| 1. |
- Kulmala, Markku, et al.
(författare)
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Overview of the biosphere-aerosol-cloud-climate interactions (BACCI) studies
- 2008
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:3, s. 300-317
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Forskningsöversikt (refereegranskat)abstract
- Here we present research methods and results obtained by the Nordic Centre of Excellence Biosphere-Aerosol-Cloud-Climate Interactions (BACCI) between 1 January 2003 and 31 December 2007. The centre formed an integrated attempt to understand multiple, but interlinked, biosphere-atmosphere interactions applying inter and multidisciplinary approaches in a coherent manner. The main objective was to study the life cycle of aerosol particles and their importance on climate change. The foundation in BACCI was a thorough understanding of physical, meteorological, chemical and ecophysiological processes, providing a unique possibility to study biosphere-aerosol-cloud-climate interactions. Continuous measurements of atmospheric concentrations and fluxes of aerosol particles and precursors and, CO2/aerosol trace gas interactions in different field stations (e.g. SMEAR) were supported by models of particle thermodynamics, transport and dynamics, atmospheric chemistry, boundary layer meteorology and forest growth. The main progress was related to atmospheric new particle formation, existence of clusters, composition of nucleation mode aerosol particles, chemical precursors of fresh aerosol particles, the contribution of biogenic aerosol particles on the global aerosol load, transport, transformation and deposition of aerosol particles, thermodynamics related to aerosol particles and cloud droplets, and the microphysics and chemistry of cloud droplet formation.
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| 2. |
- Nieminen, Tuomo, et al.
(författare)
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Global analysis of continental boundary layer new particle formation based on long-term measurements
- 2018
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 18:19, s. 14737-14756
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric 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.
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| 3. |
- Rastak, Narges, et al.
(författare)
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Seasonal variation of aerosol water uptake and its impact on the direct radiative effect at Ny-Alesund, Svalbard
- 2014
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 14:14, s. 7445-7460
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Tidskriftsartikel (refereegranskat)abstract
- In this study we investigated the impact of water uptake by aerosol particles in ambient atmosphere on their optical properties and their direct radiative effect (ADRE, W m(-2)) in the Arctic at Ny-Alesund, Svalbard, during 2008. To achieve this, we combined three models, a hygroscopic growth model, a Mie model and a radiative transfer model, with an extensive set of observational data. We found that the seasonal variation of dry aerosol scattering coefficients showed minimum values during the summer season and the beginning of fall (July-August-September), when small particles (< 100 nm in diameter) dominate the aerosol number size distribution. The maximum scattering by dry particles was observed during the Arctic haze period (March-April-May) when the average size of the particles was larger. Considering the hygroscopic growth of aerosol particles in the ambient atmosphere had a significant impact on the aerosol scattering coefficients: the aerosol scattering coefficients were enhanced by on average a factor of 4.30 +/- 2.26 (mean +/- standard deviation), with lower values during the haze period (March-April-May) as compared to summer and fall. Hygroscopic growth of aerosol particles was found to cause 1.6 to 3.7 times more negative ADRE at the surface, with the smallest effect during the haze period (March-April-May) and the highest during late summer and beginning of fall (July-August-September).
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| 4. |
- Swietlicki, Erik, et al.
(författare)
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Hygroscopic properties of submicrometer atmospheric aerosol particles measured with H-TDMA instruments in various environments : a review
- 2008
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Ingår i: Tellus. Series B, Chemical and physical meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60:3, s. 432-469
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Forskningsöversikt (refereegranskat)abstract
- 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 size-resolved 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.
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| 5. |
- Tunved, Peter, et al.
(författare)
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The natural aerosol over Northern Europe and its relation to anthropogenic emissions - implications of important climate feedbacks
- 2008
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Ingår i: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 60 B:4, s. 473-484
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Tidskriftsartikel (refereegranskat)abstract
- We use a recently developed parametrization to estimate the regional particle field in the summer time troposphere over Scandinavia that would result if the forest were the only source of particles. The calculated field is compared with available observational data. It is concluded that the needle leaf forest above 58 degrees N alone is capable of producing aerosol mass concentrations corresponding to 12-50% of today's values in the boundary layer over Scandinavia. We also demonstrate that the forest itself could produce up to 200 CCN per cubic centimetre on average over Scandinavia and further show that an increase in temperature by 5.8 degrees C compared to today's average temperature could increase this CCN population by 40%. The study shows that we are able to approximate the natural aerosol field resulting from biogenic emissions over the boreal forest in the northern hemispheric region. This information provide an important contribution in the evaluation of the climate effect caused by anthropogenic emissions of particles over the forest and also opens the possibility to better address the climate feedbacks believed to be associated with the boreal region.
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