bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractionation of Highly Siderophile Elements during reactive melt infiltration in lower oceanic crust
Authors: Tribuzio Riccardo , Renna Maria Rosaria , Armandola Sonia , Becker Harry , Sanfilippo Alessio , Wang Zaicong
Published: March 2020

The olivine-rich troctolites are Mg-rich rocks forming by open-system magmatic crystallization in response to primitive melt injections into the growing lower oceanic crust (e.g., Renna et al., 2016).

In the present study, whole-rock highly siderophile (HSE: Os, Ir, Ru, Rh, Pt, Pd, Au and Re) and chalcogen (S, Se and Te) element compositions, and Re-Os isotopes of the olivine-rich troctolites from the Jurassic Alpine ophiolites were determined with the aim to investigate the control that the formation of lower oceanic crust may exert on the fractionation of HSE and other incompatible chalcophile elements in MORB.

The olivine-rich troctolites have initial γOs (160 Ma) ranging from +0.2 to +5.9, and Primitive Mantle (PM)-normalized HSE-Te-Se-S patterns showing a gradual increase from Os to Au, and nearly flat Au-Te-Se patterns. These patterns are similar to those of little-fractionated mantle melts and are parallel, at higher concentrations levels, to those typical of MORB. The olivine-rich troctolites have higher Te and Os/Ir, and lower Se/Te than MORB, which may be reconciled with a process of sulfide accumulation. Sulfide precipitation could be promoted by interaction between melts interstitial to olivine and melts relatively rich in silica, which could migrate from an underlying gabbroic framework (cf. Renna et al., 2016). Melts residual to the formation of olivine-rich troctolites are inferred to have a markedly HSE-fractionated signature comparable to that of MORB.

Renna M.R., Tribuzio R., Ottolini L. (2016). J Geol Soc Lond 173, 916–932
Crustal and Uppermost Mantle Structure Across Central Myanmar by Joint Analysis of Receiver Functions and Rayleigh-wave Dispersion
Authors: Bai Yiming , He Yumei , Yuan Xiaohui , Thant Myo , Sein Kyaing , Ai Yinshuang
Published: March 2020

The territory of Myanmar, situated at the eastern flank of the India-Asia collision zone, is characterized by complex tectonic structure and high seismicity. From west to east, this region consists of three nearly NS-trending tectonic units: the Indo-Burma Ranges, the Central Basin and the Shan Plateau. Detailed structure of the crust and uppermost mantle beneath Myanmar can provide crucial constraints on regional tectonics, subduction dynamics as well as seismic hazard assessment. Yet seismic velocity structure beneath this region is poorly determined due to sparse regional seismic networks.

In this study, we utilize seismic data recorded at 80 broadband stations in Myanmar, among which 70 stations were deployed in 2016 under the project of China-Myanmar Geophysical Survey in the Myanmar Orogen (CMGSMO), 9 stations are operated by IRIS and the remaining one is from GEOFON. We measured the Rayleigh-wave phase velocity dispersion from the ambient noise cross-correlations at periods between 5 s and 40 s by using the automatic frequency-time analysis (AFTAN). A fast marching surface wave tomography (FMST) approach was then adopted to invert the 2-D phase velocity maps in the study region. Our preliminary results show variable crustal structure across central Myanmar, with a strong low-velocity zone north of 22°N in the Indo-Burma Ranges. Since Rayleigh-wave dispersion is more sensitive to absolute velocity speed than to velocity contrasts, the ongoing study jointly inverts the dispersion data with P-wave receiver functions to better determine the velocity discontinuities and thus provides tighter constraints on the shear-velocity structure beneath central Myanmar.
Signature of coseismic slip in unconsolidated Quaternary gravels, Campo Imperatore, Italy
Authors: Demurtas Matteo , Balsamo Fabrizio , Pizzati Mattia
Published: March 2020

Faulting in seismically active regions commonly involves the deformation of unconsolidated to poorly lithified sediments. The seldom occurrence of seismic slip within these deposits appears to be counterintuitive if compared to classic crustal strength profiles that predict a velocity-strengthening behaviour for the first few km of depth. Therefore, the investigation of geological evidence for coseismic faulting within unconsolidated deposits is a key step towards a broader understanding of mechanisms of strain accommodation at shallow to near-surface depth.

Here we document the occurrence of minor faults within an unconsolidated colluvial fan at the hanging wall of the Vado di Corno Fault Zone (VCFZ) in the Central Apennines, Italy. The VCFZ is part of the active Campo Imperatore Fault System and accommodated 1-2 km of displacement since Early-Pleistocene. The deposits lie in direct contact with the master fault surface, are Late-Pleistocene to Holocene in age, and consist of angular carbonatic clasts, up to tens of centimetres in size, derived from the dismantling of the VCFZ footwall.

Studied faults are organised in two main sets: (i) subvertical, N-S trending dip-slip faults, parallel to the fan long axis, and (ii) WNW-ESE striking faults, synthetic and antithetic to the VCFZ master fault surface (N195/55°). Both fault sets are striated and commonly have positive relief with respect to the host deposits. Some of these faults show a fault core up to 5-6 cm thick, bounded by discrete and well-developed polished surfaces. Locally, particularly in fine-grained gravel levels, the occurrence of extreme strain localisation (i.e. millimetric ultracataclastic layers with truncated clasts) along mirror-like fault surfaces is observed. Grain size analysis of undeformed and faulted gravels shows an increase of the power-law exponent (fractal dimension) from values of D = 1.65-2.2 in the undeformed host rocks up to D = 2.9 in the cataclastic slip zones. Microstructural analysis suggests cataclasis is the main deformation mechanism leading to grain size reduction along faults, whereas intergranular pressure solution becomes widespread moving away from the slip zone where fluid circulation was present.

Collectively, our observations provide new insights into the mechanics of faulting and strain accommodation in the shallowest part of the crust (< 1 km) and new evidence to understand the propagation of seismic ruptures within shallow unconsolidated deposits.
Laboratory lysimeters and proximal sensing data for optimizing irrigation water needs
Authors: Paciolla Nicola , Ben Charfi Imen , Corbari Chiara , Mancini Marco
Published: March 2020

The increase of irrigation efficiency and crop productivity in agriculture is nowadays a general requirement at national and international level to mitigate planet food security problems due to: the freshwater supply variability and scarcity enhanced by climate change (FAO, 2018), the increasing water demand due to population growth and also due to using ancient and sometimes empirical agricultural techniques.

To test the effectiveness of these irrigation strategies, on-field surveys alone are not enough. In the laboratory environment, a higher degree of insight is accessible, with a number of measurements that would be difficult on site.

In this work, we have tested the water dynamics related to the particular irrigation strategy developed in the SIM project (Smart Irrigation from soil moisture forecast using satellite and hydro-meteorological Modelling). The basic principle behind the strategy is that the soil moisture in the root-zone should be kept between the plant stress threshold and reducing deep percolation at all times. In that way, the irrigation amount is always enough so that the crop does not suffer water stress, and any water loss is avoided. As a comparison, two more common irrigation strategies have been tested in the same conditions: potential and deficit irrigation.

The laboratory set-up involves a wide range of instruments and devices: a lysimeter, a high-resolution (2g tolerance) scale, a thermal camera, a spectrometer, an infrared and an ultraviolet lamp, a radiometer and a leaf porometer. To increase the accuracy of the measurements, instead of working directly on the lysimeter, the crops have been cultivated in separate boxes, placed directly above the lysimeter. Three boxes have been managed according to each irrigation strategy. As a reference, one box has been kept with bare soil throughout the whole testing period, one has been filled with water and, finally, dense grass has been cultivated in another, totalling 12 boxes. The subdivision in boxes allows weighing each separately, guaranteeing higher accuracy.

The laboratory routine consisted of daily measurements of the weight of the boxes, together with measurements of temperature and leaf irradiance spectra. The evapotranspiration and percolation from each box are derived from the weight difference, and the water mass balance is closed for every box. At the end of the experimental set-up, the productivity for each irrigation strategy has been computed by measuring the final crop yield of each box.

Positive results, in terms of crop health and water savings, have been obtained with the SIM strategy.
Implementation and assessment of a flux-limiter based wetting and drying scheme
Authors: O'Dea Enda , Bell Mike , Coward Andrew , Holt Jason
Published: March 2020

Wetting and drying processes in shallow water systems by surges, tides and seiches have important societal, physical and biological impacts. Operational regional models are now of sufficient resolution, O(1 km), that the processes of wetting and drying need to be included. Here we describe a flux limiter based approach that allows a numerical ocean model with a flux formulation of tracer advection to wet and dry. Following Warner et al. (2013), the flux limiter approach limits the outflow from a cell whose depth is below a critical value defined by the user. The limiter can be a step function or a smooth function of the water depth flux limiter, the latter increases model stability and avoids rapid alternation between dry and wet states on long slopes as the critical depth is approached. Furthermore, the user may proportionally limit the baroclinic fluxes as a cell transitions from wet to dry over the course of the large baroclinic time step. The simplicity of the flux limiter approach lends itself to its application within existing numerical models without significant intrusion into the code base. Here we explore the scheme's effectiveness, sensitivities and limitations within the 3D NEMO ocean model by assessing it using test cases of increasing complexity. It is shown to perform well in classic channel test cases and 2D parabolic test cases with analytic solutions. Its performance against analytical 1D dam break experiments is explored and used to interpret its performance against laboratory measurements of a 2D dam break. The scheme is also shown to run stably for a realistic 3D regional domain of the North West European shelf and to improve some aspects of the model's performance against tide gauges.
UAV magnetic survey for geological exploration: A case study of the Synnyr Massif, Buryatia, Russia
Authors: Maev Igor , Karaman Anastasiya , Kajukov Alexander
Published: March 2020

The Synnyr alkaline massif is a concentrically zoned body located in the Baikal Vitim folded area, Holodninskiy graben. It is controlled by the deep-seated Precambrian Baikal-Synnyr fault, while major rock types of the massif were dated as 230-350 Ma (Kostuk et al., 1990; Mitrofanova 2009). However, there were no young strike-slip faults or thrusts identified throughout the massif. Studying the area is compounded by the climate and landscape conditions, which makes the airborne geophysical survey a very cost-effective mapping tool. Main geological investigations of the Synnyr massif were made in the 1960s and in the 1980s. In those times, an airborne geophysical survey was not as accurate as it was required and didn’t bring up any significant results.

The next stage of Synnyr massif exploration began in 2016. The first airborne magnetic survey based on unnamed aerial vehicles (UAV) was made in 2018 and increased our knowledge about the geological situation in the studying area. Main goals of the UAV magnetic survey were tracing highly magnetic foidal gabbroids named shonkinites, which are located in the central part of the ore zone, and mapping major faults.

The airborne geophysical complex included a multirotor aerial vehicle and quantum magnetometer with a rubidium magnetic field sensor that was placed in the special gondola and attached to the UAV. The study area was surveyed at 20 meters height with detailed terrain following and accuracy of magnetic field measurements comparable with the ground magnetic survey.

As a result, airborne magnetic data helped to clarify geological structure and tectonics in the areas covered with glacier or without any outcrops. Furthermore, magnetic field measurements allowed to locate faults and lineaments which were not traced in previous geological studies of the Synnyr massif and to make an assumption about the neotectonic activity of Baikal-Synnyr fault system.

Due to cost-efficiency, informativeness and high accuracy of geophysical surveys based on UAV, we are planning to continue research and extend the studying area.

References:

Mitrofanova N.N. Report for Aldan-Transbaikal geological maps, 2009

Kostuk V.P., Panina L.I., Zhidkov A. Y., Orlova M.P., Bazarova T.Y. Potassium alkaline magmatism in Baikal-Stanovoi rift system, 1990
Incomplete and complete PCO/PCV chamber calibrations – impact of Galileo observations
Authors: Araszkiewicz Andrzej , Kiliszek Damian
Published: March 2020

The poster presents the impact of the use of Galileo observations on daily GNSS position solutions. Analysis were carried out at EUREF Permanent Network. For 34 EPN stations full calibration tables developed by IGG, Univ. Bonn and containing correction E01 and E05 are available. We prepared for them a daily solutions, independently for GPS and Galileo. In most analysis for GPS solutions, also here, L1 and L2 frequencies are used. For them phase centre corrections are available for long time. For Galileo solutions generally E1 and E5a frequencies are used. In this analysis we prepare two Galileo solutions. To correct the E5a signal we used E05 values and in the second case the G02 values (as it is done in most cases when there are no full PCO/PCV tables available). There is a clear bias in height between this two Galileo solutions. Analysis has shown also that we get more consistent GPS and Galileo solutions, when G02 values instead of E05 are used for E5a signal.
Experiences in applying Bayesian network models in interdisciplinary water quality decision analysis
Authors: Kuikka Sakari
Published: March 2020

I review the experience obtained in using integrative Bayesian models in interdisciplinary analysis focusing on oil spill risk analysis and water quality in the Baltic Sea. We have applied BBN especially to interdisciplinary analysis, which is easily needed in decision analysis. In the environmental risk analysis, we have mainly focused on the oil spills, where the data sets are poor and also the published papers are scarce. More importantly, the aim of the decision analysis here is to avoid seeing the data, i.e. to avoid accidents. Therefore, some of our applications are based mainly on the use of expert knowledge, especially when we consider decision options that have not been applied before.

  In the oil spill risk analysis, we have chosen the state of the threatened species as the decision criteria, as they have a status in other parts of Finnish legislation. There is no single clear objective in oil spill legislation which could be used as a utility function, and our analysis have shown, that the legislation should be updated to include well defined objectives. One of the scientific quality criteria for using the Bayesian decision analysis for management is that the uncertainty estimates are scientifically justified. Especially in cases where society is assumed to be highly risk averse, the uncertainty estimates related to alternative management options may have a crucial role.

   Biology, sociology and environmental economics have their own scientific traditions. Bayesian models are becoming traditional tools in fisheries biology, where uncertainty estimates of management options are frequently required. In sociology, the traditions allow the subjective treatment of the information, which supports the use of prior probability distributions.  Many of the environmental risks have also economic components, or at least actions have a price, which favors the use of quantitative risk analysis. However, the traditions and quality criteria of these three scientific fields are in many respects different. This creates both technical and human challenges to the modeling tasks.

 

Keywords: Bayesian networks, fisheries management, environmental management, interdisciplinary risk and decision analysis

 
Mapping the spatial and temporal dynamics in vulnerability of smallholder farming systems in Ethiopia
Authors: Shukla Roopam , Yalew Amsalu Woldie , Gleixner Stephanie , Schauberger Bernhard , Gornott Christoph
Published: March 2020

Vulnerability to climate change differs spatially within the country owing to regional differences in exposure, sensitivity, and adaptive capacity. The paper aims to assess the vulnerability of smallholder farming systems in Ethiopia to observed climate change, to gain insight into factors that may shape vulnerability in the future. Spatial dynamics in vulnerability is assessed at subnational level (zone-level) and temporal dynamics is studied across three time periods i.e. historical (1985-2005), current (2005-2015), and future (2035-2045). The study uses an index-based approach, which is suitable for assessing vulnerability as it includes both biophysical and socio-economic dimensions. This approach combines the environmental and socio-economic data from different sources (agricultural surveys, climate, and remote sensing data) to capture the multi-dimensional attributes of vulnerability. This research contributes to evidence-based adaptation planning in Ethiopia by identifying areas and patterns of high vulnerability and its components.
Reverse Engineering Earthquakes using Lab-scale Replicas: Application to Mw5.5 2017 Pohang Earthquake
Authors: Turquet Antoine L. , Toussaint Renaud , Eriksen Fredrik K. , Flekkøy Eirik Grude , Måløy Knut Jørgen
Published: March 2020

An earthquake can happen due to many different phenomena such as sliding faults, fluid/gas injection into the subsurface or volcanic activities. Understanding the cause of earthquakes is one important step towards a better hazard assessment and better mitigation. In this study, we explore the physics behind different types of earthquakes by inducing similar mechanics in lab-scale experiments using an analogous model. Inside a transparent rectangular Hele-Shaw cell, we induce lab-scale microseismicity via pneumatic fracturing. An 80 x 40 cm transparent setup is prepared using a 1 mm thin layer of uncompacted granular medium having a fixed grain size is placed between two glass plates.
The seismic location results are compared with the image correlation results for displacement maps corresponding to the event times. Using air injection, this porous medium is compacted and fractured. This system is monitored using a camera recording 1000 images per second and accelerometers recording with 1 MHz sampling rate. Sources of earthquake-like vibrations are both located using acoustic recordings and image processing. We have observed that the deformation starts with compaction inside the medium; this compaction propagates toward the channel tips and causes the fingers to advance further inside the medium. We have observed (using optics and acoustics) that the movement starts inside the porous medium and progresses toward the channel tips, eventually causing channels to grow further. We also compared the characteristic patterns in these lab-scale events that are very similar to large scale correspondents, in particular with 2017 Mw 5.5 Pohang Earthquake. We reverse-engineered the signature of the recorded lab-scale signals to have a better understanding of this industrial hazard.
Climate change and Silk Road civilization in the arid central Asia
Authors: Chen Fahu , Chen Jianhui , Dong Guanghui , Huang Wei , Hou Juzhi , Wang Tao
Published: March 2020

The arid central Asia composed of northwestern China and central Asia, is one of the most arid regions in the mid-latitudes and also the core area of the Silk Road civilization. Climate have dramatically changed during Holocene in the region. Prior to 6 ka, moisture conditions increased gradually, and then rapidly, with the most humid period occurring during the late Holocene. Over the last millennium, a dry climate during the Medieval Warm Period and a wet climate during the Little Ice Age is present on the centennial timescale. Instrumental observations showed that precipitation, moisture, and stream runoff all have gradually increased on the decadal scale under global warming. Comparing these results to those in the mid-latitude monsoonal Asia and Mediterranean, the moisture evolution since the Holocene over westerlies Asia featured unique characteristics on various timescales. We proposed the theoretical framework of a ‘westerlies-dominated climatic regime’ (WDCR) for hydroclimatic changes. Further studies of physical mechanisms showed that external factors e.g. orbital-induced insolation changes generated WDCR on the sub-orbital timescale, while a circum-global teleconnection/Silk Road pattern was the most important factor responsible for WDCR on the centennial and decadal timescales. Climate change has impacted on the civilization evolution along the Silk road in arid central Asia. The oasis route in this region played a significant role in the development of trans-Eurasia exchange since the late third Millennium BCE. Such route laid the foundation for the formation of ancient Silk Road during the second century BCE that accounted for the most important center for civilization evolution in the planet till the sixteenth century CE. Multi-discipline studies suggest that special warm-humid climate might have facilitated the rise and development of ancient empires, e.g. Tubo Empire (618-842 CE) in and around the high Tibetan Plateau. But climate deterioration, especially severe droughts lasting decades-centuries, triggered the expansion of deserts and shrinkage of oases along the Silk Road. Such land degradation led to the delayed onset of transcontinental exchange, the decline of ancient civilizations such as ancient Loulan Kingdom (176 BCE-630 CE), and the abandonment of Dunhuang area between 1539-1723 CE by Chinese central government that was ascribed as a landmark event for the end of the traditional Silk Road. Further analysis proposed that the evolution of ancient civilizations was likely influenced by precipitation variation in surrounding mountains instead of basins in arid areas of the Silk Road.
Orographic gravity wave and low-level jet interaction above a tall and dense Amazonian forest
Authors: Mortarini Luca , Corrêa Polari Batista , Cava Daniela , Dias-Júnior Cléo Quaresma , Manzi Antônio Ocimar Manzi , Acevedo Otavio , Araújo Alessandro , Sörgel Matthias , Machado Luiz Augusto Toledo
Published: March 2020

The Wavelet and the Multiresolution analysis are applied to ten nocturnal hours of observations of 3-D wind velocity taken within and above a forest canopy in Central Amazonia. Data from the ATTO Project, consisting in 7 levels of turbulence observations along both 81 and 325-meter towers, are used. The presented night is dynamically rich presenting three distinct periods. In the first one the boundary layer is characterized by canopy waves and coherent structures generated at the canopy top. In the second period an intense orographic gravity wave generated at around 150 m strongly influences the boundary layer structure, both above and below the canopy. In the third period, a very stable stratification at the canopy top enables the development of a low-level jet that interferes and disrupts the vertical orographic wave. During the night the wavelet cospectra identified turbulent and non-turbulent structures with different length and time-scales that are generated at different levels above the canopy and propagated inside it. The contributions of the different temporal scales of the flow above and within the canopy were identified using Wavelet and Multiresolution two-point cospectra. The analysis showed how turbulent and wave-like structures propagates in different ways and, further, the ability of low-frequency processes to penetrate within the canopy and to influence the transport of energy and scalar in the roughness sublayer and within canopy.

Keywords: Coherent structures, Canopy Waves, Gravity Waves, Stable Boundary Layer, Low-Level Jet, wave-turbulence interaction.

 
Physical mechanisms driving the global ocean breathe
Authors: Portela Rodriguez Esther , kolodziejczyk Nicolas , Thierry Virginie
Published: March 2020

The physical transport of dissolved oxygen across the mixed layer base is the main process to oxygenate the interior ocean. This ventilation mechanism is suspected to play a dominant role in the predicted ocean deoxygenation over the 21st century, however, it has not yet been properly quantified or described at global scale. Here we show the mean distribution of the mechanisms driving the oxygen exchanges between the mixed layer and the ocean interior and their relation with water-mass formation. Most of the oxygen uptake occurs in well-defined hot-spots located in the subpolar North Atlantic (30%) which provide oxygen to deep and waters and in the Southern Ocean (37$%) that oxygenates intermediate and bottom waters. The oxygen release is concentrated within the ACC belt (37%), in the subtropical-subpolar North Atlantic (22%) and within the equatorial strip (13%). Globally, the mode waters account for about 72% of the subducted oxygen during their formation process. The oxygen uptake by the Subantarctic and Subpolar Mode Water is driven by strong currents flowing through large mixed layer depth gradients at localized hot-spots while the spatial continuity of the wind-driven vertical velocity over broad areas in the Subtropical gyres accounts for most of the oxygen subduction during the Subtropical Mode Water formation.
Field and experimental evidence of frictional melting in fluid-rich faults
Authors: Di Toro Giulio , Fondriest Michele , Mitchell Tom , Gomila Rodrigo , Jensen Erik , Masoch Simone , Bistacchi Andrea , Magnarini Giulia , Faulkner Dan , Cembrano José , Mittempergher Silvia , Spagnuolo Elena
Published: March 2020

Pseudotachylytes (solidified friction melts produced during seismic slip) are considered to be rare in the geological record because they should be typical of particular seismogenic environments characterized by water-deficient cohesive rocks. Here we present field and experimental evidence that frictional melting can occur in “fluid-rich” faults hosted in the continental crust.

Pseudotachylytes were found in the >40 km long Bolfin Fault Zone of the Atacama Fault System (Northern Chile). The pseudotachylytes (1) are associated with a ~1 m thick ultracataclastic fault core which accommodated > 5 km of strike-slip displacement at 6-8 km depth and 280-350°C ambient temperature, (2) cut a ca. 50 m thick damage zone made of sub-greenschists facies hydrothermally altered diorites and gabbros, (3) cut and are cut by epidote+chlorite+calcite bearing veins. The microstructure of the pseudotachylytes include (1) tabular microlites of feldspar hosted in a glassy-like matrix and (2) vesicles filled by post-seismic sub-greenschist facies minerals hosted in a strongly altered matrix of albite, chlorite, and epidote crystals.

Experiments reproducing seismic slip in the presence of pressurized water and conducted with the rotary shear apparatus SHIVA on experimental faults made of the sub-greenschists (hydrothermally altered) facies damage zone rocks from the Bolfin Fault Zone, resulted in the production of vesiculated pseudotachylytes. In these experiments, fault weakening mainly occurred by melt lubrication rather than by pore fluid thermal pressurization.

The identification of pseudotachylytes and its association with intense pre- and post-seismic hydrothermal alteration challenges the common belief that pseudotachylytes are rare. Consistent with the experimental evidence, pseudotachylytes (1) could be a common coseismic fault product in the continental crust, (2) may easily be produced in fluid-rich hydrothermal environments but, (3) are easily lost from the geological record because they are prone to alteration.
Microplastics and earthworms in soils: A case study on translocation, toxicity and fate
Authors: Dietrich Nils , Wilkinson Daniel , Hirsch Florian , Sut-Lohmann Magdalena , Geschke Antonia , Raab Thomas
Published: March 2020

Microplastics are not only found in marine and lacustrine environments but also in soils. Microplastics enter natural soil environments from legal or illegal waste deposition. In arable soils, microplastics often stem from the decomposition of plastic sheeting. The accumulation of (micro-)plastic from garbage bags in which biological waste is often disposed, is also a significant problem for the recycling and composting of organic waste. Commercially available compostable bags are advertised as degradable. Thus, these compostable bags ought to accumulate less in soils than non-compostable bags. We present a pilot study to determine the preference of earthworms (Lumbricus terrestris and Eisenia hortensis) for taking up and translocating different types of microplastic in soils. Our initial findings from the soil column experiment suggest that the earthworms show a strong tendency for the uptake of microplastic.  We also observed direct and indirect transport of microplastic by earthworms from the surface to deeper parts of the soil columns.
Exploring Inter-Basin Correlations of Tropical Cyclones and Tropical Cyclone Losses
Authors: Hillier John , Done James , Steptoe Hamish
Published: March 2020

Tropical cyclones (TCs) are one of the most costly natural hazards on Earth, and there is a desire to mitigate this risk. It is securely established that TC activity relates to ENSO in all oceanic basins (e.g. N. Atlantic). However, when a recent multi-basin review of correlation coefficients to ENSO was applied to a financial model of losses related to TCs, there appeared to be no significant inter-relationship between the losses between regions (e.g. US, China). It is therefore of interest to examine the chain of environmental and anthropogenic processes from TC genesis to financial loss to examine how correlations degrade. A number of hypotheses are statistically investigated, primarily using Spearman's coefficient and ranks to decouple dependency structures from the marginal distributions, but also Poisson regression.
Backward piping erosion detection in levees by fiber optic acoustic sensing
Authors: Aguilar-López Juan Pablo , Garcia-Ruiz Andres , Bogaard Thom , Gonzalez-Herraez Miguel
Published: March 2020

Backward piping erosion (BEP) is considered the most dangerous failure mode for levees due to its unpredictable nature. This erosive process happens most of the time underneath the impermeable layers on which levees are commonly founded. This makes it very difficult to detect as conventional geophysical methods are either too expensive or too imprecise for real time monitoring of longitudinal soil made structures such as Dams or levees. Fiber optic based distributed acoustic sensing (DAS) is an innovative technology which allows to retrieve information from an acoustic propagating medium in a spatially dense manner by using a fiber optic cable. The present study aimed to explore the potential of DAS for early detection of BEP  under levees based on the frictional emissions of the sand grains during the erosive process. The tests were performed in the lab under controlled ambient noise conditions. The technology was tested by embedding fiber optic based microphones underneath and outside a laboratory scaled aquifer set up capable of recreating BEP. The results show that indeed the process emits certain characteristic frequencies which may be located between 1200 to 1600 Hz and and that they can easily be captured by the fiber optic cables.
Reconstructed expression for aerosol extinction coefficient by considering mass extinction efficiency and hygroscopic growth for polydipersed aerosol
Authors: Jung Chang Hoon , Lee JiYi , Um Junshik , Kim Yong Pyo
Published: March 2020

In this study, simplified analytic type of expression for size dependent MEs (Mass efficiencies) are developed. The entire size was considered assuming lognormal size distribution for sulfate, nitrate and NaCl aerosol species and the MEE of each aerosol chemical composition was estimated by fitting Mie’s calculation. The obtained results are compared with the results from the Mie-theory-based calculations and showed comparable results.

The mass efficiencies of all aerosol components for each size range are compared with Mie’s results and approximated as a function of geometric mean diameter in the form of a power law formula. Finally, harmonic mean type approximation was used to cover entire particle size range.

Also, analytic expression of approximated scattering enhancement factor which stands for the effect of hygroscopic growth factor for polydispersed aerosol on aerosol optical properties are obtained.

Based on aerosol thermodynamic models, mass growth factor can be obtained and their optical properties can be obtained by using Mie theory with different aerosol properties and size distribution. Finally, scattering enhancement factor was approximated fRH for polydispersed aerosol as a function of RH.

Finally, we also compared the simple forcing efficiency (SFE, W/g) of polydisperse aerosols between the developed simple approach and by the method using the Mie theory. The results show that current obtained approximated methods are comparable with existing numercal calculation based results for polydipersed particle size.
Filed observations of spray production function during Tropical Cyclones Olwyn and Veronica
Authors: Babanin Alexander , Ma Hongyu , Xu Xingkun , Qiao Fangli
Published: March 2020

Spray produced in Tropical Cyclones affects the dynamic and heat fluxes between the atmosphere and ocean, and thus can influence the Cyclone intensity in a number of ways. Measurements of the Sea Spray Generation Function (SSGF) in situ, however, are extremely challenging and correspondingly rare, and uncertainties in quantifying SSGF reach 1000 times.

In the presentation, measurements of the total volume of spray by means of a laser array in Tropical Cyclones Olwyn (2015) and Veronica (2019) in the Indian Ocean will be reported. They are used to develop a parameterisation of SSGF at wind speeds ranging from light to extreme. It is argued that the spray is produced by wind-over-the-waves, and therefore wave properties are also accounted for in the parameterisation.
Does lateral stirring really take place along neutral surfaces in double-diffusive regions of the oceans?
Authors: Wolf Gabriel , Remi Tailleux , David Ferreira , Till Kuhlbrodt
Published: March 2020

Potential temperature/salinity (theta/S) characteristics of water masses in the ocean interior can often be traced back over long distances to their source regions. In practice, understanding how water masses are altered by interior mixing and stirring requires a detailed understanding of the interior pathways linking fluid parcels to their source regions. So far, oceanographers have generally assumed that these pathways are strongly constrained to take place on potential density surfaces of some kind, of which the most commonly employed have been the Jackett and McDougall neutral density variable and sigma2, the potential density referenced to 2000 dbar. Because sigma2 is a somewhat ad-hoc and artificial construct, the more physically-based neutral density variable has been widely assumed to represent the most accurate variable to describe interior pathways, but the analysis of van Sebille et al. (2011) intriguingly suggests otherwise. In order to shed light on the issue, this work hypothesizes that if neutral surfaces were optimal to describe lateral stirring in the ocean, they should be the surfaces along which the observed spread in potential temperature and salinity anomalies should be minimum, since lateral stirring is about 7 orders of magnitude more vigorous in the lateral directions than perpendicular to them. Surprisingly, it is found that this is actually never the case in ocean regions with positive density ratios, traditionally associated with double-diffusive regimes. In those regions, indeed, it is always possible to find material surfaces, not necessarily definable in terms of potential density, along which the spread is reduced for both potential temperature and salinity compared to that over neutral surfaces. In doubly-stable regions, on the other hand, it is not possible to find material variables able to simultaneously reduce both the spread in potential temperature and salinity compared to that over neutral surfaces. Given the widespread nature of double-diffusive regimes in the world oceans, especially in the Atlantic Ocean, these results have strong implications for the ability of ocean climate models to accurately simulate water masses, as it is unclear how to maintain water masses properties by mixing vigorously along directions along which the spread in theta/S is far from its minimum.
Extended-range prediction of heatwave events over North India: role of atmospheric blocking over North Atlantic
Authors: Thanigachalam Arulalan , AchutaRao Krishna , Mitra Ashis K , Ashrit Raghavendra , Gupta Ankur
Published: March 2020

Abstract:

During the summer of 2015, heatwave events claimed 2422 lives in India. Following that disaster, India’s National Disaster Management Authority (NDMA), formulated a Heat Action Plan to protect citizens and minimize fatalities. Improved forecasts from the India Meteorological Department (IMD) together with NDMA’s heat action plan played a major role in the reduction of heatwave mortality since 2016. However, forecasts at longer lead times are required to improve action plans ahead of the heatwave events.

IMD uses extended-range forecast products provided by the National Centre for Medium Range Weather Forecasting (NCMRWF), but we show the improved prediction of high probability from a mutli-model ensemble of the subseasonal-to-seasonal (S2S) database (Vitart et al. 2017). The S2S prediction project that provides Global weather forecasts at lead time of 15 to 60 days, is a joint project of the World Weather Research Program (WWRP) and the World Climate Research Program (WCRP). This provides an opportunity to study the skill of predicting heatwaves over India at extended-range (15 to 30 days). 

In a recent study Ratnam et al., 2016 showed that atmospheric blocking patterns over the north Atlantic region have linkages with heatwave events over northwest India at 2-day lag using ERA-Interim reanalysis and IMD observation. Using ERA5 reanalysis, we found that during 1979-2018, a third of the blocking events over North Atlantic caused heat events over India.

Using the "reforecast" outputs in the S2S database to bias correct the real-time extended range forecast results in improved prediction of frequency, timing,  and spatio-temporal pattern evolution of heatwaves and severe heatwaves at 2 to 3 weeks forecast lead time. The atmospheric blocking anomalies at high-latitudes which precede the heatwave events in India could be predicted three weeks in advance. Based on the S2S models’ skills, the prospects for early warning and disaster preparedness look promising in the coming years.

 

References:

Vitart, F., C. Ardilouze, A. Bonet, A. Brookshaw, M. Chen, C. Codorean, M. Déqué, et al. 2017. "The Subseasonal to Seasonal (S2S) Prediction Project Database", Bulletin of the American Meteorological Society 98: 163–173. doi:10.1175/BAMS-D-16-0017.1.

V. Ratnam, Swadhin K. Behera, Satyaban B. Ratna, M. Rajeevan and Toshio Yamagata.: "Anatomy of Indian heatwaves", Scientific Reports, volume 6, Article number: 24395 (2016) doi:10.1038/srep24395
Shallow water UAV based habitat monitoring of seagrass meadows in the Baltic Sea
Authors: Gross Felix , Etter Kilian , Held Philipp , Schneider von Deimling Jens
Published: March 2020

Seagrass meadows are crucial habitats since they serve as fish nurseries and food sources for many marine species. They prevent nearshore erosion and are an important CO2 sink. As the plants are bound to the photic zone, seagrass meadows normally populate the shallow coastal zones. Unmanned aerial vehicles (UAV) are gaining popularity within the earth sciences community. Most surveys are of terrestrial nature and carried out by using the camera of the UAV to obtain orthophotos and three-dimensional surface models of a survey area. In comparison to space-borne systems, UAVs are capable of higher resolution image quality and time independent measurements, which enables an event-based surveying approach. We here present a submarine habitat mapping study, obtained by using an UAV flying 75 m above the water surface. Within the frame of the BONUS ECOMAP project, we aim to conduct repeated UAV surveys over the seasonal cycle to observe changes within coastal seagrass bed habitats. The key study area is located in the Baltic Sea offshore Heidkate (near Kiel, Germany). For data acquisition, we are using a commercial DJI Inspire 2 UAV with a gimbal mounted 20.8 megapixel Zenmuse X5S camera with a 15 mm/ 1.7 ASPH lens. For less reflection and distortion at the air-water interface, we are using a B&W circular polarized filter. Ground control points are measured and leveled with a Leica RTK system, which has a lateral resolution of ~2 cm. We process the data with the commercial software Pix4D™ and Agisoft PhotoScan™ to compute orthomosaic images and digital elevation/surface models. Since February 2018, we were able to conduct repeated surveys offshore Heidkate and Wendtorf (Germany). The average resolution of the orthomosaic data is better than 5 cm/px. First results show that we can obtain high-resolution images of habitats within water depths less than ~4 m in the Baltic Sea. Penetration is limited to factors like wave action, suspended sediment load and angle of the solar radiation. We perform supervised classification and pattern detection for habitat identification and discrimination. The data show the presence of seagrass, algae but also rocks, which are exposed at the seafloor. All scenes show a seasonal variability of the extent of seagrass meadows which are affected by migrating sand bars and major storm events. These data are the basis for a long-term monitoring framework, we are currently establishing in the working area.
Extreme rainfall from Tropical Cyclones described through the Metastatistical Extreme Value Distribution
Authors: Miniussi Arianna , Marani Marco , Villarini Gabriele
Published: March 2020

Tropical Cyclones (TCs) represent a threat in several areas of the world, among which the Eastern/South-Eastern United States are one of the highly impacted regions. In addition to the frequently analyzed hazards related to the strong winds and storm surges associated with TCs, they are also responsible for heavy rainfall, which can affect areas located very far from the storm center. The accurate estimation of rainfall extremes is crucial in several TC-related impacts, such as engineering design of buildings and prevention/protection measures, flood mapping, risk estimation and mitigation, insurance and re-insurance purposes, policy-making support. Statistical approaches considering the physical drivers of hydrological phenomena, besides their conceptual relevance, can help reducing the estimation uncertainty of extremes. Under these premises, here we use the Metastatistical Extreme Value Distribution (MEVD), a recent approach that improves the estimation of high-return period values over the traditional Extreme Value Theory. We leverage the property of the MEVD to explicitly include in the statistical formulation different rainfall-generating phenomena and we examine the potential advantage of distinguishing TC-induced and non-TC rainfall events in the estimation of extremes. Hence, we apply the MEVD both in a single-component formulation (i.e., assuming that all rainfall events are generated by one single mechanism, so that they can be described by the same probability distribution) and a mixed-population formulation (i.e., separating non-TC and TC-induced rainfall events) to long time series of daily precipitation in six American metropolitan areas, historically known for being impacted by TCs. Moreover, due to the characteristic time scale of these mechanisms, which can significantly influence precipitation for several days, we focus also on aggregated values of rainfall on consecutive days. We find that the mixed approach is advantageous in some cases when looking at daily rainfall, especially when there is a rather uniform frequency of TC events over years. When considering cumulative rainfall on time windows of three days, we show that the reduction of the estimation error by the mixed MEVD is generally higher than in the case of daily rainfall and it is consistent for all the cases studied, except for Houston. A possible reason for the mixed MEVD not to outperform the single-component MEVD in this area is the presence of tornadic supercell convective mechanisms, which also generate heavy rainfall though concentrated in short time intervals.
Mobile GNSS reflectometry measurements
Authors: Strandberg Joakim , Haas Rüdiger
Published: March 2020

A major benefit of ground-based GNSS reflectometry (GNSS-R) over e.g. traditional tide gauge installations is the lower cost and basically maintenance-free operations. Still, a geodetic GNSS antenna is not exactly free of charge, so using cheaper equipment can make the technology available to even more people. With the ever increasing computing power and functionality in mobile phones and tablet computers, some new models are capable of recording raw GNSS data in e.g. RINEX-files. Therefore, they can act as a complete GNSS-R system, with both antenna, receiver, and processing done on a single unit. We make a proof of concept by using GNSS data received with a tablet computer to calculate sea level heights using spectral Lomb-Scargle retrievals. The latter strategy is used  for their low computational cost and simplicity. In comparing the resulting sea level retrievals to a traditional tide gauge and a geodetic quality GNSS-R installation, we show that the two GNSS-R installations perform on similar levels of precision. At the same time, the recorded GNSS data can also be used to derive the position of the tablet computer. Thus, mobile devices can be used as a cheap, and mobile, GNSS-R installation with possible applications in both oceanography and agriculture.