bluuebunny/crossref_metadata_2025 huggingface dataset:
Interior of Jupiter in the context of Juno and Galileo: signature of a decoupling between the atmosphere and the interior
Authors: Debras Florian , Chabrier Gilles
Published: March 2021

Juno's observations of Jupiter's gravity field have revealed extremely low values for the gravitational moments that are difficult to reconcile with the high abundance of metals observed in the atmosphere by both Galileo and Juno. Recent studies chose to arbitrarily get rid of one of these two constraints in order to build models of Jupiter.

In this presentation, I will detail our new Jupiter structure models reconciling Juno and Galileo observational constraints. These models confirm the need to separate Jupiter into at least 4 layers: an outer convective shell, a non-convective zone of compositional change, an inner convective shell and a diluted core representing about 60 percent of the planet in radius. Compared to other studies, these models propose a new idea with important consequences: a decrease in the quantity of metals between the outer and inner convective shells. This would imply that the atmospheric composition is not representative of the internal composition of the planet, contrary to what is regularly admitted, and would strongly impact the Jupiter formation scenarios (localization, migration, accretion).

In particular, the presence of an internal non-convective zone prevents mixing between the two convective envelopes. I will detail the physical processes of this semi-convective zone (layered convection or H-He immiscibility) and explain how they may persist during the evolution of the planet.

These models also impose a limit mass on the compact core, which cannot be heavier than 5 Earth masses. Such a mass, lower than the runaway gas accretion minimum mass, needs to be explained in the light of our understanding of the formation and evolution of giant planets.

I will finally detail the application of our work to Saturn, and what we can expect to learn about the interior of the giant planets in the years to come. 
How does the diurnal cycle of incoming solar radiation affect self-aggregation of convective clouds?
Authors: Shamekh Sara , Muller Caroline , Duvel Jean-Philippe , Hohenegger Cathy , D'Andrea Fabio
Published: March 2021

This study investigates the impact of the diurnal cycle of incoming solar radiation on the spontaneous organization of convective clouds, hereafter self-aggregation. We run 3D cloud-resolving simulations in the RCE framework with interactive sea surface temperature (SST). SST is allowed to interact with the atmosphere using a slab ocean ( H = 1 - 200 meters) with a fixed mean but locally varying temperature. The self-aggregation of deep clouds starts with the appearance of dry patches that grow in size while getting drier, and confine the moist convention into a small fraction of the domain, consistent with previous studies of self-aggregation.

Interactive SST has been confirmed to decelerate or prevent self-aggregation. However, our finding shows that including the diurnal cycle reduces the impact of slab depth on the self-aggregation so that the aggregation proceeds much faster for shallower slabs (1,2 or 5 meters). For deeper slabs (50 and 200 meters) the self-aggregation progress is negligibly affected by the diurnal cycle. The accelerated self-aggregation with shallow slabs is found to be related to the mechanism by which the dry patches are triggered.

The triggering of dry patches is typically assumed to be a random process; however, we find that, especially with shallow ocean slabs, the dry patches form in places of cold pools. In other words, the lower tropospheric and boundary layer dryness induced by cold pools as well as surface temperature cooling by cloud shading can persist long enough to ensure a divergent flow, which was found to be important for self-aggregation. With shallow slabs, the negative SST anomaly under the cold pools thermally enhances the radiatively driven night time divergent flow and dries the boundary layer rapidly. The negative moisture anomaly persists even during daytime when the surface warms in dry regions and ensures a divergent flow, however weak, that then leads to the formation of dry patches in the following days. This process significantly accelerates the appearance of first dry patches. Moreover, this mechanism results in the occurrence of self-aggregation for shallow slabs (H=1 or 2 meters ) for which the self-aggregation does not proceed with constant solar radiation in our simulations. The enhanced divergent flow does not play a role for deep slabs as the SST anomalies are very small. Once the self-aggregation is triggered, its progress becomes negligibly affected by the diurnal cycle.
Downscaling EDGAR emissions to local emission sectors for Switzerland
Authors: Edebeli Jacinta , Spirig Curdin , Anet Julien
Published: March 2021

The fifth version of the Emission Database for Global Atmospheric Research (EDGAR 5.0) provides an impressive inventory of various pollutants. Pollutants from different emission sectors are available with daily, monthly and yearly temporal profiles at a high global resolution of 0.1°×0.1°. Although this resolution has been sufficient for regional air quality studies, the emissions appeared to be too coarse for local air quality studies in areas with complex topography. With Switzerland as a case study, we present our approach for downscaling EDGAR emission data to a much finer resolution of 0.02°×0.02° with the aim of modelling local air quality.

We downscaled the EDGAR emissions using a combination of GIS tools including QGIS, ArcGIS, and a series of python scripts. We obtained the surface coverage of different land use features within the defined EDGAR emission sectors from Open Street Map (OSM) using the QuickOSM tool in QGIS. With the calculated local surface area coverage of the emissions sectors, we downscaled the EDGAR inventory data within ArcGIS using a set of developed Arcpy script tools.

The outcome was a much finer resolved emission dataset which we fed into the WRF-CHEM air quality model within a pilot project. A comparison of the modelled pollutant concentrations using the two datasets (original EDGAR data and the downscaled data) shows an improved agreement between the downscaled dataset and the measurement data.

Studies investigating the impact of urbanization, land use change or traffic pattern on air quality may benefit from our downscaling solution, which, thanks to the global coverage of OSM, can be globally applied.
Dynamical features of the near-Hermean environment under different solar wind conditions
Authors: Milillo Anna , Alberti Tommaso , Ivanovski Stavro L. , Laurenza Monica , Massetti Stefano , Mangano Valeria , Mura Alessandro , Ippolito Alessandro , Plainaki Christina , De Angelis Elisabetta , Orsini Stefano , Rispoli Rosanna
Published: March 2021

The interaction between the interplanetary medium and planetary environments gives rise to different phenomena on several temporal and spatial scales. Here we use the Hilbert-Huang Transform (HHT) to characterize both local and global properties of Mercury's environment as seen during two MESSENGER flybys with different upstream solar wind conditions. Hence, we may infer that the near-Mercury environment presents some different local features with respect to the ambient solar wind, due to both interaction processes and intrinsic structures of the Hermean environment. Our findings support the ion kinetic nature of the Hermean plasma structures, with the magnetosheath being characterized by inhomogeneous ion-kinetic intermittent fluctuations, superimposed to both MHD fluctuations and large-scale field structure. We show that the HHT analysis allow to capture and reproduce some interesting features of the Hermean environment as flux transfer events, Kelvin-Helmholtz vortices, and ULF wave activity, thus providing a suitable method for characterizing physical processes of different nature. Our approach demonstrate to be very promising for the characterization of the structure and dynamics of planetary magnetic field at different scales, for the identification of boundaries, and for discriminating the different scale-dependent features of global and local source processes that can be used for modelling purposes.
Carbon allocation in early successional tree species at elevated air humidity and different soil nitrogen sources
Authors: Sell Marili , Ostonen Ivika , Rohula-Okunev Gristin , Rezapour Azadeh , Kupper Priit
Published: March 2021

Global climate change scenarios predict increasing air temperature, enhanced precipitation and air humidity for Northern latitudes. We investigated the effects of elevated air relative humidity (RH) and different inorganic nitrogen sources (NO3-, NH4+) on above- and belowground traits in different tree species, with particular emphasis on rhizodeposition rates. Silver birch, hybrid aspen and Scots pine saplings were grown in PERCIVAL growth chambers with stabile temperature, light intensity and two different air humidity conditions: moderate (mRH, 65% at day and 80% at night) and elevated (eRH, 80% at day and night). The collection of fine root exudates was conducted by a culture-based cuvette method and total organic carbon content was determined by Vario TOC analyser. Fine root respiration was measured with an infra-red gas analyser CIRAS 2.  

We analysed species-specific biomass allocation, water and rhizodeposition fluxes, foliar and fine root traits in response to changing environmental conditions. The eRH significantly decreased the transpiration flux in all species. In birch the transpiration flux was also affected by the nitrogen source. The average carbon exudation rate for aspen, birch and pine varied from 2 to 3  μg C g-1 day -1. The exudation rates for deciduous tree species tended to increase at eRH, while conversely decreased for coniferous trees (p=0.045), coinciding with the changes in biomass allocation. C flux released by fine root respiration varied more than the fine root exudation, whereas the highest root respiration was found in silver birch and lowest in aspen. At eRH the above and belowground biomass ratio in aspen increased, at the expense of decreased root biomass and root respiration.  

Moreover, eRH significantly affected fine root morphology, whereas the response of specific root area was reverse for deciduous and coniferous tree species. However, fine roots with lower root tissue density had higher C exudation rate. Our findings underline the importance of considering species-specific differences by elucidating tree’s acclimation to environmental factors and their interactions.   
Greenland melting signatures in model simulations and oceanic observations
Authors: Stolzenberger Sophie , Rietbroek Roelof , Wekerle Claudia , Uebbing Bernd , Kusche Jürgen
Published: March 2021

The impact of Greenland freshwater on oceanic variables in the North Atlantic has been controversially discussed in the past. Within the framework of the German research project GROCE (Greenland Ice Sheet Ocean Interaction), we present a comprehensive study using ocean modelling results including and excluding the Greenland freshwater flux. The aim of this study is whether signatures of Greenland ice sheet melting found in ocean model simulations are visible in the observations. Therefore, we estimate changes in temperature, salinity, steric heights and sea level anomalies since the 1990s. The observational database includes altimetric and gravimetric satellite data as well as Argo floats. We will discuss similarities/differences between model simulations and observations for smaller regions around Greenland in the North Atlantic. As these experiments are available for two different horizontal resolutions, we will furthermore be able to assess the effects of an increased model resolution.
Monitoring of slow-moving landslides. The importance of integration between surface and depth measurements
Authors: Godone Danilo , Allasia Paolo , Guenzi Diego , Notti Davide , Baldo Marco
Published: March 2021

In landslide monitoring, the attention is mainly focused on rapidly evolving phenomena. However, slow and very slow landslides are equally significant as they often involve settlements and infrastructures. Additionally, they are characterized by remarkable extension and depth. Due to their low displacement rate, often they are underestimated as impacting events; but in a longer timespan, their continuous and slow activity may lead to damages to buildings and roads thus worsening the living conditions of the involved area. In order to assure a peaceful coexistence between phenomena and inhabitants, a multi-source monitoring network is recommended, by integrating surface data with subsoil ones in order to better understand the whole and real kinematic. Moreover, the data acquisition rate should be high enough to detect early any increases in displacements rate. Surface monitoring approaches are extremely wide (GNSS, remote sensing, InSAR…); on the contrary subsoil measurement systems, are few and limited to in-place inclinometers. Concerning them, the Geohazard Monitoring Group (IRPI-CNR) has developed and manufactured a robotic measuring system for the acquisition of deep-seated ground deformations and, particularly, deep horizontal displacements. The instrumentation combines the advantages of the traditional measurement technique (double readings 0/180˚) with a robotized approach improving the results in terms of revisit time, repeatability and accuracy. The robotized device also called “Automated Inclinometer System” (AIS) allows the automatic check of all the length of the borehole (up to 120m tube length) with just one inclinometer probe. The traditional cable (including probe signal and power supply) is replaced with a thin polyethylene cable (φ 2mm) for sustaining and moving the probe up/down into the standard inclinometer borehole. AIS is completely automatized, but can be also controlled by a remote web interface and, with the same mean, transmits measurement results and system diagnostic messages, such as alerts, warnings, etc. The described system is, currently and extensively, employed in landslide monitoring networks in European mountain ranges obtaining interesting results. In fact, thanks to the described features it is able to rapidly define the deep and surface kinematics of the observed phenomena and, consequently, evaluate the displacements accelerations. Furthermore, due to its high-frequency measurement, it is possible to find a relationship between rainfalls/snow melting and piezometric water levels measured by nearby stations. AIS represents a trustworthy option to realize a more complete integrated network for landslide interpretation and monitoring.
Reuse of Pineapple Residue in Philippine Agriculture: determination of the net ecosystem C balance for a CAM plant in a pot-scale experiment
Authors: Macagga Reena , Vaidya Shrijana , Antonijevic Danica , Schmidt Marten , Lueck Matthias , Jancsó Mihály , Augustin Juergen , Sanchez Pearl , Hoffmann Mathias
Published: March 2021

The Philippines is one of the world’s leading producers of pineapples, wherein production is comprised mostly of small family farms that are less than 2 hectares in size. As by-product, they generate a large amount of plant residues (e.g., crowns and stems) that are commonly left at the edge of the field. This practice releases substantial amount of greenhouse gas (GHG) emissions and neglects the potential value of pineapple residue. Enabling a waste treatment by returning them to the field through incorporation or mulching holds the potential to maintain soil fertility, reduce climate impact, secure yield stability, and achieving a high resource efficiency by closing material cycles locally. It may also increase soil organic carbon stock (SOC) and reduce greenhouse gas (GHG) emissions. To date, however, the knowledge about this is still very sparse.

The rePRISING project aims to demonstrate that returning pineapple residue either through mulching or incorporation to the field may help promote the closing of nutrient-cycles (C/N/P/K) locally, thus helping to increase soil fertility and soil C sequestration, while reducing GHG emissions. Within the project, the recycling of pineapple residue together with various local organic and inorganic amendments will be studied during a two-year field experiment using the manual closed chamber method. The field study will be supplemented by pot-scale greenhouse and incubation experiments, used inter alia to determine baseline GHG emissions and carbon budgets of pineapple cultivation systems and residue treatments.

Here we present first results of a pot experiment performed during winter 2020-2021 used to develop a suitable procedure for the in-situ determination of dynamic net ecosystem C balances (NECB) for pineapple cultivation systems. This will be further utilized for upcoming field study. This is challenging in so far as pineapple plants use the Crassulacean acid metabolism (CAM photosynthesis) and the manual closed chamber method has not yet been applied to determine NECB from CAM plants.

Keywords: nutrient-cycling, carbon sequestration, greenhouse gas (GHG) emissions, pineapple residue, climate change mitigation
From sub-Rayleigh to intersonic crack propagation in snow slab avalanche release
Authors: Trottet Bertil , Simenhois Ron , Bobillier Gregoire , van Herwijnen Alec , Jiang Chenfanfu , Gaume Johan
Published: March 2021

Snow slab avalanche release can be separated in four distinct phases : (i) failure initiation in a weak snow layer buried below a cohesive snow slab, (ii) the onset and, (iii) dynamic phase of crack propagation within the weak layer across the slope and (iv) the slab release. The highly porous character of the weak layer implies volumetric collapse during failure which leads to the closure of crack faces followed by the onset of frictional contact. To better understand the mechanisms of dynamic crack propagation, we performed numerical simulations, snow fracture experiments, and analyzed the release of full scale avalanches. Simulations of crack propagation are based on the Material Point Method (MPM) and finite strain elastoplasticity. Experiments consist of the so-called Propagation Saw Test (PST). Concerning full scale measurements, an algorithm is applied to detect changes in image pixel intensity induced by slab displacements. We report the existence of a transition from sub-Rayleigh anticrack to supershear crack propagation following the Burridge-Andrews mechanism. In detail, after reaching the critical crack length, self-propagation starts in a sub-Rayleigh regime and is driven by slab bending induced by weak layer collapse. If the slope angle is larger than a critical value, and if a so-called super critical crack length is reached, supershear crack propagation occurs. The corresponding critical angle may be lower than the weak layer friction angle due to the loss of frictional resistance during volumetric collapse. The sub-Rayleigh regime is driven by mixed mode anticrack propagation while the supershear regime corresponds to a pure mode II propagation with intersonic crack speeds (v: crack speed, cs: shear wave speed, cp: longitudinal wave speed, E: slab Young's modulus and ρ: slab density). This intersonic regime of crack propagation thus leads to pure tensile slab fractures initiating from the bottom of the slab as opposed to top initiations induced by slab bending in the sub-Rayleigh regime. Key ingredients for the existence of this transition are discussed such as the role played by friction angle, collapse height and slab secondary fractures. 
Two-dimensional internal gravity wave beam instability
Authors: Harlander Uwe , Kurgansky Michael
Published: March 2021

The instability of propagating internal gravity waves is of long-standing interest in geophysical fluid dynamics since breaking gravity waves exchange energy and momentum with the large-scale flow and hence support the large-scale circulation. In this study a low-order gravity wave beam model is used to delineate the linear stability of wave beams and also to study subcritical non-modal transient instability. Assuming that the dissipation of the linearly unstable beam equilibrates with the small-scale turbulence, the model explains the constancy with the height of the amplitude of the wave beam, so that oblique wave beams can reach significant altitudes without disintegrating due to the instability that arises [1]. We further study the robustness of the transient growth when the initial condition for optimal growth is randomly perturbed [2]. It is concluded that for full randomization, in particular, shallow wave beams can show subcritical growth when entering a turbulent background field. Such growing and eventually breaking wave beams might add turbulence to existing background turbulence that originates from other sources of instability.

[1] Kurgansky and Harlander (2021) Two-dimensional internal gravity wave beam instability. Part I: Linear theory, submitted.

[2] Harlander and Kurgansky (2021) Two-dimensional internal gravity wave beam instability. Part II: Subcritical instability, submitted.
Economic benefits of establishing honeybee hives on solar parks in agricultural landscapes
Authors: Armstrong Alona , Brown Lauren , Davies Gemma , Whyatt Duncan , Potts Simon
Published: March 2021

To mitigate climate change, land take for renewable energy is accelerating at a time of increasing land use pressure and environmental degradation. Given land use change is the dominant driver of nature decline, over and above that of climate change, inclusion of local ecosystem consequences of land take for renewable energy decisions is critical. However, consideration of ecosystem impacts is hindered by lack of understanding and robust quantification methodologies. Here, we quantify the economic benefits of installing honeybee hives in solar parks by estimating the potential contribution to crop yields. We estimated that if honeybee hives were installed in all existing solar parks within England, pollination service benefits for pollinator dependent field crops, top fruits and soft fruit would have been £5.9 million in 2017, grounded in honeybee pollination crop values of £4.81-£75.04 ha-1 for field crops and £635-£10,644 ha-1 for fruit. If crop distributions were optimised to maximise solar park honeybee pollination, economic benefits could reach up to £80 million per year. However, this indicative of the maximum possible return and is unlikely to be viable given the other factors that influence crop distribution. Quantification of ecosystem co-benefits and costs of land take for renewable energy could inform location and management decisions, with the potential to improve ecosystem health in addition to energy system decarbonisation.
Heavy precipitating events in satellites and rain-gauge products over the Sahel
Authors: Sanogo Sidiki , Peyrillé Philippe , Roehrig Romain , Guichard Françoise , Ouedraogo Ousmane
Published: March 2021

The Sahel has experienced an increase in the frequency and intensity of extreme rainfall events over the recent decades. These trends are expected to continue in the future. However the properties of these events have so far received little attention. In the present study, we define a heavy precipitating event (HPE) as the occurrence of daily-mean precipitation exceeding a given percentile (e.g., 99th and higher) over a 1°x1° pixel and examine their spatial distribution, intensity, seasonality and interannual variability. We take advantage of an original reference dataset based on a rather high-density rain-gauge network over Burkina Faso (142 stations) to evaluate 22 precipitation gridded datasets often used in the literature, based on rain-gauge-only measurements, satellite measurements, or both. Our reference dataset documents the HPEs over Burkina Faso. The 99th percentile identifies events greater than 26 mm d-1 with a ~2.5 mm confidence interval depending on the number of stations within a 1°x1° pixel. The HPEs occur in phase with the West African monsoon annual cycle, more frequently during the monsoon core season and during wet years. The evaluation of the gridded rainfall products reveals that only two of the datasets, namely the rain-gauge-only based products GPCC-DDv1 and REGENv1, are able to properly reproduce all of the HPE features examined in the present work. A subset of the remaining rainfall products also provide satisfying skills over Burkina Faso, but generally only for a few HPE features examined here. In particular, we notice a general better performance for rainfall products that include rain-gauge data in the calibration process, while estimates using microwave sensor measurements are prone to overestimate the HPE intensity. The agreement among the 22 datasets is also assessed over the entire Sahel region. While the meridional gradient in HPE properties is well captured by the good performance subset, the zonal direction exhibit larger inter-products spread. This advocates for the need to continue similar evaluation with the available rain-gauge network available in West Africa, both to enhance the HPE documentation and understanding at the scale of the region and to help improve the rainfall dataset quality.
Neural Partial Differential Equations for Simple Climate Models 
Authors: Gelbrecht Maximilian , Boers Niklas , Kurths Jürgen
Published: March 2021

When predicting complex systems such as parts of the Earth system, one typically relies on differential equations which can often be incomplete, missing unknown influences or higher order effects. By augmenting the equations with artificial neural networks we can compensate these deficiencies. The resulting hybrid models are also known as universal differential equations. We show that this can be used to predict the dynamics of high-dimensional chaotic partial differential equations, such as the ones describing atmospheric dynamics, even when only short and incomplete training data are available. In a first step towards a hybrid atmospheric model, simplified, conceptual atmospheric models are used in synthetic examples where parts of the governing equations are replaced with artificial neural networks. The forecast horizon for these high dimensional systems is typically much larger than the training dataset, showcasing the large potential of the approach. 
Detecting coastal change around the North Sea from open-source satellite images
Authors: Fenwick Freya , Price Timothy , Ruessink Gerben
Published: March 2021

Wave-dominated sandy coastlines worldwide are susceptible to change under the expected climate-change induced developments in sea level rise, mean wave conditions and storm events. For coastal management it remains important to observe and quantify these coastal changes, especially in low-lying developed coastal areas susceptible to flooding. The beaches surrounding an ocean basin have a variety of orientations, tidal ranges and management strategies, to name a few, which will lead to a range of morphological responses to future changes in hydrodynamic conditions within the basin. In addition, the conditions under which these varied responses mainly occur (e.g., under regular conditions or only during storm conditions) is not clear. Here, we used satellite imagery to compare the morphological response of a selection of beaches surrounding the North Sea.

The position of the shoreline is generally considered as a key variable to monitor the morphological evolution of sandy coasts. This research used the open-source software toolkit CoastSat (Vos et al., 2019) to automatically map shorelines from publicly available satellite imagery from 1984 to present, which are retrieved via Google Earth Engine (Gorelick et al., 2017). We selected five long, sandy beaches around the North Sea with varying tidal ranges, orientations and wave exposure for our analysis: (1) Skallingen in Denmark, (2) Egmond aan Zee and (3) the barrier island of Schiermonnikoog, both in the Netherlands, (4) Groenendijk in Belgium, and (5), Theddlethorpe in the UK. Approximately 2000 images per site were used for the shoreline extraction. Offshore wave buoy measurements and numerical model output provided the tidal water levels and wave conditions for the different sites. To account for tidal correction of the shoreline to a reference elevation, we used the dataset of Athanasiou et al. (2019) to estimate characteristic beach face slopes. At the conference we will present our analysis of the shoreline responses around the North Sea over the last few decades.

Athanasiou, P., Van Dongeren, A., Giardino, A., Vousdoukas, M., Gaytan-Aguilar, S., & Ranasinghe, R. (2019). Global distribution of nearshore slopes with implications for coastal retreat. Earth system science data, 11(4).

Gorelick, N., Hancher, M., Dixon, M., Ilyushchenko, S., Thau, D., & Moore, R. (2017). Google Earth Engine: Planetary-scale geospatial analysis for everyone. Remote sensing of Environment, 202, 18-27.

Vos, K., Splinter, K. D., Harley, M. D., Simmons, J. A., & Turner, I. L. (2019). CoastSat: A Google Earth Engine-enabled Python toolkit to extract shorelines from publicly available satellite imagery. Environmental Modelling & Software, 122, 104528.
Progressive landscape transformation from a fluvial to a glacial topography
Authors: Liebl Moritz , Robl Jörg , Egholm David , Prasicek Günther , Stüwe Kurt , Gradwohl Gerit , Hergarten Stefan
Published: March 2021

Mid-latitude mountain ranges such as the Eastern Alps are characterized by a strong topographic imprint of Pleistocene glaciations. The characteristic geometry of glacial landforms has been quantified in various ways, but studies about the evolution of glacial landscape metrics are lacking. However, such information is needed to interpret the evolutionary state of glacial topography.

By employing a landscape evolution model for cold climate processes, we trace the fluvial-to-glacial transformation of a synthetic landscape. Our simulations inspired by alpine glaciations of mid-latitude mountain ranges with peaks and ridges towering above the glacier network lead to a general increase in relief. This is expressed as the formation of overdeepened valleys with steepened flanks. Overdeepening starts at the glacier front and progressively extends upstream with ongoing glacial erosion.

The topographic signature of the progressively transforming landscape is characterized by an increase of mean channel slopes and its variance. However, above the steep flanks, the initial fluvial topography is persisting. Whereas the initial fluvial mountain range is characterized by a monotonic increase of channel slope with elevation, a transition from increasing to decreasing channel slope with elevation emerges above the equilibrium line altitude where (tributary-)headwalls transition to ridges and summits. This turning point and a high slope variance becomes progressively distinctive with ongoing glacial occupation.

By comparing landscape metrics derived from model time series with those of the Eastern Alps, we found that the temporal transition observed in our numerical experiments occur as spatial transition from the fully glaciated western to a minorly glaciated eastern part of the Alps. Thus, slope-elevation plots serve as a diagnostic tool for interpreting the glacial - fluvial influence in mountain landscapes. However, catchments of the unglaciated part of the Eastern Alps show also turning points in their slope-elevation distributions, but the variance of slope is significantly smaller at all elevation levels, when compared to the glaciated part.
Modelling the climate change impact on the largest White Sea estuarine areas
Authors: Panchenko Evgeniya , Alabyan Andrei , Krylenko Inna , Lebedeva Serafima
Published: March 2021

Possible sea level rise and changes in hydrological regime of rivers are the major threats to estuarine systems. The sensibility of hydrodynamic regime of the Northern Dvina delta and the Onega estuary under various scenarios of climate change has been investigated. Hydrodynamic models HEC-RAS (USA, US Army Corps of Engineers Hydrologic Engineering Center) and STREAM_2D (Russia, authors V.Belikov et.al.) were used for analysis of estuarine flow regime (variations of water levels, discharges and flow velocities throughout tidal cycles). Input runoff changes were simulated for different climate scenarios using ECOMAG model (Russia, author Yu.Motovilov) based on data of global climate models (GSM) of CMIP5 project for the White Sea region.

ECOMAG modelling has demonstrated that the maximum river discharges averaged for 30-year period 2036 – 2065 can reduce for about 20 – 27% for the Onega and 15 – 20% for the Northern Dvina river compared against the historical period 1971 – 2000.Averaged minimum river discharges can reduce for about 33 – 45% for the Onega and 30 – 40% for the Northern Dvina.

The White Sea level rise by 0.27 m in average (with inter-model variation from 0.20 to 0.38 m) can took place by the middle of the XXI century according to input data of GSM models. The 12 scenarios of estuarine hydrodynamic changes were simulated for the both rivers based on combining river runoff changes and sea level elevation.

In general, the expected flow changes are negative for the local industry and population. According to modelling results for ‘high runoff/spring tide’ scenarios the flooding area in the Northern Dvina delta will increase by 13-20% depending on the intensity of sea level rise. In the low water seasons the distance from the river mouth to the upper boundary of the reach, where reverse currents can be observed, will move upstream by 8 - 36 km depending of sea/river conditions due to decrease in minimum river runoff. It may adversely effect on shipping conditions at the city of Arkhangelsk and on brackish water intrusion up-to industrial and communal water intakes.

The reverse currents also will intensify in the Onega estuary (tidal flow velocities increase for 11 – 19%) that leads to the change of the sediment regime and can significantly deteriorate the navigation conditions at the seaport of the Onega town. The problem of the intensification of salt intrusion can arise there as well.

The research was supported by the Russian Foundation for Basic Research (Projects No. 18- 05-60021 in development of the scenarios; No. 19-35-90032 in providing hydrodynamic modelling of the Onega; Project No. 19-35-60032 in providing hydrodynamic modelling of the Northern Dvina).
Star dunes: Global distribution, characteristics and formation
Authors: Herzog Manuel , Bubenzer Olaf
Published: March 2021

The distribution, characteristics and formation of mega-dune forms (esp. star dunes) is, compared to smaller dune forms, for example barchans and linear dunes, much more complex and still poorly investigated. Although occurring globally nearly in all sand seas (ergs), due to their location in often remote and hyper-arid environments and their complexity, they are highly underrepresented in recent research. Last methodological research and reviews, apart from regional case studies (e.g. Zhang et al. 2016), were published decades ago (e.g. Lancaster 1989). In consequence, definitions and development theories remain more or less constant over time, describing star dunes of pyramidal shape with three to four arms, of significant size and mostly situated in depositional centers. Recognized by most researcher, their formation seems to be bound to a regional wind system with a high directional variability by concurrent and sufficient sediment availability. However, a modern assessment of the global star dune distribution is missing.

Therefore, we will present first results of an analysis of global star dune occurrence and distribution via freely available and also highly resolute satellite data provided by Google Earth and ESRI base map services in order to summarize their locations, morphometric characteristics as well as their environmental setting and to explore similarities and differences. Overall, an assessment of a global star dune inventory can lead to a more precise morphometric description, definition, and a better comparison of these dune forms and therefore can contribute to a better understanding of their evolution.

Lancaster, N. (1989). Star dunes. Progress in Physical Geography 13, 67-91.

Zhang, W., Qu, J., Tan, L., Jing, Z., Bian, K. and Niu, Q. (2016). Environmental dynamics of a star dune. Geo­morphology 273, 28-38.
Comparing machine learning metamodels of different scale for pasture nitrogen response rate prediction
Authors: Pylianidis Christos , Snow Val , Overweg Hiske , Athanasiadis Ioannis N.
Published: March 2021

In this work we compare the performance of machine learning metamodels of different scale for the prediction of pasture grass nitrogen response rate using a case study across different locations in New Zealand. We first used a range of soil, plant and management parameters known to affect grass growth and/or nitrogen response. These generated a complete factorial that enabled us to run virtual nitrogen response rate experiments, using the APSIM simulation model, in eight locations around the country. We included 40 years of weather data to capture the effect of weather variability on response rate. This created a large database with which to train machine learning models. We created local, regional, and nation-wide models using Random Forest and tested them on known and unknown locations. To evaluate the models, we first calculated the RMSE, MAE and R2 and then determined if the distributions of the predictions were statistically different using the Mann-Whitney U test. Finally, we explore the generalizability of the models using the error metrics and the results of the statistical test.
Pacific CO2 fluxes pattern analysis through SST clustering
Authors: Vaittinada Ayar Pradeebane , Tjiputra Jerry
Published: March 2021

Elucidating the coherent spatio-temporal patterns of historical ocean CO2 fluxes is an essential step to understand the dominant drivers of their variability and predict how they may be altered by future climate change. Here, we applied an unsupervised classification of SST to tease out and assess the spatial and temporal variability of marine CO2 uptake in the Pacific basin. The classification is performed using a Gaussian Mixture Model (GMM) that decomposes the Probability Density Function of a dataset into a weighted sum of Gaussian distribution. Classification is performed on monthly SST anomalies from the JRA-55 reanalysis and CMIP6 historical simulations. The associated patterns of CO2 fluxes anomalies in both observations and models are evaluated for consistencies. Our objective is to determine the ability of the GMM-based clustering method, applied on surface temperature, to retrieve relevant physical mechanisms that predominantly explain the observed spatial and temporal CO2 fluxes patterns. The evolution of these clustering-based patterns, as projected by the models, under future scenario will also be presented.
Large-scale scour in response to tidal dominance in estuaries
Authors: Leuven Jasper , van Keulen Daan , Nienhuis Jaap , Canestrelli Alberto , Hoitink Ton
Published: March 2021

Channel beds in estuaries and deltas often exhibit a local depth maximum at a location close to the coast. There are two known causes of large-scale (i.e. >10 river widths along-channel) channel bed scours: width constriction and draw down during river discharge extremes, both creating a local flow acceleration. Here, we systematically investigate a potential third mechanism. We study the effect of tidal dominance on the equilibrium channel bed in estuaries with a 1D-morphodynamic model. In estuaries, a morphodynamic equibrium is reached when the net (seaward) transport matches the upstream supply along the entire reach. The residual (river) current and river-tide interactions create seaward transport. Herein, river-tide interactions represent the seaward advection of tide-induced suspended sediment by the river flow. Tidal asymmetry typically creates landward transport. The main reason for scour formation is the amplification of tidal flow through funnelling of tidal energy. Only for a scouring profile the drop in river induced current magnitude reduces the river-tide interaction term, so that the net sediment transport matches the upstream sediment transport. When tidal influence is relatively large, and when channel convergence is strong, a equilibrium is only obtained with a scouring profile. We propose a predictor dependent on the width convergence, quantified as SB, and on the ratio between the specific peak tidal discharge at the mouth and the specific river discharge at the landward boundary (qtide/qriver). Scours develop if (qtide/qriver)/SB exceeds 0.3. These results are independent of scale and allow the prediction of scour in estuaries under future changes.
The impact of liquid organic fertilization and associated application techniques on N2 and N2O fluxes from agricultural soils
Authors: Grosz Balázs , Well Reinhard , Burkart Stefan
Published: March 2021

Fertilizing arable soils with liquid manures affects gaseous N losses to the atmosphere including NO, N2O and N2 as well as nitrate leaching. These emissions impair nitrogen use efficiency of crops and contribute to the greenhouse effect and stratospheric ozone destruction and pollution of aquatic resources. Their extent depends on the complex interaction between manure application techniques and properties of manures and soil. Whereas the types of manure effects on N transformations and associated gaseous fluxes are known, their prediction is still poor because previous investigations mostly excluded N2 flux.

Our mesocosm experiment addresses the questions, (1) how liquid manure fertilization and its application mode impact N2, N2O and CO2 fluxes from agricultural soil, and (2) how the water and dissolve organic carbon content and the pH of the manure amended soil change between the soil layers. We use these data to set up a dataset to test and develop new biogeochemical model approach to describe the manure-soil interactions.

A sandy arable soil (Fuhrberg, Germany) was used for the experiments and amended with artificial slurry (artificial liquid and cow digestate mixture) in various treatments. The soil was incubated in laboratory incubation systems over 10 days. N2, N2O and CO2 fluxes were quantified by gas chromatography and isotope-ratio mass spectrometry. Incubations were conducted with (surface or injected application) or without (control) of slurry treatment and initial water content was adjusted equivalent to 40% and 60% water-filled pore space. The environmental conditions were kept constant during that experiment.

The average N2+N2O flux decreased at the 40% WFPS surface and injected treatments with 70% and 60%, respectively, compared to the non-fertilized control. For the 60% WFPS surface and injected treatments, the average N2+N2O flux increased with more than 610% and 1690%, respectively. The results show that the initial water content and the application method can influence drastically the N2+N2O flux of the manure amended soil.
Examination and Enhancement of solar radiation pressure model for BDS-3 satellites
Authors: Li Jie , Yuan Yongqiang , Huang Shi , Liu Chengbo , Lou Jiaqing , Li Xingxing
Published: March 2021

With the successful launch of the last Geostationary Earth Orbit (GEO) satellite in June 2020, China has completed the construction of the third generation BeiDou navigation satellites system (BDS-3). BDS-3 global services have been initiated in July 2020 with the constellation of 3 GEO, 3 Inclined Geosynchronous Orbit (IGSO) and 24 Medium Earth Orbit (MEO) satellites. In order to further improve the performance of BDS-3 services, the quality of BDS-3 precise orbit product needs further enhancements.

       The solar radiation pressure (SRP) is the main non-conservative orbit perturbation for GNSS satellites and is the key to improve BDS-3 precise orbit determination. In this study, we focus on the SRP models for BDS-3 satellites. Firstly, the widely used Extended CODE Orbit Model with five parameters (ECOM-5) is assessed. With one-year observations of 2020 from both iGMAS and MGEX networks, the five parameters of ECOM model (D0, Y0, B0, Bc and Bs) are estimated for each BDS-3 satellite. The D0 estimates show an obvious dependency on the elevation angle of the Sun above the satellite orbital plane (denoted as β). In addition, large variations can be noticed in eclipse seasons, which indicate the dramatic changes of SRP. The Y0 estimates vary from -0.6 nm/s2 to 0.6 nm/s2 for MEO, -1.0 to 1.0 nm/s2 for IGSO and -1.0 to 1.5 nm/s2 for GEO satellites. The B0 estimates of several satellites exhibit a clear dependency on the β angle. The largest variation of B0 appears at C45 and C46, changing from 1.0 nm/s2 at 15 deg to 8.3 nm/s2 at 64 deg, which implies that the solar panels of these two satellites may have an obvious rotation lag. To compensate the deficiencies of BDS-3 SRP modeling, we introduce several additional parameters into ECOM-5 model (e.g. introducing higher harmonic terms). The POD performances can be improved by about 10% and 40% for BDS-3 MEO/IGSO and GEO satellites, respectively.

       Except for the empirical model, we also study the semi-empirical SRP model such as the a priori box-wing model. Since the geometrical and optical properties from BDS-3 metadata are general and rough, we apply more detailed geometrical and optical coefficients for BDS-3 satellites. The POD performance can be improved by about 10% compared to empirical SRP models. Furthermore, considering Earth radiation pressure will have an impact of about 1.3 cm in radial component for MEO satellites.
Sea-ice freeboard or thickness? Design choices in the context of data assimilation in the coupled numerical prediction system EC-Earth3 for seasonal Arctic sea ice prediction
Authors: Massonnet Francois , Fleury Sara , Garnier Florent , Blockley Ed , Ortega Montilla Pablo , Acosta Navarro Juan C. , Ponsoni Leandro , Klein François
Published: March 2021

It is well established that winter and spring Arctic sea-ice thickness anomalies are a key source of predictability for late summer sea-ice concentration. While numerical general circulation models (GCMs) are increasingly used to perform seasonal predictions, they are not systematically taking advantage of the wealth of polar observations available. Data assimilation, the study of how to constrain GCMs to produce a physically consistent state given observations and their uncertainties, remains, therefore, an active area of research in the field of seasonal prediction. With the recent advent of satellite laser and radar altimetry, large-scale estimates of sea-ice thickness have become available for data assimilation in GCMs. However, the sea-ice thickness is never directly observed by altimeters, but rather deduced from the measured sea-ice freeboard (the height of the emerged part of the sea ice floe) based on several assumptions like the depth of snow on sea ice and its density, which are both often poorly estimated. Thus, observed sea-ice thickness estimates are potentially less reliable than sea-ice freeboard estimates. Here, using the EC-Earth3 coupled forecasting system and an ensemble Kalman filter, we perform a set of sensitivity tests to answer the following questions: (1) Does the assimilation of late spring observed sea-ice freeboard or thickness information yield more skilful predictions than no assimilation at all? (2) Should the sea-ice freeboard assimilation be preferred over sea-ice thickness assimilation? (3) Does the assimilation of observed sea-ice concentration provide further constraints on the prediction? We address these questions in the context of a realistic test case, the prediction of 2012 summer conditions, which led to the all-time record low in Arctic sea-ice extent. We finally formulate a set of recommendations for practitioners and future users of sea ice observations in the context of seasonal prediction.