bluuebunny/crossref_metadata_2025 huggingface dataset:
Historical trend and future projection of climate extremes over the southern slope of Himalayas
Authors: Aryal Deepak , Pokharel Binod
Published: March 2024

Uncontrolled human activities during the past few decades, specifically the burning of fossil fuels that release greenhouse gases have resulted in global warming and climate change. Climate change affects everyone and every region around the globe,but mountainous areas are particularly vulnerable because of their fragile topography, unique climate-sensitive ecosystems and dependency of billions of population on mountain resources. Due to the unique setup of the environment, warming in the mountainous areas, specifically the Himalayan region is expected more rapidly than the global average. Situating at the central part of the world’s largest and most complex mountain ranges, the Nepal Himalayas is not an exception;instead,the region is considered a climate change hotspot. The consequences of climate change around this region mainly include rapidly melting glaciers, formation and rapid expansion of glacier lakes, erratic rainfall, increasedfrequency and magnitude of extreme weather events, change in monsoon pattern, etc.The historical data shows increasing precipitation in the monsoon season while precipitation is declining in dry seasons including winter. The downscaled and bias-corrected CMIP6 also consistently projects a similar pattern of precipitation in Nepal. The increasing precipitation in summer monsoon, particularly high-intensity events will bring more floods and landslides while the decreasing precipitation in dry seasons will create drought and forest fires over the region. We will present the different climate extreme indices to evaluate the impact of future climate for the Himalayan region.
What limits the growth of lightning fires in the remote northeast Siberian taiga?
Authors: Janssen Thomas , Veraverbeke Sander
Published: March 2024

In recent years, boreal forests have experienced unprecedented fire activity. These fires have contributed substantially to carbon emissions and posed hazards to human health. In the remote northeast Siberian taiga, the vast majority of fires are ignited by lightning strikes and not by human activity. Furthermore, active fire suppression is largely absent in these remote areas, resulting in uncontrolled fire growth. Here, we present a detailed look at the places and times where these lightning fires do finally stop spreading and aim to identify the causes. We employ various remote sensing and geo-spatial datasets including fire weather as well as landscape variables such as the presence of surface water, road networks, woody fuel load, fire history, elevation and landcover, to pinpoint the limitations to fire growth along fire perimeters recorded between 2012 and 2022 at a 300-meter spatial resolution. We were able to attribute 87% of all fire perimeter locations to a statistically significant (p < 0.01) change in one or more of these fire limitations over either time (fire weather) or space (landscape). The analysis reveals that fire growth is mainly limited by a change in the vegetation (fuel type and fuel load) as well as a change to less favourable weather for fire spread, although there are clear regional differences in the importance of specific limitations. Overall, fire weather seems to be the most important limitation to fire growth in the north of the Siberian taiga where continuous permafrost is present. With a rising frequency of lightning strikes, droughts, and heatwaves in boreal regions, uncontrolled lightning fires have the potential to expand even further in the future, leading to significant implications for vulnerable permafrost landscapes and, consequently, the global carbon cycle.
Global hydro-climatological indicators and changes in the global hydrological cycle and rainfall patterns
Authors: Dobler Andreas , Lussana Cristian , Benestad Rasmus
Published: March 2024

There are only a few climate indicators that describe the state of the global hydrological cycle. In this presentation, we argue that important climate indicators based on global daily precipitation are lacking and propose three new indicators: 1) the daily global precipitation amount, 2) the daily global surface area receiving precipitation, and 3) the global mean daily precipitation intensity. Historically, assessing these indicators is limited by the extent of global observational networks. However, recent advancements in satellite observations and reanalysis data, particularly the ERA5 reanalysis, have enabled better estimations.We present an analysis of the proposed indicators using ERA5 data and other data sources. We also discuss limitations and biases of the data sources, e.g. ERA5's tendency to overestimate precipitation. Further, a wavelet analysis of spatial characteristics of 24-hour precipitation is conducted, offering insights into the spatial extent and intensity of precipitation systems and their variations over time. To address the question whether long-term changes reflect real changes in Earth's global hydrological cycle due to warming, or may be artefacts from changes in the assimilated (satellite) data in ERA5, we examine an ensemble of CMIP6 simulations under scenarios of increasing greenhouse gas concentration.Our analysis reveals that ERA5 shows a decrease in the global area of daily precipitation from 43% to 41% between 1950 and 2020. At the same time, the total daily global precipitation amount increased from 1440 Gt to 1510 Gt. The wavelet analysis of ERA5 data indicates that individual precipitation systems have become smaller in spatial extent but more intense over this period, suggesting an accelerated global hydrological cycle with reduced global rainfall area. The CMIP6 simulations show a robust decrease in the precipitation area towards the end of the 21st century in agreement with ERA5. However, compared to the reanalysis the changes are smaller and less rapid.  Nevertheless, our results suggest that in a warming climate the daily precipitation area may shrink, contributing to an increase in the mean daily precipitation intensity.
Cloud types frequency over Poland in satellite-based (MODIS) and surface-based (SYNOP) observations
Authors: Wojciechowska Izabela
Published: March 2024

Clouds significantly affect Earth's energy budget by absorbing, reflecting and transmitting short- and long-wave radiation. They can either intensify, or weaken the greenhouse effect. The overall impact of cloudiness on radiating transfer depends on macro- and micro-physical properties of clouds (e.g., optical thickness, altitude, water content, cloud drop effective radius) and still remains one of the greatest uncertainties in global climate predictions.Recent studies based on traditional, synoptic (surface) data have shown several statistically significant trends in cloud types (genera) frequency over Poland. Those changes included an increase in high and convective clouds, along with a decrease in Stratus, Altostratus and Nimbostratus. As the ability to observe mid and high-level clouds from the ground is limited due to clouds overlapping, in this research we aim to explore whether these trends can be confirmed by satellite records.We use Moderate Resolution Imaging Spectroradiometer (MODIS) data, restricted to the area of Poland, as well as surface (SYNOP) observations of cloud genera from the country's 27 ground-based stations for the period 2003–2021. In order to define cloud types from MODIS records, we analyze cloud optical thickness (COT) and cloud top pressure (CTP) parameters and use International Satellite Cloud Climatology Project (ISCCP) COT–CTP classification.We found that while for some cloud types (Cirrus, Altostratus + Nimbostratus and Cumulus) MODIS and SYNOP show the similar trends over the last two decades, for other cloud types (Cumulonimbus, Altocumulus, Stratocumulus) the two sources of data are not consistent. Hence, we conclude that they should be treated as independent rather than complementary. Additionally, we demonstrated that the increase in high-level clouds over Poland, which has been observed by other authors who based their research on synoptic data, is not due to a decrease in the frequency of low- and mid-level clouds, but can be confirmed by satellite records.This research was funded by the University of Warsaw.
Evaluation of river discharge simulated with CTRIP forced by the CERRA-Land regional reanalysis over Europe.
Authors: Le Moigne Patrick , Barella-Ortiz Anaïs , Munier Simon
Published: March 2024

The study and understanding of the water cycle is vital, and especially significant due to challenges like climate change and effective water management, among others.  The work herein presents a comparison designed in such a way that it covers different spatial scales (at European, basin, and gauging station levels), as well as providing results that offer a characterization of discharge as complete as possible. For this, standard and well known metrics, like NSE and KGE are given, but also low, medium, and high flows are considered through percentile analysis and specific metrics. Observations used in this study belong to the Global Runoff Data Centre (GRDC), which provides data over the globe, and French and Spanish public databases. An offline simulation of the CTRIP routing model was used to simulate river discharge over the period 1993 to 2019. It was forced with surface and subsurface runoff from the CERRA-Land European regional reanalysis at a spatial resolution of 5.5 km.This study is conducted within the framework of the CERISE project (grant agreement No101082139). The results will enable us to evaluate the hydrological quality of the CERRA-Land reanalysis. Additionally, our contributions aim to enhance future reanalyses, thereby improving the next generation of Copernicus Climate Change Service (C3S) Earth system reanalyses.
Mid-Cretaceous Oceanic Anoxic Events in the outer Eastern Carpathians: biostratigraphic and chemostratigraphic events
Authors: Apotrosoaei Vlad , Roban Relu-Dumitru , Briceag Andrei , Melinte-Dobrinescu Mihaela
Published: March 2024

The mid-Cretaceous times are characterized by the presence of the most numerous Oceanic Anoxic Events (OAEs) in the whole Mesozoic, reflecting the occurrence of superplumes, associated with high ocean crust formation rates and increased volcanism (i.e., Larson, 1991; Jenkyns, 2010). In general, the Romanian Carpathians, and especially the Eastern Carpathian bend, enclose significant successions of a deep-water setting, deposited during mid-Cretaceous times. The investigated successions are mainly composed of black and dark-grey shales, grey marls, and sparse cm-thick radiolarites. Based on the calcareous nannofossil biostratigraphy, the studied successions cover the late Albian-Cenomanian interval, encompassing the UC0 up to UC3a biozones. Within the studied successions, the isotope δ13Corgshow several fluctuations. The oldest peak is situated in the UC0 nannofossil zone, across the Albian-Cenomanian boundary interval, starting slightly below the LO (last occurrence) of the nannofossil Hayesites albiensis. The youngest recorded peak is placed in UC3a nannofossil subzone and encloses the FO (first occurrence) of the nannofossil Lithraphidites acutus. We assume that the oldest positive excursion identified correspond to the Albian-Cenomanian Boundary Event (ACBE), while the youngest one is most probably the chemostratigraphic overprint of the MCE (mid-Cenomanian Event). Both depositional intervals that contains the ACBE and MCE are characterized by the deposition of rich-organic black shales.
Friction, Mineralogy, and Microstructures: How Complex is the Brittle Deformation of Faults?
Authors: Pozzi Giacomo , Volpe Giuseppe , Ruggieri Roberta , Collettini Cristiano , Scuderi Marco , Tesei Telemaco , Marone Chris , Cocco Massimo
Published: March 2024

Faults accommodate most of the brittle deformation that occurs in the lithosphere  through a spectrum of fault slip behaviours including, but not limited to, seismic and aseismic slip. The rocks deforming inside the core of the faults are the main actors that control the modality of slip and thus their mechanical properties are a key subject of study that is carried out through experimental investigation. The most relevant characterization is that of friction, a property that commensurates the resistance to shear motion of the rocks. Nevertheless, friction is not an intrinsic constant feature of the investigated materials. It is instead modulated by several attributes and external factors. For instance, the rate and state constitutive framework describes the sensitivity of friction to the sliding velocity, proving a successful theory to quantify the potential of the onset of dynamic instabilities and seismic slip in natural faults. Several works have also demonstrated that the frictional properties of the same material can dramatically change as function of the fabric (textural, geometrical attributes of the deforming rock). It is therefore evident that brittle deformation of rocks cannot be assessed in isolation of the conditions at which the phenomenon is measured. To fully understand the complex bulk behaviour of a deforming fault zone material we must investigate the interaction of several scale-dependent mechanisms that are active from the grain-scale up to the entire fault zone thickness.In this work we present the results of several case-studies that cover relevant lithotypes: anhydrite-dolomite, quartz-calcite-mica, lizardite-magnetite mixtures. These studies collect more than 60 friction experiments performed on BRAVA biaxial apparatus (INGV, Italy), presented here by associating the analysis of mechanical data with the analysis of rock microstructures. This joined investigation highlights the mechanisms that control rock friction: cataclasis, crystal plasticity, pressure-solution, grain-boundary sliding, cementation, and indentation. We also show the emergence of complex slip behaviours (experimental fault stability) as function of the coexistence of processes with different timescales and explained by the spatial arrangement of the mineral phases in the fault core.Our results shed light on the origin of the macroscopic frictional properties of fault rocks, stressing the fact that they are not a characterising property but rather the observable of a complex, dynamic, and highly non-linear system.
Satellite data assimilation at regional scale using the Chimere model
Authors: Descombes Gaël , Colette Augustin , Ung Anthony
Published: March 2024

The quantity and accuracy of satellite data is constantly growing up for air quality monitoring. They are already widely used to perform better forecast and analysis for global modeling. Even if, high resolution modeling at regional scale has been relying on surface observation for a long time, we will focus on data assimilation over Europe looking especially for satellite data assimilation.In this study, the Chemistry model transport CHIMERE is associated to the Data Assimilation Research Testbed (DART from the National Center Atmospheric Research) to simulate recent events of pollution using for the Sentinel 5P data. Preliminary results coming from the CAMs EvOlution (CAMEO) project will be presented for the Sentinel 5P data. Special emphasis will be made on the regional set-up of the Adjustment Ensemble Kalman Filter (AEKF) ensemble data assimilation system used and future developments
Late Pleistocene East Asian monsoon intensity variations and driving mechanisms: Evidence from a multi-proxy analysis of loess deposits on an East China Sea island
Authors: Wang Zhigang , Marquer Laurent , Cheng Yuanyu , Ren Xiuxiu , Long Hao , Ren Shaofang , Qian Peng , Zheng Xiangmin
Published: March 2024

Shengshan Island (SSD), located in East China Sea, contains loess deposits that serve as an excellent carrier for recording environmental changes in the eastern subtropical region of China. Different from the continental Loess Plateau, SSD loess possesses distinctive characteristics due to its coastal location. Here we conducted the first pollen analysis to reconstruct vegetation dynamics in the SSD region during the middle to late Late Pleistocene period (75-40 ka). Biological indicators (i.e., total organic concentration and δ13Corg), along with geochemical proxies (i.e., quartz grain size, magnetic susceptibility, iron oxide ratios, clay minerals, and trace elements), were employed to reconstruct climatic dynamics in the SSD area. The study identified two stages in the evolution of the East Asian Monsoon. In Stage I (75-60 ka), various indicators (i.e., pollen concentration, Pinus concentration, magnetic susceptibility, C4 abundance, K/(I+Ch), Illite crystallinity, CII, Hm/Gt, quartz median grain size, Zr/Rb) increased, suggesting a strengthening of both winter and summer monsoons. In Stage II (60-40 ka), some indicators (i.e., pollen concentration, Pinus concentration, quartz median grain size, Zr/Rb) continued to increase while others (i.e., magnetic susceptibility, C4 abundance, K/(I+Ch), Illite crystallinity, CII, Hm/Gt) decreased, indicating a continued intensification of the winter monsoon but a weakening of the summer monsoon. Further, we explored the driving forces behind variations in monsoon intensity, analyzing changes in various δ18O proxies and sea-level fluctuations. The findings suggest that different mechanisms influence the winter and summer monsoons. Summer monsoon intensity is linked to changes in summer solar radiation at mid-latitudes in the Northern Hemisphere, while winter monsoon dynamic is affected by changes in ice volume and ice sheets. These insights contribute to our understanding of environmental changes related to the East Asian Monsoon, offering valuable perspectives on how these mechanisms could respond to future climate changes.
Crustal transtension and associated high-T/low-P metamorphism in the North Tianshan Arc, NW China
Authors: Ni Xinghua , Wang Bo , Soret Mathieu , Cluzel Dominique , Chen Yan , Liu Jiashuo , Faure Michel
Published: March 2024

Crustal evolution of the North Tianshan during the late Paleozoic remains controversial due to the lack of structural and metamorphic constraints. We present new structural, petrological and geochronological data of the Xiaopu metamorphic complex (XMC) to address this issue. The XMC shows a well-preserved Buchan-type metamorphic sequence made of garnet, andalusite-staurolite and sillimanite zones. Structural observations indicate that garnet, sillimanite, andalusite and staurolite grew syn-kinematically during a transtensional event (D2). Inclusion trails in garnet cores oriented at high angle with the external foliation probably record an earlier deformation stage (D1). Synchronous ductile normal faults and thrusts (D3) overprinted previous structures and control the exhumation of the metamorphic complex. LA-ICP-MS zircon U-Pb ages of pre-D2 gneissic granodiorite, syn-D2 granitic dikes and post-D2 diorites constrain the occurrence of D2 between 332 and 305 Ma. Apatite U-Pb ages of mylonitic rocks from the ductile fault indicate that D3 occurred at ~285 Ma. Phase modelling and geothermobarometers were used to estimate the pressure-temperature (P-T) conditions of the XMC. Peak conditions show progressive temperature increase from andalusite-staurolite schists (~580 °C) to sillimanite migmatites (~680 °C) at nearly constant pressure (~4 kbar), suggesting a significant thermal effect of nearby large intrusive bodies. The schists display a pre-peak heating with slight decompression and the migmatites show retrograde cooling and decompression to ~600 °C and ~3 kbar. Their P-T paths and high/T and low/P thermal regimes are in line with an extensional setting. Monazite U/Th-Pb ages of 313-311 Ma for sillimanite-bearing schists and migmatites suggest monazite growth during the retrogression. 40Ar/39Ar ages of mica from sillimanite schists are in the range of 298-275 Ma, consistent with a later cooling and exhumation associated with D3. These data reveal the crustal transtension during the middle to late Carboniferous (~330-310 Ma) and cooling and exhumation during the early Permian (~285 Ma) of the North Tianshan arc. Such transtensional tectonics probably facilitated decompression melting of the lower crust and lithospheric mantle of the arc. Subsequent ascent and emplacement of the resulting melt could yield high thermal gradient, produce partial melting of the mid-crustal rocks and promote crustal exhumation. 
From novelty to norm: towards standardising drone quantification of gas emissions
Authors: McQuilkin Jamie , Ricketts Hugo , Allen Grant
Published: March 2024

New developments in the availability of precision robotics, battery technology, and miniaturised sensors have enabled hitherto impossible techniques in emissions quantification. Airborne drones can now retrieve a dense plane of gas concentration measurements in the cross-section of an advecting plume in a matter of minutes, revealing its structure, density, and variability. When interpolated spatiotemporally, and combined with wind measurements, a simple Eulerian mass balance model can be used to estimate emissions flux relatively quickly, with the potential to repeat measurements many times in a day to constrain uncertainty and characterise source dynamics. 

The drone mass balance method offers a cost-effective, precise, and flexible approach to measuring complex emitting sources that are otherwise challenging to monitor, at rates as low as 0.1 kg/h. Due to this, the method has received significant attention from industry and regulators in the context of the urgent need to understand and reduce greenhouse gas emissions, particularly methane. Its general applicability reaches wider, most notably to volcanology and other hazardous emission sources. 

However, as yet there is no consistent method of conducting drone mass balance, and different approaches in analysis of even the same data can lead to significant discrepancies in emissions estimates. This has thus far hindered the method's credibility, comparability, and regulatory uptake. 

We offer here a proposal for a protocol, based on more than ten years of flux method development, presented in a real-world context with results from campaigns and controlled release tests across Europe. The issues discussed will include best practices in flight planning, signal processing, interpolation, measurement and estimation of wind fields, sensor precision; and the ever-present issue of environmental sciences: how many replicates is sufficient. 
3D thermo-mechanical modelling of oblique continental collision: relative role of slab tearing in along-strike topography evolution
Authors: Maiti Giridas , Koptev Alexander , Baville Paul , Gerya Taras , Crosetto Silvia , Andrić-Tomašević Nevena
Published: March 2024

It is assumed that slab tearing (or the lateral propagation of slab break-offs) in collisional belts controls the progressive along-strike uplift of mountains and the development of adjacent basins. However, differential continental collision due to obliquity or other irregularities of the original passive margin can introduce additional complications and influence the progressive topographic growth. Here, we use a 3D thermo-mechanical numerical modelling approach to distinguish the topographic response to slab break-off propagation from the surface uplift caused by along-strike differential collision. To this end, we examine the effects of several key factors, including (1) the obliquity of the passive margin, (2) the age of the oceanic slab, (3) the rate of convergence between colliding plates, and (4) the presence of a microcontinental block between passive and active margins. In all experiments, slab break-off initiates earlier than continental collision due to the transition from oceanic to continental subduction beneath the fore- and back-arc domain formed during the previous retreat of the subduction zone. The topographic uplift associated with slab tearing is more pronounced and spreads laterally much faster than in the subsequent collision phase. The parametric analysis shows that the lateral migration of the continental collision is controlled by the convergence rate, while the horizontal velocity of slab tearing depends mainly on the obliquity angle and slab age. The presence of additional structural complexity - a microcontinental block that has detached from the passive margin - leads to a transition from horizontal to vertical slab tearing and to more intense syn-collisional mountain growth.
(Dis)connected mountain headwaters: advocating for a paradigm shift in sediment management strategies
Authors: Galia Tomáš , Škarpich Václav , Macurová Tereza
Published: March 2024

Beyond land-use alterations at the catchment scale, numerous mountain catchments across Europe have experienced significant morphological changes and shifts in sediment transport dynamics over the past two centuries, largely attributable to the implementation of torrent control structures. A notable example is the mountainous part of the Czech Carpathians, where a comprehensive sediment management regime was introduced at the turn of the 19th and 20th centuries. This approach, based on methodologies established in the Austrian Alps, encompassed the installation of check dams and artificial bank stabilizations. Such practices have remained predominant in these areas, with certain catchments smaller than 25 km² exhibiting substantial portions of their stream lengths stabilized through sequences of consolidation check dams, bed sills, and riprap bank stabilizations.However, it is crucial to consider the distinct nature of external factors influencing rainfall-runoff processes and sediment supply in the 19th century. This period was marked by the end of the Little Ice Age and a higher prevalence of deforested areas, linked with active gully development. Given the contemporary context of extensive reforestation and subtly altered hydroclimatic conditions, the appropriateness of continuing such 'hard and intensive' management strategies for local streams warrants reassessment.Consequently, a sediment deficit in both mountain channels and foothill gravel-bed rivers has been observed. It resulted in channel transformation with sediment coarsening, the loss of gravel bars (as vital habitats), and, in some instances, channel incision into the bedrock. This situation necessitates a reconsideration of sediment-control strategies within the frameworks of fluvial continuum and sediment (dis)connectivity, particularly since these headwaters function as primary sediment sources. Without modifying these management approaches, enhancing the hydromorphological state of streams and rivers in the Czech Carpathians remains a formidable challenge.
Fractal diffusion analyses of periodic pumping tests
Authors: Jimenez Martinez Victoria Alegria , Cheng Yan , Renner Jörg
Published: March 2024

We investigated the usefulness of the fractal diffusion equation, also known as generalized radial flow (GRF) equation, to characterize hydraulic properties and flow dimensions of the subsurface. Unlike other methods for deriving hydraulic properties that require selecting the flow dimension, analyses based on the GRF equation in principle constrain both, flow dimension and hydraulic properties. We utilized the GFR equation to analyze periodic pumping tests carried out in boreholes penetrating gneiss rocks in the research mine Reiche Zeche, Freiberg, Germany. These tests involved one injection borehole, where flow rate and injection pressure were recorded, and four monitoring boreholes, where pressure responses were monitored. Phase-shifts and amplitude ratios were derived through interference analysis, involving a comparison of the periodic signals of injection and monitoring pressure, as well as injectivity analysis, consisting of a comparison of the periodic flow rate and injection pressure. The pumping tests were conducted at three distinct intervals within the injection borehole, isolated by a double-packer probe and selected based on the characteristics of the fractures intersecting the borehole.  One interval contained a natural fracture zone characterized by a high fracture density with a high mean aperture. The others were previously hydraulically stimulated. While one of them had a single pre-existing fracture, the other was entirely intact before the stimulation that led to an induced fracture with feather geometry, as typical for a borehole that does not follow a principal stress axis. Several observations suggest that the gneiss volume is hydraulically heterogeneous: a) the hydraulic properties and flow dimensions vary with pumping period; b) estimated diffusivity values and flow dimensions differ for interference and injectivity analyses; c) discernible differences in diffusivity values and flow dimensions along diverse hydraulic paths, as determined by interference analysis. Furthermore, pressure dependence in hydraulic properties and flow dimensions are observed for all intervals. The hydraulic response of the fault-zone interval exhibits a greater sensitivity to variations in mean pumping pressure than the two stimulated intervals.
Evolutions of Stream Interaction Region in the Inner Heliosphere and Coronal Hole Morphologies
Authors: Milošić Daniel , Temmer Manuela , Heinemann Stephan , Hofmeister Stefan
Published: March 2024

Stream interaction regions (SIRs) are formed when the fast solar wind streams with their origin in coronal holes (CHs) interact with the surrounding slow solar wind in the Heliosphere. Previous studies have analyzed different types of CHs and the resulting characteristics of SIRs at 1 AU (e.g., Heinemann et al., 2018, Samara et al., 2022). For the inner heliosphere, however, research on the relation between CH morphology and HSS/SIR characteristics is scarce. We extract CH morphologies from SDO/AIA and use solar wind parameters from multiple spaceraft, including Parker Solar Probe, Solar Orbiter, STEREO-A, ACE and WIND. Combining in-situ measurements and remote sensing image data, we show the evolution and statistics of solar wind profiles in HSSs/SIRs in the inner Heliosphere for multiple cases from Solar Cycle 24 and 25. 
The importance of in-situ soil moisture observations to evaluate the main drivers of event runoff characteristics in a small-scale catchment
Authors: Hövel Adriane , Stumpp Christine , Bogena Heye , Lücke Andreas , Stockinger Michael
Published: March 2024

A catchment’s runoff response to precipitation largely depends on the antecedent soil moisture in the catchment, but also on hydro-meteorological conditions in terms of, e.g., evapotranspiration. Studies investigating the effects of hydro-meteorological conditions on runoff event characteristics at the small catchment scale with daily temporal resolution mostly used surrogate measures for soil moisture, e.g., derived from hydrological models or using the antecedent precipitation index (API). Here, we applied a time-series based pattern search to 11 years of daily in-situ measured soil moisture in three depths (5, 20, 50 cm) at 33 locations in the Rollesbroich catchment (40 ha) in Germany to identify key variables influencing runoff event characteristics under similar wetness patterns. After identifying wetness patterns, we split the corresponding runoff responses into similar and dissimilar ones by means of goodness-of-fit criteria and analyzed their respective hydro-meteorological variables and event runoff coefficients (ERC), i.e., the proportion of rainfall that transforms into runoff during an event. Results showed that for similar soil moisture patterns, mean potential evapotranspiration, and antecedent soil moisture in all three depths had a smaller standard deviation for similar runoff responses than for dissimilar. This indicates a larger influence on the runoff response compared to rainfall-derived variables such as total event rainfall, maximum event rainfall intensity, or API. Furthermore, during runoff events under similar wetness conditions, the Spearman rank correlation coefficient (ρ) indicated a low average correlation between ERC and API (ρ=0.17). In terms of antecedent soil moisture conditions, the highest correlation between ERC and antecedent soil moisture was observed in the topsoil at 5 cm depth (ρ=0.43), while at 20 cm (ρ=0.16) and 50 cm (ρ=0.30) depths, the correlations were comparatively lower. Our study indicates that using the API as a substitute for antecedent wetness conditions may not be able to comprehensively reflect the relation between the runoff response and antecedent soil moisture conditions in the topsoil in the given catchment. Consequently, the results show that topsoil moisture measurements are more suitable than the surrogate API for assessing the impact of hydro-meteorological variables on daily runoff characteristics.
The role of grain fragmentation in understanding shear localization via DEM simulation
Authors: Casas Nathalie , Mollon Guilhem , Scuderi Marco Maria
Published: March 2024

Mature fault zones are formed by abrasive wear products, such as gouge, which results from the frictional sliding occurring in successive slip events. Shear localization in fault gouge is strongly dependent on, among others, fault mineralogical composition and grain size distribution, originating a wide variety of microstructural textures that may be related to different types of fault motion from aseismic creep, slow earthquakes to fast slip events. Within a quartz fault zone, one can encounter different stages of maturity, ranging from an incipient and poorly developed fault zone (i.e. discontinuous and thin gouge layer) to a mature fault zone that has experienced a lot of wear from previous sliding events (i.e. well-developed gouge layer). The localization of deformation within a mature gouge layer has been identified as possibly responsible for mechanical weakening and as an indicator of a change in stability within the fault.However, to upscale the physics of shear deformation, we need to unveil the physical parameters and micro-mechanisms that govern shear localization. To gain insights on the role of dynamic changes in grain size (i.e. fragmentation), in slip behavior and fault rheology, we performed 2D numerical simulations of quartz fault gouges in a direct shear configuration using the Discrete Element Method (code MELODY). We can reproduce angular particles that can fragment during the simulation as the fault gouge accumulates strain. These experiments were performed to understand the micro-mechanical processes happening during fragmentation and shearing at a constant normal stress. Three mixtures of quartz were sheared to reproduce different initial grain size distributions within the fault (average grain sizes 100 μm, 10.5 μm, and a 50% mixture of both). The minimum grain size was set to 10 μm, meaning that all the coarser particles are subdivided into smaller ones (size 10 μm) that can fragment during the experiment.Thanks to visual and data outputs, we can observe how particles behave during the compaction and shearing of the gouge. We use four main parameters to describe fault gouge evolution: the damage of coarse particles, the force chains, the change of porosity, and the kinetic energy linked to each particle breakage. Moreover, these numerical experiments were designed to reproduce and be directly compared with shear experiments realized on a double direct shear apparatus in the Laboratory (Casas et al., in prep). The fragmentation algorithm in the code can reproduce the shear localization observed within the real quartz microstructures and the progressive formation of Riedel bands. The connection between numerical and laboratory experiments gives important information on the connection between grain size distribution, shear localization, Acoustic Emissions, and the resulting fault slip behavior. In this context, the proportion between small/coarse particles within the fault plays an important role in controlling fault rheology.
Analysis of the frequency of critical low water levels and flood warning water levels for the Uppest-Tisza catchment for the 21st century
Authors: Kis Anna , Pongrácz Rita , Szabó János Adolf
Published: March 2024

Climate change affects several sectors and environmental conditions, in particular the statistical characteristics of the runoff processes of a certain watershed. As a consequence of the higher temperature values and the altered precipitation distribution, the intensity and timing of floods and droughts, as well as their severity, may change in the coming decades. In order to develop adaptation strategies and implement an adequate water management, it is necessary to project the future trends of variables that can essentially influence water management, taking into account possible climate change scenarios, including the quantification of uncertainty.Our aim is to investigate the runoff conditions with a special focus on the frequency of critical low water levels and the different levels of flood warnings for selected river sections (i.e. Tiszabecs, Uszti Csorna, Rahiv) in the Uppest-Tisza Basin, located in Central-Eastern Europe. For this purpose, simulations with the physically based, distributed DIWA hydrological model driven by a regional climate model simulation are completed. In order to analyse the projected changes, simulations are made for a historical period (1972–2001) as well as for two future periods (2021–2050 and 2069–2098). We also investigate how the choice of the RCP scenario (i.e. RCP2.6, RCP4.5 or RCP8.5) affects the output of the hydrological simulation. In order to assess uncertainty, time series of meteorological parameters (providing inputs for the hydrological model) are generated by a weather-generator embedded in a Monte-Carlo cycle. Therefore, several hundreds of scenarios with equal probability are available, by using only one climate model. Furthermore, a bias-correction of the climate model simulation is implemented for which the weather-generator is used by fitting the crucial distribution parameters to the reference, i.e. the so-called CARPATCLIM database.
Spatially resolved MAX-DOAS measurements of Formaldehyde at Torrejon de Ardoz (41 N).
Authors: Blanco Marcos , Puentedura Olga , Navarro-Comas Monica , Gomez-Martin Laura , Iglesias Javier , Prados-Roman Cristina , Yela Margarita
Published: March 2024

The presence of formaldehyde (HCHO) in the atmosphere is an indicative of the existence of oxidation processes of volatile organic compounds (VOCs), and plays a big role in a number of tropospheric chemical processes, most importantly in the formation of tropospheric ozone. It can also be used as a proxy for local air quality and air pollution studies. In the framework of the FRM4DOAS project, a series of MAX-DOAS measurements has been carried out in an unpolluted environment situated at the north of the city of Torrejón de Ardoz (Madrid, Spain, 41° N), to determine the distribution of NO2 and HCHO in both urban and green areas, with special emphasis on the detection of the spatial heterogeneity of both species. The instrumentation’s operation site was situated in TOTEM, an observation station inside the premises of INTA, and on the top of a tower which height ensures that there are no immediate obstacles in the observations’ lines of sight.This work is focused on HCHO measurements. The series of measurements spans from 2019 to 2022, with some gaps in between due to instrumental problems, and 4 different azimuth angles that enable the study of airmasses around nearby urban areas, highways and airport landing strips, and also around nearby fields and mountains. Some measurements have also been filtered out with a HCHO detection limit criterion to ensure that the studied spectra properly detect this trace gas.The instrument involved in these measurements was a MAX-DOAS spectrometer observing in the UV region (320-415 nm), with a resolution of FHWM 0.55 nm, and equipped with a calibrated inclinometer to precisely adjust to the selected elevation angles. The instrument was configured to measure in the following elevation angles: 0°, 1°, 2°, 3°, 5°, 10°, 30°, 60° and zenith, and in 4 different azimuth angles (50°, 100°, 180° and 220° N, clockwise).The spectral analysis for the HCHO retrieval was made by a software developed at INTA. O4 retrieval was also performed, at a different spectral range than that used for HCHO but still in the UV region, to obtain information of the optical paths that the light followed before being measured by our instrument.A clear seasonality can be observed throughout the years, with a maximum peak around July- August, and a minimum in the months of February-March. This seasonal behaviour can be observed in all azimuthal directions, but it’s more prevalent in the 100° N azimuth direction, pointing to the city of Alcalá a few kilometers away.
Spatio-temporal evolution of Land Use Land Cover and hydrological components in the Lake Kivu catchment, Rwanda.
Authors: Kayitesi Naomie , Guzha C. Alphonce , Tonini Marj , Mariethoz Gregoire
Published: March 2024

The African Great Lakes Region has experienced substantial Land Use and Land Cover Change (LULCC) over the last decades, significantly impacting landscapes and ecosystems. The main drivers of LULCC in the region involve a complex interplay of political, economic, and socio-demographic factors. This study focused on the Lake Kivu catchment in Rwanda, a critical ecosystem in the African Great Lakes Regions, exploring both historical and future LULC scenarios. The methodology involved supervised image classification using seasonal composites and integrating spectral indices with topographic features to capture dynamic seasonal variations. Historical LULCC analysis showed significant changes, particularly the first decade of the study (1990-2000) marked by substantial forest loss (from 26.6% to 18.7%) and a notable increase in agricultural land (from 27.7% to 43%). These changes were attributed to conflicts in the region and population movements. Subsequent decades (2000-2010 and 2010-2020) witnessed marked forest recovery (24.8% by 2020) and a balance between agricultural increase and loss, reflecting Rwanda's commitment to environmental conservation. Additionally, a multi-layer perceptron artificial neural network was employed to predict future LULC scenarios, considering natural and socio-economic explanatory variables with historical LULC transitions. The predicted future LULC for 2030 and 2050 indicate distinct trajectories influenced by factors like political will, demographic trends, and socio-economic developments. By integrating the observed historical trends and predicted future LULC, along with climate scenarios, this study will use a hydrological model to understand the impacts of these changes on the catchment’s hydrological components. Providing essential insights for policy and strategic planning, we explore how the intricate dynamics of water-related ecosystem services are influenced by LULC and climate changes, with the ultimate goal of harmonizing ecological sustainability with socio-economic development in the Lake Kivu catchment and similar environments.
Restricted root growth caused by traffic induced soil compaction – a field study in wheat and maize
Authors: Wiedermann Elron , Reinelt Laura , Rolfes Lennart , Don Axel
Published: March 2024

Soil compaction has adverse impacts on key soil functions and can result in restricted root distribution. However, deep roots provide access to water and nutrient reservoirs and might enhance carbon (C) storage in subsoils. Deep rooting is thus a central element for climate-adapted plant productivity and has potential for climate mitigation. Clarity is missing, to what extent different soil traffic intensities impact root depth distribution and root-derived C inputs at field scale.The present study was conducted to assess the impact of differing soil traffic intensities (i) on soil physical parameters related to compaction, and (ii) to what extent this affects root length density and depth distribution, as well as (iii) above ground biomass and (iV) SOC-stocks. Negative effects of increasing traffic intensities on soil physical parameters are expected to result in reduced root depth distribution and therefore reduced biomass productivity and root-induced carbon allocation.Soil and plant biomass were sampled along increasing soil traffic intensities at three field sites in central Germany characterized as Luvisols. Penetration resistance was measured in the field, and undisturbed soil rings of top and sub soils were analyzed for bulk density and air capacity. Undisturbed soil cores were taken up to one meter depth during peak root biomass. Root biomass, depth distribution and root length density were evaluated with the core-break method using an automated root spectroscopy imaging system. Based on the results, root-derived C inputs were estimated and C/N-measurement of soil core samples was conducted.Preliminary findings indicate higher penetration resistance and bulk density, coupled with reduced air capacity in top and subsoils on the headland, where greater traffic intensity takes place. The complete data set will be presented and discussed at the conference.The conclusions of this study will provide a better understanding of the interactions between soil compaction, root growth and carbon storage. These findings are relevant to assess how soil management affects soil compaction and thus may hinder climate-adapted agriculture.
Changing impact of large-scale atmospheric circulation variability on the water mass exchange and circulation of the Baltic Sea for the period 1950-2022
Authors: Lehmann Andreas , Post Piia
Published: March 2024

Different North Atlantic winter climate regimes force different circulation patterns in the Baltic Sea. Furthermore, as the atmospheric circulation, to a large extent, controls patterns of water circulation and biophysical aspects relevant for biological production, such as the vertical distribution of temperature, salinity and oxygen, alterations in weather regimes may severely impact the trophic structure and functioning of marine food webs (Hinrichsen et al. 2007). To understand the processes linking changes in the marine environment and climate variability of the Baltic Sea, it is essential to investigate all components of the climate system which of course include also the large-scale atmospheric circulation variability. Here we focus on the link between changes/shifts in the large-scale atmospheric conditions and their impact on the regional scale variability over the Baltic Sea area for the period 1950-2022. This work is mostly an extension of previous studies which focused on the response of the Baltic Sea circulation to climate variability for the period 1958-2008 (Lehmann et al. 2011, Lehmann et al. 2014). Now extended time series ECMWF ERA 5 reanalysis for 7 decades are available, highlighting recent changes in atmospheric conditions over the Baltic Sea area. The main focus of this work is to identify predominant large scale atmospheric circulation patterns (North Atlantic winter climate regimes) on a monthly/seasonal time scale controlling the development of regional atmospheric weather types over the Baltic Sea area, which in turn can be associated with different Baltic Sea circulation patterns and water mass exchange with the North Sea.
Dynamics of global lightning activity on different time scales as indicated by Schumann resonance frequency variations
Authors: Sátori Gabriella , Bozóki Tamás , Williams Earle , Prácser Ernő , Puig Raidiel , Albrecht Rachel
Published: March 2024

The electromagnetic waves in the Schumann resonance (SR) frequency range (