bluuebunny/crossref_metadata_2025 huggingface dataset:
Imaging large-scale geological structures using Deep ERT: a case study on the Booze Val-Dieu block in Belgium
Authors: Forth Yannick , Michel Hadrien , Caterina David , Hase Joost , Kemna Andreas , Chudalla Nils , Wellmann Florian , Vink Bjorn , Nguyen Frédéric
Published: March 2024

The geophysical investigation of geologic structures is an essential prerequisite for the preparatory phase of large subsurface construction projects like caverns or tunnels and to study structural geology. This type of investigation is crucial to guide boreholes for relevant ground truth, knowledge of the local geology, or to adjust the position of underground constructions.Typical approaches to image large structures are seismic reflection surveys or Airborne Electromagnetic surveys (AEM). However, seismic surveys might fail due to an absorbing soft top layer or steeply inclined layers. AEM surveys generally are poorly adapted to applications in urbanized areas. To overcome these issues, another method for large-scale subsurface imaging is the application of Deep Electrical Resistivity Tomography (Deep ERT), a recent approach where employing separated injection and measurement systems allows for large injection dipoles that retrieve information from depth.We conducted a Deep ERT campaign in the framework of the E-TEST project for the investigation for a suitable location for the Einstein Telescope, a gravitational wave observatory consisting of a set of subsurface laser interferometers in a triangular shape at a depth around 300 m. Here, we present the results from a 2D Deep ERT survey in Val Dieu, Belgium with a total length and maximum injection dipoles of 7,5 km and a total of 14040 measured datapoints. We show the challenges during preparation, performance and data processing and discuss its capability in imaging large and deep geological structures.
Understanding global warming impact on climate extremes by mean of Coordinated Ensemble Experiments of Convection-Permitting Climate Projections
Authors: Coppola Erika
Published: March 2024

Over the last decade, researchers have devoted considerable efforts to exploring the feasibility of attaining convection-permitting scales in regional climate model projections. The primary objective has been to comprehend the effects of global warming on climate extremes. Initially conducted as isolated model experiments, these investigations have evolved into coordinated ensemble experiments operating at convection-permitting scales across diverse continents. The implementation of such coordinated ensembles has provided a platform for evaluating model reliability at high resolutions and conducting signal-to-noise analyses on identified climate change signals. Nevertheless, the constraints imposed by limited computational resources have confined these experiments to smaller domains compared to the conventional continental scale employed in dynamical downscaling, as seen in initiatives like the CORDEX community and time slice mode. Despite these inherent limitations, these experiments have successfully showcased the models' capacity to simulate present-day climate conditions. Notably, improvements in various statistical metrics at sub-daily scales have been observed in contrast to parametrized models. Furthermore, the ensemble approach has contributed to reducing uncertainties in assessing both present-day climate and future projections, particularly in terms of frequency, intensity, and extreme precipitation at the hourly time scale. The explicit representation of convection has additionally enabled the study of convective storm system evolution, allowing for an assessment of large-scale feature changes and related physical mechanism driving observed extreme precipitation variations. Preliminary attempts have also been carried on for building convection permitting climate emulator to reduce the computational HPC demand required by the dynamical downscaling models.These collective findings underscore the necessity of advancing to the next phase of coordination, involving the establishment of multiple coordinated platforms spanning different continents. These platforms will serve as collaborative spaces for discussing model enhancements, aiming to refine existing models by incorporating a more precise representation of Earth system components and defining domains that maximize the number of models capable of generating convection-permitting climate projections.
Investigating remotely sensed spectral indicators of tree vitality across scales and forest types
Authors: Fawcett Dominic , D'Odorico Petra , Ginzler Christian , Gessler Arthur
Published: March 2024

Environmental stresses exacerbated by climate change create increasing pressure on forest ecosystems, challenging their resilience and functioning. As part of the Forestward Observatory to Secure Resilience of European Forests (FORWARDS) we seek to bridge the gap between ground-based measurements of tree vitality and remote sensing methods. Multi- and hyperspectral reflectance data have the potential to map visible damages but also pre-visual vulnerability symptoms (e.g. downregulation of photosynthesis) due to their relation to leaf pigment contents (D’Odorico et al., 2021). However, the interpretation of spectral indicators such as vegetation indices can vary at leaf, crown and stand level, as well as between species and forest structure (Gamon et al., 2023).We make use of multiple scales of remote sensing observations to investigate how indicators derived from reflectance behave at crown, stand and landscape level and which approaches are promising for operational use in Europe-wide forest vitality monitoring, particularly in the context of the new-generation spaceborne imaging spectrometers.We present first results from a pilot phase of this project focused on three intensively monitored sites in Switzerland, including a rainfall exclusion experiment for investigating drought stress. For these sites, leaf and tree-level data in the field as well as acquisitions by drone (
Estimate of the global and regional Ocean Heat Content changes from space gravimetry and altimetry observations to assess the Earth Energy Imbalance variations and trend
Authors: Fraudeau Robin , Marti Florence , Meyssignac Benoit , Blazquez Alejandro , Fourest Sebastien , Ablain Michael , Rousseau Victor , Larnicol Gilles , Restano Marco , Benveniste Jérôme , Sabia Roberto , Dibarboure Gérald
Published: March 2024

The Earth energy imbalance (EEI) at the top of the atmosphere (TOA) is the cause of the energy accumulation in the climate system. Measuring the EEI is challenging because it is a globally integrated variable whose variations are small (0.5-1 W.m−2) compared to the amount of energy entering and leaving the climate system (~ 340 W.m-2). 91% of the excess of energy stored by the planet in response to the EEI is accumulated in the ocean in the form of heat making the ocean heat content (OHC) change an accurate proxy of EEI.In this work, we adopt the space geodetic approach which relies on the sea level budget equation to estimate the OHC changes. The thermosteric sea level change is derived at regional scale from a combination of space altimetry and space gravimetry observations, and divided by the integrated expansion efficiency of heat  to estimate the OHC changes. The global OHC (GOHC) change is then estimated by a spatial integration of the regional OHC changes. The uncertainty in GOHC is estimated by propagation of the uncertainty of input data using the input data error variance-covariance matrix to account for the instrumental and post-processing errors and for the time correlation in errors.Regional estimates of the OHC changes are validated over the Atlantic Ocean directly against data from in-situ Argo profiles and indirectly by an energy budget approach. In the energy budget approach, surface heat flux derived from ERA5 and CERES TOA radiation budget are combined with regional OHC changes to estimate the north Atlantic meridional heat transport which is then validated against in-situ RAPID and OSNAP estimates. Both validations show good agreement in terms of signal amplitudes and variability with time correlations above 0.6.  Over the period 1993-2022, the GOHC shows a significant positive trend of 0.75 W m-2 [0.61, 1.04] at the 90% confidence level, indicating a positive mean ocean heat uptake or EEI. Comparisons with GOHC estimates based on in-situ ocean temperature measurements over the full ocean depth show good agreement over 2005-2019 (Marti et al. 2023, in review). Over 2000-2020, the ocean heat uptake presents a positive trend of 0.33 W/m²/decade, significant at the 90% confidence level and in agreement with CERES estimate. This EEI trend  reflects an acceleration in ocean warming. The two space geodetic products based on space altimetry and space gravimetry are freely available on the AVISO website. One estimating the GOHC and EEI (https://doi.org/10.24400/527896/a01-2020.003), the other estimating regional OHC over the Atlantic Ocean (https://doi.org/10.24400/527896/a01-2022.012).
Using fiducial reference measurements for assessing soil moisture product stability
Authors: Aberer Daniel , Bader Nicolas , Himmelbauer Irene , Preimesberger Wolfgang , Boresch Alexander , Tercjak Monika , Gibon François , Mialon Arnaud , Crapolicchio Raffaele , Dorigo Wouter , Gruber Alexander
Published: March 2024

The Global Climate Observing System Essential Climate Variables (GCOS ECVs) requirements define a target threshold of 0.005 m³/m³ per decade for satellite soil moisture product stability. As admitted by GCOS, this threshold lacks robust justification in the scientific literature, prompting critical assessment. Moreover, no commonly-accepted method exists to assess satellite soil moisture product stability to begin with.In this study, we investigate the suitability of existing in situ soil moisture monitoring networks contained in the International Soil Moisture Network (ISMN) for stability assessment. The selection of such stable reference sites is based on two criteria: (i) sites that are considered “fiducial reference sites” as defined by the Fiducial Reference Measurements for Soil Moisture (FRM4SM) project; and (ii) sites that provide suitable temporal coverage for the time spans over which satellite product stability is required (i.e., 10 years or more).  Using these select reference sites, we assess the stability of various common satellite soil moisture products (e.g., ASCAT, SMOS) using Theil-Sen slopes that are calculated for various validation metrics (e.g., median annual Pearson correlations or unbiased Root Mean Square Differences). In addition, we investigate the impact of data gaps and scarcity on the calculated stability metrics.Analyses were carried out using the the python toolbox for evaluating soil moisture observations (pytesmo; https://github.com/TUW-GEO/pytesmo). The goal is to include stability metrics as part of the QA4SM online validation service in the future (https://qa4sm.eu/).
3D Attenuation Tomography of the Kashmir ‘Seismic Gap’ in NW Himalaya
Authors: Kumar Amarjeet , Chaudhuri Dibyajyoti , Mitra Supriyo , Wanchoo Sunil Kumar , Priestley Keith
Published: March 2024

Lateral variation in seismic-energy attenuation is necessary to unravel the tectonic and thermal structure of the lithosphere, and to quantify ground-motion from future earthquakes. We study the 3D variations in intrinsic, scattering and body-wave attenuation across the Kashmir ‘seismic gap’ in the NW Himalaya, which is among the least studied segments of the Himalayan arc. This region is situated between the rupture zones of the 1905 Kangra earthquake (Mw  ∼ 7.9) and the 2005 Muzaffarabad earthquake (Mw ~ 7.6), and spans the meizoseismal zone of the 1555 Kashmir earthquake (Mw ∼ 8.0). Over the last five centuries, this region has accumulated sufficient strain-energy to drive a future mega-thrust earthquake of similar magnitude. We use 507 local earthquake (Mw ≥ 2) waveform data recorded by the Jammu And Kashmir Seismological NETwork between 2013 to 2017. These earthquakes have been re-located using the non-linear location algorithm. Intrinsic attenuation is calculated using coda waves modeled as a composite of multiple forward-scattered energies in a diffusive regime (Qc ~ Qi). The exponential decay of the coda-wave envelopes are used to invert for the intrinsic attenuation using sensitivity kernels, whose parameters like albedo and extinction length are computed using the Multiple Lapse Time Window Analysis (MLTWA). Scattering attenuation is imaged using peak delay-time method, which is a direct measure for multiple forward-scattering. The body wave (P- or S-wave) attenuation is computed using the coda-normalization method, by taking the ratio of the measured direct and coda wave energies, which depends only on Q, thereby using a linearized inversion. The preliminary results show a spatial variation in frequency dependent 3D scattering, absorption, and body-wave attenuation, which are related to the different geologic/tectonic features across the NW Himalaya. These results will be jointly interpreted with local S-wave velocity models to understand the tectonic and thermal structure of the lithosphere.
On the potential of highly accurate clocks and inter-satellite clock synchronization for GNSS satellite precise orbit and geocenter determination
Authors: Schreiner Patrick , Glaser Susanne , König Rolf , Neumayer Karl Hans , Raut Shrishail , Schuh Harald
Published: March 2024

Improving the concepts of Global Navigation Satellite Systems (GNSS) has become a vital task for subsequent GNSS applications like the determination of the Terrestrial Reference Frame (TRF). A promising goal is the reduction of uncertainties in non-conservative force modeling such as Solar Radiation Pressure (SRP) modelling in Precise Orbit Determination (POD) and the effect on the estimated orbits and geocenter coordinates. In previous simulation studies, accelerometers on next-generation GNSS satellites have proven to be a promising opportunity. In this way, the periodic signals in the estimated geocenter coordinates induced by SRP mismodeling can be eliminated regardless of the angle of the Sun to the satellite and its orbital plane. At the same time, the satellite clock can be effectively decoupled from the satellite position estimates. In this study, we focus on the impact of highly accurate clocks and the synchronization of clocks between satellites, which would make it possible to estimate common clock parameters for the synchronized satellites. In doing so, we start with Galileo-type POD using prior simulated observations with the assumption of perfectly known clocks. Then, we simulate various scenarios assuming different clock models and compare the results with the perfect case scenario. This procedure will explore the potential of various ground reference and satellite clock accuracies. Additionally, we use inter-satellite links to synchronize the satellite clocks over one and over multiple orbital planes. Finally, we strive to assess the potential of improved clock modeling on the TRF, focusing on the estimation of geocenter coordinates.
Rock glacier inventorying and validation across the Hindu Kush Himalaya from deep learning and high-resolution images
Authors: Racoviteanu Adina , Sun Zhangyu , Hu Yan , Liu Lin , Harrison Stephan
Published: March 2024

Rock glaciers are important to monitor due to their importance (i) as indicators of permafrost distribution, (ii) as integral components of the mountain hydrological systems, (iii) as indicators of permafrost temperature and pore-water pressure reflected in their kinematic behaviour under climate change and (iv) as potential triggers for geohazards such as rockfalls, debris flows, and lake outbursts related to their destabilization. Understanding these aspects requires accurate, systematic and updated rock glacier inventories. Currently, these remain patchy over extensive areas of High Mountain Asia. In a recent study, we presented a deep-learning-based approach for mapping rock glaciers across the Tibetan Plateau based on Deeplabv3+ deep learning network, trained using visually consistent and cloud-free Planet Basemaps and multi-source rock glacier inventories from multiple regions. This resulted in 44,273 rock glaciers covering a total area of ~6,038 km2, including both intact and relict types. In this work, we used the well-trained model to extend the mapping of rock glaciers over the entire Hindu-Kush Himalaya (HKH) range, resulting in an additional 46,425 rock glaciers candidates covering an area of ~5,700 km2. The raw number of rock glaciers mapped is significantly higher than previous estimates based on upscaled samples. We first screened the deep learning output based on AW3D30 elevation data to remove outliers and then validated the remaining candidates over several key regions in HKH (Manaslu, Khumbu and Ladakh regions) using independent satellite data from Pléiades, SPOT etc.The now complete inventory over the Tibetan Plateau-KHK constitutes a significant contribution to the IPA RGIK action group and serves as a benchmark dataset for modeling and monitoring the state of permafrost in a changing climate. Furthermore, this provides an important dataset for training deep learning models for global application.
 Dynamics of N2O under coastal hypoxia: the case of Lake Grevelingen (The Netherlands) 
Authors: Arévalo-Martínez Damian Leonardo , Bange Hermann W. , Dotsios Nicky , van Erk Marit R. , van Helmond Niels A.G.M. , ter Horst Peter A.G. , van Kessel Maartje A.H.J. , Lenstra Wytze , Lücker Sebastian , Rigutto Isabel , Schrammeck Sarah , Zygadlowska Olga , Jetten Mike S.M. , Slomp Caroline P.
Published: March 2024

Coastal margins play a crucial role for greenhouse gases (GHG) budgets because biological cycling and sediment-water-air exchanges are more intense than in the open ocean. Given the tight connection between marine GHG cycling (production, consumption, fluxes) and dissolved oxygen dynamics, ongoing deoxygenation is of particular concern in coastal systems that experience seasonal or perennial hypoxia, and could therefore have a large impact on regional GHG budgets. N2O stands out among other long-lived GHG because of its role as ozone-depleting compound and its effectiveness in enhancing Earth’s warming. Based on the vast majority of studies, marine coastal margins are expected to be hotspots of N2O emissions to the atmosphere, with nitrification and partial denitrification as the main sources. However, despite significant advances in constraining the marine budget of N2O over the last decade, the magnitude and seasonal variability of coastal emissions are still highly uncertain. While N2O depletion in marine settings is usually associated to complete denitrification, recent evidence indicates the possibility of consumption at oxic-hypoxic interfaces or under fully oxic conditions. Moreover, a mechanistic understanding on the benthic-pelagic coupling of N2O fluxes and its potential changes with deoxygenation is still rudimentary. To amend this deficit, we conducted a comprehensive study in Lake Grevelingen (Netherlands), a marine coastal reservoir characterized by seasonally hypoxic/anoxic conditions resulting from limited water exchange with the North Sea and eutrophication. Our study combined biogeochemical and microbial analyses and comprised multiyear (2020–2023) shipboard observations. We observed that unlike most coastal systems, surface waters of Lake Grevelingen are a rather weak source of atmospheric N2O, with annual sea-air fluxes that represent
Calculations of the 3D stress fields in mid-ocean ridge systems: a fluid-structure interaction (FSI) modelling approach
Authors: Mandal Nibir , Sen Joyjeet , Sarkar Shamik
Published: March 2024

Mid-ocean ridge (MOR) systems form multi-layered mechanical structures, constituted by a solid elastic crustal layer and an underlying melt-rich mush complex (MC) in the mantle. This article presents a new integrated solid-fluid modelling approach to show the development of complexly heterogeneous stress field in MORs. The modelling is implemented in two steps: 1) simulation of multi-ordered 3D convective circulations, produced by decompression melting in the mushy region, subjected to random thermal perturbations, and 2) mechanical coupling of the sub-ridge mushy regions with the overlying elastic crustal layer within a mathematical framework of fluid-structure interaction (FSI) mechanics. Using an enthalpy-porosity-based fluid-formulation of uppermost mantle the model accounts for a one-way FSI interaction for transmission of viscous forces of the MC region to the overlying upper crust. It is demonstrated from the model runs that a MOR spontaneously develops strongly heterogeneous stress fields on a time scale of million years, characterized by their segmented patterns. The stress mapping reveals a distinct 30 km wide axial zone of ridge-normal tensile stresses ( < 250 MPa), flanked by ridge-parallel linear belts of ridge-normal compression (median < 100 MPa). The FSI model results suggest that ridge-parallel compression belts can develop in MORs without involving flexural bending of lithospheric plates. In addition, a MOR system produces narrow along-axis compressional zones transverse to the ridge axis, resulting in segmentation of the stress field on a wavelength of 40-150 km. These segmented stress fields conforms to the second-order magmatic segmentation patterns of MORs, as reported in the literature.
Evidence of rapid conduit sealing driving explosive activity at El Reventador (Ecuador) underpinned by a permanent SO2 camera installation.
Authors: Wilkes Thomas C. , Hidalgo Silvana , Battaglia Jean , Pering Tom D. , Almeida Marco , Vásconez Freddy , Macías Carlos , García Dario
Published: March 2024

El Reventador is a highly active stratovolcano located ≈90 km east of Quito (Ecuador). Since a paroxysmal eruption (VEI 4) in 2002, it has exhibited persistent open-vent degassing accompanied by frequent vulcanian-/strombolian-style explosions, as well as lava flows and small pyroclastic density currents. The relatively remote nature of this volcano, requiring 4-5 hours of arduous uphill hiking through thick jungle, hinders extensive research on this system. Furthermore, with changeable and often wet weather conditions in the region, reliable remote spectroscopic measurements of gas emissions can be particularly difficult to achieve. These complications highlight the importance of permanent instrument installations that can work autonomously, thus reducing the need for field campaigns and improving the chances of capturing high-quality data and/or interesting volcanic phenomena. Here, we present the first measurements from a permanent SO2 camera installation on El Reventador, focussed on a window of good measurement conditions lasting a few hours on 24th April 2022. During this period, explosions typically occurred at a sub-hourly rate, with varying sizes and repose periods. Prior to a number of the explosions we find a decrease in SO2 emissions suggestive of gas accumulating under a reduced-permeability magma seal in the upper conduit. Sealing appears to occur on the order of 10-20 minutes prior to explosions, although establishing a baseline emission rate for the freely degassing system is often precluded by the frequency of explosions. Indeed, we find periods where permeability in the upper conduit appears to begin reducing immediately after the previous explosion. 
Consistency assessment of EOP estimated by different VLBI correlators
Authors: Belda Palazón Santiago , Karbon Maria , Escapa Alberto , Ferrándiz José M. , Azcue Esther , Moreira Mariana , Modiri Sadegh
Published: March 2024

The VLBI technique provides an extremely precise measurement of the geometric relationship between the receiving radio observatory and the celestial target. It utilizes methods of recording the signals at each antenna. These recordings are physically brought together and played back into a processing device, known as a correlator, which combines the signals in such a way that delivers the fundamental observables of geodetic VLBI, the time delays between signals arriving at the individual antennas as a function of time. Nowadays, numerous correlator software and strategies are employed which may result in inconsistencies on the geodetic products.In this study, we empirically assess the consistency between the different correlators by analyzing the R1/R4 VLBI sessions from 2002 to 2022 to reflect the impact on the EOP estimates. To compare the different pairs of EOP time series estimates, we calculated the Weighted Mean (WM) of the differences and the Weighted Root Mean Square (WRMS) differences between each of them. Besides, we empirically evaluate the consistency, systematics, and deviations of the IAU 2006/2000A precession-nutation model using several CPO time series derived from the different correlators, providing a new set of empirical corrections to the precession offsets and rates, and to the amplitudes included in the nutation models. Finally, we study the impact on the estimation of new free core nutation (FCN) models.This research was supported partially by Generalitat Valenciana (SEJIGENT/2021/001) and the European Union—NextGenerationEU (ZAMBRANO 21-04); and also by Spanish Projects PID2020-119383GB-I00 funded by Ministerio de Ciencia e Innovación (MCIN/AEI/10.13039/501100011033/) and  PROMETEO/2021/030 funded by Generalitat Valenciana.
Near Surface Imaging with Zig-Zag shaped DAS Arrays Based on Cross Correlation of Ambient Noise
Authors: Wu Peng , Gu Chen , Zhong Yichen , Yuan Zhi , Chen Zhuoyu , Kang Borui
Published: March 2024

Distributed Acoustic Sensing (DAS) has effectively transformed traditional telecommunication fiber-optic cables into highly efficient, dense seismic arrays. In this paper, we perform cross-correlation and stacking on the signals recorded by DAS fiber arrays in a Zig-Zag pattern, which increases the spatial coverage and improves the ability to detect and analyze various seismic waves modes. We observed that the resulting signals include both Rayleigh and Love waves. Additionally, the propagation characteristics of the wave field exhibit a Zig-Zag distribution pattern, consistent with the spatial distribution of the fibers. The challenge arises from the need to distinguish and accurately interpret the overlapping signals of Rayleigh and Love waves, which have different propagation characteristics. To address these challenges, we propose an inversion method specifically tailored for the near surface imaging with DAS array data when the fiber-optic cables are not laid in straight lines. We also conducted an on-site experiment using Zig-Zag shaped DAS arrays with known subsurface velocity model. This experiment was designed to record ambient noise signals over a week and analyze the propagation characteristics of both Rayleigh and Love waves within the surface waves captured by the DAS system. The inversion results obtained from the analysis of the recorded data showed a high degree of consistency with the ground truth subsurface structure of the test area. This demonstrates the effectiveness of the proposed method in overcoming the limitations of traditional dispersion curve-based inversion techniques, particularly in the context of non-linear fiber layouts. This research provides strong support for the practical application of dark fibers in near surface imaging, demonstrating the potential of dark fibers.
Effect of irrigation on joint evolution of water resources and hydroclimate variables under climate change
Authors: Arboleda Pedro , Ducharne Agnès , Tiengou Pierre , Cheruy Frédérique
Published: March 2024

Irrigation is one of the main human landscape management activity, and has seen a dramatic increase during the XXth century, with a direct local increasing effect on soil moisture (SM) and evapotranspiration (ET). To sustain the increase of ET, irrigation withdraws water from rivers and groundwater reservoirs. As a result, irrigation activities have a direct impact on water and energy balance, and drive the evolution of ET under the ongoing climate change in intensively irrigated regions. On the other hand, irrigation induces feedbacks from the atmosphere, that includes changes in precipitation patterns, air temperature cooling and changes in energy-related variables. Moreover, future climate change will complexify these interactions, and it is not clear what would be the future implications of irrigation activities in water resources management and key hydroclimate variables.To assess the joint evolution of irrigation, water resources and hydroclimate variables, we use an irrigation scheme that was recently evaluated in ORCHIDEE, the land surface component of the IPSL climate model. This scheme calculates water demand based on a soil moisture deficit approach, and restrains water supply to water available in small and large rivers and in groundwater, considering the facility to access the water source and an environmental volume for ecosystems. To assess the effect of irrigation on water resources and climate, we use two transient coupled simulations at global scale, for the period 1950-2100, under SSP5-RCP8.5 scenario to have a strong climate change signal during the future period. One of the simulations runs with the irrigation scheme activated, while the second one runs without irrigation.Preliminary results at global scale show that irrigation will increase under the chosen scenario, due to the prescribed increase of the irrigated surface from scenario SSP5-RCP8.5 and a warmer climate. This increase will counteract part of the increasing trend of groundwater storage and will complexify the evolution of river storage in irrigated areas. On the other hand, it will enhance the increase of ET at global scale. We will extend our analysis to water and energy-related variables, including key climate variables like precipitation and air temperature, at different seasons and regions. We will also focus our analysis in some intensively irrigated areas, to assess the causes of possible water supply shortages in irrigation activities. These results should help to understand future implications of irrigation in water resources management in irrigated areas, and also effects in non-irrigated zones via remote land-atmosphere feedbacks.
Genotypic variability and phenotypic plasticity of leaf minimum conductance
Authors: Wang Songwei , Hoch Günter , Hopf Sven , Kahmen Ansgar
Published: March 2024

During drought, when trees have lost access to soil moisture, the survival time of trees is intimately linked to leaf minimum water conductance (gmin), which determines the residual water loss after a tree has fully closed its stomates. Large differences in gmin are known among different tree species from contrasting climates. In addition, gmin typically exhibits strong and highly species-specific thermal sensitivity (T) with rising temperatures. Within a species, the genetic variability (G) and phenotypic plasticity (P) of gmin, and especially the G and P of the thermal sensitivity, in natural tree populations remains unknown. Here we examined the thermal sensitivity of four tree species (Acer pseudoplatanus, Fagus sylvatica, Picea abies, and Pseudotsuga menziesii) and assessed G, P, and the interaction of G x P of gmin and T in a provenience trial. Additionally, we determined the relative distance plasticity index (RDPI) among populations for each species and how leaf cuticular and stomatal traits are related to the intraspecific variation in gmin. The trees that we investigated were grown in three trials with different hydroclimatic conditions in Switzerland. Our results show a strong effect of T on gmin, which increased by a factor of two to seven when the temperature increased from 30 to 50 °C for all studied species. Importantly, gmin in two deciduous broadleaf tree species displayed strong G, with gmin values being higher for genotypes originating from wet climates than those of trees originating from dry climates. In contrast, there was little G in gmin for two evergreen conifers. On the other hand, significant P of gmin was found in all tested tree species, with higher gmin values for trees grown in wet rather than dry environments. RDPI was typically low across provenances for all studied tree species, suggesting the limited absolute P of gmin. Interestingly, there was a dramatic interaction of P x T for Fagus, showing stronger temperature responses under wet growing conditions rather than dry growing conditions. Interestingly, G and P of gmin could not be simply explained by leaf stomatal and cuticular traits. Our study provides novel insights into the long-term evolution and short-term adaptation of gmin, suggesting that gmin may be capable of acclimating to future hotter and drier environments in some but not all species. Our findings provide practical measurements for improving European forest management in the context of global-change-type drought.
Challenges and Strategies in the Development and Operation of High-Frequency Marine Radar Systems in Taiwan
Authors: Chang Huan Meng , Lai Jian Wu , Yu Hsin Yu , Chien Hwa , Mau Jenq Chi
Published: March 2024

    The pivotal role of oceanographic parameters in informed decision-making spans a spectrum of marine issues, including resource management, ecological preservation, maritime safety, and national security. Conventional data acquisition methods, such as buoys and survey ships, have become increasingly inadequate in addressing the complex demands of these domains. This insufficiency has propelled the global development of spatially-oriented observational technologies, among which High-Frequency (HF) ocean radar is a standout. Globally, the deployment of HF ocean radar systems has surpassed 1000 units. Taiwan, since the 1990s, has installed 48 HF radar systems, including variants like CODAR, WEAR, and LERA. Despite initial successes, a decline in system performance post-deployment is a recurring issue, often linked to policy discontinuity, fluctuating financial support, team dynamics, technical proficiency, and data application and dissemination challenges. This study explores Taiwan's unique experiences with these impediments in the evolution of HF ocean radar systems, aiming to strategize effective long-term operational planning.    A case in point is the Taiwan Ocean Radar Observation System (TOROS), established by the Taiwan Ocean Research Institute (TORI) in 2016. This system confronted operational challenges due to insufficient maintenance budgets soon after its inauguration, leading to the cessation of some station operations. Further analysis identified a reactive data dissemination model, requiring user applications and approvals, as a primary issue. This inefficiency, compounded by inadequate promotion, weakened the system's perceived utility, resulting in unsustainable policy support, budget cuts, and the loss of specialized personnel, thereby adversely impacting system functionality in a cyclic manner.    This paper argues that the ubiquity of data fosters demand, a critical metric for evaluating system utility. Such utility influences administrative decisions, which in turn affect financial commitment, vital for cultivating a skilled technical team. The strategic deployment of this workforce is crucial for consistent system operation and maintenance, ultimately determining operational success. Leveraging insights from past installations and operational experiences, the study proposes methodologies to sustain operational continuity and bolster the efficacy and resilience of HF ocean radar systems.
Revisiting border irrigation management: benefits of new in-field sensor-based control compared to conventional cutoff times
Authors: Vandôme Paul , Berkaoui Amine , Guillemin Cedric , Leauthaud Crystele
Published: March 2024

Surface irrigation is often described as low performing insofar as its practice is labour intensive and involves the use of large water flows that are difficult to quantify and manage. However, this method remains predominant worldwide, and modernisation towards localised irrigation systems is not always feasible or advisable. To support border irrigation management, we previously developed a low-cost sensor for surface irrigation management, which remotely informs the farmer of water arrival downstream of his or her field and therefore of the moment to stop irrigation. The objectives of this study were: i) to determine the optimal position of this sensor lengthwise in the field throughout the season, and ii) to compare the influence of management scenarios (sensor-based or time-based cutoff) on irrigation performance. To this end, an integrated agro-hydraulic model was developed to simulate surface water flow dynamics throughout the season including variations in infiltration and roughness. The model was fed using monitoring data from the border irrigation of a hay field during a whole season. The results showed that the optimal sensor position can change by 10% over the course of the season, depending on inflow rates, initial soil moisture and Manning’s roughness. Sensor-based irrigation control was found to be more efficient than actual practices, and more effective than an optimised cutoff time in limiting performance gaps induced by variability or uncertainty in the initial conditions. The methods and findings should serve as a basis for larger-scale studies integrating the adoption of sensors and real-time data for surface irrigation management.
The combustion conversion coefficient for constructing open biomass fire burning emission based on satellite FRE
Authors: Wu Jian
Published: March 2024

The pollutant emissions from biomass fire burning significantly impact on global climate change, regional air quality and detrimental effects on human health. It is necessary to convert fire radiant energy (FRE) to biomass fire burning consumption by the combustion conversion coefficient, when adopting the satellite FRE to estimate the emission of  open fire burning. To date, the combustion conversion coefficients are considered to be scalar constants, which ignores the influence of multiple factors during the combustion process and regional differences. This study aims to conduct a systematic analysis of combustion conversion coefficients, by the view of ground experiment measurement, satellite data verification and emission results improvement. Firstly, the combustion conversion coefficients of typical biomass sources in China are obtained and the effects of fuels type, combustion state, combustion scale and combustion temperature on the combustion conversion coefficient are revealed, based on the ground experiment. Then, the satellite data are used to estimate the regional combustion conversion coefficient, so as to verify the reliability of the ground experimental measurement results on the regional scale. Finally, the verified combustion conversion coefficients are applied to improve the accuracy of the emission inventory. The uncertainty of the emission inventory caused by the combustion conversion coefficient has been estimated. The research results provide a new parametric scheme for improving the accuracy of the open biomass fire burning emission in China.
A global daily gap-filled chlorophyll-a dataset in open oceans during 2001–2021 from multisource information using convolutional neural networks
Authors: Hong Zhongkun , Long Di , Li Xingdong , Wang Yiming , Zhang Jianmin , Hamouda Mohamed , Mohamed Mohamed
Published: March 2024

Ocean color data are essential for developing our understanding of biological and ecological phenomena and processes and also of important sources of input for physical and biogeochemical ocean models. Chlorophyll-a (Chl-a) is a critical variable of ocean color in the marine environment. Quantitative retrieval from satellite remote sensing is a main way to obtain large-scale oceanic Chl-a. However, missing data are a major limitation in satellite remote-sensing-based Chl-a products due mostly to the influence of cloud, sun glint contamination, and high satellite viewing angles. The common methods to reconstruct (gap fill) missing data often consider spatiotemporal information of initial images alone, such as Data Interpolating Empirical Orthogonal Functions, optimal interpolation, Kriging interpolation, and the extended Kalman filter. However, these methods do not perform well in the presence of large-scale missing values in the image and overlook the valuable information available from other datasets for data reconstruction. Here, we developed a convolutional neural network (CNN) named Ocean Chlorophyll-a concentration reconstruction by convolutional neural NETwork (OCNET) for Chl-a concentration data reconstruction in open-ocean areas, considering environmental variables that are associated with ocean phytoplankton growth and distribution. Sea surface temperature (SST), salinity (SAL), photosynthetically active radiation (PAR), and sea surface pressure (SSP) from reanalysis data and satellite observations were selected as the input of OCNET to correlate with the environment and phytoplankton biomass. The developed OCNET model achieves good performance in the reconstruction of global open ocean Chl-a concentration data and captures spatiotemporal variations of these features. The reconstructed Chl-a data are available online at https://doi.org/10.5281/zenodo.10011908. This study also shows the potential of machine learning in large-scale ocean color data reconstruction and offers the possibility of predicting Chl-a concentration trends in a changing environment.
Fast stress-loading and -unloading below the seismogenic zone
Authors: Trepmann Claudia , Brückner Lisa , Dellefant Fabian
Published: March 2024

At depth just below the seismogenic zone of the continental crust, i.e. at greenschist facies conditions, stresses increase during seismic rupturing within minutes from differential stresses on the order of a few tens of MPa to several hundreds of MPa. These fast stress-loading rates are manifested in characteristic microfabrics in fault rocks (cataclasites and pseudotachylytes) exhumed from these depths. The microfabrics indicate quasi-instantaneous cataclasis of almost all rock-forming minerals including garnet and quartz, as well as mechanical twinning of pyroxenes, amphiboles and titanite. In combination with experiments, the microfabrics can be used as paleo-stress gauges, i.e., paleopiezometers. The characteristic microstructures can occur distributed over the whole width of large-scale thrust faults, as the Silvretta basal thrust in the Central European Alps. There, twinned amphiboles record transient differential stresses of more than 400 MPa in a rock volume to about 300 m above the basal thrust exposed at the contact to the Penninic units of the Engadine window over several tens of km. Fast stress-unloading is indicated by growth of new undeformed quartz grains along cleavage cracks in host quartz generated coeval with seismic rupturing and missing evidence of quartz dislocation creep after pseudotachylyte formation. This fast stress-loading and unloading is recorded in pseudotachylytes, i.e., close to the seismic rupture, whereas at larger distance to the seismic rupture accelerated creep at hundreds of MPa occurs on a longer time scale. 
What are the best strategies for managing a single extreme flood event in hydrological model evaluation? – Insights from the extreme flood 2021 in Western Germany
Authors: Han Li , Guse Björn , Nguyen Viet Dung , Rakovec Oldrich , Najafi Husain , Guan Xiaoxiang , Vorogushyn Sergiy , Samaniego Luis , Merz Bruno
Published: March 2024

Extraordinary floods like the one in July 2021 have induced catastrophic consequences on both societal and economic domains. Robust model simulations are crucial for mitigating the adverse effects of such extreme events on human life. However, accurately reproducing and predicting exceptional floods remain a challenge in particular when only one such flood extreme is available in the reference record period. This single flood could be included either in calibration and evaluation period. In both cases, extreme events are missing in the other period. To analyze how to best handle a single extreme flood, we present a framework for calibrating and evaluating the mesoscale Hydrologic Model (mHM) using the July 2021 flood in western Germany as a case study. Hereby, we tested the effect of including the extreme 2021 flood in calibration or evaluation periods.Our study shows that including the exceptional 2021 flood event in model calibration proves crucial for accurately reproducing high streamflow. Without including the 2021 flood in the calibration period, the model cannot learn how to reproduce extreme floods. Our findings reveal that employing the modified weighted Nash-Sutcliffe Efficiency (wNSE) as the objective function significantly improves mHM's performance in capturing flood peaks. This leads to a notable reduction from -35% to -7.8% in the difference between the simulated and observed/reconstructed peaks as demonstrated for the catchment outlet. The hydrological model performance was validated spatially for an independent set of gauges. Spatial validation is necessary for assessing model performance when only one exceptional historical event is available. In conclusion, our framework provides valuable insights into improving hydrologic modeling accuracy, emphasizing the importance of specific calibration strategies and spatial validation in capturing exceptional flood events.
Assessment of the Türkiye Heat Flow Database 2023
Authors: Balkan-Pazvantoglu Elif , Neumann Florian , Norden Ben , Fuchs Sven
Published: March 2024

Terrestrial heat-flow determinations are crucial for understanding the thermal structure of the lithosphere. This study presents the results of a revision of the heat flow database in Türkiye contributing to the Global Heat Flow Data Assessment Project conducted by the International Heat Flow Commission (IHFC). The database includes 750 heat flow determinations reported in Türkiye between 1991 and 2023, and are reassessed according to the new IHFC specific structure documented by Fuchs et al. (2023). The data are gathered from the original literature and examined to ensure complete documentation of relevant metadata. The quality score is assigned based on the uncertainty, methodology and environmental disturbances. The new national wide database shows that heat-flow determinations are predominantly distributed in the western part of the country. However, the eastern part of the country has been poorly investigated to date. Despite numerous exploration-based studies conducted in the region concerning its substantial geothermal potential, a noteworthy portion of thermal data remains archived and is not accessible. The study reveals a significant demand for additional heat flow determinations to allow the drawing of a substantially revised and robust heat-flow map. However, the ongoing update of the Türkiye Heat Flow Database already allows a more transparent identification of areas with thermal anomalies.