[MITgcm-devel] SHELFICEBoundaryLayer ustar calculation with hFacC>1

[Daniel Goldberg]

i had not run a testreport yet, i thought that isomip didn't use
shelficeboundarylayer=.true. but i see it does. i will run a testreport
today.

However, if it *does* lead to a testreport failure, should the changes not
go in? I'm assuming this could only happen if the implicit free surface
leads to hfacC(kTopC)>1 at some point -- and as per our discussion, this
should not make use of the shelficeboundarylayer modifications in
shelfice_thermodynamics and shelfice_forcing.

Thanks
Dan

On Wed, Apr 22, 2015 at 9:22 AM, Martin Losch <Martin.Losch at awi.de> wrote:

> Hi Dan,
>
> I am absolutely fine with limiting drkp1/drloc to be >=0. As I wrote
> before, that’s consistent with the boundary layer scheme (which should only
> be active when hfacc<1). You code looks OK to me. Does it affect the
> testreport examples in isomip?
>
> Martin
>
> > On 21 Apr 2015, at 13:15, Daniel Goldberg <dngoldberg at gmail.com> wrote:
> >
> > Thanks for pointing this other one out, Martin. Not sure we want that
> behavior (with drLoc<0) for the forcing either..
> >
> > For now, I propose a quick fix to revert to non-shelficeboundarylayer
> behaviour for shelfice_forcing.F when hfacC(kTopC)>1, by setting drLoc=0 in
> this case. (This will mean that if hFacC(kTopC)>>1, then shelfice
> temperature and salinity forcing will have a smaller effect, but we are
> trying to limit how large hFacC becomes as the shelf thins..)
> >
> > Would these changes be OK to check in:
> >
> http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/dgoldberg/shelfice/shelfice_thermodynamics.F?revision=1.2&view=markup
> (see line 283)
> >
> >
> http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/dgoldberg/shelfice/shelfice_forcing.F?revision=1.1&view=markup
> (see lines 78, 86, 170, 178)
> >
> > Thanks
> > Dan
> >
> > On Tue, Apr 21, 2015 at 7:43 AM, Martin Losch <Martin.Losch at awi.de>
> wrote:
> > Hi Dan,
> >
> > clearly, this code was written with hFac<=1 in mind. I think your
> limiting drKp1 from below makes absolute sense, because this scheme was
> only meant to work for hFac<1, and as you can see from the code, the
> largest effect is larger the smaller hFacC is. For a fully wet cell, it
> should do anything. There are two more occurence of this in
> shelfice_forcing (there the variable is drLoc).
> >
> > M.
> > > On 18 Apr 2015, at 21:56, Daniel Goldberg <dngoldberg at gmail.com>
> wrote:
> > >
> > > Hi Martin
> > >
> > > At the moment we are using ShelficeBoundaryLayer for the calculation
> of melt rates, but are allowing hFacC to be larger than 1.
> > >
> > > But we find this allows the factor drKp1 to become negative (line 280
> of shelfice_thermodynamics.F) and velocities from the cell below even when
> the top cell is thicker than drF(kTopC).
> > >
> > > Is this correct, or was this written with only hFacC(kTopC)<1 in mind?
> At the moment we are simply inserting the line
> > >
> > > drKp1 = MAX(drKp1, 0.0)
> > >
> > > after line 282 (although long term we hope to implement something like
> what J-M has suggested, using wet-point averaging to find ustar at the
> center of the cell).
> > >
> > > Many thanks
> > > Dan
> > >
> > >
> > >
> > > --
> > >
> > > Daniel Goldberg, PhD
> > > Lecturer in Glaciology
> > > School of Geosciences, University of Edinburgh
> > > Geography Building, Drummond Street, Edinburgh EH8 9XP
> > >
> > >
> > > em: Dan.Goldberg at ed.ac.uk
> > > web: http://ocean.mit.edu/~dgoldberg
> > > _______________________________________________
> > > MITgcm-devel mailing list
> > > MITgcm-devel at mitgcm.org
> > > http://mitgcm.org/mailman/listinfo/mitgcm-devel
> >
> >
> > _______________________________________________
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> > 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: Dan.Goldberg at ed.ac.uk
> > web: http://ocean.mit.edu/~dgoldberg
> > _______________________________________________
> > MITgcm-devel mailing list
> > 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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