[MITgcm-devel] seaice adjoint and EVP

[Jinlun Zhang]

I wouldn't think C-grid is problematic with EVP as we have seen. But 
just to make sure, is it possible to use the original B-grid EVP to see 
if the same things occur? There was a B-grid ice model setup in place 
that may be used for doing B-grid.
Better not zap out things over open ocean. Otherwise, discontinuity may 
occur and ocean may be screwed up.
Jinlun

>> Hi Martin,
>>
>>> 1. Are these figures all with with zMin = 0?
>>
> In this case it may be worth turning of individual terms in the rhs  
> of the momentum equations
> 1. dphiSurf/dx and dphiSurf/dy (in seaice_dynsolver)
> 2. surface wind stress (taux/y=0 in seaice_get_dynforcing)
> 3. ice-ocean stress (DWATN in seaice_evp)
> 4. Coriolis
> 5. stressDivergence
> 4 and 5 should be zero over open ocean anyway so I do not see how  
> these terms can lead to the stripes.
> We should get to the bottom of what is causing these stripes. that  
> way we can probably understand the noise in the ice fields, too.
>
>>
>> Yes, all the figures and results under
>> http://ecco2.jpl.nasa.gov/data1/arctic/output/tests/
>> (except for the oldtest subdirectory) are with zMin=0.
>>
>>> 2. Do you have an EVP run that does not blow up at all (regardless  
>>> of noise)?
>>
>> I have not run any of the zMin=0/SEAICEuseFlooding=.true. tests out  
>> for very
>> long, but I am almost certain that none of these new integrations  
>> will crash,
>> including the SEAICE_deltaTevp=60.
>> The crashes had to do with snow accumulation and could happen to  
>> both LSR or to
>> EVP solutions.
>
> That's good news. It mean that we can (in principle) maskRHS flag and  
> not worry about the stripes.
>
>>
>>> 3. What's the convergence criterion for LSR, and how many  
>>> interations do you allow/do? In other words how close is the LSR  
>>> solution to VP?
>>
>>
>>       LSR_ERROR          = 2e-4,
>>       SOLV_MAX_ITERS=1500
>
> That's not very much, is it? For an accurate VP solution I would put  
> LSR_ERROR = 1e-7 to 1e-13, right?
>
>>
>>> c. the same is true for the wind-ice/ocean-ice stress terms which  
>>> in involve
>>>  averaging perpendicular to the stripes (unless the turning angle  
>>> is not
>>> equal to zero, in which case there is also averaging in the other  
>>> directions,
>>> but you don't do that, do you?).
>>
>>
>> No I use SEAICE_airTurnAngle=SEAICE_waterTurnAngle=0.
>
> Good.
>
>>
>>> About question 3 (is it really a VP solution): Could you diagnose  
>>> SIsigI and SIsigII (snapshots!!!! I guess one is enough) for all  
>>> (or some) solutions and
>>>  plot them (plot(SIsigII(:),SIsigI(:),'x')? These should be the  
>>> principle components of sigma normalized by the strength/pressure P.
>>
>>
>> With SEAICE_dumpFreq, SIGMA1, SIGMA2, and SIGMA12 are diagnosed by  
>> default for
>> the EVP solutions but not for LSR.  Are these the same as SIsigI  and 
>> SIsigII?
>> Figure for SIGMA1, SIGMA2 for EVP solution is here:
>> http://ecco2.jpl.nasa.gov/data1/arctic/output/tests/figs/SIGMA2232.ps
>> Does it look as expected?
>
> sigma1/2/12 are not the principle stress components. I have added  
> diagnostics that are called SIsigI and SIsigII, which is what you  
> want. In principle you could computed them yourself (from snapshots):
> SIsigI = 0.5*(sigma1 + sqrt(sigma2^2 + 4*sigma12^2)/Press
> SIsigII = 0.5*(sigma1 - sqrt(sigma2^2 + 4*sigma12^2)/Press
>
> Press = max(1.e-13,Pstar * HEFF *exp( -20*(1-AREA)));
>
> see seaice_do_diags.F (and seaice_dynsolver.F)
>
>>
>>> I am also a little concerned that the LSR and EVP solutions look  so 
>>> different
>>> in the ice-covered area, can that be attributed to that different  
>>> boundary
>>> conditons? Can you try a run with no slip for the evp solver?
>>
>>
>> Is LSR no slip by default?  How do you specify no slip for evp solver?
>
> LSR is half slip and that's hardwired. I didn't want to bother this  
> the boundary conditions if EVP works, because it's so much simpler to  
> do that in EVP. But now I may have to reconsider this decision.
> EVP is free slip by default. SEAICE_no_slip = .true. makes it no slip.
>
> Martin
>
> _______________________________________________
> MITgcm-devel mailing list
> MITgcm-devel at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-devel


-- 

Jinlun Zhang
Polar Science Center, Applied Physics Laboratory
University of Washington, 1013 NE 40th St, Seattle, WA 98105-6698

Phone: (206)-543-5569;  Fax: (206)-616-3142
zhang at apl.washington.edu
http://psc.apl.washington.edu/pscweb2002/Staff/zhang/zhang.html