bluuebunny/crossref_metadata_2025 huggingface dataset:
Application of the signal processing to a short-offset seismic data in the Hupo basin, offshore Korea
Authors: Son Woohyun , Kim Byoung-Yeop , Yoo Dong‑Geun
Published: February 2023

In this study, seismic data were acquired using Tamhae2 R/V to identify the subsurface fault structures in the Hupo basin. The seismic data were generated by the air-gun source (30 cu. in.). The source distance is 12.5 m, and the receiver distance is 6.25 m. The number of channels is 32. The offset range of the seismic data is 50 to 250 m. The data processing for short-offset seismic data is mainly applied with simple processing techniques such as frequency filter, trace editing, and velocity analysis in consideration of cost efficiency. However, these simple data processing techniques cannot accurately image complex subsurface structures because it is difficult to remove severe noise and water-bottom (WB) multiples effectively. Therefore, in order to accurately identify the geological structures, it is necessary to apply high-resolution signal processing techniques that can remove severe random noise and WB multiples included in raw seismic data. Severe noise was removed by applying data processing techniques such as a low-cut filter, trace editing, swell noise attenuation, and random noise attenuation. In addition, predictive deconvolution, SRME, and Radon filter were applied to effectively attenuate WB multiples that cause difficulties in geological interpretation. Finally, pre-stack Kirchhoff time migration was applied to more accurately image the subsurface structures. From the data processing results, we confirmed that the high-resolution signal processing techniques applied in this study greatly improved the signal-to-noise ratio of seismic data and effectively eliminated WB multiples.
Hybrid ANN and physically-based models for regional PM2.5 forecasts
Authors: Kow Pu-Yun , Liou Jia-Yi , Chang Li-Chiu , Chang Fi-John
Published: February 2023

Air pollution has affected people's health and lowered our living quality. Among all pollutants, PM2.5, which is smaller than 2.5 microns, can easily penetrate human lungs and seriously affect human health. Therefore, PM2.5 control is a very crucial action. Air pollution modelling can roughly categorize into two types, stochastic model (Artificial neural network (ANN) model) and deterministic model (physically-based model). Since the variation of PM2.5 concentrations is dynamic, the physically-based model struggles to handle the uncertainty from its complex interaction. With the aid of the nonlinearity of ANNs, we can overcome these uncertainties. We proposed a hybrid convolutional (CNN)-based ANN to extract features from the dataset to provide three days ahead PM2.5 forecast. The physically-based model first generates the simulated dataset. Over 40 thousand historical and simulated hourly datasets are collected to construct the deep learning model. This hybrid model that learns historical information and future trends performs better in terms of R2 (0.58-0.72) than the baseline model (0.40-0.44). Besides that, its forecast time horizon is relatively long (<72 hours) if we compare it with the pure ANN model (<12 hours). As a result, the proposed hybrid model can provide accurate regional air pollution forecasts by inheriting the characteristics of physically-based model and ANN.Keywords: Artificial Neural Network; Deep learning; Convolutional neural network (CNN); Regional air quality forecast
Improved identification and monitoring of meteorological, agricultural, and hydrological droughts using the modified nonstationary drought indices in the Yellow River Basin of China
Authors: Niu Ben , Li Yi , Liu De Li , Wei Kangkang , Jiang Xiaohui , Yao Ning , Feng Hao , Yu Qiang , He Jianqiang , Yang Zhe , Jiang Yanan , Yang Guang , Lin Haixia
Published: February 2023

The nonstationarity exists in the drought indicator series, making drought monitoring and assessment more complex and accurate. Our study aimed to better identify and monitor meteorological, agricultural, and hydrological droughts in the Yellow River Basin (YRB) of China. We constructed the temporal-variate nonstationary standardized drought indices for precipitation (NSPI), evapotranspiration (NSPEI), soil moisture (NSSMI), and runoff (NSRI) based on nine Generalized Additive Models for Location, Scale, and Shape (GAMLSS). Further, we investigated the performance of NSPI/NSPEI/NSSMI/NSRI by comparing with the historical drought events in YRB. The results show that: (1) The probability distribution function (PDF), smoothing function (SF), and degree of freedom (DF) had a significant influence on the fitting goodness of the GAMLSS model. Additionally, PDF was the most important factor to determine the fitting goodness, while the appropriate SF and DF improved the fitting effects of the model. (2) The stationary GAMLSS model mainly was applied to lower-timescale series, and the nonstationary GAMLSS models were more suitable for the higher-timescale series. (3) The NSPI and NSPEI were more sensitive to identifying meteorological drought, but NSPEI was more accurate in identifying drought intensity and duration. The agricultural drought identified by NSSMI agreed well with the historical drought events but had a poor response to mild and moderate drought. (4) Form NSRI, hydrological drought in the tributaries of the YRB was affected by meteorological drought, and the intensity of hydrological drought was heavier than that in the mainstream of the YRB. In conclusion, the nonstationary drought indices could identify drought events more accurately and provide valuable information for drought-resistant work in the YRB.
The Seismogenic Potential of the Southernmost Ryukyu Subduction Zone as Revealed by Historical Earthquakes and Slow Slip events
Authors: Chen Sean Kuanhsiang , Wu Yih-Min , Chan Yu-Chang
Published: February 2023

The southernmost Ryukyu subduction zone may have a geodetically inferred Mw 7.5 to 8.7 megathrust earthquake in a shallow locked region, the Ryukyu fault. Paleoseismological evidence of historical earthquakes available from the last 417 years indicates that only a 1920 Mw 7.7 earthquake occurred within this magnitude range, near the downdip end of the Ryukyu fault. As slow slip events downdip the locked seismogenic zone may trigger a large subduction earthquake, we investigate how the first observed slow slip events in 2005, 2009, and 2015 initiated downdip in the Ryukyu fault interface affect the occurrence of a megathrust. We establish possible megathrust earthquake cycles from Mw 7.5 to 8.7 on the Ryukyu fault using constraints from the magnitude-frequency relation based on local historical earthquakes. This analysis shows a b value of 1.2 for magnitudes greater than Mw 7.0, which is higher than the empirical 1.0 value. This indicates that the recurrence of an event up to Mw 8.7 is longer than previously thought if the megathrust events follow the observed magnitude-frequency relation. Then, we quantify the influence of slow slip events on the triggering of a potential megathrust earthquake by calculating the static stress increase. We find that stress perturbations caused by the three slow slip events are generally consistent with the values that have triggered the large interplate earthquakes in several subduction zones. However, a large earthquake has not yet been triggered on the Ryukyu fault after a sequence of slow slip events. If the 1920 Mw 7.7 earthquake is the last rupture of the Ryukyu fault, the earthquake cycle on the Ryukyu fault is very likely in an early stage. However, this is not true if the slow slip events occur toward the end of the earthquake cycle and there has been no megathrust earthquake at the fault interface in the last 417 years, as the 2011 Mw 9.0 Tohoku earthquake. Thus, higher potential for a megathrust earthquake may occur in the southernmost Ryukyu subduction zone.
Abrupt cooling event over Asia due to North Atlantic climate instability ~16 ka
Authors: Timmermann Axel , Sinha Nitesh , Jo Kyoung-nam , Wassenburg Jasper , Ruan Jiaoyang , Kim Hyuna
Published: February 2023

The last glacial termination was marked by a series of millennial-scale hemispheric climate change events. One of the most prominent examples is Heinrich event  1, which was caused by ice-sheet instabilities of the Laurentide ice-sheet between 18,000-15,000 years ago (ka) and corresponding shifts in global climate. Recent speleothem oxygen isotope data suggest the presence of yet another much more abrupt and shorter event around 16 ka.  The global extent and the origin of this elusive 16-ka event have remained a mystery. Here we present new resolution clumped isotope data from a South Korean speleothem that shed new light on this phenomenon. Combined with LA-ICPMS trace element analysis, we demonstrate that the 16-ka event likely caused abrupt cooling over Eastern Asia of ~5-7oC and massive shifts of both the winter and summer monsoon systems.  Using an isotope-enable earth system model, we show the observed oxygen isotope evolution is consistent with an abrupt meltwater lake surge into the North Atlantic, of unknown origin, with impacts on ocean stratification, sea-ice and northern hemispheric climate.
Development of an earthquake early warning and shakemaps system using low-cost sensors in Taiwan
Authors: Wu Yih-Min
Published: February 2023

Building an earthquake early warning (EEW) network requires the installation of seismic instruments around the seismogenic zone. Using low-cost sensors to build a seismic network for EEW and to generate shakemaps is a cost-effective way in the field of seismology. The National Taiwan University (NTU) network employing 770 P-Alert low-cost sensors based on micro-electro-mechanical systems (MEMS) technology is operational for almost the last 10 years in Taiwan. This instrumentation is capable of recording the strong ground motions of up to ± 2g and is dense enough to record the near-field ground motion. The NTU system has shown its importance during various earthquakes that caused damage in Taiwan. Although the system is capable of acting as a regional as well as an on-site warning system, it is particularly useful for onsite warning. Using real-time seismic signals, each P-Alert device provided a 2–8 s warning time for the near-source earthquake regions situated in the blind zone of the Central Weather Bureau (CWB) regional EEW system, during the 2016 Mw6.4 Meinong and 2018 Mw6.4 Hualien earthquakes. The shakemaps plotted by the P-Alert dense network help to assess the damage pattern and act as key features in the risk mitigation process. These shakemaps are delivered to the intended users, including the disaster mitigation authorities, for possible relief purposes. Currently, the P-Alert network can provide peak ground acceleration (PGA), peak ground velocity (PGV), spectral acceleration (Sa) at different periods, and CWB intensity shakemaps. Using shakemaps it is found that PGV is a better indicator of damage detection than PGA. Encouraged by the performance of the P-Alert network, more instruments are installed in Asia-Pacific countries.
HISAR: Hydrologic Indices of South American Rivers
Authors: Ribeiro Larissa , Paiva Rodrigo , Collischonn Walter , Sorribas Mino , Paul Leonardo
Published: February 2023

Effective water resources management for environmental conservation requires a proper understanding of the behavior of rivers. Rivers can be understood through the analysis of the flow regime synthesized by hydrologic indices. While the density of in situ river observation networks is heterogeneous across several continents, such as South America, recent advances in continental scale hydrologic modeling bring new opportunities for systematic characterizations over large domains. We build the HISAR (Hydrologic Indices of South American Rivers) dataset to study the natural flow regime of South American rivers. It is composed of 73 hydrological indices computed from observed and modeled discharge datasets. We evaluated the performance of the continental-scale hydrological model (MGB, Modelo de Grandes Bacias), comparing the hydrological indices computed from modelled and observed discharges. The results allow the identification of patterns in the flow regime of rivers and evidence relationships between climate and hydrology and between different indices. The indices of modelled discharges regarding magnitudes had more agreement with indices of observed data (e.g., mean flow and runoff ratio), while indices representing temporal variability were more different. Despite the disagreement of some indices (baseflow recession constant, hydrograph skewness, and number of hydrologic reversals), the simulated discharges dataset can be utilized in hydrologic indices for understanding rivers' flow regimes and behaviors on a continental scale. The relative error median modulus varied from approximately zero to 99.4%, with a mean of 15.4%. The HISAR dataset is freely available at https://doi.org/10.5281/zenodo.7296577.This work has been partially supported by the Brazilian agency CAPES.
Photo-induced enhancement of radioactive 137Cs removal by adsorption on Prussian blue analogues
Authors: Kim Soonhyun , Kim Minsun , Eun Semin
Published: February 2023

Prussian blue analogue (PBA) has been received great attention as a material for radioactive Cs removal because of its high Cs ion adsorption efficiency. In this study, we synthesized PBA with three different transition metal ions (Ni(II), Co(II), and Fe(II) for NiFe-PBA, CoFe-PBA, and FeFe-PBA, respectively) and adjusted their particle sizes and surface areas by controlling the amount of stabilizing agent. They also composited with TiO2 and then compared the efficiencies of Cs ion adsorption under dark or UV light. The larger the surface areas and the smaller the particle size, the better the Cs ion adsorption, and the NiFe, NiFe-TiO2 and FeFe-TiO2 showed additional Cs ion adsorption under UV light irradiation. In particular, NiFe has an adsorption capacity of about 0.8 mmolg-1 and 1.7 mmolg-1 under dark and UV light, respectively, which is a result of about twice the increase in the adsorption capacity by UV light irradiation. In addition, the NiFe-TiO2 nanocomposite shows adsorption capacities of about 0.45 mmolg-1 and 1.5 mmolg-1 under dark and UV light, respectively, which is a result of about three times the increase in the adsorption capacity by UV light irradiation. Photo-induced additional adsorption on NiFe showed even with radioactive 137Cs adsorption. This enhanced Cs ion adsorption of NiFe happens due to photoinduced charge transfer in NiFe molecular, which leads to additional adsorption of Cs ions. This is very meaningful result because it is first study of photo-induced additional removal of Cs on PBAs.
Fault strength dependency of natural earthquake-size distribution based on the precise focal mechanism data
Authors: Matsumoto Satoshi , Iio Yoshihisa , Sakai Shinichi , Kato Aitaro
Published: February 2023

“b-value”, which degree of power law decay in the earthquake-size distribution, is known showing spatial and temporal variation based on observational studies. Especially, the temporal variation sometime have detected before a large earthquake occurrence, showing that it can be an indicator for the occurrence and may help earthquake hazard mitigation. The b-value changes due to tectonic stress regime. In addition, laboratory experiments have revealed acoustic emission size distribution depends on differential stress magnitude and criticality of failure condition. However, it is unclear in natural earthquake activity that which factor controls b-value condition. In this study, we show b-value change of small earthquake sequences in normalized shear and normal stress.We carried out dense seismic observation composed by over 1000 stations deployed in hypocentral area (with diameter about 35 km) of the 2000 Western Tottori Earthquake (M7.3). About one year observation enabled us to obtain hypocenters and focal mechanisms about 5000 small earthquakes. Relative stress tensor have been inverted by the focal mechanism data in spatial bins and relative shear and normal stress for individual earthquake also estimated.  We investigated b-value change in relative shear and normal stress condition of small earthquake dataset. The b-value dependency on relative shear stress were detected, showing that the b-value decrease with increasing shear stress. In addition, the b-value takes minimum value at normal stress at critical point where line following Coulomb Failure condition with friction coefficient of 0.6 touches the unit Mohr circle. This suggests that the b-value become small in case of fault plane in optimal direction.
Optimization of analytical method for volatile organic compounds released from plastics and their emission characteristics by selected-ion flow tube mass spectrometry.
Authors: Choi Narin , An Joongeon , Kim Donghwi , Loh Andrew , Yim Unhyuk
Published: February 2023

While plastics are indispensable to our lives, they are known to emit harmful chemicals which can cause devastating effects to the environmental and human health. With the increasing concerns for global air pollution and climate change, the potential contributions of volatile organic compounds (VOCs) released from plastics have also been receiving increasing attention in recent years. Here, we developed and optimized a method for characterization of VOCs emitted from plastics. Using a selected-ion flow tube mass spectrometry (SIFT-MS), VOCs emissions were measured in real-time and data interpretations were performed using multivariate analysis. Expanded polystyrene (EPS), polypropylene (PP), high- and low-density polyethylene (HDPE and LDPE) and polyethylene terephthalate (PET) pellets were selected by their dominance as marine plastic debris. Emission characteristics of VOCs from selected polymers were monitored according to temperatures from 30℃ to 80℃. The emission of VOCs significantly increased with increasing temperatures for all plastic types, but varied in the order of LDPE, HDPE, PP, EPS, and PET. Partial least squares (PLS) analysis showed significant differences in compound group types, especially for compounds with relatively high molecular weight when heated at 80℃. The less-distinct differences in clustering of VOCs emitted at temperatures below 80℃, especially 60℃, were likely represented by additives and residuals during plastic production while VOCs emitted with temperatures above 80℃ were likely due to thermal degradation of polymers. The emitted compounds showed the highest mass concentrations with hydrocarbons such as alkane and alkene followed by monomers of each plastic type. These results suggested that the temperature threshold for VOCs emissions from residual materials and thermal degradations needs to be considered as one of the main factors for the analysis of VOCs from plastic debris.
Why does the October effect not occur at night?
Authors: Wendt Vivien , Schneider Helen , Banys Daniela , Hansen Marc , Clilverd Mark
Published: February 2023

Radar waves with very low frequency (VLF) are reflected at the lower edge of the ionosphere, in the D-region. The D-region (60 - 90km) is influenced by the solar zenith angle and space weather from above as well as by dynamical and chemical processes in the mesosphere. During October there is a well-known sharp decrease of the daytime VLF amplitude between transmitter and receiver combinations whose great circle paths lie mainly in polar latitudes. Until now we do not know what causes the October effect. Space weather phenomena can be ruled out as a cause since their time scales are either too short or too long. The solar zenith angle, strongly influencing the seasonal variation of the VLF amplitude can also be ruled out as a similar behavior is not observed in spring. Thus, there is a strong assumption that neutral dynamical processes in the mesosphere play a major role. We assume and confirm that a regional warming in the lower mesosphere, occurring simultaneously and with similar characteristics as the October effect, plays a major role in the formation process of the October effect. The VLF reflection height is about 15km higher during nighttime than during daytime. This difference in combination with the location of the regional warming explains, why the October effect can not be observed during nighttime.
Predicting stick-slips in FDEM simulated sheared granular faults using machine learning
Authors: Gao Ke
Published: February 2023

Predicting earthquakes has been a long-standing challenge. Recently, machine learning (ML) approaches have been employed to predict laboratory earthquakes using stick-slip dynamics data obtained from shear experiments. However, the data utilized are often acquired from only a few sensor points, thus insufficient in feature dimension and may limit the predictive power of ML. To address this issue, we adopt the combined finite-discrete element method (FDEM) to simulate a two-dimensional sheared granular fault system, from which abundant fault dynamics data (i.e., displacement and velocity) during stick-slip cycles are collected at 2203 “sensor” points densely placed in the numerical model. We then use the simulated data to train the LightGBM (Light Gradient Boosting Machine) models and predict the normalized gouge-plate shear stress (an indicator of stick-slips). Meanwhile, to optimize features, we build the importance ranking of input features and select those with top importance for prediction. We iteratively optimize and adjust the feature data, and finally reach a LightGBM model with an acceptable prediction accuracy (R2 = 0.91). The SHAP (SHapley Additive exPlanations) values of input features are also calculated to quantify their contributions to prediction. We show that when sufficient fault dynamics data are available, LightGBM, together with the SHAP value approach, is capable of accurately predicting the occurrence time and magnitude of laboratory earthquakes, and also has the potential to uncover the relationship between microscopic fault dynamics and macroscopic stick-slip behaviors. This work may shed light on natural earthquake prediction and open new possibilities to explore useful earthquake precursors using ML.
Antarctic subglacial flux: a driver of climate sensitivity on coastal margins
Authors: Seabrook Sarah , Law Cliff , Druce Matt , Cummings Vonda , Deppeler Stacy , Cox Simon , Westerhoff Rogier , Hillman Jess , Paytan Adina , Mikucki Jill , Ladroit Yoann , Maurice Alicia , Spain Erica , Safi Karl
Published: February 2023

Climate warming is increasing glacial melt on the Antarctic continent, in turn shifting hydrostatic pressure on subglacial and surface lakes. This has a direct impact on the rates ofgroundwater discharge, with feedbacks to local and regional ocean and climate dynamics, as well as ice sheet retreat rates. The magnitude and diversity of Antarctic subglacial flux and its interaction with the marine realm is currently unknown, yet it may be critical to projecting hydrologic dynamics and the fate of coastal ecosystems in the Ross Sea under future climate change scenarios. Here, we report the first holistic quantification of the magnitude, composition, and impact of subglacial fluxes documented in the Antarctic region. With extensive water column, sediment, and ecological sampling we have explored the magnitude, biogeochemical composition, and temporal variability of subglacial water and dissolved constituent fluxes in the Ross Sea. We will highlight initial findings from this research, including the magnitude and spatial variability of subglacial fluxes from the Victoria Land coast, and the sphere of influence of these fluids on the coastal marine ecosystem in the Ross Sea.  We will place discoveries to date in the context of this emerging field, including incorporation into ice sheet and oceanographic models of the region. With this, we provide the first direct evidence of land-sea connectivity in the Ross Sea coastal environment through submarine groundwater discharge (SGD) and establish a critical baseline for measuring and predicting future change. 
Oceanic Rossby waves induced two types of ocean-atmosphere response and opposite Indian Ocean Dipole phases
Authors: Zhang Yuhong , Du Yan
Published: February 2023

This study analyzed the downwelling Rossby waves in the south Indian Ocean induced spring asymmetric mode and the relationship with the Indian Ocean Dipole (IOD) event based on observations and reanalysis data sets. The westward downwelling Rossby waves favor significant sea surface temperature (SST) warming in the Seychelles thermocline dome that triggers atmosphere response and the asymmetric mode in spring. The zonal sea level pressure gradient causes anomalous easterly winds in the central and eastern equatorial IO, cooling the SST off Sumatra-Java. Meanwhile, the remainder of the downwelling Rossby waves reach the west coast, transform to northward coastal-trapped waves, and then reflect as eastward downwelling Kelvin waves along the equator. The downwelling Kelvin waves reach the Sumatra-Java coast during late spring to early summer, favoring SST warming in the southeastern tropical Indian Ocean. Thus, there are two types of ocean-atmosphere response almost at the same time along the equator. The final SST status depends on which process is stronger, and as a consequence, triggers a negative or a positive phase of the IOD event in the fall season. The results show four positive and three negative IOD events related to the above processes from 1960 to 2019. The strong downwelling Rossby waves are easier to induce intense asymmetric mode and negative IOD event, usually associated with preceding strong El Niño in the Pacific. In contrast, the weak downwelling Rossby waves tend to induce weak asymmetric mode and positive IOD event, usually associated with preceding weak El Niño or anomalous anti-cyclonic atmospheric circulation in the southeastern IO.
Progressive failure characteristics of different rock types through fractal analysis
Authors: Dinç Göğüş Özge , Avşar Elif , Develi Kayhan , Çalık Ayten
Published: February 2023

The deformation and failure processes of rocks under stress are primarily induced by microcracking. Detecting this micro-interaction phenomenon before the ultimate failure has paramount importance for predicting the post-failure rock damage characteristics. In this study, we aim to quantify the evolution of microcracking through fractal analyses of scanning electron microscope (SEM) images, captured from three different rock types subjected to uniaxial loading at various stress levels. In terms of uniaxial compressive (UCS) and tensile strength (UTS) values, the rocks range from the strongest to the weakest as being diabase, ignimbrite, and marble, respectively.  All rock samples are uniaxially loaded up to critical stress thresholds as crack initiation (σci), crack damage (σcd), and peak stress (σp) levels, considering their pre-defined characteristic stress-strain curves. Using the box-counting technique, the fractal dimension values (DB) of cracking intensity, induced by loading are determined for all these three stages. Here, it should be noted that higher fractal dimensions represent more intense microcracking according to the fractal theory. The results show that the DB values are increasing with the increasing amount of microcracks and the greatest DB values are calculated for Diabase due to its highest strength ratio (UCS/UTS). Although the marble has the weakest strength values, it presents a higher DB value than that of ignimbrite (DBmarble = 1.215 and DBignimbrite = 1.133) once the σcd stress threshold is reached. Furthermore, the DBmarble value is also greater than the DBignimbrite value for the σp stress level. It is because marble has a higher UCS/UTS ratio than the ratio of ignimbrite. Our results highlight the important role of rock texture on brittleness which exerts a primary control on fractal dimensions (DB). A decrease in volumetric rigidity is more dramatic in marble than in ignimbrite with incremental loading. The insights provide a better understanding of the microcracking process that leads to macro-scale deformations in rock engineering.
Leaching of carbon, metals, and additives from microplastics to water
Authors: Novotna Katerina , Cermakova Lenka , Pivokonsky Martin
Published: February 2023

The occurrence of microplastics (MPs) has been evidenced worldwide in various aquatic environments, and while quite many studies have been devoted to the quantification and characterisation of these MPs, the knowledge of potential leaching from MPs to water is yet limited. In the current study, a range of different MPs prepared from consumer plastic products were soaked in water for 12 weeks, and variable composition of the water leachates was continuously analysed. Majority of investigated MPs released substantial amounts of dissolved organic carbon, with the maximum of approximately 65 mg per g of MPs after the 12 weeks, and some MPs also released dissolved inorganic carbon. Additionally, up to 10 other elements were detected in individual leachates – including metals (Al, Ba, Ca, Fe, K, Mg, Mn, Na, Zn) and one metalloid (Si). Out of those, Ca, K, and Na occurred most frequently, while Ca reached the highest values (up to approximately 2.5 mg per g MPs). In general, the overall highest leaching was observed in the case of MPs comprising polyurethane, polyvinyl chloride, and acrylonitrile-butadiene copolymer as the main polymers. Another general observation is that the leaching was usually most rapid during the first few weeks of MP contact with water. Further, in order to provide a better insight into composition and properties of the leachates, non-target analysis was conducted, and dozens of chemical individuals were tentatively identified in the leachates. Considering that the amounts of some elements released from MPs were quite high, and that some of the tentatively identified compounds are considered harmful to human health and/or to the environment, the leaching from MPs to ambient water might be important from different perspectives, including toxicology as well as fluxes of carbon and metals.
Investigating microplastics at two drinking water treatment plants within a river catchment
Authors: Cermakova Lenka , Novotna Katerina , Pivokonsky Martin
Published: February 2023

Microplastics (MPs) are emerging globally distributed pollutants of aquatic environments. Nowadays, MPs are being detected in seas, oceans and freshwater bodies worldwide, even in very remote areas. Studies have reported also the occurrence of MPs in potable water. Despite the potential adverse effects on human health are still largely unknown, the presence of MPs in drinking water deserves more attention. Besides the need for elimination of MPs in natural environments, it is necessary to focus also on their fate and removability at drinking water treatment plants (DWTPs) that pose a barrier for MPs to enter water for human consumption. In our study, we decided to provide unique insight into the occurrence of MPs at two different DWTPs situated on the same river but differing in treatment technology. Quantification and characterization of MPs ≥ 1 μm was conducted not only in raw and treated water but also after each technological treatment step. The results showed that the content of MPs varied greatly between the DWTPs. There were 23 ± 2 and 14 ± 1 MPs L−1 in raw and treated water, respectively, at the upstream DWTP. By contrast, 1296 ± 35 and 151 ± 4 MPs L−1 were found in raw and treated water, respectively, at the downstream DWTP. The majority (>70%) of MPs were smaller than 10 μm, and irregular fragment shape prevailed over fibres. Cellulose acetate, polyethylene terephthalate, polyvinyl chloride, polyethylene, and polypropylene were the most frequently occurring materials. Total removal of MPs of 88% was achieved at the DWTP with a higher initial MP number and more complicated treatment technology consisting of coagulation-flocculation-sedimentation, deep-bed filtration through clay-based material, and granular activated carbon adsorption. These steps contributed to MP elimination by 62%, 20%, and 6%, respectively. These results contribute to filling the knowledge gap regarding the removability of different types of MPs by distinct drinking water treatment technologies operating under ordinary conditions.
A Regional Lagrangian Model for Assessing the Dispersion of Floating Macroplastics from Different Source Types over the Iberian Peninsula in the North Atlantic Ocean
Authors: Cloux Sara , Pérez Patricia , de Pablo Hilda , Pérez-Muñuzuri Vicente
Published: February 2023

Plastic debris in the oceans is a major environmental concern that knows no borders. This material, which is the result of poor waste management on land, is spread across the ocean over long distances and over long periods of time. When macroplastics (those larger than 5 mm) break down through mechanical and chemical processes, they become microplastics. It is difficult to estimate the extent and predict the behavior of these tiny pieces of plastic, but their presence in a variety of organisms, including mollusks and humans, has raised concerns about the potential consequences, which are not yet fully understood but are believed to be significant. To address this problem at a global scale, it is important to identify and quantify the sources of plastic waste that end up in the ocean. We use a validated Lagrangian model (Cloux et al., 2022) to track floating particles coming from potential sources. We studied three types of sources along the Atlantic coast of Spain: rivers, land-based points, and maritime traffic. Over a 7-year period, we analyzed the concentrations of these plastics in the open seas. Our results showed that a significant contribution comes from these sources, both at short and medium distances from the coast. If we consider the fact that some of the simulated particles get washed up on the shore, the concentration of particles near the coast is even higher in certain locations and the concentrations at medium distances are reduced.  Considering semi-enclosed areas, the influence of seasonality was studied for the Bay of Biscay, the Gulf of Cadiz and the Alboran Sea.  The presence of particles in each zone varies between warm and cold seasons, depending on the dynamics of the zone.  The results of this study are under review processes (Cloux et al., n.d.).
 
Cloux, S., Allen-Perkins, S., de Pablo, H., Garaboa-Paz, D., Montero, P., & Pérez-Muñuzuria, V. (2022). Validation of a Lagrangian model for large-scale macroplastic tracer transport using mussel-peg in NW Spain (Ría de Arousa). Science of The Total Environment, 822, 153338. https://doi.org/10.1016/j.scitotenv.2022.153338
Cloux, S., Pérez-Pérez, P., de Pablo, H., & Pérez-Muñuzuri, V. (n.d.). A Regional Lagrangian Model to Evaluate the Dispersion of Floating Macroplastics in the North Atlantic Ocean from Different Types of Sources in the Iberian Peninsula. Available at SSRN 4306128.
Electric fields in a small scale comet magnetosphere
Authors: Nilsson Hans
Published: February 2023

We present two new methods to study the electric fields and their effect on ions and electrons in a cometary environment. One method is to look at the energy spectra of cometary ions, ions that are produced by ionisation of the gas emanating from the comet nucleus. The new production of such ions falls off with distance r to the nucleus proportionally to the fall-off of the parent neutral gas, as 1/r2. For ions having been significantly accelerated, the energy of observed ions shows the electric potential difference between the point of ionisation and the observation point. When such ionisation occurs in a homogeneous electric field, the ion flux as function of energy is predicted to show a simple power law relation, the flux falling off as 1/E2. This is indeed sometimes seen. We also discuss the possibility to interpret ion energy spectra in terms of somewhat inhomogeneous electric fields.To this we can now add a new method where by comparing the speed of solar wind H+ and He2+ after interaction with the comet environment we can estimate the electric potential of the observation point relative to the upstream solar wind. Combining these methods opens up a whole new possibility to study in detail the electric fields acting on small scales when two plasma populations interact. Our study is specific to the cometary environment we are looking at, but the physical interactions we study are universal. 
A Continental Stochastic Precipitation Generator
Authors: Rakotoarimanga Hugo , Meynadier Rémi , Weisman Anna , Wing Oliver , Winsemius Hessel
Published: February 2023

AXA proposes a novel continental-scale generator of synthetic gridded rainfall daily timeseries (10km resolution) with applications to cross-country risk assessment under current and future climate scenarios. Europe serves as a case-study to demonstrate and assess its performance in terms of hazard modelling and extrapolation to unobserved extreme local and regional events. This generator belongs to the class of time and space reshuffling Stochastic Weather Generators (SWGs) and generates unobserved events by re-sequencing historical multisite timeseries (E-OBS). Consistency at continental scale is ensured by relying on weather regimes and atmospheric situations characterized from the ERA5 reanalysis over Europe. The use of atmospheric drivers and dry-wet alternating cycles allows for the determination of both precipitation-prone situations or on the contrary drier spells, while preserving the physics of the atmospheric water cycle. Spatial reshuffling is introduced by regional differentiation. Transitions between regimes can be either calibrated from the historical data or extrapolated to represent future states of the climate along with an appropriate uplifting of the humidity-related variables. This generator is operationally used at AXA as part of a European flood risk model and serves as the main input to an hydrological and hydraulic model.
The Model Intercomparison Project on the Climatic Response to Volcanic Forcing (VolMIP): Status and Future Perspectives of the Initiative
Authors: Zanchettin Davide , Timmreck Claudia , Khodri Myriam , Hegerl Gabi , Krüger Kirstin , Pausata Francesco S. R. , Robock Alan , Schmidt Anja , Toohey Matthew
Published: February 2023

The Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP) is a protocol-driven international initiative under the umbrella of the sixth phase of the Coupled Model Intercomparison Project (CMIP6) aiming at coordinating the activities of different Research Institutes involved in numerical climate modelling focused on a multi-model assessment of climate models' performance under strong volcanic forcing conditions. The main objective of the initiative is to assess to what extent responses of the coupled ocean-atmosphere system to the same applied strong volcanic forcing are robustly simulated across state-of-the-art coupled climate models and identify the causes that limit robust simulated behavior, especially differences in their treatment of physical processes. To this purpose, four Tier-1 (mandatory) experiments branched into two main sets, named “volc-pinatubo” and “volc-long” were defined, together with eight more lower-priority experiments. Six years since the definition of the VolMIP protocol (Zanchettin et al., 2016), ensemble simulations of most of the mandatory VolMIP experiments have been completed and made publicly available through the Earth System Grid Federation open platform, with the first VolMIP results being currently published and several analyses in progress. The long turnover time between the experiment design, the integration of the simulations and the analysis of the output motivates an assessment of the overall effectiveness of the VolMIP strategy, particularly in the light of a possible second phase of the initiative.In this contribution, we will illustrate the status of the initiative, highlight its major achievements and discuss its future perspective in the light of emergent scientific questions regarding volcanically forced climate variability.Zanchettin, D., Khodri, M., Timmreck, C., Toohey, M., Schmidt, A., Gerber, E. P., Hegerl, G., Robock, A., Pausata, F. S. R., Ball, W. T., Bauer, S. E., Bekki, S., Dhomse, S. S., LeGrande, A. N., Mann, G. W., Marshall, L., Mills, M., Marchand, M., Niemeier, U., Poulain, V., Rozanov, E., Rubino, A., Stenke, A., Tsigaridis, K., and Tummon, F.: The Model Intercomparison Project on the climatic response to Volcanic forcing (VolMIP): experimental design and forcing input data for CMIP6, Geosci. Model Dev., 9, 2701–2719, https://doi.org/10.5194/gmd-9-2701-2016, 2
Improved assessment of automated gap imputation in large groundwater level data sets
Authors: Retike Inga , Bikše Jānis , Haaf Ezra , Kalvāns Andis
Published: February 2023

Uneven measurement frequencies and continuous gaps in hydrographs are among the major challenges when dealing with regional-scale groundwater level data sets, especially if compiled from different countries. A variety of automated gap imputation methods can be applied to infill a large number of missing values, yet the assessment of modeling performance remains a difficult task often performed by randomly introduced missing values. However, large groundwater level data sets rarely have random gaps and more complex gap patterns can be observed. Here we present a new artificial gap introduction technique (TGP - typical gap patterns) mimicking realistic gap patterns characteristic to regional scale groundwater level data sets thus improving the assessment of gap imputation methods. Imputation performance of machine learning algorithm missForest and imputePCA were compared with routinely used linear interpolation to create gapless groundwater hydrographs for the Baltic states (Estonia, Latvia, Lithuania). Our results showed that infilling performance varies among different gap patterns (TGP). Overall, the missForest algorithm significantly outperformed imputePCA and linear interpolation even when infilling up to 2.5 years long gaps, while linear interpolation produced similarly good results to missForest when infilling relatively short (random-like) gaps. It was observed that imputation performance substantially decreased when infilling previously unseen extremes (such as severe drought episodes in 2018) or groundwater hydrographs likely affected by water abstraction (located near major agglomerations).The study has been founded by Iceland, Liechtenstein and Norway through the EEA and Norway Grants Fund for Regional Cooperation project No.2018-1-0137 “EU-WATERRES: EU-integrated management system of cross-border groundwater resources and anthropogenic hazards”. The research further contributes to the grant TRV2019/45670 awarded by the Swedish Transport Administration (Trafikverket).
On singularity point in-between the symmetry planes in elastic orthorhombic media
Authors: Stovas Alexey
Published: February 2023

The singularity points are very important for elastic waves propagation in low-symmetry anisotropic media (Stovas et al., 2021a). Being converted into the group velocity domain, they result in internal refraction cone with anomalous amplitudes and very complicated polarization fields. In elastic orthorhombic (ORT) media, there is always one singularity point in the essential symmetry plane, (0,1,2) singularity points in remaining non-essential symmetry planes and (0,1) points in-between the symmetry planes (Stovas et al., 2021b).I analyze the conditions for existence of a singularity point in-between the symmetry planes.In order to do that I fix the diagonal elements of the stiffness coefficient matrix, cjj , j=1,6, and introduce new variables d12 = c12 +c66, d13 = c13 +c55 and d23 = c23 +c44. I also assume that the symmetry plane 2-3 is the essential one by introducing the inequality c55 < c44 < c66 . If c66 < c44 < c55, the 2-3 plane is still essential one but the properties of non-essential planes will interchange. In case of other inequalities for “S wave” stiffness coefficients, the corresponding properties of singularity points can be obtained by a cyclic rotation of stiffness coefficients and symmetry planes (Stovas et al., 2023).For selected essential symmetry plane (2-3), I propose to fix two variables d12 and d13, and set the variable d23 as a free variable. By changing d23 only, I can define the trajectory of a singularity point in-between the symmetry planes. This trajectory is given by a continuous line connecting the symmetry planes. Then I define the traces of this trajectory on symmetry planes (maximum two points for each plane) by a specific value of the variable d23. These 6 values can be used for intervals of d23 where the singularity point in-between the symmetry planes exists. Analysis shows that there are 7 zones in (d12 , d13) plane with different intervals of d23, which guarantee the existence of singularity point in-between the symmetry planes. There are 3 intervals of d23 in one zone, two intervals in two zones and one interval in three zones. There is no singularity point in-between the symmetry planes for any d23 in remaining zone. These zones are separated by three straight lines that defined by d12 = d12(critical) , d13 = d13(critical)  and d13 = α d12, where α guarantees that trajectory of singularity point meets the essential symmetry plane. ReferencesStovas, A., Roganov, Yu., and V. Roganov, 2021a, Geometrical characteristics of P and S wave phase and group velocity surfaces in anisotropic media, Geophysical Prospecting, 68(1), 53-69.Stovas, A., Roganov, Yu., and V. Roganov, 2021b, Wave characteristics in elliptical orthorhombic medium, Geophysics, 86(3), C89-C99.Stovas, A., Roganov, Yu., and V. Roganov, 2023, On singularity points in elastic orthorhombic media, Geophysics, 88(1), C11-C32.
Fast observation operator for GNSS tropospheric gradients
Authors: Zus Florian , Thundathil Rohith , Dick Galina , Wickert Jens
Published: February 2023

Raw data collected at a single Global Navigation Satellite System (GNSS) station allow the estimation of the Zenith Total Delay (ZTD) and the tropospheric gradient. In order to make use of such data in Numerical Weather Prediction (NWP) the observation operators must be developed. Our current observation operator for tropospheric gradients is based on a linear combination of ray-traced tropospheric delays (Zus et al., 2022). Although this observation operator is tuned for high speed and precision it remains difficult to be implemented into NWP Data Assimilation (DA) systems. In this contribution we introduce a simple and fast observation operator which is based on the closed-form expression depending on the north–south and east–west horizontal gradients of radio refractivity (Davis et al., 1993). We run the Weather Research and Forecasting (WRF) model (horizontal resolution of 10km) and find that for the considered geographical region (central Europe) and time period (summer season) the root-mean-square deviation between the tropospheric gradients calculated by the fast and original approach is about 0.15 mm. In essence, the observation operator error is non negligible but acceptable for assimilation. In a first step we implemented the developed operator in our experimental DA system (Zus et al., 2019) and run a series of experiments to check the usefulness of the new approach. We present results from this assimilation experiments where we utilize both simulated and real observations. In the next step we will implement the fast observation operator in the WRF DA system in support of the research project EGMAP (Exploitation of GNSS tropospheric gradients for severe weather Monitoring And Prediction).Davis, J., Elgered, G., Niell, A., and Kuehn, K.: Ground-based measurement of gradients in the “wet” radio refractivity of air, Radio Sci., 28, 1003–1018, 1993. Zus, F.; Douša, J.; Kačmařík, M.; Václavovic, P.; Dick, G.; Wickert, J. Estimating the Impact of Global Navigation Satellite System Horizontal Delay Gradients in Variational Data Assimilation. Remote Sens. 2019, 11, 41.Zus, F., Galina, D., and Wickert, J.: Development of a cost efficient observation operator for GNSS tropospheric gradients, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-1079