Inconsistent subhourly visibility variable

[janac4]

Hello everyone,
I have wanted to analyse subhourly visibility and precipitation values in my WRF simulations. I'm using a my_d01.txt file with:
:h:7:RAINC,RAINNC,AFWA_VIS
And my namelist looks like:
end_minute = 00
end_second = 00
interval_seconds = 3600
input_from_file = .true.
history_interval_m = 60
history_interval = 60
frames_per_outfile = 1
restart = .false.
restart_interval_m = 1980
io_form_history = 2
io_form_restart = 2
io_form_input = 2
io_form_boundary = 2
io_form_auxinput2 = 2
iofields_filename = "my_d01.txt"
ignore_iofields_warning = .true.
auxhist7_outname = "timestep_d<domain>_<date>"
auxhist7_interval = 5,
frames_per_auxhist7 = 1,
io_form_auxhist7 = 2
I don't get any errors and actually timestep_d01_date files have correct values of RAINC and RAINNC every 5 minutes. However, visibility values are constant during the same hour and change at H:00:00 times (when wrfouts are also outputed).
I attach two images where this behaviour is exposed.
Is it because of the AFWA diagnostics methodology? How can I solve this?
Thanks a lot.

 

[Ming Chen]

The visibility diagnosed in AFWA package is dependent on multiple factors. Specifically, if your lowest model level is above 20m, then the model will use 2m T and RH in the interpolation to obtain data at 20m height. This will to a certain degree affect the result.
Please take a look at the code phys/module_diag_afwa.F, which performs the calculation of visibility. I am suspicious that the input data for its calculation might be an issue in the overestimation of your case. I don't think the method itself is wrong. To confirm this, you may extract the code, provide GFS data as input and see whether you can get similar results to GFS.