bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of pore fluid chemistry  on the localized to ductile transition of sandstone.
Authors: Lazari Francesco , Meyer Gabriel , Violay Marie
Published: March 2024

In geothermal reservoirs, pore fluid chemistry can affect mechanical and hydraulic properties of rocks inducing mineral dissolution, precipitation, weakening and alteration. Moreover, with increasing pressure and temperature deformation mode can change from localized to ductile (diffused), leading to a major decrease in permeability, thus affecting the exploitability of the reservoir. The effect of fluid chemistry on the transition between localized and ductile deformation of rocks is still marginally understood.To investigate the effect of water presence and fluid chemistry on localized and ductile deformation, two sets of triaxial experiments (at 20 and 100 MPa effective confinement pressure, in the localized and ductile field respectively) were performed on a porous silicate sandstone (Adamswiller sandstone), dry, with deionized water and with a 6 M NaCl solution (Na+ rich solution), with a 0.1 M HCl solution (pH 1 solution) and a 0.1 M NaOH solution (pH 13 solution). To complement the mechanical properties, complex spectral electrical conductivity was measured during deformation to monitor pore fluid ion content; pore fluid was collected at the beginning and at the end of the experiments and analyzed with ICP-MS; post-mortem microstructural analyses were performed.In the localized domain, both water presence and pore fluid chemistry had a marginal effect on the strength of the rock, leading to a 5/10% strength reduction over dry rock strength indipendently of the pore fluid composition. In the ductile domain, de-ionized water weakens the rock by 25%, a Na+-rich or pH 1 fluid leads to a 35% weakening and a pH 13 fluid weakens the rock by 40% over dry rock strength. Spectral electrical conductivity does not change during localized deformation, while it increases by 2 to 5 times during ductile deformation when the rock is saturated with deionized water; conductivity does not change with the Na+-rich fluid regardless of the deformation mode and conductivity decreases by half an order of magnitude with both pH 1 and pH 13 fluids both with localized and ductile deformation.

 

 
Interferometric Phase Optimization Method for Mountainous Regions Considering Geometric Decorrelation of Distributed Scatterers
Authors: Guo Aoqing , Sun Qian
Published: March 2024

Distributed scatter interferometric synthetic aperture radar (DS-InSAR) technology has been extensively employed for surface deformation monitoring, with phase optimization as a pivotal step. Currently, phase optimization techniques utilize the statistical intensity distribution of pixels to select homogeneous pixels. Pixels with low temporal intensity stability are excluded from consideration, avoiding their involvement in the phase optimization. However, it is noteworthy that distinguishing between homogeneous and heterogeneous pixels becomes more challenging in mountainous areas. Additionally, pixels with low stability are affected not only by thermal or environmental noise but also by the influence of local incidence angles, causing ground deformation beyond the Maximum Detectable Deformation Gradient (MDDG) of InSAR, resulting in geometric decorrelation. These pixels are often erroneously classified as noise and discarded. Nevertheless, these pixels contain rich and crucial deformation information, indicating disaster risks. Therefore, optimizing the phase of these pixels is essential.This paper introduces a method for interferometric phase optimization of distributed scatterers in mountainous regions, considering geometric decorrelation (GD-DS). Using real InSAR differential interferometric phases as a basis, the study simulates interferometric phase datasets with rich spatiotemporal features, ensuring the correlation between simulated GD-DS phases and MDDG. Subsequently, K-means clustering is applied to segment the MDDG map, with resulting connected regions representing homogeneous pixels with similar local incidence angles. Convolutional denoising training is performed on homogeneous pixels using the generative adversarial network model (Pix2pix), and the trained model is then applied to real interferometric phase images. The proposed strategy and method are successfully applied to interferometric phase optimization in the Jishishan region of Gansu Province, China. Compared to traditional methods, the new approach demonstrates superior phase optimization performance, particularly in the case of GD-DS. Discussion and analysis of the spatial correlation between GD-DS and MDDG in the real experimental area confirm that introducing MDDG as a reference to optimize GD-DS is a key factor in improving phase optimization. Furthermore, the computational time of the new method is significantly reduced compared to traditional methods.
Uncovering variations in solar activity through tree-ring radiocarbon measurements
Authors: Wacker Lukas , Brehm Nicolas , Christl Marcus , Synal Hans-Arno , Pearson Charlotte C. , Nicolussi Kurt , Pichler Thomas , Bayliss Alex , Brown David , Bleicher Niels
Published: March 2024

While the sun, as the primary source of energy on earth, is considered to have a constant energy output, small fluctuations can be observed over time. Historical records of solar activity (e.g., sunspot numbers) are however scarce, and only available over the last 400 years. Cosmogenic nuclides stored in tree rings (14C) or ice cores (10Be, 36Cl) can be used as proxies for solar activity and allow solar reconstructions reaching much further back in time1,2. However, only recently the presence of the eleven-year solar cycle could be revealed in an annually resolved 14C record from tree-rings covering the past 1000 years. The amplitude of this so called Schwabe cycles is found to correlate with the general level of the solar activity with high amplitudes during periods of strong solar activity and vice versa3.Here, we present the solar activity, and specifically the 11-year cycles, reconstructed from 14C in tree-rings covering two grand solar minima, one around 400 BCE and another one around 3400 BCE. The results will be compared with the two previously analysed grand solar minima (Spörer and Maunder) of the last millennia, coinciding with the Little Ice Age. 1 Bard, E. et al. (2000) Solar irradiance during the last 1200 years based on cosmogenic nuclides. Tellus Series B-Chemical and Physical Meteorology 52, 985-992.2 Muscheler, R. et al. (2007) Solar activity during the last 1000 yr inferred from radionuclide records. Quaternary Science Reviews 26, 82-97.3 Brehm N. et al. (2021) Eleven-year solar cycles over the last millennium revealed by radiocarbon in tree rings. Nature Geoscience. 14(1), 10-15.
How to read the seafloor and the importance to offshore wind projects. Examples from Sørlige Nordsjø II, Norwegian North Sea
Authors: Gehrmann Anna , Lekens Wim
Published: March 2024

Offshore wind projects benefit immensely from a good understanding of the seafloor. Together with the sub-bottom geology and geotechnical properties as well as geohazards and physical hazards, the seafloor conditions can be integrated in ground models and hazard maps as part of a holistic offshore wind site characterization, that enables successful wind farm development and reliable power production.A full understanding of the seafloor requires “seafloor reading skills”: appropriate data mining, utilization, and interpretation. The seafloor is full of geological, environmental, and anthropogenic features which may affect a wind farm during its lifecycle, such as boulders, mobile sediment, escarpments/faults, wrecks, UXO, cables, seabed habitats and much more. However, when understood properly, we can comprehend the seabed conditions and processes and handle the different challenges at the seabed from installation to production, affecting e.g., foundation feasibility and HSE.Sørlige Nordsjø II is an envisaged offshore wind site in the southern Norwegian North Sea. Following a multi-method approach, we utilized different geological and geophysical data, such as MBES bathymetry and backscatter, side scan sonar data, boreholes and vibrocores, sub-bottom profiler data, and 2DUHR seismic.Key results that were achieved include:Detailed seafloor lithology map: Differentiation between different sand facies and glacial lag deposits.
Understanding of sediment mobility: Sand waves and megaripples mapped; bedforms, grain size variations and anthropogenic features linked to zones of erosion, transport, and deposition.
Determination of boulder locations: Boulder fields and individual boulders mapped; size of boulders determined to mostly up to 3 m.
Update of cable and wreck positions, by utilizing backscatter and side scan sonar images, and magnetic anomalies.
We were able to pull out deep knowledge from the available data, to bring it in a coherent order and provide a holistic understanding of the site’s seafloor. This is a major step towards the aim of making informed cost-saving decisions throughout the offshore wind lifecycle.
Challenges in simulating ground surface temperature based on remote sensing land surface temperature over mountain grasslands
Authors: Șerban Raul-David , Bertoldi Giacomo , Bartkowiak Paulina , Castelli Mariapina , Andreoli Andrea
Published: March 2024

Ground surface temperature (GST), measured at a depth of around 5 cm below the ground surface, is essential for understanding the climate change impacts in the Earth Critical Zone. Large spatiotemporal variations of GST have been reported in mountain regions due to the heterogeneity of surface cover and topography. This work aims to improve the monitoring of GST using a physical land-surface model driven by satellite-based land surface temperature (LST). In this regard, GST was simulated using the physical GEOtop model at 1500 m elevation in Matsch Valley, north-eastern Italian Alps, from 2014 to 2017 during the phenological cycle, between April and October. The model was forced only by the LST derived from the Terra MODerate resolution Imaging Spectroradiometer (MODIS). The 1-km MODIS LST was first downscaled to a finer spatial resolution of 250-m using data-driven sharpening from random forest algorithm. The simulated GSTs correlate well with the in-situ observations with a Pearson correlation of 0.88 and a coefficient of determination of 0.77. However, the model overestimated the GST for the whole period with a mean bias of 8.72 °C. These overestimations are similar to the differences between in-situ GST and MODIS LST which range from 4.8 to 19 °C with an average of 8.5 °C. They are mainly caused by the low temporal resolution of LST data with only one observation per day which is additionally limited by frequent cloud cover contamination and the low spatial resolution of the MODIS thermal channels. Modelling the damping of the LST signal in the first centimeters of soil to simulate GST in very heterogeneous areas like alpine pastures is still challenging. This is mainly due to the resolution mismatch between ground and remote sensing observations and the poor knowledge of soil and vegetation properties needed to parametrize physical models.
Resonant excitation of Kelvin waves by interactions of subtropical Rossby waves and the zonal mean flow
Authors: Holube Katharina Meike , Lunkeit Frank , Vasylkevych Sergiy , Žagar Nedjeljka
Published: March 2024

Kelvin waves are an important component of the tropical wave circulation. While the excitation of Kelvin waves by tropical convection is well understood, the influence of subtropical Rossby wave dynamics on the Kelvin waves has received relatively little attention. Our research investigates a Kelvin wave excitation mechanism through interactions of Rossby waves and the zonal subtropical jet. The investigation is carried out with a spherical rotating shallow-water model, using a quasi-geostrophic zonal jet as initial condition. The basis functions of the model are the eigensolutions of the linearized equations, which are identified with atmospheric waves. The model formulation thus includes the Rossby and Kelvin waves as prognostic variables. With an external forcing that impacts only the Rossby waves, Kelvin waves can be excited in the model through the wave-mean flow interactions and wave-wave interactions. The main finding is that Kelvin waves are resonantly excited by interactions of the Rossby waves and the mean flow, provided the Doppler-shifted frequencies of the Rossby waves and the Kelvin waves match. The wave-mean flow interactions are found to be stronger than the wave-wave interactions. The resonant Kelvin wave excitation is one of the possible mechanisms for the influence of the extratropical circulation on tropical waves.
Climate Stress Testing for Enhanced Understanding of the Flood Hazard and its Socioeconomic Impacts in Italy
Authors: Perosa Francesca , Clarke Alastair , Bhola Punit , McMullan Caroline , Lewington Emma , Reinhardt Bernhard
Published: March 2024

To contribute to a more resilient flood risk management in Italy, we employ the recently published Verisk Inland Flood Model for Italy to conduct climate stress testing. We focus on the sensitivity of modeled losses to precipitation and leverage the meteorological dataset obtained from the Climate Model Intercomparison Project Phase 6 (CMIP6) for identifying projected precipitation trends and analyzing the potential effects of climate change on inland flood losses in the future, exploring different Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs). The methodology involves analyzing correlations between annual or seasonal precipitation and the corresponding annual loss cost, which is defined as annual loss divided by the total insured value. By exploring these relationships, we seek to enhance our understanding of how precipitation patterns influence the financial implications of flood events in various Italian regions. Additionally, we use the 10,000-year stochastic catalog embedded in the Verisk Inland Flood Model to explore the impact of expected climate change-related changes in annual precipitation for each Italian region, addressing the climate change-based precipitation targets. This enables us to run the fully probabilistic Verisk Inland Flood model and to assess whether anticipated alterations in precipitation levels correspond to expected changes in Annual Average Loss (AAL). This approach allows us to dynamically adapt our flood risk model to varying climate scenarios, providing valuable insights for the (re)insurance industry, as well as academia and government agencies that are seeking to navigate the evolving landscape of flood-related risks.
A mix Lagrangian Eulerian approach for volatile particles and contrails formation
Authors: Bonne Nicolas
Published: March 2024

Condensation trails (contrails) are considered the main non CO2 effect of aviation on global warming (Lee 2021) However, the uncertainty remains important and therefore a better understanding of the physical process underlying contrail formation is required. For a Jet A-1 kerosene fuel burned with a rich burn engine, the formation of contrails is mainly due to the condensation of water around soots emitted by the engine. In the case of Sustainable Aviation Fuels (SAF) or lean burn engines, the soots emitted are in very weak quantity so to let other nucleation process to occur (Kärcher 2018) such as homogeneous nucleation based on water and sulfuric acid (Rojo 2014). In order to perform contrail formation simulation with the details of the jet dilution due to the interaction between the plume and the aerodynamic of the aircraft, it is important to include the nucleation process strongly coupled with the aerodynamic in the simulation. This has been done for nucleation around soots (Khou 2016) but not for homogeneous nucleation. In this work, we propose a mix Lagrangian Eulerian approach in order to evaluate the homogeneous nucleation.Lee D.S. et al., The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018, Atmospheric Environment, 2021Kärcher B, Formation and radiative forcing of contrail cirrus, Nature, 2018Rojo C. et al., Impact of alternative jet fuels on aircraft-induced aerosols, Fuel, 2014Khou JC. et al., CFD simulation of contrail formation in the near field of a commercial aircraft: Effect of fuel sulfur content, Atmospheric Chemistry, 2
Enhancing fascine techniques for slopes erosion control: A comprehensive technical guide
Authors: Didier Marie , Evette André , Schmitt Emma , Leblois Solange , Jaymond Delphine , Evette Jean-Baptiste , Mira Eleonore , Raymond Pierre , Frossard Pierre-Andre , Vivier Anne
Published: March 2024

Fascines are Soil and Water Bioengineering techniques for erosion control and slopes stabilisation. As Nature-based solutions, these age-old and highly adaptable techniques generally rely on the installation of living willow bundles fixed to either dead or living stakes. Fascines are the most widely used techniques to protect riverbanks toe in France; they are also implemented on slopes, and gullies making wide their possible use. They are often employed as part of a combination of techniques to meet specific local needs. Despite the common implementation of fascines, no guidelines cover the entire diversity of fascines. The technical guideline proposed describes the full scope of possibilities fascines offer, their advantages and disadvantages and technical details and specifications of implementation. Drawing on a foundation of technical literature, historical documentation, research experiments, and empirical knowledge, the guide delves into no fewer than 112 references. The objective is to enhance the use, success, and overall confidence in fascine-based techniques.This guide presents comprehensive information on no fewer than 12 fascine techniques that have transcended through the ages, originating from structures dating back over 2,000 years in China and continuing to be relevant in the contemporary world.  Although fascines may seem simple and are known for their high mechanical strength, these techniques require high expertise to ensure lasting resistance and satisfactory plant growth. Several critical factors contribute to the success and durability of these structures, including the choice of plant species, the quality of planting materials, the nature of soil contact, and the positioning of the bundle relative to infiltration or groundwater levels. Application methods vary based on the specific technique and context: Fascines can be alive or inert; placed parallel or perpendicular to the slope; they come in different diameters with one or multiple bundles and can be used as barriers or drains. The most illustrative example is the implementation of fascines along the toe of the bank, which stands as the most widely used technique. For this approach, bundles should measure between 100 and 300 cm in length, with a diameter ranging from 15 to 50 cm. Branches should have a minimum diameter of 2 cm and a length of approximately one meter.This technical support is intended for designers, river managers, technicians, and the general public, providing precise technical recommendations for the successful creation of fascines, from materials to maintenance, as well as implementation methods and environmental conditions appropriate to this type of structures.
Data assimilation of temperature and water-vapor mixing-ratio lidar profiles in WRF
Authors: Lange Vega Diego ,   WaLiNeAs (Water vapor Lidar Network Assimilation) Team
Published: March 2024

The lack of accurate observations affects the initial conditions of numerical weather prediction (NWP) models resulting in suboptimal forecasts. The assimilation of temperature and moisture profiles obtained from active remote-sensing lidar systems offers great potential for improving the predictive skills of NWP models (Thundathil et al., 2021, Bauer et al. 2023). Advanced data assimilation (DA) techniques, with suitable observational forward operators, enable the model to make use of such observations efficiently.New lidar systems provide temperature and humidity observations with high accuracy and resolution, which is highly beneficial for DA. The high accuracy avoids the need for a challenging bias correction of the data. It also simplifies operational use and minimizes the latency of the lidar data available for DA.In this regard, we make use of lidar observations to investigate the extent to which the assimilation of these data through advanced DA systems improves the analyses and corresponding forecasts.Our automated thermodynamic profiler based on the Raman lidar technique, the Atmospheric Raman Temperature and Humidity Sounder (ARTHUS) (Lange et al. 2019) was deployed in the framework of the WaLiNeAs (Water vapor Lidar Network Assimilation) (Flamant et al. 2021) initiative at the west coast of Corsica between 15 September and 10 December 2022. The participation of ARTHUS was possible due to a project funded by the German Research Foundation (DFG).Together with ARTHUS, a network of several other autonomous water-vapor lidars was deployed for providing more thermodynamic data across the Western Mediterranean. We expect that this network during its operation closed critical gaps present in lower tropospheric observations of current operational networks and satellite observations.We will present the first results of the impact of high-resolution temperature and water vapour mixing ratio lidar profiles in our data assimilation studies on heavy precipitation events, using  the WRF 3DVAR-ETKF approach on the kilometer-scale.
Resilience Assessment of Flood Detention Zones in the 2023 catchment-scale floods in Hai River Basin, China
Authors: Lin Yiling , Hu Xie , Wang Fang , Zhao Yong
Published: March 2024

As a typical flood-prone area, the Hai River Basin (HRB) in the Beijing-Tianjin-Hebei metropolis of China has been struck by devastating floods in history. Since the 1960s, a series of flood-control programmes in the HRB have been launched to reduce the flood risks. As planned, flood detention zones serve as the last line by storing and detaining floodwaters when the water levels exceed the defense limits of reservoirs, levees, and diversion channels. Land use crisis has been a long-lasting problem in China. People are allowed to use the flood detention zones as their residential communities when these zones are not in use. A dual role played by these specific zones requires not only an effective floodwater storage in response to floods, but also an efficient floodwater recession in the aftermath of floods. However, we lack a quantitative assessment of the functionability of flood detention zones. Our study synergizes multi-source SAR images from Sentinel-1 and Gaofen-3 satellites in the framework of deep learning to accurately and efficiently extract inundation paths which evolved for two months encompassing HBR. A joint use of digital elevation model allows us to recover the three-dimensional inundation structures. We also propose the flood detention resilient coefficient based on our derived lifespan of floodwaters. Our results demonstrate that the flood detention zones in HRB can effectively trap the floodwater within to secure lives and properties, but resilience of some flood detention zones can still be improved.
Impact of organic soil amendments on heavy metal losses and nutrient cycling –  medium-sized controlled lysimeter experimental assessment
Authors: Đukanović Nina , Weihermuller Lutz , Kruse Jens , Siebers Nina , Tenodi Slaven , Kragulj Isakovski Marijana , Bol Roland , Maletić Snežana
Published: March 2024

Heavy metals accumulate due to various human activities in sediments thereby negatively impacting on aquatic ecosystems and potentially via food chain transfers harming human health. To maintain the hydraulics of water bodies heavy metal (HM) polluted sediments are frequently simply dig out of the riverbeds and channels, and subsequently dumped on sites in their vicinity. We studied the ability of such clay and organic rich ‘waste’ sediments to acts as amendments for marginal soils. Their added organic matter could play a crucial positive role in soil fertility, nutrient cycling, and carbon sequestration.The introduction of organic amendments can either diminish or mobilize heavy metals when applied to marginal soils. Lysimeters were filled with marginal sandy soil collected from the Danube riverbanks in Novi Sad, Serbia, ensuring it was free of HM contamination. Six distinct organic soil amendments (OSA) were introduced to the lysimeters: i) biochar, ii) sludge, iii) compost, iv) biochar + sludge, v) biochar + compost, and vi) biochar + sludge + compost.The sludge utilized is derived from aquatic sediment in the Begej Canal, Serbia, known for its heavy pollution. Among others, this study aims to assess whether this specific sludge type can serve as a viable soil amendment rather than being relegated to landfill disposal. The compost utilized originated from green waste in Novi Sad, while the biochar was produced from Miscanthus, a C4 plant feedstock, at 550°C at the Technical University Aachen. Both the OSA and sandy soil underwent chemical and physical characterization before application. The maximum added amendments varied from 1 to 5% (w/w), depending on the OSA type.All probes were established at Faculty of Science, University of Novi Sad, in triplicates, featuring lysimeters with a height of 435 mm and a diameter of 180 mm. The results of heavy metal leaching data under different OSAs will be presented at the meeting, highlighting key findings and conclusions. Additionally, we will discuss the role of water event-driven transport in the overall process.Acknowledgement: "Funded by EU grant #101059546"
Landsifier 2.0: Towards automating landslide trigger and failure movement identification
Authors: Nava Lorenzo , Bhuyan Kushanav , Kapoor Manan , Rana Kamal , Rosi Ascanio , Vicente Ferrer Joaquin , Ozturk Ugur , Floris Mario , van Westen Cees , Catani Filippo
Published: March 2024

Understanding landslide failure processes is pertinent to predict and minimize the effects of landslides. A variety of elements, such as geology, topography, and soil conditions, can lead to slope failures triggered via natural causes e.g., rainfall and earthquakes, setting off the failure movements. Proper geotechnical analysis requires knowledge of both the triggering event and the subsequent movement patterns of the landslide. This information is vital for accurately predicting when and where landslides might occur. To integrate this information into existing landslide inventories, we introduce Landsifier 2.0, a tool designed to meet the needs of the landslide research community. This Python-based library allows seamless usage of machine learning models to extract information regarding landslide triggers and failure movements solely based on inventories of landslides. Powered by topology, a high-dimensional feature extraction module encapsulated within our library, information accessed via a landslide's shapes and configurations allows the identification of triggers (e.g., earthquake-and rainfall-triggered landslides) and failure movements (e.g., rotational slides, translational slides, debris flows, rock falls) of undocumented landslide inventories through continuous remote sensing missions. We showcase the library’s application in diverse geomorphological and climatic settings e.g., South-western China, Denmark, Turkey, Japan, Italy and more. We anticipate that Landsifier 2.0 will be particularly useful in the predictive modelling domain (including susceptibility and hazard modelling) of landslide studies, where precise information about triggers and failure dynamics is essential for developing reliable predictive models.References:Rana, Kamal, Uğur Öztürk, and Nishant Malik. 2021. “Landslide Geometry Reveals Its Trigger.” Geophysical Research Letters 48(4). doi: 10.1029/2020gl090848.Rana, Kamal, Nishant Malik, and Uğur Öztürk. 2022. “Landsifier v1.0: A Python Library to Estimate Likely Triggers of Mapped Landslides.” Natural Hazards and Earth System Sciences 22(11):3751–64. doi: 10.5194/nhess-22-3751-2022.Rana, Kamal, Kushanav Bhuyan, Joaquin Vicente Ferrer, Fabrice Cotton, Uğur Öztürk, Filippo Catani, and Nishant Malik. 2023. “Landslide Topology Uncovers Failure Movements.” arXiv (Cornell University). doi: 10.48550/arxiv.2310.09631.
Leveraging inland radar altimetry over rivers with low cost GNSS reflectometry
Authors: Rietbroek Roelof , K. Challa Zeleke , Kizza Michael , Zaroug Modathir , Kanyike Tom , Wara Calvince
Published: March 2024

The monitoring of surface water levels in lakes and rivers is essential for adequate water resource management and timely responding to extreme events. Monitoring an entity as large as the Nile river comes with significant challenges. The cross-boundary nature of the Nile, complicates its management due to different jurisdictions and interests, furthermore there are logistical challenges related to accessibility and site safety.Radar altimetry has the potential to offer remotely sensed water heights, but still requires expert knowledge and site-specific trial and error. Generating in-situ records of water level heights is therefore invaluable activity both for monitoring and validation purposes.Low-cost Global Navigations Satellite Systems (GNSS) interferometric reflectometry promises a low-cost solution for monitoring water heights, and devices can be locally constructed using off the shelf components which are now widely available. Furthermore, the development of internet of things (IoT) networks in Africa is moving forward and creates opportunities for remotely controlled measurement stations.Here, we present our activities on designing and deploying low-cost GNSS-R receivers on the shores of Lake Victoria. We show several designs based on raspberry Pi’s and a low-power version based on the Actinius Icarus platform (zephyr based). We further explore possibilities to apply on-board processing of GNSS signal to noise ratio series, which will pave the way for using low bandwidth networks.
Identifying Windows of Opportunity in Deep Learning Weather Models
Authors: Banciu Daniel , Thuemmel Jannik , Goswami Bedartha
Published: March 2024

Deep learning-based weather prediction models have gained popularity in recent years and are effective in forecasting weather over short to medium time scales with models such as FourCastNet being competitive with Numerical Weather Prediction models. However, on longer timescales, the complexity and interplay of different weather and climate variables leads to increasingly inaccurate predictions. Large-scale climate phenomena, such as the active periods of the Madden-Julian Oscillation (MJO), are known to provide higher predictability for longer forecast times.These so called Windows of Opportunity thus hold promise as strategic tools for enhancing S2S forecasts.In this work, we evaluate the capability of FourCastNet to represent and utilize the presence of (active) MJO phases.First, we analyze the correlation between the feature space of FourCastNet and different MJO indices.We further conduct a comparative analysis of prediction accuracy within the South East Asia region during active and inactive MJO phases.
The International DORIS Service: new challenges
Authors: Soudarin Laurent , Lemoine Frank , Boniface Claude , Moreaux Guilhem , Saunier Jérôme
Published: March 2024

The International DORIS Service (IDS) had its 20th anniversary in 2023 and is now looking forward to new challenges.Over a 30-year period, between 1990 and 2020, the DORIS constellation contributing to the IDS has totaled nine satellites with lifetimes ranging from 3 to 19 years (with the lifetime of SPOT-2, at 19 years, being a record). Since the launch of the SWOT mission in December 2022, nine satellites have been in simultaneous operation and are supplying DORIS data to the IDS. This large number of missions is a challenge for the Analysis Centers, which must integrate them into their processing, taking into account each mission’s special characteristics (w.r.t shape, altitude, attitude law). New missions are expected from 2025 including Sentinel-3C & 3D, Sentinel-6B & 6C, HY-2E & 2F, GENESIS. In addition, the DORIS system continues to evolve. The ground network is growing while providing a high level of service, 4G beacons are gradually replacing those of the previous generation, and a new more powerful DORIS instrument is under study.New groups have approached IDS in recent years, bringing new processing capabilities, or wishing to become involved in DORIS processing in the medium term. These new strengths are also opening up new applications. Since 2021, DORIS data from the Jason-3 mission have been made available to IDS with a delay of less than three hours. This has enabled the IDS Working Group “NRT data” to demonstrate the value of these data for validating existing GNSS-based ionosphere models. In 2024, NRT DORIS data will be made available for additional missions (Sentinel-3A, Sentinel-3B, Sentinel-6A, Saral…). A new established IDS Working Group will focus on using these data for further ionospheric modelling applications.In this presentation, we provide information on DORIS system developments and upcoming missions. We also present the recent achievements made by IDS and its components, and the future plans for the service.
Reframing the Arctic: An interdisciplinary and multi-scalar perspective on the divergence of boundaries and risk change in the Anthropocene
Authors: Lundén Aapo , DeRepentigny Patricia , Nanni Ugo , Popovaitė Virginija , Shen Yiyi , Basaran Ilker K , Neubern Natalia Duarte , Mascorda-Cabre Llucia , Bennett Alec , Vold Hansen Tiril , Holmes Felicity A , Kavvatha Eleni , Meyer Alexandra , Prakash Abhay , Wołoszyn Aleksandra
Published: March 2024

The Arctic is experiencing rapid transformations driven by global warming and increased human activities. These changes have significant implications for the region's established boundaries and the risks tied to its transformation. Here, we investigate the complex dynamics and consequences of contemporary pressure on these boundaries through a socio-environmental perspective. By employing an interdisciplinary and multi-scalar approach, we examine the intricate interconnections between global, regional, and local changes within the Arctic. Our analysis revolves around three spheres: the boundaries historically used to define the Arctic and how recent changes in climate and political interest challenge our perception of the Arctic as a region; the complexity of bio-physical boundaries and jurisdictional disputes surrounding the Svalbard Archipelago; and the relationship between changing natural hazards and societal perception of risk in the town of Longyearbyen. Altogether, we underscore the interplay between policy-based science, science-based policy, and performative behavior in shaping borders and boundaries. In order to avoid crossing tipping points and irreversible limits of human adaptation, we argue for the adoption of a holistic approach that integrates diverse perspectives and scales to effectively manage resources, preserve the environment, mitigate risks, and uphold international relations within and beyond the Arctic. By considering ecological and social factors, our study emphasizes the need for integrated approaches to address time-sensitive challenges surpassing the resilience capacities of local communities and encompassing vast spatial scales extending beyond their usual spheres of influence.
Detecting climatic change in AMOC observations
Authors: McCarthy Gerard , Hug Guillaume , Smeed David , Moat Ben
Published: March 2024

The detection of trends and variations in the Atlantic Meridional Overturning Circulation (AMOC) is an important and at times controversial topic. On average, CMIP6 models project a 1 Sv/decade decrease in the strength of the AMOC in response to anthropogenic climate change. Atlantic subpolar decadal sea surface temperature variations of 0.5º indicate an associated change in AMOC strength of 2 Sv. These are challenging thresholds of signal detection for AMOC observing. Estimates of the AMOC streamfunction, such as those from the RAPID array, have a number of sources of variability ranging from short term Ekman transport to variations in the strength of North Atlantic Deep Water associated with deep water formation that have a slower timescale. Climate model studies have shown that Ekman transport contributes little to the signal of future AMOC decline. We look at the nearly 20 years of data from the RAPID array from a signal to noise perspective. Fluctuations associated with Ekman transport are the largest contribution to noise in the AMOC estimates and hold no signal of low frequency change. Deeper layers show more of the low frequency signal. We amplify this low frequency signal by removing the impact of noise derived from the Ekman transport on the deep temperature and salinity. Finally, we show that the best place for detection of low frequency, climatic changes in AMOC is in the deepest North Atlantic Deep Water, with the noise of the wind removed.
A detailed statistics of cloud and precipitation processes in the trades from the RV M.S. Merian
Authors: Acquistapace Claudia , Schnitt Sabrina , Krause Sibylle , Risse Nils , Ori Davide , Chatterjee Dwaipayan , Seelig Torsten , Lange Diego , Späth Florian , Mccoy Isabel
Published: March 2024

Shallow cumulus clouds always played an essential role in the uncertainties in climate predictions. The EUREC4A campaign was conceived to tackle the problem of how such clouds will respond to climate change. Recent studies showed that although the research outcomes of the EUREC4A campaign constrained their response to climate sensitivity, open questions remain on the importance of mesoscale processes and the role of precipitation in the cloud organization, both aspects not well represented in climate models. The research vessel (RV) Maria S. Merian, during the campaign, continuously provided high-resolution observations of clouds, precipitation, and atmospheric boundary layer properties in a vast area of the Atlantic Ocean east and south of Barbados island. Here, we exploit such observations to statistically characterize clouds and precipitation properties and the surrounding environment in which they develop. In agreement with the literature, we define shallow clouds with cloud tops within 600 m of lifting condensation level (LCL) and congestus clouds with cloud tops between 600 and 4000m. We characterize their cloud properties, rain rates, and raindrop size distributions. We investigate virga generated from shallow and congestus clouds and describe how humidity and temperature change with the different cloudy conditions. We also display the relation between the W-band radar reflectivity and the radar skewness, revealing insights into the precipitation onset for shallow and congestus clouds and characterizing their cloud lifetime. Finally, we connect the local boundary layer and cloud properties to configurations occurring at the mesoscale, providing additional characterizations of flower, fish, sugar, and gravel in terms of ship-based observations.
Gas measurement method based on Angle dependence of F-P cavity transmittance
Authors: Lv Yinsheng , Xie Pinhua , Xu Jin , Duan Jun , Tian Xin
Published: March 2024

Correspondence: Pinhua Xie(phxie@aiofm.ac.cn)This study introduces a gas measurement method employing Fabry–Pérot (F-P) interferometer correlation spectroscopy. The methodology capitalizes on the angle-dependent characteristics of the F-P interferometer transmission spectrum, aligning interference peaks with gas absorption cross-section features. The experimental setup features a dual-beam synchronous incidence F-P cavity, and a forward model is developed to scrutinize the impact of system parameters on measurement outcomes. A comprehensive investigation into factors affecting the effective transmittance of the F-P cavity is conducted. The analysis reveals that controlling the beam divergence angle significantly influences the spectral resolution of gas measurements, particularly when utilizing the angle-dependent nature of the F-P cavity with oblique beam incidence. Ultimately, this study conducts concentration measurement experiments for gases such as SO2 and CH4, demonstrating the method's efficacy in quantitatively assessing gas concentrations. Given that this approach relies on hardware-based spectral selection to achieve differential measurements, it emerges as a highly selective method for gas measurement. It exhibits robust resistance to cross-interference, holding promise for applications in imaging and facilitating rapid measurements.Funding. Project supported by the National Natural Science Foundation of China (Grant No. U19A2044), the National Natural Science Foundation of China (Grant No. 41975037), and the Key Technologies Research and Development Program of Anhui Province (Grant No. 202004i07020013).Acknowledgment. My sincere gratitude goes to Mr. Yingjie Ye for his invaluable assistance in conducting the experiments. 
The first application of a new 3D octree finite element inversion framework to CS/MT data
Authors: Patzer Cedric , Xiao Longying , Kamm Jochen
Published: March 2024

At GTK we are currently developing the entire workflow of the controlled source EM (CSEM) method, ranging from data acquisition to time series processing to modelling and inversion. Part of this work is the development of a 3D modelling and inversion framework, which is mostly done within the DroneSOM project. The flexible implementation allows not only for modelling and inversion of semi-airborne drone EM data, but also land-based CSEM/MT data. The forward problem is solved using the finite element method on hexahedral meshes. We separate forward and inverse mesh using octree mesh refinement. This helps in solving the trade-off between the required accuracy in the forward modelling and computational cost. It is also a great tool to combine different multiresolution EM data (e.g., CSEM and MT) in a single comprehensive inversion framework. This work will focus on first applications of land-based CSEM and (CS)MT.In 2022 we collected controlled source MT data using a grounded electric dipole transmitter along the Koillismaa ultra-mafic intrusion in North-Eastern Finland. Despite transmitter receiver offsets of 3-5 km far field condition does not apply for frequencies below 4kHz, which permits the use of standard MT inversion. Here we show first inversion results of these data using our new EM inversion routine taking the transmitter position into account. In addition to the active source MT data, we also collected conventional MT data on a larger scale crossing the Koillismaa intrusion. Our inversion routine also allows the inversion of MT data. We are thus showing first inversion results of joint inversion of both datasets. 
On the variation of ocean surface waves with wind speed and direction: A case study from offshore Svalbard, Norway
Authors: Rørstadbotnen Robin André , Landrø Martin
Published: March 2024

Distributed Acoustic Sensing (DAS) has become increasingly popular due to its capacity of extremely high spatial and temporal strain sensing over long distances. Due to the long reach of the current fiber sensing technology, and that all the electronic components are placed on land, it holds great potential in marine applications. This presentation shows how DAS can be used to observe ocean surface waves inside Kongsfjord and in the open ocean West of Svalbard.A well-known problem when monitoring ocean phenomena is the sensor undersampling in the world’s oceans. This problem limits observations of fundamental scientific questions, like the dynamics of the oceans (Sladen et al., 2019). Fiber optic sensing has already been used to observe numerous ocean phenomena, such as tides, OSGW (Ocean-Surface-Gravity-Wave), and internal waves (Lindsey et al., 2019, Ide et al, 2021, Williams et al., 2023).A comprehensive DAS data set is being collected at the Centre for Geophysical Forecasting’s (CGF) research lab in Ny-Ålesund, Svalbard. Data has been collected continuously since June 2022 providing the possibility of investigating oceanographic signals over a long time period in different marine environments. In this presentation, we focus on how ocean surface wave signals are influenced by local wind conditions and how the signal changes characteristics as a function of wind speed and direction.The results from analyzing this data will be presented, and it will be demonstrated how the local wind-induced waves interact with the background swell signal which hit West Svalbard from a South-West direction. The difference between the portion of the fiber located inside Kongsfjorden will be compared to the portions in open ocean. Additionally, the obtained results will be compared to previous studies from the area (e.g., Wojtysiak et al., 2018). Finally, we use the well-known dispersion relation for OSGW to compute the associated phase velocity along the whole stretch of the fiber cable.
Studying Cloud Transformations in Cold Air Outbreaks using Large-Eddy Simulations Exclusively Driven by HALO-(AC)³ Campaign Data
Authors: Paulus Fiona , Neggers Roel
Published: March 2024

Cold air outbreaks (CAOs) are a key component of the Arctic climate system, featuring intense convective cloud fields embedded in cold, dry air masses over relatively warm surfaces. Large-Eddy Simulation (LES) is a technique often used to investigate CAOs at high spatial and temporal resolutions, resolving the intricate processes involved and providing a wealth of virtual data. A complication with LES studies of CAOs is the typical absence of suitable observational data to fully constrain the simulations, and thus anchor them in reality. This study aims to use observational data from the recent airborn HALO-(AC)³ campaign in the Atlantic sector of the Arctic to drive LES experiments exclusively with observations. To this purpose data from Research Flights 10 and 11 are used, which probed a weak CAO in the Fram Strait on 29 and 30 March 2022. A Lagrangian model framework is adopted, making use of observations along the two-day low-level trajectory that stretched from close to the North Pole to the sea-ice free area Southwest of Svalbard. HALO observations are integrated into the reanalysis-based model forcing in an incremental way, yielding a suite of forcing datasets. These observational data consist of vertical soundings of thermodynamic state, pressure gradients, mesoscale divergence and advective tendencies, as well as surface properties to act as boundary conditions. The LES code incorporates advanced representations for mixed-phase microphysical processes and radiative transfer, to allow a realistic representation of clouds and turbulence in the transforming low-level airmass. LES results obtained with this setup are evaluated against independent HALO datasets on clouds and other boundary-layer properties. Inter-comparing the suite of LES runs with different forcing datasets elucidates the impacts of individual forcing components on the air mass transition and associated cloud evolution. 