Horizon Restoration by Best Fitting of Finite Elements and Rotation Constraints: Sensitivity to the Mesh Geometry and Pin-Element Location     

María José Ramón  José Luis Briz  Emilio L. Pueyo  Oscar Fernández 《Mathematical Geosciences》2016,48(4):419-437

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The role of ENSO and PDO in variability of winter precipitation over North America from twenty first century CMIP5 projections     

Ramón Fuentes-Franco  Filippo Giorgi  Erika Coppola  Fred Kucharski 《Climate Dynamics》2016,46(9-10):3259-3277

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Wall temperature oscillation on convection flow in a rotating fluid with hall and ion-slip currents     

P. C. Ram 《Astrophysics and Space Science》1991,175(1):119-123

An analysis of Hall and ion-slip current effects on the MHD free-convection flow of a partiallyionised gas past an infinite vertical porous plate in a rotating frame of reference is carried out. A strong magnetic field is applied perpendicular to the plate and the plate temperature oscillates in time about a constant non-zero mean. The problem has been solved for the velocity and temperature fields and the effects of _e (the Hall parameter), _i (the ion-slip parameter),E _r (rotation parameter), and have been discussed and shown graphically.  相似文献   

Are traditional and modern forestry institutions complementary or do they prescribe contradictory rights in Trans-Himalayan Nepal? A lesson to be learned for REDD+ implementation     

Dilli Prasad Poudel 《Norsk geografisk tidsskrift. Norwegian journal of geography》2018,72(1):13-26

Rights to forest products are difficult to decide in situations when traditional management institutions exist parallel to formal ones. Such situations raise the question of whether the institutions are complementary or prescribe contradictory rights and management principles. Based on a household survey and key informant interviews, the article focuses on how diverging management principles can be harmonized to satisfy national forestry goals in Nepal. Villages in the Trans-Himalayan district of Mustang used to manage forests according to their traditional institutions but after 1993 they were included in a new management regime called Conservation Area Management Committees (CAMCs). The findings revealed that the villagers appreciated development initiatives undertaken by the CAMCs but three disjunctions regarding forest management existed between the CAMCs and traditional institutions: there was a disjunction between the two sets of rules for forest resource utilization; there were role dilemmas of local residents who were entrusted with CAMC implementation; and there were spatial disjunctions when formal administrative forest borders did not coincide with customary ones. The simultaneous existence of two institutions thus blurred the rights to forest resources. The author concludes that knowledge of the disjunction between parallel institutions is vital for accommodating new management schemes such as REDD+.  相似文献   

Channel incision by headcut migration: Reconnection of the Colorado River to its estuary and the Gulf of California during the floods of 1979–1988     

Steven M. Nelson  Eloise Kendy  Karl W. Flessa  J. Eliana Rodríguez-Burgueño  Jorge Ramírez-Hernández  Tomás E. Rivas-Salcedo 《水文研究》2020,34(22):4156-4174

The macrotidal Colorado River Delta at the northern end of the Gulf of California in Mexico is hydrologically complex. We review historical accounts, data, field notes and photographs to evaluate the hydrological processes active on the delta prior to the advent of upstream dams. We also employ satellite imagery as well as recent LIDAR data to illustrate the critical role played by headcut erosion in restoring the river's fluvial/tidewater connection during the 1979–1988 floods. Prior to human manipulation, the river's contribution of fresh water to the Gulf was periodically interrupted by natural overflowing, avulsing, and flooding into the sub-sea level Salton Sink on the north slope of the delta plain. River flow south towards the Gulf was also subject to occasional overflow into Laguna Salada, another sub-sea level basin. In the mid-20th century, the Delta was disconnected from its fluvial supply following installation of upstream dams and reservoirs. A tidal sediment obstruction developed in the estuary channel, forming a final barrier to fluvial connectivity. Release of Colorado River floodwaters into Mexico between 1979 and 1988 provided a natural experiment on the hydrological response of a long-disconnected macrotidal delta to restoration of fluvial supply.  相似文献   

Comparison of streamflow recession between plantations and native forests in small catchments in Central-Southern Chile     

Francisco Balocchi  Neftali Flores  José Luis Arumí  Andrés Iroumé  Don A. White  Richard P. Silberstein  Pablo Ramírez de Arellano 《水文研究》2021,35(6):e14182

In central Chile, many communities rely on water obtained from small catchments in the coastal mountains. Water security for these communities is most vulnerable during the summer dry season and, from 2010 to 2017, rainfall during the dry season was between 20% and 40% below the long-term average. The rate of decrease in stream flow after a rainfall event is a good measure of the risk of flow decreasing below a critical threshold. This risk of low flow can be quantified using a recession coefficient (α) that is the slope of an exponential decay function relating flow to time since rainfall. A mathematical model was used to estimate the recession coefficient (α) for 142 rainstorm events (64 in summer; 78 in winter) in eight monitored catchments between 2008 and 2017. These catchments all have a similar geology and extend from 35 to 39 degrees of latitude south in the coastal range of south-central Chile. A hierarchical cluster analysis was used to test for differences between the mean value of α for different regions and forest types in winter and summer. The value of α did not differ (p < 0.05) between catchments in winter. Some differences were observed during summer and these were attributed to morphological differences between catchments and, in the northernmost catchments, the effect of land cover (native forest and plantation). Moreover, α for catchments with native forest was similar to those with pine plantations, although there was no difference (p < 0.05) between these and Eucalyptus plantations. The recession constant is a well-established method for understanding the effect of climate and disturbance on low flows and baseflows and can enhance local and regional analyses of hydrological processes. Understanding the recession of flow after rainfall in small headwater catchments, especially during summer, is vital for water resources management in areas where the establishment of plantations has occurred in a drying climate.  相似文献   

Chronicle of a forecast flood: exposure and vulnerability on the south-east coast of Spain     

Giménez-García  Rubén  Ruiz-Álvarez  Víctor  García-Marín  Ramón 《Natural Hazards》2022,114(1):521-552

Natural Hazards - In recent years, floods have become one of the natural hazards that generate the greatest economic and human losses on the planet. As is well known, torrential rainfall events are...  相似文献   

Self-Similar and Self-Affine Properties of Two-Dimensional Fracture Patterns in Rocks   总被引：1，自引：0，他引：1  

Alejandra Aguilar-Hernández  Guillermo Ramírez-Santiago 《Mathematical Geosciences》2010,42(8):925-954

In this paper, we investigate the fractal properties of binary maps of rock fractures at different scales and different geological types, as well as different families of fracture patterns obtained from a two-dimensional Laplacian growth model (LGM). From these analyses we figure out which families of the LGM patterns match the structural properties of the fracture binary maps. The LGM is defined in terms of a nonlinear map that depends on two parameters, λ and \mathfraka\mathfrak{a}, that respectively define the area and shape of the elements of the aggregate that conforms the patterns. The fractal dimension and roughness exponent of the LGM patterns are found to depend on \mathfraka\mathfrak{a}, with 0 < \mathfrak a < 10<\mathfrak {a}<1. From a detailed statistical analysis of these patterns we found that the fractal dimensions of capacity, correlation and information decrease monotonically as \mathfraka\mathfrak{a} increases. We also found that the values of these three fractal dimensions tend to collapse on top of each other as \mathfraka\lessapprox1\mathfrak{a}\lessapprox1. Remarkably, the fractal properties of rock fractures in the scales from millimeters up to a few meters appear to be well represented by the fractal structure of the LGM families of patterns with \mathfraka=0.15\mathfrak{a}=0.15 and 0.30, while the fractal properties of rock fractures in the scale of kilometers seems to be well represented by the LGM family with \mathfraka=0.90\mathfrak{a}=0.90. In addition, the three fractal dimension values of fracture binary maps in the scales from millimeters up to meters were found to be different between them. Nonetheless, for fractures in the scale of kilometers, the values of the three fractal dimensions are very close to each other as an indication of self-similar behavior. Analysis of the corrections to the scaling of the roughness exponent, ζ, suggests that they are negligible for the LGM family of fracture patterns with \mathfraka=0.9\mathfrak{a}=0.9. This finding points to a self-affine structure for this family of patterns. In fact, the calculated roughness exponent results are in the range of values characteristic of rock fractures.  相似文献   

Multiscale analysis of vegetation surface fluxes: from seconds to years   总被引：2，自引：0，他引：2  

Gabriel Katul  Chun-Ta Lai  Karina Schfer  Brani Vidakovic  John Albertson  David Ellsworth  Ram Oren 《Advances in water resources》2001,24(9-10)

The variability in land surface heat (H), water vapor (LE), and CO₂ (or net ecosystem exchange, NEE) fluxes was investigated at scales ranging from fractions of seconds to years using eddy-covariance flux measurements above a pine forest. Because these fluxes significantly vary at all these time scales and because large gaps in the record are unavoidable in such experiments, standard Fourier expansion methods for computing the spectral and cospectral statistical properties were not possible. Instead, orthonormal wavelet transformations are proposed and used. The are ideal at resolving process variability with respect to both scale and time and are able to isolate and remove the effects of missing data (or gaps) from spectral and cospectral calculations. Using the spectra, we demonstrated unique aspects in three appropriate ranges of time scales: turbulent time scales (fractions of seconds to minutes), meteorological time scales (hour to weeks), and seasonal to interannual time scales corresponding to climate and vegetation dynamics. We have shown that: (1) existing turbulence theories describe the short time scales well, (2) coupled physiological and transport models (e.g. CANVEG) reproduce the wavelet spectral characteristics of all three land surface fluxes for meteorological time scales, and (3) seasonal dynamics in vegetation physiology and structure inject strong correlations between land surface fluxes and forcing variables at monthly to seasonal time scales. The broad implications of this study center on the possibility of developing low-dimensional models of land surface water, energy, and carbon exchange. If the bulk of the flux variability is dominated by a narrow band or bands of modes, and these modes “resonate” with key state and forcing variables, then low-dimensional models may relate these forcing and state variables to NEE and LE.  相似文献   

Seismic ray direction anomalies and relative residuals of earthquakes recorded at Gauribidanur array     

Avadh Ram  Lalaji Yadav  O P Singh 《Journal of Earth System Science》1981,90(1):63-74

Slowness and azimuthal anomalies provide valuable information about lateral inhomogeneities within the crust and mantle of the earth. Over 300 earthquakes (distance range 14°–36° and azimuth 0°–360°) recorded at Gauribidanur seismic array (GBA) in southern India, were analysed using adaptive processing techniques. Slowness anomalies upto 1·3 sec/deg and azimuthal anomalies upto 8° have been observed in the present analysis. Slowness anomaly patterns for Java trench, Mid-Indian oceanic ridge earthquakes are more consistent as compared to the events originating in the Himalayan and Hindukush regions. A significant feature of the azimuthal anomaly pattern was the distinct absence of any positive anomalies from earthquakes occurring in mid-oceanic ridge. These anomalies have also been analysed as a function of epicentral distance and are mainly attributed to the transition zones occurring between 400–700 km depth ranges in the Indian upper mantle regions. Relative residuals between the stations of GBA have very little dependence on azimuth and distance. An anomalous structure beneath the array in the direction of the Java trench region (azimuth 116–126°) has been postulated on the basis of large systematic slowness vectors observed.  相似文献