temporal resolution

From 5min to 1 hour, depending on the user choice

Horizontal resolution

1km to 100km

Vertical resolution

50m to 500m


Advection & Convection

Three advection schemes are implemented: The Parabolic Piecewise Method (PPM, a three-order horizontal scheme, after Colella and Woodward, 1984), the Godunov scheme (VanLeer, 1979) and the simple upwind first-order scheme.


Vertical turbulent mixing takes place only in the boundary-layer. The formulation uses K-diffusion following the parameterization of [Troen and Mahrt, 1986], without counter-gradient term.


Dry deposition is considered for model gas species i and is parameterized as a downward flux F(d,i)= -v(d,i) c(i) out of the lowest model layer with c(i) being the concentration of species i. The deposition velocity is, as commonly, described through a resistance analogy [Wesely, 1989]. The wet deposition follows the scheme proposed by [Loosmore, 2004]


CHIMERE offers the option to include different gas phase chemical mechanisms. The original, complete scheme [Lattuati, 1997], hereafter called MELCHIOR1, describes more than 300 reactions of 80 gaseous species.

The hydrocarbon degradation is fairly similar to the EMEP gas phase mechanism [Simpson, 1992]. Adaptations are made in particular for low NOx conditions and NOx-nitrate chemistry. All rate constants are updated according to [Atkinson, 1997] and [De More, 1997].

Heterogeneous formation of HONO from deposition of NO2 on wet surfaces is now considered, using the formulation of [Aumont, 2003]. In order to reduce the computing time a reduced mechanism with 44 species and about 120 reactions is derived from MELCHIOR [Derognat, 2003], following the concept of chemical operators [Carter, 1990]. This reduced mechanism is called MELCHIOR2 hereafter.

Solution technique

The numerical method for the temporal solution of the stiff system of partial differential equations is adapted from the second-order TWOSTEP algorithm originally proposed by [Verwer, 1994] for gas phase chemistry only. It is based on the application of a Gauss-Seidel iteration scheme to the 2-step implicit backward differentiation (BDF2) formula.


Availability and Validation of Input data

All chimere input data are free and available on line on the chimere web site with references and documentation.


The model provides an interface combining several emissions sources such as EMEP (Yearly totals), IER (Time variations), TNO (Aerosol emissions), UK Dept of Environment (VOC speciation, Passant, 2002). see documentation for details and


CHIMERE can use many meteorological models but users should provide their own interface, except for MM5, for which an interface is proposed in the code, which takes as input standard MM5 output files (MMOUT files). If MM5 (which is a free software, available on the NCAR ( web site, is chosen as the meteorological driver, it has to be initialized with other global meteorological data (analyses), which often are not public. However the NationalCenters for Environmental Prediction (NCEP) and the NationalCenter for Atmospheric Research provide a wide variety of meteorological data, analyses etc... online. Our experience deals with real-time AVN/NCEP analyses and forecasts that can be obtained on a web server. When setting up a meteorological simulation using MM5, choose a meteorological domain entirely containing the CHIMERE domain, and a time period entirely containing the CHIMERE period to simulate. The PBL option MRF (Option 5), based on the Troen and Mahrt (1986) parameterization should be prefered because it is most consistent with the model mixing formulation. The Schultz (Option 8) microphysics parameterization has also been tested with CHIMERE and is recommended.

Initial conditions


Boundary conditions

The LMDz-INCA model [Hauglustaine et al., 2005] for gas-phase chemical species.

The global aerosol model GOCART for mineral aerosols [Chin et al., 2004]. The output concentrations are averaged over each month of the year.

Data assimilation options

Information not available. For more details, please, refer directly to the contact person.

Other input requirements

The proposed domain interface is based on the Global Land Cover Facility (GLCF: 1kmx1km resolution database from the University of Maryland, following the methodology of Hansen et al. (2000, J. Remote Sensing). no other input requirement.

Output quantities

Four dimensional (x-y-z-t) concentrations fields of all active species, following the usr selection.

Diagnosed turbulent parameters (boundary layer height, friction velocity etc.), dry and wet deposition fluxes.

Portability and computer requirements


LINUX systems.

CPU time

Depending on resolution, application. The model is now parallelized and may run over an European domain with 10km resolution and for 5 days in less that 10min (with gas and aerosols) on a PC linux cluster.


Depending on resolution, application. For example, a forecast of 5 days, over a large western europe domain needs 2G disk storage.

última atualização a 15-04-2014
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