Namelist setting regarding aerosol type for aerosols-aware Thompson scheme (mp=28)

[MMaria]

Hello,

I’m currently running WRF with the Thompson aerosol-aware microphysics scheme (mp_physics=28) and using the aerosol climatology file QNWFA_QNIFA_SIGMA_MONTHLY.dat to provide nwfa and nifa. In my namelist, I’ve set aer_opt=3, which I understand corresponds to G. Thompson’s water/ice-friendly climatological aerosol approach. My goal is to account for both the microphysical and radiative effects of aerosols in my simulations.
I have a few questions about how the aerosol data from the climatology file interacts with the radiation scheme, and I’d greatly appreciate any insights you can share:

1. Role of nwfa and nifa in AOD Calculation
   When aer_opt=3, are nwfa and nifa from the QNWFA_QNIFA_SIGMA_MONTHLY.dat file used only to compute the aerosol optical depth at 550 nm (aod550) via the gt_aod subroutine? Or do they influence other parts of the radiation calculations as well? To be specific, with aer_opt=3, are the single scattering albedo (aer_ssa_val), asymmetry parameter (aer_asy_val), and Angstrom exponent (aer_angexp_val) set to constant values? If so, what are these default values, and is there a way to modify them within this configuration?
2. Modifying Aerosol Type with aer_type
   I’d like to know if it’s possible to change the aerosol type (and thus its optical properties) by adjusting aer_type while still using the aerosol climatology file. I’ve tried setting aer_type=1 in the namelist (with use_aero_icbc=.true. and aer_opt=3), but I didn’t observe any changes in the model output. Is aer_type being overridden by aer_opt=3, or am I missing something in how these options interact? How should I configure the namelist to successfully modify the aerosol type?

For reference, here’s the relevant section of my namelist（the complete namelist.input file is attached）:
&physics
mp_physics = 28, 28,
use_aero_icbc = .true.,
aer_opt = 3,
aer_angexp_opt = 3, 3,
aer_ssa_opt = 3, 3,
aer_asy_opt = 3, 3,
aer_type = 1, 1,
/
I’m puzzled why changing aer_type doesn’t seem to affect the output, and I’d love to understand the interplay between these settings and the climatology file better. Thank you in advance for your time and expertise!
Best regards,
Maria

 

[kwerner]

Hi Maria,

Apologies for the long delay in response while our team tended to time-sensitive obligations. Thank you for your patience.

All the aer_* options (besides aer_opt) are only applicable with aer_opt=2, which requires its own AOD input. They don't work with aer_opt=3. The QNWFA and QNIFA optical properties are hardwired in the "gt_aod" code (in phys/module_radiation_driver.F), so any changes would need to be made there.