bluuebunny/crossref_metadata_2025 huggingface dataset:
Monitoring the cryoseismic activity of the Astrolabe glacier, Terre Adélie, Antarctica
Authors: Le Bris Tifenn , Barruol Guilhem , Le Meur Emmanuel , Gimbert Florent , Zigone Dimitri
Published: February 2023

In coastal Antarctica, outlet glaciers exhibit complex dynamics materialized by intense internal deformation, enhanced basal sliding and strong thermo-mechanical interactions with the ocean. Here we aim to use seismic observations to unravel these various processes and their link with glacier and ocean dynamics. As part of the SEIS-ADELICE project (2020-2024) supported by the French Polar Institute IPEV, in January 2022 we deployed four permanent and six temporary (1 month long) broadband seismic stations on and around the Astrolabe Glacier (Terre Adélie, East Antarctica), as well as four ocean-bottom seismometers at sea near the terminus of the floating tongue. In January 2023 we will be supplementing this setup by a temporary network of 50 seismic nodes above the grounding line of the glacier.
Preliminary detection and classification of seismic events reveals a wide variety of cryo-seismic signals. The most pervasive events correspond to icequakes, are located close to the surface, and exhibit clear tidal modulation. We interpret these events as being generated by the brittle fracturing of ice associated with crevasse opening. We also observe numerous short and similar repetitive events of much lower amplitude that are located at few restricted locations near the ice-bedrock interface. These events are likely produced by basal stick-slip over punctual bedrock asperities. Finally, we observe glacial tremors which could result from hydraulic sources at the ice-bedrock interface, although further analysis is required to confirm this hypothesis.
This preliminary work provides useful grounds for deeper analysis to be done in the future on source characteristics and their more quantitative links with glacier dynamics.
Drought mitigating nature-based solutions: a critical state-of-the-art review at global and regional scales
Authors: Yimer Estifanos Addisu , De Trift Lien , Nossent Jiri , Van Griensven Ann
Published: February 2023

Natural disasters are creating a major collapse in human existence. Among the many, drought is becoming more frequent and intense. Therefore, mitigation/adaptation measures have to be set to reduce the impact. This can be achieved via the application of Nature-based solutions (NBSs). This concept is now gaining more attention than ever but with fewer applications. The primary goal of this review paper is to analyze the different NBSs targeted for drought impact mitigation. The study constitutes the application of NBS at a global, continental and regional scale. Extensive literature was made to assess; NBS type, location, start and ending period of implementation, status, and level of effectiveness, recommendations set by researchers, and insight for future applications.
The comprehensive review revealed that there are only a few scientific publications, hence, grey and non-scientific literature need to be included. Only four papers included a quantitative assessment for evaluating the effectiveness of NBS targeting drought. However, the continental and regional performance of NBS is not mentioned. Therefore, a common effectiveness evaluation framework shall be created to give policymakers a clear view of the different NBS’s. Furthermore, a more collaborative approach, including different stakeholder groups, is recommended, with specific attention to the local communities. In Flanders, most projects are in the pilot project stage. Moreover, the few successfully implemented projects are only very local and have a long realization time which the earlier limits to acquire visible impact at a larger scale. Finally, the loss of wetlands at a global scale and in Flanders (70% are lost), increases the vulnerability of catchments to drought. Therefore, future research should increase the evidence base and implementation of NBS, such as wetlands, in Flanders.
The Dutch heat wave of July 2019 in a warmer world: How much hotter could it get?
Authors: de Vries Hylke , Lenderink Geert , van Meijgaard Erik , de Rooij Wim , van Ulft Bert
Published: February 2023

Summertime heat waves are extreme meteorological events with a high impact. Three defining aspects are their intensity, duration and spatial extent. All three will change for the worse in a warming world. We illustrate how these changes could play out for the heat wave that produced the hottest day to date in the Netherlands (40.7◦C, Gilze-Rijen 25 July 2019, a record-shattering event of more than 2 degrees). This is done using a chain of hydrostatic and non-hydrostatic regional climate models of increasing horizontal resolution (12km-2.5km-500m-150m) in combination with the Pseudo Global Warming (PGW) approach. Various scenarios are explored using an ensemble approach to examine robustness. Results indicate that if the 2019 July heat wave were to occur in a +2K warmer world: (i) temperatures would likely reach 45◦C in many places; (ii) the cumulative heat-wave intensity sum would double; (iii) the time to “cool off” in between heat waves would reduce to a level where the total number of days spent in heat waves roughly equals the number of cool days (Tx<25◦C); (iv) the area where the 40◦C threshold is passed will increase strongly; (v) the heat wave will last longer as a simple consequence of the higher temperatures (i.e., an earlier start and a later end). Further persistence increases occur if large-scale circulation changes are supportive; (vi) the temperature response is between 1.5-2 degree per degree global warming, with higher values occurring in scenarios with a stronger future drying. (vii) Finally, during heat waves cities become ‘islands of heat’ where the daily maximum temperatures and the night-time minima are 1-5◦C higher than in nearby more rural areas. A first impression of these differences is obtained from experimental simulations with the convection permitting model HCLIM43 in ultra-high ‘resolution-of-the-future’ mode (500-150m).
Quantifying emission dynamics of coal mine ventilation shafts with a stationary hyperspectral camera
Authors: Knapp Marvin , Scheidweiler Leon , Külheim Felix , Kleinschek Ralph , Necki Jaroslaw , Jagoda Pawel , Butz Andre
Published: February 2023

The global warming potential of methane on a 20-year scale is 80 times larger than that of carbon dioxide. Therefore reducing anthropogenic methane emissions can mitigate greenhouse gas-induced atmospheric warming in the short term. Thus, source attribution and budgeting of methane emissions have received particular attention in recent years. Coal mining activities were found to be accountable for approximately one-tenth of anthropogenic methane emissions. Observations of point sources (like coal mine ventilation shafts) by plume imagery from aircraft of satellites are emerging as a powerful and reliable tool for emission estimates. Yet, while these measurements cover large areas in a short time, the instrument revisiting rates do not allow observation of temporal variability of sources.We present the results of a case study on source dynamics of coal mine ventilation shafts conducted in the Upper Silesian Coal Basin (USCB), Poland, in June 2022. We deployed a HySpex SWIR-384 hyperspectral camera at 1 km distance to a coal mine ventilation shaft. The camera repeatedly observed blue-sky scattered sunlight above the shaft in the shortwave infrared spectral range, taking approximately 1 minute per image. We detect methane plumes reliably using an adapted matched filter algorithm in the 2.3 μm absorption band. Co-located wind-lidar measurements allow us to estimate source emissions rates by the integrated mass enhancement (IME) method. Thereby, we produce several hundred emission estimates per day based on plume imagery, with an average uncertainty below 300 kg/h for minutely estimates under favourable measurement conditions. Our case study covers four consecutive days and reveals substantial source dynamics on all observed time scales from minutes to days. A 10-minute running average of the emissions can be a factor of 2 smaller or larger than the daily mean and daily averaged emissions ranged from 1.39 tCH4/h to 4.44 tCH4/h.
Raising dikes and the large-scale implementation of managed realignment are not sufficient to mitigate increasing flood risk along the German Baltic Sea coast
Authors: Kiesel Joshua , Honsel Lars , Lorenz Marvin , Gräwe Ulf , Vafeidis Athanasios
Published: February 2023

Across Europe, the North- and the Baltic Sea coasts are expected to experience the highest increase in extreme sea levels until the end of the century, mostly due to rising sea levels. This increase will have serious implications for coastal flooding and adaptation planning, which is particularly true for Germany. Without adjusted and/or upgraded adaptation, Germany is projected to be among those European countries that suffer largest absolute flood damages in 2100.Here we use a fully validated modelling framework to explore the effectiveness of raised dike crest elevations and managed realignment as a nature-based adaptation option in reducing flood extent and exposed population during a 200-year surge event, also accounting for two sea-level rise scenarios (1 m and 1.5 m). We explore the potential for managed realignment in the study region by introducing a fully automated modelling approach that considers elevation, land use and infrastructure.We find that managed realignment is more effective in reducing the population exposed to coastal flooding compared to increasing dike crest elevations. However, maximum reduction in population exposure amounts to 26 %, suggesting that redesigning existing dikes by managed realignment is not enough for maintaining flood risk at today´s levels. Our results show that the greatest potential for protecting people and property from coastal flooding in the future lies in developing adaptation strategies for those coastal sections, where currently no dikes are present. Here we argue that more landward dike lines, as created by managed realignment, allow for a wider buffer zone between land and sea, and constitute a promising option to complement conventional coastal defense schemes.
Coupled thermo-mechanical growth of multiple fractures in brittle heterogeneous rocks during thermal shock and resulting aperture distributions
Authors: Paluszny Adriana , Suchoy Lior , Saceanu Maria Cristina , Zimmerman Robert W.
Published: February 2023

Understanding the mechanisms that control the development of fractures in complex thermally deformed media, as well as how they interact with smaller-scale and larger-scale heterogeneiies in material properties, is relevant to a number of natural and engineered processes. In this study, we investigate the results of numerical simulations of thermal shock and the resultant fracturing of brittle rock slabs in the context of a fracture growth benchmark. The benchmark, based on multiple laboratory experiments, induces the non-planar formation of multiple fractures due to thermal shock on ceramic mm-scale slabs. The benchmark experiment tracks fracture geometries for a series of shock temperatures and is used to directly validate our numerical approach, which utilises a three-dimensional in-house finite element code to simulate thermo-mechanical deformation. The ensuing damage and spatially variable fracture apertures are quantified, as well as the resulting fracture network patterns. In our approach, fractures are represented as NURBS surfaces, which are discretised using quadrilaterals and triangles. The matrix is discretised using isoparametric tetrahedral and hexahedral elements. We show in our results how thermal shock affects the fracture aperture distributions, and how these aperture distributions depend on the initial heterogeneities in the modelled slab. We discuss how the simulated fracture interactions are self-organising, and compare well to the proposed multi-fracture benchmark. Additionally, we discuss the manner in which geometry, scale, and heterogeneity influence the resulting fracture pattern and aperture distribution. 
Advances in development of OSI geophysical techniques for mountainous environments
Authors: Koivisto Emilia , Gaya-Pique Luis R. , Rowlands Aled , Colbalchini Remi , Toon Samuel , Labak Peter
Published: February 2023

On-site inspection (OSI) is the final verification measure of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). According to paragraphs 69(e), 69(f) and 69(g) of Part II of the Protocol to the CTBT, an OSI may involve the following seismic and non-seismic geophysical techniques to search for, locate and characterize underground anomalies associated with a nuclear explosion: passive seismological monitoring for aftershocks; resonance seismometry and active seismic surveys; magnetic and gravitational field mapping; ground penetrating radar; and electrical conductivity measurements. In this presentation we review recent advances in development of OSI geophysical techniques, with a focus on the application of techniques in challenging mountainous environments. Previously, techniques were primarily tested in relatively flat or gently undulating terrain conditions.Most recent advances in passive seismological monitoring include the upgrade of the telemetry system for data transmission and development of the data processing software to accommodate topographically challenging environments. To assess current OSI geophysical imaging capabilities for the other geophysical techniques and for deep site characterization applications in an integrated manner, an extensive OSI field test was conducted in the Austrian Ybbstaler Alps in September 2022. This was the first OSI field test in a challenging mountainous environment. Therefore, a number of operational, logistical and technical challenges had to be addressed. The implemented OSI geophysical techniques included resonance seismometry (passive seismic imaging) and active seismic surveys, magnetic and gravitational field mapping, as well as electrical conductivity measurements along three profiles over a cave system at 40-350 m depths mimicking underground cavities produced by an underground nuclear explosion. A newly acquired active seismic data recording system was tested for the first time, with the aim to mature OSI methods for active seismic surveys. Prior to this field test active seismic surveys have only been applied in a limited capacity. A recently developed concept of operations for resonance seismometry was also tested. Furthermore, based on the results of the field test, a new OSI workflow for gravitational field mapping is being developed. During the field test, full OSI data workflow for geophysical techniques was implemented using current functionalities within the Geospatial Information Management system for OSI (GIMO).Overall, these recent advances in development of OSI geophysical techniques demonstrate the applicability of the full range of OSI geophysical techniques in mountainous terrain, and results of these projects will be used to further develop the geophysical techniques for challenging environments.
Mesoscale dynamics off the Congo River in the Gulf of Guinea and its impact on the exchange of waters between coastal and open ocean.
Authors: cardot camille , Dadou Isabelle , Napolitano Dante , Aguedjou Micaël , Baudet Florent , Morel Yves , Ngakala Roy , Morvan Guillaume , Alory Gaël , Juanno Julien
Published: February 2023

The aim of this study is to characterize and quantify the mesoscale dynamics off the Congo River in the Gulf of Guinea and evaluate its impact on the exchange of fresh and salty waters between the coastal and open ocean in this area. The study area, centered at the mouth of the Congo River (2°S-10°S and 3°E-13.5°E), is characterized by an intense seasonal freshwater cycle related to rainfall-driven fluvial input. We used a 1/36° resolution NEMO model configuration for the Gulf of Guinea, optimised to improve the realism the Congo River plume. Results from this configuration were validated with observations and we analyzed the year 2016. The Congo River combined with the wind forcing strongly influences the ocean circulation in the area. The river plume is associated with positive sea level height at the river mouth and strong horizontal density gradients. Moreover, the river plume stratifies the surface waters leading to a very shallow mixed layer (<10 m) enhancing the wind forcing on the surface waters. Our analysis of the mesoscale dynamics for the year 2016 reveals several events, especially a dipole, with a lifetime of 40 days for the anticyclone and 70 days for the cyclone. This dipole appears between March and April 2016, when the river discharge is high, winds are weak, and the river plume is located south of the mouth. The anticyclonic structure carries low-salinity water (S≈32.5) from the southward extension of the river plume. Lagrangian analyses confirm that the waters trapped in the mesoscale dipole originate partly from the Congo river plume. To investigate the processes driving the offshore water transport, we analyze the salinity variations in a box encompassing the river plume. The horizontal/vertical advection through its boundaries increase salinity whereas vertical diffusion decreases it. At the boundaries, the role of the mesoscale dynamics accounts for up to 53 % of the total fresh/salty transport, showing the key role of mesoscale dynamics, especially towards the open ocean.
A study of defects on infrasound Wind-Noise-Reduction Systems (WNRS) using in-situ calibration
Authors: Vincent Paul , Kristoffersen Samuel , Le Pichon Alexis , Alcoverro Benoit
Published: February 2023

Infrasound stations, including those of the International Monitoring System (IMS) as part of the Comprehensive Nuclear Test-Ban Treaty Organization (CTBTO), are used to determine the location of infrasound sources (such as earthquakes, volcanoes, explosions etc.). The triangulation of these sources is done by considering the delay of the arrival times of the signal using several detectors at precisely known locations in an array with an aperture of typically a few kilometers. It is, therefore, of great importance that the amplitude and, especially, the phase of the signal at each sensor in the array is precisely known. Although the calibration of microbarometers can be performed in a laboratory setting, it is much more difficult to determine the transfer function of the wind noise reduction systems (WNRS), designed to reduce the wind associated noise. In-situ calibration of these WNRS’s can be performed using a co-located reference sensor, and comparing the response to that of the array sensor (considering only highly coherent signals) to determine the relative response of the WNRS. System defects, such as flooded pipes or blocked inlets, have significant impacts on the response of the WNRS, and are therefore of interest for the infrasound community. Comparisons between models of these defective WNRS’s and experimental results will allow for the characterization of these effects on the measurements and improvements of the models and WNRS designs. The results of these calibration and WNRS defect experiments will be presented, and compared with models.
Children disproportionally exposed to attributable heatwaves at low-latitude low-income countries
Authors: Pietroiusti Rosa , Thiery Wim
Published: February 2023

Heatwaves are increasing in frequency, intensity, and duration, and represent the category of extreme event that is most easily attributable to anthropogenic warming. Yet how the spatiotemporal patterns of attribution outcomes link to population dynamics is still poorly understood.  Here we show that children and young people are already being affected by a disproportionately greater number of attributable heatwaves, especially in the Global South. Using observations, reanalysis, and simulations of temperature changes available through the ISIMIP3b and CMIP6 projects in combination with demographic data, we show that temperature extremes emerge more clearly and consistently from the noise across low-income countries in lower latitudes, which have some of the youngest populations. Our findings have important implications for children and young people seeking redress from climate harms, for example through climate lawsuits.
Landform detection on Mars using image segmentation with a u-net convolutional neural network architecture
Authors: Auer-Welsbach Florian , Windisch Andreas , Nodjoumi Giacomo
Published: February 2023

The detection and classification of landforms on planetary surfaces is a time-consuming task which deeply relies on expert knowledge. Such a process can be partially automated and optimized in a resource-efficient way using image processing algorithms. By classifying the surface into different landforms, such as volcanic craters, asteroid impacts, dunes, and more, several analyses can be performed, for instance the widely used crater counting age estimation method. In addition, by conducting these analyses, information about the characteristics and properties of a planet can be revealed. One of the major challenges for the implementation of these algorithms is to provide a generalized model. In many cases the generalization error tends to be very large and therefore a satisfactory accuracy on the test data set cannot be accomplished. This prevents reliable evaluation of new unseen data. In this work, a multi-class image segmentation algorithm is presented, which is based on a U-net convolutional neural network architecture. U-nets classify each pixel of a given input image and can thus produce segmentation masks for various landforms. Given that enough labeled data is available, such a classifier can replace manual detection and classification, thereby saving resources by providing a fast method for landform detection.
What can we learn from observational data about vegetation resistance to increasing aridity?
Authors: Abel Christin , Berdugo Miguel , Abdi Abdulhakim M. , Tagesson Torbern , Horion Stéphanie , Fensholt Rasmus , Maestre Fernando T.
Published: February 2023

Natural ecosystems are under increasing pressure from environmental changes such as climate change, natural disasters, or anthropogenic disturbances. Prolonged droughts, heat waves and increasing aridity are generally considered major consequences of ongoing global climate change and are expected to produce widespread changes in key ecosystem attributes, functions and dynamics. Drylands are especially vulnerable to potential adverse consequences of climate change. Recent research documented the existence of three major thresholds in aridity associated with distinct changes in multiple ecosystem attributes and a gradual reduction in vegetation productivity when a threshold is crossed. We hypothesise that different environmental conditions such as climate, drought intensity and topography, as well as specific soil and plant related attributes impact the vegetation resistance to disturbances. Here, we define disturbance as a crossing of an aridity threshold and vegetation resistance as the inverse of the magnitude of disturbance, which is measured as a reduction in vegetation productivity when crossing the threshold.We used a generalised linear model on observational data from the BIOCOM (Biotic community attributes and ecosystem functioning: implications for predicting and mitigating global change impacts) and BIODESERT (Biological feedbacks and ecosystem resilience under global change: a new perspective on dryland desertification) databases complemented with remote sensing-based data to test our hypothesis.Generally, a field site’s slope, nitrogen content, soil texture and pH, as well as changes in rainfall are significantly related to the magnitude of disturbance. Preliminary results further suggest that the magnitude of disturbance is negatively related to drought intensity in years prior to crossing a threshold. Interactions of some soil properties with drought intensity may also play an important role in explaining the magnitude of disturbance.
Hydraulic and mechanical behaviour of volcanic soils and implications for evaluating slope stability
Authors: Delvoie Maxime , Delmelle Pierre , Rattez Hadrien , Pereira Jean-Michel , Tang Anh Minh
Published: February 2023

Landslides are more widespread than any other geological events on Earth. Due to their steep topography and contrasted weather conditions, volcanic regions are especially prone to water-triggered landslides. Indeed, examples of volcanic slope failures abound. Regions endowed with volcanic soils are often densely populated and landslides are causing devastating impacts including loss of human lives, damage to critical infrastructure and disruption to livelihoods. There is growing concern that the intensifying effects of climate change on the hydrological cycle – changing the amount and frequency of rainfall and meltwater input – will exacerbate shallow-seated landslide susceptibility. Soil is the weakest material involved in landslide-related disasters, and soil properties are pivotal in determining the susceptibility of a slope to mass movement. Volcanic soils have unique, but hitherto poorly constrained, hydraulic and mechanical properties. Depending on the volcanic parent materials and weathering conditions, these soils can display clay fractions of different mineralogical composition which likely influence their hydraulic and mechanical properties.Our study aims to advance understanding of the relationships between the hydraulic and mechanical properties of volcanic soils. We sampled undisturbed volcanic soils in Tenerife (Spain) and Ecuador characterized by different mineralogies in order to measure their microstructural and hydraulic properties (particle size distribution ; pore size distribution ; hydraulic conductivity ; water retention curve). We also determined the mechanical properties (shear strength) of these soils and quantified the effect of soil water content on these properties conducting triaxial tests at different moisture level. The mineralogical analysis performed reveal clay fractions either enriched in allophanes or halloysites for the different sampled sites. The allophanic soils display large porosities and water retention values, whereas halloysites-rich soils are less efficient to retain water but seem to conduct it faster. Halloysites-rich soils also show higher, but more water content dependent shear strengths. Indeed, maximum shear stresses reached during triaxial tests are largely increased with drying while allophanic soils’ shear strength are less impacted by a decreased water content. This could be explained by the aggregation of allophane particles in clumps during drying, causing a reduction of shear strength offsetting the classic increasing shear strength due to the increased capillary effects. 
A new opportunity to measure snow depth from space: evaluation of retrievals from ICESat-2 using airborne laser-scanning data
Authors: Deschamps-Berger César , Gascoin Simon , Shean David , Besso Hannah , Guiot Ambroise , López Moreno Juan Ignacio
Published: February 2023

The unprecedented precision of the altimetry satellite ICESat-2 and the increasing availability of high-resolution elevation datasets open new opportunities to measure snow depth in the mountains, a critical variable for ecosystems and water resources monitoring. We retrieved snow depth over the upper Tuolumne basin (California, USA) for three years by differencing ICESat-2 ATL06 snow-on elevations and various snow-off elevation sources, including ATL06 and external digital elevation models. The snow presence of each ATL06 segment (i.e. point measurements regularly spaced every 20 m) can be determined from the number of photons returned by the ground surface. Snow depth derived from ATL06 data only (snow-on and snow-off) provided a poor temporal and spatial coverage, limiting its utility. However, using airborne lidar or satellite photogrammetry elevation models as snow-off elevation source yielded an accuracy of ~0.2 m (bias), a precision of ~0.5 m for low slopes and ~1.2 m for steeper areas, compared to eight reference airborne lidar snow depth maps. The snow depth derived from ICESat-2 ATL06 will help address the challenge of measuring the snow depth in unmonitored mountainous areas.
The response of the regional longwave radiation balance and climate system in Europe to an idealized afforestation experiment
Authors: Breil Marcus , Krawczyk Felix , Pinto Joaquim
Published: February 2023

Afforestation is an important mitigation strategy to climate change due to its carbon sequestration potential. Besides this positive biogeochemical effect on global CO2 concentrations, afforestation also affects the regional climate by changing the biogeophysical land surface characteristics. In this study, we investigate the effects of an idealized global CO2 reduction to pre-industrial conditions by a Europe-wide afforestation experiment on the regional longwave radiation balance, starting in the year 1986 from a continent entirely covered with grassland. Results show that the impact of biogeophysical processes on the surface temperatures is much stronger than of biogechemical processes. Furthermore, biogeophysically induced changes of the surface temperatures, atmospheric temperatures and moisture concentrations are as important for the regional greenhouse effect as the global CO2 reduction. While the greenhouse effect is strengthened in winter, it is weakened in summer. On annual total, a Europe-wide afforestation has a regional warming effect, despite reduced CO2 concentrations. Thus, even for an idealized reduction of the global CO2 concentrations to pre-industrial levels, the European climate response to afforestation would still be dominated by its biogeophysical effects.
Application of the ICON-ART model for CO2 fluxes estimation in the city of Zurich
Authors: Ponomarev Nikolai , Steiner Michael , Koene Erik , Constantin Lionel , Rubli Pascal , Emmenegger Lukas , Brunner Dominik
Published: February 2023

Switzerland like many other countries has set ambitious goals to reach net zero CO2 emissions by 2050. The city of Zurich has committed to an even more ambitious goal of becoming climate neutral by 2040. Recent developments in atmospheric observations and inverse modelling, including the results of the European infrastructure project ICOS, have already laid down the foundations for estimating emissions on national and continental scales. At urban scales, however, only few emission estimation studies have been conducted so far, and it is still an open question, which observational and modeling approaches are best suited and to what level of accuracy they are able to quantify the emissions of a city. The project ICOS-Cities/PAUL aims to answer these questions by evaluating different monitoring approaches in three European pilot cities. One of these cities is Zurich, where a street-level network of about 93 low-cost sensors at 60 locations is combined with a network of 21 mid-cost sensors, located mainly on roof-tops, and high-precision instruments at 3 background sites.Our goal is to estimate the CO2 emissions of Zurich by combining the observations from the mid-cost and high-precision instruments with the state-of-the-art atmospheric transport model ICON-ART. To this end, numerical experiments were conducted for two offline-nested domains, a European domain at ~6.6 km resolution and a second domain centered over the city of Zurich with a much higher resolution of ~0.6 km to represent the main topographic features of the urban area. Anthropogenic emission inputs were produced by merging three different inventories: the TNOGHGco inventory for areas outside Switzerland, a Swiss national inventory at 100 m resolution, and a detailed inventory of point, line and area sources produced by the city of Zurich. The biogenic fluxes of CO2 were computed online using the Vegetation Photosynthesis and Respiration Model (VPRM) integrated into ICON-ART.Here we present a first analysis of comparisons between model simulations and CO2 observations inside and surrounding the city. This allows us to better understand the capabilities and weaknesses of the model at urban scales as well as to design optimal strategies for setting up an inversion framework.  A particular focus is placed on biospheric CO2 and on how much it contributes to variability within the city in comparison with anthropogenic CO2. The next steps will include the use of the CTDAS (The CarbonTracker Data Assimilation Shell) assimilation system in order to obtain information on CO2 fluxes in the urban and suburban areas of Zurich and to apply the model system also to the city of Paris. During this work, we strive to develop approaches which can then be shared and applied by researchers to other cities around the world.
Tracing the origin of imported carbon and nitrogen reserves: remobilization during spring leaf expansion and recovery following defoliation
Authors: Wiley Erin , Hart Ashley , Landhäusser Simon
Published: February 2023

Woody plants rely on the remobilization of carbon (C) and nitrogen (N) reserves to support growth and survival when resource demand exceeds supply at seasonally predictable times like spring leaf flush and following unpredictable disturbances like defoliation. Despite their importance, we still have a poor understanding of how reserve remobilization is regulated and whether remobilization and the allocation of mobilized reserves is constrained by distance between source and sink tissues. This leads to uncertainty in which reserves—and how much—are actually available to support plant functions like leaf growth during spring flush or following defoliation. To better understand the source of remobilized reserves and constraints on their allocation, we used stable isotopes (13C,15N) to label C and N reserve pools in aspen (Populus tremuloides Michx.) saplings, and then grafted unlabeled and labelled stems to labelled and unlabeled root stocks, to create organ-specific labelled reserves.  We then tested for differences in reliance on reserves from different organs between 1) upper and lower leaves 2) early and late leaves and 3) early flush and reflush leaves produced after defoliation.  During spring flush, both C and N reserves were preferentially allocated to sinks nearer the reserve source (i.e the roots), but reliance on C reserves was reduced over time.  Additionally, N appeared to be preferentially remobilized from sources closer to the developing leaves.  However, following defoliation, we found that reflush leaves imported the same proportion of N from the roots as spring flush leaves, but that a lower proportion of C was imported from root reserves. The lower import of reserve C suggests reflush leaves must rely more on their own photosynthetic gains to fuel leaf growth, which may explain the reduced total leaf mass of reflush canopies (31% of initial mass).  The reduced import of reserves occurred even though roots retained significant starch reserves (~5% dry wt), suggesting aspen prioritizes the maintenance of root C reserves at the expense of fast canopy recovery.
Soil salinization risks under current climate and irrigation management in orchards of southern Portugal
Authors: Ramos Tiago , Darouich Hanaa , Oliveira Ana , Farzamian Mohammad , Gonçalves Maria
Published: February 2023

Secondary salinization has long been reported in the Roxo Irrigation District (RID), in southern Portugal, due to use of saline prone irrigation water and the existence of poor structured soils. This study evaluates the soil water and salt budgets in nine commercial orchards located in the RID using the multiple ion chemistry module available in the HYDRUS-1D model during the 2019 and 2020 growing seasons. The study crops were almond, olive, citrus, and pomegranate. The model successfully simulated soil water contents measured in the different fields along two seasons. There was a clear underestimation of the ECe in some fields while simulations of SAR were found to be acceptable. Modeling errors were mostly associated to missing information on fertigation events rather than difficulties in simulating the effect of irrigation water quality on soil quality. The water and salt balances were also computed for the 1979-2020 period. Considering the probability of distribution of salt accumulation during this period, the risk of salt accumulation was very high, except in the citrus areas. The factors influencing the salinity build-up in the study sites were the irrigation strategy, the seasonal irrigation and rainfall depths, the crop growing period, rainfall distribution in the late and non-growing seasons, soil drainage conditions, and irrigation water quality. On the other hand, for current climate conditions and irrigation water quality, the risk of soil salinity levels affecting crop development and yields were found to be minor. Only in two of the study sites, there was the need to promote salt leaching following strategies that differed between locations. This study further aims to promote sustainable irrigation management practices through the better use of soil and water resources in the Alentejo region of southern Portugal.
Towards development of a P- and L-band Tb assimilation framework in the JULES Land Surface Model
Authors: Prajapati Richa , Jayaluxmi Indu , Walker Jeffrey , Mahfouf Jean-François
Published: February 2023

The L-band (1.4 GHz) microwave radiometer provides soil moisture (SM) information limited to around 5 cm soil depth. Deeper information (up to 10 cm) can be obtained using low frequency sensors (P-band: 0.3-1 GHz) with reduced effects of surface roughness and vegetation. The present study explored the capability of P-band and/or L-band singly or in combination, via direct assimilation of brightness temperature (Tb) into the Joint UK Land Environment Simulator (JULES) land surface model. JULES was driven by ERA-5 (ECMWF Reanalysis v5) meteorological forcing data and calibrated model parameters for bare soil. The assimilation framework consists of a radiative transfer model to convert simulated SM to Tb and an Ensemble Kalman Filter to generate an observation corrected SM trajectory. This framework was first validated with an open loop experiment in a synthetic environment over Cora Lynn, Victoria, Australia for the period of 9th May to 14th June, 2019. Assimilation experiments with synthetic observations were then set-up to investigate the sensitivity of i) number of ensembles, ii) observation error, iii) incidence angle, iv) assimilation interval, and iv) frequency bands. The diagnostics (Kalman gain and Jacobians) showed that P band was more sensitive to the deeper layers as compared to L-band. The results also showed substantial improvement in the soil moisture analysis state in both the dry and wet period of the study when both L- and P-band Tbs were assimilated. Further study will include investigating improvement in soil moisture estimates when using real field observations and assimilating Tb with multiple incidence angles.Keywords: Ensemble Kalman filter, Tb assimilation, P-band, JULES Land surface model, Radiative Transfer Model
Recent advancement in water quality indicators for eutrophication in global freshwater lakes
Authors: Suresh Keerthana , Tang Ting , T.H. van Vliet Michelle , F.P. Bierkens Marc , Strokal Maryna , Sorger-Domenigg Florian , Wada Yoshihide
Published: February 2023

Excessive nutrient (nitrogen and phosphorus) loadings to freshwater lakes cause eutrophication, which is a global water quality issue. Anthropogenic activities in lake basins emit nutrients, either as point- (e.g., sewage) or diffuse sources (e.g., agricultural runoff). Their typical impacts on lake water quality include the occurrence of harmful algal blooms, hypoxia and fish kills. These impacts are likely to worsen due to climate change, population growth and economic development. The response of lakes to a change in nutrient inputs depends on their interactions with the climate, land-use, hydrology and socio-economic conditions of a lake basin. These feedback mechanisms, however, are not often included in the eutrophication assessments for lakes. In this study, we present a new causal network of the drivers-pressure-state-impact-response (DPSIR) framework using a total of 58 sub-indicators to characterize all the DPSIR elements and systematically conceptualize the complex interactions of nutrients in freshwater lake basins. The network provides a holistic perspective on nutrient dynamics of multiple indicators and their interactive effects on water quality in lake basins, which is key to improving water quality management. Furthermore, we disentangle the complex eutrophication mechanisms using drivers and pressures, that represent different sources and nutrient pathways. The study highlights coupling of lake systems in water quality modeling frameworks and assessments which is required to understand its impact on water quality from human activities in the basin. The drivers and pressures can be used as proxies to provide meaningful information on nutrient emissions and biogeochemical pathways, that can fill the gap in water quality monitoring data, especially in data scarce regions such as Asia and Africa. These indicators can be used to set realistic water quality targets, and are, therefore, beneficial in long-term policy making and sustainable water quality management.
Cool, but Different: Climate Response to Solar Geo-Engineering Mediated by the AMOC
Authors: Pflüger Daniel , Wieners Claudia , Van Kampenhout Leo
Published: February 2023

Stratospheric Aerosol Injection (SAI) is a contentious geo-engineering proposal to lessen the impacts of global heating via an artificial shade of aerosols. While model results suggest that Earth’s global mean surface temperature (GMST) can indeed be stabilised via SAI, the same does not apply to other parts of the climate system. Especially the fate of a weakening Atlantic Meridional Overturning Circulation (AMOC) under SAI remains unclear.We simulate two SAI deployment scenarios in the Community Earth System Model 2 (CESM2) to study whether a weakened AMOC can be stabilised or recovered. To obtain a strong AMOC response, both scenarios follow a high GHG emission pathway. At the same time, proportionally chosen aerosol injections stabilise the GMST at 1.5K above pre-industrial conditions. The scenarios only differ in their deployment times: aerosol injections start either early (SAI 2020) or late century (SAI 2080).Both SAI scenarios reach the target GMST. However, we find that SAI only mitigates rather than decisively reverses AMOC decline. This relatively mild oceanic response stands in contrast to efficient surface cooling. As a result, both deployment scenarios lead to drastically different climate states. In particular, late-century deployment (SAI 2080) creates a striking temperature gradient from a cold northern to a warm southern hemisphere. This phenomenon potentially stems from impaired meridional heat transport of a much weaker AMOC in SAI 2080 compared to SAI 2020.Our findings mirror recent results on fast negative emission scenarios displaying a similar inter-hemispheric gradient likely connected to slow AMOC recovery. This affirms the need for carefully tailoring SAI deployment strategies should the technology ever be considered as part of the climate action portfolio.
French ACROSS 2022 campaign – First results from CO2/H2O, energy and VOC fluxes measurements at the Rambouillet tower supersite
Authors: Buysse Pauline , Loubet Benjamin , Lafouge Florence , Fortineau Alain , Depuydt Jeremie , Ciuraru Raluca , Esnault Baptiste , Decuq Celine , Herig-Coimbra Pedro-Henrique , Lozano Mathis , Michoud Vincent , Cantrell Christopher
Published: February 2023

Volatile organic compounds (VOC) contribute to the production of pollutants harmful to human health and the environment. Most VOC (90 %) are biogenic. At the European scale, forests account for 55 % of the total VOC emissions, crops 27 %, and grasslands, wetlands and shrubs 18 % (Karl, 2009). These estimates are hampered by lack of data acquired at the ecosystem scale. In this work we measured VOC fluxes above the mixed (oaks and pines) forest of Rambouillet (about 60 km south west of Paris) during the ACROSS 2022 summer campaign. The objectives were (1) to quantify emission and deposition of constitutive VOC, and those occurring in response to heat and drought stresses, and (2) to study VOC formation in the canopy.VOC fluxes were measured at the top of a 40 m-tall tower located at the Rambouillet ACROSS super site. A PTR-Qi-TOF-MS was installed in a shelter at the foot of the tower, and the air sucked through a 50 m heated line by a high-volume pump to ensure short residence time. The PTR-MS was synchronised at 10 Hz with an ultrasonic anemometer to compute fluxes by eddy covariance. Additionally, VOC concentrations were measured along a 5-level profile between 2m and 40m. Preliminary results show emission and deposition of more than 80 VOC compounds. The forest at this location was a strong emitter of monoterpenes, but also of isoprene and sesquiterpenes. A heatwave event has led to a clear decrease in photosynthesis and transpiration during week 28. This period also corresponded to the highest emissions observed during the whole campaign. Deposition of heavy VOC compounds (m/z  > 220) was also observed, possibly corresponding to nitrogen or sulphur containing compounds.
DORIS NRT data: an independent data source for GNSS-based ionospheric maps validation and combination
Authors: Wang Ningbo , Dettmering Denise , Li Zishen , Liu Ang , Schmidt Michael
Published: February 2023

Information on the distribution of free electrons in the Earth's ionosphere is needed for many applications, including the mitigation of single-frequency range delay errors and the monitoring of space weather. Most of the existing ionospheric models are generated using ground-based GNSS measurements, e.g., the Global Ionospheric Maps (GIM) provided by the International GNSS Service (IGS). However, the quality assessment of GIM is presently still an open question. In addition to altimetry Vertical Total Electron Content (VTEC) information over the oceanic regions, limited external data sources are available today to perform a fully independent validation of GNSS-based ionospheric models. The high-quality dual-frequency phase measurements of Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) system provide valuable opportunities to examine the Earth’s ionosphere. In this work, we analyzed the feasibility of using DORIS data to estimate the accuracy of GNSS-generated ionospheric models. To this end, the concept of DORIS differential Slant Total Electron Content (dSTEC) assessment is proposed. Using Jason-3 Near-Real-Time (NRT) DORIS data of the International DORIS Service (IDS), the accuracy of different Real-Time Global Ionospheric Maps (RT-GIM) as well as the IGS combined one is evaluated. The consistency between DORIS and GNSS dSTEC assessments in the quality analysis of RT-GIMs is also checked, and the overall Pearson correlation coefficient reaches 0.81 during the one-year test period. The DORIS dSTEC assessment can be used not only to estimate the accuracy of individual GIMs, but also to determine their weighting within a combination strategy. The performance of DORIS-dSTEC and GNSS-dSTEC combined GIMs is assessed by comparison to Jason-3 VTEC from the mission altimeter. The standard deviations are 4.71 TECu and 4.80 TECu for DORIS-dSTEC and GNSS-dSTEC combined GIMs, indicating the slightly better performance of DORIS-dSTEC combined RT-GIM in Jason-3 VTEC assessment. It was shown that NRT DORIS data can be used to independently validate and combine GNSS-derived ionospheric maps. In the future, it is also envisaged that DORIS data can be directly incorporated into ionosphere modeling. To this end, the provision of NRT data from other DORIS missions is planned (e.g., Sentinel-3).