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[THREDDS #RNZ-598093]: 360 day year support?
- Subject: [THREDDS #RNZ-598093]: 360 day year support?
- Date: Tue, 02 Feb 2010 11:00:58 -0700
Hi Steve,
Let me see if I understand what you are doing. It sounds like you are
aggregating your data files using a "joinExisting" aggregation on the dummy
time variable you added to each dataset. Instead of defining the time values in
the dummy time variables, you are defining them in the XML. (Is it just easier
that way or is there some other reason?)
Back to your main question: THREDDS aggregations don't understand different
calendars. However, the CF convention describes how to specify various
calendars in a netCDF file. So, by getting the time values and certain
attributes correct, you should end up with a 360-day calendar dataset according
to CF. Section 4.4.1 "Calendar" in the CF specification details what you'll
need with some other good info, if your not up on CF time coordinates, in
section 4.4 "Time Coordinates":
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#calendar
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#time-coordinate
I'm not that familiar with this part of CF and it isn't clear to me how to
define your time values. There aren't any examples showing how the 360 day year
interacts with the "units" value which according to udunits is a "mixed
Gregorian/Julian calendar". The best bet here is probably to post a question on
the CF mailing list. You can subscribe to that from the "Discussion" section of
the CF site (http://cf-pcmdi.llnl.gov/).
One other aggregation note. If your file names indicate the time for that file,
you may be able to use a "joinNew" aggregation instead of "joinExisting". You
could then use a "dataFormatMark" attribute to extract the run time of each
file. Though I guess you'll need to figure out what the time values should be
according to CF before proceeding with this. Anyway, more info on
"dateFormatMark" in section "Extracting date coordinates from the filename" of
the aggregation page:
http://www.unidata.ucar.edu/software/netcdf/ncml/v2.2/Aggregation.html
Hope this all helps,
Ethan
> We have some ROMS model results that are based on a 360 day calendar year.
> Is there a way to specify this kind of year in THREDDS? We have a file
> every three days, 120 files per year. To complicate the issue the files
> don't have a time variable in them.
>
> For now, in the xml file I have specified:
>
> <variable name="time" shape="time" type="float">
> <attribute name="units" value="hours since 1991-01-01 00:00 UTC"/>
> <values start="0.0" increment="73.0"/>
> </variable>
>
> and it is working. To get this to work though I did have to add a dummy
> time variable in each data file.
>
> I specified 73 hours for the increment to make up for the 5 day difference
> in calendar years.
>
> Rich Signell seemed to think that maybe there was a provision for this
> sort of thing. If so, can you help me with it?
>
> Thanks a lot,
>
> Steve
Ticket Details
===================
Ticket ID: RNZ-598093
Department: Support THREDDS
Priority: High
Status: Closed