Blar i forfatter "Fritzner, Sindre Markus"

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    • Assessment of High‐Resolution Dynamical and Machine Learning Models for Prediction of Sea Ice Concentration in a Regional Application 

      Fritzner, Sindre Markus; Graversen, Rune; Christensen, Kai Håkon (Journal article; Tidsskriftartikkel, 2020-10-17)
      In this study, the potential for sea ice concentration prediction using machine‐learning methods is investigated. Three different sea ice prediction models are compared: one high‐resolution dynamical assimilative model and two statistical machine‐learning models. The properties of all three models are explored, and the quality of their forecasts is compared. The dynamical model is a state‐of‐the‐art ...

    • Assimilation of high-resolution ice charts in a coupled ocean-sea-ice model 

      Fritzner, Sindre Markus; Christensen, Kai Håkon; Graversen, Rune; Wang, Keguang (Journal article; Tidsskriftartikkel, 2019)
      In this study, we show assimilation results from a coupled ocean sea-ice model. The model has a horizontal resolution of 2.5 km. In the assimilation system, we assimilate high-resolution ice charts, structured on a 1 km grid. We compare the assimilation of passive microwave observations with the assimilation of ice charts. It is shown that the ice charts have a larger impact on the assimilation ...

    • Barents-2.5km v2.0: an operational data-assimilative coupled ocean and sea ice ensemble prediction model for the Barents Sea and Svalbard 

      Röhrs, Johannes; Gusdal, Yvonne; Rikardsen, Edel S. U.; Durán Moro, Marina; Brændshøi, Jostein; Kristensen, Nils Melsom; Fritzner, Sindre Markus; Wang, Keguang; Sperrevik, Ann Kristin; Idzanovic, Martina; Lavergne, Thomas; Debernard, Jens Boldingh; Christensen, Kai Håkon (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-09-22)
      An operational ocean and sea ice forecast model, Barents-2.5, is implemented for short-term forecasting at the coast off northern Norway, the Barents Sea, and the waters around Svalbard. Primary forecast parameters are sea ice concentration (SIC), sea surface temperature (SST), and ocean currents. The model also provides input data for drift modeling of pollutants, icebergs, and search-and-rescue ...

    • Comparison between a multi-variate nudging method and the ensemble Kalman filter for sea-ice data assimilation 

      Fritzner, Sindre Markus; Graversen, Rune; Wang, Keguang; Christensen, Kai Håkon (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-25)
      Increasing ship traffic and human activity in the Arctic has led to a growing demand for accurate Arctic weather forecast. High-quality forecasts obtained by models are dependent on accurate initial states achieved by assimilation of observations. In this study, a multi-variate nudging (MVN) method for assimilation of sea-ice variables is introduced. The MVN assimilation method includes procedures ...

    • Impact of assimilating sea ice concentration, sea ice thickness and snow depth in a coupled ocean-sea ice modelling system 

      Fritzner, Sindre Markus; Graversen, Rune; Christensen, Kai Håkon; Rostosky, Philip; Wang, Keguang (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-02-08)
      The accuracy of the initial state is very important for the quality of a forecast, and data assimilation is crucial for obtaining the best-possible initial state. For many years, sea-ice concentration was the only parameter used for assimilation into numerical sea-ice models. Sea-ice concentration can easily be observed by satellites, and satellite observations provide a full Arctic coverage. During ...

    • Intermittent fluctuations in the Alcator C-Mod scrape-off layer 

      Garcia, Odd Erik; Fritzner, Sindre Markus; Kube, Ralph; Cziegler, Istvan; LaBombard, Brian; Terry, Jim L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)
      Fluctuations in the boundary region of the Alcator C-Mod tokamak have been analyzed using gas puff imaging data. It is found that the fluctuation amplitudes in the near scrape-off layer follow a normal distribution while the far scrape-off layer fluctuations are dominated by large amplitude bursts due to radial motion of blob-like structures and have a positively skewed and flattened amplitude ...

    • On sea-ice forecasting 

      Fritzner, Sindre Markus (Doctoral thesis; Doktorgradsavhandling, 2020-05-15)
      Accurate sea-ice prediction is essential for safe operations in the Arctic and potentially also for weather forecast at high-latitudes. The increasing number of sea-ice related satellite observations in the Arctic can be used to improve the model predictions through data assimilation. For sea ice, sea-ice concentration (SIC) observations have been available for many years. Observational information ...

    • Statistical analysis of fluctuations in the Alcator C-Mod scrape-off layer 

      Fritzner, Sindre Markus (Master thesis; Mastergradsoppgave, 2013-06-30)
      Experimental data from Alcator C-Mod have been used to analyze large density events occurring at the edge of fusion reactors. The data acquisition methods used are gas puff imaging and Langmuir probes. The data consist of long time series sampled at high frequency, excellent for statistical analysis. Large density events have been analyzed where blobs are found to be consistent with high skewness ...