bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-term observations of the strongest inflow branch of warm water to the Arctic Mediterranean
Authors: Hansen Bogi , Larsen Karin M. H. , Hátún Hjálmar , Østerhus Svein
Published: March 2020

Warm and saline water from the North Atlantic enters the Arctic Mediterranean through three gaps. The strongest of these three flows is the inflow between Iceland and Faroes, which is focused into a narrow boundary current north of the Faroes. This boundary current, the Faroe Current, has been observed with regular CTD cruises since 1988 and with moored ADCPs since 1997, as well as satellite altimetry since 1993. Once calibrated by the long-term ADCP measurements, the satellite altimetry is found to yield high-accuracy determination of the velocity field and volume transport down to fixed depth. Due to geostrophic adjustment, satellite altimetry combined with CTD data also allow fairly accurate determination of the depth of the Atlantic layer. From the combined data set, monthly transport time series have been generated for the period Jan 1993 to April 2019. Over the period, the annually averaged volume transport of Atlantic water in the Faroe Current seems to have increased slightly, while the heat transport relative to an outflow temperature of 0°C increased by 13%, significant at the 95% level. The salinity increased from the mid-1990s to around 2010, after which it has decreased, especially after 2016, leading to the lowest salinities in the whole period since 1988. To stay updated on a possible inflow reduction due to reduced thermohaline ventilation caused by this freshening, the future monitoring system of the Faroe Current is planned to be expanded with moored PIES (Pressure Inverted Echo Sounders). An experiment with two PIES in 2017-2019 has documented that these instruments allow high-accuracy monitoring of the depth of the Atlantic layer on the section, which combined with satellite altimetry and CTD observations should give more accurate transport estimates.
Latest Miocene Mediterranean-Atlantic gateway restriction: The Atlantic's side of the story
Authors: Ng Zhi Lin , Hernández-Molina Francisco Javier , Duarte Débora , Sierro Francisco Javier , Ledesma Santiago , Llave Estefanía , Roque Cristina , Rogerson Mike
Published: March 2020

The closure of Late Miocene Mediterranean-Atlantic gateways and the restriction of Mediterranean Outflow Water (MOW) led to the Messinian Salinity Crisis (MSC), the dynamics of which is not well understood. However, restriction of the Mediterranean-Atlantic exchange and the Mediterranean Outflow Water (MOW) is one of the prerequisites to generate hypersaline conditions for evaporitic deposition. During the Late Miocene, MOW circulation was active through a Mediterranean-Atlantic exchange of the Betic, Riffian, and possibly Gibraltar gateways. This connection is thought to have ceased or reduced with the onset of the MSC, before re-establishing through the Gibraltar gateway since the Pliocene to the present. In this study, we define the sedimentary evolution of the Neogene Basins of the Gulf of Cádiz to investigate MOW evolution during the latest Miocene. Seismic interpretation shows an Upper Messinian sedimentary unit of transparent seismic facies. It could also be found in the lower Guadalquivir and Gharb basins, and towards the West Portuguese margin. Biostratigraphic dating indicate an onset of deposition predating the MSC. Distribution of this transparent unit implicates the dominant deposition of hemipelagic/pelagic deposits during a period of quiescence in the Atlantic margins, subsequent to MOW disconnection. This suggests that weakening or cut-off of the intermediate bottom currents of the Mediterranean-Atlantic exchange through the Betic-Gibraltar-Riffian paleo-gateways precedes the onset of MSC evaporites. This work is crucial for the understanding of sedimentary, paleoceanographic and climatic implications of the Latest Miocene Mediterranean isolation in the Atlantic margins.
On classification of hydrologic connectivity indexes, their descriptive adequacy and predictive power
Authors: Nezlobin David , Lavee Hanoch , Sarah Pariente
Published: March 2020

In the last several decades a considerable number of hydrologic connectivity indexes have been suggested both in surface and subsurface hydrology. The hydrologic connectivity indexes can be classified according e.g. to the following criteria:

Argumentation – if the index formula is based on a strict theoretical derivation, intuitive assumptions, empiric data, or some combination of the above?

Range of applicability – only a very few indexes have been suggested as the universal ones, i.e. applicable on various scales, while the great majority of indexes have been designed exclusively for specific scales and environments.

Flow model – even at the same scales and environments the various types of flow may have considerably different morphologies. For instance, in the subsurface hydrology the saturated pressurized flows may have the morphology that is notably different from that of unpressurised flows. Consequently, for the suggested connectivity indexes the addressed flow model should be properly specified.

Descriptive adequacy – to what extent the index describes the hydrologic connectivity, and whether its value can be strongly affected by the factors unrelated (at least directly) to the connectivity?

Predictive power – what is typical accuracy of the index value (or set of values) and if the index value alterations may predict important changes in the hydrologic connectivity of addressed environments?

Several examples of the suggested classification are provided. We further compare two of the powerful connectivity approaches, such as the percolation theory approach and method of random graphs and consider some of the indexes based on these approaches. It can be shown that although both approaches can hardly lead to accurate description of connectivity in real hydrologic systems, they nevertheless may provide theoretical explanation of critical changes in connectivity. The percolation theory, especially its directional modifications, are more applicable for systems consisting of great number of similar elements, connected via their close neighbors. In turn, the approach of random graphs is preferable for systems having moderate number of elements which are connected not necessarily through their neighbors. The mentioned approaches seem to be the most adequate ones for exploring the sharp changes in the hydrologic connectivity but should be further rectified by considering realistic flow processes and their interactions.
Large-scale Groundwater Simulation using Artificial Neural Networks in the Danube River Basin
Authors: Landros Illias , Trichakis Ioannis , Varouchakis Emmanouil , Karatzas George P.
Published: March 2020

In recent years, Artificial Neural Networks (ANNs) have proven their merit in being able to simulate the changes in groundwater levels, using as inputs other parameters of the water budget, e.g. precipitation, temperature, etc.. In this study, ANNs have been used to simulate hydraulic head in a large number of wells throughout the Danube River Basin, taking as inputs, precipitation, temperature, and evapotranspiration data in the region. Different ANN architectures have been examined, to minimize the simulation error of the testing data-set. Among the different training algorithms, Levenberg-Marquardt and Bayesian Regularization are used to train the ANNs, while the different activation functions of the neurons that were deployed include tangent sigmoid, logarithmic sigmoid and linear. The initial application comprised of data from 128 wells between 1 January 2000 and 31 October 2014. The best performance was achieved by the algorithm Bayesian Regularization with a error of the order  based on all observation wells. A second application, compared the results of the first one, with the results of an ANN used to simulate a single well. The pros and cons of the two approaches, and the synergies of using both of them is further discussed in order to distinguish the differences, and guide researchers in the field for further applications.
Stratified and polygenetic en echelon detachment folds: Cases for Nankalayuergun fold zone, North Tarim Basin, NW China
Authors: Chen Jiajun , He Dengfa
Published: March 2020

The Nankalayuergun fold zone in the North Tarim Basin, NW China, provides an exceptional opportunity for documenting the structural characteristics and evolution of en echelon folds along transpressional fault zone. However, the genetic mechanism of these en echelon detachment folds remains debatable due to poor understanding of the deep structure. Combined with seismic and borehole data, we characterized the geometries and kinematics of Nankalayuergun fold zone, revealed its Cenozoic evolution, and discussed the formation mechanism. The stratified fold zone was geometrically decoupled by salt structures, and the structural style of three salt-influenced folds had individual characteristics due to differences in salt thickness. The timing and strength of Cenozoic deformation of three en echelon detachment folds has a sequential evolution tendency from northwest to southeast. The structural relief of supra-salt fold is the sum of Cenozoic detachment and sub-salt Paleozoic-Mesozoic transpressional folds, indicating that sub- and supra-salt structures are kinematically coupled. Segmentation of Deep Nankayuergun Transpressional Fault (DNTF) can be observed by gravity and seismic data. The supra-salt detachment folds differ from classic echelon structures in that it is only located on the active side of the DNTF. Furthermore, the hinges of the supra-salt folds located right above the sub-salt transpressional fold scarps, corresponding to the reactivation of three DNTF segments. The transpressinoal regimes, sub-salt structures, and the heterogeneity of salt rock are major factors forming the polygenetic echelon detachment folds. The case presented in this study displayed a specific pattern of salt-influenced en echelon structures along transpressional faults and highlighted the influence of pre-exiting structures on the geometry and kinematics of shallow folds, even though salt can decouple sub- and supra-salt deformation.
Reconstructing a Snake River Plain ‘super-eruption’ via compositional fingerprinting and high-precision U/Pb zircon geochronology
Authors: Ellis Ben , Schmitz Mark
Published: March 2020

Despite the largest explosive eruptions posing significant potential hazards, the recurrence rate of these so called ‘super-eruptions’ remains poorly constrained. The younger portion of the Yellowstone-Snake River Plain province is well-known for large-scale explosive volcanism; however, the older history within the Snake River Plain remains poorly-known and partially obscured by later basaltic volcanism. To address this, we characterised the mineral cargo of four widely spaced rhyolitic ignimbrites found at the margins of the Snake River Plain that reveal a strong compositional similarity in bulk geochemistry, major crystal phases (e.g. pyroxene and ilmenite), and radiogenic isotopes. To test whether these four compositionally similar units may have had a common origin we used a tandem in-situ and isotope dilution method for U/Pb geochronology of zircon crystals. The youngest populations of zircons from all four samples are equivalent in age, and together define a pooled weighted mean 238U/206Pb age of 11.030 ± 0.006 (MSWD = 1.44, n=24). These results reveal an event with a conservatively estimated erupted volume ~1,470 km3, of similar magnitude to the largest Yellowstone eruptions. Numerous widely dispersed tephra deposits found across the western portions of North America with geochemical affinities to the Snake River Plain province hint at the existence of other such voluminous ignimbrites. The improved ability to correlate deposits of an individual eruption shown by this and other recent studies implies that ‘super’ eruptive events are more common than previously thought.
Climate warming does not adequately translate to increased radial stem growth of coniferous species along the Alpine treeline ecotone
Authors: Oberhuber Walter , Bendler Ursula , Gamper Vanessa , Geier Jacob , Hölzl Anna , Kofler Werner , Krismer Hanna , Waldboth Barbara , Wieser Gerhard
Published: March 2020

It is well established, that tree growth at high elevations is mainly limited by low temperature during the growing season and climate warming was frequently found to lead to more growth and expansion of trees into alpine tundra. However, dendroclimatological studies revealed contradictory growth response to recent climate warming at the upper elevational limit of tree growth, and transplant experiments unveiled that high elevation tree provenances are not adequately benefiting from higher temperatures when planted at lower elevation. We therefore re-evaluated growth response of trees to recent climate warming by developing tree ring series of co-occurring conifers (Swiss stone pine (Pinus cembra), European larch (Larix decidua), and Norway spruce (Picea abies)) along several altitudinal transects stretching from the subalpine zone to the krummholz-limit (1630–2290 m asl; n=503 trees) in the Central European Alps (CEA). We evaluated whether trends in basal area increment (BAI) are in line with two phases of climate warming which occurred from 1915–1953 and from mid-1970s until 2015. We expected that BAI of all species shows an increasing trend consistent with distinct climate warming during the study period (1915–2015) amounting to >2 °C. Although enhanced tree growth was detected in all species in response to climate warming, results revealed that at subalpine sites (i) intensified climate warming since mid-1970s did not lead to corresponding increase in BAI, and (ii) increase in summer temperature primarily favored growth of Norway spruce, although Swiss stone pine dominates at high altitude in the CEA and therefore was expected to mainly benefit from climate warming. At treeline BAI increase was above the determined age trend in all species, whereas at the krummholz-limit only deciduous larch showed minor growth increase. We explain missing adequate growth response to recent climate warming (i) by strengthened competition for resources (primarily nutrients and light) in increasingly denser stands at subalpine sites leading to changes in carbon allocation among tree organs, and (ii) by frost desiccation injuries of evergreen tree species at the krummholz-limit. Our findings indicate that tree growth response to climate warming at high elevation is possibly nonlinear, and that increasing competition for resources and the influence of climate factors beyond the growing season impair stem growth. 
Kinetics of sulfuric acid-amine nucleation in the urban atmospheric environment
Authors: Cai Runlong , Yan Chao , Zheng Jun , Wang Lin , Kulmala Markku , Jiang Jingkun
Published: March 2020

The formation of new secondary aerosols form gaseous precursors is a frequent phenomenon in various atmospheric environments and it impacts aerosol number concentration, cloud formation, and hence climate. There has been a considerable number of new particle formation (NPF) studies in various atmospheric environments, but current knowledge on NPF in the polluted atmospheric boundary layer (e.g., the urban environment in megacities) is still limited. The clustering of H2SO4 and amines is a possible mechanism driving the fast nucleation and initial growth of new particles in the polluted urban environment. Laboratory studies using typical ambient H2SO4 concentrations and theoretical calculations based on quantum chemistry have provided insights into H2SO4-amine nucleation. However, the molecular-level mechanism and governing factors for H2SO4-amine nucleation have not been quantitatively investigated in the real atmosphere. Some previous studies indicate that differently from clean environments, the coagulation scavenging is a governing factor for NPF in polluted environments. In the presence of a high aerosol concentration in the polluted environment, a considerable fraction of the newly formed particles are scavenged by coagulation within minutes and hence, NPF is significantly suppressed. Similarly, the coagulation scavenging may also impact the steady-state cluster concentrations and the new particle formation rate. Due to the differences in the coagulation scavenging and perhaps some gaseous precursor concentrations between laboratory and atmospheric conditions, the reaction kinetics determined in previous laboratory studies may not directly applicable to the real atmosphere. Herein, based on long-term atmospheric measurements from January 2018 to March 2019 in urban Beijing, we show the different reaction kinetics under laboratory and atmospheric conditions and how to unify them using proper normalization approaches. The influences of governing factors on particle formation rate are then quantitatively elucidated. Based on the synergistic effects of these factors, an indicator for the occurrence of NPF in the urban environment is proposed and verified.
Absolute Magnetometer Attitude Reconstruction using Magnetospheric Modelling
Authors: Mieth Johannes Z. D. , Heyner Daniel , Glassmeier Karl-Heinz
Published: March 2020

One of the main goals of the magnetometer experiment MPO-MAG on board of the Magnetospheric Planetary Orbiter (MPO) during the BepiColombo mission is the determination of the Mercury main magnetic field, epecially in constraining the characteristics of the magnetic dipole offset.
In April 2020 BepiColombo had its Earth Gravity Assist manoeuvre on its way to planet Mercury.
The topocentric distance was lower than three Earth radii and offered a unique opportunity to compare the magnetometer measurements to a multitude of simultaneous measurements of the magnetospheric environment of the Earth performed by several other spacecraft like THEMIS and MMS.
Using a great number of probing points to constrain models of the Earh magnetosphere and compare models to actual measurements of the MPO-MAG sensors enables us to determine the absolute sensor attitude to an accuracy of only a few arc minutes.
Knowing the absolute attitude of a magnetometer sensor in planetary orbiter missions is a key component for the magnetic main field determination.
We present the modelling approach to compare to measurements from MPO-MAG and a study showing the dependence of a mainfield determination on the accuracy of the sensor orientation.
SPOT World Heritage catalogue: 30 years of SPOT 1-to-5 observation
Authors: Nosavan Julien , Moreau Agathe , Hosford Steven
Published: March 2020

SPOT 1-to-5 satellites have collected more than 30 million images all over the world during the last 30 years from 1986 to 2015 which represents an amazing historical dataset. The SPOT World Heritage (SWH) programme is a CNES initiative to preserve, open and generate positive impact from this SPOT 1-to-5 archive by providing new enhanced products to the general public.

Preservation has been supported for years by archiving raw data (GERALD format) in the CNES long term archive service (STAF) while the commercial market was served by images provided by our commercial partner Airbus. SWH opens a new era with the will to provide and share a new SPOT 1-to-5 archive at image level. The chosen image product is the well-known 1A SCENE product (DIMAP format) which has been one of the SPOT references for years. As a remind, 1A SCENE is a squared 60 km x 60 km GEOTIFF image including initial radiometric corrections from instrument distortions. Image resolution ranges from 20m to 5m depending on the SPOT satellite/instrument (2,5m using SPOT 5 THR on ground processing mode).

This new SWH-1A archive is currently composed of 17 M images which have been first extracted from STAF magnetic tapes over a period of 1 year and processed to 1A level using the standard processing chain on CNES High Processing Center (~432 processing cores). In parallel, additional images acquired by partner receiving stations are being retrieved to ensure that the archive is as exhaustive as possible.

The SPOT 1-to-5 1A archive will be accessible through a dedicated CNES SWH Web catalogue based on REGARDS software which is a CNES Open Source generic tool (GPLv3 license) used to manage data preservation and distribution in line with OAIS (Open Archival Information System) and FAIR (Findable, Accessible, Interoperable, Reusable) paradigms.

Once authenticated and in respect of the SWH license of use, users will then be able to request the catalogue and download products, manually or using APIs supporting OpenSearch requests.

This paper presents the architecture of the whole SPOT preservation process, from processing chains to data distribution with a first introduction to the SWH catalogue.

A last part of the presentation deals with some examples of use cases foreseen using this SPOT dataset.
Monitoring intermittent streams with low-cost water-presence sensors
Authors: Zanetti Francesca , Durighetto Nicola , Vingiani Filippo , Botter Gianluca
Published: March 2020

The study of intermittent and ephemeral streams is gaining more and more popularity, as the scientific community has acknowledged the fundamental impact of these streams on basic hydrological processes and important ecosystem services. Nevertheless, the understanding of the physical processes that drive this intermittency has been long hampered by the limited availability of empirical data. In fact, monitoring the event-based expansion and contraction of temporary streams through visual inspection is very demanding and time-consuming. To circumvent this limitation, several low-cost sensor designs for monitoring flow presence have been suggested in recent years. These sensor exploit either water temperature or electrical conductivity. However, these sensors are typically characterized by pointwise probes that water flows can easily dodge, particularly in streams with complex and unstable morphologies. Moreover, very few studies have been conducted that use networks of probes to monitor stream intermittency at the catchment-scale.

Here we present a field-application of an advanced version of the low-cost water presence sensor developed by Chapin et al., 2016. In particular, we tested a new probe design to continuously measure the electrical conductivity across a channel cross-section and, thus, infer the presence of water therein. More than 50 probes were installed to monitor the dynamics of several intermittent tributaries of a small headwater catchment in northern Italy during the summer and fall of 2019. This catchment encompasses a wide variety of stream types: mild and steep slopes, incised and flat geometries, rocky and vegetated riverbeds. The field application shows that the proposed probes are able to provide useful information about the temporary activation of ephemeral streams under a variety of environments and conditions. The reconstructed temporal dynamics of the stream network comply with the persistency maps previously derived based on visual inspection. This new sensor design enables the continuous-time monitoring of the activity of intermittent streams, providing easily interpretable data under diverse conditions. We conclude that low-cost water presence sensors provide a unique opportunity to expand the coverage of the available datasets about the dynamics of intermittent streams.
Substantial degradation in Air Quality due to Saddleworth Moor Wildfire
Authors: Graham Ailish , McQuaid James , Arnold Stephen , Pringle Kirsty , Pope Richard , Chipperfield Martyn , Conibear Luke , Butt Ed , Kiely Laura , Knote Christoph
Published: March 2020

On June 24th 2018 one of the largest UK wildfires in recent history broke out on Saddleworth Moor, close to Manchester, in north-west England. June 2018 was anomalously hot and dry across the UK which led to the peat on the moor drying out and becoming suscpetible to ignition. Since wildfires close to large populations in the UK have been relatively small and rare in the past, there is little knowledge about the impacts. This has prevented the development of effective strategies to reduce them. This paper uses a high-resolution coupled atmospheric-chemistry model to assess the impact of the fires on particulate matter with a diameter less than 2.5 µm (PM2.5) air quality (AQ) across the north-west region and the subsequent impact on health from short-term exposure. We find that the fires substantially degraded AQ across the north-west. PM2.5 concentrations increased by more than 300% in Oldham and Manchester and up to 50% in areas up to 80 km away such as Liverpool, Wigan and Warrington. This led to a third of the population (4.7 million people) in the simulation domain (-4.9-0.7°E and 53.0-54.4°N) being exposed to moderate PM2.5 concentrations on at least one day, according to the Daily Air Quality Index (36-53 µg m-3), between June 23rd and 30th 2018. This equates to 4.5 million people being exposed to PM2.5 above the WHO 24-hour safe-limit exposure of 25 µg m-3 on at least one day. Using a concentration-response function we calculate the short-term health impact which indicates that up to 60% of excess mortality between June 23rd and 30th 2018 was attributable to the fires. This represents up to a 165% increase in excess mortality across the region compared to a simulation with no fires. We find the impact of mortality due to PM2.5 from the fires on the economy was also substantial (£5.5m). Thus, our results indicate the need to introduce legislation and education to both reduce the likelihood of wildfires and reduce the population’s exposure to harmful air pollutants during their occurrence. This is particularly relevant given that wildfires are projected to become more common in the future through climate change and land-use change.
A mine as a source of geothermal energy - case study from Pyhäsalmi, Finland
Authors: Piipponen Kaiu , Hietava Jaakko , Leppäharju Nina , Martinkauppi Annu , Korhonen Kimmo , Ahonen Lasse
Published: March 2020

Water pumped from flooded coal mines has been considered as a promising option to extract geothermal energy in many countries situating in sedimentary rock environment, where the ground temperatures are clearly higher than those of the crystalline rocks of the Fennoscandian Shield. Extraction of metals from the 1440 m deep Cu-Zn-S mine in Pyhäsalmi, Finland, will end in the near future. This provides us an optimal environment for studying how much heat energy can be utilized at depths of 500-2500 meters and which method would be the optimal for it. In the Pyhäsalmi Energy Mine project funded by European Regional Development Fund (ERDF) we investigated the geothermal energy potential of the crystalline rock, performance of different borehole heat exchangers and optimized the deep borehole field.

Geothermal potential of the Pyhäsalmi site has the typical constraints of the Finnish crystalline bedrock. Field measurements include temperature measurements of ten different boreholes using Distributed Temperature Sensing (DTS) method. Near-surface annual average temperature is about 4 °C and geothermal gradient is 12-14 K/km. The ore deposit is hosted by metavolcanic rocks (ca. 1.9 Ga). Laboratory measurements show that felsic metavolcanics prevailing in immediate contact with ore have thermal conductivity of 3 – 3.5 W/(m·K), whereas the mafic metavolcanics mainly on the western side of the ore body have thermal conductivity of 2.5 – 3 W/(m·K). Relatively high thermal conductivity of the low-porosity crystalline rock promotes heat extraction from the bedrock temperatures 20 – 25 °C prevailing in the bottom of the mine.

The generated and optimized design concept in this project is based on an underground borehole field and a novel insulated coaxial collector type transferring heat from the bedrock to the fluid circulation system. A technical challenge to be resolved is the heat transfer from the depths of the mine to the ground surface. The borehole field placed at the bottom of the mine can be dimensioned to produce nearly 20 °C water with several megawatts power, allowing annual heat production of up to 10 GWh at the temperature range of 70 – 90 °C by means of heat pumps. This allows the use of geothermal heat in district heating network, something not yet done anywhere in Finland. Moreover, the borehole field can be utilized both for heat extraction and charging, making it possible to use the borehole field as a heat storage in a distributed heating network.

 
Multipurpose IoT network watchdog device with capability of add on sensors for multi instrument field stations.
Authors: Argyrakis Panagiotis , Chinis Theodore , Moshou Alexandra , Sagias Nikolaos
Published: March 2020

Several stations (seismological, geodetical, etc.) suffer from communications problems, such problems create data gaps in real-time data transmission, also excess humidity and temperatures further than manufacturer limits, usually make components and circuitry, of expensive instruments, failure, and results to unaffordable service or unrepairable damage.

We create a low-cost opensource device that will raise the reliability of the stations and secure the instruments from severe damage, such a device installed as prototype at UOA (University of Athens) seismological station KARY (Karistos Greece) for a year and the reliability of the station raised tremendously, since then the device upgraded to provide wireless connection and IoT GUI (mobile app). A local server was built to serve all the devices uninterrupted and provide a secured network.

The software is fully customizable and multiple inputs can provide addon sensors capability, for example, gas sensor, humidity sensor, etc., all the data are collected to a remote database for real-time visualization and archiving for further analysis.

The shell which covers the circuitry is 3D-printed with a high temperature and humidity-resistant material and it’s also fully customizable by the user. 
The effect of NOx on formation of Highly Oxidized Multifunctional Molecules and SOA formation in photochemical system of α-pinene and β-pinene
Authors: Kang Sungah , Mentel Thomas , Pullinen Iida , Springer Monika , Kleist Einhard , Schmitt Sebastian , Wu Cheng , Proff Silvia , Vereecken Luc , Wildt Jürgen , Kiendler-Scharr Astrid
Published: March 2020

Highly oxygenated organic molecules (HOM) are formed in the atmosphere by autoxidation, i.e. peroxy radicals can undergo H-shift followed by O2 addition. A sequence of these very fast steps leads to highly oxygenated peroxy radicals (HOM-RO2) and finally to stable termination products with O/C>1.
As other RO2, HOM-RO2 are terminated by reactions with RO2, HO2 and NOx and in addition form efficiently stable accretion products. In this study, three noticeable effects on HOM formation were found by introducing NOx in the photochemical system of monoterpenes. One effect is formation of highly oxygenated organic nitrates (HOM-ON) with sufficiently low vapor pressures allowing significant contributios to SOA formation. The second one is dimer suppression, because of competing dimer pathway (HOM-RO2·+ RO2·) and organic nitrate pathway (HOM-RO2·+ NOx). Thirdly, the reaction between peroxy radicals and NO increases alkoxy radicals in the system. The fragmentation of alkoxy radicals produces volatile compounds that should result in decrease of SOA yield. However, the effect of fragmentation is offset: alkoxy radicals also undergo H-shifts that produce alkyl radicals and after O2 addition peroxy radicals, that eventually are higher oxygenated.

Because of their low volatility, HOM play a crucial role in new particle formation and secondary organic aerosol (SOA) formation. Suppression of dimers and increased degree of oxidation of the HOM monomer play together with the result of only a small reduction of the SOA yields.
Advanced Earth System Modelling Capacity (ESM): Solving Grand Challenges by improving the representation of the components of the Earth system and their coupling
Authors: Cristini Luisa ,   ESM Project Consortium
Published: March 2020

With climate change and the conjoint challenges of food availability, clean water and geo-energy resources, our society is facing major challenges in the near future. These challenges are hard to address, because projections of Earth system change involve uncertainties that require quantification. Therefore, the Earth system science community tries to develop tools that provide decision-makers with the information required to effectively manage these issues.

The Advanced Earth System Modelling Capacity project (ESM) aims to enable such tools, investigating problems by looking at interactions between different Earth system components and improve their representation in numerical models. The project was funded by the German Helmholtz Association in April 2017 and involves eight research centers across Germany. The ultimate goal of the project is to represent the Earth system and how it changes with a world-leading modelling infrastructure that will support the process of developing solutions for the grand challenges we are facing.

The five different work packages of the project are working on topics such as enhancing the representation of Earth system model compartments, develop a flexible framework for coupling of Earth system model components, advance the Earth system data assimilation capacity, diagnose Earth system models, further develop cutting-edge frontier simulations, cross-scale modelling, and contribute to the shaping of a national strategy for Earth system modelling. The project also engages in training activities to educate and transfer knowledge to the next generation of scientists.

Since its initiation the project contributed with important results to several key model systems and platforms. In this presentation, we will highlight some current results and discuss advances in our Earth system modelling community and the way forward.
A new three-dimensional regularization for finite fault source inversions
Authors: Kheirdast Navid , Ansari Anooshiravan , Custódio Susana
Published: March 2020

The earthquake rupture process is often represented by a source function that defines slip in space and time. If we assume slip to occur on a planar surface, then the source function becomes a function of three independent variables: two spatial dimensions (slip down-dip and slip along-strike) and one temporal dimension (source time function at each point on the fault). Finite fault inverse problems aim at exploring this model space in order to find the source function that generates synthetic ground motion that best fits the observed data. This inverse problem is severely ill-conditioned. In order both to ensure a regular solution and to avoid over-fitting the data, both physical and mathematical constraints can be imposed.  Common methods of finite fault source inversion typically apply a one-dimensional regularization in time, which gives preference to compacted-support source-time functions, like triangular or trapezoidal functions in time, or to two-dimensional regularizations that ensure smooth variations of slip over the fault plane (Mai et. al, 2016). In this work, we propose an innovative three-dimensional regularization for kinematic source inversions in the frequency domain, which simultaneously requires smooth variations of slip over space (2D) and frequency (1D, smooth spectra) . This new three-dimensional regularization selects the spatial slip distributions that are more similar to those of neighboring frequencies, thus effectively transferring knowledge from one frequency to another. In the framework of Tikhonov regularization, having more than one regularization condition requires more than one damping factor to be inserted in the inversion misfit. Additionally, no orthogonal decomposition (like Generalized Singular Value Decomposition) exists when more than one regularization conditions are imposed. Thus, we investigate a new 3D regularization method using a Bayesian approach with a Markov Chain Monte Carlo (MCMC) simulation. The new method is tested using the SIV-inv1 benchmark exercise. The proposed method is also preliminarily applied to study the rupture process of the 2019 M5.9 Torkamanchay, Iran, earthquake.
Wildfire Detection Probability of MODIS Fire Products under the Constraint of Environmental Factors: A Study Based on Confirmed Ground Wildfire Records
Authors: Ying Lingxiao , Shen Zehao , Yang Mingzheng , Piao Shilong
Published: March 2020

The Moderate Resolution Imaging Spectroradiometer (MODIS) has been widely used for wildfire occurrence and distribution detecting and fire risk assessments. Compared with its commission error, the omission error of MODIS wildfire detection has been revealed as a much more challenging, unsolved issue, and ground-level environmental factors influencing the detection capacity are also variable. This study compared the multiple MODIS fire products and the records of ground wildfire investigations during December 2002–November 2015 in Yunnan Province, Southwest China, in an attempt to reveal the difference in the spatiotemporal patterns of regional wildfire detected by the two approaches, to estimate the omission error of MODIS fire products based on confirmed ground wildfire records, and to explore how instantaneous and local environmental factors influenced the wildfire detection probability of MODIS. The results indicated that across the province, the total number of wildfire events recorded by MODIS was at least twice as many as that in the ground records, while the wildfire distribution patterns revealed by the two approaches were inconsistent. For the 5145 confirmed ground records, however, only 11.10% of them could be detected using multiple MODIS fire products (i.e., MOD14A1, MYD14A1, and MCD64A1). Opposing trends during the studied period were found between the yearly occurrence of ground-based wildfire records and the corresponding proportion detected by MODIS. Moreover, the wildfire detection proportion by MODIS was 11.36% in forest, 9.58% in shrubs, and 5.56% in grassland, respectively. Random forest modeling suggested that fire size was a primary limiting factor for MODIS fire detecting capacity, where a small fire size could likely result in MODIS omission errors at a threshold of 1 ha, while MODIS had a 50% probability of detecting a wildfire whose size was at least 18 ha. Aside from fire size, the wildfire detection probability of MODIS was also markedly influenced by weather factors, especially the daily relative humidity and the daily wind speed, and the altitude of wildfire occurrence. Considering the environmental factors’ contribution to the omission error in MODIS wildfire detection, we emphasized the importance of attention to the local conditions as well as ground inspection in practical wildfire monitoring and management and global wildfire simulations.
Eclogitization kinetics of continental granulites : quantification and implications
Authors: Baisset Marie , Labrousse Loic , Schubnel Alexandre
Published: March 2020

When implicated in convergence zones, granulites of the lower continental crust are expected to eclogitize at depth.When exposed in the field such units show a bimodal rheological behavior between fracturing of the protolith rock (granulites) and ductile flow of the transformed parts (eclogites). It seems therefore that a competition exists between the rate at which the rocks are loaded in stress and the rate at which they transform, i.e. the overall eclogitization kinetics. The aim of the work presented here is to quantify the kinetics of the metamorphic reactions involved in eclogitization by estimating the reaction rates in plagioclase-bearing assemblages  submitted to different P-T conditions over different time spans. For this, experiments have been performed in piston-cylinder apparatus on aggregates derived from natural granulites. Special attention is paid to the location where nucleation starts and how it propagates in and between the grains. In this prospect, the presence of garnet and cpx in the plagioclase matrix is a first order control on the reaction process. This work follows previous experimental studies (e.g. Shi et al., 2017, Incel et al., 2018) which show that reaction-enhanced embrittlement may be key for fracturing at high pressure. It has been proposed that transient properties of the rocks induced by the very beginning of the reaction (e.g. volume change, small grain size nucleation products) can lead to brittle instabilities. As we assume that the rheological behavior of the crust is controlled by a competition between reaction rate and strain rate, experiments involving deformation of granulites while undergoing eclogitization are required. Preliminary results performed on Griggs-type apparatus, which constitutes the best tool for that, will also be presented.
Tackling climate change reporting needs regarding soil C pool: SOC modelling under different land-use categories in Croatia
Authors: Ostrogovic Sever Masa Zorana , Hidy Dóra , Barcza Zoltán , Marjanovic Hrvoje
Published: March 2020

Soil organic matter (SOM) is one of five mandatory pools used in reporting of national greenhouse gas inventories under UNFCCC and EU regulations. Reporting on net change in soil organic carbon (SOC) under different land uses over time is challenging. The 2006 IPCC Guidelines for National Greenhouse Gas Inventories suggest that all estimates, including carbon (C) in SOM, should be transparent and consistent throughout the time series. For some countries assessing net change of SOC is often not easy due to lack of data, infrastructure or funding. Consequently, for the mineral part of the soil, frequently used is the simplest approach of assessment (Tier 1) which assumes no change in mineral SOC stocks. However, this assumption should be substantiated.

There is a growing need for the use of higher tiers in reporting of C changes in SOM pool, by providing estimates from field measurements and modelling. While soil C modelling is cost-effective, and in some countries already found applicable for the purpose of reporting, field measurements of soil C stocks are expensive and time-consuming, but necessary for model calibration and validation.

In our research we used Biome-BGCMuSo model, a biogeochemical model that simulates the storage and flux of water, C, and nitrogen (N) in the soil-plant-atmosphere system. Biome-BGCMuSo is a new variant of the well‑known Biome-BGC model with an improved multilayer soil module. We performed spatial modelling of SOC down to 30 cm for four different land-use categories of: deciduous forests, evergreen forests, annual croplands and grasslands, for the period 1990-2014. Eco-physiological parameters for each biome (i.e. land-use) were obtained from the literature. Meteorological data was obtained from open-access meteorological database FORESEE. Management activities (i.e. thinning, planting, mowing, fertilizing, and ploughing) where estimated based on available data and consultations with the local experts. Modelling results of SOC stocks were compared to field measurements. Trends of soil C change in period 1990-2014 under different land-uses were discussed.
Trends and patterns in annually burned forest areas and fire weather across the European boreal zone in the 20th and early 21st centuries
Authors: Drobyshev Igor , Kitenberga Mara , Ryzhkova Nina , Eden Jonathan , Krikken Folmer , Pinto Gui
Published: March 2020

Fire remains the main natural disturbance factor in the European boreal zone (EBZ), which exhibits strong gradients in climate conditions, modern and historical patterns of forest use, and the modern human infrastructure density. Understanding climatic forcing on fire activity is important for projecting effects of climate change on multiple ecosystem services in this region. Here we analyzed available records of annually burned areas (ABA) in 16 administrative regions of EBZ (countries or sub-country units) and fire weather variability to test for their spatio-temporal patterns over 1901-2017. To define sub-regions of EBZ with similar fire activity we compiled 30-60 year long ABA chronologies and clustered them in Euclidian space to identify regions of EBZ with temporally synchronous fire activity. We then reconstructed 100-year long ABA chronologies for each cluster, capitalizing on its member with the highest correlation between observational fire record and climatological fire weather proxy (MDC, monthly drought code). The 100-year chronologies helped identified large fire years (LFY), i.e. years with the ABA being above 10% of its long-term distribution. The climatic forcing of these events was tested in superposed epoch analysis operated with gridded 500 hPa pressure fields. Finally, we tested trends in (a) synchrony of LFY's across clusters, (b) MDC values over the EBZ, and (c) spatial variability in July MDC over the EBZ geographic domain during 1901-2017.

EBZ exhibits large variability in forest fire activity with the fire cycles varying from ~104 (Scandinavia) to 3*102 years (Russian Republic of Komi). Clustering of administrative units in respect to their ABA suggested the presence of sub-regions with synchronous dynamics of ABA, located  along W-E and S-N gradients. LFYs in each of the cluster was associated with the development of the high pressure cell over the regions in question in July, indicating climatic forcing of LFYs. Contingency analysis indicated no long-term trend in the synchrony of LFYs observed simultaneously in several administrative units. We observed a trend towards higher values of MDC for the months of April and May in the western section of EBZ (April) and southern-eastern sections of the Baltic sea region and North sections of EBZ in Russia (May). Trends in MDC during the summer months were largely absent. We discuss teleconnections of fire activity in the EBZ with Atlantic SST.
Utilizing magnetotelluric and differential magnetometer measurements for the validation of geomagnetically induced current models in a complex power network
Authors: Huebert Juliane , Beggan Ciaran D. , Richardson Gemma S. , Thomson Alan W.P.
Published: March 2020

Space weather as a geohazard to modern technological infrastructure has come to the forefront of electromagnetic research in the past years. Geomagnetically induced currents (GICs) are generated by the rapidly changing magnetic fields during geomagnetic storms and sub-storms and the resulting induced electric fields into the ground. GICs can pose great risk to e.g. transformers in HV power grids and their monitoring and modelling is an ongoing effort in many higher and mid-latitude countries. Modelling of GICs in HV power grids requires knowledge about the magnetic field variations, the induced electric field via a conductivity model or through the magnetotelluric (MT) impedance tensor, and a detailed representation of the grid topology.

In the UK we have traditionally used a thin-sheet model for the calculation of electric fields during storm times due to very limited availability of MT data, but also as a fast and computational cost-effective approach. Using the Differential Magnetometer Method (DMM) in several locations of the grid has enabled us to indirectly measure GICs and validate them against the model. Here we present a case study from a location in Scotland, where we incorporate the different approaches and data sets that combine to a comprehensive analysis of GICs in this subset of the UK power grid.