troubleshooting open boundary problem

[rmueller]

I am having a hard time figuring out why my open boundary run doesn't run in ROMS 3.2. When I say "doesn't run", I mean that it blows up at first time step.

Here is what works:
1) closed boundaries
2) open boundary on the east (closed N,S,W). East is only open water.
3) open boundaries with non-analytical tides & OBC for a different grid.

Since I had this working with a different grid, I'm inclined to think it's the grid, but I can't figure out for the life of me why! I have looked at the mask points on the boundary as well as the water depth. Both seem fine to me (see attached graphics). I'm not sure what else could be causing the problem. Here are some cppdef options that I have tested:

ANA_BSFLUX Analytical kinematic bottom salinity flux.
ANA_BTFLUX Analytical kinematic bottom temperature flux.
ANA_INITIAL Analytical initial conditions.
ANA_SMFLUX Analytical kinematic surface momentum flux.
ANA_SRFLUX Analytical kinematic shortwave radiation flux.
ANA_SSFLUX Analytical kinematic surface salinity flux.
ANA_STFLUX Analytical kinematic surface temperature flux.
ASSUMED_SHAPE Using assumed-shape arrays.
AVERAGES Writing out time-averaged fields.
CURVGRID Orthogonal curvilinear grid.
DJ_GRADPS Parabolic Splines density Jacobian (Shchepetkin, 2002).
DOUBLE_PRECISION Double precision arithmetic.
EAST_FSCHAPMAN Eastern edge, free-surface, Chapman condition.
EAST_M2FLATHER Eastern edge, 2D momentum, Flather condition.
EAST_M3RADIATION Eastern edge, 3D momentum, radiation condition.
EAST_TRADIATION Eastern edge, tracers, radiation condition.
ICESHELF Include Ice Shelf Cavities.
LMD_BKPP KPP bottom boundary layer mixing.
LMD_CONVEC LMD convective mixing due to shear instability.
LMD_MIXING Large/McWilliams/Doney interior mixing.
LMD_RIMIX LMD diffusivity due to shear instability.
LMD_SKPP KPP surface boundary layer mixing.
MASKING Land/Sea masking.
MIX_GEO_TS Mixing of tracers along geopotential surfaces.
MIX_S_UV Mixing of momentum along constant S-surfaces.
NONLINEAR Nonlinear Model.
NONLIN_EOS Nonlinear Equation of State for seawater.
NORTH_FSCHAPMAN Northern edge, free-surface, Chapman condition.
NORTH_M2FLATHER Northern edge, 2D momentum, Flather condition.
NORTH_M3RADIATION Northern edge, 3D momentum, radiation condition.
NORTH_TRADIATION Northern edge, tracers, radiation condition.
PERFECT_RESTART Processing perfect restart variables.
POWER_LAW Power-law shape time-averaging barotropic filter.
PROFILE Time profiling activated .
RADIATION_2D Use tangential phase speed in radiation conditions.
!RST_SINGLE Double precision fields in restart NetCDF file.
SALINITY Using salinity.
SOLVE3D Solving 3D Primitive Equations.
SOUTH_FSCHAPMAN Southern edge, free-surface, Chapman condition.
SOUTH_M2FLATHER Southern edge, 2D momentum, Flather condition.
SOUTH_M3RADIATION Southern edge, 3D momentum, radiation condition.
SOUTH_TRADIATION Southern edge, tracers, radiation condition.
SPLINES Conservative parabolic spline reconstruction.
SPHERICAL Spherical grid configuration.
TS_C4HADVECTION Fourth-order centered horizontal advection of tracers.
TS_C4VADVECTION Fourth-order centered vertical advection of tracers.
TS_DIF2 Harmonic mixing of tracers.
UV_ADV Advection of momentum.
UV_COR Coriolis term.
UV_U3HADVECTION Third-order upstream horizontal advection of 3D momentum.
UV_C4VADVECTION Fourth-order centered vertical advection of momentum.
UV_QDRAG Quadratic bottom stress.
UV_VIS2 Harmonic mixing of momentum.
VAR_RHO_2D Variable density barotropic mode.
WESTERN_WALL Wall boundary at Western edge.

With OBC input files and just opening one boundary.

ANA_BSFLUX Analytical kinematic bottom salinity flux.
ANA_BTFLUX Analytical kinematic bottom temperature flux.
ANA_SMFLUX Analytical kinematic surface momentum flux.
ANA_SRFLUX Analytical kinematic shortwave radiation flux.
ANA_SSFLUX Analytical kinematic surface salinity flux.
ANA_STFLUX Analytical kinematic surface temperature flux.
ASSUMED_SHAPE Using assumed-shape arrays.
AVERAGES Writing out time-averaged fields.
CURVGRID Orthogonal curvilinear grid.
DJ_GRADPS Parabolic Splines density Jacobian (Shchepetkin, 2002).
DOUBLE_PRECISION Double precision arithmetic.
EASTERN_WALL Wall boundary at Eastern edge.
ICESHELF Include Ice Shelf Cavities.
LMD_BKPP KPP bottom boundary layer mixing.
LMD_CONVEC LMD convective mixing due to shear instability.
LMD_MIXING Large/McWilliams/Doney interior mixing.
LMD_RIMIX LMD diffusivity due to shear instability.
LMD_SKPP KPP surface boundary layer mixing.
MASKING Land/Sea masking.
MIX_GEO_TS Mixing of tracers along geopotential surfaces.
MIX_S_UV Mixing of momentum along constant S-surfaces.
NONLINEAR Nonlinear Model.
NONLIN_EOS Nonlinear Equation of State for seawater.
NORTHERN_WALL Wall boundary at Northern edge.
PERFECT_RESTART Processing perfect restart variables.
POWER_LAW Power-law shape time-averaging barotropic filter.
PROFILE Time profiling activated .
!RST_SINGLE Double precision fields in restart NetCDF file.
SALINITY Using salinity.
SOLVE3D Solving 3D Primitive Equations.
SOUTH_FSCHAPMAN Southern edge, free-surface, Chapman condition.
SOUTH_M2FLATHER Southern edge, 2D momentum, Flather condition.
SOUTH_M3RADIATION Southern edge, 3D momentum, radiation condition.
SOUTH_TRADIATION Southern edge, tracers, radiation condition.
SPLINES Conservative parabolic spline reconstruction.
SPHERICAL Spherical grid configuration.
TS_C4HADVECTION Fourth-order centered horizontal advection of tracers.
TS_C4VADVECTION Fourth-order centered vertical advection of tracers.
TS_DIF2 Harmonic mixing of tracers.
UV_ADV Advection of momentum.
UV_COR Coriolis term.
UV_U3HADVECTION Third-order upstream horizontal advection of 3D momentum.
UV_C4VADVECTION Fourth-order centered vertical advection of momentum.
UV_QDRAG Quadratic bottom stress.
UV_VIS2 Harmonic mixing of momentum.
VAR_RHO_2D Variable density barotropic mode.
WESTERN_WALL Wall boundary at Western edge.

With analytical OBCs

ANA_BSFLUX Analytical kinematic bottom salinity flux.
ANA_BTFLUX Analytical kinematic bottom temperature flux.
ANA_FSOBC Analytical free-surface boundary conditions.
ANA_INITIAL Analytical initial conditions.
ANA_M2OBC Analytical 2D momentum boundary conditions.
ANA_SMFLUX Analytical kinematic surface momentum flux.
ANA_SRFLUX Analytical kinematic shortwave radiation flux.
ANA_SSFLUX Analytical kinematic surface salinity flux.
ANA_STFLUX Analytical kinematic surface temperature flux.
ASSUMED_SHAPE Using assumed-shape arrays.
AVERAGES Writing out time-averaged fields.
CURVGRID Orthogonal curvilinear grid.
DJ_GRADPS Parabolic Splines density Jacobian (Shchepetkin, 2002).
DOUBLE_PRECISION Double precision arithmetic.
EASTERN_WALL Wall boundary at Eastern edge.
ICESHELF Include Ice Shelf Cavities.
LMD_BKPP KPP bottom boundary layer mixing.
LMD_CONVEC LMD convective mixing due to shear instability.
LMD_MIXING Large/McWilliams/Doney interior mixing.
LMD_RIMIX LMD diffusivity due to shear instability.
LMD_SKPP KPP surface boundary layer mixing.
MASKING Land/Sea masking.
MIX_GEO_TS Mixing of tracers along geopotential surfaces.
MIX_S_UV Mixing of momentum along constant S-surfaces.
NONLINEAR Nonlinear Model.
NONLIN_EOS Nonlinear Equation of State for seawater.
NORTH_FSCHAPMAN Northern edge, free-surface, Chapman condition.
NORTH_M2FLATHER Northern edge, 2D momentum, Flather condition.
NORTH_M3RADIATION Northern edge, 3D momentum, radiation condition.
NORTH_TRADIATION Northern edge, tracers, radiation condition.
PERFECT_RESTART Processing perfect restart variables.
POWER_LAW Power-law shape time-averaging barotropic filter.
PROFILE Time profiling activated .
!RST_SINGLE Double precision fields in restart NetCDF file.
SALINITY Using salinity.
SOLVE3D Solving 3D Primitive Equations.
SOUTHERN_WALL Wall boundary at Southern edge.
SPLINES Conservative parabolic spline reconstruction.
SPHERICAL Spherical grid configuration.
TS_C4HADVECTION Fourth-order centered horizontal advection of tracers.
TS_C4VADVECTION Fourth-order centered vertical advection of tracers.
TS_DIF2 Harmonic mixing of tracers.
UV_ADV Advection of momentum.
UV_COR Coriolis term.
UV_U3HADVECTION Third-order upstream horizontal advection of 3D momentum.
UV_C4VADVECTION Fourth-order centered vertical advection of momentum.
UV_QDRAG Quadratic bottom stress.
UV_VIS2 Harmonic mixing of momentum.
VAR_RHO_2D Variable density barotropic mode.
WESTERN_WALL Wall boundary at Western edge.

The above with different cppdefs for bndry

NORTH_FSCLAMPED Northern edge, free-surface, Clamped condition.
NORTH_M2FLATHER Northern edge, 2D momentum, Flather condition.
NORTH_M3GRADIENT Northern edge, 3D momentum, gradient condition.
NORTH_TRADIATION Northern edge, tracers, radiation condition.

The above with RADIATION_2D added.

Obviously, I'm just fishing at this point.

Note, I'm using ice, but there is no ice along the boundary. Also note that my thermodynamics for ice are different than is in the trunk. As I don't have ice on the boundary and the closed boundary case works fine, I have omitted my ice specifications in the above (I just mention here for transparency).

My rx0 is 0.1, rx1 is 22 (yes, this is high, I know, but I did a stratified no forcing case and it appears to be okay. High values not at boundary).

What could I be missing? Any thoughts/suggestions would be greatly appreciated. For instance, is there a more simple approach to opening the boundary than what I have already tried?

Thanks!

[rmueller]

I keep forgetting to post the solution, so--before too much time goes by--here it goes....

The problem that I described above was caused by 0m water depth in the mask region, which resulted in -dZ under land mask. This -dZ was not a problem for the closed boundary or gradient boundary conditions. It became a problem when I started to use the Chapman-Flather condition.