bluuebunny/crossref_metadata_2025 huggingface dataset:
A 3-D Seismic Tomographic Study of Spreading Structures and Smooth Seafloor Generated by Detachment Faulting – the Ultra-Slow Spreading Southwest Indian Ridge at 64˚30’E
Authors: Robinson Adam , Watremez Louise , Leroy Sylvie , Minshull Timothy , Cannat Mathilde , Corbalán Ana
Published: March 2024

At ultra-slow spreading ridges, with full spreading rates less than ~15-20 mm/yr, spreading is accommodated both by limited, highly spatially and temporally segmented magmatism, and by tectonic extension along large-scale oceanic detachment faults, which cut from the seafloor through into the upper mantle and exhume ultramafic material to the seafloor. Detachment faulting is highly asymmetric and alternates in polarity over time, producing a “flip-flopping” effect of subsequent detachment dips. The resulting seafloor in these regions displays a morphology termed “smooth seafloor” comprising elongate, broad ridges, which have peridotite/serpentinite lithologies distinct from the typical basalt-gabbro layered oceanic crustal structure. We refer to the outer layer, above the mantle, in this case as the “crustal section”.We conducted tomographic travel-time inversion of a 3-D wide-angle seismic dataset acquired over a region of smooth seafloor around 64˚30’E along the Southwest Indian Ridge (SISMOSMOOTH; Cruise MD199), to produce a seismic velocity volume through the crustal section and into the uppermost mantle. The resulting velocities support a non-magmatic origin for the crustal section, up to 100% alteration of originally ultramafic compositions to serpentinite, and a near-constant thickness of ~3.4 km into a transitional Moho zone which overlies the unaltered mantle. Patterns of velocity anomalies are interpreted as changes in the degree of alteration with depth resulting from spatial and temporal variations in fluid-rock interaction, controlled by faulting and tectonic damage processes and progressive porosity infill. The detachment faults show limited along-axis extent and are not simple planar structures at depth, instead mirroring the shapes of the bathymetric ridges they exhume. The boundaries between smooth seafloor and adjacent more magmatic segments are not vertical at depth, suggesting that detachment processes extend laterally at depth beyond their mapped extent seen at the seafloor. Magmatic input is overall highly limited and dominantly takes the form of individual flows forming superficial veneers, but there is one region on the lower part of an exhumed detachment footwall where the magmatic section is up to ~1.5 km thick, which may reflect changes in larger-scale magma segmentation which could contribute to detachment abandonment.
Steady-state dune shapes through the barchan-parabolic transition.
Authors: Alkalla Jeanne , Narteau Clément , Rozier Olivier , Courrech du Pont Sylvain , Vérité Jean
Published: March 2024

In the presence of vegetation, dunes take on specific shapes that can be observed not only on the edges of sandy deserts, but also in coastal areas and arid plains. These vegetated bedforms play a crucial role in preventing desertification and coastal erosion, and are therefore an important social issue in the context of climate change. As for barchans in the absence of vegetation, parabolic dunes can be observed in isolation or in clusters, mainly under unimodal wind regimes in zones of low sediment availability. They are both crescent-shaped, their horns extending in opposite directions on either side of the migrating central body. As both dune types are likely to emerge from each other, the barchan-parabolic transition has been extensively studied, both in the field and using different types of models. By injecting a feedback mechanism between vegetation and sediment transport into ReSCAL (Narteau et al., 2009; Rozier & Narteau, 2014), we propose here a new model for vegetated dunes. From our simulations, we show that parabolic dunes are unstable, systematically increasing or decreasing in size according to the volumes of sediment they deposit upstream in their horns and cannibalise downstream on the vegetated bed they remobilise. Using the same specific boundary conditions over the parameter space of the model, we present the complete diagrams of steady-state dune shape through the barchan-parabolic transition. Between the typical barchan and parabolic shapes, we find that all the diversity of isolated dune forms observed in the field can occur in a steady-state as vegetation stabilises increasingly thick layers of sand. To compensate for an increasing impact of vegetation, the migrating dune body becomes steeper and reverses its curvature so that the lateral sediment fluxes can now provide a positive contribution to aeolian transport in the central layers. Finally, we show that vegetated dunes can undergo smooth hysteretic transitions between steady states, explaining the resilience of parabolic dunes in the field under a wide range of climatic conditions.
Are early warning signals present for climate tipping points detected in CMIP6?  
Authors: Lenton Tim , Ritchie Paul , Boulton Chris
Published: March 2024

Many elements of the climate system are believed to be at risk of tipping in the near future due to ongoing climate change. Abrupt shifts or tipping points have found to be prevalent in several of the latest generation of climate models (CMIP6) under a range of future emission scenarios. However, by observing the time series alone it is notoriously difficult to predict an upcoming tipping point. Therefore, so-called early warning indicators are needed to try to forewarn of an approaching tipping point. Two commonly used early warning signals, designed to detect critical slowing down prior to the tipping point, are to observe an increase in autocorrelation and variance. In this presentation, we assess the reliability and performance of these indicators for a range of tipping points, scenarios and models. In examples of the indicators performing poorly, we consider the potential for system specific indicators.  
Ground Motion Prediction Equations for the Campi Flegrei volcanic area
Authors: Scala Antonio , Cito Pasquale , Strumia Claudio , Scotto di Uccio Francesco , Festa Gaetano , Iervolino Iunio , Zollo Aldo , Convertito Vincenzo , Elia Luca , Emolo Antonio , Bobbio Antonella , Iaccarino Antonio Giovanni
Published: March 2024

Ground Motion Prediction Equations (GMPEs) are semi-empirical relationships commonly used to model ground motion intensity measures, such as peak ground accelerations (PGA) and velocity (PGV) and pseudo-spectral amplitudes (SA) at a specific site, conditional to earthquake parameters such as magnitude, source-site distance, and local site amplification effects. They are used for several seismological and earthquake engineering applications, such as probabilistic seismic hazard and rapid response (ShakeMap) analyses.In the last decade, the very densely populated volcanic area of Campi Flegrei in Southern Italy, has experienced an intense seismic activity, related to the inner-caldera resurgency and ground uplift, with more than eight-thousand recorded events. During the last two years, both the uplift rate and the seismic activity accelerated, leading to the occurrence of about forty events with duration magnitude between 2.5 and 4.2 whose shaking has been well perceived by the population. Some of these earthquakes showed ground motion intensity (i.e., spectral pseudo-acceleration, SA), leading to non-negligible seismic actions on structures at specific natural vibration periods. Nevertheless, even structures located at less than few km from the source did not sustain significant damage.Due to the strong discrepancy between observed and predicted data using literature GMPEs for Campi Flegrei, in this work, ad-hoc GMPEs were calibrated for PGA, PGV and 21 SA at periods T  in the range [0.01s 10s] . Data come from the largest magnitude events (38) occurred in the last two years, and recorded at thirty-four accelerometric and/or velocimetric stations located at epicentral distance Repi < 40 km. The events were re-located with a probabilistic, non-linear approach and the moment magnitude was computed from displacement spectrum amplitudes. Results indicate that the re-calibrated GMPEs expect larger PGA and PGV very close to the source (Repi < 5 km) and a higher attenuation at larger distances with respect to the existing attenuation relations for Italian volcanic areas.The retrieved GMPEs for the Campi Flegrei caldera have been used to map the minimum magnitude of close-by earthquakes expected to exceed code-mandated design (elastic) seismic actions on structures; so-called strong earthquakes. This minimum magnitude is found in the range 4.1-5.1, depending on the ground motion intensity measure, for sites located within or in proximity of the caldera and earthquakes occurring at epicentral distances smaller than 1km.
The impact of anthropogenic activities on the geomorphological evolution of the Taro River over the last 70 years
Authors: Scorpio Vittoria , Cervizzi Alessandra , Pittau Sharon
Published: March 2024

Human pressures, in response to economic development and population growth, have been one of the main drivers of river systems changes especially since the second half of the last century. In the European context, anthropogenic impacts mainly concern with catchment land use changes, in-stream gravel mining, and in-channel works construction. The reconstruction of the past evolutionary trajectories and the temporal analysis of driving factors is considered fundamental to understand present river conditions, to support channel network management and to anticipate future changes.The aim of this study is to investigate the anthropogenic factors that have impacted the geomorphological evolution of the Taro River (Northern Apennines, Italy) over the last 70 years.Traditional methods based on multi-temporal orthophoto (1954, 1976, 1988, 1994 and 2020) analysis in GIS environment were used for studying historical channel changes along a channel segment 90 km long. Analyses of anthropogenic factors that may have influenced changes in the active channel included: (i) analysis of land use changes at the catchment scale, (ii) quantification of gravel mining activities, and (iii) analysis of in-channel work constructions.Results showed that between 1954 and 1976 the Taro River channel width decreased by 39% on average, mainly in response to gravel mining activities, and subsequently to the increase of works into the channel. To the contrary, as a result of mining activities abandonment in the early 1980s, and of the occurrence of an extreme flood event in 1982, an increase of 18% in the active channel width was observed in 1988. The decreases in active channel width in the last 30 years (since the end of the 1980s) were correlated with the increase in forested areas in the catchment and with the increasing degree of stabilization of channel banks.These studies are fundamental to identify management solutions in degraded rivers and to anticipate impacts in such rivers still featuring poorly impacted channel morphologies.
Dynamic simulation of rock-avalanche fragmentation
Authors: Pudasaini Shiva P. , Mergili Martin , Lin Qiwen , Wang Yufeng
Published: March 2024

Fragmentation is a common phenomenon in rock avalanches with complex features. The fragmentation intensity and process determines exceptional spreading and mobility of rock-avalanches in the run-out zone. However, studies focusing on the simulation of these phenomena are still limited and no operational dynamic simulation model including the effects of fragmentation has been proposed yet. By enhancing the mechanically controlled landslide deformation model, we propose a novel, unified dynamic simulation method for rock-avalanche fragmentation during propagation. Our formally derived method relies on the continuum mechanics that is applicable to rock masses of any size. The model includes three important aspects: mechanically controlled rock mass deformation, the momentum loss while the rock-mass fiercely impacts the ground, and the energy transfer during fragmentation resulting in the generation of dispersive lateral pressure. We reveal that the dynamic fragmentation, resulting from the overcoming of the tensile strength of the rock mass by the impact on the ground, leads to spreading, thinning, and run-out of the rock avalanche, and to its hypermobility. The elastic strain energy release caused by fragmentation is an important process. Energy conversion between the front and rear parts of the mass caused by the fragmentation process results in the forward movement of the frontal material and the hindered motion of the rear portion of the rock avalanche. Our new model describes this by amplifying the lateral pressure gradient in the opposite direction: enhanced for the frontal particles and reduced for the rear particles after the fragmentation process. The main principle is the switching between the compressional stress and the tensile stress, and therefore from the controlled deformation to substantial spreading of the frontal part of the mass in the flow direction while backward stretching of the rear part of the rock mass. In principle, observations in the laboratory and field events support our simulation results.
Multi-Sensor Space-Time Data Fusion of Machine Learning Generated Time Series for Wetland Inundation Monitoring
Authors: Abrahamson Jenna , Gray Josh , Schliep Erin
Published: March 2024

The biogeochemistry of wetland ecosystems is driven by the presence and absence of water. Wetlands are known hotspots of methane (CH4) emissions, particularly when inundated. Monitoring short-term, and possibly small-scale changes in inundation is therefore critical to quantifying both local and global CH4 emissions. Despite their importance, these short-term changes have historically been under-reported in efforts to monitor CH4. As sea levels rise and flood events increase, it’s imperative to account for these events to better project CH4 cycle variation in a changing climate. Remote sensing is the only method capable of monitoring these changes over time at scale; however, no current remote sensing product has the spatial and temporal resolutions required to map ephemeral changes in inundation extents accurately. To address this, we developed a method to generate high spatiotemporal resolution inundation maps combining SAR and optical data from Sentinel-1 and Sentinel-2 imagery supplemented with commercial PlanetScope imagery from 2017–2022. This method was evaluated in the Albemarle-Pamlico Peninsula, a coastal wetland region in North Carolina, United States characterized by frequent and variable inundation.Two decision-tree based machine learning algorithms were tested to map inundation extents: a random forest (RF) model and an extreme gradient boosted (XGBoost) model. The models were trained for each sensor based on a suite of spectral signals, terrain-derived features, and precipitation data for each image at the sensor’s native resolution. This work revealed minor differences between machine learning classifiers across the 5 years, with RF accuracies of 94.0%, 98.2%, and 98.6% and XGBoost accuracies of 89.1%, 98.3%, and 97.8% for PlanetScope, Sentinel-2, and Sentinel-1 respectively. The RF classified inundation maps from each sensor were then fused using a hierarchical spatiotemporal random effects model within a probit link function, to generate daily time series of inundation probabilities at 5 m resolution. This approach is unique in that we 1) address the differing sensor resolutions using a statistical change-of-support formulation with observations mapped to process locations, 2) fuse non-Gaussian (binary) responses from machine learning outputs, and 3) model spatial and temporal autocorrelation through spatial basis functions and a first-order autoregressive time series model. Overall, this work produced a novel 5-year inundation dataset, capturing both long-term and ephemeral changes in inundation extents that are critical for quantifying components of the water cycle and their interactions with biogeochemical cycles on Earth.
Examination of Ground Deformation Information in Alpine Terrain - The Potential of EGMS
Authors: Siegmund Robert , Kotzerke Paul , Langenwalter Jürgen , Berns Arnd
Published: March 2024

Alpine terrain – in high and low altitudes - faces changes in stability due to climate change (permafrost and mass movements or landslides), effecting natural conditions and therefore human infrastructure. Those changes are mainly driven by changing atmospheric patterns leading to shifts in the temperature and precipitation regime. In high alpine terrain dwindling permafrost potentially results in an increasing instability. Recently several incidents of rockfalls and massive landslides were reported, e.g. the village of Brienz only narrowly escaped a fatal disaster. Especially low-lying areas or valleys are of special socioeconomic interest forming settlement areas with transport, tourism and human infrastructure. For example, an increasing number of land- and mudslide events along the “Brenner Highway” were reported by the Austrian motorway authority (ASFINAG). The highway and railway line act as a main and highly frequented transport route connecting Innsbruck (Austria) with Bolzano (Italy). Under a changing climate regime more of these incidents are expected in the near future. With the increased dynamics and probability of landslides the risk for human infrastructure and inhabitants of alpine regions could increase.Consequently, the use of continuous and accurate ground deformation information becomes evident. EGMS, as a Pan-European service, provides validated and accurate data since 2021, therefore key information for ground deformation monitoring on a wide area basis. However, the utilisation of EGMS products in alpine terrain is not yet fully addressed due to technical plus natural constraints regarding alpine topography, climate, etc. versus the applied interferometric measurement approach.Our analysis provides an assessment of ground deformation data on a wide area plus detail level in its temporal and spatial context and its applicability to changing permafrost and ground stability conditions. Based on EGMS products the distribution of deformation features is evaluated in correspondence to alpine permafrost index maps. An indication of potential hot spots is modelled by respective active areas and their relation to infrastructure elements and settlements. This includes the integration of auxiliary and reference data.With this approach considerations of the distribution and temporal characteristics of deformation areas, in terms of mean velocities and deformation time series, are deduced together with spatial relations of measurement points to the objects of interest, e.g. settlements, road, railway or touristic infrastructure.Finally, conclusions for a wide area utilisation of EGMS deformation information are drawn including the provision of an assessment of required reference and auxiliary information plus conceptualisation of an adapted and optimised monitoring approach addressing alpine geohazards.
Dry spell frequency and duration analysis using different spell definitions
Authors: Lima Alencar Pedro Henrique , Paton Eva Nora
Published: March 2024

Dry spells, characterized by consecutive days with little to no precipitation, pose significant challenges, particularly in agriculture, and can impact various sectors including health when compounded by high temperatures, increased evaporation rates, or pollution. However, defining the thresholds for what constitutes a significant lack of precipitation or the number of consecutive days to define a notable dry spell remains ambiguous. In this study, we investigate the occurrence of different types of dry spells across Germany using twelve diverse definitions. These definitions encompass not only the conventional criteria of low/no precipitation but also consider associations with other extreme weather conditions occurring simultaneously (such as high temperatures, and potential evapotranspiration) or following the dry spell (like intense precipitation events). Leveraging continuous weather station data spanning the last 50 years, we employ the Mann-Kendall test to analyse seasonal and regional trends in the duration and frequency of these various dry spell events across Germany. Our findings reveal positive trends in both the frequency and duration of dry spells in Germany, notably prominent in the southern regions. These trends are observed in conventional low-precipitation dry spells and compound heat-dry events. Additionally, to facilitate event identification, we have consolidated these diverse dry spell definitions into an R-package called DryER (Dry spell Events in R). 
The seismic structure of the NW Moroccan margin, Gulf of Cadiz, from new high-quality multichannel seismic reflection data
Authors: Foiada Silvia , Neres Marta , Brito Pedro , Gomez de la Peña Laura , Merino Irene , Ranero César
Published: March 2024

The FRAME geophysical cruise, conducted in 2018 onboard the Spanish R/V Sarmiento de Gamboa, acquired new multichannel seismic reflection (MCS) data on the SW Iberia and NW Moroccan margins. MCS data were acquired with a 6 km long solid-state digital streamer Sercel SENTINEL towed at 19 m water depth, and a 3920 c.i. source with two sub-arrays with 20 guns towed at 10 m depth. The system was designed to provide high penetration and map the entire crust and the upper mantle structure and retain enough resolution to image well the stratigraphy.In this work we present a 220 km long seismic line acquired on the NW Moroccan margin, from the shallow continental shelf across the continental slope and extending across the deep abyssal plain of the Gulf of Cadiz. The NW Africa margin was selected because the region was the focus of several geophysical campaigns, and several DSDP drill sites that drilled into the synrift strata.  However, limited modern data has imaged the crustal-scale tectonic structure to unravel the late Triassic - early Jurassic rift history of the region.We applied a seismic processing flow tailored to the attenuation of the multiple energy, signal designature and for the creation of a detailed macro-velocity model to image the lateral changes of the synrift tectonic structure and stratigraphy. The high-quality image of the structure of this rifted margin reveals a complex tectonic structure from the shelf to the deep-water basin where a deep basement containing salt bodies across the entire profile extension. These new results are of high importance for the understanding of the rifting and continent-ocean transition (COT) processes on the northern Central Atlantic and Neothetys domains, as well as for the subsequent compressive deformation processes in the Gulf of Cadiz related to the Africa-Eurasia plate collision.This work was funded by the Portuguese Fundação para a Ciência e a Tecnologia (FCT) I.P./MCTES through national funds through the project LISA (https://doi.org/10.54499/PTDC/CTA-GEF/1666/2020).
The role of meteorological drivers and initial hydrologic conditions on streamflow drought-to-flood transition events
Authors: Muñoz-Castro Eduardo , Anderson Bailey , Astagneau Paul , Janzing Joren , Mendoza Pablo A. , Brunner Manuela I.
Published: March 2024

Extreme hydrometeorological events such as streamflow droughts and floods may have severe impacts on infrastructure, agriculture, water supply, and hydropower generation, as well as social and political systems. Even though such impacts can be enhanced if the two types of events occur consecutively, the occurrence and drivers of drought-to-flood transitions are not well understood. Here, we ask: ‘How do the properties of drought-to-flood transitions change with different meteorological drivers and initial hydrologic conditions?’ To address this question, we configure the PCR-GlobWB hydrological model in a suite of near-natural gauged catchments, included in the quasi-global large sample dataset CARAVAN, that comprise different hydroclimatic conditions and physiographic characteristics. We run numerical experiments to understand the sensitivity of consecutive drought-to-flood properties (e.g., duration, extension, intensity, etc.) to different driver scenarios. Additionally, we perform, for each catchment, a flux-mapping analysis to explore whether different combinations of drivers can lead to a similar catchment response through different combinations of fluxes. Finally, we define clusters of catchments with similar drivers and sensitivities of consecutive hydrological extremes to the different stress tests. Ongoing analyses suggest that the drivers of drought-to-flood transitions vary substantially across catchments.
Forecasting reservoir inflows with Long Short-Term Memory models
Authors: Soncin Laura , Bertini Claudia , van Andel Schalk Jan , Ridolfi Elena , Napolitano Francesco , Russo Fabio , Ramos Sánchez Celia
Published: March 2024

The increased variability of water resources and the escalating water consumption contribute to the risk of stress and water scarcity in reservoirs that are typically designed based on historical conditions. Therefore, it is relevant to provide accurate forecasts of reservoir inflow to optimize sustainable water management as conditions change, especially during extreme events, such as flooding and drought. However, accurate forecasting the inflow is not straightforward, due the uncertainty of the hydrological inputs and the strong non-linearity of the system. Numerous recent studies have employed approaches based on Machine Learning (ML) techniques, such as Artificial Neural Networks (ANN), Long Short-Term Memory (LSTM), and Random Forest (RF), with successful examples of providing skilful site-specific predictions. In particular, LSTM have emerged among the pool of ML models for their performance in simulating rainfall-runoff processes, thanks to their ability to learn long-term dependencies from time series. Here we propose an LSTM-based approach for inflow prediction in the Barrios de Luna reservoir, located in the Spanish part of the Douro River Basin. The reservoir has a dual role, as its water is used for irrigation during dry summer periods, and its storage volume is used to mitigate floods. Therefore, in order to operate the reservoir in the short-term, Barrios de Luna reservoir operators need accurate forecast to support water management decisions in the daily and weekly time horizons. In our work, we explore the potential of a LSTM model to predict inflow in the reservoir at varying lead times, ranging from 1 day up to 4 weeks. Initially, we use as inputs past inflow, precipitation and temperature observations, and then we include meteorological forecasts of precipitation and temperature from ECMWF Extended Range. For the latter experiments, different configurations of the LSTM are tested, i.e. training the model with observations and forecasts together and training the model with observations only and fine tune it with forecasts.Our preliminary results show that precipitation, temperature and inflow observations are all crucial inputs to the LSTM for predicting inflow, and meteorological forecast inputs seem to improve performance for the longer lead-times of one week up to a month.Predictions developed will contribute to the Douro case study of the CLImate INTelligence (CLINT) H2020 project.
Atomic structure of pristine and water-covered microcline (001) – A prerequisite for understanding the ice nucleation mechanism on feldspar mineral dust particles
Authors: Dickbreder Tobias , Sabath Franziska , Reischl Bernhard , Nilsson Rasmus V. E. , Foster Adam S. , Bechstein Ralf , Kühnle Angelika
Published: March 2024

The aggregate state of water in clouds has a fundamental impact on the clouds’ properties such as reflectivity and lifetime. Consequently, it is crucial for the development and improvement of climate models to understand the mechanism of ice nucleation under atmospheric conditions. Most atmospheric ice nucleation is heterogeneous caused by the interaction between water droplets and ice nucleating particles. Under mixed-phase cloud conditions, one of the most important ice nucleating particles are feldspar minerals. Recent scanning electron microscopy studies have shown that ice nucleation on cleavage planes of K-rich feldspars predominantly takes place at step edges and pores (Kiselev, 2017). This has also been confirmed by video and atomic force microscopy on the micrometer scale (Holden, 2019). However, experimental insights into the atomic-scale structure of the most ice-nucleation active K-feldspar microcline are still missing, and, thus, the mechanism behind ice nucleation on feldspar minerals remains elusive. Here, we present high-resolution atomic force microscopy (AFM) data revealing the atomic structure of the microcline (001) surface in its pristine state and in contact with water (Dickbreder, 2024). AFM images of the pristine microcline (001) surface kept under ultrahigh-vacuum conditions, reveal features consistent with a hydroxyl-terminated surface. This finding suggests that water in the residual gas readily reacts with the surface highlighting the high reactivity of the as-cleaved surface. Indeed, corresponding density functional theory calculations confirm a dissociative water adsorption. Three-dimensional AFM measurements performed at the mineral-water interface unravel a layered hydration structure with two features per surface unit cell. Comparison with MD calculations suggest that the structure observed in AFM corresponds to the second hydration layer rather than the first water layer. We are convinced that the combination of structural information of the pristine and water-covered microcline (001) surface will contribute to uncovering the atomic-scale mechanism behind the exceptional ice-nucleation activity of feldspar minerals. References:Atkinson, J. D., Murray, B. J., Woodhouse, M. T., Whale, T. F., Baustian, K. J., Carslaw, K. S., Dobbie, S., O’Sullivan, D., Malkin, T. L., Nature, 498, 355-358, 2013.Dickbreder, T., Sabath, F., Reischl, B., Nilsson, R. V. E., Foster, A., Bechstein, R. and Kühnle, A., Nanoscale, DOI:10.1039/d3nr05585j, 2024.Holden, M. A., Whale, T. F., Tarn, M. D., O’Sullivan, D., Walshaw, R. D., Murray, B. J., Meldrum, F. C., Christenson, H. K., Science Advances, 5, 4316, 2019.Kiselev, A., Bachmann, F., Pedevilla, P., Cox, S. J., Michaelides, A., Gerthsen, D., and Leisner, T., Science, 355, 367–371, 2017.
High-resolution climate reanalyses datasets for hydro-climatic impact studies over Switzerland
Authors: Wood Raul R. , Janzing Joren , van Hamel Amber , Götte Jonas , Schumacher Dominik , Brunner Manuela I.
Published: March 2024

To study and model hydro-climatic extremes (e.g., droughts and floods), high quality, multivariate and spatially consistent meteorological datasets are necessary. In-situ measurements, however, often don`t cover these multivariate data needs, and are variable in space and time. New generations of high-resolution reanalysis products, with continental to global scales, are available that offer a wide range of internally consistent land surface variables. However, it is yet unclear which of these datasets are most suitable for hydro-climatic impact studies, e.g., to assess the spatiotemporal connectedness of floods and droughts, or to quantify the multivariate meteorological drivers of these extremes. Here, we present a comparison of multiple high-resolution reanalysis datasets (i.e., ERA5(-land), CERRA(-land) and CHELSA-v2) with a gridded observational product from MeteoSwiss. We compare various climatological statistics of precipitation and temperature, such as differences in the mean and the tails of the distribution, as well as the consistency of temporal trends and interannual variability. We further analyze differences in selected univariate and multivariate climate indicators, such as the annual maximum 1–5-day precipitation, the number of dry/wet days, or the fraction of solid/liquid precipitation. Lastly, we present the spatiotemporal consistency of several observed hydro-climatological extreme events, including the drought in 2018 and the floods in 2005 over Switzerland.For most of the reanalysis products the analysis shows a clear elevational dependence in the biases, i.e., increasing with elevation, compared to the gridded observational dataset. The regional reanalysis product CERRA(-land) can overall reduce the biases in the general climatological statistics (e.g., means, tails of the distribution), but shows inconsistencies when moving to the event scale. It for example shows inconsistencies in the temporal evolution and severity of the 2018 drought in Switzerland, whereas the other reanalysis products are more consistent. This presentation gives a comprehensive overview of the differences in the current state-of-the-art reanalysis datasets over the complex terrain of Switzerland.
Modeling Groundwater Resource in Northern France Amidst Rising Anthropogenic Pressure and Climate Change
Authors: Audigane Pascal , Picot-Colbeaux Géraldine , Aissat Ryma , Buscarlet Etienne , Amraoui Nadia ,   URBEAU, CALL and AMEVA SOMME Project Teams
Published: March 2024

We present a panel of numerical modeling studies aimed to improve groundwater management resources for different contexts in the Northern part of France (the 'Hauts-de-France' Region). The objective is to demonstrate the capacities and limitations of modeling tools in reproducing observed data and providing predictions on the groundwater evolution under increasing anthropic pressures and climate change. Numerical models are developed in 3D at the regional scale to evaluate various scenarios of groundwater management, considering several types of anthropic or natural constraints such as pumping for irrigation, drinking water and/or industrial use, land use evolution, and modifications in precipitation and/or evapotranspiration due to climate change.In the three case studies presented, groundwater models are developed using BRGM’s 3D volume finite numerical tool MARTHE. The first case aims to characterize groundwater dynamics to identify the risks of flooding in the sewerage network of the urban communities of Lens-Liévin. The second case explores the role of land use in groundwater modeling for the sustainable management of the Lille Metropolitan Area. The third case evaluates the impact of climate change on the groundwater resource of the Somme River watershed.Limitations and capacities to assess such complex hydrogeological systems are discussed, particularly concerning the uncertainty in the simulated results, the CPU time and space resolution constraints necessary for a meaningful calibration of observed data.
Optimized 3D rainfall thresholds: false alarms reduction and multi-source validation
Authors: Segoni Samuele , Nocentini Nicola , Medici Camilla , Barbadori Francesco , Gatto Alessio , Franceschini Rachele , Del Soldato Matteo , Rosi Ascanio
Published: March 2024

A regional-scale landslide forecasting model based on rainfall thresholds was optimized for operational early warning. In particular, we addressed two main issues that usually hinder the operational implementation of this kind of models: (i) the excessive number of false alarms, resulting in civil protection system activation without any real need, and (ii) the validation procedure, usually performed over periods too short to guarantee model reliability.To overcome these limitations, several techniques for reducing the number of false alarms were applied in this study, and a multiple validation phase was conducted using data from different sources. An intensity-duration threshold system for each of the five alert zones composing the Liguria region (Italy) was identified using a semiautomatic procedure called MaCumBA, considering three levels of criticality: low, moderate, and high. The thresholds were developed using a landslide inventory collected from online newspapers by a data mining technique called SECaGN. This method was chosen to account for only those events that echo on the Internet and therefore impact society, ignoring landslides occurred in remote areas, not of interest for civil protection intervention and resulting in false alarms. A calibration phase was performed to minimize the impact of false alarms, allowing at least one false alarm per year over the moderate criticality level. A novel datset containing only very severe disasters that required national-level emergencies was used to calibrate the high criticality threshold. In addition, we applied an innovative approach to include an antecedent rainfall indicator as third variable. The threshold is thus not represented by a traditional line in a 2D spce, but by a plane in a 3D space.This approach allowed for a consistent reduction in false alarms. The results were validated through an independent landslide inventory and were compared with (i) the alert issued by the regional civil protection agency to observe the improvements achieved with the proposed model and to evaluate to what extent the proposed model is consistent with the assessments of the civil protection and (ii) a dataset of the national states of emergency to verify the suitability of the developed thresholds for alerting citizens. The 3D thresholds showed high predictive capabilities, confirming their suitability for implementation in an operational landslide early warning system.
Glyoxal Yields from Selected Hydrocarbon Oxidations
Authors: McConnell Danny , Boustead Graham , Heard Dwayne , Hutchinson Moira , Stone Daniel , Seakins Paul , Warman William
Published: March 2024

Glyoxal is a second generation product of atmospheric volatile organic compound (VOC) oxidation with both biogenic and anthropogenic compounds being major sources. Measurements of glyoxal provide information on the mechanism of precursor oxidations. This can include information on site specific OH abstraction reactions and branching ratios of peroxy and alkoxy reactions. Glyoxal’s low vapour pressure means that glyoxal is relevant in the formation and growth of secondary organic aerosols, impacting human health and climate. Due to glyoxal’s strong and distinct UV absorption spectrum, measurements of atmospheric glyoxal concentrations via satellite are possible allowing spatial distributions on global and regional scales. Ratios of formaldehyde and glyoxal formation vary widely across different compound oxidation pathways, hence satellite measurements of formaldehyde and glyoxal can give information of initial VOC distributions. This presentation reports glyoxal yields from various OH initiated VOC oxidation processes including: ethene, ethanal, and glycolaldehyde.Experiments were carried out in the HIRAC chamber with direct detection of glyoxal via laser induced phosphorescence. Precursors and stable intermediates were tracked with PTR-MS or FTIR instruments, concentrations of relevant radicals were measured using FAGE or ROxLIF and O3 and NOx via commercial analysers. Preliminary results show glyoxal yields from ethene, ethanal and glycolaldehyde as (0.60 ± 0.07)%, (0.10 ± 0.05)% and (10 ± 1)% respectively.The implications of these glyoxal measurements on VOC oxidation mechanisms and observed atmospheric glyoxal concentrations will be discussed.
Compounding effect of fire history and freeze thaw cycles on ecosystem resilience in northern temperate peatlands
Authors: Heffernan Liam , Peacock Michael , Mehrshad Maliheh , Papadopoulou Sofia , Robroek Bjorn J.M. , Davidson Scott J.
Published: March 2024

Rising air temperatures are leading to both an increase in frequency of freeze-thaw cycles (FTCs) during the winter months, and increased fire frequency and severity during the growing season in northern temperate peatlands. Both FTCs and fires have been shown to impact plant and microbial community composition, nutrient availability, and plant-microbe interactions. Ultimately such changes may affect carbon cycling in peatlands. While examples from the vegetation are numerous, no study has assessed the resilience of peatland microbial communities and carbon cycling to the combined disturbance effect of fire and FTCs. The objectives of this study were to (a) determine how peatland microbial community structure and activity are affected following fire, and (b) assess if the impact of FTCs on peatland microbial communities and soil carbon stores is affected by fire history. To address these objectives, we conducted an FTC and incubation experiment using surface peat (2 – 15 cm) from a pristine peatland and nearby peatland that burned in 2006 located in southern Sweden. Peat from both sites was exposed to 15 FTCs, with each FTC consisting of 18 hours at -20 °C followed by 6 hours at +20 °C. Following the termination of the FTCs we incubated the peat at +20 °C for 40 days, measuring peat respiration as the change in headspace greenhouse gases throughout. We measured peat pore water chemistry, hydrolytic enzyme kinetics, and microbial community assembly using metagenomics before and after the FTCs and incubation. Extracellular enzyme kinetics and pore water chemistry data suggest a legacy effect of the fire, whereby the pristine site exhibits greater enzyme degradation and greater lability of dissolved organic matter before and after FTCs. We also saw greater rates of respiration in peat from the pristine site. We found that FTCs in fire affected peat caused an increase of dissolved organic carbon and aromatic compounds in peat pore water, leading to a reduction in extracellular enzyme and respiration rates. We conclude that while FTCs have the potential to disrupt the stability of peatlands, the legacy of fire exerts a greater constrains on biogeochemical processes. This project highlights that growing season disturbances may have a longer lasting impact on peatland resilience.
Regime-shifts in ice-shelf melt could trigger irreversible ice loss from the Antarctic Ice Sheet
Authors: Hill Emily , Gudmundsson G. Hilmar , Chandler David
Published: March 2024

Changes in ocean conditions surrounding the Antarctic ice sheet, and the impact on melt rates beneath buttressing ice shelves, is one of the largest sources of uncertainty in future ice loss projections. If conditions were to suddenly undergo a regime-shift from cold to warm, melt rates could increase drastically and trigger large and potentially irreversible changes in the interior of the ice sheet. Here, we take an ensemble of ocean-circulation model melt rates as input to an ice-sheet model, to quantify ice loss and the potential for irreversible retreat under such warm conditions. We find that the currently cold-cavity basins of the Filchner-Ronne and Ross ice shelves, in contrast to present-day, could become large contributors to future sea level relevant ice loss. In major basins in West Antarctica, we find high-melt rates can trigger instances of irreversible grounding line retreat, which could only be recovered if arguably unattainable melt rate conditions prevailed over timescales of 100s of years.
Impact-based forecast for critical infrastructure during Tropical Cyclones
Authors: Espejo Gutierrez Gabriela , Stalhandske Zélie , Mühlhofer Evelyn , Bresch David , Brönnimann Stefan
Published: March 2024

Critical infrastructures, such as healthcare facilities or roads, play a vital role in society as they provide essential services for the functioning of communities. Disruptions to these infrastructures have far-reaching consequences, affecting public health, safety, security, well-being, and economic activities. Weather extremes, such as tropical cyclones or floods, can lead to widespread failures in lifeline services such as power, communication, transportation, and healthcare. Forecasting the potential impact of weather extremes in the weeks to days before they happen can help increase the preparedness in the areas that might be affected. The emerging field of research on impact-based forecast models is instrumental in this regard, aiding international organizations and governments in making informed decisions, taking early actions, and allocating resources efficiently. This study aims to build upon the pioneering research by developing an impact forecast tool of tropical cyclones on critical infrastructure. While earlier efforts concentrated on estimating the potential affected population, our focus shifts to understanding the impact on critical infrastructure, starting with healthcare facilities, schools and road networks. We present a case study of Tropical Cyclone (TC) Freddy, which hit Mozambique and Madagascar in 2023. We calculate direct impacts using two sets of vulnerability curves for structural damage and another based on the Saffir-Simpson scale to ensure global applicability when needed. To better understand the significance of these impacts, we further assess their indirect impacts on the population. Additionally, to ensure the utility of this tool for international organizations, we exchange with stakeholders from these entities.
Correlation of Land Surface Temperature and air temperature with albedo in Maritime Antarctica using MODIS and in situ data.
Authors: Corbea-Pérez Alejandro , Recondo Carmen , Calleja Javier F.
Published: March 2024

In this work, we analyze the relationship between albedo and temperature using albedo and Land Surface Temperature (LST) MODIS collection 6 (C6) and in situ data at Livingston Island, Maritime Antarctica. It is known that the relationship between temperature and albedo could have an important impact on global climate models, especially in places where permafrost distribution is complex, as in the South Shetland Islands (SSI) archipelago. Our results show that LST is not well correlated with albedo, which is consistent with the fact that air temperature (Ta) and surface temperature (Ts) do not separately explain the albedo drop, as previous work in the study area has shown. The best agreement was obtained between Aqua and Terra LST and in situ albedo, while the comparison between albedo MODIS and LST yields the worst results, which could be due to the difference in pixel size of MODIS albedo and LST products (500 m and 1000 m, respectively). However, for Ta versus albedo for all data, the decreasing slope of the fit suggests that higher temperatures are associated with lower snow albedo values. This reaffirms the idea that in polar areas, due to their characteristics, the decrease in snow albedo depends not only or mainly on temperature, but also on multiple factors such as the evolution of snow grain size and precipitation rates, among others. 
Quantifying the Influence of Supersonic Aviation Emissions on Global Surface Air Quality
Authors: Oh Lucas , Eastham Sebastian , Barrett Steven
Published: March 2024

Studies of supersonic aviation to date have focused on the potential for stratospheric ozone depletion and climate change, due to the high altitude release of both nitrogen oxides (NOx) and water vapor. However, the impact of these high-altitude emissions on surface air quality is underexplored. We quantify the effects of emissions from a total of 35 compartments, dividing the altitude range from 8 to 22 km into 2 km intervals across nine compartments, and segmenting latitude into five compartments without differentiating by longitude. Using global atmospheric chemistry-transport modeling, 1 Tg of NOx emitted at 20-22 km, a typical cruising altitude for a supersonic aircraft, and 30-60 N° results in an addition 0.39 Gg of surface PM2.5. This is 8.4 times greater than the change in surface PM2.5 resulting from 1 Tg of NOx emitted at subsonic altitudes (8-10 km). We also find that NOx emitted at typical supersonic cruise altitudes results in a decrease in surface ozone, compared to an increase when NOx is emitted at subsonic cruise altitudes. Emissions of sulfur oxides (SOx) also cause qualitatively different impacts on surface air quality, again magnified when emitted at higher altitudes. We also assess the mechanism of why these changes occur, providing a comprehensive understanding of the high-altitude emissions impact on surface air quality. This research is not only applicable to policy-making decisions regarding supersonic aviation but also indicates the need for additional research into the global air quality impacts of other high altitude emissions such as those from launch vehicles.