bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation and Refinement of the Beer-Lambert Extinction Law in the Discontinuous Vegetation Canopy
Authors: Yan Kai , Zhang Yiman , Xu Xu , Pu Jiabin , Liu Zhao
Published: March 2020

The classical Beer-Lambert (BL) law of exponential decay in direct transmission is widely used for modeling the photon propagation in optical media and has been employed for retrieving vegetation structure parameters (e.g. leaf area index, LAI). However, BL law assumes that these absorbing obstacles are distributed in the space independently, which is the main reason of model-observation-inconsistency and arises many studies of so-called sub- and super-exponential extinction for spatially correlated media. Discontinuous vegetation canopy is the typical case of the extinction field with spatial correlations. Because of many practical difficulties, the uncertainty of the BL law used in vegetation canopy still lacks quantitive assessment. In this paper, we carry out this task by utilizing a ray-tracing-based 3-Dimensional radiative transfer model (3D RT) to simulate the photo propagation process in real vegetation canopy scenes. We confirm that the classical BL law is only suitable for both horizontally and vertically homogenous canopy (e.g. dense grasses) and shows increasing discrepancy with the decrease of the fraction of vegetation cover (FVC). When canopy clumping occurs (FVC<1), absorbing obstacles (i.e. leaves) become to be spatially correlated and lead to a slower-than-exponential (sub-exponential) extinction with propagation distance, which will result in an underestimation of LAI when classic BL law is employed. To solve this problem, we propose a new 1st order scattering extinction model by modifying the classic BL law by introducing a pair-correlation-function. This attempt is based on the stochastic radiative transfer theory and shows good performance when compared with the reference from computer 3D simulation.
Coupling machine learning with high resolution satellite imagery to estimate spatiotemporal changes of salinity in water bodies
Authors: Bayati Majid , Danesh-Yazdi Mohammad
Published: March 2020

The spatiotemporal dynamics of salinity in hypersaline lakes is strongly dependent on the rate of water flow feeding the lake, evaporation rate, and the phenomena of precipitation and dissolution. Although in-situ observations are most reliable in quantifying water quality variables, the spatiotemporal distribution of such data are typically limited or cannot be readily extrapolated for long-term projections. Alternatively, remotely-sensed imagery has facilitated less expensive and stronger ability to estimate water quality over a wide range of spatiotemporal resolutions. This study introduces a machine learning model that leverages in-situ measurements and high-resolution satellite imagery to estimate the salinity concentration in water bodies. To this end, 123 points were sampled in April and July of 2019 across the Lake Urmia surface covering the wide range of salinity fluctuations. Among the artificial neural networks, ANFIS, and linear regression tools examined to determine the relationship between salinity and surface reflectance, artificial neural networks yielded the best accuracy evidenced by R2 = 0.94 and RMSE = 6.8%. The results show that the seasonal change of salinity is linearly correlated with the volume of water feeding the lake, witnessing that dilution imposes a stronger control on the salinity than bed salt dissolution. The impact of disturbance in the lake circulation due to the causeway is also evident from the sharp changes of salinity around the bridge piers near spring when the mixing of fresh and hypersaline water from the southern and northern parts, respectively, takes place. The results of this study prove the promising potential of machine learning tools fed multi-spectral satellite information to map other water quality metrics than salinity as well.
A different perspective on how parameterized orographic gravity waves influence atmospheric transport and dynamics in current generation global climate models
Authors: Rieder Harald , Šácha Petr , Eichinger Roland , Kuchař Aleš , Samtleben Nadja , Pišoft Petr , Jacobi Christoph
Published: March 2020

In the atmosphere, internal gravity waves (GWs) are a naturally occurring and ubiquitous, though intermittent phenomenon. In addition, GWs (especially orographic; OGWs) are asymmetrically distributed around the globe. In current generation global climate models (GCMs), GWs are usually smaller than the model grid resolution and the majority of their spectrum therefore must be parameterized. To some extent, the intermittency and asymmetry of a spatial distribution of the resulting OGW drag (OGWD) is present also in GCMs. As the GW parameterization schemes in GCMs are usually tuned to get the zonal mean climatology of particular features right, an important question emerges: what kind of influence do GW parameterizations have on the individual models atmosphere locally? Here we focus on answering this question regarding the impact of spatiotemporally intermittent OGW forcing in the extra-tropical lower stratosphere region (LS). The LS region is characterized by a strong interplay of chemical, physical and dynamical processes. To date, the representation of this dynamically active region in models frequently mismatches observations. Although we can find a climatological maximum of oGWD in the LS, the role of OGW forcing for the transport and composition in this region is poorly understood. We combine observational evidence, idealized modeling and statistical analysis of GCM outputs to study both the short-term and long-term model response to the OGW forcing. The results presented will question the relationship between the advective part of the Brewer- Dobson circulation and the zonally asymmetric GW forcing, and a so-far neglected link between oGWD and large-scale quasi-isentropic stirring will be discussed.
Soils and relief relationships in subalpine grasslands in the Central Pyrenees (NE, Spain)
Authors: Badía-Villas David , Buendía-García Lucía , Longares-Aladrén Luis Alberto , Peña-Monné José Luis , Martí-Dalmau Clara
Published: March 2020

On two accumulation levels, separated by an unevenness up to 2 m, two contrasted plant communities can be differentiated in subalpine stage of the Pyrenees: the dense tussock-forming grass Nardus stricta, at the upper level (L1), and the open chalk grasslands at the lower level (L2). In order to confirm the soil-relief-grasslands relationships, we analyzed and compared soil pedogenesis and properties in both accumulation levels. In addition, we classify the soils following WRB and ST systems and we discuss the finesse of both taxonomies in these high mountain environments. The work has been carried out at 1900 masl, in the Ordesa and Monte Perdido National Park (PNOMP), in the summer grasslands site of La Estiva (Fanlo, Central Pyrenees, NE Spain). Five soil pits were studied in every accumulation level (L1 and L2) for a side-by-side comparison.

            The study of soils in the two levels of accumulation reveals a series of differences in their genesis, properties and soil classification. The accumulation of organic matter and lixiviation are the dominant edafogenetic processes in L1, to which we must add the rejuvenation by gully erosion in L2. Soils at L1 and L2 shared many physical properties as a fine granulometry, with a homogeneous particle-size distribution with depth. In both levels, the soils lack carbonates, even though limestones are the parental material. The soils in L1 have a greater thickness and, thus, a higher water holding capacity than in L2. In relation to chemical properties, soils in L1 have a significantly lower pH, a lower base saturation, and lower available calcium content than in L2, reflecting a more intense leaching process, consistent with a longer period of slope stability. Over L1 with Nardus mat-grasslands, the main soil is classified as Orthoeutric Cambisols (Clayic, Humic), and the soil over L2, with chalk-grasslands, as Hypereutric Leptosols (Loamic, Ochric). Soil taxonomy System (USDA), giving more weight to the temperature regime, classify both soils as Haplocryept, at the level of great group, separating them at the subgroup level as Typic Haplocryept (L1) and Lithic Haplocryept (L2), according to the depth at which limestone appears (lithic contact). Definitely, the microtopograhy and geomorphologic context, is linked to the pedodiversity, which goes hand in hand with plant diversity in this subalpine environment.
Capturing the influence of ENSO on land surface variables for Tropical South America
Authors: Estupinan-Suarez Lina M. , Brenning Alexander , Gans Fabian , Kraemer Guido , Sierra Carlos A. , Mahecha Miguel D.
Published: March 2020

The response of tropical vegetation to El Niño Southern Oscillation (ENSO) is considered a main driver of global annual atmospheric CO2 concentrations at inter-annual time scales. ENSO warm and cold phases, El Niño and La Niña respectively, cause contrasting climatic conditions along tropical South America. While some regions experience wetter conditions during El Niño, such as  the Pacific coast, others regions such as the Amazon are exposed to warmer and drier climates. Besides this spatial variation, the biospheric response also differs between ENSO type and intensity, overruling of local conditions and ecosystems types. Due to this complexity, there is a lack of understanding on what ecosystems and regions are systematically affected by ENSO and how biospheric variables respond. Here, we analysed the Northern region of tropical South America covering tropical savannas, forests, and mountainous ecosystems in several countries. To do this, we assessed different land surface (e.g. GPP, NDVI,  FPAR, LST) and climate data streams compiled in the regional Earth System Data Lab (ESDL, https://www.earthsystemdatalab.net/) at 1 km and 10 km pixel size from 2001 to 2015. We applied Isomap, a non-linear dimensionality reduction method in the time domain for high dimensional dynamical systems. Our analysis was constrained to the fourth order continental basins and dominant land cover types. Land use change pixels were disregarded. Further, a comparison of ENSO indexes was conducted among basins. We found that isomap components  are able to capture the biosphere variability related to ENSO in basins that have been historically affected such as Magdalena-Cauca valleys and the Caribbean region. Implementation of non-linear methods increases our understanding of ENSO impacts spatially in regions where events intensity and frequency is increasing, and effective ecosystems management is urgent.
The impact of internal variability in ocean-induced melting on Totten Glacier
Authors: McCormack Felicity , Morlighem Mathieu , Gwyther David , Roberts Jason , Pelle Tyler
Published: March 2020

The Totten Glacier, located in the Aurora Subglacial Basin of East Antarctica, drains a catchment containing approximately 3.5 m of global sea level rise equivalent ice mass. The This glacier has been losing mass over recent decades, and modelling studies indicate that it is the most vulnerable glacier in East Antarctica to warming oceans and atmosphere over the coming century. Satellite altimetry shows high internal variability in ocean-forced melting of the Totten Ice Shelf; however, the extent to which this variability signal impacts the upstream ice sheet dynamics, and therefore its mass balance, is unknown. Here we use the Ice Sheet System Model (ISSM) combined with a plume and basal melting parameterisation called PICOP to investigate the impact of variability in ocean temperature on the evolution of Totten Glacier. We find that the southernmost portion of the Totten Glacier grounding line - from which the majority of the catchment’s ice is channeled - is stable within only a limited range of background ocean temperatures close to present-day values. In the stable simulations, the magnitude of the ice mass flux depends on the extent to which the ice shelf is pinned on a bed topography rumple located approximately 10 km downstream of its grounding line, but the period of the mass flux is decadal to multi-decadal in each simulation, irrespective of the magnitude of the variability in ocean forcing. We further find that the impact of variability in ocean melt rates decreases as the mean background ocean temperature increases, suggesting that the mean state may have a relatively more important role in the evolution of the Totten Glacier than variability in ocean forcing. Our results have implications for detection and attribution of climate change and internal climate variability in modeling studies, and may inform fieldwork campaigns mapping bed topography in the Aurora Subglacial Basin.
Late Maastrichtian global warming triggered by Deccan dykes and sills, evidence from Malwa and Mandla regions, Central India.
Authors: Adatte Thierry , Eddy Michael , Schoene Blair , Keller Gerta , Khadri Syed
Published: March 2020

Recent studies indicate that the bulk (80%) of Deccan trap eruptions occurred over a relatively short time interval in magnetic polarity C29r. U-Pb zircon geochronology shows that the main phase began 250 ky before the Cretaceous-Paleogene (KPg) mass extinction and continued into the early Danian suggesting a cause-and-effect relationship. But the potential causal relationship between paleo-environmental change and Deccan volcanism remains debated. New U-Pb zircon geochronology from the Malwa Plateau (~7% of the inferred total volume of the Deccan LIP) located on the northern margin of the Deccan Traps allows  to correlate basalts from the periphery of the province with the volcanic stratigraphy of the Western Ghats as well as to global paleoenvironmental records and precise the Deccan eruption rates at larger scale. Main part of the basalts released in northern Deccan area appears to be of latest Maestrichtian age.  Moreover recent geophysical and field observations show that the Malwa and Mandla basalt plateaus erupted in the Narmada-Tapti rift, made up of 2-3.5 km of Carboniferous to Cretaceous sedimentary rocks, including  up to 60m thick Lower Permian coal interval. Numerous dolerite dykes and sills intersecting these coal beds have been observed in open and underground mines from the Satpura area. The interaction between these dykes  and the coal seams may have significantly contributed to the latest Maastrichtian warming  by releasing high amounts of CO2, SO2 and halogens into the atmosphere. These observations indicate that Deccan volcanism played a key role in increasing atmospheric CO2 levels that resulted in global warming and enhanced greenhouse effect during the latest Maastritchtian, which coupled with high SO2 emissions, increased biotic stress and predisposed faunas to eventual extinction at the KTB.
Development of a regeneration technique for aluminum-rich and iron-rich phosphorus sorption materials
Authors: S P C Scott Isis , J Penn Chad , Huang Chi Hua
Published: March 2020

Preventing dissolved phosphorus (P) accumulation in soils and its transport to water bodies has been subject of many studies. However, despite the continuous efforts and advances, excessive P is still a concern and it is especially problematic in freshwater systems: excessive dissolved P leads to eutrophic conditions, a threat for water quality and aquatic life. P removal structures are a novel technology used in urban and rural settings to intercept dissolved P in surface and subsurface flows. P sorption materials (PSMs), active media with high affinity for dissolved P, are the core components of these structures. Once the PSMs reach service life, replacing the spent media can be costly. The objective of this research is to assess potential regeneration techniques that will extend the lifetime of Aluminum (Al)/Iron (Fe)-rich PSMs. We are proposing a regeneration involving a continuous circulation of 1M KOH aiming to restore unavailable sorption sites on the PSMs. A series of flow-through experiments was conducted alternating between P sorption (0.5 and 50 mg/L input solution) and desorption with KOH (5 or 20 pore volumes), varying residence times (0.5 min and 10 min) and number of recirculations (0, 6 and 24). We tested the treatments in 3 manufactured PSMs, Alcan, Biomax and PhosRedeem. Across two cycles of sorption-desorption, Alcan, Biomax and PhosRedeem showed an average P recovery of 81%, 79% and 7%, respectively.  The comparative investigation of the tested treatments revealed that the most effective regeneration treatment is characterized by a larger KOH volume (20 pore volumes) and no recirculation, with up to 100% reported P recovery. This research demonstrates the ability of Al/Fe-rich PSMs regeneration to contribute to a circular economy of P, as P recovery enables a more sustainable P cycle in both terrestrial and aquatic environments.
The Missing link between beach and clifftop dune – Landscape evolution of the climbing dune in the Feng-Chiue-Sha area of Hengchun Peninsula, Taiwan
Authors: Ho Lih-Der , Lüthgens Christopher , Chen Chun , Chyi Shyh-Jeng
Published: March 2020

Previous study by Ho et al. (2017) proposed an evolutionary model of the Feng-Chuie-Sha (FCS) clifftop dunes in the Hengchun Peninsula, southeastern Taiwan. In this model, tectonic uplifting, eustatic sea-level falling and the fluctuations of the East Asian winter Monsoon during the late Holocene could be the major forcing factors to the development of the clifftop dune. However, the climbing dune at the bottom of the cliff has not been carefully investigated yet, as the climbing dune is an important link between the beach and the clifftop dune, in terms of aeolian sediment cascades. In this study, we aim to improve our understanding of the unique beach-climbing dune-clifftop dune system in the FCS, and to identify phases of the changing influence of geomorphological forcing factors during the Holocene. For the paleo-environmental reconstruction, a detailed chronological framework will be established by applying numerical dating techniques, such as radiocarbon and optically stimulated luminescence (OSL) dating. Landscape features and sedimentological successions were mapped in the field and samples were taken for high resolution grain size analyses. Preliminary results show that several carbonate-cemented thin layers of aeolian sediment were observed in the outcrop. Based on the sedimentological sequence, the thin layers in two sections can be correlated well. We interpret the correlated thin layers as palaeo-surfaces of the climbing dune, and they may indicate the pause time of sand accumulation. The slopes of the palaeo-surfaces gradually increase from the bottom to the top, demonstrating the morphological development of the climbing dune over time. As the OSL and radiocarbon dates of the outcrop section are still under processing, the accumulation periods and rates of the climbing dune and its relationship with the formation of the clifftop dune will be presented and discussed.

Ho, L., Lüthgens, C., Wong, Y., Yen, J., Chyi, S.(2017): Late Holocene cliff-top dune evolution in the Hengchun Peninsula of Taiwan: Implications for palaeoenvironmental reconstruction. Journal of Asian Earth Sciences 148, 13-30.
Eventlike exhumation of high-grade blocks in the young Franciscan subduction zone
Authors: Rutte Daniel , Garber Joshua , Kylander-Clark Andrew , Renne Paul
Published: March 2020

The metamorphic history of exhumed high-grade rocks provides invaluable insight into the thermomechanical processes of subduction zones. While subduction in most orogens has been terminated by continent collision entailing variably strong overprint of related units, the Franciscan Complex of California allows studying a >150 Myr long subduction history that started at ~175 Ma and ended by transformation into a transform plate boundary (San Andreas fault) without significant metamorphic overprint. The highest grade metamorphic rocks of the Franciscan Complex of California are found as blocks in serpentinite and shale matrix mélanges. They include amphibolites, eclogites, blueschists, and blueschist facies metasediments. These Franciscan mélanges inspired the subduction channel return-flow model, but other processes e.g., buoyancy-driven serpentinite diapirism have been argued to be concordant with our current understanding of their metamorphic history, too.

We investigate a suite of metabasite blocks from serpentinite and shale matrix mélanges of the Califonia Coast Ranges. Our new dataset consists of U-Pb dates of metamorphic zircon and 40Ar/39Ar dates of calcic amphibole and white mica. Combined with published geochronology, particularly prograde Lu-Hf garnet ages from the same blocks, we can reconstruct the timing and time scales of prograde and retrograde metamorphism of individual blocks. We find: (i) Exhumation from the eclogite-amphibolite facies occurred only in a short episode at 165­–160 Ma with an apparent southward younging trend. (ii) Exhumation of the blocks was uniform and fast in the eclogite-amphibolite facies with rates of 2–8 km/Myr. In the blueschist facies exhumation of the blocks was less uniform and slowed by an order of magnitude. (iii) The age of amphibole in a metasomatic reaction zone indicates that at least one amphibolite was enclosed in a serpentinite matrix by ~155 Ma. Considering the entire subduction zone system, the high-grade exhumation temporally correlates with a significant pulse of magmatism in the respective magmatic arc (Sierra Nevada) and termination of forearc spreading (Coast Range Ophiolite).

Our findings do not support a steady-state process that is continuously exhuming high-grade rocks. Instead the subduction zone system changed with an eventlike character resulting in exhumation of high-grade rocks enclosed in serpentinite.
Simulation of Floating Debris during a Flash Flood Event
Authors: Qiuhua Liang , Xiong Yan , Wang Gang
Published: March 2020

Under climate change, extreme weather events such as storms and intense rainfall has become far more frequent. This is evidenced by the outburst of multiple flood events in the recent years in the UK and other parts of the world. Induced by intense rainfall, flash flooding is one type of wide-spread natural hazards that can pose serious threats to people’s lives and properties. Most likely happening in steep rapid-response catchments following localized high intensity rainfall, flash floods are characterized by rapid rise of water level and high flow velocities in channels and floodplains. The violent flood waves can remove and transport heavy objects such as cars and tree, imposing extra risk to people and infrastructure, e.g. bridges.

On 16th August 2004, the coastal village of Boscastle in north Cornwall, UK, was devastated by a flash flood following an exceptional amount of rain that fell over eight hours. The village suffered extensive damage and notably, some 100 vehicles were washed to downstream and into the sea, some of which blocked bridges and altered flood hydraulics. This work aims to reproduce the flood event including floating debris dynamics using a new coupled hydrodynamic model. The coupled modelling tool predicts the flooding process using a finite volume shock-capturing model that solves the fully 2D shallow water equations (SWEs), which is coupled with a discrete element model (DEM) to simulate the interactive dynamics of floating objects. The coupled model is further accelerated by implementation on modern GPUs and is therefore well-suited for simulation of large-scale transient flood hydrodynamics enriched with floating debris. The simulation results are first confirmed by comparing with maximum flood depths collected after the event. Further simulations are carried out to investigate the influence of floating vehicles on flood hydrodynamics and understand how they block bridges and alter flood paths. The simulation results are consistent with observations captured during the event.

Key Words: Flash flooding; Hydrodynamic model; Shallow water equations; Discrete element model; Floating debris
Ductile shear zones – future perspectives
Authors: Schrank Christoph
Published: March 2020

About 50 years ago, John Ramsay and colleagues established the thorough foundation for the field-scale observational and mathematical description of the structures, deformation, and kinematics in ductile shear zones. Since then, these probably most important instabilities of the ductile lithosphere enjoyed an almost explosive growth in scientific attention. It is perhaps fair to say that this tremendous research effort featured four main themes:

 

[1] The historic scientific nucleus – quantification of shear-zone geometry, strain and associated kinematic history from field observations

 

[2] Qualitative and quantitative analysis of microphysical deformation mechanisms in the field and the laboratory

 

[3] Shear-zone rheology

 

[4] The development of physically consistent mathematical models for shear zones, mainly using continuum mechanics.

 

In concert, these four cornerstones of shear-zone research enabled tremendous progress in our understanding of why and how ductile shear zones form. So, what are some of the outstanding problems?

 

A truly comprehensive model for ductile shear zones must account for the vast range of length and time scales involved, each easily covering ten orders of magnitude, as well as the associated intimate coupling between thermal, hydraulic, mechanical, and chemical processes. The multi-scale and multi-physics nature of ductile shear zones generates scientific challenges for all four research themes named above. This presentation is dedicated to highlighting exciting challenges in themes 2, and 3 and 4.

 

In the microanalytical arena [2], the nano-scale is an exciting new frontier, especially when it comes to the interplay between metamorphism and ductile deformation. The nano-frontier can be tackled with new synchrotron methods. I showcase some applications to fossil shear-zone samples and discuss opportunities for in-situ experiments. In the domain of rheology [3], I present some simple experiments with strain-softening materials and field observations that support the notion: transient rheological behaviour is very important for shear localisation. In the modelling domain [4], some recent examples for the intriguing physical consequences predicted by new multi-physics and cross-scale coupling terms in ductile localisation problems are illustrated.
The application of climate adaptation algorithm to physical climate risk assessment and management of the TCFD
Authors: Liu Iwen , Tung Ching-pin
Published: March 2020

The Financial Stability Board (FSB) published “Recommendations of the Task Force on Climate-related Financial Disclosures (TCFD)” in 2017 to assist companies in assessing climate-related risks and opportunities and financial disclosure. However, the integration between climate scenarios and the corporate risk management system and the financial quantification of climate-related risks are still the challenges for corporate practice. To collect the climate scenarios mentioned in TCFD and integrate the relevant factors in corporate operations, the study will use the framework of TCFD: Governance, Strategy, Risk management, Metrics and Targets, introduce the first three steps of the Climate Change Adaptation (CCA Steps): "identifying problems and establishing objectives", "assessing and analyzing current risk", "assessing and analyzing future risk", and use climate risk template which use  Hazard, Exposure and Vulnerability as risk assessment factors to establish a framework for the evaluation and analysis of risk. After establishing a complete method for climate risk and opportunity assessment, in response to the "financial disclosure", the study will link to the financial statement items, referring to related concepts such as “Value at Risk” and “stranded assets”, to strengthen the integrity and transparency of corporate financial disclosure. At last, the study will select a specific climate physical risk in a industry for case study by the analysis of literature, international reports and historical events and introduce a climate risk assessment framework to verify the practicality of this framework. The study's results will be applied to the risk management of business operations. At the same time, the framework of climate risk can assist companies to put climate change factors into their decisions, maintaining the sustainable competitiveness in a low-carbon economy.

Key words: climate risk assessment, TCFD, enterprise risk management
Solar and Interplanetary Turbulence: Lagrangian Coherent Structures
Authors: Chian Abraham C.L. , Bellot Rubio Luis R. , Feng Heng Q. , Gomes Tiago F. P. , Gosic Milan , Grasso Daniela , Hu Qiang , Kusano Kanya , Miranda Rodrigo A. , Munoz Pablo R. , Rempel Erico L. , Ruffolo David , Silva Suzana S. A. , Wu De J.
Published: March 2020

The dynamics of solar and interplanetary plasmas is governed by coherent structures such as current sheets and magnetic flux ropes which are responsible for the genesis of intermittent turbulence via magnetic reconnections in solar supergranular junctions, solar coronal loops, the shock-sheath region of an interplanetary coronal mass ejection, and the interface region of two interplanetary magnetic flux ropes. Lagrangian coherent structures provide a new powerful technique to detect time- or space-dependent transport barriers, and objective (i.e., frame invariant) kinematic and magnetic vortices in space plasma turbulence. We discuss the basic concepts of Lagrangian coherent structures in plasmas based on the computation of the finite-time Lyapunov exponent, the Lagrangian averaged vorticity deviation and the integrated averaged current deviation, as well as their applications to numerical simulations of MHD turbulence and space and ground observations.
Gravity changes before and after the 2015 Mw7.8 Nepal earthquake
Authors: Xu Weimin , Chen Shi , Lu Hongyan
Published: March 2020

Based on the absolute gravity measurements of 4 gravimetric stations (Shigatse, Zhongba, Lhasa and Naqu) in southern Tibet surveyed from 2010 to 2013, we modeled the source region as a disk of 580 km in diameter by Hypocentroid model, shown that the gravity increase at these stations may be related to mass changes in the source region of the 2015 Mw7.8 Nepal earthquake. We analyzed the characteristics of gravity variations from the repeated regional gravity network, which including the 4 absolute gravimetric stations and 13 relative gravimetric stations from 2010 to 2019, to study the characteristics of gravity changes before and after the earthquake.

We firstly estimated the reliability of the absolute gravity measurements by the errors of each station, and considered the effect of vertical displacement, denudation of surface mass, GIA correction and the secular and background gravity changes. Secondly we employed the Bayesian adjustment method for the relative gravimetric network data analysis, which was more robust and adaptive for solving problems caused by irregular nonlinear drift of different gravimeters, and then carried out error analysis for the repeated relative gravity measurements. Furthermore, we took the Shigatse station as example, which covered absolute and relative measurements and was most close to the Hypocenter of the inversion Hypocentroid model, the hydrologic effects of the Shigatse station was modeled exactly, and the results shown that the secular and background gravity changes were much smaller than the observed gravity changes. Lastly we studied the characteristics of gravity changes before and after the earthquake through the Hypocentroid model, we found the coincident gravity increase both in absolute and repeated regional gravity results before the earthquake, and gravity decreased after the earthquake, which suggested that the pre-earthquake gravity increase may be caused by strain and mass (fluid) transfer in broad seismogenic source regions of the earthquake. Moreover, the study indicated that high-precision ground gravity measurements (absolute and relative) may provide a useful method for monitoring mass changes in the source regions of potential large earthquakes.

 

Acknowledgment: This research is supported by National Key R&D Program of China (Grant No.2018YFC1503806 and No.2017YFC1500503) and National Natural Science Foundation of China (Grant No.U1939205 and No.41774090).
Machine learning in hydrological forecasting
Authors: Tang Tiantian
Published: March 2020

With the gradual improvement of scientific and technological level and the rapid development of modern information, the hydrological field has also ushered in the era of big data. However, how to extract knowledge and its internal useful information most effectively from the data deluge? Machine learning came into being. According to different types of supervision, machine learning can be divided into supervised learning, semi-supervised learning and unsupervised learning. This study proposed a hybrid model based on K-means clustering in supervised learning and Random Forest in supervised learning to forecast monthly streamflow in Danjiangkou Reservior, China, which realizing the nesting of supervised learning and unsupervised learning. In addition, this study found that the new hybrid method performed better by comparing with the traditional method. Thus, it provides a method of improving the accuracy of monthly streamflow forecasting.

Keywords: monthly streamflow forecasting; machine learning; K-means clustering; Random Forest; Danjiangkou Reservoir basin
The Study of Crustal Velocity Structure Characteristics in Yangjiang Area of South China
Authors: Wang Xiaona , Deng Zhihui , Ye Xiuwei , Wang Liwei
Published: March 2020

This paper collects 43,225 absolute first arrival P wave arrival times and 422,956 high quality relative P arrival times of 6,390 events occurred in Yangjiang and its adjacent area from Jan, 1990 to Aug, 2019, these seismic data is recorded by 49 stations from Guangdong seismic network, Guangxi seismic network and Hainan seismic network. Based on the seismic data above, we simultaneously determine the crustal 3D P wave velocity structure and the hypocenter parameters of 6255 events in Yangjiang and its adjacent area by applying Double-Difference seismic tomography. The result shows that, shallow P wave velocity in Yangjiang area is higher due to the thinner sedimentary layer and widely exposed Yanshanian granite, Indosinian granite and Cambrian metamorphic rocks. There are obvious correspondences between the distribution of shallow velocity and fault structure as well as geological structure. A wide range of low velocity anomaly exists in 20km depth, which verifies the low velocity layer in the middle crust at Yangjiang area of South China continent. The velocity image from land to ocean in 30km depth shows low velocity in NW side and high velocity in SE side, which verifies the characteristic of crust thinning in South China coastal continent. The NEE seismic belt from Yangbianhai to Pinggang is speculated to locate in a buried fault of southwest segment of Pinggang fault. The buried thrust fault is a N78°E strike fault, dip to NW with a dip angle of 85 °. In addition, the buried fault locates in the abnormal junction of high velocity on the NW side and low velocity on the SE side, which reflects the tectonic activity characteristic of NW plate uplifting and SE plate declining from Miocene period. The characteristic of activity in the buried fault shows thrust movement with a small strike slip component, which is consistent with the focal mechanism of M4.9 earthquake occurred in 2004.
Targeting the hidden chromitite using geochemical vectoring for Bophivum area, northwestern Myanmar
Authors: Heo Chulho , Oh Ilhwan , Yang Seokjun , Lee Jaeho , Park Sungwon , Cho Seongjun
Published: March 2020

Harzburgite are the rocks that make up the mantle and consist of olivine, orthopyroxene, and clinopyroxene (<5 %). Clinopyroxene contain Ca, Al, and Ti, while orthopyroxene contain Al. On the other hand, olivine contains almost zero contents of Ca, Al and Ti. When the rising melt from the lower mantle passes through the mantle harzburgite, the clinopyroxene and orthopyroxene with lower melting points compared with olivine are fused into the melt, and the olivine is crystallized from the melt. In this genetic process, harzburgite gradually change into dunite consisting of only olivine, and Ca, Al and Ti of pyroxene in harzburgite will escape into the melt. And, as the melting point of clinopyroxene is lower than that of orhopyroxene, the Ca, Al, and Ti in clinopyroxene are escaped into the melt earlier than those in orthopyroxene. The melt with changed composition formed by melting the pyroxene are mixed with the newly rising melt with pyroxene, so that the chromian spinel in the melt becomes saturated and the chromitite are formed. By the above-mentioned mechanism, chromitite occurs with dunite and pyroxene-deficient harzburgite formed by the reaction result between melt and harzburgite. In other words, in the genetic process of high Cr chromitite, the presence of melt that fused the pyroxene within harzburgite is essential. And, in order to make high Cr chromitite, the melt must have been fused more pyroxene in harzburgite. As a result, the Ti, Ca, and Al content of harzburgite will be decreased. Therefore, considering the representative chemical composition of podiform chromitite(Robinson et al., 1997), we assumed that as we approached into harzburgite bearing high Cr chromitite(probably hidden ore body), the Ti, Ca and Al content within harzburgite will be likely to converge toward the specific contents(Ti<180ppm, Ca<0.9%, Al<0.7%). In case of Bophivum chromitite in northwestern Myanmar, it corresponds well with the representative chemical composition of high Cr chromitite in terms of the above-mentioned data. Therefore, we monitored to see whether Ti, Ca, and Al contents systematically change by the distance from the center with chromitite outcrop or high Cr anomaly zone confirmed through soil and rock geochemical exploration toward the surrounding harzburgite outcrop or not and tried to select the target element for geochemical vectoring using portable XRF. Conclusively, Ca is considered to be a more meaningful geochemical vectoring indicator than Al in terms of portable XRF measurements in the survey area.
Dynamics of the extremely elongated cloud on Mars Arsia Mons volcano
Authors: Hernandez Bernal Jorge , Sánchez-Lavega Agustín , del Río-Gaztelurrutia Teresa , Hueso Ricardo , Ordóñez-Etxeberria Iñaki , Cardesín-Moinelo Alejandro , Ravanis Eleni , Wood Simon , Titov Dmitrij , Connour Kyle , Schneider Nick , Tirsch Daniela , Jaumann Ralf , Hauber Ernst , Gondet Brigitte
Published: March 2020

Starting in September 2018, a daily repeating extremely elongated cloud was observed extending from the Mars Arsia Mons volcano. We study this Arsia Mons Elongated Cloud (AMEC) using images from VMC, HRSC, and OMEGA on board Mars Express, IUVS on MAVEN, and MARCI on MRO. We study the daily cycle of this cloud, showing how the morphology and other parameters of the cloud evolved with local time. The cloud expands every morning from the western slope of the volcano, at a westward velocity of around 150m/s, and an altitude of around 30-40km over the local surface. Starting around 2.5 hours after sunrise (8.2 Local True Solar Time, LTST), the formation of the cloud resumes, and the existing cloud keeps moving westward, so it detaches from the volcano, until it evaporates in the following hours. At this time, the cloud has expanded to a length of around 1500km. Short time later, a new local cloud appears on the western slope of the volcano, starting around 9.5 LTST, and grows during the morning.

This daily cycle repeated regularly for at least 90 sols in 2018, around Southern Solstice (Ls 240-300) in Martian Year (MY) 34. According with these and previous  MEx/VMC observations, this elongated cloud is a seasonal phenomenon occurring around Southern Solstice every Martian Year. We study the interannual variability of this cloud, the influence of the Global Dust Storms in 2018 on the cloud’s properties (Sánchez-Lavega et al., Geophys. Res. Lett. 46, 2019), and its validity as a proxy for the global state of the Martian atmosphere (Sánchez-Lavega et al., J. Geophys. Res., 123, 3020, 2018). We discuss the physical mechanisms behind the formation of this peculiar cloud in Mars.
A remote sensing approach for evaluating regional-scale topsoil loss in the Midwestern United States
Authors: Larsen Isaac , Thaler Evan , Yu Qian
Published: March 2020

Soil erosion in agricultural landscapes reduces crop yields and influences the global carbon cycle. However, the magnitude of historical topsoil loss remains poorly quantified at large, regional spatial scales, hindering predictions of economic losses to farmers and quantification of the role soil erosion plays in the carbon cycle. We focus on one of the world’s most productive agricultural regions, the Corn Belt of the Midwestern United States and use a novel spectral remote sensing method to map areas of complete topsoil loss in agricultural fields. Using high-resolution satellite images and the association between topsoil loss and topographic curvature, we use high resolution LiDAR topographic data to scale-up soil loss predictions to 3.7x105 km2 of the Corn Belt. Our results indicate 34±12% of the region has completely lost topsoil as a result of agriculturally-accelerated erosion. Soil loss is most prevalent on convex slopes, and hilltops throughout the region are often completely denuded of topsoil indicating that tillage is a major driver of erosion, yet tillage erosion is not simulated in models used to assess soil loss trends in the U.S. We estimate that soil regenerative farming practices could restore 16±4.4 Pg of carbon to the exposed subsoil in the region. Soil regeneration would offset at least $2.5±0.3 billion in annual economic losses to farmers while generating a carbon sink equivalent to 8±3 years of U.S. CO2 emissions, or ~14% of the global soil carbon lost since the advent of agriculture.  
Effects of the Tibetan Plateau on East Asian Summer Monsoon via Weakened Transient Eddies
Authors: Ren Qiaoling , Yang Song , Jiang Xinwen , Zhang Yang , Li Zhenning
Published: March 2020

Previous studies have revealed that the Tibetan Plateau (TP) can weaken the high-frequency and low-frequency transient eddies (TE) transported along the westerly jet. Here the effects of TP on East Asian summer monsoon via weakened TE are investigated based on the simulations by the NCAR Community Earth System Model, in which a nudging method is used to amplify the TP’s inhibition of TE without changing the steady dynamic and thermodynamic effects of TP. Results reveal that the weakened TE by TP weaken the East Asian westerly jet (EAWJ) and shift the jet southward via transient vorticity flux. The southward EAWJ accompanied with reduced poleward transport of moisture by TE results in less rainfall in northern East Asia but more rainfall in southern East Asia, particularly in early summer when the EAWJ is stably located over the TP and the meridional gradient of water vapor is large. Furthermore, the anomalous precipitation can move the EAWJ further southward through the anomalous diabatic heating in early summer, forming a positive feedback. Therefore, the TP’s inhibition of TE can shift the East Asian rain belt southward, different from the TP’s steady forcing which favors a poleward shift of the rain belt. It is also demonstrated that the atmospheric internal variability can lead to the south-flood-north-drought pattern of summer rainfall change over East Asia, indicating the important role of TE in East Asian summer monsoon.
Discussion on the formation mechanism of severe haze in North China and its relationship with meteorological factors
Authors: Meng Yuanyuan , Xi Jianjian , Wang Yi
Published: March 2020

In recent years, China's industrialization and urbanization have accelerated, generating high emissions of pollutants every year, which has significantly deteriorated the air quality of Chinese cities and threatened public health and the happiness of urban residents. More and more studies have shown that several megacities in China and more and more cities have experienced more severe smog pollution. The occurrence of haze seriously affects the healthy development of human beings, so the research on haze should be vigorously promoted. Although many studies have made considerable progress in the research of smog in recent years, there is no systematic and comprehensive assessment method. But scholars have not stopped the pace of research.This study takes Weinan City, Shaanxi, China as the research object, The paper describes the formation mechanism of haze and the combined effects of emission sources, chemical aerosol material formation and transformation, meteorology and climatic conditions. The mechanism of haze formation is relatively complicated. Aerosols are widely used in the research of haze composition.Organic aerosols have a very important impact on the Earth's radiation, visibility and air quality on a global scale. However, the formation of secondary pollution makes this process more complicated. Secondary organic aerosols (SOA), free radicals that form volatile organic compounds and particles with ozone (O3), hydroxyl (OH) and nitrate (NO3) and artificial volatile organic compounds (VOCs) are considered organic gases One of the most important components of sol. In the past few decades, many studies have been conducted to study the formation of SOA. However, due to the complex formation mechanism of SOA, no further reason has been clarified.The reasons for the formation of haze are more complicated. For the true solution of the haze problem is still the key for our scholars to solve in the future, the government should also formulate corresponding measures to reduce the early discharge of pollutants, control the haze from the source, in short A long way to go requires joint efforts from everyone.

Keywords:Haze  Aerosol  Meteorological conditions  Weinan
Efficacy of Vertical Evacuation Refuge from Tsunamis (VERT)
Authors: Robertson Ian
Published: March 2020

ABSTRACT:

Virtually every tsunami that has affected coastal communities in the past few decades has resulted in loss of life, often in the tens of thousands or more. Increased population density along tsunami-prone coastlines will only increase the potential for loss of life during future tsunamis. Conventional evacuation planning focuses on early warning systems and horizontal evacuation to the nearest available high ground. While  this approach should be encouraged and improved, there is also a need for vertical evacuation options for areas where horizontal evacuation is not possible, or where residents, for whatever reason, are still in the inundation zone when the tsunami waves arrive.

Vertical evacuation into sturdy buildings that are tall enough to provide refuge areas above the inundation elevation has saved innumerable lives during past tsunamis. Most of these buildings were never designed for tsunami loads, but nevertheless remained intact and protected those who sought refuge in the upper floors.  Seismic design requirements are common in tsunami-prone areas, which increases a building’s potential to survive the tsunami loads.  However, consciously designing for tsunamis would increase the reliability of vertical evacuation significantly.

The 2016 edition of “ASCE 7 – Minimum Design Loads and Associated Criteria for Buildings and Other Structures” includes a new Chapter 6 on Tsunami Loads and Effects. This chapter provides a comprehensive approach to probabilistic tsunami design of buildings and other structures for various performance levels. One section of this chapter provides specific requirements for design of vertical evacuation refuge structures for tsunamis, which results in less than 1% probability of failure during a design level tsunami. It is also strongly recommended that all buildings in the tsunami inundation zone that are tall enough to provide safe refuge should include tsunami design, even if at a less stringent level of performance.

This presentation will discuss the implications of adding tsunami design, evaluate the cost premium involved, and present some recent VERT design and construction projects.