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Best place to modify ZNT over water

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

Thanks again for the help!

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?
After you make the modifications to the code, are you recompiling your code before running again?