[MITgcm-support] timing of snapshots and time averages in pkg/timeave and pkg/diagnostics

[Menemenlis, Dimitris (3248)]

Hello MITgcm support,
is a discussion of the exact timing of diagnostic snapshots and time averages available somewhere?

I notice that pkg/diagnostics is not consistent with the old definitions in pkg/timeave.
Which time-averaging definition is correct, that of pkg/timeave or that of pkg/diagnostics?

Specifically, in pkg/timeave, except for PHL where
one-time-step-average of PHL(t) = snapshot of PHL(t)
all other variables have
one-time-step-average of VARIABLE(t) = ( snapshot of VARIABLE(t-1) + snapshot of VARIABLE(t) ) / 2

For pkg/diagnostics the correspondence between snapshots and time averages is (from diagnostics_write.F):
       myItM1 = myIter - 1
         IF ( freqSec.LT.0. ) THEN
C--     write snap-shot with suffix = myIter-1 to be consistent with
C       state-variable time-step:
           wrIter = myItM1
           wrTime = myTime - deltaTclock
         ELSE
           wrIter = myIter
           wrTime = myTime
         ENDIF
that is,
one-tine-step-average of VARIABLE(t) = snapshot of VARIABLE(t-1)

Thank you,

Dimitris Menemenlis