Contrasting Influence of Nitrogen Oxides on the Cloud Condensation Nuclei Activity of Monoterpene‐Derived Secondary Organic Aerosol in Daytime and Nighttime Oxidation

Abstract Anthropogenic nitrogen oxides may influence the cloud condensation nuclei (CCN) activity of biogenic secondary organic aerosols (SOA) in both daytime photooxidation and nighttime NO3 oxidation, which has significant implications for the climatic impact of SOA. We investigated the influence of NOx on the CCN activity of monoterpene‐derived SOA in OH oxidation and in NO3 oxidation. In OH oxidation, NOx had little influence on the hygroscopic parameter κ of organic aerosol (κOrg), which was attributed to the minor fraction of organic nitrates (ON) in SOA (