Viser treff 256-275 av 942

    • Estimating Radiative Forcing With a Nonconstant Feedback Parameter and Linear Response 

      Fredriksen, Hege-Beate; Rugenstein, Maria A.A.; Graversen, Rune (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-06)
      A new algorithm is proposed for estimating time-evolving global forcing in climate models. The method is a further development of the work of Forster et al. (2013), <a href=https://doi.org/10.1002/jgrd.50174>https://doi.org/10.1002/jgrd.50174</a>, taking into account the non-constancy of the global feedbacks. We assume that the non-constancy of this global feedback can be explained as a time-scale ...
    • Estimating solar irradiation in the Arctic 

      Babar, Bilal; Boström, Tobias (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-22)
      Solar radiation data plays an important role in pre-feasibility studies of solar electricity and/or thermal system installations. Measured solar radiation data is scarcely available due to the high cost of installing and maintaining high quality solar radiation sensors (pyranometers). Indirect measured radiation data received from geostationary satellites is unreliable at latitudes above 60 degrees ...
    • Estimating the Space Debris Density Function using Radar Beam Park Measurements 

      Vierinen, Juha; Hermann, Frank; Kastinen, Daniel; Kero, Johan; Markkanen, Jussi; Grydeland, Tom (Journal article; Tidsskriftartikkel; Peer reviewed, 2023)
      Estimating the density of space debris as a function of orbital elements and size is crucial for determining the risk of collision of spacecraft. For objects 1 cm or larger in diameter, this information can be obtained using beam park observations made with powerful ground based radars. This study presents a novel technique for estimating the density of space debris as a function of orbital elements ...
    • Estimation of atmospheric temperature and humidity profiles from MODIS data and radiosond data using artificial neural network 

      Akbari, Vahid; Amini, Jalal; Saradjian, Mohammad Reza; Motagh, Mahdi (Journal article; Tidsskriftartikkel; Peer reviewed, 2008)
      The aim of this study is to test the quality of the neural network for retrieving the temperature and humidity by comparison with the radiosond values and a linear regression method. Remote sensed images give useful information about the atmosphere. In this article, MODIS data is used to retrieve temperature and humidity profiles of the atmosphere. Two methods of linear regression and artificial ...
    • Estimation of statistical moments for single point measurements in the Scrape Off Layer 

      Kube, Ralph; Garcia, Odd Erik (Conference object; Konferansebidrag, 2014-03-17)
    • Evaluating CM-SAF solar radiation CLARA-A1 and CLARA-A2 datasets in Scandinavia 

      Babar, Bilal; Graversen, Rune; Boström, Tobias (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-26)
      Estimating/retrieving solar radiation through satellite-based remote sensing provides larger spatial coverage compared to other methods. Accurate estimates of incoming solar radiation is important when planning new solar energy installations. In addition, these estimates are also used in climate studies. Geostationary satellites are ideal for estimating solar radiation but cannot be used for high ...
    • Evaluating Landsat-8 and Sentinel-2 Data Consistency for High Spatiotemporal Inland and Coastal Water Quality Monitoring 

      Hafeez, Sidrah; Wong, Man Sing; Abbas, Sawaid; Asim, Muhammad (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-30)
      The synergy of fine-to-moderate-resolutin (i.e., 10–60 m) satellite data of the Landsat-8 Operational Land Imager (OLI) and the Sentinel-2 Multispectral Instrument (MSI) provides a possibility to monitor the dynamics of sensitive aquatic systems. However, it is imperative to assess the spectral consistency of both sensors before developing new algorithms for their combined use. This study evaluates ...
    • Evaluation of a method to derive ionospheric conductivities using two auroral emissions (428 and 630 nm) measured with a photometer at Tromsø (69.6°N) 

      Adachi, K; Nozawa, Satonori; Ogawa, Y; Brekke, Asgeir; Hall, Chris; Fujii, Ryochi (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-07-03)
      This paper mainly aims at evaluating capabilities of derivation of ionospheric conductivities using two principal auroral emissions (427.8 and 630 nm). We have evaluated a photometric method of derivation of ionospheric conductivities based on simultaneous observations of a photometer (feld of view = ~1.2°), a digital camera, and the EISCAT UHF radar (feld of view = ~0.7°) operated at Tromsø, ...
    • Evaluation of a sub-kilometre NWP system in an Arctic fjord-valley system in winter 

      Valkonen, Teresa Maaria; Stoll, Patrick; Batrak, Yurii; Køltzow, Morten Andreas Ødegaard; Schneider, Thea Maria; Stigter, Emmy E.; Aashamar, Ola B.; Støylen, Eivind; Jonassen, Marius Opsanger (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-28)
      Terrain challenges the prediction of near-surface atmospheric conditions, even in kilometre-scale numerical weather prediction (NWP) models. In this study, the ALADIN-HIRLAM NWP system with 0.5 km horizontal grid spacing and an increased number of vertical levels is compared to the 2.5-km model system similar to the currently operational NWP system at the Norwegian Meteorological Institute. The ...
    • Evaluation of adhesive-free focused high-frequency PVDF copolymer transducers fabricated on spherical cavities 

      Habib, Anowarul; Wagle, Sanat; Decharat, Adit; Melandsø, Frank (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-16)
      A layer-by-layer deposition method for fabricating a focused ultrasonic transducer from piezoelectric copolymers has been developed. The fabrication process involves engraving a spherical cavity of 2 mm diameter on polyethyleneimines (PEI) polymer substrate. Surface roughness of the engraved spherical cavity is measured and compared with simulated line scan. Then, the transducer response was ...
    • Evaluation of an emergent feature of sub-shelf melt oscillations from an idealized coupled ice sheet-ocean model using FISOC (v1.1) - ROMSIceShelf (v1.0) - Elmer/Ice (v9.0) 

      Zhao, Chen; Gladstone, Rupert; Galton-Fenzi, Benjamin Keith; Gwyther, David; Hattermann, Tore (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-15)
      Changes in ocean-driven basal melting have a key influence on the stability of ice shelves, the mass loss from the ice sheet, ocean circulation, and global sea level rise. Coupled ice sheet–ocean models play a critical role in understanding future ice sheet evolution and examining the processes governing ice sheet responses to basal melting. However, as a new approach, coupled ice sheet–ocean systems ...
    • Evaluation of crystalline structure quality of Czochralski-silicon using near-infrared tomography 

      Jensen, Mathias Novik; Hellesø, Olav Gaute (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-22)
      In this work, three silicon samples are subject to tomographic scans using a 1.6μm laser. The samples were prematurely terminated due to anomalies during the Czhochralski-process. They are taken as analogues of the in situ crystal, where one sample has known aberrant structure in its lowermost 45 mm. The results of the tomographic scans show a distinct difference in transmission profile between ...
    • Evaluation of feature ranking and regression methods for oceanic chlorophyll-a estimation 

      Blix, Katalin; Eltoft, Torbjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-03-22)
      This paper evaluates two alternative regression techniques for oceanic chlorophyll-a (Chl-a) content estimation. One of the investigated methodologies is the recently introduced Gaussian process regression (GPR) model. We explore two feature ranking methods derived for the GPR model, namely sensitivity analysis (SA) and automatic relevance determination (ARD). We also investigate a second ...
    • An evaluation of International Reference Ionosphere electron density in the polar cap and cusp using EISCAT Svalbard radar measurements 

      Bjoland, Lindis Merete; Belyey, Vasyl; Løvhaug, Unni Pia; La Hoz, Cesar (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-09-13)
      Incoherent scatter radar measurements are an important source for studies of ionospheric plasma parameters. In this paper the EISCAT Svalbard radar (ESR) long-term database is used to evaluate the International Reference Ionosphere (IRI) model. The ESR started operations in 1996, and the accumulated database up to 2012 thus covers 16 years, giving an overview of the ionosphere in the polar cap and ...
    • Evaluation of Six Atmospheric Reanalyses over Arctic Sea Ice from Winter to Early Summer 

      Graham, Robert; Cohen, Lana; Ritzhaupt, Nicole; Segger, Benjamin; Graversen, Rune; Rinke, Anette; Walden, Von P.; Granskog, Mats; Hudson, Stephen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-19)
      This study evaluates the performance of six atmospheric reanalyses (ERA-Interim, ERA5, JRA-55, CFSv2, MERRA-2, and ASRv2) over Arctic sea ice from winter to early summer. The reanalyses are evaluated using observations from the Norwegian Young Sea Ice campaign (N-ICE2015), a 5-month ice drift in pack ice north of Svalbard. N-ICE2015 observations include surface meteorology, vertical profiles from ...
    • Evaluation of the Weather Research and Forecasting (WRF) model with respect to wind in complex terrain 

      Solbakken, Kine; Birkelund, Yngve (Journal article; Tidsskriftartikkel; Peer reviewed, 2018)
      In this study the performance of the Weather Research and Forecast (WRF) model in a complex and coastal terrain has been evaluated with focus on wind resource assessment. The study area is a small community on the northern part of the island Senja, Norway. The community, with fishery and seafood as its main industry, is being limited by poor grid connection. One of the solutions is to increase ...
    • The Everchanging Pulsating White Dwarf GD358 

      Solheim, Jan Erik; Kepler, S.O.; Nather, R. Edward; Gonzalez Perez, Jose M.; Johannessen, Frank; Winget, Don E.; Nitta, Atsuko; Kleinman, S. J.; Metcalfe, Travis; Sekiguchi, Kazuhiro; Xiaojun, Jiang; Sullivan, Denis; Sullivan, Tiri; Janulis, Rimvydas; Meistas, Edmund; Kalytis, Romualdas; Krzesinski, Jurek; Ogloza, Waldemar; O’Donoghue, Darragh; Romero-Colmenero, Encarni; Martinez, Peter; Dreizler, Stefan; Deetjen, Jochen; Nagel, Thorsten; Schuh, Sonja L.; Vauclair, Gerard; Ning, Fu Jian; Chevreton, Michel; Kanaan, Antonio; Costa, Jos´e Eduardo; Costa, Alex Fabiano Murillo; Wood, Matt A.; Silvestri, Nicole; Ahrens, T.J.; Jones, Aaron Kyle; Collins, Ansley E.; Boyer, Martha; Mukadam, Anjum; Klumpe, Eric W.; Larrison, Jesse; Kawaler, Steve; Riddle, Reed; Ulla, Ana; Bradley, Paul (Journal article; Tidsskriftartikkel; Peer reviewed, 2003-01-23)
      We report 323 hours of nearly uninterrupted time series photometric observations of the DBV star GD 358 acquired with the Whole Earth Telescope (WET) during May 23rd to June 8th, 2000. We acquired more than 232 000 independent measurements. We also report on 48 hours of time-series photometric observations in Aug 1996. We detected the non-radial g-modes consistent with degree ℓ = 1 and radial ...
    • Evidence of L-mode electromagnetic wave pumping of ionospheric plasma near geomagnetic zenith 

      Leyser, Thomas B; James, H Gordon; Gustavsson, Björn Johan; Rietveld, Michael T (Journal article; Peer reviewed, 2018-02-21)
      The response of ionospheric plasma to pumping by powerful HF (high frequency) electromagnetic waves transmitted from the ground into the ionosphere is the strongest in the direction of geomagnetic zenith. We present experimental results from transmitting a left-handed circularly polarized HF beam from the EISCAT (European Incoherent SCATter association) Heating facility in magnetic zenith. The ...
    • Evidence of low-dimensional chaos in magnetized plasma turbulence 

      Živkovic, Tatjana; Rypdal, Kristoffer (Working paper; Arbeidsnotat, 2008-03-10)
      We analyze probe data obtained from a toroidal magnetized plasma configuration suitable for studies of low-frequency gradient-driven instabilities. These instabilities give rise to field-aligned convection rolls analogous to Rayleigh-Benard cells in neutral fluids, and may theoretically develop similar routes to chaos. When using mean-field dimension analysis, we observe low dimensionality, but ...
    • The evolution in graphitic surface wettability with first-principles quantum simulations: the counterintuitive role of water 

      Lu, Jin-You; Lai, Chia-Yun; Almansoori, Ibraheem; Chiesa, Matteo (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-08-08)
      The surface wettability of graphite has gained a lot of interest in nanotechnology and fundamental studies alike, but the types of adsorptions that dominate its time resolved surface property variations in ambient environment are still elusive. Prediction of the intrinsic surface wettability of graphite from first-principles simulations offers an opportunity to clarify the overall evolution. In this ...