bluuebunny/crossref_metadata_2025 huggingface dataset:
Geomorphological hazards assessment using machine learning and data fusion
Authors: Ahmed Mohammad , Farhadi Hamed , Michalis Panagiotis , Valyrakis Manousos
Published: March 2020

Turbulent flows may destabilise riverbeds and banks, transporting sediment or underscouring hydraulic infrastructure built near water bodies. For example, scour is a significant challenge that can affect the stability of bridge foundations as the transport of sediment around a bridge pier may cause structural instabilities and catastrophic failures. The aim of this study is to use machine learning techniques & data driven algorithms to predict how energetic turbulent flow events can result in the removal of individual sediment grains, resting on the bed surface or on the protective armour layer around built infrastructure. 

The flume experiments involve flow and particle motion data gathering campaigns [1]. Turbulent flow data are collected upstream the exposed target particle using acoustic Doppler velocimetry. Particle's motion data are gathered using novel micro-electro-mechanical sensors embedded within its waterproof casing, for a range of flow conditions. The obtained data are fed into neural networks having distinct algorithmic complexity (inputs, levels and neutrons). A comparison of the performance of the various model architectures, as well as with past ones [2], is conducted to identify the optimal predictive algorithm for the configuration tested. Sensor data fusion combined with artificial intelligence techniques are shown to provide a unique tool for live and robust data-driven predictions to help tackle significant engineering problems, such as geomorphological activity and scouring of infrastructure (eg bridge piers and embankments) due to turbulent flows, which become increasingly more challenging, under the scope of climate change and intensifying extreme weather hazards.

 

References

[1] Valyrakis, M., Farhadi, H. 2017. Investigating coarse sediment particles transport using PTV and “smart-pebbles” instrumented with inertial sensors, EGU General Assembly 2017, Vienna, Austria, 23-28 April 2017, id. 9980.

[2] Valyrakis, M., Diplas, P., Dancey, C.L. 2011b. Prediction of coarse particle movement with adaptive neuro-fuzzy inference systems, Hydrological Processes, 25 (22). pp. 3513-3524. ISSN 0885-6087, doi:10.1002/hyp.8228.
On the potential and challenges of using machine-learning for automated quality control of environmental sensor data
Authors: Schmidt Lennart , Mollenhauer Hannes , Rebmann Corinna , Schäfer David , Claussnitzer Antje , Schartner Thomas , Bumberger Jan
Published: March 2020

With more and more data being gathered from environmental sensor networks, the importance of automated quality-control (QC) routines to provide usable data in near-real time is becoming increasingly apparent. Machine-learning (ML) algorithms exhibit a high potential to this respect as they are able to exploit the spatio-temporal relation of multiple sensors to identify anomalies while allowing for non-linear functional relations in the data. In this study, we evaluate the potential of ML for automated QC on two spatio-temporal datasets at different spatial scales: One is a dataset of atmospheric variables at 53 stations across Northern Germany. The second dataset contains timeseries of soil moisture and temperature at 40 sensors at a small-scale measurement plot.

Furthermore, we investigate strategies to tackle three challenges that are commonly present when applying ML for QC: 1) As sensors might drop out, the ML models have to be designed to be robust against missing values in the input data. We address this by comparing different data imputation methods, coupled with a binary representation of whether a value is missing or not. 2) Quality flags that mark erroneous data points to serve as ground truth for model training might not be available. And 3) There is no guarantee that the system under study is stationary, which might render the outputs of a trained model useless in the future. To address 2) and 3), we frame the problem both as a supervised and unsupervised learning problem. Here, the use of unsupervised ML-models can be beneficial as they do not require ground truth data and can thus be retrained more easily should the system be subject to significant changes. In this presentation, we discuss the performance, advantages and drawbacks of the proposed strategies to tackle the aforementioned challenges. Thus, we provide a starting point for researchers in the largely untouched field of ML application for automated quality control of environmental sensor data.
Low watershed hydrological and erosion response after fire can be explained by connectivity
Authors: Wu Jinfeng , Baartman Jantiene E.M. , Nunes João P.
Published: March 2020

Mediterranean regions have always been affected by wildfires. However, no studies investigating post-fire hydrological responses and erosion at the watershed scale (~>10 km2) were conducted in Mediterranean. In this study, the discharge and sediment measurements at the outlet of a Mediterranean watershed were observed to test changes in hydrological responses and sediment loads before and after the fire. Besides, aid by the PCA analysis and analysis of connectivity patterns and changes using the index of connectivity (IC), we analyze the hydrological responses and erosion to a wildfire at the watershed scale. Although most of vegetation was removed after the wildfire, it did not, overall, lead to a significant increase in hydrological responses and sediment loads at the watershed scale. Our results can be explained by three major factors. Firstly, much lower rainfall the first two hydrological years after the fire occurred in our watershed. Secondly, as a result of the scale dependency of hydrological and erosion processes, fire-enhanced overland flow and sediment transport occurred locally on hillslope with high burn severity but did not (yet) reach the outlet. Finally, and arguably, most importantly, connectivity in our study area is relatively low and, although it increases after the fire, it remains generally low. Even though post-wildfire connectivity in our watershed increased by 20%, this increase in connectivity was mainly located in the upstream-most part of this catchment, with much less increased connectivity in the downstream areas, which are closer to the catchment outlet. We concluded that the fire consumed vegetation and altered hydrology and erosion processes but didn’t significantly influence downstream water quantity and quality. Connectivity linked to burn severity was suitable for evaluating the effect of wildfire on hydrological responses and erosion. Moreover, this method also appears to be reasonable in assessing and mitigating post-fire water contamination risk.
New method for hydrogen isotope analysis of non-structural carbohydrates
Authors: Schuler Philipp , Joseph Jobin , Cormier Marc-Andre , Werner Roland A. , Saurer Matthias , Lehmann Marco M.
Published: March 2020

Analysing stable isotope composition of biologic components can be a powerful tool to reconstruct past environmental conditions, physiological responses, and to trace metabolic pathways. The analysis of the carbon-bound non-exchangeable hydrogen isotope ratios (δ2HNE) in carbohydrates can be challenging, partly due to the exchangeability of oxygen-bound hydrogen in the same molecule with those in water or vapour. To eliminate such sample alterations, carbohydrates have been nitrated to substitute exchangeable hydrogen with nitrate ester. However, the nitration of carbohydrates is time consuming, needs high sample amount, has several safety issues, and the nitrated products of short-chained carbohydrates are instable. δ2HNE of sugars derived from living organisms or directly from the environment are thus still limited and not widespread available. Here we optimized recent δ2HNE methods, with the focus on plant-derived non-structural carbohydrates such as starch, sugars, and sugar alcohols. The exchangeable hydrogen is replaced via equilibration with water vapour of a known isotopic composition to calculate δ2HNE. In this presentation, we will explain the new δ2HNE method, discuss precision, accuracy, as well as referencing strategies, and give a first outlook for future applications in plant and environmental sciences.
Developing and documenting a Hydrological Model for reproducible research: A new version of Dynamic TOPMODEL
Authors: Smith Paul , Beven Keith , Kretzschmar Ann , Chappell Nick
Published: March 2020

At a minimum reproducible research requires the use of models with strict version control and documented end points (e.g executable calls) so that simulations can be repeated with (hopefully) identical code and data.

Opening the research process beyond this requires that both the model source code and documentation can be scrutinised. Achieving this in a meaningful way means going beyond documentation on the code structure, installation and use. Since models are only approximations of physical systems it is important that users appreciate their limitations and are thoughtful in their use. It is therefore suggested that integration of a model into the scientific process requires developers to go further by:

Documenting, in a way that be directly related to the code, the underlying equations and solutions used by the model and their motivation.

Automating simple reproducible tests on components of the model across a range of dynamic situations beyond those expected.

Providing reproducible case studies highlighting good practice and limitations of the model which can be used both to allow users to access the applicability of the model and to evaluate model changes.

We look at an implementation of these ideas with regards to the ongoing development of Dynamic TOPMODEL. We highlight challenges at both the technical and administrative level and outline how we are addressing them at https://waternumbers.github.io/dynatop/.
Long-term monitoring of self-potential and resistivity in Kyungju area where the largest earthquake occurred in Korea.
Authors: Kim Hyoung Soo
Published: March 2020

Long-term monitoring of self-potential (SP) and electrical resistivity was conducted to examine the correlation between seismic activity and changes of these geo-electrical components in the Kyeongju area where the largest earthquake occurred in Korea. Resistivity monitoring was carried out in 2018 and 2019 but the data was not continuos occasionally because of some accidents in the field. The longest monitoring of resistivity was about 120 days and the resistivity data were acquired in 5 minutes interval. The transmitted electrical source current has 1 Hz square periodic pattern and the received voltage for the source signal was obtained in the sampling rate 10 Hz. SP data were measured in 2019 in the sampling rate of 1 kHz. The monitored resistivity and SP data are being analyzed by some graphic charts which show the variations of resistivity and SP with earthquakes of which magnitude higher than 1.0 that occurred within 4 km of the measuring site. Unfortunately, no clear correlation between the monitored geo-electrical data and seismic activity has yet been confirmed.
Subglacial gas hydrates: ice sheet modulation of methane
Authors: Hubbard Alun , Vadakkepuliyambatta Sunil , Patton Henry , Serov Pavel , Pau Mauro , Winsborrow Monica , Wadham Jemma , Mienart Jurgen , Andreassen Karin
Published: March 2020

Gas hydrates exist within a relatively narrow envelope of thermal and pressure conditions,  small changes in which may lead to widespread dissociation and methane release.  During past glacials, extensive ice sheets covered the continental margins of the Arctic Basin yielding ideal high pressure and low temperature conditions for the sequestration of thermogenic and biogenic methane in hydrate-bearing subglacial sediments.  On ice sheet retreat at the end of the last glacial, these hydrate reservoirs experienced major perturbations in thermal and pressure conditions leading to decomposition and methane mobilization over a variety of magnitude, temporal and spatial scales. Using geophysical data to constrain state-of-the-art ice sheet/gas hydrate modelling, we investigate how past Northern Hemisphere ice sheets modulated carbon sequestration and release.  Our results provide the first quantitative assessment of widespread subglacial hydrate formation and mobilization during the last glacial, yields insights into global carbon cycle dynamics and informs potential future atmospheric greenhouse composition and feedbacks associated with shrinkage of the contemporary cryosphere.
Investigating waves and instabilities in the auroral E region via multi-points in-situ from the SPIDER sounding rockets
Authors: Giono Gabriel , Ivchenko Nickolay , Sergienko Tima
Published: March 2020

On February 2nd 2016 the SPIDER sounding rocket released ten Free Falling Units (FFUs) inside an active westward-travelling auroral electrojet (between 100 to 120 km altitude). Each FFUs carried four electric field probes and four Langmuir probes, respectively on 2 and 1-meter wire booms, as well as a 3-axis fluxgate magnetometer, a gyroscope, an accelerometer and a GPS recorder. The main scientific objective of the project was to study waves and instabilities on various spatial scales, in particular the Farley-Buneman instability, as well as providing an in-situ picture of plasma properties inside the aurora.

Six FFUs were successfully recovered after landing and, despite some mechanical issues on some units, the recorded data showed promising results. Some of these results will be discussed in this presentation, namely (i) the electron density and temperature profiles from two FFUs compared to the incoherent scatter radar measurements from the EISCAT facility, (ii) the hints of different turbulence regimes along the flight seen in the electron density, (iii) the search for Farley-Buneman instability in the electric field data via wavelet analysis, (iv) the observation of electric field waves propagating between two FFUs and the comparison with ground-based observation of the aurora from the ALIS multi-camera system, and finally (v) a global comparison between perturbations seen in the electric field, magnetic field and plasma density and temperature on two FFUs.

These results demonstrated the potential of multi-point in-situ measurements for understanding multi-scale processes in auroras, and preliminary results from the reflight of the rocket to be happening in February 2020 will also be briefly presented.
Development and application system based on static and dynamic data for disaster management
Authors: Park Jin Yi , Kim Ok Ju , Lee Sohee , Lee Junwoo
Published: March 2020

The patterns of recent disasters in Korea such as typhoons, mountain fires and earthquakes are becoming increasingly complex and extensive. It is important to look at the disaster from a unified perspective in order to reduce the damage that will occur from the disaster and promote recovery. The integration between including work systems and information among government agencies that manage disaster situations is one of the important parts in order to respond quickly and reduce damage. But most of the information used to cope with disaster situations is temporarily consumed and volatile. Also there is a lack of periodic updates or management systems. In this study, the information system was established through analysis of the status of the utilization system of static and dynamic data among disaster information used in the Republic of Korea when disaster management. In the event of a typhoon situation, the system operation and on-site survey are to derive the deficiencies to support the assessment of the situation in government agencies and local governments.
Assimilation of GOSAT XCO2 data to optimize surface CO2 flux in East Asia
Authors: Seo Min-Gyung , Kim Hyun Mee
Published: March 2020

Because East Asia is the third-largest source region of CO2 after North America and Europe, there is a need to estimate surface CO2 fluxes accurately over East Asia. Nevertheless, since the number of surface CO2 observations in East Asia is relatively small compared to that in North America and Europe, the estimation of surface CO2 fluxes in East Asia has relatively large uncertainties. To supplement sparse surface CO2 observations, satellite observations can be used.

In this study, the column-averaged dry-air mole fraction (XCO2) concentration data from the Greenhouse gas Observing SATellite (GOSAT) Project was used to estimate the surface CO2 fluxes in East Asia. CarbonTracker developed by Earth System Research Laboratory was used as an inverse modeling system. To assimilate GOSAT XCO2 data in CarbonTracker, the observation operator for GOSAT XCO2 data was developed. To determine the appropriate Model-Data-Mismatch (MDM) for GOSAT XCO2 data, a sensitivity test was conducted. The experiment assimilating GOSAT data showed lower BIAS and RMSE than that without assimilating GOSAT data. In addition, the experiment using 2 ppm MDM for GOSAT data showed lower BIAS and RMSE than that using 3 ppm MDM.

The surface CO2 fluxes over East Asia from the experiments with and without GOSAT data were also compared. By assimilating GOSAT observations, the absorption of surface CO2 fluxes in the ocean became strong and that in land became weaker. Especially, the absorption of surface CO2 fluxes in the Eurasian Boreal region became much weaker than in other regions. The uncertainty reduction was also the largest in the Eurasian Boreal region where the surface CO2 observations are sparse.

Therefore GOSAT XCO2 data have a profound impact on estimating the surface CO2 fluxes in East Asia where the surface observations are insufficient.

 

 

Acknowledgments

This study was supported by the Korea Meteorological Administration Research and Development Program under grant KMI2018-03712 and a National Research Foundation of Korea (NRF) grant funded by the South Korean government (Ministry of Science and ICT) (Grant 2017R1E1A1A03070968). The authors thank Andrew R. Jacobson for providing the CarbonTracker and JAXA/NIES/MOE for providing GOSAT data.
Optical properties of chromophoric and fluorescent dissolved organic matter in the coastal Jeju Island: Impact of the anthropogenic sources
Authors: Kim Jeonghyun , Kim Yeseul , Kim Tae-Hoon , Park Sung Eun , Kang Dong-Jin , Rho TaeKeun
Published: March 2020

The hydrological properties (temperature, salinity, pH, and dissolved oxygen), dissolved organic carbon (DOC) and nitrogen (DON), and optical absorption and fluorescence signals were measured in Jeju Island, Korea, during 2016–2018, especially in potential point-sources (e.g. coastal aquafarms, a sewage treatment facility, and coastal artesian springs). The water samples were filtered through 0.2 μm polycarbonate syringe filters. The optical analysis was conducted using a spectrophotometer (Aqualog, Horiba, USA). Absorbance spectra were converted into the absorption coefficient, and fluorescence intensities were conducted by the parallel factor analysis (PARAFAC) model. The fluorescent components were compared with previous studies through the web-based OpenFluor database.

The absorption coefficient at 350 nm ranged from 0.05 to 7.63 m −1, and it was up to 150 times higher near the point-sources than in the normal coastal ocean. In addition, a350 was observed to be exponentially increased as the reduced distance from the aquafarm outlet. Similarly, the concentration of DOC was 89 ± 29 μM near the point-sources and 78 ± 13 μM in the normal coastal area. They were also observed to be high fluorescence near the point-sources. Principal component analysis (PCA) was applied to illustrate the relationship among the five PARAFAC components, DOC, DON, a350, and fluorescence indexes (HIX, BIX, FI, TC ratio, and RI). The PCA results separated allochthonous, terrestrial components from autochthonous, microbial components, as explained 71.3% of the variance in the data. Based on the HIX (1.26 – 55.70) and BIX (0.52 – 2.87) values in this study, the organic matter around the coastal Jeju Island seem to be highly affected by the coastal groundwater. Here, we used multiple optical properties of organic matter near the coastal area to identify the key factor contributing its distribution and water qualities and to determine the significant influence of the point-sources.
Geomorphological diversity influence on population settlement
Authors: Lješević Milutin , Mihajlović Ljiljana
Published: March 2020

Since the beginning of humanity, geomorphological diversity and relief features some territories, have influenced human settlement and population density. Certainly, the more comfortable conditions of the relief caused the increasing population of the some territory. Thus, there was more intensive settlement on fluvial or marine forms of relief, while on karst, aeolian relief, landslides and areas of escarpment, human settlement was less or completely absent. The only exception is the times of wars, occupations or other disasters, when people settled in unfavorable relief areas (karst, deserts, etc.). The following elements of the relief influenced the construction of residential buildings as well as the industrial activity: the slope of the hillside, surface sunshine, surface geodynamics, water supply, horizontal and vertical terrain distribution, hypsometric features, relief energy. In the paper, the evaluation of individual elements will be presented on examples from the Republic of Serbia and the Republic of Montenegro.
Soil aggregate size affects C sequestration and microorganisms inside aggregate under straw addition
Authors: Lu Jinjing , Li Sheng ping , Wu Xueping , Degre Aurore
Published: March 2020

As the basic unit of soil, aggregates are considered as a stable soil organic ( SOC ) pool. Changes in organic subtract due to straw addition induce variations in soil microbial community or activity, which may effect the C sequestration in aggregates. Most of the previous studies on soil microorganisms assessment was done at large scale i.e. larger quantities of soil, however, few studies on SOC is known in aggregate size fractions. This study investigated the effects of soil aggregate size on the distribution of microorganism and SOC, and the relationship of microorganism and C sequestration inside aggregate size fractions with 13C-labelled straw addition. Soil samples were collected from 0-15 cm and classified into 5 aggregates sizes classes ( ＞5 mm, 2-5 mm, 1-2 mm, 0.25-1 mm and ＜0.25 mm ), and the graded aggregates were incubated for 180 days at 20 °C, with or without 13C-labelled straw residue. The incorporation of 13C into the five aggregate size fractions was analyzed.

After incubation, the SOC, DOC and ROC contents were increased more rapidly and significantly in aggregate ( ＞5 mm ) than that in aggregate ( ＜5 mm ) under straw addition, with the same trend of new carbon derived from straw. The total PLFAs was increased most significantly in aggregate ( ＞5 mm ), especially fungi and negative bacteria ( G- ), while the positive bacteria ( G+ ) increased slightly in aggregate ( ＜0.25 mm ), with no significant change in total PLFAs. The proportion of bacteria in total microorganism increased gradually, as the aggregate size increased in straw treatment. The results imply that aggregate ( ＞5 mm ) have more space for C sequestration and greater contribution to new carbon turnovering in soil than other small aggregates, and it gradually tended to be bacterial with the enrichment of carbon. In addition, the SOC contents were strongly related to the amount of fungi and G- in aggregate ( ＜5 mm ), while related to G+ in aggregate ( ＜0.25 mm ) under straw addition.
Processing of GRACE-FO satellite-to-satellite tracking data using the GRACE-SIGMA software
Authors: Koch Igor , Duwe Mathias , Flury Jakob , Shabanloui Akbar
Published: March 2020

The dual-satellite mission GRACE Follow-On (GRACE-FO) was launched in May 2018 as the successor of the Gravity Recovery And Climate Experiment (GRACE). In May 2019 first level 1 data products were made available to the community and are now published regularly. These products, among others, include orbits, accelerometer measurements, star camera data and micron and sub-micron precise inter-satellite range measurements. The data products are used by different groups to compute estimates of monthly gravity fields of the Earth. The in-house developed GRACE-SIGMA software is used at the Institut of Geodesy/Leibniz University Hannover for the estimation of monthly gravity fields. Several parts of the software’s processing chain, such as background modeling, were updated recently and different parametrization scenarios were tested. First solutions were estimated based on laser ranging interferometer measurements. Moreover, different orbit types, such as reduced-dynamic and kinematic, were tested. In this contribution, we present the influence of these updates and tests on the quality of the gravity fields. The obtained solutions are assessed in terms of error degree standard deviations and post-fit residuals of the inter-satellite measurements.
A Study on the Key Factors of Snowfall structure in mid-eastern region of the Korean Peninsula by Using idealized numerical Experiment
Authors: Yoo Soojin , Chang Eun-Chul
Published: March 2020

 In the winter season of the Gangwon region, where is located in the mid-eastern part of the Korean Peninsula, easterly wind that is induced by Siberian-high frequently causes heavy snowfall. When dry and cold air mass from continent is advected over the East sea of Korea that is relatively warmer than the continental air mass, thermal instability in the lower troposphere increases, which can induce convective cloud rolls. The clouds accompanied by the snowfall are penetrated to inland by the prevailing easterly wind. The Korean Peninsula has the geographical characteristics that mountain ranges exist along the eastern coastline, that can block easterly wind and induce upward motion over the upstream region. Previous studies presented key factors which can affect the snowfall in Gangwon region are air-sea temperature difference, wind turning layer, Froud number (FN), and the horizontal temperature contrast between land and sea. In this study, the idealized experiment is conducted by utilizing the Weather Research and Forecasting (WRF) model to examine effects of each key factor on the snowfall structure. The individual impact of each key factor is investigated by changing the variables while other factors were controlled. When the height of the wind turning layer is higher than the mountain, the maximum snowfall is located over the mountain ridge in the large FN, whereas the snowfall is limited to the windward area in the small FN. On the other hand, when the wind turning layer is lower than the mountain, it shows that the snowfall cannot cross the mountain regardless of the FN. When the horizontal temperature contrast between the land and the sea is large enough, the snowfall is limited to the seaward area off the coastal line.
Simulation of remote sensing of clouds and humidity from space using a combined platform of radar and multi-frequency microwave radiometers
Authors: Jiang Jonathan , Su Hui , Yue Qing , Kangaslahti Pekka
Published: March 2020

We present a simulated simultaneous retrieval of mass mean cloud ice particle effective diameter, ice water content, water vapor, and temperature profiles using a combination of a 94-GHz cloud radar and multi-frequency (118, 183, 240, 310, 380, 664, and 850 GHz) millimeter- and submillimeter-wave radiometers from a space platform. The retrieval capabilities and uncertainties of the combined radar and microwave radiometers are quantified. We show that this combined active and passive remote sensing approach with SmallSat technologies addresses a gap in the current state-of-the-art remote sensing measurements of ice cloud properties, especially deriving vertical profiles of ice cloud particle sizes in the atmosphere together with the ambient thermodynamic conditions. Therefore, this new approach can serve as a plausible candidate for future missions that target cloud and precipitation processes to improve weather forecasts and climate predictions.  
Inter-comparison of melt pond products with melt/freeze-up dates and sea ice concentration data
Authors: Lee Sanggyun , Stroeve Julienne , Tsamados Michel
Published: March 2020

 Melt ponds are a dominant feature on the Arctic sea ice surface in summer, occupying up to about 50 – 60% of the sea ice surface during advanced melt. Melt ponds normally begin to form around mid-May in the marginal ice zone and expand northwards as the summer melt season progresses. Once melt ponds emerge, the scattering characteristics of the ice surface changes, dramatically lowering the sea ice albedo. Since 96% of the total annual solar heat into the ocean through sea ice occurs between May and August, the presence of melt ponds plays a significant role in this transfer of solar heat, influencing not only the sea ice energy balance, but also the amount of light available under the sea ice and ocean primary productivity. Given the importance melt ponds play in the coupled Arctic climate-ecosystem, mapping and quantification of melt pond variability on a Pan-Arctic basin scale are needed. Satellite-based observations are the only way to map melt ponds and albedo changes on a pan-Arctic scale. Rösel et al. (2012) utilized a MODIS 8-day average product to map melt ponds on a pan-Arctic scale and over several years. In another approach, melt pond fraction and surface albedo were retrieved based on the physical and optical characteristics of sea ice and melt ponds without a priori information using MERIS.Here, we propose a novel machine learning-based methodology to map Arctic melt ponds from MODIS 500m resolution data. We provide a merging procedure to create the first pan-Arctic melt pond product spanning a 20-year period at a weekly temporal resolution. Specifically, we use MODIS data together with machine learning, including multi-layer neural network and logistic regression to test our ability to map melt ponds from the start to the end of the melt season. Since sea ice reflectance is strongly dependent on the viewing and solar geometry (i.e. sensor and solar zenith and azimuth angles), we attempt to minimize this dependence by using normalized band ratios in the machine learning algorithms. Each melt pond retrieval algorithm is different and validation ways are different as well producing somewhat dissimilar melt pond results. In this study, we inter-compare melt ponds products from different institutes, including university of Hamburg, university of Bremen, and university college London. The melt pond maps are compared with melt onset and freeze-up dates data and sea ice concentration. The melt pond maps are evaluated by melt pond fraction statistics from high resolution satellite (MEDEA) images that have not been used for the evaluation in melt pond products. 
Multiple detachments of thin-skinned fold-and-thrust belts in the eastern Sichuan Basin, China
Authors: Gu Zhidong
Published: March 2020

The eastern Sichuan Basin, South China, is characterized by approximately parallel thin-skinned fold-and-thrust belts with exposed narrow anticlines and wide synclines. The structural deformation, however, has remained controversial due to the previous poor seismic data. In this study, the new collected pre-stack long-offset 2D- and 3D seismic data have been applied, and a 200-km long cross section perpendicular to the fold-and-thrust belts has been constructed to analyze the structural style and geometric and kinematic evolution. The stratigraphic succession is composed of competent layers separated by three main incompetent layers being multiple detachments, which are the Cambrian evaporites, the Lower Silurian shales, and the Middle-Lower Triassic evaporites, respectively. The basal detachment, the Cambrian evaporites, played a dominant role in the structural deformation, above which the fold-and-thrust belts were generated, and the middle and top detachments accommodated the displacement during the deformation. The main structural styles are detachment folds, fault propagation folds, back thrusts and basement-involved folds. The evolution succession of the fold-and-thrust belts should be kink band, detachment folds, and sequential thrusts of the forelimb and backlimb of the folds. The style of deformation is dependent on the mechanical characters of stratigraphic succession, i.e., the thickness variation of competent and incompetent layers in the stratigraphic units.
Development of a MEMs gravimeter for drone-based field surveys.
Authors: Passey Elizabeth , Hammond Giles , Bramsiepe Steven , Prasad Abhinav , Middlemiss Richard , Paul Douglas , Walker Richard , Noack Andreas , Anastasiou Kristian
Published: March 2020

Gravimetry allows us to study sub-surface structures remotely by measuring changes in Earth's surface gravitational field and using this data to infer the density of geological structures. Of its wide range of applications, it is mostly used in the oil and gas exploration industry, volcanology, civil engineering and even archaeological studies. Airborne gravimetry is a vital method of conducting a spatial gravimetric survey in areas which are difficult to access by foot, such as mountains. Generally, sensors are modified for air crafts platforms by installing them on large gimbal systems, or a strap-down gravimeter can be used as a lower-cost alternative. Now, a new MEMs gravimeter called “Wee-g” is enabling the development of a system to deploy the gravimeter on an unmanned aerial vehicle (UAV or drone). Wee-g was first developed with the objective of developing a low-cost MEMS accelerometer for gravimetric use which could be manufactured on a large scale. In 2016, Wee-g was used to measure Earth tides - the elastic deformation of the Earth caused by gravitational fields of the Moon and Sun. Since then, the device electronics have been miniaturised to make the system portable and has been tested at the Campsie Hills just north of Glasgow. Work is underway to build an isolation platform with active stabilisation on which the Wee-g can be mounted to be deployed on a drone which will reduce airborne surveys costs further and allow for more airborne gravimetric surveys to be carried out in remote locations.
The effect of flow variability on the river meandering dynamics
Authors: Bassani Francesca , Bertagni Matteo Bernard , Ridolfi Luca , Camporeale Carlo
Published: March 2020

The dynamics of a meandering river has been widely investigated by the scientific community. However, the effects of discharge variability on the meander evolution is still an open question. In this work, we present numerical simulations of the short-term evolution of a plane river morphology (the Ikeda, Parker and Sawai model is used to describe the stream hydrodynamics) forced by a stochastic flow discharge (simulated by a compound Poisson process). The comparison of the simulation outcomes with those obtained for the same river under a constant discharge (equal to the mean of the stochastic process) shows interesting results. The discharge variability slows down both the formation of the meanders and the occurrence of the cutoff events, and induces lower meander curvilinear wavelengths and excess bank velocities. A theoretical analysis of the relationship between the channel erosion rate and the river discharge for the Kinoshita curve confirms the obtained numerical results.
Impact of land use land cover change on East Asia
Authors: Byun Ui-Yong , Chang Eun-Chul
Published: March 2020

  Many socioeconomic changes have occurred in East Asia in recent decades. Due to the economic structural change and economic growth, a large population has been concentrated in the cities, resulting in rapid urban expansion. Besides, the surrounding agricultural land for food resources has also expanded, and deforestation has also been active at the same time. These land use/land cover change (LULCC) significantly alter the energy properties of the land surface. Although land surface characteristics that have vigorous variability over time, it is common in a numerical model to treat the information as a static condition. In a numerical weather prediction model aiming at short-term forecasting, the ground characteristics without temporal change are valid; however, in the numerical climate model integrated over several decades, consideration of such variability is essential.
   In this study, we examine the impact of LULCC using the GRIMs (Global/Regional Integrated Model system), which covered regional climate simulation. Temporal change LULC over East Asia, especially cropland and urban, is constructed based on Land Use Harmonization data. Through the comparison of sensitivity experiments considered the LULCC overtime or not, it is confirmed that land surface effect on regional climate change over East Asia. 
The Transfer and Evolvement of Initial Temperature Perturbation in Ocean-Acoustic Coupled Process
Authors: Guo Wuhong , Cui Baolong , Liu Jingyi
Published: March 2020

Focusing on the transfer and evolvement of initial perturbation from temperature of ocean to the underwater acoustic propagation,comparing with the remote sensing data,optimizing Ocean-Acoustic Coupled Model, the reliability of this model is verified. On this basis,global and regional error development experiments are carried out by adding perturbation on the initial temperature of a controlled test. The results show that after 5 days evolution of the initial temperature field,the global perturbation of the propagation loss is saturated, and the perturbation structure is basically consistent with the law of the dynamic ocean.For the target area in Kuroshio region, the initial perturbation in the upstream region is the fastest. This conclusion can provide the basis for the adaptive observation of ocean acoustics.
Sap flow dynamics of xerophytic shrubs differ significantly among rainfall categories in the Loess Plateau of China
Authors: Wang Di , Gao Guangyao , Li Junran , Yuan Chuan , Lü Yihe , Fu Bojie
Published: March 2020

Global climate change is likely to change the timing, frequency and magnitude of precipitation events, studying the response of sap flow (SF) of plants to rainfall events is thus important for understanding the response of ecosystems to global climate change. Here, we conducted a comprehensive study on the SF, rainfall events, meteorological factors and soil water for two typical xerophytic shrub stands (Caragana korshinskii and Salix psammophila) on the Loess Plateau of China for two rainy seasons (from June-September) in 2015 and 2016. The rainfall events were classified into three rainfall categories using the K-means clustering based on the rainfall amount (RA), rainfall duration (RD) and rainfall intensity (RI) (category I: lowest mean RA, RD and RI, category II: moderate mean RA, RI and highest mean RD and category III: highest mean RA, RI and moderate mean RD). The results showed that the response of SF at both C. korshinskii and S. psammophila stands to rainfall events differed under the three categories. The occurrence of rainfall events significantly decreased daily SF of C. korshinskii in three rainfall categories, whereas the daily SF of S. psammophila is more strongly influenced by rainfall category II. Maximum decreases in daily SF between the pre-rainfall and the rainfall weather condition of the two stands both occurred in rainfall category II. Daily rainfall SF at both stands was strongly correlated with daily SR, RH and VPD, regardless of the rainfall categories. Diurnal variation of hourly SF at both stands also differed among the days with similar RA and RD in the same rainfall category. It can be inferred that SF of C. korshinskii is more susceptible to rainfall events than S. psammophila. Rainfall characteristics (RA, RD and RI) and rainfall distribution should be fully considered when assessing the response of SF of shrubs to rainfall events.
Nutrient addition in a Mediterranean grassland decreases species diversity, increases productivity but does not affect stability
Authors: Caldeira Maria , Nogueira Carla
Published: March 2020

Increased nutrient inputs and climate change are affecting ecosystems worldwide. However, there is a dearth of knowledge on how the interacting effects of multiple nutrient inputs and climatic variability may affect ecosystem functioning including grassland species and functional diversity, productivity or resilience to disturbances. This is particularly important in the Mediterranean Basin, a hotspot of climate change, where the frequency of autumn and spring droughts is projected to increase.

 

We conducted a 6-year nutrient addition experiment in an annual grassland site, in Portugal, that is part of a globally distributed experiment called the Nutrient Network (http://www.nutnet.org/). We added high rates of nitrogen, phosphorus and potassium to 5 × 5 m plots, following a full factorial combination in a complete randomized three block design. We established three treatments of one, two and three added nutrients and maintained control plots without addition of nutrients. We examined how a decrease in nutrient limitation and inter-annual climatic variability affected grassland productivity and diversity. We determined the community functional structure (e.g., Community Weighted Mean) and functional diversity (e.g., Function Dispersion) of key morphological and physiological leaf traits associated with the leaf economics spectrum, resource acquisition and water use strategies.

 

Our 6-year study period was characterized by contrasting climatological years, including two dry years (2017 and 2019). We found that grassland productivity was co-limited by multiple nutrients and that species richness decreased with nutrient enrichment. Dry years reduced productivity and species richness and were a critical factor reducing functional diversity of most of the studied traits. Species with competitive characteristics dominated nutrient enriched communities and were related to ecosystem stability by increasing mean biomass production relative to the standard deviation of biomass over time. Contrary to expectations species richness was not related to stability.

 

This study shows that mechanisms underlying ecological functioning of Mediterranean grasslands depend on interactions of multiple nutrient addition and precipitation variability. Understanding these mechanisms is crucial to anticipate potential effects of global changes on Mediterranean grasslands.

 

 
Seismic events associated with catastrophic fracture propagation in rock under compression
Authors: Wang Hongyu , Dyskin Arcady , Pasternak Elena , Dight Phil
Published: March 2020

Fracture growth produced by compressive stress is typically restricted to the sizes of the pre-existing defect seeding the fracture. However the biaxial compression acting near a free surface (e.g. a wall of an opening or at a large scale, the Earth’s surface) can change the fracture growth mechanism. Our experiments demonstrate that in the presence of the second, intermediate principal stress (the minor principal stress is nearly zero in the vicinity of free surface) leads to extensive fracture propagation. Furthermore, the interaction of the propagating fracture with the free surface makes the growth unstable (catastrophic). This produces a seismic event and can lead to such a dangerous and hazardous dynamic rock failure such as skin rockburst.

 

Our previous experiments on brittle transparent samples with an internal initial crack under biaxial compression showed that a small magnitude of the intermediate principal stress, around 5% of the major principal stress, is sufficient to ensure extensive fracture propagation [1- 3]. The catastrophic fracture propagation is then induced by the interaction between the fracture and the free surface as the presence of the free surface imposes additional tensile stresses on the growing fracture. The type of the associated seismic event is the Compensated Linear Vector Dipole (CLVD) source. We present a simple model that allows the determination of the conditions of unstable fracture propagation and the energy of the associated seismic event. The results of this research contribute to the understanding of the nature of seismic events and the mechanics of skin rockburst.

 

Wang, H., Dyskin, A.V. Pasternak, E Dight, P Sarmadivaleh, M. 2018. Effect of the intermediate principal stress on 3-D crack growth. Engineering Fracture Mechanics, 204, 404-420.

Wang, H., Dyskin, A.V. and Pasternak, E. (2019) Comparative analysis of mechanisms of 3-D brittle crack growth in compression, Engineering Fracture Mechanics220, 106656.

Wang, H., Dyskin, A. Pasternak, E., Dight, P. and Sarmadivaleh, M. (2019) Experimental and numerical study into 3D crack growth from a spherical pore in biaxial compression, Rock Mechanics and Rock Engineering, doi.org/10.1007/s00603-019-01899-1.

 

Acknowledgements. AVD and EP acknowledge support from the Australian Research Council through project DP190103260. The first author acknowledges financial support from the Australian Centre for Geomechanics. The authors are grateful to Mr. Frank EE How Tan for his assistance with specimen preparation. AVD acknowledges the support from the School of Civil and Transportation, Faculty of Engineering, Beijing University of Civil Engineering and Architecture.
Checking actual evapotranspiration model using remotely collected surface data: Case study
Authors: Lee Khil-Ha
Published: March 2020

Drought is a reoccurring worldwide natural hazard that affects not only food production but also economics, health, and infrastructure. It is also known that regional drought condition is sensitive to the fine particulate matters (PM) and has relationships with future changes in fine dust levels and associated health impacts under climate change. This mode is strongly correlated to evapotranspiration and land surface conditions and drought index might be good when the actual evapotranspiration and the land surface characteristics are implicitly included in the formula. The procedure for estimating actual evapotranspiration is complex and scientists often tend to select simple model that does not require intensive field data. As a preliminary study this study checks the possibility of PT-JPL which is relatively simple and requires minimum number of observations for estimating local actual evapotranspiration. The model has no calibration, tuning, or spin-up for local adjustment. The model was set up for five representative stations in East Asia. The satellite-collected normalized difference vegetation index (NDVI) and soil-adjusted vegetation index (SAVI) were used to describe the land surface characteristics. Meteorological information such as temperature, water vapor, radiation, and actual evapotranspiration was retrieved from AsiaFlux. The results show that the PT-JPL is promising for estimating local actual evapotranspiration. This study will extend to developing a drought index and its relationship to particulate matters (PM) in the near future.

 

Key words: Actual evapotranspiration, Particulate matters (PM), Drought, PT-JPL

 

Acknowledgement

This work was supported by the National Research Foundation of Korea (NRF-2017-2017001809)