bluuebunny/crossref_metadata_2025 huggingface dataset:
Deep learning for water quality prediction: the application of LSTM model to predict water quality in catchment scale
Authors: Sahraei Amir , Breuer Lutz , Kraft Philipp , Houska Tobias
Published: March 2021

The prediction of water quality is an efficient way for managing water resources and protecting ecosystems by providing an early warning against water quality deterioration. So far, the classical approach is to predict water quality by the utilization of complex process-based water quality models. However, these models are not easy to set up and require comprehensive input data. The local characteristics, detailed process understandings and eventually data from land users such as farmers are needed, to build up a valid model structure. Such constraints can end up in wrong scientific conclusions ranging from false alarms to unpredicted environmental pollution in practical water monitoring application. Long short-term memory (LSTM) algorithms are known to be able to overcome some of the typical constraints in hydrological model applications. However, their performance in water quality prediction has rarely been explored. In this study, we investigate the ability of a LSTM model to predict the complex, nonlinear behavior of water quality parameters in the Schwingbach Environmental Observatory (SEO), Germany.  We predict weekly nitrogen-nitrate concentrations, weekly stable isotopes of water concentrations (δ18O) and daily water temperature in six stream‑ and six groundwater sources with different landuse and hillslope conditions. We use meteorological forcing data and catchment attributes as input variables. To ensure an efficient model performance, we employ a Bayesian optimization approach to optimize the hyperparameters of the LSTM. The model performance is evaluated by the Root Mean Squared Error (RMSE). Our LSTM is robust in capturing the dynamics of the water quality parameters over time. The RMSE for the LSTM performance ranges from 0.27 to 3.38 mg/l, from 0.069 to 0.27 ‰ and from 1.3 to 2.1 °C for nitrogen‑nitrate, δ18O and water temperature, respectively. We compare the RMSE with statistical parameters of data. Results confirm that the LSTM is a promising tool for early risk assessment of water quality, particularly in view that only a minimal set of catchment information is needed to gain robust results.
A hybrid dynamical-statistical downscaling approach for climate change impacts analysis on high resolution in the Greater Athens Area
Authors: Varotsos Konstantinos V. , Dandou Aggeliki , Papangelis Giorgos , Roukounakis Nikolaos , Tombrou Maria , Giannakopoulos Christos
Published: March 2021

The available state-of-the art Regional Climate Model (RCM) simulations from the Euro-Cordex initiative have an horizontal resolution of about 12km which although is adequate for assessing regional climate change impacts is still coarse for studying the climate change impacts in an urban environment such as the Greater Athens Area (GAA). To this aim we propose a hybrid dynamical-statistical downscaling approach that produces high resolution, in the order of 1km, climate change projections for two future periods and under two RCP scenarios. To produce the higher resolution climate projections we combine the results of the Weather Research and Forecasting model (WRF) - Version 3.9.1 -including a single-layer urban canopy model to represent the urban tile- with available RCMs simulations obtained from the Euro-Cordex database.

Initially an annual WRF, ERA interim driven, simulation for a year identified as a “representative year” for the period 1971-2000 in the GAA is performed at an horizontal resolution of 1km. Subsequently the spatial signal of the WRF simulation is passed to the ERA interim driven RCM simulations for the period 1971-2000 using the unbiasing bias adjusting method which maintains the absolute trend as well as the variability of the RCM simulated data at all time scales. In a second step the donwscaled RCM evaluation simulations are used to bias adjust the transient RCM simulations using the empirical quantile method (EQM). EQM works by matching the transient simulations empirical cumulative distributions to the evaluation ones. This is achieved by establishing a quantile-dependent correction function between them during the reference period. The correction functions are then applied to both the historical and the future periods.

In this study we present the results for temperature and precipitation but the methodology can be extended to other variables of interest assuming that the WRF and the evaluation RCM simulations adequately reproduce their spatial and temporal variability, respectively.
New insights into the crustal architecture and tectonic evolution of the Eastern Gulf of Mexico.
Authors: Vasileiou Athanasia , Gouiza Mohamed , Mortimer Estelle , Paton Douglas , Nanfito Aleece , Lewis David
Published: March 2021

The Gulf of Mexico is an intraplate oceanic basin where rifting started in the Late Triassic, leading to drifting by Middle Jurassic and ensuing oceanic accretion, which ceased by the Early Cretaceous. Its tectonic evolution encompasses multiple rifting phases dominated by orthogonal extension, major strike-slip structures, transtensional basins, variable magmatism, and salt deposition. This complex tectonic history is captured in the rifted margins of the Gulf of Mexico, especially along the eastern part of the basin; where considerable debate remains regarding the crustal configuration and tectonic evolution.

This study presents new insights into the crustal types and an updated tectonic framework for the Florida margin. An integrated analysis of seismic, gravity, and magnetic data allows us to characterise the continental crust, which shows wide zones of hyperextension that we relate to pull-apart basins, magmatic underplating, seaward dipping reflection (SDR) packages, and a narrow zone of exhumed mantle. In addition, we identified NW-SE trending sinistral strike-slip faults altering the typical crustal configuration expected in a rifted margin.

Our results suggest the need for a new plate model of the Florida margin at the Eastern Gulf of Mexico that invokes the polyphase rifting, accounts for the Yucatan’s block counter-clockwise rotation, explains the increase in magma supply, and captures the influence of strike-slip faults on the crustal boundaries and the magmatic budget.    
An open platform version of the Fluvial Corridor Toolbox with new functionalities to map nested floodplain envelops at the network scale
Authors: Dunesme Samuel , Rousson Christophe , Piégay Hervé
Published: March 2021

Fluvial geomorphology provides an integrative space-time framework to target actions for risk mitigation, water resource preservation, and biodiversity and landscape conservation. Geomorphic data provides support critically important knowledge on stream condition, adjustment processes and sensitivity to change. Multiscale frameworks are needed to organize knowledge into useful usable and usable useful information. To move towards a more river rehabilitation or conservation strategy, a planning effort is needed at the regional or network scale, so called upscaled geomorphology, to provide large spatial datasets and new environmental monitoring facilities. This new emphasis on spatial planning resonates also with the concept of “green infrastructures” as a mean to protect fluvial corridors and identify opportunities to restore lateral connectivity and floodplain functionalities, thus providing ecosystem services such as flood expansion zones or better functioning ecological networks.

The development of a new version of the Fluvial Corridor Toolbox (FCT), following the work done by Alber and Piégay (2011) and Roux et al. (2015), started as an effort to implement port the ArcGIS code to the QGis platform for promoting open science and sharing our tools with river practitioners. The initial version of the FCT provided a spatial framework to produce metrics at a fine scale and a disaggregation-aggregation procedure to delineate floodplain functional units along a channel network. The new version of the FCT has been completely rewritten and incorporates ideas from Nardi et al. (2018) and Clubb et al. (2017) for improving the calculation of riverscape feature heights above the water level and delineate floodplain through the river network. We also borrowed the concept of swath profiles from Hergarten et al. (2014) as the basis of a new raster-based approach to characterize floodplain features on cross-sections. These new functionalities are based on high resolution DEM and landcover data to produce different floodplain envelops. Finally, we implemented tiled processing of very large raster datasets after Barnes (2016, 2017). This new version of the FCT also provides a lightweight framework for developing new processing toolchains/workflows. We successfully processed 5 m resolution landcover data over the entire (French) Rhone basin and used these layers to highlight the FCT interest. The new workflows are suitable for working at large network scale and are reproducible. 

Further perspectives include an integration of such data and some FCT functionalities in online regional observatories with a visualization interface showing raw data on cross-sections and long profiles and synthetic patterns at the network scale allowing to compare target reaches with regional references.

 
A preliminary study of empirical evaluation models for determining the thermal conductivity of sediments 
Authors: Adrinek Simona , Janža Mitja
Published: March 2021

Shallow geothermal energy is a renewable energy source that will play an important role in future energy management plans. Densely populated areas are often developed on alluvial plains, which consist of unconsolidated sediments. These have different thermal properties, so their accurate determination is important for planning subsurface heat utilization for heating and cooling of buildings in urban areas. Bulk thermal conductivity (λb) is one of the most important ground thermal properties for estimating shallow geothermal potential, as it controls the ability of sediments to transfer heat. The λb can be determined with empirical bulk thermal conductivity estimation models (λb EM), which define λb as a function of the measured physical parameters of the sediment (water content, bulk density) and the fluid. In this contribution, we present a preliminary study of three empirical evaluation models for determining the thermal conductivity of sediments – the Kersten (1949), the Johansen (1975) and the Cote & Conrad model (2005). Validation was carried out with laboratory-measured λb using 30 unconsolidated sediment samples classified into 2 different groups (cohesive, non-cohesive) and by water content. The modelled results were evaluated using the coefficient of determination (R2) and root mean square error (RMSE). The modelled λb for non-cohesive sediments has the highest λb with the Johansen model. The lowest RMSE was obtained with the Kersten model. For cohesive sediments, the highest λb and lowest RMSE, and consequently the best model, are based on the saturation of the sediments. It varies between the Cote & Conrad and the Kersten model. By dividing the sediment samples based on shear strength and water content, we obtained the better agreement of individual groups with estimation models. This showed the importance of the physical parameters in better predicting the modelled results. In the future, we will need to upgrade results with the use of more estimation models, that could improve the modelled results. With such an approach the estimation models can become a useful tool for a faster determination of the shallow geothermal potential.
Parameter transferability between multiple gridded input datasets challenges hydrological model performance under changing climate
Authors: Dembélé Moctar , Schaefli Bettina , Mariéthoz Grégoire
Published: March 2021

The diversity of remotely sensed or reanalysis-based rainfall data steadily increases, which on one hand opens new perspectives for large scale hydrological modelling in data scarce regions, but on the other hand poses challenging question regarding parameter identification and transferability under multiple input datasets. This study analyzes the variability of hydrological model performance when (1) a set of parameters is transferred from the calibration input dataset to a different meteorological datasets and reversely, when (2) an input dataset is used with a parameter set, originally calibrated for a different input dataset.

The research objective is to highlight the uncertainties related to input data and the limitations of hydrological model parameter transferability across input datasets. An ensemble of 17 rainfall datasets and 6 temperature datasets from satellite and reanalysis sources (Dembélé et al., 2020), corresponding to 102 combinations of meteorological data, is used to force the fully distributed mesoscale Hydrologic Model (mHM). The mHM model is calibrated for each combination of meteorological datasets, thereby resulting in 102 calibrated parameter sets, which almost all give similar model performance. Each of the 102 parameter sets is used to run the mHM model with each of the 102 input datasets, yielding 10404 scenarios to that serve for the transferability tests. The experiment is carried out for a decade from 2003 to 2012 in the large and data-scarce Volta River basin (415600 km2) in West Africa.

The results show that there is a high variability in model performance for streamflow (mean CV=105%) when the parameters are transferred from the original input dataset to other input datasets (test 1 above). Moreover, the model performance is in general lower and can drop considerably when parameters obtained under all other input datasets are transferred to a selected input dataset (test 2 above). This underlines the need for model performance evaluation when different input datasets and parameter sets than those used during calibration are used to run a model. Our results represent a first step to tackle the question of parameter transferability to climate change scenarios. An in-depth analysis of the results at a later stage will shed light on which model parameterizations might be the main source of performance variability.

Dembélé, M., Schaefli, B., van de Giesen, N., & Mariéthoz, G. (2020). Suitability of 17 rainfall and temperature gridded datasets for large-scale hydrological modelling in West Africa. Hydrology and Earth System Sciences (HESS). https://doi.org/10.5194/hess-24-5379-2020
Validation and development of carbonyl sulfide biosphere exchange in the Simple Biosphere Model (SiB4)
Authors: Kooijmans Linda , Cho Ara , Ma Jin , Baker Ian , Kaushik Aleya , Krol Maarten
Published: March 2021

The uptake of carbonyl sulfide (COS) in plants is strongly dependent on stomatal conductance. The COS uptake is therefore strongly related to the photosynthetic uptake of CO2 in plants. As there is a gap in the COS budget with a source missing (or an overestimated sink) in tropical regions, this asks for evaluation of all sources and sinks of COS to be able to apply COS as a photosynthetic tracer. The COS uptake by vegetation and soil is simulated by the Simple Biosphere Model (SiB4) but it has not been validated against ecosystem and vegetation fluxes across different biomes. We evaluated the SiB4 COS biosphere flux with observations and updated it with the latest insights, with the aim to get the best possible estimate of the global COS biosphere sink. Overall, we find good agreement of simulated diurnal and seasonal cycles of COS ecosystem fluxes with flux observations made over grasslands, evergreen needleleaf forest and deciduous broadleaf forests over Europe and Northern America. We improved the simulations of COS soil exchange with the implementation of the Ogee et al. (2016) soil model such that SiB4 is now capable of simulating COS emissions from soils. We found that accounting for varying COS mixing ratios (retrieved from an inversion by the TM5-4DVAR model) plays a large role in determining the global COS biosphere sink. With these modifications to the model, we find an average underestimation of the COS biosphere flux of 11 % compared to observations. Furthermore, our model modifications caused a drop in the global COS biosphere sink from 967 Gg S yr-1 in the original model to 788 Gg S yr-1 in the updated version. The largest drop in fluxes is over the tropical regions, mostly driven by lower COS mixing ratios and contributes towards closing the gap in the COS budget. However, given the underestimation of COS uptake in the boreal and temperature regions, it is unlikely that the remaining gap in the COS budget is caused by an overestimated tropical biosphere sink.   

 
Applying dense seismic array monitoring to locate fluvial processes during floods in a braided river reach
Authors: Piantini Marco , Gimbert Florent , Bakker Maarten , Recking Alain , Nanni Ugo
Published: March 2021

Over the last decade, seismic techniques have provided unique observational constraints on Earth surface processes. In particular, dense seismic array monitoring has recently allowed the detailed investigation of noise sources and their spatiotemporal dynamics. Despite their large potential, these approaches have not yet been applied for the monitoring of fluvial processes. In a context where traditional methods often do not provide data with adequate temporal and spatial resolution, the use of dense arrays could allow the identification and tracking of different sources of river-induced seismic ground vibrations (e.g. turbulence and bedload transport), which would provide insight in river functioning and morphological evolution.

Here, we study the potential of dense seismic array monitoring by analysing data from a 4-month long field survey, which we conducted in summer 2019 along a 600-m long braided reach of the Séveraisse river (French Alps). We installed a network of 40 to 80 seismometers on both river banks, predominantly deployed in 4-seismometer subarrays, and we supplement these seismic observations with flow gauging measurements and time-lapse imagery covering the study area. We present a preliminary analysis that focuses on a high-flow event that occurred at the end of the melt season. During this event, we observe impulsive signals that are coherently detected over the array, and which we interpret as being associated with the bedload transport of clusters of coarse grains. Through phase-delay analysis we are able to locate episodes of motion at high temporal resolution and investigate their spatiotemporal dynamics with respect to river morphology and morphological changes observed from the time-lapse images. Our work demonstrates the unique capability of using dense seismic arrays to better understand the fluvial processes that play an important role in storing and transferring sediments in braided rivers.
Sharing transferable methods in environmental data science: A Fuzzy changepoint approach to numerical model evaluation over Greenland.
Authors: Hollaway Michael , Henrys Peter , Killick Rebecca , Leeson Amber , Watkins John
Published: March 2021

     Numerical models are essential tools for understanding the complex and dynamic nature of the natural environment and how it will respond to a changing climate. With ever increasing volumes of environmental data and increased availability of high powered computing, these models are becoming more complex and detailed in nature. Therefore the ability of these models to represent reality is critical in their use and future development. This has presented a number of challenges, including providing research platforms for collaborating scientists to explore big data, develop and share new methods, and communicate their results to stakeholders and decision makers. This work presents an example of a cloud-based research platform known as DataLabs and how it can be used to simplify access to advanced statistical methods (in this case changepoint analysis) for environmental science applications.

     A combination of changepoint analysis and fuzzy logic is used to assess the ability of numerical models to capture local scale temporal events seen in observations. The fuzzy union based metric factors in uncertainty of the changepoint location to calculate individual similarity scores between the numerical model and reality for each changepoint in the observed record. The application of the method is demonstrated through a case study on a high resolution model dataset which was able to pick up observed changepoints in temperature records over Greenland to varying degrees of success. The case study is presented using the DataLabs framework, demonstrating how the method can be shared with other users of the platform and the results visualised and communicated to users of different areas of expertise.
Characterising extratropical near tropopause analysis humidity biases and their radiative effects on temperature forecasts
Authors: Bland Jake , Gray Suzanne , Methven John , Forbes Richard
Published: March 2021

A cold bias in the extratropical lowermost stratosphere in forecasts is one of the most prominent systematic temperature errors in numerical weather prediction models. Hypothesized causes of this bias include radiative effects from a collocated moist bias in model analyses. Such biases would be expected to affect extratropical dynamics and result in the misrepresentation of wave propagation at tropopause level. Here the extent to which these biases are connected is quantified. Observations from radiosondes are compared to operational analyses and forecasts from the European Centre for Medium-Range Weather Forecasts (ECMWF) Integrated Forecasting System (IFS) and Met Office Unified Model (MetUM) to determine the magnitude and vertical structure of these biases. Both operational models over-estimate lowermost stratospheric specific humidity by around 70% of the observed values on average, around 1km above the tropopause. This moist bias is already present in the initial conditions and changes little in forecasts over the first five days. Though temperatures are represented well in the analyses, the IFS forecasts anomalously cool in the lower stratosphere, relative to verifying radiosonde observations, by 0.2K per day. The IFS single column model is used to show this temperature change can be attributed to increased long-wave radiative cooling due to the lowermost stratospheric moist bias in the initial conditions. However, the MetUM temperature biases cannot be entirely attributed to the moist bias, and another significant factor must be present. These results highlight the importance of improving the humidity analysis to reduce the extratropical lowermost stratospheric cold bias in forecast models and the need to understand and mitigate the causes of the moist bias in these models.
Extreme rainfall events during and following heatwaves
Authors: Sauter Christoph , White Christopher , Fowler Hayley , Westra Seth
Published: March 2021

Heatwaves and extreme rainfall events are natural hazards that can have severe impacts on society. The relationship between temperature and extreme rainfall has received scientific attention with studies focussing on how single daily or sub-daily rainfall extremes are related to day-to-day temperature variability. However, the impact multi-day heatwaves have on sub-daily extreme rainfall events and how extreme rainfall properties change during different stages of a heatwave remains mostly unexplored.

In this study, we analyse sub-daily rainfall records across Australia, a country that experiences severe natural hazards on a frequent basis, and determine their extreme rainfall properties, such as rainfall intensity, duration and frequency during SH-summer heatwaves. These properties are then compared to extreme rainfall properties found outside heatwaves, but during the same time of year, to examine to what extent they differ from normal conditions. We also conduct a spatial analysis to investigate any spatial patterns that arise.

We find that rainfall breaking heatwaves is often more extreme than average rainfall during the same time of year. This is especially prominent on the eastern and south-eastern Australian coast, where frequency and intensity of sub-daily rainfall extremes show an increase during the last day or the day immediately after a heatwave. We also find that although during heatwaves the average rainfall amount and duration decreases, there is an increase in sub-daily rainfall intensity when compared to conditions outside heatwaves. This implies that even though Australian heatwaves are generally characterised by dry conditions, rainfall occurrences within heatwaves are more intense.

Both heatwaves and extreme rainfall events pose great challenges for many sectors such as agriculture, and especially if they occur together. Understanding how and to what degree these events co-occur could help mitigate the impacts caused by them.
Experimental and Numerical Modelling of Self-Potential Response to Saltwater Intrusion
Authors: Benner Eric , Hamill Gerard , Etsias Georgios , Rowan Thomas , Salinas Pablo , Thomson Christopher , Fernández Águila Jesús , McDonnell Mark , Flynn Raymond , Butler Adrian , Jackson Matthew
Published: March 2021

Saltwater intrusion (SWI) in coastal aquifers poses a significant hazard to freshwater security for many of the world’s population centers. SWI is challenging to monitor and model due to the physical complexity of real aquifers. Self-Potential (SP) has been an important method for monitoring the subsurface for many years. Previous studies have suggested that borehole measurements of SP could be used to identify saline interface movement and provide advance warning of imminent saline breakthrough at an abstraction borehole. SP produced during SWI comprises the combined effects of electro-kinetic potential, arising from transport of excess charge in response to water potential (head) gradients, and exclusion-diffusion potential, arising from transport of excess charge in response to ion (salt) concentration gradients. SP can have advantages over other geophysical methods, such as electrical resistivity tomography and borehole fluid electrical conductivity measurements, because the effect of  moving saltwater fronts can be determined using a relatively small number of localized probes.

We quantitatively investigate the relationship between SP and SWI using experimental and numerical modelling with the aim of reproducing experimentally measured SP response via simulation. Building on well-established methods, a novel laboratory setup has been developed to optically monitor SWI in a thin homogenous aquifer while simultaneously recording SP data at multiple probe points. A Matlab solver is used to calculate SP data from simulated hydrodynamic SWI data computed by the fixed-grid finite element software SUTRA. Similarly, finite element SWI simulations using adaptive meshing are carried out using the IC-FERST software, which directly computes hydrodynamic and SP solutions. We compare these numerical results with experimental data and show similarity in SP signal trends as functions of brine movement near probe locations. We conclude with a discussion of the merits of SP modelling and its suitability for interpreting SP signals for monitoring and characterization of saltwater intrusion in coastal aquifers.
Modelling the Impact of Magnetic Storms on Planetary Environments
Authors: Roy Souvik , Nandy Dibyendu
Published: March 2021

Coronal mass ejections (CMEs), large scale transient eruptions observed in the Sun, are thought to also be spawned by other magnetically active stars. The magnetic flux ropes intrinsic to these storms, and associated high-speed plasma ejecta perturb planetary environments creating hazardous conditions. To understand the physics of CME impact and consequent perturbations in planetary environments, we use 3D compressible magnetohydrodynamic simulation of a star-planet module (CESSI-SPIM) developed at CESSI, IISER Kolkata based on the PLUTO code architecture.  We explore magnetohydrodynamic processes such as the formation of a bow-shock, magnetopause, magnetotail, planet-bound current sheets and atmospheric mass loss as a consequence of magnetic-storm-planetary interactions. Specifically, we utilize a realistic, twisted flux rope model for our CME, which leads to interesting dynamics related to helicity injection into the magnetosphere. Such studies will help us understand how energetic magnetic storms from host stars impact magnetospheres and atmospheres with implications for planetary and exoplanetary habitability.
Comparison of the seismicity evolution during the 2000 and 2003 stimulations at Soultz-sous-Forêts.
Authors: Maury Julie , Aochi Hideo
Published: March 2021

The research site of Soultz-sous-Forêts (Alsace, France) was a pioneer pilot geothermal site in Europe. In this study, we use the available data from 2000 and 2003 hydraulic stimulation tests to analyze the seismicity evolution. We apply the ETAS (Epidemic-Type Aftershock Sequence) model to extract the background seismicity rate during the two stimulation periods.

For the 2003 sequence, to retrieve the nonstationary seismicity component, we use a moving window of 400 events for the whole catalog. The evolution of the background seismicity rate μ is successfully retrieved with an evolution in two peaks coherent with the wellhead pressure evolution, while the triggering parameter Κ is stable. At the end of the stimulation μ decrease significantly. Then we look at the evolution of ETAS parameter by selecting five clusters of seismicity. The evolution of μ for each cluster is in agreement with a propagation of the pressure away from the well with the cluster closer to the well showing one early peak only, the middle clusters showing two peaks and the far cluster showing a later peak. All clusters show a decrease of μ at the end of stimulation.

For the 2000 sequence, the background seismicity rate is less well constrained but it stays globally constant during the stimulation with some decrease after its end. We see no clear peak in μ as was present during 2003 and K is relatively low. However, μ also decreases at the end of the stimulation. The selection of clusters does not change this global behavior and all clusters present grossly the same characteristics.

Our results are in agreement with the different characteristics observed by several authors (e.g. Calo and Dorbath, 2013; Dorbath et al, 2009) between these two stimulations. On one hand, the 2003 stimulation consists in an activation of several existing structures that yields a seismicity well explained by the ETAS model with a combined effect of Coulomb stress transfer and perturbation induced by the stimulation (e.g. pore pressure variation).  The evolution in space is also coherent with the finding of Calo and Dorbath (2013) that the injected water goes far from the well avoiding increase in effective stress near the well. In this case, background seismicity rate can be related to the measured pressure. On the other hand, the 2000 stimulation developed a 3D reservoir with the creation of a fresh shear zone (Cornet et al, 2015) and so the direct effects of the stimulation are dominants. However, no clear relation between the background seismicity rate and the operational parameters can be observed. At the end of stimulation, we observe a decrease of background rate corresponding to a progressive return to a natural background rate, similar to what is observed in other settings (Oklahoma, Rousse).
Optimized planning and operation of interconnected multi-purpose reservoir systems using integrated modeling for climate change adaptation
Authors: Nistahl Patrick , Müller Tim , Riedel Gerhard , Müller-Thomy Hannes , Meon Günter
Published: March 2021

Climate change impact studies performed for Northern Germany indicate a growing demand for water storage capacity to account for flood protection, low flow augmentation, drinking and agricultural water supply. At the same time, larger storage volumes for hydropower plants can be used to cope with the demands of changing energy supply from fossil to renewable energies. To tackle these challenges for the next decades, a novel reservoir system planning instrument is developed, which consists of combined numerical models and evaluation components. It allows to model simultaneously the current interconnected infrastructure of reservoirs as well as additional planning variants (structural and operational) as preparation for climate change. This planning instrument consists of a hydrological model and a detailed reservoir operation model.

As hydrological model, the conceptual, semi-distributed version of PANTA RHEI is applied.  Bias-corrected regional climate models (based on the RCP 8.5 scenario) are used as meteorological input. The hydrological model is coupled with a detailed reservoir operation model that replicates the complex rules of various interconnected reservoirs based on an hourly time step including pumped storage plants, which may have a subsurface reservoir as a lower basin. Downstream of the reservoirs, the hydrological model is used for routing the reservoir outflows and simulating natural side inflows. In areas of particular interest for flood protection, the hydrological routing is substituted with 2D hydraulic models to calculate the flood risk in terms of expected annual flood damage based on resulting inundation areas.

For the performance analysis, the simulation runs for all integrated modeling variants are evaluated for a reference period (1971-2000) and for future periods (2041-2070). Performance criteria involve flood protection, drinking water supply, low flow augmentation and energy production. These performance criteria will be used as stake holder information as well as a base for further optimization and ranking of the planning variants.

The combination of the hydrological model and the reservoir operation model shows a good performance of the existing complex hydraulic infrastructure using observed meteorological forcing as input. The usage of regional climate models as input shows a wide dispersion of several performance criteria, confirming the expected need for an innovative optimization scheme and the communication of the underlying uncertainties.
Opportunities related to Moroccan mine wastes valorisation
Authors: Taha Yassine , Hakkou Rachid , Benzaazoua Mostafa
Published: March 2021

Large amounts of solid wastes are produced by the mining industry. These wastes are often considered as problematic materials as they can lead to harmful impacts on the surrounding environment and the society. However, it was proved by many studies that most of mine wastes are inert but sometimes mixed with problematic components such as sulfidic minerals and hazardous metals and metalloids. Reprocessing and retreatment of mine wastes is a key sustainable solution to remove the sources of pollution and to recover the remaining high value products. Many studies around the world have demonstrated the big interest in recovering the residual metals and the use of mine wastes in other applications such as the construction sector.

 

In this study, a special accent will be given to the current management practices of mine wastes in Morocco as well as the possible opportunities related to the reuse of mine wastes coming from different mining activities. Three main materials categories are targeted: phosphate waste rocks and tailings, coal waste rocks and zinc tailings. The goal is to suggest more sustainable management methods and to explore new future opportunities related to the re-use and reprocessing of these wastes. Some possible high value-added products from these types of wastes are suggested based on their characteristics, location and volume. Construction aggregates, ceramics, bricks, cement, glass, acid mine drainage control, and road-base construction are among the possible explored channels.
Modelling the source of glacial earthquakes
Authors: Bonnet Pauline , Yastrebov Vladislav , Mangeney Anne , Castelnau Olivier , Leroyer Alban , Queutey Patrick , Rueckamp Martin , Stutzmann Eleonore , Montagner Jean-Paul , Sergeant Amandine
Published: March 2021

One current concern in Climate Sciences is the estimation of the annual amount of ice lost by glaciers and the corresponding rate of sea level rise. Greenland ice sheet contribution is significant with about 30% to the global ice mass losses. Ice loss in Greenland is distributed approximately equally between loss in land by surface melting and loss at the front of marine-terminating glaciers that is modulated by dynamic processes. Dynamic mass loss includes both submarine melting and iceberg calving. The processes that control ablation at tidewater glacier termini, glacier retreat and calving are complex, setting the limits to the estimation of dynamic mass loss and the relation to glacier dynamics. It involves interactions between bedrock – glacier – icebergs – ice-mélange – water – atmosphere. Moreover, the capsize of cubic kilometer scale icebergs close to a glacier front can destabilize the glacier, generate tsunami waves, and induce mixing of the water column which can impact both the local fauna and flora.

We aim to improve the physical understanding of the response of glacier front to the force of a capsizing iceberg against the terminus. For this, we use a mechanical model of iceberg capsize against the mobile glacier interacting with the solid earth through a frictional contact and we constrain it with measured surface displacements and seismic waves that are recorded at teleseismic distances. Our strategy is to construct a solid dynamics model, using a finite element solver, involving a deformable glacier, basal contact and friction, and simplified iceberg-water interactions. We fine-tune the parameters of these hydrodynamic effects on an iceberg capsizing in free ocean with the help of reference direct numerical simulations of fluid-structure interactions involving full resolution of Navier-Stokes equations. We simulate the response of a visco-elastic near-grounded glacier to the capsize of an iceberg close to the terminus. We assess the influence of the glacier geometry, the type of capsize, the ice properties and the basal friction on the glacier dynamic and the observed surface displacements. The surface displacements simulated with our model are then compared with measured displacements for well documented events. 
Investigating microplastic behaviour in a well-mixed estuary
Authors: Jones Nia , Neill Simon , Robins Peter , Lewis Matthew
Published: March 2021

Rivers and estuaries act as conduits of microplastic transport, linking terrestrial and marine environments: however, it is unclear to what extent estuaries act as sources or sinks for marine plastic waste. In densely populated catchments, microplastic pollution could impact human populations and natural ecosystems including through industry, domestic activities or direct exposure. An investigation into the physical behaviour of microplastic within estuarine systems will allow for a greater understanding of plastic retention and exportation to coastal and offshore environments. A high resolution 3D model (Delft D-Flow FM) of the Conwy Estuary (UK) is under development, with current and future projections of microplastic concentrations used to determine local exposure levels, residence times and temporal variability.

The Conwy Estuary (UK) is a well-mixed macro-tidal, embayment type system connecting the Conwy catchment to the North Wales coast and Irish Sea – where waters are used for leisure and aquaculture. Microplastics derived from the catchment population, industry and agriculture are thought to flow into the estuary primarily from the Conwy river network. Because of this, this study will incorporate in-situ samples of microplastic concentrations in river water to be able to predict microplastic levels in the estuary with greater accuracy. Plastic dispersal simulations through particle tracking and water quality monitoring will be undertaken using known concentrations and future projections of microplastic.

The results of the model validation as well as application to plastic dispersal simulations will be presented.
BKG’s new series of 24-hour and 1-hour VLBI experiments
Authors: Girdiuk Anastasiia , Engelhardt Gerald , Ullrich Dieter , Thaller Daniela , Hellmers Hendrik
Published: March 2021

With the VLBI technique radio sources are observed in dedicated time intervals. The most usual length of these observing sessions are 24 and 1-hour long. 24-hour long experiments usually incorporate a global network of stations, and, thus, are the prominent source of a consistent determination of all Earth Orientation Parameters (EOPs), celestial and terrestrial reference frames. The shorter experiments are designed to determine dUT1 parameter only. The number of short or intensive sessions is growing every year. Also some of them involve 3-4 stations in observation programs instead of standard 2-station mode. This leads to a larger number of observations per session, a better coverage of the Earth, and, consequently more accurate dUT1 estimates.

All 24-hour and 1-hour sessions since 1984 up to now were re-processed by BKG using the most up-to-date modelling within the parameter estimation. This results in new series of consistently estimated EOPs, station coordinates and troposphere parameters.

In this contribution we present our new series and investigate the quality of the obtained geodetic products, especially the EOPs. The work is focused on the consistency between dUT1 parameters derived from 24-hour and 1-hour sessions, respectively. In this study we pinpoint challenges and prospects of the inclusion of 1-hour experiments into the standard analysis of the 24-hour experiments.
A data assimilation application for improving estimates of Arctic sea ice thickness variability and change since the turn of the 21st century
Authors: Wieringa Molly , Bitz Cecilia
Published: March 2021

Current sea ice prediction systems exhibit significant room for improvement compared to idealized estimates of sea ice predictability, a gap that could be closed by improving the initial conditions provided to prognostic models. Sea ice volume, the area-weighted integral of sea ice thickness (SIT), in particular, demonstrates long initial value predictability; in other words, accurate forecasting of Arctic sea ice requires highly accurate SIT initial conditions. Continuous records of SIT are, unfortunately, few and far between. To address this conundrum, we have explored applications of the Data Assimilation Research Testbed (DART) to constrain the Los Alamos Sea Ice Model (CICE5) within the Community Earth System Model using satellite-derived SIT observations from 2003 to present day. Our data assimilation system has been fine-tuned using new and highly accurate freeboard measurements from NASA’s ICESat-2 mission. Using SIT information alone, we generate two assimilation products: the first using DART with CICE5 and the second with an offline assimilation method. We compare these products to one another and to the community standard SIT record, PIOMAS. Future work will introduce multivariate assimilation of SIT with other sea ice variables, including sea ice concentration, sea ice skin temperature, and sea surface temperature.
Impact of excess diesel NOx emisions upon NO2 pollution in a compact city: the role of model resolution
Authors: Benavides Jaime , Guevara Marc , Snyder Michelle G. , Rodríguez-Rey Daniel , Soret Albert , Pérez García-Pando Carlos , Jorba Oriol
Published: March 2021

Diesel light-duty-vehicles (LDV) largely exceed the Euro emission standards of nitrogen oxides (NOx) in real-world driving conditions. Air quality models at meso- and large-scale resolutions have recently been used to quantify the impact of such an emission excess upon air quality and human health. In this work, we argue that these approaches can significantly underestimate the impact of diesel LDV excess NOx emissions upon NO2 pollution in compact and heavily trafficked cities. We design two modeling scenarios for the study: a business-as-usual scenario where diesel LDV emit NOx in excess, and a counterfactual scenario where emissions are compliant with the Euro emission standards. We compare then NO2 concentrations of the air quality mesoscale model CALIOPE at both 4 km and 1 km resolution with the street-scale model CALIOPE-Urban in Barcelona city (Spain). The EU annual NO2 limits are repeatedly exceeded in Barcelona where a large share of passenger cars are diesel (65 %). Results show that the street scale model is able to largely represent the observed NO2 concentration gradients between traffic and background stations in the city in contrast to the mesoscale model. The mesoscale model strongly underestimates the impact of diesel LDV excess NOx emissions upon NO2 pollution both in absolute terms (by 38 to 48 %) and relative terms (by 10 to 35 %). Using the street scale model, we find that diesel LDV excess NOx emissions are associated with about 20 % of NO2 levels in the city, contributing to an increase of citizens exposed to levels above the EU annual NO2 limits of 15%.
Inland Coastal Flooding Risk by Tropical Cyclone 
Authors: Sarhadi Ali , Emanuel Kerry
Published: March 2021

Heavy and prolonged rainfall from one of the most destructive natural hazards, Tropical Cyclone (TC) generate devastating inland coastal flooding in the US. In this study, we introduce a pluvial hydrodynamic model to translate rainfall intensity of TCs as the main driver into extreme flooding hazard in coastal areas on the west side of Buzzard Bay in Massachusetts. The model implements a 2D hydraulic modeling and landscape characteristics, including geometry, land use, surface roughness, river networks, and soil infiltration. Using the continuity of mass and momentum equations, the model translates rainfall intensity of TCs that make landfall in the area into dynamic flooding during each event. The rainfall intensity data are derived from a large number of synthetic TCs (generated from historical climate through 1979-2019). The high spatial resolution rainfall intensity with short and long duration scenarios (1-hr, 2-hr, 3-hr, 6-hr, 12-hr, 24-hr, 48-hr, and 72-hr) are then used to simulate the corresponding extreme flooding during each TC. The accuracy of the developed model is evaluated by comparing flood inundation areas during observed TCs (extracted from the Synthetic-Aperture Radar (SAR) image processing) with those simulated by the model from NEXRAD data for the same events. The maximum simulated flood depth during each synthetic TC is then applied in a probabilistic framework to estimate flood levels in different return periods (up to 200 year) for each of the short and long duration scenario. The results of flood depth and inundated extent from low probable and high consequence TC floods provide critical insight for designing resilient infrastructure and reducing damages and cost against these destructive extremes. Our methodology can be applied for other susceptible coastal regions, helping identify vulnerable areas to extreme flooding induced by short and long duration TCs.  