bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of complex organosulfur compounds by sulfur implantation in astrophysical ice analogs – implications for the chemical evolution of the surface of icy objects
Authors: Bouquet Alexis , Ruf Alexander , Boduch Philippe , Schmitt-Kopplin Philippe , Vinogradoff Vassilissa , Duvernay Fabrice , Giovanni Urso Riccardo , Brunetto Rosario , Le Sergeant d'Hendecourt Louis , Mousis Olivier , Danger Grégoire
Published: March 2020

Irradiation of ices is a ubiquitous cause of chemical evolution of the surface of icy bodies of the solar system, due to solar UVs, solar wind particles, and magnetospheric particles. Sulfur is present in the solar wind and, in large quantities, in the jovian magnetosphere; in addition of acting as a projectile and inducing radiation chemistry, it is reactive and may be incorporated into the compounds produced. This may be a factor in increasing the chemical complexity of the surface of KBOs, TNOs, and jovian moons.

We have performed implantation of 105 keV sulfur ions into a water-methanol-ammonia ice at the Grand Accélérateur National d’Ions Lourds (GANIL) in Caen, France. Similar samples were also irradiated with argon (non-reactive projectiles). The samples were monitored in the infrared during the implantation process. The organic residues left after heating and sublimating the volatiles were then analyzed with Very High Resolution Mass Spectrometry (VHRMS). The infrared spectra of the argon-irradiated and sulfur-irradiated samples are qualitatively the same, but VHRMS shows the residue of the sulfur-irradiated sample contains more than a thousand of CHNOS formulas that are not present in the argon-irradiated sample. This indicates an active and rich sulfur chemistry induced by the implantation. The compounds formed are mostly aliphatic and can reach masses up to 700 amus. We discuss the implications for icy objects of the solar system and other ongoing experiments to explore the chemistry induced by sulfur implantation on the surface of the jovian moons.
NIOSH Elongate Mineral Particle Research
Authors: Mischler Steven
Published: March 2020

During the mining and processing of some mineral commodities and other rock types there is the potential to produce respirable dust containing naturally occurring elongate mineral particles (EMPs), including both asbestos and/or non-asbestos fibers. The United States National Institute for Occupational Safety and Health (NIOSH) estimated that 44,000 mine workers may be exposed to EMPs. EMPs have been documented to cause lung cancer and mesothelioma in humans in addition to fibrotic lung disease (asbestosis), with some estimating up to 76,700 EMP-caused lung cancer deaths between the years of 1980 and 2009. Unfortunately, there is little information available relating the geologies of the materials being mined to the potential for EMP exposure to mine workers. There is a strong need for research on fundamental mineralogical properties of EMPs—relevant to toxicology, epidemiology, and exposure assessment— and their geographic distribution, which industry can use as a basis for exposure monitoring and miner protection. This presentation will outline the NIOSH research addressing these concerns including; 1) assessment of miners’ potential exposure to asbestos and other EMPs by analyzing bulk material samples previously collected from copper, granite, gold, iron, limestone, sand and gravel, coal, and other types of mines across the country, 2) further elucidation of the toxicology of EMPs by creating new separation methods to allow both in vitro and in vivo toxicity tests on EMPs of specific lengths, widths and other characteristics of concern, 3) establishment of an application of qualitative and quantitative analysis of regulated asbestos and other EMPs for end-of-shift measurement using newly developed and novel techniques for EMP analysis, and 4) making new reference materials (anthophyllite asbestos and actinolite-tremolite asbestos) available to laboratories analyzing the elongate mineral particle fraction of bulk rocks and airborne dusts, and for toxicity testing.

 
Exploring ice core sea ice proxies through process-based modelling
Authors: Rhodes Rachael , Yang Xin , Wolff Eric
Published: March 2020

It is important to understand the magnitude and rate of past sea ice changes, as well as their timing relative to abrupt shifts in other components of Earth’s climate system. Furthermore, records of past sea ice over the last few centuries are urgently needed to assess the scale of natural (internal) variability over decadal timescales. By continuously recording past atmospheric composition, polar ice cores have the potential to document changing sea ice conditions if atmospheric chemistry is altered.  Sea salt aerosol, specifically sodium (Na), and bromine enrichment (Brenr, Br/Na enriched relative to seawater ratio) are two ice core sea ice proxies suggested following this premise.

Here we aim to move beyond a conceptual understanding of the controls on Na and Brenr in ice cores by using process-based modelling to test hypotheses. We present results of experiments using a 3D global chemical transport model (p-TOMCAT) that represents marine aerosol emission, transport and deposition. Critically, the complex atmospheric chemistry of bromine is also included. Three fundamental issues will be examined: 1) the partitioning of Br between gas and aerosol phases, 2) sea salt aerosol production from first-year versus multi-year sea ice, and 3) the impact of increased acidity in the atmosphere due to human activity in the Arctic.
Zooplankton and Micronekton products from the CMEMS Catalogue for better monitoring of Marine Resources and Protected Species
Authors: Lehodey Patrick , Titaud Olivier , Conchon Anna , Senina inna , Stum Jacques
Published: March 2020

Since 2019, the Copernicus Marine portfolio is providing a new model-based product on Zooplankton and Micronekton, representing the low and mid-trophic levels (LMTL) of the ocean food chain (Global Ocean low and mid trophic levels biomass multi year product: ). Zooplankton are organisms in the size range of less than 1 to a few millimeters (e.g., copepods) constituting prey of all fish larvae and small pelagic fish species (e.g herring, sardines and anchovies). Micronekton are also relatively small but actively swimming organisms such as crustaceans, fish, and cephalopods that are typically about 1 to 10 centimeters in size. Micronekton are prey of large fish and other oceanic predators. They are also predators of fish larvae. Therefore, zooplankton and micronekton distributions are key explanatory variables to understand fish recruitment mechanisms, individual behaviour of satellite tracked individuals of protected species (e.g., marine turtles, seabirds, sharks and marine mammals), and dynamics of large populations of fish species either targeted by fisheries (mackerel, tuna, swordfish, etc.) or strictly controlled in by-catch (e.g., bluefin tuna or sharks). The product includes 2-dimensional (latitude-longitude) maps of biomass for zooplankton and groups of micronekton on a weekly basis from 1998 to 2018 at a 25 km horizontal resolution. It is a model-based estimation of micronekton biomass, relying on the most possible realistic forcings (temperature, currents and primary production) assimilating satellite and in situ data. Continuous progress in the development and validation of these new models and products will help to reduce our knowledge gaps and will also support the Science & Climate sector as zooplankton and micronekton are key to better quantifying the carbon uptake and storage in the ocean, known as the “biological carbon pump”.
Coordinating sustained coastal and ocean observing efforts in Germany
Authors: Jochumsen Kerstin , Bachmayer Ralf , Baschek Burkard , Brandt Angelika , Fritz Jan-Stefan , Gaye Birgit , Janssen Felix , Karstensen Johannes , Kraberg Alexandra , Martinez Pedro , Vink Annemiek , Zielinski Oliver
Published: March 2020

Germany’s national ocean observing activities are carried out by multiple actors including governmental bodies, research institutions, and universities, and miss central coordination and governance. A particular strategic approach to coordinate and facilitate ocean research has formed in Germany under the umbrella of the German Marine Research Consortium (KDM). KDM aims at bringing together the marine science expertise of its member institutions and collectively presents them to policy makers, research funding organizations, and to the general public. Within KDM, several strategic groups (SGs), composed of national experts, have been established in order to strengthen different scientific and technological aspects of German Marine Research. Here we present the SG for sustained open ocean observing and the SG for sustained coastal observing. The coordination effort of the SG’s include (1) Representing German efforts in ocean observations, providing information about past, ongoing and planned activities and forwarding meta-information to data centers (e.g., JCOMMOPS), (2) Facilitating the integration of national observations into European and international observing programs (e.g. GCOS, GOOS, BluePlanet, GEOSS), (3) Supporting innovation in observing techniques and the development of scientific topics on observing strategies, (4) Developing strategies to expand and optimize national observing systems in consideration of the needs of stakeholders and conventions, (5) Contributing to agenda processes and roadmaps in science strategy and funding, and (6) Compiling recommendations for improved data collection and data handling, to better connect to the global data centers adhering to quality standards.
Instability in Himalayan Rock Slope under Recurrent Freeze-Thaw
Authors: Sardana Sahil , Sinha Rabindra Kumar , Jaswal Mamta , Verma Amit Kumar , Singh Trilok Nath
Published: March 2020

The highways in the Himalayas region have an important concern as these are the only connecting corridors to the nearby land area. Manali-Leh highway is one such important route in India which is interrupted frequently by landslides and rockslides events due to freeze-thaw activity, earthquake, heavy rainfall and anthropogenic activities are major triggering factors. In the freeze-thaw activity, water enters into the cracks in rocks during rainfall, subsequently, it freezes, leads to enlargement of cracks and/or the initiation of new cracks due to the volumetric expansion of ice. In the summer season, the ice melts and water migrates to the newly generated cracks and later freezes in the winter season. This, in turn, weakens the rock structure that leads to the reduction of the rock mass strength which promotes instability in the rock slopes. This study focuses on the stability assessment of rock slope along the highway from Solang Valley in Himachal Pradesh, India. This highway connects the Solang Valley to the south portal of the Rohtang tunnel and provides all-weather connectivity, as the Manali-Leh highway shut down during the winter season due to heavy snowfall.

An extensive geotechnical survey was carried out on the studied slope and the rock samples were collected from the field. The artificial freeze-thaw environment was created in the laboratory for the rock specimens to account the natural freeze-thaw effect. Laboratory tests were conducted on the rock specimen conditioned with freeze-thaw to determine the physico-mechanical parameters of intact rock prior to the numerical simulation. The results indicate the significant loss in compressive and tensile strength of rock as the number of freeze-thaw cycles increases. A three-dimensional numerical modelling was performed to assess the stability of the rock slope using the Distinct Element Code (3DEC software). Slope geometry was prepared to represent the actual slope and the various discontinuity sets observed at the field was mapped on the model. The behaviour of the discontinuity sets was modelled using a Mohr-Coulomb slip with residual strength. Normal stiffness of the joints was calculated from rock mass deformation modulus, intact rock young’s modulus and joint spacing. Similarly, the shear stiffness was calculated. The results of numerical modelling show that the displacement of blocks increases and the factor of safety of the slope decreases as the number of freeze-thaw cycles increases.
Nanotephra in environmental archives – method development for single-particle multi-element fingerprinting in tephrochronology
Authors: Schüürman Jan , Tepe Nathalie , Daxer Christoph , Huang Jhy-Jaan Steven , Strasser Michael , von der Kammer Frank , Hofmann Thilo
Published: March 2020

Nano-scale volcanic ash particles (nanotephra) are produced during explosive volcanic eruptions. They can travel laterally above the tropopause for thousands of kilometers before returning to Earth’s surface. Within a short time, they will aggregate, settle, and end up in sedimentary sinks, such as lakes and oceans, and might be used as a tephrochronological age marker. These ultra-distal tephra deposits can be highly diluted by geogenic or biogenic background sedimentation. Consequently, the identification of nanotephra in these environmental archives poses an immense analytical challenge. A new generation of time-of-flight mass spectrometers (TOF-MS) can deliver particle specific multi-element information providing the analytical prerequisite to tease out a signal of trace amounts of nanotephra among a majority of background nanoparticles.

Here, we present the first single-particle geochemical data of Eyjafjallajökull nanotephra, Iceland. The sub-micron particles were separated from bulk reference ash collected close to the eruption site and measured in a single-particle inductively coupled plasma TOF-MS. We tested their identification based on trace element heterogeneities in a mixture of tephra and sediment from Millstätter Lake, Austria, serving as a model archive deposition. We are developing this method to identify the source eruption of nanotephra deposited in lake sediment and thereby allow for better dating of the corresponding layer.
Influence of sudden stratospheric warmings on the polar vortex enhancement related to energetic electron precipitation
Authors: Asikainen Timo , Salminen Antti , Maliniemi Ville , Mursula Kalevi
Published: March 2020

The northern polar vortex experiences considerable inter-annual variability, which is also reflected to tropospheric weather. Recent research has established a link between polar vortex variations and energetic electron precipitation (EEP) from the near-Earth space into the polar atmosphere, which is mediated by EEP-induced chemical changes causing ozone loss in the mesosphere and stratosphere. However, the most dramatic changes in the polar vortex are due to sudden stratospheric warmings (SSW), a momentary breakdown of the polar vortex associated to enhanced planetary wave convergence and meridional circulation. Here we consider the influence of SSWs on the atmospheric response to EEP in 1957-2017 using combined ERA-40 and ERA-Interim re-analysis data and geomagnetic activity as a proxy of EEP. We find that the EEP-related enhancement of the polar vortex and other associated dynamical responses are seen only during winters when a SSW occurs, and that the EEP-related changes take place slightly before the SSW onset. We show that the atmospheric conditions preceding SSWs favor enhanced wave-mean-flow interaction, which can dynamically amplify the initial polar vortex enhancement caused by ozone loss. These results highlight the importance of considering SSWs and sufficient level of planetary wave activity as a necessary condition for observing the effects of EEP on the polar vortex dynamics.
A convolutional neural network for nowcasting rainfall intensities at fine temporal and spatial scales
Authors: Shehu Bora , Gerchow Malkin , Haberlandt Uwe
Published: March 2020

The short term forecast of rainfall intensities for fine temporal and spatial resolutions, has always been challenging due to the unpredictable nature of rainfall. Commonly at such scales, radar data are employed to track and extrapolate rainfall storms in the future. For very short lead times, the Lagrange persistence can produce reliable results up to 20 min whilst for longer lead times hybrid models are necessary, in order to account for the birth, death and non-linear transformations of storms that might increase the predictability of rainfall. Recently, data driven techniques, are gaining popularity due to their high learning skills, although their performance is highly dependent on the size of the training dataset and don’t include any physical background. Thus the aim of this study is to investigate the use of data driven techniques in increasing the predictability of rainfall forecast at very fine scales.

For this purpose, a deep convolutional artificial neural network (CNN) is employed to predict rainfall intensities at 5min and 1km2 resolutions for the Hannover radar range area at lead times from 5min to 3 hours. The deep CNN is trained for each lead time based on a past window of 15 minutes. The training dataset consist of 93 events (convective, stratiform and mixed events) from the period 2003-2012 and the validating dataset of 17 convective events from the period 2013-2018. The performance is assessed by computing the correlation and the root mean square error of the forecasted fields from the observed radar field, and is compared against the performance of an existing Lagrange-based nowcast method; the Lucas-Kanade optical flow. Special attention is given to the quality of the radar input by using a merged product between radar and gauge data (100 recording stations are used) instead of the raw radar one.  

The results of this study reveal that the deep CNN is able to learn complex relationship and improve the nowcast for short lead times. However there is a limit that a CNN cannot pass; for those lead times a blending of the radar based nowcast with NWP might be more desirable. Moreover, since most urban models are validated on gauge observations, forecasting on merged data yields more reliable results for urban flood forecasting as the forecast agrees better with the gauge observation.
Changes in soil conservation service and its driving factors: case studies in global top five largest basins
Authors: An Yiming , Zhao Wenwu
Published: March 2020

Soil conservation service is an important regulating ecosystem service. We estimated the soil conservation rate of the top five largest basins in the world from 2000 to 2018, classified the trend of conservation rate for each basin and each location as four types (i.e., significant decrease, decrease, increase and significant increase), and analyzed the relationships between soil conservation rate and driving factors. Results show that the Yangtze River basin produces the highest average soil conservation rate (with the value of 1429.68 t ha-1 yr-1). The Yangtze, Mississippi and Yellow River basins show a generally increasing conservation trend. Partial principal component analysis between soil conservation rate and driving factors show that slope gradient has the greatest impact on soil conservation rate, followed by rainfall and NDVI. Vegetation greening (increasing NDVI) could partly offset the effect of increasing rainfall on soil conservation rate in the Mississippi and Yellow River basins. More direct and quantitative variables should be used to represent human activities to analyze the impact on soil conservation change.
Impact of climate change on biome distribution and productivity of the tropical ecosystems under RCP scenarios in South Asia
Authors: Kumar Dushyant , Pfeiffer Mirjam , Gaillard Camille , Langan Liam , Martens Carola , Scheiter Simon
Published: March 2020

South Asia is one of the world’s most vulnerable regions to climate change and provides a home to approximately 1.7 billion people. South Asian vegetation is essential for ecosystem services, biodiversity and carbon storage in the region. Vegetation distribution and biome niches are likely to be severely altered by future climate change and rising atmospheric CO2 concentration. Assessing how ecosystems will respond to these changes is of vital importance. We used the aDGVM2 to simulate vegetation patterns of South Asia under RCP4.5 and RCP8.5. We found good agreement between observed and simulated biomass, height and potential vegetation maps. 

Model results show that large areas are susceptible to biome shift by the end of the 21st century. Woody encroachment is predicted in open savanna regions which are at high risk of transitioning into forest. We simulated vegetation under both scenarios with fixed CO2 concentration and found decreased tree dominance and biomass. Simulations under elevated CO2 concentrations predicted an increase in biomass, canopy cover, tree height and decrease in evapotranspiration. Changes in above ground biomass and canopy cover trigger biome shifts toward trees dominated the system. C3 vegetation is not saturated at current CO2 concentrations as the model simulated strong CO2 fertilization effect which will increase further with the rising CO2. Although there is considerable uncertainty in the biome projections, the geographic patterns of biomes are generally consistent across the RCP4.5 and RCP8.5 scenarios. The results provide potential future trajectories of the response of South Asian vegetation to the climate change. The results will help to understand the regional climate-vegetation interaction and to develop regional strategies for biodiversity conservation to cope with climate change. 
Seismic stratigraphy and tectonic structure from a long multi-channel seismic profile across the southern of South China Sea
Authors: zhaocai wu
Published: March 2020

In order to grasp the Cenozoic extension and tectonic deformation characteristics of the crust in the southern of the South China Sea, a newly acquired multi-channel seismic profile (DZ02) acrossing the conjugate continental margin of the Southwest Subbasin, Nansha block, and Nansha Trough is explained. Four stratigraphic units (syn-rift unit, drift unit1, drift unit2 and post-rift unit) were determined with six sequence boundaries (Tg, T70, T60, T40, T20, T10). Based on the differences in tectonic units and the features of stratigraphic and structural in the southern of the South China Sea, it is divided into five structural belts from northwest to southeast, which are the northern continental margin extension zone, the Southwest Subbasin, the Nansha intracontinental extension zone, the Nansha forebulge zone, and the Nansha trough. The fault derived and whole crustal extension factors of the Nansha block are also calculated. The results show that in time, the Nansha block has undergone two phases of extension, namely the syn-rift period and the seafloor spreading period. The syn-rifting stage accounted for about 69% of the total extension, and the seafloor spreading stage of the South China Sea accounted for about 26%. In space, the whole crust extension factor is greater than the fault derived extension factor in most areas. By comparing with the multi-channel seismic profile of the eastern part of the Nansha block imply that the crustal extension process is synchronous, but the extent of the extension in the western of Nansha is always greater.
The VEI 2 Christmas 2018 Etna Eruption: A small but intense eruptive event or the starting phase of a larger one?
Authors: Calvari Sonia , Bilotta Giuseppe , Bonaccorso Alessandro , Caltabiano Tommaso , Cappello Annalisa , Corradino Claudia , Del Negro Ciro , Ganci Gaetana , Neri Marco , Pecora Emilio , Salerno Giuseppe G. , Spampinato Letizia
Published: March 2020

The Etna flank eruption started on 24 December 2018 lasted a few days and involved the opening of an eruptive fissure, accompanied by a seismic swarm and shallow earthquakes, and by large and widespread ground deformation especially on the eastern flank of the volcano. Lava fountains and ash plume from the uppermost eruptive fissure have accompanied the opening stage causing disruption of Catania international airport, and have been followed by a quiet lava effusion within the barren Valle del Bove depression until 27 December. This is the first flank eruption occurring at Etna in the last decade, during which eruptive activity was confined to the summit craters and resulted in lava fountains and lava flow output from the crater rims. In this paper we use ground and satellite remote sensing techniques to describe the sequence of events, quantify the erupted volumes of lava, gas and tephra, and assess volcanic hazard.
Glacier surface elevation changes in Rongbuk Catchment of the Central Himalayas in the last four decades
Authors: Ye Qinghua , Nie Wei , Chen Yimin , Li Gang , Tian lide , Zhu Liping , Kargal Jeff S
Published: March 2020

Glaciers in the central Himalayas are important water resources for the downstream habitants, and accelerating melting of the high mountain glaciers speed up with continuous warming. We summerized the geodetic glacier surface elevation changes (Dh) by 6 data sets at different time periods during 1974-2016 in RongbukCatchment(RC) on the northern slope of Mt. Qomolangma (Mt. Everest) in the Central Himalayas. The result showed that glacier Dh varied with altitude and time, from -0.29 ± 0.03m a-1 in 1974-2000, to -0.47 ±0.24 m a-1 in 1974-2006,and -0.48 ±0.16 m a-1 in 1974-2012. Dh increased to -0.60 ± 0.20 m a-1 in 2000-2012, then decreased to-0.46 ± 0.24 m a-1 in 2000-2014, and by -0.49 ± 0.08 m a-1 in 2000-2016, showing a diverse rate being up - down- a little up. However, it generally presented a similar glacier thinning rate by -0.46~-0.49 m a-1 in the last four decades since 1970s in RC according to Dh1974-2006, Dh1974-2012, Dh2000-2014, and Dh2000-2016. Local meteorological observations revealed that, to a first order, the glacier thinning rate was kept the same pace with the number of annual melting days (MD). In spite of the obviously arising summer air temperature (TS) in 2000-2014, a slowdown glacier melting rate by -391 mm w.e.a-1 occurred in 2000-2014 because of less melting days with more precipitation and less annual mean temperature(Tm). It shows that MD is another important indicator and controlling factor to evaluate or to estimate glacier melting trend, especially in hydrological or climate modeling.
A downward counter-factual climate risk analysis of the impact of tropical cyclones in the Caribbean islands
Authors: Ciullo Alessio , Romppainen-Martius Olivia , Strobl Eric , Bresch David
Published: March 2020

Climate risk analysis and assessment studies are typically conducted relying on historical data. These data, however, represent just one single realization of the past, which could have unfolded differently. As an example, Hurricane Irma might had struck South Florida at Category 4 and, had it done so, damages could have been as high as 150 billion, about three times higher than damage estimated from the actual event. To explore the impacts of these potentially catastrophic near-misses, downward counter-factual risk analysis (Woo, Maynard and Seria, 2017) complements standard risk analysis by exploring alternative, plausible realization of past climatic events. As downward counter-factual risk analysis frames risk in an event-oriented manner, corresponding more closely to how people perceive risk, it is expected to increase climate risk awareness among people and policy makers (Shepherd et al., 2018).

We present a counter-factual risk analysis study of climate risk from tropical cyclones on the Caribbean islands. The analysis is conducted using the natcat impact model CLIMADA (Aznar-Siguan and Bresch, 2019). Impact is estimated based on forecasts of past tropical cyclones tracks from the THORPEX Interactive Grand Global Ensemble (TIGGE) dataset, as they all represent plausible alternative realizations of past tropical cyclones. The goal is to study whether, and to what extent, the estimated impacts from forecasts provide new insights than those provided by historical records in terms of e.g. cumulated annual damages, maximum annual damages and, in so doing, perform a worst-case analysis study to support climate risk management planning.

Aznar-Siguan, G. and Bresch, D. N.: CLIMADA v1: a global weather and climate risk assessment platform, Geosci. Model Dev., 12, 3085-3097, doi.org/10.5194/gmd-12-3085-2019, 2019.

Woo, G., Maynard, T., and Seria, J. Reimagining history. Counterfactual risk analysis. Retrieved from: https://www.lloyds.com/~/media/files/news-and-insight/risk-insight/2017/reimagining-history.pdf, 2017.

Shepherd, T.G., Boyd, E., Calel, R.A. et al.: Storylines: an alternative approach to representing uncertainty in physical aspects of climate change. Climatic Change 151, 555–571, doi.org/10.1007/s10584-018-2317-9 , 2018.
How grass contributes to controlling hillslope erosion
Authors: Pan Chengzhong , Ma Lan
Published: March 2020

The aim of this study was to investigate how the spatial distribution of grass influenced run-off and erosion from a hillslope with loess and cinnamon soils in the rocky area of Northern China. We set up a trial to test the two soils with different treatments, including bare soil (BS), grass strips on the upper (UGS) and lower (DGS) parts of the slope, grass cover over the entire slope (GS), and a grass carpet on the lower part of the slope (GC), under simulated rainfall conditions. The results showed that the run-off coefficients for the loess and cinnamon soils decreased by between 4% and 20% and by between 2% and 37%, respectively, when covered with grass. Grass spatial distribution had little effect on the run-off, but more effect on erosion than vegetation coverage degree. The most effective location of grass cover for decreasing hillslope erosion was at the foot, and the high efficiency was mainly due to controlling of rill formation and sediment deposition. The soil loss from GS, DGS, and GC on the loess and cinnamon soils was between 77% and 93% less and 55% and 80% less, respectively, compared with the loss from BS. However, the soil characteristics had little effect on soil erosion for well-vegetated slopes. The results highlight the importance of vegetation re-establishment at the foot of hillslope in controlling soil erosion.
Simulation of sediment transportation on Natorsa Creek by RiverFlow2D and SRH-2D
Authors: Su Po-Nien
Published: March 2020

In recent years, two-dimensional sediment transportation on movable bed models have been widely used in hydraulic engineering. Because of different assumptions, each model has its own feasibility on specified issues and areas. The SRH-2D model is an implicit method of the finite-volume method without CFL stability conditions, and requires more calculations than the explicit one at each time step. On the other hand, RiverFlow2D is an explicit method of finite-volume method with CFL conditions and saves much more time. In order to compare the results from these two software, a case study of Natorsa Creek, Kaohsiung, Taiwan, is carried out on the sensitivity analysis and different structure setups associated with rainfall data, water level record and DTM. The principle results are as following: This study uses average absolute error (MAE) and mean square root error (RSML) to investigate the sensitivities of SRH-2D and RiverFlow2D models and finds out the operation time increased with shorter time interval. Although SRH-2D supports three formulas while RiverFlow2D supports ten, it takes more factors into account like secondary flow, sediment size distribution, and the bed armoring effect. The simulation of scour-and-fill condition by these two models has shown similar result. However, there still exists small discrepancy between software simulation and field investigation.
New insight on the paleoclimatic evolution in the Boreal Realm at the onset of the Early Cretaceous chalk sea
Authors: Blok Carlette , Fantasia Alicia , Anderskouv Kresten , Ineson Jon , Edvardsen Niklas , Adatte Thierry , Bodin Stéphane
Published: March 2020

During the Albian, the open marine carbonate production underwent a profound revolution with the onset of the dominance of planktonic production in the total carbonate budget. This led to the deposition of vast amounts of chalk across the world’s Oceans as a result of the accumulation of large amounts of nannoplankton. The worldwide Upper Cretaceous white chalks are however not the first true chalks (i.e. deposits dominated by calcareous nannofossils) to be recorded in Earth’s History. Already during the Barremian, chalks were deposited in the North Sea Central Graben. These chalks did not extend until the Albian, since a ‘nannoconid crisis’ occurred at the onset of the early Aptian OAE-1a, with the deposition of an organic-rich marlstone layer named the Fischschiefer. To better understand if climatic changes have governed the occurrence of the Barremian true chalks and the switch to organic-rich marlstones during OAE-1a, we have reconstructed the evolution of climate in the North Sea Basin based on clay mineral assemblages. Clay mineral composition and distribution are proven indicators of paleo­climate and evolution of a basin as the formation of clay minerals in soils depends on the climate under which it develops. Hence, based on high-resolution clay mineral data from various cores from the North Sea, a paleoclimatic reconstruction of the late Hauterivian to early Aptian stratigraphic interval is proposed. Based on a long-term decrease of kaolinite content, a trend toward aridification is observed during the late Barremian, concordant with the development of the first true chalks. A sharp increase in kaolinite content is recorded at the onset of OAE-1a, with its highest peak occurring towards the end of the event. This suggest that a significant increase in humidity accompanies the unfolding of OAE-1a in the North Sea Basin. Further investigation is needed to confirm the hypothesis that paleoclimatic changes in the Boreal Realm are responsible for the onset of chalk deposition and the change in clay mineral assemblages.
A Study on Rigorous Combination of GNSS and VLBI Observations
Authors: Herrera Pinzón Iván Darío , Rothacher Markus
Published: March 2020

The ITRF is realized through the combination of the individual solutions (station coordinates and velocities) of the four space geodetic techniques. This combination features two main aspects: 1) precise local ties, to establish the link among techniques, and 2) full variance-covariance information of each solution, to account for the accuracy of each technique. Although this approach strives to obtain accurate geodetic products, this combination is not entirely "rigorous'', especially when it comes to the Earth Orientation Parameters (EOPs). In the current realization of the ITRF only polar motion (x-pole and y-pole) are combined, whereas UT1-UTC and nutation offsets and rates are taken from the solution of a single technique (VLBI). Furthermore, parameters such as troposphere delays and clock offsets are not part of the combination strategy. Thus, a rigorous estimation of the ITRF, with consistent EOPs and with appropriate tropospheric and clock ties, is still a challenge to be met.

To achieve a rigorous combination, all parameter types common to more than one space geodetic observation technique should be combined including their full variance-covariance information as well as the corresponding ties. In particular, as both, GNSS and geodetic VLBI, are based on microwave frequencies, their physical models and their parameter types are closely related. These common parameters are the site coordinates and velocities, troposphere estimates, EOPs and (possibly) clock estimates. Thus, using the data from the CONT17 campaign as a case study, we discuss the processing scheme, the challenges and initial results of a rigorous combination of VLBI and GNSS observations, in order to estimate and densify EOPs, particularly diurnal and sub-diurnal variations for polar motion and UT1-UTC, and to realize an inter-technique tropospheric tie, thus remedying the deficiencies mentioned above. The results obtained constitute an important step towards the realization of a rigorous ITRF solution that is able to improve the accuracy and consistency of all geodetic products.
Solar wind interaction with the lunar surface: Observation of energetic neutral atoms on the lunar surface by the Advanced Small Analyzer for Neutrals (ASAN) instrument on the Yutu-2 rover of Chang'E-4.
Authors: Wieser Martin , Barabash Stas , Wang Xiao-Dong , Zhang Aibing , Wang Chi , Wang Wenjing
Published: March 2020

A fraction of up to 20% of the solar wind impinging onto the lunar surface is reflected as energetic neutral atoms back to space, as established by remote sensing, e.g. by the SARA instrument on Chandrayaan-1 or by IBEX. Mapping of these reflected energetic neutral atoms to the surface opened a new way to remotely study the solar wind precipitation onto the surface. However, the high reflection rate remained an enigma given the high porosity of the lunar regolith, but no measurements directly on the surface were available.

With the Advanced Small Analyzer for Neutrals (ASAN) mounted on the Yuyu-2 the rover of Chang'E-4, for the first time measurements of the energetic neutral atom flux originating from the lunar surface were preformed directly on the lunar surface itself. ASAN measures with a single angular pixel the energy spectrum of energetic neutral atoms reflected or sputtered form the surface with coarse mass resolution. ASAN uses the mobility of the rover to cover different solar wind illumination angles and scattering angles from the surface.

Since the landing of Chang'E-4 in the Von Kármán crater on the lunar far side in January 2019, ASAN has spent more than one year on the lunar surface and performed typically two measurement sessions per lunar day with nominal performance.

We review the ASAN instrument status and operations; present energy and mass spectra of energetic neutral atoms backscattered and sputtered from the surface, and discuss sputtering yields observed during different observation sessions. We put these observations into context of earlier remote sensing data by the SARA instrument on Chandrayaan-1.
Penman and Priestley-Taylor approaches in Atmospheric Boundary-Layer Dynamics
Authors: Yin Jun , Porporato Amilcare
Published: March 2020

By linearizing the saturation water vapor curve, Penman (1948) not only found the famous explicit approximation of wet-surface evaporation but also obtained a less well-known expression of surface temperature. Here the latter has been taken into the slab model of Atmospheric Boundary Layer (ABL) to derive multiple analytical approximations of ABL dynamics, which share the features of the Penman equation with evaporation driven by energy and drying power of the air. Noticing that these two parts of evaporation are proportional to each other within the Priestley-Taylor approximation at sub-daily timescale, a unified framework is obtained that links the Penman approach and Priestley-Taylor method to the diurnal behaviors of ABL. The resulting model is useful for diagnosing the land-atmosphere interactions.
Imaging segmentation in early stage rifting (prior to breakup) using a joint inversion of Rayleigh waves from teleseisms and ambient noise tomography in the northern East African Rift
Authors: Chambers Emma L. , Harmon Nicholas , Keir Derek , Rychert Catherine , Gallacher Ryan
Published: March 2020

Within the melt-rich northern East African Rift system, extension progresses from continental rifting in the Ethiopian rift to near continental breakup in Afar. Multiple models have been proposed to understand the evolution of lithospheric stretching and magmatism, but previous studies do not provide a single absolute seismic velocity model of the crust and upper mantle for all stages of the rift. Here we jointly invert surface waves from ambient noise and teleseismic Rayleigh waves to obtain shear velocity maps from 10 to 210 km depth, enabling us to analyse variations in crustal and upper mantle shear wave velocity structure spatially and in depth. Using one model allows us to interpret and understand the pattern of crustal and lithospheric thinning from the rift flanks into the rift, the depth and locus of melt generation, and how these processes vary as a rift evolves towards incipient seafloor spreading.

We observe in areas unaffected by rifting, a fast lid (>0.1 km/s faster than surroundings) at lithosphere-asthenosphere-boundary depths (~60 - 80 km). The fast-lid is not visible directly beneath the rift and we instead observe slow velocities (slow enough to contain partial melt (3.95 – 4.10 ± 0.03 km/s)), which we interpret as evidence for melt infiltration into the uppermost mantle beneath the rift. In addition, the fast lid thins into the rift, until it is no longer observed, suggesting the rift is more stretched than the surrounding plate (~18% thinner). The slow velocities in the asthenosphere beneath the rift are segmented, ~110 km wide, ~60 – 120 km deep with ~70 km spacing between segments.  The shallowest and slowest anomalies occur beneath Afar, which is at later stage rifting. At crustal depths we observe a broadening in the slow velocity zones along the length of the Main Ethiopian Rift. Furthermore, the slow crustal velocities laterally spread to beneath areas of the Ethiopian Plateau that were affected by flood basalt volcanism (velocities of 3.30 – 3.80 ± 0.04 km/s). We interpret the broadening of the slow velocity as the Moho acting as a barrier causing lateral migration of melt into areas of pre-existing weakness. Our model provides the first comprehensive seismic model of the northern East African Rift allowing us to interpret rift structure. The segmented slow velocities in the asthenosphere suggest discrete melt-rich upwelling may drive the early the breakup process, with shallowing of the top of the melt-rich zone as the rift evolves and the lithosphere is modified by melt infiltration, with the Moho and lithosphere thinning later in the rifting process.
Analysis of the diurnal evolution of atmospheric ammonia over the Paris megacity from ground-based and satellite remote sensing
Authors: Kutzner Rebecca D. , Cuesta Juan , Chelin Pascale , Petit Jean-Eudes , Hase Frank , Orphal Johannes , Blumenstock Thomas , Schneider Matthias , Viatte Camille , Clerbaux Cathy
Published: March 2020

Ecosystems and human health are directly affected by atmospheric ammonia, by unbalancing the vegetation nutrient cycle and causing respiratory troubles both directly and through the formation of fine particles. In Europe, agricultural practices are the dominant source of atmospheric ammonia. It is released to the atmosphere by volatilization of fertilizer applied to soils and decay of organic matter. Then, it reacts with acids (such as sulphuric, nitric and chlorine acids) or nitrogen oxides (all produced in high concentrations from anthropogenic activities) to produce ammonium aerosols, whose concentrations over Europe and Paris megacity are particularly high during springtime pollution events, as occurred in 2014 and 2015.

Difficulties for measuring ammonia by in situ techniques are induced by its polarity, which causes accumulation in inlets and sampling tubes. Remote sensing is therefore a valuable alternative method to measure ammonia, without direct interaction with the sample. Measurements of ammonia total atmospheric columns using the OASIS observatory are routinely made in the Paris suburbs since 2009 using a medium spectral resolution BRUKER Fourier transform infrared spectrometer. Spectra of radiation emitted by the sun and absorbed by the atmosphere were recorded every 10 minutes, under clear sky conditions, enabling the observation of the diurnal evolution of ammonia concentrations.

Our work provides a new analyse of the diurnal evolution of ammonia over the Paris megacity during springtime pollution events. For this, we use measurements of total atmospheric columns of ammonia derived from the ground-based OASIS observatory for the first time and from satellite approaches, such as that from IASI and other available satellites. Furthermore, this study takes into account the influence of meteorological conditions and atmospheric chemical composition, of gaseous and particulate phases, from surface measurements simultaneously performed at Palaiseau, in the Paris region.
Characterization of fracture networking and connectivity: Insights from Discrete Fracture Network Model and Multi-Scale analysis from the Buxa Dolomite of the Main Boundary thrust sheet, Siang widow, Arunachal Himalayan Fold thrust belt
Authors: Ahmed Farzan , Bhattacharyya Kathakali
Published: March 2020

Fracture systems develop at different stages of progressive deformation and are often genetically associated with folding. The frontal Main Boundary thrust (MBT) sheet is folded in a fault bend fold (Ahmed et al., 2018) and is exposed in Siang window in far eastern Arunachal Himalayan fold-thrust belt (FTB). The Buxa dolomite of the Lesser Himalayan sequence forms part of the MBT sheet and records four different sets of fractures (Basa et al., 2019). We present results from Discrete Fracture Network (DFN) model from the Buxa dolomite. Integrating fold test, cross-cutting, offset and abutting relationships, we have established that the low-angle fracture set (0°-20°) formed as a result of early layer parallel shortening.  These low-angle and the two sets of medium angle fractures (20°-60°) formed prior to the fault-bend folding. The late stage, high-angle fractures (60°-90°) developed synchronous to the fault-bend fold (Basa et al., 2019). We model the fractures formed before and during the folding event using 3D MOVE’s Fracture Modeling module to evaluate how the properties of secondary porosity and permeability, induced by fracture sets, fracture area/unit volume (P32) and overall connectivity are affected by the folding event. The input parameters of fracture orientation, intensity, length and aperture were measured from the field. For the aspect ratio, theoretical value of 1:2 (Olding, 1997; Olson, 2003) was considered.

Results from DFN analysis indicate that the average porosity increases from pre-folding (model-1) (~0.0028) to syn- to post-folding (model-2) (~0.0071). The permeability also increases from ~231 Darcy in model-1 to ~3988 Darcy in model-2. There is also a significant rise in P32 (~2.8m2/m3 to ~4.3m2/m3) value from model-1 to model-2. The late high-angle fracture set led to increase in overall connectivity, including porosity, permeability and fracture intensity. This is also corroborated from the field results that reveal high-angle fractures are more conducive to vein formation (~41%) compared to the lower angle fracture-sets (~15 %).