bluuebunny/crossref_metadata_2025 huggingface dataset:
The ROMY project: A 4-component ring laser for geophysics and geodesy
Authors: Igel Heiner , Bernauer Felix , Wassermann Joachim , Yuan Shihao , Gebauer Andre , Schreiber Ullrich
Published: March 2020

The ROMY ring laser was constructed with 4 non-orthogonal triangular-shaped cavities of 12 m side length in the Geophysical Observatory outside Munich, Germany, in 2016. The large dimensions of the individual rings have the benefit of allowing high sensitivity surpassing in principle the sensitivity of the G-ring at the Fundamentalstation Wettzell. However, the concrete construction of ROMY is geometrically less stable than the G-ring that is built on a rigid Xerodur plate. Each of the four rings has its own Sagnac frequency. The horizontal triangular ring laser at the top of the inverted tetrahedral ROMY structure allows direct comparison of teleseismic signals and noise with the G-ring at a distance of 200km. It also serves as redundant component. In principle, three orthogonal components of rotational ground motion can be obtained by linear combination from any combination of three rings, that - due to the variable Sagnac frequency - have different noise characteristics. We report on the behavior and observations of ROMY from a seismological point of view. It is fair to say that ROMY provides the most accurate direct 3-component rotational ground motion seismic observations to date. In combination with a collocated broadband seismometer as well as a surrounding small-scale seismic array, we analyse regional, teleseismic events, and ocean-generated noise and compare with array-derived rotation.
Shedding light into the forest: improved understanding of DOM processing in freshwater using complementary experimental and machine learning approaches
Authors: Lechtenfeld Oliver , Wentzky Valerie , Rinke Karsten , Kamjunke Norbert , von Tümpling Wolf , Wilske Christin , Friese Kurt , Böhrer Bertram , Reemtsma Thorsten , Herzsprung Peter
Published: March 2020

Dissolved organic matter (DOM) plays important roles in aquatic ecosystems but can interfere with drinking water production. However, its highly complex composition and chemical diversity makes it difficult to understand molecular reactivity in natural systems. Here we used ultra-high resolution mass spectrometry (FT-ICR-MS) and data from two independent studies (a lake monitoring and a photo-irradiation experiment) to disentangle DOM reactivity based on photochemical and microbial induced transformations.

Monitoring in Germany’ largest drinking water reservoir (Rappbode reservoir, Harz Mountains) was conducted over one year on seven dates using water from nine depths. Water chemistry and limnological parameters, including chlorophyll a (chl a) concentration were determined. Stratification of the lake allowed to determine depths and periods, where an accumulation of chl a corresponded with an accumulation of DOM compounds. Chl a served as a surrogate for microbially (i.e. primary) produced DOM. In addition, we used data from a photodegradation experiment using river water from a catchment with similar land use (tributary to Muldenberg reservoir in the Ore Mountains, Germany). The water had been irradiated for 6 days in triplicates using natural sunlight. Thirteen time points had been sampled and used to determine the photochemical reactivity of DOM compounds.

We used robust rank correlations to establish relationships between predictor (chl a concentration or cumulated sunlight irradiation) and response variables (normalized FT-ICR mass peak intensities) for each dataset. Combining the resulting data further allowed for an orthogonal classification of 1277 molecular formulas, which were present in all samples. Using this approach, we could identify 11 reactivity groups and attributed chemical properties to these groups based on molecular information. Photodegradation was observed for high molecular weight molecules - similar to microbial degradation - whereas photo products were aliphatic and oxygen rich. We found that in the lake studied, DOM turnover was dominated by photochemical processes. Exclusively microbial products were comparably low in number and of small molecular weight compounds.

Based on the molecular-property-reactivity-relationships, we trained a random forest model and predicted the molecular reactivity for the remainder of molecular formulas, for which insufficient data were initially available.

The approach presented here offers an expandable tool to integrate reactivity of DOM from specific environments and link it to its molecular properties and chemistry. This will lead to enhanced understanding of the ecological function and biogeochemical cycling of DOM.
Solar wind radial evolution via future multi-spacecraft in-situ observations
Authors: Štverák Štěpán , Maksimovic Milan , Hellinger Petr , Trávníček Pavel M.
Published: March 2020

Our understanding of the solar wind evolution, its energy budget, and role of the key mechanisms providing the energy exchange between the plasma particles and electromagnetic fluctuations along the expansion, is highly limited by the single point nature of most in situ spacecraft measurements. Obviously it is difficult to observe and track the individual processes in space and time from this narrow perspective. One way to improve our knowledge of these large-scale variations is to employ multi-spacecraft observations, namely rather rare so called line-up events where one can potentially observe the true evolution of individual solar wind plasma parcels. A pioneering work in this field was done using Helios I&II missions. Here we present an analyses of using such tool for future events predicted to be available from the very recent missions Parker Solar Probe and Solar Orbiter (and optionally BepiColombo).
Toward CO2 and CH4 measurements by ground-based observations of surface-scattered sunlight: Instrumentation and experiments
Authors: Hemmer Benedikt , Holzbeck Philip , Kleinschek Ralph , Knapp Marvin , Kostinek Julian , Müller Robin , Proß Christin , Hase Frank , Butz André
Published: March 2020

Precise knowledge of sources and sinks in the carbon cycle is desired to understand its sensitivity to climate change, and to account and verify man-made emissions. An important role herein play extended sources like urban areas. While in-situ measurements of carbon dioxide (CO2) and methane (CH4) are highly accurate but localized, satellites measure column-integrated concentrations over an extended footprint. Our innovative measurement technique aims at determining CO2 and CH4 concentrations on the scale of a few kilometers near the ground, and therefore fills the sensitivity gap between in-situ and satellite measurements.

 

Our development starts out from the EM27/SUN Fourier transform spectrometer, which is a reliable, mobile and commercially available spectrometer for the measurement of CO2 and CH4 column densities using direct sunlight spectra. We increased the radiometric sensitivity of the instrument by enhancing optical throughput and replacing the detector module by a thermoelectrically cooled detector. This enables the measurement of surface scattered sunlight spectra in the range of 4000 - 11000 cm-1 under various viewing directions. Our setup is independent of sun position and exhibits a high sensitivity to the concentrations in the lower boundary layer, due to the near ground horizontal path component.

 

Here, we report progress on our instrumental developments, as well as first retrievals of column averaged CO2 and CH4 mole fractions from ground-scattered sunlight spectra recorded with this setup. We present the instrument modifications and extensions to the experimental setup: A Lambertian reflector allows for reference measurements without horizontal path component, a coaligned camera enables specific targeting and the motorized tracking system facilitates automated alternation between multiple targets. We characterize the setup with a spectral resolution of 0.54 ± 0.03 cm-1 a signal to noise ratio above 200 for solar zenith angles < 85°, and precision of 1.8 ppm and 9 ppb regarding the inferred column averaged CO2 and CH4 mole fractions obtained from retrievals with a simple radiative transfer model, neglecting atmospheric scattering.
Deepening our understanding of shallow precipitation measurements from space
Authors: Bogerd Linda , Leijnse Hidde , Overeem Aart , Uijlenhoet Remko
Published: March 2020

Satellite-based remote sensing provides a unique opportunity for the estimation of global precipitation patterns. In order to use this approach, it is crucial that the uncertainty in the satellite estimations is precisely understood. The retrieval of high-latitude precipitation (especially shallow precipitation) remains challenging for satellite precipitation monitoring. This project will quantify the quality of the precipitation estimations obtained from the Global Precipitation Measurement (GPM) mission, where the focus will be on the level II and III products. Initially, the Netherlands is chosen as research area, since it has an excellent infrastructure with both in-situ and remotely sensed ground-based precipitation measurements, its flat topography, and the frequent occurrence of shallow precipitation events. The project will study the influence of precipitation type and the impact of the seasons on the accuracy of the GPM products. Hereafter, the project will focus on the physical causes behind the discrepancies between the GPM products and the ground validation, which can be used to improve the retrieval algorithms. The presentation will outline the project structure and will demonstrate the initial results.
Exceptionally preserved Milankovitch cycles in Lower Devonian argillaceous limestone of the Hudson Valley, New York State (USA)
Authors: Da Silva Anne-Christine , Bartholomew Alex , Brett Carlton , Hilgen Frits , Ver Straeten Charles , Dekkers Mark
Published: March 2020

Uncertainties on the radiometric ages of Devonian stage boundaries are currently on the order of several millions of years. A cyclostratigraphic approach is the foremost way forward to improve the Devonian geological time scale. To do so requires well-preserved continuous records, as well as reliable paleoclimatic proxies.  The NY Route 199 section, from Kingston, in the Hudson Valley of eastern New York, is a road cut outcrop, which exposes most of the Schoharie Formation. It corresponds to the upper portion of the Emsian Stage (upper Lower Devonian, ~400 to ~394 Ma), with essentially continuous deposition. The lithology consists of a mixed siliciclastic-carbonate succession with overall increasing carbonate upsection, showing various degrees of bioturbation (traces includes primarily Zoophycos, Planolites and Chondrites); colors range from white to beige, brown or dark grey. The quality of most of the outcrop is so remarkable that the color variations by themselves permit recognition of Milankovitch cycles, with prominent bundles of light and dark beds. One type of cycle expression is represented by a succession of about six darker beds nested between lighter beds, which is interpreted as six precession cycles within a short eccentricity cycle (precession in the Devonian was ~17 kyr).

Samples were collected every 2 cm through 38 m of the section for magnetic susceptibility measurements. On top of these measurements, we provide elemental geochemistry, carbon isotopes and hysteresis measurements (every 50 cm) to constrain the depositional setting and the diagenesis. Hysteresis measurements show that despite being remagnetized (throughout the Appalachians, these Paleozoic rock sequences are all remagnetized during the Variscan-Alleghenian Orogeny), the magnetic susceptibility reflects depositional information. The geochemistry and carbon isotopes give insight into the occurrence of oxic/reducing conditions and detrital inputs. Milankovitch cycles are visible on the outcrop and in the magnetic susceptibility record, allowing a precise floating timescale framework to be constructed for this interval.
Real-time discrimination of earthquake foreshocks and aftershocks
Authors: Gulia Laura , Wiemer Stefan
Published: March 2020

Immediately after a large earthquake, the main question asked by the public and decision-makers is whether it was the mainshock or a foreshock to an even stronger event yet to come. So far, scientists can only offer empirical evidence from statistical compilations of past sequences, arguing that normally the aftershock sequence will decay gradually whereas the occurrence of a forthcoming larger event has a probability of a few per cent.

We analyse the average size distribution of aftershocks of the 2016 Amatrice–Norcia (Italy) and Kumamoto (Japan) earthquake sequences and we suggest that in many cases it may be possible to discriminate whether an ongoing sequence represents a decaying aftershock sequence or foreshocks to an upcoming large event.

We propose a simple traffic light classification (FTLS, Foreshock Traffic Light System) to assess in real time the level of concern about a subsequent larger event and test it against 58 sequences, achieving a classification accuracy of 95 per cent.

We finally test, in near-real-time, the performance of the FTLS to the 2019 Ridgecrest sequence, California: a Mw6.4 followed, about 2 days later, by a Mw7.1. We find that in the hours after the first Ridgecrest event (Mw 6.4, the b-value drops by 23% on average, when compared to the background value, resulting in a ‘red’ foreshock traffic light.

Mapping in space the changes in b, we identify an area to the north of the rupture plane as the most likely location of a subsequent event. The second mainshock of magnitude 7.1 then indeed occurred in this location and after this event, the b-value increased by 26 percent over the background value, resulting in a green traffic light state.
NGIC: turning concepts into reality
Authors: Miloshev Nikolay , Trifonova Petya , Georgiev Ivan , Marinova Tania , Dobrev Nikolay , Slabakova Violeta , Milusheva Velichka , Gurov Todor
Published: March 2020

The National Geo-Information Center (NGIC) is a distributed research infrastructure funded by the National road map for scientific infrastructure (2017-2023) of Bulgaria. It operates in a variety of disciplines such as geophysics, geology, seismology, geodesy, oceanology, climatology, soil science, etc. providing data products and services. Created as a partnership between four institutes working in the field of Earth observation: the National Institute of Geophysics, Geodesy and Geography (NIGGG), the National Institute of Meteorology and Hydrology (NIMH), the Institute of Oceanology (IO), the Geological Institute (GI), and two institutes competent in ICT: the Institute of Mathematics and Informatics (IMI) and the Institute of Information and Communication Technologies (IICT), NGIC consortium serve as primary community of data collectors for national geoscience research. Besides the science, NGIC aims to support decision makers during the process of prevention and protection of the population from natural and anthropogenic risks and disasters.

Individual NGIC partners originated independently and differ from one another in management and disciplinary scope. Thus, the conceptual model of the NGIC system architecture is based on a federated model structure in which the partners retain their independence and contribute to the development of the common infrastructure through the data and research they carry out. The basic conceptual model of architecture uses both service and microservice concepts and may be altered according to the specifics of the organization environment and development goals of the NGIC information system. It consists of three layers: “Sources” layer containing the providers of Data, Data products, Services and Soft-ware (DDSS), “Interoperability”- regulating the access, automation of discovery and selection of DDSS and data collection from the sources, and “Integration” layer which produces integrated data products.

The diversity of NGIC’s data, data products, and services is a major strength and of high value to its users like governmental institutions and agencies, research organizations and universities, private sector enterprises, media and the public. NGIC will pursue collaboration with initiatives, projects and research infrastructures for Earth observation to enhance access to an integrated global data resource.
Dynamics and drivers of extreme seasons in the Arctic region
Authors: Hartmuth Katharina , Papritz Lukas , Böttcher Maxi , Wernli Heini
Published: March 2020

Single extreme weather events such as heavy storms or heat waves can have a major impact on Arctic surface temperatures, melting rates and sea-ice extent. If weather conditions in the Arctic become anomalous on the time scale of an entire season, this could affect the Arctic energy budget and sea ice coverage even more.

From a meteorological perspective, in a certain region an extreme season can be defined as a season when a specific meteorological parameter, such as surface temperature, reaches extremely high or low seasonal-mean values in this region. The dynamical processes leading to such anomalous seasons in the Arctic region as well as their possible change in a warmer climate have not yet been analysed in detail. Furthermore, it is yet unknown if climate models are able to correctly represent the processes leading to extreme seasons, which is an important aspect for the validation and potential further improvement of such models.

Here we focus on a detailed analysis of Arctic extreme seasons and their underlying atmospheric dynamics in the ERA5 reanalysis data set. Specifically, extreme seasons are determined based on departures from a transient climatology of four parameters (surface temperature, sea-ice extent, surface energy balance and net surface freshwater flux) in distinct regions of the Arctic with different climatological sea-ice extents. Using EOF analysis, the overall most extreme seasons, which occur as significantly anomalous for several parameters, are selected to perform extended case studies. Highly anomalous seasons occur on a broad range of spatial scales as well as for areas nearly covering the whole Arctic Ocean. The formation of small and large extreme seasons may vary significantly, including local processes as well as large-scale atmospheric features.

The winter of 1984/1985 shows one of the largest positive departure of surface temperature from the background warming trend together with a significant sea-ice reduction in the region of the High Arctic and the Greenland Sea. An analysis of the synoptic situation for this winter shows a slightly positive cyclone frequency anomaly over the Greenland Sea combined with a more pronounced negative cyclone frequency anomaly over the Kara-Barents Sea, favouring the advection of warm mid-latitude air masses towards the pole.
Subsoil organo-mineral associations under contrasting climate conditions
Authors: Inagaki Thiago M. , Possinger Angela R. , Grant Katherine E. , Schweizer Steffen A. , Mueller Carsten W. , Derry Louis A. , Lehmann Johannes , Kögel-Knabner Ingrid
Published: March 2020

Organo mineral associations intermediated by Fe and Al are considered one of the most important mechanisms for soil organic carbon (SOC) stabilization. However, since Fe and Al are normally mentioned together as stabilizing agents, we still lack knowledge about their relative role. In addition, this stabilization mechanism can be profoundly affected by climate differences, but the magnitude of this influence whether as a direct effect or an indirect consequence due to changes in soil mineralogy is not yet fully understood. In this study, we evaluated a series of subsoil samples throughout a climate gradient (1800–2400 mm precipitation year-1 and 15–24º C) on Kohala Mountain, Hawaii to understand the impact of climate differences on organic matter protection. We have used a combined approach of analyses at the bulk soil and microscale using NanoSIMS. At the bulk soil scale, we have observed a concurrent decline of subsoil Fe, Al (i.e., dithionite citrate and ammonium oxalate extractions) and SOC above a precipitation level of 2000 to 2200 mm year-1. This decline co-occurred with more reduced forms of Fe s (evaluated by Fe K-edge XANES) and declines in carboxyl-C (evaluated by CP-MAS 13C NMR). We found significant positive correlations between SOC with Fe and Al in the bulk soil throughout the gradient, and we could discern the relative role of Fe and Al in promoting organo-mineral associations in contrasting climate conditions (e.g., ~1800 and ~2300 mm year-1) using NanoSIMS. While Fe contributed to approximately 40% of the microscale organo-mineral associations in the lower precipitation site (assessed by co-localizations with OM segments), this contribution at the higher rainfall regime was only 5%. In contrast, the contribution of Al was approximately the same in both rainfall levels (approximately 30%). This fact indicates that Al may be more important than Fe in stabilizing SOC especially under high precipitation levels. The normalized CN:C ratio was higher when associated with Fe and Al especially in the high precipitation level, which demonstrates the importance of Fe and Al in stabilizing N-rich organic matter. Here we demonstrate that spatial relationships between Fe and Al with SOC at the microscale display a shift towards Al-dominated SOC associations at higher precipitation that could not be ascertained from bulk measurements alone. Thus, they are of great importance to understand the impact of climatic differences on SOC sequestration in organo-mineral associations.

 
Freshwater pathways and litter
Authors: Cabrera Fernández María
Published: March 2020

In recent years, there has been an increasing number of studies about freshwater micro-litter  and how it ends up in the ocean. Nevertheless, macro-litter studies are not common in freshwater landscapes and yet less frequent among rivers. Almost always, research is focused on estuaries rather than rivers.

The Asociación Paisaje Limpio has been developed, for some years, several studies as an affordable methodology to measure macro-litter in rivers throughout its.

This way, our methodology is a combination between research and action. We don’t just tackle the macro-litter data field, but also identify specific litter problems along the river. We act through campaigns, agreement for companies and public administrations, etc.

A need have been observed to combined different types of methodology to monitoring different types of rivers in order to be able to draw a conclusion:

Visual counting: counting floating macro-litter on surface using RIMMEL app.

By the riverbank,through a Citizen Science tool create by Asociación Paisaje Limpio and Asociación Vertidos Cero, called eLitter. Elitter is harmonized with other marine-litter methodologies (Marine litter watch, MARNOBA in Spain) and its litter classification is based on OSPAR protocol.

If the riverbed is accessible eLitter is also used, but when is not accessible a dredge "Van Veen" have been used instead. This method has been applied in other marine-litter projects on seabed.

Floating booms: it lets us know plastics rate in captured floating litter, and the water flow extrapolation.

Nets from a kayak: to study the plastic concentration  in the water column and the water flow extrapolation.

Water quality general analysis:this analysis is useful to support the hypothesis about litter’s source in a river, mainly where the source is the sewage as happens with wet wipes, ear sticks...

-Case study: river Lagares, a spanish river in Pontevedra, Galicia. The river Lagares flows into the Atlantic, in a Special Protection Area (SPA), a designation under the European Union Directive on the Conservation of Wild Birds.

The Asociación Paisaje Limpio is working on this river since 2018. We have applied the different methodologies explained before, in the river Lagares.
Comparing three approaches to the ground geoelectric field modelling due to space weather events
Authors: Marshalko Elena , Kruglyakov Mikhail , Kuvshinov Alexey , Sokolova Elena , Pilipenko Viacheslav , Kozyreva Olga
Published: March 2020

In order to estimate the potential hazard to technological systems from space weather, it is necessary to understand the spatiotemporal evolution of the geoelectric field during geomagnetic disturbances. Once the geoelectric field is quantitively estimated, geomagnetically induced currents can be calculated from the geometry of transmission lines and system design parameters. To address the complex problem of the ground electromagnetic (EM) field modelling due to space weather events, it is necessary to consider the spatiotemporal structure of the source of the EM induction in a realistic way and take into account a realistic three‐dimensional (3‐D) distribution of the Earth's electrical conductivity.

In this work we compare three approaches to the geoelectric field modelling. All approaches are based on the numerical solution of Maxwell's equations in Earth's models with 3-D conductivity distribution. The difference between them lies in different setting of the EM induction source. In the first two methods the source is represented by a laterally varying sheet current flowing above the Earth. The current in the first approach is computed on the base of 3-D magnetohydrodynamic simulation of near-Earth space. In the second one the source is constructed using ground-based magnetometers' data. In the third approach the geoelectric field is calculated using plane wave excitation. We carry out geoelectric field modellings for Kola Peninsula and Karelia using these three approaches. In our simulations we utilise the 3-D conductivity model of Fennoscandia (SMAP). The geoelectric field is computed using 3-D EM forward modelling code extrEMe based on a contracting integral equation method. We compare modelling results to EM field observations and discuss advantages and disadvantages of the considered approaches.
Holocene paleoclimate and environmental reconstruction from Urmia Lake sediments in southwest Asia
Authors: Haghipour Negar , Hunziker Daniela , Darvishi Javad , Mohammadi Ali , Eglinton Tim Ian
Published: March 2020

Lake Urmia, in northwest Iran, is the largest saline lake in the Middle East with surface area of 5000 km2. Despite its potential as an archive of paleoclimate and paleoenvironmental information for Southwest Asia there has been no molecular organic geochemical investigation or precise dating of these sediments, especially for the Holocene. This study used multi-proxy analysis combining sedimentological, bulk and stable organic geochemical and compound specific stable isotopes along with high-resolution radiocarbon dating on organic and carbonate material to understand the Holocene climate and environmental variability in SW Asia.

The age model based on sixty calibrated radiocarbon dates shows variation of sedimentation rates between early and middle Holocene and a sudden increase in late Holocene. The most prominent change, at 4.3 Ka, closely corresponds to the well-documented 4.2 ka event (Medieval Optimum) in the Mediterranean and Middle East.

We used compound-specific hydrogen isotope ratios (δD) in long chain n-alkanes and n-alkonic acids as paleohydrological proxy. The fact that Urmia Lake is large and little affected by in-situ production of iso-GDGTs from methanogenic Euryarchaeota makes the measured TEX86 proxy reliable. Therefore, we used this proxy to reconstruct the Holocene paleotemprature.  The analyzed record reveals multi-decadal to centennial pacing of paleoclimate and paleoenviromental changes, with most prominent events recorded at 8.1, 4.3 and 2.5 ka BP.

 
Impacts of Heinrich events upon Human existence potential in Europe
Authors: Rostami Masoud , Klein Konstantin , Wegener Christian , Shao Yaping , Weniger Gerd-Christian
Published: March 2020

Heinrich events are recognized as the dominant periods of extreme cold terrestrial climate conditions during the last glacial period. The role of climate forcing alone upon Human Existence Potential (HEP) during extreme events, e.g. Heinrich and Dansgaard-Oeschger events, is not yet sufficiently resolved. By reproducing climate variables during the two extreme cold and warm cycles by means of an Earth System Model, employing an improved HEP model, and utilizing archaeological excavation sites, we report the spatial distribution of HEP over Europe during both cold stadials and warm interstadials corresponding to the two Upper Palaeolithic technocomplexes: Late Gravettian and Aurignacian. By introducing some other diagnostics like Environmental Human Catchment, which is defined as an area delimited by low HEP, cooling-aridity index, and Least Cost Path among colonized people, we shed light into population dynamics in this epoch. Consecutive extreme cold and warm cycles, corresponding to contraction-expansion of HEP, supports the hypothesis of repetitive depopulation–repopulation cycles of habitats. Regarding the controversial issue of late survival location of Neanderthals, we illustrate that western coastlines had such a suitable and stable HEP scores for all human taxa including Neanderthals to survive during Heinrich events.
On the Feasibility and Applicability of Multipath Mitigation Maps as an IGS Product
Authors: Hunegnaw Addisu , Ejigu Yohannes Getachew , Teferle Felix Norman , Elgered Gunnar
Published: March 2020

Multipath is a largely unmodelled source of error and causes large range errors in Global Navigation Satellite System (GNSS) observations. The effects have strong site-specific characteristics and impact each receiver differently. Multipath errors can propagate and can cause in-situ position and velocity biases and are also contributing to the pervasive draconitic harmonic signals. We employ an empirical approach to reducing the effects of multipath by stacking one-way post-fit carrier phase residual observations by applying an appropriate averaging scheme. Our processing is based on static multi-GNSS observations using various scientific GNSS software packages (Bernese GNSS Software, NAPEOS, GAMIT-GLOBK, PRIDE and GINS). Our multipath stacking (MPS ) uses the stacking of individual residuals generated by variable azimuth cell size (congruent cells) by allocating carrier phase residuals in each cell, unlike fixed azimuth cell resolution in the standard MPS approaches. This reduces the binning of fewer residuals at higher elevation angles. Before stacking, we also apply rigorous statistical outlier screening tests for each one-way post-fit carrier phase residual assigned to each of the congruent cells. We thus correct the multipath effects by subtracting the stacked multipath map from the post-fit carrier phase residual. Using this technique we produce a model available in the form of the Antenna Exchange (ANTEX) file format, that can potentially be implemented in routine GNSS analysis with no or little additional overhead for individual analysis centers (ACs).

In this study, we assess the feasibility and applicability of the MPS maps as an International GNSS Service (IGS) product for routine GNSS analysis. We have selected a subset of IGS stations with and without known multipath issues in different climatic zones. We demonstrate the multipath stacking technique to result in a significant reduction of the variation in the one-way post-fit carrier phase residuals. For GPS-only solutions, the MPS technique shows a decrease of up to 30% in the RMS value of the one-way post-fit carrier phase residuals. We have also tested our MPS for other constellations such as GLONASS, Galileo and BeiDou, and combinations of these .
Augmenting Catastrophe Models to Quantify Financial Losses Under Prescribed Climate Scenarios
Authors: Latchman Shane , Clarke Alastair , Zapatka Boyd , Sousounis Peter , Stransky Scott
Published: March 2020

In 2019, the Bank of England, through the Prudential Regulation Authority (PRA), became the first regulator to ask insurers how financial losses could change under prescribed climate scenarios. Insurers readily use catastrophe models to quantify the likelihood and severity of financial losses based on at least 40 years of past climate data. However, they cannot readily use these models to answer the climate scenarios posed by the PRA.

We present four novel methods for how to use existing catastrophe models to answer what-if climate scenario questions. The methods make use of sampling algorithms, quantile mapping, and adjustments to model parameters, to represent different climate scenarios.

Using AIR’s Hurricane model for the United States (US), Inland Flood model for Great Britain, and Coastal Flood model for Great Britain, we quantify the sensitivity of the Average Annual Loss (AAL) and the 100-year exceedance probability aggregate loss (100-year loss) to four environmental variables under three climate scenarios. The environmental variables include the (i) frequency and (ii) severity of major US landfalling hurricanes; (iii) the mean sea level along the coast of the US and Great Britain; and (iv) the surface run-off from extreme precipitation events in Great Britain. Each of these variables are increased in turn by low, medium and high amounts as prescribed by the PRA.

We compare each variable and rank their influence on loss. We find that the AAL and 100-year loss are more sensitive to changes in the severity of major US hurricanes than changes in the frequency. We will show whether sea level rise has a greater influence on coastal flooding losses in the US or in Great Britain, and we show how sensitive inland flooding losses are to surface run-off.     

The methods yield approximate results but are quicker and easier to implement than running Global Circulation Models. The methods and results will interest those in insurance, the public sector, and academia, who are working to understand how society best adapts to climate change.
A study on cloud cover in reanalysis datasets in tropical south India
Authors: Chirikandath Kalath Unnikrishnan
Published: March 2020

Clouds play a key role in Earth’s energy and water budgets. This study examines the cloud cover changes in two nearer and distinct locations in tropical south India, one location is a near-coastal region in Thiruvananthapuram (8.52oN, 76.90oE) and another one in Western Ghats mountain ranges (10.15oN, 77.01oE). The study validated the following reanalysis product with Lufft CHM 15k ceilometer observations in both locations during 2017: ERA5, ERA-Interim and MERRA-2 reanalysis. ERA5 daily cloud cover data has the lowest RMSE (20 %) than other reanalysis datasets in these tropical locations. Correlation between daily ceilometer cloud cover observation and reanalysis datasets shows that ERA5 data has better temporal cloud cover anomaly (0.8) in the mountain location. All reanalysis datasets show significant correlation (0.01 level) with observation. RMSE (correlation) is higher (lower) in coastal region. Further, a long period cloud cover trend (1985-2016) in both locations are calculated from multiple reanalysis and ISCCP datasets. All datasets show a consistent and significant (0.01 level) increasing cloud cover in both locations.  ISCCP Mean IR cloud amount (marginal) shows the highest increasing trend compared to reanalysis datasets (5.9 %). In the coastal location, the cloud cover increasing trend is much higher and all datasets agree well on it. A long period correlation analysis is performed between cloud cover variability in the study region and north Indian ocean SST to study their relation. Bay of Bengal SST is highly positively correlated with the cloud cover in the study region (significant at 0.01 level). This suggests that the observed increase in cloud cover has a strong relationship with the north Indian Ocean warming.
Virtual energy storage-gain due to spatiotemporal coordination of hydropower over Europe
Authors: Wörman Anders , Crochemore Louise , Pechlivanidis Ilias , Gions Lopez Marc , Brandimarte Luigia , Riml Joakim , Hao Shuang , Bertacchi Uvo Cintia , Busse Stefan
Published: March 2020

The viability of a renewable electricity system depends on long-term climate variations, uneven spatiotemporal distribution of renewable energy, and technical constraints. A major problem is to achieve a sustainable balance of water usage and consumption, as well as adequate energy and water distribution and storage capacities. In particular, hydropower offers a large capacity for energy storage and production flexibility, but only stands for a minor part of the total energy potential. In this study we explored the spatial and temporal variance of hydropower availability for a 35-year period based on historical hydro-meteorological data from large parts of Europe. A spectral analysis of these historical time-series shows that spatiotemporal coordination of the hydropower system covered in the Global Reservoir and Dam Database (GRanD) can potentially contribute with a “virtual” energy storage capacity that is up to four times the actual energy storage capacity contained in the existing hydropower reservoirs. Such virtual energy storage capacity implies reduced water storage demand, hence, indirectly contributes to reduced constraints of the food-water-energy nexus also in a wider system perspective. We found that the most significant benefits from a spatiotemporal management arise at distances of 1,200 – 3,000 km, i.e. on the continental scale, which can have implications for a future renewable energy system at large. The analysis also covers what we denote “energy-domain-specific drought”, which implies a shortage of energy storage capacity to avoid a deficit of energy for a given time period, and which may be reduced by the spatiotemporal coordination of power production.
Precursor of the Highland silk road on the Tibetan Plateau
Authors: Yang Xiaoyan
Published: March 2020

Ancient silk road had two main branches, one is north line across Xinjiang and the other is south line proposed as Highland Silk Road, jointing Tibetan Empire, Tang Dynasty and states in South Asia. Due to the harsh natural environment on the Tibetan Plateau (TP), a little archaeological work had carried out, and a few archaeological sites were excavated on the TP. How the highland silk road was developed is unclear.

In 2018, researchers from the Chinese Academy of Sciences (CAS) launched the second scientific expedition to the Qinghai-Tibet Plateau (STEP) that will last 5 to 10 years, following an expedition in the 1970s. Sponsored by the STEP, we had two systematic surveys along the Yarlung Tsangpo River regions, esp. the middle and lower regions to understand the prehistoric human activities on the central Tibetan Plateau where the mean altitude is above 4000 meters. We investigated the terraces along the River and its tributoraries, and terraces circled the lake banks. 99 archaeological sites were surveyed, including 58 new findings. The anthropic deposits were found at 31 sites and a profile was cleared at each site to collect dating materials. Charcoals and charred seeds were floated from the anthropic deposits and dated 60 samples by the AMS 14C.

In combination with previous published dates, we set up a brief history of human activities on the central TP that is, Neolithic people had occupied the Yarlung Tsangpo Valley in the third millennium BC, and moved along the River and its tributaries. The route of dispersal is similar with the historic highland silk road, indicating that this road had developed in prehistory.
Source size and Position of a Type IIIb-III Pair with LOFAR
Authors: Zhang Peijin , Zucca Pietro , Sridhar Sarrvesh , Wang Chuanbing
Published: March 2020

Solar radio bursts originate mainly from high energy electrons accelerated by solar eruptions like solar flares, jets, and coronal mass ejections (CMEs).  A sub-category of solar radio bursts with a short time duration may be used as a proxy to understand the wave generation and propagation within the corona.  Complete case studies of the source size, position, and kinematics of short-term bursts are very limited due to instrumental limitations.
LOw-Frequency-ARray (LOFAR) is an advanced radio antenna array. It is capable of a variety of processing operations including correlation for standard interferometric imaging, the tied-array beam-forming, and the real-time triggering on incoming station data-streams. With recently upgraded LOFAR, we can achieve high spatial and temporal imaging for solar radio bursts.
Here we present a detailed analysis of the fine structures in the spectrum and of the radio source motion with imaging, the radio source of a type IIIb-III pair was imaged with the interferometric mode using the remote baselines of the (LOFAR). This study shows how the fundamental and harmonic components have a significant different source motion.  The apparent source of the fundamental emission at 26 MHz is about 4 times the speed of light, while the apparent source of the harmonic emission shows a speed of < 0.02 c.  We show that the apparent speed of the fundamental source is more affected by the scattering and refraction of the coronal medium.
Extending Ocean Drilling Pursuits [eODP]: Making Scientific Ocean Drilling Data Accessible Through Searchable Databases
Authors: Fraass Andrew , LeVay Leah , Sessa Jocelyn , Peters Shanan
Published: March 2020

Scientific ocean drilling through the International Ocean Discovery Program (IODP) and its predecessors, has a far-reaching legacy. They have produced vast quantities of marine data, the results of which have revolutionized many geoscience subdisciplines. Meta-analytical studies from these efforts exist for micropaleontology, paleoclimate, and marine sedimentation, and several outstanding resources have curated and made available elements of offshore drilling data (e.g., Neptune), but much of the data remain heterogeneous and dispersed. Each study, therefore, requires reassembling a synthesis of data from numerous sources; a slow, difficult process that limits reproducibility and slows the progress of hypothesis testing and generation. A computer programmatically-accessible repository of scientific ocean drilling data that spans the globe will allow for large-scale marine sedimentary geology and micropaleontologic studies and may help stimulate major advances in these fields.

The eODP project, funded through the NSF’s EarthCube program, seeks to facilitate access to, and visualization of, these large microfossil and stratigraphic datasets. To achieve these goals, eODP will be linking and enhancing the existing database structures of the Paleobiology Database (PBDB) and Macrostrat. This project is targeting shipboard drilling-derived data, but the infrastructure will be put in place to allow the addition of data generated post-cruise. eODP will accomplish the following goals: (1) enable construction of sediment-grounded and flexible age models in an environment that encompasses the deep-sea and outcrops; (2) expand existing lithology and age model construction approaches in this integrated offshore-onshore stratigraphically-focused environment; (3) adapt key microfossil data into the PBDB data model; (4) develop new API-driven web user interfaces for easily discovering and acquiring data; and (5) establish user working groups for community input and feedback. The success of eODP hinges upon interaction, feedback, and contribution of the scientific ocean drilling community, and we invite anyone interested in participating in this project to join the eODP team.
Organic Carbon and Nitrogen stocks in two soil types of Northwestern Tunisia: Temporal and spatial variation
Authors: Tlili Ahlem , Dridi Imene , Gueddari Moncef
Published: March 2020

Soil organic matter has generated international interest in carbon and nitrogen sequestration. In reality, small fluctuations of soil organic stock could have large impacts on global warming. Therefore, quantification of Soil Organic Carbon (SOCs) and Total Nitrogen (TNs) stocks in surface and deep horizons are important to control the release of greenhouse gases. The present research was undertaken in order to determine SOCs and TNs evolution over 50 years. For this aim, we selected two soils (P1 and P2) developed under contrasted pedogenetic conditions in North-West of Tunisia (Beja governorate). P1 is a Luvisol located in a forest region. However, P2 is a Cambisol situated in an agriculture zone. Soil samples were gathered from surface (0-30 cm) and deep (50-100 cm) horizons in 1971, 2005, 2012 and 2019. SOCs declined in surface and deep horizons during the experimental period in both studied soils. In the case of Luvisol, the values declined from 91.01 t/ha to 75.54 t/ha and from 53.00 t/ha to 24.51 t/ha, respectively in surface horizons and deep horizons. Likewise, the SOCs values decreased from 84.24 t/ha to 25.52 t/ha in surface horizons and from 24.45 t/ha to 14.20 t/ha in deep horizons of the Cambisol. The TNs recorded lower values than SOCs. Nevertheless, they showed the same behavior. Our results showed that the highest values of SOCs and TNs were recorded in the Luvisol. This soil exhibited the greatest amount of organic matter since it was developed under forest vegetation. In addition, the results showed an enrichment in SOCs and TNs of superï¬cial horizons to the detriment of the deep horizons. Nevertheless, this decrease in organic stocks with depth occurred following different patterns according to soil type. In fact, the Cambisol reported an important depletion of soil organic stocks as compared to the Luvisol. The loss of SOCs and TNs were estimated to be 69.71% and 54.17% in surface horizon, and 41.94 % and 28.28 % in deep horizon, respectively. Indeed, the land-use change increases the decomposition of soil organic matter principal source of SOCs and TNs. Such a reduction has wider implications on global warming and soil fertility.  
Developing geodetic tools for early warning and monitoring of tectonic activity at the Gulf of Cadiz
Authors: Garate Jorge , Ramirez Zelaya Javier , Rosado Belen , Berrocoso Manuel , de Gil Amos , Fernandez Ros Alberto , Prates Gonçalo , Peci Luis Miguel
Published: March 2020

Gulf of Cadiz from the Strait of Gibraltar to the Western Coast of the Iberian Peninsula is a natural hazard risky region due to the existence  of several active faults related to the Eurasian and Nubian Plate interaction. The 1755 Lisbon Earthquake was remarkable example. With the epicenter located SW of Cape San Viente, and a Richter scale magnitude around 8.3, the earthquake triggered a devastating tsunami hitting the Portuguese, Moroccan and Southern Spain coasts, resulting in thousands of casualties. More recently, in 1969 a 7.8 magnitude earthquake with its epicenter located in the same region, originated another tsunami but smaller than the previous one, resulting nineteen casualties.

To prevent natural hazards like these, the Astronomy, Geodesy and Cartography Laboratory at the Universidad de Cadiz, is drawing and implementing early warning systems, trying to detect and evaluate tectonic activity in near real time at the Gulf of Cadiz. The system includes the GNSS network SPINA  receivers together with MEMS acelerometers, meteo equipments, and ancillary instrumentation for data adquistion, monitoring, quality control and results display at a dedicated control center.