bluuebunny/crossref_metadata_2025 huggingface dataset:
Feedbacks between sediment input, bed state and threshold for motion in gravel-bed rivers: an experimental study
Authors: Saletti Matteo , Hassan Marwan
Published: March 2021

In gravel-bed rivers the relation between the magnitude and frequency of sediment input, the threshold for motion and channel stability is still not fully understood.

Here we present results from a 280-hour long flume experiment, in which poorly sorted sediment was fed episodically in an 18-m long, 2.2%-steep channel. The experiment included 7 consecutive runs lasting 40 hours each characterized by a constant water discharge but different sediment supply regimes (i.e., with no feed, constant feed and sediment pulses). Several measurements of sediment transport, flow depth and bed structures were taken along the flume, to assess how changes in sediment supply influence particle mobility and channel stability.

Our results show that the surface grain‐size distribution coarsened quickly, developing an armored layer that persisted throughout the entire experiment with only short-lived changes after sediment pulses. Grain clusters and other bed structures developed continuously during the experiments, changing dynamically in response to sediment pulses.

We estimated the thresholds of motion with three different methods, all of which yielded consistent results. Overall, the threshold for motion increased during the experiment, fluctuating in response to changes in sediment input. Our results provide further evidence to the idea that the threshold for motion in gravel-bed rivers is not a constant, but changes as a state parameter. These changes in our experiments are controlled by (a) the sediment supply regime, (b) the degree of bed structuring, and (c) the history of bed evolution. These outcomes suggest that sediment supply regime is a primary control on bed surface evolution and the channel stabilizing function played by surface structures.
Persistent Homology, Regimes and Climate Data
Authors: Strommen Kristian , Otter Nina , Chantry Matthew , Dorrington Joshua
Published: March 2021

The concept of weather or climate 'regimes' have been studied since the 70s, to a large extent because of the possibility they offer of truncating complicated dynamics to vastly simpler, Markovian, dynamics. Despite their attraction, detecting them in data is often problematic, and a unified definition remains nebulous. We argue that the crucial common feature across different dynamical systems with regimes is the non-trivial topology of the underlying phase space. Such non-trivial topology can be detected in a robust and explicit manner using persistent homology, a powerful new tool to compute topological invariants in arbitrary datasets. We show some state of the art examples of the application of persistent homology to various non-linear dynamical systems, including real-world climate data, and show how these techniques can shed light on questions such as how many regimes there really are in e.g. the Euro-Atlantic sector. Future directions are also discussed.
Monitoring ambient aerosol size distributions from 1 – 55 nm with the GRIMM-AIRMODUS PSMPS 
Authors: Steiner Gerhard , Flentje Harald , Väkevä Minna , Keck Lothar , Vanhanen Joonas
Published: March 2021

Here, we present the final, commercially available, version of a mobility particle size spectrometer that is able to access the 1 nm particle size range for ambient atmospheric measurements.

The overall system performance was tested in a multitude of laboratory experiments, determining various size dependent parameters like DMA’s transfer function, DMA penetration efficiency, PSM and CPC counting efficiency. With the knowledge of these parameters, we are able to define a well-known overall system performance, a critical prerequisite for measurements that start at 1 nm sized particles.

The instrument originates from a collaboration of Grimm Aerosol Technik, Germany and Airmodus Ltd, Finland, combining a Grimm SMPS+C system with the Airmodus Particle Size Magnifier (PSM). Accordingly, it is named: PSMPS.

The main system components comprise a modified version of the short Grimm Differential Mobility Analyzer (Grimm S-DMA), the diethylene glycol-based PSM (Airmodus A10) and the new butanol-based CPC (Grimm 5417). The modified S-DMA is specially optimized for the transmission of small ions. Typically, it is operated with an aerosol sample flow rate of 2.5 L/min and a sheath flow rate of 10 L/min, allowing particle size distribution measurements from 1.1-55.7 nm. The PSM is used to lower the detection efficiency of the Grimm CPC below 2 nm in electrical mobility equivalent diameter. The new Grimm 5417 CPC is an upgraded version of the well-known 5416 CPC, that features two switchable aerosol sample flow rates of 0.3 and 0.6 L/min and also supplies the S-DMA with sheath airflow rates of either 3.0 or 10.0 L/min.

In this presentation, we will introduce the features and performance of the PSMPS system, will highlight some laboratory characterization tests and report the results from an ambient aerosol measurement campaign at the Hohenpeissenberg Observatory of the German meteorological service (DWD), monitoring new particle formation events starting at a particles size of 1nm.
Immersive Visualization of Ocean Data in a Game Engine
Authors: Brisc Felicia , Serra Nuno
Published: March 2021

Virtual Reality is expanding rapidly in many academic and industry areas as an important tool to represent 3D objects, while graphics hardware is becoming increasingly accessible. Conforming to these trends, we present an immersive VR environment created to help earth scientists and other users to visualize and study ocean simulation data and processes. Besides scientific exploration, we hope our environment will become a helpful tool in education and outreach. We combined a 1-year 3km MITgcm simulation with daily temporal resolution and a bathymetry digital elevation model in order to visualize the evolution of  Northeast Atlantic eddies enclosed by warm and salty Mediterranean Water. Our approach leverages the advanced rendering algorithms of a game engine in order to enable users to move around freely, interactively play the simulation and observe the changes and evolution of eddies in real time.
Decadal Variability of Rainfall in Senegal : beyond total seasonal amounts
Authors: Badji Aissatou , Diakhaté Moussa , Gaye Amadou Tierno , Mignot Juliette , Mohino Elsa
Published: March 2021

The intraseasonal characteristics of rainfall have important implications for agriculture in the Sahel. For example, the development and yield of millet, sorghum and maize depend not only on the rainfall seasonal total amounts, but also on the onset of the rainy season and the seasonal distribution of rainy days as well as the occurrence of dry spells. However, the decadal variability of intraseasonal rainfall characteristics in the Sahel and in particular in Senegal has received little attention in the literature so far. In this study, we analyze the decadal modulations of the intraseasonal characteristics of the monsoon season in Senegal over the period 1918-2000. From daily rainfall data measured at different stations in Senegal, we have defined indices characterizing, among others, the number of rainy days, the average intensity of rainy days, the starting day and ending day of the rainy season. The spatial patterns of the mean indices generally show a north/south gradient and their temporal modulations show a clear decadal signal. Application of EOF (Empirical Orthogonal Function) analysis provides a main mode of variability showing same-signed loads throughout the territory. The associated PCs show strong decadal variability for most indices with a strong link to the Atlantic Multidecadal Variability. The exception are the indices related to the duration of the monsoon season, which show a weaker decadal variability with a clear trend.
Internal dynamics of steady and nearly uniform granular avalanches
Authors: Trewhela Tomas , Ancey Christophe
Published: March 2021

We experimentally investigated the internal dynamics of stationary mono- and bidisperse granular avalanches in an inclined conveyor belt flume. We used the refractive index matching technique to visualize and obtain information from within the granular bulk. In combination with particle tracking velocimetry and coarse-graining techniques, we were able to calculate continuum particle distributions and velocity fields. The experimental avalanches had distinct flow regions: (i) a convective-bulged front, (ii) a compact-layered tail, and (iii) a breaking size segregation wave structure, serving as a transition between the former two. To describe the dynamics of these regions, we computed local strain rates in the form of its tensor invariants. The invariants varied notably between regions; while the largest values and non-linear distributions were found at the front, linear distributions were observed in the tail. In general, and although that slip was considerable at the base of the flow, time-averaged velocity profiles were found to be well captured by a Bagnold model. Based on recent developments in particle-size segregation theory, we calculated the segregation flux within the bidisperse avalanches. In those experiments, we found that segregation flux was higher at the front than at the back, a fact that was confirmed by the observed recirculation of large particles at the front. All our experimental data show a strong link between rheology and segregation, a result that will provide grounding for new developments in segregation theory.
Low-salinity Mediterranean gypsum deposits: chemical vs biological products
Authors: Aloisi Giovanni , Natalicchio Marcello , Guibourdenche Laetitia , Caruso Antonio , Dela Pierre Francesco
Published: March 2021

Large deposits of gypsum accumulated in the marginal basins of the Mediterranean Sea during the Messinian Salinity Crisis. These form the marginal portions of the Mediterranean Salt Giant (MSG) that also occupies the deep, central Mediterranean basins. Although the marine, evaporitic origin of the MSG is undisputed, the analysis of gypsum fluid inclusions and of gypsum-bound water (d18OH2O and dDH2O) suggest that marginal basin gypsum formed from low- to moderate-salinity water masses (5 - 60 ‰), rather than from high-salinity brines (130 - 320 ‰), as expected during the evaporation of seawater. We present a new set of water isotope and fluid inclusion salinity data that extends the low salinity signature of gypsum to include five Mediterranean Sea marginal basins: Caltanissetta Basin (Sicily), Sorbas Basin (Spain), Piedmont Basin and Vena del Gesso Basin (northern Italy) and Catanzaro Trough (Southern Italy). With a simple geochemical model we explore the salinity-d18OH2O-dDH2O evaporation path and the 87/86Sr and d34SSO4 composition of the Mediterranean Sea subject to a variety of evaporation conditions and mixing ratios with continental runoff. This approach suggests that evaporation and mixing with continental runoff - including freshwater transiting via the Paratethys - cannot lead to the observed geochemical signature of MSC gypsum deposits. An alternative process that decouples the saturation state with respect to gypsum from salinity must have been active. We are exploring the possibility that the biogeochemical sulfur cycle leads to spatially and temporally localized gypsum supersaturation conditions via the production of SO42- by the oxidation and disproportionation of reduced sulfur compounds.
Using a new divergence method to quantify methane emissions with TROPOMI on Sentinel-5p
Authors: Liu Mengyao , Van der A Ronald , Van Weele Michiel , Eskes Henk , Lu Xiao , de Laat Jos , Kong Hao , Sun Jiyunting , Ding Jieying , Zhao Yuanhong , Weng Hongjian
Published: March 2021

The high-resolution Tropospheric Monitoring Instrument (TROPOMI) satellite observations of atmospheric methane offer a powerful tool to identify emission hot spots and quantify regional emissions. The divergence of horizontal fluxes of NO2 has already been proven to be an efficient way to resolve and quantify high sources on a global scale. Since the lifetime of CH4 is in the order of 10 years, the sinks can be ignored at the synoptic time scale which makes the divergence method even more applicable to CH4 than to short-lived NO2. 
Because plumes of newly emitted CH4 disperse within the Planetary Boundary Layer (PBL), we first convert the satellite observed total column average (XCH4) to a regional enhancement of methane in the PBL (∆XCH4_PBL) by using the CAMS global methane background reanalysis fields above the PBL. These model fields represent the transport- and chemically-modulated large-scale distribution of methane. Secondly, the divergence of ∆XCH4_PBL is derived by the use of the wind speeds halfway within the PBL. Based on the divergence, methane emissions are estimated on a 0.25°× 0.25° grid. We tested our new method for Texas in the United States and quantified methane emissions from the well-known oil-gas fields in the Permian Basin, as well as from – less well quantitatively established – oil-gas fields located in southern coastal areas. 
Compared to traditional inverse methods, our method is not restricted by an a priori emission inventory and so far unidentified local sources (i.e. emissions from livestock in feed yards) may be found. Due to its computational efficiency, the method might be applied in the near future globally on the current spatial resolution.
Near-Ground-Based Optical Plant Phenology Measurements at China Ecological Meteorology Sites
Authors: Yang Dasheng , Cui Shilin , Zhang Benzhi , Wu Dongli , Lei Yong , Shen Chao , Zhu Jingqun , Wang Yingshun , Wang Wenyan
Published: March 2021

Abstract Climate change is a hot issue in the global scale. The some varieties of phenological phase of plants (trees, grasslands and crops et al.) can directly and objectively reflected climate change and Commonly, the response of plant phenology to climate change is sensitive, especially to climatic factors such as precipitation, temperature, soil characteristics in the growing environment, and sometimes can be considered as an indicator of climate change. Those meteorology and soil factors must be taken into account when we build phenological model so as to quantitatively study the relationship between climate change and plant phenology. Beside of those factors, the high frequency and multi-scale acquisition of phenological observation data is also the basis for phenological model researches. Since February of 2020, China Meteorological Administration (CMA) has established 25 vegetation ecological observation sites in Inner Mongolia autonomous region, Shaanxi, Hebei, Sichuan, Guangxi, Fujian and Anhui provinces. The automatic vegetation eco-meteorological observation instruments, whichi are composed of image sensor (digital camera), multispectral sensor, laser altimeter, point cloud laser radar and sound sensor, have been installed in the sites. They can provide so much products as image of plant community, normal difference vegetation index (NDVI), plant height, canopy height and animal sound at present. Of all these products, image data of plant community can be further retrieved to generate the greenness chromatic coordinate (Gcc) data, which can be widely applied into the phenological studies and the validations of satellite terrestrial vegetation products. After months of experimental operation, these equipments show the great ability to monitor the growth and development of terrestrial plants in China. This ability also lays a foundation for the establishment of the plant ecological observation network in China (China Vegetation Ecological Meteorological Observation Network).

KEYWORDS：Plant phenology, near-surface-based measurement, observation network
Perceptions of Climate Information in the Caribbean: Implications for Adaptation
Authors: Dookie Denyse , Conway Declan , Dessai Suraje
Published: March 2021

Despite an increasing recognition of the value of climate information and broader weather and climate services (WCS) for decision-making, understanding its wider dimensions for effective delivery and use remains an ongoing discussion. In particular, a focus on barriers and enablers of using climate information can be helpful for policy-directed efforts, as this underscores challenges and streamlines strategies for action. For smaller and developing countries with particular vulnerabilities to climate variability and change, and various barriers to climate information/WCS uptake, this is especially true but often limited within research. This paper addresses this research gap by offering perceptions of climate information use in the insular Caribbean. We engaged with 26 potential WCS end-users in the form of region-wide experts and decision-makers who focus on climate adaptation, disaster risk reduction, and resilience, and analysed semi-structured interview responses to understand barriers and enablers of WCS delivery and use within the region. Against a history of projectised adaptation initiatives in the Caribbean, the results highlight that while finance is critical, there is rather a range of interlinked enabling conditions necessary for the effective use of climate information. Caribbean respondents stressed the need for island-contextualised climate information and the importance of adequate human resource capacity, loud voices/climate champions, and effective political and legislative mandates for understanding and using climate information for climate-related decision-making. As well, a factor visualisation illustrates that the practical awareness of climate information for decision-making is closely tied to proactive climate champions, and that available finance should be noted within the context of donor interests. Moving ahead, it is clear that an integrated approach for effective WCS delivery and use is necessary, requiring engaged WCS partnerships amongst multiple stakeholders. The highlighting of such challenges within an under-researched area such as the Caribbean provides insights for developing adaptation strategies within the region, and can also signal critical elements relevant for other small developing countries.
Geographical representation at EGU General Assemblies in the period of 2015-2019
Authors: Jesus-Rydin Claudia , Montanari Alberto , Wingate Lisa , Beniest Anouk , Popp Andrea , van Rijsingen Elenora
Published: March 2021

The European Geosciences Union (EGU) is the leading organisation for Earth, planetary and space science research in Europe. Each year the EGU holds a General Assembly that is the largest and most prominent European geosciences event, attracting over 16,000 scientists from all over the world. This presentation provides an overview of the geographical representation of participants to the EGU General Assembly in recent years.

The presentation focuses on a five-year dataset spanning 2015 to 2019 and provides an insight on growth rates of the different countries individually and in comparison to the EGU General Assembly average growth (38% during the period 2015-2019).

China has the fastest-growing representation at the EGU General Assembly with a growth rate close to 300% in the period 2015-2019. The growth rates of the Republic of Korea and Canada have also climbed, and now represent the second and third fastest-growing countries attending the EGU respectively, with growth rates just over 80%.

The representation of Central and Eastern European countries (also known as EU-13 countries) at the EGU General Assembly has also grown steadily at a rate comparable with the EGU average, i.e. around 38%. Western European countries are the most represented at the annual general assembly accounting on average for 58% of the total participants over the 2015-2019 period. In addition the participation of Western Europeans to the general assembly continues to grow at the EGU but a slightly slower pace 29% than for Eastern Europe, but at a rate similar to participants from the USA.

This analysis leads to the conclusion that participation at the EGU General Assembly has grown both in the total number of attendees and in their geographical diversity. The most striking shift in the representation of countries has been towards an increase in the participation of Asian countries (China, Taiwan, Rep. of Korea & Japan) that collectively now exceeds the participation of North American participants (USA + Canada). In particular, if the current rate of growth in participation is sustained by China over the coming years this dataset suggests that their representation will surpass that of the USA shortly. It was also clear that the EU-13 countries continue to participate in the EGU General Assembly in growing numbers and with particular representation in certain scientific divisions such as Soil System Sciences (SSS), Hydrological Sciences (HS) and Climate: Past, Present & Future (CL). Overall, the above data provide valuable guidance in how to shape future EGU actions to promote diversity, equality and inclusivity at the annual EGU meeting.
The Meteoric Ni Layer in the Upper Atmosphere
Authors: Plane John , Daly Shane , Feng Wuhu , Mangan Thomas , Gerding Michael , Carrillo Sanchez Juan Diego , Bones David
Published: March 2021

The ablation of cosmic dust particles is a source of metallic vapours in planetary upper atmospheres. Recently, ground-based lidars have made the first observations of a layer of Ni atoms peaking around 86 km in the terrestrial atmosphere (in contrast, the layers of Na and Fe have been observed for several decades).  In order to understand these Ni layer observations, we have developed a new version of the Leeds Chemical Ablation Model (CAMBOD) to include a Ni-Fe-S metallic phase in addition to the bulk silicate phase. The validity of the new model was tested using our laboratory Meteoric Ablation Simulator, where micron-size meteoritic particles were flash heated to temperatures as high as 2700 K to simulate their atmospheric entry, and the ablating Ni atoms monitored by fast time-resolved laser induced fluorescence.

The first global atmospheric model of Ni (WACCM-Ni) was then developed with three components: the Whole Atmosphere Community Climate Model (WACCM6); a meteoric input function derived by coupling an astronomical model of dust sources in the solar system with CABMOD; and a comprehensive set of neutral, ion-molecule and photochemical reactions pertinent to the chemistry of Ni in the upper atmosphere. The kinetics of these reactions were mostly measured in our laboratory, or else modelled theoretically using ab initio quantum calculations combined with statistical rate theory. WACCM-Ni simulates satisfactorily the observed neutral Ni layer peak height and width, as well as Ni+ ion measurements from rocket-borne mass spectrometry. The Ni layer is predicted to have a similar seasonal and latitudinal variation as the Fe layer, and its unusually broad bottom-side compared with Fe is caused by the relatively fast NiO + CO → Ni + CO2 reaction. The quantum yield for photon emission from the reaction between Ni and O3, which has been observed in the nightglow from space-based spectrometers, is estimated to be between 6 and 40%.
Assessing Seismic Resilience of School Educational Sector. An attempt to establish the initial conditions in Calabria Region, Southern Italy
Authors: Fontana Cora , Cianci Eleonora , Moscatelli Massimiliano
Published: March 2021

School education constitutes one of the strategic functions to be recovered after an earthquake. The structural improvement of school buildings together with the strengthening of the administrators’ capacity to react positively following an earthquake are key factors that contribute to social vulnerability’s reduction. Nevertheless, in Italy, the issue of risk reduction policies related to school sector is not yet consolidated in the institutional agendas. Observing the last major Italian earthquakes what remains predominant is school buildings’ damage degree with consequent interruption of the system functionality. Among the causes: the building heritage vulnerability and the lack of risk mitigation policies, capable of building a resilient community for future earthquakes. That of resilience is considered a relevant paradigm to address the issue of how to strengthen the school sector’s capacity to ensure the buildings physical safety and to guarantee the maintenance of the school function, looking at pre and post-event phases.

The paper proposes a set of indicators and a methodology for a preliminary assessment of the educational sector’s seismic resilience, in terms of initial conditions. The method has been tested on a first case study: Calabria Region, Southern Italy. The results show that spatial differences in the educational sector’s seismic resilience are evident. Except for some large urban areas, the less resilient areas are grouped mainly in the southern part of the Region, while the most resilient ones are located mostly in the central-northern sector. The ambition is to identify a repeatable approach, useful as guidelines for school seismic prevention policies.
Evolution of Denmark Strait Overflow Cyclones and Their Relationship to Overflow Surges
Authors: Almansi Mattia , Haine Thomas , Gelderloos Renske , Pickart Robert
Published: March 2021

Denmark Strait, the channel located between Greenland and Iceland, is a critical gateway between the Nordic Seas and the North Atlantic. Mesoscale features crossing the strait regularly enhance the volume transport of the Denmark Strait overflow. They interact with the dense water masses descending into the subpolar North Atlantic and therefore are important for the Atlantic Meridional Overturning Circulation. Using a realistic numerical model, we find new evidence of the causal relationship between overflow surges (i.e., mesoscale features associated with high-transport events) and overflow cyclones observed downstream. Most of the cyclones form at the Denmark Strait sill during overflow surges and, because of potential vorticity conservation and stretching of the water column, grow as they move equatorward. A fraction of the cyclones form downstream of the sill, when anticyclonic vortices formed during high-transport events start collapsing. Regardless of their formation mechanism, the cyclones weaken starting roughly 150 km downstream of the sill, and potential vorticity is only materially conserved during the growth phase.
Geochemical Effects of Reclamation at Disturbed and Polluted Mine Sites
Authors: Alekseenko Alexey , Bech Jaume
Published: March 2021

The extraction of mineral resources results in a gigantic increase in the volume of overburden and host rocks mined and stored on the Earth's surface. Mine sites are constantly disturbed and polluted; the major changes are found in the soil cover, affecting the migration and accumulation of chemical elements; the cycles of nutrients, which are important for the development of biocenosis, are altered. The study on concentrations of pollutants in the Technosols revealed that they are determined to a greater extent by anthropogenic impact and subsequent possible remediation than by parent rocks. Soil sampling was conducted in the changing climatic zones of Russia where the impact is experienced both directly and indirectly by the water and air environments and, ultimately, this leads to economic losses and poses a danger to human health. The studies of the soil samples were performed using the equipment of the Common Use Centre of the Saint Petersburg Mining University. Reclamation of the studied mine sites was regulated by law to ensure environmental sustainability, that is, to preserve the possibility of land use for future generations, but its methods and ultimate goals varied significantly. Geological, geomorphological, hydrological, climatic, and soil characteristics of the site, as well as socio-economic conditions, determined the tasks of reclamation and the resulting new ecosystems. We analyzed that the most common uses of the restored landscapes include afforestation; if the soil cover complies with sanitary and hygienic standards, it is possible to start an agricultural business or create a reservoir for household or fishery purposes; land can be used for construction and recreation; in some situations, waste disposal is possible. Ecosystems that are restored or completely constructed differ greatly not only in their functions but also in geochemical conditions, on which the prospects for the return of disturbed and contaminated lands to an acceptable state largely depend. In this regard, the study goal was to identify general geochemical patterns inherent in reclaimed landscapes in different geographic zones, since the geochemical transformation of restored ecosystems depends on several natural and technogenic factors. The research outcomes indicate that the oxidation-reduction and alkaline-acid milieu, water and temperature regimes, sorption capacity, and other landscape-geochemical conditions are being ambiguously transformed in new ecosystems and can be derived from both natural conditions and the measures taken to eliminate damage. Concentrations of Pb, Zn, Ba, and Cu were found exceeding the average contents in the Earth's soils tens and even hundreds of times. We discussed the case within the framework of the Working Group on Land Reclamation, Environmental Protection, and Best Available Techniques (BAT) in Mining, and recommended reusing the studied mine sites with particular attention paid to phytoextraction, construction of geochemical barriers, and thermal desorption.
Seasonal and spatial variability of the CO2 system parameters in the Northeast Atlantic based on measurements from a surface ocean observation platform.
Authors: Curbelo Hernández David , González Dávila Melchor , González González Aridane , González Santana David , Santana Casiano Juana Magdalena
Published: March 2021

The seasonal and spatial variability of the CO2 system parameters and CO2 air-sea exchange was studied in the Northeast Atlantic Ocean between the northwest African coastal upwelling and the oligotrophic open-ocean waters of the North Atlantic subtropical gyre. Data was collected aboard a volunteer observing ship (VOS) from February 2019 to February 2020. The seasonal and spatial variability of CO2 fugacity in seawater (fCO2,sw) was strongly driven by the seasonal temperature variation, which increased with latitude and was lower throughout the year in coastal regions where the upwelling and offshore transport was more intense. The thermal to biological effect ratio (T/B) was approximately 2, with minimum values along the African coastline related to higher biological activity in the upwelled waters. The fCO2,sw increased from winter to summer by 11.84 ± 0.28 µatmºC-1 on the inter-island routes and by 11.71 ± 0.25 µatmºC-1 along the northwest African continental shelf. The seasonality of total inorganic carbon (CT) normalized to constant salinity of 36.7 (NCT) was studied throughout the region. The effect of biological processes and calcification/dissolution on NCT between February and October represented >90% of the reduction of inorganic carbon while air-sea exchange described <6%. The seasonality of air-sea CO2 exchange was controlled by temperature. The surface waters of the entire region acted as a CO2 sink during the cold months and as a CO2 source during the warm months. The Canary basin acted as a net sink of -0.26 ± 0.04 molC m-2 yr-1. The northwest African continental shelf behaved as a stronger sink at -0.48 ± 0.09 molC m-2 yr-1. The calculated average CO2 flux for the entire area was -2.65 ± 0.44 TgCO2 yr-1 (-0.72 ± 0.12 TgC yr-1).
Lake Chad hydrological cycle under current climate change
Authors: Sylvestre Florence , Crétaux Jean-François , Berge-Nguyen Muriel , Pham Duc Binh , Mahamat Nour Abdallah , Bouchez Camille , Frappart Frédéric , Papa Fabrice
Published: March 2021

In a near future, the Sahara and Sahelian regions could experience more rainfall than today as a result of climate change. Wetter conditions in the hottest and driest place of the planet today raise the question of whether the near future might hold in store environmental transformations, particularly in view of the growing human-induced climate, land-use and land-cover changes. Reflecting an enhancement of the global hydrological cycle under warmer conditions, some experiments provide support for the notion of a strengthening of the monsoon in the future and more rainfall in central Sahel and Sahara. However, some remote forcing could counterbalance the decadal trend. Modeling experiments suggest that the freshwater discharge coming from Greenland melting could significantly impact the sea surface temperature of North Atlantic and induce a decrease in Sahel rainfall for the next decades, remaining left open the question how Sahara will be in a warmer climate?

By chance, Lake Chad, located at the southern edge of the Sahara, is recognized for being the best site in Africa for deciphering hydrological and climate change. After being ranked at the world’s sixth largest inland water body with an open water area of 25,000 km2 in the 1960s, it shrunk dramatically at the beginning of the 1970s and reached less than 2000 km2 during the 1980s, decreasing by more 90% in area. Because it provides food and water to 50 millions of people, it becomes crucial to observe precisely its hydrological cycle during the last 20 years.

Here by using a new multi-satellite approach combined with ground-based observations, we show that Lake Chad extent has remained stable during the last two decades, slightly increasing at 14,000 km2. We extend further this reconstruction by adding new data from the hydrological year 2019-2020, which is considered at an extreme in precipitation recorded over the Sahel. Moreover, since the 2000s, groundwater which contributes to 70% of Lake Chad’s annual water storage, is increasing due to water supply provide by its two main tributaries draining a catchment area 610,000 km2 wide. Because the current climate change seems to be characterize by a higher interannual variability affecting from year to year the amount of precipitation during the rainy season and increasing the vulnerability of the economy of the region mainly based of agropastoral activities, we investigate the yearly cycle and see how it is impacted the hydrological cycle of Lake Chad and changed over time.
PAHs accumulation in soil-plant system in Atamanskoe lake bottom sediments in the long-term chemical contamination effect
Authors: Barbashev Andrey , Batukaev Abdulmalik , Sushkova Svetlana , Minkina Tatiana , Tarigholizadeh Sarieh , Kalinitchenko Valerii , Glinushkin Alexey , Antonenko Elena , Dudnikova Tamara , Chernikova Natalya , Fedorenko Alexey , Tihonenko Elena , Deryabkina Irina , Shportun Igor , Yakovlenko Alexand
Published: March 2021

The concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) in soils, under- and above-ground tissues of reed (Phragmites australis) on monitoring plots in the zone of industrial sewage tanks and sludge reservoirs in the city of Kamensk-Shakhtinskyi (southern Russia, Rostov Region), were determined. The total PAHs concentration in soil of monitoring site D3 (4229.4 ± 5.7µg kg-1) was significantly higher than those in monitoring sites: D4 (3873.7 ± 17.1 µg kg-1), TR1 (2217.3 ± 9.1µg kg-1), 43 (2001.1 ± 13.0µg kg-1), and also D0 (140.4 ± 1.0µg kg-1) plots. Accordingly, the maximum accumulation was found for phenanthrene among the 16 priority PAHs in the most of the soil and plants samples. It was determined the PAHs pollution effect in the studied monitoring sites on cellular and sub-cellular organelles changes of P. australis. The data received shows that increasing of PAHs contamination negatively affected on the cellular and sub-cellular organelles changes of the studied pants. Using of electron-microscopic method for plants sub-cellular structure showed ultrastructural changes in the cell membranes, and the main cytoplasmic organelles of plant cells. It was established the P. australis had a high level of adaptation to the effect of stressors by using of tissue and cell levels. In general, the detected sub-cellular alterations under the PAHs effect were possibly connected to changes in biochemical and histochemical parameters as a response for reactive oxygen species and also as a protective response against oxidative stress. The results received carry in innovative findings for cellular and sub-cellular changes in plants exposed to 16 priority PAHs as very persistent and toxic contaminants.

The research was financially supported by the Russian Science Foundation project no. 19-74-10046.
Features, Events and Processes of geological hydrogen storage: Which pose highest risk for leakage?  A three-scenario analysis: Depleted Gas Fields, Porous Aquifers and Salt Caverns.
Authors: Fuentes Tobin Gabriella Elise
Published: March 2021

The role of hydrogen as a potential renewable energy storage vector is essential for carbon emission reduction and a corresponding low-carbon renewable energy supply and demand in the future. The geological storage of hydrogen is central to a steady transition from carbon emitting fuels to renewable energy resources as an off-grid energy supply, supporting intermittencies from renewable technologies. The depletion of gas reservoirs (DGRs) creates potential for hydrogen storage, whilst porous aquifers (PAs) and salt caverns (SCs) also provide the necessary conditions for potential hydrogen storage plays. However, the containment of hydrogen is challenging, and leakage from store has adverse economic and environmental consequences. 

This project has examined and investigated risks associated with the components required for subsurface storage in three geological scenarios, and their relevant influences on the assessment of the long-term security of hydrogen in the subsurface. The construction of a database using a Features Events, Process (FEP) model comprising all concomitant aspects of hydrogen storage enabled the identification of key factors contributing to hydrogen leakage from geological stores. Information on the geological storage of hydrogen is sparse, hence the various risks associated with geological storage facilities were drawn from other subsurface operations (Nuclear Waste Storage and CO2 storage) to develop a generic FEP database. The final database contains a comprehensive overview of risks involved in a hydrogen storage operation and forms the basis of an expert elicitation.

The identified risks were then incorporated within an expert elicitation exercise to quantify and analyse risks in terms of the severity of leakage extent, the probability of their occurrence over time, and those of high impact. Discrepancies in expert opinion emphasised high uncertainty risks that may contribute to leakage across the three subsurface storage facilities. The assessment of risks across three scenarios enabled comparisons of the confidence in their security to be made. A total of 12 risks were highly ranked in impact and uncertainty across two or more geological scenarios and were put forward for enhanced prevention, operation and monitoring strategies. 
Forest fuel assessment by LiDAR data. A case study in NE Italy
Authors: Taccaliti Flavio , Venturini Lorenzo , Marchi Niccolò , Lingua Emanuele
Published: March 2021

Fuel management is a crucial action to maintain wildland fires under the threshold of manageability; hence, in order to allocate resources in the best way, wildland fuel mapping is regarded as a necessary tool by land managers. Several studies have used Aerial Laser Scanner (ALS) data to estimate forest fuels characteristics at plot level, but few have extended such estimates at a zonal level.

In the context of the EU Interreg Project CROSSIT SAFER, a test of the possibilities of ALS data to predict fuels attributes has been performed in three different areas: an alpine basin, a coastal wildland-urban interface and a karstic highland. Eighteen sampling plots have been laid out over 6 forest categories, with a special focus on Pinus nigra J. F. Arnold artificial forests. Low density (average 4 points/m2) discrete return LiDAR data has been analysed with FUSION, a free point cloud analysis software tailored to forestry purposes; field and remote sensing data have been connected with simple statistical modelling and results have been spatialised over the case study areas to provide wall-to-wall inputs for FLAMMAP fire behaviour simulation software.

Resulting maps can be of relevance for land managers to better highlight the most vulnerable or fire prone areas at a mesoscale administrative level. Limitations and room for improvement are pointed out, in the view that land management should keep updated with the latest technology available.
The role of air-sea coupling on the simulation of intraseasonal rainfall variability over the South Pacific in ECHAM5-SIT
Authors: Pariyar Sunil Kumar , Keenlyside Noel , Tseng Wan-Ling
Published: March 2021

We investigate the impact of air-sea coupling on the simulation of the intraseasonal variability of rainfall over the South Pacific using the ECHAM5 atmospheric general circulation model coupled with Snow-Ice-Thermocline (SIT) ocean model. We compare the fully coupled simulation with two uncoupled simulations forced with sea surface temperature (SST) climatology and daily SST from the coupled model. The intraseasonal rainfall variability over the South Pacific Convergence Zone (SPCZ) is reduced by 17% in the uncoupled model forced with SST climatology and increased by 8% in the uncoupled simulation forced with daily SST. The coupled model best simulates the key characteristics of the two intraseasonal rainfall modes of variability in the South Pacific, as identified by an Empirical Orthogonal Function (EOF) analysis. The spatial structure of the two EOF modes in all three simulations is very similar, suggesting these modes are independent of air-sea coupling and primarily generated by the dynamics of the atmosphere. The southeastward propagation of rainfall anomalies associated with two leading rainfall modes in the South Pacific depends upon the eastward propagating Madden-Julian Oscillation (MJO) signals over the Indian Ocean and western Pacific. Air-sea interaction seems crucial for such propagation as both eastward and southeastward propagations substantially reduced in the uncoupled model forced with SST climatology. Prescribing daily SST from the coupled model improves the simulation of both eastward and southeastward propagations in the uncoupled model forced with daily SST, showing the role of SST variability on the propagation of the intraseasonal variability, but the periodicity differs from the coupled model. The change in the periodicity is attributed to a weaker SST-rainfall relationship that shifts from SST leading rainfall to a nearly in-phase relationship in the uncoupled model forced with daily SST.
Extending the TSIS-1 Hybrid Solar Reference Spectrum (HSRS) to Span 0.202 to 200 um
Authors: Coddington Odele , Richard Erik , Harber Dave , Pilewskie Peter , Woods Tom , Chance Kelly , Liu Xiong , Sun Kang
Published: March 2021

Recently, we incorporated our new understanding of the absolute scale of the solar spectrum as measured by the Spectral Irradiance Monitor (SIM) on the Total and Spectral Solar Irradiance Sensor (TSIS-1) mission and the Compact SIM (CSIM) flight demonstration into a solar irradiance reference spectrum representing solar minimum conditions between solar cycles 24 and 25. This new reference spectrum, called the TSIS-1 Hybrid Solar Reference Spectrum (HSRS), is developed by re-normalizing independent, very high spectral resolution datasets to the TSIS-1 SIM absolute irradiance scale. The high-resolution data are from the Airforce Geophysical Laboratory (AFGL), the Quality Assurance of Ultraviolet Measurements In Europe (QASUME) campaign, the Kitt Peak National Observatory (KPNO) and the Jet Propulsion Laboratory’s (JPL) Solar Pseudo-Transmittance Spectrum (SPTS). The TSIS-1 HSRS spans 0.202 µm to 2.73 µm and has a spectral resolution of 0.01 nm or better. Uncertainties are 0.3% between 0.4 and 2.365 mm and 1.3% at wavelengths outside that range

Recently, we have extended the long wavelength limit of the TSIS-1 HSRS from 2.73 µm to 200 µm with JPL SPTS solar line data through ~ 16 µm and theoretical understanding as represented in a computed solar irradiance spectrum by R. Kurucz. The extension expands the utility of this new solar irradiance reference spectrum to include Earth energy budget studies because it encompasses an integrated energy in excess of 99.99% of the total solar irradiance.

In this work, we discuss the TSIS-1 HSRS, the extension and uncertainties, and demonstrate consistency with TSIS-1 SIM and CSIM solar spectral irradiance observations and TSIS-1 Total Irradiance Monitor (TIM) total solar irradiance observations. Additionally, we compare the TSIS-1 HSRS against independent measured and modeled solar reference spectra.
ITU/WMO/UNEP Focus Group on AI for Natural Disaster Management: Introduction and call for participation
Authors: Kuglitsch Monique
Published: March 2021

The International Telecommunication Union (ITU), World Meteorological Organization (WMO), and United Nations Environment Programme (UNEP) have recently partnered to establish the Focus Group on Artificial Intelligence for Natural Disaster Management (FG-AI4NDM). FG-AI4NDM is exploring the potential of AI-based algorithms to support data collection and handling, to improve modeling (i.e., reconstructions, forecasts, and projections) across spatiotemporal scales through extracting complex patterns (and gaining insights) from a growing volume of geospatial data, and to provide effective communication. To achieve these objectives, FG-AI4NDM is building an interdisciplinary, multi-stakeholder, and international community to explore specific natural disaster use cases. Special effort is made to support participation from low- and mid-income countries and those countries shown to be particularly impacted by these types of events. Here, we will explore: what is an ITU focus group, what are the objectives and planned deliverables of FG-AI4NDM, what progress has been made since its inception, and how members of the geoscience community can become involved.
Mediterranean climate change projections: an update from CMIP5 and CMIP6.
Authors: Cos Josep , Doblas-Reyes Francisco J , Jury Martin
Published: March 2021

The Mediterranean has been identified as a climate change hot-spot due to increased warming trends and precipitation decline. Recently, CMIP6 was found to show a higher climate sensitivity than its predecessor CMIP5, potentially further exacerbating related impacts on the Mediterranean region.

To estimate the impacts of the ongoing climate change on the region, we compare projections of various CMIP5 and CMIP6 experiments and scenarios. In particular, we focus on summer and winter changes in temperature and precipitation for the 21st century under RCP2.6/SSP1-2.6, RCP4.5/SSP2-4.5 and RCP8.5/SSP5-8.5 as well as the high resolution HighResMIP experiments. Additionally, to give robust estimates of projected changes we apply a novel model weighting scheme, accounting for historical performance and inter-independence of the multi-member multi-model ensembles, using ERA5, JRA55 and WFDE5 as observational reference. 

Our results indicate a significant and robust warming over the Mediterranean during the 21st century irrespective of the used ensemble and experiments. Nevertheless, the often attested amplified Mediterranean warming is only found for summer. The projected changes vary between the CMIP5 and CMIP6, with the latter projecting a stronger warming. For the high emission scenarios and without weighting, CMIP5 indicates a warming between 4 and 7.7ºC in summer and 2.7 and 5ºC in winter, while CMIP6 projects temperature increases between 5.6 and 9.2ºC in summer and 3.2 to 6.8ºC in winter until 2081-2100 in respect to 1985-2005. In contrast to temperature, precipitation changes show a higher level of uncertainty and spatial heterogeneity. However, for the high emission scenario, a robust decline in precipitation is projected for large parts of the Mediterranean during summer. First results applying the model weighting scheme indicate reductions in CMIP6 and increases in CMIP5 warming trends, thereby reducing differences between the two ensembles.