Auflistung nach Autor:in "Boulon, Julien"

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EUCAARI ion spectrometer measurements at 12 European sites – analysis of new particle formation events
(Copernicus, 25.08.2010) Manninen, Hanna E.; Nieminen, Tuomo; Asmi, Eija; Gagné, Stéphanie; Häkkinen, Silja; Lehtipalo, Katrianne; Aalto, Pasi Pekka; Vana, Marko; Mirme, Aadu; Mirme, Sander; Hõrrak, Urmas; Plass-Dülmer, Christian; Stange, Gert; Kiss, Gyula; Hoffer, András; Törő, N.; Moerman, Marcel; Henzing, Bas; de Leeuw, Gerrit; Brinkenberg, Marcel; Kouvarakis, Giorgos N.; Bougiatioti, Aikaterini; Mihalopoulos, Nikolaos; O'Dowd, Colin D.; Ceburnis, Darius; Arneth, Almut; Svenningsson, Brigitta; Swietlicki, Erik; Tarozzi, Leone; Decesari, Stefano; Facchini, Maria Cristina; Birmili, Wolfram; Sonntag, André; Wiedensohler, Alfred; Boulon, Julien; Sellegri, Karine; Laj, Paolo; Gysel, Martin; Bukowiecki, Nicolas; Weingartner, Ernest; Wehrle, Günther; Laaksonen, Ari; Hamed, Amar; Joutsensaari, Jorma; Petäjä, Tuukka; Kerminen, Veli-Matti; Kulmala, Markku
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.
01A - Beitrag in wissenschaftlicher Zeitschrift
New particle formation and ultrafine charged aerosol climatology at a high altitude site in the Alps (Jungfraujoch, 3580 m a.s.l., Switzerland)
(Copernicus, 05.10.2010) Boulon, Julien; Sellegri, Karine; Venzac, Hervé; Picard, David; Weingartner, Ernest; Wehrle, Günther; Collaud Coen, Martine; Bütikofer, Rolf; Flückiger, Erwin; Baltensperger, Urs; Laj, Paolo
We investigate the formation and growth of charged aerosols clusters at Jungfraujoch, in the Swiss Alps (3580 m a.s.l.), the highest altitude site of the European EUCAARI project intensive campaign. Charged particles and clusters (0.5–1.8 nm) were measured from April 2008 to April 2009 and allowed the detection of nucleation events in this very specific environment (presence of free tropospheric air and clouds). We found that the naturally charged aerosol concentrations, which are dominated by the cluster size class, shows a strong diurnal pattern likely linked to valley breezes transporting surface layer ion precursors, presumably radon. Cosmic rays were found not to be the major ion source at the measurement site. However, at night, when air masses are more representative of free tropospheric conditions, we found that the cluster concentrations are still high. The charged aerosol size distribution and concentration are strongly influenced by the presence of clouds at the station. Clouds should be taken into account when deriving high altitude nucleation statistics. New particle formation occurs on average 17.5% of the measurement period and shows a weak seasonality with a minimum of frequency during winter, but this seasonality is enhanced when the data set is screened for periods when the atmospheric station is out of clouds. The role of ions in the nucleation process was investigated and we found that the ion-mediated nucleation explains 22.3% of the particle formation. The NPF events frequency is correlated with UV radiation but not with calculated H2SO4 concentrations, suggesting that other compounds such as organic vapors are involved in the nucleation and subsequently growth process. In fact, NPF events frequency also surprisingly increases with the condensational sink (CS), suggesting that at Jungfraujoch, the presence of condensing vapours probably coupled with high CS are driving the occurrence of NPF events. A strong link to the air mass path was also pointed out and events were observed to be frequently occurring in Eastern European air masses, which present the highest condensational sink. In these air masses, pre-existing cluster concentrations are more than three time larger than in other air masses during event days, and no new clusters formation is observed, contrarily to what is happening in other air mass types.
01A - Beitrag in wissenschaftlicher Zeitschrift
Primary versus secondary contributions to particle number concentrations in the European boundary layer
(Copernicus, 05.12.2011) Reddington, Carly L.; Carslaw, Ken S.; Spracklen, Dominick V.; Frontoso, Maria Grazia; Collins, Lisa M.; Merikanto, Joonas; Minikin, Andreas; Hamburger, Thomas; Coe, Hugh; Kulmala, Markku; Aalto, Pasi Pekka; Flentje, Harald; Plass-Dülmer, Christian; Birmili, Wolfram; Wiedensohler, Alfred; Wehner, Birgit; Tuch, Thomas; Sonntag, Alfred; O'Dowd, Collin D.; Jennings, Stephen G.; Dupuy, Regis; Baltensperger, Urs; Weingartner, Ernest; Hansson, Hans-Christen; Tunved, Peter; Laj, Paolo; Sellegri, Karine; Boulon, Julien; Putaud, Jean-Philippe; Gruening, Carsten; Swietlicki, Erik; Roldin, Pontus; Henzing, J.S.; Moerman, Marcel; Mihalopoulos, Nikolaos; Kouvarakis, Giorgos; Ždímal, Vladimir; Zíková, Nadezda; Marinoni, Angela; Bonasoni, Paolo; Duchi, Rocco
It is important to understand the relative contribution of primary and secondary particles to regional and global aerosol so that models can attribute aerosol radiative forcing to different sources. In large-scale models, there is considerable uncertainty associated with treatments of particle formation (nucleation) in the boundary layer (BL) and in the size distribution of emitted primary particles, leading to uncertainties in predicted cloud condensation nuclei (CCN) concentrations. Here we quantify how primary particle emissions and secondary particle formation influence size-resolved particle number concentrations in the BL using a global aerosol microphysics model and aircraft and ground site observations made during the May 2008 campaign of the European Integrated Project on Aerosol Cloud Climate Air Quality Interactions (EUCAARI). We tested four different parameterisations for BL nucleation and two assumptions for the emission size distribution of anthropogenic and wildfire carbonaceous particles. When we emit carbonaceous particles at small sizes (as recommended by the Aerosol Intercomparison project, AEROCOM), the spatial distributions of campaign-mean number concentrations of particles with diameter >50 nm (N50) and >100 nm (N100) were well captured by the model (R2≥0.8) and the normalised mean bias (NMB) was also small (−18% for N50 and −1% for N100). Emission of carbonaceous particles at larger sizes, which we consider to be more realistic for low spatial resolution global models, results in equally good correlation but larger bias (R2≥0.8, NMB = −52% and −29%), which could be partly but not entirely compensated by BL nucleation. Within the uncertainty of the observations and accounting for the uncertainty in the size of emitted primary particles, BL nucleation makes a statistically significant contribution to CCN-sized particles at less than a quarter of the ground sites. Our results show that a major source of uncertainty in CCN-sized particles in polluted European air is the emitted size of primary carbonaceous particles. New information is required not just from direct observations, but also to determine the "effective emission size" and composition of primary particles appropriate for different resolution models.
01A - Beitrag in wissenschaftlicher Zeitschrift