bluuebunny/crossref_metadata_2025 huggingface dataset:
Using robust baseline extraction to examine synoptic-scale variability in European CO2
Authors: Resovsky Alex , Ramonet Michel , Rivier Leonard , Conil Sebastien , Spain Gerard
Published: March 2020

Continuous measurements of long-lived greenhouse gases at ground-based monitoring stations are frequently influenced by regional surface fluxes and atmospheric transport processes, which induce variability at a range of timescales.  Dissecting this variability is critical to identifying long-term trends and understanding regional source-sink patterns, but it requires a robust characterization of the underlying signal comprising the background air composition at a given site.  Methods of background signal extraction that make use of chemical markers or meteorological filters yield reliable estimates, but often must be adapted for site-specific measurement conditions and data availability.  Statistical baseline extraction tools provide a more generally transferable alternative to such methods.  Here, we apply one such technique (REBS) to a continuous time series of atmospheric CO2 readings at Mace Head, Ireland and compare the results to a modeled baseline signal obtained from local wind observations. We then assess REBS’ performance at two continental sites within the Integrated Carbon Observation System (ICOS) network at which baseline signals are derived using back-trajectory analyses.  Overall, we find that REBS effectively reduces the bias in wintertime baseline estimation relative to other statistical techniques, and thus represents a computationally inexpensive and transferable approach to baseline extraction in atmospheric time series. To investigate one potential application of such an approach, we examine wintertime synoptic-scale CO2 excursions from the REBS baseline during the period 2015-2019.  Our goal is to identify relationships between the timing and strength of such events and to better understand sub-seasonal variability in CO2 transport over Europe.
Analysis of Swarm Electric Field Data in View of Tsunami Events and related Earthquakes
Authors: Jarmolowski Wojciech , Wielgosz Pawel , Krypiak-Gregorczyk Anna , Milanowska Beata
Published: March 2020

Three Swarm satellites are equipped with Langmuir Probes (LP) measuring in-situ electron density of Earth electric field and POD GNSS receivers determining topside total electron content (TEC) in the upper ionosphere. It is proved that different events on the Earth and in its atmopshere have their own impact on Earth electric field, and the earthquakes are in this group. Many strong earthquakes induce tsunamis, which are also suspected as contributing to the gravity waves having an impact on the ionospheric TEC. These reasons encourage to the study on the sensitivity of Swarm LP and POD GNSS data to the abovementioned phenomena. Referring to the sensitivity of TEC data derived from GNSS stations to Earthquakes, sensitivity of GNSS and LP data at around 500 km high orbit is analyzed here. A similar orbital height can be found in case of many LEO missions equipped at least with GNSS POD receivers, which makes Swarm especially interesting data acquisition platforms.

The investigation of Swarm data in view of Tsunamis and earthquakes is difficult due to several factors. There are only three satellites, the two of which fly almost together, which gives in fact only two points of the survey. The orbital repetition period is long, which seriously limits the number of comparable observations in terms of the location and time of the day. Finally, the number of large earthquakes and tsunami events in time of Swarm science mission is low, and many Earthquakes do not coincide sufficiently with Swarm passes in time and space. All these factors, however, doesn’t exclude an opportunity of analyzing of Swarm data passes above the earthquakes of magnitude nearby 8, linked with the tsunamis reaching several decimeters.

Swarm LP data is detrended and analyzed before the earthquakes and also during the earthquakes and resulting tsunami events. The GNSS POD topside TEC from Swarm is analyzed together as a background for LP data. In-situ electron density disturbances occurring during a pass close to the earthquake is compared to selected STEC measurements between LEO and GNSS satellites. Additionally absolute STEC values from selected nearby ground stations are analyzed in order to  find existing correlations for detected disturbances in the electric and magnetic fields. All the observations are sparse in time and space, and therefore, leave some unanswered questions and uncertainties. However, several interesting perturbations over earthquake/tsunami events are observable in both Swarm LP data and GNSS TEC data.
Benchmark data for verifying background model implementations in orbit and gravity field determination software
Authors: Lasser Martin , Mayer-Gürr Torsten , Kvas Andreas , Koch Igor , Lemoine Jean-Michel , Neumayer Karl Hans , Dahle Christoph , Flechtner Frank , Flury Jakob , Meyer Ulrich , Jäggi Adrian
Published: March 2020

In the framework of the COmbination Service of Time-variable Gravity fields (COST-G) gravity field solutions from different analysis centres are combined to provide a consolidated solution of improved quality to the user. As in many other satellite-related sciences, the correct application of background models plays a crucial role in gravity field determination. Therefore, we publish a set of data of various commonly used forces in orbit and gravity field modelling (gravity field, tides etc.) evaluated along a one day orbit arc of GRACE, together with some additional data to enable easy comparisons. The benchmark data is compiled with the GROOPS software by the Institute of Geodesy (IfG) at Graz University of Technology. It is intended to be used as a reference and provides the opportunity to test the implementation of these models at various analysis centres. In view of the COST-G GRACE (-FO) gravity field combinations, we show the outcome of such a background force field software validation for the GRACE-SIGMA software of the Leibniz University of Hannover (LUH), the GRGS GINS software, EPOS of the German Research Centre for Geosciences (GFZ) and the Bernese GNSS software from AIUB (Astronomical Institute, University of Bern). We consider differences in the force modelling for GRACE (-FO) of one order of magnitude less than the accelerometer noise to be negligible, and make an attempt to quantify and explain differences exceeding this threshold.
Automatic detection of the electron density from the WHISPER instrument onboard CLUSTER
Authors: Gilet Nicolas , De Leon Emmanuel , Jegou Klet , Bucciantini Luca , Vallières Xavier , Rauch Jean-Louis , Décréau Pierrette
Published: March 2020

The Waves of HIgh frequency and Sounder for Probing Electron density by Relaxation (WHISPER) instrument, is part of the Wave Experiment Consortium (WEC) of the CLUSTER mission. The instrument consists basically of a receiver, a transmitter, and a wave spectrum analyzer. It delivers active (sounding) and natural electric field spectra. The characteristic signature of waves indicates the nature of the ambient plasma regime and, combined with the spacecraft position, reveals the different magnetospheric boundaries and regions. The electron density can be deduced from the characteristics of natural waves in natural mode and from the resonance triggered in the sounding mode. The electron density is a parameter of major scientific interest and is also commonly used for the calibration of the particles instruments.

Until recently, the electron density required a manual intervention consisting in visualizing input parameters from the experiments, such as the WHISPER active/passive spectrograms combined with the dataset from the other instruments onboard CLUSTER.

Work is being carried out to automatize the detection of the electron density using Machine Learning and Deep Learning methods.

To automate this process, knowledge of the region (plasma regime) is highly desirable. In order to try to determinate the different plasma regions, a Multi-Layer Perceptron has been implemented. This model consists of three neuronal network dense layers, with some additional dropout to prevent overfitting. For each detected region, a second Multi-Layer perceptron was implemented to determine the plasma frequency. This model has been trained with 100k spectra using the plasma frequency values manually found. The accuracy can reach until 98% in some plasma regions.

These models of the electron density automated determination are also currently applied on the dataset of the mutual impedance instrument (RPC-MIP) onboarded ROSETTA and will be useful for other space missions such as BepiColombo (especially for PWI/AM2P experiment) or JUICE (RPWI/MIME experiment).
Modelling the impact of increased lateral connectivity on nutrient retention in Austrian Danube floodplains
Authors: Tschikof Martin , Natho Stephanie , Hein Thomas , Bondar-Kunze Elisabeth
Published: March 2020

In the last centuries, rivers in Central Europe have severely suffered from hydro-morphological alterations and excessive nutrient inputs. Their adjacent floodplains have the ability to retain transported nutrients in case of inundation, but are subject to progressing decoupling from the main river stem. In the Austrian Danube Floodplain National Park, restoration measures have been carried out and are planned for the near future to increase lateral connectivity in accordance with navigation purposes.

We investigated nutrient retention capacity in seven differently connected side arms and the potential effects of further proposed reconnection measures using two complementary modeling approaches. With existing monitoring data on hydrology, nitrate and total phosphorus concentrations for three side arms, we derived a multivariate statistical model and compared these results to a larger scaled semi-empirical retention model (Venohr et al. 2011). We modelled nutrient retention at current state and after completion of side arm reconnections in a dry (2003) and wet (2002) hydrologic year.

Both models show comparable annual retention rates and agree in calculating higher nutrient retention in floodplains where reconnection allows more frequent inundations at low discharges. The semi-empirical approach results in highest retention rates at low hydraulic loads and shows more reasonable results at high floods. On the other hand, the statistical approach predicts increasing retention rates with higher nutrient loads entering the side arms and also takes into account nitrate reduction in the remaining water bodies at times of no surface water connection.

Our results suggest that water quality of the Danube River could be improved by increasing parameters related to lateral connectivity between river and floodplain. These include in particular the frequency and area of inundation, as well as nutrient input loads into the reactive zones of floodplains. Still, a frequently hydrologically connected national park stretch after restoration reduces nutrient loads of the Upper Danube by less than 0.1% due to its small areal extent in relation to transported river nutrient loads. In order to sustain an adequate water quality in future, both a reduction in nutrient emissions and a larger area of functional floodplains along the Danube River are required.

References:

Venohr, M., Hirt, U., Hofmann, J., Opitz, D., Gericke, A., Wetzig, A., ... & Mahnkopf, J. (2011). Modelling of nutrient emissions in river systems–MONERIS–methods and background. International Review of Hydrobiology, 96(5), 435-483.

Key words:

River floodplains, lateral connectivity, nutrient retention, river restoration, floodplain reconnection, water quality
Lower crustal structures at Rockall Trough (west of Ireland) by Full waveform inversion
Authors: Tomar Gaurav , J. Bean Christopher , C. Singh Satish
Published: March 2020

Rockall trough lies to the west of Ireland in NE Atlantic, it has a complex geology and has been debated for controversial geology for more than two decades. We have performed Full waveform inversion (FWI) on 2D seismic data set that is recorded in 2013-14 by using 10 km long streamer, this 2D seismic line is situated near the North-West margin in the Rockall Bank area. Full waveform inversion (FWI) is a powerful technique for obtaining elastic properties of the sub-surface from the seismic data. FWI provides properties of the sub-surface at the scale of the wavelength of the data set. We used travel time tomography on downward extrapolated data set to obtain a smooth starting velocity model for FWI. Downward continuation is a technique that enhances the first arrival and also reduces the computation time for forward modelling in FWI. The velocity model obtained from refraction travel time tomography, indicates the velocity from 1.6-4 km/s for the sediments and we have also observed very high velocity ~ 6-7.5 km/s just 3 km below sea-floor. We have performed FWI using these TTT velocity model as a starting model and inverted the refractions along with the wide angle reflections in the frequency range of 3-10 hz. FWI results gives the velocity of 6-7.2 km/s as well as defines geological structures that can be seen in the migrated seismic section. These high velocity structures could be a part of the continental crust and/or lower oceanic crustal igneous rocks like Gabbro.
Storm surge modelling in the North Sea-Baltic sea transition zone: model inter-comparison of static wind simulations
Authors: Andrée Elin , Bendix Hansen Asger , Dahl Larsen Morten Andreas , Skovgaard Madsen Kristine , Drews Martin
Published: March 2020

Extreme water levels in the micro-tidal transition zone between the North Sea and the semi-enclosed Baltic sea are predominantly determined by wind forcing associated with synoptic-scale weather systems. This connection between the two seas is partly blocked by low-lying islands, and the bathymetry comprises a complex mixture of narrow, deep channels and shallow sills. Coastlines in the Southern Kattegat and the Western Baltic Sea are therefore exposed to wind forcing from a large range of directions, and the extent of water build-up varies strongly between locations.

In the present study, we aim to determine the most critical wind direction for most of the Danish coastlines by employing numerical modelling experiments. The simulations are conducted with two different regional 3D ocean models to enable model inter-comparison. The DMI-HBM model implements a structured grid with fully dynamic 2-way nesting, while the MIKE 3 FM invokes an unstructured mesh. Both models have grid resolutions of ~0.5–1 km within the Danish Straits and 4–6 km in the offshore Baltic Sea. The models are forced by synthetic wind fields, where both wind speed and wind direction are maintained at fixed levels over the entire model domains. Pairs of model simulations are then obtained by varying the angle from which the wind is blowing.

From the model outputs, we describe the temporal evolution of the water level by the site-specific peak water level, and the time required for the response to reach its peak value. Our results show a steady rise of the water level up until the peak value. The peak water level significantly overshoots the final equilibrium water level, which develops further into the simulations. Our study facilitates a better understanding of the sea level's response to extreme and persistent winds in a region with highly complex geometry.
Water vapour in the Upper Troposphere and Lower Stratosphere (UTLS): A new vertically resolved dataset from limb and nadir satellite observations
Authors: Ye Hao , Hegglin Michaela , Krämer Martina , Rolf Christian , Laeng Alexandra , Hurst Dale , Vömel Holger
Published: March 2020

Water vapour in the upper troposphere and lower stratosphere (UTLS) has a significant impact both on the radiative and chemical properties of the atmosphere. Reliable water vapour observations are essential for the evaluation of the accuracy of UTLS water vapour from model simulations, and thereafter of the contribution to the global radiative forcing and climate change. Limb-viewing and nadir satellites provide high quality water vapour observations above the lower stratosphere and below the upper troposphere, respectively, but show large uncertainties in the tropopause region.  Within the ESA Water Vapour Climate Change Initiative, we have developed a new scheme to optimally estimate water vapour profiles in the UTLS and in particular across the tropopause, by merging observations from a set of limb and nadir satellites from 2010 to 2014. The new data record of vertically resolved water vapour is validated against the aircraft in-situ water vapour observations from the JULIA database and frostpoint hydrometer records from WAVAS. Furthermore, the new data record is used to evaluate the UTLS water vapour distribution and interannual variations from chemistry-climate model (CCM) simulations and the ERA-5 reanalysis.
Dating rapid climate change in the North Atlantic during Heinrich Stadial 1
Authors: Burke Andrea , Greenop Rosanna , Rae James , Rees-Owen Rhian , Reimer Paula , Heaton Timothy
Published: March 2020

Paleoclimate records from the North Atlantic show some of the most iconic signals of abrupt climate change during the ice ages. Here we use radiocarbon as a tracer of ocean circulation and air-sea gas exchange to investigate potential mechanisms for the abrupt climate changes seen in the North Atlantic over the last deglaciation. We have created a stack of North Atlantic surface radiocarbon reservoir ages over the past 20,000 years, using new synchronized age models from thirteen sediment cores refined with thorium normalization between tie-points. This stack shows consistent and large reservoir age increases of more than 1000 years from the LGM into HS1, dropping abruptly back to approximately modern reservoir ages before the onset of the Bolling-Allerod. We use the intermediate complexity earth system model cGENIE to investigate the potential drivers of these reservoir age changes. We find that sea ice, circulation and CO2 all play important roles in setting the reservoir age. We use these coherently dated records to revisit the sequence and timing of climatic events during HS1 and the last deglaciation, and show that Laurentide Heinrich Events are a response to stadial conditions, rather than their root cause.
The kinematic evolution of the Demerara plateau and Guyana-Suriname margins
Authors: Gómez-Romeu Júlia , Masini Emmanuel , Kusznir Nick , Calassou Sylvain
Published: March 2020

The Caribbean region has undergone a complex plate kinematics evolution due to the interaction between Central Atlantic pre-subduction paleogeography and Caribbean subduction dynamics. To better understand the initiation and dynamics of the Caribbean subduction it is important to determine the pre-subduction template. However, this template cannot be easily recognized as it either suffered from pervasive tectonic overprinting or has been consumed by subduction. To address this problem, it may be valuable to first unravel the structure and deformation history of the surrounding areas of the Caribbean region.

Here we investigate the kinematic evolution of the Triassic-Jurassic Demerara plateau and Guyana-Suriname (i.e Dp and G-S) margins which are present-day located to the south of the Caribbean subduction. To achieve our aim, we use seismic, gravity and magnetic data and apply a gravity anomaly inversion technique to determine Moho depth, crustal basement thickness and crustal thinning factor.

The Dp and G-S margins avoided subduction and consequently preserve the divergent history of Early Jurassic to Early Cretaceous rifting related to the opening of the Central Atlantic and Equatorial Atlantic respectively. This is inferred by a complex architecture of the Dp and G-S margins characterized by a set of transfer zones that crosscut each other.

By unravelling the kinematic evolution of the Dp and G-S margins we attempt to determine the pre-subduction template of the surrounding area of the Caribbean region.
Multi scale smoothed particle hydrodynamics using particle agglomeration for simulating rainfall-runoff processes
Authors: Somasundaram Manickam , Gelleszun Marlene , Meon Günter
Published: March 2020

We present a novel particle based numerical method, which supports regions of particle agglomeration, for simulating water flow in hydrological applications. This is done to tackle the difficulties that arise while modeling due to diverse operation scales, both in space and time. In this study we aim to concentrate only on multiple spatial scales. Smoothed particle hydrodynamics (SPH) is a mesh free method and it enables the interactions of particles in different media, for example media with different porosities. We use a technique of agglomerating particles based on parameters like velocity and treat the agglomerated mass as a single particle. With the presented method, the SPH method can be extended to rainfall-runoff models with multi-phase soil properties. First, the numerical method associated with SPH to solve the shallow water equation (SWE) is introduced. Then the way in which the mass term is replaced during agglomeration is derived. Calculating the modified parameters of a newly agglomerated particle to satisfy the continuity criteria is also introduced and derived. In order to validate the method, benchmark cases that align with our target application with experimental data were chosen from literature study. These include, uniform rainfall falling on an one-dimension flat slope channel, non-uniform rainfall with different duration over an one-dimension flat slope. In order to explore the extent of method a three-dimension test case, where water particles are allowed to pass through a different medium stacked on top of one another with different porosity, is chosen. The three-dimension benchmark case is not inspired from a real time application like the one-dimension test cases, but the results can be scaled and deployed into a flood-forecasting simulation. Also, the proposed method was proven robust and the one-dimension test cases show good agreement with experimental results. The three-dimension test case shows decent improvement in computational time and can provide new possibilities for simulating practical hydrological applications.
From Silos to FAIR Services: Interoperable application of geospatial data for longitudinal surveys in the Social Sciences.
Authors: Löwe Peter , Gebel Tobias , Steinhauer Hans Walter
Published: March 2020

Due to the european INSPIRE directive to establish an infrastructure for spatial information in Europe, the number of national data sources in Europe which are open to the public or at least science continues to grow. 

However, challenges remain to enable easy access for society and science  to these previously unavailable data silos based on standardized web-services, as defined by the Open Geospatial Consortium (OGC). This is crucial to ensure sustainable data generation and reuse according to the FAIR principles (Findable, Accessible, Interoperable, Reusable). 

We report on an interdisciplinary application, using spatial data to improve longitudinal surveys in the social sciences, involving building plans encoded in CityGML, PostGIS, MapServer and R.

The Socio-economic Panel (SOEP) as part of the German Institute for Economic Research (DIW Berlin) provides longitudinal data on persons living in private households across Germany. Lately the SOEP sampled households in certain neighborhoods within cities, areas of the so called „Soziale Stadt“ (social town). Because of restricted area, spatially referenced data has been used. Information on the level of census tiles provided by the Federal Statistical Office was used to form regional clusters. 

Within these clusters addresses, spatially referenced by the German Federal Agency for Cartography and Geodesy (BKG), have been sampled. This way, we made sure addresses are within the neighborhoods to be surveyed. As this procedure turned out to reduce organizational burden for the survey research institute as well as for the interviewers and at the same time allows for generating random household samples, it is considered for future use. Yet, addresses can belong to residential buildings as well as cinemas or hotels. 

To meet with this obstacle we evaluate the use of 3D Building Models provided by the German Federal Agency for Cartography and Geodesy (BKG).
This data is distributed as compressed data archives for the 16 states of Germany, each containing very large numbers of CityGML files containing  LoD1 data sets for buildings. The large storage footprint of these data sets makes their reuse by social scientists using standard  statistical software (such as R or Stata) on desktop computers difficult at best. This is overcome by providing flexible access to Areas of Interest (AOI) through OGC Webservices (WMS/WFS) based on a PostGIS database. The ingestion process is based on the new GMLAS driver of the ogr software project for Complex Features encoded in Geographic Markup Language (GML) based on application schemas.
Trapped Sea-Lakes, the anomalous water bodies that herald the birth and demise of the oceans
Authors: Palcu Dan Valentin , Krijgsman Wout
Published: March 2020

The tectonic opening and closure of oceans presents windows of opportunity for the formation of anomalous waterbodies which we term “trapped-sea-lakes” (TSL); poorly connected or isolated water basins characterized by anomalohaline (brackish, hyperhaline, mixohaline or limnetic according to the Venice system) conditions that change over time, reflecting the fluctuating connectivity with the global ocean and the climatic history of their watershed. TSLs contain elements typical for a sea (basin bathymetry, marine chemistry, faunistic elements), but also reflect lacustrine aspects like endemism and major environmental fluctuations over geological time. They are characterized by unusual large dimensions, long life-span (compared with classic lakes), anomalous environments with salinity and chemistry controlled by the limited connectivity with the global ocean and by climate forcing.

Here we present a classification of TSLs, supported by key studies, showing that Anoxic Giants, Salt Giants and brackish mega-basins are all related forms of TSLs and that transition between them is possible. We showcase several key TSLs that occurred over the last 100 Million years: the East African rift basins and the early South Atlantic basins providing a reference for the lacustrine - evaporitic transitions that characterize the opening of oceans and similarly the key moments in the closure of the Tethys ocean, presented to showcase the post-oceanic restriction episodes of the Paratethys waterworld in Central Eurasia, with its particular evaporite-brackish environment transitions.

The transition from marine basins to TSL is reversible and our model predicts that TSLs that lie in the proximity of the global ocean are likely to trigger cataclysmic floods during the partial or full reconnection with the global ocean if the reconnected water bodies have different water levels. These floods can be either in the form of marine flooding events, such as the Zanclean deluge of the Mediterranean, when TSL’s water level is below the global sea-level or in the form of “lake burst-floods”, if the isolated TSL evolves to a mega-lake with water levels above the global ocean. We present a first example of such lake burst-floods that scarred the Aegean Sea and likely turned the Mediterranean-Paratethys realm into a unique system of double-locked TSLs, in the eve of the Messinian Salinity Crisis.
Water Flux Partitioning for Eddy Covariance Data
Authors: Nelson Jacob
Published: March 2020

Here we present an overview of methods for partitioning evapotranspiration (ET) from eddy covariance data. We focus on methods that are designed to use the core energy and carbon fluxes, as well as meteorological data, and do not require supplemental measurements or campaigns. A comparison of three such methods for estimating transpiration (T) showed high correlations between them (R2 of  daily T between 0.80 and 0.87) and higher correlations to daily stand T estimates from sap flow data (R2 between 0.58 and 0.66) compared to the tower ET (R2 = 0.49). However, the three methods show significant differences in magnitude, with T/ET values ranging from 45% to 77%. Despite the differences in magnitude, the methods show plausible patterns with respect to LAI, seasonal cycles, WUE, and VPD; moreover, they represent an improvement compared to using ET as a proxy for T even when filtering for days after rain. Finally, we outline practical aspects of applying the methods, such as how to apply the methods and code availability.
Re-establishing mass balance measurements on Aktru glaciers (Altai).
Authors: Smirnov Andrey , Kutuzov Stanislav , Erofeev Aleksandr , Kopysov Sergey , Lavrentiev Ivan , Abbasov Zamir , Nikitin Kirill
Published: March 2020

The rate of glaciers decline in the late 20th-early 21st centuries increased substantially. These circumstances are of particular relevance in mountainous areas, where glaciers are one of the most important landscape-forming factors, regulate river flow and serve as a potential source of hazardous processes and phenomena that threaten economic and recreational activities. The Aktru Glaciers (Maliy Aktru since 1962, Leviy Aktru and Vodopadniy since 1977) are the ‘reference’ glaciers of the World Glacier Monitoring Service (WGMS).

The Aktru glacier monitoring programs were suspended in 2012. There were only two glaciers with a continuous series of measurements in Russia. Both of these glaciers are located in the Caucasus. The vast area of Northern Eurasia at the current time is not covered with direct measurement data on glaciers, which does not allow to validate the results of global and regional projections of climate and environmental change and causes serious concern to the scientific community.

Here we present the first results of mass balance measurements on Leviy Aktru glacier re-established in 2019. The detailed accumulation measurements supplemented with new ablation stakes network and AWS enabled calculation of the mass balance of -425 mm w.e. in 2018/19. Ice thickness and bedrock topography was estimated using the GPR measurements. Additionally, the glacier volume changes from 2000 to 2019 were assessed for the region using SRTM-X and Pleiades DEM. The data obtained can be used to validate regional hydrological and mass balance models for Altai mountains.

The Pléiades stereo-pair used in this study was provided by the Pléiades Glacier Observatory initiative of the French Space Agency (CNES).
Smart Geospatial System Design for Real-Time Risk Assessment at the Highly Active Area of the Ionian Islands, Greece
Authors: Kotsi Evelina , Mavroulis Spyridon , Diakakis Michalis , Vassilakis Emmanuel , Lekkas Efthymios
Published: March 2020

The Ionian Islands are located in the northwestern part of the Hellenic Arc and constitute one of the most seismically active areas in the Mediterranean. Building a geospatial database including all the available geo-information layers was the initial step for identifying and delineating the earthquake-related environmental effects by using various mapping algebra techniques and algorithms. Landslide, liquefaction and tsunami related inventories were created. Real time recording network of sensors such as meteorological instruments, seismographs, accelerometers etc was designed to trans pond data telemetrically and feed a dynamically interactive geodatabase, which in turn act as a smart tool for declaring an area as vulnerable to a specific hazard. The abovementioned approach can contribute to the reduction of the consequences after a disastrous event, as it will provide useful information to the civil protection authorities for increased alertness during an ongoing threat.

The identification of the risk areas by using various methods has become significant in recent years due to the fact that among others it serves as a valuable tool for revealing and highlighting sites of significant hazards. In this study we present a smart tool, specially developed for recording and taking under consideration any changing parameters that affect the susceptibility of an area to any of the studied geo-hazards and highlight it on a digital real time updateable map.
Pore Scale Analysis of Suitability for Geological Carbon Storage, Implications for the UK Geoenergy Observatories Project
Authors: Payton Ryan L , Fellgett Mark , Kingdon Andrew , Clark Brett , Hier-Majumder Saswata
Published: March 2020

Geological carbon storage (GCS) has been identified as a crucial process in tackling rising anthropogenic CO2 emissions. We examine 4 sandstone cores from the Scottish Middle Coal Measures Formation at the UK Geoenergy Observatories (UKGEOS) site in Glasgow using X-ray micro computed tomographic images to assess the carbon storage capacity. Each 3D microtomographic image was processed by binary segmentation to extract the macroporosity from the greyscale images, pore network analysis to establish the effective porosity, and permeability simulation using a finite volume solver. We compare this location to 7 samples from the Wilmslow Sandstone Formation in Sellafield as a precursor analysis of the laterally equivalent Sherwood Sandstone at the under construction Cheshire UKGEOS site. We find a significant difference in porosity and permeability between the two sites with Sellafield samples showing a porosity range of 9.73-25.31% whilst Glasgow samples display a range of 0.38-1.65%. The Sellafield samples also show a significant proportion of connected porosity ranging between 8.85 and 25.26%, whilst no connected porosity was found in the Glasgow samples. This is deemed due to the presence of a ubiquitous cement phase occupying up to 26.28% of the sample volume, significantly reducing the viability for fluid injection and therefore GCS at the Glasgow site. Carbon storage is dependent on the availability of pore space for mineralisation and the pore connectivity which allows for fluid flow of CO2. Our measured values of porosity and permeability also indicate that the Sellafield site and sandstones similar to the samples from this site will be highly effective as CCS target formations.
The role of cover and pattern of installed resource sinks in the recovery of degraded patchy drylands
Authors: Garcia Mayor Angeles , Berghuis Paul , Rietkerk Max , Baudena Mara
Published: March 2020

A low-cost restoration in patchy drylands aiming at recovering the ability of the ecosystem to capture and store water and nutrients is the installation of obstructions to break runoff pathways and retain these resources (hereafter, resource sinks). Field works in drylands worldwide have studied how the effectiveness of this action depends on the materials used to build the obstructions. However, the spatial pattern attributes of the resource sinks can also affect the effectiveness of the restoration and has not yet been investigated. In this work, we cover this knowledge gap by using a well-known dryland model to investigate how different initial amounts of cover and spatial distribution of installed resource sinks (i.e., random vs. regular) affects the recovery of the system. In agreement with field-work studies, our model results confirm that the installation of resource sinks can restore degraded drylands that are not able to recover naturally. More importantly, we found that a very small cover of resource sinks was sufficient to trigger the recovery of vegetation, while a high cover could lead to a complete failure of vegetation recovery. This was found for both random and regular distributions of resource sinks. However, a distribution similar to that of vegetation in the reference healthy system (i.e., regular distribution in our study system) was more effective: higher plant densities were reached for a given initial cover of resource sinks. Given the high efficiency of low covers of resource sinks suggested by our work, combined with the low-cost materials needed, the installation of resource sinks in severely degraded drylands has the potential to be a key contributor to the large restoration efforts needed to achieve land-degradation neutrality in the coming decades, particularly in developing countries.
Simplified model for axial dipole moment of the geomagnetic field from Brownian fluctuations
Authors: Molina Cardín Alberto , Dinis Vizcaíno Luis , Osete López María Luisa
Published: March 2020

The magnetic field of the Earth is generated in its core by the process called the geodynamo, which involves convection in the fluid and electrical conducting outer core. The evolution of this complex process is simulated by magnetohydrodynamic models, which provide the state of the core and the magnetic field at any point and any time of the simulation. Nevertheless, the complexity of these models implies a high computational cost. That is why conceptual simple models describing only the main mechanisms from a statistical perspective can also be useful.

In this work we present a conceptual model that reproduces the main features of the axial dipole moment (ADM) of the Earth magnetic field. It is based on the stochastic dynamics of two Brownian particles interacting with each other within a double-well potential. The obtained simulations are able to mimic the random temporal distribution of reversals and excursions and the asymmetric temporal evolution of ADM during reversals. The relation between the model features and the real mechanisms that lead to the observed behaviour is discussed.
Modelling the cooling potential of street trees at city-scale with COSMO-BEP-Tree
Authors: Mussetti Gianluca , Brunner Dominik , Henne Stephan , Krayenhoff Scott , Carmeliet Jan
Published: March 2020

Street trees are more and more regarded as a potential measure to mitigate the excessive heat in urban areas resulting from climate change and the urban heat island. However, the current knowledge of the cooling effect of street trees relies on studies at the micro-scale while potential interactions at the city-scale are yet to be understood. In fact, the vast majority of large-scale modelling studies only represent street trees outside the street canyon, neglecting important effects such as the shading and sheltering.

In order to explicitly represent street trees in coupled urban climate simulation, the multi-layer urban canopy model BEP-Tree was coupled with the regional weather and climate model COSMO-CLM. The coupled model, named COSMO-BEP-Tree, enabled simulating the radiative, flow and energy interactions between street trees, canyon surfaces and the atmosphere during weather and climate simulations.

In this study, COSMO-BEP-Tree is used to model the cooling potential of street trees during a heatwave event in Basel, Switzerland. The impact of street trees is explored in terms of near-surface air temperature and thermal comfort. The impact of greening scenarios is simulated and compared with other heat mitigation strategies.

The results highlight contrasting urban climate effects of street trees during daytime and night-time, where different processes become dominant. The daytime cooling was primarily a local effect and proportional to the local density of street trees.  In contrast, the impact was more widespread at night, where city-scale interactions become important. Beside air temperature, the model results suggest a significant impact of street trees on wind speed and canyon surface temperature. Owing to these effects, street trees produced a larger impact on thermal comfort than on air temperature. Finally, the need for further model development with respect to urban hydrology is outlined.
Modelling the impacts of climate change and land-use change on the hydrology of Vietnam’s river basins
Authors: Moschini Francesca , Ferrario Iacopo Federico , Hofmann Barbara
Published: March 2020

Quantifying how land-use change affects hydrological components is a challenge in hydrological science. It is not yet clear how changes in land use relate to runoff extremes and why some catchments are more sensitive to land-use change than others. Identifying which areas are hydrologically more sensitive to land-use change can lead to better land-use planning, reduction of the impacts of extreme rainfall events and extended dry periods. In this study we aim to quantify how land-use change and climate change are affecting the hydrological response of  Vietnam’s basins. Over the past decades the country’s land use has shifted from forest to agriculture, with very high production of rice, coffee, tea, pepper and sugar cane.

We combine the historical, the Intergovernmental Panel on Climate Change’s (IPCC) Representative Concentration Pathway (RCP) RCP4.5 and RCP8.5 climate change scenarios developed for Vietnam, with two different land cover maps (from the years 1992 and 2017). The combined and separate effect of land use and climate change are assessed and the most sensitive to change areas are identified. The Variable infiltration Capacity (VIC) surface water and energy balance model applied here is a grid-based model that calculates evapotranspiration, runoff, base flow, soil moisture and other hydrological fluxes. Surface heterogeneity within VIC is represented by a tiled approach, whereby the surface of each grid-box comprises fractions of the different surface types. For each surface type of the grid-box, the energy and water balances are solved, and a weighted average is calculated from the individual surface fluxes for each grid-box. Hydrological fluxes were compared for each grid cell and basin to analyse the degree of difference between the scenarios.

Significant changes in future hydrologic fluxes arise under both climate change scenarios pointing towards a severe increase in hydrological extremes. The changes in all the examined hydrological components are greater in the combined land-use and climate change experiments.
Predictor dataset selection method for construction of ML-based Models in flood detection using mutual information
Authors: Bateni Mohammad Mehdi , Martina Mario , Cesarini Luigi
Published: March 2020

The field of information theory originally developed within the context of communication engineering, deals with the quantification of the information present in a realization of a stochastic process. Mutual information is a measure of mutual dependence between two variables and can be determined from marginal and joint entropies. It is an efficient tool to investigate linear or non-linear dependencies. In this research, some transformed variables, each based on rainfall data from different datasets in Dominican Republic, are adopted in Neural Network and SVM models to classify flood/no-flood events. A selection procedure is used to select skillful inputs to the flood detection model. The relationship between the flood/no-flood output datasets and each predictor (relevance) and also among predictors (redundancy) were assessed based on the mutual information metric. The minimum redundancy between predictors and maximum relevance to the predictand is targeted in order to choose a set of appropriate predictors. 
Pressure evolution inside the high voltage modules of plasma instrumentation when exposed to vacuum during ground test campaigns or after launch to space
Authors: Wittmann Philipp , Wieser Martin , Trost Florian , Barabash Stas
Published: March 2020

The Jovian plasma Dynamics and Composition analyzer (JDC), which is part of the Particle Environment Package (PEP) on board of the JUICE spacecraft, uses high voltages up to 5kV, during operations. These high voltages are used in the ion-optical part of the instrument, where the strongest electrical fields are encountered. Preventing internal high voltage discharges in this region is a key design driver. For this reason, a design rule of keeping the field strength <3kV/mm is applied. However, the dielectric strength of a vacuum gap has a pronounced minimum much below the 3kV/mm design rule at the Paschen minimum at about 10-2 to 1 mbar. To successfully operate using the <3kV/mm design rule, the sensor needs proper venting of its inner volume to get the internal pressure significantly below the Paschen minimum pressure.

Below the Paschen minimum pressure the gas flow in the instrument is a non-collisional molecular flow. The time spent to further reduce pressure inside of the instrument when the instrument is exposed to vacuum (e.g. in space or in a test facility) depends on the internal outgassing source strength, the temperature and the geometric shape of the outgassing path.

We determine the time constants of the pressure reduction in molecular flow regime by placing micro pirani pressure sensors inside critical volumes of real instruments.

We compare the outgassing performance of the Miniature Ion Precipitation Analyzer (MIPA) on Bepi Colombo with the JDC sensor. Measurements showed too long outgassing time constants for JDC in order to be able to operate the instrument during the very time constraint on-ground test campaign where only approximately 3 days are available to reach a save vacuum of <10-5 mbar inside of the instrument. We present the implemented solution to improve outgassing performance of JDC and show it is sufficient for the on-ground test campaign.
Harmony's ocean elevation measurements: potential and performance
Authors: Theodosiou Andreas , Lopez Dekker Paco , Kleinherenbrink Marcel , Mulder Gert
Published: March 2020

Harmony, an Earth Explorer 10 candidate mission, consists of two receive-only Synthetic Aperture Radar (SAR) satellites using Sentinel-1D as the illuminator. The mission will switch between close formation phases and StereoSAR phases, dedicated to relative surface elevation and relative surface motion respectively. Interferometric observations of the ocean have, in the past, been hindered by the quick temporal decorrelation of the sea surface; a result of the along-track baseline that often comes with the cross-track baseline necessary for interferometry. Specialised SAR systems aiming to observe the oceans need to account for the decorrelation of the surface. SWOT overcomes the issue by fixing the two SAR antennas to physically eliminate their along-track separation. Due to the squinted, bistatic nature of the formation, Harmony can act as an altimeter, observing relative sea-surface heights (SSH) over unprecedented wide swaths. Hence, the mission promises to have highly coherent observations of the sea surface, leading to accurate surface elevation measurements. The wide swath will enable the recovery of mesoscale features of the ocean surface in a single pass. We will present the first results of the performance analysis of the mission's observations of elevation over the oceans. The effect of errors, namely the residual Doppler, baseline errors and sea-state bias, on the observations will also be discussed.