bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards microseismic moment tensor inversion in boreholes with DAS
Authors: Tuinstra Katinka , Lanza Federica , Fichtner Andreas , Zunino Andrea , Grigoli Francesco , Rinaldi Antonio Pio , Wiemer Stefan
Published: March 2022

We present preliminary results on a moment tensor inversion workflow for Distributed Acoustic Sensing (DAS). It makes use of a fast-marching Eikonal solver and synthetically modeled data. The study specifically focuses on borehole settings for geothermal sites. Distributed Acoustic Sensing measures the wavefield with high spatial and temporal resolution. In borehole settings, individual DAS traces generally prove to be noisier than co-located geophones, whereas the densely spaced DAS shot-gathers show features that would have otherwise been missed by the commonly more sparsely distributed geophone chains. For example, the coherency in the DAS records shows the polarity reversals of the arriving wavefield in great detail, which can help constrain the moment tensor of the seismic source. The synthetic tests encompass different source types and source positions relative to the deployed fiber to assess moment tensor resolvability. Further tests include the addition of a three-component seismometer at different positions to investigate an optimal network configuration, as well as various noise conditions to mimic real data. The synthetic tests are tailored to prepare for the data from future microseismicity monitoring with DAS in the conditions of the Utah FORGE geothermal test site, Utah, USA. The proposed method aims at improving amplitude-based moment tensor inversion for DAS deployed in downhole or underground lab contexts.
Impact of different corner reflectors installation on InSAR time-series
Authors: Horváth Roland , Magyar Bálint , Tóth Sándor
Published: March 2022

Identification of relatively stable ground control points is always difficult in satellite-based remote sensing microwave technology. In our case, we have analyzed the amplitude and phase of backscattered signal of artificial objects in the resolution cell. In 2020, we have temporarily installed a compact active transponder (CAT) to the top of the Satellite Geodetic Observatory (SGO). During this probation period we had tested the operation of this electronic corner reflector (ECR).

In November, 2021 we have deployed, adjusted and precisely aligned the CAT and also mounted a 90 cm inner leg of passive double-backflip triangular corner reflector pair (part of the Integrated Geodetic Reference Station) to serve as Persistent Scatterers. Hence, we have observed the behaviour of the complex microwave signal using interferometric synthetic aperture radar technique (InSAR), utilizing Sentinel-1 SAR high resolution images. We have concentrated to demonstrate the effect of the corner reflector (CR) installation: estimate the Signal-to-Clutter Ratio (SCR), calculate the Radar Cross Section (RCS), define the phase center in sub-pixel dimension over well-specified stack of time-series.

We are expecting and focusing to integrate the CRs as benchmarks, into our developing processing algorithm system to achieve more accurate results of surface displacement using ground control points. In addition, the function of this project is to contribute and ensure the extension of our passive corner reflector reference network (SENGA). In this paper, we present the interpretation of the recent outcomes.
How to publish your data with the EPOS Multi-scale Laboratories data publication chain
Authors: ter Maat Geertje , Wessels Richard ,   the EPOS TCS Multi-scale Laboratories Team
Published: March 2022

The Multi-scale Laboratories (MSL) are a network of European laboratories bringing together the scientific fields of analogue modeling, paleomagnetism, rock and melt physics, geochemistry and microscopy. MSL is one of nine Thematic Core Services (TCS) of the European Plate Observing System (EPOS) (https://www.epos-eu.org/). The overarching goal of EPOS is to establish a comprehensive multidisciplinary research platform for the Earth sciences in Europe. It aims at facilitating the integrated use of data, models, and facilities, from both existing and new distributed pan-European Research Infrastructures, allowing open access and transparent (re-)use of data.

Laboratory facilities are an integral part of Earth science research. The diversity of methods employed in such infrastructures reflects the multi-scale nature of the Earth system and is essential for understanding its evolution, assessing geo-hazards, and sustainably exploiting geo-resources.

Experimental data from these laboratories provide the backbone for many scientific publications, but are often available only on request from the author, as supplementary information to research articles or in a non-digital form (printed tables, figures), limiting data re-use, re-interpretation and availability. Moreover, the raw data remains often unpublished, inaccessible, and unpreserved for the long term.

The TCS MSL is committed to making Earth science laboratory data Findable, Accessible, Interoperable, and Reusable (FAIR). For this purpose, the TCS MSL encourages the community to share their data via DOI-referenced, citable data publications. To facilitate this and ensure the provision of rich metadata, we offer user-friendly tools, plus the necessary data management expertise, to support all aspects of data publishing for the benefit of individual lab researchers via partner repositories. Data published via TCS MSL are described with the use of sustainable metadata standards enriched with controlled vocabularies used in geosciences. The resulting data publications are also exposed through a designated TCS MSL online portal that brings together DOI-referenced data publications from partner research data repositories (https://epos-msl.uu.nl/). As such, successful efforts have already been made to interconnect new data (metadata exchange) with existing databases such as MagIC (paleomagnetic data in Earthref.org) and, in the future, we expect to broaden and improve this practice with other repositories. 
Effects of temperature and shearing rate on the residual shear strength of two pure clays
Authors: Scaringi Gianvito , Loche Marco
Published: March 2022

The residual shear strength is the sole available strength in regular shear zones of landslides after large displacements. While it does not depend on the stress history, it has been shown to depend on the rate of shearing. Various mechanisms have been proposed to explain the shear-rate strengthening and weakening observed, in particular, in soils containing clay minerals. Frictional heating has been shown to be involved in shear weakening under very large shearing rates. However, changes in temperature (imposed as boundary conditions and propagating into the shear zone) also can affect the residual shear strength, even in drained condition, but evidence in the literature is scarce.

Here, we show results of temperature-controlled ring-shear tests on two pure clays (a commercial bentonite, very active, and a commercial kaolin, inactive), conducted under a wide range of shear displacement rates (0.02–45 mm/min) and normal stresses (50–150 kPa) typical of slow to rapid landslides. After attaining the residual shear strength under the chosen stress and displacement-rate conditions at room temperature (20 °C), we increased the temperature of the cell up to 55 °C and kept it constant over a sufficient shearing distance before gradually decreasing it back to the initial value.

We observed a clear effect of temperature on the residual shear strength of the active clay. We evaluated, in particular, a shear strengthening under slow shearing (up to +1.5 %/°C) which turned into a shear weakening under fast shearing (-0.5 %/°C) under any normal stress. We evaluated that the transition between the two behaviours occurred at a shear displacement rate of 0.1–1 mm/min, which is consistent with the range for the onset of shear rate-dependent behaviours. The effect produced by the increase in temperature was shown to be reversible, although in some cases we noticed a net decrease in strength that could be attributed to an improved alignment of the clay platelets resulting from the thermal cycle. Notably, little thermal effects were seen for the inactive clay, suggesting that such effects should originate from changes in physico-chemical forces of interaction at the microstructural level, which are indeed especially relevant in active clays.

Changes in residual shear strength with temperature could be related to changes in landslide activity (particularly for creeping landslides in clay soils) in terms of seasonal/progressive acceleration or deceleration driven by external hydro-meteorological forcing. Furthermore, these changes could also control the potential for runaway motion if a transition from a strengthening to a weakening behaviour occurs. 
Multi-channel rivers characterization using Gaussian Mixture Model applied to topobathymetric LiDAR data
Authors: Andréault Alex , Rodrigues Stéphane , Gaudichet Corentin
Published: March 2022

Morphological classifications are often poorly adapted to complexity of rivers. One way of improving them is based on new technologies such as topo-bathymetric LiDAR (LTB). This tool captures a large quantity of data (more than 10 pts.m-2) with a centimetric accuracy. A survey, carried out on the Loire River between Nevers and Nantes (ca. 450 km) allowed to test the potential of the LTB to define morphological signatures in contrasted river sectors (Garcia-Lugo et al., 2015). As a working hypothesis, we propose that the morphology of a river reach on its active width presents a specific morphological signature indexed on elevations and slopes.

Five sites were retained for this work 1) anabranching, 2) sinuous single channel, 3) braided, 4) formerly trained by groynes and 5) trained by groynes. 

The morphological signature corresponds to the statistical distribution of dimensionless elevations. Density curves were calculated for elevation and slope data of nondimentionalized detrended Digital Elevation Models. Simplification of complex density curves was reached using a Gaussian Mixture Model to divide the signal. These, simplified signals were compared to corresponding DEMs and correlation was established between statistical signal and spatial data. 

Distributions are varying in terms of shape and location on the x-axis. The shape gives an information of lateral connectivity of the system while the location of the curve on the x-axis indicates the predominance of low or high elevations regarding elevation magnitudes. As an example, the description of the anabranching site leads to the identification of the secondary channels network that is also recognized by the GMM. The latter appears to be efficient for identifying the morphological units of a river. For the braided reach, the signature is different from the previous and highlight a system with relative homogeneous elevations . For the site with groynes, the signature clearly highlights 2 morphological disconnected units. 

Results of this study are in line with literature concerning both braided and trained rivers (Ashmore et al., 2013 ; Campana et al., 2011). Methodology proposed here allows to identify and assess the meaning of the statistical signal by directly projecting it on a DEM. GMM shows its relative capacity to discretize complex topobathymetrical signal and link it with morphological units. The methodology presented herein is promising for the understanding of river morphodynamics and their classification. It also opens perspectives for river restoration and management.
Mixing and air-sea buoyancy fluxes drive the overturning circulation in the subpolar North Atlantic
Authors: Evans D. Gwyn , Holliday N. Penny , Bacon Sheldon , Oltmanns Marilena
Published: March 2022

The overturning streamfunction as measured at the OSNAP (Overturning in the Subpolar North Atlantic Program) mooring array represents the transformation of warm/salty Atlantic Water into cold/fresh North Atlantic Deep Water (NADW). The magnitude and variability of the overturning at the OSNAP  mooring array can therefore be linked to the water mass transformation by air-sea buoyancy fluxes and mixing in the region to the north of the OSNAP array. Here, we estimate these water mass transformations using a combination of observational-based, reanalysis-based and model-based datasets. Our results highlight the complementary roles of air-sea buoyancy flues and mixing in setting the time-mean magnitude of the overturning at OSNAP. A cooling by air-sea heat fluxes and a mixing-driven freshening in the Nordics Seas, Iceland basin and Irminger basin, precondition the warm/salty Atlantic Water, forming subpolar mode water classes. Mixing in the interior of the Nordic Seas, over the Greenland-Scotland ridge and along the boundaries of the Irminger and Iceland basins drive a water mass transformation that leads to the convergence of volume in the water mass classes associated with NADW. In contrast to the time-mean magnitude, the seasonal variability of the overturning streamfunction at OSNAP cannot be linked to changes in the transformation by air-sea fluxes and mixing. The seasonal variability of air-sea fluxes and mixing greatly exceed the seasonal variability measured in the overturning at OSNAP. This implies that water mass transformation anomalies in the region to the north of the OSNAP array don't manifest as overturning variability at the latitude of the OSNAP array on seasonal timescales. Air-sea buoyancy fluxes and mixing therefore play key and complementary roles in setting the overturning within the subpolar North Atlantic and Nordic Seas. Further, this study highlights that for climate models to realistically simulate the overturning circulation in the North Atlantic, the small scale processes that lead to the mixing-driven formation of NADW must be adequately represented within the model's parameterisation scheme.
Convection-Permitting Ensemble All-sky Satellite Radiance Assimilation for the Prediction of Rapidly Intensifying Tropical Cyclones
Authors: Minamide Masashi , Posselt Derek
Published: March 2022

Prediction of rapidly intensifying tropical cyclones (TCs) have been a challenging topic. Because most TCs are born and develop over tropical oceans with limited in-situ observation networks and infrequent low Earth orbiting satellite overpasses, geostationary satellite observations are often the only available information to capture the lifecycle of TCs.

In this study, the impacts of assimilating all-sky satellite radiances from GOES-16, together with the set of conventional observations, on the prediction of the rapid intensification process of TCs are examined using convection permitting ensemble Kalman filter data assimilation system originally developed at Penn State University with WRF and CRTM. We have conducted assimilation experiments for 2017 Atlantic hurricane season. The assimilation of all-sky satellite radiances contributed to better constraining the dynamic and thermodynamic state variables, which helped to capture the developing convective activity within the inner-core region of TCs. The TC intensity forecast error was reduced by roughly 20 % at the peak time. We found that the all-sky satellite radiances contributed to more than 90 % of error reduction. This study will provide implications about what are the sources of uncertainty in predicting rapidly intensifying TCs, as well about the design of future observation networks tasked with better initializing and predicting developing TCs.
Numerical modelling of current state of stress in the Geneva Basin and adjacent Jura fold-and-thrust belt (Switzerland and France).
Authors: Borderie Sandra , Mosar Jon , Hauvette Louis , Marro Adeline , Sommaruga Anna , Meyer Michel
Published: March 2022

The Northern Alpine foreland is divided into two domains: the Molasse Basin and the Jura fold-and-thrust belt (FTB). The Mesozoic and Cenozoic sedimentary cover of this area is deformed by thrust-related folds and strike-slip faults. The main structures root in a basal Triassic décollement. The Geneva Basin, located in western Switzerland, is part of the Plateau Molasse (belonging to the Molasse Basin), and is limited to the NW by the Jura FTB, to the SW by the Vuache fault, and to the SE by the Mont Salève ramp related anticline and the Subalpine Molasse.

If current seismicity indicates that the Geneva Basin is tectonically active, few data regarding the state of stress in the area are currently available. The goal of this study is to densify the knowledge of the state of stress in the Geneva Basin and in the adjacent Jura FTB, by using numerical modelling.

The first part of the study is a regional study. In a 2D section, we study the impact of the friction along the basal décollement, on the localisation of deformation and on the associated stress field. Results indicate that depending on the friction, deformation will localise at the rear of the Mont Salève, in the Geneva Basin or at the frontal part of the Jura FTB. In the range of frictions where deformation localises in the Geneva Basin, the distribution of stress varies. Differential stress is higher and more localised for higher basal frictions.

The second part of the study is more local. The prototype section is based on seismic interpretation of a seismic surveys in the Geneva Basin. We study the impact of friction along the inherited faults on incipient deformation. Results indicate that a decrease in the fault’s friction allows forwards propagation of deformation and allows reactivation of inherited faults. If the friction in the faults is too low, deformation will localise at the first inherited fault (i.e. the Salève thrust in this case study). The stress fields vary depending on the localisation of deformation. Stress magnitudes are lower and more distributed when all faults have the same friction. The more deformation is localised on a structure, the more stress concentration is observed.

These results allow to better constrain the mechanical context of these sections and to populate this part of the Northern Alpine foreland with stress data.
Sediment connectivity assessment through a geomorphometric approach: a review of recent applications
Authors: Cavalli Marco , Crema Stefano , Cucchiaro Sara , Macchi Giorgia , Trevisani Sebastiano , Marchi Lorenzo
Published: March 2022

Sediment connectivity, defined as the degree to which a system facilitates the transfer of sediment through itself by means of coupling relationships between its components, has recently emerged as a paramount property of geomorphic systems. The growing interest of the earth sciences community in connectivity led this property to become a key concept concerning sediment transfer processes analysis and one of the building blocks of modern geomorphology. The increasing availability of high-resolution Digital Elevation Models (DEMs) from different sources as LiDAR and Structure from Motion (SfM) paved the way to quantitative and semi-quantitative approaches for assessing sediment connectivity. A geomorphometric index of sediment connectivity, based on DEM derivatives as drainage area, slope, flow length and surface roughness, has been developed along with related freeware software tool (SedInConnect). The index aims at depicting spatial connectivity patterns at the catchment scale to support the assessment of the contribution of a given part of the catchment as sediment source and define sediment transfer paths. The increasing interest in the quantitative characterization of the linkages between landscape units and the straightforward applicability of this index resulted in numerous applications in different contexts. This work presents and discusses the main applications of the sediment connectivity index along with a recent application in the frame of the Interreg ITAT3032 SedInOut Project (2019-2022). Being a topography-based index, it is focused on structural aspects of connectivity, and quality and resolution of DEMs may have a significant impact on the results. Future development should consider process-based connectivity and incorporate temporal variability directly into the index. Moreover, this work demonstrates that, when carefully applied considering the intrinsic limitations of the topographic-based approach, the index can rapidly provide a spatial characterization of sediment dynamics, thus improving the understanding of geomorphic system behavior and, consequently, hazard and risk assessment.
Across the Straits: a review of methods to compute mass and nutrients transports through straits and channels
Authors: Pasculli Lorenzo , Falcieri Francesco Marcello , Chiggiato Jacopo , Schroeder Katrin , García Lafuente Jesús , Sammartino Simone , Sánchez-Garrido Jose Carlos , Rubino Angelo
Published: March 2022

Ocean straits connect basins characterized by different fluid properties. They are important exchange areas showing peculiar phenomena that often strongly influence physical as well as biogeochemical exchange processes. These are mostly unique for each strait, depending on its specific bathymetry, local air-sea interactions, and remote forcing. Consequently, different methods for observing straits dynamics and fluxes have been developed. Starting from analogue current meters, technological development has led to the use of increasingly complex instruments, such as acoustic as well as microwave devices. Hence, in situ measurements are complemented by remote sensing methods to accurately determine current velocities across the straits. The advent of very high-resolution numerical models, which are able to reproduce small-scale features of the near surface as well as of the interior water masses, yielded a strong improvement in the understanding of straits dynamics. Starting from the 1960s, much work has been devoted at developing an integrated approach to the study of sea straits, including in situ and remote sensing observations, and modelling analysis. In this work, we examine different methods used to observe, monitor and simulate the dynamics of sea straits and their biogeochemical impact, focusing particularly on integrated approaches.
Basalt production controlled by mantle source fertility at Fagradalsfjall, Iceland
Authors: Sigmarsson Olgeir , Marshall Edward W. , Bosq Chantal , Auclair Delphine , Rasmussen Maja B. , Kleine Barbara I. , Ranta Eemu J. , Matthews Simon , Halldórsson Sæmundur A. , Jackson Matthew G. , Gudfinnsson Gudmundur H. , Bali Enikö , Stefánsson Andri , Gudmundsson Magnús T.
Published: March 2022

Mantle melting processes and the characteristics of the source lithologies are mostly derived from basalt compositions of the mid-ocean ridge system and from oceanic islands. However, these basalts are in most cases the products of crustal processes resulting from magma storage, mixing, differentiation and crustal interaction. In Iceland, magma mixing and homogenization in thoroughly stirred magma reservoirs appear to be the norm, leading to restricted variations of Sr and Nd isotope ratio for a given volcanic system. In contrast, more primitive basalts were erupted during the 2021 Fagradalsfjall eruption on the Reykjanes Peninsula with a large spread in isotope ratios. A strong negative correlation between Sr and Nd isotopes is observed from ratios that span a range from a depleted mantle composition to values akin to the Icelandic mantle such as that of the basalts of the Grímsvötn volcanic system. The isotope ratios are also correlated with the measured discharge rate during the eruption, with a depleted Sr isotope ratio appearing during the period of low discharge (around 5 m3/s) for the first month and a half of the eruption. In early May, the magma flux doubled and basalts with more radiogenic Sr isotope composition were produced. During the summer 2021, the Sr isotope ratios declined, due to lower proportions of melts from undepleted mantle source in the basalt mixture erupted. Whether the eruption ended when melts from the enriched mantle was exhausted or not remains to be elucidated, but clearly the highest eruption discharge rate resulted from melts of a more fertile mantle source.

The variable proportions of depleted versus enriched melts in the eruption products demonstrate the absence of a magma reservoir in which homogenization could take place, and from which decreasing discharge rate with time would be expected.  Instead, the initially low and steady and then increasing magma extrusion rate measured, strongly indicate direct mantle melt ascent to surface, which is also supported by the primitive mineralogy of the high-MgO basalt produced. Leaky-transform faults on the mid-ocean ridge system are characterized by eruptions of primitive basalts on intra-transform spreading centres (e.g. Garrett and Siqueiros fracture zones in the East Pacific). The Fagradalsfjall complex appears to be of similar nature, and the primitive magma and the important compositional and temporal variations demonstrate the effect of mantle source composition and associated processes on the eruption behaviour, as reflected in the magma discharge rate.
Geomorphometric Analysis of the Martian Uzboi-Nirgal Region
Authors: Szilágyi-Sándor András , Székely Balázs
Published: March 2022

The area on the eastern slopes of Tharsis (Thaumasia), northern from Argyre and southern from Margaritifer is dominated by the Uzboi Vallis and Nirgal Vallis. Their (at least partial) fluvial origin is accepted since the Mariner-Viking era. Uzboi Vallis thought to be part of the ancient Uzboi–Ladon–Morava River System (ULM). ULM is thought to be created while it served as the overflow channel of the southern Argyre crater. Nirgal Vallis is the largest tributary of Uzboi. Its source region is in the direction of the Thaumasia Mountains.

The area experienced numerous effects during its history. In this study our goal was to separate these effects in a chronological order as far as it is possible. Therefore comprehensive investigations (using MOLA and THEMIS) were carried out and a detailed analysis of these two valleys was made using HiRISE images and HiRISE-derived digital elevation models. HiRISE DEMs allow the surfaces to be studied and evaluated with a resolution of better than one meter.

Several geomorphometric methods were applied for the area: swath analysis, the distribution of the tributary valleys, sinuosity calculation, and runoff modeling. The vallis was divided into sections based on its main features. Section A, unlike other sections, is characterized by dendritic tributary system. Tributaries are found both on left and right sides. Section B is a kind of transitional zone, the tributaries are getting rare. Section C was defined as a sinuous segment. Tributaries here are very rare.  Section D is deeply incised, the thalweg is broken at several points and has a subhorizontal trend. According to the extremely low number of tributaries and the modifying effect of the neighboring impact craters the water divides are fuzzy. The path of this section is also sinuous. Section E is the deepest part of the whole Nirgal Vallis this is an unusual condition, because in the case of the terrestrial rivers the deepest part is regularly at the end of the confluence. Section F has to be separated from Section E because it shows influence of several effects. Section F has got only one (SW-NE) tributary which is significant in length and dominates the morphology of the area south from the Nirgal‒Uzboi confluence.

In our interpretation the sections detailed above seem to be at least partially related to wrinkle ridges noticeable from Thaumasia Mountains to Uzboi Vallis and are similar to those on Solis Planum. The effect of the wrinkle ridges is controlling the morphology of the plateau, and may be in connection with the tributaries.

Further geomorphological investigation may lead to the separation of the different effects formed Nirgal throughout its history.
Matryoshka Neural Operators: Learning Fast PDE Solvers for Multiscale Physics
Authors: Lütjens Björn , Crawford Catherine H. , Watson Campbell , Hill Chris , Newman Dava
Published: March 2022

Running a high-resolution global climate model can take multiple days on the world's largest supercomputers. Due to the long runtimes that are caused by solving the underlying partial differential equations (PDEs), climate researchers struggle to generate ensemble runs that are necessary for uncertainty quantification or exploring climate policy decisions.

 

Physics-informed neural networks (PINNs) promise a solution: they can solve single instances of PDEs up to three orders of magnitude faster than traditional finite difference numerical solvers. However, most approaches in physics-informed machine learning learn the solution of PDEs over the full spatio-temporal domain, which requires infeasible amounts of training data, does not exploit knowledge of the underlying large-scale physics, and reduces model trust. Our philosophy is to limit learning to the hard-to-model parts. Hence, we are proposing a novel method called \textit{matryoshka neural operator} that leverages an old scheme called super-parametrizations developed in geophysical fluid dynamics. Using this scheme our proposed physics-informed architecture exploits knowledge of approximate large-scale dynamics and only learns the influence of small-scale dynamics onto large-scale dynamics, also called subgrid parametrizations.

 

Some work in geophysical fluid dynamics is conceptually similar, but fully relies on neural networks which can only operate on fixed grids (Gentine et al., 2018). We are the first to learn grid-independent subgrid parametrizations by leveraging neural operators that learn the dynamics in a grid-independent latent space. Neural operators can be seen as an extension of neural networks to infinite-dimensions: They encode infinite-dimensional inputs into a finite-dimensional representations, such as Eigen or Fourier modes, and learn the nonlinear temporal dynamics in the encoded state.

 

We demonstrate the neural operators for learning non-local subgrid parametrizations over the full large-scale domain of the two-scale Lorenz96 equation. We show that the proposed learning-based PDE solver is grid-independent, has quasilinear instead of quadratic complexity in comparison to a fully-resolving numerical solver, is more accurate than current neural network or polynomial-based parametrizations, and offers interpretability through Fourier modes.

 

Gentine, P., Pritchard, M., Rasp, S., Reinaudi, G., and Yacalis, G. (2018). Could machine learning break the convection parameterization deadlock? Geophysical Research Letters, 45, 5742– 5751. https://doi.org/10.1029/2018GL078202
Projected changes in near-surface wind speed over Iberian Peninsula and associated atmosphere-ocean oscillations. 
Authors: Andres Martin Miguel , Azorin-Molina Cesar , Deng Kaiqiang , Shen Cheng , Bedoya-Valestt Shalenys , Utrabo-Carazo Eduardo
Published: March 2022

Near-surface wind speed has been one of the forgotten parts of the climate system due to poor quality of observational data and the challenges in its homogenization.  During the last two decades the interest in near-surface wind variability and trends has increased and two main phenomena have been found: the first one is termed “stilling”, indicating a decline of near-surface wind speed between around 1978 and 2010; the other is related to an interruption in the “stilling” since 2000s, known as a “reversal” of the wind speed trends at global and regional scales like China, Sweden or Iberian Peninsula, among others. There are uncertainties about the plausible causes of the variability of the near-surface wind speed, but last research pointed to the role played by decadal atmosphere-ocean oscillations. Under this assumption and a climate change context, a new “stilling” phase is expected for the 21st century. In order to advance in the evaluation and attribution of the causes of the “stilling” and the “reversal” phenomena, the main objective of this study is to analyze projected changes in near-surface wind speed at regional scale, e.g. the Iberian Peninsula. The methodology consists in a comparison between observed wind speed data of the Iberian Peninsula and historical simulations from CMIP6 models, followed by a study of wind speed variability and trends of CMIP6 models under low to high greenhouse gas forcing scenarios in the future. The analyses will focus on quantifying the long-term changes in near surface wind speed and their relationship with dominant modes of variability in the Pacific and Atlantic (e.g., the Pacific Decadal Oscillation and the Atlantic Multi-decadal Oscillation).

 
Rockfall triggering mechanism analyzed from video using optical flow technique
Authors: Sun Chunwei , Baumann Traine Valérie , Derron Marc-Henri , Jaboyedoff Michel
Published: March 2022

This work presents an approach to identify the rockfall triggering mechanism from video employing Optical Flow Technique. The video was captured by phone camera on 3rd, October 2017 when the massive rockfall happened at a quarry in Le Locle Jura mountains, Switzerland. Time-series frames were extracted from the video and registered using SIFT (Scale-Invariant Feature Transform), kNN (k-nearest neighbor classification) and affine transformation algorithm, which efficiently eliminate the video jitters. After that, the transformation of pixels in the time-series image sequence and the correlation between adjacent frames are used to find the correspondence, so as to calculate the motion data of the object between adjacent frames by Optical Flow Technique. The instantaneous velocity of pixel movement of failure rock mass or debris on the video frames during rockfall dynamic behavior can be obtained. The basal failure surfaces and two main phases of the failure have been anlayzed for the rockfall triggering mechanism. The workflow proposed here can be applied in a slope disaster monitoring and early warning system to identify and track rockfall events effectively.
Forecasting agricultural drought using VCI and VHI across Africa
Authors: Rowhani Pedram , Salakpi Edward , Bowell Andrew , Tran Minh , Oliver Seb
Published: March 2022

Droughts are complex and a major threat globally as they can cause substantial damage to society, especially in regions that depend on rain-fed agriculture. It is understood that acting early based on alerts provided by early warning systems (EWS) can potentially provide substantial mitigation, reducing the financial and human cost of such hazards. Several satellite-based indicators such as the Vegetation Condition Index (VCI) or the Vegetation Health Index (VHI) are included in these EWS to monitor the agricultural and ecological droughts. In this presentation, we first present a suite a machine-learning techniques that we developed to forecast up to 12 weeks ahead these indicators at the second administrative boundaries across Kenya. Our approaches (Gaussian Process, auto-regressive distributed lag model, Hierarchical Bayesian Model) all provided skilful forecasts at various lead times. Finally, we show our Africa-wide forecasts of VCI and VHI using Gaussian Processes where we analyse whether the performance of the forecasts is influenced by season, land cover, or agro-ecological zone. Providing highly skilful forecast on vegetation condition will allow disaster risk managers act early to support vulnerable communities and limit the impact of a drought hazard.
Using different seismic approaches to detect submarine permafrost and gas hydrates on the continental Beaufort shelf of the Canadian Arctic
Authors: Grob Henrik , Riedel Michael , Duchesne Mathieu J. , Krastel Sebastian , Bustamante Restrepo Jefferson , Fabien-Ouellet Gabriel , Kläschen Dirk , Preine Jonas , Jin Young Keun , Hong Jong Kuk
Published: March 2022

In the Canadian Arctic, permafrost and permafrost-associated gas hydrates formed extensively during the last 1 Ma. After the last glaciation, a marine transgression followed and former terrestrially exposed shelf areas became submerged. Subaerial mean annual temperatures of -20°C or even less changed to present submarine bottom water temperatures near -1°C. The relict submarine permafrost and gas hydrates present in the Beaufort Sea still react to this ongoing thermal change which results in their continued degradation. Thawing permafrost and destabilisation of permafrost-associated gas hydrates may release previously trapped greenhouse gases and can lead to even further gas hydrate dissociation. Moreover, thawing permafrost poses a geohazard in form of landslides and ground collapses. Yet, both the extent of the submarine permafrost and the permafrost-associated gas hydrates are still not well known. Here, we present three different approaches using marine 2D multichannel seismic data to improve the current knowledge of the distribution of offshore permafrost and gas hydrates occurrences in the southern Canadian Beaufort Sea. The acoustic properties of permafrost are determined by the content of ice and unfrozen pore fluids. Changing permafrost conditions affect the elasticity of the medium making seismic methods appropriate for permafrost detection. First, we identify direct and indirect seismic reflection indicators from permafrost and gas hydrates by the presence of cross-cutting, polarity-reversed, and upward-bend reflections as well as velocity pull-ups and shallow pronounced high-amplitude reflections. Second, using diving-wave tomography provides insights into the near-surface permafrost structure by imaging the velocity structure in greater detail than achievable by standard velocity analyses.  And third, diffractions separated from the reflected wavefield yield insights into the sub-wavelength architecture of the permafrost realm on the southern Canadian Beaufort Shelf that may add information about weak phase-boundaries and small-scale heterogeneities. All methods are applied to seismic lines crossing the outer continental margin, where a maximum thermal effect of the transgression is expected, and thus a maximum lateral variation in permafrost and permafrost-associated gas hydrate phase boundaries is expected to be present. 
Statistical modeling of fire brigade operations with respect to extreme precipitation events over Berlin
Authors: Pasternack Alexander , Langer Ines , Rust Henning W. , Ulbrich Uwe
Published: March 2022

Large cities and urban regions are highly sensitive to impacts caused by extreme meteorological events (e.g. heavy rainfall). As problems caused by hazardous atmospheric events are expected to intensify due to the anthropogenic climate change, planning of adequate adaptation measures for urban infrastructure is needed. Planning adaptation measures does not only require further research on potential impacts in a changing climate as a basis, but also a check of the practical feasibility for stakeholders. 

Under the BMBF research program “Urban Climate Under Change” ([UC]²), we relate heavy precipitation events over Berlin to the respective fire brigade operations. Here, the precipitation data are based on temporally high resolved radar data. The fire brigade operation data are available on time and location, but the number of recorded events is small, and their distribution is highly overdispersive compared to a Poisson model. To account for this problem we apply a two part hurdle model with one part modeling the probability of the occurrence of fire brigade operations and one part modeling the actual number of operations given that at least one operation occurs. In the corresponding statistical models the parameters of the distributions are described by additive predictors, which are based on precipitation duration and intensity as well as building density. With a fire brigade dataset covering the years 2002 - 2013 we already could show with a cross validation setup that both the occurrence model and the model for the number of operations significantly outperform the reference forecast of the climatology for certain areas over Berlin. For this study we are able to investigate the behaviour of both statistical models for an extended dataset including the years 2018 - 2020. Morevover we examine the effects of the orography as additional predictor on the statistical models, since sinks may have an importent influence on fire brigade operations w.r.t. water damage.
Global view of oceanic cascades from the Global Circulation Model
Authors: Song Jingjing , Zhang Dan , Peng Yan , Gao Yang , Huang Yongxiang
Published: March 2022

In his seminal work "Weather Prediction by Numerical Process" in 1922, Lewis Fry Richardson proposed the famous cascade picture qualitatively for a turbulent flow that energy transferring from large to small scale  structures, until the viscosity one where the kinetic energy is converted  into heat. This picture has been recognized further as the forward energy  cascade.  But, it cannot be applied directly to the real atmospheric  or oceanic motions. Whatever, the global circulation model is indeed established within this framework by considering more complex situations, e.g., earth rotation, stratification, tide, mesoscale eddies, to list a few. In  this work, an improved Filter-Space-Technique (FST) is applied to a reanalysis product provided by the CMEMS global ocean eddy-resolving (1/12o degree horizontal resolution).   The FST provides a global view of the  energy flux ΠE  that associated with the oceanic cascades for all resolved  scales, e.g., from mesoscale eddies to global circulations. For instance, at scale r=160 km (i.e., radius of the Gaussian filter kernel), a rich dynamic pattern is observed for an instantaneous flow filed. Both forward (ΠE>0, energy transferring from large scale to small scale structures) and inverse (ΠE<0, energy transferring from small scale to large scale structures) cascades are evident in the equator, western boundary current regions, Antarctic Circumpolar Current region, to name a few. While, the long-term averaged flux field show mainly a negative ΠE (inverse energy cascade) except for the equatorial region. Moreover, a high intensity negative flux is found for both the Loop Current and Kuroshio Current, indicating that the mesoscale eddies might be absorbed by the main flow.

 

Ref.

Charney, J. G. (1971). Geostrophic turbulence. J. Atmos. Sci., 28(6), 1087-1095.

Frisch, U.,  Kolmogorov, A. N. (1995). Turbulence: the legacy of AN Kolmogorov. Cambridge University Press.

Alexakis, A.,  Biferale, L. (2018). Cascades and transitions in turbulent flows. Phys. Rep., 767, 1-101.

Dong, S., Huang, Y.X., Yuan, X., & Lozano-Durán, A. (2020). The coherent structure of the kinetic energy transfer in shear turbulence. J. Fluid Mech., 892, A22.
Sulfur and carbon isotope measurements of carbonyl sulfide (COS) from small air samples using GC-IRMS
Authors: Baartman Sophie , Krol Maarten , Röckmann Thomas , Popa Maria Elena , Kooijmans Linda , Driever Steven , Wassenaar Maarten , Mossink Leon , van Heuven Steven
Published: March 2022

Carbonyl sulfide (COS) is the most abundant sulfur-containing trace gas in the atmosphere, with an average mixing ratio of 500 parts per trillion (ppt). It has a relatively long lifetime of about 2 years, which permits it to travel into the stratosphere. There, it likely plays an important role in the formation of stratospheric sulfur aerosols (SSA), which have a cooling effect on the Earth’s climate. Furthermore, during photosynthetic uptake by plants, COS follows essentially the same pathway as CO2, and therefore COS could be used to estimate gross primary production (GPP). Unfortunately, significant uncertainties still exist in the sources, sinks and global cycling of COS, which need to be overcome. Isotopic measurements of COS could be a promising tool for constraining the COS budget, as well as for investigating its role in the formation of stratospheric sulfur aerosols.

Within the framework of the COS-OCS project, we developed a measurement system at Utrecht University using GC-IRMS that can measure δ33S and δ34S from S+ fragment ions of COS from small air samples of 2 to 5 L. This system was recently expanded to also measure δ13C from the CO+ fragment ions of COS, which has never been measured before. We will present the preliminary results from a plant chamber experiment conducted at Wageningen University, in which one of the goals was to quantify the COS uptake and isotopic fractionation factors of different C3 and C4 plants.
Climate change impacts on snow avalanche risk in alpine regions
Authors: Ortner Gregor , Bründl Michael , Kropf Chahan M. , Bühler Yves , Bresch David N.
Published: March 2022

Various studies show that changes in the climate system, such as temperature rise and extreme precipitation events, strongly influence gravity driven hazards. Within the  research program "Climate Change Impacts on Alpine Mass Movements'', we develop a framework to model mass movement risk altered by climate and socio-economic drivers. In a first approach, we've modeled snow avalanche risk in Switzerland for the current climate situation and three avalanche hazard scenarios. For each of these scenarios we've considered different 3-day increases in snow height for avalanche formation, derived from meteorological stations. For the modelling we've applied the RAMMS::LSHIM Large Scale Hazard Indication Mapping algorithm combining the delineation of potential release areas from a high-resolution terrain model with a forest layer to depict the spatial distribution of avalanche impact for each of the chosen scenarios.
To model possible climate change effects on snow avalanche hazard, we use down-scaled data from the CH2018 climate change scenarios as input for the  model "SNOWPACK''. The so-derived changing avalanche hazard disposition is simulated with the RAMMS::LSHIM method and risks are analysed with the probabilistic, Python-based risk assessment platform CLIMADA using high resolution building layers to identify monetary assets and assign vulnerabilities. The results are spatio-temporally explicit risk maps, depicting changes of snow avalanche risks based on the combination of exposure and vulnerability information. These maps allow for the appraisal of appropriate risk management options and thereby contribute to decision support and highlight areas where adaptation measures to climate change might be needed.