How to convert the units of the variables(so4_a1,bc_a1)?

I am currently conducting sensitivity experiments using CESM, but I have encountered some issues. Could you please explain the meaning of the unit "kg/kg" for the aerosol concentration variables such as so4_a1 and so4_a2 in the model outputs? Additionally, how can these values be converted into µg/m³? I look forward to your reply.

Hi Ivzy,
The unit kg/kg is a mass mixing ratio: kg of species per kg of air.
You can convert from kg/kg to kg/m3 by dividing by the density of air.
Best,
Rebecca