CF data model

The CF (Climate and Forecast) metadata conventions (http://cfconventions.org) provide a description of the physical meaning of data and of their spatial and temporal properties and are designed to promote the creation, processing, and sharing of climate and forecasting data using netCDF files and libraries (https://www.unidata.ucar.edu/software/netcdf).

The CF data model 1 (https://doi.org/10.5194/gmd-10-4619-2017) identifies the fundamental elements (“constructs”) of the CF conventions and shows how they relate to each other, independently of the netCDF encoding.

The CF data model defines a “field construct” for storing data with all of its metadata. It is defined as follows:

field construct

corresponds to a CF-netCDF data variable with all of its metadata. It consists of

  • descriptive properties that apply to field construct as a whole (e.g. the standard name),

  • a data array, and

  • “metadata constructs” that describe the locations of each cell of the data array (i.e. the “domain”), defined by

    domain axis constructs

    corresponding to CF-netCDF dimensions or scalar coordinate variables

    dimension coordinate constructs

    corresponding to CF-netCDF coordinate variables or numeric scalar coordinate variables

    auxiliary coordinate constructs

    corresponding to CF-netCDF auxiliary coordinate variables and non-numeric scalar coordinate variables

    coordinate reference constructs

    corresponding to CF-netCDF grid mapping variables or the formula_terms attribute of a coordinate variable

    domain ancillary constructs

    corresponding to CF-netCDF variables named by the formula_terms attribute of a coordinate variable

    cell measure constructs

    corresponding to CF-netCDF cell measure variables

  • metadata constructs that describe the physical nature of the data array, defined by

    field ancillary constructs

    corresponding to CF-netCDF ancillary variables

    cell method constructs

    corresponding to a CF-netCDF cell_methods attribute of data variable


_images/field.png

The nine constructs of our CF data model described using UML The field construct corresponds to a CF-netCDF data variable. The domain provides the linkage between the field construct and the constructs which describe measurement locations and cell properties. It is not a construct of the data model but an abstract concept that is useful for understanding it. Similarly, it is useful to define an abstract generic coordinate construct that can be used to refer to coordinates when the their type (dimension or auxiliary coordinate construct) is not an issue.

1

Hassell, D., Gregory, J., Blower, J., Lawrence, B. N., and Taylor, K. E.: A data model of the Climate and Forecast metadata conventions (CF-1.6) with a software implementation (cf-python v2.1), Geosci. Model Dev., 10, 4619-4646, https://doi.org/10.5194/gmd-10-4619-2017, 2017.