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  • 1
    Publication Date: 2013-08-31
    Description: [1]  One of the primary goals for the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard the Suomi National Polar-orbiting Partnership (SNPP) is to provide the science and user communities with the data continuity of the Environmental Data Records (EDR) (or Level-2 products) over global oceanic waters for various research and applications, including assessment of climatic and environmental variations. The ocean color EDR is one of the most important products derived from VIIRS. Since ocean color EDR is processed from the upstream Sensor Data Records (SDR) (or Level-1B data), the objective of this study is to evaluate the impact of the SDR on the VIIRS ocean color EDR. The quality of the SDR relies on pre-launch sensor characterizations as well as on-orbit radiometric calibrations, which are used to develop the sensor F-factor lookup tables (F-LUTs). VIIRS F-LUTs derived from solar and lunar calibrations have been used in processing data from the VIIRS Raw Data Records (RDR) (or Level-0 data) to SDR. In this study, three sets of F-LUTs with different generation schemes have been used to reprocess the SDR and then the ocean color EDR for product evaluations. VIIRS ocean color products are compared with in situ data from the Marine Optical Buoy (MOBY) and products from the Moderate Resolution Imaging Spectroradiometer (MODIS) on the satellite Aqua. It is found that the data quality of VIIRS operational ocean color products before 6 February 2012 is poor due to the inappropriate use of the at-launch F-LUTs for the SDR calibration, and that the recently updated VIIRS F-LUTs have significantly improved the SDR and ocean color EDR. Using reprocessed SDR with updated F-LUTs and including vicarious calibration, VIIRS ocean color EDR products are consistent with those from MODIS-Aqua in global deep waters. Although there are still some significant issues with VIIRS ocean color EDR, e.g., poor data quality over coastal regions, our results demonstrate that VIIRS has great potential to provide the science and user communities with consistently high quality global ocean color data records that are established from heritage ocean color sensors such as MODIS-Aqua.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 2
    Publication Date: 2017-01-11
    Description: Unusual cold filaments are uncovered during the spring intermonsoon season in the South China Sea (SCS) using a suite of satellite observations. They have a width of about 100 km on average and extend several hundreds of kilometers offshore on the sea surface, providing significant cross-shelf transport of heat and nutrients. The eastward current associated with mesoscale eddies in spring in the western SCS is found to play an important role in the filament formation by advecting coastal cold waters far offshore. The meridional location of the cold filament displays considerable interannual variability ranging between 9 o N and 18 o N, which can be attributed to the interannual south-north shift of the eastward current associated with eddies. It is also found that in the spring, cold filaments have profound effects on the chlorophyll a concentration in the upper ocean and the overlying atmosphere. These findings provide new insights into the role of eddies in cross-shelf exchange and mesoscale air-sea interaction in the marginal seas.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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  • 3
    Publication Date: 2014-08-13
    Description: P-n junction BiOBr/ZnO composites were prepared by a facile solvothermal process with double Br sources of CTAB and KBr. The samples were characterized by XRD, XPS, SEM, TEM, HRTEM, DRS, BET and PL. The BiOBr/ZnO composites exhibited much higher photocatalytic activity than single BiOBr and ZnO for the degradation of phenol under simulated sunlight irradiation. The enhanced photocatalytic activity of BiOBr/ZnO composites could be mainly ascribed to the high-efficiency separation of photogenerated electron-hole pairs through BiOBr/ZnO p-n junction. The reaction mechanism for the removal of phenol was also discussed. Hole and ·OH were the main reactive species. Moreover, the influence of disparate ratios of double Br sources to BiOBr/ZnO composites was also investigated. The results indicated that the BiOBr/ZnO composites prepared by double Br sources showed better photocatalytic activities than the sample prepared by single Br source. P-n junction BiOBr/ZnO composites were prepared by a facile solvothermal process with double Br sources and the composites exhibited higher photocatalytic activity than BiOBr and ZnO for the degradation of phenol, which could be ascribed to two reasons. One reason may be the high efficient separation of photogenerated electron-hole pairs through BiOBr/ZnO p-n junction. Another one would be the high surface area achieved by adjusting the content of CTAB.
    Print ISSN: 0232-1300
    Electronic ISSN: 1521-4079
    Topics: Geosciences , Physics
    Published by Wiley-Blackwell
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  • 4
    Publication Date: 2018-03-09
    Description: IJGI, Vol. 7, Pages 85: Assessment of Multiple GNSS Real-Time SSR Products from Different Analysis Centers ISPRS International Journal of Geo-Information doi: 10.3390/ijgi7030085 Authors: Zhiyu Wang Zishen Li Liang Wang Xiaoming Wang Hong Yuan The real-time State Space Representation (SSR) product of the GNSS (Global Navigation Satellite System) orbit and clock is one of the most essential corrections for real-time precise point positioning (PPP). In this work, the performance of current SSR products from eight analysis centers were assessed by comparing it with the final product and the accuracy of real-time PPP. Numerical results showed that (1) the accuracies of the GPS SSR product were better than 8 cm for the satellite orbit and 0.3 ns for the satellite clock; (2) the accuracies of the GLONASS (GLObalnaya NAvigatsionnaya Sputnikovaya Sistema) SSR product were better than 10 cm for orbit RMS (Root Mean Square) and 0.6 ns for clock STD (Standard Deviation); and (3) the accuracies of the BDS (BeiDou Navigation Satellite System) and Galileo SSR products from CLK93 were about 14.54 and 4.42 cm for the orbit RMS and 0.32 and 0.18 ns for the clock STD, respectively. The simulated kinematic PPP results obtained using the SSR products from CLK93 and CLK51 performed better than those using other SSR products; and the accuracy of PPP based on all products was better than 6 and 10 cm in the horizontal and vertical directions, respectively. The real-time kinematic PPP experiment carried out in Beijing, Tianjin, and Shijiazhuang, China indicated that the SSR product CLK93 from Centre National d’Etudes Spatiales (CNES) had a better performance than CAS01. Moreover, the PPP with GPS + BDS dual systems had a higher accuracy than those with only a GPS single system.
    Electronic ISSN: 2220-9964
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
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  • 5
    Publication Date: 2011-06-01
    Description: Cases of convergent evolution, particularly within ecomorphological contexts, are instructive in identifying universally adaptive morphological features across clades. Tracing of evolutionary pathways by which ecomorphological convergence takes place can further reveal mechanisms of adaptation, which may be strongly influenced by phylogeny. Ecomorphologies of carnivorous mammals represent some of the most outstanding cases of convergent evolution in the Cenozoic radiation of mammals. This study examined patterns of cranial shape change in the dog (Canidae) and hyena (Hyaenidae) families, in order to compare the evolutionary pathways that led to the independent specialization of bone-cracking hypercarnivores within each clade. Geometric morphometrics analyses of cranial shape in fossil hyaenids and borophagine canids provided evidence for deep-time convergence in morphological pathways toward the independent evolution of derived bone-crackers. Both clades contained stem members with plesiomorphic generalist/omnivore cranial shapes, which evolved into doglike species along parallel pathways of shape change. The evolution of specialized bone-crackers from these doglike forms, however, continued under the constraint of a full cheek dentition and restriction on rostrum length reduction in canids, but not hyaenids. Functionally, phylogenetic constraint may have limited borophagine canids to crack bones principally with their carnassial instead of the third premolar as in hyaenids, but other cranial shape changes associated with durophagy nevertheless evolved in parallel in the two lineages. Size allometry was not a major factor in cranial shape evolution in either lineage, supporting the interpretation of functional demands as drivers for the observed convergence. The comparison between borophagines and hyaenids showed that differential effects of alternative functional "solutions" that arise during morphological evolution may be multiplied with processes of the "macroevolutionary ratchet" already in place to further limit the evolutionary pathways available to specialized lineages.
    Print ISSN: 0094-8373
    Electronic ISSN: 0094-8373
    Topics: Geosciences
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  • 6
    Publication Date: 2013-03-26
    Description: AmyP is a raw-starch-degrading α-amylase newly identified from a marine metagenome library. It shares low sequence similarity with characterized glycoside hydrolases and was classified into a new subfamily of GH13. In particular, it showed preferential degradation to raw rice starch. Full-length AmyP was cloned and overexpressed in Escherichia coli , then purified and crystallized in the presence of its substrate analogue β-cyclodextrin. X-ray diffraction data were collected to a resolution of 2.1 Å. The crystal belonged to space group P 2 1 2 1 2, with unit-cell parameters a = 129.824, b = 215.534, c = 79.699 Å, α = β = γ = 90°, and was estimated to contain two molecules in one asymmetric unit.
    Electronic ISSN: 1744-3091
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Physics
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  • 7
    Publication Date: 2015-04-01
    Description: The effectiveness of grouting scheme has been simulated to prevent the coal spontaneous combustion at a goaf in Haizi Colliery, China. The colliery has been operated for long period over 27 years and has a complex ventilation network including airflow leakages which could possibly lead to the spontaneous combustion of coal at goafs. Firstly, the mine ventilation simulator MIVENA was used to analyze the mine ventilation network airflows to control airflows in and out of working faces and goafs. As the second approach, numerical simulations were carried by the simulator FLUENT in order to predict spontaneous combustion of residual coal with leakage flow in the #3205 goaf. It was cleared that the goaf can be divided into three zones based on oxygen concentration in the goaf area. Finally, the numerical simulation results show that the slurry grouting method is able to be an effective and economical method by reducing porosity in the goaf area to prevent spontaneous combustion of residual coal.
    Print ISSN: 1687-8833
    Electronic ISSN: 1687-8841
    Topics: Geosciences
    Published by Hindawi
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  • 8
    Publication Date: 2015-08-27
    Description: The cloud water content (CWC) in rainy clouds is a crucial parameter to determine the onset and the growth rate of precipitation, and to quantify the associated latent heating rate. No direct retrieval of CWC in rainy cloud from satellite observations is reported due to the difficulties of separating cloud particles from precipitation sized particles. However, based on multiple cloud simulations from the Weather and Research Forecasting (WRF) model, we have found that the CWC profile in warm rains can be well determined by three macro-physical cloud properties of cloud water path (CWP), cloud top height (CTH), and cloud bottom height (CBH). The CBH can be estimated using CWP, CTH and near surface rain rate. We proposed an algorithm with a lookup table for estimating the CWC profile using CWP, CTH and near surface rain rate as inputs. The performance of this algorithm was tested with WRF model simulations and a real drizzle case observed by the CloudSat satellite. Testing verified that the algorithm can retrieve the vertical distribution of CWC correctly with few errors at different spatiotemporal scales. In addition, the algorithm is not confined to particular microphysics schemes and is valid for multiple cloud systems in different areas over the world. This algorithm is expected to improve current knowledge of cloud water content in rainy clouds.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
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