Dear all,
I’m using CMAQv5.3.2 now and want to test a relationship between RH and complex refractive index of sea spray aerosol which means I will do some modification in related module.
What confused me was that there were so many subroutines about calling complex variables that I could not find the module and location that was originally used to calculate the complex refractive index .
I have found the setting of the relationship between wavelength and complex refractive index in 5 different species at /CMAQv532/UTIL/inline_phot_preproc/water_clouds/ssam00 which included SSA. But I still haven’t found the computation for complex refractive index. Maybe I missed some key parts about them.
I will be grateful if you can give me some advice.
Liu
2024.7.30
Hi Liu,
I just wanted to reach out and let you know that I am on this - I just need to consult with a few others about approaches you could take. Seems like a very interesting research effort!
-Sara
Hi Sara,
Very Glad to see your reply. Maybe what I need to do is to create a new relationship between RH and complex refractive index of sea spray aerosol to instead the wavelength - complex refractive index. And hope to find out where the nr variable in twoway_rrtmg_aero_optics.F90 comes from.
Liu
Hi Liu,
Just to try and help you better, are you trying to calculate the complex refractive index of SSA in a way that all of the individual aerosol components’ refractive indices are aggregated up to calculate that of total SSA?
As far as encoding optical properties of RH+SSA, this might be a little involved but not impossible. One “simple” approach:
- You could look aerosol liquid water (ALW) + SSA and create additional optical surrogates for varying ratios of SSA:ALW (See Marley et al., 1993; Fig. 3 for guidance on how to envision how optical properties can change with increasing ALW, granted this is with respect to hydrating sulfate, so you would need to find literature values for SSA+ALW). You can think of each level of hydration as having its own set of complex refractive index for each wavelength, which can be calculated with respect to the wavelength bands used in CMAQ. Once you have your SSA+ALW wavelength dependent refractive indices (for your different ratios of SSA+ALW), you can use the inline_phot_preproc to make sure those refractive indices get aggregated into the correct bands used in CMAQ for photolysis calculations.
In variable tracking of refractive indices (real/nr and imaginary/ni) (and I am new to this myself):
- Band (which is an interval of wavelength) dependent (and there are 7 considered currently) refractive indices are calculated from the inline_phot_preproc and stored in the PHOT_OPTICS.dat file
- These refractive indices are read in in the CSQY_DATA.F LOAD_OPTICS_DATA subroutine and set up into the REFRACTIVE_INDEX array
- This array is then used by AERO_PHOTDATA.F GET_AERO_DATA subroutince which uses the refractive indices in the REFRACTIVE_INDEX array along with aerosol size pulled in from other subroutines/modules and aggregated into wavelength-size bins
- The AERO_PHOTDATA.F GET_AERO_DATA subroutine calls on the AERO_OPTICAL_CS and AERO_OPTICAL2 subroutines that are pulled from CMAQ_RRTMG_AERO_OPTICAL_UTIL_MODULE which are then pulled from the twoway_rrtmg_aero_optics.F90 to calculate the scattering, extinction, and asymmetry parameters
- These parameters are then pulled back into the AERO_PHOTDATA.F GET_AERO_DATA to create arrays 2-d arrays of scattering, extinction, and asymmetry parameters that are (altitudinal layer,wavelength) dependent which then gets used for calculating photolysis rates….
I’m not sure what you are interested in looking at with respect to SSA+RH/ALW (photolysis, aerosol-radiative properties, etc.) but in offline/stand-alone CMAQ optical properties of aerosols are used solely for photolysis rates. If you wanted to look at aerosol-radiative feedbacks you could build WRF-CMAQ and turn on aerosol-radiative two-way feedbacks.
Hi Sara,
Big thanks for your generous reply. It helps me understand the mechanism of refractive index in CMAQ modules and subroutines a lot.
I notice that some of the responses mentioned module_ra_rrtmg_aero_optical_util_cmaq.F module in the two-way model WRF-CMAQ, but for me, modifying the real part of refractive index in file /UTIL/inline_phot_preproc/water_clouds/ssam00 maybe can achieve similar results. This may involve the content of Cauchy dispersion, which is used to obtain nr at different wavelengths. The problem is I only have observations based on a fixed wavelength, maybe this part is my next to work on.
Thank you again for your kindness.
Liu
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