Jonathan,
For what it's worth, the UDUNITS "year" is a "tropical year", which is
the interval between two successive passages of the sun through the
vernal equinox. This is approximately 365.242198781 days or
3.15569259747e7 seconds).
Regards,
Steve Emmerson
UDUNITS Developer
Jonathan Gregory wrote:
> Dear Jon
>
> If the model has a seasonal cycle, it must have a calendar, so the appropriate
> unit is of the form "time-unit since reference-time", with the calendar
> specified using the calendar attribute. Indeed, many models use 360-day years,
> which is one of the possibilites supported by the calendar attribute. The use
> of the reference time ties the times to the seasonal cycle. The year itself
> might be arbitrary, as you say - it often is, in control runs.
>
> "year" is not a good unit to use, because in udunits it does not mean a
> calendar year, but exactly 365.242 days, which is almost certainly not what
> would be intended. It is better to use days or shorter units.
>
> For models with no seasonal cycle, CF permits calendar="none".
>
> Cheers
>
> Jonathan
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Received on Fri Mar 30 2007 - 08:35:25 BST
