in the atmosphere, ocean, and other physical domains. It was designed primarily to address gridded data types such as numerical weather prediction model outputs and climatology data in which data binning is used to impose a regular structure. However, the CF conventions are also applicable to many classes of observational data and have been adopted by a number of groups for such applications. Supported data formats CF originated as a standard for data written in netCDF, but its structure is general and it has been adapted for use with other data formats. For example, using the CF conventions with Hierarchical Data Format data has been explored. Design principles Several principles guide the development of CF conventions: Data should be self-describing, without external tables needed for interpretation. Conventions should be developed only as needed, rather than anticipating possible needs. Conventions should not be onerous to use for either data-writers or data-readers. Metadata should be readable by humans as well as interpretable by programs. Redundancy should be avoided to prevent inconsistencies when writing data. Specific CF metadata descriptors use values of attributes to represent Data provenance: title, institution, contact, source (e.g. model), history (audit trail of operations), references, comment Description of associated activity: project, experiment Description of data: units, standard_name, long_name, auxiliary_variables, missing_value, valid_range, flag_values, flag_meanings Description of coordinates: coordinates, bounds, grid_mapping (with formula_terms); time specified with reference_time ("time since T0") and calendar attributes. Meaning of grid cells: cell_methods, cell_measures, and climatological statistics. A central element of the CF Conventions is the CF Standard Name Table. The CF Standard Name Table uniquely associates a standard name with each geophysical parameter in a data set, where each name provides a precise description of physical quantities being represented. Note that this is the string value of the standard_name attribute, not the name of the parameter. The CF standard name table identifies over 1,000 physical quantities, each with a precise description and associated canonical units. Guidelines for construction of CF standard names are documented on the conventions web site. As an example of the information provided by CF standard names, the entry for sea-level atmospheric pressure includes: standard name: air_pressure_at_sea_level description: sea_level means mean sea level, which is close to the geoid in sea areas. Air pressure at sea level is the quantity often abbreviated as MSLP or PMSL. canonical units: Pa Software NetCDF-Java Library parses CF Conventions and creates Coordinate System objects from them