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1.
An experimental method to investigate submarine bedform signatures at the sea surface is described. The study area was the Lister Tief in the German Bight of the southeastern North Sea, a semienclosed tidal basin with asymmetric and very large sand waves. In-situ and remote measurements of surface roughness were obtained simultaneously. An X-band wave monitoring radar, an oceanographic multisensor sea surface buoy, an acoustic Doppler current profiler, and a standard echo sounder were operated on and from board a research vessel while drifting along the tidal channel 相似文献
2.
Saint-Hilaire Pascal von Praun Christoph Stolte Etzard Alonso Gustavo Benz Arnold O. Gross Thomas 《Solar physics》2002,210(1-2):143-164
The RHESSI Experimental Data Center (HEDC) at ETH Zürich aims to facilitate the use of RHESSI data. It explores new ways to
speed up browsing and selecting events such as solar flares. HEDC provides pre-processed data for on-line use and allows basic
data processing remotely over the Internet. In this article, we describe the functionality and contents of HEDC, as well as
first experiences by users. HEDC can be accessed at http://www.hedc.ethz.ch. Additional graphical material and color versions of most figures are available on the CD-ROM accompanying this volume.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022413302246 相似文献
3.
Finite element modelling of the saturated–unsaturated surface–subsurface flow mechanisms operative in a small salinized catchment in south‐western Australia was used to help define the flow system and explain the causes of waterlogging and salinization there. Data available at the site from a previous study were used to obtain a first approximation to the flow system. Altering the properties of some of the strata gave a closer calibration. It was found that the modelled saturated hydraulic conductivity of the B horizon in the duplex soil zone needed to be at least an order of magnitude lower than that measured in order to reproduce the perching conditions observed in the field. Also, the model indicated the influence of a doleritic dyke, whose presence was confirmed by field measurement. Our analysis showed that there were two main flow systems operating in the hillslope. The first, and most dominant, was the recharge occurring through the upslope gradational soil zone and percolating down to both the deeply weathered regolith and the basal aquifer. The second flow system is an unsaturated flow system operating in the high permeability A horizon in the downslope duplex soil zone. The first system is primarily responsible for the saline seepage zone in the valley bottom. The second contributes to the waterlogging and perching occurring upslope of the seepage zone. Vertical flow through the higher permeability B horizon in the gradational soil zone in the upper slopes is a major contributor of recharge. Recharge by flow through macropores occurs where, but only where, perched aquifers develop and allow the macropores to be activated. Areas with perched aquifers occurred in downslope locations and near a doleritic dyke located upslope. Thus, the area where macropore recharge occurred was not large. The recharge rate required to maintain the piezometric levels at present values is only about 30 mm/yr (about 5% of the annual rainfall). The piezometric levels under the upper part of the catchment varied greatly with only small changes in recharge rate. A 50% reduction in recharge rate had the effect of reducing the length of the seepage zone at the end of winter by 40%. Changes in recharge rate had little effect on the extent of the perched aquifer at the end of winter. Deep‐rooted perennial forages, shrubs or trees on the gradational soil zone in the upper part of the catchment and on the zones upslope of geological barriers to flow would be required to reduce the recharge and to allow for rehabilitation of the saline valley floor. Waterlogging associated with the perched water table in the bottom part of the catchment would be best addressed by tree plantations located just upslope of the salinized zone in the valley floor. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
4.
M. Markiewicz J. Henke A. Brillowska-Dąbrowska S. Stolte J. Łuczak C. Jungnickel 《International Journal of Environmental Science and Technology》2014,11(7):1919-1926
Extensive research and increasing number of potential industrial applications made ionic liquids (ILs) important materials in design of new, cleaner technologies. Together with the technological applicability, the environmental fate of these chemicals is considered and significant efforts are being made in designing strategies to mitigate their potential negative impacts. Many ILs are proven to be poorly biodegradable and relatively toxic. Bioaugmentation is known as one of the ways of enhancing the microbial capacity to degrade xenobiotics by addition of specialized strains. The aim of current work was to select microbial species that could be used for bioaugmentation in order to enhance biodegradation of ILs in the environment. We subjected activated sewage sludge to the selective pressure of 1-methyl-3-octylimidazolium chloride ([OMIM][Cl]) and isolated nine strains of bacteria which were able to prevail in these conditions. Subsequently, we utilized axenic cultures (pure cultures) of these bacteria as well as mixed consortium to degrade this IL. In addition, we performed growth inhibition tests and found that bacteria were able to grow in 2 mM, but not in 20 mM solutions of [OMIM][Cl]. The biodegradation conducted by the isolated consortium was higher than conducted by the activated sewage sludge when normalized by the cell density, which indicates that the isolated strains seem specifically suited to degrade the IL. 相似文献
5.
The small-scale roughness of the sea surface acts as an important link in air-sea interaction processes. Radar and sonar waves are scattered by short surface waves providing the basis for remote sensing methods of the sea surface. At high wind speeds, breaking waves occur. Bubbles penetrate into the water and drastically increase acoustical reverberation, transmission loss and ambient noise. Thus, the development of short waves and wave breaking have to be known to apply radar remote sensing to the surface and to deduce from radar backscatter which sonar conditions prevail. To measure the wind dependence of short waves an experimental device was constructed for use from stationary platforms. It is nearly all-weather capable and can easily be handled by a crane. On the other hand, frequencies of short waves measured in a fixed position are extremely frequency shifted by currents. This limits the usefulness of tower-based measurements, e.g., the short wave modulation by wind and waves or currents can only be estimated in a rough approximation. Consequently, a buoy was developed to reduce the frequency shifts. The principle of the buoy is to drift in the local surface current and to follow the amplitudes of long waves. Therefore, short waves are measured in facets of long waves and the Doppler shifts are minimized. The wind is measured at a constant height above the long wave profile and relative to the moving facets. The paper describes the conventional measuring device and points out the necessity of the drifting buoy system. Examples of wind and wave spectra are presented and short wave modulations by long waves are depicted, too. From these measurements, new insights in short wave behaviour have to be expected 相似文献
6.
Sonar and radar signals are scattered by small-scale roughness elements of the sea surface. The characteristics of the roughness depend on wind, sea state, and other parameters. The dynamic behavior of this roughness is related to radar backscatter. This provides a basis for oceanographic radar remote sensing and links radar backscatter to sea surface sonar conditions. Radar, sonar, and roughness experiments have been conducted at the research platform NORDSEE. The results are combined and provide a method to estimate shallow water sonar conditions from the radar backscatter cross section 相似文献
7.
A hydrological model (SLURP) that was designed for simulating hydrological processes taking place in large river basins was, with minimal modification, used successfully to simulate water level variations over a 28‐year period (1969–1996) for a 3‐ha prairie wetland in Saskatchewan. The model calculates a water balance based on precipitation, snowmelt, evaporation, surface runoff and subsurface flow on a daily time‐step. The model was first calibrated for two periods (1969–1973 for cropland and 1987–1990 for grassland), then it was applied to records outside the calibration periods. The model reproduced the wetland water level variations during a 28‐year period with good accuracy. The wetland water levels were most sensitive to the infiltration coefficient of surface soil under frozen conditions and to maximum soil moisture storage. The applicability of the model and the calibrated parameters to a smaller wetland, with an area of 0·24 ha, was examined. This simulation indicated that scale effects are important, probably largely in relation to snow redistribution by wind. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
8.
Andrea Stolte Andrea Ghez Mark Morris Jessica Lu Wolfgang Brandner Keith Matthews 《Astrophysics and Space Science》2009,324(2-4):137-140
We have measured the proper motion of the Arches cluster near the Galactic Center (GC) with respect to the ambient field, using Keck/NIRC2 LGS-AO and VLT/NAOS-CONICA NGS-AO observations spanning a baseline of 4.3 yr. Combined with the radial velocity, we derive a 3D space motion of 232±30 km?s?1 for the Arches cluster. This motion is exceptionally large compared to molecular cloud orbits at the GC, and places stringent constraints on the formation scenarios for starburst clusters in dense, nuclear environments. 相似文献
9.
Knowledge of soil microtopography and its changes in space and over time is important to the understanding of how tillage influences infiltration, runoff generation and erosion. In this study, the use of a terrestrial laser scanner (TLS) is assessed for its ability to quantify small changes in the soil surface at high spatial resolutions for a relatively large surface area (100 m2). Changes in soil surface morphology during snow cover and melt are driven by frost heave, slaking, pressure exertion by the snowpack and overland flow (erosion and deposition). An attempt is undertaken to link these processes to observed changes at the soil surface. A new algorithm for soil surface roughness is introduced to make optimal use of the raw point cloud. This algorithm is less scale dependent than several commonly used roughness calculations. The results of this study show that TLSs can be used for multitemporal scanning of large surfaces and that small changes in surface elevation and roughness can be detected. Statistical analysis of the observed changes against terrain indices did not yield significant evidence for process differentiation. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd. © 2019 The Authors. Earth Surface Processes and Landforms Published by John Wiley & Sons Ltd. 相似文献
10.
Kavousi Alireza Reimann Thomas Wöhling Thomas Birk Steffen Luhmann Andrew J. Kordilla Jannes Noffz Torsten Sauter Martin Liedl Rudolf 《Hydrogeology Journal》2023,31(4):1005-1030
Characterization of karst systems and forecast of their state variables are essential for groundwater management and engineering in karst regions. These objectives can be met by the use of process-based discrete-continuum models (DCMs). However, results of DCMs may suffer from inversion nonuniqueness. It has been demonstrated that the joint inversion of observations regulated by different natural processes can tackle the nonuniqueness issue in groundwater modeling. However, this has not been tested for DCMs thus far. This research proposes a methodology for the joint inversion of hydro-thermo-chemo-graphs, applying to two small-scale sink-to-spring experiments at Freiheit Spring, Minnesota, USA. In order to address conceptual uncertainty, a multimodel approach was implemented, featuring seven mutually exclusive variants. Spring hydro-thermo-chemo-graphs, for all the variants simulated by MODFLOW-CFPv2, were jointly inverted using a weighted least squares algorithm. Subsequently, models were compared in terms of inversion and forecast performances, as well as parameter uncertainties. Results reveal the suitability of the DCM approach for simultaneous inversion and forecast of hydro-physico-chemical behavior of karst systems, even at a scale of meters and seconds. The estimated volume of the tracer conduit passage ranges from approximately 46–51 m3, which is comparable to the estimate from the flood-pulse method. Moreover, it was demonstrated that the thermograph and hydrograph contain more information about aquifer characteristics than the chemograph. However, this finding can be site-specific and should depend on the analysis scale, the considered conceptual models, and the hydrological state, which are potentially affected by minor unaccountable processes and features.
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