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Does WRF LES mode calculate PBL Height correctly?

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N

n1o1o3n

New member
Hi,

I'm carrying out the WRF simulation with nesting like YSU-YSU-LES or YSU-LES-LES, where the innermost domain has the grid resolution of 100 m.
When I checked the result, I found that the PBLH of the LES domain shows much lower values (approximately 50 m) compared to those with PBL scheme. The 5 lowest half levels of my simulation are approximately 10, 37, 70, 108 and 149m.
I guess this is because the LES domain doesn't use the PBL scheme.

In the fortran codes of the PBL scheme module, I found the lines for calculating the PBL height.
However, I also found similar codes in surface scheme module. And even though I used clay surface scheme, PBLH was the same strange value...


So, my questions are
1) why the clay scheme with LES (it also means without PBL scheme) doesn't calculate the PBL height correctly?
2) why the PBLH shows 50 m, which is not the lowest level in my simulation?

and do you have any papers regarding the detection of the PBL height?

Thanks in advance


Best regards
 
Hi,
Can you let me know which version of the model you are using, and can you attach your namelist.input file here?

Thanks,
Kelly
 
Hi

Thank you for your quick reply.

Attached is the namelist.input I used. for the simulation with MYJ PBL scheme (the first and second domains) and LES (innermost domain)
View attachment namelist.input


I run the simulation on WRFV4.0.3

Please kindly refer to the namelist.

Best,
 
Hi,
I apologize for the delay in response. I had to do a bit of searching, but found that for an LES run, there is no PBL height calculated, which may explain why the value you see is not accurate. It may just be a default value that is given and not actually calculated.
 
Hi,
Thank you for your reply.

I totally understand why PBL height seems to have an inaccurate value.
I just wondered if configurations for my simulation are not correct or some errors happen implicitly.

Then, I need to be careful of the grid nudging with the options like "if_no_pbl_nudging_xxx", right?


Anyway, thank you for your kind reply.
 
Hi,
I'm not sure whether those will be affected with an LES run, but yes, I would check to make sure things look accurate if you do use a nudging option. You can do a small test to determine whether you should have those turned on/off.
 
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