[MITgcm-devel] Hack to increase mixing near bottom/surface

[Daniel Goldberg]

Hi Jean Michel

Thank you for this. I am now able to reproduce your figures. We had many
differences between our setups, but the critical one is that pcellMix_delR
must be set in the data file.

(I was not doing this because I thought your notes had meant that its
default value is delR, but of course your modified ini_parms.F does not do
this.)

Thanks
Dan

On Sat, Apr 25, 2015 at 9:33 PM, Jean-Michel Campin <jmc at ocean.mit.edu>
wrote:

> Hi Dan,
>
> I've just made a tar file with code and input files that I used for
> "p15" test (linearDrag & pCellMix_select= 2),
> It's there: http://mitgcm.org/~jmc/pCellMix/visc_2d_setup.tgz
>
> Let me know is something is not clear.
>
> Cheers,
> Jean-Michel
>
> On Sat, Apr 18, 2015 at 08:43:16PM +0100, Daniel Goldberg wrote:
> > Hi J-M and Martin --
> >
> > Jean-Michel, I am following up on the hack to increase mixing, and am now
> > trying to reproduce your results shown below so that I can apply the hack
> > to SHELFICE and investigate wet-point averaging in the ustar calculation.
> >
> > I use the latest version of your modified source files and PCELL_MIX.h. I
> > tried to reverse engineer the description and figures you show but I am
> > unable to do so -- I show the results corresponding to type 1 test here
> > http://www.geos.ed.ac.uk/~dgoldber/pcell_mix_bottom_test/figs/
> > w_p02 corresponds to your p02. Vertical velocity can be seen elsewhere
> than
> > the edge of the step but is still very large in the column at the the
> edge
> > of each step.
> >
> > I am not sure if this is because I have not made the same setup as you, I
> > did not see your input file so I had to guess at some things -- my input
> > folder is here
> > http://www.geos.ed.ac.uk/~dgoldber/pcell_mix_bottom_test/input/
> > and my guess at obcs velocity (i did not see your magnitude?) is here
> > http://www.geos.ed.ac.uk/~dgoldber/pcell_mix_bottom_test/figs/obcs_u.jpg
> >
> > Or alternatively do you still have your input folder? This would be
> easiest
> > to see what I did wrong..
> >
> > Thanks very much
> > Dan
> >
> >
> > On Fri, Jan 16, 2015 at 7:05 PM, Jean-Michel Campin <jmc at ocean.mit.edu>
> > wrote:
> >
> > > Hi Dan and Martin,
> > >
> > > I made some simple test with a hack to increase mixing near above
> bottom
> > > and/or
> > > below surface when the bottom/surface grid cell is thin (small hFac).
> > >
> > > I put some files here: http://mitgcm.org/~jmc/pCellMix/
> > > with some documentation in file "pCellMix.notes"
> > >  and some plots from my simple test.
> > >
> > > the hack: it should move to the main code at some point, but
> > > 1) need more tests (and feedback)
> > > 2) it involves changing more S/R (> 7 but only 2 right now) since it
> > >  needs to be pushed where vertical diffusion and viscosity are applied:
> > >  ( mom_u/v_implicit_r.F mom_u/v_rviscflux.F
> > >    impldiff.F gad_diff_r.F gad_implicit_r.F )
> > >  and passing more arguments to these S/R (-> also changing the calling
> S/R)
> > >
> > > Some remarks:
> > > 1) we should probably always use selectBotDragQuadr=1 or 2 instead of
> the
> > > original
> > >   discretisation (selectBotDragQuadr=0), see
> > > http://mitgcm.org/~jmc/pCellMix/fig_wt4.ps
> > > 2) accounting for partial cell in the interior (interViscAr_pCell=T,
> > >   interDiffKr_pCell=T) is safe when using implicit visc/diff ;
> > >   but also accounting for hFac in bottom friction (bottomVisc_pCell=T)
> when
> > >   using no-slip-bottom=T can be unstable; and we don't have code for
> > > implicit
> > >   bottom friction + it would not work with present solve_for_pressure
> code.
> > >
> > > Regarding how this could be use with pkg/shelfice (to avoid using
> > > SHELFICEboundaryLayer):
> > > 1) in isomip test experiment, no_slip_shelfice=F and this is good,
> > > otherwise
> > >    the velocity below ice-shelf is strongly reduced when hFac is small
> > > (and it's
> > >    physical) and make the melt-rate very dependent on hFac.
> > > 2) using a type of quadratic drag: the equivalent of
> selectBotDragQuadr >
> > > 0 is not
> > >    coded in shelfice_u/v_drag.F but should not be hard (+ I added the
> new
> > > argument)
> > > 3) might need to test different averaging (e.g. wet-point) of the
> velocity
> > >    to the grid-cell center (in shelfice_thermodynamics.F)
> > >    I don't know if there is a diagnostic for this (but could be useful)
> > > 4) would be interesting to try SHELFICEboundaryLayer=F and
> > > pCellMix_select=10 ;
> > >
> > > Cheers,
> > > Jean-Michel
> > >
> > > _______________________________________________
> > > MITgcm-devel mailing list
> > > MITgcm-devel at mitgcm.org
> > > http://mitgcm.org/mailman/listinfo/mitgcm-devel
> > >
> >
> >
> >
> > --
> >
> > Daniel Goldberg, PhD
> > Lecturer in Glaciology
> > School of Geosciences, University of Edinburgh
> > Geography Building, Drummond Street, Edinburgh EH8 9XP
> >
> >
> > em: D <dgoldber at mit.edu>an.Goldberg at ed.ac.uk
> > web: http://ocean.mit.edu/~dgoldberg
>
> > _______________________________________________
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> > MITgcm-devel at mitgcm.org
> > http://mitgcm.org/mailman/listinfo/mitgcm-devel
>
>
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-- 

Daniel Goldberg, PhD
Lecturer in Glaciology
School of Geosciences, University of Edinburgh
Geography Building, Drummond Street, Edinburgh EH8 9XP


em: D <dgoldber at mit.edu>an.Goldberg at ed.ac.uk
web: http://ocean.mit.edu/~dgoldberg
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