bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Energetic Electron Precipitation on the Northern Polar Vortex: Explaining the QBO Modulation via Control of Meridional Circulation
Authors: Salminen A. , Asikainen T. , Maliniemi V. , Mursula K. 
Published: May 2019

AbstractEnergetic electron precipitation (EEP) affects the high‐latitude middle atmosphere by producing NOX compounds that destroy ozone. Earlier studies have shown that in the wintertime polar stratosphere, increased EEP enhances the westerly wind surrounding the pole, the polar vortex. This EEP effect has been found to depend on the quasi‐biennial oscillation (QBO) of equatorial winds, but the mechanism behind this modulation has so far remained unresolved. In this study we examine the atmospheric effect of EEP and its modulation by QBO using the corrected electron flux measurements by NOAA/POES satellites and the ERA‐Interim reanalysis data of zonal wind, temperature, and ozone in winter months of 1980–2016. We verify the EEP‐related strengthening of the polar vortex, warming (cooling) in the upper (lower) stratosphere and a reduction of ozone mass mixing ratio in the polar stratosphere. We also verify that the EEP effect is stronger and more significant especially in late winter, when the QBO at 30 hPa is easterly. We find here that the difference in the EEP effect between the two QBO phases is largest using a roughly 6‐month lag for QBO. We demonstrate that ozone mass mixing ratio in the lower polar stratosphere, a proxy for the strength of Brewer‐Dobson circulation, is also larger during QBO‐E than QBO‐W, with the difference maximizing when the QBO is lagged by 6 months. Our findings indicate that the modulation of the Brewer‐Dobson circulation by QBO controls how the EEP affects the polar vortex.
Influence of Black Carbon Aerosol on the Atmospheric Instability
Authors: Talukdar Shamitaksha , Venkat Ratnam M. , Ravikiran V. , Chakraborty Rohit 
Published: May 2019

AbstractTo date, influence of aerosols on the atmospheric stability and hence on the convection/precipitation is not well understood. From the detailed analysis carried out using high‐accuracy radiosonde and Aethalometer measurements, a significant decrease in the convective available potential energy has been noticed in association with the increase in surface concentration of black carbon (BC) for a restricted range of precipitable water vapor and under similar environmental background (wind speed, direction, and cloud cover) over Gadanki (13.5°N, 79.2°E), a tropical rural site in southern peninsular India. A number of case studies along with statistical analysis indicate a notable perturbation in the temperature profile associated with high‐surface BC concentration conditions compared to the regional mean concentration of the same. A discernible fall in the temperature lapse rate within and above the local boundary layer in association with the higher BC concentration has been observed, which in turn reduces the available potential energy for convection decreasing the positive buoyancy required for a rising moist air parcel. This observation has been noticed over a nonurban location, but the phenomenon is not location dependent and is more applicable to the urban regions where BC concentration is likely to be much higher.
Capillary Length and Field Capacity in Draining Soil Profiles
Authors: Aldrees A. , Nachabe M. 
Published: May 2019

AbstractThe capillary length (λs) and time (ts) are dynamic scalars that emerge routinely in the infiltration problem when gravitational and pressure gradients forces are involved. During drainage, however, capillary gradients oppose gravity and retain soil moisture close to surface. In this case, the pull of capillary gradients increases with drainage time and offsets gravity resulting in a quasi‐hydrostatic pressure distribution and negligibly small drainage flux in the profile. In this paper, it is proposed to anchor the dynamic concept of field capacity—the attainment of a small negligible drainage flux—in the physics of soil moisture redistribution as influenced by gravity and capillary forces. Similar to infiltration, this dynamic approach grounds the concept of field capacity in soil hydrology and allows its estimation from readily measured intrinsic physical characteristics such as λs, ts, and Ks. Finally, we exploit an analytical solution by Broadbridge and White (1988, https://doi.org/10.1029/WR024i001p00145) to track the drainage front as soil water redistributes in an initially saturated soil profile. While initially large, the downward migrating drainage front decelerates with time reaching near steady state condition at t ≈ 1,000ts. Quasi‐hydrostatic pressure matric head and water content profiles develop above the drainage front.
Risks and Causes of Population Exposure to Cumulative Fine Particulate (PM2.5) Pollution in China
Authors: Han Lijian , Zhou Weiqi , Pickett Steward T. A. , Li Weifeng , Qian Yuguo 
Published: May 2019

AbstractChina's policy on atmospheric pollution is changeable in recent years. The single‐year estimated population exposure to air pollution is widely used in China where has the largest population and the heaviest fine particulate (PM2.5) pollution worldwide. However, the single‐year estimate introduces considerable uncertainty and loses consideration on multiyear cumulative exposure, thus may underestimate the burden of disease and mislead decisions regarding environmental conservation. We thus estimate the cumulative population exposure to PM2.5 pollution from 2000 to 2015. Areas with PM2.5 > 35 μg/m3 within China's territory increased from an average of 39% (2000–2005) to 42% (2006–2015), causing 471.6 million population at 58.8 × 104 km2 were exposed to 16 years' cumulative exposure to PM2.5 > 35 μg/m3. The migrant population contributed a major proportion of the increased population exposure, especially in East China's rapidly urbanizing areas. Cumulative population exposure to air pollution would provide a better understanding on the long‐term health risk and may suggest to a long, stable, and effective environmental protection regulation and policy should be carried out in China.
The Infrastructure Trolley Problem: Positioning Safe‐to‐fail Infrastructure for Climate Change Adaptation
Authors: Kim Yeowon , Chester Mikhail V. , Eisenberg Daniel A. , Redman Charles L. 
Published: May 2019

AbstractMotivated by the need for cities to prepare for and adapt to climate change, we advance the paradigm of safe‐to‐fail by focusing on the decision dilemmas and the consideration of infrastructure failure consequences in developing infrastructure. Infrastructures are largely designed as fail‐safe; that is, they are not intended to fail, and when failure happens, the consequences are severe. Safe‐to‐fail has been recently presented as the antithesis of fail‐safe, without any specific guidance of what the paradigm is or how to apply it. There is an emerging need for stakeholders, including policy makers, planners, engineers, utilities, and communities to understand infrastructure failures, bring their knowledge into the infrastructure development process, and help adapt cities to unpredictable and changing climate risks. We frame safe‐to‐fail as an infrastructure development paradigm that internalizes the consequences of infrastructure failure in the development process. This framing of safe‐to‐fail further reveals an emerging “infrastructure trolley problem” where the adaptive capacity of some regions is improved at the expense of others. We demonstrate practical dilemmas in developing infrastructure under nonstationary climate and guide managing trade‐offs in the prioritization of different consequences of infrastructure failure.
Strain Rate Distribution in South‐Central Tibet From Two Decades of InSAR and GPS
Authors: Wang Hua , Wright Tim J. , Liu‐Zeng Jing , Peng Lincai 
Published: May 2019

AbstractThe degree to which deformation and seismicity is focused on major mapped structures remains a key unknown in assessing seismic hazards and testing continental deformation models. Here we combine 208 Global Positioning System (GPS) velocities with 12‐track Interferometric Synthetic Aperture Radar (InSAR) rate maps to form high‐resolution velocity and strain rate fields for south‐central Tibet. Our results show that deformation is not evenly distributed across the region. We find a few zones with high strain rates, most notably the Yutian‐Zhongba strain rate zone. However, the average of the strain rates is similar within and outside the mapped fault zones. In addition, the slip rates are low on all the conjugate strike‐slip faults widespread in central Tibet. The observations are difficult to reconcile with time‐invariant block models or with continuum models that lack mechanisms for strain localization. Our results support arguments that the most robust estimates of seismic hazard should integrate seismicity catalogues, active fault maps, and geodetic strain rate models.
Melting Experiments on Liquidus Phase Relations in the Fe‐S‐O Ternary System Under Core Pressures
Authors: Yokoo Shunpei , Hirose Kei , Sinmyo Ryosuke , Tagawa Shoh 
Published: May 2019

AbstractMelting experiments on the Fe‐S‐O ternary system were performed to 208 GPa in a laser‐heated diamond‐anvil cell. Compositions of liquids and coexisting solids in recovered samples were examined using a field‐emission‐type electron microprobe. The results demonstrate that the ternary eutectic point shifts toward the oxygen‐rich, sulfur‐poor side with increasing pressure, in accordance with changes in eutectic liquid compositions in the Fe‐O and Fe‐S binary systems. We also found that solid Fe crystallizing from liquid Fe‐S‐O does not include oxygen, while the partitioning of sulfur into solid Fe is enhanced with increasing pressure. These indicate that oxygen‐rich, sulfur‐poor liquid crystallizes Fe at the inner core boundary; however, it makes a large density difference between the liquid and solid core, which is inconsistent with observations. Alternatively, we found that a range of C‐bearing, S‐poor/O‐rich liquids account for the density and velocity in the outer core and the density in the inner core.
The 2017–2018 Maple Creek Earthquake Sequence in Yellowstone National Park, USA
Authors: Pang Guanning , Koper Keith D. , Hale J. Mark , Burlacu Relu , Farrell Jamie , Smith Robert B. 
Published: May 2019

AbstractWe explore the detailed spatiotemporal evolution of 3,345 earthquakes that occurred near Maple Creek, Yellowstone, for the time period of 12 June 2017 to 13 March 2018. We generate high‐accuracy relocations and near source VP/VS ratios using 4.4 million P wave and S wave differential travel times derived from waveform cross correlation. The hypocenters can be subdivided geographically into two major subpopulations: a northern cluster with planar structures striking mainly NW‐SE and a southern cluster with planar structures striking mainly E‐W. We observe VP/VS ratios of 1.39–1.66 in the northern cluster and a steady ratio of 1.50 in the southern cluster, suggesting the presence of CO2‐filled cracks. We interpret the northern earthquake cluster primarily as long‐lived aftershocks of the 1959 Mw 7.2 Hebgen Lake earthquake but with some influence of magmatic fluids. We interpret the southern earthquake cluster as a more classic, swarm‐like sequence induced primarily by the migration of magmatic fluids.
Modeling a Transient Secondary Paleolunar Atmosphere: 3‐D Simulations and Analysis
Authors: Aleinov I. , Way M. J. , Harman C. , Tsigaridis K. , Wolf E. T. , Gronoff G. 
Published: May 2019

AbstractThe lunar history of water deposition, loss, and transport postaccretion has become an important consideration in relation to the possibility of a human outpost on the Moon. Very recent work has shown that a secondary primordial atmosphere of up to 10 mbar could have been emplaced ∼3.5×109 years ago due to volcanic outgassing from the maria. Using a zero‐dimensional chemistry model, we demonstrate the temperature dependence of the resulting major atmospheric components (CO or CO2). We use a three‐dimensional general circulation model to test the viability of such an atmosphere and derive its climatological characteristics. Based on these results, we then conjecture on its capability to transport volatiles outgassed from the maria to the permanently shadowed regions at the poles. Our preliminary results demonstrate that atmospheres as low as 1 mbar are viable and that permanent cold trapping of volatiles is only possible at the poles.
Source Complexity of the 2015 Mw 4.0 Guthrie, Oklahoma Earthquake
Authors: Wu Qimin , Chen Xiaowei , Abercrombie Rachel E. 
Published: May 2019

AbstractWe demonstrate the complex source process of a potentially induced Mw 4.0 earthquake near Guthrie, Oklahoma. Relative source time functions (RSTFs), retrieved using a time domain empirical Green's function (EGF) deconvolution method, show clear evidence of rupture complexity with the presence of multiple pulses and systematic azimuthal variations. Directivity analysis reveals a well‐defined rupture propagation at ~120° toward the southeast. Detailed modeling of the RSTFs results in a four‐subevent model spanning ~1 s in time and ~1.5 km in space, in which the earthquake ruptured four successive slip episodes unilaterally to the southeast. Multiple EGF spectral ratio analysis also shows significant complexity as evidenced by azimuth‐dependent deviations from the omega‐square (Brune) model. The observations of the concentration of early aftershocks at the periphery of the inferred rupture model along the rupture direction and amplified ground motions at stations to the southeast can both be well explained by the directivity effect.
EMIC Waves Converted From Equatorial Noise Due to M/Q = 2 Ions in the Plasmasphere: Observations From Van Allen Probes and Arase
Authors: Miyoshi Y. , Matsuda S. , Kurita S. , Nomura K. , Keika K. , Shoji M. , Kitamura N. , Kasahara Y. , Matsuoka A. , Shinohara I. , Shiokawa K. , Machida S. , Santolik O. , Boardsen S. A. , Horne R. B. , Wygant J. F. 
Published: May 2019

AbstractEquatorial noise (EN) emissions are observed inside and outside the plasmapause. EN emissions are referred to as magnetosonic mode waves. Using data from Van Allen Probes and Arase, we found conversion from EN emissions to electromagnetic ion cyclotron (EMIC) waves in the plasmasphere and in the topside ionosphere. A low‐frequency part of EN emissions becomes EMIC waves through branch splitting of EN emissions, and the mode conversion from EN to EMIC waves occurs around the frequency of M/Q = 2 (deuteron and/or alpha particles) cyclotron frequency. These processes result in plasmaspheric EMIC waves. We investigated the ion composition ratio by characteristic frequencies of EN emissions and EMIC waves and obtained ion composition ratios. We found that the maximum composition ratio of M/Q = 2 ions is ~10% below 3,000 km. The quantitative estimation of the ion composition will contribute to improving the plasma model of the deep plasmasphere and the topside ionosphere.
Is There a Classical Inertial Sublayer Over the Amazon Forest?
Authors: Dias‐Júnior Cléo Quaresma , Dias Nelson Luís , dos Santos Rosa Maria N. , Sörgel Matthias , Araújo Alessandro , Tsokankunku Anywhere , Ditas Florian , de Santana Raoni Aquino , von Randow Celso , Sá Marta , Pöhlker Christopher , Toledo Machado Luiz Augusto , de Sá Leonardo Deane , Moran‐Zuloaga Daniel , Janssen Ruud , Acevedo Otávio , Oliveira Pablo , Fisch Gilberto , Chor Tomas , Manzi Antonio 
Published: May 2019

AbstractOn the basis of measurements over different surfaces, an inertial sublayer (ISL), where Monin‐Obukhov Similarity Theory applies, exists above z=3h, where h is canopy height. The roughness sublayer is within h<z<3h. Most studies of the surface layer above forests, however, are able to probe only a narrow region above h. Therefore, direct verification of an ISL above tall forests is difficult. In this study we conducted a systematic analysis of unstable turbulence characteristics at heights from 40 to 325 m, measured at an 80m, and the recently built 325‐m Amazon Tall Tower Observatory towers over the Amazon forest. Our analyses have revealed no indication of the existence of an ISL; instead, the roughness sublayer directly merges with the convective mixed layer above. Implications for estimates of momentum and scalar fluxes in numerical models and observational studies can be significant.
A New Ring Current Model for Saturn
Authors: Carbary J. F. 
Published: May 2019

AbstractThe ring current of Saturn is obtained by taking the curl of the observed magnetic field. An analytical model of this ring current can then be obtained by fitting it to a lognormal in ρ and a Gaussian in z. Local time dependence is included as a harmonic expansion in ϕ for coefficients of the lognormal; radial dependence is included as a quadratic expansion in ρ of the width of the Gaussian. In this model, the ring current peaks at ~0.25 MA/RS2 at ~10 RS on the nightside near ~1 hr. The ring current strength minimizes at ~0.17 MA/RS2 on the dayside near ~16 hr. The cross‐sectional shape of the ring current is a teardrop extending from ~5 to ~20 RS or more.
Whole Atmosphere Climate Change: Dependence on Solar Activity
Authors: Solomon Stanley C. , Liu Han‐Li , Marsh Daniel R. , McInerney Joseph M. , Qian Liying , Vitt Francis M. 
Published: May 2019

AbstractWe conducted global simulations of temperature change due to anthropogenic trace gas emissions, which extended from the surface, through the thermosphere and ionosphere, to the exobase. These simulations were done under solar maximum conditions, in order to compare the effect of the solar cycle on global change to previous work using solar minimum conditions. The Whole Atmosphere Community Climate Model‐eXtended was employed in this study. As in previous work, lower atmosphere warming, due to increasing anthropogenic gases, is accompanied by upper atmosphere cooling, starting in the lower stratosphere, and becoming dramatic, almost 2 K per decade for the global mean annual mean, in the thermosphere. This thermospheric cooling, and consequent reduction in density, is less than the almost 3 K per decade for solar minimum conditions calculated in previous simulations. This dependence of global change on solar activity conditions is due to solar‐driven increases in radiationally active gases other than carbon dioxide, such as nitric oxide. An ancillary result of these and previous simulations is an estimate of the solar cycle effect on temperatures as a function of altitude. These simulations used modest, five‐member, ensembles, and measured sea surface temperatures rather than a fully coupled ocean model, so any solar cycle effects were not statistically significant in the lower troposphere. Temperature change from solar minimum to maximum increased from near zero at the tropopause to about 1 K at the stratopause, to approximately 500 K in the upper thermosphere, commensurate with the empirical evidence, and previous numerical models.
The Mechanism of Methane Gas Migration Through the Gas Hydrate Stability Zone: Insights From Numerical Simulations
Authors: Liu Jinlong , Haeckel Matthias , Rutqvist Jonny , Wang Shuhong , Yan Wen 
Published: May 2019

AbstractFree gas migration through the gas hydrate stability zone (GHSZ) and subsequent gas seepage at the seabed are characteristic features in marine gas hydrate provinces worldwide. The biogenic or thermogenic gas is typically transported along faults from deeper sediment strata to the GHSZ. Several mechanisms have been proposed to explain free gas transport through the GHSZ. While inhibition of hydrate formation by elevated salinities and temperatures have been addressed previously in studies simulating unfocused, area‐wide upward advection of gas, which is not adequately supported by field observations, the role of focused gas flow through chimney‐like structures has been underappreciated in this context. Our simulations suggest that gas migration through the GHSZ is, fundamentally, a result of methane gas supply in excess of its consumption by hydrate formation. The required high gas flux is driven by local overpressure, built up from gas accumulating below the base of the GHSZ that fractures the overburden when exceeding a critical pressure, thereby creating the chimney‐like migration pathway. Initially rapid hydrate formation raises the temperature in the chimney structure, thereby facilitating further gas transport through the GHSZ. As a consequence, high hydrate saturations form preferentially close to the seafloor, where temperatures drop to bottom water values, producing a prominent subsurface salinity peak. Over time, hydrates form at a lower rate throughout the chimney structure, while initial temperature elevation and salinity peak dissipate. Thus, our simulations suggest that the near‐surface salinity peak and elevated temperatures are a result of transient high‐flux gas migration through the GHSZ.
Effects of Continental Clouds on Surface Aitken and Accumulation Modes
Authors: Noble Stephen R. , Hudson James G. 
Published: May 2019

AbstractRelationships between clouds and surface aerosol are investigated at the Oklahoma Atmospheric Radiation Measurements Southern Great Plains site. Cloud chemical transformations, coalescence, and Brownian capture increase material within cloud droplets. Then when cloud droplets evaporate, as they often do, their residuals are larger than unnucleated particles. This creates a bimodal particle size distribution by moving some Aitken mode (25‐ to 100‐nm diameter) particles to the accumulation mode (100‐ to 825‐nm diameter). Clouds also block solar radiation that causes photochemical reactions that produce small particles that grow by coagulation and condensation into the Aitken mode. Highly significant positive correlations of remotely sensed cloud fraction (cf) with time‐lagged Aitken and accumulation mode mean particle diameter (mpd) isolated the effects of cloud processing on both modes. Positive correlations of cf with accumulation concentrations and negative correlations of cf with Aitken concentrations also provided evidence of cloud processing. Photochemical production of very small particles under clear daylight skies worked together with cloud processing to enhance Aitken mpd and concentration correlations with cf. Cloud‐processed aerosol was evident only during daylight and when the boundary layer mixing height exceeded the remotely sensed cloud base altitude. Greater cf, especially consecutive high cf hours increased accumulation and Aitken mpd and accumulation concentrations while it decreased Aitken concentrations. Lower cf, especially consecutive hours of no clouds, decreased overall mpd and did not enhance the accumulation mode. All of these results implicated clouds as a source of the accumulation mode, and thus, clouds seemed to explain bimodal aerosol over the mid‐North American continent.