bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification of different skarn deposits based on the compositional variability of associated grandite garnets: a data science and Machine Learning approach
Authors: Ghosh Urmi , Chakraborty Tuhin
Published: March 2021

Rapid technological improvements made in in-situ analysis techniques, including LA-ICPMS, have transformed the field of analytical geochemistry. This has a far-reaching impact for different petrogenetic and ore-genetic studies where minute major and trace element compositional changes between different mineral zones within a single crystal can now be demarcated. Minerals such as garnet although robust are quite sensitive to the changing P-T and fluid conditions during their formation. These minerals have become powerful tools to characterize mineralization types. Previously, Meinert (1992) has used in-situ major element EPMA analysis results to classify different skarn deposit based on the end-member composition of hydrothermal garnets. Alternatively, Tian et al. (2019) used the garnet trace element composition for the similar purpose. However, these discrimination plots/ classification schemes show major overlap in different skarn deposits, such as Fe, Cu, Zn, and Au. The present study is an attempt to use machine learning approach on available garnet data to found a more potent classification scheme for skarn deposits, thus reaffirming garnet as a faithful indicator for hydrothermal ore deposits. We have meticulously collected major and trace element data of Ca-rich garnets, associated with different skarn deposits worldwide from 40 publications. This collected data is then used to train a model for fingerprinting the skarn deposits. Stratified random sampling method has been used on the dataset with 80% of the samples as test set and the rest 20 % as training dataset. We have used K-nearest neighbour (KNN), Support Vector Machine (SVM) and Random Forest algorithms on the data by using Python as a platform. These ML classification algorithm performs better than the earlier existing models available for classification of ore types based on garnet composition in skarn system. Factor importance is calculated that shows which elements play a pivotal role in classification of the ore type. Our results depict that multiple garnet forming elements taken together can reliably be used to discriminate between different ore formation settings.
Spatial variation of the kappa index in the Earth’s plasma sheet: RCMI results
Authors: Sadeghzadeh Sina , Yang Jian , Mousavi Ameneh
Published: March 2021

Astrophysical plasmas are collisionless and correlated systems in which particles are out of thermal equilibrium and can be characterized by non-Maxwellian distribution functions. Amongst those nonthermal distribution functions, the kappa distribution has been widely used and satisfactorily modeled numerous space plasma environments such as ring current and plasma sheet. The particles spectra observed by detector measurements onboard the satellites (e.g., Time History of Events and Macroscale Interactions during Substorms (THEMIS)) indicate that the energy fluxes of plasma sheet particles can be fitted well by the kappa distribution (or combinations thereof). Besides, many empirical models have also used such distributions to estimate fluxes at different energies. Statistically, in the RCM simulations, at all times, even geomagnetically quiet conditions, the initial plasma distribution is assumed to be a kappa function with κ≈6. However, based on the flux spectra constructed by THEMIS data, the kappa index has a significant dawn-dusk asymmetry and a clear dependency on the geocentric distance (R) and the magnetic local time (MLT). Using the averaged RCMI calculated energy fluxes in the equatorial plane we intend to analyze the spatial distribution of the spectral index both for ions (κi) and electrons (κe) in this region and compare the simulation results with observations.
Data flow, harmonization, and quality control
Authors: Silva Brenner , Fischer Philipp , Immoor Sebastian , Denkmann Rudolf , Maturilli Marion , Weidinger Philipp , Rehmcke Steven , Düde Tobias , Anselm Norbert , Gerchow Peter , Haas Antonie , Schäfer-Neth Christian , Schäfer Angela , Frickenhaus Stephan , Koppe Roland ,   Computing and Data Centre of the Alfred-Wegener-Institute
Published: March 2021

Earth system cyberinfrastructures include three types of data services: repositories, collections, and federations. These services arrange data by their purpose, level of integration, and governance.  For instance, registered data of uniform measurements fulfill the goal of publication but do not necessarily flow in an integrated data system. The data repository provides the first and high level of integration that strongly depends on the standardization of incoming data. One example here is the framework Observation to Archive and Analysis (O2A) that is operational and continuously developed at the Alfred-Wegener-Institute, Bremerhaven. A data repository is one of the components of the O2A framework and much of its functionality depends on the standardization of the incoming data. In this context, we focus on the development of a modular approach to provide the standardization and quality control for the monitoring of the near real-time data. Two modules are under development. First, the driver module transforms different tabular data to a common format. Second, the quality control module that runs the quality tests on the ingested data. Both modules rely on the sensor operator and on the data scientist, two actors that interact with both ends of the ingest component of the O2A framework (http://data.awi.de/o2a-doc). We demonstrate the driver and the quality control modules in the data flow within Digital Earth showcases that also connect repositories and federated databases to the end-user. The end-user is the scientist, who works closely in the development approach to ensure applicability. The result is the proven benefit of harmonizing data and metadata of multiple sources, easy integration and rapid assessment of the ingested data. Further, we discuss concepts and current development that aim at the enhanced monitoring and scientific workflow.
Combined magnetic and gravity measurements probe the deep zonal flows of the gas giants
Authors: Galanti Eli , Kaspi Yohai
Published: March 2021

The strong zonal flows observed at the cloud-level of the gas giants extend thousands of kilometers deep into the planetary interior, as indicated by the Juno and Cassini gravity measurements. However, the gravity measurements alone, which are by definition an integrative measure of mass, cannot constrain with high certainty the detailed vertical structure of the flow below the cloud-level. Here we show that taking into account the recent magnetic field measurements of Saturn and past secular variations of Jupiter's magnetic field, give an additional physical constraint on the vertical decay profile of the observed zonal flows in these planets. In Saturn, we find that the cloud-level winds extend into the planet with very little decay (barotropically) down to a depth of around 7,000 km, and then decay rapidly, so that within the next 1,000 km their value reduces to about 1% of that at the cloud-level. This optimal deep flow profile structure of Saturn matches simultaneously both the gravity field and the high-order latitudinal variations in the magnetic field discovered by the recent measurements. In the Jupiter case, using the recent findings indicating the flows in the planet semiconducting region are order centimeters per second, we show that with such a constraint, a flow structure similar to the Saturnian one is consistent with the Juno gravity measurements. Here the winds extend unaltered from the cloud-level to a depth of around 2,000 km and then decay rapidly within the next 600 km to values of around 1%. Thus, in both giant planets, we find that the observed winds  extend unaltered (baroctropically) down to the semiconducting region, and then decay abruptly. While it is plausible that the interaction with the magnetic field in the semiconducting region is responsible for winds final decay, it is yet to be understood whether another mechanism is involved in the process, especially in the initial decay form the strong 10s meter per seconds winds.
Large Equatorial Seasonal Cycle during Marinoan Snowball Earth
Authors: Liu Yonggang
Published: March 2021

In the equatorial regions on Earth today, the seasonal cycle of the monthly mean surface air temperature is <10°C. However, deep (>1 m) sand wedges were found near the paleoequator in the Marinoan glaciogenic deposits at ~635 million years ago, indicating a large seasonal cycle (probably >30°C). Such observations have been used to argue that the Earth had a very high obliquity (>54°) during that time, leading to the proposal of high-obliquity hypothesis. Although the hypothesis was criticized for not being able to find a mechanism for the Earth to return to a low-obliquity state, there was no other explanation for the observed large equatorial seasonal cycle. Through numerical simulations, we show that the equatorial seasonal cycle could reach >30°C at various continental locations if the oceans are completely frozen over, as would have been the case for a snowball Earth, or could reach ~20°C if the oceans are not completely frozen over, as would have been the case for a waterbelt Earth or slushball Earth. It is pointed out that the eccentricity is important for the equatorial seasonal cycle especially when the climate is cold and dry. These large equatorial seasonal cycle above are obtained at the maximum eccentricity of the Earth orbit, i.e., 0.0679, and will be approximately 10°C smaller if the present-day eccentricity is used. For these seasonal cycles, theoretical calculations show that the deep sand wedges form readily in a snowball Earth while hardly form in a waterbelt Earth. Therefore, our results remove a loophole of the (hard) snowball Earth hypothesis, while make the waterbelt Earth and high-obliquity Earth hypotheses much less appealing.
Modeling a modern-like pCO2 Warm period with two versions of IPSL AOGCM
Authors: Tan Ning , Contoux Camille , Ramstein Gilles , Sun Yong , Dumas Christophe , Sepulchre Pierre , Guo Zhengtang
Published: March 2021

The mid-Piacenzian warm period (3.264 to 3.025 Ma) is the most recent geological period with present-like atmospheric pCO2. A specific interglacial (Marine Isotope Stage KM5c, MIS KM5c; 3.205 Ma) has been selected for the Pliocene Model Intercomparison Project phase 2 (PlioMIP 2). We carried out a series of experiments according to the design of PlioMIP2 with two versions of IPSL atmosphere–ocean coupled general circulation model (AOGCM): IPSL-CM5A and IPSL-CM5A2. Our results show that the simulated MIS KM5c climate presents enhanced warming at mid- to high latitudes when compared to the PlioMIP 1, resulting from the enhanced Atlantic Meridional Overturning Circulation caused by the high-latitude seaway changes. The sensitivity experiments, conducted with IPSL- CM5A2, show that, apart from the pCO2,  both modified orography and reduced ice sheets contribute substantially to mid- to high latitude warming in MIS KM5c. When considering the pCO2 uncertainties (+/−50 ppmv) during the Pliocene, the response of the modeled mean annual surface air temperature to changes to pCO2 (+/−50 ppmv) is not symmetric, which is likely due to the nonlinear response of the cryosphere (snow cover and sea ice extent).
Experimental Study of Three-Dimensional Obstacle Effect on Velocity Structure of Density Currents
Authors: Chen Jingyao , Chen Yanan , He Zhiguo , Kneller Benjamin
Published: March 2021

The density currents’ velocity structure, which can be divided into a jet region (JR) and a wall region (WR, thickness hr) according to their distinct dynamics, may be significantly modified as the current crosses an obstacle, thus leading to variations in the flow propagation process. However, there is a lack of direct observation of the response of different parts of the velocity structure to a three-dimensional obstacle due to the challenges in 3-D flow field measurement. To address this knowledge gap, a series of laboratory experiments have been devised to examine the separate influence of the WR and JR on mixing and propagation processes of density currents. A particle image velocimetry system and a high-speed camera are used to obtain the detailed velocity and vorticity fields with high temporal resolution. Compared with the no-obstacle counterpart that is uniform in the spanwise direction, the time-averaged current height (hc) in obstacle cases gradually thickens in that direction, and both the WR and JR thicken accordingly. The ratio of the obstacle height (ho) to hc influences the velocity structure. Specifically, hr/hc upstream is larger than that downstream when ho>hc, and vice versa. It is noteworthy that the variation of hr/hc in the spanwise direction is nonmonotonic with ho. Furthermore, the obstacle also influences the velocity profile upstream. The flow is obstructed on the center line when ho>hc. When ho<hr, the obstacle divides the wall region upstream into two parts above and below ho, and the gradient of the velocity profiles of the upper one is larger than the lower one. The results suggest that the obstacle plays an important role in determining the dissipation on the interface between the JR and the environment, and changing the current’s capacity on carrying the sediment since both the settling and resuspension of particles and sediment mostly happen in the WR. Our findings can improve understanding of the influence of submarine topography and provide a reference for underwater engineering.
Modelling uniform and preferential flow in bioretention systems
Authors: Asry Asra , Bonneau Jérémie , Fernandes Gersende , Lipeme Kouyi Gislain , Chocat Bernard , Fletcher Tim D. , Lassabatere Laurent
Published: March 2021

Bioretention systems are increasingly used worldwide to mitigate the impacts of urban stormwater runoff on the water cycle. The proper management of bioretention systems requires accurate modeling of physical processes occurring within these systems. This study developed and tested a generic and physically-based model called Infiltron-mod. This model makes use of the Darcian approach (assuming Mualem-van Genuchten model for the description of the soil hydraulic properties) and mass conservation. The first version of the model considers evapotranspiration, overflow, exfiltration to surrounding soils, along with the filter hydraulic head and underdrain discharge. The proposed model was tested against field data from a monitored bioretention basin in Melbourne, Australia. We used two rainfall events to calibrate the model and 20 rainfall events for its validation. We achieved quite nice fits of experimental data with median NSE values in the order of 0.7-0.75 for the outflow rates. Despite good performance for outflow rates, we noticed the potential for improvement for the simulation of the height of water in the systems. Such discrepancy is probably the result of preferential flows.

As a second step, we developed a specific module to implement the dual permeability approach to model preferential flow. Such an approach may simulate the concomitancy of matrix flow in part of the system and rapid preferential infiltration into macropores. The new module Infiltron-mod-pref was implemented and investigated. Prior to its use for field data, we validated the new module against more straightforward water infiltration experiments. Several large ring infiltration tests were performed on a field dedicated to infiltrating stormwater, and the two versions of the proposed model, Infiltron-mod and Infiltron-mod-Pref. We clearly showed the benefit to account for the preferential flow in the model. The next step will be the use of Infiltron-mod_Pref for field data from the monitored bioretention basin in Melbourne.

The proposed approach then seems a useful first step to assess both performance and impact of bioretention basins for catchment-scale flow regime management and has real potential for application where user-friendly and simple model calibration and deployment are desired.
Thermal UAS Imaging to Monitor Restored Peatlands
Authors: Ikkala Lauri , Marttila Hannu , Ronkanen Anna-Kaisa , Ilmonen Jari , Rehell Sakari , Kumpula Timo , Klöve Björn
Published: March 2021

Globally peatlands are degrading due to drainage and intensified land use e.g. for forestry, agriculture and peat extraction. Peatland restoration can recover biodiversity of the threatened habitats, reestablish the natural hydrological role of the peatland as retaining water and nutrients and diminish greenhouse gas emissions.

Restoration monitoring for peatlands is urgent in order to reveal the peatland hydrological recovery and ecological succession after restoration, needs for corrective actions and to enable further method development. Restoration monitoring with conventional approaches is laborious, time-consuming and does not cover large areas. Visual evaluation is biased, and the traditional systematic methods give only focused information while conditions for most of the site remain hidden.

Unmanned Aircraft Systems (UAS) imaging produces large coverage information on restoration success in high spatial resolution. Aerial perspective with superior resolution alone extends the monitoring aspect together with the photogrammetric high-precision digital elevation models (DEMs) allowed by the Structure from Motion (SfM) technology.

Additionally, external instruments such as thermal cameras attached in the drone allow revealing temperature anomalies and moisture patterns. We used thermal infrared (TIR) imaging to monitor changes at a boreal rewetted peatland site. The uncalibrated thermal data alone turned out to be useful showing near-surface flow routes recovered in restoration. We further applied a variety of processing methods for the data to explore their applicability on boreal peatlands. The results show the thermal UAS imaging to have great potential in monitoring the hydrological changes due to peatland restoration in high spatial resolution.
Global remotely sensed phenology of Blue-Green Ecosystems
Authors: Lever Jelle , Vitasse Yann , Gilarranz Luis J. , D'Odorico Petra , Odermatt Daniel
Published: March 2021

Changing environmental conditions have significantly altered the phenology, spatial distribution, and abundances of species in terrestrial and freshwater ecosystems. Recent work has shown that such changes may alter the strengths of interactions between species and may jumble structural patterns in networks of trophic, mutualistic and/or other interactions that are crucial for biodiversity. ‘Blue’ (aquatic) and ‘green’ (terrestrial) ecosystems are closely interlinked through biogeochemical cycles and species that inhabit both ecosystems. When the effects of abiotic drivers of global environmental change, such as a change in temperature, precipitation, or land use, are different for lakes and their surrounding watersheds, a blue-green phenological mismatch may therefore occur. In particular, because such changes in seasonal patterns may cascade down food webs.
Remote sensing provides spatially and temporally dense information on biochemical properties of the Earth surface, including biomass and primary production indicators for both aquatic and terrestrial ecosystems. Deriving phenology metrics for these indicators is routine practice for terrestrial vegetation, and several case studies demonstrate the feasibility of analogous metrics for lakes and inland seas. In this study, we used remote sensing data to extract phenology metrics (e.g. start of the growing season) for 4264 lakes distributed across a wide range of biomes from daily chlorophyll estimates and vegetation indices spanning a time-period of 15-20 years. We investigate whether changes in the phenology of lake phytoplankton and the surrounding terrestrial vegetation have occurred during this period, and how the phenology in either ecosystem type is synchronized.
Analysis are underway, but preliminary results suggest contrasting results across different biomes as well as substantial differences in the way in which the phenology of primary producers in lakes and on their surrounding watersheds has changed within these biomes.
An east-west contrasting changes of Antarctic Bottom Water properties in the Southern Indian Ocean over the last three decades
Authors: Choi Yeon , Nam SungHyun
Published: March 2021

Physical properties of Antarctic Bottom Water (AABW) derived from mixture of multiple source waters of different properties, are significantly affected by and contribute to the climate change. This study reveals a contrasting east-west pattern of changes in AABW temperature and salinity in the Southern Indian Ocean (SIO), which continues to become warmer (0.04 ± 0.01°C/decade) and more saline (0.002 ± 0.001 kg/g/decade) in the western SIO whereas warmer (0.03 ± 0.01°C/decade) and fresher (-0.004 ± 0.001 kg/g/decade) in the eastern SIO over the past three decades, based on repeat hydrographic observations along meridional lines (1993, 1996, 2008, and 2019 in the western SIO and 1995, 2004, and 2012 in the eastern SIO). Warming and salinification of AABW consisting of the Cape Darnley Bottom Water (CDBW), Weddell Sea Deep Water (WSDW), and Lower Circumpolar Deep Water (LCDW) in the western SIO, are explained by changing proportion of source waters during the period, e.g., decreasing portion of relatively fresh CDBW (from 68% to 59%), and increasing portions of saline WSDW (from 30% to 34%) and warm and saline LCDW (from 2% to 7%). In contrast, in the eastern SIO, warming and freshening of the AABW consisting of the Ross Sea Bottom Water (RSBW), Adélie Land Bottom Water (ALBW), and LCDW are not explained by the changing proportion but properties of the source waters during the period, e.g., warming and freshening of RSBW (0.08°C/decade and -0.013 kg/g/decade) and ALBW (0.01°C/decade and -0.008 kg/g/decade). The east-west contrasting changes of AABW properties (eastern freshening and western salinification) over the last three decades have important consequences within and beyond the SIO.
Assessment of nitrogen and organic carbon stocks in agricultural soils: uncertainties and significance of temporal evolution
Authors: Tabaud Lucas , Walter Christian , Blancfene Clotilde , Gascuel Chantal , Lemercier Blandine , Michot Didier , Pichelin Pascal
Published: March 2021

Soils are crossroads of carbon and nitrogen geochemical cycles and were consequently identified as a potential sink for carbon (C) and a compartment storage for nitrogen (N). Monitoring the joint evolution over time of organic C and total N stocks in soils appears interesting because of the C/N ratio is an indicator of changes in the organic matter quality. Nevertheless, the temporal evolutions detected in most of the existing studies are in the order of a few gC.m-2.yr-1 (C) and mgN.m-2.yr-1 (N). This study aims to assess uncertainties of soil organic carbon (SSOC) and soil total nitrogen (SSTN) stocks in the topsoil layer (0-25 cm) using three different methods (stochastic, deterministic and experimental), in order to identify the main sources of uncertainty and to evaluate the significance of SSOC and SSTN evolutions over the time. This study was based on a 1200 ha agricultural catchment area in Brittany (France) where systematic soil sampling was repeated at 108 sites in 2013 and 2018. Moreover, soil sampling was repeated three times in 2020 at the same sites by 3 different teams of experienced samplers. Comparing the three methods of uncertainty assessment, we found they provided equivalent results with a SSOC standard deviation of 0.85, 0.74 and 0.68 kgC.m-2 respectively for stochastic, deterministic and experimental approaches and 0.08, 0.07 and 0.06 kgN.m-2 for SSTN. Variance decomposition identified variations of fine earth mass as the main source of uncertainty (77 % of total variance) and attributed at least 16% of the uncertainties due to the operator procedure and were therefore reducible. Using the stochastic approach, the width of the 90 % confidence interval was estimated at each sampling site for C, N and C/N temporal changes. Changes were considered significant at respectively 59, 77 et 99 sites for SSOC, SSTN and C/N: a majority of sites lost organic carbon (-0.03 ± 0.07 kgC.m-2.yr-1), gained total nitrogen (0.006 ± 0.005 kgN.m-2.yr-1) and the C.N-1 (-0.17 ± 0.09 yr-1) ratio decreased. Finally, stock measurements uncertainty was mainly explained by soil natural variability but may still be reduced by a better control of the measurement procedure. In the agricultural context of the study area, the accuracy of the direct measurement appeared sufficient to detect SSOC and SSTN evolution over a time span of 5 years.
Last Interglacial sea ice variability and paleoceanography of the Labrador Sea
Authors: Steinsland Kristine , Ninnemann Ulysess , Fahl Kirsten , Stein Rüdiger , Grant Danielle , De Schepper Stijn
Published: March 2021

Sea ice provides strong feedback in the climate system, and it plays an important role in modulating the strength of the Thermohaline Circulation through glacials, and even interglacials. The warmer than present Last Interglacial (LIG, ~116-128 ka) is thought to have a less stable climate than the current interglacial. Proxies from the deep- and surface subpolar North Atlantic Ocean show prominent instabilities pointing toward coupled ocean-climate variability.  Here we reconstruct sea surface and sea ice changes of the subpolar gyre through the penultimate deglaciation and LIG in order to evaluate sea ice’s role as a driver and amplifier of these ocean circulation and climate changes. We reconstruct the sea ice and sea surface conditions using biomarkers (IP25, sterols) and dinoflagellate cyst assemblages from the Eirik Drift. Low productivity combined with an absence of IP25 could indicate a potential full sea ice cover through MIS 6. The surface ocean experienced large variability through the first half of the LIG, including an early cooling with potential seasonal sea ice cover evident from the dinoflagellate cyst assemblage and IP25. The peak warm period of the LIG is seen in the second half, followed by a brief cooling period towards the end. Following the LIG, MIS 5d is characterized by an IP25 signal and high relative abundances of round brown dinocysts indicating cooling with seasonal sea ice cover. Initial comparisons with deep ventilation proxies (benthic foraminiferal δ13C data) indicate a potential close link between sea ice, surface hydrography and deep circulation. In future studies, we aim to compare the sea ice record to benthic foraminiferal δ13C data from the same samples to better understand the connection between surface and deep-ocean variability.

 
A reevaluation of the atmospheric pressure dependence of secondary cosmic-ray neutrons in the context of Cosmic-Ray Neutron Sensing
Authors: Weimar Jannis , Schattan Paul , Schrön Martin , Köhli Markus , Gugerli Rebecca , Stevanato Luca , Achleitner Stefan , Schmidt Ulrich
Published: March 2021

Secondary cosmic-ray neutrons may be effectively used as a proxy for environmental hydrogen content at the hectare scale. These neutrons are generated mostly in the upper layers of the atmosphere within particle showers induced by galactic cosmic rays and other secondary particles. Below 15 km altitude their intensity declines as primary cosmic rays become less abundant and the generated neutrons are attenuated by the atmospheric air. At the earth surface, the intensity of secondary cosmic-ray neutrons heavily depends on their attenuation within the atmosphere, i.e. the amount of air the neutrons and their precursors pass through. Local atmospheric pressure measurements present an effective means to account for the varying neutron attenuation potential of the atmospheric air column above the neutron sensor. Pressure variations possess the second largest impact on the above-ground epithermal neutron intensity. Thus, using epithermal neutrons to infer environmental hydrogen content requires precise knowledge on how to correct for atmospheric pressure changes.

We conducted several short-term field experiments in saturated environments and at different altitudes, i.e. different pressure states to observe the neutron intensity pressure relation over a wide range of pressure values. Moreover, we used long-term measurements above glaciers in order to monitor the local dependence of neutron intensities and pressure in a pressure range typically found in Cosmic-Ray Neutron Sensing. The results are presented along with a broad Monte Carlo simulation campaign using MCNP 6. In these simulations, primary cosmic rays are released above the earth atmosphere at different cut-off rigidities capturing the whole evolution of cosmic-ray neutrons from generation to attenuation and annihilation. The simulated and experimentally derived pressure relation of cosmic-ray neutrons is compared to those of similar studies and assessed in the light of an appropriate atmospheric pressure correction for Cosmic-Ray Neutron Sensing.
Large-Scale Mapping of Boulder Distribution in Acoustic Backscatter Data of the Baltic Sea by Neural Networks 
Authors: Feldens Peter , Feldens Agata , Herbst Anne , Darr Alexander , Papenmeier Svenja
Published: March 2021

The identification of marine cobbles and boulders (stones) based on acoustic remote sensing is important for the detection, delineation and for an ecological assessment of important seafloor habitats. Due to the large areas involved and the required high-resolution data, a manual interpretation is not feasible. In recent years, automated methods for stone detection were developed. However, these developments were only applied in comparatively small proof of concept areas, and a common barrier to practical implementation by authorities is the required upscaling. This case study aims to apply automated methods for boulder detection based on convolutional neural networks to larger areas, by identifying and validating boulder densities over several hundred km2 in the western Baltic Sea in acoustic backscatter data and derived datasets. The use of distributed training sites of less than 0.5 km2  in size is proposed to improve the model capacity to adapt to variations of boulder appearance in remote sensing data related to local geological variation and survey conditions. Distributed validation sites of similar size are suggested to provide quality control during reprocessing with adapted models. Current limitations for the automated identification of individual boulders in backscatter data are demonstrated, which can be caused by survey geometry, data quality or obstacles and seafloor with similar acoustic characteristics.
Sea ice deformation and thickness in the Western Ross Sea
Authors: Rack Wolfgang , Price Daniel , Haas Christian , Langhorne Patricia J. , Leonard Greg H.
Published: March 2021

Sea ice cover is arguably the longest and best observed climate variable from space, with over four decades of highly reliable daily records of extent in both hemispheres. In Antarctica, a slight positive decadal trend in sea ice cover is driven by changes in the western Ross Sea, where a variation in weather patterns over the wider region forced a change in meridional winds. The distinguishing wind driven sea ice process in the western Ross Sea is the regular occurrence of the Ross Sea, McMurdo Sound, and Terra Nova Bay polynyas. Trends in sea ice volume and mass in this area unknown, because ice thickness and dynamics are particularly hard to measure.

Here we present the first comprehensive and direct assessment of large-scale sea-ice thickness distribution in the western Ross Sea. Using an airborne electromagnetic induction (AEM) ice thickness sensor towed by a fixed wing aircraft (Basler BT-67), we observed in November 2017 over a distance of 800 km significantly thicker ice than expected from thermodynamic growth alone. By means of time series of satellite images and wind data we relate the observed thickness distribution to satellite derived ice dynamics and wind data. Strong southerly winds with speeds of up to 25 ms-1 in early October deformed the pack ice, which was surveyed more than a month later.

We found strongly deformed ice with a mean and maximum thickness of 2.0 and 15.6 m, respectively. Sea-ice thickness gradients are highest within 100-200 km of polynyas, where the mean thickness of the thickest 10% of ice is 7.6 m. From comparison with aerial photographs and satellite images we conclude that ice preferentially grows in deformational ridges; about 43% of the sea ice volume in the area between McMurdo Sound and Terra Nova Bay is concentrated in more than 3 m thick ridges which cover about 15% of the surveyed area. Overall, 80% of the ice was found to be heavily deformed and concentrated in ridges up to 11.8 m thick.

Our observations hold a link between wind driven ice dynamics and the ice mass exported from the western Ross Sea. The sea ice statistics highlighted in this contribution forms a basis for improved satellite derived mass balance assessments and the evaluation of sea ice simulations.
Spatiotemporal Trend and Variability of Precipitation in Taiwan Based on Multi-dimensional Ensemble Empirical Mode Decomposition (MEEMD)
Authors: Tang Chun-Hsiang , Tsai Christina W.
Published: March 2021

Abstract

Most of the time series in nature are nonlinear and nonstationary affected by climate change particularly. It is inevitable that Taiwan has also experienced frequent drought events in recent years. However, drought events are natural disasters with no clear warnings and their influences are cumulative. The difficulty of detecting and analyzing the drought phenomenon remains. To deal with the above-mentioned problem, Multi-dimensional Ensemble Empirical Mode Decomposition (MEEMD) is introduced to analyze the temperature and rainfall data from 1975~2018 in this study, which is a powerful method developed for the time-frequency analysis of nonlinear, nonstationary time series. This method can not only analyze the spatial locality and temporal locality of signals but also decompose the multiple-dimensional time series into several Intrinsic Mode Functions (IMFs). By the set of IMFs, the meaningful instantaneous frequency and the trend of the signals can be observed. Considering stochastic and deterministic influences, to enhance the accuracy this study also reconstruct IMFs into two components, stochastic and deterministic, by the coefficient of auto-correlation.

In this study, the influences of temperature and precipitation on the drought events will be discussed. Furthermore, to decrease the significant impact of drought events, this study also attempts to forecast the occurrences of drought events in the short-term via the Artificial Neural Network technique. And, based on the CMIP5 model, this study also investigates the trend and variability of drought events and warming in different climatic scenarios.

 

Keywords: Multi-dimensional Ensemble Empirical Mode Decomposition (MEEMD), Intrinsic Mode Function(IMF), Drought
Past, Present and Future Sea Levels in Singapore 
Authors: Shaw Timothy , Chua Stephen , Majewski Jedrzej , Tanghua Li , Samanta Dhrubajyoti , Kopp Robert , Horton Benjamin
Published: March 2021

Singapore is a small (728 km2) island nation that is vulnerable to rising sea levels with 30% of its land surface area less than 5 m above present sea level. Rising relative sea level (RSL), however, is not uniform with regional RSL changes differing from the global mean due to processes associated with vertical land motion (e.g., glacial-isostatic adjustment) and atmospheric and ocean dynamics. Understanding magnitudes, rates, and driving processes on past and present-day sea level are therefore important to provide greater confidence in accurately quantifying future sea-level rise projections and their uncertainty. Here, we present a synopsis of Singapore’s past and present RSL history using newly developed proxy RSL reconstructions from mangrove peats, coral microatolls and tide gauge data and conclude with probabilistic projections of future RSL change.

Past RSL is characterized by rapid rise during the early Holocene driven primarily by deglaciation of northern hemisphere ice sheets. Sea-level index points (SLIPs) from mangrove peats show sea levels rose rapidly from -20.7 m at 9.5 ka BP to -0.6 m at 7 ka BP at rates of 6-12 mm/yr. This is substantially greater than predicted magnitudes of RSL change from the ICE-6G_C GIA model which shows RSL increasing from -6.4 m at 9.5 ka BP to a ~2.8 m highstand at ~7 ka BP. SLIPs show the mid-Holocene highstand of ~4 ± 3.6 m at 5.2 ka BP before falling towards present at rates up to -2 mm/yr driven by hydro-isostatic processes. The nature of RSL changes during the mid- to late-Holocene transition remains poorly resolved with evidence of sea levels falling below present level to -2.2 ± 2.0 m at 1.2 ka BP. Present RSL reconstructions from coral microatolls coupled with tide-gauge data extend the limited instrumental period in this region beyond ~50 years. They show RSL rose ~0.03 m from 1915 to 1990 at 0.7 ± 1.4 mm/yr before increasing to 1.5 ± 2.1 mm/yr after 1990 to 2019. Future RSL change from probabilistic projections to 2100 under low (RCP 2.6) and high (RCP 8.5) emission scenarios show sea levels rising 0.43 m (50th percentile) (0.06 – 0.96 m; 95% credible interval) and 0.74 m (0.28 – 1.4 m), respectively. However, projected magnitudes of sea-level rise driven by rapid ice sheet dynamics and the unknown contribution of atmospheric and ocean dynamics in Southeast Asia have the potential to exacerbate projection magnitudes.
Parametric simulation studies on the wave propagation of solar radio emission: the source size, duration, and position
Authors: Zhang Peijin , Wang Chuanbing , Kontar Eduard
Published: March 2021

The solar atmosphere is fluctuated and highly refractive for low frequency waves (<300MHz), the observed features of solar radio sources have indicated the existence of complex propagation effects. The propagation effect has two major parts: refraction and scattering, these two parts have combined influence on the observed source size and position of radio imaging and temporal-frequency features in the radio spectroscopy.

We present a parametric simulation for the propagation effect of the radio wave from solar radio bursts, with the method of parametric simulation, we can build connections between the solar atmosphere plasma condition and the observed radio source properties. By comparing the simulation results with the observed source size and property we estimated the scattering rate and the degree of anisotropic of the background electron, and from the simulation results we propose a possible explanation for the co-spatial phenomena of the fundamental wave and harmonic wave in single frequency.
Validation of Sentinel-5P TROPOMI tropospheric NO2 with airborne imaging, ground-based stationary, and mobile DOAS measurements from the S5P-VAL-DE-Ruhr campaign
Authors: Lange Kezia , Meier Andreas C. , Van Roozendael Michel , Wagner Thomas , Ruhtz Thomas , Schüttemeyer Dirk ,   S5p-VAL-DE-Ruhr campaign team
Published: March 2021

Airborne imaging DOAS and ground-based stationary and mobile DOAS measurements were conducted during the ESA funded S5P-VAL-DE-Ruhr campaign in September 2020 in the Ruhr area. The Ruhr area is located in Western Germany and is a pollution hotspot in Europe with urban character as well as large industrial emitters. The measurements are used to validate data from the Sentinel-5P TROPOspheric Monitoring Instrument (TROPOMI) with focus on the NO2 tropospheric vertical column product.

Seven flights were performed with the airborne imaging DOAS instrument, AirMAP, providing continuous maps of NO2 in the layers below the aircraft. These flights cover many S5P ground pixels within an area of about 40 km side length and were accompanied by ground-based stationary measurements and three mobile car DOAS instruments. Stationary measurements were conducted by two Pandora, two zenith-sky and two MAX-DOAS instruments distributed over three target areas, partly as long-term measurements over a one-year period.

Airborne and ground-based measurements were compared to evaluate the representativeness of the measurements in time and space. With a resolution of about 100 x 30 m2, the AirMAP data creates a link between the ground-based and the TROPOMI measurements with a resolution of 3.5 x 5.5 km2 and is therefore well suited to validate TROPOMI's tropospheric NO2 vertical column.

The measurements on the seven flight days show strong variability depending on the different target areas, the weekday and meteorological conditions. We found an overall low bias of the TROPOMI operational NO2 data for all three target areas but with varying magnitude for different days. The campaign data set is compared to custom TROPOMI NO2 products, using different auxiliary data, such as albedo or a priori vertical profiles to evaluate the influence on the TROPOMI data product. Analyzing and comparing the different data sets provides more insight into the high spatial and temporal heterogeneity in NO2 and its impact on satellite observations and their validation.
Water Quality across the River Ganga Basin in India: Trends, Dominant Geochemical Processes and Impacts
Authors: Richards Laura A. ,   Team SAPTANADI
Published: March 2021

In a basin-wide survey of the River Ganga and key tributaries, from the Himalayan source to the Bay of Bengal in India, we aim to improve the conceptual understanding of downstream water quality trends along > 2000 km.  Here we explore the spatial distribution of a suite of inorganic and organic chemicals, nutrients and wastewater indicators to determine the dominant geochemical process controls across the basin.  Sampling was undertaken at 81 sites in the post-monsoon period of 2019.  We use chemical signatures to identify likely sources, characterise potential higher-pollution zones and to determine the relative importance of regional versus localized controls on the observed water quality parameters, including in relation to contaminant type.  The influence from key tributaries is determined.  We seek to unravel the relative importance of mechanisms such as dilution, evaporation, water-rock interactions and anthropogenic inputs in controlling contaminant distribution.  We assess the representativeness of river bank sampling in comparison to cross-river transects in select locations.  We compare our data to historical records across previous annual cycles, noting differences in extent of agreement according to contaminant type.  This coordinated, catchment-wide survey presents a much broader and more comprehensive dataset than typically reported, hence leading to substantially improved process understanding of dominant controls on contaminant distribution across the catchment.  This work may have implications on informing future monitoring efforts and in identifying future remediation priorities.

Acknowledgements This research was supported by the NERC-DST Indo-UK Water Quality Programme (NE/R003386/1 and DST/TM/INDO-UK/2K17/55(C) & 55(G) to DP et al; NE/R003106/1 and DST/TM/INDO-UK/2K17/30 to DR et al.), NE/R000131/1 to Jenkins et al. and a Dame Kathleen Ollerenshaw Fellowship (LR).
Climadjust: easing the Bias Adjustment process through a user-friendly web service
Authors: Sáenz de la Torre Juan José , Suárez Elena , Iglesias David , Sánchez Iván , Pérez Antonio , Tuni Max , García Markel , San-Martín Daniel , Iturbide Maialen , Gutiérrez José Manuel
Published: March 2021

Climate projections obtained from global and regional climate models usually exhibit biases: systematic deviations from observations. Adjusting these biases is typically the first step towards obtaining actionable climate information to be used in impact studies. However, this bias adjustment process is highly technical and demands a lot of resources, both infrastructures (e.g. access to high performance and cloud computing) —particularly for continental wide applications— and human (e.g. personnel specialised in climate data post-processing).

Climadjust (accessible through https://climadjust.com/) is a web service developed with the support of the Copernicus Climate Change Service  implementing user-friendly bias adjustment for climate projections from the C3S catalogue using customized methods and reference datasets. The service was developed by Predictia —a company with a strong focus on climate services development and climate modelling— in collaboration with the Spanish Research Council (CSIC). 

Climadjust provides scalable cloud resources to compute bias-adjusted climate projections from the ensembles of CMIP and CORDEX datasets or customized areas of interest. In this process, the users are able to (i) upload their own dataset of observations to adjust the climate projections, or choose among reference datasets such as ERA5-Land or WFDE-5, (ii) choose among six state-of-the-art Bias Adjustment techniques implemented using the open source Climate4R package, and (iii) validate the results through the standard framework developed in the European VALUE COST Action. The output is a validated netCDF file, ready to be used by the climate modellers working in climate studies.

This climate service is targeted at the end tail of the downstream market of climate services, namely climate modellers working in sectoral climate adaptation in the agriculture, hydrology, biodiversity, insurance and forestry management fields, among others. Currently, the service counts with over 100 registered users.

To promote the user uptake of the service, the project faced several barriers, such as a lack of understanding on the need of adjusting biases by the end-users, and communication barriers between the climate science community and the end-user community. The session will present the lessons learnt during the user uptake campaigns, the user needs gathered through the user engagement activities performed within it, as well as relevant use-cases of the service, developed hand in hand with the end users.
Comparison of Mann Turbulence and atmospheric turbulence as inflow conditions on a wind turbine in large-eddy simulations (LES)
Authors: Wrba Linus , Englberger Antonia
Published: March 2021

This study deals with different inflow conditions on wind-turbines in LES in order to analyse the impact on the wake. The wind turbine regarded in this study has a hub height of 57.19 m while the radius of the blade measures 40m. Furthermore, the blade element momentum method (BEM) is used to calculate the development forces of the wind turbine blades on the flow. First, the syntheticly generated turbulence of a Mann[1] box generator is considered. Second, atmospheric boundary layer simulations from Englberger and Dörnbrack (2018) are applied as inflow conditions for the three wind components and the potential temperature to calculate the wake of the wind turbine. The distribution of turbulent kinetic energy in eddys of different sizes is worked out in their energy spectrum.The inflow conditions represent the -5/3 Kolmogorov spectrum. The wake characteristics are evaluated for both inflow datasets and the arising differences are discussed in this study

[1] Mann, J. (1994). The spatial structure of neutral atmospheric surface-layer turbulence. Journal of fluid mechanics 273

 