bluuebunny/crossref_metadata_2025 huggingface dataset:
Is growth of Swiss stone pine at the alpine treeline impaired or enhanced by competition with N2-fixing green alder?
Authors: Oberhuber Walter , Salino Ethan , Obexer Lena , Wieser Gerhard , Gruber Andreas
Published: February 2023

Green alder (Alnus alnobetula (Ehrh.) K. Koch = Alnus viridis (Chaix) DC) is a nitrogen-fixing pioneer species that is widely distributed at high altitude and latitude in the northern hemisphere. Due to changes in land management green alder is currently the most expanding shrub in the European Alps. It forms dense, tall thickets that are thought to impair establishment and growth of trees. The main focus of this study therefore was (i) to compare annual increments of Swiss stone pine (Pinus cembra L.), which is the dominant tree species at high elevation in the Central Eastern Alps, with that of green alder, and (ii) to determine radial growth of Swiss stone pine in competition and in absence of competition with green alder. The study area is situated within the treeline ecotone stretching from c. 1950 up to 2200 m in the Central Tyrolean Alps (Mt. Patscherkofel: 47.21 N, 11.46 E; Kühtai: 47.22 N, 11.04 E). A comparison of radial growth between similar aged stems (c. 20 yrs) revealed that annual increments of Swiss stone pine (2311 ± 628 µm) were more than four-times larger than those of green alder (519 ± 92 µm). This finding can be explained by different carbon allocation strategies, i.e., favouring vertical stem growth in single stemmed Swiss stone pine over preference of horizontal spreading in multi-stemmed green alder. This interpretation is supported by aerial photographs, which show that green alder stands are spreading vigorously within the treeline ecotone on Mt. Patscherkofel, amounting to c. 450 m2 ha−1 decade−1. Radial growth measurements of Swiss stone pine occurring inside and outside green alder thickets (canopy height 2–3 m) revealed that Swiss stone pine individuals with a comparable height to green alder (tree height: 2.9 ± 0.8 m) showed significantly lower growth inside green alder stands than outside, while Swiss stone pine trees taller than green alder thickets (tree height: 6.1 ± 1.6 m) grew better inside than outside green alder thickets. We explain these findings by source limitation of Swiss stone pine growth at low tree height, whereas with increasing tree height carbon assimilation is no longer a limiting factor and the higher N2 availability within green alder thickets can be exploited for stem growth. We conclude from this study that due to its horizontal competition strategy and dense cover of its foliage green alder is able to strongly impede the establishment and growth of co-occurring late-successional Swiss stone pine. Hence, spreading of green alder due to land abandonment and decrease in grazing pressure causes a delay in the development of closed forest stands, and also hampers climate warming induced advance of the alpine treeline.This research was funded by the Austrian Science Fund (FWF), P34706-B.
Comparison of eddy permitting, eddy rich and sub-mesocale permitting global configurations based on NEMO 4.2 OGCM.
Authors: Bricaud Clement , Abjean Perrine , Chanut Jérôme , Bourdallé Badie Romain , Garric Gilles
Published: February 2023

In the framework of the Copernicus Marine Environment Monitoring Service, Mercator Ocean International operates a global high-resolution forecasting systems at the resolution of 1/12°. Increasing resolution appears necessary to improve the quality of service and to satisfy the users’ needs in the operational application (Le Traon, 2019). Resolving scales below 100 kilometers, and in particular sub mesoscale processes (1-50 km), appears to be essential to better represent the circulation in the open ocean (Chassignet, 2017), and, to improve the large-scale representations thanks to a more explicit energy transfers between finer and larger scales (Fox-Kemper Baylor, 2019). A deeper understanding of their various contributions (geostrophic flows, tidal motions, waves, inertial currents) and their role in the global ocean kinetic energy budget will improve the knowledge of these energy transfers between different scales.
In 2019, it has been decided to go towards higher resolution and develop a new global sub mesoscale-permitting model. Benefiting from the context of the European H2020 IMMERSE project, a new 1/36° global configuration (2 to 3 km resolution), based on the NEMO 4.2 OGCM, has been developed. Thanks to the resolution increase, this model can resolve the Rossby radius in almost all open oceans areas at global scale quite everywhere and to span a large part of the internal wave spectrum.
In 2022, a hierarchy of multi-year simulations at 1/4°, 1/12° and 1/36° resolution and with/without explicit tide representation has been performed: for each resolution, after a 3-years spin up without tidal forcing, 2 twin 3-years runs have been realized: one without tidal forcing and one forced by the 5 tidal components K1, O1, S2, M2, N2. These models are driven at the surface by the 8km/1hour ECMWF IFS system. Atmospheric pressure forcing have been activated.
We propose a first evaluation of the benefits due to the resolution increase and tidal forcing. Circulation, energy, tidal representation and mixing of the experiments are compared to each other’s.
 
Does metabolic water control the isotopic composition of water in microbial cells?
Authors: Angert Alon , Weiner Tal , Tamburini Federica , Zer Hagit , Keren Nir
Published: February 2023

Metabolic water, the water that is produced from O2 during respiration, carries an isotopic signature that can be different from that of the water the cell is growing in. It has been well known that for large land organisms, like birds and mammals, metabolic water contributes significantly to the water balance and has an important control on the signature of the oxygen-stable-isotopes of the water inside the organism. This isotopic signature is then carried over through isotopic equilibrium to other oxygen-bearing species like phosphate. However, for small organisms like bacteria, it has been widely assumed for decades, that the large surface area to volume ratio enables a fast exchange of the cell water with the ambient water. As a result, the isotopic signature of the metabolic water will be heavily diluted and erased. In contrast, a recent work reported indirect evidence of significant control of metabolic water on the oxygen isotopes inside microbial cells. This indirect evidence is based on deviations of oxygen isotopes in phosphate from the expected equilibrium with the ambient water. Here we report the results of experiments that directly tested the possible contribution of metabolic water to phosphate oxygen isotopes in bacteria. We found that ambient water did control the oxygen isotopes in the phosphate. However, there were large deviations from the expected equilibrium. Nevertheless, we found that these deviations were not correlated with the isotopic composition of metabolic water. Hence, other mechanisms, which will be discussed, are responsible for these deviations.
Landscapes of sandy areas along a rainfall gradient of 90-450 mm, average annual rainfall
Authors: Yair Aaron
Published: February 2023

Dryland areas are regarded as highly sensitive to climatic changes. A positive relationship between average annual rainfall, and environmental factors is often assumed for areas with an average annual rainfall of 100-400 mm. The above assumption disregards the fact that a climate change in some dry-land areas is not limited to climatic factors. In addition, the climatic models, based on average annual rainfall, disregard the rainfall characteristics at the rain-shower level, which greatly influence the degree to which rainwater will percolate, thereby significantly affecting the spatial redistribution of water resources. The present work deals with the complex relationships between average annual rainfall, and environmental variables in sandy areas, along a rainfall gradient of  90-450 mm, in the south eastern Mediterranean area, Israel. Data obtained clearly show that average annual rainfall is not a good indicator of water resources, and ecosystem characteristics. The controlling factors vary from one site to another.
Fabrication of PAC sludge-valorized biochars and their practical application to the remediation of methyl arsenic in wetlands
Authors: Ryu Jungho , Han Young-Soo , Cho Dong-Wan , Kim So-Jeong , Cho Yong-Chan , Chon Chul-Min , Ahn Joo Sung , Nam In-Hyun
Published: February 2023

This study aims to mitigate As pollution in wetlands by using biochar composites, which are a byproduct of valorizing drinking water treatment sludge (i.e., polyaluminum chloride (PAC) sludge). PAC sludge produced when PAC is used as a coagulant contains various aluminum and iron components because of the high affinity of PAC for heavy metals. Therefore, the valorization of PAC sludge by pyrolysis can be a strategic method to secure environmental safety for sludge utilization by destroying the organic pollutants and immobilizing heavy metals while simultaneously producing biochar composites that can be used as an environmental adsorbent. Biochar composites were fabricated under N2 and CO2 environments, systematically characterized by X-ray diffraction, thermogravimetric, and Brunauer–Emmett–Teller/Barrett–Joyner–Halenda analyses, and tested for the adsorption of As species. Both biochar composites exhibited excellent adsorption performance for both inorganic As (As(III) and As(V)) and organic As (dimethylarsinic acid, DMA). A lab-scale microcosm test showed that ~30% of spiked DMA was removed by biochar and that the total As fixed in the sediment decreased by ~20%. In addition, the As speciation results for the sediment and biochar revealed demethylation of the DMA and reduction of As(V) to As(III) by microorganisms, which was confirmed by a microbial growth batch test. Finally, a large-scale field experiment carried out in an artificial ecological wetland ensured that the addition of biochar could reduce the total amount of As to be immobilized in wetland sediment by 19%. In addition, the presence of biochar could alter the migration trend of As species in plants by reducing the amount of organic As to be fixed in the sediment. The aforementioned results demonstrate the practical feasibility of using PAC sludge-derived biochar as an adsorbent for As species.
Predicting CMEs Using ELEvoHI With STEREO-HI Beacon Data
Authors: Bauer Maike , Amerstorfer Tanja , Weiss Andreas J. , Davies Jackie A. , Möstl Christian , Amerstorfer Ute V. , Reiss Martin A. , Harrison Richard A.
Published: February 2023

Coronal mass ejections (CMEs) are the main drivers of geomagnetic storms at Earth and are capable of impacting power grids on the planet’s surface as well as satellites in orbit. Developing models to accurately predict the arrival time and speed of CMEs is a necessary step towards ensuring that we are capable of providing advance warning to mitigate potential severe space weather effects. We use the Ellipse Evolution model based on Heliospheric Imager observations (ELEvoHl) to predict the arrival of CMEs at Earth using data from STEREO-A’s heliospheric imagers. The HI instruments provide both real-time, lower-quality beacon data as well as higher- quality science data which is downlinked to Earth with some delay. Issuing alerts for approaching CMEs before they arrive at Earth necessitates the utilization of real-time data. HI data for each event and data type is compiled into a time-elongation plot (Jmap) in which every CME’s trajectory is tracked manually. We predict the arrival time and speed of 10 Earth-directed CMEs from 2010 to 2020 using both science and beacon data with the ELEvoHI model and compare the results in terms of accuracy across both data types. We find that predictions made using beacon data are generally worse than those made using science data and give an outlook on possible future perspectives for improving the real-time prediction of CMEs.
Post-sedimentary pedogenesis in colluvial soils in the context of the landscape sedimentary history (Czechia)
Authors: Zádorová Tereza , Penížek Vít , Koubová Magdalena , Lisá Lenka , Žížala Daniel , Pavlů Lenka , Tejnecký Václav , Drábek Ondřej
Published: February 2023

Colluvisols, representing a significant part of the erosional catena in undulating landscapes, often changed by long-term agricultural management, undergo a complex development with alternating phases of material deposition and slope stability, with subsequent initiation of soil formation processes. The presented study focuses on the detailed description of the post-depositional evolution of four up to 4m-deep colluvial profiles, formed in different colluvial positions in two environmentally and historically distinct areas of Czechia, situated in the loess region of South Moravia and Central Bohemian Upland, built on plutonic rocks. A multi-proxy approach consisting of analyses of clay mineralogy, micromorphology, humic acids and geochemical parameters was applied to distinguish the inherited and in-situ developed pedogenetic features and link them with the sedimentary history of the studied soils, assessed using optically stimulated luminescence dating and 137Cs activity. Marked differences in the type and maturity of pedogenetic features were identified not only in individual plots but also in different colluvial positions within the same plot. While signs of bioturbation, mainly related to root activity and soil fauna, were observed even in recent colluvial layers after a short period of stabilization, more advanced processes of weathering, organic matter stabilisation and clay illuviation are typical only for early-sedimented layers with long post-depositional development. Redoximorphic features were more pronounced in the side valleys compared to the toe-slope colluvial positions; similarly marked differences between colluvial positions were observed for humus quality, with significantly more stable organic matter concentrated within side valleys. In both sites, distinct and largely contradictory trends in the transformation of clay minerals, reflected in the proportions of different phyllosilicate layers, were observed, corresponding to the specific conditions of soil development. Study was supported by grant nr. 21-11879S of the Czech Science Foundation.
Disposal of HLW and ILW/LLW at the same site: challenges in an international context
Authors: Maurer-Rurack Ute , Poller Andreas , Hardie Susie , Poppei Joachim , Voss Marie , Smith Paul
Published: February 2023

Title:  Disposal of HLW and ILW/LLW at the same site: challenges in an international contextAuthors:  Maurer-Rurack, U.*, Poller, A., Hardie, S., Poppei, J., Voss, M. **, Smith, P. **** Federal Office for the Safety of Nuclear Waste Management (BASE), Berlin, Germany** CSD Ingenieure AG, Switzerland*** Safety Assessment Management GmbH, Switzerland Abstract:Germany is looking for the site with best possible safety for an HLW (high level waste) repository. In the site selection procedure of Germany three host rocks: rock salt, clay and crystalline rock are considered. In accordance with §1 (6) of the StandAG (German Site Selection Act), an additional disposal of ILM/LLW (intermediate level/low level waste) might be allowed at the same site, provided that its characteristics satisfy the best possible safety criteria for the sole disposal of HLW waste. This point will be addressed within the framework of preliminary safety investigations pursuant to §27 (5) of the StandAG in the individual phases of site selection process for the HLW repository, according to the current state of science and technology.The GemEnd research project (2022, in press) investigates the possible mutual influence of these different types of repositories at the same site and the resulting safety-relevant consequences for the HLW repository system in Germany.This contribution provides an overview of the currently existing international disposal programs of non-heat-generating waste (ILW/LLW) and heat-generating waste (HAW) at the same site in the following countries: Belgium, France, Finland, Germany, Japan, Sweden, Switzerland and the United Kingdom.The IAEA (International Atomic Energy Agency) also considers co-disposal of HLW and ILW/LLW as an option that has advantages over separate repositories. But particular critical interactions caused by gas formation and gas transport as well as interactions of cementitious materials with other engineered components and the host rocks should not be forgotten (IAEA 2009, 2018).On this basis, existing international disposal programs for HLW and ILW/LLW at the same site are compared with each other. Important similarities and differences for the transferability of the findings to the site selection procedure in Germany are presented. Finally, the approach of other countries can contribute to a better assessment of the safety implications in Germany. 
Sub-seasonal snowline dynamics of glaciers in Central Asia from multi-sensor satellite observations, 2000-202
Authors: Kim Dilara , Callegari Mattia , Ullmann Tobias , Barandun Martina
Published: February 2023

Glaciers are an important contributor to the freshwater supply in the Central Asian region. Their response to climate change has profound consequences for the land-use applications, and is thus essential to understand. The collapse of the Soviet Union has interrupted the vast majority of the conducted glacier mass balance observations, which began to re-establish in 2010. The existing data gap, limited spatial resolution of glaciological measurements, and the high heterogeneity of the region limits the use of in-situ data. Mass balance models rely on observation-based calibration and validation data, such as transient snowlines (TSLs), a transition between snow and ice-covered surfaces on a glacier at a given point in time. At the end of the ablation season TSL approximates the equilibrium line. From TSL we can calculate the snow-covered area fraction (SCAF), the area on the glacier surface that is snow covered in relation to the total glacier area. The TSL and SCAF can be mapped from satellite imagery due to the distinctive spectral and structural signature of snow over time. Our approach presented in this contribution is based on the MODIS time-series, harnessing the advantage of long and close-to-daily observations records for the period before high-resolution satellites became available. To resolve the issue of MODIS coarse spatial resolution, we retrieved SCAF from multispectral Sentinel-2 and cloud-independent Sentinel-1 SAR imagery using established workflow. The automatic classification and calculation of SCAF is performed using the cloud computing service of the Google Earth Engine, which makes the entire approach easily applicable on a large number of remote glaciers worldwide. We validated the results independently with Landsat data over selected glaciers in Central Asia. From the  SCAF time-series we analysed changes in various parameters indicative for the atmospheric conditions and its changes  (amongst others the length of ablation period, the minimum SCAF, and the seasonal SCAF changes ) as well as their 20-year trends. Our results provide a unique time series of temporally and spatially high-resolved SCAF estimates giving observation-based information on the heterogeneity of the region’s climatic setting as well as its changes on subseasonal scale. 
Influence of irrigation on land-surface interactions and the atmospheric boundary layer in a semi-arid region – Results from the LIAISE campaign
Authors: Lunel Tanguy , Boone Aaron , Le Moigne Patrick
Published: February 2023

Irrigation is still widely neglected in land surface models which are used for numerical weather prediction. However, with the general improvement of coupled surface-atmosphere models and the evolution towards kilometer or hectometer grids, this omission is beginning to be reconsidered. Better understanding the links between the strong surface heterogeneity and local meteorology is one of the objectives of the LIAISE (Land surface Interactions with the Atmosphere In Semi-Arid Environment) project. The work presented here focuses on two clear and warm days of the special observation period of the LIAISE campaign that took place during the summer of 2021 in northeastern Spain. The coupled surface-atmosphere model Surfex-MesoNH is used to model two days of interest with and without an irrigation parameterization. The model outputs are then compared to multiple surface-based and airborne observational data. A clear improvement is provided by the irrigation representation. In particular, the modeled sensible and latent heat fluxes are reconciled with the observations, the temperature biases at 2m are corrected up to 5°C, and the specific humidity is increased by about 50% around noon near the surface. It is also shown that irrigation leads to changes in the structure and height of the atmospheric boundary layer. A breeze-like, non-classical mesoscale circulation induced by the surface contrasts between the irrigated area and the surrounding semi-arid area is highlighted.
Accurate heavy precipitation prediction in an (pre-)alpine area: The benefit of trend conservation in circulation pattern conditional statistical downscaling.
Authors: Böker Brian , Laux Patrick , Olschewski Patrick , Kunstmann Harald
Published: February 2023

The reliable prediction of flash flood relevant heavy precipitation events under climate change conditions remains a challenging task for the downscaling community. Therefore, a huge variety of downscaling approaches have been proposed and successfully applied, however, there is still potential for improvements. The conducted study aims to investigate potential improvements by circulation pattern (CP) trends conservation and their utilization for CP conditional statistical downscaling of daily summer precipitation in the (pre-)alpine region of Bavaria. The CPs have been created taking only atmospheric variables into consideration and the link to precipitation is established via CP conditional cumulative distribution functions (CDF) of the observed precipitation at selected measurement sites across the region. The derived CDFs allow for the sampling of CP conditional precipitation values at the station scale which are subsequently bias corrected by quantile mapping (QM) and parametric transfer functions (PTFs) as tested methods. The predicted precipitation values have been evaluated against obervations using different performance measures such as Kling-Gupta Efficiency (KGE), Root Mean Squared Error (RMSE) and Mean Absolute Error (MAE). In order to properly account for extreme events the evaluation has been conducted for the complete precipitation distribution and for the distribution above the 95th percentile seperately. The results show that the described CP conditional downscaling approach is capable of yielding more accurate daily precipitation values especially in the extremes compartment in which an average gain in prediction skill of + 0.24 and a maximum gain of + 0.6 in terms of KGE has been observed. This shows that the conservation of trends and atmospheric information through CPs and their utilization for downscaling can lead to improved precipitation downscaling results.
Deformation-dependent aftershocks in laboratory earthquakes sequences
Authors: Amon Axelle , Mathey Ambroise , Marsan David , Weiss Jerome , Crassous Jerome
Published: February 2023

We study an experimental model of a fault consisting in a stationary shear band in a compressed granular sample. To obtain those bands, we perform a biaxial compression of a granular sample constituted of glass beads during which we observe the spontaneous formation of shear planes along the Mohr-Coulomb directions in the sample. We study the post-failure regime during which all the deformation occurs along the stationary shear bands. Using an interferometric method of measurement of micro-deformations based on multiple scattering, we obtain full-field measurements of the local incremental deformation in the sample. The deformation measured are typically of $10^{-5}$ with a resolution of about 300 microns (3 bead diameters). Our technics gives access to the strain fluctuations inside the shear band and we show that the macroscopic mean deformation in the bands is the result of the accumulation of local, intermittent, shear events. The size distribution of those shear events follows the Gutenberg-Richter law. We observe clustering of those events following Omori's law and we apply a declustering method to reveal the causal structure underlying our sequences of events (Houdoux et al. 2021). In my talk, I will focus on recent experimental results regarding the dependence of the series statistics on the driving velocity. We have studied sequences of aftershocks for different compression velocities and we have shown that surprinsingly the aftershock sequences we observe are deformation-dependent and not time-dependent. We discuss such a deformation memory effect in the framework of an Olami-Feder-Christensen model.Houdoux et al. Commun Earth Environ 2, 90 (2021)
Orbital control of relative sea level changes in the Plio-Pleistocene of the Northeast Brazilian Equatorial Margin.
Authors: Tortarolo Lucas , Rabineau Marina , Gorini Christian , Boulila Slah , Do Couto Damien , Dos Reis Tadeu , Guizan Silva Cleverson
Published: February 2023

We address the evolution of the shelf architecture of the Northeast Brazilian Equatorial Margin during the Plio-Pleistocene, using a coupled approach of sequence stratigraphy based on 3D seismic data, and cyclostratigraphy based on well-log data. The main purpose of this study is to highlight the major forcing processes that control evolution and architecture of the shelf during the Plio-Pleistocene.Our results reveal nine pronounced seismic sequences within the Plio-Pleistocene series, which are correlated to the long 405-kyr eccentricity cycles. Inside the two youngest 405-kyr cycles, we observe nine Falling Stage System Tracts (FSST) matching the short (97-128 kyr) eccentricity cycles. Finally, we identify three major depositional episodes (mega-sequences) in the Plio-Pleistocene: (i) the first episode (from ~4 to ~2.4 Ma) is characterized by small amplitudes of sea-level variations with low to none erosive structures and the absence of clear transgressive series, (ii) the second phase (from ~2.4 to ~0.9 Ma) records a drastic increase of erosional features as well as the apparition of thicker transgressive series and slope failures, and (iii) the third phase (from ~0.9 to present-day) is characterized by a dramatic change in the shelf geometry, most of the sediments are deposited on the slope during FSST while the outer shelf is greatly exposed and eroded during low sea levels. Our results suggest that long-term increase in amplitude of sea level variation is the main driver of the geometrical changes of the Brazilian shelf.  Boundaries of mega-sequences at 0.9 and 2.4 Ma likely reflect major climatic phases at respectively the Intensification of Northern Hemisphere Glaciation and the Mid-Pleistocene Transition. A significant change in the shelf architecture at around 0.4 Ma, acting as a prominent shift in the depositional system from one prograding to another aggrading, is likely related to the substantial sea-level rise together with the long-lasting Marine Isotopic Stage 11. We conclude that changes in the Brazilian shelf geometry during the Plio-Pleistocene was likely paced by orbitally forced sea-level cycles superimposed on long-term trends and phases in the climate and sea level.
Rheological behavior of dense granular suspensions of cohesive particles
Authors: Khodabakhshi Alireza , Konidena Sudarshan , Vowinckel Bernhard
Published: February 2023

Intense sediment transport situations such as debris flows and mudslides consisting of fine-grained particles can pose serious threats to human infrastructures and lives. A thorough understanding of the rheology of such cohesive granular flows is crucial to predict the behavior of these types of flow and to mitigate their damaging effects. Whereas the rheology of non-cohesive granular flows has been studied extensively in the literature, the effect of cohesive inter-particle forces on the rheological behavior is still obscure and has not been sufficiently addressed. In this study, employing particle-resolved Direct Numerical Simulations, we simulate non-cohesive and cohesive dense suspensions sheared by moving walls. We perform several high-resolution simulations and compare the rheological parameters of the suspensions for different values of a dimensionless cohesive number, Co. Direct Numerical Simulations enable us to delve into the stress profiles in the vertical and streamwise directions and explore the contribution of different particle and fluid stresses to the total stress in each direction. We will also investigate the microstructure of the suspension and relate the microscopic interactions to macromechanical, rheological behavior of the dense cohesive suspension. 
Evaluating solute-Trapping Induced Non-Fickian Transport in Partially Saturated Porous Media
Authors: Ben-Noah Ilan , Hidalgo Juan J. , Jimenez-Martinez Joaquin , Dentz Marco
Published: February 2023

We study the upscaling of pore-scale solute transport in partially saturated porous media at different saturation degrees. The interaction between structural heterogeneity, phases distribution and small-scale flow dynamics induces complex flow patterns and broad probability distributions of flow. In turn, this spatial distribution of flow velocities, at the pore scale, induces irregular (non-Fickian) transport of dissolved substances (e.g., contaminants), causing an earlier arrival and longer tailing, which may have grave consequences in underestimating risk assessments and prolonged cleanup times of contaminated sites.Here, we suggest an integrated continuous time random walk (CTRW) modeling framework, which accounts for also the entrapping of particles in zones of low flow velocities, to estimate the resident times of solutes in the media. Furthermore, comparing the results of the CTRW model to a well-established numerical simulation method allows a phenomenological evaluation of the model's physical parameters for different conditions (i.e., volume of entrapped air, mean water flow rate, or solute molecular diffusion coefficient).   In this study we show that entrapped air promotes preferential solute transport and solute trapping in low flow regions. Moreover, we demonstrate that the trapping frequency and trapping time depend on the interaction between advection and diffusion (i.e., the Péclet number). An integrative CTRW model captures the effects of trapping in stagnant regions and preferential transport on non-Fickian dispersion of solutes.
Modelling lateral meltwater flow atop the GreenlandIce Sheet’s near-surface ice slabs
Authors: Clerx Nicole , Machguth Horst
Published: February 2023

The Greenland ice sheet is losing mass. Thereby, the location of the runoff limit, the highest elevation from which meltwater finds its way off the ice sheet, plays an important role. Above the runoff limit all meltwater refreezes and does not contribute to mass loss. In recent years surface runoff has increasingly occurred from higher elevations, thereby expanding the area of mass loss: between 1985 and 2020, the maximum runoff limit rose by on average 194 metres, expanding the visible runoff area by around 29%.The observed rise in the runoff limit might be related to intensive meltwater refreezing within the firn which leads to the formation of thick ice layers, also called ice slabs. Our field experiments, carried out at around 1750 m a.s.l. on the K-Transect, have shown that meltwater generated over ice slabs is generally forced to flow laterally: initially through a near-surface slush matrix and then forming streams and rivers. It remains unclear, however, how much of the meltwater contributes to runoff, and which percentage refreezes and contributes to ice slab formation or expansion.Here we present a conceptual quasi 2D-model of runoff, that simulates lateral meltwater flow on top of an ice slab using firn hydrological properties measured on the southwest Greenland ice sheet. We adapted a gridded linear-reservoir runoff routing model to calculate (i) the distance meltwater can travel within one melt season, and (ii) when meltwater breakthrough at the snow surface (i.e. slush formation) occurs. First results provide insight into the evolution of the water table height over time that matches observations made during our summer field campaign. We are exploring ways to incorporate meltwater refreezing, to better understand ice slab evolution and their impact on the fate of meltwater between vertical percolation, refreezing and lateral runoff.
Sustainable Agriculture Waste Management Strategies: Case Study from Al-Ahsa Oasis, Saudi Arabia
Authors: Tawabini Bassam
Published: February 2023

Extended over 85.4 km2 with more than 2.5 million date palm trees, Al-Ahsa oasis in the eastern part of Saudi Arabia is the largest oasis in Arabian Peninsula and probably in the world. The oasis became a World Heritage site in 2018 and has also been part of the UNESCO Creative Cities Network since 2015. The urban expansion and the transition from farms being the main source of income to farms being lifestyle properties, has changed the farm management practices. However, farm ownership continues to be a very strong feature of Al Ahsa communities, with livestock raising integrated with the cultivation of date palms. In oasis farms, date palms products are used as animal feed while animal manure is used as date palm fertilizer. Unfortunately, the huge stockpiles of date palm fronds and burning within the oasis suggest that the waste management practices may not be environmentally sustainable. Therefore, this study was carried out to assess the impact of livestock raising on the oasis farms soil conditions. The methodology followed in the study involved site visits to farms, reviewing related reports and articles on farm management practices and water quality. Key findings of the study indicated that livestock raising on date palm farms has significantly increased over the last 4 decades. Since the 1970’s, the number of farms housing cows has increased from 34% to 100%, and the number with hybrid poultry farms has increased from 4% to 50%. Results indicated that the reuse of all cow and chicken sand / manure mixes, generated on oasis farms, as fertilizer would increase the nitrogen, phosphorus and potassium by 17, 32 and 8 times respectively, over the recommended levels. Moreover, further application of manure from intensive chicken and dairy enterprises located near the oasis as fertilizer is not sustainable and lead to several environmental impacts. To reduce these impacts, the study recommends the development of a composting facility for the date palm fronds which may provide a sustainable alternative waste management system for the green and livestock wastes. In addition, farmers could benefit from both a high volume, low cost mulch that could be produced from date palm pruning, and a low volume, higher cost composted soil conditioner that could be produced from low nutrient shredded green waste and high nutrient livestock waste. Reuse of these recycled products within the urban centers could improve water use efficiency and protect landscape plantings from sand storms, and could replace imported soil conditioners. These alternative waste management strategies will reduce the nutrient pressure on the oasis by redirecting organic products processed from farm wastes for beneficial reuse in urban centers.   
Why should structural solutions for flood control be adapted to climate change?
Authors: hosseinipoor mahdi , Mollaei Rudsary Armin , Yeganeh Yasna , Kazempour Zahra , Danesh-Yazdi Mohammad
Published: February 2023

The combined impacts of climate change and anthropogenic activities have altered runoff generation and flood regime in many regions, worldwide.  While hydraulic structures have been successfully operated to control flood for decades, their expected performance may be currently less certain under the augmented frequency of extreme precipitation events. The goal of this study was to examine the above hypothesis by utilizing both remote sensing and field data on the Imamzadeh Davood catchment in the northern Iran, which experienced a devastating flash flood in the summer of 2022. To this end, we surveyed the main river path to collect data on river morphology, structural characteristics of check dams, and sedimentation patterns. We also processed satellite imagery to extract and temporally trace back land-use land-cover change in the study area. Finally, we used recorded data from synoptic stations to explore the distinct role of extreme precipitation in intensifying the flood hazard. The results proved the occurrence of unprecedented precipitation with a return period of over 100 years, supporting the climate change effect in the region. In-situ observations revealed that all 18 check dams were destroyed between 20% and 100% during the flood event, while higher degree of destruction was observed towards upstream. The sliding and overturning stability analysis demonstrated that all check dams were stable with respect to sliding, while 30% of them were prone to overturning. Given the destruction of all check dams during the flood event, as well as the observed high deposition depth of sediment in the river corridor, we concluded that the shock imposed by the debris flow was responsible for the cascade failure of check dams from upstream to downstream. The findings of this study highlight the need for revisiting the design principles of hydraulic structures, such that they are adapted to the ongoing impacts of climate change in order to increase the resiliency of flood control systems.
Hydrogen underground storage in a saline aquifer at the Ketzin site (Germany) – a numerical pre-feasibility assessment
Authors: Döpp Lea , Weinzierl Wolfgang , Schmidt-Hattenberger Cornelia , Sass Ingo
Published: February 2023

For integrating green hydrogen to the future energy system, underground storage facilities are needed. So far, there is no underground hydrogen pore storage facility in Germany. However, there is a lot of experience in town gas, natural gas , and CO2 underground storage which now can be used for hydrogen storage pre-feasibility assessments, explorations and operations.In this approach the Ketzin anticline (Germany) is used for a pre-feasibility assessment for hydrogen underground storage in a saline aquifer by using experimental and measurement data from its time as a CO2 test site during 2004 to 2017.For this first feasibility assessment we focused on the influence of several reservoir parameters on hydrogen solubility and the production rate. Therefore, the influence of the brine´s salinity, capillary pressure, reservoir pressure and temperature of two potential storage formations at Ketzin site is analyzed.The Stuttgart formation was already used as a CO2 storage formation during the projects CO2SINK, CO2MAN, COMPLETE. Due to loss reduction by a optimal structural trapping the potential hydrogen injection and production well is located at the top of the anticline –  about 1.5 km north to the former CO2 storage test site. Based on Fleury´s experimental data from 2013, including capillary pressure, six parameter setups are created to simulate six hydrogen production and injection cycles.For the second storage formation, the Exter formation, less experimental and measurement data is available. Therefore, six scenarios were designed on the basis of literature values. The end members represent a low and a high hydrogen recovery scenario which combine the best and worsed possible parameter setup for this formation.The results show that it is important to consider the regional conditions individually and to respond to the specifications of the site to minimize economic and safety risks in hydrogen underground storage.
Increasing likelihood of global compound hot-dry extremes from temperature and runoff during the past 120 years
Authors: Min Ruiying , Gu Xihui
Published: February 2023

High temperatures and droughts pose a great threat to the human health, social economy and ecosystems. A large number of previous studies have focused on meteorological hot-dry events (based on temperature and precipitation), but there is a lack of comprehensive studies about hydrological hot-dry events (based on temperature and runoff). Here, using the ensemble empirical mode decomposition method and Copula function, we assess spatio-temporal evolution of global compound hot-dry events from temperature and runoff, and quantify their drivers based on monthly temperature and runoff data during 1902-2019. We find there is a significant warming at an unprecedented pace over the past 118 years, especially in the mid-latitudes of the Northern Hemisphere. However, changes in accumulated trends in precipitation and runoff show complex patterns globally. Probabilities of meteorological and hydrological hot-dry events both have been increasing significantly, but hydrological events are more likely to occur with higher spatial homogeneity, wider coverage and more severe damage. To analyze its underlying driving mechanism, we estimate quantitatively the contribution of high temperature, low runoff and the dependence between high temperature and low runoff to the compound event. High temperature plays a dominant role in the driving mechanism. In several regions, such as Australia, Europe and South America, hot-dry events could be considered as a potential hazard caused by increasing temperatures. Runoff deficit and dependence between the two, together with high temperature, exacerbate the occurrence of compound hot-dry events. Our findings provide a promising direction to predict joint probability of hot-dry events. Hydrological hot-dry events have seldom been considered, so far, in strategic policy formulation and risk assessment. Our results offer a powerful tool to improve planning and strategies to adapt to climate change.
3D MHD Modeling of an Observed Solar Prominence
Authors: Torok Tibor , Mason Emily I. , Downs Cooper , Lionello Roberto , Titov Viacheslav S.
Published: February 2023

The physical mechanisms by which solar prominences (or filaments) form are still not well understood. The presently favored scenario invokes the evaporation of chromospheric plasma via localized heating at the footprints of a magnetic flux rope (MFR) or sheared arcade, and the subsequent condensation of this plasma in the corona due to thermal non-equilibrium (TNE). This scenario has been modeled extensively in one-dimensional (1D) hydrodynamic simulations along static magnetic field lines, and recently also in fully 3D magnetohydrodynamic (MHD) simulations, using idealized MFR configurations. However, such configurations lack the complexity of real prominence magnetic fields. In this presentation, we first briefly discuss our prominence modeling approach for the case of an idealized 3D MFR configuration. We then report on our recent attempts to employ data-constrained MHD simulations to model the formation of observed filaments. To this end, we selected the filament that erupted in a spectacular manner on June 7, 2011 in NOAA AR 11226. To model its formation, we first develop a semi-realistic ("thermodynamic MHD") model of the solar corona, using SDO/HMI data as boundary condition for the magnetic field. Next, we insert an MFR constructed with the RBSL method (Titov et al., 2018) into the source region of the filament. Finally, we impose localized heating at the MFR's footprints. We compare our results with our idealized simulations and discuss the challenges that arise once realistic cases are considered.
On AMOC and climate feedback: Evidence from Coupled and Slab-ocean models
Authors: Eiselt Kai-Uwe , Graversen Rune
Published: February 2023

It has recently been established that in numerical model experiments climate sensitivity and feedback change over time and that this time dependence may result from a so-called “pattern effect”, i.e., changing patterns of surface warming. The Atlantic Meridional Overturning Circulation (AMOC) influences surface warming patterns as it redistributes energy across the globe. Thus, it may be an important factor for climate feedback change over time.In this study, members of the Coupled Model Intercomparison Project (CMIP) phases 5 and 6 are investigated and two groups of models distinguished, one with weak and one with strong feedback change over time. It is found that the model groups differ significantly in the AMOC response to quadrupling of CO2. To investigate if the difference in AMOC development between the two groups may be responsible for the differences in feedback, experiments with a slab-ocean model (SOM) are performed where the AMOC change is mimicked by changing the ocean heat uptake pattern. Especially in the Northern-Hemisphere Extra-Tropics the differences between the CMIP model groups are found to be qualitatively reproduced but other factors are needed to explain differences in the Southern Hemisphere and the Tropics.
An analytical generalization of Budyko framework with physical accounts of climate seasonality and water storage capacity
Authors: Zhang Xu , Li Jinbao , Dong Qianjin , Woods Ross A.
Published: February 2023

The Budyko framework is an effective and widely used method for describing long-term water balance in large catchments. However, it only considers the limits of water and energy in evaporation (E), and ignores the impacts of climate seasonality and water storage capacity (Sc), resulting in errors for Mediterranean climate and catchments with small Sc. Here we combined the Ponce-Shetty model with Budyko hypothesis, and analytically generalized Budyko framework with physical accounts of climate seasonality and Sc. Precipitation (P), potential evaporation (PE), and Sc are used to represent the limits of water, energy, and space for E, respectively. Our results show that previous Budyko-type equations can be treated as special cases of generalized Budyko-type equations with uniform P and PE and infinite Sc. The new generalized equations capture the observed decrease in E due to asynchronous P and PE and small Sc, and perform better than the Budyko-type equations with varying parameters in the contiguous United States with fewer parameters. Overall, our generalization of Budyko framework improves the robustness and accuracy for estimating mean annual E with the aid of physical interpretation, and will facilitate water balance assessment at regional to global scales.
The use of random forest to identify climate and human interference on vegetation NDVI changes in Southwest China
Authors: Wang Yuyi , chen xi
Published: February 2023

Identifying vegetation changes and the associated driving forces provides a valuable reference for developing ecological restoration strategies. However, it remains a challenge to disentangle the impacts of climate, vegetation, and human interference impacts on vegetation changes. In this study, the temporal variations of the Normalized Difference Vegetation Index (NDVI) during 2000 ~ 2015 in space were used to identify the greening (restoration) and browning (degradation) areas in southwest China. The Random Forest (RF) approach was applied to distinguish the main driving forces of the greening and browning areas. Results showed that the RF approach can be effectively used to learn the complex non–linear interactions between vegetation change, local climate, and human interferences. Vegetation greening was prominent in 85.90% of the study area, while 5.59% of the area still experienced significant vegetation degradation. Population pressure was an important factor to alter the sign of long-term vegetation trends. The greening trends are mainly observed in the high elevation areas with low population density (e.g., population density lower than 180 people/km2 and altitudeabove 1000m), which are attributed to both artificial reforestation measures and climate warming. In contrast, the browning trend was concentrated in the low elevation areas with high and temporally intensified population density due to urbanization with a high population density (over 1000 people/km2) and an increased rate (over 20 people/km2 per year). The results of this study strengthen our understanding of the complex convolutions among climate, human activities, and vegetation in southwest China.