bluuebunny/crossref_metadata_2025 huggingface dataset:
Unraveling Gravity Wave Coupling from Surface to Stratosphere above La Réunion's Maïdo Observatory (21°S, 55.5°E) from Doppler and Rayleigh lidar observations
Authors: Trémoulu Samuel , Chane Ming Fabrice , Khaykin Sergey , Ratynski Mathieu , Hauchecorne Alain , Keckhut Philippe , Bellisario Christophe
Published: March 2024

The study investigates the vertical wave coupling from the Earth's surface to the middle atmosphere over the Maïdo Observatory at La Réunion (21°S, 55.5°E). Wind velocity and temperature profiles from the ground-based instruments, including the LiWind Doppler Rayleigh-Mie and Li1200 Rayleigh Lidars, in conjunction with other observations (radiosoundings, COSMIC-2 radio-occultation, SABER) and ERA5 reanalysis, are analyzed to characterize gravity waves (GW) and their vertical propagation during the period from November 20th to November 24th, 2023. Notably, a tropospheric subtropical westerly jet manifested above La Réunion during this period and jet instabilities contributed to enhance GW activity in the troposphere. Wavelet methods are employed for denoising purposes and for highlighting multiscale GW from raw wind and temperature profiles. In particular, our analysis reveals the existence of a GW with a 5-km vertical wavelength and approximately a 24-hour period, propagating upward from lower troposphere to the middle atmosphere above La Réunion’s Maïdo Observatory. Among others, the horizontal distribution of this structure surrounding La Réunion is examined using COSMIC-2 radio-occultation and SABER data. In addition, the ERA5 analysis also provides supporting evidence of such structures and GW filtering in the stratosphere.
Effect of combustion conditions on aerosol particle emissions from savanna and grassland fires
Authors: Vakkari Ville , Buchholz Angela , Hao Liqing , Ihalainen Mika , Jaars Kerneels , Köster Kajar , Le Viet , Miettinen Pasi , Mukherjee Arya , Peltokorpi Saara , Pullinen Iida , Siebert Stefan J. , Sippula Olli , Somero Markus , Vettikkat Lejish , Virtanen Annele , Yli-Pirilä Pasi , Ylisirniö Arttu , van Zyl Pieter G.
Published: March 2024

Fire is an integral part of savanna and grassland biomes and globally approximately half of landscape fire emissions originate from savannas and grasslands. Emissions of trace gases and aerosol particles from landscape fires are characterised by emission factors (EFs), which denote the amount of emitted substance per mass of combusted biomass. EFs vary depending on both the biomass that is consumed in the fire and the combustion characteristics of the fire, i.e. the ratio of flaming to smouldering combustion. However, emission inventories tend to use only one average EF for each biome.Here, we use a set of 27 laboratory experiments to characterise the effect of combustion characteristics on submicron aerosol EFs from savanna and grassland biomass acquired from South Africa as well as boreal forest floor samples from Finland. Combustion experiments were carried out at the ILMARI facility in Kuopio, Finland from May to June 2022 under an open stack mimicking natural burning and dilution. Sample was injected into a 29 m3 environmental chamber for ageing studies. Chemical and physical properties of both fresh and aged smoke were observed with a host of instruments including e.g. AMS, FIGAERO-CIMS, VOCUS, SP2 and SMPS. The ratio of flaming to smouldering combustion was characterised by modified combustion efficiency (MCE), i.e. CO2/(CO2+CO).The increase of organic aerosol EF with increasing smouldering fraction (i.e. decreasing MCE) was very similar for both the grassland and savanna combustion experiments. Surprisingly, also the boreal forest floor EFs closely follow the same trend, where smouldering-dominated combustion EFs are more than 10 times higher than EFs for flaming combustion. We observed also that the submicron aerosol particle size distribution shifts towards larger sized particles with increasing smouldering fraction. Furthermore, both the number and the mass of the size distribution cannot be fully characterised with a single log-normal size distribution, which needs to be considered when converting mass emissions into number size distribution in simulations.
Seasonal variation of Ca and Ca-bearing molecules in Mercury's exosphere as a product of micro-meteoroids and comet stream particles impact
Authors: Moroni Martina , MIlillo Anna , Mura Alessandro , Plainaki Christina , Mangano Valeria , Aronica Alessandro , Berezhnoy Alexey , De Angelis Elisabetta , Del Moro Dario , Di Bartolomeo Pier Paolo , Kazakov Adrian , Massetti Stefano , Orsini Stefano , Rispoli Rosanna , Sordini Roberto , Stumpo Mirko
Published: March 2024

The NASA/MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission provided measurements of Mercury’s Ca exosphere, allowing the study of its configuration and its seasonal variations. The observed Ca column densities exhibit a scale height consistent with a temperature > 50,000 K, and with a source located mainly on the dawn-side of the planet. It was suggested that the originating process is due to MMIV (Micro-Meteoroids Impact Vaporization), but previous estimations were not able to justify the observed intensity and energy. The most likely origin of this exospheric element is very probably a combination of different processes involving the release of atomic and molecular surface particles. We use an exospheric Monte Carlo model (Mura et al., 2007) to simulate the 3-D spatial distribution of the Ca-bearing molecule and atomic Ca in the exosphere of Mercury generated by the MMIV process. We investigate the possible pathways to produce the observed Ca exosphere and we discuss about the generating mechanism. Following previous studies, we consider that the atomic Ca in Mercury’s exosphere may be produced in a sequence of different processes: the exospheric energetic Ca component derives from the shock-induced non-equilibrium dissociative ionization and neutralization of Ca+ during the vapor cloud expansion, while a low energy Ca component is generated later by the photo-dissociation of the CaO molecules released by micro-meteoroid impact vaporization. Since the exact temperature, the photolysis lifetimes of the produced molecules and the excess energy during photolysis processes are still not well constrained by observations, we investigate different model assumptions. The theoretical calculations better agree with observations at shorter photolysis lifetimes and higher excess energy of Ca atoms obtained during photolysis of Ca-bearing species. In that case we show the presence of two Ca components: energetic Ca component more intense at high altitudes, and a low energy component in the post-dawn region at low altitudes. The total Ca content obtained through a best fit to the observations shows excess emission near TAA ∼ 25° and TAA ∼150°, which was attributed to the vaporization of surface material induced by the impact of a meteor stream. We investigate the possible contribution due to the comet 2P/Encke for explaining the excess Ca emission at specific orbit positions; the simulation results show some discrepancy when compared to the observations.
Snowfall variability, trends and their altitudinal dependence in the European Alps from ERA5, HISTALP and in-situ observations
Authors: Terzago Silvia , Gatti Ludovica Martina , Arnone Enrico , Matiu Michael Christian
Published: March 2024

Mountain precipitation is a key feature of the hydrological cycle since it feeds snowpack, glaciers, river runoff and supports ecosystems and human life both locally and downstream. However, available precipitation datasets are affected by large uncertainties in mountain regions, especially during the cold season when most of the precipitation falls as snow: on one hand, commonly used precipitation gauges can have systematic losses up to 80-100% in case of snow precipitation, mainly owing to wind undercatch; on the other hand, reanalysis datasets generally provide much larger precipitation amounts when compared to observations and observation-based datasets. So, an accurate quantification of the snowfall component is crucially needed to reduce the uncertainty on mountain total precipitation in the cold season.    In this work we present an extensive analysis of snowfall precipitation over the Greater Alpine Region (GAR) considering snowfall data from different data sources, including long-term in-situ observations, reanalysis and gridded datasets. We analyze: i) the most comprehensive observational dataset of monthly fresh snow depth (commonly employed as a measure of snowfall precipitation), consisting of more than 2000 in-situ station time series, covering 6 alpine countries (Switzerland, Austria, Germany, Slovenia, Italy and France); ii) the snowfall dataset provided by the ECMWF ERA5 global reanalysis at 0.25° spatial resolution, and iii) the HISTALP gridded snowfall dataset at 0.08° spatial resolution, which is based on temperature and precipitation observations. We compare the three datasets over the last decades to investigate i) climatological features of seasonal and monthly snowfall over the GAR; ii) snowfall variability and trends in relation to elevation; iii) snowfall trends in relation to temperature and total precipitation, based on the best available observational datasets; iv) uncertainties in the snowfall climatology and trends, by comparing the different data sources. This study provides a first comprehensive evaluation of the quality of ERA5 and HISTALP snowfall datasets against ground observations. Moreover, by quantifying the snowfall component, it contributes to better characterize mountain precipitation in the cold season.  
Fracture growth using fully coupled thermo-mechanical model in brittle rocks during thermal shock and resulting network patterns
Authors: Suchoy Lior , Paluszny Adriana , Zimmerman Robert W
Published: March 2024

The utilisation of geothermal heat as a form of clean energy is experiencing global growth. Many sites designated for geothermal energy extraction are in regions with elevated heat gradients, such as Iceland and Japan. However, the repercussions of the migration of cold fluids in rock formations at high temperatures, and the subsequent fracturing of the host rock, which is relevant in the context of deep geothermal energy systems, remains insufficiently understood.  In this study, we explore the three-dimensional evolution of fractures in 50×9.8×1 mm3  homogeneous slabs of various brittle rocks, subjected to a thermal shock of ΔT=580°C, through numerical simulations over 10 seconds. Initially, we validate our numerical approach using a benchmark of Al2O3  slab, and subsequently, we examine fracture development in granite, basalt, and shales. Our numerical methodology employs a three-dimensional finite-element-based simulator to model thermo-mechanical deformation. The in-house code is a fully coupled THM code which considers damage to predict fracture initiation. Fracture growth is predicted per fracture tip using stress intensity factors. The code uses adaptive meshing and NURBS for fracture surfaces to facilitate mesh-independent fracture growth. In our simulations, we apply triangles and tetrahedra elements to discretise surface and volume elements, respectively. Our results show the development of dozens of fractures in bi- or tri-modality, which penetrate up to 85% of the depth of the slab, for the various simulations. These results demonstrate both qualitative and quantitative agreement between the simulated slab and the benchmark by reproducing the same intertwined short-long fracture patterns and modal distribution of fracture lengths. Furthermore, they illustrate how the fracturing rates (ranging between 1-100 mm/sec), fracture length distribution (unimodal, bimodal or trimodal), and penetration depth of fractures in front of the shock front vary among the different brittle rock types.
Large-Eddy Simulations of Methane Dispersion at the Utrecht University Campus
Authors: van der Linden Steven , Tettenborn Judith , Röckmann Thomas , de Roode Stephan , van de Wiel Bas
Published: March 2024

Last June 2023 a controlled release experiment (CRE) of methane was conducted at the campus of the Utrecht University, the Netherlands, with the aim of improving models for emission quantification. The methane was released at different flow rates and subsequently measured in the local area (along closed paths of approximately 500 m length) using vehicle mounted sensors. In addition, several wind sensors were deployed at approximately 35 meters distance of the release location covering the dominant flow pathways between the buildings.Although the setup enables us to relate the variability in wind direction and concentration peaks in the direct vicinity of the release, the limited spatial extent of the setup still makes it challenging to determine the dispersion of methane on the larger campus scale. Therefore, we explore the possibility to use meter-scale Large-Eddy Simulations (LES) in which the flow around the buildings is explicitly resolved with an immersed boundary method. With this approach, we aim to provide detailed information on the dispersion of methane ranging from the street-level to the campus scale.Here, we will show the first results of our simulations and a comparison with the observations. The controlled release experiment and wind measurements serve as validation for the LES, with the LES ideally reproducing the observed concentrations and wind directions in a statistical sense. We will discuss the model complexity required to accurately model observed dispersion features and look at the dependence of this result to changes in model setup. For example, how the model result changes with respect to a change in the prescription of large-scale meteorological conditions.Such validated urban LES may in the future be used not only for forward-in-time prediction of pollutant concentrations but also for inverse modelling to estimate the location of pollutant release, when only a limited number of observations are available.
Assessing the variations in hyporheic flow exchange by isotopic and chemical analysis 
Authors: Mahindawansha Amani , Gassmann Matthias
Published: March 2024

The hyporheic zone plays a critical role in nutrient cycling, biogeochemical processes, and overall stream ecosystem health. Variation of physical and chemical properties in the hyporheic zone affects the quality and quantity of the exchange process. To gain a depth-oriented insight into the hyporheic functioning, isotopic (18O and 2H) and chemical analysis (major ions such as K+, Na+, Mg2+, Ca2+, Cl-, SO42-, NO3-) was carried out focusing on the differences between upstream and downstream conditions. Multi-level interstitial probes were used to take subsurface water samples up to 0.6 m depth from two streams named Ahna and Losse in North Hesse, Germany.Fast downward flow and higher mixing rates were observed for Losse compared to Ahna and no differences were detected between the two locations in Losse. In Ahna, due to changes in effective porosities and the hydraulic conductivities, the water extraction rates were decreased along the depth. Downstream water was more isotopically enriched than upstream being subject to more evaporation and mixing with other waters. Higher concentrations of  K+, Na+, Mg2+, Cl-, and NO3- were found in downstream than the upstream due to the addition of wastewater, agricultural runoff, pollutants, and road salt while flowing. Denitrification and thus decrease in nitrate and increase in nitrite concentrations were more dominant in the upstream due to the high oxygen consumption. By combining isotopic and chemical analyses with detailed hydrogeological measurements, this study can provide valuable insights into the spatial dynamics of hyporheic flow exchange in a stream ecosystem.
An innovative Drinking Water Data Space in times of water scarcity and extreme events: the WQeMS platform
Authors: Serral Ivette , Bauer Philipp , Kita Afroditi , Vlachos Kostas , Matera Marco , Basile Matteo , Masó Joan , Manakos Ioannis
Published: March 2024

In the era of global challenges and big Earth data computation it’s becoming increasingly important to have proper interoperable solutions for describing, cataloguing, finding, accessing, and distributing highly valuable datasets. The usability and reproducibility of data under FAIR and GEO Data Sharing and Data Management Principles, with accurate description of datasets in terms of semantics and uncertainty, can make data more valuable. EC is pushing Data Spaces as a tool to manage data and generate and provide knowledge ready to use for managers and decision makers.The contribution presents a standard-based Data Space for automatically monitoring Water Quality specifically designed for European Lakes, based on remote sensing derived datasets, in-situ monitoring stations and web services. A web map browser gives access to water quality time series products (turbidity, Chl-a, floods, hydroperiod, etc) based on EO in Cloud Optimized GeoTIFF and in-situ observation stations connected using OGC STAplus standard. The map browser integrates the overall set of capabilities: data and metadata visualization, data analytics, quality indicators linked to the QualityML dictionary; semantic tagging of the Essential Water Variables; and OGC Geospatial User Feedback (GUF). The system is accessible through the OpenID-connect authentication standard which extends the OAuth 2.0 authorization protocol that allows different rights for different users to guarantee the preservation of data.This approach has been developed and tested under the Horizon 2020 WQeMS - Copernicus Assisted Lake Water Quality Emergency Monitoring Service (nº 101004157). Some parts of the solution have been developed under the HORIZON-CL6 AD4GD - An Integrated, FAIR Approach for the Common European Data Space (nº 101061001) co-funded by the European Union, Switzerland and the United Kingdom.
Analysis of fine-scale dynamics in the Balearic Sea through high-resolution observations and SWOT satellite data
Authors: Verger-Miralles Elisabet , Mourre Baptiste , Barceló-Llull Bàrbara , Gómez-Navarro Laura , R. Tarry Daniel , Zarokanellos Nikolaos , Pascual Ananda
Published: March 2024

The FaSt-SWOT experiments aim to integrate SWOT measurements with in-situ observations from two high-resolution multi-platform ocean campaigns and advanced data-assimilative models. The goal is to evaluate the performance of the satellite, characterize fine-scale (10-100 km) dynamics and quantify the associated horizontal and vertical transports. The FaSt-SWOT experiments were specifically designed to collect multi-platform in-situ observations within the swath of the SWOT satellite for validation, focusing on the area around the Balearic Sea. The campaigns took place in April and May 2023 and involved the simultaneous use of various ship-based instruments (CTD, Moving Vessel Profiler (MVP), thermosalinograph, ADCP, GoPros), autonomous platforms (surface drifters and gliders), and satellite observations (SST, ocean color, altimetry). In this presentation, we will focus on the analysis and processing of the multi-platform data collected during FaSt-SWOT. The sampling location was defined a few days before the first experiment based on the presence of a remarkable small-scale anticyclonic eddy (~20 km-diameter) detected in SST imagery and in the trajectory of a drifter within one of the SWOT swaths north of the Ibiza Island. Subsequent SST and ocean color maps showed the temporal evolution of the sampled eddy, which evolved into finer-scale features. Therefore, the context was ideal for analyzing SWOT's capability to detect this type of small structures. Indeed, the signature of the eddy was detected in the first sea level maps provided by SWOT and unresolved by conventional altimetry.The analyzed data consist of ~1000 MVP profiles of temperature and salinity from the surface down to a depth of 200 m along the ship trajectory (100 m during the first phase), combined with CTD rosette casts at fixed stations down to 700 m depth. Additionally, we will present data from two gliders that conducted 2 back-and-forth transects along the satellite swath with a 1-day delay between them, and the data from the 45 surface drifters deployed during both phases of the experiment. We will discuss the processing of the MVP observations, as well as the cross-calibration performed between CTD, MVP, and gliders measurements. This is a really important step to ensure that we are providing accurate and reliable quality-controlled observations, as well as a necessary process since these data will be available. Finally, we will provide a comparison between in-situ observations and SWOT data, and an analysis of the dynamics in the sampled area.
Exploring the interplay of shoot to root hydraulic conductance in varying soil water contents
Authors: Spinoso Sosa Samantha , Hafner Benjamin , Adamczewski Ruth , Zare Mohsen
Published: March 2024

Understanding how plants regulate their hydraulic systems in response to varying soil conditions is crucial for comprehending water fluxes in the soil-plant-atmosphere continuum. This study examines hydraulic conductance in maize plants grown in loamy soil under different soil water contents. We hypothesize that plants actively adjust both aboveground and belowground hydraulic conductance in response to soil texture and moisture to balance their water loss with water uptake.Maize plants were grown in loamy soil with varying moisture levels, simulating optimal and water-stressed conditions. Pre-germinated seeds were planted in PVC pots (10 cm diameter, 24 cm height). At different growth stages (2, 3, 4 and 6 weeks), shoots were delicately separated from the roots. We assessed both total aboveground (Kab) and belowground hydraulic conductance (Kbe). The Kbe was determined by subjecting soil and roots to incremental pressure increases in a pressure pot, collecting the sap to derive water flow at a given pressure. To calculate the total aboveground hydraulic conductance (Kab,tot), effective internal aboveground xylem hydraulic conductance (Kab,xyl), and stomatal conductance (Kab,sto), we measured transpiration, leaf water potential, temperature, and vapor pressure.In optimal conditions (OC), our initial findings show a linear increase during the initial growth stage in both above- and belowground conductance, followed by deceleration at the late developmental stage. Significantly,  Kbe surpassed  Kab,tot by over two orders of magnitude. It's worth noting that although Kab,xyl displayed a higher magnitude in our measurements, exceeding Kbe , the Kab,sto took precedence as the primary controlling factor when considering the overall soil-plant hydraulics. Under water-stressed conditions, plants exhibited an overall increase in hydraulic conductance with growth, where Kbe once again surpassed Kab,tot by over two orders of magnitude. However,  Kab,tot values were approximately half of those obtained in OC. Notably,  Kab,xyl decreased with plant age but remained greater than  Kbe. These results provide valuable insights into the intricate interplay between root and shoot hydraulic conductance. This research contributes to our understanding of how plants dynamically regulate their hydraulic systems under varying soil conditions, contributing to the broader knowledge of the soil-plant-atmosphere continuum.
Merits of Data Assimilation on Improving Flood Forecasting - A case study of Ohio Cannelton-Newburgh
Authors: Ricci Sophie , Nguyen Thanh Huy , Piacentini Andrea , Rodriguez-Suquet Raquel , Pena-Luque Santiago , Bonassies Quentin , Fatras Christophe , Astifan Brian , Davis Raymond , Durand Michael , Coss Stephen
Published: March 2024

Flooding is represented with a 2D hydrodynamic model over a reach of the Ohio river between Cannelton and Newburgh locks and dams. The geometry of the river and floodplain was provided by the National Oceanic and Atmospheric Administration (NOAA), based on U.S. Army Corps of Engineers (USACE) survey channel data merged with United States Geological Survey (USGS) LiDAR in the overbank regions. The description of hydraulic structures from USACE and in-situ water depth measurements from USGS stations were also used. Working from the 1D HEC-RAS model from Ohio University that covers a much larger area, the friction for our 2D local model was set uniformly over the floodplain. These values were further calibrated to 45 m1/3s-1 over the river bed and 17 m1/3s-1 with in-situ water depth measurements from USGS stations at Cannelton, Owensboro, and Newburgh over high flows periods in 2022 and 2023. The performance of the model was first assessed for the significant flooding event in February 2018, with RMSEs of the order of a few tens of centimeters. Remote-sensing (RS) products provided by satellite missions such as Sentinel-1 SAR, Sentinel-2 optical and Landsat-8 optical imagery undoubtedly offer opportunities to improve our ability to monitor and forecast flooding. For this study, the performance of the TELEMAC-2D (www.opentelemac.org) Ohio model was improved with the joint assimilation of in-situ and remote-sensing data within an EnKF framework that accommodates 2D RS-derived observations alongside with in-situ water level time-series. The RS-derived flood extent maps are expressed in terms of wet surface ratios (WSR) in selected subdomains of the floodplain. The assimilation of in-situ data reduces the RMSE to tenths of a centimeter. Ongoing work on the assimilation of WSR aims at improving the dynamic of the floodplain.  This 2D Ohio model will serve as a demonstrative test case for the FloodDAM-DT (https://www.spaceclimateobservatory.org/flooddam-dt) prototype dedicated to flood detection, mapping, prediction and risk assessment.
Addressing the 'Black Hole' amidst Sediment Connectivity and Multi-Hazards
Authors: Kabir Ishmam , Gems Bernhard , Rutzinger Martin , Keiler Margreth
Published: March 2024

‘Sediment Connectivity’ and ‘Multi-Hazard’ – two booming topics over the last decade; have experienced intensive methodological and conceptual developments. Research so far has acknowledged their interrelationships and established sediment connectivity as a crucial component in the framework of hazard and risk research, but mostly through the so called ‘single-hazard’ approaches. Sediment connectivity referring to the entire assemblage of connectivity network would by definition occupy a significant amount of space, which may often accommodate multiple interactive and interrelated hazards, making a single-hazard approach fairly inadequate and thus leaving a crucial research gap.
The primary aim of this study is to draw the attention of future research on this gap while attempting to address it through developing a new perspective to look into multi-hazard events. In line of that we propose a semi-quantitative index based on the classification of hazard events and their interactions through an inverse event tree approach – assuming a cascading process flow. The event classification is based on the type of interactions (e.g. process-process, triggering, impeding, structure-process, etc.) to facilitate the understanding and inclusion of the connectivity concept. The index would assess each step and the interlinkages of such cascading events and assign weights to them based on their significance from a sediment connectivity viewpoint. Furthermore, it would also address how these weights may alter the probabilities across the event tree. Overall, this study proposes a novel perspective into the inter-connectedness of geomorphic/sediment connectivity and multi-hazard events, in line with the ‘Gaia’ and ‘Systems’ theories. 
Long-Term Trends in Senegalese Dryland Tree Density
Authors: Lee Rene , Oehmcke Stefan , Abel Christin , Kovács Gyula Mate , Brandt Martin , Fensholt Rasmus
Published: March 2024

The historical extent and distribution of trees is central to our understanding of the current and future dynamics within the terrestrial biosphere. Typically, trees outside of forests, that characterise drylands, are often left out of coarse-grained analyses as they cannot be reasonably detected. However, 29% of tree cover within drylands is found outside of areas previously classified as forest.The rapid advancement of remote sensing technology over the last 50 years has seen a paralleled increase in both computational capacity and algorithmic sophistication. However, it is challenging to utilise older data sources with long-term image coverage and a coarser pixel resolution than the phenomenon being observed. There has been little research exploring the potential for modern data science methods, such as deep learning, for extracting more information from older data sources.Here, we propose a method for creating long-term tree density maps at the 15-meter scale, based on sub-meter resolution tree information. By utilising high resolution imagery to automatically detect and count individual trees, we have produced a deep learning-based method to predict tree density from coarser satellite imagery for Senegal over the past 25 years. Validation of our predictions will be conducted against on-site measurements from national forest inventory sites, facilitating an evaluation of high-resolution trends in dryland woody vegetation across time.The intricate and nonlinear nature inherent in neural networks renders them adept at managing noise and discontinuities within data sources. Here, we show that common artifacts produced by gap filling which often result from cloud cover and sensor error, can be minimised with the use of a deep learning framework. Such an analysis unlocks the possibility to extract less noisy and more continuous information from poorer image sources.
Numerical sensitivity analysis of energy performance of geothermal deep closed loop heat exchangers derived from the reuse of abandoned oil and gas wells
Authors: Facci Marina , Galgaro Antonio
Published: March 2024

Since the end of the XIX century, many wells have been drilled worldwide for both Oil & Gas exploration purposes. Most of them are now abandoned and subjected to mining closure because exhausted or sterile. In the new epoch of energy transition scenario, the possibility to adapt and reuse these existing boreholes to exploit geothermal energy seems very promising. In fact, considering that approximately 40% of the total costs for a new geothermal project are devoted to drilling activity, the possibility of repurposing abandoned oil and gas wells offers a wide range of applications and exploitation of underground heat uses. The drilled borehole available data (e.g., underground temperature, lithology) provide helpful information about the sub-surface reservoirs, reducing the mining risk level, and wells allow direct access to the sub-surface heat energy. However, to develop a commercially viable geothermal power/thermal generating system, one must consider several factors, i.e., available prospecting, drilling and reservoir technologies, energy costs in the area, and resource durability.This research aims to analyze the potential and feasibility of deep closed-loop systems solutions for heat and power energy production in Italy, in areas characterized by both normal and anomalous geothermal gradients and the distribution of available abandoned oil and gas wells. A prominent result is the development of a workflow leading to the feasibility assessment of deep closed-loop systems development, based on the identification of suitable abandoned O&G wells through the geological and thermal underground characterization and wells construction characteristics (diameter, depth, borehole material). Furthermore, a sensitivity analysis of the main parameters affecting most of the retrofitting of abandoned wells for geothermal purposes is performed thanks to thermal FEM modelling.Finally, identifying the possible end-users in a suitable case study area, this research work provides preliminary insights into the quantity of thermal energy and electric power that this technology could produce.
Evolution of palaeoenvironmental and palaeoclimatic conditions recorded in Jura lakes since the Late Glacial Period
Authors: Bomou Brahimsamba , Zappa Damien , Rachoud-Schneider Anne-Marie , Haas Jean-Nicolas , Gärtner Marina , Spangenberg Jorge E. , Bichet Vincent , Adatte Thierry
Published: March 2024

Since the retreat of the Würm ice sheet, numerous glacial paleolakes have formed in the French and Swiss Jura. This project investigates two sites: the Amburnex Valley site (Switzerland) and the Lake Val (France). During the Late Glacial period, both sites were glacial lakes with significant accumulation of lacustrine sediments, providing a complete record of paleoclimatic and paleoenvironmental evolution.The aim of this study is to reconstruct the paleoclimatic and the paleoenvironmental evolution recorded in lacustrine sediment deposits over the last 15’000 years. The Amburnex core displays a basal morainic deposit from the Würm period, overlain by three meters of lacustrine deposits and four meters of peatland deposits. The Lake Val core exhibits the same lithological succession. A multiproxy approach based on palynological, mineralogical and geochemical analyses was used to characterise hydrological and climatic fluctuations, trophic levels, and the origin of organic matter. This approach was employed to reconstruct the paleoenvironmental and paleoclimatic evolution of this area. The analyses included total organic carbon (TOC), nitrogen, phosphorus and mercury contents, major and trace elements, and organic carbon isotopes.The Bølling-Allerød, the Younger Dryas and the beginning of the Preboreal period have been recognised in the Amburnex site, by palynological analyses and carbon 14 dating. The Oldest Dryas was characterised by oligotrophic conditions, as evidenced by the very low concentrations of nitrogen and organic matter. During the warmer Bølling period, there was an enrichment in TOC, indicating the development of eutrophic conditions. Later, during the Allerød period, low TOC and phosphorus contents, associated with varved carbonate deposits, indicate a return to more oligotrophic conditions. In the interval corresponding to the colder Younger Dryas period, new organic matter enrichments were observed. These trends are quite consistent with those observed in the Lake Val and reflect significant changes in runoff and nutrient inputs at least at a regional scale.No evidence of a tephra layer or significant mercury anomalies were found at the Amburnex site. However, significant increases in magnetic susceptibility were observed during the Allerød and Younger Dryas periods at the Amburnex site. These increases are well correlated with those recorded in other Jura lakes containing tephra layers, corresponding to the Laacher See Tephra and the Vedde Ash, respectively. A significant peak in Ptot is observed at the same level as the magnetic susceptibility peak during the Allerød period.This peak appears to be independent of nitrogen and TOC and is related to apatite present in tephra glass in the volcanic ash deposits of the Laacher See Tephra.
A baseline approach for downscaling the Euro-CORDEX data for wind risk assessment of the Metsovo village in Greece
Authors: Chatzidaki Akrivi , Vamvatsikos Dimitrios , Barmpas Fotios , Hellsten Antti , Auvinen Mikko , Tsegas George
Published: March 2024

A methodology is presented for downscaling the wind projections of Euro-CORDEX in order to derive temporally and spatially correlated region-wide wind fields that can be used for assessing the wind risk for cultural heritage sites. The coarse spatial and temporal resolutions of the Euro-CORDEX projections prohibit their use as a direct input for such purposes, especially for cultural heritage assets that are spatially distributed within the Euro-CORDEX grid and dynamically respond differently to wind. To improve the temporal resolution of the Euro-CORDEX data, we leverage machine learning tools and weather station measurements, aiming to generate composite “Frankenstein” days at the locations of the weather stations that comprise 144 jigsaw pieces of actually measured 10min wind time-series that are matched together to form a continuous daily record. The “Frankenstein” days are expanded spatially to all locations where critical assets can be found by employing spatially distributed wind fields that are computed via high-fidelity computational fluid dynamics simulations and provide contemporaneous wind values at all locations of interest. This process allows generating “Frankenstein” days and wind fields with a temporal resolution of 10min and spatial resolution that allows assessing the wind risk for spatially distributed assets. As a case study, the Euro-CORDEX wind projections are downscaled for the cultural heritage village of Metsovo that is found at the Western part of Greece. Most of the buildings within this village are made of stone masonry and tiled roofs and are vulnerable to extreme wind actions as wind can cause damages e.g., on the tiled roofs thus making the buildings vulnerable to rainfall, or even lead to their partial or complete failure. Thus, the Frankenstein days and wind fields are employed for assessing the wind risk for the cultural heritage buildings of Metsovo both on an event-basis and in the long-term.
Typical design hydrograph method based on a joint distribution approach combining flood peak discharge, volume and duration
Authors: Lacko Martina , Potočki Kristina , Škreb Kristina Ana , Bezak Nejc , Gilja Gordon
Published: March 2024

Determination of flood magnitude and shape characteristics are necessary to provide a more complete assessment of flood severity and its impact in scour development analysis. Our recent research has focused on a joint distribution approach to account for the multivariate nature of flood characteristics, resulting in probability of occurrence of different pairs of flood variables: flood peak (Q), volume (V) and duration (D). To extend the results of this research, a method for deriving a design hydrograph is applied to the study area by using the typical hydrograph method. As it is recommended to test multiple scenarios in a scour analysis, different typical flood hydrographs were selected at several gauging stations on the Sava and Drava rivers in Croatia and multiplied by the design discharge values. The aim of this study is to complement the ongoing research of the relationship between climate change indicators, flood wave characteristics and scour development next to the bridges crossing large rivers in Croatia with installed scour countermeasures by preparing hydrological input data for a hydraulic scour analysis.
Characteristics of precipitating convection and moisture-convection relationships in global km-scale simulations
Authors: Becker Tobias , Takasuka Daisuke , Bao Jiawei
Published: March 2024

In this study, we compare convection characteristics in three models that are at the forefront of global km-scale modelling, the ICON model developed by the Max Planck Institute for Meteorology (MPI-M) and German Weather Service (DWD), the IFS developed by the European Centre for Medium-Range Weather Forecasts (ECMWF), and the NICAM model developed by the University of Tokyo, the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and the National Institute for Environmental Studies (NIES). For IFS and ICON, we analyse 1-year coupled simulations at 4.4 and 5 km resolution, respectively, which stem from Cycle 3 of the H2020 Next Generation Earth Modelling Systems (nextGEMS) project. For NICAM, we analyse a 1-year AMIP-type simulation at 3.5 km resolution. Convection schemes have been switched off in ICON and NICAM, while in the IFS the deep convection scheme’s cloud base mass flux is strongly reduced. Modelling convection at km-scale resolutions is both exciting and challenging because some important processes are already resolved at these scales (e.g., deep convection) but other important processes remain under-resolved (e.g., mixing of grid-scale updrafts with their environment). Thus, we analyse in this study what common issues exist in ICON, IFS and NICAM with respect to the convection characteristics in the tropics, in what respects all models do well and where there are substantial inter-model differences.Specifically, we analyse local convection characteristics and show that compared to satellite observations, the models tend to overestimate precipitation intensity (NICAM and ICON), while they underestimate precipitation cell size and precipitation duration. We study mesoscale organisation by using different organisation metrics and show that the models tend to underestimate organisation, even though they all consistently show that when organisation is enhanced, heavy precipitation is enhanced as well. We also investigate moisture-convection relationships and show that the models generally do not moisten enough during a convective event compared to ERA5 reanalysis data. Consistently, the sensitivity of lower-tropospheric moisture variations to the life cycle of deep convection over ocean looks too weak in ICON and IFS.Finally, we look at land-ocean differences of the convection characteristics and show that while all models capture the diurnal cycle of precipitation over ocean well, there are some substantial differences over land, even though biases are not consistent between the models. Over coastal regions of the Maritime Continent, ICON has too strong mean precipitation and a too strong diurnal cycle, whereas IFS overall underestimates both, connected to a too weak propagation of convection onto the ocean during nighttime, potentially connected to too weak cold pools. Meanwhile, NICAM has more realistic convection characteristics in these coastal regions.
Microscale modelling of NOx concentrations in a real urban hot-spot for several meteorological and traffic conditions
Authors: Rodríguez-Sánchez Alejandro , Santiago José Luis , Vivanco Marta G. , Rivas Esther , Sánchez Beatriz , Martilli Alberto , Martín Fernando , Theobald Mark R. , Gil Victoria , Garrido Juan Luis , Hernández Coralina
Published: March 2024

Recently, air quality has become a major concern for policy makers around the world, which has led to the implementation of mitigation measures. In urban areas, most measures affect the road transport sector, as this is one of the main contributors to air pollution in those areas. Due to the fact that spatial variability of urban air pollution is very heterogeneous, high spatial resolution modelling is necessary. In this context, this study aims to evaluate the air quality impacts of several measures applied to the traffic network around a real urban hot-spot (Plaza Elíptica, Madrid) at high spatial resolution.The methodology used is based on Computational Fluids Dynamics (CFD) modelling, but uses different modelling tools to obtain all the necessary input data. The SUMO microscopic traffic simulator is used to obtain a dataset of traffic flows for each scenario selected in the study. This dataset represents the regular traffic during the week, avoiding the cost of computational time and resources to run simulations for each hour. Emissions are computed for each timestep of the simulations (0.75 s) using the emissions model PHEMLight5 coupled with SUMO. A set of steady-state CFD simulations are previously performed for all wind direction sectors and scenarios, using the previously described emissions. The horizontal spatial resolution of these simulations is of 5x5 m2, which higher resolutions (up to 1x1 m2) near buildings. Relevant meteorological variables are obtained from WRF simulations using the urban parameterization BEP-BEM. These are necessary for both selecting the appropriate CFD simulations from the dataset according to the observed wind direction at each hour and estimating NOx maps from pre-calculated CFD simulations based on the wind speed observed at each hour. Finally, background NOx concentrations are obtained from an urban background air quality monitoring station (AQMS) in Madrid, located 1.6 km NW from the AQMS of Plaza Elíptica.Using this methodology, we have studied four scenarios:Base scenario. (Year 2016)
Reorganization of traffic flows by changing traffic directions in some streets. (Year 2019)
The initial phase of the implementation of a Low Emissions Zone (ZBE) affecting the most polluting vehicles; with still some reduction of traffic due to the COVID-19 pandemic. (Year 2022)
The recovery of traffic after the COVID-19 pandemic. (Year 2023)
Results were evaluated for February 2016, 2019, 2022 and 2023 using the observed concentrations at the AQMS in the study area. The impacts of the traffic variations are investigated for different meteorological conditions.
Implementing the first indirect radiative effect of aerosols in the ECMWF model
Authors: Andreozzi Paolo , Fielding Mark , Forbes Richard , Hogan Robin
Published: March 2024

For many years, aerosol-cloud-radiation interactions (ACI) have been incorporated in climate models, due to the high sensitivity of the Earth’s climate to changes in cloud microphysical properties. Despite this, such representations are still fraught with uncertainty, strongly limiting the capacity of such models to precisely predict climate change. For numerical weather prediction (NWP), the impact of ACI on forecast skill is controversial, though regional radiative fluxes can be affected significantly. Their representation in NWP models has therefore usually been neglected. We will present early results from an ongoing investigation to calculate the number of droplets (Nd) in liquid-phase clouds online from global aerosol fields in the ECMWF global Integrated Forecasting System (IFS), i.e. the first indirect radiative effect of aerosols. Our ACI scheme uses a lookup table, produced from offline cloud parcel model simulations, to estimate the number of aerosol particles activated into cloud droplets. This approach allows the effect of large sea salt to suppress the activation of sulfate aerosols to be included. We will then constrain the representation of ACI by verifying weather forecast against available satellite and station-based observations. Ultimately, the impact of such simulated processes on the model can be assessed in different configurations of the IFS, spanning from the NWP medium range (10-15 days) to seasonal forecasts to climate projections. We will show how such a computationally inexpensive approach can effectively increase realism of the simulated liquid-phase cloud microphysics in the model, resulting in improved representation of global and regional top-of-the-atmosphere radiative fluxes. We can apply the same approach both to the climatological and prognostic aerosol representations supported by the IFS (the latter being used operationally for air quality forecasts by the Copernicus Atmospheric Monitoring Service, CAMS), allowing sensitive comparison between different configurations of the model. We will conclude by showing advantages of the new ACI scheme when aerosols are prognostic variables, and how such experiments could inform our work towards introducing ACI into the operational IFS forecasts, where currently a climatological representation of aerosols is used.