OBC for idealized simulation

Dear all,

I need some help to set up OBC for idealized simulation. I am trying to simulate internal tides on the shelf and imposed tides manually along the offshore boundary (east). Here what I mean by manually is to impose semi-diurnal tides (zeta_east) along the offshore boundary rather than letting ROMS calculate tides. Ubar_east/Vbar_east is manually calculated based on the tidal elevation. OBC for TS is the same as the initial conditions throughout the simulation. North-South OBC is periodic.
The baroclinic time step (dt) is 10 sec and ndtfast = 30. The minimum spatial resolution is 100 m on the shelf and the maximum is ~1500 m at the offshore boundary in the deep water.

The following is my cppdefs for OBC.

# define NS_PERIODIC
# define OBC_EAST
# undef OBC_WEST      /* closed */
# define OBC_M2CHARACT
# define FRC_BRY
# define Z_FRC_BRY
# define M2_FRC_BRY
# define SPONGE_GRID

However, it seems that the model did not prescribe zeta and ubar/vbar along the offshore boundary and blew up after having a huge zeta (-250m) near the offshore boundary. I wonder if someone pointed out the above setting is correct.
A screenshot of zeta, ubar, and w right before the model blow-up is attached.

Thanks in advance.



I would try simply using OBC_M2CHARACT without OBC_ZSPECIFIED. The boundary information on zeta is used in the characteristic equation…