# question about best practices for domains

D

#### Deleted member 3607

##### Guest
 max_dom An integer specifying the total number of domains/nests, including the parent domain, to be used in the simulation. Best Practice Nested domains are necessary when scaling down from coarse first-guess (input) data to a fine resolution, and the recommended ratios for coarse data resolution to the parent domain are odd ratios of 3:1 or 5:1. For example, if your domain of interest needs to have a resolution of 3 km, but your input data have a resolution of 27 km, and you are using a 3:1 ratio, your domain 01, should be around 9 km, and then you can have a nested domain with 3 km grid spacing. In this case, max_dom = 3.

Maybe I am reading this wrong since it is very early in the morning. But the way I read this is the best practices show a domain of 2 not three.

Input data: 27km

Using a 3:1 ratio

d01: 9x9km
d02: 3x3km

max_dom = 2 ????

Am I mistaken?

For the forcing data with resolution of 27km, the WRF domain setting of 9-3km nesting is reasonable.

For the forcing data with resolution of 27km, the WRF domain setting of 9-3km nesting is reasonable.
Good evening,

So the best practice listed above makes it sound like

d01: 27km
d02: 9km
d03: 3km
So we don't need the d01 domain if the ratio from forcing data is 3:1

I don't think it is necessary to run the case in 27-9-3km nesting. if the forcing data is 27km resolution, then it is fine to run 9-3km nesting case.

Thank you

Best Practice
It is recommended to have domains no smaller than about 100x100. Note that there will be about 10 grid points (minimum of 5) on each side, in the boundary zone. If domains are too small, the solution will be determined by forcing data.