Fig. 1.

Hygroscopic growth and CCN activity of secondary organic material derived from ozonolysis of biogenic monoterpenes. a Mass-based hygroscopic growth factors g_m measured by the quartz crystal microbalance for different organic films as a function of increasing relative humidity. b Critical supersaturation ratios s_c (%) of CCN activation as a function of dry diameter d_m,dry (nm). Gray lines in a, b show modeled results using constant κ values. c Hygroscopicity parameters κ_HGF calculated from the data shown in a. d Effective hygroscopicity parameter κ_CCN calculated based on the size-resolved CCN measurements for the surface tension value of pure water (0.072 N m⁻¹). Colored dashed and solid lines in a–d represent results of Model I (single-phase model) and Model II (LLPS model), respectively (see main text). In a, dashed lines of Model I are hidden behind the solid lines of Model II because two models yield identical results in the absence of LLPS (RH < 95%). For clarity, model lines for κ_HGF at high RH are shown in the inset of c