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1.
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2.
  • 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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3.
  • 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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4.
  • 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.
5.
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6.
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7.
  • Jones, Ashley, 1977- (författare)
  • Validation and time series analysis of global stratospheric data sets
  • 2009
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • The depletion of ozone from the stratosphere and the impact of global warming have been identified as phenomena caused as a result of anthropogenic activity. Scientists are thus trying to find quicker and more reliable ways to analyse these environmental problems. Remote sensing of the atmosphere using satellites is perhaps the most cost effective method. One beneficial application is the acquisition of vertical profiles of atmospheric species on a global scale with good spatial and temporal resolutions. An example of an instrument that can achieve this is the Sub-Millimetre Radiometer (SMR) aboard the Odin satellite that launched in 2001, which retrieves vertical limb profiles of numerous trace gases, including stratospheric ozone. This thesis presents a validation summary for primarily the Odin/SMR ozone data products, v1.2, v2.0 and v2.1 (for the 501.8 GHz band in the microwave region). Comparisons are made to v4.61 data obtained from the Interferometer for Passive Atmospheric Soundings (MIPAS) instrument, on board the ENVISAT satellite. Further analysis compares Odin/SMR mixing ratios to balloon sonde data. It is suggested from the results found here that Odin/SMR v2.1 ozone data should be used for scientific purposes. Odin/ SMR is also compared to its sister instrument, the Optical Spectrograph Infra-Red Imaging System (Odin/OSIRIS). Results show an excellent agreement between coincident profiles (typically < 10%). The fact that the two fundamentally different measurement geometries agree so well, provides confidence in the robustness of both techniques. Data assimilation is also shown to be a viable application for validation of satellite measurements when very few coincident data are available between satellite measurements and balloon sondes. The second topic covered in this thesis concerns time series analysis. One study involves modelling ozone’s evolution using linear regression. It is shown that by combining various atmospheric data sets that it is possible to estimate trends of stratospheric ozone, using an example of six satellite instruments covering 1979-2008. It is found that the upper stratosphere (35-45 km) at mid-latitudes shows the most promising signs of ozone recovery (1.7%/decade), although trend values are found not to be significant at a 95% confidence level. A similar method is applied to other shorter data sets of various other molecules such as; water vapour (H2O), chlorine monoxide (ClO), and hydrochloric acid (HCl), all three of which play important roles in the stratosphere and ultimately the recovery of stratospheric ozone. Trend analyses of ClO and HCl show that since the late 1990s abundances of these molecules have reduced in the upper stratosphere (35-45 km). The results found here confirm how effective the 1987 Montreal protocol and its amendments have been in reducing the total amount of stratospheric chlorine.
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8.
  • Löfgren, Johan, 1983-, et al. (författare)
  • Tropospheric correction for InSAR using interpolated ECMWF data and GPS zenith total delay from the Southern California Integrated GPS Network
  • 2010
  • Ingår i: Proceedings of the 2010 IEEE International Geoscience and Remote Sensing Symposium, Proceedings DVD-ROM. - 978-1-4244-9566-5 ; s. 4503-4506
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • A tropospheric correction method for Interferometric Synthetic Aperture Radar (InSAR) was developed using profiles from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Zenith Total Delay (ZTD) from the Global Positioning System (GPS). The ECMWF data were interpolated into a finer grid with the Stretched Boundary Layer Model (SBLM) using a Digital Elevation Model (DEM) with a horizontal resolution of 1 arcsecond. The output were converted into ZTD and combined with the GPS ZTD in order to achieve tropospheric correction maps utilizing both the high spatial resolution of the SBLM and the high accuracy of the GPS. These maps were evaluated for three InSAR images, with short temporal baselines (implying no surface deformation), from Envisat during 2006 on an area stretching northeast from the Los Angeles basin towards Death Valley. The RMS in the InSAR images was greatly reduced, up to 32%, when using the tropospheric corrections. Two of the residuals showed a constant gradient over the area, suggesting a remaining orbit error. This error was reduced by reprocessing the troposphere corrected InSAR images with the result of an overall RMS reduction of 15 − 68%.
9.
  • Löfgren, Johan, 1983-, et al. (författare)
  • Tropospheric Correction for InSAR Using Interpolated ECMWF Data and GPS Zenith Total Delay From the Southern California Integrated GPS Network
  • 2010
  • Ingår i: IEEE International Geoscience and Remote Sensing Symposium, 25 - 30 July 2010, Honolulu, Hawaii, USA.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • A tropospheric correction method for Interferometric Synthetic Aperture Radar (InSAR) was developed using profiles from the European Centre for Medium-Range Weather Forecasts (ECMWF) and Zenith Total Delay (ZTD) from the Global Positioning System (GPS). The ECMWF data were interpolated into a finer grid with the Stretched Boundary Layer Model (SBLM) using a Digital Elevation Model (DEM) with a horizontal resolution of 1 arcsecond. The output were converted into ZTD and combined with the GPS ZTD in order to achieve tropospheric correction maps utilizing both the high spatial resolution of the SBLM and the high accuracy of the GPS. These maps were evaluated for three InSAR images, with short temporal baselines (implying no surface deformation), from Envisat during 2006 on an area stretching northeast from the Los Angeles basin towards Death Valley. The RMS in the InSAR images was greatly reduced, up to 32%, when using the tropospheric corrections. Two of the residuals showed a constant gradient over the area, suggesting a remaining orbit error. This error was reduced by reprocessing the troposphere corrected InSAR images with the result of an overall RMS reduction of 15 − 68%.
10.
  • Mattsson, Eskil, 1981-, et al. (författare)
  • Tropisk avskogning måste lösas globalt
  • 2007
  • Ingår i: Göteborgsposten. ; :12 dec 2007
  • Tidskriftsartikel (populärvet., debatt m.m.)abstract
    • Det pågående klimatmötet ska ta ställning till hur den tropiska avskogningen ska minska. Ett förslag är att låta markägare få större ekonomisk kompensation än den intäkt en avverkning skulle ge. Norge går före genom att satsa 17,5 miljarder kronor och Världsbanken har gått in med stora summor, skriver Eskil Mattsson, Madelene Ostwald och Matilda Palm, som är på plats på Bali.
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