摘要：We analyzed the size distributions of atmospheric aerosol particles measured during 2013–2014 at Värriö (SMEAR I) in northern Finland, Hyytiälä (SMEAR II) in southern Finland and Järvselja (SMEAR-Estonia) in Estonia. The stations are located on a transect spanning from north to south over 1000 km and they represent different environments ranging from subarctic to the hemi-boreal. We calculated the characteristics of new-particle-formation events, such as the frequency of events, growth rate of nucleation mode particles, condensation and coagulation sinks, formation rate of 2 nm and 3 nm particles, and source rate of condensable vapors. We observed 59, 185 and 108 new-particle-formation events at Värriö, Hyytiälä and Järvselja, respectively. The frequency of the observed events showed an annual variation with a maximum in spring. The analysis revealed size dependence of growth rate at all locations. We found that the growth rate and source rate of a condensable vapor were the highest in Järvselja and the lowest in Värriö. The condensation sink and particle formation rate were of a similar magnitude at Hyytiälä and Järvselja, but several times smaller at Värriö. Tracking the origin of air masses revealed that the number concentration of nucleation mode particles (3–25 nm) varied from north to south, with the highest concentrations at Järvselja and lowest at Värriö. Trajectory analysis indicated that new-particle-formation events are large-scale phenomena that can take place concurrently at distant stations located even 1000 km apart. We found a total of 26 days with new-particle-formation events occurring simultaneously at all three stations.
