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 <[email protected]> To: [email protected] CC: Mariana Vertenstein <[email protected]>, [email protected] 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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