Now showing items 261-280 of 1402

    • Subseasonal Predictions of Polar Low Activity Using a Hybrid Statistical-Dynamical Approach 

      Boyd, Kevin; Wang, Zhuo; Walsh, John; Stoll, Johannes Patrick (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-21)
      The subseasonal prediction of polar low (PL) activity is explored using a hybrid statistical-dynamical approach. A previously developed PL genesis potential index is paired with ECMWF reforecasts and forecasts to predict regional statistics of PL activity across the sub-Arctic. Regional PL activity is skillfully predicted in all regions at forecast ranges of up to a month. Additionally, the ...
    • 21st Century Scenario Forcing Increases More for CMIP6 Than CMIP5 Models 

      Fredriksen, Hege-Beate; Smith, Christopher J.; Modak, Angshuman; Rugenstein, Maria (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-16)
      Although the Coupled Model Intercomparison Project 6 (CMIP6) protocol provides an experiment to estimate effective radiative forcing (ERF), it is only quantified for few models. We present new estimates of ERF for models participating in CMIP6 by applying the method developed in Fredriksen et al. (2021, https://doi.org/10.1029/2020JD034145), and validate our approach with available fixed-SST forcing ...
    • Improving sea surface temperature in a regional ocean model through refined sea surface temperature assimilation 

      Iversen, Silje Christine; Sperrevik, Ann Kristin; Goux, Olivier (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-26)
      Infrared (IR) and passive microwave (PMW) satellite sea surface temperature (SST) retrievals are valuable to assimilate into high-resolution regional ocean forecast models. Still, there are issues related to these SSTs that need to be addressed to achieve improved ocean forecasts. Firstly, satellite SST products tend to be biased. Assimilating SSTs from different providers can thus cause the ocean ...
    • 3D full-wave multi-scattering forward solver for coherent microscopes 

      Qin, Yingying; Butola, Ankit; Agarwal, Krishna (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-21)
      A rigorous forward model solver for conventional coherent microscope is presented. The forward model is derived from Maxwell’s equations and models the wave behaviour of light matter interaction. Vectorial waves and multiple-scattering effect are considered in this model. Scattered field can be calculated with given distribution of the refractive index of the biological sample. Bright field images ...
    • The altitude of green OI 557.7 nm and blue N2+ 427.8 nm aurora 

      Whiter, Daniel K.; Partamies, Noora; Gustavsson, Bjorn Johan; Kauristie, Kirsti (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-06)
      We have performed a large statistical study of the peak emission altitude of green O(1D2–1S0) (557.7 nm) and blue 1 N (427.8 nm) aurora using observations from a network of all-sky cameras stationed across northern Finland and Sweden recorded during seven winter seasons from 2000 to 2007. Both emissions were found to typically peak at about 114 km. The distribution of blue peak altitudes is more ...
    • Horizontal Correlation Functions of Wind Fluctuations in the Mesosphere and Lower Thermosphere 

      Poblet, Facundo L.; Vierinen, Juha; Avsarkisov, Victor; Conte, J. Federico; Charuvil Asokan, Harikrishnan; Jacobi, Christoph; Chau, Jorge L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-01)
      Measurements of kinetic energy in vortical and divergent fluctuations in the mesosphere and lower thermosphere can be used to study stratified turbulence (ST) and gravity waves. This can be done using horizontal correlation functions of the fluctuating component of velocity. This study introduces a novel method for estimating these correlation functions using radars that observe Doppler shifts ...
    • A Comparison of Arctic Ocean Sea Ice Export Between Nares Strait and the Canadian Arctic Archipelago 

      Howell, S.E.L.; Babb, D.G.; Landy, Jack Christopher; Moore, G.W.K.; Montpetit, B.; Brady, M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-13)
      Nares Strait and the channels of the Canadian Arctic Archipelago (CAA) act as conduits for sea ice export from the Arctic Ocean but have never been directly compared. Here, we perform such a comparison for both the sea ice area and volume fluxes from October 2016 to December 2021. Nares Strait provided the largest average seasonal (October through September) ice area flux of 95 ± 8 × 10<sup>3</sup> ...
    • Synoptic Variability in Satellite Altimeter-Derived Radar Freeboard of Arctic Sea Ice 

      Nab, Carmen; Mallett, Robbie; Gregory, William; Landy, Jack Christopher; Lawrence, Isobel; Willatt, Rosemary; Stroeve, Julienne; Tsamados, Michel (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-09)
      Satellite observations of sea ice freeboard are integral to the estimation of sea ice thickness. It is commonly assumed that radar pulses from satellite-mounted Ku-band altimeters penetrate through the snow and reflect from the snow-ice interface. We would therefore expect a negative correlation between snow accumulation and radar freeboard measurements, as increased snow loading weighs the ice floe ...
    • Transmission structured illumination microscopy with tunable frequency illumination using tilt mirror assembly 

      Samanta, Krishnendu; Ahmad, Azeem; Tinguely, Jean-Claude; Ahluwalia, Balpreet Singh; Joseph, Joby (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-26)
      We present experimental demonstration of tilt-mirror assisted transmission structured illumination microscopy (tSIM) that offers a large field of view super resolution imaging. An assembly of custom-designed tilt-mirrors are employed as the illumination module where the sample is excited with the interference of two beams reflected from the opposite pair of mirror facets. Tunable frequency structured ...
    • Stiffness tensor estimation of anisotropic crystal using point contact method and unscented Kalman filter 

      Kalimullah, Nur M.M.; Shukla, Kaushik; Shelke, Amit; Habib, Anowarul (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-02)
      The potential application of Lithium Niobate (LiNbO3) crystal is immense, specifically in the domain of metasurfaces and nano-resonators. However, the practical application of LiNbO<sub>3</sub> is impeded due to unreliable experimental techniques and inaccurate inversion algorithms for material characterization. In the current research, material characterization of anisotropic crystal is proposed ...
    • Image inpainting in acoustic microscopy 

      Habib, Anowarul; Banerjee, Pragyan; Mishra, Sibasish; Yadav, Nitin; Agarwal, Krishna; Melandsø, Frank; Prasad, Dilip K (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-27)
      Scanning acoustic microscopy (SAM) is a non-ionizing and label-free imaging modality used to visualize the surface and internal structures of industrial objects and biological specimens. The image of the sample under investigation is created using high-frequency acoustic waves. The frequency of the excitation signals, the signal-to-noise ratio, and the pixel size all play a role in acoustic image ...
    • A clinically motivated self-supervised approach for content-based image retrieval of CT liver images 

      Wickstrøm, Kristoffer; Østmo, Eirik Agnalt; Radiya, Keyur; Mikalsen, Karl Øyvind; Kampffmeyer, Michael; Jenssen, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-09)
      Deep learning-based approaches for content-based image retrieval (CBIR) of computed tomography (CT) liver images is an active field of research, but suffer from some critical limitations. First, they are heavily reliant on labeled data, which can be challenging and costly to acquire. Second, they lack transparency and explainability, which limits the trustworthiness of deep CBIR systems. We address ...
    • Highly sensitive quantitative phase microscopy and deep learning aided with whole genome sequencing for rapid detection of infection and antimicrobial resistance 

      Ahmad, Azeem; Hettiarachchi, Ramith; Khezri, Abdolrahman; Ahluwalia, Balpreet Singh; Wadduwage, Dushan; Ahmad, Rafi (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-12)
      Current state-of-the-art infection and antimicrobial resistance (AMR) diagnostics are based on culture-based methods with a detection time of 48–96 h. Therefore, it is essential to develop novel methods that can do real-time diagnoses. Here, we demonstrate that the complimentary use of label-free optical assay with whole-genome sequencing (WGS) can enable rapid diagnosis of infection and AMR. Our ...
    • The Departure from Mixed-Layer Similarity During the Afternoon Decay of Turbulence in the Free-Convective Boundary Layer: Results from Large-Eddy Simulations 

      Elguernaoui, Omar; Reuder, Joachim; Li, Dan; Maronga, Bjørn; Bakhoday Paskyabi, Mostafa; Wolf, Tobias; Esau, Igor (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-21)
      This study analyses the departure of the velocity-variances profiles from their quasi-steady state described by the mixed-layer similarity, using large-eddy simulations with different prescribed shapes and time scales of the surface kinematic heat flux decay. Within the descriptive frames where the time is tracked solely by the forcing time scale (either constant or time-dependent) describing the ...
    • Extreme Horizontal Wind Perturbations in the Mesosphere and Lower Thermosphere Over South America Associated With the 2022 Hunga Eruption 

      Poblet, Facundo L.; Chau, Jorge L.; Conte, J. Federico; Vierinen, Juha; Suclupe, Jose; Liu, Alan; Rodriguez, Rodolfo R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-13)
      On 15 January 2022, the Hunga volcano produced a massive explosion that generated perturbations in the entire atmosphere. Nonetheless, signatures in the mesosphere and lower thermosphere (MLT) have been challenging to identify. We report MLT horizontal wind perturbations using three multistatic specular meteor radars on the west side of South America (spanning more than 3,000 km). The most ...
    • Sea Ice Remote Sensing—Recent Developments in Methods and Climate Data Sets 

      Sandven, Stein; Spreen, Gunnar; Heygster, Georg; Girard-Ardhuin, Fanny; Farrell, Sinéad L.; Dierking, Wolfgang Fritz Otto; Allard, Richard A. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-03)
      Sea ice monitoring by polar orbiting satellites has been developed over more than four decades and is today one of the most well-established applications of space observations. This article gives an overview of data product development from the first sensors to the state-of-the-art regarding retrieval methods, new products and operational data sets serving climate monitoring as well as daily operational ...
    • Single-Molecule Sizing through Nanocavity Confinement 

      Jacquat, Raphaël P. B.; Krainer, Georg; Peter, Quentin A. E.; Babar, Ali Nawaz; Vanderpoorten, Oliver; Xu, Catherine K.; Welsh, Timothy J.; Kaminski, Clemens F.; Keyser, Ulrich F.; Baumberg, Jeremy J.; Knowles, Tuomas P. J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-24)
      : An approach relying on nanocavity confinement is developed in this paper for the sizing of nanoscale particles and single biomolecules in solution. The approach, termed nanocavity diffusional sizing (NDS), measures particle residence times within nanofluidic cavities to determine their hydrodynamic radii. Using theoretical modeling and simulations, we show that the residence time of particles ...
    • Solved and unsolved riddles about low-latitude daytime valley region plasma waves and 150-km echoes 

      Chau, Jorge Luis; Longley, William; Reyes, Pablo; Pedatella, Nick; Otsuka, Yuichi; Stolle, Claudia; Liu, Huixin; Vierinen, Juha; Milla, Marco; Hysell, David L.; Oppenheim, Meers; Patra, A.; Lehmacher, G; Kudeki, Erhan (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-27)
      The Earth’s atmosphere near both the geographic and magnetic equators and at altitudes between 120 and 200 km is called the low-latitude valley region (LLVR) and is among the least understood regions of the ionosphere/thermosphere due to its complex interplay of neutral dynamics, electrodynamics, and photochemistry. Radar studies of the region have revealed puzzling daytime echoes scattered from ...
    • Efficient Fuel Consumption Minimization for Green Vehicle Routing Problems using a Hybrid Neural Network-Optimization Algorithm 

      Fossum, Astrid (Master thesis; Mastergradsoppgave, 2023-06-01)
      Efficient routing optimization yields benefits that extend beyond mere financial gains. In this thesis, we present a methodology that utilizes a graph convolutional neural network to facilitate the development of energy-efficient waste collection routes. Our approach focuses on a Waste company in Tromsø, Remiks, and uses real-life datasets, ensuring practicability and ease of implementation. In ...
    • Wind resource assessment and siting for the expansion of Fakken wind park 

      Bjugg, Martine (Master thesis; Mastergradsoppgave, 2023-05-31)
      Norway is anticipated to experience an energy deficit in the coming years, and one solution to address this issue is the implementation of new renewable energy sources. To mitigate the projected energy deficit, increased energy production is required. With its considerable wind potential, the country offers ample opportunities for wind energy development. Consequently, there is a growing demand for ...