bluuebunny/crossref_metadata_2025 huggingface dataset:
Rainfall and soil moisture conditions for the triggering of torrential flows at the Rebaixader catchment (Central Pyrenees)
Authors: Oorthuis Raül , Hürlimann Marcel , Abancó Clàudia , Moya José , Lloret Antonio , Vaunat Jean
Published: March 2020

Torrential flows, like debris flows and debris floods, can mobilize large volumes at high velocities in mountainous regions. Therefore, they represent an important erosional process and a significant hazard towards infrastructures and people (sometimes catastrophic).

Monitoring-based analysis is a crucial task to improve the understanding of the mechanisms triggering torrential flows and its propagation, which are necessary to implement early warning systems. The monitoring of triggering conditions generally focusses on rainfall measurements and the characterization of the critical rainfall conditions. However, rainfall data do not provide a complete picture of the physical processes involved. Very few studies include soil moisture and/or pore water pressure measurements to define the hydrologic response at the natural slopes of the catchment. In that respect, this study analyses both rainfall and soil moisture data at a Mediterranean-influenced torrential basin located in Central Pyrenees (the Rebaixader site).

The Rebaixader site has a high torrential activity, with 11 debris flows and 24 debris floods detected since 2009. The temporal distribution of rainfall episodes and torrential flows shows a clear shift between the most frequent rainfall episodes (beginning of June) and torrential flows (mid-July). This suggests that soil moisture conditions, depending on antecedent rainfall and/or snowmelt, affect the triggering of torrential flows. Regarding critical rainfall conditions, a previously published rainfall threshold was updated including total rainfall duration and mean intensity of 2009-2019 rainfalls. On the other hand, measured volumetric water content (VWC) was analysed for triggering and non-triggering rainfall events. Preliminary results show lower VWC increment on wetter soils at the beginning of rainstorms that triggered torrential flows. This indicates that soil saturates with lower rainfall amount if the soil is initially wetter; which subsequently generates higher runoff rate and therefore a higher erosion and transport energy that may trigger torrential flows. In addition, a slight trend was observed when comparing rainfall intensity and soil moisture; generally larger rainfall intensity is necessary to trigger torrential flows when soil is drier.  

The analysis of VWC data was more complicated in contrast to the one of rainfall data, since the time series are shorter (2013-2019) and the physical interpretation is not straightforward. Therefore, additional data are necessary to confirm and define soil moisture thresholds triggering torrential flows.
Multi-platform volcanological imaging: Two decades of thermal infrared data from the ASTER and MODIS sensors
Authors: Ramsey Michael
Published: March 2020

For the past 20 years, the ASTER and MODIS instruments on Terra have acquired thermal infrared (TIR) data of the world’s volcanoes. These observations have improved our knowledge of long-term volcanic behavior, eruption monitoring, and post-eruption change. MODIS acquires images twice per day (later doubling this after the launch of Aqua) with 1 km TIR and mid-IR resolution. The volcano data from MODIS were later organized into global automated observation programs such as MODVOLC (USA) and later MIROVA (IT). These systems continually detect and track the amount of emitted energy at each active volcano, resulting in vast databases over time that are critically important for ongoing eruptions. Unlike MODIS, ASTER is scheduled and acquires TIR data at 90 m spatial resolution nominally every 5 – 16 days depending on the latitude. This can be improved to hours with proper scheduling and orbital dependencies using its expedited data system. For the past 15 years, an ASTER program called the Urgent Request Protocol (URP) has combined the rapid detection capability of MODIS with the high resolution expedited observations of ASTER in a sensor-web approach. The URP is operated by the University of Pittsburgh in conjunction with (and the support of) the Universities of Alaska, Hawaii, Turin (IT), Clermont Auvergne (FR), and Bristol (UK) as well as the USGS, the LP DAAC and the ASTER science team. The data are used for: operational response to new eruptions; determining thermal trends months prior to an eruption; inferring the emplacement of new lava lobes; and mapping the constituents of volcanic plumes, to name a few. This ASTER TIR archive of volcanic data is now being mined to provide statistics for future TIR orbital concepts being considered by NASA. As TIR instruments get smaller and more numerous with the use of uncooled detectors, they will become CubeSat compatible and could operate in a multi-platform, sensor-web architecture. This would improve response times to volcanic crises and enable new measurements such as the global inventory of volcanic degassing, thermal precursory trends at every volcano, and active flow temperatures at the minute timescale required for predictive flow and hazard assessment models. The combined spatial, spectral and temporal resolutions of ASTER and MODIS enabled a new multi-platform, multi-scale approach to volcanic remote sensing, a model which could be greatly improved depending on future instrument/mission selections.
Commemorating the 50th anniversary of the Freeze and Harlan (1969) Blueprint for a physically-based, digitally-simulated hydrologic response model
Authors: Simmons Craig T. , Brunner Philip , Therrien Rene , Sudicky Edward A.
Published: March 2020

The year 2019 marked the 50th anniversary of a pioneering publication in hydrology. Allan Freeze and Richard Harlan published their Blueprint for a physically-based, digitally-simulated hydrologic response model (Freeze and Harlan, 1969) in Journal of Hydrology. Their vision was for a futuristic model that would integrate key processes and compartments in the hydrologic cycle: precipitation, evapotranspiration, overland runoff, infiltration and groundwater exchange (into and out of) surface water bodies, such as rivers and lakes. Today, the original Blueprint is a reality.

We recently published a paper in Journal of Hydrology to commemorate the 50 year anniversary of the original Blueprint paper (Simmons et al., 2019). In this talk, we present an overview of, and highlights from, this paper.

Through personal communications with Allan Freeze, we present the history and genesis of the Blueprint paper. We reflect on the uptake of the Blueprint into modern hydrology, the development of numerical models that enabled this, and the range of challenges being tackled by these models. Finally, we consider challenges and opportunities for the future of this area of modelling and hydrologic science.

 

Reference

Simmons, C.T., Brunner, P., Therrien, R., and Sudicky, E.A., 2019. Commemorating the 50th anniversary of the Freeze and Harlan (1969) Blueprint for a physically-based, digitally-simulated hydrologic response model, Journal of Hydrology, https://doi.org/10.1016/j.jhydrol.2019.124309  
Application of Improved U-Net and ResU-Net Based Semantic Segmentation Method for Digitization of Analog Seismograms
Authors: Zhao Jiahua , Ishii Miaki , Ishii Hiromi , Lee Thomas
Published: March 2020

Analog seismograms contain rich and valuable information over nearly a century. However, these analog seismic records are difficult to analyze quantitatively using modern techniques that require digital time series. At the same time, because these seismograms are deteriorating with age and need substantial storage space, their future has become uncertain. Conversion of the analog seismograms to digital time series will allow more conventional access and storage of the data as well as making them available for exciting scientific discovery. The digitization software, DigitSeis, reads a scanned image of a seismogram and generates digitized and timed traces, but the initial step of recognizing trace and time mark segments, as well as other features such as hand-written notes, within the image poses certain challenges. Armed with manually processed analyses of image classification, we aim to automate this process using machine learning algorithms. The semantic segmentation methods have made breakthroughs in many fields. In order to solve the problem of accurate classification of scanned images for analog seismograms, we develop and test an improved deep convolutional neural network based on U-Net, Improved U-Net, and a deeper network segmentation method that adds the residual blocks, ResU-Net. There are two segmentation objects are the traces and time marks in scanned images, and the goal is to train a binary classification model for each type of segmentation object, i.e., there are two models, one for trace objects and another for time mark objects, for each of the neural networks. The networks are trained on the 300 images of the digitizated results of analog seismograms from Harvard-Adam Dziewoński Observatory from 1939. Application of the algorithms to a test data set results in the pixel accuracy (PA) for the Improved U-Net of 95% for traces and nearly 100% for time marks, with Intersection over Union (IoU) of 79% and 75% for traces and time marks, respectively. The PA of ResU-Net are 97% and nearly 100% for traces and time marks, with IoU of 83% and 74%. These experiments show that Improved U-Net is more effective for semantic segmentation of time marks, while ResU-Net is more suitable for traces. In general, both network models work well in separating and identifying objects, and provide a significant step forward in nearly automating digitizing analog seismograms.
Comparisons of different definitions of the western Pacific pattern and associated winter climate anomalies in Eurasia and North America
Authors: Aru Hasi
Published: March 2020

The western Pacific pattern (WP) is one of the most prominent teleconnection patterns over the Northern Hemisphere (NH) in boreal winter. There exist several methods employed to identify the WP in the literature. This study compares eight WPs defined by different methods. Correlation coefficients among the eight WP indices (WPIs) show considerable spreads, though most of them are statistically significant. The meridional dipole structure of WP can be captured by all of the WPIs, but it shows large spreads in the locations of the centers. Several WPIs produce a significant correlation with the winter Arctic Oscillation, with marked signals of atmospheric anomalies over the Arctic region. Connections of the WPs with the simultaneous winter El Niño-Southern Oscillation (ENSO) depend largely upon their definitions. Impacts of the WPs on the surface air temperature over many parts of Eurasia and North America are also sensitive to their definitions. Differences in the surface air temperature anomalies are closely related to differences in the spatial structure of the WPs. Finally, we define a new WP index as differences in the area-average 500-hPa geopotential height anomalies between subtropics and mid-latitude of northwestern Pacific. This newly defined WP index has a close relation with the above eight WPIs, the tropical Pacific sea surface temperature and surface air temperature anomalies over Eurasia and North America.
Outlining a stepwise, multi-parameter debris flow monitoring and warning system: an example of application in Aizi Valley, China
Authors: Chen Ningsheng
Published: March 2020

Abstract: In recent years, the increasing frequency of debris flow demands enhanced effectiveness and efficiency are essential not only from an economic point of view but are also considered as a frontline approach to alleviate hazards. Currently, the key issues are the imbalance between the limited lifespan of equipment, the relatively long period between the recurrences of such hazards, and the wide range of critical rainfall that trigger these disasters. This paper attempt to provide a stepwise multi-parameter debris flow warning system after taking into account the shortcomings observed in other warning systems. The whole system is divided into five stages. Different warning levels can be issued based on the critical rainfall thresholds. Monitoring starts when early warning is issued and it continues with debris flow near warning, movement warning and hazard warning stages. For early warning, historical archives of earthquake and drought are used to choose a debris flow susceptible site for further monitoring, Secondly, weather forecasts provide an alert of possible near warning. Hazardous precipitation, model calculation and debris flow initiation tests, pore pressure sensors and water content sensors are combined to check the critical rainfall and to publically announce a triggering warning. In the final two stages, equipment such as rainfall gauges, flow stage sensors, vibration sensors, low sound sensors and infrasound meters are used to assess movement processes and issue hazard warnings. In addition to these warnings, community-based knowledge and information is also obtained and discussed in detail. The proposed stepwise, multi-parameter debris flow monitoring and warning system has been applied in Aizi valley China which continuously monitors the debris flow activities.
Using historical data to identify future water quality trends at a regional scale
Authors: Lintern Anna , Kho Natalie , Guo Danlu , Liu Shuci , Duvert Clement
Published: March 2020

Using historical data to identify future water quality trends

Lintern

Kho

Guo

Liu

Duvert

 

Climate change is expected to have a severe impact on water resources management in Australia. This is expected to lead to increasing frequency in extreme hydrological events such as droughts and floods, which will in turn contribute to higher risks of bushfires, fish kills, and water shortage for both humans and the environment. The potential impacts of these climate-change-induced extreme events on the quantity of water available to humans and the environment are relatively well understood. However, we have little understanding of the effect on the water quality of Australian rivers. This project aims to start filling this gap in our understanding.

Our key objectives are:

(1) to identify how extreme hydrological events such as droughts and floods have affected river water quality over the last two decades, and explore how spatially variable these impacts have been across the Australian continent.

(2) to use these past observations as a basis to predict how river water quality will be affected by climate change across the continent, and identify the locations within Australia that will be most vulnerable to water quality deterioration in the near future.

There is a wealth of historical water quality data for each state in Australia, but these datasets have not yet been investigated systematically to develop a nation-wide understanding of water quality patterns. We believe that only a continental-scale understanding of the response of river water quality to extreme hydrological events will allow for the development of robust predictive models of climate change impacts on water quality. Knowing the potential hotspots for future water quality deterioration will be a key step towards identifying priorities for catchment planning and management.

In this poster, we will present the preliminary findings of this project by detailing the spatial variability in the impact of hydrological events on water quality across the state of Victoria in South-East Australia.
Single-crystal elasticity of Ice at high pressures
Authors: Mao Zhu , Shi Weigang
Published: March 2020

Recent astronomy studies observed the existence of hundreds of ice giants in the universe. Ice is one of the major components of these ice giants. Experimental studies on the physical properties of ice at high pressures are thus important for understanding the composition and evolution of these ice giants. Here, we have synthesized high-quality single-crystal H2O-ice with 0.5 m NaCl. Single-crystal elasticity of ice was measured by Brillouin spectroscopy combined with X-ray diffraction up to 93 GPa at 300 K using diamond anvil cells. All the elastic moduli of ice-VII exhibit a nearly linear increase with pressure up to 43 GPa at 300 K, although the off-diagonal modulus C12 and shear modulus C44 slightly deviate from the Cauchy relation between 10 and 20 GPa. The longitudinal modulus, C11, and C12 show a clear softening when ice-VII changes to the pre-transition ice-VII state. Meanwhile, we also observed a weak drop in the unit cell volume across this change in our high-quality single-crystal X-ray diffraction measurements. We also present first experimental measurements on the single-crystal elasticity of ice-X. Our experimental results were also used to model the anisotropy of ice at high pressures.
Laminar-turbulent transition in debris flow: measurement of basal pore fluid pressure in an open channel flow experiment
Authors: Sakai Yuichi , Hotta Norifumi
Published: March 2020

The fluidity of a debris flow varies by grain size. Flows containing principally coarse grains are considered to be laminar and those featuring largely incohesive fine grains turbulent. The transition from laminar to turbulent flow depends on the ratio of flow depth to grain size (i.e., the relative flow depth). Debris flows with relative flow depths of approximately 10 are entirely laminar; those with relative flow depths over approximately 20 exhibit transitional flow behavior from entirely laminar to partially turbulent. This transitional flow has been investigated in the laboratory using the resistance law and the vertical distribution of streamwise velocity. The flow exhibits a two-layer structure; the lower layer remains laminar but the upper layer becomes turbulent. However, transition modeling remains incomplete given the lack of data on the internal stresses associated with transitional flow. Here, we studied the laminar-turbulent transitions of debris flows by measuring basal pore fluid pressures using flume tests.

We flowed saturated monodisperse granular materials over an open-channel rigid bed; we used sediment particles of diameters 2.9, 2.2, 1.3, 0.8, 0.5, and 0.2 mm. When the debris flow attained the steady state, the flow depth and basal pore fluid pressure were measured using an ultrasonic sensor and pressure gages respectively, and the basal total normal stress estimated using the bulk density of the debris flow assessed at the downstream end.

The relative flow depths ranged from 5 to 130. Comparisons among the measured pore fluid pressures and the hydrostatic and total normal stresses indicated that a pore fluid pressure of 0.2 mm differed greatly from the hydrostatic pressure, equaling, in fact, the total normal stress, and indicating fully turbulent flow. In contrast, pore fluid pressures of 2.9, 2.2, and 1.3 mm were slightly higher than the hydrostatic pressures, indicating that the Reynolds stresses of the pore fluid due to the strong shears imparted by the sediment particles were in play; flow was entirely laminar. Pore fluid pressures of 0.8 and 0.5 mm were intermediate between the hydrostatic and total normal stresses, indicating the transition from fully laminar to partially turbulent flow.

By analogy with the Reynolds number for Newtonian fluid, we investigated the transition based on the non-dimensional number for debris flows (thus, the ratios of inertial to dynamic stresses caused by interparticle collisions and the Reynolds stresses of the debris flow pore fluid). This identified the critical Reynolds number in terms of transition commencement. We describe the transitional flow behavior of monodisperse granular debris flows using a two-layered model in which the position of the between-layer interface is estimated based on that critical Reynolds number.
Estimation of spatial soil depth and its application for shallow landslides and debris flow assessment: case study at Mt. Jiri, S. Korea
Authors: Kim Minseok , Kim Jisu , Oh Hyun-Joo , Kim Jinkwan
Published: March 2020

Soil depth plays critical role in prediction studies reflecting hydrologic mechanism such as shallow landslide and debris flow although there are many parameters. Thus, many researchers are studying the estimation of soil depth distribution using various methods such as a kriging and artificial neural networks (ANNs) since it is not easy to get a detailed soil depth distribution in field. The aims of this study are 1) to estimate detailed spatial distribution of soil depth (various methods such as ANNs, Kriging, s- and z-model, and c-model) and, 2) to apply them for assessment of shallow landslide instability and debris flow. To do this, soil depth of 760 points using knocking pole test method and elevation datasets using GPS-RTK were collected at Mt Jiri, South Korea. To analysis the accuracy of each estimated soil depth distribution, the lowest root mean square error (RMSE), mean absolute error (MAE) and the highest values of the coefficient of determination (R2) were applied and, ANNs method showed reasonable result better than did others. In the effect of shallow landslide instability and debris flow assessment with the each soil depth distribution results, soil depth distribution using an ANNs method also showed high simulated model performance by modified success ratio (MSR). These results indicated that ANNs can be one of the methods to estimate the soil depth distribution for improvement of accuracy of shallow landslide instability mapping and debris flow assessment.
The evolution trend of geological disasters over spatial and temporal in the context of global warming —— taking the Qinghai-Tibet Plateau as an example
Authors: Jia Yiru
Published: March 2020

The Tibetan plateau (QTP) has the highest average elevation in the world. As the third pole in the world, it has the largest cryosphere system at low and mid latitudes. It is a sensitive area of climate change, and the climate change is more significant. Global climate change has led to higher temperatures and increased rainfall on the Tibetan Plateau. This will lead to changes in the frequency and pattern of geological disasters. This spatiotemporal change and its influencing factors are not clear, so we collected a total of 898 geological disasters in the QTP from 1905 to 2015. Then we process the data to obtain various meteorological indicators of the QTP and combine them with the changes in the distribution of disaster points. Furthermore, the distribution pattern of the disaster points with the spatiotemporal changes of slope, altitude, precipitation and temperature is obtained. Statistics on the disaster data corresponding to each meteorological index are then made. Through the analysis of the distribution map and the statistical results of the data, the correlation between the occurrence of geological disasters and each element is obtained. The disaster points are superimposed with multiple influencing factors, and the influence of multiple factors on the distribution of geological hazards is discussed. The results showed that geological disasters have gradually expanded from the traditional high-incidence area of southern and eastern edges to the interior. The frequency of disasters in high altitude areas is increasing, and gradually extended from the rainy season to the non-rainy season.
Fault tectonic analysis of aftershocks of the 2011 Tohoku, Japan, earthquake: interaction between three different tectonic domains and approximation of stress magnitude
Authors: Choi Pom-yong
Published: March 2020

In order to elucidate the regional variation of stress field in the eastern part of Japan after the 2011 Tohoku earthquake of M=9.3, we tried to analyze focal mechanism data of earthquakes that occurred in 2011, presented by the Japan Meteorological Agency (JMA). Although earthquakes (aftershocks) occurred largely in the offshore area along the subduction zone of the Pacific plate under the North American and Eurasian plates, focal mechanism data presented by JMA are mainly those on land. For fault tectonic analysis, the suggested focal mechanism data are classified into appropriate populations on the basis of clusters and focal depths to reduce the bias and errors of stress tensors resulting from areal stress variation and varying vertical load. According to the results, the stress types of determined stress tensors consist of reverse, wrench and normal faulting ones. As for reverse faulting stresses in which the vertical load is the minimum principal stress axis, those of NW-SE compression prevail, which may be tightly related to northwestward movement of the Pacific plate. Those of E-W compression are determined in the continental crust deeper than about 9 km around Yamagata and in the lower part of subducting oceanic crust. In the Kanagawa and Chiba areas, determined stress tensors display NNW-SSE compression as well as NW-SE and E-W compressions. The NNW-SSE compression seems to be related to the movement of the Philippine Sea plate. Stress tensors of wrench faulting type are found in the continental crust far from the subduction zone of the Pacific plate, displaying NW-SE and E-W compressions in the shallower and deeper parts of crust, respectively. The E-W compression is presumably associated with the Himalayan tectonic domain. Determined stress tensors of normal faulting type show diverse extension directions: NW-SE extension in the coastal area, parallel to the Pacific compression, and E-W or NE-SW extension elsewhere. Especially, numerous focal mechanism data showing normal faulting stresses are present in the coastal area of Fukushima and Ibaraki, from which Poisson’s ratio of shallow crust was determined to be 0.25 to 0.27 using friction lines on Mohr’s circles and focal depths (or corresponding vertical loads). Additional horizontal stress related to the northwestward motion of the Pacific plate was estimated to be 46, 122 and 286 MPa in three groups of 0 to1.5, 1.5 to 4.5 and 3.5 to 11.5 kilometers in depth, respectively.
Impacts of Anthropogenic Aerosols on Springtime Mesoscale Convective Systems over Southern China
Authors: Zhang Lijuan , Fu Tzung-May
Published: March 2020

Precipitation over Southern China for the month of April, which is largely associated with mesoscale convective systems (MCSs), has declined significantly in recent decades. It is unclear how this decline in precipitation may be related to the concurrent increase in anthropogenic aerosols in the atmosphere over this region. Using observation analyses and model simulations, we showed that anthropogenic aerosols significantly reduced MCS occurrences by 21% to 32% over Southern China in April, leading to less and weaker rainfall. Half of this MCS occurrence reduction was due to the direct radiative scattering and the indirect enhancement of non-MCS liquid cloud reflectance by aerosols, which stabilized the regional atmosphere. The other half of the MCS occurrence reduction was due to the microphysical and dynamical responses of the MCS to aerosols. The model simulations showed that the higher levels of aerosols and the resulting increase in liquid cloud droplets both enhance the scattering of sunlight, cool the surface, and stabilize the lower atmosphere. As a result, the occurrence of strong convective systems is suppressed, leading to decreased rainfall in April over Southern China. Our results demonstrated the complex effects of aerosols on MCSs via impacts on both convective systems and non-convective cloud systems in the regional atmosphere.
Combining GGM and RTM to model the gravity gradient tensor
Authors: Liu Jinzhao
Published: March 2020

In this paper, by combining the Global Geopotential Model (GGM, specifically, EGM2008 is used) and the Residual Terrain Model (RTM) data, we have modeled the Gravity Gradient Tensor (GGT) in eastern Tian shan mountains areas, China. The RTM data are obtained from the Shuttle Radar Topography Mission (SRTM) elevation model and the DTM2006.0 high degree spherical harmonic reference surface. The integration of RTM data reduces the truncation errors (or called omission errors) due to the finite expansion terms of the spherical harmonic coefficients of the GGM, and compensates for the high frequency information and spatial resolution of the GGT within the study area.
Effectiveness of green areas and impact of the spatial pattern on water infiltration within cities
Authors: Ferreira Carla , Frigione Barbara , Gazdic Milan , Pezzagno Michelle , Ferreira António
Published: March 2020

Soil is a non-renewable resource subject to increasing degradation favoured by human activities, such as the creation of impervious surfaces. Driven by increasing global population, soil sealing became a major challenge due to growing expansion and its impact on decreasing ability of soil to provide ecosystem services. In order to mitigate the environmental and social impacts of sealing, a worldwide interest in greening the cities have been noticed among politicians and stakeholders. Urban green areas provide benefits for the urban water cycle, namely through reducing stormwater runoff and flood hazard. The effectiveness of green areas inside the cities on runoff reduction, is still not well understood. This is partially due to the role of complex landscapes, including distinct urban types (e.g. residential vs commercial) and spatial patterns, on rainfall-runoff processes. This study aims to investigate the impact of different spatial patterns of sealing and green areas on surface runoff. Inspired on the spatial patterns of green areas observed in several Portuguese city centres crossed by rivers, three spatial patterns were investigated: dispersed gardens with a narrow green strip along the stream (SS); small gardens along contours, with a large green strip downslope (HD); linear gardens along the slope, with a large green strip downslope (VD). The impact of these three patterns was assessed through lysimeter experiments, using concrete blocks to simulate sealed surfaces and turfgrass to mimic gardens. All the configurations included 60% sealing and 40% greening, which is the maximum allowed in several Portuguese municipalities for urban areas. The lysimeters have an area of 1.24 m2 and a depth of 0.15 m, filled with sandy loam soil (1.4 kg/m3) bellow the pavement and the turfgrass, and are placed with a 13º-16º slope. The lysimeters were installed in October 2019 and are subject to natural rainfall. After each storm, runoff and leachate measurements have been performed. Three soil moisture sensors were installed per lysimeter, at 10 cm depth, and provide continuous records with 5 min intervals. Rainfall data is collected with a rain gauge installed nearby, with a 5 min resolution. Results show that 40% turfgrass is able to cope with the majority of rainfall and runoff from upslope paved surfaces. Runoff coefficient is typically less than 2% and attained a maximum of 4% during the largest (40 mm) and more intensive storm (9.4 mm/h). Although increasing soil moisture slightly enhances runoff generation, the spatial patterns investigated at small scale did not show significant impacts on rainfall-runoff processes. Turfgrass revealed effective to retain and infiltrate rainfall and runoff from paved surfaces. It may provide an adequate solution to mitigate the impact of urbanization on the water cycle and flood hazard within cities.
Determinants of ~1000-year woody vegetation dynamics at the southern boreal forest margin in Northeast China
Authors: Zhu Chenyi , Liu Hongyan , Wang Hongya , Feng Siwen , Han Yue
Published: March 2020

The most dramatic permafrost degradation is expected to occur at its southernmost distribution, which causes significant vegetation changes in the southernmost boreal forests and consequently affects the carbon stock. To reveal determinants of vegetation change and, in particular, the role of permafrost dynamics, the reconstruction of the long- term vegetation history spanning a warming-cooling cycle is required. Here, we showed that over the last 990 years, vegetation development was characterized by changes in the relative proportions of taxa, such as Larix, Pinus and Corylus, corresponding to the variation in temperature. However, since ~1950 AD, rapid warming has led to the breakdown of the stable relationship among vegetation, climate and permafrost, and the proportion of conifers has shown an increasing trend in the short term due to the influence of permafrost thawing regulated by terrain. In general, we have observed that the coupling system of vegetation, climate and permafrost was stable before ~1950 AD; however, there has been a transition in the most recent rapid warming-induced permafrost thawing. As the southern boundary of permafrost moves northward, it is suspected that the boreal forest in this region will be unstable or may even collapse in the future, and the complete replacement of conifers by broad-leaved trees could greatly reduce the carbon stock in this area by that time.
Smart algorithms for monitoring plastic litter
Authors: Garaba Shungu , Gnann Nina , Zielinski Oliver
Published: March 2020

Plastic Litter (PL) has become more ubiquitous in the last decades posing socio-economic as well as health problems for the blue and green economy. However, to date PL monitoring strategies have been based on field sampling by citizens and scientists during recreational, sporting, scientific and clean-up campaigns. To this end, remote sensing technologies combined with artificial intelligence (AI) have gained rising interest as a potential source of complementary scientific evidence-based information with the capabilities to (i) detect, (ii) track, (iii) characterise and (iv) quantify PL. Within the smart algorithms, convoluted and recurrent neural networks ingest vast multi to hyperspectral images from smartphones, unmanned aerial systems, fixed observatories, high-altitude pseudo-satellites and space stations. Detection would involve the application of object recognition algorithms to true colour Red-Green-Blue (RGB) composite images. Typical essential descriptors that are derived from RGB images include apparent colour, shape, type and dimensions of PL. In addition to object recognition algorithms supported by visual inspection, AI is also used to classify and estimate counts of PL in captured imagery. Quantification assisted by smart systems have the advantage of uncertainties associated with predictions, a cruial aspect in determing budgets of PL in the natural environment. Hyperspectral data is then utilized to further characterise the polymer composition of PL based on spectral reference libraries of known polymers. Fixed observatories and repeated image capture at regions-of-interest have prospective applications in tracking of PL. Here we present plausible applications of remote detection, tracking and quantification of PL assisted by smart AI algorithms. Smart remote sensing of PL will be integrated in future operational smart observing system with near real-time capabilities to generate user (citizens, stakeholders, policymakers) defined end-products relevant to plastic litter. These tailor-made descriptors will thus contribute towards scientific evidence-based knowledge important in assisting legislature in policy making, awareness campaigns as well as evaluating the efficacy of mitigation strategies for plastic litter. Essential descriptors proposed need to include geolocations, quantities, size distributions, shape/form, apparent colour and polymer composition of PL.
Mineralogy and petrography of the Keban Pb-Zn-(Cu) skarn deposit, Elaziğ, eastern Turkey
Authors: Kirat Ece , Mutlu Halim
Published: March 2020

The Keban Pb-Zn-(Cu) skarn deposit in the Elazığ region, Turkey, was formed at the contact zone of the Permo-Triassic metamorphics and the Late Cretaceous plutonic rocks in the Eastern Taurus orogenic belt. The mineralization is hosted by skarn and meta-clastic/carbonate rocks of the Keban Metamorphics intruded by alkali syenite porphyry, which is associated with the Pb-Zn-(Cu) mineralization. The rock units in the region are partly hydrothermally altered graphite calc-schist containing crystallized limestone interlayers and lenses, meta-pellitic rocks (phylitte/calc-phyllite), dolomitic limestone, calc-silicate hornfels, marble and plutonic rocks. Calc-silicate hornfels is an initial metamorphic product occurred in contact zone of the intrusive unit. Results of mineralogical studies indicate that garnet and pyroxene-rich skarn formed in early (prograde) stage of skarnization whereas epidote, chlorite, tremolite, phlogopite, muscovite, calcite, quartz and fluorite are typical minerals of the retrograde stage. Using the Raman spectroscopy investigations, garnets in alteration zone are subdivided into two groups. Garnets in andradite composition are zoned and occur close to the intrusion reflecting high-temperature conditions and those of grossular composition represent low-temperature conditions. The sill/dykes and stock-like Keban plutonic rocks hosting foid syenite porphyry and nepheline syenite are of holocrystalline hipidiomorph porphyritic texture including large nepheline and plagioclase phenocrysts. Metallic minerals comprise sphalerite, galena, chalcopyrite, magnetite, bornite, pyrite, fahlore and hematite, which mainly occur as dissemination, vein and massive forms and crosscut by late-stage quartz, fluorite and calcite veinlets. Sphalerite is medium-coarse grained, semi-euhedral and contain chalcopyrite inclusions. Blebs of chalcopyrite are widely recognized in sphalerite (chalcopyrite disease). Galena replaces sphalerite and in some cases, it hosts several sulfo-salt minerals. Magnetite partly or completely transforms to limonite and chalcopyrite inclusions in sphalerite occur among the magnetite grains.

Key words: Keban, Pb-Zn-(Cu) skarn deposits, Mineralogy, Petrography, Ore Microscopy, Raman Spectroscopy
Incision migration across Eastern Tibet controlled by monsoonal climate, not tectonics?
Authors: Groves Katharine , Allen Mark , Saville Christopher , Hurst Martin , Jones Stuart
Published: March 2020

The formation and uplift history of the Tibetan Plateau, driven by the India-Eurasia collision, is the subject of intense research. Geomorphic indices capture the landscape response to competition between climate and tectonics and reflect the spatial distribution of erosion. We analyse the link between climate and tectonics in the eastern part of the Tibetan Plateau using the mean annual precipitation, digital elevation data, and by calculating the geomorphic indices hypsometric integral (HI), surface roughness (SR) and elevation relief ratio (ZR). This is a region where competing tectonic models suggest either early Cenozoic plateau growth, or a late phase of crustal thickening, surface uplift and plateau growth driven by lower crustal flow (“channel flow”).

Swath profiles of rainfall, elevation and the geomorphic indices were constructed, orthogonal to the internal drainage boundary. Each profile was analysed to find the location of maximum change in trend. A broad transition zone is present in the landscape, where changes in landscape and precipitation are grouped and in alignment. The zone cuts across structural boundaries. It represents, from East to West, a sharp decline in precipitation below ~650 mm/yr (interpreted as the western extent of the East Asian monsoon), a change from a high relief landscape to smoother elevations at 4500-5000 m, a transition to low HI (< 0.05), a decrease in SR and an increase in ZR. This zone is not a drainage divide: the main rivers have their headwaters further West, in the interior of the plateau.

We argue that this geomorphic-climatic transition zone represents a change from incised to non-incised landscapes, the location of which is controlled by the western extent of the monsoon. Published low temperature thermochronology data suggest the plateau had reached its modern extent at the Eocene, but has been exhumed since ~15 Ma to the East of the transition zone, at least along major drainage networks. We therefore also suggest that the transition zone is the current position of a long-term wave of incision that has migrated from East to West, driven by late Cenozoic intensification of the monsoon climate. This work supports a model of early Cenozoic growth of the eastern Tibetan Plateau, superimposed by incision driven by climate change; it does not support the channel flow model.
Indian irrigation effects on precipitation over the Tibetan Plateau
Authors: Lu Yaqiong , Lin Shan
Published: March 2020

Indian agriculture equipped the most intensive irrigation worldwide and still maintains an increasing trend of irrigation due to the decreasing of Indian summer monsoon rainfall. Irrigation could largely increase soil moisture and evapotranspiration while cooling air temperature. Several researches showed that Indian irrigation did not significantly contribute to local precipitation, so will the Indian irrigation affect the adjacent regions, such as the Tibetan Plateau is unclear. Here, we set up 10-years simulations for two nested domains (30-10km) over the South-East Asia to quantify the irrigation effects with a coupled dynamic crop model and regional climate model (WRF4.0-CLM4Crop). Besides the numeric simulations, we adopted a water vapor back trajectory tracking method to track where the evaporation from the irrigated land fall as precipitation. Our preliminary results showed that Indian irrigation did not significantly affects temperature, sensible heat flux, and latent heat flux over the Tibetan Plateau, but the water vapor from Indian irrigation contributed to 10% of the summer precipitation on the Tibetan Plateau.
Impact of horizontal resolution on the tropical cyclone activity over the western North Pacific in CORDEX-East Asia phase I and II experiments
Authors: Cha Dong-Hyun , Lee Minkyu , Suh Myoung-Seok , Chang Eun-Chul , Ahn Joong-Bae , Min Seung-Ki , Byun Young-Hwa
Published: March 2020

 This study evaluated tropical cyclone (TC) activity simulated by two regional climate models (RCMs) incorporated in the Coordinated Regional Climate Downscaling Experiment (CORDEX) framework with two different horizontal resolutions. Evaluation experiments with two RCMs (RegCM4 and MM5) forced by reanalysis data were conducted over the CORDEX-East Asia domain with 25 km and 50 km horizontal resolutions. The 20-year (1989–2008) mean performances of the experiments were investigated in terms of TC genesis, track, intensity, and TC-induced precipitation. In general, the simulated TC activities over the western North Pacific (WNP) varied depending on the model type and horizontal resolution. The MM5 tended to simulate more reasonable TC activity compared with the RegCM4. For both models, higher horizontal resolution improved the simulation of TC tracks near the coastal regions of East Asia, whereas the coarse horizontal resolution led to underestimated TC genesis compared with the best track data because of greater convective precipitation and enhanced atmospheric stabilization. In addition, the increased horizontal resolution prominently improved the simulation of TCs landfalling in East Asia and associated precipitation around coastal regions. This finding implies that high-resolution RCMs can produce added value in improving the simulation of TCs over the WNP; thus, they have an advantage in climate change assessment studies.
Formulating an elasticity approach to quantify the effects of ecological restoration and climate variability on streamflow and sediment discharge changes in the Loess Plateau of China
Authors: Gao Guangyao
Published: March 2020

Ecological restoration (ER) has strong consequences on hydrological responses. The China’s Loess Plateau (LP) contributed nearly 90% of sediment load in the Yellow River, which was once the world’s largest carrier of fluvial sediment. ER efforts including the soil and water conservation measures (SWCMs, especially terracing and construction of check dams) since 1950s and large-scale ecological restoration campaigns such as Grain-for-Green project (i.e., returning sloping cropland to afforestation and pasture reestablishment) in 1999, has resulted in extensive land use/cover change, leading to considerable decreases of streamflow (Q), suspended sediment yield (SSY) and sediment concentration (C) in the LP over the past 60 years. However, it remains challenging to quantify the impacts of ER and climate variability on declines of Q and especially SSY. In this study, we formulate the notion of elasticity of sediment discharge, by associating SSY change to climate variability and ER over the period 1950s to 2014. Our results strongly support the hypothesis that changes to both streamflow volumes and to the suspended sediment concentration versus water discharge (C-Q) relationships result in reduced SSY, so that streamflow is reduced but runs clearer. We find that two of the ER strategies resulted in weaker relative impacts of climate variability, largely by reducing streamflow (by 55% to 75%). Meanwhile, ER predominantly decreased SSY (by 63% to 81%). Regarding ER practices, (i) the predominant measure acting to reduce SSY changed, over time, from engineering to reforestation; (ii) check-dams preferentially act to regulate the C-Q relationships whereas reforestation preferentially acts to moderate streamflow. Overall, our results suggest that a combination of engineering and vegetation measures is critical to achieving high-efficiency ER. While change to the ER strategy increased the efficiency of streamflow for SSY control, the lost water discharge per unit SSY reduction increased from 5.2 to 6.4 m3·t-1. Conflicting demands for water necessitate that further ER should target precision management by revegetation of targeted areas in the Loess Plateau.
Power Output Efficiency in Large Wind Farms with Different Streamwise Turbine Spacing
Authors: Wu Yu-Ting , Tsao Yu-Hsiang
Published: March 2020

A large-eddy simulation (LES) model, coupled with a dynamic actuator-disk model, is used to investigate the turbine power production and the turbine wake distribution in large wind farms where the streamwise turbine spacing of 7, 9, 12, 15, and 18 rotor diameters are considered. Two incoming flow conditions, three wind turbine arrangements, as well as the five turbine spacings are involved in this study, which leads to a total of 30 LES wind farm scenarios. The two incoming flow conditions have the same mean velocity of 9 m s-1 but different turbulence intensity levels (i.e., 7% and 11%) at the hub height level. The considered turbine arrangements are the perfectly-aligned, laterally-staggered, and vertically-staggered layouts. The simulated results show that the turbine power production has a significant improvement by increasing the streamwise turbine spacing. With increasing the streamwise turbine spacing from 7 to 18 rotor diameters, the overall averaged power outputs are raised by about 27% in the staggered wind farms and about 38% in the aligned wind farms. The wind farm scenarios with the turbine spacing of 12d or greater in a large wind farm can lead to an increasing trend in the power production from the downstream turbines in the high-turbulence inflow condition, or also avoids the degradation of the power output on the turbines with the low-turbulence inflow condition. The flow adjustment above the wind farm results in the generation of the internal boundary layer (IBL), which grows up vertically along with the wake-wise direction. The growth of the IBL is found to be affected by the changes in the inflow condition and the turbine spacing. The IBL depth above the wind farms is found to be influenced by the turbine spacing, whereas the IBL depth in the downstream wake region of the wind farms shows a rapid increase under the high-turbulence inflow condition.