[MITgcm-devel] [MITgcm-cvs] MITgcm/pkg/seaice CVS Commit

[Martin Losch]

Hi Jean-Michel,

thanks for catching this. 
It appears that the change that breaks this experiment is in line 166ff where etaZ ist computed. I used to do it like this:
 	           etaZ(I,J,bi,bj) = 
      &         ( eta (I,J  ,bi,bj)  + eta (I-1,J  ,bi,bj)
      &         + eta (I,J-1,bi,bj)  + eta (I-1,J-1,bi,bj) )
      &         / MAX(1.D0,maskC(I,J,  k,bi,bj)+maskC(I-1,J,  k,bi,bj)	 
      &         +          maskC(I,J-1,k,bi,bj)+maskC(I-1,J-1,k,bi,bj) )
now it's like this:

          sumNorm  = maskC(I,J,  k,bi,bj)+maskC(I-1,J,  k,bi,bj)
     &             + maskC(I,J-1,k,bi,bj)+maskC(I-1,J-1,k,bi,bj)
          IF ( sumNorm.GT.0. _d 0 ) sumNorm = 1. _d 0 / sumNorm
          etaZ(I,J,bi,bj) = sumNorm *
     &         ( eta (I,J  ,bi,bj)  + eta (I-1,J  ,bi,bj)
     &         + eta (I,J-1,bi,bj)  + eta (I-1,J-1,bi,bj) )
I think that this should give the same results as long as there is one wet point, but maybe, if the masking of eta is not appropriate, I can also get a non-zero result over land with the old formulation (with all maskC=0). In that case the new version give the correct answer, doesn't it? On the boundary the result should be that same, shouldn't it?
For free slip, etaZ = 0 on the boundaries (on also on land), that's why it only shows up in the no-slip case.

I think we can modify the result of the experiment. Do you agree?

Martin

PS. I also seem to have to forgotten to check in an updated tag-index, it's still in my files, but not in the repository.





On Apr 29, 2013, at 6:46 PM, Jean-Michel Campin <jmc at ocean.mit.edu> wrote:

> Hi Martin,
> 
> It looks like the changes you made in seaice_calc_viscosities.F
> are producing small differences for lab_sea standard experiment.
> It used to pass with 16 digits (baudelaire, gfortran) but now we
> are only getting 11 digits:
> < Y Y Y Y>11<16 16 16 16 16 16 16 16 16 16 13 16 16 16 12 14 22 16 16 16 22 16 16 16 pass  lab_sea
> Might be related to the fact that this experiment is using LSR with
> SEAICE_no_slip=T (whereas the others use the default SEAICE_no_slip=F).
> 
> It would be usefull to check if these different results are somehow expected,
> and if it's the case, then we should update lab_sea/results/output.txt
> 
> Cheers,
> Jean-Michel
> 
> On Tue, Apr 23, 2013 at 05:53:44AM -0400, Martin Losch wrote:
>> Update of /u/gcmpack/MITgcm/pkg/seaice
>> In directory forge:/tmp/cvs-serv8331/pkg/seaice
>> 
>> Modified Files:
>> 	seaice_check.F seaice_calc_viscosities.F 
>> Log Message:
>> clean up: remove/retire two options for SEAICetaZmethod (1,2),
>> introduce area weighting for method 3
>> 
>> 
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