The Ny-Ålesund Aerosol Cloud Experiment (NASCENT): Overview and First Results

J. T. Pasquier; R. O. David; G. Freitas; R. Gierens; Y. Gramlich; S. Haslett; G. Li; B. Schäfer; K. Siegel; J. Wieder; K. Adachi; F. Belosi; T. Carlsen; S. Decesari; K. Ebell; S. Gilardoni; M. Gysel-Beer; J. Henneberger; J. Inoue; Z. A. Kanji; M. Koike; Y. Kondo; R. Krejci; U. Lohmann; M. Maturilli; M. Mazzolla; R. Modini; C. Mohr; G. Motos; A. Nenes; A. Nicosia; S. Ohata; M. Paglione; S. Park; R. E. Pileci; F. Ramelli; M. Rinaldi; C. Ritter; K. Sato; T. Storelvmo; Y. Tobo; R. Traversi; A. Viola; P. Zieger
2022 | Bull. Amer. Meteor. Soc. (E2533-E2558)

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Ålesund, Svalbard. The campaign’s primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications.

Composition and mixing state of Arctic aerosol and cloud residual particles from long-term single-particle observations at Zeppelin Observatory, Svalbard

Kouji Adachi; Yutaka Tobo; Makoto Koike; Gabriel Freitas; Paul Zieger; Radovan Krejci
2022 | Atmos. Chem. Phys. | 22 (14421-14439)

The Arctic region is sensitive to climate change and is warming faster than the global average. Aerosol particles change cloud properties by acting as cloud condensation nuclei and ice-nucleating particles, thus influencing the Arctic climate system. Therefore, understanding the aerosol particle properties in the Arctic is needed to interpret and simulate their influences on climate. In this study, we collected ambient aerosol particles using whole-air and PM10 inlets and residual particles of cloud droplets and ice crystals from Arctic low-level clouds (typically, all-liquid or mixed-phase clouds) using a counterflow virtual impactor inlet at the Zeppelin Observatory near Ny-Ålesund, Svalbard, within a time frame of 4 years. We measured the composition and mixing state of individual fine-mode particles in 239 samples using transmission electron microscopy. On the basis of their composition, the aerosol and cloud residual particles were classified as mineral dust, sea salt, K-bearing, sulfate, and carbonaceous particles. The number fraction of aerosol particles showed seasonal changes, with sulfate dominating in summer and sea salt increasing in winter. There was no measurable difference in the fractions between ambient aerosol and cloud residual particles collected at ambient temperatures above 0 ∘C. On the other hand, cloud residual samples collected at ambient temperatures below 0 ∘C had several times more sea salt and mineral dust particles and fewer sulfates than ambient aerosol samples, suggesting that sea spray and mineral dust particles may influence the formation of cloud particles in Arctic mixed-phase clouds. We also found that 43 % of mineral dust particles from cloud residual samples were mixed with sea salt, whereas only 18 % of mineral dust particles in ambient aerosol samples were mixed with sea salt. This study highlights the variety in aerosol compositions and mixing states that influence or are influenced by aerosol–cloud interactions in Arctic low-level clouds.

Using Novel Molecular-Level Chemical Composition Observations of High Arctic Organic Aerosol for Predictions of Cloud Condensation Nuclei

Siegel, K.; Neuberger, A.; Karlsson, L.; Zieger, P.; Mattsson, F.; Duplessis, P.; Dada, L.; Daellenbach, K.; Schmale, J.; Baccarini, A.; Krejci, R.; Svenningsson, B.; Chang, R.; Ekman, A.; Riipinen, I.; Mohr, C.
2022 | Environ. Sci. Technol. | 56 (19) (13888-13899)
aerosol chemistry , aerosol−cloud interactions , atmospheric aerosol , CCN closure , chemical ionization mass spectrometry (CIMS) , cloud droplet activation , High Arctic

Predictions of cloud droplet activation in the late summertime (September) central Arctic Ocean are made using κ-Köhler theory with novel observations of the aerosol chemical composition from a high-resolution time-of-flight chemical ionization mass spectrometer with a filter inlet for gases and aerosols (FIGAERO-CIMS) and an aerosol mass spectrometer (AMS), deployed during the Arctic Ocean 2018 expedition onboard the Swedish icebreaker Oden. We find that the hygroscopicity parameter κ of the total aerosol is 0.39 ± 0.19 (mean ± std). The predicted activation diameter of ∼25 to 130 nm particles is overestimated by 5%, leading to an underestimation of the cloud condensation nuclei (CCN) number concentration by 4–8%. From this, we conclude that the aerosol in the High Arctic late summer is acidic and therefore highly cloud active, with a substantial CCN contribution from Aitken mode particles. Variability in the predicted activation diameter is addressed mainly as a result of uncertainties in the aerosol size distribution measurements. The organic κ was on average 0.13, close to the commonly assumed κ of 0.1, and therefore did not significantly influence the predictions. These conclusions are supported by laboratory experiments of the activation potential of seven organic compounds selected as representative of the measured aerosol.

Physical and Chemical Properties of Cloud Droplet Residuals and Aerosol Particles During the Arctic Ocean 2018 Expedition

Linn Karlsson; Andrea Baccarini; Patrick Duplessis; Darrel Baumgardner; Ian M. Brooks; Rachel Y.-W. Chang; Lubna Dada; Kaspar R. Dällenbach; Liine Heikkinen; Radovan Krejci; W. Richard Leaitch; Caroline Leck; Daniel G. Partridge; Matthew E. Salter; Heini Wernli; Michael J. Wheeler; Julia Schmale; Paul Zieger
2022 | J. Geophys. Res.-Atmos. | 127 (e2021JD036383)

Detailed knowledge of the physical and chemical properties and sources of particles that form clouds is especially important in pristine areas like the Arctic, where particle concentrations are often low and observations are sparse. Here, we present in situ cloud and aerosol measurements from the central Arctic Ocean in August–September 2018 combined with air parcel source analysis. We provide direct experimental evidence that Aitken mode particles (particles with diameters ≲70 nm) significantly contribute to cloud condensation nuclei (CCN) or cloud droplet residuals, especially after the freeze-up of the sea ice in the transition toward fall. These Aitken mode particles were associated with air that spent more time over the pack ice, while size distributions dominated by accumulation mode particles (particles with diameters ≳70 nm) showed a stronger contribution of oceanic air and slightly different source regions. This was accompanied by changes in the average chemical composition of the accumulation mode aerosol with an increased relative contribution of organic material toward fall. Addition of aerosol mass due to aqueous-phase chemistry during in-cloud processing was probably small over the pack ice given the fact that we observed very similar particle size distributions in both the whole-air and cloud droplet residual data. These aerosol–cloud interaction observations provide valuable insight into the origin and physical and chemical properties of CCN over the pristine central Arctic Ocean.

Tropical and Boreal Forest – Atmosphere Interactions: A Review

Paulo Artaxo; Hans-Christen Hansson; Meinrat O. Andreae; Jaana Bäck; Eliane Gomes Alves; Henrique M. J. Barbosa; Frida Bender; Efstratios Bourtsoukidis; Samara Carbone; Jinshu Chi; Stefano Decesari; Viviane R. Després; Florian Ditas; Ekaterina Ezhova; Sandro Fuzzi; Niles J. Hasselquist; Jost Heintzenberg; Bruna A. Holanda; Alex Guenther; Hannele Hakola; Liine Heikkinen; Veli-Matti Kerminen; Jenni Kontkanen; Radovan Krejci; Markku Kulmala; Jost V. Lavric; Gerrit de Leeuw; Katrianne Lehtipalo; Luiz Augusto T. Machado; Gordon McFiggans; arco Aurelio M. Franco; Bruno Backes Meller; Fernando G. Morais; Claudia Mohr; William Morgan; Mats B. Nilsson; Matthias Peichl; Tuukka Petäjä; Maria Praß; Christopher Pöhlker; Mira L. Pöhlker; Ulrich Pöschl; Celso Von Randow; Ilona Riipinen; Janne Rinne; Luciana V. Rizzo; Daniel Rosenfeld; Maria A. F. Silva Dias; Larisa Sogacheva; Philip Stier; Erik Swietlicki; Matthias Sörgel; Peter Tunved; Aki Virkkula; Jian Wang; Bettina Weber; Ana Maria Yáñez-Serrano; Paul Zieger; Eugene Mikhailov; James N. Smith; Jürgen Kesselmeier
2022 | TELLUS B | 74 (24-163)

This review presents how the boreal and the tropical forests affect the atmosphere, its chemical composition, its function, and further how that affects the climate and, in return, the ecosystems through feedback processes. Observations from key tower sites standing out due to their long-term comprehensive observations: The Amazon Tall Tower Observatory in Central Amazonia, the Zotino Tall Tower Observatory in Siberia, and the Station to Measure Ecosystem-Atmosphere Relations at Hyytiäla in Finland. The review is complemented by short-term observations from networks and large experiments.

The review discusses atmospheric chemistry observations, aerosol formation and processing, physiochemical aerosol, and cloud condensation nuclei properties and finds surprising similarities and important differences in the two ecosystems. The aerosol concentrations and chemistry are similar, particularly concerning the main chemical components, both dominated by an organic fraction, while the boreal ecosystem has generally higher concentrations of inorganics, due to higher influence of long-range transported air pollution. The emissions of biogenic volatile organic compounds are dominated by isoprene and monoterpene in the tropical and boreal regions, respectively, being the main precursors of the organic aerosol fraction.

Observations and modeling studies show that climate change and deforestation affect the ecosystems such that the carbon and hydrological cycles in Amazonia are changing to carbon neutrality and affect precipitation downwind. In Africa, the tropical forests are so far maintaining their carbon sink.

It is urgent to better understand the interaction between these major ecosystems, the atmosphere, and climate, which calls for more observation sites, providing long-term data on water, carbon, and other biogeochemical cycles. This is essential in finding a sustainable balance between forest preservation and reforestation versus a potential increase in food production and biofuels, which are critical in maintaining ecosystem services and global climate stability. Reducing global warming and deforestation is vital for tropical forests.

The Role of Convective Up- and Downdrafts in the Transport of Trace Gases in the Amazon

Bardakov, R; Krejci, R; Riipinen, I; Ekman, AML
2022 | J. Geophys. Res.-Atmos. | 127 (18)

Secondary aerosol formation in marine Arctic environments: a model measurement comparison at Ny-angstrom lesund

Xavier, C; Baykara, M; de Jonge, RW; Altstadter, B; Clusius, P; Vakkari, V; Thakur, R; Beck, L; Becagli, S; Severi, M; Traversi, R; Krejci, R; Tunved, P; Mazzola, M; Wehner, B; Sipila, M; Kulmala, M; Boy, M; Roldin, P
2022 | Atmos. Chem. Phys. | 22 (15) (10023-10043)

Tropical and Boreal Forest Atmosphere Interactions: A Review

Artaxo, P; Hansson, HC; Andreae, MO; Back, J; Alves, EG; Barbosa, HMJ; Bender, F; Bourtsoukidis, E; Carbone, S; Chi, JS; Decesari, S; Despres, VR; Ditas, F; Ezhova, E; Fuzzi, S; Hasselquist, NJ; Heintzenberg, J; Holanda, BA; Guenther, A; Hakola, H; Heikkinen, L; Kerminen, VM; Kontkanen, J; Krejci, R; Kulmala, M; Lavric, JV; de Leeuw, G; Lehtipalo, K; Machado, LAT; McFiggans, G; Franco, MAM; Meller, BB; Morais, FG; Mohr, C; Morgan, W; Nilsson, MB; Peichl, M; Petaja, T; Prass, M; Pohlker, C; Pohlker, ML; Poschl, U; Von Randow, C; Riipinen, I; Rinne, J; Rizzo, LV; Rosenfeld, D; Dias, MAFS; Sogacheva, L; Stier, P; Swietlicki, E; Sorgel, M; Tunved, P; Virkkula, A; Wang, J; Weber, B; Yanez-Serrano, AM; Zieger, P; Mikhailov, E; Smith, JN; Kesselmeier, J
2022 | Tellus Ser. B-Chem. Phys. Meteorol. | 74 (1) (24-163)

Comparison of particle number size distribution trends in ground measurements and climate models

Leinonen, V; Kokkola, H; Yli-Juuti, T; Mielonen, T; Kuhn, T; Nieminen, T; Heikkinen, S; Miinalainen, T; Bergman, T; Carslaw, K; Decesari, S; Fiebig, M; Hussein, T; Kivekas, N; Krejci, R; Kulmala, M; Leskinen, A; Massling, A; Mihalopoulos, N; Mulcahy, JP; Noe, SM; van Noije, T; O'Connor, FM; O'Dowd, C; Olivie, D; Pernov, JB; Petaja, T; Seland, O; Schulz, M; Scott, CE; Skov, H; Swietlicki, E; Tuch, T; Wiedensohler, A; Virtanen, A; Mikkonen, S
2022 | Atmos. Chem. Phys. | 22 (19) (12873-12905)

Estimates of mass absorption cross sections of black carbon for filter-based absorption photometers in the Arctic

Sho Ohata; Tatsuhiro Mori; Yutaka Kondo; Sangeeta Sharma; Antti Hyvärinen; Elisabeth Andrews; Peter Tunved; Eija Asmi; John Backman; Henri Servomaa; Daniel Veber; Konstantinos Eleftheriadis; Stergios Vratolis; Radovan Krejci; Paul Zieger; Makoto Koike; Yugo Kanaya; Atsushi Yoshida; Nobuhiro Moteki; Yongjing Zhao; Yutaka Tobo; Junji Matsushita; Naga Oshima
2021 | Atmos. Meas. Tech. | 14 (6723-6748)

Long-term measurements of atmospheric mass concentrations of black carbon (BC) are needed to investigate changes in its emission, transport, and deposition. However, depending on instrumentation, parameters related to BC such as aerosol absorption coefficient (babs) have been measured instead. Most ground-based measurements of babs in the Arctic have been made by filter-based absorption photometers, including particle soot absorption photometers (PSAPs), continuous light absorption photometers (CLAPs), Aethalometers, and multi-angle absorption photometers (MAAPs). The measured babs can be converted to mass concentrations of BC (MBC) by assuming the value of the mass absorption cross section (MAC; MBC= babs/ MAC). However, the accuracy of conversion of babs to MBC has not been adequately assessed. Here, we introduce a systematic method for deriving MAC values from babs measured by these instruments and independently measured MBC. In this method, MBC was measured with a filter-based absorption photometer with a heated inlet (COSMOS). COSMOS-derived MBC (MBC (COSMOS)) is traceable to a rigorously calibrated single particle soot photometer (SP2), and the absolute accuracy of MBC (COSMOS) has been demonstrated previously to be about 15 % in Asia and the Arctic. The necessary conditions for application of this method are a high correlation of the measured babs with independently measured MBC and long-term stability of the regression slope, which is denoted as MACcor (MAC derived from the correlation). In general, babs–MBC (COSMOS) correlations were high (r2= 0.76–0.95 for hourly data) at Alert in Canada, Ny-Ålesund in Svalbard, Barrow (NOAA Barrow Observatory) in Alaska, Pallastunturi in Finland, and Fukue in Japan and stable for up to 10 years. We successfully estimated MACcor values (10.8–15.1 m2 g−1 at a wavelength of 550 nm for hourly data) for these instruments, and these MACcor values can be used to obtain error-constrained estimates of MBC from babs measured at these sites even in the past, when COSMOS measurements were not made. Because the absolute values of MBC at these Arctic sites estimated by this method are consistent with each other, they are applicable to the study of spatial and temporal variation in MBC in the Arctic and to evaluation of the performance of numerical model calculations.

The SALTENA experiment: Comprehensive observations of aerosol sources, formation and processes in the South American Andes

Federico Bianchi; Victoria A. Sinclair; Diego Aliaga; Qiaozhi Zha; Wiebke Scholz; Cheng Wu; Liine Heikkinen; Rob Modini; Eva Partoll; Fernando Velarde; Isabel Moreno; Yvette Gramlich; Wei Huang; Markus Leiminger; Joonas Enroth; Otso Peräkylä; Angela Marinoni; Chen Xuemeng; Luis Blacutt; Ricardo Forno; Rene Gutierrez; Patrick Ginot; Gaëlle Uzu; Maria Cristina Facchini; Stefania Gilardoni; Martin Gysel-Beer; Runlong Cai; Tuukka Petäjä; Matteo Rinaldi; Harald Saathoff; Karine Sellegri; Douglas Worsnop; Paulo Artaxo; Armin Hansel; Markku Kulmala; Alfred Wiedensohler; Paolo Laj; Radovan Krejci; Samara Carbone; Marcos Andrade; Claudia Mohr
2021 | Bull. Amer. Meteor. Soc.

A long-term study of cloud residuals from low-level Arctic clouds

Linn Karlsson; Radovan Krejci; Makoto Koike; Kerstin Ebell; Paul Zieger
2021 | Atmos. Chem. Phys. | 21 (1-27)

To constrain uncertainties in radiative forcings associated with aerosol–cloud interactions, improved understanding of Arctic cloud formation is required, yet long-term measurements of the relevant cloud and aerosol properties remain sparse. We present the first long-term study of cloud residuals, i.e. particles that were involved in cloud formation and cloud processes, in Arctic low-level clouds measured at Zeppelin Observatory, Svalbard. To continuously sample cloud droplets and ice crystals and separate them from non-activated aerosol, a ground-based counter-flow virtual impactor inlet system (GCVI) was used. A detailed evaluation of the GCVI measurements, using concurrent cloud particle size distributions, meteorological parameters, and aerosol measurements, is presented for both warm and cold clouds, and the potential contribution of sampling artefacts is discussed in detail. We find an excellent agreement of the GCVI sampling efficiency of liquid clouds using two independent approaches. The 2-year data set of cloud residual size distributions and number concentrations reveals that the cloud residuals follow the typical seasonal cycle of Arctic aerosol, with a maximum concentration in spring and summer and a minimum concentration in the late autumn and winter months. We observed average activation diameters in the range of 58–78 nm for updraught velocities below 1 m s−1. A cluster analysis also revealed cloud residual size distributions that were dominated by Aitken mode particles down to around 20–30 nm. During the winter months, some of these small particles may be the result of ice, snow, or ice crystal shattering artefacts in the GCVI inlet; however, cloud residuals down to 20 nm in size were also observed during conditions when artefacts are less likely.

Contact information

Visiting addresses:

Geovetenskapens Hus,
Svante Arrhenius väg 8, Stockholm

Arrheniuslaboratoriet, Svante Arrhenius väg 16, Stockholm (Unit for Toxicological Chemistry)

Mailing address:
Department of Environmental Science
Stockholm University
106 91 Stockholm

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Stella Papadopoulou
Science Communicator
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