bluuebunny/crossref_metadata_2025 huggingface dataset:
Compound drought and heatwave events in the eastern part of the Baltic Sea region
Authors: Klimavičius Laurynas , Rimkus Egidijus
Published: February 2023

Both droughts and heatwaves cause negative impact on human health, agriculture, economy and other areas while occurring separately. However, in recent years the impact of these phenomena acting together has been increasingly analysed as it was found that such events, called compound drought and heatwave events (CHDE), may induce even more damage. The aim of this research is to identify droughts, heatwaves and CDHE in the eastern part of the Baltic Sea region during the summer months (June-August) from 1950 to 2022 and to assess their frequency and intensity. For the purpose to identify droughts the 1-month Standard Precipitation Index (SPI) values calculated for each day were used. Droughts were distinguished if the SPI values were lower than -1 for at least five or more days in a row and this condition was met in at least one third of the study area.  Heatwaves were defined as a period of five or more consecutive days when daily maximum air temperature (Tmax) was higher than 90th percentile of Tmax of the study period (1951–2022) for each summer day (on a 5-day moving average) and for one or more days covered at least one third of the study area. Daily Tmax data as well as precipitation data that was needed to calculate SPI were obtained from European Centre of Medium-range Weather Forecast ERA-5 reanalysis dataset with a spatial resolution of 0.25° x 0.25°. CDHE events were defined as time periods when heatwave occurs during the drought period. Study showed that the number of heatwaves in the study area since 1950 increased significantly (by 1.25 per decade). The number of droughts during investigation period slightly decreased. The majority of droughts were identified in 1990’s when dry periods were recorded during six summers in a row (from 1992 to 1997). In total, 19 CDHE during the summer months were distinguished, while a lot of them occurred during 1990‘s (5 events). As a consequence, statistically significant increase of such events during the study period was not observed. CHDE of the highest intensity was found in 1994 while the longest CDHE occurred in 2022 and lasted for 19 days (from August 11th to August 29th).
Oceanic and Atmospheric Feedbacks Associated with the Spreading of Pacific Coastal Niño Events
Authors: Rudloff Daniel , Lübbecke Joke
Published: February 2023

In early 2017 a very strong coastal warming occurred off the coast of Peru. This event, which caused heavy rainfalls and flooding over land, marked the strongest so called ‘Pacific Coastal Niño Event’ observed. Most intriguing about this event was the fact that the central Pacific was not showing any significant anomalies during that time. Since then several studies have investigated Pacific Coastal Niños but the exact mechanisms of how such events behave are still not clear. While most studies focus on their onset mechanisms, we here analyze their evolution and decay and in particular their connection to the central equatorial Pacific.To address those questions, we are using the coupled climate model FOCI (Flexible Ocean Climate Infrastructure). Starting from a long control simulation with pre-industrial conditions we perform sets of 2-year long sensitivity experiments in which a coastal warming is generated by a local wind stress anomaly utilizing a partial coupling approach. Once the warming is initiated by reduced upwelling the wind forcing is switched off and the model can evolve freely, which enables us to investigate the evolution and decay of the warming. The approach allows to vary the forcing in strength, location and timing. By starting from different conditions in terms of equatorial heat content and applying the forcing during different months, the influences of both the background state of the equatorial Pacific during the Coastal Niño and the seasonality of the coastal warming are investigated. To understand which factors influence the spreading of the warm anomaly we analyze both local coastal feedbacks, which lead to an alongshore extension of the anomaly, and equatorial feedbacks that are crucial for a spreading along the equator.
Advances in cosmic-ray muography for Earth sciences and geophysical applications
Authors: Oláh László
Published: February 2023

Muography is a passive and non-destructive imaging technique that utilizes cosmic-ray muons for visualizing and monitoring the interior of geological structures and human-made objects. A rapid development of muographic observation technologies was achieved in the recent years, which allowed to resolve Earth's shallow subsurface with a resolution of a few meters and conduct long-term muon monitoring in harsh and varying environment. Muography can be applied as a complementary technique for Earth sciences and related engineering fields, e.g., for studying active volcanism, characterizing the overburden above underground sites, structural health monitoring infrastructures, exploring hidden cultural heritages, etc. We overview the recent progress in development of muography and we discuss case studies from volcanology to mining engineering from the Americas, Asia and Europe.
Particulate organic matter as electron acceptor for microbial respiration in peatlands
Authors: Schmitz Rob A. , Obradović Nikola , Schroth Martin H. , Sander Michael
Published: February 2023

Northern peatlands store approximately 500 Pg carbon in the form of peat particulate organic matter (POM). Ombrotrophic bogs are peatlands that only receive water and nutrients through precipitation, creating anoxic, water-logged soils deprived of inorganic terminal electron acceptors (TEAs). In the absence of suitable TEAs for anaerobic respiration, methanogenesis prevails as final step in the degradation of organic matter and is expected to result in equimolar CO2:CH4 production ratios. However, field and laboratory studies revealed higher CO2:CH4 production ratios than expected based on low concentrations of canonical inorganic TEAs, suggesting the presence of a previously unrecognized TEA used in anaerobic microbial respiration. It has been hypothesized that oxidized particulate organic matter (POMox) functions as TEA, explaining elevated CO2:CH4 production ratios. Through seasonal water table fluctuations, POM gets re-oxidized abiotically, creating a microbial hotspot at the oxic-anoxic interface. To investigate these processes, incubation studies linking CO2 and CH4 production to the reduction of POMox are indispensable. Here, we present data strongly indicating that POM collected from ombrotrophic bogs in Sweden functions as TEA in anaerobic respiration, suppressing methanogenesis. We ran anoxic incubations with various initial ratios of oxidized and reduced POM and hence a range of starting electron accepting capacities, which we quantified using a novel spectrophotometric assay. Increasing contributions of POMox resulted in higher CO2:CH4 production ratios and prolonged transition times from anaerobic respiration to methanogenesis. These findings strongly support the use of POM as TEA, suppressing methanogenesis until POMox was depleted through respiration. Additionally, we developed an incubation system that allowed amending incubations with 13C-labeled substrates to selectively track their conversion to 13CO2 and 13CH4. Using 13C-glucose we successfully linked 13CO2 and 13CH4 formation ratios to POM redox state. Our results advance our understanding of microbial carbon turnover in peatlands in the present and future climate.
CO2 concentration and stable isotope surveys in the ambient air of populated areas of La Palma (Canary Islands) by means of mobile Delta Ray measurements using an electrical car
Authors: Pérez Nemesio M. , Asensio-Ramos María , Barrancos José , Padrón Eleazar , Melián Gladys V. , Rodríguez Fátima , Padilla Germán D. , Albertos Violeta T. , Hernández Pedro A. , Álvarez Díaz Antonio J. , de los Ríos Díaz Héctor , Afonso Falcón David , Cutillas Juan
Published: February 2023

Anomalous CO2 degassing of volcanic origin was observed by the end of November 2021 in the neighborhoods of La Bombilla and Puerto Naos, located in the western flank of La Palma, about 5 km distance southwestern of the 2021 Tajogaite eruption vents (Hernández et al., 2021). In this study zone, continuous monitoring of CO2 concentration in the outdoors ambient air at 200 cm from the surface has reached a daily average of maximum and mean values about 28,000 and 10,000 ppm, respectively. We started recently to perform CO2 concentration and stable isotope surveys in the outdoors ambient air of Puerto Naos at 140 cm from the surface by means of a Delta Ray analyzer installed in an electrical car which was driving through the streets of Puerto Naos. This instrument is a high performance, mid-infrared laser-based, isotope ratio infrared spectrometer (IRIS) which offers the possibility of performing simultaneous determination of δ13C and δ18O in CO2 at ambient concentrations with a precision as low as 0.05‰. One major advantage of IRIS techniques with respect to more traditional ones (e.g., isotopic ratio mass spectrometry -IRMS-) is the possibility to perform (semi)continuous measurements at high temporal resolution. Since October 2022, seven surveys have been performed at Puerto Naos making up a total of about 600 measurements. The observed CO2 concentrations and the δ13C-CO2 values in the outdoors ambient air ranged from 420 to 3,500 ppm and from -9.0 to -3.2 ‰ vs. VPDB, respectively. Survey data analysis showed a good spatial correlation between relatively high CO2 concentrations with δ13C-CO2 values less 13C-depleted (i.e., volcanic CO2). These observations highlight that stable isotope surveys allow to evaluate the impact of volcanic degassing on the air CO2 concentration and provide valuable results to identify the volcanic CO2 gas hazard zones.Hernández, P. A., Padrón, E., Melián, G. V., Pérez, N. M., Padilla, G., Asensio-Ramos, M., Di Nardo, D., Barrancos, J., Pacheco, J. M., and Smit, M.: Gas hazard assessment at Puerto Naos and La Bombilla inhabited areas, Cumbre Vieja volcano, La Palma, Canary Islands, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-7705, https://doi.org/10.5194/egusphere-egu22-7705, 2022.
A Framework for Water Supply Regulation in Coastal Areas by Avoiding Saltwater Withdrawal Considering Upstream Streamflow Distribution
Authors: Wu Haiou , Tu Xinjun , Chen Xiaohong , Singh Vijay P , Alfonso Leonardo , Lin Kairong , Liu Zhiyong , Lai Rongbiao
Published: February 2023

Freshwater availability in coastal areas depends on the withdrawal from tidal rivers and is severely threatened by saltwater intrusion, especially in the dry season. Freshwater availability is associated with natural factors and human activities. Although analyses of freshwater availability under saltwater intrusion is problematic, it has received limited attention in the literature. We propose a new framework, i.e. regulation by avoiding saltwater withdrawal (RASW), where the relationships among saltwater intrusion, upstream streamflow, and water supply are established, using hybrid data-driven method coupling wavelet transform and random forest, and considering data on streamflow, tide, wind, salinity of withdrawal stations, capacities of withdrawal projects and reservoirs, and water demand. RASW contains three phases, i.e. estuary salinity-exceedance simulation, upstream streamflow distribution design, and local water supply security analysis. The method is tested on the water supply for Zhuhai-Macao of the Guangdong-Hong Kong-Macao Great Bay Area, South China. Results demonstrate that the salinity-exceedance simulation model using a hybrid data-driven method is quite accurate. The meta-Gaussian copula efficiently simulates the six-dimensional distribution of upstream monthly streamflow and is appropriate for streamflow distribution scenario design. Water supply security benefits greatly from the joint river-reservoir regulation mode. But for a given exceedance frequency of average streamflow, the modes and security situations are diverse, due to various streamflow distributions, i.e. extremely low streamflow and its occurrence time. The proposed framework facilitates integrated decision-making for water supply security in coastal areas. Moreover, the capacities of facilities should be carefully considered according to local conditions, and streamflow distribution design can be utilized as a management tool to regulate water supply system. 
Usage of long-term forest research networks to advance understanding of ecosystem services – CLIMB-FOREST
Authors: Lange Holger , Bäck Jaana , Jocher Georg , Kljun Natascha , Klosterhalfen Anne , Knohl Alexander , Kowalska Natalia , Kristensson Adam , Rebmann Corinna , Saura-Yera Teresa , Vilagrosa Alberto
Published: February 2023

Utilizing forest ecosystems to mitigate climate change effects and to preserve biodiversity requires detailed insights into the feedbacks between forest type, climatic and soil conditions, and in particular forest management history and practice. Analysis of long-term observations at the site level, remote sensing proxies and understanding relevant biogeochemical and biophysical processes are key to achieving these insights. In the recently started EU H2020 project “CLimate Mitigation and Bioeconomy pathways for sustainable FORESTry” (CLIMB-FOREST), we address these issues based on intensely monitored sites with flux measurements (ICOS, Fluxnet), other ecosystem research and observation networks (eLTER, National Forest Inventories), remotely sensed observations and process understanding. This presentation outlines the activities of CLIMB-FOREST regarding (1) carbon stocks and fluxes according to stand age, species distribution, management and disturbance history; (2) biophysical effects of forest structure; (3) effects and importance of short-lived climate forcers (e.g. BVOCs) and (4) management and extreme event (drought, fire) impact on SOC and N dynamics. We also outline how the gained knowledge informs scenario runs of the Vegetation and Earth System Model RCA-GUESS in the project.
Estimating Curie depth and Heat Flow in the Circum-Arctic Region
Authors: Freienstein Judith , Szwillus Wolfgang , Ebbing Jörg
Published: February 2023

We estimate the depth of the Curie isotherm and the associated heat flow for the Circum-Arctic Region using a Monte Carlo Markov Chain approach. In the first step, Curie depths are determined where heat flow measurements are available. For the depth estimates, different parameters and concepts are tested (e.g. pure conduction compared to half-space cooling) in order to assess the uncertainty underlying the depth estimates, but also of the observing point. Hereby, we rely on existing models of the Arctic lithosphere including ArcCRUST and LithoRef18. Half of the calculated Curie depth points show a low sensitivity to the choice of the parameters and models and hence can be regarded as stable, representing the thermal field of the lithosphere and not local effects. Hence, we can use these points as constraints for the second step, where we invert an aeromagnetic anomaly map for both the Curie depth and susceptibility for the Circum-Arctic Region. The new model shows that in areas where reliable constraints exist, the magnetic inversion is preferring to explain the magnetic anomalies with lateral susceptibility distribution, reflecting hereby the main geological features of the region.
Hydro-eco-morphodynamics and carbon cycling at coastal scales and beyond
Authors: Zhang Wenyan , Arlinghaus Peter , Porz Lucas , Schrum Corinna
Published: February 2023

Morphological change of coastal and shelf seas is controlled jointly by physical, biological and anthropogenic processes and their interactions. While physical and anthropogenic drivers are normally regarded to exert a primary control on morphodynamics, the role of biota, especially benthos, in guiding long-term and large-scale evolution of coastal landscape/seascape is often overlooked and has received less attention. It was not until recent decades that research has revealed the importance of benthos in coastal protection. Further, as an indispensable part of the ecosystem, benthos not only consists of a significant part of organic carbon, but also plays a vital role in mediating carbon and nutrient fluxes across the sediment-water interface. The interaction between benthos and its ambient environment is twofold and dynamic. On one hand, coastal morphology, oceanographic forcing (e.g. tides, waves) and carbon/nutrient availability exert a first-order control on the type of habitats, as well as abundance and trait expression of benthos. On the other hand, benthos actively modifies its habitats and beyond to attain an optimized fitness for living conditions. Understanding such dynamic interactions is essential in management of coasts and shelf seas against present and future climatic threats and for sustainable use of coastal resources.In this talk, we demonstrate the quantitative importance of fluid-sediment-benthos interactions in (1) guiding morphological development of a tidal embayment in the Wadden Sea and (2) carbon cycling in the great North Sea as exemplary case studies. We applied a novel 3-Dimensional physics-ecosystem coupled numerical model to resolve dynamic interactions among fluid forcing, organic carbon, sediment and benthos. Specifically, we aim to address two different but interrelated questions:How important are fluid-sediment-benthos interactions in coastal morphological development? and
To what extent can such interactions affect carbon sequestration at a regional scale?
Kalka Shimla Railways – A UNESCO World Heritage Site Exposed to Landslides
Authors: Sharma Ankur , Sandhu Har Amrit Singh
Published: February 2023

The Kalka Shimla Railway was built in the mid-19th century during British rule in India to connect Shimla, then the British summer capital and the headquarters of the British army, with the Indian rail network. Considered the “Crown Jewel” of the Indian National Railways during British times, the rail network features in the Guinness Book of World Records for its steepest rise in altitude, from 656 m at Kalka to 2,076 m at Shimla in a span of 96.57 km. It was granted UNESCO World Heritage Status in 2008 for its profound impact on the social and economic development of the high mountain areas. Despite conservation management plans and regular permanent maintenance, the track faces the vagaries of nature. Slips and landslides, in particular, cause frequent disruptions in its operations. The present study focuses on susceptibility mapping for the Kalka Shimla Railway, often dubbed the “Toy Train”, to determine the degree of its exposure to landslides. Data from 1,484 past landslide locations is used to train a Random Forest classifier with Bayesian hyperparameter optimization to ensure accurate classifications. The trained model is validated using 5-fold cross-validation with an accuracy of 90.6% and an area under the receiver operating characteristic curve (AUROC) value of 0.97. The accuracy and AUROC values during the testing stage for the model are 91.7% and 0.97, respectively. The final susceptibility map is validated using the landslide density method after dividing the posterior probabilities into five classes based on Jenks optimization. The landslide densities of the five susceptibility zones, namely “Very High”, “High”, “Medium”, “Low” and “Very Low” are 17.180, 0.196, 0.036, 0.008, and 0.001 respectively, which reflect the quality of susceptibility zonation mapping because 96.55% of all the landslides lie within only 5.62% of the study area with “Very High” susceptibility. The results of the study show that 36.9% of the total length of the railway is exposed to either “High” or “Very High” landslide susceptibility. The degree of exposure is particularly severe in the Solan district where landslides have interrupted the normal operations of the railway as recently as the last monsoon spell in the region. The results of this study may help policymakers and concerned authorities implement decisive protection measures for the preservation of this heritage site and its outstanding legacy.
Tethys carbon cycle, India-Eurasia collision, and Cenozoic climate evolution
Authors: Vimpere Lucas , Castelltort Sébastien , Sternai Pietro , Bouilhol Pierre
Published: February 2023

 Since the industrial revolution, the constant increase in atmospheric CO2 had pivotal impacts on global climate with current concentrations being the highest of the last 800 ka. In order to better understand the Earth system and the future evolution of climates, it is essential to study past hyperthermals during which global surface temperature dramatically increased above present levels. The Himalaya arose from the biggest known continental collision and has been associated with a bustling volcanism, which most likely steered the global warming (+12-14 °C) during the Early Eocene Climatic Optimum (EECO).We here present the analytic strategy that will be implemented to quantify the carbon cycle within the Kohistan-Ladakh forearc sediments. Whilst the CO2 input (warming) in the atmosphere related to the intensity of subduction magmatism will be quantified using the mercury isotopes, the CO2 sink (cooling) induced by continental alteration of the exhumed units will be studied through different isotopic analyses (e.g., Hf, Nd, Sr). The stratigraphy and the reconstruction of depositional environments will be assessed through conventional field surveys and various dating methods such as, detrital zircon, nannofossils, radiolarians, and calibrated carbon isotopic curves. The overall objective is to establish the influence of the collisional Himalayan chain on global climate changes.
Intense Anticyclones and Near Inertial Trapped Waves at the Global Argentine Basin Array of the Ocean Observatory Initiative
Authors: Artana Camila , Provost Christine
Published: February 2023

We analyzed physical oceanic parameters gathered by a mooring array at mesoscale spatial sampling deployed in Argentine Basin within the Ocean Observatory Initiative, a National Science Foundation Major Research Facility. The array was maintained at 42°S 42°W, a historically sparsely sampled region with small ocean variability, during 34 months from March 2015 to January 2018. The data documented four anticyclonic extreme structures events in 2016 and the presence of near-inertial waves (NIWs) trapped at depth within the anticyclones. Although the four anticyclonic structures had different characteristics (size, vertical extension, origin, lifetime, Rossby Number) they all featured low Richardson values well below the mixed layer associated to NIWs. Low Richardson values suggest favorable conditions for mixing. The anticyclonic features act as mixing structures at the pycnocline bringing heat and salt from the South Atlantic Central Water to the Antarctic Intermediate Waters. The extreme events were unique in the 29-year-long satellite altimetry record at the mooring site. However, the Argentine Basin is populated with many anticyclones and mixing associated to trapped NIWs probably plays an important role in setting up the upper water masses characteristics in the Basin.
Better prepared but less resilient: the paradoxical impact of flood experience on adaptive behavior and social resilience
Authors: Köhler Lisa , Masson Torsten , Köhler Sabrina , Kuhlicke Christian
Published: February 2023

In natural hazards research, social resilience is becoming a topic of high scientific interest. Due to global climate change, most natural hazards are occurring more often and put individuals' mental and physical health, economic endowments, and the existence of their valued objects at risk. One way to decrease the impacts of these hazards is to increase individual's resilience. Consequently, the knowledge of the drivers behind it becomes more desirable as it is necessary to design strategies to prepare households for future hazards. The central question of the research project is if flood experience impacts adaptive behavior and self-perceived social resilience and, if so, in what ways. The applied empirical method is an ordered logistic regression model using data from a panel dataset (2020-2021), including 1750 residents (Germany, state of Saxony). Four main conclusions from the investigations can be drawn. First, more experienced individuals are statistically significantly more likely to have taken precautionary measures in the past. Second, flood experience has a statistically significant negative impact on self-perceived social resilience. Third, the impact of flood experience on the capacity to resist is not linear. Fourth, putting together these results reveals the paradox that more flood-experienced people are better prepared but feel less resilient at the same time. It can be concluded that more research is needed to obtain deeper insights into the drivers behind social resilience and that this study can be seen as a piece of the puzzle, taking flood experience as the primary target point. While this study contributes with more profound knowledge of what role experiences play in building social resilience, it connects theories from social and natural sciences. Consequently, it enriches the existing knowledge with more interdisciplinarity.
Climate mediated changes in seawater chemistry and their potential effects on marine lightning intensity
Authors: Asfur Mustafa , Silverman Jacob
Published: February 2023

In 2016, the World Meteorological Organization declared that lightning is an essential climate variable. To date, global change studies have only considered the effect of warming on lightning flash frequency and the global distribution of lightning activity. Furthermore, none of these studies considered the effects of climate change on lightning flash intensity. In our previous studies we suggested based on laboratory experiments that lightning intensity over water surfaces may be influenced by their chemical properties, including salinity (S), pH and total alkalinity (TA). In this study we tested the combined effects of changes in S, TA and pH in Mediterranean Sea surface water on the intensity of laboratory generated electrical sparks, which are considered to be analogous to cloud to sea-surface intensity of lightning discharges. The range of values tested in the lab correspond to changes in S, pH and TA of Mediterranean surface water that were caused by the anthropogenic climate change, ocean acidification and damming of the Nile in the 1960s. Where, the damming of the Nile is generally accepted to have caused nearly 30% of the total salination of Mediterranean surface water until now. The experimental results were used to develop a multivariate linear model of Lightning Flash Intensity (LFI) as a function of S, TA/S, which  and pH. The model was validated with wintertime (DJF) LFI measurements along a Mediterranean Sea zonal profile during the period 2009-2020 compared to corresponding climate model outputs of S, TA and pH. Based on this model, the combined effects of climate change, ocean acidification and the damming of the Nile, may have increased LFI in the Levantine Sea by 16±14% until now relative to the pre-Aswan Dam period. Furthermore, assuming that salinization and acidification of the Levantine Sea will continue at current trends, the LFI is predicted to increase by 25±13% by the year 2050.
An iterative data-driven emulator of an ocean general circulation model
Authors: Furner Rachel , Haynes Peter , Jones Dan(i) , Munday Dave , Paige Brooks , Shuckburgh Emily
Published: February 2023

Data-driven models are becoming increasingly competent at tasks fundamental to weather and climate prediction. Relative to machine learning (ML) based atmospheric models, which have shown promise in short-term forecasting, ML-based ocean forecasting remains somewhat unexplored. In this work, we present a data-driven emulator of an ocean GCM and show that performance over a single predictive step is skilful across all variables under consideration. Iterating such data-driven models poses additional challenges, with many models suffering from over-smoothing of fields or instabilities in the predictions. We compare a variety of methods for iterating our data-driven emulator and assess them by looking at how well they agree with the underlying GCM in the very short term and how realistic the fields remain for longer-term forecasts. Due to the chaotic nature of the system being forecast, we would not expect any model to agree with the GCM accurately over long time periods, but instead we expect fields to continue to exhibit physically realistic behaviour at ever increasing lead times. Specifically, we expect well-represented fields to remain stable whilst also maintaining the presence and sharpness of features seen in both reality and in GCM predictions, with reduced emphasis on accurately representing the location and timing of these features. This nuanced and temporally changing definition of what constitutes a ‘good’ forecast at increasing lead times generates questions over both (1) how one defines suitable metrics for assessing data-driven models, and perhaps more importantly, (2) identifying the most promising loss functions to use to optimise these models.
Dendrogeomorphic reconstruction of debris-flow activity in Sancy Massif (French Massif Central)
Authors: Pop Olimpiu
Published: February 2023

Debris flows (DFs) are one of the main geomorphic processes occurring in mountain regions, where they may repeatedly cause economic losses and even fatalities. Usually, along the same track, DFs may recur with various frequencies and magnitudes. Generally, because of the short collective memory and the lack or uncomplete archival records, little is known about the spatial and temporal frequency of past DFs. Dendrogeomorphic methods may be applied to reconstruct debris-flow activity in mountain areas where historical records of past DF events are uncomplete or lacking. In the Sancy Massif (1885 m a.s.l.), one of the medium-altitude stratovolcanoes of the French Massif Central, DFs are triggered during extreme rainfall events. One of the DF tracks located in the Mont Dore tourism resort starts on the steep slopes of unconsolidated volcaniclastic materials and follows a channel which cross a forested debris cone. It is the aim of this study to reconstruct past DF activity which occurred along the track in the Mont Dore tourism resort by using dendrogeomorphic methods. Based on a detailed geomorphic mapping and the identification of growth anomalies found in 42 disturbed silver fir trees (Abies alba Mill.) sampled, a minimum chronology of 13 events has been reconstructed spanning the period 1900 - 2008. Meteorological data recorded by the nearby weather station have been also analysed, to estimate the possible rainfall thresholds for past DF events.
Linking Atmospheric Moisture Transport to Extreme Precipitation Events Associated with Floods over India
Authors: Singh Raghuvanshi Akash , Agarwal Ankit
Published: February 2023

The primary component of the atmospheric branch of the water cycle is atmospheric moisture transport, and its amplitude has a strong influence on drought and precipitation extremes. Vertically integrated water vapor transport (IVT) is evaluated to assess atmospheric moisture transport (AMT) over the Indian Subcontinent. Linkages to flood-causing extreme precipitation events are understood using case studies that were in accordance with their intense rainfall conditions and flooding that resulted in huge losses over a specified region. Using a high-resolution daily gridded rainfall data set, an attempt has been made to analyze the spatiotemporal characteristics of atmospheric moisture transport (AMT) responsible for extreme events. The spatiotemporal characteristics of specific rainfall events associated with the occurrence of AMT show the existence of a strong relationship between the presence of high AMT and extreme precipitation events for the northwestern region where AMT penetrates inland and for the east coast region where AMT makes landfalls. Further analysis suggests that extreme precipitation events are predominantly influenced by the strong moisture convergence associated with the low-level pressure systems, wind speed, and wind direction developed in the vicinity of affected regions.
Sea surface temperature fronts in the Levantine Basin of the Mediterranean Sea
Authors: Akpınar Anıl , Fach Bettina
Published: February 2023

Fronts are ubiquitous features in the ocean, having significant implications for oceanic and atmospheric environments, including; water masses, currents, ocean-atmosphere interactions, and ecosystems, particularly through cross-front exchanges of water masses, materials and biota. In this work, we investigate thermal fronts in the Levantine Basin of the Mediterranean Sea, using remotely sensed sea surface temperature data. First, a frontal detection algorithm is used to determine the fronts. Then the spatial and temporal variability of the fronts are presented. A specific focus lies on the fronts associated with the Asia Minor boundary current, due to its frontal instabilities and associated eddy activity. Detected fronts are used as a basis to investigate these features and their contribution to cross-frontal exchanges. Further work includes identification of in-situ data gaps in existing observatories around fronts to provide an effective monitoring strategy of fronts in the region. This work has been produced benefiting from the 2236 Co-Funded Brain Circulation Scheme2 (CoCirculation2) of TÜBITAK (Project No: 121C411). However, the entire responsibility of the publication belongs to the owner of the publication. The financial support received from TÜBITAK does not mean that the content of the publication is approved in a scientific sense by TÜBITAK.
Integrating NGS GRAV-D gravity observations into high-resolution global models
Authors: Roman Daniel , Li Xiaopeng , Zingerle Philipp , Willberg Martin , Pail Roland
Published: February 2023

Within this contribution we present a method that allows a smooth integration of in-situ ground gravity observations into high-resolution global models up to d/o 5400 (2’ global resolution). The functionality is shown on the example of the airborne GRAV-D gravity dataset which is integrated into a global satellite-topographic spherical harmonic model. Conceptually, the method is divided into three steps: firstly, since the processing is based on residuals, a precursor model needs to be identified which is used for reducing the observations. In the actual example a combination between a satellite-only model (GOCO06s) and topographic model (EARTH2014) is chosen (named SATOP2) to ensure independency to the observations. Secondly, the previously reduced (GRAV-D) observations are gridded onto a regular geographic grid making use of the recently developed partition-enhanced least squares collocation approach (PE-LSC). PE-LSC allows an efficient collocation of virtually arbitrary large datasets using a partitioning technique that is optimized for computational performance and for minimizing fringe effects. As a third and last step, the obtained regular grid gets analyzed and combined with a satellite-only model (GOCO06s) on the normal equation level up to d/o 5400. This can be achieved efficiently by using a so-called kite-normal equation system which emerges when combining dense and block-diagonal normal equation systems (assuming equal accuracies for the ground gravity grid). The herby obtained global gravity field model, named SGDT, is dominated by the satellite information in the lower frequencies (up to d/o 200), by GRAV-D in the mid-frequencies (d/o 200-2000) and by the topographic information in the high frequencies (above d/o 2000). The main purpose of the SGDT model is to validate the method itself and to allow a comparison of GRAV-D observations to pre-existing ground-gravity data by synthesizing SGDT to actual observation sites.
Improving GNSS meteorology by fusing measurements of multi-receiver sites on the observation level
Authors: Wang Rui , Hobiger Thomas , Marut Grzegorz , Hadas Tomasz
Published: February 2023

In GNSS analysis, tropospheric modelling is done in the form of Zenith Hydrostatic Delay (ZHD), which can be empirically computed from surface pressure and temperature, and Zenith Wet Delay (ZWD), which is estimated together with the other unknown parameters.  Analysis methods based on undifferenced GNSS code- and carrier-phase observations like Precise Point Positioning (PPP), which can achieve millimeter-accurate positioning results, provide therefore also time-series of ZWD, which can be used for meteorologic applications. However, due to receiver noise and system characteristics like cycle-slips the accuracy as well as the precision of such ZWD estimates is limited. Thus, we propose a novel approach for sites, which have several receivers connected to a single antenna or which are separated horizontally by only a few meters. For such sites, one can simultaneously process multi-frequency GNSS data by fusing observations from several receivers, while estimating a common ZWD parameter.For this purpose, we have implemented a PPP algorithm based on an Extended Kalman Filter (EKF) approach, which has the advantage that ZWD estimates are available in real-time for meteorologic applications. We demonstrate that those combined ZWD estimates are superior to single receiver estimates in term of precision and accuracy. For the latter measure, we make use of a GNSS hardware simulator and show that the RMS between the simulated and estimated ZWD significantly decreases when having two or more receivers at that site. Based on real-data we show that this concept provides less noisy ZWD estimates which agree better with physical properties of the local wet refractivity field.Moreover, we demonstrate that fusing data from several receivers by estimating a common ZWD parameter improves also positioning accuracy and precision, in particular in the up-component. In order to properly combine observations from geodetic-grade and low-cost GNSS receivers, we present our adaptive Kalman filter approach, which adjusts the observation noise covariance matrix automatically during processing. The presentation concludes with an outlook on the usage of this approach for larger networks and answers the question how arrays of low-cost GNSS receivers can compete against geodetic-grade GNSS hardware in term of providing ZWD estimates for meteorology.
A new sigmoidal but non-asymptotic soil water retention curve for the entire soil water content range brings together the van Genuchten and Brooks-Corey models
Authors: de Rooij Gerrit H.
Published: February 2023

The most important parameterizations of the soil water retention curve do not perform very well in either the wet or the dry end. Rossi and Nimmo (WRR 1994) therefore gave the Brooks-Corey (1966) power-law model of the soil water retention curve a non-asymptotic dry range. Ippisch et al. (Adv. Water Resour., 2006) added an air-entry value to the sigmoidal retention model of van Genuchten (SSSAJ 1980). The models of Rossi and Nimmo and Ippisch et al. were Adapted by de Rooij (HESS 2021) to arrive at a sigmoidal, non-asymptotic soil water retention curve with an air-entry value, dubbed RIA. In RIA, the matric potential at oven-dryness, hd, appeared as a derived parameter.Bittelli and Flury (SSSAJ 2009) showed that dry-range soil water retention data points often are unreliable. In order to make RIA robust when this is the case, this presentation explains how hd was made a fitting parameter that can be fixed if needed. This modification was complicated by the peculiar behavior of shape parameter α that made adequate parameter fitting impossible. The presentation elucidates this behavior and explains how this problem was solved by a reformulated model (de Rooij, HESS 2022). It then shows how earlier fits (when the problem had not yet been discovered) corroborate the reformulated model.The work also offers support for a theoretical value for hd proposed by Schneider and Goss (Geoderma 2012), which is very helpful if dry-range data are lacking or of poor quality. The mathematical structure of RIA is such that, for α → ∞, Rossi and Nimmo’s model arises as a special case of RIA, and, by implication, Brooks-Corey as a special case of Ippisch et al.A public-domain code to fit the parameters using shuffled complex evolution (SCE) is available on Zenodo (de Rooij, 2022). It has features that help the user identify issues with local minima and overparameterization, and provides more information than most codes to offer better insight into the fitting process for those familiar with the SCE algorithm. These features may be useful for other parameter identification problems, so they will be discussed as well.
The effects of dust content on surface sediment transport by carbon dioxide ice sublimation on Mars
Authors: Conway Susan , Beck Calvin , Herny Clémence , Cesar Camila , Sizemore Hanna , Sylvest Matthew , Patel Manish
Published: February 2023

During the martian year the surface temperatures in winter dip below the condensation temperature of carbon dioxide and it freezes onto the surface. In the spring, it sublimates directly back into the atmosphere and observations reveal that this cycle of condensation-sublimation results in identifiable sediment transport on the martian surface. We use data from the Colour and Stereo Surface Imaging System (CaSSIS) on ESA's Exomars Trace Gas Orbiter to illustrate the range of landforms thought to be created by these sublimation processes. Previous experiments have revealed that condensation of CO2 ice into the regolith pore space and its subsequent sublimation can result in downslope sediment transport. they also showed that aeolian sand was less prone to sediment motion triggered by sublimation than martian regolith simulant and it was suggested the presence of dust could be responsible for this difference. As dust is an important component of the martian atmosphere and surface, in these experiments we explore the influence of dust content on the sediment transport processes and capacity for sediment transport.Our experimental setup consists of a liquid nitrogen cooled copper sample holder ~30cm long by 20 cm wide within which the sediment is formed into a slope at 30° (max. depth 10 cm). This container is placed inside the Open University’s Mars Chamber which has has a length of 2 m and a diameter of 1 m. One experiment typically takes 2hrs, and the preparation takes 12-14hrs. First the chamber is evacuated and backfilled with CO2 gas twice to purge terrestrial gases including H2O. Once this is complete the sample holder is cooled with liquid nitrogen until all the sediment temperatures reach the condensation temperature of CO2. The experiment then starts and a heat lamp is used to force the CO2 sublimation.  The experiments are monitored by an array of cameras for photogrammetry, a high definition video camera to record the processes, pressure gauges to maintain/monitor the pressure and thermocouples to monitor the sediment and surface temperature.In this series of experiments we vary the dust content in an aeolian sand matrix from 0 to 20% by weight by adding the clay fraction of the MSC simulant. We find no significant difference in the results between 0 and 5% dust content, then at higher values the transported volume and activity increases suddenly and the transported volume and activity remains stable at a higher level from 10% dust upwards. Our results reveal that a sediment transport threshold seems to exist between 5% and 10% dust content and therefore this factor must be considered when studying seasonally active surface processes on Mars.
Estimation and Prediction of Solar Wind Propagation from L1 Point to Earth’s Bow Shock
Authors: Tasnim Samira , Zou Ying , Borries Claudia , Baumann Carsten , Walsh Brian , Khanal Krishna , O'Brien Connor , Zhang Huaming
Published: February 2023

Having precise knowledge of the near-Earth solar wind (SW) and the embedded interplanetary magnetic field (IMF) is of critical importance to space weather operation due to the usage of SW and IMF in almost all magnetospheric and ionospheric models. The most widely used data source, OMNI, propagates SW properties from Lagrangian point L1 to the Earth’s bow shock by estimating the propagation time of the SW. However, the time difference between OMNI timeshifted IMF and the best match-up of IMF can reach ˜15 min. Firstly, we aim to develop an improved statistical algorithm to contribute to the SW propagation delay problem of space weather prediction. The algorithm focuses on matching SW features around the L1 point and upstream of the bow shock by computing the variance, cross-correlation coefficient, the plateau-shaped magnitude index, and the non-dimensional measure of average error index between the measurements at the two locations. The obtained propagation times are then compared to OMNI. Factors that limit the OMNI accuracy are also examined. Secondly, the automatic algorithm allows us to generate large sets of input and target variables using multiple spacecraft pairs at L1 and near-Earth locations to train, validate, and test machine learning models to specify and forecast near-Earth SW conditions. Finally, we offer a machine learning (ML) approach to specify and predict the propagation time from L1 monitors to a given location upstream or at the bow shock and forecast near-Earth SW conditions with the gradient boosting and random forest prediction models in the form of an ensemble of decision trees.
A Stacking Ensemble Deep Learning Approach for Post Disaster Building Assessment using UAV Imagery
Authors: Sim Leon , Tsai Fang-Jung , Lin Szu-Yun
Published: February 2023

Traditional post-disaster building damage assessments were performed manually by the response team, which was risky and time-consuming. With advanced remote sensing technology, such as an unmanned aerial vehicle (UAV), it would be possible to acquire high-quality aerial videos and operate at a variety of altitudes and angles.  The collected data would be sent into a neural network for training and validating. In this study, the Object Detection model (YOLO) was utilized, which is capable of predicting both bounding boxes and damage levels. The network was trained using the ISBDA dataset, which was created from aerial videos of the aftermath of Hurricane Harvey in 2017, Hurricane Michael and Hurricane Florence in 2018, and three tornadoes in 2017, 2018, and 2019 in the United States. The Joint Damage Scale was used to classify the buildings in this dataset into four categories: no damage, minor damage, major damage, and destroyed. However, the number of major damage and destroyed classes are significantly lower than the number of no damage and minor damage classes in the dataset. Also, the damage characteristics of minor and major damage classes are similar under such type of disaster. These caused the YOLO model prone to misclassify the intermediate damage levels, i.e., minor and major damage in our earlier experiments. This study aimed to improve the YOLO model using a stacking ensemble deep learning approach with a image classification model called Mobilenet. First, the ISBDA dataset was used and refined to train the YOLO network and the Mobilenet network separately, and the latter provides two classes predictions (0 for no damage or minor damage, 1 for major damage or destroyed) rather than the four classes by the former. In the inference phase, the initial predictions from the trained YOLO network, including bounding box coordinates, confidence scores for four damage classes, and the predicted class, were then extracted and passed to the trained Mobilenet to generate the secondary predictions for each building. Based on the secondary predictions, two hyperparameters were utilized to refine the initial predictions by modifying the confidence scores of each class, and the hyperparameters were trained during this phase. Lastly, the trained hyperparameters were applied to the testing dataset to evaluate the performance of the proposed method. The results show that our stacking ensemble method could obtain more reliable predictions of intermediate classes. 