Re: Potential issues in module_lightning_driver, WRF-Chem v3.7.1

[Mary Barth]

Hello Auke,

Thank you for your email. No, we were not aware of these issues. Thank
you for pointing them out. We will fix these two issues for the upcoming
WRF release.

Also, since you are working with the lightning-NOx parameterization, I
invite you to join the wrf-chem-lightning discussion forum. You can
learn more at https://www2.acom.ucar.edu/wrf-chem/discussion-forum

Thanks,

Mary

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Mary Barth Phone: 303-497-8186
Senior Scientist email: bar...@ucar.edu

National Center for Atmospheric Research
P.O. Box 3000
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https://staff.ucar.edu/users/barthm
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On 1/5/18 3:02 AM, Visser, Auke wrote:
> Dear Ms. Barth and WRF-Chem helpdesk staff,
>
>
> In setting up WRF-Chem simulations with activated lightning NOx, I found two issues in the code of model version 3.7.1. I am attempting to simulate lightning NOx for parameterized convection (lightning_option = 11) and with a constant IC:CG ratio (iccg_method = 1). The output arrays contained arrays filled with 0 for CG_FLASHCOUNT, IC_FLASHCOUNT and lnox_total even though I ensured that the settings were specified correctly in the namelist, which could be traced back to two issues in module_lightning_driver in the phys/ directory.
>
>
>
> First, in subroutine lightning_driver, the following line (in my version on line 310):
>
>
> IF ( MOD((itimestep * dt - lightning_start_seconds), lightning_dt ) .ne. 0 ) RETURN
>
>
> will exit the subroutine if lightning_start_seconds is a multiple of lightning_dt (in the default case where lightning_dt is set to the model time step). This can easily be circumvented by changing lightning_start_seconds: in my case, with a time step of 180s, setting lightning_start_seconds to 720s instead of 600s resolved the issue. I believe this should be either modified in the code or specified in the user's guide.
>
>
>
> Second, after correcting lightning_start_seconds, the model crashed. I traced this back to a write statement in the same subroutine on line 475:
>
>
> WRITE(message, * ) ' lightning_driver: using user-prescribed IC:CG ratio = ', iccg_prescribed_num, iccg_prescribed_den
>
>
> results in an error because only one variable can be added to the string. Changing this to:
>
>
> WRITE(message, * ) ' lightning_driver: using user-prescribed IC:CG ratio = ', iccg_prescribed_num / iccg_prescribed_den
>
>
> resolves the issue.
>
>
>
> Were those issues already known? I look forward to hearing back from you.
>
>
>
> Best regards,
>
>
> Auke Visser
>
>
> PhD Candidate - SASODIE
> Meteorology and Air Quality Group
> Wageningen University
> Lumen, A.127