bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of volcanic halogens on the ozone layer and climate, a look to the past to highlight the present
Authors: Balcone-Boissard Hélène , D'Augustin Thiébaut , Boudon Georges , Bekki Slimane , Bonifacie Magali , Boudouma Omar , Bouvier Anne-Sophie , Carazzo Guillaume , Deloule Etienne , Fialin Michel , Rividi Nicolas
Published: March 2020

Explosive eruptions of the Plinian type inject large amounts of particles (pumice, ash, aerosols) and volatile species into the atmosphere. They result from the rapid discharge of a magma chamber and involve large volumes of magma (from a km3 to hundreds of km3). Such eruptions correspond to a rapid ascent of magma in the conduit driven by the exsolution of volatile species. If the magma supply is continuous, this jet produces a convective eruptive column that can reach tens of km in height and transports gas and particles (pumice, ash, aerosols) directly into the stratosphere. Depending on the latitude of the volcano, the volume of implied magma, the height of the eruptive plume and the composition of the released gaseous and particulate mixture, these events can strongly affect the environment at the local or even at a global scale. Almost all studies on global impacts of volcanic eruptions have largely focused on the sulfur component. Volcanoes are also responsible for the emission of halogens which have a crucial impact on the ozone layer and therefore the climate.

The objective of our project is to revisit the issue of the impact of volcanism on the atmosphere and climate by considering not only the sulfur component but also the halogen component. We will provide field work-based constraints on the strength of halogen (Cl and Br) emissions and on degassing processes for key eruptions, we will characterise the dynamics of volcanic plumes, notably the vertical distribution of emissions and we will explore and quantify the respective impacts of sulfur and halogen emissions on the ozone layer and climate.

 

Here we will shed light on the methodology that will combine field campaign, laboratory analysis of collected samples and a hierarchy of modelling tools to study. We use an approach combining field studies, petrological characterization, geochemical measurements including isotopic data, estimation of the volume of involved magma and the height of injection of gases and particles by modelling the eruptive plume dynamic and numerical simulation of the impacts at the plume scale and at the global scale.  The first halogen budget will also be presented.
Filesystem and object storage for climate data analytics in private clouds with OpenStack
Authors: Cimadevilla Alvarez Ezequiel , Palacio Hoz Aida , Cofiño Antonio S. , Lopez Garcia Alvaro
Published: March 2020

Data analysis in climate science has been traditionally performed in two different environments, local workstations and HPC infrastructures. Local workstations provide a non scalable environment in which data analysis is restricted to small datasets that are previously downloaded. On the other hand, HPC infrastructures provide high computation capabilities by making use of parallel file systems and libraries that allow to scale data analysis. Due to the great increase in the size of the datasets and the need to provide computation environments close to data storage, data providers are evaluating the use of commercial clouds as an alternative for data storage. Examples of commercial clouds are Google Cloud Storage and Amazon S3, although cloud storage is not restricted to commercial clouds since several institutions provide private or hybrid clouds. These providers use systems known as “object storage” in order to provide cloud storage, since they offer great scalability and storage capacity compared to POSIX file systems found in local or HPC infrastructures.

Cloud storage systems, based on object storage, are incompatible with existing libraries and data formats used by climate community to store and analyse data. Legacy libraries and data formats include netCDF and HDF5, which assume the underlying storage is a file system and it’s not an object store. However, new libraries such as Zarr try to solve the problem of storing multidimensional arrays both in file systems and object stores.

In this work we present a private cloud infrastructure built upon OpenStack which provides both file system and object storage. The infrastructure also provides an environment, based on JupyterHub, to perform  remote data analysis, close to the data. This has some advantages from users perspective. First, users are no required to deploy the required software and tools for the analysis. Second, it provides a remote environment where users can perform scalable data analytics. And third, there is no constraint to download huge amounts of data, to users local computer, before running the analysis of the data.
A probabilistic approach for the retrieval of mineral dust properties from infrared spaceborne observations
Authors: Samaras Stefanos , Popp Thomas
Published: March 2020

Mineral dust has far reaching impact on atmospheric dynamics and the biosphere, altering both the hydrological and the carbon cycle, as well as on human health and the economy. Scattering and absorption effects of dust are enhanced in the terrestrial infrared due to the Si-O resonance bands and thus dust remote sensing with infrared sounders such as IASI (Infrared Atmospheric Sounding Interferometer) is well motivated. This work pertains to current updates on the Infrared Mineral Aerosol Retrieval Scheme (IMARS) on IASI hyperspectral data. IMARS algorithm estimates probabilistically the atmospheric state with respect to desert dust and ice clouds based on simulations of the observed signal for various dust and ice cloud properties.

A preprocessor compresses IASI radiance data in three pseudo-channels exploiting their high redundancy and accounting for the unequal distribution of their information content. From these, four distinct  brightness temperatures differences (BTD) are formed with respect to these channels, which reflect the spectral variation of dust or cloud or surface signal. By varying dust particle size distributions (s), mineralogical compositions (c), infrared optical depths (τ) and layer heights(h) we construct a simulation database constituting 6000 brightness temperature difference sets. The deviation of simulated and observed BTDs by means of a Gaussian metric yields a probability distribution function (PDF), with which the state vector as well as its probability and uncertainty are determined. The calculation of aerosol optical depth (AOD), dust layer temperature, dust effective radius, and other dust properties follows from correspondingly adding contributions (s, c, τ, h) weighted by this PDF. The ice cloud retrieval is realized in the same manner using cloud optical properties from a range of parameterizations found in literature. The distinction between dust and cloud is generally based on quality flagging in terms of the emission temperature relative to the approximated surface temperature and its expected range, and the (dust/cloud) probabilities and uncertainties with stricter criteria for the so-called dust belt. Finally, the IMARS pixel-wise product offers four levels of quality filtering in terms of probabilities, uncertainties, quality flags and information entropy.

Preliminary evaluation of IMARS AOD against AERONET coarse mode AOD obtained by the Spectral Deconvolution Algorithm, is done with data of mild level quality filtering restricted in the dustbelt and using Barnes objective analysis. Results show an overall moderate correlation (and small bias) and a stronger one for focused AERONET stations.
Multiscale analysis of Hall-MHD and Hybrid-PIC simulations of plasma turbulence: structures or waves?
Authors: Papini Emanuele , Cicone Antonio , Piersanti Mirko , Franci Luca , Landi Simone , Hellinger Petr
Published: March 2020

Turbulence in space and astrophysical plasmas is an intrinsically chaotic and multiscale phenomenon that involves nonlinear coupling across different temporal and spatial scales. There is growing evidence that plasma instabilities, such as magnetic reconnection taking place in localized current sheets, enhance the energy dissipation toward small sub-ion scales. However, it is hotly debated whether the dominant contribution to the scale-to-scale energy transfer at kinetic scales is due to non-linear wave interactions or to coherent structures. Here we present the results from a multiscale study of 2D Hall-MHD and hybrid Particle-in-cell (PIC) numerical simulations of decaying turbulence, performed by means of Multidimensional Iterative Filters (MIF), a new technique developed for the spatio-temporal analysis of non-stationary non-linear multidimensional signals. Results show that, at the maximum of turbulent activity, the power spectrum of magnetic fluctuations at sub-ion scales is formed by localized structures and/or perturbations with temporal frequencies smaller than the ion-cyclotron frequency. Going toward smaller kinetic scales, the contribution of low-medium frequency perturbations to the magnetic spectrum becomes important. However, the dispersion relation and polarization properties of such perturbations are not consistent with those of Kinetic Alfvèn Waves (KAW). We conclude that the dynamics of turbulence at sub-ion scales is mainly shaped by localized intermittent structures, with no apparent contribution of KAW-like interactions at small scales.
A contourite drift succession in north-east Baffin Bay: a high-resolution Pleistocene archive of Greenland ice sheet and ocean variability
Authors: Knutz Paul C. , Andresen Katrine Juul , Hopper John R. , Perez Lara F. , Campbell Calvin , Dorschel Boris , Bennike Ole , Detlef Henrieka , Hansen Katrine Elnegaard , Jackson Rebecca , Jennings Anne , Larsen Nicolaj Krog , Nørgaard-Pedersen Niels , Pearce Christof , Røy Hans , Ribeiro Sofia
Published: March 2020

The Greenland ice sheet’s response to anthropogenic warming will have major consequences for global sea levels but its behavior and stability during past warm intervals is poorly known. To elucidate the long-term behavior of the Greenland ice sheet, high-resolution marine records in ice proximal settings are required. Here we report the first results of a study of a deep-water contourite system on the north-east slope Baffin Bay based on geophysical and shallow core data obtained during two marine expeditions in 2017 and 2019. The contourite drift is incised by channels extending from the slope that is build up by prograding ice stream deposits (Melville Bugt trough-mouth fan). As a result, the contourite system presents a complex architecture. While the mechanisms for deposition and erosion are not yet clear, it is likely that the drift accumulated as a result of interactions between a deep contour current and downslope transport of sediments, presumably of glacigenic origin and therefore constitutes an example of an intertwined contourite-turbidite system. A preliminary age-depth model of the trough-mouth fan evolution indicates that the contourite system began to form during the late Early Pleistocene, possibly around 1 million years ago. The contourite drift is a key target for IODP proposal 909, aimed at unravelling the late Cenozoic evolution of the northern Greenland ice sheet and associated changes in Arctic paleoclimate. Shallow sediment cores from this target area have been retrieved and will be analyzed to generate high-resolution multi-proxy records of ocean circulation and sea-surface conditions including sea ice and paleoproductivity for the late Quaternary-Holocene.
Electromagnetic experiments for the detection and characterization of seafloor massive sulfides: two case studies from the Mediterranean and Northern Mid-Atlantic Ridge
Authors: Sebastian Hölz , Amir Haroon , Reeck Konstantin , Marion Jegen
Published: March 2020

Seafloor massive sulfides (SMS) are regarded as a potential future resource to satisfy the growing global demand of strategic metals. Aside from mining and retrieving profitable amounts of massive sulfides from the seafloor, the present challenge is to detect and delineate significant SMS accumulations, which are generally located near mid-ocean ridges and along submarine volcanic arc and backarc spreading centers.

In the past years we have used the marine transient electromagnetic induction system MARTEMIS, a coincident-loop TEM system developed at GEOMAR (Kiel, Germany), in various marine geological settings for the detection and characterization of SMS in the shallow seafloor down to a depth of ~30m. The system was also used in combination with remote EM receivers (Coil2Dipole experiment) to allow for investigations of conductive structures, which are covered by up to ~100m of sediments.

We present experiments from two locations, one at an inactive site in the Mediterranean (Palinuro, Tyrrhenian Sea) where the occurrence of SMS had previously been confirmed by drilling, and one active site on the Northern Mid-Atlantic Ridge (Grimsey Hydrothermal Field, offshore Northern Iceland) where no SMS have been found in gravity cores up to now. The results demonstrate the suitability of the system to detect, delineate and characterize SMS even in scenarios, where the mineralizations are no longer connected to any hydrothermal activity or are buried under a sedimentary cover.
Evaluating microbarom source models using infrasound recorded on a stratospheric balloon
Authors: Le Pichon Alexis , De Carlo Marine , Bowman Daniel , Ardhuin Fabrice
Published: March 2020

The global International Monitoring System (IMS) network continuously detects coherent ambient infrasound noise between 0.1 and 0.5 Hz. This noise, referred to as microbaroms, is generated by second order non-linear interaction of ocean waves. Various source models have been developed in earlier works; e.g. Brekhovskikh et al. (1973) and Ardhuin & Herbers (2013) who considered a source directivity effect in infinite depth ocean, and Waxler (2007) who investigated the radiation model in finite depth ocean from monopolar sources. De Carlo et al. (2020) proposed a two-dimensional energy spectrum ocean wave model accounting for bathymetry and source directivity effects. First comparisons between the observed and modelled directional microbarom amplitudes at IMS infrasound stations show first order agreement. In order to further evaluate these models, microbarom observations from the Carolina Infrasound secondary payload on board the NASA Ultra Long Duration Balloon flight in 2016 (Bowman and Lees, 2018), that flew over spatially extended microbarom source regions along the Antarctic Circumpolar Current, are compared with the modelled source energy flux. The simulated source strength power spectrum is integrated over an extended source region beneath the balloon and compared with the observed one. The relative importance of modelled source parameters (e.g. bathymetry, launching ray parameters) is assessed. In this presentation, we describe the infrasound observations on the balloon and the supporting microbarom source models, and discuss the implications of these results on the remote estimation of the acoustic energy flux from the ocean surface to the upper atmosphere.
Radiation of multi-source and multi-band internal waves in the northwestern Pacific
Authors: Wang Yang , Yin Baoshu
Published: March 2020

The northwestern Pacific is the most energetic area of internal waves in the world ocean. Generation and evolution processes of multi-source and multi-band internal waves at tidal frequency are examined by driving high-resolution numerical model. The semidiurnal and diurnal internal waves exhibit distinct-different generation and radiation patterns. The multi-source distribution of internal waves favours the occurrence of complex interference patterns which contribute significantly to the inhomogeneous internal wave field. The improved ideal line-source model can well reproduce the interference processes of both semidiurnal and diurnal internal waves. Simulation results show that geostrophic circulations such as Kuroshio Current, North Equator Current, influence both semidiurnal and diurnal internal waves’ radiation path. And this modulation process is further demonstrated by theoretical model. Energetic dissipation occurs both near the sources and in the basin. A locally dissipated fraction q ≤ 0.4 is estimated at the generation sites with continuous bathymetry features, while q ≥ 0.6 is estimated at areas with discrete topographic variability. A lower locally dissipated fraction indicates a higher proportion of internal wave energy radiating into the basin, where enhanced dissipation coincides closely with the interference-modulated flux field.
Understanding distributed data – a semantic web approach for data based analysis of NDT data in civil engineering
Authors: Völker Christoph , Moreno-Torres Benjamin , Kruschwitz Sabine
Published: March 2020

In the field of non-destructive testing (NDT) in civil engineering, a large number of measurement data are collected. Although they serve as a basis for scientific analyses, there is still no uniform representation of the data. An analysis of various distributed data sets across different test objects is therefore only possible with high manual effort.

We present a system architecture for an integrated data management of distributed data sets based on Semantic Web technologies. The approach is essentially based on a mathematical model - the so-called ontology - which represents the knowledge of our domain NDT. The ontology developed by us is linked to data sources and thus describes the semantic meaning of the data. Furthermore, the ontology acts as a central concept for database access. Non-domain data sources can be easily integrated by linking them to the NDT construction ontology and are directly available for generic use in the sense of digitization. Based on an extensive literature research, we outline the possibilities that this offers for NDT in civil engineering, such as computer-aided sorting, analysis, recognition and explanation of relationships (explainable AI) for several million measurement data.

The expected benefits of this approach of knowledge representation and data access for the NDT community are an expansion of knowledge through data exchange in research (interoperability), the scientific exploitation of large existing data sources with data-based methods (such as image recognition, measurement uncertainty calculations, factor analysis, material characterization) and finally a simplified exchange of NDT data with engineering models and thus with the construction industry.

Ontologies are already the core of numerous intelligent systems such as building information modeling or research databases. This contribution gives an overview of the range of tools we are currently creating to communicate with them.
PREMHYCE: An operational tool for low-flow forecasting
Authors: Nicolle Pierre , Besson François , Bourgin François , François Didier , Le Lay Matthieu , Perrin Charles , Rousset Fabienne , Thiéry Dominique , Tilmant François , Magand Claire , Jacob Elise
Published: March 2020

In many countries, rivers are the primary supply of water. A number of uses are concerned (drinking water, irrigation, hydropower…) and they can be strongly affected by water shortages. Therefore, there is a need of early anticipation of low-flow periods to improve water management. This is strengthened by the perspective of having more severe summer low-flows in the context of climate change. Several French institutes (Irstea, BRGM, Météo-France, EDF and Lorraine University) have been collaborating to develop an operational tool for low-flow forecasting, called PREMHYCE. It is tested in real time since 2017, and implemented on 259 catchments in metropolitan France, in cooperation with operational services which provide streamflow observations and use low-flow forecasts from the tool. PREMHYCE includes five hydrological models which can be calibrated on gauged catchments and which assimilate flow observations. Low-flow forecasts can be issued up to 90 days ahead, based on several inputs scenarios: ECMWF 10-days ensemble forecasts, ensemble streamflow prediction (ESP) using historical climatic data as ensembles of future input scenarios, and a no precipitation scenario. Climatic data (precipitation, evapotranspiration and temperature) are provided by Météo-France with the daily gridded SAFRAN reanalysis on the 1959-2019 period, which includes a wide range of conditions. The tool provides text files and graphical representation of forecasted low-flows, and probability to be under low-flow thresholds provided by users. Outputs from the different hydrological models can be combined within a multi-model approach to improve robustness of the forecastsThe presentation will show the main characteristics of this operational tool, the probabilistic evaluation framework, results on the recent low-flow periods, and how feedbacks from end-users can help improving the tool.
Statistics of Coherent Structures Collisions and their Dynamics on the Surface of Deep Water
Authors: Dremov Sergey , Kachulin Dmitriy , Dyachenko Alexander
Published: March 2020

        The present work is devoted to the study of coherent structures collisions dynamics in the models of deep water waves equations: the model of a supercompact equation for deep water unidirectional waves (SCEq) and the model of Dyachenko equations for potential flows of incompressible fluid with free surface. In these models there are special solutions in the form of coherent wave structures called breathers. They can be found numerically by using the Petviashvili method. One can consider the combination of such breathers as a model of rarefied soliton gas, and their paired collisions in this case are a key feature in forming of dynamics and statistics in the model. To describe statistical characteristics of breathers collision Probability Density Function (PDF) is used. PDF of breathers wave amplitudes during their collision was calculated and compared with the known results in the model of Nonlinear Schrodinger equation (NLS). In contrast to the NLS model there is a number of interesting features in the model of SCEq. For instance, the amplitude maximum of wave arising during the collision can exceed the sum of interacting breathers amplitudes, what cannot happen in NLS model. Moreover, it depends on the initial breathers steepness. In addition, it is shown that the breathers acquire phase and space shifts after each collision, and thus their velocity also changes. Depending on the relative phase breathers can give their energy or take it, and as a result their amplitude can be decreased or increased respectively. The same situation can be seen in the model of equations for potential flows of incompressible fluid with free surface. In addition to the dependence on relative phase the duration of the collision also affects the energy exchange. Breathers collisions are accompanied by appearance of little radiation, and its value is relatively less than the value of energy exchange. The results of statistics calculating and dynamics studying in the rarefied gas of coherent structures will be shown in the present work.

           The work was supported by Russian Science Foundation grant № 18-71-00079.
Mapping soil phosphorus sorption capacity in four depths with uncertainty propagation
Authors: Møller Anders Bjørn , Hechrath Goswin Johann , Hermansen Cecilie , Nørgaard Trine , Knadel Maria , de Jonge Lis Wollesen , Greve Mogens Humlekrog
Published: March 2020

Phosphorus (P) is one of the most important plant nutrients, and farmers regularly apply P as mineral fertilizer and with animal manures. Typically, reactions with amorphous aluminum and iron oxides or carbonates retain P in the soil. However, if P additions exceed the soil’s ability to bind them, P may leach from soil to surface waters, where it causes eutrophication. The phosphorus sorption capacity (PSC) is thus an inherent soil property that, when related to bound P, can describe the P saturation of the soil. Detailed knowledge of the spatial distribution of the PSC is therefore important information for assessing the risk of P leaching from agricultural land.

In weakly acidic soils predominant in Denmark, the PSC depends mainly on the oxalate-extractable contents of aluminum and iron. In this study, we aimed to map PSC in four depth intervals (0 – 25; 25 – 50; 50 – 75; 75 – 100 cm) for Denmark using measurements of oxalate-extractable aluminum and iron from 1,623 locations.

We mapped both elements using quantile regression forests. Predictions of oxalate-extractable aluminum had a weighted RMSE of 13.9 mmol kg-1. For oxalate-extractable iron, weighted RMSE was 33.5 mmol kg-1.

We included depth as a covariate and therefore trained one model for each element. For each element in each depth interval, we predicted the mean prediction value as well as 100 quantiles ranging from 0.5% to 99.5% in 1% intervals. The maps had a 30.4 m resolution. We then calculated PSC by convoluting the prediction quantiles of the two elements, using every combination of quantiles, in order to obtain the prediction uncertainty for PSC.

Oxalate-extractable aluminum was roughly normal distributed, while oxalate-extractable iron had a large positive skew. The age and origin of the parent material had a large effect on oxalate-extractable aluminum, and soil-forming processes such as weathering and podzolization had clear effects on the distribution in depth. Meanwhile, organic matter, texture and wetland processes were the main factors affecting oxalate-extractable iron, so much so that they obscured any trends with depth.

The weighted RMSE of the predicted PSC was 19.1 mmol kg-1. PSC was highest in wetland areas and lowest in young upland deposits, such as aeolian deposits and the loamy Weichselian moraines of eastern Denmark. The sandy glaciofluvial plains and Saalian moraines of western Denmark had intermediate PSC. In most cases, PSC was highest in the top soil, but in the sandy soils of western Denmark, PSC was highest in the depth interval 25 – 50 cm due to podzolization.
SIMILE: An integrated monitoring system to understand, protect and manage sub-alpine lakes and their ecosystem
Authors: Strigaro Daniele , Cannata Massimiliano , Lepori Fabio , Capelli Camilla , Rogora Michela , Brovelli Maria
Published: March 2020

Lakes are an invaluable natural and economic resource for the insubric area, identified as the geographical area between the Po River (Lombardy, Italy) and the Monte Ceneri (Ticino, Switzerland). However, the increased anthropic activity and the climate change impacts are more and more threatening the health of these resources. In this context, universities and local administrations of the two regions, that share the trans-boundary lakes, joined their efforts and started a project, named SIMILE, to develop a system for the monitoring of lakes’ status providing updated and continuous information to support the management of the lakes. This project results from a pluriannual collaboration between the two countries, Switzerland and Italy, formalized in the CIPAIS commission (www.cipais.org). The aim is to introduce an innovative information system based on the combination of advanced automatic and continuous observation system, high resolution remote sensing data processing, citizen science and ecological and physical models. The project will capitalize the knowledge and experience of the resource managers with the creation of a Business Intelligence platform based on several interoperable geospatial Web services. The use of Open software and data will facilitate its adoption and will contribute to adequately keep the costs limited. The project, started few months ago is here presented and discussed.
Exploring the existence of hydrological tipping points at the catchment-scale
Authors: Jaramillo Fernando , Manzoni Stefano , Crepin Anne-Sophie , Rocha Juan , Wang-Erlandson Lan , Zipper Sam , Gleeson Tom , D’Odorico Paolo
Published: March 2020

The identification of tipping points in the water cycle has been recently ranked Nr. 1 in the list of the top 23 unresolved problems in Hydrology by the International Association of Hydrological Sciences (IAHS) and as a priority in the field of hydrology and water resources by several studies. Such daunting task is mainly attributed to the concerns that greenhouse gas emission climate change may tip the water cycle into an unfavorable new state. Up to date, tipping points occurring in complex dynamical systems have been identified across a large set of disciplines. In most proven tipping points, hydrologic variables are always taken as the control variables, as changes in water fluxes and stocks are known to act as stressors of socioecological systems, and the affected aquatic and terrestrial ecosystems as the response variables. The main objective of this study is to explore the existence of tipping points in catchment-scale freshwater availability, that is, the tipping points were the response variable is catchment water storage. We first review the existence of reported tipping points in the field of hydrology and water resources, to establish a coherent framework for the identification of hydrological tipping points. We explore their mathematical existence at the catchment scale by Linear Stability Analysis, illustrating cases with potential functions and bifurcation diagrams. We then explore any possible contribution to the existence of hydrological tipping points by adding complexity to the hydrological dynamic system through the inclusion of sociological feedbacks. We find that even with the inclusion of the moisture feedback of evapotranspiration to precipitation, constant socioecological conditions will most likely not present tipping points of water storage in the catchment. However, the inclusion of socioecological feedbacks does generate tipping points under certain assumptions, even without assuming a moisture feedback between evapotranspiration and precipitation. We hope that this study sheds some light on the existence, conditions, assumptions and characteristics of large-scale hydrological tipping points with long-term implications.
Probing a post monsoon Mesoscale Convective System (MCS) and the generated Transient Luminous Events (TLEs) over Indian Region
Authors: Moharana Sidha Sankalpa , Singh Rajesh
Published: March 2020

A Mesoscale Convective System (MCS), consisting of three Super Cells
formed over South-east Indian, is assessed in detail with satellite and ground based
data-sets. The MCS under investigation generated a total of Ten (10) upward
electrical discharges (9 Sprites and 1 Gigantic Jet) commonly named as Transient
Luminous Events (TLEs). The TLEs were recorded from TLE observation station
located at Allahabad, India. The event occurred in the Post-Monsoon period of 2013
on October 7, during 15-23 UT hours. The MCS was spread over a region of 25000 sq.
Kilometers. A lowest cloud top temperature value of -84.7 0 C was observed in the
mature stage of the MCS, during 2130 UT hours, and the cloud top altitude was
reaching 17.6 km. The coldest cloud top region was covering an average area of
13000 sq. Km. The measured Convective Available Potential Energy (CAPE) value was
606.9 J/kg at 00 UT on 7 th October which dropped to 211 J/kg at 00 UT on 8 th
October. The mean lightning flash rate during the formation and maturity stages of
the MCS was around 46.03 min -1 . During the entire lifespan of the thunderstorm,
peak currents were found to be reaching ±400 kA. Such high electric currents,
extreme cold temperature and towering altitudes of the convective complexes show
how much a MCS is dynamically active and the TLEs which it produced are known to
electrically connect the lower atmosphere to the upper space environment.
Snowpack modelling in central Italy: analysis and comparison of high-resolution WRF-driven Noah LSM and Alpine3D simulations
Authors: Raparelli Edoardo , Tuccella Paolo , Ferretti Rossella , Marzano Frank S.
Published: March 2020

Italy is a territory characterized by complex orography. Its main mountain chains are the Alps, which identify the northern Italian border, and the Apennines, which cross the entire Italian peninsula ranging from north-west to south-east. The major Apennines peaks reach almost 3000 meters and are located in central Italy, in the Abruzzo region. The near Mediterranean sea is an important source of moisture, which permits to this region to experience a substantial snow cover during winter. Thanks to the orientation of the Apennines chain and the height of its peaks the Abruzzo region is characterized by different climate types. This affects the precipitation patterns and the snowpack evolution, resulting in high regional variability of the snow cover. The goal of this study is to investigate the snow cover evolution in the Abruzzo region, using and comparing different snowpack models. To this end we have used the Weather Research and Forecasting (WRF) model to drive the Noah Land Surface Model (LSM) and the sophisticated three-dimensional snow cover model Alpine3D to simulate the snow cover evolution at regional scale. Noah LSM is already on-line coupled with WRF, but this is not the case for Alpine3D. Thus we have modified and used the interfacing library MeteoIO to force Alpine3D with the meteorological data simulated with WRF, off-line coupling the two models. We have validated the WRF simulation using a dense network of automatic weather stations (AWS), obtaining good agreement between simulated and observed data. We have found that the snow depth simulated with Noah LSM presents a negative bias, caused by the inability of the model to reproduce correctly the snow densification rate. Instead, Alpine3D is capable to better reproduce the observed densification rate, thanks to its more detailed description of the snow metamorphism processes. However, the snow depth simulated with Alpine3D presents a negative bias, caused by an underestimation of the new snow depth, which has a negative impact on the entire simulation.
Present-day Saharan dust fluxes across the Atlantic Ocean
Authors: Stuut Jan-Berend , Guerreiro Catarina , Brummer Geert-Jan , Korte Laura , Van der Does Michèlle
Published: March 2020

Mineral dust plays an important role in the ocean’s carbon cycle through the input of nutrients and metals which potentially fertilise phytoplankton, and by ballasting organic matter from the surface ocean to the deep sea floor. In addition, mineral dust feeds back on climate through many different pathways like changing the radiative balance of the atmosphere, by stimulating cloud formation, dampening hurricane formation and by changing the earth’s albedo. Because open-ocean dust-flux measurements are either based on shipboard- or sediment-trap data, they are biased by interpolation and extrapolation of point observations in space and time. Alternatively, dust-flux estimations can be made using satellite observations, but these are often hampered by the presence of clouds. For these reasons we have been studying Saharan dust along a Transatlantic transect between northwest Africa and the Caribbean, focussing on temporal and spatial variability of dust-deposition fluxes and how these are reflected in terms of dust particle size and composition. One important finding deals with the deposition of Saharan dust by rain, which seems to be an important way to make nutrients available to phytoplankton living in the surface ocean. Nutrient-release bottle experiments in ambient sea water carried out along the same transect demonstrate how wet deposition of Saharan dust increases the release of both macro- (P, Si) and micronutrients (Fe) up to an order-of-magnitude as opposed to dry deposition. Rain-amplified bioavailability of these nutrients may well be the key to increased surface-ocean productivity in the remote and oligotrophic parts of the oceans and, potentially, also continental ecosystems. See: www.nioz.nl/dust
Changing atmospheric acidity as a modulator of nutrient deposition and ocean biogeochemistry
Authors: Baker Alex , Kanakidou Maria , Nenes Athanasios , Croot Peter , Duce Robert , Gao Yuan , Guieu Cecile , Ito Akinori , Jickells Tim , Mahowald Natalie , Middag Rob , Myriokefalitakis Stelios , Perron Morgane , Sarin Manmohan , Shelley Rachel , Turner David
Published: March 2020

Anthropogenic emissions of nitrogen and sulphur oxides and ammonia have altered the pH of aerosol, cloud water and precipitation, with significant decreases over much of the marine atmosphere. Some of these emissions have led to an increased atmospheric burden of reactive nitrogen and its deposition to ocean ecosystems. Changes in acidity in the atmosphere also have indirect effects on the supply of labile nutrients to the ocean. For nitrogen, these changes are caused by shifts in the chemical speciation of both oxidized (NO3- and HNO3) and reduced (NH3 and NH4+) forms that result in altered partitioning between the gas and particulate phases that affect transport. Other important nutrients, notably iron and phosphorus, are impacted because their soluble fractions increase due to exposure to low pH environments during atmospheric transport. These changes affect not only the magnitude and distribution of individual nutrient supply to the ocean but also the ratios of nitrogen, phosphorus, iron and other trace metals in atmospheric deposition.  Since marine microbial populations are sensitive to nutrient supply ratio, the consequences of atmospheric acidity change include shifts in ecosystem composition in addition to overall changes in marine productivity. Nitrogen and sulphur oxide emissions are decreasing in many regions, but ammonia emissions are much harder to control. The acidity of the atmosphere is therefore expected to decrease in the future, with further implications for nutrient supply to the ocean.

This presentation will explore the impact of increased atmospheric acidity since the Industrial Revolution, and the projected acidity decreases, on atmospheric nutrient supply and its consequences for the biogeochemistry of the ocean.
Geochemical and geological evidence for a Triassic transition from subduction- to rift-related volcanic activity in the Cycladic Blueschist Unit in Attica (Greece)
Authors: Stouraiti Christina , Lozios Stelios , Soukis Konstantinos , Downes Hilary , Carter Andy
Published: March 2020

Triassic geodynamic phenomena in the Aegean area are largely controlled by subduction of the Paleotethys ocean and opening of the Neotethys oceans. Triassic volcanosedimentary sequences have a complex composition in many cases, reflecting both subduction and rifting setting.

Detailed mapping of NE Attica (Penteli Mt., Marathonas, Varnavas) revealed the existence of a structurally lower meta-volcanosedimentary sequence, which, comprises quartzofeldspathic rocks, schists, quartzite, metabasite and acid meta-volcanics This sequence is isoclinally folded in the macro-scale with marble layers and the axial plane foliation displays greenschist facies assemblages, whereas earlier HP minerals are mostly preserved as inclusions in albite porphyroblasts. The sequence of rocks has been investigated for their geochemical composition and their field relationships. Two assemblages of volcanic rocks are distinguished based on geochemical criteria: (a) a predominant subalkaline andesite-rhyolite series with a significant proportion of meta-tuffs in the stratigraphic sequence and (b) minor alkali basalts. Lenses of felsic meta-volcanic rocks alternate with siliciclastic layers showing sedimentary banding and allow for an interpretation of a volcano-sedimentary succession.

The geochemical characteristics of the alkali basalts are typical of rift settings (positive anomalies in Nb, Ta, Ti and P) and plot in the field of within plate basalts in the tectonic discrimination diagrams.  The trace element and Rare Earth Element characteristics of the andesites and rhyolites in the subalkaline group show many characteristics of subduction zone melts e.g. negative Nb and Ta anomalies, positive Pb anomaly and LREE-enriched suggesting that a metasomatized mantle wedge source played an important role in the formation of the calcalkaline magmas. A geodynamic model of rift formation in the active continental margin of Pelagonia is proposed to explain the transition from a subduction- to an extension-related magmatic activity in the Late Permian/Triassic time in the broader NE Attica-central Evvia region.
Quantifying the uncertainty in riverbank erosion for risk-informed river engineering
Authors: Langendoen Eddy , Ursic Mick
Published: March 2020

Riverbank erosion is a ubiquitous, natural process. Typically, it occurs during larger flood events when the applied forces exerted by the flowing water on a bank exceed some erosion-resistance threshold. Riverbank protection may be needed when critical infrastructure is present or planned near eroding banks, which requires the quantification of the risk of infrastructure failure by bank erosion. Similarly, renaturalization of many European streams, for example through removal of bank protection measures, necessitates the quantification of expected river width adjustment. Unfortunately, we have been unable to accurately quantify bank erosion rates to date. Limitations exist in characterizing both the applied and resisting forces. For example, bank roughness co-evolves with erosion, which makes it difficult to adequately resolve the forces acting on the bank material. Bank material erosion-resistance of fine-grained soils varies significantly, that is over orders of magnitude, both spatially and temporally. Moreover, existing techniques to measure bank material erosion-resistance do not always produce repeatable results. As a consequence, existing bank erosion models, such as the widely used Bank Stability and Toe Erosion Model (BSTEM), require extensive calibration and validation. This is often unsatisfactory to river engineering professionals that have to make decisions on where to place bank protection measures and the level of protection required. The decision-making process could benefit from a risk-based analysis that quantifies the uncertainty in calculated bank retreat rate. Recent enhancements to the BSTEM model allow users to input probability density functions of (measured) bank roughness and bank material erosion-resistance properties. A Monte Carlo analysis then quantifies the effects of both variability and uncertainty in these parameters on bank retreat. We will present how the shape of different probability density functions affect the probability density function of bank retreat. Results will be further presented of application of the new model to assist in prioritizing riverbank restoration measures along the Lower American and Sacramento Rivers, CA, USA, to prevent failure of levees that protect the City of Sacramento from flooding.
Isotope-age-dating of alpine spring water and global change : Evidence from temperature, chemistry and tritium data
Authors: Kralik Martin , Papp Erika
Published: March 2020

Global air-temperature changes over the last 150 years and in particular during the last 30 – 40 years are well documented world-wide. In alpine areas in Europe the increase in air-temperature is even higher in the range of 2° C. Very few studies exist about groundwater temperature changes due to global warming. The increase or decrease in temperature at the point of discharge depends besides the air temperature at the time of infiltration on the amount of precipitation, the local meteorological conditions, the mean residence time, the land use, and the natural and anthropogenic heat flow during the passage underground.

Nearly no papers exist about the water quality changes due to global change impacts and Mean Residence Times (MRT). This is very difficult to evaluate due to missing long-term quality measurements and strong impacts by anthropogenic activities and land use changes. To avoid the complication by anthropogenic land use changes and activities the authors investigated the on-line discharge, temperature, and electric conductivity measurements as well as quarterly hydro-chemical and isotope analyses of 40 Alpine springs from a monitoring network all over the Austrian Alps (approx. 60,000 km2). All the selected springs have a recharge area with no or minimal anthropogenic impacts during the last 30 – 40 years. About 235,000 on-line measurements and 11,000 chemical analyses were evaluated for trends and compared to daily measurements at meteorological and surface water stations close to the recharge areas of the springs. To show the connection to the paleoclimatology changes of existing δ18O measurements on precipitation and spring water was evaluated as well indicating altitudes of recharge areas in range of 500 – 2400m.

Forty springs with a minimum record of 16 years have been selected for trend analysis over a period of 20 years (1993 – 2013). 28 (74%) of the selected spring show a significant mean increase in water temperature of 0.34 °C in the range of 0.06 to 1.03 °C. This increase is half of the air- and water temperature increase in meteorological stations and surface waters close to the recharge areas of the investigated springs. The electric conductivity linearly increased in 21 (55%) of the investigated springs at about 4%. The discharge stayed the same in most springs. In 23 (72%) springs the content of dissolved oxygen decreased over these 20 years at about 9% percent.

The reasons of the changes in water-temperature, dissolved load and the oxygen content as well as the impact of different Mean Residence Times (MRT) will be discussed and interpreted.
Intra-sonic propagation of sliding zones in a fault
Authors: Dyskin Arcady , Pasternak Elena
Published: March 2020

Seismic events associated with pre-existing faults are traditionally assumed to be caused by rupture propagation, that is in-plane shear crack propagation. However what appears to be a shear crack is a sliding zone over a fault; it grows by overcoming friction (either in direct contact or in the gouge) rather than rock rupture. When modelling frictional sliding, two important factors need to be considered: (1) the elasticity of the surrounding rocks which causes self-oscillations resulting in the movement resembling stick-slip even in constant friction; (2) the rotation of real gouge particles which being non-spherical lead, in the presence of compression, to the effect of negative shear stiffness. The latter effectively works to transfer the elastic energy stored in the compressed rock into the energy of the sliding zone propagation.

This presentation introduces 1D models accounting for these factors. Both lead to the so-called telegraph equation which is a wave equation with a non-derivative term referring to the fact that the movement is considered against a stationary solid. The equation with respect to displacement corresponds to the case of apparent negative stiffness, while the equation with respect to the displacement rate corresponds to the pure frictional sliding. The rock elasticity leads to the sliding zone propagation speed equal to the p-wave velocity making the propagation speed intra-sonic [1]. The rate-dependent friction can slightly reduce the speed. It is interesting that the sliding zone propagation is related to p-wave rather than s- or Raylegh waves as one would anticipate. The results of this research contribute to the understanding of the mechanics of seismicity.

Karachevtseva, I, A.V. Dyskin and E. Pasternak, 2017. Generation and propagation of stick-slip waves over a fault with rate-independent friction. Nonlinear Processes in Geophysics (NPG), 24, 343-349.

Acknowledgements. AVD acknowledges the support from the School of Civil and Transportation, Faculty of Engineering, Beijing University of Civil Engineering and Architecture.