A confusion about change Aerosol Refractive Indices

CMAQ
1

Hi

There seems two way to change Aerosol Refractive Indices, when I search in /CMAQ/UTIL/inline_phot_preproc/readne.md. One is use enviroment vars in AE_REFRAC_LIST , another is change the OPTICS entries in the aerosol species name list.
Is this two way as a same thing? If I change all OPTICS in zero, is this means all Aerosol Refractive Indices is zero?

Looking forward your reply !!

2

Both ways deal with the aerosol refractive indices used by the CMAQ model but they do not accomplish the same function.

  • AE_REFRAC_LIST defines what raw data files to process for refractive indices in PHOT_OPTICS, an input file for the CMAQ model. The processing converts the raw data to the wave bands used by the inline calculation of CMAQ photolysis frequencies. A CMAQ aerosol species or component can use any of these refractive indices. The defaults are assigned in the AERO_DATA.F file.
  • OPTICS allows overriding the default assignments to different refractive indices available in the PHOT_OPTICS files. The value should be a character string not a real number used as a scaling factor.

As a side note, I recommend against setting refractive indices to zero. Such materials have weird properties affecting light’s phase and probably do not exist naturally. Researchers are trying create them for applications such as quantum computing computer chips. Also, the CMAQ code will encounter floating point errors (division by zero) if all aerosol refractive indices equal zero.

1 Like
3

I want to conduct a sensitivity experiment where the refractive indices of all aerosols is set to zero to test the impact of aerosols on other substances. Does this imply that there is currently no straightforward method to achieve this in CMAQ?

4

I believe that a method exists. Try commenting out the line CALL GET_AERO_DATA in phot.F and recompile the model.

5

Thank you very much. I will do a test.