bluuebunny/crossref_metadata_2025 huggingface dataset:
Modification of icy planetesimal interiors by early thermal evolution and collisions
Authors: Golabek Gregor , Jutzi Martin
Published: March 2022

In the early solar system radiogenic heating by 26Al and collisions are the two prominent ways expected to modify the internal composition of icy planetesimals, building blocks of comets, by removing highly volatile compounds like CO, CO2 and NH3. However, observations indicate that even large comets like Hale-Bopp (R ≈ 35 km) can be rich in these highly volatile compounds [1].
Here we constrain under which conditions icy planetesimals experiencing both internal heating and collisions can retain pristine interiors [2]. For this purpose, we employ both the state-of-the-art finite difference marker-in-cell code I2ELVIS [3] to model the thermal evolution in 2D infinite cylinder geometry and a 3D SPH code [4] to study the interior heating caused by collisions among icy planetesimals. For simplicity we assume circular porous icy planetesimals with a low density (≈ 470 kg/m3) based on measurements for comet 67P/Churyumov-Gerasimenko [5].
For the parameter study of the thermal history we vary (i) icy planetesimal radii, (ii) formation time and the (iii) the silicate/ice ratio. For the latter we keep the mean density fixed and change the porosity of the icy planetesimal. For the impact models we use porous, low-strength objects and vary (i) target and (ii) projectile radii, (iii) impact velocity as well as (iv) impact angle. Potential losses of volatile compounds from their interiors are calculated based on their critical temperatures taken from literature [6]. Our combined results indicate that only small or late-formed icy planetesimals remain mostly pristine, while early formed objects can even reach temperatures high enough to melt the water ice.

REFERENCES
[1] Morbidelli & Nesvorný, In: The Trans-Neptunian Solar System. 25–59 (2019). [2] Golabek & Jutzi, Icarus 363, 114437 (2021). [3] Gerya & Yuen, Phys. Earth Planet. Int. 163, 83-105 (2007). [4] Jutzi, Planet. Space Sci. 107, 3–9 (2015). [5] Sierks et al., Science 347, 1044 (2015). [6] Davidsson et al., Astron. Astrophys. 592, A63 (2016).
Multiscale analysis of physical rock properties at Stromboli Volcano: what controls the frictional properties?    
Authors: Alcock Thomas , Vinciguerra Sergio , Benson Phillip
Published: March 2022

Stromboli volcano, located in the north-easternmost island of the Aeolian archipelago (Southern Italy) and well known for its persistent volcanic activity, has experienced at least four sector collapses over the past 13 thousand years. The most recent activity resulted in the formation of the Sciara del Fuoco (SDF) horseshoe-shaped depression and a tectonic strain field believed to have promoted flank collapses and formed a NE / SW trending weakness zone across the SDF and the western sector of the island. The tectonic strain field interplayed with dyking and fracturing appears to control the episodes of instability and the onset of slip surfaces. This study presents new data identifying areas of damage that could promote fracturing via remote sensing and rock friction measurements taken on rocks around the SDF and the coupled “weak” zone. We have carried out a multiscale approach by integrating satellite observations with block and sample scale physical and mechanical properties and frictional tests carried out in triaxial configuration on cm scale slabs. Over 5000 individual fractures have been at first processed through the MatLab toolbox FracPaQ to determine fracture density, slip and dilatancy tendency around the collapse scarp with results showing that dilation and slip 0.6< is more common the northern side of the SDF as well as around areas of eruptive activity.

Key units have been sampled on the field (Paleostromboli, Vancori and Neostromboli) with reference to SDF and the weak zone. Physical and mechanical properties defined using elastic wave velocities, electrical resistivity, uniaxial compressive strength and elastic moduli have been assessed and inverted for comparison to field scale geophysical investigations. Finally, direct-shear tests in triaxial configuration were carried out to explore the frictional properties using rectangular basalt slabs at 5 – 15 MPa confining pressure in dry and saturated conditions. Preliminary results show a variation in the friction coefficient (µ) between 0.55 and 0.7 with a general µ decrease with increasing confining pressure and saturation. The most porous Neostromboli units show the lowest friction.  This suggests that the textural and pre-existing crack damage variability due to the complex and different magmatic history and cooling rates do control the evolution of the frictional properties and evolving fracturing processes. Further work will structurally quantify the slip evolution throughout post-mortem microstructural observation in order to interpret the relations to the field scale weakness zone and the SDF.
Could the moderate-sized earthquakes trigger pre-seismic ionospheric irregularities? Study of the 2011 Murcia earthquake in the Mediterranean region (SE-Spain).
Authors: Tachema Abdennasser
Published: March 2022

The interest of this research work is focused on the detection of possible pre-seismic perturbations related to medium-sized earthquakes (5≤Mw≤5.9) occurring in the upper ionized atmosphere (about 350 km above the Earth, ionospheric F2-region). For this specific purpose, we have exploited several geodetic data, derived through signal processing of dual-frequency permanent ground-based Global Positioning System (GPS)/Global Navigation Satellite Systems (GNSS) receivers, located at the Euro-Mediterranean basin.

To find out whether the ionospheric F2-layer is responsive to the energy released during the preparation periods of medium magnitude earthquakes, the Lorca seismic event (May 11th, 2011, Mw 5.1, Murcia region) was taken as an initial sample. For this shallow-focus earthquake (4 km depth), the longitude-latitude coordinates of the epicenter are 1.7114° W, 37.7175° N. As result, modeling regional ionosphere using GPS/GNSS-total electron content (TEC) measurements over the epicentral area through spherical harmonic analysis, allowing us to identify pre-earthquake ionospheric irregularities in response to the M5.1 Lorca event. After discerning the seismo-ionospheric precursors from those caused by space weather effects, via wavelet-based spectral analysis, these irregularities were identified about a week before the onset of the mainshock.

The seismo-geodetic technique adopted in this study validates our hypothesis that stimulates the existence of a strong correlation between deep lithospheric deformations and pre-seismic ionospheric anomalies due to moderate magnitudes.

Keywords: Murcia earthquake, Seismo-ionospheric precursors, Spherical harmonic analysis, Wavelet transform, GPS/GNSS-TEC, Lithospheric deformations, Regional F2-ionosphere maps.
Spatio-temporal patterns of NEE based on upscaling eddy covariance measurements in the alpine grassland of the Tibetan Plateau
Authors: Wang Yuyang , Ma Yaoming
Published: March 2022

By integrating data from 25 flux observation sites in the alpine grasslands of the Tibetan Plateau with corresponding remote sensing and reanalysis data, a data-driven Extremely Randomized Trees regression (ETR) was used to estimate the NEE of alpine grasslands on the Tibetan Plateau from 1982-2018. The spatial and temporal variation patterns of the NEE were also analyzed. The results show that the annual mean NEE of alpine meadows on the Tibetan Plateau from 1982 to 2018 was -35.59 g C m-2 yr-1, and showed a significant decreasing trend at -0.78 g C m-2 yr-1; on the spatial scale, the alpine meadows in the relatively wet eastern and northeastern parts of the Tibetan Plateau were strong carbon sinks with the intensity around -150 ~ -100 g C m-2 yr-1. From the alpine meadows in the east to the semi-arid or arid alpine grasslands in the west and north, the carbon sink intensity gradually decreased along the longitudinal gradient and becomes a weak carbon sink or a weak carbon source (0 ~ ± 20 g C m-2 yr-1). The sensitivity analysis showed that precipitation and mean temperature contributed significantly to the interannual trend variation of NEE in grasslands on the Tibetan Plateau during the 1982-2018. The contribution of precipitation was large in the alpine steppe region in the western and northwestern part of the plateau, while the contribution of mean temperature was highest in the alpine meadow region in the east and south, where precipitation dominated 84% of the interannual NEE variation of the entire alpine steppe region, while mean temperature accounts for 55% of that of the alpine meadow region. In general, the interannual variability of NEE in the alpine steppe region tended to be dominated by precipitation, while the alpine meadow region tended to be regulated by temperature. In addition, the NEE of alpine meadow region showed a significant decreasing trend with -0.91 and -0.67 g C m-2 yr-1 during 1982-1999 and 2000-2018, respectively, while the alpine steppe region showed a non-significant decreasing trend change with -0.37 and -0.19 g C m-2 yr-1, respectively. The different changes of NEE in different vegetation type regions at different time periods were mainly caused by the changes of temperature and precipitation.
The ROM SAF radio occultation climate data records and trend analyses
Authors: Lauritsen Kent B. , Gleisner Hans , Nielsen Johannes K. , Syndergaard Stig
Published: March 2022

Many studies have by now demonstrated the accuracy of GNSS Radio Occultation (RO) data, and their usefulness as a stable climate reference. Homogeneity of the data records are obtained by reprocessing of the data using uniform processing software throughout the length of the climate record. Version 1 of the ROM SAF Climate Data Record (CDR), based on Metop, CHAMP, GRACE, and COSMIC data, covers a continuous 15-year period from 2002 to 2016. The CDR is extended in time by an Interim CDR (ICDR) which is regularly updated nearly up to present time, and the combined time series is now long enough (20 years) to begin detection of climate trends. We here present results from recent climate applications of RO data: bending angle and temperature trends in the upper troposphere and stratosphere, including the first RO contribution to the IPCC 6th Assessment Report. Furthermore, we outline ROM SAF plans for generating RO climate data records. This includes calculating uncertainty estimates and generating homogenized water vapour climate data records based on a one-dimensional variational retrieval using detrended background data.

The Radio Occultation Meteorology Satellite Application Facility (ROM SAF) is a decentralized operational processing facility under EUMETSAT. The main objective of the ROM SAF is to generate and deliver operational radio occultation products from GNSS RO instruments onboard Metop, Metop-SG, Sentinel-6 Michael Freilich and other satellites for NWP and climate applications. The ROM SAF CDR and ICDR is publically available from: http://www.romsaf.org. Further information about the ROM SAF products and services are available at this website.
Large scale installation of multilayer blue-green roofs as solution for a sustainable urban water management
Authors: Cristiano Elena , Annis Antonio , Viola Francesco , Deidda Roberto , Nardi Fernando
Published: March 2022

The modern society is facing multiple challenges, that are reshaping urban areas: the fast population growth, with a consequent high urbanization, combined with an increase of the average temperature and an intensification of extreme rainfall events, facilitates the pluvial flood risk in cities. Several solutions have been proposed in the literature to mitigate the runoff generation from rooftops and to contribute to a sustainable water management. In this context, multilayer blue-green roofs incorporate the high retention capacity of traditional green roofs with the storage capacity that characterizes rainwater harvesting systems. Moreover, these innovative nature-based solutions present countless benefits for the creation of smart, resilient and sustainable cities, e.g., they contrast the urban heat island, reducing the surrounding air temperature, they contribute to the building thermal insulation, limiting the energy consumption, they attract multiple species of insects and small animals, increasing the biodiversity, etc. 

The potential impacts of multilayer and traditional blue-green roofs and rainwater harvesting systems on the runoff generation reduction have been investigated mostly at local scale, analysing the impact of the installation of these tools on single buildings. However, in order to estimate and to evaluate the potential benefits and limitations for a sustainable urban development, it is fundamental to simulate the potential implications of a large-scale installation of these tools on large neighbourhoods or entire cities. For these reasons, in this work we simulate the installation of multilayer blue-green roofs on all the suitable roofs of the cities of Cagliari and Perugia (Italy). Thanks to the two multilayer blue-green roofs, installed in Cagliari and Perugia as part of the EU Climate-KIC Polderroof field lab project, it was possible to calibrate an ecohydrological model to simulate the potential retention and storage capacities of these nature based solutions. The potential discharge reduction and water storage capacity at large urban scale are discussed using as input for the model long historical time series of local rainfall and temperature.
Intra-seasonal characteristics of cold winters in Europe
Authors: Ionita-Scholz Monica , Scholz Patrick , Nagaviuc Viorica
Published: March 2022

Extreme cold spells exert serious impacts on society by affecting agriculture, the energy supply and the environment. In this respect, here we investigate the spatio-temporal characteristics of extremely cold winters in Europe over the last 70 years and their large-scale drivers. The characteristics of extreme cold events (e.g. magnitude, frequency, trends) are investigated in terms of month-to-month variability from December to March. Overall, we observed a significant decreasing trend both in the length and the frequency of cold spells at the European level. Long-lasting cold spells are most frequent in January in the south-eastern part of Europe and in March over the central part of Europe. The most severe cold spells occurred in 1955/1956, 1962/1963, and 2010/2011. Widespread cold extremes over the central and the northern part of Europe are favored by the negative phase of North Atlantic Oscillation, associated with advection of continental air masses from the east, clear skies and negative anomalies in downward longwave radiation. Over the Mediterranean region, cold spells are less common and are mainly influenced by the East Atlantic teleconnection pattern. Our results add to the understanding of the spatio-temporal variability of cold winters, at the European level, as well as their driving mechanisms.
Efficiency of different signal processing methods to isolate signature characteristics in altimetric water level measurements
Authors: Iran Pour Siavash , Eicker Annette , Balidakis Kyriakos , Karimi Hamed , Amiri-Simkooei Alireza , Dobslaw Henryk
Published: March 2022

Observed time-series of water transport in rivers can be perceived mathematically as a superposition of non-linear long-term trends, periodic variations, episodic events, colored instrument noise, and other components. Various statistical methods are readily available to extract and quantify both stationary and non-stationary components in order to subsequently attribute parts of the signal to underlying causal mechanisms. However, the available algorithms differ vastly in terms of computational complexity and implicit assumptions, and may thus have their own individual advantages and disadvantages. By employing a suite of time-series analysis methods for 1D (Wavelets, Singular Spectrum Analysis, Empirical Mode Decomposition) and additional statistical assessments like Pruned Exact Linear Time (PELT) tests for change point detection, we will analyze data from two virtual stations at Elbe River (Germany) and Urmia Lake (Iran) that are representative for the central European region with a rather humid climate, and the more arid conditions of Central Asia with much smaller hydrological signal variations, respectively. It is in particular the latter region with a much less developed in situ hydrometeorological observing system, where we expect that carefully processed geodetic data might contribute most to the monitoring of large-scale terrestrial water dynamics. This contribution will highlight the benefits of more advanced signal analysis methods for extracting relevant hydrometeorological information over more conventionally applied algorithms.
Ion-molecule reaction laboratory experiments show that iodine oxides explain CIMS atmospheric observations attributed to iodine oxoacids 
Authors: Gomez Martin Juan Carlos , Lewis Thomas R. , James Alexander D. , Plane John M. C. , Saiz-Lopez Alfonso
Published: March 2022

Iodine chemistry is a driver of new particle formation in the marine and polar boundary layer, with potential influence on cloud formation and properties. There are however conflicting views about how iodine gas-to-particle conversion proceeds. Laboratory studies indicate that iodine photooxidation yields iodine oxides, which are well-known particle precursors1. By contrast, nitrate ion chemical ionization mass spectrometry (CIMS) field and environmental chamber observations have been interpreted as evidence of nucleation of iodine oxoacids2,3. Here, we report flow tube laboratory experiments showing that iodine oxides react with nitrate core ions to generate the same ions observed by CIMS instruments. Therefore, we conclude that molecules unlikely to form in the atmosphere in the gas-phase such as iodic acid are not necessary to explain CIMS field measurements, but rather obscure their meaning, whereas iodine oxides explain the field observations and provide a thermochemically feasible mechanism to model the climatic impact of iodine-containing particles. In addition, we propose that a key iodine reservoir species such as iodine nitrate, which we observe as a product of the reaction between iodine oxides and the nitrate anion, can be also detected by CIMS in the atmosphere and has been potentially overlooked in previous field observations4.

References

1 Gómez Martín, J.C., et al. A gas-to-particle conversion mechanism helps to explain atmospheric particle formation through clustering of iodine oxides. Nat. Commun., 11, 4521, https://doi.org/10.1038/s41467-020-18252-8, 2020

2 Sipilä, M., et al. Molecular-scale evidence of aerosol particle formation via sequential addition of HIO3. Nature 537, 532–534, https://doi.org/10.1038/nature19314, 2016.

3 He et al., Role of iodine oxoacids in atmospheric aerosol nucleation, Science, 371, 589–595, https://doi.org/10.1126/science.abe0298, 2021.

4 Baccarini et al. Frequent new particle formation over the high Arctic pack ice by enhanced iodine emissions, Nat. Commun., 11, 4924, https://doi.org/10.1038/s41467-020-18551-0, 2020.
Statistical study of oxygen ion cyclotron harmonic waves observed by Van Allen Probes
Authors: Wang Yan , Liu Kaijun , Min kyungguk , Yao Fei , Xiong Ying , Cheng Kun , Liu Yuqi , Zheng Xianming , Zhou Jingyi
Published: March 2022

We report the first statistical survey of the oxygen ion cyclotron harmonic waves observed by Van Allen Probes throughout the mission. An example event observed on 19 February 2014 after a strong magnetic storm and a substorm was first presented to demonstrate the general properties of OCH waves. The observed waves have multiple spectral peaks around harmonics of the oxygen ion gyrofrequency. During the event, oxygen ionsof 10s keV had a ring-like partial shell velocity distribution which might have driven the wave excitation through the oxygen ion Bernstein instability. On the other hand, the phase space densities of He+ and O+ less than a few hundred eV were larger around 90° pitch angle, indicating transverse heating of these ions. Our statistical study shows that the waves occurred over 2 < L < 6 and across all magnetic local time. More than 50% of the events were observed just outside the plasmapause, and the typical wave amplitude is between ~0.1 and several nT. The frequency spacing between two consecutive wave harmonics decreases with increasing L but stabilizes when L > 5. The frequency spacing is larger than the local oxygen ion gyrofrequency for many events, especially those observed at larger L, suggesting that these waves propagated there from lower L shell regions. The waves are mainly on the dayside at L > 4 under quiet geomagnetic conditions, but can occur at lower L shells with a more uniform MLT distribution under more active geomagnetic conditions.
Dynamic effects of the Tibetan Plateau on the sustained drought in southwest China
Authors: Ye Yiwei , Tian Rongxiang
Published: March 2022

A continuous drought event happened in Southwest China from the winter of 2009 to the spring of 2014, which has a wide range of impacts and a long duration, causing great economic losses to southwest China.  This research focuses on the dynamic field anomalies of the Tibetan Plateau during this event using statistical analysis methods. Moreover, a further conclusion is drawn about the mechanism of the dynamic effect of the Tibetan Plateau on drought in Southwest China. And a regression model is given. Here we show that, the absolute values of relative divergence, relative vorticity and vertical velocity of the lower layer over the Tibetan Plateau were abnormally low during the winter half year from 2009 to 2014, that is, the downdraft and anticyclone over the Tibetan Plateau were weaker than usual. It would weaken the southward cold airflow from the north of the Tibetan Plateau, while the westerly wind from dry central Asia would intensify on the south of the plateau. As a result, the intersection position of the cold and warm air shifted to north and to east, so that a larger area of the southwest China was controlled by the warm and dry air mass, which was against the precipitation. The conclusion and regression model will be referential to the forecast of drought in Southwest China and help reduce damages.
An integrated two-layer model for simulating shallow flow, sediment transport and overtopping-induced breach processes
Authors: Zhao Jiaheng , Hou Jingming , Özgen Xian Ilhan , Wang Tian , Hinkelmann Reinhard
Published: March 2022

Extreme rainfall may generate flash floods, which may overtop the flood defences (e.g., dam, dike, and levees) and subsequently lead to structure failure, threatening the safety of the downstream population and properties. This work presents a new two-layer modelling approach to simulate surface water flooding and the subsequent dam/dike breach process caused by overtopping. The new modelling framework simulates the surface water flooding process in the upper layer using a high-resolution hydrodynamic model that also considers sediment transport and morphodynamic change. A cell-based infinite slope model is implemented to identify unstable slope/soil and estimate the sliding depth for the lower layer. And a cellular automaton method based on diffusion-wave assumption is further developed to simulate the dynamics of the resulting bed granular movement. The momentum and bed elevation source terms of the hydrodynamic governing equations (the flood layer) and the soil depth of debris flow (the granular layer) are simultaneously calculated in a fully coupled way. This results in a fully coupled flooding induced breach chain model. The proposed model is validated against experimental and real-world tests with different breach types. And the sensitivities of calibrated parameters and mesh sizes are discussed in detail. The results indicate that the proposed model can simultaneously simulate overtopping flooding and the associated slope failure and breach processes.
Deep groundwater – the most vulnerable part of the water cycle to climate change
Authors: Lischeid Gunnar
Published: March 2022

Deep groundwater is the backbone of the regional water cycle, ensuring stream baseflow even after extended drought periods. The thicker the overlying vadose zone the more groundwater head dynamics is buffered against short-term fluctuations of groundwater recharge.  Thus deep groundwater is usually considered to be the least susceptible to climate change effects. However, the opposite is true. Long-term trends (20-41 years) of groundwater head in more than 200 wells in a 50,000 km2 region in Northeast Germany have been analysed. Both increasing and decreasing trends were found, irrespective of land use, geology, etc. Factoring out local, mostly anthropogenic effects from the time series did hardly affect the results. In contrast, sign and size of long-term trends was very closely related to the degree of damping of the groundwater recharge signal. Damping was clearly related to mean depth to groundwater. The stronger the damping the more clearly groundwater head exhibited a 40-year decrease, whereas positive trends were found only for shallow groundwater sites.

A thorough analysis revealed a fundamental but widely ignored physical cause for these counter-intuitive results. From a thermodynamic perspective, seepage flux in the vadose zone can be described as dissipation of a hydrological input signal. This dissipation is subject to dispersion: The vadose zone acts as a low-pass filter due to preferential damping of the high frequency part of the input signal, recognizable by strong smoothing of soil hydrological time series at greater depth. Consequently, the smoother the time series the more probably a trend analysis would indicate a long-term monotonic increase or decrease even when no trend can be detected in the corresponding input signal. Note that in terms of spectrum analysis climate can be defined as a low-pass filtering of weather dynamics. Then it is only logical that deep groundwater as the part of the water cycle with the strongest low-pass filtering would be the first to clearly exhibit climate change signals.

This interpretation is consistent with an alternative perspective in terms of hydrological processes: The more shallow the groundwater, the more likely seepage flux will reach down to the groundwater table even after minor rain storms due to a smaller soil volume that needs to be refilled and to preferential flow. Consequently, groundwater recovers more rapidly from drought here. This holds especially true for groundwater in the riparian zone where most of the short-term response of stream discharge to rain storms is generated. In fact, none of these streams exhibited any clear trend. However, discharge in minor streams and water level in lakes at mid-slope positions already started to decline during the last decade. We would do well taking deep-groundwater dynamics as an early warning tool against climate change effects.
Incipient lithospheric collision throughout the East Mediterranean
Authors: Fernández-Blanco David , R. Ranero César
Published: March 2022

We propose that lithospheric collision of Africa and Eurasia is incipient throughout the entire East Mediterranean. Our evidence confirms the incipient continent-continent collision that has been recently proposed for the Cyprus Arc and showcases how collision is expressed at depth and across the Hellenic Arc. We provide evidence of basin-wide lithospheric-scale collision by coupling, at tectonic scale (1.5M km2), quantitative joint analysis of submarine and terrestrial relief, and the interpretation of a compilation of regional vintage multichannel seismic data (>46.000 km), reprocessed with modern techniques. No megathrust surface marking a subduction interplate contact is imaged in any seismic line, and the relief across sedimentary piles is not shaped as mechanically-accreted wedges. Instead, continent-continent collision is expressed across plates in two modes along longitude. In the offshore regions south of Cyprus and Crete, submarine thrust systems with no frontal structure nor imbrication, and lacking latitudinal continuation, record collision stacking basin sediments vertically. Onshore, concurrent uplift and extension are recorded by uplifting strandlines, hanging valleys, and normal faulting, in both continents, and neatly so in the African margin in front of Crete. Joint plate deformation at lithospheric scale is further inferred as wavelengths of relief coherent across both plates. Regions located latitudinally to these collisional sites extrude away obliquely, either rigidly along transpressional systems, as immediately east of Cyprus and Crete, or through flow and halokinesis of Messinian salts, as on the eastern and western sectors of the Mediterranean Ridge. Our evidence typifies incipient lithospheric collision as expressed throughout the East Mediterranean.
Combining active-learning approaches with support vector machines for landslide mapping
Authors: Wang Zhihao , Brenning Alexander
Published: March 2022

Cost-effective spatial landslide models play a critical role in landslide mapping after an event and landslide susceptibility modelling for spatial planning and hazard mitigation. Challenges faced by many researchers in compiling the necessary landslide inventories are the time-consuming instance labelling and imbalanced data when training machine-learning models. Active learning is a practical way of reducing labelling costs by selecting more informative instances for labelling by an expert. Although this method has increasingly been adopted in remote-sensing classification, it is relatively new in the context of landslide mapping. To test the performance and potential benefits of active learning in this context, we combined two common active learning strategies, uncertainty sampling and query by committee with a state-of-the-art machine-learning technique, the support vector machine (SVM). Their utility is illustrated in a case study in the Ecuadorian Andes by comparing their performances to SVMs with simple random sampling of training locations. Based on the mean AUROC (area under the receiver operating characteristic curve) as a performance measure, SVMs with uncertainty sampling tended to perform better than random sampling and query-by-committee strategies. Meanwhile, uncertainty sampling achieved more stable performances according to a lower AUROC standard deviation across repetitions. Taken together, under limited data conditions, active learning with uncertainty sampling is more efficient by selecting more informative instances for SVM training. Therefore, we suggest that this strategy can be incorporated into the workflow of interactive landslide modeling not only in emergency response settings but also to more efficiently generate landslide inventories for event-based landslide susceptibility modeling.
Recent advances in global analysis of critical infrastructure networks in a changing climate
Authors: Hall Jim , Russell Tom , Verschuur Jasper , Pant Raghav , Robertson Max , Lestang Thibault , Tkachenko Nataliya , Lamb Rob , Oughton Edward
Published: March 2022

There has been rapid progress in the development of capabilities to analyse infrastructure networks on very large scales, up to global scales. This is enabled by the growing availability of geospatial data products with global coverage and computational capabilities, which enable processing of these datasets and analytics on large-scale. Global analyses of the risks from climatic hazards to infrastructure networks serve several important purposes:

Quantified risk estimates in future climate scenarios contribute to the overall picture of the scale of climate risks worldwide, which helps to motivate climate mitigation and adaptation.

Geospatial analysis of hotspots of infrastructure vulnerability helps to target adaptation actions.

Cost-benefit analysis of adaptation enables the prioritization of scarce adaptation resources.

Quantified climate risk analysis is increasingly required for financial disclosure of physical climate risks by infrastructure investors.

There are inevitable limitations to global-scale analyses, but they enable cross-country comparisons, and the monitoring of changing risks and national infrastructure resilience. Global analyses also provide a convenient starting point for national analyses and a motivation to collect better data to inform national-scale decisions.

 

Here we present recent developments in capability for global-scale climate risk analysis to infrastructure networks. The analysis combines (i) global-scale probabilistic hazard layers (including floods, hurricanes and coastal storm surges); (ii) infrastructure asset and network exposure, for energy, transport and telecommunications networks (iii) analysis of the people and economic activities that are dependent upon these networks. This quantified risk analysis framework has been efficiently implemented for global-scale computations, yielding new results on the scale of climate-related risks. Analysis of resource flows on networks and their connection to infrastructure users is enabling calculation of the numbers of people and economic activity that may be disrupted in catastrophic events. A recent development has been in the introduction of probabilistic event sets for hurricanes and flooding, which enables accurate estimation of the impacts from spatially extensive extreme events. The research is being made available as part of the Global Resilience Index Initiative https://www.cgfi.ac.uk/global-resilience-index-initiative/ and as an open source toolset and interface for geospatial visualisation.

 

 

 

 
Plasmoid-dominated turbulent reconnection in symmetric and asymmetric systems
Authors: Zenitani Seiji , Yamamoto Momoka , Miyoshi Takahiro
Published: March 2022

In magnetohydrodynamics (MHD), magnetic reconnection has been discussed by three theoretical models: Sweet--Parker reconnection, Petschek reconnection, and plasmoid-dominated turbulent reconnection. Among these models, properties of plasmoid-dominated reconnection remain unclear, because it was discovered only recently. In this talk, we explore basic properties of plasmoid-dominated reconnection in a low-beta plasma such as in a solar corona, by using large-scale MHD simulations [1]. We have found that the system becomes highly complex due to repeated formation of plasmoids and shocks. We have further found that the reconnection rate goes higher than previously thought. Next we explore influence of asymmetry in background plasma densities in plasmoid-dominated reconnection. We have found that the average reconnection rate follows Cassak-Shay's hybrid relation [2]. Many signatures become asymmetric across the reconnection layer, and plasmas inside the plasmoids start to swirl in specific directions. Formation processes of these vortices and a potential extension of our numerical survey will be discussed.

References:
[1] S. Zenitani and T. Miyoshi, Astrophys. J. Lett., 894, L7 (2020)
[2] P. A. Cassak and M. A. Shay, Phys. Plasmas, 14, 102114 (2007)
Observed inter-annual melt rate variability beneath the Filchner-Ronne Ice Shelf
Authors: Vankova Irena , Nicholls Keith
Published: March 2022

We have assessed inter-annual melt rate variability at the base of the Filchner-Ronne Ice Shelf using in-situ phase sensitive radars and historic data from ocean moorings. We have identified several oceanographic features beneath the ice shelf. Near the western Ronne ice front we have inferred seasonal lateral shifts in an Ice Shelf Water outflow current. Deeper in the western Ronne part of the cavity we have found little inter-annual variability over the 13-year long record except for three different modes of seasonal cycle expression in basal melting, the causes of which would be consistent with year-to-year stratification and circulation changes, depending on the mode. Contrary to that, in the southeastern part of the Ronne cavity, along the main barotropic flow pathway, the shape of the seasonal melt rate cycle does not substantially change from year to year, with inter-annual melt rate variability superimposed on top of it. In addition to providing insight into the ocean circulation beneath the ice shelf, these data also serve as a valuable benchmark for melt rate estimates derived using satellite altimetry and we provide a comparison of these products.
Accounting for transient effects in water pressure in sliding laws 
Authors: Gagliardini Olivier , Gilbert Adrien , Gimbert Florent , Roldan Blasco Juan Pedro
Published: March 2022

The flow of glaciers and ice-sheets is controlled by internal deformation and basal sliding. Daily to seasonal variations in ice flow are mostly the result of changes at the interface between the ice and the bedrock induced by the presence of water. More than six decades ago, Lliboutry (1958) formulated the role of this water in its ability to modulate the friction at the base of glaciers through the opening of water cavities. Since this pioneer work, a number of efforts have been undertaken to formalize mathematically the form of a water-pressure-dependent friction law for glaciers, i.e. the relation that gives the basal shear stress as a function of the sliding velocity, the water pressure and potentially other state variables. If a number of initial assumptions used to derive these friction laws have been overcome recently (e.g. three dimensional geometries, synthetical or realistic, existence of solid friction at the interface ice-bed, validation against datasets), all these recent efforts still assume that the geometry of the cavities instantaneously adapt to any change in water pressure. Whereas this might hold for long term water pressure variations at seasonal scale, this is certainly not true for daily variations during which the cavity geometry cannot adapt sufficiently fast.  In this presentation, using the same finite element method framework as in Gagliardini et al. (2007), the effect of non-steady water pressure within the cavity is studied. For daily variations of water pressure, it is shown that the solution strongly departs from the steady-state one, but still instantaneously depends on effective pressure. Following Thøgersen et al. (2019) and Gilbert et al. (submitted), a cavity ratio is introduced as a new state variable in the friction law to account for departure to steady-state geometry. Using different types of perturbation, a transient friction law associated to an evolution equation for the cavity ratio is proposed to reproduce the numerical experiments. This new law can further be useful for a consistent coupling between ice flow and hydrological models where cavity geometry is modeled as a transient process in both models.

References:
Gagliardini et al. (2007) Finite-Element Modeling of Subglacial Cavities and Related Friction Law. J. of Geophys. Res., Earth Surface, 112.
Gilbert et al. (submitted) A Consistent Framework for Coupling Basal Friction with Subglacial Hydrology on Hard-bedded Glaciers, GRL.
Lliboutry (1958) Contribution à la théorie du frottement d'un glacier sur son lit. Compte Rendus à l’Académie des Sciences, pp 317-320.
Thøgersen et al. (2019) Rate-and-state friction explains glacier surge propagation. Nature Communications, 10(1), 2823.
Frequency of radionuclides in remote atmospheric observations of historic nuclear test explosions compared to lists of radionuclides considered for nuclear explosion monitoring
Authors: Kalinowski Martin
Published: March 2022

The frequency of radionuclides in remote atmospheric observations of historic nuclear test explosions is established from a collection of papers. These report on tests conducted between 1964 and 1996. Most of these tests occurred in the atmosphere but observation of nuclear debris from venting of underground nuclear tests were also found. The review is limited to off-site monitoring and many observations were done at large distances including several tests that were detected on multiple locations on the same hemisphere. The isotope frequency is compared to several radionuclide lists considered for nuclear explosion monitoring to explore whether these lists match the historic evidence. The objective is to identify opportunities for further studies on validating monitoring methods, including atmospheric transport simulations with the objective of identifying the source of an event that is of relevance for atmospheric radioactivity monitoring for the Comprehensive-Nuclear-Test Ban Treaty (CTBT).
Quantifying the impact of environmental loading on Zenith Tropospheric Delays in Europe
Authors: Klos Anna , Bogusz Janusz , Pacione Rosa , Humphrey Vincent , Dobslaw Henryk
Published: March 2022

We assess the impact of the environmental loading on the Zenith Total Delay (ZTD) time series estimated within the second re-processing campaign of the EUREF Permanent GNSS Network (EPN). In particular, we used one solution provided by the ASI (Agenzia Spaziale Italiana Centro di Geodesia Spaziale, Italy), and two solutions provided by the GOP (Geodetic Observatory Pecny, Czech Republic) EPN analysis centers, along with the combined products. We find that ZTD time series derived within individual solutions are characterized by pure autoregressive noise, which is reduced during the combination in favor of white noise. This reduces the error of ZTD trends and is of great importance for numerous applications, as climate analyses, where trend is taken into account. Combination procedure does not however affect spatio-temporal patterns of ZTD residuals (linear trend and seasonal signals removed beforehand). We observe no impact of non-tidal oceanic loading on the ZTD residuals. Then, we compute ZTD differences from the two GOP solutions, which only differ by unmodelled non-tidal atmospheric loading. We prove that there is a similarity between the ZTD differences and non-tidal atmospheric loading which is strongly demonstrated in terms of unusual loading events, as significant inter-annual signals or large seasonal peaks. As these similarities account for 54% of ZTD differences, this indicates that unmodelled non-tidal atmospheric loading effect contributes to the ZTD residuals interpreted as a noise, affecting errors of trends. Therefore, we recommend that the non-tidal atmospheric loading is included at the observation level, once high-significance of ZTD parameters is required.
The 2017 Ischia Earthquake (Southern Italy): Source Mechanism and Rupture Model From the inversion of a Near-Source Strong Motion Record
Authors: Nazeri Sahar , Zollo Aldo , Maria Adinolfi Guido , Amoroso Ortensia , Picozzi Matteo
Published: March 2022

With the aim to investigate the rupture complexity and the radiated wave field of 2017, Mw 3.9, Ischia earthquake, south-west of Naples (Italy), we used finite-fault modeling to invert the near-source (<1-km epicentral distance) horizontal component velocity records of the accelerometric station (IOCA)
and searched for the best-fit kinematic rupture parameters. This analysis showed that the rupture nucleated at about 600 m west of IOCA and 1.1-km depth, along a 1 km, NW-SE striking fault (i.e., thrust with right-lateral component), with a rupture velocity of about 0.7 km/s. The retrieved rupture model coupled with multipath reverberations effects related to a thin, low-velocity near-surface volcanic sedimentary layer, well explains the observed long ground motion duration and the large amplitudes recorded all over the island. Finally, the apparent source time function (STF), obtained from inverse modeling using a theoretical Green’ function (GF), is validated by implementing an empirical GF (EGF) analysis.
A 4D-Localized Particle Filter Method for Regional Data Assimilation at DWD
Authors: Schenk Nora , Walter Anne , Potthast Roland
Published: March 2022

Nonlinear ensemble data assimilation methods like particle filters aim to improve the numerical weather prediction and the uncertainty quantification in a non-Gaussian setting. The localized adaptive particle filter (LAPF), introduced by R. Potthast, A. Walter and A. Rhodin in 2019, overcomes filter collapse in a high-dimensional framework. This particle filter was further developed by Walter et al. (2021) to the local mixture coefficients particle filter (LMCPF) which was tested within the global ICON model. In the LMCPF method the background distribution is approximated by Gaussian mixtures. After a classical resampling step, Bayes' formula is carried out explicitly under the assumption of a Gaussian distributed observation error. Furthermore, the particle uncertainty can be adjusted which affects the strength of the shift of the particles toward the observation. Lastly, Gaussian resampling is employed to increase the ensemble variability. All steps are carried out in ensemble space and observation localization is applied in the method.

Following a study of Kotsuki et al. (2021), we recently substituted the approximated particle weights in the LMCPF method with the exact Gaussian mixture weights which leads to an increase of the effective ensemble. Using the exact weights, Kotsuki et al. (2021) detected an improvement of  the stability of the LMCPF method with respect to the inflation parameters within the SPEEDY model.

Furthermore, we explore the potential of the LMCPF with the exact particle weights in the kilometre-scale ensemble data assimilation (KENDA) system with the limited area mode of the ICON model (ICON-LAM) and compare the particle filter method to the localized ensemble transform Kalman filter (LETKF) which is operationally used at the German Meteorological Service (DWD). Both methods describe four-dimensional data assimilation schemes if the observation operators are applied during the model forward integration at the exact observation times and not only at analysis time. This leads to four-dimensional background error covariance matrices at times and locations of the observations which are employed to derive the analysis ensemble.

In addition to a mathematical introduction of the LMCPF method, we present experimental results for the LMCPF in comparison with the LETKF method in KENDA used at DWD for the ICON-LAM model. Moreover, we discover the improvements of the LMCPF with exact particle weights over the method with approximated weights.
Paleomagnetism of Middle Devonian pillow lavas from Germany
Authors: de Boer Rosa A. , van der Boon Annique , Königshof Peter , de Groot Lennart V.
Published: March 2022

For decades, scientists have tried to obtain paleomagnetic data from Devonian rocks, but acquiring accurate data from this time period remains problematic. The lack of data has traditionally been interpreted as caused by overprinting during the Kiaman reverse superchron, but recent studies have suggested that the field could have had a non-dipolar configuration. Either way, overprinting is a common problem, although an overprinting mechanism is sometimes lacking. In other cases, data is not interpretable due to large scatter, and a clear explanation has not been found to date.

The lack of paleomagnetic data from the Devonian significantly hampers the fundamental understanding of long-term (>100 Myr) magnetic field behaviour and the creation of geodynamo models. However, paleointensities can sometimes be successfully determined, and show that the field was weak to extremely weak during the Late Devonian, with values similar to the Ediacaran.

To further constrain the onset of the weak field period, we sampled a succession of Middle Devonian pillow lavas that outcrop in the Philippstein Quarry near Braunfels, Germany. These lavas are subject to some faulting, but are fresh looking and consist of unaltered, unmetamorphosed igneous rock. Pillow lavas cool quickly, which leads to stable magnetic behavior, making them well-suited for magnetic analyses.

Here we present our results of traditional paleomagnetic analyses to determine the direction and intensity of the Devonian paleomagnetic field.