bluuebunny/crossref_metadata_2025_split huggingface dataset:
Late Miocene Deformation Kinematics Along the NW Zagros Fold‐Thrust Belt, Kurdistan Region of Iraq: Constraints From Apatite (U‐Th)/He Thermochronometry and Balanced Cross Sections
Authors: Koshnaw Renas I. , Stockli Daniel F. , Horton Brian K. , Teixell Antonio , Barber Douglas E. , Kendall Jerome J. 
Published: November 2020

AbstractApatite (U‐Th)/He (AHe) thermochronometric results are integrated with geologic cross sections, structural relationships, and stratigraphic data to reconstruct the growth of the NW Zagros orogenic belt in the Kurdistan region of Iraq. Prolonged exhumation is documented across the belt with deformation advances and retreats from ~14 Ma onward. After in‐sequence propagation of deformation during middle to late Miocene times, preserved growth strata and AHe data show a deformation retreat by latest Miocene time (~5 Ma). In the NW Zagros, the Phanerozoic succession contains two principal décollements in Lower Triassic and middle Miocene units. The Triassic strata are interpreted as the main décollement for a thin‐skinned system that was dominant during most of the Cenozoic. By ~8–5 Ma, the fold‐thrust belt shifted to basement‐involved deformation in association with growth of the mountain front flexure and reactivation of frontal structures. The shift from thin‐skinned to a hybrid thin‐ and thick‐skinned mode of shortening may reflect variations in the mechanical behavior of the upper crust and the presence of inherited basement discontinuities. On the basis of two NE‐SW balanced cross sections spanning the NW Zagros, the estimated total minimum horizontal shortening is ~18.2 km (6%) in the central and ~16 km (7%) in the southern sectors of the Kurdistan region of Iraq. These findings suggest that the evolution of the NW Zagros orogenic belt was likely driven by the mechanical stratigraphy of the sedimentary cover, inherited basement discontinuities, and the dynamic and thermomechanical effects of potential slab breakoff and lithospheric mantle delamination events.
The USDA‐ARS Experimental Watershed Network: Evolution, Lessons Learned, Societal Benefits, and Moving Forward
Authors: Goodrich D. C. , Heilman P. , Anderson M. , Baffaut C. , Bonta J. , Bosch D. , Bryant R. , Cosh M. , Endale D. , Veith T. L. , Havens S. C. , Hedrick A. , Kleinman P. J. , Langendoen E. J. , McCarty G. , Moorman T. , Marks D. , Pierson F. , Rigby J. R. , Schomberg H. , Starks P. , Steiner J. , Strickland T. , Tsegaye T. 
Published: November 2020

AbstractThe U.S. Department of Agriculture‐Agricultural Research Service's (ARS) Experimental Watershed Network grew from Dust Bowl era efforts of the Soil Conservation Service in the mid‐1930s with the establishment of small experimental watersheds. In the 1950s, five watershed research centers with intensively instrumented watersheds at the scale of 100 to 700 km2 were established. Primary network research objectives were to quantify on‐site and downstream effects of conservation practices and develop rainfall‐runoff relationships for design of water conservation structures. With passage of the Clean Water Act in 1972, research objectives have evolved to add a variety of observations relevant to the water quality issues. Many of the watersheds within the network have served, and continue to serve, as core validation sites for satellite sensors. As a result of the network's long history and intensive monitoring, coupled with mission‐driven research, a deep knowledge base of watershed processes has been developed. This has led to the extensive development and validation of numerous watershed models that are in widespread use today. The visionary investments in building and maintaining this network and associated scientific investigations for more than half a century have not only resulted in numerous high‐impact research accomplishments but also a wide array of accomplishments that directly benefit society. The ARS Experimental Watersheds formed the core of the Conservation Effects Assessment Project (CEAP) as well as the recently established Long‐Term Agroecosystem Research (LTAR) network. LTAR will expand the mission of the ARS Watersheds Network to include agricultural intensification, maintaining or improving ecosystem services while enhancing rural prosperity.
ICESat‐2/ATLAS Onboard Flight Science Receiver Algorithms: Purpose, Process, and Performance
Authors: McGarry J. F. , Carabajal C. C. , Saba J. L. , Reese A. R. , Holland S. T. , Palm S. P. , Swinski J.‐P. A. , Golder J. E. , Liiva P. M. 
Published: November 2020

AbstractThe Advanced Topographic Laser Altimetry System (ATLAS) is the sole instrument on the Ice, Cloud, and land Elevation Satellite 2 (ICESat‐2). Without some method of reducing the transmitted data, the volume of ATLAS telemetry would far exceed the normal X‐band downlink capability or require many more ground station contacts. The ATLAS Onboard Flight Science Receiver Algorithms (hereinafter Receiver Algorithms or Algorithms) control the amount of science data that is telemetered from the instrument, limiting the data volume by distinguishing surface echoes from background noise, and allowing the instrument to telemeter data from only a small vertical region about the signal. This is accomplished through the transfer of the spacecraft's location and attitude to the instrument every second, use of an onboard Digital Elevation Model, implementation of signal processing techniques, and use of onboard relief and surface type reference maps. Extensive ground testing verified the performance of the Algorithms. On‐orbit analysis shows that the Algorithms are working as expected from the ground testing; they are performing well and meeting the mission requirements.
The State of the Art in Modeling Waterlogging Impacts on Plants: What Do We Know and What Do We Need to Know
Authors: Liu Ke , Harrison Matthew Tom , Shabala Sergey , Meinke Holger , Ahmed Ibrahim , Zhang Yunbo , Tian Xiaohai , Zhou Meixue 
Published: November 2020

AbstractModels are key tools in our quest to better understand the impacts of soil waterlogging on plant growth and crop production. Here, we reviewed the state of the art of modeling approaches and compared the conceptual design of these models with recent experimental findings. We show that many models adopt an aeration stress (AS) principle where surplus water reduces air‐filled porosity, with implications for root growth. However, subsequent effects of AS within each model vary considerably. In some cases, AS inhibits biomass accumulation (e.g. AquaCrop), altering processes prior to biomass accumulation such as light interception (e.g. APSIM), or photosynthesis and carbohydrate accumulation (e.g. SWAGMAN Destiny). While many models account for stage‐dependent waterlogging effects, few models account for experimentally observed delays in phenology caused by waterlogging. A model intercomparison specifically designed for long‐term waterlogged conditions (APSIM‐Oryza) with models developed for dryland conditions with transient waterlogging would advance our understanding of the current fitness for purpose of exsiting frameworks for simulating transient waterlogging in dryland cropping systems. Of the point‐based dynamic models examined here, APSIM‐Soybean and APSIM‐Oryza simulations most closely matched with the observed data, while GLAM‐WOFOST achieved the highest performance of the spatial‐regional models examined. We conclude that future models should incorporate waterlogging effects on genetic tolerance parameters such as (1) phenology of stress onset, (2) aerenchyma, (3) root hydraulic conductance, (4) nutrient‐use efficiency, and (5) plant ion (e.g. Fe/Mn) tolerance. Incorporating these traits/effects into models, together with a more systematic model intercomparison using consistent initialization data, will significantly improve our understanding of the relative importance of such factors in a systems context, including feedbacks between biological factors, emergent properties, and sensitive variables responsible for yield losses under waterlogging.
Mapping Artisanal and Small‐Scale Gold Mining in Senegal Using Sentinel 2 Data
Authors: Ngom N. M. , Mbaye M. , Baratoux D. , Baratoux L. , Catry T. , Dessay N. , Faye G. , Sow E. H. , Delaitre E. 
Published: November 2020

AbstractArtisanal and small‐scale gold mining (ASGM) represents a significant economic activity for communities in developing countries. In southeastern Senegal, this activity has increased in recent years and has become the main source of income for the local population. However, it is also associated with negative environmental, social, and health impacts. Considering the recent development of ASGM in Senegal and the difficulties of the government in monitoring and regulating this activity, this article proposes a method for detecting and mapping ASGM sites in Senegal using Sentinel 2 data and the Google Earth Engine. Two artisanal mining sites in Senegal are selected to test this approach. Detection and mapping are achieved following a processing pipeline. Principal component analysis (PCA) is applied to determine the optimal period of the year for mapping. Separability and threshold (SEaTH) is used to determine the optimal bands or spectral indices to discriminate ASGM from other land use. Finally, automatic classification and mapping of the scenes are achieved with support vector machine (SVM) classifier. The results are then validated based on field observations. The PCA and examination of spectral signatures as a function of time indicate that the best period for discriminate ASGM sites against other types of land use is the end of dry season, when vegetation is minimal. The classification results are presented as a map with different categories of land use. This method could be applied to future Sentinel scenes to monitor the evolution of mining sites and may also be extrapolated to other relevant areas in the Sahel.
Relation Between Shock‐Related Impulse and Subsequent ULF Wave in the Earth's Magnetosphere
Authors: Zhang Dianjun , Liu Wenlong , Li Xinlin , Sarris Theodore E. , Wang Yongfu , Xiao Chao , Zhang Zhao , Wygant John R. 
Published: November 2020

AbstractThe generation of Pc4‐5 ultralow frequency (ULF) waves after interplanetary shock‐induced electric field impulses in the Earth's magnetosphere is studied using Van Allen Probes measurements by investigating the relationship between the first impulses and subsequent resonant ULF waves. In the dayside, the relevant time scales of the first impulse is correlated better with local Alfvén speed than with local eigenfrequency, implying that the temporal scale of the first impulse is more likely related to fast‐mode wave propagation rather than local field line resonance. There are only 20 out of 51 events with narrow‐band poloidal ULF waves induced after the first impulse, showing a higher chance for ULF wave generation at the locations where the impulse equivalent frequency scale matches the local eigenfrequency. It is suggested that the shock‐related ULF wave can be excited in the magnetosphere on condition that shock‐induced impulse has large enough amplitude with its frequency matching the local eigenfrequency.
Moisture‐ Versus Wind‐Dominated Flavors of Atmospheric Rivers
Authors: Gonzales Katerina R. , Swain Daniel L. , Barnes Elizabeth A. , Diffenbaugh Noah S. 
Published: November 2020

AbstractAtmospheric rivers (ARs) are essential features of the global water cycle. Although AR definitions are commonly based on integrated vapor transport (IVT), ARs of a given IVT can induce a wide range of surface precipitation and wind impacts. We develop an AR “flavor” metric that partitions AR IVT into moisture‐dominant and wind‐dominant components. We use this metric to create a climatological catalog of “wet” and “windy” ARs along the U.S. West Coast from 1980 to 2016. Windy ARs are generally associated with stronger surface winds than are wet ARs, with the largest differences at low IVT. Windy ARs are also associated with greater daily precipitation totals than are wet ARs, with the difference widening at higher IVT, notably over mountainous regions. Pacific Northwest ARs have become increasingly moisture dominated over 1980–2016, which has important implications for western U.S. water availability and flood risk.
Temporal Evolution of Flux Tube Entanglement at the Magnetopause as Observed by the MMS Satellites
Authors: Qi Y. , Russell C. T. , Jia Ying‐Dong , Hubbert M. 
Published: November 2020

AbstractFlux transfer events (FTEs), as flux ropes (FRs), are considered key agents for solar wind energy to enter the terrestrial magnetosphere. Recent observations identify entangled flux tubes that collide and pull against each other. Reconnection occurs to disentangle and produce a new pair of FRs with different connectivity. In this paper, we examine the entanglement interface and how such an entanglement process evolves in time by comparing 17 entanglements observed by the Magnetospheric Multiscale (MMS) mission. The By‐dominated interplanetary magnetic field (IMF) distribution of the 17 events agrees with previous findings. We have identified three evolutionary stages characterized by the magnetic field and pressure enhancement. Our study confirms the FR nature of these events and explains how a disparate pair of ropes is formed from two entangled flux tubes, each initially connected to a different hemisphere of the magnetosphere.
Nonlinear Interactions Between Relativistic Electrons and EMIC Waves in Magnetospheric Warm Plasma Environments
Authors: Yu Jiang , Li L. Y. , Cui Jun , Cao J. B. , Wang Jing , He Zhaoguo , Yang Jian 
Published: November 2020

AbstractWith the kinetic dispersion relation and test particle simulation, we examine the effect of hot protons on the nonlinear interactions of relativistic electrons with electromagnetic ion cyclotron (EMIC) waves. We find that hot protons alter the refractive index of EMIC waves at a given wave frequency along latitude and thus modify resonance latitude. Consequently, resonance refractive index gradient along the magnetic field line, which plays a dominant role in controlling the electron behaviors, changes. Overall, the involvement of hot protons enlarges the resonance region (linear and nonlinear) but narrows the nonlinear resonance region. Additionally, hot protons weaken the electron phase bunching process and shift the electron phase trapping region to larger equatorial pitch angles. When the abundance or temperature anisotropy of hot protons increases, their effects on electron behaviors become more significant.
Multiple Technique Observations of the Ionospheric Responses to the 21 June 2020 Solar Eclipse
Authors: Zhang Ruilong , Le Huijun , Li Wenbo , Ma Han , Yang Yuyan , Huang He , Li Qiaoling , Zhao Xiukuan , Xie Haiyong , Sun Wenjie , Li Guozhu , Chen Yiding , Zhang Hui , Liu Libo 
Published: November 2020

AbstractWe investigate the ionospheric response to the 21 June 2020 annular solar eclipse using the multiinstrument observations including ionosondes, Global Navigation Satellite System (GNNS) receivers, COSMIC2, and DMSP and SWARM satellites. During the course of the eclipse, total electron content (TEC) decreased slightly in the morning at 20–70°E and largely in the afternoon at 80–150°E. However, maximum TEC depletion did not occur at the maximum obscuration, but stayed close to the southern edge of the running totality during the eclipse and near the northern edge of the elapsed totality after the eclipse. NmF2 showed the similar variation as TEC around 110°E. Meanwhile, a northward disturbance field‐aligned plasma drift was observed in the eclipse region and the disturbance became strong in the southern side of the totality around 120°E. The TEC and Swarm data revealed that the crests of the equatorial ionization anomaly (EIA) enhanced on both sides of the equator around noon in ~50–100°E although the northern crest was still in the Moon's shadow. The COSMIC2 profiles displayed the enhanced electron density in ~300–500 km altitudes and decreased density below ~300 km altitudes around the EIA crests in ~70°E. The Swarm observations recorded a drop in the electron temperature both in eclipse region and in conjugate hemisphere in 77°E and 96°E. The combined effect from the electric field, neutral wind, thermal conduction, and interhemispheric photoelectron transport might result in the complicated space and time variations of ionospheric responses to the eclipse.
Westward Electric Fields in the Afternoon Equatorial Ionosphere During Geomagnetically Quiet Times
Authors: Zhang Ruilong , Liu Libo , Yu You , Le Huijun , Chen Yiding 
Published: November 2020

AbstractThe daytime average zonal electric field is well known to be eastward in the equatorial ionosphere. Geomagnetic observations have revealed that the equatorial electrojet or zonal electric field occasionally becomes westward in the afternoon sector during quiet times. We present the first analysis of the dependence of the afternoon downward plasma drifts on the season, longitude, solar activity, and lunar phase using the ROCSAT‐1 satellite observations during 1999–2004. The results show that there are ~20% of downward plasma drifts at 13–17 LT. The occurrence rate of the downward plasma drift shows a peak around January and a secondary peak in July. The occurrence rate presents a slight decrease trend with the solar activity. Especially, the occurrence rate can attain ~40–50% around 60°E in June solstice and 145–245°E in December solstice, which is nearly comparable with the occurrence rate of the upward plasma drifts in these longitudes. The downward plasma drift occurs most frequently around the full moon in the afternoon sector. The geomagnetic declination induces the hemispheric differences in the dynamo current in the conjugate regions and controls the occurrence of the westward electric fields. A wavenumber‐4 longitudinal structure also appears to be present in the occurrence rate in June–September, and the wavenumber‐4 peak coincides with the diurnal eastward tidal wind, which drives the generation of the westward electric fields.
Pore‐Scale 3D Morphological Modeling and Physical Characterization of Hydrate‐Bearing Sediment Based on Computed Tomography
Authors: Wu Peng , Li Yanghui , Sun Xiang , Liu Weiguo , Song Yongchen 
Published: November 2020

AbstractNatural gas hydrate is considered to be a promising future energy resource; therefore, obtaining its physical properties is crucial for evaluating gas production efficiency and developing reasonable exploitation strategies. In this study, we present a novel pore‐scale 3D morphological modeling algorithm considering various saturation and occurrences (cementing and pore‐filling) of hydrate in sediments. To evaluate the performance of the presented algorithm, 14 hydrate‐bearing sediment models were constructed based on X‐ray computed tomographic images of a consolidated sandy specimen under an effective stress of 3 MPa. Morphologically, the new algorithm generated pore‐scale hydrate occurrences coincide with published morphological behaviors of hydrate observed via computed tomography. The tortuosity and fractal dimension of pore spaces of these models were then characterized. The pore networks are also extracted, based on which the evolution of the pore characteristics including the distributions of pore radius, throat radius, throat length, and the coordination number were investigated. Using these generated models, simulations of permeability, thermal conductivity, and electrical conductivity were conducted to evaluate the influences of hydrate saturation and occurrence. These results are validated against published data, demonstrating that this algorithm could be an effective way to construct digital hydrate‐bearing sediment models using a single set of computed tomographic images of a hydrate‐free specimen. This new method can also be significant for the physical evaluation of natural cores in which hydrate has dissociated during core recovering and transferring.
Assessment of Nitrogen Oxide Emissions and San Joaquin Valley PM2.5 Impacts From Soils in California
Authors: Guo Lei , Chen Jianjun , Luo Dongmin , Liu Shang , Lee Hyung Joo , Motallebi Nehzat , Fong Angel , Deng Jia , Rasool Quazi Z. , Avise Jeremy C. , Kuwayama Toshihiro , Croes Bart E. , FitzGibbon Michael 
Published: November 2020

AbstractSoils are a source of atmospheric nitrogen oxides (NOx), especially in regions with significant cropland where nitrogen (N) fertilizers are used to enhance crop yields. The magnitude of soil NOx emissions, however, varies substantially by region, depending on the local land use pattern and management activities. We estimated soil NOx emissions in California based on the DeNitrification‐DeComposition (DNDC) biogeochemical model, linked to a detailed spatial‐temporal differentiated California‐specific database. The DNDC‐generated surface fluxes were used in the Community Multiscale Air Quality (CMAQ) model to evaluate impacts of soil NOx emissions on formation of ambient particulate (PM2.5) nitrate in the San Joaquin Valley (SJV) where cropland is the dominant land use. The DNDC‐generated soil NOx emissions contribute approximately 1.1% of total anthropogenic NOx emissions in California, at an emission rate of roughly 24 t day−1 (as NO2) statewide and 9 t day−1 in the SJV. Cropland is the dominant source of soil NOx emissions in California, contributing nearly 60% of statewide soil NOx emissions, driven principally by fertilizer use. The PM2.5 nitrate concentrations simulated by CMAQ using the DNDC‐generated soil NOx emissions are compatible with those observed in the SJV, suggesting that soil NOx emissions have limited impacts on PM2.5 nitrate formation in the atmosphere. Our emission and air quality modeling results are further supported by long‐term ambient NOx‐to‐carbon monoxide (CO) and satellite NO2 data analyses in the SJV, which showed diurnal, monthly, and annual trends consistent with characteristics of NOx sources dominated by traffic combustion in both urban and agricultural regions.
Long‐Term Variability and Tendencies in Migrating Diurnal Tide From WACCM6 Simulations During 1850–2014
Authors: Ramesh K. , Smith Anne K. , Garcia Rolando R. , Marsh Daniel R. , Sridharan S. , Kishore Kumar K. 
Published: November 2020

AbstractLong‐term variability and tendencies in migrating diurnal tide (DW1) are investigated for the first time using a three‐member ensemble of historical simulations by NCAR's Whole Atmosphere Community Climate Model, latest Version 6 (WACCM6) for 1850–2014 (165 years). The model reproduces the climatological features of the tide in temperature (T), zonal wind (U), and meridional wind (V). The amplitudes peak in the upper mesosphere and lower thermosphere (above ~0.001 hPa) at the equator forT(~10 K) and over 20–30°N and S latitudes forU(~15 m/s) andV(~25 m/s). The contributions of solar cycle (SC), quasi biennial oscillation (QBO) at 10 and 30 hPa, El Niño–Southern Oscillation (ENSO), ozone depleting substances (ODS), carbon dioxide (CO2), and stratospheric sulfate aerosols (volcanic eruptions) to change in annual mean amplitudes are analyzed using multiple linear regression. The tidal amplitudes in three components show a long‐term increase in the upper stratosphere (0.95–10.7 hPa) and the upper mesosphere (0.0001–0.01 hPa), predominantly due to increasing CO2with a smaller contribution from the trend in ENSO. Interestingly, the global mean tidal amplitude inTdecreases sharply after 1950–1960 until 1995 and then increases in association with changes in ODSs. The seasonal differences in tidal responses to the above indices can be as large as the overall signals. All the responses are stronger in the upper mesosphere; however, there is also a pronounced negative response of temperature tide to ODSs over middle to high latitudes around the stratopause (~1 hPa) during all seasons.