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Author: Asmi, E. × Author: Birmili, W. × Author: Bukowiecki, N. × Author: Hamed, A. × Author: Kulmala, M. × Author: Wiedensohler, A. × End date: 2019 × Start date: 2019 × End date: 2019 × Start date: 2010 × Version: publishedVersion ×

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    EUCAARI ion spectrometer measurements at 12 European sites – analysis of new particle formation events
    (München : European Geopyhsical Union, 2010) Manninen, H.E.; Nieminen, T.; Asmi, E.; Gagné, S.; Häkkinen, S.; Lehtipalo, K.; Aalto, P.; Vana, M.; Mirme, A.; Mirme, S.; Hõrrak, U.; Plass-Dülmer, C.; Stange, G.; Kiss, G.; Hoffer, A.; Törő, N.; Moerman, M.; Henzing, B.; de Leeuw, G.; Brinkenberg, M.; Kouvarakis, G.N.; Bougiatioti, A.; Mihalopoulos, N.; O'Dowd, C.; Ceburnis, D.; Arneth, A.; Svenningsson, B.; Swietlicki, E.; Tarozzi, L.; Decesari, S.; Facchini, M.C.; Birmili, W.; Sonntag, A.; Wiedensohler, A.; Boulon, J.; Sellegri, K.; Laj, P.; Gysel, M.; Bukowiecki, N.; Weingartner, E.; Wehrle, G.; Laaksonen, A.; Hamed, A.; Joutsensaari, J.; Petäjä, T.; Kerminen, V.-M.; Kulmala, M.
    We present comprehensive results on continuous atmospheric cluster and particle measurements in the size range ~1–42 nm within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) project. We focused on characterizing the spatial and temporal variation of new particle formation events and relevant particle formation parameters across Europe. Different types of air ion and cluster mobility spectrometers were deployed at 12 field sites across Europe from March 2008 to May 2009. The measurements were conducted in a wide variety of environments, including coastal and continental locations as well as sites at different altitudes (both in the boundary layer and the free troposphere). New particle formation events were detected at all of the 12 field sites during the year-long measurement period. From the data, nucleation and growth rates of newly formed particles were determined for each environment. In a case of parallel ion and neutral cluster measurements, we could also estimate the relative contribution of ion-induced and neutral nucleation to the total particle formation. The formation rates of charged particles at 2 nm accounted for 1–30% of the corresponding total particle formation rates. As a significant new result, we found out that the total particle formation rate varied much more between the different sites than the formation rate of charged particles. This work presents, so far, the most comprehensive effort to experimentally characterize nucleation and growth of atmospheric molecular clusters and nanoparticles at ground-based observation sites on a continental scale.
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    Aerosol decadal trends - Part 2: In-situ aerosol particle number concentrations at GAW and ACTRIS stations
    (München : European Geopyhsical Union, 2013) Asmi, A.; Collaud Coen, M.; Ogren, J.A.; Andrews, E.; Sheridan, P.; Jefferson, A.; Weingartner, E.; Baltensperger, U.; Bukowiecki, N.; Lihavainen, H.; Kivekäs, N.; Asmi, E.; Aalto, P.P.; Kulmala, M.; Wiedensohler, A.; Birmili, W.; Hamed, A.; O'Dowd, C.; Jennings, S.G.; Weller, R.; Flentje, H.; Fjaeraa, A.M.; Fiebig, M.; Myhre, C.L.; Hallar, A.G.; Swietlicki, E.; Kristensson, A.; Laj, P.
    We have analysed the trends of total aerosol particle number concentrations (N) measured at long-term measurement stations involved either in the Global Atmosphere Watch (GAW) and/or EU infrastructure project ACTRIS. The sites are located in Europe, North America, Antarctica, and on Pacific Ocean islands. The majority of the sites showed clear decreasing trends both in the full-length time series, and in the intra-site comparison period of 2001–2010, especially during the winter months. Several potential driving processes for the observed trends were studied, and even though there are some similarities between N trends and air temperature changes, the most likely cause of many northern hemisphere trends was found to be decreases in the anthropogenic emissions of primary particles, SO2 or some co-emitted species. We could not find a consistent agreement between the trends of N and particle optical properties in the few stations with long time series of all of these properties. The trends of N and the proxies for cloud condensation nuclei (CCN) were generally consistent in the few European stations where the measurements were available. This work provides a useful comparison analysis for modelling studies of trends in aerosol number concentrations.