bluuebunny/crossref_metadata_2025 huggingface dataset:
The American Monsoon System in UKESM1 and HadGEM3
Authors: García-Franco Jorge Luis , Gray Lesley , Osprey Scott
Published: March 2020

The American Monsoon System is the main source of rainfall for the tropical and sub-tropical Americas. CMIP6 climate model simulations from the MetOffice Hadley Centre (MOHC) models: HadGEMGC3.1 and the Earth System model UKESM1 were analyzed to evaluate the representation of this monsoon. Pre-industrial and historical experiments were compared to reanalyses and observations.  Several diagnostics, such as the Inter-tropical Convergence Zone (ITCZ) location, the Walker circulation and temperature and precipitation seasonal cycles in the American Monsoon System were assessed, as well as El Niño-Southern Oscillation teleconnections to the monsoon. 

These simulations reasonably represent the observed seasonal cycle of precipitation in the American Monsoon System. However, significant biases in the spatial distribution of rainfall in South America are evident. 
These biases in the South American Monsoon System are linked to temperature biases in the Amazon and Atlantic ITCZ biases. 
The midsummer drought regime in Central America, the Caribbean and southern Mexico is reproduced by all the simulations, although with a stronger intraseasonal cycle than observed.
The North American monsoon is relatively well represented by all the simulations, which is a noticeable improvement of these models compared to CMIP5. 

The overall performance of HadGEM3 at different horizontal resolutions was compared to that of UKESM1. 
This work evaluates the role of horizontal resolution and Earth System processes for monsoon representation which will be useful for interpreting scenario experiments or using CMIP6 runs for understanding variability and
teleconnections in this monsoon system.  
On the reliability of decadal climate prediction
Authors: Verfaillie Deborah , Doblas-Reyes Francisco J. , Donat Markus G. , Pérez-Zanón Nuria , Solaraju-Murali Balakrishnan , Torralba Verónica , Wild Simon
Published: March 2020

Decadal climate predictions and forced climate projections both provide potentially useful information to users for the next ten years. They only differ in the former being initialised with observations, while the latter is not. Bringing together initialised decadal climate predictions and non-initialised climate projections in order to provide seamless climate information for users over the next decades is a new challenging area of research. This can be achieved by comparing the forecast quality of global initialised and non-initialised simulations in their common prediction time horizons (up to 10 years ahead), and quantify in how far initialisation improves the forecast quality. Forecast quality has been usually explored through skill assessment. However, the impact of initialisation on the reliability, which quantifies the agreement between the predicted probabilities and observed relative frequencies of a given event, of decadal predictions has not yet been investigated sufficiently. Hence, users of probabilistic predictions are particularly sensitive to the potential lack of reliability which would imply that the probabilities are not trustworthy and this can have negative consequences for decision-making. In this communication, initialised decadal hindcasts (or retrospective forecasts) from 12 forecasting systems of the Coupled Model Intercomparison Project Phase 5 are compared to the corresponding non-initialised historical simulations in terms of reliability over their common period 1961-2005. We show that reliability varies greatly depending on the region or model ensemble analysed and on the correction applied. In particular, the North Atlantic and Europe stand out as regions where there is some added-value of initialised decadal hindcasts over non-initialised historical simulations in terms of reliability, mainly because of smaller biases and/or a better representation of the trend. Furthermore, we show that post-processed data display more reliable results, indicating that bias correction and calibration are fundamental to obtain reliable climate information.
Tracking post-colonisation geomorphic river sensitivity: A framework for identifying hotspots of river adjustment across a catchment
Authors: Khan Sana , Fryirs Kirstie
Published: March 2020

Contemporary geomorphic river behaviour can only be understood with a sound knowledge of the historical range of river adjustment. This is particularly the case for rivers that have experienced anthropogenic alterations. Using a case study of Richmond River, New South Wales, Australia, we track the history of geomorphic river adjustment from the time of European colonisation in the late 18th Century. We use this study to develop a novel framework, called the ‘Behavioural sensitivity logical tree’ which can be applied to any catchment for assessing and quantifying reach scale behavioural sensitivity, defined as the ease with which geomorphic units and associated water, sediment, vegetation interactions adjust within the expected behavioural regime of a river. We use this framework to develop a behavioural sensitivity index and categorise rivers as Fragile, Active sensitive, Passive sensitive, Insensitive and Resilient. When applied across a catchment, such analyses highlights hotspots of river adjustment and sensitivity.

Fragile rivers have a behavioural sensitivity index > 0.85 and have the propensity to undergo wholesale river change such that a new river type and behavioural regime is created. For example, change from discontinuous or absent channels (e.g. swamps) to continuous channelised fills. Active sensitive rivers have a behavioural sensitivity index of 0.50-0.85 and have the ability to re-configure within their contemporary behavioural regime. For example, by reducing sinuosity via abrupt chute cut-off or progressive channel straightening. The behavioural sensitivity index of Passive sensitive rivers is between 0.20-0.50. These rivers have the ability to maintain their behavioural regime and withstand adjustment. Insensitive rivers have a behavioural sensitivity index of 0.05-0.20. They do not readily adjust and may contain significant resistance elements such as fine-grained sediments that limit geomorphic adjustment.  Resilient rivers have a behavioural sensitivity index < 0.05 and tend to be confined reaches where the capacity for adjustment is controlled by bedrock or other antecedent controls, such that the river cannot readily adjust.

We further demonstrate the evolutionary nature of behavioural sensitivity itself. The behavioural sensitivity of a river is not set in space and time, rather, rivers can dynamically evolve and shift to a different sensitivity category over time and in response to different forms of direct and indirect disturbance. Analysing a rivers’ behaviour sensitivity and identifying hotspots of geomorphic adjustment, can help inform process-based river management practice.
Magnetic Curvature Analysis on Reconnection Related Structures at Earth’s Magnetopause
Authors: Qi Yi , Russell Christopher T. , Strangeway Robert J. , Jia Yingdong , Torbert Roy B. , Paterson William R. , Giles Barbara L. , Burch James L.
Published: March 2020

Magnetic reconnection is a mechanism that allows rapid and explosive energy transfer from the magnetic field to the plasma. The magnetopause is the interface between the shocked solar wind plasma and Earth’s magnetosphere. Reconnection enables the transport of momentum from the solar wind into Earth’s magnetosphere. Because of its importance in this regard, magnetic reconnection has been extensively studied in the past and is the primary goal of the ongoing Magnetospheric Multiscale (MMS) mission. During magnetic reconnection, the originally anti-parallel fields annihilate and reconnect in a thinned current sheet. In the vicinity of a reconnection site, a prominently increased curvature of the magnetic field (and smaller radius of curvature) marks the region where the particles start to deviate from their regular gyro-motion and become available for energy conversion. Before MMS, there were no closely separated multi-spacecraft missions capable of resolving these micro-scale curvature features, nor examining particle dynamics with sufficiently fast cadence.

In this study, we use measurements from the four MMS spacecraft to determine the curvature of the field lines and the plasma properties near the reconnection site. We use this method to study FTEs (flux ropes) on the magnetopause, and the interaction between co-existing FTEs. Our study not only improves our understanding of magnetic reconnection, but also resolves the relationship between FTEs and structures on the magnetopause.
Evaluation and projection of long period return values of extreme daily precipitation in the CMIP5 and CMIP6 models
Authors: Wehner Michael , gleckler Peter , Lee Jiwoo
Published: March 2020

Using a non-stationary Generalized Extreme Value statistical method, we calculate selected extreme daily precipitation indices and their 20 year return values from the CMIP5 and CMIP6 climate models over the historical and future periods. We evaluate model performance of these indices and their return values in replicating similar quantities calculated from multiple gridded observational products. Difficulties in interpreting model quality in the context of observational uncertainties are discussed. Projections are framed in terms of specified global warming target temperatures rather than at specific times and under specific emissions scenarios. The change in framing shifts projection uncertainty due to differences in model climate sensitivity from the values of the projections to the timing of the global warming target. At their standard resolutions, we find there are no meaningful differences between the two generations of models in their quality or projections of simulated extreme daily precipitation.
Soil cracking induced by overgrazing triggers the severe degradation or initiates the natural recovery of overgrazed alpine meadows on the Tibetan plateau?
Authors: Niu Yujie , Zhu Huimin , Yang Siwei , Zhou Jianwei , Chu Bin , Ma Sujie , Hua Rui , Wang Ting , Hua Limin
Published: March 2020

Soil cracking is an important feature of degraded terrestrial ecosystems, which cuts the closed and intact land, alters microtopography and also influences the dynamics of soil nutrients, water and heat, then further affect species distributions. Despite their importance, the patterns and causes of cracks related to overgrazing on alpine rangeland have rarely been reported previously, and the effects of cracks on soil properties and plant distributions are poorly understood. Therefore, we used a comprehensive cross-scale approach to investigate the distribution of crack-soil areas at the eastern Tibetan plateau (217 survey sites), then selected the grazing-induced parameter that was closely related to the cracks at a small scale, and quantified the effects of microtopography (raised areas and healed cracks) induced by cracking on the soil properties, and community composition at crack-mosaic patch from 2013-2018, then to evaluate the further roles of soil cracking on alpine rangelands. The results showed that cracks only formed in the alpine meadow after overstocking. The increased soil compaction under overgrazing was closely related to soil cracking. On crack patch scale, the healed cracks facilitated nutrient and water enrichment due to the increasing surface roughness, then improved the plant communities. To some extent, healed crack mosaics are good for the conservation of water and nutrients. We provide key and easy-to-measure indicators to prevent overgrazing and cracking: a residual biomass greater than 65 g/m2 and a height greater than 6 cm, and the soil compaction should be lower than 1044.26 ± 188.88 kPa. We should pay more attention to crack phenomena to prevent severe degradation. Overgrazed alpine meadows should be treated in the early phase of cracking and it may be able to return to optimum conditions in healthy rangelands. Otherwise, soil cracking becomes the most critical turning point in the process of alpine rangeland severe degradation.
Sediment transportation systems to the Levant basin and the role of the Nile River since the Pliocene
Authors: Sagy Yael , Dror Oz , Gardosh Michael , Reshef Moshe
Published: March 2020

The progradation of the Nile River Delta and the thick (~1500m) Sinai-Israel shelf since the Pliocene provide a world class source to sink system feeding a deep (>1.5 km) siliciclastic basin.  The general agreement that the Pliocene-to-Recent succession originates from the Nile Delta dispersing sediments via a system of counterclockwise currents does not reveal how the sediments were transported to the deep basin. Particularly, how sediments originating from the Nile Delta could have bypassed the ~50 km wide Sinai-Israeli shelf. Here, we examine the various sources that contributed to the accumulation of the Pliocene-to-Recent succession in the deep Levant basin, and the temporal and spatial contribution of each source. The analysis of a unique seismic data set covering the shelf, slope and deep basin enable us to track submarine sediment transport systems.

Following attribute analysis of the seismic volumes we map channel sets, analyze their morphological features and interpret their erosional and depositional patterns. Direction flow maps indicate that sediments sources vary from eastward remnant Arabian drainage network at the onset of the Pliocene, to direct Nilotic origin during the Pliocene. Since the Late Pleistocene reworked sediments, deriving from the Israeli shelf and northern Sinai provide a major source to the deep basin. Furthermore, our results demonstrate an increase in channel’s complexity since the Early Pliocene to Recent suggesting a gradual transition from sporadic submarine flow events, carrying fewer sediments to the deep basin at the Early Pliocene, to more frequent events during the Late Pleistocene-to-Recent characterized by an increase in sediment load. The gradual increase of channel complexity from Pliocene-to-Recent is discordant to the general trend of sea-level fluctuation, suggesting that sea-level has a minor effect on sediment accumulation in the deep basin. We propose that the balance between the northward prograding Nile Cone and the longshore currents building the Sinai-Israeli shelf dictate siliciclastic accumulation in the southeastern Mediterranean basin as well as the paleogeography of its margin.
The millennial-scale climatic variability in central Asia during last glacial
Authors: Jia Jia , Wang Zhiyuan , Wang Leibin , Chen Jianhui
Published: March 2020

In the North Atlantic and the surrounding region, more than 20 rapid millennial-scale climatic fluctuations occurred during the last glacial-interglacial cycle (Dansgaard et al. 1993). These oscillations, known as Dansgaard-Oeschger (D-O) and H-events. Simulate studies suggest that the millennial-scale climatic signals can spread to a wide area by atmospheric and oceanic circulations. However, it lacks such record in central Asia which is climatically characterized by arid and sensitive to climate change.

Here, we present the record of millennial-scale fluctuations from loess deposits in Tajikistan in Central Asia. The frequency-dependent magnetic susceptibility (Xfd, a moisture proxy) record in the Darai Kalon (DK) section (38º23′4″N, 69º50′1″N, 1561 m) can be readily matched with the NGRIP oxygen isotope curve, especially during the interval from 60-30 ka in which typical D-O cycles and H-events are well developed. Most of the long-lasting D-O cycles in Greenland, e.g., D-O 8, 12, and 14, are also evident in the Tajikistan loess. Similarly, the short-duration D-O cycles in Greenland, e.g., D-O 6, 7, 9, 10 cycles, have their damped counterparts in the Tajikistan loess. However, some significant differences in detail can be observed between the two records. The most distinct difference occurs in the case of last D-O cycle, which includes the well-documented Oldest Dryas (OD or H1), Bølling-Allerød (BA), and Younger Dryas (YD or H0) events, which are not clearly present in the Xfd curve.

The magnetic results support that the climate is humid in interstadials and dry in stadials in central Asia. And, the variation of humidity is much more remarkable in central Asia than in Chinese Loess Plateau which is climatically dominated by Asian Monsoon. It exhibits the humidity in central Asia is sensitive to millennial-scale climate oscillations during the last glacial. The comparison results further indicate propagations of millennial-scale climatic signals were different between these two regions. We assumed the former one is the Westerlier which can directly and effectively force the millennial-scale climatic variability in central Asia, and the latter one is thermohaline circulation and Asian Monsoon, the complex propagation weakened the millennial-scale climatic variability Northern China.
Head-collision of nonlinear waves in a shallow basin: wave field and bottom pressure
Authors: Rodin Artem , Rodina Natalia , Kurkin Andrey , Touboul Julien , Pelinovsky Efim
Published: March 2020

 The collision of solitary waves has been studied analytically and numerically in numerated papers for last 50 years. In the weakly nonlinear theory, the soliton interaction is inelastic. Here we study more general class of the head-collision of nonlinear waves of various shape (Riemann waves of both polarities, shock waves and solitons) in the shallow water within nonlinear shallow-water theory, Serre-Green-Naghdi and Euler equations. The structure of wave field and induced bottom pressure at the moment of wave interaction is analysed analytically and numerically. It is shown that such an interaction leads to a phase shift and shape deformation in the moment of interaction. Estimates of the height of the Riemann waves as well solitons of moderate amplitudes at the moment of interaction are in agreement with theoretical predictions. The phase shift in the interaction of non-breaking waves is small enough, but becomes noticeable in the case of the shock waves motion. The approximated analytical solution for the wave field and bottom pressure distribution is obtained analytically within Serre-Green-Naghdi system. Computed bottom pressure in dispersive theories has two-bell shape for large amplitude solitary waves in quality agreement with theoretical analysis.
Surface-modified apricot pits as biochar feedstock and phosphate sorbent
Authors: Soja Gerhard , Wyhlidal Stefan , Friesl-Hanl Wolfgang , Zwölfer Kathrin , Edlinger Julia , Reis Christina , Gattringer Heinz
Published: March 2020

Pits from fruit like apricots, peaches and cherries are an under-utilized resource. If there is any use at all, they may be extracted for special vegetable oils. Mostly the pits are combusted or left to rot. However, they are also an appropriate feedstock for pyrolytic carbonization. This study investigated the biochar produced from apricot pits for its potential to sorb phosphate from liquid media and from artificial wastewater.

Shredded apricot pits were pyrolyzed at 450 °C in a lab-scale screw reactor (Pyreka 3.0). Additionally, the impregnation of the feedstock with Mg(OH)2 before pyrolysis was studied to test the hypothesis that phosphate sorption to biochar takes advantage of metal bridges on the biochar surface.

The results of isotherm sorption experiments showed that the pre-pyrolysis Mg-surface modification of the pits improved the sorption capacity of the biochar up to 42 mg PO4-P/g whereas the unmodified biochar adsorbed only about one tenth. When KH2PO4 was used as the only sorbate, EDX-mapping showed the formation of K-struvite-crystals in the pores of the biochar. Desorption experiments showed a major release of the adsorbed phosphate within a few hours. Sorption competition experiments with phosphate and nitrate showed no negative effect of nitrate on phosphate sorption. Feedstock impregnation with Ca(OH)2 resulted in more variable sorption dynamics.

The results could be confirmed by deploying the surface-modified apricot pit biochar for the reduction of the phosphate load in artificial wastewater.
Detection of Fog Involving Heavy Pollutants by Using the New Geostationary satellite Himawari-8
Authors: Wang Hongbin , Zhang Zhiwei , Liu Duanyang
Published: March 2020

Himawari-8 is the new geostationary satellite of the Japan Meteorological Agency (JMA) and carries the Advanced Himawari Imager (AHI), which is greatly improved over past imagers in terms of its number of bands and its temporal/spatial resolution. In this work, two different methods for the detection of the different levels of fog involving heavy pollutants by using the Himawari-8 were developed in China. The two different methods are the method of the difference between the 11.2 mm and 3.9 mm brightness temperatures (BTD3.9-11.2) and the method of 3.9 mm Pseudo-Emissivity (ems3.9).  The 3.9 mm Pseudo-Emissivity is the ratio of the observed 3.9 mm radiance and the 3.9 mm blackbody radiance calculated using the 11.2 mm brightness temperature. We identified the parameters optimal threshold at the 2400 stations and the grid points using the BTD3.9-11.2 and ems3.9 for different levels of fog involving heavy pollutants. Results on land and sea from the two methods were compared with surface observations from 2400 weather stations in China and CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) VFM (Vertical Feature Mask) products. The results show that both the method of BTD3.9-11.2 and the method of ems3.9 can accurately identify the different levels of fog involving heavy pollutants and the accuracy of ems3.9 method is slightly better than the BTD3.9-11.2. The accuracy of two methods has increased significantly and the false alarm rate has significantly decreased with the decrease of the visibility. When the visibility is less than 50 m, the HR, FAR and KSS of the BTD3.9-11.2 method (the ems3.9 method) were 0.89 (0.90), 0.15 (0.15) and 0.74 (0.75), respectively. When mid- or high-level clouds were removed using surface temperature of the ground observations, the HR and KSS of two methods for the different levels of fog has increased significantly, and the FAR has significantly decreased. When the visibility is less than 1000 m, the HR of the BTD3.9-11.2 method (the ems3.9 method) is increased to 0.81(0.85) from 0.71 (0.74), the FAR is decreased to 0.12 (0.13) from 0.27 (0.28), and the KSS is increased to 0.69 (0.72) from 0.44 (0.46). The KSS of two method increase by 0.23 and 0.26, respectively. Three cases analysis show that the fog area can be clearly identified by using the BTD3.9-11.2, ems3.9 and RGB composite image. The results of the detection of sea fog by using Himawari-8 data and using CALIPSO VFM products have consistency.
Application of Internet of Things monitoring technology to the improvement of agricultural irrigation disaster management
Authors: Yang Sheng-Hsueh , Leu Wen-Hao , Chen Meng-Chen , Kuo Jiun-Hue , Yeh Keh-Chia
Published: March 2020

Climate change has gradually affected Taiwan's agricultural environment. The number of raining days has decreased, the rainfall intensity has increased, and the drought time has been prolonged. In addition, with the mountainous terrain of Taiwan, rainfall is not easy to be stored and used. The summer and autumn are rainy seasons, which are prone to flooding disasters, the lack of water in spring and winter causes droughts that cause insufficient agricultural water supply, and the stable supply of food is closely related to people's livelihood needs. Therefore, the research department uses UAV imaging technology to identify agricultural crops, grasp the agricultural crops and water supply needs in the spring and winter seasons, and try to estimate the water demand and distribution water volume as the management basis of agricultural irrigation and drainage. Use long-term meteorological models to estimate rainfall results in the next month, and determine whether there are water shortage characteristics in agricultural crop areas. If there is a water shortage, further use the Internet of Things monitoring technology to monitor the inflow and outflow of agricultural crops in irrigated areas, control and distribute the required water consumption, and then to reduce water supply at night or supplying irrigation water in turn in response to the water shortage during the irrigation period. In the summer and autumn rainfall periods, the Internet of Things technology is also used to observe the water level and flow discharge of the main irrigation waterways, and set the rainfall and water level early warning values to reduce the occurrence of flooding disasters in agricultural areas, and use the immediate hydrological and hydraulic models to forecast the future suggestions such as hourly water level and flow discharge and gate control provide timely information on agricultural disaster warnings. The relevant research area is in the Meinong Agricultural Area (about 4,000 ha) of Farm Irrigation Association of Kaohsiung Taiwan as an example. Through web pages hourly displays Internet of Things information, model analysis results, and disaster prevention early warning results to let the management units understand the actual status of agricultural irrigation areas.
Channel widening quantification under laboratory conditions
Authors: Qin Chao , Zheng Fenli , Wells Robert
Published: March 2020

Channel widening constitutes about 80% of total soil loss, especially in the presence of a plow pan which manifests a less or nonerodible soil layer. Channel bank erosion quantification is prerequisite to couple effectively the bank sediment supply system with fluvial sediment transport fluxes. The objectives of this study were to: 1) describe and evaluate methods for monitoring and data post-analysis of channel widening and 2) investigate how inflow rate, slope gradient and initial channel width affect channel widening processes in the presence of a non-erodible layer. Technology was developed to capture 5-cm spaced cross-sections along a soil flume at 3-s time intervals. Two off-the-shelf digital cameras were positioned 3-m above the soil bed and controlled by a program to trigger simultaneously and download images to the computer. Methods utilizing color differences in images and elevation differences in DEMs were applied to detect discontinuities between channel walls and the soil bed. Channel widths were calculated by differentiating the coordinates of these surface discontinuities. A volumetric method was used to calculate flow velocity with measurements of flow depths obtained from ultrasonic depth sensors. Sediment concentration was determined by manual sampling.

The results showed that different channel width calculation methods exhibited comparable outcomes and achieved satisfactory accuracy. Sediment discharge showed a significant positive linear correlation with channel widening rate, while exhibiting a 5 to 25-s time lag compared to the peak of channel widening rate. Total sediment discharge calculated by photogrammetry was 3.1% lower than that calculated by manual sampling. Flow velocity decreased with time and showed a significant negative power correlation with channel width. Sediment delivery and channel width increased with the increase of inflow rate, bed slope and the decrease of initial channel width. Exponential equations were used to predict the channel width time series. Toe scour, crack development, sidewall failure and block detachment and transport, in sequence, were the four main processes of channel widening. Basal scour arc length, tension crack length and width decreased with initial channel width and increased with time, flow discharge and bed slope. Basal scour arcs were divided into three patterns according to different shapes in comparison to the failure arcs. Sediment delivery equations based on the disaggregation of concentrated flow entrainment and mass failure were also fitted. Advantages of the described methodology include automated high spatial and temporal monitoring resolution, semi-automated data post-processing, and the potential to be generalized to large scale river/reservoir bank failure monitoring. This study provides new insight on improving channel widening measurements and prediction technology.
Hiatus Mapping at a Continental Scale for Cretaceous and Cenozoic time
Authors: Vilacís Baurier Berta , Hayek Valencia Jorge Nicolas , Bunge Hans-Peter , Friedrich Anke M. , Carena Sara
Published: March 2020

 Our results suggest that geologic maps yield geodynamically-relevant quantities, allowing one to constrain mantle-induced surface deflections of the lithosphere related to past dynamic topography.
Advances in Sparse Image Reconstruction of GPR Subsurface Targets
Authors: Hoorfar Ahmad
Published: March 2020

Over the years, the detection and imaging of targets embedded in layered media has become of paramount importance in a diverse set of problems including those in microwave remote sensing, nondestructive testing, ground penetrating radar (GPR), and through-the-wall imaging (TWRI). Specifically, development of imaging techniques for visually inaccessible targets buried under the ground has attracted growing interest in archaeology, underground weapon detection, building safety and durability assessment, geophysical exploration, etc. For high resolution imaging in these applications, usually a long aperture is synthesized using an ultra-wideband transmitted signal; this makes the approach impractical and/or costly in many realistic situations. To reduce the collected data volume in order to accelerate radar data acquisition and processing times such that prompt actionable intelligence would be possible, several research groups in recent years have applied Compressive Sensing (CS) to radar imaging in GPR to reconstruct a sparse target scene from far fewer non-adaptive measurements. The standard CS techniques, however, are mainly based on L1-norm minimization, which is primarily effective in detecting the presence of targets as it cannot accurately reconstruct the target shape and/or differentiate closely spaced targets from an extended target.

In this presentation, we give an overview of our group’s recent works on image reconstruction for both SAR-based and multiple-input multiple-output (MIMO) based GPR targets in a multilayered subsurface medium using CS. In our approach, the subsurface layers are accurately and efficiently accounted for in the sparse-image reconstruction through analytically derived expressions for the Green’s functions of multi-layered lossy dielectric media. In particular, we will discuss the use of total variation minimization (TVM) and its advantages over the L1-norm minimization which is often used in the standard radar implementation of CS. The TVM technique minimizes the gradient of the image instead of the image itself, and as a result leads to better shape reconstruction of large and/or multiple subsurface targets. In addition, we also discuss the use of group sparsity reconstruction (GPS) technique and compare its performance with that of TVM under various noise levels. Numerical results for sparse imaging in various subsurface scenarios using different reduced sets of SAR and MIMO radar transmit and receive antenna elements as well as reduced number of frequency bins will be given in the presentation.
Highly oxygenated molecules and their chemistry in polluted urban environments
Authors: Chen Qi , Cheng Xi , Li Yongjie , Zheng Yan , Liao Keren , Huang Guancong , Liu Ying , Zhu Tong , Canagaratna Manjula R.
Published: March 2020

Highly oxygenated molecules (HOMs) are important atmospheric oxidation products that may contribute to new particle formation and initial particle growth. Thousands of such compounds were quantified in both winter and summer of 2016 in Beijing by using online nitrate ion chemical ionization time-of-flight mass spectrometry. Positive-matrix factorization of the time series of the high-resolution mass spectra identified at least 10 major groups of gaseous HOMs in Beijing. We compared these PMF factors with the HOMs produced in a Potential Aerosol Mass (PAM) flow reactor in the laboratory from the oxidation of typical biogenic and aromatic precursors under various oxidation conditions. Our results show that four of the ten PMF factors perhaps correspond to biogenic precursors, and another four factors are likely related to aromatic precursors. The chemistry of these aromatic HOMs are discussed based on the results from the PAM experiments.
Using waste soil to rehabilitate degraded agricultural lands: environmental burden as resource
Authors: Argaman Eli , Becker Nir , Tanner Smadar , Ben-Hur Meni , Gruenzweig Jose , Kimhi Ayal , Stavi Ilan , Katra Itzhak
Published: March 2020

The global expansion of infrastructures is generating vast amounts of waste soil (soil excavated from construction sites that cannot be used on-site); the amount of waste soil accumulated in the European Union in 2014 was estimated at 463 x 106 tons. The regulation and management of waste soil disposal are currently limited to: (1) local use for various engineering projects; (2) stockpiling on-site for future use; (3) transferal to landfills, which are currently overfilled, as padding material or for disposal. Despite a number of permitted actions for handling waste soil, a significant portion of it is disposed of in the area surrounding the construction site, thus raising the risk of pollution and landscape spoilage. Waste soils are commonly excavated from deep layers, and are therefore saline, sodic, and lack organic matter, preventing their use without pre-treatment. Moreover, due to the intensification of crop production, one-third of the global agricultural land area is susceptible to soil loss by erosion, constituting ~50% of total estimated soil erosion. Here we show a new approach for environmentally, agronomically and economically sustainable use of reclaimed waste soil to rehabilitate degraded agricultural land. In a 3-year field experiment under rain-fed conditions in a semi-arid region of Israel, we found that waste soil ploughed into agricultural soil had low erodibility, similar to that of the original agricultural soil, despite its high sodicity. Waste soil application tended to decrease the soil organic carbon concentration but had no detrimental effect on wheat hay yield or wheat grain yield or quality in the second and third year, respectively. The economic analysis suggested an average reduction of 8.7 million USD in waste soil disposal costs if 50% of the waste soil produced in Israel annually were to be utilized in agricultural fields. Thus, waste soil can be utilized successfully in degraded agricultural lands; this opens a new route to land reclamation and provides land managers and stakeholders with a sustainable way to reduce costs while transforming an environmental burden into a resource.
Deep learning reveals seasonal patterns of Antarctic ice shelf front fluctuations
Authors: Baumhoer Celia A. , Dietz Andreas J. , Dirscherl Mariel , Kuenzer Claudia
Published: March 2020

The Antarctic ice sheet drains ice through its peripheral ice shelves and glaciers making them an important factor for ice sheet mass balance. The extent of ice shelves and their calving front position influences ice sheet discharge and can yield valuable information on ice dynamics. Moreover, glacier fronts can have strong seasonal variations of retreat and advance. Yet, little is known about the seasonal pattern of Antarctic calving front fluctuations and their effect on ice sheet dynamics. The current developments in remote sensing and big data processing allow accurate monitoring of the Antarctic coastline. But to derive monthly calving front positions, the traditional approach of manual delineation is too time-consuming to cope with the temporal and spatial abundance of contemporary satellite missions. To create an up to date monitoring of changes in the Antarctic coastline a fully-automated approach is necessary. Automation of ice front delineation is a very challenging task as conventional edge detection methods fail due to the very low contrast between shelf ice and sea ice. Therefore, to exploit the abundance of available Sentinel-1 imagery over Antarctica, we created an automated workflow to extract monthly ice shelf front positions from Sentinel-1 imagery. The core of our processing chain is the deep learning architecture U-Net trained with about 44.000 image tiles covering parts of the Antarctic coastline during various seasons. Post-processing allows generating shapefiles of front positions and creating time series of seasonal ice shelf front fluctuations. We demonstrate our proposed method on selected ice shelves along the West and East Antarctic coastline and present intra-annual changes of calving front positions. This allows us to investigate seasonal change patterns of Antarctic ice shelves between 2014 and 2019 (depending on Sentinel-1 data availability) and to obtain a better picture on current Antarctic ice shelf front dynamics.
Review and Assessment of gap-filling methods from tide-gauges: Maxima missing at the Esbjerg, Denmark station, before 1910.
Authors: Thejll Peter
Published: March 2020

Information on extremes of the sea-level is obtained from tide-gauge
records.  Such records may have gaps.

Estimates of potential changes in the size and/or frequency of sea-level
extremes are hampered by long gaps, or when just the high extremes are
missing due, e.g. to equipment failure.

Methods used for filling such gaps can be based on having multiple
records from gauges near each other; but what to do if there is
only one record? This problem can typically occur when old tide-gauge
records are used -- the use of multiple recorders at the same place is
more wide-spread today. However, especially older and therefore longer
records hold the key to obtaining long-baseline insights into the temporal
evolution of extreme tides and thus impacts of e.g. climate change.

In this work, we review and assess methods for gap filling. We asses using
the 'known truth' method, i.e. by applying realistic gaps to complete
gauge records and reconstructing and then comparing errors calculated as
the diffrence between modelled and actual values.  We compare a simple
harmonic model fit method to various spline methods as well as Neural
network and deep learning approches.  We also test a hybrid method
which uses not just tide-gauge data but also air pressure readings
from a meteorological station near the tide-gauge.

We then attempt to fill in the missing maxima of the Esbjerg, Denmark
hourly tide-gauge record since 1889. Particularly, before 1910 the maxima
above 300 cm are missing (Bijl, et al., 1999), and we try to fill these in.
Subsurface water flow detection by time-lapse reflection GPR data
Authors: Yuan Hemin , Zibar Majken Caroline Looms , Nielsen Lars
Published: March 2020

Understanding subsurface water flow is important as it e.g. controls contaminant transport, has an impact on the amount of aquifer recharge, and can be used for storm water management purposes. However, there do not exist many methods that can observe the water flow in the field. Furthermore, the flow patterns can be very diverse due to the complex geological conditions, e.g. faults, fractures, and heterogeneous permeability of the subsurface formations. In order to map the subsurface water flow in a chalk formation, we performed a water injection experiment in the Rørdal Quarry, Northeast Denmark. A total water volume of 700 liters was injected via a 50 cm deep hole within 8 hours. Around the injection hole, we conducted time-lapse GPR measurements along 6 inlines and 6 crosslines. Seven measurements campaigns were performed over an eight-hour time period. We analyze the time-lapse GPR reflection sections in order to investigate the variations of the different measurements. Initially, we subtract the repeated measurements and baseline measurements, which shows that some survey lines have clear changes after water injection, while others only show very small or no changes. To verify the differences, we pick travel times of selected horizons in the time-lapse data and compare them (cf. Truss et al., 2007; Allroggen et al., 2015). This analysis highlights the travel time variations imposed by the injected water. Moreover, we perform correlation analysis of the measurements before and after water injection. The correlation coefficients show relatively small values on the lines that exhibit clear differences, further confirming the differences caused by the water infiltration. Initial integrated analysis of the different results shows that the water mainly flows towards the southeast from the injection hole. This is consistent with the orientation of the fracture system observed in the reflection GPR profiles, indicating that the water flow is primarily controlled by the fractures.

 

[1] Truss, S., Grasmueck, M., Vega, S., and Viggiano, D. A. 2007, Imaging rainfall drainage within the Miami oolitic limestone using high-resolution time-lapse ground-penetrating radar, Water Recourses Research, 43, W03405.

[2] Allroggen, N., Schaik, N.V., and Tronicke, J. 2015, 4D ground-penetrating radar during a plot scale dye tracer experiment, Journal of Applied Geophysics, 118, 139-144.
Assessment of the spatial distribution of global soil loss tolerance by using the productivity index method
Authors: Jia Lizhi , Zhao Wenwu
Published: March 2020

The soil loss tolerance (T value) is the ultimate criterion for determining whether a soil has potential erosion risks. While the existing T value criteria are mainly on national scale, and lack of consideration of the differences in soil erosion, soil properties and soil productivity between different types of land use. We calculated the global T value by using the productivity index method. The global T values ranged from 0.84 to 4.99 Mg ha-1 yr-1, with an average of 1.49 Mg ha-1 yr-1. The distribution of T values in global scale demonstrated significant spatial differences, and the range of T values in most regions of the land (98.23%) was between 1.0 and 2.0 Mg ha-1 yr-1. The mean T values varied from c ontinent to continent, with Africa and Oceania having higher mean T values than other continents. The T values between different land use types varied widely, and the T values of five land use types were as follows: cropland (1.67 Mg ha-1 yr-1) > shrubland (1.61 Mg ha-1 yr-1) > grassland (1.59 Mg ha-1 yr-1) > forestland (1.38 Mg ha-1 yr-1) > wetland (1.28 Mg ha-1 yr-1).
On the Landslide Hazard with the Impact of Climate Change in Central Taiwan
Authors: Shou Keh-Jian
Published: March 2020

Due to active tectonic activity, the rock formations are young and highly fractured in Taiwan area. The dynamic changing of river morphology makes the highly weathered formations or colluviums prone to landslide and debris flow. For the past decade, the effect of climate change is significant and creates more and more extreme weather events. The change of rainfall behavior significantly changes the landslide behavior, which makes the large-scale landslides, like the Shiaolin landslide, possible. Therefore, it is necessary to develop the new technologies for landslide investigation, monitoring, analysis, early warning, etc.

Since the landslide hazards in Taiwan area are mainly induced by heavy rainfall, due to climate change and the subsequent extreme weather events, the probability of landslides is also increased. Focusing on the upstreams of the watersheds in Central Taiwan, this project studied the behavior and hazard of shallow and deep-seated landslides. Different types of susceptibility models in different catchment scales were tested, in which the control factors were analyzed and discussed. This study also employs rainfall frequency analysis together with the atmospheric general circulation model (AGCM) downscaling estimation to predict the extreme rainfalls in the future. Such that the future hazard of the shallow and deep-seated landslide in the study area can be predicted. The results of predictive analysis can be applied for risk prevention and management in the study area.
The effect of composite rheology on mantle convection models with plate-like behavior
Authors: Arnould Maelis , Rolf Tobias
Published: March 2020

The coupling between mantle convection and plate tectonics results in mantle flow patterns and properties which can be characterized with different seismic methods. In particular, the presence of mantle seismic anisotropy in the uppermost mantle suggests the existence of mineral Lattice-Preferred Orientation (LPO) caused by asthenospheric flow. Dislocation creep, which implies non-Newtonian mantle rheology, has been identified as a deformation mechanism responsible for such LPO leading to seismic anisotropy. While it has been proposed that the use of a composite rheology (with both diffusion and dislocation creep) significantly impacts the planform of convection and thus the resulting tectonic behavior at the surface, large-scale mantle convection studies have typically assumed diffusion creep (Newtonian rheology) as the only deformation mechanism, due to computational limitations.

Here, we investigate the role of composite rheology on mantle convection with self-consistent plate-like behavior using the code StagYY in 2D annulus (Hernlund and Tackley, 2008). We quantify the spatial distribution of dislocation creep in the mantle in models characterized by different transitional stresses between Newtonian and non-Newtonian rheology. Such models are built on previous viscoplastic cases featuring Earth-like plate velocities, surface heat flow and topography with Newtonian rheology (Arnould et al., 2018). We then investigate how composite rheology impacts the planform of convection and the style of plate-like behavior.

 

References:

Hernlund, J. W., & Tackley, P. J. (2008). Modeling mantle convection in the spherical annulus. Physics of the Earth and Planetary Interiors, 171(1-4), 48-54.

Arnould, M., Coltice, N., Flament, N., Seigneur, V., & Müller, R. D. (2018). On the scales of dynamic topography in whole‐mantle convection models. Geochemistry, Geophysics, Geosystems, 19(9), 3140-3163.