bluuebunny/crossref_metadata_2025 huggingface dataset:
Biogeophysical effects of idealised land cover and land management changes on the climate
Authors: De Hertog Steven , Vanderkelen Inne , Havermann Felix , Guo Suqi , Pongratz Julia , Manola Iris , Coumou Dim , Davin Edouard , Seneviratne Sonia , Lejeune Quentin , Menke Inga , Schleussner Carl-Friedrich , Thiery Wim
Published: March 2021

Land cover and land management (LCLM) changes have been highlighted for their critical role in low-end warming scenarios, both in terms of global mitigation and local adaptation. Yet the overall potential of LCLM options and their combination is still poorly understood. Here we model the climatic effects of four LCLM options using three state-of-the-art Earth system models, including the Community Earth System Model (CESM), the Max Planck Institute Earth System Model (MPI-ESM) and the European Consortium Earth System Model (EC-EARTH). The considered LCLM options represent idealized conditions:(i) a fully afforested world, (ii) a fully deforested world, (ii) a fully afforested world with extensive wood harvesting, and (iv) a fully deforested world with extensive irrigation. In these idealized sensitivity experiments, ran under present-day climate conditions, the effects of the different LCLM strategies represent an upper bound of the potential for global mitigation and local adaptation. To disentangle the local and non-local effects from the LCLM changes, a checkerboard perturbation, as proposed by Winckler et al. (2017) is applied.

Our first results show that deforestation leads to a pronounced warming in 2m air temperature in CESM over most regions, being most pronounced in the tropics (up to 4°C). In contrast, in the boreal regions of North America and Asia, deforestation causes a ~1°C cooling in 2m air temperature. In CESM, the local effect seems to dominate the temperature response from deforestation, while the resulting non-local effect overall has a smaller magnitude. This contrasts to the effect from afforestation, of which the non-local component dominates the 2m air temperature signal. Afforestation indeed shows a strong local cooling in the tropics and a slight local warming in the temperate and boreal regions, yet, the local cooling is regionally offset by  a global, non-local warming of up to 2 °C. In a next step, we will extend this analysis to the ensemble of Earth system models and increase our process-based understanding of these results and their implications on hot extremes as well as the effects on other temperature metrics (surface temperature and temperature of the lowest level of atmospheric column). Finally, we will perform a subgrid-scale comparison of the effects of LCLM on temperature.

References:

Winckler, J., Reick, C.H., Pongratz, J., 2017. Robust identification of local biogeophysical effects of land-cover change in a global climate model, American Meteorological society, 30(2), DOI: 10.1175/JCLI-D-16-0067.1
Several Populations of Sunspot Group Numbers – Resolving a Conundrum
Authors: Svalgaard Leif
Published: March 2021

The long-standing disparity between the sunspot number record and the Hoyt and Schatten (1998, H&S) Group Sunspot Number series was initially resolved by the Clette et al. (2014) revision of the sunspot number and the group number series. The revisions resulted in a flurry of dissenting group number series while the revised sunspot number series was generally accepted. Thus, the disparity persisted and confusion reigned, with the choice of solar activity dataset continuing to be a free parameter. A number of workshops and follow-up collaborative efforts by the community have not yet brought clarity. We review here several lines of evidence that validate the original revisions put forward by Clette et al. (2014) and suggest that the perceived conundrum no longer need to delay acceptance and general use of the revised series. We argue that the solar observations constitute several distinct populations with different properties which explain the various discontinuities in the series. This is supported by several proxies: diurnal variation of the geomagnetic field, geomagnetic signature of the strength of the heliomagnetic field, and variation of radionuclides. The Waldmeier effect shows that the sunspot number scale has not changed over the last 270 years and a mistaken scale factor between observers Wolf and Wolfer explains the disparity beginning in 1882 between the sunspot number and the H&S reconstruction of the group number. Observations with replica of 18th century telescopes (with similar optical flaws) validate the early sunspot number scale; while a reconstruction of the group number with monthly resolution (with many more degrees of freedom) validate the size of Solar Cycle 11 given by the revised series that the dissenting series fail to meet. Based on the evidence at hand, we urge the working groups tasked with producing community-vetted and agreed upon solar activity series to complete their work expeditiously.
Assessing "Drake Passage Leakage" in an eddy resolving ocean model
Authors: Wiskandt Jonathan , Ruehs Siren , Schwarzkopf Franziska , Biastoch Arne
Published: March 2021

The upper limb of the Atlantic Meridional Overturning Circulation (AMOC) is supplied in the South Atlantic from Drake Passage (DP) and Agulhas Leakage (AL). The relative contributions from DP and AL influence the stratification as well as the properties of the upper limb return flow and potentially impact the formation of deep water in the North Atlantic.
While early studies suggested a clear dominance of the AL contribution, recent studies indicate that the DP contribution is not negligible. Here, we use a set of Lagrangian experiments in the eddy-resolving (1/20 degree) ocean model INALT20 to analyze the inflow from DP into the South Atlantic in more detail. We find that the majority of water, that enters the subtropical South Atlantic across 30° S from DP, originates from the upper 2000 m of the northern branch of the ACC that follows the Sub Antarctic Front (SAF). Before  entering the South Atlantic, the majority of theses particles turn northward east of DP and follow the SAF through the Brazil Malvinas Confluence, where the SAF meets the Sub Tropical Front. In or parallel to the South Atlantic Current, particles cross the basin and become part of the subtropical gyre to follow the Benguela Current northward. We further compare pathways, volume transports, transit times and thermohaline properties of particles entering through DP and leaking into the South Atlantic to those from particles not leaking into the South Atlantic. These analyses help exploring potential recipes for building a timeseries of “Drake Passage leakage”, complementary to the already established Agulhas Leakage timeseries.
Power spectral density of magnetic field and ion velocity fluctuations from inertial to kinetic ranges
Authors: Šafránková Jana , Němeček Zdeněk , Němec František , Franci Luca , Pitňa Alexander
Published: March 2021

The solar wind is a unique laboratory to study the turbulent processes occurring in a collisionless plasma with high Reynolds numbers. A turbulent cascade—the process that transfers the free energy contained within the large scale fluctuations into the smaller ones—is believed to be one of the most important mechanisms responsible for heating of the solar corona and solar wind. The paper analyzes power spectra of solar wind velocity, density and magnetic field fluctuations that are computed in the frequency range around the break between inertial and kinetic scales. The study uses measurements of the Bright Monitor of the Solar Wind (BMSW) on board the Spektr-R spacecraft with a time resolution of 32 ms complemented with 10 Hz magnetic field observations from the Wind spacecraft propagated to the Spektr-R location. The statistics based on more than 42,000 individual spectra show that: (1) the spectra of both quantities can be fitted by two (three in the case of the density) power-law segments; (2) the median slopes of parallel and perpendicular fluctuation velocity and magnetic field components are different; (3) the break between MHD and kinetic scales as well as the slopes are mainly controlled by the ion beta parameter. These experimental results are compared with high-resolution 2D hybrid particle-in-cell simulations, where the electrons are considered to be a massless, charge-neutralizing fluid with a constant temperature, whereas the ions are described as macroparticles representing portions of their distribution function. In spite of several limitations (lack of the electron kinetics, lower dimensionality), the model results agree well with the experimental findings. Finally, we discuss differences between observations and simulations in relation to the role of important physical parameters in determining the properties of the turbulent cascade.
Tropospheric Mineral Dust Study by High Spectral Resolution Infrared Satellite during intense dust storms
Authors: Alalam Perla , Herbin Hervé
Published: March 2021

Large desert lands such as Sahara, Gobi or Australia present main sources of atmospheric mineral dust caused by intense dust storms. Transported dust particles undergo physical and chemical changes affecting their microphysical and optical properties. This modifies their scattering and absorption properties and alters the global atmospheric radiative budget.

Currently, remote sensing techniques represent a powerful tool for quantitative atmospheric measurements and the only means of analyzing its evolution from local to global scale. In order to improve the knowledge of atmospheric aerosol distributions, many efforts were made particularly in the development of hyperspectral infrared spectrometers and processing algorithms. However, to fully exploit these measurements, a perfect knowledge of Complex Refractive Index (CRI) is required.

In that purpose, a new methodology based on laboratory measurements of mineral dust in suspension coupled with an optimal estimation method has been developed. This approach allows getting access to CRI of several desert samples with various chemical compositions.

Here, we present the first results of the physical parameters (effective radius and concentration) retrievals using Infrared Atmospheric Sounding Interferometer IASI data, during dust storm events. The latter use the CRI of different desert samples obtained in laboratory and a new radiative transfer algorithm (ARAHMIS) developed at Laboratoire d’Optique Atmosphérique LOA.
Prediction and understanding of soft proton contamination in XMM-Newton: a machine learning approach
Authors: Kronberg Elena , Gastaldello Fabio , Haaland Stein , Smirnov Artem , Berrendorf Max , Ghizzardi Simona , Kuntz Kip , Sivadas Nithin , Allen Robert , Tiengo Andrea , llie Raluca , Huang Yu , Kistler Lynn
Published: March 2021

One of the major and unfortunately unforeseen sources of background for the current generation of X-ray telescopes flying mainly in the magnetosphere are soft protons with few tens to hundreds of keV concentrated. One such telescope is the X-ray Multi-Mirror Mission (XMM-Newton) by ESA. Its observing time lost due to the contamination is  about 40%. This affects all the major broad science goals of XMM, ranging from cosmology to astrophysics of neutron stars and black holes. The soft proton background could dramatically impact future X-ray missions such Athena and SMILE missions. Magnetopsheric processes that trigger this background are still poorly understood. We use a machine learning approach to delineate related important parameters and to develop a model to predict the background contamination using 12 years of XMM observations. As predictors we use the location of XMM, solar and geomagnetic activity parameters. We revealed that the contamination is most strongly related to the distance in southern direction, ZGSE, (XMM observations were in the southern hemisphere), the solar wind velocity and the location on the magnetospheric magnetic field lines. We derived simple empirical models for the best two individual predictors and a machine learning model which utilizes an ensemble of the predictors (Extra Trees Regressor) and gives better performance. Based on our analysis, future X-Ray missions in the magnetosphere should minimize observations during  times  associated with high solar wind speed  and avoid closed magnetic field lines, especially at the dusk flank region at least in the southern hemisphere. 
A microphysical scheme for secondary ice in ICON – evaluation and case studies
Authors: Lüttmer Tim , Spichtinger Peter
Published: March 2021

Several physical mechanisms of secondary ice production are proposed and studied in laboratory experiments and observational measurements. We implemented a selection of empirical parameterisations for rime splintering, frozen droplet fragmentation and ice-ice collisional break-up in the two-moment microphysics ice modes scheme within the atmosphere model ICON.

The newly developed ice modes scheme distinguishes between different ice modes of origin including homogeneous nucleation, deposition freezing, immersion freezing, homogeneous freezing of water droplets and secondary ice production respectively. Each ice mode is described by its own size distribution, prognostic moments and unique formation mechanism while still interacting with all other ice modes and microphysical classes
like cloud droplets, rain and rimed cloud particles. This allows to evaluate the contribution of each ice formation mechanism, especially
secondary ice, to the total ice content.

Using this set-up we investigated the sensitivity and behavior of rime splintering, frozen droplet fragmentation and ice-ice collisional break-up for various parameterisations, coefficients and environmental conditions. We will present findings from idealized convection simulations as well as synoptic simulations of Europe and the North Atlantic.
Predicting fracture network development in crystalline rocks
Authors: McBeck Jessica , Aiken John Mark , Cordonnier Ben , Ben-Zion Yehuda , Renard Francois
Published: March 2021

The geometric properties of fractures influence whether they propagate, arrest and coalesce with other fractures. Thus, quantifying the relationship between fracture network characteristics may help predict fracture network development, and hence precursors to catastrophic failure. To constrain the relationship and predictability of fracture characteristics, we deform eight rock cores under triaxial compression while acquiring in situ X-ray tomograms. The tomograms reveal precise measurements of the fracture network characteristics above 6.5 microns. We develop machine learning models to predict the value of each characteristic using the other characteristics, and excluding the macroscopic stress or strain imposed on the rock. The models predict fracture development more accurately in the experiments performed on granite and monzonite, than the experiments on marble. Fracture network development may be more predictable in these igneous rocks because their microstructure is more mechanically homogeneous than the marble, producing more systematic fracture development that is not strongly impeded by grain contacts and cleavage planes. The varying performance of the models suggest that fracture volume, length, and aperture are the most predictable of the characteristics, while fracture orientation is the least predictable. Orientation does not correlate with length, as suggested by the idea that the orientation evolves with increasing differential stress and thus fracture length. This difference between the observed and expected predictability of orientation highlights the significant influence of local stress perturbations on fracture growth within brittle material in laboratory-scale systems with many propagating and interacting fractures.
Dissolution, Mechanical Properties, and Thermal Stability of Microparticles Containing Radioactive Cesium on Plant Litter Derived from the Fukushima Daiichi Nuclear Power Plant Accident,  and Soil Decontamination Trials 
Authors: Tanaka Ichiro , Yamaguchi Atsushi , Kikuchi Kenji , Niimura Nobuo , Saeki Yume , Sugihara Makoto
Published: March 2021

The radioactive cesium (134Cs and 137Cs), which originated from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, has remained in the soil and on plants as water-insoluble microparticles (termed as CsMPs) to some extent, and maintained relatively high radioactivity levels in the district. However, it has been reported that the radioactive Cs has been absorbed by plants. To interpret this phenomenon, the authors investigated CsMPs to determine if they become soluble during filtration and dialysis experiments. Moreover, other physical properties, such as mechanical properties and thermal stability, were observed during the course of the relevant experiments. These properties can be obtained by using carbonized charcoal litter with CsMPs. And simple and economic decontamination trials of the soil were performed by sieving after drying and roughly crushing.
Study of internal stresses in rock massif within the framework of elastic layered block models with inclusions of the hierarchical structure of the L-rank.
Authors: Hachay Olga , Khachay Andrey
Published: March 2021

In recent years, new models of continuum mechanics, generalizing the classical theory of elasticity, have been intensively developed. These models are used to describe composite and statistically heterogeneous media, new structural materials, as well as in complex massifs in mine conditions. The paper presents an algorithm for the propagation of longitudinal acoustic waves in the framework of active well monitoring of elastic layered block media with inclusions of hierarchical type of L-th rank. Relations for internal stresses and strains for each hierarchical rank are obtained, which constitute the non local theory of elasticity. The essential differences between the non local theory of elasticity and the classical one and the connection between them are investigated. A characteristic feature of the theory of media with a hierarchical structure is the presence of scale parameters in explicit or implicit form. This work focuses on the study of the effects of non locality and internal degrees of freedom, reflected in internal stresses, which are not described by the classical theory of elasticity and which can be potential precursors of the development of a catastrophic process in a rock massif. Thanks to the use of a model of a layered block medium with hierarchical inclusions, it is possible, using borehole acoustic monitoring, to determine the position of the highest values ​​of internal stresses and, with less effort, to implement the method of unloading the rock massif. If it is necessary to conduct short-term predictive monitoring of geodynamic regions and determine a more accurate position of the source of a dynamic phenomenon using borehole active acoustic observations, it is necessary to use the values ​​of the tensor of internal hierarchical stresses as a monitored parameter.
Deployment automation of hydrological forecasting systems on a global scale.
Authors: Onate-Paladines Arianna , van Osnabrugge Bart , Verkade Jan , Weerts Albrecht
Published: March 2021

Hydrological forecasting systems represent an important decision-making tool for water and risk management. In this context, there is increasing development and implementation of such systems worldwide, which are commonly tailor-made: designed and configured according to the information and hydrological models available for a specific location and/or extent to answer to precise needs. Therefore, the concepts of setup automation and replicability of configuration of such systems are often overlooked, especially when they follow a model-centric approach.

However, in a global forecasting context such as the one adopted by Deltares’ GLOFFIS (den Toom et al. 2020), the automation of hydrological forecasting systems’ set up becomes an essential part for the development, as it enables the fast forward and constant addition of local specialized models where available in the system on a global extent, as well as by using local regional weather forecasts, reanalysis models or satellite data as forcing to produce estimates of various hydrological parameters, instead of focusing on a single model or NWP source.

In that sense, a prototype of a configuration production system for GLOFFIS was developed, which comprises two main components: (1) an external relational database holding the information regarding the set of hydrological models to be incorporated and weather data products used and, (2) a set of python scripts, that query the database and generate the configuration XML files needed for the system (as GLOFFIS is based on Delft-FEWS) to accomplish an automated deployment.

This new approach for system’s configuration boosts the potential related to system maintenance, expansion, and replicability, which could be beneficial not only when developing large hydrological forecasting systems, but also for local systems developed using Delft-FEWS, as well as to encourage the distribution of forecasting systems worldwide.

 

References:

den Toom, M., Verkade, J., Weerts, A., and Schotmeijer, G.-J.: Development of the Deltares global fluvial flood forecast system, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22344, https://doi.org/10.5194/egusphere-egu2020-22344, 2020.
Modeling saltwater intrusion with SUTRA 3.0 in Almonte-Marismas aquifer coast (Doñana Natural Space, Southern Spain). 
Authors: Serrano-Hidalgo Carmen , Fernandez-Ayuso Ana , Guardiola-Albert Carolina , Heredia-Diaz Javier , Elorza-Tenreiro Francisco Javier
Published: March 2021

 

The Almonte-Marismas aquifer is a multilayer alluvial groundwater body constituted of silts, sands and gravel of fluvial-deltaic and marine origin. It supports Doñana Natural Space (Southern of Spain). It is in direct hydraulic contact with the Atlantic Ocean to the Southwest. Nowadays, the aquifer is subjected to important losses in terms of regional groundwater resources caused by the excessive groundwater pumping for crop irrigation, as well as for tourism water supply in two coastal resorts. This fact causes a subsequent lowering of the phreatic head, and therefore, the water requirements of the ecosystems in this protected area.

Although up to date there is no evidence of saltwater intrusion in this area, there have been several studies warning that seawater advance through the deep layers would likely happen under the present exploitation pattern (Custodio, 1993). The aim of this study is to analyze the possible destabilization of the dynamic balance between the freshwater and saline water in the aquifer. This goal is assessed through numerical simulations of different seawater intrusion scenarios using a 2D model, where the density flow and solute transport model is considered using the SUTRA 3.0 package (Voss et al., 2002) of Modelmuse (Winston, 2014). This work enables the evaluation of the hydrodynamical conceptual model in the aquifer coast, the potential threat of seawater intrusion caused by coastal resort extractions and the consequences that it entails for the nearby natural environment.

Key issues: saltwater intrusion,2D model, SUTRA, Doñana, overexploitation.

 

References

Custodio E. 1993. Preliminary outlook of saltwater intrusion conditions in the Doñana National Park (Southern Spain). Study and Modelling of Saltwater Intrusion into Aquifers. Proceedings 12th Saltwater Intrusion Meeting, Barcelona, Nov. 1992. CIHS.CIMNE. Barcelona, 1993: 295-315.

Voss, C. I., and Provost, A.M., 2002 (Version of September 22, 2010), SUTRA, A model for saturated-unsaturated variable-density ground-water flow with solute or energy transport, U.S. Geological Survey Water-Resources Investigations Report 02-4231, 291 p.

Winston, R.B., 2014, Modifications made to ModelMuse to add support for the Saturated-Unsaturated Transport model (SUTRA): U.S. Geological Survey Techniques and Methods, book 6, chap. A49, 6 p., https://dx.doi.org/10.3133/tm6a49.
The role of organic matter and bacterial physiology on river metabolism at low flow
Authors: Hasanyar Masihullah , Flipo Nicolas , Romary Thomas , Wang Shuaitao
Published: March 2021

Development of accurate water quality modelling tools is necessary for integrated water quality management of river systems. The existing water quality models can simulate dissolved oxygen (DO) concentration quite well in rivers, however, there are discrepancies during summer low flow season which are assumed to be due to the heterotrophic bacterial decomposition of organic matter (OM) (Wang, 2019). Therefore, we used the C-RIVE biogeochemical model in order to evaluate the influence of controlling parameters on the DO simulations at low flow.

Four Sobol’ sensitivity analyses (SA) were carried out based on an evolving strategy of reduction in the number of parameters and hiding the inter-parameter interactions. The studied parameters are bacterial (such as growth rate of bacteria), OM-related (repartition and degradation of OM into constituent fractions) and physical (for instance reaeration of river due to navigation and wind) whose variation ranges are selected based on a detailed literature review.

Bacterial growth and mortality rates are by far the two most influential parameters followed by bacterial yield and the share of biodegradable dissolved organic matter (BDOM). More refined SA results indicate that depending on the net bacterial growth (=growth – mortality) being low or high, the bacterial yield and BDOM concentration are the most influential parameters, respectively. Reaeration constant due to navigation and the bacterial uptake of substrate are the other two influential parameters identified in this work. 

The results of this study highlight the importance of accurate in-situ sampling and measurement of these influential parameters in order to reduce modelling uncertainties, as well as the necessity for a suitable sampling frequency in order to characterize potential bacterial community switch during transient events such as combined sewer overflows. 

References:

Wang, S. (2019). Simulation Du Métabolisme de La Seine Par Assimilation de Données En Continu. These de doctorat, Paris Sciences et Lettres
Signatures of the Madden-Julian Oscillation in Stratospheric Temperature from Aura MLS
Authors: Hoffmann Christoph , Buth Lena , von Savigny Christian
Published: March 2021

The Madden-Julian oscillation (MJO) is a major source of intraseasonal variability in the tropical troposphere. It refers to a recurring pattern of strong convection, which travels from the Indian ocean over the Maritime Continent to the Pacific ocean with time scales of 30 to 90 days.

Although some studies have recently indicated that the occurrence of tropospheric MJO events could also affect stratospheric parameters, the MJO is not very much recognized as a source of stratospheric variability. This bears the risk of mixing it up with other sources of variability on this time scale, e.g., with signatures of the solar 27-day variations. Many of the studies that have found MJO signatures in the stratosphere are, however, based on either modelled or reanalyzed data. Particularly, we are not aware of any purely observational studies related to the temperature response in the middle atmosphere.

To fill this gap, we analyze the signature of the MJO in stratospheric temperatures measured by the Microwave Limb Sounder (MLS) satellite instrument aboard the Aura satellite. Analyzing the period from about 2004 to 2018, we indeed identify corresponding temperature variations in various altitudes and locations with many of them being significant according to Monte Carlo tests. The amplitudes of these signatures are on the order of 0.5 K. Moreover, basic characteristics of signatures, which have been identified in the preceding publications, are confirmed in this study based on purely observational data.

Hence, our study supports the coupling of parts of the stratospheric variability on the intraseasonal time scale to anomalous tropospheric convection represented by the MJO.
Biogeomorphic development of foredune trough blowouts quantified from medium-resolution satellite imagery
Authors: Ruessink Gerben , van Kuik Niels , de Vries Job , Schwarz Christian
Published: March 2021

Foredune trough blowouts are wind-eroded trough-shaped hollows in the most seaward coastal dune with their adjoining depositional lobes. They evolve on time scales ranging from strong wind events, seasons to multiple decades due to biogeomorphic interactions. Trough blowouts play an essential role in the sand budget of many coastal dune systems by connecting the beach with the backdune. There, the deposited sand can lead to vegetation rejuvenation and an overall larger floral diversity. In Northwestern Europe, nature and coastal managers have started to experiment with constructing trough blowouts in the hope that a positive sand budget beyond the foredune in concert with enlarged biodiversity improves coastal resilience in times of climate change. The spatio-temporal evolution of trough blowouts and the factors driving this evolution are not well understood, despite their common natural occurrence and construction for nature-based management.

The aim of this contribution is to quantify the spatio-temporal development of selected trough-blowout systems around the globe utilizing cloud-free medium-resolution Landsat and Sentinel-2 spectral imagery available in the Google Earth Engine platform. Linear spectral unmixing was applied on a single image basis to extract blowout surface area over time at one man-made blowout system (Zuid-Kennemerland, Netherlands) and two natural systems (Haurvig, Denmark; Padre Island, Texas, USA), assigning pixels with a fractional vegetation cover less than 50% to the blowout. At Zuid-Kennemerland and Haurvig, the blowout surface area fluctuated predominantly on seasonal time scales, with the smallest and largest values in late summer/early autumn and late winter/early spring, respectively. This seasonal variability reflects plant phenology in combination with increased sand accumulation in winter because of the more energetic wind conditions. In summer, vegetation regrew mainly at the edges of the depositional lobes and on the foredune between individual blowouts. The blowout surface area at the subtropical Padre Island varied predominantly on a multi-annual time scale. Most notably, multi-annual area decay was observed when a blowout progressed inland and lost its open connection to the beach, likely resulting in less physical disturbance and hence a dominance of ecological processes. In future work, we will combine our results with auxiliary information (e.g., multitemporal digital elevation models, time series of external forcing conditions, plant species and traits) to develop and test an eco-geomorphological model for blowout evolution. Such a model is adamant to understand what factors contribute to the success or failure of dune restoration projects involving blowouts as nature-based solutions to increase coastal resilience.
Assessment of Urbanization Impact On Heavy Precipitation in Istanbul, Turkey
Authors: Dönmez Kutay , Dönmez Berkay , Diren-Üstün Deniz , Ünal Yurdanur
Published: March 2021

Cities have undergone a substantial increase in urbanization over the past decades. Whether the change in land-use type and the consequent Urban Heat Island (UHI) affects the extreme precipitation was of interest and has been under investigation for various developing cities. This study pursued a similar purpose and investigated the impact of urbanization on a heavy precipitation incident that took place in Istanbul on 18 July 2017. Two particular land-use scenarios were used to simulate the event by Weather Research and Forecasting Model (WRF). First, the control simulation (WRF-urban) was performed using the default CORINE 2018 land-use dataset. Subsequently, the test simulation (WRF-nourban) was implemented by replacing the urbanized land-use type of Istanbul with the most dominant land use category of arid cultivated area. Comparison of the WRF-urban simulation with station observations and satellite data reveal that the WRF captured the heavy precipitation event reasonably well over Istanbul.  Results showed that urbanization has a notable impact on both the magnitude and timing of heavy rainfall.  Event day total precipitation amount increased considerably over and downstream of Istanbul on the control run. Although the start time and location of the incident reasonably matched for both runs, the test run without urbanization advanced the rainfall quicker, and the heavy precipitation event took place 1 hour earlier than the control run. The most pronounced distinction between the simulations with and without urbanization is detected over the northern coasts of Istanbul as the maximum daily total precipitation amount was approximately 250 mm higher just upstream and downstream of Istanbul Airport (IGA) on the WRF-urban run. Analysis of both vertical cross-sections and sensible heat fluxes on the city revealed that urbanized areas increased the atmospheric instability, thus caused heavier precipitation.
Plants, vital players in the terrestrial water cycle
Authors: ten Veldhuis Marie-Claire , van den Berg Tom , van der Ploeg Martine , Kaiser Elias , Dutta Satadal , Moene Arnold , Vialet-Chabrand Sylvere , van Emmerik Tim
Published: March 2021

Plant transpiration accounts for about half of all terrestrial evaporation (Jasechko et al., 2013). Plants need water for many vital functions including nutrient uptake, growth, maintenance of cell turgor pressure and leaf cooling. Due to the regulation of water transport by stomata in the leaves, plants lose 97% of the water they take via their roots, to the atmosphere. They can be viewed as transpiration-powered pumps on the interface between the soil and atmosphere.

Measuring plant-water dynamics is essential to gain better insight into their role in the terrestrial water cycle and plant productivity. It can be measured at different levels of integration, from the single cell micro-scale to the ecosystem macro-scale, on time scales from minutes to months. In this contribution, we give an overview of state-of-the-art techniques for transpiration measurement and highlight several promising innovations for monitoring plant-water relations. Some of the techniques we will cover include stomata imaging by microscopy, gas exchange for stomatal conductance and transpiration monitoring, thermometry for water stress detection, sap flow monitoring, hyperspectral imaging, ultrasound spectroscopy, accelerometry, scintillometry and satellite-remote sensing.

Outlook: To fully assess water transport within the soil-plant-atmosphere continuum, a variety of techniques is required to monitor environmental variables in combination with biological responses at different scales. Yet this is not sufficient: to truly solve for spatial heterogeneity as well as temporal variability, dense network sampling is needed.

In PLANTENNA (https://www.4tu.nl/plantenna/en/) a team of electronics, precision and microsystems engineers together with plant and environmental scientists develop and implement innovative (3D-)sensor networks that measure plant and environmental parameters at high resolution and low cost. Our main challenge for in-situ sensor autonomy (“plug and forget”) is energy: we want the sensor nodes to be hyper-efficient and rely fully on (miniaturised) energy-harvesting.

REFERENCES:

Jasechko, S., Sharp, Z. D., Gibson, J. J., Birks, S. J., Yi, Y., & Fawcett, P. J. (2013). Terrestrial water fluxes dominated by transpiration. Nature, 496(7445), 347-350.
Plantenna: "Internet of Plants". (n.d.). https://www.4tu.nl/plantenna/en/

 
Gridded Arctic sea ice concentration reconstruction for the first half of the 20th century based on different proxy data
Authors: Semenov Vladimir , Matveeva Tatiana
Published: March 2021

Global warming in the recent decades has been accompanied by a rapid recline of the Arctic sea ice area most pronounced in summer (10% per decade). To understand the relative contribution of external forcing and natural variability to the modern and future sea ice area changes, it is necessary to evaluate a range of long-term variations of the Arctic sea ice area in the period before a significant increase in anthropogenic emissions of greenhouse gases into the atmosphere. Available observational data on the spatiotemporal dynamics of Arctic sea ice until 1950s are characterized by significant gaps and uncertainties. In the recent years, there have appeared several reconstructions of the early 20th century Arctic sea ice area that filled the gaps by analogue methods or utilized combined empirical data and climate model’s output. All of them resulted in a stronger that earlier believed negative sea ice area anomaly in the 1940s concurrent with the early 20th century warming (ETCW) peak. In this study, we reconstruct the monthly average gridded sea ice concentration (SIC) in the first half of the 20th century using the relationship between the spatiotemporal features of SIC variability, surface air temperature over the Northern Hemisphere extratropical continents, sea surface temperature in the North Atlantic and North Pacific, and sea level pressure. In agreement with a few previous results, our reconstructed data also show a significant negative anomaly of the Arctic sea ice area in the middle of the 20th century, however with some 15% to 30% stronger amplitude, about 1.5 million km2 in September and 0.7 million km2 in March. The reconstruction demonstrates a good agreement with regional Arctic sea ice area data when available and suggests that ETWC in the Arctic has been accompanied by a concurrent sea ice area decline of a magnitude that have been exceeded only in the beginning of the 21st century.
Acceleration and Loss of Ultra-relativistic Electrons in the Earth Van Allen Radiation Belts
Authors: Shprits Yuri , Allison Hayley , Drozdov Alexander , Wang Dedong , Aseev Nikita , Zhelavskaya Irina , Usanova Maria
Published: March 2021

Measurements from the Van Allen Probes mission clearly demonstrated that the radiation belts cannot be considered as a bulk population above approximately electron rest mass. Ultra-relativistic electrons (~>4Mev) form a new population that shows a very different morphology (e.g. very narrow remnant belts) and slow but sporadic acceleration.

We show that acceleration to multi-MeV energies can not only result of a two-step processes consisting of local heating and radial diffusion but occurs locally due to energy diffusion by whistler mode waves. Local heating appears to be able to transport electrons in energy space from 100s of keV all the way to ultra-relativistic energies (>7MeV). Acceleration to such high energies occurs only for the conditions when cold plasma in the trough region is extremely depleted down to the values typical for the plasma sheet.

There is also a clear difference between the loss mechanisms at MeV and multi MeV energies The difference between the loss mechanisms at MeV and multi-MeV energies is due to EMIC waves that can very efficiently scatter ultra-relativistic electrons, but leave MeV electrons unaffected.

We also present how the new understanding gained from the Van Allen Probes mission can be used to produce the most accurate data assimilative forecast. Under the recently funded EU Horizon 2020 Project Prediction of Adverse effects of Geomagnetic storms and Energetic Radiation (PAGER) we will study how ensemble forecasting from the Sun can produce long-term probabilistic forecasts of the radiation environment in the inner magnetosphere.
Impact of Graphitic Structures in Pyrogenic Carbon on Microbial Reduction of Ferrihydrite
Authors: yu wentao , chen baoliang
Published: March 2021

Pyrogenic carbon plays important roles in microbial reduction of ferrihydrite by shuttling electrons in the extracellular electron transfer (EET) processes. Despite its importance, a full assessment on the impact of graphitic structures in pyrogenic carbon on microbial reduction of ferrihydrite has not been conducted. This study is a systematic evaluation of microbial ferrihydrite reduction by Shewanella oneidensis MR-1 in the presence of pyrogenic carbon with various graphitization extents. The results showed that the rates and extents of microbial ferrihydrite reduction were significantly enhanced in the presence of pyrogenic carbon, and increased with increasing pyrolysis temperature. Combined spectroscopic and electrochemical analyses suggested that the rate of microbial ferrihydrite reduction were dependent on the electrical conductivity of pyrogenic carbon (i.e., graphitization extent), rather than the electron exchange capacity. The key role of graphitic structures in pyrogenic carbon in mediating EET was further evidenced by larger microbial electrolysis current with pyrogenic carbon prepared at higher pyrolysis temperatures. This study provides new insights into the electron transfer in the pyrogenic carbon-mediated microbial reduction of ferrihydrite.
First results from the e Copernicus Sentinel-6 satellite mission 
Authors: Donlon Craig , Cullen Robert , Giulicchi Luisella , Fonari Marco
Published: March 2021

The threat of sea level rise to coastal communities is an area of significant concern to the well-being and security of future generations. Environmental policy actions and decisions affecting coastal states are being made now.  Given the considerable range of applications, sustained altimetry satellite missions are required to address operational, science and societal needs. This article describes the Copernicus Sentinel-6 mission that is designed to address the needs of the European Copernicus programme for precision sea level, near-real-time measurements of sea surface height, significant wave height, and other products tailored to operational services in the climate, ocean, meteorology and hydrology domains. It is designed to provide enhanced continuity to the very stable time series of mean sea level measurements and ocean sea state started in 1992 by the TOPEX/Poseidon (T/P) mission and follow-on Jason-1, Jason-2 and Jason-3 satellite missions. The mission is implemented through a unique international partnership with contributions from NASA, NOAA, ESA, EUMETSAT, and the European Union (EU).  It includes two satellites that will fly sequentially (separated in time by 5 years). The first satellite, named Sentinel-6 Michael Freilich, launched from Vandenburg Air Force Base, USA on 21st November 2020. The main payload is the Poseidon-4 dual frequency (C/Ku-band) nadir-pointing radar altimeter providing synthetic aperture radar (SAR) processing in Ku-band to improve the signal through better along-track sampling and reduced measurement noise. The altimeter has an innovative interleaved mode enabling radar data processing on two parallel chains, one with the SAR enhancements and the other furnishing a "Low Resolution Mode" that is fully backward-compatible with the historical T/P and Jason measurements, so that complete inter-calibration between the state-of-the-art data and the historical record can be assured. A three-channel Advanced Microwave Radiometer for Climate (AMR-C) developed by NASA JPL provides measurements of atmospheric water vapour that would otherwise degrade the radar altimeter measurements. An experimental High Resolution Microwave Radiometer (HRMR) is also included in the AMR-C design to support improved performance in coastal areas. Additional sensors are included in the payload to provide Precise Orbit Determination, atmospheric sounding via GNSS-Radio Occultation and radiation monitoring around the spacecraft.

Early in-orbit performance data are presented.
The role of flow-dependent oceanic background-error covariance information in air-sea coupled data assimilation during tropical cyclones: a case study
Authors: Leung Tsz Yan , Smith Polly J. , Lawless Amos S. , Nichols Nancy K. , Martin Matthew J.
Published: March 2021

In variational data assimilation, background-error covariance structures have the ability to spread information from an observed part of the system to unobserved parts.  Hence an accurate specification of these structures is crucially important for the success of assimilation systems and therefore of forecasts that their outputs initiate.  For oceanic models, background-error covariances have traditionally been modelled by parametrisations which mainly depend on macroscopic properties of the ocean and have limited dependence on local conditions.  This can be problematic during passage of tropical cyclones, when the spatial and temporal variability of the ocean state depart from their characteristic structures.  Furthermore, the traditional method of estimating oceanic background-error covariances could amplify imbalances across the air-sea interface when weakly coupled data assimilation is applied, thereby bringing a detrimental impact to forecasts of cyclones.  Using the case study of Cyclone Titli, which affected the Bay of Bengal in 2018, we explore hybrid methods that combine the traditional modelling strategy with flow-dependent estimates of the ocean's error covariance structures based on the latest-available short-range ensemble forecast.  This hybrid approach is investigated in the idealised context of a single-column model as well as in the UK Met Office’s state-of-the-art system.  The idealised model helps inform how the inclusion of ensemble information can improve coupled forecasts.  Different methods for producing the ensemble are explored, with the goal of generating a limited-sized ensemble that best represents the uncertainty in the ocean fields.  We then demonstrate the power of this hybrid approach in changing the analysed structure of oceanic fields in the Met Office system, and explain the difference between the traditional and hybrid approaches in light of the ways the assimilation systems respond to single synthetic observations.  Finally, we discuss the benefits that the hybrid approach in ocean data assimilation can bring to atmospheric forecasts of the cyclone.
A modified Coulomb failure seismicity model to study earthquake occurrence and frequency-magnitude distributions
Authors: Dahm Torsten
Published: March 2021

The linear Coulomb failure (LCM) and the rate-and-state model (RSM) are two widely-used physics-based seismicity models both assuming Coulomb stress changes acting on pre-existing populations of faults. While both predict background earthquake rates and time-dependent stress effects, only the RSM can additionally explain the time-dependent triggering of aftershocks.

We develop a modified effective media Coulomb model which accounts for the possibility of earthquake nucleation and retarded triggering of rupture. The new model has only two independent parameters and explains all statistical features of seismicity equally well as the RMS, but is simpler in its concept and provides insights in the possible nature of time-dependent frequency-magnitude distributions. Some of the statistical predictions are different compared to the RSM or LCM. For instance, the model domain is not limited to positive earthquake background or stressing rates; it can also simulate seismicity under zero stressing assumptions. The increase of background seismicity with tectonic stressing is nonlinear, different to the other models, and may even saturate if the tectonic stress loading is very strong. The Omori aftershock decay is predicted in the new model with an exponent of p=1 also for time periods much larger than the aftershock decay time, however, the productivity factor K is time dependent with a very slow exponential attenuation. The attenuation may explain the apparent variation of p in observed aftershock sequences. Interesting is also that the new model predicts a co-seismic peak of triggered aftershocks, which depends on the magnitude of the stress step and does not influence the attenuation of aftershocks following the stress step. It could be a physical explanation for the c-value in Omori’s law, the origin of which is still under discussion.

We compare the new model to RSM and LCM and discuss the possible implications for earthquake clustering and frequency magnitude distributions.