The calculation of aqueous OH radical in aerosol module

Hello, everybody! I am reaching out for assistance or suggestions regarding the calculation of aqueous OH radical concentrations in CMAQ.
In CMAQv5.4 model, the OH radical concentration is still estimated at the start of cloud processing based on the initial gas-phase concentration and held constant throughout the subsequent processes. While in the aero module, I couldn’t find a direct connection between OH aqueous-phase radicals and SOA formation. I want to get a variable OH radical concentrations in the aerosol module.
I don’t know how to implement the calculation of aqueous OH radical concentration in the CMAQ. Could you kindly provide some guidance or suggestions?

This article may provide some assistance.

Here is a more recent article by @Havala.Pye


Hi Yibo,
You are right that CMAQ SOA is not currently modulated by aqueous aerosol OH concentrations. You can get the aqueous OH predicted by ISORROPIA from the AERLIQ array, species 12 (see:, page 13). That will be the equilibrated OH for fine PM. The AERLIQ array is accessed in aero_subs.F, and that is also how we get H+ for acidity in the article Liz mentioned.

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