bluuebunny/crossref_metadata_2025 huggingface dataset:
Using stable isotopes to quantify ecohydrological flux dynamics at the soil-plant-atmosphere continuum in urban green spaces
Authors: Kuhlemann Lena-Marie , Tetzlaff Doerthe , Kleinschmit Birgit , Vulova Stenka , Soulsby Chris
Published: March 2020

Urban areas, more than many experimental catchments, are characterized by a markedly heterogeneous distribution of land covers, with different degrees of permeability that radically vary partitioning of precipitation into evapotranspiration (“green” water fluxes) and runoff and groundwater recharge (“blue” water fluxes). While the quantification of ecohydrological fluxes using stable isotopes in water as environmental tracers has been an established method for many years, surprisingly few studies have been applied to the highly complex urban water cycle. To determine the effects of representative urban green space “types” on water partitioning, we carried out plot-scale studies at a heterogenous field site in Berlin-Steglitz that integrates climate, soil moisture and sap flow data, with isotope sampling of precipitation and soil moisture on a regular basis. Soil moisture and isotope measurements were conducted at different depths and under contrasting soil-vegetation units (grassland, trees, shrub) with different degrees of permeability. Our investigations revealed uniformly decreasing soil moisture content during the dry summer of 2019, with only temporary re-wetting of the uppermost soil layers despite heavy convective precipitation events. Soils under trees were driest, whilst grassland soils were wettest, with shrubs intermediate. Isotope-based modelling indicated that this was the result, of greater interception, transpiration and – surprisingly – soil evaporation from forest sites. The isotope signatures of soil water also revealed stronger “memory effects” of summer drying in forest soils, which persisted until the major re-wetting of the system in autumn allowed drainage from the soil profile to contribute to groundwater recharge. Modelling showed that recharge under grasslands could be over 3 times higher compared to under trees and shrubs. Upscaling these findings with large-scale isotope studies of surface and groundwater across Berlin highlights the importance of the vegetation in urban green spaces to water partitioning in heterogeneous city landscapes and the need for careful integration of vegetation management in urban water and land use planning.
A 3D full-Stokes model of Store Glacier, Greenland, with coupling of ice flow, subglacial hydrology, submarine melting and calving
Authors: Cook Samuel , Christoffersen Poul , Todd Joe , Slater Donald , Chauché Nolwenn , Truffer Martin
Published: March 2020

Tidewater glaciers are complex systems, which present numerous modelling challenges with regards to integrating a multitude of environmental processes spanning different timescales. At the same time, an accurate representation of these systems in models is critical to being able to effectively predict the evolution of the Greenland Ice Sheet and the resulting sea-level rise. In this study, we present results from numerical simulations of Store Glacier in West Greenland that couple ice flow modelled by Elmer/Ice with subglacial hydrology modelled by GlaDS and submarine melting represented with a simple plume model forced by hydrographic observations. The simulations capture the seasonal evolution of the subglacial drainage system and the glacier’s response, and also include the influence of plume-induced ice front melting on calving and buttressing from ice melange present in winter and spring.

Through running the model for a 6-year period from 2012 to 2017, covering both high- and low-melt years, we find inputs of surface meltwater to the subglacial system establishes channelised subglacial drainage with channels >1 m2 extending 30-60 km inland depending on the amount of supraglacial runoff evacuated subglacially. The growth of channels is, however, not sufficiently fast to accommodate all inputs of meltwater from the surface, which means that basal water pressures are generally higher in warmer summers compared to cooler summers and lowest in winter months. As a result, the simulated flow of Store Glacier is such that velocities peak in warmer summers, though we suggest that higher surface melt levels may lead to sufficient channelisation for a widespread low-water-pressure system to evolve, which would reduce summer velocities. The results indicate that Greenland’s contribution to sea-level rise is sensitive to the evolution of the subglacial drainage system and especially the ability of channels to grow and accommodate surface meltwater effectively. We also posit that the pattern of plume melting encourages further calving by creating an indented calving front with ‘headlands’ that are laterally unsupported and therefore more vulnerable to collapse. We validate our simulations with a three-week record of iceberg calving events gathered using a terrestrial radar interferometer installed near the calving terminus of Store Glacier.
Effect of Remobilization of Pesticide Residues in Vegetative Filter Strips for Mitigation in Higher-Tier Pesticide Exposure Assessments with VFSMOD
Authors: Muñoz-Carpena Rafael , Reichenberger Stefan , Sur Robin
Published: March 2020

Vegetative filter strips (VFS) are commonly implemented in the field to mitigate runoff pesticide inputs into surface waters and protect aquatic ecosystems. The efficiency of this mitigation practice can be evaluated within the current regulatory high-tier, long-term environmental risk assessments (ERA) in combination with VFSMOD, an established and commonly used numerical model for the analysis of runoff, sediment, and pesticide transport in VFS. For every rainfall/runoff event in the long-term time series, VFSMOD takes the PRZM calculated edge-of-the-field surface runoff, eroded sediment yield, and dissolved and particle-bound pesticide load.  It then calculates infiltration, sedimentation and pesticide trapping in the VFS during the event, and the outflow into the downslope aquatic body for further calculations and risk analysis. Importantly, at the end of each event, VFSMOD calculates the amount of pesticide residue retained in the filter (sediment-bound and infiltrated in the liquid phase), its degradation until the next event in the series, and the fraction of pesticide residue that is remobilized and added to the next runoff event. In earlier VFSMOD versions, full remobilization of the pesticide residue sorbed to sediment and that dissolved in the soil surface mixing layer (typically the top 0.5-5 cm) was calculated conservatively. Recent VFSMOD ERA applications for very highly-sorbed (i.e. pyrethroids) or persistent pesticides indicate that the full remobilization scheme might be too conservative in some cases. In this work, we evaluate new alternative partial remobilization schemes in VFSMOD, i.e. no remobilization of adsorbed residues, but full remobilization of dissolved residues in the mixing layer, or alternatively just a fraction of the mixing layer by diffusive exchange with the runoff. We evaluate the effects of the alternative remobilization schemes on observed total VFS pesticide reductions from available field data. In addition, employing global sensitivity analysis, we assess the relative importance of the alternative remobilization model structures in the context of the expected field variability of other known drivers of VFS efficiency (hydrology, soils, vegetation, pesticide chemical characteristics). The study provides science-based recommendations for future high-tier pesticide ERA with VFS mitigation.
Cordilleran-type orogens and plateaus: new views from a quantitative re-evaluation of mountain-building in the western Central Andes.
Authors: Simoes Martine , Riesner Magali , Habel Tania , Lacassin Robin , Carrizo Daniel , Armijo Rolando
Published: March 2020

The processes driving Andean mountain-building and crustal thickening have been largely questioned since the ~1970's but have remained relatively unclear. However, the discovery of an active fold-and-thrust belt along its western flank at the latitude of Santiago (Chili, ~33.5 °S) has launched a recent vigorous debate on the relative contribution of these structures to Andean mountain-building. Based on an original approach for structural mapping, we have quantitatively investigated the structure of this fold-and-thrust belt, as well as that of the other structural units of the range at this latitude. By combining these data to published structural geometries of the eastern mountain flank, together with constraints on the timing of faulting and exhumation, we were able to revise the overall structure of the range and to quantify the kinematics of Andean orogenic growth at ~33°S-33.5°S. We find that crustal shortening has first primarily been sustained along the western mountain flank by west-vergent structures, synthetic to the subduction zone, with the subsequent increasing contribution of out-of-sequence thrusting, followed by late east-vergent thrusting along the eastern mountain flank. This pattern seems not to be specific to the Andes at this latitude, as similar observations can be made to the first-order by ~20°S, ie ~1300 km further north. There, the kinematics of the fold-and-thrust belt forming the western flank of the Andes cannot be as precisely documented because most structures are hidden beneath the later Cenozoic Atacama gravels. However, first-order quantitative results indicate similar kinematics, where Andean mountain building initiated on west-vergent structures synthetic to the subduction zone and where the later significant cumulated take-over by east-vergent structures towards the South American continent has led to the building of the Altiplano-Puna Plateau.

We propose that such kinematics - ie deformation initially on west-vergent structures along the western mountain flank, with significant later back-arc antithetic deformation - are first-order characteristics of Andean mountain-building, and result from the limited mechanical flexure of the underthrusting forearc, eventually locally modulated by climate-driven erosion.
Copernicus User Needs Collection
Authors: Massart Michel , Jacq Fabienne , Zunker Hugo
Published: March 2020

Copernicus is the Earth Observation Flagship programme of the European Union. It is user driven programme. It has observation capacities with currently 7 satellites in orbit, and information production services in 6 domains: land, emergency, security, climate change, atmosphere and marine. One of the objective of the programme started in 2011 is to ensure the long-term sustainability of the observation capacities for Europe. In this context, the European Commission and the European Space Agency are now preparing the Next Generation (2030) of Sentinel satellites.

To define the specifications of this Next Generation, the European Commission has launched several user requirement surveys and studies aimed at gathering the satellite observation long-term needs across different sectors.

User requirements have been gathered based on desk studies, exchanges and interactions with existing and potential user communities. They have been collected and analysed from different sources which include dedicated studies carried out between 2015 and 2018, requirements expressed by users during task forces and expert groups, and outcomes of several users’ requirement workshops and meetings organized during the last two years. Based on this collection of User Requirements, the European Space Agency has started now to define the potential specifications of the Next Generation of Copernicus satellites.

 The objective of the presentation will be to explain the process setup for collecting the User Requirements, their analysis and the outcomes.
Estimation of NO2 and SO2 concentration changes in Europe from meteorological data with Neural Network
Authors: Vlasenko Andrey , Mattias Volker , Callies Ulrich
Published: March 2020

Chemical substances of anthropogenic and natural origin released into the atmosphere affect air quality and, as a consequence, the health of the population. As a result, there is a demand for reliable air quality simulations and future scenarios investigating the effects of emission reduction measures. Due to high computational costs, the prediction of concentrations of chemical substances with discretized atmospheric chemistry transport models (CTM) is still a great challenge. An alternative to the cumbersome numerical estimates is a computationally efficient neural network (NN). The design of the NN is much simpler than a CTM and allows approximating any bounded continuous function (i.e., concentration time series) with the desired accuracy. In particular, the NN trained on a set of CTM estimates can produce similar to CTM estimates up to the approximation error. We test the ability of a NN to produce CTM concentration estimates with the example of daily mean summer NO2 and SO2 concentrations. The measures of success in these tests are the difference in the consumption of computational resources and the difference between NN and CTM concentration estimates. Relying on the fact that after spin-up, CTM estimates are independent of the initial concentrations, we show that recurrent NN can also spin-up and predict atmospheric chemical state without having input concentration data. Moreover, we show that if the emission scenario does not change significantly from year to year, the NN can predict daily mean concentrations from meteorological data only.
The CO2 Emissions of US Cities: Status, Dynamics, and Comparisons
Authors: Gurney Kevin , Liang Jianming , Roest Geoffrey , Song Yang
Published: March 2020

Urban areas are rapidly growing and are acknowledged to dominate greenhouse gas (GHG) emissions to the Earth’s atmosphere. They are also emerging as centers of climate mitigation leadership and innovation. However, fundamental quantitative analysis of urban GHG emissions beyond individual city case studies remains challenging due to a lack of comprehensive, quantitative, methodologically consistent emissions data, raising barriers to both scientific and policy progress. Here we present the first such analysis across the entire US urban landscape, answering a series of fundamental questions about emissions responsibility, emissions drivers and emissions integrity. We find that urbanized areas in the U.S. account for 68.1% of total U.S. fossil fuel carbon dioxide (CO2) emissions. Were they counted as a single country, the 5 largest urban emitters in the US would rank as the 8th largest country on the planet; the top 20 US cities as the 5th largest. In contrast to their dominant overall proportion, per capita FFCO2 emissions in urbanized areas of the US are 7% less than the country as a whole, particularly for onroad gasoline emissions (-12.3%).

Contrary to previous findings, we find that emissions grow slower than urban population growth in Eastern US cities, particularly for larger urban centers. The Western US, by contrast, shows emissions growing proportionately with population. Much of the difference between Eastern versus Western cities is determined by the onroad emissions sector. This finding, in particular, suggests that “bigger is better” when considering GHG emissions and U.S. urban population growth.

Finally we find large and persistent differences between the results presented here and 57 self-reported urban inventories. The mean difference between the self-reported inventories and the analysis here is -24% (mean absolute difference: 44.3%) with the majority of self-reported values lower than quantified in this study.
Detection and Removal of Noisy Land Magnetic Data Spikes
Authors: AlHumidan Saad
Published: March 2020

Detection of land magnetic data spikes is an important issue in magnetic data processing. In addition, the presence of noisy contributions such as spikes, stripes and zigzag effects in magnetic data visualization represents the most common flaw that may degrade the image. Rendering the correct detection and identification of features very uncertain. In this study, a script called "Window_Despike" was written to mark the spike data points and give the index of each spike point. Spikes were replaced by linearly interpolating the adjacent "good" amplitudes, or replaced by Not a Number (NaN). Different windows size starting from window size of 3 till 9 compared and found that the best window size is 5.
Properties and effects of supercritical fluids
Authors: Ni Huaiwei
Published: March 2020

Enhanced mutual solubility between silicate and water at elevated temperature and pressure in Earth’s interior (subduction zones in particular) allows the formation of supercritical geofluids with composition intermediate between silicate melts and aqueous fluids. The forming conditions of supercritical fluids are controlled by the critical curves, the wet solidi curves and the second critical endpoints of rock-H2O systems. With unusual physicochemical properties, supercritical fluids have the potential to play a crucial role in mediating material recycling at subduction zones, mobilizing and enriching ore-forming elements, inducing intermediate to deep focus earthquakes, and modulating Earth’s habitability. Challenges in the study of supercritical fluids using experimental and computational simulations as well as natural rocks and mineral deposits demand breakthroughs in future development of transformative technologies.
Ochre amendments as a means of increasing carbon sequestration in soil
Authors: Hodson Mark E.
Published: March 2020

As the climate emergency gathers pace there is a growing imperative to reduce carbon emissions and move to a low carbon economy. Such shifts in global economics and politics will inevitably take time and therefore there is also a pressing need to identify immediate actions that can help limit or reduce carbon emissions.

 

Soils store large quantities of carbon. However, chemical, physical and biological properties limit the amount of carbon that any particular soil can store. It may be possible to alter soil properties such that the carbon sequestration potential of a soil is increased without causing a reduction in (or even increasing) other important ecosystem services delivered by the soil.

 

Soil aggregates are widely acknowledged to play an important role in the storage of carbon in soil. One limiting factor for aggregate formation in some soils is the amount of iron oxide present; the iron oxide is an important binding agent, holding aggregates together.

 

Ochres comprise a variety of poorly crystalline iron (III) oxides and form in a number of environments such as mine drainage when water moves to increasingly oxygenated environments and dissolved iron (II) is oxidised and precipitates from solution. In many countries these ochres are treated as wastes and are landfilled.

 

In batch experiments in which soil was amended with 0, 0.5 or 5% by mass ochre and shaken with water in a ratio of c. 1:5 (g:mL) ochre amendments reduced the concentration of dissolved organic carbon released into solution by almost a factor of 2. In experiments that are more realistic of field deployment of ochre amendments to increase soil carbon sequestration in which soils were amended with 0, 0.5 or 5% by mass ochre and kept moist for c. 9 weeks with treatments comprising presence/absence wheat and presence/absence earthworms, ochre amendments reduced the concentration of cold water extractable carbon by a factor of 2 and hot water extractable carbon by a factor of 1.3.

In this presentation the above results together with additional results relating to impacts on other soil properties will be presented. The data confirm the potential of waste iron ochres as a soil amendment to increase soil carbon sequestration though further work with more soil types and a variety of ochres is needed and the carbon footpring of applying the amendments needs to be calculated. Whilst methods such as these may provide vital time to transition to low carbon lifestyles, it is the move to such lifestyles that must be the ultimate solution to the climate emergency.
Quantifying the precursors to brittle failure in rocks using synchrotron imaging and machine learning
Authors: Renard Francois , McBeck Jessica , Cordonnier Benoît
Published: March 2020

Predicting the onset of system-size failure in rocks represents a fundamental goal in assessing earthquake hazard. On the field, seismological, geodetic and other monitoring data may record precursors to earthquakes. In laboratory experiments, such precursors often rely on monitoring acoustic emissions and this technique has some limitations in terms of spatial resolution and the lack of detection of aseismic strain. To overcome these challenges, we have performed a series of forty rock deformation experiments where we imaged, using synchrotron X-ray microtomography, rock samples as they deformed until brittle failure, at in situ conditions of pressure, high spatial micrometer spatial resolution, and through time. On the one hand, direct processing of the X-ray tomograms allow visualizing how precursory microfractures nucleate, grow, and coalesce until failure. From these data, we propose to characterize brittle failure as a critical phase transition, with evidence of several power-laws that characterize fracture growth. On the other hand, digital volume correlation techniques quantify the evolution of the local strain field inside each sample. We analysed the statistical properties of these strain fields using several machine learning techniques to predict the main parameters that control fracture growth (length, volume, shape, distance to the nearest fracture), and the features of the strain field that best predict the distance to failure. Our rock deformation experimental results show that, under laboratory conditions, precursors to brittle deformation exist. These precursors show predictable evolution when approaching system-size brittle deformation and we demonstrate that specific components of the strain field characterize this evolution to failure.
Resolving millimeter-level storm surge loading deformations using multi-GNSS data over the subdaily timescales
Authors: Geng Jianghui , Xin Shaoming , Williams Simon
Published: March 2020

Storm surges often strike the southern coast of North Sea in Europe during the winter season. The largest event on December 5-6, 2013 since 1953 pushed the water level to rise by up to 4 m within a few hours, which caused a transient but appreciable loading on the crust under the southern North Sea. Consequently, GNSS stations around this oceanic area experienced considerable displacements, which were up to 30 mm in the vertical while 5 mm in the horizontal component as predicted by the Proudman Oceanographic Laboratory Storm Surge Model (POLSSM). We processed the GPS/GLONASS data at 18 coastal stations from Nov. 1 until Dec. 31, 2013. We computed station displacements using precise point positioning ambiguity resolution every three hours to track subdaily loading deformations, and compared them with POLSSM predictions. The second- and third-order delays were mitigated using IGS global ionosphere map derived corrections; orbital repeat time (ORT) filtering, which aimed at reducing multipath effects, were enabled for both GPS and GLONASS on the observation level. We found that GNSS derived displacements presented high correlations of up to 0.7 with POLSSM predictions in the vertical direction over the 61 days; higher-order ionosphere corrections reduced the north RMS between GNSS solutions and POLSSM predictions by 0.2-0.3 mm, whereas the ORT filtering decreased the RMS by more than 10% for all three components. Introducing GLONASS data to GPS-only solutions further reduced the RMS to 5.9, 2.2 and 2.7 mm in the vertical, east and north components, suggesting a 6-12% improvement. Despite this millimeter-level agreement, the peak-to-peak vertical displacement of about 10 mm over the 6–24-h timescales for the largest surge event on December 5 was only marked marginally in the subdaily wavelet power spectra. Thanks to the spatial coherence among the 18 stations, the principal component analysis could enhance dramatically the resolution capability of subdaily GNSS in discriminating the subdaily vertical loading signals of 5-10 mm amplitude over the 6–24-h wavelet timescales. We demonstrate that multi-GNSS data have the potential to improve significantly the detection of subdaily geophysical signals dwelling on the periods of tens of minutes to hours.
Direct evidence of secondary reconnection inside filamentary currents of magnetic flux ropes in magnetic reconnection
Authors: Wang Shimou , Lu Quanming
Published: March 2020

Magnetic reconnection is a fundamental plasma process, by which magnetic energy is explosively released in the current sheet to energize charged particles and to create bi-directional Alfvénic plasma jets. A long-outstanding issue is how the stored magnetic energy is rapidly released in the process. Numerical simulations and observations show that formation and interaction of magnetic flux ropes dominate the evolution of the reconnecting current sheet. Accordingly, most volume of the reconnecting current sheet is occupied by the flux ropes and energy dissipation primarily occurs along their edges via the flux rope coalescence. Here, for the first time, we present in-situ evidence of magnetic reconnection inside the filamentary currents which was driven possibly by electron vortices inside the flux ropes. Our results reveal an important new way for energy dissipation in magnetic reconnection.
Relative sea level highstands of the Yucatán Peninsula, Mexico, constrained by speleothem growth periods
Authors: Steidle Simon Dominik , Warken Sophie , Frank Norbert , Förstel Julius , Schorndorf Nils , Schröder-Ritzrau Andrea , Moseley Gina , Stinnesbeck Wolfgang , Olguín Jerónimo Avilés
Published: March 2020

The loading of the North American continent with ice sheets causes a geomorphologic response. As a result of this process, a NW-SE gradient of relative sea level developed in the Caribbean during periods of glaciation. In order to distinguish geomorphologic and eustatic contributions it is important to resolve timing and amplitude of relative sea level at different positions in the Caribbean.

The cave systems around Tulum, Quintana Roo, Mexico are presently submerged and well-connected to the nearby Atlantic with a low hydraulic head gradient. Speleothems must have formed during periods of lower sea level, thus providing constraints on the maximum elevation of relative sea level for given periods of time. Conversely, periods of growth cessation could have been caused by sea level rise thus indicating minimum relative sea level during highstands.

Here, we present 230Th/U dated submerged speleothems that grew during MIS5a-d as well as MIS1/2, MIS6 and MIS11/12.

Growth of a single stalagmite (QUE01) at -10.8±0.1m (relative to today's sea level) was interrupted twice. Petrographical studies and trace element analysis indicate that submergence caused millennial-scale growth stops in QUE01 during MIS5. The proposed highstands are between 109.4±0.3ka and 105.0±0.3ka as well as between 104.5±0.4ka and 96.9±0.4ka.

While a previous study [1] constrains the amplitude to <9.9m, this study further improves the timing. This is the first record in this area that yields bracketing ages for those highstands from a speleothem that is very close to the peak height. In order to reconstruct a Caribbean sea level gradient, the combined Yucatán record acts as a counterpiece to a similar study from the northern end of the Caribbean sea level gradient which reports highstands at that time with a higher relative sea level [4].

Speleothem growth during MIS1/2 (19-8ka) relates to conflicting local sea level markers [2,3] and contains century-scale growth stops. Samples dating back to MIS6 and MIS11/12 highlight the potential for sea level reconstruction in this area before MIS5.

[1] Moseley et al. (2013) Journal of Quaternary Science 28 293-300
[2] Moseley et al. (2015) The Holocene 25 1511-1521
[3] Hering et al. (2018) Journal of Quaternary Science 33 444-454
[4] Wainer et al. (2017) Earth and Planetary Science Letters 457 325-334
Seismic stratigraphy of the East-Siberian and Chukchi seas as a key to the Amerasia Basin stratigraphy end evolution
Authors: Startseva Kseniia , Nikishin Anatoly
Published: March 2020

Based on new seismic survey, offshore drilling and geological structure of the adjacent onshore a new model of geological evolution of sedimentary basins of the East-Siberian and Chukchi seas since the Mesozoic has been constructed. The main stages of their tectonic history are highlighted: 1) forming of the foreland basin in Jurassic – Early Creatceous time; 2) synrift extension in Aptian-Albian time; 3) start of postrift subsidence in Later Cretaceous; 4) uplift and deformations at the turn of Cretaceous and Paleogene, start of forming of the thick (up to 4-6 km) clinoform complex; 5) episode of synrift extension in Middle-Later Eocene, forming of the system of multiple low-amplitude normal faults; 6) inversion deformations in Oligocene-Miocene; 7) relatively calm tectonic conditions in Neogene-Quaternary time. Boundaries of the interpreted seismic complexes corresponding to these stages has been extended to the entire Amerasia basin with regards to the ages of magnetic anomalies in the Gakkel Ridge and sea-bottom sampling on the Mendeleev Rise. Volcanic areas of the De Long Islands and the North Wrangel High has been traced on the seismic profiles toward Mendeleev Rise and Podvodnikov Basin and dated as ±125 Ma. According to the seismic interpretation, the age of the Podvodnikov and Toll basins is not older than Aptian. The reported study was funded by RFBR and NSFB, project number 18-05-70011, 18-05-00495 and 18-35-00133.
Analysis of a severe precipitation process in Aksu Area under the background of the Central Asian Vortex
Authors: Guo Nannan , Zhou Yushu
Published: March 2020

Central Asian Vortices (CAVs) are deep cyclonic systems that occur in the Central Asian and are identified at the 500 hPa level. CAVs are significantly associated with many convective events in the Xinjiang province. In order to strengthen the understanding of the mesoscale systems development mechanisms in torrential rain under the influence of CAVs, we analyzes the rainstorm process occurred in the Aksu region that is near the west of Tianshan Mountains, during June 17 to 18, 2013 basing on a variety of data. The results show that the precipitation process occurs under the background of the circulation of the two ridges in a trough over the middle and high latitudes, and the CAV provides favorable large-scale dynamic and water vapor conditions for this rainstorm. The convergence line is the important mesoscale system, which is formed by the superposition of the CAV circulation and the flow stream around the special topography of the west Tianshan Mountains. Due to the difference of thermal properties between the mountain and desert, the slope wind drives convergence line to move and the strong convection developed along the convergence line triggers strong precipitation in the Aksu region. The WRF is able to well simulate not only the location and intensity of the heavy rain but also the evolution of wind field. Preliminary analysis combined with observations and simulation data shows that under the blockage of west Tianshan Mountains, the south wind accumulates and convergences near the valley. As a result, a local convergence line is formed. Meanwhile, with the adjustment of the large-scale circulation situation, especially after the CAV moves to the vicinity of the Aksu area, one part of the westward flow that comes from the south of the vortex turns into northwest wind after crossing the west Tianshan Mountains, and the other part turns into the northeast wind after passing through the Yili Valley, these two flow aggravate the northerly airflow and enhance the intensity of convergence, thereby promote the formation of mesoscale convergence lines and strengthen it. The eastward airflow-induced water vapor accumulates in front of the southern foot of the Tianshan Mountains, and strengthens as the convergence line moves towards southeast with the enhancement of the valley wind at night. Accompanied with the convergence uplift, the accumulation of water vapor at the foot of the mountain promotes the release of unstable energy and brings heavy precipitation to the Aksu region.
Landslide hazard zone mapping using Information Value model: the case of Gidole Landslide, Southern Ethiopia
Authors: Walle Filagot Mengistu , Suryabhagavan Karuturi Venkata , Raghuvanshi Tarun , Lewi Elias
Published: March 2020

Landslide hazard is becoming serious environmental constraints for the developmental activities in the highlands of Ethiopia. With the current infrastructure development, urbanization, rural development, and with the present landslide management system, it is predictable that the frequency and magnitude of landslide and losses due to such hazards would continue to increase. In the present study landslide hazard zone mapping were carried out in and around Gidole Town in Southern Ethiopia. The main objective of the study was to map landslide hazard zone using Information Value Bi-variant statistical model.  For landslide hazard zonation of the study area six causative factors namely; aspect, slope angle, elevation, Lithology, Normalized Deference Vegetation Index (NDVI) and land-use and land-cover were considered. The landslide inventory mapping for the present study area was carried out through field observations and Google Earth image interpretation. Later, Information value was calculated based on the influence of causative factors on past landslide. The distribution of landslide over each causative factor maps was obtained and analyzed. Weights for the class with in these causative factor maps was obtained using information value model. Distribution of landslide in the study area was largely governed by aspect of southwest facing, slope angel of 30-45o, elevation of 1815–2150m, NDVI of 0.27−0.37, Lithology of colluvial deposit and land-use and land-cover of agricultural land. The landslide hazard zonation map shows that 78.38km2 (36.3%) area fall within very low hazard (VLH) zone, 72.85km2 (34.2%) of the area fall within low hazard (LH) zone, 12.78 km2 (6.6%), 32.72 km2 (15.4%) and 15.89 km2 (7.5%) of the area falls into very high hazard (VHH), high hazard (HH) and moderate hazard (MH), respectively. Further, validation of LHZ map with past landslide inventory data shows that 92.3% of the existing landslides fall in very high hazard (VHH) and high hazard (VHH) zone. Thus, it can safely be concluded that the hazard zones delineated in the present study validates with the past landslide data and the potential zone depicted can reasonably be applied for the safe planning of the area.

Key words: Landslide, Gidole, Landslide hazard zone, Information Value model
Estimating mixing processes of sources contributing to baseflow in Alpine headwater catchments
Authors: Floriancic Marius G. , Roques Clément , Jimenez-Martinez Joaquin
Published: March 2020

Baseflow is fed by groundwater to a large fraction. Estimating water quantity and quality from groundwater stores is essential for water management. However, there are few datasets available that contain detailed water chemistry analysis on high spatial resolution across multiple headwater catchments in (high) Alpine environments. This information is essential to analyze mixing processes on catchment scale from distinct landscape features.

We use two data sets: i) water chemistry analysis snapshot sampling campaigns in 7 headwater streams during low‑flow periods across Switzerland, and ii) a detailed chemical screening (every 25 m) in one selected catchment during baseflow, including electric conductivity and temperature. Major ions, stable isotopes, TOC, DOC, trace elements were analyzed for some of the samples (> 80). These data reveal the chemical fingerprint of the contributing groundwater sources. The chemical composition of these contributing sources to baseflow is largely influenced by weathering products depended on lithology and geomorphology. Using maximum likelihood calculations, we define the ion composition and the isotopic signature of the potential major endmembers (up to three), based on the mixed samples along the main stem.

The proposed methodology allows to i) reduce uncertainty of the endmembers, and ii) quantify the relative contribution of different lithology and geomorphological features to streamflow and shows iii) which spatial scale of input information is needed to analyze mixing processes from various groundwater sources. Our results show how the contribution of different lithologies, along with topography and geomorphological features, varies spatially throughout Alpine headwater catchments.
Solar Radiation Modification Slows Down Permafrost Carbon Loss
Authors: Chen Yangxin , Ji Duoying
Published: March 2020

    Circumpolar permafrost is degrading under anthropogenic global warming, thus the large amount of soil organic carbon in it would be vulnerable to microbial decomposition and further aggravating future warming. However, solar radiation modification (SRM), as a theoretical approach to reducing some of the impacts of anthropogenic climate change, hopefully could mitigate the permafrost degradation and slow down permafrost carbon loss. Here we use two solar geoengineering experiments came up in CMIP6/GeoMIP6 -- G6solar and G6sulfur, to explore changes in circumpolar permafrost carbon under solar radiation modification scenarios. Earth system models' simulations show that under G6 scenarios, annual mean surface air temperature in circumpolar permafrost region is about 5℃ lower relative to the high forcing scenario SSP5-8.5 by year 2100, with a growing trend but remains below 0℃ from 2015 to 2100, which is close to that in the medium forcing scenario SSP2-4.5. The lower temperature causes lower degradation rate of permafrost area. In SSP5-8.5 scenario, almost all the permafrost thaws by year 2100, but up to half of it remains frozen in SSP2-4.5 and G6 scenarios compared to year 2015. The lower temperature also results in less carbon assimilation in this area, thus the lower vegetation carbon accumulation. By 2100, a maximum soil carbon loss of 18.09 PgC under SSP5-8.5 scenario regarding to different model constructions, while in G6 the soil carbon loss could be reduce to 3.70 PgC, even less than that of 5.29 PgC in SSP2-4.5 scenario.
UAS radiation hot-spot detection and refinement
Authors: Wood Kieran , Connor Dean , Groen Sevda , Smith Dave , White Sam , Martin Peter , Verbelen Yannick , Holland Erin , Richardson Tom , Scott To
Published: March 2020

Unoccupied Aerial Systems (UAS) are ideal tools for responding to nuclear incidents where large outdoor areas have become contaminated with a radiological hazard. They are advantageous because rapid response radiation surveys can be conducted while the human operator remains at a safe distance and avoids direct contamination of the platform. During fieldwork within the Chernobyl Exclusion Zone (Ukraine), an airborne platform was equipped with a GNSS enabled gamma spectrometer and used to survey an area surrounding a known highly contaminated building (a ‘hot-spot’), resulting in a radiation intensity map. The detected radiation pattern, however, was ‘blurred’ since the intensity recorded at any point counted nadir emissions, but also emissions from all sources within line-of-sight; The ‘hot-spot’ had an influence far outside its ground footprint. Methods exist to correct for errors introduced by varying terrain altitude, however, they do not remove the unwanted blurring. Hence, small point sources appear as broad regions of contamination which is entirely an artefact of the measurement process. The effect is further accentuated with increasing height above ground hence understanding and correcting for this phenomenon is particularly relevant to data collected using UAS. Here, we present a novel algorithm to refine the detected pattern to more accurately recover the ground-truth.

A forward model of the system is created which describes the relationship between the unknown ground-truth and the aerial measurements. Gamma ray emissions from a point source obey the inverse square law of spatial dilution and have an exponential attenuation in air. To model both effects, geometric information of the scene is required and is provided by the geotagged spectrometer data and photogrammetrically processed DEMs of the surveyed terrain. The resulting model is hyper-cube of linear equations, where every aerial measurement point is assumed to be influenced by every ground sample point. By finding the inverse solution of this system, the ground-truth radiation pattern is estimated in more detail. The Kaczmarz method is advantageous because a large system of equations can be broken down into smaller sub-routines and solved iteratively. A caveat is that the solution might settle to false positive. The refinement algorithm will be presented with simulated results, controlled laboratory experiments using robotic arms and sealed radioactive sources, and finally applied to a real-world data set collected in the Chernobyl Exclusion Zone.
Effect of Combining Catalogs with Different Completeness
Authors: Noh Myunghyun
Published: March 2020

In most seismic studies, we prefer the earthquake catalog that covers a larger region and/or a longer period. We usually combine two or more catalogs to achieve this goal. When combining catalogs, however, care must be taken because their completeness is not identical so that unexpected flaws may be caused.

We tested the effect of combining inhomogeneous catalogs using the catalog of Korea Meteorological Administration (KMA). In fact, KMA provides a single catalog containing the earthquakes occurred in and around the whole Korean Peninsula. Like the other seismic networks, however, the configuration of the KMA seismic network is not uniform over its target monitoring region, so is the earthquake detection capability. The network is denser in the land than in the off-shore. Moreover, there are no seismic information available from North Korea. Based on these, we divided the KMA catalog into three sub-catalogs; SL, NL, and AO catalogs. The SL catalog contains the earthquakes occurred in the land of South Korea while the NL catalog contains those in the land of North Korea. The AO catalog contains all earthquakes occurred in the off-shore surrounding the peninsula.

The completeness of a catalog is expressed in terms of mc, the minimum magnitude above which no earthquakes are missing. We used the Chi-square algorithm by Noh (2017) to estimate the mc. It turned out, as expected, that the mc of the SL is the smallest among the three. Those of NL and AO are comparable. The mc of the catalog combining the SL and AO is larger than those of individual catalogs before combining. The mc is largest when combining all the three. If one needs more complete catalog, he or she had better divide the catalog into smaller ones based on the spatiotemporal detectability of the seismic network. Or, one may combine several catalogs to cover a larger region or a longer period at the expense of catalog completeness.
Impact of the Equatorial Wind Stress on the Indian Ocean Shallow Meridional Overturning Circulation During the IOD Mature Phase
Authors: Zhang Linfang , Li Yaokun , Li Jianping
Published: March 2020

            This paper investigates the impact of the equatorial wind stress on the Indian Ocean Shallow Meridional Overturning Circulation (SMOC) during the India Ocean Dipole (IOD) mature phase. The results show that the equatorial zonal wind stress directly drives the meridional motion of seawater at the upper level. In normal years, the wind stress in the Indian Ocean is easterly between 30°S-0°and the westerly wind is between 0°and 30°N, which contributes to a southward Ekman transport at the upper level to form the climatological SMOC. During the years of positive IOD events, abnormal easterly wind near the equator, accompanying with the cold sea surface temperature anomaly (SSTA) along the coast of Sumatra and Java and the warm SSTA along the coast of East Africa, brings southward Ekman transport south of the equator while northward Ekman transport north of the equator. This leads the seawaters moving away from the equator and hence upwelling near the equator as a consequence, to form a pair of small circulation cell symmetric about the equator.
Management effects on glyphosate and AMPA concentrations in the PM10 emitted by soils of the central semiarid region of Argentina
Authors: Ramirez Haberkon Nancy B. , Aparicio Virginia , Aimar Silvia B. , Buschiazzo Daniel E. , De Geronimo Eduardo , Costa José Luis , Mendez Mariano
Published: March 2020

Particulate material less than 10 microns (PM10) is important because it is related to negative effects on human health. The soil is one of the most important sources of PM10 which can be emitted by wind erosion, tillage and traffic on unpaved roads. In agricultural soils different fertilizers and agrochemicals are used to produce food. Glyphosate is the main herbicide used in Argentina and in the world, being the dose and the number of applications per year variable in different management system. The objective of this study was to analyze the concentration of glyphosate and its main metabolite, AMPA, in PM10 emitted by soils with different management and uses of the herbicide. For this, the first 5 cm of the following soils were sampled: 9 soils with harvest crop (HC) mostly resistant to glyphosate, under direct sowing and with at least 3 applications of glyphosate per year; 5 soils with forage crops (FC) mostly non-glyphosate resistant, under conventional tillage and one application of glyphosate per year; and 2soils with permanent pasture (PP) that did not receive glyphosate and tillage during the last 30 years. From the soil samples were extracted and collected the PM10 using the easy dust generator coupled to an electrostatic precipitator. The glyphosate and AMPA content were determined in the soils and PM10. The results showed that the percentage of glyphosate detection in PM10 was 100% in HC and FC, and 83% in PP; whereas that AMPA detection was 100% in all management systems. In the soil the detection of glyphosate was 100% in HC, 80% in FC and 0% PP.  For AMPA the percentage of detection was 100% in HC and FC, and 66% in PP. Contents of glyphosate and AMPA in the soil were higher in HC (87.1 ug kg-1 and 1015.5 ug kg-1) than in FC (4.4 ug kg-1 and 140.3 ug kg-1) and PP (0 ug kg -1 and 8.5 ug kg-1) (p <0.05). The same results were found in PM10, where glyphosate and AMPA contents in HC (279.5 ug kg-1 and 4690.5 ug kg-1) were higher than in FC (21.1 ug kg-1 and 503.4 ug kg-1 ) and PP (33.5 ug kg-1 and 128.4 ug kg-1) (p <0.05). Content of AMPA was higher than that of glyphosate in the soil and PM10 of the three managements studied.  Glyphosate and AMPA contents in the PM10 were higher than in the soil. This study shows that the most frequent use of glyphosate increases its content and that of AMPA in the soil and PM10. It is confirmed that the contents of glyphosate and AMPA in PM10 are greater than in the soil under different management systems. Our results suggest that is highly probably the existence of glyphosate and AMPA in the PM10 emitted from agricultural soils and that, in this way, glyphosate and AMPA be transported to not target areas. All those results should by confirmed under field condition.