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• grid type
• grid rotation (optional)
• number of grid points and grid size
• location of limited area (just for LAM grids)
• FFT criteria

Grid type

First thing to do is to set 'Grd_typ_S' to the grid type you want:

Grid rotation

Next specify whether your grid is to be rotated or not (if not just skip this paragraph).
Four variables are used to define the rotation of the grid. They define two points:

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   Grd_xlat2 = 0.,  
   Grd_xlon2 = Grd_xlon1 + 90.       =>  You need to set it to the value 'Grd_xlon1 + 90.', do not actually put 'Grd_xlon1' here!!!

Number of grid points and grid size

Global uniform grid
It is enough to specify the total number of points. The model will then calculate size of the grid boxes automatically.

Global YinYang grid

You need to specify the core number of points in y-direction as well as the "overlap" in degrees. The model will calculate the size of the grid boxes automatically from that.

All other grid parameters will get adjusted automatically.


LAM grid

Specify the total number of points and the size of the grid boxes in degrees.
If possible, insure that the total number of grid points in x-direction matches the FFT criteria. This will speed up your simulation by up to 10 %.

Location of limited area (just for LAM grids)

The only thing left now when setting up a LAM grid is to specify where the limited area is located on the rotated grid.

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Click here to find out how to set blending and pilot area (halo).

FFT criteria

To fulfill the FFT criteria the number of grid points in x-direction, excluding the pilot zone, must be a multiple of 2, 3, and 5. Use the findfft GEMCLIM script to find the possible numbers of grid points fulfilling the FFT criteria.
Again you need to insure that the model environment is set.

Then you can use findfft:

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