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How can I let WRF evaluate diagnostic variable at the initial output file

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New member
Hi all,

I am doing data assimilation use WRF. In my experiment, I have to restart my simulation every six hour using the updated WRF output file.

I found that the diagnostic variable such as PBLH are always zeros at the first WRF output file (e.g. wrfout_dxx_xxxx-07-25_00:00:00, wrfout_dxx_xxxx-07-25_06:00:00...etc) but the PBLH is non-zero in the wrfinput file.

So, I was wondering could I let WRF model calculate the diagnostic variable at the first wrf output file or is there any suggestion to solve this problem?

Thank you for your help

PBLH is diagnosed from other PBL variables. At the beginning of the integration, these PBL variables are not available and PBLH is always initialized to be zero. This is for the cold-start case.
If you run DA to produce initial conditions, I suppose those variables required to diagnose PBLH should be available, In this case, you can modify the codes to calculate PBLH. Note that this will involve lots of coding and may interfere with the cold-start initialization. You need to be cautious.
Another option is, you probably can manage to let DA process PBLH and include it in DA output. I am not quite familiar with DA codes. You may post a question in DA forum to ask whether this is possible.
Thank you for your reply!

I agree that modifying the source code might be very challenging and I'll ask this question in WRF DA forum.

Besides, I was curious is it possible to directly compute PBLH offline from the WRF output variables?

There are various ways to diagnose PBLH, which require other variables as input and these variables may not be included in wrfout. This is why we usually don't recommend people to diagnose PBLH outside the WRF codes.