[MITgcm-devel] Problems in side-drag

[Jean-Michel Campin]

Hi,

Some problems with the "old" versions (but still in place, with
#define SIDEDRAG_OLD_VERSION) of mom_u,v_sidedrag.F:

1) in mom_v_sidedrag.F, we have a mixture of rAs & rAw
(from version 1.4, checked-in on Nov 2, 2004)
where we should have only rAs:
 
>       Ahtmp=min(viscAh+viscAhGrid*rAs(i,j,bi,bj)/deltaTmom,
>    &            viscAhMax)
>       A4tmp=min(viscA4+viscA4Grid*(rAs(i,j,bi,bj)**2)/deltaTmom,
>    &            viscA4Max)
>       IF (viscA4GridMax.GT.0.) THEN
>          A4tmp=min(A4tmp,viscA4GridMax*(rAw(i,j,bi,bj)**2)/deltaTmom)
>       ENDIF
>       A4tmp=max(A4tmp,viscA4GridMin*(rAw(i,j,bi,bj)**2)/deltaTmom)

2) with Non-Lin Free-Surf., we have curious things happening:
        hFacZClosedW = _hFacS(i,j,k,bi,bj) - hFacZ(i,j)
        hFacZClosedE = _hFacS(i,j,k,bi,bj) - hFacZ(i+1,j)
are supposed to catch the "side wall" where side-drag needs to be applied.

The Problem with NonLin-FreeSurf is that it will occurs:
* at the surface level (using z coordinate) far from any side wall.
* at the bottom level (using p coordinate), even with a flat bottom.
* everywhere in the domain, using z*

I think this might have something to do with the fact that global_ocean.cs32x15 
& global_ocean_pressure are so sensitive.

Cheers,

Jean-Michel