bluuebunny/crossref_metadata_2025 huggingface dataset:
Beaming cone of the Jovian decameter emission derived from different magnetic field models
Authors: Galopeau Patrick , Boudjada Mohammed
Published: March 2021

Five different Jupiter’s magnetic field models (O6, VIP4, VIT4, VIPAL and JRM09) are used to investigate the angular distribution of the Jovian decameter radiation occurrence probability, relatively to the local magnetic field B and its gradient ∇B in the source region. The most recent model JRM09, proposed by Connerney et al. [Geophys. Res. Lett., 45, 2590-2596, 2018], and derived from Juno’s first nine orbits observations, confirms the results obtained several years ago using older models (O6, VIP4, VIT4 and VIPAL): the radio emission is beamed in a hollow cone presenting a flattening in a specific direction. In this study, the same assumptions were made as in the previous ones: the Jovian decameter radiation is supposed to be produced by the cyclotron maser instability (CMI) in a plasma where B and ∇B are not parallel. The main result of our study is that the emission cone does not have any axial symmetry and then presents a flattening in a privileged direction. This flattening appears to be more important for the northern emission (34.8%) than for the southern emission (12.5%) probably due to the fact that the angle between the directions of B and ∇B is greater in the North (~10°) than in the South (~4°).
Towards a definition of Essential Mountain Climate Variables
Authors: Thornton James , Palazzi Elisa , Pepin Nicholas , Cristofanelli Paolo , Essery Richard , Kotlarski Sven , Giuliani Gregory , Guigoz Yaniss , Kulonen Aino , Li Xiaofeng , Pritchard David , Fowler Hayley , Randin Christophe , Shahgedanova Maria , Steinbacher Martin , Zebisch Marc , Adler Carolina
Published: March 2021

Numerous applications, including generating future predictions via numerical modelling, establishing appropriate policy instruments, and effectively tracking progress against them, require the multitude of complex processes and interactions operating in rapidly changing mountainous environmental systems to be well monitored and understood. At present, however, not only are environmental available data pertaining to mountains often severely limited, but interdisciplinary consensus regarding which variables should be considered absolute observation priorities remains lacking. In this context,  the concept of so-called Essential Mountain Climate Variables (EMCVs) is introduced as a potential means to identify critical observation priorities and thereby ameliorate the situation. Following a brief overview of the most critical aspects of ongoing and expected future climate-driven change in various key mountain system components (i.e. the atmosphere, cryosphere, biosphere and hydrosphere), a preliminary list of corresponding potential EMCVs – ranked according to perceived importance – is proposed. Interestingly, several of these variables do not currently feature amongst the globally relevant Essential Climate Variables (ECVs) curated by GCOS, suggesting this mountain-specific approach is indeed well justified. Thereafter, both established and emerging possibilities to measure, generate, and apply EMCVs are summarised. Finally, future activities that must be undertaken if the concept is eventually to be formalized and widely applied are recommended.
Airborne in-situ observations of Arctic clouds in spring and summer above sea ice and the open ocean
Authors: Moser Manuel , Voigt Christiane , Hahn Valerian , Jourdan Olivier , Gourbeyre Christophe , Dupuy Regis , Mioche Guillaume , Schwarzenboeck Alfons , Lucke Johannes , Jurkat-Witschas Tina , Boose Yvonne , Crewell Susanne , Herber Andreas , Lüpkes Christof , Wendisch Manfred
Published: March 2021

Two airborne campaigns (AFLUX and MOSAiC-ACA) were conducted in spring 2019 and late summer 2020 to investigate low- and midlevel clouds and related atmospheric parameters in the central Arctic. The measurements aim at better understanding the role of Arctic clouds and their interactions with the surface - open ocean or sea ice - in light of amplified climate change in the Arctic.
During the campaigns the Basler BT-67 research aircraft Polar 5 based in Svalbard (78.24 N, 15.49 E) equipped with a comprehensive in-situ cloud payload performed in total 24 flights over the Arctic ocean and in the Fram Strait. A combination of size spectrometers (CDP and CAS) and 2-dimensional imaging probes (CIP and PIP) covering the size range of Arctic cloud hydrometeors from 0.5µm to 6.2mm measured the total particle number concentration, the particle size distribution and the median volume diameter. Liquid water content and ice water content were measured with the Nevzorov bulk probe. The cloud water content (liquid and ice water content) from the Nevzorov probe is compared to the cloud water content derived from particle size measurements using consistent mass-dimension relationships.
Here we give an overview of the microphysical cloud properties measured in spring and late summer in high northern latitudes at altitudes up to 4 km. We derive the temperature and altitude dependence of liquid, mixed phase and ice cloud properties and investigate their seasonal variability. Differences in cloud properties above the sea ice and the open ocean are examined, supporting the hypothesis of an enhanced median volume diameter over open ocean compared to clouds formed over the sea ice. The comprehensive data set on microphysical cloud properties enhances our understanding of cloud formation and mixed phase cloud processes over the Arctic ocean, it can be used to validate remote sensing retrievals and models and helps to assess the role of clouds for stronger impact of climate change in the Arctic. 
Seasonal behavior of H component during solar cycle 24
Authors: Bouderba Yasmina , Aganou Ener , Lemgharbi Abdenaceur
Published: March 2021

In this work we will show the behavior of the horizontal component H of the Earth Magnetic Field (EMF) along the seasons during the period of solar cycle 24 lasting from 2009 to 2019. By means of  continuous measurements of geomagnetic components (X, Y) of the EMF, we compute the horizontal component H at the Earth’s surface. The data are recorded with a time resolution of one minute at Tamanrasset observatory in Algeria at the geographical coordinates of 22.79° North and 5.53° East. These data are available from the INTERMAGNET network. We find that the variation in amplitude of the hourly average of H component at low latitude changes from a season to another and it is greater at the maximum solar activity than at the minimum solar activity.

Keywords: Solar cycle 24, Season, Horizontal component H. 
Tracing the Origins of the Ice Giants through Noble Gas Isotopic Composition
Authors: Mandt Kathleen , Mousis Olivier , Lunine Jonathan , Marty Bernard , Smith Thomas , Luspay-Kuti Adrienn , Aguichine Artem
Published: March 2021

The current composition of giant planet atmospheres provides information on how such planets formed, and on the origin of the solid building blocks that contributed to their formation. Noble gas abundances and their isotope ratios are among the most valuable pieces of evidence for tracing the origin of the materials from which the giant planets formed. In this review we first outline the current state of knowledge for heavy element abundances in the giant planets and explain what is currently understood about the reservoirs of icy building blocks that could have contributed to the formation of the Ice Giants. We then outline how noble gas isotope ratios have provided details on the original sources of noble gases in various materials throughout the solar system. We follow this with a discussion on how noble gases are trapped in ice and rock that later became the building blocks for the giant planets and how the heavy element abundances could have been locally enriched in the protosolar nebula. We then provide a review of the current state of knowledge of noble gas abundances and isotope ratios in various solar system reservoirs, and discuss measurements needed to understand the origin of the ice giants. Finally, we outline how formation and interior evolution will influence the noble gas abundances and isotope ratios observed in the ice giants today. Measurements that a future atmospheric probe will need to make include (1) the 3He/4He isotope ratio to help constrain the protosolar D/H and 3He/4He; (2) the 20Ne/22Ne and 21Ne/22Ne to separate primordial noble gas reservoirs similar to the approach used in studying meteorites; (3) the Kr/Ar and Xe/Ar to determine if the building blocks were Jupiter-like or similar to 67P/C-G and Chondrites; (4) the krypton isotope ratios for the first giant planet observations of these isotopes; and (5) the xenon isotopes for comparison with the wide range of values represented by solar system reservoirs.

Mandt, K. E., Mousis, O., Lunine, J., Marty, B., Smith, T., Luspay-Kuti, A., & Aguichine, A. (2020). Tracing the origins of the ice giants through noble gas isotopic composition. Space Science Reviews, 216(5), 1-37.
Seismic coupling and aseismic slip along the central section of the North Anatolian Fault
Authors: Jara Jorge , Jolivet Romain , Ozdemir Alpay , Dogan Ugur , Çakir Ziyadin , Ergintav Semih
Published: March 2021

The ever-increasing amount of geodetic observations worldwide allows detailed studies on the evolution of slip along active faults. Models predicting such observations reveal the spatial and temporal distribution of slip on faults during the interseismic phase. Some fault segments are locked, building up stress that will end up being released during future earthquakes, while other segments slip slowly (mm/yr to cm/yr), releasing stress aseismically. Detailed mapping of slip behavior is critical for understanding the relationship between locked and aseismic segments, thus providing insights into seismic hazard.

We analyze GNSS and InSAR data to study fault kinematic coupling along the central section of the North Anatolian Fault (Turkey) using a Bayesian framework. This section slips aseismically at least since the 1960s, with early evidence recognized in the vicinity of the small town of Ismetpasa. This segment also hosted large earthquakes, including the 1943 and 1944 M7+ earthquakes. We combine InSAR and GNSS data acquired over the last ten years to derive ground velocity fields over the last decade. We process SAR images (ALOS and Sentinel01) as well as continuous GPS to build maps of ground velocity, confirming the presence of a 100 km-long aseismic section, at rates of ~ 1 cm/yr. We then model these velocity fields to derive the Probability Density Function of slip, inferring probabilistic estimates of interseismic coupling. The quantified spatial slip variations are interpreted in terms of the fault mechanical behavior as well as compared with the historical events in the region.
Evaluating the Ecosystem Service Benefits of Native Vegetation Management at Solar Energy Facilities
Authors: Walston Leroy , Hartmann Heidi
Published: March 2021

Concomitant with the increase in solar photovoltaic (PV) energy development over the past decade has been the increasing emphasis on land sharing strategies that maximize the land use efficiency of solar energy developments.  Many of these strategies focus on improving the compatibility of solar energy development with other co-located land uses (e.g., agriculture) and by improving several ecosystem services that could have natural, societal, and industrial benefits. One such land opportunity is the restoration and management of native grassland vegetation beneath ground-mounted PV solar energy facilities, which has the potential to restore native habitat to conserve biodiversity and restore previously altered ecosystem services (e.g., natural pollination services). This presentation will discuss various assessment and modeling approaches to evaluate the scale and magnitude of the ecosystem services provided by different vegetation management strategies at solar PV energy development sites. This work demonstrates how multifunctional land uses in energy systems represents a win-win solution for energy and the environment by optimizing energy-food-ecology synergies. This work was conducted by Argonne National Laboratory for the U.S. Department of Energy Solar Energy Technologies Office under Contract No. DE-AC02-06CH11357.
Climate change and air conditioning adoption: the role of remittances
Authors: Pavanello Filippo , Randazzo Teresa
Published: March 2021

Do remittances improve how households adapt to global warming? We explore this question exploiting a nationally-representative household data from Mexico - a country that experiences a large flow of remittances. Mexican households respond to excess heat by purchasing air conditioning and remittances can be used to adopt and use cooling devices that contribute to maintaining thermal comfort at home. Our results show that recipient households have a higher probability to adopt air conditioning at home with important implication on electricity consumption. The effect is even larger for those households living in high-temperature areas showing an important role of remittances in the climate adaptation process.
Comprehensive Methodology for the Evaluation of High-Resolution WRF Multi-Physics Precipitation Simulations for Small, Topographically Complex Domains 
Authors: Sofokleous Ioannis , Bruggeman Adriana , Michaelides Silas , Hadjinicolaou Panos , Zittis George , Camera Corrado
Published: March 2021

 

A stepwise evaluation method and a comprehensive scoring approach are proposed and applied to select a model setup and physics parameterizations of the Weather Research and Forecasting (WRF) model for high-resolution precipitation simulations. The ERA5 reanalysis data were dynamically downscaled to 1-km resolution for the topographically complex domain of the eastern Mediterranean island of Cyprus. The performance of the simulations was examined for three domain configurations, two model initialization frequencies and 18 combinations of atmospheric physics parameterizations (members). Two continuous scores, i.e., Bias and Mean Absolute Error (MAE) and two categorical scores, i.e., the Pierce Skill Score (PSS) and a new Extreme Event Score (EES) were used for the evaluation. The EES combines hits and frequency bias and it was compared with other commonly used verification scores. A composite scaled score (CSS) was used to identify the five best performing members.

The EES was shown to be a complete evaluator of the simulation of extremes. The least errors in mean daily and monthly precipitation amounts and daily extremes were found for the domain configuration with the largest extent and three nested domains. A 5-day initialization frequency did not improve precipitation, relative to 30-day continuous simulations. The use of multiple and comprehensive evaluation measures for the assessment of WRF performance allowed a more complete evaluation of the different properties of simulated precipitation, such as daily and monthly volumes and daily extremes, for different dynamical downscaling options and model configurations. The scores obtained for the selected five members for a three-month simulation period ranged for BIAS from zero to -25%, for MAE around 2 mm, for PSS from 0.25 to 0.52 and for EES from 0.19 to 0.26. The CSS ranged from 0.56 to 0.83 for the same members. The proposed stepwise approach can be applied to select an efficient set of WRF multi-physics configurations that accounts for these properties of precipitation and that can be used as input for hydrologic applications.
Abrupt transitions in past climates: How reliable are they and what do they mean?
Authors: Rousseau Denis-Didier , Bagniewski Witold , Ghil Michael
Published: March 2021

Early evidence of abrupt transitions in Camp Century and Dye 3 Greenland ice cores (Dansgaard et al. 1982) has recently been reinforced by the identification of additional abrupt transitions in the NGRIP ice core (Rasmussen et al. 2014). These additional events correspond to changes of either short duration or amplitude of d18O that visual or statistical inspections do not necessarily validate. Abrupt transitions have been described for marine (Bond et al. 1992) and continental (Wang et al. 2001) records as well, and they provide a broader spatial perspective. Finally, abrupt transitions have also been documented over much deeper timescales (Zachos et al., 2001, Hodell & Channel, 2016, Westerhold et al. 2020). In spite of the variable time resolution of all these records, the abrupt transitions seem to reflect the individual impact of external forcing, of internal climate variability, or a combination of the two on Earth’s climate system. To illustrate this, we have analyzed 4 reference datasets with timescales ranging from one glacial cycle — i.e., the last 130,000 years — to the last 70 Ma. We show patterns that repeat within a single glacial cycle and seem to be related to internal variability, along with patterns associated with longer time periods and possibly related to external forcing; such forcing may arise from changes in either Earth’s orbit or its dynamics. This study is supported by the H2020-funded Tipping Points in the Earth System (TiPES) project.
The Trash Tracker: A Macroplastic Fate and Transport Model at River Basin Scale
Authors: Mellink Yvette , van Emmerik Tim , Laufkötter Charlotte , Kooi Merel , Niemann Helge
Published: March 2021

Plastic pollution in terrestrial and aquatic ecosystems is of growing global concern due to its negative impact on environmental health and human livelihood. Most plastic research to date focused on observing and modelling plastic in the oceans, revealing that the highest plastic concentrations are found in the five ocean gyres (“the garbage patches”). Plastic waste originating from land has been identified as the main source of marine plastic debris. Yet it remains highly uncertain which processes control the mobilisation and transport of plastic waste over land to rivers and eventually to the ocean. Here, we introduce the Trash Tracker, a numerical model to forecast the pathways and fate of plastic waste in terrestrial and freshwater systems. In this model, the plastic transporting agents, wind and surface runoff, are resisted by the friction of the terrain. The terrain resistance, a function of the surface slope and the type of land use, is translated to thresholds that define the critical wind and surface runoff conditions required to mobilise and transport macroplastics. By repeatedly checking whether the wind and/or surface runoff conditions are strong enough to overcome their respective thresholds, the Trash Tracker simulates the transport of plastics and allows us to identify accumulation hotspots and high probability transport routes of plastic waste within river basins. This makes the Trash Tracker a practical tool for preventing, mitigating and reducing plastic pollution in the natural environment.
The deglacial dynamics of the Laurentide and Cordilleran ice sheets in the Mackenzie Mountains, Northwest Territories, Canada
Authors: Stoker Benjamin J , Margold Martin , Froese Duane G. , Gosse John C.
Published: March 2021

The northwestern sector of the Laurentide Ice Sheet coalesced with the Cordilleran Ice Sheet over the southern Mackenzie Mountains, and with local montane glaciers along the eastern slopes of the Mackenzie Mountains. Numerical modelling studies have identified rapid ice sheet thinning in this region as a major contributor to Meltwater Pulse 1A. Despite advances in remote sensing and numerical dating methods, the configuration and chronology of the northwestern sector of the Laurentide Ice Sheet have not been reconstructed in detail. The last available studies date back to the 1990s, when field surveys and mapping from aerial imagery were used to reconstruct the glacial history in the Mackenzie Mountains. Cross-cutting relations between glacial landforms and a series of 36Cl cosmogenic nuclide dates were used to propose a deglacial model involving a significant readvance of the Laurentide Ice Sheet in the region. However, the chronological evidence supporting the readvance is uncertain because the individual ages are few and poorly clustered. Here we present an updated map of the glacial limits during the local Last Glacial Maximum and the recessional record in the Mackenzie Mountains, based on glacial geomorphological mapping from the ArcticDEM. We provide sixteen new 10Be dates from four sites that were previously glaciated by the Laurentide Ice Sheet to constrain the deglacial sequence across the region. These dates indicate ice sheet detachment from the eastern Mackenzie Mountains at ~16 ka as summits in the mountain front became ice-free. The Mackenzie Valley at ~ 65 °N became ice-free at ~ 14 – 13  ka, towards the end of the Bølling-Allerød warm period. Combining these dates with existing 10Be dates, these chronological constraints on the deglaciation of the Laurentide Ice Sheet allow us to reinterpret landform relations in the Mackenzie Mountains in order to reconstruct the ice sheet retreat. Our reconstruction provides updated constraints on the LGM extent, and the timing and pattern of deglaciation in the Mackenzie Mountains. This new understanding is useful to future efforts to quantify past sea-level contributions from the western Laurentide Ice Sheet.
Water uptake of subpollen aerosol particles: hygroscopic growth, CCN activation, and liquid-liquid phase separation
Authors: Mikhailov Eugene , Pöhlker Mira , Reinmuth-Selzle Kathrin , Vlasenko Sergey , Pöhlker Christopher , Ivanova Olga , Pöschl Ulrich
Published: March 2021

Pollen grains emitted from vegetation can release subpollen particles (SPP) that contribute to the fine fraction of atmospheric aerosols and may act as cloud condensation nuclei (CCN), ice nuclei (IN), or aeroallergens. Here, we investigate and characterize the hygroscopic growth and CCN activation of birch, pine, and rapeseed SPP. A high humidity tandem differential mobility analyzer (HHTDMA) was used to measure particle restructuring and water uptake over a wide range of relative humidity (RH) from 2 % to 99.5 %, and a continuous flow CCN counter was used for size-resolved measurements of CCN activation at supersaturations (S) in the range of 0.2 % to 1.2 %. For both subsaturated and supersaturated conditions, effective hygroscopicity parameters к , were obtained by Köhler model calculations. Gravimetric and chemical analyses, electron microscopy, and dynamic light scattering measurements were performed to characterize further properties of SPP from aqueous pollen extracts such as chemical composition (starch, proteins, DNA, and inorganic ions) and the hydrodynamic size distribution of water-insoluble material. All investigated SPP samples exhibited a sharp increase of water uptake and k above ~95 % RH, suggesting a liquid-liquid phase separation (LLPS). The HHTDMA measurements at RH> 95% enable closure between the CCN activation at water vapor supersaturation and hygroscopic growth at subsaturated conditions, which is often not achieved when HTDMA measurements are performed at lower RH where the water uptake and effective hygroscopicity may be limited by the effects of LLPS. Such effects may be important not only for closure between hygroscopic growth and CCN activation but also for the chemical reactivity, allergenic potential, and related health effects of SPP.

This research has been supported by the Russian Science Foundation (grant no. 18-10 17-00076) and Max Planck Society.
Attributing the negative scaling of extreme precipitation with temperature over India to cloud radiative cooling during the monsoon season
Authors: Ghausi Sarosh Alam , Kleidon Axel , Ghosh Subimal
Published: March 2021

Extreme precipitation is expected to increase at the rate of 7% per degree rise in temperature as suggested by the Clausius-Clapeyron equation (also known as CC scaling). Observations however, show deviations from the CC rate, with mostly negative precipitation - temperature scaling in warm tropical regions. Here we explain the negative precipitation scaling in the tropics with the cloud radiative effect on surface temperatures. Temperatures are shaped by the surface energy balance, which is affected by clouds, and hence temperatures are not independent of precipitation. We used observations from India and found negative scaling rates over most regions as extreme precipitation scaling tends to breakdown at temperatures of about 23◦to 25◦C. We show that these negative scaling rates arise from the radiative cooling of clouds associated with precipitation events which is predominant in India during the summer monsoon season. To test our hypothesis, we used an energy balance model constrained by assumption that convective exchange within atmosphere works at its thermodynamic limit of maximum power. Using the NASA-CERES radiation product, we calculated surface temperatures for “All sky” and “Clear sky” conditions to include/exclude the effect of cloud radiative forcing. Our results show a diametric change in precipitation scaling after removing the cooling effect of clouds on surface temperatures. Negative precipitation scaling (-4% /◦C) was found when using “All sky” conditions, but these come close to the CC rate (7% to 9% /◦C) when estimated using temperatures derived from “Clear sky” conditions. The breakdown in extreme precipitation scaling at high temperatures also disappeared forthe “Clear sky” temperatures. This implies that the breakdown in scaling may not relate to changes in aridity or the lack of moisture, but rather to the associated changes in cloud cover. Negative scaling rates derived from observations are thus likely to misrepresent the response of extreme precipitation to global warming in tropical regions. Our findings suggest that an intensification of precipitation extremes at CC rate with global warming is consistent with observations.

Keywords: Extreme Precipitation, CC scaling, Maximum Power, Indian Mon-soon
Comparison of MODIS-based thin-ice thicknesses with ice draft measurements in the Laptev Sea & Chukchi Sea
Authors: Preußer Andreas , Belter H. Jakob , Fukamachi Yasushi , Heinemann Günther
Published: March 2021

Acquiring information about the thickness of thin Arctic sea-ice is an important aspect of assessing atmosphere – sea-ice – ocean interactions, as the ice thickness directly relates to the magnitude of energy fluxes at the sea-ice interfaces. In winter, these fluxes are linked to sea-ice formation and hence accompanying processes such as physically induced upper-ocean convection and turbulent mixing of the lower atmospheric boundary layer. It remains a big challenge to validate satellite-derived thin-ice thicknesses, first and foremost due to the lack of suitable in-situ data in these remote areas.

In order to address this issue, we here present the first insight into a comparison between high-resolution (2km) MODIS thermal infrared satellite data (available for 2002/2003 to 2017/2018) and comprehensive time series of ice-draft data obtained from moored Ice Profiling Sonar (IPS) data. The IPS data set comprises winter-seasons 2009/2010 to 2011/2012 in the Chukchi Sea and winter-seasons 2013/2014 to 2014/2015 in the Laptev Sea. For the MODIS data set, a 1D energy balance model serves as the base for deriving thin-ice thicknesses (0 to 50 cm) from ice-surface temperature swath-data and ERA-Interim atmospheric reanalysis data. In order to facilitate the comparison, the 1Hz IPS ice-draft data is first empirically converted to ice thickness and afterwards resampled to 5-minute modal-values to find matching MODIS swath data.

It shows that the agreement between the MODIS and IPS ice-thickness data largely depends on the thickness of the ice sampled by the IPS. We found the highest agreement for ice thickness values below 20 cm, which tend to appear more frequently at the Chukchi Sea mooring location. More generally, we notice that MODIS seems to overestimate ice thicknesses up to approximately 40 cm. For thicker ice, the limitations of the MODIS ice-thickness retrieval result in an underestimation.
A comprehensive quantification of error location uncertainties for the French earthquake catalog
Authors: Peña Castro Andres Felipe , Lambotte Sophie , Grunberg Marc , Arroucau Pierre , Mayor Jessi , Daniel Guillaume , Letort Jean
Published: March 2021

Locating earthquakes has been a longterm problem in seismology that depends on multiple parameters like station density and spacing, azimuthal gap, velocity models, and phase pick precision. Here, we analyze the current state of the earthquake French catalog for the time period between 2010 until 2018, which we divide into different regions: the Alps, Massif Central, the West, the Pyrenees, the Grand-East and the North. We perform multiple location synthetic tests using as benchmark the earthquake catalog and the evolution of the French seismic network to quantify the improvements in 1) earthquake location through time and 2) the error locations and their uncertainties. For such endeavors, we use NonLinLoc to perform the synthetic tests varying, as input, the stations, the number of stations and phase picks, 1D velocity models and 3D velocity models, and to understand the changes in 1) earthquake hypocenters, 2) ellipsoidal errors and 3) posterior density functions. Then, we relocate the entire catalog using NonLinLoc including 3D velocity models (where available) and compare the hypocentral location differences when we relocate the catalog with 1D velocity models. Additionally, we estimate a quality factor for each of the located earthquakes and report the changes on the quality factor with the temporal evolution of the national seismic network. The resulting catalog and its associated error location will help future seismic hazard estimations in the Metropolitan French area.
A novel high-resolution laser-melting sampler for discrete analyses of ion concentrations and stable water isotopic compositions in firn and ice cores
Authors: Motizuki Yuko , Nakai Yoichi , Takahashi Kazuya , Hirose Junya , Sahoo Yu Vin , Yano Yasushige , Yumoto Masaki , Maruyama Masayuki , Sakashita Michio , Kase Kiwamu , Wada Satoshi
Published: March 2021

Ice cores preserve past climatic changes and, in some cases, astronomical signals. Here we present a newly developed automated ice-core sampler that employs laser melting. A hole in an ice core approximately 3 mm in diameter is melted and heated well below the boiling point by laser irradiation, and the meltwater is simultaneously siphoned by a 2 mm diameter movable evacuation nozzle that also holds the laser fiber. The advantage of sampling by laser melting is that molecular ion concentrations and stable water isotope compositions in ice cores can be measured at high depth resolution, which is advantageous for ice cores with low accumulation rates. This device takes highly discrete samples from ice cores, attaining depth resolution as small as ~3 mm with negligible cross contamination; the resolution can also be set at longer lengths suitable for validating longer-term profiles of various ionic and water isotopic constituents in ice cores. This technique allows the detailed reconstruction of past climatic changes at annual resolution and the investigation of transient ionic and isotopic signals within single annual layers in low-accumulation cores, potentially by annual layer counting.
Multiproxy paleolimnological reconstruction of Lake Victoria’s environmental history, East Africa 
Authors: Wienhues Giulia , Temoltzin-Loranca Yunuén , Vogel Hendrik , Grosjean Martin
Published: March 2021

Lake Victoria (LV), Africa’s largest lake is situated in the African Great Rift Valley. Due to its shallowness (max.68 m; mean 40 m) and limited river inflow, LV is very sensitive to variations in climate and lake level fluctuations. As a result, LV has undergone repeated low stand periods, or even complete desiccation during the Late Pleistocene with profound effects on the aquatic ecosystem. One example is the emergence of a unique biodiversity of endemic cichlid species following the lake’s last desiccation event during the last glacial and subsequent refilling commencing ~15,000 years ago.

In an interdisciplinary project we aim at reconstructing linkages between paleoenvironmental variability, disturbances and adaptive species radiation by combining approaches from paleogenomics, paleoecology and paleolimnology. For this purpose, four sediment cores along a depth-transect (near-shore to offshore), covering ca. the past 14,000 years, are analyzed.

We present first paleolimnological results of long-term changes of using (isotope-)geochemical indicators including: Sedimentary pigments and biogenic silica to infer aquatic productivity supported by micro X-ray Fluorescence (XRF) derived element geochemistry, 13C and 15N, and sedimentary phosphorus fraction analyses providing information on changes in sediment composition.

The results suggest that the infilling of the LV basin was a long-term step-wise process. This is shown by elevated and variable indicators for lithogenic input (e.g Ti, Zr and K) and interpreted as mobilization of substrate from the shorelines by a dynamic lake level prior to its stabilization in the Early and Mid-Holocene.  This process is mainly reflected in the core taken at the greatest water depth (65 m). Simultaneously, the aquatic productivity (BSi and chloropigments) increased rapidly after the refilling of the lake basin in the Late-Glacial. A gradual drying of the climate and a following shift to a more oxygenated water column is observed in the Mid-to Late Holocene indicated by a decline in chemically weathered material (e.g Rb/K & K/Al ratios) and abundance of Mn.
Transition probabilities between synoptic weather types as a fingerprint for climate model evaluation
Authors: Fernandez-Granja Juan Antonio , Casanueva Ana , Bedia Joaquín , Fernández Jesús
Published: March 2021

Global Climate Models (GCMs) generally exhibit significant biases in the representation of large-scale atmospheric circulation. Even after bias adjustment, these errors remain and are inherited to some extent by the derived downscaling products, impairing the credibility of future regional projections. 

We perform a process-based evaluation of state-of-the-art GCMs from CMIP5 and CMIP6, with a focus on the simulation of the synoptic climatological patterns having a most prominent effect on the European climate. To this aim, we use the Lamb Weather Type Classification (LWT, Lamb, 1972). We undertake a comprehensive assessment based on several evaluation measures, such as Kullback-Leibler divergence (KL), Relative Bias and Transition Probability Matrix Score (TPMS), used to assess the ability of the GCMs in reproducing not only the frequencies of the different Lamb Weather Types (LWTs), but also the daily probabilities of transitions among them. We show that the novel TPMS score poses a stringent test on the GCM performance, allowing for a convenient model ranking based on each model’s transition probability matrix fingerprint. Deficiencies in the transition probabilities from one LWT to another might explain the misrepresentation of the synoptic conditions and their frequencies by the GCMs. Four different reanalysis products of varying characteristics are considered as pseudo-observational reference in order to assess observational uncertainty. 

Our results unveil an overall improvement of salient atmospheric circulation features of CMIP6 with respect to CMIP5, demonstrating the ability of the new models to better capture key synoptic conditions. The improvement is consistent across observational references, although it is uneven across models and large frequency biases still remain for the dominant LWTs in many cases. In particular, some CMIP6 models attain similar or even worse results than their CMIP5 counterparts. In light of the large differences found across models, we advocate for a careful selection of driving GCMs in downscaling experiments with a special focus on large-scale atmospheric circulation aspects.

 
Atmosphere-based US emission estimates of SF6 for 2007 - 2018
Authors: Hu Lei , Montzka Stephen , Dlugokencky Ed , DeCola Phil , Ottinger Debrah , Thoning Kirk , Dutton Geoff , Andrews Arlyn , Bogle Stephanie , Roshchanka Volha , Crotwell Andy
Published: March 2021

Sulfur hexafluoride (SF6) is a potent greenhouse gas (GHG) that is primarily emitted from electrical circuit breakers and heavy-duty gas-insulated switchgears in electric transmission and distribution equipment, magnesium production and processing, and electronics production. It has a 100-year global warming potential of 23500 and an atmospheric lifetime of 850 (580 - 1400) years. Because of its extremely large global warming potential and long atmospheric lifetime, its emissions, while currently small, have an outsized influence on changing climate over the long term.  However, current US emissions of SF6 are uncertain. The US SF6 consumption that was used to estimate SF6 emissions in the US EPA national GHG reporting to the UNFCCC has an uncertainty of 30 – 60%, depending on whether to use the US SF6 supplier reports or user reports. With different inventory methodologies, the national emissions estimates of SF6 from the EDGAR and US EPA’s GHG inventories differ by more than a factor of 4. Here, we will present the first detailed U.S. national and regional emissions of SF6 that were derived from an inverse analysis of an extensive flask-air sampling network from the US NOAA’s Global Greenhouse Gas Reference Network and high-resolution atmospheric transport simulations for 2007 - 2018. We will discuss our atmosphere-based top-down emission estimates in comparison with the existing bottom-up emission inventories, our derived seasonal variation of SF6 emissions, and associated implications regarding each industry’s contribution to emissions and optimal emissions mitigation strategies. Because atmospheric SF6 measurements are also used to assess atmospheric transport errors assuming no biases in SF6 emissions reported by the EDGAR inventory, our analysis also has important implications on limitations in such applications.
Multi-year variability in hydrological extremes in Africa: what are the main drivers?
Authors: Ekolu Job , Dieppois Bastien , Sidibe Moussa , Eden Jonathan , Tramblay Yves , Villarini Gabriele , Mahé Gil , Paturel Jean-Emmanuel , Van de Wiel Marco
Published: March 2021

Africa is affected by a high-level of temporal and spatial variability in climate, with large impacts on water resources, human lives and economies. Due to data scarcity, the impact of multi-year climate variations on hydrological variability and extremes, i.e. flood and drought, as well as how catchment properties could modulate those impacts, are generally poorly understood across the African continent. In this study, we first use machine learning algorithms to develop a new complete reconstructed daily streamflow dataset using more than 1500 stream gauges between 1950 and 2018, and covering most of Africa. We then examine historical trends and variability in hydrological extremes over the entire African continent, focusing on different hydrological characteristics, such as the timing, frequency and duration of high- and low-flow events, based on the peaks-over-threshold method. Following an assessment of the relative sensitivities of hydrological extreme indices to interannual (2-8-years) and decadal (>10-years) variability in the different regions of Africa, we analyze the respective contribution of different rainfall, temperature and soil moisture indices (e.g. frequency, duration and intensity of wet/dry or warmer/colder days) at both timescales, using relative importance analysis. We finally discuss how catchment properties (e.g. area, topography, land use/ land cover, drainage path lengths) modulate the relationship between hydrological extremes and climate.
Modelling hydrological droughts and floods in the Volta Basin, West Africa 
Authors: Gebrechorkos Solomon Hailu , Pan Ming , Lin Peirong , Pritchard David , Forsythe Nathan , Fowler Hayley , Sheffield Justin
Published: March 2021

Hydrological extreme events such as droughts and floods have a wide range of impacts on society and sectors such as agriculture and energy production. The impact of these extremes are projected to increase with future climate change and there is an urgent need to develop adaptation measures to reduce and manage the impacts. Long-term analysis of hydrological extremes, using a combination of models and climate data, helps better plan and manage water resources under global change. In this study, we modelled and analyzed hydrological extremes of the Volta river basin at very high-resolution (>10000 river reaches) using the Variable Infiltration Capacity (VIC) hydrological model, the vector-based river network routing model (RAPID), and high-resolution meteorological forcing datasets. The output from the VIC model is evaluated at multiple time scales (daily to annual) and for extreme events (droughts and floods) using observed streamflow data during the period 1979-2013.  The model performed very well in areas less affected by dams, with performance increasing from daily to annual time scale. The modelled streamflow data is used to assess changes and variability in droughts (duration days and severity) and floods (annual daily maximum). The results show a decreasing and increasing trend in moderate and severe droughts in northern-eastern and southern parts of the basin, respectively. An increasing trend in floods is observed in the upper part of the basin (Black and White Volta) and the main river of the Lower Volta and we found a strong correlation with changes in precipitation and soil moisture.
Iceland-Scotland Overflow Water Transport Variability through the Deep Bight Fracture Zone
Authors: Furey Heather , Bower Amy , Johns Bill , Ramsey Andree , Houk Adam
Published: March 2021

Iceland Scotland Overflow Water (ISOW), a component of the deep limb of the Atlantic Meridional Overturning Circulation (AMOC), is the equilibrated product of dense overflow into the eastern North Atlantic basin.  Modeling results and recent observations have suggested that a significant westward transport of ISOW (~1x106 m3s-1) may occur through the Bight Fracture Zone (BFZ) near 57°N, the first major channel through the Reykjanes Ridge where ISOW can cross into the Irminger Sea.  The remaining denser (and deeper) ISOW has been shown to leave the Iceland Basin westward via the Charlie-Gibbs Fracture Zone near 53°N, or southward into the West European Basin. Until now, there have been no measured time series in the BFZ to validate model results. Single moorings placed in the north and south channels of the BFZ from summer 2015 to summer 2017 were used to estimate a mean combined transport across the fracture zone of 0.8 ± 0.4 x106 m3s-1 westward, with each channel contributing about half of the mean transport. Variability between the two channels on shorter (month-long) times scales can be extreme: in March of 2016, for example, north channel transport was ~0.4 x106 m3s-1 eastward, while south channel transport was ~0.8 x106 m3s-1 westward.  For this 2-year period, transport is stronger in the summer (0.9-1.2 x106 m3s-1) than in winter (0.5-0.7 x106 m3s-1), where large fluctuations including complete reversals suggest transport variability may be affected by winter storms.  This mooring record also shows a fresh anomaly in ISOW beginning in early 2017, which has been shown by others to originate from the surface waters near the Grand Banks region of the western north Atlantic.  Transport variability in this two-year record is examined in the context of the transport variability of the OSNAP mooring arrays on the east and west flanks of the Reykjanes Ridge just north of BFZ during the same time period.  An observationally-based understanding of how the Iceland and Irminger basins communicate with each other via the deep limb of the AMOC through the BFZ will provide fundamental insight into the pathways and processes that define the subpolar AMOC system.
Promotion of women in science: the Soapbox Science outreach platform in Belgium
Authors: Bingen Christine , Pham Lê Binh San , Lamort Lucie , Lefever Karolien , Piccialli Arianna , Yseboodt Marie
Published: March 2021

Soapbox Science is quite a novel public outreach platform that was initiated in the UK in 2011 to promote women in science, and that was spread worldwide since then. Between 2011 and 2018, 40 cities hosted the initiative in not less than 8 countries over 4 continents, and in 2020, despite the pandemic, 56 events were organized in 14 countries around the world. 

In 2019, a small team of scientists and science communicators from two Belgian Scientific Federal Institutes decided to organise a Soapbox Science event in Belgium to promote the visibility and the role of women in science in Belgium. The first Belgian event took place in fall 2020, not in the centre of Brussels as initially planned, but as a virtual event live-streamed via YouTube and Facebook due to physical limitations imposed by the COVID-19 pandemic.

We present an overview of the preparation and the conduct of this first Soapbox Science Brussels event, and describe the motivations, challenges, issues and opportunities encountered throughout the process, as well as the outcome and perspectives of Soapbox Science in Belgium.
Morphodynamic stability and characteristic length scales of bifurcations and confluences loops
Authors: Ragno Niccolò , Redolfi Marco , Tubino Marco
Published: March 2021

The morphodynamics of multi-thread fluvial environments like braided and anastomosing rivers is fundamentally driven by the continuous concatenation of channel bifurcations and confluences, which govern the distribution of flow and sediment among the different branches that are reconnecting further downstream. Almost all studies performed to date consider the two processes separately, although they frequently appear as closely interconnected. In this work, we tackle the problem of analyzing the coupled morphodynamics of such bifurcation-confluence systems by studying the equilibrium and stability conditions of a channel loop, where flow splits into two secondary anabranches that rejoin after a prescribed distance. Through the formulation of a novel theoretical model for erodible bed confluences based on the momentum balance on two distinct control volumes, we show that the dominating anabranch (i.e. that carrying more water and sediment) is subject to an increase of the water surface elevation that is proportional to the square of the Froude number. This increase in water surface elevation tends to reduce the slope of the dominating branch, which produces a negative feedback that tends to stabilize the bifurcation-confluence system. A linear analysis of the coupled model reveals that the stabilizing effect of the confluence depends on the ratio between the length of the connecting channels and the average water depth, independently of the channel slope and Froude number. Furthermore, the effect of the confluence is potentially able to stabilize the channel loop in conditions where the classic stabilizing mechanism at the bifurcation (i.e. the topographical effect related to the gravitational pull on the sediment transport) is very weak, as expected when most of the sediment is transported in suspension. The identification of a characteristic length scale that produces a coupling between the confluences and bifurcations opens intriguing possibilities for interpreting the self-adjustment of the planform scale of natural multi-thread rivers.