NOCSCOMBINE is old and slow. Use REBUILD_NEMO instead.

NOCSCOMBINE is a tool to combine the per-processor NetCDF results files that are generated when NEMO is run in parallel using MPI. One description of its use can be found at The NOCSCOMBINE code was downloaded from

The nocscombine.F90 file contains this notice regarding distribution and use of the package:

Unless otherwise indicated, all other software has been authored
by an employee or employees of the National Oceanography Centre,
Southampton, UK (NOCS).  NOCS operates as a collaboration
between the Natural Environment Research Council (NERC) and
the University of Southampton.  The public may copy and use
this software without charge, provided that this Notice and
any statement of authorship are reproduced on all copies.
Neither NERC nor the University makes any warranty, express
or implied, or assumes any liability or responsibility for the
use of this software.


From the README.nocscombine file:


FORTRAN program that assembles a global NetCDF archive from a series of
NEMO output files.

USAGE :: nocscombine -f inputfile [-o outfile] [-v] [-s]
                     [-d list of variables] [-ts tstart] [-te tend]

     -f  inputfile
         Mandatory argument. inputfile is the filename of
         one of the NEMO restart or diagnostic files.
         This should be the whole filename of one of the individual
         processor files (i.e. include the
         node number, eg.
         This program works on NetCDF NEMO output files. The program will
         create a NetCDF archive covering the entire global domain.

    [-o outputfile ]
         Optional argument. outputfilename is the required name
         of the outputfile. By default this name will be constructed from
         the inputfilename by stripping off the processor number. I.e.:
         inputfile :
         The -o option permits the user to override this behaviour.

    [-c coordinatefile ]
         Optional argument. coordinatefile is the name
         of the global coordinate file relevant to the NEMO model which
         produced the individual processor files. This file is required to
         ensure complete nav_lon and nav_lat fields in cases where wholly
         land areas have been omitted from a parallel run (i.e.
         jpnij .ne. jpni*jpnj). The corrections are applied after
         the collation phase. If this argument is supplied and the output
         file exists then the collation phase is not performed but the
         coordinate corrections are still applied. In the latter scenario
         the (otherwise) mandatory inputfile argument is not required.

    [-n processor_offset ]
         Optional argument. Start collating from this processor number and
         process domains in order, cycling back through 0 if necessary. This
         is useful to prevent multiple simulataneous accesses when running
         nocscombine in a task-farming environment

         Optional argument. Switches on verbose reporting for debugging

         Optional argument. Normal behaviour is to show a limited amount
         of progress information. This option runs the utility without any
         output to stdout.

         Optional argument. Early versions of nocscombine erroneously
         copied across the halo rows and columns too. Potentially producing
         lines of unset values if the halo points were not set in the
         individual restart files (as could happen for some purely
         diagnostic fields). Use -showhaloes to reproduce this feature
         if required.

    [-d] comma-separated list of variables
         Collate only the named datasets

    [-ts] time-slice (integer) to begin extraction at

    [-te] time-slice (integer) to end extraction at. If the -te option
          is not used then only one time-instance is extracted (as set
          by the -ts option)


nocscombine -f \
            -o \
            -d "sosstsst,sosaline,sossheig,sowaflep,sowaflup,sorunoff,sowaflcd,
                sowafldp,sosafldp,sobowlin" \
            -ts 1 -te 4

On Hector the Lustre filesystem can be used to speed up i/o by "striping"
the named output file:

lfs setstripe 0 -1 3
nocscombine -f \
            -o -d votemper -ts 2
[ 0] [ 1] [ 2] ..........
Completed in  148.805 seconds

lfs setstripe 0 -1 3
nocscombine -f \
            -o -d vosaline  -ts 2
[ 0] [ 1] [ 2] ..........
Completed in  147.961 seconds

Building nocscombine

The NOCSCOMBINE.tar tarball includes several Makefiles but it is almost certainly necessary to create your own Makefile to set the FC, LDR, NCHOME, and LIBS variables appropriately. This repository contains Makefile.jasper to build nocscombine on using the values:

FC = ifort -fixed -80 -O3 -DLARGE_FILE -c
LDR = ifort -O3 -fixed -o nocscombine
NCHOME = /lustre/jasper/software/netcdf/netcdf-4.1.3
LIBS = -L$(NCHOME)/lib -I$(NCHOME)/include -lnetcdf -lnetcdff -lhdf5_hl -lhdf5 -lz -lsz