Issue with Ocean Stratification and Boundary Conditions in Idealized Ocean Model

[hyc006]

Hello ROMS Community,

I’m currently working on an idealized ocean model, and I’m facing an issue with maintaining the ocean stratification. Over time, the stratification disappears. So I'm trying to clamping the temperature and salinity inflow boundary conditions on the west and north edges.
The ocean model is relatively shallow, making it challenging to set accurate velocity boundary conditions due to the bottom boundary layer.
I've set the velocity boundary conditions to be periodic to handle the bottom boundary layer issue.

Here's a summary of my boundary conditions:

Code: Select all

Variable    | Grid | West Edge | South Edge | East Edge | North Edge
------------|------|-----------|------------|-----------|------------
zeta        | 1    | Periodic  | Periodic   | Periodic  | Periodic
ubar        | 1    | Periodic  | Periodic   | Periodic  | Periodic
vbar        | 1    | Periodic  | Periodic   | Periodic  | Periodic
u           | 1    | Periodic  | Periodic   | Periodic  | Periodic
v           | 1    | Periodic  | Periodic   | Periodic  | Periodic
temp        | 1    | Clamped   | Gradient   | Gradient  | Clamped
salt        | 1    | Clamped   | Gradient   | Gradient  | Clamped
tke         | 1    | Periodic  | Periodic   | Periodic  | Periodic

Problem:
The temperature at the boundaries is not clamped to a fixed value, causing it to vary over time. As a result, the stratification is not maintained as expected. So here's some question I have:
What could be causing the temperature and salinity not to remain fixed (clamped) at the boundaries?
Does anyone have suggestions or better approaches for maintaining stratification in an idealized ocean model?

Here's the temperature change in time on four boundary:

Any insights or advice would be greatly appreciated!
Thank you in advance for your help.
Best regards,
Hsin-Yi Chen

[wilkin]

It doesn't make any physical/logical sense to have some variables periodic and others not. Consequently, the logical flags EWperiodic and NSperiodic are set to .TRUE. if any boundary is periodic. See Utility/inp_decode.F

If you look in Nonlinear/t3dbc_im.F you'll see there are entires there for radiation, clamped, etc. but no entry for periodic. Periodicity is enforced elsewhere and since you have EWperiodic true your clamped condition is over-ridden.

If you want to reintroduce stratification internally to the domain, you might consider using nudging to climatology in a limited region. This can be done via ana_nudgcoef.h or via an input netcdf file.

[hyc006]

Thank you for your reply. I will give this a try.

I haven't used nudging in climatology before. Do you have any recommended resources on this topic? I would greatly appreciate your help!

Hsin-Yi