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Setting soil moisture to 0% and 100% in the WRF-ARW model


New member
I'm simulating some low-pressure systems using the WRF-ARW 4.5.1 model. I've set two domains (d01:9 km; parameterised convection & d02: 3km; explicit convection), initial and boundary conditions are from ERA5, and I'm using the Noah Land-Surface Model. I want to see what happens to the track of these low-pressure systems when the soil moisture (in all four layers) over the land is set to 0% at all time steps. I'd then like to repeat the experiment by setting the soil moisture to 100% at all time steps. As a test experiment, I've disabled the Noah LSM in a simulation, which sets the soil moisture (SM) to 0.3 over the land and 0 over the sea. I'm not sure why this happens (perhaps due to MAXSMC = 0.339 in SOILPARAM.TBL?). From what I've understood so far, if I tweak the REFKDT parameter in the GENPARM.TBL file, I'll be able to adjust the infiltration factor. But I'm not sure if this is the correct way to achieve SM = 0% and SM = 100%. Does anyone know how to set the SM to a constant value in a Noah LSM?
There is a variable "SMOIS" in wrfinput file. I suppose you can modify the value of this variable for your tests. However, note that such changes is only effective at the initial time. Once WRF starts running, it will predict SMOIS based on LSM (i.e. Noah in your case).
Pleas take a look at the codes phys/module_sf_noahdrv.F, in which you can find the subroutine ism. This is the code that calculated smois (suppose you run with Noah). You can comment out all the codes that involves smois calculation. In this way, smois will remain unchanged.
If you use other LSM, then you can follow the similar approach, finding the codes related to the LSM option you use, and keep smois unchanged in the codes.
Thank you for your response. I'll try editing the sf_noahdry.F file. Just one more question: after I comment out the relevant codes, do I need to re-configure & recompile WRF & WPS and then run my simulation? Can't I just run real.exe and wrf.exe after commenting out the smois related codes?

I'm not able to understand anything in the attached fortran code (sf_noahdry.F). Could you please let me know which lines I need to comment out to disable smois calculation?


  • module_sf_noahdrv.F
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