Is there an accepted convention for describing the units of a
climatological time axis? e.g. monthly averages January, February
etc.
The CF Conventions (Section 7.4)
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.4/cf-conventions.html#climatological-statistics
note the COARDS recommendation of using year ZERO:
"For compatibility with COARDS, time coordinates should also be
recognised as climatological if they have a units attribute of
time-units relative to midnight on 1 January in year 0 i.e. since
0-1-1 in udunits syntax"
But the document goes on to discourage this:
"We do not recommend this convention because (a) it does not provide
any information about the intervals used to compute the climatology,
and (b) there is no standard for how dates since year 1 will be
encoded"
Looking at how others have handled this there is a tendency to choose
an arbitrary base date, e.g. the World Ocean Atlas at NODC
http://data.nodc.noaa.gov/thredds/dodsC/woa09/temperature_monthly_1deg.nc.html
uses "days since 2008-1-1" when there is no actual relevance to year
2008 at all. All the climatologies at ERDDAP use "seconds since
1970-01-01".
Thanks,
John.
--
John L Wilkin | jwilkin at rutgers.edu | ph: +1-609-630-0559
web: marine.rutgers.edu/~wilkin | cal: tinyurl.com/jwilkincalendar
Received on Fri Jan 04 2013 - 14:12:18 GMT
