bluuebunny/crossref_metadata_2025 huggingface dataset:
Polar Mesosphere Winter Echoes and their relation to infrasound
Authors: Belova Evgenia , Kero Johan , Näsholm Sven Peter , Vorobeva Ekaterina , Godin Oleg A. , Barabash Victoria
Published: March 2020

Polar Mesosphere Winter Echoes (PMWE) are radar echoes that originate from the mesosphere at 50-80 km altitude and are observed with VHF radars during equinox and winter seasons. Strong PMWE are relatively rare phenomena, in most cases they are observed when the lower ionosphere displays high ionisation. Interpretations of observational results concerning PMWE are controversial and the origin of the echoes is still under debate. Especially intriguing is that in some cases of strong PMWE, the measured horizontal speeds of the radar reflecting structures can exceed 300 m/s. Radar reflection (scattering) by infrasound waves at frequencies below about 2 Hz was suggested in order to explain these observations. We will give recent examples of PMWE events of high horizontal speed as observed with the 52 MHz MST radar (ESRAD) located at Esrange (68°N, 21ºE) in northern Sweden. Together with this we will analyse infrasound measurements made at ground-based stations near Kiruna (67.5°N, 20.13ºE) and at the infrasound station IS37 (69°N, 18ºE) in Norway during these events. We discuss prospective relations between PMWE and the microbaroms that are generated by ocean swell in the North Atlantic.
Overview of the IBER-STILLING project: Assessment and attribution of wind speed and wind gust variability
Authors: Azorin-Molina Cesar , Brunet Manola , Aguilar Enric , Guijarro Jose A. , Safaei Pirooz Amir A. , Flay Richard G.J. , Minola Lorenzo , Zhang Gangfeng , Lopez-Bustins Joan-Albert , McVicar Tim R. , Chen Deliang
Published: March 2020

In a context of global climate change, the scientific community has evidenced a significant decrease in wind speed, a phenomenon known as «stilling». This climate trend has mainly been observed over mid-latitude continental surfaces since the 1980s. On the contrary, other studies have detected an increase in wind speed over ocean surfaces; and there is little conclusive scientific evidence on trends in wind speed across the troposphere. Furthermore, a reversal in global terrestrial stilling has recently been documented in few regional and global studies since the 2010s. The causes associated with the climate variability of wind speed have not yet been resolved and there are many uncertainties behind the «stilling» and «recovery» phenomenon because neither the quantity nor the quality of wind speed observations is adequate. This contribution shows an overview of the IBER-STILLING project (RTI2018-095749-A-I00) funded by the Spanish Ministry of Science, Innovation and Universities.  This project aims to move forward on the assessment of wind speed and wind gusts variability and underlying causes globally, with emphasis on the Spanish territory and surrounding ocean (Atlantic) and sea (Mediterranean) surfaces. The IBER-STILLING project will collect and generate climate information of wind speed from different data sources; climate data will be subject to a comprehensive protocol for quality control and homogenization. The statistical analysis of these climate databases will allow characterizing trends and climatic cycles of wind speed, allowing a pioneering global analysis of wind speed over continental and ocean surfaces, and across the boundary layer and the entire troposphere. The project will also conduct wind-tunnel experiments to quantify biases introduced by anemometers devices. 
Unveiling tipping points in long-term and experimental studies in peatlands
Authors: Lamentowicz Mariusz , Marcisz Katarzyna , Słowiński Michał , Jassey Vincent E.J.
Published: March 2020

Ecosystems are increasingly prone to climate extremes, such as drought, with long-lasting effects on both plant and soil communities and, subsequently, on carbon (C) cycling. Unveiling past tipping points is a prerequisite for a better understanding of how individual species and entire ecosystems will respond to future climate changes, especially soil moisture. In the first study we identified the response of peatland vegetation to shifts in hydrological conditions over the past 2000 years using plant macrofossils, testate amoebae-based quantitative hydrological reconstructions from seven Polish peat-records (Lamentowicz et al., 2019). Using threshold indicator taxa analysis (TITAN), we discovered that plant community composition strongly converged at a water level of c. 11.7 cm, indicating a community-level tipping-point. We identified 45 plant taxa that showed either an increase or a decrease in their relative abundance between 8 and 17 cm of water level depth. In other the experimental study (Jassey et al., 2018) we investigated the response of plant and soil fungi to drought of different intensities using a water table gradient in peatlands—a major C sink ecosystem. We show that substantial changes in ecosystem respiration, plant and soil fungal communities occurred when the water level fell below a tipping point of 24 cm. As a corollary, ecosystem respiration was the greatest when graminoids and saprotrophic fungi became prevalent as a response to the extreme drought. Graminoids indirectly influenced fungal functional composition and soil enzyme activities through their direct effect on dissolved organic matter quality, while saprotrophic fungi directly influenced soil enzyme activities. In turn, increasing enzyme activities promoted ecosystem respiration. We show that functional transitions in ecosystem respiration critically depend on the degree of response of graminoids and saprotrophic fungi to drought. Our results represent a major advance in understanding the nonlinear nature of ecosystem properties to drought and pave the way towards a truly mechanistic understanding of tipping points in peatlands with use of experiment and palaeoecology.

References

Jassey, V.E.J., Reczuga, M.K., Zielinska, M., Slowinska, S., Robroek, B.J.M., Mariotte, P., Seppey, C.V.W., Lara, E., Barabach, J., Slowinski, M., Bragazza, L., Chojnicki, B.H., Lamentowicz, M., Mitchell, E.A.D., Buttler, A., 2018. Tipping point in plant-fungal interactions under severe drought causes abrupt rise in peatland ecosystem respiration. Glob Chang Biol. 24, (3) 972–986.

Lamentowicz, M., Gałka, M., Marcisz, K., Słowiński, M., Kajukało-Drygalska, K., Dayras, M.D., Jassey, V.E.J., 2019. Unveiling tipping points in long-term ecological records from Sphagnum -dominated peatlands. Biology Letters. 15, (4) 20190043.
How to predict hydraulic conductivity of unsaturated soils from an incomplete soil water characteristic curve?
Authors: Ren Xingwei , Fang Qidong , Chen Xiaojun
Published: March 2020

Unsaturated soils are those in which pore is filled partially with water and partially with air. They are the most relevant porous medium to human activities, and cover almost all the soils near the ground surface. Hydraulic conductivity (HC) is one of the most important and useful properties of unsaturated soils in numerous studies, including governing flow process, settlement of soil foundations, migration of groundwater and gas hydrate. Unfortunately, direct measurement of HC for unsaturated soils is very difficult with high uncertainty due to its nature of complexity and limited experimental conditions. Thus, indirect estimation of HC from soil water characteristic curve (SWCC) becomes an alternative way and being widely used all over the world.

Because of the difficulty to reach high suction at the residual state of unsaturated soils, however, the SWCC obtained by laboratory experiments is often incomplete, which will lead to an unreliable estimation of hydraulic conductivity. However, no study has been published on how to estimate hydraulic conductivity of unsaturated soils with incomplete SWCC. In response to this situation, an innovative method was proposed based on the classical van Genuchten model and Mualem model. The proposed method was evaluated by extensive experimental data from existing literature and proved to have an excellent performance in predicting a complete SWCC for a wide range of soils. Also, it exhibits certain superiority in predicting hydraulic conductivity. The limitations of the proposed method were comprehensively discussed, and its corresponding improvement strategies were also addressed. This paper presents a practical way to obtain a more reliable hydraulic conductivity from incomplete SWCC.
Exploring signatures-based calibration of hydrological models for prediction in ungauged basins.
Authors: Dal Molin Marco , Kavetski Dmitri , Schirmer Mario , Fenicia Fabrizio
Published: March 2020

One of the open challenges in catchment hydrology is prediction in ungauged basins (PUB), i.e. being able to predict catchment responses (typically streamflow) when measurements are not available. One of the possible approaches to this problem consists in calibrating a model using catchment response statistics (called signatures) that can be estimated at the ungauged site.
An important challenge of any approach to PUB is to produce reliable and precise predictions of catchment response, with an accurate estimation of the uncertainty. In the context of PUB through calibration on regionalized streamflow signatures, there are multiple sources of uncertainty that affect streamflow predictions, which relate to:

The use streamflow signatures, which, by synthetizing the underlying time series, reduce the information available for model calibration;

The regionalization of streamflow signatures, which are not observed, but estimated through some signature regionalization model;

The use of a rainfall-runoff model, which carries uncertainties related to input data, parameter values, and model structure.

This study proposes an approach that separately accounts for the uncertainty related to the regionalization of the signatures from the other types; the implementation uses Approximate Bayesian Computation (ABC) to infer the parameters of the rainfall-runoff model using stochastic streamflow signatures. 
The methodology is tested in six sub-catchments of the Thur catchment in Switzerland; results show that the regionalized model produces streamflow time series that are similar to the ones obtained by the classical time-domain calibration, with slightly higher uncertainty but similar fit to the observed data. These results support the proposed approach as a viable method for PUB, with a focus on the correct estimation of the uncertainty.
3D fault network development at the Galicia magma-poor margin, North-Atlantic
Authors: Cresswell Derren , Lymer Gaël , Reston Tim
Published: March 2020

We investigate the structures of hyper-extended continental crust and the 3D nature of the development of syn-rift fault networks at the Galicia margin, West of Spain, based on observations from a 3D multi-channel seismic reflection dataset acquired in 2013. This seismic volume provides, for the first time, 3D high-resolution imaging of a fault network geometry above a detachment fault (The “S reflector”) in the distal setting of a continental margin. The Galicia margin is sediment-starved, magma-poor and salt-free, thus providing optimal observations of the structures through seismic data.

We use the 3D data to observe the geometries of the faults, to analyse the fault heaves at different levels of the litho-stratigraphic sequence (i.e. at the top of the crystalline basement, at the top of the pre-rift/early syn-rift sediments and at the top of the syn-kinematic sediments), and to make a stratigraphic analysis to constrain the dynamics and the kinematics of fault activity within the successive half-grabens.

Our 3D interpretations demonstrate that the continental crust thins to zero during the rifting by the simultaneous development of initially individual fault planes, which progressively link with adjacent faults to form a network of active faults. The linked roots of the faults altogether form the surface of the S at depth, and allow the oceanward propagation of the detachment fault during the rifting. The faults throughout the network remained active and progressively rotated with further extension, until their deactivation when they acquired an angle of ~30°. Whereupon, a new network of active, initially isolated, faults developed and linked one step (~10 km) oceanward. The system repeats until the break-up of the continental crust, resulting in the progressive focussing of the locus of the extension toward the ocean, where the continental crust is the thinnest. 

Given the similitude of the features observed at the Galicia margin with other magma poor continental margins, we expect that most margins worldwide might have formed following similar processes, thus representing a paradigm shift in the global understanding of late fault network development at rifted margins during continental break-up.
The use of Frequency Domain Electro-magnetometry for the characterization of permafrost active layers: case studies in the Swiss Alps
Authors: Boaga Jacopo , Phillips Marcia , Noetzli Jeannette , haberkorn Anna , Kenner Robert , Bast Alexander
Published: March 2020

The characterization of the active layer (AL) in mountain permafrost is an important part of monitoring climate change effects in periglagical environments and may help to determine potential slope instability. Permafrost affects 25% of the Northern Hemisphere and 17% of the entire Earth. It has been studied for decades both in the polar regions and – starting a few decades later – in high mountain environments. Typical point information from permafrost boreholes can be extended to wider areas by geophysical prospecting and provide information that cannot be detected by thermal observations alone.

During Summer 2019 we performed several geophysical surveys at permafrost borehole sites in the Swiss Alps. We focused on electrical resistivity tomography (ERT) and Frequency Domain Electro-magnetic techniques (FDEM) to compare the methods and test the applicability of FDEM for active layer characterization, i.e., its thickness and lateral continuity. ERT provides an electrical image of the subsoil and can discern active layer thickness, changes in ground ice and geological features of the subsoil. From a logistic point of view a contactless method such as FDEM would be preferable : i) it can provide electrical properties of the subsoil with no need of physical electrical contact with the soil; ii) it can cover a wider area of exploration compared to ERT, iii) it is faster and data collection is simpler than with ERT due to lighter instruments and less preparation time needed.

Based on the FDEM surveys at the Swiss permafrost sites we were able to detect the frozen/unfrozen boundary and to achieve results that were in agreement with those obtained from classical ERT and borehole temperature data. The results were promising for future active layer monitoring with the contactless FDEM method.
Stratospheric Australian fire smoke layers over Punta Arenas, Chile, measured by ground-based lidar and AEOLUS
Authors: Ohneiser Kevin , Baars Holger , Jimenez Cristofer , Bühl Johannes , Seifert Patric , Floutsi Athina , Radenz Martin , Wandinger Ulla , Ansmann Albert
Published: March 2020

Exceptionally strong wildfire activity in Australia in summer 2019-2020 triggered the evolution of pyrocumulonimbus clouds, releasing enormous amounts of fire smoke into the upper troposphere and lower stratosphere region of the usually very clean southern hemisphere. Measurements at the lidar site of Punta Arenas (53°S), Chile, show that the first stratospheric smoke layers arrived over Punta Arenas at 6 Jan 2020.

First results show striking similarities to a record-breaking event of stratospheric smoke layers from wildfires in Canada in 2017 (Baars et al., ACP 2019). At Punta Arenas, lidar ratios reach values of 45-50 sr at 355 nm, and 60-65 sr at 532 nm wavelength. Particle linear depolarization ratios reach values of 19% at 355 nm, and 15% at 532 nm wavelength.

Aeolus is able to detect these intense layers of stratospheric smoke in the southern hemisphere as well. In this contribution, we will discuss our findings of extensive and intensive smoke optical properties over Punta Arenas to the related Aeolus aerosol spin off products of nearby overpasses. Especially the particle linear depolarization ratio at 355 nm are of relevance as AEOLUS is only able to measure the co-polarized 355 nm signal.
From severe droughts in South America to marine heatwaves in the South Atlantic
Authors: Rodrigues Regina , Taschetto Andrea , Sen Gupta Alex , Foltz Gregory
Published: March 2020

In 2013/14 eastern South America experienced one of its worst droughts, leading to water shortages in São Paulo, the world’s fourth most populated city. This event was also responsible for a dengue fever outbreak that tripled the usual number of fatalities and reduced Brazilian coffee production leading to a global shortages and worldwide price increases. The drought was associated with an anomalous anticyclonic circulation off southeast South America that prevented synoptic systems reaching the region while inhibiting the development of the South Atlantic Convergence Zone and its associated rainfall. A concomitant and unprecedented marine heatwave also developed in the southwest Atlantic. Here we show from observations that such droughts and adjacent marine heatwaves have a common remote cause. Atmospheric blocking triggered by tropical convection in the Indian and Pacific oceans can cause persistent anticyclonic circulation that not only leads to severe drought but also generates marine heatwaves in the adjacent ocean. We show that increased shortwave radiation due to reduced cloud cover and reduced ocean heat loss from weaker winds are the main contributors to the establishment of marine heatwaves in the region. The proposed mechanism, which involves droughts, extreme air temperature over land and atmospheric blocking explains approximately 60% of the marine heatwave events in the western South Atlantic. We also identified an increase in frequency, duration, intensity and extension of marine heatwave events over the satellite period 1982–2016. Moreover, surface primary production was reduced during these events with implications for regional fisheries.
WRF-GC: online two-way coupling of WRF and GEOS-Chem for regional atmospheric chemistry modeling
Authors: Feng Xu , Lin Haipeng , Fu Tzung-May
Published: March 2020

We developed the two-way version of the WRF-GC model, which is an online coupling of the Weather Research and Forecasting (WRF) mesoscale meteorological model and the GEOS-Chem chemical transport model, for regional air quality and atmospheric chemistry modeling. WRF-GC allows the two parent models to be updated independently, such that WRF-GC can stay state-of-the-science. The meteorological fields and chemical variables are transferred between the two models in the coupler to simulate the feedback of gases and aerosols to meteorological processes via interactions with radiation and cloud microphysics. We used the WRF-GC model to simulate surface PM2.5 concentrations over China during January 22 to 27, 2015 and compared the results to the outcomes from classic GEOS-Chem nested-grid simulations as well as the surface observations. For PM2.5 simulations, both models were able to reproduce the spatiotemporal variations, but the WRF-GC (r = 0.68, bias = 29%) performing better than GEOS-Chem (r = 0.72, bias = 55%) especially over Eastern China. For ozone simulations, we found that including aerosol-chemistry-cloud-radiation interactions reduced the mean bias of simulated surface ozone concentrations from 34% to 29% compared to observed afternoon ozone concentrations. WRF-GC is computationally efficient, with the physical and chemical variables managed in distributed memory. At similar resolutions, WRF-GC simulations were three times faster than the classic GEOS-Chem nested-grid simulations, due to the more efficient transport algorithm and the MPI-based parallelization provided by the WRF software framework. We envision WRF-GC to become a powerful tool for advancing science, serving the public, and informing policy-making.
Are Recurrent Rossby wave packets linked to persistent extreme weather events in the Southern Hemisphere?
Authors: Ali Syed Mubashshir , Martius Olivia , Röthlisberger Matthias
Published: March 2020

Synoptic-scale Rossby wave-packets have a recurrent pattern during several episodes of persistent surface weather which is termed as 'recurrent Rossby wave-packets' (RRWP). They result in a statistically significant increase in winter cold and summer hot spells over large areas of the Northern Hemisphere mid-latitudes.

We present a global climatology of the RRWPs to study its spatial and seasonal variation. We also investigate the link of RRWPs to persistent surface extremes in the Southern Hemisphere (SH).  We find that RRWPs result in a statistically significant increase in winter cold and summer hot spells over broad areas in Australia and South America. Furthermore, we discuss the effects of climatological oscillations (Madden Julian Oscillation, ENSO, etc) on influencing the RRWPs.
Validation and interpretation of data obtained by the newly developed low-cost Geodetic Integrated Monitoring System (GIMS)
Authors: Šegina Ela , Jemec Auflič Mateja , Peternel Tina , Zupan Matija , Jež Jernej , Realini Eugenio , Colomina Ismael , Crosetto Michele , Consoli Angelo , Luca Sara , Reyes González⁷ Joaquín
Published: March 2020

Geodetic Integrated Monitoring System (GIMS) has been developed as a low-cost solution for detecting and measuring ground movements (https://www.gims-project.eu/). The prototype has been tested on the landslide on Potoška planina in the north of Slovenia that has been monitored by the seven GIMS units. These units, consisting of GNSS receiver and inclinometer, provide live monitoring data with millimetric precision. In this paper, the project consortium presents the first results of the prototype measuring system and estimate its applicability in modern landslides monitoring. The GIMS measurements have been validated by the wire crackmeter located at the site. The data were correlated to the groundwater level in a piezometer and to the amount of precipitation detected at the rain gauge. Results of GIMS units show good comparability to the wire crackmeter measurements and increased precision in detecting variations in landslide movements. The latter enables us to precisely define the rainfall threshold value for the particular landslide as crucial information needed for a reliable early warning system.

 
Proofs of non-stomatal limitations of potato photosynthesis during drought by using in-situ eddy covariance data
Authors: Beauclaire Quentin , Gourlez de la Motte Louis , Bernard Heinesch , Bernard Longdoz
Published: March 2020

Water stress in one of the main limiting factors in agro-systems, causing a reduction in gross primary production (GPP) and by extend, yields. However, it is still unclear to attribute whether the limitations of photosynthesis originate from a strict stomatal control (SOL) or from other non-stomatal limitations (NSOL). In this study, we investigated the effects of drought on potato crop by using eddy covariance data at the Lonzée Terrestrial Observatory during three consecutive cultivation periods (2010, 2014 and 2018). Regardless the years and the timing of the drought appearance, the maximum carboxylation rate Vcmax (one of the NSOL) was reduced with decreasing REW, while the stomatal sensitivity to GPP parameter in the Medlyn et al. model (G1-SOL) remained constant. We showed that below the REW threshold of 0.55 ± 0.05, the non-consideration of NSOL in the ecosystem CO2 model led to an overestimation of the modelled GPP, which was about three times higher than its unstressed corresponding value. As a result, decreasing Vcmax while maintaining G1 constant was sufficient to reproduce GPP and canopy conductance dynamics during drought. At a sub-daily scale, the intrinsic water-use efficiency did not vary during drought, neither its dependence on VPD nor its hourly dynamics. This reinforced the hypothesis of direct and feedback effects of NSOL on canopy conductance and photosynthesis, which was supported by the uniform coupling between carbon and water fluxes. We recommend the implementation of NSOL in ecosystem CO2 models since non-stomatal factors were responsible for the decrease in potato crop GPP during drought.
Glacial Isostatic Adjustment with 3D Earth models: A comparison of case studies of deglacial relative sea level records of North America and Russian Arctic
Authors: Li Tanghua , Khan Nicole , Engelhart Simon , Baranskaya Alisa , William Peltier , Wu Patrick , Horton Benjamin
Published: March 2020

The Canadian landmass of North America and the Russian Arctic were covered by large ice sheets during the Last Glacial Maximum, and have been key areas for Glacial Isostatic Adjustment (GIA) studies. Previous GIA studies have applied 1D models of Earth’s interior viscoelastic structure; however, seismic tomography, field geology and recent studies reveal the potential importance of 3D models of this structure. Here, using the latest quality-controlled deglacial sea-level databases from North America and the Russian Arctic, we investigate the effects of 3D structure on GIA predictions. We explore scaling factors in the upper mantle (βUM) and lower mantle (βLM) and the 1D background viscosity model (ηo) with predictions of of the ICE-6G_C (VM5a) glaciation/deglaciation model of Peltier et al (2015, JGR) in these two regions, and compare with the best fit 3D viscosity structures.

We compute gravitationally self-consistent relative sea-level histories with time dependent coastlines and rotational feedback using both the Normal Mode Method and Coupled Laplace-Finite Element Method. A subset of 3D GIA models is found that can fit the deglacial sea-level databases for both regions. These databases cover both the near and intermediate field regions. However, North America and Russian Arctic prefer different 3D structures (i.e., combinations of (ηo, βUM, βLM)) to provide the best fits. The Russian Arctic database prefers a softer background viscosity model (ηo), but larger scaling factors (βUM, βLM) than those preferred by the North America database.

Outstanding issues include the uncertainty of the history of local glaciation history. For example, preliminary modifications of the ice model in Russian Arctic reveal that the misfits of 1D models can be significantly reduced, but still fit less well than the best fit 3D GIA model.An additional issue concerns the extent to which the 3D models are able to improve both fits in North America and Russian Arctic when compared with 1D internal structure (ICE-6G_C VM5a & ICE-7G VM7), will be assessed in a preliminary fashion.
Solutions for providing web-accessible, semi-standardised ecosystem research site information
Authors: Wohner Christoph , Peterseil Johannes , Kliment Tomáš , Goldfarb Doron
Published: March 2020

There are a number of systems dedicated to the storage of information about ecosystem research sites, often used for the management of such facilities within research networks or research infrastructures. If such systems provide interfaces for querying this information, these interfaces and especially their data formats may vary greatly with no established data format standard to follow.

DEIMS-SDR (Dynamic Ecological Information Management System - Site and Dataset Registry; https://deims.org) is one such service that allows registering and discovering long-term ecosystem research sites, along with the data gathered at those sites and networks associated with them. We present our approach to make the hosted information openly available via a REST-API. While this allows flexibility in the way information is structured, it also follows interoperability standards and specifications that provide clear rules on how to parse this information.

The REST-API follows the OpenAPI 3.0 specification, including the usage of JSON schemas for describing the exact structure of available records. In addition, DEIMS-SDR also issues persistent, unique and resolvable identifiers for sites independent of the affiliation with research infrastructures or networks.

The flexible design of the DEIMS-SDR data model and the underlying REST-API based approach provide a low threshold for incorporating information from other research domains within the platform itself as well as integrating its exposed metadata with third party information through external means.
An improved method for the segmentation of roots from X-Ray computed tomography 3D images: Rootine v.2
Authors: Phalempin Maxime , Lippold Eva , Vetterlein Doris , Schlueter Steffen
Published: March 2020

X-ray computed tomography (CT) is acknowledged as a powerful tool for the study of root system architecture (RSA) of plants grown in soil. The study of the root system properties is however only possible after performing root segmentation, i.e. the binarization of all root voxels. Root segmentation is often regarded as a tedious and difficult task as its success depends on several factors such as the image resolution, the signal to noise during image acquisition and the gray value contrast between the roots and all other surrounding features. Here, we present an improved method for the segmentation of roots from X-Ray computed tomography 3D images. The algorithm Rootine (Gao et al. 2019) does not detect roots by their gray values but by their characteristic tubular shape. This algorithm was further developed in order to improve the root recovery rate and to reduce the number of parameters involved during the segmentation process. This was achieved by adding two key steps: (1) an absolute difference transform and (2) an automatic calculation of the parameters used during the Gaussian smoothing. The first step allows for targeting specific features based on a gray value criteria contained within a user-defined gray value range in order to better distinguish roots from pores whereas the second step allows for targeting root segments of specific diameters. On the benchmark dataset of Gao et al. 2019, the newly called “Rootine v.2” was able to recover 34 % more roots as compared to its preceding version. Moreover, the number of parameters was reduced from 10 down to 5 which allows for a faster calibration and an overall better usability of the algorithm. The presented method also allows for a more reliable estimation of root diameter derived from X-Ray CT images. This work was carried out in the framework of the priority programme 2089 “Rhizosphere spatiotemporal organization - a key to rhizosphere functions” funded by DFG (project number 403640293).
SST Variability in the Southeastern Caribbean Sea over the Past 1800 Years
Authors: Zhuravleva Anastasia , Bauch Henning , Mohtadi Mahyar , Fahl Kirsten
Published: March 2020

Sea surface temperature (SST) of the Caribbean Sea exerts a strong control on the amount of precipitation on the adjacent land. However, a clear understanding of the regional climate development on centennial timescales is missing due to scarcity of SST records. To fill this gap, we generated a new high-resolution proxy dataset of the last 1800 years from the Tobago Basin, a region that is presently affected by both Atlantic and Pacific climate variability on one hand, and by the South Atlantic circulation on the other hand. Our dataset is comprised of Mg/Ca and alkenone-derived SSTs, stable isotopes, element composition of bulk sediment and planktic foraminiferal assemblages. Our Mg/Ca-based reconstruction suggests significant SST variability over the past 1800 years CE, particularly during the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA). The MCA encompasses an abrupt 2 °C SST reduction between 1050-1100 years CE, which coincided with a distinct episode of precipitation minima in the region and was followed by a century of warm and wet MCA conditions. A 1 °C cooling also characterized the onset of the LIA between 1400-1550 years CE, which was associated with a reduction in water column stratification inferred from stable isotopes and foraminiferal assemblage data. The initial LIA cooling was followed by a robust 1 °C SST rise between 1550-1750 years CE. This warming trend is also supported by alkenone-derived SSTs. Our reconstructed SST variability across the LIA may help to explain the occurrence of alternating dry and wet conditions on the Caribbean islands.
Evaluation of tectonics and landscape evolution as predisposing factor for a Mass Rock Creep deforming slope in the Zagros Belt (Iran)
Authors: Delchiaro Michele , Della Seta Marta , Martino Salvatore
Published: March 2020

In the hillslope landscapes of tectonically active regions, the steep topography represents the most evident result of rock uplift, valley incision and landslide erosion. In response to rock uplift, relief and hillslope dip increase linearly in time mainly due to fluvial erosion processes in landscapes affected by low to moderate tectonic forcing. Nonetheless, such a linear increase in relief and hillslope dip is limited by the reaching of threshold slope conditions associated with the hillslope material strength, until the latter is exceeded by gravitational stress giving rise to bedrock landslides. In this regard, Mass Rock Creep (MRC) process may become a primary factor for damaging rock masses so leading to slope failures that generate huge rock avalanches. MRC acts on large time-space scale through a continuous and non-linear variation of stress-strain conditions of entire portions of slopes and the coupled role of tectonics and landscape evolution represents a predisposing factor for Deep Seated Gravitational Slope Deformations (DSGSD).

This research focused on the Loumar DSGSD that affects the NE slope of the Palganeh anticline in the Lorestan region (Zagros Mts., Iran), almost 90 km northwest of the Seymareh landslide which is more famous as it represents the largest landslide on Earth surface. The Loumar DSGSD evolution is strictly related to the vertical and lateral growth of the fold and to the evolution of the Seymareh river drainage system that kinematically released the slope at the bottom likely causing the initiation of the deformational process. We combined an inverse modelling of the river profiles linked to the fold uplift history and the analysis of a plano-altimetric distribution of geomorphic markers, correlated to the detectable knickpoints along the river longitudinal profiles, which allowed to constrain the main morpho-evolutionary stages of the valley. These data will be used to constrain a Landscape Evolution Model (LEM) and a stress-strain numerical model, to be performed under time-dependent creep conditions, that will be calibrated by a back analysing the slope evolution from the LEM. The final goal will be to discuss the possible role of impulsive triggers (earthquakes) in anticipating the time-to-failure of the MRC deformational process.
Using STEREO-HI beacon data to predict CME arrival time and speed with the ELEvoHI model
Authors: Bauer Maike , Amerstorfer Tanja , Hinterreiter Jürgen , Möstl Christian , Davies Jackie A. , Amerstorfer Ute V. , Bailey Rachel L. , Reiss Martin A. , Weiss Andreas J.
Published: March 2020

Coronal mass ejections (CMEs) may induce strong geomagnetic storms which have a significant impact on satellites in orbit as well as electrical devices on Earth’s surface. If we want to be able to mitigate the potentially devastating consequences which strong CMEs might have on Earth, developing models which accurately predict their arrival time is an integral step. The Ellipse Evolution model based on Heliospheric Imager observations (ELEvoHl) predicts the arrival of coronal mass ejections using data from STEREO’s HI instruments. HI data is available as high-resolution science data, which is downlinked every few days and low-resolution beacon data, which is downlinked in near real-time. Therefore, to allow for real time predictions of CME arrivals, beacon data must be used. We study different data reduction procedures to improve the quality of the measurements and compile the resulting images into time-elongation plots (J-plots). We track the leading edge of each selected CME event by hand, resulting in a series of time-elongation points which function as input for the ELEvoHI model. We compare the resulting predictions to those obtained using science data in terms of accuracy and errors of the predicted arrival time and speed.
Missing data imputation for multisite rainfall networks: a comparison between geostatistical interpolation and data-mining estimation on different terrain types
Authors: Oriani Fabio , Stisen Simon , Demirel Mehmet C. , Mariethoz Gregoire
Published: March 2020

In the era of big data, missing data imputation remains a delicate topic for both the analysis of natural processes and to provide input data for physical models. We propose here a comparative study for missing data imputation on daily rainfall, a variable that can exhibit a complex structure composed of a dry/wet pattern and anisotropic sharp variations.

The seven algorithms considered can be grouped in two families: geostatistical interpolation techniques based on inverse-distance weighting and Kriging, widely used in gap-filling [1], and data-driven techniques based on the analysis of historical data patterns. This latter family of algorithms has been already applied to rainfall generation [2, 3], but it is not originally suitable to historical datasets presenting many data gaps. This happens because they usually operate in a rigid framework where, when a rainfall value is estimated for a station, the others are considered as predictor variables and require to be informed. To overcome this limitation, we propose here i) an adaptation of k-nearest neighbor (KNN) and ii) a new algorithm called Vector Sampling (VS), that combines concepts of multiple-point statistics and resampling. These data-driven algorithms can draw estimations from largely and variably incomplete data patterns, allowing the target dataset to be at the same time the training dataset.

Tested on different case studies from Denmark, Australia, and Switzerland, the algorithms show a different performance that seems to be related to the terrain type: on flat terrains with spatially uniform rain events, geostatistical interpolation tends to minimize the error, while, in mountainous regions with non-stationary rainfall statistics, data mining can recover better the complex rainfall patterns. The VS algorithm, being faster than KNN and requiring minimal parametrization, turns out to be a convenient option for routine application if a representative historical dataset is available. VS is open-source and freely available at .

 

REFERENCES:

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Serpentine-reached mining wastes as a geochemical barrier for the soil remediation under the ongoing Cu-Ni pollution in the Russian Arctic
Authors: Slukovskaya Marina , Kremenetskaya Irina , Drogobuzhskaya Svetlana , Ivanova Liubov , Novikov Andrey , Mosendz Irina
Published: March 2020

The main factors for the degradation of the ecosystems in the metal-polluted territories are soil toxicity, organic matter degradation and violation of macro-element cycles. Heavily contaminated soils lose their ability to maintain sustainable vegetation, which leads to the formation of industrial barrens as the final stage of plant cover digression, where the vegetation cover is less than 10%. The deposition of metal mobile compounds into an insoluble form by alkaline sorbents is one of the most effective remediation techniques in situ. Technosol engineering is a trigger for the beginning of plant and soil cover development and the recovery succession under high pollution with metals compounds.

Field experiment of remediation using three types of serpentine mining wastes, expanded vermiculite and grass seeds mixture was laid down in 2010-2013 in the impact zone of the copper-nickel ore processing enterprise on the Kola peninsula (northern Europe) beyond the Arctic Circle at two sites with podzol and peat soil. The results obtained in 2019 showed that the immobilization effect was strengthened by high pH inherited from the alkaline wastes making Technosols a geochemical barrier. For the first 5-8 years of the experiment, the Technosol upper layers primary consisted of serpentine minerals, accumulated more than 1 g·kg-1 Ni and 0.1 g·kg-1 Cu which are constantly deposited from the atmosphere as a result of the Cu-Ni enterprise activity. They also affected the underlying soil and neutralized the most toxic water-soluble and exchangeable fractions of Cu and Ni. Grass growing and litter deposition (in total 4.5-6 kg·m-2) during the experiment term led to the accumulation of organic carbon by serpentine minerals about 1.5%. Organic matter accumulation also played a significant role in metal binding by upper Technosol layers. Summarily, the remediation technology through the use of serpentine-reached mining wastes bound metals emitted by smelter into insoluble forms, reduced the toxicity of water-soluble and exchangeable fractions of heavy metals and promoted the sustainable development of plant cover.

Research was carried out with the support of the Russian Science Foundation grant 19-77-00077.

 
Solar quiet daily (Sq) geomagnetic variation during minimum of solar cycle 23/24
Authors: Soloviev Anatoly , Smirnov Artem
Published: March 2020

The most regular of all daily geomagnetic field variations is the so-called solar quiet, or Sq, variation. It is attributed to the two current vortices flowing in the E-region of the dayside ionosphere. We present an investigation of the time-dependent parameters of Sq variation for the historical minimum of solar activity in 2008. We apply "Measure of Anomalousness" algorithm to detection of magnetically quiet days. The global maps of seasonal Sq amplitudes of the three orthogonal components are derived using 75 INTERMAGNET and 46 SuperMAG stations at low and middle latitudes. The global Sq amplitudes are compared to the previous Coupled Magnetosphere-Ionosphere-Thermosphere (CMIT) model simulations and show good agreement. Significant variability was found in Sq(X) and Sq(Y) based on the solar activity and latitude, while almost no difference is observed in Sq(Z) for across all latitudes and seasons. We analyze equivalent Sq current system using observatory data from the Australian mainland and narrow European-African latitudinal segment. Sq current system also strongly depends on solar activity, as current vortices are strongest in the local summer-hemisphere and disintegrate during local winter. The dynamics of Sq variation along the solar cycles 23 and 24 is also discussed and compared to Swarm-based spherical harmonic Sq model.
IMERG Multi-Satellite Products Across Two Decades
Authors: Huffman George J , Bolvin David T. , Braithwaite Dan , Hsu Kuolin , Joyce Robert J. , Kidd Christopher , Nelkin Eric J. , Sorooshian Soroosh , Tan Jackson , Xie Pingping
Published: March 2020

The Version 06 Global Precipitation Measurement (GPM) mission products were completed over the last year, capping five years of development since the launch of the GPM Core Observatory, and covering the joint Tropical Rainfall Measuring Mission (TRMM) and GPM eras with consistently processed algorithms.  The U.S. GPM team’s Integrated Multi-satellitE Retrievals for GPM (IMERG) merged precipitation product enforces a consistent intercalibration for all precipitation products computed from individual satellites with the TRMM and GPM Core Observatory sensors as the TRMM- and GPM-era calibrators, respectively, and incorporates monthly surface gauge data in the Final (research) product.  Mid-latitude calibrations during the TRMM era necessarily are more approximate because TRMM only covered the latitude band 35°N-S, while GPM covers 65°N-S.  Starting in V06, IMERG employs precipitation motion vectors (used to drive the quasi-Lagrangian interpolation, or “morphing”) that are computed by tracking the vertically integrated vapor as analyzed in MERRA2 and GEOS FP.  This approach covers the entire globe, expanding coverage beyond the 60°N-S latitude band provided by IR-based vectors in previous versions, although we choose to mask out microwave-based precipitation over snowy/icy surfaces as unreliable.

We will provide examples of performance for the V06 IMERG products, including comparison with the long-term record of GPCP and TMPA, showing higher values by about 8% in the latitude band 50°N-S over oceans; diurnal cycle, demonstrating improvement over previous versions; and daily precipitation PDFs for the entire record, showing a shift at the TRMM/GPM boundary, as well as interannual variations.  These analyses have important implications for the utility of V06 IMERG data for long-record calculations.  Finally, we will review the retirement of the predecessor TMPA multi-satellite dataset.
Modelling the water-system in the Pyrenean Aure-Louron Valley
Authors: Huang Peng , Sauquet Eric , Vidal Jean-Philippe , Dariba Natacha
Published: March 2020

The increasing demand for renewable energy renders the optimal management of the water-energy nexus highly important, and the complexity of global change compromises the sustainability of current water use. Therefore, models representing human interventions on water resource are crucial. This work takes the multipurpose reservoir system of the Aure-Louron Valley in the center of the Pyrenees as a typical study case to establish an integrated hydrological modelling framework. Hydropower and downstream consumption represent the main water uses in the study case. The work is a scientific contribution to the Interreg PIRAGUA project (https://www.opcc-ctp.org/en/piragua). Detailed work aims to develop a modelling chain that integrates a water resource model, a water demand model, and a water management model. This study focuses on the water resource model and the water demand model for energy. Water resource is characterized by the hydrological model GR6J (Riboust et al., 2019), calibrated with the SAFRAN surface reanalysis (Vidal et al., 2010) with a dedicated Pyrenean 2.5 km resolution version, and gap-filled MODIS data (Gascoin et al., 2015) for better robustness of snowpack modelling. The energy demand model is based on the air temperature of France and calendar day (Hendrickx and Sauquet, 2013). It is validated with the historical data of water used for hydropower production over the 2001-2018 period. Tools are being developped to make the models transposable to a wide range of water management contexts. The next steps of the study will focus on establishing a water demand model for downstream consumption, and a water management model. Finally, the modelling chain will be applied under various global change scenarios to assess the vulnerability of the system.

References:

Hendrickx, F. and Sauquet, E. (2013). Impact of warming climate on water management for the Ariège river basin (France). HYDROLOG. SCI. J., 58(5): 976-993.

Riboust, P., Thirel, G., Le Moine, N., and Ribstein, P. (2019). Revisiting a simple degree-day model for integrating satellite data: Implementation of SWE-SCA hystereses. J. HYDROL. HYDROMECH., 67(1): 70-81.

Vidal, J.-P., Martin, E., Franchistéguy, L., Baillon, M., and Soubeyroux, J.-M. (2010). A 50-year high-resolution atmospheric reanalysis over France with the SAFRAN system. INT. J. CLIMATOL., 30(11):1627–1644.