bluuebunny/crossref_metadata_2025 huggingface dataset:
Floating marine macro-litter distribution in the Russian Arctic Seas in relation to oceanographic characteristics
Authors: Pogojeva Maria , Yakushev Evgeniy
Published: March 2021

The main objectives of this work was the acquisition of new data on floating marine macro litter (FMML) and natural floating objects in the Arctic seas, an initial assessment of the level of pollution by FMML and an analysis of potential sources. The results of this study present the first data on FMML distribution in Russian Arctic shelf seas in relation to oceanographic conditions (i.e. position of water masses of different origin as described by temperature, salinity, dissolved oxygen and pH). The main finding of this study is that FMML was found only in the water of Atlantic origin, inflowing from the Barents Sea, where FMML average density on the observed transects was 0.92 items/ km2. Eastern parts of the study, Kara Sea, Laptev Sea and East Siberian Sea were practically free from FMML. The input from rivers appears to be negligible, at least in autumn.
The Magnetospheric “Zebra Stripes”: A Tracer of Near-Earth Space Dynamics
Authors: Lejosne Solène , Mozer Forrest S.
Published: March 2021

High-energy resolution measurements of energetic (tens to hundreds of keV) electron fluxes in the Earth’s inner radiation belt and slot region (below L~ 3) revealed the presence of drift-periodic structures named the “zebra stripes”.

We show that analyzing the characteristics of the zebra stripes provides a new tool to shed light on important, yet mostly uncharted drivers of the Earth’s inner magnetosphere, namely, (a) radial displacements of geomagnetically trapped particles in the inner belt and slot region, and (b) electric field variations in the subauroral region.

With the large database of high-quality observations provided by the NASA Van Allen Probes mission, it is for the first time possible to perform long-term statistical analysis of the zebra stripe pattern.

Because Earth-like zebra stripes were also recently discovered at Saturn, the analysis of the zebra stripes present at Earth could constitute a benchmark to determine the electric fields and associated radiation belt dynamics at other magnetized planets.
3D mantle flow induced by retreating and advancing slabs: insights from analogue subduction models analysed with a tomographic Particle Image Velocimetry technique
Authors: Strak Vincent , Schellart Wouter Pieter , Xue Kai
Published: March 2021

Slab rollback-induced mantle flow in retreating subduction zones is known to have a significant geodynamic impact on Earth. The resulting quasi-toroidal circulation can deflect mantle plumes, transport geochemical signatures and have an upwelling component that thereby generates atypical intraplate volcanism near lateral slab edges. Nevertheless, the mantle flow generated by advancing slabs remains unstudied and its geodynamic significance unclear. We therefore conducted analogue buoyancy-driven subduction models to investigate the mantle flow generated in both retreating and advancing subduction modes. We analysed our models using a novel tomographic Particle Image Velocimetry technique, allowing us to compute the 3D velocity field in a volume of the mantle. Our model results show that the advancing subduction mode develops a slab rollover geometry that produces a quasi-toroidal mantle flow with mantle material displaced from the mantle wedge domain to below the subducting plate, opposite to mantle flow during the retreating mode. This slab rollover-induced mantle flow generates an upwelling component that is laterally offset from the subducting plate and is located some ~1000 km from the trench on the subducting plate side. Such newly imaged mantle flow may have implications for intraplate volcanism and the distribution of mantellic geochemical signatures associated with advancing subduction zones, such as the Makran, and continental subduction zones, such as the Himalaya.
Non-Stationarity of Wintertime Atmospheric Circulation Regimes in the Euro-Atlantic Sector
Authors: Falkena Swinda , de Wiljes Jana , Weisheimer Antje , Shepherd Ted
Published: March 2021

Atmospheric circulation regimes can be used to study links between regional weather and other climate processes, like sudden stratospheric warmings. For these studies it is important to know whether there is any background non-stationarity in the regimes themselves. To identify regime non-stationarity model ensemble data is needed to have sufficient data. However, models are noisy in their representation of circulation regimes making obtaining the signal difficult. We propose a new method, in the form of a constraint on the ensemble-member similarity in the clustering method, to identify the signal of the non-stationary regime dynamics.

We use ECMWF SEAS5 hindcast data to identify six wintertime circulation regimes over the Euro-Atlantic sector (NAO+/-, Atlantic Ridge (AR) +/- and Scandinavian Blocking (SB) +/-), which has been found to be the optimal number of regimes in a previous study. Implementing the constraint leads to more robust regimes and the identification of a stronger inter-annual signal in the regime occurrence rates than without the constraint. The clearest signal on inter-annual timescales is found during strong El Niño years. During those years the NAO+ becomes less frequent, while the SB- occurs more often. The signal in the occurrence rate of the NAO- is weaker than for the NAO+. Without the implementation of the constraint this difference in the strength of the signal between the two phases of the NAO cannot be detected. Thus, the constraint on the ensemble-member similarity allows for identifying a non-stationary signal that otherwise is more difficult to obtain.
Convection-circulation interactions over West Africa in simulations with explicit and parameterised convection
Authors: Morris Francesca , Schwendike Juliane , Parker Doug , Bain Caroline
Published: March 2021

This work examines the representation of convection-circulation coupling over tropical West Africa in convection-permitting models. Tropical West Africa is not only a region characterised by extremely high-impact weather, in the form of intense and frequent organised convection, but it is also a region of strong baroclinicity and wind shear, and therefore an excellent natural laboratory for examining the connections between mesoscale convection and synoptic circulations. Developing understanding ofconvection-circulation coupling is crucial to informing development of convection parameterisations and improving regional forecasts of high-impact weather.

We evaluate output from the CP4-Africa configuration of the Met Office Unified Model to investigate links between convective activity and synoptic motions. To illustrate its strengths in representing convection-circulation feedbacks, CP4 output is compared to that from a similar UM configuration which uses a convection parameterisation.

We examine the mean diurnal cycle of circulation during the storm season. Distinct diurnal patterns in circulation tendency are compared to patterns in updraughts and precipitation, which illustrate different forms of convection which can be observed at different points during the day. A “congestus” mode convects up to around the freezing level from morning until early evening, while deep organised convection triggers in the mid-to-late afternoon and persists overnight. The two forms of convection appear to cause characteristically different responses in the synoptic circulation.

To confirm which physical processes cause changes to circulation in the region, we calculate terms in the circulation tendency equation. Separating these terms into mean and eddy-flux contributions allows us to establish the extent to which mesoscale systems and synoptic structures each influence the diurnal changes to circulation.
Translating weather forecasts to road accident probabilities
Authors: Becker Nico , Rust Henning , Ulbrich Uwe
Published: March 2021

In Germany about 1000 severe road accidents are recorded by the police per day. On average, 8 % of these accidents are related to weather conditions, for example due to rain, snow or ice. In this study we compare several versions of a logistic regression models to predict hourly probabilities of such accidents in German administrative districts. We use radar, reanalysis and ensemble forecast data from the regional operational model of the German Meteorological Service DWD as well as police reports to train the model with different combinations of input datasets. By including weather information in the models, the percentage of correctly predicted accidents (hit rate) is increased from 30 % to 70 %, while keeping the percentage of wrongly predicted accidents (false-alarm rate) constant at 20 %. Accident probability increases nonlinearly with increasing precipitation. Given an hourly precipitation sum of 1 mm, accident probabilities are approximately 5 times larger at negative temperatures compared to positive temperatures. When using ensemble weather forecasts to predict accident probabilities for a leadtime of up to 21 h ahead, the decline in model performance is negligible. We suggest to provide impact-based warnings for road users, road maintenance, traffic management and rescue forces.
Process-based analysis of land carbon flux predictability
Authors: Dunkl István , Spring Aaron , Brovkin Victor
Published: March 2021

The land-atmosphere CO2 exchange exhibits a very high interannual variability which dominates variability in atmospheric CO2 concentration. Despite efforts to decrease the discrepancy between simulated and observed terrestrial carbon fluxes, the uncertainty in trends and patterns of the land carbon fluxes remains high. This difficulty raises the question to what extent the terrestrial carbon cycle is even predictable, and which processes explain the predictability. In this study, the perfect model approach is used to assess the potential predictability of net primary production (NPP) and heterotrophic respiration (Rh) by using initialized ensemble experiments simulated with the Max Planck Institute Earth System Model. In order to determine which processes are causing the derived predictability patterns, carbon flux predictability was decomposed into individual drivers. Regression analysis was used to determine the contribution of the predictability of different environmental drivers to the predictability of NPP and Rh (Soil moisture, temperature and radiation for NPP and soil organic carbon, temperature and precipitation for Rh). The main drivers of NPP predictability are soil moisture and temperature, while the predictability signal from radiation is lost after the first month of simulation. Rh predictability is predominantly driven by soil organic carbon, temperature and locally by precipitation. This decomposition of predictability shows that the relatively high Rh predictability is due to the generally high predictability of soil organic carbon. The assessed seasonality in predictability patterns can be explained by the change in limiting factors of NPP and Rh over the wet and dry months. This leads to the adjustment of carbon flux predictability to the predictability of the currently limiting environmental factor. Differences in the predictability between initializations can be attributed to the interannual variability in soil moisture and temperature predictability. This variability is caused by the state dependency of nonlinear ecosystem processes. These results reveal the crucial regions and ecosystem processes to be considered when initializing a carbon prediction system.
Random forests in water resources
Authors: Tyralis Hristos , Papacharalampous Georgia , Langousis Andreas
Published: March 2021

Random forests is a supervised machine learning algorithm which has witnessed recently an exponential increase in its implementation in water resources. However, the existing implementations have been restricted in applications of Breiman’s (2001) original algorithm to regression and classification models, while numerous developments could be also useful for solving diverse practical problems. Here we popularize random forests for the practicing hydrologist and present alternative random forests based algorithms and related concepts and techniques, which are underappreciated in hydrology. We review random forests applications in water resources and provide guidelines for the full exploitation of the potential of the algorithm and its variants. Relevant implementations of random forests related software in the R programming language are also presented.
Polarimetric radar-sounding to infer and quantify shear margin ice fabric anisotropy
Authors: Young Tun Jan , Jordan Thomas M , Martín Carlos , Schroeder Dustin M , Christoffersen Poul , Tulaczyk Slawek M , Culberg Riley , Bienert Nicole L
Published: March 2021

Glaciers and ice streams channel the majority of ice mass discharge into the ocean, and are modulated by basal slip at the ice-bed interface, deformation within the ice interior, and lateral shear at the margins separating fast- and slow-moving ice. The anisotropy of glacier ice (i.e. ice that deforms preferentially in certain modes and directions) at shear margins greatly facilitates streaming ice, however it is still poorly understood due to a lack of in-situ measurements and is usually incorporated into models as a simple scalar enhancement factor. The resurgence of polarimetric radar techniques to detect bulk fabric anisotropy through exploiting the birefringence of ice crystals has greatly aided quantification of the ice crystal orientation fabric (COF) across the Antarctic Ice Sheet. In our study, we invert these techniques to infer the azimuthal fabric strength at the Eastern Shear Margin of Thwaites Glacier from non-polarimetric airborne radargrams collected during the 2018-19 field season. From these results, we infer the evolution of the crystal orientation fabric across the shear margin, where ice is subjected to varying levels of both pure and simple shear. Our findings suggest the potential of the upper reaches of the ESM having undergone recent inward migration. Together with compatible ground-based polarimetric radar experiments, our study highlights the potential of radar sounding to observe and infer variations in fabric strength from regions of complex flow at multiple spatial scales. Because the bulk COF of ice sheets records the past history of ice sheet deformation and influences present-day ice flow dynamics, accurate measurements of ice fabric strength and orientation not only places constraints on present and past ice flow history, but also aids in the incorporation of anisotropic rheology in ice flow models.
Optical properties of Gobi dust and its pure compounds: experimental extinction spectra and complex refractive indices determination.
Authors: Deschutter Lise , Herbin Hervé , Petitprez Denis
Published: March 2021

Spectrometers are powerful instruments to detect atmospheric aerosols, especially on satellites since they allow measurements at a global scale and over different spectral ranges with high spectral resolution. However, to fully exploit their capabilities and to link optical properties, chemical composition and mass concentration, it is essential to have reference optical properties of various particles and mainly the complex refractive indices (CRI). The CRI of a natural aerosol source can be determined from a real sample of it or applying the effective medium approximation using the CRI of the pure compounds present in the natural sample. But in that case, it is necessary to know the mass fraction of each individual compound and above all their CRI. Nevertheless, the literature and CRI databases provide only reflectance measurements on bulk materials or pressed pellets and over a limited wavelength range (Querry et al., 1987).

In the present work, dust from the Gobi desert is studied as it is the second most active dust source, after the Sahara desert, in terms of mass emissions (Querol et al., 2019). For that extinction spectra have been recorded for natural Gobi dust sample and for its major compounds (Illite, Calcite and Quartz). Particles as a powder in a vessel are generated thanks to a magnetic stirring and a flow of nitrogen (Hubert et al., 2017). The continuous flow of aerosols is directed into a 10-meters multipass cell fitted to a Fourier transform infrared spectrometer and a 1-meter singlepass cell within a UV-Visible spectrometer which cover a continuous spectral range from 650 cm-1 to 40000 cm-1. Moreover, at the exit of the spectrometers the size distribution is recorded by an aerodynamic particle sizer and a scanning mobility particle sizer which allow to measure size particles from 14 nm to 20 µm. An inversion algorithm is carried out using experimental extinction spectra and the size distribution as input data (Herbin et al., 2017). Applying the Mie theory and the single subtractive Kramers-Kröning integral, the real and the imaginary part of the CRI are retrieved at each wavelength with an optimal estimation method.

For the first time, CRI of Illite has been retrieved with a high spectral resolution (1 cm-1) and over a wide spectral range for suspended particles. For calcite and quartz particles, the crystalline phase has to be considered by introducing the ordinary and extraordinary indices. These pure compound sets of CRI will be used for testing effective medium approximation on Gobi dust for which effective CRI have been also retrieved.
Inference of barchan interaction properties from a comparison of theoretical modelling and observation
Authors: Robson Dominic , Baas Andreas , Annibale Alessia
Published: March 2021

It is well known that barchan dunes are not isolated bedforms but are able to interact with one another both directly, through collisions and the emission/absorption of flux, and indirectly, due to the effects of turbulence in the wake of a dune.  In recent years, wave-tank experiments, continuum simulations, and cellular automata models have enabled researchers to model barchan-barchan interactions.  The findings from these studies have been fed into object-based models of entire fields of barchans and used to predict the size distributions.  Although there has been some success with these techniques, each model has failed to reproduce certain known properties on the field-scale; for instance, that the mean width is constant with downwind distance.  Furthermore, previous attempts have not been based on a theoretical understanding of the role of interactions in determining the dune size distribution, thus limiting their potential as universal models of barchan swarms.

Mean-field models are relatively simple in terms of the mathematics, but have shown some degree of success in the modelling of barchan fields, although previous work has  focused only on specific cases of interaction rules.  We have developed a more general mean-field model which can include many different forms of interaction, making it applicable to a variety of problems, including socio-economic systems as well as fields of interacting barchans.  Despite the generality of our model, we have been able to derive expressions for the dependence of the steady-state size distribution, and its moments, on the choice of interaction rules.  This means that, by making a measurement of the size distribution of a barchan field, we are able to infer properties of the interactions at play. 

To demonstrate the power of such a model we have measured size distributions of several barchan fields in the area of Tarfaya, Morocco.  Measurements were made by recording locations of seven distinct points on each barchan to yield morphometric parameters of each dune and compile the size-distribution.  By comparing the distribution and its moments to those predicted by the model, we can infer certain properties of the interaction rules, such as the relative probabilities of the different forms of collision.  The results show an example of how our model provides a more comprehensive understanding of the way in which dune-dune interactions determine properties on the scale of the field. 
Enhanced wind variability in the orographic gravity wave parameterisation and its influence on dynamics
Authors: Eichinger Roland , Sacha Petr , Kuchar Ales , Pisoft Petr , Garny Hella
Published: March 2021

Comprehensive global climate simulations are still conducted in fairly low resolution. Current general circulation models therefore rely on gravity wave parameterisations to simulate atmospheric dynamics correctly. Among other parameters, the surface wind determines gravity wave launching in orographic gravity wave parameterisations. However, the mountainous terrain in regions where orographic gravity waves occur suggests larger surface wind variability on unresolved topography than the model grid box wind can provide. To account for this variability, we here present a stochastic modification of the low-level wind direction when it is used in the orographic gravity wave scheme of the EMAC (ECHAM MESSy Atmospheric Chemistry) model. For our first application, we implemented a random normal function to evoke a modest deviation of the wind direction at each time step when it is used in the subgrid scale scheme.

An EMAC simulation shows that this gravity wave modification locally leads to significant changes of orographic gravity wave drag, but this does not result in significant annual or seasonal differences in temperatures or winds. However, the Arctic polar vortex is stretched and its center shifts in February. Moreover, we find a shift in the Antarctic polar vortex breakdown date, resulting in a significant zonal mean temperature change in October and possibly in an alleviation of the EMAC low bias in Antarctic polar vortex strength. In this presentation, we discuss our results, the method and possible further developments like allowing gusts in the modified scheme.
Mapping the aerodynamic roughness of the Greenland ice sheet surface using ICESat-2
Authors: van Tiggelen Maurice , Smeets Paul C.J.P. , Reijmer Carleen H. , Wouters Bert , Steiner Jakob F. , Nieuwstraten Emile J. , Immerzeel Walter W. , van den Broeke Michiel R.
Published: March 2021

The roughness of a natural surface is an important parameter in atmospheric models, as it determines the intensity of turbulent transfer between the atmosphere and the surface. Unfortunately, this parameter is often poorly known, especially in remote areas where neither high-resolution elevation models nor eddy-covariance measurements are available.

In this study, we take advantage of the measurements of the ICESat-2 satellite laser altimeter. We use the geolocated photons product (ATL03) to retrieve a 1-m resolution surface elevation product over the K-transect (West Greenland ice sheet). In combination with a bulk drag partitioning model, the retrieved surface elevation is used to estimate the aerodynamic roughness length (z0m) of the surface.

We demonstrate the high precision of the retrieved ICESat-2 elevation using co-located UAV photogrammetry, and then evaluate the modelled aerodynamic roughness against multiple in situ eddy-covariance observations. The results point out the importance to use a bulk drag model over a more empirical formulation.

The currently available ATL03 geolocated photons are used to map the aerodynamic roughness along the K-transect (2018-2020). We find a considerable spatiotemporal variability in z0m, ranging between 10−4 m for a smooth snow surface to more than 10−1 m for rough crevassed areas, which confirms the need to incorporate a variable aerodynamic roughness in atmospheric models over ice sheets.
Terrestrial frame solutions from the IGS third reprocessing
Authors: Rebischung Paul
Published: March 2021

The International GNSS Service (IGS) recently finalized its third reprocessing campaign (repro3). Ten Analysis Centers (ACs) reanalyzed the history of GPS, GLONASS and Galileo data collected by a global tracking network over the period 1994-2020. Combinations of the daily repro3 AC terrestrial frame solutions constitute the IGS contribution to the next release of the International Terrestrial Reference Frame, ITRF2020.

Compared to the previous IGS reprocessing campaign (repro2), a number of new models and strategies have been implemented in repro3, including the new IERS linear pole model, the new IERS-recommended sub-daily EOP tide model, and rotations of phase center corrections for tracking antennas not oriented North. Besides, a new set of satellite antenna phase center offsets was adopted in repro3, based on the published pre-flight calibrations of the Galileo satellite antennas. As a consequence, the IGS contribution to ITRF2020 provides for the first time an independent Galileo-based realization of the terrestrial scale, instead of being conventionally aligned in scale to the previous ITRF.

In this presentation, quality metrics from the daily repro3 terrestrial frame combinations are first introduced and compared to those from repro2. The impacts of the newly adopted models are then assessed and discussed. The terrestrial scale realized by the IGS repro3 solutions is in particular confronted to independent estimates from SLR and VLBI. The precision of the IGS repro3 station position time series is finally compared to that of the IGS repro2 series as well as of station position time series from independent groups.
Late Cenozoic two-phase rapid exhumation of the Daliang Mountains, Southeastern Tibetan Plateau
Authors: Lei Haijia , Shen Xiaoming , Liu Xijun , Tang Xiudang , Zhang Shiming
Published: March 2021

The southeastern Tibetan Plateau experienced significant tectonic uplift, fault activity, climate change and reorgnization of fluvial systems during the late Cenozoic. All these processes were probably accompanied by rapid rock exhumation. Therefore, rock exhumation history in this region could provide a key to reveal the interaction between tectonics, climate and surface processes. Here, we report new apatite and zircon (U-Th)/He dates from a ~1200 m granite vertical profile, located at Shimian county in the Daliang Mountains, southeastern Tibetan Plateau. The age-elevation relationship and thermal history simulation exhibit a two-phase rock exhumation history, one at ~25 Ma (~1 km/Myr) and a second moderate exhumation from ~15 Ma to present (~ 0.2 km/Myr). This two-phase rapid exhumation history is consistent with that of Longmen Shan and Jiulong in the adjacent areas. For the first phase in Oligocene, abundant geological evidence indicates that it was related to the regional uplift caused by the transpressional deformation during India-Asia convergence. However, there are two distinct explanations for the rapid exhumation from ~15 Ma to present: one group suggested this exhumation was related to the rapid river incision caused by regional uplift; By contrast, based on paleo-altimetry data another group proposed the uplift was ceased before the late Miocene in southeastern Tibetan Plateau, and then the enhanced rainfall caused by the East Asian monsoon resulted in rapid exhumation since the Middle Miocene. Our study suggests that the fast exhumation in southeastern Tibetan Plateau since ~15 Ma cannot be attributed solely to the regional uplift or the intensification of Asian monsoon. Combined with the activity history of the Anninghe fault in the study area and the East Asian monsoon evolution history, we suggest that the regional rock exhumation of southeastern Tibetean Plateau since the Middle Miocene could be the result of the combination of tectonic activity and climate change.
Increase in seismic activity near the footprints of new radiation belts forming after geomagnetic storms
Authors: Toyshiev Nursultan , Khachikyan Galina , Zhumabayev Beibit
Published: March 2021

Recently, attention was drawn [1] that after geomagnetic storms that cause formation of new radiation belts in slot region or in the inner magnetosphere, after about 2 months, there is an increase in seismic activity near the footprints of geomagnetic lines of new radiation belts. More detailed studies showed [2] that on May 30, 1991, an earthquake M=7.0 occurred in Alaska with (54.57N, 161.61E) near the footprint of geomagnetic line L = 2.69 belonging to new radiation belt, which was observed by the CRRES satellite [3] around geomagnetic lines 2<L<3 after geomagnetic storm on March 24, 1991. After geomagnetic storm on September 3, 2012, the Van Allen Probes satellites observed new radiation belt around 3.0≤L≤3.5 [4], and about 2 months later, on October 28, 2012, earthquake M=7.8 occurred off the coast of Canada (52.79N, 132.1W) near the footprint of geomagnetic line L=3.32 belonging to the new radiation belt. Also, Van Allen Probes observed new radiation belt around L=1.5-1.8 after geomagnetic storm on June 23, 2015 [5], and ~2 months later, in September 2015, seismic activity noticeably increased near the footprint of these geomagnetic lines. We consider variations in seismic activity in connection with the strongest geomagnetic storms in 2003 with Dst~- 400 nT (Halloween Storm) and the formation of a belt of relativistic electrons in the inner magnetosphere around L~1.5 existed until the end of 2005 as observed SAMPEX [6]. Analysis of data from the USGS global seismological catalog showed that near the footprint of geomagnetic lines L=1.4-1.6 the number of earthquakes with M≥4.5 increased in 2003-2004 by ~70% compared with their number in two previous years. On the Northern Tien Shan, on December 1, 2003 a strong for the region earthquake M=6.0 occurred on the border of Kazakhstan and China (42.9N, 80.5E) near the footprint of L = 1.63, adjacent to the new radiation belt.
Preventing waterlogging in irrigated agriculture with a multi-satellite sensor approach
Authors: den Besten Nadja , Steele-Dunne Susan , de Jeu Richard , van der Zaag Pieter
Published: March 2021

Satellite sensors have been used widely to determine water shortages to detect crop stress, with special emphasis on water stress. However, stress resulting from waterlogging has so far received little attention. This is surprising because approximately twenty percent of the global agricultural land suffers from the consequences of waterlogging and secondary soil salinization. While irrigation is expected to increase productivity, excess water can hamper the crop growth and decrease water use efficiency.

Traditionally, satellite driven water accounting for irrigation assistance uses optical and/or thermal sensors that can detect crop stress. The observed crop stress is often interpreted as water stress, whereby stress resulting from waterlogging cannot be distinguished. We hypothesize that a multi-sensor approach is required to distinguish waterlogging from water shortage, by including microwave observations that can determine the soil moisture status. However, localizing a small-scale phenomena as waterlogging with multi-sensor data with different resolutions is a major challenge.

In our research we focus on an irrigated sugarcane plantation along the river Incomati in Xinavane, Mozambique. Waterlogging is a common issue in the estate and is threatening productivity. We assess and combine optical and passive microwave data for a large drought (2016) and flooding event (2012) to look at the possibility of downscaling the data for detection of waterlogging. We find that optical indices are able to localize waterlogged areas. Additionally, the built up of the drought event and retreat of the flooding event are clearly visible in the brightness temperature in different frequencies. We demonstrate a procedure to combine brightness temperature with optical data to detect waterlogging at a higher spatial resolution. 

The results show that a combination of optical and passive microwave data can detect regions within the sugarcane plantation of waterlogging. However, high resolution topographic data is required to enhance the detection of waterlogging to finer scales. 
Influence of Loess Plateau check dams on catchment flood hydrology across varying stages of lifespan
Authors: Yuan Shuilong , Li Peng , Shi Peng , Zhang Zeyu
Published: March 2021

The over 100,000 check dams constructed across the Loess Plateau for soil and water conservation may have substantially changed the hydrological processes in the region, which, however, has not been understood yet. As a critical step towards revealing the lumped effect of check dams at the regional scale, this study explored the modified flood hydrology induced by check dams in Wangmaogou catchment, a representative small Loess Plateau watershed. A coupled hydrological and hydraulic modeling approach was applied to simulate the flooding process for different stages of deposition and topographic changes in the check dam reservoir. The results suggest a paradigm shift of the dam effect on flood attributes, which transits from a total interception in the early stage of the dam to peak reduction and flood detention, rather than a complete loss of flood control functions, when it approaches the maximum capacity of sedimentation. Under a given level of deposition, the reduction to a minor flood by a check dam was higher than that to a major flood. With the progression of siltation behind the check dam, the flood peak reduction rate, flood volume reduction rate, and flood lag time decreased accordingly. Although the check dam with a reservoir fully filled by sediment lost its ability of intercepting floods, it still exhibited a considerable ability to reduce the peaks of floods. The topographical changes contributed to the reduction of flood peak appreciably by reducing the flow velocity and retarding the flood propagation. Noticeably, this reduction augmented with the advancement of siltation and the topographic change, indicating the persistence of the hydrologic effect of check dams in a long run. As a result of hydrological changes, the reduction in flood flow velocity due to check dam suggests a substantial reduction in sediment transport and channel erosion during floods. In addition, a dam system containing multiple, cascading check dams exhibits much more significant effect in modifying both hydrologic and hydraulic properties of flood than individual dams. The current research provides a mechanistic understanding of the check dam effect on watershed hydrology under heavy rainstorms in small catchments, which sheds light on evaluating the upscaled effect of the large number of check dams on Loess Plateau regional hydrology and water resources.
Model evaluation of compound precipitation and wind extremes over Europe
Authors: Owen Laura , Catto Jennifer , Stephenson David , Dunstone Nick
Published: March 2021

Extreme precipitation and winds can have a severe impact on society, particularly when they occur at the same place and time. Studies have investigated the frequency of co-occurring extreme precipitation and wind using observational data. However, due to the rarity of very extreme events, these results are limited, since a large number of samples is needed to get robust estimates. Additionally, it is very difficult for estimates based on observations alone to help us understand the risk of future unprecedented events. Using the UNSEEN method (UNprecedented Simulated Extremes using ENsembles) this risk can be estimated from large ensembles of climate simulations. The Met Office's Global Seasonal forecast system version 5 (GloSea5) model ensembles are evaluated against ERA5 reanalysis data to find out how well they represent extreme precipitation, extreme wind and extreme co-occurring events over Europe. This model has not been evaluated in such a way before and this is needed before the model can be used to estimate the likelihood of unprecedented events using the UNSEEN method. We find that although the intensity of precipitation and wind extremes differ between the model and observations (by up to 12 mm and 9 m/s), the frequency of co-occurring events is well represented. The extremal dependency measure, χ, which measures co-occurrence, compares well spatially over Europe between GloSea5 and ERA5. However, significant differences in χ are found over areas of high topography, over the North Atlantic, Western Europe and the Norwegian Sea. Generally, GloSea5 underestimates χ over the ocean, and performs better over land. Mean sea level pressure anomaly composites for co-occurring extreme events show that at a number of selected locations, the co-occurring extremes are produced by very similar synoptic situations in the model and reanalysis. This gives increased confidence in the model. The model ensembles can then be used to assess the present day likelihood of unprecedented 3 hourly compound precipitation and wind extremes for winter over Europe, and to find out how the NAO index influences the frequency of co-occurring events over Europe.
Deep Learning for Climate Model Output Statistics
Authors: Steininger Michael , Abel Daniel , Ziegler Katrin , Krause Anna , Paeth Heiko , Hotho Andreas
Published: March 2021

Climate models are an important tool for the assessment of prospective climate change effects but they suffer from systematic and representation errors, especially for precipitation. Model output statistics (MOS) reduce these errors by fitting the model output to observational data with machine learning. In this work, we explore the feasibility and potential of deep learning with convolutional neural networks (CNNs) for MOS. We propose the CNN architecture ConvMOS specifically designed for reducing errors in climate model outputs and apply it to the climate model REMO. Our results show a considerable reduction of errors and mostly improved performance compared to three commonly used MOS approaches.
Monitoring Bee Diversity in Natural Systems – Novel Aerial and Classical Ground Methods to Evaluate Biotic and Abiotic Indicators
Authors: Di Pietra Vincenzo , Dabove Paolo , Mandelik Yael , Mishael Yael , Levy Karmit , Dor Maoz
Published: March 2021

Bees provide essential pollination services to natural ecosystems and agricultural crops. However, managed and wild (unmanaged) bee populations are in decline worldwide. In order to better manage and restore bee populations, long-term monitoring programs are required. Direct bee monitoring is costly, labor intensive, and requires high expertise. Therefore, cost-effective indicators for bee diversity and community composition are essential.
Here we propose to test the cost-efficacy of novel aerial techniques along with classical ground methods to collect biotic and a-biotic indicators of bee diversity and community composition. We will couple classical ecological monitoring approach with advanced photogrammetric tools, in order to develop a multi-scale and multi-temporal platform for monitoring bees. To this end, we formed a complementary, interdisciplinary research group of a pollination ecologist, soil chemists, environmental engineer, geomatics engineer, and topography surveyot. The study will include field work in two complimentary study systems in central Israel, light sandy vs heavy vertisol soils. In each study system we will concurrently conduct bee, flower, bee nesting substrates and soil surveys using classical tools/approaches, as well as apply advanced photogrammetric tools, based on RGB images, with thermal, multispectral data. The indicative ability for bee diversity and community composition of the different biotic and a-biotic measures collected, will be tested using advances statistical tools. Our findings may be instructive to other insects and plant groups, thus provide a novel generic approach towards the ecological monitoring of terrestrial systems.
Surprisingly thick active layer of permafrost in the mountain slope in the SW Svalbard
Authors: Majdanski Mariusz , Marciniak Artur , Owoc Bartosz , Dobiński Wojciech , Wawrzyniak Tomasz , Osuch Marzena , Nawrot Adam , Glazer Michał
Published: March 2021

Two high arctic expeditions have been organized to use seismic methods to recognize the shape of the permafrost along inclined profile between the coast and the mountain slope in two seasons: with the unfrozen ground (October 2017) and frozen ground (April 2018). For measurements, a stand-alone seismic stations has been used with accelerated weight drop with in-house modifications and timing system. Seismic profiles were acquired in a time-lapse manner and were supported with continuous temperature monitoring in shallow boreholes.

Joint interpretation of seismic data using Multichannel analysis of surface waves, First arrival travel-time tomography and Reflection imaging show clear seasonal changes affecting the permafrost where apparent P-wave velocities are changing from 3500 to 5200 m/s. This confirms the laboratory measurements showing doubling the seismic velocity of water-filled high-porosity rocks when frozen. Independent refraction seismic analysis in two seasons shows in average 10 m thick sedimentary layer on top of compacted bedrock. In sediments P wave velocity is changing from 1500 m/s to 4000 m/s between seasons. Velocities in the bedrock are also changing from 4000 m/s to 5500 m/s. Moreover, tomographic interpretation shows that significant change in P wave velocities is observed down to 30 meters.

Such unusual active layer behavior is confirmed in in-situ thermal observations with above 0C temperatures at the depth of 19m. Those observations can be explained with strong underground flow during the frozen period confirmed with borehole. 

 

Acknowledgements               

This research was funded by the National Science Centre, Poland (NCN) Grant UMO-2015/21/B/ST10/02509.
Detection of drainage ditches using high-resolution LIDAR data in the Swedish forest
Authors: Paul Siddhartho S. , Ågren Anneli M. , Lidberg William
Published: March 2021

Drainage ditches are common in boreal forests and provide better soil aeration and tree growth by draining the wet soils. Peatland drainage in the last century has created about 1 million km of artificial streams in Sweden, making it one of the most widespread human-induced environmental disturbances. This extensive use of ditches over a long period resulted in a major shift in forest hydrology and impacted the ecosystem functions. Therefore, there is a pressing need for an accurate database of forest ditches so that sustainable management can be practiced to improve the overall functioning of the forest ecosystem. Comparisons with national field datasets show that existing maps only show a small fraction (<10%) of the ditches across the country. To address this knowledge gap, we applied AI methods on high-resolution (1 m) LIDAR data to map drainage ditches in a subset of the Swedish forest. We developed a suite of topographic indices and analyzed those with machine learning and deep learning algorithms to perform automatic ditch detection. Both models produced reasonably accurate results and a substantial improvement over the existing maps in terms of ditch detection. The impoundment index and high pass medium filter from the digital elevation model were among the top predictors of drainage ditches. The study introduced a new avenue for accurate detection of forest ditches across the whole country. Our AI-generated maps of ditches provide effective tools for the restoration of degraded land and support ditch cleaning operations to increase forest growth.
Digital soil mapping of soil fertility index for agricultural lands in tropical environment
Authors: Hounkpatin Ozias , Bossa Aymar , Igué Mouinou , Yira Yacouba , Sinsin Brice
Published: March 2021

Indicators of soil production function such as soil fertility index can potentially be a key decision tool in spatial planning for sustainable land management. The establishment of such soil fertility index requires basic soil properties which can be modelled for spatial mapping. The objective of this study was to take advantage of the soil legacy data of Benin to produce a digital soil map of soil fertility index at a national scale based on 8 soil properties (soil organic carbon matter, nitrogen, pH, exchangeable potassium, assimilable phosphorus, sum of base, cation exchange capacity and base saturation). Speciﬁc research aims were: (1) to model and develop digital soil maps; (2) to identify important factors influencing soil nutrients; (3) to establish soil fertility potentials using digital soil maps. For each soil property, modelling procedures involved the use of diﬀerent covariates including soil type, topographic, bioclimatic and spectral data along with the comparative assessment of the Cubist and Quantile Random Forest model. Results revealed that apart from N and exchangeable K, significant models can be produced for most of the soil properties with R-square varying between 28% and 72% with the Quantile Random Forest presenting a more accurate prediction interval coverage probability. The analysis revealed that the distance to the nearest stream has strong predictive ability for all the soil properties along with the bioclimatic variables. Visualisation of the soil fertility map showed that most of the soils in Benin have low fertility level suggesting that the use of fertilizers and organic materials will be critical in sustaining crop productivity. A limited number of high and average fertility level soils were found in the low elevation areas of southern Benin and policy could advocate for their sole use for agriculture purpose as well as promote sustainable management practices.
The under-ice microbiome, a five-year study at Lake Tovel
Authors: Obertegger Ulrike
Published: March 2021

Little is known about changes in microbial abundance and community composition during persistent ice cover of lakes. Here, the under-ice 16S rRNA diversity was assessed for different pelagic layers and compared between years (2015, 2017, 2018, 2019, 2020) at Lake Tovel (1177 m above sea level; Italy). Functional profiling of amplicon sequences variants (ASVs) was also done with Piphillin. Environmental parameters (chemistry, temperature, light climate, oxygen concentration) were linked to the observed diversity patterns. Despite relatively uniform temperature and chemistry profiles, the pelagic and hypolimnetic microbiome of different years were different as assessed by a Principal Coordinates Analysis. The under-ice light climate was a driving factor of the observed differences and related to different precipitations patterns. These results underline how a changing climate also influences life under ice.   
Syn-deformational melt percolation through a high-pressure orthogneiss and the exhumation of a subducted continental wedge (Orlica-Śnieżnik Dome, NE Bohemian Massif)
Authors: Aguilar Carmen , Štípská Pavla , Chopin Francis , Schulmann Karel , Pitra Pavel , Závada Prokop , Hasalová Pavlína , Martelat Jean-Emmanuel
Published: March 2021

High-pressure granitic orthogneiss of the south-eastern Orlica–Śnieżnik Dome (NE Bohemian Massif) shows relics of a shallow-dipping S1 foliation, reworked by upright F2 folds and a mostly pervasive N-S trending subvertical axial planar S2 foliation. Based on macroscopic observations, a gradual transition perpendicular to the subvertical S2 foliation from banded to schlieren and nebulitic orthogneiss was distinguished. All rock types comprise plagioclase, K-feldspar, quartz, white mica, biotite and garnet. The transition is characterized by increasing presence of interstitial phases along like-like grain boundaries and by progressive replacement of recrystallized K-feldspar grains by fine-grained myrmekite. These textural changes are characteristic for syn-deformational grain-scale melt percolation, which is in line with the observed enrichment of the rocks in incompatible elements such as REEs, Ba, Sr, and K, suggesting open-system behaviour with melt passing through the rocks. The P–T path deduced from the thermodynamic modelling indicates decompression from ~15−16 kbar and ~650–740 ºC to ~6 kbar and ~640 ºC. Melt was already present at the P–T peak conditions as indicated by the albitic composition of plagioclase in films, interstitial grains and in myrmekite. The variably re-equilibrated garnet suggests that melt content may have varied along the decompression path, involving successively both melt gain and loss. The 6–8 km wide zone of vertical foliation and migmatite textural gradients is interpreted as vertical crustal-scale channel where the grain-scale melt percolation was associated with horizontal shortening and vertical flow of partially molten crustal wedge en masse.