[MITgcm-devel] monthly, inter-annually varying forcing with exf

[Martin Losch]

Hi Oliver,

sounds good to me. 

It may be a little confusing that in general *RepCylce is in seconds, except for this particular case when it is in months. I can see that this is as confusing (or not confusing) as the *period = -12., but in that case the negative sign makes it clear that -12 is a special value. I am not sure if that should really be a concern, but would negative *RepCycles make sense in this context?

Martin



> On 15. Nov 2019, at 15:54, Oliver Jahn <jahn at mit.edu> wrote:
> 
> Hi Developers,
> 
> I have some code for extending the exf package to read calendar-monthly
> forcing fields that vary from year to year.  I think other people could
> find this useful too, see for instance
> 
> http://mailman.mitgcm.org/pipermail/mitgcm-support/2019-October/012213.html
> 
> I'd like to get some input on how to enable this feature.  Right now the
> magic value of *period = -12 is used for monthly climatologies.  I have
> talked to Jean-Michel about this and we think the most logical extension
> would be to use the same value for inter-annually varying monthly fields
> and distinguish by *RepCycle.  A *RepCycle of 0 would be for
> non-repeating forcing, and 12 could be for climatology.  One could also
> support monthly forcing that repeats after a different number of months
> (well, years, usually), and *RepCycle could be in units of months - as
> suggested by *period = -12.  So, *RepCycle = 120 would be monthly
> forcing that repeats every 10 years.
> 
> We do not want to break existing setups, of course, so we were thinking
> of defaulting *RepCycle to 12 when *period is -12 and to repeatPeriod in
> all other cases.  This would be accomplished by an UNDEF default value
> that is then changed to either 0 or repeatPeriod once *period has been set.
> 
> Any thoughts on this would be very welcome!  Maybe this breaks someone's
> use case we didn't think of.  Please let us know!
> 
> Cheers,
> Oliver
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