Particle Formation in the PBL

New formation of ultrafine particles (< 10 nm) from gaseous precursors can be observed in the continental boundary layer at 20-30% of all days. This phenomenon occurs within so-called "nucleation bursts", often simultaneously over distances of hundreds of kilometres. Which nucleation mechanisms and precursor gases are responsible for these particle formation events has not yet been answered conclusively. Empirical studies (ACTOS) suggest that atmospheric turbulence is important for the formation of burst events. A coupled one-dimensional chemistry-aerosol column model of the boundary layer was developed for the interpretation of in-situ observed nucleation bursts, in particular to investigate the role of turbulence. The model is based on third-order turbulence closure (Hellmuth, 2006). It is used for sensitivity studies and verification of different nucleation mechanisms, making use of field measurements in the planetary boundary layer. Homogeneous (binary and tertiary nucleation) and heterogeneous nucleation processes (nucleus formation at particle surfaces and formation of films on deliquescent particles) are investigated