[MITgcm-devel] changes in tracer vertical implicit scheme

[Jean-Michel Campin]

Hi Patrick,

The 2 majors changes (on Dec 01, 2011) are:
1) new argument "recip_hFacNew" computed in thermodynamics.F
 and passed to gad_implicit_r.F , and then passed to the selected
 gad_*_impl_r.F S/R ;
2) the term: tracer* del_k(wtrans)* deltaT has been moved from
 gad_implicit_r.F (in version 1.14i of gad_implicit_r.F, lines 210 - 213):
           gTracer(i,j,k,bi,bj) = gTracer(i,j,k,bi,bj)
     &      + deltaTLev(1)*recip_rA(i,j,bi,bj)
     &       *_recip_hFacC(i,j,k,bi,bj)*recip_drF(k)
     &       *tracer(i,j,k,bi,bj)*(rTransKp1(i,j)-rTrans(i,j))*rkSign
to gad_calc_rhs.F :
in gad_calc_rhs.F, now we have line 164:
    IF (implicitAdvection) rAdvFac = rkSign
but before it was:
    IF (implicitAdvection) rAdvFac = 0. _d 0

What could be tried is to have only 1 of the 2 changes, and see 
how this goes.

Cheers,
Jean-Michel

On Wed, Feb 01, 2012 at 12:01:16PM -0500, Patrick Heimbach wrote:
> 
> Jean-Michel,
> 
> for the record, are you aware that your changes to tracer vertical implicit scheme
> break the adjoint (which we now use in several production calculations)?
> 
> Easy way to test  (I had thought it's already tested by default) is in
> verification/global_ocean.cs32x15/input_ad/ 
> to set
>  tempImplVertAdv=.TRUE.,
>  saltImplVertAdv=.TRUE.,
>  tempVertAdvScheme=3,
>  saltVertAdvScheme=3,
> 
> If you point me to likely culprit routines, I'll take a look.
> 
> Thanks
> -Patrick
> 
> On Dec 1, 2011, at 9:43 AM, Jean-Michel Campin wrote:
> 
> > Hi,
> > 
> > Some fix/changes related to tracer vertical direction implicit method:
> > 
> > 1) implicit vertical advection conservation with Adams-Bashforth 
> > and/or non-lin free-surf:
> > the term Tr*d/dz(w) was not going through AB and neither was
> > rescaled (NonLin-FreeSurf) and this was breaking tracer conservation.
> > I remove Tr*d/dz(w) in gad_implicit_r.F and add it in gad_calc_rhs.F;
> > this fix conservation in both cases.
> > 2) implicit vertical diffusion or advection with non-lin free-surf:
> > Was using current recip_hFacC instead of future recip_hFacC.
> > This lead to small error when using NonLin-FreeSurf and also break 
> > conservation with NonLin-FreeSurf in r-coordinate (but not with r*).
> > The right recip_hFac is now computed in thermodynamics.F and passed
> > to all vertical implicit S/R.
> > 
> > I also added diagnostics for gtNm1 & gsNm1, so that it's easier
> > to check tracer conservation with NonLin-FreeSurf + AB (the quantity
> > being conserved is Tr + (0.5+abEps)*deltaT*gtNm1).
> > And will add a secondary test to advect_xz to test implicit vertical
> > advection (+ NonLin-FreeSurf).
> > 
> > I don't know why those changes affect bottom_ctrl_5x5 (adjoint gradient)
> > and break agreement with forward gradient.
> > I removed all the implicit vertical code in thermodynamics.F (checked-in),
> > and it's better, but still not as good than what it used to be.
> > If someone has time to take a look at this experiment.
> > 
> > Cheers,
> > Jean-Michel
> > 
> > _______________________________________________
> > MITgcm-devel mailing list
> > MITgcm-devel at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-devel
> 
> ---
> Patrick Heimbach | heimbach at mit.edu | http://www.mit.edu/~heimbach
> MIT | EAPS 54-1420 | 77 Massachusetts Ave | Cambridge MA 02139 USA
> FON +1-617-253-5259 | FAX +1-617-253-4464 | SKYPE patrick.heimbach
> 
> 
> 
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