bluuebunny/crossref_metadata_2025 huggingface dataset:
Strengthening climate-resilience in the Mekong Delta – an application of the Economics of Climate Adaption (ECA) methodology
Authors: Rana Arun , Bresch David N. , Detken Annette , Souvignet Maxime
Published: March 2020

Climate Change has presented an ongoing and eminent threat to various regions, communities and infrastructure worldwide and in-turn increasingly pressuring national and local governments to take action. In the current study we identify and evaluate climate impacts faced by the city of Can Tho in Vietnam and the broader Mekong Delta and appraise preparedness options to manage today’s as well as future climate risk. We first, identify the climate risks in co-operation with various local, national and international stakeholders in the region. This is done on the current and future time scales under Socio-Economic Pathways (SSPs) as suggested in the current iteration of IPCC evaluation process. Based on these development pathways, we apply the Economics of Climate Adaptation (ECA) methodology to quantify the climate risks various sectors of the economy will be facing until 2050 with a focus on flood. Further we assess a range of possible adaption measures - including behavioral, environmental, physical as well as financial measures that can mitigate the identified risks by providing a cost-benefit analysis for each of the adaptation measures as well as for bundles thereof. The ECA methodology has proven to be an established tool to enhance our knowledge on the topic and its application in this specific context will enable stakeholders to strengthen societal resilience in the context of both socio-economic development and climate change.
Pesticide concentrations in hydraulic shortcuts exceed environmental quality criteria
Authors: Dax Anne , Schönenberger Urs , Beck Birgit , Vogler Bernadette , Singer Heinz , Stamm Christian
Published: March 2020

Agricultural pesticides can enter surface waters through various pathways and impair the water quality. In the past, numerous studies have been conducted for certain entry paths such as surface runoff, direct drift into water bodies or preferential flow to drainage systems. Man-made hydraulic shortcuts (e.g. road storm drains or manholes of tile drainage systems) might potentially also play a major role for pesticide inputs into surface waters. However, they have been largely overlooked in the past. This study is the first one to measure pesticide concentrations in hydraulic shortcuts in agricultural catchments.

For our analysis, we selected a small catchment (2.8km2) with predominant arable land use in the Swiss Plateau. We installed a rain event-based sampling system at six locations in the catchment: water level proportional samplers at four road storm drainage inlets, one auto sampler in a manhole collecting water from the tile and road drainage system, and another auto sampler in the stream at the outlet of the catchment. In addition, we measured rainfall in the catchment as well as discharge or water level at each of the six sampling locations.

During spring and summer of 2019, samples were collected during 19 rain events. In a first step, the samples from the drainage inlets were analyzed. Liquid chromatography coupled to high-resolution mass spectrometry was used to quantify concentrations of 40 pesticides known to be applied in the catchment.

The obtained results support the hypothesis that hydraulic shortcuts can be relevant for pesticide transport. First, a wide variety of compounds was detected: 33 substances were found in the samples, 7 were not detected. Per rain event, 4 to 15 pesticides were measured on average. Second, some of the compounds were found in very high concentrations: some exceeded concentrations of 5 µg/L and reached up to 60 µg/L.

Ecological quality criteria are known for 15 of the analyzed substances. Based on the sum of the respective risk quotients, nearly a third of the samples posed an acute ecological risk. In most cases, the elevated risk could almost exclusively be attributed to the two herbicides Dimethenamide and Terbuthylazine, as well as to the fungicide Epoxiconazole. Azoxystrobin, Cyproconazole, Mesulfuron-methyl, Metamitron and Metribuzin added to the overall risk to a lesser extent.

In a next step, samples taken by the auto sampler will be analyzed to obtain time series of the rain events and to link the findings from storm drain inlets to the concentration dynamics observed in the receiving drainage system and the river itself.
Evaluating WRF in highly complex terrain – a city surrounded by mountains
Authors: Ward Helen , Rotach Mathias , Gohm Alexander , Graus Martin , Karl Thomas , Umek Lukas , Haid Maren , Muschinski Thomas
Published: March 2020

Accurate prediction of meteorological conditions is particularly important for cities in mountainous terrain, where populations are frequently exposed to extreme weather and poor air quality. However, the wide range of processes that interact across different scales and considerable spatiotemporal variability in these regions present challenges to measurement and modelling. Analysis of turbulence observations in and around Innsbruck reveals similarities and differences in the climate of this alpine city compared to previously-studied urban sites. In particular, the effect of the wind regime (e.g. thermally-driven circulation, foehn) on the timing and magnitude of the surface energy budget is explored. These observations are then used in a detailed assessment of the performance of the Weather Research and Forecasting (WRF) model (at 1-km grid spacing) including the multi-level urban surface scheme. It is found that WRF captures the valley-wind circulation reasonably well, although underestimates the turbulent kinetic energy both inside and outside the city. Even in this complex mountainous setting, the multi-level urban scheme is able to improve model performance.
Dynamics of annual nutrinets and bloom-forming cyanobacteria, revealed by daily observation in a hyper-eutrophic lake
Authors: Zhu Mengyuan , Zhu Guangwei , Paerl Hans , Zhang Wei , Xu Hai
Published: March 2020

Daily monitoring over a period of one year in Lake Taihu, China, included chlorophyll a (Chl-a) and nutrient measurements, determining the taxonomic composition of the phytoplankton community and various water column physicochemical parameters. Chl-a and nutrient concentrations showed strong circadian variations ‒ Chl-a rised during daylight hours, while ammonium and phosphate rised at night. Chl-a concentrations also showed strong seasonal variations, with one annual peak in spring and another from summer to autumn, dominated by Dolichospermum spp. and Microcystis spp. respectively. Temperature appeared to exert the most important effect in this species succession. A nutrient‒Chl-a balance calculation indicated that both nitrogen and phosphorus in the water column could be limiting factors for phytoplankton growth during bloom periods. Over two thirds of particulate nutrients was attributed to phytoplankton biomass during blooms. Daily (or weekly) monitoring data provided more precise description of water quality, capturing short-term peaks in phytoplankton biomass, and reduced risks of under- or overestimating trophic levels in lakes, which always happened when using monthly monitoring data.
What controls erosion (exhumation) along the humid eastern margin of the Northern Andes? Insights from U-Th/He thermochronology
Authors: Perez-Consuegra Nicolas , Sobel Edward R , Mora Andres , Sandoval Jose R , Fitzgerald Paul G , Zapata Sebastian , Parra Mauricio , Glodny Johannes , Hoke Gregory D
Published: March 2020

The relative controls of rock uplift (tectonics) and precipitation (climate) on the exhumation of earth’s rocks in tectonically active mountain ranges are still debated. In low latitude tropical regions where rates of precipitation and the amount of vegetation cover are higher, more data is required to test the relative contribution of these factors to the evolution of orogenic topography. To contribute to this debate, cooling ages were derived for 25 bedrock and four detrital samples using the apatite (U-Th-Sm)/He (AHe) low temperature thermochronometer. AHe ages are reported along a ~450-km-wide swath on the eastern flank of the Northern Andes in Colombia (South America). The AHe cooling ages, that range from 2.5 Ma to 17 Ma, are compared to precipitation rates and geomorphic parameters in order to discern the relative importance of climate and/or tectonics on exhumation. Along the transect, AHe cooling ages are poorly correlated with the rates of precipitation but show a good correlation with landscape parameters such as average hillslope and average channel steepness. Moreover, young AHe cooling ages coincide with areas where deformation is mainly compressional; older AHe cooling ages are found in the middle part of the study area where strike-slip deformation dominates. The spatial distribution of the new AHe cooling ages suggests that in mountainous regions, in this case with high precipitation rates (> 1500 mm/yr), denudation is mainly controlled by the rate of vertical advection of material via tectonic processes. The spatial variations in precipitation may only have a second-order role in modulating exhumation rates.
Future compound climate extremes and exposed population in Africa
Authors: Weber Torsten , Bowyer Paul , Rechid Diana , Pfeifer Susanne , Raffaele Francesca , Remedio Armelle Reca , Teichmann Claas , Jacob Daniela
Published: March 2020

The African population is already exposed to climate extremes such as droughts, heat waves and extreme precipitation, which cause damage to agriculture and infrastructure, and affect people's well-being. However, the simultaneous or sequential occurrence of two single climate extremes (compound event) has a more severe impact on the population and economy than single climate extremes. This circumstance is exacerbated by the increase in the African population, which is expected to double by the middle of this century according to the UN Department of Economic and Social Affairs (DESA). Currently, little is known about the potential future change in the occurrence of compound climate extremes and population exposed to these events in Africa. This knowledge is however needed by stakeholder and decision makers to develop measures for adaptation.

This research analyzes the occurrence of compound climate extremes such as droughts, heat waves and extreme precipitation in Africa under two different emission scenarios for the end of the century. For the analysis, we applied regional climate projections from the newly performed Coordinated Output for Regional Evaluations (CORE) embedded in the WCRP Coordinated Regional Climate Downscaling Experiment (CORDEX) Framework for Africa at a grid spacing of 25 km, and spatial maps of population projections derived from two different Shared Socioeconomic Pathways (SSPs). In order to take into account a low and a high emission scenario, the Representative Concentration Pathways (RCPs) 2.6 and 8.5 were used in the regional climate projections.

We will show that compound climate extremes are projected to be more frequent in Africa under the high emission scenario at the end of the century, and an increase in total exposure is primarily expected for West Africa, Central-East Africa and South-East Africa. Furthermore, combined impacts of population growth and increase in frequencies of compound extremes play an important role in the change of total exposure.
Evaluation of NMR and other soil water content measurement methods at the point and field scale
Authors: Bauckholt Matteo , Pohle Marco , Schrön Martin , Zacharias Steffen , Landmark Solveig , Kathage Susanne , Kathage Andreas , Zengerle Carmen , Kasner Mandy , Werban Ulrike
Published: March 2020

Soil water content in the unsaturated zone is a key parameter of the environmental system. The understanding of soil moisture plays a major role with regard to questions of water and nutrient supply to plants, groundwater recharge, soil genesis and climatic interactions.

In our study we aim to test a new technology for the non-invasive measurement of soil moisture profiles, the so-called Surface-NMR (Nuclear Magnetic Resonance). The instrument applies magnetic fields to the ground and detects its changes caused by mobile and immobile hydrogen atoms in the soil column. Using four different frequencies, the data may provide insights into the water content of four distinct soil layers between the surface and 20 cm depth.

We carried out multiple NMR measurements at four different field sites in Germany and compared the data with conventional methods, such as gravimetric soil samples, Time Domain Reflectometry (TDR), and Cosmic-Ray Neutron Sensing (CRNS).

The dataset will be used to investigate the following research questions:

Is the Surface-NMR method suitable to provide depth-resolved information of soil moisture under field conditions?

Does Surface-NMR have the potential to replace or complement conventional methods of soil moisture measurement in the field?

What can we learn about the spatial variability and scale dependency of soil moisture by combining three measurement methods of different scale (TDR, NMR, CRNS)?
Multi-decadal offshore wind power variability can be mitigated through optimized European allocation
Authors: Neubacher Charlotte , Wohland Jan , Witthaut Dirk
Published: March 2020

Wind power generation is a promising technology to reduce greenhouse gas emissions in line with the Paris Agreement.  In the recent years, the global offshore wind market grew around 30% per year but the full potential of this technology is still not fully exploited. In fact, offshore wind power has the potential to generate more than the worldwide energy demand of today. The high variability of wind on many different timescales does, however, pose serious technical challenges for system integration and system security.  With a few exceptions, little focus has been given to multi-decadal variability. Our research therefore focuses on timescales exceeding ten years.

Based on detrended wind data from the coupled centennial reanalysis CERA-20C, we calculate long-term offshore wind power generation time series across Europe and analyze their variability with a focus on the North Sea, the Mediterranean Sea and the Atlantic Ocean. Our approach is based on two independent spectral analysis methods, namely power spectral density and singular spectrum analysis. The latter is particularly well suited for relatively short and noisy time series. In both methods an AR(1)-process is considered as a realistic model for the noisy background. The analysis is complemented by computing the 20yr running mean to also gain insight into long term developments and quantify benefits of large-scale balancing.

We find strong indications for two significant multidecadal modes, which appear consistently independent of the statistical method and at all locations subject to our investigation. Moreover, we reveal potential to mitigate multidecadal offshore wind power generation variability via spatial balancing in Europe. In particular, optimized allocations off the Portuguese coast and in the North Sea allow for considerably more stable wind power generation on multi-decadal time scales.
D-MOSS: Dengue Fever Forecasting for Vietnam – Assessment of an Operational System.
Authors: Hofmann Barbara , Tsarouchi Gina , Colon Felipe , Ainscoe Eleanor , Ferrario Iacopo , Harpham Quillon , James Sam , Lumbroso Darren , Malde Sajni , Moschini Francesca , Robertson Claire
Published: March 2020

Dengue fever is now present in over 150 countries world-wide, affecting 390 million people per year. In Vietnam the number of cases has increased by 100% since 2000, and 2019 exhibited exceptional high numbers of reported dengue fever cases. Transmission of this mosquito-borne disease is dependent on a variety of climate and socio-economic factors. Among those water availability plays a crucial role in creating or destroying suitable mosquito breeding grounds.

At present mitigating actions are taken based on reported dengue fever cases and local knowledge, leading to a reactive rather than proactive approach of disease control. By combining Earth Observation and vector-borne disease modelling expertise we have developed D-MOSS (Dengue Model Forecasting Satellite based System). The D-MOSS system is funded by the UK Space Agency’s International Partnership Programme and aims to predict the likelihood of future dengue epidemics for Vietnam on a province scale with a lead time of up to six months.

D-MOSS integrates multiple stressors such as water availability, land-cover, precipitation and temperature with data of past dengue fever incidents.  This information is used to develop statistical models of disease incidence, that can then be used to forecast dengue outbreaks based on seasonal weather and hydrological forecasts.  It is the first fully integrated dengue fever forecasting system incorporating Earth Observation data and seasonal climate forecasts to routinely issue warnings. 

D-MOSS takes the form of a web-based platform.  The system’s architecture is based on open and non-proprietary software, where possible, and on flexible deployment into platforms including cloud-based virtual storage and application processing. Working closely with public health authorities in Vietnam enabled us to develop a system tailored to the local needs and decision making procedures.
The Fate of Subduction Fluids above the Subduction Interface: Implications for Mantle Wedge Deformation Processes
Authors: Angiboust Samuel , Glodny Johannes , Cambeses Aitor , Raimondo Tom , Monié Patrick , Deldicque Damien , Garcia-Casco Antonio
Published: March 2020

The physical and mechanical processes rooted in the hydrated, serpentinized mantle above subduction zones (the “cold nose”) remain debated and poorly understood, despite fundamental consequences on the elastic loading of the seismogenic interface. The fluids crossing this interface are expected to generate nests of seismicity and at the same time weaken the interface hanging wall through serpentinization and metasomatic processes. Ultramafic and jadeitite samples from two natural laboratories where such fossil settings are now visible at the Earth’s surface are used here to document multi-scale deformation mechanisms and fluid-rock interaction processes. Field relationships enable tracking the pathways followed by the fluids during HP metamorphism. Petrographic, geochemical, geochronological and microstructural observations demonstrate the complex interplay between brittle and plastic deformation processes throughout the gradual hydration of the cold nose mantle over millions of years. Changes in bulk rock geochemical and paragenetic sequence also reveal the evolution of the composition of the fluid source through time. These results shed light on the geometry of the cold nose above the interface, with implications for volatile budget estimates, rheology of the plate interface (including the various types of seismicity) as well as the interpretation of Vp/Vs ratios from active subduction settings worldwide.
A machine learning model to link ecological response and anthropogenic stressors: a tool for water management in the Tagus River Basin (Spain)
Authors: Valerio Carlotta , Garrido Alberto , Martinez-Muñoz Gonzalo , De Stefano Lucia
Published: March 2020

Freshwater ecosystems are threatened by multiple anthropic pressures. Understanding the effect of pressures on the ecological status is essential for the design of effective policy measures but can be challenging from a methodological point of view. In this study we propose to capture these complex relations by means of a machine learning model that predicts the ecological response of surface water bodies to several anthropic stressors. The model was applied to the Spanish stretch of the Tagus River Basin. The performance of two machine learning algorithms -Random Forest (RF) and Boosted Regression Trees (BRT) - was compared. The response variables in the model were the biotic quality indices of macroinvertebrates (Iberian Biomonitoring Working Party) and diatoms (Indice de Polluosensibilité Spécifique). The stressors used as explanatory variables belong to the following categories: physicochemical water quality, land use, alteration of the hydrological regime and hydromorphological degradation. Variables describing the natural environmental variability were also included. According to the coefficient of determination, the root mean square error and the mean absolute error, the RF algorithm has the best explanatory power for both biotic indices. The categories of land cover in the upstream catchment area, the nutrient concentrations and the elevation of the water body are ranked as the main features at play in determining the quality of biological communities. Among the hydromorphological elements, the alteration of the riparian forest (expressed by the Riparian Forest Quality Index) is the most relevant feature, while the hydrological alteration does not seem to influence significantly the value of the biotic indices. Our model was used to identify potential policy measures aimed at improving the biological quality of surface water bodies in the most critical areas of the basin. Specifically, the biotic quality indices were modelled imposing the maximum concentration of nutrients that the Spanish legislation prescribes to ensure a good ecological status. According to our model, the nutrient thresholds set by the Spanish legislation are insufficient to ensure values of biological indicators consistent with the good ecological status in the entire basin. We tested several scenarios of more restrictive nutrient concentrations and values of hydromorphological quality to explore the conditions required to achieve the good ecological status. The predicted percentage of water bodies in good status increases when a high  Riparian Forest Quality Index is set, confirming the importance of combining physico-chemical and hydromorphological improvements in order to ameliorate the status of freshwater ecosystems. 
The role of eccentricity in determining the spacing between interglacials
Authors: Wolff Eric , Crucifix Michel , Tzedakis Chronis
Published: March 2020

In a recent paper Tzedakis et al (2017) described a simple rule that predicts, using only caloric summer half-year insolation as input, which insolation cycles lead to the onset of an interglacial. The rule is based on an energy threshold, one of whose characteristics is that it reduces with time since the last interglacial onset, reflecting increased fragility of glacial climate as ice sheets get larger. The rule correctly predicts every complete deglaciation of the past million years, a period in which interglacial onset skips both precession and obliquity cycle maxima. This then raises the question to what extent the approximate 100 ka period observed in the last million years is due simply to internal dynamics rather than to the period of eccentricity present in the insolation record. Here we will test this by creating synthetic insolation curves from which eccentricity (or other orbital components) have been removed.  We will then use the proposed rule to test to what extent eccentricity influences the spacing of interglacials. We will also assess the impact of other orbital components and the impact earlier in the Quaternary when the energy threshold was lower.
A Monte Carlo Markov Chain Approach to Stress Inversion and Forecasting of Eruptive Vent Locations
Authors: Mantiloni Lorenzo , Davis Tim , Gaete Rojas Ayleen Barbara , Rivalta Eleonora
Published: March 2020

Current approaches to vent opening forecast produce probabilistic maps on the base of the spatial density of past eruptive vents, as well as the surface distribution of structural features such as faults and fractures. One of the main challenges in forecasting future vent locations in the case of distributed volcanism is that we usually deal with scarce, spatially scattered data to support these approaches. As sophisticated as our statistical analysis can be, such data are difficult to interpolate between and extrapolate from, resulting in spatially coarse forecasts and large uncertainties. More recently, Rivalta et al. (2019) proposed a forecasting strategy to predict future vent locations, combining the physics of magma transport at depth (where magma trajectories are assumed to be driven entirely by stress) with a Monte Carlo inversion technique for key stress parameters. This method has been first tested on the Campi Flegrei caldera; however, further validations and development are needed. Here we validate the strategy of Rivalta et al. with data from analog models (air injection in gelatine). We stress a gelatine block in controlled conditions (extension/compression, surface loading/unloading, layering) and observe air-filled crack trajectories. With these data, we test a flavour of the strategy that combines boundary element magma trajectory calculations with a  Monte Carlo Markov chain approach. We find the scheme is able to retrieve the parameters of the stress imposed on the gelatine and forecast subsequent vents in the same experimental setups. We also discuss how it may be applicable to natural cases, and what data are necessary for the approach to be feasible.
Recent results from the imagery of Juno’s Stellar Reference Unit
Authors: Becker Heidi , Alexander James , Atreya Sushil , Bolton Scott , Brennan Martin , Brown Shannon , Florence Meghan , Guillaume Alexandre , Guillot Tristan , Ingersoll Andrew , Levin Steven , Lunine Jonathan , Steffes Paul , Aglyamov Youry
Published: March 2020

The Juno Mission has recast its spacecraft engineering star camera as a visible wavelength science imager. Developed and primarily used to support onboard attitude determination, Juno’s Stellar Reference Unit (SRU) has been put to use as an in situ high energy particle detector for profiling Jupiter’s radiation belts and as a low light sensitive camera for exploring multiple phenomena and features of the Jovian system. Juno’s unprecedented polar orbit and closest approach of ~4000 km have yielded high resolution SRU imagery of Jupiter’s lightning and aurorae from as little as 50,000 km from the 1 bar level and unique Jovian dust ring and satellite images. We will present recent SRU results and discuss the implications for Jupiter’s atmosphere that stem from the SRU lightning observations.
Specular meteor observations and full wave scattering modelling: observing faint meteors
Authors: Stober Gunter , Brown Peter , Schult Carsten , Weryk Rob , Campbell-Brown Margaret , Pokorny Petr
Published: March 2020

There is a continuous flux of meteoroids entering the Earth's atmosphere, which are decelerated and heated by collisions with atmospheric molecules, and, depending on the meteoroid kinetic energy, they vaporize and form an ambipolar diffusing plasma trail, which is easily detectable using radar remote sensing. Specular meteor observations are a widely used radar technique to measure winds at the Mesosphere and Lower Thermosphere (MLT). The altitude dependent lifetime (decay time) of the meteor plasma columns provides valuable information about the mean temperature of the atmosphere.  Part of the success of these systems is based on the efficient scattering process compared to meteor head echoes.

Here we present observations with the Middle Atmosphere Alomar Radar System to detect the faintest observable meteors using the specular geometry, but a focused beam with a beamwidth of 3.6° and the full power of 866kW of the system. We compare our observations to an orbital dynamics model of JFC comets and derive a meteor velocity distribution for the observed population.

Further, we performed extensive modeling using a full-wave scattering model based on the model presented in Poulter and Baggaley, 1977. We conducted extensive simulations with the full-wave scattering model to investigate how different plasma distributions would affect the detectability of the meteoric plasma cylinders considering the initial trail radius, diffusion, and electron line density. The obtained reflection coefficients are validated with the triple frequency CMOR (Canadian Meteor Orbit Radar) measurements convolving them with the Fresnel integrals. Our results indicate that the plasma distribution can significantly alter the detectability. Further, the model shows that the observed decay time depends on the polarization of the transmitted wave relative to the meteor trajectory, which also revealed resonance effects for certain critical plasma frequencies. 
Simulations of dated radiostratigraphy for the Greenland ice sheet
Authors: Born Andreas , Robinson Alexander
Published: March 2020

As layers of accumulated snow compact into ice and start to flow under its own weight, their deformations are recorded in the vertical structure of the glacier. Therefore, the isochronal stratigraphy of the Greenland ice sheet provides comprehensive dynamic constraints, which, with adequate methods, can be used to calibrate ice sheet models and greatly improve their accuracy.

We present the first three-dimensional ice sheet model that explicitly resolves isochrones. Individual layers of accumulation do not exchange mass with each other as the flow of ice deforms them, resembling the Lagrangian description of flow in the vertical dimension, while lateral flow within each layer is Eulerian. Direct comparison with dated radiostratigraphy is used to filter an ensemble of simulations of the Greenland ice sheet. The abundant information implied by the shape of the three-dimensional layering enables us to constrain a large number of degrees of freedom. The mismatch in the thickness of certain isochrones is used to calibrate the climate forcing of different periods of the last glacial cycle.
Development of a Fast Solar Tracker Enabling Atmospheric Direct Sun Remote Sensing Applications on Different Moving Platforms
Authors: Kleinschek Ralph , Kostinek Julian , Holzbeck Philip , Knapp Marvin , Luther Andreas , Hase Frank , Butz André
Published: March 2020

Spectroscopic direct sun remote sensing of the atmosphere offers an essential tool for the validation of models and satellite observations as well as for the monitoring of emissions. Validation missions for greenhouse gas monitoring satellites are essential to improve the performances of the satellite products, thereby gaining a better understanding of the dynamics between sources and sinks. Furthermore, the monitoring of ozone-depleting substances is a vital contribution to observe the progress in restoring the ozone layer. A high tracking precision is in particular for measuring CO2 and CH4 columns required. We aim for an accuracy better than 0.05°.

This work presents the development of a compact and reliable stand-alone sun tracker for mobile applications. The tracking is camera-based and has two modes. In the first mode, image processing using the image of a fish-eye lens with a field of view of 185° monitoring the entire hemisphere above the instrument calculates the coarse position of the sun. On reaching this coarse position, the other camera-based tracking system takes over and centers the projection of the sun with high precision and fast response times (100 Hz control loop). The tracker is compatible with different kinds of spectrometers like grating spectrometers and Fourier transform infrared spectrometers (FTIR). The tracking is also suitable for different mobile platforms like cars, ships, or stratospheric balloons. 

During the CoMet (Carbon Dioxide and Methane Misson 2018) campaign, the tracking has performed well in a stop and go manner on a car-mounted setup. On every stop, the tracker was able to autonomously find the sun regardless of the relative position of the vehicle. For the MORE-2 (Measuring Ocean REferences 2) campaign onboard a research vessel over the Pacific ocean, the tracking allowed for using over 99 % of the measuring time for high-precision retrievals of CO2 and CH4 using an EM27/SUN FTIR. Based on the lessons learned during the performed campaigns, a further improved version of the tracker for flying on a stratospheric balloon in August 2020 is in development. 
The variation in genetic material of a high Alpine catchment reveals (sub)surface exchange
Authors: Maechler Elvira , Ceperley Natalie , Salyani Anham , Walser Jean-Claude , Larsen Annegret , Schaefli Bettina , Altermatt Florian
Published: March 2020

In the past years, it has been proposed that stream networks can accumulate genetic material over a given area. Accordingly, a sample of environmental DNA (eDNA) from streamflow at the outlet of a catchment can be used as an indicator of the upstream biodiversity. eDNA’s use in ecological studies is becoming more and more common and it seems reasonable to assume that eDNA might also offer a powerful tool as a hydrologic tracer. However, the original ecological proposition largely simplifies the complexity of any seasonal, diurnal, or spatial variation according to hydrologic flow paths and processes. From a hydrological perspective, this shortcoming is particularly problematic in Alpine headwater catchments, where the combination of snowmelt-dominated summer flow and particularly high climatic and geomorphologic heterogeneity results in hydrologic flow paths that are especially dynamic in space and time. 

We were interested to see if on one hand, eDNA could teach us something new about hydrologic (subsurface) flow paths, and on the other hand, if biodiversity assessment should consider hydrologic variation in detail. To do so, we sampled natural occurring eDNA at 11 points distributed over the 13.4 km2, intensively monitored Vallon de Nant (1189-3051 m. a.s.l., Switzerland) between March and September 2017. We chose points corresponding to three different potential microhabitats and flow regimes (main channel, tributary, and spring) likely both inhabited by characteristic organismal communities and of interest for identifying hydrologic flow paths. We found that at moments when streamflow was increasing rapidly, biological richness in upstream points in the main channel and in tributaries was highest contrary to springs, where richness was higher when electrical conductivity was highest.  Thus, the main conclusion from our work is that elevated richness corresponds to moments in time when multiple mechanisms transport additional, probably terrestrial, DNA into water storage or flow compartments. These mechanisms could include overbank flow, stream network expansion, and hyporheic exchange. Our data demonstrates that biodiversity assessments using eDNA do need to consider hydrologic processes and shows that there is a potential future for eDNA among hydrologic tracers.  We will give recommendations in this talk about how to sample eDNA to answer hydrologic questions.

 
Nighttime to daytime transition of the oxidation products of isoprene by NO3 radicals
Authors: Tsiligiannis Epameinondas , Wu Rongrong , Kang Sungah , Hantschke Luisa , Thornton Joel , Fuchs Hendrik , Mentel Thomas , Hallquist Mattias
Published: March 2020

Biogenic volatile organic compounds (BVOC) dominate the overall VOC emissions. Isoprene is the most common BVOC emitted from vegetation, accounting up to 50% of the total BVOC emissions. Despite being emitted in daytime it can accumulate in the stratified nocturnal layer. Thus, the oxidation of isoprene by nitrate radicals (NO3) may be of high importance. A series of experiments were conducted in the atmospheric simulation chamber SAPHIR in Jülich, Germany, in order to investigate the gas and particle phase products of the oxidation of isoprene by NO3, under a variety of conditions (e.g. high RO2, high HO2, nighttime to daytime transition, with and without seed aerosol) using a wide range of instrumentation. However, herein the focus is on the results of gas-phase product characterisation using high resolution time of flight chemical ionization mass spectrometers (HR-ToF-CIMS) using iodide or bromide as the primary reagent ion. The use of two HR-ToF-CIMS with different primary reagents provides possibilities to scrutinise the time profiles of isomers of selected products.

We will discuss qualitatively and quantitatively how the distribution of oxidation products change under different conditions, with a focus on the nighttime daytime transition of the major products and the role of subsequent OH oxidation on the products initially formed by NO3 oxidation. Generally, the dominant gas phase products include compounds like nitrooxy hydroperoxide (INP) & dihydroxy nitrate (IDHN) (C5H9NO5), carbonyl nitrate (ICN) (C5H7NO5), hydroxy nitrate (IHN) (C5H9NO4), hydroxy hydroperoxy nitrate (IHPN) (C5H9NO6), as well as a C4 compound (C4H7NO5) among others.
Synchronicity and drivers of river flooding
Authors: Berghuijs Wouter , Kirchner James
Published: March 2020

When rivers flood, surrounding rivers often flood at the same time. When large precipitation events occur, floods do not always occur. Here we explore the drivers and synchronicity of river flooding. Using flood data from thousands of European and US rivers, we demonstrate that the flood synchrony scale—the distance over which multiple rivers flood near synchronously—far exceeds the size of individual drainage basins and varies regionally by more than an order of magnitude. Regions of large flood synchrony scales are mostly uncorrelated with regions of large precipitation synchrony scales; across most of Europe and the US few floods are caused by the biggest rainfall peaks. Instead, most floods are caused by the concurrence of heavy precipitation with high antecedent soil moisture. Risk finance, flood forecasting, and interpretations of flood trends can benefit from accounting for what drives flooding and how flood risks extend beyond the borders of individual drainage basins.
Glacial cycle ice-sheet evolution controlled by ocean bed properties
Authors: Schannwell Clemens , Drews Reinhard , Ehlers Todd A. , Eisen Olaf , Mayer Christoph , Malinen Mika , Smith Emma C. , Eisermann Hannes
Published: March 2020

Shortcomings in the description of ice dynamics have been recognized as a major limitation for projecting the evolution of the Greenland and Antarctic ice sheets. If current sea-level rise rates continue unabated, up to 630 million people will be at annual flood risk by 2100; making improved ice-sheet model projections a priority and of high socio-economic impact. Since the boundary condition at the underside of the ice-sheet is poorly known, improving constraints on the basal ice/bed properties is essential for accurate prediction of ice-sheet stability and grounding line positions. Furthermore, the history of grounding-line positions since the Last Glacial Maximum has proven challenging to understand due to uncertainties in bed conditions. Here we use a 3D full-Stokes ice-sheet model to investigate the effect of differing ocean bed properties on ice-sheet advance and retreat over a glacial cycle of 40,000 years. We do this for the Ekström Ice Shelf catchment, East Antarctica. We find that predicted ice volumes differ by >50 % under almost equal forcing when comparing (low-friction) sediment-covered with (high-friction) crystalline ocean beds. Grounding-line positions differ by >100 % (49 km), show significant hysteresis, and migrate non-steadily in both scenarios with long quiescent phases disrupted by leaps of rapid migration. Our new modelling framework extends the applicability of 3D full-Stokes ice-sheet models by an order of magnitude to previous studies. The simulations predict evolution of two entirely different catchment geometries (namely thick and slow vs. thin and fast), triggered exclusively by variable ocean-bed properties. This highlights that constraints not only for the bathymetry but also its geological properties are urgently needed for predicting ice-sheet evolution and sea level change.
Influence of Subway Construction on Groundwater Environment in Downtown Area of Chengdu
Authors: qiang zhang , jinyu sun , jinping tamg , jiashen zhang , sishuang huang
Published: March 2020

Located at the southeast of the Minjiang alluvial-proluvial fan, the downtown area of Chengdu mainly composed of sand gravel layer. Now Chengdu has 8 subway lines operated; in the next 10 years, more than 34 routes will be constructed. Metro Line 7 forming a transfer relationship with multiple urban MRTS and urban commuter radiation built completly in downtown area, with depth of subway station 1.73-11.3 m, and the depth of interval tunnel 6.47-28.01 m. In order to study how the groundwater will be influenced, 3 3d groundwater numerical models in different scales have been constructed using FeFlow software, the results illustrated regional groundwater seepage field and local seepage field.

Baed on 1 regional model (417 km2 for downtown Chengdu ) and 2 models of typical underground space (Taipingyuan station and Yipintianxia station), at the same time with the basic geology and hydrogeology Analysis, shows that:

(1) The influence of metro line 7 on the seepage field is relatively limited in regional scale, and the change of groundwater level is very little(4-10cm) at several typical observation points; in the long-term, the raising of groundwater level will decrease gradually.

(2) Comparing the simulation results of Taipingyuan station and Yipintianxia station shows the impact of subway construction on the groundwater environment in the downtown Chengdu. In the big view, from northwest to southeast, the phenomenon of underground water interception or raising in subway stations decrease gradually, this is owing to the influence of aquifer thickness, groundwater flow direction and the direction of underground station structure.

(3) As the main body or long section of the underground structure is coincide with the groundwater flow direction, the cross-section blocking the groundwater is minimized, so its influence on the groundwater seepage field is not notable even with development of the underground space, this is also help avoiding the floatation effect on the building foundation due to the raising of the groundwater flow.
Microbial formation of thiols control the chemical speciation and methylation of Hg(II)
Authors: Gutensohn Mareike Franziska , Schaefer Jeffra K. , Skyllberg Ulf , Björn Erik
Published: March 2020

The formation of the neurotoxin methylmercury (MeHg) is a biotic process where anaerobic bacteria methylate inorganic divalent Hg (Hg(II)) intracellularly. The cellular uptake mechanisms are still not identified, but low molecular mass (LMM) thiols play an important role together with thiol groups on the outer membrane in controlling the chemical speciation of Hg(II). For example, increased concentration of specific LMM thiols, especially cysteine, is known to enhance the formation of MeHg. A recent study showed that metabolically active anaerobic microorganisms produced LMM thiols in vivo and exported them to concentrations up to 100 nM in the assay medium. The concentration range was sufficient to significantly affect the chemical speciation, uptake and methylation of Hg(II) without any external addition of LMM thiols.

In this study we investigate the kinetics of microbial formation and cellular export of LMM thiols by the iron-reducing bacterium Geobacter sulfurreducens and the sulfate-reducing bacterium Desulfovibrio sp. ND132 in high time resolution and the impact on the chemical speciation and methylation of Hg(II).

LMM thiols were separated by liquid chromatography and determined by electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). Hg(LMM-RS)2 complexes were determined by thermodynamic modeling and by direct measurements using LC-Inductively coupled plasma MS (LC-ICPMS).

Results will be presented for the production of LMM thiol compounds, formation of Hg(LMM-RS)2 complexes and how this change in Hg speciation impacts the Hg(II) methylation rate in short-term washed cell assays. Characterizing the time-dependent molecular composition of LMM thiols associated with methylating microbes are important to further understand their multiple roles on Hg(II) uptake and MeHg formation in bacteria assays and in the environment. 
Seismic P-wave receiver function modelling of Archean cratonic crust: A global perspective
Authors: Roy Poulami , Borah Kajaljyoti
Published: March 2020

Cratons are representative of the oldest cores of continental crusts. Study of cratons is important  as they preserve the pristine nature of continental crusts as well as they have economic significance as a major source of the world's mineral deposits. The crustal thickness, crustal composition, structure and physical properties of crust-mantle transition (the Moho) are the key parameters for understanding the formation and evolution of continental crust. The ratio of  seismic P-wave and S-wave velocity (Vp/Vs) is used as a parameter to understand the petrologic nature of the Earth's crust. Using these parameters, we address the crustal properties of all Archean cratons. The teleseismic P-wave receiver function analysis reveals that all the Eoarchean (4-3.6 Ga) cratons (Superior, North Atlantic Craton, North China Craton, Yilgarn, Zimbabwe, Kaapvaal) have crustal thickness ranges between 34-42 km and Vp/Vs ratio 1.68-1.79, the Paleoarchean (3.6-3.2 Ga) cratons (Baltic shield, Pilbara, Tanzania, Grunehogna) have 29-52 km crustal thickness and Vp/Vs ratio 1.7-1.85, the Mesoarchean (3.2-2.8 Ga) cratons (Sao Francisco, Guapore, Yangtze, Antananarivo) have 36-53 km thickness and Vp/Vs ratio 1.7-1.9, and Neoarchean (2.8-2.5 Ga) cratons (Guiana, Anabar, Gawler, Napier, Tarim) have 36-59 km thickness and Vp/Vs ratio 1.64-1.95. The nature of crust-mantle transition is overall sharp and flat.  We also found that the crusts which are stabilized earlier, are thinner compared to the later stabilized crusts. Our findings are well-correlated with the craton evolution process predicted by Durrheim and Mooney (1994), where older crusts are thin due to delamination process and relatively younger crusts are thick due to basaltic underplating. Our result of higher Vp/Vs ratio in the relatively younger crusts corroborates with the mafic nature of the crust whereas the older crusts are felsic-intermediate resulting lower Vp/Vs ratio. Our study is unique as it includes most of the global cratons and suggests a global model of continental crust formation and evolution process.