Many others have contributed to the development of CF through their participation in discussions about proposed changes.

**Abstract**

This document describes the CF conventions for climate and forecast metadata designed to promote the processing and sharing of files created with the netCDF Application Programmer Interface [NetCDF]. The conventions define metadata that provide a definitive description of what the data in each variable represents, and of the spatial and temporal properties of the data. This enables users of data from different sources to decide which quantities are comparable, and facilitates building applications with powerful extraction, regridding, and display capabilities.

The CF conventions generalize and extend the COARDS conventions [COARDS]. The extensions include metadata that provides a precise definition of each variable via specification of a standard name, describes the vertical locations corresponding to dimensionless vertical coordinate values, and provides the spatial coordinates of non-rectilinear gridded data. Since climate and forecast data are often not simply representative of points in space/time, other extensions provide for the description of coordinate intervals, multidimensional cells and climatological time coordinates, and indicate how a data value is representative of an interval or cell. This standard also relaxes the COARDS constraints on dimension order and specifies methods for reducing the size of datasets.

**Table of Contents**

- Preface
- 1. Introduction
- 2. NetCDF Files and Components
- 3. Description of the Data
- 4. Coordinate Types
- 5. Coordinate Systems
- 5.1. Independent Latitude, Longitude, Vertical, and Time Axes
- 5.2. Two-Dimensional Latitude, Longitude, Coordinate Variables
- 5.3. Reduced Horizontal Grid
- 5.4. Timeseries of Station Data
- 5.5. Trajectories
- 5.6. Grid Mappings and ProjectionsHorizontal Coordinate Reference Systems, Grid Mappings, and Projections
- 5.7. Scalar Coordinate Variables

- 6. Labels and Alternative Coordinates
- 7. Data Representative of Cells
- 8. Reduction of Dataset Size
- 9. Discrete Sampling Geometries
- A. Attributes
- B. Standard Name Table Format
- C. Standard Name Modifiers
- D. Dimensionless Vertical Coordinates
- E. Cell Methods
- F. Grid Mappings
- G. Revision History
- H. Annotated Examples of Discrete Geometries
- H.1. Point Data
- H.2. Time Series Data
- H.2.1. Orthogonal multidimensional array representation of time series
- H.2.2. Incomplete multidimensional array representation of time series
- H.2.3. Single time series, including deviations from a nominal fixed spatial location
- H.2.4. Contiguous ragged array representation of time series
- H.2.5. Indexed ragged array representation of time series

- H.3. Profile Data
- H.4. Trajectory Data
- H.5. Time Series of Profiles
- H.6. Trajectory of Profiles

- Bibliography

**List of Tables**

**List of Examples**

- 3.1. Use of
`standard_name`

- 3.2. Instrument data
- 3.3. A flag variable, using
`flag_values`

- 3.4. A flag variable, using
`flag_masks`

- 3.5. A flag variable, using
`flag_masks`

and`flag_values`

- 4.1. Latitude axis
- 4.2. Longitude axis
- 4.3. Atmosphere sigma coordinate
- 4.4. Time axis
- 4.5. Perpetual time axis
- 4.6. Paleoclimate time axis
- 5.1. Independent coordinate variables
- 5.2. Two-dimensional coordinate variables
- 5.3. Reduced horizontal grid
- 5.4. Timeseries of station data
- 5.5. Trajectories
- 5.6. Rotated pole grid
- 5.7. Lambert conformal projection
- 5.8. Latitude and longitude on a spherical Earth
- 5.9. Latitude and longitude on the WGS 1984 datum
- 5.10. British National Grid
- 5.11. British National Grid + Newlyn Datum in CRS WKT format
- 5.12. Multiple forecasts from a single analysis
- 6.1. Several parcel trajectories
- 6.2. Northward heat transport in Atlantic Ocean
- 6.3. Model level numbers
- 7.1. Cells on a latitude axis
- 7.2. Cells in a non-rectangular grid
- 7.3. Cell areas for a spherical geodesic grid
- 7.4. Methods applied to a timeseries
- 7.5. Surface air temperature variance
- 7.6. Mean surface temperature over land and sensible heat flux averaged separately over land and sea.
- 7.7. Thickness of sea-ice and snow on sea-ice averaged over sea area.
- 7.8. Climatological seasons
- 7.9. Decadal averages for January
- 7.10. Temperature for each hour of the average day
- 7.11. Extreme statistics and spell-lengths
- 7.12. Temperature for each hour of the typical climatological day
- 7.13. Monthly-maximum daily precipitation totals
- 8.1. Horizontal compression of a three-dimensional array
- 8.2. Compression of a three-dimensional field
- B.1. A name table containing three entries
- H.1. Point data.
- H.2. Timeseries with common element times in a time coordinate variable using the orthogonal multidimensional array representation.
- H.3. Timeseries of station data in the incomplete multidimensional array representation.
- H.4. A single timeseries.
- H.5. A single timeseries with time-varying deviations from a nominal point spatial location
- H.6. Timeseries of station data in the contiguous ragged array representation.
- H.7. Timeseries of station data in the indexed ragged array representation.
- H.8. Atmospheric sounding profiles for a common set of vertical coordinates stored in the orthogonal multidimensional array representation.
- H.9. Data from a single atmospheric sounding profile.
- H.10. Atmospheric sounding profiles for a common set of vertical coordinates stored in the contiguous ragged array representation.
- H.11. Atmospheric sounding profiles for a common set of vertical coordinates stored in the indexed ragged array representation.
- H.12. Trajectories recording atmospheric composition in the incomplete multidimensional array representation.
- H.13. A single trajectory recording atmospheric composition.
- H.14. Trajectories recording atmospheric composition in the contiguous ragged array representation.
- H.15. Trajectories recording atmospheric composition in the indexed ragged array representation.
- H.16. Time series of atmospheric sounding profiles from a set of locations stored in a multidimensional array representation.
- H.17. Time series of atmospheric sounding profiles from a set of locations stored in an orthogonal multidimensional array representation.
- H.18. Time series of atmospheric sounding profiles from a single location stored in a multidimensional array representation.
- H.19. Time series of atmospheric sounding profiles from a set of locations stored in a ragged array representation.
- H.20. Time series of atmospheric sounding profiles along a set of trajectories stored in a multidimensional array representation.
- H.21. Time series of atmospheric sounding profiles along a trajectory stored in a multidimensional array representation.
- H.22. Time series of atmospheric sounding profiles along a set of trajectories stored in a ragged array representation.