bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Environmental Impact of Ground Source Heat Pumps and Air Source Heat Pumps for Dwellings with high and low insulation profiles
Authors: Aresti Lazaros , Makarounas Christos , Christodoulides Paul
Published: March 2024

Following the European Union (EU) targets towards the “Fit for 55”, the heat pump (HP) sales have seen an increase. The recent increasing demand in the utilization of HP towards space heating and cooling, underscores the pivotal role of Shallow Geothermal Energy (SGE) systems and the Ground Source Heat Pumps (GSHPs). Although GSHPs exhibit higher performance compared to Air Source Heat Pumps (ASHPs), the high initial cost and the consequent long payback period has been a preventive factor for the GSHP systems. The GSHP systems however also benefit for additional CO2 reduction. The evolving efficiency of ASHP systems in recent studies challenge the perceived advantages associated with GSHPs, particularly in light of the continual refinement of ASHP systems.This research embarks upon a comprehensive analysis to compare the environmental impacts, in terms of CO2 emissions, between ASHP and GSHP systems using different case studies. High insulation profile case studies were considered, following the nearly Zero Energy Buildings (nZEB) technical characteristics, as well as retrofitting at older dwellings with a low insulation profile. The current study engages a Life Cycle Analysis (LCA) with the OpenLCA software in conjunction with the Ecoinvent database, and the employment of the ReCipe impact method, both from a midpoint and an endpoint perspective. The findings derived from this investigation demonstrates a favorable performance of the GSHP systems where there is an increasing demanding in heating such as in the retrofitting cases. This research highlights the important environmental implications of employing the GSHPs over the use of ASHPs.
Statistical Downscaling for urban meteorology at hectometric scale
Authors: Garcia Cristobal Julia , Wurtz Jean , Masson Valéry
Published: March 2024

Predicting the weather in urban environments is a complex task because of the highly heterogeneous nature of the urban structure. However, there are many issues inherent in urban meteorology, such as thermal comfort and building’s energy consumption. Those stakes are linked to highly heterogeneous meteorological variables within the city such as temperature, humidity, wind, net radiative flux and city characteristics such as building uses and characteristics. State-of-the-art meteorological models with hectometric resolution, such as the Meso-NH (Lac et al. 2018) research model, can provide accurate forecasts of urban meteorology. However, they require too much computing power to be deployed operationally. Statistical downscaling techniques are machine learning methods enabling the estimation of a fine resolution field based on one or several lower resolution fields. ARPEGE is the operational planetary model of Météo-France and operates at a resolution of 5km on France. Using Meso-NH simulations covering Paris and the Île-de-France region, a statistical downscaling has been carried out to obtain a temperature field at 300m resolution using simulation outputs from the ARPEGE planetary model at 5km. The deduced temperature reproduces the urban heat island and the temperature heterogeneity simulated in Meso-NH. The estimated temperature field is able to represent the links between temperature and topography as well as the sharp gradients between the city and the urban parks. Lac et al. 2018 : https://doi.org/10.5194/gmd-11-1929-2018
Geophysical monitoring of engineering infrastructure foundations
Authors: Rizzo Enzo , Boldrin Paola , Andreotti Lorenzo , Fornasari Giacomo
Published: March 2024

The geophysical methodologies can give for providing useful information about the subsoil, environment, buildings, and civil infrastructures and supporting the public administrations in planning interventions in urban scenarios. In the past years, the geophysical prospection methods have been improved for the inspection of foundation soils, civil structure, and engineering infrastructures. Anyway, the potential of geophysical techniques in urban sites is mainly known in characterisation contexts, while a monitoring use has not yet been developed. Therefore, new applications and laboratory experiments are needed to enhance their capability and development.This work introduces a time lapse three-dimensional Electrical Resistivity Tomography (3D ERT) monitoring on the effects of the standard practice of shallow polyurethane resin injected below the settled foundations of a villa. The application was performed to monitor the effectiveness of the consolidation beneath the building with time. The 3D ERT was applied before and after the injection phase. The geoelectrical acquisitions were performed with electrodes arranged close the external walls with an electrode space of about 1m. Therefore, non-conventional setting of the electrode layout was adopted permitting to obtain a 3D model of the geophysical parameter distribution close the foundations. The time-lapse 3D ERT highlighted the effects of the resin injections. In addition, an experiment was carried out in the laboratory through the creation of a physical model of a foundation placed in a sandbox in which the conditions of resin injection after a subsidence are simulated.
A new approach to understanding fluid mixing in process-study models of stratified fluids
Authors: Hartharn-Evans Sam , Stastna Marek , Carr Magda
Published: March 2024

Well established energy-based methods of quantifying diapycnal mixing in process-study numerical models are often used to provide information about when mixing occurs, and how much mixing has occurred. However, describing how and where this mixing has taken place remains a challenge. Moreover, methods based on sorting the density field struggle with under resolution and uncertainty as to the definition of the reference density when bathymetry is present. Here, an alternative method of understanding mixing is proposed. Paired histograms of user selected variables (which we abbreviate USP) are employed to identify mixing fluid, and are then used to display regions of fluid in physical space that are undergoing mixing. Here, two case studies are presented to showcase this method: shoaling internal solitary waves and a shear instability in cold water influenced by the nonlinearity of the equation of state. For the first case, the USP method identifies differences in the mixing processes associated with different internal solitary wave breaking types, including differences in the horizontal extent and advection of mixed fluid. For the second case, the method is used to identify how density, and passive tracers are mixed within the core of the asymmetric cold-water Kelvin-Helmholtz instability.
Revealing the origin, age and seasonality of streamflow, soil waters and transpiration
Authors: Floriancic Marius G. , Allen Scott T. , Kirchner James W.
Published: March 2024

The forest water cycle is dominated by vegetation-mediated processes, such as interception, infiltration, and transpiration, that greatly impact the redistribution of waters between the atmosphere and subsurface. Based on a three-year time series of water stable isotopes in precipitation, soils of various depths, groundwater, streams and xylem from the “WaldLab Forest Experimental Site” in Zurich, Switzerland, we estimated seasonal signals and the fractions of more recent and older waters across the different compartments of the forest water cycle. These findings yield new understanding of water transport in forest ecosystems.Seasonal variation in streamflow isotopic signatures was small, indicating that annual streamflow was dominated by old waters draining from subsurface storages. Mobile and bulk soil waters all showed a distinct seasonal signature, with the seasonal amplitude decreasing with depth and mobile soil waters varying less than bulk soil waters. Young water fractions and new water fractions in forest soils decreased with increasing depth, indicating different degrees of subsurface mixing with waters from previous events and seasons. The fractions of recent precipitation in soil waters were generally smaller in summer than in winter, revealing the effects of interception and evaporation. Xylem water signatures in beech and spruce trees largely matched the bulk soil water signatures. The relative lack of soil water recharge in summer led to both species predominantly transpiring winter precipitation. Canopy interception did not substantially alter the isotopic signal of precipitation, but where it is more significant it could bias interpretations of transit times and seasonal precipitation partitioning.
Combining stand-level and remote sensing data to model post-fire recovery of Mediterranean tree-forest communities – A case study in Spain.
Authors: Hoffren Raul , de la Riva Juan , Domingo Darío , Lamelas María Teresa , Ibarra Paloma , García-Martín Alberto , Rodrigues Marcos
Published: March 2024

Mediterranean forests are recurrently affected by wildfires. Fire activity is expected to accelerate in the future due to landscape homogenization, fuel accumulation, and climate warming. A key aspect to prevent and mitigate the negative impacts of wildfires on ecosystems is to understand the factors that govern the recovery of forest communities. This study analyzes the post-fire recovery potential of four representative Mediterranean tree-communities (Pinus halepensis, Pinus nigra, Pinus pinaster, and Quercus ilex) affected by large wildfires (> 500 ha) during the summer of 1994 in Spain. For this purpose, information collected in the field 25 years after the fires in 203 forest plots (131 burned and 72 unburned control plots) was coupled with remote sensing, geospatial, and forest inventory data, to build an empirical model capable of assessing recovery. Remote sensing data provided a proxy for burn severity, through the Composite Burn Index, and allowed modelling the local topography (slope and aspect) of the terrain. The geospatial data included climatic information on temperature and precipitation trends. These data were entered into the model, calibrated using Random Forest, to provide information on the degree of recovery, inferred from the similarity (in terms of vegetation height, aboveground biomass, species diversity) between the burned and unburned control plots. Results showed that only the 25% of the burned plots can be considered as recovered. The burn severity had a significant effect on the recovery albeit strongly modulated by local topography. Overall, the key features of the recovered plots were a low-to-moderate burn severity and a favorable topographical setting, especially the shading effect of steep northwestern slopes. Furthermore, a warmer and more humid climate improved the capacity of recovery. These results constitute a valuable tool for improving forest management and preserving ecosystem services.
Regional variation of climatological cloudburst frequency estimated from historical observations of daily precipitation sums
Authors: Schmith Torben , Thejll Peter , Vejen Flemming , Christiansen Bo
Published: March 2024

Cloudburst are geographically localized extreme rainfall events where a large amount of rain falls within a few hours. The combination of small spatial scale, short duration and scarceness makes it difficult to reveal any systematic regional differences in occurrence. Here we estimate climatological cloudburst frequencies from the daily precipitation sums for a dense network of 161 historical Danish stations covering the period 1914-2010. We do this using supplementary sub-hourly precipitation observations from a modern network and relate the daily probability of cloudburst occurrence to the corresponding daily precipitation sum using binary regression. This allows a subsequent estimation of the cloudburst frequency from the daily sums from the historical observations. To validate the method, we use stations from the modern network that have been operating for 30 years or longer. For these stations, we demonstrate significant skill by comparing observed and estimated cloudburst frequencies with a jackknife procedure. We then apply the binary regression model using the 161 historical series as input and estimate climatological cloudburst frequencies throughout Denmark. We find large and systematic regional variations across Denmark. The methodology also allows determining temporal changes of cloudburst frequency and we find large differences across Denmark.
Constraining near to mid-term climate projections by combining observations with decadal predictions
Authors: Bonnet Rémy , Boé Julien , Sanchez Emilia
Published: March 2024

The implementation of adaptation policies requires seamless and relevant information on the evolution of the climate over the next decades. Decadal climate predictions are subject to drift because of intrinsic model errors and their skill may be limited after a few years or even months depending on the region. Non-initialized ensembles of climate projections have large uncertainties over the next decades, encompassing the full range of uncertainty attributed to internal climate variability. Providing the best climate information over the next decades is therefore challenging. Recent studies have started to address this challenge by constraining uninitialized projections of sea surface temperature using decadal predictions or using a storyline approach to constrain uninitialized projections of the Atlantic Meridional Overturning Circulation using observations. Here, using a hierarchical clustering method, we select a sub-ensemble of non-initialized climate simulations based on their similarity to observations. Then, we try to further refine this sub-ensemble of trajectories by selecting a subset based on its consistency with decadal predictions. This study presents a comparison of these different methods for constraining surface temperatures in the North-Atlantic / Europe region over the next decades, focusing on CMIP6 non-initialized simulations.
Estimates of heat release to the atmosphere related to effusive volcanic eruptions and intrusive activity during the 1975-84 rifting episode of Krafla, NE-Iceland
Authors: Fehrentz Patricia , Guðmundsson Magnús Tumi , Reynolds Hannah Iona , Gunnarson Sidney R. , Belart Joaquin Munoz Cobo , Chodora Michaela
Published: March 2024

The heat transfer dynamics in volcanic geothermal areas determine the options for geothermal energy exploration. Intrusive and eruptive events provide additional heat input into the geothermal system, as cooling and solidification of the magma heats the surrounding host rock and water in the porous matrix. The evaporation of the water leads to convection and an advective rise of steam in the fissures. Steam rises further and diffuses into the atmosphere depending on wind conditions. The heat lost by steam released to the atmosphere is in many cases one of the significant parameters that determine the heat budget of a geothermal system.The Krafla fires describe a period of volcanic activity at the Krafla volcano in North-East Iceland from 1975 to 1984 with nine volcanic eruptions and several more intrusive events. This activity was part of a major rifting episode where several meters of widening occurred along the Krafla fissure swarm. The rifting and associated intrusive activity had a significant effect on the geothermal system. Aerial photographs taken during or a few months after each eruption are used to determine the position and size of the fumaroles and associated steam generation. The heat output of the steam clouds is empirically related to its area, expressed as a power-law function (Hochstein & Bromley, 2001). The escape of water vapor, and thus the prevalence of fumaroles associated with these events, is mainly evident on the eruptive fissures. Surface alteration is prevalent and a sign of current or recent steaming. The results for heat lost to the atmosphere can be compared with the heat released by the cooling of the magmatic intrusions formed in the upper crust, providing heat to the existing geothermal area.
Multi-decadal variability controls short-termstratospheric water vapor trends
Authors: Tao Mengchu , Konopka Paul , Wright Jonathon S. , Liu Yi , Bian Jianchun , Davis Sean M. , Jia Yue , Ploeger Felix
Published: March 2024

Stratospheric water vapor increases are expected in response to greenhouse gas-forced climate warming, and these changes act as a positive feedback to surface climate. Previous efforts at inferring trends from the 3–4 decade-long observational stratospheric water vapor record have yielded conflicting results. Here we show that a robust multi-decadal variation of water vapor concentrations exists in most parts of the stratosphere based on satellite observations and atmospheric model simulations, which clearly divides the past 40 years into two wet decades (1986–1997; 2010–2020) and one dry decade (1998–2009). This multidecadal variation, especially pronounced in the lower to middle stratosphere and in the northern hemisphere, is associated with decadal temperature anomalies (±0.2 K) at the cold point tropopause and a hemispheric asymmetry in changes of the Brewer-Dobson circulation modulating methane oxidation. Multi-decadal variability must be taken into account when evaluating stratospheric water vapor trends over recent decades.
Modeling the evolution of hummocky topography on debris-covered glaciers
Authors: Strickland Ryan , Covington Matthew
Published: March 2024

Debris-covered glaciers develop complex, hummocky topography in their ablation zones. The development of hummocky topography coincides with the formation of supraglacial ponds and ice cliffs. Because the ponds and ice cliffs significantly increase melt rates, there is a need to understand how the hummocky topography evolves to better predict melt from debris-covered glaciers. Supraglacial ponds, and the ice cliffs that form along pond shorelines, develop within topographic depressions in the hummocky topography. Recent work (Strickland et al., 2023) showed that topographic depressions on the debris-covered Ngozumpa Glacier, Nepal, undergo positive feedback growth. The development of depressions is often attributed to contrasts in melt rates caused by contrasts in debris thickness. However, this hypothesis cannot explain positive feedback growth because it ignores the negative feedback caused by hillslope debris transport into the depression. Although not included in current models of surface evolution, meltwater drainage provides a potential mechanism for positive feedback depression growth. To better understand depression growth and the evolution of hummocky topography, we develop a two-dimensional topographic evolution model for debris-covered glaciers. Here, we explore how the emergence of englacial debris, hillslope transport of supraglacial debris, and meltwater drainage influence the development of topographic depressions. We first examine the topography that develops from a heterogeneous debris layer. Then, we add the influence of channel incision on topographic evolution. With these mechanisms included, the model only produces small, transient depressions. However, if we include englacial drainage points—locations where supraglacial meltwater and debris enters the subsurface drainage network— this spurs the growth of large, lasting depressions. These results suggest that englacial drainage is necessary to produce persistent depressions in hummocky topography.
Assessing the nonlinearity and cost effectiveness of PM2.5 in response to emission changes in North China with the adjoint method
Authors: Lu Ni , Zhang Lin , Wang Xiaolin , Guo Yixin , Ye Xingpei , Liu Zehui , Li Danyang , Xu Jiayu , Henze Daven
Published: March 2024

While great efforts have been made to China’s clean air actions since 2013 and effectively mitigated PM2.5 pollution, the emission-concentration relationships and cost-effectiveness may have changed substantially and are poorly constrained. Large emission reductions during the COVID-19 lockdown period in early 2020 did not similarly alleviate PM2.5 pollution in North China, reflecting a distinct nonlinear chemical response of PM2.5 formation to emission changes. At the same time, strengthened emissions standards and elimination of outdated industrial capacities have replaced the existing technologies and increased the cost of pollution control. Here we apply emission-concentration relationships for PM2.5 diagnosed using the adjoint approach to quantitatively assess how chemical nonlinearity affects PM2.5 over Beijing in February 2020 in response to two emission reduction scenarios: the COVID-19 lockdown and 2013-2017 emission controls, and further evaluate the marginal cost and benefit of possible technological alternatives. We find that, in the absence of chemical nonlinearity, the COVID-19 lockdown would decrease PM2.5 in Beijing by 10.6 μg m-3, and the 2013-2017 emission controls resulted in a larger decrease of 54.2 μg m-3 because of greater reductions of SO2 and primary aerosol emissions. Chemical nonlinearity offset the decrease for Beijing PM2.5 by 4.7 μg m-3 in lockdown, which was mainly attributed to enhanced sensitivity of aerosol nitrateto NOx emissions, but enhanced the efficiency of 2013-2017 emission controls by 12.5 μg m-3 due to the weakened heterogeneous reaction of sulfate. For further PM2.5 mitigation, emission reductions in ammonia by urea substitution and primary PM2.5 with electrostatic precipitator have high PM2.5 reduction potential and cost effectiveness. Such chemical nonlinearity and cost optimization are important to estimate and consider when designing or assessing air pollution control strategies. 
Volcanic activity classification trough Self-Supervised Learning applied to satellite radiance time series
Authors: Spina Marco , Bilotta Giuseppe , Cappello Annalisa , Dozzo Maddalena , Guardo Roberto , Spina Francesco , Zuccarello Francesco , Ganci Gaetana
Published: March 2024

Automated early warning systems for volcanoes, capable of early recognition of any signs of impending eruption, as well as to track the evolution of different kinds of eruptive activity in near real time, are essential to assess the volcanic hazards and mitigate the associated risk. Satellite imagery offers a systematic, synoptic framework for monitoring active volcanoes in even the most isolated corners of the Earth. Here we have applied a machine learning technique to automatically classify a pixel in SEVIRI imagery over an active volcano, in order to detect and characterize its eruptive activity. In particular, we have discriminated against five main classes of pixels: clear sky, cloud-contaminated, ash-contaminated, SO2-contaminated and thermal anomalies.Due to the enormous amount of data and the difficulty in labeling it, we have used self-supervised learning to study data acquired since 2004. We have selected an area of 5x5 pixels around the active volcano under study and followed the spectral radiance variation of each pixel in the twelve bands availables. Our technique has been applied to several active volcanoes within the SEVIRI disk, including Etna, Nyiragongo, Stromboli, Nabro, La Palma and Fogo.
Improving flood risk evaluation and communication by mapping the loss probability of pedestrians
Authors: Lazzarin Tommaso , Chen Albert S. , Viero Daniele
Published: March 2024

A proper evaluation and an effective communication of flood risk are important aspects to reinforce flood preparedness and to reduce the impacts of future flooding events. In particular, communicating the expected flood risk to different categories of people (i.e., non-technician, of different age and formation) is recognized as a real challenge.Flood maps typically present flood scenarios using spatially distributed flow depth and velocity, which are unable to convey intelligible information on the associated hazard to the general public. Similarly, hazard indexes meant to express flood hazard by combining flow depth and velocity have important intrinsic limitations. These indexes were developed to identify the critical thresholds for human instability in floodwaters, based on experimental data or conceptual models. Accordingly, they can be used to detect flood-prone areas where pedestrians cannot cope with floodwaters, but they are unable to rate intermediate hazard degrees correctly. This is because a linear relationship between flow velocity and hazard is assumed, which is an oversimplification given that human stability in floodwaters is a matter of forces, which depends on the square of the velocity.We propose using the concept of loss probability of people in floodwaters, LP, to pursue an intelligible and effective communication of flood risk. Defined as the probability of a pedestrian to be swept away by floodwaters, LP accounts for both hazard and vulnerability in a physics-based and data-consistent fashion. Its spatial distribution can be easily computed as a function of water depth and velocity.A real case study application highlights that, in slow shallow waters, hazard indexes overestimate the risk perception, whereas LP correctly predicts low risk levels. On the other hand, LP identifies high risk conditions in slow and deep waters, for which hazard indexes generally provide a severe underestimation of the real danger.
Gibraltar subduction zone is invading the Atlantic
Authors: Duarte Joao C. , Riel Nicolas , Rosas Filipe M. , Popov Anton , Schuler Christian , Kaus Boris J.P.
Published: March 2024

Subduction initiation is a cornerstone of the Wilson cycle. It marks the turning point in an ocean’s lifetime, allowing its oceanic lithosphere to be recycled back into the mantle. However, forming new subduction zones in Atlantic-type oceans is challenging, as it commonly involves the action of an external force, such as the slab pull from a nearby subduction zone, a far-field compression or the impact of a mantle plume. Notwithstanding, the Atlantic Ocean already has two fully developed subduction zones, the Lesser Antilles and the Scotia arcs. These subduction zones have been forced from the nearby Pacific subduction zones. The Gibraltar Arc is another place where a subduction zone is invading the Atlantic. This corresponds to a direct migration of a subduction zone that developed in the dying Mediterranean basin. Nevertheless, few authors consider the Gibraltar subduction zone as still active because it has significantly slowed down in the last millions of years. Here, we present new 3D buoyancy-driven geodynamic models, using the code LaMEM, that reproduce the first-order evolution of the Western Mediterranean, show how the Gibraltar Arc may have formed and test if it is still active. The numerical simulations are validated using geological and geophysical data. The results suggest that the Gibraltar arc is still active and will propagate further into the Atlantic after a period of tectonic quiescence. The models also show how a subduction zone starting in a closing ocean (the Ligurian) can migrate on its own into a new opening ocean (the Atlantic) through a narrow oceanic corridor. Subduction invasion is likely a common mechanism for introducing new subduction zones in Atlantic-type oceans and a fundamental process in the recent geological evolution of Earth. This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds (PIDDAC) – UIDB/50019/2020 (https://doi.org/10.54499/UIDB/50019/2020), UIDP/50019/2020 (https://doi.org/10.54499/UIDP/50019/2020) and LA/P/0068/2020 (https://doi.org/10.54499/LA/P/0068/2020). JCD also acknowledges FCT a CEEC Inst. 2018, CEECINST/00032/2018/CP1523/CT0002 (https://doi.org/10.54499/CEECINST/00032/2018/CP1523/CT0002).
Large Low-Velocity Provinces (LLVPs): a new model for their structure, origin, and evolution
Authors: Katsura Tomoo
Published: March 2024

The Large Low-Velocity Provinces (LLVPs) beneath West Africa and the Southern Pacific are characterized by low seismic wave velocities and are associated with plate-unrelated magmatism such as hotspots, large igneous provinces, and kimberlite. Despite their significance, the structure, origin, and feeding processes of LLVPs remain elusive.Previous studies have suggested that the LLVPs have remained stationary for over 300 million years, but their morphology appears to have changed. While geodynamic simulations favor denser LLVPs, a recent free-oscillation analysis has suggested lighter ones. The High-Velocity Region (HVR), which surrounds the LLVPs, is located beneath present and past subduction zones. Plumes of varying morphology are imaged between hotspots and LLVP margins, with intensive plumes revealing ultra-low velocity zones (ULVZs) at their roots. Ocean island basalts (OIBs) from hotspots are geochemically enriched and originate from multiple reservoirs. Interestingly, OIB chemistry does not correlate with seismic plume imaging and differs between the two LLVPs. OIB near the African LLVP is influenced by fluid-related subducted materials.In the light of these results, I propose the following new model for the LLVPs. The LLVPs are at higher temperatures than the HVR and the surrounding mantle. They are composed of Fe-enriched mono-mineral bridgmanite rock, called bridgmanitite. The large grain size of bridgmanitite results in high viscosity despite the high temperatures, thereby stabilizing the LLVPs. The LLVPs are block-structured and the relative movement of the blocks changes the LLVP morphology. Bridgmanitite was formed by the solidification of a primordial magma ocean. Its deposition at the core-mantle boundary forms LLVP precursors in the early mantle. These LLVP precursor blocks can be moved by the thrust and sweep of subducted slabs to form the present-day LLVPs. Erosion and plume formation have reduced the volume of the LLVPs and resulted in different LLVP heights. The HVR consists of harzburgite brought from the surface by subduction. It contains only a limited amount of basaltic rock because the basaltic rock was detached from slabs in the mid-mantle due to suppressed grain growth. As a result, the HVR material is high-density due to the low temperature but is intrinsically low-density due to its chemistry. The HVR material has been heated using the LLVP heat to form plumes. Plumes are geochemically depleted when they have formed in the deep mantle. However, they are enriched in incompatible elements and volatiles in the shallow mantle. This enrichment results from melt migration due to the temperature gradient around the plume. Thus, although LLVP heat drives plume formation, the plate-unrelated magmas such as OIB are not directly derived from the LLVPs.
Ionospheric absorption variation as measured by European Digisondes, riometers and determined by the NOAA D-RAP model during intense solar flares in September, 2017
Authors: Barta Veronika , Bozóki Tamás , Süle Dávid Péter , Kouba Daniel , Mielich Jens , Raita Tero , Buzás Attila
Published: March 2024

The sudden increase of Solar X-ray and EUV emission following solar flares causes ionization and increased absorption of electromagnetic (EM) waves in the sunlit hemisphere of the Earth’s ionosphere. Solar flares are also accompanied by energetic particles which can lead to additional ionization and absorption especially at the higher latitudes (> 60 °). A novel method has been developed by Buzás et al. [1] based on the amplitude data of the EM waves measured by Digisondes to calculate and investigate the relative absorption changes (compared to quiet period) occurring during solar flares. The effect of 13 intense (>C4.8) solar flares that occurred between 06:00 and 16:30 (UT, daytime LT = UT+2 h) from 04 to 10 September 2017 have been studied using the so-called "amplitude method". Total and partial radio fade-outs, furthermore, +20%–1400% amplitude changes (measured at 2.5 and 4 MHz) were experienced at three Digisonde stations (Juliusruh (54.63° N, 13.37° E), Průhonice (49.98° N, 14.55° E) and San Vito (40.6° N, 17.8° E)) during and after the investigated flares.In the present study we compare the results of the amplitude method with the absorption changes measured by the Finnish Riometer Chain and determined by the NOAA D-RAP model during the same solar flare events. The X-class flares caused 1.5–2.5 dB attenuation at 30–32.5 MHz based on riometer data, while the absorption changes were between 10 and 15 dB in the 2.5–4.5 MHz frequency range (thus 10 times higher) according to the amplitude data measured by the Digisondes. The impact caused by the energetic particles after the solar flares are clearly seen in the riometer data, while it can be observed only at Juliusruh (~55°) at some certain cases among the Digisonde stations. Therefore, the absorption changes as a result of the particle precipitation is significant at high latitudes, but decreases rapidly with decreasing latitude, and is no longer detectable below the sub-auroral region. The main conclusion from the comparison of the amplitude method with the D-RAP model is that the model underestimates the values obtained from the Digisonde's measurements at both 2.5 and 4 MHz in almost every case. The differences varied between 0.2 and 15 dB at 2.5 MHz and 2.9–10 dB at 4 MHz and they did not show any systematic trend with the intensity of the flare, or with the latitude of the station. [1] Buzás, A., Kouba, D., Mielich, J., Burešová, D., Mošna, Z., Koucká Knížová, P., & Barta, V. (2023). Investigating the effect of large solar flares on the ionosphere based on novel Digisonde data comparing three different methods. Frontiers in Astronomy and Space Sciences, 10.
Urban canopy parameters and local climate zones over Europe using OpenStreetMap data
Authors: Wurtz Jean , Bernard Jeremy , Masson Valery , Erwan Bocher
Published: March 2024

Climate modelling needs to have accurate informations about topography, type of land and land-use, size and type of wind or radiative obstacles such as trees or buildings. Explicits climate models solves heat and mass equations for each individual surfaces but they cannot be applied at regional scale for long time periods due to computational limitations. Parameterized climate models can overpass this limitations considering that within a given grid cell (being from one to several hundred meters wide), the obstacles and lands follow a given setting (e.g. street canyon for cities, with or without a garden). The heat and mass balances are applied for each of the grid cells using urban canopy parameters summarizing the main relevant parameters describing an area (e.g. mean building height, canyon aspect ratio, building fraction, fraction of road, building type and use, etc.). However, there is currently no datasets over Europe that would accurately describe all these informations.OpenStreetMap (OSM) is a free, open geographic database updated and maintained by a community of volunteers via open collaboration. It contains most of the informations needed by climate models. It can cover any part of the world and is particularly well fullfilled for the European continent. One of its limitation is the lack of building height information. GeoClimate is a tool that calculates urban canopy and land cover parameters as well as Local Climate Zones (LCZ). GeoClimate uses vector data such as the ones available through the OSM project and uses machine learning algorithm to estimate the height of building missing such information. GeoClimate has recently used the OSM data to calculate the needed informations needed by parameterized climate models such as SURFEX-MesoNH or WRF over Europe. The presentation will describe the way GeoClimate works and will show some of the results of the resulting dataset.
What does the oxygen budget of a peatland tell us about global carbon budgets?
Authors: Worrall Fred , Clay Gareth , Moody Catherine , Hirst Catherine , Burt Timothy
Published: March 2024

The oxidative ratio is a fundamental property of an environment and at global scale controls the magnitude of the terrestrial biosphere carbon sink. The oxidative ratio of the terrestrial biosphere is defined as the ratio of the O2 released to the CO2 adsorbed by a terrestrial environment. It has proved difficult to estimate the OR of environments. This study proposed that the OR of an ecosystem could be calculated from the organic matter budget of a peatland environment constrained by stoichiometry and thermodynamics of the organic matter transfers. This study used the detailed stoichiometry of the organic matter reservoirs of a peatland. The IPCC estimates global OR = 1.1; and this study showed that OR = 0.88. The OR of the study environment is independent of many of the organic matter transfer pathways but dependent on the initial fate ot primary productivity and the N cycle within the environment. The calculated OR is consistent with disproportionation of C occurring in the environment with a reduced component being accumulated into the terrestrial biosphere while an oxidised component of organic matter is lost to the atmosphere.  The method is transferrable to other environments where there is elemental analyses of the organic matter cycle. The implication of OR < 1 is that the magnitude of the carbon sink has been over-estimated.
Vulnerability of coastal cities and mangroves to the combined effects of Land subsidence, relative sea-level rise, and groundwater extraction along the low-lying coastland of Cameroon
Authors: Chounna Yemele Gergino , Teatini Pietro , Minderhoud Philip
Published: March 2024

The coast of Cameroon, which is approximately 590 km in length, is situated in the Gulf of Guinea and is characterized by its low elevation above sea level and sedimentary geology, making it particularly susceptible to erosion, subsidence, and sea level rise. The coast of Cameroon and its extensive mangrove forests are facing numerous economic pressures, including encroachment from urban expansion, agro-industrial development, port activities, oil and gas exploration and exploitation, and the increased pollution associated with these activities. Additionally, many rapidly growing cities located along the coast (Douala, Kribi, Tiko, Limbe) and neighbouring the mangroves (Duala estuary, Rio Del Rey estuary, and Ntem estuary) are currently experiencing alarming rates of coastal erosion, frequent flooding, complete loss of land, and evidence of subsidence from regional and continental research. Unfortunately, there have been no detailed investigations of the combined effects of land subsidence and sea-level rise, known as relative sea-level rise, and their present and future impacts on Cameroon's emerging coastal cities and mangroves under climate change. Therefore, this research aims to fill this knowledge gap by investigating, understanding, and projecting the causes, consequences, and coastal vulnerability related to land subsidence and sea-level rise to enable the development of information-based mitigation strategies and policies. We will use remote sensing data, InSAR analysis, hydrogeological investigations, and modelling tools to assess the real coastal elevation of Cameroon, determine the actual land subsidence rate, determine the actual local relative sea-level rise from tide gauge data, determine the factors influencing land subsidence, project future elevation evolution, and establish an integrated vulnerability assessment of the coastal areas of Cameroon. This research will contribute to a proper understanding of Cameroon's mangrove landscape dynamics, the vulnerability of coastal infrastructure, and its biodiversity to relative sea-level rise, subsidence, coastal retreat, and future flooding events. The outcome can be used to develop sustainable management strategies for Cameroon's coastal zone.
The new Austrian standard ÖNORM B4800 for torrent control work
Authors: Nagl Georg , Hübl Johannes , Suda Jürgen
Published: March 2024

Austria has a wide variety of protection structures at different condition levels due to the long tradition of torrent control works in the Austrian Alps. This has resulted in a large stock of protection structures and load models. In order to standardise the design of technical structures based on the Eurocode, including torrential processes, snow avalanches and rock fall, an interdisciplinary working group (ON-K-256) was established. The standardisation for torrential processes covers the definition and classification, the impact on structures, the design of structures, and the operation, monitoring and maintenance. These parts are based on and interact with EN 1990 (the basis of structural design), EN 1992-1-1 (the design of concrete structures), EN 1997-7 (geotechnical design) and the related documents for the Austrian national specifications. For torrential mass wasting processes with high variability in the concentration of solids, modern protection concepts are scenario-oriented. To optimize the mitigation measures for a multi-stage system, a functional chain must be implemented. This chain should have different structures to perform various functions such as dosing, filtering, and energy dissipation. When designing these torrential mitigation structures, it is necessary to simplify the model parameters, stress model, and load distribution. For debris flows, a standardized stress model combines the static and dynamic loads of debris flow impact on structures. This model was calibrated using available impact measurements of real debris flows and is in good agreement with common engineering design methods in Austria for debris flow impact on torrential barriers. The proposed method enables practitioners to design debris flow countermeasures with limited data availability.
Ammonia in Paris derived from ground-based open-path and satellite observations
Authors: Viatte Camille , Guendouz Nadir , Dufaux Clarisse , Hensen Arjan , Swart Daan , Van Damme Martin , Clarisse Lieven , Coheur Pierre , Clerbaux Cathy
Published: March 2024

Ammonia (NH3) is an important air pollutant which, as precursor of fine particulate matter, raises public health issues. This study analyzes 2.5-years of NH3 observations derived from ground-based (miniDOAS) and satellite (IASI) remote sensing instruments to quantify, for the first time, temporal variabilities (from interannual to diurnal) of NH3 concentrations in Paris.The IASI and miniDOAS datasets are found to be in relatively good agreement (R>0.70) when atmospheric NH3 concentrations are high and driven by regional agricultural activities. Over the investigated period (January 2020 – June 2022), NH3 average concentrations in Paris measured by the miniDOAS and IASI are 2.23 μg.m-3 and 7.10x1015 molecules.cm-2, respectively, which are lower or equivalent to those documented in other urban areas. The seasonal and monthly variabilities of NH3 concentrations in Paris are driven by sporadic agricultural emissions influenced by meteorological conditions, with NH3 concentrations in spring up to 2 times higher than in other seasons.The potential source contribution function (PSCF) reveals that the close (100-200km) east and northeast regions of Paris constitute the most important potential emission source areas of NH3 in the megacity.Weekly cycles of NH3 derived from satellite and ground-based observations show different ammonia sources in Paris. In spring, agriculture has a major influence on ammonia concentrations and, in the other seasons, multi-platform observations suggest that ammonia is also controlled by traffic-related emissions.In Paris, the diurnal cycle of NH3 concentrations is very similar to the one of NO2, with morning enhancements coincident with intensified road traffic. NH3 evening enhancements synchronous with rush hours are also monitored in winter and fall. NH3 concentrations measured during the weekends are consistently lower than NH3 concentrations measured during weekdays in summer and fall. This is a further evidence of a significant traffic source of NH3 in Paris.
Can the Electrospray Orbitrap be a new frontier for the stable isotope analysis of oxyanions in ice cores? A statistical study of its performances
Authors: Savarino Joel , Saville Jack , Gautier Elsa , Kuhlbusch Nils , Juchelka Dieter
Published: March 2024

Recently, the Orbitrap Exploris instrument, a mass spectrometer designed for molecular identification and classification, has been diverted from its original purpose and transformed into a new tool for quantifying the stable isotope ratios of water-soluble compounds such as nitrates, sulfates or phosphates. At first glance, this new Orbitrap IRMS system is very attractive because it requires 10 to 100 times less ice than current standard procedures, works directly with liquid solutions, quantifies isotope ratios directly on the molecule of interest, and provides a broader range of isotope ratios by moving from the elemental isotope ratio paradigm to that of molecular isotope ratios and thus challenge the regular isotope ratio mass spectrometers (IRMS or ICPMS). Moreover, by leaving the chemical bonds of the molecules of interest intact contrary to IRMS or ICPMS, the Orbitrap technology provides access to clumped isotopes, i.e. doubly substituted isotopic substances, thereby enriching our knowledge of matter. Extending the range of molecular isotope ratios opens up exciting new prospects, particularly for unravelling the mechanisms by which compounds are formed before being incorporated in ice. Such a radical change in the way isotope ratios are measured inevitably raises the question of the real capabilities of this new instrument. With a deeper look into statistics, can the Orbitrap-IRMS challenge the standard IRMS/ICPMS precision for analyzing soluble species? Does its performance live up to expectations? Preliminary results show that the Allan variance for a large variety of molecular isotope ratios of nitrate and sulfate are in the range of one per mil precision, including some of the clumped isotope ratios. However, the bootstrapping approach aimed at reducing acquisition time and thus the drift associated with the instrument appears to be ineffective in improving the Allan variance, indicating a possible limitation of sampling randomization, probably during the electrospray ionization (ESI) process. Other statistics, tests and performances are still in progress and will also be presented.