bluuebunny/crossref_metadata_2025 huggingface dataset:
Tidal asymmetry in the Sylt-Romo Bight, south-eastern North Sea
Authors: Fofonova Vera , Androsov Alexey , Sander Lasse , Kuznetsov Ivan , Amorim Felipe , Hass H. Christian , Mielck Finn , Wiltshire Karen Helen
Published: March 2020

 

The study is dedicated to the tidal dynamics in the Sylt-Rømø Bight with a focus on the non-linear processes. The FESOM-C model was used as the numerical tool, which works with triangular, rectangular or mixed grids and is equipped with a wetting/drying option. As the model’s success at resolving currents largely depends on the quality of the bathymetric data, we have created a new bathymetric map for an area based on recent studies of Lister Deep, Lister Ley, and the Højer and Rømø Deep areas. This new bathymetric product made it feasible to work with high resolution grids (up to 2 m in the wetting/drying zone). As a result, we were able to study the tidal energy transformation and the role of higher harmonics in the domain in detail. The tidal ellipses, maximum tidally-induced velocities, energy fluxes and residual circulation maps were constructed and analysed for the entire bight. Additionally, tidal asymmetry maps were introduced and constructed. The full analysis was performed on two grids with different structures and showed a convergence of the results as well as fulfillment of the energy balance. The tidal residual circulation and asymmetric tidal cycles largely define the circulation pattern, transport and accumulation of sediment and the distribution of bedforms in the bight, therefore the results are necessary and useful benchmarks for further studies in the area, including baroclinic and sediment dynamics investigations.
Understorey vegetation drives surface runoff and soil loss in teak plantation-based system of Northern Laos
Authors: Song Layheang , Boithias Laurie , Sengtaheuanghoung Oloth , Oeurng Chantha , Valentin Christian , Sounyafong Phabvilay , de Rouw Anneke , Soulileuth Bounsamai , Silvera Norbert , Pierret Alain , Ribolzi Olivier
Published: March 2020

Humid tropical mountainous area experiences serious soil erosion due to rapid changes in landuse, sometimes implying erosion prone management practices. In this study, we hypothesized that keeping understorey in teak tree plantation would protect soil and avoid soil erosion. We assessed the effects of 4 management practices in teak tree plantation area on water and soil losses using 6 replicated 1-m2 microplots in four plantations situated in Northern Laos during the wet season of 2017. The landuses in the four plantations were teak without understorey (TNU), teak with low density of understorey (TLU), teak with high density of understorey (THU), and teak with broom grass, Thysanolaena latifolia (TBG). During the wet season of 2017, we monitored surface runoff and soil loss for 22 rainfall events. We also measured some of the teak tree and understorey characteristics (i.e. height and percentage of cover) and the percentage areas of soil surface features (i.e. litter, free aggregates, crusting, etc.). Relationships among these variables was estimated through multiple statistics and regression analyses. We found that runoff coefficient and soil loss were the smallest for THU and TBG: runoff coefficient was 23% for both treatments, and soil losses were 465 and 381 g m-2, respectively. Runoff coefficient and soil loss for TLU were 35% and 1115 g m-2, respectively. We observed the highest runoff coefficient and soil loss under TNU (60%, 5455 g m-2) associated to the highest crusting rate (82%). High runoff coefficient and soil loss under TNU was explained by the kinetic energy of rain drops falling from the broad leaves of the tall teak trees down to bare soil, devoid of plant residues, thus leading to severe soil surface crusting and detachment. Overall, promoting understorey such as broom grass in teak tree plantations would (1) limit surface runoff and improve soil infiltrability, thus increase the soil water stock available for both root absorption and groundwater recharge, and (2) mitigate soil loss and favour soil fertility conservation.
Cross-comparing GPS and seismic data in advance and after great earthquakes
Authors: Liu Tai , Kossobokov Vladimir
Published: March 2020

With the accumulation of seismic and other geophysical data and update of methodologies, the accuracy and reliability of seismic risk assessment can be improved. In particular, the introduction of GPS observation data leads to better understanding of earthquake origins and sequences. For this, we cross-compare the pre- and post-seismic deformation of the 2011 Tohoku Mw9.1 earthquake in Japan, the 2010 off shore Maule Mw8.8 earthquake in Chile, the 2018 Kodiak Mw7.9 earthquake in the Gulf of Alaska, and the 2016 Kaikoura Mw7.8 earthquake in New Zealand derived from GPS observations with integral characteristics of the regional seismic regime, including the accumulated length of seismic sources derived from the catalogs of earthquake hypocenter parameters. We found that (a) the area on top the 2011 Tohoku mega-thrust keeps moving at speed of about 10 cm per year, (b) eventually, the 2016 Kaikoura unidirectional strike-slip resulted in the current position retreat nearby epicenter and steady increase on the opposite edge of its rupture zone, (c) the four cases show up different deformation vs seismicity correlation patterns in advance and after the catastrophic event, and (d) GPS data confirm the existence of intermittent long periods of regionally stable levels of seismic regime controlled by the Unified Scaling Law for Earthquakes that may switch as the result of mid- or even short-term bursts of activity associated with major catastrophic earthquakes.

The study supported from the RFBR Project No. 19-35-50059 “Study of pre- and post-seismic displacements in the areas of the strongest earthquakes in the world".
Morphometric analysis of the post-caldera monogenetic volcanoes at Deception Island, Antarctica: implications for landform recognition and volcanic hazard assessment
Authors: Pedrazzi Dario , Kereszturi Gabor , Schamuells Stefania , Lobo Agustin , Calle Janina
Published: March 2020

Deception Island is one of the most active volcanoes in Antarctica, with more than 20 monogenetic eruptions during the Holocene. The latest episodes of 1967, 1969 and 1970 have shown that volcanic activity on Deception Island can become a concern for tourists, scientists, and military personnel working on or near the island.

The objective of this work is, therefore to identify eruptive processes and the evolution of post-caldera volcanic edifices at Deception Island by morphometric analysis, supported by field observations. This methodology has been used since the 1970s to analyse mafic monogenetic volcanoes but it has not been fully developed until recently.

Tuff cones and rings, as a result of magma-water interaction, represent the most common eruptive events occurring during Deception Island's recent geological past and are therefore the most likely to occur in the near future. This work provides an opportunity to incorporate for the first time at Deception Island geomorphological observations for a better comprehension of the potential evolution of a future eruption and for a broader understanding of volcanic hazards on this island.

This research was supported by the MICINN grant CTM2011- 13578-E and was partially funded by the POSVOLDEC project (CTM2016-79617-P) (AEI/FEDER-UE). A.G. is grateful for her Ramón y Cajal contract (RYC-2012-11024). D.P. is grateful for his Beatriu de Pinós (2016 BP 00086) and Juan de la Cierva (IJCI-2016-30482) contracts. This research is part of POLARCSIC and AntVolc activities
From the Sun to the Earth: August 25, 2018 geomagnetic storm effects
Authors: Piersanti Mirko , De Michelis Paola , Del Moro Dario , Tozzi Roberta , Pezzopane Michael , Consolini Giuseppe , Laurenza Monica , Di Matteo Simone , Pignalberi Alessio , Quattrociocchi Valerio , Diego Piero
Published: March 2020

On August 25, 2018 the interplanetary counterpart of the August 20, 2018 Coronal Mass Ejection (CME) hit the Earth, giving rise to a strong geomagnetic storm. We present a description of the whole sequence of events from the Sun to the ground as well as a detailed analysis of the onserved effects on the Earth's environment by using a multi instrumental approach.
We studied the ICME propagation in the interplanetary space up to the analysis of its effects in the magnetosphere, ionosphere and at ground. To accomplish this task, we used ground and space collected data, including data from CSES (China Seismo Electric Satellite), launched on February 11, 2018. We found a direct connection between the ICME impact point onto the magnetopause and the pattern of the Earth's polar electrojects. Using the Tsyganenko TS04 model prevision, we were able to correctly identify the principal magnetospheric current system activating during the different phases of the geomagnetic storm. Moreover, we analyzed the space-weather effects associated with the August 25, 2018 solar event in terms of evaluation geomagnetically induced currents (GIC) and identification of possible GPS loss of lock. We found that, despite the strong geomagnetic storm, no loss of lock has been detected. On the contrary, the GIC hazard was found to be potentially more dangerous than other past, more powerful solar events, such as the St. Patrick geomagnetic storm, especially at latitudes higher than $60^\circ$ in the European sector.
The climatology of the Brewer-Dobson circulation and the contribution of gravity waves
Authors: Sato Kaoru , Hirano Soichiro
Published: March 2020

The climatology of residual mean circulation – a main component of the Brewer–Dobson circulation – and the potential contribution of gravity waves (GWs) are examined for the annual mean state and each season in the whole stratosphere based on the transformed-Eulerian mean zonal momentum equation using four modern reanalysis datasets. Resolved and unresolved waves in the datasets are respectively designated as Rossby waves and GWs, although resolved waves may contain some GWs. First, the potential contribution of Rossby waves (RWs) to residual mean circulation is estimated from Eliassen–Palm flux divergence. The rest of residual mean circulation, from which the potential RW contribution and zonal mean zonal wind tendency are subtracted, is examined as the potential GW contribution, assuming that the assimilation process assures sufficient accuracy of the three components used for this estimation. The GWs contribute to drive not only the summer hemispheric part of the winter deep branch and low-latitude part of shallow branches, as indicated by previous studies, but they also cause a higher-latitude extension of the deep circulation in all seasons except for summer. This GW contribution is essential to determine the location of the turn-around latitude. The autumn circulation is stronger and wider than that of spring in the equinoctial seasons, regardless of almost symmetric RW and GW contributions around the Equator. This asymmetry is attributable to the existence of the spring-to-autumn pole circulation, corresponding to the angular momentum transport associated with seasonal variation due to the radiative process. The potential GW contribution is larger in September to November than in March-to-May in both hemispheres. The upward mass flux is maximized in the boreal winter in the lower stratosphere, while it exhibits semi-annual variation in the upper stratosphere. The boreal winter maximum in the lower stratosphere is attributable to stronger RW activity in both hemispheres than in the austral winter. Plausible deficiencies of current GW parameterizations are discussed by comparing the potential GW contribution and the parameterized GW forcing.
Seismic attenuation and velocity dispersion due to squirt flow in cracks with rough walls
Authors: Lissa Simón , Barbosa Nicolás D. , Caspari Eva , Alkhimenkov Yury , Quintal Beatriz
Published: March 2020

We numerically study the effects that roughness in the walls of cracks has on the P-wave modulus dispersion and attenuation due to squirt flow. We emulate the deformation caused by a seismic P-wave by applying an oscillatory relaxation test on numerical rock models having two perpendicular fluid-filled cracks interconnected and embedded in a cubic elastic background. The deformation caused by the P-wave induces a fluid pressure gradient and then, during the consequent fluid pressure diffusion process, the friction between fluid particles dissipate seismic wave energy. In this work, we consider P-wave deformation normal to one of the cracks. We first consider binary aperture distribution for the cracks to analyse where the energy dissipation process takes place. Then, more complex geometries for the roughness of the walls are also considered. In both cases, the cracks have finite length and square-shape and no contact areas between the walls of the cracks were allowed to occur. We show that the arithmetic mean of the apertures controls the P-wave modulus magnitudes at the low- and high-frequency limits. Additionally, two attenuation peaks and modulus dispersion regimes may occur associated with squirt flow. In general, at low-frequencies, the energy dissipation tends to happen inside the minimum aperture of the cracks, and consequently, the minimum aperture determines the frequency at which the low-frequency attenuation peak occurs. For the considered models, we observed that when the percentage of minimum aperture in the cracks is lower than 10$\%$, a second attenuation peak at high frequencies become dominant. The characteristic frequency of this attenuation process is controlled by an effective hydraulic aperture. Finally, we simulate an increase in confining pressure by reducing the crack apertures by a constant value, allowing for contact areas occurrence. In this scenario, the stiffness of the cracks can not longer be explained with the arithmetic mean of the aperture, as the stiffening effect of the distribution of the contact areas plays a much stronger role. In general, from the analysis of the local energy dissipation, different apertures seem to control the energy dissipation process at each frequency, which means that a frequency-dependent hydraulic aperture might be needed to describe the squirt flow process in cracks with rough walls.
Understanding the role of water vapor and temperature in easterly wave-related convection
Authors: Vargas Martes Rosa , Adames Corraliza Angel
Published: March 2020

Easterly Waves (EW) in the Pacific Ocean (PEW) and over Africa (AEW) account for a large fraction of rainfall variability in their respective regions. Although multiple studies have been conducted to better understand EWs, many questions remain regarding their structure, development, and coupling to deep convection. Recent studies have highlighted the relationship between water vapor and precipitation in tropical motion systems. However, EW have not been studied within this context. On the basis of Empirical Orthogonal Functions (EOFs) and a novel plume-buoyancy framework, the thermodynamic processes associated with EW-related convection are elucidated. A linear regression analysis reveals the relationship between temperature, moisture, and precipitation in EW. Temperature anomalies are found to be highly correlated in space and time with anomalies in specific humidity. However, this coupling between temperature and moisture is more robust in AEWs than PEWs. In PEWs moisture accounts for a larger fraction of precipitation variability. Results suggest that the convective coupling mechanism in AEW may differ from the coupling mechanism of PEWs.
Distribution of crustal azimuthalanisotropy beneath the North China Craton: Insights from analysis of receiver functions
Authors: Zheng Tuo , Gao S. Stephen , Ding Zhifeng , Fan Xiaoping
Published: March 2020

To characterize crustal anisotropy beneath the North China Craton (NCC), we apply a recently developed deconvolution approach to effectively remove near-surface reverberations in the receiver functions recorded at 200 broadband seismic stations and subsequently determine the fast orientation and the magnitude of crustal azimuthal anisotropy by fitting the sinusoidal moveout of the P to S converted phases from the Moho and intracrustal discontinuities. The magnitude of crustal anisotropy is found to range from 0.06 s to 0.54 s, with an average of 0.25 ± 0.08 s. Fault-parallel anisotropy in the seismically active Zhangjiakou-Penglai Fault Zone is significant and could be related to fluid-filled fractures. Historical strong earthquakes mainly occurred in the fault zone segments with significant crustal anisotropy, suggesting that the measured crustal anisotropy is closely related to the degree of crustal deformation. The observed spatial distribution of crustal anisotropy suggests that the northwestern terminus of the fault zone probably ends at about 114°E. Also observed is a sharp contrast in the fast orientations between the western and eastern Yanshan Uplifts separated by the North-South Gravity Lineament. The NW-SE trending anisotropy in the western Yanshan Uplift is attributable to “fossil” crustal anisotropy due to lithospheric extension of the NCC, while extensional fluid-saturated microcracks induced by regional compressive stress are responsible for the observed ENE-WSW trending anisotropy in the eastern Yanshan Uplift. Comparison of crustal anisotropy measurements and previously determined upper mantle anisotropy implies that the degree of crust-mantle coupling in the NCC varies spatially.
Why is Snow Slippery? The Role of Abrasion in Snow Kinetic Friction
Authors: Lever James , Taylor Susan , Hoch Garrett , Asenath-Smith Emily
Published: March 2020

The mechanics of snow friction are central to competitive skiing, safe winter driving, avalanche dynamics, and efficient Polar sleds. For nearly 80 years, prevailing theory has postulated self-lubrication: dry-contact sliding warms snow-grains to the melting point, and further sliding produces melt-water that lubricates the interface. We recently published micro-scale interface observations that contradicted this explanation: contacting snow grains abraded and did not melt under a polyethylene slider, despite low friction values. We obtained coordinated infrared, visible-light, and scanning-electron micrographs that confirm that the evolving shapes observed during our tribometer tests are contacting snow grains polished by abrasion, and that the wear particles can sinter together and fill the adjacent pore spaces. Furthermore, dry-contact abrasive wear reasonably predicts the evolution of snow-slider contact area, and sliding-heat-source theory confirms that contact temperatures would not reach 0°C during our tribometer tests. Importantly, published measurements of interface temperatures also indicate that melting did not occur during field tests on sleds and skis. We postulate that abraded ice crystals form a dry-lubricant layer that makes contacting snow-grains slippery and are currently undertaking additional observations and theoretical analyses to assess this hypothesis.
Spatial variation of gully density and morphology and their controlling factors at a regional scale: a case study for the Chinese Loess Plateau
Authors: Chen Yixian , Jiao Juying , Vanmaercke Matthias , Yan Xiqin , Li Jianjun
Published: March 2020

Gully erosion is a major cause of land degradation in many regions worldwide. Recent research shows that the challenges posed by gully erosion are likely to further increase as a result of climate change and increasing land use pressure. Nonetheless, our understanding of this process remains limited in many ways. While numerous studies have focused on the occurrence and morphology of gullies at local (catchment) scale, relatively little research has explored their spatial variations at regional to continental scales. As a result, the factors controlling the density, size and morphology of gullies at such scales remain poorly understood. This is especially the case for the role of climate/weather conditions. Here we aim to advance our understanding on this topic by studying gully densities and gully morphology in the Chinese Loess Plateau (CLP), a region severely affected by gully erosion. 
We selected five representative catchments in the CLP that are relatively similar in size (7-30 km²), topographic context, soil characteristics and land use but represent a large gradient in rainfall conditions. We mapped 2511 gullies in these catchments, using Pleiades-1B (panchromatic resolution at 0.5 m) and WorldView-3 images (panchromatic resolution at 0.31 m). For each of the gullies, we calculated a range of morphological parameters including the gully length, width, surface area, length-width ratio and shape index. Next, we explored to what extent differences in gully density and morphology are correlated to contrasts in rainfall and other environmental factors.
Overall, the gullies showed large variations in gully length (2.1-308 m, average 38.1 m), width (1.3-87 m, average 11.5 m) and density (0-4.8 km/km², average 2.3 km/km²). Gully densities showed a negative correlation with rainfall amounts. This is likely partly attributable to feedbacks between rainfall amounts and vegetation cover. However, also contrasts in rainfall intensity and regime likely play an important role. Also variations in gully width appear strongly correlated with rainfall patterns (with more humid catchments resulting in overall wider gullies). Surprisingly, gully lengths (a first indicator of gully headcut retreat) showed no clear correlation with rainfall patterns. Overall, our results indicate that contrasts in rainfall regime are crucial to understand gully erosion dynamics at regional to continental scales. This is true for their initiation but also for their subsequent expansion (and especially gully widening). These findings have important implications for the development of models aiming to predict gully erosion at regional to continental scales.
Integrated Geophysical study on the subsurface structural characterization of West Beni Suef area, Western Desert, Egypt
Authors: Khalil Ahmed , El Emam Ahmed , Abdel Hafeez Tharwat , Saleh Hassan , Mohamed Waheed
Published: March 2020

The aim of this work is to study the subsurface structures in the west Beni Suef area of the Western Desert in Egypt and to determine their effects on surface geologic structures. A detailed land magnetic survey has been carried out for the total component of the geomagnetic field using two proton magnetometers. The necessary corrections concerning daily variation, the regional gradient and time variations have been applied. Then, the total magnetic intensity anomaly map (TMI) has been constructed and transformed to the reduced to the pole magnetic map (RTP). The reduction-to-pole magnetic and Bouguer anomaly maps were used to obtain regional extensions of this subsurface structure. Regional–residual separation is carried out using the power spectrum. Also, Edge detection techniques are applied to delineate the structure and hidden anomalies. Data analysis was performed using trend analysis, Euler deconvolution, the results indicate that the area is affected by tectonic forces in the N-S, NW-SE, NE-SW and E-W trends, which are correlated with the directions of surface geologic lineaments. In addition, depths to the basement rocks have been estimated using spectral analysis technique. The computed depths have been used to construct the basement relief map which resulted from gravity and magnetic data. They show that the depth to the basement rocks ranges from 2.3 km to 4.7 km.

KEYWORDS
Land magnetic, Gravity, Euler deconvolution, Edge detection and Spectral analysis.
Examination of the EUV Intensity in the Open Magnetic Field Regions Associated with Coronal Holes
Authors: Huang Guan-Han , Lin Chia-Hsien , Lee Lou Chuang
Published: March 2020

Coronal holes can be identified as the regions with magnetic field lines extending far away from the Sun, or the darkest regions in EUV/X-ray images with predominantly unipolar magnetic fields. A comparison between the locations of our determined regions with open magnetic field lines (OMF) and regions with low EUV intensity (LIR) reveals that only 12% of the OMF regions coincide with the LIRs. The aim of this study is to investigate the conditions leading to the different brightnesses of OMF regions, and to provide a means to predict whether an OMF region would be bright or dark. Examining the statistical distribution profiles of the magnetic field expansion factor (fs) and Atmospheric Imaging Assembly 193 Å intensity (I193) reveals that both profiles are approximately log-normal. The analysis of the spatial and temporal distributions of fs and I193 indicates that the bright OMF regions often are inside or next to regions with closed field lines, including quiet-Sun regions and regions with strong magnetic fields. Examining the relationship between I193 and fs reveals a weak positive correlation between log I193 and log fs , with a correlation coefficient ≈ 0.39. As a first-order approximation, the positive relationship is determined to be log I193 = 0.62 log fs + 1.51 based on the principle of the whitening/dewhitening transformation. This linear relationship is demonstrated to increase the consistency between the OMF regions and LIRs from 12% to 23%.
A regression analysis framework for the prediction of runout distance of landslides: a case study for Sichuan
Authors: Gu Peng , Valyrakis Manousos
Published: March 2020

In recent years, the impact of landslides on society has increased due to increasing urbanisation and climate change (as much as up to 30%). In about a decade, around 5000 fatal non-seismic landslides have occurred world-wide resulting in almost 56000 deaths, most of which took place in developing countries, such as China and Philippines. The purpose of studying the characteristics of landslides is to develop a better understanding of their features and to reduce any threat posed by them. Out of these characteristics the runout distance directly determines the impact of the landslide and extend of the affected area which are useful in evaluating risk to infrastructure (such as road pavement or railroad or built structures). Therefore, the study of landslide runout distance prediction has great significance for urban planning and risk assessment, specifically in mountainous areas.

 

This study focuses on conducting a review of previous literature on landslides reported at the region of Wenchuan in Sichuan (China), aiming to identify any trends connecting the cause and effect relationship between landslides in a phenomenological and empirical manner. Specifically, a dataset of landslides (20 due to rainfall and 50 due to earthquake) is used to statistically link, using multiple regression analysis, the travel distance to five main influencing factors, including landslide volume, height of landslide, landslide plane form, landslide average thickness and relative coefficient of friction. Good results are obtained through error minimisation rendering the developed framework as a useful tool for predictive analysis of the potential extend and impact of landslides using historical regional data.
Photochemistry versus biological activity towards organics in cloud water
Authors: Khaled Amina , Zhang Minghui , Amato Pierre , Delort Anne-Marie , Ervens Barbara
Published: March 2020

The aqueous phase of clouds is a complex atmospheric medium containing a multitude of organic and inorganic species with different reactivities. The main oxidant towards organics in the aqueous phase is the OH radical. Many studies have identified biological material as a major fraction of ambient aerosol loading with bacteria being a small fraction. Laboratory experiments in our and other research groups have shown that microbial degradation of small organics (e.g., formic and acetic acids) can efficiently occur in artificial and real cloud water in competition to chemical radical reactions. However, in current models, it is usually assumed that bacteria are not metabolically active in the atmosphere. The aim of our study is to identify conditions, under which biological activity is significant in the multiphase system for specific organic compounds. Using a cloud multiphase process model, we compare the predicted fractions of organics consumed by radicals in the gas and aqueous phases to that by microbial processes of bacteria in the aqueous phase over large ranges of microphysical (e.g., cloud liquid water content, drop number), biological (cell concentration and activity) and chemical parameters (reaction rate constants and Henry’s law constants). We identify the organic properties and cloud parameters under which metabolic processes represent major atmospheric sinks for organics. In our cloud model, we consider the fact that only a small number fraction of droplets contain active bacteria cells. As many other models might not be able to describe such microphysical details, we also suggest simplified model approaches to represent microbial activity in clouds.
Matching seismic activity with potential sources using machine Learning
Authors: Hein Gerrit , Novoselov Artemii , Fuchs Florian , Bokelmann Götz
Published: March 2020

Detecting seismic signals and identifying their origin is more and more used for understanding environmental activity. This usually depends on a good signal/noise ratio (S/N), especially for the more distant sources.

A test area for detection and identification is the urban setting of the University of Vienna, a challenging environment with more than 4000 strong-acceleration events per day. These repetitive noise events would normally classify the site as "too noisy" for any advanced earthquake research.

With the real-time open database from Wiener Linien it is possible to attribute many of the repetitive seismic signals (e.g. on a Raspberry Shake Citizen Science Station) to the surrounding trams and train lines. The detection challenge was initiated in a Citizen Science Hackathon, where public interest sparked this research. The available train schedule and more than one year of continuous seismic records is sufficient to train and test a machine learning classifier which finds most characteristic features in the signals of commuter trains and trams, such as the energy in each frequency band.

The labeled dataset can be used to train our detection algorithm to find similar signals and to help determine whether a certain signal is present or not. An additional second seismic Raspberry Shake sensor is installed in the vicinity, to further constrain the directionality of the trains.

Studying the vibrations of train signals and solving the classification task of these repetitive patterns first can help develop robust methods
for seismically loud environments, and might lead to the detection of lower magnitude events such as regional earthquakes or landslides. 
Ages and Hf isotopes of igneous zircons from Neoarchean TTG gneisses in the Eastern Block, North China Craton: Tectonic implications
Authors: Zhao Guochun
Published: March 2020

Available zircon ages indicate that the plutonic protoliths of Neoarchean TTG (tonalitic-trondhjemitic-granodioritic) gneisses in the Eastern Block were emplaced at two phases, with the earlier one at 2.75-2.65 Ga and the younger one at 2.55-2.50 Ga. Although the 2.75-2.65 Ga rock associations are only exposed in the Luxi and Qixia areas, the ~2.7 Ga igneous event must have occurred across the whole Eastern Block and was a major crustal accretionary or mantle-extraction event that formed a thick mafic crust beneath the whole Eastern Block based on the following lines of evidence:

(1) The 2.75-2.65 Ga TTG rocks in the Luxi granite-greenstone terrane have positive εHf(t) values (+2.7 to +10.0), with most zircon Hf model ages close to the rock-forming ages, which provides robust evidence that the ~2.7 Ga event that formed the 2.75-2.65 rock associations was a crustal accretion (mantle extraction) event, not a crust-reworking event.

(2) The 2.55-2.50 Ga TTG rocks in the Eastern Block possess mildly positive to slightly negative εHf(t) values, with most zircon Hf model ages pointing to 2.8-2.6 Ga, similar to rock-forming ages of the 2.75-2.65 Ga TTG gneisses in the Luxi granite-greenstone terrane, suggesting that the 2.55-2.50 Ga rocks in the Eastern Block were mainly derived from the partial melting of an early Neoarchean (2.75-2.65 Ga) juvenile crust that formed at ~2.7 Ga. As the 2.55-2.50 Ga TTG gneisses are ubiquitous over the whole Eastern Block, the 2.7 Ga event must have occurred over the whole Eastern Block, forming an early Neoarchean juvenile crust that experienced partial melting or reworking to form the 2.55-2.50 Ga TTG rocks.

(3) TTG rocks are generally considered to have been derived from the partial melting of a thickened mafic crust (eclogite or rutitle/garnet-bearing amphibolite). This means that an early Neoarchean (2.75-2.65 Ga) juvenile crust formed by the ~2.7 Ga event should be a mafic-dominant crust, which is either a lower continental crust or an oceanic crust. In this case, the ~2.7 Ga event in the Eastern Block may have represented a Large Igneous Province event that formed the main body of the Eastern Block. This study was financially supported by the sub-project of a NSFC Major Project, entitled “Continental Crust Growth-Stabilization and Initiation of the Early Plate Tectonics” (Project Code: 41890831) and HKU Seed Fund for Basic Research (201811159089).
The main types of river channel bedforms movement
Authors: Borisova Olga , Sidorchuk Alexei
Published: March 2020

There are two main types of movement of bedforms in the river channel. Active bedforms are three-dimensional, symmetrical, with gentle slopes. They move without significant change in shape, since all parts of their surface move at the same celerity. Passive bedforms are two-dimensional, asymmetric, with steep leeward slope. Bedform top moves faster than hollow and bedform deform, skew.

Bedforms are usually organised into hierarchical complexes in the river channels, where smaller bedforms move along the surface of larger ones. With active movement, the morphology and dynamics of bedforms of different orders in the hierarchy are relatively independent. The relationships between bedforms of different orders is increasing in the case of passive movement.

Bed load transport in the river channel depends on the type of bedforms movement. In the case of active bedforms, bedload transport rate, computed with their morphology and celerity, is different for different bedform orders. The total bedload transport rate is equal then to the sum of bedload transportation by bedforms of different orders, plus sediments transit. In the case of passive movement, the total bedload transport rate is equal to bedload transportation by bedforms with steep leeward slopes and complete deposition there of all incoming sediments. Then it is possible to use Exner’s equation of deformation for estimating of bedload transport rate.

This study was carried out under the project: “Evolution and Transformation of Erosion-Channel Systems under Changing Environment and Human Impact”
The storage and influencing factors of mercury in the permafrost of the Tibetan Plateau
Authors: Gu Jing , Pang Qiaotong , Ding Jinzhi , Yin Runsheng , Yang Yuanhe , Zhang Yanxu
Published: March 2020

Soil is one of the largest reservoir of mercury in the environment. Globally, most of the mercury in the soil is stored in permafrost, such as the Arctic and the Tibetan Plateau. Mercury in the soil is mainly derived from atmospheric deposition and tightly bound to the organic carbon. The mercury level in the permafrost over the Tibetan Plateau and its influencing factors have been less studied. This study analyzes soil total mercury (STHg) concentrations and its vertical distribution in meadow soil samples collected from the Tibetan Plateau. We adopt a nested-grid high-resolution GEOS-Chem model to simulate atmospheric mercury deposition. The relationship between STHg and soil organic carbon(OCD) as well as atmospheric deposition are explored. We also extend our analysis to data in the Tibetan Plateau and other regions of China in the literature. Our results show that the STHg concentrations in the Tibetan Plateau are 19.9±12.4 ng/g. The concentrations are higher in the south/east and lower in the north/west in the Tibetan Plateau, consistent with the previous results. Our model shows that the average deposition flux of Hg is 3.3 ug m-2 yr-1 with 57% contributed by dry deposition of Hg0, followed by dry deposition of HgII and HgP (19%) and wet deposition (24%). We calculate the Hg to carbon ratio (RHgC) of 5.52 ± 5.11 μg Hg/g C and the estimated STHg is 67.45 Gg in alpine grasslands in the Tibetan Plateau, contributing about 2.7% globally. We find a positive correlation between OCD and STHg in the Tibetan Plateau(Log(STHg) = 0.35log(OCD) + 0.99, R2 = 0.24) and a weak relationship between model residual (defined as the difference between model fitting values and observations) and atmospheric total Hg deposition. We conclude that soil organic carbon(SOC) and atmospheric deposition work simultaneously for STHg. Atmospheric deposition determines the potential levels of STHg in large spatial scales, while SOC and its characteristics modulate STHg locally by influencing the fate and transport of Hg.
Controls on coastal overwash morphology in natural and built environments
Authors: Williams Hannah , Taylor Luke , Goldstein Evan , Lazarus Eli
Published: March 2020

Overwash is a key mechanism controlling the flux of sediment from the front of a barrier island to the top and back of an island during a storm event. The process is essential for barrier environments to maintain their height and width relative to sea level. Barrier topography and vegetation – and also road networks and buildings – can direct overwash flow, and thus the shape and size of sedimentary deposits that overwash leaves behind. Controls on overwash deposition have been examined more closely in natural settings than in developed zones. But overwash poses a major hazard to coastal infrastructure, and accurate prediction of storm impacts requires quantitative insight into the dynamics of overwash morphology in built settings. Here, we compare barrier floodplain controls across a range of spatial "fabrics", both natural and built (e.g., sparse to dense vegetation coverage; sparse to dense configurations of roads and buildings), to explore how these fabrics affect scaling relationships for overwash morphology. Integrating empirical measurements from post-storm imagery, trials of an analogue model in a small experimental basin, and results from a numerical toy model, we identify thresholds at which floodplain fabrics cause scaling relationships to change, or "break". Our findings illustrate a continuum in overwash pattern formation between endogenous self-organisation and exogenous forcing templates, and set up further inquiry into the dynamics of flood deposition in built environments.
The versatile Heliosat-V method for estimating downwelling surface solar irradiance from satellite imagery
Authors: Tournadre Benoit , Gschwind Benoit , Saint-Drenan Yves-Marie , Blanc Philippe
Published: March 2020

Downwelling surface solar irradiance (DSSI) is one of the Essential Climate Variables defined by the Global Climate Observing System. The knowledge of its space and time variabilities is of primary importance for different applications, including Earth sciences, agriculture and renewable solar energies. To characterize such variabilities, the retrieval of long time series and of a dense kilometric global spatial coverage is required. The Heliosat methods are developed by Mines ParisTech since the mid-1980’s to estimate DSSI from the imagery produced by geostationary meteorological satellites. A challenge today is to use imagery from different satellites, including non-geostationary. This raises a number of issues, related among others to the different viewing geometries and spectral sensitivities of the sensors. These issues motivate the evolution of the Heliosat methods toward a more flexible version: the versatile Heliosat-V method. Other difficulties, mainly of operational types, such as massive data retrieval/processing, geometric correction, radiometric cross-calibration, missing data, seamless mosaicking, etc. are out of the scope of this communication.

Heliosat-V is designed to produce estimates of DSSI that can cover a wide variety of satellite optical sensors that have at least one radiometric channel with sensitivity in the 400-1000-nm part of the electromagnetic spectrum. The method is capable of using calibrated imagery from geostationary and also non-geostationary satellites. External remote-sensed data of surface reflectance anisotropy (Ross-Li model parameters derived from the imagery of the Moderate-Resolution Imaging Spectroradiometer (MODIS)) and atmospheric composition (ozone, water vapour and aerosol types and optical depths) from coupled meteorological and chemical transport models (Copernicus Atmospheric Monitoring Services) are used to produce fast radiative transfer simulations. Typical reflectances of cloudy scenes at the top of the atmosphere are produced via look-up tables derived from a radiative transfer model (libRadtran). They can adapt to the spectral sensitivity of the satellite channel, and to the solar and viewing geometries. This algorithm setup allows its use without past data, which were necessary for previous Heliosat methods. This is a real asset for its implementation to non-geostationary satellites.

We test the validity of the method, by comparing DSSI estimates derived from one year of Meteosat Second Generation 0° imagery, with ground-based pyranometer measurements from 10 stations of the Baseline Surface Radiation Network, on different continents and environments. Our results show root-mean square errors of 15-min averaged DSSI between 12% and 35% (71 and 133 W m-2 in absolute value), similarly to existing surface irradiance products based on Heliosat-2 or Heliosat-4.
Performance Evaluation of different time schemes for a Nonlinear diffusion equation on multi-core and many core platforms
Authors: Bessone Lucas , Gamazo Pablo , Ramos Julián , Storti Mario
Published: March 2020

GPU architectures are characterized by the abundant computing capacity in relation to memory bandwich. This makes them very good for solving problems temporaly explicit and with compact spatial discretizations. Most works using GPU focuses on the parallelization of solvers of linear equations generated by the numerical methods. However, to obtain a good performance in numerical applications using GPU it is crucial to work preferably in codes based entirely on GPU. In this work we solve a 3D nonlinear diffusion equation, using finite volume method in cartesian meshes. Two different time schemes are compared, explicit and implicit, considering for the latter, the Newton method and Conjugate Gradient solver for the system of equations. An evaluation is performed in CPU and GPU of each scheme using different metrics to measure performance, accuracy, calculation speed and mesh size. To evaluate the convergence propierties of the different schemes in relation to spatial and temporal discretization, an arbitrary analytical solution is proposed, which satisfies the differential equation by chossing a source term chosen based on it.
Land use and land cover change impact on surface temperature: the scale issue
Authors: Li Dan , Wang Liang
Published: March 2020

While land use and land cover change (LULCC) is often a temporal phenomenon (i.e., a patch transitions from one land cover type to another), many studies use a space-for-time approximation that quantifies the LULCC impact (say on surface temperature or fluxes) by comparing two adjacent patches of different land covers. An important consideration embedded in this space-for-time approximation is the scale, which determines what assumptions we can make when constructing models for studying land-atmosphere interactions over heterogeneous terrain. Most previous studies employ one-dimensional models without considering the appropriate scale associated with these models. In this presentation, the scale issue in studying LULCC-induced surface temperature anomalies will be discussed using a hierarchy of models. Typical one-dimensional models based on the surface energy balance and/or convective boundary layer dynamics will be compared to two-dimensional models where horizontal advection is explicitly considered. The results highlight the importance of scale in determining the sensitivity of land surface temperature to changes in albedo and moisture/vegetation characteristics. 
Energetic Solar Particle Access to the Near-Equatorial Inner Magnetosphere
Authors: Filwett Rachael , Jaynes Allison , Baker Daniel , Kanekal Shrikanth , Blake Bern , Kress Brian
Published: March 2020

Solar proton events are comprised of energetic protons of solar and interplanetary origin. Such energetic particles are able to access the magnetosphere at various locations according to their cutoff rigidity. The specific properties of solar proton access are of great interest for space weather prediction purposes. Using Van Allen Probes/Relativistic Electron-Proton Telescope (REPT) 20-200 MeV proton data we examine four of the strongest solar proton events over the lifetime of the mission. We present evidence of the direct magnetospheric access of these energetic solar protons and find strong flux increases at L<4. Results indicate that small and sudden flux changes measured by ACE spacecraft sensors upstream of Earth are also seen in the near-equatorial inner magnetosphere. Using the East-West asymmetry of solar protons as a proxy for cutoffs we examine the highly dynamic cutoff rigidity. We find there is evidence for: (1) cutoff rigidity dependence on MLT; (2) suppressed cutoffs with rapid Dst changes; and (3) rapid evolution of cutoffs even during quiet magnetospheric conditions.