WRF Noah-MP Longwave Radiation Budget Error When Using swint_opt=2 with couple_farms=.true.

seti

Member
Hello,

I am running several WRF sensitivity simulations with four nested domains. All simulations use the same initial and boundary conditions, land-surface configuration, modified snow fields, land use, LAI, topography, microphysics, cumulus scheme, radiation schemes, and other physics settings. The main differences between the simulations are the PBL and surface-layer schemes.

In a group of simulations, I enabled:

swint_opt = 2 , couple_farms = .true.,
These runs stopped during the simulation. In several cases, the model terminated with:

STOP Error: Longwave radiation budget problem in NoahMP LSM
Other runs stopped with a segmentation fault at approximately the same simulation time.

Because this behavior appeared repeatedly, I suspected that the combination of swint_opt = 2 and couple_farms = .true., might be involved.

To test this, I started another simulation that is otherwise identical to one of the failed runs, including the same PBL scheme, surface-layer scheme, Noah-MP configuration, modified snow fields, domains, and other physics options. The only relevant change was:

swint_opt = 2, couple_farms = .false.,
This simulation has passed the time at which the corresponding run with couple_farms = .true. failed and is still running.

Therefore, it appears that the problem occurs when FARMS is enabled with swint_opt = 2 and its shortwave radiation is coupled to the land-surface model through couple_farms = .true.,

Could you please clarify why this combination might cause instability or a Noah-MP longwave radiation budget error?

In particular, I would like to understand whether there are known compatibility issues or limitations associated with:

swint_opt = 2, couple_farms = .true., sf_surface_physics = 4 ; Noah-MP, ra_sw_physics = 4 ; RRTMG shortwave, ra_lw_physics = 4 ; RRTMG longwave,

and whether the surface shortwave flux passed from FARMS to Noah-MP could lead to unrealistic surface temperatures or an inconsistent surface energy budget, eventually triggering the Noah-MP longwave radiation budget check.

For additional information, I have attached the full namelist.input, and the relevant rsl.error and rsl.out files from the failed simulation.

Thank you very much for your help.
 

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Hi, Seti,
Thank you for raising the issues of swint_opt and couple_farms combination. It is worth noting that not all combinations of various options are well tested and it is possible that some combinations don't work as expected. Since swint_opt and couple_farms are not commonly used options in WRF, it is not our top priority to debug possible issues involved in their application. We encourage community users to explore what is going on if they really need to work with these options.
 
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