bluuebunny/crossref_metadata_2025_split huggingface dataset:
Basin‐scale runoff prediction: An Ensemble Kalman Filter framework based on global hydrometeorological data sets
Authors: Lorenz Christof , Tourian Mohammad J. , Devaraju Balaji , Sneeuw Nico , Kunstmann Harald 
Published: October 2015

AbstractIn order to cope with the steady decline of the number of in situ gauges worldwide, there is a growing need for alternative methods to estimate runoff. We present an Ensemble Kalman Filter based approach that allows us to conclude on runoff for poorly or irregularly gauged basins. The approach focuses on the application of publicly available global hydrometeorological data sets for precipitation (GPCC, GPCP, CRU, UDEL), evapotranspiration (MODIS, FLUXNET, GLEAM, ERA interim, GLDAS), and water storage changes (GRACE, WGHM, GLDAS, MERRA LAND). Furthermore, runoff data from the GRDC and satellite altimetry derived estimates are used. We follow a least squares prediction that exploits the joint temporal and spatial auto‐ and cross‐covariance structures of precipitation, evapotranspiration, water storage changes and runoff. We further consider time‐dependent uncertainty estimates derived from all data sets. Our in‐depth analysis comprises of 29 large river basins of different climate regions, with which runoff is predicted for a subset of 16 basins. Six configurations are analyzed: the Ensemble Kalman Filter (Smoother) and the hard (soft) Constrained Ensemble Kalman Filter (Smoother). Comparing the predictions to observed monthly runoff shows correlations larger than 0.5, percentage biases lower than ± 20%, and NSE‐values larger than 0.5. A modified NSE‐metric, stressing the difference to the mean annual cycle, shows an improvement of runoff predictions for 14 of the 16 basins. The proposed method is able to provide runoff estimates for nearly 100 poorly gauged basins covering an area of more than 11,500,000 km2 with a freshwater discharge, in volume, of more than 125,000 m3/s.
Limb sounders tracking topographic gravity wave activity from the stratosphere to the ionosphere around midlatitude Andes
Authors: Alexander P. , de la Torre A. , Schmidt T. , Llamedo P. , Hierro R. 
Published: October 2015

AbstractSeveral studies have shown that the surroundings of the highest Andes mountains at midlatitudes in the Southern Hemisphere exhibit gravity waves (GWs) generated by diverse sources which may traverse the troposphere and then penetrate the upper layers if conditions are favorable. There is a specific latitude band where that mountain range is nearly perfectly aligned with the north‐south direction, which favors the generation of wavefronts parallel to this orientation. This fact may allow an optimization of procedures to identify topographic GW in some of the observations. We analyze data per season to the east and west of these Andes latitudes to find possible significant differences in GW activity between both sectors. GW effects generated by topography and convection are expected essentially on the eastern side. We use satellite data from two different limb sounding methods: the Global Positioning System radio occultation (RO) technique and the Sounding of the Atmosphere using Broadband Emission Radiometry instrument, which are complementary with respect to the height intervals, in order to study the effects of GW from the stratosphere to the ionosphere. Activity becomes quantified by the GW average potential energy in the stratosphere and mesosphere and by the electron density variance content in the ionosphere. Consistent larger GW activity on the eastern sector is observed from the stratosphere to the ionosphere (night values). However, this fact remains statistically significant at the 90% significance level only during winter, when GWs generated by topography dominate the eastern sector. On the contrary, it is usually assumed that orographic GWs have nearly zero horizontal phase speed and will therefore probably be filtered at some height in the neutral atmosphere. However, this scheme relies on the assumption that the wind is uniform and constant. Our results also suggest that it is advisable to separate night and day cases to study GWs in the ionosphere, as it is more difficult to find significant statistical differences during daytime. This may happen because perturbations induced by GWs during daytime are more likely to occur in a disturbed environment that may hinder the identification of the waves.
Earth's distant magnetotail current sheet near and beyond lunar orbit
Authors: Vasko I. Y. , Petrukovich A. A. , Artemyev A. V. , Nakamura R. , Zelenyi L. M. 
Published: October 2015

AbstractWe analyze the structure of the Earth magnetotail current sheet (CS) in middle, X∈[−50,−20] RE, and distant, X∈[−100,−80] RE, regions using data set of 573 CS crossings by Geotail in 1994–1995. For a subset of 213 CSs we determine the CS thickness L, average current density j0, and velocity vD=j0/en0 (n0 is the ion number density). We find similar dawn‐dusk distributions of CS parameters for middle and distant tail: L is about 3000 km at the dusk flank and grows up to 12,000 km toward the dawn flank; j0 grows toward the dusk flank by a factor of 2–3; and the most intense CSs (with higher vD) are observed near midnight. We show that ion‐scale CSs with the thickness of several ion thermal gyroradii (say less than seven) are observed in middle and distant tail in more than 50% of crossings. For observed CSs electrons likely provide the dominant contribution to the current density. We divide the subset into intense and weak CSs (using parameter vD). Weak CSs have thickness of about 20 ion thermal gyroradii and Bz of about 1.5 nT. Intense CSs have thickness of about 3–7 thermal gyroradii and much smaller Bz implying more stretched field line configuration. Intense CSs are accompanied by fast ion flows: vD is larger for larger amplitudes of ion bulk velocity vx that is likely due to larger contribution of Speiser ions. The properties of the CS in middle and distant tail are compared with those found for the near‐Earth tail.
Pairwise surface drifter separation in the western Pacific sector of the Southern Ocean
Authors: van Sebille Erik , Waterman Stephanie , Barthel Alice , Lumpkin Rick , Keating Shane R. , Fogwill Chris , Turney Chris 
Published: October 2015

AbstractThe Southern Ocean plays a critical role in global climate, yet the mixing properties of the circulation in this part of the ocean remain poorly understood. Here dispersion in the vicinity of the Southern Antarctic Circumpolar Current Front, one of the branches of the Antarctic Circumpolar Current, is studied using 10 pairs of surface drifters deployed systematically across the frontal jet and its flanks. Drifter pairs were deployed with an initial separation of 13 m and report their position every hour. The separation of the pairs over 7 months, in terms of their Finite‐Scale Lyapunov Exponents (FSLE), dispersion, and diffusivity, is characterized and related to expected behavior from Quasi‐Geostrophic (QG) and Surface Quasi‐Geostrophic (SQG) theories. The FSLE analysis reveals two submesoscale regimes, with SQG‐like behavior at scales below 3.2 km and mixed QG/SQG behavior at scales between 3.2 and 73 km. The dispersion analysis, however, suggests QG‐like behavior for the smallest scales. Both dispersion and diffusivity appear isotropic for scales up to 500 km. Finally, there is no clear indication of a cross‐jet variation of drifter dispersion.
Geophysical constraints on the dynamics and retreat of the Barents Sea ice sheet as a paleobenchmark for models of marine ice sheet deglaciation
Authors: Patton Henry , Andreassen Karin , Bjarnadóttir Lilja R. , Dowdeswell Julian A. , Winsborrow Monica C. M. , Noormets Riko , Polyak Leonid , Auriac Amandine , Hubbard Alun 
Published: October 2015

AbstractOur understanding of processes relating to the retreat of marine‐based ice sheets, such as the West Antarctic Ice Sheet and tidewater‐terminating glaciers in Greenland today, is still limited. In particular, the role of ice stream instabilities and oceanographic dynamics in driving their collapse are poorly constrained beyond observational timescales. Over numerous glaciations during the Quaternary, a marine‐based ice sheet has waxed and waned over the Barents Sea continental shelf, characterized by a number of ice streams that extended to the shelf edge and subsequently collapsed during periods of climate and ocean warming. Increasing availability of offshore and onshore geophysical data over the last decade has significantly enhanced our knowledge of the pattern and timing of retreat of this Barents Sea ice sheet (BSIS), particularly so from its Late Weichselian maximum extent. We present a review of existing geophysical constraints that detail the dynamic evolution of the BSIS through the last glacial cycle, providing numerical modelers and geophysical workers with a benchmark data set with which to tune ice sheet reconstructions and explore ice sheet sensitivities and drivers of dynamic behavior. Although constraining data are generally spatially sporadic across the Barents and Kara Seas, behaviors such as ice sheet thinning, major ice divide migration, asynchronous and rapid flow switching, and ice stream collapses are all evident. Further investigation into the drivers and mechanisms of such dynamics within this unique paleo‐analogue is seen as a key priority for advancing our understanding of marine‐based ice sheet deglaciations, both in the deep past and in the short‐term future.
All‐sky interferometric riometry
Authors: McKay Derek , Fallows Richard , Norden Menno , Aikio Anita , Vierinen Juha , Honary Farideh , Marple Steve , Ulich Thomas 
Published: October 2015

AbstractThe first implementation of a Fourier‐based interferometric riometry technique for measuring electron density induced ionospheric opacity at VHF radio frequencies is presented. Unlike multibeam riometers, which form discrete beams on the sky, the interferometric technique permits all‐sky sampling of incoming cosmic radio noise emissions resulting in a spatially continuous radiogram of the entire sky. The map of the received power at each time may then be compared to the equivalent map from a “quiet day,” allowing the morphology of ionospheric absorption of cosmic radio noise to be ascertained. In this work, the high‐latitude Kilpisjärvi Atmospheric Imaging Receiver Array was used to carry out the first interferometric riometry measurements in late 2013, producing all‐sky absorption maps of space‐weather‐related ionization in the D region.
Uncertainty propagation through wave optics retrieval of bending angles from GPS radio occultation: Theory and simulation results
Authors: Gorbunov Michael E. , Kirchengast Gottfried 
Published: October 2015

AbstractThe wave optical technique for bending angle retrieval in processing radio occultation observations is nowadays widely used by different data processing and assimilation groups and centers. This technique uses Fourier Integral Operators that map the observed records of the amplitude and phase into the impact parameter representation, which allows for the retrieval of bending angle as a function of impact parameter. We investigate the propagation of uncertainty in the observed amplitude and excess phase to the retrieved bending angle. We construct a simple linear approximation, where the excess phase uncertainty is mapped into the bending angle uncertainty. This results in a simple analytical expression for the final uncertainty. To verify our approximation, we perform numerical Monte Carlo simulations for three example occultation events (tropical, middle, and polar latitude profiles from an atmospheric analysis). We demonstrate that our approximation basically gives good results in all cases over the entire troposphere. Exception is the narrow area near the top of the sharp boundary layer, especially in tropics, where, due to nonlinear effects, a significant systematic error arises accompanied by increased uncertainty.
Differences between the CME fronts tracked by an expert, an automated algorithm, and the Solar Stormwatch project
Authors: Barnard L. , Scott C. J. , Owens M. , Lockwood M. , Crothers S. R. , Davies J. A. , Harrison R. A. 
Published: October 2015

AbstractObservations from the Heliospheric Imager (HI) instruments aboard the twin STEREO spacecraft have enabled the compilation of several catalogues of coronal mass ejections (CMEs), each characterizing the propagation of CMEs through the inner heliosphere. Three such catalogues are the Rutherford Appleton Laboratory (RAL)‐HI event list, the Solar Stormwatch CME catalogue, and, presented here, the J‐tracker catalogue. Each catalogue uses a different method to characterize the location of CME fronts in the HI images: manual identification by an expert, the statistical reduction of the manual identifications of many citizen scientists, and an automated algorithm. We provide a quantitative comparison of the differences between these catalogues and techniques, using 51 CMEs common to each catalogue. The time‐elongation profiles of these CME fronts are compared, as are the estimates of the CME kinematics derived from application of three widely used single‐spacecraft‐fitting techniques. The J‐tracker and RAL‐HI profiles are most similar, while the Solar Stormwatch profiles display a small systematic offset. Evidence is presented that these differences arise because the RAL‐HI and J‐tracker profiles follow the sunward edge of CME density enhancements, while Solar Stormwatch profiles track closer to the antisunward (leading) edge. We demonstrate that the method used to produce the time‐elongation profile typically introduces more variability into the kinematic estimates than differences between the various single‐spacecraft‐fitting techniques. This has implications for the repeatability and robustness of these types of analyses, arguably especially so in the context of space weather forecasting, where it could make the results strongly dependent on the methods used by the forecaster.
A paleoclimate rainfall reconstruction in the Murray‐Darling Basin (MDB), Australia: 2. Assessing hydroclimatic risk using paleoclimate records of wet and dry epochs
Authors: Ho Michelle , Kiem Anthony S. , Verdon‐Kidd Danielle C. 
Published: October 2015

AbstractEstimates of hydrological risk are crucial to enable adequate planning and preparation for extreme events. However, the accurate estimation of hydrological risk is hampered by relatively short instrumental records in many parts of the world. Information derived from climate‐sensitive paleoclimate proxies provide an opportunity to resolve hydroclimatic variability, but many regions, such as Australia's Murray‐Darling Basin (MDB), currently lack the suitable in situ proxies necessary to do this. Here new MDB rainfall reconstructions are presented based on a novel method using paleoclimate rainfall proxies in the Australasian region spanning from 749 B.C.E. to 1980 C.E. Our results emphasize the need to develop additional reconstructions and, with the companion paper, demonstrate how this information can be used to benefit water resource management. This study shows that prior to the twentieth century, both dry and wet epochs have persisted for longer periods than observed in the instrumental record—with the probability of both dry and wet periods exceeding a decade at least 10 times more likely prior to 1883 than suggested by the instrumental records. Some reconstructed rainfalls exceeded the instrumental range (i.e., drier dry epochs and wetter wet spells) despite a systematic underestimation of extremes due to a combination of proxy quality and model bias. Importantly, the results demonstrate that the instrumental record does not cover the full range of hydroclimatic variability possible in the MDB. Therefore, hydroclimatic risk assessments based on the instrumental record likely underestimate, or at least misinterpret, the frequency, duration, and magnitude of wet and dry epochs.
Water table salinization due to seawater intrusion
Authors: Badaruddin Sugiarto , Werner Adrian D. , Morgan Leanne K. 
Published: October 2015

AbstractSeawater intrusion (SWI) is a significant threat to freshwater resources in coastal aquifers around the world. Previous studies have focused on SWI impacts involving salinization of the lower domain of coastal aquifers. However, under certain conditions, SWI may cause salinization of the entire saturated zone of the aquifer, leading to water table salinization (WTS) in unconfined aquifers by replacing freshwater within the upper region of the saturated zone with seawater, thereby posing a salinity threat to the overlying soil zone. There is presently limited guidance on the extent to which WTS may occur as a secondary impact of SWI. In this study, physical experiments and numerical modeling were used to explore WTS associated with SWI in various nontidal, unconfined coastal aquifer settings. Laboratory experiments and corresponding numerical simulations show that significant WTS can occur under active SWI (i.e., the freshwater hydraulic gradient slopes toward the land) because the cessation of freshwater discharge to the sea and the subsequent landward flow across the entire sea boundary eventually lead to water table salinities approaching seawater concentration. WTS during active SWI is larger under conditions of high hydraulic conductivity, rapid SWI, high dispersivity and for deeper aquifers. Numerical modeling of four published field cases demonstrates that rates of WTS of up to 60 m/yr are plausible. Under passive SWI (i.e., the hydraulic gradient slopes toward the sea), minor WTS may arise as a result of dispersive processes under certain conditions (i.e., high dispersivity and hydraulic conductivity, and low freshwater discharge). Our results show that WTS is probably widespread in coastal aquifers experiencing considerable groundwater decline sustained over several years, although further evidence is needed to identify WTS under field settings.
Gelatin‐Immobilized High Aspect Ratio Gold Nanocrystals: An Efficient Catalyst for 4‐Nitrophenol Reduction
Authors: Sharma Shyamalima , Bora Pritom J , Boruah Monalisha , Dolui Swapan K 
Published: October 2015

ABSTRACTThis article highlights the progress in the synthesis of gelatin‐immobilized anisotropic gold (Au) nanoparticles and their catalytic activity in 4‐nitrophenol (4‐NP) reduction. The catalytic process is monitored by using the UV–visible spectrophotometer, and the effect of shape and aspect ratio on the Au nanoparticles on catalytic activity is investigated. The catalytic process follows a pseudo–first‐order kinetics with the rate constant in the range of 1.1 × 10−3 s−1 to 4.5 × 10−3s−1. It is found that high aspect ratio Au/gelatin shows the best conversion (99.89%), which is comparable to the spherical seed (99.93%). After a certain catalytic reaction, the recovery of expensive catalysts and their reuse without losing their activity is an essential element in the sustainable process development. The immobilization of the catalyst into gelatin allows the high aspect ratio Au/gelatin nanocatalyst to be recovered and reused for a number of cycles.
Comparative study of reproductive skew and pair‐bond stability using genealogies from 80 small‐scale human societies
Authors: Ellsworth Ryan M. , Shenk Mary K. , Bailey Drew H. , Walker Robert S. 
Published: October 2015

ABSTRACTObjectivesGenealogies contain information on the prevalence of different sibling types that result from past reproductive behavior. Full sibling sets stem from stable monogamy, paternal half siblings primarily indicate male reproductive skew, and maternal half siblings reflect unstable pair bonds.MethodsFull and half sibling types are calculated for a total of 61,181 siblings from published genealogies for 80 small‐scale societies, including foragers, horticulturalists, agriculturalists, and pastoralists from around the world.ResultsMost siblings are full (61%) followed by paternal half siblings (27%) and maternal half siblings (13%). Paternal half siblings are positively correlated with more polygynous marriages, higher at low latitudes, and slightly higher in nonforagers, Maternal half sibling fractions are slightly higher at low latitudes but do not vary with subsistence. Partible paternity societies in Amazonia have more paternal half siblings indicating higher male reproductive skew.ConclusionsSibling counts from genealogies provide a convenient method to simultaneously investigate the reproductive skew and pair‐bond stability dimensions of human mating systems cross‐culturally. Am. J. Hum. Biol. 28:335–342, 2016. © 2015 Wiley Periodicals, Inc.
Dust in the wind: How climate variables and volcanic dust affect rates of tooth wear in central american howling monkeys
Authors: Spradley Jackson P. , Glander Kenneth E. , Kay Richard F. 
Published: October 2015

ABSTRACTObjectivesTwo factors have been considered important contributors to tooth wear: dietary abrasives in plant foods themselves and mineral particles adhering to ingested food. Each factor limits the functional life of teeth. Cross‐population studies of wear rates in a single species living in different habitats may point to the relative contributions of each factor.Materials and MethodsWe examine macroscopic dental wear in populations of Alouatta palliata (Gray, 1849) from Costa Rica (115 specimens), Panama (19), and Nicaragua (56). The sites differ in mean annual precipitation, with the Panamanian sites receiving more than twice the precipitation of those in Costa Rica or Nicaragua (∼3,500 mm vs. ∼1,500 mm). Additionally, many of the Nicaraguan specimens were collected downwind of active plinian volcanoes. Molar wear is expressed as the ratio of exposed dentin area to tooth area; premolar wear was scored using a ranking system.ResultsDespite substantial variation in environmental variables and the added presence of ash in some environments, molar wear rates do not differ significantly among the populations. Premolar wear, however, is greater in individuals collected downwind from active volcanoes compared with those living in environments that did not experience ash‐fall.DiscussionVolcanic ash seems to be an important contributor to anterior tooth wear but less so in molar wear. That wear is not found uniformly across the tooth row may be related to malformation in the premolars due to fluorosis. A surge of fluoride accompanying the volcanic ash may differentially affect the premolars as the molars fully mineralize early in the life of Alouatta. Am J Phys Anthropol 159:210–222, 2016. © 2015 Wiley Periodicals, Inc.
Ein fluoreszierender Chlorophyll‐Katabolit des Dioxobilin‐Typs als transientes und frühes Zwischenprodukt des Dioxobilin‐Astes des Chlorophyllabbaus in Arabidopsis thaliana
Authors: Süssenbacher Iris , Hörtensteiner Stefan , Kräutler Bernhard 
Published: October 2015

AbstractDer Chlorophyllabbau findet in höheren Pflanzen über den “PaO/Phyllobilin”‐Weg statt. Dabei werden zwei wichtige Phyllobilin‐Typen gebildet, die charakteristischen 1‐Formyl‐19‐oxobiline und die vor kurzem entdeckten 1,19‐Dioxobiline. Die hypothetische Verzweigung ist immer noch unbekannt, an welcher sich die ursprünglich gebildeten 1‐Formyl‐19‐oxobiline in 1,19‐Dioxobiline umwandeln. Hier klären wir diesen hypothetischen und entscheidenden Übergang durch die Identifizierung des ersten natürlichen fluoreszierenden Chlorophyll‐Kataboliten vom 1,19‐Dioxobilin‐Typ (DFCC) auf. Dieses kurzlebige Zwischenprodukt des Chlorophyllabbaus wurde aus Extrakten von Arabidopsis‐thaliana‐Blättern isoliert, die sich in einem frühen Seneszenz‐Stadium befanden. Dieser DFCC konnte als direkte Vorstufe des hauptsächlich entstehenden, nichtfluoreszierenden 1,19‐Dioxobilins identifiziert werden, das sich in seneszenten Blättern anreichert.