[MITgcm-devel] possible problem in seaice_solve4temp iteration

[Jean-Michel Campin]

Hi Martin,

Gael and me were looking at this part of the code yesterday.
But it's still not completely clear to me.
I think that thsice_solve4temp is OK (+ I understand it).

Nothing to do with that: I was planning to make checkpoint62o
and would prefer to do it on a tested version (after most of the
daily testreport output are done) and before any new morning change.
Could I try tomorrow ?

Cheers,
Jean-Michel

On Wed, Nov 24, 2010 at 04:35:48PM +0100, Martin Losch wrote:
> Hi there,
> 
> the problem described below also exists in our seaice_solve4temp.F, the "legacy" branch.
> 
> For some reason, the (forward-) verifications experiments are not affected (haven't checked the adjoint ones yet), but I still need to do a longer run to see, if this has a similar effect than for Frank Kauker (NAOSIM).
> 
> Do you think that we should correct this "bug". Our code tends to have too little ice in the Arctic, ...
> 
> M.
> 
> Begin forwarded message:
> 
> > From: Frank Kauker <Frank.Kauker at awi.de>
> > Date: April 1, 2009 2:03:00 PM GMT+02:00
> > To: Wolfgang.Dorn at awi.de
> > Cc: Qiang.Wang at awi.de, Martin.Losch at awi.de, Cornelia.Koeberle at awi.de, Ruediger.Gerdes at awi.de, Michael.Karcher at awi.de
> > Subject: NAOSIM: error in skin temperature calculation
> > 
> > Dear All,
> > 
> > we detected an error in the calculation of the skin temperature over sea ice in NAOSIM. Within each iteration of the solver for the heat conduction the temperature was set to zero if the temperature exceeds 0C. We moved that statement after the end of the iterative solver.
> > 
> > This has dramatic influence on the ice extent and ice volume. The icevolume increases by about 10000km2 in the yearly mean. I added two figures showing the domain-wide monthly extent and volume from 1948 to 2008 (ncep forced) for the corrected code and a lead closing parameter h0 of 1m (red lines). To get rid of the too high ice volume (at least we think it is too high) and to get more realistic ice extent (observed 2007 September = 4.3 10**6 km**2) we adjusted h0 to 0.5m (which is the value suggested by Bill Hibler).
> > 
> > Cheers,
> > 
> > Frank
> 

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