bluuebunny/crossref_metadata_2025 huggingface dataset:
Undrained loading in basal shear zones modulates the slow-to-fast transition of giant creeping rockslides
Authors: Agliardi Federico , Scuderi Marco M. , Fusi Nicoletta , Collettini Cristiano
Published: March 2020

Giant rockslides creep for centuries and then can fail catastrophically posing major threats to society. There is growing evidence that creeping landslides are widespread worldwide and extremely sensitive to hydrological forcing, especially in climate change scenarios. Rockslide creep is the results of progressive rock failure processes, leading to rock damage accumulation, permeability enhancement and strain localization within basal shear zones similar to tectonic faults. As shear zone accumulate strain, they become thicker and less permeable, favoring the development of perched aquifers. Since then, the creep behavior of mature rockslides becomes dominated by hydro-mechanical interaction with external triggers, e.g. rainfall and snowmelt. However, the mechanisms regulating the slow-to-fast transition toward their catastrophic collapse remain elusive, and statistical and simplified mathematical models used for collapse prediction are usually unable to account for the full spectrum of observed slip behaviors.

Here we couple laboratory experiments on natural rockslide shear zone material, sampled from high quality drillcores, and in situ observations (groundwater level and surface displacement) to investigate the mechanism of rockslide response to short-term pore pressure variations within basal shear zones at the Spriana rockslide (Italy). Using a biaxial apparatus within a pressure vessel, we characterized the strength and permeability of the phyllosilicate-rich shear zone material at in situ stress, as well as the rate and state frictional properties for shear rates typical of the slow-to-fast transition of real rockslides. Then we carried out non-conventional pore pressure-step creep experiments, in which shear stress is maintained at subcritical levels and pore pressure is increased stepwise while monitoring shear zone slip and dilatancy until runaway failure.

Our results, that are quantitatively consistent with in situ monitoring observations, provide a scale-independent demonstration that short-term pore pressure variations originate a full spectrum of creep styles, modulated by slip-induced undrained conditions. Shear zones respond to fluid pressure increments by impulsive acceleration and dilatancy, causing spontaneous deceleration followed by sustained steady-rate creep. Increasing fluid pressure results in high creep rates and eventual collapse. Laboratory experiments quantitatively capture the in situ behavior of giant rockslides, providing physically-based basis to improve forecasting models for giant mature rockslides in crystalline rocks.
Water and sustainability: improving the learning level through an integrated approach
Authors: Riva Marina , Zega Giuliana
Published: March 2020

This activity tooked place last year as a part of a training and internship project (training year) and was developed thanks to the fruitful collaboration of the teacher with her tutor, especially for the co-design and ongoing evaluation of the achieved results.

The project has been carried out, in the same period, on two different classes characterized by widespread liveliness, complex problems of some pupils and/or attention deficit. For these reasons, the teacher experienced continuous interruptions during the lesson that might provoke its ineffectiveness. Moreover, when the class is often disturbed also attentive students have difficulties in following it and, on the other hand, the teacher herself see her efforts frustrated. 

Considering these conditions, the aim of this action-research project was to tackle teaching methods effective in increasing pupils' involvement and therefore improving their learning levels.

The project was about “Water and sustainability”. The main objectives were:

increasing students' knowledge and awareness about water use and preservation and related environmental problems, leaving a trace of increased sensitivity on this topic ;

improving students involvement by raising their attention and stimulating curiosity and questions about phenomena and facts;

encouraging students to explore the problematic situation and build up personal hypotheses and/or interpretative models, and to use ICT in a conscious and correct way.

The project was divided into several phases: engagement, water pollution investigation, work group, learning by doing/enjoying  and final discussion. For each phase, a specific lesson plan was defined with an accurate scheduling and scaffolding of the different proposed activities. Observations with grids and evaluation activities (intermediate and final) were also planned and implemented.

From the evaluation of the projects and of the work groups, carried out by the students, we could observe how the integrated use of diversified teaching strategies, class settings and digital technologies improved the overall level of learning.
Microplastics: All Up in the Air?
Authors: Liss Peter S.
Published: March 2020

It is often said that plastics, and particularly microplastics (<5mm), are all

around us, especially in the oceans where there is much concern about possible harmful

effects on marine life.  The route of entry for plastics to the marine environment is generally

seen to be via rivers acting as a conduit after their production on the land by a whole host of

processes and uses by our societies.   But in all the discussion on the

topic and rapidly growing research activity, the atmosphere barely gets a mention. 

 

But, recently published results show significant amounts of microplastics

in air at a remote terrestrial location in the Pyrenees (Allen et al., 2019, Nature Geoscience

12:339).  However, there appear to be no results from measurements over the oceans.   If

these results from the Pyrenees are representative of the marine atmosphere a simple

calculation indicates a significant atmospheric route for the distribution of microplastics and

their subsequent deposition to the oceans.  If correct such a pathway would lead to the

distribution of microplastics wider and faster than by ocean circulation alone.  It would also

more readily explain why microplastics have been reported recently in Arctic snow

(Bergmann et al., 2019, Sci. Adv. 5: eaax1157).  In addition, it would also lead to a reframing

of our understanding of the budget and distribution of microplastics globally.
Uncertainties of creek evolution in coastal wetlands facing sea-level rise
Authors: Li Xiaorong , Leonardi Nicoletta , Plater Andy
Published: March 2020

Adaptation of coastal areas facing climate change is a global challenge. Some of these low‐lying regions are commonly managed and engineered to reduce damage, loss of life, and environmental degradation caused by natural hazards originating from the sea. However, sea-level rise and changes in storm regimes are putting unprecedented pressure on these managed systems, forcing the adoption of “no active intervention” or “managed realignment” strategies in areas where “hold the line” options cannot be justified due to financial constraints. The aim of this research is to explore how disintegration of sea defences would affect creek topology under present day and future sea level rise scenarios, using the Hesketh marsh as a case study.  A reduced complexity numerical model is applied to produce ensemble predictions for analysis. Without the presence of vegetation, results suggest that creek geometry efficiency and density of tidal creeks are insensitive to sea level rise.

The model assumes the erodibility of the wetland is homogeneous and constant which leaves room for improvement because coastal environment is subject to changes as a result of global climate change and human activities. Changes in environmental stressors, such as sea level rise, elevated CO2 concentration, changing storm patterns, etc. could adjust the resistance of the wetland to erosion in either way. Hence, the adequacy of current parameterizations of soil erodibility in numerical models requires further investigation.
Biochar production from waste biomass: Characterization and evaluation for potential applications
Authors: Pellera Frantseska-Maria , Regkouzas Panagiotis , Manolikaki Ioanna , Diamadopoulos Evan
Published: March 2020

In the last years, global focus has been directing towards the circular economy model. In this framework materials that had so far been regarded as waste, are now considered as valuable resources for both energy and added-value materials recovery. In this context, more and more valorization methods and technologies are being developed for waste valorization, with biomass materials of municipal and agroindustrial origin constituting ideal options, due to both composition and availability.

Biochar generation from waste biomass is a method with high potential for effectively valorizing such residual resources, by providing not only a waste management option, but also multiple agronomic and environmental benefits. In fact, biochar materials are characterized by high versatility as far as their applications are concerned. Due to their wide variety of properties, biochars can be used in various applications, such the use as an adsorbent for contaminant removal from water or wastewater, or the use as an amendment for improving soil characteristics and remediating contaminated sites.

In the present study, six different waste biomass feedstocks, specifically three of municipal origin, namely two types of sewage sludge and the organic fraction of municipal solid waste, and three of agroindustrial origin, namely grape pomace, rice husks and exhausted olive pomace, were used to generate biochar through pyrolysis at two different temperatures, i.e. 400 and 600 °C. The resulting carbonaceous materials were then characterized through a series of analyses. Based on both physical and chemical biochar properties, it was able to evaluate their potential use in different applications, for agronomic or environmental purposes.
Rootzone storage potential indicates the extent of rainforest resilience
Authors: Singh Chandrakant , van der Ent Ruud J. , Fetzer Ingo , Wang-Erlandsson Lan
Published: March 2020

Change in rainfall patterns and extended drought events can cause water stress in the rainforest which can also lead to a permanent shift of the biome into a savanna state. Rainforest in response may adapt to such environmental stress conditions to sustain ecosystem functioning or reduce functioning altogether. Previous studies related to forest resilience have mostly relied on precipitation or climatological drought as a control variable, but neither is a direct measure of forest resilience. As such, forest adaptability dynamics of the forest is poorly understood. Our research defines this adaptation capacity of vegetation as a dynamic reserve which rainforest can utilize before a potential shift to an alternate stable state, as the resilience of the rainforest. Here, we introduce the Rootzone Storage Potential (RZSP) as a direct water stress metric to understand adaptive forest resilience behaviour, using the cumulative difference between precipitation and potential evaporation (radiation-based). Since the potential evaporation used for RZSP calculation is purely radiation-based, it minimizes the effect of moisture recycling (and transport) on the system. RZSP is the potential of vegetation to optimize their resources enduring the greatest dry period. In this study, we have investigated the spatio-temporal resilience loss of the South American and African rainforest. An increasing trend of resilience loss was observed in the past few decades. Using RZSP is a useful indicator for estimating resilience dynamics and water stress characteristics of the rainforest. 
Trend analysis and transient climate sensitivity revealed by CMIP6
Authors: Yuan Menghan , Leirvik Thomas
Published: March 2020

CMIP6 (Coupled Model Intercomparison Project Version 6) is currently publishing updates on simulations for Global Climate Models (GCMs). In this paper, we focus on analyzing surface temperature and downward solar radiation (SDSR), which are two essential variables in estimating the transient climate sensitivity (TCS). We carry out the analysis for five GCMs that have published data at the moment. More GCMs will be included in the analysis when data is available. The research period dates from 1960 to 2014, providing the latest available projection for climate forcings. Temperature projections accord reasonably well with observations. This is no surprise, as data for CMIP5 was also aligned with observations.  On the other hand, a striking improvement has been observed with respect to SDSR. According to Storelvmo et al. (2018), CMIP5 models showed no statistically significant trend over time and revealed egregious mismatch with observations, casting major concerns about their fidelity. The data from CMIP6 models, however, this mismatch between simulations and observations is substantially alleviated. Not only is a negative trend recorded, but the significant fall around the beginning of the 1990s, due to the Mount Pinatubo eruption, is also reproduced, though with a slightly smaller scale compared to the observations in that period.
Based on the econometric framework from Phillips et al. (2019), we estimate the TCS for five GCMs. We find that the TCS estimates range from 2.03K to 2.65K. Each reported TCS for the five GCM’s are within it’s corresponding 95% confidence interval for the estimated TCS. It is worth noticing that a 25-year rolling window estimation indicates that average TCS for the GCMs varies greatly along time, though it has a significant upward trend from the beginning of the 1990s until 2009, and flattens, or even decreases, afterward.
We also compute the sample average of the TCS estimates. We find that for the period 1964-2005, which is used in Phillips et al. (2019), the average TCS is 1.82 for the CMIP5 models, and 2.07 for CMIP6. The difference is not significant. For the 1964-2014 period, however, the average TCS estimate for CMIP6 is 2.38, which is significantly higher than the average CMIP5 estimates. Since we find that the CMIP6 simulations reproduce observed trends in RSDS much better than the CMIP5 simulations, when compared to observations, this indicates both that the econometric framework of Phillips et al.(2019) is working very well and captures key drivers of the climate, and that the true TCS is most likely closer to the estimated TCS for observations.
Vertical profiles of wind gust statistics from a regional reanalysis using multivariate extreme value theory
Authors: Steinheuer Julian , Friederichs Petra
Published: March 2020

Wind and gust statistics at the hub height of a wind turbine are important parameters for the planning in the renewable energy sector. However, reanalyses based on numerical weather prediction models typically only give estimates for wind gusts at the standard measurement height of 10 m above the land surface. We present here a statistical post-processing that gives a conditional distribution for hourly peak wind speeds as a function of height. The conditioning variables are provided by the regional reanalysis COSMO-REA6. The post-processing is developed on the basis of observations of the peak wind speed in five vertical layers between 10 m and 250 m of the Hamburg Weather Mast. The statistical post-processing is based on a censored generalized extreme value (cGEV) distribution with non-stationary parameters. To select the most meaningful variables we use a least absolute shrinkage and selection operator. The vertical variation of the cGEV parameters is approximated using Legendre polynomials, allowing gust prediction at any desired height within the training range. Furthermore, the Pickands dependence function is used to investigate dependencies between gusts at different heights. The main predictors are the 10 m gust diagnosis, the barotropic and baroclinic modes of absolute horizontal wind speed, the mean absolute horizontal wind in 700 hPa, the surface pressure tendency and the lifted index. Proper scores show improvements of up to 60 %, especially at higher vertical levels when compared to climatology. The post-processing model with a Legendre approximation is able to provide reliable predictions of gust statistics at unobserved intermediate levels. The strength of the dependence between the gusts at different levels is not stationary and strongly modulated by the vertical stability of the atmosphere.
Spatial sampling approach to unravel the impact of soil texture and root genotype on maize root gene expression profiles
Authors: Ganther Minh , Bouffaud Marie-Lara , Gebauer Lucie , Buscot François , Vetterlein Doris , Heintz-Buschart Anna , Tarkka Mika
Published: March 2020

The complex interactions between plant roots and soil microbes enable a range of beneficial functions such as nutrient acquisition, defense against pathogens and production of plant growth hormones. The role of soil type and plant genotype in shaping rhizosphere communities has been explored in the past, but often without spatial context. The spatial resolution of rhizosphere processes enables us to observe pattern formation in the rhizosphere and investigate how spatial soil organization is shaped through soil–plant–microbiome interactions.

We applied spatial sampling in a standardized soil column experiment with two maize genotypes (wildtype vs. roothairless3) and two different soil textures (loam vs. sand) in order to investigate how in particular functions of the maize roots relating to nutrient/water uptake, immunity/defense, stress and exudation are affected. RNA sequencing and differential gene expression analysis were used to dissect impact of soil texture, root genotype and sampling depth. Our results indicate that variance in gene expression is predominantly explained by soil texture as well as sampling depth, whereas genotype appears to play a less pronounced role at the analyzed depths. Gene Ontology enrichment analysis of differentially expressed genes between soil textures revealed several functional categories and pathways relating to phytohormone-mediated signaling, cell growth, secondary metabolism, and water homeostasis. Community analysis of rhizosphere derived ACC deaminase active (acdS gene including) plant beneficial bacteria, which suppress the phytohormone ethylene production, suggests that soil texture and column depth are the major factors that affect acdS community composition.

From the comprehensive gene expression analyses we aim to identify maize marker genes from the relevant core functional groups. These marker genes will be potentially useful for future experiments; such as field plot experiments for investigation of later-emerging plant properties.

This research was conducted within the research program “Rhizosphere Spatiotemporal Organisation – a Key to Rhizosphere Functions” of the German Science Foundation (TA 290/5-1).
The pigment antenna constraining the light reactions: photosynthetic energy redistribution indicated by leaf absorbance changes
Authors: Van Wittenberghe Shari , Laparra Valero , Ignacio Garcia Nacho , Alonso Luis , Fernandez Marín Beatriz , Malenovsky Zbynek , Porcar-Castell Albert , Moreno Jose
Published: March 2020

The solar energy absorbed by the vegetation light-harvesting antenna complexes supplies the photosynthetic light reactions with a highly efficient transfer of quantum energy. The absorbed energy is efficiently transferred from one molecule to another, until being used by the reaction centres for the further carbon reactions. The energy transfer to the reaction centres is hereby highly regulated by the variable aggregation of pigments in the antenna complexes, allowing for quick and slower adjustments according to the incoming solar radiance. To control and protect the pigment antenna and the reaction centres from a potentially harmful solar radiance excess, these regulated photoprotective mechanisms are activated at different time scales at the antenna level, allowing vegetation to adapt to changing light conditions. The understanding of these energy regulative processes from optical measurements is essential in order to monitor plants' adaptation strategies to stressful environments and changing climates from remote sensing data.

Using high-spectral resolution leaf spectroscopy in a controlled laboratory set-up, we have observed detailed and significant absorbance shifts controlled by the pigment antennas themselves. Simultaneous measurements of both upward and downward spectrally-resolved leaf radiance (Lup(λ), Ldw(λ), W m-2 sr-1 nm-1) allowed us to observe the specific absorbance changes at leaf level, including changes in chlorophyll (Chl) a fluorescence emission (Fup(λ), Fdw(λ), W m-2 sr-1 nm-1). Interestingly, these changes due to shifts in energy redistribution were: 1) observed in the PAR region and even far beyond 700 nm, and 2) indicated a prominent role of both Carotenoid and Chl a molecules in the creation of alternative energy sinks, i.e. constraining the energy transfer to the reaction centres. Hereby, a significant redistribution of photosynthetic light energy was observed in the 500-800 nm range, highlighting this spectral region to be of potential interest for remote sensing. We further revealed that these energy redistributions do not necessary occur in parallel with Chl a fluorescence changes, illustrating the importance of different energy redistribution mechanisms constraining the photosynthetic light reactions. To conclude, a good quantitative understanding of all mechanisms of energy regulation in plants based on VIS-NIR wavelengths is essential 1) to be able to understand these trends using remote sensing data, 2) to better model the adaptations of vegetation to changing climate and environmental conditions, and 3) potentially better predict future trends in dynamic global vegetation models.
A method to fill-in discontinued daily precipitation series from nearby stations
Authors: Grillakis Manolis G. , Polykretis Christos , Alexakis Dimitrios D.
Published: March 2020

Cornerstone of the meteorological and climatological science is the quality measurements of the precipitation. Large instrumentation gaps occur due to network destructions (fires, wars) or even technical limitations that dictate network reorganizations. This is a difficult to tackle issue as there are legacy networks that provide decades of valuable data, but for various reasons have been discontinued. A method to work out such problems is to include only part of the data to the analyses, or to use methods to fill the measuring gaps from nearby stations, such as interpolation techniques, regression techniques. In this work, we present and assess a method to estimate missing values in daily precipitation series based on a quantile mapping approach, originally used for bias correction of climate model output. The overall methodology is based on a three-step procedure. The first is to assess the missing values from nearby stations using inverse distance weighting interpolation method. Then, as a second step, the wet day fraction is adjusted to fit the respective fraction of the target point existing data. The third step is to adjust the biases in the probability density function of the filled values towards the target point existing data, using the Multi-segment Statistical Bias Correction methodology (MSBC- Grillakis et al., 2013). The methodology is applied to each calendar month separately. The presented methodology has the advantage of correcting the number of rainy days that is usually overestimated by conventional interpolation approaches, as well as, better reproduces large daily precipitation values. The methodology is assessed for its performance on completing the timeseries of a dense precipitation stations network, using data of a second, also dense station network for the island of Crete – Greece. Conceptual limitations of the method are discussed.

Acknowledgments: This research has received funding from the Hellenic Foundation for Research and Innovation (HFRI) and the General Secretariat for Research and Technology Hellas (GSRT), under Agreement No 651.
A novel masking technique to investigate atmosphere-ocean interaction over Western Boundary Currents
Authors: Hayashi Fumi
Published: March 2020

Western Boundary Currents (WBC), such as the Gulf Stream, leave a strong imprint on the ocean-atmosphere boundary in the form of strong gradients and high variability of Sea Surface Temperature (SST). Recent studies have shown that midlatitude oceanic fronts have an influence throughout the depth of the troposphere by means of synoptic systems such as weather fronts. An understanding of how the midlatitude ocean influences the synoptic system is crucial for better climate projection, however, this has been challenging. For example, in model simulations the sensitivity of the atmosphere to SST anomalies are dependent on its resolution, with low resolution models unable to capture the air-sea interactions occurring over warm sectors of midlatitude cyclones, possibly leading to underestimations of the oceanic influence on the atmosphere. A novel modelling technique is developed in which an interactive “mask” is used to systematically isolate and study the air-sea interaction over different synoptic regimes (warm and cold sector). Here, simulations using an idealised aqua-planet atmospheric general circulation model (AGCM) are used to study the atmospheric response to a tightening of SST gradient (comparable to that of the Gulf Stream) over the cold sector (“cold path”) and the warm sector (“warm path”) separately. Same experiments will also be performed on models with higher resolution to investigate the difference in atmospheric response between the high and low resolution models and what physical processes are responsible for such change in response.
The opening of the Tyrrhenian basin and the Apennine chain formation in the kinematic context of Africa - Europe collision
Authors: Turco Eugenio , Macchiavelli Chiara , Pierantoni Pietro Paolo , Penza Giulia , Schettino Antonio
Published: March 2020

The Africa Europe collision, which produces the formation of the Alpine arc, in the Mediterranean area is accompanied by passive subduction processes, resulting from the sinking of the remnant Alpine Tethys and the Ionian lithosphere, and from the fragmentation of the Adriatic plate. In this complex deformation, back-arc basins (Alboran, Balearic, Tyrrhenian and Hellenic) and circum - Mediterranean mountain ranges are formed.

In this work we focus our attention on the opening of the Tyrrhenian basin and the contemporary formation of the Apennine chain.

In order to describe the evolution of the geodynamic processes that guided the formation of the Tyrrhenian basin and the Apennine chain we used the plate kinematics technique. Through careful observation of the regional structures we have divided the area of the Apennine Chain and the Tyrrhenian basin into polygons (crustal blocks or microplates) distinguished on the basis of the direction of the Tyrrhenian extension. The boundary between the polygons has been placed coinciding with the large structures that characterize the Tyrrhenian-Apennine area. The rotation poles of the individual polygons, in the frame of reference of the Sardo-Corso block, are based on the Tyrrhenian extension directions that characterize them. The velocity ratio between the polygons was determined by the slip vector of the structure (plate boundary) that separates them. To determine the rotation time of the polygons we used the stratigraphic records of the syn-rift sequences, while the rotation angle of the polygons is obtained comparing the crustal balance with the speed ratios.

Finally, the kinematic framework obtained, included in the global rotation model, allowed us to reconstruct the tectonic evolution of the central Mediterranean during the opening of the Tyrrhenian basin.

Key Words: Tyrrhenian-Apennine System, Non-rigid plate kinematics.
Causal Teleconnection between Pacific Decadal Oscillation and Droughts over India
Authors: Gupta Vivek , Jain Manoj Kumar
Published: March 2020

Droughts are recurring natural phenomena having devastating impacts on the ecosystem and agro-economics in almost every part of the world. The hazard caused by drought costs more than any other natural calamity. Better prediction of droughts may result in better preparedness which, in turn, helps in reducing the hazard caused by droughts. In many parts of the world, drought events have been found to possess a link with the Pacific Decadal Oscillation (PDO). A better understanding of this relationship may help us in improving the drought prediction models. However, for India, the nature of this relation largely remained unexplored. Therefore, to quantify the causal relationship between PDO and droughts in India, a Granger Causality test-based methodology has been explored. Results of the linear Granger Causality test have been compared against a recently developed neural-network-based nonlinear Granger causality-based test for Standard Precipitation Evapotranspiration Index (SPEI) at 3, 6, 9, and 12-month scales.  The results of this study suggest the significant causal teleconnections between PDO and droughts in most parts of India at all analyzed scales. Further, it was found that the nonlinear model is able to capture significant causality for more parts of the country than the traditional linear model.
Salinization sources and management strategies in South Africa
Authors: Elenius Maria , Bartosova Alena , Musuuza Jude , Arheimer Berit
Published: March 2020

Irrigation practices of various kinds are used in farming all over the world. Especially in cases of over-irrigation and inadequate drainage, evaporation losses can be high and lead to accumulation of minerals in the soils. Water uptake in crops is driven by osmosis, and as such it is reduced or diminished when salt concentrations in the soil water increase. Today, approximately 10 % of irrigated land worldwide has faced diminished production due to salinization, and losses increase every year. There is also concern that global warming can deteriorate production further due to increased evaporation, which should be considered in the light of increasing crop demands with population growth. There is therefore pressing concern to study effects and measures on a global scale.

Continental to global scale hydrological models have emerged in recent years as tools for flood forecasting and estimation of dynamic water fluxes. HYPE is a catchment-based model that simulates rainfall-runoff as well as water quality processes. Recently, an application was developed based on HYPE that covers almost the entire globe, World Wide HYPE (Arheimer et al., 2019). This tool also has great potential for future global assessments of soil salinization under different scenarios.

In this work, a salinization routine was developed in HYPE, whereby salt components follow all main natural hydrological pathways as well as irrigation using groundwater or river flow as a water source. Equilibrium reactions, complexation and cation exchange determine the distribution between dissolved and solid states in the soil. A semi-arid catchment in South Africa with salinization issues (the Crocodile River, Mpumalanga province) was chosen for code development, calibration and verification. Evaluations were based on comparison of simulated and observed mineral concentrations in rivers and groundwater. The model was also tested for all of South Africa.

Detailed analyses of the soil salinity processes were carried out for the Crocodile River catchment. Results show the sensitivity of salinization to hydrological parameters such as recession coefficients, infiltration capacities and macropore flow. This will guide future calibration of the World Wide HYPE model setup. Assessment of the major processes and sources of salinization is performed, and mitigation strategies such as irrigation control and drainage management are tested. Possible regionalization of parameters for global salinization modeling is also suggested based on the results.

Arheimer, B., Pimentel, R., Isberg, K., Crochemore, L., Andersson, J. C. M., Hasan, A., and Pineda, L. (accepted). Global catchment modelling using World-Wide HYPE (WWH), open data and stepwise parameter estimation, Hydrol. Earth Syst. Sci, https://doi.org/10.5194/hess-2019-111, in press, 2019
Late Pleistocene glacial chronologies in the Balkans: new 36Cl exposure-age dating from Montenegro and Greece
Authors: Allard James , Hughes Philip , Woodward Jamie , Fink David , Simon Krista , Wilcken Klaus , Tomkins Matt
Published: March 2020

The timing and extent of mountain glaciation during the Late Pleistocene shows considerable variability around the world. Identifying the nature and timing of glaciation is important for understanding landscape evolution and changing climatic conditions (precipitation and temperature). In the Balkans, glaciers were actually larger during the Middle Pleistocene when large ice caps formed in several mountain ranges including the Dinaric Alps, Montenegro, and the Pindus Mountains, Greece. Glaciations younger than Marine Isotope Stage 6 were characterised by smaller ice masses with glaciers mainly restricted to the highest mountains. The behaviour of Late Pleistocene glaciers in this region influenced the timing of sediment and meltwater delivery to river systems; the migration of modern humans across Europe; and the dynamics of biological refugia. However, dating control is limited for Late Pleistocene glaciers in the Balkans.

Here we report new in-situ 36Cl terrestrial cosmogenic nuclide exposure ages from moraine boulders sampled in the Velika Kalica valley, in the Durmitor massif, Montenegro. This valley was targeted because it contains the Debeli Namet glacier - the last remaining glacier in Montenegro. We have sampled 25 limestone boulders from 5 moraines situated down-valley of the current glacier at altitudes between 1650–2000 m. AgCl targets for 36Cl assay were prepared at The University of Manchester and 36Cl concentrations were measured on the SIRIUS 6MV accelerator at the Centre for Accelerator Science at the Australian Nuclear Science and Technology Organisation. At the last local glacial maximum, the Debeli Namet glacier extended almost 3 km beyond its current position. These 36Cl analyses are part of a wider regional Mediterranean study, totalling >50 new exposure ages, which also includes Mount Tymphi in the Pindus Mountains, NW Greece. The project will address both a significant spatial and temporal gap in Mediterranean glacial chronologies by targeting the hitherto undated Late Pleistocene glacial record. The work in Montenegro will also shed light on the nature of Holocene glaciation in the Balkans.
The Stokes drift in ocean surface drift prediction
Authors: Tamtare Michel Tamkpanka , Dumont Dany , Chavanne Cédric
Published: March 2020

Ocean surface drift forecasts are essential for numerous applications. It is a central asset in search and rescue and oil spill response operations, but it is also used for predicting the transport of pelagic eggs, larvae and detritus or other organisms and solutes, for evaluating ecological isolation of marine species, for tracking plastic debris, and for environmental planning and management. The accuracy of surface drift forecasts depends to a large extent on the quality of ocean current, wind and waves forecasts, but also on the drift model used. The standard Eulerian leeway drift model used in most operational systems considers near-surface currents provided by the top grid cell of the ocean circulation model and a correction term proportional to the near-surface wind. Such formulation assumes that the 'wind correction term' accounts for many processes including windage, unresolved ocean current vertical shear, and wave-induced drift. However, the latter two processes are not necessarily linearly related to the local wind velocity. We propose three other drift models that attempt to account for the unresolved near-surface current shear by extrapolating the near-surface currents to the surface assuming Ekman dynamics. Among them two models consider explicitly the Stokes drift, one without and the other with a wind correction term. We assess the performance of the drift models using observations from drifting buoys deployed in the Estuary and Gulf of St. Lawrence, Canada. Drift model inputs are obtained from regional atmospheric, ocean circulation, and spectral wave models. The performance of these drift models is evaluated based on a number of error metrics (e.g. speed, direction, separation distance between the observed and simulated positions) and skill scores determined at different lead times ranging from 3h to 72h. Results show that extrapolating the top-layer ocean model currents to the surface assuming Ekman dynamics for the ageostrophic currents, and adding the Stokes drift predicted by a spectral wave model, leads to the best drift forecast skills without the need to include a wind correction term.
Measuring and modelling high resolution rainfall fields for hydrologic process understanding
Authors: Benoit Lionel , Michelon Anthony , Schaefli Bettina , Mariéthoz Grégoire
Published: March 2020

Observing and modelling rainfall at high spatial and temporal resolution is known to be key for hydrologic applications in urban areas, but little is known about the relevance of high density observations in natural headwater catchments. In this contribution, we present the case of the Vallon de Nant experimental catchment (Switzerland) where high resolution rainfall observations have been carried out with low cost (drop-counting) sensors to develop a new sub-kilometer scale stochastic rainfall model and to investigate the relevance of high resolution rainfall observations to understand the rainfall-runoff response of a small alpine headwater catchment (13.4 km²).

We will give an overview over the experimental set-up (in place for two consecutive summers), the reliability of the used sensors (Driptych Pluvimate) and the potential of such a network to inform high resolution stochastic rainfall field models and hydrologic models. A special focus will be on the developed methodological framework to assess the importance of high resolution observations for hydrological process research. Given the relatively low cost of the deployed rainfall sensors (around 600 USD each), the presented methods are readily transferable to similar hydrologic settings, in natural as well as urban areas.
Long-term monitoring of neutron component of radiation background onboard International Space Station.
Authors: Litvak Maxim , Golovin Dmitry , Kozyrev Alexander , Mitrofanov Igor , Sanin Anton
Published: March 2020

The Board Telescope of Neutrons (BTN) is a neutron spectrometer which was installed outside of the Russian “Zvezda” module of the International Space Station (ISS) in November 2006. The main goals of this experiment include measurement of neutron flux in broad energy band from low epithermal neutrons (>0.4 eV) up to fast neutrons (<15 MeV); investigation of its spatial variations at low and high geomagnetic latitudes above the South Atlantic anomaly (SAA) and at different orbital altitudes; observations of  GCR variations on different time scales from orbital fluctuations to variations affected by the 11-year solar cycle; estimation of the neutron component of radiation background outside ISS during various flight conditions in near-Earth orbit.

In this study we present measurements of neutron-flux spectral density in the vicinity of the International Space Station (ISS) based on BTN-Neutron space experimental data for the period 2007-2019. Neutron flux shows space and time variations. It varies by several orders of magnitude between equatorial latitudes and flybys across South Atlantic anomaly region. The time profile of neutron flux also demonstrates long-periodic variations produced by variations of GCRs and modulated by 11 year solar cycle. The observed amplitude of such variations is about two times. We have compared it with other space neutron monitors installed on Moon (NASA/LRO), Mars (NASA/Odyssey, ESA/ExoMars)and Mercury (ESA/BepiColombo) missions.   

We also used neutron measurements to evaluate biological impact contributed by neutrons and expressed in neutron equivalent dose rate.  
Antarctic ice-sheet hysteresis in a three-dimensional hybrid ice-sheet model
Authors: Montoya Marisa , Alvarez-Solas Jorge , Robinson Alexander , Blasco Javier , Tabone Ilaria , Moreno Daniel
Published: March 2020

Ice sheets, in particular the Antarctic Ice Sheet (AIS), are considered as potential tipping elements (TEs) of the Earth system. The mechanism underlying tipping is the existence of positive feedbacks leading to self-amplification processes that, once triggered, dominate the dynamics of the system. Positive feedbacks can also lead to hysteresis, with implications for reversibility in the context of long-term future climate change. The main mechanism underlying ice-sheet hysteresis is the positive surface mass balance-elevation feedback.  Marine-based ice sheets, such as the western sector of the AIS, are furthermore subject to specific instability mechanisms that can potentially also lead to hysteresis. Simulations with ice-sheet models have robustly confirmed the presence of different degrees of hysteresis in the evolution of the AIS volume with respect to model parameters and/or climate forcing, suggesting that ice-sheet changes are potentially irreversible on long timescales. Nevertheless, AIS hysteresis is only now becoming a focus of more intensive modeling efforts, including active oceanic forcing in particular. Here, we investigate the hysteresis of the AIS in a three-dimensional hybrid ice-sheet--ice-shelf model with respect to individual atmospheric forcing, ocean forcing and both. The aim is to obtain a probabilistic assessment of the AIS hysteresis and of its critical temperature thresholds by investigating the effect of structural uncertainty, including the representation of ice-sheet dynamics, basal melting and internal feedbacks.
A multi-mode model applied to the tropical oceans
Authors: Dunkel Markus , Claus Martin , Greatbatch Richard
Published: March 2020

A new model for the tropical ocean is described in which variations in the vertical are taken care of using vertical normal modes and the horizontal structure is taken care of by a set of linear shallow water models. The code is written in python and run in parallel and uses domain splitting in the horizontal. The model can be run in fully nonlinear mode and using generalized vertical mixing. The advantage of this approach is an almost continuous representation in the vertical and the ability to easily diagnose mode-mode interactions. The model performance is illustrated using the model of McCreary. In its original form, the McCreary model is linear and uses a very special form for the vertical mixing. Here we show preliminary results using more general vertical mixing and including nonlinearity.
Seismo-Acoustic Shockwave Isolation for Low-Yield Local Explosions
Authors: Dickey Joshua , Pasyanos Michael , Martin Richard , Peña Raúl
Published: March 2020

Seismic and acoustic recordings have long been used for the forensic analysis of various natural and anthropogenic events, especially in the realm of nuclear treaty monitoring. More recently, multi-phenomenological analysis has been applied to these signals with great success, providing unique constraints for studying a broad range of source events, including man-made noise, earthquakes and explosions. In particular, the fusion of seismic and infrasonic data has proven valuable for the analysis of explosive yield, significantly improving on the yield estimates obtained from either seismic or acoustic analysis alone.

Unfortunately, the seismo-acoustic analysis of local explosions is complicated by the fact that the two phenomena are potentially co-dependent. Large seismic waves displace the earth like a piston, potentially inducing acoustic waves into the atmosphere as they pass. Similarly, large acoustic waves can couple into the earth, inducing ground motion along their path. This co-dependence can be problematic, particularly when the passing acoustic shockwave couples into the earth coincident with a seismic phase arrival, thereby corrupting the signal.

To address this problem, we present a method for isolating the shockwave response of a seismic sensor, such that any underlying seismic phase arrivals can be recovered. This is accomplished by employing the adaptive noise cancellation model, where a co-located infrasound sensor is used as a reference measurement for the shockwave. In this model, the adaptive filter learns the transform between the relative atmospheric pressure (as recorded by the infrasound sensor), and the resulting ground motion (as recorded by the seismometer). In this way, the filtered infrasound recording approximates the seismic shockwave response, and can be subtracted from the seismograph to recover the phase arrivals.

The experimental data comes from a set of three low-yield near-surface chemical explosions conducted by LLNL as part of a field experiment, known as FE2. The explosions were recorded at eight stations, located at varying distances from the source (between 64m and 2km), with each station consisting of a co-located three-component seismic velocity transducer and differential infrasound sensor. The adaptive technique is demonstrated for recovering seismic arrivals in both the vertical and horizontal channels across all eight stations, and evaluated using leave-one-out cross-validation across the three explosions.
On the understanding of the trade-wind cumuli daily cycle: the role of convective mixing and mesoscale organization of convection
Authors: Vial Jessica , Schulz Hauke , Vogel Raphaela
Published: March 2020

Oceanic shallow convective clouds, which prevail in the trade-wind regions, have long been of great interest, because they strongly impact climate on a wide range of scales and they are critical in the estimation of the magnitude and pace of global warming. But surprisingly, the most fundamental mode of tropical variability, that is the daily cycle, has received very little attention for this cloud category, so that our knowledge of the diurnal processes in this oceanic shallow cumulus regime and their influence on climate at broader scales remains extremely limited. We recently relaunched the exploration of this topic. New investigating tools have been used, including large-eddy simulations run over large domains in realistic configurations and in-situ observations from the Barbados Cloud Observatory, which have helped study this daily cycle in the North Atlantic trade-wind region with a lot more details than was possible 40 years ago when it was first documented. Important features of this daily cycle have been found, which can have far reaching implications for climate change studies. Our hypothesis is that understanding the processes that control trade-wind cumuli on the diurnal timescale will benefit to our understanding of the mechanisms that are involved in the tropical marine low-level cloud feedbacks. In this regard, the wealth of observational data that will be collected during the EUREC4A campaign is unprecedented and offers a tremendous opportunity to enrich the characterisation and understanding of the mechanisms of the trade-wind daily cycle. Preliminary results will be discussed with a focus on the role of the shallow convective mixing and mesoscale organization in the daily cycle of trade-wind cumuli.