bluuebunny/crossref_metadata_2025 huggingface dataset:
Suprathermal Ion Observations Associated with the Heliospheric Current Sheet Crossings during Parker Solar Probe Encounters 7, 8, and 9
Authors: Desai Mihir ,   the Parker Solar Probe ISOIS, FIELDS & SWEAP Teams
Published: March 2022

We report observations of <100 keV/nucleon suprathermal (ST) H, He, O, and Fe ions in association with three separate crossings of the heliospheric current sheet that occurred near perhelia during PSP encounters 7, 8, and 9. In particular, we compare and contrast the ST ion time-intensity profiles, velocity dispersion, pitch-angle distributions, spectral forms, and maximum energies during the three HCS crossings. We find that these unique ST observations are remarkably different in each case, with those during E07 posing the most serious challenges for existing models of ST ion production in the inner heliosphere. In contrast, the ISOIS observations during E08 appear to be consistent with a scenario in which ST ions escape out of the reconnection exhausts into the separatrix layers after getting accelerated up to ~50-100 keV/nucleon by HCS-associated magnetic reconnection-driven processes. Finally, ST ions during the E09 HCS crossing have properties that are somewhat similar to those seen during both E07 and E08 crossings, with ion intensities being higher outside the exhausts and the separatrices, but significant intensity increases are also observed inside the reconnection exhausts. We discuss these new observations in terms of local versus remote acceleration sources as well as in terms of expectations of existing ST ion production and propagation, including reconnection-driven and diffusive acceleration in the inner heliosphere.
Multi-spatiotemporal landslide mapping for landslide evolutionary investigation
Authors: Bhuyan Kushanav , Tanyas Hakan , Nava Lorenzo , Puliero Silvia , Meena Sansar Raj , Floris Mario , Catani Filippo , Van Westen Cees , Pareek Tanuj
Published: March 2022

Multi-temporal landslide inventories are crucial for understanding the changing dynamics and states of activity of landslide masses. However, mapping landslides over space and time is challenging as it requires lots of time and resources to delineate landslide bodies for affected areas. With the current advances in artificial intelligence models and acquisition of very high-resolution satellite imageries, the need to map landslides not just spatially, but also temporally, has become evident. Generating multi-spatiotemporal landslide inventories can allow to improve our understanding of evolving landslides and landslide re-activations, addressing the changing susceptibilities, and the associated risks to elements-at-risk. Furthermore, as a result of having multi-temporal inventories, the temporal probability of occurrence of landslides can also be investigated with the help of envelop curves based on variables like rainfall duration, intensity, cumulative rainfall, antecedent rainfall. Therefore, in this endeavour, we have developed a model that generates multi-temporal landslide inventories for some of the most affected landslide regions by using several inventories around the world, for example, in Nepal (Gorkha earthquake of 2015). This study is the first attempt to map landslides over space and time using the state-of-the-art artificial intelligence models and gives a new perspective at mapping landslides through a temporal lens. Subsequently, the modelled outputs are utilised to assess and understand the changing dynamic behaviour of past landslides.   
On the accuracy of selected empirical magnetopause models
Authors: Aghabozorgi Nafchi Maryam , Nemec Frantisek , Pi Gilbert , Nemecek Zdenek , Safrankova Jana
Published: March 2022

Empirical magnetopause models generally aim to predict its location as a function of upstream solar wind parameters. Many such models have been developed to date, typically based on the fitting of individual magnetopause crossings identified in spacecraft data by prescribed empirical functions deemed to reasonably characterize magnetopause shape and position dependences on selected control parameters. We use a unique list of more than 60,000 magnetopause crossings identified in THEMIS A-E, Magion, Geotail, and Interball spacecraft data to evaluate the performance of some of the most popular such models (Formisano et al., 1979; Petrinec and Russell, 1996; Shue et al., 1997; Lin et al., 2010). Differences between observed and model magnetopause locations are investigated as a function of solar wind dynamic pressure, interplanetary magnetic field magnitude, clock angle, and cone angle. A particular attention is paid to the magnetopause shape. This is studied both in terms of the level of the tail flaring, assuming a rotational symmetry around the aberrated x-axis, and in terms of asymmetries present in the real configuration. We show that although the Lin et al. (2010) model performs arguably the best, some systematic deviations are still present.
Ionospheric plasma depletions at Mars as observed by MAVEN
Authors: Basuvaraj Praveen Kumar , Nemec Frantisek , Nemecek Zdenek , Safrankova Jana
Published: March 2022

The Martian ionosphere, modulated by the solar wind from the topside and by remnant crustal magnetic fields close to the surface, possess unique structures different from Earth and Venus. Integrated observations by the plasma and magnetic field instruments onboard the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft show clear evidence of ionospheric plasma depletions, independent of seasonal variations at Mars. During such depletions, the plasma density of all ionospheric ion species is reduced by up to an order of magnitude and, at the same time, the electron temperature increases abruptly. An automated algorithm for the identification of such plasma depletions is developed. Altogether, as many as 580 events are identified in 8619 orbits available from October 2014 to May 2021. A statistical investigation of these events reveals that they are more prominent on the night side and occur at altitudes between 150 and 500 km. Considering the spacecraft velocity and the observed event durations, we suggest that the depletions are bubble-like structures, more elongated horizontally than vertically. A possible mechanism of their formation is discussed.
An examination of the magnetic fluctuations in long-lasting radial IMF events
Authors: Pi Gilbert , Pitna Alexander , Nemecek Zdenek , Safrankova Jana
Published: March 2022

This study investigates long-lasting radial interplanetary magnetic field (IMF) intervals in which IMF points along the solar wind flow direction for several hours. We use 419 such events identified in Wind observations during 1995-2019, and we focus on the behavior of magnetic field fluctuations. Using the power spectral density (PSD) calculated over 1-hour radial IMF intervals and PSDs in adjacent regions prior to and after the radial IMF interval, we address: (i) the power of IMF fluctuations, (ii) median slopes of PSDs in both inertial and kinetic ranges, (iii) the proton temperature and its anisotropy, and (vi) the occurrence rate of wavy structures and their polarization. Comparison of PSDs in radial IMF intervals with those in prior and after them revealed that the fluctuation magnitude is low in the radial IMF intervals in both MHD and kinetic ranges and the spectral power increases with the cone angle in the MHD range. It may be related to the observation limitations because the dominant 2D component of the magnetic fluctuation is hard to observe if the sampling direction is aligned with the mean magnetic field. Moreover, the proton temperature is more isotropic, and the occurrence rate of wave structures is higher for radial IMF events. The waves have no preferred polarization in the frequency range from 0.1 to 1 Hz. It suggests that the radial IMF structure leads to a different development of turbulence than the typical Parker-spiral orientation.
Vulnerability of Critical Infrastructure to biological threats
Authors: Tomalska Amelia
Published: March 2022

Critical infrastructure is a complex system that provide essential services to the society such as food, water, energy, transportation, health, financial services. Any potential dysfunction of Critical Infrastructure might result in severe consequences for the human life, the environment, the economy and the security of the country. The recently experienced repercussions of COVID-19 pandemic exposed major deficiencies in terms of protection of Critical Infrastructure. The implemented approaches focusing on the threat identification and prevention strategies, without efficient organisational resilience, proved to be ineffective, especially in case of unanticipated or low-probability threats. The biological threats, such as pandemics, are relatively rare and difficult to estimate and prevent. They affect the whole organisation and contrary to the most of the natural hazards, such as floods, fires or hurricanes, have constant, permanent character. The COVID-19 pandemic forced Critical Infrastructure operators to operate in crisis mode as a result of shortages of staff, disruption of supply chains and increased vulnerability to cyber-attacks. The occurrence of these consequences unveiled the underlying vulnerabilities of Critical infrastructure. Namely, the lack of capabilities to successfully detect the possible threats resulting from dependencies and interdependencies and vulnerabilities related to internal procedures, plans or capabilities to respond and recover after the adverse event. The protection of Critical Infrastructure based on identification and assessment of vulnerabilities would enable Critical Infrastructure operators to apply adequate measures tailored to address the causes of identified vulnerabilities, to prioritise actions and to concentrate resources on the most pressing issues. The understanding of vulnerability of Critical Infrastructure to biological threats, would help Critical Infrastructure operators to prepare better for future “black swan” events and cascading disruptions across sectoral boundaries. The elimination or reduction of vulnerabilities would make Critical Infrastructure more resilient to future crisis situations and would ensure the undisturbed continuity of the essential services.
Evaluation of the influence of Structure-from-Motion software processing parameters on the quality of digital elevation models and orthomosaics in the context of earth surface dynamics.
Authors: Śledź Szymon , Ewertowski Marek
Published: March 2022

The Structure-from-Motion (SfM) approach for developing digital elevation models and orthomosaics has been known and used in photogrammetry for several decades. Using appropriate algorithms, SfM software combines images taken from different angles and distances based on the characteristic points determined in each image. Years of practice and experience have allowed researchers to provide a solid description of the applicability and limitations of this method, but still the impact of input processing parameters in software on the quality of photogrammetric products has not been fully recognized. This study aimed to identify the most advantageous processing workflow to fill this research gap by testing 375 different setup variations in the Agisoft Metashape software for the same set of images acquired with an unmanned aerial vehicle in a proglacial area. The purpose of the experiment was to determine three workflows: 1) with the shortest calculations time; 2) as accurate as possible, regardless of the time taken for the calculations; 3) the optimum, which is a compromise between accuracy and computation time.

Each of the 375 processing setup variations was assessed based on final product accuracy, i.e., orthomosaics and digital elevation models. Three workflows were selected based on calculating the height differences between the digital elevation models and the control points that did not participate in their georeferencing. The analysis of root mean square errors (RMSE) and standard deviations indicate that excluding some of the optimization parameters during the camera optimization stage results in high RMSE and an increase in values of errors’ standard deviation. Furthermore, it has been shown that increasing the detail of individual processing steps in software does not always positively affect the accuracy of the resulting models. The experiment resulted in the development of three different workflows in the form of Python scripts for Agisoft Metashape software, which will help users to process image sets efficiently in the context of earth surface dynamics studies.

The research was funded by the National Science Center OPUS project number 2019/35/B/ST10/03928.
Peatland Formation and Carbon Accumulation : A Pantropical Synthesis
Authors: Hedgpeth Alexandra , Kuhnen Ágatha , Dommain René , Mcfarlane Karis , Cusack Daniela , Cavanaugh Kyle , Hoyt Alison
Published: March 2022

Tropical peatlands account for a small portion of global peatland area but hold over 100 Gt of carbon (C), equivalent to approximately 13% of the C stored in the atmosphere. At this point, a comprehensive synthesis on the timing and behavior of peatland formation and peat accumulation does not exist for the tropics, where long-term accumulation rates could be higher than other regions due to the high productivity and water availability characteristic of tropical regions. In this work, we synthesize data collected from tropical peatlands around the world, to identify dominant external drivers (such as climate or tectonics) that influence patterns of peat depth and accumulation. We use radiocarbon measurements compiled in the International Soil Radiocarbon Database (ISRaD) to calculate peat and C accumulation rates of peat profiles across the tropics. Currently 44 individual studies make up this synthesis that together cover 12 countries and 62 tropical peat sites. This analysis focuses on comparisons between tropical peatlands from different continents and geographic locations and with different site characteristics. We identify three geographically distinct types of peatlands across the tropics: a) inland b) coastal c) montane that differ in terms of underlying substrate, timing of initiation, and accumulation rate. Four regions have been recognized in this analysis with differences in the range of peatland ages and depth: Africa (4000-10,600 cal yr BP) with 1-3m low elevation peatlands, the Neotropics (1400-13,000 cal yr BP) with higher variability in elevation and 1-8m peat deposits, Southeast Asia (4000-47,000 cal yr BP) with 1-18m deep peat deposits, and Hawaii (115-45,000 cal yr BP) with 1-4m peat deposits. We explore possible drivers of these differences in peatland age and accumulation across the tropics. This study complements the recent progress that has been made in mapping tropical peats, identifying their specific characteristics, assessing their potential uses, and calling attention to their potential vulnerability, restoration, and conservation.
A high-resolution record of vertically-resolved seawater salinity in the Caribbean Sea mixed layer since 1700 AD.
Authors: Winter Amos , Zanchettin Davide , McCulloch Malcolm , Rigo Manuel , Sherman Clark , Rubino Angelo
Published: March 2022

The Caribbean Sea in the tropical Atlantic is one of the major heat engines of the Earth and a sensitive area for monitoring climate variability. Salinity changes in the Caribbean Sea record changes in ocean currents and can provide information about variations in ocean heat transport. Seawater salinity in the Caribbean Sea has been monitored in recent decades, nevertheless, of all oceanographic environmental parameters salinity information before the instrumental period remains limited, due to the difficulty of reconstructing salinity, arguably the most difficult natural archives to recreate. We were able to reconstruct salinity changes in the Caribbean Sea from 1700 to the present from southwest Puerto Rico using slowly growing and long-lived scelerosponges from southwest Puerto Rico. These well-dated sponges are known to precipitate their skeletons in isotopic equilibrium (i.e., their record is not affected much by vital effects) and were retrieved from various depths in the mixed layer, from the surface to 90 m depth. We were able to establish salinity changes by deconvoluting stable isotopes (d18O) and trace element (Sr/Ca) proxies taken from the sponges at regular intervals. In this contribution, we will present the salinity record and illustrate the process for salinity reconstruction. We will also discuss how we determine how salinity changes in our record relate to radiative forcing as well as connect them with dominant mechanisms operating in the region, including changes in the position of the InterTtropical Convergence Zone and intensity of the Atlantic meridional Overturning Circulation over time.
Juno MWR Revealed Points-of-interest from Error Analysis
Authors: Zhang Zhimeng , Adumitroaie Virgil , Allison Michael , Arballo John , Atreya Sushil , Bjoraker Gordon , Bolton Scott , Brown Shannon , Fletcher Leigh , Guillot Tristan , Gulkis Samuel , Ingersoll Andrew , Janssen Michael , Levin Steven , Li Cheng , Lunine Jonathan , Orton Glenn , Oyafuso Fabiano , Steffes Paul , Wong Michael
Published: March 2022

Jupiter has ubiquitous clouds and enormous surface structures shrouding the planet. Juno MWR provides the unprecedented chance to answer remaining major questions about the composition and dynamical properties of the great bulk of the atmosphere that lies beneath. Since the launch of Juno, there has been a large effort to collect complementary ground- and space-based observations to help interpret the MWR data. The Jovian Infrared Auroral Mapper (JIRAM) onboard Juno complements the observations of MWR, by giving alternative and reference tropospheric measurements that provides the boundary condition for the interpretation of the MWR data [Adriani et al 2014]. Similarly, HST has a 6-month overlap with 13 Juno orbits and color images were constructed from images of Jupiter in red, green, and blue filters by JunoCam [Hansen et al., 2014]. We study the dynamics within the atmosphere by relating the exterior information provided by these surface maps to the deep interior detected by MWR.

During Aug 27, 2016 to October 24, 2017, MWR obtained 8 perijoves (PJ1, 3, 4, 5, 6, 7, 8, 9), all scanning Jupiter’s atmosphere from North to South, covering various longitudes. By combing observations from these perijoves, we are able to study the global-averaged atmosphere and the anomalies to be compared with top atmosphere maps. The success of such a study depends on the stability of calibration between different perijoves. In order to combine those data, we investigate and remove the calibration drift with respect to time using our error analysis process. We report two outcomes from the error analysis: 1) The atmosphere stability with respect to longitude and time, as compared to the latitudinal belt and zone structures. 2) The spotted points-of-interest which lie 2 standard deviations away from the global-averaged atmosphere. We compare them with Jupiter’s surface atmosphere images taken by JunoCam, HST and JIRAM, and retrieve the corresponding NH3 volume mixing ratio from surface to over 100 bars.
Should we correct biases in the diurnal cycle of climate model for hydrological studies?
Authors: Faghih Mina , Brissette François
Published: March 2022

With the growing importance of climate change risk assessment, the use of climate models as a tool to model the impact of a warmer climate on water resources has now become quite common. When working with climate model outputs, bias correction is considered an important and necessary step to ensure that impact models provide realistic simulations in the current and future climates. The past decades have seen continuous improvements in the spatial and temporal resolution of global and regional climate models. Climate model outputs are now available at the sub-daily temporal resolution and very few studies have looked at the need for correcting biases present in the representation of the diurnal cycles of model variables. This study has looked at the impact of correcting such biases on simulated streamflow over 133 North American catchments. The temperature and precipitation hourly outputs from a 50-member large-ensemble regional climate model (ClimEx) were used to model the impact of sub-daily bias correction on simulated streamflow using a hydrological model. To better understand the importance of diurnal bias correction as a function of the spatial scale, the impact of bias-correcting the diurnal cycle was evaluated on three classes of catchment area:  small (<500 km2), medium (500< area <1000 km2) and large (>1000 km2). Bias correcting the diurnal cycle resulted in small but systematic improvements in the representation of simulated streamflow, with an average bias reduction of 5%, likely due to a better representation of the daily evapotranspiration cycle.  The improvements were especially noticeable on the small catchments.
Network-scale analysis of sedimentary hotspots in dynamic, seismically-active steepland rivers
Authors: Tamang Niraj Bal , Tunnicliffe Jon
Published: March 2022

Seismic shaking in mountain environments introduces the potential for complex fluvial response from a multitude of landslide sources. Stream networks may be impacted in multiple branches, introducing the possibility of interacting sedimentary ‘pulses’ moving through the system. Large quantities of mobile sediment added to the stream network from multiple sources during and after a co-seismic event can overload susceptible river reaches, causing changes in sediment transport and storage. Although past research works have addressed dynamic sediment movement in river networks and identification of sedimentary hotspots, the physiographic factors (e.g. canyons, bends, fans, slope change) that prompt such change remain unexplored. The catchment settings and reach sequences that contribute most to delay/acceleration of the sediment in the active mountain environments are investigated in order to improve hazard assessment in susceptible terrain. In this work, we employ the one-dimensional River Network Bed-Material Sediment model (Czuba & Foufoula-Georgiou, 2014) to explore the landscape factors that may lead to hotspot behaviour for the very coarse sand fraction (2mm), followed by multi-criteria analysis of four basic stream network parameters: slope, sinuosity, channel confinement and tributary influence. Patterns of network topology associated with delay and accumulation of river sediment in the model were systematically identified in 75,400 stream links from 16 major drainages (135 to 6425 km2) of New Zealand’s upper South Island, as assessed by sediment travel time and the cluster persistence index (CPI). Catchment size determines the number of sediment sources, and thus ultimately the magnitude of the sedimentary hotspots i.e., bigger catchments can accommodate more landslides which increases the sediment input, along with the chances of sediment accumulation at susceptible locations. Multi-criteria analysis of the top 10 reaches with highest CPI values in each catchment (160 sites, total), showed that about 30% of the hotspots occurred in partly-confined valley settings with gentle slope (<0.02m/m), moderate sinuosity (1-1.1), downstream from the confluence of two or more tributaries. This combination emerged as the most likely setting for the occurrence of sedimentary hotspots in active mountain river networks. This approach may provide a simple means to map out susceptible sites based upon reach characteristics, which will not only contribute to improved catchment hazard assessment but may also help to augment more sophisticated models of catchment response to co-seismic landslide events.
Common features of lithosphere structures in various collision zones of Eurasia based on seismic tomography studies
Authors: Medved Irina
Published: March 2022

There are a large number of different collision zones on Earth, formed in different geodynamic settings as a result of the collision of continental plates of different shapes and sizes. Researchers often use one or a combination of methods to study one region. In this study, we propose to compare the models of P and S anomalies of several regions. In this study, vertical sections were built under the collision zones of the Caucasus, Eastern Anatolia, NW Himalayas and Tien Shan using the method of local seismic tomography. 3D models of crustal inhomogeneities down to ~ 60-150 km were constructed using the LOTOS algorithm [Koulakov, 2009].

The main characteristic feature of all crustal models of collisional zones is a clear differentiation of the velocity anomalies of the orogen, formed due to shortening, and the continental plates, participating in the collision. Thus, the Arabian, East European, Indian, Tarim plates are associated with high velocity anomalies, and mountain structures, for example, the Greater and Lesser Caucasus, the Himalayas, are characterized by low velocities.

Volcanism is another geological feature that shows up well in seismic tomographic models. Young volcanism (up to ~ 2.5Ma) characterized by low-velocity anomalies in the models, while the older one characterized by high-velocity anomalies. Thus, the volcanic area of Kazbegi province including a group of Quaternary volcanoes (455-30 Ka) in Great Caucasus match to the locations of low-velocities in the P- and S-seismic models. But the Eastern Anatolia younger magmatism (6–4 Ma) occurred in the south around Lake Van, stands out as high velocity anomalies.

It is known that there is the lithospheric window under Tien Shan and Anatolia which is filled with overheated asthenospheric material that reaches the bottom of the crust, thereby weakening and heating the lower crust. It is most likely that the upper crustal high-velocity anomaly corresponds to the strong upper crust which is compacted by solidified material from Neogene-Quaternary volcanism, while the low-velocity anomaly is associated with the weak heated lower crust.

Thus, comparison of seismic tomography models of different collision zones can be the key to better understanding the processes in the crust and lithosphere.

The reported study was funded by Russian Foundation for Basic Research, project number 19-35-60002.
Biogeographic patterns and drivers of soil virosphere across the globe
Authors: Ma Bin , Wang Yiling , Xu Jianming
Published: March 2022

Soil microbes play a crucial role in terrestrial ecosystem biogeochemical cycling1 and understanding microbial biogeography has provided fundamental information to predict ecosystem function2. In contrast, the biogeography of soil viromes has been largely overlooked, even though viruses are key mediators of the soil microbiome and its function3. Here, we introduce the Global Soil Virome (GSV) dataset, the most comprehensive soil virus dataset to date, and present an overview of global biogeographic patterns and drivers of soil viromes. A total of 345,607 double stranded DNA partial viral genomes, of which 97.2% were unknown viral taxa, were assembled from 1,873 deeply sequenced soil metagenomes across the globe. We observed soil virome endemism across continents and plant biomes which were shaped by dispersal limitation and soil moisture. Unlike the scale-free pattern of most biological co-occurrence networks4,5, we found that the degree distribution of the global soil virus co-occurrence network has a random pattern. The GSV dataset provides a critical resource for elucidating soil viral diversity and host-virus interactions; it provides in-depth insight into ecological processes that determine soil viral diversity.
Onshore diffusion of Circumpolar Deep Water
Authors: Yamazaki Kaihe , Mizobata Kohei , Aoki Shigeru
Published: March 2022

Warm, salty Circumpolar Deep Water (CDW) has long been regarded as the climatological driver for Antarctica, but the mechanism of how it can reach the continental shelf remains unsettled. Motivated by the absence of observational eddy flux estimation in the Antarctic margin, we quantify isopycnal diffusivity of CDW by hydrographic records and satellite altimetry under the mixing length framework. For comparison, spiciness and thickness are used as the isopycnal tracer, and two yield similar results. Over the extent of Antarctic Circumpolar Current (ACC), we find a general agreement with the mixing suppression theory and its exception in the lee of the topography as previously reported. In contrast, no mixing length’s dependency on mean flow is obtained to the pole, reflecting a stagnant flow regime in the Antarctic margin. Isopycnal diffusivity ranges 100–500 m2 s-1 to the south of the ACC. Eddy diffusion is likely enhanced where the CDW intrusion is localized by the recirculating gyres, mostly attributable to the small gradient of isopycnal thickness. Volume transport is then estimated by the layer thickness gradient. Thickness-diffusive onshore heat flux across the continental slope (~3.6/1.2 TW in the eastern/western Indian sectors) is quantitatively consistent with cryospheric heat sinks by sea ice formation and ice shelf basal melt, suggesting that the isopycnal eddy diffusion is the main cause of the onshore CDW intrusion. We emphasize that the thickness field is essential for determining the eddy fluxes in the Antarctic margin.
Structure and Morphology of the Mid-Ocean-Ridge in the Red Sea
Authors: Delaunay Antoine , Alafifi Abdulkader , Baby Guillaume , Fedorik Jakub , Tapponnier Paul , Dyment Jérôme
Published: March 2022

This presentation describes the structure and morphologies associated with seafloor spreading in the Red Sea inferred from bathymetric, gravity, magnetic and seismic data. We show that the orientation of the structures is consistent with an Arabia-Nubia Euler pole located within the 95% confidence of Ar-Rajehi et al, (2010) Euler pole and with the tectonic model initially proposed by Girdler (1984). At the Red Sea scale, our model shows that a spreading axis extends along its entire length, even though it is mostly covered by allochthonous Middle Miocene salt and Late Miocene minibasins flowing inward from the margins. In the northern Red Sea, oceanic basement is only exposed through small windows within the salt, forming a series of deeps. The seafloor segments symmetrically bisect the new ocean in the south. Right-stepping transform faults that cluster near Jeddah, Zabargad and Ikhwan Islands offset the ridge axis as spreading is getting more oblique towards the Euler Pole. The northern, central and southern Red Sea segments display a well-developed mid-ocean ridge flanked by landward-dipping volcanic basement, typical of slow spreading ridges. In the northern magma poor spreading segment, mantle exhumation is likely at the transition between continental and oceanic crust. Transpression and transtension along transform faults accounts for the exhumation of the mantle on Zabargad Island as well as the collapse of a pull-apart basin in the Conrad deep.

We propose a new structural model for the Red Sea constrained by the geodetic rules of tectonic plates movements on a sphere. Finally, we discuss the effect of the Danakil microplate on the ridge morphology and show that the Arabia-Nubia-Danakil triple junction is likely located further north than previously described, around 18±0.5°N, where we observe a shift in the ridge axis orientation as well as in the spreading orientation.
Zonal variation of ionospheric radial current (IRC) as observed by Swarm and simulated by TIE-GCM
Authors: Xia Hao , Qian Chengyu
Published: March 2022

 Based on the magnetic field observation of Swarm satellite from 2015 to 2019, the variation of ionospheric radial current (IRC) with local time and geographic longitude at March equinox, June solstice and December solstice are analyzed, respectively. The observations are compared with the simulation results of thermosphere ionosphere electrodynamics general circulation model (TIE-GCM). The observed IRC are mainly downward in the noon section and upward in the evening section, which is reproduced well by the model. The zonal distribution of IRC shows obvious local time asymmetry. The downward IRC in the eastern hemisphere in the noon section is greater than that in the western hemisphere, while the upward IRC in the western hemisphere in the evening section is greater than that in the eastern hemisphere. This zonal variation in the evening sector is more obvious at March equinox and less obvious at June solstice. The simulation results of TIE-GCM also show similar zonal characteristics, especially on the nightside. The physical mechanisms of the local time and geographic longitude distribution of IRC are discussed in details.
Identification, characteristics, and dynamics of Arctic extreme seasons in ERA5 and CESM climate simulations
Authors: Hartmuth Katharina , Boettcher Maxi , Wernli Heini , Papritz Lukas
Published: March 2022

The Arctic atmosphere is strongly affected by anthropogenic warming leading to long-term trends in surface temperature and sea ice extent. In addition, it exhibits strong variability on time scales from days to seasons. While recent research elucidated processes causing long-term trends as well as synoptic extreme conditions in the Arctic, we investigate unusual atmospheric conditions on the seasonal time scale. We introduce a method to identify extreme seasons – deviating strongly from a running-mean climatology – based on a principal component analysis in the phase space spanned by the seasonal-mean values of surface temperature, precipitation, and the atmospheric components of the surface energy balance. Given the strongly varying surface conditions in the Arctic, this analysis is done separately in Arctic sub-regions that are climatologically characterized by either sea ice, open ocean, or mixed conditions.

Using ERA5 reanalyses for the years 1979-2018, our approach identifies 2-3 extreme seasons for each of winter, spring, summer, and autumn, with strongly differing characteristics and affecting different Arctic sub-regions. Results will be shown for two contrasting extreme winters affecting the Kara and Barents Seas, including their substructure, the role of synoptic-scale weather systems, and potential preconditioning by anomalous sea ice extent and/or sea surface temperature at the beginning of the season.

To statistically quantify and confirm these results, we further apply our method to large ensemble simulations of the CESM climate model, using roughly 1000 years of data in present-day (1990-2000) and end-of-century (2091-2100) climate, respectively. Results show a strong similarity between the characteristics of extreme seasons in ERA5 and CESM for the present-day period. The identified seasons predominantly show the most extreme seasonal-mean anomalies of the applied surface parameters, confirming that our approach captures seasons with extraordinary conditions. Preliminary results will also be shown about our current investigation of possible changes in the characteristics and driving mechanisms of Arctic extreme seasons in the warmer end-of-century climate.

The framework developed in this study and the insight gained from analyzing both, reanalysis and climate model data, will be insightful for better understanding the effects of global warming on Arctic extreme seasons.
Fully coupled modelling of non-uniform sediment transport in sewer systems
Authors: Liu Jinxin , Cao Zhixian , Li Xichun
Published: March 2022

Flushing is considered as a cost-effective technique for mitigating sediments and constraining environmental problems in sewer systems. Previous mathematical models are almost exclusively based upon simplified governing equations and weak sediment transport assumptions, of which the applicability remains to be theoretically justified. Here a fully coupled one-dimensional model is presented for non-uniform sediment transport in sewer systems, as adapted from recently established shallow water hydro-sediment-morphodynamic models for fluvial processes. The present model is tested for an experimental flushing case in the Des Coteaux catchment system of Paris city. The computational results are compared with measured data, and satisfactory agreements are acquired. It is revealed that the adaptation of bedload sediments to capacity regime can be fulfilled quickly, while the adaptation of suspended sediment transport to capacity regime requires a relatively long time and space, thereby underpinning and warranting the non-capacity modelling paradigm for sewer systems.
Extraction of ground magnetic signatures from solar quiet current systems in sub-auroral regions
Authors: Haberle Veronika , Marchaudon Aurélie , Chambodut Aude , Blelly Pierre-Louis
Published: March 2022

In order to monitor space weather events and their impacts, ground magnetic field data has proven to be a long-lasting and powerful source of information. For the determination of space weather effects, it is essential to extract and understand the evolution of the quiet-time magnetic field. However, the data shows a high degree of complexity since the Earth’s magnetic field is a superposition of sources that cover a broad amplitude and frequency spectrum. In sub-auroral regions, it is well understood that the solar quiet current system contributes to the quiet signal with smooth patterns that depend on season and local time, having distinct periods of 24 hours and beneath.

In this work, we apply signal filtering techniques on time-series magnetic data from ground observatories in sub-auroral regions. In order to extract the solar quiet current contributions, we use its specific periods of 24h and beneath and analyse the results with respect to season, local time, and day-to-day variability between 1991 and 2019. Careful investigations and interpretation of the contributing sources are given, confirming the main contribution to the filtered signal is the solar quiet current system. This implies that the filter approach is able to extract the quiet magnetic field variations and due to its simplicity may be used for real-time determination of the quiet magnetic field, including magnetic baselines. 
Hyper-resolution hydrological modelling over Europe: results and emerging challenges
Authors: Hoch Jannis , Sutanudjaja Edwin , Wanders Niko , van Beek Rens , Bierkens Marc
Published: March 2022

Modelling the terrestrial hydrological cycle at ‘hyper-resolution’, i.e., with a grid cell size of 1 km or below) was and still is a major quest in hydrological sciences. With an increase in computational power and the number of readily available and open datasets at useful spatial resolutions increasing as well, hyper-resolution modelling efforts have grown in number as well. We here present a first continental-scale application of the global hydrological model PCR-GLOBWB over Europe at 1 km spatial resolution, and offset it against runs with traditional resolutions of 10 km and 50 km, respectively. Model output was validated for more than 200 water provinces against observed discharge and the following remotely sensed data products: ESA-CCI soil moisture data and GRACE/GRACE-FO terrestrial water storage anomalies. Evaporation estimates were compared to GLEAM data. Evaluation metrics indicate good model performance over Europe and increased accuracy with finer spatial resolutions, particularly for discharge simulations. While the used validation products have the advantage of global coverage and long observational records, their spatial resolution is actually too coarse to fully assess the accuracy of models at hyper-resolution. At that scale, more recent satellite products can be of more use but at the cost of only short observation record. We thus additionally validated 1 km model output against Sentinel-1 surface soil moisture and compared it against results obtained for ESA-CCI soil moisture data. Besides challenges related to global-scale fine-resolution observational data, we also acknowledge that additional work needs to focus on model parameterization for hyper-resolution as well model improvements such as routing schemes better utilizing the available spatial detail. Another challenge we identified is required run time and computational power to analyze continental-scale 1 km data, even when using the state-of-the-art Dutch supercomputer. Here, efficient programming and use of latest parallelization techniques will become even more crucial. Despite these solvable challenges, our research shows that large-scale hyper-resolution modelling is now feasible and that further pursuing these efforts can eventually lead to more locally-relevant hydrological information and process understanding.
Flow structure at reservoir-tributary confluence with high sediment load
Authors: Zhang Junhao , Sun Yining , Cao Zhixian , Li Ji
Published: March 2022

Fluvial flow with high sediment load may plunge into the reservoir to form turbidity current, which may feature strong interaction with inflow from a tributary. However, to date, the understanding of confluent flow structure with high sediment load has remained poor. Here, a computational fluid dynamic software, Flow-3D, is applied to resolve such flows for a series of cases at laboratory-scale by solving unsteady, 3D Reynolds-averaged Navier-Stokes and sediment transport equations, based on finite difference method with structured meshes. The 3D results are compared with those due to a recently established 2D double layer-averaged shallow water hydro-sediment-morphodynamic model. One distinctive flow structure pattern is generated at the confluence with the intrusion of reservoir turbidity current from the main channel into the tributary. Apparent bed aggradation occurs inside the tributary mouth after a long-term hydro-sediment-morphodynamic process. The present finding has a more profound influence on sediment transport and morphological evolution at a reservoir–tributary confluence with high sediment load.
Significantly increased evapotranspiration reveals accelerated water cycle on the Tibetan Plateau during 1982–2018
Authors: Yuan Ling , Chen Xuelong , Ma Yaoming , Chen Deliang , Su Zhongbo , Cao Dianbin , Wang Binbin , Han Cunbo , Ma Weiqiang , Menenti Massimo
Published: March 2022

Precipitation studies suggest an accelerated water cycle over the Tibetan Plateau (TP) in recent decades. However, the exact changes to evapotranspiration (ETa) over this period remain largely unknown. Multiple ETa products for the TP region report that ETa experienced a significant increasing trend of around 8.4 ± 2.2 mm/10 a during 1982–2018. Here, we quantified and explained the ETa trend using a comprehensive process-based ETa model refined on ground-based observations over the TP. Attribution analysis revealed that a large part of the increasing ETa trend was caused by higher temperature (53.8%) and more soil moisture (23.1%) caused by the melting cryosphere and increased precipitation. The increasing rate of ETa on the TP was approximately twice that of the global ETa, providing strong and independent evidence for an accelerated hydrological cycle. The dominant role of increased temperature in ETa implies a continued acceleration of the water cycle in the future.
Optimal design of nature-based solutions in highway runoff management based on resilience to climate and pollution load changes
Authors: Ghorbani Mooselu Mehrdad , Liltved Helge , Alizadeh Mohammad Reza , Meland Sondre
Published: March 2022

Sedimentation ponds (SPs) are nature-based solutions (NBSs) for sustainable stormwater management. SPs control the quantity and quality of runoff and promote biodiversity. Hence, the optimal design of SPs is crucial for ecosystems resilience in urban and natural environments. This study aims to optimize the design of roadside SPs in terms of location and surface area, considering the resilience to stressors such as climate changes and pollution load variations. Accordingly, the highway runoff in a new 22 km highway (E18 Arendal-Tvedestrand) in southern Norway was simulated by the storm water management model (SWMM). The quantity and quality (BOD and TSS values) of highway runoff in all probable scenarios of existing uncertainties were estimated for potential outfall points using the repeated execution model of SWMM coded in MATLAB®. The scenarios were defined based on applying best management practices (BMPs), including grass swale and infiltration trench in different sections of the road that work before SPs, climatic (rainfall quantity estimated by the LARS-WG model), and modeling uncertainties (buildup and washoff coefficients). The generated dataset was then applied to assess the resilience of sedimentation ponds in potential outfalls to climate change and pollution load shocks. The resiliency was quantified for three metrics, including the quantity and quality of receiving runoff to sedimentation ponds and biodiversity in ponds over 25 years (2020-2045). The biodiversity index was defined based on Shannon's Entropy computed from field observation in 12 highway sedimentation ponds across Norway. Using this procedure, it was determined that the proper arrangement of BMPs along the road and the optimal design of ponds enhance the resilience of SPs by 40% over time. This study makes important contributions to stormwater management, the resilient design of NBS, and achieving UN SDG6 (Clean water and sanitation).
A Wavenumber–Frequency Spectrum Model for Sheared Convective Atmospheric Boundary Layer Flows
Authors: Ali Naseem , Mellado Juan Pedro , Wilczek Michael
Published: March 2022

Turbulence in the atmospheric boundary layer (ABL) plays an important role in the weather and climate system as it governs the meteorological exchanges of momentum, energy, and moisture between the free atmosphere and the Earth’s surface. Motivated by the need for conceptual physics-based models that parameterize turbulence in the ABL in terms of spectra at all spatio-temporal scales, we explore a linear random advection approach to characterize different scenarios of sheared convective boundary layer flows. As a main result, we obtain the wavenumber–frequency spectrum as a product of the wavenumber spectrum and a Gaussian frequency distribution, whose mean and variance are given by the mean advection and random sweeping velocities, respectively. The applicability of the model is evaluated with direct numerical simulations of the mixed layer and entrainment zone for the streamwise and vertical velocity components as well as buoyancy. To obtain a fully analytical formula for the linear random advection approach, we propose using a von-Kàrmàn wavenumber spectrum parameterized by the characteristic convective velocity and length scales. These scales are height-dependent and vary considerably with the relative balance of buoyancy and shear forces. The comparison of the von-Kàrmàn-based model for velocity and buoyancy to simulation results shows that the main features of the measured spectra are captured by the model. 