bluuebunny/crossref_metadata_2025 huggingface dataset:
Measuring the thermal conductivity of sandstones
Authors: Albers Anna , Koch Fabien , Menberg Kathrin , Steger Hagen , Fliegauf Christina , Schindler Linda , Wilke Sascha , Zorn Roman , Blum Philipp
Published: March 2024

The sandstones of the Middle and Upper Buntsandstein are suitable host rocks for the installation of shallow geothermal systems due to their high thermal conductivities typically ranging between 1.9 to 4.6 W m-1 K-1 (Verein Deutscher Ingenieure 2010). Knowledge of the effective thermal conductivity is crucial to efficiently dimension borehole heat exchanger (BHE) systems. The standard method for determining effective thermal conductivities at a site is the thermal response test (TRT). However, thermal conductivity can also be analysed in the laboratory from core samples. In addition, various prediction models for the estimation of thermal conductivity based on lithological properties, such as porosity, exist. In this study, depth-specific thermal conductivities of sandstone samples of the Upper and Middle Buntsandstein are comprehensively analysed by applying different methods. First, thermal conductivities of about 140 core samples are analysed in the laboratory, and relations between material properties, such as porosity and mineralogy, and thermal conductivity are investigated. Furthermore, common prediction models are applied, and in addition, the measured and estimated thermal conductivities are compared to the effective thermal conductivities evaluated with an enhanced thermal response test (ETRT). The average effective thermal conductivity analysed with the ETRT is 4.7 W m-1 K-1, while the thermal conductivities analysed in the laboratory on saturated core samples range between 2.7 to 6.4 W m-1 K-1 with an average value of 4.6 W m-1 K-1. The best estimate from the prediction models is achieved by the Voigt-Reuss-Hill model with an average error of 13 % and a maximum error of 26 %. Overall, prediction models that assume a random distribution of solid and fluid components can achieve reliable estimates of the thermal conductivity of the sandstone. Thus, the results demonstrate that laboratory analyses can provide representative values of the effective thermal conductivities at a site with negligible or low groundwater flow. However, we also show that in order to achieve a representative value a sufficient number of samples has to be analysed, which entails high expenses for laboratory analyses.Verein Deutscher Ingeniere. VDI 4640, part 1: Thermal use of the underground, fundamentals, approvals, environmental aspects, 2010.
Strong Variability in the Thermal Structure of Tibetan Lithosphere
Authors: Xia Bing
Published: March 2024

We present a model of thermal lithospheric thickness (the depth where the geotherm reaches a temperature of 1300°C) and surface heat flow in Tibet and adjacent regions based on a new thermal-isostasy method. The method accounts for crustal density heterogeneity, is free from any assumption of a steady-state lithosphere thermal regime, and assumes that deviations from crustal Airy-type isostasy are caused by lithosphere thermal heterogeneity. We observe a highly variable lithospheric thermal structure which we interpret as representing longitudinal variations in the northern extent of the subducting Indian plate, southward subduction of the Asian plate beneath central Tibet, and possible preservation of fragmented Tethyan paleo-slabs. Cratonic-type cold and thick lithosphere (200–240 km) with a predicted surface heat flow of 40–50 mW/m2 typifies the Tarim Craton, the northwest Yangtze Craton, and most of the Lhasa Block that is likely refrigerated by underthrusting Indian lithosphere. We identify a “North Tibet anomaly” with thin (80–100 mW/m2). We interpret this anomaly as the result of removal of lithospheric mantle and asthenospheric upwelling at the junction of the Indian and Asian slabs with opposite subduction polarities. Other parts of Tibet typically have intermediate lithosphere thickness of 120–160 km and a surface heat flow of 45–60 mW/m2, with patchy anomalies in eastern Tibet. While different uplift mechanisms for Tibet predict different lithospheric thermal regimes, our results in terms of a highly variable thermal structure beneath Tibet suggest that topographic uplift is caused by an interplay of several mechanisms.
Pine pollen is an important component of the Baltic Sea
Authors: Pawlik Magdalena , Ficek Dariusz
Published: March 2024

Every year, pine pollen occurs at the water surface and cover large areas of the Baltic waters in spring. Its concentrations in the Baltic are sometimes so large that they actually form a conspicuous yellow layer on the surface. Pine pollen is a very important source of carbon and nutrients to the Baltic Sea.The objective of this work was to estimate the absolute and relative concentrations of pine pollen and to show the spatial differentiation of pollen levels in Baltic Sea waters.The measurements showed that practically the whole study area was covered with pollen. substantial pollen concentrations were recorded not only in the coastal zone but also at considerable distances from the shore. Pollen levels in Baltic surface waters, measured during the 2018 pollen season, varied from 0.5 to 14.7 µl l-1, which is 10–49.2% of the total suspension, ranging from 1.25 to 250 µm. To examine the biological role of pollen in the aquatic environment, the contents of carbon C, nitrogen N and phosphorus P were measured in pollen acquired from pine trees growing close to the Baltic shore. The levels of these elements were as follows: 47.66% C, 0.32% P and 2.50% N.This work was supported by the National Science Centre of Poland (contract No. 2017/25/N/ST10/02578 to M.M.P).
Identification of flood events in large discharge datasets - reinsurance industry perspective
Authors: Kadlec Martin
Published: March 2024

The insurance sector plays a critical role in promoting disaster resilience and recovery by providing financial protection, speeding up rebuilding and recovery, and managing the financial impact of natural disasters. To fulfill this role, insurance companies must meet the capital requirements imposed by regulators. For example, the European Solvency II regulatory framework requires insurers to hold enough capital to withstand a natural catastrophe loss with a return period of 1 in 200 years. As the historical loss data are scarce and incomplete, the insurance sector uses stochastic catastrophe models (cat models) to assess the potential cost of rare but devastating events like floods.A stochastic event set is a crucial element of cat models. It is a collection of possible disasters with their likelihood and severity. One method to generate stochastic flood events is to use numerical models of the atmosphere to generate realistic precipitation fields, and then apply rainfall-runoff models to estimate how much water will flow into rivers and streams from precipitation and snowmelt. By running many simulations with different inputs and parameters, stochastic flood models can provide a range of possible outcomes, including floods with spatial patterns and magnitude missing in historical data.Output of such simulations are spatio-temporal hazard grids: precipitation grids for pluvial risk and river discharge grids for fluvial risk. These grids are large as the models typically run over large geographies (countries or continents) and simulate 10,000 years or more. This contribution will (i) provide overview of existing methods how to identify flood events in such huge discharge and precipitation datasets (i.e. peak-over threshold method), (ii) show their limitations for identifying flood events, and finally (iii) propose a new methodology designed to address specific needs of reinsurance industry such as the hours-clause condition, which specifies the time period within which losses from a single event must occur in order to be covered.As many severe floods are composed from several sub-waves (for example 2002 floods in Czech Republic), proper event identification and separation is highly relevant topic as it influences the amount of reinsurance payouts after some types of flood events and thus capital available for rebuilding and recovery. 
Reconstructing human-fire-vegetation inter-relationships in a protected dry tropical forest, Mudumalai National Park, southern India
Authors: Ramya Bala Prabhakaran , Kumar Nithin , Behera Diptimayee , Ambili Anoop , Sukumar Raman
Published: March 2024

Tropical dry forests are recognized globally as the first frontier of human land-use change, due to multiple factors that make them amenable to human occupation, especially with the use of fire. However, in southern India, biodiversity ‘hotspots’ with human habitation are not uncommon with a long-term co-existence of humans in pristine environments. This points to the need for more accurate evidence-based (using charcoal, pollen, phytoliths) understanding of if, when and how land use and land cover changes impact regional vegetation-fire relationships. We reconstruct the environmental history for Mudumalai National Park, a fire-prone dry forest with >30% of the park subject to annual fires and a west-to-east rainfall-vegetation gradient. We examined a 150 cm sediment profile from an excavation in a seasonal wetland in the wettest part. The record spans 1200 years in time (bracketing radiocarbon dates) with very low macrocharcoal counts (mean - 4), with highest numbers in the surface and near-surface layers. Molecular fire proxies Polycyclic Aromatic Hydrocarbons (PAHs) were also found present - Phenanthrene (Phe), Anthracene (Ant), Fluoranthene (Fl), Pyrene (Py), Benzo[ghi]fluoranthene (Bghi), Benz[a]anthracene (BaA), Chrysene (Chr), Benzo(b)fluoranthene (BbF), Benzo(k)fluoranthene (BkF), Benzo[e]pyrene (BeP), Benzo[a]pyrene (BaP), and Perylene (Pry). Notably, Fl, Py, Bghi, BbF, BaA,and BeP constituted 90% of the total concentrations. Diagnostic ratios of PAHs for source determination pointed at a pyrogenic source consistently across all samples. Paleovegetation proxies n-alkanes (C14-C33) were analyzed and the average chain length (ACL) showed a transition towards higher chain lengths towards the surface indicating a change towards grass sources (C31, C33) in addition to woody biomass-derived compounds (C27, C29). Further analysis to characterize the human-fire-vegetation relationships is underway and to our knowledge, as the first report from a protected forest in India, our study offers critical insights for forest fire management in forested landscapes.
Towards understanding greenhouse gas production from terrestrial gamma-ray flashes
Authors: Defranchi Bisso Federica , Fangel-Lloyd Elloise , Gammelmark Mathias , Karlsson Sven , Dujko Sasa , Koehn Christoph
Published: March 2024

Lightning creates bursts of X- and gamma-ray flashes called Terrestrial Gamma-ray Flashes (TGFs), with single photon energies of up to 40 MeV. When released into the atmosphere, these energetic photons interact with air molecules through dissociation, ionization, excitation, Compton scattering, and pair production, chemically activating Earth's atmosphere. The activated molecules will then recombine in accordance with the principle of minimal Gibbs free energy and maximal entropy to reach an equilibrium state. Our objective is to identify and quantify the impact of this process on the production of greenhouse gases.
We present a Monte Carlo particle model that can simulate the motion and interaction of electrons and photons with energies ranging from 0.1 eV to 100 MeV. When tracing electrons and photons through the atmosphere, we keep track of dissociated, excited, and ionized air constituents. We will present the rate coefficients of these processes and the spatial distribution of the activated molecules. This will lay the further basis for understanding the chemical processes leading to the production of greenhouse gases.
Exploring disaster impacts on livelihoods in the Ganga Brahmaputra Meghna Delta communities in India
Authors: Baskota Ayush , Pal Indrajit , Mukhopadhyay Anirban
Published: March 2024

The Ganga Brahmaputra Meghna (GBM) delta, situated in India and Bangladesh, represents a densely populated and precarious area. Over 200 million residents face significant environmental threats, such as tropical cyclones, land subsidence, riverine flooding, coastal inundation, rising sea levels and storm surges, particularly affecting socio-economically marginalized communities with vulnerable livelihoods.This paper investigates disaster impacts on local livelihoods in the GBM delta communities in West Bengal, India through a comprehensive household survey of 1236 respondents across Sandeshkali, Sagar, Hingalgunj, and Gosaba community blocks. The survey revealed a diverse distribution of hazard severity across the region; residents in Sagar and Hingalgunj blocks were primarily impacted by cyclones whereas Gosaba and Sandeshkali blocks were also impacted by flooding, inundation and land erosion. Furthermore, disasters have tremendous impact on the local economy, with respondents reporting a 50% decrease in income from their primary livelihood in the aftermath of a disaster. These impacts were found to be more profound in Sagar and Gosaba blocks, where people were more reliant on agriculture and farming, as compared to Sandeshkali where families were involved in diverse livelihoods. A significant proportion of disaster damages were attributed to salt-water intrusion in agricultural land and aquacultural ponds, followed by damages to critical infrastructure such as roads and power network and health-related issues in the aftermath of cyclonic events. The findings of this study demonstrate the diverse socio-economic scenario in the GBM delta, highlighting the importance of block and community specific risk management and livelihood strengthening programs.
Quantitative detection device for NOx of centimeters-discharge and its preliminary applications in laboratory long spark and rocket-triggered lightning
Authors: Jiang Rubin , Ren Yufan , Chen Ruiling , Zhang Hongbo , Liu Mingyuan , Xia Xinran , Wu Jianwen , Wang Dongfang , Liu Kun , Qie Xiushu
Published: March 2024

A quantitative detection device for nitrogen oxides (NOx) produced by the centimeters-scale discharge channel is designed, consisting of a container made of high-strength acrylic Plexiglas, two copper metal electrodes fixed to the top and bottom of the container, a pumping system and a back-end NOx detector. Inside the container, the gap between the two copper electrodes is 4 cm in length. When a discharge occurs between the electrodes, the NOx produced by the air ionization are confined within the container to provide a quantitative measurement. The device can be used in the laboratory long spark and rocket-triggered lightning scenarios, with container volumes of 12.2 L and 58.8 L, respectively, both of which ensure an accurate measurement of the discharge current. In the laboratory long spark scenario, the device is placed under the discharge electrode of the Marx generator. As the discharge is generated, the discharge strikes the upper copper metal electrode and leads to the gap breakdown within the container, then the current is released through the bottom copper metal electrode to the ground. In the rocket-triggered lightning scenario, the device is fixed between the current sensor and the grounding system. The triggered discharge leads to the gap breakdown within the container, and the current is also released through the bottom copper metal electrode to the ground. After the discharge, the gas in the canister is pumped to the NOx concentration meter. The instruments used are the Thermo, which uses a chemical method to measure NO and NOx concentrations with a time resolution of 1 minute, and the LGR-NO2, which uses an optical method to measure NO2 concentrations with a time resolution of 1 second. The preliminary experiment shows that the 4 cm long discharge due to the laboratory long spark with a peak current of about 2 kA produced 6.8×1017 NO2 molecules. In an unsuccessful triggering lightning case, the discharges due to the precursors also lead to significant NOx signals.
Recent progress on the role of chlorine radical in urban atmosphere
Authors: Tham Yee Jun , Yan Chao , Zou Shichun
Published: March 2024

Atmospheric chlorine radical plays essential roles in tropospheric photochemical processes, such as affecting the oxidation capacity and aerosol formation. Tropospheric chlorine chemistry was initially known to be important in the marine and polar atmosphere; nevertheless, more and more recent studies have indicated that chlorine chemistry was also active in inland areas. Here, we will present the vital chlorine radical precursors, such as nitryl chloride (ClNO2), molecular chlorine (Cl2), hydrochloric acid (HCl) and others that were observed in the urban atmosphere of China, as well as the recent understanding on the influence from anthropogenic chlorine sources. Our recent findings have shown the increasing importance of nocturnal chlorine activation processes in producing ClNO2 and Cl2, which ultimately contributing to the haze formation caused by NOx reduction. Another finding also showed that there is a potential atmospheric chlorine sink process in environment with low temperature and significant bromine chemistry. We will finally discuss the future challenges in the understanding of reactive chlorine chemistry in urban cities under the changing world.
Prediction of As behavior in a vadose zone using an empirical relationship between As retardation factor and the soil properties
Authors: Kim Sang Hyun , Tran Tho Huynh Huu , Chung Jaeshik , Lee Seunghak
Published: March 2024

Arsenic (As) pollution in soil from various anthropogenic sources potentially threatens groundwater by migrating downward through a vadose zone. As goes through complex biogeochemical reactions such as sorption, desorption, and/or redox transformation, which affects its retention in this zone. A retardation factor is a critical solute-transport parameter to quantitatively assess the retention of As in this zone, and eventually to predict the potential risk of groundwater contamination. Despite its importance, however, there is still limited information to quantify the retardation factor in a vadose zone, compared to in the saturated condition. This study aimed to assess the retardation factor of As using twenty-two unsaturated soil columns coupled with the non-equilibrium solute-transport modeling. We employed a multiple linear regression approach to develop a prediction model for the retardation factor based on the soil properties. Soil columns with 3-cm inner diameter and 45-cm height were packed with six different field soils at various bulk densities. Distilled water was infiltrated into each column at a constant flowrate, until a steady-state unsaturated condition was achieved. The distilled water was replaced with a solution containing As and a conservative tracer (chloride, Cl), to obtain their breakthrough curves. The retardation factor of As was determined by inversely fitting the breakthrough data of As and Cl with Mobile-Immobile model integrated in HYDRUS 1-D software. The derived retardation factors of As in the mobile and immobile zones ranged 1.58–6.93 and 1.44–25.48, respectively. These showed high degree of dependence on soil properties. In the mobile water zone, iron content and organic matter content emerged as the two most influential properties affecting As transport, impeding As mobility. Conversely, in the immobile water zone, coefficient of uniformity and bulk density were identified as the most influential factors, enhancing As retention. Based on the results, empirical equations were derived to predict the retardation factors of As in a vadose zone based on the aforementioned soil properties.
Joint inversion of potential field data to unmask sub-ice geology, from a case study in Scandinavia to application in NE Greenland
Authors: Wansing Agnes Dakota , Ebbing Jörg , Moorkamp Max , Heincke Björn
Published: March 2024

The surface geology of Greenland is only known along the ice-free coast. The remaining 80% of Earth's largest island are covered by ice that masks the surface geology and makes direct observation nearly impossible. Interpolation of the known coastal geology over the inland ice, combined with expert knowledge, can provide a first, but not well-constrained picture. In contrast, the surface geology in Scandinavia is well-studied. The formerly adjacent northeastern part of Greenland belongs to the same Caledonian orogeny and is expected to be somewhat similar to Scandinavia. Therefore, we use Scandinavia as a case study to set up a workflow of joint inversion of potential field data to find physical relations for the known geological structure and apply this workflow to NE Greenland.Results from individual inversion of potential field data are non-unique and have limited depth resolution. Combining gravity and magnetic data in a joint inversion can minimise the non-uniqueness and improve the depth resolution. The coupling furthermore creates comparable anomaly patterns for both inverted parameters. As coupling method, a variation of information (VI) constraint is used in the inversion. The VI creates representative parameter relationships where different branches reflect the numerous combinations of density and susceptibility for various rock types. Thus, the inverted parameter relationship can be used to map the surface geology.Crucial parts in the workflow setup are how deeper sources are handled for the gravity data and at which resolution and height the magnetic data are required.  The simultaneous analysis of the well-studied surface geology in Scandinavia helps to verify the analysis, providing higher confidence in the resulting sub-ice geology for NE Greenland.
Drought Changes Growing Season Length and Vegetation Productivity
Authors: Gray Josh , Choi Eunhye , Friedl Mark , Griffiths Patrick
Published: March 2024

Meteorological droughts are increasing in intensity, frequency, and duration due to climate change. These events may have substantial impacts on vegetation productivity that influence the global carbon balance. Effects vary considerably, however, with the intensity of the drought as well as local abiotic and biotic conditions such as vegetation type, soil type, and the timing of the drought. Productivity is primarily reduced because droughts decrease the efficiency with which plants can convert atmospheric CO2 into carbohydrates, largely because of stomatal closure when energy is not limiting. However, another aspect by which droughts can reduce productivity is by shortening the growing season length (GSL). GSL reduction may be particularly pronounced in vegetation communities already sensitive to precipitation variability, in particular, short-rooted grassland and croplands ecosystems. Here, we use evidence from satellite observations of ecosystem activity, meteorological measurements, and data from eddy-covariance flux towers to reveal the impact of several large-scale meteorological droughts on vegetation productivity on natural and managed ecosystems. In particular, we show that the timing of the drought is important, with late droughts being particularly diminishing to productivity. We also demonstrate that while plant physiological responses to drought dominate the reduction in productivity, the diminishment of GSL plays an underappreciated role. These results have wide implications for the future carbon balance under a changing climate, and suggests that ecosystem models could better explain productivity by incorporating the effects of droughts on GSL.
Global coastal ocean CO2 trends over the 1982–2020 period
Authors: Roobaert Alizee , Regnier Pierre , Landschützer Peter , Laruelle Goulven G.
Published: March 2024

The development of high-quality controlled databases of sea surface partial pressure of CO2 (pCO2) combined with robust machine learning-based mapping methods that fill pCO2 gaps in time and space, enable us to quantify the oceanic air-sea CO2 exchange and its spatiotemporal variability only based on in-situ observations (pCO2-products). However, most existing pCO2-products do not explicitly include the coastal ocean or have a spatial resolution that is too coarse (e.g., 1°) to capture the highly heterogeneous spatiotemporal dynamics of pCO2 in these regions thus limiting our ability to resolve long-term trends and the interannual variability of the coastal air-sea CO2 exchange (FCO2).To address this limitation, we updated the global coastal pCO2-product of Laruelle et al. (2017) using a 2-step machine learning interpolation technique (relying on Self Organizing Maps and a Feed Forward neural Network) combined with the most extensive monthly time series for coastal waters from the Surface Ocean CO2 Atlas (SOCAT), spanning from 1982 to 2020 to reconstruct monthly high spatial resolution (0.25°) continuous coastal pCO2 maps. This updated coastal pCO2-product is then used to reconstruct the temporal evolution of the global coastal FCO2 based on observations.Our results show that since 1982, the extended coastal ocean, covering an area of 77 million km² in this study, has been acting as an atmospheric CO2 sink, removing -0.4 Pg C yr-1 (-0.2 Pg C yr-1 with a narrower coastal domain roughly equivalent to continental shelves) from the atmosphere. Moreover, the intensity of this CO2 sink has been increasing over time at a rate of 0.1 Pg C yr-1 per decade (0.03 Pg C yr-1 decade-1 in the narrower domain). The long-term change in the air-sea CO2 flux is largely driven by the air-sea pCO2 gradient, dominated by the sea surface pCO2, however wind speed and sea-ice coverage play significant roles, regionally. This new coastal pCO2-product provides a valuable constraint for understanding the strengthening of the global coastal ocean CO2 sink, fill the coastal gap in synthesis studies such as the Global Carbon Budget and serves as a benchmark for evaluating emerging results of ocean biogeochemical models.
Dynamics of the tongue of ionizations at different altitudes during the geomagnetic storm on September 7, 2015
Authors: song huimin
Published: March 2024

Using the electron density (Ne) observations from the Defense Meteorological Satellite Program (DMSP), and Constellation Observing Systems for Meteorology, Ionosphere, and Climate mission (COSMIC) and simulations from the Thermosphere Ionosphere Electrodynamic General Circulation Model (TIEGCM), we investigate the dynamic evolution of the polar tongue of ionization (TOI) from double to single structures at different altitudes during a geomagnetic storm. The modeled Ne depicted that double and single TOIs occurred at altitudes above 300 km, respectively. During the northward turning of IMF Bz, the afternoon TOI disappeared and the morning TOI was reduced. The plasma transport due to neutral winds and ambipolar diffusion facilitated (prevented) the depletion of plasma density of the morning TOI at 300 (500) km, with a relative contribution of 42.8% and 28.6% (-15.4% and -76.9%), respectively. Downward E × B drifts led to an enhancement/reduction of plasma density in the SED region in the lower/upper ionosphere. During the duskward turning of IMF By, the morning TOI could be mostly attributed to the anti-sunward plasma drifts (75.8% at 300 km, 100% at 500 km), with a relatively stronger role of the zonal component than that of meridional E × B drifts. The upward E × B drifts were important/ignorable in the upper/lower ionosphere. Both the neutral winds and ambipolar diffusion resulted in an accumulation of plasma density of the morning TOI at 300 km indirectly (24.2%), however, their roles were minor at 500 km.
Global full-waveform inversion reveals previously undetected positive wave speed anomalies beneath the Pacific Ocean
Authors: Schouten Thomas , Gebraad Lars , Noe Sebastian , Gülcher Anna , Thrastarson Sölvi , van Herwaarden Dirk-Philip , Fichtner Andreas
Published: March 2024

Seismic tomography, a critical tool for studying Earth's interior structure and dynamics, has revealed positive seismic wave speed anomalies in the mantle that are commonly interpreted as slabs, the remnants of subducted lithosphere. However, classical travel-time tomography relies on the inversion of travel times of a few easily identifiable body wave phases along ray paths or volumetric sensitivity kernels, which is strongly dependent on the geometry of seismic sources and receivers. Since both of these are primarily clustered on modern convergent plate boundaries, the resulting tomographic resolution is highly variable across the mantle. Full-waveform inversion (FWI) attempts to reduce this dependence by fitting whole seismograms, thereby including many reflected and refracted body wave phases to enhance the volumetric sensitivity of the inversion.Here, we analyse a new global tomographic model constructed using FWI. The mantle structure imaged in this model reveals significantly more positive seismic wave speed anomalies in the mantle when compared to travel-time tomography, particularly in regions with low seismic activity and limited station coverage. Notably, FWI detects positive wave speed anomalies with slab-like morphologies at ~1000 km depth beneath the Pacific Ocean that fall outside the coverage of classical travel-time tomography. We demonstrate the sensitivity of FWI to wave speed anomalies below the western Pacific using forward wavefield modelling. Importantly, we find that these newly imaged positive wave speed anomalies do not correspond to reconstructed subduction zones in existing global plate reconstructions.Our work challenges the widespread assumption that positive wave speed anomalies (exclusively) represent subducted slabs, highlighting potential gaps in either global plate reconstructions or the current understanding of the nature of seismic anomalies in the mantle.
Investigating the Permeability Evolution of Artificial Rock During Ductile and Brittle Deformation Under Pressurized Flow
Authors: Edery Yaniv , Sulieman Shaimaa , Stolar Martin , Abezgauz Ludmila , Tian Shouceng
Published: March 2024

The drilling of geothermal energy, CO2 sequestration, and wastewater injection all involve the pressurized flow of fluids through porous rock, which can cause deformation and fracture of the material. Despite the widespread use of these industrial methods, there is a lack of experimental data on the connection between the pore pressure rise, the deformation and permeability changes in real rock. In order to address this gap in the literature, this study developed an artificial rock material that can be deformed and fractured at low pressures. By controlling the porosity, permeability, and strength of the material during the sintering process, it is possible to mimic various types of rock. The artificial rock was designed to accommodate radial flow and deformation, allowing for the tracking of deformation by monitoring the flux and driving pressure and thus calculating the permeability changes under various pressure conditions. The study was able to examine the impact of both ductile and brittle deformation on the permeability during pressurized flow, which were captured by two models that were adjusted to this scenario. This study provides a link between pressurized flow, rock formation permeability and ductile to brittle deformation, that can constrain risk assessment to geothermal energy and CO2 sequestration.
Ray and Halo impact craters on Ganymede: Insights into the stratification of icy crust
Authors: Baby Namitha Rose , Kenkmann Thomas , Stephan Katrin , Wagner Roland , Hauber Ernst
Published: March 2024

Ganymede, the solar system's largest moon, is captivating due to its complex geology and potential habitability. ESA's JUICE mission now focuses on exploring Ganymede [1, 2]. We investigate ray and halo impact craters on its surface, which display diverse morphologies and ejecta materials [3], including bright icy and dark non-icy materials [4,5] located at various locations on Ganymede. To better understand the vertical stratification of Ganymede's icy crust and its implications for tectonic processes like rifting or spreading, we use the knowledge of impact cratering processes [6, 7], particularly the excavation flow field of hypervelocity impacts. We utilize a global mosaic created by [8], which combines high-resolution images from the Voyager 1, Voyager 2, Galileo, and Juno spacecraft. Additionally, we incorporate NIMS-derived data on the varying abundance of water ice and dark non-ice material, as well as water ice grain sizes, as presented in [9] wherever available.
We included 36 craters in our study. Excavation depths provide clues into the vertical stratigraphy at these locations. Our findings reveal that dark ray and dark halo craters, characterized by dark ejecta, are generally small, with excavation depths not exceeding 3 km. Craters with a final diameter larger than 75 km exhibit bright rays, as exemplified by Melkart and Enkidu craters. Craters displaying both dark and bright ejecta, like Tammuz (diameter ~51 km), likely impacted at the boundary between light and dark terrains.
Dark ray craters, such as Antum and Mir, suggest that the dark terrain at Marius Regio is relatively thin, not exceeding 1.2 km. On the other hand, dark halo craters like Nergal and Khensu on light terrain indicate that the excavated dark material originates from depths of ~ 1.36 km, suggesting heterogeneity in the crust there and the presence of subsurface dark material. Dark ray craters in light terrain, like Kittu, indicate that the dark terrain material originates from a depth of around 1.2 km. These findings support the possibility of rifting as a contributing factor to light terrain formation. Additionally, the presence of a very thin uppermost ice layer atop a dark material in the light terrain suggests the potential for flooding of older dark terrain by an icy substrate, contributing to Ganymede's light terrain formation.
REFERENCES: [1] Grasset et al. (2013), PSS, v. 78, p. 1-21. [2] Stephan et al. (2021), v. 208, p. 105324. [3] Schenk et al., (2004), Cambridge University Press, p. 427 - 456. [4] Hibbitts (2023), Icarus, v. 394, p. 115400. [5] Schenk and McKinnon (1991), Space Science Reviews, v. 60, no. 1, p. 413-455. [6] Kenkmann  et al (2014), Journal of Structural Geology, v. 62, p. 156-182. [7] Melosh (1989), Oxford University Press. [8] Kersten et al. (2022), pp. EPSC2022-450. [9] Stephan et al. (2020), Icarus, v. 337, p. 113440.  
Offline-Coupling of the Lagrangian Particle Dispersion Model FLEXPART to ICON
Authors: Henne Stephan , Kaufmann Pirmin , Emmenegger Lukas , Brunner Dominik
Published: March 2024

Over the last years, the numerical weather prediction (NWP) and climate model ICON has become the operational forecasting tool for several national weather services and research groups. Operational analysis or re-analysis fields from NWP models are often used as input for offline-coupled atmospheric chemistry and transport models. Among the latter, Lagrangian Particle Dispersion Models (LPDMs) allow computationally efficient simulations, especially for point sources such as hazardous releases and for receptor-oriented studies such as determining the sensitivity of a concentration observation to upstream surface fluxes (i.e., estimating concentration footprints). One frequently used LPDM is the FLEXible PARTticle (FLEXPART) model, which is available for inputs from different global and regional NWPs (e.g., ECMWF-IFS, WRF, COSMO). Although these versions differ in the applied horizontal and vertical coordinate systems, they have in common that they interpolate gridded NWP output from a rectangular grid to particle positions. In contrast, ICON solves its state variables on a triangular grid. To make best use of ICON output, a direct interpolation from its native grid to particle positions is required. However, compared to a rectangular grid, where interpolation can be done in a straightforward fashion applying bi-linear or bi-cubic interpolation, interpolation from a triangular grid requires additional considerations concerning the choice of interpolation stencil and weight calculations.Starting from FLEXPART for COSMO, which shares the same vertical grid system with ICON, we revised and generalized how FLEXPART interpolates from grid input to particle positions. Four different direct interpolation methods were implemented: next neighbor (containing triangle), inverse distance weight, barycentric interpolation, and radial basis function interpolation. The resulting FLEXPART version is runs efficiently with outputs from both COSMO and ICON. Next to the direct implementation, we also evaluated an indirect coupling in which ICON output is first interpolated onto a COSMO-like, staggered grid and then used as input for FLEXPART-COSMO.Both direct and indirect FLEXPART-ICON approaches were thoroughly evaluated by comparison of individual plume simulations resulting from point sources. As a reference simulation, the same point sources were simulated with the Aerosols and Reactive Trace gases (ART) extension of the ICON model. We discuss differences in the performance between the direct and indirect approach and between the interpolation methods. Computational costs for the different approaches are evaluated and trade-offs between model performance and computational efficiency are discussed. 
Numerical Modeling of Fluid Flow through a Borehole-Porous Medium System: Comparison between Brinkman and Darcy Equations
Authors: Regur Joseph , Liu Jiaqi , Tokunaga Tomochika
Published: March 2024

Subsurface petroleum storage in excavated caverns sealed using a hydraulic containment system offers many advantages over traditional surface storage tanks. The challenge of accurately simulating a complex subsurface system includes accounting for the viscous shear forces within free-flow regions such as the boreholes, fractures, voids, and storage tanks. The Brinkman extended Darcy’s equation is one solution which accounts for viscous shear forces along the free-flow boundaries and momentum transfer across the porous media interface.This study aims to demonstrate the significance of fluid viscosity forces in the subsurface flow regime, and show the suitability of the Brinkman equation by using numerical modeling in COMSOL to create lab-scale simulations of a borehole coupled with porous media. It analyzes and compares the simulated velocity gradients and head gradients, calculated using the Brinkman equation and the classic Darcy equation. This study shows simulation cases at various inlet pressures, inlet velocities, porosities, and permeabilities, such as those used for subsurface storage to evaluate the influence of these parameters.The preliminary results show that the Brinkman equation predicts a non-uniform velocity profile within the borehole due to friction along the borehole interface. The two equations also predict  different velocity distributions across the borehole interface and in the porous media near the borehole. These differences are more significant at higher inlet velocities/pressures. These models could be validated by laboratory experiments, enhanced to include fractures, and enlarged to field scales. This study will have implications for numerous injection and well production activities, such as subsurface energy storage, hydraulic fracturing, and contaminant transport studies.
Studies of recent seismo-volcanic activity in the Gegham volcanic ridge (Armenia) 
Authors: Sargsyan Lilit , Sahakyan Elya , Demirchyan Hovnatan , Navasardyan Gevorg , Gevorgyan Mikayel , Meliksetian Khachatur
Published: March 2024

Armenia, SE Turkey and NW Iran are located in the central part of the Arabian lithosphere collision zone, a region, which experiences N–S shortening and E–W extension accompanied by intense faulting, strong earthquakes and active volcanism. The Gegham volcanic ridge (GVR) is located in the center part of the Neogene-Quaternary volcanic belt formed within the territory of the Armenian Highland. The duration of volcanism within the Gegham Ridge spans from the Late Miocene to the Holocene. The GVR in central Armenia represents one of the densest clusters of individual monogenetic volcanoes in the world.The study area of the Gegham Volcanic Ridge is located between the system of the Gegham Ridge Fault (GF1) and the Gavaraghet Fault (GF2).The faults in the axial part of the Gegham ridge (GF1) represent structures of fracturing related to eruptions of numerous Quaternary volcanoes. The Gavaraghet Fault (GF2) related to a few historical and recent earthquakes is the most active one in the Gegham Fault system.During the period of 2014-2018, earthquake swarms were recorded in the area of the Gegham Volcanic Ridge. Further studies of the relationship between tectonic and volcanic processes will contribute to the assessment of the volcanic hazard for this area. Beyond its importance for natural hazard assessment, the volcanically young Gegham Ridge also holds great potential as a source of geothermal energy.Seismic activity in the study area was recorded using data from the advanced and dense seismic network installed recently. This network equipped by full-broad band (permanent and temporary) stations has been developed since 2012 and covers both the study region and adjacent areas.Seismic activity of this area is manifested in the form of small-size earthquakes. Earthquake epicenters tend to concentrate in volcanic vents, as well as near active faults areas. The depths of earthquakes are up to 25 km.In this study, source mechanisms of earthquakes were investigated using digital waveform data recorded by seismic stations of the Armenian seismic networks (included the 3 temporary seismic stations). The focal mechanisms of a set of earthquakes that occurred within 2022-2023 were constructed with high reliability, based on the polarity of the first motion of the P-wave.All data were relocated using local and regional seismic network data with the aim to reduce main parameter uncertainties in the catalogue, used in the current study. 
Sensitivity analysis of input variables of a SWAT hydrological model using the machine learning technique of random forest
Authors: Abousaeidi Ali , Moezzi Seyed Mohammad Mahdi , Khorashadi Zadeh Farkhondeh , Sheikholeslami Seyed Razi , Nkwasa Albert , van Griensven Ann
Published: March 2024

Sensitivity analysis of complex models, with a large number of input variables and parameters, is time-consuming and inefficient, using traditional approaches. Considering the capability of computing importance indices, the machine learning technique of the Random Forest (RF) is introduced as an alternative to conventional methods of sensitivity analysis. One of the advantages of using the RF model is the reduction of computational costs for sensitivity analysis.The objective of this research is to analyze the importance of the input variables of a semi-distributed and physically-based hydrological model, namely SWAT (soil and water assessment tool) using the RF model. To this end, an RF-based model is first trained using SWAT input variables (such as, precipitation and temperature) and SWAT output variables (like streamflow and sediment load). Then, using the importance index of the RF model, the ranking of input variables, in terms of their impact on the accuracy of the model results, is determined. Additionally, the results of the sensitivity analysis are examined graphically. To validate the ranking results of the RF-based approach, the parameter ranking results of the Sobol G function, using the RF-based approach and the sensitivity analysis method of Sobol’ are compared. The ranking of the model input variables plays a significant role in the development of models and prioritizing efforts to reduce model errors.Key words: Sensitivity analysis, model input variables, Machine learning technique, Random forest, SWAT model.
Phase relation modelling associated with metasomatic processes in open systems: application to an example of Mg-metasomatism from the Neves area, Tauern window, Eastern Alps.
Authors: Amiot Manon , Goncalves Philippe , Choulet Flavien
Published: March 2024

Fluid flow within the continental crust, and the concomitant fluid-rock interactions, are likely responsible for mass transfer and significant change in bulk rock chemistry (i.e. metasomatism). Strain localization and formation of ore deposits are very commonly associated to metasomatism. Metasomatic processes are studied combining petrology, geochemistry, fluid inclusion analysis and/or thermodynamic modelling (P-T-X). To model and quantify the mass and fluid flux integrated with time, the driving forces and controlling factor, such as fluid chemistry (solubility, speciation, chlorinity …), P-T conditions and phase relations, the degree of disequilibrium between the fluid and the host-rock must be clearly identified.This study focuses on phase relations modelling during metasomatic processes based on the mineralogical and chemical characterisation of metasomatic rocks from the Tauern Window. Samples are amphibole- and chlorite-bearing micaschists resulting from the transformation of a granodiorite under amphibolite conditions (550-570°C and 0.5-0.6 GPa). The studied outcrop is similar to some extent to Mg-metasomatic rocks reported in several localities in the Alps, including Dora Maira, Gran Paradiso or Monte Rosa and summarised in Ferrando (2012). Although all the localities reported in Ferrando (2012) and the Tauern window have their own characteristics (eg. different P-T conditions, fluid chemistry, mineralogy, age...), they also share similar features. For instance, the gain in Mg with respect to the protolith is systematically coupled with a gain in fluid, and a loss of Ca, Na and sometimes Si. This shared feature suggests that a unique and simple process must be involved in all these localities.Thermodynamic models are developed using chemical potentials of perfectly mobile components of the system as variable (µi), following the definition of Korzhinskii (1959). It means that the chemical potential of the mobile component (MgO, CaO, Na2O, SiO2, H2O) is controlled by the environment, which we consider here as an externally-derived fluid. The computed projections and pseudo-sections show that the reequilibration of the granodiorite with the externally-derived fluid (high µMgO and low µCaO, µNa2O, µSiO2) induce a series of metasomatic reactions leading to the breakdown of the granodiorite assemblage into amphibole, then muscovite-chlorite and eventually talc. From these models, it is possible to quantify the amount of mass lost and gained along the defined reequilibration path and eventually estimated the required fluid flux.