...
Resolution → timestep → radiation timestep
Calculating the increments on different fields depending on the radiation is rather costly. Therefore, the option exists to calculate the increments only every n seconds but still apply them at every timestep. The parameter to set is called 'KntRad_S' from the 'gem_settings.nml'. It should get set to a multiple 4 to 6 of the model timestep. The unit is seconds.
Resolution → (non) hydrostatic
If the grid resolution is ~10 km or lower the model is hydrostatic and one should set 'Dynamics_hydro_L = .true.' in the 'gem_settings.nml'. For grid resolutions of ~4km and higher one should set 'Dynamics_hydro_L = .false.'
Model levels
The model levels on GEM are terrain following at the surface and pressure levels at the model top. The model levels are generally closer to each other at the surface and further apart higher up. The model is very sensitive to the location of these model levels. They must neither be too far apart nor too close and the transition from terrain following to pressure levels must be very smooth. There are ways to set up these model levels. Several sets of model levels have already been created and can get selected by setting 'CLIMAT_etaname' in the file configexp.cfg. The possible settings for this parameter can get found in the file:
~/modeles/GEMDM/*/bin/Climat_eta2preshyb
LAM grid → top piloting or sponge
...