bluuebunny/crossref_metadata_2025 huggingface dataset:
Quasi-three-dimensional simulation of crescent-shaped waves
Authors: Dosaev Alexander , Troitskaya Yuliya
Published: March 2020

Many features of nonlinear water wave dynamics can be explained within the assumption that the motion of fluid is strictly potential. At the same time, numerically solving exact equations of motion for a three-dimensional potential flow with a free surface (by means of, for example, boundary integral method) is still often considered too computationally expensive, and further simplifications are made, usually implying limitations on wave steepness. A quasi-three-dimensional model, put forward by V. P. Ruban [1], represents another approach at reducing computational cost. It is, in its essence, a two-dimensional model, formulated using conformal mapping of the flow domain, augmented by three-dimensional corrections. The model assumes narrow directional distribution of the wave field and is exact for two-dimensional waves. It was successfully applied by its author to study a nonlinear stage of of Benjamin-Feir instability and rogue waves formation.

The main aim of the present work is to explore the behaviour of the quasi-three-dimensional model outside the formal limits of its applicability. From the practical point of view, it is important that the model operates robustly even in the presence of waves propagating at large angles to the main direction (although we do not attempt to accurately describe their dynamics). We investigate linear stability of Stokes waves to three-dimensional perturbations and suggest a modification to the original model to eliminate a spurious zone of instability in the vicinity of the perpendicular direction on the perturbation wavenumber plane. We show that the quasi-three-dimensional model yields a qualitatively correct description of the instability zone generated by resonant 5-wave interactions. The values of the increment are reasonably close to those obtained from the exact equations of motion [2], despite the fact that the corresponding modes of instability consist of harmonics that are relatively far from the main direction. Resonant 5-wave interactions are known to manifest themselves in the formation of the so-called “horse-shoe” or “crescent-shaped” wave patterns, and the quasi-three-dimensional model exhibits a plausible dynamics leading to formation of crescent-shaped waves.

This research was supported by RFBR (grant No. 20-05-00322).

[1] Ruban, V. P. (2010). Conformal variables in the numerical simulations of long-crested rogue waves. The European Physical Journal Special Topics, 185(1), 17-33.

[2] McLean, J. W. (1982). Instabilities of finite-amplitude water waves. Journal of Fluid Mechanics, 114, 315-330.
Unraveling temperature and hydrological conditions of salt deposits by measuring the speed of sound in halite fluid inclusions: the case of the Last Interglacial Dead Sea
Authors: Guillerm Emmanuel , Gardien Véronique , Brall Niels , Schwab Markus J. , Lach Adeline , Neugebauer Ina , Ariztegui Daniel , Caupin Frédéric
Published: March 2020

Salt deposits found throughout the geological record and across the globe are witnesses of extreme paleoclimatic and paleoenvironmental conditions. However, little is known about the hydrological conditions that gave rise to these deposits, and the role of temperatures is even less constrained. Here we have used a new technique, Brillouin spectroscopy,  to investigate the paleoenvironmental and paleoclimatic conditions that led to the deposit of a thick salt sequence in the Dead Sea during the Last Interglacial (LIG, ~135,000 to 115,000 years before present). Through measuring the speed of sound inside halite fluid inclusions (FIs), this method provides the parent brine temperature and salinity at the moment of crystal growth. We applied it to several tens of halite intervals from the 450-meters-long core 5017-1 drilled in 2010-2011 in the deepest part of the Dead Sea in Palestine within the framework of the Dead Sea Deep Drilling Project (DSDDP). The application of Brillouin spectroscopy to this record provides a unique quantification of temperature and hydrological changes in this area during the LIG and outlines a radically new narrative for the climate of the region during this period. The example of the Dead Sea shows that Brillouin spectroscopy on halite FIs is in position to provide valuable data to test the efficiency of climate models and to better understand the processes that lead to the deposition of salt giants.
Unsteady energy dissipation in the magnetic reconnection diffusion region
Authors: Dong Xiangcheng , Dunlop Malcolm , Wang Tieyan , Giles Barbara , Torbert Roy , Russell Christopher , Burch James
Published: March 2020

Magnetic reconnection is a universal physical process during which energy can be transferred from the electromagnetic field to the plasma. Energy dissipation in the diffusion region has always been a significant issue for understanding this energy transport. Using the four MMS spacecraft data, we investigate a magnetic reconnection diffusion region event at the magnetopause. Similar magnetic field and electric current behavior between each spacecraft indicates the formation of a quasi 2D structure. However, we find that the energy dissipation results of each spacecraft are different. Further analysis indicates that the reconnection electric field, EM, plays a key role in this process. Thus, we suggest that the energy dissipation of magnetic reconnection is unsteady on this spatial or temporal scale, even under stable diffusion conditions.
Bayesian recurrent neural network as a tool for reconstructing dynamical systems from multidimensional data
Authors: Feigin Alexander , Seleznev Aleksei , Mukhin Dmitry , Gavrilov Andrey , Loskutov Evgeny
Published: March 2020

We suggest a new method for construction of data-driven dynamical models from observed multidimensional time series. The method is based on a recurrent neural network (RNN) with specific structure, which allows for the joint reconstruction of both a low-dimensional embedding for dynamical components in the data and an operator describing the low-dimensional evolution of the system. The key link of the method is a Bayesian optimization of both model structure and the hypothesis about the data generating law, which is needed for constructing the cost function for model learning.  The form of the model we propose allows us to construct a stochastic dynamical system of moderate dimension that copies dynamical properties of the original high-dimensional system. An advantage of the proposed method is the data-adaptive properties of the RNN model: it is based on the adjustable nonlinear elements and has easily scalable structure. The combination of the RNN with the Bayesian optimization procedure efficiently provides the model with statistically significant nonlinearity and dimension.
The method developed for the model optimization aims to detect the long-term connections between system’s states – the memory of the system: the cost-function used for model learning is constructed taking into account this factor. In particular, in the case of absence of interaction between the dynamical component and noise, the method provides unbiased reconstruction of the hidden deterministic system. In the opposite case when the noise has strong impact on the dynamics, the method yield a model in the form of a nonlinear stochastic map determining the Markovian process with memory. Bayesian approach used for selecting both the optimal model’s structure and the appropriate cost function allows to obtain the statistically significant inferences about the dynamical signal in data as well as its interaction with the noise components.
Data driven model derived from the relatively short time series of the QG3 model – the high dimensional nonlinear system producing chaotic behavior – is shown be able to serve as a good simulator for the QG3 LFV components. The statistically significant recurrent states of the QG3 model, i.e. the well-known teleconnections in NH, are all reproduced by the model obtained. Moreover, statistics of the residence times of the model near these states is very close to the corresponding statistics of the original QG3 model. These results demonstrate that the method can be useful in modeling the variability of the real atmosphere.

The work was supported by the Russian Science Foundation (Grant No. 19-42-04121).
Retrogressive thaw slumps along permafrost coasts transform organic matter before release into the Arctic Ocean
Authors: Tanski George , Lantuit Hugues , Wagner Dirk , Knoblauch Christian , Ruttor Saskia , Radosavljevic Boris , Wolter Juliane , Fritz Michael , Strauss Jens , Irrgang Anna M. , Ramage Justine , Sachs Torsten , Vonk Jorien E.
Published: March 2020

Changing environmental conditions in the Arctic have profound impacts on permafrost coasts, which erode at great pace. Although numbers exist on annual carbon and sediment fluxes from coastal erosion, little is known on how terrestrial organic matter (OM) is transformed by thermokarst and –erosional processes on transit from land to sea. Here, we investigated a retrogressive thaw slump (RTS) on Qikiqtaruk - Herschel Island in the western Canadian Arctic. The RTS was classified into an undisturbed, disturbed and nearshore zone and systematically sampled along transects. Collected sediments were analyzed for organic carbon (OC), nitrogen (N), stable carbon isotopes (δ13C-OC) and ammonium. C/N-ratios, δ13C-signatures and ammonium concentrations were used as general indicator for OM degradation. Permafrost sediments from the RTS headwall and mud lobe sediments from the thaw stream outlet were incubated to further assess OM degradation and potential greenhouse gas formation during slumping and upon release into the nearshore zone. Our results show that OM concentrations significantly decrease upon slumping in the disturbed zone with OC and N decreasing by >70% and >50%, respectively. Whereas δ13C-signatures remain fairly stable, C/N-ratios decrease significantly and ammonium concentrations increase slightly in fresh slumping material. Nearshore sediments have low OM contents and a terrestrial signature comparable to disturbed sites on land. The incubations show that carbon dioxide (CO2) forms quickly from thawing permafrost deposits and mud debris with ~2-3 mg CO2 per gram dry weight being cumulatively produced within two months. We suggest that the initial strong decrease in OM concentration after slumping is caused by a combination of OC degradation, dilution with melted massive ice and immediate offshore transport via the thaw stream. After stabilization in the slump floor, recolonizing vegetation takes up N from the disturbed sediment. Upon release into the nearshore zone, larger portions of OM are directly deposited in marine sediments, where they further degrade or being buried. The incubations indicate that CO2 is rapidly produced upon slumping and potentially continues to form within the nearshore zone that receives eroded material. We conclude that coastal RTS systems profoundly change the characteristic of modern and ancient permafrost terrestrial OM during transit from land to sea - a process which is likely linked to the production of greenhouse gases. Our study provides valuable information on the potential fate of terrestrial OM along eroding permafrost coasts under the trajectory of a warming Arctic.
Homogenization of long-term snow observations
Authors: Resch Gernot , Chimani Barbara , Koch Roland , Schöner Wolfgang , Marty Christoph
Published: March 2020

Climate data contains vital information about the global climate system. To get the desired information out of measurements, they have to be homogenous, where the variability of a time series is only caused by variations in weather and climate and not due to external influences.

Snow is an important component of this system, treated as one of the most obvious visual evidences of climate change and important for countries with mountainous environments. But most of the existing tools and algorithms that are being used for homogenization have been developed for air temperature and precipitation, whereas their application to snow depth measurements has only been rarely attempted. Until now, there have only been smaller efforts to develop methods and tools for snow series.

We are trying to break new ground by developing innovative methods that can be applied to the homogenization of longterm snow observations, as well as to demonstrate the impact of the developed adjustments on climatologies and trends. For that, we are using daily longterm snow measurements of the two most frequently measured parameters, snow depth (HS) and new snow height (HN) from the Swiss-Austrian domain.

As a first approach, we are applying the existing methods PRODIGE for the detection of multiple inhomogeneities and INTERP for the calculation of corrections with a quantile-mapping approach on a seasonal basis on selected time series.
A revised sea level budget equation to accurately represent physical processes driving sea level rise
Authors: Vishwakarma Bramha Dutt , Royston Sam , Riva Ricardo E. M. , Westaway Richard M. , Bamber Jonathan L.
Published: March 2020

The sea level budget (SLB) equates changes in sea surface height (SSH) to the sum of various geo-physical processes that contribute to sea level change. Currently, it is a common practice to explain a change in SSH as a sum of ocean mass and steric change, assuming that solid-Earth motion is corrected for and completely explained by secular visco-elastic relaxation of mantle, due to the process of glacial isostatic adjustment. Yet, since the Solid Earth also responds elastically to changes in present day mass load near the surface of the Earth, we can expect the ocean bottom to respond to ongoing ocean mass changes. This elastic ocean bottom deformation (OBD) has been ignored until very recently because the contribution of ocean mass to sea level rise was thought to be smaller than the steric contribution and the resulting OBD was within observation system uncertainties. However, ocean mass change has increased rapidly in the last 2 decades. Therefore, OBD is no longer negligible and recent studies have shown that its magnitude is similar to that of the deep steric sea level contribution: a global mean of about 0.1 mm/yr but regional changes at some places can be more than 10 times the global mean. Although now an important part of the SLB, especially for regional sea level, OBD is considered by only a few budget studies and they treat it as a spatially uniform correction. This is due to lack of a mathematical framework that defines the contribution of OBD to the SLB. Here, we use a mass-volume framework to derive, for the first time, a SLB equation that partitions SSH change into its component parts accurately and it includes OBD as a physical response of the Earth system. This updated SLB equation is important for various disciplines of Earth Sciences that use the SLB equation: as a constraint to assess the quality of observational time-series; as a means to quantify the importance of each component of sea level change; and, to adequately include all processes in global and regional sea level projections. We recommend using the updated SLB equation for sea level budget studies. We also revisit the contemporary SLB with the updated SLB equation using satellite altimetry data, GRACE data, and ARGO data.
Sensitivity analysis of optimization parameters on cooperative inversion of seismic reflection and gravity data
Authors: Gonçalves Maiara , Leite Emilson
Published: March 2020

Reflections of seismic waves are strongly distorted by the presence of complex geological structures (e.g. salt bodies) and their vertical resolution is usually of the order of a few tens of meters, imposing limitations in the construction of subsurface models. One way to improve the reliability of such models is to integrate reflection seismic data with other types of geophysical data, such as gravimetric data, since the latter provide an additional link to map geological structures that exhibit density contrasts with respect to their surroundings. In a previous study, we developed a cooperative inversion method of 2D post-stack and migrated reflection seismic data, and gravimetric data. Using that inversion method, we minimize two problems: (1) the problem of the distortion of reflection seismic data due to the presence of complex geological bodies and (2) the problem of the greater ambiguity and the commonly lower resolution of the models obtained only from gravimetric anomalies. The method incorporates a technique to decrease the number of variables and is solved by optimization of the gravity inverse problem, thus reducing computing time. The objective function of cooperative inversion was minimized using three different methods of optimization: (1) simplex, (2) simulated annealing, and (3) genetic algorithm. However, these optimization methods have internal parameters which affect the convergence rate and objective function values. These parameters are usually chosen accordingly to previous references. Although the usage of these standard values is widely accepted, the best values to assure effectiveness and stability of convergence are case-dependent. In the present study, we propose a sensitivity analysis on the internal parameters of the optimization methods for the previously presented cooperative inversion. First, we developed the standard case, which is an inversion performed using all parameters at their standard values. Then, the sensitivity analysis is performed by running multiple inversions, each one with a set of parameters. Each set is obtained by modifying the value of a single parameter either for a lower or for a higher value, keeping all other values at their standard values. The results obtained by each setting are compared to the results of the standard case. The compared results are both the number of evaluations and the final value of the objective function. We then classify parameters accordingly to their relative influence on the optimization processes. The sensitivity analysis provides insight into the best practices to deal with object-based cooperative inversion schemes. The technique was tested using a synthetic model calculated from the Benchmark BP 2004, representing an offshore sedimentary basin containing salt bodies and small hydrocarbons reservoirs.
Why do shelf-incising submarine canyons form? - Insights from global topographic analyses and regression trees
Authors: Bernhardt Anne , Schwanghart Wolfgang
Published: March 2020

The efficiency of environmental signal propagation from terrestrial sources to marine sinks highly depends on the connectivity of the sediment-routing system. Submarine canyons that couple river outlets with marine depocenters are particularly crucial links in the routing network as they convey terrestrial sediment, associated pollutants and organic carbon to the deep ocean. However, why and where submarine canyons incise into shelves is still poorly understood. Several factors were proposed, including narrow shelves along active continental margins, onshore sediment flux, more proximal sediment supply during sea-level lowstands, mass wasting along high-gradient continental slopes, and the occurrence of durable bedrock in adjacent catchments. In this study, we test whether we can predict shelf incision of submarine canyons from onshore and offshore parameters.

We used maps of global elevation and bathymetry and analyzed them together with a global compilation of 5900 submarine canyon heads. The analysis relies on bagged regression trees that predict the distance of each canyon head from the shelf edge as a function of numerous candidate predictor variables. These variables describe spatial relations of river mouths and canyons, shelf geometry, continental slope gradient, as well as numerous terrestrial catchment properties. Moreover, we added 120 m to the elevation of the present-day topography to simulate a coastal landscape during the Last Glacial Maximum (LGM) and recalculated the topographic terrestrial parameters and the shelf width.

The trained model explains 66% (R2) of the variance within the data set with a root mean square error (RMSE) of 31 km and a mean absolute error (MAE, less sensitive to outliers) of 17 km. The highest predictor importance is consistently reported for the weighted distance from canyon heads to the adjacent river mouths during the LGM and the present-day catchment gradient. We find no significant influence of shelf width, continental slope gradient and sediment load, and the moderate fit of the model indicates that we are still missing one or more important controls on the spatial location of canyon heads. Our predictions may be refined by including a more detailed assessment of catchment lithologies, locations of submarine groundwater discharge, locations of tectonic faults, and longshore current directions. Notwithstanding, we conclude that our model identifies important controls on the spatial occurrence and shelf incision of submarine canyons and sorts out much debated but seemingly unimportant variables.  
The Performances of GRACE Mascon Solutions in Studying Seismic Deformations
Authors: Zhang Lan , Tang He , Chang Le , Sun Wenke
Published: March 2020

The GRACE mascon solutions, called the advanced products of GRACE data, are widely used in cryosphere science or hydrology research. It has been demonstrated that the mascon solutions have the same or better performances compared with the spherical harmonic (SH) solutions at the basin scale. However, although the mascon solutions are expected to have the ability to recover the transient gravity signals due to large earthquakes, few studies have investigated the performances of the mascon solutions in studying seismic deformations systematically. In this study, we attempt to examine the performances of the mascon solutions for transient gravity signals induced by three M9 class earthquakes: the 2011 Tohoku-Oki, 2004 Sumatra and 2010 Chile earthquakes, and compare them with the SH solutions and theoretical gravity changes modelled by dislocation theory. We analyse the co-seismic gravity changes and conclude that the mascon solutions contain almost identical information as the SH solutions and can retrieve the co-seismic gravity change signals in the resolutions equivalent to the Gaussian filter radii of 210~270 km. However, the mascon solutions have other strengthening gravity change signals, with magnitudes that are the same order as that of the SH solutions and contain pre-seismic gravity change signals in the Tohoku earthquake. These strengthening and pre-seismic signals are both considered artificially introduced noise due to the mathematical treatment before releasing rather than real geophysical signals.
Soil moisture and the water cycle in the UK Climate Projections
Authors: Pirret Jennifer , Fung Fai , Mitchell John. F.B. , McInnes Rachel
Published: March 2020

Soil moisture is a key environmental factor for plant cultivation: too little and plant growth is restricted due to drought conditions; too much and soil becomes water-logged. It is important to understand how well climate models can represent current soil moisture processes as well as how soil moisture will respond to a changing climate, to inform adaptation of plant cultivation to future climate change. We explore current and future climate soil moisture conditions alongside water cycle processes such as evaporation and run-off in the latest UK Climate Projections (UKCP). Three model ensembles are available: UKCP Global, Regional and Local, with horizontal resolutions of 60km, 12km and 2.2km respectively. These each contain the Joint UK Land Environment Simulator (JULES) model as their land surface component. This suite of models offers the opportunity to understand the effects of parameter uncertainty and spatial resolution. Firstly, we assess the performance of the Global and Regional simulations by evaluating results from the baseline period (1981-2010) in terms of soil moisture (and the overall water balance) by comparing it to observations and to JULES driven by observations. Secondly, we assess how the water balance responds to a high future greenhouse gas concentration pathway. We find that soil moisture is likely to be lower in the summer and early autumn and spends a longer time below levels optimal for plant growth. The potential drivers of this change are explored, including future changes in precipitation and evaporation.
TROPOMI SO2 column retrievals: validation, inter-comparison with other satellite data sets and algorithm evolution
Authors: Theys Nicolas , Li Can , Krotkov Nickolay , De Smedt Isabelle , Lerot Christophe , Yu Huan , Vlietinck Jonas , Fioletov Vitali , Hedelt Pascal , Loyola Diego , Wagner Thomas , Van Roozendael Michel
Published: March 2020

Since nearly two years, the operational SO2 product from the TROPOspheric Monitoring Instrument (TROPOMI) onboard Sentinel-5 Precursor (S5P) platform has provided important information on volcanic and anthropogenic SO2 emissions, with an unprecedented level of details. In this presentation, we critically discuss the advantages and disadvantages of the current operational algorithm in light of the validation results obtained so far, and present how the retrieval scheme could evolve in the future.

In the first part, we briefly present the main algorithm features and an overview of the SO2 product validation. One challenge in this respect is the current lack of ground-based SO2 measurements for anthropogenic source regions. We therefore rely largely on comparisons with other satellite datasets (e.g., OMI and OMPS). The main lesson learnt is that satellite SO2 retrievals generally agree very well for large SO2 columns (mostly volcanic) while persisting differences exist for low columns when different algorithms are compared. This motivates the second part of the presentation which aims at extensively comparing the results from existing S5P SO2 operational and scientific algorithms, notably DOAS and PCA retrievals (or other alternative approaches). Here, all configuration settings and auxiliary data (e.g. absorption cross-sections) are aligned in order to better understand the differences through sensitivity tests. This effort is not only important to improve the TROPOMI SO2 results but it is also particularly relevant in the context of the forthcoming Sentinel-4 mission that will mainly probe weak anthropogenic SO2 sources. The last part of the presentation gives a general overview of new features planned for the next versions of the operational SO2 algorithm.
Characterization and valorization of the waste from the abandoned Kettara mine and the gypsum quarry in Sidi Tijji (Marrakech-Safi Region, Morocco).
Authors: Bouiji Assma , witam Omar , Ibnoussina Mounsif
Published: March 2020

In Morocco, no measures have been taken to manage residual waste from operational or abandoned mining and quarries sites.

Indeed, significant quantities of mine waste, composed of concentrator residues and sterile waste, have been abandoned after the closure of operations without any effective management or rehabilitation planning.

These residues could have harmful impacts on the environment: soil and water pollution, destruction or disturbance of natural habitats, visual impact on the countryside...

The valorization and sustainable management of mining waste appear to be adequate solutions to major environmental problems. The construction sector can be a profitable sector to absorb chemically stable mining waste.

The objective of this research work is to study the feasibility of recycling waste from the abandoned Kettara mine (Morocco) and gypsum waste rock in Sidi Tijji (Morocco) as raw materials in construction materials.

The study consists first of a geological characterization and then a characterization of the physical, chemical and mineralogical properties of the residues, followed by an evaluation of the mechanical properties of the composite mixtures based on the chemically stable residues.

The Kettara mine is located in the Jbilet Central Mountains, 30 km northwest of Marrakech. Geologically, the pyrrhotite district of Kettara corresponds to the outcrop area of the volcano-sedimentary series of Saghlef shales. For the gypsum quarry at Sidi Tijji, which is part of the Safi basin, characterized by Jurassic outcrops essentially formed by gypsum and carbonate formations.

Mineralogical and chemical analysis have shown that these waste products are still rich in minerals such as the waste from the Kettara mine; the FeO3 concentrated amounts to 55.6%. In addition, gypsum waste rock represents a concentration of 28.9% CaO. Therefore, a low water content for the majority of samples.

Adapting to the principles of integrated recovery and management of mining and quarry waste requires a cultural change within the industry, but also in the ministries concerned.

Keywords: Valorization, mine waste, mines and quarries, construction materials.
Interannual analysis of high spatially-resolved δ18O and δ2H data in precipitation across North-East Italy
Authors: Masiol Mauro , Zannoni Daniele , Stenni Barbara , Dreossi Giuliano , Zini Luca , Calligaris Chiara , Karlicek Daniele , Michelini Marzia , Flora Onelio , Cucchi Franco , Treu Francesco
Published: March 2020

Stable water isotopes are widely-used tracers to investigate hydrological processes occurring in the atmosphere and to determine the geospatial origin of water, i.e. to acquire useful information about the hydrological cycles over catchment basins and to find the origin of water recharging rivers, aquifers, and springs. Mapping the isotopic composition of precipitation provides hydrological and climate information at regional and global scales. However, the isotopic composition of precipitation is usually analyzed at large scales with a limited spatial resolution. In Italy, a few studies mapped the oxygen stable isotopes using annually-averaged data, not accounting for the strong seasonality of the isotopic composition linked to climatic and weather factors. To partially fill this gap, the present study proposes a detailed analysis of more than 2250 isotope data (δ18O, δ2H, and deuterium excess) related to precipitations collected in the Friuli Venezia Giulia (FVG) region (Italy) with monthly or seasonal frequency in 36 sites between 1984 and 2015.

The FVG region lies at the north-eastern end of Italy, bordering Austria in the North and Slovenia in the East, and extends over ~7.9·103 km2. From a hydrogeological point of view, FVG is an interesting case study. Large highly-permeable carbonate aquifers are present in the Alps and Prealps, while the southern part of the region is characterized by an alluvial plain, split by the spring belt into two sectors: the High Plain in the North, characterized by an highly-permeable unconfined aquifer, and the Low Plain in the South, characterized by a system of confined and artesian aquifers. All the aquifers are recharged by the effective precipitations which in the FVG exhibits among the highest annual precipitation rates in Italy (with peaks >3000 mm/year).

For the present research, the isotopic data were used: (i) to analyze the spatial and seasonal variability of isotopic composition; (ii) to relate water isotopes with orography and weather parameters collected from meteorological stations as well as using ECMWF ERA5 reanalysis; (iii) to reconstruct the local meteoric water lines across the FVG at annual and seasonal bases; (iv) to quantify interannual trends and analyze their spatial distribution; and (iv) to model the spatial distribution of isotope content in precipitation and create annual and seasonal maps.
The AMOC at 47° North in Observations and a High Resolution Ocean Model
Authors: Wett Simon , Rhein Monika , Biastoch Arne , Böning Claus W. , Getzlaff Klaus
Published: March 2020

The Atlantic Meridional Overturning Circulation (AMOC) is the main driver of northward oceanic volume and heat transport in the Atlantic. Due to its definition via the streamfunction the exact calculation of the AMOC requires knowledge of the full velocity field. Since the early 2000s, observations of the AMOC are available at 47° North in the form of hydrographic sections across the Atlantic and continuous current measurements from moored instruments at specific locations. However, the spatial resolution of current measurements is coarse and shipbased hydrographic sections are mostly done only once a year. Also the observational timeseries still remain too short to come to conclusions about decadal trends in the AMOC variability. Thus, today our knowledge about the role of the AMOC in the global climate system is mainly based on model simulations. Comparing these model simulations against observations remains an important task to accurately predict the future of the AMOC and adapt to changes.

We present first results of a model observations comparison in the subpolar North Atlantic between observations at 47° North and the high resolution ocean model VIKING20X. The model has a 1/20° nest in the Atlantic embedded in a global 1/4° model. It covers the years from 1980 to 2018 and thus overlaps with the whole observational period. This comparison will help assessing different methods of estimating the AMOC strength from observations.
Alternative solution to the gamma bench for the dielectric characterization of materials
Authors: boughanmi Imen , Fauchard Cyrille , Benjelloun Nabil , Riah Zouheir
Published: March 2020

In the field of civil engineering, and more particularly in the road building, it is necessary to control some physical parameters with standard methods. These controls ensure the implementation is performed according to the technical specifications. They also allow to optimize the structure dimensions  with the best safety/cost ratio and an optimal lifetime. Compactness related to density and therefore indicative of mechanical strength necessary to support traffic solicitations is a key parameter to control. Currently, density control in the laboratory is done using bench with nuclear sources on pavement cores, based on the emission and reception of gamma rays. Its replacement has now become a major issue since this method generates increasingly high costs and constraints (use, storage, transport and exposure to ionizing radiation). The objective of this work is to find an alternative non-nuclear solution to control the pavement compactness with an accuracy equivalent to the gamma-bench method . The proposed solution is an electromagnetic bench (EM), allowing cores tomography to measure permittivity. The density will then be evaluated by means of mixing rules. The EM bench consists of a vector network analyzer (Agilent E8362B) and two Ultra-Wide Band antennas [1.4-15 GHz] which are developed in this project in order to have the best performances (accuracy, dimensions…).

The antennas are placed facing each other, separated by a distance D.  A cylindrical sample (core) extracted from stratified road medium of diameter d to be tested is placed in the middle of the system and both antennas move with a given step (ranging from a few mm to 1 cm) along the sample to measure by stratification the core EM properties. The entire EM bench is motorized and driven by software developed in the laboratory. At each step, a measurement of S21 -parameter is recorded. Then signals are processed in the time domain to evaluate the relative permittivity.

The first results of modeling and measurements on laboratory asphalt samples show that the system makes it possible to evaluate the relative permittivity of different stratified materials. Accuracy, resolution and perspectives will be discussed.

key words : density, asphalt concrete, radar, electromagnetic bench
Climate Advanced Forecasting of sub-seasonal Extremes (CAFE), ITN Project
Authors: Corral Alvaro ,   CAFE-H2020-MSCA-ITN Team
Published: March 2020

The CAFE Project is a Marie S. Curie Innovative-Training-Network (ITN) project funded by the EU. The ultimate goal of the CAFE project is to contribute to the improvement of sub-seasonal predictability of extreme weather events. This will be addressed through a structured and cross-disciplinary program, training 12 early stage researchers who undertake their PhD theses. CAFE brings together a team of co-supervisors with complementary expertise in climate science, meteorology, statistics and nonlinear physics.

The CAFE team comprises ten beneficiaries (seven academic centres, one governmental agency, one intergovernmental agency and one company: ARIA, CRM, CSIC, ECMWF, MeteoFrance, MPIPKS, PIK, TUBAF, UPC, UR) and ten partner organizations (CEA and Munich Re, among them).

CAFE research is organized into three main lines: Atmospheric and oceanic processes, Analysis of extremes, and Tools for predictability, all focused on the sub-seasonal time scale. This includes the study of Rossby wave packets, Madden-Julian oscillation, Lagrangian coherent structures, ENSO-related extreme weather anomalies, cascades of extreme events, extreme precipitation, large-scale atmospheric flow patterns, and stochastic weather generators, among other topics.

Information about the CAFE project will be updated at:

http://www.cafes2se-itn.eu/

https://twitter.com/CAFE_S2SExtrem

This project receives funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 813844.
Large-scale features and evaluation of the PMIP4-CMIP6 midHolocene simulations
Authors: Brierley Chris , Zhao Anni , Harrison Sandy , Braconnot Pascale ,   PMIP4 Community
Published: March 2020

The mid-Holocene (6,000 years ago) is a standard experiment for the evaluation of the simulated response of global climate models using paleoclimate reconstructions. The latest mid-Holocene simulations are a contribution by the Palaeoclimate Model Intercomparison Project (PMIP4) to the current phase of the Coupled Model Intercomparison Project (CMIP6). Here we provide an initial analysis and evaluation of the results of the experiment for the mid-Holocene. We show that state-of-the-art models produce climate changes that are broadly consistent with theory and observations, including increased summer warming of the northern hemisphere and associated shifts in tropical rainfall.  Many features of the PMIP4-CMIP6 simulations were present in the previous generation (PMIP3-CMIP5) of simulations. The PMIP4-CMIP6 ensemble for the mid-Holocene has a global mean temperature change of -0.3 K, which is -0.2 K cooler that the PMIP3-CMIP5 simulations predominantly as a result of the prescription of realistic greenhouse gas concentrations in PMIP4-CMIP6. Neither this difference nor the improvement in model complexity and resolution seems to improve the realism of the simulations. Biases in the magnitude and the sign of regional responses identified in PMIP3-CMIP5, such as the amplification of the northern African monsoon, precipitation changes over Europe and simulated aridity in mid-Eurasia, are still present in the PMIP4-CMIP6 simulations. Despite these issues, PMIP4-CMIP6 and the mid-Holocene provide an opportunity both for quantitative evaluation and derivation of emergent constraints on climate sensitivity and feedback strength.
Ion injection triggered EMIC wave activity and its association with enhanced convection periods
Authors: Bhanu Remya , Sibeck David , Ruohoniemi Mike , Kunduri Bharat , Halford Alexa , Reeves Geoffery , Reddy Virupakshi
Published: March 2020

Electromagnetic ion cyclotron (EMIC) waves are found to be most prevalent during geomagnetic storms and solar wind pressure pulses which provide the necessary free energy for the wave growth. However, they have also been regularly observed in the absence of these two drivers. These non-storm time and non-pressure pulse EMIC events are very well associated with individual night side injections during substorms. However, not all substorm injections elicit wave activity. Our study aims to determine which substorm trigger wave activity. EMIC events excited during substorm injections are examined and various plasma parameters that are responsible for wave growth are studied. We find that injections that are associated with EMIC waves are also associated with enhanced high latitude ionospheric convection, which are manifestations of strong magnetospheric electric fields. The convective signatures occur at local times similar to those of the observed wave activity.
Assessing the role of nudging, aerosols and run-up time in medicane simulations with WRF
Authors: Gómez-Navarro Juan José , Pravia-Sarabia Enrique , Montávez Juan Pedro
Published: March 2020

Medicanes are small-scale cyclones with tropical characteristics that take place in the Mediterranean basin, showing hazardous features such as intense wind gusts and precipitation. Our ability to predict their consequences is of great importance for those cases of medicanes reaching coastal inhabited areas. Succeeding in a precise prediction of their characteristics is heavily subject to getting insight in the fundamental factors that are involved in their genesis, strengthening and maintenance. Given their small nature compared to the synoptic scale, RCMs are specially suitable for the simulation of these storms. However, when using RCMs, there are a number of configurations that must be controlled to specify the way the different physical and chemical mechanisms are solved during the simulation.

In this work, we evaluate the role of three different factors affecting the outcome of WRF, namely the run-up time, the inclusion or not of the on-line simulation of aerosols and the use of spectral nudging. To that end, six different medicanes have been simulated combining different possibilities for the aforementioned factors, resulting in a set of above 360 simulations. Although in principle the on-line simulation of aerosols is expected to have the strongest impact in the simulation of medicanes, it turns out that the run-up time -time delay from the simulation start to the medicane maximum intensity moment- is far more decisive in their successful development than the former. The results are also sensible to the use of spectral nudging, and the three considered factors end up having a considerable impact. Indeed, whereas the majority of their combinations lead to an erratic reproduction of the observed medicanes, there exist some combinations that allow reasonable results, showing that these configurations are in fact interdependent, i.e., the change in the simulation outcome due to a different configuration for one of the factors is dependent on the configuration of the others. This complicates the assessment on the influence of one factor alone, but facilitates gaining insight on the factors that control the genesis and maintenance of medicanes.
The Copernicus Young Ambassador Day: a replicable example for new technologies uptake by SMEs and Local Regional Authorities
Authors: Satriano Valeria , Colonna Roberto , Filizzola Carolina , Genzano Nicola , Lacava Teodosio , Pergola Nicola , Tramutoli Valerio
Published: March 2020

Innovation process is a very slow process especially when local regional authorities (LRA) are involved. Such an issue is further amplified when new advanced technologies/data should take the place of traditional and well-established approaches. A full exploitation of data acquired by satellite sensors, as well as of the relative services developed, has been limited in the latest years by the lack of expertise on this topic, at different level, from the general public to the human resources working at LRA and SME’s premises. This circumstance indicate the clear need of academic institutions to develop different targeted curricula for different potential users (students/researchers, SME professionals, LRA managers, etc.) of Earth Observation (EO) data and GeoInformatic (GI) tools. In the framework of the EO4GEO and CopHub.AC EU projects, the University of Basilicata (UNIBAS) is experimenting new, ad-hoc, EO/GI curricula and training tools. Among the different initiatives carried out so far, the Copernicus Young Ambassador Day is a quite simple and easily replicable action that has received evident consents in the latest years. A short course on EO/GI is offered to interested representatives of SMEs and Local Regional Authorities who are invited to identify possible applications related to their specific field of interest. These “user needs” are offered to the students of the Remote Sensing course at UNIBAS in order to propose their own possible technological solutions based on EO/GI technologies. Such solutions are presented in a public session to the representatives of LRA, SMEs and, for a feasibility evaluation, to the UNIBAS researchers.  During this exercise SME and LRA personnel receive a basic education enabling them to better understand the potential of available and incoming EO technologies; students have the occasion to proof their acquired skill facing real problems.  In this paper, after a general description of the EO4GEO and CopHub.AC projects, a summary of the main achievements of several Copernicus Young Ambassador days will be presented and discussed.
Energy demand estimates in large Russian cities and its biometeorological characteristics
Authors: Belova Iya , Krivenok Liudmila , Dokukin Sergy
Published: March 2020

To estimate the energy amount needed to heat indoor living and public spaces, the heating degree day (HDD) parameter is applied. This is the most common climatic indicator of energy consumption for the building heating, which is calculated for a certain period of the year by summing the absolute deviations of the average daily ambient temperature from the selected base temperature. However, human biometeorological sensitivity is based not only on the ambient temperature, but on a combination of temperature, humidity, and wind speed.

We have conducted a comparative analysis of the climatic and biometeorological characteristics of the regions including the largest Russian cities. For the effective ambient temperature range of 17.2 to 21.7⁰C (comfort zone), we have calculated changes in the comfort zone for Moscow, St. Petersburg, Krasnodar, Novosibirsk, and Vladivostok according to data from 1959 to the present. Despite all climate differences between regions with selected cities, allowance for wind speed leads to a decrease in the number of days with temperature within the comfort zone.

This study supported by Russian Science Foundation (project No 16-17-00114).