Dear Aaron Thank you for the suggestion. I have opened a CF trac ticket to propose such a clarification at http://cf-trac.llnl.gov/trac/ticket/123
Cheers Jonathan ----- Forwarded message from Aaron Sweeney <aaron.swee...@noaa.gov> ----- > Date: Wed, 17 Dec 2014 15:46:51 -0700 > From: Aaron Sweeney <aaron.swee...@noaa.gov> > CC: CF Metadata List <cf-metadata@cgd.ucar.edu> > Subject: Re: [CF-metadata] how to indicate a variable representing a physical > quantity is an observation, a modelled value, a difference or > residual, etc. > User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 > Thunderbird/31.3.0 > > Dear Jonathan, > > Thank you very much for your comment. The parenthetical > "...from different sources /(such as observations and models)/" is > missing from section 3.3 (Standard Name) of the CF Conventions v1.6 > (and draft v1.7). This is important for proper interpretation. On > initial reading of the section 3.3, I interpreted the word "sources" > to mean data providers. I would recommend adding your parenthetical > to the documentation and possibly refer the reader to ACDD v1.3 to > address the question of how to attribute a variable as originating > from observation, model, or other, as suggested by John Graybeal. > > Cordially, > Aaron > > > >Date: Mon, 15 Dec 2014 14:03:48 +0000 From: Jonathan Gregory > ><j.m.greg...@reading.ac.uk> To: cf-metadata@cgd.ucar.edu Subject: > >Re: [CF-metadata] how to indicate a variable representing a > >physical quantity is an observation, a modelled value, a > >difference or residual, etc. Message-ID: > ><20141215140348.ga7...@met.reading.ac.uk> Content-Type: > >text/plain; charset=us-ascii Dear Aaron > >>I think there's a reason CF names don't naturally distinguish between > >>measured or observed values?CF names tend to describe the meaning of the > >>value, and explicitly avoids saying how it was derived. The derivation is > >>reserved to other attributes, like the 'source' (which should distinguish > >>between a model and an observation, though not in a computable way), or > >>'history'. > >I agree with this remark of John's. In fact, the main purpose of the CF > >standard names is to indicate which quantities should be regarded as > >comparable. Usually, we want to compare quantities derived from different > >sources (such as obs and models), so we give the corresponding quantities the > >same standard names, in order to indicate they can be meaningfully compared: > >that they are apples from different trees, rather than apples and oranges. > > > >Best wishes > > > >Jonathan > > > > > On 12/12/2014 12:46 PM, John Graybeal wrote: > >Just yesterday (really!) I was looking at the almost-ready ACDD > >1.3 convention, and saying "What is the 'coverage_content_type' > >attribute good for?" It appears to be good for almost exactly what > >you want. This attribute is 'highly recommended' for all NetCDF > >variables, and is defined as "An ISO 19115-1 code to indicate the > >source of the data (image, thematicClassification, > >physicalMeasurement, auxiliaryInformation, qualityInformation, > >referenceInformation, modelResult, or coordinate)." However, this > >covers only 2/3 of what you want: physicalMeasurement for in-situ > >observations, and modelResult for a value from a model. The > >difference is also a modelResult in my opinion, but that doesn't > >help your use case. > > > >If you are looking for a pure CF answer, there's not a complete > >answer, but there are standard names that refer to differences -- > >these usually end with the phrase _anomaly (Definition: "anomaly" > >means difference from climatology."); or there's one, umm, anomaly > >that starts with difference_ > >(difference_of_air_pressure_from_model_reference). Because the > >phrase _anomaly is already in 5 terms, it shouldn't be an issue to > >add more as needed. And that conveniently bridges the above gap in > >your use case. > > > >I think there's a reason CF names don't naturally distinguish > >between measured or observed values?CF names tend to describe the > >meaning of the value, and explicitly avoids saying how it was > >derived. The derivation is reserved to other attributes, like the > >'source' (which should distinguish between a model and an > >observation, though not in a computable way), or 'history'. > > > >Hope that helps, at least a bit. > > > >John > > > >References: > >* ACDD 1.3 convention, almost done now: > >http://wiki.esipfed.org/index.php/Attribute_Convention_for_Data_Discovery_1-3 > >* coverage_content_type attribute: > >http://wiki.esipfed.org/index.php/Attribute_Convention_for_Data_Discovery_1-3#coverage_content_type > >* purpose of a standard name: > >http://cfconventions.org/faq.html#stdnames_purpose > > > >--------------- > >John Graybeal > >Marine Metadata Interoperability Project: http://marinemetadata.org > >MMI Ontology Registry and Repository: http://mmisw.org/orr > > > > > > > >On Dec 12, 2014, at 11:01, Aaron Sweeney <aaron.swee...@noaa.gov > ><mailto:aaron.swee...@noaa.gov>> wrote: > > > >>Hi, > >> > >> I've looked through the latest CF Conventions and CF > >>Standard Names documents, but have been unable to find an answer > >>(or example) to the following question: > >> > >> How do I indicate that a variable representing a physical > >>quantity is an in situ observation, a value that came from a > >>model, or a difference or residual between an observation and a > >>modelled value (observed minus modelled)? > >> > >> My initial thought was to use the same standard name for > >>each variable, but provide a standard name modifier. But after > >>reading the appendix on modifiers, they seem to be used for > >>something else. The standard names themselves only describe the > >>physical quantity, but not whether or not they are an observed > >>value or modelled value. > >> > >> Please point me toward the appropriate documentation, if it > >>exists. Thanks for your kind attention. > >> > >>Cordially, > >>Aaron > >> > >>-- > >>Aaron D. Sweeney > >>Water Level Data Manager > >> > >>Cooperative Institute for Research in Environmental Sciences (CIRES) > >>University of Colorado at Boulder > >>and > >>NOAA National Geophysical Data Center > >>Marine Geology and Geophysics Division > >>325 Broadway, E/GC3 > >>Boulder, CO 80305-3328 > >> > >>Phone: 303-497-4797, Fax: 303-497-6513 > >> > >>DISCLAIMER: The contents of this message are mine personally and > >>do not necessarily reflect any position of NOAA. > >> > >>_______________________________________________ > >>CF-metadata mailing list > >>CF-metadata@cgd.ucar.edu <mailto:CF-metadata@cgd.ucar.edu> > >>http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata > > > > -- > Aaron D. Sweeney > Water Level Data Manager > > Cooperative Institute for Research in Environmental Sciences (CIRES) > University of Colorado at Boulder > and > NOAA National Geophysical Data Center > Marine Geology and Geophysics Division > 325 Broadway, E/GC3 > Boulder, CO 80305-3328 > > Phone: 303-497-4797, Fax: 303-497-6513 > > DISCLAIMER: The contents of this message are mine personally and do not > necessarily reflect any position of NOAA. > > _______________________________________________ > CF-metadata mailing list > CF-metadata@cgd.ucar.edu > http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata ----- End forwarded message ----- _______________________________________________ CF-metadata mailing list CF-metadata@cgd.ucar.edu http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
