bluuebunny/crossref_metadata_2025 huggingface dataset:
Bassin study of vetically sheared currents from the dispersion of surface gravity wave
Authors: Cuevas Alexandra , Rey Vincent , Touboul Julien , Ardhuin Fabrice
Published: February 2023

Wave conditions from the open sea to the coast, provide necessary information, the good understanding and modeling of coastal dynamics, the design of coastal engineering structures coastal engineering structures, for navigation or the flooding risks evaluation. It is also a potential way to access information present below the surface. Refraction, diffraction and reflection of waves are not only forced by variations in bathymetry but also by the presence of currents. However, the effects of current in propagation models have long been limited to the consideration of homogeneous current in the water column. Nevertheless, currents are usually observed to be sheared vertically by wind, tides or waves. When wave propagate in the presence of currents their celerity is modified. It is also affected by the vertical structure of the current. This work proposes and discusses methods for reconstructing current fields from wave data based on synchronous analysis of wave spectra at different points in space. We consider here the 2D case of progressive or partially stationary waves in the presence of homogeneous currents or with a vertical sheared profile. The study is based on data from experiments carried out at the Bassin de Génie Océanique FIRST(BGO), for progressive or partially stationary waves in the framework of the ANR project MORHOC'H 2. These test campaigns allowed us to test the sensitivity of the wave’s phase evolution during its propagation in order to estimate the feasibility of reconstructing either constant or sheared currents in the water column. Under the assumption of a progressive wave, the study of the phase evolution shows a significant influence of the current, allowing to reach the intensity of a uniform current. The calculated phase evolution in the presence of sheared current is consistent with the theory, but for small values of shear, the phase velocity changes are much smaller, making the method more sensitive to "noise". Furthermore, for a partially stationary wave, a significant impact of its phase evolution is observed in the propagation direction of the incident wave even for weak reflections, making it necessary to include this parameter in the reconstruction of currents from synchronous wave measurement data.Acknowledgements:The DGA is thanked for funding the AID thesis grant of Alexandra CUEVAS, as well as for the ANR grant: ANR-21-ASM1-003.
The Main Himalayan Thrust beneath Nepal and Southern Tibet illuminated by seismic ambient noise and teleseismic P wave coda autocorrelation
Authors: Thapa Hari Ram , Pachhai Surya , Aoudia Abdelkrim , Manu-Marfo Daniel , Priestley Keith , Mitra Supriyo
Published: February 2023

Nepal is an actively deforming region due to its tectonic setting that hosts many destructive earthquakes including the most recent 2015 Gorkha earthquake of magnitude 7.8. To better understand the physics of earthquakes and their precise location as well as monitoring of seismicity and real-time seismic hazard in the region, a highly resolved 3-D structure of the crust is essential. This study presents a new 3-D shear S -wave velocity structure of the crust using group and phase velocity dispersions obtained from ambient noise tomography. This study further constrains the discontinuities beneath Himalaya Nepal using teleseismic compressional P-wave coda autocorrelation. Our results show significant variation in the crustal structure within the region and correlate well with known geological and tectonic features present there. The results from the P-wave coda autocorrelation identify major seismic discontinuities in the crust including the Main Himalayan Thrust (MHT). The MHT with two ramps correlates well with a low S-wave velocity layer obtained from the ambient noise tomography. The first ramp agrees with the duplex structure in the MHT beneath Lesser Himalaya while the second ramp connects flat low velocity beneath High Himalaya to a broad low-velocity zone beneath South Tibet. Moreover, the High Himalaya low-velocity layer is located where the GPS data show creeping north of the coseismic rupture of the 2015 Gorkha earthquake. The lateral variation of S-wave velocity on the MHT surface provides the details of lateral transitions that might have potentially controlled the rupture pattern of the 2015 Gorkha earthquake.The geometry and extent of the High Himalaya low-velocity layer mimics the decollement coupling zone inferred from GPS data with widths of 50 to 70 km north of the nucleation of the 2015 Mw 7.8 Gorkha earthquake and 90 to 100 km north of the source of the Mw 8.4 1934 earthquake. The occurrence of millenary Mw>9.0 earthquakes in Central and Eastern Nepal would require either a wider coupling low velocity zone compared to the ones identified in this work or the involvement of southernmost Tibet low velocity decoupling zone so to store enough elastic energy.
A Study on the background surface reflectance retrieval of near-UV wavelength using GK-2B/GEMS data
Authors: Sim Suyoung , Han Kyung-soo , Choi Sungwon , Seong Noh-hun , Jung Daeseong , Woo Jongho , Kim Nayeon
Published: February 2023

 Surface reflectance is the product of removing atmospheric scattering and absorption effects from the Top-Of-Atmosphere (TOA) radiation using the Radiative Transfer Model (RTM), and it refers to the reflectance according to the solar and satellite zenith angles at the time of observation. Surface reflectance is an essential input data for other Level-2 calculation algorithms such as aerosol, cloud, ozone, gas tracers, etc. Therefore, if the surface reflectance data has missing value, it will lead to missing other products that use it. However, when there are clouds in the satellite image, there is a problem with that blank pixels are generated because the surface reflectance cannot be calculated. Therefore, in this study, we conducted an algorithm to calculate background surface reflectance (BSR) without missing values with high accuracy using GK-2B/Geostationary Environment Monitoring Spectrometer (GEMS) data. The BSR is an estimate of the surface reflectance under specific observation conditions (solar and satellite zenith angles) and is a product that avoids the calculation precedence dilemma between AOD and surface reflectance. In many studies, the BSR is mainly calculated using the minimum reflectance method, but it has limitations in not considering the angular conditions at the time of observation and the reflectance characteristics of the ground surface. To overcome these limitations, a realistic BSR calculation was performed considering the anisotropic reflectance characteristics of the surface according to the observation conditions through bi-directional reflectance distribution function (BRDF) modeling. Surface reflectance, which is an input variable for BRDF modeling, was calculated based on the Look-Up Table (LUT) generated using the Second Simulation of Satellite Signal in the Solar Spectrum (6SV) RTM. At this time, LUT interpolation was additionally performed through the 6d-interploation technique to resolve discontinuities that may occur in LUT-based atmospheric correction. For BRDF modeling, the kernel-based Roujean model was used, and the optimal synthesis period for BRDF modeling considering the characteristics of the GEMS satellite was selected. To evaluate the accuracy of BSR, the simulated BSR through the BRDF model and the observed surface reflectance were compared, and it was confirmed that the BSR showed higher accuracy than the minimum reflectance method. In the future, the BSR produced through this study is expected to have a great impact on improving the calculation accuracy of aerosol and atmospheric products of GEMS satellites.
A linear-circular model to determine sub-annual flood probabilities 
Authors: Bender Jens
Published: February 2023

Flood probabilities for periods less than one year are necessary for variety of practical
applications. For example, in case of construction works within a river it is necessary
to know the probability of a flood occurring within the construction time. However, flood
probabilities are usually estimated as the occurrence per year, not least because the
underlying data are often maximum annual discharges. Several approaches have
been recently developed to estimate flood probabilities for periods less than one year.
When applying these methods in practice they are subject to some substantial
limitations: for example, users are left to choose some subjective parameters, or the
results are not consistent with annual probabilities of occurrence. In this contribution,
different approaches to determine seasonal flood probabilities are reviewed and
evaluated with respect to their suitability for practical applications. In addition, a novel
methodological approach based on a linear-circular statistical model is presented. In
this new approach, flood discharges (linear measure) are determined using a classical
POT approach. Additionally, the times of occurrence within a year (circular measure)
are modelled using a circular kernel density estimate. The combination of both
distributions with a two dimensional linear-circular distribution function subsequently
allows the determination of the probability of occurrence of a flood value within any
sub-annual season.
Lower Permian sediments of the Intrasudetic Basin: a record of cyclic, climatically-controlled transitions from lacustrine to terrestrial conditions
Authors: Peryt Tadeusz , Ploch Izabela , Raczyński Paweł , Voigt Sebastian , Kiersnowski Hubert , Pawlak Wojciech
Published: February 2023

The geology of the Intrasudetic Basin (Poland and Czech Republic) in the past was studied separately in both countries. Our project combined data from both parts of the basin to study the development of the limnic basin during the seasonally extreme climate in the Early Permian. The Lower Rotliegend Słupiec Formation (Broumov Formation in the Czech part) red bed deposits appear the most promising for palaeoenvironmental and palaeoclimatic studies. Fine-grained weathering products  (black shales), tuff admixtures and autochthonous components (limestones) in lakes contain many remains of plants, and traces of activity of invertebrates and vertebrates including extraordinarily numerous traces fossils of tetrapods (reptiles and amphibians) (e.g., Voigt et al. 2012) and fish remains (e.g., Stamberg & Zajíc, 2008). The Słupiec Formation is interpreted as a successively finning-upwards megacyclothem consisting, from base to top, of alluvial fan, fluvial and lacustrine deposits (Wojewoda and Mastalerz, 1989; Kurowski, 2004). However, the cyclicity is also clearly marked by successive transitions from lacustrine sediments with preserved fish remains to terrestrial sediments with numerous tracks of terrestrial reptiles and amphibians. This seasonal climate with dominant monsoonal rainy summer and winter seasons with low precipitation is clearly recorded in deposits of alluvial-fluvial plains and lakes. Extreme weather conditions, such as possible night frosts, were also recorded in the sediments, although the basin was located relatively close to the equator.This research was funded by the Polish National Science Centre (Grant 017/26/M/ST10/00646).Kurowski, L. (2004); Geologia Sudetica, 36: 21–38; Štamberg, S. & Zajíc, J. (2008): Carboniferous and Permian faunas and their occurrence in the limnic basins of the Czech Republic. Museum of Eastern Bohemia; Voigt, S., Niedźwiedzki, G., Raczyński, P., Mastalerz, K. & Ptaszyński, P. (2012): Palaeogeography, Palaeoclimatology, Palaeoecology, 313-314: 173-180; Wojewoda, J. & Mastalerz, K. (1989): Przegląd Geologiczny, 37: 173–180.
Identifying the zoo of waves in Magnetosheathjets using MMS burst data
Authors: Krämer Eva , Hamrin Maria , Gunell Herbert , Karlsson Tomas , Steinvall Konrad , Goncharov Oleksandr , André Mats
Published: February 2023

The magnetosheath is a region downstream of the bow shock filled with turbulent, decelerated solar wind plasma which is flowing earthwards. This solar wind flow sometimes shows signatures of localized structures with enhanced dynamic pressure, so called magnetosheath jets. These jets are often  associated with low angles between the bow shock normal and the interplanetary magnetic field (IMF) direction, the so called quasi-parallel bow shock. Less often they are also found behind the quasi-perpendicular bow shock.As jets propagate through the magnetosheath, they interact with the surrounding plasma. Studying waves inside, and in the vicinity of, jets is a step towards understanding the interaction of jets with the surrounding plasma. So far whistler waves, electrostatic waves, waves in the lower hybrid frequency range as well as low frequency waves have been reported. However, the sources of these waves are unknown. In addition, further types of waves may be associated with the jets.We conduct a study on waves in magnetosheath jets using burst mode data of the Magnetospheric Multiscale (MMS) mission. The magnetic and electric field data are provided with a sampling rate of 8 kHz, while previous studies used data sets with much lower sampling rates. The high time resolution allows us to study different waves over a large frequency range and investigate properties of these waves. In addition, we discuss possible generation mechanisms.
A skill assessment of the European Flood Awareness System notifications
Authors: Casado Rodríguez Jesús , Carton De Wiart Corentin , Grimaldi Stefania , Salamon Peter
Published: February 2023

The European Flood Awareness System (EFAS) of the Copernicus Emergency Management Service is an operational forecasting system whose aim is to raise awareness about floods in European transnational rivers. It produces probabilistic, medium-range discharge forecasts twice a day by running the open-source hydrological model LISFLOOD with four different meteorological forcings, two deterministic forecasts from the DWD (German Weather Service) and the ECMWF (European Centre for Medium Range Weather Forecasts), respectively, and two probabilistic forecasts from ECMWF and the Cosmo Consortium (COSMO-LEPS). Based on these forecasts, flood notifications are issued to the EFAS partners if a set of criteria is met: contributing area larger than 2000 km², lead time from 48 to 240 h, at least one deterministic model exceeds the discharge threshold (5-year return period), and at least one probabilistic model predicts 30% exceedance probability of that discharge threshold for three or more consecutive forecasts.The operational EFAS is being regularly updated, so the configuration of EFAS has changed since the time these notification criteria were defined. For instance, the temporal resolution has increased from daily to 6-hourly, and the spatial resolution is planned to improve from 5km to approximately 1.5 km (1 arcminute).This study aims at assessing the skill of the notification criteria above presented with the current system setup, and to derive a new set of criteria that optimizes the notification skill. We will focus on three research questions: (i) how can we combine the different models (deterministic and probabilistic) into a grand ensemble and what probability threshold optimizes skill? (ii) Is the persistence criterion (i.e. 3 consecutive forecasts need to provide persistent predictions of high flood risk) adding to the skill both at shorter and larger lead times? (iii) Can we reduce the contributing area threshold without compromising skill?The study will make use of reanalysis, driven by meteorological observations, and forecast data at over 2300 stations across Europe for a time span from October 2020, which was the release time of the last major change in the EFAS setup, until present. By comparing the reanalysis data with the simulated discharge threshold, a total of 1327 “observed” flood events have been identified in the 2 years from October 2020 to October 2022. The “notified” events will be computed by comparing the forecast data against the notification criteria; we will compute skill metrics (f1, Hanssen-Kuipers) at each daily lead time for different combinations of meteorological forcing and notification criteria in order to find the procedure that maximizes the skill of EFAS notifications and to assess the above research questions.The outcome of this study will be applied to the EFAS operational system, directly impacting the preparedness of the relevant authorities in future flood events.
Space Weather Roadmap update for iSWAT Clusters H1+H2
Authors: Temmer Manuela , Scolini Camilla , Richardson Ian G. , Heinemann Stephan G. , Paouris Evangelos , Vourlidas Angelos , Bisi Mario M. ,   iSWAT Cluster H1+H2 Writing teams
Published: February 2023

The COSPAR iSWAT (international Space Weather Action Teams) initiative is a global hub for collaborations addressing challenges across the field of space weather. We present the COSPAR Space Weather Roadmap update for the iSWAT clusters H1+H2 covering interplanetary space and its characteristics, with focus on large-scale corotating and transient structures impacting Earth. We review the physical background of different solar wind streams together with coronal mass ejections and the considerable efforts that have been made to model these phenomena. We outline the limitations coming from observations with rather large uncertainties, making reliable predictions of the structures impacting Earth difficult. Moreover, in the wake of the upcoming solar cycle 25, the increased complexity of interplanetary space with enhanced solar activity poses a challenge to models. The current paper presents the efforts and progress achieved in recent years, identifies open questions, and gives an outlook for the next 5-10 years.
A Machine Learning approach to aerosol thermodynamics embedded in aglobal chemistry-climate model
Authors: Tost Holger , Bruening Sarah , Niebler Stefan , Spichtinger Peter
Published: February 2023

The chemical composition of the aerosol phase is still a major uncertainty in global chemistry climate models. One the one hand, aerosol thermodynamics  calculations are needed to determine the chemical composition of the inorganic fraction of the aerosol particles, on the other hand these calculations are computationally expensive. However, to properly describe the combined gas and aerosol phase composition, e.g., the reactive nitrogen budget including HNO3 or chlorine displacement from sea-salt aerosol, it is mandatory to have a reasonable description of the aerosol thermodynamics. To overcome the computational costs, but to still obtain a reasonable degree of proper process description, a machine learning  approach for the aerosol thermodynamics might offer opportunities in CCM modelling.In this study, we embed a machine learning approach for the description of aerosol thermodynamics in the chemistry climate model EMAC to reduce computational load (compared to explicit thermodynamics calculations) and show the capabilities of a modern computing approach, implemented in a multi-modal aerosol scheme.The new aerosol thermodynamics scheme is formulated as a machine learning neural network, which has been trained with the help of an explicit inorganic aerosol thermodynamics box model, i.e. ISORROPIA-2.This study presents first results of global 3D simulations using the ML approach and compares the results to explicit calculations in terms of the spatio-temporal distribution of the aerosol chemical composition as well as the effective performance of the modelling system.
2D Flood Analysis considering Buildings in Urban Areas
Authors: Jun Kyewon , Kim Sunguk , Jung Minjin , Lee Seunghee
Published: February 2023

Due to climate change, the scale of flood damage by localized torrential rains in urban areas is on an increase. Meanwhile, the existing flood runoff analysis methods do not consider buildings in urban areas, resulting in an overestimation of the degree of flood damage. Therefore, this study presents a method to consider buildings when applying XP-SWMM for flood analysis in downtown areas where buildings are concentrated, in order to accurately simulate the flood spread pattern around the building. To propose an optimal method which considers buildings, water depth, maximum flooded area, and the flow pattern around the building were compared according to whether or not the building was applied. As a result of the study, the average flooded area was 172,900㎡ when the building was set as an inactive area, which was 64% of the average flooded area (271,000㎡) when the building was not considered. The average water depth was 0.32m when buildings were considered, which was 1.78 times deeper than the average water depth (0.15m) when buildings were considered. This is the reflection of the blocking effect of the building in the model analysis, resulting in a significant reduction of the flooded area. In addition, since the flood simulation considered the flow rate of the same volume, flow velocity and average submerged depth relatively increased. This study is expected to contribute to the establishment of optimal downtown flood measures, by presenting a method for accurate flood analysis using the XP-SWMM model considering the influence of buildings in urban areas. For further improvement in the accuracy of flood analysis, it would be necessary to develop flood simulation methods suitable for different basins with flood records. This research was support by a (2022-MOIS63-002) of Cooperative Research Method and Safety Management Technology in National Disaster funded by Ministry of Interior and Safety(MOIS, Korea).
Using weak constrained neural networks to improve simulations in the gray zone
Authors: Ruckstuhl Yvonne , Kriegmair Raphael , Rasp Stephan , Craig George
Published: February 2023

Machine learning represents a potential method to cope with the gray zone problem of representing motions in dynamical systems on scales comparable to the model resolution. Here we explore the possibility of using a neural network to directly learn the error caused by unresolved scales. We use a modified shallow water model which includes highly nonlinear processes mimicking atmospheric convection. To create the training dataset, we run the model in a high- and a low-resolution setup and compare the difference after one low-resolution time step, starting from the same initial conditions, thereby obtaining an exact target. The neural network is able to learn a large portion of the difference when evaluated on single time step predictions on a validation dataset. When coupled to the low-resolution model, we find large forecast improvements up to 1 d on average. After this, the accumulated error due to the mass conservation violation of the neural network starts to dominate and deteriorates the forecast. This deterioration can effectively be delayed by adding a penalty term to the loss function used to train the ANN to conserve mass in a weak sense. This study reinforces the need to include physical constraints in neural network parameterizations.
On the potential of offshore sensors and array processing for improving seismic event detection and locations in the North Sea
Authors: Jerkins Annie , Köhler Andreas , Oye Volker
Published: February 2023

CCS (Carbon Capture and Storage) is becoming an increasingly important technology to reduce global greenhouse gas emissions. The Norwegian part of the North Sea is an ideal place to conduct such projects as much of the infrastructure and experience is already in place due to current oil and gas operations. For safe CO2 storage an improved understanding of the natural background seismicity in the North Sea is still required. Currently, earthquakes in the region are monitored using onshore stations deployed on mainland Norway, resulting in low azimuthal sensor coverage and poorly constrained earthquake locations. However, permanent reservoir monitoring systems (PRMs), which are deployed offshore to surveil oil and gas fields, have the potential to reduce these station gaps and thus improve earthquake locations.In this study we test the potential of incorporating offshore sensors at the Grane oil field for earthquake locations and detection utilizing array processing techniques. The advantage of array processing is that it can enhance seismic signals, decrease the detection threshold, and put additional constraints on direction and apparent velocities. Out of the 3400 sensors deployed at the Grane field, we have access to two subsets of data: i) Continuous data from 10 sensors spread along the boundaries of the field and, ii) segments of data from 30 sensors optimized for the purpose of array processing. Since the distances between the 10 sensors are large (6 km), traditional array processing methods are not applicable, and we therefore test and develop a new method for incoherent array processing using the kurtosis characteristic function. The kurtosis function is applied to the seismic signal prior to FK-analysis to make the signal more coherent.  The method showed great potential and worked for the majority of earthquakes analyzed in this study. The 30 sensor array was superior to the 10 sensor array and could potentially decrease the detection threshold of seismic events if continuous data are available. We conclude that the Grane sensors could be implemented as a part of a system for passive seismic monitoring in the North Sea. We recommend using the 30-sensors for this purpose. However, as we only have access to continuous data from 10 sensors, we found that these sensors are an appropriate replacement when the 30 sensors are not accessible. 
Conditions for inception and propagation of negative streamers
Authors: Lehtinen Nikolai
Published: February 2023

Negative streamers play an important part in propagation of a negative stepped leader. They are emitted from the tip of a space stem or, as a streamer burst, from the tip of the space leader right after its attachment to the main leader.In the laboratory conditions, it was shown that negative streamers need a significantly higher voltage for inception than positive streamers [e.g., Briels et al, 2008, doi:10.1088/0022-3727/41/23/234004]. The higher negative threshold is in agreement with the higher field measured inside streamer channels, namely 13±2 kV/cm for negative streamers versus 5 kV/cm for positive streamers.We obtain the conditions for propagation of negative streamers using the Streamer Parameter Model (SPM) [Lehtinen, 2021, doi:10.1007/s11141-021-10108-5]. In this model, we calculate various streamer parameters from relationships between them, with the assumption of maximization of streamer velocity. This model, in the positive streamer case, was shown to agree well with both experimental measurements and hydrodynamic simulation results [Lehtinen and Marskar, 2021, doi:10.3390/atmos12121664]. In the negative streamer case, we show that the parameter equations have no solution below certain background electric fields. The threshold at which the negative streamer appears is around 12-14 kV/cm for 5-10 cm streamer length, which agrees with the experimental data. We also perform hydrodynamic simulations of negative streamers as another way to calculate the conditions for negative streamer propagation.There is an important difference from positive streamers, for which the propagation threshold is determined by the rate of free electron removal from the streamer channel (i.e., attachment): namely, we find that the negative streamer threshold field is finite even in the absence of the electron removal.
The influence of the stratosphere on the North Atlantic storm track predictability in subseasonal-to-seasonal reforecasts
Authors: Gerstman Hilla , Büeler Dominik , Wulff C. Ole , Sprenger Michael , Domeisen Daniela
Published: February 2023

Extreme stratospheric polar vortex events, such as sudden stratospheric warmings (SSW) or extremely strong polar vortex (SPV) states, can have a prolonged downward impact, influencing surface weather for several weeks to months. These events often lead to changes in the midlatitude storm track position and associated cyclone frequency over the North Atlantic and Europe. Such changes can result in infrastructure damage and health impacts due to cyclone-associated extreme winds and the risk of flooding or heavy snowfall. However, there exists a strong inter-event variability in these downward impacts on the tropospheric storm track, leading to opposite predictions of the storm track response. Therefore, identifying the biases in the forecast of the downward impact of stratospheric polar vortex extremes can improve the predictability of extratropical winter storms on subseasonal-to-seasonal timescales, and has the potential to benefit society and stakeholders.Using ECMWF reanalysis data and ECMWF reforecasts from the Subseasonal to Seasonal (S2S) Prediction Project database, we investigate the stratospheric influence on extratropical cyclones, identified with a cyclone detection algorithm. Following SSWs, there is an equatorward shift in cyclone frequency over the North Atlantic in reforecasts, and a poleward shift is observed after SPV events, consistent with the response in reanalysis. However, less than 70% of the reforecasts capture the sign of the cyclone frequency response over the North Atlantic during weeks 1-2 after SSWs, and less than 50% of the reforecasts capture the response during weeks 3-4. The cyclone forecasts following SPV events are generally more successful. We further discuss the differences in predictability of extratropical cyclones between the two types of stratospheric extremes.The results provide new insights on the role of the stratosphere in subseasonal variability and predictability of extratropical cyclones during winter that can be used for forecasting their frequency and surface impacts.
Influence of scale in water resources management for heterogeneous African semiarid rangelands.
Authors: Andreu Ana , Pimentel Rafael , Carpintero Elisabet , González-Dugo María P. , Nieto Hector , Dube Timothy , Polo María José
Published: February 2023

Semiarid rangelands (grasslands with scattered trees and shrubs) are one of Africa’s most complex and variable biomes. They are a mosaic of land uses, where extensive livestock is the main economic activity, and agriculture or conservational uses are also crucial. They are highly controlled by the availability of water, e.g., pasture and rainfed crop production. Although the vegetation is adapted to variable climatic conditions and dry periods, the increase in drought intensity, duration, and frequency, the changes in agricultural practices, and other socioeconomic and environmental factors precipitate their degradation. The combined differential functioning and characteristics of the vegetation components and communities affect water dynamics, resulting in high spatiotemporal variability that creates distinct patches. Therefore, the precision, resolution, and accuracy of the information required for water management differ according to the scales of these patches: from the local to the basin. We want to assess the optimal spatiotemporal scale when monitoring semiarid mosaic vegetation cover and its water consumption. To answer this question, we evaluated the water use patterns of the typical vegetation patches (tree+grass savanna, grassland, crop area, and creek shore) estimated by different modeling approaches (FAO56 and TSEB) with spatial resolutions of 30 m, 250 m, and 1 km. From a farm/agricultural management viewpoint, we demonstrated the need for sufficient spatial and temporal resolution when evaluating water consumption and the difficulties when significant temporal gaps are present. Higher spatial-temporal scales were crucial to determining the pasture drying cycle and crop water use. In humid or denser areas that provide essential ecosystem services (e.g., wildlife habitat), transpiration rates were higher throughout the year and often underestimated when using coarse data. Over savanna patches, products with coarse resolution (1 km) reflected well the water use pattern. These metrics reflected the severe drought experienced during the 2015-2016 seasons due to an intense El Niño event, other dry events (e.g., 2002, 2007), and the recovery time of each vegetation patch.
Impact of quality of input data on rockfall hazard zoning
Authors: Melzner Sandra , Conedera Marco , Hübl Johannes
Published: February 2023

This contribution summarizes existing challenges in the implementation of a standardised procedure for natural hazard risk analysis and zoning in the Alps. The discussion focuses on (i) the impact of data acquisition strategies on the quality of input data, (ii) the applicability of different 3D rock fall simulation models for hazard zoning in different topographic and geologic environments, (iii) the definition of thresholds for hazard zoning, and (iv) the cartographic representation of the results.The evaluation of the applicability of the model results bases on the model sensitivity to the scale-dependent accuracy of input data and on the quality of the simulated travel distances (e.g., reach probabilities) and dynamics (e.g., energies, passing heights, velocities).Depending on the source information and the method/technique used to conduct the survey, the content and detail of the collected data and simulation results can vary significantly. Calibration and validation of simulation results is usually performed using information on the geographic position of mapped rockfall boulders and/or historical rockfall events by archive research. For the latter, there is often no size specification available. To define reproducible threshold values for hazard zoning (i.e., reach probabilities) and to transfer them as a standard to other study areas, the model input data (e.g., roughness, damping) and calibration/validation data should be clearly indicated and published.A further very important step is the joined cartographic presentation of the results of both, the simulation results and the field mapping. Such combination of results issued from different approaches forms the basis for the final hazard zoning. Supplementing ÖNORM rules with guidelines explaining in more detail the different mapping strategies/techniques and the model decisions would be very useful for the end users.
Demystifying long-term changes observed by GNSS: comparison with GRACE observations and hydrological models
Authors: Mikocki Jan , Klos Anna , Gunes Ozge , Lenczuk Artur , Bogusz Janusz
Published: February 2023

Hydrogeodesy is an applied scientific field that uses precise geodetic observations to measure or infer hydrological quantities and their changes over time. Recently, modern geodesy supplies hydrology with a very powerful tools based on the Earth’s artificial satellites, notably GRACE (Gravity Recovery and Climate Experiment) and GNSS (Global Navigation Satellite System). The long-term changes of periods higher than 1 year present in the time series of GNSS station displacements may be due to real geophysical effects, but may also be coupled to effects resulting from the superposition of GNSS systematic errors as well as numerical artefacts. As a result, it is often difficult to use the aforementioned changes to study, for example, long-term changes in the hydrosphere for specific GNSS station locations. Consequently, it is impossible to exploit the main advantage of GNSS over other measurement techniques, in the sense of dense spatial distribution in some parts of the world. In this study, we use wavelet analysis to determine long-term changes from GNSS station displacement time series and displacement time series determined from GRACE data and data from GRACE-assimilating high-resolution hydrological model GLWS v2.0 (Global Land Water Storage) provided by the University of Bonn. Global GNSS time series set was processed by the International GNSS Service (IGS) in the form of the latest reprocessing repro3.We correct the GNSS displacement time series for non-hydrospheric effects, such as non-tidal atmospheric effect, non-tidal oceanic effect, draconic period, post-glacial rebound and ground thermal expansion effects. We use a range of statistical analyses, such as correlation coefficient analysis and dynamic time warping (DTW) distance to assess the similarity of long-term changes between the three data sets. On this basis, we identify GNSS stations for which long-term changes can be analyzed in terms of changes in the terrestrial hydrosphere and those for which the long-term nature of the series is not due to changes in the hydrosphere, but to other effects.
Detection of the regional concentrations of various trace gases using LP-DOAS at Hefei Xinqiao International Airport
Authors: Duan Jun , Qin Min , Fang Wu , Liao Zhitang , Gui Huaqiao , Xie Pinhua , Liu Wenqing
Published: February 2023

Correspondence: Min Qin(mqin@aiofm.ac.cn)Abstract: A measurement campaign using long-path differential optical absorption spectroscopy (LP-DOAS) instrument at Hefei Xinqiao International Airport to investigate the regional concentrations of various trace gases in the airport’s northern area and the variation characteristics of the gas concentrations during an aircraft’s taxiing and take-off phases. The total light path of the LP-DOAS system was about 964 meters and the time resolution of the LP-DOAS instrument was approximately 10 seconds. The measured light path of the LP-DOAS passed through an aircraft taxiway and take-off runway concurrently without affecting aircraft operations. The results of NO2 and SO2 pollution peaks were clearly visible, and their timing was well matched to the time the aircraft crossed the light path. While the aircraft take-offs increased the regional average NO2 concentrations by 10-20 ppbV and flight take-offs increased the regional average SO2 concentrations by 1-5 ppbV, the overall pollution levels in the airport area were low due to the airport's openness and rapid dispersion of pollutants, and the maximum hourly average NO2 and SO2 concentrations during the observation period were better than the Class 1 ambient air quality standards in China. Additionally, we discovered that the NO2 and SO2 emissions from the Boeing 737-800 aircraft used in this experiment were positively related to the age of the aircraft.Acknowledgements: This work was supported by the Plan for Anhui Major Provincial Science & Technology Project (Grant No. 202203a07020003), the Anhui Provincial Key R&D Program (No.202104i07020010) and the HFIPS Director’s Fund (Grant No. YZJJQY202205).
Critical nucleation length for frictional slipping of an elastic layer over an elastic half-space
Authors: Painuly Abhishek , Kunnath Ranjith
Published: February 2023

The interplay of geological forces and shear resistance of slipping surfaces leads to the expansion of earthquake ruptures, which nucleate in creeping zone patches. Once the dimension of the nucleating creeping zone exceeds a critical length, ruptures accelerate dynamically. The present work provides an analytic model to determine the critical nucleation length of a slip rupture. It is determined by performing a linear stability analysis of steady-state sliding of an elastic layer (having a finite height) over an elastic half-space in the quasi-static regime. Interfacial frictional behaviour is modelled using a rate- and state-dependent friction law with velocity weakening behaviour in the steady state, mimicking the experimental observations of interfacial friction. Results for critical nucleation length at the interface with similar and dissimilar materials across the interface are presented and the effect of layer height on the critical nucleation length is explored numerically.
Using integrated magnetostratigraphy, biostratigraphy, and astrochronology to evaluate the impacts of a rapidly uplifting orogen on the preservation of climate oscillations
Authors: Hsieh Amy I. , Vaucher Romain , Löwemark Ludvig , Horng Chorng-Shern , Lin Andrew T. , Dashtgard Shahin E.
Published: February 2023

Changes in Earth’s eccentricity, obliquity, and precession can cause quasi-cyclic variations in Earth’s climate that may be preserved in sedimentary archives. Recent research has shown that shallow-marine paleoclimate archives in mid- to low-latitude regions have the potential to preserve changes in hydroclimate driven by precession, given sufficient space for sediment accumulation and a high sedimentation rate. Our integrated stratigraphic study of the Kueichulin Formation in Taiwan’s Western Foreland Basin (WFB) uses magnetostratigraphy, biostratigraphy and astrochronology to constrain time, with the aim to assess how the evolution of a rapidly uplifting mountain range affected the preservation of climate cycles in the shallow-marine record.Using time-series analysis of two sets of gamma-ray borehole data from the late Miocene to Pliocene Kueichulin Formation (WFB), we found that despite increasing monsoon intensities between 8 and 3 Ma, the preservation of precession-driven East Asian Summer Monsoon variability was low during the early stages of Taiwan orogenesis (before 5.4 Ma). Prior to 5.4 Ma, the Taiwan Strait had not yet formed. Consequently, the southeastern margin of Eurasia was open to the Pacific Ocean, and so the depositional environments in the WFB were susceptible to reworking by large waves. This led to the preservation of low-frequency eccentricity and obliquity, but not higher-frequency precession.Despite increasing basin subsidence from 5.4 to 4.9 Ma, the preservation of orbital oscillations is low. This is attributed to either low sedimentation rates at deeper water depths, which could obscure variations in sediment input or result in cycles below the resolution of the gamma-ray logging tool, or cycles not being detectible in the gamma-ray proxy record due to a lack of contrasting lithology. After 4.9 Ma and up to 3.2 Ma, the Taiwan orogen became the dominant sediment source for the WFB, and rapid growth of the orogen shielded the WFB from high-energy waves generated in the Pacific Ocean. The increased sediment influx and the formation of a semi-sheltered strait, combined with increased space for sediment accumulation in the WFB, resulted in enhanced preservation of precession-driven East Asian Summer Monsoon variability.
Floating Sphagnum moss mats as a tool to lower methane emissions in restored peatlands
Authors: Ritson Jonathan , Self Rebecca , Evans Chris , Evans Martin
Published: February 2023

In the new demonstrator project, Greenhouse Gas Removals – Peat, we aim to improve the greenhouse gas balance of peatland restoration projects so that net-negative carbon projects can be achieved. To do this, we are trialling a suite of methods including gully blocking, Sphagnum planting, biomass harvesting coupled with biochar production, and methane suppression via gypsum dosing. Through these methods, we hope to increase the input of recalcitrant carbon whilst minimising methane emissions.We present the results of a survey of 17 peatland pools across four sites in the south Pennines, UK. The pools were created via different restoration methods and have either been colonised naturally by Sphagnum or have been planted with commercially available mixes. Our data show that floating Sphagnum mats create a poorly mixed zone in the restoration pools where temperature and dissolved oxygen levels are elevated, resulting in lower dissolved methane concentrations beneath the Sphagnum mats compared to the rest of the pool. When accounting for higher methane emission rates due to the elevated temperature, our results suggest an overall ~40% lowering of diffusive methane flux in areas colonised by Sphagnum.Modelling of water quality parameters from the pools suggest methane flux is controlled via different mechanisms in the two areas of the pools. In the clearwater areas, redox potential and nitrogen availability are the dominant controls on methane flux, whereas under Sphagnum, dissolved oxygen concentration was the only significant driver. We interpret this as a switch in relative activity between methanogens and methanotrophs in the two areas. Taken together, our results provide real world evidence of the role of Sphagnum in creating a habitat niche favourable for methanotrophs and thereby lowering methane flux from peatland restoration projects.In this presentation we will also discuss preliminary findings from the other treatments being trialled at our sites.
Tectonic constraints on subduction closure processes of the BangongCo - Nujiang Tethys Ocean from the Middle Jurassic to the Late Cretaceous: A magnetic fabric study in the Linzhou Basin, Lhasa Block
Authors: Qinglong Chen , Wu Hanning
Published: February 2023

Abstract: Tectonic events recorded during the Middle Jurassic to Late Cretaceous in the Linzhou Basin of the Lhasa Block are associated with the subduction closure process of the BangongCo - Nujiang Tethys Ocean. To constrain the subduction closure process of the BangongCo - Nujiang Tethys Ocean during this period, a detailed magnetic fabric study of five relatively continuous strata in the Linzhou Basin during the Middle Jurassic - Late Cretaceous was carried out. The results show that the Middle Jurassic Yeba Formation developed initial deformation magnetic fabric, pencil-like magnetic fabric and tensile lineation magnetic fabric; The Late Jurassic Duodigou and Linbuzong Formations developed initial deformation and pencil-like magnetic fabrics; The Early Cretaceous Tacna Formation developed strongly cleaved magnetic fabric and tensile lineation magnetic fabric with more intense deformation; The Late Cretaceous Shexing Formation developed initial deformation magnetic fabric and pencil-shaped magnetic fabric. Combining the movement of the fracture zone, the direction of the stress field and the analysis of the tectonic environment, it is concluded that the tectonic environment has undergone four processes of extension-extrusion-extension-extrusion from the Middle Jurassic Yeba Formation to the Late Cretaceous Shexing Formation. The fracture zone undergoes three main processes: clockwise dextral rotation - rotation stop – clockwise dextral rotation. There are also relatively frequent changes in the north-south direction of the extrusion stresses and plate drag forces to which they are subjected. Thus, under the continued northward subduction of the Neo-Tethys Ocean, the tectonic processes recorded in the Linzhou Basin are associated with altered subduction polarity of the BangongCo-Nujiang Tethys Ocean. The BangongCo-Nujiang Tethys Ocean shifted from southward subduction to northward subduction during the Middle Jurassic. It shifted again to southward subduction in the Early Cretaceous and eventually closed.