Now showing items 381-400 of 1062

    • The impact of atmospheric Rossby waves and cyclones on the Arctic sea ice variability 

      Hofsteenge, Marte G.; Graversen, Rune Grand; Rydsaa, Johanne Hope; Rey, Zoé (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-17)
      The Arctic sea-ice extent has strongly declined over recent decades. A large inter-annual variability is superimposed on this negative trend. Previous studies have emphasised a significant warming effect associated with latent energy transport into the Arctic region, in particular due to an enhanced greenhouse effect associated with the convergence of the humidity transport over the Arctic. The ...
    • Multidisciplinary biophotonics, open science, and. . . plug & pray deep learning? 

      Opstad, Ida Sundvor (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-06)
      Due to its great creative potential for innovation and scientific discovery, inter- and multidisciplinary collaboration is being increasingly encouraged by institutions and funding agencies. The increased opportunities in the multidisciplinary arena also come with significant challenges like the added experimental, analytical and logistical complexity, blended with a high likelihood of miscommunications. ...
    • First observation of the anomalous electric field in the topside ionosphere by ionospheric modification over EISCAT 

      Kosch, Michael; Vickers, Hannah; Ogawa, Yasunobu; Senior, Andrew; Blagoveshchenskaya, Natalya (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-10-24)
      We have developed an active ground-based technique to estimate the steady state field-aligned anomalous electric field (E*) in the topside ionosphere, up to ~600 km, using the European Incoherent Scatter (EISCAT) ionospheric modification facility and UHF incoherent scatter radar. When pumping the ionosphere with high-power high-frequency radio waves, the F region electron temperature is significantly ...
    • First modulation of high-frequency polar mesospheric summer echoes by radio heating of the ionosphere 

      Senior, Andrew; Mahmoudian, Alireza; Pinedo Nava, Henry; La Hoz, Cesar; Rietveld, Michael T; Scales, Wayne A.; Kosch, M.J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-07-23)
      The first high-frequency (HF, 8 MHz) observations of the modulation of polar mesospheric summer echoes (PMSE) by artificial radio heating of the ionosphere are presented and compared to observations at 224 MHz and model predictions. The experiments were performed at the European Incoherent Scatter facility in northern Norway. It is shown that model results are in qualitative and partial quantitative ...
    • Increasing Multiyear Sea Ice Loss in the Beaufort Sea: A New Export Pathway for the Diminishing Multiyear Ice Cover of the Arctic Ocean 

      Babb, David G; Galley, Ryan; Howell, Stephen; Landy, Jack Christopher; Barber, David G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-16)
      Historically, multiyear sea ice (MYI) covered a majority of the Arctic and circulated through the Beaufort Gyre for years. However, increased ice melt in the Beaufort Sea during the early 2000s was proposed to have severed this circulation. Constructing a regional MYI budget from 1997 to 2021 reveals that MYI import into the Beaufort Sea has increased year-round, yet less MYI now survives through ...
    • Segmentation of PMSE data using random forests 

      Jozwicki, Dorota; Sharma, Puneet; Mann, Ingrid; Hoppe, Ulf-Peter Jürgen (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-22)
      EISCAT VHF radar data are used for observing, monitoring, and understanding Earth’s upper atmosphere. This paper presents an approach to segment Polar Mesospheric Summer Echoes (PMSE) from datasets obtained from EISCAT VHF radar data. The data consist of 30 observations days, corresponding to 56,250 data samples. We manually labeled the data into three different categories: PMSE, Ionospheric ...
    • Trans-polar drift-pathways of riverine European microplastic 

      Huserbråten, Mats Brockstedt Olsen; Hattermann, Tore; Broms, Cecilie; Albretsen, Jon (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-17)
      High concentrations of microplastic particles are reported across the Arctic Ocean–yet no meaningful point sources, suspension timelines, or accumulation areas have been identified. Here we use Lagrangian particle advection simulations to model the transport of buoyant microplastic from northern European rivers to the high Arctic, and compare model results to the flux of sampled synthetic particles ...
    • Quantitative assessment of two oil-in-ice surface drift algorithms 

      Martins de Aguiar, Victor Cesar; Dagestad, Knut-Frode; Hole, Lars Robert; Barthel, Knut Sven (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-02-04)
      The ongoing reduction in extent and thickness of sea ice in the Arctic might result in an increase of oil spill risk due to the expansion of shipping activity and oil exploration shift towards higher latitudes. This work assessed the response of two oil-in-ice surface drift models implemented in an open-source Lagrangian framework. By considering two numerical modeling experiments, our main finding ...
    • Impacts of a sudden stratospheric warming on the mesospheric metal layers 

      Feng, Wuhu; Kaifler, Bernd; Marsh, Daniel R.; Höffner, Josef; Hoppe, Ulf-Peter; Williams, Bifford P.; Plane, John M.C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-11)
      We report measurements of atomic sodium, iron and temperature in the mesosphere and lower thermosphere (MLT) made by ground-based lidars at the ALOMAR observatory (69°N, 16°E) during a major sudden stratospheric warming (SSW) event that occurred in January 2009. The high resolution temporal observations allow the responses of the Na and Fe layers to the SSW at high northern latitudes to be ...
    • A nested high-resolution unstructured grid 3-D ocean-sea ice-ice shelf setup for numerical investigations of the Petermann ice shelf and fjord 

      Prakash, Abhay; Zhou, Qin; Hattermann, Tore; Bao, Weiyang; Graversen, Rune Grand; Kirchner, Nina (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-18)
      Three-dimensional numerical simulation of circulation in fjords hosting marine-terminating ice shelves is challenging because of the complexity of processes involved in such environments. This often requires a comprehensive model setup. The following elements are needed: bathymetry (usually unknown beneath the glacier tongue), ice shelf draft (impacting water column thickness), oceanographic state ...
    • Multiplexed Mach-Zehnder interferometer assisted ring resonator sensor 

      Yadav, Mukesh; Aksnes, Astrid (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-04)
      A Mach-Zehnder interferometer assisted ring resonator configuration (MARC)-based multiplexed photonic sensor with a large measurement range is experimentally demonstrated. The presented MARC sensor consists of a balanced Mach-Zehnder interferometer and a ring resonator acting as a sensing component. It produces transmission responses with unique spectral signatures, which depend on the physical ...
    • Uncovering Contributing Factors to Interruptions in the Power Grid: An Arctic Case 

      Chiesa, Matteo; Bianchi, Filippo Maria; Eikeland, Odin Foldvik; Holmstrand, Inga Setså; Bakkejord, Sigurd; Santos, Sergio (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-01-03)
      Electric failures are a problem for customers and grid operators. Identifying causes and localizing the source of failures in the grid is critical. Here, we focus on a specific power grid in the Arctic region of Northern Norway. First, we collected data pertaining to the grid topology, the topography of the area, the historical meteorological data, and the historical energy consumption/production data. ...
    • The long sunspot cycle 23 predicts a significant temperature decrease in cycle 24 

      Solheim, Jan Erik; Stordahl, Kjell; Humlum, Ole (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-02-16)
      Relations between the length of a sunspot cycle and the average temperature in the same and the next cycle are calculated for a number of meteorological stations in Norway and in the North Atlantic region. No significant trend is found between the length of a cycle and the average temperature in the same cycle, but a significant negative trend is found between the length of a cycle and the ...
    • Understanding Cassini RPWS Antenna Signals Triggered by Dust Impacts 

      Ye, Sheng - Yi; Vaverka, Jakub; Nouzak, Libor; Sternovsky, Zoltan; Zaslavsky, Arnaud; Pavlu, Jirka; Mann, Ingrid; Hsu, Sean; Averkamp, Terrance, F.; Sulaiman, Ali H.; Pisa, D.; Hospodarsky, George; Kurth, William, S.; Horanyi, Mihaly (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-04)
      Electric field antennas are capable of detecting dust impacts in different space environment. We analyze the dust impact signals detected by the Cassini Radio and Plasma Wave Science instrument at different locations around Saturn and compare them with dust impact signals simulated in laboratory conditions and numerically. The spacecraft potential, the size, and capacitance of the impacted element ...
    • Isotope effect on filament dynamics in fusion edge plasmas 

      Meyer, Ole; Kendl, Alexander (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-04-20)
      The influence of the ion mass on filament propagation in the scrape-off layer of toroidal magnetised plasmas is analysed for various fusion relevant majority species, like hydrogen isotopes and helium, on the basis of a computational isothermal gyrofluid model for the plasma edge. Heavy hydrogen isotope plasmas show slower outward filament propagation and thus improved confinement properties ...
    • Concepts for structured illumination microscopy with extended axial resolution through mirrored illumination 

      Manton, James D.; Ströhl, Florian; Fiolka, Reto; Kaminski, Clemens F.; Rees, Eric J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-03-20)
      Wide-field fluorescence microscopy, while much faster than confocal microscopy, suffers from a lack of optical sectioning and poor axial resolution. 3D structured illumination microscopy (SIM) has been demonstrated to provide optical sectioning and to double the resolution limit both laterally and axially, but even with this the axial resolution is still worse than the lateral resolution of ...
    • On the symmetry of ionospheric polar cap patch exits around magnetic midnight 

      Moen, Jøran Idar; Gulbrandsen, Njål; Clausen, Lasse Boy Novock (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-07-14)
      In this paper we examine how polar cap patches, which have been frozen into the antisolar flow over the polar cap, are transported into the nighttime auroral oval. First we present a detailed case study from 12 January 2002, with continuous observations of polar cap patches exiting into the nighttime auroral oval in the Scandinavian sector. Satellite images of the auroral oval and all-sky camera ...
    • Dust observations from Parker Solar Probe: Dust ejection from the inner Solar System 

      Mann, Ingrid; Czechowski, Andrzej (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-02)
      Context. The FIELDS instrument onboard Parker Solar Probe (PSP) observes dust impacts on the spacecraft. The derived dust flux rates suggest that the particles originate from the vicinities of the Sun and are ejected by radiation pressure. Radiation pressure typically ejects particles of several 100 nm and smaller, which are also affected by the electromagnetic force.<p> Aims. We aim to understand ...
    • Effects of the tropospheric large-scale circulation on European winter temperatures during the period of amplified Arctic warming 

      Vihma, Timo; Graversen, Rune; Chen, Linling; Handorf, Dörthe; Skific, Natasa; Francis, Jennifer A.; Tyrrell, Nicholas; Hall, Richard; Hanna, Edward; Uotila, Petteri; Dethloff, Klaus; Karpechko, Alexey Yu.; Björnsson, Halldór; Overland, James E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-07-08)
      We investigate factors influencing European winter (DJFM) air temperatures for the period 1979–2015 with the focus on changes during the recent period of rapid Arctic warming (1998–2015). We employ meteorological reanalyses analysed with a combination of correlation analysis, two pattern clustering techniques, and backtrajectory airmass identification. In all five selected European regions, severe ...
    • A Lagrangian Snow‐Evolution System for Sea‐Ice Applications (SnowModel‐LG): Part I – Model Description 

      Liston, Glen E.; Itkin, Polona; Stroeve, Julienne C.; Tschudi, Mark; Stewart, J. Scott; Pedersen, Stine Højlund; Reinking, A.K.; Elder, Kelly (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-08-06)
      A Lagrangian snow-evolution model (SnowModel-LG) was used to produce daily, pan-Arctic, snow-on-sea-ice, snow property distributions on a 25 × 25-km grid, from 1 August 1980 through 31 July 2018 (38 years). The model was forced with NASA's Modern Era Retrospective-Analysis for Research and Applications-Version 2 (MERRA-2) and European Centre for Medium-Range Weather Forecasts (ECMWF) ReAnalysis-5th ...