bluuebunny/crossref_metadata_2025_split huggingface dataset:
Predicting nonstationary flood frequencies: Evidence supports an updated stationarity thesis in the United States
Authors: Luke Adam , Vrugt Jasper A. , AghaKouchak Amir , Matthew Richard , Sanders Brett F. 
Published: July 2017

AbstractNonstationary extreme value analysis (NEVA) can improve the statistical representation of observed flood peak distributions compared to stationary (ST) analysis, but management of flood risk relies on predictions of out‐of‐sample distributions for which NEVA has not been comprehensively evaluated. In this study, we apply split‐sample testing to 1250 annual maximum discharge records in the United States and compare the predictive capabilities of NEVA relative to ST extreme value analysis using a log‐Pearson Type III (LPIII) distribution. The parameters of the LPIII distribution in the ST and nonstationary (NS) models are estimated from the first half of each record using Bayesian inference. The second half of each record is reserved to evaluate the predictions under the ST and NS models. The NS model is applied for prediction by (1) extrapolating the trend of the NS model parameters throughout the evaluation period and (2) using the NS model parameter values at the end of the fitting period to predict with an updated ST model (uST). Our analysis shows that the ST predictions are preferred, overall. NS model parameter extrapolation is rarely preferred. However, if fitting period discharges are influenced by physical changes in the watershed, for example from anthropogenic activity, the uST model is strongly preferred relative to ST and NS predictions. The uST model is therefore recommended for evaluation of current flood risk in watersheds that have undergone physical changes. Supporting information includes a MATLAB® program that estimates the (ST/NS/uST) LPIII parameters from annual peak discharge data through Bayesian inference.
Methane emission through ebullition from an estuarine mudflat: 2. Field observations and modeling of occurrence probability
Authors: Chen Xi , Schäfer Karina V. R. , Slater Lee 
Published: July 2017

AbstractEbullition can transport methane (CH4) at a much faster rate than other pathways, albeit over limited time and area, in wetland soils and sediments. However, field observations present large uncertainties in ebullition occurrences and statistic models are needed to describe the function relationship between probability of ebullition occurrence and water level changes. A flow‐through chamber was designed and installed in a mudflat of an estuarine temperate marsh. Episodic increases in CH4 concentration signaling ebullition events were observed during ebbing tides (15 events over 456 ebbing tides) and occasionally during flooding tides (4 events over 455 flooding tides). Ebullition occurrence functions were defined using logistic regression as the relative initial and end water levels, as well as tidal amplitudes were found to be the key functional variables related to ebullition events. Ebullition of methane was restricted by a surface frozen layer during winter; melting of this layer during spring thaw caused increases in CH4 concentration, with ebullition fluxes similar to those associated with large fluctuations in water level around spring tides. Our findings suggest that initial and end relative water levels, in addition to tidal amplitude, partly regulate ebullition events in tidal wetlands, modulated by the lunar cycle, storage of gas bubbles at different depths and seasonal changes in the surface frozen layer. Maximum tidal strength over a few days, rather than hourly water level, may be more closely associated with the possibility of ebullition occurrence as it represents a trade‐off time scale in between hourly and lunar periods.
Information theory‐based decision support system for integrated design of multivariable hydrometric networks
Authors: Keum Jongho , Coulibaly Paulin 
Published: July 2017

AbstractAdequate and accurate hydrologic information from optimal hydrometric networks is an essential part of effective water resources management. Although the key hydrologic processes in the water cycle are interconnected, hydrometric networks (e.g., streamflow, precipitation, groundwater level) have been routinely designed individually. A decision support framework is proposed for integrated design of multivariable hydrometric networks. The proposed method is applied to design optimal precipitation and streamflow networks simultaneously. The epsilon‐dominance hierarchical Bayesian optimization algorithm was combined with Shannon entropy of information theory to design and evaluate hydrometric networks. Specifically, the joint entropy from the combined networks was maximized to provide the most information, and the total correlation was minimized to reduce redundant information. To further optimize the efficiency between the networks, they were designed by maximizing the conditional entropy of the streamflow network given the information of the precipitation network. Compared to the traditional individual variable design approach, the integrated multivariable design method was able to determine more efficient optimal networks by avoiding the redundant stations. Additionally, four quantization cases were compared to evaluate their effects on the entropy calculations and the determination of the optimal networks. The evaluation results indicate that the quantization methods should be selected after careful consideration for each design problem since the station rankings and the optimal networks can change accordingly.
Modeling the probability distribution of peak discharge for infiltrating hillslopes
Authors: Baiamonte Giorgio , Singh Vijay P. 
Published: July 2017

AbstractHillslope response plays a fundamental role in the prediction of peak discharge at the basin outlet. The peak discharge for the critical duration of rainfall and its probability distribution are needed for designing urban infrastructure facilities. This study derives the probability distribution, denoted as GABS model, by coupling three models: (1) the Green‐Ampt model for computing infiltration, (2) the kinematic wave model for computing discharge hydrograph from the hillslope, and (3) the intensity‐duration‐frequency (IDF) model for computing design rainfall intensity. The Hortonian mechanism for runoff generation is employed for computing the surface runoff hydrograph. Since the antecedent soil moisture condition (ASMC) significantly affects the rate of infiltration, its effect on the probability distribution of peak discharge is investigated. Application to a watershed in Sicily, Italy, shows that with the increase of probability, the expected effect of ASMC to increase the maximum discharge diminishes. Only for low values of probability, the critical duration of rainfall is influenced by ASMC, whereas its effect on the peak discharge seems to be less for any probability. For a set of parameters, the derived probability distribution of peak discharge seems to be fitted by the gamma distribution well. Finally, an application to a small watershed, with the aim to test the possibility to arrange in advance the rational runoff coefficient tables to be used for the rational method, and a comparison between peak discharges obtained by the GABS model with those measured in an experimental flume for a loamy‐sand soil were carried out.
A soil column model for predicting the interaction between water table and evapotranspiration
Authors: Maquin Mathilde , Mouche Emmanuel , Mügler Claude , Pierret Marie‐Claire , Viville Daniel 
Published: July 2017

AbstractLateral waterfluxes are not realistically taken into account in soil column models, although they influence the dynamic evolution of the vertical soil moisture profile. By neglecting these fluxes, the modeling of the soil‐vegetation‐atmosphere continuum is incomplete, and the feedbacks between these three compartments cannot be fully simulated. These fluxes have an importance in the different fields where soil column models are used: hydrology, hydrometeorology, biogeochemical cycles, ecology, and soil weathering. This paper introduces a novel Hydrological Hillslope‐based Soil Column model (H2SC) that simulates the temporal evolution of the water table depth and evapotranspiration fluxes and their interaction. The interconnected processes are infiltration, evapotranspiration, vertical soil water movements, and the nonexplicitly modeled lateral fluxes flowing through the soil column. These lateral fluxes are modeled as a drainage function built from physically based equations that describe a simplified hillslope hydrology. This drainage function can be easily implemented in any soil column model without penalizing computational times. The H2SC model was validated on numerical experiments where a 2‐D hillslope simulation performed with an integrated hydrologic model was compared with simulations using the H2SC 1‐D model. Each of the H2SC simulations represents a specific location of a soil column along the hillslope. Different climate forcings, soil properties, and geometric shapes of the hillslope were tested. The model was then applied at the locations of two piezometers in the Strengbach catchment, France. The model reproduced the temporal evolution of the water table level fairly well for both the numerical experiments and for the real test case.
The mechanics of shallow magma reservoir outgassing
Authors: Parmigiani A. , Degruyter W. , Leclaire S. , Huber C. , Bachmann O. 
Published: July 2017

AbstractMagma degassing fundamentally controls the Earth's volatile cycles. The large amount of gas expelled into the atmosphere during volcanic eruptions (i.e., volcanic outgassing) is the most obvious display of magmatic volatile release. However, owing to the large intrusive:extrusive ratio, and considering the paucity of volatiles left in intrusive rocks after final solidification, volcanic outgassing likely constitutes only a small fraction of the overall mass of magmatic volatiles released to the Earth's surface. Therefore, as most magmas stall on their way to the surface, outgassing of uneruptible, crystal‐rich magma storage regions will play a dominant role in closing the balance of volatile element cycling between the mantle and the surface. We use a numerical approach to study the migration of a magmatic volatile phase (MVP) in crystal‐rich magma bodies (“mush zones”) at the pore scale. Our results suggest that buoyancy‐driven outgassing is efficient over crystal volume fractions between 0.4 and 0.7 (for mm‐sized crystals). We parameterize our pore‐scale results for MVP migration in a thermomechanical magma reservoir model to study outgassing under dynamical conditions where cooling controls the evolution of the proportion of crystal, gas, and melt phases and to investigate the role of the reservoir size and the temperature‐dependent viscoelastic response of the crust on outgassing efficiency. We find that buoyancy‐driven outgassing allows for a maximum of 40–50% volatiles to leave the reservoir over the 0.4–0.7 crystal volume fractions, implying that a significant amount of outgassing must occur at high crystal content (>0.7) through veining and/or capillary fracturing.
Global rates of mantle serpentinization and H2 production at oceanic transform faults in 3‐D geodynamic models
Authors: Rüpke Lars H. , Hasenclever Jörg 
Published: July 2017

AbstractPrevious studies have estimated that mantle serpentinization reactions generate H2 at a rate of 1010–1012 mol/yr along the global mid‐ocean ridge (MOR) system. Here we present results of 3‐D geodynamic simulations that predict rates of additional mantle serpentinization and H2 production at oceanic transform faults (OTF). We find that the extent and rate of mantle serpentinization increases with OTF length and is maximum at intermediate slip rates of 5 to 10 cm/yr. The additional global OTF‐related production of H2 is found to be between 6.1 and 10.7 × 1011 mol/yr, which is comparable to the predicted background MOR rate of 4.1–15.0 × 1011 mol H2/yr. This points to oceanic transform faults as potential sites of intense fluid‐rock interaction, where chemosynthetic life could be sustained by serpentinization reactions.
Spatiotemporal evolution of the 2011 Prague, Oklahoma, aftershock sequence revealed using subspace detection and relocation
Authors: McMahon Nicole D. , Aster Richard C. , Yeck William L. , McNamara Daniel E. , Benz Harley M. 
Published: July 2017

AbstractThe 6 November 2011 Mw 5.7 earthquake near Prague, Oklahoma, is the second largest earthquake ever recorded in the state. A Mw 4.8 foreshock and the Mw 5.7 mainshock triggered a prolific aftershock sequence. Utilizing a subspace detection method, we increase by fivefold the number of precisely located events between 4 November and 5 December 2011. We find that while most aftershock energy is released in the crystalline basement, a significant number of the events occur in the overlying Arbuckle Group, indicating that active Meeker‐Prague faulting extends into the sedimentary zone of wastewater disposal. Although the number of aftershocks in the Arbuckle Group is large, comprising ~40% of the aftershock catalog, the moment contribution of Arbuckle Group earthquakes is much less than 1% of the total aftershock moment budget. Aftershock locations are sparse in patches that experienced large slip during the mainshock.
Survey of Saturn electrostatic cyclotron harmonic wave intensity
Authors: Menietti J. D. , Averkamp T. F. , Kurth W. S. , Ye S.‐Y. , Gurnett D. A. , Cecconi B. 
Published: July 2017

AbstractWe conduct a survey of electrostatic electron cyclotron harmonic (ECH) emissions observed at Saturn by the radio and plasma wave science investigation on board the Cassini spacecraft. These emissions are known to be effective at interacting with electrons in the terrestrial inner magnetosphere, producing electron scattering into the loss cone and acceleration (cf. Horne and Thorne, 2000; Thorne et al., 2010). At Saturn ECH emission occurs with high probability and at strong intensity near the magnetic equator, outside the Enceladus torus in the range ~5 < L < ~10. Inside the inner boundary of the torus, ECH emissions are also observed near the equator and at higher latitude. Intensity levels of ECH emission are comparable to those observed at Earth, higher than Saturn chorus and Z‐mode emission, and are likely to scatter electrons into the loss cone as at Earth. ECH waves are particularly intense and extend to higher harmonics within some plasma injection regions. We present results for a survey of over 8 years of Saturn data for fundamental and up to three harmonics of fce, the electron cyclotron frequency.
Survey of Voyager plasma science ions at Jupiter: 2. Heavy ions
Authors: Dougherty L. P. , Bodisch K. M. , Bagenal F. 
Published: July 2017

AbstractWe take the plasma parameters derived by Bagenal et al. (2017) from Voyager plasma science data in the Jovian magnetosphere and examine the radial profiles of density, temperature, composition, and azimuthal flow. The plasma sheet shows a relatively uniform structure of decreasing electron density (Ne) and increasing temperature out to about 20 RJ, but beyond about 15 RJ there is increasing disorder with sporadic blobs of cold plasma. These small (~0.5 RJ) blobs of cold (~20 eV) plasma make a minor contribution to the net outward flux of iogenic plasma. The ion composition in the cold blobs is consistent with the ion abundances derived from physical chemistry models extending from 6 to ~9 RJ, whereupon the collisional reactions slow down and radial transport speeds up, effectively freezing in the ion composition to the following abundances: O+/Ne = 15–22%, S++/Ne = 10–19%, O++/Ne = 4–8%, S+++/Ne = 4–6%, and S+/Ne = 1–5%. Beyond about 7 RJ the component of hot (suprathermal, approximately hundreds of eV) ions becomes a significant fraction of the total density. The radial profile of the plasma's azimuthal flow speed shows that corotation begins to breakdown at about 9 RJ, dipping down to about 20% below corotation before increasing back up to corotation briefly (~17–20 RJ), reaching an asymptotic value of about 225 km/s (corresponding to rigid corotation at ~18 RJ). We present a 2‐D model of the plasma sheet beyond 6 RJ based on simple functions for the equatorial profiles of plasma properties and steady state diffusive equilibrium along magnetic flux tubes. Cold plasma blobs in the Jovian plasma sheet show ion composition consistent with physical chemistry models. Azimuthal flow speeds dip below corotation 9–15 Jovian radii. Radial profiles of plasma properties are combined to make a 2‐D model of plasma sheet.
On the imprint of surfactant‐driven stabilization of laboratory breaking wave foam with comparison to oceanic whitecaps
Authors: Callaghan A. H. , Deane G. B. , Stokes M. D. 
Published: July 2017

AbstractSurfactants are ubiquitous in the global oceans: they help form the materially‐distinct sea surface microlayer (SML) across which global ocean‐atmosphere exchanges take place, and they reside on the surfaces of bubbles and whitecap foam cells prolonging their lifetime thus altering ocean albedo. Despite their importance, the occurrence, spatial distribution, and composition of surfactants within the upper ocean and the SML remains under‐characterized during conditions of vigorous wave breaking when in‐situ sampling methods are difficult to implement. Additionally, no quantitative framework exists to evaluate the importance of surfactant activity on ocean whitecap foam coverage estimates. Here we use individual laboratory breaking waves generated in filtered seawater and seawater with added soluble surfactant to identify the imprint of surfactant activity in whitecap foam evolution. The data show a distinct surfactant imprint in the decay phase of foam evolution. The area‐time‐integral of foam evolution is used to develop a time‐varying stabilization function,
and a stabilization factor,
, which can be used to identify and quantify the extent of this surfactant imprint for individual breaking waves. The approach is then applied to wind‐driven oceanic whitecaps, and the laboratory and ocean
distributions overlap. It is proposed that whitecap foam evolution may be used to determine the occurrence and extent of oceanic surfactant activity to complement traditional in‐situ techniques and extend measurement capabilities to more severe sea states occurring at wind speeds in excess of about 10 m/s. The analysis procedure also provides a framework to assess surfactant‐driven variability within and between whitecap coverage data sets.
Biogeochemical sensor performance in the SOCCOM profiling float array
Authors: Johnson Kenneth S. , Plant Joshua N. , Coletti Luke J. , Jannasch Hans W. , Sakamoto Carole M. , Riser Stephen C. , Swift Dana D. , Williams Nancy L. , Boss Emmanuel , Haëntjens Nils , Talley Lynne D. , Sarmiento Jorge L. 
Published: July 2017

AbstractThe Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) program has begun deploying a large array of biogeochemical sensors on profiling floats in the Southern Ocean. As of February 2016, 86 floats have been deployed. Here the focus is on 56 floats with quality‐controlled and adjusted data that have been in the water at least 6 months. The floats carry oxygen, nitrate, pH, chlorophyll fluorescence, and optical backscatter sensors. The raw data generated by these sensors can suffer from inaccurate initial calibrations and from sensor drift over time. Procedures to correct the data are defined. The initial accuracy of the adjusted concentrations is assessed by comparing the corrected data to laboratory measurements made on samples collected by a hydrographic cast with a rosette sampler at the float deployment station. The long‐term accuracy of the corrected data is compared to the GLODAPv2 data set whenever a float made a profile within 20 km of a GLODAPv2 station. Based on these assessments, the fleet average oxygen data are accurate to 1 ± 1%, nitrate to within 0.5 ± 0.5 µmol kg−1, and pH to 0.005 ± 0.007, where the error limit is 1 standard deviation of the fleet data. The bio‐optical measurements of chlorophyll fluorescence and optical backscatter are used to estimate chlorophyll a and particulate organic carbon concentration. The particulate organic carbon concentrations inferred from optical backscatter appear accurate to with 35 mg C m−3 or 20%, whichever is larger. Factors affecting the accuracy of the estimated chlorophyll a concentrations are evaluated.
Revisiting Ocean Color algorithms for chlorophyll a and particulate organic carbon in the Southern Ocean using biogeochemical floats
Authors: Haëntjens Nils , Boss Emmanuel , Talley Lynne D. 
Published: July 2017

AbstractThe Southern Ocean (SO) ecosystem plays a key role in the carbon cycle by sinking a major part (43%) of the ocean uptake of anthropogenic CO2, and being an important source of nutrients for primary producers. However, undersampling of SO biogeochemical properties limits our understanding of the mechanisms taking place in this remote area. The Southern Ocean Carbon and Climate Observations and Modeling (SOCCOM) project has been deploying a large number of autonomous biogeochemical floats to study the SO (as of December 2016, 74 floats out of 200 have been deployed). SOCCOM floats measurements can be used to extend remote sensing chlorophyll a (chl a) and particulate organic carbon (POC) products under clouds or during the polar night as well as adding the depth dimension to the satellite‐based view of the SO. Chlorophyll a concentrations measured by a sensor embedded on the floats and POC concentrations derived from backscattering coefficients were calibrated with samples collected during the floats' deployment cruise. Float chl a and POC were compared with products derived from observations of MODIS and VIIRS sensors. We find the Ocean Color Index (OCI) global algorithm to agree well with the matchups (within 9%, on average, for the Visible Infrared Imaging Radiometer Suite (VIIRS) and 12%, on average, for the Moderate Resolution Imaging Spectroradiometer Aqua (MODIS)). SO‐specific algorithms estimating chl a are offset by ∼45% south of the Sea Ice Extent Front (
°S). In addition, POC estimates based on floats agree well with NASA's POC algorithm.
Equatorial Kelvin waves generated in the western tropical Pacific Ocean trigger mass and heat transport within the Middle America Trench off Costa Rica
Authors: Thomson Richard E. , Davis Earl E. 
Published: July 2017

AbstractSequences of correlated seafloor temperature, current velocity, and acoustic backscatter events recorded at Ocean Drilling Program (ODP) sites at 4300 m depth in the Middle America Trench have been inferred to result from tidally induced turbidity currents generated in the vicinity of the 3300 m deep sill at the southern end of the trench. New data from the borehole observatories extend the temperature records to 11 years (November 2002 to December 2013) and confirm the highly episodic nature of the events. We present satellite altimetry data and ocean circulation model results to show that event timing is correlated with intraseasonal Kelvin wave motions in the equatorial Pacific. The observed temperature events had a mean (±1 standard deviation) occurrence interval of 61 (±24) days, which spans the periods of the first two baroclinic modes. Lag times between peak bottom water temperatures at the ODP sites and the passage of eastward‐propagating Kelvin wave crests at locations in the eastern equatorial Pacific are consistent with the time for mode‐1 waves to propagate to the southern end of the trench at a mean phase speed of 2.0 m s−1. Findings indicate that Kelvin wave currents augment tidal motions in the vicinity of the sill, triggering turbidity currents that travel northwestward along the trench axis at mean speeds of ∼0.1 m s−1. We conclude that mode‐1 (or, possibly, mixed mode‐1 and mode‐2) baroclinic Kelvin waves generated by large‐scale atmospheric processes in the western tropical Pacific lead to heat and mass transport deep within Middle America Trench in the eastern tropical Pacific.