Version 16 (modified by omamce, 22 months ago) (diff)



MOSAIX is a small set of fortran routines, bash scripts, python scripts and xml files allowing to generate coupling weights for IPSL Earth System Model. It is under development, and presently not used by the production runs. It aims to replace the old MOSAIC software. It uses XIOS as a library to compute weights. In the present state, it can handle ORCA, LMDZ lon/lat and DYNAMICO grids.

MOSAIX can generate 2nd order interpolation weights. They are used in place of bilinear interpolation by OASIS-MCT.

As MOSAIX uses XIOS, it works in parallel, using MPI distributed memory.

Compatibility with MOSAIC

  • Weights are generally compatible with the weights generated by MOSAIC. The precision of the interpolation (conservation) is improved.

  • Run-off : runoff weights are computed with a different algorithm, the result can be quite different.
  • Calving : In IPSLCM6, the calving was integrated for each latitude of the grid on the LMDZ grid. Weights were use to aggregate several latitudes to compute an integral over a latitudinal band.. This is not possible with DYNAMICO, and was abandon for rectilinear LMD grid. The atmosphere model must the integral over a region (presently latitudinal bands). The final result should be the same as with MOSAIC.

Known problems

  • Must determine if weight and grid files should be in netCDF3 or netCDF4 for OASIS-MCT.

Future work

  • Geographical distribution of the calving for the northern hemisphere.

Code availability


MOSAIX has been tested on Curie and Irene (TGCC) .


  • Fortran compiler, C++ compiler, MPI.
  • A working XIOS library. Revision 1615 is known to work.
  • fcm version 1.2
  • NetCDF fortran librairies. See XIOS for a suitable version.
  • Python, version>=3.6 with netCDF4 and numpy modules. Python version>=2.7 mights work, but has not been tested recently.
  • Bash version>=4.
  • NCO. Version 4.6.0 is known to work.

Input files

MOSAIX needs files describing the grid of the models. See CreateWeightsMask.bash and the bottom of this page.

Output files

All netCDF files have a detailed header.

  • Weight files rmp_*. Should have a rather explicit name. The name is configurable at the beginning of CreateWeightsMask.bash.
  • Diagnostic file used for debug dia_*.nc for each rmp file, except for runoff and calving. Debug information are directly in weight files in this last cases.
  • Grid description file for OASIS-MCT, and
  • A file containing the fraction of ocean in each atmosphere grid box. For instance
  • A README file. Includes a checksum for each generated files.

Scripts and codes

  • CreateWeightsMask.bash. Creates the weights to interpolate between atmospheric and ocean grid. Weight files are suitable for OASIS-MCT. Creates the fraction of ocean in atmospheric grid cells. Uses parallel processing with MPI. Has a configuration section at the beginning.
  • CreateOasisGrids.bash. Creates files, and with information from both models, suitable for OASIS-MCT. Mono CPU. Launched by CreateWeights.bash.
  • Python script used to perform on the fly editing of xml files. Used by CreateWeights.bash. More information with python -h.
  • iodef_atm_to_oce.xml and iodef_oce_to_atm.xml. xml files read by interpol.f90. These files are edited by
  • MOSAIX/src/MOSAIX/interpol.f90. Fortran source using the XIOS library.
  • make_mosaix. Small script for compiling interpol.f90. You need to compile XIOS first. Uses compiler, compiler options and librairies defined by XIOS.
    make_xios [options]
    options :
           [--xios path] : path to XIOS. Default is ../XIOS
           [--full]      : to regenerate dependencies and recompile from scratch
    Example : ./make_mosaix --xios ../XIOS
  • Python code to generates weights for run-off. Launched by CreateWeights.bash. More information with python -h.

1) Defines a coastal band on land in the atmosphere model. For LMDZ rectilinear grids, the width of this band is parametrized, in grid points. For ico grids, the band contains only point with a fraction of ocean in ]0,1[.

2) Defines a coastal band on ocean in the ocean model. The width of this band is parametrized.

3) An atmosphere point of the coastal band is linked to an ocean point in the coastal band if the distance between the two is less than searchRadius.

  • Python code to generates weights for calving. Launched by CreateWeights.bash. More information with python -h.

1) The atmosphere model integrate the calving over on specific regions. Presently the regions are three latitudinal bands with limits 90°S/40°S/50°N/90°N.

2) The weights distribute the calving in the ocean in the corresponding latitudinal bands. By default, the distribution is uniform.

3) For the southernmost band, it is possible to use a geographical distribution read in a file. These files are currently available for eORCA1 and eORCA025.


  • [tuv]orc. ORCA grid at [TUV] points. Masked on land, with area equal to grid box surface.
  • tlmd. LMD rectilinear grid at scalar (physics) point. Masked on land, with area equal to grid box surface.
  • tico. LMD icosahedron grid at scalar (physics) point. Masked on land, with area equal to grid box surface.
  • olmd. LMD rectilinear grid at scalar (physics) point. Not masked, with areas equal to 1.
  • oico. LMD icosahedron grid at scalar (physics) point. Not masked, with areas equal to 1.
  • corc. ORCA grid at T point. Masked on land, duplicated (from periodicity) point masked, with area equal to grid box surface.
  • oorc. ORCA grid at T point. Masked on land, duplicated (from periodicity) point masked, with area equal 1.

Generating input grid files

Generating icosahedral grid in double precision using XIOS:

Here are the main changes:

  • File context_lmdz.xml :
     <domain id="dom_glo" data_dim="2" />
     <domain id="dom_glo_p8"  domain_ref="dom_glo"  prec="8" />
     <domain id="greordered"  domain_ref="dom_glo">
     <reorder_domain invert_lat="true" shift_lon_fraction="0"/>


     <grid id="grid_glo">
        <domain domain_ref="dom_glo" /> 
     <grid id="grid_glo_p8"> 
        <domain domain_ref="dom_glo_p8" />  

  • File field_def_lmdz.xml :
<field_definition level="1" prec="4" operation="average" freq_op="1ts" enabled=".true." default_value="9.96921e+36" domain_ref="dom_glo">
    <field_group id="fields_2D_p8" grid_ref="grid_glo_p8" prec="8"> 
      <field id="aire_p8" field_ref="aire" long_name="Grid area p8" unit="-"    />
      <field id="fract_oce_p8" field_ref="fract_oce" long_name="Fraction oce p8"   unit="1" /> 
      <field id="fract_sic_p8" field_ref="fract_sic"   long_name="Fraction sic p8"   unit="1" /> 
      <field id="fract_oce_plus_sic_p8" long_name="Fraction oce plus sic p8"   unit="1" /> 
      <field id="mask_oce_plus_sic_p8" long_name="Masque oce plus sic p8"  unit="1" /> 

  • File file_def_histmth_lmdz.xml :
    <file_group id="defile"> 
        <file id="grid_p8" name="grid_p8" output_freq="1d" sync_freq="10d" output_level="2" enabled="true" timeseries="none" time_counter="none"> 
          <field_group grid_ref="grid_glo_p8" ts_enabled="true" freq_op="1d" expr="@this">  
              <field field_ref="aire_p8" level="1" operation="once"  /> 
              <field field_ref="fract_oce_p8" level="1" operation="once" /> 
              <field field_ref="fract_sic_p8" level="1" operation="once" />  
          <field_group grid_ref="grid_glo_p8" ts_enabled="true" freq_op="1d" >  
              <field field_ref="fract_oce_plus_sic_p8" level="1" > fract_oce + fract_sic </field>   
              <field field_ref="mask_oce_plus_sic_p8" level="1" > ((fract_oce + fract_sic) &gt; 0) ? 1 : 0 </field>