Investigation of the vertical extension of nucleation events

Nucleation and growth of new particles have been observed in many different environments. But if new particle formation events within the planetary boundary layer is widely documented, the phenomenon is understudied at elevated location. Altitude sites present the advantage to be influenced both by free troposphere and planetary boundary layer according to the meteorological conditions and the hour of the day even at very high altitude sites like Everest (see Venzac et al., 2009). One essantial question is to understand if particles nucleate preferably in the surface layer from precursor gases (anthropogenic or biogenic) and then bring up to higher altitude from convection and mixing atmospheric layers processes or if the nucleation takes place in situ at high altitude. This work deals with the impact of atmospheric vertical structure, especially interactions between planetary boundary layer and low free troposphere, on the observed nucleation events and the vertical extension of such events. Long-term new particle formation studies were conducted at two different altitude nearly-located sites, the puy de Dôme station (1465m a.s.l.) and the Opme meteorological station (660m a.s.l.), using Neutral cluster and Air Ion Spectrometers (capable of measuring mobility distributions of sub-3 nm neutral and charged aerosol particles and clusters in the mobility diameter range of 0.8-40 nm). Vertical structures and mixing were investigated using ground-based LIDAR measurements and potential equivalent temperature calculations. The analysis of this statistically representative database of new particle formation events and atmospheric characterization provided us a new objective point of view on the verticale scale of the nucleation process.