bluuebunny/crossref_metadata_2025 huggingface dataset:
A New Indoor Positioning Algorithm of Cellular and Wi-Fi Networks
Authors: Chai Meiling , Li Changgeng , Huang Hui
Published: December 2019

Fluctuation of the received signal strength (RSS) is the key performance-limiting factor for Wi-Fi indoor positioning schemes. In this study, the Manhattan distance was used in the weighted K-nearest neighbour (WKNN) algorithm to improve positioning accuracy. Reference point (RP) intervals were optimised to reduce the complexity of the system. Specifically, two new positioning schemes are proposed in this paper. Scheme 1 uses the cellular network to refine the fingerprint database, while Scheme 2 uses the cellular network positioning to locate the node a priori, then uses the Wi-Fi network to further improve accuracy. The experimental results showed that the average positioning error of Scheme 1 was 1·60 m, a reduction of 12% compared with the existing Wi-Fi fingerprinting schemes. In Scheme 2, when double cellular networks were used, RP usage was reduced by 64% and the calculating time was 0·24 s, a reduction of up to 69·5% compared with the Manhattan-WKNN algorithm. These proposed schemes are suitable for high accuracy and real-time positioning situations, respectively.
Association between the IL-10-1082G/A, IL-10-819T/C and IL-10-592A/C polymorphisms and Brucellosis susceptibility: a meta-analysis
Authors: Jin Xiaochun , Yin Shuzhou , Zhang Youtao
Published: December 2019

Brucellosis is a widespread zoonosis caused by small bacteria of the genus Brucella. The promoter polymorphisms of IL-10 (-1082 loci, -819 loci and -590 loci) are closely related to the production of IL-10, leading to the alteration of development and pathogenesis of Brucellosis. However, the previous results were controversial. In the present study, we conduct the meta-analysis to get a more precise result of IL-10 polymorphisms with Brucellosis risk. The quality of the studies was assessed according to a predefined scale. The odds ratio (OR) and 95% confidence interval (CI) were counted to evaluate the association strength. No significant association was found between position -1082 loci or -590 loci polymorphism and Brucellosis risk. The significant association was found in Asian population of position -819 (T vs. C: OR 0.60, 95% CI 0.44–0.82, P = 0.001), homozygote comparison (TT vs. CC: OR 0.24, 95% CI 0.09–0.62, P = 0.003) and recessive genetic model (TT vs. TC/CC: OR 0.22, 95% CI 0.05–0.91, P = 0.036). The present meta-analysis demonstrates that IL-10-819 loci polymorphism is not associated with Brucellosis risk of Caucasian population but may contribute a decreased risk to Asian population. And neither IL-10-1082 loci nor -592 loci polymorphism is associated with Brucellosis risk.
Assessment of Cognitive-Driven Performance-Based Activities of Daily Living Dysfunction in Parkinson’s Disease
Authors: Sulzer Patricia , Bäumer Alena , Hoang Huong Giang , Becker Sara , Lönneker Hannah Dorothea , Graessel Elmar , Liepelt-Scarfone Inga
Published: December 2019

Objectives:

Parkinson’s disease (PD) patients with mild cognitive impairment (PD-MCI) have an increased risk of developing dementia (PDD). As activities of daily living (ADL) impairment is mandatory for the diagnosis of PDD, assessing early signs of instrumental ADL (iADL) dysfunction, especially in PD-MCI, is essential. In PD, self- and caregiver-reported iADL performance is often confounded by motor dysfunction and mood. Objective and time-efficient performance-based measurements are needed to screen for cognitive-related iADL dysfunction. We evaluated the Erlangen Test of Activities of Daily Living in Mild Dementia and Mild Cognitive Impairment (ETAM) in PD and determined its value for characterizing a subgroup of PD-MCI patients with mild performance-based iADL impairment.

Methods:

Twenty-one cognitively normal PD patients (PD-NC), 24 PD-MCI patients, and 18 healthy controls (HC) were analyzed. Assessments included the ETAM, a comprehensive neuropsychological test battery, iADL, mood, and motor measurements.

Results:

PD-MCI patients scored significantly lower on the ETAM total score compared to PD-NC patients (p = .002), whereas HC and PD-NC patients did not statistically differ. No HC scored lower than 27 points (diagnostic cutoff for mild iADL impairment); only PD-MCI patients scored below this cutoff (29.2%) suggesting the ETAM is able to characterize a PD-MCI subgroup with early iADL impairment. PD-MCI patients below the cutoff were more impaired in the attention domain (p = .04).

Conclusions:

The ETAM is a potentially valuable clinical assessment, able to detect first signs of iADL dysfunction in PD-MCI. Further studies in larger cohorts are needed to evaluate the prognostic ability for predicting PDD.
The Role of Motor System in Mental Rotation: New Insights from Myotonic Dystrophy Type 1
Authors: Cona Giorgia , Casagrande Arianna , Lenzoni Sabrina , Pegoraro Elena , Bozzoni Virginia , Bello Luca , Sorarù Gianni , Botta Annalisa , Semenza Carlo
Published: December 2019

Objective:

This study explored mental rotation (MR) performance in patients with myotonic dystrophy 1 (DM1), an inherited neuromuscular disorder dominated by muscular symptoms, including muscle weakness and myotonia. The aim of the study was twofold: to gain new insights into the neurocognitive mechanisms of MR and to better clarify the cognitive profile of DM1 patients. To address these aims, we used MR tasks involving kinds of stimuli that varied for the extent to which they emphasized motor simulation and activation of body representations (body parts) versus visuospatial imagery (abstract objects). We hypothesized that, if peripheral sensorimotor feedback system plays a pivotal role in modulating MR performance, then DM1 patients would exhibit more difficulties in mentally rotating hand stimuli than abstract objects.

Method:

Twenty-four DM1 patients and twenty-four age- and education-matched control subjects were enrolled in the study and were required to perform two computerized MR tasks involving pictures of hands and abstract objects.

Results:

The analysis of accuracy showed that patients had impaired MR performance when the angular disparities between the stimuli were higher. Notably, as compared to controls, patients showed slower responses when the stimuli were hands, whereas no significant differences when stimuli were objects.

Conclusion:

The findings are coherent with the embodied cognition view, indicating a tight relation between body- and motor-related processes and MR. They suggest that peripheral, muscular, abnormalities in DM1 lead to alterations in manipulation of motor representations, which in turn affect MR, especially when body parts are to mentally rotate.
Backlash against human rights shaming: emotions in groups
Authors: Snyder Jack
Published: December 2019

Human rights advocates continue to use shaming as a central tool despite recognizing its declining effectiveness. Shame is indeed a potent motivator, but its effects are often counterproductive for this purpose. Especially when wielded by cultural outsiders in ways that appear to condemn local social practices, shaming is likely to produce anger, resistance, backlash, and deviance from outgroup norms, or denial and evasion. Shaming can easily be interpreted as a show of contempt, which risks triggering fears for the autonomy and security of the group. In these circumstances, established religious and elite networks can employ traditional normative counter-narratives to recruit a popular base for resistance. If this counter-mobilization becomes entrenched in mass social movements, popular ideology, and enduring institutions, the unintended consequences of shaming may leave human rights advocates farther from their goal.
Ramadan exposure and birth outcomes: a population-based study from the Netherlands
Authors: Savitri Ary I. , Painter Rebecca C. , Lindeboom Maarten , Roseboom Tessa J. , van Ewijk Reyn J. G.
Published: December 2019

Background:

Ramadan, the Islamic month of daytime fasting, is observed by many pregnant Muslims. Although pregnant women are exempt, many prefer to fast. Previous research has shown long-term adverse effects on various health outcomes among the offspring, but evidence on effects on perinatal outcomes is mixed. This study investigates effects of Ramadan during pregnancy among Muslims in the Netherlands.

Methods:

Data from the Perinatal Registry of the Netherlands (Perined) on all births between 2000 and 2010 to mothers recorded as Mediterranean (i.e. of Turkish/Moroccan descent, a proxy for Muslim) (n = 139,322) or as ethnically Dutch (n = 1,481,435) were used. Ramadan exposure was defined using an intention-to-treat approach as the occurrence of a Ramadan during gestation. Muslims with versus without a Ramadan occurring during gestation were compared using difference-in-differences analyses. In these multiple linear/logistic regressions, non-Muslims were additionally included in order to take out potentially remaining confounding through seasonal effects.

Results:

The occurrence of a Ramadan during pregnancy among Muslims was not associated with altered birth weight, gestational length, newborn’s sex, perinatal mortality, low Apgar, or mild congenital anomalies. Odds for severe congenital anomalies were higher among the exposed (odds ratio: 1.17; 95% confidence interval: 1.00, 1.37), but this association became non-significant when adjusting for multiple testing.

Conclusions:

Despite earlier research showing long-term adverse health effects of prenatal exposure to Ramadan, there seems to be little or no relation between exposure to Ramadan during pregnancy and birth outcomes.
Determining the critical period for grass control in high-yielding cotton using Japanese millet as a mimic weed
Authors: Charles Graham W. , Sindel Brian M. , Cowie Annette L. , Knox Oliver G. G.
Published: December 2019

Field studies were conducted over five seasons from 2004 to 2015 to determine the critical period for weed control (CPWC) in high-yielding, irrigated cotton using a competitive mimic grass weed, Japanese millet. Japanese millet was planted with or after cotton emergence at densities of 10, 20, 50, 100, and 200 plants m−2. Japanese millet was added and removed at approximately 0, 150, 300, 450, 600, 750, and 900 degree days of crop growth (GDD). Data were combined over years. Japanese millet competed strongly with cotton, with season-long interference resulting in an 84% reduction in cotton yield with 200 Japanese millet plants m−2. The data were fit to extended Gompertz and logistic curves including weed density as a covariate, allowing a dynamic CPWC to be estimated for densities of 10 to 200 Japanese millet plants m−2. Using a 1% yield-loss threshold, the CPWC commenced at 65 GDD, corresponding to 0 to 7 d after crop emergence (DAE), and ended at 803 GDD, 76 to 98 DAE with 10 Japanese millet plants m−2, and 975 GDD, 90 to 115 DAE with 200 Japanese millet plants m−2. These results highlight the high level of weed control required throughout the cropping season in high-yielding cotton to ensure crop losses do not exceed the cost of weed control.
A Dirty Truth: Humans Began Accelerating Soil Erosion 4,000 Years Ago
Authors: Sima Richard
Published: December 2019

Recent research combining analysis of carbon dating, sediment accumulation rates, and pollen records from 632 lake beds worldwide finds deforestation tied to increased soil erosion.
The Topographic Signature of Ecosystem Climate Sensitivity in the Western United States
Authors: Hoylman Zachary H. , Jencso Kelsey G. , Hu Jia , Holden Zachary A. , Allred Brady , Dobrowski Solomon , Robinson Nathaniel , Martin Justin T. , Affleck David , Seielstad Carl
Published: December 2019

It has been suggested that hillslope topography can produce hydrologic refugia, sites where ecosystem productivity is relatively insensitive to climate variation. However, the ecological impacts and spatial distribution of these sites are poorly resolved across gradients in climate. We quantified the response of ecosystem net primary productivity to changes in the annual climatic water balance for 30 years using pixel‐specific linear regression (30‐m resolution) across the western United States. The standardized slopes of these models represent ecosystem climate sensitivity and provide a means to identify drought‐resistant ecosystems. Productive and resistant ecosystems were most frequent in convergent hillslope positions, especially in semiarid climates. Ecosystems in divergent positions were moderately resistant to climate variability, but less productive relative to convergent positions. This topographic effect was significantly dampened in hygric and xeric climates. In aggregate, spatial patterns of ecosystem sensitivity can be implemented for regional planning to maximize conservation in landscapes more resistant to perturbations.
Rainfall Intensity Temporal Patterns Affect Shallow Landslide Triggering and Hazard Evolution
Authors: Fan Linfeng , Lehmann Peter , Zheng Chunmiao , Or Dani
Published: December 2019

A characteristic of rainfall‐induced landslides is the gradual loading by infiltrating rainwater that weakens the soil mantle and could progress to abrupt soil mass release. The temporal patterns of similar rainfall amounts affect the hydrological response of a catchment and thus influence landslide dynamics. We use a novel catchment scale landslide hydromechanical triggering model to systematically study how different asymmetric distributions of rainfall intensities affect landslide dynamics and hazard evolution. Evaluating rainfall events with similar durations and total amounts shows that early rainfall peak intensity exerts stronger destabilizing effects, relative to delayed rainfall peak intensity. Intense rainfall events reduce landslide triggering relative to uniform‐intensity rainfall events due to reduced water infiltration. With advances in highly resolved and real‐time precipitation observations, the study offers a means for improving prediction of landslide timing and hazard evolution and identifying hydrological scenarios that enhance landslide activity.
Multiband Study of a Bidirectional Jet Occurred in the Upper Chromosphere
Authors: Cai Qiangwei , Shen Chengcai , Ni Lei , Reeves Katharine K. , Kang Kaifeng , Lin Jun
Published: December 2019

We present a study of a jet observed by the Solar Dynamics Observatory (SDO) and the Interface Region Imaging Spectrograph (IRIS), which provide high spatial‐temporal resolution observational data of (extreme) ultraviolet images, spectra, and magnetograms. The jet was observed in multiple bands of AIA and manifested clear bidirectional flows in
observations. The emission profiles of the Si IV 1402 Å line of the jet exhibited non‐Gaussian features and double‐peaked spectra, with the Doppler velocity and the nonthermal velocity up to 100 and 160 km s
, respectively. The plasma flows of the jet projected on the sky plane and in the line of sight (LOS) are the typical observational evidence of magnetic reconnection. The EM loci curves indicated that the plasma contains multi‐temperature components. The result deduced from the DEM method and changes in intensity of several spectral lines imply that the temperature of the plasma in the jet is heated to at least
 K. The electron density is about
 cm
according to the intensity ratios of the O IV 1399.77/1401.16 Å doublet and Si IV 1402.77/O IV 1401.16 Å lines. Via different approaches, we reached the conclusion that the jet occurred in the upper chromosphere. Investigating the magnetograms in the period when the jet appeared, we suggest that the jet results from the magnetic reconnection between the moving magnetic structure and the magnetic field nearby.
Multiphysics Modeling of a Brittle‐Ductile Lithosphere: 1. Explicit Visco‐Elasto‐Plastic Formulation and Its Numerical Implementation
Authors: Jacquey Antoine B. , Cacace Mauro
Published: December 2019

The long‐term strength of the lithosphere is controled by two different modes of deformation: a brittle‐like, effective pressure‐sensitive behavior at shallow crustal depth, which gradually transits to a thermally activated ductile flow rheology with increasing depth. All applications dealing with long‐term tectonics therefore share the necessity to describe in a consistent way the multiphysics coupling among the different deformation mechanisms controlling the bulk behavior of the lithosphere. We describe an efficient numerical implementation of a consistent visco‐elasto‐plastic rheology suitable to describe the first‐order aspects of continental rock masses. Different from typical long‐term geodynamics numerical frameworks, we explicitly account for both volumetric and deviatoric response of lithospheric rocks to applied loads. Plastic correction to a viscoelastic stress state is introduced via a non‐associative Drucker‐Prager model, without resorting to the assumption of a plastic limiter. The transient behavior of crustal and lithospheric rocks is accounted for by an overstress (rate‐dependent) viscoplastic rheology, which additionally helps solving for numerical issues related to plastic strain accumulation even in the absence of energetic feedbacks. When applied to the study of the dynamics of plume‐lithosphere interactions, our implementation is able to reproduce a surface topography with complex multiharmonic wavelength patterns in agreement with observations. In the final chapter, we discuss main limitations of the current rheological description when applied to the study of transient semi‐brittle rock behavior. These aspects are tackled in a companion paper, where a thermodynamically consistent formulation extending the current numerical description is presented.
Stress Transfer From Opening Hydraulic Fractures Controls the Distribution of Induced Seismicity
Authors: Kettlety T. , Verdon J. P. , Werner M. J. , Kendall J. M.
Published: December 2019

Understanding the dominant physical processes that cause fault reactivation due to fluid injection is vital to develop strategies to avoid and mitigate injection‐induced seismicity. Injection‐induced seismicity is a risk for several industries, including hydraulic fracturing, geothermal stimulation, oilfield waste disposal and carbon capture and storage, with hydraulic fracturing having been associated with some of the highest magnitude induced earthquakes (
). As such, strict regulatory schemes have been implemented globally to limit the felt seismicity associated with operations. In the UK, a very strict “traffic light” system is currently in place. These procedures were employed several times during injection at the PNR‐1z well at Preston New Road, Lancashire, UK, from October to December 2018. As injection proceeded, it became apparent to the operator that stages were interacting with a seismogenic planar structure, interpreted as a fault zone, with several
events occurring. Microseismicity was clustered along this planar structure in a fashion that could not readily be explained through pore pressure diffusion or hydraulic fracture growth. Instead, we investigate the role of static elastic stress transfer created by the tensile opening of hydraulic fractures. We find that the spatial distributions of microseismicity are strongly correlated with areas that receive positive Mohr‐Coulomb stress changes from the tensile fracture opening, while areas that receive negative Mohr‐Coulomb stress change are quiescent. We conclude that the stressing due to tensile hydraulic fracture opening plays a significant role in controlling the spatiotemporal distribution of induced seismicity.
Intermittent Propagation of Upward Positive Leader Connecting a Downward Negative Leader in a Negative Cloud‐to‐Ground Lightning
Authors: Srivastava Abhay , Jiang Rubin , Yuan Shanfeng , Qie Xiushu , Wang Dongfang , Zhang Hongbo , Sun Zhuling , Liu Minyuan
Published: December 2019

Both upward positive connecting leader (UPL) and downward negative leader (DNL) involved in a lightning striking the 325‐m meteorology tower were captured by using a high‐speed video camera with 2.7‐μs temporal resolution and 1‐m spacial resolution, in association with electromagnetic field measurements. The UPL initiated around 1.6 ms prior to the attachment when the DNL was outside the field of view of the camera, and 38 hop forwards with backward re‐illumination through the UPL channel were identified. As the stepped DNL approached, 34 space stems were observed in front of the leader tip during 0.62‐ms period prior to the attachment, while, based on the present observation system, no visible space stem was found throughout the intermittent UPL propagation. The 2‐D propagation speed of the UPL and DNL was 1.16 × 105 and 3.6 × 105 m/s, within channel extensions of 100 and 95 m, respectively. For the UPL, the inter‐step interval was longer in its initial development while the step length was similar throughout the propagation. Several steps of DNL could be identified within an inter‐step of UPL, and vice versa. The different intermittent behaviors of negative and positive leaders with temporal‐inconsistent steps suggest that their stepping was independent from each other. When the DNL was very close to the UPL, the DNL can induce and support the UPL development by enhancing the overall electric field. However, it seems that the generation of space stems and their bridging to the DNL, as involved in the DNL stepping, might not the direct cause of the UPL intermittence.
Seasonal Characteristics of Model Uncertainties From Biogenic Fluxes, Transport, and Large‐Scale Boundary Inflow in Atmospheric CO2 Simulations Over North America
Authors: Feng Sha , Lauvaux Thomas , Davis Kenneth J. , Keller Klaus , Zhou Yu , Williams Christopher , Schuh Andrew E. , Liu Junjie , Baker Ian
Published: December 2019

Regional estimates of biogenic carbon fluxes over North America from both atmospheric inversions (“top‐down” approach) and terrestrial biosphere models (“bottom‐up”) remain highly uncertain. We merge these approaches with an ensemble‐based, regional modeling system able to diagnose and quantify the causes of uncertainties in top‐down atmospheric estimates of the terrestrial sink over North America. Our ensemble approach quantifies and partitions the uncertainty stemming from atmospheric transport, the biosphere, and large‐scale CO2 boundary inflow (boundary conditions). We use meteorological data, CO2 fluxes, and CO2 mole fraction measurements to assure the reliability of the ensemble system. Our results show that all uncertainty components have clear seasonal variations. The biogenic flux component dominates modeled boundary layer CO2 uncertainty, ranging from 2.5 ppm in summer and winter to 1.5 ppm in fall and spring. Spatially, it remains highly uncertain in the U.S. Corn Belt regions. Transport uncertainty reaches a maximum of 2.5 ppm in the summer months and stays at 1.2 ppm for the rest of the year and is highly correlated with the biogenic CO2 fluxes. Boundary conditions play the smallest role in atmospheric boundary layer CO2 uncertainty with a magnitude smaller than 1 ppm. However, boundary conditions are the most important uncertainty component in column‐averaged CO2 (XCO2). The spatiotemporal variations of the uncertainties in modeled XCO2 are similar to those in atmospheric boundary layer CO2.
Characterizing Thunder‐Induced Ground Motions Using Fiber‐Optic Distributed Acoustic Sensing Array
Authors: Zhu Tieyuan , Stensrud David J.
Published: December 2019

We report for the first time on a distributed acoustic sensing (DAS) array using preexisting underground fiber optics beneath the Penn State campus for detecting and characterizing thunder‐induced ground motions. During a half‐hour interval from 03:20–03:50 UTC on 15 April 2019 in State College, PA, we identify 18 thunder‐induced seismic events in the DAS array data. The high‐fidelity DAS data show that the thunder‐induced seismics are very broadband, with their peak frequency ranging from 20 to 130 Hz. We use arrival times of the 18 events to estimate the phase velocity of the near surface, the back azimuth, and location of thunder‐seismic sources that are verified with lightning locations from the National Lightning Detection Network. Furthermore, the dense DAS data enable us to simulate thunder‐seismic wave propagation and full waveform synthetics and further locate the thunder‐seismic source by time‐reversal migration. Interestingly, we found that thunder‐seismic power recorded by DAS is positively correlated with National Lightning Detection Network lightning current power. These findings suggest that fiber‐optic DAS observations may offer a new avenue of studying thunder‐induced seismics, characterizing the near‐surface velocity structure, and probing the thunder‐ground coupling process.
Pore‐Scale Simulation of Immersed Granular Collapse: Implications to Submarine Landslides
Authors: Yang G. C. , Jing L. , Kwok C. Y. , Sobral Y. D.
Published: December 2019

The collapse of granular columns in a viscous fluid is a common model case for submarine geophysical flows. In immersed granular collapses, dense packings result in slow dynamics and short runout distances, while loose packings are associated with fast dynamics and long runout distances. However, the underlying mechanisms of the collapse initiation and runout, particularly regarding the complex fluid‐particle interactions at the pore scale, are yet to be fully understood. In this study, a three‐dimensional approach coupling the lattice Boltzmann method and the discrete element method is adopted to investigate the influence of packing density on the collapsing dynamics. As a supplement to previous experimental measurements, the direct numerical simulation of fluid‐particle interactions explicitly provides micromechanical evidence of the pore pressure feedback mechanism. In dense cases, a strong arborescent contact force network can form to prevent particles from sliding, resulting in a creeping failure behavior. In contrast, the granular phase is liquefied substantially in loose cases, leading to a rapid and catastrophic failure. This opposing dilative/contractive behavior linked to the initial packing is robust and does not depend on the column size. Furthermore, hydroplaning can take place in large enough loose cases due to the fast‐moving surge front, which reduces the frictional resistance dramatically and thereby results in a long runout distance. More quantitatively, we are able to linearly correlate the normalized runout distance and the densimetric Froude number across a wide range of length scales, including small‐scale numerical/experimental data and large‐scale field data.
Sociological Perspectives on Earth System Modeling
Authors: Grundmann Reiner , Rödder Simone
Published: December 2019

How can we understand climate change from a sociological perspective? In asking this question, we assume that Sociology has something to contribute to such an enterprise. The argument that we put forward is twofold: We argue that Sociology provides a much needed alternative to two dominant approaches that have influenced public discourse, behaviorist theories, mainly employed in Economics, and a belief in the centrality of science in policy making (“evidence first”), mainly entertained by physical scientists. We critically discuss both approaches, showing the limits of behaviorism and the linear model of policy making and provide an alternative framework, which emphasizes the role of social action, of organizations, and of structural differences between different social worlds. We then apply our framework to assess the role of evidence at the climate science‐policy interface and the Intergovernmental Panel on Climate Change (IPCC) as a boundary organization in particular. We argue that science and politics follow different logics and that the IPCC is simultaneously both more political and less policy relevant than its self‐description as “policy‐relevant, never policy prescriptive” tries to make us believe. We conclude that a depoliticization of politics by IPCC expert advice and a politicization of climate science occur simultaneously and mutually reinforce one another. The result is a lack of progress in climate policy as science has taken center stage but is unable to offer political solutions.
Philosophical Perspectives on Earth System Modeling: Truth, Adequacy, and Understanding
Authors: Gramelsberger G. , Lenhard J. , Parker W.S.
Published: December 2019

We explore three questions about Earth system modeling that are of both scientific and philosophical interest: What kind of understanding can be gained via complex Earth system models? How can the limits of understanding be bypassed or managed? How should the task of evaluating Earth system models be conceptualized?
Using an Arbitrary Moment Predictor to Investigate the Optimal Choice of Prognostic Moments in Bulk Cloud Microphysics Schemes
Authors: Igel Adele L.
Published: December 2019

Most bulk cloud microphysics schemes predict up to three standard properties of hydrometeor size distributions, namely, the mass mixing ratio, number concentration, and reflectivity factor in order of increasing scheme complexity. However, it is unclear whether this combination of properties is optimal for obtaining the best simulation of clouds and precipitation in models. In this study, a bin microphysics scheme has been modified to act like a bulk microphysics scheme. The new scheme can predict an arbitrary combination of two or three moments of the hydrometeor size distributions. As a first test of the arbitrary moment predictor (AMP), box model simulations of condensation, evaporation, and collision‐coalescence are conducted for a variety of initial cloud droplet distributions and for a variety of configurations of AMP. The performance of AMP is assessed relative to the bin scheme from which it was built. The results show that no double‐ or triple‐moment configuration of AMP can simultaneously minimize the error of all cloud droplet distribution moments. In general, predicting low‐order moments helps to minimize errors in the cloud droplet number concentration, but predicting high‐order moments tends to minimize errors in the cloud mass mixing ratio. The results have implications for which moments should be predicted by bulk microphysics schemes for the cloud droplet category.
Quantifying Dissolved Organic Carbon Dynamics Using a Three‐Dimensional Terrestrial Ecosystem Model at High Spatial‐Temporal Resolutions
Authors: Liao Chang , Zhuang Qianlai , Leung L. Ruby , Guo Laodong
Published: December 2019

Arctic terrestrial ecosystems are very sensitive to the global climate change due to the large storage of soil organic carbon and the presence of snow, glacier, and permafrost, which respond directly to near surface air temperature that has warmed in the Arctic by almost twice as much as the global average. These ecosystems play a significant role in affecting regional and global carbon cycling, which have been traditionally quantified using biogeochemical models that have not explicitly considered the loss of carbon due to lateral flow of water from land to aquatic ecosystems. Building upon an extant spatially distributed hydrological model and a process‐based biogeochemical model, we have developed a three‐dimensional terrestrial ecosystem model to elucidate how lateral water flow has impacted the regional dissolved organic carbon (DOC) dynamics in the Tanana Flats Basin in central Alaska. The model explicitly simulates the production, consumption, and transport of DOC. Both in situ observational data and remote sensing‐based products were used to calibrate and validate the model. Our simulations show that (1) plant litter DOC leaching exerts significant controls on soil DOC concentration during precipitation and snowmelt events, (2) lateral transport plays an important role in affecting regional DOC dynamics, and (3) DOC export to the Tanana River is approximately 9.6 × 106 kg C year−1. This study provides a modeling framework to adequately quantify the Arctic land ecosystem carbon budget by considering the lateral transport of carbon affected by permafrost degradation. The quantification of the lateral carbon fluxes will also improve future carbon cycle modeling for Arctic aquatic ecosystems.
A Processes‐Based Dynamic Root Growth Model Integrated Into the Ecosystem Model
Authors: Lu Haibo , Yuan Wenping , Chen Xiuzhi
Published: December 2019

Plant roots play a critical role in regulating the uptake of soil water and nutrients. Shifts in root growth and biomass distribution resulting from climate change can impact ecosystem water and carbon cycling. Such interactions between root growth and ecosystem functioning have not been integrated into current terrestrial ecosystem models. Here a three‐dimensional dynamic root model (DyRoot) was developed and implemented into the Integrated Biosphere Simulator (IBIS) ecosystem model for simulating root growth, architecture (i.e., fine and coarse roots), and distribution driven by soil water and nitrogen availabilities. Field root biomass observations were used for model calibration and validation. Results showed that DyRoot was able to simulate the root biomass distribution across five forest ecosystem types with good performance (R2 = 0.79, P < 0.01). The validations of root distribution in three forest chronosequences suggested that DyRoot captured the changes in rooting depth with the increase in stand age. The sensitivity of simulated root distribution to soil water availability was compared against root biomass observations from two precipitation reduction experiments. Results indicated that DyRoot reasonably represented the decrease of root biomass in topsoil layers in response to the deficits of soil moisture simulated by (IBIS). The DyRoot model algorithm in this study has great implications for representing an optimized root distribution in ecosystem models, which can improve model performance by simulating the feedbacks of root evolution in response to climate change. Furthermore, allowing explicit root architecture in the DyRoot model also sheds light on depicting the responses of root traits to environmental changes.
Error Analysis for an Algorithm That Reduces Radiative Transfer Calculations in High‐Resolution Atmospheric Models
Authors: Barker Howard W. , Qu Zhipeng , Cole Jason N. C.
Published: December 2019

This study assesses characteristics of spatial and temporal errors for net (shortwave + longwave) surface irradiances and atmospheric heating rates predicted by the Partitioned‐Gauss‐Legendre Quadrature (PGLQ) algorithm, whose aim is to economize computation of radiative transfer (RT) in high‐resolution cloud system‐resolving models (CSRMs). Most results reported here are for PGLQ having made 200 times fewer calls to the RT models than the Independent Column Approximation, which applies the RT models to each column in CSRM domains. Due to the nature of GLQ, PGLQ yields almost unbiased domain averages. This is shown for data pertaining to two convective cloud systems produced by a CSRM. Relative to the Independent Column Approximation, PGLQ works with much reduced amounts of information, and so it has the potential to produce rare, but sizable, localized errors. Two methods are employed to assess the “randomness” of spatial and temporal series of PGLQ flux and heating rate errors; one of which is developed here. Regarding spatial transects of net surface irradiance errors ΔFNET, ~30–60% of them are considered by both assessment techniques, simultaneously, to be indistinguishable, at the 95% confidence level, from fully uncorrelated sequences. Correspondingly, for time series of ΔFNET (at 8‐s time step), ~15–20% of 128‐step series, and ~10–70% of 30‐step series are considered by both methods, simultaneously, to be random. For time series of errors for net radiative heating rates, ~40% of cloudless series get classed, by both tests simultaneously, as random, compared to ~20% of those that contain some cloud.
Superposed Epoch Analysis of the Energetic Electron Flux Variations During CIRs Measured by BD‐IES
Authors: Yin Zefan , Zou Hong , Ye Yuguang , Zong Qiugang , Wang Yongfu
Published: December 2019

The flux variations of energetic electrons is one of the most important topics to understand dynamic processes in the space environment and the forecast for high‐energy electron burst. BeiDa Image Electron Spectrometer (BD‐IES), an imaging energetic elecstron spectrometer onboard a Chinese navigation satellite at an inclined geosynchronous orbit, can provide 50–600 keV electron flux data, which is used to investigate electron flux variations at GEO orbit during Co‐rotating Interaction Region events (CIRs). The superposed epoch analysis is applied to study the electron flux variations in different energy channels of BD‐IES during CIRs and the results support previous works. It reveals that electron fluxes in different channels all have a dropout before or at CIR interface and then the recovery of electrons with low energy reaches maximum earlier than that of electrons with high energy, with longer time differences for larger energy gap, which is consistent of two major mechanisms for energizing particles: inward radial diffusion and local acceleration. In addition, we investigate the relationship between electron flux enhancement in each energy channel and magnetic locals time and the extent of enhancement for electron flux peak value compared with average value before interface. These results can contribute to our understanding of electron flux variations at GEO during CIRs, and thus lay foundations for forecast research on high‐energy electron enhancement during CIRs.
Threshold of Motion Conditions Under Stokes Flow Regime and Comparison With Turbulent Flow Data
Authors: Shih WuRong , Diplas Panayiotis
Published: December 2019

The present study numerically investigates the effects of bed geometrical properties on particle entrainment driven by Stokes flow. We use different substrate arrangements to alter two important factors: The angle of repose, φ, and degree of exposure, e, of the test particle. The effectiveness of shear flow in mobilizing surface particles will change with e and φ, or collectively, η = e/tanφ, yielding a wide range of critical Shields parameter, θc, values. The use of η is better suited for describing local bed geometry as both e and φ values will change simultaneously during substrate rearranging processes. Furthermore, the range of θc values obtained in this study stems from the limitation of this parameter to relate the applied force variation to local flow and bed conditions. We therefore propose an effective shear ratio, α, to establish such connections between the global and local flow shear intensities. These results provide a unique perspective to examine typical θc data obtained from both Stokes and turbulence regimes. For the case of a single‐particle entrainment under given grain protrusion, Stokes flow‐based θc values are found to be 2 to 3 times larger than the counterpart turbulence data. For the case of channel bed mobility, however, the Shields curve suggests an order of magnitude difference in θc between the two regimes. In part, we attribute this significant θc variation to turbulent flow fluctuations in the first case and varied bed mobility levels in the second, given their distinct theoretical and empirical nature, respectively.
Bias Correction of Airborne Thermal Infrared Observations Over Forests Using Melting Snow
Authors: Pestana Steven , Chickadel C. Chris , Harpold Adrian , Kostadinov Tihomir S. , Pai Henry , Tyler Scott , Webster Clare , Lundquist Jessica D.
Published: December 2019

Uncooled thermal infrared (TIR) imagers, commonly used on aircraft and small unmanned aircraft systems (UAS, “drones”), can provide high‐resolution surface temperature maps, but their accuracy is dependent on reliable calibration sources. A novel method for correcting surface temperature observations made by uncooled TIR imagers uses observations over melting snow, which provides a constant 0 °C reference temperature. This bias correction method is applied to remotely sensed surface temperature observations of forests and snow over two mountain study sites: Laret, Davos, Switzerland (27 March 2017) in the Alps, and Sagehen Creek, California, USA (21 April 2017) in the Sierra Nevada. Surface temperature retrieval errors that arise from temperature‐induced instrument bias, differences in image resolution, retrieval of mixed pixels, and variable view angles were evaluated for these forest snow scenes. Applying the melting snow‐based bias correction decreased the root‐mean‐square error by about 1 °C for retrieving snow, water, and forest canopy temperatures from airborne TIR observations. The influence of mixed pixels on surface temperature retrievals over forest snow scenes was found to depend on image resolution and the spatial distribution of forest stands. Airborne observations over the forests at Sagehen showed that near the edges of TIR images, at more than 20° from nadir, the snow surface within forest gaps smaller than 10 m was obscured by the surrounding trees. These off‐nadir views, with fewer mixed pixels, could allow more accurate airborne and satellite‐based observations of canopy surface temperatures.
Multiscale Feature‐feature Interactions Control Patterns of Hyporheic Exchange in a Simulated Headwater Mountain Stream
Authors: Herzog Skuyler P. , Ward Adam S. , Wondzell Steven M.
Published: December 2019

Recent predictions of hyporheic exchange at the basin‐scale assume individual features control exchange independently of each other, which has been demonstrated in relatively uniform, low‐gradient rivers. However, this assumption may not hold in steep catchments where both the type and size of individual features may vary over short distances, leading to irregular patterns of feature dominance on hyporheic exchange flows. Also, steep longitudinal gradients support substantial downvalley flows in the subsurface, which may create feedbacks between adjacent features. In this study, we test the extent to which features interact with one another and whether they can be aggregated to make reach‐scale predictions in a headwater mountain stream. Using systematic manipulations of a 2‐D stream centerline model and spectral analyses, we test for the presence of both feature‐feature and multiscale interactions. Our results show that changing the height of individual step‐pool features can alter hyporheic flow fields in neighboring, and sometimes distant, features. Spectral analyses revealed two scales of streambed topography—a local scale of single features and an intermediate scale that spanned multiple local‐scale features. All features produced hyporheic exchange, but turnover of deeper hyporheic water only occurred at a few key locations where local‐ and intermediate‐scale features amplified each other. Further, shallow bedrock increases the ratio of local‐ and intermediate‐scale flowpaths to regional‐scale flowpaths. Conceptual models portraying hyporheic exchange as a series of nested flowpaths should include the interactions among streambed topographic features in mountain streams. These results have implications for upscaling, field experiments, and stream restoration in steep catchments.
Multiorder Hydrologic Position in the Conterminous United States: A Set of Metrics in Support of Groundwater Mapping at Regional and National Scales
Authors: Belitz Kenneth , Moore Richard B. , Arnold Terri L. , Sharpe Jennifer B. , Starn J. J.
Published: December 2019

The location of a point on the landscape within a stream network (hydrologic position) can be an important predictive measure in hydrology. Hydrologic position is defined here by two metrics: lateral position and distance from stream to divide, both measured horizontally. Lateral position (dimensionless) is the relative position of a point between the stream and its watershed divide. Distance from stream to divide (units of length) is an indicator of position within a watershed: generally small near a confluence and generally large in headwater areas. Watersheds and watershed divides are defined here by Thiessen polygons rather than topographic divides. Lateral position and distance from stream to divide are also defined in the context of hydrologic order. Hydrologic order “n” is defined as the network of streams, and associated divides, of ordernand higher. And given that a point can have different positions in different hydrologic orders the term multiorder hydrologic position (MOHP) is used to describe the ensemble of hydrologic positions. MOHP was mapped across the conterminous United States for nine hydrologic orders at a spatial resolution of 30 m (about 8.7 billion pixels). There are 18 metrics for each pixel. Four case studies are presented that use MOHP metrics as explanatory factors in random forest machine learning models. The case studies show that lower order MOHP metrics can serve as indicators of hydrologic process while higher‐order metrics serve as indicators of location. MOHP is shown to have utility as a predictor variable across a large range of scales (50,000 to 8,000,000 km2).
Subtidal Flow Reversal Associated With Sediment Accretion in a Delta Channel
Authors: Zhang Wei , Feng Haochuan , Zhu Yuliang , Zheng Jinhai , Hoitink A. J. F.
Published: December 2019

In branching delta channel networks, tides intrude into parallel river outlets causing complex tidal behavior. The tidal motion can impact the division of river discharge over distributary channels. Under some circumstances, the discharge averaged over a tidal cycle may even reverse, drawing ocean water into the delta, such as observed in the Yangtze Delta, the Fly Delta and the Colorado Delta. Here, we study the flow reversal associated with sediment accumulation of a distributary channel in terms of tidal propagation and subtidal discharge dynamics, by focusing on the Yangtze Delta. The Yangtze Delta channel configuration represents a deep and wide main channel and a smaller side channel that has rapidly accreted over the past decades. A new mechanism is presented, which results in seawater transport across the shallow side channel, posing a risk to freshwater availability. The shallowest section in the side channel nearly acts as a tidal divide. In this section, the tide has the character of a standing wave, which implies that Stokes transport converges from opposite sides of the channel. This leads to significant variation of the total water storage in the side channel and subtidal water levels in the side channel being elevated above that in the main channel. The bulge of water that is stored during spring tide leaves the side channel toward neap tide, explaining reversal of the tide‐averaged discharge and seawater intrusion when the river discharge is low.