Coupling restart files

At the beginning of a coupled run, some coupling fields may have to be initially read from their coupling restart file on their source grid (see section 4.8). When needed, these files are also automatically updated by the last prism_put_proto call of the run (see section 4.6.1) . To force the writing of the field in its coupling restart file, one can use the routine prism_put_restart_proto (see section 4.6.3). Warning: the date is not written or read to/from the restart file; therefore, the user has to make sure that the appropriate restart file is present in the working directory.

Note that all restart files have to be present in the working directory at the beginning of the run even if one model is delayed with respect to the others.

The name of the coupling restart file is given by the 6th character string on the first configuring line for each field in the namcouple (see section 5.3). Coupling fields coming from different models cannot be in the same coupling restart files, but for each model, there can be an arbitrary number of fields written in one coupling restart file. (Note that in the NONE techniques, output files with the same format are also created for writing the resulting field after transformation.)

In the coupling restart files, the fields must be provided on the source grid in single or double precision REAL arrays (depending on PSMILe and OASIS3 compilation options) and, as the grid data files, must be dimensioned (nx, ny), where nx and ny are the grid first and second dimension, except for fields given on Unstructured ('U') and Reduced ('D’) grid, for which the arrays are dimensioned (nbr_pts,1), where nbr_pts is the total number of grid points. The shape and orientation of each restart field (and of the corresponding coupling fields exchanged during the simulation) must be coherent with the shape of its grid data arrays.

Both binary and NetCDF formats are supported; for NetCDF file the suffix .nc is not mandatory. If the coupling restart file for the first field is in NetCDF format, OASIS3 will assume that all coupling restart files (and output files for NONE communication techniques) are NetCDF¹⁹.

In the NetCDF restart files, the field arrays must have the source symbolic name indicated in the namcouple, except for IGNORED fields for which the target symbolic name must be used. (see section 5.3).

In binary restart file, each field is written in the following way:

        ...
        WRITE(LU) array_name
        WRITE(LU) restartdata
        ...

where

• LU is the associated unit,
• array_name is the source symbolic name of the field (CHARACTER*8),
• restartdata is the restart field REAL array dimensioned (nx, ny) or (nbr_pts,1)²⁰

Note that if using OASIS in the IPSL parallel mode (see section 8.2.1), the different OASIS3 executables cannot share the same coupling restart file. The recommendation here is to use one separate coupling restart file per coupling field.

Footnotes

... NetCDF¹⁹

Note that even if the grid auxiliary data files are in NetCDF format, the restart coupling files may be in binary format, or vice-versa.

...(nbr_pts,1)²⁰

If REDGLO is the first transformation applied on a Reduced grid field, the Reduced field must be given is an array restartdata(nx*ny) where nx and ny are the global Gaussian grid dimensions and the Reduced field is completed by trailing zeros. Note that this transformation is obsolete in the current OASIS3 version and should not be used anymore.