Wave climate in a groin field     

V. Sundar  H. Noethel  K. P. Holz 《Ocean Engineering》1992,19(5)

Wave records at seven different locations within a groin field have been analysed by both statistical and spectral approaches to study the general wave climate. The wave heights and periods from the wave records were obtained by both upcross and downcross methods for the statistical approach. The variation of different wave height and wave period parameters with respect to the time of measurement at a particular location and its variation at different locations within the groin field at a particular instant of time are presented and discussed in detail in this paper. It is generally found that the wave heights follow the Weibull distribution.  相似文献   

Retrieving cloud fraction in the field-of-view of a high-spectral resolution infrared radiometer     

Turner  D.D. Holz  R.E. 《Geoscience and Remote Sensing Letters, IEEE》2005,2(3):287-291

The combination of radiance from both clear and cloudy regions of sky within the instrument's field of view (FOV) adds significant uncertainty to retrievals of atmospheric state profiles and cloud microphysical properties from infrared spectroradiometers. In this letter, we use observations of radiance from both the 8-13 and 3-5 /spl mu/m bands to retrieve estimates of the cloud fraction in the instrument's FOV, as well as microphysical cloud properties, from high-spectral-resolution infrared radiometers. Cloud fraction derived from imagers as well as high-time-resolution observations show good agreement and high correlation with our derived cloud fraction values. This is shown for both ground-based and aircraft-based observations. We also demonstrate that the use of the additional information in the 3-5 /spl mu/m band extends the dynamic range and accuracy of microphysical properties that can be retrieved from infrared radiance data.  相似文献   

Inter‐laboratory Characterisation of Apatite Reference Materials for Chlorine Isotope Analysis     

Alicja Wudarska  Ewa S&#x;aby  Michael Wiedenbeck  Jaime D. Barnes  Magali Bonifacie  Neil C. Sturchio  Grard Bardoux  Frdric Couffignal  Johannes Glodny  Linnea Heraty  Timm John  Christof Kusebauch  Sathish Mayanna  Franziska D. H. Wilke  Ewa Deput 《Geostandards and Geoanalytical Research》2021,45(1):121-142

Here we report on a set of six apatite reference materials (chlorapatites MGMH#133648, TUBAF#38 and fluorapatites MGMH#128441A, TUBAF#37, 40, 50) which we have characterised for their chlorine isotope ratios; these RMs span a range of Cl mass fractions within the apatite Ca₁₀(PO₄)₆(F,Cl,OH)₂ solid solution series. Numerous apatite specimens, obtained from mineralogical collections, were initially screened for ³⁷Cl/³⁵Cl homogeneity using SIMS followed by δ³⁷Cl characterisation by gas source mass spectrometry using both dual‐inlet and continuous‐flow modes. We also report major and key trace element compositions as determined by EPMA. The repeatability of our SIMS results was better than ± 0.10‰ (1s) for the five samples with > 0.5 % m/m Cl and ± 0.19‰ (1s) for the low Cl abundance material (0.27% m/m). We also observed a small, but significant crystal orientation effect of 0.38‰ between the mean ³⁷Cl/³⁵Cl ratios measured on three oriented apatite fragments. Furthermore, the results of GS‐IRMS analyses show small but systematic offset of δ³⁷Cl_SMOC values between the three laboratories. Nonetheless, all studied samples have comparable chlorine isotope compositions, with mean 10³δ³⁷Cl_SMOC values between +0.09 and +0.42 and in all cases with 1s ≤ ± 0.25.  相似文献   

Extension of the Paraná Basin to offshore Brazil: Implications for coalbed methane evaluation     

Michael Holz  Wolfgang Kalkreuth  Silvia Beatriz Alves Rolim 《Marine and Petroleum Geology》2010

Coalbed methane (CBM) is a worldwide exploration target of the petroleum industry. In Brazil, the most important coal-bearing succession is associated with the Permian Rio Bonito Formation of the Paraná Basin. The gas-prone areas are located at the southeastern margin of the Paraná Basin and possibly in the offshore region of the northern part of the Pelotas Basin. Coalfields end abruptly at the present day shoreline, a result of rifting of Gondwana and the evolution of the South Atlantic Ocean. All geologic indicators suggest that in pre-rift times the coal seams extended further eastwards, probably now lying deeply buried below the sedimentary succession of the Pelotas Basin. The present paper discusses structural, stratigraphic, seismic and aeromagenetic data that support the preservation of continental crust beneath ocean sediment. If the coal beds had similar lateral extent to known onshore coals, and coal beds extended across the projected extension of the Parana basin, and there was a conservative 5 m of cumulative coal thickness, then a potential methane volume can be estimated for this newly inferred resource. Average onshore coal gas content is 32 scf/ton (1.00 m³/ton). If this is similar in the offshore coal deposits, then the hypothetical methane volume in the offshore area could be in excess of 1.9 × 10¹² scf (56 × 10⁹ m³). Metamorphism from dikes associated with rifting are potential complicating factors in these deposits, and since no borehole reaching the deep-lying strata in the offshore area are available, this is a hypothetical gas resource with a certain level of uncertainty which should be tested in the future by drilling a deep borehole.  相似文献   

Multi-stage reaction history in different eclogite types from the Pakistan Himalaya and implications for exhumation processes     

Franziska D.H. Wilke  Patrick J. O'Brien  Uwe Altenberger  Matthias Konrad-Schmolke  M. Ahmed Khan 《Lithos》2010,114(1-2):70-85

Metabasites were sampled from rock series of the subducted margin of the Indian Plate, the so-called Higher Himalayan Crystalline, in the Upper Kaghan Valley, Pakistan. These vary from corona dolerites, cropping out around Saif-ul-Muluk in the south, to coesite–eclogite close to the suture zone against rocks of the Kohistan arc in the north. Bulk rock major- and trace- element chemistry reveals essentially a single protolith as the source for five different eclogite types, which differ in fabric, modal mineralogy as well as in mineral chemistry. The study of newly-collected samples reveals coesite (confirmed by in situ Raman spectroscopy) in both garnet and omphacite. All eclogites show growth of amphiboles during exhumation. Within some coesite-bearing eclogites the presence of glaucophane cores to barroisite is noted whereas in most samples porphyroblastic sodic–calcic amphiboles are rimmed by more aluminous calcic amphibole (pargasite, tschermakite, and edenite). Eclogite facies rutile is replaced by ilmenite which itself is commonly surrounded by titanite. In addition, some eclogite bodies show leucocratic segregations containing phengite, quartz, zoisite and/or kyanite. The important implication is that the complex exhumation path shows stages of initial cooling during decompression (formation of glaucophane) followed by reheating: a very similar situation to that reported for the coesite-bearing eclogite series of the Tso Morari massif, India, 450 km to the south-east.  相似文献   

Analysis and characterization of the synergistic AIRS and MODIS cloud-cleared radiances     

Hong Zhang  Hung-Lung Huang  Agnes Lim  Robert Holz  Steve Dutcher  Fred Nagle  Liam Gumley  Jinnian Wang  Runhe Shi  Wei Gao 《Frontiers of Earth Science》2010,4(3):363-373

The Atmospheric Infrared Sounder (AIRS) and MODerate-Resolution Imaging Spectroradiometer (MODIS) on board NASA Earth Observing System (EOS) Aqua spacecraft measure the upwelling infrared radiance used for numerous remote-sensing- and climate-related applications. AIRS provides high spectral resolution infrared radiances, while MODIS provides collocated high spatial resolution radiances at 16 broad infrared bands. An optimal algorithm for cloud-clearing has been developed for AIRS cloudy soundings at the University of Wisconsin-Madison, where the spatially and spectrally collocated AIRS and MODIS data has been used to analyze the characteristic of this algorithm. An analysis and characterization of the global AIRS cloud-cleared radiances using the bias and the standard deviation between the cloud-cleared and the nearby clear measurements are studied. Scene inhomogeneity for both land- and water-surface types has been estimated to account for the assessed error. Both monthly and seasonal changes of global AIRS/MODIS cloud-clearing performance also have been analyzed.  相似文献   

Future emissions of marine halogenated very-short lived substances under climate change     

Franziska?Ziska  Birgit?QuackEmail author  Susann?Tegtmeier  Irene?Stemmler  Kirstin?Krüger 《Journal of Atmospheric Chemistry》2017,74(2):245-260

Halogenated Very Short-lived Substances (VSLS), such as bromoform, dibromomethane and methyl iodide, are naturally produced in the oceans and are involved in ozone depletion in the troposphere and the stratosphere. The effect of climate change on the oceanic emissions of these compounds is not well quantified. Based on present-day observed global oceanic and atmospheric concentrations, and historic and future data from three CMIP5 models, past and future sea-to-air fluxes of these VSLS are calculated. The simulations are used to infer possible effects of projected changes of physical forcing on emissions in different oceanic regimes. CMIP5 model output for 1979–2100 from the historical scenario and the RCP scenarios 2.6 and 8.5 are used as input data for the emission calculations. Of the parameters that have the main influence on the sea-to-air fluxes, the global sea surface temperatures show a steady increase during the twenty-first century, while the projected changes of sea surface wind speed is very small. The calculated emissions based on the historical CMIP5 model runs (1979–2005) increased over the 26 year period and agree well with the emissions based on ERA-Interim data. The future sea-to-air fluxes of VSLS generally increase during the twenty-first century under the assumption of constant concentration fields in the ocean and atmosphere. The multi-model mean global emissions of bromoform increase by 29.4% (9.0%) between 1986 and 2005 and 2081–2100 under RCP 8.5 (2.6) and dibromomethane and methyl iodide emissions increase by 23.3% (6.4%) and 5.5% (1.5%), respectively. Uncertainties of the future emission estimates, driven by ongoing environmental changes such as changing oceanic productivity (not considered in this study) are discussed.  相似文献   

How appropriate is the Thiem equation for describing groundwater flow to actual wells?     

Franziska Tügel  Georg J. Houben  Thomas Graf 《Hydrogeology Journal》2016,24(8):2093-2101

The Thiem equation of radial groundwater flow to a well is more than 100 years old and is still commonly used. Here, deviations caused by some of its simplifications are quantified by comparing the analytical to a numerical model that allows the implementation of more complex geometries. The assumption of horizontal flow in the Thiem equation, which necessitates uniform inflow over the entire screen length of the fully penetrating well, was found to cause deviations from actual pumping wells where the pump is placed above the screen, resulting in non-uniform inflow and additional drawdown. The same applies to partially penetrating wells, where inflow peaks and additional drawdown occur, especially when the well is screened in the lower part of the aquifer. The use of the Thiem equation in the near-field of a well should thus be restricted to situations where the screen inflow is relatively uniformly distributed, e.g. when it covers large portions of the aquifer thickness. The presence of a gravel pack and a background gradient, on the other hand, are of limited importance.  相似文献   

Late quaternary hydrological changes at Tangra Yumco,Tibetan Plateau: a compound-specific isotope-based quantification of lake level changes     

Franziska Günther  Andrej Thiele  Sophie Biskop  Roland Mäusbacher  Torsten Haberzettl  Tandong Yao  Gerd Gleixner 《Journal of Paleolimnology》2016,55(4):369-382

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Asymmetries in waves and velocities in a groin field     

V. Sundar  H. Noethel  K.-P. Holz 《Ocean Engineering》1994,21(5)

The measured wave elevation and the corresponding two horizontal velocity components of in-line and transverse directions at eight different locations across a bar in a groin field off the East Frisian Island off Norderney at the North Sea Coast have been analysed. The variation of the wave and the velocities spectra within the groin field is reported.The waves and their kinematics are seldom linear in nearshore waters. In this paper, the results obtained through an attempt to study the asymmetries in the wave elevation and the in-line velocity time histories are reported. The probability density of the asymmetries are drawn along with theoretical Rayleigh and Weibull distributions. The variation of the different asymmetry factors within the groin field is discussed.  相似文献