Climate of the American tropics and subtropics in the 1960s and possible comparisons with climatic variations of the last millenium     

W.A. Sanchez  J.E. Kutzbach 《Quaternary Research》1974,4(2):128-135

Departures of mean annual precipitation and temperature for the decade 1961–1970 from the 1931–1960 averages are illustrated on maps of the tropical and subtropical portions of the American continents. Certain features of midlatitude climatic anomalies appear to be associated with concurrent anomalies in the tropics. There is an apparent southward shift of circulation features in this longitudinal sector of both hemispheres. A review of selected literature on latitudinal climatic shifts and atmosphere-ocean interaction suggests some similarities between the patterns of climate in the 1960s and the climate of the Little Ice Age.  相似文献   

MISCELLANEA     

P. Domingo Sanchez 《Meteoritics & planetary science》1977,12(2):159-160

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SOLAR ACTIVITY VARIATIONS RECORDED IN VARVED SEDIMENTS FROM THE CRATER LAKE OF HOLZMAAR – A MAAR LAKE IN THE WESTEIFEL VOLCANIC FIELD, GERMANY     

H. Vos  A. Sanchez  B. Zolitschka  A. Brauer  J.F.W. Negendank 《Surveys in Geophysics》1997,18(2-3):163-182

Annually laminated sediments from Lake Holzmaar (Germany) provide high resolution sedimentological and palaeoenvironmental data of the last 22,500 years. Weichselian periglacial varves and Holocene organic varves indicate different depositional environments. For the best preserved sections from both parts, spectral analyses were performed in order to detect cyclic fluctuations in varve thickness. Weichselian varves are dominated by an 88 year periodicity. Linear spectral analysis of Holocene varves provides no significant cyclicity. But, supposing nonlinear transformations of the solar signal through the Lake Holzmaar ecosystem during the Holocene, an adequate nonlinear spectral analysis method was able to detect periodicities of 11, 88, and 208 years. The existence of these cyclicities, comparable to the solar activity fluctuations, give further evidence for the existence of a sun-climate relationship, based on a not yet completely understood mechanism.  相似文献   

Improved smoothing of an altimetric ocean-tide model with global Proudman functions     

R. D. Ray  B. V. Sanchez 《Geophysical Journal International》1994,118(3):788-794

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Effect of methane leakage on the greenhouse gas footprint of electricity generation     

Nicolas Sanchez II  David C. Mays 《Climatic change》2015,133(2):169-178

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Spatial and temporal variations of nutrient concentration in the groundwater of a floodplain: effect of hydrology,vegetation and substrate     

Naima Takatert  Jos Miguel Sanchez‐Prez  Michle Trmolires 《水文研究》1999,13(10):1511-1526

Spatio‐temporal variations in nitrogen and phosphorus concentrations in groundwater were analysed and related to the variations in hydrological conditions, vegetation type and substrate in an alluvial ecosystem. This study was conducted in the Illwald forest in the Rhine Plain (eastern France) to assess the removal of nutrients from groundwater in a regularly flooded area. We compared both forest and meadow ecosystems on clayey‐silty soils with an anoxic horizon (pseudogley) at 1·5–2 m depth (eutric gley soil) and a forest ecosystem on a clayey‐silty fluviosoil rich in organic matter with a gley at 0·5 m depth (calcaric gley soil). Piezometers were used to measure the nutrient concentrations in the groundwater at 2 m depth in the root layer and at 4·5 m depth, below the root layer. Lower concentrations of nitrate and phosphate in groundwater were observed under forest than under meadow, which could be explained by more efficient plant uptake by woody species than herbaceous plants. Thus NO₃‐N inputs by river floods were reduced by 73% in the shallow groundwater of the forested ecosystem, and only by 37% in the meadow. Compared with the superficial groundwater layer, the lowest level of nitrate nitrogen (NO₃‐N) and the highest level of ammonium nitrogen (NH₄‐N) were measured in the deep layer (under the gley horizon at 2·5 m depth), which suggests that the reducing potential of the anoxic horizon in the gley soils contributes to the reduction of nitrate. Nitrate concentrations were higher in the groundwater of the parcel rich in organic matter than in the one poorer in organic matter. Phosphate (PO₄‐P) concentrations in both shallow and deep groundwater are less than 62 to 76% of those found in surface water which can be related to the retention capacity of the clay colloids of these soils. Moreover, the temporal variations in nutrient concentrations in groundwater are directly related to variations in groundwater level during an annual hydrological cycle. Our results suggest that variations in groundwater level regulate spatio‐temporal variations in nutrient concentrations in groundwater as a result of the oxidation–reduction status of soil, which creates favourable or unfavourable conditions for nutrient bioavailability. The hydrological variations are much more important than those concerning substrate and type of vegetation. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Effect of cumulative seismic damage and corrosion on the life‐cycle cost of reinforced concrete bridges     

R. Kumar  P. Gardoni  M. Sanchez‐Silva 《地震工程与结构动力学》2009,38(7):887-905

Bridge design should take into account not only safety and functionality, but also the cost effectiveness of investments throughout a bridge life‐cycle. This paper presents a probabilistic approach to compute the life‐cycle cost (LCC) of corroding reinforced concrete (RC) bridges in earthquake‐prone regions. The approach is developed by combining cumulative seismic damage and damage associated with corrosion due to environmental conditions. Cumulative seismic damage is obtained from a low‐cycle fatigue analysis. Chloride‐induced corrosion of steel reinforcement is computed based on Fick's second law of diffusion. The proposed methodology accounts for the uncertainties in the ground motion parameters, the distance from the source, the seismic demand on the bridge, and the corrosion initiation time. The statistics of the accumulated damage and the cost of repairs throughout the bridge life‐cycle are obtained by Monte‐Carlo simulation. As an illustration of the proposed approach, the effects of design parameters on the LCC of an example RC bridge are studied. The results are valuable in better estimating the condition of existing bridges and, therefore, can help to schedule inspection and maintenance programs. In addition, by taking into consideration the two deterioration processes over a bridge life‐cycle, it is possible to estimate the optimal design parameters by minimizing, for example, the expected cost throughout the life of the structure. A comparison between the effects of the two deterioration processes shows that, in seismic regions, the cumulative seismic damage affects the reliability of bridges over time more than the corrosion even for corrosive environments. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Settling velocity of the suspended sediment in three high-energy environments   总被引：1，自引：0，他引：1  

Martin Sanchez   《Ocean Engineering》2006,33(5-6):665-678

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Aquifers Shared Between Mexico and the United States: Management Perspectives and Their Transboundary Nature          下载免费PDF全文

Rosario Sanchez  Gabriel Eckstein 《Ground water》2017,55(4):495-505

Totally 36 aquifers have been identified along the Mexico‐U.S. border. Of these, only 16 have adequate data to provide a reasonable level of confidence to categorize them as transboundary. Limited and/or contrasting data over the other aquifers in the region reflects the void in transboundary groundwater management and assessment mechanisms throughout much of the Mexico‐U.S. border. This paper identifies management mechanisms, structures, and institutional prioritization related to transboundary aquifers shared between Mexico and the United States. It also evaluates the differences in the transboundary nature of these aquifers, and how their combined hydrological and geographical considerations interrelate with local and regional social, economic, political, and even scale dimensions to create complex management challenges.  相似文献   

Advances in geodynamo modelling     

Johannes Wicht  Sabrina Sanchez 《地球物理与天体物理流体动力学》2019,113(1-2):2-50

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