[MITgcm-devel] sea ice diagnostics

[Jean-Michel Campin]

Hi Martin,

For state variable diagnostic (as well as directly derived from state vars, e.g., THETASQ),
the field is available at any time (since, as a state variable, it is supposed to be in one 
of the pickup files) and it can be useful (e.g., when doing a budget, to evaluate the
rate of change of a state variable) to have the diagnostic filled up outside
the main stepping-forward part, e.g. at the end of the time-step loop or at
the beginning of the time-step loop, as currently done from S/R DO_STATEVARS_DIAGS.

But for other intermediate variables, it's better (and easier) to fill-up their 
diagnostics from where they are computed. And it avoids the problem of filling
up with zero because they have not been computed yet.
And regarding pkg/seaice, there are some diagnostics currently filled-up from 
seaice_diagnostics_state.F that should not be there, but for some other like
SIsig1 & SIsig2, it's not very clear since it depends in using EVP or not
(but could have those filled up from different places depending on SEAICEuseEVP).

Cheers,
Jean-Michel

On Tue, May 05, 2020 at 01:38:08PM +0200, Martin Losch wrote:
> Hi Jean-Michel, and others,
> 
> we are working on mechanical energy diagnostics for the sea ice model (following Bouchat and Tremblay 2014).
> 
> While doing so I realized that maybe the diagnostics of seaice are not in the right place:
> seaice_diagnostics_state is called from do_statevars_diags when ???seqFlag=0???. this is probably OK for fields like HEFF, AREA, UICE, VICE, but not for derived quantities like SIzeta, SIeta, SIdelta, because they are all 0 in the first time step (after a pickup, say). With that all of SIsig1/2, etc are also not correct because they require zeta/eta from the previous iteration. The same is true for (some of) the energy diagnostics.
> 
> I am not sure what the correct philosophy is here. The model state variables (diagnostics_fill_state) are all computed at the beginning of the time step, but not always, so it???s a bit difficult for me to diagnose, when what type of variable should be passed to diagnostics_fill.
> 
> Could you give me some advice?
> 
> Martin
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