bluuebunny/crossref_metadata_2025 huggingface dataset:
P- and S-wave Velocity Structure beneath Central and East Java, Indonesia: Preliminary Result
Authors: Muttaqy Faiz , Nugraha Andri Dian , Puspito Nanang T , Mori James J , Daryono Daryono , Rohadi Supriyanto , Supendi Pepen
Published: March 2020

The Central and East Java region is part of the Sunda Arc which has an important role in producing destructive earthquakes and volcanic complexes as a result of the subduction of the Indo-Australian plate under the Eurasian plate. Seismic tomography is one geophysical tool that is adaptable to understanding the mechanism process related to tectonic activity, seismicity, and volcanism. We collected a series of waveforms from 1,519 events in the period January 2009 to September 2017 and re-picked 11,192 phases for P- and S-waves at 34 stations of the BMKG network. We determined the 3-D P- and S-wave velocity structure beneath this high-risk region down to a depth of 200 km. In this study, we compare the tomographic images and relocated seismicity in order to represent the subducted slab geometry and the features in the seismic zones, i.e. the 2006 Yogyakarta earthquake zone (Opak fault), south of the mainland, and the 1994 Banyuwangi earthquake zone. Low-velocity anomalies beneath the volcanoes, i.e. Merapi, Merbabu, Kelud, Semeru, Bromo, and Ijen also imply the existence of fluid material and possible partial melting of the upper mantle which migrated from the subducted slab.
Finite volume method for obtaining potential magnetic field solutions
Authors: Feng Xueshang
Published: March 2020

A hyperbolic cell-centered finite volume solver (HCCFVS) is first proposed to obtain the potential magnetic field solutions prescribed by the solar observed magnetograms. By introducing solution gradients as additional unknowns and adding a pseudo-time derivative, HCCFVS transforms second-order Poisson equation into an equivalent first-order as well as pseudo-time-dependent hyperbolic system. Thus, instead of directly solving the second-order Poisson equation, HCCFVS obtains the solution to the Poisson equation by achieving the steady-state solution to this first-order hyperbolic system. The code is established in Fortran 90 with Message Passing Interface parallelization. To preliminarily demonstrate the effectiveness and accuracy of the code, two test cases with exact solutions are first performed. The numerical results show its second-order convergence. Then, we apply the code to the solar potential magnetic field problem that is often approximated analytically as an expansion of spherical harmonics. A comparison between the potential magnetic field solutions demonstrates the capability of our new HCCFVS to adequately handle the solar potential magnetic field problem, and thus it can be used as an alternative to the spherical harmonics approach. Furthermore, HCCFVS, like the spherical harmonics approach, can be used to provide the initial magnetic field for solar corona or solar wind magnetohydrodynamic (MHD) models. Using the potential magnetic field obtained by HCCFVS as input, the large-scale solar coronal structures during Carrington rotation (CR) 2098 have been studied. Meanwhile, HCCFVS automatically deals with the Poisson projection method to keep the magnetic field divergence-free constraint during the time-relaxation process of achieving the steady state. The numerical results show that the simulated corona captures main solar coronal features and the average relative magnetic field divergence error is maintained to be an acceptable level, which again displays the performance of HCCFVS.
Improvement of uncertainty estimation in global hydrological models by using high resolution satellite data as an interpolator
Authors: Westerhoff Rogier , Mourot Frederika , Tschritter Conny
Published: March 2020

Global hydrological models often ingest remotely-sensed observations supported by ground-truthed data in attempts to better quantify water balance components, e.g. soil water content, evapotranspiration, runoff/discharge, groundwater recharge. However, the scaling up process from local observations to that global, coarse, scale contains large uncertainty, often undermining the relevance of water balance calculations.

With recent more advanced high-resolution satellite data, freely available at 10m spatial resolution and (sub-) weekly temporal resolution, there is a possibility to reduce uncertainty in that upscaling. However, there are two challenges in doing so when working with global models: exponential increase of computational effort, and the need for quantifying the yet unknown uncertainty of assumptions that coarse global model cells and their underlying equations bring.

This study hypothesises that a bottom-up approach with high-resolution satellite data and in situ observations will better constrain and quantify uncertainty. By using these more spatially-explicit data, we make the case that the estimation of water balance components should become more data-driven. We propose a more data-driven model that improves uncertainty of estimation and scalability by using more sophisticated, remotely-sensed interpolation layers.

Our case study shows New Zealand-wide estimates of evapotranspiration and groundwater recharge at two resolutions: 1km x 1km, using an earlier developed model and MODIS satellite data; and a novel approach at 10m x 10m using Sentinel-1 and Sentinel-2 data to better incorporate impervious areas (e.g., anthropogenic urbanised land covers) and small land patches (e.g., small forestry areas). We then study the implications of using different spatial scales and quantify the differences between 10m x 10m versus 1km x 1km model pixel estimates. Our method is applied in the Google Earth Engine, a free-for-research high performance cloud computing facility, hence providing powerful computational resources and making our approach easily scalable to global, regional and catchment scales. 

Finally, we discuss what underlying model assumptions in traditional models could be changed to facilitate a method that works consistently at these different scales.
The Lineament South fault system (SW Iberia): New insights and a multiscale view of its seismogenic and tsunamigenic potential
Authors: Sanchez Serra Cristina , Gràcia Mont Eulàlia , Urgeles Esclasans Roger , Martínez-Loriente Sara , Bartolome Rafael , Volpe Manuela , Maesano Francesco , Basili Roberto , Romano Fabrizio , Scala Antonio , Gómez de la Peña Laura
Published: March 2020

The Lineament South (LS) is a major WNW-ESE trending dextral strike-slip fault located along all the Gulf of Cadiz (SW Iberian margin), and it has been considered as the plate boundary between Africa and Eurasia. The SW Iberian margin hosts a moderate to intermediate seismic activity, however, largest and destructive earthquakes and tsunamis have occurred in this area, such as the 1st of November 1755 Lisbon earthquake and tsunami (Mw ≥ 8.5) and the 28th February 1969 earthquake (Mw 7.8). Our work focus on the LS active structure and their potential seismic and tsunami hazard. To study the LS, we integrated the most advanced technologies in marine geosciences covering different scales of resolution, such as: a) Multibeam echosounder that allows us to obtain a bathymetric map that provides information of the seafloor; b) Sub-bottom profiler to acquire high-resolution seismic profiles of the uppermost layers below seafloor; c) Autonomous Underwater Vehicle (AUV) “Abyss” to carry out a micro-bathymetric survey (2 m resolution); and d) High-resolution 2D multichannel seismic profiles. With these dataset, we characterized the LS structure and their sub-surface, calculated the maximum magnitude earthquake and modelled the worst-case tsunami scenario that this fault may produce. The workflow to develop the tsunami modelling involves the following tasks: 1) Interpretation of the high-resolution seismic profiles; 2) Map the trace of the LS fault; 3) Generate a seismo-stratigraphic model of the fault subsurface; 4) Define the specific attributes and seismic/tsunamigenic parameters of the LS fault system; 5) Determine the maximum magnitude and slip according to Leonard (2014) scaling-laws; and 6) Run the tsunami simulation using the Tsunami-HySEA software. The LS extends for more than 370 km, from the Horseshoe Abyssal Plain to the Gulf of Cadiz Imbricated Wedge, as demonstrated for the sequence of MCS profiles across the lineament. In the AUV map, we can recognize fault traces, which are not continuous and show a set of crests and troughs of a width of 100s of meters. The deformation associated to LS span’s about 2-3 km at the seafloor cutting the seismo-stratigraphic sequences, including the Quaternary unit, which reach up to the seafloor. According to the scaling-law of Leonard (2014), the maximum magnitude earthquake that LS can generate is up to Mw 7.9. An earthquake of this magnitude can produce a tsunami that may affect the SW Iberian Peninsula, with a wave amplitude higher than 1 m. Eventually, the LS may generate a significant earthquake and tsunami along the Portuguese, Spanish and Moroccan coasts.
Foreshock Transients and Their Geoeffects
Authors: Zhang Hui
Published: March 2020

Foreshock transients are frequently observed upstream from the bow shock (such as Hot Flow Anomalies, foreshock cavities, and foreshock bubbles). They play a significant role in the mass, energy and momentum transport from the solar wind into the magnetosphere and impact the whole magnetosphere-ionosphere system. This presentation will discuss the great progress made recently toward answering some specific outstanding science questions. Some outstanding questions are listed below. What are the physical differences and relationships between different transient phenomena at the bow shock? What are the formation conditions for the transient phenomena at the bow shock? How do the magnetosphere and ionosphere respond to transient phenomena generated at bow shock? How do transient phenomena at the bow shock evolve with time?
Sediment gravity flow deposits triggered by typhoon, East China Sea Shelf, Western North Pacific
Authors: Shan Xin , Shi Xuefa , Qiao Shuqing
Published: March 2020

Hybrid event beds and a debrite are identified in a core on the mid-shelf of East China Sea. Four units are divided according to abrupt boundary identification, with assistance of grain size analysis. The hybrid event beds typically comprise four internal divisions from the base to the top: (1) structureless muddy sand (H1a, high density turbidite); (2) massive muddy sand with mud clasts (H1b, higher density turbidite); (3) linked debrite (H3); (4) homogeneous mud (H5, fluid mud). The radiocarbon ages of the core were in the range of 3890–8526 yr BP. Based on correlation with other surrounding cores, the depositional age of hybrid event beds and the debrite may be less than 500 yr BP. The TOC and δ13C values in event beds suggest a local erosional regime. The average δ13C value for turbidite (H1a and H1b) is similar to the H3 division in the hybrid event beds, implying that the organic matter in the H1a, H1b and H3 may come from the same source area. The REE data reveals the sediment source is initially from Korean rivers. Bi-plots of (La/Lu)UCC vs. (La/Y)UCC, (La/Y)UCC vs. (Gd/Lu)UCC, (La/Yb)UCC vs. (Gd/Yb)UCC and (La/Yb)UCC vs. (Sm/Nd)UCC of four units in the core are concentrated in the similar range, indicating these event beds have the same source area. Both regimes that partial transformation from a debris flow and erosional bulking are suggested. It is unlikely that the debris flow is triggered by a hyperpycnal flow or a tsunami, because both can carry continental and/or coastal signals which have not been recognized in the core. Typhoon can be a probable triggering mechanism.

 

Acknowledgements

This paper was supported by National Program on Global Change and Air-Sea Interaction (Grant No. GASI-GEOGE-03), National Natural Science Foundation of China (Grants No U1606401 and No. 41706063) and the Taishan Scholar Program of Shandong.
Thermal characteristics of the tropical tropopause layer and their implication on stratospheric moisture in CCMI models
Authors: Kim Joowan
Published: March 2020

The tropical tropopause layer (TTL) provides a major pathway for troposphere-to-stratosphere transport of radiatively active gases, thus it is an important region for understanding stratospheric composition and related climate variability. This work examines the thermal characteristics of the TTL in climate models using the results from state-of-the-art models participated in phase 1 of the Chemistry-Climate Model Initiative (CCMI).
 The CCMI models reproduce reasonable thermal structures in the TTL on climatological and seasonal timescales. However, a near-tropopause temperature bias and corresponding stratospheric moisture bias appear in many models. The temperature bias presents a strong relationship with the ozone bias in the TTL, which causes the temperature bias through local radiative processes. The CCMI models show large inter-model differences in ozone, and it is likely due to different ozone transport mechanisms in the models. These uncertainties could pose a significant limitation on understanding the Earth’s radiation budget and corresponding climate projection. 

 
Concentrations and behavior of rare earth elements in mud volcanic waters
Authors: Sobisevich Alexey , Ershov Valery , Elovskiy Evgeniy , Baloglanov Elnur , Puzich Irina
Published: March 2020

 REEs concentrations in mud volcanic waters were normalized to RPSC (Russian Platform of Shale Composite). On the Yuzhno-Sakhalinsky mud volcano (Sakhalin Island, Russia), along with the sampling for analysis of REEs concentrations, hydrogeochemical monitoring was also conducted.
Coupling model of ecohydrology and simulation of typical shrub ecosystems on the Loess Plateau
Authors: Zhang Yu , Li Xiaoyan , Li Wei , Fang Weiwei , Shi Fangzhong
Published: March 2020

Shrub is the main vegetation type for vegetation restoration in the Loess Plateau, which plays an important role in the regional ecosystem restoration. Study on the relationships between vegetation and soil water of typical shrub ecosystems are significant for the restoration and reconstruction of ecosystems in the Loess Plateau. Three typical shrub (Hippophae rhamnoides Linn., Spiraea pubescens Turcz., and Caragana korshinskii Kom.) ecosystems were chosen in the Loess Plateau. Field experiments were conducted to investigate the factors that influencing the processes of rainfall interception and root uptake of typical shrubs. S-Biome-BGC model was established based on the Biome-BGC model by developing the rainfall interception and soil water movement sub-models. The model was calibrated and verified using field data. The calibrated S-Biome-BGC model was used to simulate the characteristics of leaf area index (LAI), net primary productivity (NPP), soil water content and the interactions among them for the shrub ecosystems along the precipitation gradients in the Loess Plateau, respectively. The results showed that the predictions of the S-Biome-BGC model for soil water content and LAI of typical shrub ecosystems in Loess Plateau were significantly more accurate than that of Biome-BGC model. The simulated RMSE of soil water content decreased from 0.040~0.130 cm3 cm-3 to 0.026~0.035 cm3 cm-3, and the simulated RMSE of LAI decreased from 0.37~0.70 m2 m-2 to 0.35~0.37 m2 m-2. Therefore, the S-Biome-BGC model can reflect the interaction between plant growth and soil water content in the shrub ecosystems of the Loess Plateau. The S-Biome-BGC model simulation for LAI, NPP and soil water content of the three typical shrubs were significantly different along the precipitation gradients, and increased with annual precipitation together. However, different LAI, NPP and soil water correlations were found under different precipitation gradients. LAI and NPP have significant positive correlations with soil water content in the areas where the annual precipitation is above 460~500 mm that could afford the shrubs growth. The results of the study provide a re-vegetation threshold to guide future re-vegetation activities in the Loess Plateau.
Government, Private Enterprise and Ethnic to Build Up Local Society In South Meinong(1989s-1945s)
Authors: Zhou Hong-Jun , Hsu Shu-Chuan
Published: March 2020

Located in the northern part of the Pingtung Plain of southern Taiwan, the town of Meinong is surrounded by Jade Mountain Range in the northeast, Laonong River in the south. After a period of land management and social operation in the Qing Dynasty, Hakka ethnic groups kept traditional lifestyle in Meinong. In the Qing Dynasty, the settlement development of Meinong was mainly distributed in the northern as a result of Laonong River usually flooded and deposited to alluvial fans with gravel and developed hardly in the southern. Until the Japanese colonization period, the Japanese government and the private enterprise begun to develop the alluvial fan. This study has two mainly purposes to analyze. First, the cooperation relationship between private enterprise and government. Second, the social operation and interaction between the original residents and immigrants in Meinong by the new developments that through existing research, literature review, field study and mapping.

In 1908, the Japanese government constructed Shihzihtou Irrigation System to irrigate a new reclamation site in the south of Meinong and set up a dike to block flood on the right bank of the Laonong River. In 1909, the Governor's House gave the permission to the private enterprise—Sanwu Company—to develope the NanLong farm. The NanLong farm attracted the nearby Hoklo ethnic group, the Hakka group of the northern Taiwan and the families of the old tribes of Meinong came here for reclamation. 

The NanLong farm is alluvial soil of sandstone and shale, so it is conducive to agricultural development. It mainly grows the second-phase rice, sucrose, banana and miscellaneous grain crops. The NanLong farm controlled as a committee, representatives were from the settlements of new reclamation site and farm manager who was councilman. That built up a local society center on the NanLong farm, it was different from Meinong was mainly distributed in the northern that was center on the town office. Through state resources supported the private enterprise and private enterprise provided job opportunities for immigranst, the south of Meinong became liveable, culturally inclusive and sustainable landscapes from a alluvial fans with gravel.
High-resolution bathymetry mapping of shallow and ephemeral desert lakes using satellite imagery and altimetry
Authors: Armon Moshe , Dente Elad , Shmilovitz Yuval , Mushkin Amit , Morin Efrat , Choen Tim J. , Enzel Yehouda
Published: March 2020

Many of the world’s drylands are characterized by interior drainage systems that terminate at shallow desert lakes or playas. Except for episodic flooding these largely ephemeral water bodies, remain mostly dry. Surveying and mapping their respective floor topography in a suitable resolution for calculating water balance is a difficult and laborious task. As this is crucial for water resources management and reconstructing paleoenvironmental conditions, diverse methods and efforts were applied. However, detailed, high-quality bathymetric surveys in such environments are rare and have only been conducted in a few such lakes. This is primarily due to their shallow, low-relief, large areas, and often remote characteristics, which complicate application of conventional topographic surveying techniques.  Therefore, satellite-based remote sensing is an essential complementary approach for deriving bathymetry of such lakes.

Global digital elevation models, such as NASA’s Shuttle Radar Topography Mission (SRTM) or ASTER’s GDEM, are unsuitable for accurate measurements of these ephemeral lakes, mainly because of their impenetrability to water and their high signal-to-noise ratio in the low-relief environments. Recent studies addressed these complications by combining remote sensing data with local calibrations of in-situ measurements, or alternatively, by relating shoreline altitudes with precise altimetry. This approach requires a spatial interpolation of individual measurements. Therefore, it is prone to errors that demand intensive efforts to be reduced; even then the errors may remain larger than the actual depth of a flooded lake. Moreover, such methods are hard to apply in complex lakes with multiple sub-basins.

To tackle these problems, we developed a simple methodology to derive a high-resolution (30 m per pixel) bathymetry of shallow desert lakes. In this new method we combine two sources of data: a >30-yr record of Landsat-derived surface water occurrence data; and accurate high-resolution elevation data, acquired by the NASA’s recently launched ICESat-2 satellite (Ice, Cloud, and Land Elevation Satellite-2). We test the proposed new method over three ephemeral lakes around the world: Lake Eyre, Australia, with its complex shallow lake system, consisting of a few sub-basins; Sabkhat Al-Mellah, Algeria; Lago Coipasa, Bolivia. The accuracy of the resulted bathymetric maps was evaluated using cross-validation of ICESat-2 scans, yielding low RMSD values of ~0.3 m, versus ~2.5 m of the SRTM data (validated through other ICESat-2 scans). At Lago Coipasa, we show that bathymetry was effectively determined even when the lake was full of water (up to a few meters depth). This high-resolution, low-error bathymetry mapping complement other globally available topographic data.
Attempt to estimate historical methane emissions from the oil and natural gas sector
Authors: Franke Dieter , Bahr Andreas , Gütschow Johannes , Blumenberg Martin , Ladage Stefan , Lutz Rüdiger , Pein Martin
Published: March 2020

The worldwide operating petroleum industry is considered as one of the major contributors to global anthropogenic methane emissions. However, not only absolute numbers of methane emissions from oil and natural gas production and distribution vary greatly in different global inventories, also the relative contribution of the oil and the gas sector is under discussion. In different studies, the majority of methane emissions are assigned either to natural gas or to the oil sector. For the climate emission origins are of course irrelevant, however, for the climate budget of natural gas usage it is important to know which emissions are attributable to natural gas and what number is related to oil production with its associated natural gas.

Here we use the Federal Institute of Geosciences and Natural Resources’ (BGR) worldwide database on natural oil and gas production and consumption, dating back to 1900, and compare it to global bottom-up methane emission inventories. We will present and discuss several regression approaches that fit the global data reasonably well. In addition, methane emissions of country groups are compared to natural oil and gas production and consumption data. This study finds that the emission factors that relate to gas production released during oil and gas extraction likely vary over the time and across different production areas in the world.
On the detection of oxidized and highly oxidized organic molecules by CHARON PTR-MS via ammonium adduct ionization
Authors: Müller Markus , Piel Felix , Wisthaler Armin
Published: March 2020

Oxidized and highly oxidized organic molecules are important target analytes in atmospheric air samples. In recent years, several chemical ionization mass spectrometry (CIMS) methods have been developed for detecting these target analytes in real time and at ultra-trace levels. One of these CIMS techniques is proton-transfer-reaction mass spectrometry (PTR-MS), which, in combination with the so-called CHARON inlet, measures oxidized and highly oxidized organic molecules in the atmosphere in the gaseous and particulate state. PTR-MS typically uses hydronium ions (H3O+) as reagent ions for detecting organic analytes in their protonated form, [A+H+]. H3O+ ions react with all oxidized organics at unit efficiency, meaning that PTR-MS universally detects these target analytes, with little dependency of the signal response on their oxidation state. A drawback of PTR-MS operation in the H3O+ mode is that oxidized functional groups are often ejected upon protonation.

Herein, we present the results obtained when a CHARON PTR-MS analyzer was operated with ammonium (NH4+) ions as CI reagent ions. We studied the instrumental response to a set of oxidized and highly oxidized compounds including hydroxy, carboxy and peroxy functional groups. We found that fragmentation was greatly suppressed, with ammonium adducts, [A+NH4]+, being the main analyte ions formed. The ionization efficiency ranged from 10 to 80% of the collisional limit, meaning that the NH4+ mode is less quantitative than the H3O+ mode. The performance and advantages of ammonium adduct ionization are demonstrated on two application examples: i) secondary organic aerosol generated in the laboratory from the ozonolysis of limonene, with a particular focus on the detection of peroxides and dimers, and (ii) ambient organic aerosol in Innsbruck, Austria, which was characterized at the molecular level at single digit ng m-³ mass concentrations.
Chemical weathering pathways in the central Himalaya – new constraints from DI14C and δ34S
Authors: Lupker Maarten , Märki Lena , Paris Guillaume , Blattman Thomas , Haghipour Negar , Eglinton Timothy
Published: March 2020

Chemical weathering at Earth’s surface releases soluble elements from rocks to streams and the oceans, interacting with the global carbon cycle along multiple pathways. The carbon budget of continental erosion is strongly dependent on the nature and relative importance of these pathways [1]. Weathering of silicate minerals with carbonic acid represents a long-term net sink of atmospheric CO2. However, chemical weathering by other acids, such as pyrite oxidation-derived sulfuric acid, represents a net CO2 source to the atmosphere [2]. Constraining the net balance of acids and lithology involved in weathering reactions is therefore paramount to budget the impact of chemical weathering on the carbon cycle. In this contribution, we present preliminary radiocarbon data measured on dissolved inorganic carbon (DI14C) from stream and spring waters in the central Himalaya of Nepal. DI14C is a promising tracer of the different chemical weathering reaction pathways [3], and DI14C values in the central Himalaya span across the natural spectrum. To constrain sulfate sources, measurements of δ34S on dissolved sulfate complement this dataset [4], which also shows considerable variability ranging between -15 to +18 ‰. Inverting the dissolved ion composition and their isotopic constraints provide constraints on the proportions of carbonic and sulfuric acid weathering of silicates and carbonates. These results will then be compared with catchment lithological, geomorphological and climatic parameters.

 

[1] Berner and Berner, 2012 - Princeton University Press  

[2] Calmels et al., 2007 – Geology 35-11

[3] Blattmann et al., 2019 – Scientific Reports 9

[4] Turchyn et al., 2013 – EPSL 374
Cooperative Navigation of UAVs in GPS-denied area using an extended Kalman filter with colored RSSI measurements
Authors: Xiaofeng Ouyang , Daqian Lyu , Tianbao Dong
Published: March 2020

In this paper, we focus on UAVs (Unmanned Aerial Vehicles) positioning in GPS-denied environments and proposes a navigation mode of “track reckoning + relative ranging + heading constraint”. Internal sensors (gyros, accelerometer, barometer, etc.) measure the self-motion to obtain the flight path and attitude, and the external sensors identify and measure the relative ranging to achieve peer-to-peer constraint for UAVs. In order to guide the swarm to the intended destination when GPS is denied, the ground anchor nodes are set to provide relative heading constraints to the UAVs for target and trajectory guidance. We propose a hybrid centralized-distributed scheme including 20 UAVs, as well as its dynamic motion model and measurement model. To improve the ranging accuracy in the actual RSSI measurement, we analyze the influence of antenna pattern inhomogeneity and channel variation, respectively. The former mainly determines an antenna radiation function related to the yaw angle and relative position between the two measuring UAVs. The latter uses overlapping Allan variance to analyze and identify the measurement noises from outfield tests, that is, quantization noise, flicker noise, random walk noise and Gaussian white noise, which to some extent bridges the difference between the theoretical model and the practical measurement of RSSI. In this way, an improved extended Kalman filter is to predict and correct the colored noise by adaptively integrating the current peer-to-peer radio ranging performance and its Allan variance. To prove the effectiveness of this approach, simulation results base on practical noise modeling are demonstrated.
Fusion of Sentinel-1 radar and Sentinel-2 MSI imagery for water extraction in Tibetan plateau
Authors: Li Dan , Wu Baosheng , Chen Bowei , Wang Yanjun , Zhang Yi , Xue Yuan , Qin Chao
Published: March 2020

Abstract: Water plays a vital role in plants, animals and human survival, as well as water resources planning and protection. The spatial and temporal changes of rivers have a profound impact on climate change and the scientific protection of the regional ecological environment in Qingzang-Tibet plateau. Due to the influence of snow and cloud cover, optical remote sensing images in this region have less effective coverage. Many researches in the past mainly faced the challenge of misclassification caused by shadows from cloud and mountain. In this study, we proposed a method to improve the extraction of rivers by reducing the effect of shadows by fusing Sentinel-1 radar data and Sentinel-2 optical imagery. For the optical imagery, water indices including MNDWI (Modified Normalized Difference Water Index) and RNDWI (Revised Normalized Difference Water Index) and morphological operations were used to extract the river coverage. In addition, radar data is used to extract water in areas where there is no optical image coverage or where optical images are misclassified by using a combination of both the histogram and Otsu threshold methods. The GEE (Google Earth Engine) platform is used to implement the analysis using two classification datasets at a regional level. Relevant results from Sentinel-1 and Sentinel-2 data showed that the RNDWI has a more accurate water extraction results in this region. We further compared the final river width results with the manually measured samples from Google Earth and situ data of hydrological stations for accuracy assessment. The R2 value is 0.90, and the standard deviation is 18.663m. The river width can be estimated well by this method, which can provide basic data for the study of water in depopulated zone.

Keywords: Remote sensing, shadow removal, water extraction, water index, Otsu threshold, Google Earth Engine
Lithogeochemical Characterization of Akkoy and Edremit Geothermal Fields as Prospective CO2 Storage Sites: A Preliminary Study
Authors: Elidemir Sanem , Güleç Nilgün
Published: March 2020

CO2 Capture and Storage (CCS) is regarded as one of the most effective measures for the mitigation of the unfavourable effects of anthropogenic CO2 emissions on climate change. The implementation of CCS in geothermal fields which are considered as natural analogues for CO2 storage sites, can contribute to the reduction of CO2 emissions as well as increasing the energy production within the context of Enhanced Geothermal Systems (EGS). Given that experimental studies of CCS have certain limitations regarding the time span and reservoir conditions, the geochemical modelling studies are highly important. The geochemical modelling studies require the use of “input data” including i) modal mineralogy of the reservoir rocks and ii) hydrogeochemistry of the reservoir fluid, the variations in the former (both type and amount) particularly affecting the modelling results.

This study is concerned with a preliminary lithogeochemical characterization of the reservoir levels of two geothermal fields (Akköy-Denizli and Edremit-BalÄ±kesir) from western Anatolia, aiming to establish an input database for a prospective geochemical modelling in EGS. In this regard, drill cuttings belonging to the reservoir levels of the relevant fields are examined both macroscopically and microscopically, followed by the laboratory analyses of the samples using XRF (X-Ray Fluorescence), XRD (X-Ray Diffraction), and confocal Raman Spectroscopy techniques. The results obtained from the analyses are evaluated for the identification and quantification of the present minerals. Since the fields Akköy and Edremit have different reservoir lithologies (schist-calcschist-marble and agglomerate units, respectively), the results provide a means of comparison for the effect of mineralogical changes in possible CO2 addition to the systems.
Where does all the gravel go? Tracking landslide sediment from the 2015 Gorkha earthquake along the Kosi River, Nepal
Authors: Graf Emma , Sinclair Hugh , Attal Mikael
Published: March 2020

Rivers draining the Himalaya and feeding the Indo-Gangetic plain support around 10% of the world’s population. However, these rivers are also prone to frequent and often devastating floods such as the 2008 Kosi floods which displaced more than 2.5 million people. Changes in sediment supply from the Himalaya influence the magnitude and distribution of floods through changing capacity and routing respectively. Widespread landsliding following the 2015 Gorkha (Nepal) earthquake increased suspended sediment supply to the river network and is expected to result in some degree of coarse bedload aggradation and increased rates of channel migration at the mountain front. Given the significant amounts of channel aggradation observed in the aftermath of similar events, understanding the timescales of sediment transport following the 2015 Gorkha earthquake and the impact of any resulting sediment wave on flooding in the Gangetic plains is crucial. We track the gravel size fraction of the landslide sediment along the Kosi River (East Nepal) by mapping zones of sediment input from optical satellite imagery and constructing a time series of high-resolution channel cross-sections using an Acoustic Doppler Current Profiler (ADCP) in the years following the earthquake. We use these datasets to identify zones of channel aggradation and migrating sediment, and test whether the changes are consistent with the location of sediment sources (landslides) and magnitude of the monsoon floods with the aid of landslide inventories and flow data. While initial results show a marked increase in coarse sediment following the 2015 monsoon, we see little evidence of large-scale downstream migration of any sediment pulse, indicating the Gorkha landslides may have less of an impact on flood and sediment dynamics on the Indo-Gangetic plains than expected from comparison with similar events. We suggest that the Gorkha landslides may not be connected to the fluvial system to the same extent as for similar events and revegetated rapidly, and therefore did not release significant amounts of sediment into channels after the initial post-2015 monsoon pulse.
Revisiting drought trend over China during 1948-2016: a multivariate perspective
Authors: Ren Liliang
Published: March 2020

How drought changes in the context of global warming is a concerning issue that influences the strategies of drought mitigation and drought management. Based on the simulations of the version 2 of Global Land Data Assimilation System (GLDAS-2.0) during 1948-2016, we revisited the drought trend over China and analyzed the individual contributions of precipitation and potential evapotranspiration (PET) on varied drought patterns. Four composite drought indices including the Aggregate Drought Index (ADI), Joint Drought Deficit Index (JDI), self-calibrating Palmer Drought Severity Index (scPDSI) and Standardized Palmer Drought Index (SPDI) were employed for trend detection. Results showed that all four composite drought indices suggested a significant drying belt spreads from northeastern China to southwestern China, and a significant wetting trend in the “Three river sources” areas. Controversial patterns were mainly located in the northwestern China, Xinjiang districts, and the middle and lower reaches of the Yangtze River, where the SPDI and JDI respectively, overestimated and underestimated the moisture conditions at varying degrees. According to the change point tests, it is found that the drying pattern in the northeastern China occurred since 1970s, where precipitation deficits and expanded PET jointly aggravated the drying process, while for the “Three river sources” areas, the increased precipitation since 2000s is the main driver for the wetting pattern.
Towards Smart Water Cities – opportunities arising from Smart Rain Barrels for urban drainage and water supply
Authors: Oberascher Martin , Kinzel Carolina , Schöpf Martin , Kastlunger Ulrich , Zingerle Christoph , Puschacher Samuel , Kleidorfer Manfred , Rauch Wolfgang , Sitzenfrei Robert
Published: March 2020

In this work, the concept of the smart rain barrel (SRB) as an IoT solution for green infrastructure is presented. The SRB are real-time controlled micro-storages (200 litre) used for an advanced rainwater management. System states and high-resolution weather forecasts from the meteorological service are integrated into the control strategy to provide adequate rainwater for irrigation requirements and to reduce peak runoff in the drainage system. The integration into the smart water infrastructure and the exchange of control commands is done via LoRaWAN, a low-power radio network. For ease of development and to demonstrate the effectiveness of the SRB concept, a two-stage approach was chosen.

First, a prototype of the SRB was built, which is in operation at the university campus of Innsbruck (Austria) during the summer months since 2019. The campus area, also denoted Smart Campus, is part of a pilot project for a “Smart Water City”. This campus is used as both, demonstration object and experimental framework for smart applications in urban water management. The Smart Campus integrates water supply and urban drainage into a joint controlled system, in which natural and anthropogenic water inflows and outflows are measured in real-time. Current measurements encompass water consumptions and pressures in the distribution system, meteorological data at different locations, filling levels in the drainage system, as well as filling levels and soil moistures of decentralised stormwater retention and infiltration systems. The temporal resolution of the measurements is depending on the application between 1 and 15 minutes. By using these high-resolution measurement data, the Smart Campus is an ideal testing ground for smart applications such as the SRB.

In addition, numerical simulations were carried out to test different control strategies and to investigate the effects of a large-scale implementation of the SRBs at community level. The results show that the SRBs can significantly improve system performance (e.g. reduce potable drinking water demand and reduce the risk of flooding) despite their small storage volumes. But the results also demonstrate, that if a large number of SRBs are implemented, a coordinated control strategy to operate SRBs and urban water infrastructure is necessary to avoid a worsening of the system (e.g. generate a combined sewer overflow by simultaneous emptying the SRBs during dry weather flow).
How to reconcile OSL and TCN data: the potential of high-resolution sampling on the Choushui Tableland (West Central Taiwan)
Authors: Rizza Magali , Lebrun Brice , Siame Lionel , Guillou Valéry
Published: March 2020

The determination of fault slip rate is often inferred from dating of Quaternary, deformed geomorphological surfaces affected by fault activity. For this reason, cosmogenic and luminescence methods now are widely applied to date the emplacement of geomorphic markers, but each method relates to different geomorphic processes. While the Terrestrial Cosmogenic Nuclides (TCN) method generally dates the exposure duration of the rock surface to cosmic rays, the Optically Stimulated Luminescence (OSL) method provides burial duration of the sediment after deposition. Age differences between these two methods may relate to the erosion-transport-deposition and aggradation processes experienced by the sediment prior its final deposition but combined may provide new insights into the processes affecting alluvial landforms.

Our case study is located in the Western Foothills, south of the Choushui River (Central Taiwan). There, slip on the Changhua blind thrust fault has caused the eastward tilt of a wide flight of fluvial terraces but slip rates on frontal faults are still debated due to large epistemic uncertainties in dating alluvial surfaces with OSL and TCN methods. To achieve a finer chronology of the deposits, a high-resolution sampling strategy has been deployed leading to a direct and unique comparison between OSL and TCN dating methods. Taking advantage of a natural exposure, we collected 10 samples for 10Be dating completed by 5 OSL samples along a 7 m depth profile. The depth distribution of 10Be concentrations show a complex depositional history with at least two depositional sequences, modelled to be older than ~38.7 ka.

As previous work has shown the difficulties of OSL dating in Taiwan, particular attention has been paid to luminescence characteristics of quartz and potential dosimetry issues. Our OSL analysis are in good agreement with 10Be and previous 14C dating and also reveal three depositional units, dated between ~9 ka and ~66 ka, that are evidenced by different OSL signal characteristics and variations in dosimetry.

This study shows that it is informative to have an exhaustive, detailed, and direct comparison between dating methods on a single depth profile to discuss the geomorphic processes and allow a more detailed understanding of the long-term rates of the Changhua Fault.
Chamber Studies of NO3 reactivity during the oxidation of isoprene
Authors: Dewald Patrick , Shenolikar Justin , Friedrich Nils , Rohrer Franz , Tillmann Ralf , Reimer David , Xu Kangming , Holzinger Rupert , Bernard François , Zhou Li , Brown Steven , Fuchs Hendrik , Crowley John
Published: March 2020

Isoprene is the major volatile organic compound that is released into the environment via biogenic emissions and its oxidation can result in formation of secondary organic aerosol (SOA). Although isoprene emission occurs mainly at daytime, it can accumulate at nighttime and be oxidized by the nitrate radical (NO3) to form organic nitrates that can partition to the particle phase. A detailed understanding of the reaction between isoprene and NO3 is thus required to predict its role in e.g. NOX lifetimes and SOA formation.

The reaction between NO3 and isoprene was investigated under varying experimental conditions (high or low RO2/HO2, temperature, humidity, seed aerosols) during the NO3ISOP campaign at the atmospheric simulation chamber SAPHIR of the research centre in Jülich (Germany). Direct measurement of the NO3 reactivity was carried out with means of a flowtube coupled to a cavity-ring-down spectroscopy (FT-CRDS) setup which enabled the evolution of the NO3 lifetime during the isoprene oxidation process to be monitored.

By comparing direct NO3 reactivity measurements with those calculated from VOC mixing ratios and those calculated from a stationary-state analysis we identify the contributions of isoprene, secondary oxidation products and peroxy radicals to NO3 losses.
Drought and flood monitoring and connection to climate variability in Pearl River Basin, Southern China using GRACE data
Authors: Huang Zhiyong , Jiao Jiu Jimmy , Luo Xin , Pan Yun
Published: March 2020

Drought and flood occur frequently in the Pearl River Basin (PRB), leading to severe damage and economic losses. For better basin-scale water resources management, this study investigates drought and flood  and connection to climate variability in PRB using the total terrestrial water storage (TWS) data from the Gravity Recovery And Climate Experiment (GRACE) satellites. Water storage deficit (WSD) and WSD index (WSDI) are used to characterize drought in PRB. A total of nine drought events are identified during the study period 2003-2014. The period 2003-2006 experienced the most serious drought with a duration of 34 months and WSD (or total severity) of over 1200 mm. WSDI is comparable to self-calibarated Palmer Drought Severity Index (scPDSI) in timing with a correlation of 0.80. Overall, WSDI has higher magnitude than the scPDSI throughout the study period. Flood is characterized by a flood potential index (FPI) which is calculated using TWS anomaly and precipitation. The FPI peaked in June 2008 when the flood was the most serious with the largest rainfall and discharge. Strong correlation is found between FPI and rainfall/discharge in all the four seasons indicating the joint control of flood by rainfall and discharge. This study analyzes the relationship between drought, flood and four climate indices (i.e. El Niño–Southern Oscillation (ENSO), the Pacific Decadal Oscillation (PDO), Indian Ocean Dipole (IOD) and North Atlantic Oscillation (NAO)). Different drought events were related to different climate indices. The severe drought during 2003-2005 was triggered by a warm PDO phase. The 2009-2010 drought was jointly influenced by the warm phase of the three indices: ENSO (i.e. El Niño), IOD and PDO. The severe drought in 2011 was related to the cool phase of both PDO and ENSO (i.e. La Nina). The flood in 2008 was mainly induced by the cool PDO phase with the combined effect from IOD and NAO.
The significance and tectonic evolution of Huatung basin
Authors: Zhao Minghui , Sibuet Jean-Claude , Wu Jonny , Sun Longtao , Zhang Jiazheng
Published: March 2020

The Huatung basin (HB), located between the Philippine Sea plate (PSP) and the South China Sea (SCS), has likely existed near tectonically-active plate boundaries since the early Cenozoic. It may record SCS evolution from the SCS rifting phase to today, and is a key region to understand the broad geodynamic interactions between the SCS and PSP. A left-lateral shear plate boundary between the SCS and PSP followed the Gagua ridge and was active before 56 Ma. A slight compressive component along the Gagua ridge might have occurred from 40 to 30 Ma, giving rise to the topographic uplift of Gagua ridge and adjacent ridges with possibly some underthrusting of the PSP below the HB. A significant compressive episode also occurred along a second fracture zone around 23 Ma ago. The Manila trench inception occurred along the PSP-SCS plate boundary before the end of SCS spreading, involving the subduction of the younger SCS beneath the older HB. Later the intra-oceanic Luzon arc formed and collided in a sub-parallel fashion with the Eurasian continent around 5-6 Ma ago to form Taiwan. The PSP/EU motion was oblique with respect to this plate boundary during SCS opening. However, we have no direct evidence of the HB age (early Cenozoic or early Cretaceous) and if the PSP underthrusted below the HB. We propose to carry a deep seismic refraction survey and dredge sampling of basement units to clarify this problem. This work is supported by the Chinese National Natural Science Foundation (contracts 91958212, 41730532, 41576070 and 41676043).