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  • 550.28  (4)
  • Univ. Bremen  (4)
  • American Association for the Advancement of Science (AAAS)
  • American Institute of Physics (AIP)
  • Elsevier
  • Ottawa : Geological Survey of Canada
  • English  (4)
  • 2010-2014  (4)
  • 1990-1994
Collection
Keywords
Publisher
Language
  • English  (4)
Years
  • 2010-2014  (4)
  • 1990-1994
Year
  • 1
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    A new algorithm to retrieve the sea ice concentration using weather-corrected 85 GHz SSM/I measurements (2010)
    Univ. Bremen
    Details
    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.
    Format: application/pdf
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    CITATION GEO-LEO
  • 2
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    Atmospheric parameter retrieval from UV-vis-NIR limb scattering measurements (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: The hyperspectral UV-vis-NIR spectrometer SCIAMACHY will be launched aboard the European satellite Envisat. Its limb measurements will provide vertically resolved profiles of trace gases and other atmospheric parameters. No retrieval algorithms and radiative transfer models have been established for these measurements yet.In this thesis, a unique, fast radiative transfer model for UV-vis-NIR limb radiances has been developed, implemented, and validated. It takes into account the sphericity of the atmosphere and up to two orders of scattering and surface reflection. The weighting functions for all parameters are calculated from analytical formulae. A realistic instrument model with field-of-view integration and signal-to-noise computation and retrieval algorithms have also been implemented. All have been combined in the new program package SCIARAYS. The package has been applied for the characterisation of the limb measurements in several ways:The simulated weighting functions agree well with those due to full multiple scattering. Thus they may be used to calculate theoretical precision estimates and averaging kernels. In conformance with this, test retrievals with approximate weighting functions converge correctly. Therefore, the approximate weighting functions of SCIARAYS are well suited for retrievals from SCIAMACHYś limb measurements.Detailed theoretical retrieval precisions have been calculated for SCIAMACHYś trace gas targets. The conclusion is that a UV-vis-NIR limb sensor like SCIAMACHY is well suited for studying the vertical structure of the stratosphere and also of the upper troposphere above cloud top.Further investigations show that the vertical resolution of retrievals from SCIAMACHYś limb measurements can be improved beyond its geometrical limits. As a trade-off for better vertical resolution, the retrieval precision gets worse. Thus O3 profile features with 1km vertical extent will be detectable with a precision of 20-30%.
    Description: thesis
    Keywords: 551.5 ; 550.28 ; 550 ; TUA 850 ; TQI 000 ; TVA 210 ; Satellitenmeteorologie ; Geophysikalische Satellitenfernerkundung ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 247 S.
    Format: application/pdf
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    CITATION GEO-LEO
  • 3
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    Modeling of radiative transfer through a spherical planetary atmosphere (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: During the last years and decades issues related to the physics and chemistry of the Earthś atmosphere have attracted much scientific and public interest. The most important problems are stratospheric ozone loss and the ò̀zone hole ́́above Antarctica, global warming and climate change, and tropospheric air pollution. The understanding of the impact of human activities on the Earthś atmosphere requires measurements on a global scale. These enable the spatial and temporal variability of the atmospheric constituents to be investigated. Recently efforts have been made to establish a global observation system comprising satellite instruments and ground-based networks. To process data supplied by the instruments which belong to the global observation system, the development of radiative transfer models and retrieval algorithms is essential. This thesis contributes to the development of the radiative transfer models and retrieval algorithms intended to interprete measurements of the spectral radiance scattered in the atmosphere or transmitted through the atmosphere in UV-Vis-NIR spectral region performed by a new-generation remote sensing satellite spectrometer SCIAMACHY. In this study, main problems of radiative transfer through a spherical planetary atmosphere compared to a plane-parallel atmosphere are investigated. An efficient spherical radiative transfer model intended to simulate SCIAMACHY limb measurements was developed and validated. The model can also be used for the interpretation of measurements performed by other space-borne instruments as well as to compute air mass factors for ground-based measurements. An approximate approach allowing the simulation of limb measurements to be substantially accelerated was developed and its accuracy was investigated. Furthermore, a numerical radiative transfer model intended to simulate SCIAMACHY occultation measurements was developed and then coupled with an appropriate selected inverse technique.
    Description: thesis
    Keywords: 551.5 ; 550.28 ; 550 ; TQI 000 ; Geophysikalische Satellitenfernerkundung
    Language: English
    Type: monograph , publishedVersion
    Format: 150 S.
    Format: application/pdf
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    CITATION GEO-LEO
  • 4
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    Reconstruction of the sedimentary history offshore NW Africa (2010)
    Univ. Bremen
    Details
    Publication Date: 2021-03-29
    Description: Paleoceanography, Climate, Marine Productivity, Terrigenous Input, High-frequent Cyclicities, LGM, Holocene, XRF Core Scanner. - The goal of this thesis is to reconstruct, with high spatial resolution, the influence of coastal upwelling and terrigeneous input on the magnitude and composition of sediment accumulation off NW Africa, and to investigate how this influence has varied through the last glacial and interglacial periods. To achieve dense coverage for paleoceanographic reconstruction in the investigation area, a large number of sediment cores has been analyzed with rapid and non-destructive core-logging systems. The results of this thesis show that even the small region of the Canary Islands can be separated into several areas, with each reflecting its own sediment characteristics. Recent remote sensing images of chlorophyll concentration reflecting the present upwelling conditions are mirrored by the accumulation rates of the underlying sediment. The variation and distribution of the sediment accumulation rates in the past provides information about paleoceanographic features, such as upwelling conditions and sea-level fluctuations. The contribution of terrigeneous material to the marine sediments can be separated into eolian and a fluvial portions. Three characteristic areas ...
    Description: thesis
    Keywords: 551.46 ; 550.28 ; 550 ; VAT 240 ; TSZ 100 ; VAT 240 ; TSZ 100 ; Marine Sedimente einzelner Meere und Ozeane {Geologie} ; Atlantischer Ozean {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: application/pdf
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