Viser treff 2956-2975 av 4765

    • Observations of the urban boundary layer in a cold climate city 

      Varentsov, Mikhail; Konstantinov, Pavel; Repina, I.; Artamonov, Arseny; Pechkin, Alexander Sergeevich; Ezau (Esau), Igor; Baklanov, Aleksander (Journal article; Tidsskriftartikkel, 2022-11-30)
      Cold environment supports a large diversity of local climates. Among them, urban climates in northern cities stand out for their pronounced warm temperature anomaly known as the Urban Heat Island (UHI). UHI in northern cities has been already studies through satellite images and in-situ observations in the urban canopy layer (UCL). Yet, the vertical structure of the urban atmospheric boundary layer ...
    • Observations of thermospheric neutral winds within the polar cusp and the auroral oval using a Doppler imaging system (DIS). 

      Henriksen, K.; Rees, D.; Smith, R.W.; Signernes, F.; Brandstrom, U.; Harris, M.; Maskall, G. (Journal article; Tidsskriftartikkel, 1998)
      Two Doppler imaging systems (DIS) or wide-field imaging Fabry-Perot interferometers (FPI), have recently been commissioned, one at the Auroral Station, Adventdalen, Longyearbyen, Svalbard, and the second at the IRF, Kiruna, Sweden. These instruments can provide wide-field (600 * 800 km) images of neutral wind flows in the upper thermosphere, by measuring the Doppler shift of the atomic oxygen forbidden ...
    • Observatoriet i 80-årene 

      Trulsen, Jan (Journal article; Tidsskriftartikkel, 1980)
      På terskelen til en ny dekade er det naturlig å stille spørsmålet hva Observatoriets fremtidige rolle skal bli. Vil det fortsatt være behov for forskningsinnsats på Observatoriets tradisjonelle fagfelter, eller skal innsatsen etter hvert anta en annen retning? Vi skal forsøke å belyse dette ved først å rette blikket bakover for derigjennom å få øye på de store utviklingslinjer i den internasjonale ...
    • Observed and unobserved heterogeneity in failure data analysis 

      Zaki, Rezgar; Barabadi, Abbas; Barabady, Javad; Qarahasanlou, Ali Nouri (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-08)
      In reality, failure data are often collected under diffract operational conditions (covariates), leading to heterogeneity among the data. Heterogeneity can be classified as observed and unobserved heterogeneity. Un-observed heterogeneity is the effect of unknown, unrecorded, or missing covariates. In most reliability studies, the effect of unobserved covariates is neglected. This may lead to inaccurate ...
    • Observing electric field and neutral wind with EISCAT 3D 

      Stamm, Johann; Vierinen, Juha; Gustavsson, Björn (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-16)
      Measurements of height-dependent electric field (E) and neutral wind (u) are important governing parameters of the Earth's upper atmosphere, which can be used to study, for example, how auroral currents close or how energy flows between the ionized and neutral constituents. The new EISCAT 3D (E3D) incoherent scatter radar will be able to measure a three-dimensional ion velocity vector (v) at each ...
    • Observing Mesospheric Turbulence With Specular Meteor Radars: A Novel Method for Estimating Second-Order Statistics of Wind Velocity 

      Vierinen, Juha; Chau, Jorge L.; Charuvil, Harikrishnan; Urco, Miguel; Clahsen, Matthias; Avsarkisov, Victor; Marino, Raffaele; Volz, Ryan (Journal article; Peer reviewed, 2019-07)
      There are few observational techniques for measuring the distribution of kinetic energy within the mesosphere with a wide range of spatial and temporal scales. <br>This study describes a method for estimating the three‐dimensional mesospheric wind field correlation function from specular meteor trail echoes. Each radar echo provides a measurement of a one‐dimensional projection of the wind velocity ...
    • Observing Oil Releases from Platforms Using Synthetic Aperture Radar 

      Skrunes, Stine; Johansson, Malin; Brekke, Camilla (Conference object; Konferansebidrag, 2018)
      Synthetic aperture radar (SAR) is used for operational surveillance of ocean areas and oil spill detection. Oil spills are frequently detected around oil platforms due to the releases of so-called produced water (PW), which is water containing low concentrations of oil that can form surface slicks similar to other oil spills. PW releases are legal within given limits. Understanding the signatures ...
    • Occurence of free gas and focused fluid systems in the Veslemøy High area, SW Barents Sea 

      Pless, Gustav (Master thesis; Mastergradsoppgave, 2009-05-15)
      The high-resolution 3D seismic survey EL0001 allowed to document the subsurface fluid migration system and fluid accumulations within Veslemøy High, SW Barents Sea. Fluids migrate both through Cretaceous and Tertiary sediments, but also through younger glacial sediments. Veslemøy High is a structurally isolated high at the Cretaceous and Tertiary levels bounded by N-S trending west-dipping normal ...
    • The occurrence of flow transformations within sandy submarine fans: A case study from the Eocene on Spitsbergen 

      Broze, Elliot Alessandro (Master thesis; Mastergradsoppgave, 2017-05-15)
      The Van Keulenfjorden transect on Spitsbergen offers valuable insight into submarine processes, with well exposed seismic scale clinoforms of Paleocene and Eocene age, which show the distribution of sediments from deltaic to basin floor environments. Several progradational submarine fans are preserved as cliffs on Hyrnestabben. They serve as an analogues to coarse grained submarine fans in provinces ...
    • Ocean Applications 

      Migliaccio, M.; Nunziata, F.; Marino, A.D.; Brekke, Camilla; Skrunes, Stine (Chapter; Bokkapittel, 2021-05-11)
      In this chapter, the most promising techniques to observe oil slicks and to detect metallic targets at sea using polarimetric synthetic aperture radar (SAR) data are reviewed and critically analysed. The detection of oil slicks in SAR data is made difficult not only by the presence of speckle but also by the presence of, e.g. biogenic films, low-wind areas, rain cells, currents, etc., which increase ...
    • Ocean modeling in Northern Norway: A tidal verification study 

      Djuve, Hans Kristian (Master thesis; Mastergradsoppgave, 2014-06-02)
      The coast of Northern Norway has for the first time been modeled using an unstructured grid. The modeling is done using two separate grids of different resolution, and the model data is compared to measurements done along the coast to verify its performance for both the fine and coarse grid. The model is a 2-D depth integrated model of tidal circulation with bottom friction. The data have been ...
    • Ocean temperature variability for the past 60 years on the Norwegian-Svalbard margin influences gas hydrate stability on human time scales 

      Ferré, Benedicte; Mienert, Jurgen; Feseker, Tomas (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-10-23)
      The potential impact of future climate change on methane release from oceanic gas hydrates is the subject of much debate. We analyzed World Ocean Database quality controlled data on the Norwegian‐Svalbard continental margin from the past 60 years to evaluate the potential effect of ocean temperature variations on continental margin gas hydrate reservoirs. Bottom water temperatures in the Norwegian‐Svalbard ...
    • Oceanographic variability and change in two fjords in northern Norway 

      Bjørndalen, Elena (Mastergradsoppgave; Master thesis, 2023-06-01)
      Long-term hydrographic time series data from two fixed stations in the northern Norwegian fjords Malangen and Balsfjorden from the period 1980 - 2022 have been examined. The data have been supplemented with model results from the ocean model NorFjords160 over the period April 1st 2017 to December 31st 2022. To gain a deeper understanding of the oceanographic variability and change, the environmental ...
    • Octaiodoporphyrin and Octaiodocorrole: Isolation of a Cis Porphyrin Tautomer 

      Thomassen, Ivar Kristian (Doctoral thesis; Doktorgradsavhandling, 2018-09-28)
      Iodinated aromatics are excellent starting materials for further elaboration via transition-metal-catalyzed cross-coupling reactions. Considering the diverse applications of porphyrins and corroles - as photosensitizers in photodynamic therapy, dye sensitized solar cells, near-infrared dyes, gas sensors, nonlinear optical materials, and catalysts - the synthetic potential of β-polyiodinated or ...
    • ODEs whose Symmetry Groups are not Fiber-Preserving 

      Kruglikov, Boris Serafimovich; Schneider, Eivind (Journal article; Tidsskriftartikkel; Peer reviewed, 2023)
      We observe that, up to conjugation, a majority of higher order ODEs (ordinary differential equations) and ODE systems have only fiber-preserving point symmetries. By exploiting Lie's classification of Lie algebras of vector fields, we describe all exceptions to this in the case of scalar ODEs and systems of ODEs on a pair of functions. The scalar ODEs whose symmetry algebras are not fiber preserving ...
    • Offshore permafrost decay and massive seabed methane escape in water depths >20 m at the South Kara Sea shelf 

      Portnov, Alexey; Mienert, Jurgen; Cherkashov, Georgy; Rekant, Pavel; Semenov, Peter; Serov, Pavel; Vanshtein, Boris; Smith, Andrew James (Journal article; Tidsskriftartikkel; Peer reviewed, 2013-07-14)
      Since the Last Glacial Maximum (~19 ka), coastal inundation from sea-level rise has been thawing thick subsea permafrost across the Arctic. Although subsea permafrost has been mapped on several Arctic continental shelves, permafrost distribution in the South Kara Sea and the extent to which it is acting as an impermeable seal to seabed methane escape remains poorly understood. Here we use >1300 km ...
    • Oil Spill Analysis Using Hybrid-Polarization Synthetic Aperture Radar 

      Høifødt, Audun Leonard (Master thesis; Mastergradsoppgave, 2016-06-01)
      The goal for this thesis is to test various Hybrid-Polarization (HP) Synthetic Aperture Radar (SAR) parameters using actual HP data, and to evaluate the validity of these parameters with respect to oil slick detection. As part of the evaluation, the impact of the system noise and incidence angle on the SAR images is discussed. It is shown that the Signal-to-Noise Ratio (SNR) of the sensor has a ...
    • Oil Spill Behavior and Response in the Arctic. Risk Analysis of Existing Response Methods Applicable for the Arctic Conditions 

      Zhelezniak, Viktoriia (Master thesis; Mastergradsoppgave, 2021-06-01)
      Due to the demand for diversifying and modifying sources of raw materials and trade routes, the Arctic is the region of high interests. Development and carrying out the offshore activities associated with oil and gas industry and maritime transport are growing rapidly in the Arctic. However, an acute problem associated with the development of offshore activities is the ecological consequence caused ...
    • Oil spill characterization in the hybrid-polarity SAR domain using log-cumulants 

      Espeseth, Martine; Skrunes, Stine; Brekke, Camilla; Salberg, Arnt Børre; Jones, Cathleen; Holt, Benjamin (Peer reviewed; Journal article; Tidsskriftsartikkel, 2016-10-18)
      Log-cumulants have proven to be an interesting tool for evaluating the statistical properties of potential oil spills in polarimetric Synthetic Aperture Radar (SAR) data within the common horizontal (H) and vertical (V) polarization basis. The use of first, second, and third order sample log-cumulants has shown potential for evaluating the texture and the statistical distributions, as well as ...
    • Oil Spill Dispersion in Full-polarimetric and Hybrid-polarity SAR 

      Brekke, Camilla; Skrunes, Stine; Espeseth, Martine (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12-04)
      We show that indications of spatial dispersion effects on mineral oil slicks are observed by space-borne multipolarization synthetic aperture radar. This is readily perceived by eye when correlating multipolarization synthetic aperture radar observables with the ship track of the dispersion vessel. We investigate real full-polarimetric (linear transmit/linear receive) as well as simulated and real ...