bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental study of sediment transport processes and size selectivity of eroded sediment on steep Pisha sandstone slopes
Authors: Zhang Pan , Xiao Pingqing , Yang Chunxia
Published: March 2020

The Pisha sandstone area on the Ordos Plateau of China is the primary source of coarse sediment of the Yellow River. Sediment size distribution and selectivity greatly affect sediment transport and deposition. Hence, sediment transport processes and size selectivity by overland flow on Pisha sandstone slopes were investigated in this study. Experiments were run with Pisha sandstone soil (bulk density of 1.35 g/cm3) under rainfall intensities of 87 and 133 mm/h with a 25° slope gradient, and the duration of simulated rainfall is 1 h. Sediment and runoff were sampled at 2-min intervals to examine the size distribution change of the eroded sediment. The particle composition, enrichment rate, fractal dimension, and time distribution characteristics of median grain size (d50) of eroded sediment were comprehensively analyzed. Statistical analyses showed that the erosion process of Pisha sandstone slope mainly transported coarse sediment. More than 40% of eroded sediment particles were coarse sediment, which will become the main sediment in the lower reaches of the Yellow River bed. The particle size of eroded sediment tended to gradually decrease with the continuous rainfall but remained larger than the background value of Pisha sandstone soil after refinement. The fractal dimension was positively correlated with the slope flow velocity, while the d50 was negatively correlated with the slope flow velocity. Overall, these findings show a strong relationship between the sediment transport and flow velocity, which indicates that the selectivity and transportation of sediment particles on the Pisha sand slopes is mainly influenced by the hydrodynamic parameters of overland flow. This study provides a methodology and data references for studying the particle selectivity characteristics of eroded sediment and provides a scientific basis for revealing the mechanism of erosion and sediment yield in the Pisha sandstone area of China.
Stress-field orientation and crustal deformation in the Vienna Basin region (Alpine-Pannonian-Carpathian junction)
Authors: Schippkus Sven , Zigone Dimitri , Bokelmann Götz , Working Group AlpArray
Published: March 2020

Gaining insight into the regional stress field and deformation in the crust is challenging. As we cannot measure these directly, we rely on proxy measurements and numerical modelling to infer their orientation. For the Alpine-Pannonian-Carpathian junction, only a limited number of studies exist that provide such insights. They are based on either the interpretation of sparse and point-wise measurements of local stress-field orientations or on numerical modelling that aims to satisfy tectonic and geological constraints.

 

We infer seismic azimuthal anisotropy that relates to the orientation of the regional stress-field and crustal deformation from ambient-noise-derived Rayleigh waves in the region. This approach provides a spatially broad and independent measurement that complements previous studies. We use Rayleigh-wave group-velocity residuals after isotropic inversion at 5s and 20s center period, which are sensitive to crustal structure at different depths. They allow us to gain insight into two distinct mechanisms that result in fast orientations. At shallow crustal depths (5s), fast orientations in the region are N/S to NNE/SSW, roughly normal to the Alps. This effect is most likely due to the formation of cracks aligned with the present-day stress field. At greater depths (20s), fast orientations rotate towards NE, almost parallel to the major fault systems that accommodated the lateral extrusion of blocks in the Miocene. This is coherent with the expected direction of aligned crystal grains during crustal deformation occurring along the fault systems and the lateral extrusion of the central part of the Eastern Alps.
School on Geoethics and Natural Issues
Authors: Peppoloni Silvia , Di Capua Giuseppe , Bobrowsky Peter T.
Published: March 2020

Founded on July 2019, the “School on Geoethics and Natural Issue” (http://www.geoethics.org/geoethics-school) is a scientific, international, multicultural and multidisciplinary meeting place for teaching and learning of the principles and values of geoethics in the light of the philosophy and history of Earth sciences. Its intent is to provide background knowledge and the evaluation skills necessary to understand the complex relationship between human action on ecosystems and the decisions geoscientists make in the discipline that impact society, including improving the awareness of professionals, students, decision-makers, media operators, and the public on an accountable and ecologically sustainable development.

The School on geoethics, conformed to the Geoethical Promise (http://www.geoethics.org/geopromise) and the Cape Town Statement on Geoethics (http://www.geoethics.org/ctsg), aims to provide excellent education in geoethics (http://www.geoethics.org/definition), thus promoting the development of a scientific and critical attitude to the knowledge of the Earth and its constituent systems, by fostering a growth of awareness and responsibility towards the planet, education in the values and actions underlying a respect for ecosystems, including responsible use of resources, management of natural risks, reduction of pollution and its repercussions on human health and climate, adaptation to environmental changes, in view of an accountable and ecologically sustainable development.

Moreover, it provides the opportunity to deepen reflection on the sense and social utility of geosciences, analyzing their rational categories, values, possible perspectives, uncertainties and cognitive limits, and to learn and develop more responsible strategies, operating procedures and practical actions, that are compatible with respect for socio-ecological systems, the vocation of the territories, including the health and safety of human communities.

The courses are addressed to different categories of users: they can be useful to both secondary school students and university undergraduate/graduate students in disciplines that deal with the environment from different perspectives (planning, naturalist, geo-biological, landscape, architectural, legislative, educational, cultural and relative to communication). Scholars of the phenomena and processes of the planet (researchers, academics, scientists), as well as those who physically operate in the territories (various types of professionals, geologists, engineers, landscape architects, risk experts, media operators, decision-makers) can find valid support to their scientific and professional preparation in the courses. Finally, the School on geoethics is also aimed at the general public and others, including non-experts, who are interested in better understanding the bond that links human communities to ecosystems, within the perspective of responsible development.
Contrasting the role of regional and remote circulation in driving the Asian monsoon in HadGEM3-GA7
Authors: Liu Zhen , Bollasina Massimo A. , Wilcox Laura J. , Rodríguez José M. , Regayre Leighton A.
Published: March 2020

Monsoon biases are long-standing and an important problem to solve because nearly half of the world’s population is affected by monsoon precipitation and circulation. The effect of local and remote circulation biases on Asian monsoon biases is studied with dynamical nudging using the latest version of the atmospheric component of the HadGEM3 model. Constraining the large-scale circulation substantially reduces oceanic biases in precipitation and circulation, particularly over the extra-tropics. Tropical wet biases may become even stronger because of unconstrained convection. By contrast, model biases over land are less sensitive to nudging due to the prominent role of local planetary boundary layer processes in modulating the low-level circulation. Nudging reduces the seasonal excess (deficit) precipitation over India in winter (summer) by reducing the local cyclonic (anti-cyclonic) biases. Constraining the circulation outside Asia demonstrates that the wet (dry) biases are mostly remotely (locally) controlled in winter (summer) over India. The monsoon biases over China show small changes with nudging, suggesting they are more thermodynamically driven. Monsoon variability is improved over India but not over China in nudged simulations. Despite the remaining errors in nudged simulations, our study suggests that nudging serves as a useful tool to disentangle the contribution of regional and remote circulation in generating the monsoon responses.
Enhancement of Interplate Coupling after Recent Megathrust Earthquakes
Authors: Yuzariyadi Mohammad , Heki Kosuke
Published: March 2020

Enhanced interplate coupling has been found for segments adjacent along-strike to megathrust faults after the 2003 Tokachi-Oki and the 2011 Tohoku-Oki earthquakes, NE Japan, and was interpreted as acceleration of the subducting Pacific Plate slab. A similar enhanced coupling was also reported for the segments to the north of the rupture area of the 2010 Maule earthquake, central Chile. We utilize available GNSS data to find such enhanced coupling in worldwide subduction zones including NE Japan, central and northern Chile, Sumatra, and Mexico to investigate their common features. Our study revealed that the accelerations of landward movement of 2.1-9.0 mm per year appeared in adjacent segments following the 2014 Iquique (Chile), the 2007 Bengkulu (Sumatra), and the 2012 Oaxaca (Mexico) earthquakes. We also confirmed that the enhanced coupling is associated with the increase of seismicity for all these six cases. We found that the degree of enhancement depends on the length of the slab and the magnitude of the earthquake, which is consistent with the simple 2-dimensional model proposed earlier.
The Devonian plant revolution and its role in multiple marine extinction crises
Authors: Bond David , Stephenson Charlotte
Published: March 2020

The Devonian was one of the most dynamic periods in Earth history, with major changes on land and in the oceans that experienced at least two of the ten most severe biotic crises of the Phanerozoic. The Period saw the first extensive global floral record; prior to the Devonian, plant assemblages were low in diversity and abundance, and were restricted to areas close to water sources with little competition from co-existing taxa. By the end, plants were geographically widespread in diverse environments. Their colonisation of the land surface has been implicated in the Frasnian/Famennian marine crisis, but little is known of the effects of plants on the global biosphere during the rest of the Devonian. Synthesis of 389 publications reporting 294 Devonian plant genera has resulted in a database that we analyse at generic and stage level for trends in Devonian plant evolution and extinction. Our analysis reveals several key events within this dynamic phase of terrestrialisation: 1) an early Euramerican presence for all plant groups, suggesting this region may have been the site of origination for several higher taxa; 2) the origination of lycopsids in equatorial settings was followed by latitudinal migration northward and southward; 3) a major turnover in plants between the Late Givetian and Middle Frasnian, when significant diversity losses occurred in every palaeo-region in every extant plant group – this may be a hitherto unidentified terrestrial extinction event that coincided with one or both of the Taghanic and Frasne minor marine crises; 4) several Devonian marine black shale events coincide with major steps in terrestrialisation suggestive of a causal link and supporting the notion that plant evolution played a significant role in the Frasnian/Famennian mass extinction nexus.
Exploring the potential of solar-induced fluorescence for terrestrial evapotranspiration estimation
Authors: Zhou Kai , Xiong Lihua , Zhang Quan
Published: March 2020

Terrestrial evapotranspiration (ET) is a significant part of the hydrological cycle and it couples water cycles and carbon cycles. Accurate ET estimation is of great significance to hydrological prediction. Recently, the widely used solar-induced fluorescence (SIF) for photosynthesis estimation purpose has been applied to estimate ET given the tight coupling of water and carbon cycles. Some studies have shown that SIF has the potential to predict ET when combined with other meteorological variables. However, these ET-SIF researches in the past are mostly based on empirical relationships between ET and SIF but rarely rely on the mechanistic process of carbon-water interactions. The water and carbon cycles are naturally coupled via plants’ stomata, through which plants exchange CO2 and H2O with the atmosphere. Thus, the main objective of our research is to develop SIF-based ET estimation models by coupling the water and carbon cycles. The model estimates ET by combining SIF with remote sensing products like leaf area index (LAI), photosynthetically active radiation (PAR) and vapor pressure deficit (VPD). The model is well validated by the FLUXNET2015 tower-based ET and MODIS16 ET products.
Observed distribution of halocarbons in the Southern Hemispheric UTLS and implications for the bromine and chlorine budget of the lowermost stratosphere
Authors: Jesswein Markus , Soria Galvarro Sarah , Keber Timo , Schuck Tanja , Wagenhäuser Thomas , Engel Andreas
Published: March 2020

Since the end of the 1980's, the Montreal Protocol regulates production and use of chlorine and bromine containing substances because they thin out the ozone layer. This has led to a phase out of the long-lived halocarbons like the chlorofluorocarbons (CFCs). Next to the long-lived halocarbons, bromine and chlorine containing substances with atmospheric lifetimes of less than 6 months can reach the lower stratosphere. These substances, also known as "very short-lived" substances (VSLS), have their origin both from natural and anthropogenic sources. An increase of the relative contribution of the VSLS to the stratospheric halogen loading is assumed. Due to their short lifetime, chlorine and bromine of these gases are released quickly into the stratosphere, making them particularly effective catalysts for destruction of ozone in the lower stratosphere.

Here we present airborne measurements of halocarbons including chlorine and bromine VSL source gases. Measurements were taken on the HALO aircraft during the measurement campaign SOUTHTRAC in the Southern Hemisphere UTLS. Using an airborne GC/MS system in electron impact ionization mode, samples were taken in a time resolution of around 6 minutes. One of the focuses are the exchange processes between the Northern and Southern Hemisphere. We further compare results of this campaign with these of previous ones of the Northern Hemisphere.
Input-adaptive proxy of air quality parameters: A case study for black carbon in Helsinki, Finland
Authors: Fung Pak L , Zaidan Martha A , Sillanpää Salla , Kousa Anu , Niemi Jarkko V , Timonen Hilkka , Kuula Joel , Saukko Erkka , Luoma Krista , Petäjä Tuukka , Tarkoma Sasu , Kulmala Markku , Hussein Tareq
Published: March 2020

Urban air pollution has been a global challenge, and continuous air quality measurement is important to understand the nature of the problem. However, missing data has often been an issue in air quality measurement. In this study, we presented a modified method to impute missing data by input-adaptive proxy. We used black carbon (BC) concentration data in Mäkelänkatu traffic site (TR) and Kumpula urban background site (BG) in Helsinki, Finland in 2017–2018 as training sets. The input-adaptive proxy selected input variables of other air quality variables based on their Pearson correlation coefficients with BC. In order to avoid overfitting, this proxy used the algorithm of least squares model with a bisquare weighting function and allowed a maximum of three input variables. The generated models were then evaluated and ranked by adjusted coefficient of determination (adjR2), mean absolute error and root mean square error. BC concentration was first estimated by the best model. In case of missing data in the input variables in the best model, the input-adaptive proxy then used the second-best model until all the missing data gaps were filled up.

The input-adaptive proxy managed to fill up 100% of the missing voids while traditional proxy filled only 20–80% of missing BC data. Furthermore, the overall performance of the input-adaptive proxy is reliable both in TR (adjR2=0.86–0.94) and in BG (adjR2=0.74–0.91). TR has a generally better regression performance because the level of BC can be mostly explained by traffic count, nitrogen oxides and accumulation mode. On the contrary, the source of BC in BG is more heterogeneous, which includes traffic emission and residential combustion, and the concentration of BC is influenced by meteorological parameters; therefore, the rule of including maximum three input variables might lead to the lower adjR2. The proxy works slightly better for workdays scenario than in weekends in both sites. In TR, the proxy works similarly in all seasons, while in BG, the proxy performance is better in winter and autumn than in the other seasons. The simplicity, full coverage and high reliability of the input-adaptive proxy make it sound to further estimate other air quality parameters. Moreover, it can act as an air quality virtual sensor alongside with on-site instruments.
New and improved European satellite observation capabilities for hazardous weather to be available from 2022 onwards: Meteosat Third Generation (MTG)
Authors: Grandell Jochen , August Thomas , Coppens Dorothee , Fowler Gary , Lekouara Mounir , Munro Rosemary , Viticchie Bartolomeo
Published: March 2020

EUMETSAT has provided the user community with more than three decades worth of satellite data, starting with the geostationary missions of the Meteosat First Generation, and since 2002 with the Meteosat Second Generation (MSG) series satellites.

The development of the next generation geostationary program, the Meteosat Third Generation (MTG), is now in its final stages. The MTG system will host a more advanced 16-channel VIS/IR Flexible Combined Imager (FCI) as well as a Lightning Imager (LI) on its geostationary imaging platform (MTG-I), whereas the sounding platform (MTG-S) will host the MTG InfraRed Sounder (IRS) and the Copernicus Sentinel-4 ultraviolet/near-infrared (UVN) sounding missions. The launch of the first two satellites MTG-I1 and MTG-S1 hosting the imaging and sounding instruments is foreseen in 2021 and 2023, respectively.

The new and improved capabilities will significantly enhance the potential for convective storm monitoring, from the earliest initial phases to full maturation and dissipation. In addition, as examples of dedicated applications where the improved capabilities will play a significant role, one can mention fog monitoring and especially the enhanced fire monitoring capability.

The presentation will give an overview of the MTG system, its observation missions, and the main improvements and novelties over Meteosat Second Generation (MSG) in terms of new missions and expected product performance. As a primarily Nowcasting mission, MTG will provide significant additions to the hazardous weather observations in the coming years. The emphasis of the presentation will be on the new observational capability provided by the Lightning Imager.
Spatial and Temporal Analysis of Precipitation Extremities of Eastern Nepal in the Last Two Decades (1997–2016)
Authors: Subba Sunil , Ma Yaoming , Ma Weiqiang
Published: March 2020

In recent days there have been discussions regarding the impact of climate change and its vagaries of the weather, particularly concerning extreme events. Nepal, being a mountainous country, is more susceptible to precipitation extreme events and related hazards, which hinder the socioeconomic
development of the nation. In this regard, this study aimed to address this phenomenon for one of the most naturally and socioeconomically important regions of Nepal, namely, Eastern Nepal. The data were collected for the period of 1997 to 2016. The interdecadal comparison for two periods
(1997–2006 and 2007–2016) was maintained for the calculation of extreme precipitation indices as per recommended by Expert Team on Climate Change Detection and Indices. Linear trends were calculated by using Mann‐Kendall and Sen's Slope estimator. The average annual precipitation was found to be decreasing at an alarming rate of −20 mm/year in the last two decades' tenure. In case of extreme precipitation events, consecutive dry days, one of the frequency indices, showed a solo increase in its trend (mostly significant). Meanwhile, all the intensity indices of extreme precipitation showed decreasing trends (mostly insignificant). Thus, it can be concluded that Eastern Nepal has witnessed some significant drier days in the last two decades, as the events of heavy, very heavy, extremely heavy precipitation events, and annual wet day precipitation (PRCPTOT) were found to be decreasing. The same phenomena were also seen in the Tropical Rainfall Measuring Mission 3B42 V7 satellite precipitation product for whole Nepal.
The Angular Distribution of Whistler-Mode Chorus and the Importance of Plumes in the Chorus-Hiss Mechanism
Authors: Hartley David P. , Chen Lunjin , Kletzing Craig , Horne Richard , Santolik Ondrej
Published: March 2020

Correlations between chorus waves and plasmaspheric hiss have been directly observed, leading to the proposition that the two wave modes are causally linked. Ray tracing simulations have confirmed that chorus waves can propagate into the plasmasphere and be a source of plasmaspheric hiss, but only for a specific set of initial conditions, particularly relating to the orientation of the wave vector at the chorus source. In this study, both survey and burst mode observations from the Van Allen Probes EMFISIS Waves instrument are coupled with ray tracing simulations to determine the fraction of chorus wave power that exists with the conditions required to enter the plasmasphere. In general, it is found that only a small fraction (< 2%) of chorus wave power exists with the required wave vector orientation. An exception is found when the chorus source is located close to a plasmaspheric plume. Here, azimuthal density gradients modify the wave propagation to permit a large fraction, up to 94%, of chorus wave power to access the plasmasphere. Therefore plasmaspheric plumes are identified as an important access region if a significant fraction of chorus wave power is to enter the plasmasphere and be a source of plasmaspheric hiss. To provide context, we note that plumes are most commonly observed on the dusk side whereas chorus wave power typically peak on the dawn side. The post-noon sector, where these two statistical distributions overlap, appears to be key for observing correlations between chorus and hiss. As such, particular attention is devoted to this region.
Understanding wetland dynamics using geostatistics of multi-temporal Earth Observation datasets
Authors: Singh Manudeo Narayan , Sinha Rajiv
Published: March 2020

Wetlands are important but fragile ecosystems. Half of the world’s wetlands are already lost and most of the remaining ones are in a degraded state. Such wetlands warrant immediate management and restoration works. Further, with changing land-use patterns and climate, it is essential to monitor the dynamics of such wetlands, which is in turn driven by hydrology, vegetation pattern, and geomorphology. All biogeochemical processes in the wetlands are influenced by hydropattern and water level. Understanding vegetation-hydrology nexus is an important challenge in wetland management and restoration activities. In addition, the spatial characterization of the fragmentation and shrinkage is essential to manage the wetlands.

A geostatistics-based assessment of a large floodplain wetland namely the Kaabar Tal in eastern India has been performed using multi-temporal Landsat datasets in a GIS (Geographical Information System) framework by applying linear regression method and Mann-Kendall Trend Tests. With an area of 51 km2 and a total catchment size of 250 km2, the Kaabar Tal is the largest wetland of the north Bihar in the East Ganga Plains of India. A historical assessment of the wetland spanning over four decades (1976-2016) has been performed by formulating a novel framework which encompasses the following six indicators: (a) pixel-wise net trend assessment of wetness and vegetation, (b) seasonal hydropattern, (c) average drying rates, (d) seasonal and annual patch dynamics (fragmentation assessment), (e) annual shoreline shrinkage rates, and (f) multi-temporal geomorphic mapping. To understand the influence of these indicators in different parts of the wetland, a sectorial approach has been followed by dividing the wetland in nine zones, and each zone was ranked from least to most degraded based on the six indicators. A linear combination of these ranks was used to decide the overall degradation rank of the zones. The different zones of Kaabar Tal were ranked in terms of increasing order of degradation. The western zone W, the most degraded zone, has suffered the highest quantum of encroachments coupled with the highest rates of shoreline shrinkage. The central zone C ranked least on the degradation scale; however, it is still degrading, and the wetness trend is ‘very severely decreasing’ while the vegetation (or eutrophication) trend is ‘severely increasing.’

The framework developed in the current work is based on the freely available satellite datasets, easily implementable remote sensing and GIS approaches, and well-known geostatistical methods. Further, the method can be adapted to analyze the hydrogeomorphic dynamics and degradation scenarios of any wetland systems, irrespective of their geographical and climatic settings.
Addressing Uncertainties in Projected IDF Relationships under Climate Change
Authors: Tripathy Kumar Puran , Mujumdar Pradeep
Published: March 2020

The Intensity-Duration-Frequency (IDF) relationships are commonly used in urban hydrologic designs. A major source of uncertainty arises due to small samples of data and use of multiple GCMs, in developing the IDF for future periods. A major objective of this study is to address uncertainties in the IDF relationships for future periods, under climate change. The study proposes a Bayesian method for addressing the parameter uncertainty in the Generalized Extreme Value (GEV) distribution for the Annual Maximum Series (AMS). Uncertainties due to the use of multiple GCMs are addressed through the Reliable Ensemble Averaging (REA) method. The posterior distributions of the three parameters of GEV distribution are obtained using Markov Chain Monte Carlo (MCMC) method. Twenty-three CMIP5 GCMs with four RCPs are considered for studying the effect of climate change on the IDF relationship for the case study of Bangalore, India. Change Factor Method (CFM) is used for spatially downscaling the projected time series of precipitation and scale-invariance theory is used for temporal disaggregation. Results are compared across different CFM schemes considering multiple bin sizes. Uncertainties in design intensities are quantified through probabilistic IDF relationships.
Climate attribution of environmental catastrophes
Authors: Shepherd Theodore
Published: March 2020

The role of climate change in environmental or ecological catastrophes is generally a complex question to address, because of the importance of non-climatic factors. From a climate perspective, the latter are confounding factors, whereas from an ecological perspective, they are often the heart of the matter. How these factors are treated affects the nature of the scientific questions that can be answered. In particular, the coarse-graining required to address probabilistic questions inevitably blurs the details of any particular event, whereas these details can be retained when addressing singular questions. In this paper, based on an analysis done jointly with Lisa Lloyd, I will present several published case studies of environmental catastrophes associated with extreme weather or climate events. Whilst both the singular ‘storyline’ and probabilistic ‘risk-based’ approaches to extreme-event attribution have uses in the descriptions of such events, we find the storyline approach to be more readily aligned with the forensic approach to evidence that is prevalent in the ecological literature. Implications for the study of environmental catastrophes are discussed.
Polyphase tectonothermal events recorded in metamorphic basement rocks from the northern Altyn Tagh, southeastern Tarim Craton
Authors: Wang Zhongmei , Han Chunming , Xiao Wenjiao , Sakyi Patrick Asamoah
Published: March 2020

  Paleoproterozoic is a pivotal time for understanding the geochronological framework of the Tarim Craton. Located on the southeastern margin of the Tarim Craton, the northern Altyn Tagh is the main exposed region for Paleoproterozoic magmatic-metamorphic rocks. These rocks are diverse, diachronous and modified by multiple magmatic and/or metamorphic events. In this study, we performed systematic analyses on the amphibolite, felsic gneisses, and metasedimentary rocks in the Aketashitage area, southeastern Tarim Craton, including petrography, mineral chemistry, and whole-rock geochemistry, as well as in-situ zircon U-Pb ages and Hf isotopes, to examine the Paleoproterozoic magmatic-metamorphic events in the northern Altyn Tagh. Geochemically, the amphibolite and felsic gneisses in the Aketashitage area seemingly represent the typical bimodal associations of mafic and acidic volcanic rocks. In addition, the felsic gneisses are characterized by high Sr and low Y contents, with high Sr/Y and LaN/YbN ratios, and indistinctive Eu anomalies, closely resembling high-SiO2 adakites derived from subducted basaltic slab-melt. The palimpsest textures and geochemical features of the Aketashitage metasedimentary rocks suggest that their protoliths are argillaceous rocks. The amphibolite has a metamorphic age of 1.96 Ga, and the felsic gneisses yield crystallization ages of 2.54-2.52 Ga. For the metasedimentary rocks, the major age peaks of 2.72 Ga, 2.05 Ga and 1.97 Ga are consistent with the magmatic and/or metamorphic events in the study area. The minimum age peak suggests that the depositional age is no earlier than 1.97 Ga. The geochemical and geochronological evidences documented by the exposed rock associations in the Aketashitage area suggest a subduction-related tectonic setting in the Paleoproterozoic. Our new data combined with the previous studies indicate that the Paleoproterozoic magmatism and metamorphism in the northern Altyn Tagh area are nearly synchronous, and both are likely related to oceanic subduction.
On the Robustness of Conceptual Rainfall-Runoff Models to Calibration and Evaluation Dataset Splits Selection: A Large Sample Investigation
Authors: Zheng Feifei , Guo Danlu , Gupta Hoshin , Maier Holger
Published: March 2020

Conceptual Rainfall-Runoff (CRR) models are widely used for runoff simulation, and for prediction under a changing climate. The models are often calibrated with only a portion of all available data at a location, and then evaluated independently with another part of the data for reliability assessment. Previous studies report a persistent decrease in CRR model performance when applying the calibrated model to the evaluation data. However, there remains a lack of comprehensive understanding about the nature of this ‘low transferability’ problem and why it occurs. In this study we employ a large sample approach to investigate the robustness of CRR models across calibration/validation data splits. Specially, we investigate: 1) how robust is CRR model performance across calibration/evaluation data splits, at catchments with a wide range of hydro-climatic conditions; and 2) is the robustness of model performance somehow related to the hydro-geo-climatic characteristics of a catchment? We apply three widely used CRR models, GR4J, AWBM and IHACRE_CMD, to 163 Australian catchments having long-term historical data. Each model was calibrated and evaluated at each catchment, using a large number of data splits, resulting in a total of 929,160 calibrated models. Results show that: 1) model performance generally exhibits poor robustness across calibration/evaluation data splits; 2) lower model robustness is correlated with specific catchment characteristics, such as a higher runoff skewness, lower aridity and runoff coefficient. These results provide a valuable benchmark for future model robustness assessments, and useful guidance for model calibration and evaluation.
A Novel Two-Way Coupled Model for Simulating the Interaction between Fluid flow and Floating Debris
Authors: Xiong Yan , Liang Qiuhua , Wang Gang , Cui Yunsong
Published: March 2020

Extreme natural hazards such as tsunamis or storm surges have been frequently reported in recent years, posting serious threat to people and their properties. Numerical modelling has provided an indispensable tool to predict these hazardous events and assess their risks. However, most of the current models are based on the assumption of “clean” water and neglect the impact of floating debris as observed in reality. The interactive processes between the floating debris and the background fluid flow have not been well explored and understood. Few reliable modelling tool has been reported for simulating and predicting these complicated processes.

This work presents a two-way dynamic method to couple a 2D shallow flow hydrodynamic model with a discrete element method (DEM) model for simulating and analyzing the interactive process between fluid flow and floating debris under the extreme hydraulic conditions induced by tsunami or flash flooding. The proposed two-way coupling approach uses the high-resolution water depth and velocity predicted by the hydrodynamic model to quantify the hydrostatic and dynamic forces acting on the floating objects; the corresponding counter forces on the fluid are subsequently taken into account by including extra source terms in the governing shallow water equations (SWEs) of hydrodynamic model. This new approach lifts the limitation of traditional approaches that reply on calibrated empirical parameters to quantify the forces. In developing the resulting coupled model, a multi-sphere method (MSM) is adopted and implemented in the DEM model to simulate solid debris. This method ensures that the interaction of fluid and solid is realistically modelled and the application is not restricted by shapes and sizes of debris.

The new coupling model is validated against a dam-break flume experiment with three floating objects impacting two fixed obstacles. The predicted results in terms of water depth and floating object displacements in both horizontal and vertical directions compare well with the experimental observations. Furthermore, the new coupled model is computationally accelerated by implementation on modern GPUs to achieve high-performance computing. It provides a robust and innovative modelling tool for the simulation of large-scale flooding process including debris impact and assess the resulting risk.
Agricultural infrastructure: the forgotten key driving force on crop-related water footprints and virtual water flows in developing countries: a case for China
Authors: Huang Hongrong , Zhuo La , Wu Pute
Published: March 2020

Agricultural infrastructure plays important roles in boosting food production and trade system in developing countries, while as being a ‘grey solutions’, generates increasingly risks on the environmental sustainability. There is little information on impacts of agricultural infrastructure developments on water consumption and flows, (i.e. water footprint and virtual water flows) related to crop production, consumption and trade especially in developing countries with high water risk. Here we, taking mainland China over 2000-2017 as the study case, identified and evaluated the strengths and spatial heterogeneities in main socio-economic driving factors of provincial water footprints and inter-provincial virtual water flows related to three staple crops (rice, wheat and maize). For the first time, we consider irrigation (II), electricity (EI) and road infrastructures (RI) in the driving factor analysis through the extended STIRPAT (stochastic impacts by regression on population, affluence and technology) model. Results show that the II, EI and RI in China were expanded by 33.8 times, 4.5 times and 2.4 times, respectively by year 2017 compared to 2000. Although the II was the most critical driver to effectively reduce the per unit water footprint, especially the blue water footprint in crop production (i.e., increasing water efficiency), the developments of II led to the bigger total water consumption. Such phenomenon was observed in Jing-Jin region, North Coast and Northwest China with water resource shortage. The EI and RI had increasing effects on provincial virtual water export, and the corresponding driving strengths varied across spaces. Obviously, the visible effects from the agricultural infrastructures on regional water consumption, water productivity and virtual water patterns cannot be neglected. 
Detrital thermochronology evidence of a major morphogenic phase of mountain building in the Himalayas at 10 Ma
Authors: Malusa' Marco Giovanni , Fitzgerald Paul G.
Published: March 2020

Constraining spatial and temporal patterns of topography and exhumation along the Himalayan orogen is a starting point for studies aimed at understanding the development of Asian climate and tectonic evolution. Starting from the pioneering work of Cerveny et al. (1988), many scientists have applied a detrital thermochronologic approach to reveal the Cenozoic exhumation history of the Himalayas. Thermochronologic studies involve analyses of modern river sediments and sedimentary successions either accreted on the southern side of the orogen or accumulated in the Indus and Bengal fans. As datasets have grown and techniques evolved, the available interpretations are often contradictory.

In this contribution, we analyse previously published detrital-thermochronology datasets in the Himalayan region using the interpretive keys illustrated in Malusà and Fitzgerald (2020). These keys reinforce existing approaches and provide new perspectives for the application of detrital thermochronology to tectonic settings where the geologic evolution is often still debated. Different thermochronologic systems applied to proximal and distal sedimentary successions derived from Himalayan erosion yield a complex exhumation and tectonic history, but a relatively consistent picture for the Cenozoic evolution of India-Eurasia collision emerges. Detrital thermochronology data are supportive of a progressive southward thrust propagation towards the Himalayan foreland, progressively involving new eroding sources. The onset of fast exhumation in the Lesser Himalaya is constrained by different thermochronologic methods and datasets, indicative of onset at ~10 Ma, in line with independent geologic evidence. Coeval fast exhumation is also recorded in detritus derived from the Greater Himalaya. These findings are supportive of a major morphogenic phase of mountain building in the Himalayas at ~10 Ma, prior to the onset of fast exhumation in the Namche Barwa syntaxis.

Cerveny PF et al (1988). History of uplift and relief of the Himalaya during the past 18 million years: Evidence from fission-track ages of detrital zircons from sandstones of the Siwalik Group. In: New perspectives in basin analysis, Springer.

Malusà MG, Fitzgerald PG (2020). The geologic interpretation of the detrital thermochronology record within a stratigraphic framework, with examples from the European Alps, Taiwan and the Himalayas. Earth-Science Reviews, https://doi.org/10.1016/j.earscirev.2019.103074
The late Matuyama glaciation in the southern European Alps
Authors: Monegato Giovanni , Scardia Giancarlo
Published: March 2020

The onset of Pleistocene glaciations in the European Alps represented a significant change in the palaeoenvironmental settings of this mountain range. The stratigraphy of the event was described in the subsoil of the Po Plain (Muttoni et al., 2003; Scardia et al., 2012) and is marked by a regional unconformity (namely “Red unconformity”, Muttoni et al., 2003) at 870 ka, in the final part of the Matuyama chron. Elsewhere, in the Alpine end-moraine systems the record of early stages of glaciations is scarce and cryptic. Spots of glacigenic deposits with reverse magnetic polarity were recognized only in the Ivrea (Carraro et al., 1991) and Garda (Cremaschi, 1987; Scardia et al., 2015) end-moraine systems, while deposits related to (peri)glacial environment were recorded along the Lombardian foothills (Scardia et al., 2010). The updated record of the Garda system shows the geometry of a late Matuyama glacier overrunning the piedmont plain with comparable size in respect to the LGM (Monegato et al., 2017). This indicates a fully glaciated Adige-Sarca catchment, one of the largest of the Alps, suggesting that the Alpine Ice Sheet reached one of its waxing climax during a late Matuyama cold stage (MIS20 or MIS22).

 

References

Carraro et al. 1991, Boll. Museo Reg. Sc. Nat. Torino 9, 99-117.

Cremaschi 1987, Edizioni Unicopli, 306 pp.

Monegato et al. 2017, Scientific Reports 7, 2078.

Muttoni et al. 2003, Geology 31, 989-992.

Scardia et al. 2010, Quaternary Science Reviews 29, 832-846.

Scardia et al. 2012, Tectonics 31, TC6004.

Scardia et al. 2015, GSA Bulletin 127, 113-130.
Variations of TEC over Iberian Peninsula in 2015: effects of geomagnetic storms, solar flares, and solar eclipse
Authors: Barata Teresa , Morozova Anna , Barlyaeva Tatiana
Published: March 2020

The total ionospheric content (TEC) over the midlatitudinal area of Iberian Peninsula was studied using data from two locations on the west and east coasts of the peninsula. The data are obtained both by the GNSS receivers and an ionosonde. The principal component analysis applied to the TEC data allowed us to extract two main modes.

The variations of these modes as well as the original TEC data were studied in relation to geomagnetic disturbances observed in March, June, October, and December of 2015. Seven of eight analyzed geomagnetic events were associated with positive-negative ionospheric storms (seen both in TEC daily cycle amplitude and in Mode 1).

Four out of eight analyzed geomagnetic events were associated with variations of Mode 2 that can be described as the appearance of the second daily peak on the 1st day of the storm and a deep in TEC variations on the 2nd day.

Besides, we analyzed the effects of solar flares and overall variations of the solar UV and XR fluxes on the TEC variations during those months. Since a partial solar eclipse was observed in March 2015, the TEC variations during this event were also studied. Only the amplitude of the daily TEC cycle (Mode 1) was found to respond to these types of events.
Capacity of climate models to capture multi-decadal hydrological variations over France
Authors: Boé Julien , Bonnet Rémy
Published: March 2020

In France, large multi-decadal variations in river flows have occurred over the instrumental period. These multi-decadal variations, likely of internal origin, could be a major source of uncertainties in the evolution of river flows during the 21st century, and especially during the coming decades, when the climate change signal is weaker. Depending on their phase, these variations might indeed strongly temporarily amplify or weaken (and even possibly reverse) the signal of climate change. From an adaptation perspective, it is crucial that hydrological projections correctly capture the amplitude of these multi-decadal variations, so that the associated uncertainties can be correctly estimated. The realism of hydrological projections in this context lies to a large extent in the realism of climate models, used at the first stage of the vast majority of the studies of the impacts of climate change.

The brevity of the instrumental record makes it difficult to characterize robustly multi-decadal hydro-climate variations, and the lack of observations for important hydrological variables makes it difficult to understand the mechanisms at play. The evaluation of climate models in this context is therefore also particularly challenging. 

In this presentation, I will describe our work to better characterize hydrological variations over France in terms of amplitude and mechanisms, thanks to joint use of newly developed hydrological reconstructions beginning in the mid-nineteenth century, long observations from data-rescue efforts and paleo-climate reconstructions. Based on this work, I will then describe the results of the evaluation of multi-decadal hydrological variations in current global climate models, in terms of amplitude and associated mechanisms, taking into account the very large sampling uncertainties associated with the characterization of multi-decadal variations on relatively short periods. 
Crustal and lithospheric complexity beneath the North Tanzanian Divergence from seismological and geochemical analyses.
Authors: Gautier Stéphanie , Clutier Adeline , Parat Fleurice , Tiberi Christel
Published: March 2020

We present a joint analysis of seismological images and petrophysical data in the North Tanzanian Divergence, where the lithospheric break-up is at its earliest stage. In this part of the East African Rift, the current surface deformation is related to complex interaction between tectonic (active fault, pre-rift lithospheric structure) and magmatic processes within the mantle and the crust. We present here the compilation of seismological results such as receiver function, local tomography, regional tomography on datasets collected during CRAFTI-CoLiBrEA and HaTARi projects, in a region with clearly opposite seismological and magmatic behaviours: near Natron the seismicity is well located within the upper crust and linked to present day magmatism (Lengai edifice), whereas Manyara area is characterized by a deep seismicity and no evidence of present magmatic activity at the surface. First, these different approaches deliver Vp, Vs and deduced Vp/Vs images with both different resolution and different depth investigation. The combined images of crustal and lithospheric structure provide the appropriate scale to point out the interactions between melt, gas, faults, and inherited fabrics in specific areas. We then compare those geophysical observations with magma composition, magma storage (depth of reservoir, magma volume) and ascent as well as partial melts content at depth obtained from petrophysical and geochemical analysis of lava samples. We will analyze if this combination of seismological approaches constrained with petrological and geochemical data produce accurate images of the entire current magma plumbing system.  Finally, we will discuss the results in terms of magmatic processes and how they interact with the rifting in a cratonic lithosphere.