bluuebunny/crossref_metadata_2025 huggingface dataset:
A global perspective on Bromine monoxide composition in volcanic plumes derived from S5-P/TROPOMI
Authors: Warnach Simon , Sihler Holger , Borger Christian , Bobrowski Nicole , Schmitt Stefan , Schöne Moritz , Beirle Steffen , Platt Ulrich , Wagner Thomas
Published: March 2020

Bromine monoxide (BrO) is a halogen radical altering the atmospheric ozone chemistry, e. g. in polar regions, the stratosphere as well as volcanic plumes. In particular, the molar bromine to sulphur ratio in volcanic gas emissions is characteristic to the magmatic composition of a volcano.

The high spatial resolution of S5-P/TROPOMI (up to 3.5x5.5km²) and daily coverage offer the potential to detect BrO even during minor eruptions and determine BrO/SO2 ratios during continuous passive degassing.

Here, we present a global overview of BrO/SO2 molar ratios in volcanic plumes derived from a systematic investigation of two years (2018 and 2019) of TROPOMI data.

We retrieved BrO column densities as well as SO2 column densities using Differential Optical Absorption Spectroscopy (DOAS) and calculated mean BrO/SO2 molar ratios for each volcano. The calculated BrO/SO2 molar ratios differ strongly between different volcanoes ranging between several 10-5 and 10-4. The data are classified and discussed with regard to several volcanic parameters –  more specific the volcanic region, volcano type (i. e. subduction zone, hotspot etc.) as well as activity level.
Zooming in on Arctic clouds: A case study comparing A-Train and airborne remote sensing measurements.       
Authors: Kulla Birte Solveig , Ruiz-Donoso Elena , Kliesch Leif-Leonard , Schemann Vera , Ritter Christoph , Mech Mario , Crewell Susanne
Published: March 2020

Despite their importance, our knowledge on arctic clouds and in particular their vertical structure is limited.

In the essentially remote regions of the Arctic, the only continuous measurements available usually are those of satellites, like the A-Train constellation. Climatologies have been derived from A-Train products, i.e. the combination of radar and lidar. However, due to the coarser resolution and bigger footprints of the sensors and the blind zone of CLOUDSAT in the boundary layer many features are missed. In the framework of the Collaborative Research Centre TR 172 “Arctic Amplification” four major aircraft campaigns with the AWI research aircraft POLAR5 took and will take place in the vicinity of Svalbard with emphasis on the Atlantic Arctic region close to the marginal sea ice zone. 

 

On board of the POLAR5 aircraft active measurements by radar (MiRAC) and lidar (AMALi) were performed and supported by microwave radiometer measurements in 9 frequency channels and a high spectral resolution solar imager (AISA Eagle/Hawk). We have calibrated and processed radar and lidar measurements and deduced highly resolved (7.5 m, 1.3 Hz) vertical profiles of backscatter, attenuation and reflectivity and retrieved a preliminary classification of cloud top. The potential of these measurements for a detailed characterization of Arctic clouds is assessed via the comparison with CALIPSO and CLOUDSAT as well as MODIS measurements for an A-Train underflight. Measurements cover a cold air outbreak in May 2017 with a complex situation with multiple layers of mixed phase clouds and several inversions evident in the thermodynamic structure given by dropsondes. A high resolution model simulation with ICON, which reproduces the general features of this situation, is used together with instrument simulators to investigate how much information on cloud processes can be gained from the measurements. 
Temporal and spatial Sea Surface Temperature (SST) variability off the Southwest African coast
Authors: Nascimento Fernanda P. S. , Schmidt Martin , Mohrholz Volker
Published: March 2020

An understanding of Benguela Nino events is important for local economy, ecosystem and ocean dynamics. Aiming to see if Benguela Nino events can be seen in observations and reproduced by the models, an investigation of sea surface temperature (SST) temporal and spatial variability was done throughout the Southwest African coast.  Using SST obtained from satellite observations and from four different numerical models, a coastal strip of 1o width from 8S to 28S was calculated and averaged longitudinally. Even though models were warmer than the observations, variability seen on observations were reproduced by the models. Highly anomalous warm and cold periods that coincides with years of Benguela Niño and Niña were found both on observations and in the models, as well as SST weakening after 2000.
Mapping the soft and ethical dimensions of sea level rise in southern Sweden
Authors: Van Well Lisa , Björlin Anette , Danielsson Per , Godefroid Ndayikengurukiye Godefroid , Göransson Gunnel
Published: March 2020

Sea level rise poses profound challenges within current municipal and regional governance since it requires unusually long planning horizons, is surrounded by great uncertainties, and gives rise to novel ethical challenges. Adaptation to climate change is fundamentally an ethical issue because the aim of any proposed adaptation measure is to protect that which is valued in society. One of the most salient ethical issues discussed in the adaptation literature relates to the distribution of climate related risks, vulnerabilities and benefits across populations and over time. Raising sea-walls is typically associated with high costs and potentially negative ecological impacts as well as substantial equity concerns; managed retreat or realignment often causes problems related to property rights; and migration out of low-lying areas can involve the loss of sense and cultural identity and impact on receiving communities.

How can the soft and ethical dimensions of rising mean sea levels be characterized and how can their consequences be mapped? To help municipalities to understand the values and ethics attached to measures to deal with long-term rising sea levels in southern Sweden, we are developing a methodology of soft or ethical values to complement to GIS-mapping of coastal vulnerability based on coastal characteristics and socio-economic factors.

Rather than determining these values a priori, they are being discerned through workshops with relevant stakeholders and in interviews with citizens residing in and utilizing the coastal areas. The methodology attempts to determine the place-based of values within coastal communities with a focus on “whose” values, “what” values, and the long-term or short-term nature of values. It builds on an analytical framework developed to acquire information on the behavior, knowledge, perception and feelings of people living, working and enjoying the coastal areas.  In turn this stakeholder-based information is used to co-create “story maps” as tools to communicate complicated vulnerability analyses, highlight the ethical dimensions of various adaptation measures, raise awareness and aid decisionmakers in taking uncomfortable decisions to “wicked” planning problems around the negative effects of sea level rise, coastal erosion and urban flooding.

This paper presents the methodological development of the task as well as the results the study in four Swedish municipalities. The representation of the “soft” and ethical values provides an opportunity to help clarify these values to policymakers and increase resilience to rising sea levels.
Multisensor crop yield estimation with machine learning
Authors: Martínez Ferrer Laura , Piles Maria , Camps-Valls Gustau
Published: March 2020

Providing accurate and spatially resolved predictions of crop yield is of utmost importance due to the rapid increase in the demand of biofuels and food in the foreseeable future. Satellite based remote sensing over agricultural areas allows monitoring crop development through key bio-geophysical variables such as the Enhanced Vegetation Index (EVI), sensitive to canopy greenness, the Vegetation Optical Depth (VOD), sensitive to biomass water-uptake dynamics, and Soil Moisture (SM), which provides direct information of plant available water. The aim of this work is to implement an automatic system for county-based crop yield estimation using time series from multisource satellite observations, meteorological data and available in situ surveys as supporting information. The spatio-temporal resolution of satellite and meteorological observations are fully exploited and synergistically combined for crop yield prediction using machine learning models. Linear and non-linear regression methods are used: least squares, LASSO, random forests, kernel machines and Gaussian processes. Here we are not only interested in the prediction skill, but also on understanding the relative relevance of the covariates. For this, we first study the importance of each feature separately and then propose a global model for operational monitoring of crop status using the most relevant agro-ecological drivers.

 

We selected the Continental U.S. and a four-year time series dataset to perform the research study. Results reveal that the three satellite variables are complementary and that their combination with maximum temperature and precipitation from meteorological stations provides the best estimations. Interestingly, adding information about crop planted area also improved the predictions. A non-linear regression model based on Gaussian processes led to best results for all considered crops (soybean, corn and wheat), with high accuracy (low bias and correlation coefficients ranging from 0.75 to 0.92). The feature ranking allowed understanding the main drivers for crop monitoring and the underlying factors behind a prediction loss or gain.
Eddy-Mean flow oscillations in the Southern Ocean
Authors: Roncoroni Sebastiano , Ferreira David
Published: March 2020

Geostrophic eddies have a leading order effect on the dynamics of the Southern Ocean (SO), and numerous studies have shown that they are also key to the response of both the zonal transport and the meridional overturning circulation to wind stress changes. The role played by eddies in setting the intrinsic variability of the SO, however, is less well-understood. Here, inspired by recent work on the atmospheric jet, we investigate whether the eddy-mean flow interaction in the Antarctic Circumpolar Current can be described by a prey-predator nonlinear model.

 

To this end, we analyse data from a high-resolution eddy-resolving configuration of the MIT general circulation model: an idealised “channel” model with mechanical and thermodynamical forcing at the surface, and plausible zonal and meridional circulations.

 

Here, we show that a mechanism of eddy-mean flow interaction driving the intrinsic variability of the SO-like model is well described by a stochastic non-linear oscillator with damping. This model is a generalisation of the Ambaum-Novak oscillator, which has been successfully employed to describe the atmospheric storm track variability.

 

We find that, on length scales similar to that of individual zonal jets, the eddy-mean flow interaction is characterised by a high-frequency oscillatory mode, and that the characteristic time scale of the oscillation is comparable with classical estimates of the baroclinic life-cycle. A Gaussian smoothing of the phase space diagram also reveals the damped oscillatory character of the oscillation: this is in contrast with the atmospheric case, where damping is negligible and orbits are confined to energy surfaces.

 

This result may help inform the interpretation of the SO intrinsic and forced variability (such as, for example, the response to wind stress changes), and pave the way to further studies featuring more realistic model configurations.
Plant community evolution in a glacier foreland of the Central European Alps
Authors: Ramskogler Katharina , Müller Svenja , Knoflach Bettina , Stötter Johann , Geitner Clemens , Erschbamer Brigitta
Published: March 2020

Glacier forelands are perfect for analysing the development of plant communities from zero onward. According to Matthews (1992), the chronosequence can act as a spatial representation of the temporal sequence. Therefore, it is ideal to analyse changes in landscape and land cover in time slices. Development of plant communities does not only depend on the age of the deposits, but also on topography, microclimate, soil development, and geomorphological processes as well as on biotic interactions. In the long term, permanent plots represent an adequate method to follow the colonisation on differently aged terrain throughout time.

The main research question of the study is: Do cryospheric changes influence plant community development in time and space? During the first study year we were focused on the following questions: i) How fast does a plant community evolve? ii) How many species do occur on different moraine stages? iii) How do soil parameters correlate with primary succession stages?

The study site is located in the southern part of the Central European Alps, Martell Valley (South Tyrol, Italy). We established 12 permanent plot clusters of 2 x 5 m on areas deglaciated between 1985 and 2018, two per retreat area. In each square meter of these clusters, species composition, cover, and number of individuals were sampled. On the ground moraines of the glacier stages 1911 and approximately 1850 we recorded species composition and cover on 10 x 10 m plots (four plots in total). In all plot clusters and plots on the old moraines, soil temperature and soil water potential as well as relevant soil parameters were measured.

We found up to two vascular plant species per square meter on areas ice free for one year and up to 16 vascular plant species per square meter on areas ice free since 1985.

On the moraines of 1911 were up to 39 vascular plant species per plot with a mean cover of 52.5 %. On the moraines of 1850 we found up to 43 vascular plant species with a mean cover of 40 %.

In the next step we will analyse the effects of pioneer, early and late successional species on morphodynamic processes and their response to these processes using functional traits.

Matthews, J.A. (1992): The ecology of recently-deglaciated terrain: a geoecological approach to glacier forelands and primary succession. Cambridge University Press, Cambridge.
Conceptualisation of Sea-Water Intrusion in an Island Aquifer System
Authors: Sapiano Manuel , Baena-Ruiz Leticia , Debattista Henry , Pulido-Velazquez David
Published: March 2020

A method to conceptualise the assessment of the impact of sea-water intrusion in island and coastal aquifer systems is being proposed.  The method will enable the undertaking of a first assessment of the sea-water intrusion problem, hence providing an early-stage and simple to apply “warning system” enabling the informed and timely application of mitigation measures intended to protect the quantitative and qualitative status of the aquifer system. The method proposes the discretization of the aquifer to enable the correlation of the current aquifer “freshwater domain” with reference conditions representing the aquifer system under undisturbed conditions.  The “freshwater domain” is defined by the volume of water between the piezometric surface and the seawater interface, and can be obtained from numerical models, where available, or the application of simple analytical approaches such as the Ghyben-Herzberg solution. . The dynamic of the seawater intrusion is defined as the change in natural “freshwater domain” and chloride concentrations within it. Therefore, the method is applicable to island and coastal aquifers with low-data availability, and in particular to cases where a numerical-model is not-yet developed. The application of the method will enable the quantification of sea-water intrusion impacts at an aquifer scale, enabling the visual-conceptual representation of the sea-water intrusion affected area, as well as identify the level of intrusion.  The method also enables the temporal assessment of sea-water intrusion, identifying the evolution of intrusion throughout the exploitation period of the aquifer system.  The method has been implemented in a GIS tool, and applied to the Mean Sea Level Aquifer system in Malta.

 

Aknowledgement: This research has been partially supported by the GeoE.171.008-TACTIC project from GeoERA organization funded by European Union’s Horizon 2020 research and innovation program and by the SIGLO-AN project (RTI2018-101397-B-I00) from the Spanish Ministry of Science, Innovation and Universities (Programa Estatal de I+D+I orientada a los Retos de la Sociedad)

 
Impact of the stratosphere on El Niño-Southern Oscillation
Authors: Rodrigo Mario , Garcia-Serrano Javier , Bladé Ileana , Palmeiro Froila M. , Mezzina Bianca
Published: March 2020

The European Consortium EC-EARTH climate model version 3.1 is used to assess the effects of a well-resolved stratosphere on the representation of El Niño-Southern Oscillation (ENSO). Three 100-year  long experiments with fixed radiative forcing representative of the present climate are compared: one with the top at 0.01hPa and 91 vertical levels (HIGH-TOP), another with the top at 5hPa and 62 vertical levels (LOW-TOP), and another high-top experiment with the stratosphere nudged to the climatology of HIGH-TOP from 10hPa upwards (NUDG). The differences in vertical resolution between HIGH-TOP and LOW-TOP start at around 100hPa. This study focuses on the canonical ENSO phenomenon, which is the most important source of variability and predictability on seasonal-to-interannual timescales.

 

Preliminary results indicate that EC-EARTH realistically simulates the ENSO SST pattern in the tropical Pacific regardless of vertical resolution, although HIGH-TOP (LOW-TOP) overestimates (underestimates) the SST variability during boreal summer (winter). In both configurations, the SST tongue is narrower meridionally and slightly shifted towards the central-western Pacific compared to observations, a common bias of climate models. Resolving the stratosphere has a clear effect on the power spectrum of the Niño3.4 index: as compared to observations where there is a well-known frequency range of 2-7 years, HIGH-TOP and LOW-TOP have a prominent peak centered at 4-5 years but additionally both simulations display another peak, towards higher (~ 2yrs) and lower (~ 7yrs) frequencies, respectively. Another impact of including a well-resolved stratosphere is to systematically enhance the amplitude of the SST, wind and convective anomalies in the tropical Pacific throughout the entire ENSO cycle. Finally, similar differences are obtained when comparing HIGH-TOP and NUDG, suggesting an active role of the tropical stratospheric variability on ENSO.
Projections of global labour productivity under climate change
Authors: van Maanen Nicole , Dasgupta Shouro , Gosling Simon N. , Piontek Franziska , Otto Christian , Schleussner Carl-Friedrich
Published: March 2020

Labour productivity declines in hot conditions. The frequency and intensities of extreme heat events is projected to increase substantially with climate change across the world, which causes not only severe impacts on health and well-being but could also lead to adverse impacts on the economy in particular in developing countries. Wet bulb globe temperature (WBGT) is a commonly used metric that combines temperature and humidity to estimate the occurrence of heat stress in occupational health. Although the links between heat stress and economic effects are well established, there are substantial differences between existing impact models of labour productivity.

Here we present results of future changes in labour productivity based on a comprehensive intercomparison of labour productivity models across indoor and outdoor working environments, locations and countries. Under the framework of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP), we applied projections from multiple bias corrected global climate models to multiple labour productivity impact models and consider different socioeconomic futures. In addition to models used in existing literature, we use a newly developed model based on empirical exposure-response functions estimated from three- hundred surveys (56 million observations) from 89 countries, that allows for projections at the sub-national level. Based on our model intercomparison results, we can provide robust and spatially explicit projections for changes in labour productivity across the globe. At the same time, our approach allows us to assess and compare existing models of labour productivity estimates, therefore covering multiple dimensions of uncertainty.
How low-frequency Equatorial Kelvin Wave activity and local coastal winds modulate the south-eastern interannual Atlantic variability?
Authors: Bachelery Marie-Lou , Illig Serena , Rouault Mathieu
Published: March 2020

Several studies suggest that the mean atmospheric and oceanic features in south-eastern Atlantic have experienced changes over the last few decades with, in particular, a shift in the mean position of the Saint Helena Hight Anticyclone and an increase in the mean ocean stratification. Modification of the wind forcing and the mean state at the equator and along the south-western coast of Africa will most likely impact the characteristics of the eastward propagating interannual Equatorial Kelvin Waves (EKW) and subsequent Coastal Trapped Waves (CTW) in the south-eastern Atlantic. These changes will also affect the interannual variability in the Benguela Upwelling System, especially since the remote equatorial ocean dynamics is instrumental in the development of extreme warm and cold Benguela Niño/Niña events. The objective of this study is to document the low-frequency change in the characteristics (amplitude, duration and timing) of the interannual Benguela Niño/Niña events. Using model solutions and sensitivity experiments, we investigate the mechanisms that control the low-frequency modulation of the coastal interannual variability off the coasts of Angola/Namibia. Our results reveal that the decadal modulation of the interannual variability off the Angolan coast is controlled by change in the EKW activity. In the Southern Benguela, the modulation of the interannual is dominated by the influence of the local alongshore winds. However, periods during which the equatorial forcing is intensified, EKW propagate and imprint the oceanic variability off the coast of Namibia.

 
Arctic climate response to extreme events in synoptic and planetary scale atmospheric energy transport
Authors: Rydsaa Johanne H. , Graversen Rune G. , Stoll Patrick
Published: March 2020

Atmospheric energy transport into the Arctic (>70° N) has been shown to greatly alter the Arctic temperatures and the development of the Arctic weather and climate. Recent research suggests that latent energy transport into the Arctic by large, planetary-scale atmospheric systems cause a stronger and more long-lasting impact on near surface temperatures, than energy transported by smaller, synoptic scale systems. This implies that Rossby waves impact Arctic climate more than synoptic cyclones. Therefore, shifts in circulation patterns driving atmospheric energy transport into the Arctic on different scales have a potential to change Arctic climate.

Here, we show that the annual mean impact of latent energy transport on Arctic temperatures is dominated by the winter season transport. Furthermore, by examining the ERA5 dataset for the years 1979-2018, we find that over the past four decades, there has been a shift in the mean winter season latent energy transport, from smaller, synoptic scale systems (-0.03 PW/decade), towards larger, planetary scale systems (+0.05 PW/decade) which as mentioned, have a larger climatic impact. As a consequence, this shift is estimated to have increased the Arctic temperatures. We find that the trends are driven by an increase in the extreme transport events (here we examine the upper 97.5th percentile). The upper extremes have increased more than the average on the planetary scale, and decreased more on the synoptic scale. The decrease in extreme synoptic scale transport at 70° N has been confirmed in other analyses of high vorticity weather systems. By examining the extreme transport events on seasonal scales, we reveal differences in the temporal distribution of planetary vs. synoptic scale extreme events, and identify areas of the Arctic that receive the strongest impact with respect to increases in near-surface temperatures.
Güralp recommendations for the installation of high-performance, observatory-grade seismic stations
Authors: Filippi Sofia , Mohr Sally , Balon Marie , Hill Phil , Watkiss Neil , Goessen Shawn
Published: March 2020

In order to monitor nuclear tests on a global scale, it is one of the IMS’s fundamental tasks to maintain a network of seismic stations with high data reliability. Installation is often the most critical aspect of a successful seismic station. A poorly designed layout leads to the introduction of noise that can hugely impact data quality, therefore rendering expensive, high performance equipment inadequate.

To facilitate quality installations and encourage better practices in the global seismic monitoring community, Güralp has developed a system that will allow for observatory-grade data.

The system is a classic seismic station composed of an ultra-low noise broadband seismometer: a Güralp 3T (120s or 360s), a high-performance digitizer-datalogger: the Güralp Affinity, a sensor cable and an atmospheric pressure enclosure.

The custom-built pressure enclosure enhances performance in vault installations, protecting the sensor from minuscule fluctuations in temperature and pressure, hence considerably reducing noise levels.

Güralp also provide best practice guidelines to assist researchers in designing their station, from site selection, installation and training to data retrieval and analysis.

Since 2001, Güralp have been managing the Eskdalemuir seismic array (EKA), the United Kingdom’s auxiliary station for the International Monitoring System. These years of experience with CTBT related monitoring have taught us that good results do not come from the instrument alone. This is why Güralp endeavors to accompany operators through every step of the process with a team of specialist engineers, applying 35 years of expertise from project conception to data retrieval.
Chlorophyll and phytoplankton spatial distribution in the Arabian/Persian Gulf and the Sea of Oman
Authors: Polikarpov Igor , Saburova Maria , Al-Yamani Faiza
Published: March 2020

Spatial distribution of the chlorophyll-a and phytoplankton community composition related to different water masses were studied during regional cruise in February-March 2006 across the Arabian/Persian Gulf and the Sea of Oman, the marginal seas of the Western Indian Ocean.

Chlorophyll-a concentrations were measured using in vitro method with fluorescence detection and also were assessed as in vivo fluorescence measured by submersible fluorometer. Nearly four hundred species of phytoplankton were enumerated and identified using microscopy in the samples collected at the same stations.

High phytoplankton abundance was associated with diatom-dominated phytoplankton blooms in the central and northwestern part of the Gulf, in the Strait of Hormuz and in the Sea of Oman. The average concentration of in vitro measured surface chlorophyll-a in the studied area was 2.5 mg/m3, with the maximum over 9 mg/m3. The relationships between the concentrations of satellite remotely sensed chlorophyll and in vitro measured chlorophyll-a were found to be mostly in good agreement. The highest concentrations of the surface chlorophyll (> 4 mg/m3) were observed in the areas where diatom-dominated blooms were identified. It was revealed a significant relationship between the phytoplankton composition and water masses indexed by salinity.

The main significance of this study is in the first data set of in vitro measured precise chlorophyll-a concentrations that were obtained along with phytoplankton abundance and taxonomic diversity from the entire region of the Arabian/Persian Gulf and the Sea of Oman. This data set can be used for remote sensing measurements validation and as a baseline for future studies of the biological productivity changes in the Western Indian Ocean.
Numerical modelling of energy geo-structures for building retrofitting
Authors: Salciarini Diana , Cecinato Francesco
Published: March 2020

Energy piles (EPs), consisting in piled foundations equipped with heat exchangers, have been extensively studied in recent years, both from the thermo-mechanical response and energy performance points of view. However, most research refers to typical rotary bored, CFA or precast driven, medium diameter piles. Little attention has been devoted to so-called energy micropiles (EMPs), representing an opportunity to provide at the same time energy and structural retrofitting to existing buildings. Existing studies show that EMPs overall may thermally perform differently to EPs, but they are comparable in terms of specific heat flux.

In this work, a 3D FE numerical model is employed to perform a comprehensive parametric study considering design factors that are peculiar to EMPs, to assess the most important parameters to maximise their energy performance. The parameter space is efficiently explored resorting to a statistically-based Taguchi approach. Then, the model is employed to compare the overall energy performance of realistic EP and EMP foundation solutions, under the same building and underground conditions. Finally, practical guidance is provided about the optimal choice of design factors to achieve the best thermal performance whenever EMPs  are to be used based on geotechnical/structural design.

 

Acknowledgement: The second author wishes to acknowledge support from the EU’s Horizon 2020 Research and Innovation programme under Grant Agreement No 810980 - ENeRAG.
Influence of braided river bed morphology over concentration of geochemical constituents in river sediments: a case study of Ganga and Yamuna Rivers in and around Kait-Haridwar, Uttarakhand, India
Authors: Satyam Gyan Prakash , Dubey Rajendra Kumar
Published: March 2020

The clastic sediments and its aspect of provenance, weathering and erosion, tectonic setting, fluvial processes, paleoclimate and some other geological processes are better studied with the help of geochemical analysis. The changing geochemistry of sediment present in Himalayan river has been a great point of interest in sedimentary geochemistry because of its impact over Indian ocean chemistry and climate. In all Himalayan rivers, the Ganga and Yamuna Rivers are most important in global scenario due to their perennial nature, and peculiar flow and depositional characteristics. These two rivers had played important role in formation of Indo-Gangetic Plain during Quaternary period. Both the Ganga and Yamuna Rivers emerge from great Himalaya and carried the sediments from there to Bay of Bengal, India.

This causes sequential change in geochemistry of deposited sediments. The studied region is near by Mohand ridge and extend up to Balawali in Ganga River side and up to Kait in Yamuna River side. In this region rivers have high gradient channels and high flow speed condition. The channels are braided and have gravelly bed load. The converging channel system effects the geochemical constituent of river sediments.

The geochemical analysis of river bed sediments of both rivers by using XRF data analysis were carried out to find out the variation and effect of river bed morphology over geochemical constituents concentration. The prepared tectonic setting discriminant diagrams through plots log[K2O/Na2O] versus SiO2 and [SiO2/Al2O3] versus log[K2O/Na2O] indicate transitional tectonic setting from an active continental margin to a passive margin. The discriminant function plot indicates quartzose sedimentary provenance, and to some extent, the felsic igneous provenance, derived from weathered granite, gneissic terrain and/or from pre-existing sedimentary terrain. Further, by plotting SiO2 versus other major elements plot reveals the changing concentration of major elements with respect to changing river bed morphology with 50-60 km length of both the rivers. In braided zone of river, there is sudden increase in SiO2 concentration of river sediments. The gravels present in channel bed provide more resistance and tight pore spaces for flow of water which causes increase in abrasion phenomena. These vital change in geochemistry (which is from 65% to 81% for SiO2 concentration) of sediments indicates about the major role play of braided zone gravel deposit. The changing bed morphology of river channel has vital effect on geochemical composition of deposited sediments.
A straightforward approach for obtaining quantitative dielectric constant using reflected GNSS signals
Authors: Lee Junchan , Bisnath Sunil , Lee Regina
Published: March 2020

Dielectric constant describes the electrical properties of a material and is related to soil moisture. The latter is known as a critical parameter in hydrological and climate science; however, computing such dielectric constants is a challenging problem as many factors effect the constant values, e.g., soil type, texture and temperature. Global Navigation Satellite System-Reflectometry (GNSS-R) is a relatively new remote sensing technique being used to infer geophysical information by measuring not only the signals coming directly from the GNSS satellites, but also the reflected GNSS signals from the Earth’s surface. This research presents a new, straightforward approach for computing relative dielectric constant by means of reflectivity, which is the ratio between the signal-to-noise ratio (SNR) of direct waves and SNR of reflected waves. With the well-known relationship between the reflectivity, Fresnel coefficient, and surface roughness, the dielectric constant can be expressed as the combination of horizontal and vertical Fresnel coefficients. Dual, circular-polarized antennas in the zenith and nadir directions were used to capture electromagnetic waves emitted from GNSS satellites and transform them into electrical signals. The zenith direction antenna senses the direct signals which have right-hand circular polarization, and the nadir direction antenna senses right and left-hand circular polarization of reflected GNSS signals created by electromagnetic reflections on the surfaces. An in-house Software Defined Radio (SDR) receiver, coupled with a commercial radio frequency frontend were used to collect, store and analyze both direct and reflected signals. Data collection experiments were carried in areas of smooth surface, and the observed SNR values were applied to the method of quantitative dielectric constant. The computation results demonstrate that derived dielectric constants have the values around 10 and are independent on the incident angle of waves coming to the specular point. Applying the additional data processing to the results, it is relevant to the dielectric constant measured by Time Domain Reflectometry techniques used commercial soil moisture probes at the same time. There have been few attempts to establish the dielectric constant model using forward scattered electromagnetic signals, especially GNSS signals. The proposed calculation method is able to solve the difficulties in analyzing with respect to the incident angle, as well as the polarization. Therefore, it is expected that the inversion approach of the retrieval algorithm makes the GNSS-R applicable to not only the scientific but also the industrial applications. In the future, the dielectric constant will be enhanced to include roughness information of the Earth’s surface and to attempt to calibrate surface soil moisture measurements for various soil types.
Seismotectonics of the northern Longitudinal Valley, Taiwan, inferred from aftershock sequences of 2018 Mw6.4 and 2019 Mw6.2 Hualien earthquakes
Authors: Sun Wei-Fang , Kuo-Chen Hao , Guan Zhuo-Kang , Chang Wen-Yen
Published: March 2020

In the Hualien area, two Mw6.4 and Mw6.2 earthquakes, 20 km apart, occurred in February 2018 and April 2019 respectively. The former to the northeast, located offshore to ​​the Liwu river, triggered several earthquake clusters along the Milun fault and southward to the Longitudinal Valley, the suture of the Eurasian and the Philippine Sea plates; the latter to the southwest, located in the Central Range, also triggered several seismic swarms in the Central Range,  along the Liwu river to the northeast and at Ji'an to the southeast. Except for the Milun fault, neither GPS nor InSAR observations detects significant surface deformation after the occurrence of these two main shocks, indicating that the earthquake ruptures mainly developed within the crust. Therefore, seismic observation becomes an efficient tool for revealing the seismotectonics of the two earthquake sequences. For monitoring the aftershock sequences, two days after the main shocks, we deployed two geophone arrays, 70 Z-component RefTek 125A TEXANs for two weeks in 2018 and 47 three-component Fairfield Nodal Z-Lands for one month in 2019, with 1-5 km station spacing around the Hualien City. These earthquake swarms were well recorded and analyzed through the dense seismic networks. The numbers of aftershock sequences manually identified are two-fold more than that issued by the Central Weather Bureau, Taiwan. The seismicity of the 2018 aftershock sequence, to depths of between 5-15 km, was significantly reduced within 10 days after the main shock. however, the seismicity of the 2019 aftershock sequence, to depths of between 2-50 km, was still above background seismicity rate 30 days after the main shock. The spatial distribution of the 2018 aftershock sequence could be related to a fault zone of the plate boundary, but that of the 2019 and the relocated 1986 aftershock sequences show a conjugate thrust fault pair beneath the eastern Central Range. Our results clearly depict several local tectonic structures that have not been observed at the northern tip of the Longitudinal Valley, not only a suture but also a transitional area from collision to subduction.
A Dynamic and Flexible State Model for Rainfall Nowcasting
Authors: Schleiss Marc , Roy Venkat
Published: March 2020

We present a dynamic state model estimation method for rainfall nowcasting in which we assume that the short term spatio-temporal evolution of rainfall can be approximated by a linear state model with stochastic perturbations.  We estimate the model parameters using radar reflectivity measurements for one-step as well as multiple-step ahead rainfall nowcasting. If the rainfall intensity at location x and time index t is given by ut(x), then the overall rainfall field intensity vector at any time t over N pixels (of the target area) can be represented by ut = [ut(xN),...ut(xN)]T. Following the aforementioned formalism, the spatio-temporal evolution of the rainfall field can be described by the following linear state model given by
ut = Htut-1 + qt
where Ht is an unknown time-varying state-transition matrix of dimensions NxN and qt is a stochastic process noise vector of length N. We present an iterative least squares based method to estimate Ht and explore simpler algebraic structures (e.g., scaled affine transformations) to reduce the numbers of unknown parameters during estimation. We evaluate the performances of the proposed model using simulations and radar reflectivity data from the Royal Netherlands Meteorological Institute (KNMI). We observe that the nowcasting performances strongly depend on the size of the target area (number of pixels N), the type of events as well as the parameterization of Ht. The key advantage of the proposed approach over classical nowcasting methods based on Lagrangian persistence is the possibility to incorporate prior information about future rainfall evolution from external sources of information such as satellites or numerical weather prediction models during the estimation of the parameters.
On the permanent tide and the Earth dynamical ellipticity
Authors: Escapa Alberto , Baenas Tomás , Ferrándiz José Manuel
Published: March 2020

As other relevant quantities related to the Earth dynamics, the Earth dynamical ellipticity is influenced by tidal effects. In particular, it is affected by the permanent tide due to the time independent part of the Earth redistribution tidal potential. Hence, it is necessary to distinguish between its tide-free and non tide-free values (e.g., Burša 1995) when determining it from observations (e.g., Marchenko & Lopushanskyi 2018). This question is seldom considered in Earth rotation studies. For example, neither IAU2000/AIU2006 nutation/precession model nor IERS Conventions specify explicitly whether the dynamical ellipticity is a zero-tide parameter or not. However, current accuracy goals might be sensitive to that difference.

Within the framework of a Hamiltonian approach (Baenas, Escapa, & Ferrándiz 2019), we present a consistent treatment of the influence of the permanent tide on the dynamical ellipticity. In particular, we develop an analytical expression of the redistribution tidal potential based on Andoyer canonical variables and a semi-analytical theory of the orbital motions of the Moon and the Sun, following the same procedure as that given in Kinoshita (1977).

This method allows obtaining an expression of the zero frequency term of the redistribution tidal potential that updates that of Zadro & Marussi (1973), usually employed in reporting parameters of common relevance to Astronomy, Geodesy, & Geodynamics (e.g., Burša 1995, Groten 2004). In addition, it clarifies the procedure that must be followed in order that the dynamical ellipticity, fitted to the observations, contains the effects of the permanent tide avoiding in this way potential inconsistencies.
From 3R Approach to 4C Systems: on the Road to Sustainable, Desirable and Resilient City
Authors: Tchiguirinskaia Ioulia , Versini Pierre-Antoine , Schertzer Daniel
Published: March 2020

A wider recognition of climate change enhances in the society the 3R approach – Reduce, Recycle and Reuse –, thus broadening the spectrum of Urban Geoscience topics. This strengthens also the consensus that business models of companies are often too focused on their financial value, to the detriment of social and environmental added value. It therefore seems timely to change this way of doing things so that their growth is built more as part of a sustainable development approach, by emphasising the paradigm shift of ‘shared value’.

'Shared value' means that by meeting the needs and challenges of society, businesses can create their economic value in a way that also benefits society, in direct link with COP21's commitments and in response to energy, environmental and IT transition laws, hence bringing political ambition and market reality together. To highlight such opportunities, this presentation will capitalise on several research initiatives launched in Greater Paris during recent years related to this topic (https://hmco.enpc.fr/portfolio-archive/):

(i) research to extend non-linear approaches in environment and geophysics;

(ii) results on defining environmental indicators for our cities - considering their multimodal, multiscale and multifunctional structure - to quantify their environmental impacts (e.g., thermal, visual comfort, air quality, heat island mitigation, stormwater management etc.);

(iii) numerous instrumentation and modelling experiments related to the impacts of climate change and to the means of their attenuation;

(iv) results on the monetisation of amenities provided by Blue-Green Solutions in urban areas and their large-scale socio-economic contextualisation;

(v) environmental assessment of many (infra)structures that take into account their design method, implementation, operation, maintenance and end-of-life.

All these research initiatives constitute the basis for the ‘shared value’ theoretical emergence in the 4C framework – Cognitive, Collaborative, Coevolutionary and Complex – systems, with a practical methodology towards the sustainable, desirable and resilient city and call for larger developments of Urban Geosciences.  
A North Pacific Anomaly around 700BC: a potential analogy to the present day geomagnetic field
Authors: Nilsson Andreas , Suttie Neil
Published: March 2020

Recent advances in geomagnetic field modelling of palaeomagnetic data have led to significant improvements of our understanding of the geomagnetic field and how it varies on millennial timescales. Among other things, palaeomagnetic field reconstructions have shown that large-scale non-dipolar field anomalies, similar to or even larger than the present day South Atlantic Anomaly (SAA), have occurred several times in the past, implying that such structures are not necessarily associated with polarity reversals or excursions. A recent study even suggests that such large-scale field asymmetries could be periodically recurrent features of the field. Here we present results from a new Holocene geomagnetic field model, pfm9k.2, constructed using a novel Bayesian approach to account for chronologic uncertainties and address problems with potential smoothing induced by post-depositional remanent magnetisations. We focus our attention on a particular time period, around 700BC, where our new model shows a large-scale field asymmetry in the northern hemisphere with a weak field anomaly in the North Pacific accompanied with strong field intensities in Europe. The field evolution predicted by the model during this time period shares many similarities with the present day field, including a rapid decay of the dipole moment, suggesting that there may be common driving processes. We discuss the physical implications of these results.