bluuebunny/crossref_metadata_2025 huggingface dataset:
Big data techniques for real-time hyperspectral core logging
Authors: Thiele Samuel , Kirsch Moritz , Lorenz Sandra , Gloaguen Richard
Published: March 2024

Hyperspectral imaging is gaining widespread use in the resource sector, with applications in mineral exploration, geometallurgy, and mine mapping. However, the sheer size of many hyperspectral datasets (>1 Tb), and associated data correction and analysis challenges, limit the integration of this technique into time-critical exploration and mining workflows. We present an overview of several newly developed  real-time processing capabilities to mitigate these challenges, and so provide hyperspectral data and derived products (e.g., mineral abundance estimates) in near real-time. This allows for efficient, timely, and automated delivery of hyperspectral data to enhance geological activities.Hyperspectral data generally needs to be corrected, coregistered, cropped and masked, before derivative results can be generated, visualized and stored. To achieve real-time processing, each of these steps, which can involve the computationally intense manipulation of several Gb worth of spectral data, need to be completed within the 1-3 minutes a typical instrument or scanner takes to capture a data cube. To help with this, we have developed a python-based asynchronous processing pipeline, crunchy, that uses a file-discovery-based triggering mechanism to spawn parallel processing workflows that automatically perform these tasks. Coregistered and radiometrically corrected results are then stored using a directory-based data structure managed by a second python utility, hycore, that facilitates (1) consistent data storage, (2) file-based out-of-core processing, and (3) management of the various metadata required to localize and give meaning to hyperspectral drill core data. We have also developed a third python tool, hywiz, to enable an easy browser-based interaction with hycore databases. This includes the visualisation of sensor results and analysis products for individual trays and drillhole mosaics. Additional data such as assays, logging notes or downhole geophysical data can be overlain on these to enable integrated interpretation of otherwise disparate datasets. We hope that these tools will enable greater use of hyperspectral data in research and industry, and facilitate e.g., hyperspectrally enhanced core-logging, sample selection, vectoring and, potentially, realize self-updating 3-D geological models.
Dynamics in CO2 uptake, growth, and mortality of an old-growth temperate forest under drought stress
Authors: Koebsch Franziska , Klosterhalfen Anne , Emad Anas , Mund Martina , Ammer Christian , Dietenberger Steffen , Donfack Laura , Heidenreich Marius , Mueller Marlin M. , Seidel Dominik , Thiel Christian , Tiedemann Frank , Knohl Alexander
Published: March 2024

Understanding drought stress responses and adaptation mechanisms in forest ecosystems towards climate extremes is crucial. This knowledge aids in assessing adaptive capacities and developing supportive management measures. Here, a comprehensive long-term data set obtained in the Hainich National Park, an old-growth mixed-beech forest in Central Germany (DE-Hai), gives the opportunity to investigate stress effects and transformation processes caused by the 2018 and 2019 summer droughts on tree and stand scale. The forest displays a near-natural, diverse system with a range of tree age classes and species (main species: Fagus sylvatica, Fraxinus excelsior, Acer pseudoplatanus).In this study, we combined long-term observations of stand-level CO2 exchange obtained with the eddy covariance method with annual growth records and structural indices of 80 trees obtained from dendrometer bands and terrestrial laser scans. Further, drone and satellite imagery provided estimates of tree mortality through canopy gap dynamics. Based on this multi-scale data set, we strive to better understand the link between forest CO2 uptake and tree response dynamics under the influence of a severe drought.During the drought events in 2018 and 2019, we observed that the forest remained a net CO2 sink, but the CO2 uptake strength was considerably diminished (up to -30%) in comparison to the reference period of the previous 17 years. Moreover, the reduction in CO2 uptake extended beyond the duration of the droughts, which implies significant changes in the mechanisms and dynamics of the forest. Further, an increase in the canopy gap fraction by more than 50% in 2021 indicated a significant increase in tree mortality. Surviving trees were affected differently by the droughts depending on species-specific stress response strategies and a tree’s role as competitor or suppressed individual. In particular, the growth of older and larger trees, mostly Fraxinus excelsior, was impaired during and after the drought period. However, approximately half of the observed trees, mostly suppressed, vital Fagus sylvatica, showed a positive growth trend during and after the drought period.The structural diversity of the old-growth mixed forest could buffer the drought-induced outage in the CO2 uptake strength, though the increased growth of a large cohort of surviving, suppressed Fagus sylvatica could not compensate for the diminished CO2 uptake by a few dying dominant trees. The natural succession dynamics in the forest ecosystem seem to be accelerated due to drought events. A continuous and consistent long-term monitoring of forest ecosystems is needed to further investigate the initiated transformation processes, the stand and tree resilience, and additionally the impact of legacy effects.
Integration of laser ranging range-rate observations into the GRACE Follow-On processing at the AIUB
Authors: Lasser Martin , Meyer Ulrich , Arnold Daniel , Jäggi Adrian
Published: March 2024

We study temporal gravity field determination from GRACE Follow-On satellite-to-satellite tracking data using the inter-satellite link of the K-Band Ranging System (KBR) and kinematic positions of the satellites as observations and pseudo-observations, respectively. In addition, we introduce the range-rate observations collected by the Laser Ranging System (LRI) as further observation group. We compute our solutions with the Celestial Mechanics Approach using next to the kinematic positions either only LRI range-rate observations or combining them with the KBR derived range-rate data by the means of Variance Component Estimation (VCE).The stochastic noise of the KBR and LRI data is modelled with an empirical description of the noise based on the post-fit residuals between the final GRACE Follow-On orbits, that are co-estimated together with the gravity field, and the observations, expressed in position residuals to the kinematic positions and in KBR and/or LRI range-rate residuals. We validate the LRI-only and KBR+LRI monthly solutions by comparing them with the KBR-only derived models from the operational GRACE Follow-On processing at the AIUB, by examining the stochastic behaviour of respective post-fit residuals and by inspecting  areas where a low noise is expected. Last but not least, we investigate the influence of LRI-only and KBR+LRI monthly gravity field solutions in a  combination of monthly gravity fields based on other approaches as it is done by the Combination Service for Time-variable Gravity fields (COST-G) and make use of noise and signal assessment applying the quality control tools routinely used in the frame of COST-G.
Compound heavy rainfall and river flood events in small catchments
Authors: Simon Felix , Mudersbach Christoph
Published: March 2024

Heavy rainfall and flooding are extreme events with high hazard and risk potential for people and the environment. While there has been extensive research on the individual events of heavy rainfall and flooding, there is still a significant need for research into their combination. Analysing them separately may lead to an underestimation of the hazards and risks involved. Especially in small catchment areas or headwater catchments, a heavy rainfall event can cause flash flooding and a flood event in a river simultaneously. The relationship between the investigated area and its associated hydrological catchment area is crucial. In such areas, classic flood protection measures may not always be the most sensible option. Targeted measures and precautions must be taken, and knowledge of these events is of great importance.Analyses are carried out to understand the relationship between combined heavy rainfall and flood events and the characteristics of the study area. For this purpose, we use precipitation radar data from the German Weather Service (RADKLIM, 5 min & 1x1 km) and discharge data from water gauges provided by the NRW State Office for Nature, Environment and Consumer Protection, as well as various water associations. The data is used to generate area averages of precipitation of various durations for the catchment areas under investigation. The compound events are analysed using value pairs, which are defined based on AMAX or threshold values. Statistical extreme value analyses were conducted on individual events using different extreme value distributions, including the metastatic and general extreme value distributions. These analyses were necessary to determine the probabilities of compound events such as heavy rainfall and flooding, with the aid of copula functions. The joint occurrence probabilities and correlation between precipitation and runoff events along a watercourse are also considered.The results of these analyses provide insights into the integral consideration of floods and heavy rainfall, particularly in small catchment areas and during short heavy rainfall events. In addition, these methods can be used to define the joint probabilities of occurrence of these events. Furthermore, the investigations can not only contribute to a more precise assessment of the hazards and risks of compound events, but can also serve as a starting point for integral heavy rain and flood hazard maps. The maps derived from this can make a valuable contribution to the development of more precise and comprehensive risk management strategies.
Significant increase observed in tree mortality in boreal forests in Southern Finland
Authors: Junttila Samuli , Blomqvist Minna , Laukkanen Ville , O'Sullivan Hannah , Polvivaara Antti , Holopainen Markus , Peltola Heli
Published: March 2024

Simultaneous increases of severe drought and heat extremes with bark beetle outbreaks have recently increased tree mortality globally. The lack of accurate tree mortality data over large areas has limited the development and applications of tree mortality models. Available tree mortality data has mainly been collected using field observations with limited spatial extent. However, the use of high-resolution remote sensing data, such as aerial imagery with automated imagery analysis, may change this situation.  In this study, we analysed the development of tree mortality (standing dead wood) and factors contributing to it during 2017-2023 over an area of 117 366 ha of boreal forested landscape in Southern Finland. For this purpose, we developed a convolutional neural network (CNN) based on U-Net architecture, allowing segmenting of standing dead wood automatically from aerial imagery in 2017, 2020 and 2023 with a spatial resolution of 0.5 m. We trained the model using 22300 segments of manually delineated dead trees from various geographic regions in Finland. The model showed high accuracy in detecting the dead trees with an F1 score of 0.93 based on an independent validation dataset. We also combined the information on detected dead trees with open forest resource information based on extensive field campaigns and airborne laser scanning, to estimate standing dead wood volume during 2017-2023. The total standing dead wood volume increased substantially in our boreal study area, by 543 % from 8660 m3 to 52659 m3 between 2017 and 2023. Similarly, the total forest area of standing dead wood increased by 456 % between 2017 and 2023. Both variables followed an exponential growth curve with a nearly perfect fit for the 2017, 2020 and 2023 time series, indicating that tree mortality increased rapidly. Tree mortality occurred mainly in Norway spruce (Picea abies) dominated forests on relatively fertile soils. The mean age of forest stands suffering from tree mortality decreased from 69.7 to 62.6 years between 2017 and 2023, indicating that tree mortality has transitioned towards younger forests. Our findings highlight the increasing risk of tree mortality in boreal forests and the need for large-scale monitoring to keep up to date on the fast-paced changes in boreal forest mortality. This is also required for timely risk management measures in forestry under changing climate, associated with simultaneous increases of severe drought and heat extremes with bark beetle outbreaks.
The ecological stability of restored vegetation by ecological water conveyance project in a typical terminal wetland in an arid inland river basin, northwestern China
Authors: Hu Shun , Zhao Qian
Published: March 2024

Overexploitation of water resources has led to severe ecological degradation and even desertification in many terminal wetlands in arid inland river basins, northwestern China. To restore the degraded vegetation ecosystem, ecological water conveyance projects (EWCPs) have become an important measure. Scientific assessment of the ecological stability of restored vegetation is of great importance for formulating reasonable ecological water management. Considering this, a systematic study was conducted in a typical terminal wetland of the Qingtu Lake Wetland (QLW) in Shiyang River Basin, northwestern China. The pixel-scale restored vegetation area (RVA) each year since the start of EWCP was extracted based on remotely sensed vegetation index. RVA increased dramatically in the first five years and became stable from 2016. The time lag of the response of RVA increase to ecological water conveyance was about 2 years. A bell-shaped function between RVA and groundwater depth was obtained based on the micro terrain of QLW via UAV. Five groundwater depth thresholds were then determined. The optimal groundwater depth in the hydrometric station was 2.91±0.09 m for the maximal RVA (17.08±3.25 km2). The optimal ecological water volume into Qingtu Lake was further estimated (the volume is 2224.4×104 m3) for the maximal RVA by a polynomial function between ecological water volume and groundwater depth. With the help of remotely sensed soil salinization and water surface, the vegetation restored during the first few years of EWCP in the southwest, west and north of QLW was found to degrade again due to the aggravation of soil salinization in these regions since 2019. Soil salinization was accelerated by the low groundwater depth with high mineralization and high evaporation capacity of climate without adequate inundation of ecological water by the unreasonable water allocation strategy. Under current simple and lax ecological water management in QLW, soil salinization will intensify and vegetation will further degrade. In other words, the ecological status of restored vegetation in QLW is unstable. Based on the optimal ecological water volume, even distribution of ecological water is helpful to maintain the stability of restored vegetation.
Investigating the feasibility of resolving hydrological processes with a Differential Quantum Gravimeter by hydrological scenario modeling
Authors: Reich Marvin , Janvier Camille , Güntner Andreas
Published: March 2024

Quantum sensors have gained increased attention in the last years, both from the applied but also from the manufacturer perspective. Most instruments are still limited to operation within a dedicated lab. With the Absolute Quantum Gravimeter (AQG), one device has already proven mobile capabilities and was used in several research studies. This application perspective is an important topic for new instruments, in order to meet scientific requirements in terms of usability and usefulness for various research interests.One of these research interests is hydrology. From the monitoring perspective, hydrological observations in the field traditionally rely on point measurements, often in form of invasive sensor installations. These spatially-limited observations sometimes complicate natural hydrological process investigations. An advantage is provided when using the hydrogravimetric method, with its integral nature of monitoring water mass changes as a whole.In this contribution, we address the above-mentioned important topics for a first feasibility study of an emerging instrument: the Differential Quantum Gravimeter (DQG). Developed by Exail Quantum Sensors, the DQG measures the acceleration due to gravity and the vertical gravity gradient simultaneously. It is an industry-grade demonstrator that has been operational for three years now and has achieved state-of-the-art sensitivity on the gradient of about 60E/sqrt(tau) and a long-term stability on the gradient around 1E. For gravity measurements the performances are on par or better than the AQG with a sensitivity of 600nm/s²/sqrt(tau) and a stability down to 5nm/s².In preparation for first field measurements, we were interested in its performance for resolving hydrological dynamics and processes. We set up different hydrological modeling scenarios to forward model gravity responses and their DQG-related gravity gradients from water mass changes. Scenarios for obtaining these water mass changes consisted of vertical 1D models using the software Hydrus. Developing scenarios from very simple to more complex soil layer setups, we tested different forcing types (precipitation, evapotranspiration) with varying magnitudes and durations. The overall objective was to simulate resulting gravity gradients at different locations as the DQG would monitor them. Varying the theoretical placement of the DQG within the model domain enabled us to investigate its sensitivity to the simulated hydrological processes with respect to its location and distance to different magnitudes of water mass changes. Forward modeled data was averaged at different time periods and combined with realistically expected noise of the instrument. The study helps to evaluate the capabilities of the instrument as a tool to observe water fluxes in the soil, as well as optimal implementation of the DQG for planning first field measurements.
How far in advance can we skillfully predict meteorological drought indices?
Authors: Imamovic Adel , Büeler Dominik , Pyrina Maria , Humphrey Vincent , Spirig Christoph , Moret Lionel , Domeisen Daniela
Published: March 2024

Given the limited skill of precipitation forecasts, the question arises to what extent ensemble forecasting systems can be used for early warning systems that require longer lead times, such as drought early warning. In this study, we use ECMWF’s IFS extended range forecasts, statistically downscaled to a 2 km grid encompassing Switzerland, to quantify the spatially and seasonally stratified predictability of several precipitation statistics. Consistent with existing analyses we find the predictability of extratropical instantaneous precipitation to be limited to week 1. However, when considering accumulated precipitation and the standardized precipitation index (SPI) forecasts, which is commonly used for drought management, the forecasts are skillful well into week 3. This extension in predictability horizon is attributed to the characteristic of accumulated precipitation, which is less sensitive to differences in timing of precipitating systems. The enhanced predictability of SPI enhances the utility of extended range forecasts for monthly drought forecasts. We discuss the practical applicability of these findings in the context of the new Swiss drought early warning and monitoring platform, planned for operations in 2025. Leveraging the enhanced predictability of SPI, this platform stands to benefit from our research outcomes, providing stakeholders with tools for proactive drought management and response strategies. 
Examining Turbulent Flow Anisotropy: Insights from Simplified Variance Budget Analyses
Authors: Stiperski Ivana , Katul Gabriel , Calaf Marc
Published: March 2024

Anisotropy fundamentally defines the nature of turbulent flows in natural environments, engineering, and technology.  At large scales, turbulence rarely attains an energy state that is equipartitioned between the three velocity components or a state where turbulent stresses disappear. This deviation from isotropy underscores turbulence's essential role in promoting momentum transfer.In canonical boundary layers, turbulence anisotropy emerges primarily from two distinct mechanisms: streamwise energy injections through shear forces and the vertical modulation of turbulent kinetic energy by buoyancy, acting either as a source (unstable stratification) or sink (stable stratification) of turbulence kinetic energy. Close to a solid surface turbulence additionally experiences wall blocking, limiting the energy in the wall-normal direction. Furthermore, in complex terrain, a multitude of factors intricately modify the turbulence anisotropy, thus altering the applicability of traditional similarity scaling.Here, we use simplified Reynolds stress budgets to examine how stratification influences the normal stress components across a comprehensive range of measurement datasets from canonical to highly complex terrain. This reduced set of budget equations assume a balance between shear and buoyancy production and dissipation, and model the return to isotropy using a linear Rotta scheme adjusted by the isotropization of the production. This model provides expressions for normalized velocity variances as function of Richardson number, highlighting the change of anisotropy as stratification becomes progressively more dominant. In canonical terrain, the model is shown to capture the dependence of energy anisotropy on Richardson number away from the surface (heights above 60m), however, it fails in predicting energy anisotropy close to the surface. Furthermore, the increase of terrain complexity leads to a decoupling of the dependence of anisotropy and Richardson number not predicted by the model, and shows a consistent decrease of the contribution of streamwise  velocity variance and increase of spanwise velocity variance to the total TKE budget. Finally, a progressively more important wind turning with height with terrain complexity in neutral stratification causes near-surface turbulence to be more anisotropic over complex than over canonical terrain. Our findings outline the nuanced role of terrain in shaping turbulence anisotropy, providing avenues for enhanced turbulence modeling and highlighting limitations of conventional approaches in complex environments.
Stream Cold Water Patches identification and characterisation: acquisition and analysis approaches using Uncrewed Aerial Systems (UASs)-based imagery
Authors: Casas-Mulet Roser , Kuhn Johannes , Pander Joachim , Geist Juergen
Published: March 2024

Stream cold water patches (CWPs) play an increasingly crucial role in the persistence of cold-adapted biological communities and the resilience of river ecosystems, particularly in the context of global warming. Predicting the spatial distribution of CWPs is key to understanding their drivers and informing river management strategies targeting ecosystem resilience. Uncrewed Aerial Systems (UAS)-based Thermal Infra-Red (TIR) imagery technologies provide a novel tool to identify and thermally quantify CWPs at large spatial scales. When used in conjunction with optical (RGB) imagery, CWPs physical attributes and their surrounding riverscape can be characterised, allowing to assess drivers of potential thermal refugia at multiple spatial scales. However, several critical challenges in UAS-based data acquisition, processing and interpretation must be addressed. They include a requirement of perfect TIR-RGB overlapping during data acquisition to enable the identification and extraction of true water temperature pixels, in-situ stream temperature measurements to enable calibration and validation during post-processing, and the definitions of thermal and areal metric thresholds based on targeted ecological processes to identify, characterise and interpret CWPs distributions. We developed a set of methodological approaches used to address these challenges and obtain reliable CWPs information from UAS-based data as a basis to promote effective management of present and future freshwater ecosystems.
Statistical assessment of temporal aliasing in GRACE/-FO and NGGM induced by hydrometeorological extremes
Authors: Mielke Christian , Springer Anne , Kusche Jürgen
Published: March 2024

Hydrometeorological extreme events, such as heavy rainfall, can cause a rapid increase in local water storage over a short period of time. The duration, magnitude, and area of the event, as well as the runoff of the affected region, determine the life span of these water mass changes. This leads to temporal aliasing, which, along with instrument noise, poses a significant challenge to improving the accuracy and resolution of satellite gravimetry products from GRACE, GRACE Follow-On, and next-generation gravity missions (NGGM). The current Atmospheric Ocean Dealiasing (AOD) products can remove tidal and sub-monthly non-tidal mass variations in the ocean and atmosphere from the level-1 GRACE/-FO data. However, the reanalysis and forecast datasets underlying these AOD products only have a limited temporal and spatial resolution and do not include high-frequency hydrological mass variations and liquid cloud water content of atmospheric mass, that can significantly increase during hydrometeorological extreme events.The research group New Refined Observations of Climate Change from Spaceborne Gravity Missions (NEROGRAV), funded by the German Research Foundation (DFG), aims at improving GRACE/-FO data products by developing new analysis methods and modeling approaches. This includes a revision of existing geophysical background models as well as their spatial-temporal parameterization. Within this research group we investigate how hydrometeorological extreme events are mapping into GRACE/-FO level-1 data. In this study, we provide statistics on events that may affect GRACE/-FO/NGGM observations and are not accounted for in current AOD products. Using a 3D connected component algorithm, we determine the duration, magnitude, and area of these events for multiple test years over the entire GRACE/-FO observation time span from 2002 to 2023. As expected, the majority of hydrometeorological extreme events take place in tropical regions and areas that are frequently impacted by typhoons, hurricanes, and monsoon rains such as Japan, northern India, and around the Gulf of Mexico. Additionally, we found an increasing number of events over Europe that could significantly impact GRACE/-FO/NGGM observations. Overall, the number of events per year more than doubles from the start to the end of the observation period, which is likely due to climate change. We suspect that the GRACE-FO LRI measurement is sensitive to instantaneous precipitation and liquid cloud water content during overfly for a significant number of these extreme events. Hence, we anticipate an increased probability of NGGM observations being affected by such events, particularly in the context of ongoing climate change. Therefore, we recommend that upcoming dealiasing procedures carefully consider these events.
Extraction of recharge in variably saturated subsurface flow models
Authors: Gong Chengcheng , Cook Peter , Therrien René , Brunner Philip
Published: March 2024

Variably saturated subsurface flow models have been widely used in the context of water resources management as they conceptualize and simulate water flow in the unsaturated and saturated zone. By solving the Richards equation and using infiltration flux as an input, these models do not require groundwater recharge. As the models simulate the infiltration dynamics through the unsaturated zone, recharge is expected to be reliably extracted from such kinds of models. In this study, we explore to what extent variably saturated subsurface flow models can actually be used to extract groundwater recharge. In this context, we implement numerous definitions of groundwater recharge in a simple, variably saturated 1D model, extract groundwater recharge for a wide range of infiltration and groundwater dynamics imposed through boundary conditions, and assess the reliability of the extracted values. The results show that the value of recharge cannot be uniquely obtained from such kinds of models. The problem is attributed to the storage dynamics in the capillary fringe above the water table. However, it is important to keep in mind that if a variably saturated subsurface flow model of a project area is available, extracting recharge is superfluous as the model is capable of representing all the relevant flux and dynamics.  Keywords: Variably saturated subsurface flow models; Groundwater recharge; unsaturated zone; Water resources management.Reference: Gong, Chengcheng, Peter G. Cook, René Therrien, Wenke Wang, and Philip Brunner. "On groundwater recharge in variably saturated subsurface flow models." Water Resources Research 59, no. 9 (2023): e2023WR034920.
Using a global aerosol model to interpret satellite-derived aerosol-cloud interactions 
Authors: Kokkola Harri , Irfan Muhammed , Lipponen Antti , Calderon Silvia , Arola Antti
Published: March 2024

Determining the susceptibilities of cloud properties to perturbations in aerosols has been a persisting challenge in climate research. For example, satellite-retrieved susceptibility of cloud droplet number concentration (CDNC) to changes in cloud condensation nuclei (CCN) varies regionally, also having opposite correlations over land and ocean. Over the oceans, the correlation between CCN and CDNC is positive and in many cases, with a proper regression method, the dlogCDNC/dlogCCN exceeds 1. On the other hand, over land, many studies have found a negative correlation. As our preliminary global climate model simulations give qualitatively similar results to satellite retrievals, we have used the model together with reanalysis data of aerosol, meteorological properties, and cloud properties to interpret how other parameters such as cloud activation updrafts and vertical mixing of aerosol affect the satellite derived CCN vs CDNC correlations. In this study, we focus on ocean regions determining how these different atmospheric properties affect the derived slope between CCN and CDNC. Our results indicate that as satellite derived CCN is a columnar value, does not properly represent the true variability of cloud base CCN. Thus, the mixing of aerosol as well as cloud activation updrafts cause biases in the satellite determined CCN vs CDNC correlations.
Validation of satellite hydrological products: which goodness-of-fit to use?
Authors: Salama Suhyb
Published: March 2024

Satellite products of hydrological variables are essential to understanding the spatial and temporal variability of the earth's system of systems, for example, the hydrosphere and its intricate interactions with the biosphere and the atmosphere. Hydrological products from multiple satellites are regularly harmonised to produce long-term synoptic climate data records. The fidelity of these satellite-based climate records forms the backbone to quantify and analyse the variability of the water cycle and the effect of climate change over extended temporal and spatial scales. This fidelity is assessed with statistical metrics that measure the goodness of fit (GoF) between satellite products and in-situ measurements. Commonly used GoF metrics include: the slope and intercept of type-II regression, determination coefficient R2, and difference metrics like bias, root means squared differences, mean absolute differences (MAD) and their relative measures. These metrics do not need to be in harmony, for example, a high R2 value is not necessarily associated with a close-to-unity slope, or a low bias is not ineludibly translated to a low MAD. Presenting these metrics in a table for comparing various retrieval models makes it even more challenging to draw clear conclusions. In part, this confusion could be mitigated by using statistical charts, for example, Taylor or radar diagrams. These diagrams offer the capability to graphically summarise how closely satellite products match the measurements. Nonetheless, there is no unique measure that can be used to describe the GoF. In this essay, we develop a universal methodology with the capability of providing the scientific community with a quantitative and holistic measure of GoF of satellite products. The method ingests statistical validation metrics commonly employed in hydrology or any specific discipline of geoscience, transforms them into unity scalars with the same direction (0 is low and one is high accuracy) and projects them into a unity circle.  The resulting area is then calculated and normalised to the maximum expected area for a percentage GoF measure. As the projection is equiangular, each unique sequence of the employed metrics will give a different answer. With permutation, the GoF values are calculated from all possible sequences. The maximum possible accuracy and the largest probable uncertainty are subsequently derived from the resulting population. This procedure results in a unique GoF that integrates all used validation metrics and provides a collective measure of accuracy. Although it was developed for satellite-derived hydrological products, the proposed method can be applied to any statistical metrics used to measure the goodness of fit between modelled and measured biophysical variables.
How forest age impacts on net primary productivity: insights from future multi-scenarios
Authors: Tian Lei , Tao Yu , Li Mingyang , Simms Joanna
Published: March 2024

Forest net primary productivity (NPP) constitutes a key flux within the terrestrial ecosystem carbon cycle and serves as a significant indicator of the forests carbon sequestration capacity, which is closely related to forest age. Despite its significance, the impact of forest age on NPP is often ignored in future NPP projections. Here, we mapped forest age in Hunan Province at a 30 m resolution utilizing a combination of Landsat time series stack (LTSS), national forest inventory (NFI) data, and the relationships between height and age. Subsequently, NPP was derived from NFI data and the relationships between NPP and age was built for various forest types. Then forest NPP was predicted based on the NPP-age relationships under three future scenarios, assessing the impact of forest age on NPP. Our findings reveal substantial variations in forest NPP in Hunan Province under three future scenarios: under the age-only scenario, NPP peaks in 2041 (133.56 Gg C yr-1), while NPP peaks three years later in 2044 (141.14 Gg C yr-1) under the natural development scenario. The maximum afforestation scenario exhibits the most rapid increase in NPP, with peaking in 2049 (197.95 Gg C yr-1). However, with the aging of the forest, NPP is projected to then decrease by 7.54%, 6.07%, and 7.47% in 2060, and 20.05%, 19.74%, and 28.38% in 2100, respectively, compared to their peaks under the three scenarios. This indicates that forest NPP will continue to decline soon. Optimizing the age structure of forests through selective logging, afforestation and reforestation could mitigate this declining trend in forest NPP. Insights from the future multi-scenarios are expected to provide data to support sustainable forest management and national policy development, which will inform the achievement of carbon neutrality goals by 2060.
Effects of long-term climate responses on ice sheets' commitment to future sea-level rise
Authors: Li Dawei
Published: March 2024

Mass loss from ice sheets under the ongoing anthropogenic warming episode is a major source for sea-level rise. Due to the slow responses of ice sheets to changes in atmospheric and oceanic boundary conditions, ice sheets are projected to undergo further retreat as the climate reaches a new equilibrium, producing a long-term commitment to future sea-level rise that is fulfilled on multi-millennial scale. Future projections of ice sheets beyond 2100 have routinely employed end-of-the-century atmosphere-ocean conditions from climate model output under specified emission scenarios. This approach, however, does not account for long-term responses of the climate system to external forcings. Here we analyze the long-term atmospheric and oceanic responses to a variety of emission scenarios in several climate models and show that polar climates may see substantial changes after the atmospheric CO2 level stabilizes. With a 3-D ice sheet model, we demonstrate that the long-term climate responses are crucial for evaluating ice sheets' commitment to future sea-level rise.
Stochastic shock drift acceleration of electrons: Monte Carlo simulations
Authors: Nyberg Seve , Vainio Rami , Vuorinen Laura , Afanasiev Alexander
Published: March 2024

The presence of energetic electrons in the heliosphere is associated with solar eruptions, but details of the acceleration and transport mechanisms are still unknown. We explore how electrons interact with shock waves under the assumptions of stochastic shock drift acceleration (SSDA). Consideration of the shock wave parameter space, such as shock speed, shock obliquity, shock thickness, and plasma density upstream of the shock, helps determine electron spectra and their highest energies. With suitable simulation parameters, the SSDA model is able to produce an electron beam upstream of the shock wave, a requirement for the type II radio burst seen in radio observations associated with shock waves and particle acceleration.This presentation delves into the results of the presented model in regards to electron acceleration and transport within shock waves, contributing to our understanding of solar and interplanetary phenomena and their practical applications in space weather forecasting.Figure: The one-dimensional stochastic shock drift acceleration Monte Carlo model geometry used to investigate electron acceleration and transport at heliospheric shock waves.  
Development of low-cost soil moisture sensor to capture the response of headwater streams in lower Himalayan region
Authors: Choudhary Deependra , Sen Sumit , Kulkarni Rahul
Published: March 2024

A comprehensive exploration of streamflow dynamics at the watershed scale in non-perennial rivers is an arduous task. In the lower Himalayan region, the presence of numerous intermittent and ephemeral streams contributes to high volume of water for small duration and transports significant amount of sediment to downstream. Fluvial alterations reshape stream geomorphology, triggering flash floods. To map those head water streams, a comprehensive study within the lower Himalayan watershed of area 56.61 km2 has been done by developing the low-cost capacitive soil moisture sensors. This real time monitoring sensor is a microcontroller-based system and an indirect method for indicating the soil moisture content. These sensors have been strategically deployed across three distinct sub-watersheds within the headwater watershed to capture the continuous soil moisture response during the monsoon period in 2023. For analyzing this study, on-field data was collected from automated weather stations (AWS) to obtain rainfall data, which was complemented by the utilization of stage-discharge curves for a more thorough understanding of discharge fluctuation. During 2023 monsoon period 9 rainfall events were recorded and identified as small, medium, and high to get the rainfall- runoff relationship with antecedent moisture condition (AMC). From the analysis different signatures in capacitance value are found to be affected by several factors which include slope, % area, stream order and land cover. These thresholds will aid in accurately mapping streams, and by quantifying discharge capacity, sediment transportation analyses can be facilitated in future. This study will enhance management strategies for sediment transport and ecological health within the high-gradient headwater watersheds. 
Investigating Rainfall-Driven Resonance Frequency Changes in a Natural Rock Formation
Authors: Starke Juliane , Baillet Laurent , Larose Eric , Guillemot Antoine , Audin Laurence
Published: March 2024

Rainfall, temperature variations, and chemical processes are well-known drivers of rock erosion. The impact of rainfall on rocks is not well-understood yet but may impact the mechanical properties (including damage, rigidity, deformation) of the rock. In this study, we exhibit the effect of rainfall events on the resonance frequency of a rock column.Resonance frequencies of structures have been utilized to monitor rock columns due to their sensitivity to changes in the rock apparent rigidity (1). For instance, daily temperature changes induce stress variations in the rock column, resulting in a daily cycle of resonance frequency changes (thermal-acousto-elasticity, 2).This research involves long-term monitoring of the first resonance frequency of a 50 m high limestone cliff covering the Chauvet cave in the Ardèche plateau, SW France, exposed to climatic solicitations including daily solar radiation, air temperature fluctuations, and rain events. The rock column was equipped with seismic and meteorologic stations and monitored continuously during three years.To demonstrate the effect of rainfall events on the mechanical properties of the rock, we calculated the resonance frequency depending only on air temperature and solar radiation, using a simple bivariate linear regression. The regression provides well-fitting results for dry periods but shows larger deviations during most rainy periods. This indicates that rain has an effect on the changes in rock resonance frequency. Identifying and quantifying these changes would be a key factor in understanding the evolution of damage. 1) Bottelin, P., Baillet, L., Larose, E., Jongmans, D., Hantz, D., Brenguier, O., ... & Helmstetter, A. (2017). Monitoring rock reinforcement works with ambient vibrations: La Bourne case study (Vercors, France). Engineering Geology, 226, 136-145.2) Guillemot, A., Baillet, L., Larose, E., & Bottelin, P. (2022). Changes in resonance frequency of rock columns due to thermoelastic effects on a daily scale: observations, modelling and insights to improve monitoring systems. Geophysical Journal International, 231(2), 894-906.
Meander Mechanisms in Changing Subarctic Climate
Authors: Kasvi Elina , Blåfield Linnea , Lintunen Karoliina , Saarinen Aino , Gonzales Inca Carlos
Published: March 2024

In Subarctic regions, warming is projected to surpass the global average, potentially leading to a reduction in spring snowmelt discharges, an earlier occurrence of spring floods, and an increase in the magnitude and frequency of autumn/early winter discharges due to heightened rain and zero-crossing events. Flow peaks during summertime are becoming more prevalent due to increased heavy summer rains. Thus, it is unlikely that climate change would have no impact on the behavior of rivers.
Meandering rivers, with their unique geomorphology and evolution, their dependence on external and internal forces, and their ultimately distinctive and unpredictable development, have been the focus of researchers for decades. Despite numerous attempts, a clear theory on how environmental conditions affect their morphology has not been identified. Recent technological advancements, the availability of earth observation data time series, and increased computing capacity have revealed intriguing new aspects of meandering river evolution and its possible controls in various environments. Climate change has been claimed to impact, for instance, meandering rivers in the Arctic by slowing down their evolution.
This study specifically focuses on meandering rivers in the Subarctic in the context of climate change. The aim is to integrate detailed field-based measurements of meandering processes, earth-observation-based large-scale investigations of Subarctic meander evolution, and hydro-climatological observations to gain new insight into the hydro-climatological controls of Subarctic meandering rivers. The goal is to increase the understanding of Subarctic meandering river systems and their responses to climate change.
Quality makes a difference: a preliminary update of the global continental heat flow dataset
Authors: Fuchs Sven , Norden Ben , Neumann Florian , Balkan-Pazvantoğlu Elif , Elbarbary Samah , Petrunin Alexej , Heat Flow Data Assessment Group Global
Published: March 2024

Recently, the International Heat Flow Commission (IHFC), the Task Force VIII of the International Lithosphere Program (ILP) and a global network of geoscientists have jointly developed new standards for the structure and the quality evaluation of heat flow-density data. Heat-flow data are important for understanding the temperature field at shallow depths to the lithospheric scale and thus are fundamental for geodynamic and tectonic processes as well as for geoenergy applications, like geothermal utilizations. It often builds an essential parameter for analytical or numerical models of subsurface thermal models. Since 2021, the Global Heat Flow Database is undergoing an intensive collaborative assessment considering the new defined standards. The new quality scheme, for the first time, will allow a joint classification of data in terms of (i) numerical uncertainty, (ii) methodological evaluation, and (iii) overriding or perturbing effects. On the example of the Global Heat Flow Database Release 2024, we present for a regional example how the assessment changes the data density and detail of information stored and how the new quality standards effect regional heat flow statistics.
Water mass formation and export from the Filchner-Ronne Ice Shelf
Authors: Janout Markus , van Caspel Mathias , Darelius Elin , Davis Peter , Hattermann Tore , Hoppmann Mario , Kanzow Torsten , Østerhus Svein , Sallée Jean-Baptiste , Steiger Nadine
Published: March 2024

The Filchner-Ronne-Ice Shelf (FRIS) is the earth’s largest ice shelf by volume and its cavity a crucial part of the southern Weddell Sea ocean circulation. In mid-2017, the Filchner Ice Shelf (FIS) cavity experienced a shift towards a stronger circulation and increased outflow of Ice Shelf Water (ISW) into Filchner Trough. The increase was attributed to enhanced sea ice formation and the associated production of High Salinity Shelf Water (HSSW) in the source region north of Ronne Ice Shelf. The corresponding circulation pattern was termed “Ronne-mode”, which contrasts the “Berkner-mode”, characterized by a more locally-enhanced circulation at the northern FIS edge. Here we employ new time series from two drill hole mooring sites underneath FIS, as well as moorings from the Filchner Trough and Filchner Sill, to highlight the spatial and temporal extent of this recent ISW outflow event. Underneath FIS, the “Ronne-mode” overruled the normally-observed seasonality in currents and hydrography, and resulted in northward ISW transport for about two years. The export led to the subsequent filling of Filchner Trough with ISW from 2018 until mid-2020, which then overflowed across the Sill between late 2018 for nearly one year. Our observations provide new insights into the variability of the southern Weddell Sea shelf and FRIS cavity circulation, which is important for the abyssal water mass export and thus for global ocean circulation.