GEOS-Chem
Description
GEOS-Chem is an open?source global 3?D chemical transport model used to simulate atmospheric composition, including gases and aerosols, and their chemistry, transport, and deposition. The website provides documentation, installation and run instructions, tutorials, model version information, input datasets, and links to the user community and developer resources. Researchers use it to run simulations for air quality, climate, and biogeochemical cycling studies, and to contribute improvements back to the shared codebase.
Questions this resource can help answer
How do gases and aerosols (e.g., ozone, PM2.5, NOx, SO2, CO, methane) vary in space and time globally or regionally?
What are the contributions of different emission sectors or regions to pollution in a given area?
How might changes in emissions, climate, or land use affect air quality and atmospheric composition in the future?
How do long?range transport and chemistry influence observed pollution episodes?
How do I use this resource?
To use GEOS-Chem, start at the website’s Getting Started / Documentation sections, follow the instructions to obtain access (GitHub) and download the model code, then set up the required environment (Linux, compilers, netCDF libraries). Download or link to the official meteorology and emissions input datasets, choose a configuration (e.g., full chemistry, oxidant–aerosol only; global or nested regional domain), and run one of the benchmark/tutorial cases to verify your setup. Once that works, define your own simulation period and region, adjust configuration files and emissions as needed, run the model, and analyze outputs (netCDF) with Python/R/MATLAB or visualization tools.
Pro tips
Begin with an official benchmark simulation before changing anything—this confirms a correct install and gives you a reference.
Use the latest supported version and read its release notes; many questions are answered there.
Keep domains, chemistry options, and run lengths modest at first to reduce runtime while you debug.
Rely on the online documentation and wiki for configuration details, and search the user forum / mailing list for common issues.
Rigorously document your configuration (version, met fields, emissions inventories, switches) for reproducibility and publication.
Always perform a basic evaluation against observations before interpreting scenario differences.
Resource information
Technical specifications
GEOS?Chem is a 3?D global chemical transport model that uses assimilated or model-generated meteorological fields (winds, temperature, humidity, mixing, clouds, radiation) to drive transport and physical processes, coupled with detailed gas?phase, aerosol, and heterogeneous chemistry. It solves the continuity equation for many chemical species on a latitude?longitude?height grid, simulating advection, convection, boundary?layer mixing, emissions (anthropogenic, biogenic, fires, etc.), chemical production and loss, and dry and wet deposition. Simulations are typically “offline,” meaning meteorology is prescribed rather than fully coupled to climate dynamics, and can be run at global or nested regional scales. Outputs are gridded, time?resolved concentrations and deposition fields that can be analyzed directly or used as inputs to health, climate, or ecosystem impact studies.
