| 51. |
- Treydte, Kerstin, et al.
(författare)
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Recent human-induced atmospheric drying across Europe unprecedented in the last 400 years
- 2024
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Ingår i: NATURE GEOSCIENCE. - 1752-0894 .- 1752-0908. ; 17, s. 58-65
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Tidskriftsartikel (refereegranskat)abstract
- The vapor pressure deficit reflects the difference between how much moisture the atmosphere could and actually does hold, a factor that fundamentally affects evapotranspiration, ecosystem functioning, and vegetation carbon uptake. Its spatial variability and long-term trends under natural versus human-influenced climate are poorly known despite being essential for predicting future effects on natural ecosystems and human societies such as crop yield, wildfires, and health. Here we combine regionally distinct reconstructions of pre-industrial summer vapor pressure deficit variability from Europe's largest oxygen-isotope network of tree-ring cellulose with observational records and Earth system model simulations with and without human forcing included. We demonstrate that an intensification of atmospheric drying during the recent decades across different European target regions is unprecedented in a pre-industrial context and that it is attributed to human influence with more than 98% probability. The magnitude of this trend is largest in Western and Central Europe, the Alps and Pyrenees region, and the smallest in southern Fennoscandia. In view of the extreme drought and compound events of the recent years, further atmospheric drying poses an enhanced risk to vegetation, specifically in the densely populated areas of the European temperate lowlands. The atmosphere has dried across most regions of Europe in recent decades, a trend that can be attributed primarily to human impacts, according to tree ring records spanning 400 years and Earth system model simulations.
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| 52. |
- Yli-Juuti, T., et al.
(författare)
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Growth rates of nucleation mode particles in Hyytiala during 2003-2009 : variation with particle size, season, data analysis method and ambient conditions
- 2011
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Ingår i: Atmospheric Chemistry And Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 11:24, s. 12865-12886
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Tidskriftsartikel (refereegranskat)abstract
- The condensational growth rate of aerosol particles formed in atmospheric new particle formation events is one of the most important factors influencing the lifetime of these particles and their ability to become climatically relevant. Diameter growth rates (GR) of nucleation mode particles were studied based on almost 7 yr of data measured during the years 2003-2009 at a boreal forest measurement station SMEAR II in Hyytiala, Finland. The particle growth rates were estimated using particle size distributions measured with a Differential Mobility Particle Sizer (DMPS), a Balanced Scanning Mobility Analyzer (BSMA) and an Air Ion Spectrometer (AIS). Two GR analysis methods were tested. The particle growth rates were also compared to an extensive set of ambient meteorological parameters and trace gas concentrations to investigate the processes/constituents limiting the aerosol growth. The median growth rates of particles in the nucleation mode size ranges with diameters of 1.5-3 nm, 3-7 nm and 7-20 nm were 1.9 nm h(-1), 3.8 nm h(-1), and 4.3 nm h(-1), respectively. The median relative uncertainties in the growth rates due to the size distribution instrumentation in these size ranges were 25 %, 19 %, and 8 %, respectively. For the smallest particles (1.5-3 nm) the AIS data yielded on average higher growth rate values than the BSMA data, and higher growth rates were obtained from positively charged size distributions as compared with negatively charged particles. For particles larger than 3 nm in diameter no such systematic differences were found. For these particles the uncertainty in the growth rate related to the analysis method, with relative uncertainty of 16 %, was similar to that related to the instruments. The growth rates of 7-20 nm particles showed positive correlation with monoterpene concentrations and their oxidation rate by ozone. The oxidation rate by OH did not show a connection with GR. Our results indicate that the growth of nucleation mode particles in Hyytiala is mainly limited by the concentrations of organic precursors.
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| 53. |
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| 54. |
- Alakurtti, Kati, et al.
(författare)
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Long-term test-retest reliability of striatal and extrastriatal dopamine D-2/3 receptor binding : study with [C-11]raclopride and high-resolution PET
- 2015
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Ingår i: Journal of Cerebral Blood Flow and Metabolism. - : SAGE Publications. - 0271-678X .- 1559-7016. ; 35:7, s. 1199-1205
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Tidskriftsartikel (refereegranskat)abstract
- We measured the long-term test-retest reliability of [C-11]raclopride binding in striatal subregions, the thalamus and the cortex using the bolus-plus-infusion method and a high-resolution positron emission scanner. Seven healthy male volunteers underwent two positron emission tomography (PET) [C-11]raclopride assessments, with a 5-week retest interval. D-2/3 receptor availability was quantified as binding potential using the simplified reference tissue model. Absolute variability (VAR) and intraclass correlation coefficient (ICC) values indicated very good reproducibility for the striatum and were 4.5%/0.82, 3.9%/0.83, and 3.9%/0.82, for the caudate nucleus, putamen, and ventral striatum, respectively. Thalamic reliability was also very good, with VAR of 3.7% and ICC of 0.92. Test-retest data for cortical areas showed good to moderate reproducibility (6.1% to 13.1%). Our results are in line with previous test-retest studies of [C-11]raclopride binding in the striatum. A novel finding is the relatively low variability of [C-11]raclopride binding, providing suggestive evidence that extrastriatal D-2/3 binding can be studied in vivo with [C-11]raclopride PET to be verified in future studies.
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| 55. |
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| 56. |
- Andersson, J. C., et al.
(författare)
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Modeling the Äspö Pillar stability experiment
- 2010
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Ingår i: Rock Mechanics in Civil and Environmental Engineering - Proceedings of the European Rock Mechanics Symposium, EUROCK 2010. - 9780415586542 ; , s. 787-790
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Konferensbidrag (refereegranskat)abstract
- This paper presents results of the 1st stages ofTaskAof the Decovalex 2011 project, the numerical modeling of the Äspö Pillar Stability experiment performed by the Äspö Hard Rock Laboratory of the Swedish Nuclear Fuel and Waste Management Company (SKB). The objective is to perform back calculation of the Äspö pillar behavior using state of the art numerical modeling techniques for the material behavior. The work is divided into three stages and it is the first stage of thework that will be presented in this paper. Seven international teams from six different countries participated in the task and contributed to the results presented in this paper, concerning back calculation of uniaxial and triaxial compressive core testing and elastic back calculation of the stress path for excavation-induced stresses. The results are useful for understanding the occurrence of spalling in the upper part of the pillar during excavation and the stress path modeling gives the first approximation of the yielding strength of the pillar. The calculated results agree well with observations measured during experiment.
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| 57. |
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| 58. |
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| 59. |
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| 60. |
- Chang, Kuang Yu, et al.
(författare)
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Substantial hysteresis in emergent temperature sensitivity of global wetland CH4 emissions
- 2021
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1, s. 2266-2266
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Tidskriftsartikel (refereegranskat)abstract
- Wetland methane (CH4) emissions ([Formula: see text]) are important in global carbon budgets and climate change assessments. Currently, [Formula: see text] projections rely on prescribed static temperature sensitivity that varies among biogeochemical models. Meta-analyses have proposed a consistent [Formula: see text] temperature dependence across spatial scales for use in models; however, site-level studies demonstrate that [Formula: see text] are often controlled by factors beyond temperature. Here, we evaluate the relationship between [Formula: see text] and temperature using observations from the FLUXNET-CH4 database. Measurements collected across the globe show substantial seasonal hysteresis between [Formula: see text] and temperature, suggesting larger [Formula: see text] sensitivity to temperature later in the frost-free season (about 77% of site-years). Results derived from a machine-learning model and several regression models highlight the importance of representing the large spatial and temporal variability within site-years and ecosystem types. Mechanistic advancements in biogeochemical model parameterization and detailed measurements in factors modulating CH4 production are thus needed to improve global CH4 budget assessments.
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