This is an issue that Patrick Marchesiello solved for me ~12 years ago in an old version of ROMS_Agrif.
However, this patch was apparently not applied to the Croco model:
I have downloaded the last version of Croco and the nesting is not coded correctly when using periodic boundary conditions. To illustrate the error, I have a run an experiment of an eddy propagating in a periodic channel (EW_Periodic, North/South walls) using a nested grid (child grid is shown as a magenta frame in the figure below).
As you can see after a couple of days (2nd figure), the EW_PERIODIC is applied to the child grid while it should NOT.
If anyone wants to reproduce this example quickly (runs in a couple of minutes using 4 cpus) a simple cppdefs.h, param.h, AGRIF_FixedGrids.in, croco_grd.nc, croco_grd.nc.1, croco_ini.nc, croco_ini.nc.1, Croco.in, Croco.in.1 can be downloaded from my webpage here:
Initial Condition (SSH):
After a couple of days (Error):
It would be great if it could be fixed in the Croco code
Thanks to the development team