[MITgcm-support] Backtrace error while implementing NOBCS

[Martin Losch]

Kunal,

the error message (as usual) means that there are not enough records in your input file (‘OBNu.seaice_obcs’)
you domain dimensions are (according to STDOUT.0000):
(PID.TID 0000.0001)      nPx =   10 ; /* No. processes in X */
(PID.TID 0000.0001)      nPy =    6 ; /* No. processes in Y */
(PID.TID 0000.0001)      nSx =    1 ; /* No. tiles in X per process */
(PID.TID 0000.0001)      nSy =    1 ; /* No. tiles in Y per process */
(PID.TID 0000.0001)      sNx =   66 ; /* Tile size in X */
(PID.TID 0000.0001)      sNy =   80 ; /* Tile size in Y */
(PID.TID 0000.0001)      OLx =    4 ; /* Tile overlap distance in X */
(PID.TID 0000.0001)      OLy =    4 ; /* Tile overlap distance in Y */
(PID.TID 0000.0001)      nTx =    1 ; /* No. threads in X per process */
(PID.TID 0000.0001)      nTy =    1 ; /* No. threads in Y per process */
(PID.TID 0000.0001)       Nr =   48 ; /* No. levels in the vertical   */
(PID.TID 0000.0001)       Nx =  660 ; /* Total domain size in X ( = nPx*nSx*sNx ) */
(PID.TID 0000.0001)       Ny =  480 ; /* Total domain size in Y ( = nPy*nSy*sNy ) */

So your input file for the OBCS pkg for the northern or southern boundary for a 3D field like temperature needs to have a field with the dimensions (t,z,x) = (nrec,48,660) and for the eastern/western boundaries (nrec,48,480). nrec needs to be at least 1 (for constant obcs forcing). This is independent of the number of actual boundary points. I.e. if you have only one open boundary point (OB_Jnorth(550)=-100,) your file still need the entire array, it can be zero everywhere except for the point i=550 (for i starting at 1, for i starting a 0 as in python, it should be at 549).

For a 2D field like sea ice velocity you drop the z-dimension (but I guess you only give you files these names, and don’t use sea ice).

does that make sense?

Martin
> On 18. Aug 2021, at 15:44, kunal madkaiker <kunal.madkaiker02 at gmail.com> wrote:
> 
> Dear All,
> 
> I am using MITgcm for regional analysis. I have kept a single OB point on the northern boundary. But I keep getting backtrace error and model blows.
> 
> Error termination. Backtrace:
> At line 1946 of file mdsio_read_section.f (unit = 9, file = 'OBNu.seaice_obcs')
> Fortran runtime error: Non-existing record number
> 
> I have gone through similar asked questions on the support group and checked accordingly. The dimensions for my NOBCS pt is 1x48x2 (nx x nz x nt). I have prepared the T,S,U and V data and written as real*8. But still error persists.
> Attaching my data, data.exf, data.obcs files. Kindly assist.
> 
> Regards,
> Kunal
> <data><data.obcs><data.exf><STDOUT.0000>_______________________________________________
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