bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Atlantic water inflow on winter cyclone activity in the Barents Sea: Insights from coupled regional climate model simulations
Authors: Akperov Mirseid , Semenov Vladimir A. , Mokhov Igor I. , Dorn Wolfgang , Rinke Annette
Published: March 2020

The impact of the Atlantic water inflow (AW inflow) into the Barents Sea on the regional cyclone activity in winter is analyzed in 10 ensemble simulations with the coupled Arctic atmosphere-ocean-sea ice model HIRHAM-NAOSIM for the 1979–2016 period. The model shows a statistically robust connection between AW inflow and climate variability in the Barents Sea. The analysis reveals that anomalously high AW inflow leads to changed baroclinicity in the lower troposphere via changed static stability and wind shear, and thus favorable conditions for cyclogenesis in the Barents/Kara Seas. The frequency of occurrence of cyclones, but particularly of intense cyclones, is increased over the Barents Sea. Furthermore, the cyclones in the Barents Sea become larger (increased radius) and stronger (increased intensity) in response to an increased AW inflow into the Barents Sea, compared to years of anomalously low AW inflow.

The authors acknowledge the support by the Russian-German project funded by the Federal Ministry of Education and Research of Germany and Ministry of Science and Higher Education of the Russian Federation (grant 05.616.21.0109 (RFMEFI61619X0109)).
Curbing our expectations: Global temperature impacts from strong mitigation of individual climate forcers
Authors: Samset Bjørn H. , Fuglestvedt Jan S. , Lund Marianne T.
Published: March 2020

Achieving the goals of the Paris agreement, or a stabilization of the global climate, requires strong and sustained mitigation of a range of anthropogenic emissions. A key stepping stone in this effort would be a measurable reduction in the current rate of global warming, which has been approximately constant over time since the 1970s, or a statistically significant deviation of the time evolution of observations from a predetermined baseline expectation. The various components that contribute to anthropogenic climate change are however markedly different in their total, present day impact, and time scales from emissions reductions to an expected climate system response. Here, we investigate when a significant change in global mean surface temperature could be expected, relative to an emission pathway consistent with current global policies, for a broad range of long and short-lived climate forcers. By combining reduced complexity and Earth System modelling, we investigate a comprehensive set of idealized emission mitigation choices for the near term, while still taking into account natural variability. As expected, mitigation of anthropogenic emissions of CO2 stands out as the most efficient, both in the short and longer term, although very strong mitigation is required to have a clear effect. Further, we find that strong mitigation policy targeting black carbon (BC) emissions would have a rapid, discernible effect, but a low net effect in the longer term. Mitigation of CH4 stands out as an option that combines rapid effects on surface temperature with long term gains.
Understanding the coupled land-sea system dynamics in coastal regions through a participatory approach: A Baltic case study
Authors: Seifollahi-Aghmiuni Samaneh , Kalantari Zahra , Destouni Georgia
Published: March 2020

Eutrophication and water quality issues in the Baltic Sea and its coastal zones have strong human dimensions, including also land and water uses and their management in hinterland areas. Solutions require participatory approaches to inspire integrated long-term ‘land-sea’ systems management, and contribute to the development of harmonized guidelines at different spatial scales. Considering the source to sea case of Swedish Norrström drainage basin, its surrounding coastal areas, and the associated marine basin of the Baltic Sea, this study has used a participatory approach to enhance understanding of the land-sea system links and dynamics, and facilitate exploration of cross-system/sector cooperation opportunities for addressing water-related high-impact issues, including water pollution and eutrophication. Employing a problem-oriented system thinking approach, we investigate the following questions based on various sector perspectives in the study region: (i) What are the key underlying land-sea system elements and their interlinkages? (ii) What are the most relevant and important dynamics for evaluation of land-sea system behavior? and (iii) What are the main challenges and opportunities for sustainable coastal management and development? Different groups of relevant stakeholders are asked to co-create causal loop diagrams for characterizing the land-sea system dynamics based on their perceptions of and answers to the questions (i)-(iii). From the co-created causal loop diagrams, sector-specific and general issues, challenges, opportunities, and barriers to sustainable coastal development in the study region are identified. In further analysis, various scenarios of the land-sea system dynamics and the importance of feedback mechanisms are investigated. The scenario results and associated system behavior are also validated by stakeholders. Selected scenarios are further quantified by systems dynamics modeling, exploring the impacts of associated coastal development and policy options on the regional water-related issues and potential sustainable solutions. The scenario analysis outcomes highlight the necessity and usefulness of combining scientific knowledge with local expertise for synergistic and strategic planning of sustainable coastal region development.
Comparative Study of Alternative Binders for Concrete Sealing Structures in Rock Salt
Authors: Sturm Patrick , Gluth Gregor , Moye Janis , Garel Solen , Kühne Hans-Carsten
Published: March 2020
Spatial analysis of total content of microelements in the agricultural soils of southern Serbia - GIS study
Authors: Cakić Jovan , Aleksić Ivan , Popović-Djordjević Jelena , Bogosavljević Jelena , Djordjević Aleksandar
Published: March 2020

The occurrence and availability of microelements in agricultural soils is of great importance for the environment, the quality of food and water, as well as for human health. United States Environmental Protection Agency (USEPA) has been specified elements such as As, Cd, Cr, Cu, Hg, Ni, Pb and Zn as key contaminants. The Geographic Information System (GIS), together with the technologies of the Global Navigation Satellite System (GNSS), made possible for the agricultural fields, parcels, not to be seen in their entirety anymore, but now, greater attention can be paid to optimizing the accuracy and reliability of the location for collecting soil samples, which provides reliable data for obtaining soil and special purpose maps. The data about the content of microelements in agricultural soils in the area of Southern Serbia are scarce.

The aim of this research was to determine the total content of eleven microelements (As, B, Cd, Cr, Cu, Hg, Mn, Mo, Ni, Pb and Zn) in the agricultural soils of southern Serbia and to create a database using GIS technology with spatial analysis. A total of 150 soil samples at a depth of             0-30 cm were examined. Spatial positioning of soil sampling points was done with a handheld, professional PDA/GNSS Trimble TDC 100 4G (Android 6) device. The database was created in ArcMap 10.1. Concentrations of microelements in the soil were determined by inductively coupled plasma with optical emission spectrometry (ICP-OES).

The obtained results of analyses showed that in the agricultural soils of southern Serbia (Jablanica and Pčinja District), the content of B and Pb was slightly increased at a depth of 0-30 cm, compared to the maximum allowable concentrations set by the national regulations. Among the studied elements, the lowest total content was measured for Mo and Pb (< 1mg/kg) whereas Mn had the highest total content (> 2000 mg/kg). This can be seen clearly on the special purpose maps provided using GIS technology.

Keywords: soils, agriculture, microelements, GIS, southern Serbia
Robust determination of S-wave velocity profiles by using mini-arrays
Authors: D'Auria Luca , Alfaro Rodríguez Marina , Bermejo López Daniel , Crowther Jemma , Kennett Lucy , Cabrera-Pérez Iván , Martínez van Dorth David , Soubestre Jean
Published: March 2020

Microtremor measurements represent a useful tool to study the seismic amplification in urban areas. One of the methods that permits characterizing seismic properties of soils is the H/V spectral ratio. This technique is especially useful when dealing with shallow low velocity layers, allowing an effective determination of its velocity and thickness. The H/V technique is very convenient to realize microzonation surveys because of its simplicity and low cost. However, it is recommended to combine it with other geophysical methods and geological information to better constrain the resulting models. In recent years the use of ambient noise cross-correlation has been widely used to retrieve Rayleigh wave dispersion curves between pairs of stations. These curves carry an important information about the subsoil velocity structure and have been already exploited for seismic microzonation purposes.

The aforementioned methods, H/V spectra and Rayleigh wave dispersion curves, in principle allow obtaining 1D body wave and density profiles. However, one of the most important problems when inverting H/V and dispersion curves, is the poor constraint on density and P wave velocities. This difficulty can be partially solved by imposing some constraints over the inverse problem (e.g. fixing the Vp/Vs ratio) or by devising inverse methods allowing the different parameters to be determined in different steps.

We propose a novel approach which consists of a joint inversion of H/V spectra and Rayleigh wave dispersion curves, realized simultaneously for all the elements of the mini-array. This allows increasing the ratio between the number of available data and the number of parameters to invert, improving the stability of the inverse problem and reducing the uncertainties on the estimated parameters. For the evaluation of the retrieved model, we used the trans-dimensional Monte Carlo exploration which has shown to be very efficient in evaluating the quality of the resulting model, through an intensive exploration of the “a posteriori” probability density function over the model parameter space.

We show the improvement in the obtained results on synthetic tests as well as on actual data. In particular we apply this method, named method MARISMA (Mini ARrays for seISmic MicrozonAtion) on a dataset recorded in the town of San Cristóbal de La Laguna (Tenerife, Canary Islands, Spain) during the summer of 2019.
Evolution of a low-relief landscape in the Eastern Alps constrained by low-temperature thermochronology and cosmogenic nuclides
Authors: Wölfler Andreas , Reimers Sebastian , Hampel Andrea , Glotzbach Christoph , Dunkl István
Published: March 2020

The relief history of mountain belts is strongly influenced by the interplay of tectonics and surface processes, which both shape Earth´s landscapes. In this context, the quantification of the rates of long-term and short-term processes is key for understanding landscape evolution and requires the application of methods that integrate over different timescales. In this study, we apply low-temperature thermochronology and cosmogenic nuclides to quantify the geological and geomorphic evolution of an elevated low-relief landscape in the Eastern Alps, the so-called Nock Mountains, which are situated to the east of the Tauern Window. The low-temperature thermochronological data yield zircon fission track and zircon (U-Th)/He cooling ages of 93.4±12.9 and 77.8±7.8 Ma, respectively, which we interpret to reflect late Cretaceous cooling after Eo-Alpine metamorphism. Apatite fission track and (U-Th)/He ages are significant younger and range from 36.8 to 31.3 Ma. Time-temperature history modelling of the cooling ages suggests enhanced cooling in the Eocene followed by thermal stagnation. Thus, the rocks of the study area have been in near surface position (2-3 km) since the Late Eocene. Enhanced cooling in the Eocene is probably related to an increasing relief due to shortening, folding and thrusting in the Eastern Alps triggered by the onset of collision between the European margin and the Adriatic microplate. Under the assumption that rock exhumation occurred solely by erosion, the long-term average erosion rate derived from the thermochronological data is ~50-90 mm/kyr. Catchment-wide erosion rates derived from cosmogenic 10Be in river sediments  range from 83±7 to 205±18 mm/kyr and hence are lower than in other parts of the Alps. As the 10Be-derived erosion rates and the long-term rates derived from thermochronology agree despite the different timescales over which the two methods integrate, our new data suggest that erosion rates did not change significantly over the last ~40 Ma. This is remarkable because within this time span numerous tectonic processes and glacial-interglacial cycles affected the study area. To investigate the deglaciation history after the Last Glacial Maximum in the Nock Mountains, we sampled glacially polished quartz veins for 10Be exposure dating. The first four exposure ages obtained so far cluster between 14.5±1.4 and 16.8±1.6 ka. We interpret these ages as the record the retreat of the ice cover in the study area shortly after the Oldest Dryas stadial.
The tropical atmospheric conveyor belt: a Lagrangian perspective of the large-scale tropical circulation
Authors: Raiter Dana , Galanti Eli , Kaspi Yohai
Published: March 2020

The Hadley circulation (HC) is a key element of the climate system. It is traditionally defined as the zonally averaged meridional circulation in the tropics, therefore treated as a zonally symmetric phenomenon. However, differences in temperature between land and sea cause zonal asymmetries on Earth, dramatically affecting the circulation. The longitudinal dependence of the HC evokes questions about where and when the actual large scale tropical circulation occurs. In this study, we look into the connection between the longitudinally dependent HC and the actual large scale movement of air in the tropics using a coupled Eulerian and Lagrangian approach. Decomposing the velocity field, we identify the components affecting the actual circulation. In addition, we calculate trajectories of air parcels to analyze the actual movement. We propose an alternative definition for the circulation, that describes the actual path of air parcels in the tropics, as a tropical conveyor belt. The Indo-Pacific warm pool is the driver of the circulation, where air converges and ascends, then moves westward and poleward before entering the jet stream, moving eastward with it, eventually beginning its descent near the Americas. Furthermore, using an idealized moist GCM, we explore how tropical asymmetries affect the circulation and discuss the possible mechanisms controlling the tropical conveyor belt.
Uncertainty quantification of climate sensitivity: State-dependence, extreme values and the probability of tipping
Authors: von der Heydt Anna
Published: March 2020

The Equilibrium Climate Sensitivity (ECS) remains not very well constrained, either by climate models, observational, historical or palaeoclimate data. In particular, large values of warming as a consequence of atmospheric greenhouse gas increase cannot be excluded. Interestingly, some of the most recent state-of-the-art climate models (CMIP6) suggest much more warming than previous generations of climate models. Next to the classical (measurement) uncertainty, the spread in ECS values is due to dynamical aspects: 

The climate system has strong internal variability on many timescales such that the 'equilibrium' will only be relative to fixing slow processes. This implies the assumption that time scale separation exists and ECS values from palaeoclimate time series can be compared to short model simulations. Palaeoclimate records often determine the Earth System Sensitivity, which includes the integrated effect of slow processes and boundary conditions (e.g. geography, vegetation and land ice).

The background state dependence of fast feedback processes: Information from the late Pleistocene ice age cycles indicates that ECS varies considerably between regime because of fast feedback processes changing their relative strength over one cycle.

Tipping elements in the climate system: Extreme values of palaeo-derived ECS suggest that the climate response is in a region where the assumption of linear response to perturbations breaks down. 

Here we show for climate system models with more than one regime and occasional switches between these regimes, we can empirically determine probability of change in regime and confirm that extremes of climate sensitivity are associated with very high probabilities of tipping.
Characteristics of Hydrogeochemistry and Groundwater Quality in a Riverbank Filtration Site, Northeastern China
Authors: Teng Yanguo , Zhai Yuanzheng , Chen Haiyang , Chen Ruihui
Published: March 2020

Studies on hydrogeochemical characteristics and an assessment of the groundwater quality for drinking purposes were conducted in and around the riverside source field of Wuchang, Northeast China. Twenty-seven and twenty-three shallow groundwater samples were collected for measuring on-site parameters and major components in the years 2000 and 2014, respectively. In 2014, the average concentrations of major ions of shallow groundwater were found to be in the following order: Ca2+> Na+> Mg2+> K+ for cations and HCO3-> SO42-> Cl-> NO3- for anions. The spatial distribution patterns of K+ and NO3- had no obvious regularity, whereas Cl- and Na+ showed similar spatial distribution patterns. Ca-HCO3 and mixed type water were the dominant hydrochemical types. The analysis of the SI values for minerals and the Gibbs plot illustrated that the concentrations of major components were mainly controlled by rock weathering, such as the dissolution of calcite, dolomite, halite, gypsum and aragonite, followed by ion exchange. Indicators, such as Total hardness (TH), Total Dissolved Solids (TDS), Cl-, SO42- and NO3-, were selected to assess the groundwater quality using a comprehensive evaluation method of dividing the groundwater quality into five classes: excellent, good, fair, poor and very poor water. The results showed that 7.4% and 34.8% of the total groundwater sample in 2000 and 2014, respectively, were unsuitable for drinking use, indicating that the shallow groundwater quality has gradually worsened in the past few decades. The concentration of NO3- was a major factor that influenced the observed groundwater quality changes.

Acknowledgments

This study was supported by the NSFC (No.41877355), Beijing Advanced Innovation Program for Land Surface Science, and the 111 Project of China (B18006).
Near-surface mean and gust wind speed in ERA5 across Sweden: towards an improved gust parametrization
Authors: Minola Lorenzo , Zhang Fuqing , Azorin-Molina Cesar , Safaei Pirooz Amir Ali , Flay Richard , Hersbach Hans , Chen Deliang
Published: March 2020

Driven by the twenty-century surface air temperature rise, extreme wind events could change in their frequency and magnitude of occurrence, with drastic impacts on human and ecosystems. As a matter of fact, windstorms and extreme wind conditions contribute to more than half of the economic losses associated with natural disasters in Europe. Across Scandinavia, the occurrence of wind gust events can affect aviation security, as well as damage buildings and forests, representing severe hazards to people, properties and transport. Comprehensive extreme wind datasets and analysis can help improving our understanding of these changes and help the society to cope with these changes. Unfortunately, due to the difficulty in measuring wind gust and the lack of homogeneous and continuous datasets across Sweden, it is challenging to assess and attribute their changes. Global reanalysis products represent a potential tool for assessing changes and impact of extreme winds, only if their ability in representing observed near-surface wind statistics can be demonstrated.

In this study the new ERA5 reanalysis product has been compared with hourly near-surface wind speed and gust observations across Sweden for 2013-2017. We found that ERA5 shows better agreement with both mean wind speed and gust measurements compared to the previous ERA-Interim reanalysis dataset. Especially across coastal regions, ERA5 has a closer agreement with observed climate statistics. However, significant discrepancies are still found for inland and high-altitude regions. Therefore, the gust parametrization used in ERA5 is further analyzed to better understand if the adopted gust formulation matches the physical processes behind the gust occurrence. Finally, an improved formulation of the gust parametrization is developed across Sweden and further tested for Norway, which is characterized by more complex topography.
Historical ocean heat uptake in CMIP6 Earth System models: global and regional perspectives
Authors: Kuhlbrodt Till , Voldoire Aurore , Palmer Matthew , Killick Rachel , Jones Colin
Published: March 2020

Ocean heat content is arguably one of the most relevant metrics for tracking global climate change and in particular the current global heating. Because of its enormous heat capacity, the global ocean stores about 93 percent of the excess heat in the Earth System. Time series of global ocean heat content (OHC) closely track Earth’s energy imbalance as observed as the net radiative balance at the top of the atmosphere. For these reasons simulated OHC time series are a cornerstone for assessing the scientific performance of Earth System models (ESM) and global climate models. Here we present a detailed analysis of the OHC change in simulations of the historical climate (20th century up to 2014) performed with four of the current, state-of-the art generation of ESMs and climate models. These four models are UKESM1, HadGEM3-GC3.1-LL, CNRM-ESM2-1 and CNRM-CM6-1. All four share the same ocean component, NEMO3.6 in the shaconemo eORCA1 configuration, and they all take part in CMIP6, the current Phase 6 of the Coupled Model Intercomparison Project. Analysing a small number of models gives us the opportunity to analyse OHC change for the global ocean as well as for individual ocean basins. In addition to the ensemble means, we focus on some individual ensemble members for a more detailed process understanding. For the global ocean, the two CNRM models reproduce the observed OHC change since the 1960s closely, especially in the top 700 m of the ocean. The two UK models (UKESM1 and HadGEM3-GC3.1-LL) do not simulate the observed global ocean warming in the 1970s and 1980s, and they warm too fast after 1991. We analyse how this varied performance across the models relates to the simulated radiative forcing of the atmosphere. All four models show a smaller ocean heat uptake since 1971, and a larger transient climate response (TCR), than the CMIP5 ensemble mean. Close analysis of a few individual ensemble members indicates a dominant role of heat uptake and deep-water formation processes in the Southern Ocean for variability and change in global OHC. Evaluating OHC change in individual ocean basins reveals that the lack of warming in the UK models stems from the Pacific and Indian basins, while in the Atlantic the OHC change 1971-2014 is close to the observed value. Resolving the ocean warming in depth and time shows that regional ocean heat uptake in the North Atlantic plays a substantial role in compensating small warming rates elsewhere. An opposite picture emerges from the CNRM models. Here the simulated OHC change is close to observations in the Pacific and Indian basins, while tending to be too small in the Atlantic, indicating a markedly different role for the Atlantic meridional overturning circulation (AMOC) and cross-equatorial heat transport in these models.
A 14 - 0 ka record of trends and events of sea ice cover, primary production and freshwater discharge in the Beaufort Sea, Arctic Ocean
Authors: Wu Junjie , Stein Ruediger , Fahl Kirsten , Syring Nicole , Hefter Jens , Mollenhauer Gesine , Nam Seung-il
Published: March 2020

The Arctic is changing rapidly, and one of the main and most obvious features is the drastic sea-ice retreat over the past few decades. Over such time scales, observations are deficient and not long enough for deciphering the processes controlling this accelerated sea-ice retreat. Thus, high-resolution, longer-term proxy records are needed for reconstruction of natural climate variability. In this context, we applied a biomarker approach on the well-dated sediment core ARA04C/37 recovered in the southern Beaufort Sea directly off the Mackenzie River, an area that is characterized by strong seasonal variability in sea-ice cover, primary productivity and terrigenous (riverine) input. Based on our biomarker records, the Beaufort Sea region was nearly ice-free in summer during the late Deglacial to early Holocene (14 to 8 ka). During the mid-late Holocene (8 to 0 ka), a seasonal sea-ice cover developed, coinciding with a drop in both terrigenous sediment flux and primary production. Supported by multiple proxy records, two major flood events characterized by prominent maxima in sediment flux occurred near 13 and 11 ka. The former is coincident with the Younger Dryas Cooling Event probably triggered by a  freshwater outburst from the Lake Agassiz. The origin of the second (younger) one might represent a second Mackenzie flood event, coinciding with meltwater pulse IB/post-glacial flooding of the shelf and related increased coastal erosion. Here, our interpretation remains a little bit speculative, and further research is needed and also in progress.
Deglacial 14C reservoir ages of surface waters at the northern boundary of Peruvian coastal upwelling
Authors: Glock Nicolaas , Sarnthein Michael , Doering Kristin , Mollenhauer Gesine , Salvatteci Renato
Published: March 2020

To constrain the accurate age of a marine sediment record, the radiocarbon (14C) ages need to be corrected for short-term and small-scale changes in planktic 14C reservoir ages (Rplank). Nevertheless, accurate records of past changes in Rplank are scarce. Here we present a high-resolution record of deglacial 14C ages measured on Globigerina bulloides in sediment core M77/2-59-1 from the northern boundary (~4°S, 997 m) of the Peruvian upwelling zone. The fine structure of jumps and plateau boundaries in the 14C record were tuned to synchronous, thus global structures in the atmospheric 14C record of Lake Suigetsu (Bronk Ramsey et al., 2012) and used as tie points for an age model with semi-millennial resolution, moreover to reconstruct deglacial changes in Rplank from 17 to 11 cal. ka. In our record, Rplank drops from 1250 14C yr prior to 14 cal. ka to ~600 – 450 14C yr until the plateau named Top of Younger Dryas. The drop suggests a major decrease in coastal upwelling, possibly the result of a southward (poleward) expansion of the Intertropical Convergence Zone and related shift in the southeastern trade wind belt during the Bølling-Allerød. Subsequent to 14 cal. ka our Rplank values are roughly similar to values obtained for thermocline waters near the equator from the age difference between 14C ages of wood chunks and 14C of G. ruber (Zhao & Keigwin, 2018). Prior to 14 cal. ka our Rplank are ~800 14C yr higher, which corroborates the presumed latitudinal shift of coastal upwelling. Our 14C ages measured on G. bulloides differ in part from paired 14C ages of Neogloboquadrina dutertrei, indicating their habitat in different water masses prior to 14 cal. ka, in support of the upwelling affinity of G. bulloides. In addition, we used our Rplank values to accurately derive past ventilation ages of intermediate waters near 1000 m depth based on the difference of paired benthic and planktic 14C ages, which is important to constrain centennial to millennial scale changes in circulation influencing the extent of the Peruvian oxygen minimum zone.

References:

Bronk Ramsey, C., et al., Science, 338, 370–374, 2012.

Zhao & Keigwin, Nature communications, 9, 3077, 2018.
Global Near-Surface Wind Speed Trends in Observation and CMIP6 Historical Simulation for 1850–2014
Authors: Deng Kaiqiang , Azorin-Molina Cesar , Minola Lorenzo , Chen Deliang
Published: March 2020

The changes in near-surface (10-m height) wind speed have direct impacts on human society, such as utilization of wind energy, air pollution dispersion and dust storm frequency, which requires comprehensive assessment and improved understanding. Based on ground-based observations and multiple atmospheric reanalysis datasets, previous research revealed significant negative and positive trends in wind speed over land and oceans, respectively. In this study, we used Coupled Model Intercomparison Project Phase 6 (CMIP6) historical simulations to investigate the association between global mean wind speed changes and human-induced forcing. It is found that both unforced pre-industrial control run and historical natural forcing experiments failed in reproducing the observed trends in land and ocean wind speeds. However, the CMIP6 historical greenhouse gas forcing successfully simulated the increasing trend in ocean wind speed, while the CMIP6 historical aerosol forcing and experiments with land use changes seemed to have caused a decreasing trend in wind speeds over both land and ocean, suggesting that anthropogenic forcings are crucial drivers for the recent changes in global wind speed. Further attribution studies are needed to better understand wind speed variability under a warming climate.
Phenological data set of five taxonomic groups and agrarian activities in temperate climate: trends and influencing factors, Latvian case study
Authors: Kalvane Gunta , Kalvans Andis , Briede Agrita
Published: March 2020

A phenological data set collected by volunteers` observers from the Latvia Phenological Observation Network covering period 1970 to 2018 has digitized from original paper based publications in Nature Calendars and analysed. The data set includes more than 40 thousand observations, 148 phenological phases across five different taxonomic groups: insects, amphibian, birds, fungi and plants as well as agrarian activities like sowing, harvesting date and some meteorological parameters like first and late frost, snow, ice regime.

The phenological changes or trends was analysed in two ways: 1. by combining data rows (station-phase-species) for one phase, such as leafing (BBCH11) for all trees and bushes; 2. by performing regression analyses for each phase and for each observation point separately.

More than 80% of spring data series shows negative tendency as reported in most scientific publications on European phenology. In our data set, overall, autumn phenologies are occurring later over time or the trends are neutral.

Regression analyses of phenology date versus year shows the disparities among species and among locations within a species: spring migrants’ return earlier, while staying longer in the fall with exceptions, for example the white stork in autumn leaves earlier than in the beginning of the period.

The commencement of the agricultural activities in spring such as sowing date have not changed significantly. However, such activities as livestock grazing and sowing of winter cereals takes place latter in the autumn.  These both appear to have affected by both technological changes and changes in meteorological parameters, for example, the trend of first autumn frost and first snow is positive – they have observed latter.

We have analysed trends and cross correlation with phenology in temperature regime, heat waves, precipitation, drought indexes, evapotranspiration, and soil temperature for the last 40 years.

Research is supported by the ERDF Project No. 1.1.1.2/VIAA/2/18/265 at the University of Latvia.
Methane emissions from a palsa-mire underlayed by sporadic permafrost under rapid degradation
Authors: Łakomiec Patryk , Holst Jutta , Rinne Janne
Published: March 2020

Methane is one of the most important greenhouse gases. The largest natural source of this gas are wetlands. Quantification emission from this source, especially from subarctic regions, which are exposed to fast climate changes, is important for our understanding of biogeochemical climate feedbacks. Abisko Stordalen is one of few mires in this climatic zone in which the methane emission is being measured continuously. Here we analyze eddy covariance data from the ICOS Sweden site with respect to environmental parameters possibly controlling the methane emissions.

Due to the large scale topography at Abisko, wind is channeled along the valley, resulting in to two main wind directions. This divides the measurements into two different surface type groups. On easterly winds, the flux footprint is dominated by permafrost features, while for westerly winds it is dominated by non-permafrost fen. Measured methane fluxes from these to wetland types, exposed for the same environmental conditions, differ considerably being higher from non-permafrost area.  We will further analyze the differences in the annual methane emission from the two systems, and their dependencies from environmental parameters.
Dynamical clustering: A new approach to make distributed (hydrological) modeling more efficient by dynamically detecting and removing redundant computations
Authors: Ehret Uwe , van Pruijssen Rik , Bortoli Marina , Loritz Ralf , Azmi Elnaz , Zehe Erwin
Published: March 2020

The structural properties of hydrological systems such as topography, soils or land use often show a considerable degree of spatial variability, and so do the drivers of systems dynamics, such as rainfall. Detailed statements about system states and responses therefore generally require spatially distributed and temporally highly resolved hydrological models. This comes at the price of substantial computational costs. However, even if hydrological sub systems potentially behave very differently, in practice we often find groups of these sub systems that behave similarly, but the number, size and characteristics of these groups varies in time. If we have knowledge of such clustered behavior of sub systems while running a model, we can increase computational efficiency by computing in full detail only a few representatives within each cluster, and assign results to the remaining cluster members. Thus, we avoid costly redundant computations. Unlike other methods designed to dynamically remove computational redundancies, such as adaptive gridding, dynamical clustering does not require spatial proximity of the model elements.

In our contribution, we present and discuss at the example of a distributed, conceptual hydrological model of the Attert basin in Luxembourg, i) a dimensionless approach to express dynamical similarity, ii) the temporal evolution of dynamical similarity in a 5-year period, iii) an approach to dynamically cluster and re-cluster model elements during run time based on an analysis of clustering stability, and iv) the effect of dynamical clustering with respect to computational gains and the associated losses of simulation quality.

For the Attert model, we found that there indeed exists high redundancy among model elements, that the degree of redundancy varies with time, and that the spatial patterns of similarity are mainly controlled by geology and precipitation. Compared to a standard, full-resolution model run used as a virtual reality ‘truth’, computation time could be reduced to one fourth, when modelling quality, expressed as Nash-Sutcliffe efficiency of discharge, was allowed decreasing from 1 to 0.84. Re-clustering occurred at irregular intervals mainly associated with the onset of precipitation, but on average the patterns of similarity were quite stable, such that during the entire six-year simulation period, only 165 re-clusterings were carried out, i.e. on average once every eleven days.
Laboratory device to investigate the heterogeneity’s influence on the effective hydraulic conductivity
Authors: Brunetti Guglielmo Federico Antonio , De Bartolo Samuele , Fallico Carmine , Severino Gerardo , Tripepi Giuseppe
Published: March 2020

Groundwater flow and contaminant transport are strongly influenced by the aquifer’s heterogeneity (Chao et al., 2000; Fernàndez-Garcia et al., 2004). Generally, the flow (and transport) variables, such as the effective conductivity Keff, can be modelled as random space functions (RSFs) and determined by means of a self-consistent approximation (Severino, 2018). In particular, we aim at estimating the effective conductivity Keff of a highly heterogeneous aquifer made of 12 different porous materials, whose K-values were experimentally measured.

A heterogeneous phreatic aquifer was built in the GMI Laboratory of the Department of Civil Engineering of the University of Calabria, inside a metal box (2 m x 2 m x 1 m). The thickness (0.35 m) of the aquifer was built by overlapping 7 different layers of 0.05 m, each consisting of 361 cells (19 x 19), with dimensions equal to 0.1 m x 0.1 m x 0.05 m. For each layer, each cell was filled with one of the 12 porous materials previously characterized in the lab, making the choice randomly. A central (pumping) well and 37 piezometers were located at different distances from the first according to a radial configuration.

A pumping test was carried out by a constant flow rate of 70 L/hour. The hydraulic head data, evaluated by using the Neuman method and verified in compliance with the boundary conditions, allowed an effective hydraulic conductivity value Keff to be obtained.

Afterwards, this value was compared with K values measured in laboratory by permeameter for each of the 12 porous media used to build the heterogeneous aquifer considered here and with the main statistical parameters related to them. We found the Keff value in a very good agreement with the expression obtained by the self-consistent approximation (Severino, 2018).

 

References

Chao C.-H., Rajaram H. and Illangasekare T. H. (2000). Intermediatescale experiments and numerical simulations of transport under radial flow in a two-dimensional heterogeneous porous medium, Water Resour. Res., 36(10), 2869– 2884.

Fernàndez-Garcia D., Illangasekare T. H. and Rajaram H. (2004). Conservative and sorptive forced-gradient and uniform flow tracer tests in a three-dimensional laboratory test aquifer. Water Resour. Res., Vol. 40, W10103, doi:10.1029/2004WR003112.

Severino G., 2018. Effective conductivity in steady well-type flows through porous formations. Stochastic Environmental Research and Risk Assessment, Vol. 5, https://doi.org/10.1007/s00477-018-1639-5.
An early warning system for rainfall-triggered shallow slides and debris flows. Application in Catalonia, Spain and Canton of Bern, Switzerland
Authors: Palau Rosa M , Berenguer Marc , Hürlimann Marcel , Sempere-Torres Daniel , Berger Catherine , Peter Adrian
Published: March 2020

Risk mitigation for rainfall-triggered shallow slides and debris flows at regional scale is challenging. Early warning systems are a helpful tool to depict the location and time of future landslide events so that emergency managers can act in advance. Recently, some of the regions that are recurrently affected by rainfall triggered landslides have developed operational landslide early warning systems (LEWS). However, there are still many territories where this phenomenon also represents an important hazard and lack this kind of risk mitigation strategy.

The main objective of this work is to study the feasibility to apply a regional scale LEWS, which was originally designed to work over Catalonia (Spain), to run in other regions. To do so we have set up the LEWS to Canton of Bern (Switzerland).

The LEWS combines susceptibility maps to determine landslide prone areas and in real time high-resolution radar rainfall observations and forecasts. The output is a qualitative warning level map with a resolution of 30 m.

Susceptibility maps have been derived using a simple fuzzy logic methodology that combines the terrain slope angle, and land use and land cover (LULC) information. The required input parameters have been obtained from regional, pan-European and global datasets.

Rainfall inputs have been retrieved from both regional weather radar networks, and the OPERA pan-European radar composite. A set of global rainfall intensity-duration data has been used to asses if a rainfall event has the potential of triggering a landslide event.

The LEWS has been run in the region of Catalonia and Canton of Bern for specific rainfall events that triggered important landslides. Finally, the LEWS performance in Catalonia has been assessed.

Results in Catalonia show that the LEWS performance strongly depends on the quality of both the susceptibility maps and rainfall data. However, in both regions the LEWS is generally able to issue warnings for most of the analysed landslide events.
Visualization of 4-component borehole strainmeter data in China
Authors: Li Fuzhen , Ren Tianxiang , Zhang Huai , Shi Yaolin
Published: March 2020

With the accumulation of 4-component borehole strainmeter data and the improvement of observation reliability, it is a primary of current research to improve the efficiency of processing, analyzing and visualizing of these data. The visualization of borehole strain observation data is a key means to convey the information behind the data, display the data research results and extract the shallow surface stress state revealed by borehole strain.

Borehole strainmeter data are of great significance for earthquake prediction research due to its’ high resolution in short-medium term time scale of earthquake prediction. With the progress of observation technology, many four-component borehole strain gauges in China had experienced the data stabilization period, the early years of establishing the instrument, and the borehole strain station began to obtain a batch of high-quality observation data.

By using the normal stress petal diagram to show the change of the ground stress, it can not only qualitatively analyze the change of the relative ground stress of the station, but also quantitatively read  the observed normal stress in any direction at a certain time. In this paper, the method of normal stress petals diagram is combined with map visualization technology to process and analyze the strain observation data of four-component borehole across the country. The main works are as follows: first of all, The construction of the stress petal visualization platform can display the dynamic stress effectively in all directions of 30 stations across the country; secondly, Variable sliding window length and sliding spacing added according to specific needs can not only directly display the change of the stress petal over the years, but also show the stress petal map of the solid tide strain all over the country; thirdly, The platform can display the co-seismic stress petal variation image observed at the national borehole strain stations and visually show the stress changes observed by the local borehole strain gauge during the seismic wave propagation. Finally, The borehole strainmeter data can monitor the relative geostress state of the fault near the borehole. Then the magnitude and direction of the maximum principal stress at the borehole strain station reflected by the stress petal can further calculate the corresponding changes of dynamic coulomb stress and static coulomb stress which can help to analyze seismic dynamic triggering problems.
An alternative method to evaluate fracture network efficiency to fluid flow
Authors: Proietti Giampaolo , Romano Valentina , Conti Alessia , Tartarello Maria Chiara , Bigi Sabina
Published: March 2020

Fracture networks exist at a wide range of scale in the earth crust and strongly influence the hydraulic behaviour of rocks, providing either pathways or barriers for fluid flow. Many oil, gas, geothermal and water supply reservoirs form in fractured rocks. The main challenge is the development of numerical models that describe adequately the fracture networks and the constitutive equations governing the physical processes in fractured reservoir. The hydraulic properties of fracture networks, derived from Discrete Fracture Network (DFN), models are commonly used to populate continuum equivalent models at reservoir scale, to reduce the computational cost and the numerical complexity. However, the efficiency of fracture networks to fluid flow is strongly tied to their connectivity and spatial distribution, that continuum models are not able to capture explicitly.In this work we used field data and synthetic models to introduce a new parameter to evaluate the efficiency of fracture networks to fluid flow, reflecting a range of variability in fracture network characteristics (e.g. P32, number of fractures, stress field). This alternative method allows to model fractured systems at reservoir scale, in a variety of geological settings, using exclusively a DFN approach.
The impacts of Amazon forest degradation and fragmentation on energy, water, and carbon cycles
Authors: Longo Marcos , Saatchi Sassan , Keller Michael , Bowman Kevin , Ferraz António , Cawse-Nicholson Kerry , Fisher Joshua , Pinagé Ekena , Moorcroft Paul , Ometto Jean , Morton Douglas
Published: March 2020

Tropical forest degradation through selective logging, fragmentation, and understory fires substantially changes forest structure and composition.  In the Amazon, degradation is as widespread as deforestation; however, studies addressing the effects of forest degradation on tropical ecosystem functions are scarce. Here, we integrate small-footprint airborne lidar over the Brazilian Amazon (> 250,000 ha), collected between 2016–2018, with recent ECOsystem Spaceborne Thermal Radiometer Experiment on Space Station (ECOSTRESS) land surface temperature and evapotranspiration products (70-m resolution, data acquired in 2018–2019) to investigate the role of forest structure, forest fragmentation, and disturbance history on dry-season land surface temperature and evapotranspiration.  During the dry season, degraded forests, especially those affected by multiple degradation events, are significantly warmer (up to 9.3°C) and show reduced evapotranspiration (10% less than intact forests). Likewise, forest near the edges (< 350m) experience the greatest warming (up to 6.5°C) and the greatest reduction (9%) in evapotranspiration. We also used the airborne lidar dataset to initialize the Ecosystem Demography Model (ED-2.2) to investigate the impact of degradation on the gross primary production (GPP), evapotranspiration (ET), and sensible heat flux (H) under a broader range of climate conditions, including severe droughts. Consistent with ECOSTRESS, the simulations during the dry season in typical years showed that severely degraded forests experienced water-stress with declines in ET (34% reduction), GPP (35% reduction), and increases of H (43% increases) and daily mean ground temperatures (up to 6.5°C) relative to intact forests.  In the model, the simulated changes are mostly driven by increased below-ground water stress, which can be attributed to the shallower rooting profile of degraded forests. However, relative to intact forest, the impact of degradation on energy, water, and carbon cycles markedly diminishes under extreme droughts such as 2015–2016, when all forests experience severe stress. Our results indicate the potentially important role of tropical forest degradation changing the carbon, water, and energy cycles in the Amazon, and consequently a much broader influence of land use activities on functioning of tropical ecosystems.