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  • Copernicus  (5)
  • Potsdam : Universität Potsdam  (3)
  • Alfred Wegener Institute for Polar and Marine Research  (2)
  • 1
    Call number: AWI A4-20-93991
    Description / Table of Contents: Over the last decades, the Arctic regions of the earth have warmed at a rate 2–3 times faster than the global average– a phenomenon called Arctic Amplification. A complex, non-linear interplay of physical processes and unique pecularities in the Arctic climate system is responsible for this, but the relative role of individual processes remains to be debated. This thesis focuses on the climate change and related processes on Svalbard, an archipelago in the North Atlantic sector of the Arctic, which is shown to be a "hotspot" for the amplified recent warming during winter. In this highly dynamical region, both oceanic and atmospheric large-scale transports of heat and moisture interfere with spatially inhomogenous surface conditions, and the corresponding energy exchange strongly shapes the atmospheric boundary layer. In the first part, Pan-Svalbard gradients in the surface air temperature (SAT) and sea ice extent (SIE) in the fjords are quantified and characterized. This analysis is based on observational data from meteorological stations, operational sea ice charts, and hydrographic observations from the adjacent ocean, which cover the 1980–2016 period. [...]
    Type of Medium: Dissertations
    Pages: xv, 123 Seiten , Illustrationen, Diagramme
    Language: English
    Note: Dissertation, Universität Potsdam, 2020 , CONTENTS 1 Introduction 1.1 Context: A rapidly changing Arctic 1.1.1 Documentation of recent changes in the Arctic 1.1.2 Research relevance 1.1.3 Objective: Svalbard as a hotspot for climate change 1.2 Physical Background 1.2.1 Radiation and surface energy balance 1.2.2 Peculiarities of the Arctic climate system 1.2.3 Role of atmospheric circulation 1.3 The regional setup on Svalbard 2 data and methods 2.1 Data description 2.1.1 Era-Interim atmospheric reanalysis 2.1.2 Svalbard Station Meteorology 2.1.3 Sea Ice Extent 2.1.4 Ocean data products 2.1.5 FLEXTRA Trajectories 2.2 Statistical Methods 2.2.1 Trend estimation 2.2.2 Correlation 2.2.3 Coefficient of Determination 3 state of surface climate parameters: pan-svalbard differences 3.1 Motivation 3.2 Surface air temperature 3.2.1 Annual cycle 3.2.2 Annual temperature range 3.2.3 Long-term trends 3.3 Fjord Sea Ice coverage 3.3.1 Climatology 3.3.2 Sea ice cover trends 3.3.3 Regional classification across Svalbard 3.3.4 Drivers of regional differences 3.4 Discussion and Conclusion 3.5 Current state of climate projections for the Svalbard region 4 Air mass back trajectories 4.1 Methodology 4.2 Winter 4.2.1 Source Regions of Ny-Ålesund Air 4.2.2 Circulation changes 4.2.3 Quantification of Advective Warming 4.3 Summer 4.3.1 Source Regions of Ny-Ålesund Air 4.3.2 Circulation changes 4.3.3 Quantification of advective cooling 4.3.4 Observational Case Study: May/June 2017 4.4 Discussion and Conclusion 5 Changing drivers of the arctic near surface temperature budget 5.1 Winter 5.2 Summer 5.3 Summary 6 Summary and conclusion A Details on calculations A.1 SLP composite Index A.2 Derivation of coefficient of determination A.3 Temperature effect of changing source regions over time B Supplementary figures Bibliography
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  • 2
    Call number: AWI A6-21-94541
    Description / Table of Contents: Stratospheric variability is one of the main potential sources for sub-seasonal to seasonal predictability in mid-latitudes in winter. Stratospheric pathways play an important role for long-range teleconnections between tropical phenomena, such as the quasi-biennial oscillation (QBO) and El Niño-Southern Oscillation (ENSO), and the mid-latitudes on the one hand, and linkages between Arctic climate change and the mid-latitudes on the other hand. In order to move forward in the field of extratropical seasonal predictions, it is essential that an atmospheric model is able to realistically simulate the stratospheric circulation and variability. The numerical weather prediction (NWP) configuration of the ICOsahedral Non-hydrostatic atmosphere model ICON is currently being used by the German Meteorological Service for the regular weather forecast, and is intended to produce seasonal predictions in future. This thesis represents the first extensive evaluation of Northern Hemisphere stratospheric winter circulation in ICON-NWP by analysing a ...
    Type of Medium: Dissertations
    Pages: viii, 119 Seiten , Illustrationen, Diagramme, Karten
    Language: English
    Note: Dissertation, Universität Potsdam, 2020 , Contents1 Introduction 1.1 Motivation: Seasonal prediction 1.2 The new atmosphere model ICON 1.3 Research questions 2 Theoretical background 2.1 Fundamentals of atmospheric circulation 2.1.1 Primitive equations 2.1.2 The global energy budget 2.1.3 Baroclinic instability 2.1.4 Vertical structure of the atmosphere 2.2 Stratospheric dynamics 2.2.1 Circulation patterns 2.2.2 Atmospheric waves 2.2.3 Sudden stratospheric warmings 2.2.4 Quasi-biennial oscillation 2.3 Atmospheric Teleconnections 2.3.1 NAM, NAO and PNA 2.3.2 El Niño-Southern Oscillation 2.3.3 Arctic-midlatitude linkages 3 Atmospheric model and methods of analysis 3.1 Atmospheric model ICON-NWP 3.1.1 Model description 3.1.2 Experimental setup 3.2 Reanalysis data ERA-Interim 3.3 Methods of analysis 3.3.1 NAM index for stratosphere–troposphere coupling 3.3.2 Stratospheric warmings 3.3.3 ENSO index and composites 3.3.4 Bias and error estimation 3.3.5 Statistical significance 4 Results 4.1 Evaluation of seasonal experiments with ICON-NWP 4.1.1 Tropospheric circulation 4.1.2 Stratospheric circulation 4.2 Effect of gravity wave drag parameterisations 4.2.1 Stratospheric effects 4.2.2 Effects on stratosphere-troposphere coupling 4.2.3 Tropospheric effects 4.3 Low latitudinal influence on the stratospheric polar vortex 4.3.1 Quasi-biennial oscillation 4.3.2 El Niño-Southern Oscillation 4.4 Arctic-midlatitude linkages 4.4.1 Tropospheric processes 4.4.2 Stratospheric pathway 4.4.3 Sea ice sensitivity experiment 5 Discussion and outlook Bibliography Appendix
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  • 3
    Call number: AWI A8-20-93986
    Type of Medium: Dissertations
    Pages: VI, 129 Seiten , Diagramme
    Language: German
    Note: Inhaltsverzeichnis Kurzfassung Abstract 1 EINFÜHRUNG 2 GRUNDLAGEN 2.1 Allgemeine Zirkulation 2.2 Barokline Instabiltät 2.3 Horizontale und vertikale Wellenausbreitung 2.4 Die Rolle der Arktis im Klimasystem 2.5 Einfluss des klimatischen Wandels in der Arktis auf die mittleren Breiten 2.6 Atmosphärisches Energiespektrum und Skalenwechselwirkung 3 DATEN UND METHODEN 3.1 Verwendete Reanalyse- und Modelldaten 3.1.1 ERA-Interim 3.1.2 AFES 3.1.3 Aufteilung der verwendeten Daten in Zeiträume mit hoher und niedriger Meereisbedeckung 3.2 Methoden 3.2.1 Instabilitätsanalyse für einen zonalgemittelten Grundzustand 3.2.2 Identifikation bevorzugter großskaliger Zirkulationsmuster 3.2.3 Energie- und Enstrophiespektren 3.2.4 Statistische Testverfahren 4 ERGEBNISSE 4.1 Instabilitätsanalyse für einen zonalgemittelten Grundzustand . 4.1.1 Klimatologie ERA-Interim und AFES 4.1.2 Sensititvitätsstudie 4.2 Identifikation bevorzugter großskaliger Zirkulationsmuster 4.2.1 September 4.2.2 Oktober 4.2.3 November 4.2.4 Dezember 4.2.5 Januar 4.2.6 Februar 4.2.7 Zugehörige synoptisch-skalige Aktivität und 2m-Temperatur 4.3 Kinetische Energiespektren und nichtlineare Wechselwirkungen 4.3.1 Kinetische Energiespektren 4.3.2 Enstrophiespektren 4.3.3 Nichtlineare Energiewechselwirkungen, Energieflüsse und Enstrophieflüsse 5 ZUSAMMENFASSUNG UND AUSBLICK Tabellenverzeichnis Abbildungsverzeichnis Variablen und Symbole Literaturverzeichnis Danksagung Anhang A.1 Hough-Funktionen und vertikale Strukturfunktionen A.2 Zugeordnete Legendre-Polynome und Kugelflächenfunktionen Eidesstattliche Erklärung
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  • 4
    Publication Date: 2020-07-06
    Description: In September 2019, the research icebreaker Polarstern started the largest multidisciplinary Arctic expedition to date, the MOSAiC (Multidisciplinary drifting Observatory for the Study of Arctic Climate) drift experiment. Being moored to an ice floe for a whole year, thus including the winter season, the declared goal of the expedition is to better understand and quantify relevant processes within the atmosphere–ice–ocean system that impact the sea ice mass and energy budget, ultimately leading to much improved climate models. Satellite observations, atmospheric reanalysis data, and readings from a nearby meteorological station indicate that the interplay of high ice export in late winter and exceptionally high air temperatures resulted in the longest ice-free summer period since reliable instrumental records began. We show, using a Lagrangian tracking tool and a thermodynamic sea ice model, that the MOSAiC floe carrying the Central Observatory (CO) formed in a polynya event north of the New Siberian Islands at the beginning of December 2018. The results further indicate that sea ice in the vicinity of the CO (
    Print ISSN: 1994-0416
    Electronic ISSN: 1994-0424
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
    Publication Date: 2021-08-20
    Description: We combine satellite data products to provide a first and general overview of the physical sea ice conditions along the drift of the international Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition and a comparison with previous years (2005–2006 to 2018–2019). We find that the MOSAiC drift was around 20 % faster than the climatological mean drift, as a consequence of large-scale low-pressure anomalies prevailing around the Barents–Kara–Laptev sea region between January and March. In winter (October–April), satellite observations show that the sea ice in the vicinity of the Central Observatory (CO; 50 km radius) was rather thin compared to the previous years along the same trajectory. Unlike ice thickness, satellite-derived sea ice concentration, lead frequency and snow thickness during winter months were close to the long-term mean with little variability. With the onset of spring and decreasing distance to the Fram Strait, variability in ice concentration and lead activity increased. In addition, the frequency and strength of deformation events (divergence, convergence and shear) were higher during summer than during winter. Overall, we find that sea ice conditions observed within 5 km distance of the CO are representative for the wider (50 and 100 km) surroundings. An exception is the ice thickness; here we find that sea ice within 50 km radius of the CO was thinner than sea ice within a 100 km radius by a small but consistent factor (4 %) for successive monthly averages. Moreover, satellite acquisitions indicate that the formation of large melt ponds began earlier on the MOSAiC floe than on neighbouring floes.
    Print ISSN: 1994-0416
    Electronic ISSN: 1994-0424
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
    Publication Date: 2016-11-24
    Description: A realistic simulation of physical and dynamical processes in the Arctic atmosphere and its feedbacks with the surface conditions is still a challenge for state-of-the-art Arctic climate models. This is of critical importance because studies of, for example, transport of pollutants from middle latitudes into the Arctic rely on the skill of the model in correctly representing atmospheric circulation including the key mechanisms and pathways of pollutant transport. In this work the performance of the Weather Research and Forecast model (WRF) with two land surface model schemes (Noah and NoahMP) and two reanalysis data sets for creation of lateral boundary conditions (ERA-interim and ASR) is evaluated focusing on meteorological surface properties and atmospheric dynamics. This includes the position and displacement of the polar dome and other features characterizing atmospheric circulation associated to sea ice maxima/minima extent within the Eurasian Arctic. The model simulations analyzed are carried out at 15-km horizontal resolution over a period of five years (2008 to 2012). The WRF model simulations are evaluated against surface meteorological data from automated weather stations and vertical profiles from radiosondes. Results show that the model is able to reproduce the main features of the atmospheric dynamics and vertical structure of the Arctic atmosphere reasonably well. The influence of the choice of the reanalyses used as initial and lateral boundary condition and of the LSM on the model results is complex and no combination is found to be clearly superior in all variables analyzed. The model results show that a more sophisticated formulation of land surface processes does not necessarily lead to significant improvements in the model results. This suggests that other factors such as the decline of the Arctic sea ice, stratosphere-troposphere interactions, atmosphere-ocean interaction, and boundary layer processes are also highly important and can have a significant influence on the model results. The “best” configuration for simulating Arctic meteorology and processes most relevant for pollutant transport (ASR + NoahMP) is then used in a simulation with WRF including aerosols and chemistry (WRF-Chem) to simulate black carbon (BC) concentrations in and around the Arctic and to assess the role of the modeled atmospheric circulation in the simulated BC concentrations inside the Arctic domain. Results from simulations with chemistry are evaluated against aerosol optical depth from several Aeronet stations and BC concentrations and particle number concentrations from several stations from the EBAS database. The results with WRF-Chem show a strong dependency of the simulated BC concentration on the modeled meteorology and the transport of the pollutants around our domain. The results also show that biases in the modeled BC concentrations can also be related to the emission data. Significant improvements of the models and of our understanding of the impact of anthropogenic BC emissions on the Arctic strongly depends on the availability of suitable, long-term observational data of concentrations of BC and particulate matter, vertical profiles of temperature and humidity and wind.
    Electronic ISSN: 1680-7375
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
    Publication Date: 2018-11-22
    Description: A new version of the coupled Arctic atmosphere-ocean-sea ice model HIRHAM-NAOSIM is described. This version utilizes upgraded model components for the coupled subsystems, which include physical and numerical improvements and higher horizontal and vertical resolution, and a revised coupling procedure with the aid of the coupling software YAC. The model performance is evaluated against observationally based data sets and compared with the previous version. Ensemble simulations for the period 1979–2016 reveal that Arctic sea ice is thicker in all seasons and closer to observations than in the previous version. Wintertime biases in sea-ice extent and near-surface air temperatures are reduced, while summertime biases are of similar magnitude as in the previous version. Problematic issues of the current model configuration and potential corrective measures and further developments are discussed.
    Print ISSN: 1991-9611
    Electronic ISSN: 1991-962X
    Topics: Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research), Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 588, 198 p., ISSN: 1866-3192
    Publication Date: 2018-09-12
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 9
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    Alfred Wegener Institute for Polar and Marine Research
    In:  EPIC3Berichte zur Polar- und Meeresforschung (Reports on Polar and Marine Research), Bremerhaven, Alfred Wegener Institute for Polar and Marine Research, 520, 152 p., ISSN: 1618-3193
    Publication Date: 2018-09-07
    Repository Name: EPIC Alfred Wegener Institut
    Type: "Berichte zur Polar- und Meeresforschung" , notRev
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  • 10
    Publication Date: 2024-04-19
    Description: We combine satellite data products to provide a first and general overview of the physical sea ice conditions along the drift of the international Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition and a comparison with previous years (2005–2006 to 2018–2019). We find that the MOSAiC drift was around 20 % faster than the climatological mean drift, as a consequence of large-scale low-pressure anomalies prevailing around the Barents–Kara–Laptev sea region between January and March. In winter (October–April), satellite observations show that the sea ice in the vicinity of the Central Observatory (CO; 50 km radius) was rather thin compared to the previous years along the same trajectory. Unlike ice thickness, satellite-derived sea ice concentration, lead frequency and snow thickness during winter months were close to the long-term mean with little variability. With the onset of spring and decreasing distance to the Fram Strait, variability in ice concentration and lead activity increased. In addition, the frequency and strength of deformation events (divergence, convergence and shear) were higher during summer than during winter. Overall, we find that sea ice conditions observed within 5 km distance of the CO are representative for the wider (50 and 100 km) surroundings. An exception is the ice thickness; here we find that sea ice within 50 km radius of the CO was thinner than sea ice within a 100 km radius by a small but consistent factor (4 %) for successive monthly averages. Moreover, satellite acquisitions indicate that the formation of large melt ponds began earlier on the MOSAiC floe than on neighbouring floes.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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