The SAEON Open Data Platform allows for the storage, discoverability and download of multidimensional scientific data. Network Common Data Format (netCDF) is a file format designed for storing multidimensional data in the form of arrays, and is widely used in the atmospheric and oceanographic communities. The netCDF library has been developed by the Unidata program and is freely available. NetCDFs are self-describing, so it is essential that certain conventions are followed when creating these files. SAEON follows the requirements set out by the Climate and Forecast (CF) and Attribute Conventions Dataset Discovery (ACDD) conventions for netCDF metadata and data. NetCDF standardisation also promotes interoperability and allows us to add tools such as THREDDS data services to the data. The main components of a netCDF that should be standardized are dimensions, variables and attributes.

There are certain types of discrete sampling in atmospheric/oceanographic research, like point, time series, trajectory or profile, and each of these feature types have defined netCDF file structures. The US National Oceanographic Data Centre has developed feature type templates and examples, which are accepted widely for netCDF standardisation. Most importantly, each feature type template highlights the relationships set out for netCDF dimensions and variables.

This section contains metadata that pertains to the overall netCDF file. The following table contains global attributes derived from CF and ACDD conventions required by the SAEON ODP for multidimensional data in netCDF format. For additional resources you can refer directly to the official documentations of each convention.

Note: Time information in the global attributes should be formatted as a string in ISO 8601 standard format,“YYYY-MM-DDThh:mm:ssZ” (i.e. year – month – day “T” hour : minute : second “Z”). Where “Z” indicates UTC time zone (with zero offset).

Table 1. List of core global attributes for SAEON netCDF files

All attributes are MANDATORY to include in your netCDF unless stated: CONDITIONAL= include these fields if the information exists, or RECOMMENDED = it is recommended to include these fields but not mandatory.