bluuebunny/crossref_metadata_2025 huggingface dataset:
On the link between Beamforming and Kernel-based Source Inversion
Authors: Bowden Daniel , Sager Korbinian , Fichtner Andreas , Chmiel Małgorzata
Published: March 2020

Beamforming and backprojection methods offer a data-driven approach to image noise sources, but provide no opportunity to account for prior information or iterate through an inversion framework. In contrast, recent methods have been developed to locate ambient noise sources based on cross-correlations between stations and the construction of finite-frequency kernels, allowing for inversions over multiple iterations (i.e., Tromp et al., 2010, Ermert et al. 2017, Sager et al. 2018). These kernel-based approaches show great promise, both in mathematical rigour and in results, but may remain difficult to understand or implement for the wider community. Here we show that these two different classes of methods, beamforming and kernel-based inversion, are achieving exactly the same result in certain circumstances. This means existing beamforming and backprojection methods can also incorporate prior information in a mathematically correct manner.

We start with a description of a relatively simple beamforming or backprojection algorithm, based on time-domain shifting and measurement of waveform coherence. Only by changing the order of steps, we begin to resemble the kernel-based approaches. By adding a physical model for the distribution of noise sources, and therefore synthetic correlation functions, we can extend backprojection to an iterative, gradient-based inversion scheme. Adjoint methods and a direct simulation of correlation wavefields can later be used to increase computational efficiency, but we stress that these are not needed to understand the approach.

Given the equivalence of these approaches between these two communities, both sides can benefit from bridging the gap. For example, for kernel-based inversion schemes, a current challenge lies in defining the misfit and time window over which a correlation will be scored; a windowing function based on beamform images offers a more intuitive way to identify significant contributions in the noise wavefield, exploiting more than just the direct surface-wave arrivals.
Landscape drivers of coastal dune mobility
Authors: Smyth Thomas , Wilson Ryan , Rooney Paul , Yates Katherine
Published: March 2020

Coastal dunes are dynamic landforms whose morphology is governed primarily by climate and vegetation dynamics. Over the last 50 years, coastal sand dunes across the globe have dramatically ‘greened’ and wind speeds fallen (Pye et al., 2014; Delgado-Fernandez et al., 2019; Jackson et al., 2019), reducing aeolian transport of sediment and minimising dune reshaping by near-surface winds.  This rapid vegetation has also been attributed to a dramatic decline of several rare species of plants and invertebrates in several coastal dune systems (Howe et al., 2010; Pye et al., 2014). In an effort to increase habitat diversity, large-scale vegetation removal and dune re-profiling are becoming increasingly common interventions. However sustained aeolian activity following intervention appears to be rare (Arens et al., 2013).

In order to better understand the environmental drivers of long-term dune mobility, this work explores the landscape scale physical factors related to self-sustaining ‘natural’ mobile dunes across the United Kingdom. The analysis presented includes the use of geographically weighted regression, a spatial analysis technique that models the local relationships between predictors (e.g. wind speed, slope, elevation, aspect, surface roughness) and an outcome of interest (mobile dunes). It is hoped that the results of this work will help guide decision-making with regards the location, scale and morphology of future interventions in order to maximise their sustainability, minimising the need for maintenance and further intervention.

References

Arens, S.M., Slings, Q.L., Geelen, L.H. and Van der Hagen, H.G., 2013. Restoration of dune mobility in the Netherlands. In Restoration of coastal dunes (pp. 107-124). Springer, Berlin, Heidelberg.

Delgado-Fernandez, I., O'Keeffe, N., & Davidson-Arnott, R. G. (2019). Natural and human controls on dune vegetation cover and disturbance. Science of The Total Environment, 672, 643-656.

Howe, M. A., Knight, G. T., & Clee, C. (2010). The importance of coastal sand dunes for terrestrial invertebrates in Wales and the UK, with particular reference to aculeate Hymenoptera (bees, wasps & ants). Journal of Coastal Conservation, 14(2), 91-102.

Jackson, D. W., Costas, S., González-Villanueva, R., & Cooper, A. (2019). A global ‘greening’of coastal dunes: An integrated consequence of climate change?. Global and Planetary Change, 182, 103026.

Pye, K., Blott, S. J., & Howe, M. A. (2014). Coastal dune stabilization in Wales and requirements for rejuvenation. Journal of coastal conservation, 18(1), 27-54.
Real time physics-based solar wind forecasts for SafeSpace
Authors: Pinto Rui , Kieokaew Rungployphan , Lavraud Benoît , Génot Vincent , Bouchemit Myriam , Rouillard Alexis , Poedts Stefaan , Bourdarie Sébastien , Daglis Yannis
Published: March 2020

We present the solar wind forecast module to be implemented on the Sun – interplanetary space – Earth’s magnetosphere chain of the H2020 SafeSpace project. The wind modelling pipeline, developed at the IRAP, performs real-time robust simulations (forward modelling) of the physical processes that determine the state of the solar wind from the surface of the Sun up to the L1 point. The pipeline puts together different mature research models: determination of the background coronal magnetic field, computation of many individual solar wind acceleration profiles (1 to 90 solar radii), propagation across the heliosphere and formation of CIRs (up to 1 AU or more), estimation of synthetic diagnostics (white-light and EUV imaging, in-situ time-series) and comparison to observations and spacecraft measurements. Different magnotograms sources (WSO, SOLIS, GONG, ADAPT) can be combined, as well as coronal field reconstruction methods (PFSS, NLFFF), wind models (MULTI-VP), and heliospheric propagation models (CDPP/AMDA 1D MHD, ENLIL, EUHFORIA). We provide a web-based service that continuously supplies a full set of bulk physical parameters (wind speed, density, temperature, magnetic field, phase speeds) of the solar wind up to 6-7 days in advance, at a time cadence compatible with space weather applications.
Eccentricity-paced ice sheet variability and obliquity-driven bottom-water changes during the Oligocene-Miocene
Authors: van Peer Tim , Taylor Victoria , Liebrand Diederik , Brzelinski Swaantje , Möbius Iris , Bornemann André , Friedrich Oliver , Bohaty Steven , Xuan Chuang , Lippert Peter , Wilson Paul
Published: March 2020

Variations in solar insolation exert a fundamental control on the high-latitude climate–cryosphere system. Controversy, however, exists about the relative importance of orbital eccentricity versus axial tilt (obliquity) in driving pre-Quaternary Antarctic ice sheet variability. This problem is particularly acute during the late Oligocene-to-early Miocene interval (Oligo-Miocene, ~27-21 Ma), because several benthic foraminiferal oxygen isotopes (δ18O) records show strong pacing by obliquity, while others primarily show eccentricity pacing. The differences in orbital pacing are impossible to reconcile with the globally congruent imprint of ice volume on benthic δ18O on orbital time scales. Here we present a new astronomically tuned δ18O record generated at Integrated Ocean Drilling Program (IODP) Site U1406 (north-western Atlantic Ocean), a key area in modern-day thermohaline circulation. Clear imprints of both obliquity and eccentricity on the δ18O record are observed at Site U1406 throughout the study interval, irrespective of changes in sedimentation rate. The eccentricity variations at Site U1406 are remarkably similar to those seen in all other δ18O records, suggesting that eccentricity exerts a strong control on the high-latitude climate–cryosphere system via the modulation of the precession cycle. In contrast, the δ18O sensitivity to obliquity is globally variable, suggesting the influence of temperature in different bottom-water masses.
Direct and array-derived rotations in the Gran Sasso underground laboratory: application to earthquakes and seismic noise.
Authors: Simonelli Andreino , Desiderio Matteo , Giacomelli Umberto , De Luca Gaetano , Govoni Aladino , Di Virgilio Angela
Published: March 2020

In the present work, we analyze rotational and translational ground motions, in order to retrieve the local wavefield properties. We apply the same method of analysis to both earthquake and ambient noise signals, in order to estimate the wave field direction and the phase velocity as a function of frequency.
For the first case, the vertical rotation rate is measured by a large ring laser gyroscope (named GINGERino). Translational motions, on the other hand, are recorded by a broad-band seismometer (a station of the INGV national seismic network IV, code-named GIGS). These instruments are colocated in a gallery inside the facilities of the Laboratorio Nazionale del Gran Sasso (LNGS) of the Istituto Nazionale di Fisica Nucleare (INFN), at 1km depth, and constitute a 4 Components (4C) station. We examine the data recorded in late November 2019 i.e. the earthquakes in Northern Albania, Balkan region and off the coast of Crete. An additional event that struck the Mugello Region (Italy) in early December 2019 is also analyzed. We focus on the rotational motions induced by S and Love waves. In the second case, we exploit a temporary array (named XG) of 3-component broad-band seismometers (code-named GIN*) installed in the facilities of the LNGS. Here, the rotation rate is derived trough a finite-difference scheme involving the stations of the array. First, we test the reliability of the ADR method XG with simulated earthquake data. In a second step we analyse the secondary microseism signal recorded during a sea storm that occurred in the Mediterranean basin in early January 2019. Such workflow is also compared to an f-k analysis, that is a common array data processing method. Finally, theoretical P body waves noise sources are computed and compared to the estimated BAZ.
Investigating tropical and midlatitude drivers of Arctic atmospheric energy transport
Authors: Dunn-Sigouin Etienne , Li Camille , Kushner Paul
Published: March 2020

Planetary waves with zonal wavenumbers k ≤ 3 dominate poleward atmospheric energy transport and its associated Arctic warming and moistening impacts in reanalysis data. Previous work suggests planetary waves generated by tropical warm pool Sea-Surface Temperatures (SSTs) and midlatitude synoptic waves (k ≥ 4) can drive Arctic energy transport. Here, we investigate tropical and midlatitude drivers of Arctic planetary wave transport using an idealised aquaplanet model. First, we show that the zonally-symmetric model qualitatively captures the main characteristics of observed planetary wave transport, as well as its impacts in the Arctic. Next, we show that an idealised tropical warm pool, driven by regional SST forcing, amplifies but is not the dominant source of Arctic planetary wave transport. Finally, lag-regressions using reanalysis and model data suggest midlatitude synoptic waves compensate rather than drive Arctic planetary wave transport. The results do not support the simple geometric effect of midlatitude synoptic waves aliasing onto Arctic planetary waves on a sphere, but rather point towards more complex scale interactions and local drivers of Arctic planetary wave transport.
Latest developments of the airGR rainfall-runoff modelling R-package: inclusion of an interception store in the hourly model
Authors: Thirel Guillaume , Delaigue Olivier , Ficchi Andrea
Published: March 2020

airGR (Coron et al., 2017, 2019) is an R package that offers the possibility to use the GR rainfall-runoff models developed in the Hydrology Research Group at INRAE (formerly at Irstea), including the daily GR4J model as well as hourly, monthly and annual models. Recent model developments are regularly introduced in airGR.

Recently, an hourly model including an interception store was implemented in airGR. The additional interception store, developed by Ficchi et al. (2019), aims at better representing the impact of vegetation on evaporation fluxes. This improved model showed a better consistency of model fluxes across time and enhanced performance.

In addition, the possibility to run the hourly GR models together with the CemaNeige snow accumulation and melt module was added to airGR.

 

References:

Coron L., Thirel G., Delaigue O., Perrin C., Andréassian V. (2017). The Suite of Lumped GR Hydrological Models in an R package, Environmental Modelling & Software, 94, 166-171. DOI: 10.1016/j.envsoft.2017.05.002.

Coron, L., Delaigue, O., Thirel, G., Perrin, C. and Michel, C. (2019). airGR: Suite of GR Hydrological Models for Precipitation-Runoff Modelling. R   package version 1.4.3.30. URL: https://CRAN.R-project.org/package=airGR.

Ficchì, A., Perrin, C., and Andréassian, V., 2019. Hydrological modelling at multiple sub-daily time steps: model improvement via flux-matching, Journal of Hydrology, 575, 1308-1327, https://doi.org/10.1016/j.jhydrol.2019.05.084.
Synoptic representation of P.oceanica ecosystem services in the Italian seas
Authors: Scanu Sergio , Mellini Simone , Piazzolla Daniele , Bonamano Simone , Mancini Emanuele , Frattarelli Francesco Manfredi
Published: March 2020

This work analyzes and quantifies the value of ecosystem services in the P.oceanica meadows of the Italian seas, defining methodological approaches and creating synoptic maps through the use of GIS. Ecosystem Services can be defined as benefits provided to mankind by natural ecosystems. Their contribution is essential for human progress and of fundamental importance in the long run.

Posidonia oceanica was chosen as the object of study because its meadows represent one of the Mediterranean "climax community". P. oceanica is, therefore, one of the most important ecosystem in the Mediterranean and has been indicated as "priority habitat" according to the Habitat Directive (Dir. N. 92/43 / EEC), which groups together all the Sites of Community Importance (SCI) that need to be protected.

The method of evaluating the ecosystem services for P.oceanica is derived from what reported in Costanza et al. (1997) applying the specific site approach for the definition of benefits and services (Marcelli et al. 2018).

The identified benefits for P.oceanica are carbon sequestration, oxygen production, erosion protection, bioremediation and food production.

P.oceanica data are organized from the dataset collected by the Italian Institute for the Protection of the Environment and Research (ISPRA) for the Marine Strategy Framework Directive and include parameters such as coverage and shoots number (m2), average leaf area, leaf area index, average number of leaves, average height of the rhizomes, average foliar and rhizomes production. The data were used for the calculation of the benefits of P. oceanica which are represented in synoptic maps through GIS with the creation of the Atlas of the values ​​of ecosystem services in the Italian seas.
Model studies on vibrationally-rotationally excited hydroxyl molecules in the mesopause region
Authors: Notholt Justus , Winkler Holger , Noll Stefan
Published: March 2020

One of the standard methods to remotely sense the temperature of the mesopause region is based on spectroscopic measurements of near-infrared emissions of vibrationally-rotationally excited hydroxyl molecules, and to calculate  rotational temperatures. For the interpretation of the retrieved temperatures, the aspect of rotational thermalization is of great importance. We present results of a first-principle kinetic model of vibrationally-rotationally excited hydroxyl molecules which accounts for chemical production and loss processes as well as radiative and collision-induced vibrational-rotational transitions. The model allows one to assess deviations of the rotational populations from local thermodynamic equilibrium, and to identify the key parameters which control the rotational thermalization processes. The model simulations reproduce the observed bimodality in temperatures, i.e. a cold temperature component dominating the population of low rotational states, and a hot temperature component dominating higher states. The model results are compared to measurement data from the UVES echelle spectrograph at Cerro Paranal in Chile (Presentation EGU2020-3169) which allows us to confine free model parameters such as the rotational state changes in vibrational quenching process.
The 3D stress state within typical salt structures
Authors: Baumann Tobias , Kaus Boris , Popov Anton , Urai Janos
Published: March 2020

Salt caverns are created during the process of solution mining or built actively for underground storage purposes required for the energy transition. In most cavern-scale numerical models, deviatoric stresses within the salt dome are assumed to be negligible in magnitude. However, as salt structures are typically not homogeneous, this assumption is known to be incorrect. Stress variations may be caused by internal heterogeneities such as the presence of anhydrite layers, or by the large-scale structure and ongoing deformation of the salt dome or pillow as a result of their lower density compared to the overlying rocks. The rheology of the salt itself, a not very well constrained parameter, which varies significantly between different types of salt, may also have a significant effect.

In the scope of the Dutch KEM-17 project (Knowledge Programme on Effects of Mining) on Over-pressured salt solution mining caverns and possible leakage mechanisms, we examined which differential stresses can develop in a typical salt-structure (salt pillow, salt wall, and flat-bedded salt).  In order to make recommendations for avoiding undesired interference effects between caverns and salt dome boundaries, it is crucial to understand better how the stresses caused by salt-deformation vary within the salt dome. Which lower/upper bounds are to be expected for a particular type of structure? Where are such stresses likely to be negligible, and can we safely use existing approaches that neglect the background stress field? To what extent do uncertainties in the model parameters and geometries affect the stress state in the salt dome? To answer these questions, we used 3D thermomechanical models, for which we incorporated the state-of-the-art rheological flow laws of salt and assessed the stress state over approximately 300 kyrs, including the effect of tectonic regimes and glacial (un-)loading.
Investigating the anthropogenic influence on the mesoscale over Kilimanjaro
Authors: Pickler Carolyne , Mölg Thomas
Published: March 2020

Anthropogenic influence on climate change has increased over time and has been detected in all major components of the climate system.  High altitude mountains constitute a highly-sensitive region.  This has lead to many studies, on varying scales, with detection of climate change as motivation.  However, questions persist as to how this anthropogenic influence is manifested in the mesoscale over these mountains and how it transfers between various scales.

A case of study of Kilimanjaro and the glaciers on its summit is undertaken to start addressing these questions.  Its unique location, an isolated peak with a summit at almost exactly 500 hPa, allows for the examination of the large and local scale climate change dynamics and how they are linked by the mesoscale circulation over the mountain.  Furthemore, it has been extensively studied on the large and local scale and has decadal automated weather station records.  A first step involves running the limited-area Weather and Research Forecasting (WRF) regional climate model over the East African region for the period of 1985-2015 using multiple grid nesting centred over Kilimanjaro.  The lateral boundaries of WRF will be forced with output from two simulations, historical and historicalNat, of a global climate model (BNU-ESM r1i1p1) from the Coupled Model Intercomparison Project Phase 5 (CMIP5).  These two simulations differ by the addition of anthropogenic forcing in the historical simulation.  The model was carefully selected by a rigorous testing procedure, where analysis of the top 5 ranked models yielded a first estimate of anthropogenic influence in East Africa.  Comparison of WRF output from both simulations will be undertaken to assess how anthropogenic forcing has affected dynamical (e.g. flow regimes) and microphysical processes (e.g. cloud composititon and stability) in the mesoscale over Kilimanjaro.
Pore scale simulations of how mucilage alters connectivity of liquid and gas phase in the rhizosphere
Authors: Esmaeelipoor Jahromi Omid , Bentz Jonas , Haupenthal Adrian , Patel Ravi , Kroener Eva
Published: March 2020

Compared to bulk soil, rhizosphere has different properties because of the existence of root mucilage which affects the physical, chemical and also microbial processes. Hydraulic phenomena like limiting water flow at certain dry soil conditions, modulating extreme water contents by slow response to water potential changes; and also influencing solute transport and gas diffusion by varying the connectivity of liquid and gas phases are all classified under the set of the physical processes which are affected by mucilage in the rhizosphere.

Overview of the literature and previous models shows the lack of a three-dimensional pore-scale dynamic model for a better understanding of the connectivity between different phases during imbibition and drainage processes. A major challenge is that mucilage shows a complex behavior which at low concentrations is more like a liquid while at higher concentration when it is almost dry, it becomes a solid.

In particular, this study will use the Lattice Boltzmann method as a powerful tool for fluid dynamics study and the discrete element method for describing solids to present a pore-scale model for more accurate simulation and study of physical processes in the rhizosphere.
Immobilization and ligand-induced remobilization of uranium in anoxic aquifer environments
Authors: Alvarez Salas Mario Alejandro , Chardi Kyle , Schenkeveld Walter , Kumar Naresh , Giammar Daniel , Kraemer Stephan M.
Published: March 2020

Uranium (U) is a naturally occurring radionuclide that poses serious health risk owing to its chemical and radiological toxicity. The main route of U exposure towards humans is drinking (ground)water. The mobility of U is essentially driven by its speciation, where U(VI) is present as relatively mobile species and U(IV) as largely immobile in the environment. Hence, many U remediation strategies are targeted towards biotic or abiotic reduction of U(VI) to immobile U(IV) species. However, success of such remediation processes is dependent on biogeochemical conditions caused by interactions between dissolved species, mineral surfaces, and microbial activities. Protecting water quality thus requires better understanding of the geochemical factors that control U stability in the subsurface environment; one such factor is the presence of organic ligands.

            The role of naturally occurring organic ligands in affecting nutrient and contaminant mobility is well established in subsurface environments. We tested the hypothesis that these organic ligands have the potential to effectively remobilize the reduced uranium and bring it to a concentration that exceeds the WHO safety guideline for U in drinking water (30µg L-1). We utilized aquifer sediment from Retz, Austria in which uranium bioreduction is known to occur. Bioreduction and accumulation of dissolved U was observed in a flow through column experiment. These reduced U containing sediments were then treated with various organic ligands (e.g., citrate, oxalate, EDTA, DTPA, and DFO-B) in varying concentrations in batch and column experiments to elucidate the mechanism and extent of ligand-induced mobilization of U. We also used geochemical modelling with PhreeqC to generate a conceptual model for ligand-induced mobilization of U.

            The results of this study provide insights in the extent of ligand-induced mobilization of U in the environment. This information is essential in planning future aquifer management and U remediation strategies
Hafnium (and Sr-Nd) isotope analysis of mineral dust: from sample digestions to mass spectrometry
Authors: Ujvari Gabor , Klötzli Urs , Horschinegg Monika , Wegner Wencke , Hippler Dorothee , Tepe Nathalie , Kiss Gabriella , Horváth Anikó , Svensson Anders
Published: March 2020

Mineral dust in ice cores provides insight into past atmospheric circulation patterns provided that the source(s) of these aerosols can be identified. Isotopes of strontium, neodymium and lead are frequently used for source discrimination in ice cores, while those of hafnium much less so. This is because of the extremely low (1-5 ng) amounts of Hf present in 5-10 mg dust samples usually available for isotopic analyses from the dustiest periods of past glaciations, e.g. the Last Glacial Maximum. The use of 176Hf/177Hf isotopic ratios in dust fingerprinting is crucial in situations when Sr-Nd isotopes are inconclusive in source identification.

The overall Hf budget is dominated by the heavy mineral zircon in silt-sized, wind-blown material, while it is significantly depleted in the finer (<5 µm) fractions and the effects of other minerals (apatite, sphene, monazite, xenotime and clay minerals) become increasingly important. Since the major hosts of Hf are refractory heavy minerals, the complete digestion of dust material is crucial in determining reliable Hf isotope ratios.

Here we introduce a closed vessel ammonium bifluoride (NH4HF2) digestion method (220 °C), which is a fast and low blank (0.5 ng for Sr, 0.2 ng for Nd, and <25 pg for Hf) technique for dust dissolution, prior to column chemistry for combined Hf-Sr-Nd isotope analyses. Repeated measurements of the Hf isotope ratios of USGS geological reference materials (AGV-2, BCR-2 and GSP-2) demonstrate that raw, non fractionation corrected 176Hf/177Hf ratios are accurate within 5-50 ppm, while the JMC-475 fractionation corrected values are accurate to 5-10 ppm, compared to reference values using our ion exchange chemistry setup. This methodology also allows separating Sr and Nd from the same samples, and analysing the 87Sr/86Sr and 143Nd/144Nd isotopic compositions. Here we discuss mass spectrometry issues (including sensitivity) of TIMS and two different MC-ICP-MS instruments, and major limitations on dust sample size for Hf-Sr-Nd isotope analyses. Furthermore, the mineralogical background of Hf isotopic compositions, including zircon depletion effects and clay mineralogy (illite) control will be demonstrated. Hf isotope data obtained from four NorthGRIP ice core samples will be presented.

This study was financially supported by the FWF Austria through a Lise Meitner grant (project nr. M 2503-N29) and the European Regional Development Fund in the project of GINOP-2.3.2.-15-2016-00009 ‘ICER’.
Assessing a 6C Kalman filter using experimental datasets from an industrial robot
Authors: Rossi Yara , Chatzi Eleni , Rothacher Markus , Clinton John , Schmelzbach Cédric
Published: March 2020

Current best practice in monitoring earthquake strong motion are dense networks comprising strong motion accelerometers that measure acceleration over a broad frequency and amplitude range. These instruments are capable of measuring translational motions of large earthquakes, but lack sensitivity to very low frequencies or permanent displacements. However, it is widely accepted that during earthquakes the rotational component of the ground motion, both static and dynamic, is large enough to contaminate the derived displacements from these sensors. Modern rotational sensors, are also very broadband, have a large dynamic range, and are not sensitive to translational motions. We explore the value of complementing accelerometers with these rotational sensors at seismic strong motion monitoring stations.

The assessment of the errors introduced into accelerometer records from rotational ground motions is only possible with co-located rotational instruments sensitive enough to record the small rotation rates accompanying the translational motion. Operating accelerometers alongside gyros and additionally GNSS instrumentation should allow us to record the full 6 components (6C) of near-field earthquake motions, with increasing fidelity across a very broad frequency band for the strongest motions.

We aim to demonstrate how, using a combination of the three sensor types, we can recover the full 6C ground motion, and hence also more reliable displacement records, using a versatile industrial six-axis robot that can produce controlled and repeatable 6C motion across a broad frequency band. Through the precise feedback loop used by the robot to stabilize its precise trajectory, we get a 6C recording of the driven motion represented by Euler rotations and displacements, which we use as ground truth. By simulating a combination of translational and rotational motions on the robot, we show that the 6C Kalman filter can accurately reproduce the clean simulated translational motion. By using a Kalman filter, we attempt to combine the different data sets using prediction and weighting of the observation data for an optimal solution. Our methodology tries to take into account the strengths and weaknesses of the individual instruments that are providing partly redundant and partly complementary ground motion information.
An up-to-date assessment of temperature extremes over the MENA region from observational and CIMP5 data
Authors: Ntoumos Athanasios , Hadjinicolaou Panos , Zittis Georgios , Lelieveld Jos
Published: March 2020

We assess observed and modeled temperature extremes over the MENA region during the last four decades. The purpose of our analysis is two-fold: I) provide an up-to-date, observationally based estimation of recent past evolution and ii) evaluate the performance of global climate model simulations. A list of indices of temperature extremes, based on threshold, percentile, heatwave and coldwave characteristics is used, as defined by the Expert Team on Climate Change Detection and Indices (ETCCDI). We derive the indices. We use daily near-surface air (2-metre) temperature (Tmax and Tmin) to derive the extremes indices for the period 1980-2018 from: 1) re-analyses (ERA-Interim, MERRA2) and gridded observational data (Berkeley) and ii) 18 CMIP5 model runs combining historical (1950-2005) and scenario runs (2006-2018 under RCP 2.6, RCP4.5 and RCP8.5). Using these reanalyses, observational and CMIP5 multimodel ensemble data-sets we derived their statistics (climatological average, trends) and produced maps for the MENA region. In addition, the CMPI5 indices were compared with the indices derived from the observational and reanalyses and their biases were revealed through spatial (maps) and temporal (time-series) comparison. It is found, as expected, that the choice of the RCP does not make any difference in the calculations up to 2018 but nevertheless the use of the three “scenarios” provides a better model sample for the evaluation against observations. Finally, the best performing global model realizations for the temperature extremes are revealed by the comparison of individual models with the re-analyses and observational data.
Night-time vertical profiles of nitrate radical concentrations in urban environment (Paris, France)
Authors: Cirtog Manuela , Michoud Vincent , Fouqueau Axel , Cazaunau Mathieu , Bergé Antonin , Maisonneuve Franck , Zapf Pascal , Pangui Edouard , Landsheere Xavier , Giacomoni Jerôme , Gobbi Matthieu , Hanottel Loïk , Paris Alain , Roulier Nicolas , Formenti Paola , Mellouki Abdelwahid , Cantrell Christopher , Doussin Jean-François , Picquet-Varrault Bénédicte
Published: March 2020

The NO3 radical is the main atmospheric oxidant at night. The night period is favorable to the formation and accumulation of NO3 radicals in the atmosphere. On the one hand, it is formed by the reaction of nitrogen dioxide with ozone while, on the other hand, NO3 being highly photosensitive, it cannot accumulate significantly during the day (S. S. Brown and J. Stutz, Chem. Soc. Rev. 2012). In addition, the reaction between NO and NO3 is very fast and so, urban environment is considered so far, being not favorable to the occurrence of NO3 radicals. However, atmospheric nitrogen chemistry near the earth surface is strongly linked to the dynamics of the boundary layer and in summer NO is rapidly depleted by ozone. A large variability of the mixing ratios for NO3 as a function of height above the ground is thus expected with non-negligible concentrations in altitude (Brown et al., Atmos. Chem. Phys., 2007). The contribution of NO3 radical to the atmospheric evolution of VOCs in urban and sub-urban areas may therefore also be influenced by this vertical distribution.

To demonstrate the potential importance of NO3 radical even in urban environment, a field campaign was carried out at night during July 2018 inside Paris. A newly developed field instrument dedicated to the measurement of NO3 radical was deployed on a high payload touristic tethered balloon located in Paris 15th district that was used as vertical vector. The NO3 instrument is a compact, robust and easily deployable on field instrument based on the IBB-CEAS (Incoherent Broad band Cavity Enhanced Absorption Spectroscopy) technique. NO3 measurements were completed by ground and airborne measurements of NO (chemiluminescence analyzer), NO2 (CAPS cavity) and O3 (absorption analyzer) concentrations as well as particle number concentrations (OPC GrimmTM) and 355 nm lidar (Leosphere ALS300) measurement for mixing layer probing.

Vertical profiles from 0 to up to 300 m were obtained at night characterized by high concentrations of ozone and moderate humidity. In this presentation, vertical profiles of the species measured and implications for VOC oxidation in urban environment will be discussed.
Multimineral chronology of a complex high pressure terrane: insights from the Theodul Gletscher Unit (Western Alps, Switzerland)
Authors: Bovay Thomas , Smit Matthijs A. , Rubatto Daniela
Published: March 2020

Reconstructing the tectonic history of metamorphosed terranes is a key step towards establishing a comprehensive model for collisional orogens such as the Alps. Single chronometers tend to record one specific component of such history—be it inheritance, reactions or cooling—or record several of these, without a clear indication of what each age datum means. Resolving the complex evolution of such terranes requires chronometric data of different minerals, which on the basis of their chemistry, may be linked to distinct stages. Here we present a multi-mineral geochronology of the Theodul Gletscher Unit (TGU; Western Alps). The tectonic unit is a metamorphic sequence containing a variety of pelitic and mafic rocks that mainly record Alpine low-temperature, high-pressure metamorphism. In addition, however, the rocks are known to host age components related to events and processes in the Permian and Jurassic; these could be attributed to inherited components and pervasive fluid-rock interaction during oceanic alteration and subduction. To investigate this, we subjected pelitic schists and mafic rocks from the TGU to a multi-method analysis, involving thermometry, oxygen isotope analysis in garnet, and zircon U-Pb and garnet Lu-Hf dating.

Zircon crystals in all rock types are Permian in age and have no significant record of Alpine metamorphism; they are interpreted as dating the source of the felsic and mafic sediments. Complex garnet textures in the schists reveal multiple growth stages: whereas the garnet rim reflects the subduction stage, the relict nature of the garnet core allows for speculation of an older, perhaps Permian age (Bucher et al., 2019). A distinct and abrupt rim-ward drop in δ18O coherent with major-element zoning in garnet from the schists indicates open system fluid-rock interaction. Rutile included in the different garnet zones as well as in the matrix of the schists provided consistent Zr-in-rutile thermometry results of 520–560 °C (calculated at 2.5 GPa). Similarly, Raman spectroscopy of carbonaceous material in the same textural positions indicates 540–580 °C. These results indicate a single Alpine metamorphic cycle. To look back beyond that stage, Lu-Hf data will be presented for garnet with and without seemingly inherited cores, as well as for cores that were physically isolated from the sample material. The results, together, provide new insight into the petrological and tectonic processes that affected rocks in the TGU during and prior to their Alpine history.

REFERENCES:

Bucher, K., Weisenberger, T. B., Klemm, O., Weber, S. (2019). Decoding the complex internal chemical structure of garnet porphyroblasts from the Zermatt area, Western Alps. Journal of Metamorphic Petrology, 37, 1151-1169
The influence of the tropical troposphere on the QBO in model simulations
Authors: Serva Federico , Cagnazzo Chiara , Christiansen Bo , Yang Shuting
Published: March 2020

The equatorial Quasi-Biennial Oscillation (QBO) and the
El Niño-Southern Oscillation (ENSO) are major patterns of climate variability.
Mutual interactions between these two modes have been highlighted in
the observational record, but this has not been much tested
using climate model simulations.
In observations, the amplitude is larger during cold and smaller
during warm events, while the descent rate is slower during
cold and faster during warm events.
Here we discuss how climate models represent this relationship, in
terms of the changes of the QBO properties.
The results for a multi-model ensemble, with atmosphere-only and
ocean-atmosphere simulations, are discussed.
The phase alignment of the QBO after the 1997/98 warm ENSO,
already documented in previous works, is also present in a
large ensemble of uncoupled experiments.
It is found that a high horizontal resolution is needed to
realistically reproduce the observed modulation of the QBO descent rate
under strong ENSO events. The QBO amplitude response is instead
weak at any horizontal resolution.
Robust changes emerging in the projections and aspects of the
modelled stratosphere-troposphere coupling in the tropics are presented. 
Transpiration and transporters: teasing apart passive and active transport of plant silicon
Authors: Cooke Julia , Carey Joanna
Published: March 2020

All plants contain some silicon (Si), but some species take it up passively through the transpiration stream while others additionally actively accumulate Si by producing transporters. Here, we review the literature, both qualitatively and quantitatively, to investigate the importance of transpiration for Si uptake across diverse plant groups with different accumulation capacities.  We will use variation among species in terms of phylogeny, habitat (e.g. aquatic vs. terrestrial), and environmental conditions (e.g. water or nutrient stress) to tease apart the roles of transporters and transpiration in controlling rates of Si accumulation, and make use of published manipulative experiments to explore how Si availability impacts the importance of these two uptake mechanisms.
Real-time regional VTEC modeling based on B-splines using real-time GPS, GLONASS and GALILEO observations
Authors: Erdogan Eren , Goss Andreas , Schmidt Michael , Dettmering Denise , Seitz Florian , Müller Jennifer , Görres Barbara , Kersten Wilhelm F.
Published: March 2020

The project OPTIMAP is at the current stage a joint initiative of BGIC, GSSAC and DGFI-TUM. The development of an operational tool for ionospheric mapping and prediction is the main goal of the project.

The ionosphere is a dispersive medium. Therefore, GNSS signals are refracted while they pass through the ionosphere. The magnitude of the refraction rate depends on the frequencies of the transmitted GNSS signals. The ionospheric disturbance on the GNSS signals paves the way of extracting Vertical Total Electron Content (VTEC) information of the ionosphere.

In OPTIMAP, the representation of the global and regional VTEC signal is based on localizing B-spline basis functions. For global VTEC modeling, polynomial B-splines are employed to represent the latitudinal variations, whereas trigonometric B-splines are used for the longitudinal variations. The regional modeling in OPTIMAP relies on a polynomial B-spline representation for both latitude and longitude.

The VTEC modeling in this study relies on both a global and a regional sequential estimator (Kalman filter) running in a parallel mode. The global VTEC estimator produces VTEC maps based on data from GNSS receiver stations which are mainly part of the global real-time IGS network. The global estimator relies on additional VTEC information obtained from a forecast procedure using ultra-rapid VTEC products. The regional estimator makes use of the VTEC product of the real-time global estimator as background information and generates high-resolution VTEC maps using real-time data from the EUREF Permanent GNSS Network. EUREF provides a network of very dense GNSS receivers distributed alongside Europe.

Carrier phase observations acquired from GPS, GLONASS and GALILEO constellations, which are transmitted in accordance with RTCM standard, are used for real-time regional VTEC modeling. After the acquisition of GNSS data, cycle slips for each satellite-receiver pair are detected, and ionosphere observations are constructed via the linear combination of carrier-phase observations in the data pre-processing step. The unknown B-spline coefficients, as well as the biases for each phase-continuous arc belonging to each receiver-satellite pair, are simultaneously estimated in the Kalman filter.

Within this study, we compare the performance of regional and global VTEC products generated in real-time using the well-known dSTEC analysis.
The trans-disciplinary and community-driven subduction zone initiation (SZI) database
Authors: Chotalia Kiran , Cooper George , Crameri Fabio , Domeier Mathew , Eakin Caroline , Grima Antoniette Greta , Gürer Derya , Király Ágnes , Magni Valentina , Mulyukova Elvira , Peters Kalijn , Robert Boris , Shephard Grace , Thielmann Marcel
Published: March 2020

Numerous studies have provided insights into one of the key problems of the Earth Sciences: subduction zone initiation (SZI). The insights into SZI are both numerous and diverse with evidence from multiple disciplines in Earth Sciences. SZI studies exploit the geological record, reconstruct regional or global plate motion back in time, interpret seismic tomography to identify the tip depth of sunken plate portions, and diagnose theoretical and numerical models of rock and plate deformation based on known physics.

Getting and keeping an overview over the many discipline-specific advances is challenging for many reasons: one being the dispersed sources of information, another being the missing communication across the individual disciplines. The latter shortcoming also arises from the multiple incompatible scientific jargons currently in use.

The SZI database now unifies the scientific jargon, and brings together old and new insights relating to SZI into a common, community-wide platform online (www.SZIdatabase.org). The SZI database builds bridges between individual communities, opening a community-wide discussion by making SZI data readily available and understandable. This keeps data and knowledge up-to-date, and can therefore provide the most complete picture of our current understanding of SZI.

In this presentation, we outline where to find, how to use, and why to contribute to the SZI database. This community-wide project has already yielded interesting results regarding the fascinating question about how and where SZI occurs on present-day Earth and back to around 100 Ma. Work thus far suggests ‘subduction breeds subduction’, highlighting the beginning of crucial insights from these ongoing cross-disciplinary efforts.
Automatic quality control and quality control schema in the Observation to Archive
Authors: Silva Brenner , Kaffashzadeh Najmeh , Nixdorf Erik , Immoor Sebastian , Fischer Philipp , Anselm Norbert , Gerchow Peter , Schäfer Angela , Koppe Roland ,   Computing and data center
Published: March 2020

The O2A (Observation to Archive) is a data-flow framework for heterogeneous sources, including multiple institutions and scales of Earth observation. In the O2A, once data transmission is set up, processes are executed to automatically ingest (i.e. collect and harmonize) and quality control data in near real-time. We consider a web-based sensor description application to support transmission and harmonization of observational time-series data. We also consider a product-oriented quality control, where a standardized and scalable approach should integrate the diversity of sensors connected to the framework. A review of literature and observation networks of marine and terrestrial environments is under construction to allow us, for example, to characterize quality tests in use for generic and specific applications. In addition, we use a standardized quality flag scheme to support both user and technical levels of information. In our outlook, a quality score should pair the quality flag to indicate the overall plausibility of each individual data value or to measure the flagging uncertainty. In this work, we present concepts under development and give insights into the data ingest and quality control currently operating within the O2A framework.
Tree death as a crucial geomorphic agent in temperate forests: effects of weak and severe disturbances from local to continental scale
Authors: Šamonil Pavel , Daněk Pavel , Lutz James A. , Jaroš Jakub , Rousová Anna , Anderson-Teixeira Kristina J. , Adam Dušan
Published: March 2020

Hillslope processes in terrestrial ecosystems are significantly modified by changes in climate and land use. At the same time they strongly influence ecosystem retention capacity, pedocomplexity and biodiversity. This undoubtedly makes hillslope processes one of the crucial components of terrestrial ecosystem dynamics. In this study we focus on the long overlooked biogeomorphological impact of tree death in forested landscapes. Tree uprooting caused by strong storms affects soil and regolith formation and movement quite differently from the decomposition of intact root systems of standing trees that died due to e.g. fire or bark beetle infestation. We quantify the biogeomorphic processes associated with tree death in various terrestrial forest ecosystems and specifically assess (i) the significance of these processes in hillslope dynamics (e.g. slope denudation) of forested landscapes and (ii) the extent to which infrequent severe disturbances can shape these dynamics.

We used data from repeated tree censuses carried out in ten permanent forest plots (13–74 ha in area) located in Central Europe and North America, differing in a range of characteristics such as tree species composition, climate and disturbance regime. In total, life history of more than 134,000 trees was recorded over periods of up to 47 years, during which about one third of these trees died. Using this information together with empirical models and allometric equations we were able to quantify the average areas and volumes of soil annually affected by dying trees. These quantities differed markedly between sites with different disturbance regimes. Tree uprooting-related volumes accounted annually for 0.01–13.5 m3ha−1 reaching maximum values on sites with occurrence of infrequent strong windstorms (Zofin and Boubin primeval forests, Czech Republic). Volumes related to trees that died standing ranged anually between 0.17 and 20.7 m3ha−1 and were highest in the presence of stand-replacing fires (Yosemite National Park, U.S.). Comparison of these quantities with long-term erosion rates derived using cosmogenic nuclides (10Be) suggests that on certain sites, over the last few millennia, tree uprooting can be the main driver of soil erosion.