bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil carbon persistence linked to mineralogy across sub-Saharan Africa
Authors: von Fromm Sophie F. , Hoyt Alison M. , Butler Benjamin M. , Berhe Asmeret Asefaw , Doetterl Sebastian , Haefele Stephan M. , McGrath Steve P. , Shepherd Keith D. , Six Johan , Towett Erick K. , Winowiecki Leigh A. , Trumbore Susan E.
Published: March 2021

Recent compilations of global soil radiocarbon data suggest that current Earth System Models underestimate the mean age of soil carbon (C). The discrepancy between data-derived estimates and model calculations might be due to an inadequate representation of processes that control C persistence in soils – especially in understudied regions.

Here, we investigate the relationships between soil mineralogy, soil properties, climate and radiocarbon (Δ14C) in soils sampled as part of a comprehensive soil survey (AfSIS) for sub-Saharan Africa. A total of 510 samples were analyzed, comprised of soils collected from two depths (0–20 cm and 20–50 cm) at 30 sites in 14 countries. To determine soil mineralogy, we analyzed X-ray powder diffraction (XRPD) data, which provides a precise and detailed mineralogical signature of each soil sample. The studied soil profiles vary greatly in their mineralogy, reflecting a diverse range of parent materials and soil forming factors.

The median soil C age is 182 years in the topsoils and 563 years in the subsoils, corresponding to a total Δ14C value range of -432 to 95 ‰. In general, Δ14C values decrease (older mean C ages) with increasing clay particle size fractions. This corresponds to an increase in short range-order minerals expressed as oxalate-extractable aluminum and iron (Alox and Feox). Separately, mineralogically defined variables – derived from the XRPD data using principal component analysis – are found to correlate strongly with a range of soil properties (pH, weathering status, exchangeable calcium, Alox and Feox, and soil texture) and climatic variables (aridity index and mean annual temperature). This provides a holistic assessment of the processes that have formed each soil along with the properties that it currently exhibits. Our analyses with random forests show that these XRPD-derived mineralogical variables alone can explain up to 30% of the variation in Δ14C across sub-Saharan Africa. They also allow the identification of specific minerals that contribute to this variation and how they are linked to the C mean age of the soil. In conclusion, our results suggest that soil mineral data can help to better understand C persistence in subtropical and tropical soils.
Footprints of palaeocurrents in sedimentary sequences of the Cenozoic across the Maurice Ewing Bank
Authors: Najjarifarizhendi Banafsheh , Uenzelmann-Neben Gabriele
Published: March 2021

High-resolution 2D multichannel seismic data collected by the Alfred Wegener Institute in 2019 across the Maurice Ewing Bank, the high-altitude easternmost section of the Falkland Plateau in the SW South Atlantic, are integrated with information from DSDP Leg 36, Sites 327, 329, and 330 and Leg 71 Site 511. A seismostratigraphic model is defined, including five units ranging in age from the Middle Jurassic to Quaternary and are interpreted with respect to the evolutional history of the oceanic circulations in the South Atlantic sector of the Southern Ocean. Sedimentary sequences of late Cretaceous and early Paleogene include little and restricted evidence of current activity, attributable to shallow-intermediate depth connections between the developing South Atlantic and Southern Ocean. In contrast, sedimentary sequences of the late Eocene/Oligocene and Neogene reveal a strong history of current-related erosion and deposition. These features exhibit specific water-depth expressions attesting to the long-term activity of different water masses, in stable circulation patterns as those of the present day. We thus suggest that proto-Upper and -Lower Circumpolar Deep Waters have been shaping the bank since the Oligocene. This implies that this bathymetric high has been acting as a barrier for the deep and bottom water masses flowing within the Antarctic Circumpolar Current since its establishment about the Eocene-Oligocene boundary.
Using OpenFOAM for landslide tsunamis modeling and comparison with a 2D depth-integrated model
Authors: Paris Alexandre , Heinrich Philippe , Abadie Stéphane
Published: March 2021

In the literature, OpenFOAM has been used to simulate landslide tsunamis, modeling the landslide as a solid or a two-phase flow. Here we present an approach using three phases (air, water and sediment) modeled as Newtonian fluids. This 3D model is validated against two benchmarks with deformable landslides: one subaerial (Viroulet et al. 2016) and one submarine (Grilli et al. 2017). These benchmarks are also run by a 2D depth-integrated model, AVALANCHE, recently used to reproduce the 2017 Karrat Fjord, Greenland and the 2018 Anak Krakatau, Indonesia events. Both models are able to reproduce either the water waves or the landslide behavior but not both at the same time.

Considering OpenFOAM as a reference code, sensitivity studies on the slope angle, the landslide viscosity and the landslide initial submergence showed that AVALANCHE produces similar results for slope angles between 10 and 45°, for subaerial or close to the surface landslide and/or for low viscosity values. In the other cases (submarine landslides and higher viscosity values) results indicated that OpenFOAM should be preferred to a 2D depth-integrated model.

 

References:

Grilli, S., Shelby, M. & Kimmoun, O. (2017), ‘Modeling coastal tsunami hazard from submarine mass failures: effect of slide rheology, experimental validation, and case studies off the US East Coast’, Natural Hazards 86, 353-391.

Viroulet, S., Sauret, A., Kimmoun, O. & Kharif, C. (2016), Tsunami waves generated by cliff collapse: comparison between experiments and triphasic simulations, in E. Pelinovsky & C. Kharif, eds, ‘Extreme Ocean Waves’, Springer International Publishing, Cham, pp. 173-190.
Flow pattern and residence time of conduit flow and diffuse flow in calcareous sandstones (Bohemian Cretaceous Basin, Czech Republic)
Authors: Kůrková Iva , Bruthans Jiří
Published: March 2021

Localities containing karst features were studied in the northwestern part of Bohemian Cretaceous Basin. Namely Turnov area in facies transition between coarse-delta sandstones and marlstones (Jizera Formation, Turonian) and Miskovice area in limestones and sandy limestones - sandstones (Peruc-Korycany Formation, Cenomanian). Evolution of karst conduits is discussed elsewhere (Kůrková et al. 2019).

In both localities, disappearing streams, caves and karst springs with maximum discharge up to 100 L/s were documented. Geology and hydrogeology of this area was studied from many points of view to describe formation of karst conduits and characterize groundwater flow. Tracer tests were performed using NaCl and Na-fluoresceine between sinkholes and springs under various flow rates to evaluate residence times of water in conduits and to describe geometry of conduits. Breatkthrough curves of tracer tests were evaluated by means of Qtracer2 program (Field 2002). Groundwater flow velocity in channels starts at 0.6 km/day during low water levels up to 15 km/day during maximum water levels, the velocity increases logarithmically as a function of discharge. Similar karst conduits probably occur in other parts of Bohemian Cretaceous Basin where lot of large springs can be found.

Mean residence time of difussed flow based on tritium, CFC and SF6 sampled at karst springs is 20 years for 75% of water and 100 years for remaining 25%, based on binary mixing dispersion model. This shows that most of the water drained by karst conduits is infiltrated through the soil and fractured environment with relatively high residence time. Residence times in different types of wells and springs were also measured in whole north-western part of Bohemian Cretaceous Basin. Results indicate long residence times in semi-stagnant zones represented by monitoring wells and short residence times in preferential zones represented by springs and water-supply wells.

 

Research was funded by the Czech Science Foundation (GA CR No. 19-14082S), Czech Geological Survey – internal project 310250

 

Field M. (2002): The QTRACER2 program for Tracer Breakthrough Curve Analysis for Tracer Tests in Karstic Aquifers and Other hydrologic Systems. – U.S. Environmental protection agency hypertext multimedia publication in the Internet at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54930.

Kůrková I., Bruthans J., Balák F., Slavík M., Schweigstillová J., Bruthansová J., Mikuš P., Grundloch J. (2019): Factors controlling evolution of karst conduits in sandy limestone and calcareous sandstone (Turnov area, Czech Republic). Journal of Hydrology: 574: 1062-1073
Why and how does CDGP limit access to some deep geothermal data
Authors: Turlure Mathieu , Schaming Marc , Schmittbuhl Jean , Grunberg Marc
Published: March 2021

The Data Centre for Deep Geothermal Energy (CDGP – Centre de Données de Géothermie Profonde, https://cdgp.u-strasbg.fr) was launched in 2016 by the LabEx G-EAU-THERMIE PROFONDE - now ITI GeoT, https://iti-geot.unistra.fr/ - to preserve, archive and distribute data acquired on geothermal sites in Alsace. Since the beginning of the project, specific procedures are followed to respect international requirements for data management. In particular, FAIR recommendations are used to distribute Findable, Accessible, Interoperable and Reusable data “As Open as Possible, as Closed as Necessary”.

CDGP distributes data originating from academic institutions as well as industrial partners. The former are obviously open and disseminated without restriction, to fulfil Open Science requirements. The latter are nevertheless less opened, depending on the access restrictions given by the data owner. Up to now, the industrial data may be open, restricted to academic, distributed case-by-case (after owner’s agreement), or closed. Metadata are fully open. The access rights are also pushed to the EPOS TCS-AH platform (https://tcs.ah-epos.eu).

CDGP implemented an Authentication, Authorization and Accounting Infrastructure (AAAI) to handle the distribution rules. Business category is verified at least for academics to grant access. Datasets are provided (or denied) automatically if possible. If necessary, the user’s request is forwarded to the provider who can accept or disallow access. Reports listing datasets distributed to users are sent to providers every six months. This AAAI is build to earn and keep data providers’ trust, as well as to publicized data.

CDGP is trying to broaden the number of open datasets. There are questions on access restrictions to some vintage industrial data of Soultz-sous-Forêts, since some of them where acquired with public European funding. Also, industrial data from Vendenheim area where several felt earthquakes occurred (2019, 2020), currently not available, may become partly accessible since some exploration was done for “scientific purpose” and that expertise studies are required to understand the induced seismicity.
How important is accounting for serial correlation and field significance in trend detection of extreme rainfall occurrences? 
Authors: Farris Stefano , Deidda Roberto , Viola Francesco , Mascaro Giuseppe
Published: March 2021

A number of studies have shown that the ability of statistical tests to detect trends in hydrologic extremes is negatively affected by (i) the presence of autocorrelation in the time series, and (ii) field significance. Here, we investigate these two issues and evaluate the power of several trend tests using time series of frequencies (or counts) of precipitation extremes from long-term (100 years) precipitation records of 1087 gauges of the Global Historical Climate Network database. For this aim, we design several Monte Carlo experiments based on simulations of random count time series with different levels of autocorrelation and trend. We find the following. (1) The observed records are consistent with the hypothesis of autocorrelation induced by the presence of trends, indicating that the existence of serial correlation does not significantly affect trend detection. (2) Tests based on the linear and Poisson regressions are more powerful that nonparametric tests, such as Mann Kendall. (3) Accounting for field significance improves the interpretation of the results by limiting the rejection of the false null hypothesis. We then use these results to investigate the presence of trends in the observed records. We find that, depending on the quantiles used to define the frequency of precipitation extremes, 34-47% of the selected gages exhibit a statistically significant trend, of which 70-80% are positive and located mainly in United States and Northern Europe. The significant negative trends are mostly located in Southern Australia.
Quantification of soil erosion (using 239+240Pu) on periglacial chronosequences reveals the importance of vegetation cover in soil stabilisation
Authors: Musso Alessandra , Ketterer Michael E. , Greinwald Konrad , Geitner Clemens , Egli Markus
Published: March 2021

High mountainous areas are are strongly shaped by redistribution processes of sediments and soils. Due to the projected climate warming and the continued retreat of glaciers in the 21st century, we can expect the area of newly exposed, highly erodible sediments and soils to increase. While soil and vegetation development is increasingly well understood and quantified, it has rarely been coupled to soil erosion. The aim of this study was to assess how soil erosion rates change with surface age. We investigated two moraine chronosequences in the Swiss Alps which were situated in a siliceous and calcareous lithology and spanned over 30 – 10’000 yrs and 110 – 13’500 yrs, respectively. We used 239+240Pu fallout radionuclides to quantify the average soil erosion rates over the last 60 years and compared them to physico−chemical soil properties and the vegetation coverage. At both chronosequences, the erosion rates were highest in the young soils. The erosion rates decreased markedly after 3−5 ka of soil development to reach a more or less stable situation after 10−14 ka. This decrease  goes hand in hand with the development of a closed vegetation cover. We conclude that depending on the relief and vegetational development, it takes up to at least 10 ka to reach soil stability. The establishment of a closed vegetation cover with dense root networks appears to be the controlling factor in the reduction of soil erodibility in periglacial areas.
Long term changes in the functioning of a karst aquifer under anthropogenic forcing
Authors: Yohann Cousquer , Hervé Jourde
Published: March 2021

A quantitative estimation of the sustainability of groundwater resources is a challenge for water supplies. This study focuses on karstic hydro systems, which provide water resources to a large part of the Mediterranean population. Here, we address the long-term changes in the functioning of the Lez karst aquifer, which has been providing water to the city of Montpellier since the XIXth century.  Before 1965, only the natural overflow of the spring was used, then pumping in the spring, down to -6.50 m below the overflow level of the spring, was performed until 1981. After this date, the management of the water resource consisted in pumping groundwater at a much greater flow rate (up to 2000 l/s) than the natural discharge during low flow (200 l/s), which seasonally generates important drawdowns (down to ~25 m) at regional scale.

The available time series consist in more than 70 years of discharge and water table (with some gaps) that encompass the three kinds of groundwater management, spanning from a passive management to the current active management. The change in water budget terms over time (before and after active management) highlights the modification of transfers and storage in the different karst compartments (epikarst, unsaturated zone, saturated zone), and the climatic variability of precipitation, evapotranspiration at inter-annual. A lumped parameter model was set up in order to simulate spring discharge, while accounting for surface water and grandwater level dynamics, and better assess the changes in the storage dynamics within the different compartments (matrix-conduits) of the karst. A robust parameter estimation, accounting for groundwater discharge and surface water discharge observations, has been conducted using a Monte-Carlo procedure. In order to obtaines a robust model, divers data type such as groundwater flow, surface flow and water level, have been used. [H1]  Once the model was calibrated over (1955-2020) reference period, several prospective management scenarios based on pumping discharge were simulated with an estimation of predictive uncertainty. This allowed evaluating the influence of pumping at large flow rate (active management) on the flux and storage on matrix-conduits exchanges of such karst hydrosystem. A modification on both the discharge rates and the direction of water exchanges between compartments, and especially between matrix and conduits, have been noted. The importance of climatic variability at inter-annual scale on water availability has been discussed as well.
The vaporization behavior of carbon and hydrogen from the early global magma ocean
Authors: Solomatova Natalia , Caracas Razvan
Published: March 2021

Estimating the fluxes and speciation of volatiles during the existence of a global magma ocean is fundamental for understanding the cooling history of the early Earth and for quantifying the volatile budget of the present day. Using first-principles molecular dynamics, we predict the vaporization rate of carbon and hydrogen at the interface between the magma ocean and the hot dense atmosphere, just after the Moon-forming impact. The concentration of carbon and the oxidation state of the melts affect the speciation of the vaporized carbon molecules (e.g., the ratio of carbon dioxide to carbon monoxide), but do not appear to affect the overall volatility of carbon. We find that carbon is rapidly devolatilized even under pressure, while hydrogen remains mostly dissolved in the melt during the devolatilization process of carbon. Thus, in the early stages of the global magma ocean, significantly more carbon than hydrogen would have been released into the atmosphere, and it is only after the atmospheric pressure decreased, that much of the hydrogen devolatilized from the melt. At temperatures of 5000 K (and above), we predict that bubbles in the magma ocean contained a significant fraction of silicate vapor, increasing with decreasing depths with the growth of the bubbles, affecting the transport and rheological properties of the magma ocean. As the temperature cooled, the silicate species condensed back into the magma ocean, leaving highly volatile atmophile species, such as CO2 and H2O, as the dominant species in the atmosphere. Due to the greenhouse nature of CO2, its concentration in the atmosphere would have had a considerable effect on the cooling rate of the early Earth.
Analyses of Laser Propagation Noise for TianQin Gravitational Wave Observatory Based on the Global Magnetosphere MHD Simulation
Authors: Wei Su
Published: March 2021

TianQin is a proposed space-borne gravitational wave (GW) observatory composed of three identical satellites orbiting around the geocenter with a distance of 105 km. It aims at detecting GWs in 0.1 mHz – 1 Hz. The detection of GW relies on the high precision measurement of optical path length at 10−12 m level. The dispersion of space plasma can lead to the optical path difference (OPD, ∆l) along the propagation of laser beams between a pair of satellites. Here, we study the OPD noises for TianQin. The Space Weather Modeling Framework is used to simulate the interaction between the Earth magnetosphere and solar wind. From the simulations, we extract the magnetic field and plasma parameters on the orbits of TianQin at four relative positions of the satellite constellation in the Earth magnetosphere. We calculate the OPD noise for single link, Michelson, and Time-Delay Interferometry (TDI) data combinations (α and X). For single link and Michelson interferometer, the maxima of ∆l are on the order of 1 pm. For the TDI combinations, these can be suppressed to about 0.05 pm. The OPD noise of Michelson combination is colored in the concerned frequency range; while the ones for the TDI combinations are roughly white. Furthermore, we calculate the ratio of the equivalent strain of the OPD noise to that of TQ, and find that the OPD noises for the TDI combinations can be neglected in the most sensitive frequency range of f < 0.1 Hz.
Insights into the Red Sea area from magnetic and gravity analysis
Authors: Issachar Ran , Ebbing Jörg , Yixiati Dilixiati , Holzrichter Nils
Published: March 2021

We explore the lithosphere structure of the Red Sea using gravity and magnetic data.

We re-processed marine data form past surveys conducted during the 70’s and the 80’s, available at the NGDC database. By correcting the magnetic measurements according to the DGRF (definitive magnetic reference field), leveling and replacing the long wavelengths with satellite data (LCS1 model) we managed to generate a consistent magnetic anomaly map for the entire length of the Red Sea that is composed of 10 different surveys and contain overs 100,000 measuring points. The magnetic anomaly map highlights structural differences between the southern, central and northern parts of the Red Sea.

Using forward gravity approach, constrains from seismic, wells and petrophysical data, and by integrating insights from magnetic analysis, we define the lithospheric model of the Red Sea to address key questions regarding rifting, sea floor spreading and transition processes.  For example, the southern parts of the Red Sea are characterized by shallow and wide asthenosphere upwelling, while in the axial trough lithosphere is thin with thicknesses of less than 15 km. The lithosphere thickness increase asymmetrically towards the rift shoulders. In general, the lithosphere is thicker on the eastern sides than on the western sides. In the central parts of the Red Sea, the lithosphere structure is not significantly different from the southern parts, however, asthenosphere upwelling is slightly narrower. In northern parts of the Red Sea asthenosphere upwelling significantly narrows and focused mainly beneath the axial trough and the lithosphere is thicker. This architecture reflects the currently transition from continental rifting (in the north) to oceanic seafloor spreading (in the south) in the Red Sea.
Geophysical investigations of medieval paintings at St. Petri Cathedral Schleswig (Germany) with georadar and thermography
Authors: Esel Yunus , Erkul Ercan , Schulte-Kortnack Detlef , Leonhardt Christian , Meier Thomas
Published: March 2021

The preservation of culturally significant buildings is challenging due to the variety of historical building materials, the often complex building history and damage patterns. It is usually associated with high financial costs. Non-destructive testing may help to plan, optimize, and monitor conservation measures. Here, we report on non-destructive testing of moisture distribution at the Cathedral St. Petri in Schleswig (Germany) using thermography and georadar measurements.  These methods are standard methods in engineering geology and construction. In the field of heritage conservation, however, the application and especially the combination of several of these methods is not yet established.

The walls of the ‘Schwahl’ (a three-sided cloister) show medieval paintings from the 14th century. In the Schwahl, large-scale alterations occur due to gypsum deposits and a shellac coating.   Active thermography measurements were taken before and after test treatments to evaluate the effectiveness of the use of different solvents to remove the shellac and the gypsum deposits. Passive thermography and georadar measurements indicate increased moisture content in the area of the gypsum deposits likely caused by a permeable horizontal sealing barrier below the paintings. Examples of the measurements are shown and the processing of the thermography and georadar measurements including the attenuation analysis are discussed.
Higher order schemes in time for the surface quasi-geostrophic system under location uncertainty
Authors: Fiorini Camilla , Li Long , Mémin Étienne
Published: March 2021

In this work we consider the surface quasi-geostrophic (SQG) system under location uncertainty (LU) and propose a Milstein-type scheme for these equations. The LU framework, first introduced in [1], is based on the decomposition of the Lagrangian velocity into two components: a large-scale smooth component and a small-scale stochastic one. This decomposition leads to a stochastic transport operator, and one can, in turn, derive the stochastic LU version of every classical fluid-dynamics system. 

    SQG is a simple 2D oceanic model with one partial differential equation, which models the stochastic transport of the buoyancy, and an operator which relies the velocity and the buoyancy.

    For this kinds of equations, the Euler-Maruyama scheme converges with weak order 1 and strong order 0.5. Our aim is to develop higher order schemes in time: the first step is to consider Milstein scheme, which improves the strong convergence to the order 1. To do this, it is necessary to simulate or estimate the Lévy area [2].

    We show with some numerical results how the Milstein scheme is able to capture some of the smaller structures of the dynamic even at a poor resolution. 

References

[1] E. Mémin. Fluid flow dynamics under location uncertainty. Geophysical & Astrophysical Fluid Dynamics, 108.2 (2014): 119-146. 

[2] J. Foster, T. Lyons and H. Oberhauser. An optimal polynomial approximation of Brownian motion. SIAM Journal on Numerical Analysis 58.3 (2020): 1393-1421.
An Unsupervised Machine Learning Pipeline to study the shape of  solar WINQSEs  
Authors: Alam Ujjaini , Bawaji Shabbir , Mondal Surajit , Oberoi Divya
Published: March 2021

The perplexing mystery of what maintains the solar coronal temperature at about a million K, while the visible disc of the Sun is only at 5800 K, has been a long standing problem in solar physics. A recent study by Mondal et al. (2020, ApJ, 895, L39)  has provided the first evidence for the presence of numerous ubiquitous impulsive emissions at low radio frequencies from the quiet sun regions, which could hold the key to solving this mystery. These Weak Impulsive Narrowband Quiet Sun Emissions (WINQSEs) occur at rates of about five hundred events per minute, and their strength is only a few percent of the background steady emission. Based on earlier work with events of larger flux densities and theoretical considerations, WINQSEs are expected to be compact in the image plane. To characterise the spatial structure of WINQSEs, we have developed a pipeline based on an unsupervised machine learning approach. We first identify the boundaries of the radio sun using edge detection techniques, and detect peaks within the solar boundary. Density-Based Spatial Clustering of Application with Noise (DBSCAN), an unsupervised machine learning algorithm, is used to classify the peaks as isolated or clustered. It is also used to find the optimal hyper-parameters for peak-fitting. The peaks are then fit with Gaussian models, and statistical and heuristic filtering criteria are used to obtain robust fits for a subset of these WINQSEs . We find that the vast majority of WINQSEs can be described by well behaved compact Gaussians. By its very design, this approach is focused on morphological characterisation of these weak features and is better suited for identifying them than earlier attempts. We present here our first results of the observed distributions of intensities, sizes and axial ratios of the Gaussian models for WINQSEs arrived at from analysis of multiple independent datasets.
Using hillslope-scale groundwater model to bridge the gap between basin inputs and river concentrations. The case of nitrates in Brittany (France).
Authors: Guillaumot Luca , Aquilina Luc , de Dreuzy Jean-Raynald , Marçais Jean , Durand Patrick
Published: March 2021

Over the past decades, intensive agriculture has altered surface water and groundwater resources quality. Nutrient surplus increased nitrate concentrations in groundwater and rivers resulting in eutrophication or drinking water risk having ecosystem, sanitary and economic repercussions. Legislations led to a reduction of agricultural inputs of nitrogen since 1990’s followed by a decrease of nitrate concentrations in rivers, but still difficult to predict and evaluate. Indeed, the incomplete knowledge of the spatial variability of climate and nitrogen inputs, cumulated to the unknown groundwater heterogeneity,  leads to hydrological and biogeochemical processes difficult to model. This study deals with the long-term variations (~decades) of nitrate concentrations in three rivers (~30 km² catchment) located in Brittany. Thus, we focus on groundwater modelling because they constitute the bigger hydrological reservoir. We developed a parsimonious equivalent hillslope-scale groundwater model. The model parameterization, which controls hydrological functioning such as mean groundwater residence times, young water contribution to the river or denitrification, relies on long-term monitored streamflow and nitrate river concentrations. In addition, dissolved CFC were sampled in the catchments. Finally, we found that uncertainty on simulated nitrate river concentrations is low. The physically-based model also brings information on temporal and spatial variability of groundwater residence times highlighting the relative importance of young (1-5 yr) and old waters (~decades) for nitrate river concentrations. Moreover, calibrated models show similar trends looking at two fictive input scenarios from 2015 to 2050.
Automatic Recognition of the Lighting Whistler waves from the Wave Data of SCM Boarded on ZH-1 satellite
Authors: Yuan Jing , Wang Zijie , Yang Dehe , Wang Qiao , Zima Zeren , Han Ying , Zhou Le , Shen Xuhui , Guo Qihang
Published: March 2021

Lightning whistlers, found frequently in electromagnetic satellite observation, are the important tool to study electromagnetic environment of the earth space. With the increasing data from electromagnetic satellites, a considerable amount of time and human efforts are needed to detect lightning whistlers from these tremendous data. In recent years, algorithms for lightning whistlers automatic detection have been conducted. However, these methods can only work in the time-frequency profile (image) of the electromagnetic satellites data with two major limitations: vast storage memory for the time-frequency profile (image) and expensive computation for employing the methods to detect automatically the whistler from the time-frequency profile. These limitations hinder the methods work efficiently on ZH-1 satellite. To overcome the limitations and realize the real-time whistler detection automatically on board satellite, we propose a novel algorithm for detecting lightning whistler from the original observed data without transforming it to the time-frequency profile (image).

The motivation is that the frequency of lightning whistler is in the audio frequency range. It encourages us to utilize the speech recognition techniques to recognize the whistler in the original data \of SCM VLF Boarded on ZH-1. Firstly, we averagely move a 0.16 seconds window on the original data to obtain the patch data as the audio clip. Secondly, we extract the Mel-frequency cepstral coefficients (MFCCs) of the patch data as a type of cepstral representation of the audio clip. Thirdly, the MFCCs are input to the Long Short-Term Memory (LSTM) recurrent neutral networks to classification. To evaluate the proposed method, we construct the dataset composed of 10000 segments of SCM wave data observed from ZH-1 satellite(5000 segments which involving whistler and 5000 segments without any whistler). The proposed method can achieve 84% accuracy, 87% in recall, 85.6% in F1score.Furthermore, it can save more than 126.7MB and 0.82 seconds compared to the method employing the YOLOv3 neutral network for detecting whistler on each time-frequency profile.

 

Key words: ZH-1 satellite, SCM,lightning whistler, MFCC, LSTM
Water Productivity; a Sustainable Pathway to Agricultural Extensification and Climate Adaptation?
Authors: Amali Amali A. , Khalifa Muhammad , Ribbe Lars
Published: March 2021

Water Productivity (WP), a pointer to crop performance vis-à-vis consumptive water use, has fevered debates around agricultural water use, away from scheme-based efficiency to field-scale productive value of water, that can be optimised in localities of increasing absolute and relative scarcity. Research on WP sprung from such debates to become a growth industry, that measures irrigation inefficiencies, poised towards developing economies and “low” value uses of water, to justify its reallocation across sectors, sometimes away from agriculture. While water allocation decisions increasingly prioritise sectoral productivity of freshwater resources, burgeoning food security measures to water scarcity adaptation is shifting management decisions from the purview of scheme managers to individual farming units, underscoring the need to parallel WP initiatives with the resilience of local livelihoods. In this study, we analyse the potential contribution of WP as an agricultural extensification mechanism for a water-scarce irrigated region. The Surface Energy Balance Algorithm for Land (SEBAL), is used to estimate evapotranspiration as a proxy for irrigated water consumption. An automated derivative, the pySEBAL model, is used to compute crop biomass combined with satellite-based evapotranspiration to estimate WP across 1680 heterogeneous groundwater irrigated fields in the eastern Azraq basin of Jordan. WP gap was hereafter estimated as the difference between the current field WP, to a selected productivity range, attainable within infrastructural and agroclimatic limits. By investigating the possibility of closing WP gaps, we show that a careful selection of WP thresholds to benchmark localised irrigated water consumption offers the potential to reduce seasonal irrigation water use within a range of 18 to 29% of the current consumption, without adversely affecting crop yield and related livelihoods. Such range (5 – 9 MCM[†]) for a water-scarce Azraq basin, offers substantial relief to groundwater resources, related ecosystems, and long-term catchment sustainability. We additionally demonstrate that this provides a window for agricultural extensification by leveraging farm management practices across irrigated fields. We finally propose entrepreneurial and capacity building opportunities from analysing dynamics in farmers' individual water use behaviour. WP, as a useful indicator for water reallocation under water-scarce conditions, would need to consider equitable utilisation of water resources and the resilience of local livelihoods.

[†] Million Cubic Meters
Turbulence driven by chromospheric evaporations in solar flares
Authors: Ruan Wenzhi , Xia Chun , Keppens Rony
Published: March 2021

Chromospheric evaporations are frequently observed at the footpoints of flare loops in flare events. The evaporations flows driven by thermal conduction or fast electron deposition often have high speed of hundreds km/s. Since the speed of the observed evaporation flows is comparable to the local Alfven speed, it is reasonable to consider the triggering of Kelvin-Helmholtz instabilities. Here we revisit a scenario which stresses the importance of the Kelvin-Helmholtz instability (KHI) proposed by Fang et al. (2016). This scenario suggests that evaporations flows from two footpoints of a flare loop can meet each other at the looptop and produce turbulence there via KHI. The produced KHI turbulence can play important roles in particle accelerations and generation of strong looptop hard X-ray sources. We investigate whether evaporation flows can produce turbulence inside the flare loop with the help of numerical simulation. KHI turbulence is successfully produced in our simulation. The synthesized soft X-ray curve demonstrating a clear quasi-periodic pulsation (QPP) with period of 26 s. The QPP is caused by a locally trapped, fast standing wave that resonates in between KHI vortices.
Replacing Coal with Wind and Solar in South Korea’s electricity system
Authors: Hörsch Jonas , Aboumahboub Tina , Ganti Gaurav , Gidden Matthew , Bir Shrestha Himalaya , Welder Lara , Zimmer Anne
Published: March 2021

South Korea’s current energy system heavily relies on fossil fuels in particular coal-fired generation followed by nuclear. Currently, the country is defining its long-term energy strategy and latest Basic Electric Power Supply and Demand Plan proposes to increase the share of renewable energies to 26% by 2034, while converting most of their older half of coal plants to LNG. However, to be consistent with Paris Agreement compatible pathways, more ambitious coal phase out schedules to retire the entire coal fleet until 2030 are also discussed. We consolidate such a schedule with an expansion plan for wind and solar capacities derived from open-source renewable resource and energy system models.

For the analysis of integrating renewable energies into South Korea’s future energy system, we perform a detailed assessment of the technical potential of renewable energy sources by applying a temporally and spatially resolved modelling. A comprehensive set of geographical constraints and land exclusion factors are applied to derive the suitable area for placement of wind onshore and offshore turbines as well as PV installations. The land eligibility analysis is followed by the simulation of generation profiles from wind turbines and PV units from ERA-5 weather data, deriving the hourly capacity factors and the corresponding levelized cost of electricity for each location.

We optimize the expansion and operation of renewable energies and storage in South Korea’s electricity system for a Paris Agreement compatible coal phase out until 2030. The model chooses from the renewable expansion potentials and their cost characteristics derived in the resource assessment to balance an hourly-resolved demand scenario for each year. Flexibility needs are met with an optimized dispatch of the existing gas power plants and additional short-term and long-term storage capacities. The detailed modelling approach at a high temporal and spatial resolution allows to have a realistic assessment of the power system integration impacts of varying renewable sources and to evaluate the system adaptation needs in terms of required storage capacities.
Multiscale Spatial and Temporal Analysis of the b-value in volcanic areas
Authors: García-Hernández Rubén , D'Auria Luca , Barrancos José , Padilla German D.
Published: March 2021

Determining the b-value of the Gutenberg-Richter law is of great importance in Seismology. However, its estimate is strongly dependent upon selecting a proper temporal and spatial scale due to the multiscale nature of the seismicity. This characteristic is especially relevant in volcanoes where dense clusters of earthquakes often overlap the background seismicity and where this parameter displays a higher spatial and temporal variability.

For this reason, we devised a novel approach called MUST-B (MUltiscale Spatial and Temporal estimation of the B-value) which allows a consistent estimate of the b-value, avoiding subjective “a priori ” choices, by considering simultaneously different temporal or spatial scales. This approach also includes a consistent estimation of the completeness magnitude (Mc) and the uncertainties over both b and Mc. We applied this method to datasets in volcanic areas proving its effectiveness to analyze complex seismicity patterns and its utility in volcanic monitoring and geothermal exploration. Besides, it may provide a way to distinguish seismicity caused by tectonic faults and volcanic sources in zones where there is a mix of both of them.

We present MUST-B applications to three volcanic areas: Long Valley caldera (USA), Tenerife and El Hierro (Canary Islands). The spatial analysis of the b-value in Long Valley shows an impressive chimney-like volume characterized by high b-values which coincide with the main pathway of geothermal fluids inferred by independent studies. For Tenerife, we applied MUST-B to analyze both spatial and temporal variations. The spatial pattern shows an interesting variation between 2004-2005 and the period 2016-2020. In both cases, high b-values appear in an area that hosted increased seismicity because of seismo-volcanic crises. These high b-values are also evidenced by the temporal analysis, which shows an increase in correspondence between these two periods. For El Hierro, we analyzed the seismicity preceding the 2011 submarine eruption of Tagoro volcano using a joint spatio-temporal analysis. Results show high b-values in the area where the vent opened and a drop of this parameter just before the beginning of the eruption.
Saharan dust episodes and giant quartz particles in Iceland
Authors: Varga György , Dagsson-Walhauserová Pavla , Gresina Fruzsina , Helgadottir Agusta
Published: March 2021

Saharan dust has an impact on the atmospheric environment and sedimentary units in distant regions. Although Iceland is located within one of the main atmospheric dust pathways moving towards the Arctic, no evidence of Saharan dust deposition has been provided to date for the region. Here we present the results of fourteen Saharan dust episodes, which were identified in Iceland between 2008 to 2020. Aerosol optical depth data of Terra MODIS, HYSPLIT backward trajectories and numerical simulations of Barcelona Supercomputing Center were used in this work to identify the dust episodes. 
Grain size and shape of the Saharan mineral material deposited in Iceland during two severe deposition events were investigated in detail. Icelandic dust samples from the most active local dust sources were compared with samples of deposited mineral dust from these two severe Saharan dust events to determine their granulometric (complex grain size and shape parameters) and mineralogical characteristics. An automated static optical image analysis technique was applied to thousands of individual particles, and was completed by Raman spectroscopy to identify external quartz particles. 
Saharan dust episodes were associated with enhanced meridional atmospheric flow patterns driven by unusual meandering jets. Strong southerly winds were able to carry large Saharan quartz particles (> 100 µm) towards Iceland. Our results confirm the atmospheric pathways of Saharan dust towards the Arctic, and identify new pathways of giant Saharan dust particles in the study region, including the first evidence of their deposition in Iceland as previously predicted by models.
The support of the National Research, Development, and Innovation Office (projects NKFIH KH130337 and K120620 (for G. Varga)), Czech Science Foundation (project No. 20-06168Y (for P. Dagsson-Waldhauserova)), and COST inDust Action are gratefully acknowledged.
Investigating the Effect of Tropical Cyclones on Atmospheric Chemistry in the Upper Troposphere
Authors: Chutia Lakhima , Bhuyan Pradip , Pathak Binita , Bharali Chandrakala
Published: March 2021

Tropical cyclones (TCs) containing widespread and intense convection, play a dominant role in stratosphere-troposphere exchange (STE) processes in the upper troposphere and lower stratosphere (UTLS) region. Here we examine the variation of meteorological and chemical fields associated with two different pre-monsoon tropical cyclones: MORA and FANI, by combining satellite-based observations from AIRS (The Atmospheric Infrared Sounder ) and different model reanalysis datasets from ERA5 (fifth generation of ECMWF atmospheric reanalyses), CAMS (Copernicus Atmosphere Monitoring Service), MERRA-2 (The Modern-Era Retrospective analysis for Research and Applications, Version 2), and NCEP (National Centers for Environmental Prediction). An increase in the upper-tropospheric ozone (O3) by 15– 30 ppbv is observed over the Bay of Bengal during the high phase of MORA cyclone. Intrusion of O3 from lower stratosphere to upper troposphere is clearly observed from 50 to 300 hPa during the cyclonic period, contributing enhancement in the upper tropospheric O3. There are no such indication of enhanced O3 values before and after the dissipation of MORA cyclone. General behavior of intrusion associated with severe MORA cyclone is well captured by all the models and satellite, however some differences are seen in the intensity and structure of the STE events. Strong updrafts and downdrafts present in the vicinity of tropopause during TC passage weakened the stability of tropopause layer. The low tropopause temperature with enhanced potential vorticity (PV) feature extended vertically downward from lower stratosphere to troposphere confirms the stratosphere to tropospheric intrusion during the cyclonic period. Concurrently, low relative humidity (RH) along with negative RH-O3 correlation during the overhead cyclone further supports the intrusion. Contrarily, satellite and model results revealed no significant variation in O3 mixing ratio in the lower stratosphere down to the tropopause level during the high phase of extremely severe FANI cyclone. Strong convective activity during the passage of FANI confirms the upward propagation of CO rich (O3 poor) air masses from surface to the mid/upper troposphere. The air masses are then trapped by anticyclone around the tropopause levels. This study clearly reveals that tropical cyclones play major role in exchanges of mass and energy between the stratosphere and troposphere (and vice versa) besides being general weather phenomena.
The Climate Response of Heavy Precipitation Events over the Alps and in the Mediterranean
Authors: Müller Sebastian , Pichelli Emanuela , Coppola Erika , Berthou Segolene , Brienen Susanne , Caillaud Cécile , Dobler Andreas , Tölle Merja
Published: March 2021

We here present a climate study on Heavy Precipitation Events (HPEs). To this aim we use an ensemble of convection-permitting regional climate models on a domain that covers the alps and large parts of the Mediterranean. These HPEs are generally meso-scale convective systems, which often are related to a landfall or orographic blocking. For society they are of major interest as they may damage infrastructure and threaten lives through flash floods and strong winds.

From the models' output of precipitation we identify HPEs by applying an well-established clustering and tracking algorithm (MET MTD).

Our study is organized into an evaluation and a climate study part. We evaluate the models by comparison of the evaluation scenario, driven by reanalysis data, against observations. In order to evaluate the tracking algorithm we analyse three specific historic events, occurring in southern France, central Italy and Germany. Eventually we investigate the climate response by comparison of the far future projection (2090-2100) under the rcp85 forcing against the historical scenario (1996-2006).

In regards of the model evaluation we find that the annual cycle is very well captured by model ensemble, although the models overestimate HPEs over orography and underestimated HPEs over flatter terrain.

Concerning the climate response our main result highlights that precipitation associated with HPEs is increasing in the far future, even though total annual precipitation is decreasing. Overall more HPEs occur in the far future, but only for an extended winter season (October to April), while for months May to September the occurrence of HPEs is decreasing. This behaviour motivates us to investigate the annual cycle of HPEs in greater detail.