[MITgcm-support] RBCS, OBCS and IC grid

[Martin Losch]

Hi Bertrand,

as far as I know, you need to specify the fields on their respective grids, i.e. U field on U-grid, V field on V-grid, and T/S on center points (pressure points).

This is definitely true for initial conditions (if you specify any U/V-fields, but then they need to be very consistent with the density/T/S fields for the model not to blow up due to strong initial adjustment processes).

For OBCS, it’s also true, but probably only relevant for the tangential velocities (unless you have a bathymetry gradient across your open boundary, which I would not reccommend)

For RBCS, it is also true and I am surprised that the model blows up when you do it that way. Possibly there are some zero velocities near the boundaries giving rise to large gradients?

Martin

> On 7. Jul 2017, at 21:58, Bertrand Louis Rene Delorme <bdelorme at stanford.edu> wrote:
> 
> Hello everyone,
>  
> I have a very quick question concerning the RBCS package, that I think would also apply to the OBCS package or the setting of initial conditions.
> Do we have to use the U grid for the U forcing (or initial) field, the V grid for the V forcing (or initial) field and the centered grid for the T and S forcing (or initial) fields? 
> So far, I was using the centered grid for all fields and it seemed to work well.
> With the RBCS package, I made some tests where I use for each field its specific grid and the model blows up.
> In the case of initial conditions, I also tried the two set-ups, that works well but that gives different results.
> If someone has an idea of what I should do please let me know.
>  
> Thank you,
> Bertrand
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