GEM/4.6/Changes on horizontal gird

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< GEM | 4.6

For the LAM only.
Refer to the figure below. In GEM 4.2 and up, the size of the free domain (blue squares in figure) will be Grd_ni x Grd_nj regardless of the Grd_maxcfl parameter. On the other hand, the total size of the grid including the pilot zones (blue+red squares in figure) will change with Grd_maxcfl. Therefore if one increase Grd_maxcfl, the geophysical field may become too small. It may be a good idea to produce your geophysical field with a large value of Grd_maxcfl than the one you intent to use. This will leave some room if it is found that a larger Grd_maxcfl is needed. There will be no interpolation error since the model will detect that its grid is a sub domain of the geophysical field grid and will use the closest neighbor interpolation degree.

To convert from a previous gem_settings.nml use the following equations

Grd_ni   = Grd_ni_OLD   - 2*(Grd_maxcfl+8)
Grd_nj   = Grd_nj_OLD   - 2*(Grd_maxcfl+8)
Grd_iref = Grd_iref_OLD -   (Grd_maxcfl+8)
Grd_jref = Grd_jref_OLD -   (Grd_maxcfl+8)

Note : in GEM 4 listing, the OLD values will be printed.

Use the tool grille to view your grid.