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..........
Received on Fri Oct 08 2010 - 12:00:57 BST
