[MITgcm-support] Silly question about pkg/diagnostics

Ryan Abernathey ryan.abernathey at gmail.com
Wed May 3 11:50:06 EDT 2017

If one year were an exact multiple of three months, then the yearly average
would be exactly the same using both methods.

A "month" is unfortunately not a well-defined unit of time. Unless you
define a month as 365/12 days, then you will get a slight discrepancy
between a full yearly average the average of four three-month periods.

Many models have a feature to save averages in true calendar months (i.e.
January = 31 days, February = 28 days, etc.). In this case, a yearly
average would be an exact average of 12 months. As far as I know, MITgcm
does not support this. (But it should!)


On Wed, May 3, 2017 at 10:52 AM, Anthony Joyce <ajcolett at geo.umass.edu>

> Hi all,
> I have a quick question regarding the time-averaged data using
> pkg/diagnostics. If I set THETA to output every year (in seconds), the data
> should be a time averaged value for the whole year. If I do the same
> variable, but every 3-months (in seconds), the data should be a
> time-averaged value of 3 months. Anyone know why my yearly variable output
> would be different from me using 3-month data to get a yearly average?
> Thanks,
> Anthony
> --
> Anthony J. Coletti
> Climate System Research Center
> Department of Geosciences
> University of Massachusetts-Amherst
> paleoclimate.org
> ajcolett at geo.umass.edu
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support
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