bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of filter cake deposition on the hydraulic conductivity of boreholes
Authors: Nijhof Rein , van Lopik Jan , Bloemendal Martin
Published: March 2021

Efficient construction and operation of borehole heat exchangers (BHEs) are essential in its contribution to the energy transition. In practice, implementation of BHE at larger scale requires low construction costs and high production rates. This requires small diameter drillings to reduce drilling and backfilling material costs, in which achieving a proper backfilling is a challenge. At present, there is an urgent need to improve the available techniques with more effectively and efficiently backfill methods for BHEs. In current Dutch practice, sealing (to prevent short-circuit flow between penetrated aquifers) is achieved by using either clay or grouts as backfilling materials, both have their pro’s and con’s. In optimisation of applying backfilling materials and methods, the filter cake, formed during the drilling procedure, also has a sealing capacity and is overlooked in addressing the sealing of the borehole.

 

In this study the effect of filter cake formation on sealing capacity in unconsolidated sediments is quantified. Filter cake formation in unconsolidated porous formations (aquifers) is a complex process, which is affected by pressure differences between the borehole and the aquifer, aquifer characteristics (e.g. grain size distribution, porosity and permeability) and drilling mud/fluid properties.

A laboratory configuration is designed to stimulate different scenarios during the construction of a BHE. Consequently, the effectiveness, in terms of hydraulic conductivity, of the formed filter cake is determined by falling head tests.

Uniform aquifers with the smallest grain size tested (D50 = 0.22 mm) show a two order of magnitude reduction in hydraulic conductivity, as a direct result of filter cake formation. In contrast, filter cake formation is absent in uniform more coarse sands (D50 ≥ 0.65 mm). This demonstrates that filter cake deposition is highly variable with the grain size of the aquifer penetrated. Moreover, the experiments performed indicate that the deposition of a filter cake is not limited by additive concentrations in the drilling fluid or the duration of drilling fluid exposure to the formation.

This preliminary study creates the foundation for further research, since the experiments demonstrate the potential of filter cakes to significantly contribute to the sealing capacity within a borehole.
Raiders of the Lost Code: Preserving the MOSS Codebase - Significance, Status, Challenges and Opportunities 
Authors: Löwe Peter , Nartišs Māris , Reed Carl N
Published: March 2021

We report on the current status of the software repository of the Map Overlay and Statistical System (MOSS) and upcoming actions to ensure long term preservation of the codebase as a historic geospatial source. MOSS is the earliest known open source Geographic Information System (GIS). Active development of the vector-based interactive GIS by the U.S. Department of Interior began in 1977 on a CDC mainframe computer located at Colorado State University. Development continued until 1985 with MOSS being ported to multiple platforms, including DG-AOS, UNIX, VMS and Microsoft DOS. Many geospatial programming techniques and functionalities were first implemented in MOSS, including a fully interactive user interface and integrated vector and raster processing. The public availability of the WWW in the early 1990s sparked a growth of new Open Source GIS projects, which led to the formation of the Open Source Geospatial Foundation (OSGeo). The goal of OSGeo is to support and promote the collaborative development of open geospatial technologies and data. This includes best practices for project management and repositories for codebases. From its start, OSGeo recognised MOSS as the original forerunner project. After the decline of active use of MOSS since the 1990s, the U.S. Bureau of Land Management (BLM) continued to provide the open source MOSS codebase on an FTP-Server, which allowed use, analysis and reference by URL. This service was discontinued at some point before 2018, which was eventually discovered due to a broken URL link. This led to a global search and rescue effort among the OSGeo communities to track down remaining offline copies of the codebase. In mid 2020 a surviving copy of the MOSS codebase was discovered at the University of Latvia, which is temporarily preserved at the German Institute of Economic Research (DIW Berlin). OSGeo has agreed to make MOSS the first OSGeo Heritage Project to ensure long term preservation in a OSGeo code repository. This is a significant first step to enable MOSS-related research based on the FAIR (Findable, Accessible, Interoperable, Reusable) paradigm. Follow up actions will be required to enable scientific citation and credit by persistent identifiers for code and persons, such as Digital Object Identifiers (DOI) and Open Researcher Contributor Identification Initiative-ID (ORCID-ID) within the OSGeo repository environment. This will advance the OSGeo portfolio of best practices also for other open geospatial projects.

 
Fabric based strength criterion and its application on a layered snowpack
Authors: Singh Anurag Kumar , Mahajan Puneet , Srivastava Praveen Kumar
Published: March 2021

An existing orthotropic elasto-plastic model, which takes the microstructure fabric of trabecular bone into consideration, is extended for snow and used to study the stress response in a layered snowpack. The mean intercept length, determined from X-ray tomography, represents the microstructure fabric in the macroscopic constitutive law. The yield surface for snow accounts for strength asymmetry of snow in tension and compression and shows isotropic hardening till ultimate strength is reached and then softens till complete failure. Tomographic image dataset of various snow types in conjunction with 3D μ- FE analysis of these snow types was used to evaluate the elastic and failure criteria constants in the model. The macroscopic law is implemented as a user subroutine FE code to predict the stress-strain response of snow samples and shows good agreement with the μ-FE based data.

The stress-strain law is used to study stresses in a snowpack of length 5m and thickness between 0.11 to 0.81m with a strong layer of round grain and a weak layer of faceted grains. A plane strain finite element analysis is performed. The density of the strong and weak layers is approximately 210kg/m3, and 118kg/m3, respectively. The snowpack was subjected to gravity, and a skier loads (80kg) and stresses were investigated for slope angles of 0o, 30o, and 90o. The variation of compressive stress normal to slope and shear stress along the snowpack's length for different thicknesses of the strong layer is computed. The maximum normal compressive stress and shear stresses are observed at the centre of the weak layer. The normal compressive stress pattern obtained is in agreement with the previous studies.
WACSWAIN project: isotope and chemical ice core records from Skytrain Ice Rise, Antarctica
Authors: Grieman Mackenzie , Hoffmann Helene , Humby Jack , Mulvaney Robert , Nehrbass-Ahles Christoph , Rowell Isobel , Thomas Elizabeth , Wolff Eric
Published: March 2021

The aim of the WArm Climate Stability of the West Antarctic ice sheet in the last INterglacial (WACSWAIN) project is to investigate the possible collapse of the West Antarctic Ice Sheet (WAIS) and its surrounding ice shelves during the Last Interglacial (~120,000 years ago).  As part of this project, a 651-meter ice core was drilled to bedrock at Skytrain Ice Rise in Antarctica during the 2018/2019 field season.  Ions and elements originating from marine sources along with water isotope content in this ice core can be used to infer changes in ice sheet and ice shelf extent.  The stable water isotope signal has the potential to capture both regional climate change and changes in the elevation of the drilling site through time.  Marine chemical content in the ice core could indicate variability in the proximity of the site to a marine environment.  Water isotopes and chemical impurities in the ice core were analysed continuously using cavity ring down spectroscopy and inductively coupled plasma mass spectrometry, respectively. As expected, δ18O and δD increase from the last glacial maximum to the Holocene.  δ18O and δD increase and sodium and magnesium levels decline from deglaciation into the early Holocene. δ18O and δD show an abrupt increase in the early Holocene at about 8,000 years before present.  Sea salt similarly increases 2-fold and becomes more variable about 1,000 years later (7,000 years before present).  These increases could indicate a retreat of the ice shelf to its current position.
Hydrological excitation of polar motion determined from CMIP6 climate models
Authors: Nastula Jolanta , Śliwińska Justyna , Wińska Małgorzata
Published: March 2021

Climate models provide important information to understand how the climate has changed in the past and how it can evolve in the future. Such models simulate in detail the physics, chemistry and biology of the atmosphere, oceans and land hydrosphere. Climate models are developed and constantly updated by a number of modelling groups around the world. A large number of models makes it necessary to store them in one place, so that they can be easily accessed and compared. The objective of the Coupled Model Intercomparison Project phase 6 (CMIP6) is to make the multi-model output publicly available in a standardized format. This framework aims to improve our understanding of climate changes resulting from both natural factors and changes in radiative forcing. The CMIP6 models are useful in many scientific applications regarding evolution of processes occurring in the atmosphere, ocean and continental hydrosphere.

In this study, we use the chosen climate models to assess the role of land hydrosphere changes in polar motion. The mass variations of land water storage impacts the Earth’s inertia tensor and causes disturbances of the pole motion. Such temporal variations of polar motion due to continental hydrosphere are described with hydrological angular momentum (HAM). Here, we use soil moisture and snow water equivalent variables, which are delivered by CMIP6 simulations, to compute time series of HAM. We then analyse HAM variability in a wide variety of oscillations, taking into account trends, seasonal, short-term non-seasonal and long-term non-seasonal changes. We consider past changes in HAM but also analyse its future evolution. This will allow to determine how future changes in the terrestrial hydrosphere will affect the movement of the pole. The consistency between HAM obtained from various CMIP6 models is assessed as well.
Predictability of tipping points with rate-dependent effects
Authors: Lohmann Johannes , Ditlevsen Peter
Published: March 2021

Due to non-linearities in the dynamics of crucial elements in the climate system, Earth’s safe operating space is limited. Beyond a certain level of a control parameter, such as the atmospheric Greenhouse gas concentration, qualitative regime shifts in one or more sub-systems may take place. Additionally, theoretical studies suggest that abrupt, irreversible change can happen already prior to the crossing of a critical threshold in a control parameter.

In these so-called rate-induced transitions, the effective parameter level to induce tipping depends on the rate of change, or more generally the precise trajectory of the changing control parameter. Here we show rate-induced tipping points of the overturning circulation in a global ocean model. Due to the chaotic dynamics of the system, whether there will be tipping or not depends both on the rate and initial conditions in a very sensitive, non-smooth way. This raises questions about whether the safe operating space is still well-defined, and whether an approach of its boundary can be predicted.

For tipping points associated with slow passages across a bifurcation, generic early-warning signals have been developed for these purposes. Due to the necessarily fast parameter changes involved in rate-induced tipping, early-warning is more challenging. In many cases the tipping involves a saddle escape, which results in a delay of the actual transition and can be exploited for early-warning. Here this is demonstrated in the context of low-dimensional models. While due to the sensitivity of the dynamics around the saddle one might not be able to predict with certainty whether and when the system will tip, the indicators presented here may allow issuing a warning as the system gets close to tipping.
Developing an algorithm to consider sub-grid topographic effects on surface radiation in a kilometre-scale regional climate model
Authors: Steger Christian , Schär Christoph
Published: March 2021

In mountainous regions, atmospheric and surface conditions (like snow coverage) are strongly modulated by complex terrain. One relevant process is the topographic effect on incoming/outgoing surface short- and longwave radiation by surrounding terrain. Radiation in weather and climate models is typically represented by the two-stream approximation, which only allows for vertical radiation exchange and thus no lateral interaction with terrain. In reality, surface radiation can be modulated through various processes: the direct-beam part of the incoming shortwave radiation depends on local surface inclination and on shading from the neighbouring terrain. Incoming diffuse shortwave radiation is modified by partial sky-obstruction and terrain reflection. Outgoing longwave radiation is reduced by interception from neighbouring terrain.

In this study, we develop a parameterisation which considers the above-mentioned processes on a sub-grid scale, and implement the scheme in the Regional Climate Model COSMO (Consortium for Small-scale Modeling). On the grid scale, such a parameterisation is already available and has been applied in the numerical weather prediction mode of COSMO. Applying this parameterisation in the climate mode of COSMO has revealed that biases like the over-/underestimation of snow cover duration at south-/north-facing slopes can be improved. However, the associated radiation correction appears to be too weak because only terrain effects on the resolved scales are considered. We therefore parameterise these effects on a sub-grid scale.

The (current) surface radiation correction scheme requires consideration of topographic parameters like the elevation of the horizon and the sky-view factor. The computation of these parameters on the sub-grid scale is very expensive, because non-local information of a large high-resolution Digital Elevation Model (DEM) needs to be processed. We developed a new algorithm, which allows for horizon computations from a high-resolution DEM in a fast and flexible way. We furthermore found that existing sky-view factor algorithms might yield inaccurate results for locations with very steep terrain and subsequently developed an improved method. Output of these new algorithms will be used for the new sub-grid radiation parameterisation scheme.
Time-lapse synchrotron X-ray imaging of deformation modes in organic-rich Green River Shale heated under confinement 
Authors: Kobchenko Maya , Pluymakers Anne , Cordonnier Benoit , Mondol Nazmul , Renard Francois
Published: March 2021

Shales are layered sedimentary rocks, which can be almost impermeable for fluids and act as seals and cap-rocks, or if a shale layer hosts a fracture network, it can act as a fluid reservoir and/or conduit. Organic-rich shales contain organic matter - kerogen, which can transform from solid-state to oil and gas during burial and exposure to a suitable temperature. When hydrocarbons are expelled from the organic matter due to maturation, pore-pressure increases, which drives the propagation of hydraulic fractures, a mechanism identified to explain oil and gas primary migration. Density, geometry, extension, and connectivity of the final fracture network depend on the combination of the heating conditions and history of external loading experienced by the shale. Here, we have performed a series of rock physics experiments where organic-rich shale samples were heated, under in situ conditions, and the development of microfractures was imaged through time. We used the high-energy X-ray beam produced at the European Synchrotron Radiation Facility to acquire dynamic microtomography images and monitor different modes of shale deformation in-situ in 3D. We reproduced natural conditions of the shale deformation processes using a combination of axial load, confining pressure, and heating of the shale samples. Shales feature natural sedimentary laminations and hydraulic fractures propagate parallel to these laminae if no overburden stress is applied. However, if the principal external load becomes vertical, perpendicular to the shale lamination, the fracture propagation direction can deviate from the horizontal one. Together horizontal and vertical fractures form a three-dimensional connected fracture network, which provides escaping pathways for generated hydrocarbons. Our experiments demonstrate that tight shale rocks, which are often considered impermeable, could host transient episodes of micro-fracturing and high permeability during burial history.
Lead-lag statistical analysis of simultaneous high frequency oceanographic parameters in moored coastal systems
Authors: Schmitt François
Published: March 2021

High-frequency sampling at fixed positions in oceanography are installed all over the World. These provide time series of different oceanographic parameters over large range of scales and can help obtain informations on the complex coupling existing between physical, biogeochemical and biological parameters.

Here we explore the lead-lag information existing between two quantities: this is done by extracting the dissymmetry in the cross-correlation, corresponding to the statistical lead or lag of one series with respect to the other one (it is not necessarily a causality information). This analysis is done for all available parameters, two by two, giving way to generate a network of lead-lag influences.

As example this new approach is applied to the MAREL buoy system installed in Boulogne-sur-mer (France) operated by Ifremer (https://www.seanoe.org/data/00286/39754/). It is a moored buoy equipped with physico-chemical and biological measuring devices working in continuous and autonomous conditions with measurement every 20 minutes. We consider here the measurements at high frequency of air temperature, sea temperature, salinity, dissolved oxygen, fluorescence and turbidity for all year from 2005 to 2013. The new method is applied to the whole data set and also to data every year, in order to see a time evolution of the lead-lag network of relations between all studies parameters.

 

 
Integrating adaptation dynamics in drought risk modelling: The case of smallholder farmers in Kitui
Authors: Wens Marthe , van Loon Anne , Mwangi Moses , Johnson Mike , Veldkam Ted , Aerts Jeroen
Published: March 2021

Ongoing research to capture the socio-hydrologic feedbacks between human adaptation decisions and agricultural drought risk has brought agent-based modelling (ABM) tools to the foreground. We explored how such ABM can be used to integrate heterogeneous individual adaptive behaviour in a drought risk framework. Our ABM framework focuses on adaptation decisions (irrigation, land management) by individual farmers and their interaction with drought hazard, exposure and vulnerability. This framework enables us to more correctly reflect the dynamic nature of drought risk in time and space. Moreover, as the effectiveness of disaster risk reduction policies rests on the complexities of drought adaptive behaviour of the targeted group, we completed multiple data collection activities to understand the adaptation decisions of smallholder farmers under drought risk. These activities, inclusing smallholder farmer questionaires, choice experiments and stakeholder interviews, were based on behavioural theories and their links to socio-economic aspects in semi-arid Kenya, so we could assess what drivers and barriers determine the adoption of drought adaption measures in this context.  Moreover, people’s preferences towards ex-ante cash transfers, timely extension services, tailored early-warning systems, and access to credit markets were tested.

The framework and data collection results were used to calibrate the decision rules in a new ABM (ADOPT), to simulate small-scale agricultural adaptation decisions in response to drought risk in the past. The protection motivation theory is compared with scenarios of no adaptation dynamics and of economic rationality, so as to test different behavioral assumptions. Capturing the spatio-temporal feedbacks between bounded-rational adaptation decisions by smallholder farmers and seasonal weather conditions, ADOPT is capable of mimicking the evolution of heterogeneous adaptation decisions and trends in historic yields over time. We show the benefit of assessing drought risk (poverty, food security and aid needs) on an individual household level. Additionally, we adjusted ADOPT to simulate how smallholder farmers in Kenya respond to drought policy interventions by the government and (future) drought events, explicitly modelling adoption incentives and constraints and the social interactions among farmers. As such, the effect of pro- and reactive top-down decisions by governmental institutions on the household and community vulnerability to droughts could be evaluated in order to find maximized effects on drought resilience.
The Model of Land Surface Movements Induced by Groundwater Rebound in the Area of Former Mining Exploitation
Authors: Guzy Artur , Witkowski Wojciech , Hejmanowski Ryszard , Malinowska Agnieszka
Published: March 2021

The objective of the research was to investigate the process of rock mass recompaction related to groundwater rebound induced by underground mining. Research has been conducted in the area of the closed copper ore mine (Konrad) as well as the anhydrite and gypsum mine (Lubichów) in south-eastern Poland.

The mining operation was carried out in the years 1944-2001 in the area of the Konrad mine and 1944-2015 in the area of the Lubichów mine. It resulted in substantial land subsidence of up to 1.4 m and drainage of the aquifer system. However, it is estimated that the subsidence caused by groundwater pumping during these periods was 0.3 m in total. Furthermore, the spatial extent of the depression cone in the aquifer system immediately after the cessation of exploitation significantly exceeded the limits of the mining areas. Following the closure of the mine, a continuous increase in the groundwater head and land uplift is observed.

Classical survey results and the Persistent Scatter Satellite Radar Interferometry (PSInSAR) method were used to determine land surface movements in the period from November 2015 to November 2020. The results of the research show in the area of the Lubichów mine closed in June 2015, vertical land uplift reached a maximum of approx. 92 mm in that period. At the same time, in the Konrad mine area, closed in March 2001, no significant land uplift was observed. However, the main part of the investigation concerned the development of a novel method of land uplifting prediction. As a result, an attempt was made to comparatively analyze the dynamics of land uplift associated with the life cycle of the mine and the increase in the groundwater head.

These analyzes allowed the time factor for the modelling of the land uplift to be determined. This time factor is approx. 5 months in the area of the Lubichów mine and indicates that there is a time lag between the start of the groundwater head increase and the land uplift occurrence. Also, the investigation revealed that land uplift will occur in the analyzed area for the next five years. However, the dynamics of such movements will gradually decline in the years to come.

The methodology developed could be applied to any post-mining area where groundwater rebound-related uplifts are observed. It may be an appropriate tool for estimating both the time during which the land uplift is expected to begin after the mine drainage has been stopped, as well as the total duration of the land uplift phenomena.
Building an Earth Sytem Model emulator for local monthly temperature
Authors: Nath Shruti , Lejeune Quentin , Beusch Lea , Schleussner Carl , Gudmundsson Lukas , Seneviratne Sonia
Published: March 2021

Emulators are computationally cheap statistical devices that derive simplified relationships from otherwise complex climate models. A recently developed Earth System Model (ESM) emulator, MESMER (Beusch et al. 2020), uses a combination of pattern scaling and a variability emulator to emulate ESM initial-condition ensembles. Linear scaling provides the spatially resolved yearly temperature trend projections from global mean temperature trend values. In addition, the variability emulator stochastically models spatio-temporally correlated local variability, yielding a convincing imitation of the internal climate variability displayed within a multi-model initial condition ensemble. The work presented here extends MESMER’s framework to have a monthly downscaling module, so as to provide spatially resolved monthly temperature values from spatially resolved yearly temperature values. For this purpose, a harmonic model is trained on monthly ESM output to capture monthly cycles and their evolution with changing temperature. Once the mean monthly cycle is sufficiently emulated, a process based understanding of the biases within the harmonic model is undertaken. Such entails employing a Gradient Boosting Regressor tree model (GBR) to explain the residuals from the harmonic model using biophysical climate variables such as albedo and thermal fluxes as explanatory variables. These variables can be rated according to their explanatory power when categorising residuals which furthermore elucidates the main physical processes driving biases in the harmonic model within seasons at the grid point level. Finally we add residual variability ontop of the harmonic model outputs to provide convincing imitations of ESM monthly temperature realisations. The residual variability is generated using an AR(1) process coupled to a multivariate trans-gaussian process so as to maintain spatio-temporal correlations and the non-stationarity in monthly variability with increasing yearly temperatures.

Beusch, L., Gudmundsson, L., & Seneviratne, S. I. (2020). Emulating Earth System Model temperatures: from global mean temperature trajectories to grid-point level realizations on land. Earth System Dynamics, 11(1), 139–159. https://doi.org/10.5194/esd-11-139-2020

 

 
Selecting suitable climate models for examining future changes in soil erosion
Authors: Brannigan Neil , Mullan Donal , Vandaele Karel , Graham Conor , McKinley Jennifer , Meneely John
Published: March 2021

Climate models consistently project large increases in the frequency and magnitude of extreme precipitation events in the 21st century, revealing the potential for widespread impacts on various aspects of society. While the impacts on flooding receive particular attention, there is also considerable damage and associated cost for other precipitation driven phenomena, including soil erosion and muddy flooding. Multiple studies have shown that climate change will worsen the impacts of soil erosion and muddy flooding in various regions. These studies typically drive erosion models with a single model or a few models with little justification. A blind approach to climate model selection increases the risk of simulating a narrower range of possible scenarios, limiting vital information for mitigation planning and adaptation. This study provides a comprehensive methodology to efficiently select suitable climate models for simulating soil erosion and muddy flooding. For a case study region in eastern Belgium using the WEPP soil erosion model, we compare the performance of our novel methodology against other model selection methods for a future period (2081 – 2100). The main findings reveal that our novel methodology is successful in generating the widest range of future scenarios from a small number of models, when compared with other ways of selecting climate models. This approach has not previously been achieved for modelling soil erosion by water. Other precipitation-driven impact sectors may also wish to consider applying this method to assess the impact of future climatic changes, so that the worst- and best-case scenarios can be adequately prepared for.
Developing open-source tools for reproducible inverse problems: the PyLops journey
Authors: Ravasi Matteo , da Costa Filho Carlos Alberto , Vasconcelos Ivan , Vargas David
Published: March 2021

Inverse problems lie at the core of many geophysical algorithms, from earthquake and exploration seismology, all the way to electromagnetics and gravity potential methods.

In 2018, we open-sourced PyLops, a Python-based framework for large-scale inverse problems. By leveraging the concept of matrix-free linear operators – together with the efficiency of numerical libraries such as NumPy, SciPy, and Numba – PyLops solves computationally intensive inverse problems with high-level code that is highly readable and resembles the underlying mathematical formulation. While initially aimed at researchers, its parsimonious software design choices, large test suite, and thorough documentation render PyLops a reliable and scalable software package easy to run both locally and in the cloud.

Since its initial release, PyLops has incorporated several advancements in scientific computing leading to the creation of an entire ecosystem of tools: operators can now run on GPUs via CuPy, scale to distributed computing through Dask, and be seamlessly integrated into PyTorch’s autograd to facilitate research in machine-learning-aided inverse problems. Moreover, PyLops contains a large variety of inverse solvers including least-squares, sparsity-promoting algorithms, and proximal solvers highly-suited to convex, possibly nonsmooth problems. PyLops also contains sparsifying transforms (e.g., wavelets, curvelets, seislets) which can be used in conjunction with the solvers. By offering a diverse set of tools for inverse problems under one unified framework, it expedites the use of state-of-the-art optimization methods and compressive sensing techniques in the geoscience domain.

Beyond our initial expectations, the framework is currently used to solve problems beyond geoscience, including astrophysics and medical imaging. Likewise, it has inspired the development of the occamypy framework for nonlinear inversion in geophysics. In this talk, we share our experience in building such an ecosystem and offer further insights into the needs and interests of the EGU community to help guide future development as well as achieve wider adoption.
Abundance of ice-nucleating particles from the Gruvebadet observatory in Svalbard during 2017-2019
Authors: Hou Yidi , Wilbourn Elise , Hiranuma Naruki , Bruschi Federica , Cappelletti David , Gravina Paola , Mazzola Mauro
Published: March 2021

Atmospheric ice-nucleating particles (INPs) have substantial cloud-phase feedback, and ambient INP concentration may increase in the Arctic region in response to warming (Murray, Carslaw, and Field, 2020). Currently, there are limited INP observations in the Atlantic sector of the Arctic. With the goal of generating new ambient INP data in this particular region, we have measured and studied INP concentrations from Ny-Ålesund (Spitsbergen, Svalbard) during 2017-2019. More specifically, we collected aerosol particles on membrane filters at the Gruvebadet observatory (approx. 50 m above sea level), where a custom-built isokinetic laminar flow inlet is installed. Individual filters collected aerosol particles for 27 hours (at least) to several days with a constant sampling flow of less than 12.8 LPM, which was regulated by a critical orifice. Our sampling periods were  intermittent, but covering all meteorological seasons overall. With these filter samples, we have conducted the offline immersion measurements to produce the INP number concentration dataset at temperatures above -25 °C. We will also present the comparison of our immersion data to previous Arctic INP data. Such data would be invaluable to constrain current atmospheric models and estimate their potential impact on aerosol-cloud-climate interactions in the Arctic region.

 

Acknowledgement:

The authors acknowledge the personnel of the Arctic Station Dirigibile Italia of the National Research Council of Italy for their support to the particle sampling. We also acknowledge contributions of C. A. Rodriguez and H.S. Vepuri for their technical support on WT-CRAFT measurements. This material is based upon work supported by the National Science Foundation under Grant No. 1941317 (CAREER: The Role of Ice-Nucleating Particles and Their Feedback on Clouds in Warming Arctic Climate). The authors acknowledge the NySMAC, Ny-Ålesund Atmosphere Research Flagship Programme, for allowing the organization of a collaborative workshop meeting held in Bologna, Italy, in 2017. The workshop provided a venue for authors to come together that fostered this collaboration.

 

Reference:

Murray, B. J., Carslaw, K. S., and Field, P. R.: Opinion: Cloud-phase climate feedback and the importance of ice-nucleating particles, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2020-852, in review, 2020.
Integrating Land Cover and Land Management feedbacks into climate models: an emulator approach
Authors: Lejeune Quentin , Nath Shruti , Schleussner Carl , Schwaab Jonas , Seneviratne Sonia
Published: March 2021

The role of Land Cover and Land Management (LCLM) changes in shaping the climate has garnered increasing interest, particularly in light of its potential for climate adaptation and mitigation. Earth System Models (ESMs), however, have hitherto handled LCLM-climate interactions as a unidirectional process, lacking explicit treatment of LCLM-Climate feedbacks. These feedbacks nevertheless are linked to extreme climate events such as heat waves and drought, which in turn carry economic costs through worker productivity, crop yields and food prices. It is thus essential to integrate LCLM processes and their feedbacks into a ESMs, in order to build consistent storylines for future development pathways that take into account their potential for adaptation and mitigation. Emulators represent a computationally cheap but effective way of approximating ESM with an added advantage of agility in scenario exploration. Here we outline an emulator approach to represent LCLM-Climate feedbacks based on a framework developed by Beusch et al. (2020). The emulator provides monthly, spatially explicit data from yearly global mean temperature and uses Generalised Additive Models (GAMs) to represent LCLM-Climate feedbacks. The emulator is to be used in the LAnd MAnagement for CLImate Mitigation and Adaptation (LAMACLIMA) project, and is trained on dedicated ESM simulations that isolate the effects of key land management practices focussed on by LAMACLIMA: irrigation, de/reforestation and wood. Key variables produced by the emulator include temperature, Wet Bulb Globe Temperature and labour productivity.

 

Beusch, L., Gudmundsson, L., & Seneviratne, S. I. (2020). Emulating Earth System Model temperatures: from global mean temperature trajectories to grid-point level realizations on land. Earth System Dynamics, 11(1), 139–159. https://doi.org/10.5194/esd-11-139-2020
Quantifying space-weather events using dynamical network analysis of ground based magnetometers
Authors: Chaudhry Shahbaz , Chapman Sandra , Gjerloev Jesper
Published: March 2021

Space-weather events known as storms/sub-storms can have severe impacts on technological systems, on the ground and in space, including damage to satellites and power blackouts in severe cases. Quantitative understanding of the highly non-linear magnetospheric system during storms/sub-storms is important as our reliance on space based systems increases. We perform network analysis on the 100+ ground-based magnetometer stations collated by SuperMAG. One of the key geomagnetic responses to space weather events are Pc waves which are oscillations along whole magnetospheric magnetic field lines. Recently SuperMAG has offered the full set of Pc measurements collating magnetometer data globally. High quality Pc wave data has only been available locally across magnetometer chains. However, now with SuperMAG these measurements these are available globally with uniform background calibration and time-base. To fully exploit this data requires a new application of analysis tools, for the first time we apply dynamical network analysis to this data set. Obtaining Pc waves over a range of frequencies allows us to probe multiple time and length scales, likely corresponding to different physical generation mechanisms. We will aim to obtain the global Pc wave dynamical networks over individual space weather events in order to quantify the full spatio-temporal response of the magnetosphere to storms/sub-storms with a few network parameters.

To create the network we first band-pass filter magnetometer time series data into four known frequency intervals. Next the data is time-lagged-cross-correlated (TLXC) for each band ensuring a window at least twice the Pc wave period of interest. We then we use noise surrogates to establish a threshold to filter out insignificant peak TLXC values. For each windowed TLXC we build a peak-classification routine (PCR) to determine whether a signal is wavelike or not to then determine the phase difference. The PCR determines whether a network connection is directed or undirected between two geospatially located magnetometer stations for each time window. If the signal/time-series phase difference is found as non-zero for the TLXC function there is a directed network connection pair, otherwise an undirected network connection pair is formed. We perform the TLXC and PCR for each frequency band and between all magnetometer time-series pairs to obtain four dynamical directed and four dynamical undirected networks. The undirected networks quantify the onset time, and spatial extent, of large-scale coherent Pc wave activity. While directed networks also quantify how Pc wave activity is propagating across the magnetosphere for non-coherent Pc wave activity.

Quantifying the full spatio-temporal response of the magnetosphere across 100s of ground based magnetometers with a few parameters also forms the basis of statistical studies across many events.
Visibility study of Galileo satellites from a VLBI network
Authors: Wolf Helene , Böhm Johannes , Schartner Matthias , Hugentobler Urs
Published: March 2021

Over the last years, ideas have been proposed to install a Very Long Baseline Interferometry (VLBI) transmitter on one or more satellites of the Galileo constellation. Satellites transmitting signals that can be observed by VLBI telescopes provide the opportunity of extending the current VLBI research with observations to geodetic satellites. These observations offer a variety of new possibilities such as high precision tying of space geodetic techniques but also the direct determination of the absolute orientation of the satellite constellation with respect to the International Celestial Reference Frame (ICRF) and have implications on the determination of long-term reference frames. 

This contribution provides a visibility study of the Galileo satellites from a VLBI network. The newly developed satellite scheduling module in VieSched++ is used to determine the time periods during which a satellite is observable from a VLBI network. The possible satellite observations are evaluated through the number of stations from which a satellite is observable. Moreover, the impact on determining the orientation of the satellite constellation, caused by the observation geometry, is investigated with using the UT1-UTC Dilution of Precision (UDOP) factor.
Mirror fault formation and coseismic slip at surface conditions: an example of faulting in unconsolidated deposits in the Central Apennines (Italy)
Authors: Demurtas Matteo , Plümper Oliver , Ohl Markus , Balsamo Fabrizio , Pizzati Mattia
Published: March 2021

Faulting in seismically active regions commonly involves the deformation of unconsolidated to poorly lithified sediments at shallow to near-surface depths. When compared to classic crustal strength profiles that predict a velocity-strengthening behaviour for the first few km of depth, the propagation of seismic rupture to the surface appears counterintuitive. Rock deformation experiments have shown an inverse relationship between normal stress and displacement needed to the onset of dynamic weakening during seismic slip, meaning that for a seismic rupture to be able to propagate towards the surface, displacements should be large enough to counter the progressive decrease of normal and confining stresses.

In this contribution, we document the occurrence of mirror-like faults that formed within 20-30 m-thick, unconsolidated colluvium fan deposits at the hanging wall of the active Vado di Corno Fault Zone (VCFZ) in the Central Apennines, Italy. The deposits lie in direct contact with the master normal-fault surface, are Late Pleistocene to Holocene in age, and consist of angular carbonate clasts with grain size ranging ~0.1-10 mm derived from the dismantling of the adjacent VCFZ footwall. Field observations of cross cutting relationships and marker layer displacements suggest a maximum formation depth of the faults of c. 20-30 m and slip accommodated along single faults on the order of few cm. Faults are organised in three sets: subvertical, N-S and NE-SW trending faults, and WNW-ESE striking faults, synthetic and antithetic to the VCFZ master fault surface (N195/55°). Faults are commonly lineated with a dip-slip to slightly oblique kinematic.

Detailed microstructural analysis of the mirror faults shows extreme strain localization on a 2-5 µm thick principal slip zone composed of calcite nanograins ranging 10s-100s nm in size with amorphous material and phyllosilicates occurring along grain boundaries and within intragranular porosity. Locally, aggregates of nanograins coalesce and transition to µm-sized polygonal, larger grains. Calcite nanograins are mostly equant, with straight grain boundaries, 120° dihedral angles, and negligible porosity. These microstructures strongly resemble high temperature recrystallization structures documented along seismic faults exhumed from >5 km of depth, where stresses are significantly larger. In our case, field constraints show that deformation occurred in very confining stress conditions and with limited displacement.

Collectively, our observations provide new documentation on the conditions for the formation of mirror faults and new insights into the mechanics of faulting and strain accommodation in the shallowest part of the crust (< 1 km).
The reinforcement effect of vegetation on live cribwalls
Authors: Gonzalez Ollauri Alejandro , Mickovski Slobodan , Emmanuel Rohinton , Sorolla Edo Albert
Published: March 2021

Live cribwalls are Nature-based solutions consisting of timber-based structures acting as retention walls at the toe of slopes and embankments subjected to instability and erosion events. The structure of live cribwalls resembles a multi-level crib made of timber logs from different plant species (e.g. pine, spruce, hazelnut, etc.). The crib structure is then backfilled with earth materials in which locally-available plant cuttings and/or saplings are inserted to establish a dense cover of native vegetation, providing added reinforcement and stability to the cribwall over time; particularly after the complete decay of the timber structure is reached. However, the effect of vegetation on the reinforcement of live cribwalls has not been examined systematically. Information on how vegetation can contribute to reinforce cribwalls hydrologically and mechanically is essential to evaluate the long-term performance of these Nature-based solutions against hydro-meteorological hazards. In this study, we propose a novel conceptual, numerical model based on empirical knowledge to evaluate the reinforcement effect of vegetation on live cribwalls over time. We also demonstrate how the proposed model can be applied to other Nature-based solutions concerned with slope protection and erosion control, such as live gratings or palisades.
Organic photovoltaics as a solution to overcome growing atmospheric carbon emissions
Authors: Tchognia Nkuissi Hervé , Labiod Amina , Ferry Stéphanie , Lévêque Patrick , Heiser Thomas
Published: March 2021

Nowadays, climate change is a reality because energy demand is mostly satisfied by fossil fuels which are limited resources and also responsible for greenhouse gas emissions. Actions have to be undertaken to overcome this issue. Among the solutions proposed to this is the development and use of new energy sources called renewable energies. By renewable energy, we understand energies coming from the sun, wind, geothermal, water, or biomass. Of these, solar energy is one of the most abundant, clean, effective, and easily deployed. One of the efficient ways to exploit solar energy is photovoltaics.

Two decades of research have allowed organic photovoltaics to appear today as an alternative to their conventional and inorganic counterparts. However, several issues have to be addressed in order to ease their production on an industrial level. Bulk heterojunction (BHJ) solar cells based on the blend of two types of conjugated molecules acting as an electron donor (hole transport) and an electron acceptor (electron transport) are the most efficient organic solar cells. Further, using non-fullerene acceptors (or NFA) in these BHJ solar cells have recently gained a broad interest due to their great potential to realize high conversion efficiencies (more than 18%) with a long lifetime over the conventional polymer/fullerene blend solar cells.

Here we provide an overview of the recent progress of different existing and growing photovoltaic technologies. We also provide prospects for the future development of organic photovoltaic devices.