bluuebunny/crossref_metadata_2025 huggingface dataset:
Glyphosate and AMPA dissipation at different depths in conventional and conservation agriculture
Authors: Carretta Laura , Cardinali Alessandra , Zanin Giuseppe , Masin Roberta
Published: March 2020

Glyphosate is the most used herbicide worldwide, especially in conservation agriculture, where the lack of mechanical weed control often necessitates chemical inputs. In conservation agriculture, the elimination of tillage operations leads to changes in soil physical, chemical, and biological properties. Consequently, herbicide environmental fate may be potentially altered relatively to conventional tillage systems. The aim of this study was, therefore, to investigate the effect of conservation agriculture and conventional tillage on the adsorption of glyphosate and on the dissipation of glyphosate and its primary metabolite aminomethylphosphonic acid (AMPA) at two depths, 0−5 and 5−20 cm.

The field trial was conducted from October 2018 to April 2019 at the Padua University Experimental Farm, North-East Italy. Glyphosate was applied as a formulated product (Roundup Power 2.0) at a dose of 1.44 kg/ha of the active ingredient. The dissipation of glyphosate and the formation/dissipation of AMPA were followed for 182 days after their application. The concentrations of glyphosate and AMPA in the soil were analysed by Ultra-High Performance Liquid Chromatography coupled with mass spectrometry. The dissipation of glyphosate was described by the first-order multicompartment model (FOMC), whereas the model for AMPA was composed of an FOMC degradation model for glyphosate and the single first-order degradation model for AMPA. The estimated trend of concentrations over time for both glyphosate and AMPA were used to derive their DT50 (time required for 50% dissipation of the initial concentration).

The results indicate an increase in glyphosate adsorption in non-tilled soil compared to the tilled soil, at both depths. Glyphosate initial dissipation was fast, followed by a slower decline. At 0–5 cm no significant difference was observed in glyphosate persistence between the two soil managements, whereas at 5–20 cm glyphosate was more persistent in non-tilled soil (DT50 18 days) than in tilled soil (DT50 8 days). The fast initial dissipation of glyphosate was reflected in an increase in the concentration of AMPA. AMPA persisted longer than glyphosate but, for this metabolite, no apparent effect was observed in response to the different soil management. The higher persistence of glyphosate under conservation tillage might increase the risk of on-site soil pollution due to the accumulation of this chemical, especially in the case of repeated applications of glyphosate. Nevertheless, high glyphosate adsorption observed in non-tilled soil may reduce the leaching potential to lower soil depths.

This abstract falls in the group “Soil contamination” and the subgroup “Experimental assessment”.
Magnitude of sediment transport due to extreme windthrow event in small catchments in the Tatra Mountains
Authors: Strzyżowski Dariusz
Published: March 2020

In the forested mountain areas tree uprooting plays important role among many other geomorphic processes. In some cases, during extreme wind events, large patches of forest may be destroyed, which causes transport of significant amount of sediment.

The aim of this research was to investigate magnitude of sediment transport during one intense windthrow event, which took place on 25 December 2013 in the Tatra Mountains, southern Poland. The research was conducted in three second- to third-order catchments (16-81 ha), in which 34 to 94 percent of their areas were affected by windthrow. This was achieved by combining field measurements and GIS analyses. During field work root plates located within selected research polygons were measured in order to recognize the amount of sediment transported by a single uprooted tree. Then, each root plate located in the investigated catchments was mapped in GIS software using high-resolution (40 mm) orthophoto. Based on this, total volume of sediment displaced by uprooted trees within each catchment was estimated. Next, taking into account directions of tree fall and slope inclination within each uprooted tree, sediment flux by windthrow event in 2013 was calculated.

In total 211 uprooted trees were measured in the field. Mean volume of measured root plates was 1.84 m3. It was assumed that half of that value is accounted for roots of a tree, thus on average 0.92 m3 of sediment was transported by each root plate. Analysis of the orthophoto allowed for identification of 4650 uprooted trees located in the investigated catchments. Most of the trees have fallen in downslope direction. Sediment flux by windthrow event in 2013 calculated for each catchment was 1.0–4.6 × 10–3 m3 m–1.
Evaluation of the water storage capacity of soil management practices in basin scale
Authors: Lv Zhenyu , Qin Tianling , Nie Hanjiang , Wang Jianwei
Published: March 2020

Abstract: Soil management practices, such as Terrace (TE), Contour Ridge (CR), Conservation Tillage (CT), Green Manure (GM) and Straw Mulching (SM), have been widely applied all over the word, due to their positive effects on enhancing Water Storage Capacity (WSC for short) of soil and improving the effectiveness of local precipitation.  However, there are few studies focus on the assessment of WSC of soil management practices in basin scale. In this study, a series of empirical equations for evaluating the WSC of different types of soil management practices were established, based on the fundamental assumption of SCS-CN model, and the geometric parameters of TE and CR. Taking the Sihe River Basin as an example, the current construction area of soil management practices and the potential of the design scenarios were input into the equations, to calculate the existing and potential WSC of various soil management practices. The results show that the construction area of soil management practices in the basin was 679.73 km2 in 2015, and the WSC reached 61.85 Million m3. Thereinto, the WSC of the SM was the largest, which was 19.83 Million m3; that of the GM was the smallest, which was 2.08 Million m3. The total potential construction area of soil management practices in each design scenario was 1797.13 km2. Scenario I gave priority to the TE and the CR construction, the WSC of soil management practices in the basin was 174.84 Million m3, which was 182.68% higher than that of in 2015. The WSC of soil management practices in Scenario II who gave priority to the SM, CT and CR construction, was 171.84 Million m3, which was 177.84% higher than that of in 2015. This research further compared the water storage efficiency of various soil management practices and discussed the uncertainty of the equations. The results could provide some references for integrated soil water management.
A new approach to modelling soil structure dynamics and a preliminary application to structure recovery by earthworm bioturbation after heavy compaction
Authors: Meurer Katharina , Keller Thomas , Jarvis Nick
Published: March 2020

The pore structure of soil is known to be dynamics at time scales ranging from seconds (e.g. compaction) to seasons (e.g. root growth, macro-faunal activity) and even decades to centuries (e.g. changes in organic matter content). Nevertheless, soil physical and hydraulic functions are generally treated as static properties in most soil-crop models. Some models account for seasonal variations in soil properties (e.g. bulk density) due to tillage loosening and post-tillage consolidation or soil sealing, but none can account for longer-term changes in soil structure due to biological agents and processes. Here, we present a new concept for modelling soil structure evolution impacted by biological processes such as root growth and earthworm activity. In this preliminary test of the model, we compare simulations against field observations made at the Soil Structure Observatory (SSO) in Zürich, Switzerland, that was designed to provide information on soil structure recovery following a severe compaction event. In this simple application, we modelled changes in the pore size distribution in a bare soil treatment resulting from soil ingestion and egestion by earthworms and the loosening of compacted soil by casting at the soil surface. Following calibration, the model was able to reproduce the observed temporal development of total porosity, soil bulk density and pore size distribution during a four-year period following severe traffic compaction. The modelling approach presented here appears promising and could help support the development of cost-efficient strategies for sustainable soil management and the restoration of degraded soils.
Ensemble learning for dynamic modeling in flood control operation of multi-reservoir systems
Authors: Li Jieyu , Zhong Ping-an , Yang Minzhi , Lu Qingwen
Published: March 2020

Real-time joint operation of multi-reservoirs is significant to flood control and management of river basin. The high dimension of joint operation model and complex decision-making environment are still the main problems. This paper develops a general framework for reducing the complexity of flood control operation by identifying effective reservoirs. First, considering the factors which influence the reservoir flood control effect, a criteria system for identifying effective reservoirs is proposed. Then, different classification models based on ensemble learning are established. In real-time operation, the intelligent identification of effective reservoirs is carried out by sensing real-time information of the temporal and spatial distribution of storm floods and the variation of reservoir flood control capacity. On this basis, a hybrid equivalent operation model is established adaptively, which consists of a joint operation model of effective reservoirs and separate operation models of noneffective reservoirs. A case study of the flood control system located in the Huaihe River basin in China indicates that: (1) the ensemble learning classification models can identify effective reservoirs according to real-time information of flood and reservoirs dynamically. (2) the flood control effect of the hybrid equivalent operation model is similar to that of the joint operation model of all reservoirs. Obviously, in real-time flood control operation, the proposed method can realize the dynamic combination of two operation modes under different flood control situations, make the best use of reservoir storage capacity and reduce the complexity of flood control operation.

Key words: multi-reservoir system; real-time flood control operation; effective reservoir; ensemble learning; hybrid equivalent operation model
Seismic moment evolution during hydraulic stimulations in EGS projects
Authors: Dresen Georg , Bentz Stephan , Kwiatek Grzegorz , Martinez-Garzon Patricia , Bohnhoff Marco
Published: March 2020

Recent results from an EGS project in Finland suggest a possibly successful physics-based approach in controlling stimulation-induced seismicity in geothermal projects. We analyzed the temporal evolution of seismicity and the growth of maximum observed moment magnitudes for a range of past and present stimulation projects. Our results show that the majority of the stimulation campaigns investigated  reveal a clear linear relation between  injected fluid volume, hydraulic energy and cumulative seismic moments. For most projects studied, the observations are in good agreement with existing physical models that predict a relation between injected fluid volume and maximum seismic moment of induced events. This suggest that seismicity results from a stable, pressure-controlled rupture process at least for an extended injection period. Overall evolution of seismicity is independent of tectonic stress regime and is most likely governed by reservoir specific parameters, such as the preexisting structural inventory. In contrast, there are few stimulations that reveal unbound increase in seismic moment suggesting that for these cases evolution of seismicity is mainly controlled by stress field, the size of tectonic faults and fault connectivity. Transition between the two states may occur at any time during injection, or not at all. Monitoring and traffic-light systems used during stimulations need to account for the possibility of unstable rupture propagation from the very beginning of injection by observing the entire seismicity evolution in near-real-time and at high resolution for an immediate reaction in injection strategy.
Identification of hydraulic conductivity via normal-score ensemble smoother with multiple data assimilation (NS-MDA) by assimilating hydraulic head or concentration
Authors: A. Godoy Vanessa , Napa-García Gian Franco , Gómez-Hernández Jaime
Published: March 2020

In this study, we compare the capability of the normal-score ensemble smoother with multiple data assimilation (NS-MDA) to identify hydraulic conductivity when it assimilates or hydraulic heads or concentrations. The study is performed in a two-dimensional numerical single point contamination experiment of an aquifer vertical cross section. Reference hydraulic conductivity maps are generated using geostatistics, and the groundwater flow and transport are solved to produce reference state variable data (hydraulic head and concentration). Assimilating data for the inverse problems are sampled in time at a limited number of points from the reference aquifer response. Prior variogram function of hydraulic conductivity is assumed and equally-likely realizations are generated. Stochastic inverse modelling is run using the NS-MDA for the identification of hydraulic conductivity by considering two scenarios: 1) assimilating hydraulic heads only and 2) assimilating concentrations only. Besides the qualitative analysis of the identified hydraulic conductivities maps, the results are quantified by using the average absolute bias (AAB) that represents a measure of accuracy between the reference values and the inversely identified values according each scenarios. The updated parameters reproduce the reference aquifer ones quite well for the two scenarios investigated, with better results for the scenario 1, indicating that NS-MDA is an effective approach to identifying hydraulic conductivities.
Quantifying effects of laboratory-simulated diagenetic sediment lithification on frictional slip behavior
Authors: Ikari Matt , Hüpers Andre
Published: March 2020

On major plate-boundary fault zones, it is generally observed that large-magnitude earthquakes tend to nucleate within a discrete depth range in the crust known as the seismogenic zone.  This is generally explained by the contrast between frictionally stable, velocity strengthening sediments at shallow depths and lithified, velocity-weakening rocks at seismogenic (10’s of km) depth. Thus, it is hypothesized that diagenetic and low-grade metamorphic processes are responsible for the development of velocity-weakening frictional behavior in sediments that make up fault gouges.  Previous laboratory studies comparing the frictional properties of intact rocks and powdered versions of the same rocks generally support this hypothesis, however controlling lithification in the laboratory and systematically quantifying frictional behavior as a function of lithification and remains a challenge.

Here, we simulate the lithification process in the laboratory by using mixtures of halite and shale powders with halite-saturated brine, which we consolidate under 10 MPa normal stress and subsequently desiccate.  The desiccation allows precipitation of halite as cement, creating synthetic rocks.  We vary the proportion of salt to shale in our samples, which we use as a proxy for degree of lithification.  We measure the frictional properties of our lithified samples, and equivalent powdered versions of these samples, with velocity-step tests in the range 10-7 – 3x10-5 m/s.  We quantify lithification by two methods: (1) direct measurement of cohesion, and (2) measuring the porosity reduction of lithified samples compared to powders.  Using these measurements, we systematically investigate the relationship between lithification and frictional slip behavior.

We observe that powdered samples of every halite-shale proportion exhibits predominantly velocity-strengthening friction, whereas lithified samples exhibit a combination of velocity strengthening and significant velocity weakening when halite constitutes at least 30 wt% of the sample.  Larger velocity weakening generally coincides with friction coefficients of > 0.62, cohesion of > ~1 MPa, and porosity reduction of > ~50 vol%.  Although none of our lithified samples exhibit strictly velocity-weakening friction, this is consistent with the frictional behavior of pure halite under our experimental conditions.  Scanning electron microscopy images do not show any clear characteristics attributable to velocity-weakening, but did reveal that the shear surfaces for powders tends to exhibit small cracks not seen in the lithified sample shear surfaces.  These results suggest that lithification via cementation and porosity loss may facilitate slip instability, but that microstructural indicators are subtle.
Effects of mean state of climate models on the response to prescribed forcing: Sensitivity experiments with the SPEEDY general circulation model.
Authors: Di Carlo Emanuele , Ruggieri Paolo , Davini Paolo , Tibaldi Stefano , Corti Susanna
Published: March 2020

Understanding how the general circulation of the atmosphere is affected by global warming is one of the grand challenges in climate science. Climate models are a valuable tool to: i) identifying potential mechanism for changes in general circulation, ii) recognizing signals that can be related to external forcing and iii) produce projections for future scenarios. Despite the use of large ensemble of continuosly improving climate models, uncertainty for the extratropical circulation is still large. It is therefore important to understand processes driving the variability of the circulation in climate models and how these processes are affected by model bias. To characterize the effect of models bias on the response to a given forcing, several simulations were performed with the Simplified Parameterizations, primitivE - Equation DYnamics (SPEEDY), an intermediate complexity model developed by International Center for Theoretical Physics (ICTP). Four simulations are performed with a modified orography in order to obtain an atmospheric circulation at mid-latitudes characterized by different mean states and a control climate simulation carried in standard configuration is used as baseline. For each of these experiments, we have studied the climatic response to El Niño Southern Oscillation (ENSO) and to the Atlantic Multidecadal Variability (AMV). All the Sensitivity simulations were performed with a large ensemble (~100 members).
Results show that indeed the model response is non-negligibly influenced by its mean state and reveal geographic areas where the sensitivity is large. On the other hand, they also show large scale regions of the world where the atmospheric response to ENSO and AMV is unlikely to depend on the atmospheric mean state. We also found that the relationship between changes in the model mean state and the response to the forcing appears to be non linear. These results cam be used to interpret and understand multi-model spread in atmospheric response to aforementioned surface condition.
Development of basinal scale glacier mass balance model: an approach based on satellite observation and energy balance components
Authors: Patel Akansha , Goswami Ajanta , Meloth Thamban , Sharma Parmanand
Published: March 2020

The understanding of fresh water storage in the Himalayan region is essential for water resource management of the region. As glacier mass balance is a difference between the input and output water storage in a glacier over a period, glacier mass balance can be used as an indirect method to understand the storage. In the northwestern Himalaya, microscale meteorological stations are needed for mass balance estimation due to rugged terrain and complex topography of this region. However, there are only few meteorological stations available in that region. Therefore, in this study, we have developed a new model for glacier mass balance estimation at basinal scale. This model  includes the parameterization of energy balance components viz. albedo, longwave radiation, shortwave radiation, sensible heat, latent heat and heat flux at spatial and temporal scale using earth observation data. The modeling of air temperature is performed using the multi-regression analysis over the Chenab basin of the Indian Himalayas. Simulation is driven with the 16-days Landsat optical and thermal data from 2015 to 2018 that can be used for parameterization of the variable. This model is calibrated and validated with the field data of period 2015-2016. Further, the impact of climatic change and their influence on mass balance was also assessed to understand the future glacier health and mass changes. In contrast to previous temperature index based basin scale models, this model includes most of the energy balance components for better estimation of glacier mass balance. The model can also be used to estimate possible responses of the world’s glaciers to future climate change.
Causal links between drainage and forest growth response in boreal peatlands
Authors: Laurén Ari , Palviainen Marjo , Launiainen Samuli , Haahti Kersti , Leena Stenberg , Iñaki Urzainqui Aranburu , Mika Nieminen , Raija Laiho , Hannu Hökkä
Published: March 2020

Drainage is considered as an essential pre-requisite in management of peatland forests, and it generally increases stand growth. So far, the primary reasons behind the growth response are not fully understood. The explanation must be linked to direct or indirect growth factors, such as the supply of radiation, water, oxygen, and nutrients. Applying an empirical dataset consisting of 18 drained Scots pine (Pinus sylvestris L.) stands we constructed a causal network linking meteorology and climate variables, site and stand properties, organic matter decomposition, growth regulating factors and biomass growth. The network was analysed using piecewise structural equation models (SEM). The SEM analysis indicated that the stand growth response to drainage is mainly caused by increased supply of nutrients, especially potassium.  Based on this causal model, we constructed a dynamic simulation model called Peatland simulator SUSI. SUSI describes hydrology, stand growth, site carbon balance and stand nutrient supply and demand under different management schemes and under different site types and weather conditions. The simulator was tested against a large independent dataset consisting of 69 stands and 207 plots. SUSI was parameterized according to measured stand and site data and run using daily meteorological data. The simulation revealed that SUSI can predict five-year volume growth of the stand with good accuracy. Because SUSI links the drainage and the growth response in a process level, the model facilitates cost-benefit analyses of the drainage, helps in avoiding unnecessary drainage operations and their adverse environmental effects such as increased carbon emissions, peat subsidence and nutrient leaching. Thus, it can guide in the search for optional, more acceptable management schemes for drained forested peatlands.
Developing statistically driven eco-engineering designs from LiDAR and structure from motion surveys for marine artificial structures.
Authors: Lawrence Peter , Evans Ally , Brooks Paul , D'Urban Jackson Tim , Jenkins Stuart , Moore Pippa , McNally Ciaran , Natanzi Atteyeh , Davies Andy , Crowe Tasman
Published: March 2020

Coastal ecosystems are threatened by habitat loss and anthropogenic “smoothing” as hard engineering approaches to sea defence, such as sea-walls, rock armouring, and offshore reefs, become common place. These artificial structures use homogenous materials (e.g. concrete or quarried rock) and as a result, lack the surface heterogeneity of natural rocky shoreline known to play a key role in niche creation and higher species diversity. Despite significant investment and research into soft engineering and ecologically sensitive approaches to coastal development, there are still knowledge gaps, particularly in relation to how patterns that are observed in nature can be utilised to improve artificial shores.

Given the technical improvements and significant reductions in cost within the portable remote sensing field (structure from motion and laser scanning), we are now able to plug gaps in our understanding of how habitat heterogeneity can influence overall site diversity. These improvements represent an excellent opportunity to improve our understanding of the spatial scales and complexity of habitats that species occur within and ultimately improve the ecological design of engineered structures in areas experiencing “smoothing” and habitat loss.

In this talk, I will highlight how advances in remote sensing techniques can be applied to context-specific ecological problems, such as low diversity and loss of rare species within marine infrastructure. I will describe our approach to combining large-scale ecological, 3D geophysical and engineering research to design statistically-derived ecologically-inspired solutions to smooth artificial surfaces. We created experimental concrete enhancement units and deployed them at a number of coastal locations. I will present preliminary ecological results, provide a workflow of unit development and statistical approaches, and finally discuss how these advances may improve future ecological intervention and design options.
Econometric methods for empirical climate modelling
Authors: Hendry David , Castle Jennifer
Published: March 2020

To understand the evolution of climate time series, it is essential to take account of their non-stationary nature with both stochastic trends and distributional shifts: see e.g., . Using the novel approach of saturation estimation, explained in the presentation, we model observational records on evolving climate processes that also shift, undertaking empirical studies that are complementary to analyses based on laws of conservation of energy and physical process-based models. Despite saturation estimation creating more candidate variables than observations in the initial general formulation, our machine learning model selection algorithm has seen many successful applications, illustrated here by modelling the highly non-stationary data on UK CO2 emissions annually 1860-2018 with strong upward then downward trends, punctuated by large outliers from world wars, national coal strikes and stringent legislation.
Cenozoic plankton diversity dynamics and the impact of macroevolution on the marine carbon cycle.
Authors: Renaudie Johan , Lazarus David , Trubovitz Sarah , Özen Volkan , Rodrigues de Faria Gabrielle , Asatryan Gayane , Noble Paula
Published: March 2020

The marine biological carbon pump is one of the most important mechanism to extract carbon from the atmosphere and export it to the deep-sea and the sediments, and thus take it out from the cycle for millions of years. Today, marine planktonic diatoms are the main element of that pump; however at the beginning of the Cenozoic they were too rare and not diverse enough to have much geochemical significance. Calcareous nannofossils and foraminifera on the other hand were already important components of the carbonate carbon pump; however they also contribute to the alkalinity pump which on shorter timescales have an adverse effect on carbon sequestration. In addition, heterotrophic, amoeboid protists, in particular polycystine radiolarians, are also known to contribute significantly to the carbon export to the deep-sea due to their role in forming rapidly sinking particles of aggregated organic material. We present new diversity reconstructions using the Neptune database (NSB) and case studies focussed on the Late Neogene and the Eocene-Oligocene transition using newly collected full-fauna/flora diversity data. We will then show how the diversity and abundance history of these groups changed throughout the Cenozoic, what the role of climate/oceanographic changes and competition on their evolution was, and, in the end, what consequences their evolution had on the marine carbon cycle.
Monitoring the AMOC with GRACE/GRACE-FO - How far can we push the spatial resolution?
Authors: Kvas Andreas , Bentel Katrin , Behzadpour Saniya , Mayer-Gürr Torsten
Published: March 2020

The Atlantic Meridional Overturning Circulation (AMOC) plays a key role in our global climate system and is the main mechanism of northward heat transport for a warm climate in Northern Europe. Despite its crucial role, the AMOC is only scarcely observed, as observations covering all of the Atlantic Ocean for extended time are difficult to obtain. Satellite gravimetry offers key advantages compared to existing in-situ data sources by providing ocean bottom pressure anomalies with global coverage, thus allowing the monitoring of the AMOC in the complete Atlantic Ocean basin. The Gravity Recovery And Climate Experiment (GRACE) satellite mission and its successor GRACE Follow-On have provided a nearly continuous time series of monthly gravity field snapshots since 2002. In contrast to in-situ measurements of ocean bottom pressure, which suffer from inherent drift problems, the temporally stable satellite observations allow investigations of the long-term AMOC behavior.

Preliminary studies have shown that monitoring changes in the AMOC is possible with observations from GRACE and GRACE Follow-On, however, it is pushing the limits of the current data products in resolution and accuracy. To fully exploit the information content in the gravity observations, we implemented a processing chain tailored to the Atlantic Ocean basin. Compared to existing approaches, we perform signal separation, that is the reduction of continental hydrology and glacial isostatic adjustment, on the satellite sensor data level. This has the key advantage that all background models are treated the same, thus are spectrally coherent. Geocenter motion is estimated in combination with an ocean model, as is the state-of-the-art for GRACE/GRACE-FO processing. Ocean bottom pressure anomalies are then computed through least squares collocation, which allows for point distributions tailored to the bathymetry. This consistently processed data record is then used to gauge the performance of satellite gravimetry for monitoring the AMOC.
Diverging impacts of extreme summers on European C-cycling from different regional and seasonal compensation effects
Authors: Bastos Ana ,   ICOS drought task-force
Published: March 2020

In the past 20 years, three major drought-heat events (DH) occurred in Europe: DH2003 in western Europe, DH2010 in western Russia and, more recently, DH2018 in central Europe and Scandinavia. These events were all preceded by warm and dry springs that contributed to the summer heatwaves and are comparable in magnitude. However, they varied in their geographical distribution and biomes affected, so they can be used as “natural experiments” to improve our understanding of ecosystems’ responses to climate conditions that will become more frequent in the coming decades.

We analyze anomalies in carbon, water and energy fluxes from 11 Dynamic Global Vegetation Models (DGVMs) forced with higher spatial and temporal resolution climate forcing than conventional global simulations, as well as an ensemble of estimates from the data driven FLUXCOM product. All three DH events were associated with decreases in summer gross primary productivity (GPP), but the relative strength at continental scale differed between events. The DGVMs and FLUXCOM show event-dependent agreement in estimated gross and net CO2 fluxes. We also find a progressively stronger negative effect of heat anomalies on ecosystem productivity between each event, which might indicate a transition towards more water-limited regime at continental scale by progressively warmer background conditions.

The different impacts of the three DH events on continental-scale summer GPP are in part related to regional asymmetries in climate anomalies that act to amplify or offset the impact of DH events on ecosystem productivity, depending on their geographical distribution and biomes affected. At the annual scale, both FLUXCOM and DGVMs indicate close to neutral or above-average CO2 uptake in the three years, when removing the long-term trend. This is in part because increased productivity in spring in response to warming and reduced respiration in autumn compensated for less photosynthetic uptake in summer.

All models show good skill in simulating the soil-moisture anomalies during DH events, but in general DGVMs show poor skill in simulating the increased sensitivity of GPP to soil-moisture and decreased sensitivity to temperature during extreme events. The relative skill of individual DGVMs in simulating these changes of GPP sensitivity to climate during extreme events explains the mismatch in simulated productivity anomalies with FLUXCOM estimates.
Counterfactual hydrological pesticide transport modelling: Can we detect long-term in-stream pesticide trends due to mitigation?
Authors: Chow Reynold , Sceidegger Ruth , Doppler Tobias , Dietzel Anne , Fenicia Fabrizio , Stamm Christian
Published: March 2020

In many countries, agroecological schemes are implemented in order to reduce water quality impairment from agricultural pesticide use. However, demonstrating the success or failure of these schemes is challenging because other influencing factors can confound their effects. For instance, in-stream pesticide concentrations have been found to vary greatly due to the interannual variability in weather conditions (e.g., the timing, intensity, and duration of precipitation events) and pesticide application practices (e.g., the variability in timing and spatial application of differing pesticides that have different chemical properties).

Our current work aims to investigate the necessary conditions to detect significant trends in pesticide concentrations in the context of the Swiss National Action Plan (NAP), which aims to halve the pesticide risk from agricultural activities within Swiss river networks by 2027. We use a modelling approach to explore possibilities and limitations of the existing monitoring scheme for separating long-term effects of the NAP from interannual variability due to weather conditions. For that purpose, we use an existing model for simulating pesticide transport at the catchment scale. After calibration, we simulated 10 years of herbicide concentrations with and without (i.e., the counterfactual) an assumed 50% reduction of the pesticide applied and evaluated the resulting concentration levels.

Our results indicate that the interannual variability due to weather conditions can exceed even a 50% change in pesticide application. This implies that the concentration levels themselves are insufficient to demonstrate the effectiveness of the NAP within a reasonable time horizon of a decade. This is because the lowering of in-stream pesticide concentrations may be due to the timing and intensity of precipitation relative to the application of pesticides and not from the effectiveness of pesticide mitigation measures. Therefore, we explore ways to account for the weather effects on the pesticide concentration levels. Furthermore, we found that comparing the pesticide concentrations in years that have both above average precipitation during pesticide application periods and contain precipitation events that occur shortly after pesticide application can lead to more robust statements about the effectiveness of the mitigation measures. Preliminary double mass analyses of cumulative rainfall during the application period versus cumulative maximum concentrations suggest that significant trends can be identified with 11 years of data (6 years before NAP implementation and 5 years into it). We are currently exploring how sensitive our results are to pesticide properties, such as sorption and degradation half-lives.
The LONSCAPE instrument, a Light Optical Nephelometer Sizer and Counter for Aerosols in Planetary Environments
Authors: Renard Jean-Baptiste , Mousis Olivier , Berthet Gwenaël , Geffrin Jean-Michel , Levasseur-Regourd Anny-Chantal , Rannou Pascal , Verdier Nicolas
Published: March 2020

            Liquid and solid particles are present in the atmosphere of many Solar System objects. Measuring aerosol properties can provide major constraints about both atmospheric composition and dynamics. While some bulk aerosol properties can be estimated using remote measurements, the size distributions and the typologies of the aerosols, which are related to their formation process, their origin and their evolution, are often poorly known. We propose a new concept of optical instrument dedicated to in situ measurements of aerosols as part of the science payload of an atmospheric entry probe or of a surface module. It relies the Earth atmospheric light aerosol counter LOAC used since 2013 under various types of balloons. This instrument measures the aerosol concentrations in 19 size classes between 0.2 and 50 micrometers, and estimates their typology

            The LONSCAPE (Light Optical Nephelometer Counter Sizer and Counter for Aerosols in Planetary Environments) concept combines counter measurements and nephelometric measurements at several phase angles, particle by particle, to retrieve for all size classes the concentrations and the scattering functions. This approach is the novelty of the instrument concept. The scattering functions can be compared to results of theoretical calculations but also to laboratory databases obtained for levitating particles and from the microwave analogy technics, to retrieve the refractive indices of the liquid and solid particles to better identify their nature and origin. Up to 10 angles measurements for the scattering function and one angle measurement for the counting provide an optimal configuration to distinguish between liquid, icy and possibly solid particles in the Uranus or Neptune atmosphere. Such an instrument must be able to detect up to tens of particles greater than 0.1 micrometer within 1 cm3.

            For ice giants, the instrument must work for pressures up to 10 bars. No pumping system should be needed since the aerosols will be injected in the optical chamber by an inlet parallel to the descent motion of the probe under parachutes. Considering the relative velocity between the atmosphere and the probe, the electronics must be able to detect particles crossing the laser beam up to several tens of m/s, which can be done by “conventional” electronics. Preliminary studies show that the instrument could have a total mass of about 2 kg and an electric consumption of about 2W.
Analysis of a severe geomagnetic storm on August 26, 2018 and the related effects on the GRACE-FO mission
Authors: Krauss Sandro , Temmer Manuela , Behzadpour Saniya , Lhotka Christoph
Published: March 2020

On August 20, 2018 a complex interplanetary coronal mass ejections (ICME) occurred on the Sun, which subsequently triggered an unexpected large geomagnetic storm on August 25. We present a detailed analysis of the ICME eruption and explore the occurred perturbation of the neutral mass density in the upper Earth's atmosphere. The analysis is based on accelerometer observations from the satellite mission GRACE Follow-On as well as interplanetary magnetic field measurements by the DSCOVR and ACE spacecraft. Through the evaluation of solar observations by the SECCHI instrument on-board of the STEREO-A satellite in form of white-light, the early evolution of the ICME can be aptly illustrated. Furthermore, due to the heating and the subsequent expansion of the thermosphere also the drag force acting on the spacecraft is enhanced. This leads to an additional storm induced orbit decay, which we calculate by means of variations in the semi-major axis. The findings are compared with predictions from our preliminary thermospheric forecasting tool, which is based on the study by Krauss et al. 2018.
Towards quantification of the subpolar North Atlantic circulation
Authors: Nowitzki Hannah , Rhein Monika , Roessler Achim , Mertens Christian , Kieke Dagmar
Published: March 2020

It is well known that ocean circulation impacts climate and weather patterns. One of the key regions influencing Europe is the subpolar North Atlantic, Here warm and saline water from the subtropics is imported with the North Atlantic Current (NAC), meeting cold and fresh water masses intruding from the north. To quantify the strength of the NAC, Uni Bremen and BSH Hamburg started in 2006 to continuously deploy instruments to quantify the volume transport. In a first step, the crossing of the NAC from the western into the eastern basin at the western flank oft the Midatalantic Ridge was covered, followed by boundary current moorings and PIES at a nominally zonal section at 47N in the western basin. In the last years, PIES and moorings have also been deployed in the eastern basin. Here we report about the recent results, focusing on the eastern basin.
Microseismic and Induced Seismicity Monitoring and Tomography of the Changning-Zhaotong shale gas play in China using dense nodal arrays
Authors: Yang Wen , Li Junlun , Tan Yuyang , Li Yaxing , Qian Jiawei , Zhang Haijiang
Published: March 2020

With the development of shale gas in the Changning-Zhaotong play in the southern Sichuan basin of China, which is the largest shale gas prospect in China, the frequency and magnitude of earthquakes in this region have increased significantly in recent years. For example, a M5.7 earthquake occurred on December 16, 2018, and a M5.3 earthquake on January 6, 2019 in addition to many M4.0+ earthquakes in this area. Some studies argue the large magnitude earthquakes are triggered by hydraulic fracturing in for the local shale gas development, which commenced in 2011. The frequency of the earthquake occurrence has been on steady increase in the past few years that local residents often reported felt quakes. To further understand the correlation between the shale gas development and local seismic activity, we conducted a two-phase dense array seismic monitoring with about 200 Zland 3C and SmartSolo 3C 5 Hz seismic nodes, from late February to early May, 2019 for a period of 70 days. The survey consists of roughly 340 deployments at 240 sites, with an average interstation distance of 1.5 km, covering 500 km2 in total. We have processed seismic records from late February to early April, 2019 (phase I), and picked some 600,000 P- and S-wave arrival times from 4385 detected local earthquakes. The earthquake hypocenters and the subsurface velocity structure of the Changning-Zhaotong area are inverted for using the double-difference tomography method. The relocation results show that the majority of hypocenters were located at depths ranging from 1.0km to 4.0km, in the proximity of the horizontal hydraulic fracturing wells. The tomographic results (< 3 km) correlate well with the known surface geological units, and most earthquakes occurred along the velocity discontinuities, likely characterizing a large hidden fault which, interestingly, is where the January 2019 M5.3 occurred. Our study is very important for understanding the seismic potentials in this area, and should provide useful information for the shale gas development in this region and other areas in China with similar geological, tectonic and stress conditions.
3D structure beneath Iranian plateau and Zagros using adjoint tomography
Authors: Komeazi Abolfazl , Yaminifard Farzam , Kaviani Ayoub , Rümpker Georg , Tatar Mohammad , Liu Qinya , Wang Kai
Published: March 2020

We perform an adjoint waveform tomography using a combined data set consisting of regional earthquake waveforms and Rayleigh wave ambient-noise Green's function to construct a new 3-D wave velocity model of the crust and uppermost mantle beneath the Iranian plateau. The earthquake waveforms come from 250 regional events with magnitudes of 4.5-6.5 recorded by 136 broadband seismic stations. The EGFs are derived from cross correlations of more than three years of continuous seismic noise. The inversion starts with an initial model derived from the global Crust1 model locally modified using information from previous studies. Adjoint tomography refines the initial model by iteratively minimizing the frequency-dependent travel-time misfits between real and synthetic earthquake data and EGFs and synthetic Green’s functions measured in different period bands. Our new model covers the known tectonic units such as the Central Iranian Block, Zagros fold-and-thrust belt, Sanandaj-Sirjan metamorphic zone and Urumieh-Dokhtar magmatic arc. Overall, the adjoint tomography provides images with more real resolutions and amplitudes due to the finite-frequency consideration. Using the numerical spectral-element solver in adjoint tomography provides accurate structural sensitivity kernels, which help generate more robust images rather than those generated by ray-theory tomography. Our study also demonstrates improvement of lateral resolution and depth sensitivity using combined data set instead of only earthquake data.
The International Centre for Global Earth Models (ICGEM)
Authors: Förste Christoph , Ince Elmas Sinem , Reissland Sven , Elger Kirsten , Flechtner Frank , Barthelmes Franz
Published: March 2020

The more than 15-year-old ICGEM is one of the five services coordinated by the International Gravity Field Service (IGFS) of the International Association of Geodesy (IAG). It is hosted by GFZ German Research Centre for Geosciences in Potsdam, Germany. The aim of the ICGEM service is to provide the scientific community with a state-of-the-art archive of static and time variable global gravity field models of the Earth in a standardized format with a possibility to assign DOI number. Furthermore, ICGEM contains an interactive calculation and visualization service of gravity field functionals. Development and maintenance of such a unique platform is crucial for the scientific community in geodesy, geophysics, oceanography and climatology and has a positive impact in governmental institutions and industrial practice. This poster covers the maintenance, recently established new features and future plans of the ICGEM Service. New features include the calculation of gravity field functionals at a list of user-defined distributed points and new topographic gravity field models, whereas the future plans aim to meet the needs of the scientific community. As an add-on, ICGEM provides also access to the gravity field models of some other celestial bodies (Mars, Venus, and Earth’s moon).