bluuebunny/crossref_metadata_2025 huggingface dataset:
Cereal yield forecasting combining satellite drought-based indices, regional climate and weather data using machine learning approaches in Morocco
Authors: Bouras El houssaine , Jarlan Lionel , Er-Raki Salah , Balaghi Riad , Amazirh Abdelhakim , Richard Bastien , Khabba Saïd
Published: March 2021

Cereals are the main crop in Morocco. Its production exhibits a high inter-annual due to uncertain rainfall and recurrent drought periods. Considering the importance of this resource to the country's economy, it is thus important for decision makers to have reliable forecasts of the annual cereal production in order to pre-empt importation needs. In this study, we assessed the joint use of satellite-based drought indices, weather (precipitation and temperature) and climate data (pseudo-oscillation indices including NAO and the leading modes of sea surface temperature -SST- in the mid-latitude and in the tropical area) to predict cereal yields at the level of the agricultural province using machine learning algorithms (Support Vector Machine -SVM-, Random forest -FR- and eXtreme Gradient Boost -XGBoost-) in addition to Multiple Linear Regression (MLR). Also, we evaluate the models for different lead times along the growing season from January (about 5 months before harvest) to March (2 months before harvest). The results show the combination of data from the different sources outperformed the use of a single dataset; the highest accuracy being obtained when the three data sources were all considered in the model development. In addition, the results show that the models can accurately predict yields in January (5 months before harvesting) with an R² = 0.90 and RMSE about 3.4 Qt.ha-1.  When comparing the model’s performance, XGBoost represents the best one for predicting yields. Also, considering specific models for each province separately improves the statistical metrics by approximately 10-50% depending on the province with regards to one global model applied to all the provinces. The results of this study pointed out that machine learning is a promising tool for cereal yield forecasting. Also, the proposed methodology can be extended to different crops and different regions for crop yield forecasting.
Local simulations of snow redistribution by wind with an intermediate-complexity snow cover model driven by different wind downscaling methods
Authors: Quéno Louis , Morin Paul , Mott Rebecca , Jonas Tobias
Published: March 2021

In mountainous terrain, wind-driven transport of deposited snow affects the overall distribution of snow, and can have a significant effect on snowmelt patterns even at coarser resolution.  In an operational modelling perspective, a compromise must be found to represent this complex small-scale process with enough accuracy while mitigating the computational costs of snow cover simulations over large domains. To achieve this compromise, we implemented the SNOWTRAN-3D snow transport module within the FSM intermediate complexity snow cover model. We included a new layering scheme and a historical variable of past snow wetting, but without resolving the snow microstructure. Simulations are run and evaluated over a small mountain range in the Swiss Alps at 25 to 100 m resolution. Being implemented in the model framework of the SLF operational snow hydrology service (OSHD), simulations further benefit from snow data assimilation techniques to provide improved estimates of solid precipitation fields. As complex wind patterns in mountains are the key processes driving snow transport, we tested statistical and dynamical methods to downscale 1 km resolution COSMO winds to better reflect topographically-induced flow patterns. These simulations are a first step working towards the integration of wind transport processes over large domains in an intermediate-complexity and -resolution operational modelling framework.
Are dykes just filled hydraulic fractures? - Inelastic deformation and emplacement mechanisms of igneous tabular intrusions
Authors: Galland Olivier , Schmiedel Tobias , Bertelsen Håvard , Guldstrand Frank , Haug Øystein , Souche Alban
Published: March 2021

Igneous tabular (sheet) intrusions such as dykes, sills and cone sheets, are fundamental elements of volcanic plumbing systems, as they represent the dominant pathways for magma transport and the main feeders of volcanic eruptions. When magma is intruded in the Earth’s crust, it makes its space by pushing and breaking the host rock, which can result in intense inelastic damage and fracturing. To understandand quantify the distribution of such intrusion-induced deformation patterns in the host rock is thus essential to resolve magma emplacement dynamics.

Sheet intrusions with their low thickness-to-length aspect ratios, resemble fractures. Based on this resemblance, tabular intrusions have been expected to form like (hydraulic) fractures propagating as tensile cracks with sharp and pointy tips, and assuming purely elastic deformation of the host rock. Even if some field observations support this theory, there is growing evidence that other mechanisms, involving significant inelastic deformation of the host rock, accommodate dyke and sill emplacement.

This contributionprovidesa summary review onthe role of inelastic deformation on the emplacement of tabular intrusions. (1) Field observations show that intrusion tips can be rounded, blunt, and the host deformation accommodating their propagation exhibits inelastic, compressional deformation, in drastic contradiction with theoretical predictions. (2) 3D and 2D laboratory experimentsof magma emplacement in a cohesive Mohr-Coulomb crusthighlightthat magma-induced inelastic deformation, in the form of shear damage and faulting, are first-order transient mechanical precursors for the propagating magma. In addition, these experiments show that the cohesion and friction properties of the model host rock are first-order parameters controlling the formation of intrusions of various shapes, including dykes, plugs, cone sheets, sills and laccoliths. (3) Elasto-plastic numerical models highlight that shear failure is the dominant mechanism to accommodate intrusion growth as soon as heterogeneities are introduced. We conclude that heterogeneities within the host-rock may locally "seed" shear faults ahead of the magmatic intrusion in the propagating direction, in good agreement with field observations. Given that rocks are naturally heterogeneous at multiple scale, these models suggest that shear failure is likely to be a common mechanism for accommodating magma propagation.

Overall, our field observations andmodelresultsshow that the brittle Coulomb properties of rocks, and their heterogeneities,must be accounted for revealing the nature and distribution of fractures and inelastic damage accommodating the emplacement of igneous tabular intrusions.
Combining open channel and sewer system network modelling to develop the Hydraulic Risk Management Plan for Brescia (Northern Italy)
Authors: Grossi Giovanna , Berteni Francesca , Dada Arianna , Leoni Paolo
Published: March 2021

Flood risk management is one of priorities set by the European Union to protect population and assets. In a very recent report of the European Environment Agency dealing with urban adaptation to climate change (EEA, 2020), extreme weather events (heatwaves, heavy precipitation, flooding and droughts) are expected to cause the most pronounced impacts in European cities, besides vector‑borne diseases. Italian regions are taclking flood risk management also by setting regulations on the runoff production in urban areas.

According to a recent regulation approved by Regione Lombardia municipalities are requested to prepare the Hydraulic Risk Management Plan, including measures to ensure compliance with the principle of the ‘hydraulic’ and ‘hydrological’ invariance for the urban area, in which runoff volumes generated by an intense meteoric event must remain unchanged or at least must be limited. The idea arises from the need to manage the rainwater drainage in urban contexts, where the existing sewerage system has been designed based on an inadequate return time period.

The planning activity requires a modelling framework accounting for both the open channel network (mainly addressing irrigation demand) and the sewer pipe network. While separate hydraulic models might help the management provided by separate authorities, an integrated model is ensuring a complete representation of the system hydrodynamics. This type of model is characterized by a much more complex structure which requires greater data accuracy for the construction and calibration of the model in order to obtain realistic results.

Some critical issues are being presented for Brescia, a town located in Northern Italy, at the foothills of the Alps.  Potential flood risk is linked to the dense historical irrigation and drainage channels network that cross the urban area from north to south and the old city centre. Critical areas are those hosting the post-war urban development where the waterways have been uncovered and covered in a chaotic and uncontrolled way, in some cases even under houses and other buildings.
Tropospheric delay parameters derived from GNSS-tracking data of a fast-moving fleet of trains
Authors: Aichinger-Rosenberger Matthias , Hanna Natalia , Weber Robert
Published: March 2021

Electromagnetic signals, as broadcasted by Global Navigation Satellite Systems (GNSS), are delayed when travelling through the Earth’s atmosphere due to the presence of water vapour. Parametrisations of this delay, most prominently the Zenith Total Delay (ZTD) parameter, have been studied extensively and proven to provide substantial benefits for atmospheric research and especially the Numerical Weather Prediction (NWP) model performance. Typically, regional/global networks of static reference stations are utilized to derive ZTD along with other parameters of interest in GNSS analysis (e.g. station coordinates). Results are typically used as a contributing data source for determining the initial conditions of NWP models, a process referred to as Data Assimilation (DA).

This contribution goes beyond the approach outlined above as it shows how reasonable tropospheric parameters can be derived from highly kinematic, single-frequency (SF) GNSS data. The utilized data was gathered at trains by the Austrian Federal Railways (ÖBB) and processed using the Precise Point Positioning (PPP) technique. Although the special nature of the observations yields several challenges concerning data processing, we show that reasonable results for ZTD estimates can be obtained for all four analysed test cases by using different PPP processing strategies. Comparison with ZTD calculated from ERA5 reanalysis data yields a very high correlation and an overall agreement from the low millimetre-range up to 5 cm, depending on solution and analysed travelling track. We also present the first tests of assimilation into a numerical weather prediction (NWP) model which show the reasonable quality of the results as between 30-100 % of the observations are accepted by the model. Furthermore, we investigate means to transfer the developed ideas to an operational stage in order to exploit the huge benefits (horizontal/temporal resolution) of this special dataset for operational weather forecasting. 
Identifying land cover suitability factors for photovoltaic installations with focus on cropland and urban areas
Authors: Yeligeti Madhura , Hu Wenxuan , Scholz Yvonne , von Krbek Kai
Published: March 2021

Solar photovoltaic (PV) systems will foreseeably be an integral part of future energy systems. Land cover area analysis has a large influence on estimatiin of long-term solar photovoltaic potential of the world in high spatial detail. In this regard, it is often seen in contemporary works, that the suitability of various land cover categories for PV installation is considered in a yes/no binary response. While some areas like natural parks, sanctuaries, forests are usually completely exempted from PV potential calculations, other land over categories like urban settlements, bare, sparsely vegetated areas, and even cropland can principally support PV installations to varying degrees. This depends on the specific land use competition, social, economic and climatic conditions, etc. In this study, we attempt to evaluate these ‘factors of suitability’ of different land cover types for PV installations.

As a basis, the openly available global land cover datasets from the Copernicus Land Monitoring Service were used to identify major land cover types like cropland, shrubland, bare, wetlands, urban settlements, forests, moss and snow etc. For open area PV installations, with a focus on cropland, we incorporated the promising technology of ‘Agri-voltaics’ in our investigation. Different crops have shown to respond positively or negatively, so far, to growing under PV panels according to various experimental and commercial sources. Hence, we considered 18 major crops of the world (covering 85% of world cropland) individually and consequently, evaluated a weighted overall suitability factor of cropland cover for PV, for three acceptance scenarios of future.

For rooftop PV installations in urban areas, various socio-economic and geographical influences come in play. The rooftop area available and further usable for PV depends on housing patterns (roof type, housing density) which vary with climate, population density and socio-economic lifestyle. We classified global urban areas into several clusters based on combinations of these factors. For each cluster, rooftop area suitability is evaluated at a representative location using the land cover maps, the Open Street Map and specific characteristics of the cluster.

Overall, we present an interdisciplinary approach to integrate technological, social and economic aspects in land cover analysis to estimate PV potentials. While the intricacies may still be insufficient for planning small localized energy systems, this can reasonably benefit energy system modelling from a regional to international scale.
Natural hazard risk management for cultural heritage assets: advances in the context of the RIACT research project
Authors: Romão Xavier , Figueiredo Rui , Paupério Esmeralda , Salazar Gerardo , Tikhonova Olha
Published: March 2021

Cultural heritage is universally recognized as an essential part of the socio-cultural and economic capital of a country. Current policies emphasize the strong contribution and cross-cutting nature of cultural heritage to achieve strategic goals for a smart, sustainable and inclusive growth. Furthermore, the important role that cultural heritage plays in creating and enhancing social capital has been particularly highlighted, as well as its economic impact. Nevertheless, natural hazards cause serious threats to cultural heritage, and severe damage and losses are recurrently seen to affect it due to these types of events. While such impacts can be seen to stem from a variety of sources, their physical characteristics play a significant role in their vulnerability to natural hazards. Therefore, it is imperative to explicitly consider cultural heritage in natural hazard risk reduction and management initiatives, from local to national and global scales, supported by rational and knowledge-based vulnerability and risk assessment studies.

However, the development of such assessments for a large number of cultural heritage assets in a region presents several challenges. Firstly, there is a shortage of methodological approaches to model the vulnerability and risk of cultural heritage assets to different natural hazards. Secondly, performing detailed vulnerability/risk analyses for every cultural heritage asset on a large scale (i.e. across a region or a country) would require resources that are unavailable in most cases. Finally, adequate post-disaster damage and loss data to support the development of methodologies is almost inexistent in this sector, namely due to a lack of approaches to do so, and to the difficulties in expressing intangible losses in quantitative terms.

In this context, this presentation will showcase recent advances in these fields developed within the ongoing research project RIACT (Risk Indicators for the Analysis of Cultural Heritage under Threat). These include the development of simple but robust approaches for the analysis of the vulnerability and risk of cultural heritage at various scales and their application in pilot case studies, the development of a database for collecting disaster damage and loss data in the cultural heritage sector, and the development of methodologies for cultural heritage disaster damage valuation and value-based post-disaster recovery prioritization. Ultimately, these research efforts aim to support stakeholders responsible for cultural heritage management and preservation in improving their adaptive capacity to plan for and respond to natural hazards.
Modeling the additional root cohesion of four sub-tropical shrub and tree species
Authors: Arnone Elisa , Napoleoni Quintilio , Noto Leonardo
Published: March 2021

 The effect of plant roots on hillslope stabilization against rainfall-induced shallow landslides depends on the mutual interaction between biotechnical characteristics of the root system (i.e., root length, root tensile strength, root area, root diameter profile) with the soil root-zone and the hydrological processes therein. Describing adequately the root architecture of a plant species is useful when root strength models, such as the Root Bundle Model (RBM), are applied to assess the ultimate root reinforcement.

This study describes the preliminary results of the calibration of an existing Root Topological Model (RTM) combined with a RBM model to estimate the additional roots shear resistance of vegetation typical of a subtropical climate.

Specifically, the dataset of the root system of four Hong Kong native species of shrubs (Rhodomyrtus tomentosa and Melastoma sanguineum) and trees (Schefflera heptaphylla and Reevesia thyrsoidea) has been used. The dataset includes the measurements relative to both the root architecture, i.e., root diameter classes and number of roots as function of depth, and the root resistance, i.e. root tensile strengths for each diameter classes, which were obtained from laboratory test.

The present application allows for calibrating and exploiting the potentiality of the framework RTM-RBM in a climatic environment different from the Mediterranean one analyzed so far for its development, thus testing the response and the flexibility of the modeling framework. The availability of such a tool could enhance, for example, the assessment of the most suitable plant species to be adopted for the slope stabilization in different soil and/or climatic conditions.
Numerical simulation of the evening transition in the atmospheric boundary layer using LES and RANS models
Authors: Tkachenko Ekaterina , Debolskiy Andrey , Mortikov Evgeny
Published: March 2021

This study investigates the dynamics of the evening transition in the atmospheric boundary layer (ABL) diurnal cycle, specifically the decay of the turbulent kinetic energy (TKE) taking place there. Generally, the TKE decay is assumed to follow the power law E(t) ~ t-α, where E(t) and t are normalized TKE and normalized time, respectively, and the parameter α determines the decay rate.

Two types of ABL numerical modeling are compared: three-dimensional large-eddy simulation (LES) models and one-dimensional Reynolds-averaged Navier-Stokes (RANS) models. The evening transition is simulated through facilitating the formation of the convective boundary layer (CBL) by having a constant positive surface heat flux, and the subsequent decay of the CBL when the surface heat flux is decreased.

Several features of this process have been studied in relative depth, in particular the TKE decay rate at different stages of the evening transition, the sensitivity of the results to the domain size, and the dynamics of the large- and small-scale turbulence during the transition period. LES experiments with different setups were performed, and the results were then compared to those obtained through RANS experiments based on the k-epsilon model (a two-equation model for TKE and dissipation rate, where model constants are chosen to allow for correct simulation of SBL main properties [1], as well as CBL growth rate [2]).

This study was funded by Russian Foundation of Basic Research within the project N 20-05-00776 and the grant of the RF President within the MK-1867.2020.5 project.

1. Mortikov E. V., Glazunov A. V., Debolskiy A. V., Lykosov V. N., Zilitinkevich S. S. Modeling of the Dissipation Rate of Turbulent Kinetic Energy // Doklady Earth Sciences. 2019. V. 489(2). P. 1440-1443

2. Burchard H. Applied Turbulence Modelling in Marine Waters. Berlin, Germany: Springer, 2002. P. 57-59
Quantifying microplastic particle transport and retention in an experimental flume environment
Authors: Boos Jan-Pascal , Gilfedder Benjamin , Frei Sven
Published: March 2021

Rivers and streams are the dominant transport vectors for microplastic (MP) input into marine environments. During transport, complex physicochemical interactions between particles, water and river sediments influence particle mobility and retention. The specific transport mechanisms of MP in fluvial systems are not yet fully understood, and the main reason lies in the limitation in reliable data derived from experimental analysis.

In our subproject of the ‘CRC 1357 Microplastics’, we investigate the hydrodynamic mechanisms that control the transport and retention behavior of MP in open channel flows and streambed sediments. In an experimental flume environment, we create realistic hydrodynamic and hyporheic flow conditions by using various porous media (e.g. glass beads or sand) and bedform structures (e.g. riffle-pool sequences, ripples and dunes), modelled from real stream systems.

The method developed here can quantitatively analyze the transport of pore-scale particles (1-40 µm) based on fluorometric techniques. Particle velocity distributions and particle transport are measured using Particle-Image-Velocimetry and Laser-Doppler-Velocimetry. With our setup, we can quantitatively investigate time-resolved MP transport and retention through the aqueous and solid phase in a flume scale experiment.
Subpixel determination of wormhole tip position in 4D tomography of dissolving limestone cores
Authors: Sharma Rishabh Prakash , Cooper Max P. , Ladd Anthony J.C. , Szymczak Piotr
Published: March 2021

Dissolution of porous rocks by reactive fluids is a highly nonlinear process resulting in a variety of dissolution patterns, the character of which depends on physical conditions such as flow rate and reactivity of the fluid. Long, finger-like dissolution channels, “wormholes”, are the main subject of interest in the literature, however, the underlying dynamics of their growth remains unclear. 

While analyzing the tomography data on wormhole growth.  one open question is to define the exact position of the tip of the wormhole. Near the tip the wormhole gradually thins out and the proper resolution of its features is hindered by the finite spatial resolution of the tomographs. In particular, we often observe in the near-tip region several disconnected regions of porosity growth, which - as we hypothesized - are connected by the dissolution channels at subpixel scale. In this study, we show how these features can be better resolved by using numerically calculated flow fields in the reconstructed pore-space. 

We used 70 micrometers, 16-bit grayscale X-ray computed microtomography (XCMT) time series scans of limestone cores, 14mm in diameter and 25mm in length. Scans were performed during the entire dissolution experiment with an interval of 8 minutes. These scans were further processed using a 3-phase segmentation proposed by Luquot et al.[1], in which grayscale voxels are converted to macro-porosity, micro-porosity and grain phases from their grayscale values. The macro-porous phase is assigned a porosity of 1, while the grain phase is assigned 0. Micro-porous regions are assigned an intermediate value determined by linear interpolation between pore and grain threshold using grayscale values. An OpenFOAM based, Darcy-Brinkman solver, porousFoam, is then used to calculate the flow field in this extracted porosity field. 

Porosity contours reconstructed from the tomographs show some disconnected porosity growth near the tip region which later become part of the wormhole in subsequent scans. We have used a novel approach by including the micro-porosity phase in pore-space to calculate the flow-fields in the near-tip region. The calculated flow fields clearly show an extended region of focused flow in front of the wormhole tip, which is a manifestation of the presence of a wormhole at the subpixel scale. These results show that micro-porosity plays an important role in dissolution and 3-phase segmentation combined with the flow field calculations is able to capture the sub-resolved dissolution channels. 

 

 [1] Luquot, L., Rodriguez, O., and Gouze, P.: Experimental characterization of porosity structure and transport property changes in limestone undergoing different dissolution regimes, Transport Porous Med., 101, 507–532, 2014
Vertical Analysis of Mesoscale Eddies in the Northern Bay of Bengal
Authors: Shee Abhijit , Pramanik Saikat , Sil Sourav , Das Sudeep
Published: March 2021

Mesoscale eddies, coherent rotating structure with typical horizontal scale of ~100 km and temporal scales of a month, play a significant role in ocean energy and mass transports. Here both mesoscale cyclonic and anticyclonic eddies moving towards south in the northern Bay of Bengal during 20th March 2017 to 20th May 2017 are observed using a high resolution (~5 km) nitrogen-based nutrient, phytoplankton, zooplankton, and detritus (NPZD) ecological model embedded with Regional Ocean Modeling System (ROMS). Spatial maps of sea surface height anomaly (SSHA) from satellite-derived Archiving Validation, and Interpretation of Satellite Oceanographic (AVISO), and model are well matched. The centers and effective radii of both kind of eddies are identified using SSHA to proceed for their three-dimensional analysis. The extreme intensities of cyclonic and anticyclonic eddy centers are observed on 8th April 2017 at 86.40°E, 18.19°N and 84.80°E, 16.52°N respectively. Both kind of eddies are vertically extended upto 800 m and have radius ~100 km at surface. At these two locations, time-depth variations of zonal and meridional currents, and other physical (temperature and salinity) and bio-physical (chlorophyll-a, phytoplankton, zooplankton, detritus nutrient, dissolved oxygen and NO3 nutrient) parameters are studied particularly from 8th March 2017 to 8th May 2017. Further vertical distribution of zonal and meridional currents, and other parameters are studied along the eddy diameters at their extreme intensity. In the vertical structure of both current components, an opposite sense between cyclonic and anticyclonic eddies are clearly captured, while other variables show strong upwelling and downwelling nature around the cyclonic and anticyclonic eddy centers respectively. Abundances (scarcities) of chlorophyll-a, phytoplankton, zooplankton and detritus nutrient are observed at 50 – 150 m depth of the cyclonic (anticyclonic) eddy center. The concentration of chlorophyll-a, phytoplankton, zooplankton and detritus nutrient reach to maximum of 1 mg/m3, 0.35 mMol/m3, 0.22 mMol/m3 and 0.14 mMol/m3 at ~80 m depth for the cyclonic eddy, while these are absent for the anticyclonic eddy.
Laboratory experiments on Internal Solitary Waves in ice covered waters 
Authors: Carr Magda , Sutherland Peter , Haase Andrea , Evers Karl-Ulrich , Fer Ilker , Jensen Atle , Kalisch Henrik , Berntsen Jarle , Parau Emilian , Thiem Oyvind , Davies Peter
Published: March 2021

Oceanic internal waves (IWs) propagate along density interfaces and are ubiquitous in stratified water. Their properties are influenced strongly by the nature and form of the upper and lower bounding surfaces of the containing basin(s) in which they propagate.  As the Arctic Ocean evolves to a seasonally more ice-free state, the IW field will be affected by the change. The relationship between IW dynamics and ice is important in understanding (i) the general circulation and thermodynamics in the Arctic Ocean and (ii) local mixing processes that supply heat and nutrients from depth into upper layers, especially the photic zone. This, in turn, has important ramifications for sea ice formation processes and the state of local and regional ecosystems.  Despite this, the effect of diminishing sea ice cover on the IW field (and vice versa) is not well established. A better understanding of IW dynamics in the Arctic Ocean and, in particular, how the IW field is affected by changes in both ice cover and stratification, is central in understanding how the rapidly changing Arctic will adapt to climate change.

 

An experimental study of internal solitary waves (ISWs) propagating in a stably stratified two-layer fluid in which the upper boundary condition changes from open water to ice are studied for grease, level, and nilas ice. The experiments show that the internal wave-induced flow at the surface is capable of transporting sea-ice in the horizontal direction. In the level ice case, the transport speed of, relatively long ice floes, nondimensionalized by the wave speed is linearly dependent on the length of the ice floe nondimensionalized by the wave length. It will also be shown that bottom roughness associated with different ice types can cause varying degrees of vorticity and small-scale turbulence in the wave-induced boundary layer beneath the ice. Measures of turbulent kinetic energy dissipation under the ice are shown to be comparable to those at the wave density interface. Moreover, in cases where the ice floe protrudes into the pycnocline, interaction with the ice edge can cause the ISW to break or even be destroyed by the process. The results suggest that interaction between ISWs and sea ice may be an important mechanism for dissipation of ISW energy in the Arctic Ocean.

 

Acknowledgements

This work was funded through the EU Horizon 2020 Research and Innovation Programme Hydralab+.
PyEt - a Python package to estimate potential and reference evapotranspiration
Authors: Vremec Matevž , Collenteur Raoul
Published: March 2021

Evapotranspiration (ET) is a major component of the hydrological cycle and accurate estimates of the flux are important to the water and agricultural sector, among others. Due to difficulties in the direct observation of ET in the field, the flux is often estimated from other meteorological data using empirical formulas. There is a wide variety of such formulas, with different levels of input data and parameter requirements. While some Python packages are available in the Python ecosystem for these tasks, they typically focus on one specific formula or data type. The goal of PyEt is to provide a Python package for the estimation of ET that works with many different data types, is well documented and tested, and simple to use. The source code is hosted at GitHub (https://github.com/phydrus/PyEt) and Pypi can be used to install the package. PyEt currently contains nine different methods to estimate ET and various methods to estimate surface and aerodynamic resistance. The methods are tested against other open source data to ensure proper functioning of the methods. While the methods currently are only implemented for 1D data (e.g. time series data), future work will focus on enabling the methods on 2D and 3D data as well (such as Numpy Arrays, XArray, and NetCDF files). The package allows hydrologists to compute and compare evapotranspiration estimates using different approaches with minimum effort. The presentation will focus on the problems associated with reproducibility in ET estimation and linkage with existing Python libraries to perform complex sensitivity and uncertainty analyses.
Evaluating the temperature dependence of bedrock hillslope erosion in the Mont Blanc massif using in situ cosmogenic 3He-10Be-14C
Authors: Dennis Donovan P. , Scherler Dirk , Niedermann Samuel , Hippe Kristina , Wittmann Hella , Ravanel Ludovic , Tremblay Marissa , Guralnik Benny , Lupker Maarten
Published: March 2021

The erosion of cold bedrock hillslopes in alpine environments depends not only on rates of frost weathering and accumulated rock damage, but additionally on the removal of the weathered material from the bedrock surface. In the Mont Blanc massif, steep bedrock faces with exposure ages sometimes much older than 50,000 years sit in close proximity to actively-eroding rockwalls, suggesting a more complex relationship between temperature and erosion rates than encompassed by the proposed “frost-cracking window.” Stochastic events like rockfalls and rock avalanches, despite their rarity, contribute a non-trivial proportion of the total sediment budget in alpine permafrost regions, adding to the contribution from background “steady-state” erosion. Employing a methodology based on the combination of in-situ cosmogenic nuclides 3He -10Be-14C, we test the temperature-dependence of high-alpine erosion while taking into account erosional stochasticity.

From cosmogenic 10Be concentrations of amalgamated samples collected on the Aiguille du Midi (3842 m a.s.l.) in the Mont Blanc massif, we find an order of magnitude difference in erosion rate across the peak’s surface. Our preliminary measured erosion rates, ranging between appx. 0.03 mm yr-1 and 1.0 mm yr-1, correlate neither with modern temperature measurements from borehole thermistors, nor with our current estimates of bedrock cosmogenic 3He-derived paleotemperatures. The corresponding cosmogenic 14C/10Be ratios (between 1.70 and 4.0) for these erosion rates indicate that our measurements are not biased by recent stochastic rockfall events. Our current results therefore suggest that on geomorphic timescales, bedrock hillslope erosion rates are not set solely by rates of frost-cracking, but rather by the combined effects of frost-cracking and permafrost thaw-induced rockfalls. These insights are relevant both for short-term monitoring of alpine permafrost and associated geohazards under a warming climate, as well as studies of proposed “buzzsaws” operating on glacial-interglacial timescales.
Understanding current and future impacts of public water supply on global nitrogen cycling
Authors: Flint Elizabeth M. , Ascott Matthew J. , Gooddy Daren C. , Surridge Benjamin W.J. , Stahl Mason  O.
Published: March 2021

Within in the United States some 54 km3 of water is withdrawn annually for public supply. Around 16% of this water is subsequently lost through leakage as it moves through distribution networks. These processes not only have implications both economically and for water security, but the substantial redistribution of water has also been shown to cause significant perturbations in elemental cycling. Due to its importance for ecological health and global food production, this research attempts to quantify the nitrogen (N) fluxes associated with a range of Public Water Supply processes, such as abstraction and leakage. Using county level data sets, these N fluxes will be determined across the contiguous United States, and the significance of results evaluated through comparisons with other quantified N fluxes. Assessments will also be made on how the absolute and relative significance of these fluxes may change in the future, such as due to evolving water demands as a result of the combined drivers of changing climate and increasing population. Outputs from the US will form part of a wider global assessment, including comparisons with less developed countries.
Statistical modelling of extreme temperatures on the Greenland Ice Sheet
Authors: Clarkson Daniel , Eastoe Emma , Leeson Amber
Published: March 2021

The Greenland ice sheet has experienced significant melt over the past 6 decades, with extreme melt events covering large areas of the ice sheet. Melt events are typically analysed using summary statistics, but the nature and characteristics of the events themselves are less frequently analysed. Our work aims to examine melt events from a statistical perspective by modelling 20 years of MODIS surface temperature data with a Spatial Conditional Extremes model. We use a Gaussian mixture model for the distribution of temperatures at each location with separate model components for ice and meltwater temperatures. This is used as a marginal model in the full spatial model and gives a more location-specific threshold to define melt at each location. The fitted model allows us to simulate melt events given that we observe an extreme temperature at a particular location, allowing us to analyse the size and magnitude of melt events across the ice sheet.
Adaptive ML-Models for analysis of TSS, Chlorophyll-a, in mixed water type scenarios in Ca Mau peninsula, Vietnam
Authors: Vu Huu Long , Schenk Andreas , Hinz Stefan
Published: March 2021

The multispectral mission of Sentinel-2 enables reliable, affordable and continuous environmental monitoring systems in fields like agriculture, biodiversity, environmental hazards and surface water. Several studies have proven that main water quality parameters like total suspended solids (TSS) and chlorophyll (Chl-a) can be estimated from multispectral data using different methods and algorithms. However, independently of the specific approach, these algorithms are selected and optimized to work primarily for one of the main water types i.e. open water, coastal water or inland water. This is also shown by the fact that there is not a single universal algorithm, which can be applied to all water types with consistent and reliable performance at the same time.

Ca Mau peninsula is a spacious area located in the southern part of the Mekong Delta, with an area of around 1.6 million hectares. This area has high growth rates of agricultural and aquaculture production, hence diverse water demands and water use types. In this study we use Sentinel-2 remote sensing data to monitor surface water quality using adaptive ML models to account for the different surface water types which occur in this area. Through using remote sensing data, we can provide a synoptic and sufficient view in spatial aspects about water quality parameters in the Ca Mau peninsula. Adapting the ML model will address the bio-optical model for a mixed water scenario.

The study is based on Sentinel-2 satellite images acquired in 2019 and 2020, supplemented by field data, i.e. hyperspectral measurements using close range observations, in-situ measurements and water samples, with the aim to collect a comprehensive reference data set as biophysical parameters are closely connected with spectral parameters at close range as well as at high spectral resolution. Therefore, surface hyperspectral measurement has been used to simulate Sentinel 2 multispectral image data at the respective bands.

We automatically assign the water type classes to observed surface water by integrating GIS data and remote sensing as the pre-processing step. For each class, the ML models are trained based on the experimental measurements with the multispectral and the simulated multispectral images on the respective water types. We devote special attention to water type boundaries to provide a smooth transition of estimated parameters.

The outputs of this model are surface water quality distribution maps with turbidity, TSS, and Chl-a parameters for all areas in Ca Mau peninsula, independent of the actual water type. Through the acceptable accuracy of model testing, the consolidation model will contribute water quality parameters that are crucial and meaningful to the planning and use of water for domestic use and production, besides, it also supports the decision-making of sustainable water use.
Tracking compositional changes within the High Arctic Large Igneous Province using zircon Hf isotopes from altered volcanic ash layers of the Sverdrup Basin, Canada
Authors: Pointon Michael , Flowerdew Michael , Hülse Peter , Schneider Simon , Millar Ian , Whitehouse Martin
Published: March 2021

During Late Cretaceous times the Sverdrup Basin, Arctic Canada, received considerable air-fall volcanic material. This is manifested as numerous centimetre- to decimetre-thick diagenetically altered volcanic ash layers (bentonites) that occur interbedded with mudstones of the Kanguk Formation. Previous research on bentonite samples from an outcrop section in the east of the basin (Sawtooth Range, Ellesmere Island) revealed two distinct volcanic sources for the bentonites: most of the bentonites analysed (n=9) are relatively thick (0.1 to 5 m), were originally alkaline felsic ashes, and were likely sourced from local volcanic centres on northern Ellesmere Island or the Alpha Ridge that were associated with the High Arctic Large Igneous Province (HALIP). Two thinner (<5 cm) bentonites with contrasting subalkaline geochemistry were also identified. These were inferred to have been derived from further afield, from volcanic centres within the Okhotsk-Chukotka Volcanic Belt, Russia.

To better understand volcanism within the vicinity of the Sverdrup Basin during Late Cretaceous times, and further test the above interpretations, a larger suite of bentonite samples was investigated, drawing on samples from outcrop sections in the central and eastern Sverdrup Basin. Whole-rock geochemical analyses and combined zircon U-Pb age and Hf isotope analyses were undertaken. The vast majority of bentonites analysed to date have alkaline geochemistry and were likely sourced from proximal volcanic centres related to the HALIP. The combined U-Pb and Hf isotope data from these bentonites show a progression from evolved (-2 to 0) to moderately juvenile (+9 to +10) εHf(t) values between late Cenomanian and early Campanian times (c. 97–81 Ma). This is interpreted to record compositional change through time within the local HALIP magmatic system.
Where are the peatlands? Comparing two global peatland maps through L-band brightness temperature simulations
Authors: Bechtold Michel , Mahanama Sarith P. , Reichle Rolf H. , Koster Randal D. , De Lannoy Gabrielle J. M.
Published: March 2021

Mapping the global peatland distribution is important for embedding peatland processes into Earth System Models. Peatland maps are typically compiled from nation-specific soil or ecosystem maps or based on machine learning tools trained on such data. Here, we evaluate the performance of a land surface model with two different peatland map inputs in providing critical land surface estimates (soil moisture, temperature) to a Radiative Transfer Model (RTM) for L-band brightness temperature (Tb). We hypothesize that an improved performance of the land surface model in Tb space indicates a better spatial peatland distribution input within the footprint of Tb observations (~40 km).

We employ the NASA Catchment Land Surface Model (CLSM) with a recently added module for peatland hydrology (PEATCLSM modules). We run this model at a 9-km EASEv2 resolution over the Northern Hemisphere for two soil maps that differ in their peatland distributions. The applied soil distributions are: (MAP1) a combination of the Harmonized World Soil Database and the State Soil Geographic Database, also used to generate the Soil Moisture Active Passive (SMAP) Level-4 soil moisture product, and (MAP2) a hybrid of HWSD-STATSGO and the ‘PEATMAP’ product, which is mainly compiled from national peatland maps. MAP2 indicates ~30 % more peatland area over the Northern Hemisphere. For both peat distributions, CLSM is run and parameters of the RTM are calibrated with 10 years of multi-angular L-band Tb observations from the Soil Moisture and Ocean Salinity SMOS mission. Afterwards, CLSM is run together with the calibrated RTM within a data assimilation system, with and without (open-loop) assimilating SMAP Tb observations, for the period 2015-2020. Our results demonstrate that Tb misfits (in both the open-loop and assimilation runs) are reduced in the areas with the largest differences in peat distribution, thus indicating a basic validity of assuming a peatland-like hydrological dynamics for the larger peat extent of MAP2. Results will be discussed in the context of how peatlands are defined in global peatland maps and the question of what is typically modeled as a peatland in Earth System Models. We propose the evaluation of future releases of peatland maps in Tb space as a tool to evaluate their suitability for implementation into Earth System Models.
Fire regimes and post-fire evolution of burned areas in selected plant biomes of the planet studying the phenology of the landscape with time series of satellite images
Authors: Koutsias Nikos , Karamitsou Anastasia , Nioti Foula , Coutelieris Frank
Published: March 2021

Plant biomes and climatic zones are characterized by a specific type of fire regime which can be determined from the history of fires in the area and it is a synergy mainly of the climatic conditions and the functional characteristics of the types of vegetation. They correspond also to specific phenology types, a feature that can be useful for various applications related to vegetation monitoring, especially when remote sensing methods are used. Both the assessment of fire regime from the reconstruction of fire history and the monitoring of post-fire evolution of the burned areas can be studied with satellite remote sensing based on satellite time series images. The free availability of (i) Landsat satellite imagery by US Geological Survey (USGS, (ii) Sentinel-2 satellite imagery by ESA and (iii) MODIS satellite imagery by NASA / USGS allow low-cost data acquisition and processing (eg 1984-present) which otherwise would require very high costs. The purpose of this work is to determine the fire regime as well as the patterns of post-fire evolution of burned areas in selected vegetation/climate zones for the entire planet by studying the phenology of the landscape with time series of satellite images. More specifically, the three research questions we are negotiating are: (i) the reconstruction of the history of fires in the period 1984-2017 and the determination of fire regimes with Landsat and Sentinel-2 satellite data , (ii) the assessment of pre-fire phenological pattern of vegetation and (iii) the monitoring and comparative evaluation of post-fire evolution patterns of the burned areas.

Acknowledgements

This research has been co-financed by the Operational Program "Human Resources Development, Education and Lifelong Learning" and is co-financed by the European Union (European Social Fund) and Greek national funds.

 