CF conventions
CF conventions are community standards for describing climate and forecast data in a structured, machine-readable way. They are commonly used with netCDF files so that data variables, coordinates, units, and metadata can be interpreted consistently across tools and projects.
What they standardize
CF conventions help standardize:
- coordinate variables such as time, latitude, longitude, and vertical axes
- variable names, units, and semantic meaning through standard names and attributes
- metadata describing cell methods, bounds, and grid mappings
- the overall structure needed for interoperable geoscience datasets
The gap they close
Without shared conventions, two datasets may both be readable as netCDF files while still being difficult to combine or interpret correctly. CF conventions reduce that ambiguity by making common expectations explicit.
Relation to netCDF and CDL
CF conventions are not a file format by themselves. They build on formats such as netCDF and their textual representation in common data language. netCDF provides the storage model; CF provides shared semantic structure.
Standard names are the substance
The part of CF that does the most work is the standard name table: a controlled vocabulary where air_temperature has a formal definition rather than being a plausible label someone chose. Two files claiming the same standard name really do hold the same physical quantity, which is what makes automated combination across sources possible at all.
It is also where CF is most often only partly adopted. A file can be CF-conforming in structure — correct coordinate variables, valid units — while using non-standard variable names, and it will pass a syntactic check and still need a human to interpret it. This is the same gap netCDF leaves at the format level, one layer up.
ATMODAT and the UC2 standard both build on CF and add domain requirements, which is the normal pattern: CF supplies the shared vocabulary, community profiles supply what a particular field additionally needs.
See also: netCDF, common data language, ATMODAT, UC2 data standard, Metadata, Provenance