bluuebunny/crossref_metadata_2025 huggingface dataset:
Benthic species as mud patrol - modelled effects of bioturbators and biofilms on large-scale estuarine mud and morphology
Authors: Brückner Muriel , Schwarz Christian , Coco Giovanni , Baar Anne , Boechat Albernaz Márcio , Kleinhans Maarten
Published: March 2021

Benthic species that live within estuarine sediments stabilize or destabilize local mud deposits through their eco-engineering activities, affecting the erosion of intertidal sediments. Possibly, the altered magnitudes in eroded sediment affect the large-scale redistribution of fines and hence morphological change. To quantify this biological control on the morphological development of estuaries, we numerically model i) biofilms, ii) two contrasting bioturbating species present in NW-Europe, and iii) their combinations by means of our novel eco-morphodynamic model. The model predicts local mud erodibility based on species pattern, which dynamically evolves from the hydrodynamics, soil mud content, competition and grazing, and is fed back into the hydromorphodynamic computations.

We find that biofilms reduce mud erosion on intertidal floodplains and stabilize estuarine morphology, whereas the two bioturbators significantly enhance inter- and supratidal mud erosion and bed elevation change, leading to a large-scale reduction in deposited mud and a widening of the estuary. In turn, the species-dependent changes in mud content redefines their habitat and leads to a redistribution of species abundances. Here, the eco-engineering affects habitat conditions and species abundance while species interactions determine species dominance. Our results show that species-specific biostabilization and bioturbation determine large-scale morphological change through mud redistribution, and at the same time affect species distribution. This suggests that benthic species have subtly changed estuarine morphology through space and time and that aggravating habitat degradation might lead to large effects on the morphology of future estuaries.
Validation of methods for the assessment of physical vulnerability to dynamic flooding
Authors: Papathoma-Koehle Maria , Dosser Lea , Roesch Florian , Schlögl Matthias , Borga Marco , Erlicher Marcel , Fuchs Sven
Published: March 2021

The importance of assessing the physical vulnerability of assets to natural hazards is indisputable. Recent extreme events have shown that the severity of natural hazards is strongly linked to the vulnerability of the population and the built environment. Physical vulnerability, in particular, is directly connected to monetary damages and interruptions that are in the centre of the interests of several stakeholders including governments, authorities, insurance companies, engineers, and homeowners. A plethora of different approaches is available in the literature, nevertheless, two categories of approaches are the most prominent: vulnerability curves and vulnerability indicators. In this study, both are put to the test by using data from two relatively recent dynamic flood events. In more detail, a physical vulnerability index (PVI) and a Beta model based on damage data from Italy and Austria are validated using recent damage data from an event in Dimaro Folgarida (Trento, Italy) in 2018 and an event in Schallerbach (Tirol, Austria) in 2015. The study does not just validate the methods but also investigates remaining uncertainties related to the assessment of the process intensity on buildings and the calculation of the building value by conducting a sensitivity analysis. 
What slates can tell us about strain localisation and fluid flow in accretionary wedges: a microstructural analysis of deforming foreland basin sediments
Authors: Akker Ismay Vénice , Schrank Christoph E. , Jones Michael W.M. , Kewish Cameron M. , Berger Alfons , Herwegh Marco
Published: March 2021

During the accretion of foreland basin sediments into an accretionary or orogenic wedge, the sediments dehydrate and deform. Both dehydration and deformation intensity increase from the outer to the inner wedge and are a function of metamorphic processes and strain. Here, we study the microstructural evolution of slates from the exhumed Flysch units making up a paleo accretionary wedge in the European Alps. With classic SEM imaging and synchrotron X-ray fluorescence microscopy, we document the evolution of slate fabrics and calcite veins and aim at understanding the role of the evolving slate fabrics for strain localisation and fluid flow at the micro-scale.

The investigated slate samples are from a NW-SE transect covering the outer and inner wedge from 200 to 330 °C. The metamorphic gradient directly correlates with an increasing background strain gradient. With the use of the autocorrelation function, we quantify the evolution of the microfabrics along the metamorphic gradient and document deformation stages from a weakly deformed slate without foliation in the outer wedge to a strongly deformed slate with a dense spaced foliation in the inner wedge. The foliation mainly forms by dissolution-precipitation processes, which increase with increasing metamorphic gradient.

The slate matrix reveals two main sets of veins. The first vein set includes micron-scaled calcite veinlets with very high spatial densities. The second vein set includes layer parallel calcite veins that form vein-arrays (couple of metres thick) in the inner wedge. Both vein sets could have moved large amounts of fluids through the wedge. The spatial distribution of the micron-veinlets reveals that fluids were moved pervasively. In the case of the layer parallel veins forming vein-arrays, fluid flow was localized, supported by the dense spaced foliation formed in the slate matrix in the inner wedge. This way we now establish a direct link between the microstructural evolution in the slate matrix and associated dehydration, where fluids become increasingly channelled towards the inner wedge. Knowing that the vein-arrays have length dimensions in the order or hundreds of metres to kilometres, these structures are important for larger-scale fluid flow, the feeding of fluids into megathrusts and for related seismic activity in the wedge.
 North Atlantic SST and jet stream anomalies related to European heat waves
Authors: Krüger Julian , Kjellsson Joakim , Pilch-Kedzierski Robin , Bumke Karl , Matthes Katja
Published: March 2021

This study highlights the relevance of North Atlantic SSTs and certain jet stream properties for the onset of high European temperatures by using the ERA-5/ERA20c reanalysis product and a targeted experiment with the OpenIFS model. We found that certain European heat wave events could be related to the simultaneous appearance of cold North Atlantic SST events, specific jet stream wave numbers and further to transient and recurrent Rossby wave activity.  

The coexistence of cold North Atlantic sea surface temperature (SST) and positive European surface temperature anomalies during several summer seasons, like in 1994, 2015 and 2018 motivated us to evaluate whether and how widespread and significant North Atlantic SST anomalies could be associated with European heat waves.Therefore we investigated the role of the jet stream in serving as a medium for a downstream signal propagation.  

A composite study reveals that cold North Atlantic SST anomalies in summer are accompanied by a more undulating jet stream and a preferred trough-ridge pattern in the North Atlantic-European sector. A  wave analysis covering two-dimensional probability density functions of phase speed and amplitude after compositing cold SSTs show that cold North Atlantic SST events reveal a preference for a dominance of transient waves. In the presence of a trough during cold North Atlantic events, we obtain a slow-down of the transient waves, but not necessarily an amplification or stationarity. The deceleration of the transient waves result in a longer duration of a trough over the North Atlantic accompanied by a ridge downstream over Europe, favouring the conditions for the onset of European heat episodes.

A study of the jet stream energetics via a kinetic energy power spectrum of meridional wind anomalies reveals that generally a trend shows up towards wave numbers 4 to 6. This is supported by an enhanced activity of specific wave numbers within this increased range during summer seasons of European heat wave events happening in the last two decades. An arising question poses whether the increased energy for a certain wave number originates from an SST forcing or different drivers. We investigate this by performing targeted OpenIFS model runs forced by different SST conditions.
Towards a molecular-based parameterization of the ice nucleation activity of biological macromolecules and its implications for aerosol-cloud interactions
Authors: Zhang Minghui , Khaled Amina , Amato Pierre , Delort Anne-Marie , Ervens Barbara
Published: March 2021

Primary biological aerosol particles (PBAPs) play an important role in mixed-phase clouds as they nucleate ice even at temperatures of T > -10 °C. Current parameterizations of PBAP ice nucleation are based on ice nucleation active surface site (INAS) densities that are derived from freezing experiments. However, only a small fraction of the PBAP surface is responsible for their ice nucleation activity, such as proteins of bacteria cells, fungal spores, pollen polysaccharides and other (unidentified) macromolecules. Based on literature data, we refine the INAS density parameterizations by further parameters:

1) We demonstrate that the ice nucleation activity of such individual macromolecules is much higher than that of PBAPs. It can be shown that INAS of PBAPs can be scaled by the surface fraction of these ice-nucleating molecules.

2) Previous studies suggested that ice nucleation activity tends to be higher for larger macromolecules and their aggregates. We show that these trends hold true for various groups of macromolecules that comprise PBAPs.

Based on these trends, we suggest a more refined parameterization for ice-nucleating macromolecules in different types of PBAPs and even for different species of bacteria, fungi, and pollen. This new parameterization can be considered a step towards a molecular-based approach to predict the ice nucleation activity of the macromolecules in PBAPs based on their biological and chemical properties.

We implement both the traditional INAS parameterization for complete PBAPs and our parameterization for individual molecules in an adiabatic cloud parcel model. The extent will be discussed to which the two parameterizations result in different cloud properties of mixed-phase clouds.
PEP725 a European phenological database
Authors: Ressl Hans , Scheifinger Helfried , Hübner Thomas , Paul Anita , Ungersböck Markus
Published: March 2021

“Phenology – the timing of seasonal activities of animals and plants – is perhaps the simplest process in which to track changes in the ecology of species in response to climate change” (IPCC 2007).

PEP725, the Pan-European Phenological Database, is a European research infrastructure to promote and facilitate phenological research. Its main objective is to build up and maintain a European-wide phenological database with an open, unrestricted data access for science, research and education. So far, 20 European meteorological services and 6 partners from different phenological network operators have joined PEP725.

The PEP725 phenological data base (www.pep725.eu) now offers more than 12 million phenological observations, all of them classified according to the so called BBCH scale. The first datasets in PEP725 date back to 1868; however, there are only a few observations available until 1950. Having accepted the PEP725 data policy and finished the registration, the data download is quick and easy and can be done according to various criteria, e.g., by a specific plant or all data from one country. The integration of new data sets for future partners is also easy to perform due to the flexible structure of the PEP725 database as well as the classification of the observed plants via the so-called gss format (genus, species and subspecies).

PEP725 is funded by EUMETNET, the network of European meteorological services, ZAMG, who is the acting host for PEP, and the Austrian ministry of education, science and research.

The phenological data set has been growing by about 100000 observations per year. Also the number of user registrations has continually been increasing, amounting to 305 new users and more than 28000 downloads in 2020. The greatest number of users are found in China, followed by Germany and the US. To date we could count 78 reviewed publications based on the PEP725 data set with 18 in 2020 and a total of 9 published in Nature and one in Science.

The data base statistics demonstrate the great demand and potential of the PEP725 phenological data set, which urgently needs development including a facilitated access, gridded versions and near real time products to attract a greater range of users.
The role of aerodynamic resistance in thermal remote sensing-based evapotranspiration models
Authors: Trebs Ivonne , Mallick Kaniska , Bhattarai Nishan , Sulis Mauro , Cleverly James , Woodgate Will , Silberstein Richard , Hinko-Najera Nina , Beringer Jason , Su Zhongbo , Boulet Gilles
Published: March 2021

‘Aerodynamic resistance’ (hereafter ra) is a preeminent variable in the modelling of evapotranspiration (ET), and its accurate quantification plays a critical role in determining the performance and consistency of thermal remote sensing-based surface energy balance (SEB) models for estimating ET at local to regional scales. Atmospheric stability links ra with land surface temperature (LST) and the representation of their interactions in the SEB models determines the accuracy of ET estimates.

The present study investigates the influence of ra and its relation to LST uncertainties on the performance of three structurally different SEB models by combining nine OzFlux eddy covariance datasets from 2011 to 2019 from sites of different aridity in Australia with MODIS Terra and Aqua LST and leaf area index (LAI) products. Simulations of the latent heat flux (LE, energy equivalent of ET in W/m2) from the SPARSE (Soil Plant Atmosphere and Remote Sensing Evapotranspiration), SEBS (Surface Energy Balance System) and STIC (Surface Temperature Initiated Closure) models forced with MODIS LST, LAI, and in-situ meteorological datasets were evaluated using observed flux data across water-limited (semi-arid and arid) and radiation-limited (mesic) ecosystems.

Our results revealed that the three models tend to overestimate instantaneous LE in the water-limited shrubland, woodland and grassland ecosystems by up to 60% on average, which was caused by an underestimation of the sensible heat flux (H). LE overestimation was associated with discrepancies in ra retrievals under conditions of high atmospheric instability, during which errors in LST (expressed as the difference between MODIS LST and in-situ LST) apparently played a minor role. On the other hand, a positive bias in LST coincides with low ra and causes slight underestimation of LE at the water-limited sites. The impact of ra on the LE residual error was found to be of the same magnitude as the influence of errors in LST in the semi-arid ecosystems as indicated by variable importance in projection (VIP) coefficients from partial least squares regression above unity. In contrast, our results for mesic forest ecosystems indicated minor dependency on ra for modelling LE (VIP<0.4), which was due to a higher roughness length and lower LST resulting in dominance of mechanically generated turbulence, thereby diminishing the importance of atmospheric stability in the determination of ra.
A probabilistic model for assessing debris flow propagation at regional scale: a case study in Campania region, Italy
Authors: Crescenzo Luca , Pecoraro Gaetano , Calvello Michele , Guthrie Richard
Published: March 2021

Debris flows and debris avalanches are rapid to extremely rapid landslides that tend to travel considerable distances from their source areas. Interaction between debris flows and elements at risk along their travel path may result in potentially significant destructive consequences. One of the critical challenges to overcome with respect to debris flow risk is, therefore, the credible prediction of their size, travel path, runout distance, and depths of erosion and deposition. To these purposes, at slope or catchment scale, sophisticated physically-based models, appropriately considering several factors and phenomena controlling the slope failure mechanisms, may be used. These models, however, are computationally costly and time consuming, and that significantly hinders their applicability at regional scale. Indeed, at regional scale, debris flows hazard assessment is usually carried out by means of qualitative approaches relying on field surveys, geomorphological knowledge, geometric features, and expert judgement.

In this study, a quantitative modelling approach based on cellular automata methods, wherein individual cells move across a digital elevation model (DEM) landscape following behavioral rules defined probabilistically, is proposed and tested. The adopted model, called LABS, is able to estimate erosion and deposition soil volumes along a debris flow path by deploying at the source areas autonomous subroutines, called agents, over a 5 m spatial resolution DEM, which provides the basic information to each agent in each time-step. Rules for scour and deposition are based on mass balance considerations and independent probability distributions defined as a function of slope DEM-derived values and a series of model input parameters. The probabilistic rules defined in the model are based on data gathered for debris flows and debris avalanches that mainly occurred in western Canada. This study mainly addresses the applicability and the reliability of this modelling approach to areas in southern Italy, in Campania region, historically affected by debris flows in pyroclastic soils. To this aim, information on inventoried debris flows is used in different study areas to evaluate the effect on the predictions of the model input parameter values, as well as of different native DEM resolutions.
Leaching of trace metals (Pb, Zn) from contaminated tailings: New insight from a modelling approach
Authors: Mertz Samuel , Le Forestier Lydie , Bataillard Philippe , Devau Nicolas
Published: March 2021

Reclamation measurements are commonly applied to mitigate the leaching of metal pollutants in order to reduce the risk for humans and the environment. Organic and/or inorganic amendments are often recommended to stabilize tailings and to reduce leaching of contaminants. In a recent microcosm percolation experiment (Thouin et al., 2019), the addition of a mining slurry called ochre and manure, either alone or in combination, drastically reduced the leaching of several metal pollutants, notably Pb. Nevertheless, the biogeochemical processes involved in the immobilization of metal pollutants remain unknown, preventing the management of this remediation technique from being optimized and its extension to other sites.  To fill this gap, a multicomponent reactive model was developed to simulate and forecast the impact of amendments on the leaching of metal pollutants. This model accounts for the following biogeochemical processes: kinetically-controlled dissolution and precipitation reactions, sorption reactions (i.e. surface complexation reactions), water-gas interactions and microbially-driven redox reactions with an explicit microbial growth. For all treatments, simulations revealed that Pb reactivity followed dynamic patterns driven by watering steps. The decrease in Pb concentration in the leachates of amended tailings compared to untreated tailings was also accurately reproduced. In untreated tailings, Pb reactivity is mainly controlled by the dissolution of Pb-bearing mineral phases. These reactions were maintained in thermodynamic disequilibrium due to the renewal of pore solution at each watering step. In amended tailings, this pattern was strengthened as the iron oxides contributed by ochre maintained a low Pb concentration in pore solution by sorbing released Pb. Sorption reactions were enhanced by the increase in pH induced by the dissolution of calcium carbonate initially present in ochre. The latter reaction was partially counterbalanced in tailings amended with manure as organic matter provided sufficient energy to fuel microbial aerobic respiration, leading to the release of protons. Pb desorption was promoted by this pH drop. By providing a better understanding of the effect of amendment, this multicomponent reactive model is a powerful tool to optimize the reclamation of tailings, in order to limit contaminant transfer to the environment.

Thouin H. et al. (2019), Appl. Geochem. 111, 104438
Designing sustainable energy plans for the Greater Mekong Subregion
Authors: Galelli Stefano , Siala Kais , Chowdhury AFM Kamal , Dang Thanh Duc
Published: March 2021

Fossil fuels and hydropower dams have long been at the backbone of power supply systems in the Greater Mekong Subregion (GMS), an energy policy catalyzed by the direct availability of these resources, the backing of foreign investments, and the limited coordination among the many decision-makers. Such policy has resulted in large externalities: gas and coal-fired plants contribute to the carbon footprint of all GMS countries, particularly Thailand; dams have affected the riverine ecosystems, impacting entire economic sectors. According to the official energy plans, coal will be soon sidelined, but dams will keep playing an important role. That is despite the availability of solar and other renewable resources. Is it possible to design more sustainable energy plans for the GMS? Can we limit the number of dams that will be built in the near future? What are the main technologies and policies that should be prioritized? To answer these questions, we developed a spatially-distributed numerical model that co-optimizes capacity expansion as well as hourly dispatch of generation, transmission, and storage. The model is applied to Thailand, Laos, and Cambodia, over a planning period spanning from 2016 to 2037. Optimization results show that the generation capacity planned by these countries could be met in a more sustainable manner by relying on solar PV, which could supply about one third of the projected electricity demand. Investments in renewable energy should be supported by cross-border grid interconnections, which would connect load centers to more production sites, easing the supply-demand balancing. To put the analysis in a broader water-energy context, we also assess the impact of current and proposed energy plans on river connectivity and flows. Overall, our analysis demonstrates that there are untapped opportunities for untying the fate of the Mekong River basin from that of power supply and economic development.
Internal wave shoaling in nearly linear stratifications
Authors: Stastna Marek , Lamb Kevin
Published: March 2021

In the theory of internal waves in the coastal ocean, linear stratification plays an exceptional role. This is because the nonlinearity coefficient in KdV theory vanishes, and in the case of large amplitude waves, the DJL theory linearizes and fails to give solitary wave solutions. We consider small, physically consistent perturbations of a linearly stratified fluid that would result from a localized mixing near a particular depth. We demonstrate that the DJL equation does yield exact internal solitary waves in this case. These waves are long due to the weak nonlinearity, and we explore how this weak nonlinearity manifests during shoaling.
Experimental budgets of OH, HO2 and RO2 radicals during the JULIAC 2019 campaign
Authors: Cho Changmin , Hofzumahaus Andreas , Fuchs Hendrik , Holland Frank , Bohn Birger , Bloss William J. , Dorn Hans-Peter , Glowania Marvin , Hohaus Torsten , Lu Liu , Lakshmisha Chandrakiran , Niether Doreen , Monks Paul S. , Reimer David , Rohrer Franz , Sommariva Roberto , Tan Zhaofeng , Tillmann Ralf , Kiendler-Scharr Astrid , Wahner Andreas
Published: March 2021

The Jülich Atmospheric Chemistry Project campaign (JULIAC) was performed using the atmospheric simulation chamber SAPHIR at Forschungszentrum Jülich (FZJ), Germany. Ambient air was continuously drawn into the chamber through a 50m high inlet line for one month in each season throughout 2019. The residence time of air inside the chamber was one hour. As the sampling point is surrounded by a mixed deciduous forest and is located close to a small–size city (Jülich), the sampled air was influenced by both anthropogenic and biogenic emissions. Measurements included hydroxyl radical (OH) achieved by laser induced fluorescence (LIF) instrument that implemented a newly implemented chemical modulation reactor (CMR) and by differential optical absorption spectroscopy (DOAS). Measurement of both instruments were in good agreement within about 10% and showed no evidence of unknown OH interferences. In addition to OH, hydroxyl and peroxy radicals (HO2 and RO2, respectively), and OH reactivity (kOH, inverse of the OH lifetime) were measured together with a comprehensive set of trace gases concentrations and aerosol properties, allowing for the investigation of the seasonal and diurnal variation of atmospheric oxidant concentrations and their roles in the degradation of volatile organic compounds (VOCs) and contribution to secondary pollutants (ozone and particles).

The experimental budget analyses of OH, HO2, RO2, and ROx radical production and destruction rate will be presented for the campaigns in spring and summer (April and August). For most conditions, the concentrations of radicals were sustained by regeneration of HO2 and RO2 radicals via reactions with nitric oxide (NO). The highest radical turnover rates of up to 17 ppbv·hr-1 was observed during a heat wave period in August. For NO levels below 1ppbv, the budget shows a missing OH radical source up to 4 ppbv h-1, while HO2 and RO2 productionand destruction rates were balanced. Above 2 ppbv of NO, missing HO2 production and RO2 loss paths with rates of up to 5 ppbv h-1 were found. In addition, the dataset allows for a detail examination of the importance of radical production and destruction processes from isomerization reactions, HO2 uptake on aerosol, chlorine nitrate chemistry.
A dilemma of small hydropower plants: Design with uncertainty or uncertainty within design?
Authors: Sakki Georgia-Konstantina , Tsoukalas Ioannis , Kossieris Panagiotis , Efstratiadis Andreas
Published: March 2021

Small hydropower plants (SHPPs) are subject to multiple uncertainties and complexities, despite their limited scale. These uncertainties are often ignored in the typical engineering practice, which results in risky design. As this type of renewable energy rapidly penetrates the electricity mix, the impacts of their uncertainties, exogenous and endogenous, become critical. In this vein, we develop a stochastic simulation-optimization framework tailored for small hydropower plants. First, we investigate the underlying multicriteria design problem and its peculiarities, in order to determine a best-compromise performance metric that ensures efficient and effective optimizations. Next, we adjust to the optimal design problem a modular uncertainty assessment procedure. This combines statistical and stochastic approaches to quantify the uncertainty of the inflow process per se, the associated input data, the initial selection of efficiency curves for the turbine mixing in the design phase, as well as the drop of efficiency due to aging effects. Overall, we propose a holistic framework for the optimal design of SHPPs, highlighting the added value of considering the stochasticity of input processes and parameters. The novelty of this approach is the transition from the conventional to the uncertainty-aware design; from the unique value to Pareto-optimality, and finally to the reliability of the expected performance, in terms of investment costs, hydropower production, and associated revenues.
Subsoil organic carbon turnover is dominantly controlled by soil properties in grasslands across China
Authors: Shi Yuehong , Tang Xiaolu , Yu Peng , Xu Li , Chen Guo , Cao Longxi , Song Ci , Cai Chunju , Li Jingji
Published: March 2021

Soil carbon turnover time (τ, year) is an important indicator of soil carbon stability, and a major factor in determining soil carbon sequestration capacity. Many studies investigated τ in the topsoil or the first meter underground, however, little is known about subsoil τ (0.2 – 1.0 m) and its environmental drivers, while world subsoils below 0.2 m accounts for the majority of total soil organic carbon (SOC) stock and may be as sensitive as that of the topsoil to climate change. We used the observations from the published literatures to estimate subsoil τ (the ratio of SOC stock to net primary productivity) in grasslands across China and employed regression analysis to detect the environmental controls on subsoil τ. Finally, structural equation modelling (SEM) was applied to identify the dominant environmental driver (including climate, vegetation and soil). Results showed that subsoil τ varied greatly from 5.52 to 702.17 years, and the mean (± standard deviation) subsoil τ was 118.5 ± 97.8 years. Subsoil τ varied significantly among different grassland types that it was 164.0 ± 112.0 years for alpine meadow, 107.0 ± 47.9 years for alpine steppe, 177.0 ± 143.0 years for temperate desert steppe, 96.6 ± 88.7 years for temperate meadow steppe, 101.0 ± 75.9 years for temperate typical steppe. Subsoil τ significantly and negatively correlated (p < 0.05) with vegetation index, leaf area index and gross primary production, highlighting the importance of vegetation on τ. Mean annual temperature (MAT) and precipitation (MAP) had a negative impact on subsoil τ, indicating a faster turnover of soil carbon with the increasing of MAT or MAP under ongoing climate change. SEM showed that soil properties, such as soil bulk density, cation exchange capacity and soil silt, were the most important variables driving subsoil τ, challenging our current understanding of climatic drivers (MAT and MAP) controlling on topsoil τ, further providing new evidence that different mechanisms control topsoil and subsoil τ. These conclusions demonstrated that different environmental controls should be considered for reliable prediction of soil carbon dynamics in the top and subsoils in biogeochemical models or earth system models at regional or global scales.
Combination Service for Time-variable Gravity Fields (COST-G): operational GRACE-FO combination and validation of Chinese GRACE time-series
Authors: Meyer Ulrich , Lasser Martin , Jäggi Adrian , Dahle Christoph , Flechtner Frank , Kvas Andreas , Behzadpour Saniya , Mayer-Gürr Torsten , Lemoine Jean-Michel , Koch Igor , Flury Jakob , Bourgogne Stephane , Groh Andreas , Eicker Annette , Förste Christoph , Luo Zhicai , Ran Jiangjun , Shen Yunzhong , Zhao Qile , Feng Wei ,   COST-G Team
Published: March 2021

The Combination Service for Time-variable Gravity Fields (COST-G) of the International Association of Geodesy (IAG) provides combined monthly gravity fields of its associated and partner Analysis Centers (ACs). In November 2020, the combination of monthly GRACE-FO gravity fields started its operational mode, providing consolidated L2 (spherical harmonics) and L3 (gridded and post- processed) products with a latency of currently 3 months. We present an overview and quality assessment of the available products.

COST-G aims at the extension of its service to include further GRACE and GRACE-FO analysis centers. In January 2020 a collaboration with representatives of five Chinese ACs was initiated, who provided GRACE time-series according to the COST-G requirements. We present the results of a test combination with the Chinese AC models, including comparison and quality assessment of all contributing time-series and validation of the combined gravity fields.
Impact of the model representation of PBL and convection on the PM concentrations over Europe
Authors: Bartík Lukáš , Huszar Peter , Belda Michal
Published: March 2021

The impacts of different implementations of turbulence and convection in the Regional Climate Model (RegCM, version 4.6) on the ability to predict the particle matter (PM) concentrations in the lower troposphere over selected regions of Europe are presented. PM were simulated by the chemical transport model CAMx (Comprehensive Air quality Model with extensions, version 6.50) driven by RegCM meteorology using offline coupling of these two models. The results from four simulations for a European domain driven by two different PBL parametrizations (marked as Holtslag and UW) and two different convection parameterizations (marked as Grell and Tiedtke) are compared over the four regions of Europe, namely the Alps, Benelux, Po Valley and Central Europe. Spatial differences as well vertical profiles are contrasted with each other from the different configurations. Validation of the overall PM2.5 concentrations based on EMEP data has shown better agreement between simulated and ground measured values for the simulations driven by UW scheme of PBL.
A Numerical Study of Rockslide-Structure Interactions in a Dip Slope Disaster by 3D Discrete Element Modeling 
Authors: Lee Chung-Hsun , Lin Cheng-Han , Lin Ming-Lang
Published: March 2021

The past decade has witnessed increasing case studies on the application of 3D discrete element modeling to assess potential rockslide disasters. The assessment is usually based only on the influence area related to kinematic process and final deposition by the simulation. Currently, the hazard of the rockslide-structure interaction is not well defined, and only a few studies have quantality this behavior with a parametric analysis. A dip slope disaster case history on 18 August 1997 in Taiwan was simulated in this study using discrete element method (DEM). The landslide intensely damaged a five-floor building complex of the Lincoln community and caused 28 death. This study first gathered historical aerial images, geology maps of 1:50,000 scale, post-disaster investigation reports, and in-situ photos to clarify the geological and geometry conditions of the dip slope and its spatial relationship to the Lincoln community. Most importantly, a 3D geomechanical model was developed for the numerical study. With the advantage of DEM analysis on large deformation problems, the entire impact process of the dip slope failure was simulated, starting from rock mass sliding to collision and breaking during movement, impacting on the structural buildings and progressive failure of the structures. The simulated results agree well with the field observation after the incident in 1997. The parametric results show that the configuration of the geological discontinuity dominates the magnitude of the potential sliding block, and the rockslide-structure interactions are affected by the relative location between rock slope and buildings and the strengths of rock mass and structure elements. Overall, the 3D DEM-based simulation provides qualitative information on the impact process of the rockslide and the damage states of the building complex. This validated numerical approach can be a valuable tool for assessing the building vulnerability to rockslide with scenario study.
Mars-solar wind interaction in a global hybrid model: plasma waves and ion dynamics
Authors: Jarvinen Riku , Kallio Esa , Pulkkinen Tuija
Published: March 2021

We discuss the solar wind interaction with Mars in a self-consistent, 3-dimensional global hybrid simulation, where ions are treated as macroscopic particle clouds moving under the Lorentz force and electrons form a charge-neutralizing fluid. In the model, ion populations include both the solar wind and planetary ions. We concentrate on the formation of plasma waves near Mars. Especially, we analyze properties of large-scale waves in the ion foreshock and their transmission in the magnetosheath. Further, we study the coupling of the waves with ion dynamics in the Martian plasma environment. We discuss the solar wind interaction with Mars in a self-consistent, 3-dimensional global hybrid simulation, where ions are treated as macroscopic particle clouds moving under the Lorentz force and electrons form a charge-neutralizing fluid. In the model, ion populations include both the solar wind and planetary ions. We concentrate on the formation of plasma waves near Mars. Especially, we analyze properties of large-scale waves in the ion foreshock and their transmission in the magnetosheath. Further, we study the coupling of the waves with ion dynamics in the Martian plasma environment. Finally, we compare these Mars simulations to our earlier global hybrid modeling of Venus and Mercury to investigate how the waves and ion dynamics depend on the distance from the Sun and the size of a planetary plasma environment.

References:

Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Oxygen Ion Escape From Venus Is Modulated by Ultra-Low Frequency Waves, Geophys. Res. Lett., 47, 11, doi:10.1029/2020GL087462

Jarvinen R., Alho M., Kallio E., Pulkkinen T.I., 2020, Ultra-low frequency waves in the ion foreshock of Mercury: A global hybrid modeling study, Mon. Notices Royal Astron. Soc., 491, 3, 4147-4161, doi:10.1093/mnras/stz3257 
A process-based soil erosion model ensemble to reduce model uncertainty in climate change impact assessments
Authors: Eekhout Joris , Millares-Valenzuela Agustín , Martínez-Salvador Alberto , García-Lorenzo Rafael , Pérez-Cutillas Pedro , Conesa-García Carmelo , de Vente Joris
Published: March 2021

The impact of climate change on future soil loss is commonly assessed with soil erosion models, which are potentially an important source of uncertainty. Here we propose a soil erosion model ensemble, with the aim to reduce the model uncertainty in climate change impact assessments. The model ensemble consisted of five continuous process-based soil erosion models that run at a daily time step, i.e. DHSVM, HSPF, INCA, MMF and SHETRAN. All models simulate detachment by raindrop impact (interrill erosion), detachment by runoff (rill erosion) and immediate deposition of sediment within the cell of its origin. The models were implemented in the SPHY hydrological model. The soil erosion model ensemble was applied in a semi-arid catchment in the southeast of Spain. We applied three future climate scenarios based on global mean temperature rise (+1.5, +2 and +3 ºC). Data from two contrasting regional climate models were used to assess how an increase and a decrease in extreme precipitation affect model uncertainty. Soil loss is projected to increase and decrease under climate change, mostly reflecting the change in extreme precipitation. Model uncertainty is found to increase with increasing slope, extreme precipitation and runoff, which reveals some inherent differences in model assumptions among the five models. Moreover, the model uncertainty increases in all climate change scenarios, independent on the projected change in annual precipitation and extreme precipitation. This supports the importance to consider model uncertainty through model ensembles of climate, hydrology, and soil erosion in climate change impact assessments.

This research was funded by ERDF/Spanish Ministry of Science, Innovation and Universities - State Research Agency (AEI) /Project CGL2017-84625-C2-1-R; State Program for Research, Development and Innovation Focused on the Challenges of Society.
A machine learning approach for Greenland ice sheet altimetric mass balance
Authors: Simonsen Sebastian B. , Barletta Valentina R. , Colgan William , Sørensen Louise  Sandberg
Published: March 2021

Satellite altimeters have monitored the surface elevation change of the Greenland ice sheet since 1978 and with an ice-sheet wide coverage since 1991. The satellite altimeters of interest for Greenland mass balance studies operate at different wavelengths; Ku-band radar, Ka-band radar, infrared laser, and visible laser. Some of the applied wavelengths can penetrate the surface in snow-covered regions and map the elevation change of subsurface layers. Especially the longer radar wavelength can penetrate the upper meters of the snow cover, whereas the infrared laser measurements from ICESat observes the snow-air interface of ice sheets. The pure surface elevation change derived from ICESat has been widely used in mass balance studies and may provide a benchmark for altimetric mass balance estimates after being corrected for changes in the firn-air content. The Ku-band radar observation provides the longest time series of ice sheet volume change, but the record is more difficult to convert into mass balance due to climate-induced variations in the surface penetration.

Here, we apply machine learning to build an empirical calibration method for converting the observed radar-derived volume change into mass balance. We train the machine learning model during the limited period of coinciding laser and radar satellite altimetry data (2003-2009). The radar and laser datasets are not sufficient to guide the empirical calibration alone. Hence, additional datasets are used to help build a stable predictor needed for radar calibration, such as ice velocity.  

We focus on the lessons learned from this machine learning approach but also highlight results from the resulting 28-yearlong time series of Greenland ice sheet mass balance. For example, the Greenland Ice Sheet contribution to global sea-level rise has been 12.1±2.3 mm since 1992, with more than 80% of this originating after 2003.
The interaction between society changes and hydrological extremes: the case of Yangtze River Basin, before and after the 1931 flood
Authors: Liu Chang , Kawasaki Akiyuki , Shiroyama Tomoko
Published: March 2021

As the longest river in Asia, the Yangtze River has shown its impact on human societies with floods recorded since 12th century. In 1931, the Yangtze River has manifested its force again with one of the deadliest floods ever recorded in Chinese history, causing 422,499 casualties, damages to more than 25.2 million people and 58.7 billion m2 farmland. The impact of the 1931 flood, resulting in the increment of rice price, has remained till 1933. Researches on the 1931 flood damage has shown its direct causation including political corruption, technical backwardness, and meteorological abnormality. However, in a long-term period, it is still unclear if the change of society has intensified the vulnerability of flood or some hydrological extremes has accelerated the social transformations. Here we propose a conceptual socio-hydrological framework within which the mutual influence between society and water system is analyzed. To address the issue of data scarcity, we applied the Water and Energy Budget-based Distributed Hydrological Model (WEB-DHM) to reconstruct the hydrological conditions in the early 20th century of China, based on which the potential rice production was estimated. With the reconstructed data, we found that the change of the social structure of villages aggravated the vulnerability of agricultural production towards natural hazards, and hydrological extremes speeded-up such structure change. Our results demonstrate how reconstructed data is likely to help comprehend a socio-hydrology system under a conceptual framework, shedding light on the inner correlation of a pre-industrial society like the early 20th century of China. We anticipate our study to be a starting point for more sophisticated socio-hydrological models, which will likely to be applicable to many other regions and times.
A molecular dynamic study of Soil Organic Matter stabilization mechanisms
Authors: Galicia-Andrés Edgar , Escalona Yerko , Grančič Peter , Oostenbrink Chris , Tunega Daniel , Gerzabek Marthin H.
Published: March 2021

It is well known that some fractions of soil organic matter (SOM) can resist to physical and (bio)chemical degradation which can be attributed to factors ranging from molecular properties to the preference for digesting other molecular species by microorganisms. Some mechanisms, by which organic matter is protected, are often referred to as: physical stabilization through microaggregation, chemical stabilization by formation of SOM-mineral aggregates, and biochemical stabilization through the formation of recalcitrant SOM.

Protection mechanisms are responsible for the accumulation process of organic carbon, reducing the exposure of organic matter and making it less vulnerable to microbial, enzymatic or chemical attacks. In these mechanisms, water molecular bridges and metal cation bridges play a key role. Cation bridges serve as aggregation sites on humic substances, forming dense matter, in comparison to systems where bridges are missing. This effect is enhanced in systems with cations at higher oxidation states.

By using the modeler tool developed in our group (Vienna Soil–Organic–Matter Modeler, VSOMM2) (Escalona et al., 2021), we generated aggregate models of humic substances at atomistic scale reflecting the diversity in composition, size and conformations of the constituting molecules. Further, we built models of organo-clay aggregates using kaolinite and montmorillonite as typical soil minerals. This allowed a systematic study to understand the effect of the surrounding environment at microscopic scale, not fully accessible experimentally.

Molecular simulations of the adsorption process of SOM aggregates on the reactive surfaces of led to two observations: 1) the humic substances aggregates were able to interact with the reactive surfaces mainly via hydrogen bonds forming stable organic matter-clay complexes and 2) the aggregates subsequently lost rigidity and stability after metal cations removing, consequently leading to a gradual loss of humic substance molecules, evidencing the role of metal cations in the protection mechanism of soil organic matter aggregates and possibly explaining its recalcitrance (Galicia-Andrés et al., 2021).

References

Escalona, Y., Petrov, D., & Oostenbrink, C. (2021). Vienna soil organic matter modeler 2 (VSOMM2). Journal of Molecular Graphics and Modelling, 103, 107817. https://doi.org/10.1016/j.jmgm.2020.107817

Galicia-Andrés, E., Grančič, P., Gerzabek, M. H., Oostenbrink, C., & Tunega, D. (2021). Modeling of interactions in natural and synthetic organoclays. In I. C. Sainz Diaz (Ed.), Computational modeling in clay mineralogy.
Metallogeny of the Zahedan-Nehbandan magmatic belt and implications to porphyry Cu exploration in southeastern Iran
Authors: Soleymani Majid , Niroomand Shojaeddin , Rajabi Abdorrahman , Monecke Thomas , Modabberi Soroush
Published: March 2021

The Late Cretaceous to Eocene Sistan suture zone in southeastern Iran separates the Lut continental block in the west from the Afghan continental block in the east. A major belt of Oligocene to Miocene igneous rocks occurs between the cities of Zahedan and Nehbandan, stretching for ~200 km from south to north parallel to the border with Pakistan and Afghanistan. Known porphyry Cu mineralization is associated with the intrusions and intrusive complexes at Kuh-e Janja (16.5+2.0 Ma), Kuh-e Seyasteragi (19.2+ 1.4 Ma), Kuh-e Assagie (27.5+2.0 Ma), and Kuh-e Lar (32.8+3.0 Ma).

Small intrusions and intrusive complexes in the Zahedan-Nehbandan magmatic belt are mostly intermediate to felsic in composition and have calc-alkaline or shoshonitic affinities. Associated volcanic and volcaniclastic rocks are common. The igneous rocks are hosted by deformed late Cretaceous to Eocene flysch sequences that formed in the Sefidabeh forearc basin developed during the subduction and closure of the Sistan ocean. The geochemical composition of the intrusive rocks and their ages suggest that igneous activity and related mineralization in the Zahedan-Nehbandan magmatic belt may have formed as a result of post-collisional processes. The locations of the intrusive centers in the Kuh-e Assagie and Kuh-e Lar may be controlled by strike-slip faults, which are major post-collisional structures.

The recent discovery of the Janja porphyry Cu-Au-Mo deposit below Quaternary alluvial terraces highlights the exploration potential of the Zahedan-Nehbandan magmatic belt. In addition to post-collisional porphyry deposits, other deposit types such as skarns, polymetallic veins, or epithermal deposits may be hidden below the regionally extensive Quaternary cover.