bluuebunny/crossref_metadata_2025 huggingface dataset:
Acceleration of Planetary Ions by Different Electric Field Terms in an Induced Magnetosphere
Authors: Wang Xiao-Dong , Fatemi Shahab
Published: March 2020

We report the preliminary results of a hybrid simulation to differentiate and quantify the energy gain due to different electric field terms in the acceleration of planetary ions escaping from an induced magnetosphere. 

The planetary ions gain energy from the electric field formed in the induced magnetosphere. The electric field is not directly measurable and thus has to be expressed by the generalized Ohm's law with measurable quantities:

E = -Ve×B - ∇Pe/(qene) + j×B/(qene)

Where Ve is the velocity of the electrons that freeze the magnetic field B, Pe is the thermal pressure tensor, and j is the Hall current. The three terms on the right-hand side describe the three different mechanisms of ion acceleration: the motional term, the pressure gradient term, and the Hall term. All these terms contribute to the energization of escaping ions, while they dominate in different positions in an induced magnetosphere, and play different roles in the dynamics of an escaping ion.

We will quantify the energy gain due to each electric field term of escaping ions depending on the birthplaces of the ions. Our tool is AMITIS, a GPU-based 3-D hybrid code (ions as particles and electrons as a fluid) to model the plasma interaction with a planet (Fatemi et al., 2017). For a test, we simulated the solar wind interaction with Mars at nominal space environment conditions until a quasi-steady state. We calculated different electric field terms and compared them with the MAVEN measurements. The simulation results show good agreement with measurements in both magnitude and spatial distribution.

 

We further launched test particles from different positions in the ionosphere and tracked the energy gain/loss due to different electric field terms along their escaping trajectories. The energization history of an ion depends on its trajectory, which further partly depends on the birthplace of the ion. Ions produced outside of the IMB are accelerated or “picked up” totally by the motional electric field. Ions produced in the induced magnetosphere in the dayside may be accelerated by the thermal pressure gradient of the ionosphere, while those produced in the nightside are driven more by the Hall electric field.
Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer
Authors: Bendtsen Jørgen , Richardson Katherine
Published: March 2020

The potential for vertical mixing to support new production in the upper layers of the northeastern portion of the North Sea was analysed from observations obtained during the stratified period in July 2016. Five transects across the shelf edge between the relatively shallow central North Sea and the deep Norwegian trench showed a clear frontal structure in hydrography, turbulent mixing, nutrients and chlorophyll a across the shelf edge. Relatively large (up to >0.5 mmol N m−2 d−1) nitrate fluxes due to turbulent vertical mixing into the euphotic zone were found at some stations over the shelf edge, while low values (< 0.1 mmol N m−2 d−1) were found in the deeper open area north of the shelf edge. The low vertical mixing rates implied f ratios less than 0.02 in the open waters north of the shelf edge. In the shallow (<50 m) southern and central part of the study area, inorganic nutrients were low and nitrate undetectable, suggesting negligible new production here, despite relatively high concentrations of chlorophyll a being found in the bottom layer. Thus, high rates of new production seem to be concentrated around the shelf-edge zone and in association with localized features exhibiting enhanced vertical mixing. We find that the nutricline depth is significantly deeper at the shelf edge and interference with increased mixing in this deeper depth range can explain the increased diapycnal nitrate fluxes. Overall, this suggests that the shelf-edge zone may be the major nutrient supplier to the euphotic zone in this area during the period of summer stratification. Potential impacts on plankton ecosystem structure are discussed.

Reference:

Bendtsen, J. and Richardson, K.: Turbulence measurements suggest high rates of new production over the shelf edge in the northeastern North Sea during summer, Biogeosciences, 15, 7315–7332, https://doi.org/10.5194/bg-15-7315-2018, 2018.
The global freshwater availability and water use model WaterGAP 2.2d
Authors: Müller Schmied Hannes , Cáceres Denise , Eisner Stephanie , Flörke Martina , Niemann Christoph , Peiris Thedini Asali , Popat Eklavyya , Portmann Felix T. , Reinecke Robert , Schumacher Maike , Shadkam Somayeh , Telteu Camelia Eliza , Trautmann Tim , Döll Petra
Published: March 2020

Freshwater availability is of vital importance for humans, freshwater biota and ecosystem functions. In the past decades, global hydrological models (GHMs) were developed to improve understanding of the global freshwater situation in a globalized word, by filling gaps in observational coverage and assessing scenarios of the future under consideration of different socioeconomic developments and climate change. The Water Global Assessment and Prognosis (WaterGAP) model was one of the first GHMs developed to evaluate freshwater resources and their use for both historical and future conditions. It consists of five water use models (for irrigation, domestic, cooling of thermal power plants, manufacturing, and livestock sectors) and the WaterGAP Global Hydrology Model (WGHM). Recently, the latest model version, WaterGAP 2.2d, was finalized, containing a number of enhancements and revisions such as a river storage-based flow velocity approach, improvements in modelling groundwater recharge in dry environments and integration of historical development of irrigated areas.

This presentation provides an overview about the WaterGAP 2.2d scheme and features, assesses global freshwater resources (runoff and streamflow) and water balance components, and provides insights to evaluation results against observed streamflow, GRACE total water storage and the AQUASTAT database.
Turbulence in open-channel flows over granular low-tortuosity beds
Authors: Santos Daniela , Aleixo Rui , Ricardo Ana M. , L. Ferreira Rui M.
Published: March 2020

Hyporheic/surface mass and momentum exchanges are mostly governed by bed tortuosity, porosity and grain size distribution. These determine near-bed mean flow and turbulence. Not many studies explicitly address the differences in turbulent variables between high conductivity and low conductivity bed, which justifies the objective of this paper: to investigate the effects of tortuosity and hydraulic conductivity on the integral length scale, on the parameters of the power spectral density functions (longitudinal and transverse) and 2nd order structure functions and on Reynolds stress anisotropy. Experimental tests were performed in low tortuosity beds (mono-sized glass sphere beads) are compared with the existing database of low conductivity beds of Ferreira et al. (2012), keeping constant the range of values of porosity, Shields parameters and roughness Reynolds numbers. A new database of instantaneous velocities was acquired with Particle Image Velocimetry (PIV) and processed to gather time-averaged velocities and space-time (double-averaged) quantities, namely velocities, Reynolds stresses and form-induced stresses. Turbulence variables obtained from low tortuosity bed are compared with those of the high tortuosity of the existing database, for mobile and immobile bed conditions. The main differences are identified and discussed. They include: increased anisotropy in the flow over high tortuosity beds; smaller integral scale in the near-bed region in the in the flow over high tortuosity beds; different parameters of the 2nd order structure functions. The observations may be used to explain the drag reducing behaviour of the flow over low-tortuosity beds.

This research was partially supported by Portuguese and European funds, within the COMPETE 2020 and PORL-FEDER programs, through project PTDC/CTA-OHR/29360/2017 RiverCure
Impacts of Climate and Land Use Change in the Management of a Transboundary Basin- Case Study of Mono River catchment
Authors: Houngue Rholan , Evers Mariele , Almoradie Adrian
Published: March 2020

There are evidences that climate change as a result of both natural and anthropogenic processes has exacerbated the frequency and the severity of flood hazards over past decades across the world. Moreover, changes in the pattern of precipitation and temperature during the 21st century are expected to induce region-specific impacts on floods, especially increase in local floods in some catchments. However, the future is hard to predict as there are strong discrepancies in how climate change is expected to affect runoff and river discharge at different places. Many studies have proven that not only climate, socio-economic and physical factors such as elevation and soil type are determinant for flood risk characterisation. Anthropogenic activities and impacts through land use and land cover degradation have substantial implication for hydrological processes. Moreover, catchment management play an important role in sustainable flood management which is generally based on technical knowledge. But it must also be socially and politically meaningful. This is especially relevant for transboundary catchments where riparian countries might offer different economic, social and political environment, and hence have distinct approaches of flood risk reduction and management. An effective cooperation between states sharing transboundary water resources must include a continuum comprised of data exchange, information sharing, collaboration and joint action. It is a search for cooperative management while respecting the sovereignty of each state. There is a variety of methods used for assessing transboundary management and identifying cooperative strategies. Among others, the following ones can be mentioned: the Water Cooperation Quotient, the multiobjective analysis, hydropolicy simulation models, the Multiobjective Evolutionary Algorithms (MOEAs) and a combination of the two later. Hence this study aims at exploring various approaches of transboundary management and analyses experienced over the world. Lessons will afterward be drawn in the context of climate and land use change in the transboundary Mono River catchment shared by the Republics of Benin and Togo.
A Gaussian process emulator for simulating ice sheet-climate interactions on a multi-million year timescale
Authors: Van Breedam Jonas , Huybrechts Philippe , Crucifix Michel
Published: March 2020

Fully coupled state-of-the-art Atmosphere-Ocean General Circulation Models are the best tool to investigate feedbacks between the different components of the climate system on a decadal to centennial timescale. On millennial to multi-millennial timescales, Earth System Models of Intermediate Complexity are used to explore the feedbacks in the climate system between the ice sheets, the atmosphere and the ocean. Those fully coupled models, even at coarser resolution, are computationally very expensive and other techniques have been proposed to simulate ice sheet-climate interactions on a million-year timescale. The asynchronous coupling technique proposes to run a climate model for a few decades and subsequently an ice sheet model for a few millennia. Another, more efficient method is the use of a matrix look-up table where climate model runs are performed for end-members and intermediate climatic states are linearly interpolated.

In this study, a novel coupling approach is presented where a Gaussian Process emulator applied to the climate model HadSM3 is coupled to the ice sheet model AISMPALEO. We have tested the sensitivity of the formulation of the ice sheet parameter and of the coupling time to the evolution of the ice sheet over time. Additionally, we used different lapse rate adjustments between the relatively coarse climate model and the much finer ice sheet model topography. It is shown that the ice sheet evolution over a million year timescale is strongly sensitive to the choice of the coupling time and to the implementation of the lapse rate adjustment. With the new coupling procedure, we provide a more realistic and computationally efficient framework for ice sheet-climate interactions on a multi-million year timescale.

 
The impacts of spring-summer droughts in England, 1200-1700
Authors: Pribyl Kathleen
Published: March 2020

This paper studies the occurrence and impacts of spring-summer droughts in pre-industrial England from 1200 to 1700. The study is based on documentary data, and the types of records and source availability are described, and an overview of droughts in those 500 years is provided. The focus lies on identifying the meteorological, hydrological and agricultural aspects of late medieval and early modern droughts, and on highlighting the structural impacts on the agricultural and pastoral economy, transport, energy supply and health. Due to the specific characteristics of wheat cultivation in medieval and early modern England, the grain production was comparatively resilient to drought. However, livestock farming was under threat, when rainfall levels fell noticeably below average. The most important problem in warm and dry summers was the risk to health. Partly steeply raised mortality levels were associated with these conditions during the study period, because malaria, gastrointestinal disease and plague showed an affinity to heat and drought. Adaptation strategies adopted by the people of pre-industrial England to reduce the stress posed by summer droughts will be discussed.
Snow-Hydrological modeling using remote sensing data in Vilcanota basin, Peru
Authors: Risco Eber , Lavado Waldo , Rau Pedro
Published: March 2020

Water resources availability in the southern Andes of Peru is being affected by glacier and snow retreat. This problem is already perceived in the Vilcanota river basin, where hydro-climatological information is scarce. In this particular mountain context, any water plan represents a great challenge. To cope with these limitations, we propose to assess the space-time consistency of 10 satellite-based precipitation products (CMORPH–CRT v.1, CMORPH–BLD v.1, CHIRP v.2, CHIRPS v.2, GSMaP v.6, GSMaP correction, MSWEP v.2.1, PERSIANN, PERSIANN–CDR, TRMM 3B42) with 25 rain gauge stations in order to select the best product that represents the variability in the Vilcanota basin. For this purpose, through a direct evaluation of sensitivity analysis via the GR4J parsimonious hydrological model over the basin. GSMap v.6, TRMM 3B42 and CHIRPS were selected to represent rainfall spatial variability according with different statistical criteria, such as correlation coefficient (CC), standard deviation (SD), percentage of bias (%B) and centered mean square error (CRMSE). To facilitate the interpretation of statistical results, Taylor's diagram was used to represent the CC statistics, normalized values of SD and CRMSE.

A distributed degree-day model was chosen to analyse the sensitivity of snow cover simulations and hydrological contribution. The GR4J rainfall-runoff model was calibrated (using global optimization) and applied to simulate the daily discharge and compared with the Distributed Hydrology and Vegetation Model with Glacier Dynamics (DHSVM-GDM) over the 2001-2018 period. Furthermore, the simulated streamflow was evaluated through comparisons with observations at the hydrological stations using Nash–Sutcliffe efficiency and Kling Gupta Efficiency (KGE). The results show that the snow-runoff have increased in recent years, so new water management and planning strategies should be developed in the basin. This research is part of the multidisciplinary collaboration between British and Peruvian scientists (Newton Fund, Newton-Paulet) through RAHU project.
Gravity networks for the Geodetic Reference Framework of Albania
Authors: Reci Hamza , Stampolidis Alexandros , Ndoj Perparim , Tsokas Gregory , Pašteka Roman , Hábel Branislav , Bushati Salvatore , Qirko Kristaq
Published: March 2020

This paper presents a general overview of gravimetric measurements carried out for the first order gravimetric network of Albania.   Data compensation, correction methodologies, interpretation and related results have been presented as well. Relative gravimetric measurements were carried out in 42points,  with two CG-5 instruments. Real Vertical Gradients have been measured at all the points of first order network which together with other corrections,  are used in the final data compensation in order to bring the final values at reference point as absolute ones. Apart from the first order network, other 38 second order and 138 third order gravimetric points have been measured in a grid 2x2 km, in the  flat and most dense area (Tirana-Durresi) of Albania,  with the  scope the determination of  Geoid Gravimetric Height on that region. The gravimetric measurements were realized with two Scintrex CG-5 gravimeters for three orders. For the first order points were used two gravimeters simultaneously, whereas for the points of second and third order only one. In this paper we present the results for only the first order measurements. The measurements were carried out during the period from August to October 2018, in collaboration with Aristotle University of Thessaloniki, Department of Geophysics. The project was supported by the Agency of Geospatial Information of Albania.
Study of the tsunami source in the Palu Bay following the Mw7.5 2018 Sulawesi earthquake
Authors: Romano Fabrizio , Hasan Haider , Lorito Stefano , Løvholt Finn , Brizuela Beatriz , Tolomei Cristiano , Piatanesi Alessio
Published: March 2020

On 28 September 2018 a Mw 7.5 strike-slip earthquake occurred on the Palu-Koro fault system in the Sulawesi Island. Immediately after the earthquake a powerful tsunami hit the Palu Bay causing large damages and numerous fatalities.

Several works, inverting seismic or geodetic data, clearly estimated the slip distribution of this event, but the causative source of the tsunami is still not completely understood; indeed, the strike-slip mechanism of the seismic source alone might not be sufficient to explain the large runups observed (> 6 m) along the coast of the Palu Bay, and thus one or more additional non-seismic sources like a landslide could have contributed to generate the big tsunami. An insight of that can be found in an extraordinary collection of amateur videos, and on the only available tide gauge in the Bay, at Pantoloan, that showed evidence for a short period wave of at least 2-3 minutes, compatible with a landslide.

In this study, we attempt to discriminate the contribution in the tsunami generation of both the seismic source and  some supposed landslides distributed along the coast of the Bay.

In particular, we attempt to estimate the causative source of the tsunami by means of a nonlinear joint inversion of geodetic (InSAR) and runup data. We use a fault geometry consistent with the Sentinel-2 optical analysis results and analytically compute the geodetic Green’s functions. The same fault model is used to compute the initial condition for the seismic tsunami Green’s functions, including the contribution of the horizontal deformation due to the gradient of the bathymetry (10 m spatial resolution); the landslide tsunami Green’s functions are computed the software BingClaw by placing several hypothetical sources in the Bay. In both the cases the tsunami propagation is modelled by numerically solving the nonlinear shallow water equations.

In this work we also attempt to address the validity of Green’s functions approach (linearity) for earthquake and landslide sources as well as the wave amplitude offshore as predictor of nearby runup.
Development of a Post-Wildfire Response to Debris Flow Protection
Authors: Kane William , Jones Mallory , Firestein Lesley
Published: March 2020

In January 2018, deadly debris flows swept through the community of Montecito, California. The Santa Ynez Mountains above the town had been denuded by the Thomas Fire in Fall 2017. Twenty-three people were killed by the massive boulders and debris that swept down from the canyons during an intense rain event.

After the disaster, residents realized that waiting for protection from various agencies would take too long. Instead, they banded together and formed a non-profit organization, The Partnership for Resilient Communities (TPRC), to raise private funds and construct protective measures.
      
Research indicated that flexible debris nets designed by experienced geoengineers would be the quickest and most environmentally sound approach. Geobrugg AG, Romanshorn, Switzerland was selected as the supplier of the nets since it has a long research and implementation background. KANE GeoTech teamed with Access Limited Construction, Oceano, California to actualize the project. KANE and Access have designed and installed more Geobrugg debris nets in North America than any other firms and thus were the natural choices for this fast-track project.

Money was raised from private donors and nets constructed. Once nets were installed the purpose of TPRC had been realized. However, much knowledge was gained on aspects of permitting, locating, engineering, and constructing the nets. A new organization, Presilience Partners, was formed. The organization is composed of members of the TPRC, KANE GeoTech, Geobrugg AG, Access Limited, and the University of California, Santa Barbara. Its mission is to take the lessons learned and develop a response protocol for protection from future wildfire/debris flows.

This presentation will review the innovations developed in the past and describe ongoing work.
The forming slow solar wind imaged along streamer rays by the wide-angle imager on Parker Solar Probe
Authors: Poirier Nicolas , Kouloumvakos Athanasios , Rouillard Alexis P. , Pinto Rui , Vourlidas Angelos , Stenborg Guillermo , Valette Emeline , Howard Russell A. , Hess Phillip , Thernisien Arnaud , Rich Nathan , Griton Léa , Indurain Mikel , Raouafi Nour-Edine , Lavarra Michael , Réville Victor
Published: March 2020

The Wide-field Imager for Solar PRobe (WISPR) obtained the first high-resolution images of coronal rays at heights below 15 Rsun when Parker Solar Probe (PSP) was located inside 0.25 AU during the first encounter. We exploit these remarkable images to reveal the structure of coronal rays at scales that are not easily discernible in images taken from near 1 AU. To analyze and interpret WISPR observations which evolve rapidly both radially and longitudinally, we construct a latitude versus time map using full WISPR dataset from the first encounter. From the exploitation of this map and also from sequential WISPR images we show the presence of multiple sub-structures inside streamers and pseudo-streamers. WISPR unveils the fine-scale structure of the densest part of streamer rays that we identify as the solar origin of the heliospheric plasma sheet typically measured in situ in the solar wind. We exploit 3-D magneto-hydrodynamic (MHD) models and we construct synthetic white-light images to study the origin of the coronal structures observed by WISPR. Overall, including the effect of the spacecraft relative motion towards the individual coronal structures we can interpret several observed features by WISPR. Moreover, we relate some coronal rays to folds in the heliospheric current sheet that are unresolved from 1 AU. Other rays appear to form as a result of the inherently inhomogeneous distribution of open magnetic flux tubes. This work was funded by the European Research Council through the project SLOW_SOURCE - DLV-819189.
Constraints on European temperature and rainfall changes from attributed changes
Authors: Hegerl Gabriele , Ballinger Andrew , Undorf Sabine
Published: March 2020

Quantifying and reducing the uncertainty of climate projections will benefit both mitigation and adaptation decisions. Observed climate change provides evaluation of climate model simulated change, but the contribution by different external forcing factors needs to be reliably separated in order to use observational constraints. We revisit this ASK (for Allen et al., 2000; Stott and Kettleborough, 2002) approach to use attributed responses to greenhouse gas forcing to constrain future predictions.

We derive constraints on the projected near-surface summer temperature change over Europe as well as over three European subregions. The temperature responses to different external forcings (natural and greenhouse-gas (GHG) or combined anthropogenic) are estimated as the multi-model means of historical simulations from the Coupled Model Intercomparison Project 5 and incoming CMIP6, and the range of factors by which they can be scaled and still be consistent with observations since 1950 (E-OBS) given internal variability is calculated and applied to future RCP8.5 simulations.

Results show that both the response to GHG-only and to the combined anthropogenic (including aerosols etc.) forcing are detectable in the observed temperature change over Europe, and that the response over the Mediterranean region might be underestimated. Observed precipitation changes over Europe are also detected over some regions, although the confounding effects of the North Atlantic Oscillation need to be considered carefully. The results demonstrate the successful application of the ASK method for constraining projections of regional change over Europe.

 
Observational evidence of diapycnal upwelling in a bottom enhanced mixing environment
Authors: Dengler Marcus , Visbeck Martin , Tanhua Toste , Lüdke Jan , Freund Madelaine
Published: March 2020

In the framework of the Peruvian Oxygen minimum zone System Tracer Release Experiment (POSTRE) about 70 kg of trifluoromethyl sulfur pentafluoride (SF5CF3) was injected into the bottom boundary layer of the upper Peruvian continental slope at 250m depth in October 2015. Three different injection sites, at 10°45’S, 12°20’S and 14°S were selected. At the tracer release sites and due to tide-topography interaction, mixing above the upper continental slope of Peru was intensified. Turbulent dissipation rates increase by about an order of magnitude in lower 50 to 100m above the bottom. During previous tracer release experiments, where tracer was injected into the stratified mixing layer above the bottom boundary layer, a change of the center of mass toward higher densities resulted. Newer theories suggest that this diapycnal downwelling is balanced by a diapycnal upwelling within the bottom boundary layer. Indeed, during the tracer survey it was found that the density of tracer’s center of mass had decreased by 0.13 kg m-3. This corresponds to an upward displacement of 70-100m. Using microsctructure shear data from 8 cruises, we obtain a diapycnal velocity of about 0.5 m day-1 within the bottom boundary layer. This suggests that on average, the tracer was trapped within the bottom boundary layer for a period between 1.5 and 3 month. Overall, our tracer study provides the first observational evidence of diapycnal upwelling occurring within the bottom boundary layer of a bottom enhanced mixing environment and supports recent ideas of a vigorous global overturning circulation.
Turbulent open-channel flows over mobile granular low-tortuosity beds: velocity distribution and friction factor
Authors: L Ferreira Rui M , Y Tenzin Rigden , Ricardo Ana M
Published: March 2020

Open channel flows over granular mobile beds are affected by the nature and intensity of hyporheic/surface mass and momentum exchanges. Near-bed surface mean flow and turbulence find an equilibrium with the flow in the hyporheic region and with the type and amount of granular material transported in equilibrium conditions. The processes involved in these adaptive process are not well known. This work addresses this knowledge gap and it is aimed at describing the effect of the hydraulic conductivity on the friction factor and on the parameters of the log-law that is thought to constitute a valid model for the turbulent flow in the overlapping region of fully developed hydraulically rough boundary layers over mobile cohesionless beds. To fulfil the objectives, experimental tests performed in high conductivity beds (mono-sized glass sphere beads) are compared with the existing database of low conductivity beds of Ferreira et al. (2012), keeping constant the range of values of porosity, Shields parameters and roughness Reynolds numbers. The hydraulic conductivity is varied by changing the tortuosity (and the dimensions of the pore paths) and not the porosity.

A new database of instantaneous velocities was acquired with Particle Image Velocimetry (PIV) and processed to gather time-averaged velocities and space-time (double-averaged) quantities, namely velocities, Reynolds stresses and form-induced stresses. The hydraulic conductivity was measured for both types of bed.

The parameters of log-law obtained from high conductivity are compared with low conductivity of existing database, for mobile and immobile bed conditions. The main finding can be summarized as follows.

i. Hydraulic conductivity does not affect the location of the zero plane of the log-law, the thickness of the region above the crests where the flow is determined by roughness.

ii. Increasing the hydraulic conductivity does not appear to decrease the value of bed roughness parameters such as the roughness heigh.

iii. Higher hydraulic conductivity is associated to a structural change: the same near-bed velocity can be achieved with lower shear stress in the inner region. A lower friction factor, (u*/U)2, is thus registered.

iv. Flows over high conductivity beds appear drag-reducing even if roughness parameters do not change appreciably.

 

This research was partially supported by Portuguese and European funds, within the COMPETE 2020 and PORL-FEDER programs, through project PTDC/CTA-OHR/29360/2017 RiverCure
A plea for a novel kind of ecohydrology: the interaction between hydrological processes and - endangered or not - wildlife
Authors: Griffioen Jasper , Wassen Martin , Cromsigt Joris
Published: March 2020

Ecohydrology usually refers to the effects of hydrological processes on the occurrence, distribution and patterns of plants. Here, we emphasize a new kind of ecohydrology in which the effects of hydrological processes on the occurrence of – endangered or not - wildlife become addressed via the threat of its habitat or, oppositely, where the occurrence of wildlife leads to a threat of endangered fauna. We present three examples to illustrate this.

First, the habitat of the tiger in the Terai Arc Landscape (TAL) at the foot of the Himalayas seems to increasingly become threatened by changes in the hydrological conditions. Grasslands in floodplains are an important part of the tiger habitat as these are the grounds where the tiger preferably hunts for deer as his prey. Disturbances of the water systems such as gravel and sand extraction from the river beds, intake of water for irrigation and hydropower production are increasingly happening and climate change may further alter the Himalayan water systems. This seems to disturb the grasslands in their hydrological and hydromorphological dynamics, which may negatively impact the density of deer, which may put additional pressure on the tiger populations in the nature reserves of the TAL.

Second, ungulates are important mammals in the grasslands and savannah of southern Africa. The water availability for these animals may alter upon climate change, including higher frequencies of droughts. Research suggests that the community composition of ungulates may alter by this. Here, the larger water-dependent grazers may be replaced by smaller, less water-dependent species.

Third, the beaver is well-known as hydrological ecosystem engineer. The beaver, therefore, has obtained some attention within the context of ecohydrology. The impact of the beaver as ecosystem engineer is, however, peculiar for nature reserves at the Belgian-Dutch border. Surface water with poor quality due to lack of appropriate sewage water treatment is running along nature reserves. The reintroduction of the beaver causes a rise in the surface and groundwater levels due to its dam-building activities. This induces an introduction of polluted surface water into the Dutch wetlands which contain a less eutrofied ecosystem than the Belgian ones that were fed by the polluted surface water. Nature restoration may thus go on the expense of nature degradation.

These examples show that the ecohydrology of wildlife is as fascinating and diverse as classical ecohydrology is.
Extreme events and resilience at different scales
Authors: Reichstein Markus ,   RISK-KAN
Published: March 2020

In this talk we highlight the consideration of extreme events for (Earth) system dynamics and sustainable development, as opposed to perspective which mostly perceive gradual changes. We show that climate extremes can contribute to positive carbon-cycle-climate feedbacks and conjeture that extreme events can trigger fast system changes and the instigation of "vicious cycles", illustrating this conceptually with ecosystem-related and societal examples. We further discuss risk cascades, emergent and systemic risks in this context with recent local and more global example. Counter-strategies will also be elaborated. Overall, we propose to consider more strongly risk-aware development and systems thinking in future research and implementation related to extreme events and resilience. 
ITCZ dynamics as seen by complex network theory
Authors: Wolf Frederik , Voigt Aiko , Donner Reik V.
Published: March 2020

The intertropical convergence zone (ITCZ) is an important component of the tropical rain belt. Climate models still struggle to represent the ITCZ and differ substantially in its simulated response to climate change. Here, we study to what extent complex network theory, which can effectively extract spatio-temporal variability patterns from climate data, helps to understand the dynamics of the ITCZ and model differences therein. For this purpose, we study simulations with 14 global climate models in an idealized aquaplanet setup performed within the TRAC-MIP model intercomparison project.

We construct network representations based on the spatial correlation pattern of surface temperature and perform a detailed study of the zonal mean patterns of different topological and spatial network characteristics. This allows us to identify clusters of climate models which differ not only in their current climate state dynamics but also in their response to climate change. Specifically, we address possible mechanisms controlling the seasonal change of the location of the ITCZ, and we connect our results to previous work on ITCZ controls by cross-equatorial heat transport and tropical sea-surface temperature gradients.
The signal-to-noise paradox in a conceptual framework based on the 1963 Lorenz model
Authors: Mayer Björn , Düsterhus André , Bahr Johanna
Published: March 2020

Seasonal prediction systems based on comprehensive Earth System Models are capable of skillfully predicting the winter North Atlantic Oscillation. However, the predictive skill reported for these systems is accompanied by a potential inconsistency: The quality of the predictions measured over a set of retrospective forecasts and quantified by the correlation coefficient between prediction and observation exceeds expectations based exclusively on model properties. This discrepancy is commonly referred to as the signal-to-noise paradox (SNP)

Current investigations of the SNP are predominantly looking at seasonal predictions systems based on comprehensive Earth System Models, focusing the uncertainties in the model formulation. In the present contribution, we investigate the SNP in a simple conceptual framework of an ensemble prediction system based on the simple three dimensional Lorenz 1963 Model (L63). This framework enables us to separate the influence of uncertainties in the model initialization and uncertainties in the model formulation on the occurrence of the SNP.

We show that in the absence of uncertainties in the model formulation the SNP is not apparent in L63, if the uncertainty assumed for the initialization of the ensemble is equal to the observational uncertainty. However, if we assume that the uncertainty in the initialization systematically overestimates the observational uncertainty, the SNP is also apparent in L63 - even if there are no uncertainties in the model formulation itself.

While these results obtained in the conceptual framework cannot directly translated to the SNP in comprehensive Earth System Models, we suggest to include in further investigations of the SNP in Earth System Models also a comparison of the magnitude of the initial ensemble spread and the observational uncertainty.
Evaluating water balance components for forested headwater catchment undergoing environmental changes
Authors: Mikesova Veronika , Dohnal Michal , Votrubova Jana , Vogel Tomas
Published: March 2020

Evaluating seasonal and long-term variations in water balance at catchment scale can be useful for assessing the current status and trends in water resources availability. Components of water balance reflect meteorological and climate variability, and vegetation cover development.

The experimental catchment Uhlířská is a small forested headwater catchment in the Jizera Mountains, Czech Republic. The catchment was extensively deforested in the 80´s. Damaged trees long exposed to the effects of air pollutants were poorly resistant to wind and pests. In the 90´s, new spruce forest was planted. The catchment has been subject to long-term monitoring. The 19-year series of data including air temperature, rain and snow precipitation, discharge, groundwater levels, wind velocity, and air humidity, is examined.

Our study provides basic analysis of directly measured components of water balance (precipitation and discharge, annual and seasonal runoff coefficients). The study further deals with the evaluation of the unmeasured components of the water balance (evapotranspiration and water storage). An interception model was employed to calculate the interception loss. Potential evaporation and transpiration during vegetation seasons were estimated by Penman and Penman-Monteith methods. Snow sublimation was estimated in the winter seasons. Effect of the forest development during the period of interest was considered.

The catchment water balance equation suggests significant changes of the water storage over the observation period, implying its decrease in recent years. However, baseflow and deep water storage seem to be unchanged. This discrepancy could be partly attributed to the decrease in shallow water storage and/or more pronounced transpiration reduction in recent vegetation seasons.

The research is supported by the Czech Science Foundation Project No. 20-00788S.
Short timescale magnetic field fluctuations and their impact on space weather forecasting
Authors: Santarelli Lucia , De Michelis Paola , Consolini Giuseppe
Published: March 2020

The features of the horizontal intensity of the geomagnetic field fluctuations during a geomagnetically disturbed period are analyzed. The Empirical Mode Decomposition (EMD) method is applied to separate short timescale (T<200 min) and long timescale (T>200 min) magnetic field fluctuations, which have been suggested to be related to different physical processes. The magnetic fluctuations at long timescales (T>200 min) seem to show a large degree of correlation between solar wind parameters and magnetospheric dynamics proxies, while the magnetic field fluctuations at short timescales (T<200 min) seem to be essentially related to internal magnetospheric processes and not directly driven by interplanetary changes.

Daily maps of the short timescale magnetic field fluctuations during a selected period are analyzed in order to investigate their contribution to the total magnetic signal. The aim is to evaluate the role that the internal magnetospheric processes have on the magnetic signal recorded on the ground and to investigate their dependence on the geomagnetic activity level. A comparison between the two hemispheres is also shown. The obtained results can be useful in the Space weather framework. They show the magnetic field fluctuation forecasting requires the development of models that take into account not only the solar wind parameters but also the internal dynamics of the magnetosphere that although triggered by changes of the interplanetary conditions is not directly driven by solar wind/interplanetary magnetic field.
Geostatistical representation of multiscale heterogeneity of porous media through a Generalized Sub-Gaussian model
Authors: Guadagnini Alberto , Riva Monica , Neuman Shlomo P. , Siena Martina
Published: March 2020

Characterization of spatial heterogeneity of attributes of porous media is critical in several environmental and industrial settings. Quantities such as, e.g., permeability, porosity, or geochemical parameters of natural systems are typically characterized by remarkable spatial variability, their degree of heterogeneity being typically linked to the size of observation/measurement/support scale as well as to length scales associated with the domain of investigation. Here, we address the way stochastic representations of multiscale heterogeneity can be employed to assess documented manifestations of scaling of statistics of hydrological and soil science variables. As such, we focus on perspectives associated with interpretive approaches to scaling of the main statistical descriptors of heterogeneity observed at diverse scales. We start from the geostatistical framework proposed by Riva et al. (2015), who rely on the representation of the heterogeneous structure of hydrological variables by way of a Generalized Sub-Gaussian (GSG) model. The latter describes the random field of interest as the product of a zero-mean, generally (but not necessarily) multi-scale Gaussian random field (G) and a subordinator (U), which is independent of G and consists of statistically independent identically distributed non-negative random variables. The underlying Gaussian random field generally displays a multi-scale (statistical) nature which can be captured, for example, through a geostatistical description based on a Truncated Power Variogram (TPV) model. In this study we (i) generalize the original GSG model formulation to include alternative distributional forms of the subordinator and (ii) apply such a theoretical framework to analyze datasets associated with differing processes and observation scales. These include (i) measurements of surface topography of a (millimeter-scale) calcite sample resulting from induced mineral dissolution and (ii) neutron porosity data sampled from a (kilometer-scale) borehole. We finally merge all of the above mentioned elements within a geostatistical interpretation of the system based on the GSG approach where a Truncated Power Variogram (TPV) model is employed to represent the underlying correlation structure. By doing so, we propose to rely on these models to condition the spatial statistics of such fields on multiscale measurements via a co-kriging approach.

References

Riva, M., S.P. Neuman, and A. Guadagnini (2015), New scaling model for variables and increments with heavy-tailed distributions, Water Resour. Res., 51, 4623-4634, doi:10.1002/2015WR016998.
Rhizobacteria Mediated Changes in Soil Physical and Hydrological Properties
Authors: Jin Yan , Zeng Saiqi , Kaniz Fatema , Zheng Wenjuan , LaManna Jacob , Bais Harsh
Published: March 2020

Large communities of microbes are associated with plant roots in the rhizosphere, which is a critical interface supporting the exchange of water and nutrients between plants and their associated soil environment. The diverse communities of rhizobacteria mediate plant-soil feedback through a multitude of interactions including those that contribute to plant abiotic stresses. For example, enhancement of plant drought stress tolerance by plant growth promoting rhizobacteria (PGPR) has been increasingly documented in the literature, however, investigations to date have been largely focused on PGPR-root/plant interactions and related plant responses to PGPR activities that induce drought tolerance. Comparatively, much less is known about PGPR’s role in mediating physiochemical and hydrological changes in the rhizospheric soil that may also impact plant drought stress tolerance. Using UD1022, aka Bacillus subtilis FB17, as a model bacterium, we demonstrated via soil water characteristic measurements that UD1022-treated soil samples retained more water, had lower hydraulic conductivity than its controls. In addition, we investigated the effects of UD1022 on soil water evaporation via combined neutron radiography, neutron tomography, and X-ray tomography imaging techniques. Neutron radiography images confirmed greater water retention in UD1022-treated soil samples than their controls due to reduced water evaporation. Combined neutron and X-ray tomography 3D images revealed that water distribution in UD1022-treated soil samples was heterogeneous, i.e., there were more disconnected water pockets compared with the controls where water was distributed more uniformly. Our study provides pore-scale mechanistic explanation for increased water retention and reduced evaporation rate from UD1022-treated soil samples, which is mainly attributed to the production of extracellular polymeric substances (EPS) by UD1022 due to EPS’ hygroscopic and chemical properties (viscosity and surface tension). However, our latest experiments showed similar effects by a UD1022 mutant with eps-producing genes removed, suggesting that the beneficial impacts of rhizobacteria may not be limited to their ability to EPS production alone. These findings have practical implications in, for example, “rhizosphere engineering” to improve/restore soil structure, support sustainable agricultural production, and mitigate climate change.
Tree-ring radiocarbon reveals reduced solar activity during Younger Dryas cooling
Authors: Sookdeo Adam , Kromer Bernd , Adolphi Florian , Beer Jürg , Brehm Nicolas , Büntgen Ulf , Christl Marcus , Eglinton Timothy , Friedrich Micheal , Guidobaldi Giulia , Helle Gerd , Muscheler Raimund , Nievergelt Daniel , Pauly Maren , Reinig Frederick , Tegel Willy , Treydte Kerstin , Turney Chris , Synal Hans-Arno , Wacker Lukas
Published: March 2020

The Younger Dryas stadial (YD) was a return to glacial-like conditions in the North Atlantic region that interrupted deglacial warming around 12900 cal BP (before 1950 AD). Terrestrial and marine records suggest this event was initiated by the interruption of deep-water formation arising from North American freshwater runoff, but the causes of the millennia-long duration remain unclear. To investigate the solar activity, a possible YD driver, we exploit the cosmic production signals of tree-ring radiocarbon (14C) and ice-core beryllium-10 (10Be). Here we present the highest temporally resolved dataset of 14C measurements (n = 1558) derived from European tree rings that have been accurately extended back to 14226 cal BP (±8, 2-σ), allowing precise alignment of ice-core records across this period. We identify a substantial increase in 14C and 10Be production starting at 12780 cal BP is comparable in magnitude to the historic Little Ice Age, being a clear sign of grand solar minima. We hypothesize the timing of the grand solar minima provides a significant amplifying factor leading to the harsh sustained glacial-like conditions seen in the YD.