Where Do Particles Form? – Vertical Profile Modelling of New Particle Formation Events in a Boreal Forest Site

Abstract:

Aerosols may have a great impact on climate through direct and indirect perturbations to the Earth's radiation balance. In order to quantify these effects, it is fundamental to understand the various physical, chemical and dynamic processes related to the aerosols, as well as their distribution in the atmosphere. For this reason, we applied the model SOSAA to investigate the complex processes of aerosols in a boreal forest site in summer 2013. SOSAA is the chemistry-transport model with detailed chemistry and aerosol dynamics. The meteorology and chemistry in the model have been validated against field observations in previous studies. It showed good agreements for all parameters including the concentration of sulphuric acid, which is believed to be a key component in the nucleation theories we applied in this study.

Our work emphasized on studying the growth of the secondary organic particles with a newly developed molecular based condensational growth scheme. The model results were compared to the field measurements during the Pan-European-Gas-AeroSOls-climate interaction Study (PEGASOS), which made intensive vertical observations of secondary organic aerosol formation and photochemistry in the lower troposphere at a Finnish boreal forest site in summer 2013. Analysing both the model results and PEGASOS data provided us valuable insights about the formation, evolution and transport of secondary organic aerosols in the lower troposphere.