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cu_physics, cugd_avedx settings for Grell-3D option (5)

Instructions in the manual for G3 are the following

Grell 3D is an improved version of the GD scheme that may also be used on high resolution (in addition to coarser resolutions) if subsidence spreading (option cugd_avedx) is turned on (5).

(default) number of grid boxes over which subsidence is spread, for large grid distances
for small grid distances (DX < 5 km), G3 only

Since cugd_avedx is set as a single number, if set to 3 -- will it be automatically used for nests with dx < 5km and other nests use the default 1?

I have 3-nested domains @ 27, 9, and 3 km
cu_physics = 5,5,5
cugd_avedx = 3


Should this be set to default
cugd_avedx = 1
and program automatically uses 3 for the 3rd nest with dx=3km?
Hi Sarah,
This is a good question. Unfortunately because the parameter only allows a single entry, whichever option you choose will be used on all domains. I spoke to our physics specialist about this and they recommend that you try both to see which gives the best result. You can just do a quick, simple test for this if needed. They suspect option 3 may be the better choice.