bluuebunny/crossref_metadata_2025 huggingface dataset:
Planetary waves spectrum in stratosphere-mesosphere during SSW 2018
Authors: Milinevsky Gennadi , Wang Yuke , Klekociuk Andrew , Evtushevsky Oleksandr , Han Wei , Grytsai Asen , Antyufeyev Oleksandr , Shi Yu , Ivaniha Oksana , Shulga Valerii
Published: March 2021

The planetary wave activity in the stratosphere–mesosphere during the Arctic major Stratospheric Sudden Warming (SSW) in February 2018 is discussed on the basis of the microwave radiometer (MWR) measurements of carbon monoxide (CO) above Kharkiv, Ukraine (50.0°N, 36.3°E) and the Aura Microwave Limb Sounder (MLS) measurements of CO and temperature. From the MLS temperature zonal analysis, eastward and westward migrations of wave 1/wave 2 spectral components were differentiated, to which less attention was paid in previous studies. Abrupt changes in zonal wave spectra occur with the zonal wind reversal on 10 February 2018. Eastward wave 1 and wave 2, observed before the SSW onset, disappear during the SSW event, when westward wave 1 becomes dominant. This is consistent with previous studies showing that westward wave 1 in the mesosphere is present after the onset of major SSW events with an elevated stratopause. Analysis of the wavelet power spectra of mesospheric CO variations show statistically significant periods in a band of 20–40 days using both MWR and MLS data. Approximately 10-day periods appear only after the SSW onset. Since the propagation of upward planetary waves is limited in the easterly zonal flow after the zonal wind reversal, forced planetary waves may exist after the onset of SSW due to the instability of the zonal flow in the mid-latitude mesosphere.

This work was partly supported by the projects 19BF051-08, 20BF051-02 Taras Shevchenko National University of Kyiv and by the International Center of Future Science, Jilin University (JLU), under the contract with the JLU. This work also contributed to the State Institution National Antarctic Scientific Center of the Ministry of Education and Science of Ukraine research objectives and to Project 4293 of the Australian Antarctic Program. 
Catalog of TGEs observed at Aragats during 2008-2020
Authors: Aslanyan Davit , Chilingarian Ashot , Karapetyan Tigran , Hovsepyan Gagik
Published: March 2021

For 12 years we monitored particle fluxes on Mt. Aragats 7/24 and discovered the most
powerful natural electron accelerator operated in the thunderclouds. This natural electron
accelerator provided more than 450 Thunderstorm Ground enhancement events (TGEs). We
make exhausting analysis of these events and will present yearly and monthly distributions,
as well the day hour distributions. Also, we will present the distribution of the outside
temperature and precipitation occurrences which are correlated with particle fluxes. We
address questions about TGE evolution and atmospheric conditions supporting the
origination of the relativistic runaway electron avalanches and demonstrate the relativistic
runaway electron avalanche is possible on Aragats only in Spring-Autumn seasons.
Numerical Simulations to Explore Deviations from the Beer-Lambert-Bouguer Law in a Correlated Random Medium
Authors: Blouin Christopher K. , Larsen Michael
Published: March 2021

The Beer-Lambert-Bouguer Law of exponential attenuation is ubiquitous in the study of atmospheric radiative transfer. However, previous work has shown that adherence to the classical Beer-Lambert-Bouguer law requires the scatterers in the medium to be spatially uncorrelated. As particulates in the atmosphere are often statistically correlated/clustered, it is useful to identify the magnitude of the deviation from the classical expectation under different degrees of spatial clustering.

Measuring this deviation is difficult in an experimental setting both because it is challenging to measure the spatial clustering and the deviations from the classical expectation are expected to be modest. Thus, we approach this question through a simplified “ballistic-photon” computational simulation.

Here, we use a simplified numerical model to track the extinction of a collimated light source through correlated random media. The geometry is taken to mimic a sub-volume of the Michigan Technological University Pi Chamber, and the scatterers (cloud droplets) are explicitly resolved using a variety of increasingly realistic techniques for a frozen-field representation of the particle positions.

We report on the anticipated deviations from the classical Beer-Lambert-Bouguer law through examination of the resulting intensity of the illumination leaving through different walls of the simulation domain.
Tracking the split: a non-linear iterative approach to the monitoring of recent SAA evolution
Authors: Parmentier Alexandra , Cicone Antonio , Piersanti Mirko , Tozzi Roberta , Martucci Matteo , Sotgiu Alessandro , De Michelis Paola
Published: March 2021

Still today vaguely defined, the South Atlantic Anomaly (SAA) is the vast
geographic region where the Earth’s magnetic field is weakest relative to an
ideal Earth-centered dipole field, and the inner radiation belt comes closest
to the planet. Nonetheless it represents a major concern to the space science
community, since the local reduced magnetic intensity often results in satellite
outages and radiation hazard to humans, especially in geomagnetically disturbed
periods.
Since 1958, relentless investigation of the various morphological and dynamic
features of the SAA has been taking place, robustly relying on field, plasma and
particle measurements from Low-Earth-Orbit (LEO) satellites since the late
1970s.
New readings provided by magnetometers operating at LEO altitudes show that,
within the past decade, an apparent second center of minimum field intensity
has begun to be clearly resolved southwest of Africa, suggesting a possible rapid
splitting of the SAA into two cells. In addition to magnetic determinations, the
tracking of fluxes of sub-MeV electrons that are lost to the atmosphere when
drifting into the SAA due to its increased bounce loss cone, offers a specular
view of the same phenomenon. This multi-messenger approach from different
platforms is best suited to catch fine details of the splitting.
Directly stemming from the data-adaptive Empirical Mode Decomposition (EMD)
developed at NASA in the 1990s for the analysis of non-stationary signals, the
Fast Iterative Filtering (FIF) class of signal mode decompositions is recently
taking center stage due to enhanced rigorous formalization in terms of con-
vergence and stability. Multidimensional and Multivariate FIF (MMFIF) is a
brand-new extension that handles multidimensional and multichannel datasets.
The application of MMFIF techniques to magnetic-field and particle data from
an ensemble of LEO satellites has allowed us to best characterize the dynamic
evolution of the SAA lobes in the 2010s, and compare it to analogous data in
the literature from the previous decades.
Subsurface mechanisms control hydrologic response to a multi-year drought in a mountainous watershed with a Mediterranean climate
Authors: Schreiner-McGraw Adam , Ajami Hoori
Published: March 2021

Mountain watersheds often act as water towers that supply water to large human populations in valley aquifers. Therefore, their susceptibility and resilience to droughts are of outsize importance particularly, as global climate change projections suggest more frequent droughts in the future. Previous studies have examined the impact of climate warming on mountain hydrology, but they have not explicitly linked impacts of multi-year droughts to subsurface water storage. In this study, we use the 2012-2015 California drought to examine the mechanisms via which subsurface flow paths and storage affect the hydrologic response to drought in the Kaweah River watershed in the Sierra Nevada mountains. We build and test an integrated hydrologic model using the coupled land surface-groundwater model ParFlow.CLM. The model is able to simulate the observed hydrology with a high degree of accuracy. Results reveal that mountain aquifer recharge sourced from snowmelt (MARsnow) is the primary input to the groundwater system, and much of the simulated streamflow. We find that increases in air temperature and decreases in precipitation during the drought reduces snow water equivalent (SWE), and causes a 73% reduction in MARsnow compared to the pre-drought period. Reduction in MARsnow initially results in subsurface storage losses along the ridgelines and areas of low topographic convergence. Topography induced draining of the regolith storage causes groundwater depletion and provides supplemental water to maintain streamflow and riparian evapotranspiration (ET). As the drought develops, drying of the subsurface alters lateral connectivity of the shallow groundwater system, and reduces streamflow and riparian ET. We apply machine learning models to examine the spatial patterns in groundwater storage depletion and recovery. These models reveal that topography induced draining and filling of subsurface storage in response to drought and precipitation recovery, respectively, is the key control on the streamflow response in this mountainous watershed. Warmer conditions and more frequent droughts that reduce SWE in the future are likely to amplify this cycle.
Performance evaluation of ECMWF ERA5 Reanalysis waves in the Mediterranean Sea
Authors: Görmüş Tahsin , Ayat Berna , Aydoğan Burak
Published: March 2021

This study evaluates the performance significant wave height hindcast from ECMWF’s latest atmospheric dataset ERA5 in the Mediterranean Sea. Towards this aim, in-situ products from Copernicus Marine Environment Monitoring Service are used. There are nearly 160 observation points along the Mediterranean Sea which are acquired by different institutions with fixed buoys, moorings, and fixed points. The time intervals dating back to 1980s to nowadays, with most of them belongs to the 2000s. To evaluate the verification of ERA5 wave climate with the actual observations, standard statistical metrics such as correlation coefficients (r) are used to compare two datasets in the selected points. The analysis of two time series is done for overlapping time intervals and also for values above a certain threshold, with the purpose of measuring ERA5’s predictive performance of storm conditions. Preliminary results showed that the observations and numerical results of ERA5 are relatively well-matched. The average correlation coefficient is r=0.8 for the selected points which are spatially disperse in the basin. In the Aegean Sea, the coefficient is calculated as r=0.83 between the observations and ERA5, from a moored surface buoy near the Mykonos island with the time coverage of between 2001 and 2019. Some other examples can be given from the Adriatic Sea (r=0.90, 2013-2014), Tyrrhenian Sea (r= 0.96, 2013-2015), Northwestern part of the basin (r=0.71, 2007-2019), and Balearic Sea (r=0.81, 2004-2019).
Energy landscapes resulting from climate protection goals – a GIS-based approach to carbon neutrality
Authors: Bosch Stephan , Kienmoser Dominik
Published: March 2021

To date, the spatio-temporal patterns of renewable energies brought about by a deployment that corresponds to internationally agreed climate protection goals, have been neither exactly analysed nor visualised. It is also unknown what land uses would be incorporated into these new energy landscapes due to a lack of spatial restrictions, and what social conflicts these land use changes may give rise to. Moreover, the extent to which existing land use, which is the product of a capitalist order, affects the achievement of a carbon-neutral society, has not been grasped at all. There is no knowledge about the feasibility of altering spatial restrictions for renewable energies in order to identify alternative spatial patterns of sustainable energy transition. Our objective is therefore to model and visualise a regional energy landscape whose greenhouse gas balance in the electricity sector corresponds to the target of the UN Climate Conference. The study provides a detailed analysis of the landscape transformations in rural spaces that would be caused if those forces which strive to link the energy transition to the values of the Paris Agreement were to win through. It is revealed that a precise alignment of the expansion of renewable energies with international climate protection targets would strongly mechanise rural areas and significantly transform their land use patterns.
An initial assessment of bed destabilization risk past vegetation patches using instrumented particles
Authors: Xu Yi , Manousos Valyrakis , Michalis Panagiotis
Published: March 2021

Instream vegetation may alter the mean and turbukent flow fields leading to destabilizing riverbed surface, under certain flow conditions. In particular, recent research on instream vegetation hydrodynamics and ecohydrogeomorphology has focused on how energetic flow structures and bulk flow parameters downstream a vegetation may result in riverbed destabilization. This study, demonstrated the application of a 20mm novel instrumented particle in recording entrainment rates downstream simulated vegetation patches of distinct densities, at various distances downstream these. A patch of 6mm acrilic cylinders is used to simulate the emergent vegetation having the same diameter (12cm) and different porosities or densities (void volume equal to 1.25%, 3.15%, 6.25%, 11.25%, and 17.25%). The flow velocity near the instrumented particle is recorded using acoustic Doppler velocimetry (ADV) with appropriate seeding, under clear water conditions. Preliminary results are presented with focus on the effect of vegetation patch density on the flow field and subsequent effects on particle entrainment rates and implications for bed surface destabilisation.
Dust storm frequency in relation to extreme droughts in arid regions of Iran
Authors: modarres reza , Mohit Esfahani Poria
Published: March 2021

Dust storms are frequent phenomenon in arid and semi arid regions of Iran which cover near 60 percent of the entire country in the center of Iran. Due to geographic and climatic conditions of prolonged dry conditions as well as poor land use management, dust storms occur in almost all seasons across the region. Drought is a major fator affecting the likelihood of dust storm occurrence across arid regions of Iran. We develop copula functions to investigate the effect of drought on dust storm frequency.The standardized precipitation Index (SPI) was caluclated and drought condition was defined based on SPI< -0.5. Dought severity and duration for each drought event were ca;culated and the number of dust days in each drought event ws also identified. The Archimedean copula families shoed that the probability of dust occurrence has a significant relationship to extreme drought conditions. The joint probability is then used to derive the joint return period of dust storms in relation to drought condition.
How much do modeled tropical cyclone impacts depend on the hazard set choice?
Authors: Meiler Simona , Emanuel Kerry , Bresch David N.
Published: March 2021

Tropical cyclones (TC) cause devastating damage to infrastructure and are a concerning threat to human life. Records of historical TCs are very limited and therefore the data to study impacts of this natural hazard remain sparse. The generation of synthetic storm tracks is an important tool to overcome this spatial and temporal limitation.

We perform the first global model intercomparisons of different synthetic TC track sets. We use the CLIMADA (CLIMate ADAptation, Aznar-Siguan and Bresch, 2019) platform, which integrates hazard, exposure, and vulnerability data, to compute TC risk and to quantify socio-economic impacts for different storm track sets. Our comparison shows how the selection of a TC track set might affect the estimated damage and which dataset is suitable to answer what type of research question. Specifically, we provide a qualitative overview of the different TC model types, we compare damage by return period and perform a global sensitivity analysis for selected TC damage model parameters.

We contrast the following sources of tropical cyclone tracks: i) observed storms from IBTrACS (Knapp et al., 2010), ii) probabilistic events obtained from historical ones by a direct random-walk process (Kleppek et al., 2008), synthetic tracks from coupled statistical-dynamical models iii) from Emanuel et al. (2006, 2008), and iv) CHAZ (Lee et al., 2018), and v) synthetic tracks from a fully statistical model, STORM (Bloemendaal et al., 2020). We find that the choice of event set becomes more important when studying tail events, basins with smaller historical event sets or small areas. In these cases we discover modelled losses to vary by more than an order of magnitude. This variance can partly be explained by the varying distribution of hazard intensities at landfall between event sets.
Towards the estimation of Space Weather-related corrosion on pipelines
Authors: Trichtchenko Larisa
Published: March 2021

Geomagnetically induced currents (GIC), increased during space weather events, are able to interfere with pipeline corrosion protections systems and potentially can increase corrosion of the pipeline steel.

Methods, widely used for the evaluation of annual corrosion rates, are based on exposure of steel to constant currents and voltages (DC), or alternating currents and voltages of a constant frequency (50 Hz or 60 Hz), while GIC are characterised by a continuous frequency spectrum, with the range of frequencies from 10-5 Hz to 1 Hz.

This paper introduces the methods for use in the estimation of corrosion rates on pipeline steel produced by GIC (commonly referred to as “telluric currents” in the pipeline industry) and provides results calculated for specific time periods with use of available recordings made on pipelines at the times of geomagnetic storms. As well, annual cumulative corrosion rates are estimated based on the modelling of pipeline currents and voltages.

In addition to the detailed presentation of the methods utilised, a comparison of corrosion rates produced by telluric variations on non-protected and protected pipelines located in mid- and high-latitudes is presented.
Frequency Dependent Mantle Viscoelasticity via the Complex Viscosity: cases from Antarctica and Western North America
Authors: Lau Harriet , Austermann Jacqueline , Holtzman Benjamin , Book Cameron , Havlin Christopher , Hopper Emily , Lloyd Andrew
Published: March 2021

Studies of glacial isostatic adjustment (GIA) often use paleoshorelines and present-day deformation to constrain the viscosity of the mantle and the thickness of the lithosphere. However, different studies focused on similar locations have resulted in different estimates of these physical properties even when considering the same model of viscoelastic deformation. We argue that these different estimates infer apparent viscosities and apparent lithospheric thicknesses, dependent on the timescale of deformation. We use recently derived relationships between these frequency dependent apparent quantities and the underlying thermodynamic conditions to produce predictions of mantle viscosity and lithospheric thickness across a broad spectrum of geophysical timescales for three locations (Western North America, Amundsen Sea, and the Antarctic Peninsula). Our predictions require the self-consistent consideration of elastic, viscous, and transient deformation and also include non-linear steady state deformation, which have been determined by several laboratories. We demonstrate that these frequency dependent predictions of apparent lithospheric thickness and viscosity display a significant range and that they align to first order with estimates from GIA studies on different timescales. Looking forward, we suggest that observationally based studies could move towards a framework of determining the frequency trend in apparent quantities – rather than single, frequency independent values of viscosity – to gain deeper insight into the rheological behavior of Earth materials.
Spatial heterogeneity of subsoil organic carbon turnover times in forest ecosystems across China
Authors: Yu Peng , Tang Xiaolu , Shi Yuehong , Cai Chunju , Han Yuxuan , Li Zhou , Deng Luo , Song Ci , Li Jingji
Published: March 2021

Soil organic carbon turnover time (τ, year) is an important indicator of soil carbon stability and sequestration capacity. However, our understanding of the spatial heterogeneity of subsoil τ still was poorly qualified over a large scale, even though subsoil organic carbon below 0.2 m accounts for the majority of total soil organic carbon. We compiled a dataset that consisted of 630 observations in subsoil (0.2 - 1 m) from published literatures to investigate the spatial heterogeneity of subsoil τ (defined as the ratio of soil carbon stock and net primary production) and explore its main environmental drivers using structural equation modelling (SEM) in forest ecosystems across China. Results indicated that mean (± standard deviation) subsoil τ was 72.4 ± 68.6 years with a large variability ranging from 2.3 to 896.2 years. Subsoil τ varied significantly with forest types that mean subsoil τ was the longest in deciduous broadleaf forest (82.9 ± 68.7 years), followed by evergreen needleleaf forest (77.6 ± 60.8 years), deciduous needleleaf forest (75.3 ± 78.6 years) and needleleaf and broadleaf mixed forest (71.3 ± 80.9 years), while the shortest τ in evergreen broadleaf forest (59.9 ± 40.7 years). SEM suggested that soil environment was the most important factor in predicting subsoil τ. However, the dominant driver differed with forest types, i.e. soil environment for evergreen broadleaf forest and climate for evergreen needleleaf forest. This study highlights the different dominant controlling factors in subsoil τ and improve our understanding of biogeographic variations of subsoil τ. These findings are essential to better understand (and reduce uncertainty) in biogeochemical models of subsoil carbon dynamics at regional scales.
Wave drag in oscillatory mean flows
Authors: Shakespeare Callum , Arbic Brian , Hogg Andrew
Published: March 2021

In both the atmosphere and ocean, large-scale (mean) flows over topography generate internal waves. A longstanding question in both fields is what forces – often known as ‘wave drag’ – are exerted on the mean flow in this process, as such forces must be parameterized in non-wave-resolving numerical models. For a time-invariant mean flow, it is well known that lee waves are generated which extract momentum from the solid earth and deposit it where they break and dissipate at height. Here, I address the equivalent problem for a time-periodic mean flow (e.g. the ocean tide) using theory and numerical simulations. In this situation, the waves influence the amplitude and phase of the periodic mean flow near the topography regardless of where they dissipate. Dissipation plays a role in terms of controlling the magnitude of wave reflections from an upper boundary (e.g. the ocean surface) which modifies the forces acting near the topography. Our results form a framework for parameterizing tidal internal wave drag in global ocean models.
Effect of soil heterogeneity on the optimal design of in-situ groundwater bioremediation systems
Authors: Pathania Tinesh , Eldho T Iype , Bottacin-Busolin Andrea
Published: March 2021

The use of optimization approaches for designing in-situ groundwater bioremediation systems has been demonstrated in a number of previous studies under the assumption of homogenous soil. However, in real applications the soil is typically heterogeneous and knowledge of the spatial conductivity distribution is, to some degree, uncertain. Here, a systematic attempt is made to quantify the effect of soil heterogeneity on the optimal design of in-situ bioremediation systems. To determine the optimal placement of injection and extraction wells within the computational domain, the meshless element-free Galerkin method (EFGM) was coupled with particle swarm optimization (PSO), resulting in a simulation-optimization (S/O) model which is referred to as BIOEFGM-PSO. A hypothetical case study is considered where the design of an in-situ bioremediation system is optimized considering different degrees of heterogeneity of the porous medium. Heterogeneous conductivity fields are generated using a pseudo-random field generator with same mean and varying variance and correlation lengths. The BIOEFGM-PSO model was then applied to the different soil scenarios, and the resulting bioremediation costs were compared. Results show that the optimal placement of injection and extraction wells depends on the soil properties and, on average, heterogeneous soils have higher in-situ bioremediation costs compared with a homogeneous soil with the same mean conductivity. This highlights the importance of considering soil heterogeneity in designing cost-effective in-situ bioremediation systems, and further demonstrates the general applicability of the BIOEFGM-PSO model.
Greenhouse gas and aerosol contributions to the observed global and regional changes in extreme temperature changes
Authors: Seong Min-Gyu , Min Seung-Ki , Kim Yeon-Hee , Zhang Xuebin , Sun Ying
Published: March 2021

This study carried out an updated detection and attribution analysis of extreme temperature changes for 1951-2015. Four extreme temperature indices (warm extremes: annual maximum daily maximum/minimum temperatures; cold extremes: annual minimum daily maximum/minimum temperatures) were used considering global, continental (6 domains), and subcontinental (33 domains) scales. HadEX3 observations were compared with CMIP6 multi-model simulations using an optimal fingerprinting technique. Response patterns of extreme indices (fingerprints) to anthropogenic (ANT), greenhouse gas (GHG), anthropogenic aerosol (AA), and natural (NAT) forcings were estimated from corresponding CMIP6 forced simulations. Pre-industrial control simulations (CTL) were also used to estimate the internal variability. Results from two-signal detection analysis where the observations are simultaneously regressed onto ANT and NAT fingerprints reveal that ANT signals are robustly detected in separation from NAT in global and most continental regions for all extreme indices. At subcontinental scale, ANT detection occurs especially in warm extremes (more than 60% of regions). Results from three-signal detection analysis where observations are simultaneously regressed onto GHG, AA, and NAT fingerprints show that GHG signals are detected and separated from other external forcings over global, most continental, and several subcontinental (more than 60%) domains in warm extremes. In addition, AA influences are jointly detected in warm extremes over global, Europe and Asia. The detected GHG forcings are found to explain most of the observed warming while AA forcings contribute to the observed cooling for the early decades over globe, Europe, and Asia with a slight warming over Europe during recent decades. Overall, improved detection occurs compared to previous studies, especially in cold extremes, which is due to the use of extended period which increases signal-to-noise ratios.
Investigating the sedimentary DNA of palaeotsunami deposits in Thailand.
Authors: Yap Wenshu , Switzer Adam , Gouramanis Chris , Marzinelli Ezequiel , Wijaya Winona , Dominey-Howes Dale , Labbate Maurizio , Jankaew Kruawun , Lauro Federico
Published: March 2021

Investigating palaeotsunami deposits is a primary way to extend the tsunami database beyond relatively short instrumental and historical records. Such information is essential to reconstruct the frequency and magnitude of past coastal flooding events, which are a key to assess the impact and risk of tsunami to the coastal community. However, palaeotsunami studies are limited as most of the proxies, such as microfossil and geochemical signals, can be modified or degraded with time. Here, we present the application of DNA analysis to investigate a series of palaeotsunami deposits up to ~2800-years-old from a coastal beach ridge sequence on Phra Thong Island (Thailand). Our result shows that it is possible to accurately discriminate palaeotsunami deposits from intercalating organic mud layers using the microbial communities recovered from DNA preserved in the sediment of the geological record. Our work demonstrates that environmental DNA represents a new and promising tool for investigating historical and pre-historical tsunami records.
Behaviors of Wet Plume Controlled by Olivine-Wadsleyite Phase Transition and Water Distribution
Authors: Kim Hyunseong , Lee Youngjun , Kim Doyoung , Lee Changyeol
Published: March 2021

Quaternary Intraplate volcanoes are sparsely distributed in Northeast Asia including Northeast China and Korean Peninsula and roles of the stagnant Pacific plate in the volcanoes have been studied. Recent geochemical studies suggest that the hydrated mantle in the mantle transition zone was incorporated in the wet plumes that were generated from the hydrated layer atop the stagnant slab, and the ascending wet plumes experienced partial melting in the shallow asthenosphere. To quantitatively evaluate the incorporation of the mantle in the transition zone into the wet plumes and their partial melting in the asthenosphere, we conducted a series of two-dimensional thermochemical numerical models by including the olivine-wadsleyite phase transition at the 410km discontinuity. The buoyancy is controlled by temperature, bound-water content and mineral phase. Viscosity reduction by the bound-water is added to the temperature-dependent viscosity. Particle tracers are used to track the incorporation of the mantle in the transition zone into the wet plumes. We vary the Clapeyron slope of the phase transition and water distributions in the mantle transition zone and hydrated layer of the stagnant slab to evaluate their effects on the behavior of the wet plumes. Results show that multiple wet plumes generated from atop the stagnant slab incorporate the hydrated mantle in the transition zone. Due to the endothermic phase transition at the 410 km discontinuity, the ascending wet plumes are retarded and laterally migrated beneath the 410 km discontinuity for several million years, and enter the overlying asthenosphere as merged large wet plumes. The ascending merged wet plumes laterally spread beneath the thermal lithosphere and experience partial melting, consistent with the interpretation based on the geochemical studies. The spacing of the merged wet plumes (~440 km) caused by the phase transition at the 410 km discontinuity is consistent with the sparse volcano distribution in Northeast China and Korean Peninsula.
Improved parameterization of albedo in WRF + Noah in snow events simulation in the Tibetan Plateau
Authors: Liu Lian , Menenti Massimo , Ma Yaoming , Ma Weiqiang
Published: March 2021

Snowfall and the subsequent evolution of the snowpack have a large effect on surface energy balance and water cycle, among which albedo is a major driver. However, the current widely used Noah land surface model does not describe snow albedo correctly, although it keeps snow-related variables i.e. snow cover and age into account. In our study, the impact of an improved albedo parameterization scheme in WRF coupled with Noah was investigated. In the improved albedo scheme, albedo was parameterized as functions of snow depth and age which was developed using remote sensing retrievals of albedo.

Numerical experiments were conducted to model a severe snow event in March 2017. The performance of WRF coupled with Noah applying the improved albedo scheme was compared with that of applying the default albedo scheme and with that of WRF coupled with CLM applying CLM’s complex albedo scheme. First, the improved albedo scheme largely reduces the WRF coupled with Noah default albedo overestimation in the southeastern Tibetan Plateau, remarkably reducing the large cold bias estimates by 0.7 ℃ air temperature RMSE. Second, the improved albedo scheme gives the highest correlationship between the satellite-derived and the model estimated albedo, contributing to achieve the SWE spatial pattern, heavy snow belt and maximum SWE estimates in eastern Tibetan Plateau. Third, the fine resolution simulation, such as 5 km (1 km), significantly reduces the eastern SWE overestimation by 29% (49%).

In order to investigate the applicability of the improved albedo scheme in snow events simulation in the Tibetan Plateau, 16 numerical experiments were conducted to simulate 8 snow events by using WRF coupling with Noah default and improved albedo schemes. The assessment demonstrates that the improved albedo scheme significantly reduces the air temperature underestimation, and reduces the air temperature RMSE by 0.5 - 1 ℃ for both 5 km and 1 km resolution simulations. It is expected that the improved albedo parameterization scheme will have a good prospect in high resolution simulation of snow events in the Tibetan Plateau.
Trends in total heat content in a very long climate change simulation
Authors: Stendel Martin
Published: March 2021

The equivalent potential temperature Θe is a useful measure of the total heat content in the atmosphere, as it is conserved during both dry adiabatic and wet adiabatic processes. It is defined as letting an air parcel expand pseudo-adiabatically until all the water vapour has condensed, release and precipitate all its latent heat and compress it dry-adiabatically to the standard pressure of 1000 hPa.

Changes in surface or air temperature can thus be related to changes in humidity. For example, the relative contributions of temperature and humidity changes in tropical cyclones can be addressed, Arctic amplification due to the fact that saturation mixing ratio follows an exponential curve with temperature can be investigated, and by considering Θe in different vertical levels, an assessment of changes in convective stability can be made.

We have conducted a very long climate simulation with a global model interactively coupled to a Greenland ice sheet component. An extended RCP8.5 scenario is applied, where emissions of greenhouse gases continue to increase and then eventually level out around 2250. The model is then run for another 1000 years. With such an extreme forcing, all Arctic sea ice has completely disappeared, and a large part of the Greenland Ice Sheet has melted at the end of the simulation.

We examine changes in the total heat content based on observations and model data for past and present as well as for future climate. Daily data, allowing the identification of individual weather systems will be discussed for time slices with a seasonally and later a totally ice-free Arctic.
Preprocessing of magnetograms for magnetohydrostatic extrapolations
Authors: Zhu Xiaoshuai , Wiegelmann Thomas , Inhester Bernd
Published: March 2021

Magnetohydrostatic (MHS) extrapolations are developed to model 3D magnetic fields and plasma structures in the solar low atmosphere by using measured vector magnetic fields on the photosphere. However, the photospheric magnetogram may be inconsistent with the MHS assumption. By applying Gauss‘ theorem to an isolated active region, we obtain a set of surface integrals of the magnetogram as criteria for a MHS system. The integrals are a subset of Aly’s criteria for a force-free field (FFF). Based on the new criteria, we preprocess the magnetogram to make it more consistent with the MHS assumption and, at the same time, close to the original data. As a byproduct, we also find the boundary integral that is used to compute the energy of a FFF usually underestimates the magnetic energy of an active region.
Diel Vertical migration of marine organisms and the biological carbon pump
Authors: Pinti Jerome , DeVries Tim , Norin Tommy , Serra-Pompei Camila , Proud Roland , Siegel David A. , Kiørboe Thomas , Petrik Colleen M. , Andersen Ken H. , Brierley Andrew S. , Visser André W.
Published: March 2021

Diel Vertical Migration (DVM) is a key feature of pelagic and mesopelagic ecosystems, mainly driven by predator-prey interactions along a time-varying vertical gradient of light. Marine organisms including meso-zooplankton and fish typically hide from visual predators at depth during daytime and migrate up at dusk to feed in productive near-surface waters during nighttime. Specific migration patterns, however, vary tremendously, for instance in terms of residency depth during day and night. In addition to environmental parameters such as light intensity and oxygen concentration, the migration pattern of each organism is intrinsically linked to the patterns of its conspecifics, its prey, and its predators through feedbacks that are hard to understand—but important to consider.

DVM not only affects trophic interactions, but also the biogeochemistry of the world’s oceans.  Organisms preying at the surface and actively migrating vertically transport carbon to depth, contributing to the biological carbon pump, and directly connecting surface production with mesopelagic and demersal ecosystems.

Here, we present a method based on a game-theoretic trait-based mechanistic model that enables the optimal DVM patterns for all organisms in a food-web to be computed simultaneously. The results are used to investigate the contributions of the different food-web pathways to the active component of the biological carbon pump. We apply the method to a modern pelagic food-web (comprised of meso- and macro-zooplankton, forage fish, mesopelagic fish, large pelagic fish and gelatinous organisms), shedding light on the direct effects that different trophic levels can have on the DVM behaviours of each other. The model is run on a global scale to assess the carbon export mediated by different functional groups, through fecal pellet production, carcasses sinking and respiration.

Finally, the model output is coupled to an ocean inverse circulation model to assess the carbon sequestration potential of the different export pathways. Results indicate that the carbon sequestration mediated by fish is much more important than presently recognised in global assessments of the biological carbon pump. The work we present relates to contemporary ecosystems, but we also explain how it can be adapted to fit any pelagic food-web structure to assess the contribution of the active biological pump to the global carbon cycle in past ecosystems.
Monitoring of veterinary pharmaceuticals in the Bienne river (Jura Mountain, France)
Authors: Dhivert Elie , Devillers Bertrand , Al Badany Maha , Mondamert Leslie , Labanowski Jérôme
Published: March 2021

The Bienne river (Jura Mountain, France) drains a basin of medium altitude mountains characterized by extensive cattle breeding (mostly dairy cows). A monitoring of the contamination by veterinary pharmaceuticals was performed using passive sampling devices - POCIS (Polar Organic Chemical Integrative Samplers), between September 2019 and January 2020. Four hydrological conditions were analysed: a sever low-flow periods, two flood events and a winter situation close to the mean interannual flow. Each time, POCIS were exposed over 2 weeks at 2 stations located in the upper and downstream reaches of the river. 19 pharmaceuticals were selected from information given by local veterinarians and analysed by LC MS-MS: endo and ectoparasites treatments; antibiotics and non-steroidal anti-inflammatory drugs. The monitoring shows that most of these chemicals (12 substances) are quantified in all POCIS samples and the others show relatively high occurrences, between 25 and 88%. Average concentrations in water (calculated with the sampling rate i.e. considering the time of exposition of POCIS samplers in the river) are remarkably close between the 2 monitoring stations. Concentrations are high all over the studied period and reach a maximum during flood events. Thus, hazardous effects are expected on freshwater organisms, especially for macrocyclic lactones and pyrethroids and organophosphates pesticides. The antibiotics concentrations ranges can also disturb microbial communities existing in the river. Such results highlight an important impregnation by these pharmaceuticals at the catchment scale, involving diffuse sources as grasslands receiving contaminated cow dungs and manures. Veterinary compounds are strongly remobilized during rain episodes by run off and infiltration in soils. In the hydrogeological context of the Bienne basin, karstic flows emphasize the connectivity between grasslands and the river. Therefore, an important part of the contaminated leaching waters can rapidly reach the river via the soil drains and surface / subsurface flows. Rather than another part goes through less porosity pathways and delivers pollutants over a longer period. Wastewater discharges and sludges from rural and urban treatment plants can also contribute to this pollution for pharmaceuticals also used in human medications.
All dried up: An interdisciplinary analysis of drought risk in Ladismith, South Africa  
Authors: Savelli Elisa , Rusca Maria , Cloke Hannah , Di Baldassarre Giuliano
Published: March 2021

Droughts have always been part of Earth climate, yet today these phenomena are becoming more alarming due to their increasing severity and their disastrous socio-ecological impacts. Different scientific definitions or diverse understanding of drought risk have been proposed also because of the simultaneously social and ecological complexity which characterizes droughts relative to other hazards and/or vulnerabilities. This work sets out to confront the distinctive complexity of drought risk throughout a novel approach which combines political ecology perspectives with hydro-climatological insights. Our engagement with political ecologies of land, water, and vulnerability helps to explain the socio-political processes that intersect with the production of droughts and their consequences. Concurrently, hydro-climatology unravels the physical or material processes that both constitute and transform drought phenomena into socio-ecological disasters. The drought-stricken Ladismith in Western Cape, South Africa, is the point of departure of our empirical analysis which portrays the socio-ecological disruption reached by this rural community after five years of below-average rainfall (meteorological drought). We show that Ladismith socio-ecological crisis was mostly engendered by a distinct mechanism of capital accumulation through land and water dispossession, which emerged locally in the form of white commercial agriculture. Our interdisciplinary approach examines these socio-political processes in relation to the drought physical transformations over time and across space. By relating societal and physical processes we advance a novel understanding of drought that sheds light on the crucial interactions between social power, climate, land use, and hydrology, which all too often transform a meteorological event into a soil moisture drought, a hydrological drought, and eventually into a major socio-ecological crisis. Secondly, combining hydro-climatology with political ecology reveals that social power not only influences the vulnerability of the systems affected by droughts, but also shapes the occurrence and manifestation of the hazard itself. This novel conceptualization of drought risk as socially produced is key to intercept the material spaces and physical dynamics through which social power plays out in more extreme and disruptive drought events. A similar approach, by identifying unjust and unsustainable socio-ecological changes, can make drought management policies and strategies more proactive rather than constrain them to relief or adaptation measures.
Toward implementing a grid search moment tensor (GRiD MT) tool for the rapid detection and characterization of seismic events in Metropolitan France
Authors: Menager Marine , Trilla Aurélie , Delouis Bertrand
Published: March 2021

The aim of this study is to implement at the CEA a grid search moment tensor inversion scheme (GRiD MT) for the rapid detection and characterization of seismic events, to monitor low to moderate magnitude earthquakes in France. Given the heterogeneity of the seismic network and of the crustal geology over the country, we propose to use a combination of source grids focusing on specific regions. The GRiD MT approach requires an extensive preliminary analysis to define the different inversion parameters (velocity model, frequency band, and stations) and grid spacing (in latitude, longitude and depth). Here, we present the advances made towards the GRiD MT implementation for France. Using recent earthquakes, such as the 2019 ML 5.4 Le Teil earthquake, near Montelimar in Southern France, we discuss the validity of this detection and characterization tool for earthquake routine. The GRiD MT results applied in the South-East region for moderate earthquakes are close to those published by other agencies (USGS, IPGP, OCA, INGV) in terms of location, magnitude and focal mechanism. Nonetheless, more care is needed for the smallest events. We also discuss the precision and the uncertainties in constraining the source parameters using this method, especially when considering the goodness of fit as the unique criterion to identify a potential source, and different Earth’s structures. In the end, we show that the GRiD MT approach may be an interesting tool to analyze seismic events in France within only a few minutes after their occurrence. However, their low magnitude range raises some challenging questions to be answered.
Method and challenges of tracing soil-surface transport of microplastic particles with an advanced-imaging sCMOS camera
Authors: Laermanns Hannes , Haas David , Klee Marcel , Steininger Florian , Löder Martin , Bogner Christina
Published: March 2021

Although the impact of microplastic particles (MPs) in different ecosystems has recently become subject of numerous studies, the knowledge of spatial distribution and transport of MP in terrestrial environments is still limited. While first studies in this field have focused on the abundance of MPs in soils and its vertical distribution, only little is known about the mechanisms of MP transport on the surfaces of sediments and soils. To analyse the interaction between soil surface roughness, inclination and irrigation rate, we investigate MP surface transport mechanisms and patterns by using images of an advanced scientific complementary metal–oxide–semiconductor (sCMOS) high-resolution camera. For this study an experimental set-up including a flume box with several surfaces and an artificial irrigation system was used. In this setup we traced pathways of fluorescent amorphously shaped polystyrene (PS) and Polymethyl methacrylate (PMMA) particles on surfaces of different roughnesses and inclination. Subsequently, time series of the images were analyzed by combining R and Python packages was. This included the calculation of MP particle size, estimation of pathways and path lengths.  Our first results suggest a large influence of the water film thickness and the microrelief of the studied surfaces leading to the creation of preferential pathways for the MP particles.