bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionospheric precursors of earthquakes from satellites
Authors: De Santis Angelo , Campuzano Saioa A. , Cianchini Gianfranco , Di Mauro Domenico , Marchetti Dedalo , Orlando Martina , Perrone Loredana , Piscini Alessandro , Sabbagh Dario , Soldani Maurizio , Shen Xuhui , Zhima Zeren
Published: March 2021

In-situ magnetic field and electron density, as observed by Swarm and CSES satellites, are analyzed to identify possible anomalies in geomagnetic quiet time with respect to the ionospheric background. To avoid detecting possible anomalies induced by auroral activity we investigate regions between +50 and -50 degrees in magnetic latitude. Then a superposed epoch and space approach is applied to this anomaly dataset with respect to their time and space distance from shallow M5.5+ earthquakes occurred in about last 6 years. A comparison with analogous homogeneous random distribution of anomalies shows that the real anomaly concentrations found before the occurrence of earthquakes are statistically significant. In addition, we find that, in general, the anticipation times of the ionospheric precursors scale with the earthquake magnitude, confirming the validity of the Rikitake law for ionospheric signals, previously valid for ground precursors. We also find that the anomaly duration seems to depend on the magnitude of the impending earthquake. Finally, we propose a simple scheme of potential earthquake forecast on the base of the previously mentioned characteristics.
In situ microplastics ingestion by Antarctic marine benthic invertebrates
Authors: Hurley Jessica , Hardege Jorg , Wollenberg Valero Katharina C. , Morley Simon
Published: March 2021

Microplastics have been recognised as persistent marine contaminants and mounting evidence supports their designation as anthropogenic stressors to marine organisms. Despite the remoteness of Antarctica, microplastics contamination has been reported in every marine environment investigated in this area to date. Due to ocean currents and frontal systems, microplastics may become entrapped within polar regions and increase bioavailibilty to inhabiting fauna. Antarctic marine benthic invertebrates represent a research priority due to their sensitivity to change as well as contribution to ecological functioning and food webs. The current study investigated microplastics ingestion by the epifaunal, carnivorous polychaete Barrukia cristata and the infaunal, filter-feeding bivalve, Laternula elliptica. Animals were collected by SCUBA adjacent to Rothera research station, Adelaide Island. After digestion in 10 % potassium hydroxide (KOH) followed by filtration, microplastics ingested by individual animals were separated. Microplastics were then counted and characterised by shape, colour, size and polymer type by Micro-Fourier transform Infrared spectroscopy. Polyethylene terephthalate (PET) was the most abundant polymer type, followed by polyacrylonitrile (PAN) and ethylene-vinyl acetate (EVA). Congruent to earlier reports, fibres were found to be the most abundant source of microplastics contamination. However, it must be highlighted that fragments were also recovered from the animals analysed. Results determined the current level of microplastics ingestion by two benthic marine invertebrates of different feeding strategies in coastal environments of the Antarctic Peninsula. These findings indicated the bioavailability of microplastics and highlighted the potential of trophic transfer throughout the Antarctic marine food web.
Large-scale interseismic deformation along the Altyn Tagh Fault determined from Sentinel-1 InSAR
Authors: Shen Lin , Hooper Andy , Elliott John , Wright Tim
Published: March 2021

The 1600 km-long Altyn Tagh Fault (ATF) is a major intra-continental strike-slip fault along the Northern Tibetan Plateau, the slip rate of which has significant implications for our understanding of the present-day tectonic processes of the Tibetan Plateau region. We present an interseismic velocity field along ~1500 km length of the fault, derived from Sentinel-1 interferograms spanning the period between late 2014 and 2019. It is the first time such a large-scale analysis has been carried out for this fault with Interferometric Synthetic Aperture Radar (InSAR).

Using a modified elastic half-space model, we find significant strain accumulation along the 1500 km length of the ATF, at a relatively fast rate of ~10 mm/yr and quite localised along the fault. The results indicate an eastward decrease of the slip rate along the fault from 11.6 ± 1.0 mm/yr to 7.5 ± 1.2 mm/yr over the western portion to the central portion, whereas it increases again to 11.1 ± 1.1 mm/yr over the eastern portion. Furthermore, the results suggest that no significant creeping occurs along the fault.

We find a high slip rate of 11.5 ± 1.0 mm/yr along the south-western segment of the ATF, a region not typically covered by previous studies, is transferred to the structurally linked left-lateral strike-slip Longmu-Gozha Co Fault. It demonstrates that the generation of the NS-trending normal faulting events in this region, such as the 2008 Mw 7.2 Yutian earthquake, is ascribed to the EW-trending extensional stress at the Ashikule step-over zone between the two left-lateral faults. We also find a high surface shear strain rate greater than 0.4 μstrain/yr in this region, which could be caused by the stress loading effects of the recent seismic activities.

To investigate the pattern of strain localisation along the ATF, we fit a shear zone model to the derived long-term InSAR velocity field. Inverting for shear zone width reveals two broad shear zones along the ATF, where the strain is distributed over multiple strands rather than concentrated on a single narrow strand. The broad shear zones explain the high estimates of the locking depth found when using the elastic half-space model and also off-fault seismic activity on the strands away from the ATF in these areas. The results also show a relatively wider shear zone from the central portion eastward, where the ATF breaks into three parallel strands. 

This study suggests that a slip deficit of around 1 m has been accumulated along the ATF over the last century, and indicates that the fault is capable of rupturing with the potential for a magnitude 7.5 or larger earthquake.
GOES High cadence Operational Total Irradiance: planned data products
Authors: Snow Martin , Beland Stephane , Coddington Odele , Penton Steven , Woodraska Don
Published: March 2021

The GOES-R series of satellites includes a redesigned instrument for solar spectral irradiance: the Extreme ultraviolet and X-ray Irradiance Sensor (EXIS).  Our team will be using a high-cadence broadband visible light diode to construct a proxy for Total Solar Irradiance (TSI).  This will have two advantages over the existing TSI measurements:  measurements are taken at 4 Hz, so the cadence of our TSI proxy is likely faster than any existing applications, and the observations are taken from geostationary orbit, so the time series of measurements is virtually uninterrupted.  Calibration of the diode measurements will still rely on the standard TSI composites.  

The other measurement from EXIS that will be used is the Magnesium II core-to-wing ratio.  The MgII index is a proxy for chromospheric activity, and is measured by EXIS every 3 seconds.  The combination of the two proxies can be used to generate a model of the full solar spectrum similar to the NRLSSI2 empirical model.

We are in the first year of a three-year grant to develop the TSI proxy and the SSI model, so only very preliminary findings will be discussed in this presentation.
Patterns of postglacial vegetation establishment clarified by lacustrine sedaDNA from Baffin Island, Arctic Canada
Authors: Crump Sarah E. , Power Matthew , Fréchette Bianca , de Wet Gregory , Raynolds Martha K. , Raberg Jonathan H. , Allentoft Morten , Bunce Michael , Miller Gifford H.
Published: March 2021

The colonization of recently deglaciated landscapes by tundra vegetation during the early Holocene is an important case study for understanding possible rates and patterns of plant migration in a rapidly warming world. Fossil pollen in lake sediment has traditionally served as the primary tool for reconstructing paleovegetation and understanding postglacial biogeography. However, because pollen can be wind-transported long distances and, in some cases, reworked from older deposits on the landscape, pollen-based vegetation histories can sometimes obscure the true history of plant colonization. In contrast, lacustrine sedimentary ancient DNA (sedaDNA) is sourced locally and is less likely to be adequately preserved through reworking events, thus making it a more reliable proxy for determining the precise timing of plant colonization. Here, we present three sedaDNA records from Holocene lake sediment across southern Baffin Island, Arctic Canada, that clarify the timing of postglacial vegetation changes. In particular, DNA from the subarctic shrub Betula (dwarf birch) first appears thousands of years after deglaciation in all three lake catchments, suggesting delayed colonization despite its strong pollen signal in early postglacial sediments. While moderate levels of Alnus (alder) pollen characterize early to mid-Holocene lake sediments from the region, sedaDNA suggests that Alnus was likely not present in any of the three lake catchments during the Holocene. In addition, aquatic plant community changes indicated by sedaDNA faithfully reflect the timing of early Holocene warmth in the region, highlighting the potential utility of aquatic plant DNA as a qualitative temperature proxy. We suggest that ancient plant DNA in lake sediment provides key paleoecological information that is distinct from traditional proxy records, particularly during periods of relatively rapid ecological change like the early Holocene. 
Native bacteria and cyanobacteria consortia improve seedling emergence and establishment in dryland restoration
Authors: Dadzie Frederick , Moles Angela , Erickson Todd , Munoz-Rojas Miriam
Published: March 2021

Seed-based ecosystem restoration has huge potential to restore degraded lands but currently less than 10 % of directly sown seeds successfully establish in drylands. Soil microbial communities are important for improving plant establishment in degraded land. However, current methods such as soil translocation can potentially disturb the donor site. In this study, we investigated a novel non-destructive method for improving seedling growth of native plants used in restoration through seed-soil-microbial pelleting. We assessed seedling emergence and survival of Triodia epactia and Acacia inaequilatera seeds inoculated with whole soil bacteria and cyanobacteria consortia retrieved and isolated from a pristine ecosystem. A field experiment was set-up in a 35m x 40m purpose-built rain exclusion shelter that contained reconstructed soil profiles typically encountered in mine rehabilitation programs of Australia’s arid north-west. We hypothesized that inoculated seed-soil pellets would improve seedling emergence and survival of these species. After three weeks of planting, seedling emergence in microbially inoculated Acacia inaequilatera and Triodia epactia were 48% and 55% higher than non-inoculated seeds in bacteria and cyanobacteria, respectively. We also tested whether the use of cyanobacteria consortia as inocula promoted higher seedling emergence over whole soil bacteria. We found that there was no significant difference in seedling emergence between the microbial taxa. We show that, improving the diversity of soil microorganisms improves seedling emergence and the seed-soil pellet method used is viable to improve seed-based restoration outcomes.

Key words: Seed-based restoration, microbial community, cyanobacteria, bacteria community, seedling emergence.
CAMELS-AUS: Hydrometeorological time series and landscape attributes for 222 catchments in Australia
Authors: Fowler Keirnan , Chandra Acharya Suwash , Addor Nans , Chou Chihchung , Peel Murray
Published: March 2021

Large samples of catchments are becoming increasingly important to gain generalisable insights from hydrological research.  Such insights are facilitated by freely available large sample hydrology datasets, with one example being the CAMELS (Catchment Attributes and Meteorology for Large-sample Studies) series of datasets.  Here we present CAMELS-AUS, the Australian edition of CAMELS. CAMELS-AUS comprises data for 222 unregulated catchments, combining hydrometeorological timeseries (streamflow and 18 climatic variables) with 134 attributes related to geology, soil, topography, land cover, anthropogenic influence, and hydroclimatology. The CAMELS-AUS catchments have been monitored for decades (more than 85 % have streamflow records longer than 40 years) and are relatively free of large scale changes, such as significant changes in landuse. Rating curve uncertainty estimates are provided for most (75 %) of the catchments and multiple atmospheric datasets are included, offering insights into forcing uncertainty. This dataset, the first of its kind in Australia, allows users globally to freely access catchment data drawn from Australia's unique hydroclimatology, particularly notable for its large interannual variability. Combined with arid catchment data from the CAMELS datasets for the USA and Chile, CAMELS-AUS constitutes an unprecedented resource for the study of arid-zone hydrology. CAMELS-AUS is freely downloadable from and the corresponding paper is available at https://essd.copernicus.org/preprints/essd-2020-228/.
 Can the 1.5 deg C warming target be met in a global transition to 100% renewable energy? 
Authors: Schwartzman David , Schwartzman Peter
Published: March 2021

Can the 1.5 deg C warming target still be met with an aggressive phaseout of fossil fuels coupled with a 100% replacement by renewable energy?  We address this question in our modeling study by computing the continuous generation of global wind/solar energy power along with the cumulative carbon dioxide equivalent emissions in a complete phaseout of fossil fuels over a 20 year period. We assume a baseline of energy status at 2018, as well as the EROI of currently available wind/solar energy technologies.  We compare these computed emissions with the state-of-the-science estimates for the remaining carbon budget of carbon dioxide emissions consistent with the 1.5 deg C warming target. Our conclusion is that it is still possible to meet this warming target if the creation of a global 100% renewable energy transition of sufficient capacity begins very soon, coupled with aggressive negative carbon emissions. The latter technology uses a fraction of total renewable energy delivery for direct air capture for permanent crustal storage over the last ten years of this energy transition that is compatible for simulations with no more than 10 to 15 % reinvestment of renewable energy to make more of itself. More efficient renewable technologies in the near future will make this transition easier.  The maximum amount of fossil fuel consumed in our scenarios for the complete transition is no more than 5% of the proven reserves of coal, natural gas and oil as currently estimated.  

 

 
Atmospheric processes in the Central Arctic during MOSAiC
Authors: Shupe Matthew , Rex Markus ,   MOSAiC Atmosphere team
Published: March 2021

The atmosphere plays a central role in the Arctic climate system and its recent changes. Enhanced Arctic atmospheric warming over the past decades is linked with many key processes, including variability in large-scale circulation patterns, changes in fluxes of heat, sea-ice decline, impacts on the ecosystem, and many more. It is this collection of interdependent processes, and their recent changes, that has motivated the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC, 2019-2020) expedition. Based on the Polarstern icebreaker, an international and interdisciplinary team of scientists conducted an intensive, year-long scientific exploration of the Central Arctic climate system while drifting with the sea ice. This presentation highlights the atmospheric components of this scientific expedition. These include the most comprehensive set of field observations to ever be made of the Central Arctic atmosphere, spanning from the stratosphere to the surface. Specific research activities examine atmospheric structure, winds, clouds, precipitation, aerosols, and surface fluxes of heat, momentum, gases, and moisture. Complementing these observational aspects are numerous modeling activities, including observation-based model assessment, model development, and regional process studies, among others. Finally, key links between the atmosphere and the sea ice, snow, and ocean through a variety of physical, chemical, and biological processes are discussed.
UAV-LiDAR observations increase the precision of urban flood modelling in Accra by detecting critical micro-topographic features
Authors: Trepekli Katerina , Friborg Thomas , Balstrøm Thomas , Fog Bjarne , Allotey Albert , Kofie Richard Yao , Møller-Jensen Lasse
Published: March 2021

Rapidly expanding cities are exposed to higher damage potential from floods, necessitating effective proactive management using technological developments in remote sensing observations and hydrological modelling.  In this study we tested whether high resolution topographic data derived by Light and Detection Ranging (LiDAR) and Unmanned Aerial Vehicle (UAV) systems can facilitate rapid and precise identification of high-risk urban areas, at the local scale. Three flood prone areas located within the Greater Accra Metropolitan Area in Ghana were surveyed by a UAV-LiDAR system. In order to simulate a realistic flow of precipitation runoff on terrains, Digital Terrain Models (DTM) including buildings and urban features that may have a substantial effect on water flow pathways (DTMb) were generated from the UAV-LiDAR datasets. The resulting DTMbs, which had a spatial resolution of 0.3 m supplemented a satellite-based DTM of 10 m resolution covering the full catchment area of Accra, and applied to a hydrologic screening model (Arc-Malstrøm) to compare the flood simulations. The precision of the location, extent and capacity of landscape sinks were substantially improved when the DTMbs were utilized for mapping the flood propagation. The semi-low resolution DTM projected unrealistically shallower sinks, with larger extents but smaller capacities that consequently led to an overestimation of the runoff volume by 15% for a sloping site, and up to 65 % for 1st order sinks in flat terrains. The observed differences were attributed to the potential of high resolution DTMbs to detect urban manmade features like archways, boundary walls and bridges which were found to be critical in predictions of runoff’s courses, but could not be captured by the coarser DTM. Discrepancies in the derived water volumes using the satellite-based DTM vs. the UAV-LiDAR DTMbs were also traced to dynamic alterations in the geometry of streams and rivers, due to construction activities occurring in the interval between the aerial campaign and the date of acquisition of the commercially available DTM. Precise identification of urban flood prone areas can be enhanced using UAV-LiDAR systems, facilitating the design of comprehensive early flood-control measures, especially in urban settlements exposed to the adverse effects of perennial flooding. This research is funded by a grant awarded by the Danish Ministry of Foreign Affairs (Danida).
Soil-N cycling in temperate alley cropping agroforestry and monoculture croplands
Authors: Bischel Xenia , Corre Marife D. , Schmidt Marcus , Veldkamp Edzo
Published: March 2021

Monoculture croplands are commonly associated with deleterious environmental effects due to high fertilization rates. Agroforestry (alternate alleys of trees and crops or alley cropping) has the potential to mitigate the negative environmental effects from agriculture. Understanding the soil-N cycling aids in assessing how the soil function of nutrient cycling is impacted when monoculture system is converted into agroforestry. Currently, there is no systematic comparison in soil-N cycling rates between monoculture and agroforestry croplands in Western Europe. Our study aimed to investigate gross rates of soil-N cycling between agroforestry and monoculture croplands. We measured gross rates of soil-N cycling, using 15N isotopic pool dilution in May-June 2017, at three sites in Germany (Wendhausen, Dornburg, and Forst with Vertic Cambisol, Calcaric Phaeozem, Gleyic Cambisol soils, respectively); each site has paired monoculture and agroforestry systems (established in 2008, 2007, and 2010 at the respective sites). In each management system at each site, we had four replicate plots; for agroforestry system, we conducted measurements in the tree row and within the crop row at 1 m, 4 m, and 7 m from the tree row. The crop management practices in agroforestry crop row and monoculture were the same at each site.

For gross rates of ammonium cycling, differences were observed between agroforestry tree row, crop row and monoculture at the site with Vertic Cambisol soil. Higher gross N mineralization rates were observed in monoculture than agroforestry tree row whilst agroforestry tree row exhibited higher gross NH4+ immobilization rates than agroforestry crop row (P < 0.02). This was correlated to higher soil C/N ratio and higher water-filled pore space in the tree row. Tree rows also tend to have higher microbial biomass at all sites. Gross rates of nitrate cycling were higher in the tree row than in the crop row and monoculture at the site with Calcaric Phaeozem soil. This showed a similar pattern with the gene abundance of ammonium oxidizing archeae (AOA), supporting a niche differentiation of AOA by utilizing ammonium mineralized from soil organic matter rather than from fertilizer source. At the site with Vertic Cambisol soil, dissimilatory nitrate reduction to ammonium was very high in the tree row. These changes in soil-N cycling and AOA gene abundance in the tree rows suggest that trees in sites with older agroforestry systems had enhanced the cycling of N in the soil.
Investigation of strain localization in sheared granular material using 3D numerical discrete element model
Authors: Hung Chien-Cheng , Niemeijer Andre , Raoof Amir , Swijen Thomas
Published: March 2021

We used three-dimensional numerical simulations of the discrete element method (DEM) to investigate slip localization in sheared granular faults under seismic velocities. An aggregate of non-destructive spherical particles with assigned contact properties is subjected to direct shear with periodic boundary in horizontal directions. To investigate whether particle size distribution (PSD) influences slip accommodation, three distinct PSDs, namely Gaussian, log-normal, and power-law with fractal dimension D ranging from 0.8 to 2.6, are employed. In additional simulations, we impose a thin layer of particles with smaller grain size along the boundary as well as in the middle of the granular assemblages to simulate boundary and Y shears occurring in both natural and laboratory fault gouges. Transient microscopic properties, such as particle motion and contact forces, as well as macroscopic properties, such as friction, of the granular layer, are continuously monitored during numerical shearing. Results show that no visible slip localization is observed for all different PSDs based on the current particle motion analysis. On the other hand, we find that much more strain (i.e., displacement) is accommodated in the finer-grained layer even with a small contrast in grain size. Up to 90 % of the displacement is localized in a finer-grained layer when the contrast ratio of the grain size is 50 %. Since more frictional heat will be generated in the localized slip zone, the results provide crucial information on the heat generation and associated slip accommodation in sheared gouge zones. A possible mechanism of slip localization in the simulations is the transfer of the momentum across the granular system. We conclude that the occurrence of a weaker, fine-grained layer within a dense fault zone is likely to result in self-enhanced weakening of the fault planes.  Ongoing work includes (1) varying the thickness, grain size, and internal friction of the thinner layer; (2) applying triangulation methods to further analyze the microscale stress and strain tensor between particles; (3) changing the rolling friction of particles.
Phosphorus limit to the CO2 fertilization effect in tropical rainforests as informed from a coupled biogeochemical model
Authors: Wang Zhuonan , Tian Hanqin , Pan Shufen , Shi Hao , Yang Jia , Kalin Latif , Anderson Christopher , Liang Naishen
Published: March 2021

Tropical rainforests play an important role in sequestering carbon (C) and mitigating climate warming. Many terrestrial biosphere models (TBMs) estimate productivity increase in tropical rainforests due to the CO2 fertilization effect. However, most TBMs neglect phosphorus (P) limitation on tropical rainforest productivity. Here, we used a process-based Dynamic Land Ecosystem Model with coupled C-N-P dynamics (DLEM-CNP) with varied Vcmax­25 to examine how P limitation has affected C fluxes of tropical rainforests to environmental and anthropogenic factors, including N deposition, land-use changes, climate variability, and atmospheric CO2, during 1860-2018. The model results showed that consideration of the P cycle reduced the response of tropical rainforests gross primary production (GPP) by 25% and 39%, net primary production (NPP) by 25% and 43%, and net ecosystem production (NEP) by 21% and 41% to the CO2 fertilization effect relative to CN-only and C-only models. The DLEM-CNP estimated that the tropical rainforests had a GPP of 41.1 + 0.5 Pg C year-1, NPP of 19.7 + 0.3 Pg C year-1 and NEP of 0.44 + 0.34 Pg C year-1 under 1860-2018 environmental conditions. Factorial experiments with DLEM-CNP suggested that deforestation has stronger impacts on GPP and NPP reduction compared to the enhanced GPP and NPP benefiting from the CO2 fertilization effect. Additionally, tropical rainforests NEP showed a continuously increasing trend owing to the CO2 fertilization effect. Our study highlights the importance of P limitation on the C cycle and the weakened CO2 fertilization effect due to nutrients limitation in the tropical rainforests.
A constraint to thermal conductivity of Earth’s core and CMB heat flow by assessment on a stable region of Earth’s core
Authors: Nakagawa Takashi , Takehiro Shin-ichi , Sasaki Youhei
Published: March 2021

It is still controversial for an emergence of a stable region at the top of Earth’s core in theoretical modeling because both thermal conductivity of Earth’s core and heat flow across the core-mantle boundary (CMB) have not been clearly constrained from mineral physics and geophysical observations, ranging 20 to 220 W/m/K for the thermal conductivity (denoted as ) and 5 to 20 TW for the present-day CMB heat flow (denoted as QPCMB). In this study, in order to resolve these uncertainties, we try to constrain the values of thermal conductivity of Earth’s core and the present-day CMB heat flow by requiring continuous generation of geomagnetic field in addition to existence of a stable region at the top of present Earth’s core using a one-dimensional thermal and compositional evolution model.  

Numerical experiments for various values of  and QPCMB show that the solutions satisfying both long-term magnetic field generation and emergence of a stable region is possible only when  is larger than 40 W/m/K and QPCMB is less than 18.5 TW. The specific required value of depends on QPCMB. If the expected CMB heat flow would be as large value as 17.5 TW, which is suggested by the recent studies on the core evolution theory (e.g., Labrosse, 2015),  should be a high value such as about 212 W/m/K to satisfy our requirements. The thickness of an expected stable region would be about 30 km in this case. In contrast, when QPCMB is as small as that derived from numerical mantle convection models (e.g., 10 TW; Nakagawa and Tackley, 2010), the required value of  decreases to 110 W/m/K. In this case, a stable region extends about 75 km thickness below CMB.

If the requirements assumed in this study is confirmed by certain geophysical observations and/or QPCMB can be restricted more precisely with some methods, our assessment scheme would be useful for evaluations of the radial convective structure of Earth’s core and for further constraint of the value of thermal conductivity of Earth’s core.
Application of Ground Penetrating Radar combined with 222Rn (Radon) measurements  for serch geological faults in Mexicali Baja California, Mexico
Authors: Lazaro-Mancilla Octavio , Ramirez-Hernandez Jorge , Reyez-López Jaime Alonso
Published: March 2021

The City of Mexicali and its Valley are located within the San Andrés fault system, a geological fault system generated by the activity of the Pacific and North American tectonic plates, as boudary plates the principal Faults are Imperial Fault and Cerro Prieto Fault. We present our results related to the search o traces of geological faults using ground penetrating radar combined with Radon gas ( 222Rn) measurements in the Instituto Tecnológico de Mexcali inner the urban area and Mexicali Valley.As extension of this studies we apply this approach to the urban area of Morelia City in Mexico.
Field evidence of autocatalytic iodine release from atmospheric aerosol
Authors: Tham Yee Jun , He Xu-Cheng , Li Qinyi , Cuevas Carlos A. , Ceburnis Darius , Maier Norbert M. , O’Dowd Colin , Dal Maso Miikka , Saiz-Lopez Alfonso , Sipilä Mikko ,   Mace Head Study Team
Published: March 2021

Reactive iodine plays a key role in determining the oxidation capacity of the atmosphere in addition to being implicated in the formation of new particles in the marine environment. Recycling of reactive iodine from heterogeneous processes on sea-salt aerosol was hypothesized over two decades ago but the understanding of this mechanism has been limited to laboratory studies and has not been confirmed in the atmosphere until now. Here, we report the first direct ambient observations of hypoiodous acid (HOI) and heterogeneous recycling of iodine monochloride (ICl) and iodine monobromide (IBr) at Mace Head Observatory in Ireland (53°19’ N, 9°54’ W) during the summer of 2018. A newly developed bromide based chemical ionization atmospheric pressure interface time-of-flight mass spectrometer (Br-CI-APi-TOF) was deployed to measure I2, HOI, ICl, and IBr. Significant levels of ICl and IBr, with mean daily maxima of 4.3 and 3.0 pptv (1 min-average), respectively, have been observed throughout the campaign. We show that the heterogeneous reaction of HOI on marine aerosol and subsequent production of iodine interhalogens (ICl and IBr) are much faster than previously thought. These results indicate that the fast formation of iodine interhalogens, together with their rapid photolysis, results in more efficient recycling of atomic iodine than currently estimated by the models. The photolysis of the observed ICl and IBr leads to 32% increase in the daytime average of atomic iodine production rate, thereby enhancing the average daytime iodine-catalyzed ozone loss rate by 10-20%. Our findings provide the first direct field evidence that the autocatalytic mechanism of iodine release from marine aerosol is important in the atmosphere and can have significant impacts on atmospheric oxidation capacity and new particle formation in the troposphere.
Ecosystem health assessment in coastal China
Authors: Hu Ziyuan , Sun Xiaoxia , Sun Song
Published: March 2021

Marine ecosystem health assessments are instrumental in ocean governance and the development and use of oceans and seas, provide an important scientific basis for the protection of marine ecosystems and environment and ecological management, and help us move forward on a range of issues related to the marine environment and resource protection. In this study, we improved the coastal ecosystem health assessment methodology by studying combined traits of the coastal ecosystems such as structure, services, and functions. We performed a number of assessments jointly conducted in different coastal areas in China, analyzing the current status and variation trends of these coastal ecosystems, comparing their key health elements, and investigating major contributing factors to changes in the state of marine ecosystems. The present study provided a scientific basis for the protection of marine ecosystem management by translating monitoring, observation, and research results into information that can be understood easily by policymakers.
When image correlation is needed: combining very dense radar-amplitude and optical times series for unravelling the complex dynamics of a not so slow slow-moving landslide in the tropics
Authors: Dille Antoine , Kervyn François , Handwerger Alexander , d’Oreye Nicolas , Derauw Dominique , Mugaruka Bibentyo Toussaint , Samsonov Sergey , Malet Jean-Philippe , Kervyn Matthieu , Dewitte Olivier
Published: March 2021

Slow-moving landslides exhibit persistent but non-uniform motion at low rates which makes them exceptional natural laboratories to study the mechanisms that control the dynamics of unstable hillslopes. Here we leverage 4.5+ years of satellite-based radar and optical remote sensing data to quantify the kinematics of a slow-moving landslide in the tropical rural environment of the Kivu Rift, with unprecedented high spatial and temporal resolution. We measure landslide motion using sub-pixel image correlation methods and invert these data into dense time series that capture weekly to multi-year changes in landslide kinematics. We cross-validate and compare our satellite-based results with very-high-resolution Unoccupied Aircraft System topographic datasets, and explore how rainfall, simulated pore-water pressure, and nearby earthquakes control the overall landslide behaviour. The landslide exhibited seasonal and multi-year velocity variations that varied across the landslide kinematic units. While rainfall-induced changes in pore-water pressure exerts a primary control on the landslide motion, these alone cannot explain the observed variability in landslide behaviour. We suggest instead that the observed landslide kinematics result from internal landslide dynamics, such as extension, compression, material redistribution, and interactions within and between kinematic units. Our study provides, a rare, detailed overview of the deformation pattern of a landslide located in a tropical environment. In addition, our work highlights the viability of sub-pixel image correlation with long time series of radar-amplitude satellite data to quantify surface deformation in tropical environments where optical data is limited by persistent cloud cover and emphasize the importance of exploiting synergies between multiple types of data to capture the complex kinematic pattern of landslides.
Why rogue waves occur atop abrupt depth transitions
Authors: van den Bremer Ton , Li Yan , Draycott Samuel , Zheng Yaokun , Lin Zhiliang , Adcock Thomas
Published: March 2021

Abrupt depth transitions have recently been identified as potential causes of `rogue' or extreme ocean waves. When stationary and (close-to) normally distributed waves travel into shallower water over an abrupt depth transition, distinct spatially localized peaks in the probability of extreme waves occur. These peaks have been predicted numerically, observed experimentally, but not explained theoretically. Providing this theoretical explanation using a leading-order-physics-based statistical model, we show the peaks arise from the interaction between linear free and second-order bound waves, also present in the absence of the abrupt depth transition, and new second-order free waves generated due to the abrupt depth transition.
The 4DGreenland project: Greenland hydrology assessment from remote sensing
Authors: Sandberg Sørensen Louise ,   4DGreenland team
Published: March 2021

The high latitudes of the Northern Hemisphere have experienced the largest regional warming over the last decades. On the Greenland ice sheet, rapid changes are observed in response to temperature increase, with the amount of liquid water at the surface particularly increasing. Understanding Greenland’s ice sheet hydrology is essential to assess  its contribution to global sea-level rise in a future warming climate.

With the objective of maximizing the use of Earth Observation (EO) data, the European Space Agency (ESA) has funded the 2-year project 4DGreenland (https://4dgreenland.eo4cryo.dk/) to assess and quantify the hydrology of the Greenland ice sheet. The project is focused on dynamic variations in the hydrological components of the ice sheet, and on quantifying the water fluxes between reservoirs including surface melt, supraglacial lakes and rivers, and subglacial melt and lakes. Efforts will focus on a thorough analysis of various components of the hydrological network in selected test regions and their impact on ice sheet flow. 4DGreenland started in September 2020. Here, we will present the project objectives, methods, and show initial results obtained within the project such as a comparison of supraglacial lake depths from optical imagery and ICESat-2 altimetry data, estimation of basal melt water production, and identification and mapping of surface meltwater presence and subglacial lakes from EO data.

 
Green manuring shifted the effects of crop rotation on soil EEAs activities in the Loess Plateau of China
Authors: Tao Haining , Deng Jianqiang , Li Yuan
Published: March 2021

Green manuring and crop rotation are important management practices with the potential to reduce the dependence on mineral fertilizers and to maintain soil health. Soil extracellular enzyme activities (EEAs) serve as a proxy for estimating the availability and cycling of soil nutrients and thus widely used as biological indicators of soil health. However, the effects of green manure application under different crop rotations on soil EEAs remain unclear. Here, a 5-year field experiment (2015-2020) was conducted and two crop rotations were established in the Loess Plateau of China. Specifically, forage rape (Brassica napus L.) (R) or common vetch (Vicia sativa L.) (V) was cultivated during the fallow period (F) of monoculture system, winter wheat (Triticum astivum L.) (W). Aboveground biomass of R and V were harvest in September 2020 and 50% of the biomass was chopped and returned to the soil surface. Soil EEAs activities [β-glucosidase (BG), cellobiohydrolase (CBH), β-xylosidase (Xylo) (XYL), and N-acetyl-glucosaminidase (NAG)] at 0-5 cm were determined in September and October. Observed EEAs activities were strongly affected by the pattern of crop rotation and sampling time, with greater EEAs activities in W-V-W-V than in W-R-W-R in September. Whereas, EEAs activities was higher in W-R-W-R than in W-V-W-V in October, expert for BG that had no difference between two crop rotations. Overall, our study demonstrated that green manuring shifted the effects of crop rotation on soil EEAs activities in the topsoil in the Loess Plateau of China.

Keywords: Annual forage, Residue retention, Soil health, The Loess Plateau
Combination of GNSS and VLBI data for consistent estimation of Earth Rotation Parameters
Authors: Lengert Lisa , Flohrer Claudia , Girdiuk Anastasiia , Hellmers Hendrik , Thaller Daniela
Published: March 2021

We present the current activities of the Federal Agency for Cartography and Geodesy (BKG) towards a combined processing of VLBI and GNSS data.  The main goal of the combined analyses of the two different space-geodetic techniques is the improvement of the consistency between the techniques through common parameters, i.e., mainly Earth Rotation Parameters (ERPs), but also station coordinates and tropospheric parameters through local ties and atmospheric ties, respectively.

Based on our previous combination studies using GNSS data and VLBI Intensive sessions on a daily and multi-day level, we generate a consistent, low-latency ERP time series with a regular daily resolution for polar motion and dUT1. We achieved in this way a significant accuracy improvement of the dUT1 time series and a slight improvement of the pole coordinates time series, comparing ERPs from the combined processing with the individual technique-specific ERPs.

In our recent studies, we extend the combination of GNSS and VLBI Intensive sessions by adding VLBI 24-hour sessions in order to exploit the benefit of the combination to its maximum extend. We analyse the impact of the combination on the global parameters of interest, i.e., mainly dUT1, polar motion and LOD, but also on station coordinates.

BKG’s primary interest is the combination of GNSS and VLBI data on the observation level. However, the current combination efforts are based on the normal equation level using technique-specific SINEX files as a starting point.
Generating videos of synthetic river flow for the evaluation of image-based techniques for surface velocity determination
Authors: Bodart Guillaume , Le Coz Jérôme , Jodeau Magali , Hauet Alexandre
Published: March 2021

Several studies have been carried out to evaluate image-based solutions for velocity measurement and discharge determination in river. However, these studies are limited because it is difficult to know the reference surface velocity field accurately. These data are usually extrapolated from measurement within the water column or integrated over a cross-section to determine the discharge to be compared with a reference, which is uncertain itself. Measurement uncertainties are difficult to quantify and cannot be neglected usually.

The only solution that arises to get a flow with a known surface velocity reference is synthetic imaging: we generate artificial images on which particles movements are known everywhere. However, these generators must allow a comparison between simulations and measurements for a wide range of conditions representative of the situations observed in the natural environment. Several Synthetic Image Generators have been designed for laboratory PIV but the generated images are made of white particles moving on a dark background. Such images are not representative of river applications with turbulence figures, foam, debris, sunlight effects but also some homogeneous areas with poor contrast where we can sometimes see the river bed through.

We propose a novel method to generate images from a synthetic river scene with accurate surface velocity references. It is based on the 3D computer graphics tool Blender which integrates a dedicated fluid simulation tool, Mantaflow. Blender allows many different configurations by playing on the modeling of the river, the surrounding objects, the textures and optical properties of the materials but also on the lighting and the camera settings and position. Mantaflow is then used to model and extract the characteristics (velocities, positions in time) of a flow that looks similar to real-life situations. The first synthetic videos obtained were used to study the sensitivity of the velocity results to the image-based velocimetry algorithm, its parameters and user choices.
Variability in modelled airborne dust mineralogy derived from global soil composition uncertainties
Authors: Gonçalves Ageitos María , Dawson Matt , Obiso Vincenzo , Klose Martina , Miller Ron , Jorba Oriol , Pérez García-Pando Carlos
Published: March 2021

Dust aerosols consist on a variety of minerals with different physic and chemical properties. As such, they interact with short and long wave radiation, potentially form clouds, act as nutrients modulating biogeochemical cycles, or influence atmospheric chemistry, differently. Most current state-of-the-art Earth System Models (ESMs) neglect the complexity in dust composition, mainly due to computational constraints, but also to the existing uncertainties in the size resolved composition of parent soils, the resulting distribution of minerals in airborne dust, and the scarcity of observations to constrain them.

Within this work, we assess the variability of global dust composition due to uncertainties in the characterization of the parent soil mineralogy. To that end, we consider two available global soil mineralogy atlases, developed by Claquin et al. (1999) –C1999- and Journet et al. (2014) –J2014-, which represent respectively 8 and 12 relevant minerals for climate (namely: illite, smectite/montmorillonite, kaolinite, calcite, gypsum, hematite, quartz, and feldspars in C1999, and those plus chlorite, vermiculite, goethite, and mica in J2014). Thanks to a recently developed feature of the MONARCH atmospheric-chemistry model, we are able to explicitly resolve the minerals’ atmospheric cycle. Therefore, we define two global experiments to assess changes on airborne dust composition attributed to the soil mineralogy assumptions and provide a measure of their variability. We also perform a preliminary evaluation of the global mineralogy results against available observations of mineral fractions in surface dust concentration.

Our results will inform the climate modelling community about the potential variability in dust composition, an aspect that will gain relevance as ESMs continue growing in complexity and new processes to better characterize aerosols’ forcing or biogeochemical cycles are added. Further observational constraints, such as those that will derive from the EMIT NASA mission on soil composition or the FRAGMENT experimental campaigns on airborne dust characterization, will be key in the near future to improve our understanding of the impact of dust mineralogy on fundamental climate features.
Observations by the LOFAR radio telescope of a fast negative leader propagation mode
Authors: Scholten Olaf ,   LOFAR Lightning and Cosmic ray group
Published: March 2021

We report on recent observations made by the LOFAR radio-telescope of a fast propagation mode in negative leaders we named Rapid Negative Leader (RNL).
The RNL has a variety of properties that make them clearly distinct from negative leaders or dart leaders, such as -- fast propagation, -- emission of strong broad-band pulses, -- emission of very high VHF power, -- a reduced density of located sources, and -- terminating with the spawning of a large number of negative leaders in a small area. RNLs are almost always observed in the initial stage of a lightning flash, but may also occur much later. They may occur repeatedly in a certain part of the cloud.

We interpret a RNL as negative leader developing in strong electric field due to a relatively small highly-charged cloud, probably created by a local turbulence, with a typical size of order 5 km2.  The strong field will lead to a larger than usual charge at the leader tip resulting in an increased propagation velocity as well as a strongly enhanced emission of VHF power.
Since for the initiation of a lightning flash strong ambient electric fields are required, it is thus no surprise that the initial leader is in fact a RNL. 

What do you want to do ?

New mail

What do you want to do ?

New mail