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151.
152.
José E. Capilla J. Rodrigo J. J. Gómez-Hernández 《Stochastic Environmental Research and Risk Assessment (SERRA)》1998,12(3):171-190
A common approach for the performance assessment of radionuclide migration from a nuclear waste repository is by means of
Monte-Carlo techniques. Multiple realizations of the parameters controlling radionuclide transport are generated and each
one of these realizations is used in a numerical model to provide a transport prediction. The statistical analysis of all
transport predictions is then used in performance assessment. In order to reduce the uncertainty on the predictions is necessary
to incorporate as much information as possible in the generation of the parameter fields. In this regard, this paper focuses
in the impact that conditioning the transmissivity fields to geophysical data and/or piezometric head data has on convective
transport predictions in a two-dimensional heterogeneous formation. The Walker Lake data based is used to produce a heterogeneous
log-transmissivity field with distinct non-Gaussian characteristics and a secondary variable that represents some geophysical
attribute. In addition, the piezometric head field resulting from the steady-state solution of the groundwater flow equation
is computed. These three reference fields are sampled to mimic a sampling campaign. Then, a series of Monte-Carlo exercises
using different combinations of sampled data shows the relative worth of secondary data with respect to piezometric head data
for transport predictions. The analysis shows that secondary data allows to reproduce the main spatial patterns of the reference
transmissivity field and improves the mass transport predictions with respect to the case in which only transmissivity data
is used. However, a few piezometric head measurements could be equally effective for the characterization of transport predictions. 相似文献
153.
This work analyses the climatic information content of more than 1000 letters belonging to the private correspondence of the Jesuit order during the period 1634–1648. The information obtained mainly originates in Castille, and it was codified to obtain quantitative indices representative of the evolution of the thermal and rainfall anomalies. The results show that intense rainfall and cold air waves predominated during the study period, in accordance with other results on the climatic evolution of the Iberian Peninsula during the Little Ice Age. 相似文献
154.
Pollen evidence for variations in the southern margin of the westerly winds in SW Patagonia over the last 12,600 years 总被引:1,自引:0,他引:1
We report pollen and charcoal records from Vega Ñandú ( 51°0′S, 72°45′W), a small mire located near the modern forest-steppe ecotone in Torres del Paine National Park, southern Chile. The record shows an open landscape dominated by low shrubs and herbs between 12,600 and 10,800 cal yr BP, under cold and relatively humid conditions. Nothofagus experienced frequent, large-amplitude oscillations between 10,800 and 6800 cal yr BP, indicating recurrent transitions between shrubland/parkland environments, under warm and highly variable moisture conditions. A sustained increase in Nothofagus started at 6800 cal yr BP, punctuated by step-wise increases at 5100 and 2400 cal yr BP, implying further increases in precipitation. We interpret these results as indicative of variations in the amount of precipitation of westerly origin, with prominent increases at 6800, 5100, and 2400 cal yr BP. These pulses led to peak precipitation regimes during the last two millennia in this part of SW Patagonia. Our data suggest variations in the position and/or strength of the southern margin of the westerlies, most likely linked to variations in the extent and/or persistence of sea ice and sea-surface temperature anomalies in the Southern Ocean. Over the last two centuries the record shows a forest decline and expansion of Rumex acetosella, an exotic species indicative of European disturbance. 相似文献
155.
Long-term monitoring of fish farms: application of Nematode/Copepod index to oligotrophic conditions
Riera R Sanchez-Jerez P Rodríguez M Monterroso O Ramos E 《Marine pollution bulletin》2012,64(4):844-850
Interannual variability (2003-2008) of meiofaunal assemblages were analyzed in sediments beneath fish cages (Impact group) and in areas not affected by aquaculture activities (Control group). Organisms responded with spatial and seasonal variation in meiofauna assemblages, with an abrupt increase of abundances in locations beneath fish cages throughout the study period. This increase was greater during the last sampling year (2008) and mainly due to high abundances of nematodes. Univariate analyses showed differences between control and impacted sites at both sites, however, only significant variations were found in Los Gigantes, which are consistent with seasonal meiofauna variations throughout the study period. These results are partially explained by differences in current velocity between both sampling areas. The Ne/Co index showed the same trend and it seems to be a reliable index in sediment slightly affected by aquaculture wastes. This index is especially recommended in oligotrophic areas (e.g. Canary Islands) where meiofaunal assemblages are poorly represented in terms of abundances. 相似文献
156.
Seasonal Temperature and Precipitation Fluctuations in Selected Parts of Europe During the Sixteenth Century 总被引:1,自引:1,他引:0
Rüdiger Glaser Rudolf Brázdil Christian Pfister Petr Dobrovolný Mariano Barriendos Vallvé Anita Bokwa Dario Camuffo Oldrich Kotyza Danuta Limanówka Lajos Rácz Fernando S. Rodrigo 《Climatic change》1999,43(1):169-200
The article in hand presents a comparative analysis of unweighted thermic and hygric index series of different European regions (northern Switzerland, Germany, the Czech Republic, northern Italy, ancient Hungary, Poland and Spain). Besides methodological aspects about the formation of indices, especially the progress as well as the question of similarity development of these series in the 16th century are discussed and shown on the balance sheet. It becomes evident that with respect to the temperature on the level of unweighted indices the European regions of Germany, the Czech Republic and Switzerland are very similar during all seasons. In winter and summer these correlations are especially evident, during the transitional seasons they are smaller. Larger differences exist between the central European core region and the adjacent areas of research. In principle, the hygric differences are larger than the thermic ones.In the course of the sixteenth century marked cooling phases occurred during all seasons with increasing accentuation. These phases were typical for the climate of the Little Ice Age. In addition to this long-term analysis, some outstanding years of extreme weather like those of 1540, 1573 and 1587 are presented, in the course of which questions of climatic impact are included. Finally, recent instrumental data was used to conduct an analysis that compared the similarities between the respective regions and the similarities between the empirical data and indices. On the one hand, this confirmed the spatial pattern, on the other hand the usability of the indices. 相似文献
157.
Arne Krtzinger Ludger Mintrop Douglas W. R. Wallace Kenneth M. Johnson Craig Neill Bronte Tilbrook Philip Towler Hisayuki Y. Inoue Masao Ishii Gary Shaffer Rodrigo F. Torres Saavedra Eiji Ohtaki Eiji Yamashita Alain Poisson Christian Brunet Bernard Schauer Catherine Goyet Greg Eischeid 《Marine Chemistry》2000,72(2-4)
The ‘International Intercomparison Exercise of fCO2 Systems’ was carried out in 1996 during the R/V Meteor Cruise 36/1 from Bermuda/UK to Gran Canaria/Spain. Nine groups from six countries (Australia, Denmark, France, Germany, Japan, USA) participated in this exercise, bringing together 15 participants with seven underway fugacity of carbon dioxide (fCO2) systems, one discrete fCO2 system, and two underway pH systems, as well as systems for discrete measurement of total alkalinity and total dissolved inorganic carbon. Here, we compare surface seawater fCO2 measured synchronously by all participating instruments. A common infrastructure (seawater and calibration gas supply), different quality checks (performance of calibration procedures for CO2, temperature measurements) and a common procedure for calculation of final fCO2 were provided to reduce the largest possible amount of controllable sources of error. The results show that under such conditions underway measurements of the fCO2 in surface seawater and overlying air can be made to a high degree of agreement (±1 μatm) with a variety of possible equilibrator and system designs. Also, discrete fCO2 measurements can be made in good agreement (±3 μatm) with underway fCO2 data sets. However, even well-designed systems, which are operated without any obvious sign of malfunction, can show significant differences of the order of 10 μatm. Based on our results, no “best choice” for the type of the equilibrator nor specifics on its dimensions and flow rates of seawater and air can be made in regard to the achievable accuracy of the fCO2 system. Measurements of equilibrator temperature do not seem to be made with the required accuracy resulting in significant errors in fCO2 results. Calculation of fCO2 from high-quality total dissolved inorganic carbon (CT) and total alkalinity (AT) measurements does not yield results comparable in accuracy and precision to fCO2 measurements. 相似文献
158.
Albert Cabré Dominique Remy Germán Aguilar Sebastien Carretier Rodrigo Riquelme 《地球表面变化过程与地形》2020,45(9):2091-2106
Extreme high-magnitude and low-frequency storm events in arid zones provide the necessary runoff to entrain sediments from source areas and therefore dictate the linkages between hillslopes and channels. Nevertheless, the erosive impact of large storms remains difficult to predict. Most of the uncertainty lies in the lack of topographic change maps associated with single hydro-meteorological events. Consequently, event-based erosion models are poorly constrained and their extrapolation over long time periods remains uncertain. In this study, a 15-month Sentinel-1A coherence time series, optical and field data are used to map the spatial patterns of erosion after the 5-day storm occurred on March 2015, in the Atacama Desert. The coherence change detection (CCD) analysis suggests that temporal loss of coherence is related to variations in soil moisture, while permanent loss of coherence is related to modification of soil texture by erosion and sedimentation. Importantly, permanent loss of coherence is more apparent on gentle rather than steeper slopes, likely reflecting differences in regolith cover and thickness. These findings can contradict the landscape models predicting higher erosion on steeper hillslopes. The CCD technique represents a promising tool for analysing and modelling sediment connectivity in arid areas, giving a clear picture of the relation between sediment sources and sink pathways. © 2020 John Wiley & Sons, Ltd. 相似文献
159.
In 2000, the World population was 6.2 billion people; it reached 7 billion in 2012 and is expected to reach 9.5 billion (±0.4) in 2050 and 11 billion (±1.5) in 2100, according to the 2012 UN projections (Gerland et al. in Science 346:234–237, 2014). The trend after 2100 is still one of the global demographic growths, but after 2060, Africa is the only continent where the population would still increase. The amount of water consumed annually to produce the food necessary to meet the needs of the populations varies greatly between countries, from about 600 to 2500 m3/year per capita (Zimmer in L’empreinte eau. Les faces cachées d’une ressource vitale. Charles Léopold Meyer, Paris, 2013), depending on their wealth, their food habits, and the percentage of food waste they generate (on average, 30 % of the food produced is wasted). In 2000, the total food production was on the order of 3300 million tons (in cereal equivalents). In 2014, it is estimated that about 0.8 billion inhabitants of the planet suffer from hunger (FAO in World agriculture: towards 2030–2050. FAO, Rome, 2014. http://www.fao.org/docrep/004/Y3557E/y3557e00.HTM) and do not get the nutrition they need to be in good health or, in the case of children, to grow properly (both physically and intellectually). This food deficit was on the order of 40 million tons of cereal equivalents in 2014. The number of inhabitants with a food deficit was about 0.85 billion before the 2008 crisis and was decreasing annually, but it increased abruptly after 2008 up to 1 billion inhabitants and is slowly decreasing now. Assuming a World average water consumption for food of 1300 m3/year per capita in 2000, 1400 m3/year in 2050, and 1500 m3/year in 2100, a volume of water of around 8200 km3/year was needed in 2000, 13,000 km3/year will be needed in 2050, and 16,500 km3/year in 2100 (Marsily in L’eau, un trésor en partage. Dunod, Paris, 2009). Can bioenergy be added to food production? Will that much water be available on Earth, and where will it come from? Is climate change going to modify the answers to these questions? Can severe droughts occur? Can there be conflicts related to a food deficit? Some preliminary answers and scenarios for food production will be given in this paper from a hydrologist’s viewpoint. 相似文献
160.