bluuebunny/crossref_metadata_2025 huggingface dataset:
Schumann resonance intensity as a precursor for warm ENSO episodes
Authors: Satori Gabriella , Bozoki Tamas , Williams Earle , Price Colin , Guha Anirban , Beggan Ciaran , Neska Mariusz , Atkinson Mike
Published: March 2020

Schumann resonances (SR) are the global electromagnetic resonances of the Earth-ionosphere cavity and constitute the extremely low frequency (< 100 Hz) radiation of the worldwide lightning activity (Schumann, 1952). The recording of SR intensity at a few distant SR stations is an efficient tool to monitor the global lightning. We present the variations of SR intensity in the transition months preceding the warm ENSO episodes for the two super El Niño events in 1997/98 and 2015/16 as well as for the two medium size El Niño periods in 2001/02 and 2008/09  based on SR observations at multiple locations.: Nagycenk, Hungary (47.6N, 16.7E);  Hornsund, Svalbard (77.0N, 15.6E);  Eskdalemuir, UK (55.3N, 3.2W);  Alberta, Canada (51.9N, 111.5W);  Boulder Creek, USA (37.2N, 122.1W).

A remarkable increase in SR intensity is documented two-three months before or just at the beginning of El Niño episodes as compared with the SR intensity in the same months of the preceding La Niña (or non-ENSO) phase for all cases studied here. The percentage increase in SR intensity depends on the amplitude of the warm ENSO period, and is consistently higher for the two super El Niño events. The enhanced SR intensity indicates a worldwide response of global lightning activity. Increased atmospheric instability due to the land-ocean thermal interaction during the transition interval could be responsible for the intensification of lightning activity. This systematic behavior may have been overlooked in earlier studies that compared lightning activity in the integrated ‘cold’ and the ‘warm’ phases, but without exploring the transitional variation. Our results suggest that the SR intensity variation on the interannual time scale acts a precursor for the occurrence of warm ENSO episode.
Multi-scale observation of surface temperature on Parco delle Biancane and Sasso Pisano (Italy) sites: from space to proximal measurements
Authors: Silvestri Malvina , Marotta Enrica , Buongiorno Maria Fabrizia , Hulley Glynn , Romaniello Vito , Bellucci Sessa Eliana , Caputo Teresa , Belviso Pasquale , Avvisati Gala , Teggi Sergio , Hook Simon
Published: March 2020

During the field campaign held on June 2018 at Parco delle Biancane and Sasso Pisano areas, near Grosseto (Italy), we have measured the surface temperature using data acquired by different sensors at different spatial resolutions: Earth Observation (EO) data from the ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS), Hyperspectral Thermal Emission Spectrometer (HyTES) airborne imaging data and thermal images acquired by the FlyBit drone. ECOSTRESS has five spectral bands in the range 8-12.5 μm and pixel size resolution (at nadir) of 69x38 m (2 pixels in cross track and 1 pixel in down track); HyTES is an airborne imaging spectrometer having 256 spectral channels in the range 7.5-12 μm and high spatial resolution (0.8 m for the June campaign); VUE PRO-R mounted on FlyBit drone acquires in the range 7.5-13.5 µm with a spatial resolution depending on the flight altitude (in this work the pixel size is about 0.25 m). In addition, the Sony Alpha 600 visible camera was mounted on the FlyBit drone to acquire a very high resolution optical images over the test site. Our goal is to test the possibility to integrate data at different observation scales and to use the proximal measurements to better understand the thermal structure of test sites, also related to the area morphology and to validate the methodology for estimating the surface temperature by using EO data.
Constraint of active deformation and transpression tectonics along the plate boundary in North Africa
Authors: Meghraoui Mustapha , Masson Frederic , Bahrouni Nejib , Tahayt Abdelilah , Saleh Mohamed , Kahlouche Salem
Published: March 2020

The Maghrebian tectonic domain in North Africa is here examined in the light of the recent GPS and seismotectonic results. The region includes the plate boundary in the western Mediterranean previously characterized by transpression and block rotation. The crustal deformation is documented along the Atlas Mountains in terms of the displacement field, with strain partitioning largely controlled by plate motions. The tectonic and seismotectonic analysis is based on our published data on shortening directions of Quaternary faulting and folding compared with present-day seismotectonic characteristics (earthquake moment tensors) of significant seismic events that allow an estimate of local and regional deformation rates in North Africa. Shortening directions oriented NE-SW to NW-SE for the Pliocene and Quaternary, respectively, and the S shape of the Quaternary anticline axes are in agreement with the 2°/Myr to 4°/Myr clockwise rotation obtained from paleomagnetic results on small tectonic blocks in the Tell Atlas. The continuous GPS data and results are obtained from the network in Morocco operative 1999 to 2006, the REGAT network in Algeria since 2007, and the network in Tunisia with data collected from 2014 to 2018. In addition, we add the most recent GPS results in southern Spain and southern Italy. The NW-SE to NNW-SSE 5 ±1.5 mm/yr convergence velocity and strain distribution of the Maghrebian tectonic domain is controlled by crustal block tectonics driven by E-W trending right-lateral faulting and NE-SW thrust-related folding. The correlation between the active transpression tectonic structures and velocity field shows a geodynamic framework consistent with the oblique plate convergence of Africa towards Eurasia. 
Internal Structure of Venere Mud Volcano in the Crotone Forearc Basin, Calabrian Arc, Italy, from Multibeam Bathymetry, Wide-Angle and Multichannel Seismic Data
Authors: Riedel Michael , Krabbenhoeft Anne , Papenberg Cord , Bialas Joerg , Bohrmann Gerhard , Ceramicola Silvia
Published: March 2020

Mud volcanoes (MVs) have been found in various geological settings on passive and active margins but are mostly known from collision zones on Earth. Mud volcanoes are well known to occur on land (e.g. in Azerbaijan), where at least 1000 MVs have been counted. The amount of submarine MVs is believed to be much larger and recent improvements in seafloor mapping led to the discovery of many MVs in all oceans. To contribute to the knowledge of submarine MVs, in particular the internal structure across Venere MV, we conducted a multi-geophysical imaging approach using high resolution multibeam bathymetry, (constraining seafloor expressions), multichannel, and wide-angle seismic data (constraining the internal structure and P-wave velocity distribution). Venere MV is located at the southern rim of the Crotone forearc basin of the Calabrian arc, offshore southern Italy, in a water depth of ~1500 m. The dimension of Venere MV from its bathymetric expression is ~10 km in the EW- and ~7 km in the NS-direction. Two circular cones of ~100 m elevation and ~1.5 km diameter are located in the center of Venere MV. The upper 200 m below the seafloor (bsf) consist of layers with seismic P-wave velocities gradually increasing from 1.53 to 1.7 km/s (sub-) parallel to the seafloor. A prominent reflection ~200 m bsf and a sudden increase of seismic P-wave velocities from 1.7 to 1.8 km/s mark a change with depth in the internal structure, where reflections dip, and seismic P-wave velocities laterally decrease towards the center of Venere MV. The MCS as well as seismic P-wave velocity structure indicate two separate feeder conduits of the two center cones of Venere MV. However, we do not map the roots of the MV, which are at depths beyond our data resolution. Reduced reflectivity occurs ~4 km across the center of the MV 200 m bsf and downwards. We mapped the chaotic reflections of the acoustic basement in depths varying from 500 m to 800 m bsf. Reduced reflectivity of the acoustic basement occurs beneath the center of the MV as well. Mapping of the fault system leads to the subseafloor dimension of Venere MV that exceeds its seafloor dimension by the factor of two.
Wheat yield as influenced by urea applied with nitrification inhibitor and gibberellic acid
Authors: Mirkhani Rayehe , Shorafa Mehdi , Zaman Mohammad
Published: March 2020

Among the essential plant nutrients, nitrogen (N) is the most needed. Farmer apply N fertilizer, predominantly urea to meet crop N demand. However, a greater proportion of the applied urea-N is not being used by plants and lost to the atmosphere as ammonia or greenhouse gases. Therefore, it is necessary to enhance N use efficiency (NUE) of applied urea by minimizing such losses, which has environmental and economic implications. Nitrification inhibitor, such as nitrapyrin (NP), has the most potential to minimise N losses and enhance crop yield. Similarly, plant hormones, such as GA3, has the potential to reduce abiotic stress and improve plant growth and yield.   
A field experiment was established on an arable site at University of Tehran, Karaj to determine the effect of urea applied with Nitrapyrin and GA3 on wheat yield in 2018-2019. Karaj has a Mediterranean climate with annual precipitation of 265 mm. A randomized complete block design in five replications was used in this study. Treatments were: T1 (control treatment - without urea), T2 (farmers practice - 138 kg N/ha), and T3 (best practice - 138 kg N/ha+NP+GA3). Urea was applied in three split applications (46 kg N/ha) at growth stage (GS 21) or tillering, (GS 32) or stem elongation, and (GS 40) or booting. GA3 in T3 treatment, was applied only at stem elongation stage. 
The crop yield data showed that, urea applied with NP and GA3 had a significant (p ≤ 0.01) effect on grain yield, biological yield, number of grains, 1000-grain weight and % Harvest Index (%HI) compared to other treatments. Urea applied with NP and GA3 increased grain yield (10.30 t ha-1) by 13.9% and 46.1% compared to farmer practices (9.04 t ha-1) and control treatment (7.05 t ha-1). These results suggest that co-application of urea with NP and GA3 has the potential to enhance wheat yield in semi-arid area of Iran.
Revision of the Alboran sea Tortonian-Pliocene record: possible new insights on Mediterranean-Atlantic connectivity during the Messinian Salinity Crises
Authors: Bulian Francesca , Sierro Francisco J.
Published: March 2020

In August of 1970, during Mediterranean Sea Leg 13, when the Glomar challenger ventured Mediterranean waters, nobody was expecting to run into one of the most exiting scientific discoveries regarding the Mediterranean Sea evolution. Cores and seismic surveys made possible the discovery of a basin-wide Messinian evaporitic deposit buried beneath the deep-sea Pliocene sediments which was attributed to the Messinian Salinity Crises (MSC) already known and studied in onshore outcrops in the Apennines. Now, 50 years later the debate regarding the conditions and timing of the deposition of this salt giant is still ongoing as many theories are still open and in search for validating proof.

One of the main open questions certainly regards the base level drop during the MSC and the location, efficiency and dynamics of the Mediterranean – Atlantic connectivity. The Mediterranean level is thought to have dropped somewhere between a moderate 200 m up to an extreme high amplitude oscillation of 1500 m while according to different schools of thought the watergate to the Atlantic is considered as completely closed, intermittently open or to have been always open during the MSC. Gibraltar strait is the main candidate for a possible gateway during this time interval (5.96-5.33 Ma) as well as the leading cause of the re-establishment of open marine conditions in the Mediterranean. Consequently, understanding its evolution and opening is fundamental to endorse any of the MSC theories and a thorough investigation of the Messinian and early Pliocene sedimentological record of basins in its proximity is highly needed.

In this optic, the Alboran Sea is the place where many of those answers lie and its worth of further exploration. In the hope of a new oceanographic expedition in the near future, an effort should be made towards gathering and re-interpreting all the available data. We propose a refined planktonic foraminifer chronology of the Alboran DSDP and ODP sites 976B, 121 and 978A with a careful characterization of the main MSC facies that will clarify to a certain extent the MSC expression and the degree of Atlantic water influence in the Alboran basin.

 
A pan-European GIS focused on gas hydrates: a research base-line in geohazards and geological storage of CO2
Authors: Leon Ricardo , Rochelle Christopher , Burnol André , Gimenez-Moreno Carmen Julia , Nielsen Tove , Hopper John , Reguera Isabel , Mata Pilar , Stewart Margaret , Cervel Silvia
Published: March 2020

Abstract

A pan-European GIS focused on hydrate has been developed within the frame of the GARAH project (GeoERA - GeoE.171.002) in order to assess gas hydrate information gaps in the European margins. A data-collection exercise from public sources (MIGRATE and PERGAMON COST actions ES1405 and ES0902, SeaDataNet, NOAA, etc) and European Geological Surveys (BGS, BRGM, IGME, GEUS, etc) has supplied a total of 835 information layers. All this information has been structured in four groups ((i) Geological & Geochemical evidences/indicators, (ii) Geophysical indicators, (iii) Fluid flow seabed indicators and (iv) Oceanographic variables & Geological constrains) where tables and geospatial features have been designed and harmonized following the standards of INSPIRE directives.

This GIS-database has been conceived as a first step or base-line for future gas hydrate related research. The next step as part of 'Work Package 3' of the GARAH project will be the identification of critical knowledge gaps and the definition of specific areas of interest which would benefit from further research. Theses potential future projects could be related to improving the European model of the gas hydrate stability zone (GHSZ), assess potential geohazards and risks, assess the abundance of sediment-hosted gas hydrates, and evaluate the role of CO2-rich hydrates for the geological storage of CO2.

 

Acknowledgment

GARAH project. GeoERA - GeoE.171.002

 
Combining geophysical and petrological estimates of the thermal structure of southern Tibet
Authors: Craig Tim , Kelemen Peter , Hacker Bradley , Copley Alex
Published: March 2020

The thermal structure of the Tibetan plateau remains largely unknown. Numerous avenues, both geophysical and petrological, provide fragmentary pressure/temperature information, both at the present, and on the evolution of the thermal structure over the recent past. However, these individual constraints have proven hard to reconcile with each other. This study presents a series of models for the simple underthrusting of India beneath southern Tibet that are capable of matching all available constraints on its thermal structure, both at the present day and since the Miocene. Three consistent features to such models emerge: (i) present day geophysical observations require the presence of relatively cold underthrust Indian lithosphere beneath southern Tibet; (ii) geochemical constraints require the removal of Indian mantle from beneath southern Tibet at some point during the early Miocene, although the mechanism of this removal, and whether it includes the removal of any crustal material is not constrained by our models; and (iii) the combination of the southern extent of Miocene mantle-derived magmatism and the present-day geophysical structure and earthquake distribution of southern Tibet require that the time-averaged rate of underthrusting of India relative to central Tibet since the middle Miocene has been faster than it is at present.
Atlantic Warm Pool: climate variability, thermal ocean-atmosphere interactions and remote response to ENSO and NAO.
Authors: Povea Perez Yoania
Published: March 2020

The Atlantic Warm Pool (AWP) is a big body of warm water with SST greater or equal to 28.5◦ C, that appears in the Gulf of Mexico, the Caribbean and the western tropical North Atlantic and it is a key element of the climate system. Previous studies have focused on climate variability within the AWP, but did not take into account the distinctive properties of AWP sub-regions. In other cases, obtained results had not been tested against selected databases. This work will try to deal systematically with these limitations. Ocean reanalysis databases have been used in order to detect AWP climate variability, mechanisms through which thermal component of ocean-atmosphere interactions operates and the effect of remote phenomena such as El Niño-Southern Oscillation (ENSO) and North Atlantic Oscillation (NAO).  Empirical Orthogonal Functions, spectral analysis, linear correlation and composites analysis techniques have been used. A large portion of AWP variability comes from Caribbean Sea and Gulf of Mexico while North tropical Atlantic contains a large internal variability. The thermal component of ocean-atmosphere interactions appears partitioned in Gulf of Mexico and Atlantic from Caribbean Sea. SST/latent heat feedback mechanism operates not globally in the AWP but stronger in the open Atlantic sub-region. ENSO+ enhances AWP development, while ENSO- is opposite to both development and decay of AWP. NAO effect is stronger in its negative phase by enhancing the AWP decay.
Influence of root fractal dimension on soil shear strength with 3D printing method
Authors: li jun , zhang yan
Published: March 2020

The rapid development of expressway provide convenience for our life. But during the construction and operation, the slope instability is a serious ecological problems which can threat the normal use of the expressway. As slope protection is essential, the ecological slope protection is an environmental friendly method to reinforce the slope stability as the root can make contribution to the soil shear strength. From the macro perspective, the soil reinforced ability of root system is greatly affected by the structure and distribution morphology of plant root system. So it is crucial to study the influence of root distribution characteristics on the soil shear strength. As the structure of plant root has typical fractal feature, fractal dimension which is the most important quantitative parameter is chosen to establish the relationship with the soil strength. Because the structure of the plant roots is very complex and no two roots are identical, it is difficult to find the same root to conduct contrast tests. But at least four tests with different cell pressures are essential to obtain the cohesion and internal friction angel. Thus 3d printing method is a superior choice to ensure each test condition is as same as possible. The purpose of this study is to explore the relationship between the root fractal dimension and soil cohesion, and internal friction angel. In order to reduce the influence of root difference on the triaxial compression test, 3D printing method is applied to make simulative plant roots which can maintain the fractal dimension. So single variable experiment could be guaranteed, the general rule between fractal dimension of root system and soil reinforced ability can be revealed. Four roots of Cynodon dactylon with different fractal dimension were chosen to establish 3D printing model. Corresponding to each fractal dimension, four triaxial compression test were conducted with four cell pressure. The results indicate that both of the cohesion and internal friction rise with the increasing of the fractal dimension, but the influence of fractal dimension on cohesion is slight compared with the influence on the internal friction. That is to say, the root with larger fractal dimension possess better reinforced effect on slope soil by increasing the the internal friction.
Linking direct and continuum fluid flow models for fractured media: The intersection problem
Authors: Kottwitz Maximilian O. , Popov Anton A. , Abe Steffen , Kaus Boris J. P.
Published: March 2020

Finding an adequate bridge between direct and continuum modeling approaches has been the fundamental issue of upscaling fluid flow in rock masses. Typically, numerical simulations of direct fluid flow (e.g. Stokes or Lattice-Boltzmann) in fractured or porous media serve as small-scale building blocks for larger-scale continuum flow simulations (e.g. Darcy). For fractured rock masses, the discrete-fracture-network (DFN) modeling approach is often used as an initial step to upscale flow properties by parameterizing the permeability of each fracture with its hydraulic aperture and solving steady-state flow equations within the fracture system. However, numerical simulations of Stokes flow in small fracture networks (FN) indicate that, depending on the orientation of the applied pressure gradient, fluid flow tends to localize at places where fractures intersect. This effect causes discrepancies between direct and equivalent continuum flow modeling approaches, which ought to be taken into account when modeling flow at the network scale.

In this study, we compare direct flow simulations of small fracture networks to their continuum representation obtained with several techniques in order to find an upscaling approach that takes these intersection effects into account. Direct flow simulations are conducted by solving the Stokes equations in 3D using our open-source finite-difference software LaMEM. Continuum flow simulations are realized with a newly developed parallel finite-element code, which solves fully anisotropic 3D Darcy flow with specific permeability tensors for each voxel. The direct flow simulations serve as benchmarks to optimize the continuum flow models by comparing resulting permeabilities. We tested two different schemes to generate the equivalent continuum representation: 

(1) Fully resolved isotropic permeability discretizations (fracture permeability is obtained from a refined cubic law) where voxel sizes are a fraction of the minimal hydraulic aperture of the FN or

(2) coarse anisotropic permeability discretizations (permeability tensors are rotated according to fracture orientation) with voxel sizes larger than the minimal hydraulic aperture of the FN.

We then assess different scenarios to incorporate the intersection effects by adding, averaging and/or multiplying the permeabilities of the intersecting fractures within intersection voxels. Preliminary results for scheme 1 suggest that a simple addition of both intersecting fracture permeabilities delivers the best fit to the results of the direct flow simulations, if the voxel size is about 68% of the minimal hydraulic aperture. Scheme 2 systematically underestimates the direct flow permeabilities by about 26%.
Factors controlling fracture distribution within a carbonate-hosted relay ramp: insights from the Tre Monti fault (Central Apennines)
Authors: Mercuri Marco , Carminati Eugenio , Tartarello Maria Chiara , Brandano Marco , Mazzanti Paolo , Brunetti Alessandro , McCaffrey Ken J. W. , Collettini Cristiano
Published: March 2020

Fractures constitute the main pathway for fluids in fault damage zones hosted in low-porosity rocks. Understanding the factors controlling fracture distribution is hence fundamental to better assess fluids circulation in fault damage zones, with evident implications for fault mechanics, hydrogeology and hydrocarbon exploration. Being usually characterized by a strong damage and structural complexity, this is of particularly importance for relay zones.

We integrated classical and modern structural geology techniques to investigate the factors controlling fracture distribution within a portion of a relay ramp damage zone pertaining to the Tre Monti fault (Central Italy). The damage zone is hosted within peritidal carbonates and located at the footwall of the relay ramp front segment. We analysed the distribution of the fracture density in the outcrop through (1) scanlines measured in the field, (2) oriented rock samples, and (3) scan-areas performed on a virtual outcrop model obtained by aerial structure-from-motion.

Our results highlight structural and lithological control on fracture distribution. Scanlines and virtual scan-areas show that fracture density increases with the distance from the front segment of the relay ramp. Moreover, all the methods highlight that supratidal and intertidal carbonate facies exhibit higher fracture density than subtidal limestones.

This apparently anomalous trend of fracture density, that increases moving away from a main fault segment, has two main explanations. (1) The damage is associated with the relay ramp development: approaching the centre of the relay ramp (i.e., moving away from the front segment) an increase in the number of subsidiary faults with their associated damage zones promotes high fracture densities. (2) The increase in fracture density can be attributed to the increasing content in supratidal and intertidal carbonate facies that are more abundant in the centre of the relay ramp.

Our results provide important suggestions for factors controlling fracture distribution and fluid flow within relay ramps hosted by shallow water limestones. We show that the trend of fracture distribution with respect to a main fault is not easily predictable in presence of a relay ramp, because it can be modulated by the subsidiary faults formation and slip during the relay ramp development. Moreover, carbonate facies play a non-negligible role in fracture distribution within fault zones hosted in shallow-water carbonates.
Spatio-temporal analysis of the sediment yield and water turbidity at the right-bank tributaries of the Pripyat River within Ukraine
Authors: Filippova Yuliia
Published: March 2020

Regularities of the river channel processes are closely related to the magnitude and variability of the river load, and the sediment yield, and the sediment yield is one of the principal factors of the riverbed formation. Cycling and dynamics of the sediment yield need to be taken into account when making hydrotechnical calculation, project work and investigating of the riverbed processes. The amount of the river loads, which find their way into the sub-basin of the Pripyat River each year, depends more on the meteorological conditions of the year. That’s why sediment yield and water turbidity are non-permanent from year to year. Since the rivers of the investigated region belong to different hydrological zones and regions, characterized by the uniqueness of water regime, which is caused by the peculiarities of hydrographic and orographic territory indexes, the content of the sediment yield and the amount are also not the same.

The water turbidity at the right-bank tributaries of the Pripyat River, which flow within the Ukrainian Polesie, is not large. The water turbidity of the Turia, Ubort River and Vyzhivka is especially small. In certain years the concentration of sediment yield can be bigger. Much more suspended particles are observed in the Styr, Sluch, and Horyn, the upper catchments of which are strongly cut and partially covered with easily washable sediments. The biggest annual average water turbidity was recorded on the Ikva River. Within the accumulative lowland in the downstream river sections, the right-bank tributaries of the Pripyat River carry cleaner water than in the upstream section since the part of sediment load of the river is build up on the riverbeds and creeks. It occurs as a result of the slope and speed reducing. However, on some right-bank rivers of Pripyat, which flow down from small local terrain uplands with cover of loamy forest and sandy sediments, water turbidity can be quite large.

The estimation of the spatio-temporal dynamics of the sediment load is accomplished by difference integral curves taking into account an average annual water discharge, maximum annual water discharge and also average annual sediment discharge and the biggest annual sediment discharge during the whole period of investigation of current hydrological posts for the right-bank tributaries of the Pripyat River within Ukraine. The analysis of synchronicity and equiphase condition of these oscillations had made it possible to identify general noticeable opposite orientation of the set of curves to the oscillation curve of general sediment load. Constructed graphs show interdependence of maximum annual water discharge, average annual sediment discharge, maximum annual sediment discharge because the sediment discharge has to react to hydraulic fluctuation in the flow.
A New Approach to Clarify Slow Earthquake Source Regions: Multi-band Receiver Function Analysis Including Local Deep-focus Events
Authors: Sawaki Yasunori , Ito Yoshihiro , Ohta Kazuaki , Shibutani Takuo , Iwata Tomotaka
Published: March 2020

Slow earthquakes play important roles in the occurrence of megathrust earthquakes in subduction zones. An increasing number of seismic networks have contributed to significant findings and the detection of slow earthquake activities; however, it is still unclear what sort of seismological structures exhibits each slow earthquake activity. We have developed the multi-band receiver function (RF) method, in which the RFs are composed of different higher-frequency contents. We, here, reveal smaller-scale structures from the RFs from local deep-focus earthquakes around the Philippine Sea plate boundary in Southwestern Japan, where numerous slow earthquakes have been detected (e.g., Obara, 2002; Ito et al., 2007; Nishimura et al., 2013).

Deep-focus earthquakes, frequently occurring in the Pacific slab below Southwestern Japan, can be applicable to the multi-band RF analysis because the local deep events and teleseismic events are similar in the slowness of the first-arrival phases. Local deep-focus events, however, have different variations in back azimuths from teleseismic events, which enables us to estimate seismological structures in a wider range of azimuths by stacking traces from both events. We carefully select the deep-focus events with longer S-P time than 40 sec and exclude triplication phases from mantle transition zones. Here we apply this method to short-period 3-component seismograms of Hi-net (NIED, Japan) in the Northeastern Kii Peninsula, where short-term slow slip events (SSEs) and episodic tremors are very active (e.g., Obara et al., 2010; Nishimura et al., 2013; Yabe & Ide, 2014).

Cross-sections of higher-frequency RFs (up to 2 Hz) show sharp and strong negative phases from the plate interface shallower than 35 km depth, which is one of the most active regions of episodic tremors (Obara et al., 2010). At the deeper portion, the higher-frequency RFs exhibit the mantle wedge structure with obscure phases of the plate interface, where minor and continuous tremor activities have been reported (Obara et al., 2010). These results suggest that episodic tremors accompanied by short-term SSEs occur on the interface between the continental crust and the oceanic crust, whereas the source regions of minor tremors are between the oceanic crust and the mantle wedge as indicated in Kato et al. (2010).
A comprehensive estimate of the global cooling effect from hindering homogeneous ice nucleation under cirrus conditions with CAM5
Authors: Liu Jiaojiao , Shi Xiangjun
Published: March 2020

The warming effect of cirrus clouds is well-known. In recent years, in order to mitigate global warming, cirrus cloud thinning as a newly emerging method of geoengineering has been studied based on climate modeling. Adding a few (~10 L–1) INPs (ice nucleating particles including ice crystals) might hinder homogeneous ice nucleation, which can produce a large number of ice crystals (~1000 L–1), and then reduce cirrus clouds. On the other hand, the cirrus clouds might increase if too much INPs were added. Therefore, the effectiveness of cirrus seeding on cooling our earth is still in debate. In this study, we developed a method (optimal seeding scheme) to calculate the minimum concentration of seeding INPs, which is just enough to prevent homogeneous nucleation from happening. Simulation with the Community Atmosphere Model version 5(CAM5) using the optimal seeding scheme shows a significant cooling effect (–1.4 W/m2), which is equal to two-thirds of the cooling potential (–2.1 W/m2) derived from the pure heterogeneous simulation (i.e., homogeneous ice nucleation is artificially switched off). Seeding fixed 20 L-1 and 200 L-1 concentrations of INPs show the global average radiative effect at –0.5 W m-2 (cooling) and 0.1 W m-2 (warming), respectively. The cooling effect of seeding fixed number concentration of INPs is not obvious, which is consistent with previous studies. Furthermore, using the optimal seeding scheme, the sensitivities of cooling effects to seeding area, ice nucleation parameterizations and homogeneous ice nucleation occurrence frequency are also investigated.
Are human activities main drivers of soil organic carbon losses in mountain rainfed agroecosystems?
Authors: Lizaga Ivan , Gaspar Leticia , Quijano Laura , Ramos Maria Concepción , Navas Ana
Published: March 2020

One of the principal soil degradation problems affecting European agroecosystems is the loss of topsoil by water erosion. In dry climates, soil erosion is led by two main factors, human activities such as agriculture and extreme episodic rainfalls. However, agriculture plays a crucial role in leaving the soils unprotected during part of the year. Thus, extreme rainfall can easily remove the topsoil with the subsequent removal of nutrients in surface soil layers and the reduction of soil quality.

To assess the effects of extreme storms in rainfed agriculture catchments on soil organic carbon removal, surface soil samples from different land uses were collected in a medium-sized catchment at the foot of Santo Domingo range. The study area was mostly cultivated at the beginning of the 19th century but changed to rangeland and afforestation forest in the last 50 years. The remaining cropland area is mostly rainfed agriculture that leaves soils unprotected in periods when erosive storms occur (autumn convective rainfalls). The main land uses are croplands, pine afforestation, scrubland and Mediterranean forest. To track the export of soil organic carbon associated to mobilised sediment occurring under storm events, channel bed sediment samples were collected along the principal streams of the drainage network during regular flow, after a regular storm event, and after an extreme storm event. The contents of soil organic carbon (SOC), SOC fractions and grain size were analysed and compared for the three sampling campaigns.  The results show a gradual decrease of the fine fraction from regular flood samples to samples collected after the extreme event. However, the SOC showed a sharp decrease in the post-extreme event samples, with higher decreases in the active carbon fraction (ACF) than in the stable carbon fraction (SCF).

Our findings highlight the substantial in situ hazards of extreme rainfall events removing soil organic carbon from topsoils and exporting fine sediment and nutrients out of the catchment with important indirect impacts on water resources both quantity and quality.
Land cover change detection in Crete Island, Greece, using different combinations of biophysical indices in change vector analysis
Authors: Polykretis Christos , Grillakis Manolis G. , Alexakis Dimitrios D.
Published: March 2020

Land cover describes the general biophysical state of the surface providing also information about other aspects of the land, such as soils and water. Changes in land cover may have noticeable impact on the ecosystem biodiversity, water resources, climate system and socio-economic sectors. Therefore, the need for detecting these changes is more and more imperative, especially given the emergence of unbalances caused by natural and anthropogenic driving forces like climate change, intensive agriculture and wrong land management decisions. Land cover changes are mainly represented by changes in the biophysical properties of land surface. These properties can be measured by remote sensing-derived indices representing both the vegetation and soil conditions of a given region. In this research effort, by applying a change detection technique like change vector analysis (CVA), the relationship between the dynamic changes in such indices and land cover changes in Crete Island, Greece, was assessed and mapped for the time periods of 1999–2009 and 2009–2019. Vegetation indices such as normalized difference vegetation index (NDVI) and tasseled cap greenness (TCG), and soil indices such as albedo and tasseled cap brightness (TCB), were estimated by Landsat satellite images captured in 1999, 2009 and 2019. Based on two different index combinations (NDVI–albedo and TCG–TCB), CVA produced change results for each of the periods indicating the magnitude and type (direction) of changes, respectively. The most appropriate combination for land cover change detection in the study area was determined by an evaluation process resulting to the estimation of accuracy statistics (kappa index and overall accuracy). Although promising accuracy results were provided for both examined combinations, the change maps produced by the combination of NDVI–albedo were found to be more accurate.

Acknowledgments: This research has received funding from the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology Hellas (GSRT), under Agreement No 651.
Estimating offshore wind power potentials that account for the kinetic energy removal by wind turbines: the Kinetic Energy Budget of the Atmosphere (KEBA) approach
Authors: Kleidon Axel , Miller Lee
Published: March 2020

Offshore wind power is seen as a large renewable energy resource due to the high and continuous wind speeds over the ocean.However, as wind farms expand in scale, wind turbines increasingly remove kinetic energy from the atmospheric flow, reducing wind speeds and expected electricity yields.Here we show that this removal effect of large wind farms and the drop in yields can be estimated in a relatively simple way by considering the kinetic energy budget of the lower atmosphere, which we refer to as the KEBA approach.We first show that KEBA can reproduce the estimated, climatological yields of wind farms of different sizes and locations using previously published numerical model simulations with an explicit wind farm representation.  We then show the relevance of these reductions by evaluating the contribution of offshore wind energy in specific scenarios of Germany’s energy transition in the year 2050.Our estimates suggest that due to reduced wind speeds, mean capacity factors of wind farms are reduced to 33 - 39%, which is notably less than capacity factors above 50% that are commonly assumed in energy scenarios.This reduction is explained by KEBA by the depletion of the horizontal flow of kinetic energy by the wind farms and the low vertical renewal rate, which limits large-scale wind energy potentials to less than 1 W m-2 of surface area.We conclude that wind speed reductions are likely to play a substantial role in the further expansion of offshore wind energy and need to be considered in the planning process.These reduced yields can be estimated by a comparatively simple approach based on budgeting the kinetic energy of the atmosphere surrounding the wind farms.
Hydro-morphodynamics 2D modelling using a discontinuous Galerkin discretisation
Authors: Clare Mariana , Percival James , Kramer Stephan , Angeloudis Athanasios , Cotter Colin , Piggott Matthew
Published: March 2020

The development of morphodynamic models to simulate sediment transport accurately is a challenging and highly complex process given the non-linear and coupled nature of the sediment transport problem. We implement a new depth-averaged coupled hydrodynamic and sediment transport model within the coastal ocean model Thetis, built using the code generating framework Firedrake which facilitates code flexibility and optimisation benefits. To the best of our knowledge, this represents the first full morphodynamic model using a discontinuous Galerkin based finite element discretisation, to include both bedload and suspended sediment transport. We apply our model to problems with non-cohesive sediment and account for effects of gravity and helical flow by adding slope gradient terms and parametrising secondary currents. For validation purposes and to demonstrate model capability, we present results from the common test cases of a migrating trench and a meandering channel comparing against experimental data and the widely used model Telemac-Mascaret.

There is a high degree of uncertainty associated with morphodynamic models, in part due to incomplete knowledge of various physical, empirical and numerical closure related parameters in both the hydrodynamic and morphodynamic solvers. We therefore also present examples of how an adjoint model can be used to calibrate or invert for the values of these parameters from either experimental results or real-world erosion profiles.
Mapping the continent-ocean transition in the Eastern Black Sea Basin
Authors: Minshull Tim , Monteleone Vanessa , Marin Moreno Hector , Shillington Donna
Published: March 2020

The transition from continental to oceanic crust at rifted margins is characterised by changes in a variety of parameters including crustal thickness, basement morphology and magnetisation. Rifted margins also vary significantly in the degree of magmatism that is associated with breakup. The Eastern Black Sea Basin formed by backarc extension in late Cretaceous to early Cenozoic times, by the rotation of Shatsky Ridge relative to the Mid Black Sea High. Wide-angle seismic data show that anomalously thick oceanic crust is present in the southeast of the basin, while further to the northwest the crust is thinner in the centre of the basin. This thinner crust has seismic velocities that are anomalously low for oceanic crust, but is significantly magnetised and has a similar basement morphology to the thicker crust to the southeast. We synthesise constraints from wide-angle seismic data, magnetic anomaly data and new long-offset seismic reflection data into an integrated interpretation of the location and nature of the continent-ocean transition within the basin. Northwest to southeast along the axis of the basin, we infer a series of transitions from mildly stretched continental crust at the Mid Black Sea High to hyper-thinned continental crust, then to thin oceanic crust, and finally to anomalously thick oceanic crust. We explore the geodynamic processes that may have led to this configuration.
Scientific Partnership - a new level of collaboration between environmental scientists and IT specialists
Authors: Frank Anton , Weismüller Jens
Published: March 2020

ICT technologies play an increasing role in almost every aspect of the environmental sciences. The adaption of the new technologies, however, consumes an increasing amount of scientist's time, which they could better spend on their actual research. Not adapting new technologies will lead to biased research, since many researchers are not familiar with the possibilities and methods available through modern technology. This dilemma can only be resolved by close collaboration and scientific partnership between researchers and IT experts. In contrast to traditional IT service provision, IT experts have to understand the scientific problems and methods of the scientists in order to help them to select and adapt suitable services. Furthermore, a sound partnership helps towards good scientific practice, since the IT experts can ensure the reproducibility of the research by professionalizing workflows and applying FAIR data principles. We elaborate on this dilemma with examples from an IT center’s perspective, and sketch a path towards unbiased research and the development of new IT services that are tailored for the scientific community.
Stress test modelling to assess catchment drought resistance and recovery
Authors: Stoelzle Michael , Hellwig Jost , Stahl Kerstin , Weiler Markus , Tijdeman Erik , Menzel Lucas
Published: March 2020

Dry spells and heat waves control the frequency and duration of streamflow drought events. Groundwater storage and release in catchments can modulate their timing and severities in terms of deficit volume and persistence. To better understand the role of recharge and groundwater storage for catchment sensitivity to droughts we investigate the effect of recharge scenarios on streamflow drought characteristics and baseflow for 50 mesoscale catchments with different hydrogeological characteristics in southwestern Germany. In model experiments, we simulate daily recharge on a 1 km resolution with the water balance model TRAIN reflecting the most dominant soil-vegetation processes. Then we calibrate long-term reference simulations, fitting the outflow of different conceptual groundwater box models with varying model structure to hydrograph-separated baseflow. After calibration, we define probabilistic stress tests as scenarios of reduced pre-drought recharge. The tolerance of catchments to different drought intensities is analyzed based on the concepts of resistance, resilience, and recovery to drought situations. Results suggest that catchments with higher resistance and resilience are less sensitive to recharge stress, but recovery is often much slower. However, by comparing the events of e.g. 2003 and 2018 specifically, we show that the sensitivity is also a function of the intensity and duration of the stress test simulation, the drought event characteristics, and the storage memory of catchments. Additionally, the performance ranking of all groundwater models in each catchment allows to link the variability in model structure to catchment properties (e.g. geology). The analysis shows that catchments with short-term or long-term storage memory react differently under different stress tests. Stress test simulations may help to answer planning-relevant questions such as which preconditions make a drought intensification or prolongation more likely and how long does it take for the system to recover to the reference condition. Catchment-specific stress tests with historical worst-case pre-conditions before extreme drought events may thus be a way forward to constrain relevant timescales of drought management and drought early warning.