bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric circulation, hydroclimate change, and peat accumulation over the last 250 years inferred from a Sphagnum peatland in the southern Greater Khingan Mountains of Northeast China 
Authors: Wang Zuo , Yu Zicheng
Published: March 2021

Northeast China—located near the northern limit of the influence by the East Asian summer monsoon—receives most moisture through the westerly airflow, but variations in moisture contributions from the Yellow Sea in the western Pacific Ocean determine its hydroclimate during summer monsoon season. The proportion of moisture from the Yellow Sea is strongly modulated by the location and intensity of the Western Pacific Subtropical High (WPSH). However, it is still unclear how sensitive regional hydroclimate to WPSH-modulated change in moisture sources and its impact on peatland carbon accumulation. Here, we used macrofossil data and paired δ13C and δ18O isotope analysis of Sphagnum moss cellulose from a well-dated bog from a steep mountain slope in the Greater Khingan Mountains (~47˚N) to reconstruct peatland moisture changes and elucidate past shifts in moisture sources. δ13C values reflect peatland surface moisture, as dry conditions with less water film effects would increase isotopic discrimination against 13C and result in lower δ13C values. Our results from a 250-year peat record show a decrease of ~3‰ in δ13C from -25 to -28‰—with corresponding increase in dry-adapted moss Polytrichum—suggesting a drying trend since about 1980 AD. Also, the down-core δ18O and δ13C data show a positive correlation (r = 0.65, p < 0.001), in contrast with evaporative enrichment of δ18O being the dominant effect. We argue that δ18O values reflect the input of moisture derived from the Yellow Sea—that has higher δ18O values than that from the westerlies—as modulated by the WPSH. When the WPSH extends westward, it blocks moisture transport from the Yellow Sea to North China, causing low δ18O values in summer precipitation, dry conditions, and negative shifts in δ13C, and vice versa. Furthermore, carbon accumulation rates show a major decrease after the 1980s—despite that more recent peat tends to have higher apparent accumulation rates—suggesting a sensitive response of this steep-slope mountain peatland to shift in regional hydroclimate in monsoon-margin region of Northeast China.
Towards long-term (2002-present) reconstruction of northern Indian Ocean Sea Surface Salinity based on AMSR-E and L-band Radiometer data
Authors: Montero Marie , Reul Nicolas , de Boyer Montégut Clément , Vialard Jérôme , Tournadre Jean
Published: March 2021

Salinity plays an important role in the oceanic circulation, because of its impact on pressure gradients and the upper ocean stability. This is particularly the case in the North Indian Ocean where freshwater inputs from monsoonal rain and rivers into the Bay of Bengal and strong evaporation in the Arabian Sea leads to high salinity contrasts, and a strong variability tied to the large monsoonal currents seasonal cycle.

In situ salinity data is however too sparse to allow a detailed study of the contrasted and variable Northern Indian Ocean Sea Surface Salinity (SSS). This situation has changed since the launch of SMOS in 2009, and the advent of L-band-based SSS remote sensing with a much higher spatio-temporal sampling. Here, we explore the capacity of C and X-band measurements, such as those of AMSR-E (May 2002-October 2011) to reconstruct Northern Indian Ocean SSS prior 2009. Previous studies have indeed demonstrated the ability of C- and X-band products to reconstruct SSS in high-contrast regions like river estuaries, especially at high Sea Surface Temperature (SST), like in the Northern Indian Ocean.

 

We are currently focusing on the development of the algorithm to reconstruct salinity from the C- and X-band data of AMSR-E. The ESA Climate Change Initiative (CCI) SSS dataset build from a merge of SMOS, Aquarius and SMAP data, provides a reference SSS that is both used for training our algorithm and for validation, over the common AMSR-E and CCI period (January 2010 to October 2011).

Our first results are encouraging: spatial contrast between the low-SSS values close to estuaries and along the coast and higher SSS in the middle of the Bay of Bengal as well as some aspects of the seasonal cycle are reproduced. However, spurious signals linked to either radio frequency interferences still need to be filtered out and signals associated with other residual geophysical contributions (e.g. wind, atmospheric vapor content) need to be better estimated. The long-term goal of this work is to merge the C-, X-, and L-band data with in-situ measurements and thus provide a long-term reconstruction of monthly SSS in the north Indian Ocean with a ~50km resolution.
Statistical Characteristics of Turbulence in an Urban Canyon
Authors: Repina Irina , Pashkin Artem , Stepanenko Victor , Bogomolov Vasiliy , Smirnov Sergey , Telminov Alexey
Published: March 2021

Parametrizations which traditionally are used in atmospheric modeling, energy-balance and biogeochemical calculations are based on the Monin-Obukhov similarity theory (MOST). MOST assumes a uniform horizontal distribution of aerodynamic and temperature roughness of an underlying surface. These conditions are violated in heterogeneous landscapes, what requires special experiments to establish the limits of MOST applicability. Investigation of the atmospheric boundary layer (ABL) turbulent structure within urban area is an important task. The aim of our work is to establish links between statistical characteristics of turbulence in the urban landscape under different regimes of ABL.

This paper presents some results of an experiment in which all-season monitoring of the temporal variability and spatial structure of atmospheric turbulence is carried out under conditions close to those of an urban canyon. Measurements are made on the basis of the Geophysical observatory of the Institute of monitoring of climatic and ecological systems SB RAS,Russia, Tomsk. The measurement system includes five sonic anemometers located at different points and heights. This approach makes it possible to estimate the terms of the balance equations of statistical moments and, accordingly, the value of the contribution of horizontal and vertical transport to the formation of turbulent fluxes.

The possibility of parametrizing the third moment (flux of heat flux) by the type of convective advection for the conditions of an urban canyon has been confirmed. It is experimentally shown that in the inner region of the layer at a height of 10 m this third moment is expressed as the product of the potential temperature flux and the convective advection rate. Near the underlying surface, the third moment is expressed according to the approximation of turbulent diffusion.

The data processing and analysis was supported by RFBR under grant 20-05-00834, and the experimental work was supported by the Ministry of Science and Higher Education of the Russian Federation Project № IX.138.2.3.
A progressive episode of deformation in the foreland of the West-Congo Belt: From folding to brittle shearing, in Republic of Congo
Authors: Nkodia Hardy Medry Dieu-Veill , Boudzoumou Florent , Miyouna Timothée , Ibarra-Gnianga Alex , Delvaux Damien
Published: March 2021

The West Congo belt is a Panafrican orogenic belt that evolved and resulted from the collision of the Sao Francisco craton and the Congo Craton during late Neoproterozoic (630 Ma)  to late Cambrian (490 Ma ?). It constitutes the counterpart of the most studied Araçuaì belt in Brasil. Over the past decades, most structural analysis focused in Araçuaì belt while few structural data were obtained from the West-Congo Belt. Understanding the West Congo belt and particularly in its foreland is relevant to establish a unified structural model for its evolution, as the late phases of deformation of both orogens are still debated. In the Comba basin at Mont Bélo, Loutété, Mfouati, most of the folds are gently plunging, upright to moderately inclined fold, with sometimes chevron shape, circular shape and box shape. Some of the folds show decollement within their limbs. Most of these fold display flexural slip displacements along the layers where slickensides are associated with calcite fibres. Most of the limbs developed boudinage in the carbonate layers. The folds are oriented WNW-ESE and they are cut by a system of conjugate NW-SE striking strike-slip dextral fault and NNE-SSW striking sinistral fault. A kinematic analysis from fault slip data using the Win-Tensor program reveal that faults originate from NNE-SSW shortening and ESE-WNW extension. This kinematic analysis is consistent with the orientation of the fold according the Riedel model. The brittle deformation occurred in continuity of the deformation after the folding as folds hinges are displaced in certain localities.This episode of progressive deformation probably ends with intense shearing of the belts, as several dominating regularly spaced NE-striking shear zones cut the orogen from the Republic of Congo to the democratic Republic of Congo. Further investigations will be conducted in the continuity of the west Congo Belt in the Democratic Republic of Congo in order to enlarge the regional perspective.
Assessing the feasibility of large-scale hydrogen storage in salt caverns on the UKCS using 3D seismic data
Authors: Barnett Hector , Ireland Mark T. , Acikalin Sanem
Published: March 2021

The energy industry in the UK faces a challenge to decarbonize to support reaching net zero CO2 emissions by 2050. In nearly all scenarios emission reductions are characterized not only by energy demand reductions, but also the decarbonization of electricity and heating. The use of hydrogen as a replacement for natural gas is one proposed solution, where renewable hydrogen is either blended into the gas grid or used directly. To ensure continuity of supply large scale hydrogen storage will be needed to meet this demand.

Hydrogen has been stored in small volumes (<25GWh) in salt caverns at various locations onshore in the United Kingdom since 1959. These caverns store hydrogen for industrial usage. In order to meet the demand for energy related hydrogen storage an increasing number of new and potentially larger storage options will be needed. Engineering of larger salt caverns for a hydrogen energy system will require thick salt formations which are optimally located with respect to both the hydrogen production facility and the end use. The Permian and Triassic salts deposits of both the Southern North Sea and the East Irish Sea offer vast areas for potential cavern development. Previous studies have described the landscape of underground gas storage onshore and offshore the UK, but to date there have been few detailed geophysical and geological studies on the hydrogen storage potential offshore.

The identification of suitable storage sites requires an understanding of the subsurface geology including potential structural discontinuities which could compromise the integrity of storage sites and be pathways for leakage. This analysis of hydrogen storage sites will utilise extensive existing modern 3D seismic data and well data taken from the Southern North Sea. We describe the geological setting of the Permo-triassic salt in the SNS in relation to the potential to develop salt cavern storage and develop play risk assessment maps. These risk assessment maps form part of a play fairway analysis workflow in order to identify the optimal storage sites for hydrogen on the UCKS.
METEOR: A methodology for assessing the potential for multi-hazard impacts on building exposure in developing nations.
Authors: Winson Annie , Smith Kay , Jordan Colm , Mee Katy , Huyck Charles , Silva Vitor , Paul Nicole , Wagle Sharad , Evans William , Kombe Emmanuel , Maholi Innocent , Jimee Ganesh , Dashwood Claire , Ciurean Roxana , Boon David , Sampson Christopher , Henshaw Paul , Msangi Charles , Petrarulo Luca , Pradhan Suman ,   METEOR
Published: March 2021

The METEOR project (Modelling Exposure Through Earth Observation Routines) is a three year project ending in March 2021, co-funded by the UK Space Agency International Partnership Programme. The aim of this project was to develop innovative methods to understand multi-hazard and exposure, and to deliver robust data for Disaster Risk Management (DRM) in Nepal and Tanzania.

In developing economies there is a pressing need to characterise hazard, exposure and vulnerability to allow for comprehensive DRM plans and pre-positioning. In the METEOR project these exposure protocols and standards were co-developed and validated in Nepal and Tanzania to ensure that they are fit-for-purpose.  Many multi-hazard mapping approaches focus on the frequency of events and use historical financial losses as a proxy for infrastructure impact or exposure (Bell and Glade, 2004; Tate et al., 2010; Schmidt et al., 2011; Kappes et al., 2012). Whilst such approaches may be appropriate for hazards with historic inventories detailing the distribution and scale of events, for others estimation of key factors such as historic frequency, or probability of occurrence or losses, is much more complex.

Here we will present a new methodology for assessing the national impact of multi-hazards on exposure, grounded in earth observation data, in the context of data paucity and high levels of inherent uncertainty. We explore a subset of the METEOR data for Nepal to discuss the main controls on the uncertainty of the final outputs of our model.  We also show how our model can be tied to existing vulnerability curves to link hazard assessments with expected damage.
Persistent monochromatic seismic signals across central Europe: AlpArray data indicate a man-made seismic source for regional wave propagation studies
Authors: Fuchs Florian , Bokelmann Götz , Working Group AlpArray
Published: March 2021

Consistent and monochromatic signals appear as sharp peaks in frequency spectra or as continuous lines in spectrograms on many permanent and temporary seismic stations in Central Europe, especially in South-Eastern Germany, Austria and the Czech Republic. Similar observations have already puzzled the seismic community more than 20 years ago. Here we report on new observations of such monochromatic seismic signals within a 1 – 10 Hz range across central Europe using the dense AlpArray network.

We identify several monochromatic signals on both permanent and temporary stations. The respective frequencies of e.g. 1.72 Hz, 2.08 Hz, 2.77 Hz or 4.16 Hz are generally stable even over long time spans (months to years). Strikingly, all such signals at any given station show identical and simultaneous short-term (minutes to days) frequency variations of up to 0.4% of the central frequency. These variations precisely correspond to fluctuations of the frequency of the European electric power network, which is regulated to 50 Hz +/- 0.4%. In fact, all persistent seismic signals that follow this behavior have frequencies of 50 Hz / n with n being an integer number (50 Hz / 29 = 1.72 Hz, 50 Hz / 24 = 2.08 Hz, 50 Hz / 18 = 2.77 Hz, 50 Hz / 12 = 4.16 Hz). We show that if the frequency of an observed spectral line is an integer fraction of the power network frequency (and only in that case) it will perfectly follow the fluctuations of the power network. This obviously raises questions about the nature of the signal itself, in particular if it is of seismic or maybe electro-magnetic origin.

We confirm that the signals are of seismic origin and we have identified water turbines inside river power plants as the source. The observed frequencies correspond well to reported rotation frequencies of water turbines at several different river power plants in Southern Germany and Austria. The seismic signals may propagate to almost 100 km from the corresponding plant. We analyze the spatial distribution of signal amplitudes for a selected river power plant in Austria, and show that it is similar to expected isolines of seismic shaking for an earthquake in the region.

Knowing the source of those exotic signals potentially enables us to use them for seismo-tectonic purposes. The long-term (several years) stability and the permanent availability (24h operation of water turbines) render them very interesting sources e.g. for studying temporal seismic velocity variations in the shallow crust.
Effect of Fe (oxyhydr)oxide morphology on phytic acid transport under saturated flow condition
Authors: Zhao Kang , Wang Xiang , Yuji Arai , Shang Jianying
Published: March 2021

Natural iron (oxyhydr)oxides are ubiquitous in subsurface environments. Phytic acid (myo-inositol hexaphosphate, IHP), a dominant form of organic phosphate (OP) in organic carbon-rich surface soils, strongly binds with Fe (oxyhydr)oxide. The cotransport of IHP and Fe (oxyhydr)oxide with different morphology under acid and alkaline conditions in the subsurface is mostly overlooked. These cotransport processes are critical for P (bio)geochemical processes in the subsurface that is rich in Fe (oxyhydr)oxides. Three Fe (oxyhydr)oxides (ferrihydrite, hematite, and goethite) were chosen in this study, and the cotransport of IHP and Fe (oxyhydr)oxide was investigated in saturated columns by injecting Fe (oxyhydr)oxide under different IHP concentrations (0, 10, 25, 50, and 100 µM) at pH of 5 and 10. The presence of IHP significantly enhanced the mobility of Fe (oxyhydr)oxide at both pH 5 and 10 due to the stronger electrostatic repulsion between Fe (oxyhydr)oxide and quartz sand. At low IHP concentrations (< 50 µM IHP), goethite with a rod-like morphology showed strong mobility due to its orientation transport along with the water flow streamline. The mobility of amorphous Fe (oxyhydr)oxide, ferrihydrite, was much slower than the goethite. However, ferrihydrite could facilitate more IHP transport due to its sorption capacity for IHP that is higher than goethite and hematite. At high IHP concentrations (> 50 μM), surface precipitation might have occurred on ferrihydrite because of its poorly ordered crystallinity, which contributed to its less negatively charged surface and weak ferrihydrite facilitated IHP transport. The new insight provided in this study is important for evaluating the transport behavior and impact of IHP in a saturated solum rich in Fe (oxyhydr)oxides.
Arabian sea Oxygen Minimum Zone projections under climate change: sensitivity to forcing and model resolution
Authors: Vallivattathillam Parvathi , Lachkar Zouhair , Lévy Marina , Smith Shafer
Published: March 2021

The Arabian sea (AS) hosts one of the most intense oxygen minimum zones (OMZ) in the open ocean. This OMZ is formed and maintained by the peculiar geography and the associated monsoonal productivity in the AS and  is highly sensitive to the strength of monsoonal circulation and surface heating. Model projection from the fifth phase of Coupled Model Intercomparison project (CMIP5) indicate significant changes in both the Indian monsoonal circulation, atmospheric heat fluxes and primary productivity under climate change, but the response of the AS OMZ to these changes remain largely ill-understood. The poor representation of the AS OMZ and lack of oxygen diagnostics in the CMIP5 simulations pose major limitations in exploring the response of AS OMZ to future climate change. In this study, we use a set of regional downscaled experiments with a high-resolution configuration of the Regional Ocean Modeling System (ROMS) model coupled to a nitrogen-based NPZD ecosystem model to examine the sensitivity of the AS OMZ response to a range of CMIP5 forcing anomalies and to model resolution. Our downscaled set of experiments are based on a climatological control simulation forced with observed climatological atmospheric and lateral boundary conditions, to which climate change anomalies derived from CMIP5 simulations are added to construct climate change forcing fields. The control simulation has been extensively validated against observations. We explore the sensitivity of the downscaled oxygen distribution and OMZ to the regional model setup by varying the model horizontal resolution from 1/3 - 1/12 degree. In agreement with the set of available coarse resolution CMIP5 projections, our downscaled experiments show a future increase in the oxygen levels within the core of AS OMZ. The downscaled experiments improve the realistic representation of different classes of water (Oxic - O2 > 60mmol/l; Hypoxic - 60mmol/l >= O2 > 4mmol/l; and the Suboxic - 4 mmol/l > O2 > 0 mmol/l) within the 0-1500m depth range. We find that the projected oxygen changes in the AS OMZ are largely driven by the Apparent Oxygen Utilisation (AOU), which vary with forcing and model resolution, leading to a wide spread in the AS OMZ response to climate change.
Do soil properties with elevation affect alpine "grass-line"? Findings from Haibei, northern Tibetan Plateau
Authors: Cao Zuonan , Guan Zhenhuan , Kühn Peter , He Jinsheng , Scholten Thomas
Published: March 2021

Many species showed that their richness and distribution shifts climate-driven towards higher elevation in Tibetan Plateau. However, vegetation and soil data from alpine grassland elevational gradients are rare (Huang et al., 2018). It is mostly unknown how the "grass-line" will respond to global warming and whether soils play a significant role in the vegetation pattern in high-altitude regions. At a local scale, the growth and distribution of vegetation at its upper limit may depend on nutrient limitation, as shown for treelines from the Himalayas. For example, the limited nutrient supply of soil N, K, Mg, and P becomes more intense with elevation, which declines in nutrient supply spatially coincides with abrupt changes in vegetation composition and growth parameters (Schwab et al., 2016). And low soil nutrient availability could affect tree growth in the Rolwaling Himal, Nepal treeline ecotone (Drollinger et al., 2017). To better understand the interrelationship between soil properties and grass growth at this upper limit, we took random soil samples in 3 altitudes, 3 geomorphic positions with 3 depth increments from Haibei grassland, northern Tibetan Plateau. Soil properties, like texture, bulk density, total C, N, and P fractions, were analyzed and compared to vegetation data.
Further, soil and vegetation data from open-top chambers (OTC) experiments to simulate global warming were analyzed better to understand the role of temperature for grass line-shift. The first results show that species composition change with altitude towards grassland plant communities with lower demands for P, which can be compared with the nutrient addition experiment that P addition alone significantly affects species diversity and biomass in the same area (Ren et al., 2016). We suppose that specific combinations of soil properties could limit grass growth and be even more marked than the warming, which controls biodiversity and biomass production in high mountain grassland ecosystems. 
The GravIS Portal: User-friendly Global Mass Variations from GRACE and GRACE-FO
Authors: Dahle Christoph , Boergens Eva , Dobslaw Henryk , Groh Andreas , Sasgen Ingo , Reißland Sven , Flechtner Frank
Published: March 2021

The German Research Centre for Geosciences (GFZ) maintains the “Gravity Information Service” (GravIS, gravis.gfz-potsdam.de) portal in collaboration with the Alfred-Wegener-Institute (AWI) and Technische Universität Dresden. Main objective of this portal is the dissemination of data describing mass variations in the Earth system based on observations of the satellite gravimetry missions GRACE and GRACE-FO.

The provided data sets encompass products of terrestrial water storage (TWS) variations over the continents, ocean bottom pressure (OBP) variations from which global mean barystatic sea-level rise can be estimated, and mass changes of the ice sheets in Greenland and Antarctica. All data sets are provided as time series of regular grids for each area, as well as in the form of regional basin averages. Regarding the latter, for the continental TWS data the user can choose between classical river basins and a novel segmentation based on climatic regions. For the oceans, the segmentation into different regions is derived similarly but based on modelled OBP data. All time series are accompanied by realistic uncertainty estimates.

All data sets can be interactively displayed at the portal and are freely available for download. This contribution aims to show the features and possibilities of the GravIS portal to researchers without a dedicated geodetic background, working in the fields of hydrology, oceanography, and cryosphere.
Revising the 11-year Solar Cycle Response in Stratospheric Ozone Using an Ensemble of Lasso and Ridge Regression Models
Authors: Chipperfield Martyn , Dhomse Sandip , Feng Wuhu , Hossaini Ryan
Published: March 2021

Solar flux variations associated with the 11-year solar cycle are believed to exert an important climate forcing via changes in stratospheric ozone. However, our understanding of the ozone solar cycle signal (SCS) was significantly revised with the availability of updated SAGE II v7 data. For example, Dhomse et al. (Geophys. Res. Lett., 2016) analysed SAGE II v7 data to show a much smaller upper stratosphere ozone SCS, as well as a more realistic ozone-temperature anti-correlation, that agreed with the relatively short HALOE and AURA-MLS data records. Here, we analyse AURA-MLS satellite data and output from the TOMCAT 3D chemical transport model (CTM) to estimate the ozone SCS for the 2005-2020 period, which covers one of smallest solar cycles (number 24) of the last 100 years. Along with a control simulation, various model simulations with combinations of different dynamical (e.g. ERA5, ERA-Interim, fixed), chemical (e.g. constant ozone depleting substances) and solar flux (NRL, SATIRE, SORCE solar irradiances) forcings are analysed.

Our earlier studies use an Ordinary Least Square (OLS) multivariate regression model to estimate the SCS. However, most of the relevant atmospheric variables are correlated. Hence, to avoid this collinearity problem, we use an ensemble of Lasso and Ridge multivariate regression models and their variants to quantify the SCS in stratospheric ozone. Overall, both MLS and the CTM simulations show a vertical “double-peak”-structured ozone SCS in the tropical stratosphere. However, compared to previous studies, the regression ensemble mean shows a somewhat larger signal in the middle stratosphere and does not show a negative SCS in the lower and upper stratosphere. Our analysis also shows significant inter-hemispheric and seasonal differences in lower stratospheric ozone trends over the 2005-2020 time period (i.e. recent ozone recovery phase). Our CTM simulations also confirm that recent negative ozone trends in the northern hemispheric mid-latitude lower stratosphere (Chipperfield et al., Geophys. Res. Lett., 2018), are primarily caused by changes in the stratospheric circulation.
Electromagnetic electron hole generation: theory and PIC simulations
Authors: Gauthier Gaetan , Chust Thomas , Le Contel Olivier , Savoini Philippe
Published: March 2021

Recent MMS observations (e.g. [Holmes et al, 2018, Steinvall et al., 2019]) exploring various regions of the magnetosphere have found solitary potential structures call Electron phase-space Hole (EH). These structures have kinetic scale (dozens of Debye lengths) and persist during long time (dozens of plasma frequency periods). EH are characterized by a bipolar electric field parallel to ambient magnetic field and fastly propagate along this latter (a few tenths of speed light). We have created a 3D Bernstein-Greene-Kruskal (BGK) model (as [Chen et al, 2004]) adapted to various magnetospheric ambient magnetic fields. BGK model results depend on choice of potential shape and passing distribution function at infinity (before EH potential interaction).

2D-3V Particle-In-Cell simulations have been developed with the fully kinetic code Smilei [Derouillat et al, 2017], using real magnetosphere plasma parameters. Solitary waves in the magnetotail are three-dimensional potentials which can be generated through nonlinear evolution of an electron beam instability (or bump on tail). The simulated EH are comparable to the EH observed in the magnetosphere with the same parameters.

We have also investigated the EH formation with density inhomogeneities using a BGK stability model we have developed. Indeed, density inhomogeneities exist notably in interplanetary plasmas. As a result taking into account the background density inhomogeneities, significantly alters the stability criteria. We have performed 2D-3V PIC simulations with realistic inhomogeneous density background (smaller than 10% of mean density) to understand such a type of EH formation.

References:

Holmes et al., J. Geophys. Res. Space Phys. 123, 9963, 2018

Steinvall et al., Phys. Rev. Lett. 123, 255101, 2019

Chen et al., Phys. Rev. E 69, 055401, 2004

Derouillat et al., Comput. Phys. Commun. 222, 351, 2017

 
Contrasting seasonal changes in temperature, precipitation and snow cover simulated over the European Alps during the twentieth century
Authors: Ménégoz Martin , Beaumet Julien , Gallée Hubert , Fettweis Xavier , Morin Samuel , Blanchet Juliette , Six Delphine , Vincent Christian , Jourdain Nicolas C. , Wilhelm Bruno , Anquetin Sandrine
Published: March 2021

The evolution of temperature, precipitation and snow cover in the European Alps have been simulated with the regional climate model MAR applied with a 7 kilometre horizontal resolution and driven by the ERA-20C (1902-2010) and the ERA5 reanalyses (1981-2018). A comparison with observational datasets, including French and Swiss local meteorological stations, in-situ glacier mass balance measurements and reanalysis product demonstrates high model skill for snow cover duration and snow water equivalent (SWE) as well as for the climatology and the inter-annual variability of both temperature and precipitation. The relatively high resolution allows to estimate the meteorological variables up to 3000m.a.s.l. The vertical gradient of precipitation simulated by MAR over the European Alps reaches 33% km-1 (1.21 mmd-1.km-1) in summer and 38%km-1 (1.15mmd mmd-1.km-1) in winter, on average over 1971–2008 and shows a large spatial variability. This study evidences seasonal and altitudinal contrasts of climate trends over the Alps. A significant (pvalue< 0.05) increase in mean winter precipitation is simulated in the northwestern Alps over 1903–2010, with changes typically reaching 20% to 40% per century, a signal strongly modulated by multi-decadal variability during the second part of the century. A general drying is found in summer over the same period, exceeding 20% to 30% per century in the western plains and 40% to 50% per century in the southern plains surrounding the Alps but remaining smaller (<10%) and not significant above 1500ma.s.l. Over 1903–2010, the maximum of daily precipitation (Rx1day) shows a general and significant increase at the annual timescale and also during the four seasons, reaching local values between 20% and 40% per century over large parts of the Alps and the Apennines. Trends of Rx1day are significant (pvalue<0.05) only when considering long time series, typically 50 to 80 years depending on the area considered. Some of these trends are nonetheless significant when computed over 1970–2010, suggesting a recent acceleration of the increase in extreme precipitation. Rx1day increase occurs where the annual correlation between temperature and intense precipitation is high. The highest warming rates in MAR are found at low elevations (< 1000 m a.s.l) in winter, whereas they are found at high elevations (> 2000 m a.s.l) in summer. In spring, warming trends show a maximum at intermediate elevations (1500 m to 1800 m). Our results suggest that higher warming at these elevations is mostly linked with the snow-albedo feedback in spring and summer.
3D Finite-Element Modeling of Electromagnetic Data with the Open-Source Toolbox custEM 1.0
Authors: Rochlitz Raphael , Guenther Thomas
Published: March 2021

We present enhancements and simulation capabilities of the open-source Python toolbox custEM, which was primarily designed for the 3D finite-element (FE) modeling of controlled-source electromagnetic (CSEM) surveys with arbitrary geometries on unstructured meshes. Recently, we extended the capabilities of custEM by implementing multiple approaches for time-domain (transient) electromagnetic (TEM) and magnetotelluric (MT) data.

All modeling approaches rely on the finite-element modeling library FEniCS and the direct solver MUMPS. Of the implemented FE approaches, we prefer the total electric-field formulation using Nédélec basis functions. Further potential and magnetic-field approaches, either as total- or secondary-field formulation, are available as well. Second-order basis functions usually represent a good trade-off between accuracy and computational effort. We support general anisotropic petrophysical parameters, including the conductivity, the magnetic permeability, electric permittivity, and Cole-Cole parameters to simulate induced-polarization effects. We improved all sub-modules of custEM which enabled more robust, accurate, and computationally efficient simulations. It is well-known that solving 3D FE systems with direct solvers demands plenty of memory (RAM). Though particular simulations might require up to a few TB RAM, most geometries can be handled on computer architectures with a few tens of cores and about 250 GB RAM. In addition, reusing the factorization of the system matrix significantly accelerates the solution of problems with multiple right-hand sides which is beneficial for multiple transmitters, time-domain approaches using the implicit Euler or rational Arnoldi methods, or the computation of sensitivities.

We present simulations for the three fields of electromagnetic modeling to demonstrate the accuracy and computational performance of custEM. The CSEM example is motivated by multi-frequency semi-airborne surveys as conducted in the DESMEX project. A 3D LOTEM example serves to compare three different 3D time-domain modeling approaches. The most recent support for magnetotelluric data is demonstrated by comparing our solutions of the Dublin test model 1 with those provided by the community. These and further examples are available in the code repository and can be reproduced independently. In combination with the automated online-documention of the source code, the variety of provided modeling example can help interested users to gain first experiences in custEM. Our implementation can support the community in forward modeling studies, inverse modeling applications, cross-validations, as well as understanding or teaching purposes.
The Impact of Mediterranean Droughts and Large Fires on the Carbon Balance of Vegetation
Authors: Silva Tiago E. , Russo Ana , Gouveia Célia M.
Published: March 2021

Over the last decades, the vegetation dynamics have been severely disturbed due to the increasing intensity and occurrence of extreme events. The activity of terrestrial ecosystems is particularly susceptible to the climate variability, and their recently regional changes, mainly linked to the occurrence of extreme climatic events, are leading to rapid changes on natural vegetation cycle, plants productivity and terrestrial carbon cycle.

Droughts have been broadly recognized, among a wide range of extreme events, as playing a central role on the carbon cycle. Dry conditions contribute to the occurrence of high hydrological stress on vegetation, generating disturbances on the regular photosynthesis and vegetation mechanisms. Furthermore, they may increase the risk of fires, enhancing the losses on carbon stocks and plants productivity and inhibiting the ecosystems to regenerate and recover for a long time.

A wide range of works have recently shown that Europe, and in particular, the Mediterranean region, has been affected by severe droughts and large fires in the last decades. Therefore, we propose to assess the impact of a set of the severest droughts and large fires, between 2001 and 2019, over three different regions of Mediterranean basin, in order to assess their influence on vegetation, by evaluating the persistency of soil dry conditions and the observation of the number of months that vegetation’s activity is disturbed. This analysis allowed the quantification of the carbon losses occurred due to the referred extreme events, and also, the observation of the time response and recovery process of vegetation during the following months. In this study, we used remote sense products to monitor the vegetation production and activity (MODIS GPP and PSNet), to assess the soil moisture (ESA CCI SM) and to detect burned areas (FIRE CCI51).

 This work was supported by FCT through projects IMPECAF (PTDC/CTA-CLI/28902/2017), FIRECAST (PCIF/GRF/0204/2017) and by IDL (UIDB/50019/2020).
Ranking and calibration of ground-motion models using the stochastic area metric. 
Authors: Sunny Jaleena , De Angelis Marco , Edwards Ben
Published: March 2021

The selection and ranking of  Ground Motion Models (GMMs) for scenario earthquakes is a crucial element in seismic hazard analysis. Typically model testing and ranking do not appropriately account for uncertainties, thus leading to improper ranking. We introduce the stochastic area metric (AM) as a scoring metric for GMMs, which not only informs the analyst of the degree to which observed or test data fit the model but also considers the uncertainties without the assumption of how data are distributed. The AM can be used as a scoring metric or cost function, whose minimum value identifies the model that best fits a given dataset. We apply this metric along with existing testing methods to recent and commonly used European ground motion prediction equations: Bindi et al. (2014, B014), Akkar et al. (2014, A014) and Cauzzi et al. (2015, C015). The GMMs are ranked and their performance analysed against the European Engineering Strong Motion (ESM) dataset. We focus on the ranking of models for ranges of magnitude and distance with sparse data, which pose a specific problem with other statistical testing methods. The performance of models over different ranges of magnitude and distance were analysed using AM, revealing the importance of considering different models for specific applications (e.g., tectonic, induced). We find the A014 model displays good performance with complete dataset while B014 appears to be best for small magnitudes and distances. In addition, we calibrated GMMs derived from a compendium of data and generated a suite of models for the given region through an optimisation technique utilising the concept of AM and ground motion variability. This novel framework for ranking and calibration guides the informed selection of models and helps develop regionally adjusted and application-specific GMMs for better prediction. 

 
Geology of the Charlie Gibbs transform system (52-53ºN, Mid Atlantic Ridge): preliminary results from Akademik Nikolaj Strakhov Expedition S50
Authors: Sanfilippo Alessio , Skolotnev Sergey , Peyve Alexander ,   A.N. Strakhov Expedition S50 Science Party
Published: March 2021

The Charlie Gibbs offsetting by ~340 km the Mid Atlantic Ridge (MAR) axis between 52°-53° N is one of the main transform systems of the North Atlantic. Located between long mid-ocean ridge segments influenced to the south by the Azores and to the north by the Iceland mantle plume, this transform system has been active since the early phases of North Atlantic rifting. Object of several surveys in the ‘70 and ‘80, Charlie Gibbs received great attention for its unique structure characterized by two long-lived right-lateral transform faults linked by a short ~40 km-long intra-transform spreading centre (ITR) with parallel fracture zone valleys extending continuously towards the continental margins. In October 2020 expedition S50 of the R/V A.N. Strakhov surveyed an area of 54552 km2 covering the entire Charlie Gibbs transform system and the adjacent MAR spreading segments. We collected new bathymetric, magnetic and high-resolution single channel seismic data, along with basaltic, gabbroic and mantle rocks from 21 dredges. In this contribution we present preliminary data from cruise S50 and discusses the large-scale architecture of this unique, long-lived transform system.
The interannual variability of the tropical divergence tilt
Authors: Zurita-Gotor Pablo
Published: March 2021

The large-scale divergence field tilts eastward with latitude moving away from its near-equatorial maximum in the summer hemisphere. This tilt, observed for all hemispheres and seasons, is also apparent in a hierarchy of models of varying complexity, including the simple Gill model. Previous theoretical work has shown that the divergence tilt determines the sign of the divergent momentum flux in the deep tropics, suggesting a possible connection to wave propagation.

In this presentation,  we show that changes in the divergence tilt are one of two primary drivers of the interannual eddy momentum flux variability in the tropics. We also show that interannual changes in the divergence tilt are strongly correlated with the West Pacific Oscillation, with an associated large extratropical impact. The dynamical mechanisms behind this association are also discussed.
Recent advances in applied avalanche research in Norway
Authors: Jaedicke Christian , Issler Dieter , Gleditsch Gisnås Kjersti , Salazar Sean , Robinson Kate , Gauer Peter , Langeland Henrik , Domaas Ulrik , Liu Zhongqiang , Glimsdal Sylfest , Sandersen Frode , Mo Katrine , Frauenfelder Regula , Heyerdahl Håkon , Breien Hedda , Gilbert Graham
Published: March 2021

Snow avalanches are a significant natural hazard and common phenomenon in Norway. Applied research on avalanches and their societal impact has been conducted at the Norwegian Geotechnical Institute (NGI) for nearly half a century.

Recent activities within the applied avalanche research group at NGI have focused on four areas: (1) Improved understanding of is sought through the application of simple probabilistic release models and local wind modelling. Encouraging results are obtained by analysing and refining publicly available climate time series for temperature, snow depth and precipitation on a 1 km² grid. A major remaining challenge in view of elaborating realistic large-area avalanche hazard indication maps is the a priori determination of the size of release areas as a function of return period. (2) Different aspects of are investigated by means of a wide array of experimental technologies at the Ryggfonn full-scale test site, application of aerial survey methods to derive snow distribution, and investigation of the scaling behaviour of avalanches with extreme runouts in many different paths. The results of all these analyses point towards the need for a departure from modelling avalanches with Voellmy-type models in favour of models encompassing multiple flow regimes, a more realistic rheology and entrainment as well as deposition. (3) To improve risk assessment and mitigation measures, with structures are studied by documenting destructive avalanche events, constructing vulnerability curves for persons inside buildings based on historic avalanche events, improving methods for evaluation of individual risks, and development of criteria for physical mitigation measures against powder-snow avalanches. (4) Current efforts in focus on the one hand on simple block models for studying scaling behaviour on idealised and natural slopes and on the other hand on an advanced multi-flow-regime model that also incorporates different effects of the snow cover. Ongoing work aims, among others, at an entrainment and deposition model that is dynamically consistent and only depends on measurable snow properties. This contribution will present an overview of recent activities and advancements in applied avalanche research in Norway. It is hoped that it will serve to facilitate future international collaborative efforts to address challenges in applied avalanche research.
Development of an integrated indicator to assess the multi-dimensional global environmental impact of crop production.
Authors: jwaideh Mark , Dalin Carole
Published: March 2021

Due to increased demand for food, feed, fibre and fuels, intensive resource-use for crop production causes depletion of finite natural resources imperils ecosystems’ integrity. Environmental sustainability is a major global challenge, as identified by the UN Sustainable Development Goals (SDG), which indicate environmental protection, and higher food production (to end hunger and achieve food security and nutrition), as key goals. As such, the need to measure the environmental sustainability of agriculture globally is imperative to aid decision making for long term, multidisciplinary policy and research programs.

Composite indicators are popular tools to assess environmental performance due to their operational relevance in policy-making. However, the reliability of a composite indicator heavily depends not only on the meaningfulness and accuracy of the indicators embedded within, but also on the underlying methods used to construct the composite indicator. This research takes advantage of new spatially-explicit estimates of environmental impacts of global agriculture due to the use of fertiliser, water, land-use and emissions of greenhouse gases to build an integrated environmental sustainability indicator. Different constructions of a meaningful composite indicator are formed and assessed for their sensitivity to varying biophysical and resource input factors.

The tool will be used to analyse hotspots for environmental impacts and resource intensities, providing the initial analysis to aid institutions and governments at the strategic level to compare their level of sustainability, thus encouraging improvement of standards/ranking against other regions and implement drivers for behaviour and change. The study opens the opportunity to provide sustainable food production frameworks globally, group regions and analysis trade-offs/synergies between environmental impacts. Furthermore, by using emerging environmental datasets, this work generates new knowledge and understanding of globally significant environmental processes and profile these policy relevant insights; a process that is increasingly important for global agendas such as the U.N. Sustainable Development Goals.