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The SW model still needs the ICMSH (spectral fields) and ICMGG (gridpoint) files to correctly start. In the idealized case, these are read solely to set the model's spectral and gridpoint resolution and the model will overwrite the initial state read from file (see the code in suspecb.F90). 

The model will require the vorticity, divergence, ln(Ps) (contains the geopotential of the free surface) and orography.

The Euler advection scheme can only be run on a regular Gaussian grid however (see below for example).

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titleT255 shallow-water test case

A test for the shallow-water model at spectral horizontal resolution T255 is available from the OpenIFS ftp site to try.

Code Block
ftp ftp.ecmwf.int
cd case_studies/shallow_water
get t255_swtest.tar.gz

This example comes with initial files, namelist and job. The namelist is configured to run the semi-Lagrangian advection.

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titleCreating initial fields from existing GRIB files

The GRIB files from an existing experiment can also be used to create initial files for the shallow-water model. In the following example, the initial files from the T21 test case distributed with the OpenIFS tarfile are used.

Code Block
#  Extract a single level (level 1) for the shallow water model
#  and change the experiment id in the file.

grib_copy -w level=1,shortName=vo ICMSHepc8INIT tmp
grib_set -s experimentVersionNumber=epc9 -w experimentVersionNumber=epc8 tmp vo.grb

grib_copy -w level=1,shortName=d  ICMSHepc8INIT tmp
grib_set -s experimentVersionNumber=epc9 -w experimentVersionNumber=epc8 tmp d.grb

grib_copy -w shortName=z          ICMSHepc8INIT z.grb

#  Combine the 3 files to form the spectral initial file
cat vo.grb d.grb z.grb > ICMSHepc9INIT

#  Create gridpoint file (stl1 is used in this example)
grib_copy -w shortName=stl1 ICMGGepc8INIT gg.grb
grib_set -s experimentVersionNumber=epc9 -w experimentVersionNumber=epc8 gg.grb ICMGGepc9INIT

Note that the initial fields themselves are not used with the idealized configurations. The initial files are there to correctly set the grid, hence stl1 is used in this example to get the initial gridpoint file.If you have some existing

 

If you have access to the MARS archive at ECMWF then an example of how to retrieve single level fields is:

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