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The Climate and Forecast (CF) [[metadata]] conventions are conventions for the description of [[Earth sciences]] data, intended to promote the processing and sharing of [[data file]]s. The metadata defined by the CF conventions are generally included in the same file as the data, thus making the file "self-describing". The conventions provide a definitive description of what the data values found in each [[netCDF]] variable represent, and of the spatial and temporal properties of the data, including information about grids, such as [[grid cell]] bounds and cell averaging methods. This enables users of files from different sources to decide which variables are comparable, and is a basis for building software applications with powerful [[data extraction]], grid remapping, [[data analysis]], and [[data visualization]] capabilities.
==History and
The CF conventions were introduced in 2003, after several years of development by a collaboration that included staff from U.S. and European climate and weather laboratories
| author = Gregory, Jonathan
| year = 2003
| title = The CF metadata standard
| url = http://
}}</ref>
| author = Lawrence, B.N.
| year = 2003
| title = Maintaining and Advancing the CF Standard for Earth System Science Community Data
| url = http://cf-pcmdi.llnl.gov/documents/white-papers/cf2_whitepaper_final.html
| url-status = dead
}}</ref>. In December 2008 the trio of standards, netCDF+CF+OPeNDAP, was adopted by [[IOOS]] as a recommended standard (number 08-012) for the representation and transport of gridded data. The CF conventions are being considered by the [[NASA]] Standards Process Group (SPG) and others as more broadly applicable standards <ref>{{cite news▼
| archiveurl = https://web.archive.org/web/20100527133114/http://cf-pcmdi.llnl.gov/documents/white-papers/cf2_whitepaper_final.html/
| archivedate = 2010-05-27
▲}}</ref>
| author = Rew, Russ
| year = 2010
| title = CF Metadata Conventions
| url = http://
| url-status = dead
| archiveurl = https://web.archive.org/web/20140404101632/https://earthdata.nasa.gov/sites/default/files/esdswg/spg/rfc/esds-rfc-021/ESDS-RFC-021-v0.01.pdf
| archivedate = 2014-04-04
}}</ref>
<ref>{{cite news
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| title = Web Coverage Service (WCS) 1.1 extension for CF-netCDF 3.0 encoding
| url = http://xml.coverpages.org/OGC-09-018-WCS11-ExtensionCF-netCDF.pdf
}}</ref>
==Applications and
The CF conventions have been adopted by a wide variety of national and international programs and activities in the Earth sciences
| year = 2009
| title = Report of the 12th Session of the JSC/CLIVAR Working Group on Coupled Modelling (WGCM)
| url = http://wcrp.ipsl.jussieu.fr/Documents/WMP/136_WGCM12.pdf
}}</ref>
They are promoted as an important element of scientific community coordination by the [[World Climate Research Programme]]
| author = Kinter, James L. III
| year = 2005
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| title = Issues Related to the Dissemination of Climate Model Output
| url = http://wcrp.ipsl.jussieu.fr/Documents/WMP/Presentations/WMP1_2-7Taylor.pdf
}}</ref>
| author = Doutriaux, Charles
| year = 2010
| title = Climate Model Output Rewriter
| url = http://esg-repo.llnl.gov/gitweb/?p=cmor.git;a=blob;f=Doc/cmor_users_guide.pdf
}}{{dead link|date=August 2017 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{cite news
| author = Drach, Bob
| year = 2002
| title = Metadata Standards for Gridded Climate Data in the Earth System Grid
| url = http://archive.niees.ac.uk/talks/metadata/Bob_Drach_talk.ppt
| archive-url = https://web.archive.org/web/20040912230406/http://archive.niees.ac.uk/talks/metadata/Bob_Drach_talk.ppt
}}</ref><ref name="crwr.utexas">{{cite news▼
| url-status = dead
| archive-date = 2004-09-12
{{cite news
| year = 2006
| title = NetCDF in ArcGIS 9.2
| url = http://www.crwr.utexas.edu/gis/gishydro06/Introduction/Presentations/netCDF.ppt
| access-date = 2010-06-23
}}</ref>. The CF conventions have also been used to describe the physical fields transferred between individual Earth system model [[software components]], such as atmosphere and ocean components, as the model runs▼
| archive-url = https://web.archive.org/web/20100614235111/http://www.crwr.utexas.edu/gis/gishydro06/Introduction/Presentations/netCDF.ppt
<ref>{{cite journal▼
| archive-date = 2010-06-14
| url-status = dead
}}
▲
▲.<ref>{{cite journal
| doi = 10.1007/s12145-008-0016-1
| author = Dunlap, R. L. Mark, S. Rugaber, V. Balaji, J. Chastang, L. Cinquini, C. DeLuca, D. Middleton, and S. Murphy
| year = 2008
| title = Earth system curator: metadata infrastructure for climate modeling
| journal = Earth Science Informatics
| volume = 1
| pages = 131–149
| issue = 3–4
| doi-access = free
}}</ref>
===Supported
CF is intended for use with [[state estimation]] and [[forecasting]] data, 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.<ref name="crwr.utexas" /><ref>{{cite news
| author = V. Balaji
| year = 2008
| title = Metadata Standards for Gridded Climate Data in the Earth System Grid
| url = http://esdswg.eosdis.nasa.gov/WG/SPG/pdf/esdswg-cf-balaji.pdf
| url-status = dead
| archiveurl = https://web.archive.org/web/20100528100546/http://esdswg.eosdis.nasa.gov/WG/SPG/pdf/esdswg-cf-balaji.pdf
<ref name="crwr.utexas" />. 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.▼
| archivedate = 2010-05-28
▲}}<
===Supported
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
|
| title = Investigation of using HDF5 archival information packages (AIP) to store NASA ECS data
| url = http://ams.confex.com/ams/89annual/techprogram/paper_148062.htm
| publisher = 25th Conference on International Interactive Information and Processing Systems (IIPS) for Meteorology, Oceanography, and Hydrology, 89th American Meteorological Society Meeting
}}</ref>
==Design
Several principles guide the development of CF conventions:
* Data should be self-describing, without external tables needed for interpretation.
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* Redundancy should be avoided to prevent inconsistencies when writing data.
Specific CF metadata descriptors use values of attributes to represent
* [[Data provenance]]: <code>title</code>, <code>institution</code>, <code>contact</code>, <code>source</code> (e.g. model), <code>history</code> ([[audit trail]] of operations), <code>references</code>, <code>comment</code>
* Description of associated activity: <code>project</code>, <code>experiment</code>
* Description of data: <code>units</code>, <code>standard_name</code>, <code>long_name</code>, <code>auxiliary_variables</code>, <code>missing_value</code>, <code>valid_range</code>, <code>flag_values</code>, <code>flag_meanings</code>
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* Meaning of grid cells: <code>cell_methods</code>, <code>cell_measures</code>, 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 <code>standard_name</code> 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:
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* 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==
*[https://ncas-cms.github.io/cf-python/ CF-Python] is a data analysis package built on a complete implementation ([https://ncas-cms.github.io/cfdm/ CFDM]) of the CF conventions. The authors of the CFDM and CF-Python currently assert a desire to fully support all aspects of the CF conventions.
*[https://docs.unidata.ucar.edu/netcdf-java/current/userguide/ NetCDF-Java Library] parses CF Conventions and creates [https://web.archive.org/web/20141213021852/http://www.unidata.ucar.edu/software/thredds/current/netcdf-java/CDM/index.html#CoordSys Coordinate System] objects from them
* [[Origin (data analysis software)|OriginPro]] version 2021b supports<ref> {{cite web|url=https://www.originlab.com/doc/Origin-Help/NetCDF-Importing-Processing| title=NetCDF Importing and Processing |publisher=originlab.com |access-date=2021-05-11}}</ref> netCDF CF Convention. Averaging can be performed during import to allow handling of large datasets in a GUI software.
* The [https://xarray.pydata.org xarray] Python library parses and decodes data stored according to CF Conventions.
* The [https://scitools-iris.readthedocs.io/en/stable/index.html Iris] Python library "draws heavily from the NetCDF CF Metadata Conventions as a source for its data model".<ref> {{cite web| url=https://scitools-iris.readthedocs.io/en/stable/further_topics/metadata.html| title=Metadata - Iris Documentation| access-date=2023-02-10}}</ref>
==References==
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==External links==
*[
*[https://web.archive.org/web/20110606124657/http://badc.nerc.ac.uk/help/formats/netcdf/index_cf.html The CF Metadata Convention (BADC page)]
*[https://web.archive.org/web/20110726034739/http://www.esdswg.org/spg/docindexfolder/standards-track-rfcs/ NASA Standards Process Group]
*[https://web.archive.org/web/20110717124506/http://marinemetadata.org/references/esdscfconventions Standard for the CF Metadata Conventions (Marine Metadata
*[https://web.archive.org/web/20110727140821/http://www.oceandatastandards.org/index.php?option=com_content&task=view&id=4&Itemid=8 Ocean Data Standards on Metadata]
[[Category:Metadata]]
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