bluuebunny/crossref_metadata_2025 huggingface dataset:
On the parameterization of atmospheric convection with a realistic plume model
Authors: Vraciu Cristian
Published: March 2022

In this work, we present an alternative theory for the parameterization of atmospheric convection based on plumes with a realistic description. The convective source terms, which provide the feedback of the convection upon the large-scale variables are obtained by performing a sub-grid averaging, considering that the convective variables are fluctuations from the mean, large-scale, state. In this way, we do not need to consider that the large-scale is described by the environmental state, which means that we do not need to consider that the fractional area occupied by the convection is very small. Thus, our formulation can be implemented in numerical weather prediction (NWP) and climate models with high resolutions, in which case a stochastic representation for the fractional area occupied by the convection in every grid box must be considered. In our parameterization, the convective variables in each grid box are described by one round steady-state convective plume placed in the center on the box with radial profiles which respect the condition that the convective variables represent fluctuations from the mean state. Performing an integral analysis over the plume's domain in the radial direction, we obtain a system of ordinarily differential equations (ODE) which take into consideration both the buoyancy-driven and the turbulent entrainment, offering thus a more accurate description of the convective dynamics then the classic entrainment hypothesis. Moreover, the influence of the large-scale is taken into consideration at any height, not just at the cloud base as in the standard mass-flux formulation. The system of ODE that we obtain can be analytically solved between the vertical grids of the NWP or climate models if we consider that the plume radius is constant and we use the scaling argument that the buoyancy-driven entrainment scales with the inverse of the height. The radial coefficients which result from the radial integration of the plume can be obtained by prescribing the exact form of the radial profiles of the vertical velocity, scalar components and turbulent fluxes, or determined using large-eddy simulations. The closure of our model consists in prescribing the vertical velocity and the radius of the plume at the initial level, which can be considered to follow a given probability density function as in the existing stochastic parameterizations.
The interface between magma and Earth’s atmosphere and its influence on the gas composition of volcanic plumes
Authors: Kuhn Jonas , Bobrowski Nicole , Platt Ulrich
Published: March 2022

Magmatic gases that reach Earth’s surface are among the scarce sources of information on the planet’s interior. Their composition is dominated by H2O, CO2, and sulfur species and largely differs from that of today’s atmosphere of the Earth, particularly, by the amounts of oxygen. When magmatic gases are emitted directly to the atmosphere (e.g. at lava lakes), the process is further characterised by huge temperature gradients (hundreds to more than a thousand K per metre). The rapid cooling and fast mixing with atmospheric oxygen defines an early phase in the lifetime of a volcanic plume, which can crucially influence the plume’s later composition. Few attempts have been made to include the often extreme dynamics of this early plume phase into the scope of volcanic gas studies.

Naturally, magmatic degassing processes are difficult to study and thus bound to large uncertainties in crucial parameters, such as gas temperature, gas composition, and mixing. Further, heterogeneous processes involving ash and aerosols might have a strong impact on the processes.

We developed a model to study the C-H-O-S gas phase reaction kinetics of the first seconds of a volcanic gas emission. The entire cooling process of the volcanic gases is covered and studied considering its dynamics and regarding large ranges of mixing scenarios, gas compositions and emission temperatures.

We find that many major processes are far from (the often assumed) thermal equilibrium (TE). Particularly, large amounts of HOX (OH + HO2), exceeding TE by orders of magnitude, form at high temperature as soon as sufficient O2 entered the plume. High OH levels lead to rapid oxidation of emitted species, such as CO, H2, and SO2. Strikingly, CO levels can be both, reduced and enhanced by high temperature processing, depending on the assumed initial conditions. Moreover, we observe that the enthalpy change associated with the chemical conversions can lead to a significant net heating of the plume.

Overall, and despite of the simplifications made, our model indicates a major influence of the dynamics within the interface between magma and the atmosphere (i.e. the early volcanic plume). The composition of gas samples that interacted only a tenth of a second with the atmosphere might substantially differ from the magmatic gas composition. This would lead to enhanced uncertainties in the quantification of magmatic parameters (such as temperature and redox state), when derived from measurements of gas ratios in the volcanic plume. 
Analyzing Diahaline Exchange and Mixing in the Baltic Sea
Authors: Henell Erika , Burchard Hans , Gräwe Ulf , Gröger Matthias , Klingbeil Knut
Published: March 2022

In this talk we present new insights into the overturning circulation of the Baltic Sea. Based on a state-of-the-art 3D numerical model for the entire Baltic Sea, we analyse the estuarine circulation and water mass transformation in salinity space. State and diagnostic variables are binned to salinity classes and conservatively averaged already during model runtime such that exact budgets for local isohaline volumes can be evaluated. Derived maps in salinity space for entrainment velocities, diahaline diffusive fluxes as well as physical and spurious numerical mixing contributions will be shown. The latter is based on a unique separation and quantification of mixing due to turbulence parameterisations and discretisation errors from the applied numerical advection schemes. Finally it is demonstrated that integration of the different new local diagnostics confirms existing bulk theories (e.g. Knudsen theorem, universal law of estuarine mixing).
GIS automation of large-scale flood vulnerability analysis for drainage basins, based on a single Digital Elevation Model
Authors: Enea Andrei , Iosub Marina , Stoleriu Cristian Constantin
Published: March 2022

In the context of climate change, probability of risk phenomena occurrence is more frequent and with greater intensity. This is especially valid for floods which cause significantly more damage and casualties, as flood-inducing conditions are met more often. The risk is emphasized by the fact that countless human settlements are located on the floodplain of river courses of different sizes and flow rates. The current study aims to detail an automatic GIS model that can easily compare drainage sub-basins of similar order, according to Horton-Strahler hierarchical classification, at large scale, for a given basin, based on morphometric parameters. This implies the use of a digital elevation model (DEM) as the only input layer, and setting a few parameters, in order to extract several quantifiable hydrological indicators, relevant to flood analysis. Some of the most relevant ones from the list are the elongation ratio, circularity ratio, relief ratio, roughness number, drainage density etc. All the functions have been integrated into a GIS tool, that would automatically aid in the fast creation of a final vector layer, that discerns between drainage basins with higher and lower degrees of relative vulnerability. This layer contains an attribute table with all the relevant parameters, as well as the result of the formula that assigns flood vulnerability values to each drainage basin, making possible the quantitative comparison between all the drainage sub-basins. The resulting table analysis is conducted in the background, based on the calculation of normalized values for each parameter, which are encompassed into a final vulnerability score. The model is easily applicable to most types of raster elevation layers, as long as they are in a projected coordinate system, regardless of pixel size. Furthermore, several functions were added to the model to mitigate potential errors that can occur in isolated cases, where the topography is particularly difficult to interpret by some native GIS tools. Therefore, this model is an easy to apply tool, that automatically identifies more vulnerable sub-basins, from a large drainage basin, over extended areas, with limited user-input, facilitating decision making in flood management, while providing quantifiable flood vulnerability results, in a very short period of time, without requiring extensive knowledge from the user.
Impacts of anthropogenic pressures on mountain lake underwater light conditions and diatom functional groups
Authors: Atti Sanna , Rantala Marttiina , Lami Andrea , Meyer-Jacob Carsten , Weckström Jan , Smol John , Nevalainen Liisa
Published: March 2022

Solar radiation fuels primary production and carbon uptake in aquatic environments, but shorter ultraviolet radiation (UVR) wavelengths may cause adverse effects and trigger photoprotective mechanisms in organisms inhabiting lakes. In sensitive mountain lakes, ice cover and dissolved organic matter (DOM) mainly control underwater light conditions. Climate warming and other anthropogenic pressures impact the length of the ice cover period and the concentration and composition of DOM. A prolonged growing season with increased light availability may change habitat availability and drive changes in the functional group distribution of phototrophic communities. However, the roles of changing habitats and possible adverse effects of UVR as drivers of micro-algae functional group distributions have not been separated, and lake studies have thus far mainly focused on species specific sensitivities.

This study focuses on changes in underwater light conditions and UVR exposure during the past ~200 years and the impacts on functional group distributions of diatom (Bacillariophyceae) communities in two mountain lakes with different altitude and catchment size. Dated short sediment cores from each lake were analysed for elemental composition and stable isotopes of carbon and nitrogen, as well as sediment-inferred lake water total organic carbon (TOC) and chlorophyll-a. Diatoms were analysed to the species level and further divided into eco-morphological groups to investigate parallel changes in diatom functional group distributions. Geochemical proxies were used to describe trends in lake water transparency and duration of ice cover period. In addition, changes in diatom functional group distributions were analysed from the main habitat in the shallow littoral zone to detect diatom functional groups tolerances to high UVR.

Anthropogenic pressure was identified as a likely driver of sediment-inferred lakewater TOC concentration changes within the past ~200 years, suggesting changes in light conditions and UVR. Diatom functional group distributions in the lake located at higher altitude with a smaller catchment showed an increase of planktic life-forms within the past ~100 year, which may be related to shortening of the ice cover period. Earlier studies have shown trade-offs between motility and photoprotective capacity, but in this study clear differences between occurrences of motile or non-motile functional groups in the shallow littoral zone were not found. Based on these results, further research with broader habitat sampling is needed to separate the roles of habitat availability and UVR, and their roles affecting the distribution of diatom functional groups.
Image Upscaling Assesment From UAV To Sentinel-2 In Coastal Wetlands
Authors: Martinez Prentice Ricardo , D. Ward Raymond , Peciña Miguel Villoslada , Sepp Kalev
Published: March 2022

Coastal wetlands provide a range of ecosystem services and can support quite high biodiversity as a result of their high productivity. There are a range of techniques applied to monitoring and assessing ecological status and ecosystem service provision, however, traditional techniques can be quite time consuming and costly. In recent years, there has been a strong push to use remotely sensed data to evaluate ecological condition as well as estimate a range of ecosystem services within coastal wetlands.  Unmanned Aerial Vehicles (UAV) platforms have increasingly been used in the field of remote sensing of coastal wetlands because they provide detailed radiometric data to carry out the classification of the high-resolution images. Classifications using supervised Machine Learning algorithms can be performed on those images, providing robust datasets for a range of variables.

However, in spite of the flexibility of performing flight plans to monitor coastal wetlands with high accuracy, it is often not feasible to capture large areas using UAV systems. Satellite imagery can be used to undertake evaluations of a wide range of environmental variables in coastal wetlands over much larger areas. Finding synergies between images taken from UAVs and satellite could provide the possibility to extend local observations of plant functional diversity or ecosystem service provision in coastal wetlands to larger areas or to regions. Using validation techniques based on ground-truth data, high-resolution UAV derived images can be used to characterize terrain and ecological features, such as plant communities and then upscale them to satellite resolutions.

The present study presents a methodology to compare images taken from a UAV multispectral camera and the freely available Multispectral Instrument (MSI) sensor images from the Sentinel-2 satellite because their spectral bands overlap with those commonly used for plant community assessments in coastal wetlands using drones. First, each pixel of Sentinel-2 image is characterized by the most frequent category of plant communities obtained from a ML supervised classification of high-resolution UAV image. Then, the results of classifying the study areas with the Sentinel-2 image are compared with the previous process by analyzing the differences and similarities of categories in each pixel. By this way, synergies between the UAV and Sentinel-2 images can be found in order to have a reliable upscaling of UAV-based data. 
Keywords: Remote Sensing, UAV, Machine Learning, Upscaling
Decadal climate predictions, impacts of Arctic sea ice loss, and the signal-to-noise paradox
Authors: Smith Doug
Published: March 2022

Many sectors of society are vulnerable to decadal changes in climate, which impact food security, freshwater availability, spread of pests and diseases, heat waves, droughts, floods, cyclones, wildfires, energy supply and demand, transport, migration, and conflict. On decadal timescales climate is influenced by both internal variability and changes in radiative forcing. Climate predictions that are initialised with observations are needed to account for all of these factors and will be reviewed in this talk.

Understanding the drivers of decadal climate is crucial for gaining confidence in forecasts. One hypothesis, namely that Arctic sea ice loss weakens mid-latitude westerly winds, promoting more severe cold winters, has sparked more than a decade of scientific debate. The Polar Amplification Model Intercomparison Project was developed to address this issue and results from coordinated multi-model experiments will be presented that support the above hypothesis and suggest that this effect is underestimated by current models. However, even when accounting for this underestimation, the response to Arctic sea ice is small compared to yearly variations in mid-latitude winters.

For predictions to be useful they must be skilful and reliable. There is mounting evidence that models may underestimate the strength of predictable signals, especially for atmospheric circulation in the North Atlantic. This error has been termed the “signal-to-noise paradox” since it leads to the unexpected situation that models can predict the real world better than one of their own ensemble members. Skilful predictions can be achieved using a very large ensemble, but the model output cannot be taken at face value and needs calibrating to obtain skilful and reliable forecasts. Given the potential impacts of changes in atmospheric circulation, understanding why the signal-to-noise ratio is too small in current climate models, and assessing the extent to which correcting this model error would reduce uncertainties in regional climate change projections of the coming decades, are high priority areas for future research.
The opportunities and challenges of Green Hydrogen from Africa and Iceland to decarbonize the industries
Authors: Egbe Daniel Ayuk Mbi , Finger David , Lang Reinhold
Published: March 2022

Green hydrogen has been identified as a key energy carrier to decarbonize the main emission sectors. In the industry sectors hydrogen can be used as a reducing agent in the metallurgy, in the transportation sector hydrogen can be used as a fuel and in the energy sector hydrogen can be used as an energy storage option. However, the production of hydrogen is energy intensive and can only lead to a reduction of greenhouse gas emissions if the primary energy source is renewable, carbon-free, and has a low ecological footprint. Wind, geothermal, solar and hydropower have been identified as key sources for sustainable and green hydrogen production, especially if excess energy is used for the hydrogen production. Unfortunately, large scale renewable energy production is frequently located at distant location from main consumers. We assess the challenges and opportunities of two remote production hot spots for sustainable and green hydrogen, namely Iceland and northern Africa. We will present different methods, ranging from energy modelling, life cycle assessment, to stakeholder analysis to present a holistic picture of sustainable green hydrogen production. Based on our preliminary results, we conclude that Iceland as well as northern Africa have the potential to produce sustainable and green hydrogen.
Constraining the uncertainty in CO2 seasonal cycle metrics by residual bootstrapping.
Authors: Kariyathan Theertha , Peters Wouter , Marshall Julia , Bastos Ana , Reichstein Markus
Published: March 2022

The analysis of long, high-quality time series of atmospheric greenhouse gas measurements helps to quantify their seasonal to interannual variations and impact on global climate. These discrete measurement records contain, however, gaps and at times noisy data, influenced by local fluxes or synoptic scale events, hence appropriate filtering and curve-fitting techniques are often used to smooth and gap-fill the atmospheric time series. Previous studies have shown that there is an inherent uncertainty associated with curve-fitting processes which introduces biases based on the choice of mathematical method used for data processing and can lead to scientific misinterpretation of the signal. Further the uncertainties in curve-fitting can be propagated onto the metrics estimated from the fitted curve that could significantly influence the quantification of the metrics and their interpretations. In this context we present a novel-methodology for constraining the uncertainty arising from fitting a smooth curve to the CO2 dry air mole fraction time-series, and propagate this uncertainty onto commonly used metrics to study the seasonal cycle of CO2. We generate an ensemble of fifitted curves from the data using residual bootstrap sampling with loess-fitted residuals, that is representative of the inherent uncertainty in applying the curve-fitting method to the discrete data. The spread of the selected CO2 seasonal cycle metrics across bootstrap time-series provides an estimate of the inherent uncertainty in curve fitting to the discrete data. Further we show that the approach can be extended to other curve-fitting methods by generating multiple bootstrap samples by resampling residuals obtained from processing the data using the widely used CCGCRV filtering method by the atmospheric greenhouse gas measurement community.
Bias in the Fossil Record: An arts-based approach to decolonising palaeontology
Authors: Gill Fiona , Rees Koerner Emily , Andrew Sonja
Published: March 2022

Just as there is a bias in the fossil record as to which organisms are preserved, there is a bias in who is represented in palaeontology’s history and whose perspective on the cultural significance of fossils is valued. This bias is echoed in the lack of diversity in the palaeontological community today, particularly in terms of racial or ethnic diversity.

A major contributory factor is that palaeontology’s history is entwined with and directly influenced by colonial histories, which have omitted the multifaceted ways in which a range of people and lands have contributed. This bias in the historical development of palaeontology, in particular its alignment to white, western, male privilege, has excluded and marginalised those outside this group in the historical record and today, and continues to impact the perception of fossils, palaeontology and palaeontologists by students, teachers and scientific and non-scientific publics.

We will present interdisciplinary work in progress on an arts-based approach to decolonising palaeontology. We are trialling a variety of practical, creative engagement activities via workshops that bridge art and science, in order to explore and integrate the scientific, cultural and historical significance of fossils.  

We are working with a range of audiences, with a particular focus on those currently under-represented in palaeontology. In doing so, we aim to shift perceptions of fossils and palaeontology and expand the accepted framework of cultural significance that fossils and palaeontology hold, thus contributing to a more inclusive and diverse palaeontological community in the future.
Multi-disciplinary assessment of the August 12, 2021, South Sandwich earthquake doublet
Authors: Metz Malte , Carillo Ponce Angela , Vera Felipe , Cesca Simone , Tilmann Frederik , Saul Joachim
Published: March 2022

On August 12, 2021, an earthquake doublet with a cumulative magnitude MW 8.0 – 8.3 hit the South Sandwich Trench in the South Atlantic where the South American plate is subducted beneath the Sandwich microplate. Significant differences in location, depth, and magnitude are reported by international agencies. Discrepant results might be due to the short inter-event time of ~150 s between both subevents and the lack of local and regional data.

We apply a multi-disciplinary approach to clarify the source processes and characterize different features of the doublet. Our centroid solutions of the mainshocks, separated by ~290 km, confirm the overall southward rupture directivity. The predominant thrust mechanisms, with different strike directions, suggest the activation of a bent portion of the slab. We estimate a cumulative magnitude of Mwc 7.65 inverted from body waves in the frequency band 0.01 – 0.03 Hz. Our magnitude estimate is substantially smaller than the one reported, e.g., by Global CMT, suggesting that a significant part of the moment has been released at lower frequency as a slow slip process. It is verified by a W-phase inversion in the frequency band 0.005 - 0.01 Hz with a resulting magnitude Mww of 8.0. The iterative deconvolution and stacking method (IDS) resolves high slip patches located in the area of the two mainshock centroids. High-frequency back-projection results confirm the unilateral southward rupture propagation. Complex fault and slab geometries do not significantly improve the fit, providing no clear evidence for the activation of secondary faults. Centroid moment tensors, estimated for 87 aftershocks between August 12, 2021 and August 31, 2021, support the identification and characterization of activated fault segments.
Progress towards an international comparison of river sediment pollution: Key factors influencing metal concentrations along seven Western European Rivers (1945-2020)
Authors: Dendievel André-Marie , Grosbois Cécile , Ayrault Sophie , Evrard Olivier , Coynel Alexandra , Debret Maxime , Gardes Thomas , Euzen Cassandra , Schmitt Laurent , Chabaux François , Winiarski Thierry , van Der Perk Marcel , Mourier Brice
Published: March 2022

Since 60 years, a large amount of data has been acquired to survey river sediment quality, especially concerning regulatory trace metals such as Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Large-scale syntheses are still rare and show some limits to assess the effectiveness of public regulations and the river systems' resilience. Based on a sediment contamination database comprising more than 12,000 samples, we propose a first attempt to decipher spatio-temporal trends of metal contamination along seven major rivers in Western Europe (Garonne-Lot, Loire, Meuse Rhine, Rhone, Scheldt and Seine Rivers). Facing heterogeneous sampling and analytical methods on different sediment matrices (bed and flood deposits – BFD, suspended particulate matter – SPM, dated sediment cores – DSC), this work investigates the effect of analytical protocols, spatial and temporal factors on metal concentration trends. At a large scale, an increase in metal concentrations (especially for Cd, Pb and Zn) is reported along most of the investigated rivers. It appears closely related to major urban-industrial hotspots (Paris-Rouen corridor on the Seine River, Bonn-Duisburg corridor on the Rhine River, etc.) and to the geology of each watershed, both influencing the regional sediment quality. Former mining and metallurgical districts, generally located in crystalline areas, also caused high metal concentrations on the long term (Upper Loire River, Middle Meuse River, Lot River). A global decrease of metal concentrations is observed in all river sections since the 1960s-1970s onwards, in response to European and national regulations, and to socio-economical changes affecting urban-industrial areas. The high influence of the location of the samples along the rivers and the decade of sampling is confirmed by a Factor Analysis of Mixed Data (FAMD). Secondary factors such as the influence of the sediment matrix type (BFD, SPM and DSC) and the different digestion procedures prior to elemental analysis also explained significant differences for Cr, Cd, Cu, Pb, or Zn, although this can also be locally balanced by the substratum (i.e. for alkaline rivers). This approach points out the limitations of the available data, particularly regarding the need of regional geological backgrounds and the more systematic acquisition of ancillary data such as grain-size and TOC. It also provides critical clues to intercompare metal sediment pollution in rivers at large spatial and temporal scales worldwide.
Possible Contributions of Citizen Science in the Development of the Next Generation of City Climate Services
Authors: Dietrich Peter , Ködel Uta , Schütze Sophia , Schmidt Felix , Schütze Fabian , Bonn Aletta , Herrmann Thora , Schütze Claudia
Published: March 2022

Human life in cities is already affected by climate change. The effects will become even more pronounced in the coming years and decades. Next-generation of city climate services is necessary for adapting infrastructures and the management of services of cities to climate change. These services are based on advanced weather forecast models and the access to diverse data. It is essential to keep in mind that each citizen is a unique individual with their own peculiarities, preferences, and behaviors. The base for our approach is the individual specific exposure, which considers that people perceive the same conditions differently in terms of their well-being. Individual speciﬁc exposure can be defined as the sum of all environmental conditions that affect humans during a given period of time, in a specific location, and in a specific context. Thereby, measurable abiotic parameters such as temperature, humidity, wind speed, pollution and noise are used to characterize the environmental conditions. Additional information regarding green spaces, trees, parks, kinds of streets and buildings, as well as available infrastructures are included in the context. The recording and forecasting of environmental parameters while taking into account the context, as well as the presentation of this information in easy-to-understand and easy-to-use maps, are critical for influencing human behavior and implementing appropriate climate change adaptation measures.

We will adopt this approach within the frame of the recently started, EU-funded CityCLIM project. We aim to develop and implement approaches which will explore the potential of citizen science in terms of current and historical data collecting, data quality assessment and evaluation of data products.  In addition, our approach will also provide strategies for individual climate data use, and the derivation and evaluation of climate change adaptation actions in cities.

In a first step we need to define and to characterize the different potential stakeholder groups involved in citizen science data collection. Citizen science offers approaches that consider citizens as both  organized target groups (e.g., engaged companies, schools) and individual persons (e.g. hobby scientists). An important point to be investigated is the motivation of citizen science stakehoder groups to sustainably collect data and make it available to science and reward them accordingly. For that purpose, strategic tools, such as value proposition canvas analysis, will be applied to taylor the science-to-business and the science-to-customer communications and offers in terms of the individual needs.
Preliminary stochastic analysis of the Redacted Claims data set by the USA National Flood Insurance Program
Authors: Valakos Panagiotis Andreas , Papoulakos Konstantinos , Iliopoulou Theano , Dimitriadis Panayiotis , Tsaknias Dimosthenis , Koutsoyiannis Demetris
Published: March 2022

Historically, the reporting of flood disasters worldwide is impacted by large uncertainty e.g. regarding the number of the affected people, economic losses and generated flood insurance claims. In this respect, the recently published National Flood Insurance Program (NFIP) data by the Federal Emergency Management Agency (FEMA) may provide new insights into flood impacts. The data include more than two and a half million claims records dating back to 1978 and more than 47 million policy records for transactions. The aim of this research is to perform a preliminary investigation of the insurance data derived from this dataset, comprising: (a) an exploratory analysis of the dataset including normalization of the dataset by population per state and county to allow direct comparison over time and on the spatial scale; (b) a stochastic analysis regarding the detection of the underlying spatiotemporal patterns, focusing on the characterization of the dependence structure of the dataset, and (c) an initial investigation on potential climatic drivers of insurance claims patterns, e.g. large-scale indices of climate variability.
Soil geochemistry as a major driver of carbon allocation, stocks and dynamics in vegetation and soils of African tropical forests
Authors: Doetterl Sebastian , Bukombe Benjamin , Bauters Marijn , Boeckx Pascal , Cizungu Landry , Cooper Matthew , Fiener Peter , Kidinda Laurent , Makelele Isaac , Muhindo Daniel , Rewald Boris , Verheyen Kris
Published: March 2022

The net primary productivity (NPP) of tropical forests is an important component of the global terrestrial carbon (C) cycle. The lack of field-based data, however, limits our mechanistic understanding of the drivers of NPP and C allocation. In consequence, the role of local edaphic factors for forest growth and C dynamics is unclear and introduces substantial uncertainty in estimating ecosystem C stock accrual. Here, we present data from field measurements on standing biomass as well as leaf, wood, and root production collected along topographic and geochemical gradients in old-growth African tropical mountain forests in the East African Rift System. We show that forests converge towards nutrient uptake more strongly when soil properties and parent material geochemistry indicate fertility constraints due to low amounts of rock-derived nutrients. In contrast, topography did not constrain the variability in C allocation and NPP fluxes. In consequence, aboveground:belowground biomass ratios and total NPP can differ greatly between geochemical regions for similar old-growth tropical forest types. Furthermore, soil organic carbon (SOC) stocks were not related to NPP C allocation and plant C input seemingly exceeding the maximum potential of these soils to stabilize C. We conclude that even after many millennia of weathering and the presence of deeply developed soils, tropical above and belowground C allocation, as well as soil C stocks, vary substantially due to the geochemical properties which soils inherit from parent material.
What is the thermal effect of ‘blue’ in blue-green roofs? A quantitative case study on the insulative effects of blue-green roofs in Amsterdam
Authors: Föllmi Dante , Corpel Lisanne , Solcerova Anna , Kluck Jeroen
Published: March 2022

Abstract

Green roofs received increased scientific attention with respect to climate adaptation in urban environments for their hydrological, biodiversity and insulative capacities. Yet, the thermal properties of roofs with an additional water layer underneath the vegetation substrate (blue-green roofs) are not well represented in scientific research. In this field study, we examined the impact of surface temperatures, indoor temperature and insulative properties of blue-green, green, and conventional gravel/bitumen roofs in the city of Amsterdam for early 20th century buildings. Temperature sensor (IButtons) results indicate that outside surface temperatures of blue-green roofs were more stable than for conventional roofs. For instance, for three warm periods during summer (2021) surface substrate temperatures peaked much higher for gravel roofs (+8 oC) or bitumen roofs (+18 oC) than for blue-green roofs. On top of that, during a cold period in winter average water crate layer temperatures remained 3.0 oC higher and much more stable than substrate temperatures of blue-green roofs and conventional roofs, implicating that the blue layer functions as an extra temperature buffer. The effect of lower daily variation of surface temperatures in winter and summer is also reflected by inside air temperatures. Inside temperatures showed that locations with blue-green roofs are less sensitive to outside air temperatures, as daily temperature fluctuations (standard deviations) were 0.19 and 0.23 oC lower for warm and cold periods, respectively, compared to conventional roofs. This effect seems rather small but comprises a relatively large proportion of the total daily variation of 24% and 64% of warm and cold periods respectively.
Preliminary report on δ13Ccarb isotope excursion through the Silurian of Kurtuvėnai - 161 borehole, Northwest Lithuania
Authors: Želvys Tomas , Spiridonov Andrej , Cichon-Pupienis Anna , Garbaras Andrius , Radzevicius Sigitas
Published: March 2022

Lithuania is located in the eastern part of the Silurian Baltic Basin which was located near the equator during the Silurian. Kurtuvėnai -161 borehole is located in the Northwest Lithuania. The Silurian geological section of investigated interval is composed of siliciclastic and carbonate deposits and represents deep marine environments.

Samples for stable carbon isotope analysis were collected from 1441 – 1316 m depth interval. The sampling intervals range from 0.2 up to 1m. The stable carbon isotope values from carbonates were measured using Thermo Gasbench II coupled with a Thermo Delta V isotope ratio mass spectrometer.

In the investigated interval 10 graptolites biozones were distinguished: Lapworthi Biozone is distinguished in the lowest part of the section and linked to the Adavere Regional Stage (uppermost Telychian); the centrifugus - belophorus biozones mark the Jaani Regional Stage; perneri - lundgreni biozones correspond to the Jaagarahu; and parvus - nassa biozones marks the Gėluva Regional Stage of the Wenlock.

According to the δ13Ccarb isotope analysis results, a positive excursion was detected in the lower part of the studied interval from 1422.8 m up to 1390.8 m depth. There, the δ13Ccarb maximum value is 3.87 ‰. This positive δ13Ccarb anomaly can be linked to the Ireveken positive stable carbon isotopes excursion and the centrifugus – belophorus biozones interval of the lower Wenlock. We can also observe a positive δ13Ccarb excusion in the upper part of Homerian (from 1327 m depth) which potentially can be the lower part of the Mulde positive stable carbon isotopic event.

In summary, the δ13Ccarb values varied from -1.35 ‰ up to 3.92 ‰ in studied interval of Kurtuvėnai-161 borehole. A more detailed biostratigraphic and lithological study is needed for a better understanding of the integrated stratigraphy of the Silurian geological section in the Kurtuvėnai-161 borehole in the future.
Geodynamic features of the Central part of the Greater Caucasus according to GNSS observations
Authors: Milyukov Vadim , Milronov Alexey , Steblov Grigory , Drobishev Valery , Hubaev Hariton
Published: March 2022

The Central part of the Greater Caucasus, as a part of the Alpine-Himalayan mobile belt, is a zone of complex tectonics associated with the interaction of the two major tectonic plates, Arabian and Eurasian. This work presents the strain rate and spatial distribution in the Central part of the Greater Caucasus. The assessments have been done based on long-term observations on the regional GNSS network, which currently consists of 7 continuous stations and 59 campaign sites. 45 IGS stations were used as the fiducial stations in the data analysis. The strain-rate tensor is calculated using the Shen method.

The results of our study show that, in general, this region is in the state of tectonic compression over which there are some features characteristics of particular structures of the region. The Main Caucasian Ridge and the trough of the southern slope are in the state of not only submeridional compression, but also sublatitudinal extension, which leads to an intensive dilatant expansion of the eastern segment of this area. The strain pattern of the northern part of the region differs from the southern one. The northern slope of the Main Caucasian Ridge zone and the foothill trough, including the Vladikavkaz fault zone, are in the state of compression with moderate intensity. At the same time, an analysis of the distribution of earthquake epicenters has shown that the Northern branch is currently aseismic in the central and eastern parts of the Vladikavkaz fault. This geodynamic feature indicates the high seismic potential of the Vladikavkaz Fault Zone.

This work is supported by the State assignment of the Vladikavkaz Scientific Center RAS, and partly by the Russian Foundation for Basic Research, grant no. 21-55-45007.
The role of topography in the global hydrological cycle
Authors: Gnann Sebastian , Wagener Thorsten
Published: March 2022

Topography influences how water is precipitated on, evaporated from, stored in, and routed through the landscape, often because of long-term evolutionary processes. How well do we know the links between topography and hydrology at large scales? Do we use this knowledge in, for example, large scale modelling efforts, or does topographic data contain information that is currently underused? To shed light on the role of topography in the global hydrological cycle, we explore three key themes.

First, topography leads to gradients and contrasts in climatic/weather forcing. Well-known examples are orographic precipitation, rain shadowing, or the presence of snow and ice at high elevations.

Second, topography is strongly related to different landforms, such as mountains and plains. These generic landforms provide a first broad classification, but there are further properties that vary along topographic gradients in a more nuanced way, such as sediment size or the depth of the critical zone.

Third, topographically induced differences in potential energy drive water movement. This can result in surface and subsurface flow across large (horizontal) distances, providing water to distant areas, and thus decoupling local hydrology to some extent from local climate.

The three themes (often in concert) describe partial controls on large scale hydrological processes and patterns. We derive several hypotheses based on these three themes, which would improve our understanding of large-scale hydrological processes, and help us in evaluating, constraining, and building hydrological models.
Stability dependent increases in liquid water with droplet number in the Arctic
Authors: Murray-Watson Rebecca , Gryspeerdt Ed
Published: March 2022

The response of cloud properties to aerosol perturbations is one of the greatest uncertainties associated with anthropogenic climate forcing. Clouds play a central role in the Arctic surface energy budget, so understanding how aerosols influence their radiative properties is important for projecting future changes in the region. This is especially relevant as increases in temperature and reductions in sea ice extent allow for more industrial activity in the region, thereby introducing fresh sources of aerosol.  

As it is difficult to retrieve reliable satellite observations in polar regions due to issues such as high solar zenith angles, the impact of aerosols on Arctic clouds is particularly uncertain. However, by carefully filtering the satellite data to remove cases associated with retrieval biases, this work uses multiple satellite and reanalysis datasets to develop new constraints for the influence of aerosols on cloud properties.

The factors which influence the droplet number concentration-liquid water path (Nd-LWP) relationship, a key component of the aerosol-liquid water path relationship, are investigated. The Nd-LWP relationship varies significantly geographically, with increases in LWP with Nd observed at high latitudes. A range of meteorological factors are investigated, and it is shown that the lower tropospheric stability (LTS) is the driving force behind the variability in the Nd-LWP relationship in the Arctic. At high stability, the relationship is significantly more positive, producing LWP increases in more polluted environments, in contrast to the response of clouds to aerosol perturbations seen at lower latitudes.

As the Arctic warms, the boundary layer stability is projected to decrease. Additionally, industrial activity is expected to increase in the region, which may increase the aerosol burden. When considered individually, these two effects would lead to increases in LWP in marine Arctic clouds. However, when working together they may produce clouds with lower water paths, leading to a weaker negative cloud feedback in a more polluted environment. 
Sulphate source apportionment by a 10 yr-long record at Ny-Ålesund (Svalbard Islands)
Authors: Traversi Rita , Amore Alessandra , Becagli Silvia , Caiazzo Laura , Giardi Fabio , Mazzola Mauro , Severi Mirko
Published: March 2022

Gruvebadet Observatory at Ny-Ålesund (Svalbard Islands) has been recognized as a valuable facility for long-term studies of atmospheric chemistry in the High Arctic, with particular attention to natural and anthropic aerosol sources and transport processes by using chemical tracers.

A long-term study of the chemical composition of PM10 aerosol is being accomplished at Gruvebadet Observatory since 2010 by continuous collection at high resolution (1 to 2 days) and chemical analysis of major and trace ions and elements.

The contribution of different sources (sea spray, crustal, biogenic and anthropogenic) to the total sulphate budget was estimated by using specific markers (namely sodium, calcium and methanesulphonate) and their characteristic marker-to-sulphate ratios in sea water, mineral dust and marine biogenic source. The obtained data set was also compared with the one derived from the Zeppelin Observatory, also located in Ny-Ålesund.

The anthropogenic fraction resulted to be the dominant component, reaching the highest value in March and April during the Haze period, followed by the sea salt, biogenic and crustal ones. The comparison between the two datasets confirms the seasonal trend of these fractions although some differences in extent were observed, probably due to discrepancies in the timing and resolution of sampling campaigns as well as to different analytical procedures.

The temporal profile of the anthropogenic fraction, evaluated in both sites, showed no evident continuous trend from 2010 to 2019, even though higher concentrations were observed in the 2017-19 period, with respect to the previous years. Focusing on single months, two opposite trends in the sulphate budget along 10 years were observed for March against April and September. Whereas a decrease was observed in March, April and September showed an increase in the monthly mean concentration values.

Finally, the correlation between the non-sea salt non-crustal sulphate fraction and ammonium was evaluated. An increase in the ammonia neutralizing effect, eventually causing a decrease in aerosol acidity, was observed at Gruvebadet, from the 2010 to 2017, to reach fairly constant values later. Instead, a decrease in ammonia concentration was found at Zeppelin since 2015, leading to an increase of the non sea salt sulphate/ammonium ratio in the same period.
WET-CAG2021: An international comparison of absolute gravimeters for the realization of the International Gravity Reference System
Authors: Rülke Axel , Falk Reinhard , Engfeldt Andreas , Glässel Julian , Hellerschmied Andreas , Iacovone Domenico , Kostelecký Jakub , Pálinkáš Vojtech , Reich Marvin , Timmen Ludger , Ullrich Christian , Valluzzi Alessandro , Wziontek Hartmut , Zehetmaier Barbara
Published: March 2022

Geodetic observations on Earth accurate to better than a part per billion require a common reference for the same precision as described in the goals of the Global Geodetic Observing System. The International Gravity Reference System (IGRS) is proposed as a new reference for terrestrial gravity observations (Wziontek et al. 2021).

The International Gravity Reference Frame (IGRF) as the realization of IGRS is represented by absolute gravity measurements traceable to the SI. Due to the lack of a natural reference, absolute gravimeters need to be compared and the gravity reference is realized based on a set of measurements by a group of absolute gravimeters and the functional model for their processing.

We present the international comparison of absolute gravimeters WET-CAG2021 hosted at the Geodetic Observatory Wettzell in autumn 2021. This comparison is classified as an additional comparison following the strategy paper of the Consultative Committee for Mass and related quantities (CCM) and IAG. Seven FG5/X absolute gravimeters and two AQG quantum gravimeters have observed up to four individual piers over a period of twelve weeks. The individual observation epochs are connected by recordings of the continuously operating superconducting gravimeter GWR OSG 030 in the same laboratory.

We show the procedure of data analysis following Pálinkáš et al. (2021) and discuss the results also with respect to the latest regional metrological EURAMET comparison 2018 at the same location.

 

Marti, U., Richard, P., Germak, A., Vitushkin, L., Pálinkáš, V., Wilmes, H.: CCM-IAG Strategy for Metrology in Absolute Gravimetry, 11 March 2014

Pálinkáš, V., Wziontek, H., Vaľko, M. et al.: Evaluation of comparisons of absolute gravimeters using correlated quantities: reprocessing and analyses of recent comparisons. J Geod 95, 21 (2021). https://doi.org/10.1007/s00190-020-01435-y

Wziontek, H., Bonvalot, S., Falk, R. et al.: Status of the International Gravity Reference System and Frame. J Geod 95, 7 (2021). https://doi.org/10.1007/s00190-020-01438-9