bluuebunny/crossref_metadata_2025 huggingface dataset:
A globally complete, spatially and temporally resolved estimate of glacier mass change: 2000 to 2019
Authors: Hugonnet Romain , McNabb Robert , Berthier Etienne , Menounos Brian , Nuth Christopher , Girod Luc , Farinotti Daniel , Huss Matthias , Dussaillant Ines , Brun Fanny , Kääb Andreas
Published: March 2020

The world’s glaciers distinct from the Greenland and Antarctic ice sheets are shrinking rapidly, altering regional hydrology and raising global sea level. Yet, due to the scarcity of globally consistent observations, their recent evolution is only known as a heterogeneous temporal and geographic patchwork and future projections are thus not optimally constrained.

Here, we present the first globally complete, consistent and resolved estimate of glacier mass change derived from more than half a million digital elevation models (DEMs) generated or extracted from multiple satellite archives including ASTER, ArcticDEM and REMA. Combining state-of-the-art numerical photogrammetry and novel statistical approaches, we reconstruct two decades of glacier surface elevation change at an unprecedented spatial and temporal resolution. We validate our results by comparing them to independent, high-precision elevation measurements from the ICESat and IceBridge campaigns, as well as to very high resolution DEM differences from LiDAR, Pléiades, and SPOT-6. The elevation time series are integrated to volume changes for every single glacier on Earth and, by assuming an average density, aggregated to regional and global mass changes. We compare our revised glacier mass changes to earlier estimates derived from altimetry, gravimetry, geodetic and field data. As an illustration, our integrated geodetic mass loss over all Icelandic glaciers yields -8.3 +- 1.1 Gt yr-1 over the period 2002-2016 in agreement with a recent gravimetry estimate of -8.3 +- 1.8 Gt yr-1 (Wouters et al., 2019), known to perform well in this region. Both estimates are more negative than -5.7 +- 1.2 Gt yr-1, compiled from glaciological observations and geodetic data (Zemp et al., 2019).

Our global estimate of glacier mass change constitutes a new benchmark dataset that will help to: (i) assess present-day and future climate change impacts on glaciers; (ii) close the sea-level rise budget; (iii) assess the threat on water resources and (iv) facilitate research on natural hazards related to glaciers. Our results specifically provide a strong observational basis that holds a great potential to further our understanding of the multi-scale morphologic and climatic drivers of glacier mass change, essential to improve physically-based glaciological modelling and calibrate future projections.
Effect of serpentinization on carbon speciation: an experiment with formic acid
Authors: Barbier Samuel , Andreani Muriel , Gaucher Eric C. , Daniel Isabelle , Ménez Bénédicte , Grossi Vincent , Antheaume Ingrid , Albalat Emmanuelle , Fellah Clémentine , Cardon Hervé , Jame Patrick , Saupin Xavier , Bonjour Erik
Published: March 2020

One of the principal theories about the origin of life is based on the abiotic reduction of carbon oxides to various organic molecules in hydrothermal systems. This synthesis is most favored in ultramafic environments undergoing hydrothermal alteration where the serpentinization reaction efficiently produces H2. Nevertheless, decades of hydrothermal experiments have hardly succeeded in producing abundant organic volatiles such as CH4 and short-chain hydrocarbons. On another hand, natural observations have shown the occurrence of other abiotic compounds such as organic acids in fluids and carbonaceous matter (CM) within serpentinized rocks. But organic acids as carbon source and CM as product have not been investigated so far in experiments reproducing hydrothermal peridotite alteration. Here, we explored the effect of formic acid (HCOOH) on the serpentinization reaction and possible feedback effects on carbon speciation in both fluid and solid. We performed reactions at 300°C and 250 bar using peridotite powder (<40 microns) in the presence of  0.1 M formic acid. A temperature of 300°C has been shown to be optimal for olivine serpentinization, while formic acid should partly decomposed into H2, CO, and CO2. After 4 months, H2, CO, CO2, CH4 and short-chain alkanes (mainly ethane) were measured in the fluid, and the powder was completely indurated. The solidified powder displayed a black and white layering perpendicular to fluid diffusion. Its analysis showed the advancement of the serpentinization reaction, and the incorporation of carbon compounds into the solid phase. XRD analysis indicated 70% of serpentinization. SEM-EDX observations showed peculiar texture with large and localized euhedral magnetite grains alternating with larger magnetite grains mixed with C-enriched areas of long chrysotile fibers. FT-IR measurement attested of the widespread formation of carbonaceous material in the solid. Liquid analyses are under progress. Those first results suggest that serpentine formation not only provides additional H2 to the system, but also mineral surfaces that could play a role in the precipitation of carbonaceous material and carbon speciation in natural systems. The nature and formation mechanisms of this latter remain to be addressed but this opens new paths for abiotic organic synthesis under hydrothermal conditions. In addition to their implications as an abiotic carbon source for deep hydrocarbon degraders ecosystems, it could have important implications for the total carbon cycle.
The fate and impact of internal waves induced by strong shear current over a marginal ridge
Authors: Zhang Peiwen , Min Wenjia
Published: March 2020

Internal waves with strong vertical mixing could be induced by stratified flow over seafloor obstacles. Noted that the stratified flow not only trigger internal tides, but also highly nonlinear internal waves like internal lee waves and internal solitary waves over steep topography features, and the highly nonlinear internal waves are suggested to play an important role in turbulence and mixing. As a typical seafloor obstacle, ridge could significantly modified the propagation of internal tide, internal lee wave and internal solitary wave. We focused on I-Lan ridge with asymmetrical topography feature in Kuroshio region. To the north of the I-Lan ridge, the depth of Philippine basin reached 4000m compared with the depth of 1500m in the south of the ridge, leading to different characteristics of internal wave energy field and ecological characteristics between two sides. Based on numerical simulations, we revealed the generation and propagation of internal waves over marginal ridge, causing by the shear current induced by Kuroshio. We also discussed the turbulence kinetic energy contributed by linear internal waves and nonlinear internal waves, providing the strength of vertical turbulent mixing around the I-Lan ridge. Then we demonstrated the characteristics of complex internal wave field in the strong background shear current over I-Lan ridge.
Real-time monitoring and early warning of transmission tower foundations under landslide disasters
Authors: Huang ChenChen , Yin Kunlong , Liang Xin
Published: March 2020

The Ultra High Voltage (UHV) power grids in China are playing an important role of large-region power supply, contain long-distance interconnected channels that have to span a variety of different geomorphic units. However, geological disasters around transmission lines can threaten the reliability of UHV system. Landslides, one of the most common geological disasters in China, can affect the stability of transmission towers by shearing their foundations or involving them to move overall. Once a power tower is destroyed catastrophically, it may lead to widespread power outages, which can result in serious social adverse effects and huge economic losses. This paper presents a multi-technology early warning system for monitoring landslide deformation and observing transmission tower stability. In this system, there are three categories of monitoring information, including landslide displacement, external hydrological conditions and the stability of tower, integrated that are critical to predicting slope stability. To implement this system, a variety of techniques are employed. Firstly, advanced aviation technologies, such as Interferometric Synthetic Aperture Rader (InSAR) and unmanned aerial vehicle (UAV) are used to monitor the overall deformation of the landslide. Absolute surface displacement, subsurface displacement and relative displacement of cracks are recorded by the Global Navigation Satellite System (GNSS), deep inclinometer cooperating with optical fiber sensors and surface crack meters respectively. Second, the two main factors influencing landslide deformation, rainfall and underground water level, are observed by rain gauge and pressure gauge respectively. Third, in order to evaluate the stability of tower, earth pressure sensors are installed on the four foots of the tower foundation and pylon inclinometer is installed on the tower body. This system has been applied to the Doupozi landslide, where a tower of 500KV Shen-wan UHV line is located. Compared with that of traditional methods, the recording process of the multi-technology system is automatic and continuous, which can save human resource cost. Besides, the integrated monitoring data obtained from this system can be used to analyze the interaction between geological disasters and power towers. The multi-technology early warning system is also suitable for risk mitigation of transmission lines, oil and gas pipelines, highways, railways and other linear projects in mountainous areas.
Our Coastal Futures: pathways to sustainable development
Authors: Weiss Robert , Cummins Valerie , Kelsey Heath , Ferse Sebastian , Scheffers Anja , Forbes Donald , Glavovic Bruce
Published: March 2020

The world’s sustainability opportunities and national security challenges converge in the coastal zone. Hundreds of millions of people face increasing pressure from population growth, over exploitation of natural resources, and escalating disaster-risk, as the climate changes and sea levels rise. Global Environmental Assessments have been a tool for international policy makers, and a particular favorite of UN bodies and can add value to national efforts. The first World Ocean Assessment concluded that without an integrated, coordinated, proactive, cross-sectoral and science-based approach to coastal and marine management, the resilience of coastal and marine ecosystems, and their ability to provide vital services, will continue to be reduced. The second World Ocean Assessment is currently under development and will build on the baselines established in the first assessment, by identifying key trends and relevance to the SDGs. However, global assessment processes, may be curtailed by bureaucracy and diplomatic legitimacy, whilst struggling to engage relevant stakeholders and institutions. As a result, there is a need to complement these important top-down, global environmental assessments, with more agile assessment processes, as well as facilitating bottom-up capacity building with stakeholders involved in coastal zone management. This requirement is articulated in the text of the “Our Coastal Futures Strategy”, launched in 2018 by Future Earth Coasts (FEC). We, the FEC program, observe that the assessment process is often not as inclusive as it could be, for example, by separating sectors, such as science and technology, policy, and public engagement throughout the assessment, with inter-sector connections usually made at a later stage in the process. Therefore, we stress the importance of co-designed synthesis that can reach into new knowledge, including tacit knowledge of diverse stakeholders, from the outset. Our Rapid Ocean Assessment Methodology Workshop will address this important issue and achieve a better understanding of the complexities and non-linearities of coastal-zone processes and interactions; fundamental to informing meaningful assessments and identifying potential sustainability pathways.
Validation of GEMS L2 products using ground-based remote sensing data including PANDORA measurements
Authors: Bae KangHo , Song Chang-Keun , Park Sang-Seo , Kim Sang-Woo , Kim Jhoon , Lee Chang-Seok , Yoon Jong-Min , Chang Limseok
Published: March 2020

Launch of the Geostationary Environmental Monitoring Spectrometer (GEMS) is scheduled in early 2020 to support public service and science related to air quality and climate by providing diurnal variation of concentrations of trace gases and aerosols with high spatial/temporal resolution over Asian region. We will introduce GEMS validation methodology in parallel with a strategy for integration of existed independent measurements like as low-orbit satellite, ground-based remote sensing, and ambient surface observation data. As collections of nearly real-time and quality-assured data from existing ground-based networks are still in great needs for GEMS validation, efforts to expand observational infra-structure have been going on. Currently, two PANDORA instruments started to be in operation at Seoul and Ulsan in Korea, and PANDORA Asian Network initiated by NIER, Korea will be expanded into South East Asian region beyond Korea, China and Japan in addition. In this study, we especially try to validate the initial L2 product of GEMS gathered during IOT period by utilizing PANDORA data and other ground remote sensing data as well so that availability and feasibility of those ground observations could be assessed for GEMS validation.

 

Keywords: GEMS validation, ground-based remote sensing data, PANDORA
Blockage and sheltering effects of vegetation in turbulent flow
Authors: Wang Wei-Jie
Published: March 2020

The interaction between aquatic vegetation and water flow is investigated here focusing on the drag coefficient. Compared with the standard drag coefficient of isolated cylinder, the phenomena of "blockage effect" and "sheltering effect" are put forward for vegetation clusters with different vegetation densities and Reynolds numbers. "Blockage effect" occurs when the drag coefficient of vegetation cluster is greater than the standard drag coefficient of isolated cylinder. The reason is that viscous boundary layer attached to the surface of vegetation items, resulting that the effective flowing width between adjacent vegetation items is less than the spacing of them, which brings a greater flow resistance and the drag coefficient of vegetation array is greater than the standard drag coefficient. On the other trend, "sheltering effect" is formed when the drag coefficient of vegetation array is less than the standard drag coefficient. This effect usually occurs for flow with large Reynolds numbers. In this case, Karman vortex streets forms and these vortexes are filled in the vegetation interval, thus causing the drag coefficient of vegetation cluster to be less than the standard drag coefficient of isolated cylinder.
Assessing grouting mix thermo-physical properties for shallow geothermal systems
Authors: Garbin Enrico , Mascarin Ludovico , Di Sipio Eloisa , Artioli Gilberto , Urchueguía Javier , Mendrinos Dimitris , Bertermann David , Vercruysse Jacques , Pasquali Riccardo , Bernardi Adriana , Galgaro Antonio
Published: March 2020

The main goal of the EU funded GEO4CIVHIC project is the development of more efficient and low-cost geothermal systems for conditioning retrofitting civil and historical buildings. In this framework, the identification of the most appropriate grout for different heat exchangers is a key factor for improving the overall efficiency of shallow geothermal systems. Therefore, a dedicated investigation was focused on the selection and optimization of the thermo-physical properties of grouting products to be used for:

the sealing of the coaxial geothermal probes’ head characterized by different installation depths

the sealing of the coaxial geothermal heat exchangers by filling the annular gap between the outer casing and the geological formations exposed to the wellbore

 

In both cases, the thermo-physical behavior of conventional and thermal enhanced grouts has been determined in laboratory for the purpose of manufacturing satisfactory cement based grouts with a real in-situ application. On the one hand, it is important to identify the grout mixtures having a suitable in situ workability, that is those satisfying specific conditions in terms of injection pressure, grout flowability, open working time and costs. On the other, it is essential to determine those providing optimal heat transfer between the probe and the surrounding ground.

Several lab experiments were performed on commercially available and enhanced selected mixtures to define (i) the workability and the flowability of the grouts; (ii) fundamental properties like mechanical strength, thermal conductivity and permeability of the hardened materials; (iii) leakage and calorimetric behavior, useful to identify sealing properties and grout setting times; (iv) viscosity and (v) density of the cement based mixture able to give information about the grout rate of descent and thus its pumpability under pressure.

Lastly, according to the lab results, few grout mixtures were selected as the best choice to be applied in situ for sealing the head of the geothermal probes’ and the annular space between the outer casing and the geological formations exposed to the wellbore. Therefore, this work attempts to address a knowledge gap of the thermo-physical properties, behavior and characterization of grouts for borehole heat exchangers (BHE), that are little studied and known.

 
Long-term hydrological and hydrodynamic modeling of a complex Ramsar site using HEC-RAS 5.0.7 2D – The Taim Wetland
Authors: Peruzzo Bule Bibiana , Tassi Rutinéia , Allasia Piccilli Daniel Gustavo
Published: March 2020

Wetlands are ecosystems recognized as one of the most valuable natural resources in the world. Although this importance, several wetlands around the world have lost areas due to anthropic threats. One example of a wetland with international importance is the Taim Wetland. This Ramsar Site number 2298, is a fresh-water wetland with 330 km2 located in the Southern part of Brazil, close to the border with Uruguay. The primary threat to this wetland is related to water demand conflicts on its watershed. Extensive rice fields occur around Taim Wetland and large yearly volumes of water from its main tributary Mangueira Lake are withdrawn, leading to changes in the hydrodynamics within the wetland. Thus, by one side, there is the regional economic dependence of rice cultivation and, on the other hand, conditions related to water availability are vital for maintaining the ecosystem as a whole. Different human-made infrastructures also impact local hydrodynamics as road, gates, fauna tunnels, natural effects as backwater and climate factors. Due to its importance, the Taim Wetland has been the object of different studies aiming to evaluate strategies for an integrated water management policy, allowing it to reach both environmental and economic benefits. The local complexity leads to the need for applying hydrological-hydrodynamic models able to represent the behavior accurately. Paz, 2003 and Villanueva, 1997 already applied hydrological and 2D-hydrodynamic modeling in the area; however, in the light of information available at that time and computational constraints, these studies needed to adopt several simplifications. In this study, the 2D HEC-RAS 5.0.7 was used to represent the system based on new terrain information obtained from the combination of different sources such as satellite, drone images and local measurement allowing the acquisition of information such as flooding areas, velocities, and flow patterns. New insights of local features such as internal channels, lakes, dunes, road and vegetation such as emergent macrophytes permitted new understandings of hydrodynamics. Nevertheless, hydraulic structures as a set of gates and fauna tunnels were also included in the representation, allowing the analysis of different operational scenarios during the modeling. These results also provide critical information for the environmental evaluation of habitats and points towards better management policies.
Extreme concentrations of fine particulate matter and black carbon during commute
Authors: S. Brand Veronika , Nogueira Thiago , Kumar Prashant , Andrade Maria de Fatima
Published: March 2020

Commuters are vulnerable to traffic air pollutants, especially to fine particulate matter (PM2.5) and black carbon (BC) because of their proximity to on-road vehicles. Both pollutants have been extensively associated to adverse health effects (i.e., stroke, diabetes, cardiovascular and respiratory diseases, and cancer). Therefore, this work aims to investigate the extreme concentrations of PM2.5 and BC occurrence in commuters in the megacity of São Paulo, Brazil. We carried out a field campaign measuring the commuter exposure to PM2.5 and BC concentrations inside buses, cars and undergrounds in São Paulo during morning and evening peak-hours. We fitted an Extreme Value Distribution to the collected data to investigate the behavior of the extreme values in the different transport modes and periods of the day. The results suggest that higher concentrations of PM2.5 and BC occur more frequently inside buses, followed by cars and undergrounds. Extreme concentrations for both pollutants are more likely to happen during morning peak-hours when compared to evening peak-hours. Our findings add further evidence that the transport mode and period of the day aﬀect substantially the PM2.5 and BC exposure in commuters. Furthermore, the results are quite useful for supporting urban policies that consider the improvement of the efficiency of air filtering systems inside public transport and private cars.
Global contribution of climate variability and trends to maize yield change in observations and crop models during 1980-2010
Authors: Yin Xiaomeng , Leng Guoyong
Published: March 2020

Understanding historical crop yield response to climate change is critical for projecting future climate change impacts on yields. Previous assessments rely on statistical or process-based crop models, but each has its own strength and weakness. A comprehensive comparison of climate impacts on yield between the two approaches allows for evaluation of the uncertainties in future yield projections. Here we assess the impacts of historical climate change on global maize yield for the period 1980-2010 using both statistical and process-based models, with a focus on comparing the performances between the two approaches. To allow for reasonable comparability, we develop an emulator which shares the same structure with the statistical model to mimic the behaviors of process-based models. Results show that the simulated maize yields in most of the top 10 producing countries are overestimated, when compared against FAO observations. Overall, GEPIC, EPIC-IIASA and EPIC-Boku show better performance than other models in reproducing the observed yield variations at the global scale. Climate variability explains 42.00% of yield variations in observation-based statistical model, while large discrepancy is found in crop models. Regionally, climate variability is associated with 55.0% and 52.20% of yield variations in Argentina and USA, respectively. Further analysis based on process-based model emulator shows that climate change has led to a yield loss by 1.51%-3.80% during the period 1980-1990, consistent with the estimations using the observation-based statistical model. As for the period 1991-2000, however, the observed yield loss induced by climate change is only captured by GEPIC and pDSSAT. In contrast to the observed positive climate impact for the period 2001-2010, CLM-Crop, EPIC-IIASA, GEPIC, pAPSIM, pDSSAT and PEGASUS simulated negative climate effects. The results point to the discrepancy between process-based and statistical crop models in simulating climate change impacts on maize yield, which depends on not only the regions, but also the specific time period. We suggest that more targeted efforts are required for constraining the uncertainties of both statistical and process-based crop models for future yield predictions. 
Evaluation of the enzymatic activity and diversity of soil microorganism in Andean temperate forests degradation gradient
Authors: Atenas Alejandro , Aburto Felipe , Hasbun Rodrigo , Merino Carolina
Published: March 2020

Soil microorganism are an essential component of forest ecosystem. Microbes and plant release enzymes that catalyse reactions needed to decomposed soil organic matter and crucial to release nutrient in available forms. Therefore, soil enzymes are relevant indicators of microbial activity and nutrient cycling in forest ecosystems. Anthropic disturbances in natural forest, such as logging and exotic livestock, modify the structure and composition of forest thereby altering the structure and activities of soil microbial communities.

Here we determine the effect of these disturbances on the enzymatic activity (Dehydrogenase-DHA; Phosphatase Acid-AP; Ureasa-UA) and the microbial diversity using a forest degradation gradient of native temperate forest dominated by Nothofagus dombeyi, Nothofagus obliqua and Nothofagus alpina. In addition we quantify C:N:P nutrient reservoirs, stoichiometry and available pools. Preliminary results suggest a higher activity of the DHA enzyme in degraded forest dominated by N. obliqua. AP and UA showed no relationship with the phosphorus and total nitrogen reservoirs. Forest degradation modify microbial communities, C:N:P stoichiometry, total and available nutrient pools, where the biggest pool of total C and N was registered on low degraded condition and decrease as degradation condition increase from medium to high degraded forest (74.44%; 65.35%; 48.05% for total C and 3.71; 3.41; 3.24 for total N respectively). Inverse relation was registered for total P pool were the highest pool was registered on high degraded condition (14963ppm; 13092ppm and 11299ppm from high to low degraded condition). Degraded sites were dominated mainly by members of Gammaproteobacteria, Alfaproteobacteria, Acidobacteria and Bacteroidia. Chitinophagaceae and Burkholderiacea were not detected in degraded plots, which suggest that some of the specialised functions carried by this groups could be lost. With respect to fungi Ascomycota and Basidomicota Phylum dominated the soil profiles. A species of the genus Clonostachys (Bionectriaceae) was identified, an endophyte fungus that acts as a saprophyte, also known to be a parasite of other fungi and some nematodes.

This research contributes to a better understanding of the direct effects of anthropic disturbances on the biogeochemical functioning of temperate forests and their relationship to the activity and composition of microbial communities.

Acknowledgment: Proyecto Reforestación Enel – UdeC
Intra-year distribution of water discharge in global rivers
Authors: Yue Yao , Chai Yuanfang
Published: March 2020

Intensive human interference, climate variability, and ongoing climate change affect the seasonality of runoff processes in rivers worldwide, which in turn may promote more frequent extreme flow events and cause irreversible damage to the ecological environment. Here we examine the global trend of the intra-year distribution of the seaward water discharge in 314 independent river basins, the total drainage area of which accounts for 2/3 of the total Earth land. The results show that the intra-year distribution of water discharge is homogenized between dry and flood seasons in 181 river basins, such as the Nile, Mississippi, Yangtze, Ganges, etc., but polarized in 39 basins, e.g. Amazon, Zaire, and Niger. Considering the primary factors affecting the intra-year distribution of water discharge, i.e. precipitation (P), evaporation (E), glacial runoff (G), and dam operations (D), the global river basins can be divided into GDEP, DEP, GEP, and EP types. Using the stepwise regression method, quantitative contributions of each factors to either homogenization or polarization phenomena are calculated. It is found that the homogenization of water discharge is mainly controlled by dam operations in GDEP and DEP river basins, but dominated by the homogenized precipitation in GEP and EP river basins. Homogenized evaporation and polarized precipitation are the major factors behind the polarization of water discharge. This work is of importance to flood/drought disasters control and sustainable riverine/coastal eco-system management.
Multiscale local definition of the wildland-urban interface to mitigate fire risk: an evidence-based approach
Authors: Miranda Alejandro , Carrasco Jaime , González Mauro , Pais Cristobal , Lara Antonio , Weintraub Andrés , Altamirano Adison , Syphard Alexandra
Published: March 2020

The Wildland-Urban Interface (WUI) is the spatial manifestation of the coupling of human communities and ecosystems, and wildfire is the most prominent issue. The WUI accounts for large percentages of fire prevention and suppression expenditures because it is where most human fatalities and structure losses occur. Therefore a fire-risk based definition of the spatial delimitation of the WUI may be critical to properly distributing prevention action and management investments to obtain the maximum social return. We present the first methodological approach that can be used to delineate the WUI based on a fire risk assessment. To accomplish this, we developed a geographical framework to model fire risk with the most prominent drivers and their interactions to define spatial explicit thresholds of the WUI. We built a Bagged Decision Tree (BDT) model to quantify fire risk based on Human Activity, Geographic and Topographic, and Land Cover variable interaction with fire ignition. For national and subnational threshold definition, we used Partial Dependence Plots (PDP) to analyze relationships between individual variables and predicted responses. A PDP can show the inflection point where a management action could potentially attain the best social return for decreasing fire risk. We find that the spatial threshold can vary more than double between subnational areas using the local fire risk-based approach. Subnational threshold definition accounts for 52% of fires in 3.4% of the national territory where lives 63% of the human population versus the conventional threshold or even nationally defined threshold that accounts for 36% and 54.4% of fires but in 3.3% and 4.3% of the land respectively. This multi-scale approach can be used to identify both general thresholds for large-scale applications as well as local thresholds for defining the WUI both operationally and empirically to determine optimal management areas.
Numerical study on ocean response to storm in Arctic Ocean
Authors: He Hailun , Lin Long
Published: March 2020

A one-column ocean model was used to study the ocean response to storm in Arctic Ocean. We design a number of idealized experiments by different surface forcing and initial condition. The results show the phenomena of mixed-layer extension during the storm events. The intensification of surface current reflects the momentum flux injected from wind and ice movement. Furthermore, by changing the surface heat and freshwater fluxes, the dependences of mixed-layer variation on surface forcing are discussed. Finally, the numerical tests on different initial conditions show how the pre-storm condition affects the ocean response to storm. The results therefore reveal the dependence of mixed-layer extension on the initial stratification.
Stream Interaction Regions in the Inner Heliosphere: Insights from the First Four Orbits of Parker Solar Probe
Authors: Allen Robert , Ho George , Jian Lan , Lario David , Odstrcil Dusan , Arge Charles , Badman Sam , Bale Stuart , Case Anthony , Christian Eric , Cohen Christina , Henney Carl , Hill Matthew , Jones Shaela , Kasper Justin , Korreck Kelly , Malaspina David , McComas David , Raouafi Nour , Stevens Michael
Published: March 2020

The first four orbits of Parker Solar Probe (PSP) consists of many observations of stream interaction regions (SIRs), which form when fast solar wind streams overtake slower solar wind. While it is known that SIRs accelerate ions in the heliosphere and can trigger geomagnetic storms, the temporal and radial evolution of SIRs is still an active topic of research. During the first four orbits of PSP, SIRs were observed by PSP at small heliospheric distances, as well as at 1 au by the Advanced Composition Explorer (ACE), Wind, and Solar Terrestrial Relations Observatory (STEREO) missions. These SIRs are observed not only at different heliospheric distances, but also at different points in the temporal development of the stream interface. Through analyzing the various SIRs together, insight can be gained in regards to the spatial and temporal evolution of SIR characteristics, as well as to the mechanisms of particle acceleration and transport along the SIR interface. The general characteristics of SIRs observed by PSP during the first four orbits are presented, and an in-depth comparison of a few of the SIR events is conducted to further analyze the evolution of SIR streams in the inner heliosphere. These observations show examples of a fast solar wind stream steepening into an SIR, with evidence of locally accelerated particles via compressive mechanisms at the interface distinguishable from observations of particles likely accelerated at shocks formed at larger heliospheric distances.
Recovery of forest patches in central Mongolia after fire: Which role does soil hydrology play?
Authors: Schneider Florian , Klinge Michael , Brodthuhn Jannik , Sauer Daniela
Published: March 2020

The distribution of forest patches in the foreststeppe of central Mongolia reflects the interplay of several environmental factors that together control the vegetation pattern of the landscape. Since the mean annual precipitation of this semiarid area rarely exceeds 300 mm, the existence of forest strongly depends on the hydrological properties of the system. Only north-facing slopes provide suitable conditions for the growth of larch trees (Larix sibirica Ledeb.) due to their reduced evapotranspiration. Plains and south-facing slopes are covered by open steppe.However, after disturbance of the forest patches by fire, the regrowth of larch trees does not proceed equally in all areas. During fieldworkat the northern edge of the Khangai Mountains, we identified areas that seemed to havesimilar site conditions but neverthelessshowed different regrowth of larch trees after fire, ranging from intensive regrowth to no regrowth at all.Thisobservation stimulated us to carry out a comprehensive study of soils, vegetation and landscape development in field campaigns in 2017 and 2018, followed by laboratory analyses of soil samples.Through this work, we aimed at identifying the role of soil hydrology for forest succession in this sensitive ecotone.

We described and sampled 57 soil profiles, including sites (i) under forest, (ii) under steppe, (iii) on sites with succession after forest fire, (iv) on sites without succession after forest fire. In the field, we carried out measurements of water conductivity (by use of a compact constant head permeameter). In the laboratory, we analyzed particle size distribution and carried outkfand pF measurements.

These analyses showed that the dominant grain size of the soils was sand, whereby soils with forest regrowth had slightly loamier texture than those without regrowth. We concluded that already slightly loamier texture may be important for water storage during dry periods and thus for forest regrowth.Soils with forest regrowth had higher hydraulic conductivity in the first 25 cm and lower conductivity below.Soils without forest regrowth showeda reverse depth pattern of hydraulic conductivity. We concluded that quick drainage through the upper horizons supports forest regrowth, as it reduces competition for water with grass roots in the upper part of the soil.Soils with forest regrowth hadgreater plant-available water capacity than those without regrowth. We conclude that under the given climatic conditions, storage of plant-available water is a key factor for regrowth / no regrowth of forest after disturbance.
Land Subsidence in Delhi, India investigated using Sentinel-1 InSAR measurements
Authors: Garg Shagun , Motagh Mahdi , Jayaluxmi Indu
Published: March 2020

Groundwater induced land subsidence is a growing problem worldwide and has been documented in places like Mexico, Jakarta, Tehran, and China. India is the largest user of groundwater and pumps more than the USA and China combined. The National capital region(NCR) of India, due to rapid urbanization and illegal extraction, is facing severe groundwater depletion of the order of 0.5m-2m per year and is declared as a critical zone by the government of India. The looming crisis of groundwater depletion and supporting hydrogeology makes this region prone to land surface deformation.

Monitoring subsidence by conventional methods such as extensometers, leveling, hydrogeology modeling, and GPS requires precise field measurements and are time-consuming. With the advent of Interferometry, monitoring deformation precisely from the microwave sensors onboard satellite is possible. In our study, we demonstrate the result of the Persistent Scatterer InSAR (PS-InSAR) technique to monitor the subsidence in the Delhi NCR region using Sentinel -1 Interferometric wide swath (IW) mode. Descending pass datasets are used to identify the PSs over the study area. Fifty-six differential interferograms from Aug 2016 to Sep 2018 are formed after removing flat earth and topographic phase using SRTM 30m DEM. The PS-InSAR processing is done using Stanford Method for Persistent Scatterers (StaMPS), where an amplitude threshold index of 0.4 is selected for Initial PS candidate. The PS points are the stable targets which do not decorrelate much over time.  The deformation is calculated for all these PS points and a time series, and hence a velocity map is formed.

The rate of deformation in Southwest Delhi is found to be approximately 15 cm/year (max) in the radar line of sight direction. The in-situ data provided by the Central groundwater board (CGWB) India is not consistent and has many gaps. However, after applying Spatio-temporal interpolation, it follows the decreasing trend of Land subsidence which suggests that the groundwater extraction is the major cause for the subsidence in the southwest region of NCR during the observed period i.e., from 2016 -2018.
Greenhouse gas (GHG) leakage and net mitigation of typical carbon sequestration practices in China’s terrestrial ecosystem
Authors: Lu Fei , Zhang Guo , Liu Weiwei , Liu Bojie , Zhao Hong , Zhang Lu , Wang Xiaoke , Yuan Yafei
Published: March 2020

Many management practices in cropland, forest and grassland ecosystems can extend forest area, increase carbon input or prevent C loss from vegetation and soil, and subsequently enhance C sinks and stocks. These management practices are considered as promising carbon sequestration measures. However, during implementation of these measures, the production, transportation and consumption of corresponding materials (such as synthetic fertilizers) and fossil fuel, the additional trace GHG emissions, and the processes taking place elsewhere as a result of the implementation activities may lead to GHG budget change other than the carbon stock, and form GHG leakage. Consequently, in order to reveal the true contribution of these practices to global warming mitigation and GHG reduction, full GHG budget need to be considered rather than the impact on soil and vegetation carbon alone. We built the frame of “Carbon Accounting and Net Mitigation (CANM)” and serious of CANM methods to investigate the GHG leakage and net mitigation of typical carbon sequestration practices in China's terrestrial ecosystem, including China’s national ecological restoration projects, and forest, cropland and grassland managements. The results showed large variations in carbon contributions, GHG leakages and their counteraction effects among different practices and ecosystems. The counteraction effects of GHG leakage from forest management and some forest-related ecological restoration projects were relatively small and could hardly exceed 25%. Meanwhile, the GHG leakage of some cropland management practice (e.g., straw return in rice paddies) could fully offset the carbon sequestration in soil. But reduction of synthetic fertilizer application in accordance with the national fertilization recommendations might own considerable net GHG mitigation potential. Grazing prohibition could sequester carbon in grassland ecosystem, but the transfer of grazing activity could offset about half of the carbon sequestration effect. Therefore, policies and technical approaches to minimize GHG leakage are necessary to enhance the GHG mitigation effect of the ecosystem carbon sequestration practices.
Predicting Opuntia stricta (Haw.) in arid and semi-arid environment of Kenya using Sentinel imagery and ensemble machine learning classiﬁers
Authors: Muthoka James , Rowhani Pedram , Antonarakis Alexander
Published: March 2020

To ensure effective management of Alien plant species especially the invasive demands for knowledge of their spatial availability. The use of satellite remote sensing tools has increasingly provided potential ways to assess spatial availability as compared to the traditional ways that are inadequate to provide similar information in a detailed way. The Copernicus Sentinel satellite images with a high spatial resolution and easy access at no charge provides an opportunity for mapping the spatial variability at a regional scale and in a detailed manner. In this study, we assess the potential of Sentinel 2 images vegetation indices and using ensemble machine learning techniques, map the spatial variability of invasive species (Opuntia stricta) in an arid and semi-arid region of Kenya. To actualize this, we use Sentinel 2 bands and thirty-one vegetation and elevation indices for classification. Field data collected is divided into two (training & validation) and used to get the best model to classify Opuntia stricta and eight other control classes. The best performing model and the highest contributing features are selected for final Opuntia stricta estimation. The random forest algorithm yields the highest accuracy 89% hence is used to classify Opuntia stricta species. Our observation of the overall results indicates that Sentinels in combination with the indices characterized by spatial resolution provide an importance that can be used to discriminate Opuntia stricta species hence providing an opportunity for long term monitoring and management at a fairly acceptable accuracy hence ensuring limited pasture degradation. Therefore, future research should focus on exploring Sentinel time-series images for estimating Opuntia stricta species at a temporal variability.
The Search-Coil Magnetometer onboard the ESA JUICE mission
Authors: Retinò Alessandro ,   JUICE SCM Team
Published: March 2020

The JUpiter ICy moons Explorer (JUICE) mission is the first large-class (L1) mission in ESA Cosmic Vision. JUICE is planned for launch in 2022 with arrival at Jupiter in 2029 and will spend at least four years making detailed observations of Jupiter’s magnetosphere and of three of its largest moons (Ganymede, Callisto and Europa). The Radio and Plasma Wave Investigation (RPWI) consortium will carry the most advanced set of electric and magnetic fields sensors ever flown in Jupiter’s magnetosphere, which will allow to characterize the radio emission and plasma wave environment of Jupiter and its icy moons. Here we present the scientific objectives and the technical features of the Search Coil Magnetometer (SCM) of RPWI. SCM will provide for the first time high-quality three-dimensional measurements of magnetic field fluctuations’ vector in the frequency range 0.1 Hz – 20 kHz within Jupiter’s magnetosphere. High sensitivity (~ 4 fT / √Hz  at 4 kHz) will be assured by combining an optimized (20 cm long) magnetic transducer with a low-noise (4 nV / √Hz  ) ASICs pre-amplifier for the front-end electronics. Perturbations by the spacecraft are strongly reduced by accommodating SCM more at ~ 10 m away from the spacecraft on the JUICE magnetometer boom. The combination of high sensitivity and high cleanliness of SCM measurements will allow unpreceded studies of waves and turbulence down to kinetic scales, in particular in key regions such as the magnetopause, the auroral region and the magnetotail current sheet of Ganymede’s magnetosphere. This will lead to important advances in understanding wave-particle interaction and particle energization mechanisms in Jupiter’s magnetosphere.
London Carbon Emission Experiment
Authors: Humpage Neil , Boesch Hartmut , Ramsay Robbie , Gray Andrew , Gillespie Jack , Woodwark Jerome , Williams Mathew
Published: March 2020

Carbon emissions related to fossil-fuel use are particularly localized, with urban areas being the dominant contributor responsible for more than 70% of global emissions. In the future, the share of the urban population is expected to continue to rise, leading to further increased focusing of fossil-fuel related emissions in urban areas. Cities are also the focal point of many political decisions on mitigating and stabilization of emissions, often setting more ambitious targets than national governments (e.g. C40 cities). For example, the Mayor of London has set the ambitious target for London to be a zero-carbon city by 2050. If we want to devise robust, well-informed climate change mitigation policies, we need a much better understanding of the carbon budget for cities and the nature of the diverse emission sources underpinned by new approaches that allow verifying and optimizing city carbon emissions and their trends.

New satellite observations of CO2 from missions such as OCO-3, MicroCarb and CO2M, especially when used in conjunction with ground-based sensors networks provide a powerful novel capability for evaluating and eventually improving existing CO2 emission inventories. We will set up a measurement network up-and downwind of London using portable greenhouse gas (CO2, CH4, CO) column sensors (Bruker EM27/SUN) together with UV/VIS DOAS spectrometers (NO2), which will be operated for extended time periods thanks to automatization of the sensors. The data acquired from the network will not only allow us to critically assess the quality of satellite observations over urban environments, but also to derive data-driven emission estimates using a measurement-modelling framework. In this presentation we will discuss the setup of the experiment, give a description of the sensors, and show some first observations obtained with the sensors.