Miracle-dz/UniFAR-FTUs huggingface dataset:
Monte Carlo study of the nature of the underwater light field in, and the relationships between optical properties of, turbid yellow waters

A Monte Carlo calculation procedure has been developed for computer modelling of the penetration of light into turbid, coloured waters of the type commonly found on the Australian continent. For monochromatic light the structure of the underwater light field is described in terms of the variation of the average cosine (total, downward, upward) and irradiance reflectance, as a function of optical depth at a given ratio of scattering to absorption (bla), and as a function of bia at a given optical depth. The vertical attenuation coefficient for downward irradiance at the mid-point of the euphotic zone [Kd(za)] has been studied as a function of the absorption (a) and scattering (b) coefficients and, with the particular normalized volume scattering function used in these simulations. has been found to conform closely to the equation Kd(zm) = (a2 + 0.256ab)½ The data generated by the model have been used in conjunction with radiative transfer theory to determine the contribution of the different components of the attenuation mechanism to the vertical diminution of irradiance at different ratios of b to a. Simulation of the penetration of photosynthetically available radiation into four water bodies in the southern tablelands of New South Wales has been carried out using measured absorption coefficients and indirectly estimated values for scattering coefficients. The calculated values for vertical attenuation coefficients are in good agreement with those obtained by measurement within the water bodies. The possible use of this modelling procedure as a predictive tool is discussed.
Seismic anisotropy in the eastern United States: Deep structure of a complex continental plate

We have analyzed shear wave splitting recorded by portable and permanent broadband and long-period stations located in the eastern United States. Teleseismic shear waves (SKS, SKKS, and PKS) were used to retrieve the splitting parameters: the orientation of the fast wave polarization plane ϕ and the delay time δt. In total, 120 seismic events were processed, allowing for more than 600 splitting measurements. Within the Appalachians, stations located in the western (external) part are characterized by δt≈1s and ϕ trending N50°– 70°E in the south and central regions and N30°–40°E in the north, closely following the trend of the orogenic belt in these areas. The transition region between north and central is characterized by δt≈1–1.3 s and by E-W trending ϕ that are at a high angle to the regional geologic trend. Measurements at two stations located in the eastern (internal) part of the belt indicate very weak anisotropy. The large-scale pattern of anisotropy is not consistent with that predicted for simple asthenospheric flow beneath the plate. Splitting along the southern and eastern margins of the continent is consistent with that expected for Grenvillian deformation, an alternative model of asthenospheric flow around the cratonic keel cannot be ruled out. Within the cratonic core, the correlation between δt and lithospheric thickness suggests a lithospheric anisotropy. Smaller-length-scale variations also argue for a significant contribution of lithospheric structures. The fabric responsible for shear wave splitting may have formed during tectonic episodes that affected the eastern United States, i.e., the Grenville and Appalachian orogenies and the subsequent rifting of the North Atlantic Ocean. Our observations in the western Appalachians suggest that the anisotropy may be preserved since the Grenvillian orogeny. The absence of detectable splitting in the two stations in the eastern Appalachians is attributed to the igneous intrusions related to the Atlantic rifting. The measurements in the transition between the northern and central southern Appalachians, constitute an intriguing anomaly, whose E-W ϕ have little obvious relation to the regional surface geology. We suggest two possible causes: (1) the local dominance of asthenospheric flow, motivated by the proximity of a pervasive low-velocity anomaly and (2) lithospheric deformation in a transcontinental strike-slip fault zone active during the Appalachian collision.
δ18O and δ13C isotope investigation of the Late Glacial and early Holocene biogenic carbonates from the Lake Lednica sediments, western Poland

Stable isotope composition (δ 18 O and δ 13 C) of biogenic carbonates derived from the Lake Lednica sediments at Rybitwy, western Poland, was applied to obtain data on climatic changes during the Late Glacial and early Holocene. A wide range of carbonates occurring in the sediments was analysed for δ 18 O and δ 13 C records, including shells of several gastropod species, the bivalve genus Pisidium and carapaces of ostracods belonging to the subfamily Candoninae. The δ 18 O and δ 13 C records reveal changes commonly observed for the Late Glacial and early Holocene with the exception of the low oxygen isotope values of the Bolling andAllerod Interstadials. The latter is interpreted as a consequence of 18 O-depletion of the lake water resulting from gradual melting of the dead ice that still filled the deepest parts of the Lake Lednica valley during the period described. TheYounger Dryas Stadial begins with the isotopically lightest values in the sequence; however, due to the 18O-depleted values of theAllerod Interstadial the Allerod/Younger Dryas boundary is poorly marked. The Younger Dryas/Preboreal transition is documented by a significant shift in δ 18 O values of about 2–3‰, resulting from an increase in the mean annual temperature. The δ 13 C record reflects the productivity level in the lake, with 13 C-enriched carbonates during the Bolling andAllerod Interstadials, and the Preboreal and Boreal, when photosynthetic activity of phytoplankton and macrophytes was the most intensive. Differences in δ 18 O and δ 13 C values between mollusc shells and ostracod carapaces reflect the specific season and subhabitat of each carbonate secretion.
Run Analysis of Rainfall Data Affected by Urbanization

Analyse des donnees a l'aide de la theorie des runs, theorie developpee par Downer et al. (1967) et par Llamas et Siddiqui (1969). Un run humide ou un run sec est defini comme la periode au cours de laquelle la hauteur totale de pluie est superieure ou inferieure a un certain niveau critique donne. Trois proprietes principales du run sont: la longueur du run est le nombre de termes dans un run complet, positif ou negatif, suivant qu'il est associe a un run humide ou sec; la somme du run est la somme des deviations par rapport a un certain niveau, prise sur la longueur du run; l'intensite du run est le rapport entre la somme et la longueur du run. Application aux pluies annuelles et mensuelles a La Porte (pres de Chicago). Les pluies annuelles sont supposees etre distribuees normalement et suivant gamma, celles mensuelles suivent une chaine de Markov a 2 etats avec des probabilites stationnaires pour la transition. Il s'avere que ces hypotheses sont adequates. On montre que du point de vue de ce qu'on appelle l'anomalie de La Porte, les proprietes des runs a La Porte ne sont pas differentes de celles dans les stations voisines. Enfin, l'intensite du run est meilleur indicateur de l'effet d'urbanisation, que la longueur ou la somme du run
Experimental study of kaolin particle orientation mechanism

The aim of the experimental study is to analyse the association between the behaviour of a clayey material at the macroscopic level and its local deformation properties. The approach is based on the study of the orientation of the clay particles by scanning electron microscopy picture analysis after different phases of triaxial loading. This leads to a better understanding and characterisation of the relation between the microfabric and the strain mechanisms (i.e. contractancy and dilatancy) observed at the macroscopic level. In the initial state (one-dimensional compression), the observations highlight the microstructural anisotropy of the slightly overconsolidated specimens with a preferential orientation of the particles normal to the loading direction. During isotropic loading, densification of the clayey matrix occurs associated with a re-orientation of the particles, leading to an increase in structural isotropy, indicated by the term ‘depolarisation'. On the triaxial path, up to 5% axial strain, de.
Evolution of basin architecture in an incipient continental rift: the Cenozoic Most Basin, Eger Graben (Central Europe)

The Oligo‐Miocene Most Basin is the largest preserved sedimentary basin within the Eger Graben, the easternmost part of the European Cenozoic Rift System (ECRIS). The basin is interpreted as a part of an incipient rift system that underwent two distinct phases of extension. The first phase, characterised by NNE–SSW‐ to N–S‐oriented horizontal extension between the end of Eocene and early Miocene, was oblique to the rift axis and caused evolution of a fault system characterised by en‐échelon‐arranged E–W (ENE–WSW) faults. These faults defined a number of small, shallow initial depocentres of very small subsidence rates that gradually merged during the growth and linkage of the normal fault segments. The youngest part of the basin fill indicates accelerated subsidence caused probably by the concentration of displacement at several major bounding faults. Major post‐depositional faulting and forced folding were related to a change in the extension vector to an orthogonal position with respect to the rift axis and overprinting of the E–W faults by an NE–SW normal fault system. The origin of the palaeostress field of the earlier, oblique, extensional phase remains controversial and can be attributed either to the effects of the Alpine lithospheric root or (perhaps more likely because of the dominant volcanism at the onset of Eger Graben formation) to doming due to thermal perturbation of the lithosphere. The later, orthogonal, extensional phase is explained by stretching along the crest of a growing regional‐scale anticlinal feature, which supports the recent hypothesis of lithospheric folding in the Alpine–Carpathian foreland.
Urban Heat Island in a Tropical City Interlaced by Wetlands

The most pronounced effect of urbanisation on the microclimate of a region is the development of the Urban Heat Island (UHI), which is the elevation of air temperature within the region with respect to adjoining rural areas. There are many factors like coverage area, vegetation, soil moisture, street geometry, building materials, etc., which cause or modify the intensity of UHI. The UHI in Kochi, a fast growing urban region in coastal South India, interlaced by a network of canals and wetlands which are part of the Vembanad Lake system, was investigated. The UHI during summer and winter periods were recorded through mobile traverses. The intensity of the heat island during summer was 2.2 K and during winter was 2.8 K. The heating and cooling rates in different locations within the region were also derived through stationary recorders installed at selected locations. The intensity of the UHI here is moderate compared to that observed in other cities in the region. It is inferred that the wetlands is controlling the intensity of the UHI here.
The role of debris supply conditions in predicting debris flow activity

Debris flow frequency and magnitude were determined for 33 basins in southwest British Columbia. Basins were first classifiedaseitherweathering-limitedortransport-limitedusingadiscriminantfunctionbasedondebris-contributingarea, an area-weighted terrain stability number, and drainage density. Multiple regression was used to predict magnitude, peak discharge, frequency and activity (frequency times magnitude) within each group of basins. Model performance was improved by stratifying the total sample of debris flow basins into weathering-and transport-limited groups. Explained varianceincreasedbyanaverageof15percentinthetransport-limitedsample,indicatingthatsedimentsupplyconditionsin themoreactivebasinsarefundamentalinpredictingdebrisflowactivity.Anindependenttestoftheregressionmodelswith 11basinsyieldedgenerallygoodresultsfordebrisflowmagnitudeandpeakdischarge.Predictionofdebrisflowfrequency provedproblematicalinweathering-limitedbasins.Themethodsdevelopedhereprovideestimatesofdebrisflowattributes in basins for which few data on past events are available. Copyright # 1999 John Wiley & Sons, Ltd.
A reassessment of lake and wetland feedbacks on the North African Holocene climate

Large parts of the Sahara were vegetated during the early to mid Holocene. Several positive feedbacks, most notably related to vegetation, have been shown to have favored the northward migration of the desert boundary. During this period, numerous lakes and wetlands existed in the Sahara region and might have acted as a local moisture source. However, earlier model studies of the effects of open water surfaces on the mid‐Holocene North African climate suggested that these were weak and did not contribute significantly to this northward migration of the North African climate zones. Using a state‐of‐the‐art climate model, we suggest that the effect of open‐water surfaces on the mid‐Holocene North African climate might have been much stronger than previously estimated, regionally more than doubling the simulated precipitation rates. It is thus possible that this effect, combined to other known positive feedbacks, favored the appearance of the “Green Sahara”.
Intensive field measurements of nitrous oxide emissions from a tropical agricultural soil

The amount of nitrous oxide (N2O) continues to increase in the atmosphere. Agricultural use of nitrogen fertilizers in the tropics is thought to be an important source of atmospheric N2O. High frequency, highly precise measurements of the N2O flux were made with an automated system deployed in N fertilized and unfertilized agricultural plots of papaya and corn in Costa Rica for an entire corn crop growth to harvest cycle. N2O fluxes were as high as 64 ng N‐N2O cm−2 h−1 from fertilized versus 12 ng N‐N2O cm−2 h−1 from unfertilized corn and 28 ng N‐N2O cm−2 h−1 from fertilized versus 4.6 ng N‐N2O cm−2 h−1 from unfertilized papaya. Fertilized corn released more N2O than fertilized papaya over the 125 days of the crop cycle, 1.83 kg N ha−1 versus 1.37 kg N ha−1. This represents a loss as N2O of 1.1 and 0.9% of the total N applied as ammonium nitrate to the corn and papaya, respectively. As has often been observed, N2O fluxes were highly variable. The fastest rates of emission were associated with fertilization and high soil moisture. A diurnal cycle in the fluxes was not evident probably due to the minimal day/night temperature fluctuations. Each chamber was measured between 509 and 523 times over the course of the experiment. This allows us to evaluate the effect on constructed mean fluxes of lowered sampling frequencies. Sampling each collar about once a day throughout the crop cycle (25% of the data set) could result in a calculated mean flux from any individual chamber that can vary by as much as 20% even though the calculated mean would probably be within 10% of the mean of the complete data set. The uncertainty increases very rapidly at lower sampling frequencies. For example, if only 10% of the data set were used which would be the equivalent of sampling every other day, a very high sampling frequency in terms of manual measurements, the calculated mean flux could vary by as much as 40% or more at any given site.
Relative Contribution of Rill/Interrill and Gully/Channel Erosion to Small Reservoir Siltation in Mediterranean Environments

Reservoir siltation because of water erosion is an important environmental issue in Mediterranean countries where storage of clear surface water is crucial for their economic and agricultural development. The high density of gully systems observed in Mediterranean regions raises the question of their contribution to reservoir siltation. In this context, this study quantified the absolute and relative contributions of rill/interrill and gully/channel erosion in sediment accumulation at the outlet of small Tunisian catchments (0·1–10 km2) during the last 15 years (1995–2010). To this end, a fingerprinting method based on measurements of caesium‐137 and total organic carbon combined with long‐term field monitoring of catchment sediment yield was applied to five catchments in order to cover the diversity of environmental conditions found along the Tunisian Ridge and in the Cape Bon region. Results showed the very large variability of erosion processes among the selected catchments, with rill/interrill erosion contributions to sediment accumulated in outlet reservoirs ranging from 20 to 80%. Overall, rill/interrill erosion was the dominant process controlling reservoir siltation in three catchments whereas gully/channel erosion dominated in the other two catchments. We identified the presence of marly gypsum substrates and the proportion of catchment surface covered by soil management/conservation measures as the main drivers of erosion process variability at the catchment scale. These results provided a sound basis to propose guidelines for erosion mitigation in these Mediterranean environments and suggested to apply models simulating both rill/interrill and gully/channel erosion in catchments of the region. Copyright © 2015 John Wiley & Sons, Ltd.
Statistical Analyses of Land–Atmosphere Feedbacks and Their Possible Pitfalls

Abstract In some regions of the world, soil moisture has a typical memory for atmospheric processes and can also feed back to the latter. Thus, a better understanding of feedbacks between soil moisture and the atmosphere could provide promising perspectives for increased seasonal predictability. Besides numerical simulations, statistical analysis of existing GCM simulations or observational data has been used to study such feedbacks. By referring to a recent statistical analysis of soil moisture–precipitation feedbacks in GCM simulations, the authors illustrate potential pitfalls of statistical approaches in this context: (i) most importantly, apparent soil moisture–precipitation feedbacks can often as well or even better be attributed to the influence of sea surface temperatures (SSTs) on precipitation and (ii) the discrepancy between different GCMs is large, which makes the aggregation of individual model results difficult. These aspects need to be carefully evaluated in statistical analyses of land–atm.
Structural variation across the northern margin of the Variscides in NW Europe

Summary Four areas which cross the northern margin of the Variscan fold belt are examined and models of their structural evolution, from basin development to folding etc., are compared. Foreland Britain is characterized by heterogeneous deformation localized in basins, whose development accompanied E-W dextral shear. The Munster basin in Ireland contains steep folds and cleavage. A variety of minor structures indicates an important dextral shear component to the deformation, and basin inversion by transpression is proposed. SW England is dominated by thrust tectonics, including the obduction of the Lizard ophiolite. Deformation was preceded by south to north migration of basin development. Brittany is characterized by major dextral shear zones delimiting areas of variable ductile strain. The structural geometry and history of these areas is interpreted in terms of regional dextral transpression. The common transport direction is to the NNW or NW and oblique to the belt. Variable amounts of thrusting and dextral shear produced the different structural patterns. A case is made for an essentially ‘thick-skinned’ style of heterogeneous deformation produced in a dextral, oblique collision orogen, which involved microplates and a small back-arc basin.
Atmospheric Moisture Budget and Spatial Resolution Dependence of Precipitation Extremes in Aquaplanet Simulations

AbstractThis study investigates the moisture budgets and resolution dependency of precipitation extremes in an aquaplanet framework based on the Community Atmosphere Model, version 4 (CAM4). Moisture budgets from simulations using two different dynamical cores, the Model for Prediction Across Scales-Atmosphere (MPAS-A) and High Order Method Modeling Environment (HOMME), but the same physics parameterizations suggest that during precipitation extremes the intensity of precipitation is approximately balanced by the vertical advective moisture transport. The resolution dependency in extremes from simulations at their native grid resolution originates from that of vertical moisture transport, which is mainly explained by changes in dynamics (related to vertical velocity ω) with resolution. When assessed at the same grid scale by area-weighted averaging the fine-resolution simulations to the coarse grids, simulations with either dynamical core still demonstrate resolution dependency in extreme precipitation wi.
SLOPE INSTABILITY CAUSED BY SMALL VARIATIONS IN HYDRAULIC CONDUCTIVITY

Variations in hydraulic conductivity can greatly modify hillslope ground-water flow fields, effective-stress fields, and slope stability. In materials with uniform texture, hydraulic conductivities can vary over one to two orders of magnitude, yet small variations can be difficult to determine. The destabilizing effects caused by small (one order of magnitude or less) hydraulic conductivity variations using ground-water flow modeling, finite-element deformation analysis, and limit-equilibrium analysis are examined here. Low hydraulic conductivity materials that impede downslope ground-water flow can create unstable areas with locally elevated pore-water pressures. The destabilizing effects of small hydraulic heterogeneities can be as great as those induced by typical variations in the frictional strength (approximately 4°–8°) of texturally similar materials. Common “worst-case” assumptions about ground-water flow, such as a completely saturated “hydrostatic” pore-pressure distribution, do not account for locally elevated pore-water pressures and may not provide a conservative slope stability analysis. In site characterization, special attention should be paid to any materials that might impede downslope ground-water flow and create unstable regions.
Rift flank uplift in Tibet: Evidence for a viscous lower crust

Analysis of high-resolution digital topography across 21 Plio-Pleistocene grabens in central and southern Tibet shows that high topography occurs along the graben margins. Profiles across these marginal highlands fit curves describing the flexure of an elastic plate under vertical loading. We interpret the features as flexural rift flank uplifts, resulting from regional isostatic compensation of low-density grabens. The short wavelengths of the uplifts (30–40 km) imply a low flexural rigidity for the plateau (D = 2−6 × 1020 N m), similar to values inferred for the Basin and Range of western North America. In addition, the grabens themselves are extremely narrow compared to typical continental rifts. Taken together, these observations suggest the existence of a low-viscosity lower crust and suggest that isostatic compensation is taking place within this ductile lower crust. Simple channel flow calculations suggest that crustal viscosities below ∼1022 Pa s are necessary to accommodate this compensation over reasonable timescales.