bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent offline land data assimilation results and future steps towards coupled DA at Meteo-France
Authors: Calvet Jean-Christophe , Bonan Bertrand , Xu Yiwen
Published: February 2023

Land data assimilation aims to monitor the evolution of soil and vegetation variables. These variables are driven by climatic conditions and by anthropogenic factors such as agricultural practices. Monitoring terrestrial surfaces involves a number of variables of the soil-plant system such as land cover, snow, surface albedo, soil water content and leaf area index. These variables can be monitored by integrating satellite observations into models. This process is called data assimilation. Integrating observations into land surface models is particularly important in changing climate conditions because environmental conditions and trends never experienced before are emerging. Because data assimilation is able to weight the information coming from contrasting sources of information and to account for uncertainties, it can produce an analysis of terrestrial variables that is the best possible estimation. In this work, data assimilation is implemented at a global scale by regularly updating the model state variables of the ISBA land surface model within the SURFEX modelling platform: the LDAS-Monde sequential assimilation approach. Model-state variable analysis is done for initializing weather forecast atmospheric models. Weather forecast relies on observations to a large extent because of the chaotic nature of the atmosphere. Land variables are not chaotic per se but rapid and complex processes impacting the land carbon budget such as forest management (thinning, deforestation, ...), forest fires and agricultural practices are not easily predictable with a good temporal precision. They cannot be monitored without integrating observations as soon as they are available. We focus on the assimilation of leaf area index (LAI), using land surface temperature (LST) for verification. We show that (1) analyzing LAI together with root-zone soil moisture is needed to monitor the impact of irrigation and heat waves on the vegetation, (2) LAI can be forecasted after properly initializing ISBA. This paves the way to more interactive assimilation of land variables into numerical weather forecast and seasonal forecast models, as well as in atmospheric chemistry models. 
COVID-19 Pandemic Hopeful Prospect: Air Quality Improvements over Indo-Gigantic Plain
Authors: Hina Saadia , Saleem Farhan , Ibrahim Muhammad
Published: February 2023

The COVID-19 pandemic has received enormous attention worldwide due to its environmental, and societal impacts. The present study highlights the spatio-temporal variations in air quality parameters (AOD, SO2, NO2, and O3) due to lockdown over the IGP, one of the world's most populated regions. The satellite retrievals of aerosol optical depth (AOD), sulfur dioxide (SO2), nitrogen dioxide (NO2), and Ozone (O3) were used to estimate the spatial-temporal extent of major air pollutants in the region during lock down period (March-May, 2020) in comparison to the pre-lockdown period (March-May 2015-2019) and post-lockdown (March-May, 2021) across the IGP. To provide more insight into the changes in air pollutants status, country and city scale percentage increase/decrease have also been calculated. Following strict lockdown implementation, reduction in anthropogenic activities led to a significant decline in AOD, SO2 and NO2, whereas a considerable increase in tropospheric O3 concentration has been noticed that in turns significantly improved the regional air quality. But these trends reversed as soon as the lockdown was relieved and human activities normalized.  Moreover, the comparative analysis among meteorological parameters and ambient air pollutants presented that meteorological factors were not the main reason for the dramatic reductions of pollutants in the atmosphere. The outcome of this study can be a reference to introduce new public policies for promoting adaptive socio-ecological models to understand the synergies and trade-offs between the reduced human interventions and the environmental health of cities systematically.
A hybrid MPM-CFD model for simulating earthquake-induced submarine landslides
Authors: Tran Quoc Anh
Published: February 2023

The purpose of this abstract is to describe a coupled CFD-MPM model that combines soil mechanics (saturated sediments) with fluid mechanics (seawater or air) as well as solid mechanics (structures) to consider interactions between soil, fluid, and structures. With this formulation, the Material Point Method, which models large deformations in porous media and structures in conjunction with the Implicit Continuous-fluid Eulerian Method, which models complex fluid flows, is combined to model large deformations in porous media and structures. The model has been validated through various benchmarks and then it is used to simulate submarine landslides due to earthquakes. It is shown that this model captures the complicated interactions between saturated sediment, seawater, and offshore structures. This allows us to estimate the impact of potential submarine landslides on offshore structures using the model. 
Vegetation carbon input moderates the effects of climate change on topsoil organic carbon in China
Authors: Cen Yunfeng , Gao Zhaoliang , Lou Yongcai , Liu Wenbo , Zhang Xun
Published: February 2023

Climate change affects soil organic carbon (SOC) and contributes to the uncertainty of terrestrial carbon sinks in the global carbon budget. With changes in vegetation growth and the regulation of its carbon input, the feedback of topsoil SOC to climate change is likely to become more complex at broad geographical scales. China has experienced noticeable changes in climate and surface greening in recent decades, and these changes have effectively influenced the dynamics of topsoil SOC. However, the potential role of vegetation carbon inputs in regulating and buffering climate change impacts on SOC in the context of current ecological restoration is still poorly understood. Therefore, to solve these problems, on the basis of the long-term satellite remote sensing data from 2000 to 2019, multiple linear regression and pathway analyses to investigate the dominant role of different climate factors and vegetation net primary productivity (NPP) on topsoil SOC changes in China, and further reveal the potential role of vegetation carbon inputs in regulating and buffering the effects of climate change on topsoil SOC. The results show that the overall trend of increase in topsoil SOC in China from 2000 to 2019 is significant (P < 0.05), and most regions show a good development trend in the future, except for some areas in the Central South, East, and Northeast regions, where a risk of degradation exists. Relative to climate change, the dominant areas of NPP impact on topsoil SOC in China occupy a considerable proportion, especially in the North, Northwest, and Central South regions, with area proportions of 68.15%, 49.52%, and 47.99%, respectively. Importantly, the indirect positive impacts of climate change on changes in topsoil SOC in China through vegetation carbon input offset the direct negative impacts in most areas. That is, over the past 20 years, increases in temperature and precipitation have led to decreases in topsoil SOC in most of China, whereas the ultimate net effect has been to increase topsoil SOC by promoting vegetation carbon input, particularly in the Loess Plateau region. Our study demonstrates that considering only the effects of climate change on SOC, while ignoring possible changes in carbon transfer from plants to soils, largely reduces the reliability of assessments of SOC stocks and their changes. These results have important implications for enhanced prediction of future SOC changes and provide references for terrestrial carbon sinks management strategies in the context of response to climate change.Keywords: Topsoil organic carbon, Climate change, vegetation carbon input, Pathway analysis, China.
Kinematic reconstruction of the Tibetan-Himalayan orogen since the Cretaceous
Authors: Schouten Thomas , Boschman Lydian , Li Shihu , Willett Sean
Published: February 2023

Knowledge of the kinematic evolution of the Tibetan-Himalayan orogenic system is paramount to understand the geodynamics, development of topography and climate changes in a region that contains some of the world’s most important biodiversity hotspots. The tectonic framework however has been controversial with multiple models proposed. The Late Cretaceous to Palaeogene anomalously high velocity of the Indian plate has been hypothesised to be caused by two north-dipping subduction zones, and the arrival of the continental margin of the Indian plate is considered to have triggered both the slowdown of the Indian plate as well as a phase of overriding plate deformation. Here, we present a quantitative reconstruction of the tectonic evolution of this orogen with particular focus on deformation of the upper plate, which is responsible for the topographic evolution. We build our reconstruction in GPlates using a systematic reconstruction protocol. To this end, we review the geology and orogenic architecture of the Tibetan-Himalayan orogen. We present a single reconstruction for the evolution of the overriding Eurasian plate. We show that this reconstruction is consistent with palaeomagnetic and seismic tomographic data. We then reconstruct three alternative tectonic and palaeogeographic scenarios for the lower plate based on data from the Himalaya, Burma and Kohistan, whose sparsity permits multiple interpretations. Whereas one of our scenarios is consistent with the hypothesis that Late Cretaceous acceleration of the Indian plate was driven by two subduction zones, we demonstrate that it does not explain early Eocene acceleration. Moreover, the notion that the arrival of the Indian continental margin triggers a phase of overriding plate deformation is supported by only by one of our scenarios, in which this occurs at 25 Ma. None of our scenarios however support the hypothesis that the arrival of the Indian continental margin corresponds to the middle Eocene slowdown of the Indian plate. Finally, our reconstructions provide the platform for future work to include reconstructions of palaeotopography and palaeoclimate to identify the environmental changes that may have driven the development of regional biodiversity hotspots.
Effects of the Lunar Regolith Structure and of the Solar Wind Properties on the Backscattered Energetic Neutral Atoms Flux
Authors: Verkercke Sébastien , Chaufray Jean-Yves , Leblanc François , Bringa Eduardo , Tramontina Diego , Morrissey Liam , Woodson Adam
Published: February 2023

Airless planetary bodies’ surfaces, such as the Moon’s or Mercury’s, are composed of porous regoliths which interact directly with the impinging solar wind. In the case of the Moon, this incoming flux of solar protons has been observed to be partially neutralized and backscattered as Energetic Neutral Atoms (ENA) with reflection coefficients believed to be ranging between ⁓0.1 and 0.2 depending on the study and/or the measurement. Such a large range of reflection coefficients reflects the diversity in the regolith’s interactions with the solar wind and underlines the lack of understanding of the lunar regolith and its influence on the particles impacting it.The ENA flux is thought to depend on the structure of the upper regolith layer and the solar wind characteristics. By using a model combining a Monte Carlo approach to describe a solar proton’s journey through the lunar surface, with molecular dynamics to characterize its interactions with the regolith’s grains, we highlighted key parameters which influence the backscattered ENA flux and analyzed their roles in these interactions. To describe the structure of the lunar regolith we used the open-source code LAMMPS Molecular Dynamics Simulator, which allows a realistic description of grain-on-grain contacts using a Johnson-Kendall-Roberts (JKR) contact model. The porosity of the modeled regolith is shown to be dictated by the surface energy of the grains. By considering silicate grains and a realistic range of surface energy for this material, we studied regoliths’ porosities ranging from ~0.5 to 0.85. This work showed that a large porosity favors deeper penetration of the protons inside the regolith, which increases the number of collisions, and thus the energy lost by the impinging protons and their absorption. By accounting for particular directions of observation with respect to the solar wind direction, we showed that the angular distribution of the backscattered ENA is anisotropic. We here used IBEX observations and its characteristic 90° observation angle as a demonstration of the influence of this anisotropy. We finally analyzed the effects of both the energy distribution of the hydrogen atoms after a collision with a grain and the solar wind properties on the ENA energy flux spectrum shape. The modelled spectrum was also compared to the observations of Chandrayaan-1. This work aims for a better understanding of the interactions ongoing at this interface and intents to look into the possibility to deduce information on the surface structure solely from ENA flux measurements.
Enriching radar scatterer annotation towards SAR benchmark data creation
Authors: Chang Ling , Kulshrestha Anurag , Zhang Bin , Zhang Xu
Published: February 2023

SAR imagery has been successfully employed for various machine/deep learning applications. CNN based land use land cover classification, and RNN based time series modelling are two examples. It is reported that the unavailability of extensive SAR benchmark data limits the applicability of using SAR data for machine/deep learning applications and the quality of the result. To address this, we attempt to develop methods to enrich the annotation of radar scatterers in SAR images. Particularly, when SAR images have information on multi-polarimetric channels, and additional topographic measurements are available, the annotation can include not only geometric features, but also physical and land-use features of radar scatterers. This study 1) uses a standard time series InSAR approach to obtain geometric features such as geo-position dynamics of radar scatterers; 2) utilizes a Random Forest classifier to categorize physical features of radar scatterers including surface, low, high volume and double bounce scattering mechanisms; and 3) assigns land-use features to radar scatterers with the help of external topographic measurements. We demonstrated our methods by using thirty co-polarimetric SAR PAZ data, and TOP10NL topographic base map, covering the province of Friesland, the Netherlands. In the end these annotated radar scatterers can be in the registry of SAR benchmark dataset.   
A coupled hydrodynamic-biogeochemical model for the prediction of mine pit lake water quality
Authors: Zarrinderakht Maryam , Salvador Silvano , Martin Alan
Published: February 2023

Pit lakes are a common feature of the post-closure landscape at mine sites where mining voids are allowed to fill with surface runoff, direct precipitation, and groundwater. Pit lakes also commonly serve as focal points for post-closure water management, often serving as a receptacle for various mining-related drainages and the final point of discharge for mine effluents. Therefore, an accurate and acceptable numerical model capable of predicting pit lake water balance, mixing characteristics, and water quality is needed to support post-closure management. In this paper, a coupled hydrodynamic-biogeochemical model (PitMod) for water quality prediction is described. The model, described in Crusius et al. (2002) and Dunbar (2013), simulates the physical and geochemical evolution of pit lakes over pit filling times ranging from monthly to century time scales. Within PitMod, the pit lake is approximated based on a one-dimensional, horizontally averaged vertical layer scheme. PitMod calculates the time-dependent vertical distribution of physical and geochemical pit lake properties, including temperature, salinity, conductivity, and dissolved oxygen. In this regard, the physical component of PitMod considers the effects of pit morphology, climate data, multiple surface and sub-surface (groundwater) inflows/outflows, precipitation/evaporation, surface ice formation/melting, vertical mixing due to surface wind stress, convective circulation, and turbulent mixing. The geochemical portion of PitMod utilizes a customized version of PHREEQC, capable of a wide variety of aqueous geochemical calculations, including speciation, saturation index calculations, mineral equilibria, surface complexation (adsorption) reactions, ion exchange, and redox processes. The model can also incorporate predictions of dissolved metal scavenging by biogenic particles in response to lake primary production.PitMod, which has been applied at over 50 mine projects since 2002, incorporates physical processes like those found in other lake models such as DYRESM (Imerito, 2007), and has been validated against field observations. However, unlike DYRESM, PitMod offers the advantage of being able to incorporate various non-conservative geochemical and biological processes that are relevant to predictions of long-term water quality.
The Magnetospheric Driver of the Westward Traveling Surge: Plasma-Sheet Bubble Injections
Authors: Yang Jian , Wei Dong , Zhang Fei , Wang Wenrui , Sun Weiqin , Cui Jun , Angelopoulos Vassilis
Published: February 2023

One of the most notable manifestations of auroral substorms is the westward traveling surge (WTS). Understanding the dynamics of the substorm depends on how WTS forms and develops. Our simulation of the Rice Convection Model shows that the injection of a single plasma-sheet bubble can lead to the creation of WTS. It is worthwhile to look into how successive bubble injections will impact the characteristics of WTS since the earthward-propagating bubbles inject consistently from the magnetotail during substorms. In this investigation, we discover a good correlation between the repeated WTSs seen by all-sky imagers and the ongoing plasma-sheet bubble injections picked up by the THEMIS satellite in the magnetosphere. Numerical simulations show that multiple injections of plasma-sheet bubbles cause successive surges in the ionosphere as well as to confirm that the bubble injections cause a strong upward, Region-1 field-aligned current to flow out of the ionosphere, which is what gives the auroral structure its distinctive appearance. Our findings are intriguing in that they show that the calculated WTS drift speeds are positively correlated with the increase in BZ in the magnetosphere.
Evidence for Hemispheric Spectral Albedo Inequality
Authors: Collins William , Feldman Daniel
Published: February 2023

In this study, we examine whether the interhemispheric symmetry observedin broadband shortwave albedos also applies to thehemispheric-mean visible and near-infrared albedos.  Whileseveral recent exploratory studies have examined this questionusing climate models, we explore thisquestion using direct observations of the visible andnear-infrared albedos collected by the Nimbus-7 satellite. Thisstudy builds upon earlier intercomparisons of cloud spectralalbedos from Nimbus-7 and from climate models using the samecombinations of Nimbus-7 measurements used here (Collins, 1998).We find that the hemispheric-mean spectral partitioning of albedo isconsistently and statistically significantly different between the twohemispheres.  Consistent with prior studies, the origin of thesedifferences is due to interhemispheric differences in cloud cover.Over oceans, the regional daily-mean differences between visible andnear-IR albedos are closely correlated with cloud amount.  Therelative differences are maximized for clear-sky conditions andminimized for overcast conditions.Background: The shortwave broadband albedo is a weighted sum of the albedosin the visible and near-infrared bands.  Under condensate-freeconditions, the interactions of solar insolation in these bandswith the atmosphere and surface are quite different.  To anexcellent approximation, the condensate-free atmosphere is aconservative Rayleigh-scattering medium in the visible.  Solarradiation that is not reflected back to space is, to leadingorder, transmitted to the surface.  In the near-infrared, theinteractions of sunlight with the atmosphere are dominated byabsorption, primarily with water vapor.  Additional absorption iscontributed by well-mixed greenhouse gases, oxygen, and othergaseous constituents. The solar radiationreaching the surface has therefore been reduced both byreflection to space (from atmospheric condensates and the surfacealbedo) and by absorption in the atmosphere. Hence, the relativepartitioning of net TOA insolation between the visible andnear-infrared bands will affect the relative partitioning betweenatmospheric absorption and transmission to the surface. 
Characteristics and evolution of strike-slip faults in a stable cratonic block
Authors: Wang Zhao , Huang Lei
Published: February 2023

The deformation pattern in the interior of cratonic blocks has critical implications for regional structural evolution but still remains an unresolved question. The southwestern Ordos Basin is at the convergence of multiple blocks, leading to intense and complex tectonic stress at this location. However, how the interior of the Ordos block responds to the complex stress field around it is still elusive. This study analyzes the characteristics and evolutionary history of faults in the southwestern part of the inner Ordos Basin using 3D seismic data. Three dominant sets of faults trending NW, NEE, and N–S have developed in the study area. All three sets of faults have subvertical dip angles and straight fault traces and structures that are common in such fault zones, such as flower structures and en-echelon and horsetail arrangements (all indicating strike-slip movement) are present. Structural deformation varies from the center to the periphery of the Ordos block. All three sets of fault systems exhibit small displacements. The polarity of the strike-slip changed in different periods, reflecting the transformation of the stress field in the southwestern Ordos Basin. This illustrates that the formation of cratonic faults is controlled by the regional stress field, while the related strain pattern in the interior of the cratonic block is very different from the deformation around its periphery. These characteristics also demonstrate the special nature of cratonic fault deformation.
A method for hydrometric data rescue: Challenges and solutions for working with archival data
Authors: de Smeth Kate , Comer Joanne , Murphy Conor
Published: February 2023

The availability of long, quality-controlled discharge records is crucial for hydrological research that supports water resource planning, extreme flow estimation and investigations into the effects of climate variability and anthropogenic disturbances on river flow regimes. Archival hydrometric data sources (e.g. historical staff gauge readings, autographic chart data, and historical flow measurements) provide an invaluable opportunity to extend available discharge records, however a process of transcription and digitisation known as data rescue is required to make them available to the public.In their 2014 ‘Guidelines for Hydrological Data Rescue’, the World Meteorological Organisation (WMO) provided generalised guidance to encourage Members to engage in data rescue activities to mitigate the very real risk of data loss due to physical record deterioration. Yet few published examples exist. Our work to extend discharge records for eight river stations across Ireland provides a detailed applied example that expands the methodology outlined in the WMO guidance by addressing two core challenges encountered: i) how to collect reliable data in the face of quality issues specific to historical autographic chart data; and ii) how to effectively communicate the level of confidence in the rescued data to the end user. We present procedures for data processing, quality assurance using quality codes, and compilation of key metadata and information about each measurement station. Lessons learnt are summarised in a generalised workflow and presented to the hydrology community to assist other hydrometric data rescue efforts.
Harmonic dynamic of the Earth (C)
Authors: xin xianwu
Published: February 2023

Abstract.In this paper, the physical simulation of the meridional movement of the crust is carried out by experiments; According to the geometry relationship between the peak point of the earth's crust and the earth's rotation under the action of tidal force, a mathematical model of the meridional movement of the crust is established. The velocity field of global continental drift is calculated using the meridional motion equation derived from the model, and is compared with the measured value of ITRF2000. It can be seen from the comparison between adjacent calculated values and measured values that the magnitude and direction of the two velocity vectors are basically the same. It follows that the meridional movement of the crust is a reciprocating harmonic movement. The continent and the ocean floor, under the action of the reciprocating harmonic dynamic process, float back and forth along the meridian. Due to the difference between forward and reverse resistance, there will be fixed displacement in one direction. So far, the series of papers on "Harmonic dynamic of the Earth (C)" have completed the kinematic analysis, driving force calculation, energy conversion calculation and verification of observation results of the earth harmonic dynamic process. Velocity field, driving force and energy consumption are the three basic indicators of mechanical power process. Many possibilities of geophysical evolution mechanism determine that the study of its main dynamic mechanism is inseparable from the detailed discussion of the three major indicators.
Metal oxide semiconductor (MOS) sensors to measure methane in aquatic ecosystems. An eficient DIY low cost application.
Authors: Butturini Andrea , Fonollosa Jordi
Published: February 2023

Monitoring dissolved methane in aquatic ecosystems contributes significantly to advancing our understanding of the carbon cycle in these habitats and capturing their impact on methane emissions. Low-cost metal oxide semiconductors (MOS) gas sensors are becoming an increasingly attractive tool to perform such measurements, especially at the air-water interface. However, the performance of MOS sensors in aquatic environmental sciences has come under scrutiny because of their cross-sensitivity to temperature, moisture, and sulfide interference. In this study, we evaluated the performance and limitations of a MOS methane sensor when measuring dissolved methane in waters. A MOS sensor was encapsulated in a hydrophobic ePTFE membrane to impede contact with water but allow gas perfusion. Therefore, the membrane enabled us to submerge the sensor in water and overcome cross-sensitivity to humidity. A simple portable, low-energy, flow-through cell system was assembled that included an encapsulated MOS sensor and a temperature sensor. Waters (with or without methane) were injected into the flow cell at a constant rate by a peristaltic pump. The signals from the two sensors were recorded continuously with a cost-efficient Arduino UNO microcontroller.. Our experiments revealed that the lower limit of the sensor was in the range of 0.1-0.2 uM and that it provided a stable response at water temperatures in the range of 18.5-28oC. More information at Butturini, A., & Fonollosa, J. (2022). Use of metal oxide semiconductor sensors to measure methane in aquatic ecosystems in the presence of cross‐interfering compounds. Limnology and Oceanography: Methods, 20(11), 710-720.
Impact of urbanization and climate change on spatial patterns of precipitation
Authors: Koukoula Marika , Torelló-Sentelles Herminia , Peleg Nadav
Published: February 2023

More than half of the world’s population now resides in cities and the amount of urban population is expected to further increase during the coming decades. Urbanization and the associated changes in land use/land cover can have a notable impact on the climate at local and regional scales. Specifically, several studies recently concluded that urbanization can modify the temporal and spatial properties of precipitation. On top of that, global warming is expected to enhance the magnitude and frequency of short-duration heavy precipitation, with consequential effects on the severity and frequency of urban pluvial flood events. Therefore, improving our understanding of the separate and combined effects of urbanization and climate change on short-duration precipitation is imperative for flood risk assessments and planning of future cities. To this end, we investigate the impact of climate change and urbanization on the space-time properties of precipitation by conducting current and future simulation scenarios over cities with different climates using the Weather Research and Forecasting (WRF) physically-based climate model. The results of this study elucidate the important role of urban land cover on the spatial stucture of precipitation under a changing climate.
Towards the optimisation of altimetry corrections for improved ocean tide modelling
Authors: Hart-Davis Michael , Ray Richard , Bordas Diaz Loreto , Schwatke Christian , Dettmering Denise , Seitz Florian
Published: February 2023

 Ocean tide models are created for a variety of applications ranging from serving as an altimetry correction to being applied as numerical model boundary forcings. DGFI-TUM’s Empirical Ocean Tide (EOT) and NASA's Goddard Ocean Tide (GOT) models are derived based on sea-level anomalies (SLA) from multi-mission satellite altimetry. All SLA measurements are corrected for geophysical effects, which means that the estimations of tides are reliant on the accuracy of these respective correction models. Within these corrections, tidal signals or frequencies that align closely with those of tides may be present which have clear downstream implications on the derivation of ocean tides from along-track satellite altimetry. In this study, the two different ocean tide models have been used as they utilise different techniques for tidal estimations but both are dependent on the chosen altimetric corrections. In the global EOT20 model, altimetric corrections played an important role in improving the accuracy of the model in the coastal region. However, these coastal optimised corrections may be influencing the open ocean performance of the model. This has meant that further investigations should take place to describe the best set of altimetry corrections to optimise the accuracy of tide estimations made by the EOT model in all regions. Additionally, several versions of the GOT model have been developed to contrast the influences of the different corrections both for the open ocean and coastal regions. In this presentation, the impact of different geophysical corrections (e.g. ionospheric, internal tide and mesoscale) are presented with the aim to conclude on the optimal set-up of these corrections for empirical tide models. Results here are shown in different experiments that include assessing the impacts of ocean tide estimations on both along-track as well as modelled estimations.
NASAaccess – earth observation data tool
Authors: Mohammed Ibrahim , Romero Giovanni , Bolten John , Nelson Jim
Published: February 2023

NASA has launched a new initiative; the Open-Source Initiative (OSSI) to enable and support science towards openness. The OSSI new initiative supports open-source software development and dissemination. This presentation highlights an open-source platform (i.e., NASAaccess) for accessing, reformatting, and presenting quantitative remote sensing earth observation data products. The main objective of developing the NASAaccess platform is to facilitate exploration, modeling and understanding of the data for scientists, stakeholders, and concerned citizens aligning with the new OSSI initiative goals. NASAaccess platform is available with an open-source software packages (i.e., R and python libraries), and an interactive format web-based environmental modeling application for earth observation data. NASAaccess software program is also linked to various downscaled climate change data products processed by NASA. The NASAaccess web application development and hosting environment is based on Tethys Platform (Swain et al., 2016). NASAaccess current capabilities (v.3.3.0) covers various NASA datasets and products that include the Global Precipitation Measurement (GPM) data products, the Global Land Data Assimilation System (GLDAS) land surface states and fluxes, and the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP) CMIP5 & CMIP6 climate change dataset products. NASAaccess installation instructions and documentations along with tutorial materials are available at Open Science Framework repository ‘NASAaccess Home’ (doi:10.17605/OSF.IO/CTJ2K).
Evaluating Machine Learning Approach for Regional Flood Frequency Analysis in Data-sparse Regions
Authors: Mangukiya Nikunj K. , Sharma Ashutosh
Published: February 2023

Accurate flood frequency analysis is essential for developing effective flood management strategies and designing flood protection infrastructure, but it is challenging due to the complex, nonlinear hydrological system. In regional flood frequency analysis (RFFA), the flood quantiles at ungauged sites can be estimated by establishing a relationship between interdependent physio-meteorological variables and observed flood quantiles at gauge sites in the region. However, this regional approach implies a loss of information due to the prior aggregation of hydrological data at gauged locations and can be difficult for data-sparse regions due to limited data. In this study, we evaluated an alternate approach or path for RFFA in two case studies: a data-sparse region in India and a data-dense region in the USA. In this approach, daily streamflow is predicted first using a deep learning-based hydrological model, and then flood quantiles are estimated from the predicted daily streamflow using statistical methods. We compared the results obtained using this alternate approach to those from the traditional RFFA technique, which used the Random Forest (RF) and eXtreme Gradient Boosting (XGB) algorithms to model the nonlinear relationship between flood quantiles and relevant physio-meteorological predictor variables such as meteorological forcings, topography, land use, and soil properties. The results showed that the alternate approach produces more reliable results with the least mean absolute error and higher coefficient of determination in the data-sparse region. In the data-dense region, both traditional and alternate approaches produced comparable results. However, the alternate approach has the advantage of being flexible and providing the complete time series of daily flow at the ungauged location, which can be used to estimate other flow characteristics, develop flow duration curves, or estimate flood quantiles of any return period without creating a separate traditional RFFA model. This study shows that the alternate approach can provide accurate flood frequency estimates in data-sparse regions, offering a promising solution for flood management in these areas.
New Compound Extreme Event Indicators for Detecting and Tracking Weather and Climate Extremes under Climate Change
Authors: Kirchengast Gottfried , Haas Stephanie , Fuchsberger Jürgen
Published: February 2023

Weather and climate extreme indicators are useful tools in the assessment and quantification of climate change induced alterations of key climate variables and extreme events. However, capturing both the main change aspects and the total extremity of such extreme events remains a challenging task.Climate change can affect multiple characteristics of weather and climate extremes. Most indices, such as annual maximum temperature or number of hot days, focus on only one aspect of extreme events. While annual maximum temperature aims at describing the magnitude, the number of hot days is used for assessing the frequency of an extreme. The consideration of only one characteristic is a common limitation of such metrics. Since the total severity of extremes is the result of a combination of frequency, duration, magnitude and areal extent changes, however, the extremity is more than the sum of these parts and compound indices are hence required to fully capture the overall change.Here we introduce Threshold-Exceedance-Amount (TEA) indicators as a new class of metrics that capture changes in event frequency, duration, magnitude, and spatial extent both in isolation and in total. Using a high-percentile-based threshold in a key climate variable that describes extreme magnitudes, the TEA metrics work in a cascaded manner up to expressing the total extremity of events, optionally also as an amplification vs. a suitable reference period.Besides a detailed definition, we also show example applications for heat and heavy precipitation extremes (using daily maximum temperature and precipitation amount as key variables), from local- to country-scale regions in Austria to resolving and covering the entire European land region. We discuss amplifications and climate change detection vs. the 1961-1990 reference period and natural variability.The TEA indicators are applicable for different types of extremes also beyond temperature and precipitation, making them a useful and versatile tool for the climate change-related investigation of extreme events and their impacts on natural and socio-economic systems, while also helping to fulfill the need for compound indices.
Fungal pairwise interactions shift from positive to negative under warming stress
Authors: Rineau Francois , Reyns Wouter , Carpentier Camille , Van Der Plas Fons , Bardgett Richard , Beenaerts Natalie , De Laender Frederik
Published: February 2023

The impact of climate change on soil processes depends on how abiotic stressors (drought, flood, heatwave…) affect soil species physiology directly, but also indirectly through their interactions. A number of different theoretical frameworks have been designed to conceptualize the latter. The most widely used is the stress gradient hypothesis, which states that facilitation should be more common in stressful environments. However, these interactions are notoriously difficult to investigate in soils, because of the difficulty to isolate low competitor species and of the sheer number of species in soil, and therefore of interactions to test experimentally. Consequently, this topic has been traditionally approached through network analyses, that are based on frequency of co-occurrences, but has its own flaws.In this paper, we used a combination of isolation methods to recover the widest possible range of soil fungi with randomized co-cultivation tests to cover as many interactions as possible. This way, we investigated how multiple pairwise competitive interactions were affected by abiotic stress (high temperature, low water availability).In absence of abiotic stress, the presence of another species mostly affected growth positively, demonstrating facilitation among soil fungal species under benign conditions. In presence of temperature stress, either alone or combined with water stress, these positive effects became negative, contradicting the stress gradient hypothesis. We did not find the interaction outcomes to be predictable by some of the trait data we investigated, such as abiotic stress tolerance or intrinsic growth rate.Overall, our results demonstrate that in a very simplified but controlled system, climate change shifts the interaction types from mostly facilitative to mostly negative. We discuss further potential implications in the presentation.
Hydrogeological proxies of urban weathered hard rock aquifers in Central Africa: Contribution for a sustainable water management and supply in high populated city
Authors: Fongoh Enoh Jeanot , Celle Helene , Nlend Bertil , Ngo Boum-Nkot Suzanne , Ako Ako Andrew , Huneau Frederic , Caillon Nicolas , Ntamak-Nida Marie Joseph
Published: February 2023

Shallow groundwater resources, especially in hard rock environment, constitute an important part of urban water supply in developing countries, appropriate to the low level of economic development. However, increasing urban population and dependence on shallow groundwater systems make it imperative to evaluate the availability and the contamination of these resources, and define new strategies of water exploitation taking into accounts these findings and constrains. This study has been carried out on the shallow groundwaters of Yaounde, central Africa. Based on head slug-in tests, chemical and isotope analyses, we demonstrate the importance of geomorphological and geological settings that constrain hydrogeology, urban occupation and therefore, water exploitation and contamination.  Slug test results show spatial variability of well recovery rates with higher values recorded in the valleys compare to the hills, presenting saturated hydraulic conductivity of 10-6-10-8 m/s. Groundwater evolves from recharge zone as Ca-HCO3 in the hillside lateritic system to discharge zone in the slope/valley colluvium/alluvium system as NaK-NO3. The groundwater composition dominated by silicates/water interaction in the hillside lateritic system, and anthropogenic processes in the slopes and valleys. δ15N and δ18O of nitrates indicates that nitrate pollution of groundwater is mainly from sewage and human waste. Shallow groundwater in the hillside/new urban district and to a lesser extent slopes should therefore be protected and prioritised for usability and sustainability of the resources while ensuring the abstraction of the deeper part of the shallow aquifer in the valley/central districts due to the presence of denitrification. The proposed conceptual scheme for Yaounde can then be used as a guide in the development, exploitation and management of local wells in hard rocks system of Africa.
Seismic Signal Denoising with Attention U-Net
Authors: Ertuncay Deniz , Fornasari Simone Francesco , Costa Giovanni
Published: February 2023

Seismic stations record superpositions of the seismic signals generated by all kinds of seismic sources. In earthquake seismology, seismic noise sources can be natural events such as wind or anthropogenic events such as cars. In this study, we developed a machine learning (ML) based algorithm to remove the noise from earthquake data. This is important since the information related with the features of the seismic event may be overlapped by the noise. The presence of noise in the recordings can affect the performance of the seismic network, lowering its sensibility and increasing the magnitude of completeness of the seismic catalogue. To train ML model, 10000 thousand earthquake records with relatively low signal to noise ratio (SNR) are selected and contaminated by 25 noise records that are magnified up to 50% of peak amplitude of the earthquake signal and frequency content of those signals are stored as three component traces. The architecture used consists of an Attention U-Net, i.e. an encoder-decoder model using an attention gate within the skip connections: the encoder maps samples from input space (the waveform STFTs) to a latent space while the decoder maps the latent space to the output space (the signal-noise mask). Skip connections are introduced to recover, from previous layers, fine details lost in the encoding-decoding process. Attention gates identify salient regions and prune inputs to preserve only the ones relevant to the specific task. The use of attention gates in skip connections allows to pass "fine-detailed" information to high levels of the decoder that the model itself considers useful to the waveform segmentation. Trained model is tested with a new set of data to understand its capabilities. It is found that trained model can significantly improve the SNR of noise signals with respect to standard filtering methods. Hence, it can be considered as a strong candidate for seismic data filtering method. 
The role of dispersal limitation in the post-glacial forest expansion of southern and central Europe
Authors: Zani Deborah , Lischke Heike , Lehsten Veiko
Published: February 2023

The global vegetation cover underwent strong changes during the past glacial cycle. These have been driven by climatic fluctuations but also by spatiotemporal vegetation dynamics, including migration to new climatologically suitable areas and interactions with other species. However, how much migration lag contributed to the vegetation change after the Last Glacial Maximum (LGM) is often not clear. We used the newly-implemented model LPJ-GM 2.0 to simulate the vegetation change of southern and central Europe from the end of the LGM (18.5 ka) to the preindustrial era (1.5 ka). The model couples a migration module to the dynamic global vegetation model LPJ-GUESS, thus allowing species to migrate simultaneously while interacting with each other. We compared two dispersal settings (free dispersal and dispersal limitation) against pollen data to test the reliability of the migration module to provide realistic paleo-vegetation reconstructions for biome and species distributions. Furthermore, we calculated range shifts of the leading edges and centroids to detect potential species-specific migration lags and range filling delays across simulation time. Our results show that the setting with dispersal limitation is better at capturing the initial post-glacial expansion of non-boreal forests in southern and central Europe than the scenario assuming free dispersal. Range shift analysis shows significant migration lags for most tree species at times of sudden temperature rise (start of the Bølling–Allerød warming event and following the Younger Dryas). Overall, our study suggests that it is necessary to include migration processes when simulating vegetation range expansion under rapid climate change, with implications for future vegetation projections.
Earthquake relocation at intermediate depths using automatically detected teleseismic depth phases
Authors: Blackwell Alice , Craig Timothy , Rost Sebastian
Published: February 2023

Intermediate-depth earthquakes, accommodating intra-slab deformation, typically occur within subduction zone settings at depths between 40-350 km. High magnitude events can pose a significant hazard to populations, and increase the risk of damaged infrastructure, injury and fatality. Despite improvements in recorded seismic data density and quality, the distribution and controls of these events remain poorly understood. Here, we demonstrate an automatic method for the detection of depth phases from these intermediate-depth earthquakes using seismic array data, with the aim of determining their hypocentral depths and locations to a greater level of accuracy. These will allow new comparisons and insights into the governing controls on the distribution of earthquakes in subducted slabs.Depth phases (near-source surface reflections, e.g. pP and sP) are crucial for the accurate determination of earthquake source depth using global seismic data, however, they suffer from poor signal-to-noise ratios in the P-wave coda. This reduces the ability to systematically measure differential travel times to the corresponding direct arrival, particularly for the frequent lower-magnitude seismicity which highlights considerable seismogenic regions of the subducted slabs. To address this limitation, we have developed an automated approach to group globally distributed stations at teleseismic distances into sub-arrays, before optimising and applying phase-weighted beamforming techniques to each sub-array. Resultant vespagrams allow automated picking algorithms to determine differential arrival times between the depth phases (pP, sP) and their corresponding direct P arrival. These are subsequently used to invert for a new hypocentre location. We demonstrate this method by relocating intermediate-depth events associated with the Peruvian flat slab region of the subducting Nazca plate.