[MITgcm-support] OBCS (open boundary forcing) problem

[Jonny Williams]

Hi there

I am currently running two separate regional versions of the MITgcm, one at
1 degree resolution (45 longitudes x 80 latitudes) and one at 0.1 degree
resolution (450 longitudes x 800 latitudes) with both EXF and OBCS packages
turned on.

They are essentially identical in that they use the same forcing data,
albeit regridded to differing resolutions.

My problem is essentially that although the temperature and salinity
forcing seem to be behaving themselves, the forcing of the u (zonal) and v
(meridional) velocities are not. In the output NetCDF files I get, T and S
of dimension 45 x 80, u of dimension 46 x 80 and v of dimension 45 x 81.
This makes sense since velocities and tracers are usually on staggered
grids in GCMs. What is strange however is that the 1st, 2nd and last
columns/rows of data for u/v are identical and constant, that is, the open
boundary conditions seem to be being applied at BOTH sides of the geometry.
The penultimate row/column of u/v are also constant throughout the
simulation. This constancy is good as it shows that two different sets of
OBCS boundary conditions are being applied at least!

Does anyone have any ideas about what could be going on? I can provide more
details if need be!

Many thanks

Jonny

-- 
Dr Jonny Williams
School of Geographical Sciences
University of Bristol
University Road
BS8 1SS

+44 (0)117 3318352
jonny.williams at bristol.ac.uk<https://mail.google.com/mail/?view=cm&fs=1&tf=1&to=jonny.williams@bristol.ac.uk>
bit.ly/jonnywilliams
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