Vertical characterization of highly oxygenated molecules (HOMs) below and above a boreal forest canopy

摘要: Abstract. While the role of highly oxygenated molecules (HOMs) in new particle formation (NPF) and secondary organic aerosol (SOA) formation is not in dispute, interplay between HOM chemistry atmospheric conditions continues to draw significant research attention. During Influence of Biosphere-Atmosphere Interactions on Reactive Nitrogen budget (IBAIRN) campaign September 2016, profile measurements neutral HOMs below and above forest canopy were performed for first time at boreal forest SMEAR II station. The concentrations composition distributions below above similar during daytime, supporting a well-mixed boundary layer approximation. However, much lower nighttime HOM concentrations frequently observed ground level, which was likely due to a shallow decoupled canopy. Near the ground influenced by changes precursors oxidants and enhancement loss surfaces this layer, while the canopy top significantly affected. Our findings clearly illustrate that near-ground conducted under stably stratified conditions site might only be representative small fraction of the entire nocturnal layer. This could, turn, influence the growth newly formed particles SOA where the large majority are typically conducted.