bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitrosat, a Satellite Mission Concept for Mapping Reactive Nitrogen at the Landscape Scale
Authors: Clarisse Lieven ,   Nitrosat team
Published: February 2023

Two key forms of reactive nitrogen (Nr) in the atmosphere are nitrogen oxides (NO+NO2) and ammonia (NH3). Both species are abundantly emitted from anthropogenic sources (fossil fuel combustion, agriculture) with devastating consequences on the environment, human health and climate. Complementing sparse ground-based measurements, current satellite sounders provide daily coverage of their global distribution. However, the spatial resolution of these instruments (>20 km² for NO2 and >100km² for NH3) is orders of magnitudes greater than the typical size of the main Nr sources (industries, farms, roads), which makes identification of the emitters, and corresponding quantification of their emission strengths particularly challenging.To understand and address the impacts of a perturbed nitrogen cycle, and in response to the current observational gap, a dedicated satellite for the monitoring of NO2 and NH3 at high spatial resolution has been conceptualised. Nitrosat, as it is being called, is currently in Phase 0 of ESA’s Earth Explorer 11 call. Its main objective is to quantify simultaneously the emission sources of NH3 and NOx at the landscape scale (<0.25 km²) and to characterize seasonal patterns (<1 month) in their emissions. The two imaging spectrometers onboard Nitrosat will operate respectively in the infrared for NH3 and the visible for NO2, offering gapless coverage in a single swath.Starting from representative examples of measurement techniques that are presently used to derive emission fluxes from NH3 and NO2 satellite observations, we discuss the limitations of current sounders. We introduce the Nitrosat measurement concept and, exploiting both model simulations and aircraft campaign data, provide examples from the Phase 0 studies of how Nitrosat will enable retrieval of emission fluxes from local and diffuse sources in a way that will not be possible with other current or planned missions.
ENSO–IOD Inter-Basin Connection Is Controlled by the Atlantic Multidecadal Oscillation
Authors: Xue Jiaqing , Luo Jing-Jia , Zhang Wenjun , Yamagata Toshio
Published: February 2023

The interactions between El Niño-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) are known to have great implications for global climate variability and seasonal climate predictions. Observational analysis suggests that the ENSO–IOD inter-basin connection is time-varying and related to the Atlantic Multidecadal Oscillation (AMO) with weakened ENSO–IOD relationship corresponding to AMO warm phases. A suite of Atlantic pacemaker simulations successfully reproduces the decadal fluctuations in ENSO–IOD relationship and its link to the AMO. The warm sea surface temperature (SST) anomalies associated with the AMO drive a series of Indo-Pacific mean climate changes through tropical-wide teleconnections, including the La Niña-like mean SST cooling over the central Pacific and the deepening of mean thermocline depth in the eastern Indian Ocean. By modulating ocean–atmosphere feedback strength, those mean state changes decrease both ENSO amplitude and the Indian Ocean sensitivity to ENSO forcing, therefore decoupling the IOD from ENSO.
A Kalman filtering approach for producing ice sheet surface elevation change time series using satellite altimetry data
Authors: Wassink Robert , McMillan Mal , Maddalena Jennifer , Slater Thomas , Leeson Amber , Muir Alan
Published: February 2023

Producing accurate time series of surface elevation change is vital to our understanding of ice sheet contributions to sea level rise. Such estimates are derived from a variety of sources, including automatic weather station measurements, regional climate models, and satellite altimeter observations. For satellite altimetry, a common approach for computing elevation changes is to fit a simple polynomial model to repeated measurements, from an individual satellite mission, within small (typically < 10km) ice sheet regions. However, since there now exists multiple altimeters in orbit synchronously, we instead aim to employ techniques that are more capable of fusing measurements from multiple sensors whilst also respecting any differences in uncertainties. One such technique is Kalman filtering/smoothing, which also provides opportunities for assimilating this data with ice sheet models.

Four-dimensional local ensemble transform Kalman filtering (4D-LETKF) is a Bayesian approach capable of estimating large spatiotemporally chaotic systems and has already seen use in the fields of meteorology and oceanography for assimilating observations into complex forecasting models. Therefore, we explore applying a similar approach to cryosphere datasets to generate time series of surface elevation change. Our method uses satellite altimeter observations, which provide a continuous continental-scale record of ice sheet elevation measurements. The chosen state transition model is the identity matrix, predicting no change from one day to the next, allowing the observations to drive the results. Ensembles are not required because of the model’s simplicity but will be explored in the future to enable more advanced predictive models.

Here, we present the method development for this novel application of the 4D-LETKF, demonstrating these techniques on CryoSat-2 radar altimetry measurements over the Greenland ice sheet from ESA’s Cryo-TEMPO Baseline-B dataset. Our next steps are to fuse other current and historical missions to produce a single collective gridded time series of surface elevation change over ice sheets. As such, we hope this study can provide the first steps towards more formal data assimilation of Earth observation data into physical ice sheet models.
Electric self-potential monitoring of hydraulic fracturing experiments in the Äspö Hard Rock Laboratory, Sweden.
Authors: Haaf Nadine , Guarracino Luis , Jougnot Damien , Schill Eva
Published: February 2023

A number of six in situ hydraulic fracturing experiments were carried out at the Äspö Hard Rock Laboratory (Sweden) in 2017 in a depth of 410 m. Here we present electric self-potential monitoring during the conventional and the step-wise cyclic injection experiments HF2 and HF3. Electric self-potential data were acquired through a two-sensor array, each including nine measuring probes and one base probe, that were installed at the 410 m and 280 m levels. The experimental borehole F1 is drilled in the direction of Shmin, perpendicular to the expected fracture plane. The self-potential sensors are installed sub-parallel to Shmin at level 410 at a distance of 50-75 m to the borehole F1 and sub-perpendicular to Shmin at level 280 m at a distance of 150-200 m to F1. The self-potential data were measured with a sampling rate of 1 Hz. Here, we propose a 1-D modelling of the streaming potential that approximates the measured self-potential data. These streaming potential gradients ∆V are estimated from the simulated pressure signals and the coupling coefficient.
Power of groundwater data sharing in the Mediterranean region
Authors: Jomaa Seifeddine , Chavez Rafael , Ben-Salem Nahed , Varouchakis Emmanouil , K. Copty Nadim , P. Karatzas George , Rode Michael , Gómez-Hernández J. Jaime
Published: February 2023

Groundwater is a strategic water resource in water-stressed regions such as the Mediterranean region. It used to meet the increasing domestic water demand and food production, maintaining ecosystem integrity and buffering climate change impacts. However, groundwater information that relies mainly on in-situ data observations remains fragmented and lacking standardization in the Mediterranean region due to the lack of systematic monitoring and data-sharing policy. PRIMA Foundation, launched in 2018 as a European Commission funding program, has targeted groundwater as a priority topic in its two first calls of 2018 and 2019. Sustain-COAST and InTheMED are two PRIMA-funded projects aiming for sustainable groundwater management in the Mediterranean region, adopting innovative but complementary approaches. Among their specific goals, Sustain-COAST and InTheMED projects have jointly developed a joint effort to collect groundwater-level data from around the Mediterranean. Over 14,000 time series of historical groundwater level data have been collected from different countries and have been harmonized into a common format. The resulting groundwater database has opened new horizons and perspectives for groundwater assessment that were previously invisible. In this contribution, we present and explore five new directions that have resulted from the groundwater database of the Mediterranean region: 1.  Trend analysis and groundwater patterns clustering and their controlling drivers, 2. Regional groundwater level estimates combining different global groundwater models and regional in-situ data, 3. A methodological framework using Gravity Recovery and Climate Experiment (GRACE) satellite data to retrieve groundwater storage changes, 4. Water policy timeline, harmonization and pathways for innovative governance, and 5. Lesson learned from “success stories” of groundwater trend reversal and their transfer capabilities. This contribution will shed light on the power of data-sharing and will call for future systemic groundwater data collection in the Mediterranean region and beyond.
A process based definition of the extratropical transition layer
Authors: Kaluza Thorsten , Hoor Peter , Kunkel Daniel
Published: February 2023

The existence of the extratropical transition layer (ExTL) still lacks a physical process based explanation. It is yet an empirical finding based on the observed gradient changes of species within the lowermost stratosphere (LMS). The trace gas distribution directly results from localized and transient dynamical processes in the tropopause region. However, up to this point a dynamic- or process based definition of the ExTL remains an open research question, to large parts due to limitations of the available model and measurement data and resulting uncertainties in the assessment of the relevance of individual processes. We present a synopsis of a series of recent research studies, which provide strong indications that tropopause-based wind shear and resulting dynamic instability is the key process for the formation of the ExTL. For this we use a multitude of different model and observational data sets, thus addressing the formation and maintenance of the ExTL from the chemical view, the process based dynamical view as well as from the large scale synoptics:
Process studies identify dynamic instability and turbulent cross-tropopause mixing based on trace gas measurements within distinct mesoscale layers of exceptional wind shear at the tropopause.

The analysis of several years of ECMWF ERA5 reanalysis data shows that these vertically confined transient layers of intense shear are a frequently occurring global scale feature, which is forced by the underlying large scale tropospheric dynamics.

The significance of this wind shear layer as a persistent source for dynamic instability and turbulent breakdown of the flow at the tropopause is validated with several years of operational EDR turbulence measurements from commercial aircraft.
Censored Bernstein quantile networks for probabilistic precipitation forecasting
Authors: Bremnes John Bjørnar
Published: February 2023

In recent years neural networks have successfully been applied to probabilistic post-processing of numerical weather prediction forecasts. In the Bernstein Quantile Networks (BQN) method predictive quantile distributions are specified by Bernstein polynomials and their coefficients linked to input features through flexible neural networks. However, precipitation presents an additional challenge due to its mixed distributed nature with a considerable proportion of dry events for short accumulation periods. In this presentation, it is demonstrated how the BQN method can be modified to mixed distributed variables like precipitation by introducing a latent variable and treating zero precipitation cases as censored data. The method is tested on both synthetic and real precipitation forecast data and compared to an approach where a model of the probability of precipitation is combined with a model of precipitation amounts using the laws of probability. 
Analysis and Modelling of 2009-2013 vs. 2019-2022 Unrest Episodes at Campi Flegrei Caldera
Authors: Castaldo Raffaele , Barone Andrea , Vincenzo De Novellis , Antonio Pepe , Susi Pepe , Giuseppe Solaro , Pietro Tizzani , Anna Tramelli
Published: February 2023

Geodetic modelling is a significant procedure for detecting and characterizing unrest and eruption episodes and it represents a valuable tool to infer volume and geometry of volcanic source system.In this study, we analyse the 2009–2013 and the ongoing 2019-2022 uplift phenomena at Campi Flegrei (CF) caldera in terms of spatial and temporal variations of the stress/strain field. In particular, we investigate the characteristics of the inflating sources responsible of these main deformation unrests occurred in the last twenty years. We separately perform for the two considered periods a 3D stationary Finite Element (FE) modelling of geodetic datasets to retrieve the geometry and location of the deformation sources. The geometry of FE domain takes into account both the topography and the bathymetry of the whole caldera. For what concern the definition of domain elastic parameters, we take into account the Vp/Vs distribution from seismic tomography. In order to optimize the nine model parameters (center coordinates, sferoid axes, dip, strike and over-pressure), we use the statistical random sampling Monte Carlo method by exploiting both geodetic datasets: the DInSAR measurements obtained from the processing of COSMO-SkyMed and Sentinel-1 satellite images. The modelling results for the two analysed period are compared revealing that the best-fit source is a three-axis oblate spheroid ~3.5 km deep, similar to a sill-like body. Furthermore, in order to verify the reliability of the geometry model results, we calculate the Total Horizontal Derivative (THD) of the vertical velocity component and compare it with those performed directly on the two DInSAR dataset.Finally, we compare the modelled shear stress with the natural seismicity recorded during the 2000-2022 period, highlighting high values of modelled shear stress at depths of about 3.5 km, where high-magnitude earthquakes nucleate.
Using analogue experiments to explore fundamental processes during magma ascent
Authors: Kavanagh Janine , Chalk Caitlin
Published: February 2023

The propagation mechanics and fluid dynamics of magma-filled fractures, such as dykes and sills, are fundamental to the generation of sub-surface signals which indicate magma is on the move. Dykes play a major role transporting magma from depth to the surface, and modelling the dynamics of dyke growth remains a primary objective to improve the interpretation of a wide range of geophysical, petrological and geochemical evidence of magma ascent. We present results from scaled analogue experiments using Liverpool’s new Medusa Laser Imaging Facility to quantify the fluid flow dynamics and solid deformation during magma ascent in dykes. Our results detail the characteristics of dyke ascent from inception to eruption, with magma flow regimes and host-rock deformation mode dependent on dyke geometry, host-rock properties, density contrasts and magma rheology. Our results pose new conceptual models upon which the signals of magma movement in nature should be interpreted.
Collaborative moisture tracking with WAM2layers v3
Authors: Kalverla Peter , Benedict Imme , van der Ent Ruud , Weijenborg Chris
Published: February 2023

Atmospheric moisture tracking is a valuable technique for understanding the physical processes that drive (extreme) precipitation and drought in our changing climate. By following where precipitated moisture originally evaporated (backtracking) or where evaporated moisture eventually precipitates (forward tracking) we can gain valuable insights into the connection of large-scale weather systems and hydrometeorological events, land-atmosphere interactions, or the impact of land-use changes on water availability.The WAM2layers model is an Eulerian moisture tracking code that solves the water balance equation for tagged moisture in gridded model output data. With the increasing resolution of weather and climate models, however, data handling and performance have become serious constraints. Over the past year, we have worked on a new version of WAM2layers (github.com/WAM2layers/WAM2layers), in which we tackle these computational challenges and make a substantial upgrade to the user- and developer-friendliness of the model. The most important changes are summarized below.Usability: the new version of WAM2layers separates configuration from code. This makes it possible to run many different model simulations without modifying the source code. The model can now be run with a single command, supplying a configuration file as an input argument. It is even possible to use the model without copying the code. Simply install the wam2layers Python package from PyPI.Modularity: we have made a stricter separation between preprocessing steps, the actual tracking code, and utilities for analysing the results. This is important, for example, for working with multiple datasets. So far, we've worked with ERA5 data. Adding support for other datasets requires no modifications to the tracking code, only a separate preprocessing script.Documentation: the new version of the model comes with documentation on ReadTheDocs. The documentation includes theory, installation instructions, a complete user guide, and contributing guidelines.Collaborative development: previous versions of the model were already available on GitHub, but further development often happened offline and without coordination. From the start of this project, we have opened up the development process such that everyone can ask questions, raise issues, and open pull requests. The brand-new documentation includes instructions for anyone willing to contribute. We believe this shift represents a modern perspective on collaborative research practice.
Stratospheric aerosol extinction profiles retrieved from twilight sky spectral measurements above Georgia, South Caucasus in 2021-2022.
Authors: Mateshvili Nina , Mateshvili Iuri , Baker Noel , Berthelot Antonin , Bingen Christine , Dekemper Emmanuel , Demoulin Philippe , Franssens Ghislain , Fussen Didier , Kyrölä Erkki , Paatashvili Tamar , Pieroux Didier , Vanhellemont Filip
Published: February 2023

Narrow field-of view spectral measurements of twilight sky brightness as a function of solar zenith angle in the 89°-95° range allow to retrieve lower stratospheric and tropospheric aerosol extinction profiles. The measurements were carried out over Tbilisi, Georgia, South Caucasus during 2021-2022 in the 700-800 nm wavelength range using a SBIG ST9 CCD camera and a SBIG SGS spectrograph. The Monte Carlo code Siro, developed in the Finnish Meteorological Institute was used to design a forward model. Aerosol extinction profiles at 780 nm were retrieved using the Levenberg–Marquardt algorithm.Stratospheric aerosol loading was low in the considered period whereas the upper (about 9-10 km) and lower troposphere (about 4-5 km) were sometimes disturbed due to small volcanic eruptions and dust transport events. Particularly, ash clouds from Etna eruptions on 10 and 21 February were observed at about 9 km altitude.
Climatic control on seasonal variations of moutain glacier surface velocity
Authors: Nanni Ugo , Scherler Dirk , Ayoub Francois , Millan Romain , Herman Frederic , Avouac Jean-Philippe
Published: February 2023

Glacier displacement can in principle be measured at the large-scale by cross-correlation of satellite images. At weekly to monthly scales, the expected displacement is often of the same order as the noise for the commonly used satellite images, complicating the retrieval of accurate glacier velocity. Assessments of velocity changes on short time scales and over complex areas such as mountain ranges are therefore still lacking, but are essential to better understand how glacier dynamics are driven by internal and external factors. In this study, we take advantage of the wide availability and redundancy of satellite imagery over the Western Pamir to retrieve glacier velocity changes over 10 days for 7 years for a wide range of glacier geometry and dynamics. Our results reveal strong seasonal trends. In spring/summer, we observe velocity increases of up to 300% compared to a slow winter period. These accelerations clearly migrate upglacier throughout the melt-season, which we link to changes in subglacial hydrology efficiency. In autumn, we observe glacier accelerations that have rarely been observed before. These episodes are primarily confined to the upper ablation zone with a clear downglacier migration. We suggest that they result from glacier instabilities caused by sudden subglacial pressurization in response to (1) supraglacial pond drainage and/or (2) gradual closure of the hydrological system. Our 10-day resolved measurements allow us to characterize the short-term response of glacier to changing meteorological and climatic conditions.
Methane source identification using Non-Methane Hydrocarbon (NMHC) source apportionment in the Eastern Mediterranean and Middle East region
Authors: Germain-Piaulenne Emeric , Paris Jean-Daniel , Bourtsoukidis Efstratios , Quehe Pierre-Yves , Michael Pikridas Michael , Desservettaz Maximilien , Baisnee Dominique , Liu Yunsong , Gros Valérie , Sciare Jean
Published: February 2023

Methane (CH4) is a potent greenhouse gas but its sources remain poorly quantified in the Eastern Mediterranean and Middle East (EMME) region where major oil and gas production takes place. Light alkanes, such as ethane (C2H6), are co-emitted with CH4 by oil and gas activities and are promising tracers for quantifying the methane emissions from this sector. Cyprus is an ideal location for studying the composition of regional air masses and for characterizing different emission source signatures at a regional scale. A Picarro G2401 greenhouse gas analyzer and two field-based Gas Chromatography Flame Ionization Detectors (GC-FID) for Non-Methane Hydrocarbons (NMHC) measurements were deployed during two campaigns, one in “urban” (Nicosia) and one in “regional background” (Cape Greko) environment respectively. The campaign at the regional background site consisted in continuous methane and NMHCs (C2-C12) observations using a mobile laboratory that was deployed at the south-eastern edge of the island between December 2021 and February 2022. This location was chosen to capture airmasses of remote south and eastern origin, uninfluenced by local sources. We use these observations to 1) evaluate the significance of long-range transported versus local sources in Cyprus, 2) identify and document regional anthropogenic methane sources, and 3) assess the accuracy of the EDGAR sectoral emission inventory over EMME. Positive Matrix Factorization (PMF) analysis of the NMHC dataset resulted in the identification of four distinct sources namely tropospheric background, urban, heavy oil combustion, and transported from Middle East. The latest occurred during three distinct episodes and on average, had the highest NMHC concentrations. Generally, the different urban and regional signatures/sources displayed good and variable correlations between CH4 and C2 to C6-NMHCs. By investigating the PMF results together with CH4 concentrations and an atmospheric dispersion model (FLEXPART), we provide a comprehensive characterization of the pollution sources at regional scale over the Eastern Mediterranean region.
Recent advances in monitoring surface mass balance of the Greenland ice sheet
Authors: Ahlstrøm Andreas P. , Fausto Robert S. , Box Jason E. , Karlsson Nanna B. , How Penelope R. , Wright Patrick J. , Vandecrux Baptiste , Rutishauser Anja , Mankoff Kenneth D. , Colgan William T. , Citterio Michele , Messerli Alexandra , Solgaard Anne M. , Larsen Signe H. , Korsgaard Niels J. , Kjeldsen Kristian K. , Nielsen Rasmus B. , Houtz Derek , Andersen Signe B. ,   GEUS GlacioLab Team
Published: February 2023

With temperatures in the Arctic rising rapidly at a rate of 3-4 times the global mean, monitoring the state of the Greenland ice sheet has never been more relevant.In-situ observations from the Arctic, in particular from the Greenland ice sheet, are scarce due to the cost and difficulty of maintaining instrumentation in the harsh and remote environment. Yet, the fate of the ice sheet concerns 100s of millions of people living in coastal zones worldwide. To gain understanding of the ice sheet processes leading to sea level rise and increase our ability to capture those in climate models, there is an urgent need to collect in-situ observations from the ice sheet surface. Similarly, ground-truthing observations are necessary for validation and calibration of satellite-derived estimates of ice sheet change.The Geological Survey of Denmark and Greenland (GEUS), along with partner institutions Asiaq and DTU Space, currently operates a combined network of 40 automatic weather stations (AWS) on ice in Greenland, mainly through the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) and the Greenland Climate Network (GC-Net).GEUS has implemented a new pipeline providing near-real-time hourly weather observations from the PROMICE and GC-Net stations to its users and the World Meteorological Organization (WMO) for use in numerical weather prediction. The satellite-transmitted AWS data is processed and submitted to the WMO via the Danish Meteorological Institute with a latency of 7 minutes after observations are recorded.Here, we present the recent advances in our AWS instrumentation, data processing and database solution to invite discussion on how we can best meet the community needs for in-situ observations from the ice sheet.
Evaluating state-of-art statistical downscaling and analogs approaches on historical climate statistics over European regions
Authors: Peano Daniele , Sangelantoni Lorenzo , Alvarez-Castro Carmen
Published: February 2023

Climate change impacts assessment crucially relies on climate information at high temporal and spatial resolutions, not available from global climate models (GCMs) involved in the coupled model intercomparison project (CMIP). At the same time, dynamically downscaled regional climate model simulations do not provide global-scale coverage and in several cases are computationally too expensive.For this reason, downscaling techniques are commonly applied to bridge the resolution gap between GCM simulations and impact studies. The most common methodology is the statistical downscaling approach. However, statistical downscaling fast computation comes at a price, it does not account for physical and dynamic processes potentially inflates temporal variability of the original simulations’ resolution. Given this limitation, the analogs technique may represent a valuable alternative since it considers both large and local scales dynamics balanced by a reasonable increase in computational costs.The present study explores differences, added value, and limitations characterizing state-of-the-art bias adjustment/statistical downscaling based on a stochastic quantile mapping approach and the analogs technique. In particular, the comparison applies to the data computed in the inter-sectoral impact model intercomparison project (ISIMIP) and data obtained by applying the analogs method based on the same ISIMIP reference dataset. The two approaches are compared and evaluated in terms of the historical period observed statistics reproduction for a few climate variables over European regions.This study is performed in the framework of GoNEXUS and NEXOGENESIS European projects.
The 2022 fire season over Europe
Authors: Canelas da Silva Mafalda , Durão Rita , Russo Ana , Gouveia Célia
Published: February 2023

Over the summer of 2022, Europe experienced exceptional wildfire activity, with fires occurring more frequently and intensively, mainly in Spain, France, and Portugal. Together these countries registered more than 470 000 hectares of the total 786 000 burnt area in the European Union, accordingly to the estimates of the European Forest Fire Information System (EFFIS) for this fire season. 
Southern Europe is a widely known climate change hotspot resulting in heatwaves, droughts, and wildfire activity (increase in the number and severity of fires, burnt area, and longer fire seasons) although severe droughts and heatwaves have been expanding and worsening in central and northern Europe, increasing fire risk.
This work aims to evaluate how extreme the 2022 fire season was when compared with the period 1979-2021 over Europe. The proposed methods comprise the analysis of fire-related products and atmospheric variables to evidence the fire-prone weather conditions. The European Centre for Medium-Range Weather Forecast (ECMWF) ERA5 reanalysis dataset of Fire Weather Index (FWI) and air temperature, relative humidity and wind products are used. FWI is part of a dataset from the Canadian Fire Weather Index System, and is defined as a numerical rating of the potential frontal fire intensity, that indicates fire intensity by combining the rate of fire spread with the amount of fuel being consumed. The Standardized Precipitation Evapotranspiration Index (SPEI) at time-scales of 1 to 6 months was used to assess drought conditions.
Results highlight the new fire dynamics in Europe since climate change effects are leading to new emergent hot spots (central and northern Europe), not so well known as the Mediterranean Basin. This is extremely important to allow the assessment of fire danger activity as well as the characteristics of wildfires and improve the monitoring, planning, and mitigation activities.
The History of Fire, Human Influence and Climate in Black Pine Forests, Western Anatolia
Authors: Şahan Evrim A. , Gürçay Bedirhan , Güner H. Tuncay
Published: February 2023

Wildfire is a dynamic natural phenomenon the causes and consequences have changed for millions of years. We previously found out and discussed the fire history of Western Anatolia to understand the drivers of fires over 600 years. In that study, we find out that simultaneous fires occurred in multiple sites and this period overlapped with the longest and most severe drought period of the past 550 years and the fire frequency decline after 1934 coincided with the period of the first forest protection law in 1937. Dry, as well as prior wet conditions were the main drivers of fires in the black pine forests in western Anatolia. On the other hand, to highlight the direct human influence in a high-risk fire region, we sampled one additional site from Antalya (Türkiye) and collected fire-scarred wood samples from both living trees and remnant woods. In this study, we developed a 519-year-long site-level composite chronology using dendrochronological methods with low frequency and no significant relationship was found between dry and major fire years. The recorded fire years for each individual showed that a fire in one tree did not spread and grow to other neighbouring trees. Despite the high risk of fire, fires occurred less frequently can be interpreted as an intense human influence in the area, also observed axe marks in the catface formations and the nomadic tents right next to the site highlight the human influence. These forests were used extensively by the Turkish tribes also called “Yörüks”, who led a nomadic life in the Taurus Mountains for centuries. Although this area is under a high fire risk, the low fire frequency may be due to the reduced amount of combustible materials by goat grazing. Since goats feed not only on grass but also on fresh sprouts, helps to reduce the frequency of fires by consuming both the combustible material under the forest and the branches of the trees closer to the forest ground. Due to the grazing, shoots close to the ground decrease that also decreases the probability of the shift in fire regime from surface to crown fire. We believe that protecting and promoting the culture of Yörüks in the Taurus Mountains will be an important way to protect not only the culture but also the forests.This research was funded by the Scientific and Technological Research Council of Turkey (TÜBİTAK) (Project number: 118O306). 
Plant water use strategies drive the fate of newly fixed carbon in an experimental rainforest under drought
Authors: Huang Jianbei , Ladd Nemiah , Meredith Laura , Werner Christiane , Lehmann Marco ,   the coauthors
Published: February 2023

Nonstructural carbohydrates (NSCs) play a crucial role in plant functioning and survival. Nonetheless, substantial knowledge gaps remain regarding NSC mobilization and transport in forests experiencing more frequent extreme droughts. We combined drought manipulation and 13CO2 pulse-labeling in an enclosed rainforest, and assessed changes in tissue NSC content and allocation of recent photosynthates in eight species that represent ecosystem biomass and cover different positions and hydraulic strategies. Drought reduced starch in leaves but not in stem phloem and roots across species. However, soluble sugars remained constant or increased in understory plants and anisohydric trees, and decreased only in leaves of isohydric trees with relatively constant leaf water potential and sap flow. Drought slowed export and transport of recent photosynthates, not only for anisohydric species with a strong decrease in leaf water potential and sap flow but also for isohydric species with a strong decrease in photosynthetic supply and carbohydrate levels.  We provide evidence that tropical plants under drought mobilize starch to buffer carbon deficiency, while regulating local utilization, export and transport of soluble sugars depending on position and isohydricity. We highlight the importance of plant functional types for understanding NSC dynamics and their role in determining forest carbon balance under drought. 
Natural methane emissions at high latitudes: A study through the MAGIC2021 measurements campaign
Authors: Langot Félix , Crevoisier Cyril , Lauvaux Thomas , Guedj Axel , Pernin Jérôme , Berchet Antoine , Pison Isabelle , Wittig Sophie
Published: February 2023

Methane is a potent greenhouse gas that plays a significant role in the global climate system. High latitude methane is a particularly sensitive subject due to the uncertainty in future gas release due to multiple factors such as the thawing of permafrost and the evolution of wetland cover. Thus, these regions have the potential to significantly contribute to global warming. In this study, we present the results of the MAGIC2021 campaign, which was conducted in Lapland around Kiruna, Sweden in August 2021. The campaign included measurements with atmospheric air sampler AirCores on board weather balloons, three research aircraft equipped with in-situ sensors, and ground-based measurements of gas total columns using EM27/SUNs. We focus here on the combined measurements of 0-30 km profiles by AirCore and by ATR42 research aircraft to investigate sources of methane in the region. To this end, we employed back-trajectory Lagrangian models and conducted an in-depth comparison between model (ERA5, CAMS) and campaign data in a multi-species approach combining CH4, CO2 and CO. Our findings provide insight into the sources and transport of methane at high latitudes. They show that in order to properly study local sources of methane, it is mandatory to account for transported methane originating from regions as far as Northern Canada. Our work also highlights the importance of conducting in situ measurement campaigns like MAGIC2021, which provide valuable data for improving our understanding of atmospheric processes at high latitudes and informing the development of more accurate models and validate satellite retrievals. Plans for next campaigns will also be detailed.
Chemical and isotopic signatures of fluids circulating in the Massif Central (France) and in the Volcanic Eifel (Germany): evidences of similar features and of an ongoing degassing process.
Authors: Ricci Lisa , Frondini Francesco , Morgavi Daniele , Ariano Alessandra , Boudoire Guillaume , Laumonier Mickael , Caliro Stefano , Cardellini Carlo , Kueppers Ulrich , Chiodini Giovanni
Published: February 2023

The French Massif Central (central-southern France) and the Eifel region (central-western Germany) are both young volcanic systems and considered dormant. They are part of the European Cenozoic Rift System (ECRIS) and show similar surficial manifestations of ongoing hydrothermal activity. For example, both areas exhibit numerous low flow rate CO2-rich springs, mainly occurring in concomitance of faults and fractures inherited from the Variscan orogeny.Here, the chemical and isotopic characterization of different fresh water bodies (springs, wells, rivers and volcanic lakes) has been provided. The composition of dissolved gases and the isotopic signatures of dissolved carbon indicate that meteoric water infiltrated and then interacted with a CO2-rich, mantle-related, component. The majority of studied water samples exhibit pCO2 between 0.3 and 1 bar and the total dissolved inorganic carbon (TDIC) is of the order of 0.01 mol/kg. At surface, most spring water samples are oversaturated with calcite, dolomite, chalcedony and quartz and are in equilibrium with amorphous silica. The correlation between the TDIC and its isotopic composition (δ13CTDIC) suggests that part of the analysed water samples experienced a degassing process prior to or immediately after emergence. The computed CO2 flux transported by groundwaters is of the same order of magnitude of the global baseline theorized for geothermal areas. This indicates that passive rifts systems contribute to the atmospheric CO2 content and highlights the importance of taking into account each carbon source in the study of the global carbon cycle.
Decadal variability of extreme winds and potential storm losses in Europe using large RCM ensembles
Authors: Sethunadh Jisesh , Pinto Joaquim G. , Ludwig Patrick , Feldmann Hendrik , Ehmele Florian
Published: February 2023

Windstorms (major winter storms) are one of the most important natural hazards in Europe. Despite the large observed socioeconomic losses, the impact of windstorms and its decadal variability is not yet fully understood. This study aims to assess the loss potentials associated with European windstorms and the variability in the wind speed climatology across Europe. We use the 12,500-years LAERTES-EU (LArge Ensemble of Regional climaTe modEl Simulations for EUrope) RCM ensemble to study the spatio-temporal distribution and variability of windstorms over Europe. LAERTES-EU is validated against reanalysis data (ERA5) and available ground-based station observations. The associated windstorm losses are estimated by computing statistics of extreme wind speeds and related indices. Different loss indices are validated using historical loss data from the insurance sector. The results reveal that the loss index (LI) is a good proxy for the estimation of potential losses associated with windstorms across Europe in winter. The derived statistics of extreme windstorms such as return periods (RP) show hardly any change in the severity and frequency of windstorms during the covered period 1900-2028, but a strong decadal variability is apparent.
Deadwood: the underrated legacy of natural disturbances
Authors: Bottero Alessandra , Piazza Natalie , Ringenbach Adrian , Rigling Andreas , Bebi Peter
Published: February 2023

Disturbances are increasing in frequency and severity in many regions of the world, affecting the dynamics and provision of ecosystem services of entire forest ecosystems. Higher tree mortality is often observed following such events, generating large amounts of deadwood. The latter is commonly salvaged logged to reduce economic losses, facilitate forest recovery and lower the susceptibility to secondary disturbance agents. However, the long-term and indirect effects of deadwood on forest dynamics and future ecosystem services are still debated. Here, we examined the role of deadwood in natural hazard processes and forest dynamics following disturbance. We focused primarily on the protective function against gravitational natural hazards (snow avalanches and rockfall) and the stand dynamics in mountain forests in central Europe. In the first years following disturbance and in different environmental contexts deadwood offered protection against snow avalanches, as no avalanche release was recorded within several observed windthrown areas. Additionally, deadwood acted as efficient barrier against rockfall, reducing both run-out distance and the number of rocks surpassing the deadwood section. In the longer term, deadwood often served as an important seedbed for tree regeneration, thus, promoting uneven-aged forest structures, forest resilience and the overall provision of ecosystem services. A more comprehensive understanding of the role that deadwood can play in disturbed forests in various environmental contexts will allow us to better identify situations where deadwood can be an asset when left on site and, thus, support the management of disturbed forests.
Greenhouse gas exchange of different fen paludicultures during establishment
Authors: Köwitsch Philipp , Tiemeyer Bärbel , Antonazzo Sonia , Dettmann Ullrich
Published: February 2023

Conventional agriculture on peatlands requires drainage, but this practice causes high emissions of the greenhouse gases (GHG) carbon dioxide (CO2) and nitrous oxide (N2O). Paludiculture is an option to mitigate these adverse environmental effects while maintaining productive land use. Whereas the GHG exchange of paludiculture on rewetted bog peat, i.e. Sphagnum farming, is relatively well examined, data on GHG emissions from fen paludicultures is still very scarce. As typical fen paludiculture species are aerenchymous plants, the release of methane (CH4) is of particular interest when optimising the GHG balance of such systems. Topsoil removal is an option to reduce the CH4 emissions upon rewetting but retaining a nutrient rich topsoil might foster the biomass growth.In this project, Typha angustifolia, Typha latifolia, and Phragmites australis are grown at a fen peatland formerly used as grassland. Water levels will be kept at the surface or slightly above it. In parts of the newly created polder surrounded by a peat dam, the topsoil is removed. Four smaller sub-polders are installed to separate the effects of topsoil removal and water level. Here, the water levels can be adjusted independently from the main polder. Greenhouse gas exchange is measured for all three species with and without topsoil removal. Additionally, a reference grassland site close by and a site on the dam are included in the measurements. GHG measurements are carried out every two to four weeks on a campaign basis using manual chambers and a portable analyser for both CH4 and CO2. Here we present GHG balances of the first two years after planting the paludicultures.Despite of imperfect water management during the first year after planting, all paludiculture species were both a net CO2 and GHG sink regardless the topsoil treatment. During this period, fluctuating water levels resulted in low CH4 emissions while N2O emissions were of greater importance regarding the GHG balance. Due to more stable water levels in the second year, higher methane emissions are expected. Carbon export by the first biomass harvest will also be taken into account.
SeisBlue: a deep-learning data processing platform for seismology
Authors: Huang Chun-Ming , Chang Li-Heng , Kuo-Chen Hao , Zhuang YungYu
Published: February 2023

Deep learning has greatly improved the efficiency of earthquake detection and phase picking tasks, as demonstrated by neural network models such as PhaseNet and EQTransformer. However, the code released by these authors is not production-ready software that can be easily integrated into our lab's workflow. To solve this problem, we developed "SeisBlue," a platform that brings all the necessary steps together in one place. It includes these major components: database client, data inspector, data converter, model trainer, model evaluator, and pick associator, and is designed to be modular and interchangeable to allow for easy experimentation with different combinations.SeisBlue has been used in several major earthquake events in Taiwan, including the 918 Taitung earthquake (magnitude 6.9 Mw). In this event, we were able to capture over 1,200 events near real-time in just two days - a task that would have taken over a month to complete manually. The quickly-released earthquake catalog provided insight into the complex behavior of the blind fault.
Inertial effects on the transport of an anisotropic particle in surface gravity waves
Authors: Mishra Himanshu , Roy Anubhab
Published: February 2023

We study the transportation and rotational dynamics of a finite-sized spheroidal particle in a linear monochromatic surface gravity wave to better understand the transport dynamics of microplastics in oceanic flows. A spheroidal particle, modeled as an anisotropic tracer, attains preferential alignment in a linear wavy flow. We analyze the drift of a finite-size anisotropic particle and find that the horizontal drift of such particles can either increase or decrease depending on the initial orientation and the ratio of the size of the particle to the wavelength of the background wave field. Next, we derive the finite-size modification to the preferred alignment of the spheroidal particle with the flow propagation direction of the wave. In most scenarios, particles in the ocean can have a wide range of densities and are classified into positively and negatively buoyant particles. Negatively buoyant particles settle in a wavy flow with complex trajectories. We study the effect of the orientation and size of such particles on settling and show that the aspect ratio of the particle could alter the trajectory in the wave propagation direction. We also obtain a non-zero vertical Stokes drift. Finally, we consider the effects of fluid and particle inertia in our coupled evolution equations and study the drift and the orientation of an anisotropic particle in a wavy flow field. We demonstrate that considering such an effect could provide a complete picture of the transport and dynamics of microplastics in the upper part of the ocean that can be described more accurately. 