bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical mechanics of the electrons in the solar wind: stability and instability of whistler waves in the inner heliosphere
Authors: Verscharen Daniel , Micera Alfredo , Innocenti Maria Elena , Coburn Jesse , Boella Elisabetta , Pierrard Viviane , Liu Jingting , Owen Christopher J. , Nicolaou Georgios , Klein Kristopher G.
Published: March 2024

The electrons in the solar wind often exhibit non-equilibrium velocity distribution functions. Observed non-equilibrium electron features in the inner heliosphere include a field-aligned beam (called "strahl"), a suprathermal halo population, a sunward deficit in the distribution, and temperature anisotropy. These features are the result of a complex interplay between global expansion effects, collisions, and local interactions between the particles and the electromagnetic fields. Global effects create, for example, the strahl via the mirror force in the decreasing magnetic field and the sunward deficit via reflection effects in the interplanetary electrostatic potential. Local wave-particle interactions such as instabilities and wave damping change the shape of these signatures and thus the overall properties and moments of the electron distribution.We discuss the formation of the relevant features in the electron distribution and analyse their impact on the linear stability of whistler waves in the inner heliosphere. We then present results from our numerical ALPS code that is capable of evaluating the linear stability of plasma with arbitrary background distributions. With results from our ALPS code, we show that the strahl-core-deficit configuration near the Sun drives oblique whistler waves unstable. However, it leads to enhanced damping of parallel whistler waves compared to a Maxwellian configuration. As the distribution evolves, the sunward deficit fills with electrons, at which point the plasma becomes unstable and drives parallel whistler waves. Our results highlight the need to treat electrons statistically as a globally inhomogeneous plasma component and to account for the detailed shape of their distribution in the evaluation of the plasma's linear stability.
From sediments to the atmosphere: a mass spectrometry approach revealing structural dissimilarities of common NOM components
Authors: Zherebker Alexander , Babcock Oliver , Vasilevich Roman , Giorio Chiara
Published: March 2024

Natural organic matter (NOM) is a complex mixture of thousands of organic molecules that reflects environmental conditions and chemical transformations occurring nowadays or in the past. Fourier transform mass spectrometry (FTMS) resolves isobaric constituents and it is widely applied to obtain aquatic, terrigenous and aerosol NOM fingerprints. Traditionally, comparison of mass peak intensities is used to make a distinctive conclusion about samples behavior, but it has the limitation of omitting structural information on the corresponding ions. Due to the stochastic character of NOM synthesis, drastically different samples may appear as resembling, which hampers mechanistic study of NOM dynamics and its attribution to the source. Here we present how implementation of chemical and isotopic tagging in combination with FTMS helps to overcome this issue. The developed approach provides an upper boundary for the presence of specific structural features, e.g. functional groups, in individual NOM components. This facilitates a clear distinction between different NOM samples, which would share isobaric ions, and provides insights on isomeric complexity of these ions. The advantages of the method were demonstrated on two sets of samples. Firstly, we collected permafrost peat cores from different depths in the European Arctic region, which varied in corresponding botanical conditions, peat degradation and oxidation states. Selective deuteromethylation and bromination coupled to FTMS enabled to capture structural differences between shared ions, which differed in carboxylic functionality and aromaticity. Surprisingly, structural differences were found for ions, which abundance positively correlated with peat characteristics and geo-temporal conditions. The second set included aerosol particles collected in marine, rural and urban areas. Application of in-source H/D exchange for FTMS analysis of extracted NOM enabled to enumerate functional groups in shared ions and point molecular constituents with similar and distinct structural features. The observed trends serve to better understand aerosol formation processes and accompanied conventional formula-based statistical analysis including better understanding of Kendrick mass defect series.
A Multi-Criteria Analysis procedure for the evaluation and classification of flood risk mitigation strategies
Authors: Gallazzi Alice , Molinari Daniela , Ballio Francesco , Credali Marina , Tolone Immacolata , Muratori Simona , Asaridis Panagiotis
Published: March 2024

The study aims to provide the Lombardy Region, the primary stakeholder in the project, with a procedure for evaluating and classifying structural flood risk mitigation measures. The primary objective is to assist the regional authority in identifying priority interventions for public funding. A step-by-step procedure has been developed to assess and rank all projects submitted to the Region, selecting priority projects based on technical considerations—evaluating feasibility, effectiveness, and sustainability of the proposed measures—and the preferences of policymakers. The assessment procedure's conceptual structure was tested using case studies, including both feasibility studies and executive projects, to determine the level of technical insights required at each planning phase of public works. The methodology relies on Multiple Criteria Analysis (MCA) techniques, enabling the simultaneous consideration of various, non-directly comparable criteria in a complex decision-making context. These criteria encompass technical features of proposed works, potential territorial constraints, and interferences in the intervention area (feasibility); the effectiveness of measures in reducing flood risk and associated costs; and the environmental and social co-benefits and disbenefits of each intervention (sustainability). Specific indicators, either ad hoc defined for the study or referenced from current regulations and guidelines at national and regional levels, are employed to evaluate the criteria. Stakeholder participation, particularly from the Region, River District Authorities, and Municipalities, is crucial throughout the process, especially in the final phase of aggregating (weighting) all criteria. This aggregation produces an overall performance score for each option, enabling the derivation of a regional ranking of flood risk mitigation strategies. The collaboration between academia and public institutions is highlighted as essential for enhancing the efficiency of disaster risk reduction policies.
Research on Building-level Operational Carbon Emissions in Shenzhen Based on Multi-Source Data
Authors: Lin Zirong , Huang Bo
Published: March 2024

Carbon emissions are closely related to climate change and sustainable development. Despite the existence of a large amount of research on carbon emissions, previous studies have focused more on regional analysis and lacked building-level research. When it comes to building-level carbon emissions, it usually involves a limited number of buildings, or collects a large amount of survey data within a specific region, which cannot be extended to large areas. This study takes buildings in Bao'an District, Shenzhen as the basic unit and uses statistical yearbooks, population density and nighttime light images to allocate total carbon emissions into each building through a top-down approach, to gain a more comprehensive understanding of the distribution of carbon emissions and their relationship with human activities. The findings of this study are expected to promote energy conservation and emission reduction and provide data support for achieving the goals of carbon peak and carbon neutrality.
A New Approach to Infrasound Sensor Design
Authors: Guralp Cansun , Minchinton Paul , Rademacher Horst , McGowan Murray
Published: March 2024

Current infrasound sensor designs have shortcomings inherent in their open-loop arrangement. Among them are the limited dynamic range, the lack of linearity of the response function over the desired frequency range and – may be most importantly – the fact that such sensors can only be calibrated in the laboratory and not under real conditions in the field.Here we present a novel infrasound sensor design, which overcomes these and other shortcomings. At the core of our new sensor lies a feedback loop. It is based on a proven technology already applied in many sensor and control systems, particularly relevant for Earth science in the design and manufacturing of high fidelity broadband seismic sensors.The new infrasound sensor uses a precision bellow, which deflects in response to pressure variations or atmospheric infrasound waves. The movement of the bellow in single degree of deflection is measured with a differential capacitive displacement transducer. Its circuitry is a Blumlein bridge arrangement operating at a frequency of 45 KHz and a driver signal amplitude of 20 V. The transducer's output signal is then synchronously fed back to the regular linearised magnetic force transducer after passing through a Proportional Integral and Differential (PID) controller.This design increases the bandwidth of the sensor to five decades, from 2.7 mHz to more than 200 Hz. At the same time the response of the sensor is essentially flat over the entire frequency range with only minor variations of less than +/- 0.1 dB. We measured the dynamic range of the sensor to be in excess of 155 dB, a significant increase compared to current open loop systems.The infrasound sensors theoretical transfer function is compared to practical measurements providing sensors characteristics including its detection levels over the complete frequency response.The system calibration is carried out analogously to the calibration of broadband seismic sensors. We inject a known calibration signal (either sinusoidal, square wave or broadband noise) directly into the feedback force transducer. This setup allows the calibration of the infrasound sensor in the laboratory as well as after deployment in a field station.
Satellite derived bathymetries through high space-time resolution videos
Authors: Marco-Peretó Candela , Simarro Gonzalo , Calvete Daniel , Palombo-Blascetta Nicola , Durán Ruth , Guillén Jorge
Published: March 2024

Coastal bathymetric datasets are critical to improve our understanding of morphodynamic processes in the coastal area, as well as for decision-making on future adaptation measures. Originally designed for analyzing snapshots and time-exposure images from coastal video monitoring stations installed on buildings near the coastline, video techniques have enormously evolved over the last three decades. Recent advancements, e.g., extend their application to derive bathymetry estimations from ∼10-minutes videos captured at few frames per seconds (fps), allowing for more frequent and cost effective bathymetric estimations.New algorithms, such as cBathy (Holman et al., 2013) or uBathy (Simarro and Calvete, 2022), depart from the linear dispersion relation and different signal processing tools to infer bathymetry from the propagation of surface water waves (which is considered as a footprint of the bed shape). They have already been tested and applied not only to videos from coastal monitoring stations, but also to videos from UAVs (unmanned aerial vehicles, commonly known as drones).  In this work we explore the potential use of these techniques to 45-seconds satellite videos captured at 10 fps and with a spatial resolution of 1 pixel per meter.For this purpose, departing from uBathy, the nearshore bathymetry at Castelldefels beach has been estimated over a 6-months period using three satellite videos. The results are compared against those obtained from drones (ten 10-minutes videos over the same period) and from the fixed video monitoring station at Castelldefels beach (coo.icm.csic.es), recording 10-minutes videos three times daily. Furthermore, an echo-sounder bathymetric survey is used as Ground Truth for validation purposes.The proposed approach presents a promising alternative to existing techniques for satellite imagery which are based on the analysis of single multior hyper-spectral snapshots (color-based techniques). On the one hand, from previous experience, the expected errors are smaller than those typically obtained with color-based techniques for snapshots and, on the other hand, they eliminate well-known problems of color-based techniques when water turbidity is high.Holman, R., Bergsma, E. W. (2021). Updates to and performance of the cbathy algorithm for estimating nearshore bathymetry from remote sensing imagery. Remote Sensing, 3996.
Simarro, G., Calvete, D. (2022). UBathy (v2.0): a software to obtain the bathymetry from video imagery. Remote Sensing, 14(23), 6139.
Keywords: Remote sensing, Video imagery, Bathymetry inversion, UAV, Satellite.
Trace metals interaction to soil properties, and their ecological risk assessment in different disturbance regimes of sal forests of the western Himalaya, India
Authors: Shankar Anand , Garkoti Satish Chandra
Published: March 2024

Disturbance is an important factor in controlling vegetation diversity, and distribution of trace metals in the environment, including through their mobilization by disturbance-induced runoff and related to movement of soil particles. Disturbance-induced access of these trace metals into the ecosystem is toxic for soil contamination and experiences varying degrees of ecological implications in different ecosystems. The present study aimed to evaluate the impact of different degrees of land disturbances on the changes in vegetation diversity, soil characteristics, and trace metals in the Himalayan forest ecosystem, which is limitedly documented. Forest sites were categorized into four distinct disturbance classes based on disturbance index score (DI): no disturbance (ND, DI ≤ 5 %), low disturbance (LD, 5 < DI ≤ 20 %), moderate disturbance (MD, 20 < DI ≤ 50 %), and high disturbance (HD, DI > 50 %). Data comprised trace metals, and soil physicochemical characteristics across the distinct disturbance classes and soil layers (0-15 and 15-30 cm). Using two-way ANOVA, vegetation attributes (diversity (H′), and tree density), soil properties, and trace metals were tested for their effects, including interactions among different disturbances and depths. Multivariate correlation was used to investigate the relationship between disturbance classes, depths, soil characteristics, and trace metals. The important findings of the study are the following: (1) The recruitment of new trees (Treerecru.), diversity, and soil organic carbon (Corg) were significantly varied across the disturbance classes (p< 0.05) and followed the order: MD > HD > LD > ND; (2) Average concentration metals were significantly distributed along disturbances gradient HD > LD > MD > ND in the order: B > Mn > Pb > Cu > Ni in distinct soil layer. (3) Contamination factor of trace metals in order B > Mn > Pb > Ni > Co > Cu in 0-15 and 15-30 cm soil depths. (4) Persistent ecological risk index (PERI) was higher for HD sites and lowest for ND sites. The result illustrated that moderate disturbance increases diversity and soil nutrients. The study highlighted the important role of disturbance in regulating the trace elements in association with changes above-below ground interaction, suggesting HD sites as a potential source of environmental contamination.
Mapping glacier structure in inaccessible areas from turning seismic sources into a dense seismic array
Authors: Nanni Ugo , Roux Philippe , Gimbert Florent
Published: March 2024

Understanding glaciers structural heterogeneity is crucial for assessing their fate. Yet, places where structure changes are strong are often inaccessible for direct instrumentation, such as in crevasses fields. To overcome this limitation, we introduce an innovative technique that transforms seismic sources, here generated by crevasses, into virtual receivers using source-to-receiver spatial reciprocity. We demonstrate that phase interference patterns between well-localized seismic events can be leveraged to retrieve phase velocity maps using seismic Michelson interferometry. The obtained phase velocity exhibit sensitivity to changes in glacier structure, offering valuable insights into the origins of mechanical properties changes, with spatial resolution surpassing traditional methods by a factor of four. In particular, we observe sharp variations in phase velocity related to strongly-damaged subsurface areas and indicative of a complex 3-D medium. Applying this method more systematically and in other contexts will enhance our understanding of the structure of glaciers and other seismogenic environments. 
Modeling optimal initial conditions for propagation of seismotectonic tsunamis: a database of smoothed unit sources based on an efficient and accurate numerical integration
Authors: Abbate Alice , González Vida José Manuel , Castro Díaz Manuel J. , Romano Fabrizio , Bayraktar Hafize Başak , Babeyko Andrey , Lorito Stefano
Published: March 2024

The initial conditions for the numerical simulation of a seismically-induced tsunami are modeled by transferring the impulse produced by the co-seismic seafloor deformation to the sea-surface. In this process, the water column acts as a hydraulic filter for the smaller wavelengths. The numerical simulation of this process is computationally demanding; this makes  the application of this filter unaffordable in studies that require a large number of simulations, such as the long-term probabilistic tsunami hazard assessment (PTHA). Here, we optimize the numerical modeling of the filter in the case of an instantaneous vertical seafloor deformation, given by an improper Fourier expansion integral in the wave number domain presented by Nosov and Kolesov (PAGEOPH, 2011); the contribution of elementary seafloor displacements can then be linearly combine to obtain a static tsunami initial condition. We first explore the convergence of the integral in one dimension, to identify the range of wavenumbers significantly contributing to the integral. We find that its support can be limited to , being H the sea-depth. We then compare several quadrature formulae, selecting the optimal one in terms of accuracy and efficiency. We grid the domain into cells of equal size and constant depth, and verify that the nonlinear effects are negligible when we recombine them to obtain the initial sea level displacement. In two dimensions, the integral is solved with the optimal quadrature and the results tested on the tsunamigenic Kuril doublet sequence - a megathrust and an outer-rise - occurred in the Central Kuril Islands in late 2006 to early 2007. We also consider the horizontal co-seismic deformation projected on a slope and a simple model of the inelastic deformation of the wedge, on a realistic bathymetry. The approach proposed results accurate and fast enough to be relevant for practical applications, taking a few seconds for solving a single cell, depending on the local depth, and ~3min to recombine ~91k elementary initial conditions. We finally build a database of elementary initial conditions, as a function of the local sea depth, which can be linearly combined to obtain a discretization of any sea floor displacement globally.
Establishing Relation Between Variance of Permeability and Tortuosity for Composite Liner Material
Authors: Chaudhary Ekta , Swami Deepak
Published: March 2024

Landfill liners are necessary for protecting groundwater from contamination due to leachate percolation. The usage of composite materials like fly ash and silt as landfill liner material has gained popularity as their use would alleviate waste management challenges and, as a result, preserve natural resources. Physical properties of such composite materials, like estimation of hydraulic conductivity, porosity, and diffusion characteristics, which affect the transport characteristics of these mediums, are lesser known. The evaluation criteria for a liner are based on limiting the hydraulic conductivity of the liner, k, to less than 10-7 cm/s. For low permeability materials, transport by advection is essentially non-existent, while diffusion is the dominant contaminant transport phenomenon. To assess the service life of a liner, various numerical and experimental studies have reported the need for a detailed comprehension of the diffusive transport through liners to predict the fate and transport of solute. To account for the impact of porosity on diffusion in heterogeneous porous media, the diffusion coefficient must be scaled with tortuosity. Tortuosity is influenced by a number of parameters, including the type, size, and shape of the grains, the pores and pore channels, and the interconnectivity of the pore spaces. Therefore, to estimate the diffusion coefficient precisely, one must establish a method to estimate tortuosity. This study focuses on establishing a relation between the variance of hydraulic conductivity measured on-site with random sampling and the probability distribution function of the tortuosity matrix for a stochastic flow domain. Numerical experiments for two different composite materials were carried out using HYDRUS 2D/3D, assuming stochastic distribution of hydraulic conductivity. Estimation of the hydraulic tortuosity is carried out using the vector-based method based on the velocity profiles. Analysis were conducted to identify the probability distribution function for accurately estimating tortuosity using simple field-based permeability measurements. Pore-scale numerical experiments demonstrate a strong correlation between permeability variance and tortuosity. 
A twisted ribbon of subducted lithosphere beneath southeast Anatolia and its seismotectonic implications
Authors: Yeung Sonia , Lister Gordon , Spakman Wim , Göğüş Oğuz , Forster Marnie , Simmons Adam , Jelsma Hielke
Published: March 2024

Forensic analysis of the geological architecture in the aftermath of destructive earthquakes is an essential step to identify controlling structures that need to be monitored. Here we suggest the sequence of events during the February 2023 Turkey–Syria earthquakes was driven by the roll back of a twisted ribbon of subducted lithosphere beneath southeast Anatolia. We assume that the February 2023 Turkey–Syria earthquakes were short-term manifestations of a longer-term tectonic process. To investigate, we built a three-dimensional (3D) mesh frame defining the geometry of subducted Tethyan lithosphere in the Eastern Mediterranean, using the UU-P07 global tomography model, and where appropriate, earthquake hypocentre sets from the Global Centroid Moment Tensor project (GCMT) and from the International Seismic Centre (ISC). The 3D model of the subducted Tethyan lithosphere exhibits three variably twisted ribbons. The Cyprus ribbon is subducted to ~280 km depth and is ~120 km wide, and it twists and curls parallel to its length by ~20 degrees anticlockwise.The geometry prior to subduction can be estimated by floating the mesh back to the surface using the Pplates program. The process of subduction can be visualised by incorporating the floated mesh into a 2D+time tectonic reconstruction from 125 Ma to the present. This leads to the inference that the ribbons are associated with slab tearing during roll back of the Tethyan lithosphere, due to the accretion of the Lycian block and the Cyprus promontory. The twisting motions can be related to a lateral push sideways caused by anticlockwise vertical axis rotation of the Arabia indenter during opening of the Red Sea rift and the Gulf of Aden. We suggest that the Anatolian lithosphere is being stretched by ongoing differential roll back caused by drag of the Cyprus ribbon through the asthenosphere underlying southeast Anatolia. This motion continually triggers failure along strike-slip faults while facilitating the continued indentation of Arabia. Seismotectonic analysis of aftershock sequences highlights the underlying geodynamics.
Impacts of Spring East Pacific SST and Arctic Sea Ice on Interannual Variability of Summer Burned Area in boreal North America
Authors: Zhao Zhiyi , Lin Zhongda , Li Fang
Published: March 2024

Wildfires pose an increasing threat to boreal forest and tundra ecosystems in boreal North America (Alaska and northwestern Canada), as their frequencies rise under global warming. These fires exhibit strong interannual variability that is influenced by regional atmospheric circulation. However, potential impacts of remote boundary forcings on regional fires and the underlying mechanisms remain unclear. This study provides a comprehensive analysis on the impacts of spring sea surface temperature (SST) and sea ice on interannual variability of burned area in this region during fire season (summer) from 1997 to 2020 using GFED5 burned area, SST and sea ice concentration data from the Met Office Hadley Centre, and ERA5 reanalysis data. Results show that in spring a warmer SST in the East Pacific and reduction of sea ice in the northern Chukchi Sea lead independently to an increase in burned area in boreal North America. The correlation coefficients between the SST and sea ice factors with the burned area in boreal North America are 0.43 and –0.44 respectively. The SST-fire relationships can be explained as follows: A warm SST anomaly in the East Pacific triggers a northeastward-propagated Rossby wave, inducing a high-pressure anomaly over boreal North America in spring. Consequently, this circulation anomaly causes a higher surface temperature and thus vegetation growth or drying. As temperatures rise and lightning activity intensifies in summer, burned area increases. On the other hand, the process of sea ice affecting burned area is different. A reduction in sea ice coverage in the northern Chukchi Sea leads to a decrease in surface albedo, resulting in an increase in heat flux. The heat release persists from spring to summer and causes a high-pressure circulation anomaly in boreal North America in summer, which suppresses regional water vapor convergence and precipitation, reducing soil moisture and surface air humidity and increasing vapor pressure deficit (VPD) thereby promoting fuel flammability.
Dissolved Oxygen Dynamics in Arctic and Boreal Lakes in Late Winter
Authors: Asirok Ezgi , Kirillin Georgiy , Grossart Hans-Peter , Goldhammer Tobias
Published: March 2024

Arctic and boreal lakes in the Northern Hemisphere experience annual ice cover lasting 4 to 7 months. Freshwater lakes in cold regions are sensitive to subtle environmental changes and influenced by various physical and biogeochemical factors. Our study focuses on comparative analysis of under-ice metabolism shaped by the thermal and oxygen dynamics of Arctic Lake Kilpisjarvi and Boreal Lake Paajarvi during the late winter. We aim to understand the effect of different trophic levels and light regimes on lake metabolism within cold regions by using high-frequency data on temperature, dissolved oxygen, and solar radiation for Lake Kilpisjarvi in 2019 and 2020, and Lake Paajarvi in 2022. Besides the long-term data, we compared the phytoplankton biomass and chemical parameters obtained from water samples collected from different depths. We studied the changes in the vertical distribution of lake metabolism by diel cycles by considering the strength and influence of internal motions on temperature and oxygen data.Our results demonstrate that following prolonged darkness, a significant increase in dissolved oxygen occurs in the upper water column of Lake Kilpisjarvi. The depth of the mixed layer increases with depth, ranging from 1.1 m/day to 2.3 m/day for 2019 and 2020 in Kilpisjarvi. In contrast, Lake Paajarvi has a slower and steady rate of deepening at 0.55 m/day, resulting in a comparatively shallow mixed layer.
Graphene oxide as a component of a Permeable Reactive Barrier for aquifer pollution remediation
Authors: Liang Chuchao , Rodriguez Escales Paula , Sanchez Vila Xavier
Published: March 2024

Groundwater contamination sources are ubiquitous, with the heavy metal ion lead being released to the aquifer systems as a common anthropogenic contaminant. Lead can cause serious damage to both human and ecosystem health. In this sense, its remediation through sorption technologies, such as Permeable Reactive Barriers (PRBs), is basic to minimize its impact. Quartz as the most common and economically heavy metal adsorbent has been widely studied. However, the new generation of potential adsorbents, here including graphene oxide (GO), has not been fully researched. Particularly, there is little research on how to set surface adsorption models of GO, with most studies limited to batch and transport experiments.This study aimed to investigate the performance of quartz and graphene oxide (GO) as adsorbents in PPRBs. We evaluated the adsorption capacity of quartz sand and GO under different conditions through batch experiments, examining factors including pollutant concentration, pH, and competing ions. The experimental results were validated using a coupled surface complexation and precipitation model developed with the Phreeqc code, and the findings from the batch experiments will also be used as calibration data for the Phreeqc model, and the code (PEST) was used for parameter estimation.Keywords: Graphene oxide, Heavy metal, Permeable Reactive Barriers, Surface complexation, Phreeqc.
Climatology of Lower Tropospheric Turbulence at Kochi using S-T radar.
Authors: K k Ahana , Karathazhiyath Satheesan , Kottayil Ajil
Published: March 2024

This study investigates the climatology of atmospheric turbulence, focusing on the dissipation rate of turbulent kinetic energy (ε) in the lower troposphere. Utilizing data from the 205 MHz S-T radar located in Kochi, Kerala, India, our examination extends to the lower troposphere, particularly the boundary layer characterized by meteorological factors such as temperature gradients, wind shear, and convective processes that contribute to turbulent air motion. Turbulence in the atmosphere can arise either thermally through convection-related instability or mechanically through phenomena like Kelvin–Helmholtz billows, the reversal or disruption of gravity waves, and inertial gravity waves. A thorough understanding and prediction of turbulence in this atmospheric layer are critical for ensuring the safety and efficiency of air travel and advancing our understanding of the intricate interplay of atmospheric dynamics. The study employs the spectral width method for estimating turbulence dissipation rate, accounting for broadening effects due to shear and beam. After filtering out convective data, turbulence dissipation rates are estimated over 6 years from March 2017 to December 2022 from a height of 0.4 to 5 km. Monthly median analysis reveals a subtle increasing trend in the lower troposphere, with a slope of 1.6 x 10-3. The vertical distribution indicates maximum data in the range of -4.5 to 1.75 m2 s-3, exhibiting a decrease in ε with height. ε displays definite seasonal variations, with maximum values and the least variation occurring within a specific range in the monsoon season. Winter season marks the least turbulent season. The study also explores the periodicity of the turbulence dissipation rate in the study region.
A machine learning based approach for forecasting remotely sensed vegetation health in Italy.
Authors: Suman Swati , Valentini Riccardo , Srivastava Prashant K.
Published: March 2024

Machine learning approaches are increasingly popular for monitoring and predicting vegetation health and activities. Satellite-based vegetation health indices such as Normalised Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) have been extensively utilized to monitor vegetation activities. These indices are quantitative assessments of the vegetation that indicate a monthly pattern. In this study, remotely sensed (Sentinel-2) and in situ (Tree Talker) data were used to extract NDVI and EVI values. Trend analysis was performed using Mann-Kendall (MK) test and Sen’s slope to understand the vegetation activities pattern. Four machine learning algorithms Linear and Polynomial Regression, Random Forest (RF) and Support Vector Regression (SVR) were tested for forecasting the vegetation indices. Results demonstrate good performance of the models in reproducing the spatiotemporal variability of NDVI and EVI, even under extreme conditions. These models show great potential for monitoring vegetation dynamics and as an alternate approach in predicting vegetation health.
Keywords: Trend Analysis, Machine Learning, Sentinel 2, Tree Talker.
Differential Tillage Practices in Agronomy Influence Soil Carbon Content, Nutrient Availability and Microbial Community Dynamics: Field to Genomics
Authors: Majumdar Arnab , Upadhyay Munish Kumar , Giri Biswajit , Srivastava Ashish Kumar , Roychowdhury Tarit
Published: March 2024

Globally, there is a dilemma in using tillage practice1 and here we establish that using tillage is beneficial for maintaining soil quality. Consecutive four seasonal rotations (two wintery and two monsoonal in two years) during rice cultivation in India have compared a tilled field (TF) to a non-tilled field (NTF). The novelty of our study lies in the combination of the alternate wetting-drying (AWD) cycle in this tillage/no-tillage practice2. Before the field trial started, we conducted a survey of literature and farmers to set the optimal degree of tillage, 5 cm from the top in this case. The analyzed parameters are soil pH, redox potential, conductivity, total soil organic carbon (SOC), labile carbon (LC) content, and microbial biomass (MB), followed by a thorough assessment of nutrients3,4 like total nitrogen (N), phosphorus (P), potassium (K), iron (Fe), calcium (Ca), magnesium (Mg), copper (Cu), zinc (Zn). Further, we used metagenomics and high throughput sequencing to define the total microbial community change5 during tillage and non-tillage practices. Using genomics, we found that genes responsible for nutrient modulation in soil were actively expressed under tilled soil in many of these microbial species. Clear differences in SOC and LC content, microbial biomass and nutrient bioavailability were found6 in TF and NTF by 9.87%, 13.69% and 14.25% respectively when AWD was applied (Figure 1). Nutrients were higher in TF due to the ‘Birch effect’, which enriched the soil and induced the microbial genus Nitrospira, Bacillus, Pseudomonas, Azospira, and Bradyrhizobium. These genera contribute significantly to nutrient modulation and availability. Gene ontology, KEGG Pathway and Panther Pathway analyses showed a higher gene expression and greater metabolic activities were maintained in TF-AWD microbes (Figure 2) resulting in better soil quality under tillage practice proving the benefit of surface tillage practice.1Mondal, S., et al., 2020. Land Degradation & Development, 31(5), pp.557-567. 2Majumdar, A., et al., 2020. Arsenic in Drinking Water and Food, pp.425-443. 3Wang, H., et al., 2020. Archives of Agronomy and Soil Science, 66(11), pp.1509-1519. 4Majumdar et al., 2023. Soil and Tillage Research, 232, p.105752 5Majumdar, A., et al., 2021. Journal of Hazardous Materials, 409, p.124443. 6Liu, X., et al., 2022. Soil and Tillage Research, 215, p.105188.Figure 1. Figure 2. 
Landslides along the Engineering Corridors in the Northeastern Margin of the Qinghai-Tibet Plateau: Comprehensive Inventory and Distribution Patterns
Authors: Zhang Jing , Yuan Renmao , Chen Jie
Published: March 2024

The Engineering Corridors (ECs) in the northeastern margin of the Qinghai-Tibet Plateau (NE-QTP) include sections of highways, railways, and pipelines that are constructed on permafrost terrain, seasonally frozen ground, and loess. Climate change, earthquakes, and human disturbance are accelerating the degradation of permafrost, causing loess failures, and developing slope instability that are leading to numerous freeze-thaw landslides (FTLs), loess landslides (LLs), and general landslides (GLs). These events often result in road cracks and infrastructure damage. However, few systematic investigations have been carried out in this area. To compile a comprehensive landslide inventory, this study utilizes visual interpretation to identify landslides in Gaofen-6 images (2 m) taken between 2021 and 2022, covering an area of 30×104 km2. Then, field investigations were conducted to validate and evaluate the inventory accuracy. We identified 11,914 landslides, including 1,095 FTLs, 7,930 LLs, and 2,889 GLs, while 10,825 of the landslides occurred within a 20 km range of the ECs. More specifically, FTLs are distributed in the boundary regions between permafrost and seasonal frozen ground. LLs and GLs have a dense cluster distribution along rivers. In addition, landslides are prone to develop on north-facing slopes, with steep slopes for LLs and GLs and gentle slopes for FTLs. Moreover, LLs and GLs occurred mainly at lower-medium elevations (1500-3000 m), while FTLs developed at higher elevations (3000-4000 m). Landslides primarily occur in regions that are covered with meadows, shrublands, and agricultural vegetation. Our inventory is helpful for in-depth research on landslides in the NE-QTP. It will also provide a significant and valuable dataset for quantifying the analysis of landslides along the ECs that are experiencing climate changes, strong earthquakes, and extensive human activities.
Higher-order Tides in the Variation of Post-sunset Meridional Winds and, consequently, OI 630.0 nm nightglow emissions over Low-latitudes
Authors: Saha Sovan , Pallamraju Duggirala , Kumar Sunil , Laskar Fazlul I. , Pedatella Nicholas M.
Published: March 2024

Airglow emissions act as a tracer of the altitudinal region of 100 km width centred around 250 km. Various dynamical processes such as neutral, electrodynamics, and atmospheric waves modulate the atmospheric parameters, such as temperature, density, etc., of the ionosphere-thermosphere system (ITS), which vary day-to-day, season, and solar flux as well. We have carried out investigations of ITS by measuring the OI 630.0 nm (redline) nightglow emissions over Gurushikhar, Mt. Abu (24.6°N, 72.7°E, 19°N Mag), a low-latitude location, using the High Throughput Imaging Echelle Spectrograph (HiTIES). On several occasions, a bell-shaped enhancement in these emissions has been noticed around 21 local time, following the typical monotonic decrement after sunset. The cause of this enhancement in redline emissions has been explored by investigating the equatorial electrodynamics and neutral winds. The meridional winds have been obtained by using two digisondes located at equatorial and low-latitude locations. Contrary to the conventional expectation of pre-reversal enhancement bringing additional plasma over the low-latitudes to cause such enhancement, the role of meridional winds has been demonstrated in our study. The poleward winds over the low-latitudes bring additional plasma down to the redline emission altitudes, resulting in the observed enhancement in emissions. The winds at these post-sunset hours are usually equatorward, and thus, this brings the question as to what is the cause for the reversal in wind during those times. We have analysed the winds, electron densities obtained from the global free-run model of Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (WACCM-X) data. It has been found that higher-order tides, such as quarter-diurnal tides, play an important role in causing a reversal in meridional winds from their usual equatorward to poleward direction. This clearly explains the root cause for the variation in meridional winds during the post-sunset hours as well as the reason why the post-sunset enhancements in OI 630.0 nm nightglow occur on one night and not the next, even though the electrodynamic forcing was similar on these two occasions. These new findings will be discussed.
Assessment of GPS-based accelerometry performance with adaptive filter settings
Authors: van den IJssel Jose , Siemes Christian , Visser Pieter
Published: March 2024

High-quality GPS observations from low Earth orbiting (LEO) satellites can be used to derive thermosphere densities along the satellite orbit. Such GPS-derived densities are currently computed operationally for all three Swarm satellites, in the framework of the Swarm Data, Innovation, and Science Cluster. Considering the increasing number of LEO satellites equipped with GPS receivers, this so-called GPS-based accelerometry approach offers great potential for improving thermosphere models and for studying the influence of solar and geomagnetic activity on the thermosphere.To better quantify the accuracy that can be obtained with this approach, we assess the performance using the GRACE mission as a test case. For this mission high quality accelerometer data are available, which we can use to validate our GPS-based results. In addition, the GRACE mission has experienced a large variation in density signals, which allows us to assess the performance under a large range of conditions.We present our GPS-based accelerometry processing strategy, which is based on a Kalman filter approach. The radiation pressure accelerations are accurately modelled and empirical accelerations capture the remaining aerodynamic signal. The empirical accelerations are modeled as Gauss-Markov processes defined by a steady-state variance, process noise and correlation time, which require careful tuning. This applies in particular to the setting of the process noise in the along-track direction, due to the large variations in the encountered aerodynamic signal. Best performance is obtained when the process noise setting is adapted to these variations. Using these adaptive filter settings, results are shown for periods with low, moderate, and high density. In a next step, we will implement the improved filter settings into our regular Swarm GPS-derived density processing chain.
Contribution of patchy reconnection to the ion to electron temperature ratio in the Earth’s magnetotail
Authors: Chen Chuxin , Wang Chih-Ping
Published: March 2024

The ion-to-electron temperature ratio is a good indicator of the processes involved in the plasma sheet. Observations have suggested that patchy reconnection and the resulting earthward bursty bulk flows (BBFs) transport may be involved in causing the lower temperature ratios at smaller radial distances during southward IMF periods. In this paper, we estimate theoretically how a patchy magnetic reconnection electric field can accelerate ions and electrons differently. If both ions and electrons are non-adiabatically accelerated only once within each reconnection, the temperature ratio would be preserved. However, when reconnection occurs closer to the Earth where magnetic field lines are shorter, particles mirrored back from the ionosphere can cross the reconnection region more than once within one reconnection; and electrons, moving faster than ions, can have more crossings than do ions, leading to electrons being accelerated more than ions. Thus as particles are transported from tail to the near-Earth by BBFs through multiple reconnection, electrons should be accelerated by the reconnection electric field more times than are ions, which can explain the lower temperature ratios observed closer to the Earth.
Contrasting responses of drought and floods to background aridity in a changing climate across global terrestrial ecosystems
Authors: Tabari Hossein
Published: March 2024

The aridity of a region plays a pivotal role in shaping a diverse range of hydrological processes, encompassing critical aspects such as the sensitivity of evaporation to variations in temperature and precipitation, water use efficiency, and the intricate interactions between precipitation, soil moisture, and evaporation. These processes, in turn, influence the response of hydrological extremes, such as drought and flood, to global warming. Understanding the impact of aridity on these extreme events in the context of changing climate conditions across global terrestrial ecosystems is essential for comprehending water availability and ecological resilience in different regions. This study investigates the relationships of changes in drought and flood intensities for the end of the twenty-first century with background aridity across global terrestrial ecosystems. Background aridity is quantified using an aridity index, calculated as the ratio between precipitation and evaporation. Drought is characterized by the standardized precipitation index (SPI), and flood by fitting a generalized extreme value distribution (GEV) to the annual maxima flow time series of the Inter-Sectoral Impact Model Intercomparison Project models. The results show opposite responses of drought and floods to background aridity under climate change across global terrestrial ecosystems. As aridity decreases from dry to wet regions, the intensification of flood events in the future is expected to increase. In contrast, drought intensification is more pronounced in dry and semi-dry regions. These findings hold significant implications for developing effective and region-specific water resource management policies to address hydrological extremes in a changing climate.
Observations of Electron Secondary Reconnection in Magnetic Reconnection Front
Authors: Chengming Liu
Published: March 2024

Magnetic reconnectio­n, a fundamental plasma process transforming magnetic field energy into particle energy, is ubiquitous in space and responsible for many explosive phenomena, such as solar flares and gamma ray bursts. Recent numerical theories have predicted that reconnection fronts far from the primary reconnection region can host secondary reconnection in three-dimensional scenarios, different from the conventional two-dimensional diagram where only one X-line stands to sustain reconnection. In this study, we provide direct observational evidence for ongoing secondary reconnection in the reconnection front, via using the unprecedently high-cadence data from NASA’s MMS mission. The secondary reconnection is identified by the presence of X-line, super-Alfvénic electron jet, and non-ideal energy dissipation. Different from the primary ion-electron reconnection, the secondary reconnection is electron-only, with its X-line quasi-perpendicular to the primary X-line. Hence reconnection, when evolving from local to global scales, becomes essentially three-dimensional with different patterns developed. These results provide crucial insights into understanding cross-scale energy transport driven by reconnection in space plasmas.