Unexpected Wave Patterns in ROMS Output

Hello:

I am running ROMS within COAWST and using PyROMS to generate the input files. While I believe the input files are correctly prepared, the model output shows strange wave patterns in the physical fields.

I used PyROMS to generate the grid, initial conditions, and forcing files. The model runs without crashing, but the output displays unexpected oscillations/waves in the physical fields. I have checked the bathymetry, boundary conditions, and time-stepping parameters, but the issue persists.


In the image, you can see a wave originating from the coast and propagating across the simulation domain. We are looking at a U-momentum component, but it is also noticeable in free surface and other variables that do not have a smooth behavior. However, it is not visible in temperature and salinity, which appear to be unaffected.

Could this be related to numerical instability, grid resolution, or incorrect input file formatting?
Are there any recommended checks or debugging steps to identify potential issues in the input files?
Has anyone encountered similar wave artifacts in ROMS simulations, and what solutions worked for you?

The report names ROMS within COAWST and PyROMS-generated grid, initial-condition, and forcing files, but no repository file, test, or reproducible case. Start by collecting those inputs and the run configuration, then compare the affected U-momentum and free-surface fields with unaffected temperature and salinity. Done means a reproducible diagnosis and a confirmed cause.

Written by the indexing model from the issue text.