[MITgcm-devel] seaice adjoint and EVP

[Jinlun Zhang]

Martin,

I am not sure what is going on, but setting e=1 is no good, too 
unphysical. Also, zeta, eta over open water should be zero. I used the 
value of 4e8 for testing and forgot to change it back to zero.

Jinlun

Martin Losch wrote:
> Hi Dimitris,
>
> this thread it getting very confusing, because it talks about many 
> different things. Here I will only answer to EVP related things, OK?
>
> 1. thanks for your plots and data, too bad that the bug fix did not 
> help (updating to latest code will not either, but you can always try).
> 2. I plotted the gradients of sigma1/2/12 as they appear in the stress 
> divergence and the stripes in the velocity do show up in dsigma12/dx 
> (for v) and dsigma12/dy (for u) which is expected as sigma12 is really 
> 2*eta*(du/dy + dv/dx)
> 3. sigma1 is different from sigma2 because it contains P:
> sigma1 = sig11+sig22 = 2*zeta*(du/dx+dv/dy) - P
> sigma2 = sig11-sig22 = 2*eta(du/dx-dv/dy)
> so the big negative contribution is the ice strength P, eta and zeta 
> are the same except for the factor e^2=4. If you diagnose P (SIpress) 
> you could have a look at sigma1+P vs. sigma2 and they should have a 
> similar structure (may actuallly be worth trying for one timestep just 
> to make sure for snapshots it's even trivial to compute P = 
> Pstar*Heff*exp(-20*(1-Area), what's your Pstar?).
>
> I still do not have any clue what's going on. P (and zeta and eta) is 
> set to some (large) constant over open what (see seaice_evp, 
> seaice_dynsolver, etc) but that should not change the divergence of 
> the stress. Currently I am having a similar problem with stripes in a 
> highly anisotropic grid (dx=2deg, dy=0.5deg), and I am suspecting that 
> the viscosity that Leith computes is too low for the coarse direction. 
> Maybe we have similar problem here:
> When you write down the divergence of the stress tensor you'll get 
> something like this:
> dsig11/dx+dsig12/dy = d/dx[(e^2+1)*eta du/dx] + d/dy[2*eta du/dy] + 
> d/dx[(e^2-1)*eta dv/dy] + d/dy[2*eta dv/dx]
> for the u equation and analogously for the v-equation. If you set 
> e=SEAICE_ecc = 1 (not elliptic but circular yield curve), the second 
> last term will drop out (unfortunately), but zeta=eta and the 
> components of the stress divergence will be symmetric (dd/dxx + 
> dd/dyy, except fo the last term). The problem is, that if this works, 
> I still don't know how to fix the problem because we do want to have 
> e=2. May we can increase the value of zeta/eta over open ocean (so 
> zMin which is 4e8 right now, in seaice_dynsolver)? After all the 
> stripes appear where velocity is high.
>
> Do you (especially Jinlun) think that this is worth a  try?
>
> Martin
>
> On 15 May 2007, at 20:50, Dimitris Menemenlis wrote:
>
>> Martin,
>>
>>> I have corrected the bug in seaice_ocean_stress (I am wondering if 
>>> this will
>>> fix the problem that Dimitris has with evp. I don't think so, but 
>>> there is
>>> always hope o:), and updated lab_sea but not the
>>
>> Unfortunately the stripes are still there.  This is not with very 
>> latest code. It is yesterday's pkg/seaice code with
>>
>>> columbia15: diff seaice_ocean_stress.F 
>>> ../MITgcm/pkg/seaice/seaice_ocean_stress.F 184c184
>>> <           fuIceLoc=HALF*( DWATN(I,J,bi,bj)+DWATN(I-1,J,bi,bj) )*
>>> ---
>>>>           fuIceLoc=HALF*( DWATN(I,J,bi,bj)+DWATN(I,J+1,bi,bj) )*
>>> 195c195
>>> <           fvIceLoc=HALF*( DWATN(I,J,bi,bj)+DWATN(I,J-1,bi,bj) )*
>>> ---
>>>>           fvIceLoc=HALF*( DWATN(I,J,bi,bj)+DWATN(I+1,J,bi,bj) )*
>>
>> So I am assuming EVP will eventually crash as before.
>> Figure comparing evp to lsr solution is here
>> http://ecco2.jpl.nasa.gov/data1/arctic/output/tests/evp/evp_vs_lsr.ps.gz
>> Directory
>> http://ecco2.jpl.nasa.gov/data1/arctic/output/tests/evp/
>> contains pkg/seaice output, including sigmas, matlab routine to 
>> read/plot and an additional figure
>> http://ecco2.jpl.nasa.gov/data1/arctic/output/tests/evp/evp.ps.gz
>> of all the evp fields
>> sigma* colorscale is chosen to emphasize open water.
>> character of sigma1 over open water is much different from sigma2 and 
>> sigma12, is this what you expect?
>>
>> D.
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>
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