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WRF Model Version 3.8 : Known Problems and Fixes

New Option bl_mynn_edmf for MYNN (posted April 8, 2016)

Problem: This new sub-option when using MYNN (bl_pbl_physics = 5) is still experimental. Some stability issues still exist with bl_mynn_edmf = 2.

Solution: Use with caution, or wait until later.

New Tiedtke (posted April 8, 2016)

Problem: Water budget issue has been improved in this version, but further improvement could still happen.

Solution: Use with caution and feedback is welcome.

Problem when using tmn_update (posted September 8, 2016)

Problem: An error was introduced beginning with WRF Version 3.7 in a restart run when the tmn_update option is used. This error is present in WRF Versions 3.7, 3.7.1, 3.8 and 3.8.1. When tmn_update is activated, a moving-averaged skin temperature (TLAG) is used as a lower boundary condition for the land model. Since TLAG is left out of the restart file, any restart using the tmn_update option will start with 0 K as the lower boundary condition for the land model. This will cause the soil temperature to cool gradually, eventually affecting the skin and atmospheric temperature. The tmn_update option can be used for the following land models: SLAB, Noah, NoahMP, RUC and CLM.

Solution: The fix is to add the letter 'r' (for restart) in the 8th column of the Registry.EM_COMMON file, for the variable TLAG, so that the original line:

state real TLAG i&j misc 1 - d=(interp_mask_field:lu_index,iswater)u=(copy_fcnm) "TLAG" "DAILY MEAN SFC TEMPERATURE OF PRIOR DAYS" "K"

becomes state real TLAG i&j misc 1 - rd=(interp_mask_field:lu_index,iswater)u=(copy_fcnm) "TLAG" "DAILY MEAN SFC TEMPERATURE OF PRIOR DAYS" "K"

One must do 'clean -a', reconfigure, and recompile the code after making this registry change.

If you have not previously made any changes to your Registry.EM_COMMON file, and you are okay with replacing it, instead of making the above change, you can simply replace your current file with the corrected Registry.EM_COMMON.v38 file. Once you download the file, you will need to unpack it, change the name to Registry.EM_COMMON, and place it in your WRFV3/Registry/ directory. After this, go back to WRFV3/, issue a 'clean -a', reconfigure, and recompile.

(Thanks to Heimo Truhetz of University of Graz, Austria, for reporting and finding the fix for the problem.)

Problem with Cloud Fraction (posted November 30, 2016)

Problem: Beginning in V3.8, a bug was introduced to cloud fraction. This is seen by most radiation schemes, when a microphysics scheme is used that does not have cloud ice (e.g. WSM3, Kessler). When WSM3 or Kessler is used, cloud fraction is not computed, and hence a radiation scheme will not see any cloud. This results in unrealistic surface temperature and incorrect upwelling long-wave radiation at the top of the atmosphere.

Solution: To correct the problem, download this modified module_radiation_driver.F.fix-for-v3.8.tar.gz file. You will need to unpack the file and place it in the WRFV3/phys/ directory. Rename the file to 'module_radiation_driver.F' and recompile the code. It will not be necessary to issue a 'clean -a' or to reconfigure. Simply recompile, and the compilation should be rather quick.



Known-problems in previous version.

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