bluuebunny/crossref_metadata_2025_split huggingface dataset:
Meteorological anomalies lead to elevated O3 in the western U.S. in June 2015
Authors: Jaffe D. A. , Zhang L. 
Published: February 2017

AbstractIn winter through early summer of 2014–2015, temperatures in the western U.S. were substantially enhanced due to a persistent high‐pressure ridge and warm water in the northeastern Pacific Ocean. Concurrently, monthly averaged maximum daily 8 h average (MDA8) O3 in June 2015 was enhanced by 3–13 ppb across a large portion of the western U.S. At the Mount Bachelor Observatory (2.8 km above sea level) in central Oregon, O3 in June 2015 was enhanced by 11 ppbv compared to the long‐term mean. Some urban areas had many days in June 2015 with MDA8 values above the current air quality threshold of 70 ppbv. We show that the high O3 was associated with enhanced temperatures, reduced cloud fraction, increased stagnation, and increased biogenic emissions. The data in June 2015 show enhanced ΔO3/Δtemperature slopes at several sites, compared to previous June data, due to these multiple factors.
Radiocarbon in dissolved organic and inorganic carbon of the Arctic Ocean
Authors: Druffel E. R. M. , Griffin S. , Glynn C. S. , Benner R. , Walker B. D. 
Published: February 2017

AbstractDissolved organic carbon (DOC) in the ocean is thousands of 14C years old, yet a portion of the DOC cycles on much shorter time scales (days to decades). We present 14C measurements of DOC in the Arctic Ocean and estimate that ≥8% of the DOC in the deep Eurasian Basin contains bomb 14C. While this is a limited data set, there appears to be selective loss of modern DOC in the surface and halocline waters of the open Beaufort Sea versus the Beaufort slope. At one of the Beaufort Sea stations, there is a linear relationship between DOC Δ14C values and previously measured total hydrolysable amino acid concentrations as reported by Shen et al. (2012), indicating that deep DOC contains small amounts of bioavailable DOC. The 14C data show that not all of the deep DOC is recalcitrant.
A novel type of transient luminous event produced by terrestrial gamma‐ray flashes
Authors: Xu Wei , Celestin Sebastien , Pasko Victor P. , Marshall Robert A. 
Published: February 2017

AbstractTerrestrial Gamma‐ray Flashes (TGFs), discovered in 1994 by the Compton Gamma‐Ray Observatory, are high‐energy photon bursts originating in the Earth's atmosphere in association with thunderstorms. In this paper, we demonstrate theoretically that, while TGFs pass through the atmosphere, the large quantities of energetic electrons knocked out by collisions between photons and air molecules generate excited species of neutral and ionized molecules, leading to a significant amount of optical emissions. These emissions represent a novel type of transient luminous events in the vicinity of the cloud tops. We show that this predicted phenomenon illuminates a region with a size notably larger than the TGF source and has detectable levels of brightness. Since the spectroscopic, morphological, and temporal features of this luminous event are closely related with TGFs, corresponding measurements would provide a novel perspective for investigation of TGFs, as well as lightning discharges that produce them.
Subtidal circulation in a deep‐silled fjord: Douglas Channel, British Columbia
Authors: Wan Di , Hannah Charles G. , Foreman Michael G. G. , Dosso Stan 
Published: February 2017

AbstractDouglas Channel, a deep fjord on the west coast of British Columbia, Canada, is the main waterway in the fjord system that connects the town of Kitimat to Queen Charlotte Sound and Hecate Strait. A 200 m depth sill divides Douglas Channel into an outer and an inner basin. This study examines the low‐frequency (from seasonal to meteorological bands) circulation in Douglas Channel from data collected at three moorings deployed during 2013–2015. The deep flows are dominated by a yearly renewal that takes place from May/June to early September. A dense bottom layer with a thickness of 100 m that cascades through the system at the speed of 0.1–0.2 m s−1, which is consistent with gravity currents. Estuarine flow dominates the circulation above the sill depth, and the observed landward net volume flux suggests that it is necessary to include the entire complex channel network to fully understand the estuarine circulation in the system. The influence of the wind forcing on the subtidal circulation is not only at the surface, but also at middepth. The along‐channel wind dominates the surface current velocity fluctuations and the sea level response to the wind produces a velocity signal at 100–120 m in the counter‐wind direction. Overall, the circulation in the seasonal and the meteorological bands is a mix of estuarine flow, direct wind‐driven flow, and the barotropic and baroclinic responses to changes to the surface pressure gradient caused by the wind stress.
Improved TEC retrieval based on spaceborne PolSAR data
Authors: Wang Cheng , Liu Lu , Chen Liang , Feng Jian , Zhao Hai‐Sheng 
Published: February 2017

AbstractIt is well known that for Earth observations, the spaceborne synthetic aperture radar (SAR) systems at L‐band can be seriously affected by the ionosphere. Fortunately, the destructive ionospheric information, total electron content (TEC), can be retrieved and removed by model inversion from SAR echoes and becomes a subject of interest for ionospheric research. Considering the system noise and channel phase imbalance, this paper focuses on accurate TEC retrieval from the Faraday rotation angle, which is embedded in Advanced Land Observing Satellite phased array L‐band synthetic aperture radar (PALSAR) full‐pol data. For the consideration of denoising, averaging filtering is widely used in existing studies to remove the system noise. In order to further reduce the noise effects, a fast total variation (FTV) denoising method is applied in this paper. By using the PALSAR full‐pol data sets, a series of simulation results show that the FTV denoising is effective for noise suppression and markedly reduce the standard deviation. For the error of channel phase imbalance, a new Faraday estimator based on the covariance matrix of circular basis is proposed. Compared with previous estimators, theoretical analysis and simulation results show that this new estimator can give the best performance for sensors that are dominated by channel phase imbalance errors. Thus, the proposed estimator can be a candidate method for TEC retrieval when phase imbalance is the domain error.
A comparison of methods for estimating the geoelectric field
Authors: Weigel R. S. 
Published: February 2017

AbstractThe geoelectric field is the primary input used for estimation of geomagnetically induced currents (GICs) in conducting systems. We compare three methods for estimating the geoelectric field given the measured geomagnetic field at four locations in the U.S. during time intervals with average Kp in the range of 2–3 and when the measurements had few data spikes and no baseline jumps. The methods include using (1) a preexisting 1‐D conductivity model, (2) a conventional 3‐D frequency domain method, and (3) a robust and remote reference 3‐D frequency domain method. The quality of the estimates is determined using the power spectrum (in the period range 9.1 to 18,725 s) of estimation errors along with the prediction efficiency summary statistic. It is shown that with respect to these quality metrics, Method 1 produces average out‐of‐sample electric field estimation errors with a variance that can be equal to or larger than the average measured variance (due to underestimation or overestimation, respectively), and Method 3 produces reliable but slightly lower quality estimates than Method 2 for the time intervals and locations considered.
Understanding watershed hydrogeochemistry: 1. Development of RT‐Flux‐PIHM
Authors: Bao Chen , Li Li , Shi Yuning , Duffy Christopher 
Published: February 2017

AbstractModel development in hydrology and geochemistry has been advancing separately with limited integration. We developed a watershed hydrogeochemical code RT‐Flux‐PIHM to understand complex interactions between hydrological processes (PIHM), land‐surface processes (FLUX—Noah Land Surface Model), and multicomponent subsurface reactive transport (RT). The RT module simulates geochemical processes including aqueous complexation, surface complexation, mineral dissolution and precipitation, and cation exchange. The RT module is verified against the widely used reactive transport code CrunchFlow. The code uses semidiscrete finite volume method and irregular gridding and offers data harvesting capabilities from national databases. The application of RT‐Flux‐PIHM is demonstrated in the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO). We aim to understand key processes that govern hydrogeochemical dynamics of the nonreactive chloride and reactive magnesium. Simulation results indicate that watershed characteristics, in particular topography, dictate the spatial distributions of water content and soil dissolution rates. Ion exchange provides buffering capacities and leads to a hysteresis loop of concentration and discharge relationship of magnesium, which differs from the open hysteresis of chloride. RT‐Flux‐PIHM offers physics‐based modeling capabilities to integrate the vast amount of water and chemistry data that have now become available, to differentiate the relative importance of competing processes, and to test hypotheses at the interface of hydrology and geochemistry.
Efficient evaluation of small failure probability in high‐dimensional groundwater contaminant transport modeling via a two‐stage Monte Carlo method
Authors: Zhang Jiangjiang , Li Weixuan , Lin Guang , Zeng Lingzao , Wu Laosheng 
Published: February 2017

AbstractIn decision‐making for groundwater management and contamination remediation, it is important to accurately evaluate the probability of the occurrence of a failure event. For small failure probability analysis, a large number of model evaluations are needed in the Monte Carlo (MC) simulation, which is impractical for CPU‐demanding models. One approach to alleviate the computational cost caused by the model evaluations is to construct a computationally inexpensive surrogate model instead. However, using a surrogate approximation can cause an extra error in the failure probability analysis. Moreover, constructing accurate surrogates is challenging for high‐dimensional models, i.e., models containing many uncertain input parameters. To address these issues, we propose an efficient two‐stage MC approach for small failure probability analysis in high‐dimensional groundwater contaminant transport modeling. In the first stage, a low‐dimensional representation of the original high‐dimensional model is sought with Karhunen‐Loève expansion and sliced inverse regression jointly, which allows for the easy construction of a surrogate with polynomial chaos expansion. Then a surrogate‐based MC simulation is implemented. In the second stage, the small number of samples that are close to the failure boundary are re‐evaluated with the original model, which corrects the bias introduced by the surrogate approximation. The proposed approach is tested with a numerical case study and is shown to be 100 times faster than the traditional MC approach in achieving the same level of estimation accuracy.
Analytical solution for tension‐saturated and unsaturated flow from wicking porous pipes in subsurface irrigation: The Kornev‐Philip legacies revisited
Authors: Kacimov A. R. , Obnosov Yu. V. 
Published: February 2017

AbstractThe Russian engineer Kornev in his 1935 book raised perspectives of subsurface “negative pressure” irrigation, which have been overlooked in modern soil science. Kornev's autoirrigation utilizes wicking of a vacuumed water from a porous pipe into a dry adjacent soil. We link Kornev's technology with a slightly modified Philip (1984)'s analytical solutions for unsaturated flow from a 2‐D cylindrical pipe in an infinite domain. Two Darcian flows are considered and connected through continuity of pressure along the pipe‐soil contact. The first fragment is a thin porous pipe wall in which water seeps at tension saturation; the hydraulic head is a harmonic function varying purely radially across the wall. The Thiem solution in this fragment gives the boundary condition for azimuthally varying suction pressure in the second fragment, ambient soil, making the exterior of the pipe. The constant head, rather than Philip's isobaricity boundary condition, along the external wall slightly modifies Philip's formulae for the Kirchhoff potential and pressure head in the soil fragment. Flow characteristics (magnitudes of the Darcian velocity, total flow rate, and flow net) are explicitly expressed through series of Macdonald's functions. For a given pipe's external diameter, wall thickness, position of the pipe above a free water datum in the supply tank, saturated conductivities of the wall and soil, and soil's sorptive number, a nonlinear equation with respect to the total discharge from the pipe is obtained and solved by a computer algebra routine. Efficiency of irrigation is evaluated by computation of the moisture content within selected zones surrounding the porous pipe.
Potential vorticity patterns in Mediterranean “hurricanes”
Authors: Miglietta M. M. , Cerrai D. , Laviola S. , Cattani E. , Levizzani V. 
Published: February 2017

AbstractThe potential vorticity (PV) anomalies due to the intrusion of dry stratospheric air and those generated by the tropospheric diabatic latent heating are qualitatively analyzed for five Mediterranean tropical‐like cyclones (also known as Medicanes). Model simulations show the presence of an upper level PV streamer in the early stages of the cyclone, located on the left exit of a jet stream, and a middle‐low level PV anomaly generated by the convection developing around the low‐level vortex. In the mature stage, the upper level PV anomaly around the cyclone evolves differently for each case and appears somehow dependent on the lifetime. Only for the 2006 Medicane, the PV anomalies form an intense PV tower extending continuously from the lower troposphere to the lower stratosphere.
Long‐term trends of typhoon‐induced rainfall over Taiwan: In situ evidence of poleward shift of typhoons in western North Pacific in recent decades
Authors: Liang Alice (Ting‐Yu) , Oey Leo , Huang Shiming , Chou Simon 
Published: February 2017

AbstractA significant poleward shift of tropical cyclones (TCs or typhoons) and TC‐induced storm surge in the western North Pacific has occurred in recent decades. Here we use 64 year rainfall observations around Taiwan to provide an independent evidence of the shift. We show that, due to the island's unique location relative to typhoon tracks, TC‐induced rainfall trends are significantly rising west and north of the island but are insignificant east and southeast, caused by a preference in recent decades for TCs to veer more poleward. Analyses of large‐scale fields indicate that the TCs' poleward shift is caused by the weakening of the steering flow and western North Pacific subtropical high, which in turn is due to tropic‐subtropical Indo‐Pacific warming and a weakened monsoon, consistent with the expansion of the tropics due to climate change.
Exploratory Data Analysis
Authors: Hoaglin David C. 
Published: February 2017

Abstract

Since about 1970, “exploratory data analysis” (EDA) has most often meant the attitude, approach, and techniques developed, primarily by
John W. Tukey
, for flexible probing of data. Four main themes run through EDA: resistance, residuals, reexpression, and displays. The article describes the general approach, discusses the four themes, presents a stem‐and‐leaf display and parallel boxplots to illustrate the theme of displays, and mentions related literature.
Simulation Models, Validation of
Authors: Deaton Michael L. 
Published: February 2017

Abstract
Simulation models should be validated at all stages of a simulation study. Moreover, the criteria for validation are dependent on the intended uses of the model. Many statistical challenges exist for successful model validation, but a rich literature exists for addressing those challenges. The article summarizes the principles of simulation model validation, its context within a simulation study, and the issues that it should address. Sources for validation methods are provided.
Systematic Sampling
Authors: Kalton Graham 
Published: February 2017

AbstractSystematic sampling is a simple and flexible way of selecting a probability sample from a finite population. It was introduced in the early days of probability sampling in survey research and it remains in widespread use today. A systematic sample is obtained by selecting a random start between 1 andkfrom a list of the population and then taking everykth element thereafter. The ordering of the list determines the precision of the survey estimates; a random order produces a sample that has the same precision as a simple random sample, whereas an order that is monotonically associated with the variables under study gives greater precision than a simple random sample. A single‐stage systematic sample is equivalent to the selection of a single cluster and, hence, variance estimation is not possible without a model assumption. Systematic sampling is widely used to select units with unequal probabilities without replacement, as, for instance, with probability proportional to size sampling in multistage surveys. In such cases, the collapsed stratum technique is frequently used for variance estimation. Systematic sampling is often applied in two dimensions in spatial surveys of geographical areas.
Processing of Survey Data
Authors: Biemer Paul P. 
Published: February 2017

AbstractUpon completion of data collection, the survey data must be converted from its raw and unedited state to a verified and corrected state that is ready for analysis and/or dissemination to the users. These steps may include questionnaire inspection, data entry, editing, coding, file preparation, documentation, and data analysis. The article discusses these steps as well as their potential effect on data quality.
Interviewing Techniques
Authors: Sjoblom Micah , Schechter Susan 
Published: February 2017

Abstract
Interviewing techniques play an important role in the successful implementation of survey methodology and instrumentation to collect high quality data in a standardized format. Interviewers perform a variety of roles in survey administration, and the development of standardized interviewer protocols and procedures are critical to ensure the data collected meet the requirements of research objectives. Interviewers are trained on study protocols and techniques that define rules for initial outreach and study introduction with eligible participants, engagement with study participants to gain their confidence, and consistent and uniform questionnaire administration. With the introduction of Computer Assisted Interviewing over three decades ago came the need to develop techniques and strategies for interviewers to conduct interviews while manipulating computer‐based instrumentation. As the mode of administration and types of data interviewers collect have evolved over time, so have the techniques and procedures interviewers use to collect systematic, high quality observations.
Law and Environmental Statistics
Authors: Esterby Sylvia R. 
Published: February 2017

AbstractMany environmental regulations and standards are based on statistical data and inferences drawn from them. Often the statistical analysis used by the US Environmental Protection Agency (EPA) or other governmental body, in developing an exposure or effluent limit or a monitoring program, is challenged by the industry or public interest group that is most affected by its decision. Then, the courts need to examine the record on which the EPA or other agency relied in setting the standard. Because there are several statutes regulating the environment in the United States and other countries, in assessing the adequacy of the underlying scientific support of a regulation or protocol, one needs to be aware of the relevant statute. This article discusses several important statistical issues that have arisen in actual cases and describes some other topics that arise in this area.
Time Series, Periodic
Authors: Lund Robert B. 
Published: February 2017

Abstract
This article overviews time series with periodic structures. Periodic series frequently arise in the environmental sciences. Here, extensions to covariance stationary time series are developed and used to describe series with periodic means and autocovariances. Detection of autocovariance periodicities is considered. A series of monthly averaged temperatures from Griffin, Georgia (United States), is used to illustrate the discourse.
Bayesian Methods in Project Management
Authors: Zafari Babak , Kettunen Janne 
Published: February 2017

AbstractBayesian approaches have been coupled with the conventional project management methods, such as the project evaluation and review technique, critical path method, and earned value management. The Bayesian versions of these methods rely on updating the forecast about the project's performance, measured via duration or cost at the completion, inferring from the observed data about the project's past performance. The Bayesian project management methods have been reported to provide more accurate forecast than their conventional counterparts.
Surrogate Endpoints: Statistical Validation
Authors: Burzykowski Tomasz 
Published: February 2017

AbstractA surrogate endpoint is intended to replace a clinical endpoint for the evaluation of new treatments when it can be measured more cheaply, more conveniently, more frequently, or earlier than the clinical endpoint. A surrogate endpoint is expected to predict the clinical benefit, harm, or lack of these. We review the statistical approaches that have been proposed to evaluate the validity of a candidate surrogate endpoint. In particular, we consider the approaches developed for the single and multiple trial settings, describe the concepts of the “individual‐level” and “trial‐level” validity of a surrogate, and discuss suitable measures of validity. We also briefly review the methods developed using the causal inference framework.
Clustering Categorical Data
Authors: Andreopoulos Bill 
Published: February 2017

AbstractA growing number of clustering algorithms for categorical data have been proposed. This article describes the goals of clustering categorical data, such as scalability, robustness, and insensitivity to object ordering and minimal user‐specified parameters. We describe the main similarity metrics for categorical data, including Hamming distance and probabilistic metrics. We compare the different approaches to categorical data clustering, such as partition‐based, hierarchical, density‐based, and model‐based methods. We give examples of algorithms in each category and we explain what types of clustering goals each algorithm satisfies. We explain locality‐sensitive hashing as a fast similarity retrieval method for very large categorical datasets. We describe challenges for future work.
Frequentist Probability
Authors: Spanos Aris 
Published: February 2017

AbstractThe primary objective of this article is to discuss a model‐based frequentist interpretation that identifies the probability of an event with thelimitof its relative frequency of occurrence. What differentiates the proposed interpretation from the traditional ones are several key features: (i) events and probabilities are defined in the context of a statistical model , (ii) it is anchored on the strong law of large numbers, (iii) it is justified on empirical grounds by validating the model assumptions vis‐à‐vis data , (iv) the “long‐run” metaphor can be rendered operational by simple simulation based on , and (v) the link between probability and real‐world phenomena is provided by viewing data as a “truly typical” realization of the stochastic mechanism defined by . This link constitutes a feature shared with the Kolmogorov complexity algorithmic perspective on probability, which provides a further justification for the proposed frequentist interpretation.