bluuebunny/crossref_metadata_2025 huggingface dataset:
From “Liceu de Ponta Delgada” to “Antero de Quental Secondary School” (Past and Present)
Authors: Rebuge José
Published: March 2020

Created in 1852 as the “Liceu de Ponta Delgada”, the “Antero de Quental Secondary School” is today a institution of reference in the teaching and dissemination of culture. In the past, in it, they taught or/and studied great personalities of São Miguel Island, like Dr. João de Moraes Pereira (astronomer,…), Dr. Carlos Machado (botanist,…), ……. Like these personalities, many other teachers (and students) at present confirm the plural vocation of this school, giving their students the possibility to engage in varied activities, from arts to sciences. Taking advantage of its collections of minerals and animals, the school motivates its students to study geology and biology; to contextualizes the study of physics from the collection of the Museum of Physics; to promotes arts creativity of students by inviting them to reinterpret pieces from the school's art collection. Even the rich natural and built heritage of the school gardens are harnessed to develop activities with educational purposes. Throughout the school year, most teachers and students engage in various activities, often with the collaboration/contribution of local science institutions (like Expolab, Astronomical Observatory of Santana Azores - OASA, ….) and others national and international organizations (NUCLIO, International Astronomical Search Collaboration – IASC, Ciência Viva; ….), that promote students' interdisciplinarity and citizenship, while addressing the concepts that constitute the curriculum of the various teaching modalities in the school.
GRIPS-HI - a Novel Interferometer for Measuring Two-Dimensional Temperature Distributions at the Mesopause
Authors: Stehr Johannes , Knieling Peter , Olschewski Friedhelm , Kaufmann Martin , Mantel Klaus , Koppmann Ralf
Published: March 2020

The NDMC (Network for the Detection of Mesopause Change) is a global network of ground based observatories with the objective of monitoring key parameters of the mesopause region. For temperature monitoring GRound-based Infrared P-branch Spectrometers (GRIPS) are widely deployed. These spectrometers allow for the retrieval of the mesopause temperature from the OH* P-band emission lines around 1530 nm. A common technology for GRIPS instruments are spectrometers based on diffraction gratings. To overcome the limitations of conventional grating spectrometers, a new type of spectrometer is being developed within the project Metrology for Earth Observation and Climate - 3 (MetEOC-3) which is coordinated by the European Metrology Project for Innovation and Research (EMPIR). The new spectrometer shall improve the quality and traceability of the atmospheric data obtained by the NDMC. It is intended to serve as a reference instrument with significantly smaller measurement uncertainties. It is also designed to identify temperature trends of 1K/decade. A Spatial Heterodyne Interferometer (SHI) was chosen as the most promising technology, offering several advantages. Compared to conventional grating spectrometers, the throughput and resolution of the interferometer is one order of magnitude larger. The use of a two-dimensional detector array in combination with an imaging optics enables the detection of spatial temperature distributions in the mesopause region, as caused by dynamical processes like gravity waves. The talk gives an introduction to the technology of spatial heterodyne interferometry, and the new instrument design and calibration results are presented.
FAME: Fibre optic cables: an Alternative tool for Monitoring volcanic Events
Authors: Jousset Philippe , Currenti Gilda , Napoli Rosalba , Krawczyk Charlotte , Weber Michael , Clarke Andy , Reinsch Thomas , Chalari Athena , Lokmer Ivan , Pellegrino Daniele , Larocca Graziano , Pulvirenti Mario , Contrafatto Danilo , Consoli Salvatore
Published: March 2020

In the framework of EUROVOLCs Trans-national grants, we propose the FAME project aiming at validating Distributed Acoustic Sensing (DAS) technology as a complementary and alternative tool for monitoring volcanic and seismic activity at Etna volcano. DAS technology provides records of strain signals with unprecedented spatial and temporal resolution.

We deployed a fibre optic cable connected to an iDAS (Silixa) interrogator set-up at the Observatory Pizzi Deneri in the summit area. To allow for a continuously recording of the iDAS, a solar panel power system was designed using battery back-up and inverter to supply 200 W at 220 V/AC. An internet connection was set up for a full remote control capability. The iDAS interrogated a 1.5 km long fibre cable, buried at a depth of about 30 cm by digging a trench in Piano delle Concazze area. The DAS measurements were validated with conventional measurements from 26 broadband seismometers and 3 arrays of 3 infrasound sensors from the Geophysical Instrument Pool Potsdam (GIPP). We deployed instruments along the fibre optic cable, covering an area of about 0.1 km2. The DAS and conventional sensors acquired data from 4 July to 23 September 2019 without major interruptions.

Here, we show key features of this the extraordinary multidisciplinary dataset. Thanks to the high spatial resolution (2 m), we could find locations of hypothesized faults in Piano delle Concazze area. Thanks to the long acquisition period, we continuously tracked Etna activity, marked by several eruptive episodes, including ash emissions, strombolian and effusive activities from the summit craters. The most intense and sustained eruptive events occurred in 18-20 July, 27-28 July and 9-13 September. We investigate the application of well-established analysis techniques in volcano-seismology to DAS dataset in order to assess the performance of the system in detecting and characterizing volcanic events.

Our findings demonstrate that DAS technology can record on a long term basis volcanic activity, which suggests DAS technology can be integrated to volcanic monitoring systems.
To creep or to snap? How induced heat governs the brittleness of matter
Authors: Vincent-Dospital Tom , Toussaint Renaud , Santucci Stéphane , Vanel Loïc , Bonamy Daniel , Hattali Lamine , Cochard Alain , Flekkøy Eirik Grude , Måløy Knut Jørgen
Published: March 2020

The growth of fractures within mechanically loaded materials often shows two different behaviors. When loaded below a particular threshold in energy release rate, cracks tend indeed to creep at very slow velocities, while the rupture becomes catastrophic beyond this threshold, with propagation velocities approaching that of the material mechanical waves. Understanding according to which of these two behaviors a material is prone to break is of paramount importance, notably in engineering, where the brittle rupture of structures can lead to unpredicted disasters. It is also fundamental in Earth science, as damaging earthquakes  are rather generated by abrupt ruptures in the crustal rocks than by their slow deformations. To explain both behaviors, we focus here on the thermal effects which are auto-induced by the growth of cracks. During their propagation, some of the system’s energy is indeed partly dissipated by Joule heating, which is arising from the friction in a damaged zone around the fracture fronts. The heat hence generated can in return have a significant impact on the physics of the propagation. For instance, the stability of faults is believed to be affected by the thermo-pressurization of their in situ fluids. Independently of this effect, we show, how statistical physics, as understood by an Arrhenius law that includes the dissipation and diffusion of heat around the fracture tip, can explain the full dynamics of cracks, from the slow creep to the fast rupture.

We indeed show that such a model can successfully describe most of the experimentally reported fracture rheology, quantified in terms of velocity / energy release rate relations, in two different types of polymers, acrylic glasses and pressure sensitive adhesives, over eight decades of crack velocities. In these two cases, it is sufficient to assume that these polymers are homogeneous to model their failure. Yet, we in addition illustrate how the thermal disorder, from both the ambient temperature and the propagation induced heat, should interact with the matter typical quenched disorder in fracture energy. Numerical simulations of planar cracks in heterogeneous media indeed show that such quenched disorder helps to trigger hot avalanches in the propagation of cracks, making the overall toughness of a material highly dependent on both its heterogeneities, as it is often reported in the literature, and its thermal properties.
Post-fire mobilization of metals and polycyclic aromatic hydrocarbons in a recently burnt eucalypt stand in North-Central Portugal
Authors: Serpa Dalila , I. Machado Ana , Santos Martha , Campos Isabel , R. F. Oliveira Bruna , Gholamahmadi Behrouz , Martins Martinho , González-Pelayo Oscar , Jesus Fátima , Keizer Jacob , Abrantes Nelson , Consortium Life-Reforest
Published: March 2020

Wildfires constitute a diffuse source of contamination to aquatic ecosystems. In burnt areas, the increase in surface runoff and associated sediment losses after fire, promotes the mobilization of hazardous substances, such as metals and polycyclic aromatic hydrocarbons (PAHs), posing a risk for the adjacent water bodies. In the present study, post-fire metals and PAHs export by surface runoff was evaluated in 16 m2 bounded plots in a eucalypt stand in Albergaria-a-Velha (Aveiro district, North-Central Portugal) burnt in September 2019. Runoff samples were collected on a weekly to bi-weekly basis, depending on the occurrence of rainfall, during the first 6 months after fire. The metals analyzed in this study were, vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb). As for PAHs, the analyses focused on the 16 compounds classified as priority pollutants by the United States Environmental Protection Agency. Both dissolved and particulate fractions of metals and PAHs in runoff waters were analysed in this work. Preliminary results suggest that metals are more likely to affect the water quality of fire-affected water bodies than PAHs, since low levels of PAHs were found in runoff waters. This work provides valuable information for water managers to minimize the risks of wildfires both to the environment and to public health.
Assimilation of soil moisture data for improving streamflow prediction: Is there a role for the hydrological model structure?
Authors: Nayak Aruna Kumar , Biswal Basudev , Sudheer Kulamulla Parambath
Published: March 2020

Soil moisture data assimilation has found increased applicability in hydrology due to easily available remotely sensed soil moisture data. Numerous studies in the past have explored the possibility of assimilating soil moisture information for improving streamflow forecasting. The general understanding is that if better soil moisture data can provide better streamflow forecast. However, to our knowledge no study has so far focused on understanding if the hydrological model itself has a role in assimilation of soil moisture data. In this regard, here we use three different conceptual hydrological models for soil moisture assimilation: (1) Dynamic Budyko (DB), (2) GR4J, and (3) PDM model. Assimilation of GLDAS observed soil moisture is carried out for four MOPEX basins using Ensemble Kalman Filter. DB model’s performance improved after soil moisture data assimilation for all the study basins. However, deterioration in performance was observed for GR4J and PDM for all the basins after the assimilation exercise. The performance of the assimilated models is evaluated in terms of Assimilation Efficiency (AE), which was found to be varying from 17.11 to 22.56%, from -20.98 to -41.29%, and from -8.4 to -38.23%, respectively, for DB, GR4J, and PDM. Overall, our results highlight the importance of the hydrological models structure in a soil moisture data assimilation exercise.
Guiding drained peatland management towards negative GHG emissions
Authors: Kasimir Åsa , Belyazid Salim , Andresen Louise , Kljun Natascha , Toet Sylvia , Akselsson Cecilia , Hammer Edith , Kritzberg Emma , Gärdenäs Annemarie , Vestin Patrik , Jansson Per-Erik , Klemedtsson Leif
Published: March 2020

In a world of climate change we need to minimize and stop greenhouse gas (GHG) emissions and instead accumulate carbon in ecosystems - we call this ‘negative emissions’. Drained peatlands are in many cases large sources of GHGs to the atmosphere but rewetting of a peatland can mitigate these emissions and possibly reach a net uptake. However, carbon accumulation in peatlands is a dynamic and complex balance between uptake and release, which is mainly driven by the groundwater table (WT) depth.

                           Our new project funded by the Swedish Research Council FORMAS (2020-2022) aims to produce a handbook with guidance on how to change management of drained organic soil in order to convert them into low or negative emission peatlands. Researchers from Gothenburg, Stockholm, Lund and York Universities will collaborate with landowners, public authorities and NGO’s to assemble the most relevant knowledge.

We will compare GHG fluxes from organic soils under different traditional and newly suggested land uses in the Swedish landscape, by collected field data, which will be the input for upscaling in time and space by using state-of-the-art process models (CoupModel and ForSAFE). For modelling purposes, extensive abiotic and GHG datasets will be available from the research station ‘Skogaryd’ in Västra Götaland, Sweden (https://gvc.gu.se/english/research/skogaryd), from a drained peat with spruce forest, before and after the clear-cut in 2019. This clear-cut area will now be partly rewetted by building a dam, and GHG flux measurements will be collected in response to different soil WT and vegetation types. Other available data are from a variety of drained and rewetted peat soils in neighboring countries. In addition, GHG measurements in Sweden on restored bogs are starting during summer 2020. Models will allow us to assess and examine the influence of 1) WT fluctuations, 2) soil fertility, and 3) management on both carbon storage and GHG fluxes for rewetted cases with moss vegetation, meadow or swamp forest.
The Aegean - Anatolian region: insights on seismic hazard from geodetic and seismological observations
Authors: Sparacino Federica , Galuzzi Bruno Giovanni , Palano Mimmo , Segou Margarita , Chiarabba Claudio
Published: March 2020

Geodetic and seismic moment-rates comparison provides significant insights into the seismic hazard of regions subjected to relevant crustal deformation. We performed such a comparison for the Aegean-Anatolian region, marking the collision zone between the African, Arabian and Eurasian plates, and characterized by a complex tectonic evolution. First we provided an improved description of the ongoing crustal deformation field of the Aegean-Anatolian region, based on an extensive combination of novel observations rigorously integrated with the published GNSS-based geodetic velocities. Then, the geodetic velocity field is used as model input to estimate the 2D strain-rate and moment-rates fields over a geographic 1° x 1° grid. Second, we collected the historical and instrumental earthquake data in order to define the long-term moment release rate by adopting a truncated Gutenberg-Richter relation. Finally, the geodetic and seismic moment-rates comparison allowed to differentiate crustal deformation modality (seismic versus aseismic), as well as to highlight seismic cycle gaps over the investigated region.
Understanding and forecasting the subseasonal meteorological drivers of the European electricity system in winter
Authors: Bloomfield Hannah , Brayshaw David , Charlton-Perez Andrew , Gonzalez Paula , Livings David
Published: March 2020

Renewable electricity is a key enabling step to globally decarbonise the energy sector. Europe is at the forefront of renewable deployment and this has dramatically increased the weather sensitivity of the continent's power systems. Despite the importance of weather to energy systems, the meteorological drivers remain difficult to identify, and are poorly understood. This study presents a new and generally applicable approach, targeted circulation types (TCTs). In contrast to standard meteorological circulation typing methods, such as weather regimes, TCTs convolve the weather sensitivity of an impacted system of interest (in this case, the electricity system) with the intrinsic structures of the atmospheric circulation to identify its meteorological drivers.

A new, freely available, 38 year reanalysis-based reconstruction of daily electricity demand, wind power and solar power generation across Europe is created and used to identify the winter large‐scale circulation patterns of most interest to the European electricity grid. TCTs are shown to provide greater explanatory power for power system variability and extremes compared with standard weather regime analysis. Two new pairs of atmospheric patterns are highlighted, both of which have marked and extensive impacts on the European power system. The first pair resembles the meridional surface pressure dipole of the North Atlantic Oscillation, but shifted eastward into Europe and noticeably strengthened, while the second pair is weaker and corresponds to surface pressure anomalies over Central Southern and Eastern Europe. These patterns are shown to be robust features of the “present-day” European power system.

 The use of TCTs to increase the utility and skill of subseasonal forecasts during the winter season is discussed.  It is shown that TCTs provide additional useful information compared to standard “grid-point” or weather-regime techniques for applications in energy system forecasting and operations.
Frictional anisotropy in casted seismic faults: or how to 3D print a fault to better characterize it
Authors: Steyer Alain , Vincent-Dospital Tom , Toussaint Renaud
Published: March 2020

Anisotropic phenomena have long been studied in the vicinity of seismic faults. It has for instance been shown that both in situ pore fluids and seismic mechanical waves travel at different velocities along various directions of a fault zone. Yet, while more and more complexity and disorder in seismic models are introduced to better understand earthquakes, frictional anisotropy is only rarely regarded. In many other domains than geophysics, however, such anisotropy in solid friction is believed to be crucial. For instance, the tribology of rubber tires, skis or advanced adhesives is improved when those are designed to have a preferential frictional direction. But numerous natural systems also benefit from such anisotropy: is is notably essential in the motion of numerous animal skins and in the efficient hydration of some plants. In most cases, these frictional anisotropies derive from the existence of preferential topographic orientations on, at least, one of the contact surfaces, with scales for such structural directivity that can be multiple and various. Seismic faults also exhibit such preferential directions in their topography: unique rock crystals, such as antigorite, can already display some frictional anisotropy, fault zones are  initiated by early fractures that often propagates through layered sediments, generating ramp-flat morphology in their surfaces and, finally, mature faults are marked by grooves of various wavelengths due to the slip induced erosion.

 

In this work, we study how the morphology of faults affects their stability, as understood by their Coulomb static coefficient of friction. In particular we study its anisotropy with the slip direction. To do so, we make use of the 3D-printing technology and print actual fault surfaces, that were measured in the field. We perform friction experiments with gypsum casts of these 3D-printed faults, as mineral-like materials might deform differently under shear than plastic materials. With these experiments, we show that the friction coefficient along seismic faults is highly anisotropic, with slip motions that are easier in, but not limited to, the direction of the main grooves. This anisotropy could for instance be paramount to better predict the next direction of rupture along some faults under a varying stress state. In some cases, it could indeed not only be related to the orientation of the main regional stress, but also to the structural anisotropy, and  depending on stress and friction anisotropy, along which orientation a rupture criterion will first be exceeded.
Exploration of submerged Mesolithic landscapes around the Brown Bank, southern North Sea
Authors: Muru Merle , Harding Rachel , Fitch Simon , Missiaen Tine , Gaffney Vince
Published: March 2020

During the late glacial and early Holocene, vast areas of dry land stretched from the British Isles to continental Europe over what is now the southern part of the North Sea. Whilst it is known that this landscape was inhabited, little is known about the cultures that lived there and the surrounding environment. This study focuses on the Brown Bank area, between the UK and Dutch coasts, with its significant 25 km long and 10-15 m high ridge on the seabed which has provided many Mesolithic ex-situ finds. However, all of these finds have been recovered serendipitously due to commercial fishing and dredging, and thus the landscape and sedimentary context of these archaeological finds is unclear.
The goal of this study is to map the terrestrial features in the Brown Bank area and reconstruct the palaeolandscape and its inundation to determine the potential locations from which this archaeological material derives, and potentially locate Mesolithic settlement sites. The project uses high-resolution parametric echosounder surveys in a dense survey network to record the area and facilitate later targeted dredging and vibro-core sampling.
The seismic surveys revealed a pre-marine inundation landscape with fluvial channels eroded into post glacial sediments. A peat layer was located on the top of the banks of the channels where it continues laterally hundreds of metres. Radiocarbon dating of the top part of the peat layer, just below the transgressive deposits gave ages around 10.2-9.9 cal ka BP. Palaeogeographic reconstructions based on the mapped terrestrial features and the available relative sea level change data suggest that the final inundation of the area happened c. 1000 years later. Where dredging was carried out in areas of interest, primarily where the early Holocene surface outcropped onto the seabed, a large number of blocks of peat with pieces of wood and other macrofossils were recovered, suggesting a good potential for preservation of possible archaeological material and possible locations of origin for the serendipitous finds made by fishermen.
We conclude that this study provides new insights into the palaeogeography and the timing of the inundation of the Brown Bank area and gives the landscape context to the potential Mesolithic habitation of this part of the southern North Sea.
First observations of the Search Coil Magnetometer on Solar Orbiter / RPW: results and performances
Authors: Kretschmar Matthieu , Krasnoselskikh Volodya , Brochot Jean-Yves , Jannet Guillaume , Dudok de Wit Thierry , Froment Clara , Maksimovic Milan , Chust Thomas , Le Contel Olivier , Soucek Jan , Pisa David
Published: March 2020

The Search Coil Magnetometer (SCM) onboard Solar Orbiter is part of the Radio and Plasma Waves (RPW) experiment and measures the variations of the magnetic field between 10 Hz and 50 kHz on three axes and between 1 kHz and 1MHz in one axis. The SCM is located on the boom of the spacecraft and its signal is processed by the LFR, TDS, and HFR analyzers of the RPW experiment. These measurements are essential for the characterization of waves and turbulence in the solar wind. We will describe the first observations made by the instrument with an emphasis on its performances. 
The impact of baroclinity on tidal ranges in the North Sea
Authors: Li Wenguo , Mayer Bernhard , Pohlmann Thomas
Published: March 2020

Tidal range is one of significant contributors of coastal inundation. Therefore, it is very important to investigate the dynamics of tidal range variations over different time scales. The baroclinity has the potential to modulate surface tides through ocean stratification on seasonal scale. In order to better understand the impact of ocean stratification on tidal ranges in the North Sea, the numerical simulations were carried out in baroclinic and barotropic modes covering the period from 1948 to 2014, using the regional 3D hydrodynamic prognostic Hamburg Shelf Ocean Model (HAMSOM). In the barotropic mode, the river forcing was also included, which only increases the local sea level without any influence on the density. The tidal range difference between baroclinic and barotropic modes in winter (less stratification) and summer (strong stratification) are compared at 22 tide-gauge stations, where the simulated sea surface elevations agree well with observations from 1950 to 2014. The statistical analysis generally shows that the difference at 19 stations (86% of total stations) in summer is much larger than that in winter during more than 32 years (50% of the analysis period). This suggests that the stratification decouples the surface and bottom layers weakening the damping effects of bottom friction, which is visible even at the coastal tide-gauge stations, where the ocean water is well-mixed. Obviously, the signal induced by stratification is propagated by the tidal Kelvin wave through the North Sea. Additionally, the spatial distribution of tidal range differences indicate that the amphidromic points in the North Sea moved westward in the baroclinic mode. Regarding the seasonal mean sea level at the stations, the results show that the coastal sea level could be increased by baroclinity itself, since the river runoff freshens the coastal water in the baroclinic mode, and thus the local sea level increases due to steric effect. Consequently, the increased sea level could further weaken the damping effect. However, this is a relatively minor impact on the tidal range.
Density currents induced by differential cooling in lake
Authors: Bouffard Damien , Ramón Cintia , Doda Tomy , Ulloa Hugo
Published: March 2020

Differential cooling occurs in the littoral region of lakes, during calm and cold nights in summer and continuously in fall/ winter. For uniform heat loss over the lake surface, shallower regions cool faster than deeper regions leading to horizontal density gradients. Nearshore waters become negatively buoyant and start to plunge creating a cold downslope density current that can reach the pelagic zone. This cross-shore flow, also referred to as “thermal siphon”, has the potential to transport biogeochemical constituents offshore and deeper into the water column. However, its significance for the lake ecosystem remains unknown. Here we combine high resolution numerical simulations and field observations to evaluate the global significance of lateral boundaries and differential cooling on the lake dynamic. We focus on a small elongated lake: Lake Rotsee (Switzerland) and investigated the dynamic of the density current as well as the consequences of this flow such as the flushing of the littoral water.
Seeing through the fluid dynamics of flexible vegetation and canopy turbulence
Authors: Houseago Robert C. , Hong Liu , Best James L. , Parsons Daniel R. , Chamorro Leonardo P.
Published: March 2020

Submerged aquatic vegetation within river and coastal environments alters the local flow hydraulics, in turn influencing sediment dynamics and bed morphology. Vegetation canopies complicate bottom topography, with flexible elements often invoking complex spatial variability. Acquisition of quantitative, long time-scale data concerning the fluid dynamics associated with flexible aquatic canopies has remained limited due to the physical and visual obstruction presented by vegetation.

The experimental based research detailed here implements a novel Refractive Index Matching (RIM) technique, combined with Particle Image Velocimetry (PIV), to acquire flow field measurements within, and above, a dynamically scaled surrogate flexible seagrass canopy. RIM provides an undistorted optical view through the vegetation canopies, facilitating the investigation of coherent flow structures and canopy dynamics at five different Reynolds numbers. A flexible vegetation canopy of length 1.4m, width 0.45m, and height 0.12m, occupied the entire width of the 2.5m long RIM flume facility at the University of Illinois. The flume was operated in a free surface mode with a flow depth of 0.36m. Results from a counterpart rigid canopy also offer comparability and broader application of these findings to a range of flow-biota environments. Transparent rods formed the rigid canopy, while the flexible canopy elements comprised of four thin polymer blades extending from a short rigid stem. Vegetation elements were placed in a staggered arrangement to form canopies with a density of 566 stems m2.

The results provide insights into canopy-based turbulence processes, including mixing layer properties associated with the canopy and vortex penetration. Deflection of the canopy and its waving motion is quantified, and linked to distinct hydrodynamic differences between the rigid and flexible canopies. Spatiotemporal variability associated with deflection of the flexible canopy, combined with the plant morphology, is shown to promote the spatial heterogeneity in turbulence distribution. Elucidation of instantaneous turbulent flow structures at various time intervals also reveals the links between above-canopy and in-canopy flow processes. This research provides new insights into the hydraulic processes of complex vegetated beds, including quantification of coherent flow structure evoultion. Application of these findings will help advance our knowledge of associated sediment transport dynamics, which is essential for interpreting larger-scale morphodynamic response and its role in environmental management.
On Statistical Modeling of Extreme Rainfall Processes for Urban Water Infrastructure Design in the Context of Climate Change
Authors: Nguyen Van-Thanh-Van
Published: March 2020

There exists an urgent need to assess the possible impacts of climate change on the Intensity-Duration-Frequency (IDF) relations in general and on the design storm in particular for improving the design of urban water infrastructure in the context of a changing climate. At present, the derivation of IDF relations in the context of climate change at a location of interest has been recognized as one of the most challenging tasks in current engineering practices. The main challenge is how to establish the linkages between the climate projections given by Global Climate Models (GCMs) at the global scale and the observed extreme rainfalls at a given local site. If these linkages could be established, then the projected climate change conditions given by GCMs could be used to predict the resulting changes of local extreme rainfalls and related runoff characteristics.  Consequently, innovative downscaling approaches are needed in the modeling extreme rainfall (ER) processes over a wide range of temporal and spatial scales for climate change impact and adaptation studies in urban areas. Therefore, the overall objective of the present paper is to provide an overview of some recent progress in the modeling of extreme rainfall processes in a changing climate from both theoretical and practical viewpoints. In particular, the main focus of this paper is on recently developed statistical downscaling (SD) methods for linking GCM climate predictors to the observed daily and sub-daily rainfall extremes at a single site as well as at many sites concurrently. In addition, new SD procedures are presented for describing the linkages between GCM outputs and rainfall characteristics at a given location where the rainfall data are limited or unavailable, a common and crucial challenge in engineering practice.
The 2018 drought and its consequences: Investigating the resilience of different tree species based on comprehensive long-term monitoring of forest hydrology
Authors: Blume Theresa , Balanzategui Daniel , Schneider Lisa , Rasche Daniel , Morgner Markus , Güntner Andreas , Heinrich Ingo
Published: March 2020

Many forests in Central Europe experienced unprecedented drought conditions in 2018. The exceptionally long dry period, lasting from early-summer 2018 and into the winter, was followed by another dry summer with record-breaking temperatures.   Ecohydrological consequences of extended droughts for these temperate forest systems are difficult to anticipate, and investigating the resilience of forest hydrological systems requires comprehensive and systematic long-term observations.

Monitoring at the TERENO-NE temperate forest observatory in northeastern Germany includes input characterization (throughfall and stemflow), high-resolution soil moisture observations in 14 different forest stands down to a depth of 2 m below the soil surface, shallow and deep groundwater observations, sap flow, tree water deficit and high-resolution tree growth measurements since 2012. The investigated forest stands cover the three tree species pine, oak and beech in both pure and mixed stands. This is complemented by terrestrial gravimetric measurements of total water storage changes. Steep hillslope transects allow us to investigate the impact of presence or absence of groundwater availability on tree water uptake and growth.

We find that after the unprecedented drought in 2018, which already had pronounced ecohydrological effects, the rainfall amounts over the winter 2018/19 were insufficient to refill the subsurface water storages. Dry conditions altered the growth phenology of each monitored tree species, while tree-water deficit and tree growth were negatively impacted in both years, but to varying extent. Soil moisture storage and dynamics are strongly affected and the drought caused a long-term memory effect.
NEW EOP, TRF and CRF determination by GNSS & VLBI COMBINATION
Authors: Richard Jean-Yves , Karbon Maria , Bizouard Chrsitian , Lambert Sebastien , Becker Olivier
Published: March 2020

The Earth orientation parameters (EOP), the regular products of IERS Earth Orientation Centre, are computed at daily bases by combination of EOP solutions using different astro-geodetic techniques. At SYRTE we have developed a strategy of combination of the Global Navigation Satellite Systems (GNSS) and Very Long Baseline Interferometry (VLBI) techniques at normal equation level using Dynamo software maintained by CNES (France). This approach allows to produce the EOP at the daily bases, which contains polar coordinates (x,y) and their rates (xr,yr), universal time UT1 and its rate LOD, and corrections from IAU2000A/2006 precession-nutation model (dX,dY), and in the same run station coordinates constituting the terrestrial frame (TRF) and the quasar coordinates constituting the celestial frame (CRF). The recorded EOP solutions obtained from GNSS and VLBI combination at weekly bases is recently maintained by SYRTE.

The strategy applied to consistently combine  the IGS and IVS  solutions provided  in Sinex format over the time period 2000-2020 are presented and the resulting  EOP, station positions (TRF) and quasars coordinates (CRF) are analysed and evaluated, differences w.r.t. the individual solutions and the IERS time-series investigated.
Quantification of micron-scale structural and hydraulic properties of long-term pig manure and lime amended red soil aggregates using the lattice Boltzmann method and pore network modelling
Authors: Qu Rong , Zhou Hu , Hallet Paul
Published: March 2020

Lime and animal manure can have major impacts on soil physical properties, particularly in degraded and highly weathered soils that are naturally acidic. Here we evaluate how treatment of a regular till Acrisol in southeast China with different amounts of lime and/or pig manure, and planted with maize, affects pore scale properties down to micron size using synchrotron microtomography (SR–mCT). Soil macroaggregates (2 - 5 mm) from 4 treatments were measured: 1) Control, no manure amendment; 2) low manure (150 kg N ha-1 y-1); 3) high manure (600 kg N ha-1 y-1); and 4) high manure (600 kg N ha-1 y-1)+ lime (3000 kg Ca(OH)2 ha-1 every 3 years). Pore structure at a resolution of 3.7 µm was reconstructed in 3D and the Multi- Relaxation- Time (MRT) Scheme for Multi- Phase Lattice Boltzmann Method (LBM) was used to simulate water flow and retention. Topological analysis was performed based on the extracted pore network by using the maximal ball-based pore network extraction. A quasi-static pore network solver was applied to compute the capillary pressure based on the extracted pore networks. The application of a high amount of pig manure increased the fraction of macropores (>100 µm) to 38.61% compared to the controlled level (18.15%). A high amount of pig manure also decreased total porosity to 8.08% compared to 11.35% for the control, suggesting less micropores caused by high pig manure treatment. The application of high amount of pig manure and lime also caused more uniform water flow. Control samples had a velocity frequency at around e11 of the normalized velocity (respect to the mean), while the samples from the other treatments had more evenly distributed peaks. Water flows most quickly due to least impediment by pores in the samples with high manure amendment. The slope between permeability and porosity increased from 8.10 Darcy (controlled) to 174.47 Darcy (high amount of manure treatment). The amendment of 600 kg N ha-1 y-1 pig manure increased water retention ability calculated by the simulations. For the capillary pressure > -50 kPa, control samples had the greatest water saturation level compared with the samples from the other treatments, while there were no significant differences of water saturation of samples from all the treatments for the capillary pressure < -1000 kPa . The simulated water retention results had the same trend with the measured results.
Accurate reconstruction of comet 67P orbit through re-analysis of Rosetta ranging data acquired during proximity operations
Authors: Lasagni Manghi Riccardo , Zannoni Marco , Tortora Paolo , Küppers Michael , O'Rourke Laurence , Martin Patrick , Mottola Stefano , Keller Uwe , Budnik Frank , Taylor Matt , Jorda Laurent , Groussin Olivier , Thomas Nicolas
Published: March 2020

Following its arrival at comet 67P/Churyumov-Gerasimenko in August 2014, the Rosetta spacecraft successfully navigated in its proximity for two years, using a combination of Earth-based astrometric and radiometric tracking data as well as space-based optical navigation data. 

Depending on the mission phase, the orbital navigation system was tasked with the simultaneous estimation of both spacecraft and comet state, in addition to several other physical parameters including amongst others the comet rotational state, its gravitational field and the body-fixed coordinates of surface landmarks.

Estimating the heliocentric trajectory of 67P has proven to be challenging, due to the lack of reliable models to take into account the non-gravitational accelerations acting on the comet (particularly close to perihelion) and to occasional degradations of the ranging observables caused by geometrical constraints (solar conjunctions).

The accuracy of the resulting comet heliocentric trajectories, which show discontinuities in the order of tens of kilometers between consecutive short-arc solutions, was sufficient for spacecraft proximity operations, where navigators are mostly concerned by the relative comet/spacecraft position. However, a continuous and more accurate orbital solution is strictly coupled with the development of analytical models for non-gravitational accelerations and comet outgassing for which the Rosetta mission represents an ideal test case.

The work presented here represents a joint effort between academic institutions and ESA’s Flight Dynamics team to improve the accuracy of 67P’s orbit, by re-analyzing the radiometric data over long time scales for the whole duration of Rosetta proximity operations at comet 67P.

Details on the orbit determination process and filter implementation will be presented, together with a discussion on the achieved formal uncertainties and on the observables’ residuals.
Mean Age from in situ observations with AirCore: Accuracy of altitude attribution investigated with the CO-spiking experiment
Authors: Wagenhäuser Thomas , Engel Andreas , Sitals Robert , Kistner Irina
Published: March 2020

In order to monitor possible changes of the mean age of air in the stratosphere, in situ high altitude observations of suitable tracers are required. The AirCore is a simple sampling technique, which can be deployed to weather balloons in order to capture a continuous vertical profile of atmospheric trace gases up to 30 km. During ascent it empties due to the decreasing ambient pressure with height. During descent the AirCore fills with ambient air due to the positive change in ambient pressure. The analysis results from a continuous gas analyzer are merged with the recorded in-flight information to obtain the vertical distribution of the target trace gases mole fractions.

In context of the Goethe-University data processing procedure, an instantaneous pressure equilibrium is assumed across the whole AirCore. Since the amount of collected air sample is especially low at high altitudes, the assumptions made for data processing affect the accuracy of the altitude attribution primarily in the stratosphere. In order to evaluate the sample-to-altitude attribution procedure, the setup for an altitude dependent CO-spiking experiment was developed, tested and deployed to an AirCore that was flown and analyzed in Traînou, France, in June 2019. This setup allows for releasing small spikes of high CO signal gas in the inlet of the AirCore during descent at predefined GPS altitudes. By assigning the associated mole fraction measurements to the sampling altitude, the spiking signals are assigned to a modelled altitude as well. The quality of the altitude retrieval can be evaluated by comparing the assigned signal altitudes to the GPS release altitudes. In principle, every laboratory can deploy this experiment to its respective AirCores in order to evaluate its altitude attribution quality. Here we present the experimental details and the results of the evaluation to show the accuracy of the altitude registration of Goethe-University AirCore profiles. In addition, the long-term time series of mid-latitude stratospheric mean age observations from Engel et al 2017 is extended with mean age calculated from CO2-profiles obtained from recent AirCore observations.
Quantification of Microplastics in environmental samples using pressurized liquid extraction and Pyr-GC/MS
Authors: Földi Corinna
Published: March 2020

Fast and reliable quantification of microplastics in environmental samples is currently a challenging task. To enable monitoring of microplastics, a fast and robust method in sample preparation and subsequent analysis is of extraordinary need and urgency. Therefore, the combination of pressurized liquid extraction and Pyr-GC/MS has been developed. The fully automated extraction includes a pre-extraction via methanol for matrix elimination and a subsequent main extraction for microplastics using tetrahydrofuran to enrich microplastics on silica gel which is hence analyzed by means of Pyr-GC/MS.

Several commonly occurring organic matrices known to result in GC interferences were tested to be eliminated by pressurized liquid extraction.  For the most frequently used synthetic polymers PE, PP, and PS extraction efficiencies of 113-131, 80-98, and 70-118 %, respectively, and limits of quantification down to 0.005 mg/g were achieved.

The developed method was validated and applied to environmental samples with complex matrices such as roadside soils, potting soils, and sewage sludge. In all these matrices PE, PP, and PS were detected with contents ranging from 0.8 to 3.3, 0.01 to 0.36, and 0.06 to 0.61 mg/g. However, calcined sea sand spiked with wood, leaves, and humic acids, respectively, were found to interfere with PE quantification (0.140, 0.210, and 0.050 mg/g). Reduction of these interferences will be further evaluated.
Magnetization of lower crustal rocks - potential sources of long wavelength anomalies
Authors: ter Maat Geertje , McEnroe Suzanne , Church Nathan , Oda Hirokuni
Published: March 2020

The occurrence and nature of primary magnetic phases in ultramafic rocks is a subject of debate. Studies of ultramafic rocks originating in the deep crust commonly report secondary magnetic phases due to later metamorphism, serpentinization, or alteration as sources for long-wavelength anomalies. To assess the potential magnetic contribution from primary magnetic minerals occurring ‘in situ’ in deep-seated ultramafic rocks, the stability of these phases at lower crustal pressure and temperature conditions must be addressed. However, to study the magnetization of deep-crustal rocks, we are limited to exposures of unaltered uplifted rocks. Studying the petrophysical and rock magnetic properties of these ultramafic rocks can aid in predicting magnetic behavior deeper in the crust. 

Here, we present the results of a petrophysical and rock magnetic study on the ultramafic rocks of the Reinfjord Ultramafic Complex (RUC). These rocks are part of the Seiland Igneous Province, a magmatic plumbing system that formed in the deep crust (25-35 km depth). The dunites and wehrlites are minimally serpentinized, which indicates that the magnetic oxides in these rocks may be representative of those at depth. The primary magnetic carriers in these rocks were characterized using optical and electron microscopy, hysteresis and FORC measurements, backfield unmixing curves, and scanning magnetic microscopy. The primary magnetic carriers in the RUC are Cr-magnetite blebs exsolved from Al-chromite, and exsolved magnetite lamellae within clinopyroxene. The magnetic carriers have a range of domain states from SD to MD. 

The ultramafic rocks from the RUC are remarkably pristine and therefore provide insight into the magnetization of the lower crust. Due to the presence of SD magnetic carriers, these rocks may hold a stable remanence at lower crustal conditions and therefore be a potential source for long-wavelength anomalies.