bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Ionospheric Densities and Flows in Crustal and Draped Magnetic Fields at Mars
Authors: Renzaglia Antonio , Cravens Thomas , Fowler Christopher , Rahmati Ali , Sakai Shotaro , Connerney Jack , Benna Mehdi , Andersson Laila
Published: March 2020

NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) explorer has been in orbit around Mars for over 5 years now, collecting valuable data about the planet. Specifically, the Langmuir Probe and Waves (LPW), the Neutral Gas and Ion Mass Spectrometer (NGIMS), and the Suprathermal and Thermal Ion Composition (STATIC) instruments measure important ionospheric properties. The instruments measure electron densities and temperature (LPW), neutral gas and ion composition (NGIMS), and the properties of escaping ions (STATIC). Electron and ion density and flux measurements are presented. The data indicates significant differences in ion properties between open crustal, closed crustal, and draped magnetic fields. Similar differences are noted for electrons as well. An ionospheric model has been developed that produces a profile of the ionosphere. The model then explores the evolution of the ionosphere, via chemistry and transport. At low altitudes (z<300 km), chemistry dominates, while transport dominates at higher altitudes. Results show significant differences in the ionosphere between the types of fields. The model utilizes data from the Magnetometer (MAG) instrument to provide properties of magnetic fields at Mars. The model may also help explain some of the atmospheric loss occurring at Mars. This is compared to data from STATIC. Analytic arguments for subsonic vs supersonic flow speeds (in the open field case) are also presented.
Remote Sensing of Magnetic Fields Induced by Electrojets From Space: Measurement Techniques and Sensor Design Requirements
Authors: Yee Jeng-Hwa , Gjerloev Jesper , Merkin Viacheslav , Laundal Karl
Published: March 2020

The Zeeman effect of the O2 118 GHz spectral radiance measurements can be utilized to remotely measure the magnetic field perturbations at altitudes close to the auroral electrojets. The technique has been demonstrated using the measurements provided by the Microwave Limb Souncer onboard the Aura spacecraft.  The derived current-induced magnetic field perturbations were found to be highly correlated with those coincidently obtained by ground magnetometers and to be consistent with the well-known auroral electrojet current distribution thereby providing a strong argument for the validity of the technique. With today's technology, a 118 GHz instrument, can be miniaturized allowing it to fly on small satellites such as CubeSats.  A constellation of small satellites with each one carrying a number of these identical mini-radiometers would have the ability to provide simultaneous multipoint measurement of the magnetic field perturbations at altitudes close to the electrojet, thereby greatly advancing our understanding of the ionospheric current system.  In this paper, we present the Zeeman magnetic field sensing technique, the requirements and specifications of the instrument, and an example of a cost effectively cubesat mission that provides unprecedented measurements of the evolution and structure of the auroral electrojet system.
Controls of boundary conditions on accelerating turbidity currents in a reservoir: Case study of Xiaolangdi Reservoir on the Yellow River, China
Authors: Ma Hongbo , Parker Gary , Nittrouer Jeffrey , McElory Brandon , Wang Yuanjian , Chen Xingyu , Fu Xudong
Published: March 2020

Turbidity currents are a major way to transport sediment along reservoir, lake and sea beds. They are not fully understood yet due to the difficulty of accessibility. Theoretical criteria have been established for the conditions that generate accelerating turbidity currents, which can produce strong erosion of channel beds, transmit over long distances and thus have important significance for reservoir and sea bed morphology. However, the current theoretical criterion only utilizes local factors of hydraulic, morphology and grain size, which do not necessarily depend on the up- and down- stream boundary conditions. Here, we conducted field surveys on turbidity currents and bed morphology of the Xiaolangdi reservoir on the Yellow River, China. The survey results show clear evidence of accelerating turbidity currents. We identify two types of accelerating turbidity currents: one locates closely to the upstream plunging point where fluvial sediment-laden flow collapses to a stratified turbidity current, concentrating momentum and producing acceleration locally, and the other is located downstream and shows dependence on the enhancement of local slope and potentially on downstream boundary (flushing condition at flow outlets of the dam). So both ends of the boundaries may work together to produce long run-out turbidity currents that transmit through the entire reservoir.  Although preliminary, our dataset indicates that the conditions for accelerating turbidity currents are not only controlled by local morphology and grain size, but also by both upstream and downstream conditions. A comprehensive understanding of the boundary conditions so as to determine conditions for the generation of accelerating turbidity currents will help enhance the sustainability of the dam and reservoir system.
Multipoint observations of spatial and temporal characteristics of Pc 4-5 pulsations in the dayside magnetosphere and particle signatures.
Authors: Korotova Galina , Sibeck David , Engebretson Mark
Published: March 2020

We use  multipoint magnetic field, plasma  and particle observations to study the spatial, temporal  and spectral characteristics of Pc 4-5 pulsations   observed  in the recovery phase of a strong magnetic storm on January 1, 2016.   The magnetosphere was compressed and periodic increases of the total magnetic field strength occurred every 20-40 min at the times of generation of the pulsations.  The frequencies of the Pc4 pulsations varied  from 14 mHz to 25 mHz with radial distance. An explanation for this behavior can be given in terms of standing Alfvén waves along resonant field lines.  By contrast, Fourier analysis of the magnetic field observations  shows that the compressional  Pc5 pulsations  exhibited  similar spectra at different radial distances.  The long duration of the Pc5 pulsations and their nearly constant frequencies indicate that the plasma conditions in the morning sector of magnetosphere were stable for more than two hours.  The Pc4 and Pc5   pulsations displayed wave properties consistent with the second harmonic waves. The energetic particles   observed by Van Allen Probes and GOES 15  exhibited  a regular periodicity over a  broad range of energies from tens of eV to 2 MeV  with periods  corresponding to  those of the compressional component   of the  ULF magnetic field.   We searched for possible solar wind triggers and discussed generation mechanisms for the compressional Pc5 pulsations  in terms of drift mirror instability and  drift bounce resonance. 
Complementary numerical and experimental study in the baroclinic annulus for the microgravity experiment AtmoFlow
Authors: Szabo Peter , Zaussinger Florian , Haun Peter , Travnikov Vadim , Meier Martin , Egbers Cristoph
Published: March 2020

The experimental investigation of large-scale flows on atmospheric circulation and climate such as Earth, Mars or even distant exoplanets are of great interest in geophysics. Gaining the fundamental knowledge of the origin of planetary waves or global cell formation is interesting from a meteorological point of view but up till now difficult to reproduce in laboratory scale. The limitation is based on the central force field which may be induced by the dielectrophoretic effect. However, the established radial force field is overpowered by the gravitational field unless experiments are conducted in a microgravity environment. The AtmoFlow project provides the possibility to study convective flow patterns in a spherical shell under microgravity conditions, planned after 2022, on the International Space Station (ISS) and is in fact the follow-up experiment of the GeoFlow project which served between 2008 and 2016 on the ISS.

 

Without losing the overall focus of complex planetary atmospheres, the AtmoFlow experiment is able to model the intake and outtake of energy (e.g. radiation) and the rotational forcing via rotating or co-rotating boundaries. The gap is filled with a Fluor-based fluid with physical properties sensitive to temperature and electric fields. With an electric potential applied between the spherical shells a central force field is established that is based on the above mentioned dielectrophoretic effect. By adjusting rotation, thermal forcing and strength of the applied electric potential the AtmoFlow experiment can simulate different planetary atmospheres to investigate local pattern formation or global planetary cells. An interferometry system similar to the one used in the GeoFlow experiment uses the Wollaston shearing technique (WSI) to record the evolving temperature fields.

 

To provide a benchmark solution for the experimentally recorded WSI interferograms a ground experiment is used to develop a validation method and to find the best postprocessing method for the AtmoFlow experiment. The ground experiment consists of a thermally forced baroclinic wave tank with a corresponding WSI setup and an infrared (IR) camera that are used to record the evolving temperature field. Here, we present first numerical simulations of the ground experiment that include the formation of the convective wave patterns and the numerical evaluated interferograms and IR pictures. The numerical calculated data will then be compared to the experimental recorded data to find a technique to best process the recorded WSI interferograms of the AtmoFlow project.
Adaptive thinking and the global fire crisis
Authors: Bowman David
Published: March 2020

Vegetation fires are an ancient, powerful, and pervasive biogeophysical process that affects the Earth System through complex interactions and feedbacks. The evolution and geographic spread of fire-wielding hominins in the Pleistocene has led to drastic, and ongoing, changes to the Earth System, a syndrome captured by the Anthropocene concept. Contemporary fire regimes are increasingly causing detrimental social, environmental and economic impacts, driven by the interaction between climate change and inappropriate land management practices. Achieving global environmental sustainability demands rethinking the relationship of humans, landscapes and fire. This requires careful blending of transdisciplinary thinking, translational research practices, and incorporation of indigenous and local knowledge. 
Deadly coastal landslides and increased risk due to severe climatic events
Authors: Haque Ubydul , da Silva Paula F. , Soltani Arezoo
Published: March 2020

Deadly landslides are becoming more frequent and disruptive with increasingly severe weather events associated with a changing climate. These changes are putting coastal slopes under stress due to extreme climatic events that contribute to their instability by two processes: due to intense rainfall and also to important storm waves that rise to unusual heights in coastal areas affected by atmospheric depressions. This study was conducted in 83 coastal locations to investigate the climate-induced extreme rainfall, population density and detect the role of severity of hurricane/cyclone where deadly landslides reported worldwide since 1995 to 2018. The global landslide database was used to locate and analyze sea cliffs already under stress where deadly landslides are reported. The analysis was conducted using R (ver 3.5.1) and ArcGIS (ver 10.4.1) software. Population distribution, the severity of hurricanes/ cyclones and extreme rainfall proved the strongest predictor of deadly landslides in coastal areas particularly in the Caribbean and Southeast Asian countries. This research will help improve resilience and forecast future erosion and hot spots for cliff retreat and will contribute not only to our understanding of landslide processes associated with extreme weather events but will also enlighten decision-makers and help them manage the coastal changes in the near future.
Understanding and predicting species- and elevation-dependent dynamics in East Asian temperate forests
Authors: Kim Moonil , Strigul Nick , Rovenskaya Elena , Kraxner Florian , Lee Woo-Kyun
Published: March 2020

The velocity and impact of climate change on forest appear to be site, environment, and tree species-specific. The primary objective of this research is to assess the changes in productivity of major temperate tree species in South Korea using terrestrial inventory and satellite remote sensing data. The area covered by each tree species was further categorized into either lowland forest (LLF) or high mountain forest (HMF) and investigated. We used the repeated Korean national forest inventory (NFI) data to calculate a stand-level annual increment (SAI). We then compared the SAI, a ground-based productivity measure, to MODIS net primary productivity (NPP) as a measure of productivity based on satellite imagery. In addition, the growth index of each increment core, which eliminated the effect of tree age on radial growth, was derived as an indicator of the variation of productivity by tree species over the past four decades. Based on these steps, we understand the species- and elevation-dependent dynamics. The secondary objective is to predict the forest dynamics under climate change using the Perfect Plasticity Approximation with Simple Biogeochemistry (PPA-SiBGC) model. The PPA-SiBGC is an analytically tractable model of forest dynamics, defined in terms of parameters for individual trees, including allometry, growth, and mortality. We estimated these parameters for the major species by using NFI and increment core data. We predicted forest dynamics using the following time-series metrics: Net ecosystem exchange, aboveground biomass, belowground biomass, C, N, soil respiration, and relative abundance. We then focus on comparing the impact of climate change on LLF and HMF. The results of our study can be used to develop climate-smart forest management strategies to ensure that both LLF and HMF continue to be resilient and continue to provide a wide range of ecosystem services in the Eastern Asian region.
Improved numerical solvers for coupled chemistry-climate model simulations
Authors: Esenturk Emre
Published: March 2020

A key and expensive part of coupled atmospheric chemistry-climate model simulations is the integration of gas phase chemistry, which involves dozens of species and hundreds of reactions. These species and reactions form a highly-coupled network of Differential Equations (DEs). There exists orders of magnitude variability in the lifetimes of the different species present in the atmosphere and so solving these DEs to obtain robust numerical solutions poses a “stiff problem”. With newer models having more species and increased complexity it is now becoming increasingly important to have chemistry solving schemes that reduce time but maintain accuracy.

A sound way to handle stiff systems is by using implicit DE solvers but the computational costs for such solvers are high due to internal iterative algorithms (e.g., Newton-Raphson (NR) methods). Here we propose an approach for implicit DE solvers that improves their convergence speed and robustness with relatively small modification in the code. We achieve this by using Quasi-Newton (QN) methods. We test our approach with numerical experiments on the UK Chemistry and Aerosol (UKCA) model, part of the UK Met Office Unified Model suite, run in both an idealized box-model environment and under realistic 3D atmospheric conditions. The box model tests reveal that the proposed method reduces the time spent in the solver routines significantly, with each QN call costing 27% of a call to the full NR routine. A series of experiments over a range of chemical environments was conducted with the box-model to find the optimal iteration steps to call the QN routine which result in the greatest reduction in the total number of NR iterations whilst minimising the chance of causing instabilities and maintaining solver accuracy. The 3D simulations show that our method for the chemistry solver, speeds up the chemistry routines by around 13%, resulting in a net improvement in overall run-time of the full model by approximately 3% with negligible loss in the accuracy (relative error of order 10-7) . The QN method also improves the robustness of the solver by significantly reducing (40% ) the number of grid cells which fail to converge hence avoiding unnecessary timestep adjustments. 
Impact of the Korea Rapid Developing Thunderstorms (K-RDT) product nudging to the convective parameterization over the Korean Peninsula
Authors: Yeo Namgu , Chang Eun-Chul , Min Ki-Hong
Published: March 2020

In this study, Korea Rapid Developing Thunderstorms (K-RDT) product from geostationary meteorological satellite which represents developing stage of convective cells is nudged to the Simplified Arakawa Schubert (SAS) deep convection scheme using a simple nudging technique in order to improve prediction skill of a heavy rainfall caused by mesoscale convective system over South Korea in the short-term forecast. Impact of the K-RDT information is investigated on the Global/Regional Integrated Model system (GRIMs) regional model program (RMP) system. For the selected heavy rainfall cases, the control run without nudging and two nudging experiments with different nudging period are performed. Although the simulated precipitations in the nudging experiments tend to depend on the distribution of convective cells detected in the K-RDT algorithm, the nudging experiment shows improved precipitation forecast than the control experiment. Particularly, the experiment with nudging for longer time produces better prediction skill. The results present that the small-scale convective cells from the K-RDT which are detected with a 1-km resolution have clear impacts to large-scale atmospheric fields. Therefore, it is suggested that utilizing small-scale information of convective system in the numerical weather prediction can have critical impact to improve forecast skill when the model system, which cannot properly represent sub-grid scale convections.
Analysing the effectiveness of groundwater regulation: a comparative study of Turkey and California
Authors: Ak Muhammed Yasir , Benson David , Scott Karen
Published: March 2020

Groundwater abstraction has increased significantly around the world in the last three decades, placing a strain on the sustainability of domestic and agricultural use plus negatively impacting the role groundwater plays in water storage in the absence of surface water. While the proportionality of surface water use has decreased as a result, groundwater has expanded its share of freshwater use. Groundwater management challenges are particularly acute in semi-arid zones due to low replenishment rates. Multiple regulatory innovations are consequently emerging in different countries to regulate groundwater usage but comparative analyses of their effectiveness are limited. In addressing this gap, our paper therefore compares the regulatory performance of the Water Framework Directive (WFD) in Turkey with the Sustainable Groundwater Management Act (SGMA) in California, two semi-arid zones, as a basis for policy learning. Both legislative measures impose river basin planning to protect groundwater resources and should provide them with strong protection. In analysing the effectiveness of these measures, this paper firstly identifies the key regulatory requirements of each legislative framework regarding groundwater protection. Secondly, it compares the institutional arrangements for implementing them, using specific river basin case studies. Thirdly, it quantifies groundwater use trends in river basins to assess the effectiveness of the WFD and SGMA. Finally, it comparatively discusses outcomes to determine the factors influencing implementation effectiveness, in order to inform future regulatory design.
Sensitivity study of urban energy balance to albedo, emissivity and heat capacity in Seoul Metropolitan Area
Authors: Moon Byung-Kwon , Hong Seon-Ok , Byon Jae-Young , Ha Jong-Chul , Wie Jieun
Published: March 2020

As urban populations increase, urban heat island effect is enhanced and urban heat stress and air pollutant concentrations increase. Sensitivity experiments of changing the albedo, emissivity, and heat capacity of urban facets can provide information to mitigate the heat island effect and allow the model to study urban climate more accurately. Experiments on sensitivity of the surface energy balance of albedo, emissivity and heat capacity in the metropolitan area of ​​Seoul were conducted using Met-Office-Reading Urban Surface Exchange Scheme (MORUSES) of Unified Model Local Data Assimilation and Prediction (UM LDAPS) model. The analysis period is a heat wave period from July 15 to 21, 2018, which is a clear day without cloud and precipitation. Comparing 1.5-m temperature of AWS data, it overestimated about 0.5-2K in the model. If the albedo decreases, the net radiation, storage heat, sensible heat and ground heat fluxes increase after sunrise. Storage heat becomes negative in the afternoon, and sensible heat is positive during the night. When the albedo decreases, the air temperature increases. As the emission rate decreases, the air temperature increases as storage heat decreases and sensible, latent and geothermal heat increases, which is more intense at night than during the day. When heat capacity decreases, sensible and ground heat increase during the day, storage heat decreases, and vice versa at night. Air temperature increases during midday when solar radiation is strong and decreases elsewhere. Considering that the LDAPS-MORUSES model underestimates the air temperature, albedo and emission rates can be reduced to achieve more accuracy.

Acknowledgement: This research was supported by the Korea Meteorological Administration’s National Institute of Meteorological Sciences "Development of Biomechanical Meteorological Technology" (1365003004).
UAV-based digital image processing applied to the fossiliferous tanks prospection: insights at Guanambi region, northeast Brazil
Authors: Magalhães José , Pereira Gessica , Leão Alexsander , Scherer Carolina
Published: March 2020

This study reveals the use of high resolution images collected by small Unmanned Aerial Vehicle (UAV) and Digital Image Processing (DIP) from Structure from Motion (SfM) technique applied to the prospection and geometric characterization of fossil tanks in the Guanambi region, located at Bahia state, Brazil. Geologically, the region is located in the Guanambi Batolith, composed of granites, migmatites and orthognaisses. In the research region for example, there was the Lagoa das Abelhas fossiliferous tank, which was previously excavated and in which bone fragments of various pleistocene mammal taxa, such as those of the order Xenarthra, were found, represented by sloths, glyptodonts and armadillos. Considering that there are no records of an effective scientific method to identify these features, the main objective of this work is to map the distribution of fossiliferous tanks excavated as well as those with prospective potential, and to estimate the geometries that they present through the use of the high resolution DIP. The Phantom 4 Advanced equipped with RGB 1’’ CMOS effective 20 M sensor were the UAV model type and camera used for conducting the flight plan. The Pix4D Capture was the tablet/smartphone application used for conducting the flight operation and image collection in an area with ​​80 ha. After this step, the images were submitted as DIP routines using the SfM technique from the Agisoft Metashape software, version 1.5.1. The DIP is divided into stages like point cloud calculation, 3D models generation from mesh and texture procedures, digital elevation model (DEM) and orthomosaic. With the integration of images (DEM and orthomosaic) it was possible to identify and delineate a total of 14 targets through geometric information such as surface area, length, width, depth and internal format. The configuration in relation to soil type, vegetation and rock outcrops was the same around the Lagoa das Abelhas fossil tank. After that, the team came back to fieldwork and found fossil fragments of three out of fourteen targets. Thus, this study could show the potential of using UAV to cover large areas directed to the prospecting part of fossiliferous tanks with good flight autonomy, low cost and fast data analysis. Some of the 11 targets can be prospected because they have a high prospective potential due to their similarity to past prospects which became sites for future paleontological prospection.
Modelling Historical Adaptation Rates to Inform Future Adaptation Pathways
Authors: Schwarz Moritz , Pretis Felix
Published: March 2020

Quantifying the climate impacts onto economic outcomes is crucial to inform mitigation and adaptation policy decisions in the context of anthropogenic climate change. Existing macro-level economic impact projections are often derived using calibrated Integrated Assessment Models (IAMs) or empirically-estimated econometric models. Both approaches, however, rarely consider how such impacts would change under macro-level adaptation interventions. Here, we present approaches to econometrically test climate impact estimates for their historical stability to approximate empirical macro-adaptation rates. By modelling deterministic trends and structural breaks as well as socio-economic drivers of adaptation, our approach could provide the basis for a new set of macro-economic impact projections that control for adaptation measures. Ultimately, adaptation-explicit impact projections could be used to inform both mitigation and adaptation decisions and further allow benchmarking of non-empirical modelling approaches.
Water contents of mantle xenoliths from Sytykanskaya kimberlite pipe (Yakutian diamondiferous province, Russia)
Authors: Kolesnichenko Maria , Zedgenizov Dmitriy , Ashchepkov Igor
Published: March 2020

Water plays a key role in evolution and dynamic of the Earth. It can change physical and chemical properties of mantle minerals, or the part of the mantle, for instance, the effect on mineral deformation and its impact on mantle rheology (Miller et al., 1987). Mantle xenoliths from kimberlites are one of direct source of information on the petrology and geochemistry of the deep mantle rocks.

Sytykanskaya pipe located in the central part of Yakutian diamondiferous province is characterized by a large amount of deep-seated xenoliths which contain relics of fresh minerals, e.g. clinopyroxenes, garnets, olivines, phlogopites, amphiboles, chromites, ilmenites and some other rare phases (Ashchepkov et al., 2015). Moreover it is known that there are several processes which can affect the mantle xenoliths, including metasomatism. Five peridotite xenoliths have been studied in order to indentify water enrichment. Using calibration coefficients (Bell et al., 2003) we calculated water content in the olivines. Water contents in olivine range from 12 to 92 ppm. In previous research (Kolesnichenko et al., 2017) we have studied peridotites from Udachnaya kimberlite pipe and found similar water content in olivines (2-95 ppm). So, the variably low water contents suggest a heterogeneous distribution of water beneath the mantle, which can be connected with metasomatism of essentially dry diamondiferous cratonic roots by hydrous and carbonatitic agents, and its related hydration and carbonation of peridotite accompanied by oxidation and dissolution of diamonds.

This work was supported by the Russian Science Foundation under Grant No 16-17-10067.

Miller, G. H., Rossman, G. R., & Harlow, G. E. (1987). The natural occurrence of hydroxide in olivine. Physics and chemistry of minerals, 14(5), 461-472.

Ashchepkov, I. V., Logvinova, A. M., Reimers, L. F., Ntaflos, T., Spetsius, Z. V., Vladykin, N. V., & Palesskiy, V. S. (2015). The Sytykanskaya kimberlite pipe: Evidence from deep-seated xenoliths and xenocrysts for the evolution of the mantle beneath Alakit, Yakutia, Russia. Geoscience Frontiers, 6(5), 687-714.

Bell, D. R., Rossman, G. R., Maldener, J., Endisch, D., & Rauch, F. (2003). Hydroxide in olivine: A quantitative determination of the absolute amount and calibration of the IR spectrum. Journal of Geophysical Research: Solid Earth, 108(B2).

Kolesnichenko, M. V., Zedgenizov, D. A., Litasov, K. D., Safonova, I. Y., & Ragozin, A. L. (2017). Heterogeneous distribution of water in the mantle beneath the central Siberian Craton: Implications from the Udachnaya Kimberlite Pipe. Gondwana Research, 47, 249-266.
Holocene ‘megadroughts’ in south-eastern Australia: deciphering regional patterns from lake sediment archives
Authors: Tyler Jonathan , Barr Cameron , Tibby John , Dhar Asika , Andrew Chapman , Dean Chloe , Gadd Patricia , Zawadzki Atun , Child David , Jacobsen Geraldine
Published: March 2020

Documenting and understanding centennial scale hydroclimatic variability in Australia is significant both to global climate science and to regional efforts to predict and manage water resources. In particular, multidecadal to centennial periods of low rainfall – ‘megadroughts’ – have been observed in semi-arid climates worldwide, however they are poorly constrained in Australia. Here, we bring together multiple, sub-decadally resolved records of hydrological change inferred from lake sediments in western Victoria, Australia. Our analyses incorporate new elemental (ITRAX µXRF) and stable isotope (oxygen, carbon isotopes) geochemical data from West Basin and Lake Surprise, both augmented by high quality radiometric chronologies based on radiocarbon, 210Pb and 239/240Pu analyses. Collectively, the records document a transition towards a more arid and variable climate since the mid-late Holocene, which is comparable to reports of an intensification of the El Nino Southern Oscillation (ENSO) through this period. Furthermore, during the last 2000 years, the records exhibit marked periods of reduced effective moisture which contrast with records of Australian hydroclimate inferred from distal archives, as well those predicted by climate model hindcasts. Our analyses indicate that megadroughts are a natural phenomenon in south-eastern Australia, requiring greater attention in efforts to predict and mitigate future climatic change.
A first glimpse from the EUREC4A-OA/ATOMIC air-sea experiment
Authors: Speich Sabrina , Karstensen Johannes , Fairall Chris , Zuidema Paquita , Gentemann Chelle , Zhang Dongxiao , Bellenger Hugo , Reverdin Gilles , Thompson Elizabeth , Bigorre Sebastien , Mohr Wiebke , Kinne Stefan ,   EUREC4A team
Published: March 2020

Ocean mesoscale eddies create specific air-sea interaction patterns that can have an integral effect on the large scale atmosphere and ocean dynamics. Recent advances in the state of the art of these processes has been predominately obtained from modeling efforts, but only very few observational studies exist, and there are all located in the extra-tropics. Adding a dedicated ocean mesoscale eddy air-sea interaction experiment to the EUREC4A campaign will enhance the objectives and success of the whole program as it sets a local, oceanic constrain to the atmospheric evolution (as been outlined in the overall EUREC4A design: www.eurec4a.eu; Bony et al. 2017). Temporal variability over a fixed mesoscale (500 km x 500 km) study area allows for sampling varying atmospheric states, on the time-scales of the EUREC4A field study. The oceanographic component that add on EUREC4A consists of four ships and many autonomous platforms (gliders, Saildrones, specific surface drifters, Argo floats) sampling the mesoscale ocean and air-sea exchanges at different edges of the Northwest Atlantic tropical region. This will enable the extended spatial sampling required to characterize ocean variability and gather enough air-sea observations at different locations to assess with accuracy the involved processes and impacts.

The western tropical Atlantic is an ideal laboratory for the proposed study. It hosts rich ocean mesoscale variability under an atmosphere characterized by a rather steady trade wind regime. In this region, eddies have a diameter of 200 to 300 km and lifetimes of several months up to years. In particular south of Barbados, very energetic and long-lived anticyclonic North Brazil Current rings are commonly found. These eddies are key for the northward transport of properties from the South to the North Atlantic within the Atlantic Meridional Ocean Circulation. Moreover, preliminary studies based on satellite observations have suggested that they play a crucial role in air-sea interactions and on the atmosphere. This region and eddies are the focus of EUREC4A-OA, the French oceanographic component of the larger EUREC4A field experiments.

In this talk we will present the preliminary lessons learned and results obtained by this unprecedented observing effort.
Quantification of the impact of lunar semidiurnal tides on groundwater dynamics in estuarine aquifers
Authors: Zhang Xiaoying , Dai Zhenxue , Hu Bill , Dai Heng , Ma Ziqi , Qi Linlin , Dong Fan , Cao Yang , Ma Funing
Published: March 2020

The influences of lunar semidiurnal tides on coastal groundwater aquifers have been conceptualized for decades. However, in estuarine aquifers, comprehensive work is needed to quantify the impact of the tides on groundwater dynamics due to the widely distributed waterways and heterogeneous sediments. Taking the Pearl River estuary in southeast China as a study site, the tidal impacts on the groundwater dynamics have been investigated through wavelet and time series analysis. The groundwater level and electrical conductivity (EC) in four monitoring wells, along with waterway water level (tidal level) at three tidal stations, were monitored every 30 minutes over a 2-month period to determine how nearshore groundwater responds to tidal forcing. The results show that the estuarine groundwater fluctuations have two significant short periodicities (0.51 and 1 day), which correspond to the major tidal constituents in the tides: M2 (semidiurnal), K1 and O1 (diurnal) signals. The significant impacts decrease with increasing distance inland of the locations of the wells. Additionally, the coherence analysis displays a higher correlation between tides and groundwater levels for the spring tide than for the neap tide. The tidal influences on groundwater EC are weaker. In addition, when the tide level increases, the EC decreases in the wells located in the estuarine entrance. This phenomenon is related to the high salinity of retained paleo-seawater in the strata lens. A conceptual model is proposed to illustrate the complex groundwater flow dynamics, which provides useful insights into understanding groundwater systems in other geographically similar coastal estuarine regions.
Thermal data collection in and around Japan and its implications for lithospheric rheology and deformation
Authors: Tanaka Akiko
Published: March 2020

Heat flow data contribute to the imaging the lithospheric thermal structure, which greatly influences tectonic and geological processes and constrains the strength of the lithosphere, the modes of deformation, and the depth distribution of earthquakes. To provide more reliable estimation of the lithospheric thermal structure, some complementary approaches are possible. One of approaches is to update and incorporate the existing thermal data. A new version of database “Thermal Data Collection in and around Japan”, which contains continuously updated of heat flow and geothermal gradient data and adds thermal conductivity data in and around Japan, has been released in March 2019 [https://www.gsj.jp/data/G01M/GSJ_MAP_TDCJ_2019.zip]. This provides an opportunity to revisit the thermal state of the lithosphere along with other geophysical/geochemical constraints and on the lithospheric rheology and deformation, which is sensitive to temperature.
Testing the veracity of turbidite paleoseismology using the Kaikōura earthquake-triggered turbidite, New Zealand
Authors: Orpin Alan , Howarth Jamie , Maier Katherine , Nodder Scott , Strachan Lorna
Published: March 2020

To better understand earthquake reoccurrence and hazard, records of ancient earthquakes spanning millennia are routinely generated using seabed turbidite deposits, inferred to be synchronously triggered by strong ground motions over large geographic areas. However, the use of turbidites for paleoseismology is underpinned by untested hypotheses due to the dearth of verified earthquake-triggered turbidite deposits produced by well-characterised earthquakes. The aim of a RV Tangaroa voyage in October 2019 was to use the unique opportunity provided by the widespread and documented occurrences of the 2016 Mw7.8 Kaikōura earthquake-triggered turbidite to determine whether synchronous turbidite deposition can be reconstructed from the sedimentary record alone. Our presentation will summarise insights gleaned from precision short cores and high-resolution sub-bottom profiles collected along and across the axis of submarine canyons that preserve turbidite deposits triggered by the Kaikōura earthquake. Planned detailed laboratory characterisation of the turbidites will include high-resolution core imaging, texture, densitometry, down-core physical properties and geochemical characterisation combined with radioisotope-derived chronology. Through repeat coring at historical sites and future coring campaigns we hope to also quantify the impact of biological mixing on the Kaikōura event deposit to determine its likely preservation potential in the geological record. Our results have the potential to provide the first robust test of turbidite paleoseismology.
Chaos in Estimates of Climate Change Impacts
Authors: Massetti Emanuele , Di Lorenzo Emanuele
Published: March 2020

Estimates of physical, social and economic impacts of climate change are less accurate than usually thought because the impacts literature has largely neglected the internal variability of the climate system. Climate change scenarios are highly sensitive to the initial conditions of the climate system due the chaotic dynamics of weather. As the initial conditions of the climate system are unknown with a sufficiently high level of precision, each future climate scenario – for any given model parameterization and level of exogenous forcing – is only one of the many possible future realizations of climate. The impacts literature usually relies on only one realization randomly taken out of the full distribution of future climates. Here we use one of the few available large scale ensembles produced to study internal variability and an econometric model of climate change impacts on United States (US) agricultural productivity to show that the range of impacts is much larger than previously thought. Different ensemble members lead to significantly different impacts. Significant sign reversals are frequent. Relying only on one ensemble member leads to incorrect conclusions on the effect of climate change on agriculture in most of the US counties. Impacts studies should start using large scale ensembles of future climate change to predict damages. Climatologists should ramp-up efforts to run large ensembles for all GCMs, for at least the most frequently used scenarios of exogenous forcing.
Large-scale flume modelling of segregation processes in debris flows
Authors: Kimball Julia , Take W Andrew
Published: March 2020

Debris flows are powerful natural hazards posing risk to life, infrastructure, and property.  Understanding the particle scale interactions in these flows is a key component in the development of models to predict the mobility, distal reach, and hazard posed by a given event. In this study we focus on the process of segregation in debris flows, using a large-scale landslide flume to explore segregation in mixtures of 25 mm, 12 mm, 6 mm, and 3 mm diameter particle sizes. Sample volumes, consisting of a multicomponent mixture of materials, up to 1 m3 in size are released at the top of a 6.8 m long, 2.1 m wide slope, inclined at 30 degrees to the horizontal to initiate flow. Subsequent analysis is completed to determine the extent of vertical and longitudinal segregation of the post-landslide deposit morphology. A range of experimental strategies are explored to provide quantitative measures of particle segregation. Particle size is identified via image analysis and various techniques are applied for the longitudinal sectioning of the deposit, using measurements of segregation at the sidewall of the transparent flume, contrasted with planes measured from within the centre of the deposit. Further, replicate experiments are shown to quantify the probabilistic variation in segregation for multicomponent mixtures of dry granular flows, as well as initially saturated granular flows, to explore the effect of pore fluid on segregation processes.
Examination of Dielectric Models in AMSR2 Soil Moisture Estimation Algorithm for Japanese and Cambodian Soils
Authors: Tsujimoto Kumiko , Ohta Tetsu
Published: March 2020

The Advanced Microwave Scanning Radiometer 2 (AMSR2) onboard the Global Change Observation Mission – Water (GCOM-W) satellite provides global surface soil moisture as well as other water-related variables over the earth. With its brightness temperature observations at 10 and 36 GHz, the global soil moisture product is operationally created by the Japan Aerospace Exploration Agency (JAXA) based on the Koike’s algorithm (Koike et al., 2004) using the Polar Index (PI) and the Index of Soil Wetness (ISW). A land data assimilation system, LDAS-UT, has been also developed by Yang et al. (2007) to retrieve the optimized soil moisture estimates using both the brightness temperature observation and a land surface model.

In this study, we applied the distributed hydrological model, WEB-DHM (Wang et al., 2009), which incorporates the same land surface model with LDAS-UT, to a river basin in Cambodia and then calculated the brightness temperature at 6.9GHz from the simulated soil moisture distribution, using the same forward model as LDAS-UT. The temporal and spatial distribution of soil moisture was calibrated and validated against in-situ observation through river discharge using WEB-DHM, and the calculated brightness temperature was compared with the AMSR2 observation at 6.9 GHz. In addition to the dielectric mixing model by Dobson (Dobson et al., 1985) which is originally used in the LDAS-UT as well as in the JAXA's soil moisture retrieval algorithm, the performance of the Mironov model (Mironov et al., 2004) was examined as an alternative for the dielectric mixing model in the forward calculation and the calculated results from the two models were compared.

Along with the hydrological simulation, field measurements and laboratory experiments were conducted in Cambodia and Japan to evaluate the dielectric behavior of wet soils with different soil water content at a point scale. A ground microwave radiometer was temporally installed over a paddy field in Japan to measure the brightness temperature at 6.9GHz directly from the near surface. Soil samples were also taken from this field as well as several other locations in Japan and Cambodia to measure the permittivity with different soil moisture content with a network analyzer in the laboratory, in order to examine the dielectric behavior of wet soils for different soil textures. The measured results were then compared with the Dobson and Mironov models to evaluate their performance for Asian soils.
Structural framework: a new way to organise and communicate geological information
Authors: Piessens Kris , Barros Renata , Dirix Katrijn , Deckers Jef , ten Veen Johan , Debacker Timothy N. , Jähne-Klingberg Fabian
Published: March 2020

A structural framework is a well-defined concept, being used primarily to add structural understanding to a geological model. Within GeoConnect³d, a new approach is used, i.e. the structural framework concept is modified to become the leading model, in which geological maps and models can be inserted and related to. This structural framework is being developed and implemented for two areas of interest - Roer-to-Rhine in northwest Europe and Pannonian Basin in eastern Europe - and will soon be implemented in two pilot areas, Ireland and Bavaria. The organisation of information is strongly linked to different scales of visualisation, starting from the pan-European view (1:15,000,000) with the possibility to zoom in to the scale of local geological models and maps in these four areas.

The GeoConnect³d structural framework reorganises geological information in terms of geological limits and geological units. Limits are defined as broadly planar structures that separate a given geological unit from its neighbouring units, e.g. faults (limits) that define a graben (unit), or an unconformity (limit) that defines a basin (unit). Therefore, the key relationship between these two structural framework elements is that units are defined by limits i.e. all units must be bounded by limits. It is important to note that this relationship is not necessarily mutual: not all limits have to be unit-defining.

A first test of the structural framework methodology was carried out in the Netherlands and Belgium for the Roer Valley graben, as the faults in this area were already modelled in a cross-boundary project (H3O-Roer Valley Graben). Displaying different elements according to scale of visualisation coupled with vocabulary information (definition, grouping and semantic relations between elements, etc.) following the SKOS-system proved a powerful tool to display geological information in an understandable way and improve insights in large-scale geological structures crossing national borders. Additionally, links with other GeoERA projects such as HIKE and its fault database are being successfully established. We consider the outcomes of this test promising to fulfil one of the main goals of GeoConnect³d, i.e. preparing and disclosing geological information in an understandable way for stakeholders. We also consider this as the way forward towards pan-European integration and harmonisation of geological information, where the ultimate challenge is to correlate or otherwise link information from different geological domains and of different scales.

This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 731166.