bluuebunny/crossref_metadata_2025 huggingface dataset:
Swarm Mission: instruments performance, data availability, quality and future evolutions
Authors: Qamili Enkelejda , Catapano Filomena , Tøffner-Clausen Lars , Buchert Stephan , Siemes Christian , Mizerska Anna , Bregnhøj Nielsen Jonas , Nilsson Thomas , Miedzik Jan , Mazzocato Maria Eugenia , Trenchi Lorenzo , Bouffard Jerome , Stromme Anja , Vogel Pierre , Hoyos ortega Berta
Published: March 2021

The European Space Agency (ESA) Swarm mission, launched on November 2013, continue to provide very accurate measurements of the strength, direction and variation of the Earth’s magnetic field. These data together with precise navigation, accelerometer, electric field, plasma density and temperature measurements, are crucial for a better understanding of the Earth’s interior and its environment. This paper will provide a status update of the Swarm Instrument performance after seven years of operations. Moreover, we will provide full details on the new Swarm Level 1b product baseline of Magnet and Plasma data which will be generated and distributed soon to the whole Swarm Community.  Please note that the main evolutions to be introduced in the Swarm L1B Algorithm are: i) computation of the Sun induced magnetic disturbance (dB_Sun) on the Absolute Scalar Magnetometer (ASM) and Vector Field Magnetometer (VFM) data; ii) computation of systematic offset between Langmuir Probes (LP) measurements ad ground observations derived from Incoherent Scatter Radars (IRS) located at middle, low, and equatorial latitudes. These and further improvements are planned to be included in the upcoming versions of the Swarm Level 1b products, aiming at achieving the best data quality for scientific applications.
Aggregating over land surface heterogeneity systematically biases evapotranspiration estimates in large-scale evaporation models
Authors: Rouholahnejad Freund Elham , Zappa Massimiliano , James Kirchner
Published: March 2021

Land surface models are highly uncertain in estimating evapotranspiration (ET) fluxes, and differ substantially in their projections of how ET will evolve in the future. Biases in estimated ET fluxes will affect the partitioning between sensible and latent heat, and thus alter simulated temperatures and model predictions of droughts and heatwaves. One potential source of bias is the "aggregation bias" that arises whenever nonlinear processes, such as those that regulate ET fluxes, are modeled using averages of heterogeneous inputs. Here we demonstrate that this aggregation bias leads to substantial overestimates in ET fluxes in a typical large-scale land surface model. The proposed methodology can be used to correct for aggregation biases in ET estimates by quantifying the effects of finer-resolution spatiotemporal variability in ET drivers at each modeling time step, without explicitly representing sub-grid heterogeneities in large-scale land surface models. 
Multicomponent multiphase reactive fluid flow in viscoelastoplastic porous media: localization patterns of fluid flow and strain
Authors: Khakimova Lyudmila , Belov Nikolai , Myasnikov Artyom , Vershinin Anatoly , Krapivin Kirill , Isaeva Anna , Dobrozhanskiy Vladimir , Podladchikov Yury
Published: March 2021

This work is devoted to developing the self-consistent thermo-hydro-chemo-mechanical reactive transport model to predict and describe natural and industrial petroleum processes at different scales.

We develop a version of the front tracking approach for multicomponent multiphase flow in order to treat spontaneous splitting of discontinuities. We revisit the solution for the Riemann problem and systematically classify all possible configurations as functions of initial concentrations on both sides of the discontinuity. We validate the algorithm against finite volume high-resolution technics and high-order spectral finite elements.

To calculate the parameters of phase equilibria, we utilize an approach based on the direct minimization of the Gibbs energy of a multicomponent mixture. This method ensures the consistency of the thermodynamic lookup tables. The core of the algorithm is the non-linear free-energy constrained minimization problem, formulated in the form of a linear programming problem by discretization in compositional space.

The impact of the complex rheological response of porous matrix on the morphology of fluid flow and shear deformation localization is considered. Channeling of porosity waves and shear bands morphology and their orientation is investigated for viscoelastoplastic both shear and bulk rheologies.
The role of slow magnetostrophic waves in dipole formation in rapidly rotating dynamos
Authors: Varma Aditya , Sreenivasan Binod
Published: March 2021

It is known that the columnar structures in rapidly rotating convection are affected by the magnetic field in ways that enhance their helicity. This may explain the dominance of the axial dipole in rotating dynamos. Dynamo simulations starting from a small seed magnetic field have shown that the growth of the field is accompanied by the excitation of convection in the energy-containing length scales. Here, this process is studied by examining axial wave motions in the growth phase of the dynamo for a wide range of thermal forcing. In the early stages of evolution where the field is weak, fast inertial waves weakly modified by the magnetic field are abundantly present. As the field strength(measured by the ratio of the Alfven wave to the inertial wave frequency) exceeds a threshold value, slow magnetostrophic waves are spontaneously generated. The excitation of the slow waves coincides with the generation of helicity through columnar motion, and is followed by the formation of the axial dipole from a chaotic, multipolar state. In strongly driven convection, the slow wave frequency is attenuated, causing weakening of the axial dipole intensity. Kinematic dynamo simulations at the same parameters, where only fast inertial waves are present, fail to produce the axial dipole field. The dipole field in planetary dynamos may thus be supported by the helicity from slow magnetostrophic waves.
Particle energization inside plasmoids: numerical and analytical investigations
Authors: Zhao Xiaozhou , Keppens Rony , Bacchini Fabio
Published: March 2021

In an idealized system where four magnetic islands interact in a two-dimensional periodic setting, we follow the detailed evolution of current sheets forming in between the islands, as a result of an enforced large-scale merging by magnetohydrodynamic (MHD) simulation. The large-scale island merging is triggered by a perturbation to the velocity field, which drives one pair of islands move towards each other while the other pair of islands are pushed away from one another. The "X"-point located in the midst of the four islands is locally unstable to the perturbation and collapses, producing a current sheet in between with enhanced current and mass density. Using grid-adaptive resistive magnetohydrodynamic (MHD) simulations, we establish that slow near-steady Sweet-Parker reconnection transits to a chaotic, multi-plasmoid fragmented state, when the Lundquist number exceeds about 3×104, well in the range of previous studies on plasmoid instability. The extreme resolution employed in the MHD study shows significant magnetic island substructures. Turbulent and chaotic flow patters are also observed inside the islands. We set forth to explore how charged particles can be accelerated in embedded mini-islands within larger (monster)-islands on the sheet. We study the motion of the particles in a MHD snapshot at a fixed instant of time by the Test-Particle Module incorporated in AMRVAC (). The planar MHD setting artificially causes the largest acceleration in the ignored third direction, but does allow for full analytic study of all aspects leading to the acceleration and the in-plane, projected trapping of particles within embedded mini-islands. The analytic result uses a decomposition of the test particle velocity in slow and fast changing components, akin to the Reynolds decomposition in turbulence studies. The analytic results allow a complete fit to representative proton test particle simulations, which after initial non-relativistic motion throughout the monster island, show the potential of acceleration within a mini-island beyond (√2/2)c≈0.7c, at which speed the acceleration is at its highest efficiency. Acceleration to several hundreds of GeVs can happen within several tens of seconds, for upward traveling protons in counterclockwise mini-islands of sizes smaller than the proton gyroradius.
The ecosystem service benefits of green-roof as a part of smart ecosystem-based management: A case study in Dublin, Ireland
Authors: Sannigrahi Srikanta , Basu Bidroha , Basu Arunima Sarkar , Pilla Francesco
Published: March 2021

The concept of Ecosystem-Based Management (EBM) as part of Nature-Based Solutions (NBS) have frequently been adopted in different strategic planning as a cross-sectoral mechanism to manage environmental problems. The EBM combines all relevant approaches, methods, tools, and software that collectively provide key scientific and socioeconomic evidence and eventually address environmental issues more sustainably. The specific application of EBM in different environmental problems, including flooding, have been proven effective in many cases. This ensures the superiority of EBM approaches for designing collaborative programs for solving environmental problems. The EBM offers a variety of sustainable interventions such as reducing impervious surface through porous paving, green parking lots, brownfield restoration, and deployment of green-roofs, which collectively attenuates water runoff and peak discharge, and offers protection against extreme precipitation events by enhancing water infiltration. In addition to the targeted benefits and cost-effectiveness of EBM, the supply of potential ecosystem service co-benefits that usually comes with EBM can contribute substantially to generating environmental benefits and adds community well-being. In order to analyse the superior effects of green-roof as a part of a smart-EBM framework, which has been deployed in CHQ building in Dublin, Ireland, a conceptual upscaling scenario framework has been formulated for measuring the city scale impact of green-roofs in providing multiple-valued ecosystem services. The biophysical and economic benefits of smart green-roof EBM will be estimated using varied ecosystem service modelling and standard cost-benefit analysis. The proposed smart green-roof framework is expected to have a more significant impact in minimising the flooding problems in Dublin city and expected to provide multiple regulating, supporting provisioning, and cultural benefits that can collectively surpass the deployment cost of green-roofs in the long run.
 The tsunami energy radiation directivity on the example of the 1994, 2006 and 2007 events
Authors: Ivanova Anastasia
Published: March 2021

Determining the tsunami source danger is currently one of the most urgent tasks. The vast majority of recorded tsunamis are of seismic origin. Part of the energy released during an earthquake passes into the energy of the initial tsunami source. The tsunami excitation efficiency depends on a number of factors: the depth of the sea above the source and its location relative to the coast and continental slope; the shape and area of residual post-seismic bottom displacements, as well as the bottom relief directly in the zone of the seismic source; inhomogeneities of the ocean floor relief along the path of tsunami propagation (for estimating wave heights in the zone farthest from the source); time inhomogeneities of tsunami wave radiation from the source zone; non-isotropy of the tsunami radiation spectrum.

To study the tsunami source efficiency, we considered three tsunamis in the Kuril ridge region: the Shikotan tsunami of 1994, and two Simushir tsunamis of 2006 and 2007. The choice of events was largely determined by the close geographical location – all of them belong to the Kuril-Kamchatka subduction zone. Also, these events are well studied, and there is quite a large amount of data on tsunami measurements onshore and in the deep ocean. At the same time, all three sources differ in the mechanisms of the seismic focus and location relative to the coast and the continental slope.

We analyzed the tsunami wave field for three events near the Russian Pacific coast. Tsunami energy flow calculations show that frontal energy flow is mainly directed to the southeast. The flux magnitude decreases with distance from the source as a result of geometric divergence and scattering. At longer distances, the effect of refraction becomes more significant – the flow is divided into separate rays due to the focusing on the irregular bottom relief.

The radiation patterns of each source that also were created show the part of wave energy that penetrated the Sea of Okhotsk through the Kuril Straits. It is easy to indicate the effect of the capture of tsunami waves by the shelf and the formation of edge waves that carry the wave energy away from the source area along the Kuril Ridge shelf. For 2006 and 2007 events a relatively small part of the wave energy went into the captured waves, but for 1994 the initial sea surface displacement area was in the shelf zone and a significant part of the energy was transferred to the captured edge waves, radiated mainly in the northeast direction.
Towards a sub-seasonal agricultural drought forecast for Germany
Authors: Leppelt Thomas , Brauch Jennifer , Paxian Andreas
Published: March 2021

Insufficient precipitation and subsequent water stress for crop production are among the biggest risks in agriculture. Especially the past three years (2018, 2019, 2020) in central Europe show that dry and hot summers enhance the probability of harvest failures due to long term drought situations. Hence, a better prediction of long-term crop water stress situations could improve the resilience and adaptation of agriculture. One important indicator for agricultural drought is the plant available water in the top soil (0-60 cm). This soil moisture is a storage parameter which depends not only on the meteorological input but also on the vegetation cover and soil properties. In comparison to precipitation the soil moisture changes slowly with moderate variability, due to its buffer capacity for incoming rainfall. Here we try to take advantage of this persistence behaviour by performing long range soil moisture forecasts for Germany based on sub-seasonal forecasts. Therefore we combined the ECWMF extended range forecasts with a 1-D hydrological model AMBAV, which is capable of parameterizing regional soil properties and crop growth. Reasonable skill for predicting low soil moisture under winter wheat in early summer can be found with a 3-4 week forecast lead time. Therefore, a forecast of the hot and dry summer in 2018 was possible. The soil moisture forecasts had lower mean absolute error rates and higher rank correlation skill than regarding the precipitation directly as drought predictor, though the precipitation forecast is used as input for the subsequent hydrological modelling. However, further analyses are necessary in order to evaluate forecast skills for less extreme soil moisture situations. Nonetheless these results could be a first step towards an improved sub-seasonal agricultural drought forecast for Germany, which could be applied in other European countries similarly.
3D geomodelling in the complex metamorphic and poly-deformed units of the Italian Western Alps (Conca di By, Aosta Valley, Italy)
Authors: Arienti Gloria , Bistacchi Andrea , Monopoli Bruno , Dal Piaz Giorgio Vittorio , Dal Piaz Giovanni , Bertolo Davide
Published: March 2021

3D geological modelling of complex metamorphic terrains that underwent a sequence of ductile and brittle deformation events is an extremely challenging task. Difficulties start from the input data that are frequently sparse and heterogeneous in quality and distribution. In projects based on field data only (without significant subsurface data) uncertainties are even more pronounced, but, in our project, we had the rugged topography of the Western Alps on our side, with elevations ranging from c. 1200 m to c. 3200 m and very continuous outcrops. Other problems, that we address in this contribution, arise during the modelling process. We tested different commercial software packages and some open-source research libraries and we found that no one is capable of modelling our complex structures out-of-the-box. This is not surprising since generally these codes, and particularly the commercial ones, are geared towards modelling gently deformed sedimentary sequences. However, it is possible to overcome a large range of obstacles by “fooling” implicit structural modelling algorithms, simply “cheating” on the geological meaning of model entities. This means (1) developing a conceptual model of polyphase ductile and brittle deformation, (2) finding geological/mathematical entities that are at the same time implemented in the code and able to represent the complex structures, and finally (3) carrying out the implicit modelling. For instance, tectonic contacts between large-scale tectono-metamorphic units can be treated as unconformities (and not as faults) to obtain a realistic representation. In some cases, also conformal lithological boundaries can be considered as unconformities with the goal of allowing larger thickness variations. In other situations, a “fake” stratigraphy where the same units are repeated several times can be used to model sequences of isoclinal folds and thin tectonic slices. In this contribution, some of these modelling solutions are compared in terms of (1) their straightforward implementation, and (2) their ability to generate models that properly fit the very detailed geological maps available in our study area (c. 60 km2 mapped at 1:5.000-1:10.000 with a dense set of structural stations).
The geomagnetic field behavior inside Vrancea zone (Romania) in correlation with tectonic, atmospheric and solar activity
Authors: Moldovan Iren Adelina , Mihai Andrei , Toader Victorin Emilian , Enescu Bogdan Dumitru , Ghita Cristian
Published: March 2021

The present study assesses two signal processing methods on geomagnetic data to detect precursory signals appearing before M>5.0 Vrancea, Romania earthquakes occurred between 2016 and 2021. Geomagnetic data are obtained from Muntele Rosu Seismological Observatory situated in one corner of Vrancea seismogenic zone – as primary station, and from Intermagnet Surlari National Geomagnetic Observatory of IGR, located about 150Km South-East to Vrancea zone as remote station respectively. The first method, the diurnal variation ratio method computes difference between daily maximum with minimum value before finding ratio of primary to remote station for each individual component. The second method, the polarization ratio analysis is performed on both stations data to compute the ratio of vertical to total horizontal component in ultra-low frequency range. Geomagnetic indices taken from NOAA/Space Weather Prediction Center are compared to separate the global variation from seismo-electromagnetic anomalies possibly presented in a seismic area like Vrancea zone and to ensure that any geomagnetic fluctuations are not caused by solar-terrestrial effect.

In the end, the paper aims to compare the results from both methods in term of reliability and effectiveness.

Acknowledgements. This work was funded by: PN19 08 01 01/2019 Multirisc Nucleu Project, by MCI , Phenomenal Project PN-III-P2-2.1-PED-2019-1693, 480PED/2020 and AFROS Project PN-III-P4-ID-PCE-2020-1361, PCE/2021 supported by UEFISCDI
Global sensitivities of forest carbon changes to environmental conditions 
Authors: Besnard Simon , Santoro Maurizio , Cartus Oliver , Fan Naixin , Linscheid Nora , Nair Richard , Weber Ulrich , Koirala Sujan , Carvalhais Nuno
Published: March 2021

Quantifying the responses of forest dynamics to fluctuations in the atmosphere, hydrosphere and land surface conditions at global scales have been rather challenging. Despite the understanding that favourable environmental conditions promote forest growth, the effects have been challenging to observe across different ecosystems and climate gradients. Based on a global annual time series of aboveground biomass (AGB) from 1992 to 2018, we present forest carbon changes and provide insights on the controls of atmospheric (e.g., climate), hydrosphere (e.g., soil water availability) and land surface (e.g., changes in forest cover) conditions on forest carbon changes from local to global scales. Our findings indicate a gradient of forest gains and losses across AGB classes, with regions with carbon stocks of 50-100 MgC ha-1 depicting both the highest forest gains and losses. Furthermore, we observe that changes in forest carbon stocks were systematically positively correlated with changes in forest cover, while it was not necessarily the case with other environmental variables, such as air temperature and water availability at the uni-variate level. We also used a gradient boosted decision tree model and a variable importance metric (i.e., SHAP values) to demonstrate that atmospheric conditions largely dictate forest carbon changes followed by land surface and hydrosphere conditions. Interestingly, the observed functional relationships indicate a strong sensitivity of forest carbon changes to recent-past carbon stocks and both recent-past and concurrent atmospheric water demand. Regionally, we find evidence that carbon gains from long-term forest growth covary with long-term carbon sink inferred from atmospheric inversions at the ecosystem level. Our study quantifies the contributions from the atmosphere, hydrosphere, and land surface conditions to forest carbon changes and provides new insights into the underlying mechanisms of forest growth on the global carbon cycle.
New simplified models for earthquake-triggered landslides in large area: application to Italian case studies
Authors: Mendicelli Amerigo , Mori Federico , Falcone Gaetano , Peronace Edoardo , Moscatelli Massimiliano , Giuseppe Naso , Alvioli Massimiliano
Published: March 2021

Shake maps, produced a few hours after a seismic event, represent the key input for the rapid assessment of earthquake triggered landslides scenario maps in near real time.

The IGAG20 approach (Falcone et al., 2021) improves the prediction of these by contemplating the site effects that are calculated as a function of the Vs30 (Mori, 2020) and the intensity of the shaking.

The method originally calculates the amplification factor for some intensity measures at the surface level for the national hazard, in Italy.

Here, we present applications of the method, in terms of scenarios, for a few main shocks of past seismic events in Italy: Friuli 1976, Umbria-Marche 1997 and L’Aquila 2009. We used the OpenQuake engine (Silva et al., 2014), to produce PGV and PGA stochastic maps including amplification factors. The PGV map helped calculating landslide probability maps within the Nowicki et al. (2018) model, while the PGA map was a key input for landslide rockfall maps obtained within the STONE model (Antonini et al., 2002, Guzzetti et al., 2002; Alvioli 2020).

Results of both models were compared with available landslide records for the corresponding earthquake events, either in the form of points or polygons (Govi 1977; Guzzetti et al 2009).
Twinned calcite within polymict impact breccias from the Nördlinger Ries impact structure, Germany – shock effects and post-shock annealing
Authors: Seybold Lina , Trepmann Claudia A. , Hölzl Stefan , Kaliwoda Melanie
Published: March 2021

Approximately one third of the worlds known impact structures are formed in carbonate-bearing target rocks. However, the response of their main constituent mineral, calcite, upon shock loading and unloading is still not well understood. Mechanical twins in calcite are described from natural impactites and shock experiments, yet, reliable indicators to distinguish these shock effects from the very common calcite twins generated in tectonites are missing. Here, we present scanning electron microscopic investigations of twinned calcite within calcite cemented brecciated gneisses from the Ries impact structure.

Calcite cemented brecciated gneisses occur at several outcrops of the Ries impact structure as well as in samples recovered from depth as low as 977 m in the research drilling 1973. At Maihingen, the polymict impact breccias contain shocked gneiss fragments and various generations of calcite in veins. The occurrence of rhombohedral PDFs in quartz from the gneiss fragments indicates shock conditions of >10 GPa. Coarse calcite grains, representing an early generation of calcite in the veins, show exceptionally fine-lamellar twins, indicating high stress and strain rates. The calcite twins show widths of < 0.5 µm, a high density of up to a few hundred lamellae per mm, and appear to crosscut each other, which has been suggested as a criterion for shock-induced twinning. Furthermore, a high density of sets of planar features occur associated and parallel to these twins, but along which no twin domains were resolved in the scanning electron microscope. Twin systems detected by EBSD measurements include e-twins, common also in calcite from tectonites, and another more rarely occurring twin system, characterized by a rotation axes parallel to <-2110> and a rotation angle of ca. 35°. A second generation of calcite without twins is represented by elongate palisade calcite, fine-grained aggregates and rims forming sutured grain boundaries surrounding twinned coarse calcite grains. EDS measurements show that these calcite grains contain up to 2.5 % Fe as well as traces of Mn, Mg, Si, Na and Al. In contrast, the coarse twinned calcite is almost pure CaCO3. Whereas the fine-grained aggregates and sutured grain boundaries indicate recrystallization, the palisade grains indicate precipitation from the pore fluid.

The twinned coarse calcite grains within the polymict impact breccias are interpreted to be shock induced. As coarse calcitic sedimentary target rocks are not known from the Ries area, they can either represent pre-shock calcite veins within the gneisses or possibly marbles that were brecciated together with shocked gneisses during impact cratering. The second generation of calcite represents post-shock recrystallization and precipitation from a fluid.
Unravelling the dynamics of magma emplacement through palaeomagnetic backstripping of intrusion-induced host rock deformation: Analysis from the Sandfell Laccolith, SE Iceland
Authors: McCarthy William , Twomey Vincent , Magee Craig , Petronis Michael , Mattsson Tobias
Published: March 2021

Injection and inflation of magma in the shallow crust is commonly accommodated by uplift of the surrounding host rock, producing intrusion-induced forced folding that mimics the geometry of the underlying intrusion. Whilst such forced folds have previously been described from field exposures, seismic reflection images, and modelled in scaled laboratory experiments, the dynamic interaction between progressive emplacement of hot magma, roof uplift, and any associated fracture/fault development remains poorly understood. Analysis of ancient examples where magmatism has long-since ceased typically only provides information on final geometrical relationships, while studies of active intrusions and forced folding only capture brief phases of the dynamic evolution of these structures. If we could unravel the spatial and temporal evolution of ancient forced folds, we could therefore acquire critical insights into magma emplacement processes and interpretation of ground deformation data at active volcanoes.

 

We put forth a new hypothesis suggesting that thermoremanent magnetization records progressive deflection of the host rock during laccolith construction where these measurements can be used to measure the rate and dynamics of the magma emplacement of. Our test site is located within the basaltic lava pile of the ~800 m wide structural aureole surrounding the rhyolitic Sandfell Laccolith in SE Iceland, which intruded <1 Km below the palaeosurface at ~11.7 Ma. Our results show heat from the laccolith resets the remanence from samples within 50 m of the contact. Several variations in thermoremanent vectors observed further outward along the structural aureole reflect stepwise folding from incremental injection of magma suggesting as and the laccolith develops, different sections of the host rock are incrementally tilted and possibly reheated. This procedure could be tested in other ancient structure aureoles to investigate whether single or multiple thermal wm37@st-andrews.ac.ukoverprints coupled with structural observations could be used a proxy for ground deformation patterns in volcanic hazard assessment.
The spatiotemporal pattern of the Bond 4 event (5.2 ka) : a global data-based review
Authors: Jalali Bassem , Sicre Marie-Alexandrine
Published: March 2021

The Bond 4 event starting at 7000 yr BP and culminating around 5200 yr BP corresponds to the largest (in magnitude and duration) invasion of drifting ice across the subpolar North Atlantic during the Holocene (Bond et al., 2001). While several studies have focused on other events of the Holocene, such as the 8.2 ka, the 4.2 ka and the Little Ice Age, little is known about the mid-Holocene 5.2 ka event. Here we present a global compilation of carefully selected high-resolution time series of sea surface temperature (SST; N=58) and humidity/precipitation (N=35) to characterize in space and time the 5.2 ka event pattern.

The SST records show the occurrence of cold conditions in the North Atlantic, western Mediterranean as well as in the western Pacific Ocean. However, they indicate warming in the high latitude North Atlantic, the southeastern Atlantic, the eastern Mediterranean and the Arabian and Red seas. Humidity/precipitation data (mainly based on oxygen  isotope records in speleothems) indicate dry conditions in the northern hemisphere subtropical and mid latitude regions of all continents. Based on these data and others from marine and lacustrine records in tropical regions, we suggest a possible weakening of monsoon systems, i.e. in Africa, North America, southwest Asia as well as East Asia. Precipitation reduced as well in most regions of the Mediterranean (i.e. except Iberian Peninsula). All together these data indicate severe climate conditions during the 5.2 ka event.

Based on the recent compilation of sortable silt from the high latitude North Atlantic of McCave and Andrews (2019), the 5.2 ka event coincides with a decrease of the main Shallow and bottom ocean ﬂows (i.e. North Iceland Irminger Current, East Greenland Current, Iceland-Scotland overﬂow) probably reflecting a weakening of the North Atlantic Deep Water formation. This event also corresponds to the occurrence of several solar minima as well as several tropical volcanic mega-eruptions that could have triggered a global colder and drier climate (Steinhilber et al., 2012; Kobashi et al., 2017). 
Temperature-sensitive biochemical 18O-fractionation and humidity-dependent attenuation factor of leaf water 18O-enrichment are needed to predict 18O composition of cellulose
Authors: Ogee Jerome , Hirl Regina , Ostler Ulrike , Schäufele Rudi , Baca Cabrera Juan , Zhu Jianjun , Schleip Inga , Wingate Lisa , Schnyder Hans
Published: March 2021

We explore here our mechanistic understanding of the environmental and physiological processes that determine the oxygen isotope composition of cellulose (δ18Ocellulose). A new allocation-and-growth model was designed and added to the 18O-enabled soil-vegetation-atmosphere transfer model MuSICA to predict seasonal (April–October) and multi-annual (2007‑2012) variation of δ18Ocellulose and 18O-enrichment of leaf cellulose (Δ18Ocellulose) in a drought-prone, temperate grassland ecosystem. Modelled δ18Ocellulose agreed best with observations when integrated over c. 400 growing degree-days, similar to the average leaf lifespan observed at the site. Over the integration time, air temperature ranged from 7 to 22°C and midday relative humidity from 47 to 73%. Model agreement with observations of δ18Ocellulose (R2 = 0.57) and Δ18Ocellulose (R2= 0.74), and their negative relationship with canopy conductance, were improved significantly when both the biochemical 18O-fractionation between water and substrate for cellulose synthesis (ϵbio, range 26‑30‰) was temperature-sensitive, as previously reported for aquatic plants and heterotrophically grown wheat seedlings, and the proportion of oxygen in cellulose reflecting leaf water 18O-enrichment (1 ‑ pexpx, range 0.23‑0.63) was dependent on air relative humidity, as observed in independent controlled experiments with grasses. These recently published results (Hirl et al. 2020, The New Phytologist, doi: 10.1111/nph.17111) demonstrate that disentangling the physiological and climatic information in δ18Ocellulose requires quantitative knowledge of direct climatic effects on pexpx and ϵbio.
Parametric instability in the expanding solar wind
Authors: Verdini Andrea , Grappin Roland , Malara Francesco , Primavera Leonardo , Del Zanna Luca
Published: March 2021

Recent measurments of Parker Solar Probe show that alfvenic fluctuations in the solar wind often appear in the form of swithcback with constant total magnetic field. Our aim is to understand if and how such fluctuations can contribute to the heating or acceleration of the solar wind, via the Parametric Instability. The intability of one dimensional Alfvénic fluctuations has been extensively studied in both homogenoeus plasma and in the expanding solar wind, less so for the two-dimensional case which is closer to expected three-dimensional nature of switchbacks. In this work we study under which condition an Alfvén wave with a two dimensional spectrum (as introduced in Primavera et al ApJ 2019) can decay in the expanding solar wind and we will present preliminary results.
Long and short orbital forcing of Jurassic wildfires.
Authors: Hollaar Teuntje P. , Baker Sarah B. , Hesselbo Stephen P. , Deconinck Jean-Francois , Mander Luke , Ruhl Micha , Belcher Claire M.
Published: March 2021

Fire regimes are changing due to anthropogenic climatic drivers and fuel management challenges in all regions of Earth. However, the planet is also subject to natural background variability due to Earth’s orbital parameters (Milkankovitch cycles). To date no studies have assessed a sedimentary record that is sufficiently long or has a resolution that is high enough to assess both long eccentricity and precessional forcings on fire.  Here we present a ~350,000 yr record of wildfire activity, using fossil charcoal from Jurassic sediments.

The studied interval is part of the astronomically constrained Upper Pliensbachian of the Mochras borehole, Cardigan Bay Basin. The site was located within the Laurasian Seaway, south of the Viking Corridor that linked the north-western Tethys Ocean to the Boreal Sea, at a palaeolatitude of ~35°N. Clear lithological couplets of carbonate-rich and TOC-enhanced beds are observed, which show an orbital control on deposition. High resolution macrocharcoal (>125 um) and microcharcoal (10-125 um) abundance data have been obtained at a ~2 ky resolution over the studied interval. Charcoal data are coupled to estimates of variations in the hydrological cycle using clay mineral analyses, along with palynofacies and elemental analyses, and lithological and biogeochemical signatures.

We show that fire activity was strongly increased during (1) a period of maximum eccentricity (405,000 yr cycle) and (2) inferred maximum in seasonal contrast due to precession (20,000 yr cycles). In these periods with a strong seasonality, charcoal abundance indicates enhanced wildfire activity. This is coupled to a more seasonal pattern of rainfall as indicated by the relative abundance of smectite versus kaolinite. We argue that the shift to a more seasonal climate would have led to the increase in dry-adapted conifer forests. Conifers have biochemical and morphological traits that make them particularly flammable whether dry or live.This climate induced change in vegetation contributed to increased wildfire activity in the seasonal dry periods.

Increase in wildfire activity on an orbital time scale indicates that currently wildfires should be suppressed as Earth is close to an eccentricity minimum, such that man may have counteracted a relatively fire limited period.
A new sedimentary cover model for the southern area of the East European Platform and the Pre-Caucasus based on decompensation gravity anomalies data
Authors: Kaban Mikhail , Gvishiani Alexei , Sidorov Roman , Oshchenko Alexei , Krasnoperov Roman
Published: March 2021

A new model has been developed for the density and thickness of the sedimentary cover in a vast region at the junction of the southern part of the East European Platform, the Pre-Caucasus and some structures adjacent to the south, including the Caucasus. Structure and density of sedimentary basins was studied by employing the approach based on decompensation of gravity anomalies. Decompensative correction for gravity anomalies reduces the effect of deep masses providing compensation of near-surface density anomalies, in contrast to the conventional isostatic or Bouguer anomalies. . The new model of sediments, which implies their thickness and density, gives a more detailed description of the sedimentary thickness and density and reveals new features which were not or differently imaged by previous studies. It helps in better understanding of the origin and evolution of the basins and provides a background for further detailed geological and geophysical studies of the region.
Evaluation of PAZ satellite imagery for the assessment of intra-seasonal dynamics of permafrost coasts (Beaufort Sea, Canada)
Authors: Mora Carla , Vieira Gonçalo , Pina Pedro , Whalen Dustin , Bartsch Annett
Published: March 2021

Arctic permafrost coasts represent about 34% of the Earth’s coastline, with long sections affected by high erosion rates, increasingly threatening coastal communities. Year-round reduction in Arctic sea ice is forecasted and by the end of the 21st century, models indicate a decrease in sea ice area from 43 to 94% in September and from 8 to 34% in February (IPCC, 2014). An increase of the ice-free season leads to a longer exposure to wave action. Monitoring the Arctic coasts is limited by remoteness, climate harshness and difficulty of access for direct surveying, but also, when using satellite remote sensing, by frequent high cloudiness conditions and by illumination. In order to overcome these limitations, three sites at the Beaufort Sea Coast (Clarence lagoon, Hopper Island and Qikiqtaruk/Herschel Island) have been selected for monitoring using very high-resolution microwave X-band spotlight PAZ imagery from Hisdesat. Bluff top, thaw-slump headwalls and water lines were digitised from images acquired during the ice-free seasons of 2019 and 2020 at sub-monthly time-steps. The effects of coastal exposure on delineation accuracy in relation to satellite overpass geometry have been assessed and coastal changes have been quantified and compared to meteorological and tide-gauge data. The results show that PAZ imagery allow for monitoring and quantifying coastal changes at sub-monthly intervals and following the evolution of coastal features, such as small mud-flow fans and retrogressive thaw slumps. This shows that high resolution microwave imagery has a strong potential for significantly advancing coastal monitoring in remote Arctic areas. This research is part of project Nunataryuk funded under the European Union's Horizon 2020 Research and Innovation Programme (grant agreement no. 773421) and of Hisdesat project Coastal Monitoring for Permafrost Research in the Beaufort Sea Coast (Canada). 
A comparison between coincident laser and Ku radar versus S- to C-band 'snow radar' data for airborne retrievals of snow depth on sea ice
Authors: de Rijke-Thomas Claude , Landy Jack , King Joshua , Tsamados Michel
Published: March 2021

Snow depth estimates remain a large uncertainty for constraining the accuracy of sea ice thickness retrievals from polar altimetry. There have been several recent investigations into methods for estimating snow depth from airborne observations over sea ice; this poster outlines a comparison between two different methods applied to Operation IceBridge data from the Spring 2016 campaign. The first co-locates visible-band laser scanner data from the Airborne Topographic Mapper with Ku-band data from the CReSIS radar, using a fixed threshold first-maximum retracker algorithm for retracking radar waveforms and applying a calibration step to remove the vertical offset between sensors at leads. This method represents an airborne proxy for the newly-aligned ICESat-2 and CryoSat-2 orbits of the Cryo2Ice campaign. The second method uses the conventional CReSIS ultrawide-band frequency‐modulated continuous‐wave ‘snow radar’ system, that ranges between S- and C-band, applying the retracker algorithm described by Newman et al 2014. We evaluate properties of the estimated snow depth distribution, and alignment of air-snow and snow-ice interfaces, along the aircraft track and the scale of correlation between sensors.
A Comparison of Machine Learning Algorithms for the Segmentation and Classification of Snow Micro Penetrometer Profiles on Arctic Sea Ice
Authors: Kaltenborn Julia , Clay Viviane , Macfarlane Amy R. , King Joshua Michael Lloyd , Schneebeli Martin
Published: March 2021

Snow-layer classification is an essential diagnostic task for a wide variety of cryospheric science and climate research applications. Traditionally, these measurements are made in snow pits, requiring trained operators and a substantial time commitment. The SnowMicroPen (SMP), a portable high-resolution snow penetrometer, has been demonstrated as a capable tool for rapid snow grain classification and layer type segmentation through statistical inversion of its mechanical signal. The manual classification of the SMP profiles requires time and training and becomes infeasible for large datasets.

Here, we introduce a novel set of SMP measurements collected during the MOSAiC expedition and apply Machine Learning (ML) algorithms to automatically classify and segment SMP profiles of snow on Arctic sea ice. To this end, different supervised and unsupervised ML methods, including Random Forests, Support Vector Machines, Artificial Neural Networks, and k-means Clustering, are compared. A subsequent segmentation of the classified data results in distinct layers and snow grain markers for the SMP profiles. The models are trained with the dataset by King et al. (2020) and the MOSAiC SMP dataset. The MOSAiC dataset is a unique and extensive dataset characterizing seasonal and spatial variation of snow on the central Arctic sea-ice.

We will test and compare the different algorithms and evaluate the algorithms’ effectiveness based on the need for initial dataset labeling, execution speed, and ease of implementation. In particular, we will compare supervised to unsupervised methods, which are distinguished by their need for labeled training data.

The implementation of different ML algorithms for SMP profile classification could provide a fast and automatic grain type classification and snow layer segmentation. Based on the gained knowledge from the algorithms’ comparison, a tool can be built to provide scientists from different fields with an immediate SMP profile classification and segmentation. 

 

King, J., Howell, S., Brady, M., Toose, P., Derksen, C., Haas, C., & Beckers, J. (2020). Local-scale variability of snow density on Arctic sea ice. The Cryosphere, 14(12), 4323-4339, https://doi.org/10.5194/tc-14-4323-2020.
A semplified method for flood risk evaluation at micro-scale level in Benevento city (Southern Italy)
Authors: Festa Gianna Ida , Revellino Paola , Guadagno Francesco Maria , Guerriero Luigi , Focareta Mariano , Meoli Giuseppe
Published: March 2021

In the latest decades, the impact of floods has generated an increase of loss of human lives, as well as the interruption of economic activities in the affected areas. In this context, we present an implemented methodology for micro-scale flood risk evaluation that considers direct and tangible damages as a function of the hydrometric height and allows for quickly estimates of the damage level caused by alluvial events. The method has been applied and tested for economic and residential buildings in the town of Benevento (southern Italy), which was hit by destructive floods in the past. As the limitation of this original method is connected to the huge amounts of input data, we tried to overcome this limit by applying a simplified procedure in defining the physical data of buildings (e.g. type of buildings, n° of floors, presence of cellar). More specifically, during data collection on building features, two different criteria were used:1) data were acquired through a careful field survey, and 2) data were obtained through the topographical database of the Campania region and through the generalization of heights for each type of building. Data obtained using the first criterion result in a highly accurate risk assessment but, at the same time, the method is non-immediate and time-consuming. On the other hand, the second one is more expeditious. By comparison, the two criteria show very similar results and minimal differences, making the generalized data acquisition the most expeditious. In conclusion, the basic method allows estimating highly detailed potential losses for representative buildings categories in the urban context, but involves a higher degree of resolution; the generalised method, instead, thought the simplification of the data, responds to the need of reaching in a short time a damage value extremely similar to the real one.
Representation of tropical convection in a near-global convection permitting seasonal simulation with WRF
Authors: Warrach-Sagi Kirsten , Schwitalla Thomas , Wulfmeyer Volker
Published: March 2021

Precipitation observations between March to May 2015 show several coherent propagating systems in an area between 10°N and 10°S with a lifetime of 3-4 weeks demonstrating the importance of simulations beyond a month. The eastward propagation speed is typically 1100 km day-1. The main origins of significant amounts of precipitation along this belt are the tropical warm pools in the Western Pacific around 158-174°E and the eastern Indian Ocean around 90°E as well as the tropical rainforest over South America around 69°W.

We investigated the lifetime and propagation of tropical precipitating systems based on observations and a near-global convection permitting seasonal simulation with the Weather Research and Forecasting (WRF). The latitude-belt simulation covers an area between 57°S to 65°N with a grid increment of 0.03° over a period of 5 months forced by sea surface temperature (SST) observations.

Results of this simulation with respect to tropical convection were investigated by means of comparison with satellite-based cloud and precipitation observations and ECMWF operational analysis. Wavenumber-frequency spectra of the tropical convection and the detection of various wave pattern were derived from the 3-h outgoing longwave radiation at the top of the atmosphere (TOA OLR) fields and revealed by Wheeler-Kiladis diagrams. The simulation shows the observed spectral signatures of eastward propagating EIGs and Kelvin waves.

The EOF decomposition of the monthly averaged sea level pressure fields demonstrates that 65 % of the sea surface pressure fluctuations in the ECMWF analyses can be explained by the correlation pattern shown in the 1st EOF. The agreement with the 1st EOF of the WRF simulation is excellent despite a slight underestimation of the strength of the correlations. The spatial structure is very similar and 61 % of the variance are contained in first EOF. The EOF analyses provided strong evidence that the seasonal simulation with a convection permitting horizontal resolution captures the representation of the teleconnection pattern.