[Go-essp-tech] Corrected THREDDS group wiki page link
Karl Taylor
taylor13 at llnl.gov
Tue Feb 21 09:51:11 MST 2012
Hi all,
I've just looked up the output requirements, and found that we were very
explicit about the basetime not changing from one file to another within
an experiment and also in going from the historical run to a future
scenario run. Here are the requirements taken from the document (
CMIP5_output_metadata_requirements.pdf
<http://cmip-pcmdi.llnl.gov/cmip5/docs/CMIP5_output_metadata_requirements.pdf>)
linked at http://cmip-pcmdi.llnl.gov/cmip5/output_req.html#metadata .
There it says:
? For all time coordinates the units must be "days since <basetime>",
where <basetime> must be specified by the user, typically in the form
year-month-day (e.g., "days since 1800-01-01").Follow these rules:
? The same 'base time' should apply to all time samples in a single
simulation (i.e., when creating a series of files containing model
output for a single run, don't change the units or 'base time' from one
file to the next; in the above example 1800-01-01 is the 'base time').
? For simulations meant to represent a particular historical period, set
the 'base time' to the time at the beginning of the simulation.A
historical run initialized with forcing for year 1850 would, for
example, have units of "days since 1850-01-01".The 'base time' used in
the control run is irrelevant as is the time in the control run when the
historical run was initialized.
? For the future scenario runs, retain the same 'base time' as used in
the historical run from which it was initiated.
? For simulations not tied to a particular date, the 'base time' is
arbitrary, but it should correspond to the beginning of the run.Thus, in
these simulations, 'base time' is whatever time one decides to assign to
the beginning of the run.
? All values of the time coordinate should be positive, which will be
ensured by following the above rules.
I guess the QC or publisher should object if these rules are not followed.
Best regards,
Karl
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