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- ItemEUCAARI 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.
- ItemA European aerosol phenomenology-5: Climatology of black carbon optical properties at 9 regional background sites across Europe(Amsterdam : Elsevier, 2016) Zanatta, M.; Gysel, M.; Bukowiecki, N.; Müller, T.; Weingartner, E.; Areskoug, H.; Fiebig, M.; Yttri, K.E.; Mihalopoulos, N.; Kouvarakis, G.; Beddows, D.; Harrison, R.M.; Cavalli, F.; Putaud, J.P.; Spindler, G.; Wiedensohler, A.; Alastuey, A.; Pandolfi, M.; Sellegri, K.; Swietlicki, E.; Jaffrezo, J.L.; Baltensperger, U.; Laj, P.A reliable assessment of the optical properties of atmospheric black carbon is of crucial importance for an accurate estimation of radiative forcing. In this study we investigated the spatio-temporal variability of the mass absorption cross-section (MAC) of atmospheric black carbon, defined as light absorption coefficient (σap) divided by elemental carbon mass concentration (mEC). σap and mEC have been monitored at supersites of the ACTRIS network for a minimum period of one year. The 9 rural background sites considered in this study cover southern Scandinavia, central Europe and the Mediterranean. σap was determined using filter based absorption photometers and mEC using a thermal-optical technique. Homogeneity of the data-set was ensured by harmonization of all involved methods and instruments during extensive intercomparison exercises at the European Center for Aerosol Calibration (ECAC). Annual mean values of σap at a wavelength of 637 nm vary between 0.66 and 1.3 Mm−1 in southern Scandinavia, 3.7–11 Mm−1 in Central Europe and the British Isles, and 2.3–2.8 Mm−1 in the Mediterranean. Annual mean values of mEC vary between 0.084 and 0.23 μg m−3 in southern Scandinavia, 0.28–1.1 in Central Europe and the British Isles, and 0.22–0.26 in the Mediterranean. Both σap and mEC in southern Scandinavia and Central Europe have a distinct seasonality with maxima during the cold season and minima during summer, whereas at the Mediterranean sites an opposite trend was observed. Annual mean MAC values were quite similar across all sites and the seasonal variability was small at most sites. Consequently, a MAC value of 10.0 m2 g−1 (geometric standard deviation = 1.33) at a wavelength of 637 nm can be considered to be representative of the mixed boundary layer at European background sites, where BC is expected to be internally mixed to a large extent. The observed spatial variability is rather small compared to the variability of values in previous literature, indicating that the harmonization efforts resulted in substantially increased precision of the reported MAC. However, absolute uncertainties of the reported MAC values remain as high as ± 30–70% due to the lack of appropriate reference methods and calibration materials. The mass ratio between elemental carbon and non-light-absorbing matter was used as a proxy for the thickness of coatings around the BC cores, in order to assess the influence of the mixing state on the MAC of BC. Indeed, the MAC was found to increase with increasing values of the coating thickness proxy. This provides evidence that coatings do increase the MAC of atmospheric BC to some extent, which is commonly referred to as lensing effect.
- ItemA synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network(München : European Geopyhsical Union, 2015) Paramonov, M.; Kerminen, V.-M.; Gysel, M.; Aalto, P.P.; Andreae, M.O.; Asmi, E.; Baltensperger, U.; Bougiatioti, A.; Brus, D.; Frank, G.P.; Good, N.; Gunthe, S.S.; Hao, L.; Irwin, M.; Jaatinen, A.; Jurányi, Z.; King, S.M.; Kortelainen, A.; Kristensson, A.; Lihavainen, H.; Kulmala, M.; Lohmann, U.; Martin, S.T.; McFiggans, G.; Mihalopoulos, N.; Nenes, A.; O'Dowd, C.D.; Ovadnevaite, J.; Petäjä, T.; Pöschl, U.; Roberts, G.C.; Rose, D.; Svenningsson, B.; Swietlicki, E.; Weingartner, E.; Whitehead, J.; Wiedensohler, A.; Wittbom, C.; Sierau, B.Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (NCCN) to the total number concentration of particles (NCN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations – exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A50 and A100, respectively) renders a much more stable dependence of A on S; A50 and A100 also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter κ decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations κ increased with size. In fact, in Hyytiälä, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5 % significance level. In a boreal environment the assumption of a size-independent κ can lead to a potentially substantial overestimation of NCCN at S levels above 0.6 %. The same is true for other locations where κ was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of NCCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol–cloud interactions in various environments.
- ItemHygroscopic properties of submicrometer atmospheric aerosol particles measured with H-TDMA instruments in various environments - A review(Milton Park : Taylor & Francis, 2017) Swietlicki, E.; Hansson, H.-C.; Hämeri, K.; Svenningsson, B.; Massling, A.; Mcfiggans, G.; Mcmurry, P.H.; Petäjä, T.; Tunved, P.; Gysel, M.; Topping, D.; Weingartner, E.; Baltensperger, U.; Rissler, J.; Wiedensohler, A.; Kulmala, M.The hygroscopic properties play a vital role for the direct and indirect effects of aerosols on climate, as well as the health effects of particulate matter (PM) by modifying the deposition pattern of inhaled particles in the humid human respiratory tract. Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA) instruments have been used in field campaigns in various environments globally over the last 25 yr to determine the water uptake on submicrometre particles at subsaturated conditions. These investigations have yielded valuable and comprehensive information regarding the particle hygroscopic properties of the atmospheric aerosol, including state of mixing. These properties determine the equilibrium particle size at ambient relative humidities and have successfully been used to calculate the activation of particles at water vapour supersaturation. This paper summarizes the existing published H-TDMA results on the sizeresolved submicrometre aerosol particle hygroscopic properties obtained from ground-based measurements at multiple marine, rural, urban and free tropospheric measurement sites. The data is classified into groups of hygroscopic growth indicating the external mixture, and providing clues to the sources and processes controlling the aerosol. An evaluation is given on how different chemical and physical properties affect the hygroscopic growth.