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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.<ref>{{cite news
| author = Gregory, Jonathan
| year = 2003
| title = The CF metadata standard
| url = http://
}}</ref> The conventions contained generalizations and extensions to the earlier Cooperative Ocean/Atmosphere Research Data Service (COARDS) conventions <ref>{{cite web|url=http://ferret.wrc.noaa.gov/noaa_coop/coop_cdf_profile.html|title=Conventions for the Standardization of NetCDF files|date=May 1995|access-date=2010-06-23|archive-url=https://web.archive.org/web/20100527095818/http://ferret.wrc.noaa.gov/noaa_coop/coop_cdf_profile.html|archive-date=2010-05-27|url-status=dead}}</ref> and the Gregory/Drach/Tett (GDT) conventions.<ref>{{cite web|url=http://www-pcmdi.llnl.gov/drach/GDT_convention.html|title=GDT netCDF conventions for climate data, version 1.3|date=March 14, 1999|access-date=June 23, 2010|archive-url=https://web.archive.org/web/20100610102527/http://www-pcmdi.llnl.gov/drach/GDT_convention.html|archive-date=June 10, 2010|url-status=dead}}</ref> As the scope of the CF conventions grew along with its user base, the CF community adopted an [[open governance]] model.<ref>{{cite news
| 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> 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
| author = Rew, Russ
| year = 2010
| title = CF Metadata Conventions
| url = http://earthdata.nasa.gov/sites/default/files/esdswg/spg/rfc/esds-rfc-021/ESDS-RFC-021-v0.01.pdf
| 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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}}</ref>
==Applications and
The CF conventions have been adopted by a wide variety of national and international programs and activities in the Earth sciences.<ref>[http://cf-pcmdi.llnl.gov/projects-and-groups-adopting-the-cf-conventions-as-their-standard Projects and Groups Adopting or Encouraging the CF-Conventions as a Standard] {{webarchive |url=https://web.archive.org/web/20100823061034/http://cf-pcmdi.llnl.gov/projects-and-groups-adopting-the-cf-conventions-as-their-standard |date=August 23, 2010 }}</ref> For example, they were required for the [[climate model]] output data collected for [[Coupled model intercomparison project]]s, which are
| year = 2009
| title = Report of the 12th Session of the JSC/CLIVAR Working Group on Coupled Modelling (WGCM)
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| 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
| archive-date = 2010-06-14
| url-status = dead
}}
▲
.<ref>{{cite journal
| doi = 10.1007/s12145-008-0016-1
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| 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
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| 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
| archivedate = 2010-05-28
}}</ref> 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
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.<ref>{{cite news
|
| 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
Line 85 ⟶ 102:
}}</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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