[MITgcm-support] Crashes with EVP seaice

Pochini, Enrico epochini at inogs.it
Fri Jan 22 11:03:48 EST 2021

Hi Martin,

Eventually I went around the problem and used the LSR Picard solver.. I
also had a problem with surface fluxes giving wild summer warming, which I
fixed, so the sea ice I get with Picard is not absurd anymore.
I've followed your advice and run two other experiments with same setup
using aEVP with the parameters as in the manual section:
 SEAICEaEVPcoeff = 0.5,

and another with

These runs didn't crash and ran for 8 years.
There are some differences between the three cases, especially between aEVP
(starSteps=500) and LSR, especially close to the coast, with LSR having
more often open water. All the three develop cracks and features. However
the aEVP with 500 starSteps is 50% slower than LSR. (aEVP with 200 steps
only 15% slower). The two EVPs are similar, except the timing of appearance
of features which may differ slightly.

I can send a link to the output if you would like to have a look. I'm yet
unsure which one would be better to use...
I wonder which of the two SEAICEaEVPcStar or the SEAICEaEVPcoeff is the
tuning parameter c aEVP in Koldunov et al 2019:  (set to 1.5 after tuning)

Thank you Martin,


Il giorno gio 21 gen 2021 alle ore 12:46 Martin Losch <Martin.Losch at awi.de>
ha scritto:

> Hi Enrico,
> did you get anywhere with this?
> The error just means, that the model has exploded (and MOM_IMPLICIT_R is
> probably the first routine in the new timestep that notices that). If you
> want more output, the first thing to do is set the monitorFreq to 1.
> The EVP solver is not my preferred choice, and I don’t plan to do too much
> more development there, so that’s why the debugging information is sparse.
> You’ll have to add your debugging information yourself.
> If you really need to use EVP, I suggest that you use the mEVP (as you do)
> or aEVP. For mEVP the alpha/beta values should be at least order 100 if not
> 500 in your case (see Kimmritz et al papers, 20 is definitely too small).
> aEVP is probably even better (because it sets alpha/beta somewhat
> dynamically). Please try the parameter set recommended at the end of this
> section in the documentation: <
> https://mitgcm.readthedocs.io/en/latest/phys_pkgs/seaice.html#more-stable-variants-of-elastic-viscous-plastic-dynamics-evp-mevp-and-aevp
> >
> There’s no guarantee that the solver is stable at all times, but the
> better (smoother) the convergence the larger the chance of good behavior.
> aEVP is a good way of doing that.
> Otherwise I recommend the default Picard solver. I am surprised that it
> gives very different ice solutions (usually the differences are small, and
> usually the EVP solver give the funny solutions).
> The ice field is suprisingly smooth at this resolution, another indication
> that the EVP solver does not converge properly (see eg. Koldunov et al
> 2019, https://doi.org/10.1029/2018MS001485).
> Martin
> > On 7. Jan 2021, at 15:33, Pochini, Enrico <epochini at inogs.it> wrote:
> >
> > Dear community,
> >
> > I am trying to run a regional model with SHELFICE and SEAICE packages.
> > However I'm still having problems with crashes while employing the EVP
> solver.
> >
> > The error I get is the general
> > ERROR STOP MOM_IMPLICIT_R: error when solving 3-Diag problem.
> > and I only get it with the EVP; with the LSR solver the model runs fine
> for more years but the ice I get seems to be less realistic.
> >
> > I was able to run the model for just two years with EVP without crashes
> with the namelist files attached.
> >
> > To restart the model I have tried playing with OBCS_SEAICE options,
> sponge layer thickness and relaxation times and EVP alpha/beta parameters
> (from 10 to 600). I tried also disabling OB for seaice. I have 5km
> resolution, 300 seconds deltaT, vertical levels with min 10m thickness.
> >
> > Can you point me to some tests to fix this problem?
> > How can I print debugging information in the STDOUT? In the
> SEAICE_OPTIONS.h I set #define SEAICE_DEBUG and have debugLevel>0 in "data"
> but it doesn't seem to work with EVP.
> >
> > Kind regards,
> >
> > Enrico
> >
> >
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