bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Mesoscale Convective Systems near the Tropical Andes: Insights from Convection-Permitting Simulations of Two Events
Authors: Martinez J. Alejandro , Camacho Juan Carlos , Vasquez Daniel , Espinosa Daniel , Arias Paola A.
Published: March 2021

Mesoscale Convective Systems (MCSs) are associated with an important fraction of total precipitation in the vicinity of the Tropical Andes, and are related to high impact weather events and extreme rainfall.  Important ingredients include input of moisture and synoptic conditions particular of each location, depending on the regional scale circulation and the local topography.  Convection-Permitting (CP) simulations can help to better describe events with MCSs, including details of surface processes, low-level moisture transport and mountain-related circulations. Here we present a description of two MCSs in the vicinity of the Tropical Andes based on gridded observation-based data (ERA5 and GPM), in situ measurements and CP simulations with the Weather Research and Forecasting (WRF) model.  One of the events took place near the Andes-Amazon transition region (Mocoa-Colombia), with, reportedly, more than 100mm of precipitation accumulated in 3 hours in one location, accompanied with strong low-level transport of moisture by the (nocturnal) Orinoco Low-Level Jet (OLLJ) and strong mid-tropospheric easterly winds towards the Andes, favorable for orographic enhancenment of precipitation.  The other event took place over the low-lands of the Magdalena-Cauca basin (Cordoba-Colombia), with an approximate size of 71304 km2 , according to its cloud top temperature pattern.  In this region a sea-breeze provides moisture from oceanic origin, and the nearby Andes might help to enhance low-level convergence via orographic blocking and other mountain-related effects.  Based on kilometer-scale CP simulations we describe details of the initiation and life cycle of these two MCSs as simulated by WRF, including a description of the low-level input of moisture provided by the sea-breeze and the nocturnal jet during the initiation and mature stages, the corresponding mesoscale circulations in the vicinity of the Andes, and the intensity of the simulated precipitation.  Preliminary 3-km simulations of the Mocoa event show the low-level flow blocking by the Andes, the enhanced orographic precipitation, and an underestimation of the maximum intensity of rainfall. This study might help on understanding the skill and limitations of CP simulations for representing weather systems associated to extreme rainfall in the Tropical Andes. 
Development of a new phenological model based on the carbon balance of tree in boreal conifers
Authors: Deslauriers Annie , Carteni Fabrizio , Balducci Lorena , Dupont Alain , Mazzoleni Stefano
Published: March 2021

Traditional phenological models use the concepts of chilling and thermal forcing (temperature sum or degree-days) to predict buds break. Even if new model formulations get more sophisticated with time, the bases of phenological model still rely on the effect of the time of chilling and forcing temperature in interaction, or not, with photoperiod. Because of the increasing impact of climate or other related biotic or abiotic stressors, a model with more biological support is urgently needed in order to accurately predict bud break. We have developed and calibrated a new mechanistic model that is based on the physiological processes taking place before and during budbreak in several conifers species. This model describes the phenology and growth dynamics of a conifer branch as representative of the whole tree. As a general assumption, we assume that phenology will be driven by the carbon status, which is closely related to the annual cycle of dormancy – activity state through the year and to the environmental variables. The carbon balance of a branch was thus modelled i) from autumn to winter–when aboveground parts exhibit cold acclimation and dormancy– and ii) from winter to spring and summer –when deacclimation and growth resumption occurs. After being calibrated in a field experiment, the model was tested across a large area in Québec (Canada), based on observed phenological data. For the 20 field sites in Quebec, the model proved to be accurate in predicting the date of budbreak with an average error of ±3.8 days (R2=0.72). This model also allowed us to better understand the effects of winter and spring temperature on bud burst, offering new simulation perspectives under global warming and insect defoliation.

 
Cenozoic reshaping of the Barents Shelf: Influence of erosion, sedimentation, and glaciation
Authors: Medvedev Sergei , Faleide Jan Inge , Hartz Ebbe
Published: March 2021

Morphology evolution of the Barents Shelf is a key question in understanding how erosion and glaciation reshape the face of the Earth. The Cenozoic history is a subject of a longstanding debate in the Barents realm, in part, due to decades of petroleum exploration in the region. We address here the whole-region study of the influence of a set of mechanisms and factors on the erosion and sedimentation estimations. Several local studies along the edges of the Barents shelf enlighten the relation between sediments accumulated off-shelf and amount of erosion in the adjacent areas. There are only few studies of the entire Barents region but precision of these studies is limited due to uneven distribution of measurements and uncertainties in paleo-conditions. We compare the masses of sediments accumulated along the edges of the Barents shelf with erosion predicted in Henriksen et al. (2011) and estimate that erosion is significantly overestimated. Local corrections to this erosional model do not bring balance close. The major part of the erosional estimate is based on seismic methods and well logs reflecting sedimentary rock’s compaction changes caused by (now partly removed) load from above. This load, however, may be caused not by eroded material alone, but also by ice cap during the glacial cycles. Reduction of erosional estimates by accounting for ice load bring balance between existing erosional model and accumulated sediments close. We also model the glacial erosion using the numerical approach erosion backward in time (Medvedev et al., 2018). The method was modified for this study to account for difference in the lateral length scale of on- and off-shore erosion and flexural isostasy. We compare this erosional model with estimated masses of glacial-induced sediments off-shelf the Barents Sea. The results performed for a range of controlling parameters show that the Barents shelf was mainly submarine at the beginning of glaciation.

Henriksen, E., Bjørnseth, H., Hals, T., Heide, T., Kiryukhina, T., Kløvjan, O., Larssen, G., Ryseth, A., Rønning, K., and Sollid, K., 2011, Uplift and erosion of the greater Barents Sea: impact on prospectivity and petroleum systems. Geological Society, London, Memoirs 35, 271-281.

Medvedev, S., Hartz, E. H., and Faleide, J. I., 2018, Erosion-driven vertical motions of the circum Arctic: Comparative analysis of modern topography. Journal of Geodynamics 119, 62-81.
False Spring over Europe: risk and uncertainties
Authors: Zurita-Milla Raul , Vermeltfoort Rens , Girgin Serkan , Izquierdo-Verdiguier Emma
Published: March 2021

Understanding the impact of the climate crisis on our planet, and hence, on human and natural life, is a pressing but challenging scientific endeavor. Phenological studies help to build such an understanding by analyzing changes in the timing of biological events. Such changes are, in turn, linked to changes in the likelihood of experiencing false springs. Here we examine the risk and uncertainty of false springs over Europe using the extended spring indices models and the E-OBS weather dataset (1950-onwards). False spring uncertainty is evaluated using the full ensemble of 100 daily weather realizations that accompany the E-OBS dataset. Smart computing is used to handle this relatively large amount of gridded data. Our results show that changes in false spring risk are heterogeneous in space, with increasing risks mostly found in the mid-latitudes and decreasing risks mostly found at high and low latitudes. From 1950 until 1979, there was a substantial increase in false spring risk, whereas the change in false spring risk from 1980 onwards is negligible. Our results also show that false spring uncertainty is highest in western Europe. These results highlight the importance of considering temperature uncertainty in phenological modeling, especially when examining the risk of false springs.

 
Improving tree carbon use efficiency for climate-adapted more productive forests (iCUE-Forest)
Authors: Thurner Martin , Beer Christian , Manzoni Stefano , Prokushkin Anatoly , Wang Zhiqiang , Yu Kailiang , Hickler Thomas
Published: March 2021

The rate at which forests take up atmospheric CO2 is critical with regard to their potential to mitigate climate change as well as their value for wood production. The allocation of carbon fixed through photosynthesis into biomass is crucially dependent on tree carbon use efficiency (CUE), which is determined by gross primary production (GPP) and plant respiration (Ra) via the relation CUE=(GPP-Ra)/GPP. The effect of future climate on CUE is unclear due to the unknown response of plant respiration to more severe increases in temperature. This motivates assessing spatial patterns in CUE across climatic gradients with marked temperature variations.  

Within the ”Improving tree carbon use efficiency for climate-adapted more productive forests” (iCUE-Forest) project, we aim to develop novel data-driven estimates of plant respiration, net primary production (NPP=GPP-Ra) and tree CUE covering the northern hemisphere boreal and temperate forests. These will be based on recent satellite-driven maps of tree living biomass, databases of N concentration measurements in tree compartments (leaves, stem/branches, roots) and the relationships between respiration rates and tissue N concentrations and temperature. Such estimates will enable the detection of spatial relationships between CUE and environmental conditions and facilitate the parameterization of dynamic global vegetation models which allow predicting the change in CUE in response to future climate and forest management.

Here we will present an extensive database of N concentration measurements in tree stems/branches and roots that we have compiled in addition to data available mainly for leaves from databases like TRY. More than 5000 measurements have been collected from the literature covering all common boreal and temperate tree species. Currently, we are exploring how the variation in tissue N concentrations is influenced by climate and tree species. Subsequently, we apply the derived tree-level relationships between tissue N concentrations and underlying drivers in combination with tree species distribution maps and estimates of tree compartment biomass based on satellite remote sensing products. In this way, we will derive novel estimates of the spatial distribution of N content in northern boreal and temperate forests that will in turn be used to assess CUE variations.
Estimating the hydrodynamic and morphodynamic characteristics using Entropy theory at the confluence of Negro and Solimões Rivers
Authors: Bahmanpouri Farhad , Barbetta Silvia , Gualtieri Carlo , Ianniruberto Marco , Filizola Naziano , Termini Donatella , Moramarco Tommaso
Published: March 2021

When two mega rivers merge the mixing of two flows results in a highly complex three-dimensional flow structure in an area known as the confluence hydrodynamic zone. In the confluence zone, substantial changes occur to the hydrodynamic and morphodynamic features which are of significant interest for researchers. The conﬂuence of the Negro and Solimões Rivers, as one of the largest river junctions on Earth, is the study area of the present research. During the EU-funded Project “Clim-Amazon” (2011-2015), velocity data were collected using an ADCP vessel operating under high and low flow conditions in different locations at that confluence (Gualtieri et al., 2019). By applying the Entropy theory developed by Chiu (1988) for natural channels and simplified by Moramarco et al. (2014), the two-dimensional velocity distribution, as well as depth-averaged velocity, were calculated at the different transects along the confluence zone, using only the surface velocities observation. The estimated data yielded 6.6% and 6.9% error percentage for the discharge data related to high and low flow conditions, respectively, and 8.4% and 8.3% error percentage for the velocity data related to high and low flow conditions, respectively. Regardless of the flow condition, these preliminary results also suggest the potential points at the confluence zone for the maximum local scouring. The findings of the current research highlighted the potential of Entropy theory to estimate the flow characteristics at the large river’s confluence, just starting from the measure of surface velocities. This is of considerable interest for monitoring high flows using no-contact technology, when ADCP or other contact equipment cannot be used for the safety of operators and risks for equipment loss.

 

Keywords: Amazon River, Negro/Solimões Confluence, Entropy Theory, Velocity Distribution, Local Scouring

References

Gualtieri, C., Ianniruberto, M., Filizola, N. (2019). On the mixing of rivers with a difference in density: the case of the Negro/Solimões confluence, Brazil. Journal of Hydrology, 578(11), November 2019, 124029,

Chiu, C. L. (1988). “Entropy and 2-D velocity distribution in open channels”. Journal of Hydrologic Engineering, ASCE, 114(7), 738-756

Moramarco, T., Saltalippi, C., Singh, V.P. (2004). “Estimation of mean velocity in natural channels based on Chiu’s velocity distribution equation”. Journal of Hydrologic Engineering, ASCE, 9 (1), pp. 42-50
The Solar Energetic Particle Event of March 15 2013 - Characterization of the interplanetary medium conditions 
Authors: Niemela Antonio , Wijsen Nicolas , Rodriguez Luciano , Magdalenic Jasmina , Poedts Stefaan
Published: March 2021

On March 15, 2013, an Earth directed halo CME, associated with an SEP event, was observed. This study aims to characterize the interplanetary medium conditions in which the event propagated, in order to make the first steps towards the validation of the modeling of SEPs employing two recently coupled models, EUHFORIA (EUropean Heliosferic FORcasting Information Asset) and PARADISE (PArticle Radiation Asset Directed at Interplanetary Space Exploration).

The Sun in the days prior and after the event was very active, with several strong flares and coronal mass ejections during this period. The main event was associated with the long duration GOES M1.1 X-ray flare originating from the active region (AR) 11692, located at N11E12. Imagers aboard SOHO and STEREO spacecrafts observed the CME launch at 7:12 UT and the projected line of the sight speed was estimated to be about 1060 km/s. A rise in the $>$10 MeV GOES proton count was observed the following day, with flux exceeding the 1000 pfu threshold, and stayed above it for several days. Another strong CME was launched, within the following hours, towards the west but with a good magnetic connection to Earth's position, which could have accelerated even further the particle population seeded by the main event.

We model the solar wind and its transients CMEs with EUHFORIA, in order to obtain the realistic conditions of the ambient plasma through which the associated particles are propagating. Different spatial and temporal resolutions of the model will be explored to run the newly developed model for energetic protons PARADISE in an optimal environment and make a step towards better SEP predictions.
Morphological effect of ZnO nanoparticles for photocatalytic degradation of azo dyes in water
Authors: Amininejad Sayed , Baumann Thomas , Talebian Nasrin , Amininezhad Seyedeh Matin
Published: March 2021

Discharge of organic dyes from different industries into receiving rivers and natural streams poses serious problems for the environment because of their toxicity. These dyes are not readily biodegradable and therefore, their removal from effluents is urgent. Various methods used for removal of dyes from wastewater, such as coagulation, ﬂocculation, filtration or reverse osmosis are quite expensive and have a low removal efficiency. On the contrary, Advanced oxidation processes (AOPs) using metal oxide semiconductors like ZnO, are capable to operate effectively and efficiently to degrade many dye pollutants.

In this work, ZnO nanoparticles were successfully synthesized via a simple solvothermal method with different solvents. Scanning electron microscopy (SEM) imaging showed that nanoflower, nanorod, and nanosphere ZnO particles were produced when water, 1-hexanol, and ethylene glycol were used as the solvent, respectively. Nanoflower ZnO particles exhibited higher photocatalytic reduction efficiencies under UV light irradiation than nanosphere and nanorod particles. Results suggested a close relationship between the photocatalytic activity and the particle morphology and size which was due to using different solvents in preparation processes. Also, the recovery of ZnO nanoparticles was investigated and samples showed stable photodegradation efficiencies after being reused for three times.
Particle acceleration in 3D current sheets with magnetic islands: energy, density and pitch angle distributions
Authors: Zharkova Valentina , Xia Qian
Published: March 2021

We will overview particle motion in 3D Harris-type RCSs without and with magnetic islands using particle-in-cell (PIC) method considering the plasma feedback to electromagnetic fields. We evaluate particle energy gains and pitch angle distributions (PADs) of accelerated particles of both changes in different locations inside current sheets as seen under the different directions by a virtual spacecraft passing through. The RCS parameters are considered comparable to heliosphere and solar wind conditions. 

The energy gains and the PADs of particles are shown to change depending on a topology of magnetic fields.  We report separation of electrons from ions at acceleeration in current sheets with strong guiding fields  and formation of transit and bounced beams from the particles of the same charge. The  transit particles are shown to form  bi-directional energetic electron beams (strahls), while bounced particles are mainly account from driopout fluxes in the heliosphere. In topologies with weak guding field strahls are mainly present inside the magneticislands and located closely above/below the X-nullpoints in the inflow regions. As the guiding field becomes larger, the regions with bi-directional strahls are compressed towards small areas in the exhausts of current sheets. Mono-directional strahls with PADS along 0 or 180 degrees are found quasi-parallel to the magnetic field lines near the X-nullpoint due to the dominant Fermi-type magnetic curvature drift acceleration. Meanwhile, high-energy electrons confined inside magnetic islands create PADs about 90◦. 
The impact of climate change on swell events significant wave heights from multiple origins
Authors: Lemos Gil , Semedo Alvaro , Hemer Mark , Menendez Melisa , Miranda Pedro
Published: March 2021

Swell waves dominate the ocean surface, propagating across ocean basins, with minor attenuation. Here, a state-of-the-art swell tracking algorithm is applied to a global dynamic ensemble of CMIP5 wave climate simulations, isolating swell events from the remaining local sea state conditions based on the behavior of the peak wave period (Tp) and peak mean wave direction (MWDp). The swell events related significant wave height (Hs) projected changes for the late 21st century, as well as the overall contribution of swells from different origins to the total Hs projections, are then characterized. The propagation of the projected changes, from the overlaying winds (U10) at the wave generation areas, to the swell arrival locations, through swell waves, is also analyzed and quantified. Results indicate that the arriving swells’ Hs projected changes, along the tropical and subtropical latitudes, are highly dependent on the direction of the incoming waves, being mostly compatible with the Hs and U10 projections at the respective wave generation areas, especially when statistical significance is accounted for. Clear implications on sediment transport, coastal accretion and erosion, and offshore infrastructures and navigation arise from the disproportionate flux of energy carried by swell waves in each direction, increasing the need for adequate measures to mitigate its effects, towards the end of the 21st century.
Effective rheology of a two-phase subduction shear zone: insights from numerical simple shear experiments and implications for subduction zone interfaces
Authors: Ioannidi Paraskevi Io , Le Pourhiet Laetitia , Agard Philippe , Angiboust Samuel , Oncken Onno
Published: March 2021

Exhumed subduction shear zones often exhibit block-in-matrix structures comprising strong clasts within a weak matrix (mélanges). Inspired by such observations, we create synthetic models with different proportions of strong clasts and compare them to natural mélange outcrops. We use 2D Finite Element visco-plastic numerical simulations in simple shear kinematic conditions and we determine the effective rheology of a mélange with basaltic blocks embedded within a wet quartzitic matrix. Our models and their structures are scale-independent; this allows for upscaling published field geometries to km-scale models, compatible with large-scale far-field observations. By varying confining pressure, temperature and strain rate we evaluate effective rheological estimates for a natural subduction interface. Deformation and strain localization are affected by the block-in-matrix ratio. In models where both materials deform viscously, the effective dislocation creep parameters (A, n, and Q) vary between the values of the strong and the weak phase. Approaching the frictional-viscous transition, the mélange bulk rheology is effectively viscous creep but in the small scale parts of the blocks are frictional, leading to higher stresses. This results in an effective value of the stress exponent, n, greater than that of both pure phases, as well as an effective viscosity lower than the weak phase. Our effective rheology parameters may be used in large scale geodynamic models, as a proxy for a heterogeneous subduction interface, if an appropriate evolution law for the block concentration of a mélange is given.
How Many Soil Samples Do We Need to Take to Determine Concentrations of Micro- and Nanoplastics in Terrestrial Systems?
Authors: Yu Yingxue , Flury Markus
Published: March 2021

Plastics pollution of terrestrial environments is a global problem, and plastics have been observed even in remote areas. However, how much plastic is present in terrestrial ecosystems is not well known. Here, we present a theoretical framework for representative sampling of randomly distributed plastic particles in soils or sediments. Based on geostatistical analysis, we determined optimal sampling strategies to quantify micro- and nanoplastics in soils or sediments. We used numerical simulations to test the sampling of randomly distributed plastic particles, and determined the sampling support (number of cores or sampling area) needed to obtain plastic concentrations within a specific error. Plastic pollution in the field was numerically simulated by placing plastic particles randomly in two dimensional space. We then took soil samples with differently sized cores, and determined plastic concentration as a function of number of cores taken. We will show how many cores are needed to determine the plastic concentrations within a given error.
Developmental and environmental factors driving xylem anatomy and micro-density
Authors: Deslauriers Annie , Buttò Valentinà , Cartenì Fabrizio , Rossi Sergio , Morin Hubert
Published: March 2021

The current research on the dynamics of tree ring formation in conifers has provided new insights into how rate and duration xylem-cell production and development control the size of the xylem conduits leading to the formation of earlywood and latewood. So far, the physiology behind wood formation processes and the associated kinetics has rarely been considered, leading to the impossibility to grasp the drivers of wood density changes along the tree-rings. Despite the importance of wood density for carbon sequestration and tree hydraulics, little is known about the factors controlling variations in wood density across the tree ring, i.e. micro-density, at the intra-annual scale. We first developed a process-based mechanistic model that simulates the development of conifer tracheids from a simple sugar signal that we discuss together with the main kinetics and environmental variables leading to the formation of micro-density in black spruce, the main conifers species in the boreal forest of Canada. At the beginning of the growing season, low sugar availability in the cambium results in slow wall deposition that allows for a lengthier enlargement time thus producing large cells with thin walls (i.e. earlywood). In late summer and early autumn, high sugar availability produces narrower cells with thick cell walls (i.e. latewood). Wood formation dynamics had an indirect effect on micro-density. Micro-density increased under longer periods of cell wall deposition and shorter durations of enlargement. Cell diameter indirectly affected micro-density via cell wall thickness, which was the most important parameter affecting micro-density. Cell traits experienced the joint action of enlargement and secondary wall deposition in shaping the intra-annual patterns of tree rings. Our results point to the predictive power of a simple sugar signal. During the growing season, the amount of carbon allocated to wood formation largely influences the duration of cell differentiation, thus modulating cell diameter, cell wall thickness and by result tree-ring micro-density.

 
Diachronism as process-inherent part of Pleistocene river terrace formation: First results based on luminescence dating for testing a well-established theoretical concept and possible implications for practical field work
Authors: Kolb Thomas , Fuchs Markus
Published: March 2021

There are two main statements of a long-accepted paradigm of fluvial morphodynamics formalized inter alia by S.A. Schumm: (i) changes in fluvial systems strongly depend on exceeding external and / or internal thresholds ​​and (ii) they are always characterized by a nonlinear and asynchronous character. While the first aspect of this paradigm is part of numerous studies on fluvial morphology and river dynamics, the second aspect has so far tended to be sidelined in practical geomorphology.

With particular respect to the field of paleo-environmental research, this is evident from studies that aim at determining ages of Pleistocene river terraces in order to provide a time frame for the reconstruction of paleo-environmental conditions. Typically, numerical dating approaches are only applied to a single location that is supposed to be exemplary for the respective terrace level. Numerical ages determined for this specific location are then extrapolated and interpreted in a generalizing way to derive "THE age" of the river terrace as a whole.

With respect to the concept of asynchronism of fluvial reactions to environmental changes, such an approach seems problematic. In fact, asynchronism implies different sections of a river showing different and specific reactions to environmental changes at a given point in time. For fluvial terraces, this means that the processes controlling their formation may already have started in some sections of a valley, while in other sections they do not yet have any impact on landscape evolution.

In this contribution, we present luminescence ages of fluvial deposits originating from an Upper Pleistocene river terrace in a small valley located in the headwater of the Main River, Germany. Here, several samples from various locations throughout the river longitudinal course have been analysed. The luminescence ages determined for the lowermost part of the valley are significantly older than those from the middle section, which in turn are older than those from the valley’s upper reaches.

Our results suggest a diachronic alignment of sedimentation ages for fluvial deposits, starting with old ages close the mouth of a river and getting progressively younger for locations approaching the upper reaches. If these findings are confirmed in other fluvial systems and are not only the result of specific local conditions, they will be of great relevance for geomorphological research in fluvial landscapes. As a result, the widespread approach of deriving age estimates for fluvial terraces from numerical results merely determined for a single location appears to be inadequate and should be subjected to a critical review.
Preliminary forecast model of crustal earthquakes in southwest Japan based on GNSS data
Authors: Nishimura Takuya
Published: March 2021

In Japan, the Headquarters for Earthquake Research Promotion has developed a nationwide probabilistic earthquake model called “National Seismic Hazard Maps for Japan” since the destructive 1995 Kobe earthquake. This model covers both subduction and crustal earthquakes based on a history of past large earthquakes from seismological, archaeological, and geological data. The model for crustal earthquakes relies on geological and geomorphological data of active faults and never use geodetic data, whereas contemporary deformation of the Japanese Islands has been observed by a dense GNSS network. Here, we attempt to develop a preliminary forecast model of shallow crustal earthquakes using GNSS velocity data.

We follow the procedure of Shen et al.(2007) to calculate the forecast model. The GNSS velocities at continuous GNSS stations from April 2005 to December 2009 are used for the model in southwest Japan. Elastic deformation due to interplate coupling along the Nankai Trough is removed using the block model of Nishimura et al. (2018). Strain rate field is calculated at a grid point of 0.2º x 0.2º by a method of Shen et al (1994). The strain rates are converted to geodetic moment rates by a formula proposed in Savage and Simpson (1997). The thickness of a seismogenic layer, rigidity, b value of the Gutenberg-Richter law, and magnitude of the maximum earthquake are assumed to be 12 km, 30 GPa, 0.9, and 7.5, respectively. They are uniform in the modeled region. Previous studies (e.g., Shen-Tu et al., 1994) revealed that geodetic strain rates were much larger than seismological ones in southwest Japan because geodetic strain includes both elastic and inelastic strain. Elastic strain rates presumably equal to seismological ones on a long-term average. We compared seismic moment rates released by shallow historical earthquakes since AD1586 with the geodetic moment rates. Their ratio is 0.24 and 0.16 in the Chubu, Kinki, and Chugoku region and the whole southwest Japan. This difference is probably attributed to the distribution of historical documents and may also reflect the regionality of the ratio between elastic and inelastic strain. Applying 0.16 for calculating elastic rates and the stationary Poisson process of the earthquake occurrence, a probability of M≥6 earthquakes for 30 years ranges from 5.1 % to 0.2 % in each 0.2º x 0.2º grid of southwest Japan. We verify this probability model by using shallow (Depth≤ 20 km) M≥5 earthquakes occurred in 2010-2019, which is a period after the used GNSS data. The number of earthquakes was 36, which is roughly concordant to the predicted number of the model (3.04 per year). About 58 % of the earthquakes occurred with 25 % of the area with the highest strain rates, which suggests many crustal earthquakes occur in high strain-rate regions. The verification suggests the preliminary forecast model has the predictive power reasonably.
Near-isothermal exhumation of lower crust in the Caledonian Orogen: Metamorphic path of kyanite eclogite from the Danmarkshavn area, North-East Greenland Caledonides
Authors: Cao Wentao , Gilotti Jane , Massonne Hans-Joachim
Published: March 2021

Kyanite eclogite from the North-East Greenland Caledonides – the upper plate of the Caledonian orogeny – preserves a mineral assemblage and petrographic texture that are consistent with an initial near-isothermal exhumation path. Two medium-grained kyanite eclogites from the Danmarkshavn area (76°46’N, 18°40’W) located west of the Germania Land shear zone contain the peak assemblage of garnet + omphacite + kyanite + phengite + amphibole + rutile. Subhedral garnet encloses monomineralic omphacite and polymineralic inclusions of clinopyroxene + plagioclase ± quartz ± amphibole ± K-feldspar ± kyanite. X-ray mapping of garnet indicates a homogenous core with a composition of Py51–52Alm28–29Gr19–20Sp0–1, along with a slightly zoned rim of Py54Alm31Gr15Sp1 that is replaced by a corona of symplectitic amphibole + plagioclase. Omphacite (XNa up to 0.41), rarely present in the matrix, is indicated by symplectite of clinopyroxene + amphibole + plagioclase. Symplectites of corundum + plagioclase, spinel + plagioclase and sapphirine + plagioclase replace former kyanite. These symplectites are typically surrounded by a plagioclase corona with decreasing Ca (from XAn = 92–97 to XAn = 47–53) from the symplectite to the matrix. Isochemical phase equilibrium modeling along with homogenous garnet core and peak omphacite compositions yielded a peak metamorphic pressure-temperature (P-T) condition at 1.9 GPa, 840 ˚C. Assuming local equilibrium at the microscopic scale, an attempt to model a symplectite of spinel + sapphirine + plagioclase after kyanite using a pseudosection yielded estimated P-T conditions at 0.8–1.3 GPa and 700–900 ˚C. Integrating the calculated P-T conditions and previous geochronological results, an initial exhumation path from 1.9 GPa to ~1.0 GPa from ~415–390 Ma to ~375 Ma is nearly isothermal at around 800 ˚C.
A Fundamental Mechanism of Solar Eruption Initiation
Authors: Jiang Chaowei , Feng Xueshang , Liu Rui , Yan Xiaoli , Hu Qiang , Moore Ronald L.
Published: March 2021

Solar eruptions are spectacular magnetic explosions in the Sun's corona and how they are initiated remains unclear. Prevailing theories often rely on special magnetic topologies, such as magnetic flux rope and magnetic null point, which, however, may not generally exist in the pre-eruption source region of corona. Here using fully three-dimensional magnetohydrodynamic simulations with high accuracy, we show that solar eruption can be initiated in a single bipolar configuration with no additional special topology. Through photospheric shearing motion alone, an electric current sheet forms in the highly sheared core field of the magnetic arcade during its quasi-static evolution. Once magnetic reconnection sets in, the whole arcade is expelled impulsively, forming a fast-expanding twisted flux rope with a highly turbulent reconnecting region underneath. The simplicity and efficacy of this scenario argue strongly for its fundamental importance in the initiation of solar eruptions.
An investigation of two-phase grain-fluid model on the development process of debris flow fan
Authors: Wong Hock Kiet , Ma Ching-Yuan , Ko Chi-Jyun , Tai Yih-Chin
Published: March 2021

The movement of a debris flow is channelized by the mountain topography. It slows down and begins to deposit, forming the so-called debris-flow fan, when the slope is gentle. Since the flow body is composed of solid grains with interstitial fluid, the solid fraction may vary and plays a crucial role in the deposition process. In the present study, an entrainment-deposit law together with the two-phase model for grain-fluid flows (Tai et al., 2019) is proposed for describing the development of a debris flow fan. The model equations are derived in a terrain-following coordinate system, in which the coordinates are in coincidence with the topographic surface and the deposition/erosion is treated as the sub-topography. Numerical validation is performed against flume experiments (Tsunetaka et al., 2019), where the sediment-water mixture is released from a channel and merging into a gentle inclined flat plain via a steady water inflow. In this study, we shall illustrate the impacts of the sediment concentration on the evolution of the debris-flow fan, such as the location, distribution, geometry of debris-flow fan as well as the flow paths. 
Evaluation of climate change risks faced by the mining industry in Chile: spatiotemporal analysis of extreme precipitation for 2035-2065
Authors: Perez Gabriel , Pagliero Liliana , McIntyre Neil , Aitken Douglas , Rivera Diego
Published: March 2021

Climate change poses significant challenges for many industrial activities around the world, including mining. Changes in precipitation patterns and the increasing frequency of extreme weather events can trigger severe droughts or flash floods that can easily disrupt the minerals value-chain and increase environmental pollution risks. This research focuses on evaluating climate change risks faced by the mining industry in Chile during the period 2035-2065 under the assumptions of the RCP 8.5 scenario (business as usual).  This research presents risk maps, at the national scale, based on different databases that describe the location and characteristics of the mining infrastructure and spatiotemporal analysis of daily precipitation changes between present climate conditions and future predictions. The present climate conditions are depicted by historical observations for the period 1980-2010 while the future predictions are represented by an ensemble of 34 downscaled Global Circulation Models (GCMs) from the CMIP5.  On one hand, the results show that mining operations located in northern and central Chile (Atacama, Coquimbo and Valparaiso regions), will face significant flash flood risks due to the predicted increase of extreme precipitation events for 2035-2065. On the other hand, the results suggest that mining operations located in the regions of Coquimbo, Valparaiso, Biobio, Libertador G.B.O, and Metropolitan area of Santiago are those under the most significant risks due to droughts. The results obtained in this research are part of a more comprehensive project titled “Climate Risk Atlas of Chile”, developed by the Center for Climate and Resilience Research (CR2) and the Center for Global Change of Universidad Católica de Chile (https://arclim.mma.gob.cl/), which analyses the risks of climate change for different industries of the Chilean economy.
Detecting drought conditions related to vegetation at west continental Europe based on variations from the North and Caspian Seas
Authors: Xu Bolin , He Qing , Chun Kwok Pan , Klaus Julian , Schoppach Rémy , Yetemen Ömer
Published: March 2021

Teleconnections relate regional pressure patterns to local climate anomalies, influencing the variation of vegetation patterns. Over west continental Europe, droughts have been widely investigated with persistent low-frequency atmospheric circulation patterns (e.g. the North Atlantic Oscillation, NAO) with the centers over the Atlantic based on the 500mb height anomalies of the Northern Hemisphere. However, the effects of teleconnection patterns with the centers of active variability over the North and Caspian Seas is largely unexplored for droughts related to vegetation patterns. In this study, we explored the impact of the North Sea-Caspian Pattern (NCP) on regional ecohydrologic conditions in the Greater Region of Luxembourg in Western Europe. Using a Principal Component Analysis (PCA), we first decomposed the annual Normalized Difference Vegetation Index (NDVI) from the Global Inventory Monitoring and Modeling System (GIMMS) between 1981 and 2015. In the first PCA component, a distinctive greening trend of NDVI is detected since the late 1980s. However, the corresponding station observations and the ERA5 reanalysis data show that the region in west continental Europe became increasingly drier based on the difference between precipitation and evaporation. We explain the above paradoxical greening but drying patterns by the mechanism of NCP over the region. During the positive phase of NCP, the high pressure over the North Sea weakens circulation over the region and leads to warmer conditions in west continental Europe. These conditions are good for vegetation growth because the region was mainly energy-limited during the observed period at the annual scale based on a Budyko analysis. However, the positive phase of NCP also promotes divergent conditions at the lower troposphere and it reduces moisture flux over the region. In the Budyko space, the persistent positive phase of NCP would lead the energy-limited region to be water-limited. As the positive phase of NCP is expected to be more frequent along with the increasing global temperatures, the region may start to experience increasing water stress on vegetation. These results suggest that unforeseen droughts related to vegetation may be emerging in the region. New drought monitoring and management measures related to vegetation should be developed at west continental Europe, especially during the positive phase of NCP.
Geochronological evidence for repeated brittle reactivations of a pre-existing plastic shear zone: The Himdalen–Ørje deformation zone, Southern Norway
Authors: Torgersen Espen , Gabrielsen Roy , Nystuen Johan Petter , van der Lelij Roelant , Ganerød Morgan , Schönenberger Jasmin , Brask Sofie , Braathen Alvar
Published: March 2021

It is well known that faults, once formed, become permanent weaknesses in the crust, localizing subsequent brittle strain increments. The case of repeated brittle reactivations localized along pre-existing plastic shear zones is less recognized, although this situation is frequently observed in many geologically old terranes.

We have studied the prolonged deformation history of the Himdalen–Ørje Deformation Zone (HØDZ) in SE Norway by combining K–Ar and 40Ar–39Ar geochronology with structural analysis. The HØDZ consists of a large variation of deformation products from mylonites and cataclasites to pseudotachylites and fault gouge. Several generations of mylonites make up the ductile part of HØDZ, called the Ørje shear zone, a km-think SW-dipping shear zone within the late Mesoproterozoic Sveconorwegian orogen. 40Ar–39Ar dating of white mica from one of these mylonites give a plateau age of c. 908 Ma, interpreted to constrain the timing of late-Sveconorwegian extensionial reactivation of the Ørje shear zone.

This mylonitic fabric is extensively reworked in a brittle fashion along the SW-dipping Himdalen fault, a 10–25 m thick fault zone of cataclasite, breccia, fault gouge and, in places, abundant pseduotachylite veins. 40Ar–39Ar dating of pseduotachylite material gives several small plateaus between c. 375 and 300 Ma, whereas K-feldspar clasts from the cataclasitically deformed host rock carry a Caledonian signal (plateau at c. 435 Ma). K–Ar dating of three fault gouges constrain the timing of gouge development at c. 270 and 200 Ma. Two of the fault gouges also contain protolithic K-bearing mineral phases that overlap in age with the c. 375 Ma pseudotachylite 40Ar–39Ar plateau age, consistent with field observations of the former reworking the latter.

In sum, the HØDZ records multiple Paleozoic and Mesozoic brittle reactivations of the early Neoproterozoic (and older) mylonitic Ørje shear zone. Most of the brittle deformation is interpreted to have accumulated during development of the Permian Oslo rift and its subsequent latest Triassic evolution. The suggested late Devonian (c. 375 Ma) initiation of brittle deformation does not have a clear tectonic association, but we speculate that it relates to strike-slip displacements caused by the Variscan orogen, as also suggested for the sub-parallel Tornquist zone to the south.
Applying ensemble Kalman Filtering to improve operational flood forecasting for the Berkel catchment (Eastern Netherlands)
Authors: Burke Eoin
Published: March 2021

The Berkel catchment in the east of the Netherlands and western Germany is an area with a long history of river flooding. Flooding in the area is caused by a combination of fast responding hydrological characteristics in the upper catchment and impermeable glacial till in the shallow sub-surface. In the past, flood mitigation in the Berkel catchment involved straightening river channels, minimising vegetation growth in the watercourse and an extensive weir network to control water flow. The changing climate and an integral approach to water management demand a modern, robust approach to mitigating flood damage in the Berkel catchment. As a result, an operational flood forecasting system (Delft-FEWS) which utilises recently developed hydrologic rainfall-runoff models and state of the art data assimilation (DA) methods has been developed. This system generates 7-day discharge forecasts at hourly intervals using meteorologic forecast and local discharge observations.

The lowland rainfall-runoff model, WALRUS (Brauer et al., 2014) is implemented to generate discharge forecasts. The WALRUS model set-up has been designed and calibrated in a semi-distributed layout to ensure the spatial and temporal elements of discharge peaks are captured. Importantly, this flood forecasting system has adopted recent advancements in DA to strengthen the accuracy of flood forecasts. Specifically, the DA method used in this system follows the work by Sun et al. (2020). The DA allows the model to be updated using field observations at 5 locations in the catchment, available in near real-time. Reforecasting illustrates the advantages of using rainfall-runoff models that capture the specific hydrologic characteristics of a catchment as well as the benefit of using advanced DA methods in flood forecasting.

 

Reference

Brauer, C. C., Teuling, A. J., Torfs, P. J. J. F., & Uijlenhoet, R. (2014). The Wageningen Lowland Runoff Simulator (WALRUS): a lumped rainfall–runoff model for catchments with shallow groundwater. Geoscientific model development, 7(5).

Sun, Y., Bao, W., Valk, K., Brauer, C. C., Sumihar, J., & Weerts, A. H. (2020). Improving forecast skill of lowland hydrological models using ensemble Kalman filter and unscented Kalman filter. Water Resources Research, 56(8), e2020WR027468.