bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of consecutive extratropical cyclones Daniel, Elsa, and Fabien on drought busting during December 2019 in the Minho-Limia-Sil Hydrographic demarcation
Authors: Stojanovic Milica , Gonçalves Ana , Sorí Rogert , Vázquez Marta , Liberato Margarida L.R.
Published: March 2021

Three consecutive extratropical cyclones named Daniel, Elsa, and Fabien affected the northwest of the Iberian Peninsula during December 2019. In this region is located the Miño-Limia-Sil Hydrographic Demarcation (MLSHD), which includes part of Galicia, in Spain and the north of Portugal. The water resources of the MLSHD are of great importance for the socio-economic framework of both countries, particularly for the agricultural and livestock activities, tourism, and the production of electrical energy from renewable sources like the eolic and the hydroelectric. In this study was analysed the synoptic characteristics of these extratropical cyclones, particularly during the life cycle close to the Iberian Peninsula, when the greatest damages associated with strong winds and intense rainfall occurred. The storm Daniel was formed from a secondary low located to the west and close to the Iberian Peninsula during the afternoon of December 15. Nevertheless, Elsa was formed in the Gulf of Mexico and Fabian in the north Atlantic Ocean, then both crossed the north Atlantic Ocean to finally affect with intense rainfall that caused floods in the MLSHD from 18 to 21 December 2019. The moisture supplies from the tropical north Atlantic Ocean, revealed by the integrated water vapour transport favoured the intensification of all these systems. The consecutive impact of these systems provided great amounts of rainfall to the MLSHD, causing positive anomalies of the total accumulated rainfall for this month. An assessment of drought conditions through the SPI and the SPEI on time scales of 1, 3, 6, and 12 months exposed the role of these systems on drought busting in the MLSHD. Therefore, despite the negative impacts, these systems favoured a recovery of the hydrological conditions of the Demarcation. Our results confirm the importance of studying for a long study period the role of extratropical cyclones on hydrological conditions of the MLSHD.

Acknowledgements:
This study is supported by Fundação para a Ciência e a Tecnologia, Portugal (FCT), under project WEx-Atlantic (PTDC/CTA-MET/29233/2017).
Realizing ITRF-Consistent Continental-Scale Geodetic Reference Frames
Authors: Gomez Demian , Bevis Michael , Caccamise Dana
Published: March 2021

To achieve a regional or continental-scale reference frame that is a densification of the International Terrestrial Reference Frame (ITRF), one can use a set of fiducial GPS / GNSS stations in the ITRF and regional frames.  Predicting coordinates in the realization epoch using the fiducial stations’ trajectory parameters in the ITRF and applying a Helmert transformation aligns the regional solution’s polyhedron onto the ITRF.  This paper shows inconsistencies in the regional realization of ITRF when the fiducial stations’ trajectory model ignores the periodic terms, resulting in a periodic coordinate bias in the regional frame.  We describe a generalized procedure to minimize this inconsistency when realizing any regional frame aligned to ITRF or any other ‘primary’ frame. We show the method used to realize the Argentine Geodetic Positions (Posiciones Geodésicas Argentinas, POSGAR) reference frame and discuss its results. Inconsistencies in the vertical were reduced from 4 mm to less than 1 mm for multiple stations after applying our technique.  We also propose adopting object-oriented programming terminology to describe the relationship between different reference frames, such as a regional and a global frame. This terminology assists in describing and understanding the hierarchy in geodetic reference frames.
Hengill, SW-Iceland: Operating a fractured reservoir for geothermal production and carbon storage
Authors: Snæbjörnsdóttir Sandra , Ratouis Thomas , Gunnarsdóttir Sveinborg
Published: March 2021

Fractures and fracture networks play fundamental roles in the operation of subsurface systems such as geothermal production and geological carbon storage: Fractures are the circulatory systems of such reservoirs, driving them via transport of fluids, gases, heat, and dissolved elements, channelling the flow as both carriers and barriers, and providing connection to the rock matrix. Furthermore, due to their role, they provide important insights into the reservoirs, such as the dominant flow paths, the thermal evolution and the dominant chemical processes taking place and affecting e.g. the permeability via dissolution, precipitation and mechanics within the subsurface.

At Hengill central volcano, SW-Iceland, the subsurface reservoir is utilised for geothermal production, re-injection of geothermal fluids and injection of carbon dioxide (CO2) for the means of mineral CO2 storage, at the two field sites in Nesjavellir and Hellisheidi. The operation involves thousands to millions of tonnes of fluid, steam, and gases that are circulated annually through the subsurface bedrock via extraction and injection. Over 100 production and injection wells have been drilled in the two fields, ranging in depths from 800 m to 3300 m. The increased emphasis on the mapping of surface and subsurface faults and structures, and the opportunity of tracing the fluid flow via injection of tracers into the reinjection wells of the fields has provided deeper understanding of the role of fractures in this fracture dominated reservoir. This knowledge has benefitted the field operation by the drilling of very powerful production wells, and successful injection wells – both in terms of injectivity and their locations, providing pressure support to the geothermal production while preventing thermal breakthrough of colder fluids. Furthermore, the use of tracers has been an invaluable tool for managing injection of dissolved CO2 into fractured basaltic reservoirs for mineral carbon storage, both in terms of quantitative monitoring and detection of dissolved and mineralised CO2.

The utilisation of the Hengill field sites at Nesjavellir and Hellisheidi offers unique opportunities to increase our understanding of subsurface processes, providing large-scale field laboratories with enormous datasets, and building bridges between industry and academia.

 
The impact of large-scale circulation on daily fine particulate matter (PM2.5) in major populated regions of China during winter 
Authors: Jia Zixuan , Doherty Ruth , Ordóñez Carlos , Li Chaofan , Wild Oliver
Published: March 2021

With rapid economic growth and urbanization, air pollution episodes with high levels of particulate matter (PM2.5) have become common in China. While emissions of pollutant precursors are important, meteorology also plays a major role in pollution episodes, especially in winter. We examine the influence of the dominant large-scale circulation and the key regional meteorological features on PM2.5 over three major regions of China: Beijing–Tianjin–Hebei (BTH), the Yangtze River Delta (YRD), and the Pearl River Delta (PRD). The East Asian winter monsoon (EAWM) is primarily studied, including some of its main large-scale components such as the East Asian trough and the Siberian high, as it influences PM2.5 differently in different parts of China. In the BTH region, the shallow East Asian trough curbs the invasion of northerly cold and dry air from the Siberian high which induces high relative humidity and heavy pollution, possibly via relative humidity-promoted aerosol formation and growth. A weak southerly wind in Eastern and Southern China associated with a weakened Siberian high suppresses horizontal dispersion, contributing to pollution accumulation over YRD. In addition, the El Niño-Southern Oscillation (ENSO) as the dominant mode of global ocean-atmosphere interaction has a substantial modulation on precipitation over southern China. In the PRD, weak southerly winds and precipitation deficits over southern China are conducive to atmospheric pollution possibly via reduced wet deposition. Furthermore, we construct new circulation-based indices based on the dominant large-scale circulation: a 500 hPa geopotential height-based index for BTH, a sea level pressure-based index for YRD and an 850 hPa meridional wind-based index for PRD. These three indices can effectively distinguish different levels of pollution over BTH, YRD and PRD, respectively. We also show how additional regional meteorological variables can improve the prediction of regional PM2.5 concentrations for these three regions. These results are beneficial to understanding and forecasting the occurrence of severely polluted days for BTH, YRD and PRD from a large-scale perspective.
Imaging the East Asia using waveform tomography with massive datasets 
Authors: Dou Hui , Lebedev Sergei , Chagas de Melo Bruna , Wang Baoshan , Wang Weitao
Published: March 2021

We present a new shear-wave velocity model of the upper mantle beneath the East Asia, ASIA2021, derived using the Automatic Multimode Inversion technique. We use waveform fits of over 1.3 million seismograms, comprising waveforms of surface waves, S and multiple S waves.  In total, data from 9351 stations and 23344 events constrain ASIA2021, which maps in detail the structure of the lithosphere and underlying mantle beneath the region. Our model reveals deep structure beneath the tectonic units that make up East Asia. It shows agreement with previous models at larger scales and, also, sharper and stronger velocity anomalies at smaller regional scales. High-velocity continent roots are mapped in detail beneath the Sichuan Basin, Tarim Basin, Ordos Block, and Siberian Craton, extending to over 200 km depths. The lack of a high-velocity continental root beneath the Eastern North China Craton (ENCC), underlain, instead, by a low-velocity anomaly, is consistent with the destruction of this Archean nucleus. Strong low-velocity anomalies are mapped within the top 100 km beneath Tibet, Pamir, Altay-Sayan area, and back-arc basins. At greater depths, ASIA2021 shows high-velocity anomalies related to the subducted and underthrusted lithosphere of India beneath Tibet and the subduction of the Pacific and other plates in the upper mantle. In the mantle transition zone (MTZ), we find high-velocity anomalies probably related to deflected subducted slabs or detached portions of ancient continent cratons. In particularly, ASIA2021 reveals separate bodies, probably originating from the Indian Plate lithosphere beneath central Tibet, with one at 100-200 km beneath Songpan-Ganzi Block (SGFB) and the other in the MTZ. A strong low-velocity anomaly extending from the surface to the lower mantle beneath Hainan volcano and South China Sea is consistent with the hypothesis of the Hainan mantle plume. The high-velocity anomaly beneath ENCC in MTZ can be interpreted as a detached Archean continent root. The Pacific Plate subducts beneath the eastern margin of Asia into the MTZ and appears to deflect and extend horizontally as far west as the Songliao Basin. The absence of major gaps in the stagnant slab is consistent with the origin of Changbaishan volcano above being related to the Big Mantle Wedge, proposed previously. The low-velocity anomalies down to ~ 700 km depth beneath the Lake Baikal area suggest a hot upwelling (mantle plume) feeding the widely distributed Cenozoic volcanoes in central and western Mongolia.
Efficient spherical harmonic transforms on GPU and its use in planetary core dynamics simulations
Authors: Schaeffer Nathanael
Published: March 2021

Most of the new supercomputers now use acceleration technology such as GPUs. They promise much higher performance than traditional CPU-only servers, both in terms of floating point operation throughput and memory bandwidth. Furthermore, the electric consumption is significantly reduced, resulting in lower carbon emissions.
However, such high computation speeds can only be achieved if a set of more or less stringent rules are followed with respect to memory access and program flow. As a consequence some algorithms more easily approach peak performance.

Here, we present the results of an effort to achieve high performance on recent nvidia GPU accelerators for the spherical harmonic transform. The spherical harmonic transform can be split into a Legendre transform (which is compute bound) and a Fourier transform (which is memory bound).
By taking advantage of recent algorithmic improvements as well as by tuning the Fourier transform, the can now compute a full forward or backward spherical harmonic transform up to degree 8191 on a single 16GB Volta GPU in less than 0.35 seconds.
For lower resolution (up to degree 1023), a single Volta GPU performs a full transform more than 3 times faster than a 48-cores dual socket Skylake Xeon Platinum server.

We also present results of an ongoing effort to port the (simulation of planetary core fluid and magnetic field dynamics) to GPU-accelerated computers.
Sources of atmospheric methane in Arctic: observations and model simulation
Authors: Shtabkin Yury , Moiseenko Konstantin , Skorokhod Andrey
Published: March 2021

The second most important greenhouse gas in atmosphere after carbon dioxide (CO2) is methane, CH4. The limited data of surface methane observations in Arctic makes it difficult to quantify the impact of methane emissions from major regional anthropogenic and biogenic sources on this region. This gap is partially filled by long-term observations at arctic and subarctic stations. According to these observations, since 2005, there has been a noticeable increase in the surface methane concentration. The reasons of this increase are still not fully understood. This work provides quantitative estimates of possible contribution into surface CH4 observed long-term variability from the most important regional sources of methane emissions.

To analyze variations in surface methane concentration was used the data from observations at background monitoring stations, as well as numerical calculations performed by GEOS-Chem chemical-transport model, which is widely used in international community for calculating the fields of chemically active and greenhouse gases.
Mean zonal flow driven by precession in planetary cores: numerical simulations with a semi-lagrangian scheme
Authors: Schaeffer Nathanael , Cébron David
Published: March 2021

We revisit the generation of mean zonal flows in fluid planetary interiors subjected to precession.
The main effect of precession on a (nearly) spherical fluid envelope is to make the fluid rotate along an axis tilted with respect to the rotation axis of the solid mantle. This is the so-called "spin-over" response of the fluid.
 also shows that a steady shear flow develops on top of the spin-over mode due to non-linear effects in the boundary layer equation.
This mean zonal shear flow has been studied theoretically and numerically by .

With faster computers and more efficient codes, we compute this flow down to very low viscosity and compare with the inviscid theory of Busse (1968).
In addition we investigate the width and the intensity of the detached shear layer, which is controlled by viscosity and therefore not present in the theory.

We also use this problem as a benchmark to assess the benefits of using a semi-lagrangian numerical scheme, where solid-body rotation is treated exactly.
Quantifying US Fossil Fuel CO2 Emissions Using Precise Measurements of 14C in Atmospheric CO2
Authors: Lehman Scott , Basu Sourish , Miller John , Andrews Arlyn , Sweeney Colm
Published: March 2021

We report the first national scale estimates of CO2 emissions from fossil fuel combustion and cement production in the US based directly on atmospheric observations, using a dual-tracer inverse modeling framework and CO2 and Δ14CO2measurements obtained primarily from the North American portion of NOAA’s Global Greenhouse Gas Reference Network. The derived US national total for 2010 is 1653±60 TgC/yr, with an uncertainty (2σ) that takes into account random errors associated with atmospheric transport, atmospheric measurements, and specified prior CO2 and 14C fluxes. The atmosphere-derived estimate is significantly (>3σ) larger than US national emissions for 2010 from three global inventories widely-used for CO2 accounting, even after adjustments for emissions that might be sensed by the atmospheric network but which are not included in inventory totals. In contrast, the atmosphere-derived estimate is within 1σ of a similarly adjusted 2010 annual total and 9 of 12 adjusted monthly totals aggregated from the latest release of the high-resolution, US-specific “Vulcan” emissions data product. Here we focus our presentation on determination and reduction of methodological uncertainties and future applications of the method for annual emissions detection and emissions trend detection at scales ranging from the US as a whole to contiguous groups of US states, such as those participating in the Regional Greenhouse Gas Initiative.
The Impulsive Nature of Lightning Initiation
Authors: Sterpka Christopher , Dwyer Joseph , Liu Ningyu , Hare Brian , Scholten Olaf
Published: March 2021

We report results from imaging the initiation region of lightning via 3D interferometric beamforming on data collected by the Netherlands-based core of the Low Frequency Array of Antennas (LOFAR). LOFAR achieves 1 nanosecond timing accuracy and meter-scale spatial precision in lightning imaging on pulses observed in the 30-80 MHz band via the 38 Dutch-based stations. This project complements and enhances the previous work of the LOFAR lightning group of Groningen [Hare, B.M., et al., Nature 568, 360363 (2019)], and [Scholten, O., et al., ESSOAr 10503153] in order to improve image detail in regions with weak sources. This project incorporates beamforming techniques to improve upon previously employed methods with the result of improving both spatial and time resolution of lightning sources. In doing so, we have located and imaged the first non-impulsive sources in lightning flashes. These sources are believed to be caused by a streamer-cascade-like initiation event leading to the formation of the first leader in two separate lightning flashes. The initiation starts from essentially background and within a tens of microseconds ramps up a few orders of magnitude before the first impulsive sources connected with lightning leaders are observed. The events are likely an analog of fast breakdown in narrow bipolar events, and here we report their ramp-up rate, propagation speed, and trajectories.
The role of small wetlands for resilient ecological networks in a wetlandscape 
Authors: Kim Bin , Park Jeryang
Published: March 2021

Wetlands, affected by the hydro-climatic condition and human activities, are key elements in providing valuable ecosystem services for ecology, environment, and human. Wetlands can exist in various states (e.g., area, volume, depth, etc.) driven by both natural and human forcing, and are often distributed in a wetlandscape. In these specific landscapes, wetlands (node) and dispersal path (link) of inhabiting species organize ecological networks. Here, we generated the three ecological networks with three dispersal models (threshold distance, exponential kernel, and heavy-tailed dispersal model) and analyzed network characteristics (degree, efficiency and clustering coefficient) associated with the seasonal change of hydro-climatic condition on wetland hydrology. To identify the role of small wetlands, we analyzed two different scenarios in which the sum of wetland areas are similar but their area distributions are distinct. In the first scenario, most of the small wetlands are hydrologically disappeared while the second scenario maintains the small wetlands with a shrunk area of large wetlands. When the area of large wetlands was reduced, a slight decrease in the values of network metrics was observed due to an increase in distances between wetlands. On the other hand, when a number of small wetlands were hydrologically disappeared, all the metric values were significantly decreased compared to the network in which all wetlands were hydrologically maintained. Especially, when the disappeared wetlands were not recovered even after rainfall, possibly due to long-term dehydration of supporting soil, the network characteristics also did not recover even if the total area of wetlands were recovered. However, when the dried small wetlands were hydrologically recovered, the network characteristics also recovered rapidly. Based on our observation, we confirmed that the small wetlands, despite their extremely low areal portion in the entire wetlandscape, play a key role in maintaining the ecological network resilience. Our findings can be used for a decision-making process for wetland conservation and restoration by reflecting the functional importance of small wetlands with physical characteristics requirements such as wetland areas.
Evidence of river flow regulation loss over time in the Magdalena river basin 
Authors: Marín Diver E. , Salazar Juan F. , Posada-Marín José A.
Published: March 2021

Some of the main problems in hydrological sciences are related to how and why river flows change as a result of environmental change, and what are the corresponding implications for society. This has been described as the Panta Rhei context, which refers to the challenge of understanding and quantifying hydrological dynamics in a changing environment, i.e. under the influence of non-stationary effects. The river flow regime in a basin is the result of a complex aggregation process that has been studied by the scaling theory, which allows river basins to be classified as regulated or unregulated and to identify a critical threshold between these states. Regulation is defined here as the basin’s capacity to either dampen high flows or to enhance low flows. This capacity depends on how basins store and release water through time, which in turn depends on many processes that are highly dynamic and sensitive to environmental change. Here we focus on the Magdalena river basin in northwestern South America, which is the main basin for water and energy security in Colombia, and at the same time, it has been identified as one of the most vulnerable regions to be affected by climate change. Building upon some of our previous studies, here we use data analysis to study the evolution of regulation in the Magdalena basin for 1992-2015 based on the scaling theory for extreme flows. In contrast to most previous studies, here we focus on the scaling properties of events rather than on long term averages. We discuss possible relations between changes in the scaling properties and environmental factors such as climate variability, climate change, and land use/land cover change, as well as the potential implications for water security in the country. Our results show that, during the last few decades, the Magdalena river basin has maintained its capacity to regulate low flows (i.e. amplification) whereas it has been losing its capacity to regulate high flows (i.e. dampening), which could be associated with the occurrence of the extremes phases of  El Niño Southern Oscillation (ENSO) and anthropogenic effects, mainly deforestation. These results provide foundations for using the scaling laws as empirical tools for understanding temporal changes of hydrological regulation and simultaneously generate useful scientific evidence that allows stakeholders to take decisions related to water management in the Magdalena river basin in the context of environmental change.
Analysing the retrieval quality and column densities of iodine monoxide from multiple satellite sensors
Authors: Schoenhardt Anja , Richter Andreas , Blechschmidt Anne-Marlene , Bracher Astrid , Burrows John P.
Published: March 2021

Iodine compounds are emitted from the ocean and ice covered areas through organic and inorganic pathways involving macroalgae and microalgae as well as inorganic surface processes and volcanic eruptions. Iodine monoxide (IO) molecules are produced after photolysis of precursors and reaction with ozone. IO is thus an indicator of active iodine chemistry, and impacts on ozone levels, the NO/NO2 ratio and particle formation. Rapid changes in Polar sea ice coverage and conditions may affect iodine levels in Polar Regions with respective consequences for tropospheric composition in the Arctic and Antarctic.

Remote sensing of IO faces the challenge that IO column densities are fairly small with a maximum absorption optical depth on the order of a few times 10-4, which is close to the detection limit of satellite instruments. IO column densities are retrieved from several satellite sensors including SCIAMACHY (2002 to 2012), GOME-2 (since 2006) and TROPOMI (since 2017) by using Differential Optical Absorption Spectroscopy. Previous studies have shown slightly enhanced IO column densities above the Antarctic Region and in a strong volcanic plume, while IO column densities in the Arctic remain mostly below the detection limit. These areas are in the focus of iodine measurements from space. Retrieval quality and resulting IO column densities are investigated and compared between the different sensors with a focus on the recent instrument TROPOMI.

The small IO absorption signal complicates the identification of optimal retrieval settings, such as the choice of an adequate wavelength window. Aspects for quality control are discussed. In addition to the immediate retrieval RMS, also the IO standard deviation in (reference) areas with expected low IO absorption, consistency checks with other retrieval parameters as well as plausibility of IO column density results are considered. Finally, the idea of an ensemble retrieval strategy is discussed, which is based on the fact that for small trace gas quantities, the retrieval result depends unfavourably on the fit settings. After selection of reasonable quality criteria, the remaining fit parameter sets are all used for the retrieval of IO. The selected ensemble of parameter sets yields a result for IO as well as uncertainty estimates induced by the choice of fit settings. Due to computational effort, application of this strategy is restricted to case studies.
Relationship between the formation of flow paths and elution behavior with water flow through the soil column
Authors: Tsuchida Kyouhei , Nakamura Kengo , Kondo Monami , Watanabe Noriaki , Komai Takeshi
Published: March 2021

The transport phenomenon of pollutants in soil is complicated because of the formation of the flow path in soil. In this study, the relationship between the flow path in the soil and the elution behavior of various components was evaluated by the column tests with different filling methods to change the flow path in the column. The flow path in the column was visualized by using potassium iodide aqueous solution and X-ray CT. Our result shows that the elution behavior of the easily eluted components was not significantly affected by the flow path in the column. In addition, the cation more eluted when the flow path spread throughout the column than when the flow path was intensive. This suggests that eluted components may be affected by anions in soil. From these results, it was found that the elution behavior of components is influenced by the flow path in the column and some were not, and when it was influenced, the degree of influence is different depending on the components.
Deep marine anoxia of the southern Panthalassa during the Permian-Triassic – global impacts of the Siberian Traps
Authors: Grasby Stephen , Bond David , Wignall Paul , Yin Runsheng , Strachan Lorna , Takahashi Satoshi , Ardakani Omid
Published: March 2021

The deep-water record of marine anoxia across the Permo-Triassic mass extinction (PTME) is highly controversial; both the length of time and severity of anoxic conditions are uncertain. Panthalassa Ocean circulation models show varying results, ranging from a well-ventilated deep ocean to rapidly developing northern, but not southern, latitude anoxia in response to Siberian Traps driven global warming. To address this uncertainty we examined a southern paleo-latitude pelagic record. Trace metal and pyrite framboid data show bottom water euxinc conditions developed in the southern Panthalassa Ocean at the PTME, coincident with enhanced volcanic activity indicated by Hg geochemistry. While a global deep-ocean euxinic event at the PTME placed extraordinary stress on marine life, southern surface waters appear to have recovered more quickly as radiolarian populations return several million years before they do in northern Panthalassa.
Fractal-multifractal ensembles of downscaled precipitation and temperature sets as implied by climate models
Authors: Maskey Mahesh Lal , Serrano Suarez David Joseph , Viers Joshua H. , Medellin-Azuara Josue , Sivakumar Bellie , Diaz Laura Elisa Garza
Published: March 2021

Describing the specific details and textures implicit in real-world hydro-climatic data sets is paramount for the proper description and simulation of variables such as precipitation, streamflow, and temperature time series. To this aim, a couple of decades ago, a deterministic geometric approach, the so-called fractal-multifractal (FM) method,1,2 was introduced. Such is a holistic approach capable of faithfully encoding (describing)3, simulating4, and downscaling5 hydrologic records in time, as the outcome of a fractal function illuminated by a multifractal measure. This study employs the FM method to generate ensembles of daily precipitation and temperature sets obtained from global circulation models (GCMs). Specifically, this study uses data obtained via ten GCM models, two sets of daily records, as implied from the past, over a year, and three sets projected for the future, as downscaled via localized constructed analogs (LOCA) for a couple of sites in California. The study demonstrates that faithful representations of all sets may be achieved via the FM approach, using encodings relying on 10 and 8 geometric (FM) parameters for rainfall and temperature, respectively. They result in close approximations of the data's histogram, entropy, and autocorrelation functions. By presenting a sensitivity study of FM parameters' for historical and projected data, this work concludes that the FM representations are useful for tracking and foreseeing the records' complexity6 in the past and the future and other applications in hydrology such as bias correction.

 

 

References
Solitons in a box-shaped wavefield with noise: perturbation theory and statistics
Authors: Gelash Andrey , Mullyadzhanov Rustam
Published: March 2021

The propagation of nonlinear waves is well-described by a number of integrable models leading to the concept of the scattering data also known as the nonlinear Fourier spectrum. Here we investigate the fundamental problem of the nonlinear wavefield scattering data corrections in response to a perturbation of initial condition using inverse scattering transform theory. We present a complete theoretical linear perturbation framework to evaluate first-order corrections of the full set of the scattering data within the integrable one-dimensional focusing nonlinear Schrodinger (NLSE) equation, see our recent preprint [1]. The general scattering data portrait reveals nonlinear coherent structures - solitons - playing the key role in the wavefield evolution. Applying the developed theory to a classic box-shaped wavefield we solve the derived equations analytically for a single Fourier mode acting as a perturbation to the initial condition, thus, leading to the sensitivity closed-form expressions for basic soliton characteristics, i.e. the amplitude, velocity, phase and its position. With the appropriate statistical averaging we model the soliton noise-induced effects resulting in compact relations for standard deviations of soliton parameters. Relying on a concept of a virtual soliton eigenvalue we derive the probability of a soliton emergence or the opposite due to noise and illustrate these theoretical predictions with direct numerical simulations of the NLSE evolution. Note that the evolution of the box field within the NLSE model represents a classical so-called dam-break problem. A wide box-shaped field is unstable to long wave perturbations constituting the phenomena of modulation instability. In conclussion we discuss possible applications of the developed theory to these fundamental problems of physics of nonlinear waves.

The work was supported by Russian Science Foundation grant No. 20-71-00022.

[1] R. Mullyadzhanov and A. Gelash. Solitons in a box-shaped wavefield with noise: perturbation theory and statistics. arXiv preprint arXiv:2008.08874, 2020.
Effects of native forest replacement to exotic plantations on forest C, N, and P pools and dynamics in south-central Chile
Authors: Aburto Felipe , Crovo Oscar , Albornoz Maria Fernanda , Southard Randal
Published: March 2021

Native forest substitution by intensively managed tree plantations can significantly alter carbon and nutrient biogeochemical cycling due to changes in forest dynamics and alterations on biogeochemical fluxes. To evaluate the magnitude of these alterations, we quantify the main C, N, and P pools and fluxes in paired plots established in secondary deciduous native forests and exotic pine plantation plots in five contrasting soils. Forest main fluxes were monitored for two years. We quantified total biomass and biomass C and nutrient pools, litterfall production, litter decomposition, soil CO2 efflux, LAI, and annual root production. Besides, DOC, Nitrate, Ammonium, and DTP was determined on leachates.

Overall ecosystem C storage (soil and aboveground biomass) showed no differences between forest types across sites (p=0.07). However, two of the soil types displayed significantly higher C pools in the native forest sites. Besides, most native forest sites have higher total aboveground N and P stocks. Nitrate and ammonium leachate losses tend to be higher in native forests, but not significantly. On the contrary, phosphate losses were higher in plantations. Native forests and plantations differ on their annual C fluxes, particularly on their root and DOC productions. Native forests showed a significantly higher annual root production (1.76 ± 0.99 Mg ha-1) than pine plantations (0.81 ±0.88 Mg ha-1) (p=0.0001). Of the Measured variables, only root production showed a positive correlation (R2 = 0.49) with soil total C (p=0.001). Exotic pine plantations display higher litterfall but a significantly lower root production modifying the main source of carbon to the system. Also, DOC losses increased considerably under plantations. Continuous monitoring of these pair plots will help to address the potential long term effect of this land-use change and the relative sensitivity of these systems to changes in environmental conditions.
The Role of Isostasy in the Evolution of Thin-Skinned Fold and Thrust Belt
Authors: Ibrahim Youseph , Rey Patrice
Published: March 2021

The stacking of thrust sheets and mass transfer of sediment during fold and thrust belt accretion imposes a load on the basement and underlying mantle. This load induces an isostatic adjustment through a flexural response, which may also contribute to the overall architecture of the fold and thrust belt. Whereas plate kinematics imposes its tempo to evolving fold and thrust belts, the rheology of the mantle controls the tempo of the isostatic flexure. Using two-dimensional high-resolution numerical experiments, we explore how the interplay between the tectonic compressional rate and the isostatic flexural rate influences the structural evolution and final architecture of fold and thrust belts. 

We run a suite of numerical experiments using the well-tested code Underworld. Our geological model is mapped over a 42 km by 16 km numerical grid, with a cell resolution of 80 m. The geological model consists from top to bottom of  ‘sticky air’, 4 km of sediment that alternates in competence at 500 m intervals, a 3 km thick basement, and a basal layer which - in combination with a basal kinematic boundary condition - controls the amount of isostatic flexure. Materials have a mechanical behavior that results from elasto-visco-plastic rheology. The pressure at the base of the model is held constant, and the vertical velocity is updated at each timestep. The amount of material entering or exiting the model at each point along the base scales with the density of the basal layer, which is used to control the isostatic rate. Sedimentation and erosion are self-consistent through mechanical erosion and a hillslope diffusion law. Our models show that as the ratio between tectonic and flexural rates decreases (i.e. flexure gets faster), fold and thrust belts become narrower, lower in elevation, and structurally more complex. We compare these results with natural analogs including the Cordilleran and Jura fold and thrust belts.
Magnetite Redistribution during Multi-stage Serpentinization: Evidence from the Taishir massif, the Khantaishir Ophiolite, Western Mongolia
Authors: Dandar Otgonbayar , Okamoto Atsushi , Uno Masaoki , Tsuchiya Noriyoshi
Published: March 2021

Magnetite commonly forms during serpentinization of mantle peridotite, involving the hydrogen generation within the oceanic lithosphere. Although magnetite is concentrated in veins, the mobility of iron during serpentinization is still poorly understood. The completely serpentinized ultramafic rocks (originally dunite) within the Taishir massif in the Khantaishir ophiolite, western Mongolia, include abundant magnetite + antigorite veins, which manifest novel distribution of magnetite. The serpentinite records the multi-stage serpentinization, in order of (1) Al-rich antigorite + lizardite mixture with hourglass texture (Al2O3 = 0.46-0.69 wt%; Atg+Lz), (2) Al-poor antigorite composed of thick veins and their branches (Atg), and (3) chrysotile that cut all previous textures. The Mg# (= Mg/ (Mg + Fetotal)) of Atg+Lz (0.94-0.96) is lower than Atg (0.99) and chrysotile (0.98). In the region of Atg+Lz, magnetite occurs as the arrays of fine grains (<50 μm) around the hourglass texture. In the Atg veins replacing Atg+Lz, magnetite disappears and re-precipitated as coarse grains (100-250 μm) in the center of some veins. As the extent of replacement of Atg+Lz by Atg veins increases, both modal abundance of magnetite and the bulk Fe content decrease. These characteristics indicate that hydrogen generation mainly occurred at the stage of Atg+Lz formation, and magnetite distribution was largely modified via dissolution and precipitation in response to later fluid infiltration associated with the Atg veins. This also indicates the high iron mobility within the serpentinized peridotites even after the primary stage of magnetite formation.
Strain accumulation along various faults in the Kashmir Himalaya from InSAR
Authors: Sana Hamid , Fielding Eric , Liang Cunren , Yunjun Zhang
Published: March 2021

We are using InSAR time-series analysis to measure the interseismic deformation across various faults of the Kashmir Himalaya. Active faults reaching the surface include the Main Boundary Faults, Bagh-Balakot Fault, which ruptured in the 2005 Kashmir earthquake (Mw 7.6), Jhelum Fault, Reasi Thrust and intra-Kashmir basin faults. We concentrate on these shallow faults that are closest to the people living in Kashmir. The Main Boundary Faults and other faults likely connect to the Main Himalayan Thrust (MHT) that is the plate-boundary megathrust beneath Kashmir and the rest of the Himalayas. The MHT has been suggested as a possible source for Mw 8 to Mw 8.5 earthquakes in this area. We have processed interferometric pairs from the Japan Aerospace Exploration Agency ALOS-2 L-band (24 cm wavelength) Synthetic Aperture Radar (SAR) wide-swath (ScanSAR) data acquired between 2015 and 2020. Initial interferometric SAR (InSAR) processing was carried out using the alos2App application of the InSAR Scientific Computing Environment (ISCE2) package, with ionospheric corrections enabled. We found that many scenes acquired in the winter form pairs that have low coherence due to snow cover in the High Himalayas and Pir Panjal Range. We also found that phase unwrapping in the mountains was improved by taking 10 range and 56 azimuth looks from the full-aperture ScanSAR for an effective resolution of about 200 meters. We are running a co-registered stack processing of the ALOS-2 SAR data, with self-consistent ionospheric corrections estimated using the split-spectrum method, using the new alosStack application of ISCE2 package to carry out time-series InSAR analysis, using an open-source Python toolbox, MIntPy.
Estimating the Probability of Compound Discharge/surge Events in a Complex Estuarine System Under Data Constraints 
Authors: Santos Victor M. , Wahl Thomas , Jane Robert , Misra Shubhra K. , White Kathleen D.
Published: March 2021

Compound flooding may result from the interaction of two or more contributing processes, which may not be extreme themselves, but in combination lead to extreme impacts. Estuarine environments are particularly prone to compound flooding due to the interplay between coastal storm surge and river discharge processes, both often being driven by the same storm event. A detailed understanding of compounding mechanisms, including the dependence between flooding drivers, is necessary to avoid flood risk miscalculations when building/upgrading flood defences to mitigate risks associated with high impact events. Here, we use statistical methods to assess compound flooding potential in Sabine Lake, TX. Sabine Lake receives discharge from two rivers and is connected to the Gulf of Mexico coast through Sabine Pass. These geographic characteristics make it susceptible to compound flooding. We employ several trivariate statistical models (and simplified bivariate models for comparison) to examine the sensitivity of results to the choice of data pre-processing steps, statistical model setup, and outlier removal. We define a response function that represents water levels resulting from the interaction between discharge and storm surge inside Sabine Lake, and explore how the water level response is affected by including or ignoring dependencies between the contributing flooding drivers. Our results show that accounting for dependencies leads to water levels that are up to 30 cm higher for a 2% annual exceedance probability (AEP) event and up to 35 cm higher for a 1% AEP event, compared to assuming independence. We also find notable variations in the results across different sampling schemes, multivariate model configurations, and sensitivity to outlier removal. This highlights the need for testing various statistical modelling approaches in order to reliably capture potential compounding effects, especially under data constraints.

 
Visualizing the Energy Production, Imports and Exports for Countries
Authors: Vargas Suarez Luisa , Donev Jason
Published: March 2021

There are extensive conceptual difficulties in understanding a country’s energy story. Every country in the world uses some combination of energy production, imports, and exports energy to meet their society’s needs. Thermal inefficiencies converting primary energy into electricity further confuse the issues. A visualization using large, publicly available data can help illustrate these different energy perspectives. This data visualization helps clarify the following perspectives: Production, Imports, Exports, Total Primary Energy Supply (TPES), Total Final Consumption (TFC), and the conversion losses from turning TPES into TFC. TPES refers to the total amount of energy a country obtains directly from natural resources such as fossil fuels or wind. TFC refers to the addition of the all energy directly consumed by a user for an energy service such as electricity for lighting in a house. This paper discusses the interactive simulation that was built to allow users to explore the composition of a country’s energy production, imports and exports through the conversion into energy people consume. The simulation allows users to explore the energy stories for different countries, and how these change over the decades.
Seasonal Changes in Molecular Distributions of Diacids, Oxoacids and α-Dicarbonyls in PM2.5 in Tianjin, North China: Implications for Origins and Secondary Formation Pathways in Cold and Warm Periods
Authors: Li Peisen , Pavuluri Chandra Mouli , Dong Zhichao , Xu Zhanjie , Fu Pingqing , Liu Cong-Qiang
Published: March 2021

Organic aerosols (OA) that make up a large fraction (up to 90%) of the fine aerosol (PM2.5) mass have severe impact on the Earth’s climate system and can cause adverse risk to human health. Diacids and related compounds are ubiquitous in PM2.5 in different environments and accounts for a substantial fraction in OA. Because of their high water-solubility, they can influence the hygroscopic properties and capacity of cloud condensation nuclei formation activity of aerosols and thus affect the indirect radiative forcing in the atmosphere. However, their origins, secondary formation and transformations and seasonality are not fully understood yet. To better understand the seasonal characteristics, origins and photochemical processing of OA in the Tianjin region, North China, we studied the molecular distributions and seasonal variations of water-soluble diacids, oxoacids and α-dicarbonyls in PM2.5 collected at an urban and a suburban sites in Tianjin, an ideal location to study the aerosols, over a one-year period from July 2018 to June 2019. We found significant changes in concentrations and composition of diacids and related compounds from season to season at both the sites. Here, based on the results obtained together with the meteorology, oxidants (O3 and NO2) and SO2, loading and the backward air mass trajectories, we discuss the possible origins and possible secondary formation pathways of diacids and related compounds in the Tianjin region.
Astronomically paced marine biological evolution during the Late Paleozoic icehouse-to-greenhouse transition
Authors: Fang Qiang , Wu Huaichun , Shen Shuzhong , Fan Junxuan , Hinnov Linda , Zhang Shihong , Yang Tianshui
Published: March 2021

Late Paleozoic deglaciation is the Earth’s first icehouse-to-greenhouse transition in a vegetated world, but the climatic and biological responses to this transition have not yet been fully addressed. We conducted cyclostratigraphic analysis on the magnetic susceptibility from a deep marine carbonate succession in South China, to reconstruct the astrochronology of the late Early Permian, and to decipher evolutionary responses to astronomically forced climate changes in a marine diversity time series. Our results indicates that the minima of ~1.8 m.y. short orbital eccentricity amplitude modulation cycles led to seasonally stable precipitation patterns and a constant input of nutrients, which spurred marine biodiversity during this deglaciation. Synchronizing global biotic and abiotic records reveals that peaks of marine biodiversity occurred during nodes of ~1.3 m.y. obliquity amplitude modulation cycles, when ice sheet expansion triggered enhanced precipitation and organic carbon burial during icehouse conditions (290−285.1 Ma). Starting at 285.1 Ma, the insolation-biodiversity relationship began to change, paced by glacial termination and tropical aridification. With the transition to greenhouse conditions (~279.1−272 Ma), obliquity nodes became associated instead with terrestrial aridity and marine anoxia, and suppression of marine speciation. Our results bring into focus a pattern of shifting dynamics involving Earth’s astronomical parameters, climate change and marine biodiversity for icehouse and greenhouse worlds in the late Paleozoic Era.