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

[Martin Losch]

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
> > _______________________________________________
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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: Dan.Goldberg at ed.ac.uk
> web: http://ocean.mit.edu/~dgoldberg
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