bluuebunny/crossref_metadata_2025 huggingface dataset:
How clean is your ‘clean’ energy? The ENVIRO module for energy system models
Authors: Martin Nicholas , Madrid-López Cristina , Talens-Peiró Laura , Pickering Bryn
Published: March 2021

A decarbonized, renewable energy system is generally assumed to represent a cleaner and more sustainable one. However, while they do promise day-to-day reductions in carbon emissions, many other environmental impacts could occur, and these are often overlooked. Indeed, in the two documents that form the EU Energy Union Strategy (COM/2015/080) the words ‘water’, ‘biodiversity’ or ‘raw materials’ do not appear. This ‘tunnel vision’ is often also adopted in current energy systems models, which do not generally provide a detailed analysis of all of the environmental impacts that accompany different energy scenarios. Ignoring the trade-offs between energy systems and other resources can result in misleading information and misguided policy making.

The environmental assessment module ENVIRO combines the bottom up, high resolution capabilities of life cycle assessment (LCA) with the hierarchical multi-scale upscaling capabilities of the Multi-Scale Integrated Assessment of Socioecosystem Metabolism (MuSIASEM) approach in an effort to address this gap. ENVIRO also takes the systemic trade-offs associated with the water-energy-food-(land-climate-etc.) nexus from MuSIASEM while considering the supply chain perspective of LCA. The module contains a built-in set of indicators that serve to assess the constraints that greenhouse gas (GHG) emissions, pollution, water use and raw material demands pose to renewable energy system scenarios. It can be used to assess the coherence between energy decarbonization targets and water or raw material targets; this can be extended to potentially any economic or political target that has a biophysical component.

In this work, we introduce the semantics and formalization aspects of ENVIRO, its integration with the energy system model Calliope, and the results of a first testing of the module in the assessment of decarbonization scenarios for the EU. The work is part of the research developed in the H2020 Project SENTINEL: Sustainable Energy Transition Laboratory (contract 837089).
Trace metal concentrations and OH defects in quartz from Amazon River sands & and perspectives for application to the marine record
Authors: Jaeger Dominik , Stalder Roland , Chiessi Cristiano , Sawakuchi André , Strasser Michael
Published: March 2021

Trace metal concentrations and associated hydrous lattice point defects (OH defects) in quartz can help reveal its host rock’s crystallization history and are easily quantified using electron microprobe and infrared spectroscopy, respectively. These chemical impurities are preserved throughout the sedimentary cycle and thus lend themselves as tracers for sediment provenance analyses, particularly in settings where “traditional” provenance tools, e.g., thermochronology and heavy mineral analysis, are difficult due to factors like low mineral fertility and aggressive tropical weathering.

In this study, we apply this provenance analysis tool to detrital, sand-sized quartz grains from the Amazon River and its major tributaries, draining the Andean orogen as well as the Guiana- and Central Brazil Shields. Trace metal and OH defect concentrations from individual catchments are spread out over wide and mutually overlapping ranges of values. This means that each individual quartz grain cannot be unequivocally attributed to one catchment. However, evaluation of a statistically sound number of grains reveals that Andean quartz is, on average, richer in the trace metal aluminum (and Al-related OH defects) than quartz derived from one of the shield sources.

We evaluate our findings in the context of previous provenance studies on Amazon River sediments and discuss a potential future application of analyzing trace metals and OH defects in quartz in the offshore sediment record. Any past, major rearrangements in the Amazon watershed affecting the ratio of Andean vs. Shield-derived quartz grains should be detectable and our approach may therefore contribute to the reconstruction of Amazon drainage basin evolution.
Effects of riparian woody vegetation on EPT functional connectivity in Western Germany
Authors: Peredo Arce Andrés , Palt Martin , Schletterer Martin , Kail Jochem
Published: March 2021

In the degraded European landscapes riparian corridors had have become key features to maintain connectivity between habitat patches for multitude of organisms. This role of riparian forests has been assessed from the purely structural point of view, to complex models specific for particular species or groups of species, from mammals to plants, from endangered to invasive species.

Dispersion is a key part of the lifecycle of EPTs (Ephemeroptera, Plecoptera and Trichoptera) as they live most of their lives as aquatic juveniles, being drifted downstream, and disperse back upstream when they become short-lived winged adults. These three families of aquatic macroinvertebrates are widely used as bioindicators because of their sensitivity to water pollution and habitat degradation, but little is known about how the riparian vegetation impacts their ability to disperse and recolonize. For example, riparian vegetation could help EPTs dispersion by protecting them from harsh weather conditions, or by helping them to orientate themselves by changing how the reflexion of the light on the water polarises.

Nevertheless, connectivity is not the only driver of the EPT community as other parameters can have a direct effect on the community composition. For example, water pollution is an important driver of the freshwater macroinvertebrate community and in locations where pollution is high is not expected to find almost any EPTs individual regardless of the landscape connectivity. Furthermore, other landscape features can hinder the role of riparian forests as corridors for being a barrier to EPT dispersion, like dams or coniferous forests.

In this study we compare the EPT communities on 120 pairs of sites, each pair located in the same river at 1 to 5 km distance, with different riparian vegetation conditions in Western Germany. The communities are characterised by their overall dispersion capacity using the Species Flying Propensity index (Sarremejane et al. 2017). The riparian vegetation is identified using areal images in the 10 meters and 30 meters buffer from the river.

We expect that riparian forest fragmentation will directly impact functional connectivity, and therefore, in locations with less fragmented riparian forests the EPT community will be mainly composed by weak dispersers (and vice versa). Nevertheless, covariates that can impact or mask this effect were taken into account: catchment land use, saprobic pollution, naturalness, hidromorphological hydromorphological degradation and also other features as coniferous forests or dams.
How does wildfire impact carbon delivery to peatland drainage networks?
Authors: Pickard Amy , Felgate Stacey , Fernandez Garcia Paula , Gilbert Peter , Mayor Dan , Monteith Don , Andersen Roxane
Published: March 2021

Peatlands are a globally important carbon (C) store, although it is well understood that anthropogenic pressures including drainage can reduce potential for C sequestration, in part due to increased losses of C via the aquatic pathway. Superimposed onto land-use pressures on peatlands are those caused by extreme climate events. Following a drought in 2018 and a subsequent dry period in spring 2019, a large wildfire burnt approximately >60 km2 of blanket bog and wet heath within the Flow Country peatlands, North Scotland in May 2019. The fire burned various peatland land types, including near-natural peatland and drained peatland areas. This event created an urgent opportunity to quantify the interacting effects of peat condition and wildfire on water quality, with a focus on dissolved organic matter (DOM) losses. An extensive water monitoring programme was established, covering 40 individual headwater stream sampling locations across the Flow Country, and monthly sampling ran from September 2019 to October 2020, with samples analysed for dissolved organic carbon (DOC), nutrients and UV-vis-based measurements to inform DOM composition. Initial data shows that samples from burned, drained areas are associated with higher DOC concentrations relative to both burned, near natural peatland areas, and unburned control sites. Furthermore the DOM from burned, drained sites is of a more aromatic nature, as indicated by elevated specific UV absorbance (SUVA), compared to unburned control sites. Such findings imply that wildfires may adversely affect water quality through changes DOM quantity and quality in areas of damaged (drained) peatland. However, more detailed compositional analyses are required to accurately predict changes in the ecological functioning of this peatland derived DOM as it enters the aquatic environment and, therefore, its likely end-fate.
Multiple-hazards and their interactions in urban low-to-middle income countries: a case study from Nairobi
Authors: Malamud Bruce D. , Mwangi Emmah , Gill Joel , Hussain Ekbal , Taylor Faith , Sakic Trogrlic Robert
Published: March 2021

Global policy frameworks, such as the Sendai Framework for Disaster Risk Reduction 2015-2030, increasingly advocate for multi-hazard approaches across different spatial scales. However, management approaches on the ground are still informed by siloed approaches based on one single natural hazard (e.g. flood, earthquake, snowstorm). However, locations are rarely subjected to a single natural hazard but rather prone to more than one. These different hazards and their interactions (e.g. one natural hazard triggering or increasing the probability of one or more natural hazards), together with exposure and vulnerability, shape the disaster landscape of a given region and associated disaster impact.  Here, as part of the UK GCRF funded research grant “Tomorrow’s Cities” we first map out the single natural hazardscape for Nairobi using evidence collected through peer-reviewed literature, grey literature, social media and newspapers. We find the following hazard groups and hazard types present in Nairobi: (i) geophysical (earthquakes, volcanic eruptions, landslides), (ii) hydrological (floods and droughts), (iii) shallow earth processes (regional subsidence, ground collapse, soil subsidence, ground heave), (iv) atmospheric hazards (storm, hail, lightning, extreme heat, extreme cold), (v) biophysical (urban fires), and vi) space hazards (geomatic storms, and impact events). The breadth of single natural hazards that can potentially impact Nairobi is much larger than normally considered by individual hazard managers that work in Nairobi. We then use a global hazard matrix to identify possible hazard interactions, focusing on the following interaction mechanisms: (i) hazard triggering secondary hazard, (ii) hazards amplifying the possibility of the secondary hazard occurring.  We identify 67 possible interactions, as well as some of the interaction cascade typologies that are typical for Nairobi (e.g. a storm triggers and increases the probability of a flood which in turn increases the probability of a flood). Our results indicate a breadth of natural hazards and their interactions in Nairobi, and emphasise a need for a multi-hazard approach to disaster risk reduction.
Geological context of recent Lunar landing sites using Multispectral analysis. 
Authors: Mcilquham Jourdain , Borst Anouk M , Allender Elyse J , Foing Bernard
Published: March 2021

Geological context of recent lunar landing sites using multispectral analysis. (Mcilquham J, Borst A, Allender E and Foing B)

The Moon Mineralogy Mapper (M3) was a guest instrument aboard the Chandrayaan-1 mission. The instrument collected spectral data, ranging from 430 nm to 3000 nm at an average resolution of 140 m/pixel. This research utilises M3 spectral data to visualise and understand the geology of lunar landing sites visited by Chang’e 4 and 5. The aims of this study are aligned to lunar exploration goals produced by the National Research Council. We use Python scripts to undertake data analysis, creating site maps using continuum removal methods and assigning RGB image channels to highlight absorption features of interest. The Chang’e 4 landing site is located on the lunar far side within the Von Karman crater, located in the large South Pole Aitken impact basin. At Von Karman lunar mantle or lower crustal material may be exposed in the central peak. This could provide valuable insights into lunar geological history. We create maps to visualise the location of pyroxene end-members and olivine-rich rocks of the Von Karman crater, adding data to understand the composition of the deeper lunar lithologies. Orbital data presented in this study can be compared with ground-truth data gathered from the Yutu 2 rover to confirm the minerals present. More recently the Chang’e 5 mission provided a further landing site for study. Using the same methods as presented above we will compare its spectral composition to the Chang’e 4 landing site. Our maps can help to understand the key factors used to determine a suitable landing site and potentially a suitable location for a lunar base. By comparing Chang’e landing sites this study provides a unique insight into the craters in which they landed, allowing direct comparisons to be drawn. Preliminary findings identify non-mare units within the Von Karman crater as well as various Ca-rich and Ca-poor pyroxene-bearing lithologies.
Snow depth on Antarctic sea ice: a Lagrangian model-based approach 
Authors: Lawrence Isobel R. , Ridout Andy , Shepherd Andrew
Published: March 2021

Snow on Antarctic sea ice is an important yet poorly resolved component of the global climate system. Whilst much attention over the past few years has been dedicated to producing reanalysis-forced models of snow on sea ice in the Arctic, none currently exist for the Southern Hemisphere. Here we present a Lagrangian-framework model of snow depth on Antarctic sea ice, in which “parcels” of ice accumulate snow as they drift around the ocean according to daily ice motion vectors. Snow accumulates from two sources; (i) snowfall from ERA5 atmospheric reanalysis and (ii) snow blown off the Antarctic continent, which we estimate using the RACMO2 ice sheet mass balance model. Ice parcels lose snow via wind-redistribution into leads and through snow-ice formation. We validate our dynamic snow product against ship-based measurements from the ASPeCT data archive, and we compare our long-term climatology against estimates derived from passive microwave (AMSR-E/2) satellites. Finally, we assess regional trends in snow depth over the past four decades and investigate whether these are driven by changes in snowfall or divergence/convergence of the Antarctic sea ice pack. 
Analysis of ozone budget in CMIP6 experiments
Authors: Griffiths Paul , Guang Zeng , Shim Sungbo , Mulcahy Jane , Murray Lee , O'Connor Fiona , Archibald Alex , Pyle John
Published: March 2021

A grand challenge in the field of chemistry-climate modelling is to understand the connection between anthropogenic emissions, atmospheric composition and the radiative forcing of trace gases and aerosols.   The AerChemMIP model intercomparison project, part of CMIP6, focuses on calculating the radiative forcing of gases and aerosol particles over the period 1850 to 2100.  We present an analysis of the trends in tropospheric ozone budget in the UKESM1 and other models from CMIP6 experiments. We discuss these trends in terms of chemical production and loss of ozone as well as physical processes such as transport and deposition.  Where possible, AerChemMIP attribution experiments such as histSST-piCH4, will be used to quantify the effect of individual emissions and forcing changes on the historical ozone burden and budget.  For future experiments, we focus on analogous experiments from the SSP3-70 scenario, a ‘regional rivalry’ shared socioeconomic pathway involving significant emissions changes.
Climate change in chestnut producing regions in Portugal
Authors: Gonçalves Mário , Amraoui Malik , Laranjo José , Pereira Mário
Published: March 2021

The chestnut trees are well adaptated to temperate and humid climates, with moderate annual thermal contrast and without long and severe summer droughts. Bioclimatic studies suggest that chestnut trees have special needs, including at least six months with average monthly air temperature above 10 ⁰C, total annual precipitation of 800 – 900 mm, and 25% of annual precipitation in summer. Weather is also determinant in the phenology of the species. For example, the suitable average air temperature range is: 13 – 15⁰C to initiate the phenological activity, 18 – 20⁰C for flowering, and 20 – 22⁰C for maturation. Therefore chestnut production is highly affected by adverse weather conditions and can be severely reduced by the occurrence of extreme weather/climate extremes: late frosts, heat waves, heavy rainfall, wind gusts, maximum air temperature lower than 25⁰C during flowering or above 32⁰C, which cause thermoinhibition of vegetative activity. Thus, it is important to characterize the chestnut producing regions in present and future climate and estimate how, when and where the weather conditions will be maintained or changed. For this study we used meteorological data from ERA5 for the 1981 – 2010 period and several GCM-RCM simulations from CORDEX Bias-adjusted RCM data for 2011 – 2100 period to assess the climate for current and two future scenarios (RCP 4.5 and RCP 8.5). The meteorological variables selected for this study have been identified in previous studies as having the greatest influence in the phenological activity of the chestnut tree and on the chestnut productivity. The results include the identification of the regions where: (i) the variables will have significantly different statistical distributions in the future; (ii) will be necessary to adopt hazard risk management and climate adaptation measures, including substitution by other varieties more adapted to future conditions or the development of genetic improvement programs; and, (iii) the identification of new production areas.
Gap formation around 0.5Ωe of whistler-mode waves excited by electron temperature anisotropy
Authors: Chen Huayue , Gao Xinliang , Lu Quanming , Sauer Konrad
Published: March 2021

With a 1-D PIC simulation model, we have investigated the gap formation around 0.5Ωe of the quasi-parallel whistler-mode waves excited by an electron temperature anisotropy. When the frequencies of excited waves in the linear stage cross 0.5Ωe, or when they are slightly larger than 0.5Ωe but then drift to lower values, the Landau resonance can make the electron distribution form a beam-like/plateau population. Such an electron distribution only slightly changes the dispersion relation of whistler-mode waves, but can cause severe damping around 0.5Ωe via cyclotron resonance. At last, the wave spectrum is separated into two bands with a power gap around 0.5Ωe. The condition under different electron temperature anisotropy and plasma beta is also surveyed for such kind of power gap. Besides, when only the waves with frequencies lower than 0.5Ωe are excited in the linear stage, a power gap can also be formed due to the wave-wave interactions, i.e., lower band cascade. Our study provides a clue to reveal the well-known 0.5Ωe power gap of whistler-mode waves ubiquitously observed in the inner magnetosphere.
Roles of poro-elastic compressibility, rate-dependent strength and strain-stress dependent dilation for spontaneous generation of seismicity along fluid-bearing fault structures
Authors: Gerya Taras , Petrini Claudio , Dal Zilio Luca
Published: March 2021

We present a newly developed marker in cell staggered finite difference poro-visco-elasto-plastic numerical model for spontaneous seismic cycle along fluid-bearing fault structures. The fully coupled hydro-mechanical multi-physics model includes poro-elastic compressibility of the solid matrix together with experimentally calibrated rate-dependent strength laws and strain-stress dependent dilation. Localised brittle/plastic deformation is treated accurately through global Picard iterations. To simulate deformation on both long- and short-time scale, an adaptive time stepping is used allowing the resolution of large seismic events with time steps on the order of milliseconds.

Our new numerical modelling tool allows to explore how the presence of pressurised fluids in the pore space of subduction interface and strike-slip zones triggers poro-elastic stress accumulation and release in form of various seismic cycles. The model is capable of simulating spontaneous quasi-periodic seismic events along self-consistently forming highly localized self-pressurised ruptures accommodating shear displacement between the plates. The generated elastic rebound events show slip velocities ranging from the order of Nm/s to m/s, covering the entire range of seismic and slow slip phenomena. The governing strength decrease along the propagating fracture is related mainly to the significant increase of fluid pressure generated by deformation induced plasto-elastic collapse of pores. The reduction of the effective pressure decreases the brittle/plastic strength of fluid-bearing rocks along the rupture, thus providing a dynamic feedback mechanism for the accumulated elastic stress release at the fault interface.  It is remarkable that the seismic behaviours for both slow slip and ordinary earthquakes can be generated within the same self-consistent poro-visco-elasto-plastic rheological framework without any involvement of rate- and state-dependent friction commonly used for seismicity modelling. We furthermore analyse how this process and the seismic cycle are affected by poro-elastic, rate weakening and dilation parameters.
Complex networks approach for detecting tropical basin interactions
Authors: Rodríguez de Fonseca Belen , Martín-Gómez Veronica , Aliganga Jose María
Published: March 2021

Interaction between the tropical Pacific, Atlantic, and Indian Ocean basins is increasingly recognized as a key factor in understanding climate variability on interannual to decadal timescales. Most of the studies deal with the connection between pair of basins and less attention has been paid to analyze the degree of collective interaction among the three tropical oceans and its variability along time.In this study, we consider a complex network perspective to analyze the collective connectivity among the three tropical basins. To do so, we first construct a climate network considering as network’ nodes the indices that represent the variability of the SST over the tropical Pacific, the tropical north Atlantic, the equatorial Atlantic and the tropical Indian Ocean. Then, we focus on detecting periods of maximum degree of collective connectivity (synchronization periods) using the mean network distance definition.Results show that the degree of collective connectivity among the three tropical oceans present a large muti-decadal variability and that during the observed period there were two synchronization periods: one developed over the period (1900-1935) and the other from 1975 to present. A period center in the 1950’s is characterized by being the three basins uncoupled .Using this information, an analysis of background conditions in the ocean and the atmosphere has been conducted in order to elucidate causes for this change in connectivity.
Effects of fine roots on the distribution of soil water and soil organic carbon in a shelterbelt modified agricultural system
Authors: Xiao Huijie , Li Junran , Xin Zhiming , Wang Guan , Wang Dong
Published: March 2021

Shelterbelts, also termed windbreaks, play a significant role in reducing soil erosion, sand drift, and protecting crops, livestock and farmstead. Cropland shelterbelts are known to improve the microclimate and provide protection against sand-related damages to crops. However, the protection of shelterbelts to crops may be complicated by fine roots near the edge of the shelterbelt, which directly affects the absorption of soil water and the accumulation of soil organic carbon. In this study, we investigated the effects of shelterbelt fine roots on farmland soil water content (SWC) and soil organic carbon density in an agricultural system located in northern China. The distribution characteristics of fine-root biomass density, soil water content and soil organic carbon density were measured at the 0-200 cm soil depth in a farmland shelterbelt system at distances of 0.3H (H is the windbreak height), 0.5H, and 0.7H from the shelterbelt with three replicates. Soil samples were randomly collected in the center of the cropland. The results showed that fine roots of shelterbelts concentrated at the depth of the 20-60 cm soil layer, whereas the fine roots of the crop summer squash (Cucurbita pepo L.) were mainly found within the top 20 cm of the soil profile. With the presence of shelterbelt fine roots, strong SWC deficiency that occurred up to100 cm in the soil profile was observed. The SWC was deficient at all sampling points, the overall shallow layer deficient was larger than the deep layer. In contrast, the soil organic carbon was cumulative, and the overall deep accumulation was greater than the shallow layer. The effects of fine roots on SWC and soil organic carbon density variations in different soil layers were inconsistent. The information accrued in this study can be used to evaluate the effect of farmland shelterbelt on soil water and soil carbon in the Hetao irrigation area of Inner Mongolia, northern China.
Multi-GNSS Slant Wet Delay Retrieval Using Multipath Mitigation Maps
Authors: Hunegnaw Addisu , Ejigu Yohannes Getachew , Teferle Felix Norman , Elgered Gunnar
Published: March 2021

The conventional Global Navigation Satellite System (GNSS) processing is typically contaminated with errors due to atmospheric variabilities, such as those associated with the mesoscale phenomena. These errors are manifested in the parameter estimates, including station coordinates and atmospheric products. To enhance the accuracy of these GNSS products further, a better understanding of the local-scale atmospheric variability is necessary. As part of multi-GNSS processing, station coordinates, carrier phase ambiguities, orbits, zenith total delay (ZTD) and horizontal gradients are the main parameters of interest. Here, ZTD is estimated as the average zenith delay along the line-of-sight to every observed GNSS satellite mapped to the vertical while the horizontal gradients are estimated in NS and EW directions and provide a means to partly account for the azimuthally inhomogeneous atmosphere. However, a better atmospheric description is possible by evaluating the slant path delay (SPD) or slant wet delay (SWD) along GNSS ray paths, which are not resolved by ordinary ZTD and gradient analysis. SWD is expected to provide better information about the inhomogeneous distribution of water vapour that is disregarded when retrieving ZTD and horizontal gradients. Usually, SWD cannot be estimated directly from GNSS processing as the number of unknown parameters exceeds the number of observations. Thus, SWD is generally calculated from ZTD for each satellite and may be dominated by un-modelled atmospheric delays, clock errors, unresolved carrier-phase ambiguities and near-surface multipath scattering.

 

In this work, we have computed multipath maps by stacking individual post-fit carrier residuals incorporating the signals from four GNSS constellations, i.e. BeiDou, Galileo, Glonass and GPS. We have selected a subset of global International GNSS Service (IGS) stations capable of multi-GNSS observables located in different climatic zones. The multipath effects are reduced by subtracting the stacked multipath maps from the raw post-fit carrier phase residuals. We demonstrate that the multipath stacking technique results in significantly reduced variations in the one-way post-fit carrier phase residuals. This is particularly evident for lower elevation angles, thus, producing a retrieval method for SWD that is less affected by site-specific multipath effects. We show a positive impact on SWD estimation using our multipath maps during increased atmospheric inhomogeneity as induced by severe weather events.
Pathways of change in the socio-shysical dynamics of the Western Indian Ocean deltas
Authors: Paron Paolo , Duvail Stephanie , Hamerlynck Olivier , Hervé Dominque , Juizo Dinis , Mwansasu Simon , Nyingi Wanja , Robison Laurent
Published: March 2021

We present the output of a research combining field based, expert knowledge and remote sensing, based on Google Earth Engine, aimed at the identification of the rates of changes and pathways during the past 35 years, in four Western Indian Ocean River Catchments and Deltas: Tana River in Kenya, Rufiji River in Tanzania, Limpopo River in Mozambique and Betsiboka River in Madagascar. These findings are a set of preliminary results of the collaborative and multidisciplinary effort produced within the GDRI-Sud network DELTAS and as a follow-up of the West Indian Ocean Deltas Exchange and Research network (WIODER) project that brought together the National Museum of Kenya, , University of Dar Es Salaam in Tanzania, University Eduardo Mondlane in Mozambique, Centre National de Recherches sur l'Environnement in  Madagascar, University of Southampton in UK, IHE Delft in the Netherlands, Institut de Recherche pour le Développement in France, and International Development Research Centre in Canada and Kenya.

We highlight the similarities in the physical environment and, where possible, also in the socio-economic-political environments that are leading the current changes, potentially affecting resilience of the local population and their sustainable development.

We focused on the substantial changes in the following aspects: precipitation seasonality, flooding patterns and frequency, land cover, dry forest cover, mangrove cover, crop production, fish population, human population, human migration flow, frequency of human conflicts within the delta population.

The observed changes call for reflection given the IPCC projections in climate towards an aridification of the Southern Africa river basins and a wetter condition in the Eastern Africa region. Some signals of these climatic forecast are already recorded in both regions and will be explored in the DIDEM project.
Regional calibration and electromagnetic conductivity imaging for assessing the dynamics of soil salinity
Authors: Paz Maria Catarina , Farzamian Mohammad , Paz Ana Marta , Castanheira Nádia Luísa , Gonçalves Maria Conceição , Monteiro Santos Fernando
Published: March 2021

Electromagnetic conductivity imaging (EMCI) is a state-of-the-art methodology for soil salinity assessment over large areas. It involves the following rationale: (1) use of the electromagnetic induction (EMI) geophysical technique to measure the soil apparent electrical conductivity (ECa, mS m−1) over an area; (2) inversion of ECa to obtain EMCI, which provides the spatial distribution of the soil electrical conductivity (σ, mS m−1); (3) calibration process consisting of a regression between σ and the electrical conductivity of the saturated soil paste extract (ECe, dS m−1), used as a proxy for soil salinity; and (4) conversion of EMCI into salinity maps using the obtained calibration equation.

In this study, we applied EMCI and a regional calibration in Lezíria Grande de Vila Franca de Xira, located in Portugal. The study area is an important agricultural system where soil faces the risk of salinization due to climate change, as the level and salinity of groundwater are likely to increase as a result of the rise of the sea water level and consequently of the estuary. These changes can also affect the salinity of the irrigation water which is collected upstream of the estuary.

EMI surveys and soil sampling were carried out between May 2017 and October 2018 at four locations with different salinity levels across the study area. A regional calibration was developed and its ability to predict ECe from EMCI was evaluated. The validation analysis showed that ECe was predicted with a root mean square error of 3.14 dS m−1 in a range of 52.35 dS m−1, slightly overestimated (−1.23 dS m−1), with a strong Lin’s concordance correlation coefficient of 0.94 and high linearity between measured and predicted data (R2 = 0.88). It was also observed that the prediction ability of the regional calibration is more influenced by spatial variability of data than temporal variability of data.

Because of the transient nature of data, it was also possible to perform a preliminary qualitative analysis of soil salinity dynamics in the study area, revealing salinity fluctuations related to the input of salts and water either through irrigation, precipitation, or level and salinity of groundwater.
Near-inertial dissipation due to stratified flow over abyssal topography
Authors: Zemskova Varvara , Grisouard Nicolas
Published: March 2021

Linear theory for steady stratified flow over topography sets the range for topographic wavenumbers over which freely propagating internal waves are generated, whose radiation and breaking contribute to energy dissipation in the interior. Previous work demonstrated that dissipation rates can be enhanced over large-scale topographies with wavenumbers outside of such radiative range. We conduct idealized rotating 3D numerical simulations of steady stratified flow over 1D topography and quantify kinetic energy dissipation. We vary topographic width, which determines whether the obstacle is within the radiative range, and height, which measures the degree of flow non-linearity. Simulations with certain width and height combinations develop periodicity in wave breaking and energy dissipation, which is enhanced in the domain interior. Dissipation rates for tall and wide non-radiative topography are comparable to those of radiative topography, even away from the bottom, which is important for the ocean where wider hills also tend to be taller. 
A record of slush and water extent on Antarctic ice shelves from 2013 to present day
Authors: Dell Rebecca , Banwell Alison , Arnold Neil , Willis Ian , Halberstadt Anna Ruth W. , Chudley Tom , Pritchard Hamish
Published: March 2021

Supraglacial melt is observed across the majority of Antarctic ice shelves and is expected to increase in line with rising air temperatures. Surface meltwater may run off the ice shelf edge and into the ocean, or be stored within firn pore spaces (slush) and supraglacial water bodies (ponds, lakes or streams). When stored either as slush or supraglacial water bodies, the water can indirectly impact ice shelf dynamics, and potentially facilitate ice shelf collapse. Numerous studies have quantified ice shelf meltwater in supraglacial water bodies, however, despite its importance, no studies exist that quantify the extent of slush on a pan-Antarctic scale.

Here, we develop a supervised classifier in Google Earth Engine capable of identifying both slush and ponded water on a pan-Antarctic scale using Landsat 8 imagery. We train and test our classifier on six ice shelves: (1) Nivlisen, (2) Roi Baudouin, (3) Amery, (4) Shackleton, (5) Nansen, (6) George VI. A k-means clustering algorithm is applied to selected Landsat 8 training scenes, and the output clusters are manually interpreted to form training classes (i.e. slush, water, and other surface types (e.g. blue ice, dirty ice)). These training classes are then used to train a Random Forest Classifier, and the accuracy of the outputs are assessed using expert elicitation. Overall, the classifier accuracy for water and slush is 78 % and 70 % respectively. The validated classifier is then applied to numerous ice shelves across Antarctica, in order to produce estimates of slush and water extent from 2013 to the present day.
ESA’s Campaign Activities in Support of Earth Observation Projects: A focus on validation
Authors: Schüttemeyer Dirk , Casal Tania , Davidson Malcom , Drusch Matthias , Kubanek Julia , Oetjen Hilke , Tudoroiu Marin
Published: March 2021

In the framework of its Earth Observation Programmes the European Space Agency (ESA) carries out ground based and airborne campaigns to support geophysical algorithm developments, calibration/validation activities, simulation of future space-borne earth observation missions, as well as application developments related to remote sensing of the atmosphere, land, oceans, solid earth and cryosphere.

ESA has conducted over 150 airborne and ground based measurement campaigns in the last 37 years, of which more than 80 were carried out since 2005. During this period a large number of campaigns have supported the validation of ESA’s satellite missions including for example SMOS and CryoSat. Ongoing activities are focusing on e.g. Sentinel-5Precursor and the preparation of upcoming Earth Explorer missions such as BIOMASS, FLEX, and FORUM. These validation campaigns aim to provide fundamental information about the confidence of data products and their required uncertainties One challenge in this context is a comprehensive understanding and characterization of measurement uncertainty of the validation dataset and the spatial and temporal support or representativity of these.

We will provide an overview of applied strategies to tackle these aspects for existing satellite missions and outline concepts for future missions, and how these integrate into broader earth observation science strategies. In addition, we will highlight recent activities and outline planned activities for the coming years.

 
A method for simultaneous minimal-cost supply node location and network design in pipelined infrastructure.
Authors: Yeates Christropher , Schmidt-Hattenberger Cornelia , Bruhn David
Published: March 2021

Designing low-cost infrastructure networks for transport of hydrogen represents a key step in the adoption and penetration of hydrogen technology in a low-carbon energy future.

For hydrogen distribution, network design amounts to creating pipeline systems in which supply is matched to demand through a transportation system that respects multiple constraints (technical, social, environmental) and minimizes cost. This can equate to recycling pre-existing pipelines or building new ones, but also involves the placement of carefully chosen supply nodes.

In a multi-level distribution network, supply nodes may assume many roles from large-capacity geological storage facilities, to local relay nodes addressing the end customers.

Finding minimum-cost pipeline network designs in which supply node locations are already chosen is itself a well-studied combinatorial optimization problem (Cayley’s formula predicts  possible spanning trees for  nodes) for which multiple heuristic and exact methods are known [1].

Allowing the supply node to take any position within the network renders the problem significantly more complex as the minimum-cost network topology (the specific connections to between nodes) will potentially change for each new supply node position.

We propose a heuristic algorithm that finds good solutions in a reasonable amount of time based on a back-and-forth between:

- Repositioning optimally the supply node, while maintaining the same connections to the supply node (reduces cost)

- Optimizing the network topology, assuming a fixed supply node position (also reduces cost)

The algorithm stops once no further cost reductions for the network design are found. The algorithm output is found to be sensitive to the initial guess of the supply node position, the initial guess of the connections to the supply node, and to the specific “path” of the back-and-forth taken to reach the given local minimum. As such, a good initial guess for a “housing polygon”, i.e. the nodes to which supply node is directly connected to, is crucial in finding the minimum-cost solution, and in the shortest time possible. We attempt to make this initial guess with a machine learning algorithm, with features describing the geometrical distribution of node capacity, as well as elementary network concepts.

Finally, an example is provided on a model hydrogen network comprised of typical elements and realistic cost-functions.

 

[1]: Brimberg J, Hansen P, Lin K, Mladenovi N, Breton M, Brimberg, J (2003) An oil pipeline design problem. Operations Research, 51(2):228–239. https://doi.org/10.1287/opre.51.2.228.12786
GNSS antenna calibration tables evaluated by means of large volume metrology
Authors: Bergstrand Sten , Jarlemark Per , Herbertsson Magnus
Published: March 2021

We have developed a novel method in which a pair of GNSS antennas with similar characteristics are used to evaluate hidden systematic errors in existing GNSS calibrations with the help of high-end industrial metrology equipment. We tilt the calibrated antennas out of parallel and sort the observations in individual antenna reference frames rather than epoch time. With the combined and compared measurements, we can sort out the different elevation dependent uncertainties in the GNSS observations and quantify the errors of the calibration methods. We show the extent to which the calibration method error systematically maps as troposphere and height components in the GNSS processing and in the worst case found this to be > 1 cm in the vertical when using the ionosphere-free frequency combination L3. While showing results in the presentation for the full elevation range in 5° elevation cells, we report here the 1σ uncertainties of our method for 30° elevation at ±0.38 mm on L1 and ±0.62 mm on L3 with respect to the antenna phase centers. Once uncertainties have been characterized at this level, the etalon antennas can be deployed as space geodetic anchor points at core sites without compromising existing installations.
How Quaternary climate changes build and erode sedimentary deposits in an intraplate large fluvial system: the São Francisco River, Brazil
Authors: Mescolotti Patricia , do Nascimento Pupim Fabiano , Bernardes Ladeira Francisco Sérgio , Oliveira Sawakuchi André , Santa Catharina Amanda , Assine Mario Luis
Published: March 2021

Climate, tectonic and sea level factors contribute to the geomorphic evolution of large rivers. Rivers draining settings where the tectonic activity and sea level influence are minors allow clearer signals from climate variation to be identified. Thus, rivers that run exclusively in tectonically quiescent areas and away from coastal regions are the most suitable targets to understand the climate drivers. In northeastern Brazil, the São Francisco River is one of the largest cratonic rivers in South America, with an extension of 2,900 km, and its thousand years evolution is registered by Quaternary deposits preserved as terraces. With the upper course in semi-humid settings, the São Franciscos flows northward, but with a watershed mostly under semi-arid conditions. Hence, the São Francisco River’s deposits are an excellent fluvial sedimentary record to shed light on how large tropical rivers responded to climatic changes of the Quaternary. We studied a 200 km stretch of the middle course of the São Francisco in the State of Bahia by using remote sensing methods and field surveys for geomorphological and sedimentological analyses combined with optically stimulated luminescence dating (OSL). We recognized at least four phases of fluvial aggradation (>90 ka; 65 to 39 ka; 18 to 9.5 ka and 380 years to recent) and three phases of incision (I1 - 85 to 65 ka; I2 - 39 to 18 ka and I3 - 9.5 to 1.0 ka). Two aggradation events and the incision event I2 are also observed in the upper course of the São Francisco River. The river incision events agree with precession insolation cycles (~25 ka) at latitude 10° S, which influence the rainfall in the area. The incision events occurred probably due to increased fluvial discharge produced by intensification of the South Atlantic Convergence Zone (SACZ), which has great influence on precipitation over the upper São Francisco river. Thus, we conclude that the aggradation-incision cycles of the São Francisco River during the last 100 ka are likely products of millennial precipitation variation, possibly related to precession cycles. The events of high sedimentation rate in the São Francisco river mouth are partially correlated with incision phases in its middle course. This suggests that sedimentation in plains of large plateau rivers can be decoupled from the coastal area.

Keywords: Late Quaternary, fluvial response, OSL dating, aggradation-incision cycles, precession cycles
Changes in extreme surface solar radiation in EURO-CORDEX Regional Climate Models
Authors: Bartok Blanka
Published: March 2021

As solar energy share is showing a significant growth in the European electricity generation system, assessments regarding long-term variation of this variable related to climate change are becoming more and more relevant for this sector. Several studies analysed the impact of climate change on the solar energy sector in Europe (Jerez et al, 2015) finding light impact (-14%; +2%) in terms of mean surface solar radiation. The present study focuses on extreme values, namely on the distribution of low surface solar radiation (overcast situation) and high surface solar radiation (clear sky situation), since the frequencies of these situations have high impact on electricity generation.

The study considers 11 high-resolution (0.11 deg) bias-corrected climate projections from the EURO-CORDEX ensemble with 5 Global Climate Models (GCMs) downscaled by 6 Regional Climate Models (RCMs).

Changes in extreme surface solar radiation frequencies show different regional patterns over Europe.

The study also includes a case study determining the changes in solar power generation induced by the extreme situations.

 

 

Jerez et al (2015): The impact of climate change on photovoltaic power generation in Europe, Nature Communications 6(1):10014, 10.1038/ncomms10014

 
Modelling the progression in the mix of particles within the Arctic stratospheric aerosol layer, including the seasonal source of meteoric smoke particles from the Arctic winter polar vortex 
Authors: Sengupta Kamalika , Mann Graham , Weigel Ralf , Brooke James , Dhomse Sandip , Borrmann Stephan , Plane John
Published: March 2021

Meteoric smoke particles (MSPs) provide a steady source of condensation nuclei to the Arctic lower stratosphere, with heterogeneous nucleation to sulphuric acid aerosol particles.  Internally mixed meteoric-sulphuric particles likely also play a significant role in the formation of polar stratospheric clouds and thereby influence stratospheric ozone depletion chemistry, particularly in the quiescent stratosphere.

In several Arctic winter field campaigns (EUPLEX 2002/3, RECONCILE 2009/10, ESSenCe 2010/11),  in-situ stratospheric aerosol particle concentrations measurements were made from the high-altitude Geophysica aircraft, the COPAS instrument measuring total and refractory (non-volatile) particle concentrations at 20 km altitude (see Curtius et al., 2003; Weigel et al., 2014).  

These measurements are consistent with there being a substantial seasonal source of meteoric-sulphuric particles to the lower Arctic stratosphere, from each year’s influx of MSPs  within the winter-time Arctic polar vortex. In this study we investigate the effect of MSPs on the quiescent Junge layer particle concentration as the polar vortex builds up and after it dissipates. 

We use the nudged configuration of the UM-UKCA stratosphere-troposphere composition-climate model to reproduce the vertical profile of stratospheric particles measured in-situ during the COPAS 2003 campaign. Our model simulates two types of stratospheric aerosol particles - pure sulphuric acid particles and sulphuric acid particles with a MSP-core. We show that the model is able to reproduce the vertical profile of aerosol particles observed during the COPAS measurements in winter 2003.

Our findings illustrate the influx of MSP and SO2 from higher altitudes through the polar vortex, the winter-time build-up of SO2 triggering homogeneous nucleation of pure sulphuric particles, also with the seasonal source of MSP-core sulphuric particles nucleated heterogeneously. We assess the effects of MSPs on the quiescent period particle concentration in the Arctic during winter through to spring.