Difference in WRF output for lightning schemes

[joyeede]

Hi,
Using the same namelists, in 1km grid-spacing, for WRFv3.8.1, DLP3 lightning scheme is underestimating lightning count whereas for WRFv4.5, DLP3 is overestimating.
Can anyone please explain the reason to me?

Thanks.

 

[Ming Chen]

Please upload your namelist.input for me to take a look. What variables did you check?

 

[joyeede]

Hi,
Please check the namelist.input attached below. This is the namelist used for both the wrf-versions.
For lightning option = 11, ie DLP3, the wrf ouput when checked spatially and temporally is overestimating when it comes to WRFv4.5, but underestimates in the older version.

Thanks.

 

[joyeede]

Hi,
If anyone has any answer/explanation for the original query, I would be highly grateful.
Thanks.

 

[Ming Chen]

Thank you for uploading namelist.input.

Your case is a high-resolution run with dx = dy =1km. I have a few concerns regarding your namelist options:

(1) At the resolution of 1km, it is inappropriate to turn on cumulus scheme, but in your case you set cu_physics = 93

(2) lightning_option 11 is recommended to be activated when dx> 10km and dx < 50km. For your case with dx = 1km, 11 is not a good option.

Also, note that neutral buoyancy from convective parameterization are affected by many factors. From WRFV3.8 to WRFV4.5, various updates and bug fixes may affect neutral buoyancy, leading to different model behavior.

 

[joyeede]

Thank you for the response.

(1) At the resolution of 1km, it is inappropriate to turn on cumulus scheme, but in your case you set cu_physics = 93

The CPS is turned on because DLP3 lightning scheme doesn't work without any CPS. The run was stopping whenever I tried with CPS off.

(2) lightning_option 11 is recommended to be activated when dx> 10km and dx < 50km. For your case with dx = 1km, 11 is not a good option.

Yes, I am aware of this. I think this is because DLP3 feeds on CPS, and model explicitly resolves the convection for higher resolutions where CPS is not required. So by default, even for high resolutions, DLP3 uses CPS, even though model explicitly does a better job here.
Actually, my research objective requires me to compare all the lightning schemes in this resolution. So I have to use CPS for DLP3 in 1km resolution for comparison with other schemes.

Also, note that neutral buoyancy from convective parameterization are affected by many factors. From WRFV3.8 to WRFV4.5, various updates and bug fixes may affect neutral buoyancy, leading to different model behavior.

So can I get the information of what are the updates and the bug fixes that were done that might affect the outputs?

Thanks.

 

[Ming Chen]

There are too many updates and bug fixes from WRFV3.8 to WRFV4.5 Honestly I am not sure which one might affect neutral buoyancy and subsequently affect the lightning option. I guess it is hard to check impacts of these changes one by one.
Sorry for the inconvenience caused the inconsistent model behavior.

 

[joyeede]

Thank you for the help. I will let you know in this thread if I find something.