[MITgcm-support] obcs/exf interactions

[Tom Haine]

Jinlun, Alistair,

Barotropic modes are forced by windstress variability so I'm not very
surprised there's evidence in 300m velocities of the ice edge. In some
animations I occasionally see hints of it. 

Alistair, are your figures from iteration 41400 or so?  I guess you
start from iter=0 when the ice edge is much sharper (yes, I realize I'm
the source of all that's not beautiful in the MITgcm!). Maybe this
explains your result?  If you start from iter=41400 maybe your velocity
anomalies will have the smooth, natural-looking curves of my ice edge at
that time?

We should clearly favor the new pkg/seaice solver.

Tom.


On Thu, 2004-10-07 at 15:42, Jinlun Zhang wrote:
> Tom,
> The results look good to me, no straight line here. Ice model runs ok even with some
> bugs. Not sure why a straight line would show up at 300m and looks like using the
> bug-fixed solver would not help.
> Jinlun
> 
> 
> Tom Haine wrote:
> 
> > Jinlun,
> >
> > Attached are figures of various surface fields, forcing fields, and ice
> > fields from close to the time Alistair is starting his integrations.
> > These results are from the old code.
> >
> > I guess pkg/exf changes (presumably in the stress computation) might
> > explain the difference Alistair sees, although I don't know why they
> > would be concentrated at the ice edge.
> >
> > Tom.
> >
> >
> > On Thu, 2004-10-07 at 14:32, Jinlun Zhang wrote:
> > > I am puzzled by the straght line after some time steps. The initial ice
> > > condition is a straght line, but after a while it should change. Here is my
> > > guess:
> > > (1) Ice model might not be excuted so the initial ice edge is kept unchanged.
> > > Need to look at ice output.
> > > (2) Different ocean model versions might get surface flux differently over areas
> > > partially covered by ice (exf to blame?)
> > > Jinlun
> > >
> > > Tom Haine wrote:
> > >
> > > > Dear Jinlun,
> > > >
> > > > I don't know. Alistair's plots are differences between our code (hacked
> > > > ecco_c50_e29 with 2/2003 pkg/seaice) and the latest HEAD release. The
> > > > plots he showed are difference plots at (guessing) 300m after a few
> > > > steps. There is a difference in 300m velocity at the position of the ice
> > > > edge at that time. My guess is that it persists but I don't know for
> > > > sure. The ice is moderately thick (about 1m) and dense northwest of the
> > > > line you see (my ugly attempt to put seaice on the shelf). Elsewhere
> > > > there is no seaice.
> > > >
> > > > Of course, I don't know which velocity field is better (do you have a
> > > > preference?). But it would be nice to locate the origin of the
> > > > discrepancy.
> > > >
> > > > Tom.
> > > >
> > > > On Thu, 2004-10-07 at 13:15, Jinlun Zhang wrote:
> > > > > Tom,
> > > > >
> > > > > OK you are using the LSR solver.  I don't think the solver has been changed
> > > > > since 2/2003,  only some cosmetic changes. Do you see the ice edge just at
> > > > > initial 1 or 2 time steps or the ice edge persists?
> > > > >
> > > > > JInlun
> > > > >
> > > > > Tom Haine wrote:
> > > > >
> > > > > > Hi Jinlun,
> > > > > >
> > > > > > We use lsr:
> > > > > >
> > > > > >       SEAICEuseLSR = .TRUE.,
> > > > > >
> > > > > > in data.seaice. Without this line (i.e., with the adi solver) it doesn't
> > > > > > work in parallel (following discussion on this list in April this year).
> > > > > >
> > > > > > We're using pkg/seaice from around February 2003. I think several of the
> > > > > > key routines have been updated since then. Can this account for the
> > > > > > velocity differences Alistair sees?
> > > > > >
> > > > > > Tom.
> > > > >
> > >
>