Estimation of Surface-Layer Scaling Parameters in the Unstable Boundary Layer: Implications for Orographic Flow Speed-Up     

José Luís Argaín  Miguel A. C. Teixeira  Pedro M. A. Miranda 《Boundary-Layer Meteorology》2017,165(1):145-160

A method is proposed for estimating the surface-layer depth \((z_s)\) and the friction velocity \((u_*)\) as a function of stability (here quantified by the Obukhov length, L) over the complete range of unstable flow regimes. This method extends that developed previously for stable conditions by Argaín et al. (Boundary-Layer Meteorol 130:15–28, 2009), but uses a qualitatively different approach. The method is specifically used to calculate the fractional speed-up \((\varDelta S)\) in flow over a ridge, although it is suitable for more general boundary-layer applications. The behaviour of \(z_s \left( L\right) \) and \(u_*\left( L\right) \) as a function of L is indirectly assessed via calculation of \(\varDelta S\left( L\right) \) using the linear model of Hunt et al. (Q J R Meteorol Soc 29:16–26, 1988) and its comparison with the field measurements reported in Coppin et al. (Boundary-Layer Meteorol 69:173–199, 1994) and with numerical simulations carried out using a non-linear numerical model, FLEX. The behaviour of \(\varDelta S\) estimated from the linear model is clearly improved when \(u_*\) is calculated using the method proposed here, confirming the importance of accounting for the dependences of \(z_s\left( L \right) \) and \(u_*\left( L \right) \) on L to better represent processes in the unstable boundary layer.  相似文献   

Joint Management of Surface and Ground Water Supplies   总被引：10，自引：0，他引：10  

Hakan Ba&#;a&#;ao&#;lu  Miguel A. Mari&#;o 《Ground water》1999,37(2):214-222

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Tectonic significance of an earthquake sequence in the Zacoalco half-graben, Jalisco, Mexico     

Javier F. Pacheco  Carlos A. Mortera-Gutirrez  Hugo Delgado  Shri K. Singh  Raúl W. Valenzuela  Nicolai M. Shapiro  Miguel A. Santoyo  Alejandro Hurtado  Ricardo Barrn  Esteban Gutirrez-Moguel 《Journal of South American Earth Sciences》1999,12(6):55

We studied a sequence of small earthquakes that occurred during the months of April and May of 1997, in Jalisco, southwestern Mexico. The earthquakes were located along a set of active faults that form the Zacoalco half-graben (La Lima fault system), west of Lake Chapala, within the rift–rift–rift triple junction. A total of 33 events were located, with magnitudes ranging from 1.5 to 3.5, recorded by a portable array of broadband seismographs. We identified two groups of events: one corresponding to a shallow normal fault, synthetic to La Lima fault system, and another group associated with a deeper fault. The events that occurred on the synthetic fault show normal faulting oriented on a NW–SE plane, dipping shallowly towards the SW. The other group of mechanisms showed either a normal fault oriented NW–SE and dipping steeply to the NE, or a very shallow-dipping normal fault, dipping to the SW. Earthquake distribution and fault plane solutions suggest that the Zacoalco half-graben developed from blocks that rotate as slip occurs on listric faults. These mechanisms could represent the type of motion expected for larger earthquakes in the area, like the one that occurred in 1568.  相似文献   

Tectonic implications of the earthquake swarm of 1997 in the Michoacan Triangle, Mexico     

Javier F. Pacheco  Carlos Valds-Gonzlez  Hugo Delgado  Shri K. Singh  F. Ramn Zuiga  Carlos A. Mortera-Gutirrez  Miguel A. Santoyo  Jaime Domínguez  Ricardo Barrn 《Journal of South American Earth Sciences》1999,12(6):73

An earthquake swarm occurred during February and March 1997 in the vicinity of the Tancitaro Volcano, in the southern part of the tectonically complex Michoacan Triangle. A study of these events provides an opportunity to map the active faults in the area and to learn if the orientation and the sense of motion on these faults are consistent with the mapped faults and the alignment of cinder cones in the region. The foci of 230 earthquakes, which could be located, are distributed between 10 and 18 km depth, and show an alignment in, roughly, a NE direction. The focal mechanisms and seismic moments of the 27 best-recorded events were determined by waveform modeling of P and S waves. These mechanisms show two distinct patterns. More than 50% of the solutions are left-lateral strike–slip mechanisms with a normal component. The preferred fault plane strikes NE. Another group of events, probably caused by triggered seismicity on the Chapala–Oaxaca fault zone, shows left-lateral strike–slip mechanisms with a large-thrust component on NW-trending faults. S wave splitting shows 1–2.5% crustal-anisotropy. The direction of the anisotropy coincides with the NE alignment of events, and the preferred nodal plane. This is also the alignment of cinder cones, suggesting that preexisting fractures and cracks are responsible for the seismicity and anisotropic behavior of the crust. The resulting stress orientation, NE compression, is the one expected for the fore-arc region. We conclude that although Michoacan Triangle lies in the Trans-Mexican Volcanic Belt, it does not form part of this stress province where the stress orientation is NS extension.  相似文献   

Palaeokarst and rauhwacke development,mountain uplift and subaerial sliding of tectonic sheets (northern Sierra de los Filabres,Betic Cordilleras,Spain)     

Orozco  Miguel  Molina  José Miguel  Crespo-Blanc  Ana  Alonso-Chaves  Francisco Manuel 《Geologie en Mijnbouw》1999,78(1):103-117

The rauhwackes near Serón in the northern Sierra de los Filabres (S Spain), previously considered as true tectonic breccias, are reinterpreted on the basis of sedimentological, geomorphological and geometrical evidence as subaerial or nearly subaerial sedimentary deposits. Channel fills, parallel lamination, cross-lamination, graded bedding, sedimentary clastic dykes and other sedimentary structures and features occur in the rauhwacke body. These sedimentary rocks correspond to continental deposits of alluvial and karstic origin deposited over a karstified erosional surface of Nevado–Filabride marbles. Although no fossils have been found in the rauhwackes, a Tortonian age for these rocks is suggested on the basis of structural arguments and lithostratigraphic data from the nearby Almanzora basin. The rauhwackes were buried by slabs of Alpujarride rocks that gravitationally slid over them during the uplifting of the Sierra de los Filabres.  相似文献   

Taxonomic revision of Cylindroporella ? lusitanica Ramalho, 1970: In search for the origins of the Family Dasycladaceae          下载免费PDF全文

Bruno R. C. Granier  Ana C. Azerêdo  Miguel M. Ramalho 《Island Arc》2017,26(3)

A study of new material of Cylindroporella ? lusitanica Ramalho, 1970, from the Upper Jurassic (Oxfordian) strata of Portugal identified features not observed previously. This includes the pattern of its laterals, including the gametophores. The algal body plan is unique and justifies the taxonomic reassessment of this species and the introduction of Barattoloporellopsis n. gen. Furthermore this species is most likely a primitive Dasycladaceae, a “missing link” between the modern ones (starting from the Cretaceous times) and their Jurassic ancestors.  相似文献   

Spectral density regression for bivariate extremes     

Daniela?Castro Camilo  Miguel?de CarvalhoEmail authorView author&#;s OrcID profile 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(7):1603-1613

We introduce a density regression model for the spectral density of a bivariate extreme value distribution, that allows us to assess how extremal dependence can change over a covariate. Inference is performed through a double kernel estimator, which can be seen as an extension of the Nadaraya–Watson estimator where the usual scalar responses are replaced by mean constrained densities on the unit interval. Numerical experiments with the methods illustrate their resilience in a variety of contexts of practical interest. An extreme temperature dataset is used to illustrate our methods.  相似文献   

Assessment of soil factors controlling ephemeral gully erosion on agricultural fields   总被引：1，自引：0，他引：1       下载免费PDF全文

Paul Ollobarren Del Barrio  Miguel A. Campo‐Bescós  Rafael Giménez  Javier Casalí 《地球表面变化过程与地形》2018,43(9):1993-2008

The soil factor is crucial in controlling and properly modeling the initiation and development of ephemeral gullies (EGs). Usually, EG initiation has been related to various soil properties (i.e. sealing, critical shear stress, moisture, texture, etc.); meanwhile, the total growth of each EG (erosion rate) has been linked with proper soil erodibility. But, despite the studies to determine the influence of soil erodibility on (ephemeral) gully erosion, a universal approach is still lacking. This is due to the complex relationship and interactions between soil properties and the erosive process. A feasible soil characterization of EG erosion prediction on a large scale should be based on simple, quick and inexpensive tests to perform. The objective of this study was to identify and assess the soil properties – easily and quickly to determine – which best reflect soil erodibility on EG erosion. Forty‐nine different physical–chemical soil properties that may participate in establishing soil erodibility were determined on agricultural soils affected by the formation of EGs in Spain and Italy. Experiments were conducted in the laboratory and in the field (in the vicinity of the erosion paths). Because of its importance in controlling EG erosion, five variables related to antecedent moisture prior to the event that generated the gullies and two properties related to landscape topography were obtained for each situation. The most relevant variables were detected using multivariate analysis. The results defined 13 key variables: water content before the initiation of EGs, organic matter content, cation exchange capacity, relative sealing index, two granulometric and organic matter indices, seal permeability, aggregates stability (three index), crust penetration resistance, shear strength and an erodibility index obtained from the Jet Test erosion apparatus. The latter is proposed as a useful technique to evaluate and predict soil loss caused by EG erosion. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

A geostatistical protocol to optimize spatial sampling of domestic drinking water supplies in remote environments     

Eulogio?Pardo-Igúzquiza  Pedro?Martínez-SantosEmail author  Miguel?Martín-Loeches 《Stochastic Environmental Research and Risk Assessment (SERRA)》2018,32(8):2433-2444

This paper deals with the design of optimal spatial sampling of water quality variables in remote regions, where logistics are complicated and the optimization of monitoring networks may be critical to maximize the effectiveness of human and material resources. A methodology that combines the probability of exceeding some particular thresholds with a measurement of the information provided by each pair of experimental points has been introduced. This network optimization concept, where the basic unit of information is not a single spatial location but a pair of spatial locations, is used to emphasize the locations with the greatest information, which are those at the border of the phenomenon (for example contamination or a quality variable exceeding a given threshold), that is, where the variable at one of the locations in the pair is above the threshold value and the other is below the threshold. The methodology is illustrated with a case of optimizing the monitoring network by optimal selection of the subset that best describes the information provided by an exhaustive survey done at a given moment in time but which cannot be repeated systematically due to time or economic constrains.  相似文献   

Reservoir architecture and heterogeneity distribution in floodplain sandstones: Key features in outcrop,core and wireline logs     

Luis Miguel Yeste  Augusto N. Varela  César Viseras  Neil D. Mcdougall  Fernando García-García 《Sedimentology》2020,67(7):3355-3388

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