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[THREDDS #RNZ-598093]: 360 day year support?



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


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