bluuebunny/crossref_metadata_2025 huggingface dataset:
156 Nature-based solutions in the German Alps to mitigate hydro-meteorological risks
Authors: Zingraff-Hamed Aude , Lupp Gerd , Schedler Jonathan , Huang Josh , Pauleit Stephan
Published: March 2021

Nature-based solutions (NBS) are increasingly recognized as robust, sustainable and cost-effective measures for reducing the risk of extreme weather events. Their widespread implementation has become an important goal of the European Union’s political agenda. Many types of measures are included under the umbrella term of NBS. As their number is increasing, knowledge transfer should support effective implementation. Efforts have been made by a number of EU funded projects to develop and assess NBS implementation and enhance the transfer of experience. European databases as OPPLA has been created for this purpose. Interestingly, while mountain areas are highly vulnerable and already have experienced numerous extreme hydro-meteorological events and related natural hazards, NBS implementation in mountain area have received very little attention in both the research and practices until recently. The EU funded project PHUSICOS intends to partly fill this research gap by contributing in the knowledge transfer effort in making an inventory of NBS at their case study sites located in mountain areas. Given this background, the goal of our study is to provide a detailed overview of the NBS implementation effort for the case of German Alps. In this contribution, we present a systematic survey performed in the German Alps. We found 156 solutions implemented. Descriptive and qualitative analyses provided an overview of the implementation efforts in the German Alpine areas. Most of the measures were located within river systems and targeted flood protection. Few measures were implemented in the upper catchment to retain water on the land. Furthermore, few solutions exist to mitigate soil erosion and landslide. Further analysis concentrated on the stakeholders driving the NBS implementation. This survey may help, in the future to develop practical guidelines, identify governance enablers, ease cross-fertilization and identify successfully strategies.
Impacts of freeze-thaw processes and subsequent runoff on 137Cs washoff from bareland in Fukushima
Authors: Igarashi Yasunori , Onda Yuichi , Wakiyama Yoshifumi , Yoshimura Kazuya , Kato Hiroaki , Kozuka Shohei , Manome Ryo
Published: March 2021

The impact of freeze-thaw processes and subsequent runoff affecting the 137Cs flux and concentration in sediment discharge were revealed in bareland erosion plot following the Fukushima nuclear power plant accident by detailed monitoring and laser scanner measurement on the soil surface. We found that surface topographic changes due to the frost-heaving during the winter-spring period, and rill formation during the summer. We also found the evident seasonal changes in 137Cs concentration; high during the early spring and gradually decreased thereafter, then surface runoff from the plot frequently occurred during spring and autumn when rainfall was high and reached a maximum in summer. From these results, the higher 137Cs concentration in spring was caused by a mixture of unstable surface sediment following freeze-thaw processes and then transported in the early spring, but erosion amount is not significant because of the less rainfall event. The sediment with a lower 137Cs concentration, which was supplied from the rill erosion and its expansion, was wash-offed during the summer, contributing most of the flux from erosion in bareland in Fukushima region. In case,  heavy rainfall occurs in the early spring, caution is required because high concentrations of cesium may flow down into the river.
LANDInG (Leadership Academy and Network for Diversity & Inclusion in Geosciences): AGU’s New Program to Build, Develop, and Sustain DEI Leaders
Authors: Fraiser Margaret , Williams Billy , Goodwin Stephanie , Asher Pranoti
Published: March 2021

An equitable and inclusive geosciences discipline requires a systemic cultural shift. Despite four decades of consideration and federal investment, persons identifying as both white and men overwhelmingly outnumber people from marginalized groups in geosciences courses of study and professions. Cultural shifts can be facilitated by leadership, and research indicates that diversity and inclusion initiatives are more often effective when championed from the top. AGU, in strong partnership with other organizations and institutions, created the LANDInG program based on the rationale that both increasing capacity for DEI leadership within the geosciences and fostering recognition for the value for DEI champions are needed to significantly improve DEI outcomes across geosciences. LANDInG comprises: (1) a sustainable DEI Community of Practice Network, to engage and support a broad representation of DEI champions within the geosciences; and (2) a DEI Leader Academy, to build the DEI leadership capacity of select cohorts of DEI champions in the geosciences through intensive, cohort-based professional development tailored for them. The LANDInG DEI Leader Academy will include opportunities for direct experience leading DEI initiatives in the geosciences. Also part of the LANDInG program will be increasing the visibility and recognition of DEI champions and leaders in order to elevate their value within the discipline. Our model for change draws from research and theory spanning social and organizational sciences, including the literatures on professional networks/mentoring, and implementing effective diversity and leader training. Our methods for enacting change are evidence-based and framed by national models for cohort-based professional development within higher education/STEM. A steering committee and an advisory board of leading DEI scholars, social scientists, and representatives of other geoscience societies will broaden the expertise and diversity perspectives over the project’s life.
Underplating altered oceanic crust: Insights from numerical modelling
Authors: Braden Zoe , Ruh Jonas B. , Behr Whitney M.
Published: March 2021

Observations of several active shallow subduction megathrusts suggest that they are localized as décollements within sedimentary sequences or at the contact between sedimentary layers and the underlying mafic oceanic crust.  Exhumed accretionary complexes from a range of subduction depths, however, preserve underplated mafic slivers, which indicate that megathrust faults can occasionally develop within the mafic oceanic crustal column. The incorporation of mafic rocks into the subduction interface shear zone has the potential to influence both long-term subduction dynamics and short-term seismic and transient slip behaviour, but the processes and conditions that favour localisation of the megathrust into deeper oceanic crustal levels are poorly understood.

In this work, we use visco-elasto-plastic numerical modelling to explore the long-term (million year) factors influencing the incorporation of mafic volcanic rocks into the subduction interface and accretionary wedge through underplating. We focus on the potential importance of oceanic seafloor alteration in facilitating oceanic crustal weakening, which is implemented through a temperature-dependent pore-fluid pressure ratio (lambda = 0.90-0.99 between 160 and 300oC). We then examine the underplating response to changes in sediment thickness, geothermal gradient, sediment fluid pressure, and surface erosion rates. Our results indicate that a thinner incoming sediment package and a lower geothermal gradient cause oceanic crustal underplating to initiate deeper beneath the backstop (overriding plate) compared to thicker incoming sediment and a higher geothermal gradient. Relative pore fluid pressure differences between sediments and altered oceanic crust control the amount of altered oceanic crust that is underplated, as well as the location of underplating beneath the backstop or accretionary wedge. When sediments on top of the altered oceanic crust have the same fluid pressure as the altered oceanic crust, no oceanic crustal underplating occurs. Modelling results are also compared to exhumed subduction complexes to examine the amount and distribution of underplated mafic rocks.
Co-production of knowledge: towards a co-design of geothermal heat utilization
Authors: Schill Eva , Bauer Florian , Schätzler Katharina , Rösch Christine , Mbah Melanie , Benighaus Christina , Kuppler Sophie , Krohn Judith
Published: March 2021

In regions with favourable subsurface condition, geothermal resources provide a significant contribution to the reduction of man-made CO2 emissions. Its economic utilization often requires reservoir engineering that bears the risk of a number of environmental challenges such as induced seismicity, groundwater pollution or radioactive scaling.

In order to develop a socially feasible geothermal utilization concept in the Upper Rhine Graben close to the city of Karlsruhe we designed a research approach in which interdisciplinary (between natural and social sciences) knowledge production is combined with transdisciplinary knowledge production. This means that besides the collaboration of scientists of various disciplines, stakeholder and citizens s from surrounding communities get the possibility to take part in the project through workshops and interviews. The results of those transdisciplinary interactions will be integrated through translation into technical parameters in the technical design of a geothermal utilization concept. For the development of utilization scenarios, technical criteria were adopted into technical parameter ranges. Furthermore, socio-ecological criteria such as “no induced seismicity” are translated into technical parameters by an experience-based approach. The resulting scenarios are substantiated by numerical models that address the energy outcome. They will be reflected in a second stakeholder workshop. Finally, recommendations for a geothermal heat utilisation concept will be formulated.
Electron cooling at a weakly outgassing comet
Authors: Stephenson Peter , Galand Marina , Deca Jan , Henri Pierre , Carnielli Gianluca
Published: March 2021

The Rosetta spacecraft arrived at comet 67P in August 2014 and then escorted it for 2 years along its orbit. Throughout this escort phase, two plasma instruments (Mutual Impedance Probe, MIP; and Langmuir Probe, LAP) measured a population of cold electrons (< 1 eV) within the coma of 67P (Engelhardt et al., 2018; Wattieaux et al, 2020; Gilet et al., 2020). These cold electrons are understood to be formed by cooling warm electrons through collisions with the neutral gas. The warm electrons are primarily newly-born and produced at roughly 10eV within the coma through ionisation. While it was no surprise that cold electrons would form near perihelion given the high density of the neutral coma, the persistence of the cold electrons up to a heliocentric distance of 3.8 au was highly unexpected. With the low outgassing rates observed at such large heliocentric distances (Q < 1026 s-1), there should not be enough neutral molecules to cool the warm electrons efficiently before they ballistically escape the coma.

We use a collisional test particle model to examine the formation of the cold electron population at a weakly outgassing comet. The electrons are subject to stochastic collisions with the neutral coma which can either scatter or cool the electrons. Multiple electron neutral collision processes are included such that the electrons can undergo elastic scattering as well as collisions inducing excitation and ionisation of the neutral species. The inputted electric and magnetic fields, which act on the test particles, are taken from a 3D fully-kinetic, collisionless Particle-in-Cell (PiC) model of the solar wind and cometary ionosphere (Deca et al., 2017; 2019), with the same neutral coma as used in our model. We use a pure water coma with spherical symmetry and a 1/r2 dependence in the neutral number density to drive the production of cometary electrons and the electron-neutral collisions.

We first demonstrate the trapping of electrons in a potential well around the comet nucleus, formed by an ambipolar field. We show how this electron-trapping process can lead to more efficient cooling of electrons and the subsequent formation of a cold electron population, even at low outgassing rates.
A hydromorphic re-evaluation of Central Asia's Medieval floodwater farming civilizations
Authors: Toonen Willem , Macklin Mark , Dawkes Giles , Durcan Julie
Published: March 2021

The Aral Sea basin in Central Asia and its major rivers the Amu Darya and Syr Darya were the center of advanced river civilizations, and a principal hub of the Silk Roads trade network. The region’s decline has been traditionally attributed to the Mongol invasion of the early-13th century CE. In this study, we demonstrate the role of changing hydroclimatic conditions on the development of these culturally influential potamic societies that were depending on floodwater farming. Radiometric dating of irrigation canal abandonment and an investigation of regional river channel dynamics at Otrār oasis, a UNESCO World Heritage site located at the confluence of the Syr Darya and Arys rivers in southern Kazakhstan, revealed that major phases of fluvial aggradation occurred between the 7th to early-9th century CE and the mid-14th to mid-16th century CE. These periods coincide with economic flourishing of the oasis, facilitated by NAO-induced wet climatic conditions and higher river flows that favored floodwater farming. Periods of abandonment of the irrigation network and cultural decline primarily correlate with fluvial entrenchment during periods of drought. As the decline of the region seems to have initiated before the arrival of Ghenghis Khan and his armies, climate change has to be considered as a pivotal factor in the region's final demise.  
Flow recession behavior of dendritic subsurface ﬂow patterns
Authors: Strüven Jannick , Hergarten Stefan
Published: March 2021

Spring discharge curves can be seen as the fingerprint of an aquifer. In particular, the recession of flow after strong recharge events has been widely used for aquifer characterization. Several conceptual models for recession curve analysis were proposed. They either provide a mathematical fit to empirical relations or approximate a solution to the diffusion equation.

This study investigates the flow recession behavior of aquifers with preferential flow paths with a structure according to the concept of minimum energy dissipation.
Assuming a power-law relationship between hydraulic conductivity and porosity, the subsurface flow patterns used in our model are organized towards an optimal spatial distribution of these two parameters in a way that the total energy dissipation of the flow is minimized. This leads to two-dimensional dendritic network structures similar to river networks. Starting from a steady-state initial condition with a constant recharge rate we model the decrease of discharge over time, under the assumption of a linear storage behavior.

Our model produces recession curves that follow an exponential function at large time scales, which is a behavior often observed in nature and corresponds to many previous studies. The recession coefficient of this exponential decay shows a power law relation to the catchment size of each individual spring. This relation however is significantly less prevalent than for corresponding linear flow in 1 or 2D. 
Projecting the exponential portion of flow over the complete recession time period shows that the majority of available water is drained in this baseflow component. The overall share ranges from 85-100% but is independent from spring catchment sizes.
The “Sub-regional Mediterranean Sea indicators” viualization tool: from event detection to climate change estimations
Authors: Juza Mélanie , Tintoré Joaquin
Published: March 2021

In line with international initiatives (e.g. UN Decade of Ocean Science for Sustainable Development, UN Sustainable Developement Goal 14, OceanObs’19), one of the main objectives of the Balearic Islands Coastal Observing and Forecasting System (SOCIB) is to respond to science and society needs providing oceanographic data and added-value ocean products. In particular, SOCIB is developing a comprehensive set of multivariate sub-regional indicators in the Mediterranean Sea from past (last four decades) to present (today), with a specific interest on the Balearic Islands region and its adjacent basins (North-western Mediterranean Sea, Alboran Sea and Algerian sub-basin).

Two categories of oceanic variables are currently processed: (1) surface ocean data (sea surface temperature, chlorophyll-a concentration, currents, sea level and wind) from satellite products distributed by CMEMS, and (2) vertically integrated data (ocean heat and salt content, mixed layer depth properties, and water mass transports in key sections) from in situ platforms (gliders from SOCIB, profiling floats from Met-Office). These sub-regional indicators are an integral part of an operational product that provides continuous information about the ocean state and variability at sub-regional scale from daily (events) to interannual/decadal (climate) scales. These indicators allow to detect specific events in real time (e.g. marine heat wave, atmospheric storm, extreme river discharge, mesoscale eddy, deep convection). Long-term variations of the physical and biogeochemical components of the ocean, in response to climate change, are also addresssed as well as sub-regional differences.

An interactive and user-friendly interface has been implemented to monitor, visualize and communicate ocean information that is relevant for a wide range of sectors, applications and end-users (e.g. scientific community, educators in marine science, decision-makers and environmental agencies). The “Sub-regional Mediterranean Sea indicators” visualization tool is positioned as a complementary product to the CMEMS Ocean Monitoring Indicators at regional level addressing sub-regional variablity at various time scales and contributes to respond to the societal and environmental challenges.
Automatic offset detection using R open source libraries
Authors: Bhattacharjee Shambo , Santamaría-Gómez Alvaro
Published: March 2021

Long GNSS position time series contain offsets typically at rates between 1 and 3 offsets per decade. We may classify the offsets whether their epoch is precisely known, from GNSS station log files or Earthquake databases, or unknown. Very often, GNSS position time series contain offsets for which the epoch is not known a priori and, therefore, an offset detection/removal operation needs to be done in order to produce continuous position time series needed for many applications in geodesy and geophysics. A further classification of the offsets corresponds to those having a physical origin related to the instantaneous displacement of the GNSS antenna phase center (from Earthquakes, antenna changes or even changes of the environment of the antenna) and those spurious originated from the offset detection method being used (manual/supervised or automatic/unsupervised). Offsets due to changes of the antenna and its environment must be avoided by the station operators as much as possible. Spurious offsets due to the detection method must be avoided by the time series analyst and are the focus of this work.

Even if manual offset detection by expert analysis is likely to perform better, automatic offset detection algorithms are extremely useful when using massive (thousands) GNSS time series sets. Change point detection and cluster analysis algorithms can be used for detecting offsets in a GNSS time series data and R offers a number of libraries related to performing these two. For example, the “Bayesian Analysis of Change Point Problems” or the “bcp” helps to detect change points in a time series data. Similarly, the “dtwclust” (Dynamic Time Warping algorithm) is used for the time series cluster analysis. Our objective is to assess various open-source R libraries for the automatic offset detection.
Remote research in lunar and martian analog international missions to rise knowledge about life in isolation
Authors: Kolodziejczyk Agata , Harasymczuk Matt , Lagiewka Karolina
Published: March 2021

Analog simulations of space missions transform from educational activities to advanced interdisciplinary research related with future Moon and Mars exploration. Here we present results from Analog Simulations Campaign 2020 at Analog Astronaut Training Center in Poland. We organised 10 analog missions starting with six missions BRIGHT engaging 9 students, mission ETERNITY, DESTINY, and two EMMPOL missions engaging 18 people, what gives 27 analog astronauts in total for the whole campaign. Analog astronauts were supported by the Mission Control Center. Several experts from various disciplines - professional researchers, participated remotely in this project. Analog astronaut samples of serum, urine, stool and saliva were transported and analysed in professional laboratories of Collegium Medicum at Jagiellonian University in Kraków, Poland. 

Organised analog simulations had a common scientific and operational objectives. The main aim was to study life in isolation to support the general public in pandemic times. Missions were organised in specially equipped with environmental sensors isolated AATC habitat in the South of Poland. We collected multiple physiological and psychological data related with stress, motivation and efficiency of analog astronauts during their missions. We observed changes in physical activity, appetite, circadian rhythms, mood, and motivation, as well as interesting results from physiological samples. We defined the most critical aspects of life in isolation and tested putative solutions for improvement of the comfort of such type of existence. Based on our 4 month studies, we characterised a list of common problems strictly related with life in isolation, which were observed in tested groups. At the end, we propose solutions to improve life and well-being in restricted spaces.
Inverting surface-elevation data and velocity for basal topography beneath Thwaites Glacier, West Antarctica
Authors: Ockenden Helen , Curtis Andrew , Goldberg Daniel , Giannopoulos Antonios , Bingham Robert
Published: March 2021

Thwaites Glacier in West Antarctica is one of the regions of the fastest accelerating ice thinning and highest observed ice loss. The topography of the bed beneath the glacier is a key control of future ice loss, but is not currently well enough known to satisfy the requirements of ice sheet models predicting glacier behaviour. It has previously been suggested that in fast flowing ice streams the shapes of landforms at the bed should be reflected in the ice surface morphology, which is known to a much higher resolution. Indeed, recently published radar grids from Pine Island Glacier reveal bed landforms with a definite resemblance to the ice surface above them. Here, we present a new high resolution bed topography map of Thwaites Glacier, inverted from REMA and ITSLIVE data using linear perturbation theory, a mathematical formulation of this resemblance between bed and surface.  As it is based on linear physics, this method is faster than mass conservation and streamline diffusion interpolation, the two main techniques utilised by existing bed topography products in this region. Furthermore, as the theory is based on both mass and momentum balance, it provides a physically consistent estimate of elevation and basal slipperiness, in contrast to these more widely used methods. The resulting bed matches well with existing airborne and swath radar surveys, with significant detail between these radar lines. Variation in the results obtained using different reference models provides a measure of validity of the linear perturbation theory. Due to the importance of form drag in patterns of ice retreat, the inverted topographic features are potentially important for the future behaviour of Thwaites Glacier.
Analysis of organic compounds in Mars soil analog samples using SuperCam-Raman of Mars2020
Authors: Torre-Fdez Imanol , Fornaro Teresa , Aramendia Julene , Ollila Ann ,   Mars2020 SuperCam-Raman Science Group
Published: March 2021

One of the main objectives of the Perseverance rover is to find signs of ancient life in the Martian surface, seeking biosignatures and signs of past habitable conditions. This could be achieved with the finding of organic compounds related to life. Raman spectroscopy is among the techniques that the rover is capable of performing, which is able to detect and discern organic molecules. Perseverance carries in its payload two instruments that are able to use this technique, SuperCam for remote sensing and SHERLOC for proximity measurements. SuperCam is a long-distance instrument capable of performing several techniques (Raman, LIBS, luminescence, VISIR, microphone) in order to assess the chemical and molecular composition of rocks (mineral phases and organic molecules) from a distance up to 7 m. Therefore, it could detect organics, or traces of them, from a distance before the rover gets closer.

In this work, a set of Mars soil analog samples were analyzed using the Flying Model-Body Unit / Engineering Qualification Model-Mast Unit (FM-BU/EQM-MU) setup of SuperCam. Specifically, the samples were prepared in the laboratory by adsorbing adenosine 5’-monophosphate, L-glutamic acid, L-phenylalanine, and phthalic acid with different known concentrations (5 wt%, 1 wt% and 0.1 wt%) on the clay mineral montmorillonite doped with 1 wt% of Mg-perchlorate. The preparation and characterization of those samples can be found in literature [1]. The analyses were carried out at a 2 m distance from the targets, with a laser spot size of around 300 µm at that distance. SuperCam showed excellent results for the pure compounds, before adsorption on the clay mineral. At 5 wt% concentration, the Raman signals of the organics were barely visible and at 1 wt% they were no longer visible. This fact means that if the laser of SuperCam hits an organic “hotspot” in a rock from a distance, it will be able to detect it as long as it has a concentration around 5 wt% or greater in the analyzed area, allowing SHERLOC to do further contact analysis afterwards. In addition, the SuperCam results were compared with those obtained with a commercial laboratory instrument (Renishaw inVia), obtaining the same main signals and only missing some minor secondary bands.

[1] T. Fornaro, J. R. Brucato, G. Poggiali, M. A. Corazzi, M. Biczysko, M. Jaber, D. I. Foustoukos, R. M. Hazen, A. Steele, UV irradiation and Near Infrared characterization of laboratory Mars soil analog samples, Frontiers in Astronomy and Space Sciences, 2020, 7, 1-20
Deciphering train-induced body waves in correlation functions to promote fault monitoring
Authors: Sager Korbinian , Brenguier Florent , Boué Pierre , Mordret Aurélien , Tsai Victor C.
Published: March 2021

Continuous monitoring of active faults at seismogenic depths is key for the detection of potential precursors and to advance our understanding of earthquakes. In the context of the FaultScan project, we use seismic waves generated by freight trains – energetic and repetitive sources – recorded by two dense seismic arrays on both sides of the San Jacinto fault to directly observe transient deformation. Computing correlation functions for specific time segments corresponding to the passage of the trains reveals clear signals around the expected P-wave arrival time. The principle of Green’s function retrieval cannot be invoked for their interpretation, since the required assumption of a homogeneous source distribution is far from being met. To address this problem, we rely on correlation seismology, an emergent field of research that acknowledges the fact that correlations are shaped by both the distribution of ambient noise sources and Earth structure. Correlations are interpreted as self-consistent observables.

We first give a general introduction to (i) the forward problem of modeling correlation functions for arbitrary noise source distributions in space and frequency in potentially 3D heterogeneous and attenuating media, and to (ii) the computation of sensitivity kernels for noise sources and Earth structure. We then present an application of this framework to study the described problem of reconstructed body waves in the context of the FaultScan project. Studying structure kernels illustrates how signals are formed by the interaction of different P-wave phases and which parts should be used to monitor the fault. Forward modelling different source scenarios and structural changes further contributes to the understanding of the observed signals and highlights source-structure trade-offs.

Combining new and creative data-driven experiments with methodological developments is a promising way forward and has the potential to accelerate new discoveries.
Suitability of 2D modelling to evaluate flow properties in 3D porous media
Authors: Marafini Ester , La Rocca Michele , Fiori Aldo , Battiato Ilenia , Prestininzi Pietro
Published: March 2021

Limitations stemming from the employment of 2D models to investigate the properties of 3D flows in porous media are generally overlooked. In this study, the extent to which 2D modelling can be employed for the representation of genuinely 3D flows in porous media is quantified. To this scope, Representative Elementary Volume (REV) sizes of 2D and 3D media sharing the same porosity are compared. The spatial stationarity of several Quantities of Interest (QoIs) namely, porosity, permeability, mean and variance of velocity, is numerically evaluated. In order to extend conclusions to transport phenomena, the analysis of the velocity variance, which is closely associated to the hydrodynamic dispersion process, is included. Porous media adopted in this study are composed by spheres and disks in 3D and 2D domains respectively, where both 2D and 3D geometries are characterized by random locations. Specifically, for 3D random packings creation, a sphere packing generator program is used. Pore scale flow is simulated by means of the Lattice Boltzmann Model (LBM): the LBM is employed as a numerical flow solver to reproduce the Darcy's experiment through the aforementioned domains. The LBM represents a powerful tool to model flow in porous media and it is able to accurately predict flow paths, permeability and hydraulic conductivity. Hydraulic QoIs are analysed at steady state conditions. To this purpose, the flow velocity field is used to inspect stationarity. The quantitative approaches adopted in the REV assessment procedure allow one to determine the residual variability of the quantity associated to the REV and consequently the level of accuracy that the modeller wants to achieve with respect to the QoIs. Such criteria show that REV estimations through 2D models are much larger than their 3D counterparts. In conclusion, pore scale LBM simulations highlight that the 2D approach leads to inconsistent results, due to the profound difference between 2D and 3D porous flows.
A simple model to predict hydraulic conductivity in medium to dry soil from the water retention curve
Authors: Peters Andre , Hohenbrink Tobias L. , Iden Sascha C. , Durner Wolfgang
Published: March 2021

The mathematical representation of the soil hydraulic properties is of central importance for modeling water, solute and energy transport in the vadose zone. The established models of the soil water retention and hydraulic conductivity curves account for capillary water retention and capillary conductivity, but neglect water adsorption and water flow in films and in pore corners. They are therefore suited for modeling flow and transport processes in the medium to wet moisture range, but are susceptible to failure in dry soil. The model system developed by Peters (2013, 2014) and Iden and Durner (2014) (PDI in the following) is a simple parametric framework that overcomes these structural shortcomings. However, it requires an additional parameter to scale the hydraulic conductivity curve in the medium to dry moisture range where non-capillary flow is dominant. Measured conductivity data are required to estimate this scaling parameter and to compute the hydraulic conductivity over the complete moisture range. In this contribution, we first analyze the original model formulation and show that it is in close agreement with a comprehensive physically-based model for film conductivity in porous media. We then suggest a physically based method to predict the film conductivity from the water retention curve. This reduces the number of free parameters by one and gives a complete prediction of the hydraulic conductivity curve if only water retention data and the saturated conductivity are known. Application to literature data covering a broad range of textures shows a very good agreement between measured data and predictions.
Possible pathways to a Dansgaard-Oeschger (DO) PMIP protocol
Authors: Malmierca-Vallet Irene , Sime Louise C. , Valdes Paul J.
Published: March 2021

The DO events of the last ice age represent one of the best studied abrupt climate transitions, yet we still lack a comprehensive explanation for them. There is uncertainty whether current IPCC-relevant models can effectively represent the processes that cause DO events. Current Earth system models (ESMs) seem overly stable against external perturbations and incapable of reproducing most abrupt climate changes of the past (Valdes, 2011). If this holds true, this could noticeably influence their capability to predict future abrupt transitions, with significant consequences for the delivery of precise climate change projections.  In this task, the objectives of this study are (1) to cross compare existing simulations that show spontaneous DO-type oscillations using a common set of diagnostics so we can compare the mechanisms and the characteristics of the oscillations, and (2) to formulate possible pathways to a DO PMIP protocol that could help investigate cold-period instabilities through a range of insolation-, freshwater-, GHG-, and NH ice sheet-related forcings, as well as evaluating the possibility of spontaneous internal oscillations.

Although most abrupt DO events happened during MIS3, only few studies investigate DO events in coupled general circulation models under MIS 3 conditions (e.g., Kawamura et al., 2017; Zhang and Prange, 2020). Here, we thus propose that the MIS3 period could be the focus of such a DO-event modelling protocol. More specific sensitivity experiments performed under MIS 3 boundary conditions are needed in order to (1) better understand the mechanisms behind millennial-scale climate variability, (2) explore AMOC variability under intermediate glacial conditions, and (3) help answer the question: “are models too stable?”.
On stable boundary-layer height estimation using backscatter lidar data and variance processing
Authors: Araujo da Silva Marcos Paulo , Muñoz-Porcar Constantino , Saeed Umar , Rey Francesc , Pay Maria Teresa , Rocadenbosch Francesc
Published: March 2021

This study describes a method to estimate the nocturnal stable boundary layer height (SBLH) by means of lidar observations. The method permits two approaches which yield independent retrievals through either spatial or temporal variance vertical profiles of the attenuated backscatter. Then, the minimum variance region (MVR) on this profile is identified. Eventually, when multiple MVRs are detected, a temperature-based SBLH estimation derived from radiosonde, launched within the searching time, is used to disambiguate the initial guess. In order to test the method, two study cases employing lidar-ceilometer (Jenoptik CHM 15k Nimbus) measurements are investigated. Temperature-based estimates from a collocated microwave radiometer permitted validation, using either temporal or spatial backscatter variances. The dataset was collected during the HD(CP)2 Observational Prototype Experiment (HOPE) [1].   

[1] U. Saeed, F. Rocadenbosch, and S. Crewell, “Adaptive Estimation of the Stable Boundary Layer Height Using Combined Lidar and Microwave Radiometer Observations,” IEEE Trans. Geosci. Remote Sens., 54(12), 6895–6906 (2016), DOI: 10.1109/TGRS.2016.2586298.

[2] U. Löhnert, J. H. Schween, C. Acquistapace, K. Ebell, M. Maahn, M. Barrera-Verdejo, A. Hirsikko, B. Bohn, A. Knaps, E. O’Connor, C. Simmer, A. Wahner, and S. Crewell, “JOYCE: Jülich Observatory for Cloud Evolution,” Bulletin of the American Meteorological Society, 96(7), 1157-1174 (2015). DOI: 10.1175/BAMS-D-14-00105.1
Machine learning cloud top height detection based on GNSS radio occultations: a step ahead towards an operational use
Authors: Biondi Riccardo , Tournigand Pierre-Yves , Hammouti Mohammed
Published: March 2021

The Global Navigation Satellite Systems (GNSS) Radio Occultation (RO) technique allows the sounding of the atmosphere with a vertical resolution of about 100 m in the upper troposphere. It has already been demonstrated that the RO bending angle, by showing clear anomalies at the cloud top heights, is an efficient parameter to highlight the presence of dense clouds in the atmosphere. The objective of this work is to use the bending angle anomaly technique to systematically detect the presence of dense clouds in the atmosphere as well as their altitude and type. Several studies demonstrated the detection efficiency of the bending angle on tropical cyclones, severe convection and volcanic clouds altitude with high accuracy. However, the clouds type differentiation remains a challenge. One of the main issue on this regard, is the lack of volcanic cloud case studies, due to the low number of eruptions in comparisons to the extreme weather events, and to the large uncertainties on volcanic clouds detection techniques.

In this work we collected all the RO collocate in a short time range with tropical cyclones and volcanic clouds, and we collocate them with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) backscatter. The bending angle anomaly profile is given in input to a machine learning algorithm to retrieve the presence of the cloud and its height. The CALIOP backscatter has 30-meter vertical resolution in the troposphere and 60-meter in the upper troposphere/lower stratosphere. We manually constrain the cloud edges, compute the cloud top height from each cloud and use this value as target for the algorithm output. To get a balanced training of the algorithm, we add to the dataset an equal number of clear sky samples.

The algorithm aims at quickly providing the cloud top height to be used for aviation and nowcast issues and to be included in early warning systems.
Power-law thermal stratification in lake Geneva and its seasonal evolution
Authors: Beltram Tergolina Vinicius , Jiang Yueting , Schmitt François , Berti Stefano , Calzavarini Enrico , Anneville Orlane
Published: March 2021

Lake Geneva is one of the largest bodies of water in western Europe and the largest one in the Alps region. Besides its obvious touristic importance it supplies drinking water for a large portion of Switzerland and work for hundreds of commercial fishermen. It has been under constant monitoring since the 1970's, for the impact of human activities on its water quality and biodiversity. The lake is known to be a warm monomictic lake, thermally stratified through most of the year with the exception of winter, when small thermal vertical gradients permit mixing from top to bottom. In lake Geneva, thermal stratification is one of the main environmental drivers of phytoplankton communities which are widely used as bioindicators for freshwater ecosystems. Studies on thermal stratification are thus essential to better predict phytoplankton seasonality and the development of harmful species blooms. In this work we examine more than 20 years of surveillance data from the INRAE (National Research Institute for Agriculture, Food and Environment) regarding temperature vertical profiles and meteorological data. We review both the climatology and the temperature stratification history of the lake and refine the temperature depth profiles obtaining the yearly progressions of the mixed layer depths. We then discuss the fitting of the depth profiles through the use of power-law and exponential functions, finding that in 66% of the cases the power-law better describes the experimental data, and we report the probability density function of the related statistics throughout the seasons.  Finally, we discuss the implications of our results for the modelling of the lake turbulent regime and phytoplankton seasonality.
A GPR based estimation of concrete strength changes under extreme temperatures exposure: An experimental study
Authors: Artagan Salih Serkan , Yurdakul Özgür , Borecky Vladislav , Lunak Miroslav
Published: March 2021

There are certain situations where concrete structures are required to resist high temperatures. This applies to cases where exposure to high temperature is expected due to the special character of buildings or where the concrete structure is required to resist severe conditions caused by traffic accidents, terrorist attacks, or natural disasters (earthquakes, fires, etc.). Under such applications, the effect of elevated temperature on mechanical and physical properties may determine whether the concrete element or structure will maintain its structural integrity or not. In this context, fire resistance is defined as the ability to withstand exposure to fire without loss of load-bearing function or ability to act as a barrier to spread a fire. In most cases, structural health monitoring of concrete structures is performed as the visual appraisal of the external characteristics of structures or destructive testing (e.g., concrete coring), and little use has been made of the modern non-destructive testing (NDT) techniques including Ground Penetrating Radar (GPR). GPR, emitting short pulses of electromagnetic energy into the material, is primarily used for location of rebar, estimation of rebar size, industrial quality control, defect and decay detection, and measurement of electrical properties, in case of concrete diagnostics.

This paper comprises a series of GPR and core compressive strengths on low-strength concrete samples. The samples were produced and tested by GPR before and after extreme temperature exposure in an electric furnace at the following temperature levels: 300, 400, 500, 600, and 700 ℃. Then, the compressive test results of the cores taken from the specimens are compared with the GPR data for each temperature level. For GPR tests, the IDS Aladdin system was used with a double polarized 2 GHz antenna. For compressive strength tests, a compression test machine with a capacity of 3000 kN was used.

Based on GPR measurement, Relative Dielectric Permittivity (RDP) values were calculated based on known dimensions of samples and two-way travel time (twt) values obtained from A-scans. The change in RDP values of samples before and after exposure to extreme temperature was then calculated. This variation was then correlated with the change of compressive strength values with regard to the applied temperature levels. This experimental study thus gives an insight into the potential use of GPR, as an NDT tool, in estimating the strength loss in concrete structural elements exposed to aggressive fire.

All GPR tests were conducted in Educational and Research Centre in Transport; Faculty of Transport Engineering; University of Pardubice. This work is supported by the University of Pardubice (Project No: CZ.02.2.69/0.0/0.0/18_053/0016969).
Statistical Investigation of Fluctuations around the Lower Hybrid Frequency at the Dipolarization Front in the near-Earth Magnetotail
Authors: Hosner Martin , Nakamura Rumi , Nakamura Takuma , Panov Evgeny , Schmid Daniel , Burch James L. , Giles Barbara L. , Torbert Roy
Published: March 2021

At the leading edges of reconnection jets in the magnetotail, commonly referred to as Dipolarization Fronts (DF), strong fluctuations in the electric field δE and the magnetic field δB are observed. Recent results from a fully kinetic PIC simulation (Nakamura et al., 2019) demonstrate that a Lower Hybrid Drift Instability-driven (LHDI) disturbance at the DF front region can be responsible for these electric and magnetic field fluctuations. These findings are well in line with an observed event (Liu at al., 2018), comparable to the simulated plasma conditions. However, a general experimental validation under a wider range of conditions yet remains absent. The present work experimentally investigates δE and δB fluctuations for a selection of DF events between July 2017 and September 2018 using Magnetospheric Multiscale (MMS) mission data. Aiming for a statistical approach, the analysis consists of a quantitative evaluation of dynamic wave power spectra of both δE and δB in the lower hybrid frequency range. Furthermore, propagation properties of associated wave structures are analyzed and related to present plasma conditions. Findings include the identification of peak wave power occurrence times relative to the magnetic DF structure and the associated density gradient.
The Diurnal Cycle of Precipitation: A Comparison of State-of-the-Art IMERG Observations, CMIP6 Models and ERA5 Reanalysis
Authors: Watters Daniel , Battaglia Alessandro , Allan Richard
Published: March 2021

Simulations of the diurnal cycle of precipitation from CMIP6 models and the ERA5 reanalysis are evaluated against the observed diurnal cycle from NASA’s IMERG observations.  The IMERG observation product, which combines the GPM/TRMM microwave constellation, spaceborne infrared sensors and ground-based gauge measurements, provides 20+ years of gridded global precipitation estimates at 0.1˚ every half hour.  Using IMERG’s long precipitation record, the first multi-decade evaluation of the simulated diurnal cycle is conducted (IMERG and ERA5: 2000-2019; CMIP6: 1979-2008).  After spatial and temporal matching of IMERG to the hourly CMIP6 (NCAR-CESM2, CNRM-CM6-1, CNRM-ESM2-1) and ERA5 simulations, the diurnal cycle for boreal summer is compared between products across the globe (60˚N-S).  To avoid bias in the results, regions with yearly mean precipitation < 100 mm are excluded from all analyses, as well as regions with weak diurnal amplitudes when analysing the time of maximum precipitation.  CMIP6 and ERA5 simulations underestimate the observed diurnal amplitude over ocean (14-66% of the precipitation mean, for the 5th-95th percentile range), with varying performance over land (26-134%).  Maximum precipitation is observed to accumulate over land in the afternoon and at night (14-21 LST over flatter terrain, and 21-6 LST over mountainous regions), and in the morning over ocean (0-12 LST).  CMIP6 and ERA5 are identified to better simulate the time of maximum over ocean than over land, though typically earlier in the day than observed.  In particular, ERA5 and CMIP6 fail to capture the propagating night-time peaks in precipitation accumulation close to mountainous regions.  Further analyses over CONUS, which include the ground-based radar network, highlight the improved performance of models in regions susceptible to convection (e.g. the Rocky Mountains).  Furthermore, IMERG’s skill in capturing the diurnal cycle over CONUS is demonstrated, and the current capability of the GPM Core Observatory’s dual-frequency precipitation radar is assessed.