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1.
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2.
  • Sonesten, Lars (författare)
  • Belastning på havet
  • 2014
  • Ingår i: Havet : om miljötillståndet i i svenska havsområden. 2013/14. - 978-91-637-5737-2
  • Bokkapitel (refereegranskat)
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3.
  • Podgrajsek, E., et al. (författare)
  • Comparison of floating chamber and eddy covariance measurements of lake greenhouse gas fluxes
  • 2014
  • Ingår i: Biogeosciences Discussions. - 1810-6277. ; 11, s. 4225-4233
  • Tidskriftsartikel (refereegranskat)abstract
    • Fluxes of carbon dioxide (CO2) and methane (CH4) from lakes may have a large impact on the magnitude of the terrestrial carbon sink. Traditionally lake fluxes have been measured using the floating chamber (FC) technique; however, several recent studies use the eddy covariance (EC) method. We present simultaneous flux measurements using both methods at lake Tämnaren in Sweden during field campaigns in 2011 and 2012. Only very few similar studies exist. For CO2 flux, the two methods agree relatively well during some periods, but deviate substantially at other times. The large discrepancies might be caused by heterogeneity of partial pressure of CO2 (pCO2w) in the EC flux footprint. The methods agree better for CH4 fluxes. It is, however, clear that short-term discontinuous FC measurements are likely to miss important high flux events.
4.
  • Olsson, Mikael, 1948- (författare)
  • Polaris
  • 2009
  • Ingår i: http://www.polarisen.se. - Göteborg : University of Gothenburg.
  • Annan publikation (övrigt vetenskapligt)abstract
    • Polaris is a Swedish based web site dealing with Antarctic, Arctic and sub-polar areas around the globe, including sub-Arctic regions of Scandinavia and Eurasia. Polaris is focusing on peoples and places, research and resources on high latitudes. In particular, the site's ambition is to depict the interaction between the components and put them in a context of global environmental and climate change. The web site also addresses the Swedish polar and mountain research, exemplified by the depiction of a number of Swedish polar researchers' work and choice of career. Polaris main target group is high school students. We aim at establishing Polaris as the popular web site in Sweden for polar research. Polaris was a joint production by Gothenburg and Stockholm Universities and others during the International Polar Year 2007-09. The initiative to the website was taken by the Swedish Committee for International Polar Year, the Swedish Research Council and the Universeum Science Center in Gothenburg. There are many scientific contributors, mainly from the Centre of Earth Systems Science at the University of Gothenburg, the Tarfala Research Station at Stockholm University and the Swedish Polar Research Secretariat . Interviews and articles are made by professional science writers. All texts are in Swedish.
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5.
  • Abbott, Benjamin W., et al. (författare)
  • Biomass offsets little or none of permafrost carbon release from soils, streams, and wildfire an expert assessment
  • 2016
  • Ingår i: Environmental Research Letters. - 1748-9326. ; 11:3
  • Tidskriftsartikel (refereegranskat)abstract
    • As the permafrost region warms, its large organic carbon pool will be increasingly vulnerable to decomposition, combustion, and hydrologic export. Models predict that some portion of this release will be offset by increased production of Arctic and boreal biomass; however, the lack of robust estimates of net carbon balance increases the risk of further overshooting international emissions targets. Precise empirical or model-based assessments of the critical factors driving carbon balance are unlikely in the near future, so to address this gap, we present estimates from 98 permafrost-region experts of the response of biomass, wildfire, and hydrologic carbon flux to climate change. Results suggest that contrary to model projections, total permafrost-region biomass could decrease due to water stress and disturbance, factors that are not adequately incorporated in current models. Assessments indicate that end-of-the-century organic carbon release from Arctic rivers and collapsing coastlines could increase by 75% while carbon loss via burning could increase four-fold. Experts identified water balance, shifts in vegetation community, and permafrost degradation as the key sources of uncertainty in predicting future system response. In combination with previous findings, results suggest the permafrost region will become a carbon source to the atmosphere by 2100 regardless of warming scenario but that 65%-85% of permafrost carbon release can still be avoided if human emissions are actively reduced.
6.
  • Gålfalk, Magnus, et al. (författare)
  • Making methane visible
  • 2016
  • Ingår i: Nature Climate Change. - Nature Publishing Group. - 1758-678X. ; 6, s. 426-430
  • Tidskriftsartikel (refereegranskat)abstract
    • Methane (CH4) is one of the most important greenhouse gases, and an important energy carrier in biogas and natural gas. Its large-scale emission patterns have been unpredictable and the source and sink distributions are poorly constrained. Remote assessment of CH4 with high sensitivity at a m2 spatial resolution would allow detailed mapping of the near-ground distribution and anthropogenic sources in landscapes but has hitherto not been possible. Here we show that CH4gradients can be imaged on the <m2 scale at ambient levels (~1.8 ppm) and filmed using optimized infrared (IR) hyperspectral imaging. Our approach allows both spectroscopic confirmation and quantification for all pixels in an imaged scene simultaneously. It also has the ability to map fluxes for dynamic scenes. This approach to mapping boundary layer CH4 offers a unique potential way to improve knowledge about greenhouse gases in landscapes and a step towards resolving source–sink attribution and scaling issues.
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7.
  • Hallquist, Åsa Marita, et al. (författare)
  • On-board Measurements of Nanoparticles from a SCR-Equipped Marine Diesel Engine
  • 2013
  • Ingår i: Environmental Science & Technology. - 0013-936X. ; 47:2
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study nanoparticle emissions have been characterised on-board a ship with focus on number, size and volatility. Measurements were conducted on one of the ship’s four main 12 600 kW medium–speed diesel engines which use low sulphur marine residual fuel and have a Selective Catalytic Reduction (SCR) system for NOX abatement. The particles were measured after the SCR with an engine exhaust particle sizer spectrometer (EEPS), giving particle number and mass distributions in the size range of 5.6-560 nm. The thermal characteristics of the particles were analysed using a volatility tandem DMA system (VTDMA). A dilution ratio of 450-520 was used which is similar to the initial real-world dilution. At a stable engine load of 75% of the maximum rated power, and after dilution and cooling of the exhaust gas, there was a bimodal number size distribution, with a major peak at ~10 nm and a smaller peak at around 30-40 nm. The mass distribution peaked around 20 nm and at 50-60 nm. The emission factor for particle number, EFPN, for an engine load of 75% in the open-sea was found to be 10.4 ± 1.6 × 1016 (kg fuel)-1 and about 50% of the particles by number were found to have a non-volatile core at 250 °C. Additionally, 20 nm particles consist of ~40% of non-volatile material by volume (evaporative temperature 250 °C) while the particles with a particle diameter <10 nm evaporate completely at a temperature of 130-150 °C. Emission factors for NOX, CO and CO2 for an engine load of 75% in the open-sea were determined to 4.06 ± 0.3 g (kg fuel)-1, 2.15 ± 0.06 g (kg fuel)-1 and 3.23 ± 0.08 kg (kg fuel)-1, respectively. This work contributes to an improved understanding of particle emissions from shipping using modern pollution reduction measures such as SCR and fuel with low sulphur content.
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8.
  • Khosravi, Maryam, 1975- (författare)
  • Diurnal variation of stratospheric short-lived species
  • 2012
  • Licentiatavhandling (övrigt vetenskapligt)abstract
    • Diurnal variation of stratospheric short-lived species Maryam Khosravi Chalmers University of Technology Department of Earth and Space Sciences Abstract The depletion of ozone in the stratosphere has a direct impact on the amount of ultraviolet radiation reaching the Earth’s surface. The ozone abundance and distribution is controlled by the photo-chemical reactions and catalytic cycles involving halogens (chlorine and bromine), odd hydrogen and odd nitrogen species as well as by atmospheric transport. An introduction to ozone related chemistry of the stratosphere and modelling of short-lived species using photo-chemical models is presented. A one dimensional (1D) atmospheric model is used in two distinct studies: modeling of short-lived species in the Arctic lower stratosphere (paper I) and in the tropical mid to upper stratosphere (paper II). The first part of this thesis describes the diurnal variation of chlorine monoxide, ClO, which is the most important short-lived species controlling ozone in the polar lower stratosphere during winter and early-spring. The ClO-dimer cycle, involving ClO and its nighttime reservoir Cl2O2, contributes to about 75%of the polar ozone loss. ClO measurements from an airborne submillimeter radiometer in the Arctic twilight have been compared with the results from a 1D photo-chemical model (MISU-1D), in order to validate the model and to test the kinetics of the reactions controlling the partitioning of chlorine species during the course of a day. The results show that cross sections leading to faster photolysis rates of Cl2O2 match best with the ClO observations. This is consistent with the recent version of the chemical kinetics evaluation by the Jet Propulsion Laboratory. Slower photolysis rates can not be reconciled with the observations since active chlorine higher than the total available chlorine would be required. The model reproduces higher nighttime ClO than the observations, however the nighttime ClOmodelled using recent JPL recommendations of the thermal equilibrium constant agree within the uncertainty range of the observations. The sensitivity of the model to the assumed albedo and temperature are also tested. Neither the temperature nor the albedo uncertainties allow us to reconcile the model with the lower observed nighttime ClO. Moreover, it is found that the ClO-BrO cycle decreases ClO mostly around sunrise and sunset. The second part of the thesis presents the partitioning and diurnal variation of chlorine, bromine, hydrogen, nitrogen and oxygen species in the tropics from the stratosphere to the lower mesosphere. Model results of the diurnal variation of HOCl (as one of the chlorine reservoirs), the related short-lived species ClO and HO2 and HCl (as the main chlorine reservoir) for the tropics and three altitudes (35, 45 and 55 km) are compared with measurements from five satellite instruments. The model results generally agree with the observations both in terms of the absolute values and the differences between day and night.
9.
  • Lopez-Hilfiker, F D, et al. (författare)
  • Molecular Composition and Volatility of Organic Aerosol in the Southeastern U.S.: Implications for IEPOX Derived SOA.
  • 2016
  • Ingår i: Environmental science & technology. - 1520-5851. ; 50:5, s. 2200-2209
  • Tidskriftsartikel (refereegranskat)abstract
    • We present measurements as part of the Southern Oxidant and Aerosol Study (SOAS) during which atmospheric aerosol particles were comprehensively characterized. We present results utilizing a Filter Inlet for Gases and AEROsol coupled to a chemical ionization mass spectrometer (CIMS). We focus on the volatility and composition of isoprene derived organic aerosol tracers and of the bulk organic aerosol. By utilizing the online volatility and molecular composition information provided by the FIGAERO-CIMS, we show that the vast majority of commonly reported molecular tracers of isoprene epoxydiol (IEPOX) derived secondary organic aerosol (SOA) is derived from thermal decomposition of accretion products or other low volatility organics having effective saturation vapor concentrations <10(-3) μg m(-3). In addition, while accounting for up to 30% of total submicrometer organic aerosol mass, the IEPOX-derived SOA has a higher volatility than the remaining bulk. That IEPOX-SOA, and more generally bulk organic aerosol in the Southeastern U.S. is comprised of effectively nonvolatile material has important implications for modeling SOA derived from isoprene, and for mechanistic interpretations of molecular tracer measurements. Our results show that partitioning theory performs well for 2-methyltetrols, once accretion product decomposition is taken into account. No significant partitioning delays due to aerosol phase or viscosity are observed, and no partitioning to particle-phase water or other unexplained mechanisms are needed to explain our results.
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10.
  • Zhao, D. F., et al. (författare)
  • Size-dependent hygroscopicity parameter (κ) and chemical composition of secondary organic cloud condensation nuclei
  • 2015
  • Ingår i: Geophysical Research Letters. - 1944-8007. ; 42:24
  • Tidskriftsartikel (refereegranskat)abstract
    • Secondary organic aerosol components (SOA) contribute significantly to the activation of cloud condensation nuclei (CCN) in the atmosphere. The CCN activity of internally mixed submicron SOA particles is often parameterized assuming a size-independent single-hygroscopicity parameter κ. In the experiments done in a large atmospheric reactor (SAPHIR, Simulation of Atmospheric PHotochemistry In a large Reaction chamber, Jülich), we consistently observed size-dependent κ and particle composition for SOA from different precursors in the size range of 50 nm–200 nm. Smaller particles had higher κ and a higher degree of oxidation, although all particles were formed from the same reaction mixture. Since decreasing volatility and increasing hygroscopicity often covary with the degree of oxidation, the size dependence of composition and hence of CCN activity can be understood by enrichment of higher oxygenated, low-volatility hygroscopic compounds in smaller particles. Neglecting the size dependence of κ can lead to significant bias in the prediction of the activated fraction of particles during cloud formation.
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