GEOS-Chem reads and writes data using the netCDF file format. For a general introduction to the netCDF file format, please follow this link.
If you are using GEOS-Chem on the Amazon EC2 cloud, then a version of netCDF will ship with the machine image (or software container) that you'll use to initialize your computational environment. Therefore, you will not have to install netCDF yourself (unless you are an advanced user and need a specific version for a particular application). Please see our cloud computing tutorial cloud.geos-chem.org for more information.
If you are using GEOS-Chem on your institution's computer system, chances are that your IT staff will have already installed one or more netCDF library versions that you can use. For users that do not have the netCDF libraries intstalled on their system, the GEOS-Chem Support Team has provided instructions on how to install netCDF on your system. Please visit the links below for detailed instructions.