Browsing by Author "Kulmala, Markku"
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- ItemAerosol particle formation events and analysis of high growth rates observed above a subarctic wetland-forest mosaic(Milton Park : Taylor & Francis, 2017) Svenningsson, Birgitta; Arneth, Almut; Hayward, Sean; Holst, Thomas; Massling, Andreas; Swietlicki, Erik; Hirsikko, Anne; Junninen, Heikki; Riipinen, Ilona; Vana, Marko; Dal Maso, Miikka; Hussein, Tareq; Kulmala, MarkkuAn analysis of particle formation (PF) events over a subarctic mire in northern Swedenwas performed, based on number– size distributions of atmospheric aerosol particles (10–500 nm in diameter) and ions (0.4–40 nm in Tammet diameter). We present classification statistics for PF events from measurements covering the period July 2005–September 2006, with a break over the winter period. The PF event frequency peaked during the summer months, in contrast to other Scandinavian sites where the frequency is highest during spring and autumn. Our analysis includes calculated growth rates and estimates of concentrations and production rates of condensing vapour, deduced from the growth rates and condensational sink calculations, using AIS and SMPS data. Particle formation events with high growth rates (up to 50 nm h-1) occurred repeatedly. In these cases, the newly formed nucleation mode particles were often only present for periods of a few hours. On several occasions, repeated particle formation events were observed within 1 d, with differences in onset time of a few hours. These high growth rates were only observed when the condensation sink was higher than 0.001 s-1.
- ItemAtmospheric new particle formation at the research station Melpitz, Germany: Connection with gaseous precursors and meteorological parameters(Katlenburg-Lindau : EGU, 2018) Größ, Johannes; Hamed, Amar; Sonntag, André; Spindler, Gerald; Manninen, Hanna Elina; Nieminen, Tuomo; Kulmala, Markku; Hõrrak, Urmas; Plass-Dülmer, Christian; Wiedensohler, Alfred; Birmili, WolframThis paper revisits the atmospheric new particle formation (NPF) process in the polluted Central European troposphere, focusing on the connection with gas-phase precursors and meteorological parameters. Observations were made at the research station Melpitz (former East Germany) between 2008 and 2011 involving a neutral cluster and air ion spectrometer (NAIS). Particle formation events were classified by a new automated method based on the convolution integral of particle number concentration in the diameter interval 2-20 nm. To study the relevance of gaseous sulfuric acid as a precursor for nucleation, a proxy was derived on the basis of direct measurements during a 1-month campaign in May 2008. As a major result, the number concentration of freshly produced particles correlated significantly with the concentration of sulfur dioxide as the main precursor of sulfuric acid. The condensation sink, a factor potentially inhibiting NPF events, played a subordinate role only. The same held for experimentally determined ammonia concentrations. The analysis of meteorological parameters confirmed the absolute need for solar radiation to induce NPF events and demonstrated the presence of significant turbulence during those events. Due to its tight correlation with solar radiation, however, an independent effect of turbulence for NPF could not be established. Based on the diurnal evolution of aerosol, gas-phase, and meteorological parameters near the ground, we further conclude that the particle formation process is likely to start in elevated parts of the boundary layer rather than near ground level.
- ItemCauses and importance of new particle formation in the present-day and preindustrial atmospheres(Hoboken, NJ : Wiley, 2017) Gordon, Hamish; Kirkby, Jasper; Baltensperger, Urs; Bianchi, Federico; Breitenlechner, Martin; Curtius, Joachim; Dias, Antonio; Dommen, Josef; Donahue, Neil M.; Dunne, Eimear M.; Duplissy, Jonathan; Ehrhart, Sebastian; Flagan, Richard C.; Frege, Carla; Fuchs, Claudia; Hansel, Armin; Hoyle, Christopher R.; Kulmala, Markku; Kürten, Andreas; Lehtipalo, Katrianne; Makhmutov, Vladimir; Molteni, Ugo; Rissanen, Matti P.; Stozkhov, Yuri; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Wagner, Robert; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Yan, Chao; Carslaw, Ken S.New particle formation has been estimated to produce around half of cloud-forming particles in the present-day atmosphere, via gas-to-particle conversion. Here we assess the importance of new particle formation (NPF) for both the present-day and the preindustrial atmospheres. We use a global aerosol model with parametrizations of NPF from previously published CLOUD chamber experiments involving sulfuric acid, ammonia, organic molecules, and ions. We find that NPF produces around 67% of cloud condensation nuclei at 0.2% supersaturation (CCN0.2%) at the level of low clouds in the preindustrial atmosphere (estimated uncertainty range 45–84%) and 54% in the present day (estimated uncertainty range 38–66%). Concerning causes, we find that the importance of biogenic volatile organic compounds (BVOCs) in NPF and CCN formation is greater than previously thought. Removing BVOCs and hence all secondary organic aerosol from our model reduces low-cloud-level CCN concentrations at 0.2% supersaturation by 26% in the present-day atmosphere and 41% in the preindustrial. Around three quarters of this reduction is due to the tiny fraction of the oxidation products of BVOCs that have sufficiently low volatility to be involved in NPF and early growth. Furthermore, we estimate that 40% of preindustrial CCN0.2% are formed via ion-induced NPF, compared with 27% in the present day, although we caution that the ion-induced fraction of NPF involving BVOCs is poorly measured at present. Our model suggests that the effect of changes in cosmic ray intensity on CCN is small and unlikely to be comparable to the effect of large variations in natural primary aerosol emissions.
- ItemCollocated observations of cloud condensation nuclei, particle size distributions, and chemical composition(London : Nature Publ. Group, 2017) Schmale, Julia; Henning, Silvia; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Bougiatioti, Aikaterini; Kalivitis, Nikos; Stavroulas, Iasonas; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Kristensson, Adam; Iwamoto, Yoko; Pringle, Kirsty; Reddington, Carly; Aalto, Pasi; Äijälä, Mikko; Baltensperger, Urs; Bialek, Jakub; Birmili, Wolfram; Bukowiecki, Nicolas; Ehn, Mikael; Fjæraa, Ann Mari; Fiebig, Markus; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Furuya, Masaki; Hammer, Emanuel; Heikkinen, Liine; Herrmann, Erik; Holzinger, Rupert; Hyono, Hiroyuki; Kanakidou, Maria; Kiendler-Scharr, Astrid; Kinouchi, Kento; Kos, Gerard; Kulmala, Markku; Mihalopoulos, Nikolaos; Motos, Ghislain; Nenes, Athanasios; O’Dowd, Colin; Paramonov, Mikhail; Petäjä, Tuukka; Picard, David; Poulain, Laurent; Prévôt, André Stephan Henry; Slowik, Jay; Sonntag, Andre; Swietlicki, Erik; Svenningsson, Birgitta; Tsurumaru, Hiroshi; Wiedensohler, Alfred; Wittbom, Cerina; Ogren, John A.; Matsuki, Atsushi; Yum, Seong Soo; Myhre, Cathrine Lund; Carslaw, Ken; Stratmann, Frank; Gysel, MartinCloud condensation nuclei (CCN) number concentrations alongside with submicrometer particle number size distributions and particle chemical composition have been measured at atmospheric observatories of the Aerosols, Clouds, and Trace gases Research InfraStructure (ACTRIS) as well as other international sites over multiple years. Here, harmonized data records from 11 observatories are summarized, spanning 98,677 instrument hours for CCN data, 157,880 for particle number size distributions, and 70,817 for chemical composition data. The observatories represent nine different environments, e.g., Arctic, Atlantic, Pacific and Mediterranean maritime, boreal forest, or high alpine atmospheric conditions. This is a unique collection of aerosol particle properties most relevant for studying aerosol-cloud interactions which constitute the largest uncertainty in anthropogenic radiative forcing of the climate. The dataset is appropriate for comprehensive aerosol characterization (e.g., closure studies of CCN), model-measurement intercomparison and satellite retrieval method evaluation, among others. Data have been acquired and processed following international recommendations for quality assurance and have undergone multiple stages of quality assessment.
- ItemComparison of particle number size distribution trends in ground measurements and climate models(Katlenburg-Lindau : EGU, 2022) Leinonen, Ville; Kokkola, Harri; Yli-Juuti, Taina; Mielonen, Tero; Kühn, Thomas; Nieminen, Tuomo; Heikkinen, Simo; Miinalainen, Tuuli; Bergman, Tommi; Carslaw, Ken; Decesari, Stefano; Fiebig, Markus; Hussein, Tareq; Kivekäs, Niku; Krejci, Radovan; Kulmala, Markku; Leskinen, Ari; Massling, Andreas; Mihalopoulos, Nikos; Mulcahy, Jane P.; Noe, Steffen M.; van Noije, Twan; O'Connor, Fiona M.; O'Dowd, Colin; Olivie, Dirk; Pernov, Jakob B.; Petäjä, Tuukka; Seland, Øyvind; Schulz, Michael; Scott, Catherine E.; Skov, Henrik; Swietlicki, Erik; Tuch, Thomas; Wiedensohler, Alfred; Virtanen, Annele; Mikkonen, SanttuDespite a large number of studies, out of all drivers of radiative forcing, the effect of aerosols has the largest uncertainty in global climate model radiative forcing estimates. There have been studies of aerosol optical properties in climate models, but the effects of particle number size distribution need a more thorough inspection. We investigated the trends and seasonality of particle number concentrations in nucleation, Aitken, and accumulation modes at 21 measurement sites in Europe and the Arctic. For 13 of those sites, with longer measurement time series, we compared the field observations with the results from five climate models, namely EC-Earth3, ECHAM-M7, ECHAM-SALSA, NorESM1.2, and UKESM1. This is the first extensive comparison of detailed aerosol size distribution trends between in situ observations from Europe and five earth system models (ESMs). We found that the trends of particle number concentrations were mostly consistent and decreasing in both measurements and models. However, for many sites, climate models showed weaker decreasing trends than the measurements. Seasonal variability in measured number concentrations, quantified by the ratio between maximum and minimum monthly number concentration, was typically stronger at northern measurement sites compared to other locations. Models had large differences in their seasonal representation, and they can be roughly divided into two categories: for EC-Earth and NorESM, the seasonal cycle was relatively similar for all sites, and for other models the pattern of seasonality varied between northern and southern sites. In addition, the variability in concentrations across sites varied between models, some having relatively similar concentrations for all sites, whereas others showed clear differences in concentrations between remote and urban sites. To conclude, although all of the model simulations had identical input data to describe anthropogenic mass emissions, trends in differently sized particles vary among the models due to assumptions in emission sizes and differences in how models treat size-dependent aerosol processes. The inter-model variability was largest in the accumulation mode, i.e. sizes which have implications for aerosol-cloud interactions. Our analysis also indicates that between models there is a large variation in efficiency of long-range transportation of aerosols to remote locations. The differences in model results are most likely due to the more complex effect of different processes instead of one specific feature (e.g. the representation of aerosol or emission size distributions). Hence, a more detailed characterization of microphysical processes and deposition processes affecting the long-range transport is needed to understand the model variability.
- ItemThe effect of acid-base clustering and ions on the growth of atmospheric nano-particles(London : Nature Publishing Group, 2016) Lehtipalo, Katrianne; Rondo, Linda; Kontkanen, Jenni; Schobesberger, Siegfried; Jokinen, Tuija; Sarnela, Nina; Kürten, Andreas; Ehrhart, Sebastian; Franchin, Alessandro; Nieminen, Tuomo; Kulmala, Markku; Riccobono, Francesco; Sipila, Mikko; Yli-Juuti, Taina; Duplissy, Jonathan; Adamov, Alexey; Ahlm, Lars; Almeida, Joa˜o; Amorim, Antonio; Bianchi, Federico; Breitenlechner, Martin; Dommen, Josef; Downard, Andrew J.; Dunne, Eimear M.; Flagan, Richard C.; Guida, Roberto; Hakala, Jani; Hansel, Armin; Jud, Werner; Kangasluoma, Juha; Kerminen, Veli-Matti; Keskinen, Helmi; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Kupiainen-Määttä, Oona; Laaksonen, Ari; Lawler, Michael J.; Leiminger, Markus; Mathot, Serge; Olenius, Tinja; Ortega, Ismael K.; Onnela, Antti; Petäjä, Tuukka; Praplan, Arnaud; Rissanen, Matti P.; Ruuskanen, Taina; Santos, Filipe D.; Schallhart, Simon; Schnitzhofer, Ralf; Simon, Mario; Smith, James N.; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Tomé, António; Vaattovaara, Petri; Vehkamäki, Hanna; Vrtala, Aron E.; Wagner, Paul E.; Williamson, Christina; Wimmer, Daniela; Winkler, Paul M.; Virtanen, Annele; Donahue, Neil M.; Carslaw, Kenneth S.; Baltensperger, Urs; Riipinen, Ilona; Curtius, Joachim; Worsnop, Douglas R.; Kulmala, MarkkuThe growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.
- ItemEnhanced volatile organic compounds emissions and organic aerosol mass increase the oligomer content of atmospheric aerosols(London : Nature Publishing Group, 2016) Kourtchev, Ivan; Giorio, Chiara; Manninen, Antti; Wilson, Eoin; Mahon, Brendan; Aalto, Juho; Kajos, Maija; Venables, Dean; Ruuskanen, Taina; Levula, Janne; Loponen, Matti; Connors, Sarah; Harris, Neil; Zhao, Defeng; Kiendler-Scharr, Astrid; Mentel, Thomas; Rudich, Yinon; Hallquist, Mattias; Doussin, Jean-Francois; Maenhaut, Willy; Bäck, Jaana; Petäjä, Tuukka; Wenger, John; Kulmala, Markku; Kalberer, MarkusSecondary organic aerosol (SOA) accounts for a dominant fraction of the submicron atmospheric particle mass, but knowledge of the formation, composition and climate effects of SOA is incomplete and limits our understanding of overall aerosol effects in the atmosphere. Organic oligomers were discovered as dominant components in SOA over a decade ago in laboratory experiments and have since been proposed to play a dominant role in many aerosol processes. However, it remains unclear whether oligomers are relevant under ambient atmospheric conditions because they are often not clearly observed in field samples. Here we resolve this long-standing discrepancy by showing that elevated SOA mass is one of the key drivers of oligomer formation in the ambient atmosphere and laboratory experiments. We show for the first time that a specific organic compound class in aerosols, oligomers, is strongly correlated with cloud condensation nuclei (CCN) activities of SOA particles. These findings might have important implications for future climate scenarios where increased temperatures cause higher biogenic volatile organic compound (VOC) emissions, which in turn lead to higher SOA mass formation and significant changes in SOA composition. Such processes would need to be considered in climate models for a realistic representation of future aerosol-climate-biosphere feedbacks.
- ItemA European aerosol phenomenology - 6: Scattering properties of atmospheric aerosol particles from 28 ACTRIS sites(Katlenburg-Lindau : EGU, 2018) Pandolfi, Marco; Alados-Arboledas, Lucas; Alastuey, Andrés; Andrade, Marcos; Angelov, Christo; Artiñano, Begoña; Backman, John; Baltensperger, Urs; Bonasoni, Paolo; Bukowiecki, Nicolas; Collaud Coen, Martine; Conil, Sébastien; Coz, Esther; Crenn, Vincent; Dudoitis, Vadimas; Ealo, Marina; Eleftheriadis, Kostas; Favez, Olivier; Fetfatzis, Prodromos; Fiebig, Markus; Flentje, Harald; Ginot, Patrick; Gysel, Martin; Henzing, Bas; Hoffer, Andras; Holubova Smejkalova, Adela; Kalapov, Ivo; Kalivitis, Nikos; Kouvarakis, Giorgos; Kristensson, Adam; Kulmala, Markku; Lihavainen, Heikki; Lunder, Chris; Luoma, Krista; Lyamani, Hassan; Marinoni, Angela; Mihalopoulos, Nikos; Moerman, Marcel; Nicolas, José; O'Dowd, Colin; Petäjä, Tuukka; Petit, Jean-Eudes; Pichon, Jean Marc; Prokopciuk, Nina; Putaud, Jean-Philippe; Rodríguez, Sergio; Sciare, Jean; Sellegri, Karine; Swietlicki, Erik; Titos, Gloria; Tuch, Thomas; Tunved, Peter; Ulevicius, Vidmantas; Vaishya, Aditya; Vana, Milan; Virkkula, Aki; Vratolis, Stergios; Weingartner, Ernest; Wiedensohler, Alfred; Laj, PaoloThis paper presents the light-scattering properties of atmospheric aerosol particles measured over the past decade at 28 ACTRIS observatories, which are located mainly in Europe. The data include particle light scattering (σsp) and hemispheric backscattering (σbsp) coefficients, scattering Ångström exponent (SAE), backscatter fraction (BF) and asymmetry parameter (g). An increasing gradient of σsp is observed when moving from remote environments (arctic/mountain) to regional and to urban environments. At a regional level in Europe, σsp also increases when moving from Nordic and Baltic countries and from western Europe to central/eastern Europe, whereas no clear spatial gradient is observed for other station environments. The SAE does not show a clear gradient as a function of the placement of the station. However, a west-to-east-increasing gradient is observed for both regional and mountain placements, suggesting a lower fraction of fine-mode particle in western/south-western Europe compared to central and eastern Europe, where the fine-mode particles dominate the scattering. The g does not show any clear gradient by station placement or geographical location reflecting the complex relationship of this parameter with the physical properties of the aerosol particles. Both the station placement and the geographical location are important factors affecting the intraannual variability. At mountain sites, higher σsp and SAE values are measured in the summer due to the enhanced boundary layer influence and/or new particle-formation episodes. Conversely, the lower horizontal and vertical dispersion during winter leads to higher σsp values at all low-altitude sites in central and eastern Europe compared to summer. These sites also show SAE maxima in the summer (with corresponding g minima). At all sites, both SAE and g show a strong variation with aerosol particle loading. The lowest values of g are always observed together with low σsp values, indicating a larger contribution from particles in the smaller accumulation mode. During periods of high σsp values, the variation of g is less pronounced, whereas the SAE increases or decreases, suggesting changes mostly in the coarse aerosol particle mode rather than in the fine mode. Statistically significant decreasing trends of σsp are observed at 5 out of the 13 stations included in the trend analyses. The total reductions of σsp are consistent with those reported for PM2.5 and PM10 mass concentrations over similar periods across Europe.
- ItemEvaporation of sulfate aerosols at low relative humidity(Katlenburg-Lindau : EGU, 2017) Tsagkogeorgas, Georgios; Roldin, Pontus; Duplissy, Jonathan; Rondo, Linda; Tröstl, Jasmin; Slowik, Jay G.; Ehrhart, Sebastian; Franchin, Alessandro; Kürten, Andreas; Amorim, Antonio; Bianchi, Federico; Kirkby, Jasper; Petäjä, Tuukka; Baltensperger, Urs; Boy, Michael; Curtius, Joachim; Flagan, Richard C.; Kulmala, Markku; Donahue, Neil M.; Stratmann, FrankEvaporation of sulfuric acid from particles can be important in the atmospheres of Earth and Venus. However, the equilibrium constant for the dissociation of H2SO4 to bisulfate ions, which is the one of the fundamental parameters controlling the evaporation of sulfur particles, is not well constrained. In this study we explore the volatility of sulfate particles at very low relative humidity. We measured the evaporation of sulfur particles versus temperature and relative humidity in the CLOUD chamber at CERN. We modelled the observed sulfur particle shrinkage with the ADCHAM model. Based on our model results, we conclude that the sulfur particle shrinkage is mainly governed by H2SO4 and potentially to some extent by SO3 evaporation. We found that the equilibrium constants for the dissociation of H2SO4 to HSO4-(KH2SO4) and the dehydration of H2SO4 to SO3 (KSO3) are KH2SO4 Combining double low line 2-4 × 109 kg-1 and KSO3 ≥ 1.4 × g 1010 at 288.8± 5K.
- ItemExperimental particle formation rates spanning tropospheric sulfuric acid and ammonia abundances, ion production rates, and temperatures(Hoboken, NJ : Wiley, 2016) Kürten, Andreas; Bianchi, Federico; Almeida, Joao; Kupiainen-Määttä, Oona; Dunne, Eimear M.; Duplissy, Jonathan; Williamson, Christina; Barmet, Peter; Breitenlechner, Martin; Dommen, Josef; Donahue, Neil M.; Flagan, Richard C.; Franchin, Alessandro; Gordon, Hamish; Hakala, Jani; Hansel, Armin; Heinritzi, Martin; Ickes, Luisa; Jokinen, Tuija; Kangasluoma, Juha; Kim, Jaeseok; Kirkby, Jasper; Kupc, Agnieszka; Lehtipalo, Katrianne; Leiminger, Markus; Makhmutov, Vladimir; Onnela, Antti; Ortega, Ismael K.; Petäjä, Tuukka; Praplan, Arnaud P.; Riccobono, Francesco; Rissanen, Matti P.; Rondo, Linda; Schnitzhofer, Ralf; Schobesberger, Siegfried; Smith, James N.; Steiner, Gerhard; Stozhkov, Yuri; Tomé, António; Tröstl, Jasmin; Tsagkogeorgas, Georgios; Wagner, Paul E.; Wimmer, Daniela; Ye, Penglin; Baltensperger, Urs; Carslaw, Ken; Kulmala, Markku; Curtius, JoachimBinary nucleation of sulfuric acid and water as well as ternary nucleation involving ammonia are thought to be the dominant processes responsible for new particle formation (NPF) in the cold temperatures of the middle and upper troposphere. Ions are also thought to be important for particle nucleation in these regions. However, global models presently lack experimentally measured NPF rates under controlled laboratory conditions and so at present must rely on theoretical or empirical parameterizations. Here with data obtained in the European Organization for Nuclear Research CLOUD (Cosmics Leaving OUtdoor Droplets) chamber, we present the first experimental survey of NPF rates spanning free tropospheric conditions. The conditions during nucleation cover a temperature range from 208 to 298 K, sulfuric acid concentrations between 5 × 105 and 1 × 109 cm−3, and ammonia mixing ratios from zero added ammonia, i.e., nominally pure binary, to a maximum of ~1400 parts per trillion by volume (pptv). We performed nucleation studies under pure neutral conditions with zero ions being present in the chamber and at ionization rates of up to 75 ion pairs cm−3 s−1 to study neutral and ion-induced nucleation. We found that the contribution from ion-induced nucleation is small at temperatures between 208 and 248 K when ammonia is present at several pptv or higher. However, the presence of charges significantly enhances the nucleation rates, especially at 248 K with zero added ammonia, and for higher temperatures independent of NH3 levels. We compare these experimental data with calculated cluster formation rates from the Atmospheric Cluster Dynamics Code with cluster evaporation rates obtained from quantum chemistry.
- ItemA full year of aerosol size distribution data from the central Arctic under an extreme positive Arctic Oscillation: insights from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition(Katlenburg-Lindau : EGU, 2023) Boyer, Matthew; Aliaga, Diego; Pernov, Jakob Boyd; Angot, Hélène; Quéléver, Lauriane L. J.; Dada, Lubna; Heutte, Benjamin; Dall'Osto, Manuel; Beddows, David C. S.; Brasseur, Zoé; Beck, Ivo; Bucci, Silvia; Duetsch, Marina; Stohl, Andreas; Laurila, Tiia; Asmi, Eija; Massling, Andreas; Thomas, Daniel Charles; Nøjgaard, Jakob Klenø; Chan, Tak; Sharma, Sangeeta; Tunved, Peter; Krejci, Radovan; Hansson, Hans Christen; Bianchi, Federico; Lehtipalo, Katrianne; Wiedensohler, Alfred; Weinhold, Kay; Kulmala, Markku; Petäjä, Tuukka; Sipilä, Mikko; Schmale, Julia; Jokinen, TuijaThe Arctic environment is rapidly changing due to accelerated warming in the region. The warming trend is driving a decline in sea ice extent, which thereby enhances feedback loops in the surface energy budget in the Arctic. Arctic aerosols play an important role in the radiative balance and hence the climate response in the region, yet direct observations of aerosols over the Arctic Ocean are limited. In this study, we investigate the annual cycle in the aerosol particle number size distribution (PNSD), particle number concentration (PNC), and black carbon (BC) mass concentration in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This is the first continuous, year-long data set of aerosol PNSD ever collected over the sea ice in the central Arctic Ocean. We use a k-means cluster analysis, FLEXPART simulations, and inverse modeling to evaluate seasonal patterns and the influence of different source regions on the Arctic aerosol population. Furthermore, we compare the aerosol observations to land-based sites across the Arctic, using both long-term measurements and observations during the year of the MOSAiC expedition (2019-2020), to investigate interannual variability and to give context to the aerosol characteristics from within the central Arctic. Our analysis identifies that, overall, the central Arctic exhibits typical seasonal patterns of aerosols, including anthropogenic influence from Arctic haze in winter and secondary aerosol processes in summer. The seasonal pattern corresponds to the global radiation, surface air temperature, and timing of sea ice melting/freezing, which drive changes in transport patterns and secondary aerosol processes. In winter, the Norilsk region in Russia/Siberia was the dominant source of Arctic haze signals in the PNSD and BC observations, which contributed to higher accumulation-mode PNC and BC mass concentrations in the central Arctic than at land-based observatories. We also show that the wintertime Arctic Oscillation (AO) phenomenon, which was reported to achieve a record-breaking positive phase during January-March 2020, explains the unusual timing and magnitude of Arctic haze across the Arctic region compared to longer-term observations. In summer, the aerosol PNCs of the nucleation and Aitken modes are enhanced; however, concentrations were notably lower in the central Arctic over the ice pack than at land-based sites further south. The analysis presented herein provides a current snapshot of Arctic aerosol processes in an environment that is characterized by rapid changes, which will be crucial for improving climate model predictions, understanding linkages between different environmental processes, and investigating the impacts of climate change in future Arctic aerosol studies.
- ItemA global analysis of climate-relevant aerosol properties retrieved from the network of Global Atmosphere Watch (GAW) near-surface observatories(Katlenburg-Lindau : Copernicus, 2020) Laj, Paolo; Bigi, Alessandro; Rose, Clémence; Andrews, Elisabeth; Lund Myhre, Cathrine; Collaud Coen, Martine; Lin, Yong; Wiedensohler, Alfred; Schulz, Michael; Ogren, John A.; Fiebig, Markus; Prenni, Anthony; Reisen, Fabienne; Romano, Salvatore; Sellegri, Karine; Sharma, Sangeeta; Schauer, Gerhard; Sheridan, Patrick; Sherman, James Patrick; Schütze, Maik; Schwerin, Andreas; Tuch, Thomas; Sohmer, Ralf; Sorribas, Mar; Steinbacher, Martin; Sun, Junying; Titos, Gloria; Toczko, Barbara; Tulet, Pierre; Tunved, Peter; Vakkari, Ville; Velarde, Fernando; Velasquez, Patricio; Villani, Paolo; Vratolis, Sterios; Wang, Sheng-Hsiang; Weinhold, Kay; Gliß, Jonas; Weller, Rolf; Yela, Margarita; Yus-Diez, Jesus; Zdimal, Vladimir; Zieger, Paul; Zikova, Nadezda; Mortier, Augustin; Pandolfi, Marco; Petäja, Tuukka; Kim, Sang-Woo; Aas, Wenche; Putaud, Jean-Philippe; Mayol-Bracero, Olga; Keywood, Melita; Labrador, Lorenzo; Aalto, Pasi; Ahlberg, Erik; Alados Arboledas, Lucas; Alastuey, Andrés; Andrade, Marcos; Artíñano, Begoña; Ausmeel, Stina; Arsov, Todor; Asmi, Eija; Backman, John; Baltensperger, Urs; Bastian, Susanne; Bath, Olaf; Beukes, Johan Paul; Brem, Benjamin T.; Bukowiecki, Nicolas; Conil, Sébastien; Couret, Cedric; Day, Derek; Dayantolis, Wan; Degorska, Anna; Eleftheriadis, Konstantinos; Fetfatzis, Prodromos; Favez, Olivier; Flentje, Harald; Gini, Maria I.; Gregorič, Asta; Gysel-Beer, Martin; Hallar, A. Gannet; Hand, Jenny; Hoffer, Andras; Hueglin, Christoph; Hooda, Rakesh K.; Hyvärinen, Antti; Kalapov, Ivo; Kalivitis, Nikos; Kasper-Giebl, Anne; Kim, Jeong Eun; Kouvarakis, Giorgos; Kranjc, Irena; Krejci, Radovan; Kulmala, Markku; Labuschagne, Casper; Lee, Hae-Jung; Lihavainen, Heikki; Lin, Neng-Huei; Löschau, Gunter; Luoma, Krista; Marinoni, Angela; Martins Dos Santos, Sebastiao; Meinhardt, Frank; Merkel, Maik; Metzger, Jean-Marc; Mihalopoulos, Nikolaos; Nguyen, Nhat Anh; Ondracek, Jakub; Pérez, Noemi; Perrone, Maria Rita; Petit, Jean-Eudes; Picard, David; Pichon, Jean-Marc; Pont, Veronique; Prats, NataliaAerosol particles are essential constituents of the Earth's atmosphere, impacting the earth radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei. In contrast to most greenhouse gases, aerosol particles have short atmospheric residence times, resulting in a highly heterogeneous distribution in space and time. There is a clear need to document this variability at regional scale through observations involving, in particular, the in situ near-surface segment of the atmospheric observation system. This paper will provide the widest effort so far to document variability of climate-relevant in situ aerosol properties (namely wavelength dependent particle light scattering and absorption coefficients, particle number concentration and particle number size distribution) from all sites connected to the Global Atmosphere Watch network. High-quality data from almost 90 stations worldwide have been collected and controlled for quality and are reported for a reference year in 2017, providing a very extended and robust view of the variability of these variables worldwide. The range of variability observed worldwide for light scattering and absorption coefficients, single-scattering albedo, and particle number concentration are presented together with preliminary information on their long-term trends and comparison with model simulation for the different stations. The scope of the present paper is also to provide the necessary suite of information, including data provision procedures, quality control and analysis, data policy, and usage of the ground-based aerosol measurement network. It delivers to users of the World Data Centre on Aerosol, the required confidence in data products in the form of a fully characterized value chain, including uncertainty estimation and requirements for contributing to the global climate monitoring system.
- ItemGlobal analysis of continental boundary layer new particle formation based on long-term measurements(Katlenburg-Lindau : EGU, 2018) Nieminen, Tuomo; Kerminen, Veli-Matti; Petäjä, Tuukka; Aalto, Pasi P.; Arshinov, Mikhail; Asmi, Eija; Baltensperger, Urs; Beddows, David C. S.; Beukes, Johan Paul; Collins, Don; Ding, Aijun; Harrison, Roy M.; Henzing, Bas; Hooda, Rakesh; Hu, Min; Hõrrak, Urmas; Kivekäs, Niku; Komsaare, Kaupo; Krejci, Radovan; Kristensson, Adam; Laakso, Lauri; Laaksonen, Ari; Leaitch, W. Richard; Lihavainen, Heikki; Mihalopoulos, Nikolaos; Németh, Zoltán; Nie, Wei; O'Dowd, Colin; Salma, Imre; Sellegri, Karine; Svenningsson, Birgitta; Swietlicki, Erik; Tunved, Peter; Ulevicius, Vidmantas; Vakkari, Ville; Vana, Marko; Wiedensohler, Alfred; Wu, Zhijun; Virtanen, Annele; Kulmala, MarkkuAtmospheric new particle formation (NPF) is an important phenomenon in terms of global particle number concentrations. Here we investigated the frequency of NPF, formation rates of 10 nm particles, and growth rates in the size range of 10–25 nm using at least 1 year of aerosol number size-distribution observations at 36 different locations around the world. The majority of these measurement sites are in the Northern Hemisphere. We found that the NPF frequency has a strong seasonal variability. At the measurement sites analyzed in this study, NPF occurs most frequently in March–May (on about 30 % of the days) and least frequently in December-February (about 10 % of the days). The median formation rate of 10 nm particles varies by about 3 orders of magnitude (0.01–10 cm−3 s−1) and the growth rate by about an order of magnitude (1–10 nm h−1). The smallest values of both formation and growth rates were observed at polar sites and the largest ones in urban environments or anthropogenically influenced rural sites. The correlation between the NPF event frequency and the particle formation and growth rate was at best moderate among the different measurement sites, as well as among the sites belonging to a certain environmental regime. For a better understanding of atmospheric NPF and its regional importance, we would need more observational data from different urban areas in practically all parts of the world, from additional remote and rural locations in North America, Asia, and most of the Southern Hemisphere (especially Australia), from polar areas, and from at least a few locations over the oceans.
- ItemHeterogeneous ice nucleation of viscous secondary organic aerosol produced from ozonolysis of α-pinene(München : European Geopyhsical Union, 2016) Ignatius, Karoliina; Kristensen, Thomas B.; Järvinen, Emma; Nichman, Leonid; Fuchs, Claudia; Gordon, Hamish; Herenz, Paul; Hoyle, Christopher R.; Duplissy, Jonathan; Garimella, Sarvesh; Dias, Antonio; Frege, Carla; Höppel, Niko; Tröstl, Jasmin; Wagner, Robert; Yan, Chao; Amorim, Antonio; Baltensperger, Urs; Curtius, Joachim; Donahue, Neil M.; Gallagher, Martin W.; Kirkby, Jasper; Kulmala, Markku; Möhler, Ottmar; Saathoff, Harald; Schnaiter, Martin; Dulac, François; Tomé, Antonio; Virtanen, Annele; Worsnop, Douglas; Stratmann, FrankThere are strong indications that particles containing secondary organic aerosol (SOA) exhibit amorphous solid or semi-solid phase states in the atmosphere. This may facilitate heterogeneous ice nucleation and thus influence cloud properties. However, experimental ice nucleation studies of biogenic SOA are scarce. Here, we investigated the ice nucleation ability of viscous SOA particles. The SOA particles were produced from the ozone initiated oxidation of α-pinene in an aerosol chamber at temperatures in the range from −38 to −10 °C at 5–15 % relative humidity with respect to water to ensure their formation in a highly viscous phase state, i.e. semi-solid or glassy. The ice nucleation ability of SOA particles with different sizes was investigated with a new continuous flow diffusion chamber. For the first time, we observed heterogeneous ice nucleation of viscous α-pinene SOA for ice saturation ratios between 1.3 and 1.4 significantly below the homogeneous freezing limit. The maximum frozen fractions found at temperatures between −39.0 and −37.2 °C ranged from 6 to 20 % and did not depend on the particle surface area. Global modelling of monoterpene SOA particles suggests that viscous biogenic SOA particles are indeed present in regions where cirrus cloud formation takes place. Hence, they could make up an important contribution to the global ice nucleating particle budget.
- ItemHigh Gas-Phase Methanesulfonic Acid Production in the OH-Initiated Oxidation of Dimethyl Sulfide at Low Temperatures(Columbus, Ohio : American Chemical Society, 2022) Shen, Jiali; Scholz, Wiebke; He, Xu-Cheng; Zhou, Putian; Marie, Guillaume; Wang, Mingyi; Marten, Ruby; Surdu, Mihnea; Rörup, Birte; Baalbaki, Rima; Amorim, Antonio; Ataei, Farnoush; Bell, David M.; Bertozzi, Barbara; Brasseur, Zoé; Caudillo, Lucía; Chen, Dexian; Chu, Biwu; Dada, Lubna; Duplissy, Jonathan; Finkenzeller, Henning; Granzin, Manuel; Guida, Roberto; Heinritzi, Martin; Hofbauer, Victoria; Iyer, Siddharth; Kemppainen, Deniz; Kong, Weimeng; Krechmer, Jordan E.; Kürten, Andreas; Lamkaddam, Houssni; Lee, Chuan Ping; Lopez, Brandon; Mahfouz, Naser G. A.; Manninen, Hanna E.; Massabò, Dario; Mauldin, Roy L.; Mentler, Bernhard; Müller, Tatjana; Pfeifer, Joschka; Philippov, Maxim; Piedehierro, Ana A.; Roldin, Pontus; Schobesberger, Siegfried; Simon, Mario; Stolzenburg, Dominik; Tham, Yee Jun; Tomé, António; Umo, Nsikanabasi Silas; Wang, Dongyu; Wang, Yonghong; Weber, Stefan K.; Welti, André; Wollesen de Jonge, Robin; Wu, Yusheng; Zauner-Wieczorek, Marcel; Zust, Felix; Baltensperger, Urs; Curtius, Joachim; Flagan, Richard C.; Hansel, Armin; Möhler, Ottmar; Petäjä, Tuukka; Volkamer, Rainer; Kulmala, Markku; Lehtipalo, Katrianne; Rissanen, Matti; Kirkby, Jasper; El-Haddad, Imad; Bianchi, Federico; Sipilä, Mikko; Donahue, Neil M.; Worsnop, Douglas R.Dimethyl sulfide (DMS) influences climate via cloud condensation nuclei (CCN) formation resulting from its oxidation products (mainly methanesulfonic acid, MSA, and sulfuric acid, H2SO4). Despite their importance, accurate prediction of MSA and H2SO4from DMS oxidation remains challenging. With comprehensive experiments carried out in the Cosmics Leaving Outdoor Droplets (CLOUD) chamber at CERN, we show that decreasing the temperature from +25 to -10 °C enhances the gas-phase MSA production by an order of magnitude from OH-initiated DMS oxidation, while H2SO4production is modestly affected. This leads to a gas-phase H2SO4-to-MSA ratio (H2SO4/MSA) smaller than one at low temperatures, consistent with field observations in polar regions. With an updated DMS oxidation mechanism, we find that methanesulfinic acid, CH3S(O)OH, MSIA, forms large amounts of MSA. Overall, our results reveal that MSA yields are a factor of 2-10 higher than those predicted by the widely used Master Chemical Mechanism (MCMv3.3.1), and the NOxeffect is less significant than that of temperature. Our updated mechanism explains the high MSA production rates observed in field observations, especially at low temperatures, thus, substantiating the greater importance of MSA in the natural sulfur cycle and natural CCN formation. Our mechanism will improve the interpretation of present-day and historical gas-phase H2SO4/MSA measurements.
- ItemHighly Oxygenated Organic Molecules (HOM) from Gas-Phase Autoxidation Involving Peroxy Radicals: A Key Contributor to Atmospheric Aerosol(Washington, DC : ACS Publ., 2019) Bianchi, Federico; Kurtén, Theo; Riva, Matthieu; Mohr, Claudia; Rissanen, Matti P.; Roldin, Pontus; Berndt, Torsten; Crounse, John D.; Wennberg, Paul O.; Mentel, Thomas F.; Wildt, Jürgen; Junninen, Heikki; Jokinen, Tuija; Kulmala, Markku; Worsnop, Douglas R.; Thornton, Joel A.; Donahue, Neil; Kjaergaard, Henrik G.; Ehn, MikaelHighly oxygenated organic molecules (HOM) are formed in the atmosphere via autoxidation involving peroxy radicals arising from volatile organic compounds (VOC). HOM condense on pre-existing particles and can be involved in new particle formation. HOM thus contribute to the formation of secondary organic aerosol (SOA), a significant and ubiquitous component of atmospheric aerosol known to affect the Earth's radiation balance. HOM were discovered only very recently, but the interest in these compounds has grown rapidly. In this Review, we define HOM and describe the currently available techniques for their identification/quantification, followed by a summary of the current knowledge on their formation mechanisms and physicochemical properties. A main aim is to provide a common frame for the currently quite fragmented literature on HOM studies. Finally, we highlight the existing gaps in our understanding and suggest directions for future HOM research. © 2019 American Chemical Society.
- ItemHorizontal homogeneity and vertical extent of new particle formation events(Milton Park : Taylor & Francis, 2017) Wehner, Birgit; Siebert, Holger; Stratmann, Frank; Tuch, Thomas; Wiedensohler, Alfred; PetäJä, Tuukka; Dal Maso, Miikka; Kulmala, MarkkuDuring the SATURN campaign 2002, new particle formation, i.e. the occurrence of ultrafine particles was investigated simultaneously at four ground-based measurement sites. The maximum distance between the sites was 50 km. Additionally, vertical profiles of aerosol particles from 5–10 nm have been measured by a tethered-balloonborne system at one of the sites. In general, two different scenarios have been found: (i) new particle formation was measured at all sites nearly in parallel with subsequent particle growth (homogeneous case) and (ii) new particle formation was observed at one to three sites irregularly (inhomogeneous case) where subsequent particle growth was often interrupted. The homogeneous case was connected with stable synoptical conditions, i.e. the region was influenced by a high pressure system. Here, the horizontal extent of the phenomenon has been estimated to be 400 km at maximum. In the vertical dimension, the ultrafine particles are well mixed within the entire boundary layer. In the inhomogeneous case the new particle formation depends mainly on the incoming solar radiation and was often interrupted due the occurrence of clouds. Thus, single point measurements are not representative for a larger region in that case.
- ItemHydroxyl radical-induced formation of highly oxidized organic compounds(London : Nature Publishing Group, 2016) Berndt, Torsten; Richters, Stefanie; Jokinen, Tuija; Hyttinen, Noora; Kurtén, Theo; Otkjær, Rasmus V.; Kjaergaard, Henrik G.; Stratmann, Frank; Herrmann, Hartmut; Sipila, Mikko; Kulmala, Markku; Ehn, MikaelExplaining the formation of secondary organic aerosol is an intriguing question in atmospheric sciences because of its importance for Earth’s radiation budget and the associated effects on health and ecosystems. A breakthrough was recently achieved in the understanding of secondary organic aerosol formation from ozone reactions of biogenic emissions by the rapid formation of highly oxidized multifunctional organic compounds via autoxidation. However, the important daytime hydroxyl radical reactions have been considered to be less important in this process. Here we report measurements on the reaction of hydroxyl radicals with a- and b-pinene applying improved mass spectrometric methods. Our laboratory results prove that the formation of highly oxidized products from hydroxyl radical reactions proceeds with considerably higher yields than previously reported. Field measurements support these findings. Our results allow for a better description of the diurnal behaviour of the highly oxidized product formation and subsequent secondary organic aerosol formation in the atmosphere.
- ItemIon-induced nucleation of pure biogenic particles(London : Nature Publishing Group, 2016) Kirkby, Jasper; Duplissy, Jonathan; Sengupta, Kamalika; Gordon, Hamish; Williamson, Christina; Heinritzi, Martin; Simon, Mario; Yan, Chao; Almeida, João; Tröstl, Jasmin; Nieminen, Tuomo; Ortega, Ismael K.; Wagner, Robert; Adamov, Alexey; Amorim, Antonio; Bernhammer, Anne-Kathrin; Bianchi, Federico; Breitenlechner, Martin; Brilke, Sophia; Chen, Xuemeng; Craven, Jill; Dias, Antonio; Ehrhart, Sebastian; Flagan, Richard C.; Franchin, Alessandro; Fuchs, Claudia; Guida, Roberto; Hakala, Jani; Hoyle, Christopher R.; Jokinen, Tuija; Junninen, Heikki; Kangasluoma, Juha; Kim, Jaeseok; Krapf, Manuel; Kürten, Andreas; Laaksonen, Ari; Lehtipalo, Katrianne; Makhmutov, Vladimir; Mathot, Serge; Molteni, Ugo; Onnela, Antti; Peräkylä, Otso; Piel, Felix; Petäjä, Tuukka; Praplan, Arnaud P.; Pringle, Kirsty; Rap, Alexandru; Richards, Nigel A.D.; Riipinen, Ilona; Rissanen, Matti P.; Rondo, Linda; Sarnela, Nina; Schobesberger, Siegfried; Scott, Catherine E.; Seinfeld, John H.; Sipilä, Mikko; Steiner, Gerhard; Stozhkov, Yuri; Stratmann, Frank; Tomé, Antonio; Virtanen, Annele; Vogel, Alexander L.; Wagner, Andrea C.; Wagner, Paul E.; Weingartner, Ernest; Wimmer, Daniela; Winkler, Paul M.; Ye, Penglin; Zhang, Xuan; Hansel, Armin; Dommen, Josef; Donahue, Neil M.; Worsnop, Douglas R.; Baltensperger, Urs; Kulmala, Markku; Carslaw, Kenneth S.; Curtius, JoachimAtmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood1. Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours2. It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere3,4, and that ions have a relatively minor role5. Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded6,7. Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of α-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.
- ItemLong-term cloud condensation nuclei number concentration, particle number size distribution and chemical composition measurements at regionally representative observatories(Katlenburg-Lindau : EGU, 2018) Schmale, Julia; Henning, Silvia; Decesari, Stefano; Henzing, Bas; Keskinen, Helmi; Sellegri, Karine; Ovadnevaite, Jurgita; Pöhlker, Mira L.; Brito, Joel; Bougiatioti, Aikaterini; Kristensson, Adam; Kalivitis, Nikos; Stavroulas, Iasonas; Carbone, Samara; Jefferson, Anne; Park, Minsu; Schlag, Patrick; Iwamoto, Yoko; Aalto, Pasi; Äijälä, Mikko; Bukowiecki, Nicolas; Ehn, Mikael; Frank, Göran; Fröhlich, Roman; Frumau, Arnoud; Herrmann, Erik; Herrmann, Hartmut; Holzinger, Rupert; Kos, Gerard; Kulmala, Markku; Mihalopoulos, Nikolaos; Nenes, Athanasios; O'Dowd, Colin; Petäjä, Tuukka; Picard, David; Pöhlker, Christopher; Pöschl, Ulrich; Poulain, Laurent; Prévôt, André Stephan Henry; Swietlicki, Erik; Andreae, Meinrat O.; Artaxo, Paulo; Wiedensohler, Alfred; Ogren, John; Matsuki, Atsushi; Yum, Seong Soo; Stratmann, Frank; Baltensperger, Urs; Gysel, MartinAerosol-cloud interactions (ACI) constitute the single largest uncertainty in anthropogenic radiative forcing. To reduce the uncertainties and gain more confidence in the simulation of ACI, models need to be evaluated against observations, in particular against measurements of cloud condensation nuclei (CCN). Here we present a data set - ready to be used for model validation - of long-term observations of CCN number concentrations, particle number size distributions and chemical composition from 12 sites on 3 continents. Studied environments include coastal background, rural background, alpine sites, remote forests and an urban surrounding. Expectedly, CCN characteristics are highly variable across site categories. However, they also vary within them, most strongly in the coastal background group, where CCN number concentrations can vary by up to a factor of 30 within one season. In terms of particle activation behaviour, most continental stations exhibit very similar activation ratios (relative to particles 20nm) across the range of 0.1 to 1.0% supersaturation. At the coastal sites the transition from particles being CCN inactive to becoming CCN active occurs over a wider range of the supersaturation spectrum. Several stations show strong seasonal cycles of CCN number concentrations and particle number size distributions, e.g. at Barrow (Arctic haze in spring), at the alpine stations (stronger influence of polluted boundary layer air masses in summer), the rain forest (wet and dry season) or Finokalia (wildfire influence in autumn). The rural background and urban sites exhibit relatively little variability throughout the year, while short-term variability can be high especially at the urban site. The average hygroscopicity parameter, calculated from the chemical composition of submicron particles was highest at the coastal site of Mace Head (0.6) and lowest at the rain forest station ATTO (0.2-0.3). We performed closure studies based on -Köhler theory to predict CCN number concentrations. The ratio of predicted to measured CCN concentrations is between 0.87 and 1.4 for five different types of . The temporal variability is also well captured, with Pearson correlation coefficients exceeding 0.87. Information on CCN number concentrations at many locations is important to better characterise ACI and their radiative forcing. But long-term comprehensive aerosol particle characterisations are labour intensive and costly. Hence, we recommend operating migrating-CCNCs to conduct collocated CCN number concentration and particle number size distribution measurements at individual locations throughout one year at least to derive a seasonally resolved hygroscopicity parameter. This way, CCN number concentrations can only be calculated based on continued particle number size distribution information and greater spatial coverage of long-term measurements can be achieved.