bluuebunny/crossref_metadata_2025 huggingface dataset:
Importance of site-specific factors for the immobilization of contaminants using biochar and wood-based activated carbon
Authors: Chaudhuri Sampriti , Sigmund Gabriel , von Rautenkranz Hary , Hueffer Thorsten , Hofmann Thilo
Published: March 2021

The use of environmentally friendly low-cost sorbents such as biochar and wood-based activated carbon as soil amendment has shown promising results in immobilizing organic and inorganic contaminants. They can be suitable soil remediation options at sites with residual contamination, where the contaminated hotspot has been removed. The effectiveness of biochar and activated carbon application is site dependent. Specifically, dissolved organic carbon (DOC), pH, and ionic strength in the pore water are important factors which can influence the extent of contaminant immobilization. Although there has been significant progress in developing alternative carbonaceous sorbents, the efficiency of these materials in a diverse range of soil and pore water conditions remains an open question. To address this knowledge gap, the present study investigates the influence of pore water chemistry on sorption of organic and inorganic contaminants to biochar and wood-based activated carbon. Sorption of selected non-polar, polar and ionizable polycyclic aromatic compounds (PACs) and inorganic Cadmium (Cd) to biochar and a wood-based activated carbon was studied under different pore water chemistry conditions. Batch sorption experiments were conducted using an experimental design approach (Box Behnken Design) with three different levels of DOC, pH, and ionic strength, yielding background solutions mimicking a wide spectrum of pore water chemistries. Sorption KD values [L/kg] were calculated from aqueous contaminant concentrations after equilibration. Results were analyzed using a response surface methodology (RSM) approach on Minitab 19 and fitted to a model equation using linear, squared and two-way interactions terms.

Our results show that the ionizable PAC (phenyl phenol) and Cd were most affected by changes in pore water chemistries. For phenyl phenol, the presence of a phenolic group can cause H-bonding and electrostatic attraction and repulsion, while pH-dependent changes in speciation, precipitation and electrostatic attraction can occur for Cd. Sorption of all PACs negatively correlated with DOC, indicating competition of DOC with PACs for sorption sites. Sorption of non-polar (acenaphthene), polar N substituted (carbazole) and ionizable (phenyl phenol) PACs was hindered under acidic conditions, due to precipitation of DOC. For Cd, higher pH and low DOC levels favored sorption. This can be attributed to a lower Cd solubility in the presence of leached phosphate at higher pH, and a predominance of Cd(OH)2 in the neutral to alkaline regime. Our findings highlight the importance of considering a combination of site- and contaminant-specific factors when planning to apply carbonaceous sorbents for contaminant immobilization, with pH and DOC generally being more important than ionic strength.
Diabatic processes associated with an extratropical dry intrusion reaching into the western North Atlantic trade wind region
Authors: Müller Sara , Boettcher Maxi , Villiger Leonie , Aemisegger Franziska
Published: March 2021

Intrusions of dry upper-level extratropical air into the tropics play an important role in shaping the synoptic time-scale variability of the low-level cloud cover over the tropical oceans. In this study, we present a detailed Lagrangian analysis of an extratropical dry intrusion in the western North Atlantic, which occurred in January-February 2018. During this period, the easterly trade winds were interrupted for several days by coherent packages of rapidly descending air parcels reaching from the mid-latitude jet stream region into the sub-cloud layer close to Barbados. As those air parcels are anomalously dry and cold, they have a notable impact on diabatic processes in the vicinity of the trade wind cloud tops such as longwave cooling and cloud evaporation and sublimation. To quantify the Lagrangian heat budget along the dry intrusion, we performed a simulation with the Integrated Forecasting System (IFS, 0.4° horizontal resolution, 137 vertical levels) from the European Centre for Medium Range Weather Forecasts (ECMWF) with diabatic heating rate (DHR) output. We calculated back-trajectories based on hourly three-dimensional wind fields and analysed the DHR along the dry intrusion air parcels. In the first part of their descent from the mid-tropospheric jet stream region, the dry intrusion air parcels’ heat budget is dominated by adiabatic warming. In the second part of their descent, they experience strong diabatic cooling at cloud tops, due to microphysical and radiative processes. This leads to cross-isentropic flow, which allows these air parcels to pass through the inversion and to penetrate into the boundary layer. Thereafter they experience strong diabatic warming by turbulent fluxes. The presented detailed case study thus illustrates, how the rapidly subsiding extratropical dry intrusion air interacts with the parametrised subgrid-scale processes at cloud top in the model, thereby affecting the thermodynamic conditions in the boundary layer.
Ocean alkalinity enhancement as a tool to mitigate ocean acidification and facilitate CO2 uptake from the atmosphere
Authors: Rønning Jakob , Löscher Carolin
Published: March 2021

Anthropogenic global warming over the last century has led to a steady increase of CO2 in the atmosphere. One of the consequences of increasing CO2 concentrations is ocean acidification, a phenomenon problematic to marine biodiversity and biogeochemistry. The ocean reservoir takes up 25% of CO2 from the atmosphere both chemically and biologically. This potential can be made use of to promote CO2 uptake from the atmosphere while mitigating ocean acidification and protecting biodiversity using negative emission technologies associated with the ocean. We have investigated the potential of various alkaline minerals to stabilize seawater pH overtime on a small scale. Those alkaline minerals were predicted to be appropriate for ocean alkalinity enhancement and can offer a toolset to mitigate CO2 from the atmosphere. Specifically, we have examined how chalk, calcite, dolomite, limestone, and olivine affects seawater pH and total alkalinity (TA) on timescales of several months. Thereby, we could identify two promising minerals, dolomite and olivine, and develop a strategy for mineral additions to buffer the seawater pH. Importantly, the often proposed had an unexpected opposite impact and massively lowered the seawater pH over a timescale of 100 days. The identified advantageous minerals will inform our experiments on primary producer cultures and natural consortia.
Ecological effects of flow disturbance on phytobenthos communities in natural and regulated alpine streams
Authors: Bonacina Luca , Fornaroli Riccardo , Mezzanotte Valeria , Marazzi Francesca
Published: March 2021

Phytobenthos is the dominant primary producer in streams and sustains, with the allochthonous organic matter inputs, the higher trophic levels. Among the different groups that constitute the phytobenthos community some, especially diatoms, have been studied deeply while others remain quite overlooked. Hence, a characterisation of the overall phytobenthos community is needed, considering all the main taxonomic groups (diatoms, green algae, cyanobacteria and red algae), as related to the environmental conditions characterizing different alpine streams. Moreover, despite the ecological role played by the phytobenthos the knowledge about the factors that control the variations of the community among streams and throughout the different seasons is still poor. Among the different drivers that regulate the phytobenthos component, a pivotal factor is the occurrence of high-flow events that, controlling the stability of riverbed substrates, influences both the phyto and the zoobenthos composition and distribution. Thus, the frequency and the magnitude of flow disturbances are determinant in regulating the phytobenthos density and the recolonization patterns. The aim of this work was to characterize and compare the phytobenthos communities in different streams highlighting the role of the flow regulation due to hydropower reservoirs accounting for the influence of the lithology and the seasonality. The presented phytobenthos data derive from a one-year sampling campaign in four alpine streams representative of different flow conditions (natural vs regulated flow discharge) and lithology (silicate vs carbonate). The riverbed coverage has been estimated monthly in each stream and the biomass has been quantified. In lab, phytobenthos samples have been analysed to measure the photosynthetic activity and define their composition. The main groups (cyanobacteria, green algae, diatoms and algae with phycoerythrin) have been determined both by phyto-PAM deconvolution and by the quantification of the photosynthetic pigments. In order to estimate the bed disturbance, painted stones of different size classes were located in regular arrays along three transversal transects and the distance travelled was measured during every sampling. The preliminary results indicate that regulated streams seem characterized by a greater algae biomass possibly due to a more stable environment. Concerning the community composition, the percentage of diatoms is significatively higher in silicate substrates. Despite the few hours of light, winter promotes phytobenthos colonisation especially for the low frequency of relevant high-flow events but also for the absence of the shadow due to tree canopy on the riverbed.
Global trends in air-water CO2 exchange over seagrass meadows revealed by atmospheric Eddy Covariance
Authors: Van Dam Bryce , Polsenaere Pierre , Barreras-Apodaca Aylin , Lopes Christian , Sanchez-Mejia Zulia , Tokoro Tatsuki , Kuwae Tomohiro , Gutiérrez Loza Lucia , Rutgersson Anna , Fourqurean James , Thomas Helmuth
Published: March 2021

Coastal vegetated habitats like seagrass meadows can mitigate anthropogenic carbon emissions by sequestering CO2 as “blue carbon” (BC). Already, some coastal ecosystems are actively managed to enhance BC storage, with associated BC stocks included in national greenhouse gas inventories. However, the extent to which BC burial fluxes are enhanced or counteracted by other carbon fluxes, especially air-water CO2 flux (FCO2) remains poorly understood. To this end, we synthesized all available direct FCO2 measurements over seagrass meadows made using a common method (atmospheric Eddy Covariance), across a globally-representative range of ecotypes. Of the four sites with seasonal data coverage, two were net CO2 sources, with average FCO2 equivalent to 44 - 115% of the global average BC burial rate. At the remaining sites, net CO2 uptake was 101 - 888% of average BC burial. A wavelet coherence analysis demonstrates that FCO2 was most strongly related to physical factors like temperature, wind, and tides. In particular, tidal forcing appears to shape global-scale patterns in FCO2, likely due to a complex suite of drivers including: lateral carbon exchange, bottom-driven turbulence, and pore-water pumping. Lastly, sea-surface drag coefficients were always greater than prediction for the open ocean, supporting a universal enhancement of gas-transfer in shallow coastal waters. Our study points to the need for a more comprehensive approach to BC assessments, considering not only organic carbon storage, but also air-water CO2 exchange, and its complex biogeochemical and physical drivers.
Sensitivity of global river flood simulations to the choice of climate forcing and hydrological model
Authors: Mester Benedikt , Willner Sven , Frieler Katja , Schewe Jacob
Published: March 2021

Global flood models (GFM) are increasingly being used to estimate societal and economic risks of river flooding. A recent collective validation of several GFMs highlighted substantial differences in performance between models and between validation sites. However, it has not been systematically quantified to what extent the choice of the underlying climate forcing and global hydrological model (GHM) influence flood model performance. Here, we investigate this sensitivity by comparing simulated flood extent with satellite imagery of past flood events, for an ensemble of three climate reanalyses and 11 GHMs. We study eight historical flood events covering four continents and various climate zones. Our results show that model performance varies greatly among the events. For most regions, the simulated inundation extent is relatively insensitive to the choice of GHM. For some events, however, individual GHMs lead to much lower agreement with observations than the others, mostly resulting from an overestimation of inundated areas. Two of the climate forcings show very similar results, while with the third, differences between GHMs become more pronounced. We further show that neither a previously used flood-volume adjustment procedure, nor the application of a global flood protection database, substantially improves model performance. Our study guides future applications of these models, and highlights regions and models where targeted improvements might yield the largest performance gains.
Deformation and reaction fabrics in eclogites from the Western Gneiss Region (Norway) - evidence of dehydration reactions attributed to episodic deformation
Authors: Trepmann Claudia A. , Engvik Ane K. , Prince Gutierrez Erick G.
Published: March 2021

The eclogites from Vårdalneset, Western Gneiss Region, Norway, show an exceptional large variety of reaction and deformation microfabrics that document the processes and conditions during burial and exhumation. Coarse grained eclogites comprise about 35% omphacite, 25% garnet and 20% amphibole with various amounts of white mica, zoisite, kyanite, rutile, zircon and pyrite. Their fabric is characterized by few mm long and several hundred µm wide amphibole and omphacite grains aligned in the foliation plane with zoned garnet porphyroblasts up to several mm in diameter. In contrast, finer-grained mylonitic eclogites with grain diameters of few hundred µm comprise systematically higher amounts of garnet (45%) and omphacite (35%) and generally less amphibole (< 5%) but similar amounts of zoisite, white mica, rutile and quartz. In the coarse-grained eclogite, amphibole shows evidence of dislocation creep as indicated by undulatory extinction, subgrains and recrystallized grains in necks of boudinaged coarse amphibole layers as well as in contact to garnet. The large garnet porphyroblasts generally show a complex zonation with an inclusion-rich Fe-poor and Mg-rich inner core surrounded by a zone with Fe- and Ca-rich patches and a broad Mg-rich, Ca- and Fe-poor rim. Only at contact to coarse amphibole an additional, a few tens of µm thin serrated rim further enriched in Mg can occur. At the direct contact to such serrated Mg-rich rims, amphibole is partly replaced by a fine-grained quartz-kyanite ± rutile aggregate, indicating dehydration reactions of amphibole. Quartz - kyanite ± rutile aggregates are surrounding garnet also in contact to omphacite, zoisite and to other garnet crystals. The microstructures suggest that deformation and dehydration of amphibole are coupled and played an important role during deformation of the eclogites finally leading to the mylonitic eclogites with higher amounts of garnet and omphacite. Deformation is suggested to have triggered the dehydration reaction by a slight and local increase in temperature. Furthermore, deformation provided additional pathways for the escaping fluids along the increased grain and phase boundary area, as indicated by commonly present quartz within interstitials between recrystallized amphibole grains. In all samples, few µm wide amphibole rims replacing garnets document restricted rehydration-reactions at a later stage. The large variety of the deformation and reaction microfabrics exemplarily show that both deformation and metamorphic reactions did not proceed at long-term continuous conditions, but that both are coupled and occurred episodically.
Exploring the ionic composition of the Asian Tropopause Aerosol Layer using medium duration balloon flights
Authors: Vernier Hazel , Rastogi Neeraj , Liu Hongyu , Fairlie Duncan , Pandit Amit , Bedka Kristopher M. , Patel Anil , Ratnam M. Venkat , Kumar B. Suneel , Gadhavi Harish , Weinhold Frank G. , Berthet Gwenael , Vernier Jean-Paul
Published: March 2021

Satellite observations have revealed an enhanced aerosol layer near the tropopause over Asia during the summer monsoon, called the Asian Tropopause Aerosol Layer (ATAL). The chemical composition of the ATAL is investigated here using offline ionic analysis of aerosols collected with a balloon-borne impactor near the tropopause region over India onboard extended duration balloon flights in the summer of 2017 and winter 2018. We found NO3- and NO2- dominant among other ions with values ranging between 87-343 ng/m3 during the summer campaign. In contrast, SO4 levels were found above detection limit (>10 ng/m3) only in winter. In addition, we determined the origin of the air masses sampled during the flights through back trajectory analysis combined with convection. The results obtained therein were put into a context of large-scale transport and aerosol distribution with GEOS-Chem chemical transport model simulations. The first flight of summer 2017 sampled air mass within the Asian monsoon anticyclone (AMA), associated with smaller particle size found on stage 2 (particle size cut off > 0.15 microns) of the impactor, while the second flight sampled air mass at the edge of the AMA associated with larger particle size on stage 1 (particle size cut off between 2 and 0.5 microns). The sampled air masses in winter 2018 were affected by smoke from the Pacific Northwest fire event in Canada, which occurred 7 months prior to our campaign. Concentrations of SO42-, NH4+, and Ca2+ were enhanced. Overall, our results suggest that nitrogen- containing particles represent a large fraction of aerosols populating the ATAL in agreement with aircraft measurements during the StratoClim campaign. Furthermore, GEOS-chem model simulations suggest that lightning NOx emissions had a minimal impact on the production of nitrate aerosols sampled during the two flights. 
Luminescence dating Hajar Mountain alluvial fan systems, northern Oman 
Authors: Woor Sam , Durcan Julie , Parton Ash , Thomas David
Published: March 2021

The alluvial/fluvial fan systems of northern Oman act as sensitive geoproxy records of Late Quaternary palaeohydrology and past landscape evolution, offering records of palaeoenvironmental change which cannot be reconstructed from nearby speleothem records alone (Parton et al., 2013). These systems also provide evidence for the important link between the changing abundance of freshwater in the Arabian interior and the dispersal of anatomically modern humans (AMHs) out of Africa (Rosenberg et al., 2012). Limited previous luminescence dating analyses have reported fan activation west of the Hajar during insolation maxima and monsoon intensification throughout the Late Quaternary (Parton et al., 2015). However, there are currently no studies to date which present chronologies for the fan systems to the east of the Hajar Mountains.

We present the first luminescence based chronology for the fan systems to the east of the Hajar Mountains, providing landform scale data on fan behaviour, including spatial-temporal complexity and variability. This facilitates comparison of the temporal response of fans east and west of the mountains, including differential responses to external forcing. Ages will also be compared with regional palaeoenvironmental and palaeoclimatic records, to inform landscape reconstructions in northern Oman during the late Quaternary.

References

Rosenberg, T.M., Preusser, F., Blechschmidt, I., Fleitmann, D., Jagher, R. and Matter, A., 2012. Late Pleistocene palaeolake in the interior of Oman: a potential key area for the dispersal of anatomically modern humans out‐of‐Africa?. Journal of Quaternary Science, 27(1), pp.13-16.

Parton, A., Farrant, A.R., Leng, M.J., Schwenninger, J.L., Rose, J.I., Uerpmann, H.P. and Parker, A.G., 2013. An early MIS 3 pluvial phase in Southeast Arabia: climatic and archaeological implications. Quaternary International, 300, pp.62-74.

Parton, A., Farrant, A.R., Leng, M.J., Telfer, M.W., Groucutt, H.S., Petraglia, M.D. and Parker, A.G., 2015. Alluvial fan records from southeast Arabia reveal multiple windows for human dispersal. Geology, 43(4), pp.295-298.

 
In-depth comparison of the spectral-element and finite-element method for 3D CSEM forward modelling
Authors: Weiss Michael , Rulff Paula , Kalscheuer Thomas
Published: March 2021

We developed two forward modelling approaches to simulate 3-dimensional land-based controlled-source electromagnetic (CSEM) problems in frequency domain with hexahedral spectral-element meshes and tetrahedral finite-element meshes. In recent years, the geo-electromagnetic community made a lot of progress in modelling and inversion of EM data in three dimensions using a variety of approaches. The available software is used to verify the accuracy of newly developed codes, which apply e.g. different element shapes or interpolation schemes. However, a direct comparison in terms of advantages and disadvantages of different modelling strategies, especially discretisation methods in 3D, is often not focused on in publications.

Having two modelling codes and their developers available at the same place, gives us the unique opportunity to compare the approaches in a very detailed way. Our spectral-element as well as our finite-element solution is based on Galerkin’s weighted residual method and we solve the electromagnetic diffusion equations for the total electric field on the element edges.
The main differences between both codes are the choice and order of the interpolation functions and the discretisation of the modelling domain employing hexahedral and tetrahedral elements. While the tetrahedral meshes used in our finite-element approach are known for being able to properly resolve complex structures in the subsurface, this issue is addressed in the spectral-element method by utilising curvilinear instead of orthogonal hexahedral elements.

In this contribution, we focus on the comparison of both approaches for a simple 1D model and a complex 3D model in terms of accuracy, effort in mesh generation and computational resources such as simulation time and memory requirement. Moreover, we contrast the influence of mesh discretisation on the solution for the two methods as well as the order of approximation. A preliminary test simulation of a  model consisting of a conductive body buried within a resistive background covered by a thin conductive layer yielded comparable results in terms of accuracy. It also revealed significant differences concerning the mesh discretisation meaning the solution's dependency on the meshing of the model domain.

Acknowledgements: This work was partly funded by Uppsala’s Center for Interdisciplinary
Mathematics and the Smart Exploration project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No.775971.
Identifying the drivers of stochastic Dansgaard–Oeschger scale variability in a GCM
Authors: Armstrong Edward , Valdes Paul , Izumi Kenji
Published: March 2021

The driver of the Dansgaard-Oeschger (DO) events remains uncertain, in part because many models do not show similar behaviour of a climate system tipped into a DO oscillatory state. Here we present results from glacial simulations of the HadCM3 GCM that show stochastic DO-scale variability. This is driven by variations in AMOC strength in response to North Atlantic salinity fluctuations. This represents a salt oscillator, driven by the salinity gradient between the subtropical gyre and Nordic seas. We give a mechanistic explanation of the feedbacks that drive this oscillator, particular the interplay between surface fluxes and advection. We identify that the key trigger that pushes the system into this oscillatory mode is the height of the North American ice sheet, which alters atmospheric and subsequently ocean circulation patterns. Our results highlight that glacial background conditions and ice sheet height act to push the system past a tipping point and into an oscillatory state on a timescale comparable to the DO events.
Spatial analysis of riverine microplastic in a Rhine floodplain soil in Germany
Authors: Rolf Markus , Löder Martin G. J. , Laermanns Hannes , Kienzler Lukas , Steininger Florian , Möller Julia , Laforsch Christian , Bogner Christina
Published: March 2021

The Rhine River flows through six European countries and is in exchange with diverse land use forms and human activities that potentially release microplastics (MPs). The Rhine interacts permanently with its surrounding banks and floodplains by changing water-levels. Several studies have documented the presence of MPs in the Rhine along its course as well as in its tributaries. However, the spatial distribution of MPs due to certain flood events in alluvial floodplains remains widely unclear. The knowledge about the amount and distribution of MPs and on their potential entry pathways into Rhine floodplains is essentially important for an ecological risk assessment. In this study, we analysed the amount and distribution of MPs in a floodplain soil in the nature reserve Merkenich-Langel, in the northern periphery of Cologne (Germany). We hypothesize that MPs are transported by the Rhine and are deposited at the site during flood events. For spatial analysis we used the MIKE software (DHI A/S, Hørsholm Denmark) merged with a digital terrain model of the study site to analyse past flood events and their potential deposition of MP. We chose three sampling transects located within the past flooded area each with three sampling spots with increasing distance and elevation to the river. Samples were taken from two different soil depths (0–5 cm and 5–20 cm) and the samples of the three sampling spots and same depth were combined to one mixed soil sample per transect. MP concentrations were analysed via ATR-FTIR and µ-FPA-FTIR spectroscopy after density separation and enzymatic-oxidative purification. We found an increase of MP concentration per kg of dry soil in the depth 5–20 cm with increasing distance to the river ranging from 25.612 particles/kg to 85.076 particles/kg. The results of MP concentration in 0–5 cm topsoil layer will be compared to the concentration in the soil depth of 5–20 cm. We correlate these results to the frequency of flood events.
On the variability of the DWBC transport between 26.5°N and 16°N in an eddy-rich ocean model and its implications for meridionally coherent changes.
Authors: Schulzki Tobias , Getzlaff Klaus , Biastoch Arne
Published: March 2021

The southward flow of North Atlantic Deep Water makes up the major component of the AMOC's deepwater limb. In the subtropical North Atlantic, it's flow is concentrated along the continental slope, forming a coherent Deep Western Boundary Current (DWBC). Both, observations and models show a high variability of the flow in this region.
We use an eddy-rich ocean model to show that this variability is mainly caused by eddies and meanders that are generated by barotropic instability. They occur along the entire DWBC pathway and introduce several reciruculation gyres that result in a decorrelation of DWBC transport at 26.5°N and 16°N, despite the fact that a considerable mean transport of 20 Sv connects the two latitudes. Water in the DWBC at 26.5°N is partly returned northward. Because the amount of water returned depends on the DWBC transport itself, a stronger DWBC does not necessarily lead to an increased amount of water that reaches 16°N. 
Along the pathway to 16°N, the transport signal is altered by a broad and temporally variable transit time distribution. Thus, advection in the DWBC cannot account for coherent AMOC changes on interannual timescales seen in the model.
Characterization of hydraulic properties in the upper vadose zone for two aquifers in Slovenia
Authors: Zupanc Vesna , Glavan Matjaž , Curk Miha , Pečan Urša , Stockinger Michael , Kammerer Gerhard , Vadibeler Devakunjari , Stumpp Christine
Published: March 2021

Environmental tracers, present in the environment and provided by nature, provide integrative information about both water flow and transport. For studying water flow and solute transport, the hydrogen and oxygen isotopes are of special interest, as their ratios provide a tracer signal with every precipitation event and are seasonally distributed. In order to follow the seasonal distribution of stable isotopes in the soil water and use this information for identifying hydrological processes and hydraulic properties, soil was sampled three times in three profiles, two on Krško polje aquifer in SE Slovenia and one on Ljubljansko polje in central Slovenia. Isotope composition of soil water was measured with the water-vapor-equilibration method. Based on the isotope composition of soil water integrative information about water flow and transport processes with time and depth below ground were assessed. Porewater isotopes were in similar range as precipitation for all three profiles.  Variable isotope ratios in the upper 60 cm for the different sampling times indicated dynamic water fluxes in this upper part of the vadose zone. Results also showed more evaporation at one sampling location, Brege. The information from stable isotopes will be of importance for further analyzing the water fluxes in the vadose zone of the study sties. 
This research was financed by the ARRS BIAT 20-21-32 and IAEA CRP 1.50.18 Multiple isotope fingerprints to identify sources and transport of agro-contaminants.  
Quality Control and Bias Correction of Citizen Science Wind Observations
Authors: Chen Jieyu , Whan Kirien , Saunders Kate
Published: March 2021

Wind observations collected at citizen science wind stations (CWS) could be an invaluable resource in climate and meteorology studies, yet these observations are underutilised because scientists do not have confidence in their quality. While a few studies have considered the quality of CWS wind speed observations, none have addressed the biases, likely caused by instrumentation biases and station placement errors. These systematic biases introduce spatial inconsistencies that prevent comparison of these stations spatially and limit the possible usage of the data. In this paper, we address these issues by improving and developing new methods for identifying suspect observations and calibrating systematic biases in the wind speed observations collected at CWS.

Our complete quality control system consists of four steps: (1) performing within-station quality controls to check the plausible range and the temporal consistency of observations; (2) correcting the bias, mainly caused by low sensor heights, using empirical quantile mapping; (3) implementing between-station quality control that compares observations from neighbouring stations to identify spatially inconsistent observations; (4) providing estimates of the true wind when CWS falsely report zero wind speeds, as a complement to bias correction.

We apply these methods to CWS from the Weather Observation Website (WOW) in the Netherlands, comparing the citizen science data with official data, and statistically assessing the improvements in data quality after each step. The results demonstrate that the citizen science wind data are comparable with official data after quality control checks and bias corrections. Our quality assessment methods therefore give confidence to CWS, converting their observations into a usable data product and an invaluable resource for applications in need of additional wind observations.
Subsurface Preferential Flow Enhances Hydrological Connectivity in the Shale Hills Catchment: Perspective from Wavelet-based Analysis
Authors: Liu Hu , Zhao Wenzhi , Yu Yang , Guo Li , Liu Jintao
Published: March 2021

Preferential flow (PF)-dominated soil structure is often considered a unique system consisting of micropores and macropores and thus supposed to provide dual-pore filtering effects on hydrological signals, through which smoothing effects are likely to be stronger for matrix flow and weaker for PF via macropores. By using time series of hydrological signals (precipitation, canopy interception, throughfall, soil moisture, evapotranspiration, water storage in soil and groundwater, and catchment discharge) propagating through the Shale Hills Catchments and representative soil series, the filtering effects of the catchment and soil profiles were tested through the wavelet analysis. The hypothesized dual-pore-style filtering effects of the soil profile were also confirmed through the coherence spectra and phase differences, rendering them applicable for possible use as “fingerprints” of PF to infer subsurface flow features. We found that PF dominates the catchment’s discharge response at the scales from three to twelve days, which contributes to the catchment discharge mainly as subsurface lateral flow at upper or middle soil horizons. Through subsurface PF pathways, even the hilltop is likely hydrologically connected to the valley floor, building connections with or making contributions to the catchment discharge. This work highlights the potential of wavelet analysis for retrieving and characterizing subsurface flow processes based on the revealed dual-pore filtering effects of the soil system.
Simulation of the record Arctic stratospheric ozone depletion in 2020
Authors: Grooß Jens-Uwe , Müller Rolf
Published: March 2021

In Arctic winter/spring 2019/2020, the stratospheric temperatures  were exceptionally low until early April and the polar vortex was  very stable.  As a consequence, significant chemical ozone depletion  occurred in Northern polar regions in spring 2020.  Here, we present  simulations by the Chemical Lagrangian Model of the Stratosphere  (CLaMS) that address the development of chlorine compounds and  ozone in the polar stratosphere in 2020.  The simulation reproduces  relevant observations of ozone and chlorine compounds, as shown by  comparisons with data from Microwave Limb Sounder (MLS), Atmospheric  Chemistry Experiment - Fourier Transform Spectrometer (ACE-FTS),  in-situ ozone sondes and the Ozone Monitoring Instrument (OMI).  Although the concentration of chlorine and bromine compounds in the  polar stratosphere has decreased by more than 10% compared to the  peak values around the year 2000, the meteorological conditions in  winter/spring 2019/2020 caused an unprecedented ozone depletion. The  simulated lowest ozone mixing ratio was around 0.05 ppmv and the  calculated partial ozone column depletion in the vortex core in the  lower stratosphere reached 141 Dobson Units between 350 and 600 K  potential temperature, which is more than the  loss in the years 2011 and 2016 which until 2020 had seen the  largest Arctic ozone depletion on record.
Controls of the TCRE in Earth system models
Authors: Williams Ric , Ceppi Paulo , Katavouta Anna
Published: March 2021

The controls of a climate metric, the Transient Climate Response to cumulative carbon Emissions (TCRE), are assessed using a suite of Earth system models, 9 CMIP6 and 7 CMIP5, following an annual 1% rise in atmospheric CO2 over 140 years. The TCRE is interpreted in terms of a product of three dependences: (i) a thermal response involving the surface warming dependence on radiative forcing (including the effects of physical climate feedbacks and planetary heat uptake), (ii) a radiative response involving the radiative forcing dependence on changes in atmospheric carbon and (iii) a carbon response involving the airborne fraction (involving terrestrial and ocean carbon uptake). The near constancy of the TCRE is found to result primarily from a compensation between two factors: (i) the thermal response strengthens  in time from more surface warming per radiative forcing due to a strengthening in surface warming from short-wave cloud feedbacks and a declining effectiveness of ocean heat uptake, while  (ii) the radiative response weakens in time due to a saturation in the radiative forcing with increasing atmospheric carbon. This near constancy of the TCRE at least in complex Earth system models appears to be rather fortuitous given the competing effects of physical climate feedbacks, saturation in radiative forcing, changes in ocean heat uptake and changes in terrestrial and ocean carbon uptake.

Intermodel differences in the TCRE are mainly controlled by the thermal response, which arise through large differences in physical climate feedbacks that are only partly compensated by smaller differences in ocean heat uptake. The other contributions to the TCRE from the radiative and carbon responses are of comparable importance to the contribution from the thermal response on timescales of 50 years and longer for our subset of CMIP5 models, and 100 years and longer for our subset of CMIP6 models.

 
The Earth's magnetic field variations at the Algerian magnetic observatory of Tamanrasset from 1932 to 2020.
Authors: Abdenaceur Lemgharbi , Mohamed Hamoudi , Abdeslam Abtout , Bendekken Abdelhamid , Aganou Ener , Abderrahman Hemmi , Abdallah Mansouri
Published: March 2021

In order to understand the spatial and temporal behavior of the Earth's magnetic field, scientists, following C.F. Gauss initiative in 1838 have established observatories around the world. More than 200 observatories aiming to continuously record, the time variations of the magnetic field vector and to maintain the best standard of the accuracy and resolution of the measurements.

This study focused on the acquisition and analysis of the magnetic data provided by the Algerian magnetic observatory of Tamanrasset (labelled TAM by the International Association of Geomagnetism and Aeronomy). This observatory is located in southern Algeria at 5.53°E longitude, 22.79°N Latitude. Its altitude is 1373 meters above msl. TAM is continuously running since 1932, using old brand variometers, like Mascart and La Cour with photographic recording at the very beginning. Nowadays modern electronic equipment are used in the framework of INTERMAGNET project. Very large geomagnetic database collected over a century is available. We will describe the history and the various improvement of the methods and instrumentation.

Preliminary analysis of time series of the observatory data allowed to distinguish two kinds of data: the first type, with low resolution, collected between 1932 and 1992. This data set comes from the annual, monthly, daily and hourly means. The second one with high resolution is represented by minutes and seconds sampling rate since 1993 when TAM was integrated to the world observatory network, INTERMAGNET. Part of the second dataset contains many gaps. We try to fill these gaps thanks to mathematical methods. Absolute measurements and repeat station data allow better accuracy in the secular variations and an improved regional model.

Keywords: TAM observatory, temporal variation, terrestrial magnetic field, secular variations, INTERMAGNET.
Remote Sensing based investigation of secondary mining deformation processes in a postglacial landscape of the Muzakow Arch Geopark (Western Poland) – preliminary results
Authors: Blachowski Jan , Becker Miłosz , Buczyńska Anna , Bugajska Natalia , Janicki Dominik , Koźma Jacek , Kwaśny Leszek , Wajs Jarosław , Warchala Ewa
Published: March 2021

The area of the present day Muzalkow Arch Geopark located on the border of Poland and Germany was subjected to a long term mining of lignite and other rock raw materials that ceased in the 70’ties of the 20th Century. The present-day geomorphological landscape of the research area is characterised by numerous and differentiated forms of anthropogenic origin (e.g. artificial lakes, subsidence troughs, sink holes, waste heaps) associated with underground and subsequently opencast mining of lignite in complex geological and tectonic conditions that result from glaciotectonic processes of subsequent stages of accumulation and weathering. It is thought that the area is presently subjected to geodynamic processes associated with weathering of exposed areas (lignite outcrops and waste heaps), destruction of shallow underground workings (subsidence troughs, sink holes) and changing hydrogeological conditions of the rock mass. The scale of these secondary deformations is presently unknown and these processes pose a threat the present day tourist development of the area, such as: sudden development of discontinuous terrain deformations, slope instability, flooding and subsequent dying of vegetation, etc.
Geodetic surveying and remote sensing (terrestrial, aerial and satellite) observations have been employed, apart from other in-situ investigations (geophysical and geological prospecting), to study the processes in one of the former coal mining fields in the geopark.
In this study preliminary results of selected geodetic field investigations, i.e. terrestrial laser scanning of a sink hole that showed on the surface in Autumn 2019 and UAV photogrammetric monitoring of an artificial waste rock tips have been reported. It has been found, based on mapping of old mining maps in GIS, that the sink hole is directly related to old shallow underground workings. Maximum depth of the analysed sink hole below ground level is  5.5 m and volume of subsidence is 35 m3. The location is being monitored to check if the geometry changes in time.
Whereas, comparison of digital elevation models of the investigated waste heap (one of three measured so far) showed development of gully erosion and downward movement of the weathered material. The deposition of material at the bottom of the heap averaged over a dozen cm and maximum of over 50 cm for a half year Summer period (from 15.05.2020 to 07.11.2020).
The presented results constitute a first approximation of 3D mapping and modelling the post-mining deformations in glaciotectonic landscape and constitute part of an ongoing research project financed from the Polish National Science Centre OPUS funds (no 2019/33/B/ST10/02975).
Estimating the snow-rain transition zone in a semi-arid Andean catchment
Authors: Schauwecker Simone , Palma Gabriel , MacDonell Shelley , Goubanova Katerina
Published: March 2021

The height of the snow-rain transition during infrequent but high impact precipitation events, closely related to the 0⁰C-isotherm, is a crucial variable for snow cover extent, high discharge flows and flash floods in semi-arid northern Chile. Estimations of the snow-rain transition zone and its past and future changes are therefore fundamental for adaptation strategies and might eventually serve to develop early warning systems in this region. However, there are important challenges that hinder the assessment of the snow-rain transition zone in semi-arid environments and little is known about past and future changes under different global warming scenarios. For example, there are few radiosonde observations along the Andes and most weather stations are located in valley bottoms, influenced by local conditions and the assumption of free-air temperature lapse rates contributes to the uncertainty. We combine different data sets to estimate the past snow-rain transition zone of our study site, the semi-arid Elqui river catchment. Pictures of the snow line after precipitation events - available from social networks - are used to visually estimate the snow line elevation. These values are in high agreement with vertically extrapolated temperature from meteorological stations. Furthermore, we identified considerable biases between the extrapolated 0⁰C-isotherm from meteorological stations and ERA5 reanalysis data. These large biases are probably due to the lowering of the freezing level over complex terrain and need further analysis. Our results contribute to an improved understanding of the snow-rain transition in this region, but also serve to derive a climatology of this key variable along the Andes mountain range, needed for future projections.
Recent updates to the atmospheric chemistry modeling of the ECMWF IFS in support to CAMS
Authors: Huijnen Vincent , Williams Jason , Bouarar Idir , Belamari Sophie , Chabrillat Simon , Remy Samuel , Flemming Johannes
Published: March 2021

The Integrated Forecasting System (IFS) of ECMWF is the core of the Copernicus Atmosphere Monitoring Service (CAMS) which provides global analyses and forecasts of atmospheric composition, namely reactive gases, aerosol and greenhouse gases. With respect to the atmospheric chemistry component, the operational system currently relies on a modified version of the CB05 chemistry scheme for the troposphere, combined with the Cariolle scheme to describe stratospheric ozone. In an alternative, more recent configuration also stratospheric ozone chemistry is included based on the BASCOE chemistry module. Alternative atmospheric chemistry modules which can be employed are based on MOZART and MOCAGE chemistry. 
Recently, further revisions to the modified CB05 tropospheric chemistry scheme have been developed, focusing both on inorganic and organic chemistry, with the aim of improving the quality of existing air-quality products, and the development of new products. On major update is a revision of the isoprene oxidation scheme based on those employed in existing chemistry transport models, as well as inclusion of the basic chemistry describing C8 and C9 aromatics degradation. 
An example of a new product derived from these updates include a description of global distribution of glyoxal, while this also resulted in an improved modeling of OH recycling particularly over tropical forests. Also we support improved secondary organic aerosol formation due to gaseous anthropogenic, biogenic and biomass burning sources.
In this contribution we provide an overview of these revisions, and provide a first quantification of their uncertainties, by comparing products to observations and to those from alternative chemistry modules.