Those are reference files containing the default parameters used in generating E3SM emissions data. No need to modify them. They are used in `surfEmis_driver.py` and `elevEmis_driver.py` under src.

Explanation
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* sulfactor: MW of Ammonium-bi-sulfate / Sulfate
* frac: Fraction of emission specific to emitted species
* numstr: Variable mode naming in number emission files specific to species
* numfile: Mode of number emission specific to species

