bluuebunny/crossref_metadata_2025 huggingface dataset:
Feasibility of Ion-cyclotron Resonant Heating in the Solar Wind
Authors: Navarro Roberto E. , Muñoz Victor , Valdivia Juan A. , Moya Pablo S.
Published: March 2021

Wave-particle interactions are believed to be one of the most important kinetic processes regulating the heating and acceleration of Solar Wind plasma. One possible explanation to the observed preferential heating of alpha (He+2) ions relies on a process similar to a second order Fermi acceleration mechanism. In this model, heavy ions are able to resonate with multiple counter-propagating ion-cyclotron waves, while protons can encounter only single resonances, resulting in the subsequent preferential energization of minor ions. In this work, we address and test this idea by calculating the number of plasma particles that are resonating with ion-cyclotron waves propagating parallel and anti-parallel to an ambient magnetic field in a proton/alpha plasma with cold electrons. Resonances are calculated through the proper kinetic multi-species dispersion relation of Alfven waves. We show that 100% of the alpha population can resonate with counter-propagating waves below a threshold ΔUαp/vA<U0+a(β+β0)b in the differential streaming between protons and alpha particles, where U0=-0.532, a=1.211, β0=0.0275, and b=0.348 for isotropic ions. This threshold seems to match with constraints of the observed ΔUαp in the Solar Wind for low values of the proton plasma beta. Finally, it is also shown that this process is limited by the growth of plasma kinetic instabilities, a constraint that could explain alpha-to-proton temperature ratio observations in the Solar Wind at 1 AU.
Developing emulators of regional climate responses to regional aerosol perturbations using three coupled chemistry-climate models
Authors: Westervelt Daniel , Fiore Arlene , Shindell Drew , Lamarque Jean-François
Published: March 2021

The climatic implications of regional aerosol and precursor emissions reductions implemented to protect human health are poorly understood. However, quantitative estimates of climate responses to emission perturbations are needed by the climate assessment and impacts community. To address this need, we investigate the global and regional mean climate response to regional changes in aerosol emissions using three coupled chemistry-climate models: NOAA GFDL-CM3, NCAR-CESM1, and NASA GISS-E2. Our approach contrasts a long present-day control simulation from each model (up to 400 years with perpetual year 2000 or 2005 emissions) with fourteen individual aerosol emissions perturbation simulations (160-240 years each). We perturb emissions of sulfur dioxide (SO2) and/or carbonaceous aerosol within six world regions and assess the statistical significance of temperature and precipitation responses relative to internal variability determined by the control simulation and across the models. Using the three models and their statistical significance as an indicator of robustness of climate responses to aerosols, we develop emulators of the climate response to changes in aerosol emissions. Emulators are defined as the change in a climatic variable (e.g. temperature) in a region i normalized by the change in emissions and/or radiative forcing for species S in region j, i.e. dTi/dEj,S, where T is temperature and E is emissions. In all models, the emulators for global mean surface temperature response (perturbation minus control) to aerosol is positive (warming). Results also indicate that the Arctic is the most sensitive region to nonlocal aerosol emissions or forcing, as the emulators are largest for the Arctic. Emulator calculations indicate a robust regional response to aerosol emissions or forcing within the northern hemisphere mid-latitudes, regardless of where the aerosol forcing is located longitudinally. We assess the utility of our emulators by applying them to an ensemble of historical and future CESM simulations in which anthropogenic aerosol emissions are removed to isolate the climate response to aerosols. We find good agreement between the ensemble mean temperature response to aerosols as simulated by CESM and the reconstructed temperature response from the emissions-based emulators and the emissions input to CESM.  This work is a first step towards providing statistical relationships between the changes in regional aerosol emissions and the statistically significant changes in climate that can be attributed to them. Such relationships would allow for the generation of regional climate change scenarios without having to simulate computationally demanding chemistry-climate models.
Effect of stress history on sediment transport and channel adjustment in graded gravel-bed rivers
Authors: An Chenge , Hassan Marwan A. , Ferrer-Boix Carles , Fu Xudong
Published: March 2021

Recently, there has been an increasing attention on the environmental flow management for the maintenance of habitat diversity and ecosystem health of mountain gravel-bed rivers. More specifically, much interest has been paid to how inter-flood low flow can affect gravel-bed river morphodynamics during subsequent flood events. Such an effect is often termed as “stress history” effect. Previous research has found that antecedent conditioning flow can lead to an increase in the critical shear stress and a reduction in sediment transport rate during a subsequent flood. But how long this effect can last during the flood event has not been fully discussed. In this study, a series of flume experiments with various durations of conditioning flow are presented to study this problem. Results show that channel morphology adjusts significantly within the first 15 minutes of the conditioning flow, but becomes rather stable during the remainder of the conditioning flow. The implementation of conditioning flow can indeed lead to a reduction of sediment transport rate during the subsequent hydrograph, but such effect is limited only within a relatively short time at the beginning of the hydrograph. This indicates that bed reorganization during the conditioning phase, which induce the stress history effect, is likely to be erased with increasing intensity of flow and sediment transport during the subsequent flood event.
Lake microbial communities are not resistant or resilient to repeated large-scale natural pulse disturbances 
Authors: Brasell Katie , Howarth Jamie , Pearman John , Fitzsimons Sean , Pochon Xavier , Zaiko Anastasija , Simon Kevin , Vandergoes Marcus , Wood Susanna
Published: March 2021

Opportunities to study and understand community level responses to extreme natural pulse disturbances in unaltered ecosystems are rare. Lake sediment records that span thousands of years can contain well resolved sediment pulses, triggered by earthquakes. These paleo-records provide a means to study repeated pulse disturbance and the processes of resistance (insensitivity to disturbance) and ecological resilience (capacity to regain structure, function and process). In this study, DNA preserved in lake sediment layers was extracted from a sediment core from a lake in a near-natural catchment.  Metabarcoding and inferred functions were used to assess the lake microbial community over the past 1,100 years – a period that included four major earthquakes. Microbial community composition and function differed significantly between highly perturbed (postseismic, c. 50 yrs) phases directly after the earthquakes and more stable (interseismic, c. 260 yr) phases, indicating a lack of community resistance to natural pulse disturbances. A decoupling between community structure and function in successive postseismic phases suggest potential functional redundancy in the community. Significant differences in composition and function in successive interseismic phases demonstrates the communities are not resilient to large scale natural pulse disturbances. The clear difference in structure and function, and high number of indicator taxa in the fourth interseismic phase likely represents a regime shift, possibly due to the two-fold increase in sediment and terrestrial biospheric organic carbon fluxes recorded following the fourth earthquake. Large pulse disturbances that enhance sediment inputs into lake systems may produce an underappreciated mechanism that destabilises lake ecosystem processes. 
Anthropogenic causes of landslides and their implications for monitoring
Authors: Ramanathan Kaushik , Vasudevan Nirmala
Published: March 2021

Are we justified in referring to all landslides as natural hazards? With the effects of climate change, landslide incidences are increasing all over the world, and many of them accompany floods and occur due to extreme weather events. It has been unequivocally established that humans are responsible for global climate change. Further, landslides also occur in deforested areas. Even if one were to discount the effects of deforestation on climate change and the subsequent occurrence of landslides, one cannot ignore the fact that deforestation leads to slope instabilities in multiple ways. It decreases the effective retaining strength of the slope materials and also exposes more slope material to weathering and consequent leaching. Thus, deforestation and climate change, caused directly or indirectly by human beings, have a significant bearing on landslide occurrence. Furthermore, several catastrophic landslides in recent times have occurred due to indiscriminate human activity, such as constructing dams and other structures on fragile slopes, blasting slopes for road construction without providing adequate toe support, excessive mining, constructing faulty retaining structures on unstable slope material, etc. Over the years, such human activity has resulted in landslides of all types and at various scales. Whether a landslide is natural, caused due to anthropogenic factors, or a combination of the two, the investigation approach and monitored parameters remain the same; we still need to identify the various causative factors and quantify their rates of change over time in the run up to the landslide event. However, we need a paradigm shift in our perspective and treatment of landslides. We need to accept that human activity is, or can be, responsible for landslide occurrence. With this change in perspective, we would monitor slopes with an increased awareness that human actions could negatively impact slope stability. This, in turn, would entail monitoring at every stage to ensure that no human activity adversely impacts the natural balance, thus paving the way for truly sustainable development. We would be doing great disservice to the investigation and monitoring of landslides by such preconceived notions as all landslides are natural hazards. It is high time that we accept our part in compounding the problem of landslide occurrences and come up with solutions to monitor the impact of human activity on the environment to prevent landslides.
Improvement of the early detection and quantitative risk prediction method with the three-dimensional wind field from multiple-doppler radar analysis
Authors: Kim Hwa-yeon , Nakakita Eiichi
Published: March 2021

 The localized severe heavy rainfalls, which has not been experienced in the past, have frequently occurred in Japan due to the effects of climate change. Especially, the Guerrilla heavy rainfall (abbreviated as GHR) by isolated rapidly growing single cumulonimbus is triggering flash floods in a small river basin and has caused huge damage to human life and property. If we alert the hazardous rainfall in 5 to 10 min earlier for evacuation, we could minimize human injuries such as isolation, death, and disappearance. For hydrometeorological disaster prevention, a system of the early detection and quantitative risk prediction methods is necessary to detect the initial stage of a cumulonimbus cloud before it is generated into heavy rainfall. In previous research, by analyzing the volume scan with some heavy rainfall events, an important sign named as the first echo (Baby-rain cell) was verified. Also, the vertical vortex tubes with positive and negative pairs did exist in the GHR. Most of the severely developed storm had a certain criterion of vertical vorticity. By using those analyses, we developed the early detection and quantitative risk prediction method as follows. We collect the radar variables (i.e. the vorticity, doppler velocity, and reflectivity, etc.) at each event and set the risk level when the maximum rainfall reached the ground. Then, we select an appropriate set of explaining variables considering the risk level. With the Receiver Operating Characteristic (ROC) analysis, we could find the most appropriate method to predict the risk level. However, we would like to improve the early detection and quantitative risk prediction method by estimating vertical vorticity, divergence and convergence with real wind field data. So, we apply the multiple-doppler radar analysis to estimate the variables reflecting real phenomena. As a result, the improved early detection and quantitative risk prediction method could predict the risk of GHR development accurately by using only the observed radar data. It is expected that the quantitative risk prediction could represent realistic flood prediction system and increase the leading time enough to reduce disaster.
Seismicity Detection in Skopje Region Using Tomographic Methods and 3-D Modelling
Authors: Sinadinovski Cvetan , Pekevski Lazo , Cernih Dragana , Drogreska Katerina , Najdovska Jasmina
Published: March 2021

A novel geotomography technique has been applied at the epicentral area around capitol of Macedonia - Skopje, using selected earthquakes that occurred over a period of 57 years and were recorded on temporary and permanent seismograph stations. This study will test the tomography method for the first time in investigation of the crustal shape and structures in our tectonic environment using specially designed datasets covering 1964-1967 and 2016-2020 periods.

In the initial phase, the analysis will show the potential of the geotomography application in revealing detailed velocity perturbation in the lithosphere. Then, the events are relocated in the 3-D models and new cross-sections of the crust produced by a simultaneous approach. The images can help in constraining the velocity vs depth relationship and thus can contribute towards redefinition of the earthquake zones. The results are discussed in terms of general stress and seismic regime and their temporal changes.

Better understanding of the seismicity and tectonics processes in the Skopje region will lead to an overall improvement of the earthquake hazard assessment at local and national level, as well as further integration in research programs with other geophysical methods.

 
Diagnosis of Pre-Depression Large-Scale Vortex Instability in the Tropical Atmosphere
Authors: Levina Galina
Published: March 2021

An approach is proposed [1] for determining the precise time of the start of tropical cyclogenesis, which includes a combined analysis of data from cloud-resolving numerical modeling and GOES Imagery. The approach is based on the similarity of patterns in the fields of vertical helicity (numerical simulation) and temperature (satellite data), allowing for the localization of intense rotating convective clouds known as the Vortical Hot Towers. As a theoretical ground, we applied a hypothesized (to date) interpretation of tropical cyclogenesis as a large-scale instability caused by the mechanism of the turbulent vortex dynamo in the atmosphere [1,2], and with bearing in mind the crucial role of Vortical Hot Towers in providing the dynamo-effect [2]. In this context, birth of a hurricane is considered as an extreme threshold event in the helical atmospheric turbulence of a vorticity-rich environment of a pre-depression cyclonic recirculation zone. Helical turbulence is characterized by the broken mirror symmetry and permits an existence of inverse energy cascade in three-dimensional cases. In order to trace and analyze processes of self-organization in the tropical atmosphere, that span scales from convective clouds with horizontal dimensions of 1-5 km to mesoscale vortices of hundreds of kilometers, we used the post-processing [1-3] of data from cloud-resolving numerical simulations [4].  Implementation of the proposed approach revealed that large-scale vortex instability can begin a few hours, or even dozens of hours, before the formation of the Tropical Depression. This work was supported by the research project “Monitoring” No. 01200200164.

References

[1] Levina, G. V., 2020. Birth of a hurricane: early detection of large-scale vortex instability. J. Phys.: Conf. Ser., 1640  012023,  doi:10.1088/1742-6596/1640/1/012023

[2] Levina, G. V., 2018. On the path from the turbulent vortex dynamo theory to diagnosis of tropical cyclogenesis. Open J. Fluid Dyn., 8, 86–114,  https://doi.org/10.4236/ojfd.2018.81008

[3] Levina, G. V. and M. T. Montgomery, 2015. When will Cyclogenesis Commence Given a Favorable Tropical Environment?  Procedia IUTAM, 17, 59–68, https://doi.org/10.1016/j.piutam.2015.06.010

[4] Montgomery, M. T., M. E.  Nicholls, T. A. Cram, and A. B. Saunders, 2006: A vortical hot tower route to tropical cyclogenesis. J. Atmos. Sci., 63, 355–386,  https://doi.org/10.1175/JAS3604.1
Numerical simulation of dam-break mudflow based on the Herschel-Bulkley model
Authors: Tang jinbo , Cui Peng , Chen Jiangang
Published: March 2021

Mudflow behaves normally the flowing properties of viscoplastic or pseudo-plastic stemming from flocculent network structures formed by fine particles within the mud. In order to obtain the dynamical characteristics of the dam-break of mudflow, a numerical model has been developed in the present study. The numerical model solved the Navier-Stokes equation with the Herschel-Bulkley model, which exhibits a plastic properties of fluid with shear-thinning. The two-step projection method are employed to solve the velocity field in present numerical model, and the Bi-CGSTAB technique are implemented to solve the pressure Poisson equation. The volume of fluid (VOF) method is used to track the broken the free surface. In this study, the numerical simulation of dam-break with Herschel-Bulkley fluid are implemented, the numerical results agree well with the other numerical results. Furthermore, when the shear-thinning index is equals to unity, the Herschel-Bulkley model becomes Bingham model. In this study, laboratory experiments of dam-break of slurry in the flume have been conducted to record data with time of the surface height of mudflow and pressure in the bottom of flume. The same cases with laboratory experiments are implemented in our numerical model, the numerical results match with the laboratory experiments. Finally, as a demonstration, the impact of mudflow on the structures   are simulated and discussed.
Integration of flower structures in strike-slip fault damage zones classification – examples from the West-Congo belt and foreland
Authors: Nkodia Hardy Medry Dieu-Veill , Miyouna Timothée , Boudzoumou Florent , Delvaux Damien
Published: March 2021

Damage zones around strike-slip faults constitutes important site of earthquake initiation, propagation, rupture or barrier. They also constitute important sites that host and conduct fluids. Most investigations of these strike-slip damage zones focus on plan view geometries and little attention is paid to subsurface or profile geometries associated. Depending on the presence of a shortening or extensional component during deformation, strike-slip faults do not often show straight path in cross-section. Understanding the expression of damage zones in cross-section is therefore important in predicting subsurface strike-slip faults features. The Paleozoic red feldspathic sandstones of the Inkisi Group in the foreland of the West-Congo Belt show beautiful examples of strike-slip faults with damage zones in both the Republic of Congo and the Democratic Republic of Congo (Nkodia et al., 2020). These strike-slip faults are organized in two major faults system developed in a pure strike-slip regime. The oldest system is dominated by NNW–SSE trending sinistral strike-slip faults and minor E–W striking dextral strike-slip faults. The youngest system consists of dominant NE–SW trending dextral strike-slip faults and minor NW–SE trending sinistral strike-slip faults. Field investigation show four arrangement of flowers structures along the strike-slip faults: (i) those associated with wall damage zones; (ii) those associated with linking damage zones; (iii) those associated with tip damage zones; and (iv) “hourglass” flower structures. Further investigation of strike-slip faults in the Schisto-calaire Group of the West-Congo Belt show also similar flower structures arrangement in limestones. In the Inkisi Group, these arrangements are dependent on the fault growth and propagation. Both strike-slip faults system in the Inkisi Group show an evolving pattern, from closely spaced short faults segments, to highly spaced long faults segments with few interactions of pattern. 

Nkodia, H.M.D.V., Miyouna, T., Delvaux, D., Boudzoumou, F., 2020. Flower structures in sandstones of the Paleozoic Inkisi Group (Brazzaville, Republic of Congo): evidence for two major strike-slip fault systems and geodynamic implications. South African Journal of Geology 123(4), 531-550. Doi: 10.25131/sajg.123.0038.
Debris-induced stagnation and ensuing morphological evolution of a central Himalayan glacier
Authors: Garg Purushottam Kumar , Shukla Aparna , Rai Santosh Kumar , Yadav Jairam Singh
Published: March 2021

This study presents field evidences (October 2018) and remote sensing measurements (2000-2020) to show stagnant conditions of lower ablation zone (LAZ) of the ‘companion glacier’, central Himalaya, India and its implication on the morphological evolution. The Companion glacier is named so as it accompanied the Chorabari glacier (widely studied benchmark glacier in the central Himalaya) in the distant past. Supraglacial debris thickness, supraglacial ponds anf other morphological features (e.g. lateral moraine height, supraglacial mounds) were measured/observed in the field. Glacier area, length, debris extent, surface elevation change and surface ice velocity were estimated using satellite remote sensing data from Landsat-TM/ETM+/OLI, Sentinel-MSI, Terra-ASTER and SRTM, Cartosat-1 and Google Earth images. Results show that the glacier has very small accumulation area and it is mainly fed by avalanches. The headwall of glacier is very steep which causes frequent avalanches leading to voluminous debris addition to the glacier system. Consequently, about 80% area of the glacier is debris-covered. The debris is very thick in the LAZ exceeding several meters in the LAZ and comprised of big boulders making debris thickness measurements practically impossible particularly in the snout region. However, debris thickness decreases with increasing distance from the snout and is in the order of 20-40 cm at about 2.5 km upglacier. The huge debris cover has protected the glacier ice from rapid melting. That’s why surface lowering of the glacier is less as compared to nearby Chorabari glacier. Moreover, due to (a) less mass supply from upper reaches and (b) huge debris cover, the glacier movement is very slow. The movement is too low that is allowed vegetation (some big grasses with wooded stems) to grow and survive on the glacier surface. The slow moving LAZ also causing bulging on the upper ablation zone (UAZ). Consequently, several mounds have developed on the UAZ. Thin debris slides down from mounds exposing the ice underneath for melting. Owing to these processes, spot melting is now a dominant mechanism of glacier wastage in the companion glacier. Thus, it can be summarized that careful field observations along with remote sensing estimates can be very important for understanding the glacier evolution.
Carbon sequestration in mixed deciduous forests: The importance of mid-storey trees for forest productivity
Authors: Holtmann Anne , Huth Andreas , Pohl Felix , Rebmann Corinna , Fischer Rico
Published: March 2021

Forests play an important role in climate regulation due to carbon sequestration. However, a deeper understanding of forest carbon flux dynamics are often missing due to a lack of information about forest structure and species composition, especially for non-even-aged and mixed forests. In this study, we combined field inventory data of a mixed deciduous forest in Germany with an individual-based forest gap model to investigate daily carbon fluxes and to examine the role of tree size and species composition for the overall stand productivity. Simulation results show that the forest model is capable to reproduce daily eddy covariance measurements (R2 of 0.73 for gross primary productivity and of 0.65 for ecosystem respiration). The simulation results showed that the forest act as a carbon sink with a net uptake of 3.2 tC ha-1 yr-1  (net ecosystem productivity) and an overall gross primary productivity of 18.2  tC ha-1 yr-1. At the study site, medium sized trees (30-60cm) account for the largest share (66%) of the total productivity. Small (0-30cm) and large trees (>60cm) contribute less with 8.5% and 25.5% respectively. Simulation experiments showed, that species composition showed less effect on forest productivity. Stand productivity therefore is highly depended on vertical stand structure and light climate. Hence, it is important to incorporate small scale information’s about forest stand structure into modelling studies to decrease uncertainties of carbon dynamic predictions. Experiments with such a modelling approach might help to investigate large scale mitigation strategies for climate change that takes local forest stand characteristics into account.
Determination of Absorption Lengths using PWP Model in the Bay of Bengal
Authors: Gupta Hitesh , Sil Sourav
Published: March 2021

In this study, we model the upper layers of the Bay of Bengal, which is rather a unique water body in terms of its dynamics which is controlled by the advection of large fresh water from the adjoining rivers as well monsoonal precipitation thus changing the turbulent mixing in the upper layers. The fresh water influx from rivers and precipitation, leads to low saline water overlying hypersaline water, creates a strong stratification due to which turbulent mixing is inhibited. The resulting halocline inhibits the wind driven mixing of the upper layers thus changing or affecting the optical characteristics of the water body. With the exception of shortwave insolation, the air – sea heat exchange occurs at the sea surface and is vertically redistributed by mixing and advection. The present study focuses on generating these optical or absorption lengths (e-folding depths) at different locations in the Bay of Bengal as a function of time itself, showing absorption length changes with both the space and the time, using the PWP – 1D model for which data is obtained from RAMA Buoys located along 900E in the Bay of Bengal. The shortwave and longwave absorption length is directly related to heating up of the upper layers of the ocean and thus change its state and dynamics. Heating of the upper oceanic layers are also related to increase in SST as well as the Ocean Heat content of the ocean leading to changes in various systems like monsoon, cyclones, fluxes, etc. These absorption lengths are related to the Mixed layer heat budget directly but it may also be related to the salt budget of the Bay too. The model results highlight that the absorption length affects the SST as well as the temperature of the upper layers and also that the absorption length changes from one season to another season done using the data of - RAMA Buoy located at 900E and 150N (northern Bay of Bengal) and 900E and 120N as well as data from INCOIS tropflux. The study encourages to use the generated results for the Mixed layer heat budget analysis, or for the modelling purpose, etc.

 

Keywords - Bay of Bengal, Mixing in the upper layers, Absorption lengths, extinction lengths, Penetration depths, E-folding depth, RAMA buoy, Solar insolation, Water type and quality, Sea surface temperature, PWP – 1D model, Seasonality.
An Overview of Secondary ice Processes.
Authors: Choularton Tom , Lloyd Gary , Bower Keith , Gallagher Martin
Published: March 2021

Ground based and airborne observations of ice crystal concentrations are often found to exceed the concentration of ice nucleating particles by many orders of magnitude. This discrepancy between the expected ice particle concentrations formed through primary ice nucleation and observed ice particle concentration has led to the search for missing physical processes capable of creating new ice crystals. Secondary ice production (SIP) is a mechanism that produces new ice crystals without requiring the action of an ice nucleating particle. Evidence has now been found for several of these

Increasingly sophisticated cloud microphysical representations are being used in Numerical Weather Prediction and climate models to provide more realistic simulations of clouds. This drive towards greater complexity is motivated by the recognition of the importance of microphysical processes to the evolution of clouds, precipitation and the atmospheric environment.  

One important challenge for the successful implementation of cloud microphysics is the prediction of ice crystal concentrations, these influence the water budget of the cloud s through precipitation processes and the radiative properties of clouds especially when the ice crystals are in the majority over water droplets. The understanding and quantification of primary ice nucleation has grown in recent years, secondary ice production processes have received relatively little attention but are potentially very important for controlling the ice concentrations found in some types of clouds. 

In this stalk a number of SIP mechanisms will be discussed: The Hallett-Mossop process, by far the most powerful mechanism when conditions are right; the fracture on freezing of supercooled raindrops, the fragmentation of falling snow flakes; the detachment of frost crystals from a surface.
On the phase detrending to disentangle refraction and diffraction on GNSS signals: a case study over Antarctica
Authors: Spogli Luca , Ghobadi Hossein , Cicone Antonio , Alfonsi Lucilla , Cesaroni Claudio , Linty Nicola , Romano Vincenzo , Cafaro Massimo
Published: March 2021

We investigate the reliability of the phase scintillation index determined by receiving Global Navigation Satellite System (GNSS) signals at ground in the high-latitudes. To the scope, we report about the capabilities of recently introduced detrending scheme based on the signal decomposition provided by the Fast Iterative Filtering (FIF) technique. This detrending scheme enables a fine tuning of the cutoff frequency for phase detrending used in the phase scintillation index definition, aimed at disentangling diffraction and refraction effects. On a single case study based on GPS and Galileo data taken by a GNSS Ionospheric Scintillation Monitor Receiver (ISMR) in Concordia Station (Antarctica), we show how the FIF-based detrending allows deriving adaptive cutoff frequencies, whose value changes minute-by-minute. They are found to range between 0.4 Hz and 1.2 Hz. This allows better accounting for diffractive effects in phase scintillation index calculation and also showing the limitations on the use of such index, being still widely used in the community, both to characterize the features of ionospheric irregularities and to adopt mitigation solutions.
Hydrogeological controls on stream discharge dynamics in bedrock catchments: exploring the combined effects of seepage development and heterogeneity
Authors: Cornette Nicolas , Roques Clément , Boisson Alexandre , Launay Josette , Pajot Guillaume , de Dreuzy Jean-Raynald
Published: March 2021

Surface/subsurface interactions and geological heterogeneity have important effects on the dynamics of streamflows. Surface/subsurface interactions speed up transfers through the development of seepage zones, which reduce the response time of the aquifer and increase the proportion of rapid infiltration excess overland flow. On top of it, geological heterogeneity modulates spatially the extent of the seepage zones as well as the intensity of drainage of the underlying aquifer.

We investigated the combined effect of the surface/subsurface interactions and geological heterogeneity in a crystalline basement region under temperate climate (Brittany, France), where the limited aquifer capacities, the hydraulic conductivity enhanced by weathering and fracturing and the significant recharge rate promote surface/subsurface interactions. We analysed 40-year of discharge data monitored on two catchments (Arguenon 104 km2 and Aber Plabennec 27.4 km2) using 1D hillslope models (hs1D). The hs1D hillslope model resolves the vertically integrated Boussinesq subsurface flows with a spatially and temporally varying saturation-limited boundary condition on equivalent 1D hillslope structures. We specifically analysed the effect of accounting for heterogeneity on improving the discharge predictions, accounting for the presence of 2 equivalent hillslope with different hydraulic properties. This heterogeneity was defined based of the presence of two main geological lithologies in the catchments. Calibration was performed by a systematic parameter space exploration.

The calibrated models display significant differences between the two catchments. In the Aber Plabennec catchment, the homogeneous and heterogeneous hillslope models had very close performances showing an effective geological homogenization of the hydraulic conductivity and porosity. In the Arguenon catchment, the heterogeneous model outperformed the homogeneous model with a 46% increase of the Nash-log criterion showing persistant and significant differences in hydraulic conductivities and porosity. Successful calibration in both cases demonstrated by Nash-log values larger than 0.75-0.8 showed the overall relevance of the hillslope approach and its capacity to check for the presence of hydraulic heterogeneity at the catchment scale. Differences between catchments hints on the potential identification of hydrogeological properties at the regional scale by the combined use of the geological map and stream discharges.
Low density-microplastics detected in sheep faeces and soil: A case study from the intensive vegetable farming in Southeast Spain
Authors: Beriot Nicolas , Peek Joost , Zornoza Raul , Geissen Violette , Huerta Lwanga Esperanza
Published: March 2021

One of the main sources of plastic pollution in agricultural fields is the plastic mulch used by farmers to improve crop production. The plastic mulch is often not removed completely from the fields after harvest. Over time, the plastic mulch that is left of the fields is broken down into smaller particles which are dispersed by the wind or runoff. In the Region of Murcia in Spain, plastic mulch is heavily used for intensive vegetable farming. After harvest, sheep are released into the fields to graze on the vegetable residues. The objective of the study was to assess the plastic contamination in agricultural soil in Spain and the ingestion of plastic by sheep. Therefore, three research questions were established: i) What is the plastic content in agricultural soils where plastic mulch is commonly used? ii) Do livestock ingest the microplastics found in the soil? iii) How much plastic could be transported by the livestock? To answer these questions, we sampled top soils (0–10 cm) from 6 vegetable fields and collected sheep faeces from 5 different herds. The microplastic content was measured using density separation and visual identification. We found ~2 × 103 particles∙kg−1 in the soil and ~103 particles∙kg−1 in the faeces. The data show that plastic particles were present in the soil and that livestock ingested them. After ingesting plastic from one field, the sheep can become a source of microplastic contamination as they graze on other farms or grasslands. The potential transport of microplastics due to a herd of 1000 sheep was estimated to be ~106 particles∙ha−1∙y−1. Further studies should focus on: assessing how much of the plastic found in faeces comes directly from plastic mulching, estimating the plastic degradation in the guts of sheep and understanding the potential effects of these plastic residues on the health of livestock.
Comparison of PV potential models for africa and their potential cost implications.
Authors: Wasike Arnold , Cader Catherina
Published: March 2021

We currently have more than 7500 planned mini grids, most of them in Africa. These will soon connect more than 27 million people and cost about 12 billion dollars [1]. Africa is in a good position for Photo voltaic (PV) mini grid optimization, receiving more than 1800 KWh/m2 Global Horizontal Irradiation (GHI) every year [2], for most parts of the continent. However, the lack of a coordinated renewable energy monitoring and distribution network works against optimization of PV potential models [3]. This study shows the accuracy of existing photo voltaic potential estimators like renewables ninja [3], the National Renewable Energy Laboratory (NREL), International Renewable Energy Agency (IRENA), and the global solar atlas [2], by comparing the modeled values with long term measurements from ground solar stations. This is done for more than 20 stations distributed over Africa. Our results show best correlations [4] of up to 65.3% from version 2 of the Surface Radiation Data Set from Heliosat (SARAH) derived from the Photovoltaic Geographical Information System (PVGIS). However, we also have correlations as low as 16.2% for models commonly used in off grid simulations. The sensitivities of the modeled cost of a mini grid to the variation in PV potential were tested [5][6] using the statistical range in sourced PV potential from the different estimators, giving us cost variation of more than 2.8% that may arise from the different sources.

References

1. World Bank, ESMAP - Mini grids for half a billion people

2. https://globalsolaratlas.info/map

3. doi: 10.1016/j.energy.2016.08.060

4. Wikipedia contributors. (2021, January 7). Pearson correlation coefficient. In Wikipedia, The Free Encyclopedia. Retrieved 09:00, January 20, 2021, from https://en.wikipedia.org/w/index.php?title=Pearson_correlation_coefficient&oldid=998963119

5. Cader. 2018

5. Hoffmann. 2019

7. https://doi.org/10.2136/vzj2018.03.0062
Predicting Convective Storm Characteristics using Machine Learning from Hi-Resolution NWP Forecasts
Authors: Jardines Aniel
Published: March 2021

Convective weather represents a significant disruption to air traffic flow management (ATFM) operations. Thunderstorms are the cause for a substantial amount of delay in both the en-route and airport environment. Before the day of operations, poor prediction capability of convective weather prohibits traffic managers from considering weather mitigation strategies during the pre-tactical phase of ATFM planning. As a result, convective weather is mitigated tactically, possibly leading to excessive delays.  

The skill of weather forecasting has greatly improved in recent years. Hi-resolution weather models can predict the future state of the atmosphere for some weather parameters. However, incorporating the output from these sophisticated weather products into an ATFM solution that provides easily interpreted information by the air traffic managers remains a challenge. 

This paper combines data from high-resolution numerical weather predictions with actual storm observations from lightning detecting and satellite images. It applies supervised machine learning techniques such as binary classification, multiclass classification, and regression to train neural networks to predict the occurrence, severity, and altitude of thunderstorms. The model predictions are given up to 36hr in advance, within timeframes necessary for pre-tactical planning of ATFM, providing traffic managers with valuable information for developing weather mitigation plans. 
The role of knowledge networks in facilitating the creation of climate information services
Authors: Larosa Francesca , Bruno-Soares Marta
Published: March 2021

Knowledge networks are collections of individuals who work together across organizational, spatial and disciplinary boundaries to develop and share a body of knowledge. Climate services are tools and applications that help support decision-making by transforming climate data into information tailored to specific users. They call for co-development practices to facilitate successful collaboration between different stakeholders. Knowledge networks for climate services are intermediaries that can facilitate the interaction between upstream (providers) and downstream (users) actors operating at various scales (local, national, regional and supranational). Such knowledge networks can therefore assist decision-making processes of a wide set of users by creating networking opportunities and disseminating usable climate information. The aim of this work is to frame and assess the efficiency of knowledge networks for climate services in promoting innovation and facilitate its diffusion. We used semi-structured interviews with knowledge networks managers to collect information about their purpose, process and audience.  We then assess the efficiency of knowledge networks by performing content analysis of interviews with knowledge network managers and by checking for the existence of inconsistencies or gaps with the initial objectives. We find that knowledge networks for climate services pursue four objectives: coordination, innovation promotion, science-policy interface and support to members. We also find that knowledge networks are well-recognised players in disseminating knowledge and opportunities to climate services practitioners and policy makers. However, we observe a lack of adequate tools to monitor the activities of different members. On the communication side, knowledge networks for climate services mostly interact with developers of climate services but face challenges in sharing members’ activities with users. Our work fills a significant knowledge gap and helps providing new tools of performance assessment in absence of a clearly defined methodology. The identification of bottlenecks and under-performing mechanisms in the climate information services sphere allows the elaboration of strategies to improve the status quo and facilitates the diffusion of innovations such as climate services.
Climate Change, Humanitarian Risks, and Social-Political (In)stability Along the Gulf of Aden: Expert Elicitation for the Case of Somalia and Yemen
Authors: Lambert Laurent , Almehdhar Mahmood , Haji Mustafa
Published: March 2021

Abstract: Changes in the global oceanic system have already negatively affected the world’s marine life and the livelihoods of many coastal communities across the world, including in the Middle East' and Eastern Africa's Least Developed Countries (LDCs). Coastal communities in Somalia and Yemen for instance, have been particularly affected by extreme environmental events (EEEs), with an increase in the frequency of tropical cyclones over the past 20 years. Using expert elicitation as a method to generate data to assess and quantify a specific issue in the absence of sufficient and/or reliable data, the authors interviewed selected specialists in or from Somalia and Yemen, from diverse fields of expertise related to climate change, extreme environmental events, disaster risk reduction, and humanitarian affairs. Ten experts followed the elicitation protocol and answered a specific series of questions in order to better quantify the expectable mid-to-long-term climatic and humanitarian levels of risks, impacts, and consequences that climate change and related issues (e.g., sea-level rise, tropical cyclones, and sea surge) may generate in coastal areas along the Gulf of Aden's coastal cities of Aden and Bossaso, in Yemen and Somalia, respectively.

The findings indicate that there is cause for significant concern as climate change is assessed by all interviewees - irrespective of their background -, as very likely to hold a negative to a devastating impact on (fresh) water security, food security, public health, social conflicts, population displacement, and eventually political stability; and to strongly worsen the humanitarian situations in Somalia and Yemen, both in the medium-term (i.e., 2020-2050) and the long-term (i.e., 2020-2100). The authors call on the scientific community to further research the issue of climate change in the understudied coastal areas of the Gulf of Aden, and on the international community to pro-actively and urgently help the local populations and relevant authorities to rapidly and strongly build up their adaptation capacities, especially in the niche of coastal EEEs.
Assessing the effect of the Vaia storm on sediment source areas and connectivity storm in the Liera catchment (Dolomites)
Authors: Boretto Gabriella , Crema Stefano , Marchi Lorenzo , Monegato Giovanni , Arziliero Luciano , Cavalli Marco
Published: March 2021

Extreme meteorological events are important causes of environmental damages, particularly in mountain areas that can be heavily affected by destructive processes such as landslides and debris flows. From 27 and 30 October 2018, an extraordinary storm - named Vaia - hit Northeastern Italy. The Vaia storm triggered mass wasting processes, generated new slope instabilities, caused widespread windthrows, and damaged human infrastructure. This work aims at assessing the effect of the Vaia storm in the Liera Torrent basin (Venetian Dolomites, Italy), by building and comparing sediment source inventories before and after the Vaia storm. The Liera basin drains an area of 35 km2 and elevation ranges between 976 and 3192 m a.s.l. The mapping and classification of the sediment sources have been carried out through the interpretation of high-resolution orthophotos and Digital Terrain Models (DTMs) derived from airborne LiDAR data (1-m resolution) acquired in 2015 and 2019. A topography-based index of sediment connectivity has been applied to characterize connectivity spatial patterns at catchment scale and identifying the sediment sources on the hillslopes effectively connected to the Liera torrent. A preliminary connectivity analysis showed that the upstream sector the catchment located in the Pale di San Martino plateau is not effectively connected to the lower Liera valley because of its karstic environment and debris originated from the highest portion of the relief are confined in a hollow. Thus the inventories have been limited to the medium and lower parts of the catchment considering an area of 20 km2. Results indicated a total of 1650 sediment source areas after the Vaia event, with an areal increase of about 20% with respect to 2015 inventory, especially due to the development of landslide (843 in total for the 2019 inventory), expansion of the debris flow channel (257) and areas subject to surficial erosion (127). Other areas that have been identified encompass debris flow deposit (288), rock fall deposit (31), stream bank erosion (45), and other sediment source areas which need field survey to be properly classified (59). The analysis allowed: (1) obtaining reliable and detailed pre- and post- event sediment sources inventories, (2) assessing sediment connectivity at the catchment scale, which is fundamental for estimating the contribution of sediment sources and related transfer paths, (3) improving sediment dynamics understanding related to the Vaia storm in the study area. Future analysis will focus on field validation and residual sediment availability for the investigated areas. This study was carried out in the frame of the Interreg V-A Italy - Austria SedInOut project.