Should dx and dy be the same in both namelist.wps and namelist.input?

[ehsantaghizadeh]

Hi everybody,
I hope you are doing well.
As you know there dx and dy in both namelist.wps and namelist.input files. I would like to know should dx and dy be the same in both namelist.wps and namelist.input files? Actually, I could run WRF (global) with different dx and dy as the following sections in namelist.wps and namelist.input, and it seems to work well. Did I do something wrong? I should mention using GFS0.50 for forcing (initial and boundary data). Thanks in advance.

namelist.wps
e_we = 1537, 220,
e_sn = 769, 214,
map_proj = 'lat-lon',
stand_lon = 180.
pole_lat = 90.0
pole_lon = 0.0
ref_lat = 45.0
ref_lon = 50
dx = 0.5
dy = 0.5

namelist.input
e_we = 1537, 41, 41,
e_sn = 769, 81, 81,
dx = 26057.22,20000, 4000,
dy = 26057.22,20000, 4000,

 

[kwerner]

Hi,
There is a small paragraph in the WPS section of the WRF Users' Guide that may be helpful. It states:
For global WRF simulations, the coverage of the coarse domain is, of course, global, so ref_lat and ref_lon do not apply, and dx and dy should not be specified, since the nominal grid distance is computed automatically based on the number of grid points. Also note that the latitude-longitude, or cylindrical equidistant projection (map_proj = ‘lat-lon’) is the only WRF projection that can support a global domain.

 

[ehsantaghizadeh]

Dear kwerner,
I really appreciate your helpful reply. I apologize for the delay in getting back to you.
If I'm not wrong, for global WRF simulations, dx and dy should not be specified in both namelist.wps and namelist.input, as you mentioned. So, could I delete lines related to dx and dy from two namelists (namelist.wps and namelist.input)?
Could you help me determine e_we and e_sn values in order to run global WRF and have 15 km resolution? There must be a formula to determine it in the global run, which unfortunately I could not find again by searching the internet.

 

[kwerner]

So, could I delete lines related to dx and dy from two namelists (namelist.wps and namelist.input)?

Yes, you can delete those lines.

Could you help me determine e_we and e_sn values in order to run global WRF and have 15 km resolution?

To determine these values, you will need to divide the circumference of the Earth (in km) by 15 for the e_we, and if you want your domain to extend from pole to pole, you'll need to divide that distance (in km) by 15, as well for e_sn. If you only want it to extend to specific points, you will need to calculate the distance for those specific points.