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251.
In situ-produced cosmogenic nuclides provide a means for quantitative evaluation of a wide range of weathering and sediment transport processes. Although these nuclides have received attention for their power as geochronometers of surface exposure, it may be argued that they are more broadly suited for study of surface processes. In many environments, they may be used to evaluate collapse, erosion, burial, bioturbation, and creep, as well as providing a qualitative basis for distinguishing allochthonous from autochthonous materials. In addition, these nuclides can provide quantitative information on rates of erosion on scales of landforms and drainage basins. Here, we review the systematics of cosmogenic nuclide production within the Earth's surface, and present field examples demonstrating the utilization of in situ-produced cosmogenic nuclides distributions for evaluation of a range of soil evolution processes. To cite this article: E.T. Brown et al., C. R. Geoscience 335 (2003). 相似文献
252.
Cheng Sibo Argaud Jean-Philippe Iooss Bertrand Ponçot Angélique Lucor Didier 《Mathematical Geosciences》2021,53(8):1751-1780
Mathematical Geosciences - An original graph clustering approach for the efficient localization of error covariances is proposed within an ensemble-variational data assimilation framework. Here,... 相似文献
253.
The groundwater flow pattern of the western part of the Guarani Aquifer System (GAS), Brazil, is characterized by three regional recharge areas in the north, and a potentiometric divide in the south, which trends north–south approximately. Groundwater flow is radial from these regional recharge areas toward the center of Paraná Sedimentary Basin and toward the western outcrop areas at the border of the Pantanal Matogrossense, because of the potentiometric divide. The isotopic composition of GAS groundwater leads to understanding the paleoclimatic conditions in the regional recharge areas. The δ18O and δ2H isotopic ratios of GAS groundwaters vary, respectively, from –9.1 to –4.8‰ V-SMOW and –58.4 to –21.7‰ V-SMOW. In the recharge zones, enriched δ18O values are observed, while in the confined zone lighter δ18O values are observed. These suggest that climatic conditions were 10°C cooler than the present during the recharge of these waters. The δ13C ratios in groundwater of GAS, in the study area, vary from –19.5 to –6.5‰ VPDB, increasing along the regional flow lines toward the confined zone. This variation is related to dissolution of carbonate cement in the sandstones. 相似文献
254.
Reservoir characterization needs the integration of various data through history matching, especially dynamic information
such as production or 4D seismic data. Although reservoir heterogeneities are commonly generated using geostatistical models,
random realizations cannot generally match observed dynamic data. To constrain model realizations to reproduce measured dynamic
data, an optimization procedure may be applied in an attempt to minimize an objective function, which quantifies the mismatch
between real and simulated data. Such assisted history matching methods require a parameterization of the geostatistical model
to allow the updating of an initial model realization. However, there are only a few parameterization methods available to
update geostatistical models in a way consistent with the underlying geostatistical properties. This paper presents a local
domain parameterization technique that updates geostatistical realizations using assisted history matching. This technique
allows us to locally change model realizations through the variation of geometrical domains whose geometry and size can be
easily controlled and parameterized. This approach provides a new way to parameterize geostatistical realizations in order
to improve history matching efficiency. 相似文献
255.
H. K. Roscoe P. V. Johnston M. Van Roozendael A. Richter A. Sarkissian J. Roscoe K. E. Preston J-C. Lambert C. Hermans W. DeCuyper S. Dzienus T. Winterrath J. Burrows F. Goutail J-P. Pommereau E. D'Almeida J. Hottier C. Coureul R. Didier I. Pundt L. M. Bartlett C. T. McElroy J. E. Kerr A. Elokhov G. Giovanelli F. Ravegnani M. Premuda I. Kostadinov F. Erle T. Wagner K. Pfeilsticker M. Kenntner L. C. Marquard M. Gil O. Puentedura M. Yela D. W. Arlander B. A. Kastad Hoiskar C. W. Tellefsen K. Karlsen Tornkvist B. Heese R. L. Jones S. R. Aliwell R. A. Freshwater 《Journal of Atmospheric Chemistry》1999,32(2):281-314
In June 1996, 16 UV-visible sensors from 11 institutes measured spectra of the zenith sky for more than 10 days. Spectra were analysed in real-time to determine slant column amounts of O3 and NO2. Spectra of Hg lamps and lasers were measured, and the amount of NO2 in a cell was determined by each spectrometer. Some spectra were re-analysed after obvious errors were found. Slant columns were compared in two ways: by examining regression analyses against comparison instruments over the whole range of solar zenith angles; and by taking fractional differences from a comparison instrument at solar zenith angles between 85° and 91°. Regression identified which pairs of instruments were most consistent, and so which could be used as universal comparison instruments. For O3, regression slopes for the whole campaign agreed within 5% for most instruments despite the use of different cross-sections and wavelength intervals, whereas similar agreement was only achieved for NO2 when the same cross-sections and wavelength intervals were used and only one half-day's data was analysed. Mean fractional differences in NO2 from a comparison instrument fall within ±7% (1-sigma) for most instruments, with standard deviations of the mean differences averaging 4.5%. Mean differences in O3 fall within ±2.5% (1- sigma) for most instruments, with standard deviations of the mean differences averaging 2%. Measurements of NO2 in the cell had similar agreement to measurements of NO2 in the atmosphere, but for some instruments measurements with cell and atmosphere relative to a comparison instrument disagreed by more than the error bars. 相似文献
256.
China Ocean Engineering - Wave energy is a renewable source with significant amount in relation to the global demand. A good concept of a device applied to extract this type of energy is the... 相似文献
257.
Djim M. L. Diongue Christine Stumpp Olivier Roupsard Didier Orange Frederic C. Do Serigne Faye 《水文研究》2023,37(1):e14787
Sustainable water management in semi-arid agriculture practices requires quantitative knowledge of water fluxes within the soil-vegetation-atmosphere system. Therefore, we used stable-isotope approaches to evaluate evaporation (Ea), transpiration (Ta), and groundwater recharge (R) at sites in Senegal's Groundnut basin and Ferlo Valley pasture region during the pre-monsoon, monsoon, and post-monsoon seasons of 2021. The approaches were based upon (i) the isothermal evaporation model (for quantifying Ea); (ii) water and isotope mass balances (to partition Ea and Ta for groundnut and pasture); and (iii) the piston displacement method (for estimating R). Ea losses derived from the isothermal evaporation model corresponded primarily to Stage II evaporation, and ranged from 0.02 to 0.09 mm d−1 in the Groundnut basin, versus 0.02–0.11 mm d−1 in Ferlo. At the groundnut site, Ea rates ranged from 0.01 to 0.69 mm d−1; Ta was in the range 0.55–2.29 mm d−1; and the Ta/ETa ratio was 74%–90%. At the pasture site, the ranges were 0.02–0.39 mm d−1 for Ea; 0.9–1.69 mm d−1 for Ta; and 62–90% for Ta/ETa. The ETa value derived for the groundnut site via the isotope approach was similar to those from eddy covariance measurements, and also to the results from the previous validated HYDRUS-1D model. However, the HYDRUS-1D model gave a lower Ta/ETa ratio (23.2%). The computed groundwater recharge for the groundnut site amounted to less than 2% of the local annual precipitation. Recommendations are made regarding protocols for preventing changes to isotopic compositions of water in samples that are collected in remote arid regions, but must be analysed days later. The article ends with suggestions for studies to follow up on evidence that local aquifers are being recharged via preferential pathways. 相似文献