bluuebunny/crossref_metadata_2025 huggingface dataset:
Community Mapping Supports Comprehensive Urban Flood Modeling for Flood Risk Management in a Data-Scarce Environment
Authors: Petersson Louise , ten Veldhuis Marie-Claire , Verhoeven Govert , Kapelan Zoran , Maholi Innocent , Winsemius Hessel
Published: March 2021

We demonstrate a framework for urban flood modeling with community mapped data, particularly suited for flood risk management in data-scarce environments. The framework comprises three principal stages: data acquisition with survey design and quality assurance, model development and model implementation for flood prediction. We demonstrate that data acquisition based on community mapping can be affordable, comprehensible, quality assured and open source, making it applicable in resource-strained contexts. The framework was demonstrated and validated on a case study in Dar es Salaam, Tanzania. The results obtained show that the community mapped data supports flood modeling on a level of detail that is currently inaccessible in many parts of the world. The results obtained also show that the community mapping approach is appropriate for datasets that do not require extensive training, such as flood extent surveys where it is possible to cross-validate the quality of reports given a suitable number and density of data points. More technically advanced features such as dimensions of urban drainage system elements still require trained mappers to create data of sufficient quality. This type of mapping can, however, now be performed in new contexts thanks to the development of smartphones. Future research is suggested to explore how community mapping can become an institutionalized practice to fill in important gaps in data-scarce environments.
AGW manifestations in the Earth neutral atmosphere and ionosphere
Authors: Syrenova Tatiana , Beletsky Alexander
Published: March 2021

Acoustic gravity waves (AGW) manifestations spread from the lower atmosphere to the upper layers due to processes such as orography, weather fronts, deep convection atmosphere, and vice versa, can form in the upper atmosphere during geomagnetic activity, receiving energy from the magnetosphere. These wave processes can be considered as a dynamic process that transfers energy between different atmospheric and latitudinal regions, therefore it is important to understand their basic parameters and behavior.

In this work, to study wave disturbances, we used the Keo Sentinel optical system data, designed to record the spatial pattern of the 630 nm emission intensity (emission height 180-300 km). The system is located at the Geophysical Observatory (GPO) of the ISTP SB RAS, near the Tory, Buryatiya, Russia (520 N, 1030 E, height 670 m). The  interference filter transmission half-width is ~ 2 nm. Sight direction - zenith, field of view 145 degrees, exposure time 30-60 s (http://atmos.iszf.irk.ru/ru/data/keo).

For the analysis, we chose data obtained on clear, moonless nights from 2014 to March 2019. The total number of nights selected for analysis was 71 (~ 491 hours). An algorithm for the wave events and their characteristics automatic identification from the optic data was developed and tested. The approbation was carried out on a data set previously processed manually [Syrenova, Beletsky, 2019]. A comparison was made with traveling ionospheric disturbances (TID) characteristics obtained from the ISTP SB RAS radio-physical complex data [Medvedev et al., 2012].

The main directions of wave disturbances propagation obtained with automatic optical system data processing - southward (~ 175º) and eastward (~ 90º) - are similar to the TID directions. From the radiophysical complex data, the TID distribution from North to South prevails, the most probable azimuth is ~ 135º during the day, and ~ 205º at night. The most probable values ​​of the wave disturbances propagation velocity obtained as a result of automatic processing are about 80 m/s. These values ​​also accept well with the TID values.

The main characteristics obtained using the data of the optical and radiophysical complexes agree with each other. Differences in the preferred propagation direction of the recorded wave structures from the KEO Sentinel data from the directions obtained with photometers at the same observation point [Tashchilin, 2010, Podlesny, 2018], probably, associated with different observation heights.
Multi-level fluid monitoring to understand the origin of transients
Authors: Woith Heiko , Daskalopoulou Kyriaki , Zimmer Martin , Fischer Tomáš , Vlček Josef , Trubač Jakub , Rosberg Jan-Erik , Vylita Tomáš , Dahm Torsten
Published: March 2021

Anomalies in timeseries are frequently reported in the context of earthquake precursor studies. The state of knowledge can be summarized as follows: (i) significant anomalies exist, (ii) seismo-tectonically induced anomalies might exist, (iii) anomalies of non-tectonic origin exist and may look very similar to tectonic ones. Thus, presumably only a fraction of all reported precursors is real in the sense that they are of seismo-tectonic origin. A key problem in earthquake prediction research is to understand the origin of an anomaly and thus the separation of internal and external drivers like e.g. rainfall.  

State-of-the-art fluid monitoring techniques allow for a high temporal resolution compared to the low-resolution discrete sampling approach used in the last decades. A unique approach will allow to monitor ascending fluids along a vertical profile in a set of drillings from a depth of a few hundred metres to the surface. This setup can provide hints on the origin of temporal variations related to the opening of fault-valves, admixture of crustal fluids to a background mantle-flow or the release of hydrogen during fault rupturing. Gas migration velocities can thus be measured directly from the arrival times of anomalies at different depth levels. In addition, potential admixtures of mantle fluids with crustal or meteoric fluids during the ascent to the Earth’s surface can be quantified.

A prototype of a multi-level gas monitoring system has been implemented at a mofette. Mofettes are gas emission sites where CO2 ascends through long-lived, narrow channels from the deep crust and possibly the Earth’s upper mantle and thus provide natural windows to magmatic processes at depth. The primary objective of our research on mofettes is to clarify physical links between fluid properties, their pathways and the relation to swarm earthquakes. The Hartoušov mofette field with an estimated daily CO2 flux between 23 and 97 t over an area of about 350,000 m2 has been chosen as a key site in the frame of the ICDP project: “Drilling the Eger Rift: Magmatic fluids driving the earthquake swarms and the deep biosphere.” It is located in the Cheb Basin, which terminates the Czech part of the Eger Rift to the West and is known for recurring earthquake swarms and mantle degassing. Gas and isotope compositions will be continuously analyzed in-situ at different depth levels (30 m, 70 m, 230 m) reached by three adjacent boreholes.
Radiocarbon in modern carbon cycle research
Authors: Levin Ingeborg
Published: March 2021

Atmospheric nuclear weapon testing in the 1950s and 1960s has been worrying, however, in many aspects it was extremely beneficial for environmental sciences. The artificial production of more than 6 x 1028 atoms or about 0.6 tons of radiocarbon (14C), leading to a doubling of the 14C/C ratio in tropospheric CO2 of the Northern Hemisphere, has generated a prominent spike in 1963. This “bomb-spike” has been used as transient tracer in all compartments of the carbon cycle, but also to study atmospheric dynamics, such as inter-hemispheric and stratosphere-troposphere air mass exchange. Moreover, our attempt to accurately determine total bomb produced 14C led to improved estimates of the atmosphere-ocean gas exchange rate and to a new constraint of the residence time of carbon in the terrestrial biosphere. Today, the transient bomb-radiocarbon signal has levelled off, and the anthropogenic input of radiocarbon-free fossil fuel CO2 into the atmosphere has become the dominant driver of the 14C/C ratio in global atmospheric CO2. The observed decreasing 14C/C trend in atmospheric CO2 may thus help scrutinising the total global release of fossil fuel CO2 into the atmosphere. On the local and regional scale, atmospheric 14C/C measurements are already routinely conducted to separate fossil fuel from biogenic CO2 signals and to estimate trends of regional fossil fuel CO2 emissions. Some prominent examples where the bomb 14CO2 disturbance has been successfully used to study dynamic processes in the carbon cycle are discussed as well as our current activities applying this unique isotope tracer for continental scale carbon cycle budgeting.
Impact of Environmental Change on Biogeochemical Cycling in Soil Systems
Authors: Sparks Donald
Published: March 2021

Environmental change, particularly the impact of climate change, is having a profound impact on humankind. Rising seas and temperatures are causing increasing flooding and melting of ice and permafrost soils. The impact of these processes on biogeochemical cycling of metals, carbon, and nutrients in soils and water is not well understood. For example, how do rising seas, which cause inundation of soils with saline water, followed by retrenchment, and salinization of groundwater, affect cycling of redox active elements such as arsenic and iron as well as nutrients such as phosphorus.  Complexation of carbon with iron-bearing minerals is a major mechanism for carbon retention. Under changing climatic conditions, how will carbon cycling be impacted, particularly in permafrost soils, which are sinks for a large portion of terrestrial carbon? This presentation will explore these questions, and others, over a range of spatial and temporal scales.
Is there an environmental crisis in Madagascar’s highlands? Insights from the spatio-temporal evolution and demographic modelling of lavaka (large gullies)
Authors: Brosens Liesa , Campforts Benjamin , Jacobs Liesbet , Razanamahandry Vao Fenotiana , Van Moerbeke Quinten , Broothaerts Nils , Razafimbelo Tantely , Rafolisy Tovonarivo , Bouillon Steven , Govers Gerard
Published: March 2021

The Malagasy highlands are scattered with large inverse teardrop-shaped gullies called lavaka, which are by many considered as the prime indication of a currently ongoing human-induced environmental crisis. Yet, these gullies are known to have existed long before human arrival on the island, resulting in the highly debated role of anthropogenic disturbances on their formation. Here, we assess the dynamics of 700 lavaka in the lake Alaotra region from 1949 to the 2010s by using historical aerial pictures and present day satellite imagery. An overall birth to stabilization ratio of 6.1 indicates a currently rapid growing lavaka population. Observed growth-, birth- and stabilization rates allowed us to calculate a mean lavaka population age of 410 ± 40 years, and estimate that the current crisis started at 943 ± 430 cal. yr BP. This timeframe corresponds well with the “subsistence-shift”, where people move from hunting and foraging to farming and herding practices upon the introduction of cattle in the region. These findings were integrated into a novel, temporally explicit lavaka population model - building upon the observed lavaka growth-, birth- and stabilization rates and lavaka size distributions - where different environmental pressure scenarios were tested. Modelling outcomes show that the currently observed lavaka crisis largely results from a rapid increase in environmental pressure over the last centuries, likely caused by the combined effects of deforestation and overgrazing related to human population growth and the introduction of cattle. With this study we show the potential of an integrated data-modeling approach, where demographic concepts are applied to geomorphological features, allowing to link their evolution with past anthropogenically driven environmental changes.
Rapidly detecting icebergs using ArcticDEM and Google Earth Engine
Authors: Shiggins Connor , Lea James , Fahrner Dominik , Brough Stephen
Published: March 2021

High resolution digital elevation models (DEMs) allow for the detection of icebergs and their size distribution, potentially giving insights into spatial and temporal changes in calving dynamics and iceberg cover. Here we present a fully automated tool for iceberg detection in glaciated fjords, utilising timestamped ArcticDEM tile data within the Google Earth Engine cloud computing platform. The automated tool requires only definition of a region of interest (ROI) through the following workflow:

1. Automatically filter timestamped ArcticDEM tiles to obtain only high-quality images with high data coverage within a ROI

2. Apply elevation correction to account for the geoid and tidal state, ensuring sea level is the equivalent to 0 m elevation

3. Apply an iceberg detection elevation threshold (any object at/or above 0.9 m)

4. Automatically delineate icebergs based on elevations above this threshold

5. Iceberg area, volume (total, below and above surface), freeboard height, mass and the ArcticDEM acquisition date are appended to each iceberg

This workflow allows for rapid, fully automated analysis of all available ArcticDEM tiles within a given ROI. The workflow does not require manual supervision, and can be easily related back to the original ArcticDEM data through Google Earth Engine. As an example, we apply our workflow to a 33 km2 ROI at Nuup Kangerlua (Godthåbsfjorden), southwest Greenland, detecting a total of 57,735 icebergs from 6 images with an execution time of 19 minutes. This workflow will provide a user-friendly platform for users of any coding ability requiring a large data set of icebergs with an area size greater than approximately 40 m2. Results obtained from these data will be utilised to identify potential seasonal to multi-annual timescale changes in calving behaviour, though is dependent on ArcticDEM data availability. 
From the North Atlantic Oscillation to the Tropics and back...
Authors: Greatbatch Richard
Published: March 2021

We start with the severe European winter of 1962/63, a winter when the North Atlantic Oscillation (NAO) index was strongly negative with persistent easterly wind anomalies across northern Europe and the British Isles. We then note that the NAO is a manifestation of synoptic Rossby wave breaking. The positive feedback with which synoptic eddies act to maintain the atmospheric jet stream against friction turns out to also be the mechanism by which the equatorial deep jets in the ocean are maintained against dissipation. We were fortunate to be able to demonstrate this in both a simple model set-up that supports deep jets and directly from mooring data at 23 W on the equator in the Atlantic Ocean. The deep jets offer some potential for prediction over the neighbouring African continent on interannual time scales. This then leads to a discussion of the importance of the tropics for prediction on both seasonal and decadal time scales and longer, linking back to the winter of 1962/63.  A simple statistical model is used to illustrate many features of predictability, including non-stationarity and the so-called signal to noise paradox.
Randomised preconditioning for the forcing formulation of weak constraint 4D-Var
Authors: Dauzickaite Ieva , Lawless Amos , Scott Jennifer , van Leeuwen Peter Jan
Published: March 2021

There is growing awareness that errors in the model equations cannot be ignored in data assimilation methods such as four-dimensional variational assimilation (4D-Var). If allowed for, more information can be extracted from observations, longer time windows are possible, and the minimization process is easier, at least in principle. Weak constraint 4D-Var estimates the model error and minimizes a series of linear least-squares cost functions using the conjugate gradient (CG) method; minimising each cost function is called an inner loop. CG needs preconditioning to improve its performance. In previous work, limited memory preconditioners (LMPs) have been constructed using approximations of the eigenvalues and eigenvectors of the Hessian in the previous inner loop. If the Hessian changes signicantly in consecutive inner loops, the LMP may be of limited usefulness. To circumvent this, we propose using randomised methods for low rank eigenvalue decomposition and use these approximations to cheaply construct LMPs using information from the current inner loop. Three randomised methods are compared. Numerical experiments in idealized systems show that the resulting LMPs perform better than the existing LMPs. Using these methods may allow more efficient and robust implementations of incremental weak constraint 4D-Var.
Flood monitoring in remote areas: integration of multi-frequency SAR data
Authors: Refice Alberto , D'Addabbo Annarita , Chini Marco , Zingaro Marina
Published: March 2021

The monitoring of inundation phenomena through synthetic aperture radar (SAR) data on vegetated areas can be improved through an integrated analysis of different spectral bands. The combination of data with different penetration depths beneath the vegetated canopy can help determine the response of flooded areas with distinct types of vegetation cover to the microwave signal. This is useful especially in cases, which actually constitute the majority, where ground data are scarce or not available.

The present study concerns the application of multi-temporal, multi-frequency, and multi-polarization SAR images, specifically data from the Sentinel-1 and PALSAR 2 SAR sensors, operating in C band, VV polarization, and L band, HH and HV polarizations, respectively, in synergy with globally-available land cover data, for improving flood mapping in densely vegetated areas, such as the Zambezi-Shire basin, Mozambique [1], characterized by wetlands, open and closed forest, cropland, grassland (herbaceous and shrubs), and a few urban areas.

We show how the combination of various data processing techniques and the simultaneous availability of data with different frequencies and polarizations can help to monitor floodwater evolution over various land cover classes. They also enable detection of different scattering mechanisms, such as double bounce interaction of vegetation stems and trunks with underlying floodwater, giving precious information about the distribution of flooded areas among the different ground cover types present on the site.

This kind of studies are expected to assume increasing importance as the availability of multi-frequency data from SAR satellite constellations will increase in the future, thanks to initiatives such as the EU Copernicus program L-band satellite mission ROSE-L [2], and their tight integration with Sentinel-1 as well as with other national constellations such as ALOS 2, or SAOCOM.

References

[1] Refice, A.; Zingaro, M.; D’Addabbo, A.; Chini, M. Integrating C- and L-Band SAR Imagery for Detailed Flood Monitoring of Remote Vegetated Areas. Water 2020, 12, 2745, doi:10.3390/w12102745.

[2] Pierdicca, N.; Davidson, M.; Chini, M.; Dierking, W.; Djavidnia, S.; Haarpaintner, J.; Hajduch, G.; Laurin, G.V.; Lavalle, M.; López-Martínez, C.; et al. The Copernicus L-band SAR mission ROSE-L (Radar Observing System for Europe). In Active and Passive Microwave Remote Sensing for Environmental Monitoring III; SPIE: Washington, DC, USA, 2019; Volume 11154, p. 13.
Are catchment-scale nitrogen and phosphorous use efficiencies controlled by climate?
Authors: Scaini Anna , Manzoni Stefano
Published: March 2021

Nutrient loss from agricultural fields imparts increased fertilizer costs as well as negative consequences for the natural environment. Given that water availability mediates both nutrient uptake by plants as well as nutrient leaching, we hypothesize that hydrologic conditions can explain variations in nutrient use efficiencies, defined as ratios of the nutrient amounts in harvested yield and in inputs. We analyze data from 110 US catchments with agricultural area comprising more than 10% of the watershed and compute nitrogen and phosphorus use efficiencies (NUE and PUE) over the period 1988-2007. To assess if NUE and PUE are related to hydrologic conditions, we consider the evaporative ratio ET/P (calculated as evapotranspiration divided by precipitation) as a predictor in a linear mixed effect model. We test the hypotheses that the nutrient use efficiencies increase with ET/P, through increased water and nutrient retention, and that the nutrient efficiencies increase through time. We found that both nutrient use efficiencies increased through time: NUE increased in the period analyzed in 88% of catchments, while PUE in 90% of catchments. Both NUE and PUE were largely driven by significant increases in N and P amounts in yield. The evaporative ratio was positively related to NUE. Moreover, we found an interaction between ET/P and time, such that the ET/P effect on NUE decreased in the period 1998–2007. The evaporative ratio was also positively related to PUE. Other potential drivers were assessed, including interaction between ET/P and time, as well as the percentage of agricultural area in each catchment. Our results show that changes in climate that include increased evaporation and decreased precipitation can lead to increase N use efficiencies without decreasing yields. The implications of our findings in terms of the release of N and P to water bodies has particular relevance in terms of climate change, as higher temperatures and lower precipitation (i.e. increasing evaporative ratios) will potentially lead to increased nutrient retention and therefore decreased nutrient leaching from agricultural fields.
Free Evaluation System Framework (Freva) - New Features and Development
Authors: Lucio-Eceiza Etor E. , Kadow Christopher , Bergemann Martin , Ramadoss Mahesh , Illing Sebastian , Kunst Oliver , Schartner Thomas , Grieger Jens , Schuster Mareike , Richling Andy , Kirchner Ingo , Rust Henning , Sommer Philipp , Cubasch Ulrich , Ulbrich Uwe , Thiemann Hannes , Ludwig Thomas
Published: March 2021

The Free Evaluation System Framework (Freva - freva.met.fu-berlin.de , xces.dkrz.de , www-regiklim.dkrz.de - https://github.com/FREVA-CLINT/Freva) is a software infrastructure for standardized data and tool solutions in Earth system science. Freva runs on high performance computers (HPC) to handle customizable evaluation systems of research projects, institutes or universities. It combines different software technologies into one common hybrid infrastructure, where all its features are accessible via shell and web environment. Freva indexes different data projects into one common search environment by storing the metadata information of the self-describing model, reanalysis and observational data sets in a database. The database interface satisfies the international standards provided by the Earth System Grid Federation (ESGF). This implemented metadata system with its advanced but easy-to-handle search tool supports users, developers and their plugins to retrieve the required information. A generic application programming interface (API) allows scientific developers to connect their analysis tools with the evaluation system independently of the programming language used. Facilitation of the provision and usage of tools and climate data automatically increases the number of scientists working with the data sets and identifying discrepancies. Plugins are also able to integrate their e.g. post-processed results into the database of the user. This allows e.g. post-processing plugins to feed statistical analysis plugins, which fosters an active exchange between plugin developers of a research project. Additionally, the history and configuration sub-system stores every analysis performed with the evaluation system in a database. Configurations and results of the tools can be shared among scientists via shell or web system. Therefore, plugged-in tools benefit from transparency and reproducibility. Furthermore, the system suggests existing results already produced by other users – saving CPU hours, I/O, disk space and time. An integrated web shell (shellinabox) adds a degree of freedom in the choice of the working environment and can be used as a gate to the research projects on a HPC. Freva efficiently frames the interaction between different technologies thus improving the Earth system modeling science. New Features and aspects of further development and collaboration are discussed.
High efficiency and portable monitor of atmospheric radon concentration activity for environmental applications
Authors: Curcoll Masanes Roger , Grossi Claudia , Vargas Arturo
Published: March 2021

The natural radioactive noble gas radon (222Rn) is originated from the decay of radium into the soil and then continuously exhaled to the lower atmosphere. Its diffusion and exhalation rate depend both on the physical and environmental conditions of the soil layers and on the meteorological conditions. With a half-life of 3.8 days and a very limited chemical activity, the 222Rn is nowadays being used as an atmospheric tracer for: i) the improvement of atmospheric transport models used, among others, to identify greenhouse gas (GHG) emission sources; ii) for the indirect estimation of GHG fluxes by the Radon Tracer Method (RTM). These previous applications need high sensitivity and precision at low radon concentrations range (< 100 Bq m-3).

A new monitor, based on alpha spectrometry of 218Po electrostatically collected on a PIPs detector, has been designed and developed at the Institute of Energy Technologies (INTE) of the Universitat Politecnica de Catlunya (UPC)  in the mark of the project ‘High efficiency monitor of atmospheric radon concentration for radiation protection and environmental applications (MARE2EA), reference: 2019-LLAV-00035, funded by the Catalan Agency for Management of University and Research Grants. The aim is building an instrument able to measure atmospheric radon concentration activities with high precision in order to be running at GHG atmospheric networks for the RTM applications.

The monitor is an improved version of a previous prototype instrument (Grossi et al., 2012, 2020). The new instrument will allow a higher efficiency, robustness and portability. In addition, it will have a GUI interface to be user friendly. Finally, in order to reduce the air sample humidity within the detection volume of the instrument which affects the 218Po collection, a portable drying system has also been built to keep the instrument ongoing without maintenance during several weeks.

 

References

Grossi, C., Arnold, D., Adame, J. A., López-Coto, I., Bolívar, J. P., De La Morena, B. A., & Vargas, A. (2012). Atmospheric 222Rn concentration and source term at El Arenosillo 100 m meteorological tower in southwest Spain. Radiation Measurements, 47(2), 149–162. https://doi.org/10.1016/j.radmeas.2011.11.006

Grossi, C., Chambers, S. D., Llido, O., Vogel, F. R., Kazan, V., Capuana, A., Werczynski, S., Curcoll, R., Delmotte, M., Vargas, A., Morguí, J.-A., Levin, I., & Ramonet, M. (2020). Intercomparison study of atmospheric 222Rn and 222Rn progeny monitors. Atmospheric Measurement Techniques, 13(5). https://doi.org/10.5194/amt-13-2241-2020
Alternative energy resources in Lithuania - shale gas perspective
Authors: Lozovskis Saulius , Šliaupa Saulius , Lazauskienė Jurga , Šliaupienė Rasa
Published: March 2021

In Worlds practice it is known that shale gas can be viable source of energy. Lithuania is situated in the central and eastern parts of the pericratonic Baltic Sedimentary Basin. The Lower Silurian shales are considered as a most prospective formation for gas exploration due to high amount of organic matter (more than 2%) and large thickness (120-200 m). Mineralogical composition and related petrophysical and mechanical properties were assessed for west Lithuanian shales that occur at the depths of 1500-2000 m. Thermal maturity of organic matter Tmax ranges from 432 to 455oC (oil window). Shales contain 37–57% of clay minerals. Illite predominates and chlorite is less abundant mineral. Quartz and feldspars compose about 35–45% of shale volume. The carbonate content ranges from 1% to 28%. TOC content is about 2%, while interpretation of well logs show higher average amount of TOC ranging from 2.5 to 8%. The Middle Llandovery “hot” shales of 4-11m thick show anomalous TOC content up to 20%. The mineral brittleness index was calculated to range mainly from 0.35 to 0.40 (bellow the lower exploitation limit), while logging brittleness index varies from 0.40 to 0.60 (good quality). This difference is explained by logging coverage of the whole Lower Silurian section by contrast to selective drill coring of wells. The bulk porosity decreases with depth from 16% to 3% (linear correlation Depth=-0.0107×Porosity+25.7). The low cation exchange capacity (0.2-8.8 meq/100g) is accounted to specific mineral composition. The low erodibility (Roller Oven technique) is related to high shale compaction. The capillary suction time method was used to estimate the swelling capacity of shales. Rather low values are explained in terms of predominance of illite in clay fraction and high amount of detrital grains. In summary, the exploitation parameters estimated for west Lithuanian shales are classified as good and excellent and can be used to minimize the impact on the environment.
Geophysical characterization of an engineering infrastructure: laboratory tests.
Authors: Fornasari Giacomo , Capozzoli Luigi , De Martino Gregory , Giampaolo Valeria , Rizzo Enzo
Published: March 2021

The increase of the metropolises stresses the urban areas and intensive planning works is necessary. Therefore, the development of new technologies and methodologies able to explore the subsoil and manage its resources in urban areas becomes an important source in terms of saving time and money. In the last decade, a new subdiscipline in the Applied Geophysics started: Urban Geophysics (Lapenna, 2017). Urban Geophysics analyzes the contribute, in terms of limits and potentialities, that geophysical methodologies can give for providing useful information about the subsoil, environment, buildings and civil infrastructures and supporting the public administrations in planning interventions in urban scenarios.

This work introduces a laboratory test, that was performed at the Hydrogeosite CNR-IMAA laboratory of Marsico Nuovo (Basilicata region, Italy). The test consisted in a multisensor geophysical application on an analogue engineering model. Thanks to the possibility to work in laboratory conditions, a detailed knowledge of the structure was available, providing great advantages for assess the capability of the geophysical methodologies for analyze engineering issues, regarding the characterization of the infrastructural critical zone placed at the interface soil-structure. For this purpose, geoelectrical and electromagnetic methodologies, including Cross hole Electrical Resistivity Tomography and Ground Penetrating Radar, were used to characterize the geometry of the foundation structures and the disposition of the rebar for the reinforced concrete frame. Finally, new geophysical approaches were applied in order to define the corrosion rate of reinforcement.
Silicification and mechanical stratigraphy control on flow pathways and hypogenic karst development in carbonate rocks
Authors: Pisani Luca , Antonellini Marco , Bezerra Francisco Hilario , Auler Augusto , De Waele Jo
Published: March 2021

Fractured and karstified carbonate rocks are important targets for the hydrocarbon exploration industry as they usually represent very productive reservoirs. Most of the karst features in carbonate reservoirs are the result of rising fluid flow in deeply buried settings (i.e., hypogenic karst), whose origin and solutional efficiency are not connected to surface processes. Hypogenic conduits are often intercepted by drilling during hydrocarbon exploration, and their occurrence is sometimes associated with high-permeability horizons characterized by intense silicification. Silicification is a common diagenetic process in sedimentary basins, in which Si-rich fluids modify textures, mineralogy, and petrophysical properties of the host rock.  

We present the preliminary results of a multidisciplinary study performed in a cave developed within a mixed carbonate-siliciclastic succession of the Salitre Formation, in Northeastern Brazil (Calixto Cave). This cave offers the opportunity to study an accessible and extensive (more than 1 km long) conduit system associated with silicification. We performed a detailed stratigraphic and structural characterization of the sedimentary sequence in the cave, identifying different SiO2 facies and textural associations. Furthermore, we described cave geometry and pattern by topographic and morphometric observations using terrestrial laser scanner 3D models. Petrographic observations at the optical microscope were complemented with porosity-permeability analyses on rock plugs, XRD, XRF, and SEM-EDX analyses to highlight composition and petrophysical properties of the different lithostratigraphic units in the cave.

We found that silicification and mechanical stratigraphy determined the formation of high-permeability and seal units, whose distribution was fundamental for controlling paleo-flow pathways, karstification, and the spatial-morphological organization of the resultant conduit system. Cave morphologies, evidence of silica dissolution, crystalline quartz deposits and their associated paragenesis suggest that the speleogenetic phase contributing to the main karst formation happened in deeply buried hypogenic conditions, involving rising alkaline fluids probably of hydrothermal origin.
Large-Eddy Simulation for the Roughness Sublayers over Real Urban Surfaces 
Authors: Yao Lan , Liu Chun-Ho
Published: March 2021

ABSTRACT:

    With the continuous spreading of global pandemic, environmental issues have aroused worldwide unprecedented attention. Airflow plays a crucial role in aerosol motions and pollutants removal in dense cities. Large-eddy simulation (LES) is conducted for a typical metropolitan, Hong Kong, to investigate the dynamics in the atmospheric boundary layer (ABL) over real urban surfaces. Full-scale building models (average building height hm = 36 m) from Tsim Sha Tsui to Sham Shui Po, Kowloon Peninsula, are digitalized. Southerly wind with speed U∞ (= 10 m sec-1) in neutral stratification is prescribed at the domain inlet. The turbulence statistics extracted from three subdomains in Mong Kok neighborhood, each with size 800 m (streamwise) × 100 m (spanwise) × 500 m (vertical), are analyzed. Linear regression of the wind profile with the logarithmic law of the wall (log-law) show that the interface between inertial sublayer (ISL) and roughness sublayer (RSL) is in the range of 2.5hm to 4.5hm. In the RSL, the streamwise and vertical velocities are positively (Su > 0) and negatively (Sw < 0) skewed, respectively. Their kurtosis Ku and Kw is less than 3. Conditional sampling of vertical momentum, flux u’’w’’ showed that ejection Q2 occurs more frequently than does sweep Q4. On the contrary, the contribution of Q4 exceeds that of Q2. These characteristics switch to the other way round in the ISL. Furthermore, the difference between Q4 and Q2, either in terms of occurrence or contribution, shows a local maximum around 50% of the total momentum flux, suggesting the major energy-carrying scales. Coherent structures depict elongated, (massive,) accelerating (decelerating) and descending (ascending) RSL (ISL) flows. Hence, the fresh (aged) air entrainment (detrainment) are signified by fast and extreme (slow and frequent) flows. These distinct features of RSL flows over real urban morphology provide an inspiration to improve the ground-level air quality by proper urban planning.

KEYWORDS: Large-eddy simulation (LES), real urban morphology, turbulent boundary layer (TBL), conditional sampling, hole filtering

 

 
An innovative, timeseries-analysis-based method to extract rainfall-streamflow events from continuous timeseries
Authors: Giani Giulia , Rico-Ramirez Miguel Angel , Woods Ross
Published: March 2021

A widely accepted objective methodology to select individual rainfall-streamflow events is missing and this makes it difficult to synthesize findings from independent research initiatives. In fact, the selection of individual events is a fundamental step in many hydrological studies, but the importance and impact of the choices made at this stage are largely unrecognised.

The event selection methods found in the literature start by looking at either the rainfall timeseries or the streamflow timeseries. Moreover, most of the methodologies involve hydrograph separation, which is a highly uncertain step and can be performed using many different algorithms. Further increasing the subjectivity of the procedure, a wide range of ad hoc conditions are usually applied (e.g. peak-over-threshold, minimum duration of rainfall event, minimum duration of dry spell, minimum rainfall intensity…).

For these reasons, we present a new methodology to extract rainfall-streamflow events which minimizes the conceptual hypotheses and user’s choices, and bases the identification of the events mainly on the joint fluctuations of the two signals. The proposed methodology builds upon a timeseries analysis technique to estimate catchment response time, the Detrending Moving-average Cross-correlation Analysis-based method.

The proposed method has the advantage of looking simultaneously at the evolution in time of rainfall and streamflow timeseries, providing a more systemic detection of events. Moreover, the presented method can easily be adapted to extract events at different time resolutions (provided the resolution is fine enough to capture the delay between the rainfall and streamflow responses).

Properties of the events extracted with the proposed method are compared with the ones of the events extracted with the most traditional approach (based on hydrograph separation) to show strengths and weaknesses of the two techniques and suggest in which situations the proposed method can be most useful.
Reparametrizing rainfall generators with convective-permitting models to generate high-resolution rainfall for climate impact studies
Authors: Chen Yuting , Paschalis Athanasios , Peleg Nadav , Onof Christian
Published: March 2021

A high-resolution rainfall data at a km and sub-hourly scales provides a powerful tool for hydrological risk assessment in the current and the future climate. Global circulation models or regional circulation models generally provide projections at much coarser space-time resolutions of 10-100 kilometres and daily to monthly. In the recent decade, convection-permitting models (CPM) have been developed and enable the projection at a kilometre and sub-hourly scales. CPMs, due to their very high computational demand, are still limited to a small number of ensemble simulations. This limits their skill in hydrology, where quantification of extremes and their variability is essential for risk assessment and design. In this project, we propose the combined use of CPMs with stochastic rainfall generators to simulate ensemble of climate change at hydrologically relevant scales.

To achieve this, we used the STREAP space-time stochastic rainfall generator, a 1 km resolution composite rain radar data and a 2.2km CPM dataset from the UK Met Office. For the mid-land region of the UK, we parameterised STREAP for the present climate using rainfall observations. CPM simulations were used to derive the change of STREAP parameters with a changing climate. These parameters describe the change in weather patterns, the rainfall intensification, and changes in the structure of rainfall. Our results show that by combining a physics-based model and a stochastic weather generator we can simulate robust ensemble of rainfall at a minimal computational cost while preserving all physical attributes from climate change projections.
Third Revision of the Bottom-up Global Surface Seawater Dimethyl Sulphide Climatology (DMS-Rev3) 
Authors: Hulswar Shrivardhan , Manville George , Simo Rafel , Gali Marti , Bell Thomas G. , Halloran Paul , Lana Arancha , Mahajan Anoop S.
Published: March 2021

An updated estimation of the bottom-up global surface seawater dimethyl sulphide (DMS) climatology, DMS-Rev3, is the third of its kind and includes five significant changes from the last climatology, ‘L11’ (Lana et al., 2011) that was released about a decade ago. The first change is the inclusion of new observations that have become available over the last decade, i.e., the total number of observations included in DMS- Rev3 are 865,109 as compared to 47,313 data points used in the last estimation (~1728% increase in raw data). The second was significant improvements in data handling, processing, filtering, to avoid bias due to different observation frequencies. Thirdly, we incorporated the dynamic seasonal changes observed in the ocean biogeochemical provinces and their variable geographic boundaries. Fourth change was refinements in the interpolation algorithm used to fill up the missing data. And finally, an upgraded smoothing algorithm based on observed DMS variability length scales (VLS) which helped reproduce a more realistic distribution of the DMS concentration data. The results show that DMS-Rev3 estimates the global annual mean DMS concentration at 2.34 nM, 4% lower than the current bottom-up ‘L11’ climatology. However, significant regional differences of more than 100% are observed. The largest changes are observed in high concentration regions such as the polar oceans, although oceanic regions which were under-sampled in the past also show large differences. DMS-Rev3 reduces the previously observed patchiness in high productivity regions.
Three-dimensional geometry and growth of salt-detached strike-slip faults, Outer Kwanza Basin, offshore Angola
Authors: Erdi Aurio , Jackson Christopher
Published: March 2021

Strike slip faults are a prominent tectonic feature in Earth to accommodate horizontal and/or oblique slip that trend parallel to fault strike. These faults are commonly formed on plate boundaries setting, where they are basement-involved and driven by elastic crustal loading at seismogenic depths. Still, we also observe the strike slip faults on salt-bearing slopes, where the faults are typically thin-skinned and accommodate spatial variability in the rate of seaward flow of salt and its overburden. In both cases, relatively little is still known of their three-dimensional geometry and growth in comparison to both normal and reverse fault, that have been extensively studied.

We use a high-quality, depth-migrated 3D seismic dataset to investigate salt-detached strike-slip faults in the mid-slope translational domain of the Outer Kwanza Basin, offshore Angola. We show that NE-SW-striking faults are presently located above elongate, margin-parallel, NE-trending ramps, more amorphous, dome-like structural highs, and areas of relatively subdued relief. The faults are broadly planar, display normal and/or reverse offsets, and may locally bound negative flower structures. These faults offset a range of salt and overburden structures, including salt walls and anticlines, and salt -detached thrusts and normal faults, defining six major structural compartments. Our displacement-distance (Tx) analysis of several faults reveal they are characterized by complex throw distributions that define 3-to-10, now hard-linked segments. In vertical profiles, these segments are characterized by symmetric-to-asymmetric throw distributions (Tz) that record throw maxima at the top of the Albian, Eocene and/or Early Miocene. Expansion indices (EI) and isopach maps demonstrate the presence of fault-related growth strata, with complex thickness patterns also reflecting the combined effect of vertical (i.e. diapirism) and horizontal (i.e. translation) salt tectonics.  Taken together, our observations suggest the salt detached strike-slip faults evolved during three key phases: (i) Albian – nucleation and local linkage of individual segments; (ii) Eocene-to-Oligocene – reactivation, propagation, and death of many now-linked segments; and (iii) Miocene – local fault reactivation due to salt diapirism.  

We show that salt detached strike-slip faults in the translational domain of the Outer Kwanza Basin grew above either rugose or relatively flat base-salt surface. More specifically, salt detached strike-slip faults, like normal and reverse faults documented elsewhere, grew in response to the propagation and eventual linkage of initially isolated segments. We also highlight that the coeval growth of salt walls can play a role in controlling the three-dimensional geometry and kinematics of salt detached strike-slip faults.
Insights into deep learning for earthquake magnitude and location estimation
Authors: Münchmeyer Jannes , Bindi Dino , Leser Ulf , Tilmann Frederik
Published: March 2021

The estimation of earthquake source parameters, in particular magnitude and location, in real time is one of the key tasks for earthquake early warning and rapid response. In recent years, several publications introduced deep learning approaches for these fast assessment tasks. Deep learning is well suited for these tasks, as it can work directly on waveforms and can learn features and their relation from data.

A drawback of deep learning models is their lack of interpretability, i.e., it is usually unknown what reasoning the network uses. Due to this issue, it is also hard to estimate how the model will handle new data whose properties differ in some aspects from the training set, for example earthquakes in previously seismically quite regions. The discussions of previous studies usually focused on the average performance of models and did not consider this point in any detail.

Here we analyze a deep learning model for real time magnitude and location estimation through targeted experiments and a qualitative error analysis. We conduct our analysis on three large scale regional data sets from regions with diverse seismotectonic settings and network properties: Italy and Japan with dense networks (station spacing down to 10 km) of strong motion sensors, and North Chile with a sparser network (station spacing around 40 km) of broadband stations.

We obtained several key insights. First, the deep learning model does not seem to follow the classical approaches for magnitude and location estimation. For magnitude, one would classically expect the model to estimate attenuation, but the network rather seems to focus its attention on the spectral composition of the waveforms. For location, one would expect a triangulation approach, but our experiments instead show indications of a fingerprinting approach. Second, we can pinpoint the effect of training data size on model performance. For example, a four times larger training set reduces average errors for both magnitude and location prediction by more than half, and reduces the required time for real time assessment by a factor of four. Third, the model fails for events with few similar training examples. For magnitude, this means that the largest events are systematically underestimated. For location, events in regions with few events in the training set tend to get mislocated to regions with more training events. These characteristics can have severe consequences in downstream tasks like early warning and need to be taken into account for future model development and evaluation.