bluuebunny/crossref_metadata_2025 huggingface dataset:
On the surface apparent reflectance exploitation: Entangled Solar Induced Fluorescence emission and aerosol scattering effects at oxygen absorption regions
Authors: Sabater Neus , Kolmonen Pekka , Alonso Luis , Vicent Jorge , Moreno José , Arola Antti
Published: March 2020

Monitoring vegetation photosynthetic activity and its link with the carbon cycle at a global scale is a leading breakthrough that the scientific community has been seeking in recent years. Pursuing this goal, one of the most important advances in the last decade has been the measurement of the Solar Induced Fluorescence (SIF) at a satellite scale. Current satellite-derived SIF estimations provide SIF measured at certain specific wavelengths depending on the retrieval strategy and the instrument capabilities. However, for the time being, no global observations of the total spectrally resolved and integrated SIF signal have been yet achieved. In a near-future context, spectrally resolved SIF estimations will be provided by missions such as the FLuorescence EXplorer (FLEX) from the European Space Agency.

When disentangling the total SIF contribution, emitted between 650-800 nm, from the acquired satellite signal, molecular and aerosol absorption and scattering effects must be carefully accounted for.  Particularly, within the oxygen absorption features, the characterization of the aerosol scattering effects represents the most critical step prior to the SIF estimation.

In the context of the FLEX/Sentinel-3 tandem mission concept, this work presents a novel technique that refines any a priori aerosol characterization process through the exploitation of the high spectral resolution surface apparent reflectance signal at the oxygen absorption regions. Within the absorption features, SIF contribution on satellite-derived surface apparent reflectance generates a characteristic peaky spectrum. However, the shape of these peaks can be simultaneously distorted through the atmospheric correction process due to inaccuracies in the aerosol characterization among other secondary sources. Inaccuracies in the estimation of aerosol optical thickness, Angstrom exponent, asymmetry of the scattering or single scattering albedo translate into characteristic distortions in the shape of the peaks in the apparent reflectance. This particular behaviour allows inferring the magnitude of the errors and correcting them. The presented technique improves the accuracy of any a priori aerosol retrieval.

Authors expect this study to be also of interest to other hyperspectral missions when exploiting, at high spectral resolution, information from oxygen absorption regions.
Reliability Ensemble Averaging (REA) of the European regional climate change
Authors: Nogherotto Rita , Stocchi Paolo , Coppola Erika , Giorgi Filippo
Published: March 2020

The Reliability Ensemble Averaging (REA) method calculates average, uncertainty range and a measure of reliability of simulated regional climate changes from ensembles of different model simulations. The REA method is applied to mean seasonal temperature and precipitation changes in three different European spatial regimes in the period 2041-2060 and 2081-2100 relative to the reference period 1995-2014. Regional ensemble results of 55 scenario simulations for the RCP8.5 and RCP2.6 at 0.11 degree resolution over the common EURO-CORDEX domain, using 8 GCMs and 11 RCMs, are compared with the driving CMIP5 global models. For each region we show the median and the 25th-75th and 5th-95th percentile spreads of the weighted temperature and precipitation change. The spread of the changes (both 25th-75th and 5th-95th percentiles) are strongly reduced by the weightening as expected, while the best estimate changes (median) of the projection ranges varies according to the region and the season. The method is also applied to evaluate the reliability of the extreme precipitation simulations.

 
New paleoelevation constraints on the Mid-Miocene Central Alps
Authors: Krsnik Emilija , Methner Katharina , Löffler Niklas , Kempf Oliver , Fiebig Jens , Mulch Andreas
Published: March 2020

Reconstructing past elevations of mountain ranges improves our understanding of crustal- and mantle-scale geodynamic processes involved in formation of orogenic belts. Recent studies suggest that slab breakoff beneath the Central Alps occured ~30 Ma ago (e.g. Schlunegger and Castelltort, 2016), while the breakoff reached the Eastern Alps about 10 Ma later (~20 Ma, e.g. Handy et al., 2015). The proposed west-to-east slab tear migration would imply variations in topography. This raises the question of a diachronous surface uplift history for the Central and Eastern Alps. Although being extremely well studied over the last century and serving as a prime exemple for orogenic belt evolution, there are very few investigations addressing the Neogene paleoelevation history of the European Alps. Obtained paleoelevation constraints suffer from inconsistency and range from average elevations of 2300 m (Kocsis et al., 2007) to at least 5000 m (e.g. Sharp et al., 2005).

In order to provide quantitative robust paleoelevation estimates for the Mid-Miocene Central Alps we applied stable isotope paleoaltimetry on authigenic soil carbonates from the Northern Alpine Foreland Basin (NAFB) and contrast these with syntectonic high-Alpine fault zone mica. This δ-δ paleoaltimetry approach benefits from the advantage of comparing a low-elevation site and a high-elevation site of the same age which allows us to circumvent the basic issue of climate bias in paleoaltimetry studies.

We obtained stable isotope (δ18O) records of pedogenic carbonate from the Swiss Molasse Basin and δD values of fault mica from the Simplon Fault Zone, for the Middle Miocene (15.5 – 14.0 Ma). The key element in conducting stable isotope paleoaltimetry is the prevailing temperature during low-elevation proxy material formation. Here we present new Mid-Miocene paleoelevation data for the European Central Alps based on precisely defined clumped isotope (∆47) derived carbonate formation temperatures and new low-elevation stable isotope records. A conservative approach renders Mid-Miocene Central Alps mean elevation of approximately 4000 m, which contrasts modern Alpine topography with average elevations of ca. 2000 m in the Central Alps (Kühni and Pfiffner, 2001).
Modeling of pluvial flash floods in pre-Alpine regions and assessment of potential climate change impacts
Authors: Huber Andreas , Lumassegger Simon , Leidinger David , Achleitner Stefan , Formayer Herbert , Kohl Bernhard
Published: March 2020

In recent years the topic of flash flooding away from rivers and permanent watercourses has attracted increasing attention from the scientific community, public authorities and affected parts of the general public. Not only urban areas with a high proportion of sealed surfaces, but also rural areas have been adversely affected by pluvial flash floods (PFFs) or surface water floods (SWFs) in the recent past. Empirical evidence suggests that amongst others pre-Alpine areas (e.g. in Austria, Germany, Switzerland, ...) might be especially susceptible to this type of flooding. From a water-management perspective knowledge about potentially endangered areas is important for involved stake-holders as a basis for informed decisions on a variety of topics ranging from protection of existing infrastructure and adaptation of current land use practices to future settlement development. In the light of changing climatic conditions also information on projected future developments is highly desirable. With respect to the latter, an increasing number of datasets from national and pan-European climate-services has become publicly available. Also a growing proportion of two-dimensional hydrodynamic models supports direct rainfall as a boundary condition, thus addressing the special requirements for modeling of PFFs/SWFs.

We utilize different two-dimensional hydrodynamic models (unstructured-mesh, raster-based) in combination with an event-based hydrological approach to simulate the spatial distribution of surface runoff in response to heavy precipitation events for present conditions and under projected future conditions for small rural areas (< 2km²) in Upper Austria. The general applicability of the used modeling approach is demonstrated. However, also a number of remaining challenges related to the limited quantity and quality of observational data for model calibration and the definition of representative future scenarios is identified and discussed.
Stochastic time-dependent parameters to improve the modeling and characterization of catchments
Authors: Bacci Marco , Fenicia Fabrizio , Sukys Jonas
Published: March 2020

Catchments are complex dynamical systems exposed to highly-variable inputs (rainfall). Despite this complexity, it is uncommon to model these systems as stochastic ones. Previous works offer a large number of examples where deterministic (conceptual or physics-based) models are used to describe hydrological basins in spite of the fact that, in some cases, the output of the model shows substantial deviations from the observed data even after meticulous calibration.
There are different ways to include stochasticity in the hydrological modeling of catchments. With this contribution we explore a systematic way to improve our knowledge of the system at hand by using time-dependent parameters, which are driven by suited stochastic processes. The fundamental idea, which dates back to seminal works carried out about ten years ago, is to correlate the evolution of the selected time-dependent parameters to catchment features, input variables, or possible changes over time within the catchment area, to improve the structure of the model in a data-driven fashion, rather than to merely resort to including a bias term on the output of the model.
In doing so for different catchments, we make use of a newly-developed inference framework called SPUX, which is particularly suited to deal with non-linear stochastic models as it enables the usage of high-performance computing clusters for (Bayesian) inference coupled with the particle filter method. This allows us to explore and show our approach at work on different settings, such as models of different complexity and data-sets of different resolutions, lengths, and relevant to catchments with different characteristics, which have (or not) changed over time.
Particle energisation and energy transport in Multiscale MHD - Hybrid - Kinetic PIC models of magnetospheres
Authors: Lapenta Giovanni , Berchem Jean , Walker Raymond , El Alaoui Mostafa , Schriver David , Richard Robert , Travnicek Pavel
Published: March 2020

A grand challenge in physics is to understand how and where electrons and ions accelerate to high energy, often forming power law distributions. We report the result of a combined kinetic-fluid effort [1]. For Earth, a full kinetic model of sizeable chunks of the magnetosphere (e.g. the magnetopause up to the bow shock, or the magnetotail) of order 10-20 RE in size in each dimension is hosted within a MHD simulation that provides it with initial and boundary conditions. For Mercury, it is possible to treat the whole magnetosphere that in this case is spawn from a state derived from a hybrid code [2].
With this approach, we search for regions of most intense particle heating and acceleration, comparing the full kinetic (i.e. we treat both electrons and ions as particles) evolution with the evolution of the host global simulation: MHD for the Earth and hybrid for Mercury.

The results highlight some significant effects peculiar to kinetic models. First, of all full kinetic models provide a detailed view of the electron role in energy transfer, with a distinct role for the enthalpy, bulk and heat flux. Second, the full kinetic approach, allows for the development of modes and instabilities absent in global fluid or hybrid models [3].
Modeling effects of physical and chemical heterogeneity of alluvial sediments on hyporheic exchange
Authors: Boano Fulvio , Pescimoro Eugenio , Sawyer Audrey , Soltanian Mohamad Reza
Published: March 2020

Exchange of water and nutrients between a river and the surrounding hyporheic zone is controlled by multiple factors, including river morphology, streamflow variability, connection with groundwater, and sediment properties. Among these factors, the heterogeneity of river sediments is known to strongly affect the fate of nutrients exchanged with the hyporheic zone, but this influence has received relatively little attention compared to other factors. Moreover, sediments are heterogeneous in terms of both physical properties (i.e., hydraulic conductivity) and chemical composition (e.g., organic carbon content), but studies about heterogeneity have mostly focused on variations of hydraulic conductivity compared to the variations of chemical properties of sediments.

This contribution presents a modeling analysis of the influence of physical and chemical heterogeneity of alluvial sediments on lateral hyporheic exchange in meandering rivers. Sediments are treated as a binary mixture of mineral sand and organic silt, and a coupled hydraulic and biogeochemical model is employed to simulate the effect of different silt/sand ratios on exchange and reaction of organic carbon, oxygen, nitrate, and ammonium. Model results show that sediments with higher content of silt are characterized by lower exchange fluxes, but their higher carbon availability fosters higher rates of biochemical reactions and hence leads to higher nitrogen removal by net denitrification. These results indicate the importance of improving the description of sediment heterogeneity in modeling studies of hyporheic exchange.
High precision and high resolution monitoring of subsurface changes with DAS and airgun
Authors: Wang Baoshan , Zeng Xiangfang , Yang Jun , Zhang Yuansheng , Song Zhenghong , Li Xiaobin , Lin Rongbin , Qin Manzhong , Wei Congxin
Published: March 2020

Recently large-volume airgun arrays have been used to explore and monitor the subsurface structure. The airgun array can generate highly repeatable seismic signals, which can be traced to more than 200 km. And the airgun source can be ignited every 10 minutes. The airgun source makes it possible to precisely monitor subsurface changes at large scale. The spatial resolution of airgun monitoring is poor subjecting to the receiver distribution. The distributed acoustic sensing (DAS) technique provides a strategy for low-cost and high-density seismic observations. Two experiments combing DAS technique and airgun source were conducted at two sites with different settings. At the first site, a telecommunication fiber-optic cable in urban area was used. After moderate stacking, the airgun signal emerges on the 30-km DAS array at about 9 km epicentral distance. In the second experiment, a 5-km cable was deployed from the airgun source to about 2 km away. About 800-m cable was frozen into the ice above the air-gun, the rest cable was cemented on the road crossing through a fault. And the airgun has been fired continuously for more than 48 hours with one-hour interval. On the stacking multiple shots’ records, the wavefield in fault zone emerges too. These two experiments demonstrate the feasibility of using various fiber-optic cables as dense array to acquire air-gun signal in different environments and to monitor the subsurface changes.
Effect of a heterogeneity on tensile failure: interaction between fractures in a limestone
Authors: Pluymakers Anne , Bakker Richard , Barnhoorn Auke
Published: March 2020

Not all rocks are perfect. Frequently heterogeneities will be present, either in the form of pre-existing fractures, or in the form of sealed fractures. Tensile strength and strength anisotropy of rocks has been investigated for strongly layered rocks, such as shales, sandstones and gneisses, but data is lacking on the effect of single planar heterogeneities, such as pre-existing fractures or stylolites. We have performed Brazilian Disc tests on limestone samples containing pre-existing fractures and stylolites, investigating Brazilian test Strength (BtS) and fracture orientation. We used Indiana limestone samples, pre-fractured with the Brazilian Disc method, and Treuchtlinger Marmor samples which contained central stylolites. All experiments were filmed. The planar discontinuity was set at different rotation angles of approximately 0–20–30–45–60–90⁰, where 90⁰ is parallel to the principal loading direction, and 0⁰ to the horizontal axis of the sample. Pre-fracturing Indiana limestone samples results in a cohesion-less planar discontinuity, whereas the stylolites in the Treuchtlinger Marmor samples are discontinuities which have some strength.

The results show that our imperfect samples with a planar discontinuity are always weaker than an intact sample. For the Indiana limestone, with a cohesion-less interface, there is 10 to 75% of weakening, which is angle-dependent. Once the angle is 30 or lower there is no influence from the initial fracture for the orientation of the new fracture. The stress-displacement pattern followed the expectation for Brazilian Disc testing. However, in the samples with a stylolite, strength is isotropic and between 25 and 65% of the strength of an intact sample. For all cases several new cracks appeared, of which the orientation is influenced by the orientation of the stylolite. The fracture pattern and associated stress drops are more complex for high angles. Interestingly, in the samples with stylolites, always more than one fracture was formed, whereas in the samples with a cohesionless interface usually only one new fracture formed, which for natural settings suggests a potential for higher fracture density when hydrofracturing a stylolite-rich interval.

A second difference between these datasets is the amplitude of the pre-existing interface. The effect of amplitude will be qualitatively investigated with a 2D Comsol model, to investigate the location of the first fracture occurring, which can then be compared to the camera data of the experiments.
OCO-3 Snapshot Area Mapping Mode: Early Results
Authors: Nelson Robert Roland , Eldering Annmarie , Kurosu Thomas , Kiel Matthäus , Fisher Brendan , Pavlick Ryan , Spiers Gary , Rosenberg Rob , Crisp David , O'Dell Christopher , Somkuti Peter , Taylor Thomas , Kort Eric , Oda Tomohiro , Nassar Ray , Lauvaux Thomas
Published: March 2020

The NASA Orbiting Carbon Observatory-3 (OCO-3) was launched on May 4, 2019 to the International Space Station and has been taking measurements since August. OCO-3, like its predecessor OCO-2, makes hyperspectral measurements of reflected sunlight in three near-infrared bands. However, one of the unique features of OCO-3 is its ability to scan large contiguous areas on the order of 80 km by 80 km using a pointing mirror assembly. This capability, known as snapshot area mapping (SAM) mode, is being used to look at cities, forests, volcanos, and multiple other areas that are of interest to the carbon dioxide (CO2) and solar-induced chlorophyll fluorescence (SIF) scientific communities. For example, OCO-3 can measure column-mean CO2 (XCO2) over the entire Los Angeles, CA basin during the span of only two minutes. With several hundred SAMs having been collected so far and upwards of 25 possible per day, there is a wealth of data to investigate for scientific features and for any potential instrument biases. Additionally, this type of dense sampling will be a proof-of-concept for multiple future wide-swath CO2 missions. Here, we present several OCO-3 SAM mode measurements and discuss interesting features, XCO2 results, and future mission plans.
Quaternary evolution of the northern North Sea
Authors: Batchelor Christine , Ottesen Dag , Bellwald Benjamin , Planke Sverre , Løseth Helge , Henriksen Sverre , Johansen Ståle , Dowdeswell Julian
Published: March 2020

The North Sea has arguably the most extensive geophysical data coverage of any glacier-influenced sedimentary regime on Earth, enabling detailed investigation of the thick (up to 1 km) sequence of Quaternary sediments that is preserved within the North Sea Basin. At the start of the Quaternary, the bathymetry of the northern North Sea was dominated by a deep depression that provided accommodation for sediment input from the Norwegian mainland and the East Shetland Platform. Here we use an extensive database of 2D and 3D seismic data to investigate the geological development of the northern North Sea through the Quaternary.

Three main sedimentary processes were dominant within the northern North Sea during the early Quaternary: 1) the delivery and associated basinward transfer of glacier-derived sediments from an ice mass centred over mainland Norway; 2) the delivery of fluvio-deltaic sediments from the East Shetland Platform; and 3) contourite deposition and the reworking of sediments by contour currents. The infilling of the North Sea Basin during the early Quaternary increased the width and reduced the water depth of the continental shelf, facilitating the initiation of the Norwegian Channel Ice Stream.
Investigating lateral variations in the kinematics of active deformation along the Western Kunlun mountain front (Xinjiang, China): structural and morphological analysis of the Hotan anticline
Authors: Guilbaud Christelle , Simoes Martine , Barrier Laurie , Van der Woerd Jérôme , Baby Guillaume , Li Haibing , Pan Jiawei , Tapponnier Paul , Harlet Déborah
Published: March 2020

The Western Kunlun Range is a mountain range located at the northwestern boundary of the Tibetan Plateau, facing the Tarim Basin. Our previous combined structural and morphological investigations of the mountain front, nearby the city of Pishan where a Mw 6.4 earthquake occurred in 2015, revealed the existence of a duplex uplifting Cenozoic strata, in which only the most frontal blind ramp is presently active and slips at a probable rate of 2 to 2.5 mm/yr. Located ~100 km further east along the mountain front, the Hotan anticline seems to present a different structure from surface geology, as older strata from Mesozoic and Paleozoic outcrop. Additionally, some authors proposed that the deformation would be here accommodated by a large blind basement thrust sheet, in clear contrast with the duplexes documented further west.

To further document potential lateral variations in the structural style and how they may affect the kinematics of active deformation along the mountain front of the Western Kunlun, we carry out a structural and morphological analysis of the Hotan anticline. We build structural cross-sections based on seismic reflection profiles, and calculate the incremental uplift recorded by dated fluvial terraces to quantify shortening rates over the last ~300 kyr. Our analysis reveals that a duplex structure, located below the basement thrust sheet, presently accommodates active deformation at a rate of 0.5 to 2.5 mm/yr, with a preferred rate of ~1.6 to 2.3 mm/yr. In more detail, uplifted terraces reveal that all ramps of the duplex are active in the case of the Hotan anticline, while only the most frontal ramp is documented as active in the case of the Pishan anticline further west. These results indicate that the style and rate of active shortening are rather homogeneous all along the mountain front, in contrast with the first impression provided by surface geology. Moreover, the discrepancy between surface geology and active morphology reveals progressive structural changes over geological times, from a blind basement ramp to duplexes. However, in the details, active deformation still remains segmented as its partitioning on the various ramps of the duplexes is variable along strike.
Competition of monomeric and polymeric silicic acid with natural organic matter for binding sites at goethite
Authors: Dobritzsch Jana , Klotzbücher Anika , Klotzbücher Thimo , Kaiser Klaus , Mikutta Christian , Mikutta Robert
Published: March 2020

Silicon (Si) is not considered an essential element for plant growth but improves blade stability and enhances the plant’s ability to resist metal toxicities. In soil solution, dissolved Si can be present as monomeric and polymeric silicic acid. Pre-experiments showed that monomeric Si is much less competitive than dissolved organic carbon (DOC) in sorption to Fe oxides, suggesting that monomeric Si can easily be leached from upper soil layers. However, drying of soil can increase Si pore water concentrations, thus facilitating the formation of Si polymers. We tested the sorption of monomeric versus polymeric silicic acid to goethite (a-FeOOH) at pH 4.5, and presumed stronger binding and less desorption by DOC for polymeric Si because of its multidentate mineral surface attachment. Equilibrium solutions were analysed for dissolved Si by optical emission spectrometry and Si species present at the mineral surfaces were revealed by X-ray photoelectron spectroscopy. Adsorption experiments indicated that the initial binding of polymeric Si was followed by surface polymerization at higher Si loads. Due to surface polymerization, the sorption of polymeric Si greatly exceeded that of monomeric Si. Besides adsorption experiments, desorption experiments using a DOC solution produced from an organic soil surface layer will provide information on the remobilization potential of the sorbed Si species. We hypothesize that (1) the displacement of monomeric as well as of polymeric Si by organic compounds depends on its surface loading and (2) polymeric Si is less desorbable than monomeric Si. Knowledge on the resistance of monomeric and polymeric Si against desorption by DOC will improve our understanding of processes controlling Si leaching and phytoavailability in soil.
Automatic estimation of parameter transfer functions for distributed hydrological models - a case study with the mHM model
Authors: Feigl Moritz , Thober Stephan , Herrnegger Mathew , Samaniego Luis , Schulz Karsten
Published: March 2020

The estimation of parameters for spatially distributed rainfall runoff models is a long-studied, complex and ill-posed problem. Relating parameters of distributed hydrological models to geophysical properties of catchments could potentially solve some of the major difficulties connected to it.

One way to define this relationship is by the use of explicit equations called parameter transfer functions, which relate geophysical catchment properties to the model parameters. Computing parameter fields using transfer functions would result in spatially consistent parameter fields and the potential to extrapolate to other catchments. A further advantage is that the dimensionality of the parameter space is reduced because the transfer function parameters are applied to all computational units (i.e., grid cells). However, the structure and parameterization of transfer functions is often only implicitly assumed or needs to be derived by a laborious literature guided trial and error process.

For this reason we use Function Space Optimization (FSO), a symbolic regression approach which automatically estimates the structure and parameterization of transfer functions from catchment data. FSO transfers the search of the optimal function to a searchable continuous vector space. To create this space, a text generating neural network with a variational autoencoder (VAE) architecture is used. It is trained to map possible transfer functions and their distributions to a 6-dimensional space. After training, a continuous optimization is applied to search for the optimal transfer function in this function space. FSO was already tested in a virtual experiment using a parsimonious hydrological model, where its ability to solve the problem of transfer function estimation was shown.

Here, we further test FSO by applying it in a real world setting to the mesoscale hydrological model (mHM). mHM is a widely applied distributed hydological model, which uses transfer functions for all its parameters. For this study, we estimate transfer functions for the parameters porosity and field capacity, which both influence a range of hydrologic processes, e.g. infiltration and evapotranspiration. We compare the FSO estimated transfer functions with the already existing mHM transfer functions and examine their influence on the model performance.

In summary, we show the general applicability of FSO for distributed hydrological models and the advantages and capabilities of automatically defining parameter transfer functions.
On the use of LSPIV-based free software programs for the monitoring of river: testing the PIVlab and the FUDAA-LSPIV with synthetic and real image sequences
Authors: Pumo Dario , Alongi Francesco , Ciraolo Giuseppe , Noto Leonardo
Published: March 2020

The development of new image-based techniques is allowing a radical change in the environmental monitoring field. The fundamental characteristics of these methods are related to the possibility of obtaining non-intrusive measurements even in adverse circumstances, such as high flow conditions, which may seriously threaten the operators’ safety conditions in traditional approaches.

Optical techniques, based on the acquisition, analysis and elaboration of sequences of images acquired by digital cameras, are aimed at a complete characterization of the river instantaneous surface velocity field, through the analysis of a floating tracer, which may be naturally present or artificially introduced. The growing availability of a new generation of both low-cost optical sensors and high-performing free software programs for image processing, is a key aspect explaining the rapid development of such techniques in recent years. The best known optical techniques are the large scale particle velocimetry (LSPIV) and the large scale particle tracking velocimetry (LSPTV).

This work is aimed to analyze and compare the performance of the two most common free software packages based on LSPIV (i.e. the PIVlab and the FUDAA-LSPIV), which use different cross-correlation algorithms. The test is carried out by analyzing several sequences of both synthetic images and real frames acquired on natural rivers under different environmental conditions (with tracers artificially introduced). An image sequences generator has been implemented ad-hoc with the aim to create, under fixed configurations, synthetic sequences of images, simulating uniformly distributed tracers moving under controlled conditions. The various configurations are characterized by different parameterization in terms of: (i) flow velocity (S=slow or F=fast flow conditions, according to a logarithmic transverse flow profile); (ii) tracer particles size (CON= disks of constant diameter; VAR=disks of variable size with given mean diameter); (iii) seeding density per frame (density: low -LD, medium -MD, high -HD).

The synthetic sequences are processed by the two software packages together with the real sequences, analyzing the errors in terms of mean value of the surface velocity field and velocity along a transverse transect, with respect to a benchmark velocity (i.e. that imposed in the image sequence generator for the synthetic sequences and that deriving from the use of traditional sensors, i.e. ADCP, for the real sequences).
The road towards an EU-wide tiered approach assessment of pesticide concentration at drinking water abstraction locations - a combined approach of GIS analysis and modelling on catchment level
Authors: Gebler Sebastian , Schröder Tom , Li Shanghua
Published: March 2020

The exposure assessment of plant protection products (PPP) at drinking water abstraction points is of growing interest for authorities, water suppliers, industry, and other stake holders and is hence particularly addressed in the EU regulatory framework (regulation 1107/2009). However, there is no generic guidance available on the derivation of drinking water abstraction concentrations in the EU. An exception is the national approach of the Netherlands, a simplistic but very solid first Tier approach, which considers edge-of-field PECsw, use intensity including cropping area within a drinking water catchment, application practice and dissipation in the water system amongst others.  The Dutch approach underlies worst-case assumptions e.g. all agricultural land is connected and releases water to a water body. Our work explores the feasibility of a general tiered EU-wide approach to derive realistic PPP concentrations at drinking water abstraction points. Specifically, our goals are: (i) the characterization of EU-wide drinking water catchments, (ii) the identification of vulnerable catchments based on agricultural area or specific crops, (iii) to enable substance specific modelling for agricultural area/crop using a landscape-level assessment model.

On this account, we analyzed the European catchments for specific crops on the basis of the Water Framework Directive (WFD). The focus was on catchment characteristics (e.g. crop area, soil hydraulic properties) which have a strong impact on runoff as well as drainage generation and therefore on the mixing of PPPs in surface water. In a first step, the spatial variation of the mixing factor by crop area was investigated taking into account the stream course from headwater catchment to a larger main river. In the second step, we identified typical abstraction areas for surface water and groundwater using proxy data (e.g. protection zones and other proxy data) with the aim to explore the most vulnerable combinations in the EU. These data can then be used for the definition of specific (vulnerable) scenarios regarding the mixing of PPPs in surface water for a specific crop on EU level.

It is expected that these data in combination with landscape-level modelling using the Soil and Water Assessment tool (SWAT) can be used as starting point for a tiered exposure assessment to derive generic mixing factors and drinking water concentrations at abstraction locations.
Numerical Analysis of Floating Offshore Structures Using Overset Method
Authors: Li Sing-Ya , Hsiao Shih-Chun
Published: March 2020

The consciousness of global warming gradually transforms the energy dependency from fossil fuels to renewable energy resources such as waves, wind, solar, and geothermal heat. The flexible deployment range of floating offshore wind turbines makes this technology more popular in the offshore wind energy sector recently. However, this technique is still under development and the fluid-structure interaction (FSI) needs to be further investigated to improve the design of the floating wind turbine platform. Due to the significant evolvement of computer and numerical methods in recent years, computational fluid dynamics (CFD) has been widely applied to solve FSI problems. Grid morphing technique is commonly used to solve FSI problems, however, using this technique to deal with large body displacement problems will lead to large grid deformation and consequently induce numerical instabilities. In this study, overset grid was used to understand the interaction between fluid and floating structures to avoid calculation divergence due to excessive grid deformation. The open-source CFD solver was developed using OpenFOAM for offshore floating structures and the numerical wave tank was developed by integrating the overset grid Navier-Stokes solver, overInterDyMFoam, with a wave generation library in OpenFOAM. The accuracy of the developed model was validated using a series of benchmark tests including heave decay test, roll decay test, and a floating structure subject to different wave conditions. The influences of the overlapping zone properties on the model accuracy were discussed and the results obtained by the current study and those computed by dynamic grid solver were compared. Overall, the computed results presented in this study show good agreement with the results of the benchmark tests.
Upper mantle anisotropy and it's geodynamical implications in Sri Lanka region
Authors: chandra shivam
Published: March 2020

Anisotropy in the Earth’s upper mantle is a signature of past and present deformation. Sri Lanka comprises four main lithological units, viz. the Highland Complex (HC), the Wanni Complex (WC), the Vijayan complex (VC) and the Kadugannawa complex (KC). To calculate the upper mantle anisotropy, we have collected the earthquake data from IRIS (Incorporated Research Institutions for Seismology) network. The upper mantle anisotropy beneath Sri Lanka is measured in the frequency band 0.01–0.15 Hz, with magnitude (Mw) of six or more and within the epicentral distance of 90°-140°. We have analyzed (the fast direction and delay time) shear wave splitting of SKS/SKKS phases at 3 stations, namely, MALK (WC), HALK (HC) and PALK (KC) in Sri Lanka. In this study, shear wave splitting measurements were done using high-quality seismograms (~30) of many earthquakes occurring in the region. We have used rotational correlation (RC) , minimum energy (SC) and eigenvalue techniques. The result of the shear-wave splitting measurement shows the presence of two anisotropic layers in the upper mantle. The upper and lower layer’s fast-polarization direction is found to be NE-SW and NW-SE, has the delay time varies from 0.4-0.5s in the upper layer, and 0.6-0.8s in the lower layer. We found two major fast directions in the upper and lower layers, viz. NE-SW in the upper layer of MALK and PALK and NW-SE for the HALK stations, and NNE-SSW in the lower layer beneath MALK and HALK stations and NW-SE in the PALK station. Overall, Fast direction for Sri Lanka region is found to be NE-SW in the lower layer and NW-SE in the upper layer. Our study suggests that fast axis direction of lower layer with an average delay time of 0.6 s depicts a ~67 km thick anisotropic layer with 4% anisotropy (from previous studies) beneath Sri Lanka region. However, if we assume an anisotropy range of 3–5%, then the calculated delay time of 0.6 s would correspond to thickness variation of 89.3 to 53.59 km, respectively, for the inferred anisotropic layer. Comparing from APM (Absolute Plate Motion) direction with our fast directions, we infer that the SAF(Simple Asthenospheric Flow) model prevails in this region and secondly, when Shmax (Maximum Horizontal stress) and the GPS (Global Positioning System) data compared with the fast direction we infer that there is partial contribution from lithospheric mantle. So, we confirmed that anisotropy in the region is mainly governed by asthenospheric flow and partially due to lithospheric mantle.
Existence and Stability of Morphodynamic Equilibria in Double Inlet Systems
Authors: Deng Xiao , Boelens Thomas , De Mulder Tom , Schuttelaars Henk
Published: March 2020

Tidal inlet systems, ubiquitous along sandy coasts, are very valuable areas in terms of ecology
(breeding and feeding areas), economy (gas–mining and dredging) and recreation, and important
for coastal safety. To properly manage these systems, good insight into their morphodynamic
behaviour is essential.
In this presentation, we focus on morphodynamic equilibria of so-called double inlet systems,
i.e., systems in which the tidal basin is connected to the open sea by two tidal inlets. In our model,
the water motion is described by the cross-sectionally averaged shallow water equations, and forced
by prescribed tidal elevations at both seaward sides. The sediment transport is modeled by an
advection–diffusion equation with source and sink terms, while the bed evolution is governed by the
convergences and divergences of sediment transports. The sediment transport consists of various
contributions, a diffusive contribution, a transport term related to the variations in topography
and an advective contribution (ter Brake and Schuttelaars, 2010).
To directly identify morphodynamic equilibria, we employ continuation methods and bifurcation
techniques. By systematically varing the amplitude φM2 at one of the inlets, while keeping all other
parameters fixed, a region in the φM2 parameter space is found where the bed level reaches the
water surface, resulting in two single inlet systems. Outside this region, morphodynamic equilibria
exist. These equilibria are characterized by their minimum water depth and location. There are
branches of stable equilibria, while there are also branches of unstable equilibria, coinciding with
the stable equilibria at so-called limit points. Varying both the amplitude and phase of the M2 tide
at one of the inlets while keeping the other parameters fixed, results in limit points in AM2 − φM2
space that form an ellipse.
In our presentation, we will systematically discuss the number and stability of morphodynamic
equilibria and compare our results to observations in the Marsdiep-Vlie system, a double inlet
system in the Nothern Dutch Wadden Sea.
References
ter Brake, M. C. and Schuttelaars, H. M. (2010). Modeling equilibrium bed profiles of short tidal embayment. on
the effect of the vertical distribution of suspended sediment and the influence of the boundary conditions. Ocean
Dynamics, 60:183–204.
Comparing the impact for hydrology of the new ERA5 reanalyses dataset over ERA-Interim for 8 hydrological models in 6 catchments using the eWaterCycle community modelling environment.
Authors: Hut Rolf , Drost Niels , Aerts Jerom , Bouaziz Laurene , van Verseveld Willem , Jagers Bert , Baart Fedor , Sutanudjaja Edwin , Melsen Lieke , Bennett Andrew , Arnal Louise , Fenicia Fabrizio , Santos Leonard , Gelati Emiliano , Dal Molin Marco , Knoben Wouter , Gharari Shervan , Hall Caitlyn , Hutton Eric , van de Giesen Nick ,   the eWaterCycle comparison team from the Netherlands eSciencecenter.
Published: March 2020

The release of the European Centre for Medium-Range Weather Forecasts (ECMWF)’s Re-Analysis 5 (ERA-5) global climate forcing dataset is expected to greatly improve the quality of hydrological modeling. Following this release there is great interest in assessing the improvements of ERA-5 relative to its predecessor ERA-Interim for hydrological modeling and predictions.

In this study we compare streamflow predictions when using ERA-interim vs ERA-5 as forcing data for a suite of hydrological models from different research groups that capture the variation in modelling strategies within the hydrological modelling community. We check whether physically based models, defined as those that do not require additional parameter calibration, would lead to different conclusions in comparison to conceptual models, defined as those that require calibration. Based on the hydrological model structure we expect that conceptual models that need calibration show less difference in predicting discharge (skill) between ERA-5 and ERA-Interim, where-as the physical based (non-calibrated) models most likely will benefit from the improved accuracy of the ERA-5 input. This assessment will provide the HEPEX community with answers on how the ERA-5 dataset will improve hydrological predictions based on different hydrological modelling concepts.

An additional key objective while conducting this study is compliance to the FAIR principles of data science. To achieve this we held a workshop in Leiden, the Netherlands, where multiple hydrological models were integrated into the eWatercycle II system. eWatercycle II is a hydrological model platform containing a growing number of hydrological models. The platform facilitates research and cohesivity within the hydrological community by providing an Open-Source platform built specifically to advance the state of FAIR and Open Science in Hydrological Modeling. We also use this study to demonstrate the feasibility of eWatercycle II as a platform for FAIR hydrological models.

Preliminairy results from this comparison study were presented at the AGU Fall Meeting 2019. Here we will present the full results of the comparison study.
Formation of Microaggregates and organo-mineral composite building units: Novel pathways in the soil-parent rock continuum
Authors: Totsche Kai Uwe
Published: March 2020

Formation of Microaggregates and organo-mineral composite building units: Novel pathways in the soil-parent rock continuum

 

Summary

 

Microaggregates and organo-mineral composite building seem to be unique structural features of natural permeable media like soils, rocks and aquifers. Thee develop in response to various aggregation processes and mechanisms that result in a non-random spatial arrangement of the solid phase already at the submicron scale. Soil microaggregates are defined as compound structures smaller <0.25mm, comprising the colloidal-sized and nanoparticulate composite building units and the organo-mineral composites (Totsche et al. 2018). Noteworthy, microaggregates, may be present as suspended or colloidally-dispersed components of the mobile phase. As such, they are prone to transport with the seepage and may affect the surface and pore-space properties. Surface alteration by interactions of seepage components with immobile surfaces is likely an important, yet essentially unexplored pathway triggering formation of microaggregates in the soil-parent rock continuum. In matured soils, the commonly found associations of clays with other, often poorly crystallized but highly reactive minerals and organic matter is the consequence of nucleation in the chemically heterogeneous soil suspension. Both pathways coexist and can be studied in the soil-parent-rock transition zone were weathering and formation/alteration of secondary mineral phases are still in the early stage. The stability of microaggregates and their interactions are dependent on wetting-drying and in turn by hydration-dehydration cycles. Such moisture-related dynamics regularly take place in soils of the temperate regions even down to the soil-parent-rock transition zone and suggests that the hydraulic and osmotic stress and their history results in attachment, detachment, translocation and accumulation. The presentation will We focus on two so far vastly ignored formation pathways of microaggregates and composite building units, i.e., the “geochemical inheritance” and “heteroaggregation from suspension”, thereby considering the role of dynamic relocation of composite building units and microaggregate forming materials from upstream compartments.

 

Totsche K.U., Amelung W., Gerzabek M.H., Guggenberger G., Klumpp E., Knief C., Lehndorff E., Mikutta R., Peth S., Prechtel A., Ray N., Kögel-Knabner I. (2018) Microaggregates in soils. Journal of Plant Nutrition and Soil Science 181(1), 104-136.
Impacts of mean sea-level rise and marine extremes on islands
Authors: Marcos Marta , Amores Angel
Published: March 2020

For how long low-elevation coastal areas will be habitable under the effects of mean sea-level rise and marine extreme hazards? Mean sea-level rise, despite having a global origin, has severe local coastal impacts, as it raises the baseline level on top of which extreme storm surges and wind-waves reach the coastlines and, consequently, increases coastal exposure. In this presentation we will show coastal modelling exercises, fed with regionalised climate information of mean sea level and marine extremes, and applied in different environments that include sandy beaches and atoll islands. The outputs are aimed at anticipating the potential impacts of the dominant drivers in terms of land loss, coastal flooding and erosion. Our examples will be focusing on islands, for which the effects of increased coastal exposure are relatively larger, where local economy is often linked to coastal activities and retreat and migration are hampered by the limited land availability.