bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lithospheric Structure of the Northern Ordos From Ambient Noise and Teleseismic Surface Wave Tomography
Authors: Li Shilin , Guo Zhen , Chen Yongshun John , Yang Yingjie , Huang Qinghua 
Published: July 2018

AbstractWe constructed a high‐resolution 3‐D Vs model of the northern Ordos block and its surrounding areas by surface wave tomography, which reveals significant intracratonic heterogeneities. In the western Ordos, the lithosphere thickness is ~200 km with shear velocities comparable to the high velocities of other Archean cratons worldwide. However, the lithosphere thins gradually toward the east and Vs drops by 2–3% in the uppermost mantle beneath the eastern Ordos, coincident with the high surface heat flow (~68 mW/m2 in average) there. This observation suggests that the thick, cratonic keel is only locally preserved beneath the western Ordos, and the eastern part of the Ordos seems to undergo local rejuvenation. At greater depths (>180 km), a low‐velocity channel is observed beneath the high‐velocity keel of the Ordos. Beneath the Datong volcanoes, a low‐velocity anomaly is observed, dipping westward with depth and closely following the slope of the lithosphere beneath the northern Ordos. This prominent low velocity is connected with the low‐velocity zone beneath the northern Ordos, which is further connected with the low‐velocity zone beneath the northeastern Tibetan Plateau (NET). We propose that the asthenosphere beneath the NET flows toward the northern Ordos in response to the continuous northward convergence of the Indian‐Eurasian continents, and the asthenosphere flows upward following the eastward thinning lithosphere which leads to decompression partial melting, which migrates upward to feed the Datong volcanoes. The significant variations of the lithospheric thickness of the Ordos block may control the distribution of the asthenospheric flow.
Constraining Frictional Properties on Fault by Dynamic Rupture Simulations and Near‐Field Observations
Authors: Weng Huihui , Yang Hongfeng 
Published: July 2018

AbstractFrictional properties of seismogenic faults play critical roles in earthquake generation and rupture propagation. Although laboratory measurements have well revealed the frictional parameters of a variety of rock samples, those on seismogenic faults remain difficult to determine due to the strong trade‐off between critical slip‐weakening distance (d0) and strength drop. Here we conduct dynamic rupture simulations to determine the frictional parameters on the fault where the 2015 Mw7.8 Nepal earthquake occurred, with constraints from near‐field seismic and geodetic observations, and kinematic source models. By utilizing different trade‐off patterns of source parameters and multiple observations for the first time, we can determine the frictional parameters of the seismogenic fault. The best fit dynamic model yields a d0value of ~0.6 m, in contrast to the previous kinematical estimation of ~5 m (Galetzka et al., 2015, https://doi.org/10.1126/science.aac6383). The average fracture energy of this event is
J/m2. Such approach can be used to determine the frictional parameters on seismogenic faults, which could serve for seismic hazard assessment by predicting ground motion from dynamic rupture simulations.
Lidar Observations of Stratospheric Gravity Waves From 2011 to 2015 at McMurdo (77.84°S, 166.69°E), Antarctica: 2. Potential Energy Densities, Lognormal Distributions, and Seasonal Variations
Authors: Chu Xinzhao , Zhao Jian , Lu Xian , Harvey V. Lynn , Jones R. Michael , Becker Erich , Chen Cao , Fong Weichun , Yu Zhibin , Roberts Brendan R. , Dörnbrack Andreas 
Published: July 2018

AbstractFive years of Fe Boltzmann lidar's Rayleigh temperature data from 2011 to 2015 at McMurdo are used to characterize gravity wave potential energy mass density (Epm), potential energy volume density (Epv), vertical wave number spectra, and static stability N2 in the stratosphere 30–50 km. Epm (Epv) profiles increase (decrease) with altitude, and the scale heights of Epv indicate stronger wave dissipation in winter than in summer. Altitude mean
and
obey lognormal distributions and possess narrowly clustered small values in summer but widely spread large values in winter.
and
vary significantly from observation to observation but exhibit repeated seasonal patterns with summer minima and winter maxima. The winter maxima in 2012 and 2015 are higher than in other years, indicating interannual variations. Altitude mean
varies by ~30–40% from the midwinter maxima to minima around October and exhibits a nearly bimodal distribution. Monthly mean vertical wave number power spectral density for vertical wavelengths of 5–20 km increases from summer to winter. Using Modern Era Retrospective Analysis for Research and Applications version 2 data, we find that large values of
during wintertime occur when McMurdo is well inside the polar vortex. Monthly mean
are anticorrelated with wind rotation angles but positively correlated with wind speeds at 3 and 30 km. Corresponding correlation coefficients are −0.62, +0.87, and +0.80, respectively. Results indicate that the summer‐winter asymmetry of
is mainly caused by critical level filtering that dissipates most gravity waves in summer.
variations in winter are mainly due to variations of gravity wave generation in the troposphere and stratosphere and Doppler shifting by the mean stratospheric winds.
A Study of Soil Thermal and Hydraulic Properties and Parameterizations for CLM in the SRYR
Authors: Chen Jinlei , Wen Jun , Tian Hui , Zhang Tangtang , Yang Xianyu , Jia Dongyu , Lai Xin 
Published: July 2018

AbstractLocated in the northeast part of the Qinghai‐Tibet Plateau, the source region of the Yellow River is a crucial water conservation area. Laboratory tests and observations are used to determine the soil thermal and hydraulic properties in this key area. Furthermore, their physical processes in the Community Land Model (CLM) are revised to better apply to the plateau. The main results are as follows. (1) The thermal conductivity in frozen soil is mainly controlled by the content of air and is positively correlated with subzero temperatures (−5 to −20 °C); however, it slightly increases with increasing temperature (5 to 20 °C) in thawed soil, and obvious layering exists. The influence of temperature can be ignored for dry soil. (2) The thermal conductivity of thawed soil is positively correlated with water content and shows a nonlinear variation. The rate of increase is rapid during the early stage of thawing and then slows. (3) The saturated hydraulic conductivity decreases with depth. Soil matric potential exhibits large fluctuations and is spatially heterogeneous due to the feedback to soil moisture. (4) The simulation differences of soil temperature and moisture are narrowed to approximately 1 °C and by half, respectively, by the revised schemes in CLM4.5. The simulation of energy fluxes and ground temperature also improved, but the latent heat flux performed less well due to the deficiencies in the hydraulic schemes. This study is of great significance for research on land surface processes and the application of the CLM in the Qinghai‐Tibet Plateau.
Impact of the Generation and Activation of Sea Salt Aerosols on the Evolution of Tropical Cyclone Dumile
Authors: Hoarau T. , Barthe C. , Tulet P. , Claeys M. , Pinty J.‐P. , Bousquet O. , Delanoë J. , Vié B. 
Published: July 2018

AbstractAn original coupling between an aerosol scheme and a two‐moment microphysics scheme has been developed in the cloud‐resolving model Meso‐NH to fully represent the aerosol‐microphysics‐dynamics interactions in tropical cyclones. A first evaluation of this coupling is performed through the simulation of tropical cyclone Dumile (2013) in the South‐West Indian Ocean. MACC (Monitoring Atmospheric Composition and Climate project) analysis and CALIPSO (Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations) data agree about the predominance of sea salt aerosols. The aerosol‐microphysics coupled system reproduces the track and intensity of Dumile well, with a transition from a monsoon depression to a tropical cyclone, and produces ice water contents that compare well with the DARDAR (raDAR/liDAR) product. Using a one‐moment microphysics scheme produces a more intense and symmetric system tracking too far to the west. In the aerosol‐microphysics coupled simulation, sea salt aerosols, the main source of cloud condensation nuclei (CCN), are preferentially produced in regions with high winds and waves, which reinforce convective asymmetries compared to the simulation with the one‐moment scheme. Using a two‐moment microphysics scheme without explicit sea salt emission led to a dramatic weakening of Dumile after 24 hr of simulation due to the consumption and scavenging of all interstitial CCN in the inner core. The importance of explicitly taking account of sea salt aerosol emissions associated with high winds and waves in tropical cyclones is a critical point for simulating long‐lasting systems that need to generate their own CCN.
A Billion Tons of Unaccounted for Carbon in the Southeastern United States
Authors: Gonzalez Yaslin N. , Bacon Allan R. , Harris Willie G. 
Published: July 2018

AbstractBecause Earth's soil contains more carbon than the atmosphere and all terrestrial vegetation combined, forecasting and managing the global carbon cycle in the face of natural and anthropogenic change requires accurate representations of this carbon. Here from regional geomorphic and soil databases, we characterize the mass, distribution, and cycling of previously unaccounted for soil carbon across the southeastern U.S. Coastal Plain, referred to as “deep‐podzolized carbon.” We show that geomorphologic‐hydrologic interactions stabilize approximately 1.1 × 10−9 t of deep‐podzolized carbon (equivalent to roughly 18% of the soil organic carbon stored across the entire region from 0–30 cm), and that this potentially ancient carbon is predictably distributed coincident with Pleistocene marine transgressions. We not only redefine soil carbon storage in the region but we also introduce the Earth Sciences to a massive organic carbon pool that interacts with landscape evolution and hydrology, has essentially never been studied, and is ripe for interdisciplinary research.
Vertical Structure of Diurnal Englacial Hydrology Cycle at Helheim Glacier, East Greenland
Authors: Vaňková Irena , Voytenko Denis , Nicholls Keith W. , Xie Surui , Parizek Byron R. , Holland David M. 
Published: July 2018

AbstractThe interior dynamics of Helheim Glacier were monitored using an autonomous phase‐sensitive radio‐echo sounder (ApRES) during two consecutive summers. The return signals from all observational sites exhibited strong non‐tidal, depth‐dependent diurnal variations. We show that these variations in the glacier interior can be explained by an englacial diurnal meltwater cycle: a data interpretation that assumes constant ice‐column composition through time leads to dynamical inconsistencies with concurrent observations from GPS and terrestrial radar. The observed diurnal meltwater cycle is spatially variable, both between different sites and in the vertical, consistent with the existence of a dense and complex englacial hydrologic network. Future applications of this observational technique could reveal long‐term meltwater behavior inside glaciers and ice sheets, leading to an improved understanding of the spatiotemporal evolution of the basal boundary conditions needed to simulate them realistically.
Development and Recovery of Stress‐Induced Elastic Anisotropy During Cyclic Loading Experiment on Westerly Granite
Authors: Passelègue François. X. , Pimienta Lucas , Faulkner Daniel , Schubnel Alexandre , Fortin Jérôme , Guéguen Yves 
Published: July 2018

AbstractIn the upper crust, where brittle deformation mechanisms dominate, the development of crack networks subject to anisotropic stress fields generates stress‐induced elastic anisotropy. Here a rock specimen of Westerly granite was submitted to differential stress cycles (i.e., loading and unloading) of increasing amplitudes, up to failure and under upper crustal conditions. Combined records of strains, acoustic emissions, and P and S elastic wave anisotropies demonstrate that increasing differential stress promotes crack opening, sliding, and propagation subparallel to the main compressive stress orientation. However, the significant elastic anisotropies observed during loading (≥20%) almost vanish upon stress removal, demonstrating that in the absence of stress, crack‐related elastic anisotropy remains limited (≤10%). As a consequence, (i) crack‐related elastic anisotropies measured in the crust will likely be a strong function of the level of differential stress, and consequently (ii) continuous monitoring of elastic wave velocity anisotropy along faults could shed light on the mechanism of stress accumulation during interseismic loading.
Microseismicity Simulated on Asperity‐Like Fault Patches: On Scaling of Seismic Moment With Duration and Seismological Estimates of Stress Drops
Authors: Lin Yen‐Yu , Lapusta Nadia 
Published: July 2018

AbstractObservations show that microseismic events from the same location can have similar source durations but different seismic moments, violating the commonly assumed scaling. We use numerical simulations of earthquake sequences to demonstrate that strength variations over seismogenic patches provide an explanation of such behavior, with the event duration controlled by the patch size and event magnitude determined by how much of the patch area is ruptured. We find that stress drops estimated by typical seismological analyses for the simulated sources significantly increase with the event magnitude, ranging from 0.006 to 8 MPa. However, the actual stress drops determined from the on‐fault stress changes are magnitude‐independent and ~3 MPa. Our findings suggest that fault heterogeneity results in local deviations in the moment‐duration scaling and earthquake sources with complex shapes of the ruptured area, for some of which stress drops may be significantly (~100–1,000 times) underestimated by the typical seismological methods.
Curiosity's Investigation of the Bagnold Dunes, Gale Crater: Overview of the Two‐Phase Scientific Campaign and Introduction to the Special Collection
Authors: Lapotre M. G. A. , Rampe E. B. 
Published: July 2018

AbstractBetween November 2015 and April 2017, Curiosity performed the first in situ investigation of an extraterrestrial dune field—the active Bagnold Dunes of Gale crater, Mars. The campaign consisted of two phases: Phase 1 occurred in southern fall/winter at Namib and High Dunes, two barchan dunes along the trailing edge of the dune field; Phase 2 occurred in southern summer at the Nathan Bridges Dune, a linear dune, and Mount Desert Island, a ripple field along the southern margin of the dune field. Both phases included a suite of observations and measurements that bear significance to our understanding of modern winds, associated sand fluxes, bedform morphology, and physical properties, composition, provenance, and sorting of eolian materials. Altogether, results described in a total of 26 manuscripts (11 of which are presented in this special collection) define the current understanding of Martian eolian processes at subdune scales, complementing previous orbiter‐based studies that encompassed larger scales.
Effect of Disturbance Electric Fields on Equatorial Electrojet Over Indian Longitudes
Authors: Bulusu Jayashree , R. K. Archana , Arora Kusumita , Chandrasekhar N. Phani , Nagarajan Nandini 
Published: July 2018

AbstractPrompt penetration (PP) and ionospheric disturbance dynamo (Ddyn) are two expressions of the disturbed electric field developed during a geomagnetic storm in the Earth's ionosphere. Earlier investigations treated these two processes independently over longitudinal separation beyond 20°. In the present study, we investigate the conjunction of these phenomena on equatorial electrojet at 20° longitude separations using daytime magnetic field data from three equatorial sites viz., Minicoy, Vencode, and Campbell Bay and three low‐latitude sites viz., Alibag, Hyderabad, and Nabagram, located within 20° longitude over Indian region, during three intense storms (Dst <− 150 nT). We propose a statistical method to identify PP signatures from large data set. In addition, we distinguish the signatures of PP and Ddyn during early recovery phase of intense storms and compute pure Ddyn signature in the late recovery phase. It is seen that the effect of PP is similar at the three equatorial sites for each storm. We find that signatures of Ddyn are amplified at Minicoy and Vencode compared to Campbell Bay, and their magnitude decreases toward low‐latitude stations, also reflected in the current vector patterns. Our investigations of intense geomagnetic storms show that PP effect dominates the main phase, followed by a combined effect of PP and Ddyn in the early recovery phase. Eventually the Ddyn signature dominates in the late recovery phase with decreasing amplitudes of Ddyn with increasing time. Such investigations can provide new information about variations in ionospheric parameters.
Longitudinal Dependence of Whistler Mode Electromagnetic Waves in the Earth's Inner Magnetosphere
Authors: Záhlava J. , Němec F. , Santolík O. , Kolmašova I. , Hospodarsky G. B. , Parrot M. , Kurth W. S. , Bortnik J. , Kletzing C. 
Published: July 2018

AbstractWe use the measurements performed by the DEMETER (2004–010) and the Van Allen Probes (2012–016, still operating) spacecraft to investigate the longitudinal dependence of the intensity of whistler mode waves in the Earth's inner magnetosphere. We show that a significant longitudinal dependence is observed inside the plasmasphere on the nightside, primarily in the frequency range 400 Hz to 2 kHz. On the other hand, almost no longitudinal dependence is observed on the dayside. The obtained results are compared to the lightning occurrence rate provided by the Optical Transient Detector/Lightning Imaging Sensor mission normalized by a factor accounting for the ionospheric attenuation. The agreement between the two dependencies indicates that lightning‐generated electromagnetic waves may be responsible for of the observed effect, thus substantially affecting the overall wave intensity in the given frequency range. Finally, we show that the longitudinal dependence is most pronounced for waves with oblique wave of normal angles.
Statistical Properties of Mesoscale Plasma Flows in the Nightside High‐Latitude Ionosphere
Authors: Gabrielse Christine , Nishimura Yukitoshi , Lyons Larry , Gallardo‐Lacourt Beatriz , Deng Yue , Donovan Eric 
Published: July 2018

AbstractThe field of space weather has made great strides in understanding and simulating large‐scale, global responses of the Earth's upper atmosphere to various inputs from the Sun; however, the mesoscale phenomena (~30–500 km wide) that are much more dynamic and powerful in the coupled system have remained uncharacterized. We therefore present key parameters of mesoscale ionospheric plasma flows in order to evaluate their relationship within the coupled system and to inform global models. We characterize mesoscale plasma flow properties in the nightside polar cap and auroral oval using nine years of Super Dual Auroral Radar Network (SuperDARN) line‐of‐sight velocity data from the stations at Rankin Inlet and Saskatoon. We quantify their width, velocity, occurrence rates, duration, and orientation, and how these characteristics depend on latitude, magnetic local time (MLT), season, substorm activity (AL), solar cycle (F10.7), and interplanetary magnetic field (IMF) clock angle. Measuring the ionospheric footpoint of magnetospheric fast flows, our analysis technique from the ground also provides a 2‐D picture of flows and their characteristics that spacecraft alone cannot provide. Results include a characteristic equatorward flow width of ~180 km in the polar cap and ~140–150 km in the auroral oval. Flow velocities vary under the different conditions we studied. Equatorward polar cap flows and poleward flows everywhere have a postmidnight preference, suggesting a connection to polar cap arcs. Equatorward auroral oval flows have a premidnight preference, suggesting a connection to substorm‐related phenomena. The location and orientation of mesoscale flows dependent on IMF clock angle suggests that mesoscale flows follow the large‐scale background convection.
Generation of Electron Whistler Waves at the Mirror Mode Magnetic Holes: MMS Observations and PIC Simulation
Authors: Ahmadi N. , Wilder F. D. , Ergun R. E. , Argall M. , Usanova M. E. , Breuillard H. , Malaspina D. , Paulson K. , Germaschewski K. , Eriksson S. , Goodrich K. , Torbert R. , Le Contel O. , Strangeway R. J. , Russell C. T. , Burch J. , Giles B. 
Published: July 2018

AbstractThe Magnetospheric Multiscale mission has observed electron whistler waves at the center and at the edges of magnetic holes in the dayside magnetosheath. The magnetic holes are nonlinear mirror structures since their magnitude is anticorrelated with particle density. In this article, we examine the growth mechanisms of these whistler waves and their interaction with the host magnetic hole. In the observations, as magnetic holes develop and get deeper, an electron population gets trapped and develops a temperature anisotropy favorable for whistler waves to be generated. In addition, the decrease in magnetic field magnitude and the increase in density reduce the electron resonance energy, which promotes the electron cyclotron resonance. To investigate this process, we used expanding box particle‐in‐cell simulations to produce the mirror instability, which then evolve into magnetic holes. The simulation shows that whistler waves can be generated at the center and edges of magnetic holes, which reproduces the primary features of the MMS observations. The simulation shows that the electron temperature anisotropy develops in the center of the magnetic hole once the mirror instability reaches its nonlinear stage of evolution. The plasma is then unstable to whistler waves at the minimum of the magnetic field structures. In the saturation regime of mirror instability, when magnetic holes are developed, the electron temperature anisotropy appears at the edges of the holes and electron distributions become more isotropic at the magnetic field minimum. At the edges, the expansion of magnetic holes decelerates the electrons, which leads to temperature anisotropies.