Contribution of new particle formation to cloud condensation nuclei in Asian outflow

New particle formation (NPF) and subsequent growth has been recognized an important process contributing to the cloud condensation nuclei (CCN). Freshly formed nuclei have very short lifetimes in the atmosphere due to loss by coagulation with larger particles. Thus, freshly nucleated particles must grow quickly to larger sizes to act as CCN. Previous studies on the potential contribution of NPF to CCN have performed primarily on model simulations, but little on the basis of filed measurements has been done. In this study, we investigate NPF events were investigated by applying the Cyclostationary Empirical Orthogonal Function (CSEOF) technique to 3-year (2008–2010) aerosol number size distribution data at Gosan and Anmyeon in Korea. Based on the first mode loading vectors and the corresponding principle components in the CSEOF analysis, we classified strong, weak, and non NPF days. A strong NPF event was observed on 7.5% of days (60 days out of a total 800 days) at Gosan and on 14.6% of days (140 days out of a total 958 days) at Anmyeon. We present also direct evidence that freshly nucleated particles are capable of growing to sufficiently large sizes and act as CCN from simultaneous observations of condensation nuclei (CN) and CCN at Gosan in summer 2008. The increase in CCN concentrations showed a delay over the increase of the nucleation-mode particle concentration (10-25 nm) by about 6-8 hour, because newly formed particles are small to act as CCN and a substantial particle growth is needed to reach the CCN size.