bluuebunny/crossref_metadata_2025 huggingface dataset:
Combining UAV LiDAR and Terrestrial Laser Scanning to investigate the impact of shrub expansion on local-scale Arctic snowpack distribution.
Authors: Lamare Maxim , Arnaud Laurent , Picard Ghislain , Pelletier Maude , Domine Florent
Published: March 2020

Climate warming induces shrub expansion on Arctic herb tundra, with effects on snow trapping and hence snow depth. We have used UAV-borne LiDAR and Terrestrial Laser Scanning (TLS) to investigate the impact of shrub height on snow depth at two close sites near Umiujaq, eastern Canadian low Arctic, where dwarf birch and willow shrubs are expanding on lichen tundra. The first site features lichen and high shrubs (50-100 cm), a moderate relief, and a snowpack averaging 95 cm in spring. The second site consists of lichen and low shrubs (20-60 cm), more pronounced topography, and a deeper snowpack (101 cm). Digital Terrain and Surface Models were acquired in early fall to obtain topography and vegetation height. A Digital Surface Model obtained in spring produced snow depth maps at peak depth. TLS over a 400 m2 area produced time series of snow depth throughout the winter. TLS data show preferential snow accumulation in shrubs, but also preferential melting in shrubs during fall warm spells and in spring. UAV data at the first site show a strong correlation between vegetation height and snow depth, even after snow depth has exceeded vegetation height. This correlation is not observed at the second site, probably because snow depth there is much greater than vegetation height. These data show the need to reconsider some paradigms on snow-vegetation interactions, for example that vegetation does not affect snow accumulation beyond its height.
Evaluation of mining decommissioning strategies on catchment hydrology
Authors: Lompi Marco , Pacetti Tommaso , Caporali Enrica
Published: March 2020

Sediment management can represent a key point for the water resources conservation, as the land use control can limit soil erodibility, ensuring a reduction of the silting volume in the reservoir. This study is focused on the nexus between coal mining activity and the hydrological cycle at the catchment scale, analysing how environmental interventions can be an excellent strategy against the impacts of former mining areas. Lake San Cipriano represents an excellent case study to explore the effects of mining activity on water storage because it is downstream of a river basin in which one of the most important lignite mine in central Italy has worked for years. A hydrological model is implemented on the Soil Water Assessment Tool (SWAT) to choose which decommissioning strategies brings the best results in terms of water resource conservation. Since no flow data are available, the model is calibrated in the solid transport equations, pointing to the convergence of the silting volume in the lake, which has been estimated thanks to multiple bathymetric campaigns carried out over the years. Two environmental restoration scenarios have been analysed: the first is only focused in the land use change with the afforestation of native plants; the second is a wider landscape restoration project that include also river bodies rehabilitation. The results show the quantitative effects of the proposed decommissioning strategies, showing the strong reduction of solid transport and reservoir silting in the two proposed scenarios.
The effect of nanolites on degassing of silica-rich magma
Authors: Cáceres Francisco , Wadsworth Fabian , Scheu Bettina , Colombier Mathieu , Madonna Claudio , Cimarelli Corrado , Hess Kai-Uwe , Kaliwoda Melanie , Ruthensteiner Bernhard , Dingwell Donald B.
Published: March 2020

Magma degassing dynamics play an important role controlling the explosivity of volcanic eruptions. Some of the largest explosive eruptions in history have been fed by silica-rich magmas in volcanic systems with complex dynamics of volatiles degassing. Degassing of magmatic water drives bubble nucleation and growth, which in turn increases magma buoyancy and results in magma ascent and an eventual eruption. While micro- to milli-meter sized crystals are known to cause heterogeneous bubble nucleation and to facilitate bubble coalescence, the effects of nanolites remains mostly unexplored. Nanolites have been hypothesized to be a primary control on the eruptive style of silicic volcanoes, however the mechanisms behind this control remains unclear.

Here we use an experimental approach to show how nanolites dramatically increase the bubble number density in a degassing silicic magma compared to the same magma without nanolites. The experiments were conducted using both nanolite-free and nanolite-bearing rhyolitic glass with different low initial water content. Using an Optical Dilatometer at 1 bar ambient pressure, cylindrical samples were heated at variable rates (1-30 °C min-1) to final temperatures of 820-1000 °C. This method allowed us to continuously monitor the volume, and hence porosity evolution in time. X-ray computed microtomography (µCT) and Scanning Electron Microscope (SEM) analyses revealed low and high bubble number densities for the nanolite-free and nanolite-bearing samples respectively.

Comparing vesicle number densities of natural volcanic rocks from explosive eruptions and our experimental results, we speculate that some very high naturally occurring bubble number densities could be associated with nanolites. We use a magma ascent model with P-T-H2O starting conditions relevant for known silicic eruptions to further underpin that such an increase in bubble number density caused driven by the presence of nanolites can feasibly turn an effusive eruption to an eventually explosive behavior.
The origin of large zoned ignimbrites: the case of Aso caldera, Japan
Authors: Keller Franziska , Bachmann Olivier , Geshi Nobuo , Miyakawa Ayumu
Published: March 2020

Silicic magmas are the most evolved, most viscous and potentially most explosive melts present on Earth. Despite their importance, the processes leading to accumulation of large amounts of silicic magma in the crust are still a matter of debate. Ignimbrite sheets of large caldera forming eruptions are interpreted to be unique snapshots of upper crustal magma reservoirs just prior to eruption and hence represent an exceptional possibility to study pre-eruptive magmatic conditions within silicic reservoirs.

The Aso System, in Central Kyushu (Japan), is an archetypical example of a multicyclic caldera-forming volcanic edifice; it was built by four catastrophic caldera forming eruptions, with the latest (Aso 4) taking place approximately 90 ka ago. The ignimbrite sheets produced during the Aso eruptions are some of the first ever described compositionally zoned pyroclastic flow deposits and are interpreted to be the result of extensive magma mixing of two compositionally distinct magmas in an upper crustal reservoir.

Here, we propose an alternative view of the Aso 4 ignimbrite sheets based on re-evaluation of whole rock data combined with mineral and glass geochemistry. The relatively scarce presence of mafic pyroxenes and plagioclases indicate recharge of hot, mafic magmas occurring shortly prior to eruption. However, the large amount of crystal-poor, felsic material in early erupted units in combination with late-erupted, crystal-rich basaltic andesite clasts, which are enriched in compatible elements and rich in compositionally highly evolved minerals, lead to the conclusion that magma mixing alone is not able to explain the complexities observed in Aso 4 deposits. Evidence for crystal accumulation in late erupted basaltic andesite clasts implies the formation of melt-rich lenses within a crystal-rich reservoir due to significant crystal-melt separation. We therefore propose an origin of the compositionally zoned Aso 4 ignimbrite largely by erupting a heterogeneous upper crustal reservoir, consisting of crystal-poor rhyodacitic melt pockets within a cumulate mush. The emptying of this heterogeneous magma storage zone was likely triggered by a recharge event from deeper in the system, initiating partial melting of previously-formed crystals (rejuvenation), mingling/ mixing, pressurization, and finally catastrophic evacuation of the eruptible portions of the subvolcanic reservoir, including parts of the cumulate mush.
Tree species detection and identification from UAV imagery to support tropical forest monitoring
Authors: Dutrieux Loïc , Azzabi Radhouene , Bauwens Sébastien , Bouka Dipelet Ulrich Gaël , Chenoz Olivier , Couturier Antoine , Dérian Pierre , Doumenge Charles , Dubois Hubert , Gond Valéry , Laverdunt Arnaud , Olé Julien , Prosperi Juliana , Rivière Laurent , van Loon Tom
Published: March 2020

As part of a project aiming to support FSC certified logging concessions in their tasks of forest inventory and management, we collected aerial imagery over 9000 ha of tropical forests in Northern Congo using long range Unmanned Aerial Vehicles (UAVs). Once processed into orthomosaics, the aerial imagery is used in combination with reference training samples to train a deep learning object detection model (FasterRCNN) capable of detecting and predicting tree species. The remoteness and diversity of these forests make both data acquisition and generation of a training dataset challenging. Unlike natural images containing common objects like cars, bicycles, cats and dogs, there is no easy way to create a training dataset of tree species from overhead imagery of tropical forests. The first reason is that a human operator cannot as easily recognize and label objects. The second reason is that the polymorphism of tree species, phenological variations and uncertainty associated with visual recognition makes the exhaustive labeling of all instances of each class very difficult. Such exhaustive labeling is required to successfully train any object detection model. To overcome these challenges we built an interactive and ergonomic interface that allows a human operator to work in a spatial context, being guided by the approximate geographic location of already inventoried trees. We solved the issue of non-exhaustive instance labeling by building synthetic images, hence allowing full control of the training data. In addition to these specific developments related to training data generation, we will present details of the UAV missions, modelling results on synthetic images, and finally preliminary results of model transfer to aerial imagery.
The use of MSW-compost on land, a study of metal and nutrient leaching
Authors: Graca Jessica , Kelleher Brian , Murphy Brian
Published: March 2020

It is estimated that up to 138 million tonnes of bio-waste are produced in Europe annually, with only 25% being recycled into high-quality compost and digestate. Currently, residual organic waste is generated as by-product of municipal solid waste treatment. Its reuse options vary across EU countries, due to the lack of clear guidance at European level. In some countries, compost derived from municipal solid waste (MSW – compost) is restricted to being used as landfill cover or in land reclamation, under the premises of meeting national legal criteria. Other countries, have regulated its used as marketable compost if it meets defined compost standards. However, for many countries the value-added use of MSW derived compost is uncertain.

The restricted use of MSW - compost is linked to the organic and inorganic contamination associated with such a heterogeneous material. Despite this, under the European view of the Circular Economy, MSW-compost has great potential to be reused and recycled for the benefit of all. Controlled use on land would off-set carbon emissions by diverting the material from a waste that is largely incinerated or added to landfill to a carbon positive soil additive that increases soil quality particularly in restoration sites. 

Our study aims to risk-assess the use of MSW-compost as a soil amendment by monitoring resulting water run-off for metal and nutrient content. Leaching trials, conducted over 6 months were performed in a forest soil (20 cm depth) with a history of Sitka Spruce plantation (c.a 20 years). Adapted water storage tanks were set-up to conduct the trials. Leachate was collected weekly in the first two months, and monthly thereafter. Four treatments 1) control, 2) sewage sludge chemically stabilized (10 t/ha), 3) MSW-compost (10 t/ha) and 4) MSW-compost (25 t/ha) were established in duplicate. Sewage sludge was used as a comparison material, due to its current legal status allowing for controlled land spreading. Leachate samples were analysed for nitrate, ammonium and the metals aluminium, cadmium, copper, total chromium, mercury, nickel, zinc and lead. 

Preliminary results from the first 6 weeks show that metals concentrations in the leachate from all trials were below threshold criteria in surface water quality regulations. Levels of ammonium above detection limits were only detected at week one and surpassed 0.2 mg/L. Nitrate concentration in the leachates was found to be below 50 mg/L and it peaked in the sewage sludge and MSW-compost (25 t/ha) at week 2.

Results gathered so far show that the use MSW-compost in land compares to sewage sludge application in relation to their potential for water pollution. MSW-compost could be used as a soil improver under a regulatory alignment similar to the sewage sludge regulations, aligned with the current European Circular Economy goals.
FlowVeloTool: Measuring flow velocities in terrestrial and UAV image sequences automatically with PIV and PTV
Authors: Eltner Anette , Grundmann Jens
Published: March 2020

We introduce a Python based software tool to measure surface flow velocities and to estimate discharge eventually. Minimum needed input are image sequences, some camera parameters and object space information to scale the image measurements. Reference information can be provided either indirectly via ground control point measurements or directly providing camera pose parameters. To improve the reliability and density of velocity measurements the area of interest has to be masked for image velocimetry. This can either be performed with a binary mask file or considering a 3D point cloud, for instance retrieved with Structure from Motion (SfM) photogrammetry, describing the region of interest. The tracking task can be done with particle image velocimetry (PIV) considering small interrogation regions or using particle tracking velocimetry (PTV) and thus detecting and tracking features at the water surface. To improve the robustness of the tracking results, filtering can be applied that implements statistical information about the flow direction, flow steadiness and average velocities.

The FlowVeloTool has been tested with two different datasets; one at a gauging station and one at a natural river reach. Thereby, UAV and terrestrial data were acquired and processed. Velocities can be estimated with an accuracy of 0.01 m/s. If information about the river topography and bathymetry are available, as in our demonstration, discharge can be estimated with an error ranging from 5 to 31 % (Eltner et al. 2019). Besides these results we demonstrate further developments of the FlowVeloTool regarding filtering of tracking results, discharge estimation, and processing of time series. Furthermore, we illustrate that thermal data can be used, as well, with our tool to retrieve river surface velocities.

 

Eltner, A., Sardemann, H., and Grundmann, J.: Flow velocity and discharge measurement in rivers using terrestrial and UAV imagery, Hydrol. Earth Syst. Sci. Discuss., https://doi.org/10.5194/hess-2019-289, 2019.
Functionning of the Katari-Lago Menor Basin aquifer, Lake Titicaca-Bolivia, inferred from geophysical, hydrogeological and geochemical data
Authors: Duwig Céline , Flores Gabriela , Descloitres Marc , Rossier Yvan , Spadini Lorenzo , Legtchenko Anatoly , Soruco Alvaro , Argollo Jaime , Pérez Mayra , Medinacelli Waldo
Published: March 2020

The population of the semi-arid Bolivian Northern Altiplano depends greatly on groundwater resources, surface water being intermittent and often contaminated by human activities. The aim of this study is to provide a first insight into the hydrogeological structure and groundwater dynamics of the Katari-Lago Menor Basin aquifer located between the Eastern Cordillera and Lake Titicaca, Bolivia. Resistivity profiles combined with geology, borehole lithology, topography as well as additional groundwater level and geochemical measurements, were helpful in resolving the spatial limits of the aquifer, the vertical and lateral continuity of the Quaternary porous geologic media, the shape and position of the bottom of the aquifer (depth to the bedrock, i.e. Tertiary or Devonian Formations), and revealed a general overview of the natural dynamic behaviour of the aquifer at the scale of the Katari and Lago Menor Basin. The quaternary sediments are hydraulically connected and behave as a single regional basin-aquifer. The main groundwater flow system starts in the upper Piedmont (high mountain ranges of the Eastern Cordillera) and follows the topographic Piedmont gradient (NE to SW). Most groundwater recharge results from the infiltration of precipitation and runoff on the high mountain ranges. Indeed, groundwater circulating in the upper and lower Piedmont layers present primarily  facies. In the regions of the lower Piedmont urbanized areas, groundwater presenting  facies, show a noticeable enrichment of sulphate and chloride relating mainly anthropogenic contamination (mining and urban nature). A large portion of the aquifer presents an unconfined behaviour whereas it remains confined below the Ulloma Formation. The thickness of the unconfined portion varies from 50 to 150 meters and that of the confined from 100 to 150 meters. Values of hydraulic conductivity for the unconfined portion range from 1.1×10-4 m s-1 (alluvial fan deposit), 2.5×10-6 m s-1 (fluvioglacial deposits,) to 5.9×10-8 m s-1 (glacial deposits), while for the confined part transmissivity values range around 6.0×10-6  m2 s-1 (paleo-lacustrine deposits).

 This multidisciplinary approach proved to be an appropriate method to derive a consistent picture of the hydrogeological functioning of the Katari-Lago Menor Basin aquifer.
Front related model evaluation of multi-year simulations from hydrostatic to convection-permitting scales in the greater Alpine region
Authors: Truhetz Heimo , Heinzeller Dom , Ritter Robert , Herbsthofer Laurin
Published: March 2020

Atmospheric fronts play a major role in day-to-day life and are well known for sharp changes in local weather conditions. In mountainous regions, the interaction between fronts and the orography supports the development of characteristic precipitation patterns and may even cause specific weather phenomena, like thunderstorms, föhn events, and others. It is therefore an interesting question, how such fronts evolve in the next few days or how they will behave under changing climate conditions.

However, due to the complexity of fronts and limitations in numerical weather prediction or climate models, state-of-the-art automated front detection algorithms are largely restricted to the model they are applied onto. In particular, the outcome of these algorithms depends the discretization scheme of the underlying model (e.g. the grid spacing) and hence they may fail in model intercomparison or evaluation studies when data is given in various different grids.

In the present work, a diagnostic front detection algorithm, that is designed to overcome such model dependencies, is introduced and its applicability for model intercomparison is demonstrated by means of simple analytic test functions and idealized simulations of a baroclinic wave (i.e. the Jablonowksi and Williamson test) conducted with MPAS (60 km and 15 km grid spacing). Finally, the algorithm is exemplarily applied onto latest WRF evaluation simulations (15 km and 3 km grid spacing) from the CORDEX-FPS Convection initiative and the Integrated Forecast System (IFS) of the European Centre for Medium-Range Weather Forecasts (ECMWF) (~25 km grid spacing) to investigate differences in front statistics in the greater Alpine region of the period 2006 to 2009.

The study is funded by the Austrian Klima- und Energiefonds through the Austrian Climate Research Programme (ACRP) by means of the project "Research for Climate Protection: Value-adding Convection-Permitting Climate Simulations Austria" (reclip:convex, project id: B769999).
Equatorial Atlantic ventilation over the last century revealed by deep-sea bamboo coral radiocarbon records
Authors: Liu Qian , Robinson Laura F. , Stewart Joseph A. , Knowles Timothy , Hendy Erica , Li Tao , Samperiz Vizcaino Ana
Published: March 2020

Despite growing interest in ocean-climate interactions in response to recent anthropogenic warming, historical hydrographic data with which to assess changes in the deep ocean over the last century are limited. With their robust calcium carbonate skeletons, deep-sea corals, especially long-lived bamboo corals, serve as a potential archive for reconstructing continuous high-resolution paleoceanographic records extending back hundreds to even thousands of years.

Here we use deep-sea bamboo corals collected between 800 and 2000 m water depth in the eastern equatorial Atlantic to reconstruct the ventilation history over the last century. Deep-sea bamboo corals have a jointed axis consisting of organic nodes and internodes composed of calcium carbonate. The radiocarbon content of the organic nodes documents the radiocarbon of surface water and likely records the distinctive bomb 14C signal that can be used to generate a chronology for each coral specimen. By contrast, the radiocarbon content of calcite internodes records the radiocarbon signature of deep water over the lifetime of the coral. The reconstructed calcite radiocarbon record shows a quasi-periodic cycle of about two-decades, which is likely linked to multidecadal fluctuations in North Atlantic climate influencing the ventilation state of the water mass. In addition to radiocarbon records, we show that trace metal compositions of bamboo coral also provides key information with regard to both biomineralization processes, past environmental conditions, and chemistry of seawater. By combining radiocarbon and elemental composition of bamboo coral, we are building a set of tools with which to reconstruct deep ocean dynamics over the last century.
Characterization and Quantification of Methane Emissions from Waste in the UK
Authors: Bakkaloglu semra , Lowry David , Fisher Rebecca , France James , Lanoiselle Mathias , Fernandez Julianne
Published: March 2020

Mitigation of climate change is a key scientific and societal challenge. CH4 emissions are a major contributor to global warming impact and these are not well quantified yet. There are significant discrepancies between official inventories of emissions and estimates derived from direct atmospheric measurement. Effective emission reduction can only be achieved if sources are properly quantified, and mitigation efforts are verified.

CH4 from waste is dominantly of biogenic origin and its levels can vary with temperature and production process, which results in variation of emissions with time of day and time of year. Selected waste streams are now commonly sent to biogas plants, where the waste is digested to produce methane, which may be utilised directly, or combusted to provide power. Different waste streams, such as maize stubble or paper products, are characterized by distinct δ13C-CH4 signatures.  Emissions from each stage of the biogas production process can be identified by analysing the methane isotopic composition.

This study focuses on identification and quantification of CH4 emissions from waste sources in the UK from 2018-2020 using laser-based mobile surveys downwind of landfills, biogas plants and wastewater treatment plants. Air samples were collected and analysed for isotopic characterization using high precision Gas Chromatography Isotopic Ratio Mass Spectrometry. Survey data were used to map concentration excess over background, identify isotopic composition and estimate fugitive emissions from selected sources.

Average carbon isotopic signatures for new data on methane sources in the UK are -53 ‰ for wastewater treatment plants and -55 ‰ for biogas plants. CH4 emissions range from 6.2 to 50 g/h depending on size and operating conditions of plants. Also, isotopic signature of methane emission from active sites in the landfill are in the range -60 to -58 ‰ with 2 - 10% oxidation rate, which is characteristically more depleted than closed sites.

 
Quantification of biogeomorphic interactions between small-scale sediment transport and primary succession in the Gepatschferner glacier foreland, Austria
Authors: Haselberger Stefan , Ohler Lisa Maria , Junker Robert R. , Otto Jan-Christoph , Kraushaar Sabine
Published: March 2020

Landscape change is an interplay of abiotic and biotic processes with bi-directional and interwoven relationships. Glacier foreland areas can act as open-air laboratory to observe biogeomorphic interactions. Paraglacial adjustment establishes initial conditions for ecological succession and requires constant feedbacks between plants and landscapes. Frequency and magnitude of geomorphic processes and functional composition and abundance of plants govern these responses. Up to now, biogeomorphic studies have mainly focused on the qualitative description of the relationship between biotic and abiotic processes. However, in order to test biogeomorphic concepts, it is necessary to jointly quantify (i) geomorphic process rates as a function of vegetation and (ii) successional development as a function of geomorphic conditions.

The proglacial area of the Gepatschferner (Kaunertal) in the crystalline Central Eastern Alps presents a showcase environment to investigate these interactions as the retreating glacier and highly active slope processes provide the ground for different stages of ecological succession and promotes high rates of sediment reworking within the proglacial deposits.

In this particular study, we investigate small-scale biogeomorphic interactions at 30 test sites of 2*3m size. Experimental plots are established on slopes along an ecological succession gradient that reflect different stages of erosion-vegetation interaction. To cover the abiotic condition for the plot sites morphometric characteristics and edaphic variables were determined. In order to quantify abiotic process rates, we use mechanical measurements (i.e. erosion plots) to determine sediment yield and to measure the effect of vegetation on particle size distribution. Relative Dating, historical image analysis and knowledge of glacial retreat helped to estimate time since last perturbation. A detailed vegetation survey was carried out to capture biotic conditions at the sites. Species distribution and abundance at each site, as well as plant functional types provide information on successional stage and functional diversity.

This data set provides a vital opportunity to test conceptual models on biogeomorphic succession in glacier forelands and to evaluate the bi-directional influence of primary succession on small-scale sediment transport and vice versa.
Stress and strain rate variations and strain localisation in ice: Another complexity to be considered apart from a simple enhancement factor
Authors: Bons Paul D. , de Riese Tamara , Gomez-Rivas Enrique , Griera Albert , Llorens Maria-Gema , Weikusat Ilka
Published: March 2020

To describe the rheology of ice, it is customary to employ a flow law that relates the (differential) stress to the strain rate, typically as a function of temperature. The flow law thus predicts a single strain rate for a given stress and temperature. However, ice 1h is highly anisotropic when deforming by dislocation creep as is usually assumed to be the case in glaciers and polar ice sheets. Ice is effectively much softer in shearing parallel to the basal plane compared to deformation that requires activation of the non-basal crystallographic slip planes. Numerical simulation of ice deformation with the full-field crystal plasticity code (VPFFT, Lebensohn & Rollett, 2020) coupled with the numerical simulation platform Elle (Llorens et al., 2016) show that deformation in aggregates of ice grains is highly heterogeneous and typically shows strong strain heterogeneity and strain localisation in shear zones. This localisation remains when lattice rotation has resulted in a strong crystallographic preferred orientation (CPO) with basal planes all oriented approximately parallel to the shear plane in simple-shear deformation.

 

Plots of the differential stress versus strain rate of all points of the full field model at one point in time show a wide scatter within the polycrystal. Although most basal planes have an orientation close to optimal for slip along this plane, few, if any material points actually show a stress-strain rate state close to the one predicted by the flow law for basal glide. On the contrary, the hard non-basal slip planes contribute significantly to the overall deformation. Shear zones show a stronger alignment of basal planes than the surrounding material. However, differential stress tends to be highest inside these shear zones, suggesting that shear zones are not simply the result of the presence of "soft" ice.

 

The results give insight in the highly complex behaviour of the strongly anisotropic material ice. This complexity is insufficiently described with a simple enhancement factor. We discuss how this complexity may help explain variations in grain size and apparent strength found in deep drill cores in the polar ice sheets.

 

Lebensohn, R.A., Rollett, A.D. 2020. Spectral methods for full-field micromechanical modelling of polycrystalline materials. Computational Materials Science 173, 109336.

Llorens, G.-M., Griera, A., Bons, P.D., Lebensohn, R.A., Evans, L.A., Jansen, D., Weikusat, I. 2016. Full-field predictions of ice dynamic recrystallisation under simple shear conditions. Earth and Planetary Science Letters 450, 233-242.
Towards operational postprocessing of cloud cover at MeteoSwiss
Authors: Hemri Stephan , Spirig Christoph , Bhend Jonas , Moret Lionel , Liniger Mark
Published: March 2020

Over the last decades ensemble approaches have become state-of-the-art for the quantification of weather forecast uncertainty. Despite ongoing improvements, ensemble forecasts issued by numerical weather prediction models (NWPs) still tend to be biased and underdispersed. Statistical postprocessing has proven to be an appropriate tool to correct biases and underdispersion, and hence to improve forecast skill. Here we focus on multi-model postprocessing of cloud cover forecasts in Switzerland. In order to issue postprocessed forecasts at any point in space, ensemble model output statistics (EMOS) models are trained and verified against EUMETSAT CM SAF satellite data with a spatial resolution of around 2 km over Switzerland. Training with a minimal record length of the past 45 days of forecast and observation data already produced an EMOS model improving direct model output (DMO). Training on a 3 years record of the corresponding season further improved the performance. We evaluate how well postprocessing corrects the most severe forecast errors, like missing fog and low level stratus in winter. For such conditions, postprocessing of cloud cover benefits strongly from incorporating additional predictors into the postprocessing suite. A quasi-operational prototype has been set up and was used to explore meteogram-like visualizations of probabilistic cloud cover forecasts.
Greatness from small beginnings: Impact of oceanic mesoscale on weather extremes and large-scale atmospheric circulation in midlatitudes
Authors: Kjellsson Joakim , Park Wonsun , Martin Torge , Maisonnave Eric , Latif Mojib
Published: March 2020

We study how mesoscale air-sea interactions over the North Atlantic can influence weather extremes, e.g. heavy precipitation and wind storms, and the overall atmospheric circulation both locally and downstream in the midlatitudes. We use a global coupled climate model with a high-resolution North Atlantic grid (dx ~ 8 km) and an atmosphere model resolution of either 125 km or 25 km. The high-resolution North Atlantic grid allows the model to resolve the current systems and SST fronts associated with e.g. the Gulf Stream and North Atlantic Current. As air-sea fluxes of momentum, heat and freshwater are calculated on the atmosphere grid, spatial variations in fluxes associated with sharp SST fronts are much better represented when using the high-resolution atmosphere then when using the low-resolution model. 

 

Preliminary results show that coupling to the high-resolution (dx ~ 25 km) rather than low-resolution (dx ~ 125 km) atmosphere model increases the intensity and variance of surface heat and freshwater fluxes over eddy-rich regions such as the Gulf Stream. As a result, the high-resolution model simulates more intense heavy precipitation events over most of the North Atlantic Ocean. We also show that more frequent coupling between the atmosphere and ocean components increases the intensity of the air-sea fluxes, in particular wind stress, which has a large impact on the ocean. More intense air-sea fluxes can provide more energy for cyclogenesis and we will discuss how the oceanic mesoscale, in particular in the eddy-rich regions, can alter the storm tracks and jet stream to influence extreme weather and the climate over Europe.

 

The coupled model comprises NEMO 3.6/LIM2 ocean and OpenIFS 40r1 atmosphere, and works by allowing the global OpenIFS model to send and receive fields from both a global coarse-resolution ocean grid and a refined grid over the North Atlantic grid via the OASIS3-MCT4 coupler. The ability to run these simulations is a very recent development and we will give a brief overview of the coupled modelling system and benefits of using regional grid refinement in coupled models.

 
Large Aperture Scintillometer measurements above a large green roof to assess the evapotranspiration flux
Authors: Castellanos Diaz Leydy Alejandra , Versini Pierre Antoine , Tchiguirinskaia Ioulia , Bonin Olivier , Ramier David
Published: March 2020

The challenges induced by the continuous urbanization and the climate change effects, such as extreme events (e.g. flooding or heat waves) or the intense increase of the urban temperatures (Urban Heat Island), encourage the implementation of Blue and Green Solutions (BGS). These solutions are inspired by the nature, favouring natural process in the cities like water infiltration or evapotranspiration (ET), reducing air temperature during heatwaves events.

Characterize the thermal behavior governing a BGS is necessary to promote their implementation. Consequently, this research studies the energy fluxes –and particularly the evapotranspiration one- of a 1 ha wavy-shape green roof located in Champs-Sur-Marne (France), called Blue Green Wave (BGW). Therefore, a Large Aperture Scintillometer MKI, a CNR4 radiometer and 4 Type K thermocouples were installed on the BGW to measure the sensible heat flux of convection, the net radiation and the heat conduction into the soil substrate. The latent heat flux of ET was deduced from the energy balance.

Each LAS unit was placed on the highest locations of the roof with about 100 m of distance between them. Diaphragms for short-range applications were placed in front of the units. The measurements were conducted on sunny and randomly days during the 2019 summer over an average time period of 7 hours.

It appears that LAS sensible heat flux measurements on completely sunny days follow the net radiation flux trend. However, on cloudy days important flux fluctuations are noticed. Therefore, a sensitivity analysis was carried out to illustrate the significant correlation between the wind and the sensible heat flux during short time periods. In parallel, the heat conduction was analysed through a thermal gradient of temperature and a Fourier analysis demonstrating a poor conduction rate mainly on drier conditions of the BGW.

Finally, the deduced latent heat was compared with the measurements of a dynamic evaporation chamber, confirming a significant over estimation of the latent heat computed from the energy balance. This can be explained by the sum of uncertainties related to each energy flux component, in addition to the restraint conditions of LAS measurement operation on the BGW (application over the limits of MOST theory). A multifractal analysis to determinate the temporal and spatial scaling behaviour of latent heat flux is ongoing.
Participatory mapping and collaborative action for inclusive and sustainable mountain landscape development in Far West Nepal
Authors: Khadka Prakash , Liu Wei , Parajuli Binod Prasad , Pudasaini Uttam
Published: March 2020

Nepal is one of the world’s most vulnerable countries to the impacts of climate change due to its high-relief topography, heavy monsoon rainfall, and weak governance. Landslides are common across almost all Nepal’s vast Himalaya mountains, of which the Far Western region suffers most, and climate change, coupled with severe under-development is expected to exacerbate the situation. Deficiency in spatial data and information seriously hinder the design and effective implementation of development plans, especially in the least developed areas, such as Seti River Basin in Far Western Nepal, where landslides constantly devastate landscapes and communities. We adopted a participatory mapping process with emerging collaborative digital mapping techniques to tackle the problem of critical information gaps, especially spatial risk information at local levels which compromise efforts for sustainable landscape planning and uses in disaster prone regions. In short, participatory here refers to working with local stakeholders and collaborative refers to crowdsourced map information with citizens and professionals. Engaging a wide range of stakeholders and non-stakeholder citizens in this integrated mapping processes eventually structure human capital at local scales with skills and knowledge on maps and mapping techniques. Also, this approach increases spatial knowledge and their uses in development planning at the local level and eventually increases landscape resilience through improved information management. We will further discuss how this integrated approach may provide an effective link between planning, designing, and implementing development plans amid fast policy and environmental changes and implications for communities in the developing world, especially in the context of climate change and its cascading effects.
A modified dielectric probe for increased measurement volume of soil water content
Authors: Woszczyk Aleksandra , Szerement Justyna , Lewandowski Arkadiusz , Kafarski Marcin , Szypłowska Agnieszka , Wilczek Andrzej , Skierucha Wojciech
Published: March 2020

The information of water amount in soil is essential in many fields (e.g. agriculture, forestry, hydrology). Methods to determine water content (WC) can be classified as direct and indirect. Direct methods are connected with the destruction of a sample, are time-consuming and impractical for the measurements in the crop fields. Indirect methods ensure non-destructive and in situ measurements and depend on monitoring a dielectric soil property which is a function of WC. The soil dielectric permittivity is one of the used properties which may be determined by time domain reflectometry (TDR) or frequency domain reflectometry (FDR) techniques. TDR probes are expensive and can be easily damaged at multiple insertions to soil. The open-ended (OE) probes, well-known for their application in the measurements of the complex dielectric permittivity of materials in broadband frequency range, are more resistant to mechanical damage but they are characterized by low penetration depth of electromagnetic waves. Therefore, there is a need to develop sensors able to measure bigger volumes and at the same time sufficiently durable for multiple insertions in soil.     

The objective of this work was to test the performance of an open-ended dielectric probe with an antenna (OE-A) in the frequency range 1 MHz – 6 GHz for two mineral soils using vector network analyzer (VNA) one port (reflective) measurements. Firstly, numerical simulations of the probe using Ansys HFSS software were performed. Secondly, the probe calibration was done on the reference materials (air, distilled water and ethanol). Thirdly, the soils measurements were done to check the possibility to determine soil moisture.   

The obtained results show that the tested probe can be applied for fast moisture measurement with minimal soil disturbance. The real part of dielectric permittivity (ε’) obtained for the tested soils was connected with their moisture and the relation between ε’ and volumetric water content was determined. Additionally, the effect of the sample volume was considered and the relation between the high-frequency limit and diameter of the sample was determined.     

Acknowledgement:

This research was supported by the National Centre for Research and Development (BIOSTRATEG/343547/8/NCBR/2017).
Relationship of hydraulic parameters with diagenetic evolution and depositional preconditions (Buntsandstein, Central Germany)
Authors: Kunkel Cindy , Aehnelt Michaela , Pudlo Dieter , Gaupp Reinhard , Totsche Kai Uwe
Published: March 2020

The Lower Triassic Buntsandstein is an economically important clastic underground reservoir and aquifer unit in the Central European Basin (e.g. for hydrocarbon reservoirs, gas storage, geothermal energy use, drinking water supply). Its quality mainly controls its prospectivity, storage capacity and exploitability. Thus, predictions for the realization of economic intentions depend most notably on a substantial understanding of the parameters that control reservoir quality, such as facies and diagenetic alterations resulting from fluid-rock interaction. Therefore, research of even small-scale relationships between hydraulic heterogeneities and rock properties is necessary.

The study area is the Thuringian Syncline, which is a small sub-basin of the North German Basin located at its southern margin. One of its major aquifers is built from siliciclastic sediments of the Buntsandstein, which are characterized by rapid changes of depositional environments from channel to sandflat to lacustrine depositions resulting in large heterogeneities at a relatively small scale (few to some hundred meters). Furthermore, burial history and subsequent basin inversion and uplift led to only minor depths of 700 to 1000 m in the center of the syncline and an exposure at the surface at syncline margins, which allows for the exploration of the recent impact of meteoric water infiltration vs. former burial evolution on aquifer quality. We combined a petrographic study focusing on mineral composition and diagenesis with a study of depositional facies and linked the results with petrophysical data like permeability and porosity. The corresponding dataset consists of measurements on more than 300 plug samples from 12 wells and additionally more than 400 thin sections.

All in all, the Buntsandstein exhibits a very complex relationship of hydraulic parameters with diagenetic evolution in relation to depositional preconditions. For example, high amounts of channel deposits in the sandstones result in better aquifer qualities. The same holds true for increasing grain sizes. Finally, there is a major influence of telodiagenetic processes and meteoric water infiltrations. Thus, major pathways for fluid flow are not solely controlled by sedimentary facies, but also by present-day cement dissolution and mineral alteration, especially in the vadose zone.
Braided rivers networks dynamics: analyzing topographic data from a large flume experiment
Authors: Papa Daniel , Ancey Christophe
Published: March 2020

Braided rivers are highly dynamical systems characterized by varying network-like structures even under quasi-steady conditions. Understanding their dynamics is crucial in geomorphology and river engineering (e.g., river restoration in Alpine and piedmond streams). Open questions about these dynamics include the definition and quantitative description of bed equilibrium. Here we propose to tackle this problem using a new method based on graph theory. This algorithm, called low-path allows one to extract the network structure of a braided river from its Digital Elevation Model (DEM). It is then possible to quantify and analyse the dynamics of the braided system, and not just the bed evolution, as has been done in earlier studies. To assess the dynamics and equilibrium of a braided river, we study two runs representing two distinct phases of the same braided river: the transition from a single channel to a braided river (run 1) and the equilibrium state of this river (run 2). A set of control parameters was used to characterise both runs and supplement the low-path method. We find that although a clear distinction can be made between straight channel and braided channel for both methods, it is more difficult to distinguish between transitional braided and equilibrium braided rivers. Finally we propose a set of dimensionless numbers that specify the braided network and can be used with numerical or stochastic simulations of a braided network. To illustrate their utility, we apply the Low Path method to a real Alpine braided river (the River Navisence, Wallis, Switzerland) and compare the results to our experimental data.
Agent-based modelling for wildfire behaviour prediction
Authors: Voltolina Debora , Sterlacchini Simone , Cappellini Giacomo , Zazzeri Marco , Apuani Tiziana
Published: March 2020

The Third United Nations World Conference on Disaster Risk Reduction, held in Sendai in 2015, has defined a global strategy directed at enhancing risk-exposed communities’ resilience. In line with those needs, the study intends to improve and optimize decision-making processes in wildfire risk management by implementing predictive spatially distributed models of wildfire behaviour.

The proposed methodology has been applied to simulate some large and fully documented wildfire events in Umbria and Sardinia regions, in Central and Southern Italy respectively. The predictive model for wildfire behaviour is based on the reviewed Rothermel’s quasi-empirical mathematical model, which investigates propagation-driving parameters, i.e. the local geomorphometrical and meteorological parameters along with the pyrological and phenological characteristics of the local plant communities, to estimate the rate of spread of the fire. Propagation-driving parameters and their spatiotemporal variability have been estimated in the pre-fire environment by applying and adapting empirical relationships well-established in literature. Remote sensing-derived data have been analysed over phenologically distinct periods, along with ancillary data, to elicit information necessary to distinguish the mosaic of fuel model types and to monitor spatiotemporal variations in either live or dead fuel moisture content. According to input data availability, the methodology has been adapted to different case studies, focusing major attention on MODIS instrument by NASA on board the Terra satellite as well as on Sentinel constellations of satellites of the ESA Copernicus programme due to their accessibility and to their medium-high spatial and temporal resolution. A two-dimensional Agent-Based Model with a hexagonal grid, which, given a map of the rate of spread and an ignition point as inputs, returns a map of the cumulative propagation time, has been developed in order to simulate the wildland surface fire behaviour.

Satellite estimated propagation-driving parameters have been compared with information collected in the field and recorded by the regional annual reports on wildfire events, revealing a good predictive ability. Likewise, the wildfire behaviour model has provided accurate predictions, up to 70% in terms of morphological matching between obtained simulations and respective documented historical events boundaries, also if compared with results from other well-known wildfire simulation toolset and software. Obtained results suggest the developed wildfire behaviour model could represent a promising tool in prioritizing firefighting interventions in near-real time.