[MITgcm-devel] gentim2d controls - nonperiodic forcing

[Daniel Goldberg]

Hi,

I was wondering if anyone uses the gentim2d control for NON-periodic
time-dependent cases, and/or whether there are thoughts on the following:

the S/R ctrl_get_gen_rec uses the S/R get_periodic_interval to determine
the indices of the time-dependence between which to interpolate, and the
interpolation weights (called count0, count1, and fac within
ctrl_get_gen_rec).

1) get_periodic_interval has a case for a non-periodic time-record sequence
(line 100) if externForcingCycle is set to zero -- but ctrl_get_gen_rec
ensures that this is never called! (i am not using ALLOW_CAL)

2) if this is modified to allow get_periodic_interval to be called, this
returns a given count0, count1, and fac according to the
get_periodic_interval algorithm in the nonperiodic case. But I am unsure if
the result is what should be done.

For example, if the period of gentim2d as set in data.ctrl
(xx_gentim2d_period) is 1 day, and the simulation is 10 days, an
appropriate-seeming way to define time-dependent forcing would be to have
11 fields, applied at t=0 days, 1 days, 2 days, ... I think currently they
are defined at 0.5 days, 1.5 days, etc.. and I am unsure how the
interpolation should be done at t=0.25 days.

So for example, in the scheme i propose and the above example, count0 could
take on values from 0 to 10, and count1 from 1 to 11, and at

t=0 days --> count0 = 1, count1 = 2, fac=1
t=0.25 days --> count0=1, count1=2, fac=0.75
t=1 days --> count0=2, count1=3, fac=1
t=10 days --> count0=10, count1=11, fac=0

This is not, I believe, the way things are defined now, but I could be
wrong. Assuming I am not, and changes were made to ctrl_get_gen_rec to
address (1), and to get_periodic_interval to implement the following *only
when exter_forcing_cycle = 0*, would this impact anyone?

Thanks
Dan

-- 

Daniel Goldberg, PhD
Lecturer in Glaciology
School of Geosciences, University of Edinburgh
Geography Building, Drummond Street, Edinburgh EH8 9XP


em: D <dgoldber at mit.edu>an.Goldberg at ed.ac.uk
web: http://ocean.mit.edu/~dgoldberg
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