bluuebunny/crossref_metadata_2025 huggingface dataset:
Physics based ground motion model in seismic hazard assessment
Authors: Stg Raghukanth
Published: February 2023

Ground motion prediction equations (GMPE) are traditionally used in site specific seismic hazard analysis to obtain design response spectra. These equations are obtained by regression analysis on the available strong motion data in a given tectonic and geological region. Assuming ergodicity regional GMPE are routinely used in site-specific probabilistic seismic hazard analysis. Since these empirical equations are region specific, However the obtained seismic hazard curves are not specific to the site. Due to lack of data for all possible combinations of magnitude and distances, development of site-specific GMPE is not possible in the near future. The only way to develop a site-specific GMPE is through numerical models. Given a 3D velocity structure, topography and source information these models can simulate site-specific ground motion. Once calibrated with the recorded strong motion data, numerical models can be used to simulate ensemble of ground motions by including the uncertainty in the slip models. In regions lacking strong motion data, these models have an additional advantage compared to GMPE. In the present study, an broad band simulation model is developed for a typical site in peninsular India. Spectral finite element method (SPECFEM) is used to simulate the low frequency ground motion by incorporating the 3D velocity structure in the medium. The high frequency ground motion is simulated from the stochastic seismological model (Otarola and Ruiz, 2016). Statistical kinematic rupture model is used to represent the earthquake source (Dhanya and Raghukanth 2018). The rupture length, width and correlation lengths of the random field are estimated from magnitude. Assuming the phase as random, a total of 30 rupture models are simulated for each magnitude. An ensemble of ground motions is simulated at the site for various possible combination of faults and magnitudes in a region around 500 km from the site. The simulated low-frequency and high-frequency ground motions are combined in the frequency domain to obtained broad band ground motions (0-100 Hz). The mean and standard deviation of the response spectra are estimated from these simulated motions for all possible combinations of magnitudes and distances at the given site. Further, probabilistic seismic hazard analysis is carried out using the simulated data to obtain hazard curves for spectral accelerations at various natural periods. Uniform hazard response spectra (UHRS) for 475yr and 2475 yr is obtained from the hazard analysis. A comparison with traditional hazard analysis using region specific GMPE is also presented. It is observed GMPE based UHRS show a smooth trend compared with site-specific UHRS obtained from broad band models. The PGA values obtained from physics based model are slightly higher than that obtained from GMPE based PSHA.
Heatwaves of 2018: connecting large-scale to synoptic scale circulation
Authors: Pyrina Maria , Domeisen Daniela
Published: February 2023

The intensity of heat extremes has been increasing in recent decades, with several recent notable heatwaves afflicting highly populated areas. Previous studies have related heatwaves to slow moving amplified Rossby waves, due to the formation of circumglobal teleconnections (i.e., European heatwaves of 2003 and 2010). Other studies have found that there is a statistical link between high amplitude upper-tropospheric transient Rossby wave packets (RWPs) and increased probability of lower-tropospheric temperature extremes. These non-circumglobal RWP amplitudes were found to be better linked to temperature extremes than Fourier amplitudes quantifying circumglobal waviness, including the European heatwaves of 2003 and 2010. In the summer of 2018, several record-breaking and persistent heatwaves occurred simultaneously around the globe and were linked to an amplified hemisphere-wide wavenumber 7 circulation pattern. Here, we investigate the relation of the synoptic RWPs and the circumglobal characteristics of atmospheric circulation characteristics with the heatwaves during 1998-2018, with a focus on the heatwaves that occurred during the summer of 2018.  Preliminary results show that the dominant circumglobal pattern for the 2018 summer heat extremes was dominated by a zonal wavenumber 6 circulation pattern and that its amplitude was connected to high amplitude RWPs that occur across the Northern Hemisphere.
Minor effects of no-till treatment on GHG emissions of boreal cultivated peat soil
Authors: Honkanen Henri , Kekkonen Hanna , Heikkinen Jaakko , Lång Kristiina
Published: February 2023

Greenhouse gas emissions of a spring cereal monoculture under conventional tillage and no-till treatments were measured in a peatland in Southwestern Finland for three years in 2018-2021. Nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) fluxes were measured with an opaque chamber technique approximately biweekly throughout the years. During the growing season, canopy net ecosystem exchange (NEE) was measured with a transparent chamber technique and hourly ecosystem respiration (ER) and gross photosynthesis (GP) were modelled with empiric models. On average, the annual emissions were 6.4±2.4 Mg CO2-C ha -1 yr-1, 7.6±3.5 kg N2O-N ha-1 yr-1, and -0.35±0.42 kg CH4-C ha-1 yr-1 for NEE, N2O and CH4, respectively. The effect of no-till management on the GHG balance was non-consistent through years and thus generally of minor significance. No-till reduced annual CO2 emissions by 24% in 2019 and N2O emissions by 33% in 2020 compared to conventional tillage while there were no differences in other years. Measured differences in ER occurred mostly during the winter periods, especially after ploughing. The results indicated that no-till may reduce CO2 and N2O emissions from cultivated peat soil, but it does not lead to large consistent reductions during the first years of NT management.
Atmospheric contribution of nanoplastics to rural and remote surface waters
Authors: Materic Dusan , Peacock Mike , Dean Joshua , Futter Martyn , Maximov Trofim , Moldan Filip , Röckmann Thomas , Holzinger Rupert
Published: February 2023

There is growing evidence for global environmental pollution caused by plastic particles <1 µm, here referred to as nanoplastics. Nanoplastic concentrations have been below the detection limits of many methods for quite some time, and thus they have passed undetected in complex environmental samples. However, recently using Thermal Desorption – Proton Transfer Reaction – Mass Spectrometry, many common nanosized polymers have been detected in seawater, ice and snow of rural and remote sites. In this work, we focused on the waterbodies of two contrasting sites: remote Siberian Arctic tundra and a forest landscape in southern Sweden. Nanoplastics of four polymer types (polyethylene, polyvinyl chloride, polypropylene, polyethylene terephthalate) were detected in all sampled Swedish lakes and streams (mean 563 µg/L, seven lakes, four streams). The amount of nanoplastic polymers showed a correlation with plastic demand in Europe (R2 = 0.91). In Siberia, two nanoplastic polymers (PVC and polystyrene) were detected in lakes, ponds and surface flooding, and concentrations were lower (mean 51 µg/L, three lakes, five ponds, overland flow from thawing permafrost and flooded tundra). Based on potential source analysis and HYSPLIT modelling of air mass trajectories and particle dispersion, we infer that nanoplastics predominantly arrive at both sites by atmospheric deposition from local and regional sources.
When are energetic electrons producing NO directly in the upper stratosphere?
Authors: Salice Josephine , Nesse Hilde , Partamies Noora , Kilpua Emilia , Kavanagh Andrew , Babu Eldho , Smith-Johnsen Christine
Published: February 2023

Compositional NOx changes caused by energetic electron precipitation (EEP) at a specific altitude are called the EEP direct effect. Changes co-dependent on vertical transport are referred to as the EEP indirect effect. The relative importance of EEP’s direct and indirect effect on NO and its subsequent impact on ozone and dynamic changes remain unresolved. The challenges are partly due to inadequate particle measurement and the relative scarcity of NO observations over the polar MLT region. Moreover, lower production rates in the mesosphere make it challenging to determine EEP’s direct impact on NO since small in-situ enhancements cannot be easily distinguished from the descending NO-rich air masses in the winter hemisphere. In this study, the uncertainty of the EEP observations is bypassed by exclusively identifying events applying NO-observations from the SOFIE instrument on board the AIM satellite. SOFIE daily averaged data from 2007 to 2014 is used to create a climatology based on the mean of the lower half of the data (lower 50 percentile mean). A direct EEP-produced NO-event at 90 km (“90km-event”) is identified when the NO density surpasses the climatology by 100%. If the NO density exceeds 25% above the climatology at 80, 70, 60, and 50 km, the event qualifies as a “50km-event”. By contrasting the 90km and 50km events, the characteristics of the solar wind and geomagnetic indices, as well as observed electron fluxes from POES, are studied. The goal is to unravel when EEP can produce NO directly in the upper stratosphere. The result will contribute to developing a parameterization of EEP from the radiation belt that includes both the direct and indirect impact of EEP to decipher the total EEP effect on the ozone and atmospheric dynamics.
Assessment of airborne remote sensing data for high-resolution mapping of invasive Prosopis spp. in a semi-arid environment in Kenya
Authors: Vuorinne Ilja , Heiskanen Janne , Ocholla Ian , Kihungu Rose , Pellikka Petri
Published: February 2023

Invasive alien plant species are a major global problem threatening biodiversity and livelihoods and their mapping is needed for understanding their distribution dynamics, and for facilitating control and eradication measures. Prosopis spp., a fast-growing woody species native to South America, have been widely introduced into the tropics to restore degraded areas, but they have spread uncontrollably. For example, in East Africa, Prosopis spp. have invaded rangelands and thus decreased plant diversity and affected the livelihoods of pastoral communities. Remote sensing instruments mounted on an aircraft can be used to map such species and especially a combination of different sensors holds a potential for accurate detection.The objective of this study was to test how a combination of airborne light detection and ranging (LiDAR), hyperspectral, and fine resolution multispectral data can be used to map Prosopis spp. in a semi-arid environment in Kenya. The remotely sensed spectral, structural, and textural features were used in a one-class machine learning algorithms to detect these species in a complex landcover. The results provide information on the use of different airborne remote sensing instruments and their combination in mapping woody alien invasive species and offer insights on the distribution of Prosopis spp. in the study area.
Analysis of land subsidence caused by groundwater overexploitation in the Gediz River Basin based on Sentinel-1 observations
Authors: Navarro-Hernández María , Tomás Roberto , Valdes-Abellan Javier , Bru Guadalupe , Ezquerro Pablo , Guardiola-Albert Carolina , Elçi Alper , Batkan Elif Aysu , Caylak Baris , Hakan Ören Ali , Meisina Claudia , Pedretti Laura , Rygus Michelle
Published: February 2023

Land subsidence induced by groundwater withdrawal affects many regions around the world and is considered one of the most extensive phenomena caused by human activity nowadays. The Gediz River Basin is located in the western part of Türkiye, and develops along a regional extension of a horst-graben system. This basin has an agricultural and industrial importance in the region, increasing the water demand and positioning the Gediz Basin as one of the most stressed basins in the country. The main aims of this study are to evaluate the role of tectonics and groundwater withdrawal on land subsidence and on the evolution of faults in the Gediz River Basin. Additionally, other conditioning factors such as soft soil thickness layers are also studied. For this purpose, we processed 123 SAR images in descending orbit and 98 in ascending orbit acquired from Sentinel-1 between 2016 and 2021 by the parallel solution of the Small BAseline Subset (SBAS) algorithm (P-SBAS), allocated in the Geohazard Exploitation Platform (GEP). Secondly, we applied an Independent Component Analysis (ICA) to the InSAR time series in order to separate spatiotemporal patterns of long-term deformation and seasonal variations. P-SBAS results reveal that the maximum subsidence rates measured along the line of sight (-6.40 cm/year) are mainly concentrated in agricultural and urban areas. The results also suggest that there is a direct relationship between InSAR deformation and soft soil thickness, indicating that land subsidence is induced by the compaction of aquitard layers due to the groundwater withdrawal and piezometric head depletion. The analysis of the time series through the ICA shows two types of spatiotemporal deformation trends, one of them corresponds to long term and quasi-linear deformation due to the compaction of the aquitard, and the other represents the long-term deformations with seasonal rebounds produced by the seasonal loading and unloading cycles due to water level fluctuations. AcknowledgementsThis research was funded by the PRIMA programme supported by the European Union under grant agreement No 1924, project RESERVOIR and by ESA-MOST China DRAGON-5 project (ref. 59339)
The effect of different high carbon soil amendments on N retention capacity under winter conditions in silty clay soil with low organic carbon content: An incubation study
Authors: Zhao Kerui , Reichel Rüdiger , Wissel Holger , Brüggemann Nicolas
Published: February 2023

Average soil temperatures in winter in Germany are frequently between 0 and +10℃, usually at high soil moisture levels. Therefore, the decomposition of soil organic matter and soil nitrogen (N) cycling are still active and could be substantial under these conditions, potentially leading to high N losses both in the form of nitrate to the groundwater and nitrous oxide to the atmosphere. High carbon soil amendments (HCA) have the potential to immobilize excess mineral N in the soil due to stimulation of microbial biomass growth. However, to date, it is not sufficiently known how well this N immobilization works at lower temperatures, and how long the effect will last over winter. In order to elucidate how the application of different HCA affects N immobilization in soil under winter conditions, we conducted a 7-month laboratory incubation experiment with silty clay soil low in soil organic carbon from a recultivation area after open-cast lignite mining near Jülich, Germany. Each soil column contained about 500 g of recultivation soil sieved at 2 mm. A scenario of a typical mineral N content after harvest was created by adding 50 kg NH4+-N ha-1 to the soil before application of the different HCA, which were then added at a rate of 4 t C ha-1. Eight different treatments were implemented: application of NH4+ only (B), and then NH4+ applied with wheat straw (WS), biochar (BIO), spruce sawdust (SS), lignite (LIG), cellulose (CEL), a combination of wheat straw (2 t C ha-1) and spruce sawdust (2 t C ha-1) (CWS), and a combination of wheat straw (2 t C ha-1) and biochar (2 t C ha-1) (CWB), respectively. In the three straw treatments, carbon dioxide (CO2) emissions peaked 14 days after the start of the experiment. In all treatments, CO2 emissions decreased with time. In the end, the CEL treatment had the highest cumulative CO2 emission during the entire incubation period. In contrast, the CEL treatment had a significantly lower soil nitrate content than all other treatments over the whole duration of 7 months, indicating that cellulose was most effective and long-lasting in stimulating microbial N immobilization under temperate winter conditions in silty clay soil.
Modelling the just allocation of energy infrastructure - Implications of assumptions and definitions of justice on model results
Authors: Vågerö Oskar , Zeyringer Marianne , Inderberg Tor Håkon Jackson
Published: February 2023

What constitutes socially just or unjust energy systems or transitions can be derived from the philosophy and principles of justice. Assessments of justice and modelling outputs leads to great differences based on which justice principles are applied. From the little research so far published in the intersection between energy systems modelling and justice, we find that comparisons between the two principles of utilitarianism and egalitarianism dominate in assessments of distributive justice, with the latter most often considered representing a 'just energy system'. Not recognising alternative and equally valid principles of justice, resting on e.g. capabilities, responsibilities and/or opportunities, may contribute to a narrow understanding of justice that fail to align with the views of different individuals, stakeholders and societies. More importantly, it can lead to the unjust design of future energy systems and energy systems analysis. In this work, we contribute to the growing amount of research on justice in energy systems modelling by assessing the implications of different philosophical views on justice on modelling results. Through a modelling exercise with a power system model for Europe (highRES Europe), we explore different designs of a future net-zero European energy system, and its distributional implications based on different justice principles. In addition to the utilitarian and egalitarian approach, we include, among others, principles of 'polluters pay' and 'ability-to-pay', which take historical contributions of greenhouse gas emissions and the socio-economic conditions of a region into account. We find that socially just energy systems look significantly different depending on the justice principles applied. Key output metrics include costs, technology mixes and spatial deployment of electricity generation infrastructure. The results should contribute to a greater discussion among researchers on the implications of different constructions of justice in modelling, expansion of approaches, and demonstrate the importance of transparency and assumptions when communicating such results. 
Local seismicity in the obliquely spreading setting of Fram Strait constrained from ocean bottom seismometers: Implications for fluid flow and methane seepage
Authors: Domel Przemyslaw , Schlindwein Vera , Plaza-Faverola Andreia , Bünz Stefan
Published: February 2023

The Fram Strait opening is associated with a complex stress regime that results from the oblique relation between two ultra-slow spreading mid-ocean ridges, the Molloy ridge (MR) and the Knipovich Ridge (KR), offset by the Molloy Transform Fault (MTF). Gas-charged thick sedimentary deposits developed over both oceanic and continental crust. Sedimentary faulting reveals recent stress transfer into the sub-surface. However, the mechanisms by which stress accommodates across the west Svalbard margin and its effect on fluid flow and seepage dynamics remain poorly understood. An analysis of earthquake occurrence and focal mechanisms can shed light on the present state of tectonic forces in the area, their origin and potential influence on nearby faults. Conventional studies using land instrumentation provide incomplete seismological records even for such comparatively land proximal settings, due to still large distances to the nearest permanent observatories and a poor azimuthal coverage. We deployed 10 ocean bottom seismometers (OBS) for 11 months between 2020-2021 about 10 km north of the northern termination of KR to investigate patterns of stress transfer off the ridge and the influence on the sedimentary system. OBSs are spaced by about 10 km around an area characterized by fault-related seepage and sedimentary slumps visible on the bathymetry. Using partially automated routines we built a catalogue of local earthquakes and computed their epicenters and magnitudes. Earthquake locations roughly follow the plate boundaries and better focus seismicity along their bathymetric imprint versus the land observations. Along the MTF, we observe that the earthquakes are concentrated southwards on the North American plate and seismicity across the west-Svalbard margin is limited. A large number of earthquakes extend beyond the MTF and KR corner and concentrate at a bathymetric depression, adjacent to the recently revised continental-oceanic transition boundary. Focal mechanisms from past observations show a gradual change from strike-slip movement along the MTF to extensional faulting at the corner. The distribution of earthquakes correlates with highly faulted sedimentary overburden interpreted in high resolution seismic data, and with major structures in gravity and magnetic maps. This suggests an efficient stress release at the plate boundary and little to no transfer northward from the KR termination onto the Eurasian plate. We detected only a few events recorded along the Vestnesa contourite drift and on the continental shelf. These earthquakes may indicate reactivation of crustal faults under the weight of thick sedimentary deposits or other processes such as glacial isostacy. The inferred stress distribution in the region has implications for understanding fault-related gas transport and methane seepage at Arctic margins.
ICESat-2 Ice Sheet Mass balance: Going below the surface
Authors: Hansen Nicolaj , Sørensen Louise S. , Spada Giorgio , Melini Daniele , Forsberg Rene , Mottram Ruth , Simonsen Sebastian B.
Published: February 2023

We use the land-ice surface height data product (ATL06 release 5) from NASA’s latest satellite laser altimetry, the Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) to compute surface elevation changes (SEC) from October 2018 to September 2021 over both Antarctica and Greenland. To convert the SEC to mass change we need to remove the non-ice related SEC processes. To remove the signal from the firn compaction, we use an offline surface energy and firn model. The model is driven by outputs from the atmospheric regional climate model HIRHAM5, forced with reanalysis dataset ERA5, and it simulates the physics of the firn pack. The vertical bedrock movement also creates non-ice related signals, the glacial isostatic adjustment has been computed using the ICE-7G model and SELEN4, and the elastic rebound has been computed using a modified version of the REAR code. When the SEC are corrected for signals that are not associated with a change in snow or ice mass, we convert to mass change by multiplying the height change with an appropriate density.  The corrected SEC can result from a change in either melt, snow accumulation, or dynamical behavior, this means that the appropriate density depends on which physical processes are driving the observed SEC. In this study, we have made a new density parametrization to convert the volume change into mass change. The density parametrization determines if one should multiply with snow densities (250-350 kg/m³) or ice density (917 kg/m³) based on a number of criteria; the sign of SEC, ice flow velocity, and the altitude of the area. With our new density parametrization, we get that the Greenland Ice Sheet has lost 237.5±10.3 Gt/year and the grounded Antarctic Ice Sheet has lost -137.6±27.2 Gt/year in the period. These results are in agreement with other mass balance estimates derived with different methods.
Key Signatures of Prominence Materials and Category of Unknown-origin Cold Materials identified by Machine Learning Classifier
Authors: Meng Shuyi , Yao Shuo , Cheng Zexin
Published: February 2023

The origin of cold materials identified by different criteria is unclear. They are highly suspected to be the erupted prominence. However, some cold materials defined by charge depletion exist in both solar wind and ICMEs. Recently, solar observations show failed prominence eruption in CMEs that it did not propagate into the interplanetary space. Besides, the related prominence eruptions of the earth-directed ICMEs at 1 au are difficult to identify before the launch of STEREO mission. This work uses Random Forest (RF) that is an interpretable classifier of supervised machine learning to study the distinct signatures of prominence cold materials (PCs) compared to quiet solar wind (SW) and ICMEs. 12 parameters measured by ACE at 1 au are used in this study, which are proton moments, magnetic field component Bz, He/H, He/O, Fe/O, mean charge of oxygen and carbon, C6+/C5, C6+/C4+, and O7+/O6+. According to the returned weights from RF classifier and the training accuracy from one black box classifier, the most important in situ signatures of PCs are obtained. Next, the trained RF classifier is used to check the category of the origin-unknown cold materials in ICMEs. The results show that most of the cold materials are from prominence, but 2 of them are possibly from quiet solar wind. The most distinct signatures of PCs are lower charges of C and O, proton temperature, and He/O. This work provides quantitative evidence for the charges of C and O being most effective solid criteria. Considering the obvious overlaps on key parameters between SW, ICMEs, and PCs, multi-parameter classifier of machine learning show an advantage in separating them than solid criteria.
Comparison of NWP Models Used in Training Surrogate Wave Models
Authors: Pillai Ajit , Ashton Ian , Chen Jiaxin , Steele Edward
Published: February 2023

Machine learning is increasingly being applied to ocean wave modelling. Surrogate modelling has the potential to reduce or bypass the large computational requirements, creating a low computational-cost model that offers a high level of accuracy. One approach integrates in-situ measurements and historical model runs to achieve the spatial coverage of the model and the accuracy of the in-situ measurements. Once operational, such a system requires very little computational power, meaning that it could be deployed to a mobile phone, operational vessel, or autonomous vessel to give continuous data. As such, it makes a significant change to the availability of met-ocean data with potential to revolutionise data provision and use in marine and coastal settings.This presentation explores the impact that an underlying physics-based model can have in such a machine learning driven framework; comparing training the system on a bespoke regional SWAN wave model developed for wave energy developments in the South West of the UK against training using the larger North-West European Shelf long term hindcast wave model run by the UK Met Office. The presentation discusses the differences in the underlying NWP models, and the impacts that these have on the surrogate wave models’ accuracy in both nowcasting and forecasting wave conditions at areas of interest for renewable energy developments. The results identify the importance in having a high quality, validated, NWP model for training such a system and the way in which the machine learning methods can propagate and exaggerate the underlying model uncertainties.
Mapping the ratio of meteoric and continental ice in Antarctic Ice Shelves as a metric for susceptibility to future climate change
Authors: Visnjevic Vjeran , Drews Reinhard , Moss Guy , Schannwell Clemens
Published: February 2023

Ice shelves encircling the Antarctic perimeter buttress ice flow from the continent towards the ocean, and their evolution and integrity are governed by surface accumulation, basal melting, and ice dynamics. The disintegration of ice shelves, caused by future changes in the climate, leads to an increase in ice discharge towards the ocean and a consequent increase in global sea level – making their future stability important.In this study we focus on the structure and composition of ice shelves. We model ice shelf stratigraphy for all ice shelves around Antarctica using a simplistic and observationally driven ice-dynamic forward model (validated on the Roi Baudouin Ice Shelf, Visnjevic et al., 2022), and map spatial variations in the percentage of locally accumulated ice on the ice shelf (local meteoric ice - LMI) compared to the ice inflowing from the continental ice sheet (continental meteoric ice - CMI). We investigate differences between LMI and CMI dominated ice shelves in the context of ice shelf stability, and discuss their susceptibility to future atmospheric and oceanic changes in climate. Expanding the analysis to the continental scale allows us to identify zones where future changes in climate might strongly impact ice shelf geometry and composition.
Lagrangian modeling used for improving ice core interpretation
Authors: Plach Andreas , Eckhardt Sabine , Pisso Ignacio , McConnell Joseph R. , Stohl Andreas
Published: February 2023

Atmospheric transport modeling with the Lagrangian Particle Dispersion Model (LPDM) FLEXPART has been used for the interpretation of ice core records in several studies in the recent past. Here we present (1) the methodology and results of a study looking into the historical black carbon (BC) emissions based on inverse modeling of ice core records, (2) discuss preliminary results and further plans for a similar study looking into the historical sulphur dioxide (SO2) emissions, (3) and give a short overview of other ice core studies using FLEXPART simulations.Both, BC and SO2 emissions, are caused by anthropogenic as well as natural processes, e.g., (incomplete) combustion of fossil fuels / biomass and volcanic eruptions. And, both negatively influence our health and environment, e.g., causing premature mortality, lowering surface albedo, producing acid rain. However, both species also act as climate forcers, and therefore an accurate knowledge of past BC/SO2 emissions is essential to quantify and model associated global climate forcing. Nowadays, commonly used bottom-up BC/SO2 emission inventories for historical Earth System Modeling (ESM), e.g., for the Coupled Model Intercomparison Project Phase 5 / Phase 6 (CMIP5/CMIP6) are poorly constrained by observations prior to the late 20th century.In a recent study, we revisit and evaluate these historical 1850 to 2000 BC emission inventories used for ESM simulations, based on an array of deposition ice core records, Lagrangian atmospheric modeling with the FLEXPART model, and an objective inversion technique in order to bring the spatial-temporal patterns of emission inventories in accordance with observed deposition at the ice core sites. We find substantial discrepancies between our reconstructed BC emissions and the existing bottom-up inventories which do not fully capture the complex spatial-temporal BC emission patterns. Our findings imply changes to existing historical BC radiative forcing estimates are necessary, with potential implications for observation-constrained climate sensitivity.
Dry grassland restoration in Mediterranean degraded lands: the NewLife4Drylands pilot case in Alta Murgia
Authors: Labadessa Rocco , Forte Luigi , D’Ambrogi Serena , Mazzetti Paolo , Tomassetti Laura , Tarantino Cristina
Published: February 2023

The need of adopting practices to restore degraded land has been stressed by the new Soil Strategy, with regard to dry ecosystems showing greater risk of desertification. To assess the effectiveness, feasibility and replicability of restoration techniques applied to Mediterranean dry ecosystems, a set of different restoration techniques has been tested in Alta Murgia National Park (Southern Italy), one of the NewLife4Drylands project (NL4D; https://www.newlife4drylands.eu) pilot sites. This area is particularly subjected to land degradation processes as a result of recent and widespread activities of rock shattering for the conversion of calcareous pastures to croplands, which had caused an extensive loss of semi-natural vegetation and ecosystem functions. Experimental efforts were aimed at testing sustainable techniques for the restoration of protected dry grassland types that naturally occur in the study area. Within an overall surface of 9000 m2, 42 experimental plots of 20x10m areas (14 treatments with 3 replicates) were selected in either recently ploughed or unploughed surfaces. For each soil type, a set of restoration techniques was tested, including different combinations of soil processing (i.e. harrowing, topsoil inversion, sod cutting, soil compression), transfer of plant material (i.e. dry hay, seed-enriched hay, shrub seeds) and soil cover (jute bionet). Unmanaged surfaces were selected as control plots for each soil type. Restoration effects, in terms of changes in plant community and soil features, will be monitored in comparison with initial conditions. The experimented approaches, along with the assessment of its effectiveness and feasibility, will provide useful information to guide the users to the identification of the most suitable nature-based solutions for the restoration of degraded lands. Within the aims of the NL4D project, the results of this experiment will be used to validate protocols and monitoring tools for environmental management and planning at local and regional scale based on the use of remote sensing techniques.
Modelling interranual variability of methane emissions from a temperate degraded peatland
Authors: Jourdain Line , Salmon Elodie , Guimbaud Christophe , Qiu Chunjin , Gogo Sebastien , Guenet Bertrand , Jégou Fabrice , Lagoun Défarge Fattima , Ciais Philippe
Published: February 2023

Wetlands are the largest natural source of methane in the atmosphere. How the methane emissions from wetlands will evolve with global change is a subject of debate. In this study, we investigate the interannual variability of methane emissions from a temperate degraded peatland located in the Sologne region (French Region Centre) and test the ability of the land surface model ORCHIDEE to reproduce this variability. The site is instrumented for long term monitoring of the hydrological parameters, greenhouse gas emissions, dissolved organic content and biodiversity. The peat has undergone several perturbations due to the urbanization of the site that led to drainage and invasion by vascular plants (Molinia Caerula, Erica Tretalix). Our study focuses on the 2014-2020 period after a hydrological restoration was undertaken. The model, driven by meteorological data and constrained by in situ hydrological data, primary productivity and total soil carbon, is able to reproduce the general temporal trend in methane emissions. The model is used to investigate the effect of climatological conditions (droughts) and vegetation changes (invasion by vascular plants) on the observed trend of methane fluxes. The model is also used to study the relative contributions of different methane transport processes (by the plants, from ebullition and diffusion) to the methane flux observed in La Guette peatland.
Study on long-term variation of river water quality in Japan
Authors: Kodera Koji , Oda Masato , Igari Yoshihiro , Morimoto Yoichi
Published: February 2023

１．introductionDuring Japan's period of rapid economic growth, water pollution became a problem throughout the country, but water quality has improved rapidly thanks to the enactment of laws and the heightened environmental awareness of society as a whole. However, even now, not only is the concentration concentrated in Tokyo, but urbanization is also progressing in rural areas, and there are still areas with severe water pollution in the suburbs. What used to be point source pollution has spread to non-point source pollution. Due to problems with wastewater treatment facilities in mountainous areas, many large river basins are more polluted upstream than downstream. The results of the ``Survey of the Water Environment in Public Water Areas,'' which has been continued by the government since 1971, and the ``National Simultaneous Survey of Familiar Water Environments,'' which was started in 2004 by citizens' groups, are available on a nationwide scale. I have mainly studied long-term changes in river water quality in Japan. We will also consider the results of measurements by Hosei University in 2020 and 2021.２．Results and considerations１）Water quality survey results for public water areasThere were about 1,000 observation points in 1971, but 15 years later, in 1986, the number exceeded 5,000, and since then observations have continued at just under 6,000 points. In 1971, half of the BOD values were 3 or more, but in 1976 half were 2 or less, and recently, 2 or less accounted for about 80% (2018). The number of points with 1 to 4 remained unchanged, but 4 or more decreased, and 1 or less increased to about half of the total.２）Nationwide Simultaneous Survey of Familiar Water EnvironmentIn 2004, when the survey began, there were about 2,500 sites, but in 2005 there were about 5,000 sites, and after that, although it remained around 6,000 sites, it reached about 7,000 sites in 2018. COD4 or less is about half.３．conclusionIn addition to the nationwide long-term observation results, data from before 1971 were collected and organized in an attempt to reconstruct past water quality. With regard to recent water quality, we independently conduct observations at more than 1,500 points nationwide every year to clarify the current situation. In addition to the coastal area in 2020, we were able to investigate the inland area in 2021 and the municipality unit in 2022. We would like to improve the accuracy while continuing the wide-area survey.
Electron transfer to peat particulate organic matter in ombrotrophic bogs and implications for methane formation: a combined field and laboratory study
Authors: Obradović Nikola , Läubli Saskia , Schmitz Rob , Schroth Martin , Sander Michael
Published: February 2023

Ombrotrophic bogs are rainwater-fed, water-logged, anoxic, and carbon-rich ecosystems with low concentrations of dissolved inorganic terminal electron acceptors (TEAs), such as nitrate and sulfate. Consequently, methanogenesis is expected to dominate carbon turnover in many of these systems and to result in an approximatively equimolar formation of CO2 and CH4. Yet, numerous studies have reported elevated molar CO2:CH4 formation ratios in peat bog soil incubations, indicating that anaerobic respiration prevails over methanogenesis despite the apparent scarcity of inorganic TEAs. To explain anaerobic respiration, particulate organic matter (POM) was proposed to act as previously unrecognized TEA. Here, we present results from combined in situ field studies and laboratory peat soil incubations to assess electron transfer to oxidized POM (POMox) and its effects on CO2 and CH4 formation. In situ studies consisted of deploying litter mesh bags containing POMox in the anoxic, water saturated subsurface of three ombrotrophic bogs – Lungsmossen (LM), Storhultsmossen (SM), and Björsmossen (BM) – for one year. The electron accepting capacity (EAC) of the retrieved POM decreased by 0.16±0.02 mmol e-/g dry POM in LM, 0.15±0.02 in SM, and by 0.17±0.01 mmol e-/g dry POM in BM, as compared with the buried POMox, demonstrating extensive electron transfer to the buried POM over the course of one year. Extents of POMox reduction were similar for different depths, as tested in BM bog. Exposure of the reduced POM to air (i.e. O2)resulted in an increase in its EAC, supporting that POM acts as a reversible TEA at the oxic-anoxic interface of peat soils. We complemented these in situ field studies with laboratory incubations of reduced POM collected from the same three bogs. Methanogenic conditions were observed in BM peat soil incubations, which were used for further studies. Amending BM soils with POMox and glucose resulted in increases in CO2:CH4 formation ratios of several orders of magnitude. These findings pointed towards anaerobic respiration using POMox as TEA, thereby suppressing methanogenesis. Taken together, our work provides evidence for POMox reduction in situ and substantiates the important role of POM as TEA in controlling CH4 formation in ombrotrophic bogs.
High-resolution loss modeling for European Windstorms
Authors: Kumar Dhirendra , Shaffrey Len , Dixon Richard , Bloomfield Hannah , Bates Paul , Hillier John
Published: February 2023

European windstorms are a frequent and damaging natural hazard that can cause loss of human life and damage to property and infrastructure. As there is a high degree of uncertainty in climate projections, it is crucial to understand the physical risks and economic losses at regional and local scales associated with European Windstorms. In this study, we develop a simple model to estimate historical windstorm losses over the European region. The model uses winds from the ERA5 reanalysis and different exposure datasets based on countrywide total insured property values, gross domestic product, and historical population density.We find that the estimated losses associated with major historical storms in North-western Europe and estimated average EU-wide losses are comparable to the reported estimates and those from propriety vendor models. However, estimated losses from windstorms in France and Germany are lower than reported. Differences in the estimated losses are attributed to the contrasts in the regional-level exposure within and between different exposure datasets. We also tested the sensitivity of regional-level vulnerabilities and find that accounting for regional-level vulnerability differences slightly improves the biases in countrywide losses. Further, we also find that the major contribution to the estimated losses comes from the United Kingdom, France, and Germany for most of the storm seasons, and thus it is important to correctly represent the exposure and vulnerabilities over these countries. The ability of the model to estimate reported losses is also limited by the representation of the winds in ERA5, which has limited skill in representing the hazard footprint, especially for specific storms such as the Great October Storm of 1987.Keywords: Losses, Windstorms, Climate Change, Natural Hazards
Modeling dynamic ruptures on extended faults for microearthquakes induced by fluid injection
Authors: Mosconi Francesco , Tinti Elisa , Casarotti Emanuele , Gabriel Alice , Dorozhinskii Ravil , Dal Zilio Luca , Rinaldi Antonio Pio , Cocco Massimo
Published: February 2023

Understanding the dynamics of microearthquakes is a timely challenge to solve current paradoxes in earthquake mechanics, such as the stress drop and fracture energy scaling with seismic moment. Dynamic modeling of microearthquakes induced by fluid injection is also relevant for studying rupture propagation following a stimulated nucleation. We study the main features of unstable dynamic ruptures caused by fluid injection on a target preexisting fault (50m x 50m) generating a Mw=1 event. The selected fault is located in the Bedretto Underground Laboratory (Swiss Alps) at ≈1000m depth. We perform fully dynamic rupture simulations and model seismic wave propagation in 3D by adopting a linear slip-weakening law. We use the distributed multi-GPU implementation of SeisSol on the supercomputer Marconi100. Stress field and fault geometry are well constrained by in-situ observations, allowing us to minimize the a priori imposed parameters. We investigate the scaling relations of stress drop, slip-weakening distance (Dc) and fracture energy (Gc) focusing on their role in governing dynamics of rupture propagation and arrest for a target Mw=1 induced earthquake. We explore different homogenous conditions of frictional parameters, and we show that the spontaneous arrest of the rupture is possible in the modeled stress regime, by assuming a high ratio between stress excess and dynamic stress drop (the fault strength parameter S), characterizing the fault before the fluid pressure change. The rupture arrest of modeled induced earthquakes depends on the heterogeneity of dynamic parameters due to the spatially variable effective normal stress. Moreover, for a fault with high S values (not ready to slip), small variations of Dc (≈0.5÷1.2 mm) can drive the rupture from self-arrested to run-away. Studying dynamic interactions (stress transfer) among slipping points on the rupturing fault provides insight on the breakdown process zone and shear stress evolution at the crack tip leading to failure. The inferred spatial dimension of the cohesive zone in our models is nearly ~0.3-0.4m, with a maximum slip of ~0.6 cm. Finally, we compare stress drop and fracture energy estimated from synthetic waveforms with assumed dynamic parameters. Our results suggest that meso-scale processes near the crack-tip affect rupture dynamics of micro-earthquakes.
PseudoSpectralNet: A hybrid neural differential equation for atmosphere models
Authors: Gelbrecht Maximilian , Boers Niklas
Published: February 2023

When predicting complex systems such as parts of the Earth system, one typically relies on differential equations which often can be incomplete, missing unknown influences or include errors through their discretization. To remedy those effects, we present PseudoSpectralNet (PSN): a hybrid model that incorporates both a knowledge-based part of an atmosphere model and a data-driven part, an artificial neural network (ANN). PSN is a neural differential equation (NDE): it defines the right-hand side of a differential equation, combining a physical model with ANNs and is able to train its parameters inside this NDE. Similar to the approach of many atmosphere models, part of the model is computed in the spherical harmonics domain, and other parts in the grid domain. The model consists of ANN layers in each domain, information about derivatives, and parameters such as the orography. We demonstrate the capabilities of PSN on the well-studied Marshall Molteni Quasigeostrophic Model.
Variations in particulate matter chemical composition in the urban coastal city of India
Authors: Tripathi Shruti , Chakraborty Abhishek , Mandal Debayan
Published: February 2023

Particulate matter (PM) is collected in the urban coastal city of Mumbai. The PM2.5 concentrations averaged from 200 μg m−3 to 90 μg m−3 throughout the year during sampling. These values were substantially higher than national ambient air quality standards (60 μg m−3). The Organic carbon (OC) concentration in PM ranged from 6 μg m−3 to 17 μg m−3 from summer to winter, whereas elemental carbon (EC) has varied from 1.2 μg m−3 to 4.8 μg m−3. The OC/EC ratio was lower in winter than summer because of high EC emissions during winter and low photochemical activities. The summer samples have a high percentage of low volatile OC fraction (53%) than the winter samples. The calculated secondary organic carbon (SOC) also varies seasonally. The fraction of SOC in overall OC was highest in summer (65.7%), whereas the concentration of SOC was higher in winter, i.e., 9 μg m−3. High temperatures and strong solar radiation favor SOC formation during the summer, resulting in a high percentage of low volatile OC in total OC. The overall chemical composition of PM2.5 reveals that almost 68% of the total mass was elemental composition (SO42−, NO3−, NH4+, Na+, Ca2+and K+) in winter and 16% in summer. Seasalt contribution to PM2.5 was 32% and 5% in winter and summer, respectively. Chlorine to sodium molar ratios was below the seawater ratio line in both seasons (0.69 winters and 0.30 summers), but the drop in the summer season might indicate more loss of chlorine. In summer, aerosols are slightly less acidic than in winter and pH value ranged from 3.2 to 7.1. Therefore, we can say that Mumbai suffers from air pollution problems during the winter, despite being a coastal city. These high concentrations of PM have an adverse effect on the health of the urban population.