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(RESOLVED) how to set dx and dy based on input data grid spacing

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New member

I am trying to run metgrid.exe and after correctly establishing the WPS, but I get some errors.


a part of my namelist.wps:
e_we = 248, 145,
e_sn = 120, 109,
dx = 27000,
dy = 27000,
map_proj = 'lambert',
ref_lat = 37.00,
ref_lon = 104.00,
truelat1 = 30.0,
truelat2 = 60.0,
stand_lon = 104.0,

When I change dx and dy to 6 km,run it again, it be right.

I would like to ask, because I have seen that some scholar’s papers are all 1 degree data with 27km(dx,dy), 0.5 degree data is used 4km(dx,dy), all are in China. And my 0.25 degree data with 27km should have problems, so I am very confused now, the calculation of this spacing, I think of a grid point of 0.25 degrees, the spacing is about 1 longitude length / 4, so I use 27km.

Thank you!

I'm not sure I understand your question. Your data has a resolution of 0.25 by 0.25 degrees. Is that correct?

Is your question whether your dx and dy need to correspond to the resolution of your input data?


My data do has a resolution of 0.25 by 0.25 degrees. And my dx and dy both are 27000, because I think 1 degree is 110 Km.

But it might be wrong, I saw other people's data has a resolution of 1 by 1 degrees and dx is 27000.

So I can't undersant why.

Thanks for your reply.

If the input data have a spatial resolution of 0.25 degrees, they are about 27km. For the parent domain (if using nesting), it is safe to scale down to a ratio of about 5:1 (similarly to the parent_grid_ratio recommended settings - see, so d01 could have a dx/dy or 6km and that should be perfectly fine. There is no need to start with an outer domain of 27km.