bluuebunny/crossref_metadata_2025 huggingface dataset:
Sensitivity analysis for numerical modeling of a generic repository for nuclear waste in bedded salt
Authors: Liu Wenting , Eickemeier Ralf , Fahland Sandra
Published: March 2020

Numerical models of a generic repository for nuclear waste were created to analyze the long-term barrier integrity of bedded salt formations. This study focuses on sensitivity analysis and validation for numerical simulation by using 2D models. Under consideration of thermal loading caused by the disposal of heat generating nuclear waste, thermal and thermomechanical coupled calculations were performed using FEM code JIFE (Faust et al. 2016). Thermal analyses were conducted to investigate the influence of mesh density on the temperature results in both near and far field of disposal area. Thermomechanical coupled calculations were carried out to evaluate boundary influence of different model dimension on the results of temperature and vertical displacement. Furthermore, since the overburden are assumed to be elastic, variation of Young’s modulus shows sensitivity of overburden stiffness in thermomechanical coupled calculations of the generic model for bedded salt. The calculated stress and deformation were compared to investigate the influence of overburden stiffness on the results of geomechanical assessment of the salt barrier integrity. The observation of this study gives a better understanding of how to establish a 2D or 3D model in bedded salt formation for barrier integrity analysis.
Characteristics of seismic activity of Villarrica Volcano
Authors: Lehr Johanna , Rabbel Wolfgang
Published: March 2020

Villarrica is one of the most active and dangerous volcanoes in Chile. During the last decade it consisted of a single open vent hosting an active lava lake which produced mild stombolian explosions, persistent tremor and continuous degassing.

We present an analysis of the seismic activity of Villarrica between 2010 and 2012. Periods of increased lava lake activity are characterized by numerous small transient events which exibit a variety of waveforms and spectral characteristics. Statistical analysis of interevent times revealed a periodic occurrence. At comparable volcanic systems (Stromboli, Erebus), such distributions of events indicated unusual periods of activity corresponding to magma injection. Methods of blind signal separation (ICA, PCA) were used to analyse the wavefield. While regional and local tectonic earthquakes can easily be separated, the tremor and transient events from the crater can not.
Aerosol retrieval based on 10 years of passive remote sensing satellite measurements over the Arctic – validation and trend analysis
Authors: Jafariserajehlou Soheila , Vountas Marco , Istomina Larysa , P. Burrows John
Published: March 2020

The Aerosol Optical Thickness (AOT) retrieval over the Arctic region is a challenging task due to uncertainties and difficulties in its prerequisites, mainly (i) cloud masking methods and (ii) modeling the underlying snow/ice surface. In the past this led to a large data gap over the Arctic which hampered our understanding of the direct/indirect aerosol effect on Arctic and global climate change. For the purpose of improving our knowledge, we present, for the first time, long-term AOT maps of snow and ice covered areas based on satellite remote sensing.

In this study, a previously developed aerosol retrieval algorithm over snow/ice, (Istomina et al., 2012; in IUP, University of Bremen) is used to retrieve AOT for a period of 10 years, 2002-2012, over the Arctic and to analyze its spatial and temporal changes. This algorithm is based on a multi-angle approach and uses pre-computed look-up tables to retrieve AOT.

The algorithm has been improved with respect to cloud masking (based on clear snow spectral shape) using the ASCIA cloud identification algorithm (Jafariserajehlou et al., 2019). The modified AOT retrieval algorithm is applied to observations from Advanced Along-Track Scanning Radiometer (AATSR) on European Space Agency’s (ESA) measurements. The retrieved dataset provides long-term AOT at a spatial resolution of 1 km2 over snow/ice covered surface in the extended Arctic region (60°- 90°) during polar day. The results show that Arctic haze events appearing every late-winter and early spring are very well captured in AATSR derived AOTs. To validate the retrieved AOTs, results are compared with ground-based AERONET data. The comparisons revealed partially excellent agreement but also limits of the retrieval algorithm are discussed. In addition, some preliminary results of a trend analysis of the long-term record will be presented. It is foreseen to use the results in the trans-regional research project (AC)³ investigating Arctic amplification.

References

[1] Istomina, L.: Retrieval of aerosol optical thickness over snow and ice surfaces in the Arctic using Advanced Along Track Scanning Radiometer, PhD thesis, University of Bremen, Bremen, Germany, 2012.

[2] Jafariserajehlou, S. and Mei, L. and Vountas, M. and Rozanov, V. and Burrows, J. P. and Hollmann, R., A cloud identification algorithm over the Arctic for use with AATSR/SLSTR measurements, Atmos. Meas. Tech., 12, 1059-1076, doi:10.5194/amt-12-1059-2019, 2019.

 
Comparison of one year of XCH4 and XCO measurements using a EM27/SUN low resolution FTIR spectrometer to S5P/TROPOMI methane and carbon monoxide columns at Thessaloniki, Greece
Authors: Topaloglou Chrysanthi , Mermigkas Marios , Koukouli Maria-Elissavet , Balis Dimitrios , Hase Frank , Landgraf Jochen , Aben Ilse
Published: March 2020

The column-averaged dry air mole fractions of carbon dioxide (XCO2), methane (XCH4) and carbon monoxide (XCO) have been measured for the first time for a whole year in Thessaloniki, Greece, using the portable Bruker EM27/SUN ground-based low-resolution Fourier Transform spectrometer, provided by the Karlsruhe Institute of Technology. The EM27/SUN is a reliable, easy-to-deploy, mobile, low-cost supplement to the Bruker IFS 125HR, a high-resolution spectrometer used in the Total Carbon Column Observing Network (TCCON). Approximately 30 of the EM27/SUN instruments constitute the Collaborative Carbon Column Observing Network (COCCON), with stations around the globe for the quantification of local sinks and sources, working as an important supplement of TCCON to increase the global density of column-averaged greenhouse gas observations

One year of measurements of XCH4 and XCO are presented for Thessaloniki, Greece. The station is located in the center of the city. The data are compared to collocated measurements from S5P/TROPOMI using 50km and ±30 min as criteria. For the XCH4 comparisons, the ground based XCH4 is constantly found to be lower than the satellite product. However, for ground based retrievals of XCH4 using the TROPOMI algorithm and IR band, the comparison with the satellite data shows a percentage difference lower than ±2%, well within product requirements. Satellite XCO is also compared to ground observations to examine if EM27/SUN concentrations are reproduced by S5P/TROPOMI and whether the temporal variations are captured

 

 

Aknowledgments

This work was co-funded by ESA within the Contract No. 4000117151/16/l-LG “Preparation and Operations of the Mission Performance Centre (MPC) for the Copernicus Sentinel-5 Precursor Satellite”. The satellite data were obtained through Sentinel-5P Expert Users Data Hub (https://s5pexp.copernicus.eu/).

This research was co-funded by the project "PANhellenic infrastructure for Atmospheric Composition and climatE change" (MIS 5021516) which is implemented under the Action "Reinforcement of the Research and Innovation Infrastructure", funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and co-financed by Greece and the European Union (European Regional Development Fund).
Uncertainty in remaining carbon budgets increases with less ambitious targets
Authors: Mentzoni Endre Falck , Johansen Andreas , Martinsen Andreas Rostrup , Rypdal Kristoffer , Rypdal Martin
Published: March 2020

In this work, we present estimates and uncertainties of the remaining carbon budget for a range of different global temperature targets. To model how atmospheric CO2 and methane concentrations depend on emissions, we use impulse response functions estimated from emission-pulse experiments in Earth System Models (ESMs). We use box-model ESM emulators to model the temperature response to radiative forcing and analyze a range of emission scenarios from Integrated Assessment Models. Taking into account uncertainties in the approximately linear relationship between cumulative emission and peak temperature, as well as internal climate variability and uncertainties in the carbon and climate models, we estimate the remaining carbon budgets for varying targets. The results show that the carbon-budget-uncertainties increase significantly with less ambitious targets.
Generic Source Parameter Determination for Earthquake Early Warning: Theory, Observations and Implications for the Mw 7.1 Ridgecrest Earthquake
Authors: ziv alon , Lior Itzhak
Published: March 2020

A generic approach for real-time magnitude and stress drop is introduced that is based on the omega-squared model (Brune, 1970) and results from Lior and Ziv (2018). This approach leads to approximate expressions for earthquake magnitude and stress drop as functions of epicentral distance and ground motion root-mean-squares (rms). Because the rms of the ground motion (acceleration, velocity and displacement) may be calculated directly from the seismogram in the time domain, the use of this approach for automated real-time processing is rather straightforward. Once the seismic moment and stress drop are known, they may be plugged in the ground motion prediction equations (GMPE) of Lior and Ziv (2018) to map the predicted peak shaking.

This method is generic in the sense that it is readily implementable in any tectonic environment, without having to go through a calibration phase. The potential of these results for automated early warning applications is demonstrated using a large dataset of about 6000 seismograms recorded by strong-motion and broadband velocity sensors from different tectonic environments. Optimal real-time performance is achieved by integrating magnitude and stress drop estimates into an evolutionary algorithm. The result of such an evolutionary calculation for the Mw 7.1 Ridgecrest earthquake indicates close agreement with the true magnitude.
Comparison of different geostatistical approaches to estimate wind speed at hourly scale in the province of Granada (Southern Spain)
Authors: Baena-Ruiz Leticia , Collados-Lara Antonio-Juan , Pardo-Igúzquiza Eulogio , Pulido-Velazquez David
Published: March 2020

Wind plays a key role in different processes of the earth system such as the earth's energy and water cycles. The use of the wind to produce clean energy as a substitute of other traditional systems may help to reduce the emission, and, therefore, to mitigate climate change. Wind is defined by two variables, direction and speed. This work is focused on the assessment of the second one. The aim is to estimate wind speed at ten meters (U10) fields in the province of Granada (Southern Spain). A grid with a spatial resolution of 300 m and an hourly temporal resolution has been adopted to estimate it for the period 1986 to 2016. Different geostatistical estimation approaches (ordinary kriging, kriging with external drift, regression and regression kriging) have been evaluated considering a monthly variogram model. Elevation showed a good correlation with wind speed and has been used as secondary variable for the external drift and the regression approaches. We have also tested mesoscale (U80) and logarithm transformations of U10 for each of the geostatistical techniques. The performance of each transformation and geostatistical approach was assessed using a cross validation experiment. In general, geostatistical techniques that takes into account elevation as secondary information and approaches without transformation of data showed better accuracy. The regression kriging without transformation showed the lower mean error and mean squared error (0.03 m s-1 and 3.46 [m s-1]2 respectively) for the considered period but other approaches such as kriging with external drift showed similar results (0.04 m s-1 and 3.52 [m s-1]2 respectively).

This research has been partially supported by the SIGLO-AN project from the Spanish Ministry of Science, Innovation and Universities (Programa Estatal de I+D+I orientada a los Retos de la Sociedad).
Estimation of groundwater recharge from time series modeling of groundwater levels in non-linear systems
Authors: Collenteur Raoul , Birk Steffen , Klammler Gernot , Bakker Mark
Published: March 2020

Groundwater recharge remains a notoriously difficult flux to estimate, despite ongoing scientific efforts. In recent years, time series modeling using impulse response functions has gained popularity to simulate groundwater levels and is quickly becoming a common tool for hydrogeologists. Several approaches have been developed to estimate recharge from time series models for both linear and non-linear systems (e.g., [1], [2], and [3]). In this study, we introduce a novel approach to estimate groundwater recharge from observed groundwater levels in nonlinear systems (i.e., twice the precipitation does not necessarily lead to twice the recharge). We extend a time series model using impulse response functions with a non-linear unsaturated zone module that simulates recharge. The model parameters are estimated by fitting the simulated to the observed groundwater levels, with the groundwater recharge as an intermediate model result. 

The method is tested on a time series of groundwater levels observed in Southeastern Austria (Wagna), where lysimeter data of seepage to the groundwater is available for model validation. The simulated groundwater recharge suggests an event-based recharge behavior, with most recharge occurring shortly after larger precipitation events. This finding agrees with the behavior observed in the lysimeter data. The estimated recharge fluxes show a high correlation with the observed seepage on time scales from years to months or weeks, while daily recharge rates show larger errors. Advantages of the method include limited data requirements (only precipitation, potential evapotranspiration, and groundwater time series are required) and the possibility to correct for other factors causing groundwater level fluctuations (e.g., pumping, river levels). This makes it possible to apply the method in locations where little system knowledge (e.g., soil profiles) is available.

References:
[1] Besbes, M. and De Marsily, G. (1984) From infiltration to recharge: use of a parametric transfer function, Journal of Hydrology.
[2] Peterson, T.J. and Fulton, S. (2019) Joint estimation of gross recharge, groundwater usage, and hydraulic properties within HydroSight, Groundwater.
[3] Obergfell, C., Bakker, M. and Maas, K. (2019) Estimation of average diffuse aquifer recharge using time series modeling of groundwater heads, Groundwater.
Light absorption properties of brown carbon over the western Pacific region
Authors: Pani Shantanu Kumar , Lin Neng-Huei , Lee Chung-Te , Wang Sheng-Hsiang
Published: March 2020

Brown carbon (BrC) is generally emitted during coal combustion, biomass burning, and the formation of secondary organic aerosols. BrC is an exceptional type of organic compound that absorbs the incoming solar radiation efficiently at near-ultraviolet wavelengths and can influence the direct radiative forcing estimates. Lulin Atmospheric Background Station (LABS, 23.47°N, 120.87°E; 2862 m above sea level) on the summit of Lulin Mountain in central Taiwan is the only high-altitude background station in the western Pacific region to study the impact of various long-range transported air pollutants. LABS usually receives the westerly winds coupled with biomass-burning emissions from peninsular Southeast Asia during the springtime. Aerosol measurements are carried out at LABS as a part of the Seven South East Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment (7-SEAS/BASELInE) 2013 spring campaign. Light absorption coefficients are measured by the Aethalometer (AE 31, Magee Scientific, USA). Assuming a negligible contribution from dust, absorption solely due to BrC is estimated by subtracting the absorption of black carbon (BC) from total absorption. The relationships between BrC light absorption and carbonaceous fractions are investigated during the sampling period. The atmospheric radiative forcing due to BrC over the western Pacific region accounts for approximately 30% of that from BC. The detailed results will be presented.
High resolution seismicity catalog of the Marmara Sea region during the 2009-2014 period using template matching
Authors: Karabulut Hayrullah , Lengliné Olivier , Schmittbuhl Jean , Matrullo Emanuela , Bouchon Michel
Published: March 2020

A massive template-matching approach is successfully applied in Marmara Sea region along  the North Anatolian Fault, during the 2009-2014 period to enrich the description of the time and space evolution of the seismicity. Detection of events are performed on the continuous data recorded from 2009 to 2014 combining two types of catalogs as templates: a finely constructed catalog for the three first year (2009-2011) (Schmittbuhl et al, 2016) and a raw catalog from KOERI for the last three years (2012-2014).  Magnitudes (Ml) are estimated for all detected events using relative amplitudes of the highly coherent waveforms between new events and template events. The template database provides a nearly threefold increase of the number of small events (more than 15000 earthquakes compare to the 4673 events of the initial catalog). Combined with a double-difference relocation based on cross-correlation differential travel-time data, the database is shown to be a relevant framework for the long term monitoring of specific remanent structures like seismic swarms or repeating earthquakes. The obtained catalog confirms the strong contrast of behaviors along the Main Marmara Fault (MMF): deep creeping to the west (Central Basin), fully locked in the center (Kumburgaz Basin) and dominated by fluid and off-fault activity to the east (Cinarcik Basin).
Experimental investigations on the temperature and strain-rate dependence of failure and friction criteria for a porous sandstone
Authors: Ahrens Benedikt , Duda Mandy , Saenger Erik H.
Published: March 2020

Understanding the deformation-related thermomechanical state of reservoir rocks under in-situ conditions is essential for modelling the stress distribution and stability of subsurface structures, for example associated with aftershock activity and induced seismicity. Commonly, reservoir modelling approaches make use of the generalized friction criterion according to Byerlee, which distinguishes between depths below and above approximately 6 km. However, numerous studies have shown that thermomechanical rock properties under elevated pressure and temperature conditions differ significantly from those at the surface and among rock types. The significant influence of the geothermal gradient on elastic and inelastic rock properties has already been demonstrated for temperature variations as low as 150 °C. Studies on the effect of in-situ stress and temperature conditions on post-failure behaviour and frictional properties are completely lacking.

In our experimental study we determined the thermomechanical properties of porous Ruhr sandstone samples during conventional triaxial deformation tests to derive stress- and temperature-dependent failure and friction criteria. Effective confining pressures and temperatures applied in the tests cover the range of in-situ conditions equivalent to depths up to three kilometres. Simultaneously, ultrasonic P- and S-wave measurements were performed to determine properties of ultrasound wave propagation (i.e. dynamic elastic properties) as a function of in-situ conditions. Triaxial deformation experiments were conducted at various strain rates to investigate the deformation-rate dependence of the failure and friction criteria and the correlation between dynamic and static elastic properties.
Hypothesis testing and uncertainty propagation in paleo climate proxy data evidencing abrupt climate shifts
Authors: Riechers Keno , Boers Niklas , Fohlmeister Jens , Marwan Norbert
Published: March 2020

Reconstruction of ancient climate variability relies on inference from paleoclimate proxy data. However, such data often suffers from large uncertainties in particular concerning the age assigned to measured proxy values, which makes the derivation of clear conclusions challenging. Especially in the study of abrupt climatic shifts, dating uncertainties in the proxy archives merit increased attention, since they frequently happen to be of the same order of magnitude as the dynamics of interest. Yet, analyses of paleoclimate proxy reconstructions tend to focus on mean values and thereby conceal the full range of uncertainty. In addition, the statistical significance of the reported results is sometimes not or at least not accurately tested. Here we discuss both, methods for rigorous propagation of uncertainties and for hypothesis testing with applications to the Dansgaard-Oeschger (DO) events of the last glacial interval and their varying timings in different proxy variables and archives. We scrutinized the mathematical analysis of different paleoclimate records evidencing the DO events and provide results that take into account the full range of uncertainties. We discuss several possibilities of testing the significance of apparent leads and lags between transitions found in proxy data evidencing DO events within and across different ice core archives from Greenland and Antarctica.
Broad-band electric field measurements above thunderstorms by the IME-HF instrument prepared for the TARANIS mission
Authors: Santolík Ondřej , Kolmašová Ivana , Lán Radek , Uhlíř Luděk , Rauch Jean-Louis , Millet Aude-Lyse , Pincon Jean-Louis
Published: March 2020

A broad-band analyzer of the IME-HF instrument (“Instrument de Mesure du champ Electrique Haute Frequence”) is prepared for the TARANIS (Tool for Analysis of RAdiation from lightNIng and Sprites) micro-satellite of the French space agency CNES. The spacecraft is based on the MYRIADE series platform. It will be launched on a Sun synchronous polar orbit at 700 km altitude. TARANIS will carry a complex payload of six scientific instruments to study radiation from lightning and optical phenomena (Transient Luminous Events) observed at altitudes between 20 and 100 km (blue jets, red sprites, halos, elves). The scientific instruments onboard TARANIS will detect electromagnetic radiation from very low frequencies up to 37 MHz, optical radiation, X rays (with an aim to study the Terrestrial "Gamma-ray" Flashes), and energetic electrons.

The IME-HF instrument will record waveform measurements of fluctuating electric fields in the frequency range from a few kHz up to 37 MHz, with the following scientific aims: (i) Identification of possible wave signatures associated with transient luminous phenomena during storms; (ii)    Characterization of lightning flashes from their HF electromagnetic signatures; (iii) Identification of possible HF electromagnetic or/and electrostatic signatures of precipitated and accelerated particles; (iv) Determination of characteristic frequencies of the medium using natural waves properties; (v) Global mapping of the natural and artificial waves in the HF frequency range, with an emphasis on the transient events. The instrument will be also able to trigger and record interesting intervals of data using a flexible event detection algorithm.
The potential of satellite derived surface state to empirically estimate pan-arctic ground temperature at specific depths and the essential role of in-situ data
Authors: Kroisleitner Christine , Bartsch Annett , Heim Birgitt , Wiezorek Mareike
Published: March 2020

Surface state information, derived from ASCAT microwave sensors (C-band scatterometer), were empirically linked to in-situ arctic ground temperature measurements. The resulting FT2T-regressionmodel was established using the sum of days of year frozen and in-situ mean annual ground temperatures, both at specific depths and years. Regionally, the model showed the best results in Scandinavia and northern Russia with less than 1°C difference to the in-situ data. Overall, the results were valid for most depths and regions, with a slight tendency for underestimation of the ground temperatures on the Eurasian continent (about -1°C) and an overestimation on the American continent up to 2 °C.  The most northern parts of Greenland, the Canadian High Arctic Islands and Alaska, however, showed a high positive bias of more than 10°C. Reasons for this overshooting include the limited amount of measurements in those regions, the oceanic influence and possibly snow cover effects. 
Due to the inaccessibility of many arctic regions, in-situ data availability is still sparse and if available not harmonized. We used the currently revised annual ground temperature dataset from CCI+ Permafrost, which combines in-situ data from the GTNP-database, RosHydroMet and additional regional arctic ground temperature datasets (e.g. Nordicana). The resulting determination coefficients of the FT2T-model showed 55% explained variance at shallow borehole-depths below 80cm and decrease with depth to around 25% at 20 meters. This suggests that the sum of frozen days of year delivers better result at shallow depths in the active layer than at the actual permafrost table. The RMSE showed a dependency on the spread of measurement stations considered in the model calibration step. The more input regions we could use, the larger the RMSE got due to the increase of variability in the input data. Inevitably, it’s the in-situ information which enables the translation between ground temperatures and microwave backscatter and thus it fundamentally affects the accuracy of the result.
The recovery of the Shuram anomaly and paleoproductivity balance
Authors: Cañadas Blasco Fuencisla , Papineau Dominic , Shields Graham , Zhu Maoyan , Li Chao , Leng Melanie J.
Published: March 2020

The global Shuram anomaly records the longest and most negative carbonate carbon isotopic excursion in Earth history. It took place during the late Ediacaran (c. 570 – c. 551 Ma) with δ13Ccarbvalues down to −12‰. In South China, Doushantuo Formation Member IV (c. 555-551 Ma) consists mainly of organic-rich black shales and records the recovery of this anomaly, with values going from –6‰ to +0.5‰. The origin of this anomaly is thought to be related to the existence of a vast pool of dissolve organic carbon (DOC) in the ocean that was episodically oxidized thereby providing a source of 13C-depleted inorganic carbon. However, the main processes that ultimately drove to its recovery remain elusive. Here, we present new δ13Corgand δ15N dataset along a shelf-to-basin transect of the Nanhua basin (South China) as robust organic proxies to reconstruct the spatial and temporal evolution of paleoproductivity at basin scale. In addition, Raman spectroscopy is used to assess the thermal maturity of the samples. These new results define areas of high primary productivity and suggest the existence of an oxygen minimum zone (OMZ) together with other reduced oxic areas. From base to top of Member IV, the observed increasing and covariant trends in δ13Ccarb and δ13Corgdata together with a decreasing drift in δ15N values in platform and mid-lower slope environments are interpreted as areas where primary productivity became the main source of organic matter. Conversely, decreasing trends in δ13Ccarb and δ13Corg data together with invariant δ15N values in the upper slope and deep basin environments are interpreted as areas where reduced DOC dominated as the principal source or organic carbon. Based on that, we propose that a new balance was established between primary and secondary paleoproductivity, whereby the former succeeded to the latter as one of the principal contributors that led to the carbon isotope recovery in carbonates. This new model represents a plausible solution to the enigmatic negative δ13Ccarbisotopic excursion of the late Ediacaran.
Low-elevation of Svalbard glaciers drives high mass loss variability
Authors: Noël Brice , Jakobs Constantijn , Van Pelt Ward , Lhermitte Stef , Wouters Bert , Reijmer Carleen , Van de Berg Willem Jan , Van den Broeke Michiel
Published: March 2020

With a maximum in glaciated area below 450 m elevation (peak in the hypsometry), most Svalbard glaciers currently experience summer melt that consistently exceeds winter snowfall. Consequently, these glaciers can only exist through efficient meltwater refreezing in their porous firn layers. Before the mid-1980s, refreezing retained 54% of the meltwater in firn above 350 m. In 1985-2018, atmospheric warming migrated the firn line upward by 100 m, close to the hypsometry peak, which triggered a rapid ablation zone expansion (+62%). The resulting melt increase in the accumulation zones reduced the firn refreezing capacity by 25%, enhancing runoff at all elevations. In this dry climate, the loss of refreezing capacity is quasipermanent: a temporary return to pre-1985 climate conditions between 2005 and 2012 could not recover the meltwater buffer mechanism, causing strongly amplified mass loss in subsequent warm years (e.g. 2013), when ablation zones extend beyond the hypsometry peak.
Basin scale dissolved oxygen interannual variability of the Mediterranean Sea: Analysis of long-term observations
Authors: Mavropoulou Apostolia-Maria , Vervatis Vassilios , Sofianos Sarantis
Published: March 2020

The Mediterranean Sea is characterized by a combination of long-term trends and climatic shifts known in the literature as “transients”, that impact the biogeochemical processes.  We focus on the dissolved oxygen (DO) concentration, as it is an essential oceanic parameter for the marine ecosystem functioning. Dissolved oxygen distribution in the ocean interior is controlled by air-sea interaction processes, ocean circulation patterns, and biological effects. Understanding the related mechanisms and the variability of the above processes requires systematic oceanographic measurements over long periods and at high spatial resolution. Taking advantage of the Mediterranean monitoring systems, we can examine the sensitive physical and biogeochemical processes in the Mediterranean ecosystem. In this study, we investigate and combine all available data of temperature, salinity and dissolved oxygen over the period 1960-2011 (taking into consideration the scarcity of the available DO observations during the last years). In order to receive a direct and accurate evaluation of the interannual changes in the Mediterranean Sea, we constructed a gridded dataset interpolated into 1/8ο x 1/8ο grid using Data-Interpolating Variational Analysis (DIVA). At the surface layer, the solubility-driven changes determine the dissolved oxygen concentration. In deeper layers, the interannual variability is more related to dynamical processes that may involve dense-water convection, biological consumption or mixing, rather than temperature trends. The observed changes in minimum/maximum oxygen zones are mostly related to abrupt shifts. The attribution of the observed variability involves complex physical and biogeochemical processes as well as anthropogenic activities and requires further analysis using modeling techniques and available operational tools.
Knowledge, Attitudes and Practices on extreme heat: Insights from outdoor workers in Hanoi, Vietnam
Authors: Lohrey Steffen , Chua Melissa , Faucet Jerôme , Lee Jason
Published: March 2020

Purpose: Extreme heat threatens poor urban populations, and particularly those who are economically forced to work in the outdoors and hot environments. Thus, the Vietnamese Red Cross, with technical support from the German Red Cross, is implementing a Forecast-based Financing project to assist vulnerable population groups in urban areas before and during heatwaves. In order to inform this humanitarian project on choosing appropriate early actions, this research investigates empirical evidence on heat vulnerability using data from a “Knowledge Attitudes Practices” (KAP) survey conducted in 2018 among outdoor workers in Hanoi, Vietnam.

Methods: We analyze the outcome of the KAP survey, which comprised 1027 respondents classified into four different occupation groups. Key questions comprised respondents’ self-reported economic and health situation, impacts from past heatwaves, as well as on knowledge about measures reducing health impacts from extreme heat. We first use descriptive statistics to assess the basic properties of the surveyed population groups. We then use a principal component analysis to identify properties that best captured the variability of responses and to identify sub-groups.

Results: The different occupation groups surveyed (builders, vendors, bikers) showed distinctively different properties, not only in mean age (28 year, 45 years and 43 years respectively), but also in their knowledge about heat-health symptoms and their access to night-time air-conditioning (builders: only 14% compared to 42% for bikers). Air-conditioning access did not correlate with reported income.  Builders knew considerably less about heat risk than other groups, but also reported fewer perceived symptoms. The three most common health symptoms reported were tiredness, sweating and thirst, with 22% of respondents having sought medical advice because of heat-related symptoms. Income reduction during heat events was reported by 48% of respondents. The vast majority of respondents have reported to increase drinking (89%) or to remain in shaded areas (87%). Most respondents (76%) could access and understand weather forecasts and early warnings.

Conclusion: Our data and analysis highlight how different occupation groups of outdoor workers in Hanoi vary in their socio-economic properties and their vulnerability to extreme heat. These insights into different groups can be used to direct the implementation of early actions for anticipatory humanitarian assistance before and during heatwaves.
Complexity of low-frequency earthquakes activity in western Shikoku
Authors: Poiata Natalia , Vilotte Jean-Pierre , Shapiro Nikolai , Supino Mariano , Obara Kazushige
Published: March 2020

Short-duration transient seismic events known as low-frequency earthquakes (LFEs) are a component of the slow earthquakes family observed in the transition zone, at the root of seismogenic regions of the subduction zones or active faults. LFEs are the signature of impulse seismic energy radiation associated to and often mixed within complex tectonic tremor signal. Detailed analysis and characterization of LFE space-time activity in relation to other slow earthquake phenomena can provide important information about the state and the processes of fault interface.

We derive a catalog of LFEs in western Shikoku (Japan) by applying a full waveform coherency-based detection and location method to the 4-year continuous data covering the period of 2013-2016 and recorded at Hi-net seismic stations of NIED. The obtained catalog of over 150,000 detected events allows looking into the details of LFE space-time activity during the tectonic tremor sequences and inter-sequence periods.

We use this catalogue of LFEs to perform a systematic statistical analysis of the event occurrence patterns by applying correlation and clustering analysis to infer the large-scale (long temporal ~ 1-2 day duration) space-time characteristics and interaction patterns of activity and its potential relation to the structural complexity of the subducting plate. We also analyze the correlation between the migration of clustered LFE activity during energetic tremor sequences and short-term slow slip events occurring in the area during the analyzed period.
Seismotectonic regions for Germany - Concept and results
Authors: Hahn Tim , Kley Jonas , Kaiser Diethelm , Spies Thomas , Schlittenhardt Jörg , Geisler Claudia
Published: March 2020

Seismotectonic regions are a basic input in seismic hazard assessment. Several seismotectonic regionalizations for Germany were proposed in the past. We are presently developing a new regionalization based on the definition in the Safety Standard of the Nuclear Safety Standards Commission KTA 2201.1 (2011-11): “A seismotectonic unit is a region for which uniformity is assumed regarding seismic activity, geological structure and development and, in particular, regarding neotectonic conditions. A seismotectonic unit may also be an earthquake source region.” Our new concept focusses on a transparent implementation of the required geological criteria. Our approach is to initially analyze those separately from present-day seismicity. Compared to existing source area models we strive for a better documentation and justification of the geological elements used to delimit seismotectonic regions. This includes an analysis of the geological history of structures in six time slices from the Permian to the Present that will be considered in the regionalization. The time slices are (1) Permian, (2) Triassic, (3) Jurassic to Early Cretaceous, (4) Late Cretaceous, (5) Cenozoic > 20 Ma and (6) Recent (< 20 Ma). They were chosen because they are separated by marked changes of stress and kinematic regimes and were associated with the evolution of new fault systems or reactivation of existing ones. The tectonic characteristics of the time slices are briefly described.

The present-day observable fault network comprises faults from all time slices. For each time slice, a subset of active faults will be extracted based on geological evidence for fault activity at that time, e.g. syntectonic deposits. The uncertainties of these age assignments will be documented. The fault subset will be used to estimate overall kinematics, a paleo-stress field and to delimit little deformed or stable areas. Faults, kinematics, stress and stable areas can then be compared to present-day seismicity/active faults, slip directions, stress and undeformed areas as well as other parameters such as crustal and lithospheric thickness. These steps are repeated for each time slice. The superposition of active faults and stable regions across all time slices will identify faults prone to reactivation and regions that remained undeformed over geological time, potentially indicating areas of increased or reduced present-day seismic hazard.

A comparison with seismicity of the last 1000 years shows partial agreement between regions of strong (or repeated) deformation and regions of higher seismicity. On the other hand, stronger earthquakes occasionally cluster in regions appearing stable since Permian time, the Anglo-Brabant Massif being a prominent example of this type.
Dynamics of spatial and temporal outflow from a soil column influenced by earthworm activity
Authors: Bibi Sidra , Van Schaik Loes
Published: March 2020

Earthworms are known as ecosystem engineers, which influence the chemical and physical properties in their own environment and thereby strongly modify soil processes. Soil structure (soil aggregates and macropores) formed by earthworms during burrowing activity may influence the soil moisture retention and water flow, enhancing infiltration into deep soil layers.

We will study the influence of anecic earthworms (Lumbricus terrestris fed on poplar leaves) on the spatial and temporal variability in water outflow and storage through a soil column. Therefore, we established a cylinder (30cm diameter, 50cm high) with silty loamy soil. At the bottom boundary, 15 fiberglass wicks drain the water from the soil column. With these wicks, the water outflow is measured with a spatial and temporal resolution.  After an initial wetting of the soil (), [LvS1] irrigation of the soil cylinder takes place twice per week with a full cone nozzle, with an intensity of 40 mm/h and a duration of 10 minutes. The research design consists of three phases (i) soil-filled column (4 weeks) (ii) transition phase: initial earthworm activity (4 weeks) (iii) soil column with earthworm created structure (4 weeks).

We expect the outflow of water from the soil column to change due to the earthworm activity: on the one hand, the creation of macroaggregates is expected to increase the water retention in the soil and on the other hand, the macropores are expected to create a spatial variability in outflow and a more rapid reaction of outflow to the irrigation events. 
First results of combined ground- and rocket-based measurements for investigation of polar mesospheric winter echoes (PMWE)
Authors: Staszak Tristan , Strelnikov Boris , Latteck Ralph , Renkwitz Toralf , Friedrich Martin , Lübken Franz-Josef
Published: March 2020

Two experimental sounding rockets were launched from Andøya Space Center
(Norway) devoted to investigate the phenomenon of polar mesospheric winter
echoes (PMWE). PMWE are relatively strong radar returns during winter,
observed at various frequencies (e.g. ≈ 50 MHz Maarsy or ≈ 224 MHz with
EISCAT). Despite possible tracing capabilities for dynamics in the Meso-
sphere over a wide annual and altitudinal extend, the formation process is
still not understood. To clarify the formation mechanism and proof theories,
an experimental setup consisting of two rocket payloads were designed. Aim-
ing for measuring neutral air temperature, relative and absolute densities of
plasma constituents (electrons, ions, charged aerosols), neutral air and trace
gases as well as turbulence. In-situ measurements were complemented by
ground based measurements of multiple radars and lidars.
We show results from contemporaneous multi instrumental in-situ measure-
ments and ground based observations based on the first part of the PMWE-
Project and discuss them in the context of most relevant theories.
A Global Landslide Non-Susceptibility Map: variation and applicability
Authors: Jia Guoqiang , Alvioli Massimiliano , Gariano Stefano , Guzzetti Fausto , Tang Qiuhong , Marchesini Ivan
Published: March 2020

Areas non susceptible to landslides are regions where landslides are not expected, or where susceptibility is negligible. Thus they can provide new insights into landslide hazard assessment and land use management and can be targeted as areas for urban planning and dwelling. Non-susceptible landslide areas can be determined with substantially less information as compared with landslide susceptibility. Previous works in Italy and the Mediterranean region and in the USA showed that only morphometric information is needed to distinguish non-susceptible landslide areas. We used 90-m digital terrain data (SRTM DEM V4.1) to calculate global slope and relief maps, and applied globally the quantile non-linear (QNL) model previously obtained in Italy. We define the output map a global landslide non-susceptibility map (GLNSM).  The QNL model is a relationship between terrain relief and slope based on an Italian landslide inventory dataset with high completeness and accuracy. Results indicate that 82.89% of the landmasses are non-susceptible areas across the globe, which is more than the percentage of non-mountainous areas (73.6% based on GEO-GNOME). We further considered GLNSM in relation to global climate, elevation, geology, land use, precipitation and seismicity classifications. High percentage (more than 85.0%) of non-susceptible areas are detected in the tropical and arid, flat (low than 500 m), sedimentary, artificial and high vegetated, less rainy (less than 400 mm per year) and seismicity inactive (less than 0.4) regions. Our results of GLNSM was also validated with some well-represented regional landslide inventory datasets, for which we used four national (Austria, China, Ireland and USA) datasets and nine regional (Arizona, Missouri, Oregon, Utah and Washington in USA, Guangdong and Yunnan in China, and Koshi river region in Nepal) datasets. Applicability of GLNSM reveals that 0.7% of non-susceptible areas are covered by artificial structures, about three times of that in susceptible areas (i.e., not non-susceptible areas), while population density of non-susceptible areas are about twice of that in susceptible areas. About 90.5% of population resides in the non-susceptible areas.
Bayesian inference and uncertainty quantification for source reconstruction of radionuclides release: application to recent European radionuclide detection events
Authors: Dumont Le Brazidec Joffrey , Bocquet Marc , Saunier Olivier , Roustan Yelva
Published: March 2020

In case of an accidental radioactive release, the Institute for Radiological Protection and Nuclear Safety (IRSN) uses atmospheric dispersion models to assess radiological consequences for human health and environment. The accuracy of the models’ results is highly dependent on the meteorological fields and the source term, including the location, the duration, the magnitude and the isotopic composition of the release.

Inverse modelling methods have proven to be efficient in assessing the source term. Variational deterministic inverse methods have been used on the Fukushima accident and are suitable in operational use since they are able of quickly providing an optimal solution.
However the quantification of the uncertainties of the source term assessed is usually not easily accessible. In contrast, Bayesian inverse methods are developed in order to efficiently sample the distributions of the variables of the source, thus allowing to get a complete characterisation of the source.

In this study, we propose to tackle the Bayesian inference problem through two types of sampling methods: Monte Carlo Markov Chains methods (MCMC) with the parallel tempering algorithm and Stein variational gradient descent. The distributions of the control variables associated to the source and the observations errors are presented. To better quantify observations errors, different approaches based on the definition of the likelihood, the reduction of the number of observations and the perturbation of the meteorological fields and dispersion model parameters are implemented.

These different methods are applied on two case studies: the detection of Ruthenium 106 of unknown origin in Europe in autumn 2017 and the accidental release of Selenium 75 from a nuclear facility in Mol (Belgium) in May 2019. For both of these events, we present a posteriori distributions enable to identify the origin of the release, to assess the source term and to quantify the uncertainties associated to the observations, the dispersion model and meteorological fields. Finally, we show that the Bayesian method is suitable for operational use.
Image-velocimetry techniques under particle aggregation for streamflow monitoring: a numerical approach
Authors: Pizarro Alonso , Dal Sasso Silvano Fortunato , Manfreda Salvatore
Published: March 2020

Monitoring extreme events with high accuracy and consistency is still a challenge, even by using up-to-date approaches. On the one side, field campaigns are in general expensive and time-consuming, requiring the presence of high-qualified personnel and forward planning. On the other side, non-contact approaches (such as image velocimetry, radars, and microwave systems) have had promising signs of progress in recent years, making now possible real-time flow monitoring. This work focuses on the estimation of surface flow velocities for streamflow monitoring under particle aggregation, in which tracers are not necessarily uniformly distributed across the entire field of view. This issue is extremely relevant for the computing stream flows since velocity errors are transmitted to river discharge estimations. Ad-hoc numerical simulations were performed to consider different levels of particle aggregation, particle colour and shapes, seeding density, and background noise. Particle Tracking Velocimetry (PTV) and Large-Scale Particle Image Velocimetry (LSPIV) were used for image velocimetry estimations due to their widely used worldwide. Comparisons between the theoretical and computed velocities were carried out to determine the associated uncertainty and optimal experimental setup that minimises those errors.