[MITgcm-devel] seaice revisited

[Jinlun Zhang]

Hi Martin,

I have not got around to take a look at the B-grid stuff. Sorry. But 
this is the way to go.

Jinlun

Martin Losch wrote:
> Hi there,
> (mainly for Dimitris and Jean-Michel, but I don't know how much this 
> will affect the ECCO runs)
>
> after all my problems with the seaice package, I have recoded the lsr 
> solver. I finally realized how much easier it is to discretize 
> everything in finite volumes (after being involve with the MITgcm for 
> how many years?). I attached the discretization FYI (and maybe for 
> checking). I also found that I made a mistake with the metric terms in 
> the EVP solver.
>
> Unfortunately my new code breaks all verification experiments with 
> seaice:  lab_sea and the like because, I changed (fixed) the treatment 
> of the metric terms, fixed the EVP code, etc. global_ocean.cs32x15 
> because I switched from some finite differences somehow copied and 
> adapted from the B-grid code to finite volumes. Even without metric 
> terms the code is different.
>
> But now the best: I have finally added the full metric terms (also for 
> curvilinear grids) because it is so easy to do with finite volumes 
> (see the attached PDF). I hope I understood how metric terms are 
> computed on a curvilinear grid. So Dimitris can rerun all his cubed 
> sphere experiments with metric terms (not that it will matter too much 
> in the end at high resolution), and I am anxious to see if it works.
>
> How should I check in the fixes? The old seaice_lsr is not quite 
> correct (bugs in the metric terms) and the evp code needs to be fixed, 
> it is clearly wrong in the metric terms, too. We can have new routine 
> seaice_lsr_fv.F or so, or we can replace the old seaice_lsr.F with a 
> new finite volume version, thereby loosing all backward compatibility. 
> Because the old seaice_lsr.F is not very nice and contains erros, 
> which I would need to fix anyway (but only concerning the metric 
> terms), old results will be lost for spherical grids anyway (but maybe 
> not for cubed sphere). I will include a new flag that allows you to 
> switch of the metric terms (mainly for testing).
>
> If I make all these changes, I would also in a second step change a 
> few defaults that are senseless (e.g. that now is not advected by 
> default is really annoying, also the flooding algorithm, no_slip is 
> not turned on, cliped ice velocities is turned on, etc. etc.)
>
> What do you think?
> Martin
>
> PS. We shouldn't worry about the ceaice-manuscripts, because there we 
> do not use metric terms, the conclusions will not be affected.
>
>
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