bluuebunny/crossref_metadata_2025 huggingface dataset:
Validation of seasonal time series of remote sensing derived LAI for hydrological modelling
Authors: Wirion Charlotte , Verbeiren Boud , Sterckx Sindy
Published: March 2020

In urban environments, due to climate change urban heat waves are predicted to occur more frequently. Urban vegetation and the linked evapotranspiration rate can play a mitigating role. However, a major challenge in urban hydrological modelling remains the mapping of vegetation dynamics and its role in hydrological processes in particular interception storage and evapotranspiration. Conventional mapping of vegetation usually implies intensive labor and time consuming field work. We explore the potential of different remote sensing sensors (Proba-V, Landsat, Sentinel2, Apex) to characterize the urban vegetation dynamics for hydrological modelling. The here proposed remote sensing sensors show differences in the spectral and spatial resolutions as well as in their revisit time. However, in the urban environment we need a high spatial and spectral resolution to distinguish the urban landcover and a frequent revisit time to capture seasonal vegetation dynamics. Therefore, we propose a combination of different remote sensing sensors to derive leaf area index (LAI) timeseries in the urban environment. To improve the consistency in time series generated from different remote sensing sources a harmonization of the multi-sensor time series is proposed and validated with a multi-resolution validation approach using ground-truthing LAI (BELHARMONY project). The LAI timeseries, derived from the different remote sensing sensors, are then introduced into the hydrological modelling framework for a location- and time- specific assessment of the interception storage and evapotranspiration component. The effect of the sensor differences to the LAI timeseries on the hydrological response is analyzed.
A new free drift sea ice velocity dataset for improved representations of ice drift trajectories
Authors: Brunette Charles , Tremblay Bruno , Newton Robert
Published: March 2020

Previous work shows that tracking the motion of sea ice in a Lagrangian framework can be used to produce skillful seasonal forecasts of sea ice at the pan-Arctic scale (Williams et al. 2016) and at the regional scale (Brunette et al. 2019) and can also be used to analyze socio-environmental impacts related to sea ice circulation (Newton et al. 2017). However, the Polar Pathfinder sea ice motion dataset from the National Snow and Ice Data Centre (Tschudi et al. 2019), which is commonly used for calculations of ice drift trajectories, contains biases in sea ice drift speed and angle. The bias is particularly strong in the summer when less satellite drift-vectors are available, and the Polar Pathfinder composite product relies more heavily on poorly-constrained free drift estimates (ice motion in response to wind forcing and ocean drag in the absence of internal stresses), that have up to a 60% low speed bias when compared to buoy drifts. These free drift estimates are notoriously ill-constrained, since information on the ocean forcing from below and lateral forces within the ice pack are lacking. To improve the quality of ice motion estimates in the summer, we propose to compile a new free drift sea ice motion dataset, based on surface winds from ERA-Interim and calibrated on drifting buoys from the International Arctic Buoy Program. We include dependencies of free drift velocity on sea ice concentration and thickness, which will improve the representation of temporal and spatial variability of sea ice in a free drift regime. We present work on the parameterization of an ice state dependent transfer coefficient between wind velocity and ice velocity, and estimates of the near surface oceanic currents that are necessary to constrain ice motion.
Stepwise improvement of hydrological model concepts using satellite based evaporation and total water storage estimations
Authors: Hulsman Petra , Savenije Hubert , Hrachowitz Markus
Published: March 2020

Traditionally, rainfall runoff models are calibrated on discharge observed at the basin outlet. This may result in accurate flow predictions, but not necessarily correctly represent internal processes in space and time; especially in poorly gauged regions where limited ground observations are available. More and more satellite observations become available which can be valuable for model development and calibration to improve the representation of internal processes in space and time. In this study, satellite based evaporation and total water storage observations were used to improve, in a stepwise analysis, the structure of a hydrological model and the selection of feasible parameter sets. For this purpose, a semi-distributed rainfall runoff model, accounting for sub-grid process heterogeneity, was developed for the poorly-gauged Luangwa River basin in Zambia. As benchmark, this model was calibrated with respect to observed discharge. Then, the model was modified by (1) including upwelling groundwater in low-elevation parts of the landscape close to the river, depending on the water availability in the (un-) saturated zone and (2) adjusting the spatial representation of the groundwater. Next, each model was calibrated to all variables simultaneously with respect to discharge, evaporation and total water storage. In the benchmark case, calibrated on discharge only, the model reproduced the discharge well, but failed to provide an adequate spatiotemporal representation of evaporation and total water storage, especially in wetland dominated areas. Overall model performance improved most when including upwelling groundwater as a function of the saturated zone and when calibrating on all variables (discharge, evaporation and total storage) simultaneously. Hence including satellite based data on evaporation and total water storage improved model structure development and identifying feasible parameter sets.
Remarks on the micro-earthquake detection problem: Refining the outcome using stochastic modeling
Authors: Lois Athanasios , Kopsaftopoulos Fotis , Giannopoulos Dimitrios , Polychronopoulou Katerina , Martakis Nikos
Published: March 2020

Methodologies dealing with the detection of micro-earthquakes and the accurate estimation of body waves’ arrival time constitute, during the last decades, a topic of ongoing research. The extraction and efficient analysis of the useful information from the continuous recordings is of great importance, since it is a prerequisite for reliable interpretations.  Small magnitude seismic events, either naturally-occuring or induced, have been increasingly used in a wide range of industrial fields, with applications ranging from hydrocarbon and geothermal reservoir exploration, to passive seismic tomography surveys.

A great number of algorithms have been proposed and applied up to now for seismic event detection, exploiting specific properties of the seismic signals both in time and in frequency domain, with the energy-based detectors (STA/LTA) to be the most commonly used, due to their simplicity and the low computational cost they require. A significant obstacle emerging at seismological identification problems lies on the fact that such processes usually suffer from a number of false alarms, which is significantly increased in extremely noisy environments.

For that scope, we propose a “Decision-Making” mechanism, independent of the applied detection algorithm, which controls the results obtained during the detection process by minimizing false detections and providing the best possible outcome for further analysis. The specific scenario is based on the comparison among autoregressive models estimated on isolated seismic noise recordings, as well as on the detected intervals that resulted during the event identification procedure. A number of examples, associated with the implementation of the proposed scenario on real data, is presented with the scope of evaluating its performance. Several issues concerning the isolation of the seismic noise from the raw data, the estimation of the autoregressive models, the choice of the orders of the stochastic models etc., are discussed.
Soil organic matter build-up during soil formation in glacier forefields around the world
Authors: Khedim Norine , Cécillon Lauric , Poulenard Jérome , Barré Pierre , Baudin François , Marta Silvio , Gielly Ludovic , Ambrosini Roberto , Rabatel Antoine , Dentant Cédric , Cauvy Sophie , Anthelme Fabien , Tielidze Levan , Messager Erwan , Choler Philippe , Ficetola Francesco
Published: March 2020

Due to the continued ice retreat with global warming, areas of deglaciated forefields will strongly increase in the future, leading to the emergence of new terrestrial ecosystems in many regions of the world. The soil chronosequences resulting from glacier retreat have long been a key tool for studies focusing on the mechanisms of soil formation and soil organic matter storage.

This study aimed at identifying general patterns in soil organic matter (SOM) build-up during the initial stage of soil formation and ecosystem development (0–500 years) in different glacier forefields around the world. For this purpose, we measured total soil organic matter concentration (C and N), its stable isotopic composition (13C, 15N) and its distribution in carbon pools of different biogeochemical stability over time in ten soil chronosequences on glacier forefields (four Andeans, one Canadian Rockies, one Greenland, two Alps, one Caucasus, one Himalaya). The distribution of SOM in carbon pools was estimated with Rock-Eval® thermal analysis. We then tested the effect of time and climatic variables (temperature, precipitation) on the build-up of soil organic matter (total concentration, isotopic signature and distribution in carbon pools).

We found a positive correlation between the rate of SOM accumulation and the average temperature of the warmest quarter (three-month period). We also noted significant traces of atmospheric deposition of anthropogenic origin in some forefield glaciers, particularly in the northern hemisphere. The build-up of soil carbon pools showed consistent trends across the soil chronosequences of the ten glacier forefields. During the first decades of soil formation, the very low SOM quantities were dominated by a very stable carbon with a small but significant labile carbon pool. This may highlight the presence of organic matter derived from ancient carbon on the different forefield glaciers, decomposed by an active living trophic network of soil microorganisms. The overall stability of SOM then slowly decreased with time, reflecting the soil carbon input from plants.

We conclude that while the rate of SOM accumulation is driven by climate (air temperature of the growing season), the build-up of soil carbon pools shows a consistent temporal trajectory on the different glacier forefields around the world.
Micronutrient export from glacier to fjord, southwest Greenland: potential impacts on open ocean primary productivity
Authors: Ward Rachael , Hendry Kathrine , Wadham Jemma L. , Hawkings Jon R. , Sherrell Robert M. , Annett Amber
Published: March 2020

The accelerated melting of the Greenland Ice Sheet could potentially enhance fluxes of key nutrients, to the surrounding oceans, impacting marine biogeochemical processes and ecosystems. Iron (Fe) is one key micronutrient for marine phytoplankton that may be affected by this increase in meltwater flux, with high export of dissolved and particulate Fe from glacial meltwaters into fjords and a potentially significant increase in the supply of labile and potentially bioavailable Fe to the Greenlandic shelf. However, biogeochemical processing within estuarine-like fjord systems may result in depletion of nutrients, acting as a sink of micronutrients before they can reach the coastal ocean. The extent to which glacially derived micronutrients, specifically Fe, reach coastal waters remains an unanswered question.

Here, we address this question by assessing the concentration of dissolved (<0.45 µm) and labile particulate (determined using the Berger leach) bio-essential trace metals (Fe, Cd, Mn, Ni, Cu, Zn) in two contrasting glaciated fjords in southwest Greenland; one fed predominantly by marine terminating glaciers and the other by a land terminating glacier. We investigate the difference in size fractionated concentrations between fjords and the transport of these metals from stations close to glacial termini down to the fjord mouths. Our findings reveal that each micronutrient exhibits a distinctive behaviour, with some metals enhanced in meltwaters (e.g. dissolved Fe and Mn) and some depleted (e.g. dissolved Cd), relative to marine waters. The spatial variability in our dataset highlights that concentration of Fe and other trace metals (Cd, Mn, Ni, Cu, Zn) enriched in meltwaters become depleted towards the mouth of the fjords, with non-conservative loss from surface waters. Despite this depletion, the concentrations of these metals in waters that reach the coastal zone are significantly higher than typical surface ocean values, both in dissolved and labile particulate form. These data can ultimately be used in combination with a physical understanding of the fjord systems to constrain the capacity of fjords to enhance productivity downstream and deliver micronutrients into coastal and open ocean systems. Furthermore, the direct comparison of land- and marine-terminating glacial fjords could provide valuable information on the potential future impact of retreating glacial systems with enhanced melting.
A narrow plume conduit anchored in the lower mantle beneath la Réunion hotspot
Authors: Dongmo wamba Mathurin , Romanowicz Barbara , Montagner Jean-Paul , Barruol Guilhem
Published: March 2020

The arrival of some plumes and the birth of hotspots at the Earth surface have broken up the Pangea in many continents 200 Ma ago. La Réunion hotspot is known as one of the largest on the Earth. Its birth, 65Ma ago, creating the Deccan volcanic traps in India (almost 2 million km2) and the death of more than 90% of life on the Earth including dinosaurs. So far the origin of the mantle plumes and their role in geodynamics are still controversial in Earth sciences. In that respect, we use the dataset from the French-German RHUM-RUM experiment around La Réunion hotspot (2012-2013), from IRIS data center and FDSN to investigate the deep structure of the plume along its complete track from its birth to its present stage. The use of spectral element method allows us to perform forward modelling for several thousand paths across the Indian ocean. The sensitive matrix (first order approximation of the Hessian matrix) is built from the coupling of normal modes along and across the branches, by using nonlinear asymptotic theory. This waveform inversion approach enables us to resolve deep anomalies in the mantle underneath Indian ocean. So far we found out a low velocity zone channel (extended from the west to the east) in the upper mantle beneath the Mascarene bassin, and plume conduit with a broad head in the upper mantle and narrow tail anchored in the lower mantle. The connection between la Réunion hotspot and the African LLSVP is also brought to light by our model.
Partitioning between strike-slip and orthogonal extension in the western South China Sea
Authors: Luo Pan , Ren Jianye , He Xi , Lei Chao , Xu Junjie , Manatschal Gianreto , Kusznir Nick , Chao Peng
Published: March 2020

Our study focuses on the Zhongjianna (ZJN) (Phu Kham) Basin, located at the western termination of the South China Sea (SCS) and separated from the Indochina continent by the N-S striking East Vietnam Boundary Fault Zone, which is a large scale strike-slip fault system. The sedimentary infill history of the ZJN basin records the complete evolution and interaction of the Indochina-SCS system and allows the tectonic and kinematic evolution of the basin to be understood.. The discovery of hyper-extended continental crust and mantle exhumation in this basin leads to the question of what is the relative role of large-scale strike-slip and orthogonal faulting in controlling crustal thinning in the ZJN basin.  

  Our preliminary results confirm the existence of hyperextended continental crust flooring the ZJN basin. Two different types of structures can be identified in this area: extension related deformation in the eastern part and strike-slip related deformation in the western part. The analysis of fault geometries and kinematics linked to timing and subsidence rates suggest that the N-S-orientated strike-slip structures dominated the continental shelf and slope area on the west side of the basin. In the basin, however, most faults strike NE-SW and are parallel to the mid-ocean ridge. Thus, it appears that the ZJN basin resulted from the partitioning between strike-slip and orthogonal extension.

In our presentation we show the results of our seismic interpretation, strain and subsidence analysis and discuss the interaction between strike-slip and orthogonal extension in setting up the hyper-extended ZJN basin and its implications for the large scale tectonic and geodynamic framework.
Combining concentration–discharge relationships with mixing models
Authors: Tallec Gaëlle , Tunqui Neira José Manuel , Vazken Andréassian , Mouchel Jean-Marie
Published: March 2020

Discharge is one of the major factors influencing the evolution of solute concentration in river water. Different modeling approaches exist to characterize the dependency of concentration on discharge: the simplest require calibration, they are based on measurable quantities (stream discharge and stream water concentration) but do not allow for an explicit, physical, flow-path interpretation; the more complex are based on mixing assumptions with different end-member sources, but require knowledge of the (unmeasurable) flow components. Here, we present a combination between the simple concentration–discharge (C-Q) approach with the mass balance (MB) mixing approach, which we apply to a new high-frequency series on the Oracle-Orgeval Observatory (France) (Tunqui et al., submitted). This new methodology shows a better performance than the two approaches applied separately, allowing us to better describe the concentrations measured in the stream.

Reference : Tunqui et al. Combining concentration-discharge relationships with mixing models. Submitted to Journal of Hydrology
Seasonal streamflow forecasting - Which are the drivers controlling the forecast quality?
Authors: Pechlivanidis Ilias , Crochemore Louise , Bosshard Thomas
Published: March 2020

Streamflow information for the months ahead is of great value to existing decision-making practices, particularly to those affected by the vagaries of the climate and who would benefit from better understanding and managing climate-related risks. Despite the large effort, there is still limited knowledge of the key drivers controlling the quality of the seasonal streamflow forecasts. In this investigation, we show that the seasonal streamflow predictability can be clustered, and hence regionalised, based on a priori knowledge of local hydro-climatic conditions. To reach these conclusions we analyse the seasonal forecasts of streamflow volumes across about 35400 basins in Europe, which vary in terms of climatology, scale and hydrological regime. We then link the forecast quality to various descriptors including physiography, hydro-climatic characteristics and meteorological biases. This allows the identification of the key drivers along a strong hydro-climatic gradient. Results show that, as expected, the seasonal streamflow predictability varies geographically and seasonally with acceptable values for the first lead months. In addition, the predictability deteriorates with increasing lead months particularly in the winter months. Nevertheless, we show that the forecast quality is well correlated to a set of drivers, which vary depending on the initialization month. The forecast quality of seasonal streamflow volumes is strongly dependent on the basin’s hydrological regime, with quickly reacting basins (of low river memory) showing limited predictability. On the contrary, snow and/or baseflow dominated regions with long recessions (and hence high river memory) show high streamflow predictability. Finally, climatology and precipitation biases are also strongly related to streamflow predictability, highlighting the importance of developing robust bias-adjustment methods.
Observation of TGFs at High Latitude
Authors: Maiorana Carolina , Marisaldi Martino , Mezentsev Andrey , Fullekrug Martin , Soula Serge , Lindanger Anders , Skeie Chris Alexander , Sarria David , Kochkin Pavlo , Lehtinen Nikolai , Bjørge-Engeland Ingrid , Østgaard Nikolai , Ullaland Kjetil , Genov Georgi , Neubert Torsten , Christiansen Freddy , Reglero Victor
Published: March 2020

Terrestrial Gamma-ray Flashes (TGFs) are short bursts of gamma radiation originating from thunderclouds; they propagate upwards and are then detected by satellites such as AGILE, Fermi and ASIM. ASIM is the first mission specifically designed for the study of thunderstorm-related phenomena (Neubert et al., 2019); being placed on the ISS, it can for the first time detect TGF events up to more than 51 degrees in latitude.

Among the previous missions, RHESSI was the one reaching the highest latitude: 38 degrees. We then consider “high-latitude” for ASIM the band between 35 and 51 degrees of latitude. 9 events have already been observed in this band, inside four distinct geographical regions. At such latitudes, TGFs are expected to experience greater absorption in the troposphere, which makes them more difficult to detect. Moreover, we expect an intrinsically lower production rate due to the lower lightning activity (Smith et al., 2010, Williams et al., 2006).

In this work we present the characteristics of those events, in the context of the global ASIM sample collected so far. We also examine whether the observed number of events is statistically compatible with the atmospheric absorption, taking into account the local flash activity and ASIM’s exposure at high latitude.
Impact of mining on geochemical signatures of riverine sediments in adjacent ecosystems
Authors: Friedland Giulia , Grüneberg Björn , Hupfer Michael
Published: March 2020

As a result of the open-cast lignite mining in Lusatia (Eastern Germany), large quantities of iron (Fe) and sulphate (SO42-) are fed into small streams discharging into the Spree river system. The study examined whether the inputs of Fe and SO42- lead to longitu­dinal and depth-dependent gradients in the riverine sediments downstream the mining region in terms of element composition and mineral formations.

We sampled the surface (upper 0-3, 3-6 cm) sediment using a gravity corer at 18 sites from the heavily mining impacted Spreewald region downstream 200 km to the Bänke at Lake Müggelsee. We also included sampling sites at a pit water purification system in Vetschau, one neutral mining lake and a reference site without mining impact. Sedi­ments were analysed for total C, N using an element analyser, for various elements (incl. Fe, S, Mn, Al, P, heavy metals) by ICP-OES after digestion with hot aqua regia. A sequential Fe-extraction from fresh sediments and XRD was performed to differenti­ate solid iron forms and other minerals, respectively.  Characteristic sediment signatures are investigated with the help of a Principal Component Analysis (18 sites, 19 parameters).

We discovered a decreasing sedimentary Fe-content in flow direction from 300 mg g-1 in Vetschau, 130 mg g-1 close to the mining region in Lübbenau down to 30 mg g-1 at Bänke near Lake Müggelsee. In contrast, the S-content increased with decreasing mining impact from 3 mg g-1 in Vetschau up to 35 mg g-1. Minimum Fe- and S-contents are similar to Bautzen reservoir as a non-mining impacted reference location with Fe 28 mg g-1 and S 4 mg g-1. The statistical analysis with the PCA revealed the longitudinal influence of mining products within Spree river. Two major groups emerge from the score plot. First, there are those samples, which are clearly influenced by mining activities. Second, there are samples, which include the reference point and samples more distant from mining, where we expect no or only minor mining impact. This separation becomes even more apparent after taking heavy metals into account. Furthermore, the Fe binding shifts from more easily reducible Fe/amorphous minerals to less easily reducible Fe/more crystalline minerals in flow direction, which probably has consequences for the microbial degradability of organic matter and the strength of the ability of Fe to bind phosphorus.  

We were able to prove that the sedimentary ele­ment composition and especially the Fe mineral characteristics are influenced by mining activities at least 100 km downstream the Spree river system, probably affecting the phosphorus availability and carbon turnover.
Compression wood has a minor effect on the climate signal in tree-ring stable isotopes of montane Norway spruce
Authors: Janecka Karolina , Kaczka Ryszard , Gärtner Holger , Harvey Jill E. , Treydte Kerstin
Published: March 2020

Compression wood is a common tissue present in the trunk, branches and roots of mechanically stressed coniferous trees. Its main role is to increase the mechanical strength and regain the vertical orientation of a leaning stem. Compression wood is thought to influence the climate signal in different tree-ring measures. Hence trees containing compression wood are mostly excluded from tree-ring studies reconstructing past climate variability. There is a large gap of systematic work testing the potential effect of compression wood on the strength of the climate signal in different tree-ring parameters, and especially stable isotope records.

Here we test for the first time the effect of compression wood contained in montane Norway spruce (Picea abies L. Karst) on both δ13C and δ18O tree-ring cellulose records by analyzing compression and opposite wood radii from several disturbed trees together with samples from undisturbed reference trees. We selected four trees tilted by geomorphic processes that were felled by wind, and four undisturbed reference trees in the Tatra Mountains, Poland. We qualitatively classified the strength of compression wood using wood cell anatomical characteristics (tracheid shape, cell wall thickness and presence of intercellular spaces). Then we developed tree-ring width, δ13C and δ18O chronologies from the compression wood radii and the opposite radii of the tilted trees, and from the radii of the reference trees. We tested the effect of compression wood on tree-ring cellulose δ13C and δ18O variability and on the climate signal strength. Only minor differences were found in the means of δ13C and δ18O compression, opposite and reference radii. The statistical relationships between climate variables, δ13C and δ18O remained consistent among all chronologies. Our findings suggest that moderately tilted trees containing compression wood can be used to both reconstruct past geomorphic activity, and stable-isotope based dendroclimatological research.
Predicting Climate Change through Response Operators in a Coupled General Circulation Model
Authors: Lembo Valerio , Lucarini Valerio , Ragone Francesco
Published: March 2020

Global Climate Models are key tools for predicting the future response of the climate system to a variety of natural and anthropogenic forcings. Typically, an ensemble of simulations is performed considering a scenario of forcing, in order to analyse the response of the climate system to the specific forcing signal. Given that the the climate response spans a very large range of timescales, such a strategy often requires a dramatic amount of computational resources. In this paper we show how to use statistical mechanics to construct operators able to flexibly predict climate change for a variety of climatic variables of interest, going beyond the limitation of having to consider specific time patterns of forcing. We perform our study on a fully coupled GCM - MPI-ESM v.1.2 - and for the first time we prove the effectiveness of response theory in predicting future climate response to CO2 increase on a vast range of temporal scales. We specifically treat atmospheric  (surface temperature) and oceanic variables (strength of the Atlantic Meridional Overturning Circulation and of the Antarctic Circumpolar Current), as well as the global ocean heat uptake.
Mapping cation exchange capacity using a quasi-3d joint-inversion of EM38 and EM31 data
Authors: Zhao Dongxue , Triantafilis John
Published: March 2020

The cation exchange capacity (CEC, cmol(+)/kg) is a measure of soil’s capacity to retain exchangeable cations. However, it is expensive to collect CEC across a heterogenous field and at different depths. To value-add to limited data, proximal sensed electromagnetic (EM) data has been coupled to CEC through linear regression (LR) models, because they measure apparent soil electrical conductivity (ECa, mS/m). However, these LRs have been depth-specific. This approach was compared with one universal LR between estimates of true electrical conductivity (s, mS/m) and CEC from various depths, including topsoil (0-0.3 m), subsurface (0.3-0.6 m), shallow subsoil (0.6-0.9 m) and deeper subsoil (0.9-2.1 m). We estimated s from inversion of EM38 and EM31 ECa either alone or in combination (joint-inversion), in horizontal (ECah) and vertical (ECav) modes, using a quasi-3d (q3-d) inversion software (EM4Soil) and various parameters, including EM38 at two different heights (i.e. 0.2 or 0.4 m). In terms of performance, the LR correlation (R2 > 0.60) was largest between deeper subsoil CEC and EM38 ECah at 0.2 m. However, the LR was unsatisfactory for CEC calibration in the topsoil (0.31), subsurface (0.37) and shallow subsoil (0.52). In comparison, a universal LR between CEC and σ was well correlated (0.72), when both EM38 (0.2 m) and EM31 ECa in both modes, were inverted using a forward model (CF), inversion algorithm (S2) and small damping factor (λ = 0.03). The calibrations tested using a leave-one-out cross validation, showed CEC prediction was precise (RMSE, 2.35 cmol(+)/kg), unbiased (ME, -0.002 cmol(+)/kg) with good concordance (Lin’s, 0.83). To improve areal prediction, closer spaced transects need to be collected, while improved vertical resolution of CEC prediction we recommend DUALEM-421 ECa data be acquired. 
Model performance in simulating the Global Monsoon: Skill evolution across CMIP generations
Authors: Gómez Luz Adriana , Hoyos Carlos D. , Cruz Diana Carolina , Webster Peter J.
Published: March 2020

Improving projections of future changes in the global hydrological cycle is essential in order to understand the potential impacts of climate change and develop appropriate strategies of mitigation and adaptation to their socio-economics implications. This improvement requires a rigorous global climate model (GCM) evaluation, considering that several models often misrepresent fundamental processes of the global climate system. Recently, monsoons have been seen not just as independent systems that modulate the regional hydrology and climate but as a dominant global mode referred to as the Global Monsoon (GM). The GM is tied to global atmospheric circulation processes such as seasonal precipitation variations, the migration of the Inter-Tropical Convergence Zone (ITCZ), and the variability of the Hadley and Walker cells. Additionally, it can be seen as the response of the climate system to the annual solar radiation cycle. In this context, it is essential to consider not only regions with a marked seasonal change in the direction of surface winds but also the variation of precipitation in the tropics and subtropics. Reliable representations of its main characteristics are crucial for global simulations and climate change projections. 

This work assesses the ability of 64 GCMs part of three generations of the CMIP (phases 3, 5 and 6) simulating the most relevant characteristics of the global monsoon. Emphasis was placed on the GM domain and the two main modes of annual variation of precipitation and surface winds, referred to as Solstitial and Equinoctial modes. The GM wind domain and GM precipitation domain are well captured in most of the GCMs, and CMIP6 models show a significant improvement especially over the Asian-Australian monsoon (AAM) region. In order to evaluate the main modes of variability, we used projections of the model simulations onto the first two multivariate empirical orthogonal functions (MV-EOF) from observations. As a result, we find that in general, model performance is higher simulating the Solstitial mode compared to Equinoctial mode, but it has improved for both modes across the CMIP generations in terms of spatial variability and magnitude. Despite this, a regional analysis shows that performance over some regions, such as South America, does not exhibit significant improvement neither for the monsoon domain nor the annual variation modes.

We also considered the annual and seasonal mean of precipitation and surface winds, and we observed a notable improvement across CMIP generations to reproduce their spatial patterns of variability. However, biases of magnitude remain significant, mainly for global precipitation. Finally, it is relevant to point out that dispersion among GCMs was considerably reduced within CMIP6 and that we do not find a direct relationship between model performance and horizontal resolution. 
On Space Weather Data Assimilation
Authors: Codrescu Mihail , Codrescu Stefan , Fedrizzi Mariangel , Borries Claudia
Published: March 2020

Most if not all terrestrial weather prediction services today are based on data assimilation and numerical weather prediction models. Space Weather services are expected to follow a similar path towards data assimilation. However, the application of data assimilation in Space Weather requires a different implementation compared to terrestrial weather because space systems tend to be strongly forced and because the amount of data available for assimilation is critically small. In this paper we review the implementation of an ensemble Kalman filter data assimilation system based on the Space Weather Prediction Center operational Coupled Thermosphere Ionosphere Plasmasphere Electrodynamics (CTIPe) model. We present assimilation results for neutral mass density during geomagnetically quiet and disturbed conditions and discuss the future use of data assimilation for the thermosphere ionosphere system. 
On the characterization of VLF radio signal propagation in atmosphere in quite solar conditions
Authors: Nico Giovanni , Nina Aleksandra , Ermini Anita , Biagi Pierfrancesco
Published: March 2020

In this work we use Very Low Frequency (VLF) radio signals, having a frequency in the bands 20-80 kHz, to study the VLF signal propagation in the atmosphere quite undisturbed conditions by selecting the signals recorded during night. As a good approximation, we can model the propagation of VLF radio signals as characterized by a ground-wave and a sky-wave propagation mode. The first one generates a radio signal that propagates in the channel ground-troposphere, while the second one generates a signal which propagates using the lower ionosphere as a reflector. The VLF receivers of the INFREP (European Network of Electromagnetic Radiation) network are used. These receivers have been installed since 2009 mainly in southern and central Europe and currently the INFREP network consists of 9 receivers. A 1-minute sampling interval is used to record the amplitude of VLF signals. Long time-series of VLF signals propagating during night are extracted from recorded signals to study possible seasonal effects due to temporal variations in the physical properties of troposphere. A graph theory approach is used to investigate the spatial correlation of the aforementioned effects at different receivers. A multivariate analysis is also applied to identify common temporal changes observed at VLF receivers.

This work was supported by the Ministero dell'Istruzione, dell'Università e della Ricerca (MIUR), Italy, under the project OT4CLIMA. This research is supported by the Ministry of Education, Science and Technological Development of the Republic of Serbia, under the projects 176002 and III44002.
Evolution in geometry of firn in ice sheets detected by dielectric anisotropy
Authors: Fujita Shuji , Fukui Kotaro , Hirabayashi Motohiro , Iizuka Yoshinori , Matoba Sumito , Miyamoto Atsushi , Motoyama Hideaki , Saito Takeshi , Suzuki Toshitaka
Published: March 2020

Ice in polar ice sheets once experience a state of firn at near-surface depths. Therefore, it is important to understand physical processes of firn formation, metamorphism and deformation for ice core studies. We investigated firn through measurement of tensorial values of the dielectric permittivity at microwave and millimeter-wave frequencies. This method can detect presence and strength of anisotropic structure in the geometry of pore spaces and ice matrix. We applied the method to many firn cores drilled at both ice sheets. We find that firn that have shorter residence time at the near-surface depths does not form strong vertical anisotropy that is caused by vertical movement of moistures. In contrast, firn that have longer residence time at the near-surface depths tend to form vertical anisotropy. When density exceeds  ~600 kg/m3, a common feature of firn at many polar sites is that there are evolution of vertically elongated features of pore spaces in firn despite growth of vertical compression. We hypothesize an explanation as follows. As firn becomes denser, air within firn needs escape paths to upward directions as compared to sinking firn. In firn, porous structure tend to have vertically elongated structure because of this vertical escape movement of air. The observed phenomena of the grow th of the vertical dielectric anisotropy
can be understood by this vertical movement of the air w ithin firn.
FAIR access to soil and agricultural research data: The BonaRes Data Repository
Authors: Hoffmann Carsten , Specka Xenia , Svoboda Nikolai , Heinrich Uwe
Published: March 2020

In the frame of the joint research project BonaRes (“Soil as a sustainable resource for the bioeconomy”, bonares.de) a data repository was set-up to upload, manage, and provide soil-, agricultural- and accompanying environmental research data. Research data are stored consistent and based on open and widely used standards within the repository over the long-term. Data visibility as well as its accessibility, reusability, and interoperability with international data infrastructures is fostered by rich description with standardized metadata and DOI allocation.

The specially developed metadata schema combines all elements from DataCite and INSPIRE. Metadata are entered by an online metadata editor and include thesauri (AGROVOC, GEMET), use licenses (Creative Commons: CC-BY for research data, CC-0 for metadata), lineage elements and data access points (geodata portal with OGC services). The repository meets thus the needs of the FAIR principles for research data.

In this paper we present and discuss functionalities and elements of the BonaRes Data Repository, show a typical data workflow from data owner to data (re-)user, demonstrate data accessibility and citeability, and introduce to central data policy elements, e.g. embargo times and licenses. Finally we provide an outlook of the planned integration and linkage with other soil-agricultural repositories within a government-funded comprehensive national research data infrastructure NFDI (NFDI4Agri, Germany).
Asymmetries in the Earth's dayside magnetosheath: results from global hybrid-Vlasov simulations
Authors: Turc Lucile , Tarvus Vertti , Dimmock Andrew , Battarbee Markus , Ganse Urs , Johlander Andreas , Grandin Maxime , Pfau-Kempf Yann , Dubart Maxime , Palmroth Minna
Published: March 2020

The magnetosheath is the region bounded by the bow shock and the magnetopause which is home to shocked solar wind plasma. At the interface between the solar wind and the magnetosphere, the magnetosheath plays a key role in the coupling between these two media. Previous works have revealed pronounced dawn-dusk asymmetries in the magnetosheath properties, with for example the magnetic field strength and flow velocity being larger on the dusk side, while the plasma is denser, hotter and more turbulent on the dawn side. The dependence of these asymmetries on the upstream parameters remains however largely unknown. One of the main sources of these asymmetries is the bow shock configuration, which is typically quasi-parallel on the dawn side and quasi-perpendicular on the dusk side of the terrestrial magnetosheath because of the Parker-spiral orientation of the interplanetary magnetic field (IMF) at Earth. Most of these previous studies rely on collections of spacecraft measurements associated with a wide range of upstream conditions that have been processed to obtain the average values of the magnetosheath parameters. In this work, we use a different approach and quantify the magnetosheath asymmetries in global hybrid-Vlasov simulations performed with the Vlasiator model. We concentrate on three parameters: the magnetic field strength, the plasma density and the flow velocity. We find that the Vlasiator model reproduces accurately the polarity of the asymmetries, but that their level tends to be higher than in spacecraft measurements, probably due to the different processing methods. We investigate how the asymmetries change when the IMF becomes more radial and when the Alfvén Mach number decreases. When the IMF makes a 30° angle with the Sun-Earth line instead of 45°, we find a stronger magnetic field asymmetry and a larger variability of the magnetosheath density. In contrast, a lower Alfvén Mach number leads to a decrease of the magnetic field asymmetry level and of the variability of the magnetosheath density and velocity, likely due to weaker foreshock processes.
Aeolus: Payload Ground segment operations. Status, performances and evolution
Authors: Fischer Peggy , Mellano Luca , De Laurentis Marta , Aprile Stefano , Biscuso Antonio
Published: March 2020

After about 1.5 years in operations, the Aeolus Ground Segment is performing very well for all core functions including X-band data acquisition, mission planning, systematic science data production in Near Real Time, data access, data archival and thus continues to secure successfully important operational mission objectives.

Aeolus Payload Ground Segment operations are implemented through a set of service contracts that are either based on a full service approach, e.g. for payload data acquisition, or on a delegated service approach as for systematic data production and mission planning, in which ground segment components specifically developed for Aeolus mission are operated. The Services performances are agreed and measured through service level agreements.

Global scientific payload data acquisition is guaranteed by KSAT with the combined usage of Svalbard and Troll X-band receiving stations. Level-2B and Level-2C products are systematically generated at ECMWF, European Centre for Medium-Range Weather Forecasts.

The current performances of the overall Aeolus ground segment will be provided, including its operations and planned evolution in the near future.
Vertical extent related characteristics of the explosive cyclones in the Northern Hemisphere: A 40-yr climatology study based on the ERA-I reanalysis
Authors: Fu Shenming , Jiang Lizhi , Sun Jianhua
Published: March 2020

The explosive cyclone (EC), which is the most destructive subcategory of the extratropical cyclone, has been a research center for decades. Many key features of this type of cyclone have been shown, however, as a three-dimensional system, their vertical extents and associated important characteristics still remain vague. This study attempts to fill this vacancy by focusing on ECs’ vertical extents related features in the Northern Hemisphere on the basis of the ERA-I reanalysis data during a 40-yr period. Some new findings are reached: (i) overall, the EC is a type of deep weather system, as more than 63% of them reach an upmost level above 300 hPa, whereas only less than 12% of them maintain below 500 hPa during their whole life spans. (ii) ECs’ vertical extents show remarkable latitude dependent features (maximum vertical extents appear in the zone of 55oN-65oN), and they also show obvious seasonal changes, with the minimum vertical extents appeared in January. (iii) ECs’ maximum vertical extents show a significant positive correlation with their minimum central pressure, whereas, their maximum vertical extents show no obvious relationship to the ECs’ maximum deepening rates and maximum 10-m winds. (iv) in general, ECs over the northern Pacific Ocean have larger intensity, longer life spans, and thicker vertical extents than those of the ECs over the northern Atlantic Ocean.
Adapting afforestation patterns considering their local biogeophysical induced cooling and warming
Authors: Windisch Michael , Humpenöder Florian , Popp Alexander
Published: March 2020

Afforestation is expected to take on a key role in the fight against climate change. A quarter of the emission reductions pledged by countries under the Paris Agreement are to be provided by newly established forests. Low emission scenarios equally rely heavily on land-based mitigation options to remove hundreds of gigatons of carbon dioxide from the atmosphere within this century. This proposed extensive change of the terrestrial land-cover will exert a biogeophysical (BGP) impact on climate by altering the surface albedo as well as the evapotranspiration capacity. These BGP processes are mostly absent in the land-use components of Integrated Assessment Models which currently only focus on carbon sequestration. Hence, their afforestation prospect does not take into account the local BGP induced cooling or warming that either enhances or counteracts the mitigation effort. Neglecting BGP processes can lead to under- or overestimating the benefits of afforestation depending on the location of the forest. In the worst case it even risks proposing afforestation in regions where new forests would warm the climate. We incorporate observation-based estimates of the BGP effect of afforestation into the land-use model MAgPIE (Model of Agricultural Production and its Impact on the Environment). MAgPIE is a land-use optimization model driven by the cost of agricultural production. It produces cost optimal land-use patterns for a set of climatic (Representative Concentration Pathways) and societal (Shared Socioeconomic Pathways) developments and has already been used to investigate afforestation and forest protection as mitigation options. We translate the BGP induced local cooling or warming to a carbon equivalent metric by using the local climate sensitivity and add it to the mitigation benefit of carbon sequestration. The mitigation incentive for afforestation will be enhanced or reduced by considering the local cooling or warming. Hence, the model will be able to endogenously judge afforestation decisions regarding both their carbon sequestration potential and BGP impact. We will report the changes in afforestation patterns imposed by considering their combined BGP and biogeochemical effects.