bluuebunny/crossref_metadata_2025 huggingface dataset:
Rhenium distribution and behaviour in the salinity gradient of a highly stratified estuary
Authors: Bura-Nakić Elvira , Knežević Lucija , Mandić Jelena , Cindrić Ana-Marija , Omanović Dario
Published: March 2021

In oxic waters, ReVII is the stable oxidation state which undergo hydrolysis to the relatively unreactive perrhenate ion, ReVIIO4- [1]. The oceanic dissolved Re exhibits quite conservative behaviour with the concentration of about 40 pM [2]. Despite the frequent utilization of Re for the atmosphere and the ocean past redox state reconstructions, the geochemical behaviour of Re in the modern surface environments such as rivers, estuaries as well as in seawater is not well studied. Understudy is partially arising from the fact that Re has low seawater and riverine concentration of 4 pM and 16.5 pM, respectively[1, 3]. In the Amazon and the Hudson estuaries, in crease of Re concentration at low and middle salinity regions is observed [4]. On the other hand, Re exhibits complete conservative behaviour in Indian river estuaries, i.e. Narmada, Tapi and the Mandovi estuaries in the Arabian Sea and the Hooghly estuary in the Bay of Bengal [5]. Deviation from conservative behaviour in Re can be explained as the interplay of variety of factors including the nature and composition of the particles, Eh-pH conditions, biological productivity and fate of the organic matter. [5].

Here we present the Re concentration profiles in the freshwater part of the karstic Krka river (Croatia) and its 23 km long estuarine segment, covering a full salinity range (0.1 to 38.6). Analysis of Re was performed by its preconcentration and separation using an anion exchange resin (Dowex 1X8) followed with the ICP-MS quantification using isotope dilution (ID) method. The Krka River spring is characterised by the low Re concentration (~6 pM). A noticeable anthropogenic influence at the point of the wastewater discharge of the Knin town was observed (27 pM). This input probably caused a progressive downstream increase of Re concentration to 12 pM at the freshwater end-member in the winter period (with a high Krka River discharge) and 17 pM in the summer period (low Krka River discharge). In the estuarine segment, a near-conservative behaviour of Re was found, with the "oceanic" concentration of 38 pM in the seawater end-member.

 

References:

[1] Hasse AA et al., (2019) Coordination chemistry reviews 394: 135-161.

[2] Anbar AD et al., (1992) Geochimica et Cosmochimica Acta 56:4099-4103.

[3] Miller CA et al., (2011) Geochimica et Cosmochimica Acta 75:7146-7179.

[4] Colodner D et al., (1993) Earth and Planetary Science Letters 117:205-221.

[5] Rahaman W and Singh SK (2010) Marine Chemistry 118: 1-10.
New communication strategies in NEMO
Authors: Epicoco Italo , Mocavero Silvia , Mele Francesca , D'Anca Alessandro , Aloisio Giovanni
Published: March 2021

One of the main bottlenecks for NEMO scalability is the time spent performing communications. Two complementary strategies are here proposed to reduce the communication frequency and the communication time: the MPI3 neighbourhood collective communications instead of multiple point to point exchanges and the increasing of the halo region size.

NEMO performs Lateral Boundaries Conditions update by using four point to point MPI communications at north, south, east and west for each MPI domain. The model completes east-west exchange before performing north-south communications. The order of the exchanges allows us to preserve both 5-point and 9-point stencils. MPI3 neighbourhood collectives provide a way to have sub-communicators used to perform collective communications. Two different sub-communicators can be defined in order to support the two different stencils. A single MPI message is needed to be built for all neighbours instead of 4 different messages before calling the collective communication, while the received message is used to update the halo region, following the order of the neighbours in the sub-communicator.

The new communication strategy has been tested on two computational kernels (i.e. one for 5-point stencil and one for 9-point stencil), selected among the main relevant routines from the computational point of view. Preliminary tests, performed on a domain size of 3000x2000x31 grid points on the Zeus Intel Xeon Gold 6154 machine, available at CMCC, show a gain in communication time for the 5-point stencil use case up to 31% on 2016 cores. The improvement is reduced when communications with processes on the diagonal are activated. However, a modest gain is still achieved, depending on the number of cores.

On the other side, the analysis of some NEMO routines shows how the exchange of more than one row/column of halo would allow to move communications outside the routine, preserving data dependencies. A wider halo size reduces the frequency of message exchanges whilst increases the message size at each exchange. It allows us to adopt some optimisation strategies (i.e. loop fusion, tiling, etc.) to improve the data locality. Nevertheless, the use of a wider halo introduces itself some improvements for some kernels like for the MUSCL advection scheme which shows a gain of ~23% in the execution time comparing the original version and the new one with halo extended to 2 lines and the communication moved outside the computing region.

The current work has been performed according to the NEMO development strategy plan, defined by the NEMO Consortium, which establish the priorities of the design strategies to reduce the bottlenecks to the scalability and the time to solution.

 

Acknowledgments

This work is co-funded by the EU H2020 IS-ENES project Phase 3 (ISENES3) under Grant Agreement number 824084.
The impact of climate change in wheat and barley yields in the Iberian Peninsula
Authors: Bento Virgílio A. , Ribeiro Andreia F.S. , Russo Ana , Gouveia Célia M. , Cardoso Rita M. , Soares Pedro M.M.
Published: March 2021

World food and drink production largely depends on wheat and barley crops, which are the basis of nutrition for both humans and animals. The Iberian Peninsula (IP), and particularly Spain, is responsible for a large percentage of farming areas dedicated to these two crops. Furthermore, the IP is known as a prominent climate change hot spot, with expected rising temperatures and a decrease in mean precipitation (with more extreme events). Thus, it is vital to understand the effects of climate change in wheat and barley yields in the IP.

Multiple linear regression (MLR) models were developed based on the relation between temperature and precipitation and both crop yields, with the aim of projecting these into the future. Three main objectives were pursued: (1) to establish the existence of a relationship between wheat and barley yields and temperature and precipitation, taking advantage of data from the EURO-CORDEX regional climate models (RCMs) forced with ERA-Interim; (2) to calibrate and validate MLR models using a selection of predictors from the same EURO-CORDEX RCMs; and (3) to apply these MLR models to EURO-CORDEX RCMs forced with global climate models (GCMs) for an historical period (1971-2000) and two future periods (2041-2070 and 2071-2100) according to two greenhouse gas emission scenarios (RCP4.5 and RCP8.5). Results show a dichotomic behaviour of wheat and barley future yields depending on the crop’s production region. Projections for the southern cluster of the IP show severe yield losses for both cereals, which may be a consequence of the increase in maximum temperatures in spring, particularly for RCP8.5 at the end of the 21st century. Conversely, projections for the northern cluster of the IP show an increase in yield output, which may be a result of the projected warming taking place within the early winter months.

This study reinforces the worth to implementing changes in the society to mitigate losses and to assess production gains/losses due to climate change. These may be implemented locally (different cultivar species), countrywide (implementing sustainable policies), or even globally (alleviate greenhouse gas emissions). This work was supported by project IMPECAF (PTDC/CTA-CLI/28902/2017), LEADING (PTDC/CTA-MET/28914/2017) and by IDL (UIDB/50019/2020).
Quality assessment for objective inter-comparison of coronal models
Authors: Wagner Andreas , Temmer Manuela , Asvestari Eleanna
Published: March 2021

With the increasing amount of space weather forecasting simulation codes being developed, assessing their performance becomes crucial. Especially the errors resulting from coronal magnetic field models are a critical factor, because these will get propagated further by various solar wind models. We present a first result for a benchmarking system that allows a rather easy-to-implement  assessment of the performance quality of any coronal magnetic field model. This will allow for a standardized comparison between different models. The benchmarking system is based on stepwise visual and semi-automatized comparisons between model output and EUV on-disk and coronograph white-light data. We are using various viewpoints and instrumental data provided by STEREO, SOHO and SDO. 
In our work we exemplarily apply this scheme to the coronal model currently implemented in EUHFORIA, an adaption of the Wang-Sheeley-Arge (WSA) model, with varying input parameters. Furthermore, with this system we also show its possible usage for the derivation of an ideal parameter set. 
GPS z-PCO and GNSS-based scale determined by integrated processing with LEOs and Galileo
Authors: Huang Wen , Männel Benjamin , Brack Andreas , Schuh Harald
Published: March 2021

The Global Positioning System (GPS) satellite transmitter antenna phase center offsets (PCOs) in z-direction and the scale of the terrestrial reference frame are highly correlated when neither of them is constrained to an a priori value in a least-squares adjustment. The commonly used PCO values offered by the International GNSS Service (IGS) are estimated in a global adjustment by constraining the ground station coordinates to the current International Terrestrial Reference Frame (ITRF). As the scale of the ITRF is determined by other techniques, the estimated GPS z-PCOs are not independent. Consequently, the z-PCOs transfer the scale to any subsequent GNSS solution. To get a GNSS-based scale that can contribute to a future ITRF realization, two methods are proposed to determine scale-independent GPS z-PCOs. One method is based on the gravitational constraint on Low Earth Orbiters (LEOs) in an integrated processing of the GPS satellites and LEOs. The correlation coefficient between the GPS PCO-z and the scale is reduced from 0.85 to 0.3 by supplementing a 54-ground-station network with seven LEOs. The impact of individual LEOs on the estimation is discussed by including different subsets of the LEOs. The accuracy of the z-PCOs of the LEOs is very important for the accuracy of the solution. In another method, the GPS z-PCOs and the scale are determined in a GPS+Galileo processing where the PCOs of Galileo are fixed to the values calibrated on ground from the released metadata. The correlation between the GPS PCO-z and the scale is reduced to 0.13 by including the current constellation of Galileo with 24 satellites. We use the whole constellation of Galileo and the three LEOs of the Swarm mission to perform a direct comparison and cross-check of the two methods. The two methods provide mean GPS z-PCO corrections of -186±25 mm and -221±37 mm with respect to the IGS values, and +1.55±0.22 ppb (part per billion) and +1.72±0.31 ppb in the terrestrial scale with respect to the IGS14 reference frame. The results of both methods agree with each other with only small differences. Due to the larger number of Galileo observations, the Galileo-PCO-fixed method leads to more precise and stable results. In the joint processing of GPS+Galileo+Swarm in which both methods are applied, the constraint on Galileo dominates the results. We also discuss how fixing either the Galileo transmitter antenna z-PCO or the Swarm receiver antenna z-PCOs in the GPS+Galileo+Swarm processing propagates to the respective freely estimated z-PCOs of Swarm or Galileo.
Oxidation of sulfamethoxazole by rice husk biochar-activated persulfate: factors affecting the process’s efficiency
Authors: Avramiotis Efstathios , Frontistis Zacharias , Vakros John , Manariotis Ioannis , Mantzavinos Dionissios
Published: March 2021

Valorization of biomass can be performed with a variety of processes. An interesting process is the production of fuels during pyrolysis. The solid remaining of this process is called biochar. Biochar, a carbonaceous material, has unique physicochemical properties and, as a result, it can be used in several processes. In this study, biochar from rice husk was produced under different pyrolysis temperatures and used as persulfate activator for the oxidation of sulfamethoxazole.

Specifically, biochar from rice husk was synthesized pyrolyzing the raw material for 1 hour under limited-oxygen atmosphere at four different pyrolysis temperatures: 400, 550, 700, and 850°C, and employed as catalyst of persulfate activation for the removal of sulfamethoxazole (SMX). SMX degradation experiments were performed mainly in ultra-pure water (UPW) using various biochar, persulfate and SMX concentrations and altering solution pH (3 < pH < 10). More complex matrices, besides UPW, were also tested, namely treated wastewater (WW) and bottled water (BW). Also, synthetic matrices were prepared by spiking UPW with some possible inhibitors of the process.

Τhe presence of the biochar was crucial for the process as it contributes to the SPS activation resulting in faster and higher removal of the target compound. Adsorption and oxidation rates increase when biochar, produced at higher pyrolysis temperature, is used. The maximum removal is observed in the case of the highest pyrolysis temperature (T = 850°C) biochar.

Acidic environment generally facilitates the adsorption of the micro-pollutant compared to the basic environment, while the oxidation reaction decelerates accordingly to the complexity of the water matrix. The addition of alcohol has only a slightly negative effect on the efficiency of the process contrary to the addition of sodium azide which causes a major reduction. This may indicate that the reaction pathway is under electron transfer / singlet oxygen control rather than the active radicals’ one.

 

The research work was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: 81080).
Online counter gradient LC-FT-ICR-MS enables detection of highly polar natural organic matter fractions
Authors: Han Limei , Kaesler Jan M. , Peng Chang , Reemtsma Thorsten , Lichentfeld Oliver J.
Published: March 2021

Natural organic matter (NOM) is a highly complex mixture of natural organic molecules. The hyphenation of liquid chromatography (LC) with ESI-FT-ICR MS for the molecular characterization of NOM have shown to be a promising approach. However, due to changing solvent composition during gradient elution in LC-FT-ICR-MS, ionization conditions also change throughout the chromatographic separation process. In this study, we applied a post-LC column counter gradient (CG) to ensure stable solvent conditions for transient ESI-MS signals. SRFA and a peat pore water samples were used as representative dissolved NOM samples for method development and validation. Our results show that in the isocratic range segment, the TIC intensities of CG was increased by a factor of 1.5 fold, as compared to the standard gradient (SG) method. In addition, the application of the CASI mode for low abundance fractions revealed over 3 times more molecular formulas (especially for CHNO, CHOS, CHNOS formula classes) than in full scan mode. The number of detected highly polar NOM compounds (with elemental ratios H/C < 1, O/C > 0.6) were more than 20 times larger for CG-LC mode as compared to direct infusion (DI) (5715 vs 266 MF).We conclude that the new CG-LC-FT-ICR MS method achieved a novel insight into the highly polar fractions of NOM, which are inaccessible in conventional DI measurements.

Key words: Natural organic matter (NOM), online LC-FT-ICR MS method, CASI mode, ESI

 
A kinetic energy budget perspective to understand efficiency reductions of offshore wind generation in the German Bight in the North Sea
Authors: Minz Jonathan , Imberger Marc , Kleidon Axel , Badger Jake
Published: March 2021

The European Commission’s net zero decarbonization scenarios estimate that up to 450GW of offshore wind capacity could be installed in Europe by 2050. German energy scenarios estimate that 50 to 70 GW of this could be installed in the German Bight in the North Sea and yield about 4000 full load hours (FLH) per year of power. However, these assume that wind speeds and yields are not reduced by the increased extraction of kinetic energy from the regional atmospheric flow by large wind farms. Our initial assessment of these assumptions, using two different approaches - the simple Kinetic Energy Budget of the Atmosphere model (KEBA) and the Weather Research and Forecasting model with Explicit Wake Parameterization (WRF-EWP), showed that emplacing such a large turbine capacity within the German Bight may lower expected yield down to 3300-3000 FLH. Here, we identify the major factors leading to this reduction. We use the two models to evaluate the role of atmospheric variables like wind directions, atmospheric stability, boundary layer height and surface friction in constraining large scale offshore wind energy generation. We test the KEBA model concept of limited kinetic energy fluxes through the boundary layer determining generation potential, and investigate deviations between the models to identify limitations of the simpler approach.The WRF model sets our ”best guess” of energy yield from regional wind turbine deployments (at scales of 104km2) since the scale of deployments that we assess are not in operation yet. Our analysis will provide insights about key atmospheric variables that shape regional offshorewind energy potential of the German Bight. We propose that estimating regional wind energy potential should account for atmospheric response.
Modelling gas dispersal phenomena at La Soufrière volcano (Guadeloupe, Lesser Antilles)
Authors: Massaro Silvia , Dioguardi Fabio , Sandri Laura , Tamburello Giancarlo , Selva Jacopo , Moune Sèverine , Jessop David , Moretti Roberto , Komorowski Jean-Christophe , Costa Antonio
Published: March 2021

In recent decades, reliable computational models have significantly advanced, and now represent a valuable tool to make quantitative and testable predictions, supporting gas dispersal forecasting and hazard assessments for public safety. In this study, we carried out a number of tests aimed to validate the modelling of gas dispersal at La Soufrière de Guadeloupe volcano (Lesser Antilles), which has shown quasi-permanent degassing of low-temperature hydrothermal nature since its last magmatic eruption in 1530 AD. In particular, we focused on the distribution of CO2 and H2S discharged from the three main present-day fumarolic sources at the summit, using the MultiGAS measurements of continuous gas concentrations collected during March-April 2017. We implemented the open-source Eulerian code DISGAS-2.0 for passive gas dispersion coupled with the mass consistent Diagnostic Wind Model (DWM), using wind measurements and atmospheric stability information from a local meteorological station and the ECMWF-ERA5 reanalysis data. We found that model outputs are highly dependent on the resolution of the topographic data, which affect mainly the reliability of DWM meteorological fields, especially on and around the steep dome. Our results satisfactory reproduce the observed data, indicating the potential usefulness of DISGAS-2.0 as a tool for quantifying gas hazard and reproducing the fumarolic degassing and at La Soufrière de Guadeloupe.

 
era5cli: the command line interface to ERA5 data
Authors: Smeets Stef , Camphuijsen Jaro , Drost Niels , Alidoost Fakhereh , Andela Bouwe , Weel Berend , Kalverla Peter , van Haren Ronald , Zimmermann Klaus , Aerts Jerom , Hut Rolf
Published: March 2021

With the release of the ERA5 dataset, worldwide high-resolution reanalysis data became available with open access for public use. The Copernicus CDS (Climate Data Store) offers two options for accessing the data: a web interface and a Python API. Consequently, automated downloading of the data requires advanced knowledge of Python and a lot of work. To make this process easier, we developed era5cli. 

The command line interface tool era5cli enables automated downloading of ERA5 using a single command. All variables and options available in the CDS web form are now available for download in an efficient way. Both the monthly and hourly dataset are supported. Besides automation, era5cli adds several useful functionalities to the download pipeline.

One of the key options in era5cli is to spread one download command over multiple CDS requests, resulting in higher download speeds. Files can be saved in both GRIB and NETCDF format with automatic, yet customizable file names. The info command lists correct names of the available variables and pressure levels for 3D variables. For debugging purposes and testing the dryrun option can be selected to return only the CDS request. An overview of all available options, including instructions on how to configure your CDS account, is available in our documentation. Recent developments include support for ERA5 back extension and ERA5-Land. The source code for era5cli is available on https://github.com/eWaterCycle/era5cli.
Variability in the erosion response of vertical sections of salt marsh sediments exposed to tidal flat conditions
Authors: Shears Olivia , Möller Iris , Spencer Tom , Evans Ben , Royse Kate
Published: March 2021

Salt marsh ecosystems are important for supporting biodiversity, sequestering carbon and providing natural coastal protection. Evidence for their existing and potential future loss through marginal erosion is therefore of concern. However, the factors governing spatial variability in the rates of erosion at salt marsh margins – including between creek banks within individual salt marsh sites – remain relatively poorly understood. Accurate prediction of changes to the marsh edge, and thus marsh areal extent, requires more complete understanding of the dynamics and mechanisms occurring at exposed marsh fronts.

In this study, we present observations of the responses of vertical sections of marsh substrate exposed to tidal flat conditions, during a field experiment over a six-month period. Vertical sections were extracted from natural and restored sites at two salt marshes in the UK: Northey Island, eastern England, where sediment is fine-grained, and Hesketh Out Marsh West, north-west England, where sediment is typically sand/silt-dominated. The study specifically investigates the role of different sedimentology and downcore substrate properties, including lamination and rooting structures, on observed change in the exposed vertical sections. Images captured in the field are analysed using structure-from-motion photogrammetry and used to create 3-D models of surface change. This is coupled with laboratory testing of downcore sedimentary characteristics, such as particle size distribution and organic matter content.

The study finds that within-core and between-core variability in substrate response to erosive forcing appears to be partly related to variability in sedimentology. Sediment from sand-dominated layers, such as those found in the cores extracted from Hesketh Out Marsh West, was more rapidly and consistently (i.e. across the sediment cores) removed than clay-silt rich sediment. This grain-scale sediment removal resulted in specific morphological responses, whereby ‘chunks’ of substrate were lost, creating cavity areas further exposed to hydrodynamic forcing. Intrinsic biophysical characteristics, including sediment type and the presence of vegetation structures, can impact vertical connectivity within salt marsh substrates. Observations of structural change in the vertical sections over the six-month study period suggest that reduced downcore connectivity in restored salt marsh substrates results in increased desiccation, cracking and bulk sediment removal. An improved understanding of how such intrinsic substrate properties impact marsh front dynamics will facilitate more accurate predictions of marsh evolution and potential ecosystem service provision under future conditions.
Soil pollution in a decommissioned shooting range: a preliminary survey of the spatial variability of legacy pollutants.
Authors: Albanese Stefano , Guarino Annalise , Aruta Antonio , Roberto De Mascellis , Carlo Perreca , Massimo Fagnano , Simona Vingiani
Published: March 2021

Outdoor shooting ranges provide recreational facilities for millions of people in the world. However, there are many negative effects on the environment and public health arising from this activity.

In particular, potential risks are mostly associated with the residential or agricultural use of decommissioned outdoor ranges, where bullets and targets have been deposited during the shooting activity.

This is the case of an outdoor shooting range in Campania region (Southern Italy), located in an area of historical and naturalistic value, close to the ancient Etruscan village of Suessola (VII century b.C.). Specifically, the study site is located within an agricultural land declared unsuitable for agricultural and forest-pastoral production by the Italian Ministry of Agricultural, Food and Forestry Resources, due to an extensive long term soil contamination associated with Pb, Sb, PAHs, dioxins, PCBs and C> 12 hydrocarbons.

With the purpose of planning a detailed site characterization of the shooting range area, a preliminary environmental survey was carried out by means of field investigations (ultrasonic penetrometry, electromagnetic induction - EMI -  and gamma spectroscopy) and geochemical prospecting.

Cone index data, obtained by ultrasonic penetrometer measurements, indicated the presence of a very dense, hard and impenetrable to hand hauger layer, recognised as travertine rock, from 25 to more than 55 cm of depth, and dipping northward.

Continuous EMI data and gamma spectroscopy (K %, eU ppm, eTh ppm) parameters were acquired in the field in order to identify homogeneous zones in which further geochemical investigations should have been focused. In fact, apparent electrical conductivity (ECa) map, consistently with the gamma ray dose rate distribution map, allowed to highlight three separated singularity areas  N-S oriented.

XRF analyses, carried out through a portable analyzer on soil samples collected along soil profiles digged from topsoil until the travertine layer, showed a high contamination by Pb (greater than 1000 mg/kg) and Sb (greater than 30 mg/kg) in the first 15 cm of depth, at a distance of approximately 90 m from the shooting lanes.

Chemical analyses were also performed on 32 topsoil samples collected on the basis of a regular grid across the study area. Concentrations of 13 PAHs compounds were determined and the highest values were found close to the firing lanes where in soil a huge amount of shooting target fragments are present.

The preliminary results showed how the contamination due to the previous activity in the area produced a spatial distribution of contaminats differentiated on the basis of their source material and their role in the shooting process.
Quantifying and characterising contemporary rockfall supply to a debris-covered glacier catchment
Authors: Stewart Rebecca , Westoby Matthew , Dunning Stuart , Pellicciotti Francesca , Woodward John
Published: March 2021

Supraglacial debris extent and thickness is an important control on the ablation rate of a debris-covered glacier. Debris is supplied to the surface of a debris-covered glacier through several pathways with the primary source of this debris originating from rockfall in both the accumulation area, where debris is transported englacially downglacier, and the upper ablation area, where debris remains in the supraglacial environment while transported downglacier. Current quantification of debris supply to debris-covered glaciers is limited to headwall erosion rates determined through the dating of headwall derived supraglacial debris using 10Be concentrations, or estimations of these rates using a ratio of supraglacial debris flux to the headwall catchment area. To increase the knowledge of the contemporary short-term estimations of these processes, repeat LiDAR scans of debris-contributing slopes were acquired during a single ablation season in both July and September at Miage Glacier, Italy. An area of ~7.7 km2 comprising > 1.8 billion 3D points was scanned per survey epoch, covering ~33% of the glacierised area of Miage Glacier. Sequential scans were co-registered using an iterative closest point adjustment algorithm within CloudCompare. Manual filtering was used to remove snow, artefacts, and the glacier surface from the raw point clouds. To ease processing, the rock walls were segmented both horizontally and vertically within the catchment. Change detection was carried out using the M3C2 algorithm at a projection scale of 0.3 m and point clouds representing areas of significant change within the segment were obtained using a distributed 95th percentile confidence interval. The DBSCAN clustering algorithm was used to identify individual rockfall clusters, and the volume of each rockfall was calculated using both an iterative alpha-shapes approach. Finally, a bounding box approach was used to estimate the a, b and c axes and therefore shape of the individual rockfalls. Increasing the projection scale used within the M3C2 algorithm decreases the frequency of significant rockfalls found exponentially, and an iterative alpha shapes approach is the most computationally efficient volume estimation method. Our results show that the Miage Glacier catchment is dominated by small scale rockfall events, although at least one large-scale rockfall event is evident in the upper ablation area (validated by time-lapse imagery). This failure on a recently deglaciated area of rock wall highlights that slope response to glacial erosion can be rapid following periods of deglaciation.
The sensitivity of CRNS and Sentinel-2 products to detect differences in soil water content along a toposequence with two contrasting parent materials
Authors: Gaspar Leticia , Franz Trenton , Lizaga Ivan , Latorre Borja , Navas Ana
Published: March 2021

Soil moisture controls hydrological processes in natural and agricultural systems. A clear understanding of their temporal dynamics and spatial variability is essential to control soil degradation processes, irrigation management and water use efficiency. In recent years, the measurement of soil water content (SWC) with ground-based neutron sensors and remote sensing products have become promising non-invasive methods for different spatial scales. In this study, we are investigating the sensitivity of using cosmic ray neutron sensor (CRNS) and Sentinel-2 SWC index for quantifying different dynamics of soil moisture along a toposequence with underlying contrasting parent materials. For this study, three sites were selected in the upper section (US) soils on limestones correspond to Muschelkalk facies, and another three in the lower section (LS) siliciclastic materials composed of low-permeability marls and claystone formation with primarily silty clay texture (Keuper facies). During two surveys, which correspond to wet (spring 2018/05/05) and dry conditions (summer 2018/08/05), a set of soil moisture data were obtained by using i) portable CRNS backpack, ii) satellite-based information and iii) HS200 sensor Delta-T Devices. The physical composition of the studied soils reflects the clear difference in parent material, with mean content of soil organic carbon of 6% in US against 1% in LW, while the mean clay content was lower in US (21%) than in LS (26%). The infiltration measurements also show different responses for water infiltration capacity, with a much higher mean value of hydraulic conductivity for the soils in the US (317 mm per day), reflecting the karst features, than in the LS (35 mm per day) corresponding to the siliciclastic materials. Our results show similar trends during the two surveys, obtaining significantly lower soil water content on limestones at the US where infiltration processes prevailed thus facilitating leaching and limiting runoff. In contrast, the higher soil water content was on siliciclastic soils at the LS where the low permeability of soils due to the clayed substrate promoted increased runoff. Focusing on the comparison of soil moisture data obtained during the wet and dry surveys, a soil characteristic dependency is observed, with a more different soil moisture state on siliciclastic soils (LS) between the two surveys than for the soils on limestones. Our preliminary results pinpoint that CRNS, Sentinel-2 index and field data captured soil moisture dynamics along the toposequence and demonstrated the sensitivity of neutron sensors and remote sensing products to investigate the effect of parent material on soil water content at sampling scale.
Lake Chala 2k: the last two millennia of environmental change in equatorial East Africa
Authors: Meyer Inka , Papadimitriou Irina , Verschuren Dirk , De Batist Marc
Published: March 2021

In order to disentangle natural climate variability from anthropogenically caused variations, environmental reconstructions of the past 2000 years have gained renewed scientific interest during the last ~20 years. Whereas climatic and environmental changes during this period, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are fairly well expressed in western Europe and the North Atlantic area, knowledge about equivalent changes in African climate and environment (e.g. changes in temperature and precipitation, monsoonal activity and resulting vegetation feedbacks) can be much improved. Here we present new results from Lake Chala, a crater lake in equatorial East Africa, based on sedimentary grain-size distributions. Notwithstanding the relatively minor clastic mineral component, we are able to discriminate between different aeolian and fluviatile sources of terrigenous material and to reconstruct temporal trends in their contribution to the sediment. This can be linked to both local environmental dynamics and changes in the large-scale monsoonal systems over the East African landmass. Our findings point to arid conditions during the MCA and humid conditions during the LIA, in support of regional hydroclimate history as reconstructed from other moisture-balance proxies. The results of this study form an important piece of the puzzle to better understand past changes in African environments, which is a key aspect in the debate about future climate change in one of the most climate-sensitive regions on the planet.
Greenhouse gas emissions of aquifer thermal energy storage (ATES)
Authors: Stemmle Ruben , Blum Philipp , Schüppler Simon , Fleuchaus Paul , Limoges Melissa , Bayer Peter , Menberg Kathrin
Published: March 2021

Aquifer Thermal Energy Storage (ATES) is an open-loop geothermal system enabling seasonal storage of thermal energy in groundwater. It is a promising technology for environmentally friendly energy generation that can overcome the seasonal mismatch between demand and supply of heating and cooling and helps to reduce greenhouse gas (GHG) emissions. Yet, there are only few studies quantifying GHG emissions caused by ATES systems over their entire life cycle. This study presents a novel life cycle assessment (LCA) regression model focusing on the GHG emissions that is a fast alternative to conventional time-consuming LCA. Due to its parametric structure, the regression LCA model can be used to perform Monte Carlo simulations of a wide range of different ATES configurations. Accordingly, it allows the environmental evaluation of the technology as a whole.

The application of the model reveals that the median value of investigated ATES configurations is 83.2 gCO2eq/kWhth with most of the emissions resulting from electricity consumption during the operational phase. Compared to conventional heating systems based on heating oil and natural gas, this value reveals potential GHG savings of up to 74 %. In terms of cooling, ATES can save up to about 59 % of GHG emissions compared to conventional, electricity-based technologies. Specific GHG emissions from a modified LCA regression model considering a projected electricity mix for the year 2050 add up to 10.5 gCO2eq/kWhth forecasting even higher emission savings of up to 97 %. A sensitivity analysis reveals that in particular the operational time for cooling and the coefficient of performance (COP) of the heat pump should be carefully considered when planning or optimizing new systems under current conditions. In contrast, when considering the projected 2050 electricity mix, the most important system parameter is the number of wells. This reflects the decreasing importance of the electrical power necessary for ATES operation due to the much lower specific GHG emissions of the projected 2050 electricity mix.
What is the impact of earth observation and in-situ data assimilation on seasonal hydrological forecast quality?
Authors: Musuuza Jude Lubega , Crochemore Louise , Pechlivanidis Ilias G.
Published: March 2021

Earth Observations (EO) have become popular in hydrology because they provide information in locations where direct measurements are either unavailable or prohibitively expensive to make. Recent scientific advances have enabled the assimilation of EOs into hydrological models to improve the estimation of initial states and fluxes which can further lead to improved  forecasting of different variables. When assimilated, the data exert additional controls on the quality of the forecasts; it is hence important to apportion the effects according to model forcings and the assimilated datasets. Here,  we investigate the hydrological response and seasonal predictions over the snowmelt driven Umeälven catchment in northern Sweden. The HYPE hydrological model is driven  by two meteorological forcings: (i) a downscaled GCM meteorological product based on the bias-adjusted ECMWF SEAS5 seasonal forecasts, and (ii) historical meteorological data based on the Extended Streamflow Prediction (ESP) technique. Six datasets are assimilated consisting of four EO products (fractional snow cover, snow water equivalent, and the actual and potential evapotranspiration) and two in-situ measurements (discharge and reservoir inflow). We finally assess the impacts of the meteorological forcing data and the assimilated EO and in-situ data on the quality of streamflow and reservoir inflow seasonal forecasting skill for the period 2001-2015. The results show that all assimilations generally improve the skill but the improvement varies depending on the season and assimilated variable. The lead times until when the data assimilations influence the forecast quality are also different for different datasets and seasons; as an example, the impact from assimilating snow water equivalent persists for more than 20 weeks during the spring. We finally show that the assimilated datasets exert more control on the forecasting skill than the meteorological forcing data, highlighting the importance of initial hydrological conditions for this snow-dominated river system.
Quantifying Intrinsic and Extrinsic Contributions to Elastic Anisotropy Observed in Seismic Tomography Models
Authors: Magali John Keith , Bodin Thomas , Hedjazian Navid , Ricard Yanick , Capdeville Yann
Published: March 2021

Large-scale seismic anisotropy inferred from seismic observations has been loosely interpreted either in terms of intrinsic anisotropy due to Crystallographic Preferred Orientation (CPO) development of mantle minerals or extrinsic anisotropy due to rock-scale Shape Preferred Orientation (SPO). The coexistence of both contributions misconstrues the origins of seismic anisotropy observed in seismic tomography models. It is thus essential to discriminate CPO from SPO in the effective anisotropy of an upscaled/homogenized medium, that is, the best possible elastic model recovered using finite-frequency seismic data assuming perfect data coverage. In this work, we investigate the effects of upscaling an intrinsically-anisotropic and highly-heterogeneous Earth's mantle. The problem is applied to a 2-D marble cake model of the mantle with a binary composition in the presence of CPO obtained from a micro-mechanical model. We compute the long-wavelength effective equivalent of this mantle model using the 3D non-periodic elastic homogenization technique. Our numerical findings predict that overall, upscaling purely intrinsically anisotropic medium amounts to the convection-scale averaging of CPO. As a result, it always underestimates the anisotropy, and may only be overestimated due to the additive extrinsic anisotropy from SPO. Finally, we show analytically (in 1D) and numerically (in 2D) that the full effective radial anisotropy ξ* is approximately just the product of the effective intrinsic radial anisotropy ξ*CPO and the extrinsic radial anisotropy ξSPO:

ξ* = ξ*CPO × ξSPO

Based on the above relation, it is imperative to homogenize a texture evolution model first before drawing interpretations from existing anisotropic tomography models. Such a scaling law can therefore be used as a constraint to better estimate the separate contributions of CPO and SPO from the effective anisotropy observed in tomographic models.
Improvements to the Simplified Level 2 Prototype Processor for Retrieving Canopy Biophysical Variables from Sentinel 2 Multispectral Instrument Data
Authors: Fernandes Richard , Baret Fred , Brown Luke , Canisius Francis , Dash Jadu , Djamai Najib , Hong Gang , MacDougall Camryn , Shah Hemit , Weiss Marie , Zhong Detang
Published: March 2021

The Sentinel 2 (S2) constellation mission was designed to facilitate the systematic mapping canopy biophysical variables at medium resolution on a global basis and in a free and open manner.  The mission concept requires the development of downstream services to map variables such as the fraction of absorbed photosynthetically active radiation (fAPAR), fraction of canopy cover (fCOVER) and leaf area index (LAI) using Level 2A surface reflectance inputs from the S2 ground segment.  Currently, free and open products generation can be performed using the Simplified Level 2 Prototype Processor (SL2P) applied on a product granule basis.  Considering that the processor is a prototype this study addresses three questions: 1) Can the SL2P algorithm, or subsequent versions, be engineered to facilitate systematic product generation over large extents in a free and open manner? 2) What is the uncertainty of SL2P products over North America during the growing season? 3) Can the uncertainty be reduced by changing the calibration database used within SL2P?  

To facilitate validation and product generation, SL2P was ported to a Google Earth Engine application (the Landscape Evolution and Forecasting Toolbox).  This now allows mapping of up to one million square kilometers in near real time using either the original SL2P algorithm or updated versions.  SL2P uncertainty was quantified over North America using direct comparison to 20 in-situ sites within the National Environmental Observing Network in the continental United States of America and within a Canada wide field campaign over forests and shrublands conducted by Canada Centre for Remote Sensing. SL2P outputs were also compared to MODIS and Copernicus Global Land Service products over the Belmanip II regional sites and 30 additional forested regions in North America.  Results from NEON validation indicate SL2P is generally within uncertainty requirements except for forests; where it underestimates fAPAR, fCOVER and LAI.  Results for other sites will also be presented.  To address the forest bias, SL2P was recalibrated using simulations from the FLIGHT 3D radiative transfer model representative of North American forests.  The uncertainty of the recalibrated SL2P algorithm will be compared to baseline SL2P estimates to determine if increased model complexity is warranted.
Carbonate pore type quantification through digital image analysis – dual-porosity reservoir example of the Arabian Gulf.
Authors: Barata Joao , Gomes Jorge , C. Azerêdo Ana , V. Duarte Luís
Published: March 2021

The Barremian Upper Kharaib Formation reservoir unit was deposited in a carbonate ramp setting and shows moderate vertical facies variability, transitioning from a wackestone-dominated transgressive phase into a grainstone-dominated regressive phase. A dual-porosity system containing micro and macro-pores characterizes this reservoir, with microporosity as the dominant fraction of total porosity and holding large amounts of hydrocarbons in place. Porosity variations in the reservoir section shows no clear vertical trends, while permeability shows significantly higher values in the regressive phase sediments.

Digital image analysis (DIA) was done on this study using the different methods of visual estimation, colour selection based on histogram analysis and trained machine learning, with the measured area seen as a proxy for the total pore volume. A total of 285 images captured from 142 thin sections from 4 different wells were analysed. Colour selection through automated batch processing was done to quantify total macroporosity in all thin sections, using the petrographic images captured under XPL. Different RGB color codes and tolerance parameters were used in different runs on the same image, in an attempt to address the uncertainty in macroporosity measurements. Machine learning was applied using selected training images and manually classified pixel sets defining 2 classes (porous and non-porous space).

Total macroporosity is separated into interparticle and intraparticle/mouldic porosity (intrafossil porosity and probable dissolution of bioclasts/peloids/intraclasts) based on visual estimations, given that an unambiguous automated classification of these pore types is practically impossible to obtain. Microporosity is estimated to represent more than 60% of the total porosity. Considerable differences exist between the pore networks of the transgressive and regressive phase deposits, with the latter showing stronger heterogeneity and higher average interparticle macroporosity values in grainstone intervals containing coarser carbonate particles and small or no amount of interparticle micrite. These carbonate particles are, however, micritized and contain considerable volumes of microporosity within.

Pore type quantification through DIA can provide an objective, relatively quick and inexpensive methodology to provide useful insights into petrophysical relationships and to complement petrographic observations and core analysis results. Detailed depositional and stratigraphic models coupled with this quantitative data would help to better understand the depositional and diagenetic controls on rock properties variability.