bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of Surface Motion Characteristics Determined by InSAR to Assess Peatland Condition
Authors: Alshammari Lubna , Boyd Doreen S. , Sowter Andrew , Marshall Chris , Andersen Roxane , Gilbert Peter , Marsh Stuart , Large David J. 
Published: December 2019

AbstractPeatland surface motion is a key property of peatland that relates to condition. However, field‐based techniques to measure surface motion are not cost‐effective over large areas and long time periods. An alternative method that can quantify peatland surface motion over large areas is interferometric synthetic aperture radar. Although field validation of the accuracy of this method is difficult, the value of interferometric synthetic aperture radar (InSAR) as a means of quantifying peat condition can be tested. To achieve this, the characteristics of InSAR time series measured over an18‐month period at 22 peatland sites in the Flow Country northern Scotland were compared to site condition assessment based on plant functional type and site management history. Sites in good condition dominated by Sphagnum display long‐term stability or growth and a seasonal cycle with maximum uplift and subsidence in August–November and April–June, respectively. Drier and partially drained sites dominated by shrubs display long‐term subsidence with maximum uplift and subsidence in July–October and February–June, respectively. Heavily degraded sites with large bare peat extent display subsidence with no distinct seasonal oscillations. Seasonal oscillation in surface motion at sites with a dominant nonvascular plant community is interpreted as resulting from changes in seasonal evaporative demand. On sites with extensive vascular plants cover and falling water table, surface oscillations are interpreted as representing sustained drawdown during the growing season and subsequent recharge in late winter. This study highlights the potential to use InSAR to characterize peatland condition and provide a new view of the surface dynamics of peatland landscapes.
On the Emergence Mechanism of Carrot Sprites
Authors: Malagón‐Romero A. , Teunissen J. , Stenbaek‐Nielsen H. C. , McHarg M. G. , Ebert U. , Luque A. 
Published: December 2019

AbstractWe investigate the launch of negative upward streamers from sprite glows. This phenomenon is readily observed in high‐speed observations of sprites and underlies the classification of sprites into carrot or column types. First, we describe how an attachment instability leads to a sharply defined region in the upper part of the streamer channel. This region has an enhanced electric field, low conductivity and strongly emits in the first positive system of molecular nitrogen. We identify it as the sprite glow. We then show how, in the most common configuration of a carrot sprite, several upward streamers emerge close to the lower boundary of the glow, where negative charge gets trapped and the lateral electric field is high enough. These streamers cut off the current flowing toward the glow and lead to the optical deactivation of the glow above. Finally, we discuss how our results naturally explain angel sprites.
A Machine‐Learning Approach for Earthquake Magnitude Estimation
Authors: Mousavi S. Mostafa , Beroza Gregory C. 
Published: December 2019

AbstractIn this study, we present a fast and reliable method for end‐to‐end estimation of earthquake magnitude from raw waveforms recorded at single stations. We design a regressor (MagNet) composed of convolutional and recurrent neural networks that is not sensitive to the data normalization, hence waveform amplitude information can be utilized during the training. The network can learn distance‐dependent and site‐dependent functions directly from the training data. Our model can predict local magnitudes with an average error close to zero and standard deviation of ~0.2 based on single‐station waveforms without instrument response correction. We test the network for both local and duration magnitude scales and show a station‐based learning can be an effective approach for improving the performance. The proposed approach has a variety of potential applications from routine earthquake monitoring to early warning systems.
Ionospheric Perturbations Induced by a Very Severe Cyclonic Storm (VSCS): A Case Study of Phailin VSCS
Authors: Dube Adarsh , Singh Rajesh , Maurya Ajeet K. , Kumar Sanjay , Sunil P. S. , Singh Abhay K. 
Published: December 2019

AbstractWe investigate F region ionospheric perturbations associated with very severe cyclonic storm Phailin which occurred in Bay of Bengal during 09–12 October 2013. Very severe cyclonic storm Phailin was the most intense supercyclone over the Bay of Bengal with intensity ~T6.0. The primary data used are lightning data from Global Lightning Detection 360 network, Global Position System‐derived total electron content information from seven Global Position System stations located in the cyclone impact region, and meteorological data. This is the first report from north Indian Ocean which investigates the perturbations induced in the ionosphere associated with a cyclone. Investigation of lightning discharges occurrence at the storm center along the cyclone track line showed that the lightning growth pattern closely follows the cyclone intensity during the initial, mature, and decay stages. The total electron content computed from seven Global Position System stations showed that differential total electron content is enhanced during very severe cyclonic storm days, compared with precyclone and postcyclone days. The maximum peak‐to‐peak perturbation in differential total electron content values at Port Blair located at Andaman‐Nicobar Islands in Bay of Bengal was ~0.33 TECu during the cyclone days, whereas it was only ~0.11 TECu during the no‐cyclone days. The results show that most probably gravity waves generated from cyclonic thunderstorms can couple with the upper atmosphere and modify the dynamics of the ionosphere. Tropical cyclones and large thunderstorms are an important source from below which couple with ionosphere and manifest in the form of ionospheric perturbations.
Asymmetric Reconnection Within a Flux Rope‐Type Dipolarization Front
Authors: Marshall A. T. , Burch J. L. , Reiff P. H. , Webster J. M. , Torbert R. B. , Ergun R. E. , Russell C. T. , Strangeway R. J. , Giles B. L. , Nakamura R. , Hwang K. ‐J. , Genestreti K. J. 
Published: December 2019

AbstractOn 8 September 2018, at nearly 14:51:30 UT, the Magnetospheric Multiscale (MMS) spacecraft encountered an electron diffusion region near the center of a flux‐rope type dipolarization front. The observed signature of the magnetic field in geocentric solar ecliptic included a bipolar Bz coinciding with a peak in By and |B| as is typical for a flux rope. At the same time, all three spacecraft with available plasma data observed a decrease in density and an increase in temperature over ion scales near the reversal in Bz. These ion‐scale changes are expected in a dipolarization front. The three spacecraft with available electron plasma data also observed clear evidence of electron‐scale reconnection just after the Bz reversal including ideal magnetohydrodynamics violation, a large out‐of‐plane current, a large j · E′ energy conversion, and crescent‐shaped electron velocity distributions. This is the first time reconnection has been observed near the center of a flux rope on an electron‐scale during such an event, and MMS was likely very close to the reconnection X‐line.
A Comparative Analysis of the OI 130.4‐nm Emission Observed by NASA's TIMED Mission Using a Monte Carlo Radiative Transfer Model
Authors: Qin Jianqi , Harding Brian J. 
Published: December 2019

AbstractRemote sensing of the OI 130.4‐nm emission is potentially a useful means for routine monitoring of the atomic oxygen abundance in the upper atmosphere, especially for altitudes above
300 km where the OI 135.6‐nm emission becomes too dim to be useful. However, to date, the interpretation of the OI 130.4‐nm emission as a proxy for the O density remains ambiguous in that the relative contribution of the external and internal sources to the production of this emission has not been fully understood. In this study, we perform a comparative analysis of the OI 130.4‐nm dayglow observed by NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission using a Monte Carlo radiative transfer model to investigate the consistency between models and the TIMED/Global UltraViolet Imager (GUVI) data. The solar 130.4‐nm flux is measured by TIMED/Solar EUV Experiment (SEE). The Global Airglow (GLOW) and the Atmospheric Ultraviolet Radiance Integrated Code (AURIC) models are used to calculate the initial volume emission rates due to photoelectron impact excitation, and the NRLMSISE‐00 model is used to provide the atmospheric density and temperature profiles. Our data‐model comparisons suggest that the model predicted contributions from photoelectron impact excitation need to be scaled by a factor of
0.1–0.5 to achieve good fits with the data. Moreover, the modeled solar contributions need to be scaled up/down to fit the observations at small (
20
)/large (
60
) solar zenith angles, with a factor of
0.5–1.7. These scale factors are larger than the uncertainties in the GUVI and SEE instrument calibrations, which might suggest inaccurate model predictions of the dayside O density and temperature variations with solar zenith angles.
Coordinated Ground‐Based and Space‐Based Observations of Equatorial Plasma Bubbles
Authors: Aa Ercha , Zou Shasha , Eastes Richard , Karan Deepak K. , Zhang Shun‐Rong , Erickson Philip J. , Coster Anthea J. 
Published: December 2019

AbstractThis paper presents coordinated and fortuitous ground‐based and spaceborne observations of equatorial plasma bubbles (EPBs) over the South American area on 24 October 2018, combining the following measurements: Global‐scale Observations of Limb and Disk far ultraviolet emission images, Global Navigation Satellite System total electron content data, Swarm in situ plasma density observations, ionosonde virtual height and drift data, and cloud brightness temperature data. The new observations from the Global‐scale Observations of Limb and Disk/ultraviolet imaging spectrograph taken at geostationary orbit provide a unique opportunity to image the evolution of plasma bubbles near the
peak height over a large geographic area from a fixed longitude location. The combined multi‐instrument measurements provide a more integrated and comprehensive way to study the morphological structure, development, and seeding mechanism of EPBs. The main results of this study are as follows: (1) The bubbles developed a westward tilted structure with 10–15° inclination relative to the local geomagnetic field lines, with eastward drift velocity of 80–120 m/s near the magnetic equator that gradually decreased with increasing altitude/latitude. (2) Wave‐like oscillations in the bottomside
layer and detrended total electron content were observed, which are probably due to upward propagating atmospheric gravity waves. The wavelength based on the medium‐scale traveling ionospheric disturbance signature was consistent with the interbubble distance of
500–800 km. (3) The atmospheric gravity waves that originated from tropospheric convective zone are likely to play an important role in seeding the development of this equatorial EPBs event.
Determining Crack Aperture Distribution in Rocks Using the 14C‐PMMA Autoradiographic Method: Experiments and Simulations
Authors: Bonnet M. , Sardini P. , Billon S. , Siitari‐Kauppi M. , Kuva J. , Fonteneau L. , Caner L. 
Published: December 2019

AbstractBecause cracks control the global mechanical and transport properties of crystalline rocks, it is of a crucial importance to suitably determine their aperture distribution, which evolves through alteration processes and rock weathering. Due to the high variability of crack networks in rocks, a multiscale approach is needed. The 14C‐PMMA (polymethylmethacrylate) method was developed to determine crack apertures using a set of artificial crack samples with different controlled apertures and tilt angles and also using Monte Carlo simulations. The experiments and simulations show the same result: the estimation of apparent aperture wA was successful regardless of tilt angle, even if the estimates are less accurate for low tilt angles (<30°). The uncertainties on the estimation of the real crack aperture wR arise from the unknown tilt angle. The ability of the 14C‐PMMA autoradiography method to estimate crack aperture distributions in rock samples was successfully confirmed on a sample of Grimsel granodiorite.
A Decadal Climatology of Chemical, Physical, and Optical Properties of Ambient Smoke in the Western and Southeastern United States
Authors: Bian Qijing , Ford Bonne , Pierce Jeffrey R. , Kreidenweis Sonia M. 
Published: December 2019

AbstractBiomass burning is a major source of summertime fine particulate matter in the United States, degrading air quality and affecting human health and climate. Fuels, burn conditions, and fire types vary across the United States, which may impact smoke composition and optical properties. We use the Hazard Mapping System to track smoke plumes for 10 years from 2008 to 2017, focusing on three U.S. regions: Southeast, Pacific West, and Southwest. Combining this geospatial data set with AErosol RObotic NETwork (AERONET) columnar data, and Interagency Monitoring of Protected Visual Environments (IMPROVE) network in situ observations, we define “smoke‐influenced days” and derive the properties of smoke aerosol for April through September, encompassing the main fire seasons across the United States. We find in the IMPROVE surface measurement that the elemental carbon fraction of smoke in the Southeast is statistically different from and lower than that in the west, consistent with more‐smoldering prescribed fires in the southeast. We find in the AERONET columnar observations that the mean single scattering albedo of smoke (at 675 nm) is lower in the two western regions (~0.94) compared to the southeast (~0.96), consistent with the differences in composition and fire types, which implies that the compositional differences at the surface may be representative of the column. Higher relative humidity in the southeast and less dust associated with smoke also appear to contribute to the higher smoke single scattering albedo relative to the west. Our results show that smoke properties vary regionally, with implications for models, data assimilation, and remote‐sensing.
Carbon Budget for a Large Drowned River Valley Estuary Adjacent to an Emerging Megacity (Sydney Harbour)
Authors: Tanner E. L. , Eyre B. D. 
Published: December 2019

AbstractAnnual organic and inorganic carbon budgets were constructed for the Sydney Harbour Estuary. Net ecosystem metabolism was the main control on carbon fluxes in the system. Sydney Harbour Estuary was slightly net heterotrophic, which is consistent with a small CO2 emission of 0.8 × 108 mol C yr−1. Terrestrial carbon loads were 70% dissolved inorganic carbon, 21% dissolved organic carbon, and 9% particulate organic carbon. Dissolved inorganic carbon was exported to the ocean (4.19 × 108 mol C yr−1), and an import of organic carbon (1.92 × 108 mol C yr−1) from the ocean was required to balance the budget. Sydney Harbour had high sediment organic carbon burial rates similar to other river valley estuaries including the Hudson River and Chesapeake Bay. Productivity was the main sink of inorganic carbon followed by sediment burial, emissions of CO2 to the atmosphere, and oyster sequestration. This study highlights the importance of determining the sources, sinks, and transformations of all carbon forms in constructing estuarine budgets.
The Propagation of Fluvial Flood Waves Through a Backwater‐Estuarine Environment
Authors: Dykstra S. L. , Dzwonkowski B. 
Published: December 2019

AbstractCoastal cities and ports are located along estuaries and deltas where flooding from rivers can be as devastating as storm surges. Precise river discharge measurements are taken far inland of marine influences and backwater environments, creating large timing and magnitude uncertainties downstream at the coast. Long‐term discharge, water level, velocity, and salinity measurements in coastal Alabama were used to observe the timing and magnitude of discharge events flowing 238 km from rivers to the Gulf of Mexico as river flood (fluvial) waves. Waves were described and simplified using a momentum balance, phasing techniques, and wave theory from inland rivers. Results showed the coastal backwater environment transitioned to a drawdown (i.e., plunging water profile) at bankfull discharge and suggested the drawdown location and intensity was strongly influenced by the frictional transition of the delta from tupelo‐cypress forest to oligohaline marsh. The horizontal (velocity) and vertical (water level) components of fluvial waves were observed propagating through this dynamic deltaic‐estuarine environment transitioning from in phase diffusive waves to out of phase dynamic waves. The wave celerity increased with surface water slope and decreased with cross‐sectional area. Instead of larger events propagating faster, the geometry (i.e., levees and floodplains) and flooding significantly delayed and attenuated the magnitude of discharge reaching the gulf. This flooding downstream of discharge measurements modulated the estuarine water level, velocity, and flushing of salt. The use of fluvial wave theory will increase the precision of coastal flooding predictions for stakeholders and research now, as well as under future sea level rise.
Pore‐Scale Modeling of Fluid‐Fluid Interfacial Area in Variably Saturated Porous Media Containing Microscale Surface Roughness
Authors: Jiang Hao , Guo Bo , Brusseau Mark L. 
Published: December 2019

AbstractA pore‐scale model is developed to simulate fluid‐fluid interfacial area in variably saturated porous media, with a specific focus on incorporating the effects of solid‐surface roughness. The model is designed to quantify total (film and meniscus) fluid‐fluid interfacial area (Anw) over the full range of wetting‐phase fluid saturation (Sw) based on the inherent properties of the porous medium. The model employs a triangular pore space bundle‐of‐cylindrical‐capillaries framework, modified with three surface roughness‐related parameters. The first parameter (surface roughness factor) represents the overall magnitude of surface roughness, whereas the other two parameters (interface growth factor and critical adsorptive film thickness) reflect the microscale structure of surface roughness. A series of sensitivity analyses were conducted for the controlling variables, and the efficacy of the model was tested using air‐water interfacial area data measured for three natural porous media. The model produced good simulations of the measured Anw data over the full range of saturation. The results demonstrate that total interfacial areas for natural media are typically much larger than those for ideal media comprising smooth surfaces due to the substantial contribution of surface roughness to wetting‐film interfacial area. The degree to which fluid‐fluid interfacial area is influenced by roughness is a function of fluid‐retention characteristics and the nature of the rough surfaces. The full impact of roughness may be masked to some degree due to the formation of thick wetting films, which is explicitly quantified by the model. Application of the model provides insight into the importance of the interplay between pore‐scale distribution and configuration of wetting fluid and the surface properties of solids.
Simulation of Gravitational Instability and Thermo‐Solutal Convection During the Dissolution of CO in Deep Storage Reservoirs
Authors: Singh Mrityunjay , Chaudhuri Abhijit , Stauffer Philip H , Pawar Rajesh J 
Published: December 2019

AbstractThe temperature of deep hydrothermal sedimentary reservoirs varies between 50 and 250 °C, while the temperature of injected CO
can be much below the reservoir temperature. Most past studies did not consider temperature effect on the CO
dissolution trapping in storage reservoirs. We have performed numerical simulations of coupled multiphase flow, solute, and heat transport for liquid/supercritical CO
injection in a storage reservoir for different reservoir temperature, injection temperature, and reservoir permeability. During the injection of relatively cool CO
in a warmer storage reservoir, brine density increases with CO
concentration causing solutal fingering in the diffusive boundary layer and the creation of an isolated dissolved CO
plume (gravity trunk) below the injection zone. We have found that in many cases, the formation of a gravity trunk creates a large convection roll beneath the injection point. For low and moderate reservoir temperatures (100 and 175 °C), solutal fingers are pulled towards the injection zone by the large gravity trunk convection roll. In contrast, for higher temperature reservoirs (>206 °C), brine density decreases with dissolved CO
concentration. Hence, for a reservoir temperature of 250 °C, solutal fingers do not develop, but reverse fingering from a dissolved CO
mound is visible. We conclude that dissolution trapping achieves greater effectiveness for a reservoir temperature of 175 °C than those at 100 and 250 °C. We have also observed that free‐phase CO
below the caprock spreads faster for higher reservoir temperature and higher permeability, but it is not sensitive to injection temperature.
Modified Capanna’s Technique (Vascularized Free Fibula Combined with Allograft) as a Single-Stage Procedure in Post-traumatic Long-Segment Defects of the Lower End of the Femur: Outcome Analysis of a Series of 19 Patients with an Average Gap of 14 cm
Authors: Jayaramaraju Dheenadhayalan , Venkataramani Hari , Rajasekaran Raja Bhaskara , Agraharam Devendra , Sabapathy Shanmuganathan Raja , Rajasekaran Shanmuganathan 
Published: December 2019

Abstract
Objectives Salvage and reconstruction of posttraumatic defects of the long bone are complex due to the multiple procedures involved and increased chances of poor outcomes. We present the outcomes of the modified Capanna’s technique—a reliable single-stage procedure of combining allograft and free vascularized fibular graft—in treating large posttraumatic bone defects in the distal third of the femur.
Study Design This is a retrospective analysis.
Materials and Methods Between April 2012 and September 2016, 19 patients with an average age of 33.8 years (range: 18–49 years) and an average defect of 14.5 cm (range: 9.5–20 cm) in the distal femur were managed by the modified Capanna’s technique. Bone union time and functional outcome using lower extremity functional score (LEFS) after union were noted.
Outcomes and Results Eighteen grafts went onto achieve bony union at an average of 6.6 months (range: 5–9), with an average knee flexion of 80 degrees (range: 45–110 degrees) and an average LEFS of 63 (range: 46–72). One patient had a nonunion with graft resorption at 8 months following persistent infection and was revised with debridement and augmenting the vascularized fibula from the other leg which went on to achieve union. Three patients had superficial infection, and three patients had delayed union.
Conclusion The modified Capanna’s technique provided increased biology and enhanced structural stability and therefore is a good single-stage procedure in the reconstruction of posttraumatic long-segment defects of the distal femur.
Level of Evidence Level 4.
Level of Clinical Care Level I tertiary trauma center.