New particle formation (NPF) is the main source of secondary aerosols in the atmosphere. Observations show NPF can enhance CCN concentrations by a factor of 0.5-11 at the regional scale (S.-H. Lee et al., 2019). Global modeling simulations also show NPF can contribute up to 70% of the global CCN (Gordon et al., 2017). NPF events have been observed at various locations and occur most frequently in the free troposphere and lower stratosphere, extremely polluted Chinese mega-cities, and boreal forests (