bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of injection parameters on the dynamics of Hydraulic Fracturing monitored by Acoustic Emission
Authors: Bobrova Maria , Filev Egor , Shevtsova Anna , Stanchits Sergey , Stukachev Vladimir , Lecampion Brice
Published: March 2020

Understanding the processes of Hydraulic Fracturing (HF) initiation and propagation in different types of rocks is important for the design and optimization of HF during the exploitation of underground resources. The main goals were to study the dynamics of the process of hydraulic fracture growth and possible optimization of HF technology for both homogeneous and heterogeneous rocks. Laboratory experiments on HF with different injection parameters were carried out on natural limestone, dolomite and shale specimens. The dynamics of HF process was monitored by Acoustic Emission (AE) technique, on the analogy of induced microseismicity monitoring of HF in the field conditions. The shape of created HF and the size of leak-off zone were analyzed by X-Ray CT scanning technique after the testing.

Experiments on dolomite were conducted using fluids with different viscosities (1000-10000 cP) injected into the rock with a rate of 0.5 ml/min. In case of low viscosity, we observed low AE activity. After the test, the sample was cut in several pieces transverse to the expected fracture plane. We have found that HF has initiated, but did not reach the sample boundaries and leak-off was significant. The ten times increase of fluid viscosity resulted in significantly increased AE activity, smaller size of leak-off zone and higher breakdown pressure (21.8 against 18.7 MPa). The post-test 3D shape of HF surface obtained by X-Ray CT closely correlates with 3D shape of localized AE events, confirming that the fracture propagated in the direction of maximal stress, as expected. It means that viscosity of fracturing fluid had a significant effect on fracturing breakdown pressure and fracture behavior.

The influence of different rock types on hydraulic fracturing was studied with dolomite, limestone and shale samples. In case of dolomite and shale, sufficient number of Acoustic Emission events were recorded, which allowed tracing the direction and dynamics of fracture propagation. However, for the limestone, a very small number of AE events were localized with the same parameters of injected fluid. Comparison of dolomite and shale HFs shows that the crack in the shale had a more complex shape, deviating from the maximal stress direction, which was explained by rock heterogeneity, by the presence of natural cracks and inclined planes of weakness. It led us to conclusion that the rock fabric plays an important role in the behavior of hydraulic fracture in heterogeneous rock.
Riverscape classification by using machine learning in combination with satellite and UAV images
Authors: Miyamoto Hitoshi , Sato Takuya , Momose Akito , Iwami Shuji
Published: March 2020

This presentation examined a new method for classifying riverine land covers by using the machine learning technique applied to both the satellite and UAV (Unmanned Aerial Vehicle) images in a Kurobe River channel.  The method used Random Forests (RF) for the classification with RGBs and NDVIs (Normalized Difference Vegetation Index) of the images in combination.  In the process, the high-resolution UAV images made it possible to create accurate training data for the land cover classification of the low-resolution satellite images.  The results indicated that the combination of the high- and low-resolution images in the machine learning could effectively detect waters, gravel/sand beds, trees, and grasses from the satellite images with a certain degree of accuracy.  In contrast, the usage of only low-resolution satellite images failed to detect the vegetation difference between trees and grasses.  These results could actively support the effectiveness of the present machine learning method in the combination of satellite and UAV images to grasp the most critical areas in riparian vegetation management.
The evolution of the terrestrial-terminating Irish Sea glacier during the last glaciation
Authors: Chiverrell Richard , Thomas Geoff , Burke Matthew , Medialdea Alicia , Smedley Rachel , Bateman Mark , Clark Chris , Duller Geoff , Fabel Derek , Jenkins Geraint , Ou Xianjiao , Roberts Helen , Scourse James
Published: March 2020

Comprehensive mapping and the Briticechrono geochronology provides a reconstruction of the last advance and retreat of the only land-terminating ice lobe of the western British Irish Ice Sheet. The Irish Sea Glacier was fed by ice from Lake District, Irish Sea and Wales, and extended to maximum limits in the English Midlands. During ice retreat after 27 kyrs, a series of reverse bedrock slopes rendered proglacial lakes endemic in the land-system. Not resembling the more extensive definitions of the classical ‘Glacial Lake Lapworth’, these ice contact lakes were smaller time transgressive moraine- and bedrock-dammed basins that evolved with ice marginal retreat. Combining, for the first time on glacial sediments, OSL bleaching profiles for cobbles with single grain and small aliquot OSL measurements on sands, has produced a coherent chronology from these heterogeneously bleached samples, and constrained for the Irish Sea Glacier a post 30ka ice maximum advance, 26.5±1.8ka maximum extent, and 25.3±1.6 to 20.6±2.2ka retreat vacating the region. With retreat of the Irish Sea Glacier an opportunistic Welsh re-advance 19.7±2.5ka took advantage of the vacated space and rode over Irish Sea Glacier moraines. Our geomorphological chronosequence shows a glacial system forced by climate, but mediated by piracy of ice sources shared with the larger and marine terminating Irish Sea Ice Stream to the west. The Irish Sea Glacier underwent changes flow regime and fronting environments driven by stagnation and decline as the primary impetus to advance was diverted. Ultimately, the glacier of the English Midlands display complex uncoupling and realignment during deglaciation and ice margin retreat towards upland hinterlands ~17.8 kyrs (Lake District and Pennines) and asynchronous behaviour as individual adjacent ice lobes became increasingly important in driving the landform record.
Unmanned Stratospheric Glider for Satellite Calibration
Authors: Craine Nick
Published: March 2020

Stratodynamics Aviation Inc. is an Earth Observation platform and service provider that’s pioneered a new cost-effective method of remote access the stratosphere. The platform called the HiDRON has successfully deployed scientific instruments over 100,000 feet above the earth and back again using balloon launched, autonomous technology.

Most satellites are able to self-calibrate however, optical and spectral units that are required to interpret data through the boundary layer face difficult challenges. We’ve identified opportunities to calibrate instruments by flying proxy beam/pulse emitters at stratospheric altitudes. As well, we see meaningful advantages to an Aircore integrated system that can capture high altitude air samples as a validation exercise. This method serves to extend the mission life of satellites beyond their intended length. Specifically, the RADARSAT constellation, the COPERNICUS program, AEOLUS as well as future Greenhouse Gas sensing satellites.

We would like to propose this technology to the EGU General Assembly 2020 for consideration as a calibration solution.
Data assimilation of FY-4A dust aerosol observations for the CUACE/dust forecasting system
Authors: Niu Tao , Zhang Xiaoye , Gong Shanling , Wang Yaqiang , Liu Hongli , Zhou Chunhong
Published: March 2020

A data assimilation system (DAS) was developed for the Chinese Unified Atmospheric Chemistry Environment– Dust (CUACE/Dust) forecast system and applied in the operational forecasts of sand and dust storm (SDS) in spring in Asia. The system is based on a three dimensional variational method (3D-Var) and uses extensively the measurements of surface visibility (phenomena) and dust loading retrieval from the Chinese geostationary satellite FY-2C. By a number of case studies, the DAS was found to provide corrections to both under- and over-estimates of SDS, presenting a major improvement to the forecasting capability of CUACE/Dust in the short-term variability in the spatial distribution and intensity of dust concentrations in both source regions and downwind areas.  By now The DAS was upgrade to assimilate FY-4A dust aerosol observations. The seasonal mean Threat Score (TS) over the East Asia in spring increased when DAS was used. The forecast results with DAS usually agree with the dust loading retrieved from FY and visibility distribution from surface meteorological stations, which indicates that the 3D-Var method is very powerful by the unification of observation and numerical model to improve the performance of forecast model.
Ocean surface dynamics derived from TerraSAR-X/TanDEM-X and hydrodynamic modeling
Authors: Lehmann Andreas , Suchandt Steffen
Published: March 2020

Dynamical processes at the ocean surface are of high interest because they control the exchange processes between ocean and atmosphere. Furthermore, ocean surface drift determines the dispersion of heat, salt and material such as harmful substances or plastic litter. Still the measurement of ocean surface currents is a challenge because of wave and wave-breaking processes. Here we demonstrate the usefulness of TerraSAR-X/TanDEM-X data to determine ocean surface currents, wave and wind fields. Up to now there are no spatially resolved ocean surface currents measurements available, so that for the validation of surface currents a combined SAR and hydrodynamic modeling methodology is applied. Ocean surface currents are derived from SAR Along-track Interferometry, and the hydrodynamic model is a coupled wave sea ice-ocean model of the Baltic Sea. The model is driven by ERA-Interim atmospheric reanalysis data. Hydrodynamic model data are also used to support the geophysical interpretation of the multiparametrical information of the ocean surface provided by SAR.
Test of possible standard samples for soil physical analyses
Authors: Degré Aurore , Pomes-Bordedebat Alexandre , Belazereg Imène
Published: March 2020

As they mostly deal with undisturbed samples, soil hydrophysics analyses often present variability in their results. No one can deny that soil, and particularly structured soil, is a very complex and challenging media to describe. But it remains that the lab measurements themselves deserve attention. To what extent are they reproducible? To what extent different labs following the same protocol do they provide the same results for a given soil sample? Is this uncertainty quantifiable? Is there a way to standardize or harmonize the analyses? And of course, to what extent does it really matter when it comes to produce reliable information about i.e. drought consequences?

When most of the labs related to chemical analyses can rely on ring tests to improve their capacity, soil physics labs can’t. Building reference samples that could fit into classical measurement devices is one of the options that could allow to run ring tests in soil physics measurements.

The poster will present an attempt to develop reference samples in view to measure the wet end of the retention curve.
Exploring the aerosol-cloud-radiation relationships in deep marine stratocumulus layers
Authors: Possner Anna , Eastman Ryan , Bender Frida , Glassmeier Franziska
Published: March 2020

Marine stratocumuli cover around a fifth of the worlds oceans and are a key contributor to Earth’s radiative balance at the surface. Their sensitivity to changes in anthropogenic aerosol concentrations remain a key uncertainty in the climate system. Our current understanding of their sensitivity and the plausible range of the aerosol-cloud radiative forcing is largely based on the process understanding obtained from field campaigns, high-resolution modelling, and satellite records of aerosol-induced phenomena such as volcano or ship tracks.

Yet, a large fraction of these records is only applicable to relatively shallow planetary boundary layers (PBLs). Ship tracks are only found in boundary layers up to a depth of 800m. Field campaigns and high-resolution modelling studies of aerosol-cloud-radiation interactions in marine stratocumuli have been restricted to a similar range of PBL depths in the past. Meanwhile over 70% of marine boundary layers reside in deeper PBLs.

The liquid water path (LWP) adjustment due to aerosol-cloud interactions in marine stratocumuli remains a considerable source of uncertainty for climate sensitivity estimates. An unequivocal attribution of LWP adjustments to changes in aerosol concentration from climatology remains difficult due to the considerable covariance between meteorological conditions alongside changes in aerosol concentrations.

Here, we combine a range of space-born remote sensing retrievals to investigate the relationship of cloud-radiative properties for different boundary layer depths and aerosol concentrations. As done in previous studies we utilise the susceptibility framework, i.e. the relative change in LWP scaled by the relative change in cloud droplet number concentration, to quantify the change in LWP adjustment with PBL depth. We show that the susceptibility of LWP adjustments triples in magnitude from values of -0.1 in PBLs shallower than 0.5 km to -0.33 in PBLs deeper than 1 km.

We further argue that LWP susceptibility estimates inferred from deep PBL climatologies are poorly constrained due to a lack of process-oriented observations. Meanwhile, susceptibilities inferred from climatology in shallow PBL regimes are consistent with estimates obtained from process modelling studies, but are overestimated as compared to pollution track estimates.
Marine macrophytes retain microplastics
Authors: Chubarenko Irina , Esiukova Elena , Lobchuk Olga , Volodina Alexandra , Kupriyanova Anastasiya , Bukanova Tatiana
Published: March 2020

Plastic contamination of marine beaches, sediments, water is widely reported. It is known that lot of plastic debris appears on marine shores after storms together with natural marine litter, like ragged vegetation, pieces of wood, etc. The goal of our field campaign in the southeastern part of the Baltic Sea was to check whether growing macrophytes also concentrate and retain plastics, particularly that of microplastic (MP, 0.2-5 mm here) size range. Three summer expeditions were conducted (July 30, August 5 and 7, 2019) in sea coastal zone (depth down to 10 m), where communities of attached macroalgae (Furcellaria lumbricalis, Coccotylus truncatus, Polysiphonia fucoides, Cladophora rupestris) are developed on underwater boulders off the Cape Taran. Samples were collected at 8 stations, covering areas with filamentous algae (at depths of 3.2 and 4 m) and with perennial algae furcellaria (depths of 5.6 and 8.2 m). Along with sampling of growing algae (from area 25x25 cm2 in triplicate), a hand pump was used to sample 20-100 liters of sea water from both algae thicket and algae-free water in surrounding area.

The samples were processed and examined in laboratory. Microplastic particles were found in all the collected samples. Preliminary analysis shows 1.3-5.3 times higher microplastic contamination in water samples taken from algae thicket than in samples taken in free water nearby. The majority of microparticles are fibers, mainly colorless and blue, but also red, black, golden, and yellow.

Investigations are supported by the Russian Science Foundation, grant No. 19-17-00041.
Detecting avalanche debris from SAR imaging: a comparison of convolutional neural networks and variational autoencoders
Authors: Giffard-Roisin Sophie , Sinha Saumya , Karbou Fatima , Deschatres Michael , Karas Anna , Eckert Nicolas , Coléou Cécile , Monteleoni Claire
Published: March 2020

Achieving reliable observations of avalanche debris is crucial for many applications including avalanche forecasting. The ability to continuously monitor the avalanche activity, in space and time, would provide indicators on the potential instability of the snowpack and would allow a better characterization of avalanche risk periods and zones. In this work, we use Sentinel-1 SAR (synthetic aperture radar) data and an independent in-situ avalanche inventory (as ground truth labels) to automatically detect avalanche debris in the French Alps during the remarkable winter season 2017-18. 

Two main challenges are specific to this data: (i) the imbalance of the data with a small number of positive samples — or avalanche — (ii) the uncertainty of the labels coming from a separate in-situ inventory. We propose to compare two different deep learning methods on SAR image patches in order to tackle these issues: a fully supervised convolutional neural networks model and an unsupervised approach able to detect anomalies based on a variational autoencoder. Our preliminary results show that we are able to successfully locate new avalanche deposits with as much as 77% confidence on the most susceptible mountain zone (compared to 53% with a baseline method) on a balanced dataset.

In order to make an efficient use of remote sensing measurements on a complex terrain, we explore the following question: to what extent can deep learning methods improve the detection of avalanche deposits and help us to derive relevant avalanche activity statistics at different scales (in time and space) that could be useful for a large number of users (researchers, forecasters, government operators)?
Tectonic subdivisions in thrust belts – cleaning up the western Northern Calcareous Alps (NCA)
Authors: Ortner Hugo , Kilian Sinah
Published: March 2020

Tectonic subdivisions of larger geologic units reflect the geologic knowledge at the time of creation. In many thrust belts the original subdivisions had been created during the first comprehensive mapping campaigns at the end of the 19th to early 20th century and reflect the geologic knowledge at that time. Even if many thrusts were identified correctly, no formal framework existed to give guidelines of how to distinguish tectonic units. Nevertheless, these subdivisions are still in use.

We analyze the thrust sheets of the Northern Calcareous Alps of western Austria and southern Germany and test the implicit assumptions underlying most tectonic subdivisions against field observations:

Assumption 1: Thrust transport is large and thrusts do not end laterally. However, several major thrusts do loose stratgraphic offset and end laterally.

Assumption 2: Allochthons are surrounded by thrusts on all sides. Unfortunately, any fault has been used to delimit allochthons.

Assumption 3: Thrusting should bring old on young rocks. In some cases, allochthons have been delimited by out-of-sequence thrusts, that stack young on old rocks. In other cases, the allochthon is a mountain-size glide block that was buried by younger sediments, and the trace of the thrust is an unconformity in the field.

As a consequence we propose a revised tectonic subdivision of the western part of the NCA, that avoids some of the problems discussed here, and is entirely based on the emplacement of old-on-young rocks across thrusts.
Application of Different Fractions of Anaerobic Digestate Significantly Influences the Carbon Cycle in Grassland Soils
Authors: Cattin Marta , Semple Kirk T. , Stutter Marc , Romano Gaetano , Lag-Brotons Alfonso , Parry Chris , Surridge Ben W.J.
Published: March 2020

Applying digestate to soil is of growing interest in agriculture. However, the impacts of digestate on soil biogeochemical cycles often remain unclear, especially after solid-liquid separation of whole digestate (WD). We used a 21 d incubation to examine the effects of WD and solid digestate (SD) on CO2-C efflux, dissolved organic carbon (DOC), microbial biomass C (Cmicro), phospholipid fatty acid (PLFA) and carbon use efficiency (CUE) within two grassland soils of contrasting nutrient status. Application rates for SD and WD were based on recommended N inputs to grassland soils for these organic materials. Compared to un-amended controls, cumulative CO2-C efflux, Cmicro and the fungal:bacterial in soils increased significantly following SD application, regardless of the soil nutrient content (+20% CO2-C, +29% Cmicro, +58% fungal:bacteria for high nutrient soil; +563% CO2-C, +36% Cmicro, +18% fungal:bacteria for low nutrient soil). In contrast, WD produced a significant effect on CO2-C efflux and fungal:bacterial only in the low nutrient soil. Our results also indicated that both digestate fractions and the initial soil nutrient status affected CUE. Applying both SD and WD to a low nutrient soil potential leads to decreases in soil C stocks, whilst the application of SD to a high nutrient soil can potentially enhance soil C stocks. Digestate application must be carefully planned, accounting for both the nature of the digestate and of the soil, in order to avoid adverse impacts on soil C stocks.

 
The application of chemo-mechanical coupling in the modeling of exsolution lamellae in minerals
Authors: Tajcmanova Lucie , Khakimova Lyudmila , Podladchikov Yury
Published: March 2020

The recent careful theoretical, numerical and experimental investigations of exsolution miscrostructures focus only on chemical aspect of the exsolution process. Interestingly, mechanics, i.e. stress and pressure redistribution around the exsolved lamellae, may play an important role on its evolution. In this contribution, we investigate the coupled, chemo-mechanical, effect around the exsolved lamellae. We apply a classical Cahn-Hilliard-type equation and we add more complexity considering deformation during the exsolution process. We also discuss the general importance of the exsolution process in geomaterials and its effect on rheology. At the time of the exsolution lamellae formation (coherent at initial stage), large stresses are built-up inside the host grain. The reason that we still partially see the microstructure preserved is that the stress variations were maintained during the further evolution. In other words, a strong rheology is needed to preserve such large stresses on geological timescales so that we can now detect by the analytical techniques.
Science Club Activities
Authors: Kulkarni Mukta
Published: March 2020

Mukta Kulkarni.

Saraswati Vishwa-Vidyalaya National School Gat Number169, Ganeshnagar,Talawade Rd , Pimpri-Chinchwad Pune, Maharashtra, India.411062

The science club I lead in the school includes various hands on activities for students of grade  VIII and IX where we do projects such as  model makings, art integration for global issues in the form of role play, poster making, thumb painting activities to sensitize the students to keep our planet safe for the living organisms . The issues we focused on were conservation of biodiversity, plastic pollution and its adverse effects on the water bodies. Along with this project we celebrated science week in the school to develop interest in science where we keep sessions like understanding of superstitions, magic with science, competitions such as debates, quizes, making colorful diagrams and field visits. We also ran the hub of learning programs where we shared our knowledge with other schools assembled under exchange programs. These activities helped students to understand the science concepts beyond the classroom. Learning by doing helped sthudents to understand the concepts very easily.

 
Vulnerability of terrestrial transportation lines to natural events
Authors: Eidsvig Unni , Tanasic Nikola , Hajdin Rade , Ekeheien Christina , Piciullo Luca
Published: March 2020

Our modern society relies on well-functioning transport systems providing mobility, transport safety and regularity. Maintaining the operational state of roads and railways during extreme weather events or other natural events is an important and demanding task. Natural events may cause damage to transportation assets, which can immediately or over time result in functional loss of a transportation line. For instance, a reduced culvert capacity due to debris deposition and clogging, could cause flooding of a road/rail. Some natural events can lead directly to loss of service, even without damaging an asset, like the occurrence of avalanches on a transportation line, blocking the related traffic. To reduce risks of failures posed by natural hazards, it is essential to assess vulnerability of transportation networks to such events.

A well-established way to analyse vulnerability is to use damage-, loss- or fragility functions. Such functions can express both functional vulnerability, representing the functional loss for a transportation line, and structural vulnerability representing damage degree or the exceedance probability of damage levels pertinent to a transportation asset. These functions can all be expressed in terms of event intensity, which is a parameter characterizing the damaging potential of a natural event.

In order to analyse functional vulnerability, various asset types with their interdependencies i.e. network topology and geographical coincidence must be considered. Here, the applied damage and fragility functions for evaluating structural vulnerability must account for location specific data on assets and asset properties. The review of existing damage-, loss- and fragility functions showed that these are not sufficient for intended analysis and need to be updated to consider various natural events and related failure modes. Recommendations are provided on how to elaborate new damage-, loss- and fragility functions to overcome a large number of uncertainties related to impacts of natural events on infrastructure and account for resistance of infrastructure. These recommendations concern both the choice of intensity parameters for different types of hazards and definition of possible failure modes, the methods for developing the functions and the assessment of the relationship between structural vulnerability of the asset and functional vulnerability.

The research leading to these and future results receives funding from the European Community’s H2020 Programme MG-7-1-2017 Resilience to extreme (natural and man-made) events, under Grant Agreement number: 769255 - "GIS-based infrastructure management system for optimized response to extreme events of terrestrial transport networks (SAFEWAY)".
3D reconstructions of fault surfaces and key stratigraphic horizons to define recent tectonic activity in the northern Apennines outer fronts and foredeep (northern Adriatic Sea, Italy)
Authors: Panara Yuri , Maesano Francesco Emanuele , Basili Roberto , Losi Giacomo , Fedorik Jakub , Toscani Giovanni
Published: March 2020

Fault plane attitude and dimension are important parameters for deriving seismotectonic information or input data for earthquake hazard assessment and in this sense a complete 3D view and characterization of geological and structural elements is essential. However, there is always a trade-off between structural complexity and data availability at the scale of the designed application.

In the last few years, merging public and confidential seismic reflection profiles and borehole data, were used in order to carry out a 3D reconstruction of fault planes and Plio-Pleistocene stratigraphic horizons in the northern Adriatic Sea, at the front of the northern Apennine fold-and-thrust belt and associated foredeep. The study area straddles the Italian coastline and subsurface data interpretation allowed us to reconstruct the structural setting of both onshore and offshore structures. Although it is known that this area has low rates of active tectonic deformation, it hosts important seismogenic faults associated with instrumental seismicity and historical earthquakes.

The dense distribution of seismic reflection profiles allowed us to perform an accurate 3D reconstruction of almost 50 fault planes, of different dimensions and order of importance. Their geometrical and structural features helped to define the most recent tectonic phases. To this end, we also mapped several Plio-Pleistocene regional unconformities and integrated them with previously published reconstructions of key horizons.

In some cases, where further published data were available, it was also possible to perform detailed cross sections whose restoration allowed us to reconstruct the post-Miocene (5.33 Ma) slip-rate history of some important tectonic structures with a detail of ~1 Ma. The 3D geological model revealed several structural features like fault continuity and terminations, level of connectivity, presence of lateral ramps, along strike variations of displacement that could not be fully addressed using cross sections alone.
Calibrating a regional glacier model using post-LIA glacier length changes in the Alps
Authors: Dusch Matthias , Nicolussi Kurt , Maussion Fabien
Published: March 2020

We present an approach to calibrate a regional glacier model based on the well observed period since the mid-19th century LIA maximum.
We chose 30 glaciers distributed across the entire European Alps with frequent length change observations in that period. These glaciers account for 25% of today's total glacier area in the Alps. We run simulations with the Open Global Glacier Model (OGGM, https://oggm.org) driven by HISTALP (http://www.zamg.ac.at/histalp) gridded climate data. To calibrate the glaciers individually, we vary three model parameters within a reasonable range: (i) a precipitation scaling factor governing average mass-turnover and mass-balance profiles, (ii) the ice creep parameter governing basal sheer stress and the dynamics of ice flow, and (iii) a constant mass balance perturbation applied to the yearly mass-balance. This results in  1365 unique parameter combinations which were tested for all glaciers. We chose individual parameter subsets for every glacier based on objective criteria minimizing the difference between modeled and observed length changes.

We find that there is no unique parameter combination satisfying our criteria for all glaciers. It is also challenging to identify an ideal parameter combination for each individual glacier, since there is a trade-off between reproducing variability (useful for paleo-climate interpretations) and reproducing observed length change (useful for projections and planing).
Furthermore, model and input data uncertainties are variable in time, leading to non-unique optimal parameter sets. Therefore, we rely on an ensemble of simulations consisting of the best runs with respect to multiple statistical measures. Together with a cross-validation procedure, the ensemble produces a probabilistic uncertainty range which can be applied to Holocene glacier reconstructions and future evolution scenarios.
Development of C- shear bands in brittle-ductile shear zones: Insights from analogue and numerical models.
Authors: Roy Arnab , Roy Nandan , Saha Puspendu , Mandal Nibir
Published: March 2020

Development of brittle and brittle-ductile shear zones involve partitioning of large shear strains in bands, called C-shear bands (C-SB) nearly parallel to the shear zone boundaries. Our present work aims to provide a comprehensive understanding of the rheological factors in controlling such SB growth in meter scale natural brittle- ductile shear zones observed in in Singbhum and Chotonagpur mobile belts.  The shear zones show C- SB at an angle of 0°- 5° with the shear zone boundary. We used analogue models, based on Coulomb and Viscoplastic rheology to reproduce them in experimental conditions.

These models produce dominantly Riedel (R) shear bands. We show a transition from R-shearing in conjugate to single sets at angles of ~15o by changing model materials. However, none of the analogue models produced C-SB, as observed in the field. To reconcile the experimental and field findings, numeral models have been used to better constrain the geometrical and rheological parameters. We simulate model shear zones replicating those observed in the field, which display two distinct zones: drag zone where the viscous strains dominate  and the core zone, where both viscous and plastic strains come into play.  Numerical model results suggest the formation of  C- SB for a specific rheological condition. We also show varying shear band patterns as a function of the thickness ratio between drag and core zones.
Effect of wall heating on street canyon ventilation
Authors: Salizzoni Pietro , Fellini Sofia , Ridolfi Luca
Published: March 2020

Understanding the dynamics of mass and heat exchange between a street canyon and the overlying atmosphere is crucial to predict air quality and microclimatic conditions within dense urban areas. Previous studies have demonstrated that the bulk transfer between the street and the overlying flow is entirely governed by the intensity of turbulent fluctuations within the street. The aim of this experimental study is to evaluate how the geometry of the street canyon and the solar radiation on building façades influence the turbulent velocity field within a two-dimensional street canyon and thus the global street canyon ventilation. The study was carried in a wind tunnel. The boundary conditions inside the canyon were modified by heating its windward and leeward walls and by changing the cavity aspect-ratio. The flow field in a cross-section of the street canyon was measured with particle image velocimetry. Temperatures were measured by means of thermocouples. The velocity and vorticity fields are analysed and discussed.
Analysis of Precipitation Patterns and Extremes in European Lowlands
Authors: Berényi Alexandra , Bartholy Judit , Pongrácz Rita
Published: March 2020

It is well-known that climate change affects large scale weather patterns and local extremes all over the world as well as in Europe. These changes include the changes of precipitation occurences, amounts, and spatial patterns, which may require appropriate risk management actions. For this purpose, the first step is a thorough analysis of possible hazards associated to specific precipitation-related weather phenomena.

The primary goals of this study are (i) to examine the changes in precipitation patterns and extremes, and (ii) to explore the possible connections between changes in different lowlands across Europe. Precipitation time series are used from the E-OBS v.20 datasets on a 0.1° regular grid. Datasets are based on station measurements from Europe and are available from 1950 onward with daily temporal resolution. Altogether 14 plain regions are selected in this study to represent different parts within Europe. More specifically, five plain regions are parts of the East European Plain, two regions are located in the Scandinavian basin, five regions are located in Western Europe, and the Pannonian Plain (including mostly Hungary) is also selected. For choosing the plains and their spatial representations, objective criteria are used, namely, the elevation remains under 200 m throughout the defined area and difference between the neighbouring gridpoints within the plain region does not exceed 40 m. Daily precipitation times series are analyzed and compared for these plain regions using various statistical tools. The results represent annual and seasonal changes in average and extreme precipitation amount as well as in the frequency of precipitation occurences. Climate indices and the occurence of extreme weather conditions including wet and dry spells are also analyzed.

 
Effect of biochar addition to compost on biological stability of the mixture
Authors: Marie-Liesse Aubertin , Cyril Girardin , Sabine Houot , Yann Le Brech , Sarah Bena , Cornelia Rumpel
Published: March 2020

Application of biochar, a solid product produced from biomass pyrolysis under low oxygen conditions, has been suggested as a low emission technology capable of increasing soil C sequestration to mitigate climate change. Its combined application with compost may be a promising avenue to ameliorate soil quality while increasing C sequestration. We hypothesized that biochar addition to compost reduces the mineralization of the mixture compared to compost alone. The study aimed to compare the mineralization rate of six biochar-compost mixtures differentiated by biochar feedstocks. Biochars were produced at temperatures ranging from 450 to 650°C for 10 minutes. Our conceptual approach included incubation of fresh and artificially aged biochar-compost mixtures. Physical ageing of the mixtures was performed with successive cycles of humidification/drying and freezing/thawing. We evaluated elemental composition and biological stability of the fresh and aged mixtures after incubation with a soil inoculum for 1 year. We monitored components of biochar-compost mixtures decomposition when biochar were produced from C4 feedstock by determination of the 13C signature of emitted CO2.

Combination of compost with biochar induced synergistic effects in terms of the mixtures stability. Isotopic analyses showed that carbon mineralization from compost was greatly reduced, while biochar mineralization was increased. Physical ageing induced a strong leaching of water-soluble compounds of both substrates. Carbon mineralization of aged material was however not reduced as much as expected when comparing with mineralization rates of single compounds of the mixture. Furthermore, isotopic signatures showed that compost, when amended with biochar, mineralized better after ageing. We thus suggest that the water-soluble fraction of biochar may induce an inhibitive effect on the mineralization of compost. The intensity of this effect seems to be dependent upon the feedstock of the biochar in the mixture.

We conclude that biochar addition to compost may reduce the mineralization of the mixture depending on biochar feedstock and that this effect may be alleviated after ageing.
Assessment of geodetic products from MGEX analyses for the Onsala site
Authors: Diamantidis Periklis-Konstantinos , Klopotek Grzegorz , Haas Rüdiger
Published: March 2020

The emergence of BeiDou and Galileo as operational Global Navigation Satellite Systems (GNSS), in addition to Global Positioning System (GPS) and GLONASS which are already in use, opens up possibilities in delivering geodetic products with higher precision. Apart from ensuring the homogeneity of the derived products, multi-GNSS analysis takes the advantage of new frequencies and an improved sky coverage. This should lead to better phase ambiguity resolution and an improved estimation of target parameters such as zenith wet delays (ZWD), troposphere gradients (GRD) and station positions. The International GNSS Service (IGS) has realised this potential by initiating the Multi-GNSS Experiment (MGEX) which provides orbit, clock and observation data for all operational GNSS. Correspondingly, the multi-technique space geodetic analysis software c5++ has been augmented with a MGEX-compliant GNSS module. Based on this new module and the Precise Point Positioning (PPP) approach using six-month of data, an assessment of the derived geodetic products is carried out for several GNSS receivers located at the Onsala core site. More specifically, we perform both single- and multi-GNSS data analysis using Kalman filter and least-squares methods and assess the quality of the derived station positions, ZWD and GRD. A combined solution using all GNSS together is carried out and the improvement with respect to station position repeatabilities is assessed for each station. Inter-system biases, which homogenise the different time scale that each GNSS operates in and are necessary for the multi-GNSS combination, are estimated and presented. Finally, the applied inter-system weighting is discussed as well as its impact on the derived geodetic products.
Life cycle assessment of horticultural production on UK lowland peat soils.
Authors: Freeman Benjamin , Styles David , Evans Christopher , Chadwick David , Jones David
Published: March 2020

Global peatlands store >600 Gt of Carbon (C) but are highly vulnerable to degradation following drainage for agriculture. The extensively drained East Anglian Fens include half of England’s most productive agricultural land, produce ~33% of England’s vegetables and support a food production industry worth approximately £3 billion GBP.  However under arable management, these fen peat soils produce ~37.5 t CO2 eq ha-1 of total greenhouse gas (GHG) emissions annually. This is likely to be the largest source of land use GHG emissions in the UK per unit area and there is interest in developing responsible management approaches to reduce emissions whilst maintaining economically productive systems. Lettuce (Lactuca sativa) is amongst the UK’s most valuable crops and a substantial proportion of UK production occurs in the Fens. We undertook a life cycle assessment to compare the carbon footprint of UK Fen lettuce with alternative sources of lettuce for the UK market. We also examined the potential for responsible peat management strategies and more efficient production to reduce the carbon footprint of Fen lettuce. It is hoped this study will help to inform land use decision making and encourage responsible management of UK lowland peat resources.
Improving the antenna performance for Zenith Tropospheric Delay estimations with consumer-grade antennas and a low-cost dual-frequency receiver
Authors: Krietemeyer Andreas , van der Marel Hans , ten Veldhuis Marie-claire , van de Giesen Nick
Published: March 2020

The recent release of mass-marked dual-frequency receivers opens up the opportunity to facilitate the cost-efficient estimation of Zenith Tropospheric Delays (ZTDs) from Global Navigation Satellite System (GNSS) observations. We present results of ZTD estimations from a low-cost dual-frequency GNSS receiver (U-blox ZED-F9) equipped with a range of different quality and priced antennas. It is demonstrated that the receiver itself is able to produce high quality ZTD estimations with higher grade antennas. However, the noise introduced by applying the ionosphere-free linear combination in Precise Point Positioning (PPP), makes the low-cost antenna performance initially a major challenge. With Root Mean Square Errors (RMSE) between 15 mm and 24 mm for low-cost antennas the results were at first not adequate for meteorological purposes. We demonstrate an easy-to-apply relative antenna calibration that increased the ZTD accuracy significantly for the tested low-cost antennas. After applying antenna corrections the error is reduced to a level that is adequate for meteorological applications (RMSE ~4 mm).
Remote sensing mixed layer depth using ocean ambient noise
Authors: Shajahan Najeem , Barclay David
Published: March 2020

Ambient noise measurements have been widely used to estimate environmental information such as water column sound speed, pH, seabed properties, and wind speed. In this study, 30 days of ambient noise data recorded on two vertically oriented hydrophones deployed near Alvin canyon on the New England shelf break were used to estimate the ocean mixed layer depth (MLD). The vertical noise coherence was computed and compared to a wave-number integral noise model comprised of a two-segment piecewise linear summer sound speed profile in a shallow water waveguide. Measurements of noise and sound speed profiles, together with a wavenumber integral ambient noise model were used to calculate the mixed layer thickness. Noise model results showed variations in the first zero-crossing frequency, which was in accordance with the semi-diurnal variability of the MLD. MLD was determined by matching the zero-crossing frequency of the real part of measured coherence with the model results for the entire one-month period. The comparison of the estimated MLD using ambient noise showed good agreement with the measured MLD from the temperature sensors.
How high can we go: defining and breaching the threshold for soil organic matter to improve soil water holding capacity?
Authors: Feng Gary , Li Xinhu , Reginelli Dennis
Published: March 2020

Soil water holding capacity is an important soil property which influences soil and water conservation as well as land degradation and development. Some studies indicated that field capacity (FC) was increased as soil organic matter (SOM) is improved, but the positive effect of SOM on FC was still contradictory. No consistent reports were found for the SOM potential that could be increased. Whether FC could be improved due to increase in SOM by organic amendment is not well established. It is still unknown whether or not there is benefit of improving SOM for enhancing FC; what is the threshold level of SOM for increasing FC, and how much SOM can be boosted. The field study and literature review were conducted to answer all those questions. Soil samples were taken at four sties manured and not manured in the Southern United States, then SOM and FC were measured. The soils amended with poultry litter had higher SOM (3.2%) and FC (35.38%), while the soils without amendment of poultry litter had lower SOM (1.7%) and FC (30.33%), a positive effect of SOM on FC was observed. For different soils with various clay content, a strong positive relationship was observed for soils with clay content less than 15% (R2= 0.7). We found that FC started increasing as SOM was increased over 2%, it is the threshold level of SOM for improving FC. Previous research also reported that there was no positive effect on FC for cultivated soils with a mean SOM of 1.2% in Greece. Another study found that the increase in water content is significant for sandy soils with 0 to 20% clay content. Our results revealed a pronounced effect for silt loam soils with 1 to 28% clay as SOM was larger than 2%. The SOM ranged from 0.9 to 5.42 %, with a mean value of 2.60 % for the 167 soil samples we measured. We found the highest level of SOM that amendment of poultry litter can increase was not greater than 6.0 %. We suggest SOM should be increased over 2% for improving FC, there is large room for SOM improvement in subtropical humid regions.