bluuebunny/crossref_metadata_2025 huggingface dataset:
A modeling study of physical and biogeochemical changes occurring in the tropical Indian Ocean during Miocene times.
Authors: Sarr Anta-Clarisse , Donnadieu Yannick , Bolton Clara , Suchéras-Marx Baptiste
Published: March 2020

The South Asian Monsoon (SAM) is one of the most important climatic features of the Asian continent. Proxy-based reconstructions from continuous records in the Indian Ocean suggest a settlement of modern-like monsoon during the Miocene, with a modern winds distribution and strength potentially reached by ~13 Ma. Concurrent with the SAM intensification, a major reorganization of surface ocean currents occurred in the Indian Ocean. The timing of monsoon strengthening overlaps with changes in Indian Ocean and Indonesian Gateway configurations, Himalayas uplift, global cooling, as well as East Antarctic Ice Sheet expansion. Thus, the respective influence of each factor on SAM evolution and Indian Ocean paleoceanography is still poorly understood owing to the modification of multiple forcing mechanisms.

Here we will use a set of experiments with the IPSL-CM5A2 Earth System Model under early to late Miocene configurations in order to tease apart the effects of paleogeography changes, ice-sheet growth and CO2levels on the Indian Ocean region during the Miocene. We will focus on the impact of increasing SAM winds and precipitation on the oceanographic conditions in the Indian Ocean including not only physical parameters but also biogeochemical ones.

 
Structure and englacial debris content of a Himalayan debris-covered glacier revealed by an optical televiewer
Authors: Miles Katie , Hubbard Bryn , Quincey Duncan , Miles Evan , Rowan Ann
Published: March 2020

Himalayan debris-covered glaciers contribute to the discharge of some of Earth’s largest river systems, shaping the seasonal water supply to millions of people. The supraglacial debris layer heavily influences the pattern of surface melt, producing a range of unique surface features that make it challenging to collect any data, particularly from the interior of such glaciers. Models of debris-covered glaciers therefore lack calibration and validation data, which are needed for accurate predictions of future glacier geometric change and contributions to river discharge, water resources and ultimately sea level. In 2017 and 2018, we logged four boreholes drilled using pressurised hot water into the debris-covered Khumbu Glacier, Nepal Himalaya, with a high-resolution optical televiewer. The boreholes were located at four sites across the lower glacier’s debris-covered area, down-flow of the Khumbu Icefall. The resulting logs, ranging in length from 22–150 m, produced a 360° geometrically-accurate full-colour image of each borehole at ~1 mm vertical and ~0.22 mm (1,440 pixel) horizontal resolution. The logs reveal three material facies: i) steeply-dipping ice layers, some including debris; ii) steeply-dipping sediment-rich layers; and iii) clusters of sediment and debris dispersed through the ice. On the basis of these facies, we present reconstructions of the glacier’s structure and historical flow paths and the first measurements of the englacial debris concentration of a Himalayan debris-covered glacier. From the latter, we additionally infer both the sources of this englacial debris and of the supraglacial debris layer present across much of the lower ablation area of Khumbu Glacier.
An attempt of SfM photogrammetry to narrow and dark underground building heritage
Authors: Oguchi Chiaki , Shimizu Kisara , Tamura Yasuhiko , Hayakawa Yuichi , Ogura Takuro
Published: March 2020

The 3D models creating by SfM (Structure-from-Motion) photogrammetry became one of the important and convenient methods for any kinds of objects on geomorphology, geoheritage, or geoarchaeological fields. These objects are landforms, monuments, buildings, relics and so on. In order to evaluate these objects, it is necessary to collect morphological characteristics, and then proceeding to decide investigating points or areas of these materials.

The progress of this methods developed significantly, however, there have been still remained difficulties depending on the objects. For example, it is difficult to create 3D models that the object is too flat, too dark, and/or any restricts of combination of target size and focusing distances. The present study attempts to these difficulties by targeting to narrow and dark underground space. The investigating object is an archaeological man-made cave, called Taya Cave, in central Japan. It was excavated in 13 century originally and used as study areas for Buddhists by making Buddhism bas-reliefs. The cave has a total length of 570 m underground passage with a three-layer structure. The cave also has several domes connected by narrow paths. The present study tried to make a 3D model of this complicated, dark and narrow cave by SfM photogrammetry. In order to concur to make 3D models for the whole area of the cave, it is useful making chunks; separating several areas of simple morphology and then compiled. When facing narrow path, it is better to take photographs not by perpendicularly but by inclinedly. Furthermore, it is important to use strong light with attach to camera. After obtained the image data of the whole cave, the accuracy of the created model was evaluated. The results were that the accuracy of horizontal distances are higher than that of vertical distances.
Estimates of true Polar wander since 300Ma
Authors: Besse Jean , Greff Marianne , Vicente de Gouveia Sophie
Published: March 2020

We investigate true polar wander (TPW) since 300Ma. We construct a hotspot reference frame using an updated list of active hotspots with improved criteria aimed at detecting their depth origin, a compilation of terrestrial volcanic data suspected to reveal hotspot activity, and a set of plate reconstructions, based initially on paleomagnetism corrected with respect to hotspots under the assumption of hotspot fixity. The polar motion curves (representing the motion of the mantle taken as a whole) during the periods t=[0 and 150-170] and [150-170 to 280Ma] roughly aligns along two great circles which poles  are both located close to the equator, with a  longitude differing  by some 50°, and positioned close to an axis passing through the Large Low Shear Velocity Provinces (LLSVPs), and close to the maximum degree 2 geoid high under Africa. The TPW rate is slowly decreasing with respect to time but remains close or below the observed 10cm/yr present value.

            We compare our TPW data with those obtained from a mantle density heterogeneities model which computes the temporal evolution of the Principal Inertia Axis (PIA).  The minimum PIA is shown to be in agreement with the two poles previously determined, while the maximum PIA  path (which represents the evolution of the geographic pole) displays strong similarities with the observed TPW (directions, cusps). The sudden changes of TPW direction (i.e., cusps) can be explained  by mass reorganizations within the mantle principally linked to changes in subductions, while the domes greatly stabilize the system.

 
Tree species interaction and soil depth affect the response of root exudates to drought
Authors: Brunn Melanie , Hafner Bejamin D. , Jungkunst Hermann F. , Bauerle Taryn L.
Published: March 2020

Drought is considered a severe natural risk that increases drying-rewetting frequencies of soil. Yet, it remains largely unknown how forest ecosystems respond, hampering our ability to evaluate the overall sink and source functionality for this large carbon pool. Recent investigations present that the loss of soluble carbon via root exudation increases under drought, facilitating fundamental carbon stabilization and mineralization dynamics. However, information on the vertical variation of root exudation from interacting tree species is missing. Here we show that drought increases root exudation rates only in the upper soil profile, while exudation rates decrease in the deeper profile under drought. These trends occurred in both, monocultures and species mixtures. Surprisingly, beech (Fagus sylvatica) and spruce (Picea abies) trees showed opposing results depending on species mixture. While root exudation rates increased in beech growing together with spruce, drought-susceptible spruce had higher exudation rates when grown in monoculture, suggesting the benefit of spruce in mixed cultures via reduced belowground carbon loss. Our results demonstrate that stimulation of root exudation rates with drought exists in natural temperate forest ecosystems, but only in shallow soil depths. In contrast, decreased exudation rates in deeper soil during drought suggest carbon stabilization. The exudate composition can help to determine how priming of soil organic matter relates to microbial respiration and to disclose belowground processes of complementary species interaction.
Earth and Space Science in the 21st Century: A Call for Action
Authors: McEntee Chris
Published: March 2020

Earth and space science are critically important so that society can benefit from effective solutions to address global environmental conditions, mitigate the impact of climate change, and achieve the UN Sustainable Development Goals. For that benefit, society needs evidence and facts on which to develop effective policies.  External forces such as growing populism, the rise of social media and “fake news”, along with what Oxford calls the Post Truth World,  are countervailing forces to societal acceptance and acknowledgement of evidence and facts. In addition, the reward and recognition system in science undervalues societal engagement and science graduate programs offer little training in effective ways to communicate and collaborate with external stakeholders.  This talk will explore these dynamics and suggest actions that the science community can undertake to position Earth and space science as the science for society in the 21st century.
Testing seismic noise caused by highly concentrated sediment flows in laboratory experiments
Authors: Piantini Marco , Gimbert Florent , Recking Alain , Bellot Hervé
Published: March 2020

Sediment transport processes and fluxes play a key role in fluvial geomorphology and hazard triggering. In particular, extreme floods characterized by highly concentrated flows set the pace of mountain landscape evolution, where the linkage between streams and sediment sources leads to strong solid inputs characterized by significant grain sorting processes. The main observation that river processes generate ground vibrations has led to the application of seismic methods for monitoring purposes, which provides an innovative system that overcomes traditional monitoring difficulties especially during floods. Mechanistic models have been proposed in the attempt to invert river flow properties such as sediment fluxes from seismic measurements. Although those models have recently been validated in the laboratory and in the field for low transport rates, it remains unknown whether they are applicable to extreme floods.

Here we carry a set of laboratory experiments in a steep (18% slope) channel in order to investigate the link between seismic noise and sediment transport under extreme flow conditions with highly concentrated sediment flows. The originality of this set-up is that instead of feeding the flume section directly as usually done, we feed with liquid and solid discharge a low slope storage zone connected to the upstream part of the steep channel. This allows us to produce sediment pulses of varying magnitude (up to the transport capacity) and granulometric composition, traveling downstream as a result of alternate phases of deposition and erosion occurring in the storage area. We measure flow stage, seismic noise, sediment flux and grain size distribution. We find that the previously proposed relationships between seismic power, sediment flux and grain diameter often do not hold in such sediment transport situations. We support that this is due to granular interactions occurring between grains of different sizes within the sediment mixture and leading to complex grain sorting processes. In particular, we observe that bigger grains do not directly impact the bed but rather roll over fines or smaller grains, such that observed seismic power is much lower than expected. These results constitute a starting point for the development of a new mechanistic model for seismic power generated by highly concentrated bedload sediment flows.
Management and analysis of high resolution multibeam sonar surveys for geometry characterization of riverbed material
Authors: Rover Simone , Avancini Gabriele , Vitti Alfonso
Published: March 2020

The geometric characterization of riverbed material is fundamental piece of information for the management of river basins because it allows, for example, the determination of bed-load and hydrodynamics roughness and the study of geo-morphological phenomenona.
However information such the grading curve are not easily achievable by means of traditional field sampling methods, mostly intrusive, and to the hydraulic conditions of rivers that may have high water levels and strong flows.

Multibeam sonars represent an important alternative to traditional survey methods. Nowadays, thanks to advanced scientific knowledge, it is possible to make full use of an equipment increasingly accurate and precise. State of the art solutions have dimensions compact enough to be installed on remotly piloted vehicles and allow to obtained high resolution digital surface models of river beds. The feasibility of having models of such quality and the possibility to conduct surveys more frequently, allowing the monitoring of sedimentation and erosion phenomena as well as the dynamics of the armouring layer, have motivated the development of advanced and innovative technology to analyse these models.

The aim of this work is the development of a workflow that provides an effective method to characterize riverbed material. In order to achieve this target we start from an advanced and original survey technique, that allows to obtain high resolution digital surface models, and use an appropriate post-processing procedure.
We introduce first some results obtained from the analysis of digital surface models produced in laboratory or relative to well known site. In particular advanced techniques for the study of 3D model and the detection and geometric characterization of forms are investigated.
Then we present some data acquired at high resolution (few centimeters) with a multibeam sonar mounted on a remote controlled vessel. Field surveys were conducted in real fluvial environment with the aim of produce qualitative and quantitative information about the surface layer of riverbed.
Even considering some sources of uncertainty that may be present from field survey to modeling, the obtained results show how it is possible to identify and geometrically characterize several of the forms present on the surfaces analyzed. 
On the effective recombination coefficient in Saturn's ionosphere
Authors: Dreyer Joshua , Vigren Erik , Morooka Michiko , Wahlund Jan-Erik , Buchert Stephan , Waite J. Hunter
Published: March 2020

The present study combines RPWS/LP and INMS data from Cassini's orbit 292, which reached an altitude of 1685 km at the lowest point, to constrain the effective recombination coefficient α300 from measured densities and electron temperatures at a reference electron temperature of 300 K. Assuming photochemical equilibrium at these low altitudes and linking established methods to calculate the electron production rate and the dissociative recombination rate results in a formula to calculate an upper limit for α300. This is then compared against rate constants of individual recombination reactions as measured in the laboratory.
We derive upper limits for α300 of ∼ 2.5∗10-7cm3 s-1, which suggest that Saturn's ionospheric positive ions are dominated by species with low recombination rate coefficients. An ionosphere dominated by water group ions or complex hydrocarbons, as previously suggested, is incompatible with this result, as these species have recombination rate constants > 5∗10-7 cm3 s-1 at an electron temperature of 300 K. The results do not give constraints on the nature of the negative ions.
Expert soil moisture Wireless Sensor Network for the feed-back control of irrigation in heterogeneous crop systems
Authors: Puig Sirera Angela , Rallo Giovanni , Giusti Stefano , Provenzano Giuseppe , Sbrana Andrea , Tuker Jeff , Massai Rossano
Published: March 2020

New technologies in agriculture present the opportunity to create intuitive and user-friendly decision support systems, and to improve the productivity of the systems requiring water and energy. In the last few years, the adoption of these technologies have been increasing through third mission activities, and the collaboration between researchers, consultants, agri-food managers and farmers.

The general objective of the proposed dissemination activity carried out by the AgrHySMo laboratory of the University of Pisa, was to transfer a soil moisture-based wireless sensor network (SM-WSN) to a commercial pear orchard named Illuminati Frutta (Arezzo, Italy), for the feedback control of irrigation.

The plan of the third mission activity was designed by the following phases: i) the team evaluated the hydraulic performance and management of the irrigation system in the pear orchard; ii) the use of proximal sensing provided the NDVI for the biophysical characterization of the crop in a pilot area extended thirteen ha; iii) the open-source QGIS suite program was used to elaborate the collected images, to assess a zoning analysis, and to discretize homogeneous areas inside the orchard. These zoning maps were used to define the topology of the SM-WSN.

The orchard was characterized by four homogeneous zones, inside which at least one sensor of soil water content (FDR Drill and Drop probe, Sentek Inc.) was installed. A total of 6 probes were installed in the pilot area. The hardware and the smartphone of the dedicated sensor network applications, AgriNET, were provided by Tuctronics (Walla Walla, Washington, USA). The measurements of volumetric soil water contents are sent to a platform using the MODBUS RTU protocol interfaced with a communication board and then delivered, using the cellular 3G data network, to a MySQL database operated by AgriNET/Tuctronics accessible from the web. According to the ordinary scheduling of irrigation, the expert system allowed the farmer to maintain the soil water content within a pre-defined optimal range, which upper limit corresponds to the soil field capacity and the lower is the threshold below which water stress occurs. During the first experimental growing season, by considering the results obtained in the pilot plot, compared with the ordinary irrigation scheduling the farmer saved up to 35% of the water and energy supply. In the future, the proposed feedback control of irrigation protocol will be extended to the entire farm. Thus, the adoption of this new technology aimed at identifying the most appropriate irrigation management, have the potential to generate positive economic returns and to reduce the environmental impacts.
SPUX - a Scalable Package for Bayesian Uncertainty Quantification
Authors: Sukys Jonas , Bacci Marco
Published: March 2020

SPUX (Scalable Package for Uncertainty Quantification in "X") is a modular framework for Bayesian inference and uncertainty quantification. The SPUX framework aims at harnessing high performance scientific computing to tackle complex aquatic dynamical systems rich in intrinsic uncertainties,

such as ecological ecosystems, hydrological catchments, lake dynamics, subsurface flows, urban floods, etc. The challenging task of quantifying input, output and/or parameter uncertainties in such stochastic models is tackled using Bayesian inference techniques, where numerical sampling and filtering algorithms assimilate prior expert knowledge and available experimental data. The SPUX framework greatly simplifies uncertainty quantification for realistic computationally costly models and provides an accessible, modular, portable, scalable, interpretable and reproducible scientific workflow. To achieve this, SPUX can be coupled to any serial or parallel model written in any programming language (e.g. Python, R, C/C++, Fortran, Java), can be installed either on a laptop or on a parallel cluster, and has built-in support for automatic reports, including algorithmic and computational performance metrics. I will present key SPUX concepts using a simple random walk example, and showcase recent realistic applications for catchment and lake models. In particular, uncertainties in model parameters, meteorological inputs, and data observation processes are inferred by assimilating available in-situ and remotely sensed datasets.
Groundwater recharge estimates with soil isotope profiles – is there a bias on coarse-grained hillslopes?
Authors: Krüger Nina , Külls Christoph , Bruggeman Adriana , Eliades Marinos , Christophi Christos , Rigas Michali , Eracleous Theodosia
Published: March 2020

Due to continuous changes in the meteorological conditions of Mediterranean regions, it is becoming increasingly important to improve knowledge of hydrological and hydrogeological recharge processes and their dependency on climate conditions to adapt the use of limited water resources. Within the IsoMed project (isotope hydrology in Mediterranean areas), soil profiles were sampled in November 2018 and February 2019, from various hydrogeological settings in Cyprus to estimate groundwater recharge using stable isotope equilibration methods combined with soil water balance modeling. A total of 11 soil profiles were taken from the Troodos massif (Galata and Platania) and the Mesaoria plain in Deftera, Nicosia. A vertical profile of stable isotopes has been determined with a 2 cm resolution and measured with Tunable Diode Laser spectrometry. Percolation through the soil profile has been estimated based on the convolution of a seasonal input function using advection-dispersion transport models. In Galata, groundwater percolation estimates range from 20-30 mm/y on clayey soil with natural vegetation to 100-120 mm/y at an irrigated terraced orchard. The results in Platania vary from 20-60 mm/y at steep hillslopes under natural vegetation and amount to 220-340 mm/y in the root zone at the irrigated site with olive trees in Deftera. The comparison of groundwater percolation rates based on stable isotope profiles with those derived from soil water balance modeling indicates a significant bias. While percolation rates correspond well to results obtained from a daily soil water balance model for irrigated fine-grained soils in the plain, recharge rates obtained from stable isotope profile methods on coarse-grained hillslopes tend to be much lower than expected. The observed bias suggests that stable isotope methods, regardless of water extraction or equilibration technique, mainly record the isotope signal of matrix flow. Thus, macro-pore and preferential flow components in coarse-grained soils may not be accounted for. Data collected from the same profiles in late autumn and spring suggest that macro-pore and preferential flow constitute a major component of percolation in coarse-grained shallow hillslope soils of Troodos indeed, without leaving measurable isotope traces in the soil water profile. Additional approaches need to be applied in conjunction with methods based on the evaluation of soil water isotope profiles to overcome this limitation.
Flow and Turbulence Characteristics in the Roughness Sublayer over Real Urban Morphology of Hong Kong
Authors: Mo Ziwei , Liu Chun-Ho , Ho Yat-Kiu
Published: March 2020

Mean flow and turbulence in roughness sublayers (RSLs) over urban areas are complicated because of the diversified building configurations (such as size, shape and orientation, etc.). This study investigates the RSL flows over (part of) the real urban morphology of Hong Kong downtown by wind tunnel measurements. The urban models are fabricated by 3D printing using high-resolution digital maps of building morphology and topography. Vertical profiles of mean and turbulent components in three parallel transects are measured by a constant-temperature hot-wire anemometer (CTA). The wind tunnel results reveal that individual (vertical) profiles of streamwise fluctuating velocity u’’, vertical fluctuating velocity w’’ and vertical momentum flux u’’w’’ show noticeable variations in the RSL. It is largely attributed to the wakes and recirculations after the upstream high-rise buildings. A new analytical solution is proposed to predict the mean wind profiles in the RSL as well as the inertial sublayer (ISL) that is more accurate than the conventional logarithmic law of the wall (log-law). The turbulence in the RSL and ISL are examined in terms of quadrant analysis. The ejection Q2 and the sweep Q4 are stronger in the RSL than those in the ISL, collectively improving street-level air entrainment and pollutant removal.
Earth observation videos in schools– enriching a school lesson on geographic zones with footage from the ISS
Authors: Kramm Clemens , Hodam Henryk , Jürgens Carsten , Lindner Claudia , Ortwein Annette , Schultz Johannes , Selg Fabian , Rienow Andreas
Published: March 2020

„I want to remind the students that asked me the questions, that you are the future of science, technology and exploration. You have that flame. You teachers are fanning the flame, so it becomes a fire of curiosity and future exploration. We trust your generation to come up with the questions and the answers that we need to be better humans in the future.” – Luca Parmitano, Commander of the International Space Station (ISS)

Remote sensing and space travels have become a major tool for research and development in terms of scientific problems since the 1970’s. You don’t have to be an astronaut or pilot to get in touch with the many achievements, applications and scientific findings. Everyone and especially pupils are using them on a daily basis. Therefore, to deliberate the use of these technologies in school is crucial. The topic of remote sensing and space travels is quite complex and diverse, so many teachers are struggling to integrate them into their lessons. The main goal should be to support teachers by providing useful remote sensing school material and to encourage them to use these in their lessons. However teachers need the right science-based tools to fan “the flame, so it becomes a fire of curiosity”. To assist them in an effective manner it is necessary to adapt to their standard procedure of preparing a lesson: a fully developed teaching concept which includes not only the analysis of the topic itself but also the current curricula, the class, the didactics, the method and the material. Thereby it is possible to demonstrate how beneficial and well-grounded such a lesson can be.

The presentation addresses the question of how synergies of human space travels can be used to educate pupils and enhance the fascination of earth observation imagery in the light of problem-based learning in everyday school lessons. It will be shown which possibilities the topic of earth observation from space holds ready for teaching the regular curricula and how teachers can appropriately justify the appliance in their lessons. A comprehensive teaching concept example will be discussed, which matches german teaching standards and uses NASA’s High Definition Earth Viewing (HDEV) videos from the International Space Station (ISS) to enrich a secondary school geography lesson about the different geographic zones on earth.
The solid medium deformation apparatus – reloaded
Authors: Heilbronner Renée , Stunitz Holger , Précigout Jacques , Raimbourg Hugues
Published: March 2020

Rock deformation experiments are used to compile mechanical data sets for minerals and rocks and to study microstructure and texture development.

The Griggs apparatus, a solid medium piston cylinder machine was designed about 60 years ago to investigate rock deformation mechanisms and rheology at elevated confining pressures. In a typical experiment today, the confining medium is NaCl, with confining pressures up to 3 GPa, temperatures up to 1100°C, and displacement rates between 10-8 and 10-2 ms-1 (equivalent to strain rates of 10-7 to 10-3 s-1). In axial tests, the cylindrical samples are 12 to 15 mm long with a diameter of 0.625 mm. In shearing test, split cylinder assemblies are used with 0.5 to 1 mm thick samples introduced along the 45° pre-cut. Reasonable total strains are limited to 30% axial shortening or shear strains of gamma 4. (Higher strains can be attained but are difficult to analyse mechanically. Unlike for gas rigs, torsion is not available for solid medium machines).

As of now, the operational fleet of solid medium deformation apparatus comprises worldwide over 20 machines in different labs (mainly in Europe, U.S.A. and Japan), providing the scientific community with an ever-growing rheological and microstructural data base.

In view of numerous developments in experimental design, as well as improvements of hardware and software for data acquisition and processing, the experimental community was recently invited to a two-day workshop, hosted by the experimental group of Orléans University. The main goal was to discuss the following points:

- how to further improve the apparatus, increase its scope and improve calibrations; 
- how to further improve data processing, and the precision and reliability of the results;
- how to maintain consistency among the labs and through time (backwards compatibility);
- how ensure compatibility of results from axial and shearing experiments;
- how to make the data available to the community.

The poster represents a condensed report of the meeting highlighting a few issues of special interest to the structural community. Visitors to the poster are invited to share their thoughts and to give us feed-back.
Structural controls on stresses and deformations in a large-scale lithospheric shell
Authors: Medvedev Sergei , Minakov Alexander
Published: March 2020

It is well-accepted that stresses and deformation are controlled by active forces, such as tractions applied along lateral boundaries and base of the lithosphere and body forces raised from density heterogeneities within or below the lithosphere. Here we analyze how structure, geometry and strength distribution, of the Earth crust and upper mantle can affect the pattern of stresses and deformation. As an application example, we use the North Atlantic realm which characterized by strong topography and rheological variations and subjected to active forces from, e.g., the Iceland hot spot. We conduct a series of numerical experiments modelling the lithosphere as an elastic shell of altering geometries influenced by various mechanisms. The first set of experiments demonstrates that lithosphere, as a part of the spherical Earth, is structurally stronger than the flat lithosphere if boundary moments applied. An application of more realistic, topography derived, geometry of the lithospheric shell in the second set of experiments demonstrates the importance of strong topography changes, for example along continent-ocean transition, as a concentrator of bending stresses and deformations. In the third set, we show how viscous properties of the sub-lithospheric asthenosphere may control the lateral extent of the membrane stresses in the lithosphere.
Modelling the effect of Nature Based Solutions on slope instability
Authors: Tinti Stefano , Gallotti Glauco , Zieher Thomas , Pfeiffer Jan , Zaniboni Filippo , Rutzinger Martin , Di Sabatino Silvana
Published: March 2020

In the framework of the OPERANDUM (OPEn-air laboRAtories for Nature baseD solUtions to Manage environmental risks) project, modelling the effect of the Nature Based Solutions (NBS) on selected open-air laboratories plays a determinant role. In this work, we focus the attention on the Vögelsberg (Tyrol, Austria) landslide case study, located in the municipality of Wattens. The 0.25 km2 active part of the slope shows annual movement rates in the order of 3.5-6 cm/a. Recent studies provided evidence that the motion is mainly driven by variations of the groundwater level. The latter are related to prolonged moist periods during which excessive rainfall or snow melt water can infiltrate and act on the geo-hydrological system. With the aim of enhancing the slope stability employing NBS, a detailed analysis of the hydrogeology and the slope characteristics have been carried out, obtaining the required technical parameters describing the involved soil material. Furthermore, a slope stability analysis by means of different numerical models has been performed. Results prove that variations of the groundwater level in the range of 1-2 m can strongly affect the stability of the slope. Thus, specific NBS should aim at reducing the amount of infiltrating water. Examples of such NBS include the adaptation of forest management and land use planning, the introduction and re-activation of drainage channels and the sealing of leaky streams and channels. Beside the effects of the variation of the groundwater level, results have proved that the slope could fail under the action of a moderate seismic load. In this scenario, it is likely that the effects of the NBS would be insufficient to maintain the slope intact.
Introducing EGM2020
Authors: Barnes Daniel , Barnes Daniel , Beale James , Small Howard , Ingalls Sarah
Published: March 2020

The National Geospatial-Intelligence Agency [NGA], in conjunction with its U.S. and international partners, has completed its next Earth Gravitational Model (EGM2020), to replace EGM2008. The new ‘Earth Gravitational Model 2020’ [EGM2020] will retain the same harmonic basis and resolution as EGM2008. As such, EGM2020 will be a ellipsoidal harmonic model up to degree (n) and order (m) 2159, but will be released as a spherical harmonic model to degree 2190 and order 2159. EGM2020 has benefited from new data sources and procedures. Updated satellite gravity information from the GOCE and GRACE mission, will better support the lower harmonics, globally. Multiple new acquisitions (terrestrial, airborne and shipborne) of gravimetric data over specific geographical areas (Antarctica, Greenland …), will provide improved global coverage and resolution over the land, as well as for coastal and some ocean areas. Ongoing accumulation of satellite altimetry data as well as improvements in the treatment of this data, will better define the marine gravity field, most notably in polar and near-coastal regions. NGA and partners are evaluating different approaches for optimally combining the new GOCE/GRACE satellite gravity models with the terrestrial data. These include the latest methods employing a full covariance adjustment. NGA is also working to assess systematically the quality of its entire gravimetry database, towards correcting biases and other egregious errors where possible, and generating improved error models that will inform the final combination with the latest satellite gravity models. Outdated data gridding procedures have been replaced with improved approaches. For EGM2020, NGA intends to extract maximum value from the proprietary data that overlaps geographically with unrestricted data, whilst also making sure to respect and honor its proprietary agreements with its data-sharing partners.
Hybridization of atomic and electrostatic accelerometers for satellite control and gravity field recovery
Authors: Knabe Annike , Wu Hu , Schilling Manuel , Müller Jürgen
Published: March 2020

Satellite gravimetry missions like GRACE and now GRACE-FO measure the global gravity field and its variations in time. Gravity field solutions are typically estimated monthly, but a higher accuracy and a better temporal resolution is required for various applications in the geosciences. With the addition of the laser ranging interferometer (LRI) to GRACE-FO, a significant improvement over GRACE concerning inter-satellite ranging was achieved. The determination of the non-gravitational forces acting on the satellites, however, remained conceptually unchanged. In ground-based applications, e. g., gravimetry and inertial navigation, the progress in the development of cold atom interferometry (CAI) leads to drift-free, accurate, smaller, more robust and reliable quantum sensors. Experiments on sounding rockets and aeroplanes demonstrate the potential of this technique and open up possibilities for applications on satellite missions.

We investigate potential next-generation gravity missions (NGGM) following the GRACE design, employing an LRI with GRACE-FO characteristics and the utilisation of CAI in combination with classical accelerometers. A CAI accelerometer also offers the possibility to better determine degree 2 gravity field coefficients, due to its long-term stability. A closed-loop simulator has been developed to test different scenarios of orbit configurations and system/instrument parameters. Regarding the orbit configurations, parameters like inter-satellite distance, orbit altitude and repeat cycle are varied. The results will be evaluated based on recovered gravity fields.

As further benefit, the concept of a CAI based drag-free control system is investigated and its impact on possible satellite orbits for NGGMs and the resulting gravity fields is discussed. As the control system is of critical importance for the success of the mission, key parameters are analysed. Furthermore, the requirement for the drag compensation depends on the knowledge of the accelerometer’s scale factor. Related to this aspect, requirements on the drag compensation are derived for different scenarios. We will present first results of the simulation studies.

H.W. acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy – EXC 2123 “QuantumFrontiers, Project-ID 390837967“. M.S. acknowledges initial funding for the DLR Institute by the Ministry of Science and Culture of the German State of Lower Saxony from “Niedersächsisches Vorab”.
UAV observation of the recent evolution of the Planpincieux Glacier (Mont Blanc – Italy)
Authors: Giordan Daniele , Dematteis Niccolò , Troilo Fabrizio
Published: March 2020

Planpincieux is one of the glaciers located on the Italian side of the Mont Blanc (Italy). This glacier is monitored using a permanent monoscopic time-lapse camera since 2013. In 2019, the frontal part of the glacier has been characterized by a critical acceleration that could trigger a large ice avalanche able to reach the underlying Planpincieux village. During the emergency, the working group composed of Fondazione Montagna Sicura, CNR IRPI and the Aosta Valley Region Authority improved the monitoring system with a ground-based SAR to control the glacier evolution. An important data source used for a better understanding of the structure of the more unstable glacier sector has been the acquisition of a sequence of digital terrain models (DTMs) acquired by unmanned aerial vehicles (UAV) and helicopters. The approach adopted for the DTM generation is the acquisition of a photo sequence and the application of the structure from motion algorithm. The investigated area of the glacier is located in high-mountain environment and is characterized by a complex topography that does not facilitate the use of UAV. But the availability of a sequence of DTMs has been very useful for the improvement of the knowledge of the current state and recent evolution of the Planpincieux Glacier.
Check dams effects on plant and soil interface immediately after wildfire
Authors: Timóteo  Rodrigues Bruno , Esteban Lucas-Borja Manuel , Antonio Zema Demetrio , Yu Yang
Published: March 2020

Installation of check dams is one of the approaches for erosion mitigation on watersheds all around the world, among others soil and vegetation restoration tools. National, regional and local governments have spent in the past, and still currently spend, important funds for basin scale erosion-control schemes (maintenance and new implementations) using numerous check dams. The functions of these structures are diverse and vary depending on the geomorphic context where the structures are built. However, with the number of check-dams increasing to control floods, regulate sediment transport, reduce upstream reach slopes, and stabilize torrent beds, some projects experience disappointing results and project objectives are not achieved due to many different circumstances. Causes of failure include poor construction quality, inadequate check dam location and lack of adequate design criteria. These failures lead to reduced confidence in using check-dams as restoration tools. Moreover, construction of dense networks of check-dams, or alternatively of a few large open structures, implies major economic investments, but a comprehensive evaluation of their long-term effectiveness is still lacking. This work aims to analyse the effect of check dam over soil and plant interface inmediatelly after wildfires. The proposed work pretends to share scientific  evidence of this effect using a study case located in the Mediterranean basin.
Impact of a-priori SRP models and ECOM models on GNSS precise orbit determination
Authors: Chang Xiao , Männel Benjamin , Schuh Harald , Galas Roman
Published: March 2020

As one of the products of the International GNSS Service (IGS), precise orbits for Global Navigation Satellite Systems (GNSS) play an important role in many geoscientific applications. Currently, the precision and consistency of GNSS orbits are still limited by insufficient knowledge of spacecraft response to non-conservative perturbations, of which the solar radiation pressure (SRP) has the strongest influence. SRP modeling strategies adopted by IGS Analysis Centers (ACs) can be categorized: 1) analytical SRP model like the ROCK models (Fliegel et al. 1992), 2) empirical representation, for example by estimating ECOM parameters (Beutler et al. 1994, Springer et al. 1999a, and Arnold et al. 2015), and 3) the combination of both, hybrid empirical-physical SRP model such as adjustable box-wing model (e.g. Rodriguez-Solano et al. 2012). While empirical models fit the observations well, the loss of physical explanation may cause unexpected systematic errors. Uncertainties in the a-priori SRP models, which rely on the optical coefficients and surface structure of the satellites, can also degrade the determined orbit systematically. Using a hybrid model, i.e. estimation of empirical parameters on top of a-priori model, is expected to take the advantage of the existing satellite properties and to compensate for the inaccuracy related to the satellite properties based on observations. Thus, different hybrid models have to be tested for each constellation and block type.

 

In this study, we assess the GNSS precise orbit determination (POD) based on different setups of a-priori models and ECOM parametrization. The results will be presented as follows: 1) first, the orbits difference introduced by a-priori model is analyzed by comparing orbit with the one based on pure ECOM models. 2) Second, the effect of a-priori models will be discussed by assessing the estimated ECOM parameters. 3) Third, the derived orbit will be compared with the final orbits of selected IGS ACs. 4) The effect of the selected SRP modeling strategy on geodetic parameters will be discussed with special focus on the estimated station coordinates.
The role of spatial resolution of climate data for the quality of simulated wind power generation – A multi-country analysis
Authors: Gruber Katharina , Baumgartner Johann , Klöckl Claude , Regner Peter , Schmidt Johannes
Published: March 2020

Integration of a high share of renewables into the energy system comes with its implications. In order to study long and short-term effects on the electrical system, long time series of power generation with high spatial resolution are necessary. In recent years, reanalysis data have become a popular resource for obtaining these power generation datasets, however with the drawback of a rather coarse spatial resolution of several kilometres (MERRA-2: approx. 50km, ERA5: approx. 31 km). In order to overcome this limitation, reanalysis datasets can be combined with other datasets with a higher spatial resolution.

In the present study, we assess whether applying the Global Wind Atlas (GWA) developed by the Technical University of Denmark with a spatial resolution of 1 km can improve wind power generation simulated from two reanalysis (MERRA-2 and ERA5)  datasets when compared to observed power generation. Furthermore, these two reanalysis datasets are compared to determine how different spatial resolution of underlying reanalysis datasets affects the resulting time series. Wind power generation is simulated from reanalysis wind speeds based on a physical model. For wind speed bias correction to specific locations, mean wind speeds are approximated to GWA wind speeds. A turbine-specific power curve model scaled by the turbine specific power is applied to account for different technical performance. The analysis is conducted for different regions of the world (USA, Brazil, Austria, South Africa) and for different spatial and temporal levels, to determine how different datasets perform on different spatio-temporal scales.

Preliminary results show that bias correction with the GWA has a positive impact on simulation results for MERRA-2, the dataset with lower spatial resolution, while the effect for ERA5 is ambiguous. The error between simulated and observed wind power generation time series can be decreased by spatial and temporal aggregation and a positive, but not very strong correlation between system size (defined by a wind-correlation indicator) and simulation quality (higher correlation, lower error measures) could be identified.

Based on these results, we recommend applying additional wind speed bias correction on datasets with rather coarse spatial resolution, while the quality of newer datasets with high spatial resolution may be sufficient to be used without additional bias correction.