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Author

Yrjö Viisanen

Bio: Yrjö Viisanen is an academic researcher from Finnish Meteorological Institute. The author has contributed to research in topics: Nucleation & Aerosol. The author has an hindex of 32, co-authored 94 publications receiving 4966 citations.


Papers
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Journal ArticleDOI
25 Aug 2011-Nature
TL;DR: First results from the CLOUD experiment at CERN are presented, finding that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100–1,000-fold and ion-induced binary nucleation of H2SO4–H2O can occur in the mid-troposphere but is negligible in the boundary layer.
Abstract: Atmospheric aerosols exert an important influence on climate through their effects on stratiform cloud albedo and lifetime and the invigoration of convective storms. Model calculations suggest that almost half of the global cloud condensation nuclei in the atmospheric boundary layer may originate from the nucleation of aerosols from trace condensable vapours, although the sensitivity of the number of cloud condensation nuclei to changes of nucleation rate may be small. Despite extensive research, fundamental questions remain about the nucleation rate of sulphuric acid particles and the mechanisms responsible, including the roles of galactic cosmic rays and other chemical species such as ammonia. Here we present the first results from the CLOUD experiment at CERN. We find that atmospherically relevant ammonia mixing ratios of 100 parts per trillion by volume, or less, increase the nucleation rate of sulphuric acid particles more than 100–1,000-fold. Time-resolved molecular measurements reveal that nucleation proceeds by a base-stabilization mechanism involving the stepwise accretion of ammonia molecules. Ions increase the nucleation rate by an additional factor of between two and more than ten at ground-level galactic-cosmic-ray intensities, provided that the nucleation rate lies below the limiting ion-pair production rate. We find that ion-induced binary nucleation of H_(2)SO_(4)–H_(2)O can occur in the mid-troposphere but is negligible in the boundary layer. However, even with the large enhancements in rate due to ammonia and ions, atmospheric concentrations of ammonia and sulphuric acid are insufficient to account for observed boundary-layer nucleation.

1,071 citations

Journal ArticleDOI
Joao Almeida1, Joao Almeida2, Siegfried Schobesberger3, Andreas Kürten1, Ismael K. Ortega3, Oona Kupiainen-Määttä3, Arnaud P. Praplan4, Alexey Adamov3, António Amorim5, F. Bianchi4, Martin Breitenlechner6, A. David2, Josef Dommen4, Neil M. Donahue7, Andrew J. Downard8, Eimear M. Dunne9, Jonathan Duplissy3, Sebastian Ehrhart1, Richard C. Flagan8, Alessandro Franchin3, Roberto Guida2, Jani Hakala3, Armin Hansel6, Martin Heinritzi6, Henning Henschel3, Tuija Jokinen3, Heikki Junninen3, Maija Kajos3, Juha Kangasluoma3, Helmi Keskinen10, Agnieszka Kupc11, Theo Kurtén3, Alexander N. Kvashin12, Ari Laaksonen13, Ari Laaksonen10, Katrianne Lehtipalo3, Markus Leiminger1, Johannes Leppä13, Ville Loukonen3, Vladimir Makhmutov12, Serge Mathot2, Matthew J. McGrath14, Tuomo Nieminen3, Tuomo Nieminen15, Tinja Olenius3, Antti Onnela2, Tuukka Petäjä3, Francesco Riccobono4, Ilona Riipinen16, Matti P. Rissanen3, Linda Rondo1, Taina Ruuskanen3, Filipe Duarte Santos5, Nina Sarnela3, Simon Schallhart3, R. Schnitzhofer6, John H. Seinfeld8, Mario Simon1, Mikko Sipilä15, Mikko Sipilä3, Yuri Stozhkov12, Frank Stratmann17, António Tomé5, Jasmin Tröstl4, Georgios Tsagkogeorgas17, Petri Vaattovaara10, Yrjö Viisanen13, Annele Virtanen10, Aron Vrtala11, Paul E. Wagner11, Ernest Weingartner4, Heike Wex17, Christina Williamson1, Daniela Wimmer1, Daniela Wimmer3, Penglin Ye7, Taina Yli-Juuti3, Kenneth S. Carslaw9, Markku Kulmala15, Markku Kulmala3, Joachim Curtius1, Urs Baltensperger4, Douglas R. Worsnop, Hanna Vehkamäki3, Jasper Kirkby1, Jasper Kirkby2 
17 Oct 2013-Nature
TL;DR: The results show that, in regions of the atmosphere near amine sources, both amines and sulphur dioxide should be considered when assessing the impact of anthropogenic activities on particle formation.
Abstract: Nucleation of aerosol particles from trace atmospheric vapours is thought to provide up to half of global cloud condensation nuclei(1). Aerosols can cause a net cooling of climate by scattering sun ...

738 citations

Journal ArticleDOI
16 May 2014-Science
TL;DR: It is shown, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere.
Abstract: Atmospheric new-particle formation affects climate and is one of the least understood atmospheric aerosol processes. The complexity and variability of the atmosphere has hindered elucidation of the fundamental mechanism of new-particle formation from gaseous precursors. We show, in experiments performed with the CLOUD (Cosmics Leaving Outdoor Droplets) chamber at CERN, that sulfuric acid and oxidized organic vapors at atmospheric concentrations reproduce particle nucleation rates observed in the lower atmosphere. The experiments reveal a nucleation mechanism involving the formation of clusters containing sulfuric acid and oxidized organic molecules from the very first step. Inclusion of this mechanism in a global aerosol model yields a photochemically and biologically driven seasonal cycle of particle concentrations in the continental boundary layer, in good agreement with observations.

446 citations

Journal ArticleDOI
TL;DR: In this article, the authors investigated homogeneous nucleation of water droplets in the vapor phase using the nucleation pulse technique and found that nucleation rates in supersaturated water vapor mixed with various carrier gases as functions of supersaturation and temperature were independent of the nature of the carrier gas.
Abstract: We have investigated homogeneous nucleation of water droplets in the vapor phase Nucleation in water vapor has been previously studied a number of times using various experimental techniques The nucleation pulse technique used here allows accurate measurements of homogeneous nucleation rates J vs supersaturation S in the range from 105 to 109 cm−3 s−1 The advance reported here consists of the fact that the J–S curves are measured at a selectable constant temperature We determined the nucleation rates in supersaturated water vapor mixed with various carrier gases as functions of supersaturation and temperature (217

285 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present direct observational evidence that aerosol particles formed in the atmosphere from gaseous precursors eventually participate into cloud droplet activation and further demonstrate that the albedo of clouds may be significantly influenced by atmospheric aerosol formation, and that this process needs to be taken into account when estimating the indirect climatic effects of aerosols in the global atmosphere.
Abstract: [1] In order to predict the current state and future development of the Earth's climate system, detailed knowledge on how atmospheric aerosol particles from various sources interact with clouds is needed. In this article we present, based on continuous aerosol measurements in a remote continental location, direct observational evidence that aerosol particles formed in the atmosphere from gaseous precursors eventually participate into cloud droplet activation. By combining the measurement data with theoretical calculations, we further demonstrate that the albedo of clouds may be significantly influenced by atmospheric aerosol formation, and that this process needs to be taken into account when estimating the indirect climatic effects of aerosols in the global atmosphere.

201 citations


Cited by
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Book ChapterDOI
01 Jan 2014
TL;DR: Myhre et al. as discussed by the authors presented the contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) 2013: Anthropogenic and Natural Radiative forcing.
Abstract: This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

3,684 citations

Journal ArticleDOI
TL;DR: In this article, an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and analytical techniques used to determine the chemical composition of SOA is presented.
Abstract: Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.

3,324 citations

Journal ArticleDOI
TL;DR: In this article, the authors discuss the role of chemical composition and particle size in cloud condensation nucleation processes, and the role that the chemical composition plays in the process of cloud droplet and ice nucleation.

1,347 citations

Journal ArticleDOI
27 Feb 2014-Nature
TL;DR: It is found that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the formation of large amounts of extremely low-volatility vapours, helping to explain the discrepancy between the observed atmospheric burden of secondary organic aerosol and that reported by many model studies.
Abstract: Forests emit large quantities of volatile organic compounds (VOCs) to the atmosphere. Their condensable oxidation products can form secondary organic aerosol, a significant and ubiquitous component of atmospheric aerosol, which is known to affect the Earth's radiation balance by scattering solar radiation and by acting as cloud condensation nuclei. The quantitative assessment of such climate effects remains hampered by a number of factors, including an incomplete understanding of how biogenic VOCs contribute to the formation of atmospheric secondary organic aerosol. The growth of newly formed particles from sizes of less than three nanometres up to the sizes of cloud condensation nuclei (about one hundred nanometres) in many continental ecosystems requires abundant, essentially non-volatile organic vapours, but the sources and compositions of such vapours remain unknown. Here we investigate the oxidation of VOCs, in particular the terpene α-pinene, under atmospherically relevant conditions in chamber experiments. We find that a direct pathway leads from several biogenic VOCs, such as monoterpenes, to the formation of large amounts of extremely low-volatility vapours. These vapours form at significant mass yield in the gas phase and condense irreversibly onto aerosol surfaces to produce secondary organic aerosol, helping to explain the discrepancy between the observed atmospheric burden of secondary organic aerosol and that reported by many model studies. We further demonstrate how these low-volatility vapours can enhance, or even dominate, the formation and growth of aerosol particles over forested regions, providing a missing link between biogenic VOCs and their conversion to aerosol particles. Our findings could help to improve assessments of biosphere-aerosol-climate feedback mechanisms, and the air quality and climate effects of biogenic emissions generally.

1,340 citations

Journal ArticleDOI
TL;DR: A periodic cycle of PM episodes in Beijing is demonstrated that is governed by meteorological conditions and characterized by two distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles.
Abstract: As the world’s second largest economy, China has experienced severe haze pollution, with fine particulate matter (PM) recently reaching unprecedentedly high levels across many cities, and an understanding of the PM formation mechanism is critical in the development of efficient mediation policies to minimize its regional to global impacts. We demonstrate a periodic cycle of PM episodes in Beijing that is governed by meteorological conditions and characterized by two distinct aerosol formation processes of nucleation and growth, but with a small contribution from primary emissions and regional transport of particles. Nucleation consistently precedes a polluted period, producing a high number concentration of nano-sized particles under clean conditions. Accumulation of the particle mass concentration exceeding several hundred micrograms per cubic meter is accompanied by a continuous size growth from the nucleation-mode particles over multiple days to yield numerous larger particles, distinctive from the aerosol formation typically observed in other regions worldwide. The particle compositions in Beijing, on the other hand, exhibit a similarity to those commonly measured in many global areas, consistent with the chemical constituents dominated by secondary aerosol formation. Our results highlight that regulatory controls of gaseous emissions for volatile organic compounds and nitrogen oxides from local transportation and sulfur dioxide from regional industrial sources represent the key steps to reduce the urban PM level in China.

1,291 citations