How to keep surface roughness length (ZNT) constant throughout the simulation?

[blossom_]

I modified the WRF Registry to output the ZNT (surface roughness length) variable, and I can now see it in my wrfout files. However, I noticed that ZNT changes with time during the simulation.

I tried setting the same values for Z0MIN and Z0MAX in the physics options, but this did not prevent ZNT from evolving.

How can I keep ZNT constant in time, i.e., use the initialized (or prescribed) roughness length from VEGPARM.TBL throughout the run?

 

[kwerner]

Hi, Apologies for the delay in response. ZNT is actually the "time-varying roughness length," which is why it changes over time. To keep this constant, you can probably modify the code for whichever physics scheme(s) you're using, where ZNT is calculated. If you do this, make sure to modify the "*.F" file and then recompile the code to include the changes. Unless you make modifications to the Registry file, you will not need to clean or reconfigure the code before recompiling. Just simply compile and it should be much faster than a full compile.