bluuebunny/crossref_metadata_2025 huggingface dataset:
Cs batch sorption and column transport experiments on sand from the Yamin plain, Israel – Experimental results and modelling
Authors: Klein-BenDavid Ofra , Balaban Noa , Gelfer Svetlana , Komerian Ronen , Saban David , Rosenzweig Ravid
Published: March 2020

The Yanim plain hosts the national Israeli radioactive waste disposal site. The site is located on the Miocene aged Hazeva formation, comprised of loose sand, sandstone and dispersed clay layers. The current research examines the sorption capacity of the local sand to solutions doped with Cs ions. The sand contains ~95% quartz and ~5% of various clays, carbonates, and oxides. Batch sorption experiments were conducted at a liquid to solid ratio of 10. Two end-member solutions were used, fresh (MQ) and concentrated (Na-Nitrate solution). Both solutions were doped with 0.1, 1, 10, 100 and 1000 ppm of Cs (as a nitrate). For the MQ experiments Kd values ranged between ~2 and ~1300, where the highest Kds were registered for the 1 ppm doping level, and the smallest Kds were for the 1000 ppm doping level. For the concentrated solution Kd values ranged between ~0 and ~1.5, where the highest Kds were for the 1 ppm doping level, for all other doping levels Kds were <1. Freundlich and Langmuir isotherm calculations revealed a significantly better correlation on a linearized Freundlich isotherm, indicating a multi-layer and multi-site sorption model, with a similar slope for both solutions, indicating a common sorption mechanism. Column transport experiments (L=25cm, r=2cm, φ=30%, 1PV=180cc) have shown minimal retardation of the Cs in the concentrated solution flow experiments (R= ~2). A second, probably colloid-related peak, showed an early breakthrough with respect to a conservative color tracer.  On the other hand, when MQ was run in the column no breakthrough was observed within 10 column pore volumes. In one fresh experiment a very small colloid related peak was found with breakthrough similar to the conservative tracer. We used the CXTFIT model to calculated the dispersity (λ [L]) and normalized velocity (V) of the measured tracer. For the conservative tracer the values were λ=0.13 cm and V=0.9 cm. For Cs transport in the concentrated solution λ=0.22 cm and V=1.6. Thus, it may be concluded that even in similar doping levels in the same matrix the solution chemistry will play a major role in contaminant retardation. Thus, rain episodes which abruptly change the solution chemistry, can significantly affect solute and colloid mobility.
Constraining the olivine amount and water content at 410-km discontinuity with the elasticity of wadsleyite and olivine
Authors: Wu Zhongqing , Wang Wenzhong , Walter Michael , Ye Peng , Redfern Simmon
Published: March 2020

The water content in the mantle transition zone exerts a controlling influence on the dynamical and chemical evolution of Earth, but is poorly known. In principle the water content at the top of the transition zone can be inferred by comparing the velocity and density contrasts across the 410-km seismic discontinuity with predictions based on the phase transition of olivine to wadsleyite. The high-quality elastic data of at pressure and temperature (PT) conditions of the transition zone are crucial but are very challenge for experiments to obtain. Calculating these elastic data at high PT conditions in conventional method are also very expensive. Instead, these elastic data were calculated using the method of Wu and Wentzcovitch (2011), which reduces the computational workload to tenth of the conventional method. All calculations for two phases were conducted using the same computational details as far as possible, which guarantees that the velocity and density differences between two phases have very high precise. All these calculated elastic data agree well with the available experimental data. The iron and water effect on the elasticity are also well described.

With these high-quality elastic data covered the PT condition of the transition zone, we analyze the water and wadsleyite content at the top of the transition zone. We found that the water content of wadsleyite at the top of the transition zone can be well constrained when density and velocities jumps are considered together. For a pyrolitic mantle composition with ~60% olivine, our best fit is ~ 0.5 wt% water at the top of the transition zone. If the transition zone is dry, as suggested by some electrical conductivity models, the upper mantle may only contain ~ 50% olivine (Wang et al., 2019).

 

Wang, W-Z., Walter, M.J., Peng, Y., Redfern, S., Wu, Z-Q., 2019a. Constraining olivine abundance and water content of the mantle at the 410-km discontinuity from the elasticity of olivine and wadsleyite. Earth Planet. Sci. Lett. 519, 1–11.

Wu, Z-Q., Wentzcovitch, R.M., 2011. Quasiharmonic thermal elasticity of crystals: An analytical approach. Phys. Rev. B - Condens. Matter Mater. Phys. 83, 1–8. doi:10.1103/PhysRevB.83.184115

 
Understanding traffic distribution pattern from the perspective of urban land use
Authors: Zhang Min
Published: March 2020

With the rapid development of urbanization, many problems become more serious in big cities, such as traffic congestion. Different urban land use type can have different influence on traffic, therefore, the analysis of relationship between urban traffic and urban land use is important for better understanding of urban traffic status. This study firstly utilizes spatial data analysis method and time series analysis method to obtain urban traffic pattern from the spatial and temporal perspective, using one-week traffic sensor data, we measure the urban commuting patterns, which include weekday mode and weekend mode. Secondly, this study analyzes the relationship between traffic status and land use type in traffic analysis zone (TAZ) level, which indicates traffic status has spatial autocorrelation, besides, commercial land use and mixed land use type may result in more serious traffic congestion. The research can be of value for urban understanding and decision making in areas of urban management, urban plan and traffic control.
Downscaling flows in the water-food-energy Nexus
Authors: Dekker Stefan C. , Santos Maria J. , Van 'tVeen Hanneke , van Vuuren Detlef P.
Published: March 2020

The variabilities in both time and space of the flows between the components of the water-food-energy are dependent on many driving factors. In this study we use global scenarios from the Integrated Assessment Model IMAGE to analyse future changes in flows in the water, food and energy nexus. With Sankey diagrams we show how flows between energy and food production will likely increase by 60% and water consumption by 20% in 2050 by using a reference scenario. The inclusion of climate action policies, combined with dietary changes, increased yield efficiency and food waste reduction leads to similar resources uses of water and land, and much lower greenhouse gas emissions compared to 2010.

We found that based on data, spatial scales are an important but complicating factor in nexus analysis. This is because different resources have their own physical and spatial scale characteristics within the nexus. To examine the effect of scaling on future nexus development, we analyse how local decisions and local resource availability of the use of biomass as energy source impacts other resources. Biomass use potentially impacts forest systems and might compete with land for food and water resources within the nexus. The use of biomass and more specifically charcoal will likely further increase mainly due to urbanization in developing countries. We have examined how different shared socio economic pathway (SSP) scenarios result in (i) future demand for biomass for energy and compare those to measured (with remote sensing) and modelled net primary productivity values of forested systems, (ii) estimate the amount of land needed for biomass production that might compete with food production, and (iii) estimate the water amount needed to produce biomass to meet the different biomass demands. We found that current productivity of non-protected forests is globally higher than the demand, but regionally it closely meets the demand for tropical areas in Central America and Africa. This while tropical areas in South America and Indonesia show decreasing biomass demands for energy for the SSP1-SSP3 scenarios. From this analysis we clearly see differences at regional scales in the competition between the resources land and water are found. 

We conclude that a nexus framework analysis which estimates flows between the different components across scales is fundamental to understand system sustainability. Such approach benefits from combining global scenarios of Integrated Assessment models with local conditions to understand the sustainability in the nexus in time and space.
Decoupled lithostratigraphy, orbitally-driven climate, and tectonics for a middle Pleistocene stratigraphic section in the Northern Apennines, Italy
Authors: Gelwick Katrina , Pazzaglia Frank , Kodama Kenneth , Corbett Lee , Bierman Paul , Caffee Marc
Published: March 2020

Cyclical patterns in the lithology of terrestrial Pleistocene sedimentary deposits are traditionally interpreted as the result of exogenic interglacial-glacial cycles, with deposition accommodated by constant basin subsidence. Recent challenges to this model propose that autogenic surface processes inherent to hillslope, fluvial, and marine systems can both obscure exogenic signals in the sedimentological record and encode their own quasi-periodic signal that mimics exogenic cyclicity. We used rock-magnetic cyclostratigraphy to test the canonical climate-driven sedimentation model for terrestrial Pleistocene sedimentary cycles against competing tectonic- and autogenic process-modulated sedimentation models with a continuous 60 m exposure of middle Pleistocene fluvial sedimentary cycles located at the edge of the actively subsiding Po foreland basin in the Northern Apennines of Italy. We correlated magnetic susceptibility, sampled at 40 cm intervals, to orbital cyclicity to generate a high-resultion age model anchored by terrestrial cosmogenic nuclide (TCN) burial ages, optically stimulated luminescence (OSL), and magnetostratigraphy. Two new 26Al-10Be burial ages are 160±320 ka and 680±310 ka (2σSE); the age of a third buried sample is consistent with continuous exposure and thus recent burial. We mapped the age model into section lithostratigraphy and then compared to the global benthic δ18O stack to determine whether sedimentary cyclicity coincides with glacial-interglacial cycles. In addition, we calculated paleo-erosion rates based on the 10Be concentration of six samples distributed through the age model and find that they range from 244±23 to 444±52 m/Ma, which bracket the modern TCN-determined erosion rate of the Enza River of 351±40 m/Ma. Results show no clear correlation between lithostratigraphy, glacial-interglacial climate cycles, or paleo-erosion rates, indicating that the stratigraphy is probably not driven by exogenic climate forcing. Rather, based on the decoupling of lithology and paleo-erosion rates and the little variation in paleo-erosion and modern erosion rates (<20%), the cyclicity is best explained by periodic autogenic delta processes in a system where accommodation space in the depositional basin is limited. These findings exemplify the complex interplay of tectonics, climate, and autogenic processes in the generation, transport, and deposition of sediments. Results of this study contribute to the ongoing debate over whether signals generated by large scale, exogenic forcing can survive transport to be preserved in the sedimentary record and help define the temporal and spatial scales at which these processes operate.
Socio-Hydrological Modelling of Cooperation and Conflict in the Transboundary Lancang-Mekong River
Authors: Lu You , Borzi Iolanda , Guo Liying , Patil Repush , Zhang Yujie , Liu Dengfeng , Wei Jing , Tian Fuqiang
Published: March 2020

The transboundary Lancang-Mekong River Basin has experienced both cooperation and conflict over the past several decades. Downstream countries (Thailand, Cambodia and Vietnam) rely on Mekong River for fisheries and agriculture, while upstream countries including China and Laos have been constructing dams to generate hydropower. The construction and operation of dams in upstream countries has changed the seasonality of streamflow in downstream countries, affecting their agriculture and fishery benefits. More recently, cooperation between upstream and downstream countries has led to benefit sharing and improved international relations throughout the river basin. In this presentation, we introduce a socio-hydrological model that simulates the hydrological changes in downstream countries resulting from upstream dam operation, based on collection of hydrological, economic and social data in Lancang-Mekong river basin. Our model captures the cooperation and conflict feedback loops which impacts the operation rules of upstream dams. In this way, our study generates understanding of the connections between water resources management and hydro-political dynamics underpinning cooperation and conflicts mechanism in this transboundary river basin.
Quantifying the effects of urban vegetation on water partitioning in complex cityscapes: the potential of isotope-based ecohydrological models
Authors: Gillefalk Mikael , Tetzlaff Dörthe , Hinkelmann Reinhard , Kuhlemann Lena-Marie , Smith Aaron , Meier Fred , Soulsby Chris
Published: March 2020

The continued global acceleration of urbanisation increasingly requires sustainable, adaptive management strategies for land and water use in cities. Although the effects of buildings and sealed surfaces on urban runoff generation (via storm drains) and local climate (through the urban heat island effect) are well known, much less is known about how these artificial influences integrate with water partitioning in more natural urban green spaces. In particular, little is quantitatively known about how different types of urban green spaces (lawns, parks, woodland etc.) regulate the partitioning of evaporation, transpiration and groundwater recharge. To address this crucial issue, we integrated field observations with advanced, isotope-based ecohydrological modelling at the plot scale in the urban area of Berlin, Germany. Measurements of soil moisture, sap flow, and stable isotopes in precipitation, soil water and groundwater have been made over the course of one growing season. Additionally, an eddy flux tower at the site Rothenburgstraße in Berlin-Steglitz continuously collects hydroclimate data by measuring temperature, precipitation, radiation, humidity and wind speed at high temporal resolution. These data (30-min averages) have been used as input to, and for calibration of, the process-based ecohydrological model EcH2O-iso. The model also tracks stable isotope ratios and water ages in various stores (e.g. soils and groundwater) and fluxes (evaporation, transpiration and recharge). EcH2O-iso has successfully been used to describe the effects of vegetation cover on water partitioning in a number of studies but this is the first implementation in an urban setting. It shows that ecohydrological water use by vegetation type increases in the order forests > shrubs > grass, mainly through higher interception and transpiration. Accordingly, trees can reduce groundwater recharge by >50%, but provide cooling latent heat transfers to the atmosphere.  Similarly, ages of stored water and fluxes are generally greater under trees than grass. The results, which form the basis for future upscaling, show that urban green spaces play an important role in urban hydrology and in Berlin there is a trade-off between moderating the urban heat island effect and maintaining groundwater recharge. Consequently, it is clear that vegetation management needs to be considered in sustainable water and land use planning in urban areas to build resilience in cities to climatic and other environmental change.
Application of Deep Learning to Detect Ground Deformation in InSAR Data
Authors: Anantrasirichai Pui , Biggs Juliet , Albino Fabien , Bull David
Published: March 2020

Satellite interferometric synthetic aperture radar (InSAR) can be used for measuring surface deformation for a variety of applications. Recent satellite missions, such as Sentinel-1, produce a large amount of data, meaning that visual inspection is impractical. Here we use deep learning, which has proved successful at object detection, to overcome this problem. Initially we present the use of convolutional neural networks (CNNs) for detecting rapid deformation events, which we test on a global dataset of over 30,000 wrapped interferograms at 900 volcanoes. We compare two potential training datasets: data augmentation applied to archive examples and synthetic models. Both are able to detect true positive results, but the data augmentation approach has a false positive rate of 0.205% and the synthetic approach has a false positive rate of 0.036%.  Then, I will present an enhanced technique for measuring slow, sustained deformation over a range of scales from volcanic unrest to urban sources of deformation such as coalfields. By rewrapping cumulative time series, the detection performance is improved when the deformation rate is slow, as more fringes are generated without altering the signal to noise ratio. We adapt the method to use persistent scatterer InSAR data, which is sparse in nature,  by using spatial interpolation methods such as modified matrix completion Finally, future perspectives for machine learning applications on InSAR data will be discussed.
A Methodology for Optimizing Numerical Weather Prediction Models
Authors: Sotiropoulou Rafaella - Eleni , Stergiou Ioannis , Tagaris Efthimios
Published: March 2020

Optimizing the performance of numerical weather prediction models is a very complicated process due to the numerous parameterization choices provided to the user. In addition, improving the predictability of one model’s variable (e.g., temperature) does not necessarily imply the improvement of another (e.g., precipitation). In this work the Technique of Preference by Similarity to the Ideal Solution (TOPSIS) is suggested as a method to optimize the performance of a numerical weather prediction model. TOPSIS provides the ability of using multiple statistical measures as ranking criteria for multiple forecasting variables. The Weather Research and Forecasting model (WRF) is used here for application of TOPSIS in order to optimize the model’s performance by the combined assessment of temperature and precipitation over Europe. Six ensembles optimize model’s physics performance (i.e., microphysics, planetary boundary layer, cumulus scheme, Long–and Short– wave and Land Surface schemes). The best performing option for each ensemble is selected by using multiple statistical criteria as input for the TOPSIS method, based on the integration of entropy weights. The method adopted here illustrates the importance of an integrated evaluation of weather prediction models’ performance and suggests a pathway for its improvement.

Acknowledgments LIFE CLIMATREE project “A novel approach for accounting & monitoring carbon sequestration of tree crops and their potential as carbon sink areas” (LIFE14 CCM/GR/000635).
The (mis)conception of an average Quaternary equilibrium line altitude
Authors: Spagnolo Matteo , Rea Brice , Barr Iestyn
Published: March 2020

The glacier equilibrium line altitude (ELA) represents the elevation on the glacier surface at which the amount of mass gained (via precipitation, avalanching and windblown snow, equals the amount of ice lost (via ablation and sublimation, over the mass balance year. The ELA can be measured on modern glaciers or calculated for reconstructed, former glaciers. Despite its simple definition, the ELA represents an incredibly powerful, quantitative expression of the relationship between glaciers and climate. As a glacier responds dynamically to climate, so does the ELA. Precipitation at the glacier ELA has been empirically linked to ablation season temperature. Thus, the reconstruction of former glacier geometries and their ELAs leads to the quantification of palaeoclimate.

In recent years, the concept of an “average Quaternary ELA” (or “mean Quaternary ELA”) has become popular because of the role it might play in relation to the glacial buzzsaw hypothesis, i.e. the idea that glacial erosion could offset mountain uplift and therefore control and limit the growth of mountains. Attempts to determine the average Quaternary ELA have been undertaken, leading to some interesting conclusions. For example, it has been argued that the floor altitudes of glacial cirques can be used as a measure of average Quaternary ELA, therefore implying that average Quaternary mountain glaciers expansion was confined to the topmost portion of alpine valleys.

Time has passed from these initial attempts to determine the average Quaternary ELA and more palaeoclimatic and palaeoglaciological data have become available, so it is appropriate to reconsider these calculations and perhaps question the validity of such a concept. To do so, we revisit how the idea of an average Quaternary ELA developed and what such a parameter would really mean. We do so in light of a new quantitative study on the average ELA relative to both a single glacial cycle and multiple glaciations experienced during the past   ̴2.6 million years, i.e. the Quaternary. Collectively, this new study presents a very different perspective than previously suggested.
Ground-penetrating radar surveys for the detection of preferential flow into soils
Authors: Di Prima Simone , Winiarski Thierry , Angulo-Jaramillo Rafael , Stewart Ryan D. , Castellini Mirko , Abou Najm Majdi R. , Ventrella Domenico , Pirastru Mario , Giadrossich Filippo , Lassabatere Laurent
Published: March 2020

Preferential flow is more the rule than the exception, in particular during water infiltration experiments. In this study, we demonstrate the potential of GPR monitoring to detect preferential flows during water infiltration. We monitored time-lapse ground penetrating radar (GPR) surveys in the vicinity of single-ring infiltration experiments and created a three-dimensional (3D) representation of infiltrated water below the devices. For that purpose, radargrams were constructed from GPR transects conducted over two grids (1 m × 1 m) before and after the infiltration tests. The obtained signal was represented in 3D and a threshold was chosen to part the domain into wetted and non-wetted zones, allowing the determination of the infiltration bulb. That methodology was used to detect the infiltration below the devices and clearly pointed at nonuniform flows in correspondence with the heterogeneous soil structures. The protocol presented in this study represents a practical and valuable tool for detecting preferential flows at the scale of a single ring infiltration experiment.
Laboratory observations of frictional stability and fault zone evolution under heterogeneous friction, rheology, and stress conditions
Authors: Ke Chun-Yu , Leach Cebry Sara Beth , Shreedharan Srisharan , Marone Chris , Kammer David S. , McLaskey Gregory C.
Published: March 2020

Natural faults experience a variety of frictional, rheological, and stress heterogeneities. To investigate the effects of these heterogeneities on seismic stability and the mode of fault slip behavior, laboratory experiments were conducted using a biaxial shearing apparatus with a 0.76 m by 0.076 m simulated fault where 2.5 to 5 mm thick gouge layers were sheared at applied normal stresses of 7 to 12 MPa for 25 mm of cumulative slip. Laboratory faults consisted of uniform layers of gouge, homogeneous mixtures, and/or heterogeneous patches of talc, quartz, and gypsum minerals. Experiments with a uniform layer of velocity weakening fault gouge revealed the development of two asperities at the highly stressed ends of the fault that could fail independently, and creep fronts that facilitated interaction between asperities. This behavior was also reproduced with simple numerical simulations that employ rate- and state-dependent friction. In other experiments, the fault consisted of patches of alternating velocity strengthening and velocity weakening fault gouges. Patch size and location were varied to understand how earthquake ruptures accelerate or decelerate in this heterogeneous environment. These experiments revealed that a velocity weakening fault patch was more likely to remain stable if located next to a velocity strengthening fault patch. However, stability was dependent on the patch sizes and location relative to where the load is applied. In certain cases, some sections of the fault slipped unstably while others slid stably. These experiments, and matching numerical models, highlight the complexity that can arise on natural faults due to frictional, rheological, and stress heterogeneities.
Ecosystem Amenities as Drivers for Urban Development and its Resulting Impacts: A Social-Ecological Modeling Approach for Stockholm, Sweden
Authors: Pan Haozhi , Page Jessica
Published: March 2020

A comprehensive understanding and modeling of socio-ecological systems can better assess the interactions between ecosystem amenities and human urban development. Based on the theory of supply-demand of ecosystem service, this paper constructs a comprehensive socio-ecological system modeling approach to identify ecosystem amenities’ roles in shaping human urban development and how the developments in turn affect ecosystem services. In our model, ecosystem services are regarded as both attractors and costs to human activities that cause urban land use changes. It adds to the existing ecosystem impact assessment approaches by integrating ecosystem services as both supply and demand in a socio-ecological process model with dynamic interaction and feedback between social and ecological systems. The approach couples socioeconomic, urban land use, and ecosystem interactions in a fine scaled (30×30 m) modeling framework with multiple time steps and feedback. Calibration through machine-learning techniques is applied to depict the joint driving forces from ecosystem amenities, socioeconomic attractors, and biophysical factors in influencing urban land use developments. Ecosystem Preservation District policy is tested as a policy scenario that aims to protect high-value ecosystem service areas while ensuring maximum ecosystem amenity provisions to urban inhabitants. Stockholm County, Sweden constitutes the study area with forecasts to 2040.

The analytical results will include: 1) calibrated functional forms and variable coefficients of ecosystem amenities that drive urban developments in comparison to other socioeconomic and biophysical variables; 2) assessment of ecosystem service value losses induced by human development; and 3) simulation of ecosystem service value preserved through Ecosystem Preservation District policy scenario. The analytical evidence provides further proof-of-concept of superior capability of using comprehensive socio-ecological models of understanding interactions between human and ecological systems. The policy scenario analysis offers supporting evidence for mitigating environmental impacts from urban growth through growth management policies. Finally, optimization of supply-demand of ecosystem services is critical in constituting the toolkit for nature-based solutions in urban planning and management.   

 
How to meaningfully engage key stakeholders in smart circular economy
Authors: Majercakova Gergana , Bokal Sabina
Published: March 2020

As an alternative to the traditional linear economy, the circular economy could help tackle the climate emergency, decrease resource scarcity and increase business sustainability. Implementing it successfully, maintaining sustainability and facilitating real systemic change means an effective coordination among all stakeholders is needed.

Meaningful engagement of stakeholders will help achieve a shared understanding of the concept, the new approaches and their implementation at all levels. Mobilizing different stakeholders is always a challenge and requires careful planning in order to demonstrate that the stakeholders’ input and engagement is valued, and participatory processes are in place.

The presentation will provide insights into the different stakeholder groups, their interests and methods that could be employed to reach effective engagement. It will also outline approaches, actions and tools that should help circular economy drivers develop a plan for stakeholder engagement based on clear understanding of stakeholders’ needs.

Apart from the general insights on the role of stakeholders in circular economy projects, the presentation will also provide practical knowledge on mapping and profiling stakeholders, stakeholder engagement strategy development, engagement tools and evaluation methods. Specific needs for improvement of stakeholder engagement practices into Circular economy projects will be tackled and discussed as well.
Flash size and within-flash time evolution of cloud-top optical emissions: Implications for satellite-based lightning observations
Authors: Cummins Kenneth , Zhang Daile
Published: March 2020

This full-year study spanning portions of 2017-18 quantifies GOES-16 Geostationary Lightning Mapper (GLM) flash detection efficiency (DE) in central Florida using the Kennedy Space Center Lightning Mapping Array (LMA). Findings support the expectation that about 70% of all flashes are reported when averaged over all thunderstorms and times-of-day. When quantified as a function of LMA flash parameters, GLM exhibited an average of 40% DE for small (main channel length of 5-8 km), and even lower DE for shorter-length and/or short-duration (less than 200 milliseconds) flashes. Conversely, GLM exhibited more than 95% DE for long-duration flashes with main channel lengths of 50-100 km. DE was somewhat lower during daylight and higher at night.  Flash size and duration, on average are shown to be a critical parameter influencing GLM detection.  Given that this behavior occurred for severe and non-severe storms, it is likely an important contributing factor to the low flash detection efficiency for storms with high flash rates (and resulting small/short flashes) associated with severe weather, thereby modulating the effects of optical scattering and absorption within cloud volumes.

These findings can be explained by the time-evolution of cloud-top optical emissions derived from observations using the Lightning Imaging Sensor (LIS) onboard the Tropical Rainfall Measuring Mission (TRMM) Satellite. Specifically, LIS group area, energy density, and cloud-top energy in intra-cloud flashes, on average, reached a local maximum value in the very first few milliseconds of a flash and fell to their minimum values at around 10-20 milliseconds into the flash. After that, all parameters gradually increased over the next 80-100 milliseconds to reach the initial values, and then continued to increase for longer-duration flashes. In addition, statistical simulations based on long-term LIS group area observations indicate that about half of the above-threshold light sources are smaller than a LIS pixel (~ 4 km x 4 km) and are the smallest during initial breakdown in IC flashes.

These observations have implications for expectations about the performance of all satellite lightning observing instruments that are based on optical observations operating in the near-IR portion of the optical spectrum.  The specific values for optical source size and cloud-top energy provided by this study, as a function of time-in-flash, should help refine the expectations for the performance of the upcoming Lightning Imager on the Meteosat Third Generation geostationary satellite.

 
Mantle xenoliths from Befang (Oku Massif) in the Cameroon Volcanic Line
Authors: Tedonkenfack Sylvin S. T. , Puziewicz Jacek , Ntaflos Theodoros , Aulbach Sonja , Kukula Anna , Matusiak-Małek Magdalena , Ziobro Małgorzata , Mazurek Hubert
Published: March 2020

Cameroon Volcanic Line (CVL) is a ca. 1600 km long Cenozoic volcanic chain which crosses the boundary between ocean and continent in West Africa. Its origin, as well as  the nature and age of the underlying continental lithospheric mantle (CLM), is still a matter of debate. Some of the CVL lavas contain peridotite xenoliths that can provide data elucidating the role of the CLM in the sustained magma generation along the line. In this abstract we describe xenolith suite from the Befang pyroclastic cone (< 1Ma) in the Oku Massif in the continental part of CVL, consisting of 14 spinel lherzolites, one spinel harzburgite and one websterite. The xenoliths are between 3 and 21 cm in diameter and have porphyroclastic to serial or equigranular texture, with porphyroclasts of olivine or orthopyroxene up to 9 mm in diameter. Some are weakly foliated. Olivine is Fo 88.6-90.4, contains 0.36 to 0.42 wt.% NiO and 180-750 ppm of Ca. Orthopyroxene (Mg# 0.89-0.91) contains 0.14 – 0.19 atoms of Al pfu, and clinopyroxene (Mg# 0.90-0.92) contains 0.24 – 0.31 atoms of Al pfu. The Cr# of lherzolite spinel is 0.09-0.15, in the harzburgitic one it is 0.18-0.19. Pyroxenes in all studied peridotites record a temperature range of 910 – 1010°C (Brey and Köhler 1990). Clinopyroxenes’ REE patterns are flat at HREE-MREE and make a spectrum from slightly LREE-depleted to slightly LREE-enriched (LaN/LuN from 0.08 to 2.65). The trace-element patterns are flat except well-defined negative Nb-Ta and positive Th-U anomalies. Orthopyroxenes’ REE patterns are variably depleted from HREE to LREE (LaN/LuN from 0.001 to 0.037). The REE pattern of clinopyroxene occurring in websterite exhibits enrichment from HREE towards LREE with hump in Sm/Nd, typical of silicate melt crystallization. The REE pattern of clinopyroxene The Befang lherzolites represent CLM metasomatised by melts produced by various, but generally low degrees of melting of DMM-like (Depleted MORB Mantle) source. Conversely, the harzburgite was formed by low degrees (few percent) of melting of DMM.

Acknowledgements. The study was funded by Polish National Centre for Science project UMO-2017/27/B/ST10/00365 to JP. EPMA analyses were done thanks to the Polish-Austrian project WTZ PL 08/2018.

References:

Brey, G.P. & Köhler, T. (1990). Geothermobarometry in four-phase lherzolites II. New thermobarometers and practical assessment of existing thermobarometers. Journal of Petrology 31, 1353-1378.
Beyond Cloud Microphysics: Representing Subgrid-Scale Processes in Lagrangian Cloud Models
Authors: Hoffmann Fabian
Published: March 2020

While the use of Lagrangian cloud microphysical models dates back as far as the 1950s, the integration of this framework into fully-coupled, three-dimensional dynamical models is only possible for about 10 years. In addition to the highly accurate and detailed representation of cloud microphysical processes, these so-called Lagrangian Cloud Models (LCMs) also allow for new ways of representing subgrid-scale dynamical processes and their effects on the microphysical development of clouds, typically neglected or only crudely parameterized due to computational constraints.

In this talk, I will present a new approach in which supersaturation fluctuations on the subgrid-scale of a large-eddy simulation (LES) model are represented by an economical, one-dimensional model that represents turbulent compression and folding. With a resolution comparable to direct numerical simulation (DNS), inhomogeneous and finite rate mixing processes are explicitly resolved. Applications of this modeling approach for warm-phase shallow cumuli and stratocumuli, and first applications for mixed-phase clouds will be discussed. Generally, clouds susceptible to inhomogeneous mixing show a reduction in the droplet number concentration and stronger droplet growth, in agreement with theory. Stratocumulus entrainment rates tend to be lower using the new approach compared to simulations without it, indicating a more appropriate representation of the entrainment-mixing process. Finally, the Wegner-Bergeron-Findeisen-Process, leading to a rapid ice formation in mixed-phase clouds, is decelerated.

All in all, this new modeling framework is capable of bridging the gap between LES and DNS, i.e., it enables representing all scales relevant to cloud physics, from entire cloud fields to the smallest turbulent fluctuations, in a single model, allowing to study their interactions explicitly and granting new insights.
Effect of Rheology on Afterslip and Viscoelastic Patterns Following the 2010 Mw 8.8 Maule, Chile, Earthquake
Authors: Peña Carlos , Heidbach Oliver , Moreno Marcos , Bedford Jonathan , Ziegler Moritz , Tassara Andrés , Oncken Onno
Published: March 2020

After large earthquakes at subduction zones, the plate interface continues moving due to mostly frictional afterslip processes. Below depths of 60 km, little frictional afterslip is to be expected on the plate interface due to low shear strength, lack of apparent geodetic interseismic locking, and low seismic moment release from aftershocks. However, inversion models that consider an elastic crust above a mantle with viscoelastic rheology result in a significant portion of afterslip at depths > 60 km. In this study, we present a forward 3D geomechanical-numerical model with power-law rheology that simulates dislocation creep processes for the crust and upper mantle in combination with an afterslip inversion. The linear rheology case is also considered for comparison. We estimate the cumulative viscoelastic relaxation and the afterslip distribution for the first six years following the 2010 Mw 8.8 Maule earthquake in Chile. The cumulative afterslip distribution is obtained from the inversion of the residual surface displacements between continuous GPS (cGPS) observations and predicted displacements from viscoelastic forward modelling. We investigate three simulations: two with the same dislocation creep parameters in the slab and upper mantle but different ones in the continental crust, and another with elastic properties in the crust and slab and a linear viscoelastic upper mantle. Our preferred simulation is the one with power-law rheology in the crust and upper mantle with a weak continental crust since the corresponding afterslip distribution shows the best overall fit to the cGPS displacements (cumulative and time series) as well as having a good correlation with aftershock activity. In this simulation, most of the viscoelastic relaxation occurs in the continental lower crust beneath the volcanic arc due to dislocation creep processes. The resulting afterslip pattern from the inversion is reduced at depths > 60 km, which correlates well with the spatial distribution of cumulative seismic moment release from aftershocks. We conclude that by allowing for non-linear stress relaxation in the continental lower crust due to dislocation creep processes, the resulting afterslip distribution is in better agreement with the physical constraints from the shear strength of the plate interface at depth, the predicted locking degree, and the aftershock activity.
Mechanical effects of rock cement alteration quantified using digital rock physics
Authors: Wetzel Maria , Kempka Thomas , Kühn Michael
Published: March 2020

Mineral dissolution is a micro-scale process, which may significantly alter the microstructure of rocks, and consequently affect their effective mechanical behavior at the macro scale. Predicting changes in rock stiffness is of paramount importance within the context of risk assessment for most applications related to geological subsurface utilization, where reduction of mechanical parameters is of particular relevance to assess reservoir, caprock and fault integrity [1].

In the present study, the effective elastic properties of typical reservoir rocks are determined based on micro-computer tomography (micro-CT) scans. The resulting three-dimensional rock geometry comprises a more realistic microstructure regarding the shapes of grains, cements and the overall porous network compared to available empirical approaches. Effective rock stiffness is calculated by a static finite element method, which imposes an uniform strain on the digital rock sample and calculates the resulting stresses. The effect of spatial cement distribution within the pore network is taken into account, considering passive pore filling as well as framework supporting cements. Rock stiffness increases due to the precipitation of pore-filling minerals. This quantitative approach substantially improves the accuracy in predicting elastic rock properties compared to general analytical methods, and further enables quantification of uncertainties related to spatial variations in mineral distribution.

[1] Wetzel M., Kempka T., Kühn M. (2018): Quantifying Rock Weakening Due to Decreasing Calcite Mineral Content by Numerical Simulations. Materials, 11, 4, 542. DOI: http://doi.org/10.3390/ma11040542
The Structure of Solar Coronal Mass Ejections in the Extreme-Ultraviolet Passbands
Authors: Song Hongqiang
Published: March 2020

So far, most studies on the structure of coronal mass ejections (CMEs) are conducted through white-light coronagraphs, which demonstrate about one third of CMEs exhibit the typical three-part structure in the high corona (e.g., beyond 2 Rs), i.e., the bright front, the dark cavity and the bright core. In this presentation, we address the CME structure in the low corona (e.g., below 1.3 Rs) through extreme-ultraviolet (EUV) passbands and find that the three-part CMEs in the white-light images can possess a similar three-part appearance in the EUV images, i.e., a leading edge, a low-density zone, and a filament or hot channel. The analyses identify that the leading edge and the filament or hot channel in the EUV passbands evolve into the front and the core later within several solar radii in the white-light passbands, respectively. What's more, we find that the CMEs without obvious cavity in the white-light images can also exhibit the clear three-part appearance in the EUV images, which means that the low-density zone in the EUV images (observed as the cavity in white-light images) can be compressed and/or transformed gradually by the expansion of the bright core and/or the reconnection of magnetic field surrounding the core during the CME propagation outward. Our study suggests that more CMEs can possess the clear three-part structure in their early eruption stage. The nature of the low-density zone between the leading edge and the filament or hot channel is discussed.
Gravity inversion with depth normalization
Authors: Chepigo Lev , Ivan Lygin , Bulychev Andrey
Published: March 2020

Actually the most common method of gravity data interpretation is a manual fitting method. In this case, the density model is divided into many polygons with constant density and each polygon is editing manually by interpreter. This approach has two main disadvantages:

- significant amount of time is needed to build a high-quality density model;

- if density isn’t constant within anomalous object or a layer, object must be divided into many blocks, which requires additional time, and editing the model during the interpretation process becomes more complicated.

 To solve these problems, we can use methods of automatic fitting of the density model (inversion). At the same time, it is convenient to divide the model into many identical cells with constant density (grid). In this case, solving the inverse problem of gravity is reduced to solving a system of linear algebraic equations. To solve the system of equations, it is necessary to construct a loss function, which includes terms responsible for the difference between the observed gravitational field and the theoretical field, as well as for the difference between the model and a priori data (regularizer). Further, the problem is solved using iterative gradient optimization methods (gradient descent method, Newton's method and etc.).

However, in this case, the problem arises – final fitted model differs from the initial by contrasting near-surface layer due to the greater influence of the near-surface cells on the loss function, and the deep sources of gravity field anomalies are not included in inversion. Such models can be used in the processing of gravity data (source-based continuation, filtering), but are useless in solving of geological problems.

To take into account the influence of the deep cells of the model, the following solution is proposed: multiplying the gradient of the loss function by a normalization depth function that increases with depth. For example, such a function can be a quadratic function (its choice is conditioned by the fact that the gravity is inversely proportional to the square of the distance).

The use of inversion with a normalizing depth function allows solving the following problems:

- taking into account both surface and deep sources of gravity anomalies;

- solving the problem of taking into account the density gradient within the layers (since the layer is divided into many cells, the densities of which can be differen);

- reliably determine singular points of anomalous objects;

- significantly reduce the time of  the density model fitting.
Assessment of subseasonal prediction skill of the KMA GloSea5 hindcast experiment
Authors: Ham Suryun , Jeong Yeomin
Published: March 2020

This study evaluated the basic performance of the subseasonal prediction using an ensemble hindcast runs for 20 years (1991-2010) produced by KMA GloSea5. The KMA GloSea5 is global prediction system for subseasonal-to-seasonal time scale, based on the fully-coupled atmosphere, land, ocean, and sea-ice model. To examine the fidelity of the system to reproduce and to forecast phenomena, this study focused on three important aspects: systematic biases of hindcast climatology, error diagnostics related to precipitation, and prediction skill of major climate variability. The major results show the overestimated precipitation over the western Pacific. Precipitation errors related to the enhanced convection processes, it leads to decreased incoming surface heat fluxes by clouds. As a result, SST can be decreased by cloud-radiation processes as well as ocean mixing processes. This study includes the evaluation and the identification of the systematic biases in the global prediction model. Also it focuses on the prediction skill of East Asian summer and winter monsoon with its interaction between tropics or arctic climate, which are major drivers of weather and climate variability in East Asia.