BLOW UP error on custom bathymetry dataset - Hamilton Harbour

run / config issues
1

Hi,

I’m using CROCO to study circulation in a small embayment in Ontario called Hamilton Harbour. It is roughly a 10km x 6km harbour in the shape of a triangle, and the resolution of the grid is 40 meters. I am using a land masking since it is enclosed, and the hmin within the harbour is set to 1 m to avoid division by zero. Here is the bathymetry field for reference.

Screenshot 2026-06-23 at 2.11.50 PM
Screenshot 2026-06-23 at 2.11.50 PM962×659 86.7 KB

I am using a customized initial temperature field that I define in croco/OCEAN/ana_initial.F, which is a simple tilted thermocline in the (x-z) plane and extended into the spanwise (y) direction to initialize some sort of seiche. All the other initial conditions have been set to the default ones (which are zeroed).

#   elif defined HAMILTON_HARBOR
#    define Z0          (-7.)
#    define THKNSS      2.
#    define SLOPE_DEG   .02    /* thermocline slope angle in degrees */
#    define TEMPSURF    20.
#    define TEMPBOT     10.
#    ifdef TEMPERATURE
!
!  Tilted thermocline: thermocline deepens moving east
!  z_r is the cell-center depth (negative, 0 at surface)
!  Z0 is the thermocline center depth at x = xr_min
!
        slope_val = tan(SLOPE_DEG * pi / 180.0)
        do k=1,N
          do j=JR_RANGE
            do i=IR_RANGE
              t(i,j,k,1,itemp) = TEMPBOT + 0.5*(TEMPSURF - TEMPBOT)
     &            *(1. + tanh((z_r(i,j,k) - Z0
     &                        - slope_val * (xr(i,j) - xr(1, 1)))
     &                       / THKNSS))
              t(i,j,k,2,itemp) = t(i,j,k,1,itemp)
            enddo
          enddo
        enddo
#    endif /* TEMPERATURE */
#    undef Z0
#    undef THKNSS
#    undef SLOPE_DEG
#    undef TEMPSURF
#    undef TEMPBOT

Below are the cppdefs options that have been selected:

#elif defined HAMILTON_HARBOR
/*
!                 Hamilton Harbor tilted thermocline
!                 ======== ======= ====== ===========
*/
/* Parallelization */
# undef  OPENMP
# undef  MPI
/* Grid */
# undef SPHERICAL
# define CURVGRID
# define MASKING
# define NEW_S_COORD
/*Dynamics*/
# define UV_ADV
# undef UV_COR
# define UV_VIS2
# define SOLVE3D
# define TS_DIF2
# define BODYFORCE
/* Initial and Boundary Conditions */
# define ANA_INITIAL
# define ANA_SMFLUX
# define ANA_STFLUX
# define ANA_BTFLUX
# define NO_FRCFILE

croco_out.txt (10.9 KB)

croco_in.txt (8.9 KB)

param.h (34.3 KB)

Above, I have attached my config files and param which includes the grid point dimensions. jobcomp compiles without any issues. However, when I try to run the simulation, it crashes without taking a step due to a BLOW UP error. I’m not sure how to locate the blow up error or why it may be occurring. I would be grateful if someone can help point out what I am missing or how I can move further.

Odd boundary effect in temperature initialization
2

Hello,

Have you tried to reduce the time step drastically to rule out CFL-like errors ?

Your grid is very high definition, and the fact that NaNs appears at time step 1 and that time step0 is OK can point to timr-step issues.

Enzo

1 Like
3

Hi,

While looking at the bathymetry figure, I think there may be areas with relatively steep gradients, particularly in the southeastern–eastern part of the domain (it’s a bit difficult to tell from the color bar). Did you try smoothing the bathymetry so that it satisfies the condition (r < 0.2)?

1 Like
4

Thanks for the suggestions! I realized this is happening because I was setting depth values in the land areas to be 0, but now I’ve realized that CROCO divides by them before masking land, which caused the blow up.