bluuebunny/crossref_metadata_2025 huggingface dataset:
Secondary Ice Production – development of a new experimental set-up
Authors: Hartmann Susan , Keinert Alice , Kiselev Alexei , Stratmann Frank
Published: March 2021

Mixed-phase clouds are essential elements in Earth’s weather and climate system. Aircraft measurements of mixed-phase clouds demonstrated a strong discrepancy between the observed ice particle and ice nucleating particle number concentration of one to four orders of magnitude [1-4]. Different secondary ice production (SIP) mechanisms have been hypothesized which can increase the total ice particle number concentration by multiplication of primary ice particles and hence might explain the observed discrepancy [5-7].

In a joint project of KIT and Tropos, we focus on the investigation two SIP processes: shattering of large freezing droplets (KIT) and SIP as a result of droplet-ice collisions (Tropos), commonly known as Hallett-Mossop [9] or rime-splintering process. Thereby, we aim at a quantitative understanding of the SIP underlying physical mechanisms, utilizing a newly developed experimental set-up (Ice Droplets splintEring on FreezIng eXperiment, IDEFIX).  

IDEFIX is based on a modular concept and consists of three modules, i.e., the SIP chamber, the growth section, and the ice particle detector. We developed two different versions of the SIP chamber: in the KIT-SIP chamber a freezing drizzle droplet is levitated in electrodynamic balance; and in the TROPOS-SIP chamber quasi-monodisperse droplets collide with an ice particle which is fixed on thin carbon fibers. IDEFIX is designed to match realistic fall or impact velocities and collision rates of the droplets with the ice particle. The SIP process will be observed with high-speed video microscopy and an infrared measuring system. In the growth section, which features supersaturated conditions with respect to ice, the presumably small secondarily produced ice particles will be grown to detectable sizes. Finally, to count the number of secondarily produced ice particles either an optical particle spectrometer will be used for distinguishing between droplets and ice particles, or the ice particles will be impacted on a metastable sugar solution. Currently, we characterize velocity, temperature and humidity fields of the TROPOS-collision chamber and determine droplet-ice particle collision rates.
Monthly surface water storage from a global rainfall-runoff model for signal separation of GRACE-based terrestrial water storage variations
Authors: Haas Julian , Sharifi Ehsan , Salamon Peter , Güntner Andreas
Published: March 2021

In the EU-funded project Global Gravity-based Groundwater Product (G3P), we strive to combine data on terrestrial water storage from satellite gravimetry by the GRACE and GRACE-FO missions with existing products on water storage compartments from the Copernicus portfolio to establish a new cross-cutting product on groundwater storage variations with global coverage on a monthly basis. While the focus of G3P lies on incorporating observation-based Copernicus products, some model data has to be added to fill spatial and temporal gaps. This especially applies to water storage variations in surface water bodies, i.e., lakes and rivers, where little observation-based data is available. Altimetry-based data bases such as HYSOPE and the MGB model are available for large surface water bodies. However, to account for smaller water bodies and rivers, and to have a basis for assessing uncertainties of the entire approach, the integration of well-established models is desirable. A model we deem fit to these ends is Lisflood, which underpins the Global Flood Awareness System (GloFAS) of the Copernicus Emergency Management Service, and for which a recent global re-calibration is available.

In this study, we evaluate Lisflood’s capability of modeling surface water storage variations in comparison to the above-mentioned observational data sources as well as the WaterGAP Global Hydrology Model (WGHM). As the target output of G3P is a 0.5° grid with monthly resolution, Lisflood’s output data will undergo an upscaling and temporal aggregation procedure which will also be subject of this study.

Acknowledgments: This study received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement nº 870353.
Fuel type mapping in a typical Mediterranean ecosystem using object-based image analysis of Sentinel 2 imagery and auxiliary GIS data
Authors: Karystinakis Konstantinos , Alexandridis Vasileios , Stefanidis Stefanos , Kalantzi Georgia
Published: March 2021

Wildfires have been an integral part of the Mediterranean ecosystem. Moreover, the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report emphasizes that the Mediterranean basin is expected to be drier by the end of the 21st century, while future warming will possibly be higher than the global mean. Therefore, outbreaks of wildfires are expected to increase. One of the most important factors for wildfire behavior apart from the meteorological conditions, is fuel types. In this study, a detailed fuel type mapping in a case study area was addressed. To accomplish this goal, an object-based image analysis (OBIA) approach was implemented using the open-source Orfeo toolbox. The freely available Sentinel-2A satellite images were processed in combination with auxiliary European and National scale GIS data. The classification results demonstrate a high-quality Land Cover map with 84% of overall accuracy. The classified land cover polygons were associated with high-resolution tree cover density data derived from Copernicus Land Monitoring Service. This coupling led to the synthesis of the fuel type map. To this end, this approach can fulfill the efficient mapping of fuel types for operational purposes. This research has been co‐financed by the European Regional Development Fund of the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH –CREATE –INNOVATE  (project code:T2EDK-01967)
LCZ Generator: online tool to create Local Climate Zone maps
Authors: Demuzere Matthias , Kittner Jonas , Bechtel Benjamin
Published: March 2021

Since their introduction in 2012, Local Climate Zones (LCZs) emerged as a new standard for characterising urban landscapes, providing a holistic classification approach that takes into account micro-scale land-cover and associated physical properties. In 2015, as part of the community-based World Urban Database and Access Portal Tools (WUDAPT) project, a protocol was developed that enables the mapping of cities into LCZs, using freely available data and software packages, yet performed on local computing facilities. The ‘LCZ Generator’ described here further simplifies this process, providing an online platform that maps a city of interest into LCZs, solely expecting a valid training area file and some metadata as input. The tool integrates the state-of-the-art of LCZ mapping, and simultaneously provides an automated accuracy assessment, training data derivatives and a novel approach to identify suspicious training areas. In addition, this development will ease the dissemination of maps and metadata. We anticipate this development will significantly ease the accessibility and workflow of researchers and practitioners interested in using the LCZ framework for a variety of urban-induced human and environmental impacts.
Towards synergy of GNSS and InSAR mining deformation monitoring with Sentinel-1 data
Authors: Tondaś Damian , Ilieva Maya , Rohm Witold , Kapłon Jan
Published: March 2021

The determination of ground deformation may be carried out by applying various measurement methods such as levelling, laser scanning, satellite navigation systems, Synthetic Aperture Radar (SAR) and many others. In this work, we focus on the comparison of the deformation effects measured by Global Navigation Satellite Systems (GNSS) and satellite Interferometric SAR (InSAR) methods in the Upper-Silesian coal mining region (SW Poland).

An unquestionable advantage of GNSS technology is the possibility of continuous monitoring of deformations in three-dimensional space. Moreover, the evolution of real-time (RT) techniques such as: near real-time (NRT), ultra-fast NRT or RT allows to obtain a high precise position determination with a relatively slight latency (ranging from a few seconds to less than one hour). The limitation of the satellite navigation technology is the spatial range of the measurements. The deformation can only be observed at the point where the GNSS antenna is located. Furthermore, the acquisition, installation and maintenance of the equipment may also involve high costs.

In contrast to the GNSS technique, the InSAR methods enable measurement of the large-scale subsidence areas with possibility to use free products and software (e.g. Sentinel-1 and SNAP). The large-scale InSAR investigations provide a better overview of local terrain changes. Unfortunately, InSAR methods also have some limitations related to data acquisition technology:  

a few days latency in acquiring a new image,

insensitivity to changes in the northern component,

acquiring deformation only in the LOS direction.

The main goal of this research is to analyse the deformation results obtained using GNSS and InSAR methods with respect to the capabilities and limitations of these two techniques. We investigated the level of agreement of eight GNSS and InSAR time series in areas with no subsidence, together with results acquired on seven regions of mining deformation where the maximum subsidence velocity exceeds 50 cm/year. The mean RMS time series fitting error obtained in subsidence basin is more than 5 cm and in non-deformed areas is equal to 2 cm. The study also investigated the effect of coherence threshold levels (0.3 ÷ 0.6) with introduction of the northern GNSS component on the InSAR decomposition process. Assuming the same GNSS deformation value in each directions (north, east, and up), the impact of the northern component was estimated as 10% of the total LOS subsidence.
Evaluation of key parameters controlling phenology-induced variability of surface fluxes in land surface models
Authors: De Pue Jan , Barrios José Miguel , Liu Liyang , Ciais Philippe , Arboleda Alirio , Hamdi Rafiq , Balzarolo Manuela , Janssens Ivan , Maignan Fabienne , Gellens-Meulenberghs Françoise
Published: March 2021

Over the past decades, land surface models have evolved into advanced tools which comprise detailed process descriptions and interactions at a broad range of scales. One of the challenges in these models is the accurate simulation of plant phenology. It is a key element at the nexus of the simulated hydrological and carbon cycle, where the leaf area index (LAI) plays a major role in flux partitioning, water balance and gross primary production.
In this study, three well-established models are used to simulate the intrinsically coupled fluxes of water, energy and carbon from terrestrial vegetation. ORCHIDEE, ISBA-CC and the LSA-SAF algorithm each have a different approach to represent plant phenology. Whereas ISBA-CC has a fairly simple biomass allocation scheme to represent the phenological cycle, ORCHIDEE relies on a dedicated phenology module, and LSA-SAF is driven by remote-sensed forcing variables, such as LAI. Simulations were performed for a wide range of hydro-climatic biomes and plant functional types at field scale. The simulated fluxes were validated using eddy-covariance measurements, and the simulated phenology was compared to remote-sensed observations.
These models are tools to extrapolate leaf-level processes to global scale climate predictions. The origin of the parameters controlling phenology-induced variability in these models ranges from plant-scale lab experiments to global-scale calibration. The aim of this study is to investigate the key parameters controlling phenology-induced variability in these models.
A Bayesian approach towards daily pan-Arctic sea ice freeboard estimates from combined CryoSat-2 and Sentinel-3 satellite observations
Authors: Gregory William , Lawrence Isobel , Tsamados Michel
Published: March 2021

Observations of sea ice freeboard from satellite radar altimeters are crucial in the derivation of sea ice thicknessestimates, which in turn inform on sea ice forecasts, volume budgets, and productivity rates. Current spatio-temporalresolution of radar freeboard is limited as 30 days are required in order to generate pan-Arctic coverage fromCryoSat-2, or 27 days from Sentinel-3 satellites. This therefore hinders our ability to understand physical processesthat drive sea ice thickness variability on sub-monthly time scales. In this study we exploit the consistency betweenCryoSat-2, Sentinel-3A and Sentinel-3B radar freeboards in order to produce daily gridded pan-Arctic freeboardestimates between December 2018 and April 2019. We use the Bayesian inference approach of Gaussian Process Regressionto learn functional mappings between radar freeboard observations in space and time, and to subsequently retrievepan-Arctic freeboard, as well as uncertainty estimates. The estimated daily fields are, on average across the 2018-2019season, equivalent to CryoSat-2 and Sentinel-3 freeboards to within 2 mm, and cross-validation experiments show thaterrors in predictions are, on average, within 3 mm across the same period. This method presents as a robust frameworkwhich can be used to model a wide range of statistical problems, from interpolation of altimetry data sets, to timeseries forecasting.
Time Constraints on Seepage Through Fractured Regions on the Vestnesa Ridge off the W-Svalbard Coast
Authors: Ramachandran Hariharan , Plaza-Faverola Andreia , Daigle Hugh , Buenz Stefan
Published: March 2021

Evidences of subsurface fluid flow-driven fractures (from seismic interpretation) are quite common at Vestnesa Ridge (around 79ºN in the Arctic Ocean), W-Svalbard margin. Ultimately, the fractured systems have led to the formation of pockmarks on the seafloor. At present day, the eastern segment of the ridge has active pockmarks with continuous methane seep observations in sonar data. The pockmarks in the western segment are considered inactive or to seep at a rate that is harder to identify. The ridge is at ~1200m water depth with the base of the gas hydrate stability zone (GHSZ) at ~200m below the seafloor. Considerable free gas zone is present below the hydrates. Besides the obvious concern of amount and rates of historic methane seeping into the ocean biosphere and its associated effects, significant gaps exist in the ability to model the processes of flow of methane through this faulted and fractured region. Our aim is to highlight the interactions between physical flow, geomechanics and geological control processes that govern the rates and timing of methane seepage.

For this purpose, we performed numerical fluid flow simulations. We integrate fundamental mass and component conservation equations with a phase equilibrium approach accounting for hydrate phase boundary effects to simulate the transport of gas from the base of the GHSZ through rock matrix and interconnected fractures until the seafloor. The relation between effective stress and fluid pressure is considered and fractures are activated once the effective stress exceeds the tensile limit. We use field data (seismic, oedometer tests on calypso cores, pore fluid pressure and temperature) to constrain the range of validity of various flow and geomechanical parameters in the simulation (such as vertical stress, porosity, permeability, saturations).

Preliminary results indicate fluid overpressure greater than 1.5 MPa is required to initiate fractures at the base of the gas hydrate stability zone for the investigated system. Focused fluid flow occurs through the narrow fracture networks and the gas reaches the seafloor within 1 day. The surrounding regions near the fracture network exhibit slower seepage towards the seafloor, but over a wider area. Advective flux through the less fractured surrounding regions, reaches the seafloor within 15 years and a diffusive flux reaches within 1200 years. These times are controlled by the permeability of the sediments and are retarded further due to considerable hydrate/carbonate formation during vertical migration. Next course of action includes constraining the methane availability at the base of the GHSZ and estimating its impact on seepage behavior.
Measurements of anisotropic poroelastic moduli in Westerly granite
Authors: Elsigood Bobby , Brantut Nicolas , Meredith Philip , Mitchell Tom , Healy David
Published: March 2021

We measured both drained (dry and saturated) and undrained elastic and poro-elastic moduli in a sample of thermally cracked Westerly granite. Measurements were made at nominal effective confining pressures of 30 MPa and 100 MPa. Differential stress was also applied to the sample in order to induce increasing anisotropy (transverse isotropy). Radial and axial stress were independently cycled at increasing levels of differential stress to enable the measurement of anisotropic moduli in a sample with increasing anisotropy. Measurements were first conducted under dry conditions in order to obtain the drained dynamic moduli before the sample was saturated with water.
We used newly developed, miniature differential pressure transducers were located directly around the sample surface, which allowed for direct measurement of Skempton's radial coefficient Bx and axial coefficient Bz. Wavespeeds measured on the dry sample were inverted to obtain the compliances Cijkl. The coefficients Bx and Bz were then calculated indirectly from the compliances using poro-elasticy theory for comparison with the direct measurements. Our results show that the values of Bz calculated from the compliances compare well with those measured directly, but that the calculated values of Bx significantly overestimate those measured directly, particularly at an effective pressure of 30 MPa. The discrepancy between the direct measurements and those obtained from drained moduli is likely due to nonlinear elastic effects, such as crack closure and opening, which occur during the small but finite pressure and stress steps.
GPU acceleration of the FESOM-2 ocean and sea-ice model
Authors: van den Oord Gijs , Sclocco Alessio , Moulard Georges-Emmanuel , Guibert David , Sidorenko Dmitry , Koldunov Nikolay , van Werkhoven Ben , Raffin Erwan , Rakowski Natalja
Published: March 2021

FESOM-2 is a finite volume ocean circulation and sea ice model developed by the Alfred Wegener Institute (AWI). It solves the primitive equations using the hydrostatic and Bousinessq approximations on an unstructured grid, allowing seamless mesh resolution increase towards eddy-resolving scales in regions of high variability or along coast lines. FESOM-2 is a highly optimized MPI-parallel Fortran code that displays excellent scaling to tens of thousands of cores. In the context of ESiWACE-2 services, we have explored the benefits of GPU acceleration of FESOM-2 in a six-month engineering effort. We have determined the flux-corrected tracer transport, and in particular the advection of temperature and salinity, to be a dominant factor in the application profile and we have ported this routine to GPUs using both OpenACC and CUDA-C. We conclude that the memory access patterns in FESOM-2 are suitable to map onto GPU accelerators and that both strategies are viable options, giving significant speedups for tracer advection in high-resolution mesh configurations. We have benchmarked the ported application on Nvidia Kepler, Volta and Ampere architectures and observe that our tuned kernels can approach the peak memory bandwidth, and we also see that OpenACC offers a competitive performance with less development and maintenance effort. We conclude that an expansion of the OpenACC directives is the most promising road to utilize upcoming GPU-equipped exascale machines for FESOM-2.
A postmortem approach via X-ray computed tomography and thresholding to investigate fracture network evolution in Onagawa shale
Authors: Jayawickrama Eranga , Muto Jun , Sasaki Osamu , Nagahama Hiroyuki
Published: March 2021

A postmortem technique is introduced to investigate the fracture connectivity evolution under elevated confining pressures via a sensitivity analysis. Three Onagawa shale samples are deformed under brittle, ductile, and transition conditions, by increasing the confining pressures. Brittle deformation is characterized by longitudinal splitting of the sample at 3% axial strain, and the onset of transition from brittle to ductile deformation is between 4% ~ 5% axial strain. The ductile deformation is characterized by a distributed conjugate fracture network and strain hardening. In completion of the deformation, the samples are scanned in a commercially available X-ray CT machine. The grayscale values of the primary 2D images were reversed, stacked, and surface rendered to obtain the 3D volume distribution of the fractures. Reversing and surface rendering allowed the acquisition of volume and surface data of the fractures along with their direct visualization. Further, utilizing a residual analysis, the voxel value density distribution that fabricated the fracture network is extracted (Residual histogram). Thresholding of the residual histogram generated volume segments of the final fracture network demonstrating the sensitivity of the fracture network to the choice of threshold. Voxel volumes of fractures alone are obtained by thresholding post-peak voxel values of the residual histogram and consecutive post-peak thresholding shows that the generated volume segments of the fracture network can be utilized to interpret, possible nucleation sites after strain localization, propagation of fractures, and coalescence. Fracture connectivity is quantified by means of relative entropy from information theory, and the relative entropy of size distribution of fracture volumes showed that it is closer to zero with the fractures being well connected. Moreover, the cumulative fracture volume shows a power-law growth towards the failure after a unique threshold to each sample. These results have been validated by previous acoustic emission studies and a 4D tomographic investigation on strain localization of shale. Therefore, despite the postmortem nature of the investigation, the new technique has opened possibilities to investigate the fracture properties and their evolution under elevated confining pressures.
Long-term aerosol number size distributions down to 1 nm in urban Beijing
Authors: Deng Chenjuan , Li Yiran , Chen Xiaotong , Jiang Jingkun
Published: March 2021

To reveal the characteristics of aerosols in polluted environments, we measured aerosol number size distributions in the size range of ~1 nm – 10 μm during 2018- 2020 in urban Beijing. As a vital process influencing the aerosol size distributions, new particle formation (NPF) events were frequently observed in urban Beijing. We classified NPF days into typical NPF days with a burst of sub‑3 nm particles and those with few sub‑3 nm particles. We examined their characteristics and possible reasons. The mean aerosol number size distributions were clearly different and the peak particle diameter was ~1.5 nm and 12 nm, respectively. For those with a burst of sub-3 nm particles, however, the peak diameter shifts from small diameter to larger particle diameters as the aerosol size distribution evolves during the NPF process and then becomes similar to those with few sub-3 nm particles. Meteorological analysis indicates that airmass movement may account for these observations. Despite these differences, similar diurnal patterns were observed on most days in urban Beijing, i.e., drastic change in aerosol size distributions happens around 4:00 a.m. and 4:00 p.m.
Offline-Online Change Detection for Sentinel-1 InSAR Time Series
Authors: Novellino Alessandro , Hussain Ekbal , Jordan Colm , Bateson Luke
Published: March 2021

Traditional applications of Interferometric Synthetic Aperture Radar (InSAR) data involved inverting an interferogram stack to determine the average displacement velocity. While this approach has useful applications in continuously deforming regions, new tools are needed for automatically and regularly identifying changes in the time series. Thanks to regular acquisitions across most of the world by the ESA Sentinel-1 satellites constellation, we are now in a position to explore opportunities for near-real time deformation monitoring. In this paper we present a statistical approach for detecting offsets and gradient changes in InSAR time series. Our key assumption is that 5 years of Sentinel-1 data is sufficient to calculate the population standard deviation of the detection variables. Our offset detector identifies statistically significant peaks in the first, second and third difference series. The gradient change detector identifies statistically significant movements in the second derivative series. We exploit the high spatial resolution of Sentinel-1 data and the spatial continuity of geophysical deformation signals to filter out false positive detections that arise due to signal noise. When combined with near-real time processing of InSAR data these detectors, particularly the gradient change, could be used to detect incipient ground deformation associated with geohazards such as landslides or volcanic eruptions.
Impact of Low-Degree Stokes Coefficients and Spatial Leakage on Barystatic Sea-Level Rise from GRACE/GRACE-FO
Authors: Thomas Maik , Dobslaw Henryk , Bagge Meike , Dill Robert , Klemann Volker , Boergens Eva , Dahle Christoph , Flechtner Frank
Published: March 2021

Temporal variations in the total ocean mass representing the barystatic part of present-day global-mean sea-level rise can be directly inferred from time-series of global gravity fields as provided by the GRACE and GRACE-FO missions. A spatial integration over all ocean regions, however, largely underestimates present-day rates as long as the effects of spatial leakage along the coasts of in particular Antarctica, Greenland, and the various islands of the Canadian Archipelago are not properly considered.

Based on the latest release 06 of monthly gravity fields processed at GFZ, we quantify (and subsequently correct) the contribution of spatial leakage to the post-processed mass anomalies of continental water storage and ocean bottom pressure. We find that by utilizing the sea level equation to predict spatially variable ocean mass trends out of the (leakage-corrected) terrrestial mass distributions from GRACE and GRACE-FO consistent results are obtained also from spatial integrations over ocean masks with different coastal buffer zones ranging from 400 to 1000 km. However, the results are critically dependent on coefficients of degree 1, 2 and 3, that are not precisely determined from GRACE data alone and need to be augemented by information from satellite laser ranging. We will particularly discuss the impact of those low-degree harmonics on the secular rates in global barystatic sea-level.
A strain rate model for Europe from a dense network of GNSS
Authors: Steffen Holger , Steffen Rebekka , Kenyeres Ambrus , Caporali Alessandro , Zurutuza Joaquin , Lidberg Martin
Published: March 2021

Strain rates are an important factor to find areas that are under stress. Higher strain rates are usually observed along plate boundaries, while lower strain rates are found in intraplate regions. The increased availability of velocity solutions from Global Navigation Satellite System (GNSS) for entire Europe allows a 2D strain rate to be estimated at high resolution. Thus, regions of high and low strain become clearly visible. Here, we will present a new strain rate model, which is based on a recent velocity field solution by the EUREF Permanent Network Densification (EPND2100). This velocity field is obtained by the combination of weekly position SINEX solutions generated by 28 EPND Analysis Centres. More details on EPND can be found in the www.epnd.sgo-penc.hu website. The homogenized and quality checked velocity field is then interpolated via a least-square collocation using a fixed scale length of 135 km. In addition, the effect of known plate boundaries is considered during the interpolation to avoid a smoothing of nearby velocities on different tectonic plates. We also apply a moving variance approach to avoid effects of non-stationarity, which arise due to the variable station densities. The interpolated velocity model is then used to estimate a 2D strain rate covering most of Europe. We will highlight the situation in intraplate areas with very low strain rates but dense GNSS networks.
Can hydrological model identifiability be improved? Stress-testing the concept of stochastic calibration
Authors: Kourakos Vasileios , Efstratiadis Andreas , Tsoukalas Ioannis
Published: March 2021

Hydrological calibrations with historical data are often deemed insufficient for deducing safe estimations about a model structure that imitates, as closely as possible, the anticipated catchment behaviour. Ιn order to address this issue, we investigate a promising strategy, using as drivers synthetic time series, which preserve the probabilistic properties and dependence structure of the observed data. The key idea is calibrating a model on the basis of synthetic rainfall-runoff data, and validating against the full observed data sample. To this aim, we employed a proof of concept on few representative catchments, by testing several lumped conceptual hydrological models with alternative parameterizations and across two time-scales, monthly and daily. Next, we attempted to reinforce the validity of the recommended methodology by employing monthly stochastic calibrations in 100 MOPEX catchments. As before, a number of different hydrological models were used, for the purpose of proving that calibration with stochastic inputs is independent of the chosen model. The results highlight that in most cases the new approach leads to stronger parameter identifiability and stable predictive capacity across different temporal windows, since the model is trained over much extended hydroclimatic conditions.
The Marslabor of the University of Basel: Simulation of CLUPI operations in view of the ExoMars 2022 mission
Authors: Bontognali Tomaso , Meister Yardena , Kuhn Brigitte , Josset Jean-Luc , Hofmann Beda , Kuhn Nikolaus
Published: March 2021

The Close-UP Imager (CLUPI) is one of the instruments of the Rosalind Franklin rover, which will explore Mars in the framework of the ESA/Roscosmos ExoMars mission. CLUPI will be mostly used for acquiring close up-images of geological samples, identifying materials and sedimentary structures that may record information about the hypothetical existence of past extraterrestrial life. Although the technical specifications of CLUPI are well known, it is not possible to readily translate such specifications in terms of feasibility to recognize “textures of interest” at a given distance under specific light conditions on Mars. Accurate predictions are important for taking informed decisions during the tactical planning of the rover. Here, we describe the results of some mission-preparation activities, during which a camera system analogue to CLUPI has been used to photograph rocks samples in an indoor facility (i.e., the Marslabor of the University of Basel) that has been built for simulating a Martian landscape. Under different light conditions, we performed a preliminary assessment of the minimal-working-distance required for interpreting rock textures and sedimentary structures that are potentially present on Mars, including textures that allows for differentiating sedimentary rocks from igneous rocks, grains that allows for classifying sedimentary rocks based on their granulometry, and stromatolitic laminations representing morphological biosignatures. The produced data represents a first step in identifying ideal CLUPI working-distances and illumination, and in preparing an image database that will be of help for optimizing rover operations and the scientific return of  CLUPI during the ExoMars 2022 mission.
Multi-methodological three-dimensional investigation of a closed-system Pingo in Northwestern Canada
Authors: Kunz Julius , Kneisel Christof
Published: March 2021

The Mackenzie-Delta region is known for widespread permafrost and the association of different landforms, which are characteristic of a periglacial landscape development. Especially the density of closed-system pingos is nowhere on earth higher than in the area of the Tuktoyaktuk Peninsula. This type of pingos is common only in the continuous permafrost zone and is very sensitive to changing thermal conditions. In this study, we investigated the surface and subsurface conditions in the area of such a closed-system Pingo near Parsons Lake in the southern part of the Tuktoyaktuk Peninsula to study its internal structure and evolutional state. Therefore, we used a combined approach of electrical resistivity tomography (ERT), ground-penetrating radar (GPR) and manual frost probing. In addition, a high-resolution digital elevation model and an orthophoto were generated using in situ drone acquisitions. These enabled a detailed and areawide mapping of surface characteristics (e.g. vegetation height or type) and should contribute to the investigation of linkages between surface and subsurface characteristics.

Such a linkage could be observed comparing the mapped vegetation type and heights with active layer depths derived from manual frost probing and GPR measurements. Both parameters show a significant zonation in the area of the pingo and its surrounding. In addition, the results of the quasi three-dimensional ERT measurements could deliver new insights into the three-dimensional internal structure of the pingo and a massive ice core could be detected. However, the shape as well as the position of the massive ice core in relation to the elevated surface of the pingo differ from the previous theory of closed-system pingo formation and therefore raises some questions. Also the existence of a talik could be confirmed, but its position beside the ice core within the eastern flank of the pingo and not below the massive ice core also differs from the theoretical models and should be discussed.
Time-lapse point clouds of moving granular flows: Preliminary insights and future outlook
Authors: Spielmann Raffaele , Aaron Jordan , McArdell Brian
Published: March 2021

Debris flows are extremely rapid, flow-like landslides that can impact people and infrastructure far from their source. Reducing debris flow hazard requires an understanding of the mechanisms which govern debris flow behavior, such as grain size segregation, entrainment, deposition and liquefaction, as well as accurate numerical models, which must be validated based on laboratory and field data.  Thus, knowledge of debris flow mechanisms, as well as forecasts of debris flow behavior, require accurate measurement of a number of quantities that vary through time, which include slope inclinations, front velocity, flow depth and flow volume.  These parameters are difficult to measure in moving granular flows, however newly available sensors have the potential to accurately capture them. These sensors include high resolution LiDAR and depth cameras, which are potentially useful for the field and laboratory scale, respectively.  In the present work, we implement a processing pipeline to attempt to estimate these four parameters, and associated errors, using two such sensors; a LiDAR sensor (Ouster OS1-64 Gen 1) which is planned for a field installation and a depth camera (Intel RealSense Depth Camera D415) which is useful for laboratory scale experiments. 

We performed a series of laboratory experiments, where different dry sediment mixtures were released down an inclined plane, and both sensors were used to collect time-lapse point clouds of the moving material.  These point clouds were recorded at a rate of 10 Hz and 30 Hz, for the Ouster OS1-64 sensor and Intel RealSense Depth Camera D415 respectively.  Our processing pipeline involves aligning the point cloud frames, isolating the moving material based on reflectivity or infrared thresholds, and then measuring the four parameters detailed above in each frame.  Both sensors are able to measure slope angle, velocity and volume, however the measurement of the free surface gradient was subject to more error.  The experimentally determined noise levels for the sensors were different, with  3 cm for the LiDAR scanner, and 0.5 cm for the depth camera.  Additionally, the more accurate depth camera enabled tracking of larger particles on the flow surface.  Interestingly, we measure a consistent volume dilation of the flowing debris, with a volume increase of about 39% over 0.1 s.

Thus, both sensors will be useful tools for understanding fundamental debris flow mechanisms.  Future work will focus on defining a relationship between flow velocity and material contraction/dilation, and will further refine the processing algorithm to more accurately assess these four parameters.  Additionally, we will present an overview of the set-up and installation of an OS1-64 sensor in the Illgraben catchment, Europe's most active debris flow catchment.
Geoelectric field as a GIC proxy during the intense geomagnetic storms and Polish transmission lines failures occurrence
Authors: Gil Agnieszka , Berendt-Marchel Monika , Modzelewska Renata , Moskwa Szczepan , Siluszyk Agnieszka , Siluszyk Marek , Tomasik Lukasz , Wawrzaszek Anna , Wawrzynczak Anna
Published: March 2021

We study intense geomagnetic storms (Dst < 100nT) during the first half of the solar cycle 24. This type of storm appeared only a few times, mostly associated with southwardly directed heliospheric magnetic field  Bz . Using various methodology as self-organizing maps, statistical and superposed epoch analysis, we show that during and right after intense geomagnetic storms, growth in the number of transmission lines failures, which might be of solar origin, appeared. We also examine the temporal changes in the number of failures during 2010-2014 and found the growing linear tendency of electrical grid failures occurrence possibly connected with solar activity. We confront these results with the geoelectric field calculated for the Poland region using a 1-D layered conductivity Earth model.
On the factors contributing to heat waves in Europe. A global large ensemble approach with MPAS
Authors: Smiatek Gerhard , Kunstmann Harald
Published: March 2021

The European summer heat wave of 2003 with record-breaking temperature anomalies was brought into connection with a blocking Omega circulation pattern, soil moisture deficit and high sea surface temperature, especially in the Mediterranean Sea.  We investigate the potential factors influencing extreme heat waves in Europe with a very large ensemble obtained from multiple global integrations of the Model for Prediction Across Scales (MPAS). The global MPAS runs are performed in approximately 60 km resolution with sea surface temperature (SST) and sea ice extent from ERA-Interim data as boundary condition initialized on different days.

The contribution investigates the results obtained from a total of 540 simulations. It concentrates on the regional SST and weather patterns and moisture obtained in simulations contributing to the upper 10% of the resulting probability density function (PDF) of the summer daily mean and maximum temperature. The investigation considers in total eight standard evaluation domains in Europe as defined in the PRUDENCE project.
Record of the Toarcian oceanic anoxic event in the Grands Causses Basin (southern France) and its implications for vertebrate preservation
Authors: Bomou Brahimsamba , Suan Guillaume , Schlögl Jan , Grosjean Anne-Sabine , Suchéras-Marx Baptiste , Adatte Thierry , Spangenberg Jorge , Fouché Stéphane , Zacai Axelle , Gibert Corentin , Brazier Jean-Michel , Perrier Vincent , Vincent Peggy , Janneau Kévin , Martin Jeremy E.
Published: March 2021

Paleontological excavations realized by our group in Toarcian shales (Lower Jurassic) of the Grands Causses Basin in Roqueredonde (Hérault, France), yielded several specimens of marine vertebrates. The newly discovered specimens are partly or entirely preserved in anatomical connection and include a partial ichthyosaur skeleton with soft tissues, and a 4 m-long thalattosuchian longirostrine marine crocodile. A multi-proxy approach has been developed (XRD-bulk and clay mineralogy, Rock-Eval pyrolysis, phosphorus and mercury contents) in order to replace these findings in a well-defined temporal and paleoenvironmental context, and hence constrain the factors that led to their remarkable preservation. The fossiliferous succession exposes a 3 m-thick upper Pliensbachian interval of marl and nodular carbonate beds, overlain by a 3 m-thick interval of lower Toarcian laminated shales and limestone beds. Our high-resolution ammonite biostratigraphy, combined with inorganic and organic carbon isotope chemostratigraphy, shows that the fossiliferous Toarcian strata were deposited at a time of global warming and major carbon cycle perturbation known as the Toarcian Oceanic Anoxic Event (T-OAE). The studied succession shows several similarities with the classical coeval fossiliferous levels of the Posidonia Shale in SW Germany, including high organic matter and hydrocarbon contents as well as extremely reduced sedimentation rates. These results indicate that the unusual richness in well-preserved vertebrates of the studied site can be explained by a combination of warming-induced, low salinity and stratified waters, prolonged seafloor anoxia and reduced dilution by low carbonate and terrigenous input due to rapid sea-level rise. Our results also reveal a significant peak in mercury at the base of the T-OAE interval, consistent with that recorded in several coeval sections (e.g. Portugal, Morocco, Argentina, Chile). This mercury anomaly, most likely resulting from intense volcanic activity Karoo-Ferrar large igneous province, suggests that widespread exceptional vertebrate preservation during the T-OAE was initiated by a suite of severe environmental perturbations ultimately triggered by intense volcanic emissions.
Seasonal variability of tides in the Russian Arctic seas
Authors: Kulikov Mikhail , Medvedev Igor
Published: March 2021

In this research, the sea level variability in the Russian Arctic seas caused by the Moon and the Sun tidal forces is considered. For a long time, it was thought that the tides can be easily calculated based on a small series of observations made in summer, but as shown in a few recent publications, describing tides in the different parts of the Arctic Ocean, tidal characteristics change significantly during the year. The main attention is paid to their seasonal variability in the seas of the Russian Arctic. The most interesting results have been obtained for the east sector of the Russian Arctic seas, where the tides were poorly known, and the long-term data from the tide gauges have been processed for the first time. We have used the long-term hourly sea-level data from several stations in the White, Kara, Laptev and Chukchi seas. The temporary coverage for the White Sea stations includes rather continuous sea-level records from 2004 to 2014 yrs. The maximum length of records made from 1981 to 2005 at the stations of the east sector of the Arctic was found at the Tiksi station. In this work we also analysed unique data obtained from the bottom pressure loggers installed on the Laptev-sea shelf in the period 2018-2020. The results of this study allow us to conclude that the classical harmonic analysis applied to the precomputation of tides does not provide an accurate estimate of the tidal characteristics in individual water areas in the Arctic. Accounting of the seasonal variability in the tidal characteristics will make it possible to clarify tidal maps important for navigation and coastal construction in the Arctic Region.
Analysis of the Marine Ice Sheet-Ocean Model Intercomparison Project first phase (MISOMIP1)
Authors: Asay-Davis Xylar , Bull Christopher Y. S. , Cornford Stephen , Cougnon Eva , De Rydt Jan , Galton-Fenzi Benjamin K. , Gladstone Rupert , Goldberg Daniel , Gwyther David , Jordan James , Jourdain Nicolas , Leguy Gunter , Lipscomb William , Marques Gustavo , Martin Daniel F. , Nakayama Yoshihiro , Naughten Kaitlin A. , Smith Robin S. , Seroussi Hélène , Zhao Chen
Published: March 2021

The Marine Ice Sheet-Ocean Model Intercomparison Project (MISOMIP) is a community effort sponsored by the Climate and Cryosphere (CliC) project.  MISOMIP aims to design and coordinate a series of MIPs—some idealized and realistic—for model evaluation, verification with observations, and future projections for key regions of the West Antarctic Ice Sheet (WAIS).  The first phase of the project, MISOMIP1, was an idealized, coupled set of experiments that combined elements from the MISMIP+ and ISOMIP+ standalone experiments for ice-sheet and ocean models, respectively.  These MIPs had 3 main goals: 1) to provide simplified experiments that allow model developers to compare their results with those from other models; 2) to suggest a path for testing components in the process of developing a coupled ice sheet-ocean model; and 3) to enable a large variety of parameter and process studies that branch off from these basic experiments.

Here, we describe preliminary analysis of the MISOMIP1 results.  Eight models in 14 configurations participated in the MIP.   In keeping with analysis of the MISMIP+ experiment, we find that the choice of basal friction parameterizations in the ice-sheet component (Weertman vs. Coulomb limited) has a particularly significant impact on the rate of ice-sheet retreat but the choice of stress approximation (SSA, SSA* or L1Lx) seems to have little impact.  Models with Coulomb-limited basal friction also tend to be those with the highest melt rates, confirming a positive feedback between melt and retreat in the MISOMIP1 configuration seen in previous work.  The ocean component’s treatment of the boundary layer below the ice shelf also has a significant impact on melt rates and resulting retreat, consistent with findings based on ISOMIP+.  Feedbacks between the components lead to localized features in the melt rates and the ice geometry not seen in standalone simulations, though the ~2-km horizontal and ~20-m vertical resolution of these simulations appears to be too coarse to produce long-lived, sub-ice-shelf channels seen at higher resolution.
Evolution of solar wind flows from the inner corona to 1 AU: constraints provided by SOHO UVCS and SWAN data
Authors: Bemporad Alessandro , Katushkina Olga , Izmodenov Vladislav , Koutroumpa Dimitra , Quemerais Eric
Published: March 2021

The Sun modulates with the solar wind flow the shape of the whole Heliosphere interacting with the surrounding interstellar medium. Recent results from IBEX and INCA experiments, as well as recent measurements from Voyager 1 and 2, demonstrated that this interaction is much more complex and subject to temporal and heliolatitudinal variations than previously thought. These variations could be also related with the evolution of solar wind during its journey through the Heliosphere. Hence, understanding how the solar wind evolves from its acceleration region in the inner corona to the Heliospheric boundaries is very important.

In this work, SWAN Lyman-α full-sky observations from SOHO are combined for the very first time with measurements acquired in the inner corona by SOHO UVCS and LASCO instruments, to trace the solar wind expansion from the Sun to 1 AU. The solar wind mass flux in the inner corona was derived over one full solar rotation period in 1997, based on LASCO polarized brightness measurements, and on the Doppler dimming technique applied to UVCS Lyman-α emission from neutral H coronal atoms due to resonant scattering of chromospheric radiation. On the other hand, the SWAN Lyman-α emission (due to back-scattering from neutral H atoms in the interstellar medium) was analyzed based on numerical models of the interstellar hydrogen distribution in the heliosphere and the radiation transfer. The SWAN full-sky Lyman-α intensity maps are used for solving of the inverse problem and deriving of the solar wind mass flux at 1 AU from the Sun as a function of heliolatitude. First results from this comparison for a chosen time period in 1997 are described here, and possible future applications for Solar Orbiter data are discussed.