| 1. |
- Paramonov, M., et al.
(författare)
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A synthesis of cloud condensation nuclei counter (CCNC) measurements within the EUCAARI network
- 2015
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Ingår i: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7324. ; 15:21, s. 12211-12229
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Tidskriftsartikel (refereegranskat)abstract
- Cloud condensation nuclei counter (CCNC) measurements performed at 14 locations around the world within the European Integrated project on Aerosol Cloud Climate and Air Quality interactions (EUCAARI) framework have been analysed and discussed with respect to the cloud condensation nuclei (CCN) activation and hygroscopic properties of the atmospheric aerosol. The annual mean ratio of activated cloud condensation nuclei (N-CCN) to the total number concentration of particles (N-CN), known as the activated fraction A, shows a similar functional dependence on supersaturation S at many locations - exceptions to this being certain marine locations, a free troposphere site and background sites in south-west Germany and northern Finland. The use of total number concentration of particles above 50 and 100 nm diameter when calculating the activated fractions (A(50) and A(100), respectively) renders a much more stable dependence of A on S; A(50) and A(100) also reveal the effect of the size distribution on CCN activation. With respect to chemical composition, it was found that the hygroscopicity of aerosol particles as a function of size differs among locations. The hygroscopicity parameter kappa decreased with an increasing size at a continental site in south-west Germany and fluctuated without any particular size dependence across the observed size range in the remote tropical North Atlantic and rural central Hungary. At all other locations kappa increased with size. In fact, in Hyytiala, Vavihill, Jungfraujoch and Pallas the difference in hygroscopicity between Aitken and accumulation mode aerosol was statistically significant at the 5% significance level. In a boreal environment the assumption of a size-independent kappa can lead to a potentially substantial overestimation of N-CCN at S levels above 0.6 %. The same is true for other locations where kappa was found to increase with size. While detailed information about aerosol hygroscopicity can significantly improve the prediction of N-CCN, total aerosol number concentration and aerosol size distribution remain more important parameters. The seasonal and diurnal patterns of CCN activation and hygroscopic properties vary among three long-term locations, highlighting the spatial and temporal variability of potential aerosol-cloud interactions in various environments.
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| 2. |
- Lahtinen, J., et al.
(författare)
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LEED and DFT investigation on the (2 × 2)-S overlayer on Co(0 0 0 1)
- 2005
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 599:1-3, s. 113-121
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Tidskriftsartikel (refereegranskat)abstract
- The geometric surface structure of a (2 × 2)-S layer formed by adsorption of hydrogen sulfide at 185 K on the Co(0 0 0 1) surface has been determined by low energy electron diffraction (LEED) experiments and density-functional theory (DFT) calculations. The favored atomic configuration consists of sulfur atoms residing at the fcc-hollow sites with S-Co distance of 2.2 ± 0.1 Å. Buckling in the first layer is negligible and the three nearest-neighbor Co atoms below the S atom are symmetrically moved by 0.05 ± 0.09 Å along the surface away from the S atom. The DFT calculations confirm the hollow-site adsorption and give further information on the electronic structure of the system. © 2005 Elsevier B.V. All rights reserved.
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| 3. |
- Lehikoinen, Aleksi, et al.
(författare)
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Rapid climate driven shifts in wintering distributions of three common waterbird species
- 2013
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Ingår i: Global Change Biology. - : Wiley. - 1354-1013. ; 19:7, s. 2071-2081
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Tidskriftsartikel (refereegranskat)abstract
- Climate change is predicted to cause changes in species distributions and several studies report margin range shifts in some species. However, the reported changes rarely concern a species' entire distribution and are not always linked to climate change. Here, we demonstrate strong north-eastwards shifts in the centres of gravity of the entire wintering range of three common waterbird species along the North-West Europe flyway during the past three decades. These shifts correlate with an increase of 3.8 degrees C in early winter temperature in the north-eastern part of the wintering areas, where bird abundance increased exponentially, corresponding with decreases in abundance at the south-western margin of the wintering ranges. This confirms the need to re-evaluate conservation site safeguard networks and associated biodiversity monitoring along the flyway, as new important wintering areas are established further north and east, and highlights the general urgency of conservation planning in a changing world. Range shifts in wintering waterbirds may also affect hunting pressure, which may alter bag sizes and lead to population-level consequences.
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