bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterizing and detecting climate signals in observations and models using statistical learning
Authors: Sippel Sebastian , Meinshausen Nicolai , Fischer Erich , Szekely Eniko , Knutti Reto
Published: March 2020

Internal atmospheric variability fundamentally limits short- and medium-term climate predictability and obscures evidence of climatic changes on regional scales. We discuss the suitability of incorporating statistical learning techniques to detect global climate signals from spatial patterns.

Our detection approach uses climate model simulations and a statistical learning algorithm to encapsulate the relationship between spatial patterns of daily temperature and humidity, and key climate change metrics such as annual global mean temperature or Earth’s energy imbalance. Observations are then projected onto this relationship to detect climatic changes. We show that fingerprints of changes in climate can be assessed and detected in the observed global climate record at time steps such as months or days by comparison against a historical baseline from CMIP5 simulations or reanalyses. Detection can be achieved also when ignoring the long-term global mean warming trend.

We further discuss how these approaches could be extended by using statistical techniques that would work well under variations of specific external forcings, e.g. solar or volcanic forcing, to predict only variations in a specific external forcing. Overall, we conclude that statistical learning techniques that characterize multivariate signals from high-dimensional climate data are a useful tool for the detection of climate signals at regional and global scales.
Baseflow and flash flood models of the ungaged Morgó watershed
Authors: Ámon Gergely
Published: March 2020

Baseflow and flash flood models of the ungaged Morgó watershed

Gergely Amon1 and Katalin Bene2

1Department of Transport Infrastructure and Water Resources Engineering, Széchenyi István University, Győr, Hungary, amon.gergely@sze.hu

2Department of Transport Infrastructure and Water Resources Engineering, Széchenyi István University, Győr, Hungary, benekati@sze.hu

 

Abstract: A common feature of steep-sloping watersheds is that there is a significant difference between base flow and flash floods; sometimes two or three orders of magnitude. In Hungary, these streams are usually ungaged or the available flow data is very limited. The Morgó creek watershed, located in northern part of Hungary, features steep terrain, and both urban and natural land use conditions.

In this paper, different models are applied to evaluate flash floods, and baseflow conditions in the Morgó-creek watershed. High probability baseflows can help to evaluate and monitor the current and future condition and health of the local ecological systems. Modeling flash floods with low probability can help to assess and prevent damage in urban areas.

Different types of models are required to generate baseflow and flash flood scenarios. For baseflow modelling, a two-dimensional finite element method was used while for flash floods, a finite volume model was applied. Morgó creek has a high peak flow, with a sharply increasing rising limb. As a result, the finite volume model is not sensitive to mesh density. Additionally, the impact of roughness coefficient was less than expected during calibration. The low flow analysis requires a more complex model to account for turbulence; therefore, the Shallow Water equations were used in the finite element model.

Uncertainty in hydrological model parametrization are a source of significant prediction errors. Monte Carlo simulation was applied to quantify parameter uncertainty on watershed response. The analysis was then used in the hydrodynamic model to assess the final prediction error for baseflow and flash flood conditions. While the hydrodynamic baseflow and flash flood models have different space and time scales, the two model solutions do influence each other. Proper analysis and comparison of the selected scenarios can help to determine an optimal design for the Morgó-creek watershed.

This work was undertaken as part of a project funded by the EFOP-3.6.1-16-2016-00017.
Impact of rapid urbanization on the observed daily maximum wind speed variability: a case study in Yangtze River Delta (China)
Authors: Zhang Gangfeng , Azorin-Molina Cesar , Wang Xuejia , Shi Peijun , Chen Deliang , McVicar Tim R. , Guijarro Jose A.
Published: March 2020

Typhoon and windstorm induced extreme winds (e.g., daily maximum wind speed, DMWS) cause enormous economic losses and deaths in China every year, and rapid urbanization increased surface roughness might play a key role in extreme wind speed variability. Here, observed near-surface (at 10 m height) DMWS from 115 meteorological stations and combined DMSP/OLS (Defense Meteorological Satellite Program/Operational Linescan System) and NPP/VIIRS (Suomi National Polar-orbiting Partnership/Visible Infrared Imaging Radiometer Suite) nighttime light data from 1992-2016 in Yangtze River Delta, a rapidly urbanized area of China, were used to analyze the impact of urbanization on DMWS variability. Raw wind speed observations were subject to a robust quality control and homogenization protocol using the Climatol package. The stations were firstly classified into six urbanized groups by the difference of nighttime light indices of each station between 1992 and 2016. The results show that DMWS in Yangtze River Delta has significantly (p < 0.05) declined by -0.209m s-1 decade-1 annually, with negative trends in most seasons, particularly in winter (-0.470 m s-1 decade-1, p < 0.05) and autumn (-0.300 m s-1 decade-1, p < 0.05), followed by spring (-0.178 m s-1 decade-1, p > 0.10), while a weak increase in summer DMWS was found (+0.002 m s-1 decade-1, p > 0.10). The stations in the highly urbanized group show a higher magnitude in the decline of annual DMWS, indicating the key role of urbanization in weakening DMWS. Further, this is confirmed by the regional climate model (RegCM4) sensitive experiments conducted with different land use and cover data, that is, DMWS in 1992 was higher in the experiment using the real land use and cover data than in the experiment using the land use and cover data in 2016.
Hydro-mechanical Dependent Hydraulic Conductivity within Alluvial Gravelly Soil: An Experimental Study
Authors: Chen Chenghao , Mei Shiang , Chen Shengshui
Published: March 2020

Abstract:  Seepage process can be extensively observed in rainfall infiltration, natural waterways, artificial hydraulic constructions and other interactive phenomena between water and soil. Recent investigations targeting the deep water circulation as well as shifts of basin patterns induced by massive projects urge the need to enhance the understanding of seepage characteristics under profound depth (high packing state) and great hydraulic pressure. Alluvial gravelly soil is an ordinary weathering product in mountainous area, either exposed to the ground or embedded as a layer. This research focuses on the hydraulic conductivity of such soil. A novel large-scale triaxial seepage apparatus was designed with the capability of replicating densely packed soil specimen and simulating severe hydraulic conditions. Influences of both the packing state and the hydraulic pressures were experimentally studied. It is revealed while most existing permeability models present the rational description that hydraulic conductivity decreases with higher packing state, these formulas for non-plastic soil overestimate the hydraulic conductivity of gravelly soil more than one order of magnitude. The dependence of hydraulic pressure displays the similar trend, as increasing hydraulic gradient diminishes the hydraulic conductivity. Coupled hydro-mechanical permeability models are therefore introduced based on test results. No observation of obvious seepage failure illustrates that high packing state resulting from mechanical loads are favorable to prevention of soil erosion and corresponding countermeasures.
Changes in atmospheric and hydrological dynamics at the Colombian Amazon in scenarios of forest loss
Authors: Bonilla-Rodriguez Monica , Gomez-Rios Sebastian
Published: March 2020

The Colombian Amazon exhibits complex hydro-meteorological features, as it links the biggest tropical rainforest of the world with the Andes range and the savannahs of the Orinoco basin. Similar to other amazon areas in neighboring countries, this high-biodiversity region faces severe deforestation due the agricultural expansion, illegal logging, and mining. Numerous studies have stated the role of the Amazon over the climatic system, and the complex interactions between the rainforest, the atmospheric dynamics and the hydrological response of the rivers. Furthermore, previous studies have warned about the effects of the loss of vegetal coverage in the Amazon over hydro-meteorological patterns in northern South America.

This work aims to study the effects of deforestation over some atmospheric and hydrological features in the Colombian Amazon. Taking into account present and historical rates of deforestation, there are defined scenarios of moderate and intense forest loss. Changes in precipitation and moisture fluxes over the area are investigated using the atmospheric model WRF (Weather Research and Forecasting). High-resolution simulations are performed for a study period composed of typical rainy and dry months, considering the changes in land use of each scenario. The effects of forest loss over streamflow in some rivers of the region are assessed using the results from the atmospheric model and simulations in an aggregated hydrological model. The main finding suggests that low-level moisture flux over the Colombian Amazon and neighboring Andean foothills decrease with the reduction of the rainforest cover in both of the considered seasons. As a consequence, precipitation decreases over the area, triggering a reduction of the streamflow in the studied rivers.
Effects of the Solar Wind Conditions on Mercury's Exosphere: Hybrid Simulations
Authors: Travnicek Pavel M. , Schriver Dave , Orlando Thomas , Slavin James A.
Published: March 2020

We carry out a set of global hybrid simulations of the Mercury's magnetosphere with the interplanetary magnetic field oriented in the desired directions.
We study effects of changes of different solar wind parameters on the structure of the plasma circulation within Mercury’s magnetosphere. We focus our
study on the changes caused by changes in the orientation of the interplanetary magnetic field and the dynamic pressure (velocity) of the solar wind.
We study the structure of the of the Mercury’s magnetosphere under different solar wind conditions. Our primary focus is the assessment of the
precipitation levels of solar wind hydrogen on the Mercury's surface (the amount, the deposited energy, its spectra and angular distribution) and on the
formation of Mercury's exosphere. We examine density fluxes, energy levels and spectra of protons precipitating on Mercury’s surface as a function of
longitude and altitude. It has been established, that Mercury has a plasma belt formed by quasi-trapped solar wind plasma close to the Mercury’s surface.
Charged particles trapped in the belt mostly circle Mercury 1-2 times before they either precipitate on Mercury’s surface or escape into the Mercury’s
magnetospheric cavity. Lower dynamic pressure of the solar wind pushes magnetopause up above the Mercury’s surface and the plasma belt has more
space to develop. Its interaction with Mercury’s surface and dynamics under different solar wind conditions is essential on the precipitation of the plasma
on the Mercury’s surface. Higher dynamic pressure of the solar wind can push the bow shock towards Mercury’s surface and make the surface open to the
direct impact of the solar wind on the Mercury’s surface. Due to weak magnetic moment of the Mercury’s magnetosphere, the plasma environment at Mercury
is very dynamic.
Beyond Earth – Lessons learned and Challenges of Planetary Cartography
Authors: Naß Andrea , van Gasselt Stephan , Di Kaichang , Hare Trent , Karachevtseva Irina , Rossi Angelo Pio , Skinner Jim , Kersten Elke , Elgner Stefan , Manaud Nicolas , Roatsch Thomas
Published: March 2020

The standardization of cartographic methods and data products is critical for accurate and precise analysis and scientific reporting. This is more relevant today than ever before, as researchers have easy access to a magnitude of digital data as well as to the tools to process and analyze these various products. The life cycle of cartographic products can be short and standardized descriptions are needed to keep track of different developments.

Planetary Cartography does not only provide the basis to support planning (e.g., landing-site selection, orbital observations, traverse planning) and to facilitate mission conduct during the lifetime of a mission (e.g., observation tracking and hazard avoidance). It also provides the means to create science products after successful termination of a planetary mission by distilling data into maps and map-related products. After a mission’s lifetime, data and higher level products such as mosaics and digital terrain models (DTMs) are stored in archives and are eventually re-used and transformed into maps and higher-level data products to provide a new basis for research and for new scientific and engineering studies. The complexity of such tasks increases with every new dataset that has been put on this stack of information, and in the same way as the complexity of autonomous probes increases, also tools that support these challenges require new levels of sophistication. In the planetary sciences, cartography and mapping have a history dating back to the roots of telescopic space exploration and are now facing new technological and organizational challenges with the rise of innovative missions, improved instruments, global data initiatives, new organizations and opening research markets. A general aim for this Planetary Cartography community is to develop concepts and approaches to foster future cooperation between scientists, cartographers and non-cartographers.

The focus of this contribution is to summarize recent activities in Planetary Cartography, highlighting current issues the community is facing, and to derive future opportunities in this field in order to address technical and scientific objectives. Furthermore, we focus on (1) identifying and prioritizing needs of the planetary cartography community along with a strategic timeline to accomplish such goals, (2) keeping track of ongoing work across the globe in the field of Planetary Cartography, and (3) identifying areas of evolving technologies and innovations that deal with mapping strategies as well as output media for the dissemination and communication of cartographic results.

By this we would like to invite cartographers, researchers and map-enthusiasts to join this community and to start thinking about how we can jointly solve some of these challenges.
Forecasting of the Upper Atmosphere via Assimilation of Electron Density Data
Authors: Kodikara Timothy
Published: March 2020

This study presents experiments of driving a physics-based thermosphere model (TIE-GCM) by assimilating radio occultation electron density (Ne) profiles from the COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) mission using an ensemble Kalman filter. This study not only helps to gauge the accuracy of the assimilation, to explain the inherent model bias, and to understand the limitations of the framework, but it also demonstrates the capability of the assimilation technique to forecast the highly dynamical thermosphere in the presence of realistic data assimilation scenarios.

Experiments cover both solar minimum (March 2008) and solar maximum (June 2014) periods. The results show that data assimilation improves the model state. Here the improvement is shown with comparisons to Ne and neutral density data from Swarm-A, Swarm-C, CHAMP, and GRACE-A satellite missions. The root mean squared error (RMSE) of Ne is reduced in the Ne-guided lower thermosphere more than that of the higher altitudes (e.g. 1.7×104 electrons/cm3 at 200 km vs 2.9×104 electrons/cm3 at 400 km). The average RMSE in the forecasted Ne is approximately 1.3×105 electrons/cm3 at altitudes between 200 and 400 km, and  drops to 0.7×105 electrons/cm3 at 500 km. The study also reveals that only a limited number of bonafide Ne profiles are available for assimilation tasks in the experiments. These results also provide insights into the biases inherent in the physics-based model. The systematic biases that this study highlight could be an indication that the specification of plasma-neutral interactions in the model needs further adjustments.
A test development of a data driven model to simulate chlorophyll data at Tongyeong bay in Korea
Authors: Kim Sung Dae , Choi Sang Hwa
Published: March 2020

A pilot machine learning(ML) program was developed to test ML technique for simulation of biochemical parameters at the coastal area in Korea. Temperature, chlorophyll, solar radiation, daylight time, humidity, nutrient data were collected as training dataset from the public domain and in-house projects of KIOST(Korea Institute of Ocean Science & Technology). Daily satellite chlorophyll data of MODIS(Moderate Resolution Imaging Spectroradiometer) and GOCI(Geostationary Ocean Color Imager) were retrieved from the public services. Daily SST(Sea Surface Temperature) data and ECMWF solar radiation data were retrieved from GHRSST service and Copernicus service. Meteorological observation data and marine observation data were collected from KMA (Korea Meteorological Agency) and KIOST. The output of marine biochemical numerical model of KIOST were also prepared to validate ML model. ML program was configured using LSTM network and TensorFlow. During the data processing process, some chlorophyll data were interpolated because there were many missing data exist in satellite dataset. ML training were conducted repeatedly under varying combinations of sequence length, learning rate, number of hidden layer and iterations. The 75% of training dataset were used for training and 25% were used for prediction. The maximum correlation between training data and predicted data was 0.995 in case that model output data were used as training dataset. When satellite data and observation data were used, correlations were around 0.55. Though the latter corelation is relatively low, the model simulated periodic variation well and some differences were found at peak values. It is thought that ML model can be applied for simulation of chlorophyll data if preparation of sufficient reliable observation data were possible.
Comparison of remote sensing-based indices for ash vitality detection in North-East Germany
Authors: Förster Michael , Clasen Anne , Jütte Kai , Döpper Veronika , Kleinschmit Birgit
Published: March 2020

The north-East of Europe is affected by the ash (Fraxinus excelsior) dieback caused by the fungal pathogen Hymenoscyphus pseudoalbidus. A great variety of studies utilize remote sensing data and subsequently derived spectral indices to estimate the magnitude and spatial distribution of the damage for different tree types. 

Often, structural indices, such as the NDVI are applied to detect already affected tree (sometimes even for early detection). However, there are differences in the suitability of an index. While a structural index, might have advantages when the canopy is not closed, pigment-based indices can show more variation within a full crown coverage forest. Therefore, the season of data acquisition might define the preferred index-selection. The same accounts not just for seasonal but for inter-annual changes, too. Here, the pigment indices show a higher sensitivity towards changes due to damages than structural indices.

To show these differences, the presented study is evaluating a variety of indices derived by hyperspectral imagery for affected ash trees in north-east Germany. This includes images from different phenological stages within one year (2015) and a comparison between 2011, 2015, and 2019 because the decline increased severely within this timespan for the observed trees. The indices were compared with tree damage estimations from the regional forest administration. 

Preliminary results show a better relation for structural indices in autumn, but higher relation for pigment-based indices in spring and summer, once the crown is closed. A higher sensitivity to changes between 2011 and 2019 can be shown for pigment-based indices.
A High Temporal, Spatial and Energy Resolution Grid-based Energetic Neutral Atom (ENA) Imager: the Physical Design
Authors: Wang Yongfu , Zong Qiugang , Wang Linghua , Chen Hongfei , Zou Hong
Published: March 2020

Substorm is the global disruptive activity in Earth’s magnetotail, including phenomena such as reconnection, plasmoid, flux rope, BBFs, energetic particle injection, and aurora etc. The ground based observations are often hard to determine the time sequences of substorm activities, while the satellite in-situ observations often cannot distinguish between temporal and spatial variations, therefore the global imaging observations are very useful in substorm studies. In this study we demonstrate the physical design of a grid-based energetic neutral atom (ENA) imager that can provide high temporal, spatial and energy resolution ENA imaging of Earth’s magnetotail. The ENA imager takes advantage of spatial Fourier modulation to the ENA fluxes to construct the ENA images, which is inspired by RHESSI. The physical design including imaging process, the charged particle reflector, and the ENA species discrimination etc. are described, along with the engineering progresses.
Deriving sediment transport information from debris-flow impact force signals
Authors: Tang Hui , Yan Yan , Hu Kaiheng
Published: March 2020

Runoff-generated debris flow has hazardous implications for downstream communities and infrastructure in alpine landscapes. Our understanding of fluid mechanisms of debris flows is very limited, in part, by a lack of direct observations and measurements. Seismic ground motion-based observations provide new constraints on debris flow physics, but it is still not widely applied due to the missing of validated inversion models for interpreting the impact force which generates seismic ground motion. Here we propose a physical model for the high-frequency spectral distribution of impact force signal generated by debris flows. Then we present a new inversion model based on the physical model for the impact force signal and apply this to the devastating debris flows in Dongchuang, China, on 25 August 2004. The amplitude and frequency characteristics of the impact force data can enable the estimation of grain size, sediment concentration, and sediment flux. Results suggest that in-situ data from three sensors could have provided a reconstruction of sediment flux profile in the vertical direction. Meanwhile, an inversion model designed for debris flows impact force would potentially provide hydrodynamics information as well.
Concentration uncertainties in atmospheric aerosol measurement with Condensation Particle Counters
Authors: Schmitt Sebastian H. , Gendarmes Francois , Tritscher Torsten , Zerrath Axel , Krinke Thomas , Bischof Oliver F.
Published: March 2020

Condensation Particle Counters (CPCs) are the best-known and most frequently used tools for determining airborne particle number concentrations in the laboratory and a variety of real-life situations. While being a very established technique, current generations of CPCs have enhanced capabilities in terms of lower cut-off diameters, upper concentration limit as well as measurement quality features (e.g. pulse height monitoring). Knowledge of instrument accuracy is a primary matter in order to retrieve high quality data. In recent years, there has been an effort from measurement networks and within the EU’s standardization committee (CEN-TS 16976) to make ambient ultrafine particle number concentration data comparable. Long-term ambient monitoring requires frequent validation of instrument performance.

Inter-comparisons of multiple instruments against a reference instrument are important measures in order to secure long-term data quality. During inter-comparisons in the laboratory typically an aerosol of a certain type is generated and eventually classified in order to retrieve a monodisperse aerosol population. The aerosol needs to be equally distributed between the different instruments without being biased by sampling line losses.

This presentation will focus on inter-comparisons of CPCs being challenged with different types of aerosol. This includes lab-generated, highly monodisperse aerosol as well as ambient polydisperse aerosol. The accuracy of 10 units of a recently-introduced CPC (Model 3750, TSI Inc.) will be shown for ambient aerosol at data rates up to 50 Hz. All CPCs characterized agreed within 10% during the test, with concentrations of the ambient aerosol ranging from a few thousands up to 100,000 Particles/cm³.

In addition, results from inter-comparison studies using different butanol- and water-based CPC models that have been used for multiple years in different laboratories will be shown. Despite the different schedules for all instrument services and calibrations related to owners metrology requirement, these different CPC models demonstrated similar responses for the tested aerosols taking into account 10% uncertainties and are suitable candidates for reliable long-term operation in ambient ultrafine particle monitoring.
Lake Constance sediments recovered using novel piston coring system
Authors: Harms Ulrich , Raschke Ulli , Schwalb Antje , Wittig Volker
Published: March 2020

Key archives in environmental and past climate research are buried in soft sediment but investigations are often hampered by the lack of continuous, complete and undisturbed samples. We have developed the new core-drilling instrument Hipercorig to overcome these issues and we have tested this tool successfully on the perialpine Lakes Mondsee and Constance at up to 204 m water depths and down to 64 m core length.

Hipercorig comprises a hydraulically hammered down-the-hole piston coring system capable to reach up to 100 m core length in up to 200 m water depths. The well-proven piston system ensures high-quality intact cores while the hydraulic hammer drive allows penetrating hard-layers such as sand, gravel or tephra. The piston-hammer system, casing string and ground plate is connected via Kevlar ropes to a coring rig and deployment is controlled via underwater cameras. For lake, estuarine and shallow marine projects buoyance and working space is provided through a barge with four anchors and winches. The complete system is consisting of modular elements to be shipped in four 20-foot-containers including two boats and outboard motors. Hipercorig allows for about 10 m rate of penetration per shift and produces 7.5 cm cores in 2 m long core runs.

A first deployment on Lake Mondsee to initially test and modify Hipercorig recovered 64 m sediment core from glacial tills. A follow on shake-down cruise on Lake Constance served as deep-water trial and to sample so far unearthed pre-Holocene strata below about 12 m sediment depth. Coring was performed in summer 2019 in 204 m water depth, 2 km SSW of Hagnau, Germany. The site is located close to the deepest part of this basin with best possible preservation of a continuous and undisturbed depositional record. Two sediment cores of 24 and 20.5 mblf were retrieved and complemented by three 2-m-long surface cores. The uppermost 11 m of sediments consist of Holocene lacustrine clays with increasing intercalations of silt, while late Quaternary glacial sands dominate below 11 m. The piston coring device was modified to allow for penetrating these rigid sand layers, but the sands slowed down core recovery and caused core loss of ~15 cm at the end of each core run but overlapping coring was used to compensate the loss. While samples for microbiology have been taken immediately, core opening, description, and sampling will be performed at Bern University, Switzerland, in October 2019.

Currently Hipercorig receives final upgrades for safety and flexibility so that the whole system will be available from spring 2020 on for scientific coring projects on a non-for-profit base to teams with funded research projects. They will have to raise transport and operations costs as well as a maintenance fee that will serve to sustain the tool. The German Scientific Earth Probing Consortium GESEP will provide an oversight board to prioritize projects and support projects in implementation.
A state-of-the-art parameterization of atmospheric nutrient deposition fluxes in the global ocean
Authors: Myriokefalitakis Stelios , Gröger Matthias , Hieronymus Jenny , Döscher Ralf
Published: March 2020

Atmospheric deposition of trace constituents of natural and anthropogenic origin act as a nutrient source into the open ocean, affecting the marine ecosystem functioning and subsequently the exchange of CO2 between the atmosphere and the global ocean. Among other species that are deposited into the open ocean, nitrogen (N), iron (Fe), and phosphorus (P) are considered as highly significant nutrients that can limit marine phytoplankton growth and thus directly impact on ocean carbon fluxes in the ocean, particularly where the nutrient availability is the limiting factor for productivity. For this work, we take into account the up-to-date understanding of the effects of air quality on the atmospheric aerosol cycles to investigate the potential ocean biogeochemistry perturbations via the atmospheric input with the European Community Earth System Model EC-Earth (http://www.ec-earth.org/), which is jointly developed by several European institutes. In more detail, state-of-the-art N, Fe, and P atmospheric deposition fields are coupled to the embedded marine biogeochemistry model and the response of oceanic biogeochemistry to natural and anthropogenic atmospheric aerosols deposition changes is demonstrated and quantified. Model calculations show that compared to the present day, the preindustrial atmospheric deposition fluxes are calculated lower (~1.7, ~1.5, and ~1.4 times for N, Fe, and P, respectively) corresponding to a respective lower marine primary production. On the other hand, future changes in air pollutants under the RCP8.5 scenario result in a modest decrease of the bioaccessible nutrients input into the global ocean (~ -15%, ~ -16% and ~ -22% for N, Fe and P, respectively) and overall to a slightly lower projected export production compared to present day. Although the impact of atmospheric processing on atmospheric inputs to the ocean results in a relatively weak response in total global-scale simulated marine productivity estimates, strong regional changes up to 40-60% are calculated in the subtropical gyres. Overall, this study indicates that both the atmospheric processing and the speciation of the atmospheric nutrients deposited in the ocean should be considered in detail in carbon-cycling studies, since they may significantly affect the marine ecosystems and thus the current estimates of the carbon cycle feedbacks to climate.

This work has been financed by the National Observatory of Athens internal grant (number 5065), the “Atmospheric deposition impacts on the ocean system”, and the European Commission's Horizon 2020 Framework Programme, under Grant Agreement number 641816, the "Coordinated Research in Earth Systems and Climate: Experiments, kNowledge, Dissemination, and Outreach (CRESCENDO)".
Impact of ocean-atmosphere coupling on regional climate: the Iberian Peninsula case
Authors: Cabos William , Sein Dmitry , de la Vara Alba , Alvarez Garcia Francisco
Published: March 2020

Regional models used for downscaling the European climate usually include a relatively small area of the Atlantic Ocean and are uncoupled, with the SST used as lower boundary conditions much coarser than the mesh of the regional atmospheric model. Concerns thus arise about the proper representation of the oceanic influence and the role of air-sea coupling in such experiments.  A complex orography and the exposure to different air and ocean masses make the Iberian Peninsula (IP) an ideal test case for exploring the impact of including explicitly the North Atlantic in the regional domain and the added value that coupling brings to regional climate modeling. To this end, the regionally-coupled model ROM and its atmospheric component, the regional atmospheric model REMO are used in a set of coupled and uncoupled experiments forced by the ERA-Interim reanalysis and by the global climate model MPI-ESM. The atmospheric domain is the same in all simulations and includes the North Atlantic and the ocean component is global and eddy permitting. Results show that the impact of air-sea coupling on the IP winter biases can be traced back to the features of the simulated North Atlantic Ocean circulation. In summer, it is the air-sea interactions in the Mediterranean that exert the largest influence on the regional biases. Despite improvements introduced by the eddy-permitting ocean, it is suggested that a higher resolution could be needed for a correct simulation of the features of the large-scale atmospheric circulation that impact the climate of the IP.     
Conflict and Cooperation Analysis on Transboundary River Basins Using News Media Text Mining Approach
Authors: Guo Liying , Tian Fuqiang , Wei Jing , Lu You
Published: March 2020

Transboundary water problems are complex systems, which involve interdependence and interconnectedness between elements, uncertainty and feedbacks between processes, and emergence and adaptation through evolution of the systems. There is nearly no way to formulate transboundary water problems in an equation fitting-one-size-for-all. As nature-human coupled systems, transboundary water problems should consider actual stakeholders and parties in context-specific situations as well as natural conditions.

News media are good recorders for us to have an insight into the transboundary water problems down-to-earth. Local news media are the first-hand and direct reflections of societal values among the riparian countries and stakeholders, and are documentaries of what is going on in transboundary river basins. International news media are also good sources to know about how people in the world perceive transboundary river issues from the perspectives as “outsiders”. Therefore, text analysis of news articles concerning conflict and cooperation on transboundary river basins can tell us a whole story about the past history and on-going “real” life in the basins.

To uncover the patterns and dynamics of conflictive and cooperative events on a global scale, people usually read news articles, extract information manually in the past, which is tedious and time-commanding. In the era of big data, we collect large news media datasets automatically, and employ machine learning techniques to do data mining out of those news media data. The aim of our research is to minimize manual labor in searching, filtering, reading and understanding the related news media articles by computer, and to provide potent tools for researchers to retrieve useful information  in the related areas. To validate our methodology, we look Mekong River Basin and Brahmaputra River Basin as case studies into details. To apply our methodology in a global scale, we intend to draw a world map with a timeline to show how water conflict, and cooperation occurs, grows, and transforms. By capturing characteristics of the life cycles of water conflict and cooperation, we aim to throw light upon water management in transboundary river basins, provide some hints for water resources decision-makers, and enhance global water security.
Investigation of long-term fate of mercury in the ocean using a new global model
Authors: Kawai Toru , Sakurai Takeo , Suzuki Noriyuki
Published: March 2020

Numerical modeling is useful for evaluating the international efforts, such as the Minamata Convention on Mercury, that are directed towards the reduction of anthropogenic emissions. We have developed a new global model for mercury, denoted FATE-Hg, which is based on a fully coupled atmosphere-ocean chemical transport model and low and high-order marine ecosystem models. The model considers methylated mercury production in the open ocean seawater, bioconcentration, and food-web biomagnification from particle organic matter to fish. In this study, we performed a long-term simulation over three centuries with changes in anthropogenic emission since the Industrial Revolution, and investigated the long-term evolution of total mercury (THg) in the ocean. The simulated oceanic THg showed a phase lag of 5–10 years from the anthropogenic emission in the surface-intermediate oceans. As of 2010, oceanic THg was 410 Gg, which is 1.6–16.9 times higher than that estimated by the previous model. The estimated overall turnover time of oceanic THg determined by our model was 320 years, which is significantly shorter than those estimated by previous model-based studies. Additionally, we estimated geographic THg sources in the upper ocean. The results showed that North America (NA), Europe (EU), and East Asia are the dominant source regions in most ocean sections in the Northern Hemisphere, though the emissions from NA and EU have fall considerably since the 1970s. This result indicated that a significant amount of mercury that had been emitted from NA and EU in the past persists in present-day seawater.
The flow-to-sliding transition in crystalline magma
Authors: Qin Zhipeng , Suckale Jenny
Published: March 2020

Magmatic flows are rarely, if ever, entirely free of crystals. If these crystals distribute in an approximately homogeneous way, their impact on flow can be captured by defining a suitable effective viscosity for the suspension. A spatially heterogeneous crystal distribution, however, can build up to the degree that the flow behavior of the crystal-bearing magma becomes substantially different from that of a pure melt. One example is the transition from flow to sliding, in which the deformation in the crystalline magma is concentrated almost entirely in a thin interfacial layer as opposed to being distributed in a typical flow profile throughout the domain. The transition is particularly consequential for the large-scale dynamics of the system, because it can be associated with transport rates increasing by orders of magnitudes.

 

Most conduit models associate the flow-to-sliding transition with a critical crystal fraction, often in the 60% range. Here, we hypothesize that the flow to sliding transition can occur at crystal fraction as low as a few percents under certain conditions. We test our hypothesis by numerically reproducing existing laboratory measurements of the effective viscosity of plagioclase-bearing basalt in a rotational viscometer. We utilize a direct numerical method to resolve the interactions between the crystals and the magmatic melt at the scale of individual interfaces in 2D. Our numerical approach only requires assumptions about the pure phase including the crystal fraction and crystal shape. All phase interactions and their aggregate effect on the flow emerge self-consistently from the simulation itself. 

 

Our simulations suggest that the behavior of multiphase suspensions at low fluid Reynolds number is highly variable and depends sensitively on the characteristics of the immersed phases and the geometry of the flow domain. We show that there is no meaningful dilute limit in which the phase interactions can be neglected or captured by adjusting the effective rheology of the suspension in a way that removes dependencies on the properties of the immersed phase. Since our models operate at the scale of individual crystals, our model results are testable in both field and laboratory settings. In fact, they suggest that observations of microstructure provide valuable constraints on the large scale flow dynamics at the time. Particularly important is the degree of preferential crystal alignment and the existence of force chains or crystal clusters.
Locating and characterizing seismic events in Los Humeros (Mexico) using time-reverse imaging
Authors: Finger Claudia , Saenger Erik H.
Published: March 2020

Locating and characterizing the seismicity in a reservoir is crucial for any geothermal project. This study is the first time that the seismicity in a geothermal reservoir is characterized using time-reverse imaging (TRI). The spatio-temporal distribution of events in combination with focal mechanism solutions may enable the mapping of existing fault networks, the estimation of local stress regimes and the distinction between tectonic and induced events. Combining these results with results from other methodologies will in the future lead to an informed understanding of the physical processes occurring in reservoirs.

TRI is a method for locating and characterizing seismic events. TRI uses the whole time-reversed waveform and a seismic wave propagation solver to locate and characterize events. Therefore, it does not rely on the identification of seismic events and their onsets in the traces. In contrast to common tools that provide hypocenters and focal mechanism solutions for seismic events, TRI does not assume any a priori knowledge about the sources. Since events are not picked in the seismic traces, no assumption is made about the number of sources recorded in a certain time window. Similarly, the characterization of events does not exclude any source type or put any constraints or assumptions on the sources, such as them being only of double-couple nature. Therefore, TRI may be especially well-suited when the overall type of sources is not known or if it is suspected that common localization and characterization tools are not adequately depicting the physical processes in the subsurface.

In the first part of this study, seismic events, that occurred in the geothermal field of Los Humeros in Mexico, are located using TRI. So-called sensitivity maps are used to enhance the localization capabilities and to determine the spatial variation in source-location accuracy. In the second part of this study, the located events are characterized by determining the full time-dependent moment tensor. Since no assumption about the source type is made, these moment tensors complement results obtained from more standardized tools.
The role of turbulence strength on the acceleration of transrelativistic electrons
Authors: Trotta Domenico , Franci Luca , Burgess David , Hellinger Petr , Giacalone Joe
Published: March 2020

Energetic particles are widely observed in many astrophysical systems, but the physical mechanisms responsible for their acceleration are not yet fully understood. We address the interaction of suprathermal, transrelativistic electrons with plasma turbulence at ion and sub-ion scales using a combination of hybrid particle-in-cell and test particle simulations. First, we present results of simulations with different turbulence amplitude. Two different mechanisms for electron energisation are identified: one is consistent with the picture of stochastic acceleration in turbulence, yielding to moderate electron energisation, while the other one involves electron trapping in turbulent structures, resulting in an efficient and fast electron energisation. The latter is observed to be active only for certain combinations of turbulence amplitude and electron initial energy. Furthermore, varying the injection scale, we explore the importance of the size of turbulent magnetic structures and of the nonlinear time associated to their dynamical evolution on electron acceleration. These results have important implications for electron acceleration in a wide range of space and astrophysical systems.
Copernicus Sentinel Orbit Validation – Investigations on systematic geographical differences
Authors: Berzosa Javier , Fernández Usón Marc , Fernández Sánchez Jaime , Peter Heike , Féménias Pierre
Published: March 2020

The Copernicus POD (Precise Orbit Determination) Service delivers, as part of the PDGS of the Copernicus Sentinel-1, -2, and -3 missions, orbital products and auxiliary data files for their use in the corresponding PDGS processing chains. The precise orbit results from the three missions are validated based on orbit comparisons to independent orbit solutions from member of the Copernicus POD Quality Working Group (QWG). In the case of Sentinel-3 a validation based on satellite laser tracking (SLR) measurements is also possible. The orbit comparisons are done based on orbit time series. Typically, only daily RMS metrics are derived, and its time-series mean and standard deviation are provided. Another possibility is to analyse the dependence of orbit differences with geographical differences; this is already done for the altimeter satellites to guarantee long-term stability of the orbit solutions.

Geographical orbit differences may reveal systematics due to, e.g., different background models or different geocenter motion models used in the orbit determination process. The geographical orbit differences of all six satellites and from all POD QWG contributions are analysed and checked for model- or satellite-specific systematics to improve the orbit quality and long-term stability.   

Additionally, it is proposed to analyse the orbit differences (with respect to other orbital solutions, either reduced-dynamic or kinematic) with Fourier transformation, in order to derive amplitude vs. frequency plots. This could provide light into the sub-daily differences. The Fourier analysis of the sub-daily differences will be assessed for all the six satellites.
Global Ten-Moment Multifluid Simulations of the Solar Wind Interaction with Mercury: From the Planetary Conducting Core to the Dynamic Magnetosphere
Authors: Dong Chuanfei , Wang Liang , Hakim Ammar , Bhattacharjee Amitava , Slavin James , DiBraccio Gina , Germaschewski Kai
Published: March 2020

For the first time, we explore the tightly coupled interior‐magnetosphere system of Mercury by employing a three‐dimensional ten‐moment multifluid model. This novel fluid model incorporates the nonideal effects including the Hall effect, electron inertia, and tensorial pressures that are critical for collisionless magnetic reconnection; therefore, it is particularly well suited for investigating collisionless magnetic reconnection in Mercury's magnetotail and at the planet's magnetopause. The model is able to reproduce the observed magnetic field vectors, field‐aligned currents, and cross‐tail current sheet asymmetry (beyond magnetohydrodynamic approach), and the simulation results are in good agreement with spacecraft observations. We also study the magnetospheric response of Mercury to an extreme event with an enhanced solar wind dynamic pressure, which demonstrates the significance of induction effects resulting from the electromagnetically coupled interior. More interestingly, plasmoids (or flux ropes) are formed in Mercury's magnetotail during the event, indicating the highly dynamic nature of Mercury's magnetosphere. This novel ten‐moment multifluid model represents a crucial step toward establishing a revolutionary approach that enables the investigation of Mercury's tightly coupled interior‐magnetosphere system beyond the traditional fluid model and has the potential to enhance the science returns of both the MESSENGER mission and the BepiColombo mission.