Miracle-dz/UniFAR-FTUs huggingface dataset:
Diagnosis of the Surface Momentum Balance over the Tropical Pacific Ocean

Abstract The purpose of this study is to evaluate the suitability of using linear drag as a proxy for surface friction in the observed climatological-mean momentum balance over the tropical Pacific Ocean. The linear drag parameterization of kinetic energy dissipation in the planetary boundary layer is widely used in simplified models of the tropical atmosphere, and in numerous observational studies of the surface momentum balance. Climatological seasonal-mean fields of sea level pressure and surface wind from the Comprehensive Ocean-Atmosphere Data Set are used to calculate the pressure gradient, Coriolis, and acceleration terms in the momentum budget; friction is derived as a residual. It is found that when friction is parameterized as a linear dissipation of kinetic energy, the damping time scale for the meridional wind is ∼2−3 times faster than the damping time for the zonal wind. The preceding formulation fits the observations well, especially in the trade-wind regions. It is suggested that the differ.
Seismic Tomography of the Earth's Mantle

The analysis of information contained in seismograms is the most promis­ ing tool for retrieving the three-dimensional structure of the Earth's mantle and thereby improving our understanding of its dynamics. The procedure through which three-dimensional images of different parts of the Earth's interior arc obtained by inversion of a set of observables measured on the surface of the Earth is commonly termed "tomography," by analogy with the medical procedure with which it shares many aspects of methodology but with much less favorable experimental conditions. Ideally, one would like to be able to model entire seismograms, over a wide frequency band, for a large number of uniformly distributed sources and stations in order to obtain an optimal illumination of the inhomogeneities appropriate for tomographic inversion. In practice, a number of difficulties and limitations arise. Onc is the nonuniform distribution of sources and receivers: Seis­ micity is concentrated at plate boundaries, and the distribution of con­ tinental and island areas leaves large portions of the oceans unin­ strumented. Another difficulty is our limited ability to accurately forward model the effects of wave propagation in a realistic Earth, which presents departures from a spherically symmetric referencc model of both elastic/anc1astic and isotropic/anisotropic nature. This is why, until now, the simplest kind of tomography (travel time tomography) has prevailed, relying on simplifying assumptions concerning the interaction of asphericity with propagating seismic waves. Ray theory and the laws of geometrical optics in their
Moisture uptake in the boundary layer above the Agulhas Current : A case study

Shipboard meteorological measurements and radiosonde ascents are used to describe the modification of the marine atmospheric boundary layer as air is advected across the warm Agulhas Current toward the coast. The data were collected on April 28, 1995, during the Agulhas Current Air-Sea Exchange Experiment south of Port Alfred, South Africa, in a region characterized by a strong sea surface temperature gradient. The surface latent heat flux increased from approximately 160 W m−2 over the seaward border to 270 W m−2 over the current (approximately 80–90 km wide) and decreased dramatically to approximately 40 W m−2 over the cool shelf. This spatial heat flux gradient was reflected in the overlying atmosphere by a transition in atmospheric stability from the warm current to the cool continental shelf. A convective boundary layer over the current was replaced by a stable boundary layer over the cool shelf, where a deep residual moisture layer indicated the former vertical extent of convective eddies. A progressive accumulation of moisture occurred within the boundary layer as the air mass was advected over the current. Mean specific humidity and precipitable water vapor content in the boundary layer over the shelf were 20–25% higher than over the seaward border of the current. The results give credence to the assertion by many investigators that moisture uptake above the Agulhas Current may contribute significantly to moisture convergence and rainfall over the interior of South Africa.
Joint two‐dimensional observations of ground magnetic and ionospheric electric fields associated with auroral zone currents 1. Three‐dimensional current flows associated with a substorm‐intensified eastward electrojet

Two-dimensional distributions of ground magnetic and ionospheric electric fields in the evening sector auroral oval have been simultaneously observed by the Scandinavian Magnetometer Array and the Scandinavian Twin Auroral Radar Experiment (Stare) radars, respectively, on February 15, 1977. They were associated with varying, substorm-intensified, eastward electrojet current flows. Using both data sets, we have derived three-dimensional models for the current systems of the western, middle, and eastern segment of the eastward electrojet. We conclude that the substorm-intensified eastward electrojet was a nearly pure Hall current driven by northward electric fields. The observed eastward increase of the current in the western segment of the electrojet was due to a gradual enhancement of the Hall conductivity. Here, the electrojet was fed by a broad sheet of net downward field-aligned current. During one period, the eastern-terminating part of the eastward electrojet diverged up the field lines in a rather local area because of a strong longitudinal decrease in the northward-directed electric field. On another occasion, it diverged northward within the ionosphere and joined the westward-flowing current because of a rotation of the northward electric field with increasing latitude through west- to southward. These two observed mechanisms of current divergence in the region where eastward and westward electrojets coexist may shed some new light on the controversy over the existence of upward field-aligned current flow in the Harang discontinuity.
Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile

Abstract The Salar de Atacama is located in the most arid desert in the world. Despite its extreme conditions, it has many ecosystems of high ecological value. The Soncor ecosystem, a sequence of lagoons, is the most important environment of the region as it acts as the centre for the breeding of the Andean Flamingo. This salt flat also contains significant mining deposits and is an important water source for the region. Freshwater and brine—enriched in lithium and potassium—are being pumped from the aquifers near to the Soncor ecosystem, which has so far not been greatly affected by this groundwater extraction. However, there is a potential risk that future anthropogenic effects may disturb this fragile environment. The objective of this study is to determine the origin of the water sources of the Soncor ecosystem so as to adequately manage its water resources. Three hypotheses previously proposed in the technical literature were investigated in order to determine proactive actions to protect this fragile ecosystem. The study utilized classic hydrogeological techniques, such as the construction of stratigraphic profiles, piezometric maps and stream gauging, combined with less-common isotopic techniques, such as the 87Sr/86Sr ratio. The results confirmed the hypothesis that the origins of the water sources are associated with groundwater inputs coming from the east side of the salt flat, in the north of the basin. Editor Z.W. Kundzewicz; Associate editor M. Acreman Citation Ortiz, C. , Aravena, R. , Briones, E. , Suárez, F. , Tore, C. , and Muñoz, J.F. , 2014. Sources of surface water for the Soncor ecosystem, Salar de Atacama basin, northern Chile. Hydrological Sciences Journal, 59 (2), 336–350.
Elevated atmospheric CO 2 concentration improves water use efficiency and growth of a widespread Cerrado tree species even under soil water deficit

Changes in atmospheric CO 2 levels are accompanied by ecological interactions involving other environmental factors, such as drought, which can severely alter the water balance of plants, thereby influencing sap flow, gas exchange, and plant growth. The objective of this study was to evaluate the water use economy, leaf gas exchange, and growth of young plants of the species Lafoensia pacari subjected to high concentrations of atmospheric CO 2 ([CO 2 ]) and soil water deficit. Increased vapor pressure deficit was observed from 1200 to 1800 hours. Plants under elevated [CO 2 ] exhibited increased leaf photosynthesis, resulting in improved growth. Specific leaf area was lower in plants under high [CO 2 ], mainly after soil water deficit treatment. Daily irrigated plants growing under ambient [CO 2 ] had higher stem sap flow velocity (cm h -1 ) and hourly sap flow (kg h -1 ), mainly during the hottest hours of the day, than plants under high [CO 2 ]. Improved water use by plants growing under high [CO 2 ] may result in increased availability of water in the soil, partially offsetting future drought events and extending the growth period.
Estimation of temperature change and of gas age‐ice age difference, 108 kyr B.P., at Vostok, Antarctica

Air trapped in ice core bubbles provides our primary source of information about past atmospheres. Air isotopic composition (15N/14N and 40Ar/36Ar) permits an estimate of the temperature shifts associated with abrupt climate changes because of isotope fractionation occurring in response to temperature gradients in the snow layer on top of polar ice sheets. A rapid surface temperature change modifies temporarily the firn temperature gradient, which causes a detectable anomaly in the isotopic composition of nitrogen and argon. The location of this anomaly in depth characterizes the gas age-ice age difference (Δage) during an abrupt event by correlation with the δD (or δ18O) anomaly in the ice. We focus this study on the marine isotope stage 5d/5c transition (108 kyr B.P.), a climate warming which was one of the most abrupt events in the Vostok (Antarctica) ice isotopic record [Petit et al., 1999]. A steplike decrease in δ15N and δ40Ar/4 from 0.49 to 0.47‰ (possibly a gravitational signal due to a change in firn thickness) is preceded by a small but detectable δ15N peak (possibly a thermal diffusion signal). We obtain an estimate of 5350±300 yr for Δage, close to the model estimate of 5000 years obtained using the Vostok glaciological timescale. Our results also suggest that the use of the present-day spatial isotope-temperature relationship slightly underestimates (but by no more than 20±15%) the Vostok temperature change from present day at that time, which is in contrast to the temperature estimate based on borehole temperature measurements in Vostok which suggests that Antarctic temperature changes are underestimated by up to 50% [Salamatin et al, 1998].
The relation of solar radiation to evapotranspiration from cotton

Evapotranspiration affects the irrigation requirements of crops, and a simple method is needed for determining ET. The evapotranspiration equivalent of solar radiation (RS) is easily computed from data readily available from the U.S. Weather Bureau. The ET/RS ratio for cotton irrigated at Watkinsville, Georgia, showed that Rs data can be used to predict irrigation needs when the ET/RS ratio, daily rainfall, and available water capacity of the soil are known.
Prenatal Exposure to Organophosphate Pesticides and IQ in 7-Year-Old Children

Context: Organophosphate (OP) pesticides are neurotoxic at high doses. Few studies have examined whether chronic exposure at lower levels could adversely affect children’s cognitive development. Objective: We examined associations between prenatal and postnatal exposure to OP pesticides and cognitive abilities in school-age children. Methods: We conducted a birth cohort study (Center for the Health Assessment of Mothers and Children of Salinas study) among predominantly Latino farmworker families from an agricultural community in California. We assessed exposure to OP pesticides by measuring dialkyl phosphate (DAP) metabolites in urine collected during pregnancy and from children at 6 months and 1, 2, 3.5, and 5 years of age. We administered the Wechsler Intelligence Scale for Children, 4th edition, to 329 children 7 years of age. Analyses were adjusted for maternal education and intelligence, Home Observation for Measurement of the Environment score, and language of cognitive assessment. Results: Urinary DAP concentrations measured during the first and second half of pregnancy had similar relations to cognitive scores, so we used the average of concentrations measured during pregnancy in further analyses. Averaged maternal DAP concentrations were associated with poorer scores for Working Memory, Processing Speed, Verbal Comprehension, Perceptual Reasoning, and Full-Scale intelligence quotient (IQ). Children in the highest quintile of maternal DAP concentrations had an average deficit of 7.0 IQ points compared with those in the lowest quintile. However, children’s urinary DAP concentrations were not consistently associated with cognitive scores. Conclusions: Prenatal but not postnatal urinary DAP concentrations were associated with poorer intellectual development in 7-year-old children. Maternal urinary DAP concentrations in the present study were higher but nonetheless within the range of levels measured in the general U.S. population.
Reconciling subduction dynamics during Tethys closure with large‐scale Asian tectonics: Insights from numerical modeling

We use three‐dimensional numerical models to investigate the relation between subduction dynamics and large‐scale tectonics of continent interiors. The models show how the balance between forces at the plate margins such as subduction, ridge push, and far‐field forces, controls the coupled plate margins and interiors evolution. Removal of part of the slab by lithospheric break‐off during subduction destabilizes the convergent margin, forcing migration of the subduction zone, whereas in the upper plate large‐scale lateral extrusion, rotations, and back‐arc stretching ensue. When external forces are modeled, such as ridge push and far‐field forces, indentation increases, with large collisional margin advance and thickening in the upper plate. The balance between margin and external forces leads to similar convergent margin evolutions, whereas major differences occur in the upper plate interiors. Here, three strain regimes are found: large‐scale extrusion, extrusion and thickening along the collisional margin, and thickening only, when negligible far‐field forces, ridge push, and larger far‐field forces, respectively, add to the subduction dynamics. The extrusion tectonics develops a strong asymmetry toward the oceanic margin driven by large‐scale subduction, with no need of preexisting heterogeneities in the upper plate. Because the slab break‐off perturbation is transient, the ensuing plate tectonics is time‐dependent. The modeled deformation and its evolution are remarkably similar to the Cenozoic Asian tectonics, explaining large‐scale lithospheric faulting and thickening, and coupling of indentation, extrusion and extension along the Asian convergent margin as a result of large‐scale subduction process.
A 420,000 year deuterium excess record from East Antarctica: Information on past changes in the origin of precipitation at Vostok

Here we present and analyze the complete Vostok ice cores deuterium excess record which spans the last four climatic cycles, back to ∼420,000 years B.P. To extract paleoclimate information from this record, we use isotopic modeling showing that changes in deuterium excess (d = δD-8δ18O) of Vostok precipitation reflect changes in the average temperature of oceanic moisture sources. Over the last 250,000 years the deuterium excess is strongly anticorrelated with changes in Earth's obliquity. This reflects changes in the relative contribution of low and high latitudes to the Vostok precipitation, resulting from changes in the latitudinal annual mean insolation gradient governed by the obliquity. However, this modulation by obliquity is not observed prior to 250,000 years B.P. We attribute this difference to the ice flow, the deeper ice under Vostok station having accumulated in a location upstream Vostok, receiving precipitation from different oceanic origins. Despite this difference between the earlier and the later portions of the record, the deuterium excess changes during all the glacial inceptions are similar in amplitude and timing relative to the deuterium decrease. The glacial inceptions are characterized by high deuterium excess, indicating the significant role of the tropics in supplying moisture to the already cold poles.
Numerical Evaluation of Effective Unsaturated Hydraulic Properties of Fractured Rocks using a Stochastic Continuum Approach

This study builds on past studies that have investigated the effective properties of unsaturated porous media and merges stochastic continuum concepts to develop a numerical procedure for estimating the effective flow parameters that are independent of pressure head or saturation. The procedure involves the development of a numerical permeameter based on randomly generated, spatially correlated fields of fundamental fracture properties such as spacing and aperture. Local values of hydraulic conductivity, and the van Genuchten fitting parameters α and n in this random field are computed from local values of mechanical aperture and spacing based on the cubic law and relationships established from pore‐scale fracture simulations. By considering multiple realizations of these spatially correlated fields and by running the numerical permeameter over a range of effective saturations and flow rates, outputs are generated that can be fit with the standard van Genuchten model to estimate block effective values of saturated hydraulic conductivity and the van Genuchten unsaturated hydraulic parameters of a fracture continuum at the field scale. These parameters can then be incorporated to conventional numerical simulators originally developed for porous media. The study shows that reasonable approximations to the results obtained through computationally demanding stochastic simulations can be developed based on estimates of the mean fracture spacing and aperture. Although the example application assumes the presence of an impermeable rock matrix, the hydraulic properties estimated for the fracture continuum with this methodology can be combined with those measured or similarly estimated for a matrix continuum in dual‐permeability continuum models.
Geochemical modeling of the formation of an unconformity-type uranium deposit

Petrologic studies of alteration associated with uranium mineralization in unconformity-type uranium deposits have established a detailed paragenetic sequence of the preore and synore alteration. In addition, fluid inclusion studies have determined the presence of two distinct fluids, and thermodynamic analysis of the alteration assemblages has defined their basic characteristics. These fluids were probably basinal brines derived from the overlying sandstones and have been distinguished by their different salinities.Fluids responsible for alteration and ore formation were Na-Ca-Cl brines. Speciation calculations suggest that the hydrothermal fluids responsible for the formation of unconformity-type uranium deposits were distinguished by their high oxygen fugacity and relatively low pH. Uranium was transported mainly as uranyl chloride complexes.Reconstruction of the reactions associated with the formation of the deposits, employing chemical mass transfer calculations, helps unravel the geochemical processes operating during their genesis. Reaction path calculations indicate that Fe present in aluminosilicates in the host rocks is the principal reductant of oxidized uranium present in the ore-forming fluids. The use of variable host-rock lithologies results in the reproduction of mineralogical features unique to each deposit, along with the characteristics common to all unconformity-related uranium deposits. The calculations show that the observed paragenesis is a function not only of the fluid chemistry but also of the host-rock lithologies. The modeling indicates that although an orebody can be produced with or without graphite as a reactant, its presence leads to a better agreement with the observed alteration paragenesis.
Tree-limit rise and recent warming: a geoecological case study from the Swedish Scandes

Twentieth-century elevational tree-limit (TL) and species-limit histories have been reconstructed for Pinus sylvestris, Picea abies and Betula pubescens ssp. tortuosa within a permanent belt transect in the southern Swedish Scandes. Upward TL shifts of 100-130 m between c. 1915 and 1999 appear related to a summer warming of c. 0.7°C, and increased winter temperatures. Rates of tree recruitment and individual growth have increased substantially since 1974, notably during the 1990s, apparently mainly in response to some warm summers and a sequence of exceptionally mild winters. The distributional trend during the 20th century constitutes a fundamental and unexpected break in a monotonic, century-scale TL descent throughout most of the Holocene (exemplified by Pinus sylvestris), which was particularly accentuated during the 'Little Ice Age' of the past several centuries. Assuming that the TL stabilizes at the new, higher level for several decades, its elevation will be higher than at any time during at least the past c. 4000 radiocarbon years. This recent history is relevant as one possible model of the ecological consequences of anthropogenic climate forcing, and the TL may be an appropriate and sensitive system for monitoring the ecological effects of future climate change and variability.
Freshwater budget of the Canada Basin, Arctic Ocean, from salinity, δ18O, and nutrients

[1] The contribution of freshwater components (e.g., meteoric, sea ice, and Pacific water) in the Canada Basin is quantified using salinity, δ18O, and nutrient data collected in 2003 and 2004. The penetration depth of sea ice meltwater is limited to the upper 30 m, and brine, rejected during sea ice formation, is observed from 30 to 250 m depth. The fraction of meteoric water is high in the upper 50 m and decreases with depth. Pacific water entering via Bering Strait is the main source of freshwater below 50 m depth. Bering Strait throughflow, which transports Pacific water with salinity 32.5 together with meteoric water supplied upstream of the Bering Strait, contributes up to 75% of freshwater input (>3200 km3 a−1) to the Canada Basin. The mean residence time of Pacific water in the Canada Basin is estimated to be 11 years. Precipitation and river runoff from both North American and Eurasian continents add >800 km3 a−1 and sea ice formation removes <900 km3 a−1 (<0.6 m a−1) of fresh water. The export of ice and liquid fresh water from the Canada Basin contributes ∼40% of the freshwater flux from the Arctic Ocean to the North Atlantic Ocean.