strange ndown.exe result

[Alice_666]

Greetings,
I used the 1km wrfout results to drive a 200m simulation and completed it using ndown.exe. However, the results were very strange. I found that there were oscillations in the upper-air wind, which undoubtedly affected my simulation results. As a beginner of ndown, I'm not sure where the problem is.
Is it due to incorrect settings of some parameters? There were some errors during I use the wrfout files ,then I turned off the topo_wind.

Any thoughts are appreciated.

Thanks so much,

Interesting namelist.input variables:

 

[William.Hatheway]

I think it has something to do with the boundary conditions, can you share your namelist.input?

 

[Alice_666]

I think it has something to do with the boundary conditions, can you share your namelist.input?

ok,thank you very much ,This is my namelist.input

 

[William.Hatheway]

ok,thank you very much ,This is my namelist.input

what is your resolution of input for ndown?

 

[Alice_666]

what is your resolution of input for ndown?

Are you referring to the resolution I am using to drive ndown? Currently, I have wrfout results with a resolution of 1km, and I want to use ndown to obtain results with a resolution of 200m.

 

[Ming Chen]

Please turn on the option "diff_6th_opt", which can remove small wave structure of winds.
Let me know whether it helps.

 

[cplackner]

Has anyone ever found a solution to this problem? I believe I am running into the same problem right now. There was another thread that described what seems to be the same issue. That thread doesn't have a solution either.

I think I have traced the issue to the wrfbdy file created by ndown. These wavy structures already seem to be present in those wrfbdy files and then propagate into the domain as the simulation runs (as far as I can see). Similar to the other thread the problem does not occur when running it as one simulation as opposed to using ndown. So it is definitely happens in the ndown process, because it somehow has these waves in the boundary files. diff_6th_opt does not help because I think the waves are larger than 2dx. Not sure if I have any major mistake in my namelist used for ndown.

Thank you for any help!