[MITgcm-support] SSH drift and obcs again

[Thomas Haine]

No, there's no wall in my bathy file although most of the northern
domain is blocked.  

Tom.

On Fri, 2005-10-21 at 13:12 -0700, Chris Hill wrote:
> Hi Tom,
> 
>   When you turn off norther edges obcs (ii) do you put a wall at the 
> northern edge?
> 
> Chris
> Thomas Haine wrote:
> > Folks, 
> > 
> > I've been able to isolate the SSH drift/obc issue I reported a few weeks
> > ago to a specific part of the code. My expertise is dwindling as I get
> > deeper in, so maybe someone else can help:
> > 
> > Configuration: checkpoint57p_post, GFDL ic., linear free sfc, seaice
> > off, evap and precip off, obc sponge off, obc orlanski off. Realistic
> > Denmark Strait bathy. at 2km resolution and open bdys at (parts of) all
> > 4 walls. I've corrected the OBCS_BALANCE code to zero the net transport
> > divergence so eta won't drift. (N.B., the existing OBCS_BALANCE code has
> > several bugs - when I get all this sorted out I'll provide a cleaned up
> > version).
> > 
> > 
> > i) What works: obcs switched on at N & S boundary with net barotropic
> > inflow at the north and outflow at the south. I see no drift in eta to
> > machine precision and small O(1e-14) cg2d Sum(rhs). Looks good.
> > 
> > ii) What doesn't work: as above but switch off northern obc (in
> > data.obcs). Now eta drifts, cg2d rhs is O(1) and w diverges after 2
> > steps. Looks bad!
> > 
> > iii) Also doesn't work (dies at step 2): 
> > as i) except: pkg/obcs FALSE,
> > as i) except: N obc closed and E or W obc open.
> > 
> > iv) Also works: As i) except with solid walls at all edges in my bathy
> > file and pkg/obcs off. Reassuring.
> > 
> > The pressure solver source is vastly different in i) and ii) at the
> > first solve. This leaves little room for the problem: it's somewhere in
> > cg2d and related code in relation to obcs. Any ideas where?
> > 
> > Thanks! Tom.
> > 
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-support
> > 
> 
> 
-- 
--------------------------------------------
 Thomas W. N. Haine
                                                                                                                                                              
 Associate Professor of Physical Oceanography,
 Department of Earth & Planetary Sciences,
 329 Olin Hall, The Johns Hopkins University,
 Baltimore, MD 21218, USA.
 Tel : 410 516 7048,   Fax : 410 516 7933
 Thomas.Haine at jhu.edu
 http://www.jhu.edu/~eps/faculty/haine
--------------------------------------------