bluuebunny/crossref_metadata_2025 huggingface dataset:
The Water Gap Risk Index – a novel approach for spatially distributed and sector-specific water scarcity risk calculations in urbanized catchments
Authors: Taner Mehmet Umit , Hendiriks Dimmie , Huesken Lieke , Mulder Niels , Irato Diana Morales , Faneca Sànchez Marta , Aalst Maaike van , Vermooten Sophie
Published: March 2021

An increasing number of mega-cities, such as Cape Town, Lima, and São Paulo, are confronted with increasing droughts as well as an increase in water demand. Inevitably, this leads to increasing pressure on the available water resources and associated risks and economic impact for the water-dependent sectors (eg. drinking water supply, industry, energy production, agriculture, nature) and different user groups within the sectors (eg. low, middle- and high-income households, self-subsistence farmers, large farms). To address these problems and to develop targeted mitigation strategies, risk analyses are required that quantify the impact of water scarcity on the various sectors and users-groups in different parts of the catchment.

Here, we present the Water Gap Risk Index (WGRI) that quantifies water scarcity and its impacts on a variety of economic sectors and user groups. The WGRI provides a normalized score to reflect high spatial and temporal variability typical for urban catchments that apply to different settings and problems. Index calculation involves the combination of unmet water demand and its characteristics with socioeconomic aspects related to vulnerability and exposure. The Water Gap term quantifies water system performance over a defined time period taking into account the frequency, persistence, and severity of unmet water demand.  Vulnerability metrics provide a score for each sector and user-group separately using context-specific vulnerability indicators of each sector and user-group.

In the novel WGRI special attention is paid to the vulnerability of different water user-groups, based on their socio-economic status level (expressed in income, consumption, or other indicators) and respective water use. We consider that 1 liter of water does not have the same utility for different user groups, based on the principle of the diminishing marginal utility curve. As a result, the impact of water scarcity and mitigation measures will also play out differently for these different user groups.

The novel WGRI is being applied in the context of the WaterLOUPE approach[1], to the catchment of Sao Paolo, Lima, and Chennai.

[1] https://doi.org/10.5194/egusphere-egu2020-20505
Lightning bursts observed in the tropical cyclone during the genesis over the western north Pacific
Authors: Kubota Hisayuki , Takahashi Yukihiro , Sato Mitsuteru
Published: March 2021

The accuracy of tropical cyclone (TC) track forecast has been improved year by years, on the other hand, the forecast of tropical cyclone intensity still has a difficulty of improvement. Recently the relationship between lightning activity and tropical cyclone intensity has been investigated. Lightning tends to increase during the rapid intensification of the TC. Therefore, monitoring the lightning activity becomes important for a TC intensity forecast. Lightning observation network are deployed over the western north Pacific by five very long frequency events trigger measurements called V-POTEKA at Palau, Guam, Manila, Okinawa Japan and Serpong Indonesia under the ULAT (Understanding Lightning and Thunderstorm) of SATREPS (Science and Technology Research Partnership for Sustainable Development) in the Philippines.

Tropical storm (TS) Bavi and Maysak were generated over the Philippine Sea on August 2020. We found that lightning activity drastically increased in the TC during the TC genesis stage when the TC reached TS criteria. Numbers of lightning reached the maximum during the life cycle of the TCs. Lightning was concentrated in the convective clouds about 100 to 200 km size. They are located around 400 to 500 km and 100 to 200 km from the TC center respectively and lasted about few hours. We called this phenomenon as “lightning burst”. On the other hand, when TS Haishen and Dolphin were generated over the Philippine Sea in September 2020, they did not observe lightning burst. About half of the TCs observed lightning burst in the Philippine Sea in 2020. We will investigate further what kind of structure occurred during the lightning burst and what kind of mechanism responsible for the lightning burst.
Thunderslide - from rainfall to preliminary landslide mapping: implementing an open data-oriented framework for landscape management authorities
Authors: Crema Stefano , Marchi Lorenzo , Borga Marco , Cavalli Marco
Published: March 2021

Gathering systematic information on the effects of extreme weather events (e.g., flooded areas, shallow landslide and debris flow activations, windthrows) is a fundamental prerequisite for local authorities to put into practice management strategies and establishing early-intervention priorities. The collection of these data is a resource-demanding task requiring huge personnel effort and financial means. Furthermore, events occurring in remote areas with a low chance of intersecting human infrastructure, are rarely detected and mapped accurately, thus leading to incorrect assumptions in relation to both extreme events spatial distribution and especially to the real occurrence probability. The present work aims at tackling some of the above-mentioned issues by providing a framework for obtaining the automatic identification of severe weather events that may have caused important erosional processes or vegetation damage, combined with a quick and preliminary change detection mapping over the identified areas.
The proposed approach leverages the free availability of both high-resolution global scale radar rainfall products and Sentinel-2 multispectral images to identify the areas to be analyzed and to carry out change detection algorithms, respectively. Radar rainfall data are analyzed and areas where high intensity rainfall and/or very important cumulative precipitation has occurred are used as a mask for restricting the subsequent analysis, which, in turn, is based on a multispectral change detection algorithm.
The testing phase of the proposed methodology provided encouraging results:  applications to selected mountain catchments hit by the VAIA storm in northeastern Italy (October 2018) were capable of identifying flooded areas, debris-flow and shallow landslide activations and windthrows with good accuracy and with the ability to distinguish between erosional processes and windthrows.
The described approach can serve as a preliminary step toward detailed post-event surveys, but also as a preliminary “quick and dirty” mapping framework for local authorities especially when resources for ad hoc field surveys are not available.
Such a systematic potential change identification, in combination with regular expert-driven validation, can finally pave the way for a process of self-improvement in detection and classification accuracy: if classified changes are validated, machine-learning algorithms can be trained to learn and improve performance not only in change detection accuracy but also in single-scene classification. 
Future improvements of the described procedure could be finally devised for allowing a continuous operational activity and for maintaining an open-source software implementation.
Physical and numerical modelling of sediment guiding walls in an alpine river
Authors: Siedersleben Jakob , Schuster Marco , Ties Dennis , Zwick Benjamin , Aufleger Markus , Achleitner Stefan
Published: March 2021

The presented work is part of the optimization of the sediment management at the hydroelectric powerplants in Reutte/Höfen in Austria. The weirs of the two powerplants are situated at the alpine river Lech, located about 3 km upstream of the Lechaschau gauge (A=1012.2 km²). Totally five sluice gates and a fixed overflow weir are controlling the upstream reservoir, being subjected to high rates of coarse bed load material. In frame of a coupled approach of physical and numerical modelling, different options to (i) avoid/minimize sediment deposition and (ii) allow improved sediment flushing were tested and optimized. Besides a lowering of energy losses (reduced spilling times) the reduction of depositions downstream close to the turbine outlet were considered.

The physical model covers the hydropower and weir system of both power plants within a stretch of 400m / 150m using a model scale of 1:25. Investigated situations covered periods of reservoir sedimentation, flushing of the reservoir and typical flood flow situations (e.g. HQ1 and an unsteady HQ5 event). For model parametrization, sediment samples to quantify size distribution were taken in the field. Sediment inputs to the model were realized dynamically and were required (due to scaling effects) to exclude cohesive fractions having a minimum particle size of 0.5 mm. The full-area surface measurement of the river bed was made by means of airborne laser bathymetry and echo sounding.

As part of an optimization of the overall sediment management strategy, the focus of the presented research is on the western located runoff power plant Höfen. Via a lateral water intake, a maximum design flow of 15 m³/s is withdrawn causing that the intake structure is subjected to sediment depositions. Within the described scale model (1:25) and a partial scale model (1:15) covering the western side, several management options and configurations of sediment guiding walls were tested. Erosion and deposition as well as the transported material are assessed by 3D laser scanning and permanent monitoring of transported sediment load entering and leaving the scale model.

Complementary, a 2D hydro numerical model using a layer based multi fraction approach for sediment transport is set up for an extended area to simulate the morpho-dynamic behavior. The numerical model covers the whole weir system and 750 m of the upstream part of the Lech. The simulations made were realized at nature scale and allowed to mimic the erosion and deposition pattern obtained within the physical modelling for different tested options. Regardless of a chosen guiding wall setup, the results showed that each one is compromise between sediment defense and the effectiveness of the subsequent flushing processes.
Long-term spatio-temporal seasonal snow cover variability in the Hindu Kush Himalaya
Authors: Naegeli Kathrin , Rietze Nils , Franke Jörg , Stengel Martin , Neuhaus Christoph , Wu Xiaodan , Marin Carlo , Premier Valentina , Schwaizer Gabriele , Wunderle Stefan
Published: March 2021

The Hindu Kush Himalaya (HKH), the worlds ‘water tower’, contains the largest volume of snow and ice outside of the polar ice sheets and is the headwater area of Asia’s largest rivers. Due to the complex topography and its great spatial extent the HKH is characterised by variable temperature and precipitation pattern and thus exhibits large heterogeneity in the presence of seasonal snow cover (SSC). Previous studies usually focused on regional studies of snow cover area percentage or the influence of snow melt on the local hydrological system. Here we present a systematic overview of spatio-temporal SSC variability of the entire HKH region on a climate relevant time scale (four decades).

Our results are based on Advanced Very High Resolution (AVHRR) data, collected onboard the polar orbiting satellites NOAA-7 to -19, providing daily, global imagery at a spatial resolution of 5 km since 1982 up to today. This unique dataset is exceptionally valuable to derive pixel-based SSC information using a Normalised Difference Snow Cover (NDSI) approach including additional thresholds related to topography and land cover, and developed in the frame of ESA CCI+ snow.  Calibrated and geocoded reflectance data and a consistent cloud mask, derived in the ESA CCI cloud project, are used. A temporal gap-filling was applied to mitigate the influence of clouds. Reference snow maps from high-resolution optical satellite data as well as in-situ station data were used to validate the time series.

The dataset allows analysis of the state and trends of SSC at regional and sub-regional level. We thus investigated spatio-temporal evolution and long-term variability of SSC for the entire HKH as well as for 14 hydrological basins. We find large spatial difference in the amount of SSC depending on the regional elevation and precipitation characteristics. Furthermore, we investigate SSC phenology, which is directly linked to climate change and thus of high relevance for seasonal water storage and mountain streamflow. Our analysis indicates a significant decline in snow cover area percentage (SCA %) during warm and dry summer month and a decreasing tendency from high winter through spring to early summer. At the hydrological basin level, no significant long-term trend was detected, however, both western and central basins indicate a decrease in SCA % and generally the latest years are strongly negative. Moreover, we examine SCA % anomalies at the highest available temporal frequency (daily information) and reveal an overall shortening of the SSC occurrence and a general decrease of SSC extent in the HKH region.
Experiments with unsupervised analysis of lacunarity curves of LiDAR point clouds in forested areas
Authors: Kania Adam , Székely Balázs
Published: March 2021

Calculation of lacunarity of voxelized point clouds has been proven to be an effective characterization of the structure of empty spaces in a feature space. The natural and planted forests show various horizontal and mosaic structures in terms of distribution of void spaces; illumination, wind characteristics, predator-prey visibility, and other ecological conditions are influenced by the spatial distribution of features and intercalated volumes.

The lacunarity functions however define a 4-D dataset even if the input voxels are considered as layers of pixels. Furthermore, the large orders of magnitudes that the lacunarity values may vary in, causes difficulties in the evaluation. To overcome these problems, effective user-friendly methods are required.

The input point cloud is voxelized/rasterized, and the raster data (set of 2D rasters or volumetric 3D raster) are the intermediate preprocessed input data. The calculation of the lacunarity functions is done using sets of defined window sizes and steps (step is a shift of the calculation windows over the raster in x-y direction). The results are available as a set of raster layers that can be viewed and analysed directly: in this project we use an interactive tool to calculate and present results on an interactive map viewer.

As the lacunarity calculation is very time-consuming, special attention has been paid to optimize the computation, speeding up the generation of the output by orders of magnitudes. The intermediate multivariate dataset is then stored for further processing or visualization. Selected raw lacunarity values/curves or extracted components can be used for classification/regression using provided forestry-related reference data. The user can run a number of dimensionality-reduction algorithms to extract significant components of the lacunarity curves (PCA, non-negative factorization, SVD, ICA) and analyse resulting components (overlaid on a raster map). These derivatives of lacunarity values and components are visualized by mapping to RGB channels, applying a color-palette, or rendered using mixtures of colors from multiple-color palettes. The user can also generate a short animated video are generated on-the-fly and can be viewed interactively. A web browser connection is also in development.
Simulation of the transition between Mid Miocene Climate Optimum (17-15 Ma) and Miocene Climate Transition (14 Ma)
Authors: Segalla Diane , Ramstein Gilles , Sepulchre Pierre , Fluteau Frédéric , Colleoni Florence
Published: March 2021

Mid Miocene Climate Optimum (MMCO) is an interesting period. Indeed since Mid Eocene (40 Ma) the large trends of climate evolution are: a large decrease of pCO2 and a drastic cooling. The MMCO appears as a short period when these trends were reversed, during 2 Ma, followed by a new period of cooling. Using the IPSL CM5A2 coupled model, we simulated the MMCO using two different pCO2 values (2.5 PAL and 1.5 PAL) and for the Miocene Climate Transition MCT for which we used a pCO2 value of 1.5 PAL. Superimposed to these very long runs we further simulated sensitivity of these experiments to insolation at the top of the atmosphere for Antarctica ice-sheet. In our referent simulation, the astronomical parameters remained unchanged as present day, whereas we performed new simulations with maximum and minimum insolation at the top of the atmosphere for December, January, February (at 75°S). These series of experiments will be analyzed and compared with available data. Moreover, we will compare our results to other simulations using various OAGCMs. We will emphasize on the consistency between the climate simulated at high latitude and the prescribed ice-sheet reconstruction of Antarctica.
Reappraising the appropriate calculation of the potential temperature
Authors: Spichtinger Peter , Baumgartner Manuel , Weigel Ralf , Plöger Felix , Achatz Ulrich
Published: March 2021

The potential temperature is a widely used quantity in atmospheric science since it corresponds to the entropy and is conserved for adiabatic changes of dry air. As such, it is routinely employed in applications ranging from atmospheric dynamics to transport modeling. The common formula to compute the potential temperature is based on the assumption of a constant specific heat capacity for the dry air, even though the latter is known to vary with temperature.

We re-derive the (dry air) potential temperature for a recent temperature-dependent formulation of the specific heat capacity of dry air. The result is expected to provide values which are much closer at the true entropy value (expressed as a temperature) and hence serves as the reference potential temperature. However, its computation is less straightforward compared to the classical one, motivating the development of efficient approximations. Moreover, similarities and differences are discussed between the newly derived reference potential temperature and the classical one based on a constant specific heat capacity. The new reference shows different values and vertical gradients, in particular in the stratosphere and above. Applications of the new reference potential temperature are discussed in the context of common computations in the atmospheric sciences, including the potential vorticity or diabatic heating rates.
Incentivising peatland restoration and rewetting actions through a result-based EU carbon farming mechanism
Authors: Olesen Asger Strange , Andersen Sarah Pyndt
Published: March 2021

Intact peatland plays an important role for the carbon cycle, climate mitigation and provision of ecosystems services due to their role as a permanent water-locked carbon stock and ongoing sink. However, years of unsustainable land management practices have resulted in degradation of peatlands in the EU and around 220 Mt CO₂ eq. are emitted in the EU per year[1] from peatland drainage alone. New approaches to peatland restoration and rewetting are being explored to ensure effective and efficient climate actions. Learning from and building on already operational sub-national and national result-based payment peatland mechanism and programmes, this study provides recommendations on designing and operating an effective and efficient result-based carbon farming peatland mechanism in the EU. The findings suggest that a results-based carbon farming mechanism offers a promising way to incentivise, e.g. governments, authorities and farmers to develop and implement peatland restoration and rewetting projects. Results-based mechanisms provide new and additional sources of finance to counter high upfront restoration costs, as well as provide an opportunity to valorise GHG emissions from large, geographically confined emission sources based on current carbon credit prices.

[1] Source: Grifswald Mire Centre (2019). https://www.greifswaldmoor.de/files/dokumente/Infopapiere_Briefings/202003_CAP%20Policy%20Brief%20Peatlands%20in%20the%20new%20EU%20Version%204.8.pdf
Predicting energy and carbon fluxes using LSTM networks
Authors: Brenner Claire , Frame Jonathan , Nearing Grey , Schulz Karsten
Published: March 2021

Global land-atmosphere energy and carbon fluxes are key drivers of the Earth’s climate system. Their assessment over a wide range of climates and biomes is therefore essential (i) for a better understanding and characterization of land-atmosphere exchanges and feedbacks and (ii) for examining the effect of climate change on the global water, energy and carbon cycles. 

Large-sample datasets such as the FLUXNET2015 dataset (Pastorello et al., 2020) foster the use of machine learning (ML) techniques as a powerful addition to existing physically-based modelling approaches. Several studies have investigated ML techniques for assessing energy and carbon fluxes, and while across-site variability and the mean seasonal cycle are typically well predicted, deviations from mean seasonal behaviour remains challenging (Tramontana et al., 2016). 

In this study we examine the importance of memory effects for predicting energy and carbon fluxes at half-hourly and daily temporal resolutions. To this end, we train a Long Short-Term Memory (LSTM, Hochreiter and Schmidthuber, 1997), a recurrent neural network with explicit memory, that is particularly suited for time series predictions due to its capability to store information over longer (time) sequences. We train the LSTM on a large number of FLUXNET sites part of the FLUXNET2015 dataset using local meteorological forcings and static site attributes derived from remote sensing and reanalysis data. 

We evaluate model performance out-of-sample (leaving out individual sites) in a 10-fold cross-validation. Additionally, we compare results from the LSTM with results from another ML technique, XGBoost (Chen and Guestrin, 2016), that does not contain system memory. By analysing the differences in model performances of both approaches across various biomes, we investigate under which conditions the inclusion of memory might be beneficial for modelling energy and carbon fluxes.

 

References:

Chen, Tianqi, and Carlos Guestrin. "Xgboost: A scalable tree boosting system." Proceedings of the 22nd acm sigkdd international conference on knowledge discovery and data mining. 2016.

Hochreiter, Sepp, and Jürgen Schmidhuber. "Long short-term memory." Neural computation 9.8 (1997): 1735-1780.

Pastorello, Gilberto, et al. "The FLUXNET2015 dataset and the ONEFlux processing pipeline for eddy covariance data." Scientific data 7.1 (2020): 1-27

Tramontana, Gianluca, et al. "Predicting carbon dioxide and energy fluxes across global   FLUXNET sites with regression algorithms." Biogeosciences 13.14 (2016): 4291-4313.
Possibilities of transdimensional inversion for estimating deep Earth velocity and mantle structure
Authors: Szwillus Wolfgang
Published: March 2021

Commonly, the physical properties of the Earth (e.g., velocity, density) are parameterized as continuous fields. The most popular representation are grids and basis functions like spherical harmonics or splines. In an inversion context it is quite common that not all the parameters are fully constrained by the available inputdata. This relates to the common issues of insufficient resolution, incomplete coverage, and trade-offs due tonon-uniqueness. By applying some form of regularization to the inverse problem, a well-behaved and unique solution can be obtained, but this solution depends on the details of the chosen regularization.

Transdimensional approaches address the regularization problem by using a model representation with a variable number of parameters. The number of parameters is adjusted according to the requirements of the input data using the reversible jump Monte Carlo Markov Chain (rj-MCMC) algorithm. The output is an ensemble of variable resolution models that provides insight into the required model complexity and trade-offbetween parameters.

Here, I present synthetic tests from a joint inversion of satellite gravity gradients and normal modes for the Earth's velocity and density structure. The mantle's seismic velocity and density inside a 2-D spherical annulus are described by a variable number of discrete anomalous volumes, each with a variable size, shape, location and strength of velocity and density anomaly. The discrete anomalies are adjusted using the transdimensional approach in order to fit the gravity and normal mode data. This synthetic example shows promising results, because the synthetic model can recovered reasonably well.
Shedding light on tropospheric H2SO4 production from Criegee intermediates + SO2: a comprehensive laboratory chamber study using the highly instrumented HELIOS platform
Authors: Ren Yangang , McGillen Max , Kukui Alexandre , Daële Veronique , Mellouki Abdelwahid
Published: March 2021

Although the dominant source of H2SO4 in the atmosphere is generally considered to be the reaction of SO2 with OH, it is probable that the rapid reactions of Criegee intermediates (CIs) with SO2 can contribute significantly to the tropospheric H2SO4 budget under certain conditions. CIs are produced from alkene ozonolysis, and the vast quantities of unsaturated biogenic and anthropogenic volatile organic compounds emitted could provide a large and diverse flux of CIs to the atmosphere. There remain several key uncertainties regarding the global importance of CIs towards SO2 oxidation, which are principally related to the ambient concentrations of CIs and the competition between CI reaction with SO2 against the many other bimolecular and unimolecular loss processes. This is especially true of the larger, more complex CIs that are produced from terpene ozonolysis.

We present experimental studies of the ozonolysis of tetramethylethylene, α-pinene and limonene, using the HELIOS chamber. HELIOS is a highly instrumented large-scale outdoor atmospheric simulation chamber and consists of a hemispheric 90 m3 Teflon-foil reactor, which is interfaced to a variety of on-line measurements including FTIR, PTR-ToF-MS, FIGAERO-ToF-CIMS, OH/H2SO4-CIMS, Aerolaser HCHO, LOPAP and SMPS, together with several GC-MS/FID and LC-MS instruments and a suite of monitors (NO, NO2, O3). Equipped with this range of instrumentation we are able to conduct alkene ozonolysis under near-ambient conditions, whilst we also have a high coverage of key reactive species in the systems of interest.

From our results, we are able to provide new information regarding kinetic and mechanistic behaviour of several atmospherically important CIs and their reactive intermediates, providing new constraints on the role of CIs on the tropospheric H2SO4 budget.

Keywords: ozonolysis, Criegee Intermediate, sulfur dioxide, sulfuric acid, kinetics
Vulnerability of coastal areas to increased aquifer saturation due to climate change
Authors: Gauvain Alexandre , Abhervé Ronan , de Dreuzy Jean-Raynald , Aquilina Luc , Gresselin Frédéric
Published: March 2021

Like in other relatively flat coastal areas, flooding by aquifer overflow is a recurring problem on the western coast of Normandy (France). Threats are expected to be enhanced by the rise of the sea level and to have critical consequences on the future development and management of the territory. The delineation of the increased saturation areas is a required step to assess the impact of climate change locally. Preliminary models showed that vulnerability does not result only from the sea side but also from the continental side through the modifications of the hydrological regime.

We investigate the processes controlling these coastal flooding phenomena by using hydrogeological models calibrated at large scale with an innovative method reproducing the hydrographic network. Reference study sites selected for their proven sensitivity to flooding have been used to validate the methodology and determine the influence of the different geomorphological configurations frequently encountered along the coastal line.

Hydrogeological models show that the rise of the sea level induces an irregular increase in coastal aquifer saturations extending up to several kilometers inland. Back-littoral channels traditionally used as a large-scale drainage system against high tides limits the propagation of aquifer saturation upstream, provided that channels are not dominantly under maritime influence. High seepage fed by increased recharge occurring in climatic extremes may extend the vulnerable areas and further limit the effectiveness of the drainage system. Local configurations are investigated to categorize the influence of the local geological and geomorphological structures and upscale it at the regional scale.
Enhancing the harmonisation, QA/QC, and application of riverine macroplastic monitoring data
Authors: Hurley Rachel , Olsen Marianne , Pettersen Eidsvoll David , Buenaventura Nina , Økelsrud Asle , Nizzetto Luca , Veiteberg Braaten Hans Fredrik , Lin Yan , Hovland Steindal Eirik , Larssen Thorjørn
Published: March 2021

Several guidelines have been developed that describe methods for analysing riverine macroplastic flows. No single method has emerged as the standard approach for sampling plastic waste in rivers. This reflects the difficulty in establishing a global ‘one size fits all’ approach for river systems: there is significant variability in river morphology, hydrology, and geomorphology across the world and these differences necessitate adaptations of existing methods or the development of new approaches to assess macroplastic flows. In addition, there is a wide range of different potential objectives underpinning the monitoring of riverine macroplastic contamination, including assessments of plastic export, sources, transport, or accumulation. These generate different research questions, which require different solutions, and may necessitate the collection of data in different forms.

Nevertheless, there is an international demand for generating monitoring datasets that are comparable and can be used to create a holistic picture of macroplastic contamination across the globe. For the reasons listed above, harmonisation – through thorough method validation and quality assurance and control (QA/QC) – is likely to be more important than standardisation in this context. Additionally, in some cases there remains a disconnect between the types of data that are produced in monitoring activities and those which are desired by potential end users of the data. It is valuable, therefore, to increase the communicability of datasets and establish a common language for riverine macroplastic contamination. This study undertakes a critical review of existing methodologies for assessing macroplastic flows in river systems and identifies: i) what component of the macroplastic load is measured by each technique; ii) how can these methods be validated; iii) what QA/QC procedures could be implemented to increase the quality, robustness, and harmonisation of monitoring outputs; and iv) how can outputs be tailored to different uses of monitoring data.
3D Numerical Mineral Mechanical Modeling of Fracture Propagation in Complex Reservoirs Rocks at Microscale
Authors: Nachev Victor , Turuntaev Sergey
Published: March 2021

Improved efficiency of hydraulic fracturing (HF) operations in complex reservoir rocks requires producing an extensive network of secondary fractures alongside the main fractures. The goal of the presented research is to find optimal stress-strain conditions yielding the most extensive network of secondary fractures at the microscale. The scope includes integrating results of microstructural characterization of tight gas reservoir rock samples and geomechanics. The study addresses the problem of hydraulic fracture optimization by suggesting stress-strain conditions to maximize fracture branching and, therefore, to optimize the drainage zone. We use a multidisciplinary approach including experimental data obtaining and numerical simulations. The first step is preparing a consistent set of 2D and 3D digital rock (DR) microscale models describing the experimental geometry, mineral composition and spatial distribution of mechanical properties of real rock samples. Geomechanical and petrophysical laboratory testing provide calibration/validation data for the DR models. Lab experiments include compressive and tensile strength testing coupled with digital image correlation, and X-ray computed tomography, 2D scanning electron microscopy coupled with mineralogy mapping. The preparation of DR models involves advanced 2D-to-3D and 3D-to-3D image registration techniques. The second step is a simulation of stress-strain states and fracture propagation in the models. We build simulation grids based on the mineral model and use a commercial mechanical simulator to simulate the fracture propagation at a microscale at given stress conditions. We applied the above approach to one of the most promising gas formations located in West Siberia, Russia. The reservoir rock features low permeability and pore dimensions down to tens of nanometers. Simulations delivered fracture networks for different loading conditions at the microscale. Simulation of typical geomechanical conditions allowed choosing reasonable stress-strain conditions that sustain the highest degree of formation fracturing. The research results may be applied to unconventional plays by increasing the efficiency of HF operation and maximizing production from isolated pore systems via establishing voids connectivity in the near-wellbore zone. The knowledge of the optimal stress-strain state for a near-wellbore zone will set the goal for HF propagation modeling at a wellbore scale. Using the approach, a geomechanical modeler would focus on designing main fractures, sustaining required stress-strain conditions in its vicinity, and thus producing the maximal amount of secondary microfractures. The results novelty is related with the simulation of 3D fracture propagation in highly heterogeneous reservoirs rocks taking into account its void space structure and fabric in geometry closest to real conditions.
A global analysis of subsidence, relative sea-level change and coastal flood exposure
Authors: Lincke Daniel , Nicholls Robert J. , Hinkel Jochen , Brown Sally , Vafeidis Athanasios T. , Meyssignac Benoit , Hanson Susan E. , Merkens Jan , Fang Jiayi
Published: March 2021

Climate-induced sea-level rise and vertical land movements, including natural and human-induced subsidence in sedimentary coastal lowlands, combine to change relative sea levels around the world's coast. Global-average coastal relative sea-level rise was 2.5 mm/yr over the last two decades. However, as coastal inhabitants are preferentially located in subsiding locations, they experience an average relative sea-level rise up to four times faster at 7.8 to 9.9 mm/yr. This first global quantification of relative sea-level rise shows that the resulting impacts, and adaptation needs are much higher than reported global sea-level rise measurements would suggest. Hence, coastal subsidence is an important global issue that needs more assessment and action. In particular, human-induced subsidence in and surrounding coastal cities can be rapidly reduced with appropriate policy measures for groundwater utilization and drainage. This offers substantial and rapid benefits in terms of reducing growth of coastal flood exposure due to relative sea-level rise.
Climate change impacts on irrigation water resource in Switzerland
Authors: Linder Zoe , Holzkämper Annelie , Zappa Massimiliano
Published: March 2021

According to climate projections, rainfall rates and summer discharge from snow and glacier melt in Switzerland are expected to decrease by the end of the 21st century. This may lead to limited water availability for irrigation in agriculture in the future and high irrigation water demand especially during the summer months, which consequently enhances the problem of water scarcity for agriculture.

These predicted changes make the identification of timescales, frequencies, and geographical pattern of water scarcity a fundamental concern for future agricultural practices. Therefore, the main aim of this work is to investigate climate change impacts on water resources and the consequences on irrigation water supply in Switzerland. By creating maps of the geographic distribution of natural water resources available according to climate projections until the end of the 21st century using ArcGIS, the severity of water scarcity is quantified, while regional differences and the most affected areas can be revealed.

The expected outcomes are increasing days of water scarcity per year over the course of the 21st century, while those regions furthest away from melt water sources and lakes will be most affected. This in turn might lead to restricted irrigation potential, making more efficient water use indispensable in Switzerland, while creating general shifts to more water-resistant crops in Swiss agricultural practices.
Stochastic modeling of the oceanic mesoscale eddies
Authors: Li Long , Deremble Bruno , Lahaye Noé , Mémin Etienne
Published: March 2021

In this work, a stochastic representation [Bauer2020a, Bauer2020b] based on a physical transport principle is proposed to account for mesoscale eddy effects on the the large-scale oceanic circulation. This stochastic framework [Mémin2014] arises from a decomposition of the Lagrangian velocity into a time-smooth component and a highly oscillating noise term. One important characteristic of this random model is that it conserves the energy of any transported tracer. Such an energy-preserving representation has been successfully implemented in a well established multi-layered quasi-geostrophic dynamical core (http://www.q-gcm.org). The empirical spatial correlation of the small-scale noise is estimated from the eddy-resolving simulation data. In particular, a sub-grid correction drift has been introduced in the noise due to the bias ensuing from the coarse-grained procedure. This non intuitive term seems quite important in reproducing on a coarse mesh the meandering jet of the wind-driven double-gyre circulation. In addition, a new projection method has been proposed to constrain the noise living along the iso-surfaces of the vertical stratification. The resulting noise enables us to improve the intrinsic low-frequency variability of the large-scale current. From some statistical studies and energy transfers analysis, this improvement is well demonstrated.

[Bauer2020a] W. Bauer, P. Chandramouli, B. Chapron, L. Li, and E. Mémin. Deciphering the role of small-scale inhomogeneity on geophysical flow structuration: a stochastic approach. Journal of Physical Oceanography, 50(4):983-1003, 2020a.       

[Bauer2020b] W. Bauer, P. Chandramouli, L. Li, and E. Mémin. Stochastic representation of mesoscale eddy effects in coarse-resolution barotropic models. Ocean Modelling, 151:101646 (2020b).    

[Mémin2014] E. Mémin. Fluid flow dynamics under location uncertainty. Geophysical & Astrophysical Fluid Dynamics, 108(2):119-146, 2014.     
Phenological phases of pollination related to climate change
Authors: Monnier Samuel , Thibaudon Michel , Besancenot Jean-Pierre , Sindt Charlotte , Oliver Gilles
Published: March 2021

Knowledge:

Rising CO2 levels and climate change may be resulting in some shift in the geographical range of certain plant species, as well as in increased rate of photosynthesis. Many plants respond accordingly with increased growth and reproduction and possibly greater pollen yields, that could affect allergic diseases among other things.

The aim of this study is the evolution of aerobiological measurements in France for 25-30 years. This allows to follow the main phenological parameters in connection with the pollination and the ensuing allergy risk.

Material and method:

The RNSA (French Aerobiology Network) has pollen background-traps located in more than 60 towns throughout France. These traps are volumetric Hirst models making it possible to obtain impacted strips for microscopic analysis by trained operators. The main taxa studied here are birch, grasses and ragweed for a long period of more than 25 years over some cities of France.

Results:

Concerning birch but also other catkins or buds’ trees pollinating in late winter or spring, it can be seen an overall advance of the pollen season start date until 2004 and then a progressive delay, the current date being nearly the same as it was 20 years ago, and an increasing trend in the quantities of pollen emitted.

For grasses and ragweed, we only found a few minor changes in the start date but a longer duration of the pollen season.

Discussion:

As regards the trees, the start date of the new production of catkins or buds is never the 1st of January but depends on the species. For example, it is early July for birch. For breaking dormancy, flowering, and pollinating, the trees and other perennial species need a period of accumulation of cold degrees (Chilling) and later an accumulation of warm degrees (Forcing). With climate change these periods may be shorter or longer depending of the autumn and winter temperature. Therefore, a change in the annual temperature may have a direct effect on the vegetal physiology and hence on pollen release. It may also explain why the quantities of pollen produced are increasing.

The Poaceae reserve, from one place to another and without any spatial structuring, very contrasted patterns which make it impossible to identify a general tendency. This is probably due to the great diversity of taxa grouped under the generic term Poaceae, which are clearly not equally sensitive to climate change.

Conclusion:

Trees with allergenic pollen blowing late winter or early spring pollinate since 2004 later and produce amounts of pollen constantly increasing. Grasses and ragweed have longer periods of pollination with either slightly higher or most often lower pollen production.
Novel UAV-based tools for assessing coastal grassland structure and function 
Authors: Villoslada Miguel , Bergamo Thaisa , Ward Raymond
Published: March 2021

Coastal grasslands provide a wide range of ecosystem services worldwide. In order to better target conservation efforts in these ecosystems, it is necessary to develop highly accurate models that account for the spatial nature of ecosystem structure, processes and functions. Here, we present a novel set of UAV-based tools to accurately assess and map coastal grassland structure and functions. Firstly, a combination of UAV-derived datasets were used to produce vegetation indices and micro topographic models. A classification random forest algorithm was used to process the spectral and microtopography datasets and map the extent and spatial configuration of plant communities in coastal meadows in Estonia. The model accurately predicted the occurrence of plant communities with a very high kappa value.

In the second stage, a regression random forest algorithm was used to model and map above-ground biomass within the coastal grasslands sites. Subsequently, the above-ground biomass maps in combination with a mean-shift algorithm were used to assess grassland structural heterogeneity. The results were then related to management history at each study site, showing that continuous, monospecific grazing management tends to simplify grassland structure, which could in turn reduce the supply of a key regulation and maintenance ecosystem services: nursery and reproduction habitat for waders.

These results also indicate that UAV-based surveys can serve as reliable grassland monitoring tools and could aid in the development of site-specific management strategies.
Effects of drought conditions on VOC soil fluxes within the rainforest mesocosm of Biosphere 2
Authors: Pugliese Giovanni , Ingrisch Johannes , Klüpfel Thomas , Meeran Kathiravan , Purser Gemma , Gil Loaiza Juliana , van Haren Joost , Kreuzwieser Jürgen , Ladd Nemiah , Meredith Laura , Werner Christiane , Williams Jonathan
Published: March 2021

Volatile organic compounds (VOC) play an important role in determining atmospheric processes that control air quality and climate. Although atmospheric VOC concentrations are mostly affected by plants, soils are significant contributors as they are simultaneously a source, a sink and a storage of atmospheric VOCs. The aim of the present study was to assess the effects of a prolonged drought condition on VOC soil fluxes in the tropical rainforest mesocosm of Biosphere 2 (B2; Tucson, Arizona, USA). The absence of atmospheric chemistry due to UV light filtering by the glass and the possibility to control and manipulate the conditions of the ecosystem make the B2 an ideal set-up to study the rainforest VOC dynamics.

The experiments were conducted over the 4 months B2WALD campaign during which the rainforest was subjected to a controlled drought period of about 10 weeks followed by a rewetting period. Soil VOCs fluxes were measured continuously by means of a proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) that was connected to 12 automated soil chambers (LI 8100-104 Long-Term Chambers, Licor Inc.) placed in 4 different locations within the B2 rainforest.

The B2 rainforest soil acted as a strong sink for all isoprenoid species. The isoprene sink steadily weakened during drought period, but increased sharply back to the pre-drought levels after the rain rewet. In contrast, the monoterpene soil sink became slightly stronger during the mild drought period (up to 5 weeks after the last rainfall) but weakened during the severe drought period (up to 10 weeks after rainfall). A huge increase in monoterpene uptake was observed after the rain rewet. The oxidation products of isoprene (methacrolein, methyl vinyl ketone and isoprene peroxides) showed a similar trend to the monoterpenes, even in absence of atmospheric chemistry. The species with molecular formula C5H8O was taken up by the soil during predrought, which was reduced during mild drought period but increased again during the severe drought period.Sulfur-containing compounds including DMS and methanethiol all showed a significant emission peak immediately after the rain rewet.Oxygenated VOCs such as methanol and acetone were taken up by the soil in wet conditions. The uptake of both compounds strongly decreased with the drought and in severe drought conditions they were even emitted by the soil.

In summary, soil VOC fluxes changed markedly with the onset and development drought stages (pre, mild and severe drought) of the B2 rainforest, mirroring atmospheric VOC concentrations and soil microbial activity changes related to overall ecosystem response to drought and recovery.