bluuebunny/crossref_metadata_2025 huggingface dataset:
Towards improving a national flood early warning system with global ensemble flood predictions and local knowledge; a case study on the Lower Shire Valley in Malawi.
Authors: Teule Thirza , Couasnon Anaïs , Bischiniotis Kostas , Blasch Julia , van den Homberg Marc
Published: March 2020

Flood risk, a function of hazard, exposure, and vulnerability, is increasing globally and has led to more and more disastrous flood events. Previous research has shown that taking early action is much more cost-effective than responding once the flood occurs. Such an anticipatory approach requires flood early warning systems (EWS) that provide ample lead time and that have sufficient spatial resolution. However, in developing countries, often the skill of available forecasts is insufficient to create a more effective triggering mechanism as part of a flood EWS.

This research presents an assessment of two methods to improve an existing flood EWS using a case study of the most flood-prone area of Malawi, i.e. the Lower Shire Valley. First, the forecast skill and trigger levels of the medium-term Global Flood Awareness System (GloFAS) model are determined for four gauge locations to assess how they can improve the national EWS. Secondly, an assessment is done on how the process of integrating flood forecasts based on local knowledge with official forecasts, can help to improve the EWS. This is done by semi-structured interviews at the national level and focus group discussions at the community level. The study shows that GloFAS does not predict absolute discharge values precisely, but can be used to predict floods if the correct trigger levels are set per location. The integration of multiple forecast sources is found to be useful at both national and community levels. An integration process is proposed where village stakeholders should take the leading role by using existing disaster management and civil protection coordination mechanisms. Overall, both methods can contribute to improving the flood EWS and decreasing the flood risk in the Lower Shire Valley in Malawi.
Simple process-led algorithms for simulating habitats (SPLASH v.2.0): robust calculations of water and energy fluxes in complex terrain
Authors: Sandoval David , Prentice Iain Colin
Published: March 2020

Complex models suffer from a multiplicity of parameters, allowing many combinations of values to yield apparently acceptable results and thus entailing a risk of obtaining “right answers for wrong reasons”. Aiming to compute key components of the water and energy balances from readily available meteorological observations while reducing the need for free parameters, we propose new formulations to extend the SPLASH model of Davis et al. (2017, Geoscientific Model Development) to deal with complex topography. SPLASH is a parsimonious, multi-purpose set of algorithms designed principally for ecological and ecohydrological applications. Wherever possible we based model construction on first principles, attempting to balance realism with robustness. By adopting analytical rather than numerical solutions for many processes, we have been able to apply the model at high spatial resolution without unreasonably inflating computational demands – allowing us to include terrain effects directly in the calculations of water and energy fluxes. Slope and aspect were included in the analytical integrals originally used to compute accumulated energy fluxes through the day. Upslope area, the terrain-induced hydraulic gradient, and an analytical solution for the soil column transmittance were included in the calculations of subsurface water flow, following TOPMODEL ideas. Whenever empirical calculations were used (pedotransfer functions, albedo-snow cover functions), they were recalibrated using a combination of remote sensing data and globally distributed observational datasets. Simulations of soil water content, evapotranspiration and snow-water equivalent were compared against in situ measurements using diverse and combined data sources (including FLUXNET and SNOTEL). The statistical performance of the model was tested with pooled measurements from multiple stations. Global simulations were run at 5 km resolution and compared with remote-sensing retrievals and state-of-the-art land surface models.
Role of dynamic and thermodynamic processes for the propagation of organized convection in a large-scale flow
Authors: Jung Hyunju , Naumann Ann Kristin , Stevens Bjorn
Published: March 2020

Convective self-aggregation in radiative convective equilibrium has been studied due to its similarities to organized convection in the tropics. As tropical atmospheric phenomena are embedded in a large-scale flow, we impose a background wind to the model setup using convection-permitting simulation to analyze the interaction of convective self-aggregation with the background wind. The simulations show that when imposing a background wind, the convective cluster propagates in the direction of the imposed wind but slows down compared to what pure advection would suggest, and eventually becomes stationary. The dynamic process dominates slowing down the propagation speed of the cluster because the surface momentum flux acts as a drag on the near-surface wind, terminating the propagation. The thermodynamic process through the wind-induce surface feedback contributes to only 6% of the propagation speed of the convective cluster and is strongly modified by the dynamic process.
How different are effects of vinasse biochar on soil erosion in Loess and Marl soils?
Authors: Sadeghi Seyed Hamizedra , Kiani-Harchegani Mahboobeh , Hazbavi Zeinab , Younesi Habibollah , Sadeghi Padideh Sadat , Angulo-Jaramillo Rafael , Lassabatere Laurent
Published: March 2020

Nowadays soil erosion control using different amendments has grown up worldwide. However, the application of transformed materials like biochar has not been adequately studied. In the same vein, the application of biochars produced from waste materials that harm nature, and impose cost to managers and producers is a valuable approach for optimal utilization of the resources. Towards this, the performance of biochar produced from deleterious raw vinasse as the main by-product of sugarcane industries in controlling soil splash and interrill erosions on two marl and loess soils from Iran was investigated. The study was performed in 0.5 m×0.5 m plots in three replicates installed in the field with a slope steepness of 25% subjected to a simulated rainfall with an intensity of 50 mm h-1 and 0.5 h duration. Analysis of the results obtained from the splash and interrill erosions during the rainfall-runoff process showed that biochar decreased soil loss compared to the control plot on Marl soil but to a small extent (p > 0.05). However, the plot treated with biochar on the loess soil revealed significant (p<0.05) reduction in soil loss in comparison with that of the control plot. That study clearly demonstrates the addition of biochar may promote stability and limit both runoff and soil erosion. However, such effects strongly depend on the type of soils.
Impact of marine sand extraction on benthic communities west off Sylt (SE North Sea)
Authors: Mielck Finn , Michaelis Rune , Armonies Werner , Hass H. Christian
Published: March 2020

Ongoing erosion at coasts, beaches and dunes accompanied by a climate change-induced sea-level rise requires extensive protection measures. At the Island of Sylt (SE North Sea) beach nourishments were conducted for almost 50 years to protect the exposed western coast against erosion. Since 1984, the materials for the sand replenishments were dredged from an offshore excavation site approx. 7 km west off Sylt in the German Bight. In this study, we investigate the long-term effects of sand extraction on the local geomorphology, the associated benthic habitats and fauna. Hydroacoustic surveys and grab sampling revealed that after more than 35 years changes in bathymetry (with dredging pits of down to ~15 m below sea floor) and also changes in habitat characteristics are still present. Additionally, the sediment and benthic faunal compositions have changed. A comparison between dredged areas and undisturbed seafloor revealed significant differences in mud content (increasing), the number of individuals and species of macrozoobenthic organisms (decreasing). This indicates that the benthic communities in the dredging areas are in a persistent successional stage. Mud-loving species (e. g. Notomastus latericeus and Kurtiella bidentate) profit from the changed habitats, however sand-preferring organisms (e.g. Pisione remota and Aonides paucibranchiata) largely disappeared. Because of the slow backfill rates, we conclude that a complete backfill of the deep dredging pits is likely to take centuries. The same is expected to apply for the regeneration of the benthic communities. However, since rather coarse-to-medium sand was removed from this area and re-accumulation of this Pleistocene material is not possible because of weak transport rates, a re-establishment of benthic communities that prefer coarser sand seems to be unlikely. Since benthic communities are strongly linked to the habitat characteristics, habitat mapping using hydroacoustic techniques is an efficient and cost-effective measure to monitor the state of regeneration in this study site.
Waveform cross-correlation-based earthquake detection applied to microseismicity near the central Alpine Fault, New Zealand
Authors: Michailos Konstantinos , Chamberlain Calum J. , Townend John
Published: March 2020

The Alpine Fault is a major plate boundary oblique strike-slip fault, known to fail in large M 7-8 earthquakes, posing a significant seismic hazard to southern and central New Zealand. The central part of the Alpine Fault exhibits low seismic activity when compared to adjacent areas. We have examined the smaller-magnitude earthquake activity occurring along the central portion of the Alpine Fault using data from five temporary seismic networks from late 2008 to early 2017.

We have created the most complete and accurate earthquake catalog at the central Alpine Fault to date (9,111 earthquake locations with magnitudes ranging from ML -1.2 to 4.6). We used this catalog as templates with a matched-filtering earthquake detection method and further extend the earthquake catalog. This even more comprehensive earthquake catalog will provide more definitive evidence for the seismicity characteristics observed and better insights into the fault zone’s geometry. 

Taking advantage of this extensive earthquake catalog, we also aim to examine whether there are any repeating highly similar seismic signals (repeating earthquakes). These repeating earthquakes can potentially help better determine the locked and creeping sections of the Alpine Fault and possibly quantify the total amount of creep taking place with respect to seismic deformation.
Splash erosion experiments with silt loam and loamy sand soil under simulated rainfall produced by two types of rainfall simulators
Authors: Zambon Nives , Lolk Johannsen Lisbeth , Strauss Peter , Dostál Tomáš , Zumr David , A. Cochrane Thomas , Klik Andreas
Published: March 2020

Soil erosion by water is globally the main soil degradation process which leaves serious consequences on agricultural land and water aquifers. Splash erosion is the initial stage of soil erosion by water, resulting from the destructive force of rain drops acting on soil surface aggregates. Splash erosion studies conducted in laboratories use rainfall simulators. They produce artificial rainfall which can vary according to type of the rainfall simulator. In this study the aim was to quantify the differences in splash erosion rates affected by rainfall produced by two different rainfall simulators on two silt loam and one loamy sand soil. Splash erosion was measured using modified Morgan splash cups and the rainfall simulators were equipped with four VeeJet or one FullJet nozzle. The soil samples placed under simulated rainfall were exposed to intensity range from 28 to 54 mm h-1 and from 35 to 81 mm h-1, depending on the rainfall simulator. Rainfall characteristics such as drop size and velocity distribution were measured with an optical laser disdrometer Weather Sensor OTT Parsivel Version 1 (Parsivel) by OTT Messtechnik. Rainfall simulator with VeeJet nozzles produced smaller drops but higher drop velocity which resulted in higher kinetic energy per mm of rainfall compared to rainfall simulator with FullJet nozzles. For the same intensity rate measured kinetic energy under the rainfall simulator with VeeJet nozzles was 45% higher than rainfall kinetic energy from rainfall simulator with FullJet nozzles. Accordingly, the average splash erosion rate was 45 and 59% higher under the rainfall simulator with VeeJet nozzles for one silt loam and loamy sand soil, respectively. Splash erosion was found to be a linear or power function of the rainfall kinetic energy, depending on rainfall simulator. The obtained results highlight the sensitivity of the splash erosion process to rainfall characteristics produced by different rainfall simulators. The heterogeneity of rainfall characteristics between different types of rainfall simulators makes a direct comparison of results obtained from similar erosion studies difficult. Further experiments including comparison between more rainfall simulators could define influencing rainfall parameters on splash erosion under controlled laboratory conditions.
Using supervised machine learning to automatically detect type II and III solar radio bursts
Authors: Carley Eoin
Published: March 2020

Solar flares are often associated with high-intensity radio emission known as `solar radio bursts' (SRBs). SRBs are generally observed in dynamic spectra and have five major spectral classes, labelled type I to type V depending on their shape and extent in frequency and time. Due to their morphological complexity, a challenge in solar radio physics is the automatic detection and classification of such radio bursts. Classification of SRBs has become necessary in recent years due to large data rates (3 Gb/s) generated by advanced radio telescopes such as the Low Frequency Array (LOFAR). Here we test the ability of several supervised machine learning algorithms to automatically classify type II and type III solar radio bursts. We test the detection accuracy of support vector machines (SVM), random forest (RF), as well as an implementation of transfer learning of the Inception and YOLO convolutional neural networks (CNNs). The training data was assembled from type II and III bursts observed by the Radio Solar Telescope Network (RSTN) from 1996 to 2018, supplemented by type II and III radio burst simulations. The CNNs were the best performers, often exceeding >90% accuracy on the validation set, with YOLO having the ability to perform radio burst burst localisation in dynamic spectra. This shows that machine learning algorithms (in particular CNNs) are capable of SRB classification, and we conclude by discussing future plans for the implementation of a CNN in the LOFAR for Space Weather (LOFAR4SW) data-stream pipelines.
SuperflexPy: a new open source framework for building conceptual hydrological models
Authors: Dal Molin Marco , Kavetski Dmitri , Fenicia Fabrizio
Published: March 2020

Hydrological models represent a fundamental tool for linking data with theories in scientific studies. Conceptual models are among the most frequently used type of models in catchment scale studies, due to their low computational requirements and ease of interpretation. Model selection requires the comparison of model alternatives, which is complicated by differences in conceptualization, implementation, and source code availability of the models present in the literature. For this reason, several model-building frameworks have been introduced in the last decade, which facilitate model comparisons by enabling different model alternatives within the same software and numerical architecture. These frameworks, however, have their own limitations, including the difficulty of extension from a user perspective, the requirement of long set-up procedures, and the need of customized input files.
Building on the decennial experience with the development and usage of Superflex, a flexible modeling framework for conceptual model building, so far implemented in FORTRAN language and not available as open source, we propose SuperflexPy, an open source Python framework for building conceptual hydrological models. SuperflexPy allows the user to build fully customized models using generic elements (i.e. reservoirs, splitters, junctions, lag functions, etc.) and to arrange them as desired, for example to reflect lumped or semi-distributed model configurations. SuperflexPy is easy to configure through modular initialization scripts, easy to extend with custom functionalities, and easy to interface with other frameworks, making it an essential element for creating a continuous and reproducible pipeline that goes from raw data to model results and interpretation.
In this presentation, we will introduce this framework, showcasing some applications and highlighting its potential in the context of open science.
Wildfire-driven release of metal(loid)s from topsoils in a smelter-polluted semi-arid area: an experimental approach
Authors: Tuhý Marek , Ettler Vojtěch , Rohovec Jan , Matoušková Šárka , Mihaljevič Martin , Majzlan Juraj , Kříbek Bohdan , Mapani Ben
Published: March 2020

Wildfires contribute to global emissions of trace elements. This study focuses on highly polluted areas near an operating copper smelter and old mine-tailing disposal sites in Tsumeb (semi-arid north of Namibia), where wildfires frequently occur. Capturing of particulates windblown from the ore processing and smelting areas by vegetation (trees, grass) leads to the topsoil enrichment with metal(loid) contaminants (up to 7090 mg/kg Cu, 2070 mg/kg As, 4820 mg/kg Pb, 3480 mg/kg Zn, 75 mg/kg Cd, 7.66 mg/kg Hg). Experimental samples corresponding to representative biomass-rich topsoils (bushland with acacia and marula trees, grassland) were investigated using a combination of mineralogical and geochemical methods. Wildfires were simulated using a thermodesorption (TD) technique (75-670 °C; Hg) and an experimental setup composed of a temperature-controlled furnace (250-850 °C), an aerosol-filtering unit and a gas-trapping device (As, Cd, Cu, Pb, Zn). The obtained ashes were investigated to depict any mineralogical and chemical transformations in order to understand temperature-dependent release of metal(loid) contaminants during the simulated wildfire.

Thermodesorption experiments indicated that more than 90% of Hg was released at ~340 °C, which corresponded to predominant grassland-fire conditions. A comparison with the TD curves of the Hg reference compounds confirmed that the Hg in the biomass-rich topsoils occurs as a mixture of Hg bound to the organic matter and metacinnabar (black HgS), which exhibited similarities with the TD pattern of smelter flue dust residue. Temperature-dependent release of other metal(loid)s (As, Cd, Cu, Pb, Zn) is dependent on their solid-state speciation. Cadmium is released at ~750 °C, corresponding to the thermal decomposition of carbonates, in which Cd is mainly bound. Arsenic exhibits first remobilization step at <350 °C (decomposition of arsenolite, As2O3) and the second step at >650 °C corresponding to the instability of arsenates and As-rich slag glass. Other contaminants (Cu, Pb, Zn) were mainly bound in carbonates, slag particles and sulfides/sulfosalts. During the simulated wildfire, they were mainly retained in the ash and were remobilized to a lesser degree at >650 °C. Calculations indicated that at 850 °C (worse-case wildfire scenario) 2-17 % of total As, Cu, Pb and Zn, 27-79 % of total Cd and 100 % of Hg can be volatilized from these biomass-rich contaminated topsoils.

This study was supported by the Czech Science Foundation (GACR project no. 19-18513S) and a student grant from the Grant Agency of Charles University (GAUK no. 1598218).
Accelerating Global Science on Tsunami Hazard and Risk Analysis (AGITHAR)
Authors: Behrens Joern , Aniel-Quiroga Inigo , D'Amico Sebastiano , Dias Frederic , Didenkulova Ira , Guillas Serge , Lorito Stefano , Lovholt Finn , Macias Jorge , Murphy Shane , Necmioglu Ocal , Omira Rachid , Roedder Simone , Sorensen Mathilde
Published: March 2020

Recent tsunami disasters revealed severe gaps between the anticipated level of hazard and the true extent of the event, with resulting loss of life and property. The severe consequences were underestimated in part due to the lack of rigorous and accepted hazard analysis methods and large uncertainty in forecasting the tsunami source mechanism and strength. Uncertainty and underestimation of the hazard and risk resulted in insufficient preparedness measures. While there is no absolute protection against disasters of the scale of mega tsunamis, a more accurate analysis of the potential risk can help to minimize losses from tsunami.
After the major events in 2004 and 2011 many new initiatives originated novel methods for tsunami hazard and risk analysis. However, rigorous performance assessment and evaluation – with respect to guiding principles in tsunami hazard and risk analysis – has not been conducted. In particular, comprehensive uncertainty assessments and related standards are required in order to implement more robust and reliable hazard analysis strategies and, ultimately, better mitigate tsunami impact. This is the core challenge of the proposed COST Action Accelerating Global science In Tsunami HAzard and Risk analysis (AGITHAR).
In our presentation we will demonstrate first results of the Action, assessing research gaps, open questions, and a very coarse roadmap for future research.
The impact of biases in the tropical South Pacific and near the Agulhaus Current on the large-scale Southern Hemisphere circulation
Authors: Garfinkel Chaim , White Ian , Gerber Edwin , Jucker Martin
Published: March 2020

A common model bias in comprehensive climate models used in climate assessements such as the Coupled Model Intercomparison Project is a double inter-tropical convergence, with excessive precipitation in the tropical eastern South Pacific. In addition, the current generation of climate models cannot adequately resolve the dynamics of the Agulhas Current, and in particular the relative fraction of the Current that leaks into the Atlantic as opposed to retroflecting back into the Indian Ocean. The intermodel spread in the magnitude of the double ITCZ bias is   significantly correlated with the strength and phasing of   SH stationary waves in the CMIP archive, with models with a smaller bias generally showing more realistic stationary waves. An intermediate complexity moist General Circulation Model is used to demonstrate the causality of this connection: by fluxing heat out of  the tropical South Pacific Ocean, we can capture the  responses seen in CMIP5 models.  Finally, the same intermediate complexity moist General Circulation Model is used to demonstrate that an overly diffuse Agulhas leads to an equatorward shift of the Southern Hemisphere jet by more than  3degrees, and indeed an overly equatorward Southern Hemisphere jet is a common model bias in most CMIP5 models.
Documentary data in the study of fatalities caused by meteorological and hydrological events: the Czech Republic, 1964–2019
Authors: Chromá Kateřina , Brázdil Rudolf , Dolák Lukáš , Řehoř Jan , Řezníčková Ladislava
Published: March 2020

Reports from the newspaper “Rudé právo/Právo”, complemented by chronicles, epigraphic evidence, systematic meteorological/hydrological observations, media (including internet), professional reports and papers were used to create a database of fatalities taking place in the course of hydrological and meteorological events over the territory of the Czech Republic during the 1964–2019 period. The spatiotemporal variability of fatalities arising out of floods, flash floods, windstorms, convective storms, lightning, frosts, snow/glaze-ice calamities, avalanches, heats and other events is shown, with particular attention to closer characterisation of fatalities (gender, age, cause of death, place, type of death and behaviour). In the classification of fatalities, males and adults clearly prevail, while indirect victims and hazardous behaviour are strongly represented. Examples of two outstanding events with the highest numbers of fatalities during a flash flood on 9 June 1970 (34 fatalities) and a rain-induced flood in July 1997 (60 fatalities) are described in detail. Discussion of results includes the problem of data uncertainty, factors influencing the numbers of fatalities, and the broader context. The study emphasises the significance of documentary data and reveals its new utilisation in the study of fatalities in the Czech Republic.
Towards a better assessment of the historical climate of Extremadura region (SW Spain)
Authors: Vaquero José Manuel , Gallego María Cruz , Carrasco Víctor M. S. , Bravo-Paredes Nieves , Obregón María Ángeles , Lara Carlos
Published: March 2020

Our efforts to a better understanding of the historical climate of the region of Extremadura (interior of the SW Iberia) have been directed in two main aspects. First, we have tried to recover all the meteorological data of the pre-instrumental period. Second, we have been working on the localization and analysis of proxy data, including “pro-pluvia” rogation ceremonies and a chronology of catastrophic floods in this region.

The recovery of historical meteorological data from libraries and archives and the subsequent digitization to obtain readable-machine version has been a main task in our research. Meteorological data from different sources (manuscripts, books, newspapers, etc.) and eight different locations in Extremadura have been recovered and digitized. The oldest data were read in 1824 (Fernández-Fernández et al., 2014). Other important meteorological series can be highlighted as the actinometric measurements in Cáceres for the period 1913-1920 (Bravo-Paredes et al., 2019).

“Pro-pluvia” rogations were celebrated during dry conditions to ask God for rain. In our case, 35 “pro-pluvia” rogations were retrieved for the period 1824-1931 from different locations in Extremadura. The winter climate of this region is strongly dominated by the North Atlantic Oscillation (NAO) and, therefore, these pro-pluvia rogations were associated to the NAO index to analyze this relationship. The results of our analysis show that the rogation ceremonies in Extremadura can be considered a good proxy for the NAO index. Also, it is important to know the magnitude and the impact of the catastrophic floods occurred in Extremadura. In total, 40 floods occurred in Badajoz were recovered from different documentary sources for the period 1545-1989.

All these research efforts will allow for a better understanding of the past climate in the region of Extremadura, where such studies have been very scarce.

References

Bravo-Paredes, N. et al. (2019) “Analysis of actinometric measurements under different sky conditions in Cáceres (Spain) for the period 1913-1920” Tellus B 71, 1663597. DOI: 10.1080/16000889.2019.1663597

Fernández-Fernández, M.I. et al. (2014) "The climate of Zafra from 1750 to 1840: History and description of weather observations" Climatic Change 126, 107–118. (doi: 10.1007/s10584-014-1201-5)
Breach the dikes! How to design saltmarsh restoration schemes for mitigating coastal flooding.
Authors: Kiesel Joshua , Schuerch Mark , Christie Elizabeth K. , Möller Iris , Spencer Tom , Vafeidis Athanasios
Published: March 2020

Managed realignment (MR), a form of of nature-based coastal adaptation to reduce flood and erosion risk, involves the abandonment of existing sea defences and their relocation further inland. MR aims to (re)create intertidal habitats, such as saltmarshes, between the old and new lines of defence; as well as flood water storage. The newly created habitats dissipate wave energy and thus provide new natural coastal protection. However, the assessment of the success of MR is difficult, as restoration targets are often vague and data on project performance are scarce. The few studies that do exist show a lack of understanding about the effects of MR scheme design on high water level (HWL) attenuation and thus its coastal protection function.

Here we present the results of a 2-D hydrodynamic model, calibrated and validated against field measurements of equinoctial tides between August and October 2017, taken within, and seaward of, the Freiston Shore MR site, The Wash, eastern England. Using this model, we performed sensitivity analyses to explore whether or not, and how, the Freiston Shore MR scheme design affects HWL attenuation. For this purpose we changed the configuration of the old defence line and the breaches created within it for renewed tidal exchange and manipulated the digital elevation model of within-site topography. Specifically, we applied six scheme design scenarios (two scenarios with three breaches and varying MR areas, three single breach scenarios of different breach width and one bank removal scenario) and assessed High Water Level (HWL) attenuation rates for each scenario.

Our results show that scheme design, particularly storage area and number and size of breaches, of the Freiston Shore MR site had a significant effect on the site´s HWL attenuation capacity. When the tidal prism is varied by changing the number and size of breaches and the storage area kept constant, modelled HWL attenuation rates increased with decreasing tidal prism. However, largest HWL attenuation rates (> 10 cm km-1) were only obtained if the MR area was of sufficient size, therefore, it is only the larger sites which are exhibiting effective coastal protection. Consequently, the maximum modelled HWL attenuation rate occurred (up to 73 cm km-1) for the scenario with the largest area (142 ha).

The Mean High Water Depth (MHWD) from each of these scenarios explained most of the variation in HWL attenuation between the scenarios (R² = 0.996). This strong correlation may help to inform the construction of more efficient MR schemes with respect to coastal protection in the future.
Dependence of magnetopause reconnection events on interplanetary parameters
Authors: Gonzalez Walter , Koga Daiki
Published: March 2020

Magnetic reconnection permits topological rearrangements of the interplanetary and magnetospheric magnetic fields and the entry of solar wind mass, energy, and momentum into the magnetosphere. Thus, magnetic reconnection is a key issue to understand space weather. However, it hasnot been fully understood yet under which interplanetary/magnetosheath conditions magnetic reconnection takes place more effectively at the dayside magnetopause. For this purpose,  in the present study 25 dayside magnetopause reconnection events are investigated using the Time History of Events and Macroscale Interactions during Substorms ( THEMIS ) spacecraft  observations. It was found, (1) that the reconnection electric field is proportional to the interplanetary electric field, (2) that the reconnection electric field is inversely proportional to the solar wind-Alfvén Mach number,  (3) that thereconnection outflow speed is proportional to the solar wind Alfvén speed, and (4) that the reconnection outflow speed is  inversely proportional to the magnetosheath plasma beta. Finally, it is shown that the range of magnetic shear angles for which magnetic reconnection should occur is restricted to large shears as the magnetosheath flow direction becomes more perpendicular to the direction of the local magnetopause normal vector. Since these results refer to fairly typical solar wind-Alfvén Mach number condition, they may not apply to more extreme cases.
Visualization Strategies for Optimal 3D Time-Energy Trajectory Planning for AUVs using Ocean General Circulation Models
Authors: Theussl Thomas , Albarakati Sultan , Lima Ricardo , Hoteit Ibrahim , Knio Omar
Published: March 2020

In this presentation, we discuss visualization strategies for optimal time and energy trajectory planning problems for Autonomous Underwater Vehicles (AUVs) in transient 3D ocean currents. Realistic forecasts using an Ocean General Circulation Model (OGCM) are used to define time and energy optimal AUV trajectory problems in 2D and 3D. The visualization goal is to explore and explain the trajectory the AUV follows, especially how it exploits both the vertical structure of the current field as well as its unsteadiness to minimize travel time and energy consumption. We present our choice of visualization tools for this purpose and discuss shortcomings and possible improvements, especially for challenging scenarios involving 3D time-dependent flow and realistic bathymetry.
Hotspots of Extreme Heat under Global Warming
Authors: Suarez-Gutierrez Laura , Müller Wolfgang A. , Li Chao , Marotzke Jochem
Published: March 2020

We evaluate how hotspots of different types of the most extreme summer heat change under global warming increase of up to 4°C, to determine the level of global warming that allows us to avert the risk of these hotspots considering the irreducible range of possibilities defined by well-sampled internal variability. We use large samples of low-probability extremes simulated by the 100-member Max Planck Institute Grand Ensemble (MPI-GE) for five metrics of extreme heat: maximum reachable temperatures, return periods of extreme temperatures, maximum temperature variability, sustained tropical nights, and wet bulb temperatures. At 2°C of warming, MPI-GE projects maximum summer temperatures below 50°C over most of the world. Beyond 2°C, this threshold is overshot in all continents, with projected temperatures above 60°C in hotspots such as the Arabic Peninsula. Extreme 1-in-100-years pre-industrial temperatures occur every 10-25 years already at 1.5°C of warming. At 4°C, these 1-in-100-years extremes are projected to occur every one to two years over most of the world. The range of maximum temperature variability increases by 10-50% at 2°C of warming, and by 50-100% at 4°C. Beyond 2°C, heat stress is aggravated substantially over non-adapted areas by sustained tropical night and hot and humid conditions that occur rarely in a pre-industrial climate. At 4°C of warming, tropical night hotspots spread polewards globally, and prevail for at least 95% of the summer months; whilst extreme monthly mean wet bulb temperatures beyond 26°C spread over large tropical as well as mid-latitude regions.
Drought variability and projections over India under high emission scenario with uncertainty assessment
Authors: Saharwardi Md Saquib , Kumar Pankaj
Published: March 2020

Hydrological extremes have increased in recent decades and are expected to escalate in the future. This led to global and regional water stress and drought hazards. Further down in the chain it impacts on farming, pollution, ecosystem, and socio-economic conditions. A better understanding of both quantitative and qualitative assessment of drought under changing climate is very crucial for sustainable water security and management. In the present study, over different homogeneous regions of India, using 19 Global Climate Models (GCMs) and Regional Climate Models (RCMs) 21 simulations datasets, drought climatology is prepared. The changes in drought distribution and characteristics analyzed using density functions and its probability of occurrence associated with return period derived from Standardized Precipitation Index (SPI) and Standardized Potential Evapotranspiration Index (SPEI). Each model is evaluated for biases against Multi-Model Ensembles (MME) and observational datasets for the reference period 1976-2005. Uncertainties from various sources associated with intermodal variability, including drought type and threshold, were evaluated. Under high emission (RCP8.5) scenario, both the ensembles (GCM and RCM) are showing the consistent spatiotemporal variability of precipitation and potential evapotranspiration with noticeable differences in magnitude. Biases are reduced in RCM over GCM (ensemble) with respect to observations. Modeled SPI is showing enhanced wetness derived from increased precipitation, while SPEI is exhibiting the drying trend largely associated with enhanced potential evapotranspiration under warming climate. There is an increase in the drought severity and intensity with the same return period in the future epoch. The overall analysis suggests the water scarcity and enhanced drought risks over India under unrestricted anthropogenic warming scenario.
Ocean-atmosphere fluxes of carbon dioxide and heat in response to phytoplankton light absorption
Authors: Asselot Rémy , Lunkeit Frank , Holden Phil , Hense Inga
Published: March 2020

Oceanic phytoplankton absorbing solar radiation can influence the upper ocean physics. This process is called phytoplankton light absorption. Previous studies indicate that phytoplankton light absorption significantly impacts the oceanic heat distribution and, if taken into account in an Earth System model, can lead to different climates under similar primary production. However, the dominant processes responsible for these drastic changes in atmospheric temperature have not been yet identified. Phytoplankton light absorption increases the sea surface temperature, therefore altering the exchange of heat between the ocean and the atmosphere. Additionally, phytoplankton light absorption indirectly modifies the ocean carbon cycle and thus the CO2 flux into the atmosphere. To shed light on these aspects, we use an Earth System model of intermediate complexity coupled to an ecosystem model (EcoGENIE). By running a suite of experiements, we determine which fluxes are most important in controlling atmospheric temperature. Here, we present first results of our study.
An evaluation of the surface climatology over the Totten region (Antarctica) using COSMO-CLM2
Authors: Helsen Samuel , Vanden Broucke Sam , Gossart Alexandra , Souverijns Niels , van Lipzig Nicole
Published: March 2020

The Totten glacier is a highly dynamic outlet glacier, situated in E-Antarctica, that contains a potential sea level rise of about 3.5 meters. During recent years, this area has been influenced by sub-shelf intrusion of warm ocean currents, contributing to higher basal melt rates. Moreover, most of the ice over this area is grounded below sea level, which makes the ice shelf potentially vulnerable to the marine ice sheet instability mechanism. It is expected that, as a result of climate change, the latter mechanisms may contribute to significant ice losses in this region within the next decades, thereby contributing to future sea level rise. Up to now, most studies have been focusing on sub-shelf melt rates and the influence of the ocean, with much less attention for atmospheric processes (often ignored), which also play a key-role in determining the climatic conditions over this region. For example: surface melt is important because it contributes to hydrofracturing, a process that may lead to ice cliff instabilities. Also precipitation is an important atmospheric process, since it determines the input of mass to the ice sheet and contributes directly to the surface mass balance. In order to perform detailed studies on these processes, we need a well-evaluated climate model that represents all these processes well. Recently, the COSMO-CLM2 (CCLM2) model was adapted to the climatological conditions over Antarctica. The model was evaluated by comparing a 30 year Antarctic-wide hindcast run (1986-2016) at 25 km resolution with meteorological observational products (Souverijns et al., 2019). It was shown that the model performance is comparable to other state-of-the-art regional climate models over the Antarctic region. We now applied the CCLM2 model in a regional configuration over the Totten glacier area (E-Antarctica) at 5 km resolution and evaluated its performance over this region by comparing it to climatological observations from different stations. We show that the performance for temperature in the high resolution run is comparable to the performance of the Antarctic-wide run. Precipitation is, however, overestimated in the high-resolution run, especially over dome structures (Law-Dome). Therefore, we applied an orographic smoothening, which clearly improves the precipitation pattern with respect to observations. Wind speed is overestimated in some places, which is solved by increasing the surface roughness. This research frames in the context of the PARAMOUR project. Within PARAMOUR, CCLM2 is currently being coupled to an ocean model (NEMO) and an ice sheet model (f.ETISh/BISICLES) in order to understand decadal predictability over this region.
A Study on the Change of Arctic Ocean Surface Temperature in CESM
Authors: Xie Peiyan , He Hailun , Li Shuang
Published: March 2020

Since the 1950s, human has begun to explore the Arctic area. As the scientific research goes further, scientists gradually realize the important role the Arctic plays in the global climate system, and it has been said the Arctic has an amplifying effect on surface warming, which increases 2 to 3 times faster than the global average increment. Given the importance of this area, we try to figure out the relationship among the Arctic sea surface temperature (SST), sea ice index and the Arctic Oscillation (AO) in this paper. By using Community Earth System Model (CESM), we calculated an ocean-seaice-atmosphere coupled 200-year experiment. As a result, we found out that the variation of Arctic SST is negatively correlated with the change of sea ice area. There is a significant correlation between the change of SST and AO, which can lead to the anomaly of air heat transport between the Arctic area and the areas in lower latitude.
A better appreciation of glacial floodplain morphodynamics reveals that disturbances are not spatially homogenous: implications for biofilm development
Authors: Roncoroni Matteo , Clémençon Mélanie , Lane Stuart
Published: March 2020

Recent decades have seen worldwide glacier retreat that has resulted in a significant increase in the spatial extent of proglacial margins. Such margins, by switching from being ice-covered to light-exposed, are open to potential colonization by new organisms. However, ecological succession in glacial forefields may be slowed or even precluded by the highly unstable nature of these environments and habitability might be highly variable both in time and in space.

Discharge-related processes are likely to dominate forefields, in particular during the melt season. Discharge defines the shear forces acting upon the streambed, and ultimately bed and suspended loads and the rate of morphodynamic change through the floodplains. Evidence suggests that during the melt season glacial streams continuously rework their accommodation spaces by erosion and deposition processes, resulting in low rates of environmental stability. This means that benthic organisms, such as biofilms, inhabiting those streams may continuously be under pressure.

Biofilms are surface-attached communities composed of microorganisms, they are at the base of instream food webs, and they are involved in multiple ecosystem processes. Nevertheless, their surface-attached nature leads them to be easily removed from their lodging substrates by hydraulic disturbances. Because disturbance-dominated regimes exist during the melt season in glacial streams, it should be expected that biofilms might not be able to develop or persist during the melt season. A core idea in glacial stream ecology is that biomass, either of biofilms but also of macrozoobenthos, increases by moving away from the glacial snout, but also that it fluctuates during the year and reaches its highest mass during windows of opportunity (i.e., spring and fall). Even though this paradigm might hold, it does not fully capture the complexity of glacial floodplain morphodynamics, and the possibility that some stable zones exist even in summer. This explains why biofilms are able to develop in summer, and why well-developed biofilms can be found even close to the glacier snouts during the melt season.

In this paper, we present the first insights about the reasons why biofilms can develop in glacial floodplains during the melt season and, in particular, how important stable zones are for biofilm development. Through classical morphological and morphodynamic analysis, we seek to demonstrate that disturbances are not spatially homogenous, and geomorphic processes can shape the environment creating hot spot for biota. In this view, we argue that floodplain terraces, either permanent or temporary, play a crucial role in defining where biofilms – and consequently organisms that feed on them – settle, develop and grow.
Investigating surface morphology and transport parameters of single fractures
Authors: Frank Sascha , Heinze Thomas , Ribbers Mona , Wohnlich Stefan
Published: March 2020

In order to obtain a deeper understanding of flow and transport processes in fractures, experimental investigations and numerical modelling have been carried out focusing on the effects of fracture surface morphology. To determine a possible relationship between the roughness of fracture surfaces and hydraulic and transport parameters, two different types of sandstones has been investigated. The sandstones were a coarse-grained, inhomogeneous and strongly anisotropic Flechtinger sandstone (Bebertal, Germany) and a fine-grained, rather homogeneous, isotropic Remlinger sandstone (Würzburg, Germany).

The sandstones were first cored with a diameter of 100 mm and a height of 150 mm and split into individual fissures. The resulting fracture surfaces were scanned using a 3D scan and surface images were generated. These surface images were used to determine the Joint Roughness Coefficient (JRC) and other measures of roughness. The roughness has been characterized along 1D profiles in each direction. Mean values and spread have been calculated for each surface. The fracture surfaces are self-affine so that little variation along both surfaces has been determined. Both sandstone halves were then joined together and the reassembled fractured rock core was examined experimentally. Darcy and tracer tests were carried out for the investigations and hydraulic (permeability, fracture opening width) and transport parameters (flow velocity, dispersivity, dispersion coefficient) were derived from the results and compared with each other and with the surface roughness. For the Darcy experiments, the cores were clamped in a specially designed Darcy cell and calculations were done based on equations for the cubic law. The transport parameters were determined using a salt tracer and by evaluating the breakthrough curves, recorded by measuring the electrical conductivity, with the moment analysis.

First results show a very clear separation between Remlinger and Flechtinger sandstone. Thus, the finer-grained Remlinger cores show lower JRC than the coarser-grained Flechtinger, as expected. Further, the Flechtinger cores have larger aperture opening widths than the Remlinger cores. First comparisons show a tendency to higher dispersivity with higher JRC, and thus with the Flechtinger than in the case of the Remlinger cores. Though, in-depth analysis reveals that the JRC alone might not be sufficient to characterize transport processes along fractures, as anisotropy, as well as roughness variability along the fracture surface can influence flow and transport. Numerical modeling of flow paths across the fracture surface are used to relate experimental results with the flow pattern across the rough surface.