Flow time estimation with spatially variable hillslope velocity in ungauged basins   总被引：2，自引：0，他引：2  

Salvatore Grimaldi  Andrea Petroselli  Gustavo Alonso  Fernando Nardi 《Advances in water resources》2010

The automated spatial estimation of the hillslope runoff dynamics is used as a valuable tool for the estimation of the travel time distribution (flow time), a major factor for the hydrologic prediction in ungauged basins. In fact, while the flow time function is usually obtained by rescaling the flow paths with constant channel and hillslope velocities, in this work a spatially distributed kinematic component, as a function of terrain features and in particular slope and land use, is implemented and its influence on the hydrologic response is tested by means of the Width Function Instantaneous Unit Hydrograph (WFIUH) framework. Hillslope surface flow velocities are evaluated by applying different uniform flow formulas within an automated DEM-based (terrain analysis) algorithm. A comparison test of the performances of the Manning, Darcy, Maidment and Soil Conservation Service uniform flow equations is performed for several case studies in Italy pertaining to different climatic and geomorphic conditions. Results provide new insights for a better understanding of the flow time function also introducing a more parsimonious and physically-based calibration scheme of the WFIUH.  相似文献   

An atmospheric-to-marine synoptic classification for statistical downscaling marine climate     

Paula Camus  Ana Rueda  Fernando J. Méndez  Iñigo J. Losada 《Ocean Dynamics》2016,66(12):1589-1601

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The validity of the monocentric city model in a polycentric age: US metropolitan areas in 1990, 2000 and 2010     

Daniel Arribas-Bel  Fernando Sanz-Gracia 《Urban geography》2013,34(7):980-997

In this article, we use local indicators of spatial association (LISA) and other spatial analysis techniques to analyze the distribution of centers with high employment density within metropolitan areas. We examine the 359 metropolitan areas across the United States at three points in time (1990, 2000, and 2010) to provide a spatio-temporal panoramic of urban spatial structure. Our analysis highlights three key findings. (1) The monocentric structure persists in a majority of metropolitan areas: 56.5% in 1990, 64.1% in 2000, and 57.7% in 2010. (2) The pattern of employment centers remains stable for most metropolitan areas: the number of centers remained the same for 74.9% of metropolitan areas between 1990 and 2000 and for 85.2% between 2000 and 2010. (3) Compared with monocentric metropolitan areas, polycentric metros are larger and more dense, with higher per-capita incomes and lower poverty rates.  相似文献   

Geodynamic evolution of a forearc rift in the southernmost Mariana Arc     

Julia M. Ribeiro  Robert J. Stern  Fernando Martinez  Osamu Ishizuka  Susan G. Merle  Katherine Kelley  Elizabeth Y. Anthony  Minghua Ren  Yasuhiko Ohara  Mark Reagan  Guillaume Girard  Sherman Bloomer 《Island Arc》2013,22(4):453-476

The southernmost Mariana forearc stretched to accommodate opening of the Mariana Trough backarc basin in late Neogene time, erupting basalts at 3.7–2.7 Ma that are now exposed in the Southeast Mariana Forearc Rift (SEMFR). Today, SEMFR is a broad zone of extension that formed on hydrated, forearc lithosphere and overlies the shallow subducting slab (slab depth ≤ 30–50 km). It comprises NW–SE trending subparallel deeps, 3–16 km wide, that can be traced ≥ ∼30 km from the trench almost to the backarc spreading center, the Malaguana‐Gadao Ridge (MGR). While forearcs are usually underlain by serpentinized harzburgites too cold to melt, SEMFR crust is mostly composed of Pliocene, low‐K basaltic to basaltic andesite lavas that are compositionally similar to arc lavas and backarc basin (BAB) lavas, and thus defines a forearc region that recently witnessed abundant igneous activity in the form of seafloor spreading. SEMFR igneous rocks have low Na₈, Ti₈, and Fe₈, consistent with extensive melting, at ∼23 ± 6.6 km depth and 1239 ± 40°C, by adiabatic decompression of depleted asthenospheric mantle metasomatized by slab‐derived fluids. Stretching of pre‐existing forearc lithosphere allowed BAB‐like mantle to flow along the SEMFR and melt, forming new oceanic crust. Melts interacted with pre‐existing forearc lithosphere during ascent. The SEMFR is no longer magmatically active and post‐magmatic tectonic activity dominates the rift.  相似文献   

Chemical and structural study of 1M- and 2M 1-phlogopites coexisting in the same Kasenyi kamafugitic rock (SW Uganda)     

Maria Lacalamita  Ernesto Mesto  Fernando Scordari  Emanuela Schingaro 《Physics and Chemistry of Minerals》2012,39(8):601-611

In the present work, crystal chemical variations between 1M and 2M ₁ phlogopites coexisting in the same rock sample from kamafugite of Kasenyi (southwest Uganda, west branch of the East African Rift) were explored by electron probe microanalyses, single crystal X-ray diffraction and M?ssbauer spectroscopy. Chemical analyses revealed close similarity both within and between the two polytypic arrangements as well as high TiO₂ (~4.9?wt%) and Al₂O₃ (~12.9?wt%), and low Cr₂O₃ (~0.8?wt%), F (~0.3?wt%) and BaO (~0.2?wt%) contents. Room temperature ⁵⁷Fe M?ssbauer investigation proved that the studied mica is a tetraferriphlogopite with: ^IVFe³⁺?=?19(1)?%, ^VIFe²⁺?=?58(1)?%, ^VIFe³⁺?=?23(1)?%. Single crystal refinement showed that both polytypes have narrow range of variation in terms of some relevant unit cell parameters and similar values in terms of mean bond lengths, mean atomic numbers and distortion parameters. Similar substitutions were active in the structure of the 1M and 2M ₁ studied phlogopites. However, in 2M ₁ polytypes the oxy-type substitutions were found to occur to a greater extent. Comparison of unit layer of 1M mica (in the 2M ₁ setting) with that of the 2M ₁ ones showed that the 2M ₁ polytypes are affected to different extent by relative shifts of the upper and lower triads of octahedral oxygens along the ±b directions. This effect did not cause any symmetry lowering in the T-O-T layer of the studied samples.  相似文献   

Preface: clay mineral diagenesis and very low-grade metamorphic processes. Proceedings of the 2011 Frey–Kübler symposium     

Rafael Ferreiro M?hlmann  Fernando Nieto  ?mer Bozkaya  Sébastien Potel  Asuman Günal Türkmeno?lu 《Swiss Journal of Geoscience》2012,105(2):117-120

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Sources and behavior of arsenic and trace elements in groundwater and surface water in the Poopó Lake Basin,Bolivian Altiplano     

Oswaldo Eduardo Ramos Ramos  Luis Fernando Cáceres  Mauricio Rodolfo Ormachea Muñoz  Prosun Bhattacharya  Israel Quino  Jorge Quintanilla  Ondra Sracek  Roger Thunvik  Jochen Bundschuh  Maria Eugenia García 《Environmental Earth Sciences》2012,66(3):793-807

Water management in semiarid and arid catchments such as the Poopó Lake Basin requires improved understanding of the complex behavior of the various contaminants, which affect the drinking water quality and considered as crucial for sustainable development of the region. Mechanisms of arsenic (As) release in the surface and groundwater were studied. Hydrochemical data for surface water (4 samples) and groundwater (28 samples) were collected in a small watershed in the Poopó catchment at the highland of the Bolivian Andes (Altiplano). All of them show high electrical conductivity values and moderately oxidizing conditions. The surface water contains high concentration of sulfate and the trace elements As, Zn and Pb in the zone affected by acid mine drainage. There is a large variability of the concentration of As and of the trace elements in the groundwater in the five different regions within the Poopó catchment. The metal concentrations sensitive to changes of redox state and results of speciation modeling suggest that As (V) is a predominant aqueous species, which conforms to the prevailing oxidizing conditions in the shallow groundwater environment. Two generalized trends for As distribution were identified in groundwater: (a) high concentrations are found in the arid zone (100–250 μg/L) in the southern (region III) and in the northwestern (region V) regions, and (b) low concentrations (<50 μg/L) are found in the remaining part of the basin (region I, II and IV). However, the spatial distribution within these regions needs to be investigated further. A conclusion from the present study is that there are multiple sources of As as well as other trace elements (such as Cd, Mn and Zn) in the Poopó Lake Basin. Among the sources and the processes which led to the mobility of As and other trace metals in the region are: (a) weathering of sulfide minerals, (b) oxidation of pyrite and/or arsenopyrite in mineralized areas and (c) desorption from hydrous ferric oxide (HFO) surfaces. In non-mining areas, volcanic ash is suggested to be a significant source of As.  相似文献   

Palaeoshoreline for the Late Cretaceous marine platform in the Iberian Trough (Leonese Area, Spain) deduced from outcrop and subsurface analysis     

Antonio Herrero-Hernández  Fernando Gómez-Fernández 《Central European Journal of Geosciences》2012,4(3):395-415

The location of the Late Cretaceous paleoshoreline in the Leonese Area (Iberian Trough, Spain) has been investigated by seismic analysis through isobath and isopach maps. The succession can be divided into two depositional sequences: DS-1 and DS-2. These sequences are composed of fluvial systems at the base, with paleocurrents that flowed eastward and north-eastward. The DS-1 sequence (Late Albian-Middle Turonian) shows intertidal to subtidal and offshore deposits at the top, while the DS-2 sequence (Late Turonian-Campanian) presents intertidal to subtidal, tidal flat and shallow marine and lacustrine deposits at its top. The stratigraphic cyclicity based on systems tracts shows that these two depositional sequences exhibit remarkable eustatic control. Both sequences start at the base with a significant sedimentary supply from fluvial systems, related to eustatic fall episodes, and conclude at the top with transgressive periods. The evolution of the basin reveals the history of base-level changes and associated shifts in depositional trends during successive stages. The deeper sectors of the DS-1 sequence are located towards the northeastern part of the study area while the proximal portion of the basin-margin is located to the southwest. The paleoshoreline is placed in a direction oriented at 120. The variations in thickness are elongated in orientations between 030 and 050 and are mainly related to paleovalleys and tributary fluvial networks that supply sediment through the shoreline. It is possible that these variations may be related to active synsedimentary faults. Depocenters move toward the northeast and east during the DS-2 sequence while the proximal portion of the basin-margin moves to the southwest. The paleoshoreline has an orientation of 155 direction and moves basinward. The isopach maps show a group of corridors oriented at 130?C140 and 165?C170, interpreted as result of accumulation of sandy bodies such as inter and subtidal bars. The fluvial systems are transversal to the paleoshoreline direction.  相似文献   

Biomass expansion factor and root-to-shoot ratio for Pinus in Brazil     

Carlos R Sanquetta  Ana PD Corte  Fernando da Silva 《Carbon balance and management》2011,6(1):6

The Biomass Expansion Factor (BEF) and the Root-to-Shoot Ratio (R) are variables used to quantify carbon stock in forests. They are often considered as constant or species/area specific values in most studies. This study aimed at showing tree size and age dependence upon BEF and R and proposed equations to improve forest biomass and carbon stock. Data from 70 sample Pinus spp. grown in southern Brazil trees in different diameter classes and ages were used to demonstrate the correlation between BEF and R, and forest inventory data, such as DBH, tree height and age. Total dry biomass, carbon stock and CO₂ equivalent were simulated using the IPCC default values of BEF and R, corresponding average calculated from data used in this study, as well as the values estimated by regression equations. The mean values of BEF and R calculated in this study were 1.47 and 0.17, respectively. The relationship between BEF and R and the tree measurement variables were inversely related with negative exponential behavior. Simulations indicated that use of fixed values of BEF and R, either IPCC default or current average data, may lead to unreliable estimates of carbon stock inventories and CDM projects. It was concluded that accounting for the variations in BEF and R and using regression equations to relate them to DBH, tree height and age, is fundamental in obtaining reliable estimates of forest tree biomass, carbon sink and CO₂ equivalent.  相似文献   

Large-Eddy Simulation of Stably-Stratified Flow Over a Steep Hill   总被引：1，自引：1，他引：0  

Feng Wan  Fernando Porté-Agel 《Boundary-Layer Meteorology》2011,138(3):367-384

Large-eddy simulation (LES) is used to simulate stably-stratified turbulent boundary-layer flow over a steep two-dimensional hill. To parametrise the subgrid-scale (SGS) fluxes of heat and momentum, three different types of SGS models are tested: (a) the Smagorinsky model, (b) the Lagrangian dynamic model, and (c) the scale-dependent Lagrangian dynamic model (Stoll and Porté-Agel, Water Resour Res 2006, doi:). Simulation results obtained with the different models are compared with data from wind-tunnel experiments conducted at the Environmental Flow Research Laboratory (EnFlo), University of Surrey, U.K. (Ross et al., Boundary-Layer Meteorol 113:427–459, 2004). It is found that, in this stably-stratified boundary-layer flow simulation, the scale-dependent Lagrangian dynamic model is able to account for the scale dependence of the eddy-viscosity and eddy-diffusivity model coefficients associated with flow anisotropy in flow regions with large mean shear and/or strong flow stratification. As a result, simulations using this tuning-free model lead to turbulence statistics that are more realistic than those obtained with the other two models.  相似文献