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  • 1
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    Sea ice lead fraction for Arctic from AMSR2 data, November 2012 to April 30 2020 (2024)
    PANGAEA
    Details
    Publication Date: 2024-05-29
    Description: Röhrs and Kaleschke (2012) found that thin ice has a unique signature in the emissivity radio in the vertical polarized brightness temperature channels at frequencies between 89.0 GHz and 18.7 GHz in winter. The different sea ice classes especially for water and thin ice are characterized by the emissivity ratios above one. Following the proposed algorithm, we derive sea ice lead fraction from the AMSR2 brightness temperature data for the freezing season (November-April) north of 65°S. The spatial resolution of the data is 6.25 km. The steps are as follows. Firstly, the AMSR2 L1B brightness temperatures at frequencies of 18.7 GHz (TB,18.7V) and 89.0 GHz (TB,89V) are interpolated onto the NSIDC EASE grid with a spatial resolution of 6.25 km. Secondly, the brightness temperature radio r=TB,89V/TB,18.7V is calculated. Thirdly, a mean filter is used to enhance the signal of the leads. Finally, lead fraction which is defined as the area fraction of thin ice compared to other ice classes is computed. The proposed algorithm exhibits advanced ability in detecting sea ice leads in pack ice zone. It can detects leads wider than 3 km and resolves about 50% of the lead area compared to MODIS satellite images. File descriptions Period and temporal resolution: November 1, 2012, to April 30, 2020; Daily for freezing season: November 1 to April 30 Coverage and spatial resolution: Arctic north of 65°N Spatial resolution: 6.25 km x 6.25 km, NSIDC EASE grid. Geographic longitude: -180°E to 180°E Geographic latitude: from 65°N to 90°N Dimension: 1792 rows x 1216 column Format: NetCDF
    Keywords: AMSR2; Arctic; DATE/TIME; lead fraction; netCDF file; netCDF file (File Size); Satellite imagery; SATI; Sea ice
    Type: Dataset
    Format: text/tab-separated-values, 1429 data points
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    DATA PANGAEA
  • 2
    Electronic Resource
    Electronic Resource
    Cyclotron resonance of polarons in ternary mixed crystals (2003)
    Springer
    The European physical journal 33 (2003), S. 265-271 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 71.38.-k Polarons and electron-phonon interactions – 76.40.+b Diamagnetic and cyclotron resonances – 73.61.Ey III-V semiconductors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Rayleigh-Schrödinger perturbation theory and an improved Wigner-Brillouin perturbation theory has been used to study the cyclotron resonance of the polarons in ternary mixed crystals in the zero-temperature limit. The interaction between an electron and two branches of longitudinal optical phonon modes is taken into account in the framework of the random-element-isodisplacement model. The numerical results for several ternary mixed crystals show that the polaronic cyclotron energy and mass split successively twice related to the higher and lower branches of longitudinal optical phonon modes of ternary mixed crystals. A non-linear dependence of the polaronic cyclotron energy and mass on the composition x is found.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1140/epjb/e2003-00165-8
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Intermediate-coupling polaron in a ternary mixed crystal (1993)
    Springer
    The European physical journal 91 (1993), S. 455-461 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The intermediate-coupling polaron in a ternary mixed crystalA xB1−x C is studied within the framework of the random-element-isodisplacement (REI) model. The self-trapping energy and effective mass of the polaron are analytically derived in the mono-phonon approximation. The numerical results of the electron-LO phonon coupling constants, self-trapping energies and effective masses of the polarons for several mixed crystal materials are obtained as functions of the compositionx. It is found that there is a minimum of the polaron effects at a intermediatary value of the compositions for either the onemode or two-mode behaviour mixed crystals. The reduction of electron-LO-phonon interaction observed recently in the AgCl x Br1−x (0≦x≦0.21) mixed crystals can be qualitatively explained by our theoretical results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01316823
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    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Effect of electron-phonon interaction on surface states in a ternary mixed crystal (2000)
    Springer
    The European physical journal 15 (2000), S. 531-538 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 63.20.Kr Phonon electron and phonon phonon interactions - 71.38.+i Polarons and electron phonon interactions - 73.20.At Surface states, band structure, electron density of states
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: A variational theory is proposed to study the surface states of electrons in a semi-infinite ternary mixed crystal, by taking the effect of electron-surface optical (SO) phonon interaction into account. The energy and the wave function of the electronic surface-states are calculated. The numerical results of the energies of the surface states of the polarons and the self-trapping energies are obtained as functions of the composition x and surface potential V0 for several ternary mixed crystal materials. The results show that the electron-phonon interaction lowers the surface-state levels with the energies from several to scores of meV. It is also found that the self-trapping energy of the surface polaron has a minimum at some middle value of the composition x. It is indicated that the electron-phonon coupling effect can not be neglected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100510051156
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    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Improvement in sensitivity of fast atom bombardment mass spectrometry of amino acids by di-isopropylphosphorylation (1987)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 14 (1987), S. 331-333 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Positive ion fast atom bombardment mass spectrometric sensitivities of seven amino acids and the corresponding di-isopropylphosphorylated derivatives were carefully compared. Results showed that an improvement in sensitivity by factors of 4-29, mostly above 10, were achieved after the derivatization. The chemical noise derived from glycerol matrix was also greatly reduced by this derivatization.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200140706
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    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Mechanism of adhesion of polyurethane/polymethacrylate simultaneous interpenetrating networks adhesives to polymer substrates (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 32 (1994), S. 817-823 
    Details
    ISSN: 0887-6266
    Keywords: simultaneous interpenetrating network ; mechanism of adhesion ; polyurethane ; polymethacrylate ; polymer substrate ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Polyether-based polyurethane/poly (methyl methacrylate-co-ethyleneglycol dimethacrylate) interpenetrating polymer networks [PU/P (MMA-co-EGDMA)-IPNs] were synthesized and used as adhesives to adhere vulcanized natural rubber (NR) and soft polyvinyl chloride (PVC). The structure and morphology of the IPN adhesives in bulk and near the adhesive/substrate interfaces were investigated. A new mechanism of adhesion called conjugate interpenetration of networks across interfaces, which is suitable for IPN adhesives and polymer substrates, was put forward. According to this mechanism, while forming simultaneous interpenetrating networks in the adhesive, the monomers in the IPN adhesive can permeate polymer substrates and polymerize in situ to form gradient IPNs, thereby producing conjugate three-component IPNs near the adhesive/substrate interfaces. It is the conjugate interpenetration of the networks across the interfaces that strengthens interfacial combination remarkably and results in high bond strength of IPN adhesives. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1994.090320505
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    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Linear dependence of the intensity of the [M + H]+ ion peak in fast atom bombardment mass spectrometry on the basicity of meso-substituted octaethylporphyrins (1991)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 26 (1991), S. 267-270 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fast atom bombardment mass spectrometric study of the meso-substituent effect of Octaethylporphyrins (OEPX, X = NH2, CH3, H, CHO, Cl, CN, NO2) is reported. The intensity of the [M + H]+ ion peaks was estimated quantitatively using an external standard, which was observed to be correlated linearly with the basicity (pK3) of the OEPX. The pK3 value of the OEPXs was obtained by titration with perchloric acid and it was observed to be correlated linearly with Hammett's σp value, with a ρ value of 1.38.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210260416
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    Paper (German National Licenses)
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  • 8
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    On the Effects of Increased Vertical Mixing on the Arctic Ocean and Sea Ice (2018)
    In:  EPIC3Journal of Geophysical Research: Oceans, 123(12), pp. 9266-9282, ISSN: 2169-9275
    Details
    Publication Date: 2020-08-27
    Description: Against the backdrop of Arctic sea ice decline, vertical mixing in the interior Arctic Ocean will most likely change, but it is still unclear how the Arctic Ocean and sea ice will respond. In this paper, a sea ice‐ocean model with a simple parameterization for interior background mixing is used to investigate the Arctic Ocean and sea ice response to a scenario of increased vertical mixing. It is found that more vertical mixing reduces sea ice thickness all year round and decreases summertime sea ice concentration. More vertical mixing leads to a cooling of the Arctic halocline layer and Atlantic Water layer below. The increased vertical mixing speeds up vertical heat and salinity exchange, brings the underlying warm and saline water into the surface layer, and contributes to the sea ice decline. Vertical salinity gradient of the Arctic halocline layer reduces together with a much fresher Atlantic Water layer, and more volume of saline water enters the deep ocean below the Atlantic Water layer. As a result, the reduced Arctic Ocean stratification leads to an adjustment of the circulation pattern. Cyclonic circulation anomalies occur in the surface layer shallower than 20m depth and in the interior ocean deeper than 700m depth, while anticyclonic circulation anomalies occur between these depths. Our study suggests that the extra heat and salinity exchange induced by more vertical mixing will have a noticeable impact on the upper ocean structure, ocean circulation, and sea ice in a changing Arctic Ocean.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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    PAPER (OA)
  • 9
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    Assimilating Copernicus SST Data into a Pan-Arctic Ice–Ocean Coupled Model with a Local SEIK Filter (2017)
    AMER METEOROLOGICAL SOC
    In:  EPIC3Journal of Atmospheric and Oceanic Technology, AMER METEOROLOGICAL SOC, 34(9), pp. 1985-1999, ISSN: 0739-0572
    Details
    Publication Date: 2018-12-01
    Description: Sea surface temperature (SST) data from the Copernicus Marine Environment Monitoring Service are assimilated into a pan-Arctic ice–ocean coupled model using the ensemble-based local singular evolutive interpolated Kalman (LSEIK) filter. This study found that the SST deviation between model hindcasts and independent SST observations is reduced by the assimilation. Compared with model results without data assimilation, the deviation between the model hindcasts and independent SST observations has decreased by up to 0.28degC at the end of summer. The strongest SST improvements are located in the Greenland Sea, the Beaufort Sea, and the Canadian Arctic Archipelago. The SST assimilation also changes the sea ice concentration (SIC). Improvements of the ice concentrations are found in the Canadian Arctic Archipelago, the Beaufort Sea, and the central Arctic basin, while negative effects occur in the west area of the eastern Siberian Sea and the Laptev Sea. Also, sea ice thickness (SIT) benefits from ensemble SST assimilation.A comparison with upward-looking sonar observations reveals that hindcasts of SIT are improved in the Beaufort Sea by assimilating reliable SST observations into light ice areas. This study illustrates the advantages of assimilating SST observations into an ice–ocean coupled model system and suggests that SST assimilation can improve SIT hindcasts regionally during the melting season.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 10
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    Efficient Ensemble-Based Data Assimilation for High-Dimensional Models with the Parallel Data Assimilation Framework PDAF (2019)
    In:  EPIC3GODAE OceanView Symposium 2019 - OceanPredict '19, May 6-10, 2019, Halifax, Canada
    Details
    Publication Date: 2020-02-28
    Description: Discussed is how we can build a data-assimilative model by augmenting a forecast model by data assimilation functionality for efficient ensemble data assimilation. The implementation strategy uses a direct connection between a coupled simulation model and ensemble data assimilation software provided by the open-source Parallel Data Assimilation Framework (PDAF, http://pdaf.awi.de), which also provides fully-implemented and parallelized ensemble filters. The combination of a model with PDAF yields a data assimilation program with high flexibility and parallel scalability with only small changes to the model. The direct connection is obtained by first extending the source code of the coupled model so that it is able to run an ensemble of model states. In addition, a filtering step is added using a combination of in-memory access and parallel communication to create an online-coupled ensemble assimilation program. The direct connection avoids the common need to stop and restart a whole forecast model to perform the assimilation of observations in the analysis step of ensemble-based filter methods like ensemble Kalman or particle filters. Instead, the analysis step is performed in between time steps and is independent of the actual model coupler. This strategy can be applied with forced uncoupled models or coupled Earth system models, where it even allows for cross-domain data assimilation. The structure, features and performance of the data assimilation systems is discussed on the example of the ocean circulation models MITgcm and NEMO.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Conference , notRev
    Format: application/pdf
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