New insights into nocturnal nucleation
Formation of new aerosol particles by nucleation and growth is a\nsignificant source of aerosols in the atmosphere. New particle formation\nevents usually take place during daytime, but in some locations they\nhave been observed also at night. In the present study we have combined\nchamber experiments, quantum chemical calculations and aerosol dynamics\nmodels to study nocturnal new particle formation. All our approaches\ndemonstrate, in a consistent manner, that the oxidation products of\nmonoterpenes play an important role in nocturnal nucleation events. By\nvarying the conditions in our chamber experiments, we were able to\nreproduce the very different types of nocturnal events observed earlier\nin the atmosphere. The exact strength, duration and shape of the events\nappears to be sensitive to the type and concentration of reacting\nmonoterpenes, as well as the extent to which the monoterpenes are\nexposed to ozone and potentially other atmospheric oxidants.