Vertical fluxes and micrometeorology during aerosol particle formation events

Fluxes of aerosol particles with sizes larger than 10 nm together with flux es of momentum, sensible and latent heat and CO2 were measured 10 m above a Scots pine forest with the eddy covariance method. During days when nuclea tion events were observed particle size distribution measurements showed pa rticle growth from 3 nm sizes to the Aitken mode. Analysis of the experimen tal data showed systematic differences in fluxes during the days when new p article production was observed compared to other days. During the nucleati on events the particle flux measurements showed downward aerosol particle t ransport, i.e., indicating an elevated source, with respect to the measurem ent level, of particles larger than 10 nm. Furthermore the turbulence inten sity and the heat fluxes were observed to be significantly higher. Evidence s of mesoscale circulation were observed in wind speed records as well as i n turbulent fluxes on nucleation days. The measurement results show that mi crometeorology, the synoptic scale conditions and the particle formation ar e closely related.