bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrated biogeography and assembly process of planktonic and sedimentary bacterial communities in the Yangtze River
Authors: Liu Tang , Wang Jiawen , Liu Shufeng , Chen Qian , Zheng Chunmiao , Ni jinren
Published: March 2020

Bacterial communities are essential to the biogeochemical cycle in riverine ecosystems. However, the integrated biogeography and assembly process of planktonic and sedimentary bacterial communities in large rivers is still poorly understood. Here, the study provided the spatiotemporal pattern of bacterial communities in the Yangtze River of 4300 km continuum, which is the largest river in Asia. We found that the taxa in sediments are the main contributors to the bacterial diversity of the river ecosystem since sediments sub-group took 98.8% of the total 38, 904 Operational Taxonomic Units (OTUs) observed in 280 samples. Seasonal differences in bacterial communities were statistically significant in water, whereas bacterial communities in both water and sediment were geographically clustered according to five types of landforms: mountain, foothill, basin, foothill-mountain, and plain. Interestingly, the presence of two huge dams resulted in a drastic fall of bacterial taxa in sediment immediately downstream due to severe riverbed scouring. The integrity of the biogeography was satisfactorily interpreted by the combination of neutral and species sorting perspectives in meta-community theory for bacterial communities in flowing water and sediment. Although deterministic process had dominant influence on assembly processes in water and sediment communities, homogeneous selection was the main contributor in water, while combination of homogeneous selection and variable selection contributed selection process in sediment. In addition, homogenizing dispersal played more important role in community assembly process in sediment than water. Our study fills a gap in understanding of biogeography and assembly process of bacterial communities in one of the world’s largest river and highlights the importance of both planktonic and sedimentary communities to the integrity of bacterial biogeographic patterns in a river subject to varying natural and anthropogenic impacts.
A Lagrangian analysis of upper-tropospheric anticyclones associated with heat waves in Europe
Authors: Zschenderlein Philipp , Pfahl Stephan , Wernli Heini , Fink Andreas H.
Published: March 2020

Heat waves impose large impacts on various sectors. Meteorologically, these events are co-located to upper-tropospheric anticyclones. In order to elucidate the formation of these anticyclones and the role of diabatic processes, we trace air masses backwards from the upper-tropospheric anticyclones and quantify the diabatic heating in these air parcels. We analyse anticyclones that are connected to summer heat waves at the surface during the period 1979 – 2016 in different European regions. Around 25-45% of the air parcels are diabatically heated during the last three days prior to their arrival in the upper-tropospheric anticyclones and this amount increases to 35-50% for the last seven days. The influence of diabatic heating is larger for heat wave anticyclones in northern Europe and western Russia and smaller in southern Europe. Interestingly, the diabatic heating occurs in two geographically separated air streams. Three days prior to arrival, one heating branch (western branch) is located above the western North Atlantic and the other heating branch (eastern branch) is located to the southwest of the target upper-tropospheric anticyclone. The diabatic heating in the western branch is related to the warm conveyor belt of a North Atlantic cyclone upstream of the evolving upper-level ridge. In contrast, the eastern branch is diabatically heated by convection, as indicated by elevated mixed-layer convective available potential energy along the western side of the matured upper-level ridge. Central Europe is influenced by both branches, whereas western Russia is predominantly affected by the eastern branch. The formation of the upper-tropospheric anticyclone, and therefore of the heat wave, is highly depended on the western branch, whereas its maintenance is more affected by the eastern branch. For long-lasting heat waves, the western branch regenerates. The results from this study show that the dynamical processes leading to heat waves may be sensitive to small-scale microphysical and convective processes, whose accurate representation in models is thus supposed to be crucial for heat wave predictions on weather and climate time scales.
Weed-crop competition and the effect on spectral reflectance and physiological processes as demonstrated in maize
Authors: Ronay Inbal , Maman Shimrit , Ephrath Jhonathan E. , Eizenberg Hanan , Blumberg Dan G.
Published: March 2020

Weed-crop competition is a problem affecting food production leading to  significant yield losses in various crops. The use of remote sensing technologies in agriculture enables rapid, non-destructive measurements that can be used for research and agronomical management. Previous research has been conducted characterizing the spectral response of crops to the stress caused by weeds but not much progress has been achieved nor has this been fully connected to physiological processes. Understanding the spectral characteristics of this type of stress is a basic step in advancing precision agricultural technologies for managing weeds in the field. This research focuses on corn (Zea mays) with variable densities of redroot pigweed (Amaranthus retroflexus), a common weed that is known to reduce corn yields. The primary research goal is to characterize the physiological changes that occur in the corn during early growth stages in the presence of weeds of different densities. A secondary goal, is to examine the ability to detect those changes by means of proximal and remote sensing.

During June to August 2019, a field experiment was conducted in Sede – Boker, Israel. Hyperspectral reflectance measurements using an ASD spectrometer,

IR images acquired with a thermal camera and multispectral VIS-NIR images from a mounted UAV were taken. We combined the spectral measurements with physiological measurements (photosynthesis, stomatal conductance and transpiration). The data and results were integrated and analyzed to determine whether physiological differences between variable treatments can be detected by the sensing methods.  Results show that these can be observed, detected and we will provide new explanations associating the competition, spectral response and physiological processes.
Modeling the propagation of atmospheric waves from various tropospheric disturbances and studying their influence on the upper atmosphere
Authors: Kurdyaeva Yuliya , Borchevkina Olga , Kshevetskii Sergey
Published: March 2020

The atmosphere and ionosphere are a complex dynamic system, which is affected by sources, caused both by internal processes and external ones. It is known that atmospheric waves propagating from the troposphere to the upper atmosphere make a significant contribution to the state of this system. One of the regular sources of such waves are various tropospheric disturbances caused, for example, by meteorological processes. Numerical modeling is an effective tool for studying these processes and the effects they cause. However, a number of problems arise, while setting up numerical experiments. The first is that most atmospheric models use hydrostatic approximation (which does not allow the resolution of small-scale perturbations) and work for a limited range of heights (which does not allow studying the relationship between the lower and upper atmosphere). This demands an accurate selection of the model in accordance with the stated research goals. The second problem is the difficulty of direct definition of the wave tropospheric sources, that was mentioned before, due to the lack of experimental information for their detailed description. The authors proposed, researched and tested a way to solve this problem. It was shown that the solution of the problem of waves propagation from a certain tropospheric source is completely determined by the pressure field at the surface of the Earth. This work is devoted to solving various problems using this approach.

This study presents the results of calculations of the propagation of infrasound and internal gravity waves from tropospheric disturbances given by pressure variations at the surface of the Earth. The experimental data associated with various meteorological events and the passage of the solar terminator were obtained both directly - by a network of microbarographs in the studied region, and indirectly - based on the data from the LIDAR signal intensity and temperature changes in the coastal region. The calculations were done using the non-hydrostatic numerical model “AtmoSym”. The characteristics of atmospheric waves generated by such sources are estimated. The effect from a tropospheric sources on the state of the upper atmosphere and ionosphere is investigated. The physical processes that determine the change in atmospheric parameters are discussed.  It is shown that the main contribution from wave disturbances generated by meteorological sources belongs to infrasound. Infrasound and internal gravity waves can be sources of travelling wave packets and can also cause a sporadic E-layer.

The study was funded by RFBR and Kaliningrad region according to the research project  19-45-390005 (Y. Kurdyaeva) and  RFBR to the research project  18-05-00184 (O. Borchevkina).
Dependence of mesoscale patterns of Trade-wind clouds on environmental conditions: an investigation using satellite and in-situ observations
Authors: Bony Sandrine , Schulz Hauke , Vial Jessica , Stevens Bjorn ,   EUREC4A team
Published: March 2020

Trade-wind clouds exhibit a large diversity of spatial organizations at the mesoscale. Over the tropical western Atlantic, a recent study has visually identified four prominent mesoscale patterns of shallow convection, referred to as Flowers, Fish, Gravel and Sugar. By using 19 years of satellite and meteorological data, we show that these four patterns can be identified objectively from satellite observations, and that on daily and interannual timescales, the near-surface wind speed and the strength of the lower-tropospheric stability discriminate the occurrence of the different organization patterns. Moreover, we point out a tight relationship between cloud patterns, low-level cloud amount and cloud-radiative effects. The EUREC4A field study taking place upwind of Barbados in Jan-Feb 2020 offers an opportunity to investigate these relationships from an in-situ and process-oriented perspective. Preliminary results will be discussed.
Mapping of Coastal Cliff Erosion in Denmark
Authors: Luetzenburg Gregor , Svennevig Kristian , Bjørk Anders A. , Kroon Aart
Published: March 2020

Coastal cliff erosion is often an underestimated process to understand shoreline evolution in Denmark. Cliff failure occurs episodically and not always coincides with the highest waves, making prediction difficult. Therefore, comprehensive knowledge about the spatial distribution of cliff erosion in Denmark and the historical rates of change are required to predict future shoreline change and sediment distribution. The erosion of coastal cliffs delivers a substantial amount of sediment in to the coastal zone and future changes in storm intensities and frequencies might influence the rates of cliff erosion.

Historical aerial images, dating back to the mid of the 20th century are combined with a current high resolution digital elevation model (DEM), to map coastal cliff erosion across Denmark’s coastline and to calculate rates of change over the last decades at selected sites. Countrywide oblique aerial images further assist in mapping coastal cliff erosion processes. Landslides are characterized by polygons in the DEM. Morphometric indices are calculated out of the length, width and height of each site to distinguish between different processes. Furthermore, the rate of change is derived from the spatial displacement of the crown.

In this presentation, we present a map of around 1500 (and counting) coastal cliff erosion sites mapped all across Denmark. Steep cliffs mainly occur at the Danish inner coast and along the fjords, determining the presence of coastal cliff erosion. The multi-temporal analysis of shoreline changes revealed erosion rates up to 30 m in the last 20 years leading to considerable loss of land and sediment redistribution. The spatial distribution of the mapped coastal cliff erosion processes (e.g. topples, slides etc.) shows a connection to the maximum extend of the ice sheet covering most parts of Denmark during the Last Glacial Period (Weichsel). This indicates an ongoing emergence for the postglacial landscape and highlights the importance of coastal cliff erosion in landscape evolution.
Causes of future Mediterranean precipitation decline depend on the season
Authors: Brogli Roman , Sørland Silje Lund , Kröner Nico , Schär Christoph
Published: March 2020

The Mediterranean is among the global 'hot-spots' of climate change, where severe consequences of climate change are expected. Changes in the atmospheric water cycle are among the leading causes of the vulnerability of the Mediterranean to greenhouse gas-driven warming. Specifically, precipitation is projected to decrease year-round, which is expected to have major impacts on hydrology, biodiversity, agriculture, hydropower, and further economic sectors that rely on sufficient water supply.

We investigate possible causes of the Mediterranean drying in regional climate simulations. To isolate the influence of multiple large-scale drivers on the drying, we sequentially add the respective drivers from global models to regional climate model simulations. We show that the causes of the Mediterranean drying depend on the season. We will present in detail how the summer drying is driven by the land-ocean warming contrast, lapse-rate and other thermodynamic changes, while it only weakly depends on circulation changes. In contrast, changes in the circulation are the primary driver for the projected winter precipitation decline. Since land-ocean contrast, thermodynamic and lapse-rate changes are more robust in climate simulations than circulation changes, the uncertainty associated with the projected drying should be considered smaller in summer than in winter.

Reference: Brogli, R., S. L. Sørland, N. Kröner, and C. Schär, 2019: Causes of future Mediterranean precipitation decline depend on the season. Environmental Research Letters, 14, 114017, doi:10.1088/1748-9326/ab4438.
The rate and acceleration of the global mean sea level revisited
Authors: Moreira Lorena , Cazenave Anny , Cáceres Denise , Palanisamy Hindumathi , Dieng Habib
Published: March 2020

Since nearly 3 decades, high-precision satellite altimetry allows us to precisely measure the mean sea level evolution at global and regional scales. In terms of global mean, sea level is rising at a mean rate of 3.2 mm/yr. The altimetry record is also suggesting that the global mean sea level rise is accelerating. However, the exact value of the acceleration and even its mere existence are still debated. Determination of the global warming-related sea level rate and acceleration are somewhat hindered by the interannual signal caused by natural climate variability. During the recent years, several studies have shown that at interannual time scale, the global mean sea level is mostly due to ENSO-driven land water storage variations. But thermal expansion fluctuations may also contribute. Thus, to isolate the global warming signal in the global mean sea level, we need to remove the ENSO-related interannual variability. For that purpose we use the Water Gap Global Hydrological model developed by the University of Frankfurt for land water storage as well as GRACE space gravimetry data on land and empirical models based on ENSO indices. We also extract the ENSO-related signal in thermal expansion. After removing the total interannual variability signal due to both mass and steric components, we compute the evolution with time of the ‘residual’ rate of sea level rise over successive 5-year moving windows, as well as the associated acceleration. Using time series of thermal expansion and ice sheet mass balances, we also estimate the respective contributions of each component to the global mean sea level acceleration.
Recurrence quantification analysis of the ~620 kyr record of climate change from the Chew Bahir basin, southern Ethiopia
Authors: Trauth Martin H. , Asrat Asfawossen , Cohen Andrew S. , Duesing Walter , Foerster Verena , Kaboth-Bahr Stefanie , Kraemer Hauke , Lamb Henry , Marwan Norbert , Maslin Mark A. , Schaebitz Frank
Published: March 2020

The Chew Bahir Drilling Project (CBDP) aims to test possible linkages between climate and evolution in Africa through the analysis of sediment cores that record Quaternary environmental changes in the Chew Bahir basin. In this statistical project we used recurrence plots (PRs) together with a recurrence quantification analysis (RQA) to distinguish two types of variability and transitions in Chew Bahir and compare them with the ODP 967 wetness index from the eastern Mediterranean. The first type of variability are slow variations with cycles of ~20 kyr and subharmonics of this cycle. In addition to the these cyclical wet-dry fluctuations in the area, extreme events often occur, i.e. short wet or dry episodes, lasting for several centuries or even millennia, with rapid transitions between wet and dry episodes. The second type of variability is characterized by relatively low variation on orbital time scales, but significant century-to-millennium-scale variations with increasing frequency in the course of an episode of type 2 variability. Within this type of variability there are extremely fast transitions between dry and wet, and vice versa, within a few decades or years, in contrast to those within type 1 which have transitions lasting several hundred years. Type 1 variability probably reflects the influence of precessional forcing in the lower latitudes at times of increased eccentricity, with the tendency towards extreme events, whereas type 2 variability seems to be linked with minimum values of the long (400 kyr) eccentricity cycle, and there does not seem to be a link with atmospheric CO2 levels. The different types of variability and transitions certainly had a completely different influence on the availability of water, food and shelter, and hence eastern Africa’s biotic environment, including the habitat of H. sapiens.
Near-real time estimation of tsunami sources using a classification of waveforms observed at dense ocean bottom pressure sensor
Authors: Tanioka Yuichiro , Inoue Mayu , Yamanaka Yusuke
Published: March 2020

A dense cabled observation network, called the seafloor observation network for earthquakes and tsunami along the Japan Trench (S-net), was installed in Japan. This study aimed to develop a near-real time tsunami source estimation technique using a simple classification of waveforms observed at the ocean bottom pressure sensors in S-net. To investigate the technique, synthetic pressure waveforms at those sensors were computed for 64 tsunami scenarios of large earthquakes with magnitude ranging between M8.0 and M8.8. The pressure waveforms within a time window of 500 s after an earthquake were classified into three types. Type 1 has the following pressure waveform characteristic: the pressure decreases and remains low; sensors exhibiting waveforms associated with Type 1 are located inside a co-seismic uplift area. The pressure waveform characteristic of Type 2 is that one up-pulse of a wave is within the time window; sensors exhibiting waveforms associated with Type 2 are located at the edge of the co-seismic uplift area. The other pressure waveforms are classified as Type 3.

Subsequently, we developed a method to estimate the uplift area using those three classifications of pressure waveforms at sensors in S-net and a method to estimate earthquake magnitude from the estimated uplift area using a regression line. We systematically applied those methods for two cases of previous large earthquakes: the 1952 Tokachi-oki earthquake (Mw8.2) and the 1968 Tokachi-oki earthquake (Mw8.1). The locations of the large computed uplift areas of the earthquakes were well defined by the estimated ones. The estimated magnitudes of the 1952 and 1968 Tokachi-oki earthquakes from the estimated uplift area were 8.2 and 7.9, respectively; they are consistent with the moment magnitudes derived from the source models. Those results indicate that the tsunami source estimation method developed in this study can be used for near-real time tsunami forecasts.

This method is so simple that we do not need any numerical tsunami simulation or other sophisticated techniques but only need the classification of observed pressure data into three types.
Influence of fluid flow and heat transport on predictions of geothermal potentials in sedimentary layers of Hesse (Germany)
Authors: Koltzer Nora , Frick Maximilian , Scheck-Wenderoth Magdalena , Lewerenz Björn , Bär Kristian , Bott Judith
Published: March 2020

For the sustainable utilization of deep geothermal resources it is essential to predict the exploitable potential thermal energy from the subsurface. One main parameter influencing the geothermal potential is the reservoir temperature that may vary locally or regionally in response to fluid flow and heat transport processes.

This study aims at combining highly complex 3D thermo-hydraulic numerical simulations of heat transport and fluid flow with predictions of the geothermal potential for the application case of a hydrothermal doublet. Quantifying the influences of conductive, advective and convective heat transport mechanisms on the thermal field and moreover on the predicted heating power requires fundamental numerical investigations. We use the Federal State of Hesse in Germany as study area where heat transport processes have been quantified in recently published studies. There, the heterogeneous geology consists of outcropping Variscan Crust and up to 3.8 km and 1.8 km thick sedimentary deposits of the Upper Rhine Graben and the Hessian Depression, respectively. This geological complexity is expressed by areas of different hydraulic and thermal configurations: in the flat, but tectonically active Upper Rhine Graben high heat flow from below the graben sediments is in contrast to the variable topography of the Hessian Depression with low heat input from the Rhenohercynian Basement.

The heating power in the three reservoir units (I) Cenozoic, (II) Buntsandstein and (III) Rotliegend is only predicted to be high in the Upper Rhine Graben. There the reservoir temperature is high enough and varies between 50 °C in the convective thermal model of the Cenozoic reservoir and 170 °C in the conductive thermal model of the Buntsandstein reservoir. Predicted low temperatures in the Hessian Depression lead to negligible low heating power, but as production mass flux is above ~6 kg s-1 investigations should continue to assess the geothermal potential for other applications like seasonal energy storage or low enthalpy geothermal utilization.
Characterizing the long-period seismicity of Teide volcano in Tenerife (Canary Islands, Spain)
Authors: Soubestre Jean , D'Auria Luca , Barrancos José , Padilla Germán D. , Seydoux Léonard , Peréz Nemesio M.
Published: March 2020

The volcanic long-period seismicity, composed of long-period events and volcanic tremors, constitutes an important attribute of volcanic unrest. Its detection and characterization is therefore a key aspect of volcano monitoring. In the present work, a method based on the seismic network covariance matrix, the equivalent in the frequency domain of the cross-correlation matrix, is used to automatically detect and locate long-period events of the Teide volcano on the island of Tenerife (Canary Islands, Spain). The method is based on the analysis of eigenvalues and eigenvectors of the network covariance matrix.

Long-period events are detected through the time evolution of the width of the network covariance matrix eigenvalues distribution, which is a proxy of the number of sources acting in the wavefield. Each detected long-period event is then located using the moveout information of the corresponding first eigenvector. Three years of seismic data (from 2017 to 2019) continuously recorded by the Red Sísmica Canaria (C7), a permanent monitoring network composed of 17 broadband stations operated by the Instituto Volcanológico de Canarias (INVOLCAN), are analysed. The obtained locations are compared with potential locations from INVOLCAN’s catalog, obtained by a standard approach based on manual phases picking.
The Proton and Alpha Sensor (PAS) of Solar Orbiter Mission: design, operation, scientific return simulation, and first flight results
Authors: Louarn Philippe , fedorov andrei , Owen Christopher ,   SWA/PAS team
Published: March 2020

Solar Orbiter is an ESA/NASA mission that will provide an unprecedented opportunity to discover the fundamental connections between the rapidly varying solar atmosphere and the solar wind. The Solar Wind Analyzer (SWA) plasma package shall provide comprehensive in-situ measurements of the solar wind. In particular, the Proton-Alpha Sensor (PAS) will determine the properties of the dominant solar wind ion population through the measurement of the 3D distribution function, density, bulk velocity, temperature, and heat fluxes, at temporal cadences ranging form 4 s to ~0.1 s. The closest approach of Solar Orbiter to the Sun is 0.28 AU. At this distance the solar wind Vow, solar UV, and solar infrared fluxes increase by a factor 13 compared to near-Earth space. The PAS instrument will provide high cadence 3D distribution function measurements (up to 13 per second) all the way from closest approach to 1 AU. This paper give a basic information about PAS design, and describes the PAS measurement scheme adopted for varying solar wind conditions and our approach to the fast sampling of 3D distribution functions. We also provide a simulations of the expected scientific return. If possible, a first glance of PAS commissioning results will be presented.
Ba/Ca, P/Ca, Li/Ca and Mn/Ca ratios in the deep-sea bivalve Acesta excavata: Valuable tools to reconstruct plankton dynamics in cold-water coral ecosystems?
Authors: Schleinkofer Nicolai , Raddatz Jacek , Evans David , Gerdes Axel , Voigt Silke , Wisshak Max
Published: March 2020

Phytoplankton is one of the most important producers of oxygen, and plays an important role in the export of large amounts of carbon to the deeper ocean. Since phytoplankton is also the basis of most food webs in the ocean, understanding the dynamic system of phytoplankton is a crucial part to understand past carbon- and nutrient cycles and paleoclimatic changes. The export of nutrients is also an important factor impacting cold-water coral (CWC) reefs and may play a role in controlling their distribution. Here we present laser ablation inductively coupled mass spectrometer (LA-ICP-MS) Element/Ca measurements from Acesta excavata, a file clam, often associated with cold-water coral reefs along the European continental margin. Environmental parameters were recorded with lander systems directly deployed in the CWC reefs, which allows us to compare our geochemical data to in-situ ocean data.

Our results reveal, that Ba/Ca ratios show stable baseline values with intermittent sharp peaks. The location of these peaks in between major growth lines and temperature reconstructions with Mg/Sr ratios (Schleinkofer et al., submitted) show that these peaks occur during Winter and are repeatable between samples from the same location. This indicates a strong external forcing mechanism and allows cross-dating of different bivalve shells. While the occurrence of Ba/Ca peaks correlates with phytoplankton maxima, the absolute Ba/Ca ratio does not correlate with the phytoplankton abundance.

Mn/Ca ratios show similar trends as Ba/Ca ratios but the peaks are phase shifted and occur slightly delayed. These peaks could be triggered by decreasing oxygen concentrations in the water caused by the decomposition of organic material.

As A. excavata does not show easily distinguishable growth lines under the light microscope despite of Mutvei staining or fluorescence microscopy, we hypothesize that P/Ca ratios might be usable to locate highly phosphorylated shell areas that usually correlate with major growth lines. P/Ca ratios show no perceivable features in the vicinity of major growth lines. Instead we recognize that Ba/Ca peaks follow a minimum in P/Ca which is possibly caused by the uptake of phosphor by plankton.

These results suggest that A. excavata have potential as a promising tool for high resolution paleoenvironmental reconstructions of both intermediate and overlying surface water masses.

References

Schleinkofer N, Raddatz J, Evans D, Gerdes A, Flögel S, Voigt S, et al. Elemental to calcium ratios in the marine bivalve Acesta excavata: an archive for high-resolution paleoceanographic reconstructions of intermediate water masses. PLoS One. Submitted
Artificial Water Reservoir Triggered Seismicity (RTS)
Authors: Gupta Harsh
Published: March 2020

A variety of anthropogenic activities are now known to have triggered earthquakes. These include mining, filling of artificial water reservoirs, production of petroleum and geothermal energy, high- pressure fluid injections into shallow crust and many more. Among these, artificial water reservoir triggered seismicity (RTS) is most prominent, with the largest triggered earthquake of M 6.3 having occurred at Koyna, India in 1967. Whether, the devastating Mw 7.8 Sichuan, China earthquake of 8 May 2008 that claimed some 80,000 human lives was triggered by filling of the nearby Zipingpu reservoir, continues to be debated.

There are over 100 sites globally where RTS events of M ≥ 4 have occurred. Here we present an over view of RTS, common characteristics of the RTS earthquake sequences that help to discriminate them from normal earthquake sequences and also help selection of safer sites for locating dams to create artificial water reservoirs.

Koyna, near the west coast of India continues to be most prominent site where triggered- earthquakes have been occurring since the impoundment of the reservoir in 1962 and have continued till now with 22 M ≥ 5, ~ 200 M ≥ 4 and several thousands smaller earthquakes. It was argued that Koyna is a very suitable site for near field investigations of triggered earthquakes. Discussions were held in dedicated ICDP workshops and finally a go ahead was given. As a precursor to setting up a near field laboratory at ~ 7 km depth, a 3 km deep Pilot Borehole has been completed in June 2017 and investigations are being carried out for necessary input for setting up the deep borehole laboratory. Salient features of this project are also presented.
Soil and leaf CNP&S stoichiometry and isotopic composition in sagebrush ecosystems of Wyoming
Authors: Brédoire Félix , Ayayee Paul A , Ben Tekaya Seifeddine , van Diepen Linda T A , Williams David G
Published: March 2020

Sagebrush (Artemisia tridentata) ecosystems span a wide range of environmental conditions in the Western US, where they are the most extensive semiarid vegetation type. Water availability is recognized as the major driver of the structure of sagebrush communities, however less is known about the associated biogeochemical processes. By characterizing large-scale biogeographical patterns of carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) elemental and isotopic compositions in soil and vegetation, we aimed to: (1) detect potential nutrient limitations, (2) identify element sources (weathering, decomposition, or atmospheric deposition), and (3) identify the nature and rates of biogeochemical processes. We sampled sagebrush leaves together with intra- and inter-canopy soil at 50 sites across Wyoming, where sagebrush extends across strong climate and soil type gradients. We expect the nature, rates, and coupling of biogeochemical processes to correlate with patterns of water availability since it is a key control of microbial activity, and the diffusion of enzymes and substrates. Nutrient availability for plants may also follow the same pattern. For example, in moist sites, increased N and P availability may result from higher organic matter decomposition rates than in dry sites, potentially alleviating N limitation to plant growth. However, an excess of P relative to N may occur at high decomposition rates and where the soil parent material is P-rich, leaving N as the limiting nutrient. Conversely, warm and dry sites may have a greater proportion of N being lost through fractionating pathways and a more open N cycle, resulting in high soil and foliar d15N values. We expect leaf d34S to reflect contrasting sources, notably helping to decipher the relative importance of the inputs from atmospheric deposition and weathering (i.e. sedimentary material deposited under anoxic conditions). By improving our understanding of the biogeochemical processes associated with vegetation productivity patterns along a macro-climatic gradient, our data could provide insights into future ecosystem status and help designing disturbance recovery strategies.
OPeNDAP-based access for PCR-GLOBWB input files
Authors: Sutanudjaja Edwin , Gramsbergen Egbert , Martinez Lavanchy Paula , van der Kuil Annemiek , van der Heul Jan , Brunst Vincent , Lange Otto , Schmitz Oliver , Wanders Niko
Published: March 2020

PCR-GLOBWB (Sutanudjaja et al., 2018, https://doi.org/10.5194/gmd-11-2429-2018, https://github.com/UU-Hydro/PCR-GLOBWB_model) is an open source global hydrology and water resources model being developed over the past two decades at the Department of Physical Geography, Utrecht University, The Netherlands. The latest version of the model has a fine spatial resolution of 5 arcmin (less than 10 km at the equator) and runs on daily resolution covering several decade simulation time period, i.e. > 50 years. Due to its fine resolution and extensive spatio-temporal extent, the total size of a complete set of PCR-GLOBWB input files is huge (about 250 GB if they are uncompressed; 45 GB if compressed, see e.g. https://doi.org/10.5281/zenodo.1045338). Consequently, sharing and downloading them are difficult, even for a user that wants to run the model for a limited and specific catchment area only. 

In this presentation we aim to share our recent successful effort to prepare and upload PCR-GLOBWB input files to the 4TU.ResearchData server, https://opendap.4tu.nl, that supports OPeNDAP protocol (https://www.opendap.org) allowing users to access files from a remote server without the need to download the data files. This includes inspection of the metadata enabling subsampling specific ranges of the data (over space and time). OPeNDAP is especially suited to netCDF files, and, therefore, we have ensured compatibility of PCR-GLOBWB input files in the correct netCDF format, i.e. following CF conventions, before uploading the files to the remote server. 

The PCR-GLOBWB input files are now available on https://opendap.4tu.nl/thredds/catalog/data2/pcrglobwb/catalog.html. PCR-GLOBWB users can run the model by simply adjusting the input directory location to this address (and, therefore, without having to download the entire input files). In this presentation, we aim to demonstrate on how to make such runs, not only for global extent, but also for specific or limited regions only (river basin extent).
Determination of global geodetic parameters based on integrated SLR measurements to LEO, geodetic, and Galileo satellites
Authors: Strugarek Dariusz , Sośnica Krzysztof , Arnold Daniel , Jäggi Adrian , Bury Grzegorz , Zajdel Radosław
Published: March 2020

Numerous active low Earth orbiters (LEOs) and Global Navigation Satellite System (GNSS) satellites, including the Galileo constellation, are equipped with laser retroreflectors used for Satellite Laser Ranging (SLR). Moreover, most of LEOs are equipped with GNSS receivers for precise orbit determination. SLR measurements to LEOs, GNSS, and geodetic satellites vary in terms of the number of registered normal points (NPs) or registered satellite passes. In 2016-2018, SLR measurements to LEOs constituted 81% of all NPs and 59% of all registered satellite passes, whereas 10% of NPs and 30% of satellite passes, respectively, were assigned to GNSS. The remaining SLR measurements were completed by geodetic satellites, including LAGEOS-1/2, and LARES-1.

In this study, we show that the SLR observations to Galileo, passive geodetic and active LEO satellites together with precise GNSS-based orbits of LEOs and Galileo, can be used for the determination of global geodetic parameters, such as geocenter coordinates (GCC) and Earth rotation parameters (ERPs), i.e. pole coordinates, and length-of-day parameter.

GCC are typically determined using SLR observations to passive geodetic satellites, such as LAGEOS-1/2. Also, the SLR observations to LAGEOS-1/2 together with GNSS and Very Long Baseline Interferometry data are used for the determination of ERPs. Here, we use SLR observations to Galileo, LAGEOS-1/2, LARES-1, Sentinel-3A, SWARM-A/B/C, TerraSAR-X, Jason-2, GRACE-A/B satellites to investigate whether they can be applied for the reference frame realization and for deriving high-quality global geodetic parameters.

We present various types of solutions to investigate the best solution set-up. The studied solutions differ in terms of solution lengths, the combination of different sets of satellites and the relative weights for the variance scaling factors of technique and satellite-specific normal equations. We compare our results with the standard LAGEOS-based solutions, the combined EOP-14-C04 products and show the consistency of the results.
The role of syn-eruptive crystallization on pantelleritic eruptive dynamics
Authors: stabile paola , Appiah Ernestina , Carroll Michael Robert
Published: March 2020

Pantellerites are strongly peralkaline rhyolites occurring mainly in extensional tectonic setting, from oceanic islands (Ascension Island) to continental rift zones, as for example Pantelleria Island in the Sicily channel rift zone, Kenyan and Ethiopian Rift Valleys and Mayor Island (NZ-Taupo Volcanic Zone). Peralkaline magmas are noted for their ability to shift between explosive and effusive eruptive styles, which is strictly associated with viscosity, degassing kinetics, the initial temperature and crystal content of the magma.

The present experimental work aims at unravelling pre- and syn-eruptive crystallisation dynamics and time-scales of most explosive eruptions that are so unforeseeable and not yet systematically studied, but essential to assessing volcanic hazards of the Pantelleria system.

Crystal nucleation and growth of alkali feldspars in pantelleritic melts have been investigated by cooling and decompression experiments conducted at the T-P range more plausible for the Pantelleria system (T=680-800 °C,  [1]; 25-100 MPa). The studied melt composition belongs to the Fastuca pumice fall eruptive unit of Pantelleria which is rich in Na and Fe and it presents a peralkalinity index of 1.4.

Textural analysis on the hydrous samples reveal that crystal fraction (φ) varies from average pre-eruptive values of 0.02  to 0.2 during magma ascent from magma chamber depths (ca. 3-4 km, at 100 MPa) to shallower depths (corresponding to pressures of 50 MPa), leading to an increase of viscosity of 1 log unit (value estimated using the equation in [2], starting from the pre-eruptive low viscosity of the pure pantelleritic liquid calculated by [3]), which may contribute to enhance a more explosive magma eruptive behavior. Also considering fast decompression rates (DP/Dt) (in the range of 0.2-0.6 MPa/s), it results a large decrease in pressure along the conduit, promoting volatile exsolution and higher magma accelerations, which along with increasing viscosity, crystallinity, and velocities, could lead to magma brittle behavior and trigger explosive eruptive events.

A better understanding of how these explosive pantelleretic eruptions work will lead to improved volcano monitoring and disaster mitigation in high-risk volcano-tectonic areas as for instance is Pantelleria Island, where about 10.000 inhabitants live permanently.

References:

[1] Di Carlo I. et al. (2010) Journal of Petrology 51 (11), 2245–2276. [2] Vona A. et al. (2011) Geochimica et Cosmochimica Acta 75(11), 3214–3236. [3] Di Genova D. et al. (2013) Volcanol. Geotherm. Res. 249, 201–216.
Object-Based Flood Analysis Using a Graph-Based Representation
Authors: Debusscher Bos , Van Coillie Frieke
Published: March 2020

Describing spatio-temporal dynamics of a flood using an object-based approach with a graph-based representation proved useful for analysis of small-scale flood dynamics in Belgium (about 100 km²) (Debusscher, et al., 2019).  Starting from pre-processed Sentinel-1 SAR imagery, the water bodies are delineated in each timestep (using a thresholding algorithm), after which all water-polygons are grouped into graphs according to their spatial overlap on consecutive timesteps.  Change in (water)area and backscatter are used to quantify the amount of variation.  Products of this tool are a global variation map covering the whole study are, and a temporal profile for each waterbody, visually describing the evolution of the backscatter and number of polygons that make up the waterbody.  
After establishing this proof of concept in a small region (flood of June 2016 in Schulensbroek, a nature reserve in north-eastern Belgium), this approach is applied on floods covering larger areas (about 10000 km²).  Two cases are studied, the Mozambique flood of March 2019 (near Beira) and the India flood of September 2019 (near Patna).  The process of upscaling leads to solving issues regarding the minimal mapping unit, adding extra pre-processing in order to simplify polygons (morphological operators), increasing code efficiency (mainly regarding for-loops).
In the absence of ground truth, produced flood maps are compared to existing flood extent maps (from Disaster Charter (unitary) and Hasard (LIST)) in order to estimate accuracy.

References
Debusscher Bos and Van Coillie Frieke Object-Based Flood Analysis Using a Graph-Based Representation, Remote Sensing. - 2019. - p. p. 1883.

 
Investigating the factors affecting Monsoon precipitation under climate change
Authors: Mutton Harry , Collins Mat , Lambert Hugo , Chadwick Rob
Published: March 2020

The Monsoons produce some of the largest levels of uncertainty in projected precipitation change across the globe, and addressing this uncertainty is a key issue that must be faced in order to allow correct adaptation policy to be put in place.

 

A set of CMIP6 GCM experiments, that allow the full effect of CO2 forcing to be decomposed into individual components, highlight the leading factors that produce changes in monsoon precipitation. The results reveal a high spatial variability in these factors, with changes in the Indian Monsoon dominated by the effect of sea surface temperatures and the direct radiative effect of increased CO2, and changes in the South American Monsoon governed by the plant physiological effect and the direct radiative effect of increased CO2. The processes behind these precipitation changes are also investigated by looking at variations in atmospheric circulation and surface temperature. Results of the patterned sea surface temperature experiment demonstrate a slow-down of the Indian Monsoon circulation possibly driven by an anomalously warm Indian Ocean.

 

This analysis has been performed for all land monsoon regions, decomposing the full CO2 forcing into; uniform and patterned sea surface temperature change, the plant physiological effect, the direct radiative effect and the impact of sea-ice melt. These results can help identify emergent constraints, as well as indicate which aspects of climate models need to be improved in order to reduce model uncertainty.
The role of EEP forcing and background dynamics on the seasonal NO variability in the MLT region
Authors: Smith-Johnsen Christine , Tyssøy Hilde Nesse , Marsh Daniel , Smith Anne
Published: March 2020

 Energetic electron precipitation (EEP) ionizes the Earth's atmosphere and leads to production of nitric oxide (NO) from 50 to 150 km altitude. In this study we investigate the direct and indirect NO response to EEP using the Whole Atmosphere Community Climate Model (WACCM). In comparison to observations from SOFIE / AIM (Solar Occultation For Ice Experiment / Aeronomy of Ice in the Mesosphere), we find that EEP production of NO in the D-region is well simulated when both medium energy electron precipitation and negative and cluster ion chemistry is included in the model. However, the main EEP production of NO occurs in the E-region, and there the observed and modeled production differ. This discrepancy impacts also the D-region, and is seasonally dependent with the highest underestimate of D-region NO occuring during winter. The modeled transport across the mesopause during winter is generally weak, but strengthens with increased gravity wave activity. Increased eddy diffusion, increases NO at all altitudes through the polar MLT region
Does it pay off to link functional gene expression to denitrification rates via modelling?
Authors: Störiko Anna , Pagel Holger , Cirpka Olaf
Published: March 2020

The abundances of functional genes and transcripts have provided new insights into microbially mediated biogeochemical processes and might improve quantitative predictions of turnover rates.
However, the relationship between reaction rates and the gene and transcript abundances may not be a simple correlation.
Most mechanistic reaction models cannot predict molecular-biological data, and it is unclear how they can be informed by such data.

We developed a mechanistic model that considers transcript abundances of denitrification genes, enzyme concentrations, biomass, and solute concentrations as state variables that are interrelated by ordinary differential equations, and thus mechanistically links molecular-biological data to reaction rates.
Important features of transcript dynamics can be reproduced with the transcript-based model.

We calibrated the model using data from a batch experiment with a denitrifying organism at the onset of anoxia.
We explored the relationship between transcript abundances and reaction rates by analyzing the model results.
The transcript abundances reacted very quickly to substrate concentrations so that we could simplify the model by assuming a quasi steady state of the transcripts.

We compared our model to a classical Monod-type formulation, which was as good at simulating the concentrations of nitrogen species as the transcript-based model, but it cannot make use of any molecular-biological data.
Our results, thus, suggest that enzyme kinetics (substrate limitation, inhibition) control denitrification rates more strongly than the dynamics of gene expression.