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  • English  (35)
  • 2020-2022  (34)
  • 1990-1994  (1)
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  • 1
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    A database of damaging small-to-medium magnitude earthquakes (2020)
    In:  Journal of Seismology
    Details
    Publication Date: 2020-12-10
    Description: Interest in small-to-medium magnitude earthquakes and their potential consequences has increased significantly in recent years, mostly due to the occurrence of some unusually damaging small events, the development of seismic risk assessment methodologies for existing building stock, and the recognition of the potential risk of induced seismicity. As part of a clear ongoing effort of the earthquake engineering community to develop knowledge on the risk posed by smaller events, a global database of earthquakes with moment magnitudes in the range from 4.0 to 5.5 for which damage and/or casualties have been reported has been compiled and is made publicly available. The two main purposes were to facilitate studies on the potential for earthquakes in this magnitude range to cause material damage and to carry out a statistical study to characterise the frequency with which earthquakes of this size cause damage and/or casualties (published separately). The present paper describes the data sources and process followed for the compilation of the database, while providing critical discussions on the challenges encountered and decisions made, which are of relevance for its interpretation and use. The geographic, temporal, and magnitude distributions of the 1958 earthquakes that make up the database are presented alongside the general statistics on damage and casualties, noting that these stem from a variety of sources of differing reliability. Despite its inherent limitations, we believe it is an important contribution to the understanding of the extent of the consequences that may arise from earthquakes in the magnitude range of study.
    Language: English
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  • 2
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    A dense network of cosmic-ray neutron sensors for soil moisture observation in a highly instrumented pre-Alpine headwater catchment in Germany (2020)
    In:  Earth System Science Data
    Details
    Publication Date: 2020-12-10
    Description: Monitoring soil moisture is still a challenge: it varies strongly in space and time and at various scales while conventional sensors typically suffer from small spatial support. With a sensor footprint up to several hectares, cosmic-ray neutron sensing (CRNS) is a modern technology to address that challenge. So far, the CRNS method has typically been applied with single sensors or in sparse national-scale networks. This study presents, for the first time, a dense network of 24 CRNS stations that covered, from May to July 2019, an area of just 1 km2: the pre-Alpine Rott headwater catchment in Southern Germany, which is characterized by strong soil moisture gradients in a heterogeneous landscape with forests and grasslands. With substantially overlapping sensor footprints, this network was designed to study root-zone soil moisture dynamics at the catchment scale. The observations of the dense CRNS network were complemented by extensive measurements that allow users to study soil moisture variability at various spatial scales: roving (mobile) CRNS units, remotely sensed thermal images from unmanned areal systems (UASs), permanent and temporary wireless sensor networks, profile probes, and comprehensive manual soil sampling. Since neutron counts are also affected by hydrogen pools other than soil moisture, vegetation biomass was monitored in forest and grassland patches, as well as meteorological variables; discharge and groundwater tables were recorded to support hydrological modeling experiments. As a result, we provide a unique and comprehensive data set to several research communities: to those who investigate the retrieval of soil moisture from cosmic-ray neutron sensing, to those who study the variability of soil moisture at different spatiotemporal scales, and to those who intend to better understand the role of root-zone soil moisture dynamics in the context of catchment and groundwater hydrology, as well as land–atmosphere exchange processes. The data set is available through the EUDAT Collaborative Data Infrastructure and is split into two subsets: https://doi.org/10.23728/b2share.282675586fb94f44ab2fd09da0856883 (Fersch et al., 2020a) and https://doi.org/10.23728/b2share.bd89f066c26a4507ad654e994153358b (Fersch et al., 2020b).
    Language: English
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  • 3
    Series available for loan
    Series available for loan
    Antarctic research : proceedings of a symposium, held at Potsdam GDR, 11-14 September 1989; Vol. 2: Glaciology and periglacial processes, sea ice analysis, hydrology, life sciences (1990)
    Berlin : Nationalkomitee für Geodäsie und Geophysik bei der Akademie der Wissenschaften der DDR
    Associated volumes
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    Call number: Q 2434(16) ; MOP Per 581(1/16) ; ZSP-319/A-16
    In: Geodätische und Geophysikalische Veröffentlichungen : Reihe 1, Heft 16
    In: Antarctic research / edited by H.-J. Paech, D. Fritzsche, Vol. 2
    Type of Medium: Series available for loan
    Pages: Seiten 281-511 , Illustrationen
    ISSN: 0533-7577
    Series Statement: Geodätische und Geophysikalische Veröffentlichungen : Reihe 1 16
    Language: English
    Note: Volume II: Glaciology & Periglacial Processes. - Soviet-French cooperation on the isotopic research of cores from Dome B - Vostok - Komsomolskaya - Mirny ice taverse, East Antarctica / C. Lorius ; Ye. S. Korotkevich ; N. I. Barkov ; V. N. Petrov. - On the genesis of the Shackleton Ice Shelf according to oxygen-isotope data / L. Savatyugin; R. Vaikmäe. - G.D.R isotope research in Queen Maud Land (Abstract) / R. Haberlandt. - Isotope data from ice-cored moraines suggest a higher ice sheet surface in Central Queen Maud Land (Antarctica) during cold stages / W.-D. Hermichen ; P. Kowski ; R. Vaikmäe. - An oxygen-18 thermometer from snow of Northern Queen Maud Land / Antarctica / W.-D. Hermichen ; P. Kowski ; R. Vaikmäe. - Initial processes of pedogenesis in the Schirmacher Oasis (Abstract) / W. Krüger ; J. Balke. - Periglacial of Antarctic continent as a source of paleoglacial information / V. I. Bardin. - Sea Ice Analysis. - The major features of ice conditions in the Bellingshausen Sea / V. V. Yevsyeyev. - The duration of the cycle of the Atlantic ice massif existence and typification of the processes causing its isolation / A. M. Kozlovsky. - Hydrology. - The hydrography of the Schirmacher Oasis (Abstract) / W. Richter. - Meteorological and hydrological conditions of meltwater genesis and distribution in Antarctica / A. Loopmann. - Hydrochemical and isotope hydrological investigations in the Bunger Oasis / E. Kaup ; V. Klokov ; R. Vaikmäe ; D. Haendel ; R. Zierath. - Extremely C-13 enriched biomass in a freshwater environment: examples from Antarctic lakes / U. Wand ; K. Mühle. - Biology & Human Biology. - Das Meereis als Lebensraum / G.Hernpel Das biologische Programm "Bellingshausen" - Bericht über die vergangenen 10 Jahre und die Konzeption künftiger Forschungsarbeit / H.Oehme. - Ecological studies in the southern gigant petrel Macronectes giganteus on southwestern parts of King George Island / H.-U. Peter ; M. Kaiser ; A. Gebauer. - Development, torpor and energy balance of black-bellied storm-petrel chicks (Fregatta tropica) (Abstract) / T. Nadler ; H. Mix. - Morphometrical and ecological differences between south polar and brown skuas of Fildes Peninsula, King George Island, South Shetland Islands / H.-U. Peter ; M. Kaiser ; A. Gebauer. - Behavioural biology of the Antarctic tern Sterna vittata (Gmelin, 1789) / A. Gebauer ; M. Kaiser ; H.-U. Peter. - Thermoregulation in the Antarctic tern Sterna vittata (Gmelin, 1789) / M. Kaiser ; A. Gebauer ; H.-U. Peter. - Parasitiological studies in the Antarctic by scientists from the G.D.R / K. Feiler. - New Amphipods from the sublittoral of King George Island - Faunistic contribution to ecological investigations / M. Rauschert. - The freshwater algae of the Schirmacher Oasis - Queen Maud Land / H. Pankow ; D. Haendel ; H. Richter. - The lichens of the Schirmacher Oasis (East Antarctica) / W. Richter. - The bryoflora of the Schirmacher Oasis (East Antarctica) in relations to hydrosphere and cryosphere / W. Richter. - The animals of the Schirmacher Oasis (East Antarctica) / W. Richter ; D. Haendel ; P. Junghans. - Indoor climate and long-time-stays in Arctic and Antarctic regions (Abstract) / W. Bischof ; G. Schrader ; L. Banhidi. - Do psychical factors have an influence on the immunofunction of polar researchers and how could objective evidence be obtained? / F. Wietschel ; G. Schrader.
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  • 4
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    Approaches to analyse and model changes in impacts: reply to discussions of “How to improve attribution of changes in drought and flood impacts” (2020)
    In:  Hydrological Sciences Journal - Journal des Sciences Hydrologiques
    Details
    Publication Date: 2020-12-23
    Description: We thank the authors, Brunella Bonaccorso and Karsten Arnbjerg-Nielsen for their constructive contributions to the discussion about the attribution of changes in drought and flood impacts. We appreciate that they support our opinion, but in particular their additional new ideas on how to better understand changes in impacts. It is great that they challenge us to think a step further on how to foster the collection of long time series of data and how to use these to model and project changes. Here, we elaborate on the possibility to collect time series of data on hazard, exposure, vulnerability and impacts and how these could be used to improve e.g. socio-hydrological models for the development of future risk scenarios.
    Language: English
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  • 5
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    Barite Scale Formation and Injectivity Loss Models for Geothermal Systems (2020)
    In:  Water
    Details
    Publication Date: 2020-12-10
    Description: Barite scales in geothermal installations are a highly unwanted effect of circulating deep saline fluids. They build up in the reservoir if supersaturated fluids are re-injected, leading to irreversible loss of injectivity. A model is presented for calculating the total expected barite precipitation. To determine the related injectivity decline over time, the spatial precipitation distribution in the subsurface near the injection well is assessed by modelling barite growth kinetics in a radially diverging Darcy flow domain. Flow and reservoir properties as well as fluid chemistry are chosen to represent reservoirs subject to geothermal exploration located in the North German Basin (NGB) and the Upper Rhine Graben (URG) in Germany. Fluids encountered at similar depths are hotter in the URG, while they are more saline in the NGB. The associated scaling amount normalised to flow rate is similar for both regions. The predicted injectivity decline after 10 years, on the other hand, is far greater for the NGB (64%) compared to the URG (24%), due to the temperature- and salinity-dependent precipitation rate. The systems in the NGB are at higher risk. Finally, a lightweight score is developed for approximating the injectivity loss using the Damköhler number, flow rate and total barite scaling potential. This formula can be easily applied to geothermal installations without running complex reactive transport simulations.
    Language: English
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  • 6
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    Comparison of the effects of industrial demand side management and other flexibilities on the performance of the energy system (2020)
    Details
    Publication Date: 2021-05-06
    Description: In order to ensure security of supply in a future energy system with a high share of volatile electricity generation, flexibility technologies are needed. Industrial demand-side management ranks as one of the most efficient flexibility options. This paper analyses the effect of the integration of industrial demand-side management through the flexibilisation of aluminium electrolysis and other flexibilities of the electricity system and adjacent sectors. The additional flexibility options include electricity storage, heat storage in district heating networks, controlled charging of electric vehicles, and buffer storage in hydrogen electrolysis. The utilisation of the flexibilities is modelled in different settings with an increasing share of renewable energies, applying a dispatch model. This paper compares which contributions the different flexibilities can make to emission reduction, avoidance of curtailment, and reduction of fuel and CO2 costs, and which circumstances contribute to a decrease or increase of overall emissions with additional flexibilities. The analysis stresses the rising importance of flexibilities in an energy system based on increasing shares of renewable electricity generation, and shows that flexibilities are generally suited to reduce carbon emissions. It is presented that the relative contribution towards the reduction of curtailment and costs of flexibilisation of aluminium electrolysis are high, whereby the absolute effect is small compared to the other options due to the limited number of available processes.
    Keywords: ddc:600
    Repository Name: Wuppertal Institut für Klima, Umwelt, Energie
    Language: English
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  • 7
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    Dense GNSS Profiles Across the Northwestern Tip of the India-Asia Collision Zone: Triggered Slip and Westward Flow of the Peter the First Range, Pamir, Into the Tajik Depression (2020)
    In:  Tectonics
    Details
    Publication Date: 2021-06-12
    Description: At the northwestern tip of the India‐Asia collision zone, the Pamir orocline overrides the Tajik Depression and the Tarim Basin and collides with the Tian Shan. Currently, the Pamir's northern edge exhibits localized shortening rates of 13‐19 mm/yr. While the eastern Pamir and the Tarim Basin move northward nearly en‐block, north‐south shortening decreases westward along the Pamir front into the Tajik Depression. In the northeastern Tajik Depression, the wedge‐shaped crustal sliver of the Peter the First Range is squeezed between the dextral‐transpressive Vakhsh and the sinistral‐transpressive Darvaz faults. GPS data collected along two densely surveyed profiles detail the kinematics of north‐south shortening and westward lateral extrusion in the northwestern Pamir. 2016 campaign data suggest a short‐duration dextral‐slip activation of the Darvaz fault, which we interpret as a far‐field effect triggered by the 2015, Mw7.2 Sarez, Central Pamir earthquake. 2013‐2015 interseismic GPS velocities and kinematic modeling show that the Darvaz fault zone accommodates ~15 mm/yr sinistral shear and ~10 mm/yr fault‐normal extension below a locking depth of 9.0 +0.4/‐1.1 km. The Vakhsh fault shows shortening rates of 15 +4/‐2 mm/yr and dextral shear rates of 16 +3/‐4 mm/yr. Jointly, these faults accommodate NW‐SE shortening and southwestward material flow out of the Peter the First Range into the Tajik Depression. Together with seismic and geologic data, our and published geodetic surveys showcase the prolonged interaction of shortening and lateral material flow out of a plateau margin.
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  • 8
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    Earthquake source arrays: optimal configuration and applications in crustal structure studies (2020)
    In:  Geophysical Journal International
    Details
    Publication Date: 2020-12-08
    Description: A collection of earthquake sources recorded at a single station, under specific conditions, are considered as a source array (SA), that is interpreted as if earthquake sources originate at the station location and are recorded at the source location. Then, array processing methods, that is array beamforming, are applicable to analyse the recorded signals. A possible application is to use source array multiple event techniques to locate and characterize near-source scatterers and structural interfaces. In this work the aim is to facilitate the use of earthquake source arrays by presenting an automatic search algorithm to configure the source array elements. We developed a procedure to search for an optimal source array element distribution given an earthquake catalogue including accurate origin time and hypocentre locations. The objective function of the optimization process can be flexibly defined for each application to ensure the prerequisites (criteria) of making a source array. We formulated four quantitative criteria as subfunctions and used the weighted sum technique to combine them in one single scalar function. The criteria are: (1) to control the accuracy of the slowness vector estimation using the time domain beamforming method, (2) to measure the waveform coherency of the array elements, (3) to select events with lower location error and (4) to select traces with high energy of specific phases, that is, sp- or ps-phases. The proposed procedure is verified using synthetic data as well as real examples for the Vogtland region in Northwest Bohemia. We discussed the possible application of the optimized source arrays to identify the location of scatterers in the velocity model by presenting a synthetic test and an example using real waveforms.
    Language: English
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  • 9
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    Evidence for Bronze Age and Medieval tin placer mining in the Erzgebirge mountains, Saxony (Germany) (2020)
    In:  Geoarchaeology
    Details
    Publication Date: 2020-12-14
    Description: Tin is an essential raw material both for the copper–tin alloys developed during the Early Bronze Age and for the casting of tableware in the Medieval period. Secondary geological deposits in the form of placers (cassiterite) provide easily accessible sources but have often been reworked several times during land‐use history. In fact, evidence for the earliest phase of tin mining during the Bronze Age has not yet been confirmed for any area in Europe, stimulating an ongoing debate on this issue. For this study, a broad range of methods (sedimentology, pedology, palynology, anthracology, OSL/14C‐dating, and micromorphology) was applied both within the extraction zone of placer mining and the downstream alluvial sediments at Schellerhau site in the upper eastern Erzgebirge (Germany). The results indicate that the earliest local removal of topsoil and processing of cassiterite‐bearing weathered granite occurred already in the early second millennium BC, thus coinciding with the early and middle Bronze Age period. Placer mining resumed in this area during the Medieval period, probably as early as the 13th century AD. A peak of alluvial sedimentation during the mid‐15th century AD is probably related to the acquisition of this region by the Elector of Saxony and the subsequent promotion of mining.
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  • 10
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    How Sediment Thickness Influences Subduction Dynamics and Seismicity (2020)
    In:  Journal of Geophysical Research: Solid Earth
    Details
    Publication Date: 2021-02-25
    Description: It has long been recognized that sediments subducting along the megathrust influence the occurrence of giant (Mw ≥ 8.5) megathrust earthquakes. However, the limited observation span and the concurrent influence of multiple parameters on megathrust behavior prevent us from understanding how sediments affect earthquake size and frequency. Here, we address these limitations by using two‐dimensional, visco‐elasto‐plastic, seismo‐thermo‐mechanical numerical models to isolate how sediment thickness affects subduction geometry and seismicity. Our results show that increasing sediment thickness on the incoming plate results in a decrease of the slab dip, as the trench retreats due to the seaward growth of the sedimentary wedge that also unbends the slab. This decrease in megathrust dip results in a wider seismogenic zone, so that the maximum magnitude of megathrust earthquakes increases. Concurrently, the recurrence time of characteristic events increases and partial ruptures are introduced. The maximum magnitude estimated for subduction segments with the thickest sediment input (Makran, West‐Aegean, and Calabria) is distinctly higher than the instrumentally recorded magnitude. These segments may thus experience larger than as of yet observed earthquakes, albeit infrequently. Increasing sediment thickness also decreases megathrust normal stresses, as the seismogenic zone is more shallow and overlain by a lighter forearc structure. Thicker incoming plate sediments also favor more splay fault activity, whereas we observe more outer rise events for low sediment thickness. Finally, we demonstrate that modeling long‐term subduction dynamics and sediment subduction is crucial for understanding and quantifying megathrust seismicity and seismic potential of subduction zones.
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  • 11
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    Impact Forecasting to Support Emergency Management of Natural Hazards (2020)
    In:  Reviews of Geophysics
    Details
    Publication Date: 2020-12-14
    Description: Forecasting and early warning systems are important investments to protect lives, properties and livelihood. While early warning systems are frequently used to predict the magnitude, location and timing of potentially damaging events, these systems rarely provide impact estimates, such as the expected amount and distribution of physical damage, human consequences, disruption of services or financial loss. Complementing early warning systems with impact forecasts has a two‐fold advantage: it would provide decision makers with richer information to take informed decisions about emergency measures, and focus the attention of different disciplines on a common target. This would allow capitalizing on synergies between different disciplines and boosting the development of multi‐hazard early warning systems. This review discusses the state‐of‐the‐art in impact forecasting for a wide range of natural hazards. We outline the added value of impact‐based warnings compared to hazard forecasting for the emergency phase, indicate challenges and pitfalls, and synthesize the review results across hazard types most relevant for Europe.
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  • 12
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    Levee Breaching: A New Extension to the LISFLOOD-FP Model (2020)
    In:  Water
    Details
    Publication Date: 2021-02-04
    Description: Levee failures due to floods often cause considerable economic damage and life losses in inundated dike-protected areas, and significantly change flood hazard upstream and downstream the breach location during the event. We present a new extension for the LISFLOOD-FP hydrodynamic model which allows levee breaching along embankments in fully two-dimensional (2D) mode. Our extension allows for breach simulations in 2D structured grid hydrodynamic models at different scales and for different hydraulic loads in a computationally efficient manner. A series of tests performed on synthetic and historic events of different scale and magnitude show that the breaching module is numerically stable and reliable. We simulated breaches on synthetic terrain using unsteady flow as an upstream boundary condition and compared the outcomes with an identical setup of a full-momentum 2D solver. The synthetic tests showed that differences in the maximum flow through the breach between the two models were less than 1%, while for a small-scale flood event on the Secchia River (Italy), it was underestimated by 7% compared to a reference study. A large scale extreme event simulation on the Po River (Italy) resulted in 83% accuracy (critical success index).
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  • 13
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    Microbial Signatures in Deep CO2-Saturated Miocene Sediments of the Active Hartoušov Mofette System (NW Czech Republic) (2020)
    In:  Frontiers in Microbiology
    Details
    Publication Date: 2020-12-14
    Description: The Hartoušov mofette system is a natural CO2 degassing site in the central Cheb Basin (Eger Rift, Central Europe). In early 2016 a 108 m deep core was obtained from this system to investigate the impact of ascending mantle-derived CO2 on indigenous deep microbial communities and their surrounding life habitat. During drilling, a CO2 blow out occurred at a depth of 78.5 meter below surface (mbs) suggesting a CO2 reservoir associated with a deep low-permeable CO2-saturated saline aquifer at the transition from Early Miocene terrestrial to lacustrine sediments. Past microbial communities were investigated by hopanoids and glycerol dialkyl glycerol tetraethers (GDGTs) reflecting the environmental conditions during the time of deposition rather than showing a signal of the current deep biosphere. The composition and distribution of the deep microbial community potentially stimulated by the upward migration of CO2 starting during Mid Pleistocene time was investigated by intact polar lipids (IPLs), quantitative polymerase chain reaction (qPCR), and deoxyribonucleic acid (DNA) analysis. The deep biosphere is characterized by microorganisms that are linked to the distribution and migration of the ascending CO2-saturated groundwater and the availability of organic matter instead of being linked to single lithological units of the investigated rock profile. Our findings revealed high relative abundances of common soil and water bacteria, in particular the facultative, anaerobic and potential iron-oxidizing Acidovorax and other members of the family Comamonadaceae across the whole recovered core. The results also highlighted the frequent detection of the putative sulfate-oxidizing and CO2-fixating genus Sulfuricurvum at certain depths. A set of new IPLs are suggested to be indicative for microorganisms associated to CO2 accumulation in the mofette system.
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  • 14
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    Mineral nutrients sourced in deep regolith sustain long‐term nutrition of mountainous temperate forest ecosystems (2020)
    In:  Global Biogeochemical Cycles
    Details
    Publication Date: 2020-12-14
    Description: Primary productivity of forest ecosystems depends on the availability of plant‐essential mineral nutrients. Because nutrient demand of trees often exceeds nutrient supply from rock, tree nutrition is sustained by efficient re‐utilization of organic‐bound nutrients. These nutrients are continuously returned from trees to the forest floor in litterfall. However, over millennia nutrient limitation may develop in landscapes from which nutrients are permanently lost by drainage and erosion. Such a deficit is prevented if advection of unweathered bedrock towards the surface as driven by erosion continuously supplies fresh nutrients. Yet, the mechanisms and the depth range over which this deep nutrient resource is accessed are poorly known. We show that in two montane temperate forest ecosystems in the Black Forest and Bavarian Forest the geogenic source of nutrients was found within a depth zone of several meters. This deep zone contains a large pool of biologically available nutrients. We applied isotope ratios as proxies for nutrient uptake depth, and we tracked the regolith depth at which the isotope ratios of 87Sr/86Sr and 10Be(meteoric)/9Be match the respective values in plant tissue. We mapped the depth distribution of the biologically available calcium‐bound form of the most plant‐essential mineral nutrient phosphorus and found that the depth of phosphorus availability is as deep or even deeper as the range defined by the isotope ratios. We conclude that nutrient supply from a regolith depth of several meters is critical for forest ecosystem function in landscapes of moderate hillslopes and rainfall that are affected by permanent nutrient loss.
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  • 15
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    New insights into the structural elements of the upper mantle beneath the contiguous United States from S-to-P converted seismic waves (2020)
    In:  Geophysical Journal International
    Details
    Publication Date: 2021-03-10
    Description: The S-receiver function (SRF) technique is an effective tool to study seismic discontinuities in the upper mantle such as the mid-lithospheric discontinuity (MLD) and the lithosphere–asthenosphere boundary (LAB). This technique uses deconvolution and aligns traces along the maximum of the deconvolved SV signal. Both of these steps lead to acausal signals, which may cause interference with real signals from below the Moho. Here we go back to the origin of the SRF method and process S-to-P converted waves using S-onset times as the reference time and waveform summation without any filter like deconvolution or bandpass. We apply this ‘causal’ SRF (C-SRF) method to data of the USArray and obtain partially different results in comparison with previous studies using the traditional acausal SRF method. The new method does not confirm the existence of an MLD beneath large regions of the cratonic US. The shallow LAB in the western US is, however, confirmed with the new method. The elimination of the MLD signal below much of the cratonic US reveals lower amplitude but highly significant phases that previously had been overwhelmed by the apparent MLD signals. Along the northern part of the area with data coverage we see relics of Archean or younger northwest directed low-angle subduction below the entire Superior Craton. In the cratonic part of the US we see indications of the cratonic LAB near 200 km depth. In the Gulf Coast of the southern US, we image relics of southeast directed shallow subduction, likely of mid-Palaeozoic age.
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  • 16
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    Novel experimental setup for megahertz X-ray diffraction in a diamond anvil cell at the High Energy Density (HED) instrument of the European X-ray Free-Electron Laser (EuXFEL) (2021)
    In:  Journal of Synchrotron Radiation
    Details
    Publication Date: 2021-06-10
    Description: The high-precision X-ray diffraction setup for work with diamond anvil cells (DACs) in interaction chamber 2 (IC2) of the High Energy Density instrument of the European X-ray Free-Electron Laser is described. This includes beamline optics, sample positioning and detector systems located in the multipurpose vacuum chamber. Concepts for pump-probe X-ray diffraction experiments in the DAC are described and their implementation demonstrated during the First User Community Assisted Commissioning experiment. X-ray heating and diffraction of Bi under pressure, obtained using 20 fs X-ray pulses at 17.8 keV and 2.2 MHz repetition, is illustrated through splitting of diffraction peaks, and interpreted employing finite element modeling of the sample chamber in the DAC.
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  • 17
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    Overview: Integrative and Comprehensive Understanding on Polar Environments (iCUPE) – concept and initial results (2020)
    In:  Atmospheric Chemistry and Physics
    Details
    Publication Date: 2020-12-10
    Description: The role of polar regions is increasing in terms of megatrends such as globalization, new transport routes, demography, and the use of natural resources with consequent effects on regional and transported pollutant concentrations. We set up the ERA-PLANET Strand 4 project “iCUPE – integrative and Comprehensive Understanding on Polar Environments” to provide novel insights and observational data on global grand challenges with an Arctic focus. We utilize an integrated approach combining in situ observations, satellite remote sensing Earth observations (EOs), and multi-scale modeling to synthesize data from comprehensive long-term measurements, intensive campaigns, and satellites to deliver data products, metrics, and indicators to stakeholders concerning the environmental status, availability, and extraction of natural resources in the polar areas. The iCUPE work consists of thematic state-of-the-art research and the provision of novel data in atmospheric pollution, local sources and transboundary transport, the characterization of arctic surfaces and their changes, an assessment of the concentrations and impacts of heavy metals and persistent organic pollutants and their cycling, the quantification of emissions from natural resource extraction, and the validation and optimization of satellite Earth observation (EO) data streams. In this paper we introduce the iCUPE project and summarize initial results arising out of the integration of comprehensive in situ observations, satellite remote sensing, and multi-scale modeling in the Arctic context.
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    Probabilistic Flood Loss Models for Companies (2020)
    In:  Water Resources Research
    Details
    Publication Date: 2020-12-14
    Language: English
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    Probabilistic Tsunami Hazard and Risk Analysis: A Review of Research Gaps (2021)
    In:  Frontiers in Earth Science
    Details
    Publication Date: 2021-07-30
    Description: Tsunamis are unpredictable and infrequent but potentially large impact natural disasters. To prepare, mitigate and prevent losses from tsunamis, probabilistic hazard and risk analysis methods have been developed and have proved useful. However, large gaps and uncertainties still exist and many steps in the assessment methods lack information, theoretical foundation, or commonly accepted methods. Moreover, applied methods have very different levels of maturity, from already advanced probabilistic tsunami hazard analysis for earthquake sources, to less mature probabilistic risk analysis. In this review we give an overview of the current state of probabilistic tsunami hazard and risk analysis. Identifying research gaps, we offer suggestions for future research directions. An extensive literature list allows for branching into diverse aspects of this scientific approach.
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    Quantifying drought effects in Central European grasslands through regression-based unmixing of intra-annual Sentinel-2 time series (2022)
    In:  Remote Sensing of Environment
    Details
    Publication Date: 2021-12-15
    Description: Severe droughts caused unprecedented impacts on grasslands in Central Europe in 2018 and 2019. Yet, spatially varying drought impacts on grasslands remain poorly understood as they are driven by complex interactions of environmental conditions and land management. Sentinel-2 time series offer untapped potential for improving grassland monitoring during droughts with the required spatial and temporal detail. In this study, we quantified drought effects in a major Central European grassland region from 2017 to 2020 using a regression-based unmixing framework. The Sentinel-2-based intra-annual time series of photosynthetic vegetation (PV), non-photosynthetic vegetation (NPV), and soil fractional cover provide easily interpretable quantities relevant for understanding drought effects on grasslands. Fractional cover estimates from Sentinel-2 matched in-situ conditions observed during field visits. The comparison to a multitemporal reference dataset showed the best agreement for PV cover (MAE = 7.2%). Agreement was lower for soil and NPV, but we observed positive relationships between fractional cover from Sentinel-2 and the reference data with MAE = 10.1% and MAE = 15.4% for soil and NPV, respectively. Based on the fractional cover estimates, we derived a Normalized Difference Fraction Index (NDFI) time series contrasting NPV and soil cover relative to PV. In line with meteorological and soil moisture drought indices, and with the Normalized Difference Vegetation Index (NDVI), NDFI time series showed the most severe drought impacts in 2018, followed by less severe, but persisting effects in 2019. Drought-specific metrics from NDFI time series revealed a high spatial variability of onset, duration, impact, and end of drought effects on grasslands. Evaluating drought metrics on different soil types, we found that grasslands on less productive, sandy Cambisols were strongly affected by the drought in 2018 and 2019. In comparison, grasslands on Gleysols and Histosols were less severely impacted suggesting a higher drought resistance of these grasslands. Our study emphasizes that the high temporal and spatial detail of Sentinel-2 time series is mandatory for capturing relevant vegetation dynamics in Central European lowland grasslands under drought.
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    Quasi‐10‐Day Wave and Semidiurnal Tide Nonlinear Interactions During the Southern Hemispheric SSW 2019 Observed in the Northern Hemispheric Mesosphere. (2020)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2021-01-27
    Description: Mesospheric winds from three longitudinal sectors at 65°N and 54°N latitude are combined to diagnose the zonal wave numbers (m) of spectral wave signatures during the Southern Hemisphere sudden stratospheric warming (SSW) 2019. Diagnosed are quasi‐10‐ and 6‐day planetary waves (Q10DW and Q6DW, m = 1), solar semidiurnal tides with m = 1, 2, 3 (SW1, SW2, and SW3), lunar semidiurnal tide, and the upper and lower sidebands (USB and LSB, m = 1 and 3) of Q10DW‐SW2 nonlinear interactions. We further present 7‐year composite analyses to distinguish SSW effects from climatological features. Before (after) the SSW onset, LSB (USB) enhances, accompanied by the enhancing (fading) Q10DW, and a weakening of climatological SW2 maximum. These behaviors are explained in terms of Manley‐Rowe relation, that is, the energy goes first from SW2 to Q10DW and LSB, and then from SW2 and Q10DW to USB. Our results illustrate that the interactions can explain most wind variabilities associated with the SSW.
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    Reservoir formation damage during hydrate dissociation in sand-clay sediment from Qilian Mountain permafrost, China (2020)
    In:  Applied Energy
    Details
    Publication Date: 2021-02-23
    Description: Permeability is known as a key factor affecting the gas production effectiveness from the natural gas hydratebearing reservoir. We studied the permeability behavior of natural clayey sand core samples from a natural hydrate-bearing reservoir in the Qilian Mountain permafrost before and after hydrate formation, as well as after hydrate decomposition. We found a substantially lower permeability after hydrate decomposition and assumed a formation damage process involving fines mobilization, migration and deposition at pore throats. The assumption was proved by SEM analysis of the filter paper separating the sample and the end caps containing the fluid ports. The analysis showed fines trapped in the paper from the outlet side. Fines migration and resulting formation damage is known from enhanced oil recovery by low salinity water flooding, but was unexpected for hydrate decomposition. The underlying mechanism was identified by a series of different permeability tests. The results indicate that fresh water released from the hydrate dissociation causes the fines mobilization, migration and redeposition at pore throats leading to the observed permeability decrease. Obviously the large volume of released methane gas displaces the remaining saline water and separates it from the fresh water released from the hydrate. The fresh water in contact with parts of the grain framework causes the detachment of clay particles by increased electrostatic forces and clay swelling, if swellable clays are present. This is an important mechanism that has to be taken into account in the planning of gas production from low-permeability clayey hydratebearing formations.
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    Rock weathering and nutrient cycling along an erodosequence (2021)
    In:  American Journal of Science
    Details
    Publication Date: 2021-11-24
    Description: How flowing water and organisms can shape Earth's surface, the Critical Zone, depends on how fast this layer is turned over by erosion. To quantify the dependence of rock weathering and the cycling of elements through ecosystems on erosion we have used existing and new metrics that quantify the partitioning and cycling of elements between rock, saprolite, soil, plants, and river dissolved and solid loads. We demonstrate their utility at three sites along a global transect of mountain landscapes that differ in erosion rates – an “erodosequence”. These sites are the Swiss Central Alps, a rapidly-eroding, post-glacial mountain belt; the Southern Sierra Nevada, USA, eroding at moderate rates; and the slowly-eroding tropical Highlands of Sri Lanka. The backbone of this analysis is an extensive data set of rock, saprolite, soil, water, and plant geochemical and isotopic data. This set of material properties is converted into process rates by using regolith production and weathering rates from cosmogenic nuclides and river loads, and estimates of biomass growth. Combined, these metrics allow us to derive elemental fluxes through regolith and vegetation. The main findings are: 1) the rates of weathering are set locally in regolith, and not by the rate at which entire landscapes erode; 2) the degree of weathering is mainly controlled by regolith residence time. This results in supply-limited weathering in Sri Lanka where weathering runs to completion in the regolith, and kinetically-limited weathering in the Alps and Sierra Nevada where soluble primary minerals persist; 3) these weathering characteristics are reflected in the sites' ecosystem processes, namely in that nutritive elements are intensely recycled in the supply-limited setting, and directly taken up from soil and rock in the kinetically settings; 4) the weathering rates are not controlled by biomass growth; 5) at all sites we find a deficit in river solute export when compared to solute production in regolith, the extent of which differs between elements. Plant uptake followed by litter export might explain this deficit for biologically utilized elements of high solubility, and rare, high-discharge flushing events for colloidal-bound elements of low solubility. Our data and new metrics have begun to serve for calibrating metal isotope systems in the weathering zone, the isotope ratios of which depend on the flux partitioning between the compartments of the Critical Zone. We demonstrate this application in several isotope geochemical companion papers.
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    Role of Serpentinized Mantle Wedge in Affecting Megathrust Seismogenic Behavior in the Area of the 2010M = 8.8 Maule Earthquake (2020)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2021-04-29
    Description: What controls subduction megathrust seismogenesis downdip of the mantle wedge corner (MWC)? We propose that, in the region of the 2010 Mw = 8.8 Maule, Chile, earthquake, serpentine minerals derived from the base of the hydrated mantle wedge exert a dominant control. Based on modeling, we predict that the megathrust fault zone near the MWC contains abundant lizardite/chrysotile‐rich serpentinite that transforms to antigorite‐rich serpentinite at greater depths. From the MWC at 32–40 km depth to at least 55 km, the predominantly velocity‐strengthening megathrust accommodated dynamic propagation of the 2010 rupture but with small slip and negative stress drop. The downdip distribution of interplate aftershocks exhibits a gap around the MWC that can be explained by the velocity‐strengthening behavior of lizardite/chrysotile. Interspersed velocity‐weakening and dynamic weakening antigorite‐rich patches farther downdip may be responsible for increased abundance of aftershocks and possibly for some of the high‐frequency energy radiation during the 2010 rupture.
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    Role Of the Sun and the Middle atmosphere/thermosphere/ionosphere In Climate (ROSMIC): a retrospective and prospective view (2021)
    In:  Progress in Earth and Planetary Science
    Details
    Publication Date: 2021-10-29
    Description: While knowledge of the energy inputs from the Sun (as it is the primary energy source) is important for understanding the solar-terrestrial system, of equal importance is the manner in which the terrestrial part of the system organizes itself in a quasi-equilibrium state to accommodate and re-emit this energy. The ROSMIC project (2014–2018 inclusive) was the component of SCOSTEP’s Variability of the Sun and Its Terrestrial Impact (VarSITI) program which supported research into the terrestrial component of this system. The four themes supported under ROSMIC are solar influence on climate, coupling by dynamics, trends in the mesosphere lower thermosphere, and trends and solar influence in the thermosphere. Over the course of the VarSITI program, scientific advances were made in all four themes. This included improvements in understanding (1) the transport of photochemically produced species from the thermosphere into the lower atmosphere; (2) the manner in which waves produced in the lower atmosphere propagate upward and influence the winds, dynamical variability, and transport of constituents in the mesosphere, ionosphere, and thermosphere; (3) the character of the long-term trends in the mesosphere and lower thermosphere; and (4) the trends and structural changes taking place in the thermosphere. This paper reviews the progress made in these four areas over the past 5 years and summarizes the anticipated research directions in these areas in the future. It also provides a physical context of the elements which maintain the structure of the terrestrial component of this system. The effects that changes to the atmosphere (such as those currently occurring as a result of anthropogenic influences) as well as plausible variations in solar activity may have on the solar terrestrial system need to be understood to support and guide future human activities on Earth.
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    Search forhepsolar neutrinos and the diffuse supernova neutrino background using all three phases of the Sudbury Neutrino Observatory (2020)
    In:  Physical Review D
    Details
    Publication Date: 2020-12-14
    Description: A search has been performed for neutrinos from two sources, the hep reaction in the solar pp fusion chain and the νe component of the diffuse supernova neutrino background (DSNB), using the full dataset of the Sudbury Neutrino Observatory with a total exposure of 2.47  kton−years after fiducialization. The hep search is performed using both a single-bin counting analysis and a likelihood fit. We find a best-fit flux that is compatible with solar model predictions while remaining consistent with zero flux, and set a one-sided upper limit of Φhep〈30×103  cm−2 s−1 [90% credible interval (CI)]. No events are observed in the DSNB search region, and we set an improved upper bound on the νe component of the DSNB flux of ΦDSNBνe〈19  cm−2 s−1 (90% CI) in the energy range 22.9〈Eν〈36.9  MeV.
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    Seismic moment evolution during hydraulic stimulations (2020)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2020-12-11
    Description: Analysis of past and present stimulation projects reveals that the temporal evolution and growth of maximum observed moment magnitudes may be linked directly to the injected fluid volume and hydraulic energy. Overall evolution of seismic moment seems independent of the tectonic stress regime and is most likely governed by reservoir specific parameters, such as the preexisting structural inventory. Data suggest that magnitudes can grow either in a stable way, indicating the constant propagation of self‐arrested ruptures, or unbound, for which the maximum magnitude is only limited by the size of tectonic faults and fault connectivity. Transition between the two states may occur at any time during injection or not at all. Monitoring and traffic light systems used during stimulations need to account for the possibility of unstable rupture propagation from the very beginning of injection by observing the entire seismicity evolution in near‐real time and at high resolution for an immediate reaction in injection strategy.
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    September 2019 Antarctic Sudden Stratospheric Warming: Quasi‐6‐Day Wave Burst and Ionospheric Effects (2020)
    In:  Geophysical Research Letters
    Details
    Publication Date: 2020-12-11
    Description: An exceptionally strong stationary planetary wave with Zonal Wavenumber 1 led to a sudden stratospheric warming (SSW) in the Southern Hemisphere in September 2019. Ionospheric data from European Space Agency's Swarm satellite constellation mission show prominent 6‐day variations in the dayside low‐latitude region at this time, which can be attributed to forcing from the middle atmosphere by the Rossby normal mode “quasi‐6‐day wave” (Q6DW). Geopotential height measurements by the Microwave Limb Sounder aboard National Aeronautics and Space Administration's Aura satellite reveal a burst of global Q6DW activity in the mesosphere and lower thermosphere during the SSW, which is one of the strongest in the record. The Q6DW is apparently generated in the polar stratosphere at 30–40 km, where the atmosphere is unstable due to strong vertical wind shear connected with planetary wave breaking. These results suggest that an Antarctic SSW can lead to ionospheric variability through wave forcing from the middle atmosphere.
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    Soft stimulation treatment of geothermal well RV-43 to meet the growing heat demand of Reykjavik (2021)
    In:  Geothermics
    Details
    Publication Date: 2021-06-23
    Description: Reykjavik is almost entirely heated by geothermal energy. Yet, recent growth of the city significantly increased the heat demand. Past experiences in Iceland’s capital region showed that hydraulic stimulation of existing geothermal wells is suited to improve hydraulic performance and energy supply. However, fluid injection may also trigger felt or even damaging earthquakes, which are of concern in populated areas and pose a significant risk to stimulation operations. Consequently, soft stimulation concepts have been developed to increase geothermal well performance while minimizing environmental effects such as induced seismicity. In a demonstration project of hydraulic soft stimulation in October 2019, more than 20.000 m3 of water were injected into well RV-43 in Reykjavik in multiple stages and with different injection schemes. The hydraulic performance of the well was improved without inducing felt seismicity. An a priori seismic risk assessment was conducted and for the first time the risk was continuously updated by an adaptive traffic light system supported by a sophisticated realtime microseismic monitoring. Our results confirm that it is possible to improve the performance of geothermal wells in Reykjavik and worldwide with acceptable technical, economic, and environmental risks. Here we provide an overview of the entire stimulation project including site description, stimulation design, zonal isolation, logging, seismic risk assessment and mitigation measures, realtime seismic, hydraulic and chemical monitoring, and stimulation results and challenges.
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    Studying boundary layer methane isotopy and vertical mixing processes at a rewetted peatland site using an unmanned aircraft system (2020)
    In:  Atmospheric Measurement Techniques
    Details
    Publication Date: 2020-12-10
    Description: The combination of two well-established methods, of quadrocopter-borne air sampling and methane isotopic analyses, is applied to determine the source process of methane at different altitudes and to study mixing processes. A proof-of-concept study was performed to demonstrate the capabilities of quadrocopter air sampling for subsequently analysing the methane isotopic composition δ13C in the laboratory. The advantage of the system compared to classical sampling on the ground and at tall towers is the flexibility concerning sampling location, and in particular the flexible choice of sampling altitude, allowing the study of the layering and mixing of air masses with potentially different spatial origin of air masses and methane. Boundary layer mixing processes and the methane isotopic composition were studied at Polder Zarnekow in Mecklenburg–West Pomerania in the north-east of Germany, which has become a strong source of biogenically produced methane after rewetting the drained and degraded peatland. Methane fluxes are measured continuously at the site. They show high emissions from May to September, and a strong diurnal variability. For two case studies on 23 May and 5 September 2018, vertical profiles of temperature and humidity were recorded up to an altitude of 650 and 1000 m, respectively, during the morning transition. Air samples were taken at different altitudes and analysed in the laboratory for methane isotopic composition. The values showed a different isotopic composition in the vertical distribution during stable conditions in the morning (delta values of −51.5 ‰ below the temperature inversion at an altitude of 150 m on 23 May 2018 and at an altitude of 50 m on 5 September 2018, delta values of −50.1 ‰ above). After the onset of turbulent mixing, the isotopic composition was the same throughout the vertical column with a mean delta value of −49.9 ± 0.45 ‰. The systematically more negative delta values occurred only as long as the nocturnal temperature inversion was present. During the September study, water samples were analysed as well for methane concentration and isotopic composition in order to provide a link between surface and atmosphere. The water samples reveal high variability on horizontal scales of a few tens of metres for this particular case. The airborne sampling system and consecutive analysis chain were shown to provide reliable and reproducible results for two samples obtained simultaneously. The method presents a powerful tool for distinguishing the source process of methane at different altitudes. The isotopic composition showed clearly depleted delta values directly above a biological methane source when vertical mixing was hampered by a temperature inversion, and different delta values above, where the air masses originate from a different footprint area. The vertical distribution of methane isotopic composition can serve as tracer for mixing processes of methane within the atmospheric boundary layer.
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    Temporal Modulation of the Local Microseism in the North Sea (2020)
    In:  Journal of Geophysical Research: Solid Earth
    Details
    Publication Date: 2021-02-05
    Description: Primary and secondary microseism originating in the world oceans and peaking at around 14 and 7 s, respectively, characterize the Earth's background noise in that frequency range. Microseism generated in marginal seas with partly shorter periods and higher spatial and temporal variability is less studied and requires stations in immediate proximity to the source to be observed. Such studies can help to elucidate the exact microseism generation areas and mechanisms in a constrained area. We analyze 15 years of broadband data recorded at the seismic station on Helgoland island in the marginal North Sea. In addition to remote primary (RPM) and secondary microseism (RSM) originating in the North Atlantic, we observe strong and dominant local secondary microseism (LSM) with on average higher frequencies above 0.2 Hz, in accordance with shorter wave periods of about 4–8 s in the shallow North Sea. During times with low RSM activity we observe local primary microseism (LPM) at frequencies in agreement with local ocean wave periods. The higher horizontal to vertical (H/V) ratio of LPM with respect to LSM indicates a major non‐Rayleigh wave contribution. LSM and LPM show a strong modulation with local semidiurnal ocean tides and microseism energy maxima preceding the water level maximum by 2.5 and 1.5 hr, respectively. This time shift might be influenced by stronger currents during rising than falling tides. Active sources of tide‐modulated microseism migrate along the North Sea coast in sync with the ocean tidal signal as evidenced by comparison of LSM maxima at stations distributed along the coast.
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    Understanding the Total Electron Content Variability Over Europe During 2009 and 2019 SSWs (2021)
    In:  Journal of Geophysical Research: Space Physics
    Details
    Publication Date: 2021-10-08
    Description: The nature of the variability of the Total Electron Content (TEC) over Europe is investigated during 2009 and 2019 Northern Hemisphere (NH) SSW events in this study by using a combination of Global Navigation Satellite System (GNSS) based TEC observations and Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM) simulations. To simulate the SSW effects in TIE-GCM, the dynamical fields from the Whole Atmosphere Community Climate Model with thermosphere and ionosphere extension (WACCM-X) simulations of 2009 and 2019 SSWs are specified at the TIE-GCM lower boundary. The observed and simulated TEC are in overall good agreement and therefore the simulations are used to understand the sources of mid-latitude TEC variability during both SSWs. Through comparison of TIE-GCM simulations with and without geomagnetic forcing, we find that the TEC variability during the 2019 SSW event, was predominantly geomagnetically forced, while for the 2009 SSW, the major variability in TEC was accounted for by the changes in vertically propagating migrating semidiurnal solar (SW2) and lunar (M2) tides. By comparing the TIE-GCM simulations with and without the SW2 and M2 tides, we find that these semidiurnal tides contribute to urn:x-wiley:21699380:media:jgra56728:jgra56728-math-000120%–25% increase in the quiet background TEC.
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    VERA : VERtical coupling in Earth’s Atmosphere at mid and high latitudes ; Final Report (2020)
    German Research Centre for Geosciences GFZ
    Details
    Publication Date: 2020-11-18
    Language: English
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    Zircon and Melt Extraction From a Long‐Lived and Vertically Extensive Magma System Underneath Ilopango Caldera (El Salvador) (2021)
    In:  Geochemistry Geophysics Geosystems (G3)
    Details
    Publication Date: 2021-06-23
    Description: The Tierra Blanca (TB) eruptive suite comprises the last four major eruptions of Ilopango caldera in El Salvador (≤45 ka), including the youngest Tierra Blanca Joven eruption (TBJ; ∼106 km3): the most voluminous event during the Holocene in Central America. Despite the protracted and productive history of explosive silicic eruptions at Ilopango caldera, many aspects regarding the longevity and the prevailing physicochemical conditions of the underlying magmatic system remain unknown. Zircon 238U‐230Th geochronology of the TB suite (TBJ, TB2, TB3, and TB4) reveals a continuous and overlapping crystallization history among individual eruptions, suggesting persistent melt presence in thermally and compositionally distinct magma reservoirs over the last ca. 80 kyr. The longevity of zircon is in contrast to previously determined crystallization timescales of 〈10 kyr for major mineral phases in TBJ. This dichotomy is explained by a process of rhyolitic melt segregation from a crystal‐rich refractory residue that incorporates zircon, whereas a new generation of major mineral phases crystallized shortly before eruption. Ti‐in‐zircon temperatures and amphibole geothermobarometry suggest that rhyolitic melt was extracted from different storage zones of the magma reservoir as indicated by distinct but synchronous thermochemical zircon histories among the TB suite eruptions. Zircon from TBJ and TB2 suggests magma differentiation within deeper and hotter parts of the reservoir, whereas zircon from TB3 and TB4 instead hints at crystallization in comparatively shallower and cooler domains. The assembly of the voluminous TBJ magma reservoir was also likely enhanced by cannibalization of hydrothermally altered components as suggested by low‐δ18O values in zircon (+4.5 ± 0.3‰).
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    Zonal Wave Number Diagnosis of Rossby Wave‐Like Oscillations Using Paired Ground‐Based Radars (2020)
    In:  Journal of Geophysical Research: Atmospheres
    Details
    Publication Date: 2020-12-14
    Description: Free traveling Rossby wave normal modes (RNMs) are often investigated through large‐scale space‐time spectral analyses, which therefore is subject to observational availability, especially in the mesosphere. Ground‐based mesospheric observations were broadly used to identify RNMs mostly according to the periods of RNMs without resolving their horizontal scales. The current study diagnoses zonal wave numbers of RNM‐like oscillations occurring in mesospheric winds observed by two meteor radars at about 79°N. We explore four winters comprising the major stratospheric sudden warming events (SSWs) 2009, 2010, and 2013. Diagnosed are predominant oscillations at the periods of 10 and 16 days lasting mostly for three to five whole cycles. All dominant oscillations are associated with westward zonal wave number m =1, excepting one 16‐day oscillation associated with m =2. We discuss the m =1 oscillations as transient RNMs and the m =2 oscillation as a secondary wave of nonlinear interaction between an RNM and a stationary Rossby wave. All the oscillations occur around onsets of the three SSWs, suggesting associations between RNMs and SSWs. For comparison, we also explore the wind collected by a similar network at 54°N during 2012–2016. Explored is a manifestation of 5‐day wave, namely, an oscillation at 5–7 days with m =1), around the onset of SSW 2013, supporting the associations between RNMs and SSWs.
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