bluuebunny/crossref_metadata_2025_split huggingface dataset:
A High‐Frequency Distance Metric in Ground‐Motion Prediction Equations Based on Seismic Array Backprojections
Authors: Feng Tian , Meng Lingsen 
Published: October 2018

AbstractTypical ground‐motion prediction equations (GMPEs) measure source‐to‐site distances relative to the closest point on the rupture plane (Rrup). However, for megathrust earthquakes (Mw > 8), the oversimplification of the earthquake source characteristics in distance metrics results in significant bias. Recent studies suggest that the high‐frequency (HF) and low‐frequency (LF) energy tend to emanate from different portions of the megathrusts. This phenomenon motivates an alternative distance metric based on the array backprojection imaging technique that effectively captures regions releasing HF energy. Herein, we define an HF distance metric (Rhf) as the distance from the site to the high‐frequency radiation zone. We study five Mw > 7.2 megathrust earthquakes in Japan and Chile and find that Rhf outperforms Rrup in predicting the ground shaking intensity between 0.5 and 4 Hz. We consider Rhf as a complementary measure to conventional GMPE distance metrics and a more accurate ground‐motion predictor in many cases.
Martian Eolian Dust Probed by ChemCam
Authors: Lasue J. , Cousin A. , Meslin P.‐Y. , Mangold N. , Wiens R. C. , Berger G. , Dehouck E. , Forni O. , Goetz W. , Gasnault O. , Rapin W. , Schroeder S. , Ollila A. , Johnson J. , Le Mouélic S. , Maurice S. , Anderson R. , Blaney D. , Clark B. , Clegg S. M. , d'Uston C. , Fabre C. , Lanza N. , Madsen M. B. , Martin‐Torres J. , Melikechi N. , Newsom H. , Sautter V. , Zorzano M. P. 
Published: October 2018

AbstractThe ubiquitous eolian dust on Mars plays important roles in the current sedimentary and atmospheric processes of the planet. The ChemCam instrument retrieves a consistent eolian dust composition at the submillimeter scale from every first laser shot on Mars targets. Its composition presents significant differences with the Aeolis Palus soils and the Bagnold dunes as it contains lower CaO and higher SiO2. The dust FeO and TiO2 contents are also higher, probably associated with nanophase oxide components. The dust spectra show the presence of volatile elements (S and Cl), and the hydrogen content is similar to Bagnold sands but lower than Aeolis Palus soils. Consequently, the dust may be a contributor to the amorphous component of soils, but differences in composition indicate that the two materials are not equivalent.
Observations of Aseismic Slip Driven by Fluid Pressure Following the 2016 Kaikōura, New Zealand, Earthquake
Authors: Hamling Ian J. , Upton Phaedra 
Published: October 2018

AbstractIn this paper we examine a short‐lived aseismic slip episode which began immediately following the 2016 Kaikōura earthquake in the South Island of New Zealand. Using synthetic aperture radar data, we form an interferometric synthetic aperture radar time series over the epicentral region of the Kaikōura mainshock. Immediately following the earthquake, we observe 150 mm of localized uplift over an ∼25‐km2 region which is best explained by an increase in pore pressure within a shallow fluid trap as a result of a coseismic permeability change. After the initial uplift stops, deformation becomes focused along a NE‐SW trending discontinuity which cuts through the uplifted region. The fault lies within a large (∼−4 MPa) stress shadow induced by the coseismic stress change suggesting that failure should be inhibited. However, a reduction in the effective normal stress caused by the local pore pressure increase was sufficient to induce a short‐lived aseismic slip episode.
The Changing Seasonality of Extreme Daily Precipitation
Authors: Marelle Louis , Myhre Gunnar , Hodnebrog Øivind , Sillmann Jana , Samset Bjørn Hallvard 
Published: October 2018

AbstractGlobal warming is known to substantially increase extreme daily precipitation, but there has been little focus on changes to the seasonal timing of these extreme events. We investigate this question using global and regional climate models from the Coupled Model Intercomparison Project phase 5 and the Coordinated Regional Downscaling Experiment, in 1871–1900, 1976–2005, and 2071–2100 for an extreme future emission scenario (Representative Concentration Pathways, 8.5 W/m2). Models reproduce the observed seasonal timing and indicate very little seasonality changes during the past hundred years. However, by the end of the 21st century, extreme precipitation could substantially shift later in the year, in most regions from summer and early fall toward fall and winter. This projected shift is not regionally homogeneous, and, among analyzed regions, is strongest in Northern Europe and Northeastern America (+12 and +17 days, respectively), although local changes of more than a month are also possible.
Subglacial Conduit Roughness: Insights From Computational Fluid Dynamics Models
Authors: Chen Yunxiang , Liu Xiaofeng , Gulley Jason D. , Mankoff Kenneth D. 
Published: October 2018

AbstractFlow resistance in subglacial conduits regulates the basal water pressure and sliding speeds of glaciers by controlling drainage efficiency and conduit enlargement and closure. Flow dynamics within subglacial conduits, however, remain poorly understood due to limited accessibility. Here we report the results of the first computational fluid dynamics simulations of flow within a realistic subglacial conduit beneath Hansbreen, a polythermal glacier in Svalbard, Norway. The simulated friction factor is 2.34 ± 0.05, which is around 5 to 230 times greater than values (0.01–0.5) commonly used in glacier hydrological modeling studies. Head losses from sinuosity and cross‐sectional variations dominate flow resistance (∼ 94%), whereas surface roughness from rocks and ice features contributes only a small portion (∼6%). Most glacier hydrology models neglect head losses due to sinuosity and cross‐sectional variations and thus severely underestimate flow resistance, overestimating the conduit peak effective pressure by 2 times and underestimating the conduit enlargement area by 3.4 times, respectively.
On the Connection Between Global Hydrologic Sensitivity and Regional Wet Extremes
Authors: Thackeray Chad W. , DeAngelis Anthony M. , Hall Alex , Swain Daniel L. , Qu Xin 
Published: October 2018

AbstractA highly uncertain aspect of anthropogenic climate change is the rate at which the global hydrologic cycle intensifies. The future change in global‐mean precipitation per degree warming, or hydrologic sensitivity, exhibits a threefold spread (1–3%/K) in current global climate models. In this study, we find that the intermodel spread in this value is associated with a significant portion of variability in future projections of extreme precipitation in the tropics, extending also into subtropical atmospheric river corridors. Additionally, there is a very tight intermodel relationship between changes in extreme and nonextreme precipitation, whereby models compensate for increasing extreme precipitation events by decreasing weak‐moderate events. Another factor linked to changes in precipitation extremes is model resolution, with higher resolution models showing a larger increase in heavy extremes. These results highlight ways various aspects of hydrologic cycle intensification are linked in models and shed new light on the task of constraining precipitation extremes.
Resonant Scattering of Near‐Equatorially Mirroring Electrons by Landau Resonance With H+ Band EMIC Waves
Authors: Fu Song , Ni Binbin , Lou Yuequn , Bortnik Jacob , Ge Yasong , Tao Xin , Cao Xing , Gu Xudong , Xiang Zheng , Zhang Wenxun , Zhang Yang , Wang Qi 
Published: October 2018

AbstractBy investigating the resonant energy and latitudinal resonance region of Landau resonance between H+ band electromagnetic ion cyclotron (EMIC) waves and radiation belt electrons and performing calculations of quasi‐linear diffusion coefficients, we find that Landau resonance with EMIC waves, characterized by a very broad range of resonant energies from below 1 eV to above 10 MeV and the strikingly small extent of the latitudinal resonance region well below 0.1°, can be a feasible candidate accounting for the pitch angle scattering of near‐equatorially mirroring electrons. Compared to the dominant pitch angle scattering caused by the cyclotron resonance for greater than ~2‐MeV electrons at equatorial pitch angles less than ~80° with the rates well above 10−4 s−1, Landau resonance with H+ band EMIC waves has the potential to drive more efficient pitch angle scattering of radiation belt electrons from ~10 MeV down to tens of kiloelectron volts at equatorial pitch angles greater than ~ 85°.
The Ice‐Free Topography of Svalbard
Authors: Fürst Johannes J. , Navarro Francisco , Gillet‐Chaulet Fabien , Huss Matthias , Moholdt Geir , Fettweis Xavier , Lang Charlotte , Seehaus Thorsten , Ai Songtao , Benham Toby J. , Benn Douglas I. , Björnsson Helgi , Dowdeswell Julian A. , Grabiec Mariusz , Kohler Jack , Lavrentiev Ivan , Lindbäck Katrin , Melvold Kjetil , Pettersson Rickard , Rippin David , Saintenoy Albane , Sánchez‐Gámez Pablo , Schuler Thomas V. , Sevestre Heïdi , Vasilenko Evgeny , Braun Matthias H. 
Published: October 2018

AbstractWe present a first version of the Svalbard ice‐free topography (SVIFT1.0) using a mass conserving approach for mapping glacier ice thickness. SVIFT1.0 is informed by more than 1 million point measurements, totalling more than 8,700 km of thickness profiles. SVIFT1.0 is publicly available and represents the geometric state around the year 2010. Our estimate for the total ice volume is 6,199 km3, equivalent to 1.5‐cm sea level rise. The thickness map suggests that 13% of the glacierized area is grounded below sea level. A complementary map of error estimates comprises uncertainties in the thickness surveys as well as in other input variables. Aggregated error estimates are used to define a likely ice‐volume range of 5,200–7,300 km3. The ice front thickness of marine‐terminating glaciers is a key quantity for ice loss attribution because it controls the potential ice discharge by iceberg calving into the ocean. We find a mean ice front thickness of 135 m for the archipelago (likely range 123–158 m).
Vegetation Controls on Dryland Salinity
Authors: Perri Saverio , Suweis Samir , Entekhabi Dara , Molini Annalisa 
Published: October 2018

AbstractIn salt‐affected soils, salt stress causes a drastic reduction of plant transpiration. The extent of this reduction is a function of vegetation salt tolerance and can result in highly species‐specific controls on soil water budget and salinization levels. Despite their crucial role in regulating the hydrology of saline soils, the effects of salt tolerance on transpiration remain mostly unexplored. Here we propose a minimalist stochastic model of primary salinization which reproduces the hitherto overlooked feedback of salinity on the soil water balance and the active role of plant salt tolerance in modulating such an effect. We show that vegetation can exert significant control on leaching occurrence and soil salinization, thus imposing a species‐specific upper limit, Cmax, to the concentration of soluble salts in the soil. Since Cmax increases with plant salt tolerance, salt‐resilient species have the potential to sustain more saline conditions in the soil, eventually creating a favorable environment for their ecological success.
Anomalous Behavior of Vertical Wavenumber Spectra Over a Tropical Station of India
Authors: Ghosh Priyanka , Ramkumar T. K. , Sharma Som 
Published: October 2018

AbstractThe vertical wavenumber (VWN) spectra of height profiles of winds over a tropical station of Gadanki (13.5°N, 79.2°E; obtained using Indian Mesosphere Stratosphere Troposphere radar) show distinct nature of VWN spectra, which do not match with the so‐called universal wavenumber spectra. The universal wavenumber spectra have three distinct regions: unsaturated (having log‐log slope of 2), saturated (having log‐log slope of −3), and turbulence region (having log‐log slope of −5/3). In present work, we report the presence of positive slope at the higher end of the VWN spectra indicating the presence of unsaturated gravity waves, a kind of which is not reported so far. Many negative slopes of the order of ~−6, ~−9, and ~−12 are noticed at the end of the spectra beyond the turbulence region of the wavenumber spectra, which is also not reported in any previous studies up to now.
Madagascar Influence on the South Indian Ocean Convergence Zone, the Mozambique Channel Trough and Southern African Rainfall
Authors: Barimalala Rondrotiana , Desbiolles Fabien , Blamey Ross C. , Reason Chris 
Published: October 2018

AbstractThe rainfall mean state and variability of the tropical Southern Hemisphere are strongly affected by the Tropical Convergence Zones. Unlike the South Pacific and South Atlantic, the topography of Madagascar prevents, through the Mozambique Channel Trough, the direct transport of moisture from the Indian Ocean toward southern Africa that feeds the South Indian Ocean Convergence Zone (SICZ). Numerical experiments using regional climate models reveal that a flatter than actual topography over Madagascar results in a strengthening of the SICZ through anomalously high easterly moisture fluxes transported from the Indian Ocean and the Mozambique Channel. These in turn trigger a significant increase in precipitation over southern Africa extending from Mozambique to Angola and a decrease in rainfall over Madagascar. These results have important implications for the improvement of the representation of African rainfall mean state and variability, which has been identified as a persisting issue in different generations of state‐of‐the‐art climate models.
Anomalous Vp/Vs Ratios at Seismic Frequencies Might Evidence Highly Damaged Rocks in Subduction Zones
Authors: Pimienta Lucas , Schubnel Alexandre , Violay Marie , Fortin Jérôme , Guéguen Yves , Lyon‐Caen Hélène 
Published: October 2018

AbstractUnusually high compressional (P) to shear (S) wave velocity ratios (Vp/Vs) were measured at different subduction zones and interpreted as fluid‐pressurized regions. Because no laboratory data reported such high values in isotropic rocks, mineralogical or anisotropic constrains were assumed. However, fluid‐saturated rocks' Vp/Vs is a frequency‐dependent property so that standard laboratory measurements cannot be directly upscaled to the field. Using a new methodology, we measured the property in the elastic regime relevant to field measurements for diverse lithologies. We obtained extreme Vp/Vs values, consistent with those reported at seismic frequency in the field. Consistently with a model, it shows that if high fluid pressure is a key factor, anomalous Vp/Vs values could evidence intense degrees of microfracturation in isotropic rocks, whichever its mineralogical content. The permeability of these regions could be larger than 10−16 m2.
The Regional, Seasonal, and Lagged Influence of the Amundsen Sea Low on Antarctic Sea Ice
Authors: Holland Marika M. , Landrum Laura , Raphael Marilyn N. , Kwok Ronald 
Published: October 2018

AbstractThe Amundsen Sea Low (ASL) is an important driver of Antarctic sea ice variations largely because of wind‐driven sea ice and ocean transport anomalies. However, the nature of the relationship between the ASL and sea ice is complicated by large seasonality in the ice cover and the ASL location and depth. Here we explore these relationships as a function of region, season, and lag. We find that the ASL can have a markedly different and sometimes opposite sign influence on sea ice in some regions, such as the western Ross Sea, depending on the season. This is in part due to differing influences of ASL‐related meridional and zonal winds for ice transport in different times of year. The sea ice response to ASL variations is often largest at a lag of some months and can persist for up to 8 months.
Seasonal Permeability Change of the Shallow Crust Inferred From Deep Well Monitoring
Authors: Liao Xin , Wang Chi‐Yuen 
Published: October 2018

AbstractPermeability is a fundamental rock property that controls several important transport processes in Earth's crust. Here we use 10 years of continuous data to analyze the tidal response of water level in a well in SW China to Earth tides and show that permeability of the shallow crust may change seasonally. The relationship between permeability and the groundwater level suggests that the vertical permeability may increase ~6 folds in response to seasonal increases of water level over a threshold equivalent to ~0.1 MPa of pore pressure. The specific storage does not show corresponding change, suggesting that the change in permeability may be related to the clogging and unclogging of existing fractures in low‐porosity rock.
Long‐Lasting Poloidal ULF Waves Observed by Multiple Satellites and High‐Latitude SuperDARN Radars
Authors: Shi X. , Baker J. B. H. , Ruohoniemi J. M. , Hartinger M. D. , Murphy K. R. , Rodriguez J. V. , Nishimura Y. , McWilliams K. A. , Angelopoulos V. 
Published: October 2018

AbstractPoloidal ultralow frequency (ULF) waves between 5 and 10 mHz were observed by multiple satellites and three high‐latitude Super Dual Auroral Radar Network radars during the recovery phase of a moderate geomagnetic storm on 24–27 January 2016. The long‐lasting ULF waves were observed in the magnetic field and energetic particle flux perturbations during three successive passes by two Geostationary Operational Environmental Satellites through the dayside magnetosphere, during which plasmasphere expansion and refilling were observed by two Time History of Events and Macroscale Interactions during Substorms probes. The radial magnetic field oscillation was in phase (∼180° out of phase) with the northward (southward) moving proton flux oscillation at 95 keV, consistent with high‐energy drift‐bounce resonance signatures of protons with second harmonic poloidal standing Alfvén waves. The longitudinal extent of the waves approached 10 hr in local time on the dayside and gradually decreased with time. High‐time‐resolution (∼6 s) data from three high‐latitude Super Dual Auroral Radar Network radars show that the wave intensification region was localized in latitude with a radial extent of ∼135–225 km in the subauroral ionosphere. No signature of these waves were observed by ground‐based magnetometers colocated with the Geostationary Operational Environmental Satellites suggesting that the poloidal waves were high‐m mode and thus screened by the ionosphere. During this interval one of the Time History of Events and Macroscale Interactions during Substorms probes observed a bump‐on‐tail ion distribution at 1–3 keV, which we suggest is the source of the long‐lasting second harmonic poloidal ULF waves.
Raindrop Size Distribution Characteristics of Summer and Winter Season Rainfall Over North Taiwan
Authors: Seela Balaji Kumar , Janapati Jayalakshmi , Lin Pay‐Liam , Wang Pao K. , Lee Meng‐Tze 
Published: October 2018

AbstractRaindrop size distribution (RSD) characteristics of summer and winter seasons over north Taiwan are analyzed by using long‐term (~12 years) raindrop spectra from Joss‐Waldvogel disdrometer located at National Central University (24°58′N, 121°10′E), Taiwan. Along with the disdrometer data, radar reflectivity mosaic from six ground‐based radars, Tropical Rainfall Measuring Mission, Moderate Resolution Imaging Spectroradiometer, and ERA‐Interim data sets are used to establish the dynamical and microphysical characteristics of summer and winter rainfall. Significant differences in raindrop spectra of summer and winter rainfall are noticed. Winter rainfall has a higher concentration of small drops and a lower concentration of midsize and large drops when compared to summer rainfall. RSD stratified on the basis of rain rate showed a higher mass‐weighted mean diameter (Dm) and a lower normalized intercept parameter (log10Nw) in summer than winter. Similarly, diurnal variation of RSD showed higher Dm and lower log10Nw values in summer as compared to winter rainfall. In addition, for both seasons, the mean value of Dm is higher in convective precipitation than stratiform. Radar reflectivity (Z) and rain rate (R) relations (Z = A*Rb) showed a clear demarcation between summer and winter rainfall. Higher ground temperatures, deeply extended clouds with intense convective activity in summer modified the RSD through evaporation, drop sorting, and collision‐coalescence processes resulting with higher Dm and lower log10Nw values in summer as compared to winter rainfall.
Temporal Characteristics of Cloud Radiative Effects on the Greenland Ice Sheet: Discoveries From Multiyear Automatic Weather Station Measurements
Authors: Wang Wenshan , Zender Charles S. , van As Dirk 
Published: October 2018

AbstractThe impact of clouds on Greenland's surface melt is difficult to quantify due to the limited amount of in situ observations. To better quantify cloud radiative effects (CRE), we utilize 29 automatic weather stations and provide the first analysis on seasonal and hourly timescales in both accumulation and ablation zones. Seasonal CRE shows opposing cycles across geographical regions. CRE generally increases during melt season in the north of Greenland, mainly due to longwave CRE enhancement by cloud fraction and liquid water. CRE decreases from May to July and increases afterwards in the middle and south of Greenland, mainly due to strengthened shortwave CRE caused by surface albedo reduction. This finding resolves the contrasting seasonal distributions in previous studies at different Arctic locations. Longwave seasonal cycle also shifts from increasing in the north to decreasing in the south, implying spatial variations in cloud and atmospheric conditions. On hourly timescales, longwave downwelling radiation exhibits a bimodal distribution peaking at ∼−70 W/m2 (i.e., clear state) and ∼0 W/m2 (i.e., cloudy state), suggesting that Greenland alternates between fairly clear and overcast. In the cloudy state, CRE strongly correlates with the combined influence of solar zenith angle and albedo (r = 0.85, p < 0.01) probably because clouds are thick enough for CRE to become saturated. The close relationship between CRE and albedo over dark surfaces suggests a stabilizing feedback: Net CRE is negative at low albedo caused by snow melt and snow metamorphism and thus tends to increase albedo and decelerate surface melt.