Tony et. al.,
I support Benno's approach. This is an argument that goes back a very
long time (probably 20+ years!). I have always taken the same position
that you have -- namely that the proleptic Gregorian calendar is the
common sense one to use for scientific (though not social science)
datasets. The compromise involved in documenting "calendar:
proleptic_gregorian" seems vastly smaller, though, than the compromise
involved in breaking backwards compatibility of existing files.
- Steve
===========================
On 10/15/2010 8:58 AM, Benno Blumenthal wrote:
> Sorry, I don't understand why you simply label your datasets
>
> calendar: proleptic_gregorian
>
> if they go before 1582, and support gregorian with the restriction
> that the values correspond
> to post 1582. Much better than changing the calendar attribute
> standard (again!), and messing up existing code that does support the
> standard, and existing data that is correctly labeled with the current
> standard.
>
>
> Benno
>
>
> On Wed, Oct 13, 2010 at 8:55 PM, Earl Schwab<eschwab.esmf at gmail.com> wrote:
>> Hi,
>>
>> As Tony indicated, the ESMF Team also supports this proposal to make
>> the CF default/standard Gregorian calendar proleptic. Like CCSM, our
>> Gregorian calendar is proleptic, and, also like CCSM, we do not
>> support a mixed Julian/Gregorian historical calendar, as we've had
>> no such requirement to-date from our users.
>>
>> Regards,
>> Earl Schwab
>> ESMF Core Team
>>
>>
>> -------- Original Message --------
>> Subject: proposed change to calendar definitions
>> Date: Fri, 08 Oct 2010 11:00:57 -0700
>> From: Tony Craig<tcraig at ucar.edu>
>> To: cf-metadata at cgd.ucar.edu
>> CC: Mariana Vertenstein<mvertens at ucar.edu>, eschwab.esmf at gmail.com
>>
>> The NCAR CCSM climate model tries to follow the CF standard
>> as much as possible with regard to input and output datasets.
>> However, we are finding it nearly impossible to adhere to the
>> calendaring standard. We do not have access to time managers
>> either internally or through external sources, such as ESMF, to
>> support the default CF "gregorian/standard" calendar as documented here,
>>
>> http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#calendar
>>
>> And at the end of that section, the CF convention notes in particular
>> the challenges associated with "the discontinuity" in the mixed
>> gregorian/julian calendar. We have discussed calendaring issues with the
>> ESMF developers, and they also have no immediate plans to support
>> the mixed gregorian/julian calendar. ESMF is one of our primary tools
>> for supporting infrastructure in climate models, especially time managers.
>>
>> As a result, in our implementation, we treat the calendar naming
>> conventions differently.
>>
>> gregorian == proleptic_gregorian
>>
>> and mixed gregorian/julian is not supported.
>>
>> We would like to propose a change to the CF calendar conventions to
>> reflect what we believe the community is already doing. We propose
>>
>> 1. continued support of the name proleptic_calendar for backwards
>> compatability.
>> 2. changing the definition of gregorian and standard to be the proleptic
>> gregorian calendar instead of the mixed gregorian/julian.
>> 3. make the proleptic gregorian the default calendar
>> 4. add a new calendar name, such a gregorian_julian to provide the
>> ability to define a mixed calendar in CF conventions.
>>
>> that would change the definition in the above CF standards document to the
>> following
>>
>> gregorian or proleptic_gregorian or standard
>> A gregorian calendar extended to dates before 1582...
>> This is the default.
>>
>> gregorian_julian
>> Mixed Gregorian/Julian calendar as defined by Udunits.
>>
>> We've had discussions about this with ESMF and they are supportive
>> of this proposal. Their gregorian calendar is also proleptic and this
>> proposed change would make both their and our implementation more
>> closely aligned with the CF convention.
>>
>> If you have any questions, please feel free to contact me. thanks,
>>
>> tony..........
>>
>>
>> _______________________________________________
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>> CF-metadata at cgd.ucar.edu
>> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
>>
>
>
> --
> Dr. M. Benno Blumenthal benno at iri.columbia.edu
> International Research Institute for climate and society
> The Earth Institute at Columbia University
> Lamont Campus, Palisades NY 10964-8000 (845) 680-4450
> _______________________________________________
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> CF-metadata at cgd.ucar.edu
> http://mailman.cgd.ucar.edu/mailman/listinfo/cf-metadata
Received on Fri Oct 15 2010 - 10:11:39 BST
