bluuebunny/crossref_metadata_2025 huggingface dataset:
Satellite observations as a tool to monitor the volcanoes of Saba and St. Eustatius
Authors: de Zeeuw - van Dalfsen Elske , Korevaar Anouk , van Leijen Freek , Sleeman Reinoud , Coppola Diego
Published: March 2020

The Dutch islands of Saba and St. Eustatius are located in the far north of the Lesser Antilles arc, a subduction zone hosting seventeen active volcanoes. The volcanoes of Saba and St. Eustatius: Mount Scenery and The Quill, are currently monitored using a ground based network, operated by KNMI, comprising broadband seismometers, continuous GNNS stations and a temperature sensor in the hotspring on Saba. Satellite observations are complementary to these ground based measurements and are especially useful for these volcanoes as they are located in a remote area.

InSAR observations can be used to monitor surface deformation of volcanoes. Because considerable areas are observed with each satellite passing, subtle signals, which may be missed by continuously recording ground based GNSS stations, may be picked up. However, research using TerraSAR X-band and Sentinel-1 C-band data in the Caribbean region has shown that monitoring with InSAR is hampered due to the loss of radar coherence caused by tropical rain forest covering the Caribbean islands. Moreover many of the islands have steep slopes resulting in layover and shadowing effects. We generate interferograms and time series of ALOS-2 L-band data and Sentinel C-band data to identify which mission is more suitable for long term monitoring of the volcanoes on Saba and St. Eustatius.

The Terra satellite carries five instruments that take coincident measurements of the Earth system, among those is MODIS: a Moderate Resolution Imaging Spectroradiometer. MODIS data are used by MIROVA (Middle Infrared Observation of Volcanic Activity): an automatic volcano hot spot detection system, able to detect, locate and quantify thermal anomalies in near real-time, by providing, infrared images and thermal flux time-series on over 200 volcanoes worldwide (www.mirovaweb.it). A volcano in a non-eruptive state such as Mount Scenery on Saba would typically be checked on a monthly basis. As Saba is a very small island (12 km2) automatic triggering is challenging and therefore observations are still in a test phase.

Satellite observations can be a useful addition to the ground based monitoring of small island volcanoes although small adaptions to currently used techniques may be needed. As such they may be crucial for timely warning of local authorities in case of unrest at a remote volcano.
From storms to planetary-scale disturbances in the atmospheres of Jupiter and Saturn
Authors: Snchez-Lavega Agustín
Published: March 2020

The deep atmospheres of the giant planets Jupiter and Saturn are covered by different layers of clouds and hazes where a rich variety of dynamical phenomena take place. At the cloud tops, the winds blow along latitude circles forming a system of jet streams that alternate in East-West direction with latitude. The upper clouds are organised in parallel bands (the low reflectivity belts and the white zones) whose structure follows the winds and correlate with the temperature field over a range of altitudes.

In this zonal system of jets and bands, meteorological formations grow and evolve over a wide range of spatial and temporal scales, among others, vortices, waves, storms and chaotic and turbulent features. The most spectacular of all of them are those in which the outbreak of a small bright spot that growths and expands rapidly up to a size in the range of 5,000 - 10,000 km, produces a strong interaction with the winds generating a planetary scale disturbance that propagates zonally according to prevailing winds. Jupiter events begin at localized latitudes in the South Equatorial Belt at 16º South, where wind speeds are close to zero, and in the North Temperate Belt at 23º North where the winds have the velocity record on the planet with a jet peak reaching about 180 m/s. The disturbance produces cyclically a change in the albedo of the band, from a zone to a belt, with periods in the range 5-10 years. On Saturn, the phenomenon is known as the Great White Spot (GWS) and has been observed at different latitudes, from the Equator to near the pole, but always in the northern hemisphere. The GWS has been recorded only six times in the history of observations of the planet with a periodicity close to 30 years (about one Saturn year). The proposed models to explain these phenomena involve the trigger of an initial storm produced by moist convection at the water clouds located below the visible clouds. The associated vigorous upward motions generate massive cumulus-like clouds and their non-linear interaction with the wind system forms the series of vortices and waves that make-up the disturbance that propagates away from the active source until fully encircling the planet.
Assessing fault criticality using seismic monitoring and fluid pressure analysis
Authors: Perrochet Léa , Preisig Giona , Valley Benoît
Published: March 2020

The stability of a critically stressed fault depends on the surrounding stresses acting on it. Fluids, by reducing the effective normal stress, play a major role. It has been observed that in karstic regions, an increase in groundwater pressure following significant recharge (precipitations and/or seasonal snowmelt) can result in a fault re-activation, inducing microseismicity. This study combines the natural microseismicity and the groundwater level fluctuations observations to estimate the fault criticality. The research is carried out on two major strike-slip faults in the folded Jura in Switzerland – La Lance Fault and La Ferrière Fault – most likely critically stressed according to their position in the global stress-regime. Data acquisition mainly consists in hydrogeologic and seismic monitoring. The objectives are to have continuous discharge rates of the major karstic springs and to produce a seismic catalog for the area of interest. Combining both data sets will allow to determine relations between increasing spring discharge rates and low magnitude earthquakes and eventually to acquire a quantitative knowledge on what pressure change is affecting the fault’s stability. This knowledge will be used to develop a straighforward methodology to assess fault criticality.  In addition, the study of a possible time lag between aquifer response and fault activation, as well as back-analysis of seismic events can provide, respectively, important information about the deep-seated fluid circulation and the local stress-regime.
Seasonal changes in stable nitrogen isotopic composition in fine aerosols at a rural background station Košetice (Central Europe).
Authors: Vodička Petr , Kawamura Kimitaka , Schwarz Jaroslav , Kunwar Bhagawati , Ždímal Vladimír
Published: March 2020

The stable nitrogen isotope ratios (δ15N) of total nitrogen (TN) were studied for fine aerosol particles (PM1) collected with a 24-h time resolution every two days at a Central European rural background site from September 27, 2013, to August 9, 2014 (n=146).
We observed a seasonal cycle of enrichment and depletion of 15N in aerosol particles with lower values in winter and higher values in summer. The majority of the yearly data showed a strong correlation between δ15N and ambient temperature, supporting an enrichment of 15N via isotopic equilibrium exchange between the gas and particulate phases. This process seemed to be one of the main mechanisms for 15N enrichment at the Košetice site, especially during spring. The most 15N-enriched summer and most 15N-depleted winter samples were limited by the partitioning of nitrate in aerosols and suppressed equilibrium exchange between gaseous NH3 and aerosol NH4+. During winter, we observed an event with the lowest δ15N values which deviate from temperature dependence. The winter event was connected with prevailing southeast winds and the lowest δ15N values were probably associated with agriculture emissions of NH3 under low-temperature conditions (<0°C).

Acknowledgement:
This conference contribution was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project No. LM2018122, by the ERDF project "ACTRIS-CZ RI" (No. CZ.02.1.01/0.0/0.0/16_013/0001315) and by the Japan Society for the Promotion of Science (JSPS) through Grant-in-Aid No. 24221001. We appreciate the financial support of JSPS fellowship to P. Vodička (P16760) in Japan.

Reference:
Vodička, P., Kawamura, K., Schwarz, J., Kunwar, B. and Ždímal, V.: Seasonal study of stable carbon and nitrogen isotopic composition in fine aerosols at a Central European rural background station, Atmos. Chem. Phys., 19, 3463–3479, 2019.
Photochemical production of sulfate from dissolved organic matter and atmospheric aqueous phases: Is there something in common?
Authors: Ossola Rachele , Clerc Baptiste , Tolu Julie , Winkel Lenny H. E. , McNeill Kristopher
Published: March 2020

In a recent study, we showed that photodegradation of dissolved organic sulfur (DOS) from a wide range of natural terrestrial environments releases sulfate (SO42–) and other small and highly oxidized S-containing compounds as degradation products, similar to what had already been reported for dissolved organic carbon, nitrogen and phosphorous. However, the underlying chemical mechanism of photoproduction of sulfate is still unknown.

To fill this knowledge gap, we selected cysteine as a DOS model compound and we investigated its photodegradation to sulfate using model sensitizers as the source of singlet oxygen (1O2) and triplet excited states (3Sens*), two photochemically produced reactive species ubiquitous in sunlit surface waters. Using a combination of steady-state photochemistry experiments, kinetic modeling and mechanistic knowledge from the biochemistry literature, we reconstructed the molecular events that likely lead to the release of sulfate. We found that the release of SO2 via triplet-sensitized fragmentation of cysteine sulfinic acid, a 1O2 degradation product of cysteine, is a key step in the reaction mechanism. In the presence of oxygen and a photosensitizer, SO2 is then rapidly oxidized to SO42–.

Interestingly, nowadays there is great interest in the atmospheric chemistry community on the same transformation (i.e., aqueous phase oxidation of SO2 to SO42–) in the context of extreme haze events. Triplet-induced SO2 oxidation has already been proposed as a potential aqueous phase reaction that might explain the mismatch between measured and modelled sulfate concentrations, but the mechanism of this process is still not established. Our work provides an example of how mechanistic knowledge gained on the (photo)chemical behaviour of dissolved organic matter in aquatic systems can offer insights on processes occurring in atmospheric aqueous phases.
A case study investigating the effects of EDTA washing and amendments on trace metal-contaminated soil
Authors: Friesl-Hanl Wolfgang , Noller Christoph Sebastian , Hood-Nowotny Rebecca , Watzinger Andrea
Published: March 2020

Trace metals emissions show a sustaining decrease in western Europe since several decades. Sources like leaded fuels have been banned and the use of efficient flue gas cleaning systems have reduced industrial emissions significantly. But trace metal additions are cumulative, and the contamination is permanent. Immobilizing trace metals can be an efficient and cost effective way to prevent groundwater contamination and uptake in the food chain but cannot account for all exposure pathways (e.g. ingestion), while guideline values are only concerned about total concentrations. Soil washing techniques comprise an enormous potential for the efficient and sustainable extraction of trace metals from contaminated soils. The Garden Soil Project is a case study investigating the effect of soil amendments applied after a new ex-situ soil washing procedure (Ethylenediaminetetraacetic acid) from a Cd-, Pb-, Zn-contaminated Cambisol from Arnoldstein, located at a former lead mining and smelting region in Austria.

To investigate the success of the EDTA soil washing and amendment application, an experimental garden was set up at the University Research Center (UFT) in Tulln an der Donau. It encompasses twelve raised beds of 1 m3, filled with three soil variants in four replicates: The contaminated, unwashed soil (U) and two washed variants (W), one amended with 2 %wt biochar and 2 %wt compost (A). The amendments aim to restore soil conditions after the invasive procedure. The success of the trace metal extraction and restoration of the original soil properties is investigated by analyzing vegetable cultivars grown on the soil variants, the physicochemical and microbiological characteristics of the soil in the course of 2 years. First results show a significant reduction in trace metal uptake by different vegetables after washing and an increase in biomass for both washed soil variants W and A. The continuing analysis of trace metals in soil leachates and multiple extractable fractions in soil will allow a more detailed assessment. Furthermore, an ongoing investigation of the carbon and nitrogen cycle, using stable isotopes, will be applied as an indicator for soil functions.
Interplanetary effects on planetary environments: Earth, Venus, and Mercury
Authors: Laurenza Monica , Milillo Anna , Alberti Tommaso , Mangano Valeria , Massetti Stefano , Plainaki Christina , Mura Alessandro , De Angelis Elisabetta , Rispoli Rosanna , Ivanovski Stavro , Orsini Stefano
Published: March 2020

The interplanetary and planetary environments are characterized by several intrinsic and induced properties as magnetic fields, waves and instabilites, boundaries, and ionizing radiation components. These features usually evolve on timescales ranging from seconds up to years, mainly controlled by the solar activity.

BepiColombo and Solar Orbiter flybys will offer an interesting opportunity to investigate the dynamical features of both magnetic fields and particle populations when passing from the interplanetary to the planetary environments, thus allowing us to properly characterize different regions of the interplanetary and planetary space.

This contribution discusses some outstanding features of planetary environments (Earth, Venus, and Mercury) when they interact with the interplanetary medium by considering data coming from in-flight space missions as ACE, MESSENGER, and Venus Express. Moreover, a special attention will be devoted to BepiColombo flybys which will be helpful for deeper investigations.
On the Influence of Sea Surface Temperatures on the Development of Extratropical Cyclones
Authors: Bui Hai , Spengler Thomas
Published: March 2020

The sea surface temperature (SST) distribution can modulate the development of extratropical cyclones through sensible and latent heat fluxes. However, the direct and indirect effects of these surface fluxes, and thus the SST, are still not well understood. This study tackles this problem using idealised channel simulations of moist baroclinic development under the influence of surface fluxes. The model is initialised with a zonal wind field resembling the midlatitude jet and a different SST distribution for each experiment, where both the strength and position of the SST gradient are varied.

The surface latent heat flux plays a key role in enhancing the moist baroclinic development, while the sensible heat fluxes play a minor and dampening role. The additional moisture provided by the latent heat fluxes originates from about 1000 km ahead of the cyclone a day prior to the time of the most rapid deepening. When the SST in this region is higher than 15 degrees Celsius, the additional latent heat is conducive to explosive cyclone development. A high absolute SST with a weak SST gradient, however, can lead to a delay of the deepening stage, because of unorganised convection at early stages. In addition, the cyclone can maintain its intensity for a longer period with an SST above 20 degrees Celsius, because there is a continuous and extensive moisture supply from the surface. The cyclone in this case has characteristics of a hybrid cyclone, where the latent heat release near the cyclone’s centre plays a major role in the development.
Effects of Obstacle’s Curvature on Shock Waves in Gravity-Driven Experimental Flows Impacting a Circular Cylinder or a Wall
Authors: Chen Zheng , He Siming , Rickenmann Dieter
Published: March 2020

Geophysical granular ﬂows such as rock and snow avalanches, flow-like landslides, debris flows, and pyroclastic ﬂows are driven by gravity and often impact on engineering structures located in gullies and slopes as they flow down, generating dynamic impact pressures and causing a major threat to infrastructures. It is necessary to understand the physical mechanism of such granular flows impacting obstacles to improve the design of protective structures and the hazard assessment related to such structures. In this study, the small-scale laboratory experiments were performed to investigate the dynamic impact caused by granular flow around a circular cylinder with variable radius of curvatures and the dynamic impact against a flat wall. Pressure sensors were used to measure the impact pressure of granular flows at both the upstream cylinder surface and at the bottom of the channel. Accelerometers were mounted on the underside of channel to record the seismic signals generated by the granular flows before and during the impact with the obstacle. Flow velocities and flow depths were determined by using high-precision cameras. The results show that a bow shock wave is generated upstream of the cylinder, causing dynamic pressures on both the obstacle and the bottom of the channel. The dimensionless standoff distance of the granular shock wave decreases nonlinearly or almost exponentially with increasing Froude number (Fr) in the range of 5.5 to 11.0. The dimensionless pinch-off distance and dimensionless run-up height grow linearly with increasing Fr, and they were significantly influenced by the radius of curvature of the structure at the stagnation point (RCSSP). The dimensionless impact pressure on the structure surface is sensitive to the RCSSP, while the differences decrease as Fr increases; Seismic signals generated at the underside of the channel and at the top of the cylinder were also recorded to assist in analyzing the effects of RCSSP.
Your collective timeline of climate science history
Authors: Tournadre Benoît , Trolliet Mélodie
Published: March 2020

EGU General Assembly is one of the world’s biggest conferences dedicated to geosciences. It gathers experts from all science fields connected to the study of past, present and future climates. Many of them have an historic perspective on their area of expertise: such knowledge is useful to develop an integrated view of the history of climate sciences.

We propose EGU2020 attendees to help building a collective timeline of the history of climate science. Everyone is invited to come to our poster to add to the printed timeline a scientific breakthrough in her/his field of expertise. This will be an opportunity to come to chat on climate science history and to construct together a wider picture of climate sciences.

The final cut of the timeline produced during EGU2020 will be available on our web page EarthBreath (https://www.sophia.mines-paristech.fr/earthbreath/), and our Twitter english (@eb_climate_data) and french (@eb_climat_fr) accounts.

EarthBreath is a non-profit initiative that we develop for promoting climate and Earth sciences to diverse publics.
Developing an open-source 3D glacial isostatic adjustment modeling code using ASPECT
Authors: Weerdesteijn Maaike , Conrad Clinton , Naliboff John , Selway Kate
Published: March 2020

Models of Glacial Isostatic Adjustment (GIA) processes are useful because they help us understand landscape evolution in past and current glaciated regions. Such models are sensitive to ice and ocean loading as well as to Earth material properties, such as viscosity. Many current GIA models assume radially-symmetric (layered) viscosity structures, but viscosity may vary laterally and these variations can have large effects on GIA modeling outputs. Here we present the potential of using ASPECT, an open-source finite element mantle-convection code that can handle lateral viscosity variations, for GIA modeling applications. ASPECT has the advantage of adaptive mesh refinement, making it computationally efficient, especially for problems such as GIA with large variations in strain rates. Furthermore, ASPECT is open-source, as will be the GIA extension, making it a valuable future tool for the GIA community.

 

Our GIA extension is benchmarked using a similar case as in Martinec et al. (GJI, 2018), such that the performance of our GIA code can be compared to other GIA codes. In this case, a spherically symmetric, five-layer, incompressible, self-gravitating viscoelastic Earth model is used (Spada et al, GJI 2011). The surface load consists of a spherical ice cap centered at the North pole, and is applied as a Heaviside loading. The ice load remains constant with time, and thus we have not yet implemented the full sea level equation (SLE). Beyond this benchmark, we have incorporated lateral viscosity variations underneath the ice cap, to demonstrate the ability of efficiently implementing laterally-varying material properties in ASPECT.

 

We show the possibilities, capabilities, and potential of ASPECT for GIA modeling. In the near future we will further develop the code with the sea level equation and an ocean basin, and will explore ASPECT’s current capability of using time-varying distributed surface loads. These functions will allow for modeling of GIA for realistic ice load scenarios imposed above potentially complex earth structures.
Analysis of the foreshock sequences preceding two moderate (Mw4.7 and Mw5.8) earthquakes in the Sea of Marmara offshore Istanbul, Turkey.
Authors: Durand Virginie , Bentz Stephan , Kwiatek Grzegorz , Dresen Georg , Wollin Christopher , Heidbach Oliver , Martinez-Garzon Patricia , Cotton Fabrice , Nurlu Murat , Bohnhoff Marco
Published: March 2020

In September 2019 a sequence of two moderate earthquakes (Mw4.7 and Mw5.8) occurred in the central Sea of Marmara (Turkey), SW of Istanbul. These events took place ate the transition between a creeping and a locked segment of the North Anatolian Fault. To investigate in detail the spatiotemporal evolution of the seismicity, we apply a matched-filter technique to continuous waveforms, thus reducing the magnitude threshold for detection. Sequences of foreshocks preceding the two mainshocks are clearly seen, exhibiting different behaviors: a migration of the seismicity along the entire fault segment on the long-term (several days before the mainshocks) and a concentration around the epicenters of the large events on the short-term (during the few hours preceding the mainshocks). We infer that both seismic and aseismic slip during the foreshock sequences change the stress state on the fault, bringing it closer to failure. Our observations also suggest that the Mw 4.7 event contributed to weaken the fault as part of the preparation process of the Mw 5.8 earthquake.
DORIS infrastructure: status and plans after 30 years of service
Authors: Saunier Jerome , Moreaux Guilhem , Lemoine Frank G.
Published: March 2020

The Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) system is based on a homogeneous global geodetic network. The DORIS ground network is managed and monitored by a single entity (CNES/IGN), which makes it possible to closely steer its deployment and evolution. Moreover, thanks to infrastructure and hardware improvements, the DORIS network has continuously improved over time in order to meet the performance requirements of satellite altimetry for which it is mainly dedicated.

Today, the numerous strengths of the DORIS network built up over 30 years give it an important role in contributing to the Global Geodetic Observing System (GGOS). Our extensive experience in geodetic network maintenance and long-standing commitment to international cooperation to co-locate DORIS with other space geodetic techniques and tide gauges led us to define installation requirements at co-located sites and monuments installation specifications.

After presenting an overview of the DORIS system specificities, we review the strengths and assets of the DORIS network and the continuing improvements in the DORIS technique. Then, we present examples of concrete results achieved through improved ground station configurations. Finally, we give an update on the status and plans for the DORIS network in the coming years to overcome the current limitations of DORIS to meet the GGOS goals for the Terrestrial Reference Frame.
Evaluating the effect of wave-particle cross diffusion in radiation belts modelling using an innovative and robust numerical scheme
Authors: Dahmen Nour , Maget Vincent , Rogier Francois
Published: March 2020

The last decade has shown the prime importance of wave-particle interaction for the accurate modelling of the dynamics of energetic electrons trapped in the Earth’s radiation belts, as well as for other planets, such as Jupiter or Saturn. They have been therefore added in the sum of physical processes modeled in radiation belt codes such as Salammbô, with conclusive results. However, this upgrade of the physical representation is not straightforward and comes at the price of degrading the numerical resolution. In particular, computational instabilities and odd phase space density profiles are observed, impacting the code’s accuracy and its physical relevance. This challenging issue requires the development of a numerical scheme which supports in particular wave-particle cross diffusion terms. Thus, we will present in this talk the new dedicated numerical scheme we have developed and implemented in Salammbô. Then we will focus on quantifying the effect of wave-particle cross diffusion terms on the dynamics of highly energetic trapped electrons, in presenting results for real case storms.
Impacts of ocean model resolution in S2S forecasts with the ECMWF coupled model
Authors: Roberts Chris , Vitart Frederic , Balmaseda Magdalena , Molteni Franco
Published: March 2020

This study uses initialized forecasts to evaluate the wintertime North Atlantic response to an increase of ocean model resolution from ~100 km (LRO) to ~25 km (HRO) in the European Centre for Medium-Range Weather Forecasts Integrated Forecasting System (ECMWF-IFS). Importantly, the simulated impacts are timescale-dependent such that impacts in subseasonal and seasonal forecasts cannot be extrapolated from multidecadal climate experiments. In general, mean biases are reduced in HRO relative to LRO configurations and the impact is increased at longer lead times. At subseasonal to seasonal lead times, surface heating anomalies over the Gulf Stream are associated with local increases to the poleward heat flux associated with transient atmospheric eddies. In contrast, surface heating anomalies in climate experiments are balanced by changes to the time-mean surface winds that resemble the steady response under linear dynamics. Some aspects of air-sea interaction exhibit a clear improvement with increased resolution at all lead times. However, it is difficult to identify the impact of increased ocean eddy activity in the variability of the overlying atmosphere. In particular, atmospheric blocking and the intensity of the storm track respond more strongly to mean biases and thus have a larger response at longer lead times. Finally, increased ocean resolution drives improvements to subseasonal predictability over Europe. This increase in skill seems to be a result of improvements to the Madden Julian Oscillation and its associated teleconnections rather than changes to air-sea interaction in the North Atlantic region.
Identifying and Quantifying the Role of Magnetic Reconnection in Space Plasma Turbulence
Authors: Agudelo Rueda Jeffersson Andres , Verscharen Daniel , Wicks Robert , Owen Christopher , Nicolaou Georgios , Walsh Andrew , Zouganelis Yannis , Vargas Santiago
Published: March 2020

One of the outstanding open questions in space plasma physics is the heating problem in the solar corona and the solar wind. In-situ measurements, as well as MHD and kinetic simulations, suggest a relation between the turbulent nature of plasma and the onset of magnetic reconnection as a channel of energy dissipation, particle acceleration and a heating mechanism. It has also been proven that non-linear interactions between counter propagating Alfvén waves drives plasma towards a turbulent state. On the other hand, the interactions between particles and waves becomes stronger at scales near the ion(electron) gyroradious ρi (ρe ), and so turbulence can enhance conditions for reconnection and increase the number of reconnection sites. Therefore, there is a close link between turbulence and reconnection. We use fully kinetic particle in cell (PIC) simulations, able to resolve the kinetic phenomena, to study the onset of reconnection in a 3D simulation box with parameters similar to the solar wind under Alfvénic turbulence. We identify in our simulations characteristic features of reconnection sites as steep gradients of the magnetic field strength alongside with the formation of strong current sheets and inflow-outflow patterns of plasma particles near the diffusion regions. These results will be used to quantify the role reconnection in plasma turbulence.
Seasonal streamflow forecasts fostering hydro power cascade operation applying the adaptive policy search framework
Authors: Libisch-Lehner Christoph , Kling Harald , Fuchs Martin , Nachtnebel Hans-Peter
Published: March 2020

Hydro power assets contribute a valuable share of carbon-free energy generation worldwide. Large reservoirs are able to store energy and, combined with pump-storage capacities, they will play an important role in the future’s energy mix. In the future, the stronger integration of volatile energy sources, like solar and wind energy demands the flexibility of hydro power plants. In general, the operation of hydro power plants is a multi-stakeholder and multi-objective dynamic problem related to critical infrastructure. This requires flexible and robust reservoir operation policies, defined as closed-loop release functions where the system state is the input and turbine flows are the response of the function. Recently, Evolutionary-Multi-Objective-Direct-Policy-Search (EMODPS) yielded promising control policies for water resources systems. EMODPS is a kind of machine learning approach that relies on long records, or stochastic streamflow replicates capturing a wide range of possible conditions. A stochastic streamflow generator should actually cover all possible conditions related to the state-action-space and inflates the optimization process. Furthermore, the search procedure can implicitly identify the "most representative" states of the system and tends to approximate a better solution for these states. States that are very rarely explored but can be very important for a reliable operation have little effect on the optimized policy. In addition, artificial neuronal networks (ANN) derived from EMODPS suffer under the curse of instable sections . This is because ANN's are good at interpolating, but bad at extrapolating actions from unobserved states in the training sequence. Thus, we extend the well-known EMODPS framework by an re-optimizing approach utilizing seasonal streamflow predictions. Periodically, the reservoir policies are re-optimized based on an ensemble of streamflow predictions and the actual reservoir water levels. This adaptive policy search (APS) approach is applied to a three reservoirs cascade under Mediterranean climate, where the energy market will play an important role in the future. First results show that the hydropower operation can be improved: energy generation can slightly be increased at clearly lower cost of flood risk compared to static robust policies.
Seasonal forecasts of runoff and river discharge in South America: skill and post-processing
Authors: Greuell Wouter , Hutjes Ronald
Published: March 2020

This contribution deals with the skill of a physical model-based system built to produce probabilistic seasonal hydrological forecasts, applied here to South America and earlier to Europe (see  Greuell et al., hess-23-371-2019). The system basically consists of the Variable Infiltration Capacity (VIC) hydrological model forced with output from ECMWF’s Seasonal Forecasting System 5 (SEAS5). We analyse skill in runoff and discharge hindcasts both with real observations and with so-called pseudo-observations, i.e. with discharge data generated with VIC forced with historical meteorological observations (1981-2015). At the continental scale discrimination skill in runoff shows characteristics that are similar to Europe. Especially, even at the longest lead time (7 months) significant skill remains in 20-30% of both continents. However, in the first lead month there is less significant skill in South America, due to absence of skill in its very dry and very wet regions, than in Europe, where similar extremes do not exist. To explain the skill in runoff, we performed two suites of specific hydrological hindcasts akin to Ensemble Streamflow Predictions (ESP), which each isolate a different source of skill (meteorological forcing and initial conditions). We find that in South America the contribution to skill by forcing is larger than in Europe, which can be ascribed to differences in the skill in the precipitation forcing. Even at a lead time of 7 months, the precipitation hindcasts have significant skill in 15-30% of South America while in Europe skill is almost confined to the first lead month. Discharge hindcasts for grid cells with a sufficient amount of observations were post-processed with ensemble model output statistics (EMOS). This procedure successfully increased reliability but resulted in a small decrease of discrimination skill. Nevertheless, for the location of the Itaipu dam, used to produce 18% of Brazil’s electricity, discrimination skill is highly significant for the post-processed discharge, e.g. at all lead times in the last two months of the year.
Modelling dynamic interactions between soil structure and soil organic matter
Authors: Jarvis Nicholas , Coucheney Elsa , Chenu Claire , Herrmann Anke , Keller Thomas , Kätterer Thomas , Meurer Katharina
Published: March 2020

The aggregated structure of soil is known to reduce rates of soil organic matter (SOM) decomposition and therefore influence the potential for long-term carbon sequestration. In turn, the storage and turnover of SOM strongly determines soil aggregation and thus the physical properties of soil. The two-way nature of these interactions has not yet been explicitly considered in soil organic matter models. In this study, we present and describe a new model of these dynamic feedbacks between SOM storage, soil pore structure and soil physical properties. We show the results of a test of the model against measurements made during 61 years in a field trial located near Uppsala (Sweden) in two treatments with different OM inputs (bare fallow, animal manure). The model was able to successfully reproduce long-term trends in soil bulk density and organic carbon content (SOC), as well as match limited data on soil pore size distribution and surface elevation. The results suggest that the model approach presented here could prove useful in analyses of the effects of soil and crop management practices and climate change on the long-term potential for soil organic carbon sequestration.
The vertical profile of tropical temperature trends: Persistent model biases in the context of forced and internal variability
Authors: Mitchell Dann , Lo Eunice , Seviour William , Polvani Lorenzo
Published: March 2020

Tropospheric and stratospheric tropical temperature trends in recent decades have been notoriously hard to simulate using climate models, notably in the upper troposphere.  Aside from the warming signal itself, this has broader implications, e.g. atmospheric circulation trends depend on latitudinal temperature gradients. In this study, tropical temperature trends in the CMIP6 models are examined, from 1979 to 2014, and contrasted with trends from the RICH/RAOBCORE radiosondes, and the ERA5/5.1 reanalysis.  Confirming previous studies, we find considerable warming biases in the CMIP6 modeled trends, and show that these biases are linked to biases in surface temperature (the models warm too much).  We also uncover previously undocumented biases in the lower-middle stratosphere: the CMIP6 models appear unable to capture the time evolution of stratospheric cooling, which is non-monotonic owing to the Montreal Protocol. This troposphere-warming, stratospheric-cooling fingerprint of climate change is therefore not well captured in CMIP6 models. Finally, we quantify the relative roles of individual climate forcings in tropspheric and stratospheric temperatures, including that of internal variability.
New evidence of soot particles affecting past and future cloud formation and climate
Authors: Lohmann Ulrike , Friebel Franz , Kanji Zamin A. , Mahrt Fabian , Mensah Amewu A. , Neubauer David
Published: March 2020

Clouds play a critical role in the hydrological cycle and modulating the Earth’s climate via precipitation and radiative forcing. Aerosol particles acting as cloud condensation nuclei and ice nucleating particles aid in cloud formation, shaping their microphysical structure. Previously thought to be unimportant for cloud formation, soot particles that undergo oxidation by ozone and/or aging with aqueous sulfuric acid result in being both good centers for cloud droplets and ice crystals formation. However, the associated changes in cloud radiative properties and the consequences for Earth’s climate remain uncertain, because these processes have not been considered in global climate models. Here we present both past and future global climate simulations, which for the first time consider the effect of such aged soot particles as cloud condensation nuclei and ice nucleating particles. Our results constitute the first evidence that aging of soot particles produce a 0.2 to 0.25 Wm-2 less negative shortwave indirect aerosol forcing compared to previous estimates. We also conducted equilibrium climate sensitivity simulations representing a future warmer climate in which the carbon dioxide concentration is doubled compared to pre-industrial levels. Accounting for these soot aging processes significantly exacerbates the global mean surface temperature increase by 0.4 to 0.5 K. Thus, reducing emissions of soot particles will be beneficial for many aspects including air pollution and future climate.

 
Solving the 23 Major Mysteries in Hydrology: Who Cares and Why?
Authors: Loucks Daniel
Published: March 2020

A recent paper (Bloeschl, et al. 2019) reported on the outcome of a multi-year effort involving over 200 scientists identifying the 23 most unsolved scientific issues facing the hydrologic community today.  The purpose of this exercise was to motivate the hydrologic research community to focus their work on these issues to better understand the major causes of how water behaves in our catchments, watersheds and river basins, often in different ways at various space and time scales, and under the influence of various degrees of human interactions. Aside from the scientific value that this increased understanding might bring, this presentation focuses on two questions: Why and how might this increased understanding be beneficial and who would benefit? In other words, who should care and why? This interactive presentation attempts to provide some answers to these two questions for each of the 23 identified unsolved scientific problems. But in general it is clear much of the impact that humans are having on our environment is driven by how the hydrologic cycle fits in with the needs of humans and our supporting ecosystems. Water in our environment affects the spread of contaminants and pathogens, the energy and food and industrial goods we produce, the ecosystem services we enjoy, and the duration and extent of floods and droughts some endure. Understanding these links and their economic, health, and social consequences will allow us to manage our water resources and their use more effectively, and perhaps even reduce the risks of reaching tipping points that could forever change how we all will live and survive in the future.    
Climate Change Education: From Sustainable Development Thinking to Climate Action
Authors: Hung Wei , Tung Ching-Pin
Published: March 2020

Climate change changes the pathway to reach sustainable development. However, the spirit of sustainability is neglected in Taiwan’s education system, which ignored the relationship between climate change and sustainability. This study aims to re-examine the content of climate change education, integrate the concepts of sustainable development, climate change adaptation and transition niche in 12-Year Basic Education Curricula, in order to fill the gap between the international sustainable development trend and climate change education. The methods are literature review and data-gathering methods to understand the connotation through the implementation of international education for sustainable development and climate change education. Furthermore, climate change literacy questionnaires which examined the content validity by the experts were analyzed the sustainability assessment and indicators. At last, the combination of international sustainable development concepts, literacy surveys, questionnaires, is proved to be an effective design for climate change literacy of high school students.  As a result, these can be used as an important framework for designing effective educational strategies to improve students’ climate change literacy and raise their sustainability performance in their daily life.

 

Key Words: Education for sustainable development、Climate change education、Sustainability assessment and indicators、Climate change literacy
Effective aggregation of gappy replicated time series using INLA
Authors: Wutzler Thomas , Migliavacca Mirco , Morris Kendalynn
Published: March 2020

Soil CO2 efflux data from automated chambers provide an important constraint for ecosystem and soil respiration. Usually, half-hourly time series of several replicated chambers have to be aggregated to plot-level while gaps in the time series have to be accommodated. Gaps cause jumps and other problems in aggregation of replicated measurement in each half-hour, therefore, lookup tables and machine learning approaches are used to fill gaps beforehand.

Here, we present an alternative fully Bayesian approach for the combined gap-filling and aggregation based on Integrated Nested Laplace Approximation (INLA). This method integrates all information from every measurement across replicates and across time and therefore efficiently estimates the correlation structure among all observations. It provides the full marginal posterior distribution of the aggregated time series at the plot level across the time span of the time series. We compare several aggregation approaches using four years of data from 16 automatic chambers at the eddy-covariance site in Majadas de Tietar in Spain (ES-LM1, ES-LMa).

This approach is applicable for other replicated time series as well. We further explore its usage for analysing time-varying effects across treatments and habitats and its usage for gap-filling net ecosystem exchange (NEE) data based on the full correlation structure in a data-cube of time and environmental conditions.
Ionospheric ions in the magnetosphere: Important at large and small scales
Authors: André Mats , Toledo-Redondo Sergio , Yau Andrew W
Published: March 2020

Cold (eV) ions of ionospheric origin dominate the number density of most of the volume of the magnetosphere during most of the time. Supersonic flows of cold positive ions are common and can cause a negatively charged wake behind a positively charged spacecraft. The associated induced electric field can be observed and can be used to study the cold ions. We present observations from the Cluster and MMS spacecraft showing how a charged satellite, and also individual charged wire booms of  an electric field instrument, can be used to investigate cold ion populations. Ionospheric ions affect large scales, including the Alfvén velocity and  thus energy transport with waves and the magnetic reconnection rate. These ions also affect small-scale kinetic plasma physics, including the Hall physics and wave instabilities associated with magnetic reconnection. Concerning large scales, we summarize observations from several spacecraft and show that a typical total outflow rate of ionospheric ions is 1026 ions/s and that many of these ions stay cold also after a long time in the magnetosphere.  Concerning small scales, we show examples of how cold ions modify the Hall physics of thin current sheets, including magnetic reconnection separatrices. On small kinetic scales the cold ions introduce a new length-scale, a gyro radius between the gyro radii of hot (keV) ions and electrons. The Hall currents carried by electrons can be partially cancelled by the cold ions when electrons and the magnetized cold ions ExB drift together. Also, close to a reconnection X-line an additional diffusion region can be formed (regions associated with hot and cold ions, and with electrons, total of three).
Why can't models get the mesoscale atmospheric spectrum right?
Authors: Wang Jih-Wang Aaron , Sardeshmukh Prashant
Published: March 2020

Despite decades of development, global atmospheric models continue to have trouble in capturing the -5/3 slope of the atmospheric mesoscale kinetic energy (KE) spectrum suggested by conventional turbulence theory and upper tropospheric aircraft observations in the 1980s (e.g., Nastrom and Gage 1986). We have approached this issue in two ways: 1) How certain can we be that the “real” spectrum has a -5/3 slope? and 2) Are turbulent cascades the only determinants of the mesoscale spectrum? To address the first issue, especially in light of the vastly greater number of upper-air observations that have been analyzed since the 1980s, we have examined the 200-hPa KE spectra in several high-resolution global reanalysis datasets, including the NCEP GFS (resolution T1534 and T254), ERA-Interim (T255), ERA5 (T639), and JRA-55 (T319) datasets. We find that the mesoscale portions of the global spectra are highly mutually inconsistent. This is primarily because the global mesoscale KE has a large contribution from the KE in convective regions, which differs greatly among the various reanalyses. There is thus indeed some ambiguity concerning the slope of the “true” mesoscale spectrum.

To address the second issue, especially given the sensitivity of the reanalysis spectra to representations of convection and damping in the reanalysis models, we assessed the sensitivity of the model spectra in two ways: (a) by stochastically perturbing the physical tendencies and (b) by decreasing the hyper-viscosity coefficient, in large ensembles of 10-day forecasts made with the NCEP GFS (T254) model. Both changes increased the mesoscale KE and decreased the steep spectral slope. The impact of the stochastic physics varied with the specified length scale of the stochastic perturbations. 

Our conclusions about issues 1) and 2) raised above are that (1) we do not really know the “true” mesoscale KE spectrum, and (2) model KE spectra are sensitive to and can be manipulated by stochastically perturbing the parameterized physical tendencies and tuning the horizontal diffusion in a model.  It may therefore be misleading for modelers to pursue the -5/3 slope of the Nastrom-Gage spectrum.