bluuebunny/crossref_metadata_2025 huggingface dataset:
In situ dust measurements in the solar wind from S/WAVES TDS instrument on STEREO mission
Authors: Rackovic Babic Kristina , Issautier Karine , Zaslavsky Arnaud
Published: March 2020

Dust particles represent an important fraction of the matter composing the interplanetary medium. At 1 A.U. dust mass density is comparable to the one of the solar wind. The large number and broad diversity of dust particles detected by the radio instrument on the STEREO satellites recommend this mission for a closer dust investigation. In situ dust measurements are based on the detection of the charges generated by dust impacts, recorded by the S/WAVES instrument near 1 A.U. since the beginning of the STEREO mission. We study the electric signals produced by these impacts, using the waveform sampler data produced by the TDS subsystem of the radio instrument, connected to three monopole antennas. For this study, we concentrate on macroscopic dust particles (~0.1 microns) whose impact generated nearly simultaneous pulses on the antennas. In particular, we present statistics of typical shapes and features of these signals based on the TDS electric potential time-series and compare the data to a theoretical model of how pulses are generated by charge collection.
These results will have implications on dust detection from Parker Solar Probe and Solar Orbiter missions.
A Deep Learning Technique for Automated Detection of ULF Waves in Swarm Time Series
Authors: Antonopoulou Alexandra , Papadimitriou Constantinos , Balasis Georgios , Boutsi Adamantia Zoe , Koutroumbas Konstantinos , Rontogiannis Athanasios , Giannakis Omiros
Published: March 2020

Ultra-low frequency (ULF) magnetospheric plasma waves play a key role in the dynamics of the Earth’s magnetosphere and, therefore, their importance in Space Weather studies is indisputable. Magnetic field measurements from recent multi-satellite missions (e.g. Cluster, THEMIS, Van Allen Probes and Swarm) are currently advancing our knowledge on the physics of ULF waves. In particular, Swarm satellites, one of the most successful mission for the study of the near-Earth electromagnetic environment, have contributed to the expansion of data availability in the topside ionosphere, stimulating much recent progress in this area. Coupled with the new successful developments in artificial intelligence (AI), we are now able to use more robust approaches devoted to automated ULF wave event identification and classification. The goal of this effort is to use a deep learning method in order to classify ULF wave events using magnetic field data from Swarm. We construct a Convolutional Neural Network (CNN) that takes as input the wavelet spectra of the Earth’s magnetic field variations per track, as measured by each one of the three Swarm satellites, and whose building blocks consist of two convolution layers, two pooling layers and a fully connected (dense) layer, aiming to classify ULF wave events in four different categories: 1) Pc3 wave events (i.e., frequency range 20-100 MHz), 2) non-events, 3) false positives, and 4) plasma instabilities. Our primary experiments show promising results, yielding successful identification of more than 95% accuracy. We are currently working on producing larger training/test datasets, by analyzing Swarm data from the mid-2014 onwards, when the final constellation was formed, aiming to construct a dataset comprising of more than 50000 wavelet image inputs for our network.
Modelling Seismicity in California as a Spatio-Temporal Point Process Using inlabru: Insights for Earthquake Forecasting
Authors: Naylor Mark , Bayliss Kirsty , Lindgren Finn , Serafini Francesco , Main Ian
Published: March 2020

Many earthquake forecasting approaches have developed bespokes codes to model and forecast the spatio-temporal eveolution of seismicity. At the same time, the statistics community have been working on a range of point process modelling codes. For example, motivated by ecological applications, inlabru models spatio-temporal point processes as a log-Gaussian Cox Process and is implemented in R. Here we present an initial implementation of inlabru to model seismicity. This fully Bayesian approach is computationally efficient because it uses a nested Laplace approximation such that posteriors are assumed to be Gaussian so that their means and standard deviations can be deterministically estimated rather than having to be constructed through sampling. Further, building on existing packages in R to handle spatial data, it can construct covariate maprs from diverse data-types, such as fault maps, in an intutitive and simple manner.

Here we present an initial application to the California earthqauke catalogue to determine the relative performance of different data-sets for describing the spatio-temporal evolution of seismicity.
Deriving water content from multiple geophysical properties of a firn aquifer in Southeast Greenland
Authors: Killingbeck Siobhan , Schmerr Nicholas , Montgomery Lynn , Booth Adam , Livermore Phil , Guandique Jonathan , Miller Olivia , Burdick Scott , Forster Richard , Koenig Lora , Legchenko Anatoly , Ligtenberg Stefan , Miège Clément , Solomon Kip , West Landis
Published: March 2020

Warming of the polar ice sheets causes changes in the hydrological regime of surface layers of firn and ice. Surface meltwater may undergo perennial storage of liquid water above the firn-ice transition, which could slow sea level rise or cause sudden release events, when storage capacity is reached. Firn aquifers have been commonly observed within the lower percolation zone of the southeastern Greenland ice sheet during the past decade, and more recently, across some Antarctic ice shelves. Knowledge of the geographic extent and fractional liquid water content (and storage) of such aquifers will enable a better understanding of their effects on the sub- and en-glacial hydrologic system and is crucial for accurate predictions of the contribution of meltwater discharge to global sea level rise.

Quantitative geophysical analysis from surface observations can be used to infer hydrological properties of the firn and ice without time intensive direct drilling, providing an efficient spatial distribution of properties along with an estimate of their uncertainty. Furthermore, by combining multiple types of geophysical observations, joint inversions allow ambiguities of one methodology to be mitigated by resolution in the other.

Here, we demonstrate that this joint approach is a powerful complement to the conventional geophysical analysis of firn aquifers, by combining seismic, ground penetrating radar and borehole data to characterise aquifer properties, using the ‘MuLTI’ algorithm. In particular, we incorporate seismic shear wave velocities (Vs), derived from surface (Rayleigh) waves offering a promising means of distinguishing zones containing liquid water, into independent compressional wave velocity, density, and radar soundings of the water table. We find Vs decreases from 1600 m/s in the unsaturated firn above the water table at around 15 m depth, to 800 m/s through saturated ‘clean’ firn aquifer at around 25 m depth. However, at lower elevations, Vs increases to 1250 m/s through thicker, older firn aquifer where there are many ice lenses, which are interpreted to correspond with episodes of refreezing aquifer water as the system has evolved through time. With access to multiple seismic wave velocities (compressional and shear) through the aquifer, a more accurate estimate of liquid water content can be derived. Thus, the application of the MuLTI algorithm to this pressing new problem can deliver an accurate assessment of firn aquifer properties, and provide clear uncertainty limits which will be valuable for predictive modelling.
Investigation of the stochastic behaviour of surface wind speed using K-moments on global scale for energy management
Authors: Diakomopoulos Faidon , Dimitriadis Panayiotis , Iliopoulou Theano , Koutsoyiannis Demetris
Published: March 2020

Currently, more and more countries make a shift toward renewable energy sources to reduce the environmental impact from fossil fuel use. Wind energy has a significant position in this hierarchy, as one of the most efficient to convert to electric energy, covering the society’s needs. Typically, the characterization of the probability distribution of wind speed is based on classical and L-moments for moment orders 2 to 4, beyond which the estimation from samples is problematic. The aim of this work is to investigate the stochastic behaviour of surface wind speed and develop a model of simulation of the latter. In this framework, we also investigate and try to comprehend the occurrence of extremes, which become important for the engineering design of the wind turbine structures. Hourly datasets of wind speed from thousand stations throughout the world are used to perform various analyses based on knowable (K-)moments and comparison to classical and L-moments. The results of the K-moments’ application are used as input to a Monte-Carlo analysis, to an accurate simulate wind speed distribution tails.
Seismologically understanding the basal sliding depth and groundwater level for deep-seated landslide
Authors: Chao Wei-An , Lin Chun-Hung , Yang Che-Ming , Kang Keng-Hao , Kuo Yu-Ting , Nugi Jason , Chung Ming-Chien , Lin Chih-Pin , Tai Tung-Lin
Published: March 2020

Deep-seated landslide is one of most catastrophic and disastrous geohazards. Probing the spatial extent and basal sliding interface of the deep-seated landslide is not only particularly critical for understanding landslide size (i.e., volume and collapsed area), but also crucial for landslide hazard assessment. The conventional investigations such as the borehole drilling and seismic profiles are usually challenging for investigating landslide body comprehensively in space due to the expensive cost and the limitations of geophysical exploration. Recent studies of ambient seismic noise monitoring have provided an additional tool to monitor the subsurface medium in a non-invasive and relatively inexpensive way, which advances the investigating landslide geological structure. Here, we applied the ambient seismic noise monitoring technique to deep-seated landslide at Fanfan, Ilan area in northeastern Taiwan. The multiple geophysical, geotechnical and geodetic approaches including active multi-channel analysis of surface wave (MASW), real-time kinematic (RTK) measurement, campaign GPS, borehole time-domain reflectometer (TDR) and groundwater level (GWL) gauge are adopted during our monitoring period. A series of relation analysis found that the variations of frequency-dependent seismic velocity changes (dv/v), TDR sliding behavior, time series of groundwater level associated to two heavy rainfall episodes concurrently. With the available shear-wave velocity model (VS) derived from MASW, the depth range sensitive to different frequency band for surface wave can be certainly determined. Clear 3-5 Hz dv/v measurement at seismic station of V01 collocated with GWL gauge can be found with the largest reduction of ~ 1%, coinciding with 1 m GWL increasing. Models with different thickness layer (H), basal depth (d), Vs perturbation (dVs) were exercised, and a good fit between predicted spectral dv/v and the frequency-dependent dv/v measurements at seismic station V02 with H = 0.5 m, d = 21 m and dVs = 0.5. TDR measurement showed the obvious sliding signals is consistent with the shear zones identified by borehole log with the depth ranging from 48 to 50 m. These results demonstrate that multidisciplinary perspectives are needed to increase a better understanding of landslide structure. Consequently, a model linking variations of dv/v and TDR measurements is proposed to better understand sliding characteristics, which could potentially toward failure prediction of deep-seated landslide.
Ni and black carbon influence bacterial production, respiration and community composition in the barrier reef Lagoon of Noumea (New Caledonia): an experimental study
Authors: Weinbauer Markus
Published: March 2020

The barrier reef lagoon of Noumea (New Caledonia) is potentially influenced by Ni and black carbon (BC) rich aerosols (the two latter originating from a Ni power plant).  Experiments were performed with lagoon water collected close to the reef crest to assess the effect of anthropogenic influences on bacterial abundance (BA), production (BP), respiration (BR), growth efficiency (BGE) and community composition (BCC) in artificial produced aggregates. In both treatments, BA were not affected or enhanced compared to the unamended control (up to 40% for BA and 180% for VA). BP was not or negatively affected (up to 70%). No clear trend was found for BR in the Ni treatment; in the BC treatment BR was enhanced by 63-69%. BGE was reduced in both treatments. The strongest effects on BCC profiles as determined by 16S rDNA denaturing gradient gel electrophoresis were due to incubation time treatment particularly for BC. A phylotype corresponding to a specific BC band was closely related to Acinetobacter oleivorans DR1. Thus, this experimental study confirms potential anthropogenic influences on the bacterial community on aggregates in the Bay of Noumea.
Instrumentation for Nuclear Planetology: Present and Future
Authors: Mokrousov Maxim , Mitrofanov Igor , Kozyrev Alexander , Litvak Maxim , Malakhov Alexey , Sanin Anton , Tretyakov Vladislav , Golovin Dmitry , Anikin Artem
Published: March 2020

The method of remote neutron and gamma spectrometry of bodies in the solar system (the Moon, Mars, and Mercury) has been used for several decades to estimate the nuclear composition of these objects and the hydrogen abundance in their subsurface layers. It is known that many solid planets of Solar system with thin atmospheres, its moons, small bodies and even comets due to bombardment by heavy nucleus of Galactic Cosmic Rays (GRS) produce neutron albedo and characteristic gamma lines. Detection of escaping gammas and neutrons (remote sensing from an orbit or in situ) bringing an information about elemental composition of the subsurface and hydrogen-containing elements (as deep as tens of centimeters). Currently we can classify all nuclear planetology instruments by the field of view (uncollimated and collimated) and by type of soil irradiation (passive – using GRS, and active – using pulsing neutron generator onboard), each of those methods has pros and cons and all of them will be presented. Also, future nuclear planetology instruments and method in design will be presented.
IODP Expedition 378 South Pacific Paleogene Climate: New high-resolution high-latitude Cenozoic Section
Authors: Röhl Ursula , Thomas Deborah J , Childress Laurel ,   Expedition 378 Science Party
Published: March 2020

As the world’s largest ocean, the Pacific Ocean is intricately linked to major changes in the global climate system. International Ocean Discovery Program (IODP) Expedition 378 is designed to recover Paleogene sedimentary sections in the South Pacific to reconstruct key changes in oceanic and atmospheric circulation. These cores will provide an unparalleled opportunity to add crucial new data and geographic coverage to existing reconstructions of Paleogene climate and as part of a major regional slate of expeditions in the Southern Ocean to fill a critical need for high-latitude climate reconstructions. Appropriate high-latitude records are unobtainable in the Northern Hemisphere of the Pacific Ocean.

The drilling strategy included a transect of sites strategically positioned in the South Pacific to recover Paleogene carbonates buried under red clay sequences at present latitudes of 40°–52°S in 4650 – 5075 meters of water depth. Due to technical issues we no longer will be able to reach the deeper sites. Therefore, the focus of Expedition 378 will be now to obtain a continuous sedimentary record of a previously single hole, rotary-drilled, spot-cored, classic Cenozoic high-latitude DSDP Site 277 and provide a crucial, multiple hole, mostly APC-cored, continuous record of the intermediate-depth Subantarctic South Pacific Ocean from the Latest Cretaceous to late Oligocene.
Mathematical Reconstruction of Land Carbon Models From Their Numerical Output: Computing Soil Radiocarbon From 12C Dynamics
Authors: Metzler Holger , Zhu Qing , Riley William , Hoyt Alison , Müller Markus , Sierra Carlos
Published: March 2020

Radiocarbon (14C) is a powerful tracer of the global carbon cycle that is commonly used to assess carbon cycling rates in various Earth system reservoirs and as a benchmark to assess model performance. Therefore, it has been recommended that Earth System Models (ESMs) participating in the Coupled Model Intercomparison Project Phase 6 report predicted radiocarbon values for relevant carbon pools. However, a detailed representation of radiocarbon dynamics may be an impractical burden on model developers. Here, we present an alternative approach to compute radiocarbon values from the numerical output of an ESM that does not explicitly represent these dynamics. The approach requires computed 12C stocks and fluxes among all carbon pools for a particular simulation of the model. From this output, a time‐dependent linear compartmental system is computed with its respective state‐transition matrix. Using transient atmospheric 14C values as inputs, the state‐transition matrix is then applied to compute radiocarbon values for each pool, the average value for the entire system, and component fluxes. We demonstrate the approach with ELMv1‐ECA, the land component of an ESM model that explicitly represents 12C, and 14C in 7 soil pools and 10 vertical layers. Results from our proposed method are highly accurate (relative error <0.01%) compared with the ELMv1‐ECA 12C and 14C predictions, demonstrating the potential to use this approach in CMIP6 and other model simulations that do not explicitly represent 14C.
Evaluation of TROPOMI cloud products for NO2 retrievals
Authors: Latsch Miriam , Richter Andreas , Burrows John P. , Wagner Thomas , Silher Holger , van Roozendael Michel , Loyola Diego , Valks Pieter , Argyrouli Athina , Lutz Ronny , Veefkind Pepijn , Eskes Henk , Sneep Maarten , Wang Ping , Siddans Richard
Published: March 2020

The first European Sentinel satellite for monitoring the composition of the Earth’s atmosphere, the Sentinel 5 Precursor (S5p), carries the TROPOspheric Monitoring Instrument (TROPOMI) on board to map trace species of the global atmosphere at high spatial resolution. Retrievals of tropospheric trace gas columns from satellite measurements are strongly influenced by clouds. Thus, cloud retrieval algorithms were developed and implemented in the trace gas processing chain to consider this impact.

In this study, different cloud products available for NO2 retrievals from TROPOMI data are analyzed. The TROPOMI level 2 OCRA/ROCINN (Optical Cloud Recognition Algorithm/Retrieval of Cloud Information using Neural Networks) cloud products CRB (cloud as reflecting boundaries) and CAL (clouds as layers) as well as the FRESCO (Fast Retrieval Scheme for Clouds from Oxygen absorption bands) cloud product are compared with regard to e. g. cloud fraction, cloud height, cloud albedo/optical thickness, flagging and quality indicators. In particular, difficult situations such as snow or ice, sun glint, and high aerosol load are investigated.

The eventual aim of this study is to better understand TROPOMI cloud products and their quantitative impacts on trace gas retrievals. Here, we present first results of a statistical analysis on a limited data set comparing currently existing cloud products and their approaches focusing on NO2.
Glacial deposits in Connemara, dated with cosmogenic 10Be, document melting of terrestrial ice in Western Ireland during Heinrich Stadial 1
Authors: Foreman Adrienne , Hall Brenda , Bromley Gordon
Published: March 2020

During the Last Glacial Maximum, the terrestrially based Connemara ice dome was one of several principal ice accumulation centres in western Ireland, distributing ice radially and terminating along its western margins in the North Atlantic Ocean. Our new beryllium-10 chronology, constrained with surface-exposure ages of erratics on a longitudinal coast-to-interior transect, demonstrates that post-LGM deglaciation of Connemara was rapid and that the ice dome was gone by ~17.5 ka. Coupled with the abundance of landforms in this mountainous region indicative of glacial meltwater production, we interpret the rapid and early deglaciation of Connemara as reflecting pronounced melting during the summer ablation season driven by strong atmospheric warming. While this model contrasts with the traditional view of Heinrich stadials as periods of intense cold in the North Atlantic, we note similarities with glacial records from elsewhere in the Northern Hemisphere and globally, as well as with recent marine-geologic evidence for enhanced melting of European ice sheets during Heinrich stadials.
Hydrological Responses to Anthropogenic Disturbance in Peatlands: a Numerical Approach
Authors: Menberu Meseret , Ronkanen Anna-Kaisa , Marttila Hannu , Haghighi Ali Torabi , Kløve Bjørn
Published: March 2020

Peatland ecosystems are complex mosaics and located often in low-lying transitional zones between terrestrial and aquatic ecosystems. Peatlands in its pristine state play a significant role in regulating the hydrological, biogeochemical and ecological functions and act as long-term storage for carbon. However, up to 20% of the global peatland resources have been disturbed for a variety of human land uses (e.g., forestry and agriculture) and lost their natural functions. In this research, we tested the effectiveness and applicability of a physically-based three-dimensional fully integrated surface-subsurface numerical model (HydroGeosphere, HGS) to study hydrological disturbances in peatlands. The model was specifically implemented to assess the impact of artificial drainage and subsequent restoration on the hydrological responses (runoff and water table) of a previously disturbed, now restored (ditches-blocked) peatland catchment (about 11.4 ha) located in Western Finland. The hydrological data included two years before restoration (drained condition) and one year after restoration (ditches-blocked) collected during frost-free periods. The model domain was discretized with seven vertical finite element layers of 146744 nodes and 255206 elements to represent the ditch networks (drained condition) and blocked ditches (restored condition) in the model realistically. The HGS model was run for the two disturbed conditions (drained and restored) using forcing weather data collected in 2016, 2017 and 2018. In all the years, simulated runoff in drained conditions was significantly higher than simulated at restored conditions. The simulated water table level in restored conditions was significantly closer to the ground surface than in drained conditions, which agreed with the observed water table data. The results indicated that three-dimensional models, such as the HGS can be implemented to evaluate the effect of restoration measures on the hydrological response of peatland catchments. Thus, high-resolution physically-based models have the potential to improve our understanding of the complex hydrology of disturbed habitats spatially. Understating the spatial dependence of peatlands to inputs from groundwater and surrounding upland areas could further help us improve restoration measures.
The fate of sediment after a large earthquake
Authors: Francis Oliver , Hales Tristram , Hobley Daniel , Fan Xuanmei , Huang Runqiu
Published: March 2020
Evolution of extensional faults between two rift systems: insights from sandbox experiments
Authors: Souloumiac Pauline , Robert Romain , Maillot Bertrand , Mohn Geoffroy , Leroy Yves-Marie , Gauthier Bertrand , Gomez Jean-Paul
Published: March 2020

The interference between two offset propagating rift systems creates fractures, with a sigmoid shape in map view and previously referred to as accommodation zones (Mc Clay et al, 2002). This peculiar kinematics may be observed in the Southeastern Brazilian margin in the Santos Basin, developed between the tips of two propagating, offset rifts. In this region, northward propagating rift was aborted during the southward propagation of another rift further to the east leading eventually to the opening of this segment of the South Atlantic. Could this structural setting explain the geometry and the position of the fracture zones in this basin?

To answer this question, we explore a range of geometrical and kinematic parameters with sandbox experiments to observe the deformation between these two propagating rift systems. The basement of the rift zones were modelled with rubber strips glued to rigid metal plates, following the setup of McClay et al, 2002. However, this setup suffers from the lateral contraction of the rubber due to its elastic extension (the Poisson’s effect). This introduces a spurious kinematics, and in particular an unrealistic opening at the contact between the two rift parts. A new device, whereby thin metallic strips are glued to the sides of the rubber sheet reduces very substantially the Poisson effect and therefore improves the simulation of the overall extension. 

Two main parameters are varied: the offset between the two rifts (D) and the relative velocity of extension of each rift. Narrowly spaced cross –sections of two experiments are interpreted to build 3D patterns.

The main results from the sandbox experiments are:

- Major and minor faults with the rifting zone localized by the rubber base present dips approximately equal to 75°.

- To obtain sigmoid fault array in map view best resembling the structural interpretation of Lebreton (2012), the rifts must be offsets (D>0) and the extension must be synchronous.

- The 3D fault patterns reveal that fault planes are not continuous in the accommodation zone, between the two rifts.  If these major faults are not connected in the central zone as shown by the physical models, then the fluid flow will be certainly influenced. This central relay zone could also be considered as a diffuse strain zone.

Numerical models will be helpful to introduce further material heterogeneities in this key area. The experimental results provide the data to validate the numerical modeling and to guide in the selection of the boundary conditions.
Future changes in ENSO teleconnections over the North Pacific and North America in CMIP6 simulations
Authors: Beverley Jonathan , Collins Mat , Lambert Hugo , Chadwick Rob
Published: March 2020

El Niño–Southern Oscillation (ENSO) has major impacts on the weather and climate across many regions of the world. Understanding how these teleconnections may change in the future is therefore an important area of research. Here, we use simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) to investigate future changes in ENSO teleconnections in the North Pacific/North America sector.

Precipitation over the equatorial Pacific associated with ENSO is projected to shift eastwards under global warming as a result of greater warming in the east Pacific, which reduces the barrier to convection as the warm pool expands eastwards. As a result, there is medium confidence (IPCC AR5 report) that ENSO teleconnections will shift eastwards in the North Pacific/North America sector. In the CMIP6 models, the present day teleconnection is relatively well simulated, with most models showing an anomalously deep Aleutian low and associated positive temperature anomalies over Alaska and northern North America in El Niño years. In the future warming simulations (we use abrupt-4xCO2, in which CO2 concentrations are immediately quadrupled from the global annual mean 1850 value), in agreement with the IPCC AR5 report, the North America teleconnection and associated circulation change is shifted eastwards in most models. However, it is also significantly weaker, with the result that the positive temperature anomalies in El Niño years over North America are much reduced. This weakening is seen both in models with a projected increase and projected decrease in the amplitude of future El Niño events. The mechanisms related to these projected changes, along with potential implications for future long range predictability over North America, will be discussed.
Impact of ECMWF ERA-Interim and ERA5 reanalysis on the simulated tracer transport and polar ozone loss using a chemical transport model TOMCAT/SLIMCAT 
Authors: Feng Wuhu , Chipperfield Martyn , Dhmose Sandip , Goutail Florence , Santee Michelle , Birner Benni , Keeling Ralph , Stiller Gabriele
Published: March 2020

Three-dimensional chemical transport models (CTMs) have been widely used in a wide variety of scientific studies (e.g., to obtain a better understanding of tracer transport and to study the dynamical and chemical processes which control polar ozone losses etc). However, there are still some uncertainties in the model simulations and indeed in our understanding. For example, the accuracy of ozone simulations largely depends on the transport, chemistry and treatment of PSCs in the model as well as the forcing files. 

Here we have used a  CTM model TOMCAT/SLIMCAT with a detailed description of stratospheric and tropospheric chemistry forced by differnt wind fields (ECMWF ERA-Interim and ERA5 reanalysis datasets) to investigate the different dynamical fields on the simulated tracer transport, ozone and other chemical species. Both simulations have been run from 1979 to 2018. First we will assess the impact of different reanalysis data on the idealised tracers when the model includes additional process of the gravitational separation of gases (e.g., Ar/N2) and compare the model results with dataset of gravitational fractionation of Ar/N2 and AoA observations made on flask samples from three airborne research projects. Modelled AoA will be also compared with MIPAS data.  Then we will focus on the polar ozone loss from late 1990 to 2018 and quntify
the amount of chemical ozone loss using both models and satellite observations as well as  SAOZ measurements. The year-to-year variation of polar ozone depletion will also be discussed, in particular for the recent years of decreasing stratospheric chlorine loading. 
Sedimentation at different time scales in Yellow River delta in response to course shift and water-sediment regulation
Authors: Shuqing Qiao , Xuefa Shi , Yu Yonggui , Hu Limin , Zhou Lin , Ren Guangbo , Yang Gang , Yao Zhengquan , Bi Naishuang
Published: March 2020

The fluvial sediment to the sea is the base of coastal geomorphology and biogeochemical processes, and its transport is an important pathway to the global biogeochemical cycle. The Yellow River is one of globally well-known large rivers because of high sediment load and Chinese Mother River. Its channel shifts frequently because of high sediment load and steep river-channel gradient in the lower reaches . The terminal channel has shifted more than 50 times since 1855 and the last two changes in 1976 and 1996. Furthermore, Yellow River Conservancy Commission has began to implement Water-Sediment Regulation Scheme (WSRS) since 2002, to increase the main channel discharge capacity and to reduce deposition in the reservoirs and river channel. Surface sediment, multi-core and gravity sediment cores, remote sensing images and bathymetric data near the Yellow River delta were collected to study the impact of WSRS and river terminal change together with the water and sediment discharge at the gauging station. Especially, 7Be, 210Pb and 137Cs, grain size, sediment color and TOC/TN was measured to show sedimentary record of WSRS and channel shift on inter-and intra-annual time scale. The results show that the fresh sediment from Yellow River  during 2014 WSRS period can be transported eastward more than 80 km off the rivermouth, while cannot pass 38° easily. Meanwhile the sediment can penetrate as deep as 12 cm. The subaerial delta area is mostly stable after 2002, and its balance is mainly controlled by the surrounding artificial coastline. The subaqueous delta changed from trapping about 4.6×108 t to being eroded ~ 3.1×108 t and 1.1×108 t each year during the three stages of 1976-1996, 1996-2002 and 2002-2014. It is proposed that the subaerial delta area will change little except for the Q8 outlet area, while the subaqueous delta evolution mostly depend on the Huanghe material besides the hydrodynamic conditions. In addition, the aim of WSRS to scour the lower riverbed will recede in future. This study deepens our understanding of the fluvial sediment disperse pattern and sedimentation under the influence of human activities and hydrodynamic conditions.

Acknowledgements

This study was supported by National Programme on Global Change and Air-Sea Interaction (GASI-GEOGE-03) and the Natural Science Foundation of China (U1606401).
Potential avalanche release in windthrow areas: the effect of snow height and terrain roughness
Authors: Brožová Natalie , Baggio Tommaso , Teich Michaela , Bast Alexander , Bebi Peter
Published: March 2020

Windthrow is an important disturbance agent in forest ecosystems and is expected to become more frequent and severe under climate change. Windthrow creates large amounts of surface roughness from downed trees, root plates and stumps. In mountain forests, these elements increase the surface roughness and provide a considerable protective effect against snow avalanches during the first years following a disturbance event. However, if large volumes of snow covers the surface roughness elements, a windthrow area may become prone to avalanche release. Snow accumulation produces terrain smoothing, which is an important factor in avalanche formation.

To assess the effect of snow accumulation on surface roughness in windthrow areas, we quantified terrain smoothing using a vector ruggedness measure and corresponding snow heights, based on digital surface models from summer and winter terrain produced from repetitive UAV flights. Additionally, the snowpack structure was examined using a digital snow micro penetrometer (SMP) to quantify the heterogeneity of snow stratigraphy and to monitor a possible development of weak snow layers over distances greater than 10-20 m, which may contribute to slab avalanche formation. Four study plots were selected to characterize different conditions: i) undisturbed forest, windthrow area with ii) high and iii) low surface roughness, and iv) an open meadow control plot. We then quantified how surface roughness is smoothed depending on the snow height, and at the same time characterized the snowpack structure and the extent of potential weak layers.

We found that increasing snow height leads to decreasing surface roughness, which can produce local release areas. We expect that with continuous increase of snow height, these release areas expand in size; however, further analyses of the snowpack structure will provide deeper insights in potential weak layer formation. Critical conditions for avalanche releases in windthrow areas may thus be defined based on scenarios for snow height and close-range sensing-based roughness data.
On-site Earthquake Early Warning: Predictive Models for Acceleration Response Spectra Considering Site-Effects
Authors: Iaccarino Antonio Giovanni , Picozzi Matteo , Bindi Dino , Spallarossa Daniele
Published: March 2020

Including site specific amplification factors in ground motion prediction models represented an advance for PSHA (Atkinson 2006; Rodríguez-Marek et al. 2013; Kotha et al. 2017) that has become nowadays a standard. However, this issue has only recently received attention by the seismological community of earthquake early warning (EEW) (Spallarossa et al., 2019; Zhao and Zhao, 2019), which applications require a real-time prediction of ground motion and the delivery of alert messages to users for mitigating their exposure to seismic risk. Indeed, all EEW systems are high-technological infrastructures devoted to the real-time and automatic detection of earthquakes, rapid assessment of the associated seismic hazard for targets and the prompt delivery of alerts trough fast telecommunication networks. Among them, the on-site approaches are based on seismic networks placed near to the target, indifferently by the location of seismic threats and they issue the alert predicting the ground motion at the target from P-wave parameter. This configuration cause that On-Site EEWS are generally highly affected by site conditions.

In this work, we calibrated ground motion prediction models for on-site EEW considering acceleration response spectra (RSA) and the P-waves EEW parameters Iv2 and Pd, and we investigated the role of site-effects. We considered a dataset of nearly 60 earthquakes belonging to the Central Italy 2016-17 sequence. The high density of stations near to the sequence has allowed us to use a non-ergodic random-effect regression approach to explore and to reduce the contribution of site-effects to the uncertainty of the On-site laws predictions. We grouped the records in two ways: by stations and by EC8 classification. Then, we validated the estimated models by the Leave One Out (L1Out) technique and applied a K-means analysis to assess the performance of the EC8 classification.

The residuals analysis proved that grouping by station provides a set of relations that improves the predictions at many stations. On the contrary, L1Out cross-validation proved that the regressions retrieved grouping by EC8 classification produce higher uncertainties on the predictions than the others. Furthermore, the cross-validation proved that Iv2 is more correlated to RSA than Pd. Finally, the analysis of the random effect vs period curves confirmed that EC8 classification is unrelated to the site effect on RSA even looking only at the trend of these curves.

In conclusion, non-ergodic random-effect regression can be used also in the EEW applications to predict site-specific ground motion. EEWS that use this approach are less dependent by site-effect and able to provide more precise and reliable alerts.
Study on water infiltration characteristics in Gotjawal (forest on lava flow) wetland area
Authors: Kim Jaehoon , Choi Hyungsoon , Song Kukman , Kim Yangji , Choi Byungki , Seo Yeonok
Published: March 2020

Gotjawal is forest that was formed by the lava flow along the slopes as a result of the volcanic activity of the parasite volcanoes which distributed over Jeju Island, the Republic of Korea. Since Gotjawal has very shallow soil layer and wetland in Gotjawal does not have water for a long time, infiltration characteristics are very important. Study wetland is 48m in diameter and 2.2m in depth and water level change with respect to time was measured in 2019. The results showed that annual rainfall in this area was measured to 2,748mm and 5 rainfall events with daily rainfall more than 100mm were recorded in 2019. When the wetland was full of water, the period of drainage was 12 days. Water level started to change when the rainfall was 43~70mm taking 10~15 hours and this seems to vary depending on the period of no rainfall. This result will be helpful for estimating groundwater sources in lava flows area and for developing conservation plan of Gotjawal.
Real-Time Reservoir Operation by Tree-Based Model Predictive Control Including Forecast Uncertainty
Authors: Uysal Gokcen , Montero Rodolfo-Alvarado , Schwanenberg Dirk , Sensoy Aynur
Published: March 2020

Streamflow forecasts include uncertainties related with initial conditions, model forcings, hydrological model structure and parameters. Ensemble streamflow forecasts can capture forecast uncertainties by having spread forecast members. Integration of these forecast members into real-time operational decision models which deals with different objectives such as flood control, water supply or energy production are still rare. This study aims to use ensemble streamflows as input of the recurrent reservoir operation problem which can incorporate (i) forecast uncertainty, (ii) forecasts with a higher lead-time and (iii) a higher stability. A related technique for decision making is multi-stage stochastic optimization using scenario trees, referred to as Tree-based Model Predictive Control (TB-MPC). This approach reduces the number of ensemble members by its tree generation algorithms using all trajectories and then proper problem formulation is set by Multi-Stage Stochastic Programming. The method is relatively new in reservoir operation, especially closed-loop hindcasting experiments and its assessment is quite rare in the literature. The aim of this study is to set a TB-MPC based real-time reservoir operation with hindcasting experiments. To that end, first hourly deterministic streamflows having one single member are produced using an observed flood hydrograph. Deterministic forecasts are tested with conventional deterministic optimization setup. Secondly, hourly ensemble streamflow forecasts having a lead-time up to 48 hours are produced by a novel approach which explicitly presents dynamic uncertainty evolution. Produced ensemble members are directly provided to input to related technique. Uncertainty becomes much larger when managing small basins and small rivers. Thus, the methodology is applied to the Yuvacik dam reservoir, fed by a catchment area of 258 km2 and located in Turkey, owing to its challenging flood control and water supply operation due to downstream flow constraints. According to the results, stochastic optimization outperforms conventional counterpart by considering uncertainty in terms of flood metrics without discarding water supply purposes. The closed-loop hindcasting experiment scenarios demonstrate the robustness of the system developed against biased information. In conclusion, ensemble streamflows produced from single member can be employed to TB-MPC for better real-time management of a reservoir control system.
Operating the Absolute Quantum Gravimeter outside of the laboratory
Authors: Vermeulen Pierre , Antoni-Micollier Laura , Mazzoni Tommaso , Condon Gabriel , Ménoret Vincent , Janvier Camille , Desruelle Bruno , Landragin Arnaud , Lautier-Gaud Jean , Bouyer Philippe
Published: March 2020

The Absolute Quantum Gravimeter (AQG) is the world’s first industrial gravimeter measuring g with laser-cooled atoms [1]. Today, several units have already been delivered to end-users.

After reviewing the key principles of the AQG, we will discuss the demonstrated measurement performances of the AQG in terms of sensitivity, stability and repeatability. In particular, we report on a reproducible sensitivity to gravity at a level of 1 μGal in various types of environment (1 µGal = 1e-8 m/s2 ~ 1e-9 g). We will also present our on-going efforts towards the thorough understanding of the uncertainty budget (accuracy) of the sensor. Finally, we will share the experience that we have acquired over the past years regarding the operability of the AQG, with a specific focus on the field version of the sensor.

This new type of gravimeter is presently the only technology that allows for continuous drift-free monitoring of gravity over timescales from a few minutes to several months, which opens new perspectives for the investigation of both spatial and temporal gravity variations [2]. The AQG has been developed by Muquans in collaboration with academic laboratories LP2N and LNE-SYRTE, and RESIF (the French Seismologic and Geodetic Network, [3]).

[1] V. Ménoret et al., "Gravity measurements below 10−9 g with a transportable absolute quantum gravimeter", Nature Scientific Reports, vol. 8, 12300 (2018)

[2] M. Van Camp, O. de Viron, A. Watlet, B. Meurers, O. Francis, C. Caudron, "Geophysics from terrestrial time-variable gravity measurements", Rev. Geophys. (2017).

[3] http://www.resif.fr/
Long-term coupled permafrost-groundwater interactions at Olkiluoto, Finland
Authors: Cohen Denis , Zwinger Thomas , Koskinen Lasse , Karvonen Tuomo
Published: March 2020

Understanding permafrost development and its effect on groundwater flow patterns and fluxes in the event of future ice-age conditions is important for the long-term safety of spent nuclear fuel repositories. To assess the evolution of permafrost thickness, talik development, and groundwater flow and salinity changes at Olkiluoto, Finland, during the next 100,000 years, we solve Darcy flow coupled to heat and solute transport in three dimensions in a rectangular block representing an area of 8.8 km by 6.8 km, and down to a depth of 10 km. The set of equations is based on continuum thermo-mechanic principles. Important and highly non-linear coupling processes such as the exponential decrease of permeability with ice content in soils and rocks, solute rejection during freezing, and variable-density Darcy flow are fully taken into account. Model equations are solved using the finite element method implemented in the open source software Elmer.  High-resolution data of rock and soil permeability, thermal and physical properties, are mapped onto a 30-meter resolution grid resulting in a system of about 5 million nodes and 5 million elements. Soil layers at the surface are vertically resolved down to 0.1 meter. High contrast in permeability over short distances (from soil to granitic bedrock) make the system of equations challenging to solve numerically. Simulations are driven by RCP 4.5 climate scenario that predicts cold periods between AD 47,000 and AD 110,000. Surface boundary condition for temperature is calculated based on freezing and thawing n-factors that depend on monthly temperatures and the topographic wetness index that defines different zones of vegetation and ground cover. The thickness evolution of the six upper soil layers, including peat, above the granitic bedrock is also taken into account. Preliminary simulations are able to represent permafrost development at a high spatial resolution with evidence of important feedbacks due to permeable soil layers and faults in the bedrock that focus groundwater flow and solute transport.
Electrical signature of CO2-rich mineral groundwater systems - Application in the Ardennes, South-East of Belgium
Authors: Defourny Agathe , Kremer Thomas , Collignon Arnaud , Jobé Patrick , Dassargues Alain , Nguyen Frédéric
Published: March 2020

CO2-rich mineral groundwaters have been exploited for centuries for both bottling and thermal activities. The detection and understanding of productive areas is therefore of great interest to manage future supply in a sustainable way. CO2-rich mineral water systems are complex since they usually involve an intricated network of water bearing fractures enabling the uplift of CO2-rich groundwater to the surface, a process that is still poorly understood. Geophysical prospection is crucial to detect potential uplift zones and to address corresponding uncertainties before drilling operations.

In this context, non - to minimally - invasive near-surface geophysical methods can prove to be efficient. The objective of this contribution is to assess the ability of the induced polarization method, combined with the electrical resistivity technique, to make the distinction between CO2-rich groundwater from non-gaseous groundwater.

Several combined electrical resistivity and induced polarization tomography profiles were performed in the Ardennes (Belgium) where thousands of CO2-rich groundwater springs are observed. The profiles were all set immediately above known uplift zones. Inversion results were consistent between all profiles and important contrasts in both electrical resistivity and chargeability distributions in the vicinity of the uplift zone were observed, which were also reflected in the normalized chargeability sections computed on the basis of the measured data.

Low resistivity vertical contrasts extending in depth were observed and interpreted as saturated fractures enabling the uplift of deep groundwater to the surface. In addition, high chargeability anomalies appeared directly close to the CO2-rich groundwater resurgence. Those anomalies are thought to be associated to the presence of metallic oxides and hydroxides, as a result of dissolved metallic species precipitation in the upper part of the fractured aquifer due to the pressure decrease and change in redox conditions in up-flowing groundwater towards the land surface.

We conclude that the combined interpretation of electrical resistivity and induced polarization datasets is a very promising method for a more robust prospection of naturally sparkling groundwater.