bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact of Arctic sea ice cover on seasonal modulation of the M2 tide
Authors: Bij de Vaate Inger , Vasulkar Amey , Slobbe Cornelis , Verlaan Martin
Published: March 2020

The impact of Arctic sea ice decline on future global tidal and storm surge extreme water levels is unknown. Regional studies show that the impact can be substantial; causing increased erosion and posing higher risks to fragile Arctic ecosystems in low-lying areas. Since Arctic tides and surges influence global water levels, consequences of Arctic sea ice decline will be noticed across the globe. In the ongoing FAST4Nl project, an Arctic Total Water Level model will be used to quantify this impact. The model will be developed as an extension of the operational Global Tide and Surge Model (GTSM) and includes the effect of sea ice on tides.

Here we present the results of a study on the seasonal variability of the M2 tide with respect to differences in sea ice cover. The effect of sea ice on the M2 amplitude was modelled for minimal and maximal sea ice configurations. In addition, tidal harmonic analysis was performed on a global tide gauge data set, supplemented by SAR altimeter derived water levels from the Arctic region. The high along-track resolution of SAR altimeters (300 m) enables to derive water levels from leads in the sea ice. Here, the retrieved sea surface heights within a given region were stacked, in order to obtain a sufficiently large data set for analysis of the predominantly ice-covered areas. This allowed to gain insight in the seasonal modulation of both local and global tides and directly relate these processes to variations in sea ice.
Characterising the response of groundwater systems to major, continental-scale droughts: a multidecadal European case-study
Authors: Brauns Bentje , Bloomfield John P. , Cuba Daniela , Hannah David M. , Marchant Ben P. , Van Loon Anne F.
Published: March 2020

Groundwater systems are susceptible to droughts. However, the relationship between driving meteorological droughts and resulting groundwater droughts is particularly complex due to spatially and temporally varying climate drivers and spatially heterogeneous catchment and aquifer characteristics, as well as the potential effects of longer-term groundwater overexploitation and of groundwater abstraction and management interventions during episodes of meteorological drought. Consequently, many previous studies of the propagation of meteorological drought to groundwater systems have typically been geographically limited in scope, focussing on characterising aquifer units within a catchment or basin, and/or temporally limited to specific episodes of drought. Based on a new European-wide dataset consisting of groundwater level data from over 6,000 sites, here we describe the results of a multidecadal analysis of the expression of major episodes of meteorological drought at the continental scale in groundwater systems, independent of local hydrogeological setting.

In this study, raw groundwater level time series are modelled using an impulse response function of precipitation to obtain monthly groundwater levels that are then standardised. Sites with long-term trends in groundwater level are identified and usually inferred to be associated with overexploitation or other anthropogenic influences. Cluster analysis of the modelled standardised hydrographs is used to identify spatially coherent ‘type’ groundwater hydrographs. These type hydrographs can be characterised by differences in the autocorrelation of the underlying groundwater hydrographs, but may also reflective continental-scale variations in the driving meteorology. Finally, episodes of groundwater drought are extracted from the type groundwater hydrographs and compared with the driving meteorological droughts. The data provides evidence for the coherent response of groundwater systems to droughts across large areas of Europe depending on driving meteorology and the ‘memory’ of the groundwater system, and drought events such as in 2011-12, 2015 and 2017-18 showed spatial coherence across different European regions.             

 
Petrogenesis and Geochronology of the late-Archean Na-rich A Type granite from the Bundelkhand Craton, India: Implication for tectonic and crustal evolution
Authors: Raza Mohd Baqar , Corfu Fernando , Nasipuri Pritam
Published: March 2020

Tonalite-trondhjemite-granodiorite gneisses (TTG) are the oldest litho-units of the Bundelkhand craton. The supracrustal rocks include variable deformed mafic volcanics and Banded Iron Formation. Magmatic zircons from the TTG’s yield an upper intercept of ~ 3590 Ma. The TTG’s gradually grades to a Na-feldspar rich A type porphyric granite towards the south. In this abstract, we report mineralogical, geochemical, and geochronological information of high silica- low Ca - high Na A-type granite from Bundelkhand craton.

In the TAS diagram, the studied samples plot in the field of granite and have a metaluminous affinity with high Ga/Al and Ce + Y + Nb + Zr values typical of A-type granites. In a primitive normalized multi-element spider diagram, the studied samples exhibit negative Nb, Ti, and P anomalies characteristics of a subduction zone setting. The chondrite normalized REE’s exhibit a strong fractionated pattern with negative Eu anomaly; the LREE are enriched and the HREE depleted with moderate to high (La/Yb)CN ratios ranging from 11.12 to 26.24 ppm. The studied samples have plagioclase compositions that vary from XAb = 0.980-0.997 and chlorite compositions varying from XMg = 0.309-0.469.

Phase equilibria modeling yield an emplacement temperature of 700-750OC, at 1.0 GPa. Most of the zircon grains are prismatic with visible cores and rims in optical examinations. In a U-Pb concordia diagram, the grains yield an upper intercept of 2536.6 ± 1.8 Ma. The geochemical and geochronological data taken together, indicate the Na-rich A-type granite generated by the high temperature and high-pressure partial melting of Archaean supracrustal rocks.
Data download speed test for CMIP6 model output: preliminary results
Authors: Liu Yufu , Ren Zhehao , Chan Karen K.Y. , Bai Yuqi
Published: March 2020

The World Climate Research Programme (WCRP) facilitates analysis and prediction of Earth system change for use in a range of practical applications of direct relevance, benefit and value to society. WCRP initialized the Coupled Model Intercomparison Project (CMIP) in 1995. The aim of CMIP is to better understand past, present and future climate changes arising from natural, unforced variability or in response to changes in radiative forcing in a multi-model context.

The climate model output data that are being produced during this sixth phase of CMIP (CMIP6) is expected to be 40~60 PB. It is still not very clear whether researchers worldwide may experience a big problem when downloading such a huge volume of data. This work addressed this issue by performing data download speed test for all the CMIP6 data nodes.

A Google Chrome-based data download speed test website (http://speedtest.theropod.tk) was implemented. It leverages the Allow CORS: Access-Control-Allow-Origin extension to access to each CMIP6 data node. This test consists of four steps: Installing and enabling Allow CORS extension in Chrome, performing data download speed test for all the CMIP6 data nodes, presenting the test results, and uninstalling the extension. The speed test is performed by downloading a certain chunk of model output data file from the thredds data server of each data node.

Researchers from 11 countries have performed this test in 24 cities against all the 26 CMIP6 data nodes. The fastest transfer speed was 124MB/s, and the slowest were 0 MB/s because of connect timeout. Data transfer speed in developed countries (United States, Netherland, Japan, Canada, Great Britain) is significantly faster than that in developing countries (China, India, Russia, Pakistan). In developed countries the data transfer mean speed is roughly 80Mb/s, equal to the median US residential broadband speed provided by cable or fiber（FCC Measuring Fixed Broadband - Eighth Report, but in developing countries the mean transfer speed is usually much slower, roughly 9Mb/s. Data transfer speed was significantly faster when the data nodes and test sites were both at developed countries, for example, downloading data from IPSL, DKRZ or GFDL at Wolvercote, UK.

Although further test are definitely needed, this preliminary result clearly show that the actual data download speed varies dramatically in different countries, and for different data node. This suggests that ensuring smooth access to CMIP6 data is still challenging.
Comparison of cirrus clouds in naturally and anthropogenically influenced regions of the atmosphere
Authors: Dollner Maximilian , Gasteiger Josef , Brock Charles A. , Schöberl Manuel , Williamson Christina , Kupc Agnieszka , Philipp Anne , Seibert Petra , Froyd Karl , Schill Gregory P. , Murphy Daniel M. , Diskin Glenn , Bui T. Paul , Weinzierl Bernadett
Published: March 2020

Cirrus clouds are an important contributor to the uncertainty of future climate prediction, especially due to the weak understanding of anthropogenic impacts on cirrus clouds.

We investigate aerosol and cloud microphysical properties of the remote atmosphere over the Pacific and Atlantic Oceans from about 80°N to 86°S and the region in the Mediterranean using airborne aerosol and cloud measurements of the entire atmospheric column up to approx. 13 km from the ATom (Atmospheric Tomography; 2016-2018) and the A-LIFE (Absorbing aerosol layers in a changing climate: aging, lifetime and dynamics; 2017) field experiments, respectively. Aerosol microphysical properties are retrieved from in-situ measurements of aerosol particle size distributions between 0.003 and 50 µm, single particle mass spectrometry as well as simulations with the Lagrangian transport and dispersion model FLEXPART. The microphysical properties of cirrus clouds are obtained from size distribution measurements covering the range between 3 and 930 µm.

In this study we show microphysical properties of aerosols and cirrus clouds in regions with high mineral dust concentrations as well as pristine and anthropogenic influenced regions in order to advance the knowledge of the natural and anthropogenic impact on cirrus clouds.  We present comparisons of ice crystal number concentrations, aerosol and cloud particle size distributions, and meteorological conditions of cirrus clouds in the above-mentioned regions of the atmosphere.
The multi-2D seismic imaging of the Solfatara Volcano, Italy, inferred by seismic attributes.
Authors: Gammaldi Sergio , Ismail Amir , Chiuso Teresa , Zollo Aldo
Published: March 2020

The imaging of seismic reflection data provides a powerful high-resolution method for studying volcano structure and fluids presence. The shallow structure of the Solfatara crater, a surface marker of deep magmatic activity inside Campi Flegrei caldera (Southern Italy), is characterized in terms of seismic profile and attributes. The main contribution of this work is to provide a detailed and improved seismic reflection image of the Solfatara crater and the identification of gas accumulation. The profiles are deployed along the NNE-SSW directions, the first, and the second orthogonal to the last. The two profiles are 400 m long acquired during the active experiment RICEN (Repeated Induced Earthquake and Noise) performed in the framework of the EU project MEDSUV between May and November 2014. Pre-stack processing of the seismic data has been performed in order to remove the noisy traces, low-frequency noise and reduce the ground roll phases. A very detailed velocity analysis for the NMO correction has been performed with the integration of information derived from the Vp velocity model previously obtained by the non-linear Bayesian technique. After having applied residual statics and DMO corrections, the CMP gathering, the post-stack Kirchhoff migration technique was performed to produce the final seismic profiles in time and depth. Once having obtained the post-stack migrated imaged, the energy, root mean square, envelope and sweetness attributes were computed for defining the maximum and minimum value of amplitude zones. In addition, other attributes as the time-gain attribute in order to interpret the deep reflectors and the variance attribute to define the faults, discontinuities, and chaotic zones have been evaluated. To enhance fluids identification the Amplitude Versus Offset (AVO) variation technique has been further applied to identify the gas zone in the explored sections. By integrating all information from the original seismic profile, seismic attributes and geophysical investigation relative to the Solfatara volcano, the multi-2D image presents the fluids trapped in the Solfatara crater at depths between 10 to 50 m below the surface of the crater and their migration pathways up to 150 meters depth.
Extracting robust splitting measurements for the AlpArray using the splitting intensity method
Authors: Bokelmann Götz , Hein Gerrit
Published: March 2020

Seismic anisotropy is an important tool for studying geodynamic processes in the Earth, and a common way of constraining it is to analyse shear-wave splitting of seismological body-wave phases,
i.p. SKS. Different techniques exist to quantify shear-wave splitting, but they do not always give the same result, raising the question of how stable they are, and whether there are systematic biases. Furthermore, the strength of the splitting ("splitting delay") has generally been more difficult to determine than the other (the "fast orientation").
A robust technique for determining shear-wave splitting can be set up
based on the splitting intensity method. That technique can in particular also constrain the splitting delay well. Ambient noise can however lead to an underestimation of splitting delay, and it needs to be accounted for, e.g. by a least-squares Wiener filter.
We apply that modified splitting intensity method to data from the AlpArray. We have processed 3 years of teleseismic earthquake data for 336 stations of the AlpArray deployment and additional 315 stations of the Italian network to get a potentially broad and more complete image of anisotropic structures in and outside the Alpine region.
The technique makes restrictive assumptions, e.g. assuming single-layer anisotropy. Yet, the new constraints, especially the one of the splitting delay are rather useful for understanding the deformation under the mountain belt and around it.

 
Controls of channel morphodynamics on the intertidal dune morphodynamics and associated bedload transport in the open-coast macrotidal flats
Authors: Jo Joohee , Kim Dohyeong , Choi Kyungsik
Published: March 2020

Intertidal dune morphodynamics is closely tied to bedload transport that is variable in time and space due to the interplay between tide, wave and runoff discharge. Surprisingly the control of intertidal channel morphology on the dune morphodynamics and related bedload transport is scarcely documented. Actively migrating dunes are widely developed in the lower intertidal zone of Yeochari tidal flat in the northern Gyeonggi Bay, west coast of Korea. High-resolution aerial images, high-precision transect profiles, and hydrodynamic dataset were repeatedly obtained and analyzed to quantify the intertidal dune morphodynamics and associated bedload transport, and to address the role of channel morphodynamics. During the research period, the intertidal channel became more sinuous and an ebb barb arose concurrently at the upstream of the channel point bar. The ebb barb exerted a key role in the downstream delivery of fine-grained sediments onto the areas covered by dunes and the intertidal channel by reinforcing ebb currents with a pronounced time-velocity asymmetry. The presence of the ebb barb resulted in a rapid decrease of the width/depth ratio of the channel that had migrated laterally 130 m in six years. After the ebb-barb development, the heights and steepness (height/wavelength) of dunes on the point bar and near the ebb barb decreased notably. Simultaneously dune migration rate had increased from 0.5 m/day to 2.5 m/day, which decreases away from the channel. Bedload transport estimated by using Meyer-Peter and Muller (MPM) equation and Dune-Tracking Method (DTM) also decreases away from the channel. Bedload transport calculated by DTM (qbDTM, 0.03-0.38 m2/day) is much smaller than that estimated by MPM (qbMPM, 0.10-4.17 m2/day) by a factor of 1.5 to 62. The discrepancy ratio between the two bedload estimates (qbMPM/qbDTM) increases toward the channel and the ebb barb. Downslope flow toward the channel during the late stage of ebb tide may account for the underestimation of qbDTM by facilitating downslope sediment transport that reduced the dune steepness with the infilling of dune trough. The present study showcased a dynamic response of the dune morphodynamics and associated bedload transport in the open-coast tidal flats to the changes in the channel morphodynamics that is controlled by seasonal runoff discharge as well as tidal currents.
Forced Convective Aggregation
Authors: Dingley Beth , Dagan Guy , Stier Philip
Published: March 2020

The phenomenon of convective aggregation in idealised radiative convective equilibrium simulations has the ability to change the mean state of its domain. When compared to non-aggregation conditions, these simulations usually have warmer drier mean atmospheres, with stronger precipitation in the convective areas. Many of these idealised experiments use a fixed sea surface temperature (SST), where higher temperatures generally increase the scale of aggregation. SST gradients have been shown to organise convection, yet there has been no work done to investigate the impact of heating perturbations in the air on the aggregation of convection. Here we investigate how strong diabatic heating of the atmospheric column affect the existence and properties of convective aggregation. These perturbations provide a link to studying the effect of large pollution plumes on convection, for example during the Indian monsoon season.

An aerosol model is used to insert plumes of strongly absorbing aerosols into aquaplanet, non-rotating, global RCE simulations. We study the sensitivity of the response to aerosol optical depth (AOD) and aerosol radiative properties under different SSTs.

Without any forcing, the simulations at low SST do not aggregate while at high SST they do. We also see that adding the forcing causes aggregation at both temperatures for a wide range of AODs. Detailed investigation shows that the diabatic heating source causes two circulations to develop, one with low-level convergence towards the plume and high-level divergence away from the plume. A secondary circulation works tangentially to the plume, again with low-level convergence and high-level divergence, driving the formation of several radial branches of aggregated convection. We argue that, as we see this aggregation for plumes with realistic AODs, this could be an analogue for real-world organisation during high pollution events. Future work will investigate the difference in mechanisms between forced and unforced convective aggregation as well as conducting similar experiments in smaller, cloud resolving domains.
Flexible slope protection for the steep Pisha sandstone slopes based on hydraulic polyurethane combined with planting mate
Authors: Zhao Yanbing , Yang Caiqian , Qu Feng , Wu Zhiren , Liang Zhishui , Ma Wenbo
Published: March 2020

The vegetation and stability of Pisha sandstone slopes are insufficient due to its inherent properties, such as low erosion resistance, strength, water stability, and high porosity. In this paper, a new flexible slope protection method, which considers the combination of hydraulic polyurethane(W-OH) and planting mate technology, is proposed to realize the ecological restoration and prevent soil erosion of the steep Pisha sandstone slopes. The properties of consolidated body of W-OH and Pisha sandstone were investigated. Furthermore, the optimal proportion of the nutrient substate was obtained by orthogonal test via laboratory and on-site experiments. The results illustrate that with 5% W-OH, the average compressive strength and water stability index of the consolidated body can reach about 6.70 and 3.71 times higher than the blank group. The on-site experiments demonstrate that the vegetation coverage of the optimal group reaches 85% after three months curing, which is 5.2 times that of the blank group.
Sedimentary and geomorphic responses to changes in rate of sea-level rise: Holocene marine transgression of Dogger Bank, North Sea
Authors: Emery Andy , Hodgson David , Barlow Natasha , Cotterill Carol
Published: March 2020

Coastal landforms such as barriers are crucial in protecting coastlines and reducing the rate of erosion and retreat. Sea-level rise threatens to change the baseline in which such landforms exist, therefore changing sediment fluxes and hydrodynamics at coastlines. Understanding the stability of landforms under changing conditions is crucial to protect and mitigate against the influence of future sea-level rise on coastal infrastructure, ecology and populations. By studying past periods of sea-level rise with rates similar to those projected for the future, we can begin to understand how coastlines may evolve over the next few centuries.

Dogger Bank, in the southern North Sea, experienced marine transgression during the Early Holocene. Over a period of 800 years, sea level rose by 7-8 m. This rate of ~10 mm/yr is similar to that projected within the next century. Our study area is located on the southeastern side of the former Dogger Bank island. Between 9.5 and 8.7 ka BP, two phases of coastal barriers were present, retreating with different mechanisms at different time periods due to antecedent topographic changes and evolving hydrodynamics. Barrier phase A was drowned in place due to a low-angle topography and little reworking of the barrier. Barrier phase B retreated by continuous overstepping, which occurred due to a higher-angle topography and an increase in wave energy. Complete inundation of the study area occurred by 8.7 ka, with the barrier phase B first becoming an isolated barrier, then breaking down completely. The subsequent wave ravinement transitioned the landform from barrier to offshore sand bar. At this time, the rate of sea-level rise had increased to as much as 20 mm/yr during the pre-8.2 ka sea-level jump, causing the final barrier breakdown and inundation of Dogger Bank. The coastal morphology in the study area is now buried beneath up to 20 m of shallow marine sand, deposited as the dominant tidal current transported sediment from west to east.

The unique landform preservation at Dogger Bank allows unprecedented spatial and temporal resolution into the investigation of coastal response to sea-level rise. This study adds evidence to the growing body of work that sea-level rise is the driver of, but not necessarily the controlling factor in, barrier retreat mechanism. Furthermore, a rarely-preserved landform, the isolated barrier, is presented. The results of the study provide valuable insights into the transition from coastal to fully marine during transgression of low-relief coastal areas, which provides an analogue for future sea-level rise scenarios.
Fundamental Notions in Relativistic Geodesy - physics of a timelike Killing vector field
Authors: Philipp Dennis , Laemmerzahl Claus , Hackmann Eva , Perlick Volker , Puetzfeld Dirk , Mueller Juergen
Published: March 2020

The Earth’s geoid is one of the most important fundamental concepts to provide a gravity field- related height reference in geodesy and associated sciences. To keep up with the ever-increasing experimental capabilities and to consistently interpret high-precision measurements without any doubt, a relativistic treatment of geodetic notions within Einstein’s theory of General Relativity is inevitable. 

Building on the theoretical construction of isochronometric surfaces we define a relativistic gravity potential as a generalization of known (post-)Newtonian notions. It exists for any stationary configuration and rigidly co-rotating observers; it is the same as realized by local plumb lines and determined by the norm of a timelike Killing vector. In a second step, we define the relativistic geoid in terms of this gravity potential in direct analogy to the Newtonian understanding. In the respective limits, it allows to recover well-known results. Comparing the Earth’s Newtonian geoid to its relativistic generalization is a very subtle problem. However, an isometric embedding into Euclidean three-dimensional space can solve it and allows an intrinsic comparison. We show that the leading-order differences are at the mm-level. In the next step, the framework is extended to generalize the normal gravity field as well. We argue that an exact spacetime can be constructed, which allows to recover the Newtonian result in the weak-field limit. Moreover, we comment on the relativistic definition of chronometric height and related concepts.

In a stationary spacetime related to the rotating Earth, the aforementioned gravity potential is of course not enough to cover all information on the gravitational field. To obtain more insight, a second scalar function can be constructed, which is genuinely related to gravitomagnetic contributions and vanishes in the static case. Using the kinematic decomposition of an isometric observer congruence, we suggest a potential related to the twist of the worldlines therein. Whilst the first potential is related to clock comparison and the acceleration of freely falling corner cubes, the twist potential is related to the outcome of Sagnac interferometric measurements. The combination of both potentials allows to determine the Earth’s geoid and equip this surface with coordinates in an operational way. Therefore, relativistic geodesy is intimately related to the physics of timelike Killing vector fields.
Soil Moisture Estimation over Soybean Fields Through A Model-Based Polarimetric Decomposition
Authors: Xiao Tengfei , Xing Minfeng , He Binbin
Published: March 2020

As one of the most important parameters in earth surface, soil moisture plays a crucial role in in many fields, such as agriculture, environment, hydrology, ecology and water management. With the development of earth observation technology, Synthetic Aperture Radar (SAR) provides a powerful method to estimate soil moisture at diverse spatial and temporal scales. However, in agricultural area, soil moisture estimated by SAR often obstructed by vegetation cover. Volume scattering and vegetation attenuation can complex the received SAR backscatter signal when microwave interacts with vegetation canopy. In this study, a model-based polarimetric decomposition and the two-way attenuation parameter in Water Cloud Model (WCM) were adopted to remove the effect of volume scattering and vegetation attenuation respectively. And a deorientation process of SAR data was applied to remove the influence of randomly distributed target angles before polarimetric decomposition. After that, the Dubois model was used to describe the underlying soil backscattering and retrieve soil moisture. Optimal surface roughness was adopted to parameterize the Dubois model due to the difficulty of soil roughness measurement under vegetation cover. This soil moisture estimation method was applied to soybean fields with time-series RADARSAT-2 SAR data. Validation based on in-situ measured soil moisture demonstrates that the proposed method is capable of estimating soil moisture over soybean fields, with Root Mean Square Errors (RMSEs) of 9.2 vol.% and 8.2 vol.% at HH and VV polarization respectively.
Advanced multi-source approach for cultural heritage assessment and monitoring – the case study of the Corvin Castle and its surroundings
Authors: Moise Cristian , Mihalache Cristina Elena , Dedulescu Luminita Andreea , Lazăr Andi-Mihai , Badea Alexandru , Dana Negula Iulia Florentina
Published: March 2020

Remote sensing has already proven to represent an invaluable resource for monitoring the cultural heritage objectives by using non-invasive methods, thus enhancing the capabilities of safeguarding cultural heritage sites. Multiple types of data provide a better insight for the cultural heritage monitoring. Increasing human industrial activities in the vicinity of the Corvin Castle puts a question mark on the long-term conservation of the historic monument. Satellite imagery provides a large amount of data regarding the castle itself and its surrounding areas, enabling authorities and decision makers to assess the natural or anthropic hazards and mitigate potential damages. Freely available high-resolution satellite imagery that spans from mid 1970s until the present day enables an unprecedented opportunity for the creation of multi-sensor, multi-temporal and cross analysis.

In the field of cultural heritage and archaeological research, Light Detection and Ranging (LiDAR) is a significant technology that provides comprehensive data. LiDAR sensors acquire high-precision 3D information (point cloud) of the land surfaces and buildings.

Knowledge of structures stability is essential in early recognition of potential risks and enables preventive diagnosis of heritage sites. Vertical displacements in wide or remote areas can be identified using Persistent Scatterer Interferometry (PS-InSAR) technique. Measuring millimetric displacements using multi-temporal series of data acquired by spaceborne active sensors is less time consuming compared with in-situ measurements. The two-satellite constellation Sentinel-1 mission offers a 6-day exact repeat cycle at the equator, thus providing fast and high accuracy results for emergency situations and hazards monitoring, suitable for PS-InSAR processing. Monitoring the structure stability of this historical monument is of great importance.

The Corvin Castle, also known as Hunyadi Castle or Hunedoara Castle, is the most spectacular Gothic-style construction in Transylvania, Romania. Today, the castle is a rare historical and architectural example. Built in the mid-15th century, the Corvin Castle is split into three large areas: The Knight’s Hall, the Diet Hall, and the circular stairways. Each of these three parts is surrounded by both circular and rectangular towers that were used for both defense and as a prison.

This paper presents the ongoing activities of bringing together various geospatial technologies and data sources in order to set-up an integrated approach for site monitoring and risk assessment related to the Corvin Castle and other similar cultural heritage objectives. The outcomes will provide significant contributions for implementing suitable protection and preservation measures.
Copernicus Sentinel-5 Precursor Routine Validation
Authors: Dehn Angelika , Zehner Claus , Saavedra De Miguel Lidia , Lambert Jean-Christopher , Veefkind Pepijn , Loyola Diego
Published: March 2020

Copernicus Sentinel-5 Precursor (S-5P) is the first of a series of atmospheric chemistry missions within the European Commission’s Copernicus Programme, launched successfully in October 2017 and since end April 2018 in its operational phase. S-5P provides continuity in the availability of global atmospheric data products between its predecessor missions SCIAMACHY (Envisat) and OMI (AURA) and the future Sentinel-4 and -5 series. S-5P delivers unique data regarding the sources and sinks of trace gases with a focus on the lower Troposphere including the planet boundary layer due to its enhanced spatial, temporal and spectral sampling capabilities as compared to its predecessors.

The S-5P satellite carries a single payload, namely TROPOMI (TROPOspheric Monitoring Instrument) that was jointly developed by The Netherlands and ESA. Covering spectral channels in the UV, visible, near- and short-wave infrared, it measures various key species including tropospheric/stratospheric ozone, NO2, SO2, CO, CH4, CH2O as well as cloud and aerosol parameters.

The geophysical validation and characterization of the TROPOMI data products during the phase E2 is conducted by ESA at different levels. The so-called Mission Performance Center carries out the routine validation throughout the mission life-time and rely on the availability of independent data sets for example from ground-based measurements or the so-called Fiducial Reference Measurement data sets, as well as the contributions from independent national Validation Teams coordinated by ESA under the Sentinel 5 Precursor Validation Team (S5PVT).

The current status of the ESA S-5P routine Validation activities will be discussed in this paper.
Coherent Time and Frequency for an Improved Global Geodetic Observing System
Authors: Schreiber Karl Ulrich , Kodet Jan , Klügel Thomas , Schüler Torben
Published: March 2020

The toolbox of space geodesy contains a number of measurement techniques, which are globally distributed. In this diverse network fundamental stations are playing an important role as they are forming the backbone of the global geodetic observing system. They provide the ties for the combination of the techniques.

Until recently these ties were only considering the spatial relationship between the measurement techniques. Upon closer inspection it turns out that clocks are also playing an important role. Variable delays within the main techniques of space geodesy, namely SLR, VLBI, GNSS and DORIS are limiting the stability of the measurements and hence the entire observing system. This leads to the rather paradox situation, that each technique has to adjust the clock offsets independently. Although all main measurements systems on an observatory are usually based on the same clock, each technique provides different offsets, thus weakening the local ties. This reflects the fact that the clock adjustments are also contaminated with (variable) system specific delays. Increasing the coherence of time on these GGOS observatories disentangles erroneous system delays from local ties, thus strengthening the entire observing system. 

We have designed and built such a coherent time and frequency distribution system for the Geodetic Observatory Wettzell. It is based on a mode-locked fs- pulse laser, fed into a network of actively delay controlled two-way optical pulse transmission links. This utilizes the ultra low noise properties of optical frequency combs, both in the optical and electronic regime. Together with a common central inter- and intra- technique reference target time can provide consistency for the complex instrumentation of SLR and VLBI systems in situ, which was not possible before. This talk outlines the concept and its potential for GGOS.
Uncertainty Estimation of a global Remote Sensing Water Surface Time-Series: the DLR Global WaterPack
Authors: Mayr Stefan , Klein Igor , Künzer Claudia , Rutzinger Martin
Published: March 2020

Large-scale remote sensing products offer opportunities to address global society relevant questions. One of the most vital resources of our planet is fresh water. To monitor dynamics, the application of water surface time-series has proven to be an effective tool, but to access reliable information, validation efforts are essential. Furthermore, increased utilization of remote sensing time-series products can be seen in modelling applications. In this process, uncertainty estimation of input datasets is typically required. Especially for large-scale remote sensing products with high temporal resolution, common validation approaches as comparison to in situ data or intercomparison to similar products is hardly viable. Here we propose the use of supervised- and unsupervised outlier detection methods to yield pixel-wise uncertainty estimates in an internal validation. Therefore, several algorithms are applied on a global, MODIS (Moderate Resolution Imaging Spectroradiometer) based daily accessible water surface product (DLR Global WaterPack). Two main sources have been identified to introduce uncertainty to the binary classification of cloud free observations. As mixed pixels (water/non-water) and water impurities contribute to changes in the RED-NIR profile, we evaluate their effects by utilizing classified Landsat 8 images to determine water subpixel fractions and identify turbid water. Results are analyzed and compared in initial test regions across the globe.
Dependencies of Polychlorinated Biphenyl Concentrations Measured at the Great Lakes on Climate Variables
Authors: Ubl Sandy , Scheringer Martin
Published: March 2020

Polychlorinated biphenyls (PCBs) are persistent and hazardous chemicals that are still detected in the atmosphere and other environmental compartments although their production was banned several decades ago. At the Great Lakes region PCBs have been monitored via the IADN network since 1993. In this study, we report results from seven different PCB congeners measured at six different sites around the Great Lakes. The PCBs exhibit a strong seasonal cycle with highest concentrations in summer and lowest concentrations in winter. The concentrations measured in Chicago and Cleveland are higher compared to the concentrations reported from more remote stations. We evaluated the correlations for the seven PCB congeners at each station. PCB-53,-101,-118 and -138 are highly correlated at each of the six stations. PCB-180 is the least correlated with all the other PCBs. This is explicitly true for Eagle Harbor, where PCB-180 and -153 are not correlated with the other 6 PCBs. This may be explained by the less pronounced seasonal cycle of these heavier PCBs at Eagle Harbor. We observed significant correlations between PCB-28 concentrations at the remote stations, but PCB concentrations at the stations of Chicago and Cleveland are only poorly correlated with PCB concentrations at the other stations. The weak correlation of the PCB concentrations measured at the different stations and the relatively high concentrations of the PCB congeners at each station indicate that local conditions and small scale processes (sources, temperature, wind direction, wind speed) dictate the spatial distribution of the  PCBs. We will feed available data on temperature, wind speed, wind direction, emissions, precipitation, ice cover of the Great Lakes and large scale atmospheric teleconnection patterns into a General Additive Model (GAM) to further investigate the relationships between the measured PCB concentrations and selected environmental conditions and atmospheric parameters. 
Assessment of the IRI-2016 and modified IRI 2016 models in China: Comparison with GNSS-TEC and ionosonde data
Authors: zhang wen , Huo xingliang , Liu haojie
Published: March 2020

Ionosphere is one of the main errors in the signal propagation of global navigation system satellite (GNSS), and it is also the key issue of space weather. The International Reference Ionosphere (IRI) is the most important empirical model described the ionospheric characteristics, and it provides the monthly averages of electron densities and vertical total electron content (VTEC) in the altitude range of 50km-2000km. The IRI-2016 model is the latest version. But some studies showed that the accuracy of the IRI model is not high enough in China due to the use of fewer data sources. This paper will assess the performance of IRI-2016 model in China, and a modified IRI 2016 model by adjusting the driving parameters IG and RZ index of IRI2016 model with GNSS TEC data are also investigated. In this contribution, GNSS data from the Crustal Movement Observation Network of China (CMONC) are used to estimate TEC values, and the ionosonde data from three stations are used as references for the ionospheric electron densities. Three ionosonde stations are located at Beijing (BP440, 40.3°N/116.2°E), Wuhan (WU430, 30.5°N/114.4°E) and Sanya (SA418, 18.3°N/ 109.6°E). The above data respectively cover a period of 6 days in the high year (2015) and low year (2019) of solar activity.

The study shows that the biggest reason for the difference (DTEC) between GPS-TEC and IRI2016-TEC in China is that the poor estimation of NmF2 and hmF2 by IRI model, and the driving parameters IG and RZ index of IRI2016 can be updated by constraining DTEC. Finally, the performance of the modified IRI-2016 model is improved by the updated IG and RZ indexes as the short-term driving values of ionospheric parameters. The analysis show that the modiﬁed IRI-2016 model is more accurate at estimating both the TEC and the electron density profile than the original model.
Structure and dynamics of a case-study monsoon depression in high-resolution numerical simulations using the Met Office Unified Model
Authors: Menon Arathy , Volonté Ambrogio , Turner Andrew , Hunt Kieran
Published: March 2020

Monsoon depressions (MD) are synoptic-scale cyclonic vortices that form over the Bay of Bengal and propagate northwestward through the monsoon trough onto the Indian subcontinent, bringing substantial amounts of rainfall to central and northern India. Despite their importance, key questions on the mechanisms driving their generation and development are still open. In this study we inspect the structure and dynamics of a MD case study (1-10 July 2016) using a set of high-resolution simulations performed within the INCOMPASS project. The simulations are performed at a grid spacing of 17 km, 4.4 km and 1.5 km (with parametrised convection for the former experiment and explicit convection for the latter two). Initial results of this study show that the two higher-resolution simulations are more effective in resolving intense rainfall caused by deep convection, convergence lines and orographic enhancement. The evolution of the case-study MD can be divided into two stages: initially the MD is completely embedded in a close-to-saturated environment up to mid-troposphere, whilst in the following stage the intrusion of low-potential-temperature dry air at low- and mid-levels starts interacting with the MD. During this latter stage, the dry-air intrusion brings in low PV-air towards the centre of the depression. Further analysis of the case study takes advantage of a system-relative framework to look into detail at the time evolution of dynamic and thermodynamic parameters around the storm centre and at its small- and meso-scale structure. For example, the 1.5 km-spacing simulation enables us to highlight the presence of individual vorticity towers embedded within the MD. In summary, using a suite of high-resolution numerical simulations of a case-study MD, we are able to achieve a detailed understanding of its structure and dynamics, highlighting the processes driving its evolution.
Combined use of Raman lidar and DIAL measurements and MESO-NH model simulations for the characterization of complex water vapour field structures and their genesis: a case study from HyMeX-SOP 1
Authors: Di Girolamo Paolo , Bouin Marie-Noelle , Flamant Cyrille , Summa Donato , De Rosa Benedetto
Published: March 2020

As part of the Cevennes-Vivarais site, the University of Basilicata Raman lidar system BASIL was deployed in Candillargues and operated throughout the duration of HyMeX-SOP 1 (September-November 2012), providing high-resolution and accurate measurements, both in daytime and night-time, of atmospheric temperature, water vapour mixing ratio and particle backscattering and extinction coefficient at three wavelengths.

Measurements carried out by BASIL on 28 September 2012 reveal a water vapour field characterized by a quite complex vertical structure. Reported measurements were run in the time interval between two consecutive heavy precipitation events, from 15:30 UTC on 28 September to 03:30 UTC on 29 September 2012. Throughout most of this observation period, lidar measurements reveal the presence of four distinct humidity layers.

The present research effort aims at assessing the origin and transport path of the different humidity filaments observed by BASIL on this day. The analysis approach relies on the comparison between Raman lidar measurements and MESO-NH and NOAA-HYSPLIT model simulations. Back-trajectory analyses from MESO-NH reveal that air masses ending in Candillargues at different altitudes levels are coming and are originated from different geographical regions.

The four distinct humidity layers observed by BASIL are also identified in the water vapour mixing ratio profiles collected by the air-borne DIAL LEANDRE 2 on-board of the French research aircraft ATR42. The exact correspondence, in terms of back-trajectories computation and water budget, between the humidity layers observed by BASIL and those identified in LEANDRE2 measurements has been verified based on a dedicated simulation effort.

In the paper we also try to identify the presence of dry layers and cold pools and assess their role in the genesis of the mesoscale convective systems and the heavy precipitation events observed on 29 September 2012 based on the combined use of water vapour mixing ratio and temperature profile measurements from BASIL and water vapour mixing ratio profile measurements from LEANDRE 2, again supported by MESO-NH simulations.
A Statistical Analysis of Radar Blackout Events at Mars
Authors: Lester Mark , Sanchez-Cano Beatriz , Biddle Hannah , Potts Daniel , Blelly Pierre-Louis , Opgenoorth Hermann , Witasse Olivier , Cartacci Marco , Orosei Roberto , Bernardini Fabrizio , Putzig Nathaniel , Campbell Bruce , Lillis Robert , Leblanc François , Milan Steve , Plane John M.C.
Published: March 2020

The loss of signal detection by the sub surface radars currently operational on Mars Express and Mars Reconnaissance Orbiter can be evidence of enhanced ionisation at lower altitudes in the Martian atmosphere as a result of solar energetic particles penetrating to these altitudes.  The MARSIS instrument on Mars Express and SHARAD on MRO operate at different frequencies, with MARSIS up to 5 MHz and SHARAD between 10 and 20 MHZ.  In addition MARSIS can operate in an additional mode as an Active Ionospheric Sounder, although here we focus only on the sub surface mode.  We present an analysis of the data during the lifetimes of both instruments, extending from 2005 to 2018.  Here we identify the radar blackouts as either total or partial and investigate their occurrence as a function of solar cycle.  We find a clear solar cycle dependence with more events occurring during the solar maximum years, as expected.  However, we also note the duration of events is often much longer than expected, in excess of several days, sometimes reaching 10 – 14 days.  Investigation of other data sets, notably from the MAVEN SEP instrument complements the analysis.  We finally compare our observations at Mars with similar observations at Earth.