bluuebunny/crossref_metadata_2025 huggingface dataset:
Global models of the inner electron radiation belt and slot region investigating the effects of VLF transmitter waves
Authors: Ross Johnathan , Glauert Sarah , Horne Richard , Meredith Nigel , Clilverd Mark
Published: March 2020

Signals from man-made very low frequency (VLF) transmitters can leak from the Earth-ionosphere wave guide into the inner magnetosphere, where they propagate in the whistler mode and contribute to electron dynamics in the inner radiation belt and slot region through wave-particle interactions. These inner regions of the magnetosphere are becoming increasingly important from a satellite perspective. For instance, the newly populated Medium Earth Orbits pass though the slot region, and satellites launched via electric orbit raising are exposed to the inner belt and slot region for extended periods of time.

We have calculated diffusion coefficients associated with wave-particle interactions between radiation belt electrons and waves from each of the strongest VLF transmitters using Van Allen Probe observations. These coefficients are included into global models of the radiation belts to assess the importance of the effects of VLF transmitters individually and collectively on electron populations.
Analytical and numerical optimization of gravimetric networks: a case study from Mount Etna, Italy
Authors: Nikkhoo Mehdi , Rivalta Eleonora , Carbone Daniele , Cannavò Flavio
Published: March 2020

The transport of magma and magmatic fluids is a key process behind the occurrence, duration and intensity of volcanic crises. Volcano gravimetry allows for unequivocal inference of the location and mass of accumulated or removed magmatic fluids at volcanoes. This task is best accomplished through collecting gravity time series at multiple stations simultaneously. The performance of individual gravimeters and the configuration of the gravimetric array, however, determine the threshold of detectable mass change and the ability of the array to minimize the uncertainty on the inferred quantities.

We utilize numerical optimization techniques to design a network including one absolute quantum gravimeter (AQG), two superconducting relative gravimeters (iGRAVs) and several microelectromechanical system (MEMS) relative gravimeters at Mount Etna. We also develop analytical solutions for simple design problems. We show that the analytical solutions are essential for validating the numerical optimization procedure. We provide practical details and caveats that should be considered in similar gravimetric network optimizations. These include 1) specifying the target zone of the network by using the history of mass transport, 2) accounting for the relative importance of  different parts of the target zone, 3) accounting for logistic and instrumental constraints in the optimizations  4) calibrating the objective functions associated with various optimizations, 5) analyzing the network sensitivities to different parts of the target zone and identifying blind zones and  6) calculating the optimal number of gravimeters as a function of the sensor sensitivity and accuracies. We show that our optimal solution for Mount Etna provides an improved detection power across the target zone as compared to an equally spaced network of gravimeters with the same existing constraints, surface topography and sensor sensitivities. Furthermore, this optimal solution ensures that a certain range of mass change anywhere in the target zone can be sensed by a given minimum number of gravimeters and at the same time minimizes the impact of random observation errors on the inferred quantities.
The regionally varying effects of forests on cloud cover based on satellite observations
Authors: Li Yan , Xu Ru , Teuling Adriaan J. , Lei Zhao
Published: March 2020

Forests cover changes impact regional and global climate by altering surface roughness, albedo, and evapotranspiration. While previous research mainly focused on the impact on temperature, there has been evidence of cloud enhancement over forests at the regional level. However, how forests affect cloud cover at a global scale is unclear. In this paper, we utilized long-term cloud data from MODIS in junction with other satellite data sources to investigate the effects of forests on cloud cover in boreal summer months across the globe. Results show that forests either increase or decrease cloud cover depending on the region and such effect exhibits considerable spatial heterogeneity. We found that forests in the southern edge of tropical Amazon decreased cloud cover as much as 6%. In contrast, forests can significantly increase cloud coverage in southern part of China in temperate region. Furthermore, the cloud increase was also observed in boreal forests but with a smaller magnitude than temperate forests. Our study provides new evidence for understanding the impact of forest cover change on cloud and water cycle.
Cross-domain scenario data model for the matching of comparable disaster situations
Authors: Friedemann Monika , Henkel Fabian , Barth Benjamin , Vendrell Jordi , Martin David , Nolde Michael , Riedlinger Torsten
Published: March 2020

Our ecosystems are facing increasingly extensive and complex natural disasters originating from natural or man-made hazards. Examples include the wild fires in Portugal 2017, Chile 2017, California 2018 and most recently Australia 2019/2020 as well as widespread flood events in Austria and the Czech Republic in 2013 and in Serbia and Croatia in 2014. These complex crisis situations highlight the increasing demands of stakeholders to monitor, anticipate, prepare for and learn from disasters. Research and innovation in this area needs to revolve around the expertise and guidance from practitioners in order to find solutions that are accepted and to benefit from their domain knowledge. In the European Commission (EC) H2020-funded project HEIMDALL on a Multi-Hazard Cooperative Management Tool for Data Exchange, Response Planning and Scenario Building we address the challenge of co-designing technological solutions for an improved adaptive emergency management at local, regional, national and European level with a multi-disciplinary group of experts including firefighters, police, emergency medical services, command and control and civil protection.

In order to find the most practical scenario-based solutions we follow a three-step approach: 1) Identification of immediate and long-term prevention and response planning activities that involve complex multi-hazard scenarios and information that needs to be represented in a conceptual scenario model to improve these activities; 2) Extension of that scenario data model by a harmonized lessons learnt data structure which allows stakeholders to capture experience of the emergency management in complex disasters; 3) Development and implementation of a scenario matching tool which allows users to find situations with a similar context, environmental conditions, hazard behaviour and stressed capabilities, from local storage as well as shared by other organizations. We believe that the combination of recording and matching scenarios including lessons learnt from prior incidents can improve the ability of stakeholders to learn and evolve from complex situations and thereby allow them to respond more effectively and operate more efficiently during disasters. Results of successive user exercises and evaluations of the implemented products and tools throughout the project underpin this assumption and at the same time indicate future research needs.

The HEIMDALL project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 740689.
How standard are standardized drought indices? Uncertainty contributions for the SPI & SPEI case
Authors: Laimighofer Johannes , Laaha Gregor
Published: March 2020

Standardized drought indices such as SPI are frequently used around the world to assess drought severity across a continent or a larger region covering different meteorological regimes. But how standard are the standardized indices? In this paper we quantify the uncertainty of SPI and SPEI based on an Austrian data set to shed light on what are the main sources of uncertainty in the study area. Here we analyze the uncertainty contributions by a linear mixed model that employs a restrictive maximum likelihood estimator in order to produce unbiased variance and covariance components. Five factors that either defy the control of the analyst (record length, observation period), or need to be subjectively decided during the steps of the calculation (choice of the distribution, parameter estimation method, and GOF-test of the fitted distribution) are considered. The results show that, overall, the choice of the distribution and the observational window are the most important sources of uncertainty. We quantify the relative uncertainty contributions in greater detail in order to give guidance how to make estimates most accurate for a given data set. We finally analyze the total uncertainty of SPI and SPEI to shed light on our main question whether the indices are skillful enough to provide a quantification of atmospheric drought that is standardized enough to allow the intended comparisons across various data situations and meteorological regimes.
2D multi-layer hydrodynamic and sediment transport modelling in a tidal estuary
Authors: Bai Kai-Yi , You Jiing-Yun
Published: March 2020

This study developed a multi-layer hydrodynamic and sediment transport model for simulating tides and the estuarine flows. The flow circulation in an estuary shows complicated mixing and stratification patterns due to the combined effects from currents and tides. This kind of issues becomes more important in Taiwan in line with the more and more frequent sediment flushing operation which led to high sediment concentration flow at the estuary. In some applications,  three-dimensional (3D) models solving full Navier-Stokes equations were used. However, the extremely high computational cost, especially for the large-scale environmental problems, is always a serious concern. In the past years, continuous efforts have been devoted to the development of efficient quasi-three-dimensional models under hydrostatic and Boussinesq assumptions. Following the same state-of-the-art modelling strategy, this study develops a multi-layer shallow-water and sediment transport model with finite volume method. In this model, a terrain following coordinate with high local resolution is used to vertically divide the computational domain into multiple layers to better addressing bottom topography and velocity profile. Our model is rigorously validated against several benchmark cases including winddriven circulation, subcritical flow over a hump, tidal wave propagation, and sediment transport. The grid convergence test and accuracy both are in good agreement with analytical solutions. Subsequently, the model is applied to investigate the estuary dynamics and sediment transport under different conditions, e.g., flow discharges, bottom slopes, wind shears and tidal variations. Overall, the results show a relationship between flow conditions and sediment transport. Later, some scenarios for various upstream inflow and sediment concentration will be examined to assess the reservoir operation rules. 

Keywords: shallow water, sediment transport, multi-layer, hydrostatic, Boussinesq Assumption, a finite volume characteristics (FVC) method 
 

 
 

 
Mutual increases in flood extents and magnitudes intensify flood hazard in Central and Western Europe
Authors: Kemter Matthias , Merz Bruno , Marwan Norbert , Vorogushyn Sergiy , Blöschl Günter
Published: March 2020

Climate change has led to changing flood synchrony scales (extents) and flood magnitudes across Europe. We discovered a tight alignment between extents and magnitudes and found the drivers of their joint trends. We analyzed the annual maximum floods of 3872 hydrometric stations across Europe from 1960-2010 and classified all floods in terms of their generating processes based on antecedent weather conditions. There is a positive correlation between flood extents and magnitudes for 95% of the stations. While both parameters increased in Central and Western Europe, they jointly decreased in the East. This widespread magnitude extent correlation is caused by similar correlations for precipitation, soil moisture and snowmelt. We found trends in the relevance of the different flood generation processes, which explain the regional flood trends. The aligned increases of flood extents and magnitudes emphasize the growing importance of transnational flood risk management.
Testing a remotely-sensed snow water equivalent product in the framework of the operational European Drought Observatory (EDO)
Authors: Cammalleri Carmelo , Barbosa Paulo , Vogt Jürgen
Published: March 2020

Winter droughts, defined as periods of reduced precipitation and snow accumulation during the cold season, can have significant impacts on the subsequent summer season, especially over areas that strongly rely on stored water resources released during the spring melting.

The Snow Water Equivalent, SWE, represents a reliable means to quantify the amount of liquid water in the snowpack, and its anomalies can be used to evaluate deviations from the amount usually stored. Unfortunately, the use of SWE for operational monitoring of winter droughts is constrained by the limited availability of long time series of ground observations, and the lack of coordinated measuring networks at European continental scale.

Remote sensing data from microwave sensors, therefore, represent a valuable source of continuously-updated SWE data. Products such as the H-SAF (EUMETSAT Hydrology Satellite Application Facility, http://hsaf.meteoam.it/) SNOBS4-H13 are updated in almost near-real time, providing daily maps covering continental Europe and northern Africa. Limitations include data gaps, difficult retrievals over impervious terrain, coarse spatial resolution and a reduced length of the time series.

In this study, we tested the potential inclusion of a drought indicator based on the H-SAF SWE product in the European Drought Observatory (EDO, http://edo.jrc.ec.europa.eu), with the aim to fill the current gap faced over mountainous basins in terms of early warning of spring water deficits.

An analysis of the full dataset collected between 2013 and 2019 highlights how, currently, the main drawback of the product seems to be represented by the limited length of the time series, as well as by the difficulties to capture snow accumulation over some mountainous areas (e.g., Pyrenees) likely due to the coarse spatial resolution. Spatial aggregation at water basin scale was also tested, in order to evaluate the possibility to reduce the effects of some of these limitations.     
Forest change as a proxy for landslide occurrence - a Sentinel 2 based spatio-temporal landslide detection approach for two test sites
Authors: Mayrhofer Peter , Steger Stefan , Sonnenschein Ruth , Cuozzo Giovanni , Atzberger Clement , Schneiderbauer Stefan , Zebisch Marc , Notarnicola Claudia
Published: March 2020

Landslides represent a major threat to humans and result in high costs for the society. Landslide inventory maps depict the areas of past slope instabilities and are a valuable information source for authorities, spatial planners and risk managers. However, existing inventories are rarely complete, especially in sparsely populated and/or areas difficult to access. Previous work based on change detection and using approaches that automatically map distinct landslide events exploiting remote sensing data has shown promising results. The aim of this study was to test the applicability of multi-temporal change indices derived from Sentinel-2 (S2) for landslide detection for two landslide-prone study sites in Italy and China: South Tyrol and Longnan, respectively.

The methodical approach was built upon a change vector analysis applied to annual cloud-free S2-composites at 10m spatial resolution to extract land-cover disturbances. Landslide areas in the time period 2015-2019 were analyzed on the basis of already known landslide location points, downslope-oriented moving windows and supervised classifications using the Receiver Operating Characteristic (ROC) curve.  Subsequently, time-series analysis was applied to the detected landslide-affected areas and to derive temporal breakpoints (i.e. the timing of the landslide occurrence). Finally, applying a multi-temporal revegetation analysis, we accounted for false positives originating from agricultural activities or artefacts on single images. Our findings highlight that out of the 67 already known landslide locations in South Tyrol, only 9 (13.4%) were detectable by means of S2 data. Major challenges resulted from similar spectral characteristics of landslides and other land cover disturbances (especially tree logging). However, larger landslides were detectable both spatially and temporally by means of the multi-temporal change detection approach. By applying a quantitative accuracy assessment for the independent test site in Longnan, China, we are currently assessing the transferability and suitability of the developed approach for efficient spatial-temporal landslide mapping over large areas.
Modelling sediment resuspension and transport induced by ships propellers in ports – the study case of the Port of Genoa
Authors: Guarnieri Antonio , Saremi Sina , Jensen Jacob H. , Pedroncini Andrea , Vaccari Marco , Vincenzi Caterina
Published: March 2020

The action of propellers induced jets on the seabed of ports and harbors might be responsible of erosion and deposition of sediment around the port basin, potentially inducing important variations of the bottom topography in the medium to long time scales. Such dynamics constantly repeated for long periods can result in drastic reduction of ships’ clearance - in the case of deposition - or might be a threat for the stability and duration of the structures - in the case of erosion in the close vicinity of births and decks. These sediment processes are sources of problems for the port managing authorities, both for the safety of navigation and for the optimization of the management and maintenance of the ports’ bottom.

In the present work we study by means of integrated numerical modeling the erosion and sediment transport induced by naval traffic in the passenger Port of Genoa (Italy) and we propose a novel delayed-mode methodology and new science-based tools useful to optimize and efficiently plan the maintenance of the port sea bed. Fully operational real-time tools can be further developed starting from the proposed methodology in order to monitor the dynamics of the sediment on a daily basis.
Linkages between the occurrence of persistent organic pollutants and biogeochemical characteristics of deep-sea trenches
Authors: Horlitz Gisela , Bonaglia Stefano , Eulaers Igor , Glud Ronnie N. , Sobek Anna
Published: March 2020

The biogeochemistry of deep-sea trenches is strongly influenced by their V-shape topography and tectonic position in the ocean, leading to a focusing effect of sediment and organic matter into the trench centre. Recent findings showed elevated mineralization rates in trench sediments, suggesting both high carbon turnover and organic matter degradation rates. As persistent organic pollutants (POPs) favourably partition to organic matter, deep-sea trenches act as a sink for these substances. Composition, source and age of the organic matter have been shown to have a significant influence on contaminant dynamics in sediment from more shallow regions. Also, the trophic status of marine systems plays a significant role in transport of POPs from air to water and to sediment. However, knowledge about organic pollutants in deep-sea environments is scarce. In the present study, sediment samples from two deep-sea trenches with different trophic states and deposition regimes are analysed for POPs with a wide range of physicochemical properties. Concentrations will be compared between the semi-eutrophic Atacama and the oligotrophic Kermadec Trench. Sampling of sediment cores was performed at the slope, abyssal plain and trench at Atacama (depth between 2,500 and 8,000m) and at the abyssal plain and trench at Kermadec (depth of 6,000 and 9,600m). The total organic carbon content largely varied between 0.3 and 2.1% at different sites at the Atacama Trench, while values were more homogeneous at the Kermadec Trench (around 0.3%). Preliminary results from the Atacama samples demonstrate concentrations of PCBs at the pg g-1 dw level, and indicate highest concentrations to occur at the highest depth in the trench. Low sedimentation- and high mineralization rates in the trench centre, as well as the funnel-effect from the topology may explain these differences.
For the buildings production, the better solutions against greenhouse gas emission
Authors: Mequignon Marc , Ait Haddou Hassan , Gunia Nadege
Published: March 2020

The paper focuses on the assessment of greenhouse gas emissions produced by the walls of buildings according to their lifespan. These assessments take account the entire cycle life. The contribution of the utilization phase must be equivalent for all technical solutions for a given usage function. In the first part of the work, the methodology is described by considering a unit area of wall (i.e. 1 square metre), determining a long service life, choosing technical solutions in agreement with the specifications, establishing the lifespan of each technical solution according to experts, finding the corresponding greenhouse gas index from an appropriate database, and finally modelling the evolution of these indicators with time. Several technical solutions (concrete, brick, stone, wood, aerated concrete) are considered and lifespans range from a few years to centuries.

The results of this analysis suggest and quantify the important impact of lifespan on greenhouse gas emission indicators. Too, the stone is the best solution for a long life.
The new tiltmetric network of Tenerife: technical and scientific issues
Authors: Barrancos José , Przeor Monika , D'Auria Luca , Cabrera Iván , Montañez Ana Carolina , Hernández Pedro A. , Pérez Nemesio M.
Published: March 2020

Since 2004, the Instituto Tecnológico y de Energías Renovables (ITER) in collaboration, since 2011, with the Instituto Volcanológico de Canarias (INVOLCAN), are monitoring Canary Islands archipelago with a network of more than 30 differential GPS stations. Specifically, in Tenerife island alone there are 12 permanent GPS receivers. Data are processed automatically using Bernese software, constituting an important tool for the geodetic monitoring of Tenerife.

Since 2016, the volcanic system of Tenerife is experiencing a hydrothermal unrest, with a marked increase of the diffuse CO2 flux from the crater of Mt. Teide, the major volcanic edifice of the island. This increased flux is likely to be related to the injection of fluids of magmatic origin within the hydrothermal system of Tenerife. The subsequent pressurization of this system is reflected also by the increase in the background microseismicity observed since July 2017. Until now, the GPS network has not recorded significant ground deformation above the instrumental error.

With the aim of improving the geodetic monitoring of Tenerife, detecting possible small ground deformation below the sensitivity of the GPS network, INVOLCAN has recently started deploying, since June 2019, high-gain tiltmeters (Jewell Instruments A603-C) in the surrounding of Mt. Teide. Currently the tiltmetric network consists of 3 tiltmeters, located close to existing seismic or GPS stations. Data are automatically downloaded via UMTS connection and processed daily.

The nominal sensitivity of such instruments is less than 2.5 nradians, hence their installation and calibration require very careful operations. The sensors are equipped with leveling worm-gear feet to guarantee a perfect levelling. However, the high sensitivity of the instrumentation makes adjustments made manually totally useless. The tilt change caused by the weight of the human operator during the levelling is enough to drive the instrument out of scale. For this reason, INVOLCAN developed a robotic system to perform the required adjustments from remote. The system is based on Arduino Mega 2560, driving two servomotors to adjust the leveling worm-gears. Another servomotor allows switching the gain level. The system can be accessed and operated through an internal web page, which allows driving the servomotors and checking the leveling of the tiltmeter platform by using an Arduino Ethernet.
Human induced changes on the global carbon cycle over the last 60 years
Authors: Friedlingstein Pierre
Published: March 2020

Human activities have an unprecedented impact on the global carbon cycle.  Atmospheric CO2 concentrations have been continuously monitored since 1958, and show a 30% increase, from 315 ppm in 1958 to 411 ppm in 2019. Anthropogenic emissions, primarily from fossil fuel combustion, but also from land-use changes, are the drivers of these changes, with global emissions almost tripling over that period, from 4GtC per year in 1958 to almost 12 GtC per year at present. Although the current rate of increase in fossil fuel emission of about 1% per year is lower than over the 2000s (about 3.0 % per year), there are no sign of global emissions peaking yet, despite climate policies being put in places in many countries.

The atmospheric CO2 increase induces land and ocean carbon uptake, respectively driven by enhanced photosynthesis, leading to larger land biomass and soil carbon; and by enhanced air-sea CO2 exchange, leading to larger carbon content in the surface ocean and export to the deep ocean. These mechanism are negative feedbacks in the Earth system and are removing about 50% of the CO2 emitted in the atmosphere. Without these land and ocean carbon sinks, atmospheric CO2 would already be about 600 ppm.

However, modelling studies show that climate change reduces land and ocean carbon sinks, hence amplifying the warming. Although there is agreement that such positive feedback will develop over the course of the century, there are not yet clear evidences of a major climate driven reduction of the carbon sinks.  So far, observations and modelling studies of the historical carbon cycle do not show any sign of a tipping point in the global carbon cycle.
Flood resilience and indirect impacts in art cities
Authors: Arrighi Chiara , Castelli Fabio
Published: March 2020

Resilience is commonly defined as the ability to recover from a shock and quickly restore antecedent conditions. Although it is widely recognized as crucial to reduce adverse impacts and it is gaining importance at global level, resilience to most natural hazards is difficult to measure and predict, as both direct and indirect impacts matter. In this work the mutual connection between flood resilience and indirect flood impacts is investigated through a mathematical model which describes the temporal evolution of the state of the system after an urban inundation event. The inputs to the resilience model are i) a hydraulic model simulating the flood hazard; ii) a vulnerability and recovery model estimating the physical damage to cultural heritage and the temporal persistence of direct and indirect consequences. The method is applied to the historic district of Florence (Italy) affected by a severe flood in 1966. The variables selected as proxies of the state of the system are the number of monuments open to the public after the flood and the number of visitors, which represent a measure of indirect social and economic impacts on the city. The model results show that the resilience model helps the quantification of indirect impacts due to the loss of accessibility of cultural heritage and allows evaluating the effectiveness of prevention measures.

Acknowledgments

Authors were beneficiary of funding by Italian Ministry of Education, University and Research (MIUR) under the PRIN 2015 programme with the Project MICHe “Mitigating the impacts of natural hazards on cultural heritage sites, structures and artefacts”
The attenuation of coda waves in the RIF area.
Authors: Arab Oussama , harnafi mimoun , ouchen Ibrahim , azguet roumaissae , El Fellah younes , Jamal sebbani
Published: March 2020

This work is presenting the attenuation of coda waves in the Rif region. Using 15 broadband stations, we investigate the attenuation of coda waves utilizing the single backscattering model of aki and chouet. We collect 70 local earthquakes during 2014 for five laps time window 20, 30, 40, 50 and 60s. We computed the quality factors at different central frequencies band on which start from 1.5, 3.0, 6.0, 9.0, 12.0 and 18.0 Hz. For 40s window length, the Qc gives average value for the whole zone of about 128,51 for 1.5 Hz and 993,44 for 18 Hz band frequencies. We observed a clear dependency between the quality factor and the frequency. Also, we have found that this region is tectonic active comparing to previous studies around the world.
Operational evaluation of volcanic source terms (volcanic ash and SO2) from inverse modelling for aviation
Authors: Mulder Mariëlle , Arnold Delia , Maurer Christian , Hirtl Marcus
Published: March 2020

An operational framework is developed to provide timely and frequent source term updates for volcanic emissions (ash and SO2). The procedure includes running the Lagrangian particle dispersion model FLEXPART with an initial (a priori) source term, and combining the output with observations (from satellite, ground-based, etc. sources) to obtain an a posteriori source term. This work was part of the EUNADICS-AV (eunadics-av.eu), which is a continuation of the work developed in the VAST project (vast.nilu.no). The aim is to ensuring that at certain time intervals when new observational and meteorological data is available during an event, an updated source term is provided to analysis and forecasting groups. The system is tested with the Grimsvötn eruption of 2011. Based on a source term sensitivity test, one can find the optimum between a sufficiently detailed source term and computational resources. Because satellite and radar data from different sources is available at different times, the source term is generated with the data that is available the earliest after the eruption started and data that is available later is used for evaluation.
Natural Occurring Asbestos (NOA) in Italy: Workers' potential exposure risks and prevention and protection measures
Authors: Malinconico Sergio , Conestabile della Staffa Beatrice , Guercio Annalisa , Paglietti Federica , Rimoldi Bianca
Published: March 2020

Italy was one of the largest producers of asbestos-containing minerals and materials (ACM), with large areas affected by natural asbestos (NOA). In 1992 Italy began the first reclamation activities at the largest European asbestos mine in Balangero (Piedmont) and in 2001 in minor mines in Valle d'Aosta (Emarese), also adopting specific reclamation procedures and protective measures for the workers. Also in 2001, reclamation work was started in Biancavilla etnea (Sicily), a city with a great contamination from two quarries containing fluorine-edenite, an amphibole of volcanic origin recognized as a category 1A carcinogen by the IARC. Although the asbestos extraction and asbestos containing materials trading has been banned since 1992 (Law n.257/92), to now, the extraction of green stones as inert or ornamental stone and other anthropic activities (eg the digging, tunneling or farming activities in areas with potentially contaminated soils) are still going on in many quarry districts and wide areas, with no regulations if not at local level.

The only legislative act concerning NOA has been enacted in 1996 (the 14/5/96 decree) and it’s mainly referred to "green-stones" identification in mines and quarries. From that date no further act has been approved on NOA.

In this context, to fill the gap, Inail (Dit and Contarp) issued the NOA Project to take the most correct workers’ protection actions in the management of a territory, as NOA.

The project lists the different activities carried on in areas with green stones occurrence with a workers' potential asbestos exposure risk, together with an analysis of the specific prevention and protection measures.

The activities are:

• Extraction and processing of ornamental stones and inert gravel

• Remediation of NOA contaminated sites, slopes rearrangement and restoration works of hydrogeological instability

• Excavations for road and railway tunnels

• Excavations and urbanization at different scales

• Farming.

· Railway ballast removal and disposal / remediation.

In the final document, in the drafting phase, we also propose an updated definition of NOA sites as:

“Asbestos minerals contained in ophiolitic rocks, outcropped or buried, in variable amount and localization, not definable in advance, whose fibers can be released into the environment due to anthropic activities or exogenous agents”.
A practical, objective, robust technique to directly estimate time of concentration
Authors: Giani Giulia , Rico-Ramirez Miguel Angel , Woods Ross
Published: March 2020

Time of concentration is one of the key time variables in hydrology and it is essential for hydrograph design and hydrological modelling. Uncertainty in its estimation can cause errors in peak discharge rate and timing of flood events.

A unique recognized definition and methodology for its estimate is lacking and the multiple definitions and estimation procedures available in literature can give numerical prediction which can differ by up to 500% (Grimaldi et al., 2012). This result is not surprising given the high subjectivity of the traditionally used method to directly estimate time of concentration, also used for the calibration of the widely applied empirical formulae.

Given the importance of this time parameter in hydrology and the lack of a recognized and easily reproducible procedure for its estimate, here we propose a practical, objective, robust methodology to directly estimate time of concentration from rainfall and streamflow observations only. It’s a timeseries analysis technique used already in the Economics field (Kristoufek, 2014), that have been adapted to estimate time of concentration.

Compared to the traditionally used method, which is event based and requires hyetograph and hydrograph separation, the proposed methodology is designed to find the time delay from the original continuous timeseries but can also be applied to individual events by creating a timeseries of copies of the same event.

In the first place, the median of time of concentration distribution with the proposed methodology has been evaluated against the one with the traditionally used one in 79 catchments across the UK, showing that in most of the sites estimates coming from the two methods are very similar (correlation value of 0.82). This means that it is possible to avoid the separation of the hydrograph, required by the traditionally used method, which is a highly subjective procedure.

Secondly, we show that, when considering the proposed methodology only, for each catchment the time of concentration estimate using the continuous timeseries has a small discrepancy compared to the median of the time of concentration distribution of the single events estimates (correlation value of 0.94). Therefore, rainfall-streamflow events selection is not necessary and a reliable estimate of time of concentration can be obtained by applying the proposed methodology on the continuous timeseries at once, reducing the computational cost.

The proposed timeseries analysis technique is easy to automate, reproducible and make possible to objectively compare time of concentration estimates in all the catchments where the resolution of rainfall and streamflow timeseries is high enough to capture the runoff process.
Topological properties of aftershock clusters in a viscoelastic model of quasi-brittle failure
Authors: Baro Jordi , Davidsen Joern , Corral Álvaro
Published: March 2020

Material failure at different scales and processes can be modeled as an emergent feature in terms of avalanche dynamics in micromechanical systems. 
Event-event triggering -or aftershocks- is common in seismological catalogs and acoustic emission experiments [1] among other phenomena.
Stochastic branching and linear Hawkes processes are used to model the statistical properties of catalogs.  In the micromechanical approach, viscoelastic stress transfer and after-slip are among the proposed mechanism of aftershocks. Here we ask this simple question: 'Do aftershock sequences in micromechanical models agree with such epidemic branching paradigm?'

We introduce two fibrous models as prototypes of viscoelastic fracture [2] which (i) provides an analytical explanation to the acceleration of activity in absence of critical failure observed in acoustic emission experiments [3]; (ii) reproduce the typical spatio-temporal properties of triggering found in field catalogs, acoustic emission experiments; but (iii) display discrepancies with the branching topological properties predicted by stochastic models [4], probably due to physical constrains.

[1] J. Baró et al., Phys. Rev. Lett. 110 (8), 088702 (2013).
[2] J. Baró, J. Davidsen, Phys. Rev. E  97 (3), 033002 (2018).
[3] J. Baró, et al., Phys. Rev. Lett. 120 (24), 245501 (2018).
[4] S. Saichev, et al., Pure and App. Geoph. 162 (6), 1113-1134 (2005).
Soil and sediment microbial structure and function in intermittent stream corridors after a decade of catchment succession
Authors: Schreckinger Jose , Frossard Aline , Gerull Linda , Gessner Mark O. , Mutz Michael
Published: March 2020

Large-scale resource exploitation by open-cast mining severely alters landscapes and impairs key ecosystem properties such as soil and sediment structure and function. Understanding the ecological recovery processes starting from an initially bare landscape generated by destructive land-use is extremely limited. Here we took advantage of a 6-ha experimental catchment to assess microbial community structure and function in soils and stream sediments after 3 and 13 years of catchment succession. The catchment (Chicken Creek) was created in 2005 by depositing quaternary sands from a lignite mine forefield in northeastern Germany and has since been left to develop under undisturbed conditions. In the initial stage, 3 years after catchment construction, rills and small streams had formed and the sparse vegetation cover mainly consisted of forbs. Over the next 10 years, the geomorphology, hydrology, and vegetation structure underwent a major transformation. A nearly full vegetation cover established, including various tree, shrub and grass species. Increased evaporation lowered the shallow groundwater table and led to stream intermittency. These changes were accompanied by large modifications in the structure and function of the microbial communities in sediments and soils. Initially, microbial structure and function were strikingly disconnected, whereas linkages had established 10 years later, although some functions still remained disconnected. Potential enzymatic activities increased vastly over the course of 10 years and also became much less variable across seasons. Cyanobacteria, predominant in soils and sediments during the early successional stage, declined to become a minor component of the microbial community. Moreover, despite distinct flow intermittency of the streams, microbial structure and function distinctly differed between sediments and adjacent soils. These results demonstrate a rapid succession of microbial communities during a decade of ecosystem development, suggesting that undisturbed succession is a feasible catchment restoration strategy.
Polar vortex regimes in a simple general circulation model
Authors: Walz Roland , Garny Hella , Birner Thomas
Published: March 2020

A dry dynamical-core model is used to investigate the regime behavior of the polar vortex under the influence of tropical upper-tropospheric warming. Up to 5 K temperature increase in this region, the polar vortex strength and variability hardly changes. Only for temperature increases above 8 K the polar night jet speeds up by approximately 20 m s−1 and the probability of sudden stratospheric warmings is strongly reduced.

A comparison of climatological-mean differences of the zonal-mean zonal winds between the two regimes and the first empirical orthogonal function of the zonal-mean zonal wind closest to the regime transition at around 7.5 K temperature increase reveals that the system oscillates between both regimes at the regime transition. Every regime is present for a long time accounting for the peaked autocorrelation time scale being distinctive of a regime transition. From a dynamical point of view the strong polar vortex regime is characterized by less negative Eliassen-Palm (EP) flux divergence in the stratosphere and an equatorward refraction of EP flux in the midlatitudes compared to the weak polar vortex regime.

In order to quantify the influence of the polar vortex on the tropospheric circulation during tropospheric warming, another set of tropical upper-tropospheric heating simulations without a polar vortex is performed. This reveals that the latitudes of the tropospheric jets in both sets of simulations coincide for tropical upper-tropospheric warmings up to 5 K, or equivalently, when the polar vortex is in its weak regime. However, when the polar vortex starts to transition to the strong regime, i.e. for tropospheric warmings above 5 K, the poleward contraction of the tropospheric jet is strongly enhanced compared to the set of simulations without polar vortex.
Severe weather in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere system
Authors: Prikryl Paul , Rušin Vojto , Šťastný Pavel , Turňa Maroš , Zeleňáková Martina
Published: March 2020

Tropical and extratropical cyclones can intensify into the most destructive weather systems that have significant societal and economic impacts. Rapid intensification of such weather systems has been examined in the context of solar wind coupling to the magnetosphere-ionosphere-atmosphere (MIA) system. It has been shown [1,2] that explosive extratropical cyclones and rapid intensification of tropical cyclones tend to follow arrivals of high-speed solar wind when the MIA coupling is strongest. The coupling generates atmospheric gravity waves (AGWs) that propagate from the high-latitude lower thermosphere both upward and downward [3,4]. In the upper atmosphere, AGWs are observed as traveling ionospheric disturbances. In the lower atmosphere, they can reach the troposphere and be ducted [4] to low latitudes. Despite significantly reduced wave amplitude, but subject to amplification upon over-reflection in the upper troposphere, these AGWs can trigger/release moist instabilities leading to convection and latent heat release, which is the energy driving the storms. The release of conditional symmetric instability is known to initiate slantwise convection producing rain/snow bands in extratropical cyclones. Severe weather, including severe winter storms, heavy snowfall and rainfall events, have been examined in the context of MIA coupling [5]. The results indicate a tendency of significant weather events, particularly if caused by low pressure systems in winter, to follow arrivals of solar wind high-speed streams from coronal holes. In the present paper we review the published results and provide further evidence to support them. This includes the occurrence of heavy rainfall events and flash floods, as well as the rapid intensification of recent hurricanes and typhoons, with the goal to identify sources of AGWs at high latitudes that may play a role in triggering convective bursts potentially leading to such events.

[1] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys., 149, 219–231, 2016.

[2] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys., 183, 36–60, 2019.

[3] Prikryl P., et al., Ann. Geophys., 23, 401–417, 2005.

[4] Mayr H.G., et al., J. Geophys. Res., 89, 10929–10959, 1984.

[5] Prikryl P., et al., J. Atmos. Sol.-Terr. Phys., 171, 94–110, 2018.
A 3D numerical model of hydraulic fracturing, injection pressure and microseismicity in anisotropic stress fields
Authors: Wangen Magnus
Published: March 2020

We present a 3D numerical model for hydraulic fracturing and damage of low permeable rock in an anisotropic stress field. The 3D numerical model computes the intermittent damage propagation, microseismic event-locations, microseismic event-distribution, damaged rock volume, and injection pressure. The model builds on concepts from invasion percolation theory, where cells in a regular grid are connected by transmissibilities, also called bonds. A numerical pressure solution provides the pressure in each cell at each time step during the hydraulic fracturing operation. The numerical solution is based on a cell-centered finite volume scheme. A fast version of the numerical scheme is suggested by restricting fluid flow to the damaged rock volume. The hydraulic fracture and the damaged rock volume propagate by one cell when a bond breaks. An intact bond breaks when the fluid pressure exceeds the least compressive stress and a random uniformly distributed bond strength. The model is different from a pure invasion percolation model by using the fluid pressure in combination with a random bond strength to decide which bond to break, instead of only the random strength. The volume of damaged rock is estimated with a simple expression for cases with high permeability of the damaged rock volume. The model is tested with a published case from the Barnett Shale. It reproduces the observed main features of the Barnett case, such as the spatial and temporal distribution of the events, the magnitude – frequency distribution and the injection pressure. It is found that the microseismic event-distribution and the b-value depend on the permeability of the damaged rock volume. The b-value increases with decreasing permeability from 0.6 to a value above 2 for the maximum possible permeabilities. The damaged rock volume is non-compact and similar to a percolation cluster for ‘‘high’’ damaged rock permeabilities, and it becomes increasingly compact with decreasing permeabilities. The resulting loop-less fracture network is found to have similar characteristics for different damaged rock permeabilities.
Untangling transient groundwater mixing and travel times with noble gas time series and numerical modeling
Authors: Popp Andrea L. , Pardo-Álvarez Álvaro , Schilling Oliver S. , Musy Stéphanie , Scheidegger Andreas , Peel Morgan , Kipfer Rolf , Brunner Philip
Published: March 2020

The quality and quantity of alluvial groundwater in mountainous areas are particularly susceptible to the effects of climate change, as well as increasing pollution from agriculture and urbanization. Understanding mixing between surface water and groundwater as well as groundwater travel times in such systems is thus crucial to sustain a safe and sufficient water supply. We used a novel combination of real-time, in-situ noble gas analysis to quantify groundwater mixing of recently infiltrated river water (Frw) and regional groundwater, as well as travel times of Frw during a two-month groundwater pumping test carried out at a drinking water wellfield in a prealpine valley in Switzerland. Transient groundwater mixing ratios were calculated using helium-4 concentrations combined with a Bayesian end-member mixing model. Having identified the groundwater fraction of Frw consequently allowed us to infer the travel times from the stream to the wellfield, estimated based on radon-222 activities of Frw. Additionally, we compared and validated our tracer-based estimates of Frw using a calibrated surface water-groundwater model. Our findings show that (i) mean travel times of Frw are in the order of two weeks, (ii) during most of the experiment, Frw is substantially high (~70\%), and (iii) increased groundwater pumping only has a marginal effect on groundwater mixing ratios and travel times. The high fraction of Frw in the abstracted groundwater and its short travel times emphasize the vulnerability of mountainous regions to present and predicted environmental changes.