bluuebunny/crossref_metadata_2025 huggingface dataset:
The new COST-G deterministic signal model
Authors: Meyer Ulrich , Peter Heike , Lasser Martin , Jäggi Adrian
Published: March 2022

The precise orbit determination (POD) of Low Earth Orbiters (LEO), e.g. the Copernicus Sentinel Earth observation satellites, relies on the precise knowledge of the Earth gravity field and its variations with time. The most precise observation of time-variable gravity on a global scale is currently provided by the GRACE-FO satellites. But the monthly gravity field solutions are released with a latency of approx. 2 months, therefore they cannot be used for operational POD.

We present a deterministic signal model (DSM) that is fitted to the time-series of COST-G combined monthly gravity fields and describe the differences with respect to the available long-term gravity models including seasonal and secular time-variations. To validate the DSM, dynamic POD of the Sentinel-2B, -3B and -6A satellites is performed based on long-term or monthly gravity field models, and on the COST-G DSM. We evaluate the model quality on the basis of carrier phase residuals, orbit overlap analysis and independent satellite laser ranging observations, and study the limitation on orbit altitude posed by the reduced spherical harmonic resolution of the monthly models and the DSM.

The COST-G DSM is updated quarterly with the most recent GRACE-FO combined monthly gravity fields. It is foreseen to apply a sliding window approach with flexible window length to allow for an optimal adjustment in case of singular events like major earthquakes.
Effects of the construction of the lower Yarlung Tsangpo River tunnel project on the stability of organic carbon in forest soils
Authors: Zhao Runying , Tang Xiaolu
Published: March 2022

Effects of the construction of the lower Yarlung Tsangpo River tunnel project on the stability of organic carbon in forest soils

Abstract: Tunnels are widely used in road construction in areas such as the highlands and mountains, however, their effect on soil organic carbon stability has been less studied. Soil organic carbon stability is a sensitive index to evaluate the response of soil ecosystem to environmental changes. In order to detect the soil organic carbon (SOC) the anti-interference ability of the engineering construction of the tunnel, the stability of soil organic carbon was analyzed by using labile soil organic carbon（LOC）, soil aggregates and enzyme activities. Based on the construction of the lower Yarlung Tsangpo River tunnel, fixed monitoring plots were set up in the Engineering disturbance areas (ED) and undisturbed areas (CK) as a control to investigate the influence of tunnel construction on SOC stability . Results showed that the SOC and LOC in the ED were 291.40 mg/kg and 110.28 mg/kg, respectively, which were slightly higher than those in the CK area 255.31 mg/kg and 91.19 mg/kg, but the difference was not significant (p=0.6). The proportion of >0.25 mm aggregates in all soil fractions was more than 80%. With the decrease of aggregate size, the content of organic carbon in aggregate showed a decreasing trend, but there was no significant difference between ED and CK areas. This study showed that tunnel construction has no significant effect on soil organic carbon stability, which may be associated to the abundant precipitation in the study area. Because vegetation mainly absorbed soil water in top layer and the input and output of soil organic matter were not affected. The results of the study provide a reference basis for the evaluation of the impact of tunnel construction on the environment and for the management of the forest ecosystem in the lower Yarlung Tsangpo River.

Keywords: Tunneling; Forest soils; Organic carbon stability; labile organic carbon; Soil enzyme; soil aggregates
Representing South Indian water tanks in a hydrologic model using remote sensing data
Authors: Mahmoodi Nariman , Wagner Paul , Lei Chaogui , Narasimhan Balaji , Rosado Daniel , Fohrer Nicola
Published: March 2022

Water tanks in South India have undeniable impacts on the natural hydrological regime of rivers by storing water during the monsoon season and releasing it for irrigation purposes during the dry season. As data on water tanks is limited, they are often not considered in hydrological modeling, which could reduce model performance. Therefore, this study aims at representing water tanks in the hydrologic model SWAT+ and evaluating their impacts on the model performance for a catchment model of the upper Adyar River catchment in South India. To obtain data on the spatio-temporal variations in water storage of the tanks for the years 2015-2018 a random forest classification of water areas is carried out using Sentinel-2 satellite data. Two model setups are evaluated, one with and another one without water tanks. A multi-metric approach including the Kling–Gupta efficiency (KGE), the Nash-Sutcliffe efficiency (NSE), and the ratio of the root mean square error to the standard deviation (RSR) was applied to calibrate and validate the hydrologic model for the time periods 2012-2018 and 2004-2011 respectively. The water tanks are considered as reservoirs in the hydrologic model and the required data such as the location, the surface area, and the volume of reservoirs are extracted from the satellite data. Our results show that implementing water tanks in the SWAT+ model leads to a better representation of the monthly streamflow by having an effect on the peak flows of the wet season. A higher goodness of fit is achieved for the validation period with KGE = 0.67, NSE = 0.76, and RSR = 0.62 in comparison to the calibration period where KGE and NSE are 0.56 and 0.61, respectively. The agreement between simulated and observed streamflow is the highest for the period 2015-2018 (KGE = 0.76, NSE = 0.81 and RSR = 0.43). Therefore, it can be concluded that implementing water tanks in a hydrologic model enhances the performance of the model.
Hydraulic fracture interactions with mineral grains
Authors: Yoshioka Keita , Katou Masafumi , Tamura Kohei , Arima Yutaro , Ito Yoshiharu , Chen Youqing , Ishida Tsuyoshi
Published: March 2022

Hydraulic fractures often turn or branch, interacting with pre-existing discontinuities (e.g. natural fracture, grain boundary). Such fracture complexities, especially in the proximity of borehole, impact the subsequent well conductivity. When a fracture finds a discontinuity, it either penetrates or deflects depending supposedly on the in-situ stress and the discontinuity geometry. However, our hydraulic fracture experiments on carbonates show that the fractures deflected more frequently at a grain boundary as they propagated farther away from the borehole. In other words, the fracture complexity consistently increases with the propagation distance. In this study, using energy release rate analyses, we show that the energy dissipation of a penetrating fracture increases with the distance away from the borehole. This means, the farther away the hydraulic fracture propagates, the more easily it deflects at a grain boundary from the energetic point of view. This tendency was also confirmed by numerical hydraulic fracture simulations based on a successive energy minimization approach. Our findings challenge the conventional hydraulic fracture penetration/deflection criteria based only on the in-situ stress and the discontinuity geometry. 
A stand-alone, modular Sensorbox to exploit the potential of automotive lidar for geoscientific applications
Authors: Muckenhuber Stefan , Schlager Birgit , Gölles Thomas , Hammer Tobias , Bauer Christian , Exposito Jimenez Victor , Schöner Wolfgang , Schratter Markus , Schrei Benjamin , Senger Kim
Published: March 2022

Today, the automotive industry is a leading technology driver for lidar systems, because the largest challenge for achieving the next level of vehicle automation is to improve the reliability of the vehicles’ perception system. High costs of mechanically spinning lidars are still a limiting factor, but prices have already dropped significantly during the last decade and are expected to drop by another order of magnitude in the upcoming years thanks to new technologies like micro-electro-mechanical systems (MEMS) based mirrors, optical phased arrays, and vertical-cavity surface-emitting laser (VCSEL) sources. To exploit the potential of these newly emerging cost-effective technologies for geoscientific applications, we developed a novel stand-alone, modular Sensorbox that allows the use of automotive lidar sensors without the necessity of a complete vehicle setup. The novel Sensorbox includes a real-time kinematic differential global positioning system (RTK DGPS) and an inertial measurement unit (IMU) for georeferenced positioning and orientation. This setup enables measuring geoscientific processes and landforms reliably, at any remote location, with very high spatial and temporal resolution, and at relatively low costs. The current setup of the Sensorbox has a 360° field of view with 45° vertical angle, a range of 120m, a spatial resolution of a few cm and a temporal resolution of 20Hz. Compared to terrestrial laser scanners (TLS), such as the Riegl VZ-6000, automotive lidar sensors provide advantages in terms of size (40cm vs. 10cm), weight (20kg vs. 1kg), price (150k€ vs. 10k€), robustness (IP64 vs. IP68), acquisition time/frame rate (1h vs. 20Hz) and eye safety (class 3 vs. class 1). They can therefore provide a very useful complement to currently used TLS systems that have their strengths in range (6000m vs. 100m) and accuracy (1cm vs 5cm) performance. Automotive lidar sensors record high-resolution point clouds with very high acquisition frequencies, resulting in a data stream with order 10^6 points per second. To efficiently work with such large point cloud datasets, the open-source python package ‘pointcloudset’ was developed for handling, analysing, and visualizing large datasets that consists of multiple point clouds recorded over time.
Relationship between the Central Asian Subtropical Westerly and Northwest Indian Summer Monsoon rainfall
Authors: Sadaf Nabeela , Lin Yanluan , Dong Wenhao
Published: March 2022

In addition to various factors over the tropics, the interannual variability of northwest Indian summer monsoon (NWISM) rainfall is also regulated by extratropical signals. We defined a subtropical westerly jet index (SWJI) based on the meridional position and intensity of 200-hPa zonal wind within [25-55°N, 40-90°E]. It is found that SWJI exhibits a significant positive correlation with summer rainfall over the NWISM region during 1951-2015. During positive (negative) SWJI years, an upper-level anticyclonic (cyclonic) anomaly over Central Asia along with positive (negative) rainfall anomaly and low-level easterly (westerly) anomalies were observed over the NWISM region. The upper-level anticyclonic (cyclonic) anomaly was accompanied by the descending (ascending) motion and warm (cold) tropospheric temperature anomalies. The anticyclonic (cyclonic) anomaly increased (decreased) the land-ocean thermal contrast by warm (cold) air advection and modified the local meridional circulation. Interannual variability of rainfall over the NWISM region is associated with the meridional position and intensity of the jet that manifest in both upper- and low-level circulation anomalies. Further analysis showed that the interannual variability of SWJI is correlated with Arctic Oscillation (AO). During the positive phase of AO, an upper-level anticyclonic anomaly appeared over Central Asia and favored convection over the NWISM region.
Ecological and evolutionary processes shape belowground springtail communities along an elevational gradient
Authors: Sun Xin , Xie Zhijing , Wu Donghui , Chen Ting-Wen , Potapov Mikhail , Scheu Stefan
Published: March 2022

Aim: Both ecological and evolutionary processes shape biological communities along elevational gradients. Compared to aboveground taxa, elevational patterns and processes of belowground animal communities are little studied. Here, we investigated how environmental gradients across elevation may affect species divergence in the past and act as filters of contemporary assembly of soil detritivores via functional traits. We asked: (1) Are environmental filtering processes of belowground communities due to elevation, vegetation or microhabitat factors, (2) did most divergence events of species occur after mountain uplift by geological forces, and (3) are there environmental factors related to species divergences in the past.

Location: Changbai Mountain, northeast China.

Taxon: Isotomidae, Collembola.

Methods: We collected isotomid springtails from 800 to 2150 m above sea level and reconstructed the phylogeny using mitochondrial genome sequencing. We inspected the functional traits body length, number of ommatidia and pigmentation, and determined their evolutionary patterns. We then derived community parameters using trait-based and metacommunity phylogenetic approaches, and used linear mixed-effects models to identify environmental variables that allow predicting community trait and phylogenetic parameters.

Results: Isotomid springtails differed more in traits when co-occurring in environments with lower soil nitrogen, typically at higher elevations. Most communities exhibited phylogenetic clustering, but this pattern was not related to elevation or any environmental variables. These isotomid species mainly diverged in the Mesozoic with some divergence events associated with soil N and pH, as well as other factors covarying with the contemporary elevational gradient studied. The current communities comprised old phylogenetic lineages possessing traits that have undergone evolutionary drift.

Main conclusions: While environmental gradients act as filters for belowground detritivores, evolution of traits preconditions their assembly. Species divergence likely resulted from filtering processes of past environments resembling the present day. Belowground diversity in Changbai Mountain is mainly based on the persistence of old phylogenetic lineages, while recent speciation is of little importance.
The role of the Laurentide ice-sheet topography in the Alpine hydro-climate at glacial times
Authors: Velasquez Patricio , Messmer Martina , Raible Christoph C.
Published: March 2022

In this study, we investigate the sensitivity of the glacial Alpine hydro-climate to changes of the Laurentide ice sheet (LIS). Bridging the scale gap by using a chain of global and regional climate models, we perform sensitivity simulations of up to 2 km horizontal resolution over the Alps for the Last Glacial Maximum and the Marine Isotope Stage 4. In winter, we find wetter conditions in the southern part of the Alps during glacial conditions compared to present day, to which dynamical processes, i.e.  changes in the wind speed and direction, substantially contribute. During summer, we find the expected drier conditions in most of the Alpine region during glacial conditions, as thermodynamics suggests drier conditions under lower temperatures. The sensitivity simulations of the LIS changes show that an increase of the ice-sheet thickness leads to a significant intensification of glacial Alpine hydro-climate conditions, which is mainly explained by dynamical processes. The findings demonstrate that the Laurentide ice-sheet topography plays an important role in regulating the Alpine hydro-climate and thus permits a better understanding of the precipitation patterns in the complex Alpine terrain at glacial times.
Cryostratigraphy, chronology, and ground-ice stable isotopes of the Batagay megaslump in east Siberia indicate climate–permafrost interactions during the Middle and Late Pleistocene
Authors: Opel Thomas , Wetterich Sebastian , Meyer Hanno , Murton Julian
Published: March 2022

The Batagay megaslump (67.58 °N, 134.77 °E) is the largest known retrogressive thaw slump on Earth, and located in the Yana River Uplands near the town of Batagay in east Siberia. The slump headwall is about 55 m high and exposes ancient permafrost deposits that provide a discontinuous record of the Middle and Late Pleistocene that dates back to at least 650 ka. Such deposits are usually deeply (>45 m) buried in frozen ground.

The cryostratigraphy of the Batagay megaslump provides evidence for several periods of both permafrost formation and degradation. Permafrost formation and stability are reflected by the presence of deposits with syngenetic ice wedges and composite (i.e., ice–sand) wedges, whereas permafrost thaw and erosion are shown by sharp erosional discordances above reddish and organic-rich layers and by the accumulation of woody (forest) remains in erosional downcuts.

The main cryostratigraphic units with syngenetic ice and composite wedges indicate the formation of permafrost during MIS 16 or earlier (lower ice complex), MIS 7–6 or earlier (lower sand unit), MIS 4–2 (upper ice complex), and MIS 3–2 (upper sand unit). Intense permafrost thaw and erosion likely took place during one or several periods between MIS 16 and MIS 7–6, including MIS 5 and the late Pleistocene–Holocene transition.

In this contribution we compile cryostratigraphic observations and dating results for the permafrost exposed in the Batagay megaslump. To draw large-scale conclusions on climate–permafrost interactions we compare our data to independent climate and permafrost reconstructions from terrestrial (cave deposits, lake sediment cores, and permafrost deposits) and marine sediment cores across the Arctic with a focus on East Siberia.

To gain regional climate signals for this extremely continental region, we also present ground-ice stable-isotope data from all four main stratigraphic units of the Batagay megaslump. We consider ice and composite wedges (winter signals) and pore ice (summer to annual signals) to derive seasonal-scale information and to assess continentality for selected time periods.
The interaction of carbon and nutrient relations in trees exposed to drought
Authors: Gessler Arthur , Joseph Jobin , Hagedorn Frank , Ouyang Shengnan , Schönbeck Leonie
Published: March 2022

It is getting more and more clear that the sink activity in trees strongly determines carbon (C) uptake and within-plant C distribution. Here we show that short- and long-term changes in water availability impacted the belowground (mycorrhizosphere) C sink strength, which however, not only affected C transport to the roots but also nitrogen (N) uptake by tree roots and the N allocation to aboveground tissues. The negative drought impact on N uptake might be a result of reduced root growth and the lower availability of recent assimilates for mobilizing inorganic N in the soil as the physiological N uptake capacity of the roots was not clearly affected. On the other hand, we show that increased N availability in the soil can have positive effects on C allocation to the rooting system of trees under drought and consequently can reduce drought induced growth impairment and mortality. Our results show that the strong interaction between nutrients and carbon needs to be taken into account to understand the resilience of trees and forests towards drought events projected to occur more frequently in future.
Rigorous Exploration of Complex Environmental Models to Advance Scientific Understanding
Authors: Reinecke Robert , Pianosi Francesca , Wagener Thorsten
Published: March 2022

Environmental models are central for advancing science by increasingly serving as a digital twin of the earth and its components. They allow us to conduct experiments to test hypotheses and understand dominant processes that are infeasible to do in the real world. To foster our knowledge, we build increasingly complex models hoping that they become more complete and realistic images of the real world. However, we believe that our scientific progress is slowed down as methods for the rigorous exploration of these models, in the face of unavoidable data- and epistemic-uncertainties, do not evolve in a similar manner.

Based on an extensive literature review, we show that even though methods for such rigorous exploration of model responses, e.g., global sensitivity analysis methods, are well established, there is an upper boundary to which level of model complexity they are applied today. Still, we claim that the potential for their utilization in a wider context is significant.

We argue here that a key issue to consider in this context is the framing of the sensitivity analysis problem. We show, using published examples, how problem framing defines the outcome of a sensitivity analysis in the context of scientific advancement. Without appropriate framing, sensitivity analysis of complex models reduces to a diagnostic analysis of the model, with only limited transferability of the conclusions to the real-world system.
Internal Tide Generation by Submarine Canyons
Authors: Elmes Joseph , Griffiths Stephen , Bokhove Onno
Published: March 2022

Approximately 70% of the global dissipation of the barotropic tide occurs in the waters of the continental margins, due to bottom friction on the shelves and internal tide generation at the continental slopes. Here we are interested in the latter process, and how it depends upon the presence of submarine canyons, which are a ubiquitous feature of continental slopes. Whilst there have been modeling studies of internal tide generation at particular canyons (e.g., Monterey), our emphasis is on understanding the effects of canyon geometry more generally, given the diversity of canyons that exist across the globe.  

To do this, we study idealised canyon configurations cutting through idealised continental slopes, enabling us to define and then explore a relevant parameter space (canyon length, width, depth, etc.). For forcing by a prescribed barotropic tide, taking the form of a Kelvin wave with predominantly alongshore flow, we investigate both the amplitude and direction of the implied radiating internal tides, and generate scaling laws for how the tidal dissipation varies across parameter space.

Such a study would be challenging and extremely time consuming with traditional ocean circulation models, because of the small length scales of both the canyons and the internal tides. For efficiency, we thus use the multi-modal linear modelling strategy of Griffiths and Grimshaw (2007), but solved with cutting-edge numerics in the form of a Discontinuous Galerkin Finite Element methodology. We have generated high-quality multi-scale triangular meshes to resolve the canyons, and can deploy a range of test-function orders and numerical fluxes therein. This methodology is a key part of this study.
Monthly-resolved Freshwater Flux from the Greenland Ice Sheet on a Glacier-Basin Scale
Authors: Karlsson Nanna Bjørnholt , Mankoff Kenneth D. , Solgaard Anne M. , Larsen Signe Hillerup , Fausto Robert S. , Sørensen Louise S.
Published: March 2022

The Greenland ice sheet outputs freshwater into the Greenlandic fjords in the form of icebergs and liquid meltwater. This freshwater flux affects the fjords’ water circulation and ecosystems. In recent decades, the mass loss from the ice sheet has increased causing an increasing volume of liquid and solid freshwater to enter the fjords and ocean around Greenland. The total volume of freshwater is currently challenging to determine on a fjord-basin scale due to disparate products that are difficult to compare and combine into a cohesive product. This entails that the effect of the glacially derived freshwater on fjord circulation and ecosystem is not well constrained.

Here, we present a new glacier-basin scale product that combines three existing products into a shared temporal and spatial framework. We use publicly available datasets of solid ice discharge (icebergs), surface meltwater run-off, and basal melt to present a cohesive overview of the influx of freshwater to the Greenlandic fjords. We then quantify the different dominant term for each glacier. The dataset will be freely available and will be of use to, for example, oceanographic and marine biological research activities.

This work was supported by PROMICE (Programme for Monitoring the Greenland Ice Sheet, GEUS) and ESA Polar+ 4D Greenland.
Correlation between groundwater levels and meteorological indicators in the coastal karst aquifer of Salento (Southern Italy)
Authors: Alfio Maria Rosaria , Balacco Gabriella , Fidelibus Maria Dolores
Published: March 2022

In many regions of the Mediterranean basin, both climate variability and human pressure threaten groundwater quality and quantity. Uncertainties concerning future precipitation, temperature patterns, and water accessibility provide a challenge in understanding how groundwater reacts to the variability of the hydrological forces. This aspect is of fundamental interest for water resources planning and management, especially in those areas where groundwater is the main water source. The proposed research looks for correlations between meteorological drought indexes and groundwater levels (GWLs) to provide qualitative information about GWLs response to precipitation and temperatures changes. The GWLs time series refer to nine monitoring wells located in the coastal karst aquifer of Salento (Puglia, Southern Italy). The aquifer is challenging because of the highly complex geological, geomorphological, and hydrogeological structure and regional size. In such complex environment and under climate changes, a high and unrestricted exploitation for irrigation, industrial, and drinking purposes may deteriorate the qualitative and quantitative status of groundwater. Such features often prevent the recognition with sophisticated methods of the relationship between hydrological and hydrogeological time series, especially under data scarcity. Searching for these relationships, three correlation coefficients were applied at different time scales, with reference to the period between July 2007 and December 2011, between the SPI (Standardized Precipitation Index) and SPEI (Standardized Precipitation and Evapotranspiration Index) and GWLs time series. Results of the three coefficients outline a positive and statistically significant correlation between time series, generally for long time scales, highlighting the slow response of GWLs to precipitation. Despite the complexity of the aquifer, it linearly reacts to precipitation and temperature variability in the long term, acting as a low-pass filter with a notable inertial behavior in response to meteorological events. The aquifer response is different compared to dry and recharge periods. In most cases, the decreasing GWL courses agree with the dry SPI and SPEI ones, while the increasing GWL courses are less congruent during wet periods. This characteristic reveals crucial in defining correct measures of protection and safeguard of groundwater resources during periods of meteorological drought.

Results suggest that the selected approaches are worthy of interest for those areas characterized by severe stress conditions due to long drought periods and under excessive groundwater exploitations, demonstrating the generality of their applicability also under data scarcity.
The Multi-Channel Maximum-Likelihood (MCML) method: a new approach for infrasound detection and wave parameter estimation
Authors: Poste Benjamin , Charbit Maurice , Le Pichon Alexis , Listowski Constantino , Roueff François , Vergoz Julien
Published: March 2022

We are presenting a new and novel approach to the detection and parameter estimation of infrasonic signals. Our approach is based on the likelihood function derived from a multi-sensor stochastic model expressed in different frequency channels. Using the likelihood function, we determine, for the detection problem, the Generalized Likelihood Ratio Test (GLRT) and, for the estimation of the slowness vector, the Maximum Likelihood Estimation (MLE). We establish new asymptotic results (i) for the GLRT under the null hypothesis leading to the computation of the corresponding p-value and (ii) for the MLE by focusing on the two wave parameters back-azimuth and horizontal trace velocity. The Multi-Channel Maximum-Likelihood (MCML) detection and estimation method is implemented in the time-frequency domain in order to avoid the presence of interfering signals. Extensive simulations with synthetic signals show that MCML outperforms the state-of-the-art multi-channel correlation detector algorithms like the Progressive Multi-Channel Correlation (PMCC) in terms of detection probability and false alarm rate in poor signal-to-noise ratio scenarios. We also illustrate the use of the MCML on real data from the International Monitoring System (IMS) and show how the improved performances of this new method lead to a refined analysis of events in accordance with expert knowledge.
Using IPIM to Simulate the Ionosphere’s Response to Extreme Space Weather
Authors: Thomas Simon , Blelly Pierre-Louis , Marchaudon Aurelie , Eisenbeis Julian , Bird Samuel
Published: March 2022

The IRAP Plasmasphere Ionosphere Model (IPIM) describes the transport equations of
ionospheric plasma species along magnetic closed field lines. As input, the previous iteration
of IPIM used basic models to provide estimations of the solar wind conditions, convection,
and precipitation within the ionosphere. In this presentation, we discuss the development of
a new operational version of IPIM as part of the EUHFORIA project to monitor and forecast
space weather conditions and hazards. The developments of the model include using in-situ
solar wind observations from the OMNI data set, ionospheric radar data of plasma motions
from the Super Dual Auroral Radar Network (SuperDARN), and precipitation data from the
Ovation model, as inputs to the model. We present the first results from the latest IPIM
version, focussing on case study coronal mass ejections on 14th December 2006 and 14th
July 2012 which featured clear magnetic clouds and long-lasting southward magnetic field.
For these events, we explore simulations of plasma densities, temperature, and motions,
and compare with observations from EISCAT ionospheric radars and ionosonde launches.
With these results in mind, we will discuss the skill of using IPIM as a space weather
forecasting and analysis tool.
Measuring the eigenfrequencies of candlestick stalagmites with a custom 3D-printed sensor modified from a Raspberry Shake 3D 
Authors: Martin Aurélie , Lecocq Thomas , Lannoy Ari , Quinif Yves , Camelbeeck Thierry , Fagel Nathalie
Published: March 2022

The eigenfrequencies of speleothems are fundamental parameters in the study of their response to earthquakes. To study these, the seismic ambient noise is measured by three-component seismic sensors adapted to the geometry of the speleothems. This method is currently being studied in the Han-sur-Lesse cave (Ardenne, Belgium).

A previous study (Martin et al. 2020) was carried out with a SmartSolo IGU-16HR 3C sensor on an imposing 4.5 m tall stalagmite.  This approach demonstrated the feasibility and interest of studying the eigenfrequencies of stalagmites from ambient noise. However, this sensor was too heavy for use on thin and slender stalagmites. The challenge was to find and adapt a lighter sensor able to record very weak movements while being easily adjustable to the various shapes of the stalagmite and securely attachable on these to reduce the impact of the sensor on frequencies measurements and the risks for the fragile structure.

A solution was found by using a Raspberry Shake 3D Personal Seismograph (RS) that initially integrates three orthogonal velocity sensors (Sunfull PS-4.5B), the digitizer, and the Raspberry Pi computer into a single plexiglass box​. The RS has the advantage of being less heavy while being composed of three weak motion geophones. After a comparison study, this sensor gives similar results for eigenfrequency and polarization analyses. However, the use of this new sensor on thin and slender stalagmites requires the creation of suitable support. The RS was split and distributed around the stalagmite. The geophone wiring was modified and extended to separate the geophones from the acquisition system. A 3D-printed support was created to guarantee the orthogonality of the horizontal sensors while reducing the stresses by distributing the weight of the sensor around the stalagmite.

This new configuration allowed determining the eigenfrequencies of 16 thin and slender stalagmites in the Han-sur-Lesse cave (Ardenne, Belgium) and the polarization of the motions associated with these frequencies. Moreover, a two-week recording period allows to measure the daily and weekly variation of ambient noise and transient events like earthquakes, quarry blasts or flooding events in the cave.

Reference: Martin, A.; Lecocq, T.; Hinzen, K.-G.; Camelbeeck, T.; Quinif, Y.; Fagel, N. Characterizing Stalagmites’ Eigenfrequencies by Combining In Situ Vibration Measurements and Finite Element Modeling Based on 3D Scans. Geosciences 2020, 10, 418. https://doi.org/10.3390/geosciences10100418
The Global Gravity-based Groundwater Product (G3P): first results 
Authors: Sharifi Ehsan , Güntner Andreas ,   G3P team
Published: March 2022

The Global Gravity-based Groundwater Product (G3P) aims at developing a satellite-based groundwater storage (GW) data set as a new product for the EU Copernicus Climate Change Service. As the world’s largest distributed freshwater storage, GW is a key resource for mankind, industrial, and agricultural demands. In Copernicus, there is no service available yet to deliver data on this fundamental resource, nor is there any other data source worldwide that operationally provides information on changing groundwater resources in a consistent way, observation-based, and with global coverage. Therefore, G3P develops an operational global groundwater service as a cross-cutting extension of the existing Copernicus portfolio. G3P capitalizes from the unique capability of GRACE and GRACE-FO satellite gravimetry as the only remote sensing technology to monitor subsurface mass variations, and from other satellite-based water storage products to provide a data set of groundwater storage change for large areas with global coverage. G3P is obtained by using a mass balance approach, i.e., by subtracting satellite-based water storage compartments (WSCs) such as snow water equivalent, root-zone soil moisture, glacier mass, and surface water storage from GRACE/GRACE-FO monthly terrestrial water storage anomalies (TWSA). For a consistent subtraction of all individual WSCs from GRACE-TWSA, the individual WSCs are filtered in a similar way as GRACE-TWSA, where optimal filter types were derived by analyses of spatial correlation patterns. G3P groundwater variations are provided for almost two decades (from 2002 to the present), with the monthly resolution, and at a 0.5-degree spatial resolution globally. In this contribution, we also illustrate preliminary results of the G3P data set and of its uncertainties, as well as its evaluation by independent groundwater data.

This study has received funding from the European Union’s Horizon 2020 research and innovation programme for G3P (Global Gravity-based Groundwater Product) under grant agreement nº 870353.
Modeling horizontal currents and magnetic ground perturbations with the IPIM model
Authors: Eisenbeis Julian , Blelly Pierre-Louis , Thomas Simon , Marchaudon Aurelie
Published: March 2022

The IRAP Plasmasphere Ionosphere Model (IPIM) is an ionospheric model which describes the transport equations of ionospheric plasma species along magnetic closed field lines. The development of a new operational version of IPIM as part of the EUHFORIA project to monitor and forecast space weather conditions and hazards includes using in-situ solar wind observations from the OMNI data set, ionospheric radar data of plasma motions from the Super Dual Auroral Radar Network (SuperDARN), and precipitation data from the Ovation model, as inputs to the model. A new conductivity module has also been developed for help in the simulation of geomagnetically induced currents based on a simplified version of IPIM. This model uses the photochemical module of IPIM in place of the fluid module and the full kinetic module, so that inter-hemispheric transport of suprathermal electrons is accounted for in the ion production term. As the main contribution to the conductivities comes from the lower ionosphere (typically below 150km) where the chemistry dominates, neglecting the field-aligned transport contribution in the fluid module does not alter significantly the conductivities. Based on the conductivities, the neutral wind and the electric field, ionospheric horizontal currents are computed. The ionospheric currents are used as an input for the Biot and Savart module to compute the resulting magnetic perturbations at the ground. We present the first results from this version which explores the ionosphere's response to different conditions in different regions in mid and high latitudes.
Exploring the challenges of Digital Twins for weather & climate through an Atmospheric Dispersion modelling prototype
Authors: Haddad Stephen , Killick Peter , Hopkinson Aaron , Trzeciak Tomasz , Burgoyne Mark , Leadbetter Susan
Published: March 2022

Digital Twins present a new user-centric paradigm for developing and using weather & climate simulations that is currently being widely embraced, for example through large projects such as Destination Earth led by ECMWF.  In this project we have taken a smaller scale approach in understanding the opportunities and challenges in translating the Digital Twin concept from the original domain of manufacturing and the built environment to modelling of the earth’s atmosphere.

We describe our approach to creating a Digital Twin based on the Met Office’s Atmospheric Dispersion simulation package called NAME. We will discuss the advantages of doing this, such as the ability of nonexpert users to more easily produce scientifically valid simulations of dispersion events, such as industrial fires, and easily obtain results to feed into downstream analysis, for example of health impacts. We will describe the requirements of each of the key components of a digital twin and potential implementation approaches.

We will describe how a Digital Twin framework enables multiple models to be joined together to model complex systems as required for atmospheric concentrations around chemical spills or fires modelled by NAME. Overall, we outline a potential project blueprint for future work to improve usability and scientific throughput of existing modelling systems by creating a Digital Twins from core current modelling code and data gathering systems.
Recent trends in root-zone soil moisture over India using the GLEAM data for the period 1980-2020
Authors: Babu Kanike Raghavendra Prasad , Bhimala Kantha Rao
Published: March 2022

Root Zone Soil Moisture (RZSM) plays a critical role in land-atmospheric interactions, water & energy budget, terrestrial evaporation and vegetation health. Unfortunately, the in-situ observations of RZSM are very sparse all over the globe. The present study utilized the RZSM product (based on microwave satellite data) from the GLEAM (Global Land Evaporation Amsterdam Model) to study the trends and spatial variability over India during the period 1980-2020. The annual RZSM climatology map shows that the highest values (>0.35 m3/m3) are found over dense vegetation regions (Western-Ghats, North-East India, and foothills of Himalayas) and low values (<0.2 m3/m3) are found in arid and semi-arid regions of North-West India. The all India annual mean RZSM (area averaged) is 0.285 m3/m3 with the standard deviation of 0.0076 m3/m3 and showing a significant increasing trend (p<0.05) during the period 1980-2020. The analysis found a distinct seasonal variability in RZSM and found the highest RZSM during the southwest monsoon (June-September) season and low values in the pre-monsoon season (March-May) for most of the sub-divisions classified by the India Meteorological Department. The seasonal all India mean RZSM values are 0.23 m3/m3, 0.33 m3/m3, 0.31 m3/m3 during pre-monsoon, monsoon, and post-monsoon seasons respectively, and found a significant increasing trend in all seasons during the study period. The sub-division wise trend (Mann-Kendall test) analysis shows that the pre-monsoon RZSM showed a tremendous increasing trend in most (23 out of 34) of the sub-divisions (except north and northeast India) whereas in monsoon and post-monsoon season only 9 and 12 sub-divisions showed an increasing trend in India respectively. The present study improves our understanding of the regional scale hydrological cycle and the importance of realistic representation of irrigation and land use land cover changes in climate models for better prediction of monsoon and other natural disasters in India.
Inferring the instability of a dynamical system from the skill of data assimilation exercises
Authors: Chen Yumeng , Carrassi Alberto , Lucarini Valerio
Published: March 2022

Data assimilation (DA) aims at optimally merging observational data and model outputs to create a coherent statistical and dynamical picture of the system under investigation. Indeed, DA aims at minimizing the effect of observational and model error and at distilling the correct ingredients of its dynamics. DA is of critical importance for the analysis of systems featuring sensitive dependence on the initial conditions, as chaos wins over any finitely accurate knowledge of the state of the system, even in absence of model error. Clearly, the skill of DA is guided by the properties of dynamical system under investigation, as merging optimally observational data and model outputs is harder when strong instabilities are present. In this paper we reverse the usual angle on the problem and show that it is indeed possible to use the skill of DA to infer some basic properties of the tangent space of the system, which may be hard to compute in very high-dimensional systems. Here, we focus our attention on the first Lyapunov exponent and the Kolmogorov–Sinai entropy and perform numerical experiments on the Vissio–Lucarini 2020 model, a recently proposed generalization of the Lorenz 1996 model that is able to describe in a simple yet meaningful way the interplay between dynamical and thermodynamical variables.
Coeval volcanism and rotation of Neotethyan oceanic crust in the Oman ophiolite – fact or fiction?
Authors: Morris Antony , Di Chiara Anita , Anderson Mark , MacLeod Chris , Koornneef Louise , Hepworth James , Harris Michelle
Published: March 2022

The upper crustal volcanic section of the Oman suprasubduction zone ophiolite is divided into an older V1 sequence, overlain by slightly younger V2 lavas and (in places) a final V3 sequence. Paleomagnetic data from the V1 and V2 sequences of the northern massifs of the ophiolite have been used previously to infer that clockwise rotation of the Oman lithosphere began while the upper crust was actively accreting, with V1 lavas apparently more rotated than the overlying V2 units. This inference has been largely accepted by the geological community and has influenced models for the spreading history and geodynamic evolution of the Oman ophiolite.

Here we present new paleomagnetic data from well-exposed and structurally well-constrained volcanic sequences in the Salahi and Fizh massifs of the ophiolite that discredit this interpretation. In contrast to previous studies that employed standard structural tilt corrections, we use a net tectonic rotation approach to determine rotation parameters, taking confidence limits on input variables into account using Monte Carlo modelling. Importantly, we correct the magnetization direction and structural orientation of the older V1 lavas for the effects of the net tectonic rotation of the younger V2 lavas prior to calculating rotation parameters for the older units. Results demonstrate that both massifs rotated ~120° clockwise around steeply-plunging rotation axes after eruption of the V2 lavas. This rotation occurred during roll-back of the Neotethyan subduction zone in response to impingement of the Arabian margin with the trench. Early rotation of the Salahi V1 lavas around shallowly-plunging, broadly ridge-parallel axes indicates only simple tilting between eruption of the V1 and V2 sequences, and no early rotation of the Fizh V1 lavas is required at all. These new constraints on the evolution of the ophiolite therefore provide no evidence of vertical axis rotation during accretion of the Oman volcanic sequences.
Analysis and Monitoring Atmospheric Gases in a High-Performing and Versatile Isotope Ratio Instrument
Authors: Barker Sam , Taylor Kyle William Robert , Hackett Phil , Price Will
Published: March 2022

Biogenic gases carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) are regularly analysed in many environments to understand elemental cycling and processes through the ecosphere. They are also of interest to atmospheric chemists for their role in climate change. The Elementar Isoprime TraceGas, coupled with Elementar isotope ratio mass spectrometer (IRMS), has been a key to a significant number of studies providing data on the isotopes of these key dynamic molecules. We shall review some of the notable publications and modifications in the field of atmospheric gas monitoring.

The development of the recently launched isoprime precisION IRMS has permitted a new generation of control and automation of the mass spectrometer and integrated peripherals. This has greatly improved the accessibility and versatility of the instruments as a whole. Taking advantage of the inherent benefits of the isoprime precisION, the iso FLOW GHG has been developed for high performance analysis of CO2, N2O and CH4 as a successor to the isoprime TraceGas, and has the capacity to be rapidly customised for specific needs with options for N2 and N2O analysis, analysis of hydrogen isotopes in CH4, and high precision and sensitivity measurement of nitrate-derived N2O as generated from denitrifier techniques. We present an outline of the latest generation hardware available to the gas researcher and explain how it’s standard modes and configurations take biogenic gas analysis further than before.
Numerical simulation of dynamic rupture and ground motion on a fault non-uniformly loaded along dip
Authors: Aochi Hideo , Tsuda Kenichi
Published: March 2022

It is widely accepted that the rupture area of earthquake is controlled by fault geometry and the interaction between segments. Besides, many earthquakes do not rupture the whole seismogenic depth but only some limited depth zone. It is not so often to observe that a moderate earthquake such as the 2019 Mw4.9 Le Teil, France, earthquake shows a clear surface rupture and the very shallow rupture area limited at the first 1-2 km depth. Aochi and Tsuda (EGU, 2021) propose the concept that the fault is not uniformly loaded along dip due to the 1D layered structure. Namely, the stress is loaded mainly on the stiff layers, while the soft layers play a role of barrier. We use a boundary element method and a spectral element method for simulating the dynamic rupture propagation and wave propagation. We then demonstrate that the shallowest soft layer can be slipped if the rupture at deeper portion is sufficiently developed. On the other hand, a depth soft layer is difficult to be ruptured, mainly because the absolute stress level is high. In our synthetic scenarios, we compare the ground motions around the fault. In the usual model where the stress is uniformly loaded on all the depths, we observe a strong coherent pulse as the rupture progresses fast to the ground surface. However, we observe more than one pulse in our setting. Such heterogeneous condition along dip should be important to investigate the causality of the seismic asperity and the influence on the resultant near-field ground motion.