bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of long-term soil warming on nitrogen fluxes in forest soils
Authors: Inselsbacher Erich , Heinzle Jakob , Schindlbacher Andreas
Published: March 2020

Forests are the main contributors to the global terrestrial carbon (C) sink but several studies suggest that global warming could significantly reduce their CO2 mitigation potential. The capacity of forest plants to sequester C is closely linked to soil nitrogen (N) availability, a major control of plant growth and ecosystem functioning. An increase of soil temperature caused by global change is critically affecting soil N supply rates, both directly by increasing diffusive N fluxes in the soil solution and indirectly by accelerating soil N turn-over rates. In recent short-term laboratory incubation studies, an increase in soil temperature has not only led to a significant increase in diffusive N fluxes but also to a concomitant shift in N quality available for plant uptake towards a higher portion of inorganic N forms compared to small organic N forms such as amino acids. However, until now long-term effects of soil warming on soil N fluxes have not been studied. Here, we present first results from a study on soil N availabilities at the long-term soil warming experimental site Achenkirch (Austria) in the Limestone Alps. This site is one of the few in situ climate manipulation experiments operational for more than 10 years and has already provided a wealth of novel insights into the potential effects of global warming on forest ecosystem responses. Applying in situ microdialysis, we estimated diffusive fluxes of inorganic N and amino acids along the growing season in soils warmed by resistance heating cables since 2005 (+4 °C compared to control plots) and control soils. Fluxes of all N forms were highly variable within each subplot (2 x 2 m) and reflected the high heterogeneity of soils at this forest site. Interestingly, fluxes of amino acids were less variable than of nitrate or ammonium throughout the year, indicating comparably stable protein depolymerization rates. In summary, long-term soil warming affected diffusive N fluxes but less than other factors operating on smaller (< 1 cm) scales.
Solid ammonium nitrate aerosols: efficient ice nucleating particles in the upper troposphere during Asian monsoons investigated by aircraft, satellite and cloud-chamber
Authors: Höpfner Michael , Ungermann Jörn , Wagner Robert , Spang Reinhold , Riese Martin , Stiller Gabriele , Bucci Silvia , Friedl-Vallon Felix , Johansson Sören , Legras Bernard , Leisner Thomas , Möhler Ottmar , Müller Rolf , Neubert Tom , Orphal Johannes , Preusse Peter , Rex Markus , Saathoff Harald , Stroh Fred , Wohltmann Ingo
Published: March 2020

Strong convection within the Asian monsoon system quickly transports polluted air masses from the boundary layer into the upper troposphere where secondary aerosol formation can take place. Here we present remote sensing observations by infrared limb sounding systems providing vertical and horizontal distributions of ammonia (NH3) and solid ammonium nitrate (AN) aerosol particles. Besides the identification of trace gases, characteristic signatures in the mid-infrared spectral region are used to infer information about composition and phase of the aerosol particles. We will show an analysis of AN and NH3 in the Asian monsoon upper troposphere from a combination of two satellite limb sounders, CRISTA on SPAS in August 1997 and MIPAS on Envisat, from 2002-2011.

In addition, limb-imaging measurements obtained with the GLORIA instrument on board the Geophysica high-altitude aircraft provided the opportunity to obtain vertical cross sections along the flight path of AN aerosol mass and NH3 volume mixing ratios during the Asian monsoon field campaign of the StratoClim project in summer 2017. We analysed the airborne dataset with the help of trajectory calculations combined with temporally and locally connected satellite data of nadir-pointing instruments, like IASI, to infer the distribution of NH3 in the lower troposphere, as well as geostationary satellites to deduce the presence of convective influence.

Further, we performed experiments at the AIDA cloud and aerosol chamber laboratory (a) to support the analysis of the aerosol infrared spectral signature in remote sensing, (b) to investigate the conditions leading to the unexpected solid phase of AN particles as well as, (c) to study their potential to act as ice nucleating particles.
Soil gas CO2 emissions and fault locking along the Anninghe fault and the Zemuhe fault, in China Seismic Experimental Site
Authors: Li Ying , Yang Yao , Chen Zhi
Published: March 2020

The Anninghe fault (ANHF) and the Zemuhe fault (ZMHF) with high level of seismic hazards in the China Seismic Experimental Site, located in southeastern of Tibet, are some of the most active faults in China. Measurement of the soil gas CO2 has been conducted in three sites along the ANHF and the ZMHF for the first time. Totally, 394 sampling points along 15 profiles were measured. The fault locking degree of different segments of the ANHF and the ZMHF were inverted by the negative dislocation model using GPS velocity data  since 2013 to 2017. The measurements results show that the average and maximum value of CO2 in the ZMHF is significantly higher than that in the ANHF. Soil gas CO2 geochemistry yielded different spatial anomalous features, indicating the different properties and permeability of the faults. The inversion results reveal that the level of coupling including the locking depth and intensity along the southern segment of the ANHF was significantly larger than the northern segment of the ZMHF. Combining the CO2 emission results, we concluded that the intensive locking of the segments reduced their permeability due to the self-sealing process, results in less gas to escape from the deep. Correspondingly, the creeping fault with low level of coupling can maintain high permeability which is more favorable to gas CO2 migration.
Laboratory Experiments on the Droplet Shattering Secondary Ice Production Mechanism
Authors: Keinert Alice , Kleinheins Judith , Spannagel Dominik , Kiselev Alexei , Leisner Thomas
Published: March 2020

Supercooled drizzle droplets may produce multiple ice particles upon freezing. This mechanism could potentially explain the high ice number concentrations outside of temperature range where the well-known Hallett-Mossop mechanism of ice multiplication would take place. Limited experimental methods in the past prevented direct observations of the shattering droplets, resulting in a wide range of experimental results, unsuitable for the development of a sophisticated cloud model parameterization. Recently, we have revived experiments on secondary ice production by levitating individual drizzle droplets in electrodynamic balance (EDB) and observing the freeze-shattering with high-speed video microscopy and high-resolution infrared thermal measuring system. In this way we have been able to identify three additional SIP mechanisms (cracking, jetting and bubble bursts) associated with the freezing of drizzle droplets (Lauber et al., 2018).
Additionally, we have extended the range of experimental conditions to mimick the freezing of continental (pure water) and maritime (aqueous solution of analogue sea salt) drizzle droplets suspended in the updraft of cold moist air. We report a strong enhancement of shattering probability as compared to the previous studies conducted under stagnant air conditions. The high-definition video records of shattering events reveal the coupling between various microphysical processes caused by ice propagation inside the freezing drop and reveal striking difference between freezing of pure water and SSA solution droplets. Application of high-resolution infrared microscopy allowed us to record the evolution of the droplet temperature under realistic flow conditions and thus constrain the thermodynamic parameters controlling the pressure build-up inside the droplet. Based on these new observation data and theoretical model of freezing droplet, we discuss the physical mechanism behind the shattering of drizzle droplets and its implication for mixed-phase cloud modeling.

Lauber, A., A. Kiselev, T. Pander, P. Handmann, and T Leisner (2018). “Secondary Ice Formation during Freezing of Levitated Droplets”, Journal of the Atmospheric Sciences 75, pp. 2815–2826.
Research on emergency rescue plan of plateau area after earthquake based on road accessibility
Authors: Li Junming
Published: March 2020

Road damage in plateau mountainous areas has a significant impact on emergency rescue, and the size of the area where emergency rescue vehicle teams travel at different rescue stages is different, which also gives rise to different considerations of road demand. Current research finds that the respective characteristics of Dijkstra's algorithm and ant colony algorithm can meet the different needs of emergency rescue vehicle teams when they are traveling at different regional sizes. Therefore, the article simulates the earthquake and calculates the road accessibility results after the earthquake, and then considers the differences in road demand and considers the size of different regions, the Dijkstra algorithm and the ant colony algorithm are used respectively to plan the overall emergency rescue plan by setting different scenarios. The results show that the emergency rescue-planning route in different scenarios provided by the plan is scientific and reasonable, and can provide support in the research of key links.
Integration of point clouds from UAV photogrammetry and laserscan survey for the assessment of the risk of collapse of the vault of an underground cavity
Authors: Martinucci Davide , Pillon Simone , Bezzi Annelore , Casagrande Giulia , Fontolan Giorgio , Potleca Michele , Bieker Fiorella , Bratus Antonio , Manca Paolo , Blanos Rita , Paganini Paolo
Published: March 2020

Photogrammetric surveys from UAV and LiDAR surveys are two techniques that allow for the production of very high resolution point clouds. The use of these techniques result in a detailed reconstruction of difficult-to-access environments such as underground cavities. A rigorous georeferencing of the acquired data allows for a comparison of the hypogean development of the cave to the overlying territory. This study presents a case of integration between these two techniques, applied to the risk assessment of the collapse of the vaults in a natural cavity in the Trieste Karst (north east Italy). This site is particularly delicate given that on the slope above the cave there is an abandoned stone quarry. In order to survey the quarry above the cave, a flight was performed with UAV, while the cave was surveyed with Laser Scan from the ground. The flight was made using a UAV DJI Phantom RTK, which carried a 20 Mpixel 1“ sensor camera. 8 ha of terrain was surveyed, capturing about 733 high resolution images and surveying 22 GCPs (Ground Control Point) with a GNSS RTK receiver. It was possible to reduce the number of GCPs, since the drone recorded the shooting positions very accurately with the on-board GPS RTK. Data were analyzed using Agisoft Metashape Professional to produce an orthophoto and a DSM (Digital Surface Model) with a ground resolution of 0.02 m and 0.04 m respectively. The point cloud has a density of 586 points/m2. The LiDaR survey was carried out using an ILRIS 3D ER laser scanner from Optec. The point cloud has a density of approximately 2500 points/m2 and 5 stations were needed to cover the underground development of the cavity. The georeferencing of the data was carried out by roto-translation on geo-referenced benchmarks, surveyed with GPS RTK and total station. The point cloud was processed using Terrascan software (Terrasolid). The two point clouds were aligned, geo-referenced and combined using Polyworks software (Innovmetric), in order to check the thicknesses of the material present above the vault of the cave. The integration of epigean and hypogean data made it possible to identify some critical points related to a vault thickness of approximately 1.5 meters, located at the quarry square. This work made it possible to highlight critical issues difficult to detect without the integrated approach of these different survey methodologies.
Arctic greening, Arctic browning or Arctic drowning?
Authors: Magnússon Rúna , Heijmans Monique M. P. D. , Limpens Juul , van Huissteden Ko , Kleijn David , Maximov Trofim C.
Published: March 2020

Thawing of permafrost and the resulting decomposition of previously frozen organic matter constitute a positive feedback to global climate. However, contrasting mechanisms are at play. Gradual increases in thawing depth and temperature are associated with enhanced vegetation growth, most notably in shrubs (“greening”). In ice-rich permafrost, abrupt thaw (thermokarst) results in disturbance of vegetation and surface wetting, which may result in an opposing trend (“browning”).

We determined the balance of shrub decline and expansion in an ice-rich lowland tundra ecosystem in north-Eastern Siberia using vegetation classification and change analysis. We used random forest classification on 3 very high resolution commercial satellite images gathered between 2010 and 2019 (GeoEye-I and WorldView-II). To mitigate (slight) differences in sensor properties and vegetation phenology, a spatio-temporal implementation of Potts model was used to utilize both spectral properties of a pixel and its degree of correspondence with spatially and temporally neighbouring pixels. This reduced artefacts in change detection substantially and improved accuracy of classification for all three images.

We found that shrub vegetation declines in this lowland tundra ecosystem. Areas of thaw features (thermokarst ponds, thermoerosion gullies) and aquatic plant types (sedges and peat mosses) however show an increasing trend. Markov Chain analysis reveals that thaw features display a succession from open water / mud to sedges to peat moss. 

This transition from shrub dominated to wetland species dominated tundra may have important implications for this ecosystem's greenhouse gas balance and is indicative of wetter conditions. Thermokarst may be an important driver of such change, as thaw features are found to expand at the expense of shrub vegetation and show rapid colonization by aquatic species. 
Simultaneous fate of trace organic compounds and dissolved organic matter in surface water and the hyporheic zone of an urban river
Authors: Mueller Birgit Maria , Schulz Hanna , Putschew Anke , Lewandowski Jörg
Published: March 2020

Rivers being influenced by treated wastewater are characterized by an altered water chemistry compared to their natural state. Downstream of the outlet of a wastewater treatment plant (WWTP), concentrations of dissolved organic matter (DOM) and trace organic compounds (TrOCs) in the receiving river are increased. As DOM might serve as a metabolic co-substrate during microbial TrOC degradation, DOM influences the attenuation of TrOCs. Due to steep biochemical gradients at the surface water - groundwater interface, the hyporheic zone is considered a hotspot for microbial activity. Therefore, turnover rates in the hyporheic zone of a stream are high in comparison to the turnover rates in the water column. The River Erpe is a sandy lowland river in the East of Berlin, Germany, which receives treated wastewater from the WWTP Muenchehofe. In order to study the simultaneous fate of TrOCs and DOM in surface water and the hyporheic zone, a field sampling campaign was conducted at a side channel of the River Erpe. Surface water samples were taken at site A and both surface and pore water samples from 25 cm sediment depth were taken at site B which is 850 m downstream of site A. The sampling interval was every three hours over 48 hours. Samples were analysed for 17 TrOCs (HPLC-MS/MS) and the molecular composition of DOM (FT-ICR MS). DOM compound classes were calculated semi-quantitatively as the percentage share of each class of the whole DOM composition. Mean concentrations of the TrOCs analysed changed by an increase of 200 % to a decrease of 29 % in the surface water between site A and B and by a decrease of 5 to 93 % in the hyporheic zone at site B. The molecular composition of DOM changed at most by a single digit percentage per compound group with the attenuation being larger in the hyporheic zone. The percentage share of two out of seven DOM compound classes significantly correlated with the concentration of at least ten TrOCs between surface water at site A and B. Such a correlation was observed for five compound classes in the hyporheic zone at site B. The present study shows that the attenuation of both TrOCs and DOM in a sandy urban river mainly takes place in the hyporheic zone but it is not capable of assuming a causal relationship between the attenuation of TrOCs and DOM.
Study of Northeast Monsoon over India using a coupled land-atmosphere model RegCM4-CLM4.5
Authors: Rai Praveen , Maharana Pyarimohan , Kumar Dhirendra , Dimri Ashok Priyadarshan , Paeth Heiko
Published: March 2020

The major rainfall period over the southern peninsular part of the Indian Subcontinent generally occurs during the months of October-December (OND) through the northeast (NE) monsoon (also called winter monsoon or post-monsoon season). The present study focuses on the ability of regional climate model RegCM4 forced with MIROC5 Global Climate Model and three different land-surface parameterization schemes: Biosphere-Atmosphere Transfer Scheme (BATS, herewith referred as CONTROL), Community Land Model (CLM4.5), and Sub-grid BATS in capturing the mean features of NE monsoon for the present climate (1975-2005) over India region. Based on their ability to simulate the inter-annual and intra-seasonal variability, and seasonal mean during monsoon, the current GCM is selected for downscaling from the available literature. The model performance is evaluated against the gridded temperature and precipitation datasets from the Climate Research Unit (CRU) and India Meteorological Department (IMD) respectively. We have found that the MIROC5_CLM4.5 is simulating the precipitation and surface temperature better than other experiments with relatively less bias over the study. MIROC5_CLM4.5 experiment again performs well in capturing the precipitation and surface temperature during wet and dry years’ composite. Overall, our results show a better representation of NE Monsoon mean features by MIROC5_CLM4.5 compared to other sets. The RegCM4-CLM4.5 coupled simulation has shown promising performance in representing NE monsoon. Further, it is envisaged to test and customize this framework in order to generate reliable future projections in subsequent studies.

Keywords: RegCM4, CLM4.5, NE Monsoon, Downscaling.
Recent glacial advance in the western Weddell Sea Sector driven by anomalous sea ice circulation
Authors: Christie Frazer , Benham Toby , Dowdeswell Julian
Published: March 2020

The Antarctic Peninsula is one of the most rapidly warming regions on Earth. There, the recent destabilization of the Larsen A and B ice shelves has been directly attributed to this warming, in concert with anomalous changes in ocean circulation. Having rapidly accelerated and retreated following the demise of Larsen A and B, the inland glaciers once feeding these ice shelves now form a significant proportion of Antarctica’s total contribution to global sea-level rise, and have become an exemplar for the fate of the wider Antarctic Ice Sheet under a changing climate. Together with other indicators of glaciological instability observable from satellites, abrupt pre-collapse changes in ice shelf terminus position are believed to have presaged the imminent disintegration of Larsen A and B, which necessitates the need for routine, close observation of this sector in order to accurately forecast the future stability of the Antarctic Peninsula Ice Sheet. To date, however, detailed records of ice terminus position along this region of Antarctica only span the observational period c.1950 to 2008, despite several significant changes to the coastline over the last decade, including the calving of giant iceberg A-68a from Larsen C Ice Shelf in 2017.

Here, we present high-resolution, annual records of ice terminus change along the entire western Weddell Sea Sector, extending southwards from the former Larsen A Ice Shelf on the eastern Antarctic Peninsula to the periphery of Filchner Ice Shelf. Terminus positions were recovered primarily from Sentinel-1a/b, TerraSAR-X and ALOS-PALSAR SAR imagery acquired over the period 2009-2019, and were supplemented with Sentinel-2a/b, Landsat 7 ETM+ and Landsat 8 OLI optical imagery across regions of complex terrain.

Confounding Antarctic Ice Sheet-wide trends of increased glacial recession and mass loss over the long-term satellite era, we detect glaciological advance along 83% of the ice shelves fringing the eastern Antarctic Peninsula between 2009 and 2019. With the exception of SCAR Inlet, where the advance of its terminus position is attributable to long-lasting ice dynamical processes following the disintegration of Larsen B, this phenomenon lies in close agreement with recent observations of unchanged or arrested rates of ice flow and thinning along the coastline. Global climate reanalysis and satellite passive-microwave records reveal that this spatially homogenous advance can be attributed to an enhanced buttressing effect imparted on the eastern Antarctic Peninsula’s ice shelves, governed primarily by regional-scale increases in the delivery and concentration of sea ice proximal to the coastline.
Why are some alpine catchments debris-flow active and others not? - the influence of geomorphology on debris-flow initiation
Authors: Aigner Philipp , Sklar Leonard , Hrachowitz Markus , Kaitna Roland
Published: March 2020

Processes like flash floods or debris flows, which typically occur in small headwater catchments, represent a substantial natural hazard in alpine regions. Due to the entrainment of sediment, the discharge of debris flows can be up to an order of magnitude larger compared to 100-year fluvial flood events in the same channel, which poses a great threat to affected communities. Besides the triggering rainfall, the initiation of debris flows depends on the watershed’s hydrological and geomorphological susceptibility, which makes it hard to predict and understand where and when debris flows occur.

In this study we aim to quantify the influence of geomorphologic characteristics and long-term sediment dynamics on debris flow activity in the Austrian Alps. Based on a database of debris-flow events within the last 60+ years, a geomorphological assessment of active and non-active sub-catchments in different study regions is carried out. In a first step, we derive geomorphological characteristics, such as terrain roughness, Melton number as well as weathering potential of geological units found within the watersheds. Based on the findings of the terrain shape analysis, a set of representative watersheds will be selected for systematic monitoring of surface elevation changes over the project period of three years. This will be achieved by comparing digital surface models based on photogrammetric UAV surveys and monitoring of channel reaches with cameras.

In order to project these findings onto a larger regional scale, the derived terrain parameters will be used to integrate and extend a previously designed hydro-meteorological debris-flow susceptibility model (Prenner et al., 2018) with a sediment-disposition-model. This will form the basis for an advanced debris flow forecasting tool and help to better assess the impact of climate change on the magnitude and frequency of future debris flows.

 

References:

Prenner, D., Kaitna, R., Mostbauer, K., & Hrachowitz, M. ( 2018). The value of using multiple hydrometeorological variables to predict temporal debris flow susceptibility in an Alpine environment. Water Resources Research, 54, 6822– 6843.

 
Optimal processing and unphysical effects in seismic noise correlations
Authors: Fichtner Andreas , Bowden Daniel , Ermert Laura
Published: March 2020

A wide spectrum of processing schemes is commonly applied during the calculation of seismic noise correlations. This is intended to suppress large-amplitude transient and monochromatic signals, to accelerate convergence of the correlation process, or to modify raw correlations into more plausible approximations of inter-station Green's functions. Many processing schemes, such as one-bit normalisation or various non-linear normalizations, clearly break the linear physics of seismic wave propagation. This naturally raises the question: To what extent are the resulting noise correlations physically meaningful quantities?

In this contribution, we rigorously demonstrate that most commonly applied processing methods introduce an unphysical component into noise correlations. This affects noise correlation amplitudes but also, to a lesser extent, time-dependent phase information. The profound consequences are that most processed correlations cannot be entirely explained by any combination of Earth structure and noise sources, and that inversion results may thus be polluted.

The positive component of our analysis is a new class of processing schemes that are optimal in the sense of (1) completely avoiding the unphysical component, while (2) closely approximating the desirable effects of conventional processing schemes. The optimal schemes can be derived purely on the basis of observed noise, without any knowledge of or assumptions on the nature of noise sources.

In addition to the theoretical analysis, we present illustrative real-data examples from the Irish National Seismic Network and the Lost Hills array in Central California. This includes a quantification of potential artifacts that arise when mapping unphysical traveltime and amplitude variations into images of seismic velocities or attenuation.
Global analysis of the uncertainties prevailing in global-scale assessment of coastal flood damage and adaptation costs under 21st century sea-level rise
Authors: Rohmer Jeremy , Lincke Daniel , Hinckel Jochen , Le Cozannet Goneri , Lambert Erwin
Published: March 2020

Global scale assessment of coastal flood damage and adaptation costs under 21st century sea-level rise are associated with a wide range of uncertainties including those in future projections of socioeconomic development (SSP scenarios), of greenhouse gas emissions (RCP scenarios), and of sea-level rise (SLR). These uncertainties also include structural uncertainties related to the modeling of extreme sea levels, vulnerability functions, and the translation of flooding-induced damage to costs. This raises the following questions: what is the relative importance of each source of uncertainty in the final global-scale results? Which sources of uncertainty need to be considered? What uncertainties are of negligible influence? Hence, getting better insights in the role played by these uncertainties allows to ease their communication and to structure the message on future coastal impacts and induced losses. Using the integrated DIVA Model (see e.g. Hinkel et al., 2014, PNAS), we extensively explore the impact of these uncertainties in a global manner, i.e. by considering a large number (~3,000) of scenario combinations and by analyzing the associated results using a regression-based machine learning technique (i.e. regression decision trees). On this basis, we show the decreasing roles, over time, of the uncertainties in the extremes’ modeling together with the increasing roles of SSP and of RCP after 2030 and 2080 for the damage and adaptation costs respectively. This means that mitigation of climate change helps to reduce uncertainty of adaptation costs, and choosing a particular SSP reduces the uncertainty on the expected damages. In addition, the tree structure of the machine learning technique allows an in-depth analysis of the interactions of the different uncertain factors. These results are discussed depending on the SLR data selected for the analysis, i.e. before and after the recently released IPCC SROCC report on September 2019.
Simple solutions for the concentration fluctuations of a passive scalar
Authors: Camporeale Carlo , Bertagni Matteo , Marro Massimo , Salizzoni Pietro
Published: March 2020

The dispersion dynamics of a contaminant released in the atmosphere is crucial for risk assessments and environmental analyses. Yet, because of the unsolved problem of turbulence, analytical solutions physically-derived are currently limited to the Gaussian models for the mean concentration field. In this work, we have obtained simple solutions for the concentration statistics of a passive scalar released from a punctual source. The main result is a novel analytical solution for the passive scalar variance, which is obtained from the contaminant transport equation. We have verified this solution against wind-tunnel data, and further adopted it in a simple stochastic model to provide closed relationships for the temporal statistics of concentration (e.g., the mean duration and occurrence of the peak events). These results may serve as a rapid and practical way to estimate the intensity and duration of the concentration fluctuations of a pollutant released in the atmosphere.
Recognition of horizontal layers in a segmented radargram after the application of Canny edge detector
Authors: Vrtunski Milan , Bugarinović Željko , Pajewski Lara , Ristić Aleksandar , Govedarica Miro
Published: March 2020

This paper presents a method for the automated detection and elimination of horizontal reflections from ground penetrating radar (GPR) profiles after Canny edge filtering. Horizontal reflections are generated by interfaces between different media parallel to the air-soil interface. The recognition of horizontal layers is a crucial task when the number of layers and their thicknesses need to be estimated (e.g., in GPR road surveys). Identifying and deleting horizontal reflections from a radargram is also useful to facilitate the subsequent automated extraction of hyperbolic reflections [1-3]. It has to be noted that the removal of horizontal layers can increase the level of radargram segmentation.

In the proposed method, the first segmentation step is the application of Canny edge detector to the entire radargram. Then, horizontal layer recognition is done by carefully choosing boundary values. These values are varied many times until optimal values, depending on data acquisition parameters, are adopted. Special attention is paid to time efficiency of both segmentation steps, to investigate the possibility of employing the proposed solution in near real-time applications. The final result is an image where edge pixels arranged horizontally are removed.

Testing of this algorithm is done in MATLAB software environment, on a set of data with different levels of complexity, by varying the acquisition parameters.

 

References

[1]  A. Ristić, Ž. Bugarinović, M. Govedarica, L. Pajewski, and X. Derobert, “Verification of algorithm for point extraction from hyperbolic reflections in GPR data,” Proc. 9th International Workshop on Advanced Ground Penetrating Radar (IWAGPR 2017), Edinburgh, UK, pp. 1-5, 2017.

[2]  A. Ristić, M. Vrtunski, M. Govedarica, L. Pajewski, and X. Derobert, “Automated data extraction from synthetic and real radargrams of district heating pipelines,” Proc. 9th International Workshop on Advanced Ground Penetrating Radar (IWAGPR 2017), Edinburgh, UK, pp. 1-5, 2017.

[3]  Ž. Bugarinović, S.  Meschino, M. Vrtunski, L. Pajewski, A. Ristić, X. Derobert, and M. Govedarica, “Automated Data Extraction from Synthetic and Real Radargrams of Complex Structures,” Journal of Environmental and Engineering Geophysics, Vol. 23(4), pp. 407-421, 2018.
Effect of selecting different simulation configurations on the prediction performance of the Space Weather Modeling Framework regarding ground magnetic perturbations
Authors: Kwagala Norah Kaggwa , Hesse Michael , M. Jorgensen Therese , Tenfjord Paul , Norgren Cecilia , Toth Gabor , Gombosi Tamas , M. Kolstø Håkon , F. Spinnangr Susanne
Published: March 2020

This study investigates the effect of selecting different simulation configurations of the Space Weather Modeling Framework (SWMF) on the predictions of ground magnetic perturbations. A historic geomagnetic storm, the St. Patrick Storm 2015, is simulated with several different model configurations. The objective is to investigate how the different configurations affect the prediction performance regarding ground magnetic perturbations. For each simulation, the modeled ground magnetic perturbations are compared to the measured perturbations from several ground magnetometer stations located at sub-auroral, auroral and polar cap latitudes. Among the magnetometer stations are the Norwegian and Greenland magnetometer chains. The comparison is based on metrics for both ΔB and dB/dt. The SWMF configurations investigated include variations in grid resolution and integration schemes for the MHD equations, and different settings for the inner magnetosphere, the ionosphere electrodynamics, and the magnetosphere-ionosphere coupling.
Activity Tracking and Evaluation of Large-scale Collapse Zones using Synthetic Aperture Radar Differential Interferenc
Authors: Wu Jui Peng , Lin Chao Yuan
Published: March 2020

This study used synthetic aperture radar interference technology (InSAR) to monitor the activities of large-scale collapse zones in southern Taiwan (Tainan City, Kaohsiung City, Pingdong County). Large-scale collapse zones are widely distributed, in addition to the construction of observation instruments, how to use other telemetry technology to quickly obtain relevant change information as monitoring and early warning indicator is a vital issue. SAR images from southern Taiwan from 2015 to 2019 were analyzed to monitor the ground surface changes using synthetic aperture radar differential interference technology (DInSAR) and permanent scattering interferometry radar technology (PSInSAR), and were verified using global navigation satellite system measurements. DInSAR analysis shows that the vertical displacement of the surface is ±60mm, which is within the range of elevation tolerance error, so it is not possible to use the satellite tracking station to compare the trace displacement in large collapse areas. However, PsInSAR results show that if there is PS point in a large-scale collapse zone, the PS point may be used as index of stabilization, and once the PS point suddenly disappears, it is highly likely that the area will change, and special care should be taken.

Keywords: Interferometric SAR, large-scale collapse zones, PSInSAR

 
Benefit evaluation and annual change of soil and water conservation after converting farmland to forest in Lanlingxi watershed
Authors: Huang Zhilin , Ma Liang , Wang Tian , Zeng Lixiong
Published: March 2020

As the population has grown and human activities have intensified (predominantly agriculture) in the Three Gorges Reservoir area (TGRA) since the 1980s, the substantial areas of arable land on the steep slopes are the main living and farming space for people. Chinese government implemented the Conversion of Cropland to Forest Program from 2001, because of increasing erosion hazard by excessive cultivation and over-felling. To investigate the efficiency of a range of widely recommended program for soil conservation, long-term monitoring in the Heigou watershed was initiated from 2009. Surface runoff, sediment and nutrient transport were measured at watershed. Monitoring has been done to collect sufficient baseline data about soil erosion rate, runoff rate and quantity of soil nutrients (the sum of nutrients in sediment and runoff) in the watershed. The results showed that the soil erosion modulus varied from 138.26 to 355.28 t·km-2·a-1 among between 2016 and 2019, while average soil erosion modulus was 265.8 t·km-2·a-1, lower than the allowable soil loss in this area. The average runoff coefficient, average loss load of total nitrogen and total phosphorus were 53.9%, 11.24 t·km-2·a-1 and 0.19 t·km-2·a-1. Runoff contributed more than 90% of nitrogen loss, and sediment contributed 82.7% of total phosphorus loss. The soil erosion modulus decreased significantly from 2054.06 t·km-2·a-1 to 265.8 t·km-2·a-1 by returning farmland to forest, which was a severe erosion before. Loss load of soil nutrient diversion was high, and TN was excessive for surface water. The ratio of nitrogen to phosphorus would encourage algae growth and eutrophication in TGRA.
Fluidized-bed: As an alternative method for rill erodibility modeling
Authors: Deviren Saygin Selen , Ari Fikret , Temiz Cagla , Arslan Sefika , Unal Mehmet Altay , Erpul Gunay
Published: March 2020

Rill erodibility (Kr), which is a measure of the resistance of soil particles against disintegration in a rill under concentrated flow conditions, is a significant characteristic for rill initiation in a field.  The Process-based WEPP (Water Erosion Prediction Project) originally models Kr by linear excess shear stress (τ), and it is mostly obtained from mini-flume experiments at laboratory conditions. Alternatively, a critical value of flow stress (τcr) that points to fragmentation in rills can be modeled by a fluidized bed approach that quantifies the conditions in terms of cohesion (Co) and flow velocity (Vf) by considering the soil as a cohesive material. In there, the water as a fluid applies pressure on solid particle proportional to flow rate of the fluid (v). But, performed related studies on it were mostly tested for the limited soil types. The objectives of this study were to test these relationships and model the rill characteristic for the heavy textures of different soil types and investigate the role of basic soil properties on rill initiation. Experimental results showed that the stronger regression coefficient (R2=0.78) was found between Kr and flow velocity (Vf) monitored at the fluidization stage than that between Co & τcr at the studied soil conditions. However, correlations between constant and dynamic soil properties and the measured Kr, τcr, Co and Vf values were also quite remarkable (p<0.01) for next-generation modeling studies in terms of rill dynamics. It is believed that the fluidized-bed approach has a great potential to model Kr and encouragingly it is worth to be tested with wider data-sets under different soil-moisture conditions.

Keywords: Rill erodibility, Soil Cohesion, Fluidized bed approach, WEPP
Asbestos-like actinolite crystallization during late regional variscan exhumation in the South Armorican Massif (France)
Authors: Aertgeerts Geoffrey , Lahondère Didier , Triantafyllou Antoine , Lorand Jean-Pierre , Monnier Christophe , Bouton Pascal
Published: March 2020

In this study, two types of natural asbestos-like actinolite occurrences were sampled in order to understand their tectonic and metamorphic signification. Studied rocks were collected within two Variscan ophiolitic formations (Tréogat and Pont de Barel Formations, South Armorican Massif, Western France), mainly composed of amphibolites, and which recorded amphibolite to greenschist facies metamorphism. In these localities, the natural asbestos-like actinolite occurrences are closely related with the development of tectonic structures such as extension veins, tension gashes, σ and δ-type boudins. Field and petrostructural studies together with optical microscope, SEM and electron-microprobe analyses (EPMA) allowed to link early steps of the retrograde deformation event, during which acicular hornblende crystallizes in extension veins showing fuzzy boundaries or in hosting rock, with the late step of the same deformation event, during which hornblende is downgraded into asbestos-like actinolite synchronous with felsic melt circulation and tectonic structures opening. Field and microtectonic observations point to a sinistral strike-slip shearing for Pont de Barel formation and to a sinistral transtensive shearing for the Tréogat formation, which is consistent with the late regional variscan exhumation of the South Armorican Terrane.  SEM observations show that asbestos-like actinolite originate from hornblende crystallographic plan fragmentation, starting first along the (110) plans and continue both along the (100) and (110) plans. EPMA analyses show that Na-Al-Si metasomatism is associated with this fragmentation. Temperature estimates of chlorite crystallization after hornblende are around 300°C for the Tréogat Formation and 200°C for the Pont de Barel Formation, suggesting that amphibole fragmentation can occur over a wide temperature range. Additionally, Principal Component Analysis was performed using crystallographic sites distribution. Results show a clear correlation between actinolite Si(T) and hornblende Al(T), Al(C) and Na(A) crystallographic sites, suggesting that asbestos-like actinolite after hornblende fragmentation is rather due to a decrease of pressure within the tectonic structures, as Al in amphibole is pressure-dependent. This decrease could be due to the fluid pressure, which is supra-lithostatic during tectonic structures opening.
Effect of drying, composing and pelletizing of biowaste-based digestates on providing water soluble nutrients and stabilizing iron-cyanide (Fe-CN) complexes
Authors: Sut-Lohmann Magdalena , Knoop Christine , Raab Thomas
Published: March 2020

With recent policy developments under the German Renewable Energies Law (Erneuerbare‐Energien‐Gesetz, EEG) and the German Waste and Recycling Law (Kreislaufwirtschaftsgesetz, KrWG) increase in organic waste utilization is expected, which can be utilized for the waste sites restoration. We present a novel application of organic amendments to reduce the mobility of iron‐cyanide (Fe‐CN) complexes and simultaneously promote vegetation. Two batches of digestates from anaerobic treatment of separately collected municipal organic waste in a two-stage semi scale biogas plant have been conditioned by a) drying, b) composting and c) pelletisation. To evaluate the influence of post-treatment of digestates on nutrient and carbon release and contaminants sorption, two batch experiments were conducted, using I) deionized water and II) potassium hexacyanoferrate (II) solution. Batch experiment I resulted in a considerably higher nutrient and carbon elution from dried digestates. Batch experiment II revealed the highest significant tot. CN conc. reduction using not composted, air dried (100%) and oven dried (82%) biowaste digestates. The FTIR analysis of dried and mortared digestate materials indicated Fe-CN complexation on inorganic (K2Mn[FeII(CN)6], NH4Fe[FeII(CN)6]) and organic constituents, and possibly formation of nitriles. In terms of rapid soil fertility enhancement and feasibility to decrease Fe-CN complexes mobility, air and oven dried fresh biowaste digestates revealed the highest efficiency.
Highly explosive basaltic eruptions: magma fragmentation induced by rapid crystallisation
Authors: Arzilli Fabio , La Spina Giuseppe , Burton Mike R. , Polacci Margherita , Le Gall Nolwenn , Hartley Margaret E. , Di Genova Danilo , Cai Biao , Vo Nghia T. , Bamber Emily C. , Nonni Sara , Atwood Robert , Llewellin Edward W. , Brooker Richard A. , Mader Heidy M. , Lee Peter D.
Published: March 2020

Basaltic eruptions are the most common form of volcanism on Earth and planetary bodies. The low viscosity of basaltic magmas generally favours effusive and mildly explosive volcanic activity. Highly explosive basaltic eruptions occur less frequently and their eruption mechanism still remains subject to debate, with implications for the significant hazard associated with explosive basaltic volcanism. Particularly, highly explosive eruptions require magma fragmentation, yet it is unclear how basaltic magmas can reach the fragmentation threshold.

In volcanic conduits, the crystallisation kinetics of an ascending magma are driven by degassing and cooling. So far, the crystallisation kinetics of magmas have been estimated through ex situ crystallization experiments. However, this experimental approach induces underestimation of crystallization kinetics in silicate melts. The   crystallization experiments reported in this study were performed in situ at Diamond Light Source (experiment EE12392 at the I12 beamline), Harwell, UK, using basalt from the 2001 Etna eruption as the starting material. We combined a bespoke high-temperature environmental cell with fast synchrotron X-ray microtomography to image the evolution of crystallization in real time. After 4 hours at sub-liquidus conditions (1170 °C and 1150 °C) the system was perturbed through a rapid cooling (0.4 °C/s), inducing a sudden increase of undercooling. Our study reports the first in situ observation of exceptionally rapid plagioclase and clinopyroxene crystallisation in trachybasaltic magmas. We combine these constraints on crystallisation kinetics and viscosity evolution with a numerical conduit model to show that exceptionally rapid syn-eruptive crystallisation is the fundamental process required to trigger basaltic magma fragmentation under high strain rates. Our in situ experimental and natural observations combined with a numerical conduit model allow us to conclude that pre-eruptive temperatures <1,100°C can promote highly explosive basaltic eruptions, such as Plinian volcanism, in which fragmentation is induced by fast syn-eruptive crystal growth under high undercooling and high decompression rates. This implies that all basaltic systems on Earth have the potential to produce powerful explosive eruptions.
On the limitations of finite-frequency XKS-splitting tomography
Authors: Rümpker Georg , Kaviani Ayoub
Published: March 2020

Over the last two decades, there has been significant progress in the development of tomographic schemes to infer the anisotropic properties of the upper mantle from teleseismic XKS phases. The methods are based on linking the anisotropic material properties and their changes with surface observables and waveform proxies, such as splitting parameters and intensities, through finite-frequency sensitivity kernels. These approaches are supported by increasingly dense seismic networks that allow for a more precise characterization of short-scale waveform variations due to lateral variations of anisotropy.

Here we focus on the general capability of the tomographic schemes to uniquely resolve the anisotropic structure of the upper mantle from surface observations. For this purpose, we perform full-waveform calculations for relatively simple, canonical models of upper-mantle anisotropy. Our approach involves checkerboard-style tests similar to those typically used to assess the resolving power of tomographic schemes. The models are characterized by four zones of different anisotropic properties. Specifically, we assume orthorhombic symmetry with arbitrarily chosen strength of the anisotropy and orientation of the horizontal a-axis. XKS waveforms, generated from plane-wave initial conditions, traverse through anisotropic models and are recorded at the surface by a dense station profile. In addition to waveforms, we also consider the effects of different anisotropic models on splitting parameters and splitting intensities.

The results show that it is, generally, not possible to uniquely resolve the eight anisotropic parameters (a-axis orientation and strength of anisotropy in four zones) of a given model, even if complete waveforms (under noise-free conditions) are considered. This is related to the fact that waveforms for significantly different anisotropic models, often, are indistinguishable. We conclude that finite-frequency XKS-splitting tomography, alone, is not suited to resolve the anisotropic structures of the upper mantle and that combinations with alternative methods, based on e.g. receiver-function splitting or surface waves, are required.