[MITgcm-support] question on sponge-layer/mpi

[Uli Riemenschneider]

Hi again,

I was wondering if someone could give me a few pointers on how to setup
a sponge layer in the MITgcm. Basically what I want to do is a kind of 
climatological relaxation to a fixed/prescribed background profile of 
temperature. Following the e-mails from Theo a few weeks back I have 
figured out that I need to add a bit of code in the temperature 
subroutine of external_forcing.F along the lines of what Theo outlined n 
his mail, but for the temperature field:

        DO j=jMin,jMax
        DO i=iMin+1,iMax-1
         gT(i,j,kLev,bi,bj) = gT(i,j,kLev,bi,bj)
     &   +rayleighz(i,j,kLev,bi,bj)*
     &   ('backgound Temp (tRef ?)' - gT(i,j,kLev,bi,bj))
        ENDDO
       ENDDO

I am sure someone has done this kind of thing before so I was hoping I 
could get help with figuring out where to best add the sponge layer to 
the code. Plus I am also running the model on multiple processors and 
was wondering if the problem Theo was having has been resolved?

Many thanks!
Uli

Quoting Theo Gerkema <Theo.Gerkema at hmg.inpg.fr>:

Could someone help me sorting out the following problem:
in external_forcing.F I've added a sponge-layer; the sponge
covers (say) the first 100 points of the basin:

      DO j=jMin,jMax
       DO i=iMin,iMax
        rayleighz(i,j,kLev,bi,bj)=0.
       ENDDO
      ENDDO
      DO j=jMin,jMax
       DO i=1,100
        rayleighz(i,j,kLev,bi,bj)=0.1*(100-i)/100.
       ENDDO
      ENDDO

It works selectively on the baroclinic field (tides):

        DO j=jMin,jMax
        DO i=iMin+1,iMax-1
         gU(i,j,kLev,bi,bj) = gU(i,j,kLev,bi,bj)
     &   -rayleighz(i,j,kLev,bi,bj)*
     &    abs(uVel(i+1,j,kLev,bi,bj)-uVel(i-1,j,kLev,bi,bj))*
     &    uVel(i,j,kLev,bi,bj)
        ENDDO
       ENDDO

This works well, but I've now started doing runs in parallel,
and if I run the code on for example two processors, an additional
sponge-layer appears halfway the basin (ie at the left end of the 2nd
sub-domain), rendering the results meaningless.
Is there a way I can avoid the repetition of the sponge in parallel
runs? Many thanks!

-- 
*********************************************************
Ulrike Riemenschneider,  Postdoctoral Investigator
Physical Oceanography Dept. MS #21
Woods Hole Oceanographic Institution
Woods Hole, MA 02543, USA

Phone: (+1) 508 289 2916 Fax: (+1) 508 457 2181
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