SOSIE is Only a Surface Interpolation Environment
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src LB: 3D interp: improved downward propagation of sea values into bedro… Jun 13, 2018


Getting started with SOSIE

(Also check the online SOSIE doc for more info on the interpolation method:

You need a FORTRAN-90 compiler and the netcdf library (with f90 support) installed.

Compiling the executables:

  • Create 'make.macro', the Makefile configurable part. This files should be a symbolic link or a copy of architecture-related templates found in the 'macro' directory, this file must specify your compiler and options as well as the path to netcdf

  • It's important to specify the default INTEGER precision to 4 in your compilation flags (switch "-i4" for ifort and "-fdefault-integer-4" for Gfortran)

  • compile the executables by simply running "make" (gmake)

  • if everything goes well, the 'sosie.x' and 'corr_vect.x' executables have been created and are ready to be used

  • 'sosie.x' is the executable used to interpolate 2D fields of a scalar and "vectors onto regular grids", it requires a 'namelist' configuration file, the provided template namelist should be documented enough to start now. --> check 'template_scalar.namelist' for the interpolation of a scalar field --> check 'template_U.namelist' and 'template_V.namelist' for a vector

  • 'corr_vect.x' is used to correct vector components in the case of a distorded grid, it needs BOTH components of the vector primarly interpolated with 'sosie.x'. By default it only support ORCA grids configuration. See the EXAMPLE section for more details.

You can start to interpolate!

  • Tune the 'namelist' file according to your needs...
  • It's a good idea to use scripts to automatically generate namelists

A few working examples / test cases:

First download the two archives containing the NetCDF files for the examples:

For generic examples:

For ROMS examples:

Save and extract them into the "examples" sub-directory of SOSIE.

Into this "examples" sub-directory you will find various namelists and scripts to test SOSIE on working configurations. For each example you will find a commented and working namelist (usually namelist.exampleX, sometimes a more explicit name ) explaining the relevant namelist tuning. We encourage you to use a software like ncview to visualize fields to be interpolated and fields that have been interpolated. The common approach to test a given example (# X):

 >> cd examples/
 >> gunzip data/*.gz
 >> sosie.x -f namelist.exampleX


Example #1: basic 2D scalar field interpolation

Interpolation of Reynolds (2002) Long Term Mean SST onto the ORCA1 grid (illustrated on Fig. 3-4). Uncompress files and in ./data

  >> sosie.x -f namelist.example1

Check the newly created


Example #2: 3D scalar field interpolation

3D interpolation of Levitus (1998) temperature climatology onto the ORCA1 grid (only march). Uncompress files and in ./data

 >> sosie.x -f namelist.example2

Check the newly created


Example #3: Interpolation from an irregular (ORCA1) to a regular lat-lon 1x1 deg. grid

2D interpolation of a SST snapshot from a random NEMO-ORCA1 simulation onto lat-lon 1x1 deg. grid using the bilinear algorithm. Uncompress the file in ./data

>> sosie.x -f namelist.example3

Check the newly created


Example #4: Interpolation and correction of a 2D vector field from a regular lat-lon 1x1 deg. grid to an irregular grid (ORCA1)

As the ORCA family of grids gets distorded in the northern hemisphere it is necessary to correct (i.e. rotate) both components of the vector. In this example the input vector field is the wind at 10 from a few 6-hourly snapshots of the ERA-INTERIM re-analysis.

  >> cd examples/ex_corr_vect/

Do the "raw" interpolation for the zonal component of the wind:

  >> sosie.x -f namelist.example4_O1t_x

Do the "raw" interpolation for the meridional component of the wind:

  >> sosie.x -f namelist.example4_O1t_y

Now that uraw_1x1-deg-ORCA1_grid_T.nc4 and uraw_1x1-deg-ORCA1_grid_T.nc4 are created, time to correct onto the T-grid:

  >> corr_vect.x -G T -f namelist.example4_O1t -m ../data/mesh_mask_ORCA1v2_light.nc4

Check the newly created u10_1x1-deg-ORCA1_grid_T.nc4 and v10_1x1-deg-ORCA1_grid_T.nc4 (vector components on T-points of the grid).

It is possible to do the same correction onto U,V grid points rather than T points:

  >> corr_vect.x -G U -f namelist.example4_O1t -m ../data/mesh_mask_ORCA1v2_light.nc4

Check the newly created u10_1x1-deg-ORCA1_grid_U.nc4 and v10_1x1-deg-ORCA1_grid_V.nc4.


Example #5: 2D regular lat-lon to polar stereographic

Interpolation of high-resolution surface 2-meter air temperature from ECMWF onto a polar stereographic projection of the Arctic. Do the interpolation:

      >> sosie.x -f namelist.example5

Check the newly created


Example #6: 3D interpolation from ORCA2 to ORCA1 tri-polar grids

Interpolation of a random 3D+time monthly salinity field on the ORCA2 grid to the ORCA1 grid using the bilinear method. Do the interpolation:

      >> sosie.x -f namelist.example6

Check the newly created


Bi-linear remapping ORCA to ORCA

Examples are stored into "examples/ORCAX_to_ORCAY"

Remapping metric/weight files for big source/target configurations can be downloaded at the following link, since they are very time-consuming to generate.