bluuebunny/crossref_metadata_2025 huggingface dataset:
The seismic sound of deep volcanic processes
Authors: Cesca Simone , Dahm Torsten , Heimann Sebastian , Hensch Martin , Letort Jean , Razafindrakoto Hoby N. T. , Isken Marius , Rivalta Eleonora
Published: March 2020

Deep volcanic processes and magma intrusion episodes through the crust are typically accompanied by a variety of seismic signals, including volcano-tectonic (VT) seismicity, very long period (VLP) signals and deep low-frequency (DLF) events. These signals can reveal the migration of magma batches and the resonance of magma reservoirs and dikes. The recent 2018-2019 unrest offshore the island of Mayotte, Comoros archipelago, represents the first case of a geophysically monitored magmatic intrusion from a deep sub-Moho reservoir through the whole crust reaching the surface. At Mayotte, a huge magma movement and the following drainage of a deep reservoir were accompanied by a complex seismic sequence, including a massive VT swarm and energetic long-duration very long period (VLP) signals recorded globally. The identification and characterization of ~7000 VTs and ~400 VLPs by applying waveforms-based seismological methods allowed us to reconst the unrest phases: early VTs, migrating upward, were driven by the ascent of a magmatic dike, and tracked its propagating from Moho depth to the seafloor, while later VTs marked the progressive failure of the reservoir’s roof, triggering its resonance and the generation of long-duration VLPs. At the Eifel, Germany, weak DLFs earthquakes have been recorded over the last decades and located along a deep channel-like structure, extending from sub-Moho depth (~40-45 km) to the upper crust (~5-10 km). While not showing any clear migration, they reveal a different way of fluid transfer from depth towards the surface, possibly marking intermediate small reservoirs along a feeding channel. Here, brittle failure occurring in the vicinity of the reservoirs may cause their resonance. The Mayotte and Eifel observations are example of end member models for deep fluid transfer processes through the crust. These examples show that, by listening to seismic signals at different distances and by analysing them with modern waveform based methods, we can provide a detailed picture of deep magmatic processes and enable future eruption early warning.
Assessing and improving focal mechanisms in Switzerland: Towards a comprehensive seismotectonic model of the Central Alps and their foreland
Authors: Lanza Federica , Diehl Tobias , Deichmann Nicholas , Massin Frederick , Clinton John , Herwegh Marco , Wiemer Stefan
Published: March 2020

Seismotectonic models that combine all the relevant seismotectonic data (e.g., hypocenter locations and velocity models, focal mechanisms and moment-tensors, faults, geodetic data, and in-situ/regional stress data) constitute a pre-requisite to better understand the interplay between stress, faulting and seismicity of a region. This study is a contribution to the multiannual project SeismoTeCH funded by the Swiss Geophysical Commission (SGPK) and coordinated by the University of Bern to produce an integrative seismotectonic model for the entire territory of Switzerland. In this context, our aim is to provide an up-to-date, high-quality, and consistent catalog of first-motion focal mechanisms computed by the Swiss Seismological Service (SED) since 1976. For this purpose, we developed a quality classification scheme for existing mechanisms based on a priori independent information (mainly applied to the oldest mechanisms in the catalog) combined with statistical methods such as HASH (Hardebeck and Shearer, 2002) and probabilistic source mechanisms scanner algorithms (Massin and Malcom, 2018) to probe the solution space and translate probability density functions to a discrete quality rating.

Tests on selected problematic mechanisms are also carried out in order to assess the sensitivity of the focal mechanisms to the velocity models used to calculate location and take-off angles. In particular, we compare existing solutions using the standard 3D P-wave model of the SED with solutions based on recently derived high-resolution 3D Pg+Sg models. These tests are functional to understand the benefits of developing an updated full crustal velocity model for first-motion focal mechanisms calculations, in particular in relations to the focal depths and the accuracy of take-off angles.

Finally, to improve the completeness of the existing catalog, we explore new methodologies that would incorporate automated (possibly real-time) and semi-automated techniques for expanding the calculation of first-motion focal mechanisms (and moment tensors) to events of smaller magnitude. The Anzere/Sanetschpass sequence of November 2019 is used to assess and develop these new methods. As a preliminary result of these combined efforts, we present here a high-resolution map of strain-based deformation across Switzerland. This work represents a benchmark for future regional-scale stress inversion and sets the basis for the development of a consistent, fully accessible, and dynamic focal mechanisms database for Switzerland.
Identification of Dominant Factors Affecting Soil Erosion and Water Yield within Key Ecological Functional Areas
Authors: Gao Jiangbo , Jiang Yuan
Published: March 2020

Soil conservation and water retention are important metrics for designating key ecological functional areas. However, research on the quantitative identification of dominant environmental factors in different ecological functional areas remains relatively inadequate, which is unfavorable for zone-based management of key ecological functional areas. This paper presents a case study of Beijing’s key ecological functional areas. In order to objectively reflect the ecological characteristics of key ecological functional areas in Beijing which is mainly dominated by mountainous areas, the application of remote sensing data about high resolution is important for the improvement of model calculation and spatial heterogeneity. Based on multi-source remote sensing data, meteorological and soil observations, soil erosion and water yield were calculated using the Revised Universal Soil Loss Equation (RUSLE) and Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. Combining the influencing factors, including slope, precipitation, land use type, vegetation coverage, geomorphological type and elevation, a quantitative attribution analysis was performed on soil erosion and water yield in Beijing’s key ecological functional areas using the geographical detector. The power of each influencing factor and their interaction factors in explaining the spatial distribution of soil erosion or water yield varied significantly among different key ecological function areas. Vegetation coverage was the dominant factor affecting soil erosion in Beijing’s key ecological function areas, explaining greater than 30% of its spatial heterogeneity. Land use type can explain the spatial heterogeneity of water yield more than 60%. In addition, the combination of vegetation coverage and slope was found to significantly enhance the spatial distribution of soil erosion (>55% in various key ecological functional areas). The superposition of land use type and slope explained greater than 70% of the spatial distribution for water yield in key ecological functional areas. The geographical detector results indicated that the high soil erosion risk areas and high water yield areas varied significantly among different ecological functional areas. Thus, in efforts to enhance key ecological functional areas protection, focus should be placed on the spatial heterogeneity of soil erosion and water yield in different ecological functional areas.
Comparing the fate of N from fertilizer treatments and root litter turnover in a Mediterranean Savanna
Authors: Nair Richard , Morris Kendalynn , Moreno Gerardo , Migliavacca Mirco , Schrumpf Marion
Published: March 2020

Nutrient imbalances induced by anthropogenic N deposition may fundamentally alter plant activity and consequently, their role in biogeochemical cycling. Mechanistic understanding of N cycle processes is commonly informed by 15N tracers in fertilizer applications, but over the long term most N is obtained by plants is from litter mineralization rather than ‘new’ deposition N or mineral fertilizer applications. In many ecosystems this litter pool is dominated by root remains.

Here, we will compare results between two experiments: a 15N-labelled root litter experiment, and an associated conventional 15N-mineral fertilizer experiment, both located in a typical, spatially heterogeneous, seasonally-arid Spanish dehesa amended with N and NP fertilizers to induce nutrient imbalances. We show that recovery of the litter tracer in soil and plants was substantially higher than the fertilizer N, especially in microsites under trees, which are rich in organic inputs. In contrast, recovery of mineral tracers was strongest in more resource-poor grassland areas.  Plant acquisition of N from the organic source was also affected by the concurrent P addition treatment while we found little evidence for a similar effect in mineral additions.

Our results imply that scaling nitrogen cycle processes informed by isotope tracers from experiments to ecosystems depends heavily on appropriateness of methodology, especially in interpreting short-term traces applied as fertilizer N.
Magnetospheric Multiscale (MMS) Observations of ULF Waves and Correlated Low-Energy IonMonoenergetic Acceleration
Authors: Li Bin
Published: March 2020

Low‐energy ions of ionospheric origin with energies below 10s of electron volt dominate most

of the volume and mass of the terrestrial magnetosphere. However, sunlit spacecraft often become

positively charged to several 10s of volts, which prevents low‐energy ions from reaching the particle

detectors on the spacecraft. Magnetospheric Multiscale spacecraft (MMS) observations show that

ultralow‐frequency (ULF) waves drive low‐energy ions to drift in the E × B direction with a drift velocity

equal to VE×B, and low‐energy ions were accelerated to suffificient total energy to be measured by the

MMS/Fast Plasma Investigation Dual Ion Spectrometers. The maximum low‐energy ion energy flflux peak

seen in MMS1's dual ion spectrometer measurements agreed well with the theoretical calculation of H+ ion

E × B drift energy. The density of ions in the energy range below minimum energy threshold was

between 1 and 3 cm−3 in the magnetosphere subsolar region in this event.
Introducing seasonal hydro-meteorological forecasts in local water management. A local scale demonstrator for an intensively cultivated watershed in the island of Crete, Greece.
Authors: Koutroulis Aristeidis , Grillakis Manolis , Tsanis Ioannis
Published: March 2020

Seasonal forecasts can be interfaced with practical applications to improve and increase the operational capabilities of several targeted sectors, as for example by reducing weather related risks such as freshwater stress in agriculture. In this study we present the co-design, development and evaluation of a local scale demonstrator that brings seasonal hydro-meteorological forecasts in local water management of an intensively cultivated watershed in the island of Crete, Greece. The information included in the development of the Drought Decision Support System (DDSS) was identified during an initial user survey, in which seasonal climate predictions were rated as the most prominent from a number of information regarding weather and climate (change). The DDSS consists of three pillars of information (i) specific sources and guidance for weather and climate information not familiar to the local users, (ii) a demonstrator of seasonal forecasting of reservoir inflow and (iii) locally adjusted seasonal forecast information for precipitation over the watershed. Seasonal forecasts are demonstrated in a user-friendly probabilistic form against climatic conditions based on observations. The usefulness, the accessibility of information, as well as the barriers which currently hamper the deployment of climate services in the in the decision-making process were examined through an evaluation survey.
Precipitation scaling in the tropics with a convection-permitting model
Authors: Argüeso Daniel , Di Luca Alejandro , Jourdain Nicolas , Romero Romualdo , Homar Victor
Published: March 2020

The Maritime Continent is a major convective area and precipitation processes in the region pose great challenges to atmospheric models. A combination of large-scale drivers, such as the Madden-Julian Oscillation and ENSO, and fine-scale processes, such as orographically-forced precipitation, land-sea circulations and tropical convection, governs rainfall in the Maritime Continent. The use of convection-permitting models in the region has shown improved performance in the simulation of precipitation characteristics that are key for the region (i.e. diurnal cycle).

Most of the rainfall occurring over land is concentrated in the late afternoon and precipitation extremes often occur over short periods of time. The availability of water vapor in the lower troposphere and the high water-holding capacity of a warm atmosphere favors very intense precipitation events, according to the Clausius-Clapeyron relationship. In a warming climate, a full understanding of the so-called precipitation scaling with temperature is thus crucial. However, this potential generally requires the atmosphere be saturated and convection be initiated to become effective. Using a regional climate model operating at convection-permitting scales over 3 consecutive wet seasons, we investigate the response of intense precipitation to temperature.

In this presentation, we examine different approaches to relate precipitation extremes to near-surface temperature and dew-point temperature. We show that the relationship breaks at certain thresholds that are relatively uniform across islands. The region is well supplied with water vapor and the break is not explained by a deficit in water vapor, unlike previously proposed for other water-limited regions. We identify possible reasons for this behavior, such as the lack of environmental conditions that trigger convection. In this context, we explore the sensitivity of the modelling system to the convection representation (explicit vs. parameterized) and discuss the implications for future changes in intense precipitation events. Finally, we put forward the use of specific variables, such as temperature and equivalent potential temperature integrated in the vertical. These variables not only are coherent with the CC equation but also acknowledge the different warming rates near the surface and at higher tropospheric levels, where precipitating processes actually occur.
Application of Mann-Kendall trend test and Normalized Difference Vegetation Index (NDVI) in hydroclimatological change detection – A Case Study of Urmia Lake watershed, Iran
Authors: Tootoonchi Roshanak , Nourani Vahid , Andaryani Soghra , Tootoonchi Faranak
Published: March 2020

Urmia Lake watershed, which is located at the northwest of Iran has gone through crucial hydroclimatological changes that resulted in Urmia Lake Desiccation. Long term average temperature and precipitation trends, precipitation pattern transition and changes in precipitation-snow timing are some of the hydroclimatological changes that have occurred in this watershed. Aforementioned changes are provoked by anthropogenic activities such as land cover changes, booming urbanization, unauthorized exploitations of Urmia Lake and inefficient crop management, followed by natural factors that could be caused by climate change.

In this study we aim to address contributing hydroclimatological factors and vegetation changes that resulted in Urmia Lake desiccation. In order to examine the vegetation changes in this watershed, we analyzed remote sensing data. In this regard, normalized difference vegetation index (NDVI)-based models for two sub-basins in East Azerbaijan province and West Azerbaijan -located at two sides of Urmia Lake watershed- are developed by an ensemble of satellite data from 1990 to 2019. Data of Landsat 5 TM satellite from 1990 to 2013 and Landsat 8 OLI/TIRS satellite from 2013 to 2019, are collected and analyzed to consider vegetation changes. Hydrological data for precipitation, temperature and Urmia Lake water level elevation are also considered for analyzing hydroclimatic impacts. The adequacy of NDVI-based models and long term hydrological time series are checked by Mann-Kendall trend test.

The evaluation of NDVI-based models shows an increasing trend in vegetation. In comparison, the studied sub-basin in West Azerbaijan province has a higher level of increasing trend than the sub-basin in East Azerbaijan province. The evaluation of precipitation time series shows a decreasing trend and temperature data exhibit an increasing trend. The trend pattern changes validates the hypothesis that increasing trend of vegetation in Urmia Lake watershed is in proportion to the escalating agricultural activities. Furthermore, the escalation of land use is higher in West Azerbaijan province where there exists more agricultural activities.
Carbonate and chert genesis in the 3.35 Ga old Strelley Pool Formation (Australia): Insights from trace metals and Sm/Nd dating
Authors: Viehmann Sebastian , Hohl Simon V. , Tepe Nathalie , Van Kranendonk Martin , Reitner Joachim , Hofmann Thilo , Koeberl Christian , Meister Patrick
Published: March 2020

Stromatolites are laminated, presumably microbial structures, consisting largely of an authigenic precipitate, thus, providing potential geochemical archives of early Earth aqueous environments and their habitability. In this study, we report trace element and Sm/Nd isotope data from Palaeoarchean stromatolites and adjacent cherts of the Strelley Pool Formation (NW Australia), obtained by ICP-MS and TIMS, to test their reliability as archives for palaeo-environmental reconstruction and to understand authigenic mineral formation.

Stromatolitic carbonates plot together with the stratigraphically underlying Marble Bar cherts on a linear Sm-Nd regression line yielding an age of 3253 ±320 Ma.. In contrast, associated crystal-fan carbonates yield 2718 ±220 Ma, suggesting that their Sm-Nd isotope system was altered after deposition. Geochronological information via Sm-Nd dating of black and white cherts is limited, probably due to a reset of the isotope system during an unknown Paleoproterozoic or younger alteration event.

Carbonates, as well as white cherts, show shale-normalized rare earth element and yttrium patterns (REYSN; except for redox-sensitive Ce and Eu) parallel to those of modern seawater, indicating a seawater-derived origin. Positive EuSN anomalies (2.1 - 2.4), combined with heterogeneous ɛNd3.35Ga values (-3.2 to +5.8) within alternating stromatolite laminae, support that seawater chemistry was variably affected by both continental weathering and high-temperature hydrothermal fluids contributing elements of both young mafic or older felsic rocks. In contrast, black cherts show non-seawater like REYSN patterns and significant amounts of elements leached from the surrounding rocks, masking the pristine geochemical composition of ancient seawater. In conclusion, Archaean stromatolites indeed preserve pristine authigenic phases at the mm-scale that contain signatures representative of the water chemistry prevailing in the depositional environment.
Amorphous silica increases the water holding capacity and the phosphorus mobility in soils - solving the two main problems of agriculture
Authors: Schaller Jörg , Gilfedder Benjamin , Frei Sven
Published: March 2020

The two primary problems currently facing agriculture are drought and the availability of mineable phosphorus minerals used for fertilization. More frequent and longer drought periods are predicted to threaten agricultural yields in future. The capacity of soils to hold water is a highly important factor controlling drought stress intensity for plants during the growing phase. High phosphorus availability in soils is necessary for high agricultural yield. For both drought and phosphorus availability in soils amorphous silica (ASi) has been suggested to be able to mitigate these problems. Amorphous silica pools in natural soils are in the range of 0-6%. However ASi pools have declined in agricultural soils since the development of high intensity agriculture to values of <1% due to yearly crop harvests, decreasing water the holding capacity of the soils. Here, we analyzed the effect of ASi on the water holding capacity (WHC) of soil and how the ASi effects the mobilization of phosphorus.  ASi was mixed at varying rates with different soils. Afterwards, the retention curve of the soils was determined. Here we show that ASi increases the soil water holding capacity substantially, by forming silica gels with a water content at soil saturation higher than 700%. An increase of ASi by 1% or 5% (weight) increased the water content at all studied water potentials and plant available water increased by >40% and >60%, respectively. Additionally, we fertilized soils with ASi and measured phosphorus mobilization from the solid phase into the soil pore waters. We found a strong mobilization of phosphorus by ASi. In a lysimeter experiment we found that ASi strongly increased the WHC of soils. Furthermore, as expected from the batch experiments the ASi is decreased phosphorus sorption to soil minerals and consequently increased its mobilization. Our results suggest that ASi addition to soils enhances the water availability, potentially decreases drought stress for plants as well as increasing phosphorus mobility in soil of terrestrial ecosystems.
Synchrotron multi-modal, multi-scale chemical and structural imaging of vein-bearing shales
Authors: Schrank Christoph E. , Jones Michael W. M. , Kewish Cameron M. , van Riessen Grant A.
Published: March 2020

The coupling between fluid transport, chemical reactions, and deformation constitutes one of the frontiers of geoscientific research. From an analytical perspective, a fundamental challenge is posed by the fact that sub-nanometre- to micrometre-scale structures play a vital role in the macroscopic (centimetre- to metre-scale) response of deforming, reacting, fluid-bearing rocks. Sample analysis with conventional laboratory techniques quickly becomes prohibitively expensive and laborious when more than four orders of magnitude in length scales need to be resolved. This issue is particularly challenging in very fine-grained rocks such as mylonites and shales.

 

Here, we investigate calcite-vein-bearing shales to illustrate how synchrotron X-ray fluorescence microscopy, ptychography, and small- and wide-angle transmission scattering can be used for the quantitative multi-scale analysis of micro- and nano-textures in rock. These analytical techniques are applied to thin sections or thin rock slabs on the centimetre-scale and provide information on length scales from hundreds of micrometres down to angstroms. Therefore, the considered array of synchrotron techniques covers up to eight orders of magnitude in length scale in terms of chemical and structural information. In our case study, we demonstrate how this suite of analytical techniques can be employed to reveal, for example, the relative timing of mineralisation events, trace-element chemistry, texture, and the structural width of fluid pathways such as grain boundaries.
Cosmic ray ionization of Ice Giant atmospheres
Authors: Aplin Karen , Nordheim Tom , Sinclair James , Jasinski Jamie
Published: March 2020

Galactic cosmic rays (GCRs) represent a major ionization source in planetary atmospheres, particularly within deeper layers that are largely unaffected by solar UV and charged particle precipitation. When GCR particles undergo inelastic collisions with atmospheric nuclei they create large numbers of secondary interactions, resulting in extensive nuclear and electromagnetic particle cascades. In thick atmospheres, such as those of the giant planets, these cascades can develop much more extensively than what is the case on Mars and Earth. Furthermore, GCRs are strongly modulated by the heliosphere, and therefore GCR fluxes are significantly higher at the Ice Giants than in the inner Solar System. Intriguingly, observations of Uranus and Neptune show brightness variations that appear to be associated with known variability in the background GCR flux (Aplin and Harrison 2016;2017).

Using a full 3D Monte Carlo particle physics code, we have carried out the first detailed study of cosmic ray ionization within the atmospheres of Uranus and Neptune. We will show preliminary results of this study and discuss the possible importance of GCR ionization to atmospheric chemistry and atmospheric electricity. We will also discuss GCR shielding by the planetary magnetic fields of Uranus and Neptune, and what effect this has on predicted GCR ionization rates at different locations. 

References

Aplin K.L. and Harrison R.G. (2016), Determining solar effects in Neptune's atmosphere, Nature Communications, 7, 11976 doi:10.1038/ncomms11976

Aplin K.L. and Harrison R.G (2017), Solar-driven variability in the atmosphere of Uranus, Geophys. Res. Letts. 44, doi: 10.1002/2017GL07374
Stability assessment of submerged lateral and deltaic slopes in Lake Lucerne
Authors: Shynkarenko Anastasiia , Stegmann Sylvia , Kremer Katrina , Bergamo Paolo , Imperatori Walter , Lontsi Agostiny Marrios , Kopf Achim , Fäh Donat
Published: March 2020

Numerous studies indicate that tsunamis do not only occur in oceans but also in lakes. Lake Tsunamis are mainly caused by sublacustrine and subaerial mass movements that can be triggered by seismic or aseismic processes (Schnellmann et al. 2002, Strasser et al. 2007, Kremer at al. 2012, Hilbe and Anselmetti 2015). Such tsunamis can have devastating effects on the surrounding population and infrastructure.

To assess the tsunami hazard triggered by sublacustrine mass movements, the stability of the lake slopes needs to be examined. As a part of the SNSF funded SINERGIA project “Lake Tsunamis: Causes, Controls and Hazard”, we perform the slope stability analysis based on the comprehensive geotechnical in situ and laboratory dataset for the selected sites of Lake Lucerne, Central Switzerland.

During 2018-2019 dense geotechnical investigations were carried out along slope-perpendicular profiles at 10 sites where the slopes have failed in the past or are susceptible to failure and included more than 130 in-situ free-fall cone penetration tests with pore pressure measurement (CPTu) and laboratory analysis of 30 short sediment cores. Already existing reflection seismic dataset complements these data and provides the thickness of different sediment layers.

1D undrained, infinite slope stability analysis following Morgenstern and Price (1965) is used to define the Factor of Safety and critical conditions for deltaic and lateral slopes, where different triggers can be responsible for the failure. Based on the conducted analysis, static and dynamic stability together with critical failure conditions for different slopes in Lake Lucerne can be compared.

 

References:

Hilbe, M. and Anselmetti, F.S. (2015) Mass Movement-Induced Tsunami Hazard on Perialpine Lake Lucerne (Switzerland): Scenarios and Numerical Experiments. Pure and Applied Geophysics 172, 545-568.

Kremer, K., Simpson, G., Girardclos, S. (2012) Giant Lake Geneva tsunami in AD 563. Nature Geoscience 5, 756-757.

Morgenstern, N.R. and Price, V.E. (1965) Analysis of stability of general slip surfaces. Geotechnique 15(1): 79–93.

Schnellmann, M., Anselmetti, F.S., Giardini, D., McKenzie, J.A., Ward, S.N. (2002) Prehistoric earthquake history revealed by lacustrine slump deposits. Geology 30, 1131–1134.

Strasser, M., Stegmann, S., Bussmann, F., Anselmetti, F.S., Rick, B., Kopf, A. (2007) Quantifying subaqueous slope stability during seismic shaking: Lake Lucerne as model for ocean margins. Marine Geology 240, 77-97.
Impacts of spatio-temporal precipitation variabilities on flood event simulation with satellite-based precipitation estimates
Authors: Zhu Qian , Zhou Dongyang
Published: March 2020

Precipitation is a key factor in controlling the accuracy of runoff simulation, as well as the performance of flood event simulation. Compared with the in-situ rainfall measurement, satellite-based precipitation products provide critical precipitation sources of higher resolution along with detailed depiction of precipitation variability, especially for data-sparse or ungauged regions. This study aims to investigate the impacts of temporal and spatial resolutions of precipitation on flood simulation over a humid region of Southern China. Three versions of Integrated Multi-satellite Retrievals for GPM (IMERG-E, IMERG-L, and IMERG-F) and a gauge-satellite merged precipitation product released by China Meteorological Administration (CMA) at 0.1° and 1 h resolution are used in the study. The lumped hydrological model HBV and semi-distributed hydrological model SWAT are applied to simulate 12 flood events to investigate the impacts of temporal and spatial variabilities of precipitation on flood event simulation. The results show that the spatial resolution of precipitation data affects its capture of characteristics of precipitation events, specifically in magnitude of precipitation variability and the central location of the precipitation event. Furthermore, SWAT shows no improvement compared with HBV in flood event simulation in this case, which may due to the uncertainty of the precipitation spatial variability. The flood events simulated with SWAT indicate that the biases of flood peaks forcing by IMERG-E and IMERG-L increase with the decreasing of precipitation variability, while that forced by IMERG-F are less affected and perform the best among the three IMERG precipitation estimates. The impact of temporal variability of precipitation is conducted with HBV model and the corresponding results are that the higher temporal resolution ensures the better flood event simulation. Furthermore, the CMA source overperforms the other three satellite-based precipitation estimates, and followed by IMERG-F.
Globally estimated precipitation extremes
Authors: Gründemann Gaby , van der Ent Ruud , Beck Hylke , Schleiss Marc , Zorzetto Enrico , van de Giesen Nick
Published: March 2020

Understanding the magnitude and frequency of extreme precipitation events is a core component of translating climate observations to planning and engineering design. This research aims to capture extreme precipitation return levels at the global scale. A benchmark of the current climate is created using the global Multi-Source Weighted-Ensemble Precipitation (MSWEP-V2, coverage 1979-2017 at 0.1 arc degree resolution) data, by using both classical and novel extreme value distributions. Traditional extreme value distributions, such as the Generalized Extreme Value (GEV) distribution use annual maxima to estimate precipitation extremes, whereas the novel Metastatistical Extreme Value (MEV) distribution also includes the ordinary precipitation events. Due to this inclusion the MEV is less sensitive to local extremes and thus provides a more reliable and smoothened spatial pattern. The global scale application of methods allows analysis of the complete spatial patterns of the extremes. The generated database of precipitation extremes for high return periods is particularly relevant in otherwise data-sparse regions to provide a benchmark for local engineers and planners.
Linking frequency of rainstorms, runoff generation and sediment transport across hyperarid talus-pediment slopes
Authors: Shmilovitz Yuval , Morin Efrat , Rinat Yair , Haviv Itai , Carmi Genadi , Mushkin Amit , Enzel Yehouda
Published: March 2020

Talus-pediment slopes are a common morphologic feature in arid areas and constitute a prominent runoff and sediment source at the watershed and channel scales. The evolution of talus-pediment sequences (talus flatirons) was often linked to climatic cycles, although the physical processes that may account for such a link remained obscure. Our approach is to integrate field measurements, high-resolution radar rainfall data and numerical modeling to link the frequency of storms and the resulted hillslope runoff and sediment transport. We present a quantitative hydrometeorological analysis of rainstorms and their geomorphic impact, potentially involved in the evolution of arid talus-pediment slopes in the Negev desert (Israel). Artificial rainstorms were designed based on intensity-duration-frequency curves and simulated in the field using a rainfall simulator. Then, the obtained experimental results were up-scaled to the entire slope length using a fully distributed hydrological model. In addition, natural storms and their hydro-geomorphic impacts were monitored using X-band radar and time-lapse cameras.

These integrated analyses constrain the rainfall threshold for local runoff generation at rain intensity of 14-22 mm h-1 for a duration of 5 min for the study area conditions. We characterized small-scale runoff-generating convective rain cells using an X-band radar and found that small convective cells (~30 km2), having extremely high internal spatial gradients in rainfall intensity and low velocity (<10 m s-1), have the potential to generate local hillslope runoff. The frequency of local runoff-producing rainstorms is ~1-3 per year, but most of these storms activate only small parts of the hillslope. Modeling results indicate that a full extent hillslope runoff occurs under much rarer rainstorms of at least 100-years return interval (1% or less). During such rainstorms, the shear stress produced by the runoff flow (sheetwash) is capable of transporting surface clasts at a distance of ~80 m downslope. However, transport of coarse clasts in the upper parts of the slopes is most probably gravitationally controlled. The erosion efficiency of discrete rare events (1% or less) on the lower part of the slopes highlights their potential to trigger incision and lead to cliff dissection. This study results support the hypothesis that a climatic shift in terms of the properties and frequency of extreme rainstorms, rather than the common views of it as changing precipitation means, can play an important role in shaping and in transforming landscapes in such arid setting.
Studying hydraulic characteristics of three soils amended with superabsorbent hydrogels
Authors: Camarotto Carlo , Pozza Sara , Piccoli Ilaria , Guerrini Giacomo , Morari Francesco
Published: March 2020

Superabsorbent hydrogels (SAHs) are three-dimensional cross-linked polymeric network, with the ability to absorb large quantities of water (or other ﬂuids), keep their network stable even in the swollen state and  release the water in response to speciﬁc environmental stimuli. In last decades, several SAHs have been developed and studied for their potential to improve soil physical properties for agricultural purposes, e. g. by increasing their ability to retain water, increasing the efficiency of water use, increasing the absorption capacity or promoting the uptake of nutrients by the plant. Although various studies have shown that SAHs can contribute to soil microstructural stability and improve soil-water interactions in general, the specific impact of water content on the hydrogel effect in soil remains largely unclear. Specifically, the SAH effects needs to be inquired in dynamic water content conditions.

The aim of this study was to evaluate how the water content affects soil-water-hydrogel interactions in different soils (i.e. sandy, loamy and silty soils). Two different SAHs were studied, a polyacrylamide and a self-made cellulose-based SAH added with humic acids. Untreated and SAH-treated (4 mg g−1) samples were analysed for soil water retention and unsaturated hydraulic conductivity coupling the Wind method (−1 to −80 kPa) with WP4-T dew point (-3000 to 15000 kPa). SAH deswelling dynamic was evaluated measuring the sample volume change from −1 to −7 kPa potential. Volume was measured reconstructing the 3D shape of the soil sample employing a 3D Point Cloud Reconstruction software.

Soil-SAH mixtures changed the water retention characteristics if compared to the controls. SAHs significantly increased the water entrapment and altered the pore-size distribution according to the soil types. It can be hypothesized that in the soil-SAH mixtures there was a texture-dependent rearrangement of soil particles, depending on the various interactions between hydrogel structures and soil constituents as a function of water content. These findings demonstrated the potential of SAHs to advantageously modify the soil hydraulic characteristics, but also showed that further studies are needed to better comprehend the behaviour of hydrogels in dynamic water content conditions in different soils.
Representation of the Seasonal Cycle of sea surface temperature in CMIP6 models
Authors: Wang Yanxin , Heywood Karen , Stevens David , Damerell Gillian
Published: March 2020

Sea surface temperature (SST) seasonal extrema are important for water mass formation, intensification of tropical cyclones and coral bleaching, so should be well-represented in models used for future climate projections. Typically, climate model evaluations focus on annual or longer-term mean SST. However, accurate mean SST does not guarantee accurate seasonal extrema or annual cycles. Models that have no biases in mean SST can have biases in seasonal extrema and annual cycles, and vice versa.

Here we assess seasonal extrema in a selection of CMIP6 model historical runs (including BCC-CSM2-MR, CanESM5, CESM2, GFDL-CM4 and GISS-E2-1-G), averaged over 1981-2010, against the World Ocean Atlas (WOA18) observational climatology.  The magnitude and pattern of SST biases for seasonal extrema vary from model to model. GFDL-CM4 and CESM2 simulate SST extrema reasonably well, while BCC-CSM2-MR and GISS-E2-1-G have obvious deficiencies. The global area-weighted root mean square (RMS) difference from WOA18 is larger than 2oC in BCC-CSM2-MR and GISS-E2-1-G, and their common maximum bias (larger than 5oC) is the cold bias located in the subpolar North Pacific, Greenland Sea and Norwegian Sea. The model biases of maximum SST (summer SST) and minimum SST (winter SST) are in some cases different, leading to biased SST annual cycles. The SST biases are typically smaller for summer, except for models with significant winter cold bias in the high latitudes of the Northern Hemisphere (BCC-CSM2-MR and GISS-E2-1-G). Generally speaking, the bias of the SST annual cycle is smaller than that of seasonal extrema; models that are too cold in winter are typically also too cold in summer. In eastern boundary regions, the models have too small annual cycles. In these regions, the warm bias of winter SST is less than the warm bias of summer SST. This is because the warm bias in models due to poorly captured stratocumulus can be compensated by coastal upwelling, which cools the sea surface more in summer than in winter.

We note that extra attention should be paid when evaluating SST extrema in some polar areas as the observational climatology there can be unrealistic, particularly in winter.
A climatology of infrasound detections at Kerguelen Island
Authors: den Ouden Olivier F.C. , Assink Jelle D. , Smets Pieter S.M. , Evers Läslo G.
Published: March 2020

The International Monitoring System (IMS) is in place for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Part of the IMS are 60 infrasound arrays, of which 51 currently provide real-time infrasound recordings from around the world. Those arrays play a central role in the characterization of the global infrasonic wavefield and localization of infrasound sources.

Power Spectral Density (PSD) estimates give insight into the noise levels per station and array. The IMS global low and high noise model curves have been determined in a study by Brown et al. [2014] using a distribution of computed PSDs. All the IMS infrasound arrays, except IS23, have been included in the determination of the atmospheric ambient noise curves. IS23 is located at Kerguelen Island and exist of 15 elements that have been divided into five 100 meter aperture triplets arrays. The array is located at one of the noisiest locations in the world, due to the high wind conditions that exist year-round. The resulting high noise floor appears to hamper infrasound detection at this island array.

In this work, the effects of meteorological, oceanographic, and topographical conditions on the infrasound recordings at IS23 are studied. Five years of infrasound data is analyzed, as recorded by IS23, by using various processing techniques. Contributions within different frequency bands are evaluated. The infrasound detections are explained in terms of the stratospheric winds and ocean wave activity. Understanding and characterization of the low-frequency recordings of IS23 are of importance for successfully including this array for verification of the CTBT.
On the independence from the emission pathway of the projected changes of river runoff
Authors: Mentaschi Lorenzo , Alfieri Lorenzo , Dottori Francesco , Cammalleri Carmelo , Bisselink Berny , De Roo Ad , Feyen Luc
Published: March 2020

After the Paris Agreement of 2015 many studies on climate impact assessment, e.g. of floods, water resources and droughts, focused on understanding the projected changes at the time frame when a specific warming level is reached. The results of these studies assume that the pathway to reach a certain greenhouse concentration and corresponding warming level plays a minor role in the change of the physical variables that define the hazard. However, this hypothesis should be verified for each variable, as the links between the timing of the warming levels and the projected changes of the geophysical variables are not yet fully understood. To address this gap, in this contribution we compared the projected changes of annual mean, extreme high and extreme low river discharges in Europe at 1.5°C and 2°C under scenarios RCP8.5 and RCP4.5 from an ensemble of Regional Climate Model simulations. The statistical significance of the difference between the two scenarios for both warming levels has been then evaluated versus the other sources of uncertainty, through an Analysis of Variance (ANOVA). The results show that in the majority of Europe (>95% of the surface area for the annual mean discharge, >98% for high and low extremes), the differences in the changes projected in the two pathways are statistically small. These results suggest that in studies of changes at specific warming levels the projections of the two pathways can be merged into a single ensemble without major loss of information. With regard to the uncertainty of the merged ensemble, findings show that the projected changes of annual mean, extreme high and extreme low river discharges are statistically significant in large portions of Europe. Merging the 2 pathways comes with a two-fold advantage with respect to the separate treatment of the 2 scenarios. On the one hand, it improves the estimation of the statistical significance of the projected change, by increasing its size and by better taking into account the pathway-related uncertainty (the emission pathways are set ex-ante as a hypothesis for the CMIP experiment, and the related uncertainty is usually neglected). On the other hand, a multi-pathway ensemble can simplify the discussion of the projected changes by removing from the analysis the dependency from the emission pathway, and making the results clearer and more understandable by a non-scientific public.
Visualization of high-resolution climate model output in a Visualization dome
Authors: Ziemen Florian , Röber Niklas , Spickermann Dela , Böttinger Michael
Published: March 2020

The new generation of global storm-resolving climate models yields model output at unprecedented resolution, going way beyond what can be displayed on a state-of-the-art computer screen. This data can be visualized in photo-realistic renderings that cannot be easily distinguished from satellite data (e.g. Stevens et al, 2019). The EU-funded Centre of Excellence in Simulation of Weather and Climate in Europe (ESiWACE) enables this kind of simulations through improvements of model performance, data storage and processing. It is closely related with the DYAMOND model intercomparison project. The Max-Planck-Institute for Meteorology (MPI-M) will contribute to the second phase of the DYAMOND intercomparison with coupled global 5 km-resolving atmosphere-ocean climate simulations, internally called DYAMOND++.

Because of the great level of detail, these simulations are especially appealing for scientific outreach. In this PICO presentation we will illustrate how we turn the output of a DYAMOND++ test simulation into a movie clip for dome theaters, as used in the WISDOME contest of the IEEE EUROVIS conference and in planetaria and science centers. Our presentation outlines the main steps of this process from data generation via pre-processing to the methods employed in the rendering of the scenes.

Stevens, B., Satoh, M., Auger, L. et al.: DYAMOND: the DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domains. Prog Earth Planet Sci (2019) 6: 61. https://doi.org/10.1186/s40645-019-0304-z
Take one dispersing plume and add some precipitation: using ensembles to simulate deposition uncertainty
Authors: Leadbetter Susan , Bedwell Peter , Geertsema Gertie , Korsakissok Irene , Tomas Jasper , de Vries Hans , Wellings Joseph
Published: March 2020

In the event of an accidental airborne release of radioactive material, dispersion models would be used to simulate the spread of the pollutant in the atmosphere and its subsequent deposition. Typically, meteorological information is provided to dispersion models from numerical weather prediction (NWP) models. As these NWP models have increased in resolution their ability to resolve short-lived, heavy precipitation events covering smaller areas has improved. This has led to more realistic looking precipitation forecasts. However, when traditional statistics comparing precipitation predictions to measurements at a point (e.g. an observation site) are used, these high-resolution models appear to have a lower skill in predicting precipitation due to small differences in the location and timing of the precipitation with respect to the observations. This positional error is carried through to the dispersion model resulting in predictions of high deposits where none are observed and vice versa; a problem known as the double penalty problem in meteorology.

Since observations are not available at the onset of an event, it is crucial to gain insight into the possible location and timing errors. One method to address this issue is to use ensemble meteorological data as input to the dispersion model. Meteorological ensembles are typically generated by running multiple model integrations where each model integration starts from a perturbed initial state and uses slightly different model parametrisations to represent uncertainty in the atmospheric state and its evolution. Ensemble meteorological data provide several possible predictions of the precipitation that are all considered to be equally likely and this allows the dispersion model to produce several possible predictions of the deposits of radioactive material.

As part of the Euratom funded project, CONFIDENCE, a case study involving the passage of a warm front, where the timing of the front is uncertain in relation to a hypothetical nuclear accident in Europe was examined. In this study a ten-member meteorological ensemble was generated using time lagged forecasts to simulate perturbations in the initial state and two different model parameterisations. This meteorological ensemble was used as input to a single dispersion model to generate a dispersion model ensemble. The resulting ensemble dispersion output and methods to communicate the uncertainty in the deposition and the resulting uncertainty in the air concentration predictions are presented. The results demonstrate how high-resolution meteorological ensembles can be combined with dispersion models to simulate the maximum impact of precipitation and the uncertainty in its position and timing.