Best place to modify ZNT over water

Questions specifically related to modifying the WRF source code
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jgilbert
Posts: 14
Joined: Thu Feb 13, 2020 2:30 pm

Best place to modify ZNT over water

Post by jgilbert » Sun Nov 29, 2020 10:10 pm

WRF Community:

Which routines should I be looking at to modify the local surface roughness length (ZNT) over water? I would like to be able to parametrically vary the roughness length over specified regions of the ocean's surface and update the surface flux coefficients accordingly.

I'm currently using the MM5 surface layer option (sf_sfclay_physics = 1) and the Noah land-surface option (sf_surface_physics = 2). I've been poking around module_sf_sfclay.F, specifically the SFCLAY1D subroutine which includes an example of ZNT modification due to ocean surface winds (~line 840). This is similar to what I am trying to accomplish.

Thanks in advance,
John

kwerner
Posts: 2287
Joined: Wed Feb 14, 2018 9:21 pm

Re: Best place to modify ZNT over water

Post by kwerner » Wed Dec 02, 2020 11:30 pm

Hi John,
I think you are on the right track. Depending on what version of the code you're using, though, you may need to be modifying the "module_sf_sfclayrev.F" file, instead of "module_sf_sfclay.F." The releases in the past several years have used that file for the MM5 surface layer scheme. I believe the routine you mention (SFCLAY1D) is the correct one to modify, except in the correct file, it is called "SFCLAYREV1D."
NCAR/MMM

jgilbert
Posts: 14
Joined: Thu Feb 13, 2020 2:30 pm

Re: Best place to modify ZNT over water

Post by jgilbert » Fri Dec 04, 2020 9:36 pm

Thanks for the response. You're right, I needed to look at "module_sf_sfclayrev.F."

Thanks again for the help!

John

gverri
Posts: 9
Joined: Tue Sep 10, 2019 8:48 am

Re: Best place to modify ZNT over water

Post by gverri » Fri May 07, 2021 8:09 am

Dears,
I'm facing the same issue and I decided to simply double the coefficient CZO to reduce my overestimation error on 10m wind
I modified CZO into module_sf_sfclayrev.F, since I selected sf_sfclay_physics =2 by namelist
However when I plot the results, no changes show up
What am I doing wrong?
Thanks
best

kwerner
Posts: 2287
Joined: Wed Feb 14, 2018 9:21 pm

Re: Best place to modify ZNT over water

Post by kwerner » Tue May 11, 2021 10:53 pm

@gverri,
After you make the modifications to the code, are you recompiling your code before running again?
NCAR/MMM

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