bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulating and predicting soil water content by combining soil water balance calculations, weather forecasts and soil sensors with inverse modelling for optimal irrigation advice: A case study in Flanders, 2022
Authors: Hendrickx Marit , Diels Jan , Vanderborght Jan , Janssens Pieter
Published: February 2023

In Flanders, a cumulative precipitation deficit of no less than 330 mm was calculated during the growing season of 2022 (April - September) (Soil Service of Belgium). This high precipitation deficit reflects the importance and need of additional water supply to meet the water demand and the yield potential of the crop. However, this additional water must be administered as efficiently as possible to avoid water waste, while maximizing yields. For decades, the Soil Service of Belgium already offers paid irrigation advice based on simulations with a soil water balance model calibrated with manual soil samples, and weather data, while considering weather predictions separately. With the rise of affordable, autonomous sensors and IoT (Internet-of-Things) technology, it is possible to monitor the soil moisture in a field online and in real time. The use of these sensors offers opportunities such as data accessibility, model calibration, and optimization of irrigation advice.Soil moisture model simulations and forecasts alone may be less accurate than in situ soil moisture measurements. However, soil moisture forecasts make it possible to anticipate drought or precipitation forecasts, which makes it easier to plan irrigation in advance. Sensor data alone fall short in this respect, as sensors only provide data on the previous and current soil moisture content, but do not provide information on future soil moisture development. Both approaches can be combined by calibrating the model with sensor data via inverse modelling. In this study, DREAM is used as inverse modelling approach to estimate model parameters, including soil and crop growth parameters, as well as their uncertainty. These parameter distributions result in soil moisture simulations, and, when inserting weather forecasts, predictions, along with their uncertainty. The uncertainty of the calibrated model simulations can be used to determine the probability of the soil moisture dropping below the critical water stress threshold.When this combined approach is compared to the irrigation advice based on a model alone, the soil moisture is simulated and predicted more accurately, resulting in a more efficient water application, while the crop experiences less stress. In the dry growing season of 2022, for example, a celery trial in Flanders (Research Station for Vegetable Production) saved about 45 mm (21%) of water without sacrificing crop quality and yield. In addition to irrigation yield responses, the approach is also validated in light of parameter estimation, and soil moisture simulations, comparing simulated and measured soil moisture content.
Correlating grain-size distributions, transport mechanism, and runout distance of debris flow deposits in the Himalayas
Authors: Dewrari Manish , Subramanian Srikrishnan Siva
Published: February 2023

Debris flows are rapid mass movements with great potential energy to move and are among the most dangerous natural hazards due to their high velocities and longer runout distances. For hazard assessment, early warning systems, and to construct structural mitigation measures in mountainous catchments, it is crucial to study the origin, initiation, and dynamics of debris flows as well as the characterisation of the associated erosion and deposition processes. Debris flow deposit grain-size distributions (GSD) reflect the source properties and the transport and deposition mechanisms and control the sediment transport rates in fluvial systems. In this study, we characterise deposits of ~120 debris flows that occurred in Kedarnath, Mandakini valley, India, during the 2013 North India Floods and find the relation between GSDs and runout distances. Here, we use an approach that combines two methods of measuring GSDs, i.e., volumetric sieving and pebble count. Volumetric sieving can measure grain size only up to 80 mm and takes much fieldwork, while the pebble count method can only measure surface grain sizes but can measure all three axes of grains which is useful in the case of non-spherical grains. We measure surface and subsurface grain sizes and large boulders using this approach. After obtaining the GSDs for the number of debris flows, we do a statistical study on the relationship between GSDs, transport mechanism and runout length. Debris material characterisation is crucial, and the approach has large potential applications in understanding the initiation, failure, and transport mechanisms of extreme-precipitation induced sediment disasters.
High-resolution local earthquake tomography of seismogenic structures along the Rhone-Simplon fault zone (Swiss Alps)
Authors: Diehl Tobias , Lee Timothy , Kissling Edi , Wiemer Stefan
Published: February 2023

In this study, we explore the potential to image the seismic velocity structure of moderate-sized, upper-crustal seismogenic fault zones by means of local earthquake tomography (LET) methods. The study region, located in the transition zone between the Central and Western Alps, represents one of the most seismically active and hazardous areas within the Alpine Arc. Over the past 500 years, several damaging earthquakes with Mw up to 6.2 are documented in historical earthquake catalogs in the vicinity of the Rhone-Simplon Fault (RSF), the dominant tectonic feature of this region. In particular, two major seismogenic structures are imaged by instrumental seismicity on either side of the RSF. To the north, seismicity occurs in the approximately NE-SW striking, 30–40 km long Rawil Fault Zone (RFZ). To the south, diffuse seismicity occurs within the hanging wall of the Pennine Basal Thrust, forming the Penninic Fault Zone (PFZ).Owing to the dense instrumentation and above-average seismic activity in the study region, the Pg and Sg travel-time data recorded since the year 2000 by the Swiss Seismological Service is of exceptionally high quality and allows for high-quality 3D LET images of the uppermost crust, potentially imaging the damage zones of seismogenic faults. Relative double-difference locations of a recent earthquake sequence within the RFZ, on the other hand, indicate that the width of this fault zone is only on the order of 1 km. Imaging such narrow fault zones with standard LET methods therefore requires model parametrizations with grid spacing of few kilometers and less. Such dense grid spacing, however, poses several challenges in terms of model resolution and the reliability of LET inversion results, especially in less well constrained parts of the model.To minimize such effects, we therefore tested and applied two different LET inversion strategies to derive 3D Vp and Vs models. The first strategy follows the common approach to compute a minimum 1D model as initial model for the 3D LET. The second strategy uses a coarser 3D regional LET model as initial model for the high-resolution 3D inversion. Synthetic tests suggest that a minimum image resolution of 5x5x3 km can be achieved with the current data, covering a region of about 125x125 km between 0 and 10-15 km depth. The 3D Vp and Vs models derived with the two initial-model strategies are remarkably similar within well resolved parts of the model. This similarity indicates that the anomalies in these parts are well constrained by the data and the solution is stable with respect to differences in the two initial models. On the other hand, the results suggest that results derived with the 3D initial model are more reliable in regions of reduced resolution. Additional synthetic tests were performed to document the potential resolution for hypothetical damage-zone scenarios and to support the interpretation of the derived models presented in this study.
Controls on the spatial distribution and temporal variation of anthropogenic tracers in the sediments of the Paris sewerage system.
Authors: Asselin Camille , Jacob Jérémy , Moilleron Régis
Published: February 2023

The urban environment is made up of a complex and changing mosaic of territories. To what extent these spatial heterogeneities, between territories, determine the quality of life or social, economic or health inequalities? Within the framework of the ANR EGOUT project (egout.cnrs.fr), we assume that the spatial distribution and temporal evolution of tracers archived in the sediments of the Parisian sewerage networks can help deciphering the diversity of aboveground conditions and their temporal trajectory.We compiled the geochemical results acquired before cleaning out operations on sediments accumulated in more than 100 silt traps (STs) that line the sewerage network of the City of Paris. These STs receive sediments that transit through the Parisian combined (wastewater and stormwater) sewer system. These analyses concern granulometry, metals, polychlorinated biphenyls (PCBs), but also 16 polycyclic aromatic hydrocarbons (PAHs). These regulatory analyses (which guide the nature of the treatment processes to be implemented) have been available since the year 2000, with cleaning out and thus measurement frequencies varying from one ST to another. They therefore allow addressing not only geochemical spatial disparities but also their temporal evolution.In order to assign these results to the corresponding catchment areas for every ST, we first defined the catchment areas of each DT. The TIGRE 7 information system of the City of Paris was used to distinguish each sub-network draining the sediments to each ST. Two spatial scales of drainage (wet and dry weather), but also a sedimentary cascade system could be highlighted. The catchment areas of each ST were then defined by linking individual connections to individual addresses and cadastral parcels.Here are the most striking results from the exploitation of existing data:The Haussmannian buildings, which are present for the most part in the city Centre, are major sources of zinc emissions (Gromaire et al., 2001). This element is found in the sediments of DT draining areas with a high density of historical buildings.
Based on concentration ratios (Ayrault et al., 2008), PAHs mainly result from road traffic. The concentration of PAHs has been decreasing in ST sediments since 2000. This decrease could reflect the 59% decrease in the car traffic in Paris recorded between 2001 and 2018.
PAH levels and types differ from DT to another, as already noted by Rocher et al. (2004). These differences probably indicate local specificities in PAH production of each catchment area. Cross-referencing our data with other spatialized data related to potential PAH sources (road traffic, heating, etc.) should allow us to better understanding the factors that control their presence in sewer sediments.
Multi-scale analysis of exposure to heat in Southeast England
Authors: Simpson Charles , Brousse Oscar , Heaviside Clare
Published: February 2023

Outdoor temperatures experienced by people in urban areas are typically higher than those in rural areas due to the urban heat island, but indoor temperatures also vary as a result of differences between buildings. We combined modelling of temperature at city and building scales, to determine the most important sources of variation in exposure to heat stress across London and Southeast England. We modelled outdoor temperatures using the WRF model with BEP-BEM for the hot summer of 2018, and used the output to force the EnergyPlus building model to estimate indoor temperatures of residential buildings.We investigated variations in the residential building stock across the region, as well as demographics. The latter is important because health risks posed by heat also vary with the population’s age, health, and socioeconomic status.Within the study region, we found large differences in exposure to heat between the urban population of London and the general population of Southeast England, and that as a result outdoor heat exposure is highest for ethnic minority groups, younger people, and the more socioeconomically deprived. However, variations in outdoor temperature within the urban areas of London were much smaller than the variations between London and the rest of the southeast.We compared the variation in the outdoor temperature with the variation in indoor temperature, building on evidence that flats (apartments) are more likely to overheat, and are more often located in hotter parts of the city than houses. This has implications for interventions on the built environment designed to reduce the health impacts of heat.By combining thermal modelling at different scales with demographic data, we aim to improve understanding of the sources of personal variations in heat-hazard within the population. 
Evaluation of the spatial and seasonal variations in the Dissolved Carbon Export of a non - perennial tropical river, Cauvery, Southern India
Authors: Ramesh RamyaPriya , Keerthan Lingaiah , Lakshmanan Elango
Published: February 2023

The role of rivers in global carbon cycles are important, especially in regard to the dissolved carbon dynamics and its variability for shorter period timescales. The contribution of non - perennial rivers on global carbon cycle has not been understood clearly, where the environmental controls on dissolved carbon in such rivers is not yet defined. Hence, the objective of the present study is to assess the seasonal and spatial variations of dissolved carbon export in a non-perennial river, Cauvery, India. The river water and the adjacent groundwater samples were collected along the river at 28 locations on quarterly basis from 2013 to 2021. The samples were analysed for pH, temperature, major ions, DIC, DOC, nutrients and 13C-DIC. The DIC concentrations were low at the locations near to the origin of the river, whereas it was vice-versa for DOC concentrations. The  source of DIC  was  due to both geogenic and biogenic, where the weathering of rocks majorly influences the DIC concentration. The silicate weathering is significant during the wet periods, whereas carbonate weathering was dominant during dry periods. The soil organic carbon along with microbial process, autrotrophic production influences the DOC concentration. The transport of dissolved carbon was high during monsoon periods and was very less during dry seasons due to lower discharge and damming.  It is estimated that the Cauvery river accounts about 5% of total DIC and 1% of total DOC transported to the Bay of Bengal from the rivers. Hence, the study implies that the seasonal variation of carbon exports in the rivers should be accounted in carbon budgets.
Cross helicity modified by large-scale velocity shears in the solar wind
Authors: Soljento Juska , Good Simon , Osmane Adnane , Kilpua Emilia
Published: February 2023

Cross helicity quantifies the balance between counterpropagating Alfvénic fluctuations, which interact nonlinearly to generate turbulence in the solar wind. We have investigated how cross helicity is modified by large-scale velocity shears in the solar wind plasma. Using the linear Kelvin–Helmholtz (KH) instability threshold, we identified velocity shears at a 30-min timescale. The shears were associated with 74 interplanetary coronal mass ejection (ICME) sheaths observed by the Wind spacecraft at 1 au between 1997 and 2018. Typically weaker shears upstream of the sheaths and downstream in the ICME ejecta were also analyzed. Below the KH threshold, cross helicity was approximately invariant or weakly rising with shear amplitude. Above the KH threshold, fluctuations tended toward a balanced state with increasing shear amplitude. These findings are consistent with velocity shears being local sources of sunward fluctuations that act to reduce net imbalances in the antisunward direction, and suggest that the KH instability plays a role this process.
Application of photogrammetric approaches to studying the 1971 dike-induced surface structures on Mt Etna, Italy
Authors: Bressan Sofia , Bonali Fabio Luca , Corti Noemi , Pasquaré Mariotto Federico , De Beni Emanuela , Cantarero Massimo , Neri Marco , Russo Elena , Drymoni Kyriaki , Tibaldi Alessandro
Published: February 2023

Mt Etna, located on the east coast of Sicily, Italy, is a basaltic stratovolcano with a volcanotectonic evolution of 500 ka, characterized by a wide horse-shoe-shaped depression on its eastern flank, called Valle del Bove. The study area is located near the northern escarpment of this depression, where it is possible to recognize the 1971 eruptive fissure system, generated by the lateral propagation of a feeder dike. The purpose of this research is to thoroughly examine the area affected by dike-induced surface deformation, which is marked by a textbook example of a graben structure produced by dike propagation. Due to the presence of meters-thick, recent pyroclastic deposits covering the study area and the difficult logistics, the main outcrops are inaccessible for classical field data collection. To overcome this limitation, we used the following methodology based on the analysis of photogrammetry-derived models.We first designed a structural map related to the development of the 1971 dike-induced structures, using two sets of historical aerial photos characterized by a 2400 DPI resolution. Particularly, the 20 selected images, equally divided between 1954 and 1983, have been processed using the software Agisoft Metashape to produce two referenced orthomosaics with a resolution of 29 and 19.5 cm/pixel, respectively. By comparing the obtained orthomosaics, we identified and mapped all the normal faults associated with the 1971 dike intrusion. This structural map has been used to organize the subsequent drone surveys, performed by a DJI Phantom 4 Pro equipped with RTK high-precision technology, which allowed us to collect 656 pictures with an overlap and a side lap of 85% and 80% respectively. Afterward, we processed the drone-collected photos by using Structure-from-Motion photogrammetry techniques, so as to obtain a Digital Surface Model (DSM) and a 3D Tiled Model, with a resolution of 11 and 5.48 cm/pixel, respectively. Such models have been used to analyze in detail the graben faults, especially the ones along the Valle del Bove steep wall.The analysis of photogrammetry-derived models over different time windows enabled us to individuate 14 lineaments within the study area, 2 eruptive fissures with a NE-SW strike, and 13 fault scarps associated with the dip-slip faults of the graben. Finally, thanks to the 3D Tiled Model obtained from drone-captured pictures, we were able to quantify the dip direction and dip angles of the graben faults, their vertical offsets, and the graben width related to the elevation.
Co-created Climate information with local agents for nautical sports activities in the central-western Mediterranean
Authors: Boqué Ciurana Anna , Olano Pozo Jon Xavier , Cisneros Bermejo Mercè , Cimolai Caterina , Vásquez Yañez Ricardo , Dermit Daniel , Aguilar Enric
Published: February 2023

Coastal Tourist destinations need to adapt to climate variability and change to maintain their tourist competitiveness and appeal. To do this, it is crucial to know the climatic potential of the activities which the destination offers and to manage the location’s natural resources. The Sustainable development goals (SDG) offer guidelines for the development of a tourist destination. In the TURLIT-ODS project, we aim to contribute directly to SDG 3, Good health and well being; SDG 8, decent work and economic growth; SDG 12, Responsible consumption and production and SDG 13, Climate Action.The last decades have seen advances in climate services for multiple fields. Despite this, the determination of the expected optimal days for different nautical sports activities around the central-western Mediterranean has not been done yet.The present research explores, through a co-creation process with local agents, how the atmospheric/oceanic conditions influence nautical sports activity development. With the gained knowledge, we computed the optimal expected days for the specific activities identified by the stakeholders using ocean buoy data and wind and wave data from the SIMAR numerical model owned by Puertos del Estado.Thanks to this approach, we transform raw data into structured information to provide the knowledge of optimal expected days for different nautical sports activities: sailing, stand-up paddling, kayaking, windsurfing, swimming in open waters, diving, snorkeling, water walking, underwater fishing, SUP- yoga, rowing, kitesurfing, surfing, wing foil, jet ski and other recreative uses (like the banana boat).The computation of the optimal days for each one of these activities along Tarragona’s province coast allows us to understand the availability of that conditions and assist decision-making by looking at information that facilitates the definition of diversification strategies of the tourist activities.By considering the meteorological-oceanographical conditions of a territory and, according to the results related to a destination, new tourist products and/or redesigned products offered are depicted. In this way, the destination of Tarragona’s province makes a step closer to the path of the sustainability of their leisure and tourist activities settled on the shore.We acknowledge  Diputació Provincial de Tarragona for funding the project TURLIT (T22240S), Puertos del Estado (Ministry of Transport, Mobility and Urban Agenda of Spain), which provided the data for this study, and the Municipality of Calafell for supporting the project and facilitating spaces to generate the co-creation process.
Higher-Efficiency Inverse Atmospheric Modelling by Virtue of a Global Hexagonal Mesh
Authors: Takache Sakina , Chevallier Frederic , Lloret Zoé , Cozic Anne
Published: February 2023

Emission sources and sinks of long-lived greenhouse gases (GHGs), such as CO2 and N2O, can be localized and scaled by inversely modelling existing distributions of these tracers in the atmosphere. This is particularly useful for monitoring GHG emissions at a global level, for comparison, for instance, with the national inventory reports of the United Nations Framework Convention on Climate Change (UNFCCC).To achieve inverse transport numerically, multiple approaches can be taken, notably variational data assimilation. This involves the optimization of the Bayesian cost function accounting for prior state errors and observation errors. Variational data assimilation can be implemented by adjoint modelling. This method is based on the modification of the tracer transport equations of general circulation models (GCMs). The transpose of the tangent-linear operator, called the “adjoint”, is applied to find the initial sources and sinks. Eulerian backtracking, also called “retro-transport”, is a simplified approach to adjoint modelling, where the roles of updraughts and entrainment are switched with downdraughts and detrainment, respectively, and vice versa (Hourdin et al., 2005a).In our presented work, we implement both the adjoint method for inverse modelling (Lions, 1971; Marchuk, 1974, 1982) and the retro-transport method put forth by Hourdin et al. (2005a). Our newfound approach consists of adapting these methods to a hexagonal mesh. For this, we use the DYNAMICO dynamical core of the the Laboratoire de Météorologie Dynamique-Zoom (LMDZ) GCM, which computes forward-in-time transport equations on a hexagonal mesh (Dubos et al., 2015). We add routines to DYNAMICO’s source code for the adjoint method, and alter the direction of fluxes to implement Eulerian backtracking.The hexagonal mesh permits to reduce the computational cost traditionally attributed to inverse atmospheric modelling. Without the decreasing cell size as we approach the poles in a regular lon-lat grid, a hexagonal mesh covers the globe with a smaller number of nearly fixed-size cells. This directly reduces the size of input data and the number of operations. Further, the hexagonal mesh allows modellers to bypass the need for nonlinear cell-treatment at the poles of a regular lon-lat grid, increasing the accuracy of the retro-transport approximation. The increased computational efficiency of the hexagonal mesh paves the way for higher horizontal resolutions for global atmospheric inversion.
Precipitation Measurement from Raindrops’ Sound and Touch Signals
Authors: Hwang Seunghyun , Lee Jinwook , Sung Jeemi , Kim Hyochan , Kim Beomseo , Jun Changhyun
Published: February 2023

This study proposes a novel method for rainfall intensity estimation from acoustic and vibration data with low-cost sensors. At first, a precipitation measurement device was developed to collect sound and touch signals from raindrops, composed of Raspberry Pi, a condenser microphone, and an accelerometer with 6 degrees of freedom. To figure out whether rainfall occurred or not, a binary classification model with the XGBoost algorithm was considered to analyze long-term time series of vibration data. Then, high-resolution acoustic data was used to investigate the main characteristics of rainfall patterns at a frequency domain for the period when it was determined that rainfall occurred. As a result of the Short Time Fourier Transform (STFT), the highest frequency, mean and standard deviation of amplitudes were selected as representative values for minute data. Finally, different types of regression models were applied to develop the method for rainfall intensity estimation from comparative analysis with other precipitation measurement devices (e.g., PARSIVEL, etc.). It should be noted that the new device with the proposed method functions reliably under extreme environmental conditions when the estimated rainfall intensity was compared with measured data from ground-based precipitation devices. It shows that low-cost sensors with sound and touch signals from raindrops can be effectively used for rainfall intensity estimation with easy installation and maintenance, indicating a strong possibility of being considered in a wide range of areas for precipitation measurement with high resolution and accuracyAcknowledgementThis work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. NRF-2022R1A4A3032838).
Challenges in the usage of commercial microwave links for the generation of transboundary German-Czech rainfall maps
Authors: Blettner Nico , Fencl Martin , Bareš Vojtěch , Chwala Christian , Kunstmann Harald
Published: February 2023

Attenuation data from commercial microwave links (CMLs) has proven useful for estimating rainfall. Their major benefits are a high abundance in most regions on earth, a high resolution in time, close to ground measurement, and the absence of installation costs and efforts. The spatial and temporal coverage of CMLs would theoretically enable the generation of continental rainfall maps for various aggregation times.However, there exist limitations that have so far inhibited rainfall estimation on larger scales. The data is generally obtained on a national basis from different network providers and networks can vary significantly in characteristics such as frequency and length distributions. CML data requires careful processing that depends on these characteristics and which has so far been adjusted to independent data sets only.In this study we investigate what kind of processing is required to use independent and heterogeneous CML data sets for the generation of transboundary rainfall maps. We use 3900 CMLs from Germany and 2500 CMLs from the Czech Republic. The German data set is rather evenly distributed with respect to spatial coverage, frequencies and lengths. The Czech data set, on the other hand, varies significantly more in all these regards: it is characterized by dense networks of short CMLs in the cities, a large share of CMLs with E-Band frequency, and hence a large range of sensitivities.We find that quality control is important especially when dealing with independent data sets. We propose several algorithms and the consideration of network characteristics when combining two CML data sets, and show how adapted but straightforward processing allows the generation of transboundary rainfall maps.
Overview and first analysis of the in situ microphysical measurement dataset collected during the CADDIWA mission
Authors: Coutris Pierre , Febvre Guy , Jaffeux Louis , Bazantay Clément , Aubry Clémantyne , Caudoux Christophe , Delanoë Julien , Schwarzenboeck Alfons , Flamant Cyrille
Published: February 2023

In the frame of the Joint Aeolus Tropical Atlantic Campaigns, an airborne field campaign took place in Sal island of Cape-Verde from the 8th to 21st of September 2021, as part of the French CADDIWA mission. During this campaign, the SAFIRE F20 research aircraft equipped with in situ and remote sensing instruments performed nine 3 to 4 hour long flights sampling tropical environment underneath AEOLUS satellite tracks and performing exploration flights within the convective cloud systems of tropical disturbances. In this study, an overview of the available aerosol and cloud in situ dataset is given first, presenting the instrumental and methodological approaches relevant to the collection of data from a set of four instruments: the UHSAS (aerosol size range : 40 – 1000 nm,  Cai et al. 2008), the SPP-300 (aerosol 0.3 – 20 µm, Baumgardner 1992) and the CDP-2 (droplets 2-50 µm, Lance et al. 2010) scattering probes, and the 2D-S imager (10-1280 µm, Lawson et al. 2006). Then a detailed microphysical analysis is conducted on two case studies: a tropical perturbation referred to as Pierre-Henri in this study (unnamed/numbered by NOAA National Hurricane Center (NHC)), sampled during F20 flight #7/8, and the Tropical Storm Rose (# AL172021 according to NOAA NHC) sampled during flights #12/13. The analysis includes a discussion on the main microphysical properties such as Particle Size Distribution (PSD), Ice Water Content (IWC) retrieved at different locations in the cloud convective systems, complemented by 95GHz reflectivity and Doppler vertical velocity measured by the airborne cloud radar RASTA (Delanoe et al. 2013). The data supporting this study is illustrated in the figure below: the vertical velocity (derived from 3 Doppler non colinear measurements of the radar) and PSD time series are given on top of two samples ice crystal images taken by the 2DS imager at different location in the TS Rose. A newly developed image classification algorithm (Jaffeux et al. 2022) is applied to the 2D-S data to derive statistics on the ice particles morphological properties, yielding to a discussion on the microphysical ice growth processes occurring in these systems.
Different ways of modeling relativistic electron flux in the outer radiation belt using neural networks
Authors: Pfitzer Maximilian , Shprits Yuri , Smirnow Artem
Published: February 2023

The outer radiation belt of the Earth contains highly energetic electrons that are hazardous to satellite operation. In particular, relativistic electrons can penetrate through satellite shielding and damage the onboard electronics via the deep dielectric charging. In this study, we developed a neural network-based model of relativistic electron fluxes (with energies >1.8 MeV) based on data from the REPT instument onboard the Van Allen Probes mission in 2012-2019.  The model uses the geomagnetic index hp-30, as well as solar wind parameters, as inputs. We create the models based solely on the ground-based indices, and evaluate their accuracy in comparison to models that use solar wind parameters as additional drivers. We demonstrate that relativistic electron fluxes can be reconstructed with very high fidelity, as the model yields close-to-zero bias and >95% correlation on both training, validation and unseen test intervals. We discuss the applications of the model in combination with physics-based radiation belt codes and compare the newly created model with the current state-of-the-art simulations.
Plant community changes in the arctic: effects on Carbon and Nitrogen stocks distribution in the environment.
Authors: Potier Hugo M. G. , Raynaud Xavier , Agnan Yannick , Allain Alienor , Rouelle Maryse , Alexis Marie A.
Published: February 2023

Arctic environments undergo important climatic changes that affect, among others, hydrology, soil processes, and plant communities of these systems. At large scale, tree-line and shrub cover have been reported to expand northward, although permafrost melting, increased snow cover and raised soil water content can promote herbaceous covers at the local scale. Our study evaluated carbon (C) and nitrogen (N) stocks in diverse environments at Abisko, northern Sweden: a mire site with palsa, bog, and fen and a shrub tundra site with a bog to broad-leaved forest gradient. Based on plant community survey and vegetation and soil C and N analysis, results showed that proportions of ligneous and herbaceous covers do not reflect the total biomass C and N stocks, with 140.1 ± 56.9 and 3.7 ± 1.5 g per square meter of ground-level vegetation on average, respectively. However, differences in the distribution of short-lived (e.g. leaves) and long-lived (e.g. woody) biomasses were found, with an increase of 1% to up to 40% of woody biomass in dryer sites. Those results were even more important in the broad-leaved forest where C and N stocks in wood, leaves and deadwood of birch trees were over thrice the stock of ground-level vegetation and represented 515.0 ± 115.9 and 17.0 ± 3.8 g.m-2, respectively. Regarding soils, C and N stocks varied mainly at large scale between the mire (47.1 ± 9.1 kgC.m-2 and 2.6 ± 0.4 kgN.m-2 for palsa; 20.2 ± 6.9 kgC.m-2 and 0.9 ± 0.4 kgN.m-2 for bog subsites) and other dryer environments (5.8 ± 1.4 kgC.m-2 and 0.21 ± 0.02 kgN.m-2 for shrub tundra and forest) with differences mostly driven by soil density, soil depth, and water content and not by the composition of the plant community. Our results suggest that plant community shrubification at a large scale is likely to increase the overall C and N stocks in these ecosystems, with more important stocks in long-lived biomass such as wood. While plant community composition and proportion of ligneous/herbaceous species seemed to be a good indicator of biomass distribution, soil stocks appeared not to be well predicted by our results. Those results could be used as a base to compute C and N stocks using remote-sensing data, to obtain information at larger scales for which extensive field measurements are harder to conduct.
Emergent constraints on the future Arctic lapse-rate feedback
Authors: Linke Olivia , Feldl Nicole , Quaas Johannes
Published: February 2023

Arctic amplification (AA) is largely attributed to the effect of sea ice decline leading to greater surface solar absorption and further ice melt, and the vertical structure of the warming. The latter aspect evokes the positive lapse-rate feedback (LRF), which is commonly understood as an effect of stable stratification: The warming in the Arctic is particularly strong close to the surface, but muted aloft. This limits the outgoing long-wave radiative flux at the top-of-the-atmosphere (TOA) relative to vertically uniform warming.We estimate the future Arctic LRF in 43 global climate models (GCMs) from the highest emission pathway SSP5 of CMIP6. The GCMs simulate a large spread of future AA (2-8 K above global warming) and Arctic LRF (1-4 K warming contribution) at the end of the century 2070-2099. Our work aims to identify emerging relationships between this spread and observable aspects of the current climate to ultimately narrow down the range of future Arctic climate predictions.Previous studies have identified an emerging relationship for the surface-albedo feedback based on the observed seasonal cycle of Arctic sea ice. We similarly derive a positive relationship (r=0.70) between future and seasonal LRF, but due to its nature, no direct observation of the LRF exists. However, we find relationships between the future LRF and observable sea ice metrics, namely sea ice concentration, seasonality, extent and area. From these relationships, the sea ice concentration provides the strongest correlation (r=-0.76) for the area-averaged Arctic sea ice cover. This relationship implies a contribution of the LRF to future Arctic warming of approx. 2 K, which further relates to an AA of 4 K above global average at the end of the century.We further emphasise the physical meaning behind our constraint: The negative emerging relationship implies that models with a lower Pan-Arctic sea ice concentration produce a larger LRF in the future. However, when dividing the entire sea ice area into regions of sea ice retreat (SIR) and persisting sea ice (PSI) in the future prediction, the relationship becomes positive over these two area-averaged regions. Thereby, the negative overall relationship is merely a result of the area-size distribution of SIR vs. PSI across the spread of model simulations. We conclude that while the Pan-Arctic perspective enables the emergent constraint, the physical meaning is hidden: A higher initial sea ice concentration produces a stronger positive Arctic LRF by setting the stage for greater sea ice retreat.
Peatlands methane origin and fluxes to the atmosphere: towards an integrative conceptual model of a temperate French peatland
Authors: Lhosmot Alexandre , Jacotot Adrien , Steinmann Marc , Gandois Laure , Binet Philippe , Toussaint Marie-Laure , Gogo Sébastien , Gilbert Daniel , Moquet Jean-Sébastien , Coffinet Sarah , Boetsch Anne , Loup Christophe , Laggoun-Défarge Fatima , Bertrand Guillaume
Published: February 2023

Peatlands cover only 3 % of emerged lands, but their carbon stock represents about 30 % of the global soil organic carbon. Climate change and local anthropogenic disturbances deeply affect the hydrological functioning of peatlands. This may trigger carbon fluxes to surface waters and the atmosphere, thus leading to a positive feedback for global warming. It is therefore crucial to better estimate carbon fluxes between peatlands and the atmosphere and to delineate their major controlling constraints. To achieve this goal, we studied the functioning of a temperate mid-mountain peatland located in the French Jura Mountains, named the Frasne peatland.The methane (CH4) dynamics of the Frasne peatland appear to be constrained by a range of hydrological, physical, biogeochemical, and biotic factors. From a hydrological point of view, the system is fed by local rainwater and injection of carbonated groundwater at the bottom of the peatland, which provides a major input of dissolved inorganic carbon (DIC) to the system. Values of the δ13CDIC were high (even reaching positive values up to 8.1 ‰) compared to the expected values in a limestone and C3 plant-dominated area such as the Jura Mountains, supporting biotic CH4 production within the peatland. Consistently, high-frequency eddy-covariance monitoring during 2.5 years allowed us to show that the site acted as a source of CH4 to the atmosphere (23.9 ± 0.6 g C m-2 year-1) with interannual, seasonal, and diurnal time scale dynamics. In particular, we found an outstanding diurnal cycle for CH4 with the highest fluxes at night and lower ones at mid-day. In addition, the mid-day fluxes were negative in spring, highlighting larger oxidative processes than CH4 production attributed to photosynthesis activity (i.e., soil oxygen penetration and endosymbiotic methanotrophs of Sphagnum). The range of CH4 emissions was also controlled by the interannual variation in precipitation amounts and by the seasonal temperature variation.This conceptual production-emission model highlights that water-carbon interactions in the peatland depend on local biotic and abiotic factors but also on hydrological processes at the watershed scale. This also highlights the need to further constrain carbon transfers between the production and the emission zones (i.e., peatland-atmosphere interface and surface water exports). For this purpose, we will soon carry out a field campaign to measure the concentrations and isotopic values of dissolved gases in peat pore water along with an upstream downstream and a vertical gradient.
Simulations of ground motion in the Tehran basin based on newly developed 3D velocity model
Authors: Soltani Saeed , Cornou Cecile , Guillier Bertrand , Haghshenas Ebrahim
Published: February 2023

Tehran urban area serves as the main hub for economic and social activities in Iran. The city is located on a sedimentary basin including faults and folds, and thus it is vulnerable to large site effects. Analysis of earthquakes recorded by a temporary seismological network has approved a large amplification of seismic ground motion (about 4 to 8) over a broad frequency range.In order to better understand and predict the effects of the geometry and mechanical properties on surface ground motions, we developed a 3D shear-wave velocity model of Tehran by integrating extensive geophysical surveys including almost 600 single station measurements and 33 ambient vibrations arrays, with geotechnical and geological data. This 3D model shows that the bedrock depth varies between 100 and 900 meters with a general increasing depth from N-NE toward the S-SW. Also, there are two main velocity layers in the basin. A surface layer, which drops from 950 m/s to 600 m/s from NE to SW and a deeper layer with Vs up to 1300 m/s.We then used the open-source spectral-element code, EfiSpec3D (DiMartin et al., 2011), to simulate ground motion by this new sedimentary basin model at the defined 50*50 kilometers tilted square simulation block up to the maximum target frequency of 2 Hz. The source time function is a 2-Hz lowpass filtered Dirac impulse injected from the defined z-plane at 5 km depth.The results reveal a good correlation between real and simulated earthquake ground motion by the comparison between experimental and synthetic standard spectral ratios (SSR). The results also reproduced the experimental H/V frequency peaks over the basin relatively well and suggest that 3D geometry always should be considered for an accurate estimation of realistic basin response.
Wavelet determination of scaling exponents and intermittency seen by Solar Orbiter
Authors: Bendt Alina , Chapman Sandra , Hnat Bogdan
Published: February 2023

The solar wind provides a natural laboratory for plasma turbulence at high Reynolds number. We use Solar Orbiter (SO) observations from the Magnetometer (MAG) and the Solar Wind Analyser Suite (SWA) to study extended intervals of homogeneous turbulence. Intervals which exhibit a clear scaling range of magnetohydrodynamic (MHD) turbulence, and transitions to both the ‘1/f’ range at low frequencies, and the kinetic range at frequencies where MHD is no longer valid, are selected. We ensure that all intervals are of steady solar wind flow and do not contain isolated structures such as shocks, pressure pulses and discontinuities.Solar wind turbulence is anisotropic due to the presence of a background magnetic field. We first rotate the magnetic field into orthogonal coordinate systems with one coordinate parallel to the average direction of the magnetic field B0, a second coordinate perpendicular to both B0 and average solar wind flow direction U, and the third in the plane of both B0 and U. We then perform a Haar wavelet decomposition to obtain the timeseries of magnetic field fluctuations on multiple temporal scales. The Haar wavelet decomposition is by linearly spaced intervals in logarithmic frequency space and hence provides a precise determination of the power spectral exponents, discriminating between 5/3, 3/2 and other relevant values. It also directly estimates the Local Intermittency Measure, which characterizes localized coherent turbulent structures, and the structure functions, which quantify higher order scaling exponents.We apply these methods to SO intervals in order to test for systematic dependencies on the properties of the turbulence with different plasma conditions and at different distances from the sun.
An evaluation of the impact of irrigation and groundwater pumping on regional climate using an improved Earth-System model
Authors: Satoh Yusuke , Pokhrel Yadu , Kim Hyungjun , Yokohata Tokuta
Published: February 2023

Irrigation is one of the crucial Nature-Human interactions and also an anthropogenic forcing in the Earth system. The literature has shown that artificial water supply to soil for example water exploitation from groundwater for irrigation can alter water and heat budgets at the land surface, resulting in changes in regional climate and hydrological cycles. Due to the expected increase in irrigation to meet growing food demand, the impact of irrigation is likely to increase further in the future. Therefore, it is essential to consider to better understand the irrigation-induced changes in the various components of the Earth system, today and in the future.Our research aims to advance the quantitative understanding of the impact of irrigation and groundwater exploitation as anthropogenic drivers of regional climate and environmental changes. We developed an earth system modeling framework coupling the updated Earth system model, MIROC-ES2L (Model for Interdisciplinary Research on Climate, Earth System version 2 for Long-term simulations) and newly implemented hydrological human activity modules. This modeling framework enables to simulate a fully coupled Nature-Human system including water cycle dynamics related to irrigation.Our preliminary results show notable differences between simulations with and without the irrigation process. Here, we show the hydrological variables affected by irrigation and identify the regions and timings of significant impact. Further, we estimate the individual contribution of groundwater and surface water use to such impacts by irrigation.