bluuebunny/crossref_metadata_2025 huggingface dataset:
The Energy Budget of an Altimeter-Derived Baroclinic Tide Model
Authors: Zaron Edward , Musgrave Ruth
Published: March 2021

Over the last few years a number of groups have created maps of the baroclinic tide from satellite altimeter measurements of sea-surface height (SSH). These maps can be used as predictive models for the baroclinic tides, e.g., for removing aliased tidal signals from altimetry, but they can also be used to diagnose aspects of the tidal dynamics. This presentation uses the High Resolution Emprical Tide (HRET) model to compute the phase speed, energy, energy flux, and energy flux divergence of the first few baroclinic modes for the M2, S2, K1, and O1 tides, and compares these with independent estimates from the literature.

The phase speed of the waves in HRET are compared with the theoretically-predicted phase speeds computed from stratification. For the mode-1 M2 waves which are determined most accurately, the theoretical and observed phase speeds agree very well; however, there is a small bias, namely, the theoretical phase speed exceeds the observed phase speed by 1 to 2%. This offset could reflect either a methodological estimation bias, issues with the data used to compute the theoretical phase speed, or a limitation of the theory for the vertical modes.

The phase speed results provide some confidence in the usefulness of linear wave dynamics for interpreting the HRET SSH. Using a simplified form of the momentum equations, the area-integrated kinetic plus potential energy of the mode-1 M2 tide is found to be 43 PJ, larger than in other baroclinic tide models, and with nearly isotropic directional distribution. For mode 1, the divergence of the energy flux diagnosed from HRET agrees well with previous estimates based on the barotropic tides. For the most accurately-determined mode-1 M2 tide, the results provide new information about sources and sinks of baroclinic energy along the continental shelves, and they are used to examine the accuracy of a commonly-used approximation of the baroclinic energy flux.
Calculating the Height and the Position of Volcanic Cloud SO2 With a Lagrangian Trajectory Tool 
Authors: Gorkavyi Nick , Krotkov Nickolay , Li Can , Lait Leslie , Carn Simon , Colarco Peter , Fedkin Nikita , DeLand Matthew , Schoeberl Mark , Vasilkov Alexander , Joiner Joanna
Published: March 2021

We have developed a new trajectory tool to reconstruct the altitude and the position of SO2 in a volcanic plume. Starting with 2D map of satellite observed SO2, known volcano location, and reanalysis wind fields from the NASA Goddard Earth Observing System (GEOS) model, the Goddard trajectory tool allows us to estimate the altitude and concentration of SO2 in the volcanic plume at time of observation. We used this tool for the June 21, 2019 Mt. Raikoke eruption and the June 15, 1991 Mt. Pinatubo event. We used SO2 data from the Ozone Mapping and Profiler Suite/Nadir Mapper (OMPS/NM) onboard the NASA-NOAA Suomi satellite and obtained a distribution of SO2 altitudes between 1 and 19 kilometers in different parts of the Raikoke SO2 clouds, with the highest SO2 concentration between 11 and 16 km, in good agreement with data from independent SO2 layer height retrievals from the Ozone Monitoring Instrument (OMI) aboard the NASA Aura spacecraft; the Tropospheric Monitoring Instrument (TROPOMI) onboard the European Copernicus Sentinel 5 precursor satellite and Infrared Atmospheric Sounding Interferometer (IASI) on the European Space Agency's (ESA) MetOp series of a polar orbiting satellites. We then applied this method to the Pinatubo eruption using SO2 column measurements from the NASA Total Ozone Mapping Spectrometer (TOMS) and using wind fields from the National Centers for Environmental Prediction Reanalysis version 2. We found that the southern part of the Pinatubo plume is located in the troposphere, and the northern part is in the stratosphere.
Estimating internal variability from relatively short regional-climate simulations
Authors: de Vries Hylke , Lenderink Geert , van der Wiel Karin
Published: March 2021

Convection permitting regional climate models (CP-RCMs, typical horizontal resolution O(1-3km)) are currently state of the art when it comes to simulating regional climate. Their level of resolved spatial detail and realistic behaviour of for example summer convection is unprecedented. Consequently, impact modelers and even society at large have a strong interest in their products. However, because the computational demands of running such CP-RCMs are still huge, most of the simulations to date are relatively short, typically on the order of 10 years. Future trends are then derived from differences between two single time-slice experiments.

In contrast, conventional regional climate models (RCMs), that operate on typical “CORDEX” resolution (O(10km)), nowadays are relatively cheap to run, making it feasible to generate large ensembles of long transient integrations. These ensembles allow for a better determination of the amplitude of the internal variability and therefore come with higher signal-to-noise ratios. Invariably, it turns out that internal variability on the 10-year time scale (i.e., the typical time scale of the CP-RCM simulations) is considerable, if not very large for climate parameters like mean precipitation and temperature, let alone for climate extremes. This not only holds for the RCM results of course, but also for the CP-RCMs, perhaps even more strongly.

Two questions arise. First, to what extent are the mean trends derived from CP-RCM simulations meaningful given the large amplitude of internal variability at time scales used for the simulation? Second, how can we estimate the amplitude of internal variability at the 10-year time scale in the first place? We examine answers to these two basic questions in the GCM/RCM world where large ensembles are routinely available. The expectation is that some of the lessons learned here will carry over to the CP-RCM world.
Imaging the Upper Plate Lithosphere and Asthenosphere beneath Alaska with Sp Converted Waves
Authors: Gama Isabella , M. Fischer Karen , Hua Junlin
Published: March 2021

To resolve the signatures of subduction zone processes in the mantle wedge, and how subduction has interacted with the upper plate, we imaged seismic velocity gradients beneath the US state of Alaska with Sp receiver function common conversion point (CCP) stacking.  Pacific plate lithosphere, and lithosphere bearing the thicker crust of the Yakutat terrane, subduct to the northwest beneath the southern margin of Alaska.   We employed data from hundreds of stations of the US NSF EarthScope Transportable Array, as well as other portable arrays and permanent networks. We calculated waveform components using a free-surface transform with improved estimates of free-surface velocities that were determined from P and SV particle motions. Sp receiver functions were calculated with time-domain deconvolution, and the CCP stack was generated with weighting functions that incorporate the properties of Sp scattering kernels. The CCP stack shows a clear interface between the North American and underthrust Yakutat crust, as well as Yakutat Moho depths of up to 60 km.  Sp phases from the negative velocity gradient at the base of the upper plate are strongest in west-central Alaska, where lithosphere-asthenosphere boundary (LAB) depths lie at 65-100 km.  In west-central Alaska, joint inversions of Sp data at single stations with Rayleigh phase velocities show comparable LAB depths as well as low asthenospheric velocities. This zone includes active magmatism and the upper plate appears to have been thinned by mantle wedge volatiles, melt, and flow.  The LAB phase deepens to the north, reaching depths of ~120 km beneath the northern Arctic Alaska terrane.  This increase in the depth of the LAB phase from the arc to the back-arc is consistent with the sculpting of the upper plate by subduction-related processes. Sp phases also delineate a prominent positive velocity gradient that represents the base of a low-velocity asthenospheric layer at depths of 100-130 km.  The positive velocity gradient is consistent with the onset of partial melting in the asthenosphere.

 
Observations of Cyanogen Bromide (BrCN) in the Global Atmosphere during the NASA Atmospheric Tomography mission (ATom) and Implications for Active Bromine Chemistry.
Authors: Roberts James , Wang Siyuan , Veres Patrick , Neuman J. Andrew , Allen Hannah , Crounse John , Kim Michelle , Xu Lu , Wennberg Paul , Rollins Andrew , Bourgeois Ilann , Peischl Jeff , Ryerson Thomas , Thompson Chelsea
Published: March 2021

Bromine activation (the production of Br in an elevated oxidation state) represents a mechanism for ozone destruction and mercury removal in the global troposphere, and has been a common feature of both polar boundary layers, often accompanied by nearly complete ozone destruction. The chemistry and budget of active bromine compounds (e.g. Br2, BrCl, HOBr) reflects the cycling of Br and ultimately its impact on the environment. Cyanogen bromide (BrCN) has recently been measured by iodide ion high resolution time-of-flight mass spectrometry (I- CIMS) during the NASA Atmospheric Tomography mission, and could be a previously unquantified participant in active Br chemistry. BrCN mixing ratios ranged from below detection limit (1.5pptv) up to as high as 48 pptv (10sec avg) and enhancements were almost exclusively confined to the polar boundary layers (PBL). Likely BrCN formation pathways involve the reactions of active Br (Br2, HOBr) with reduced nitrogen compounds. Gas phase loss processes due to reaction with radical species are likely quite slow and photolysis is known to be relatively slow. These features, and the lack of BrCN enhancements above the PBL, imply that surface reactions must be the major loss processes. Known liquid phase reactions of BrCN result in the conversion of the Br to bromide (Br-) or formation of C-Br bonded organic species, hence a loss of atmospheric active Br from that chemical cycle. Thus, accounting for the chemistry of BrCN will be an important aspect of understanding polar Br cycling.
Robust, an Earthquake Early Warning System in the Lower Rhine Embayment, Germany
Authors: Najdahmadi Bita , Pilz Marco , Bindi Dino , Njara Tendrisoa Razafindrakoto Hoby , Oth Adrien , Cotton Fabrice
Published: March 2021

The Lower Rhine Embayment in western Germany is one of the most important areas of earthquake recurrence north of the Alps, facing a moderate level of seismic hazard in the European context but a significant level of risk due to a large number of important industrial infrastructures. In this context, the project ROBUST aims at designing a user-oriented hybrid earthquake early warning and rapid response system where regional seismic monitoring is combined with smart, on-site sensors, resulting in the implementation of decentralized early warning procedures.

One of the research areas of this project deals with finding an optimal regional seismic network arrangement. With the optimally compacted network, strong ground movements can be detected quickly and reliably. In this work simulated scenario earthquakes in the area are used with an optimization approach in order to densify the existing sparse network through the installation of additional decentralized measuring stations. Genetic algorithms are used to design efficient EEW networks, computing optimal station locations and trigger thresholds in recorded ground acceleration. By minimizing the cost function, a comparison of the best earthquake early warning system designs is performed and the potential usefulness of existing stations in the region is considered as will be presented in the meeting.
Humming trains as an opportune source for imaging the shallow crust
Authors: Pinzon-Rincon Laura , Lavoué François , Mordret Aurélien , Boué Pierre , Brenguier Florent , Dales Philippe , Bean Christopher J. , Hollis Daniel
Published: March 2021

Freight trains are one of the most powerful and persistent seismic sources of cultural noise. They generate tremors equivalent to earthquakes of magnitude 1 that can be detectable up to 100 km distance.  Here, we propose to use the freight train passages as an opportunistic source of noise for passive seismic interferometry (SI). Usually, passive SI relies on blind correlations of long time series of noise for imaging and monitoring purposes. We suggest an alternative method based on noise source characterization, signal and station pairs selection, and specific seismic phase extraction (surface and body waves) for each virtual source to imaging the subsurface. To illustrate our novel method's potential, we show a case study in Canada's mineral exploration context, where we use retrieved body waves to estimate travel time tomography. This noise recovery approach to create valuable sources could be applied for several seismic noise sources and in different contexts improving spatial and temporal resolutions.
Heatwave risk for two regions of the UK: Aberdeenshire and South East England 
Authors: Sahani Jeetendra , Debele Sisay , Kumar Prashant
Published: March 2021

Global warming due to anthropogenic emission of green-house gases has induced climate change which is disturbing and will continue to impact the ecology and energy balance of our earth environment. The duration, frequency and intensity of extreme hot days in summers called heatwaves have increased with the beginning of the 21st century worldwide and have been projected to increase. Associated human health loss or damage can be managed or mitigated by planning proper management strategies, such as nature-based green and/or blue solutions in advance, along with proper evaluation of the risk of heat. Since heat stress is more pronounced in urban and built areas, most studies for heatwave risk assessment have been limited to big cities. The risk variation in semi-urban, sub-urban and rural areas has not been much investigated. The heat risk develops with time because of changing climate and socio-demographics, and risk assessment is needed to be done utilising recent data on climate and population characteristics. In this study, the heatwave or extreme hot (99 percentile) temperature risk has been estimated by using statistical approach on summer daily temperature and mortality data from Aberdeenshire and South East (SE) England, UK for the duration 1981-2018. A distributed-lag nonlinear model from Poisson regression family was applied to model the relationship between daily temperature and mortality. We calculated relative risk (RR) and mortality attributable fraction (AF) due to high temperature by comparing the extreme heat with the minimum mortality temperature. AF was calculated by dividing the number of excess deaths due to heat from all the days of the time-series by the total number of deaths. The overall risk in SE England was noted 56 % higher (RR 1.067) than Aberdeenshire (RR 1.043), with 36% more excess death in SE England (AF 0.15% and 0.11% respectively) due to different levels of people’s adaptation and resilience to different climate conditions.  The outcome of this study can help in site focused mitigation strategies to certain areas at most risk and develop a scientific framework for early warning, planning and managing the health impacts of heatwave in more rustic regions.

 

Acknowledgements: This work is supported by the European Union's Horizon 2020 research and innovation programme; funded by and carried out within the framework of OPERANDUM project (Grant no. 776848).
Impact of combined nitrogen loading and long-term drought on a semi-natural temperate grassland - achieving a process based understanding across scales
Authors: Dubbert Maren , Kübert Angelika , Piayda Arndt , Werner Christiane , Rothfuss Youri
Published: March 2021

Two important threats to the sustainable functioning of seminatural grasslands in temperate zones are (1) nutrient loading due to agricultural fertilization and pollution, and (2) the increase of extreme drought events due to climate change. These threats may cause substantial shifts in species diversity and abundance and considerably affect the carbon and water balance of ecosystems. The synergistic effects between those two threats, however, can be complex and are poorly understood. Here, we experimentally investigated the effects of nitrogen addition and extreme drought (separately and in combination) on a seminatural temperate grassland, located in Freiburg (South Germany). To study the grassland response, we combined eddy-covariance techniques with open gas exchange systems. Open gas exchange chambers were connected to an infrared gas analyzer and water isotope spectrometer, which allowed the partitioning of net ecosystem exchange and evapotranspiration. In addition, leaf level physiological responses, e.g. leaf gas-exchange and water potentials, as well as vegetation parameters, e.g. species richness, species abundance, leaf area index, were assessed.

Our results suggest that grassland communities, strongly weakened in their stress response by nitrogen loading, can substantially lose their carbon sink function during drought. Over the growing season (April-September), the carbon sequestration of the studied grassland was reduced by more than 60% as a consequence of nitrogen addition. Nitrogen addition in combination with precipitation reduction decreased carbon sequestration by 73%. We observed more efficient N utilization in grasses compared to forbs. However, these clearly specific responses of the different functional groups to N loading, both functional groups were able to maintain homeostasis of leaf carbon and water fluxes. Thus, strong declines in the (community) carbon sequestration and water use efficiency were not related to leaf physiological responses in assimilation and transpiration. Instead, nitrogen addition caused a significant loss in forb species (−25%) and precipitation reduction promoted a strong dominance of grass species at season start. Consequently, the resulting grass-dominated and species-poor community suffered from a strong above-ground dieback during the dry summer months, likely caused by lower water use efficiency and weaker drought adaptations of the species community. 

Eutrophication can severely threaten the resilient functioning of grasslands, in particular when drought periods will increase as predicted by future climate scenarios. Our findings emphasize the importance of preserving high diversity of grasslands to strengthen their resistance against extreme events such as droughts.
Unravelling winter diatom blooms in temperate lakes using high frequency data and ecological modeling
Authors: Shatwell Tom , Kong Xiangzhen , Seewald Michael , Dadi Tallent , Friese Kurt , Mi Chenxi , Boehrer Bertram , Schulze Martin , Rinke Karsten
Published: March 2021

In temperate lakes, it is generally assumed that light rather than temperature constrains phytoplankton growth in winter. Rapid winter warming and increasing observations of winter blooms warrant more investigation of these controls. We investigated the mechanisms regulating a massive winter diatom bloom in a temperate lake. High frequency data and process-based lake modeling demonstrated that phytoplankton growth in winter was dually controlled by light and temperature, rather than by light alone. Water temperature played a further indirect role in initiating the bloom through ice-thaw, which increased light exposure. The bloom was ultimately terminated by silicon limitation and sedimentation. These mechanisms differ from those typically responsible for spring diatom blooms and contributed to the high peak biomass. Our findings show that phytoplankton growth in winter is more sensitive to temperature, and consequently to climate change, than previously assumed. This has implications for nutrient cycling and seasonal succession of lake phytoplankton communities. The present study exemplifies the strength in integrating data analysis with different temporal resolutions and lake modeling. The new lake ecological model serves as an effective tool in analyzing and predicting winter phytoplankton dynamics for temperate lakes.
Stratigraphic analysis of firn cores from the Müller Ice Shelf
Authors: MacDonell Shelley , Fernandoy Francisco , Villar Paula , Hammann Arno
Published: March 2021

In recent decades, several large ice shelves in the Antarctic Peninsula region have experienced significant ice loss, likely driven by a combination of oceanic, atmospheric and hydrological processes. Of these three, the role of liquid water on and in ice shelves is the lesser defined variable, largely due to the paucity of field measurements. Even though the hydrological system is largely unknown, several authors have proposed the existence of firn aquifers on Antarctic ice shelves, however little is known about their distribution, formation, extension and role in ice shelf mechanics. In this study we present the discovery of saturated firn at three drill sites distributed across the Müller ice shelf (67º 14’S; 66º52’W) (one near the front and two in the central region of the ice shelf), which leads us to the conclusion of at least one large firn aquifer or disconnected smaller firn aquifers on this ice shelf. From the stratigraphic analysis of three short firn cores extracted during February 2019 we describe a new classification system to identify the structures and morphological signatures of refrozen meltwater, identify evidence of superficial meltwater percolation, and use this information to propose a conceptual model of firn aquifer development on the Müller ice shelf. The detailed stratigraphic analysis of the sampled cores will provide an invaluable baseline for modelling studies.
Fault animation with 3D model integrating drone and satellite images.
Authors: Rocca Riccardo
Published: March 2021

This presentation describes the new improvements applied to the display of a model already presented at EGU2020.

The model was describing a strike/slip fault located in the Venezuelan Andes, and it was special because the fault movement could be animated by the user. The animation was achieved by implementing the options provided by the combination of two software, Blender and Sketchfab, that are typically used for computer games.

The new version allows a better understanding of the fault evolution by expanding the area represented in the model and by graphically highlighting the various elements of the topography. The first improvement is achieved by integrating the portion of the model acquired with a drone, with the DTM and imagery acquired by satellites. The second improvement is achieved by colouring the topography with false colours that can be switched on by the user by pressing a button.

This new version further improves the initial drone SfM model, so that it can be didactically more effective.
Atmospheric Rivers in Association with Summer Heavy Rainfall over the Yangtze Plain on Sub-seasonal Time Scale
Authors: Liang Ping , Dong Guangtao , Zhang Huqiang , Zhao Mei , Ma Yue
Published: March 2021

Atmospheric Rivers (ARs), referring to long and narrow bands of enhanced water vapor transport, mainly from the tropics into the mid-latitudes in the low atmosphere. They often contribute to heavy rainfall generations outside the tropics. However, there is a lack of such AR studies in East Asia and it is still unclear how ARs act on different time scales during the boreal summer when frequent heavy precipitation events take place over the region. In this study, climatological ARs and their evolutions on both synoptic and sub-seasonal time scales associated with heavy rainfall events over the Yangtze Plain in China are investigated. Furthermore, its predictability is assessed by examining hindcast skills from an operational coupled seasonal forecast model. Results show that ARs embedded within the South Asian monsoon and Somali cross-equatorial flow provide a favorable background for steady moisture supply of summer rainfall into East Asia. We can call this favorable background as a climatological East Asian AR which has close connections with seasonal cycle and climatological intra-seasonal oscillation (CISO) of rainfall in the Yangtze Plain during its Meiyu season. The East Asian AR is also influenced by anomalous anti-cyclonic circulations over the tropical West Pacific when heavy rainfall events occur over the Yangtze Plain. Different from orography-induced precipitation, ARs leading to heavy rainfall over the Yangtze Plain are linked with the intrusions of cold air from its north. The major source of ARs responsible for heavy precipitation events over the Yangtze Plain appears to originate from tropical West Pacific on both synoptic and sub-seasonal time scales. By analyzing 23-yr hindcasts for May-June-July with start date of 1 May, we show that the current operational coupled seasonal forecast system of the Australian Bureau of Meteorology (named as ACCESS-S1) has skillful rainfall forecasts at lead-time of 0 month (i.e. forecasting May monthly mean with initial conditions on 1 May), but the skill degrades significantly at longer lead time. Nevertheless, the model shows skills in predicting the variations of low-level moisture transport affecting the Yangtze River at longer lead time, suggesting that the ARs influencing summer monsoon rainfall in the East Asian region are likely to be more predictable than rainfall itself. This provides a potential of utilizing the skill from the coupled forecast system in predicting ARs to guide its rainfall forecasts in the East Asian summer season at longer lead time.
The response of North American ice sheets to the Younger Dryas (12.9 ka to 11.7 ka) climate event
Authors: Dalton April S , Margold Martin
Published: March 2021

The response of continental ice sheets to late glacial climate fluctuations (Bølling warming, Younger Dryas cooling) offers key insight into the interconnectedness between ice sheets and climate. The Younger Dryas was an abrupt climate cooling event that occurred between 12.9 ka and 11.7 ka, as the Northern Hemisphere was undergoing progressive deglaciation from the last glacial maximum (~25 ka). Ice sheets in Northern Europe (Fennoscandian Ice Sheet) underwent a significant re-advance at that time. However, the reaction of North American ice sheets (Laurentide, Cordilleran, Innuitian; which comprise the largest ice mass in the Northern Hemisphere at the time) to Younger Dryas cooling is not well understood. Some localized studies have shown evidence of ice re-advance or stagnation corresponding to the Younger Dryas; however, no large-scale, unifying study of the impact of Younger Dryas cooling on North American ice sheets has been attempted. Here, we present preliminary maps showing the response of North American ice sheets to the Younger Dryas climate event in key regions. To delineate changes in the ice margin, we integrate a geochronological dataset consisting of calibrated radiocarbon ages and cosmogenic nuclide ages, with mapping of glacial features (ie. moraines) and an extensive literature review. Results suggest a highly variable response of North American ice sheets to Younger Dryas cooling, notably a re-advance of remnant ice lobes in eastern Canada, and stagnation of the ice margin at more western sites.
Which management option has the highest greenhouse gas reduction potential for drained peatlands?
Authors: van den Berg Merit , Fritz Christian , van de Riet Bas , Weideveld Stefan , Gremmen Thomas , van den Elzen Eva , Vroom Renske , Geurts Jeroen , Lamers Leon
Published: March 2021

Almost all peatlands in the Netherlands are drained for agricultural purposes or in the past for peat extraction. What remains is a peatland area of about 300.000 ha of which 85 % is used for agriculture. As a result of peat oxidation, these areas are still subsiding by about 1 cm per year. Another effect is the enormous emission of CO2, which contributes to about 4% of total Dutch greenhouse gas emissions. With the awareness of a changing climate and the need for protection against flooding of coastal areas, solutions are being searched to reduce or stop peat oxidation and coinciding land subsidence and CO2 emission.

In this presentation we will show different management options (subsoil irrigation, pressurized subsoil irrigation, paludiculture) which are currently being tested in the Netherlands. They will be put into perspective of data from other European studies. These options all focus on increasing the groundwater table to lower oxygen intrusion and consequently lower aerobic decomposition. Depending on crop choices, water levels may need to stay 40 cm below the surface to maximize fodder plant yields, or go to surface level to increase peat ecosystem functions like C-sequestration. The management options range from maintaining the current land-use by elevating summer water levels, with submerged drainage, to the development of peat-forming plant species by complete rewetting. Data of the effects of these management options on CO2 emission show that Sphagnum farming is the most promising mitigation option to reduce greenhouse gas emission from drained peatlands. It turned the land from a carbon and greenhouse gas source into a sink.
The structure of precipitation and rainfall erosivity in the upper Parsęta catchment (Drawskie Lakeland, NW Poland) in 1987-2020 as an indicator of climate change
Authors: Majewski Mikolaj , Szpikowski Józef , Domańska Monika , Szpikowska Grażyna
Published: March 2021

The impact of climate change observed in recent decades can be noticed in the structure of precipitation. The increasing amount of periods without rainfall, decreasing annual snowfall totals, and shortening the duration of snow cover significantly affect water resources and the intensity of a number of environmental processes, such as soil erosion by water.

The main aim of this paper is to determine the structure of rainfall in years 1987-2020, based on series of meteorological measurements in the Parsęta Base Station of Integrated Monitoring of Natural Environment at Storkowo in Drawskie Lakeland (NW Poland). The analyzes included precipitation amounts, number of days with precipitation, rainfall intensity, kinetic energy and erosivity and several rainfall indices. During this period, there is observed a significant increase of air temperature, which equals 0.47°C for 10 years. In the case of precipitation, a small increasing trend is marked statistically insignificant. The average annual precipitation was 698.6 mm, whilst precipitation in the winter half-year equalled 41.2% of total and 58.8% in the summer half-year. The annual rainfall erosivity, calculated according to Wishmeier and Smith’s formula, changed from 144.7 to 782.1 MJmm/ha/h, while Modified Fournier Index (MFI) ranged from 53.8 mm to 119.0 mm and was not statistically significant.

The analysis of precipitation with different daily totals did not show a significant increase in the share of precipitation with higher values. The relative precipitation index (RPI) showed no increase in the number of dry months of a year. Moreover, the analysis of occurrence of periods of light droughts, dry spells and droughts does not indicate any significant increase in the number and frequency of such events. On the other hand, a similar analysis of vegetation period (April-September) shows statistically insignificant trend of decrease in the number and frequency of precipitation less series. Another indicator important for the assessment of water conditions, the Sielianinov hydrothermal coefficient was calculated for period April-October, and showed lack of long-term trend changes in the observed period.

The water shortages in the upper Parsęta catchment observed in recent years are probably the result of decrease in the contribution of snow in the precipitation structure and a significant reduction in the number of days with snow cover. This limits the underground retention and surface outflow and has an impact on the functioning of biotic environment and agriculture.
Adapting phase equilibria modelling to crustal and planetary scale problems
Authors: Mayne Matthew
Published: March 2021

Modern quantitative phase equilibria modelling techniques utilizing internally consistent datasets and activity-composition models have been successfully applied to a number of problems in metamorphic geology from hand sample to outcrop scale. Attesting to this the term “phase equilibria” appears in 1 548 articles in the Journal of Metamorphic Geology and one third of those are within the last 10 years. These techniques traditionally proceed either through the manual solution of non-linear equations or by a more automated Gibbs free energy minimization approach. However in order for these techniques to be scaled up to deal with crustal or planetary scale problems a number of hurdles still need to be overcome.

Spatial dimensions in a crustal or planetary model are estimated by grids with modelling conducted on individual cells. This allows processes within cells to effect chemical change to partner cells and thereby approximate open or conditionally open systems. Compositional constraints to the chemical system such as oxygen fugacity are pressure and temperature dependent therefore in order to model a planet wide set of conditions oxygen fugacity buffers are enabled that are dependent on the pressures and temperature of the individual grid cells. Stratigraphic layering is introduced by automating the procedure for setting the initial composition of cells and dependence relations determine the hierarchy of compositional change induced within crustal columns. Phase manipulations such as fluid, melt or crystal addition or extraction are defined by mechanistic parameters that simulate boundary conditions for example melt accumulation thresholds, fluid porosity threshold, rheological lockup conditions etc. Since certain key chemical parameters used in identifying crustal processes such as trace element ratios cannot be traditionally modelled due to their absence from the internally consistent thermodynamic datasets new methods of component approximation are introduced following the methods of trace element partitioning and accessory phase saturation for supersolidus systems.

Finally the increased complexity and number of calculations required to scale up phase equilibria modelling systems to the crustal or planetary scale provides an increased computational challenge therefore new potential strategies are explored for the optimizing of calculation load via parallel processing.
Near-surface glaciotectonic structures in the sediments of an overdeepened glacial valley revealed by a shallow 3D seismic survey
Authors: Tanner David , Buness Hermann , Burschil Thomas
Published: March 2021

Glaciotectonic structures commonly include thrusting and folding, often as multiphase deformation. Here we present the results of a small-scale 3-D P-wave seismic reflection survey of glacial sediments within an overdeepened glacial valley in which we recognise unusual folding structures in front of push-moraine. The study area is in the Tannwald Basin, in southern Germany, about 50 km north of Lake Constance, where the basin is part of the glacial overdeepened Rhine Valley. The basin was excavated out of Tertiary Molasse sediments during the Hosskirchian stage, and infilled by 200 m of Hosskirchian and Rissian glacioclastics (Dietmanns Fm.). After an unconformity in the Rissian, a ca. 7 m-thick till (matrix-supported diamicton) was deposited, followed by up to 30 m of Rissian/Würmian coarse gravels and minor diamictons (Illmensee Fm.). The terminal moraine of the last Würmian glaciation overlies these deposits to the SW, not 200 m away.

We conducted a 3-D, 120 x 120 m², P-wave seismic reflection survey around a prospective borehole site in the study area. Source/receiver points and lines were spaced at 3 m and 9 m, respectively. A 10 s sweep of 20-200 Hz was excited by a small electrodynamic, wheelbarrow-borne vibrator twice at every of the 1004 realized shot positions. We recognised that the top layer of coarse gravel above the till is folded, but not in the conventional buckling sense, rather as cuspate-lobate folding. The fold axes are parallel to the terminal moraine front. The wavelength of the folding varies between 40 and 80 m, and the thickness of the folded layer is on average about 20 m. Cuspate-lobate folding is typical for deformation of layers of differing mechanical competence (after Ramsay and Huber 1987; µ1/µ2 less than 10), so this tell us something about the relative competence (or stiffness) of the till layer compared to the coarse clastics above. We also detected small thrust faults that are also parallel to the push-moraine, but these have very little offset and most of the deformation was achieved by folding.

Ramsay, J.G. and Huber, M. I. (1987): The techniques of modern structural geology, vol. 2: Folds and fractures: Academic Press, London, 700 pp.
The northern and the eastern Adriatic Sea floods: connecting the extreme sea-levels to cyclone pathways 
Authors: Dević Tihana , Šepić Jadranka , Koračin Darko
Published: March 2021

An objective method for tracking pathways of cyclone centres over Europe was developed and applied to the ERA-Interim reanalysis atmospheric data (1979-2014). The method was used to determine trajectories of those Mediterranean cyclones which generated extreme sea levels along the northern and the eastern Adriatic coast during the period from 1979 to 2014. Extreme events were defined as periods during which sea level was above 99.95 percentile value of time series of hourly sea-level data measured at the Venice (northern Adriatic), Split (middle eastern Adriatic) and Dubrovnik (south-eastern Adriatic) tide-gauge stations. The cyclone pathways were tracked backwards from the moment closest to the moment of maximum sea level up to the cyclone origin time, or at most, up to 72 hours prior the occurrence of the sea-level maximum.

Our results point out that extreme sea levels in Venice normally appear during synoptic situations in which a cyclone centre is located to the south-west and north-west of Venice, i.e., when it can be found over the Gulf of Genoa, or the Alps. On the contrary, extreme sea levels in Dubrovnik are usually associates with cyclone centres above the middle Adriatic, whereas floods in Split seem to appear during both above-described types of situations.

Occurrence times and intensity of cyclones and extreme sea-levels was further associated with the NAO index. It has been shown that the deepest cyclones and corresponding extreme floods tend to occur during the negative NAO phase.   
An application of induced event interferometry approach at The Geysers Geothermal Field, California, USA
Authors: Shirzad Taghi , Lasocki Stanisław , Orlecka‐Sikora Beata
Published: March 2021

While the classical tomography approaches, e.g., P-, S-, and/or surface-wave traveltime tomography, provide a general structure of the Earth’s interior, new developments in signal processing of interferometry approaches are needed to obtain a high-resolution velocity structure. If the number of earthquakes is adequate, the virtual seismometer method may be a solution in regions with sparse instrumental coverage. Theoretically, the empirical Green’s functions between a pair of events can be retrieved using earthquake’s cross-correlations. Here, an event interferometry approach was used on a very small scale around Prati-9 and Prati-29 injection wells in the NW of The Geysers Geothermal Field. The study region experienced intense injection-induced seismicity. We selected all events with location uncertainties less than 50 m in a cuboid of the horizontal side ~1 × ~2 km and the vertical edge at depths between 1.0 and 2.0 km. The cuboid was cut into 100m thick layers, and we applied to events from each layer criteria enabling a quasi 2D approach. After calculating the Rayleigh wave group velocity dispersion curves, further processing was performed at a 0.2s period, selected based on the sensitivity kernel criterion. Finally, the relative velocity model of each layer at the depth z was obtained by subtracting the velocity model of the just overlying layer (at the depth z-100m) from the model of this layer. Our resultant velocity model in the study area indicated four low-velocity anomalies. The first one can be linked by the two layers interface topography variation at the top of the cuboid (depth 1000 m). The secondary faults can cause the second low-velocity anomaly. The other two anomalies look to result from fluid injection into Prati-9 and Prati-29 wells. 
This work was supported under the S4CE: "Science for Clean Energy" project, which has received funding from the European Union’s Horizon 2020 research and innovation program, under grant agreement No 764810.
Modeling large dust deposition events to alpine snow and their impacts: the role of model resolution
Authors: Baladima Foteini , Thomas Jennie , Dumont Marie , Voisin Didier , Junquas Clementine , Kumar Rajesh , Marelle Louis , Raut Jean-Christophe , Lavaysse Christophe , Tuzet Francois , Biron Romain
Published: March 2021

Mineral dust and black carbon (BC) constitute the most important aerosols present in the atmosphere and cryosphere and have well known potential effects on regional and global climate. Upon their deposition they can impact snow albedo, snowpack evolution and timing of snow-melt. However, capturing BC and dust deposition events in mountain regions is currently a challenge due to the complexity of aerosol-cloud interactions and the specifics of mountain meteorological systems, which are difficult to represent in large scale models. Here, we use a case study of dust deposition, between 30 March and 5 April 2018, when a significant dust deposition event was observed within the seasonal snowpack at the Col du Lautaret in the French Alps. This comes in addition to the background BC deposition that occurred during the same period. Specifically, we investigate the role of model resolution in capturing both mountain meteorology, precipitation, and the resulting model predicted dust and BC deposition. For this, the meteorological-chemical model WRF-Chem is used with three nested domains including the primary dust emissions region in Africa (low resolution domain), a second domain that includes Europe, and a third high resolution domain over the Alps. We compare WRF-Chem predicted aerosol and meteorological properties (at different model resolution) with in-situ, remote sensing, and reanalysis products to validate the model and quantify the added value of high resolution modelling within the Alps. We conclude that predicted mountain meteorology including precipitation is significantly better when using the high resolution configuration (3 x 3 km horizontal resolution domain). Additionally, this improved meteorology predicted by the model has significant impacts on predicted dust deposition and BC. The better representation of the mountain meteorology when the resolution becomes finer leads to improved model predicted dust and BC deposition to alpine snow. Implications for this, including improved resolution within models that consider the full aerosol lifecycle in the atmosphere and in snow covered mountain regions is discussed.
Variability of the interplanetary magnetic field as a driver of electromagnetic induction in Mercury’s interior
Authors: Zomerdijk-Russell Sophia , Masters Adam
Published: March 2021

Mercury’s magnetosphere is considered to be a unique and dynamic system, primarily due to the proximity of the planet to the Sun. The interaction between solar wind and embedded Interplanetary Magnetic Field (IMF) and the dayside Hermean magnetosphere drive an electric current on the magnetopause boundary of the system. The influence of the time-dependent magnetic field generated by this magnetopause current on Mercury’s interior is key to understanding the subsurface structure of the planet, as electromagnetic induction is a valuable technique for delineating electrical properties of planetary interiors. Here we assess the impact a changing IMF direction has on the Hermean magnetopause currents, and the resulting inducing magnetic field. Analytical models of conditions at the magnetopause are combined with measurements made by MESSENGER’s magnetometer as the spacecraft crossed the subsolar magnetopause boundary during the first ‘hot season’.

These MESSENGER magnetopause boundary crossings show that the introduction of the external IMF changes the direction of the magnetopause current by ~50°, compared to the case where only the internal planetary field is considered. Analytical modelling suggests that for a heliospheric current sheet crossing without any change in solar wind dynamic pressure (an east-west reversal of the IMF polarity typical at Mercury), the inducing field at Mercury’s surface caused by the resulting magnetopause current sheet dynamics is of the order of 10% of the global planetary field. The results suggest that variability of the IMF alone can have an appreciable effect on Mercury’s magnetopause current direction and generate a significant inducing magnetic field around the planet. The arrival of the BepiColombo mission will allow this response to be further explored as a method of probing Mercury’s interior.
Shear wave velocity from inter-source interferometry
Authors: Eulenfeld Tom
Published: March 2021

Ambient noise correlation uses the recordings of multiple, statistically distributed seismic sources (the noise sources) at two seismometers. By cross-correlating this signal, one obtains a wave traveling between two seismometers. Due to the principle of reciprocity it is possible to interchange the role of sources and receivers. This cannot be done with ambient noise, but another stochastic signal, the seismic coda is used. Using a cross-correlation of the seismic coda of two earthquakes recorded at multiple seismometers, it is possible to construct a seismic wave traveling between the two earthquakes in depth (inter-source interferometry). Here, I use the the time lag of the maxima in the cross-correlation of the coda wave field to measure the shear wave velocity in the source volume of swarm earthquakes. This technique is different from previous studies analyzing the decorrelation of the coda wave field of nearby events or using the cross-correlation for relocation purposes.

The technique is applied to five event clusters of the 2018 West Bohemia earthquake swarm. With the help of a high quality earthquake catalog, I was able to determine the shear wave velocity in the region of the five clusters separately. The shear wave velocities range between 3.5 km/s and 4.2 km/s. The resolution of this novel method is given by the extent of the clusters and better than for a comparable classical tomography. The method can be incorporated into a tomographic inversion to map the shear wave velocity in the source region with unprecedented resolution. The influence of focal mechanisms and the attenuation properties on the polarity and location of the maxima in the cross-correlation functions is discussed.