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  • 1
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    An adaptive shallow water model on the sphere (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: This thesis describes the adaptive shallow water model PLASMA-FEMmE. It solves on the sphere the shallow water equations, the prototype for partial differential equations in atmospheric modeling, using a semi-implicit semi-Lagrangian time step and linear finite elements. Both statically and dynamically adapted grids created by the grid generator amatos are investigated. The results are compared with those of the predecessor model FEMmE that uses a static uniform grid. The outcome demonstrates the capability of the chosen approach as well as its limits. Grid adaptation can easily be achieved with amatos. No reflexions at the grid interfaces are observed. Though in one test case instabilities are released at the grid interfaces. The numerical errors are reduced without a considerable enhancement of the computational effort in another test case with a well-known analytical solution. In respect to the conservation properties the results are more complicated. Mass conservation can be achieved in one test case with an appropriate static grid. In case of complex flow regimes all conservation properties are weakened during the simulation using dynamic grid adaptation...
    Description: thesis
    Keywords: 532.5 ; 551.46 ; 550 ; Meteorologische Modelle ; Fluiddynamik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 135 S.
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  • 2
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    Evaluation and application of GPS and altimetry data over central Dronning Maud Land, Antarctica (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: The polar ice sheets are unique paleoclimatic archives and play an important role in recent and future climate. The melting of the big freshwater reservoirs will not only increase the global sea level, but will also influence the ocean currents. Therefore, it will be of particular interest to improve the currently available numeric climate models to achieve more accurate statements about climatic change and its consequences. In this work, the evaluation and the different applications of GPS and altimetry data will be described in respect to enhance models. The antarctic area of investigation, Dronning Maud Land (DML), is of particular interest for German polar research, because both the overwintering station Neumayer and the summer station Kohnen are located within it. In the surroundings of these two stations, highly accurate kinematic GPS measurement were made, which will be the basis for the digital elevation model presented here. Because these data are spatially limited, they are supplemened with remotely sensed data. For this purpose, two airborne altimetry data sets and spaceborne laser altimetry data of the Ice, Cloud, and land Elevation Satellite (ICESat) are used...
    Description: thesis
    Keywords: 551.312 ; 551 ; 550 ; TWC 600 ; VAR 980 ; TQI 000 ; TSY 200 ; Geophysikalische Satellitenfernerkundung ; Antarktis {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 140 S.
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  • 3
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    Assessing the fidelity of the marine sedimentary magnetic record (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Marine sediments, diagenesis, anoxic environments, paleomagnetism, low-temperature magnetism, magnetic Fe-Ti-Oxides. - Magnetic particles usually occur in very minor concentrations in igneous and sedimentary rocks, soils, volcanic ashes, dusts and even in living organisms. Many of these magnetic grains are capable of carrying a stable permanent magnetization and therefore act as recorders of the recent and ancient Earth's magnetic field. Thus paleomagnetism refers to the study of this remanent magnetization in sedimentary and volcanic rocks through time. From this magnetization, directional intensity information can be recovered concerning the geomagnetic field that prevailed at the sample location at the time of the rock formation. The magnetic parameter on which such paleomagnetic studies are based is the natural remanent magnetization (NRM). In continental margin regions the remanence acquisition process is often complicated by post-depositional modifications of the original magnetic material. After deposition magnetic minerals can be altered or new magnetic phases can be formed. Consequently the original NRM might be obscured or even fully erased. The process of diagenesis and authigenesis may thus seriously compromise paleomagnetic interpretation. Therefore our knowledge of the geomagnetic field behavior based on sediment records from continental margin regions remains limited. To obtain fully reliable information about the geomagnetic field or paleoenvironmental conditions from continental margin regions, the effect of early diagenetic processes occurring after deposition of the sediment must be understood in detail.
    Description: thesis
    Keywords: 551.4686 ; 538.727 ; 550 ; TOT 320 ; VKB 380 ; TSZ 100 ; Paläomagnetismus {Geophysik} ; Sedimente bestimmter Regionen ; Atlantischer Ozean {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 113 S.
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  • 4
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    Seafloor seepage in the Black Sea (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Black Sea, seafloor seepage, mud volcanoes, seeps, fluid migration, gas hydrates, diapirs. - The Black Sea is the worldwide largest anoxic basin with thick gas rich sediments facilitating seafloor seepage, which is widely distributed along the continental slopes of the Black Sea. In two areas, the Sorokin Trough off Crimea and at the continental slope off Batumi (Georgia), the distribution, structure and evolution of two different vent systems and their relation to fluid migration pathways and gas/gas hydrate occurrences have been investigated by means of high resolution multichannel seismic data. In both regions, the distribution of seafloor seepage is controlled by fluid migration along permeable pathways associated with diapiric uplift in the subsurface. In the Sorokin Trough, seepage is expressed by intensive material upflow and the formation of mud volcanoes; offshore Batumi, gas seeps with low material flux dominate. In the Sorokin Trough, most mud volcanoes are associated with near-subsurface mud diapirs. The great morphological variability of the mud volcanoes reflects different driving mechanisms, which depend on the availability of permeable fluid migration pathways and the depositional environment. A 3D seismic dataset images the detailed three-dimensional ...
    Description: thesis
    Keywords: 551.466 ; 550 ; TSZ 100 ; VAT 300 ; VEZ 120 ; TQC 600 ; Atlantischer Ozean {Geophysik} ; Geologie des Meeresboden ; Randmeere {Geologie} ; Tiefseeseismik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 154 S.
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  • 5
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    Development of a novel balloon-borne optical sonde for the measurement of ozone and other stratospheric trace gases (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Ozone, balloon-borne measurements, atmospheric trace gases, concentration profiles, climate change. - In the frame of this work, a new small-size balloon-borne sonde was developed. A miniature grating spectrometer in the sonde measures simultaneously the solar spectral irradiance at a wide wavelength range from 200 to 850. As a first application, ozone profiles have been determined by measuring the changes in the spectral irradiance, caused by ozone absorption in the Huggins band. The wide spectral coverage of the spectrometer offers the possibility for measurements of other trace gases which absorb within the wavelength range, e.g. NO2 and BrO. The low weight of the new sonde (1.7 kg), the moderate price, and the autonomous portable telemetry system makes it a very versatile tool for satellite validation and for case studies, which requires a high number of launches. The newly developed sonde works well without temperature stabilisation, even so the spectrometer experiences rather large temperature changes (15 - 20 K) during the ascent through the atmosphere. Laboratory measurements were performed in ...
    Description: thesis
    Keywords: 551.5 ; 551.8 ; 550
    Language: English
    Type: monograph , publishedVersion
    Format: 148 S.
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  • 6
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    Untersuchung der Photooxidantien Wasserstoffperoxid, Methylhydroperoxid und Formaldehyd in der Troposphäre der Antarktis (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Photooxidants play an important role for the oxidation capacity of the troposphere. The presented work deals with seasonal changes of atmospheric photooxidants like hydrogen peroxide (H2O2), methylhydroperoxide (MHP) and formaldehyde (HCHO). The principal purpose was to follow and quantify the mixing-ratios of these photochemical species for the first time over a complete annual cycle in Antarctica. During two field campaigns at the German Antarctic station Neumayer (overwintering campaign from January 1997 until March 1998 and a shorter campaign from January to March 1999) continuous measurements of atmospheric mixing-ratios were performed. A continuous wet-chemical technique was used for peroxides and formaldehyde sampling and analysis. Species were quantified by fluorescence detection. In order to compare the results and measurements with well-known reaction mechanisms a photochemical box model was applied. The obtained time series show a pronounced seasonal variation with higher values during summer. For the first time atmospheric concentrations of H2O2, MHP and HCHO were documented during polar night in winter. The mixing-ratios were significantly higher than expected due to missing actinic radiation essential for photochemical production. Trajectory analyses and calculations with a three-dimensional model showed that during winter the mixing-ratios of photooxidants are mainly affected by long-range transport in the free troposphere. Investigations during the Antarctic ó́zone hole period ́́show no significant impact of the increased UV-B radiation on the photooxidants. The findings of this work contribute to a better understanding of the photochemistry of the investigated trace gases in the clean troposphere of Antarctica and provide a useful data record for further photochemical modeling.
    Description: thesis
    Keywords: 551.5 ; 551.9 ; 550 ; TYY 200 ; TVA 210 ; Antarktis {Meteorologie und Klimatologie} ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: German
    Type: monograph , publishedVersion
    Format: 176 S.
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  • 7
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    Entwicklung und Anwendung eines photochemischen schräge Säulen Modell-Paketes zur Interpretation von DOAS-Daten atmosphärischer Spurengase (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Besides measurements of atmospheric trace gases and laboratory studies of chemical reactions, modelling has been recognised to be of increasing importance to improve our knowledge of the atmosphere and the capabilities of photochemical models. Main scope of this work was the development of a photochemical atmospheric model, which was especielly designed for the interpretation of Differential Optical Absorption measurments (DOAS). This model has been used to improve our knowledge of atmospheric chemistry. For example, for the first time it was possible to demonstrate that a significant amount of IO in a range of 0.65 to 0.8 pptv is present in the stratosphere in the polar region (Ny-Alesund,Spitzbergen). Moreover it has been shown that such amounts of stratospheric IO lead to an additional Ozone loss in the range of 10 % in cold arctic winters.
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 700 ; TVA 210 ; Verfahren zur Untersuchung der freien Atmosphäre {Meteorologie} ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: German
    Type: monograph , publishedVersion
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  • 8
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    Die Ozonverteilungen der Nordhemisphäre 1997 - 2000 gemessen mit GOME (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Ozone profile retrieval, ERS-2, GOME, FURM, ozone decline, Northern hemisphere. - Measurements of stratospheric ozone over the Northern hemisphere forthe winter/spring periods of 1997 to 2000 taken with the GOMEinstrument were used to derive the chemical ozone depletion inside thepolar vortex. GOME onboard the ERS-2 satellite measures radiationcoming from the Earth in the UV/vis spectral range.To discern the chemical depletion from dynamical influences, a modelwas developed to calculate vortex averaged diabatic descent ratesusing the radiative transfer model MIDRAD and the FURM ozoneprofiles. The permeability of the Arctic vortex was analysed by usingthe trajectory model TANGO in conjunction with a reverse domainfilling algorithm, developed within the framework of this thesis.The chemical ozone ...
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 850 ; TVA 210 ; TY 100 ; Satellitenmeteorologie ; Chemische Zusammensetzung der Atmosphäre {Meteorologie} ; Nördliche Hemisphäre {Meteorologie und Klimatologie}
    Language: German
    Type: monograph , publishedVersion
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  • 9
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    A new algorithm to retrieve the sea ice concentration using weather-corrected 85 GHz SSM/I measurements (2010)
    Univ. Bremen
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    Publication Date: 2021-03-29
    Description: Sea ice is a very important component of the climate system. While the Arctic sea ice extent has retreated during the past 20 years, it has remained constant in the Antarctic. In order to better understand the role of sea ice in the climate system in the context of global warming currently used coupled Atmosphere-Ocean Global Circulation Models have to be improved. This requires to know the sea ice concentration C for a long period for both hemispheres and at the best possible spatial resolution. Currently used methods to obtain C like the NASA Team (NT) algorithm are based on data acquired by the Special Sensor Microwave/Imager (SSM/I) at 19 and 37GHz. The SEA LION (SL) algorithm presented here allows to infer C from the polarization P at 85GHz taking advantage of the higher spatial resolution at this frequency. However, the decrease of P caused by the weather influence leads to an overestimation of C. Therefore, P is corrected using a radiative transfer model and atmospheric data taken from Numerical Weather Prediction models and/or derived from SSM/I measurements. The various sea ice and snow properties are considered calculating monthly sea ice tie points. The average standard deviation of C derived with the SL algorithm is 12% for C 〈 50% and below 5% for C 〉 90%. The SL ice edge agrees within 10km with the one evident in VIS/IR images. The SL ice concentration gradient across the marginal ice zone (MIZ) agrees much better with the one evident in SAR images compared to results of the NT algorithm. Using the higher spatial resolution at 85GHz the SL algorithm allows to detect smaller open water areas than known algorithms. A major limitation of the SL algorithm arises from the quality of atmospheric data needed for the weather correction. A spatial resolution of these data lower than the 85GHz SSM/I channels and/or a time lag larger than half an hour between both data sets can cause relative errors above 100%, particulary in the cloud-covered parts of the MIZ.
    Description: thesis
    Keywords: 550.28 ; 551.31 ; 550 ; TWH 500 ; TWC 100 ; Einfluss von Eis {Klimatologie} ; Instr. Ergebn. zu Klimaänderungen und Klimaschwankungen
    Language: English
    Type: monograph , publishedVersion
    Format: 186 S.
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  • 10
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    Messungen von dynamischen Tracern und Ozon in der arktischen Stratosphäre (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Ozone chemistry, tracer measurements, radiometry, airborne,submillimeterwave, Arctic, stratosphere. - The Airborne Submillimeter Radiometer (ASUR) is a passive heterodyne instrument using a superconducting detector with an instrumental frequency range from 604.3 to 662.3 GHz.Operating onboard an aircraft to avoid absorption by tropospheric water vapor key species of the stratospheric ozone chemistry can be detected for a vertical altitude range from 15 to 55 km. In the winter 1999/2000 the ASUR instrument participated in the THESEO 2000/SOLVE project onboard the NASA research aircraft DC-8. Three deployments were carried ...
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 800 ; TVA 210 ; TYY 100 ; Radarmeteorologie ; Chemische Zusammensetzung der Atmosphäre {Meteorologie} ; Arktis {Meteorologie und Klimatologie}
    Language: German
    Type: monograph , publishedVersion
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