Basis for a streamflow forecasting system to Rincón del Bonete and Salto Grande (Uruguay)     

Stefanie Talento  Rafael Terra 《Theoretical and Applied Climatology》2013,114(1-2):73-93

This paper presents the basis for the design of streamflow prediction systems for the hydroelectric dams of Rincón del Bonete (Uruguay) and Salto Grande (Uruguay–Argentina). The prediction is made, independently, for each reservoir and each month of the year with two methodologies: data-driven statistical models and hybrid downscaling that includes atmospheric predictors. We determine a set of potential predictors and then fit linear models coupled with variable selection techniques, under the hypothesis of perfectly known predictors. The predictive skill of the schemes outperforms the climatological forecast throughout the year in both reservoirs (except August in Rincón del Bonete). This remains the case even when the forecast lead does not allow for the use of preceding flows as predictors. While in Rincón del Bonete it is not possible to distinguish a period of high predictability, in Salto Grande, there is a robust signal in March–May and October–December.  相似文献   

Comment on “General relativity resolves galactic rotation without exotic dark matter” by F.I. Cooperstock and S. Tieu     

Burkhard Fuchs  Stefanie Phleps 《New Astronomy》2006,11(8):608-610

The general relativistic model of Cooperstock and Tieu, which attempts to fit rotation curves of spiral galaxies without invoking dark matter, is tested empirically using observations of the Milky Way. In particular, predictions for the mass density in the solar neighbourhood and the vertical density distribution at the position of the Sun are compared with observations. It is shown that the model of Cooperstock and Tieu, which was so constructed that it gives an excellent fit of the observed rotation curve, singularly fails to reproduce the observed local mass density and the vertical density profile of the Milky Way.  相似文献   

Variations of sulphur isotope signatures in sulphides from the metamorphosed Ming Cu(−Au) volcanogenic massive sulphide deposit,Newfoundland Appalachians,Canada     

Stefanie M. Brueckner  Stephen J. Piercey  Graham D. Layne  Glenn Piercey  Paul J. Sylvester 《Mineralium Deposita》2015,50(5):619-640

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Proposal for applying a component-based mixture approach for ecotoxicological assessment of fracturing fluids   总被引：2，自引：2，他引：0  

Janet Riedl  Stefanie Rotter  Sonja Faetsch  Mechthild Schmitt-Jansen  Rolf Altenburger 《Environmental Earth Sciences》2013,70(8):3907-3920

Hydraulic fracturing is increasingly being used to produce gas from unconventional resource sites for energy supply. Therefore, concerns about risks of this technology related to human health and the environment have to be addressed. Among the major issues is the potential contamination of surrounding water systems by chemical additives used in fracturing fluids. In this study, the ecotoxicological hazards of fracturing fluids, both, their individual components (chemicals) as well as their mixtures (product) were assessed using a component-based mixture approach. For five exemplary fracturing fluids, 40–90 wt% of the contained substances could unambiguously be defined in their chemical identity. The concentrations used in the applied fluid mixture were considered as (maximum) exposure concentrations. For components with mass fractions between 10 and 74 wt%, the effect concentrations for acute and chronic toxicity of fish, daphnia and algae were retrieved from experimental databases and through predictive modeling. The hazard indices calculated from the ratio of exposure to effect concentration were >1 for all fracturing fluids, using different scenarios. This indicated a hazard from the undiluted fracturing fluids. The assessment framework presented in this study allows for dealing with data gaps and uncertainties in a tiered fashion and in particular accommodates for combined effects resulting from chemical mixtures. It might be employed for ecotoxicological risk assessment of products containing chemical mixtures and optimization of their environmental performance.  相似文献   

Combining global sensitivity analysis and multiobjective optimisation to estimate soil hydraulic properties and representations of various sole and mixed crops for the agro-hydrological SWAP model     

Philipp Stahn  Stefanie Busch  Thomas Salzmann  Bettina Eichler-Löbermann  Konrad Miegel 《Environmental Earth Sciences》2017,76(10):367

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Geostandards and Geoanalytical Research Bibliographic Review 2008     

Klaus Peter Jochum  Stefanie M. Brueckner  Uwe Nohl  Brigitte Stoll  Ulrike Weis 《Geostandards and Geoanalytical Research》2009,33(4):501-505

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Evaluating the source and seasonality of submarine groundwater discharge using a radon-222 pore water transport model   总被引：1，自引：0，他引：1  

Christopher G. Smith  Jaye E. Cable  Jonathan B. Martin  Moutusi Roy 《Earth and Planetary Science Letters》2008,273(3-4):312-322

Pore water radon (²²²Rn) distributions from Indian River Lagoon, Florida, are characterized by three zones: a lower zone where pore water ²²²Rn and sediment-bound radium (²²⁶Ra) are in equilibrium and concentration gradients are vertical; a middle zone where ²²²Rn is in excess of sediment-bound ²²⁶Ra and concentration gradients are concave-downward; and an upper zone where ²²²Rn concentration gradients are nearly vertical. These ²²²Rn data are simulated in a one-dimensional numerical model including advection, diffusion, and non-local exchange to estimate magnitudes of submarine groundwater discharge components (fresh or marine). The numerical model estimates three parameters, fresh groundwater seepage velocity, irrigation intensity, and irrigation attenuation, using two Monte Carlo (MC) simulations that (1) ensure the minimization algorithm converges on a global minimum of the merit function and the parameter estimates are consistent within this global minimum, and (2) provide 90% confidence intervals on the parameter estimates using the measured ²²²Rn activity variance. Model estimates of seepage velocities and discharge agree with previous estimates obtained from numerical groundwater flow models and seepage meter measurements and show the fresh water component decreases offshore and varies seasonally by a factor of nine or less. Comparison between the discharge estimates and precipitation patterns suggests a mean residence time in unsaturated and saturated zones on the order of 5 to 7 months. Irrigation rates generally decrease offshore for all sampling periods. The mean irrigation rate is approximately three times greater than the mean seepage velocity although the ranges of irrigation rates and seepage velocities are the same. Possible mechanisms for irrigation include density-driven convection, wave pumping, and bio-irrigation. Simulation of both advection and irrigation allows the separation of submarine groundwater discharge into fresh groundwater and (re)circulated lagoon water.  相似文献   

The nature of the luminous X-ray emission of NGC 6240     

Stefanie Komossa  Hartmut Schulz 《Astrophysics and Space Science》1999,266(1-2):61-66

We briefly review and extend our discussion of the ROSAT detectionof the extraordinarily luminous (>10⁴² erg/s) partly extended(>30 kpc diameter) X-ray emission from the ultraluminous infrared galaxy NGC 6240.The `standard'-model of starburst outflow is contrasted with alternatives and a comparison with the X-ray properties of ellipticals is performed.  相似文献   

Spatial and seasonal variation in soil respiration along a slope in a rubber plantation and a natural forest in Xishuangbanna,Southwest China   总被引：1，自引：0，他引：1  

Yong-li Zhao  Stefanie D. Goldberg  Jian-chu Xu  Rhett D. Harrison 《山地科学学报》2018,15(4):695-707

Soil respiration is a key component of the global carbon cycle, and even small changes in soil respiration rates could result in significant changes in atmospheric CO₂ levels. The conversion of tropical forests to rubber plantations in SE Asia is increasingly common, and there is a need to understand the impacts of this land-use change on soil respiration in order to revise CO₂ budget calculations. This study focused on the spatial variability of soil respiration along a slope in a natural tropical rainforest and a terraced rubber plantation in Xishuangbanna, Southwest (SW) China. In each land-use type, we inserted 105 collars for soil respiration measurements. Research was conducted over one year in Xishuangbanna during May, June, July and October 2015 (wet season) and January and March 2016 (dry season). The mean annual soil respiration rate was 30% higher in natural forest than in rubber plantation and mean fluxes in the wet and dry season were 15.1 and 9.5 Mg C ha^-1 yr^-1 in natural forest and 11.7 and 5.7 Mg C ha^-1 yr^-1 in rubber plantation. Using a linear mixed effects model to assess the effect of changes in soil temperature and moisture on soil respiration, we found that soil temperature was the main driver of variation in soil respiration, explaining 48% of its seasonal variation in rubber plantation and 30% in natural forest. After including soil moisture, the model explained 70% of the variation in soil respiration in natural forest and 76% in rubber plantation. In the natural forest slope position had a significant effect on soil respiration, and soil temperature and soil moisture gradients only partly explained this correlation. In contrast, soil respiration in rubber plantation was not affected by slope position, which may be due to the terrace structure that resulted in more homogeneous environmental conditions along the slope. Further research is needed to determine whether or not these findings hold true at a landscape level.  相似文献   

Fossa Carolina: The First Attempt to Bridge the Central European Watershed—A Review,New Findings,and Geoarchaeological Challenges     

Eva Leitholdt  Christoph Zielhofer  Stefanie Berg‐Hobohm  Katharina Schnabl  Britta Kopecky‐Hermanns  Jens Bussmann  Joachim W. Hrtling  Klaus Reicherter  Katrin Unger 《Geoarchaeology》2012,27(1):88-104

The Central European watershed passes through the southern Franconian Jura in Bavaria, Germany. This principal watershed divides the Rhine/Main catchment and the Danube catchment. In the early Middle Ages, when ships were an important means of transportation, Charlemagne decided to connect these catchments by the construction of a canal known as the Fossa Carolina. In this paper, we present for the first time ¹⁴C data from the Fossa Carolina fill and document a high‐resolution stratigraphic record of the Carolingian and post‐Carolingian trench infilling. Our results provide clear evidence for peat layers in different levels of the trench infill, suggesting a chain of ponds. However, the majority of these peat layers yield mid‐Medieval and younger ages. The period of major peat growth was during the Medieval climatic optimum. Therefore, our preliminary results do not prove the use of the trench during Carolingian times. However, first results from the reconstruction of the Carolingian trench bottom support the hypothesis that the Fossa was primarily planned as a navigable chain of ponds and not as a continuous canal. In the eastern part of the trench, a dam is located that was postulated in former studies to be part of a barrage for supplying the Carolingian canal with water. New ¹⁴C data indicate much younger ages and do not support the Carolingian barrage concept.  相似文献