bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of single-frequency observations in GNSS Tropospheric Tomography
Authors: Weber Robert , Adavi Zohreh , Glaner Marcus Franz
Published: March 2020

Water vapor is one of the most variable components in the Earth’s atmosphere, which has a significant role in the formation of clouds, rain and snow, air pollution and acid rain. Therefore, increasing the accuracy of estimated water vapor can lead to more accurate predictions of severe weather, upcoming storms, and reducing natural hazards. In recent years, GNSS has turned out to be a valuable tool for remotely sensing the atmosphere. GNSS tomography is one of the most valuable tools to reconstruct the Spatio-temporal structure of the troposphere. However, locating dual-frequency receivers with a sufficient spatial resolution for GNSS tomography of a few tens of kilometers is not economically feasible. Therefore, in this research, the feasibility of using single-frequency receivers in GNSS tomography as a possible alternative approach has been investigated. The accuracy of the reconstructed model of water-vapor distribution using low-cost receivers is verified using radiosonde measurements in the area of the EPOSA (Echtzeit Positionierung Austria) GNSS network, which is mostly located in the east part of Austria for the period DoYs 233-246 in 2019.
Using standards to model delayed mode sensor processes
Authors: Kokkinaki Alexandra , Buck Justin , Slater Emma , Collins Julie , Cramer Raymond , Darroch Louise
Published: March 2020

Ocean data are expensive to collect. Data reuse saves time and accelerates the pace of scientific discovery. For data to be re-usable the FAIR principles reassert the need for rich metadata and documentation that meet relevant community standards and provide information about provenance.

Approaches on sensor observations, are often inadequate at meeting FAIR; prescriptive with a limited set of attributes, while providing little or no provision for really important metadata about sensor observations later in the data lifecycle.

As part of the EU ENVRIplus project, our work aimed at capturing the delayed mode, data curation process taking place at the National Oceanography Centre’s British Oceanography Data Centre (BODC). Our solution uses Unique URIs, OGC SWE standards and controlled vocabularies, commencing from the submitted originators input and ending by the archived and published dataset. 

The BODC delayed mode process is an example of a physical system that is composed of several components like sensors and other computations processes such as an algorithm to compute salinity or absolute winds. All components are described in sensorML identified by unique URIs and associated with the relevant datastreams, which in turn are exposed on the web via ERDDAP using unique URIs.

In this paper we intend to share our experience in using OGC standards and ERDDAP to model the above mentioned process and publish the associated datasets in a unified way. The benefits attained, allow greater automation of data transferring, easy access to large volumes of data from a chosen sensor, more precise capturing of data provenance, standardization, and pave the way towards greater FAIRness of the sensor data and metadata, focusing on the delayed mode processing.
Basal melting of Dronning Maud Land ice shelves twice as high as previously estimated
Authors: Berger Sophie , Helm Veit , Hattermann Tore , Neckel Niklas , Glaude Quentin , Zeising Ole , Sun Sainan , Pattyn Frank , Eisen Olaf
Published: March 2020

Basal melting of floating ice shelves is the main process by which  the Antarctic ice sheet is currently losing ice and is responsible for the accelerating Antarctic contribution to sea-level rise. Moreover, basal melting can strongly vary both spatially and temporally. Detailed observations on high  spatio-temporal scales remain however challenging, not to mention accounting for them in ice-sheet models. 

In this study, we combine CryoSat-2 and TanDEM-X elevation changes to capture in unprecedented detail the spatial (and temporal) variability of ice-shelf basal melting in the entire region of Dronning Maud Land, East Antarctica. The high spatial resolution of TanDEM-X elevations provide us with great  details on the spatial variability of the basal mass balance, whereas CryoSat-2 elevations inform us about temporal changes.

We find sub-shelf melt rates that average 1 m/a for the whole of Dronning Maud Land. Those relatively low melt rates conceal however a significant spatial variability on a wide range of scales (from sub-kilometers to ice-shelf wide scales). Spatially integrated, this basal melting represent  an annual basal loss ~140 Gt/a. This revised estimate corresponds to a two-fold increase compared to previous estimates, which could question the relative stability of ice shelves in this region. 

This study highlights different regimes in sub-shelf melting in Dronning Maud Land and  sheds new light on ice-ocean interactions in a region of Antarctica that has long been considered as very stable and which is therfore regularly overlooked.
Seasonal analysis of photosynthetic limitations in mature Scots pine trees reveals that models based on intracellular CO2 concentration grossly underestimate photosynthetic capacity
Authors: Stangl Zsofia R. , Tarvainen Lasse , Räntfors Mats , Wallin Göran , Marshall John D.
Published: March 2020

Global models of photosynthesis commonly use photosynthetic capacity parameters (Vcmax, Jmax) that are estimated based on Ci, the intercellular CO2 concentration. The underlying assumption of these models is that mesophyll conductance (gm) is infinite and therefore the CO2 concentration at the site of carboxylation (Cc) is equal to Ci, despite a growing body of literature acknowledging that these assumptions are incorrect. Because relatively few studies on gm have been conducted under natural conditions and with high enough resolution, it is currently unclear how significant the assumption of infinite Cc is for the accuracy of long-term predictions by large-scale photosynthesis models. In this study we investigated this question with data collected in a mature Scots pine stand, one of the dominant species of the boreal region. We conducted high-resolution gas-exchange and online 13C discrimination measurements over a whole growing season (May-October), and analysed the relative contribution of diffusional and biochemical limitations to photosynthesis. We hypothesised that diffusional limitation will be significant in this species, as conifers typically have low stomatal and mesophyll conductance (gs and gm respectively). Accordingly, we found that diffusional limitations were similar or stronger than biochemical limitation during May-July, and that all limitations reached minima around the end of June when Anet values were highest. However, during August-October biochemical limitation became increasingly dominant, as the diffusional limitations were relatively small and stable. Over the whole period, both gm and the relative mesophyll limitation were similar in magnitude to gs and the stomatal limitation, respectively, resulting in a 40-100 ppm reduction in CO2 concentration between Ci and Cc. This meant that Vcmax was under-estimated by 20-40% when calculated from Cicompared to Cc, highlighting the importance of accounting for the finite gm when determining photosynthetic capacity and modelling photosynthesis under natural conditions.
Simulation and analysis for flood early warning system in small catchments caused by rainfall-induced disaster
Authors: Yu Ke-Sin , Lai Jihn-Sung , Hsieh Yi-Huan
Published: March 2020

Under the impact of climate change, rainfall-induced flood disasters have become more frequent in some areas. The development of an hourly rainfall forecast with higher time and spatial accuracy under different rainfall patterns and the connection between meteorological forecast and hydrological flood simulation are urgent issues. In this study, eight flood cases in 2019 in Taipei city, a high-risk urban area with high economic and social resource density, caused by different rainfall patterns were chosen to be analyzed. To improve the accuracy of meteorological data, WRF base ensemble prediction system (WEPS), a quantitative precipitation forecast (QPF) produced by Central Weather Bureau (CWB) of Taiwan was selected as the main meteorological data source, and after processed by objective quantitative analysis methods, the data then be input into the drainage–inundation model. As a one-dimensional and two-dimensional flood simulation system, SOBEK was used to verify the depth and location of floods. Results indicated that the WEPS data would have better performance in drainage–inundation model among the cases in 2019. Combining meteorological forecast data and hydrological simulation can somehow improve the accuracy of flood early warning system in a small catchment.
The influence of bedrock topography on grain entrainment in bedrock-alluvial channels
Authors: Hodge Rebecca , Buechel Marcus , Kenmare Sophie
Published: March 2020

Sediment grains in bedrock-alluvial channels can be entrained from bedrock surfaces or from alluvial patches. Field tracer data has shown that grains entrained from different surfaces can have very different critical shear stresses, which will affect bedload transport rates, the stability of sediment cover and bedrock incision. We hypothesise that the topography of the bedrock surface affects the critical shear stress of a sediment grain in at least three ways: the pivot angle through which the grain must move to be mobilised; the extent to which the grain is sheltered by upstream bedrock protrusions; and the impact on the flow profile via the roughness length z0. Here we quantify how bedrock topography affects these three different components, and their overall impact on critical shear stress.

Our analysis is based around six samples of bedrock river topography, from rivers with different degrees of roughness and structural characteristics. Each surface was 3D printed at a reduced scale, and pivot angles were measured by dropping grains of different sizes at different locations, and tilting the surface until the grain moved. For the surface with bedrock ribs, experiments were repeated with the ribs parallel and perpendicular to the downslope direction. Further experiments were performed after incrementally covering 25% through to 100% of the surface with fixed sediment cover. Bedrock sheltering and z0 were estimated from analysis of surface topography.

Overall, we find that measured pivot angles decrease with increasing surface roughness, similar to previous relationships from alluvial channels. However, we find that the pivot angle for a grain at any particular location cannot be predicted from the local surface topography, because of the complex interaction between grain shape and the different scales of roughness present on the surface. Rib direction also has a significant influence on mean pivot angle. The impact of sediment cover depends on the relative roughness of the cover and the bedrock surface.

We calculate critical shear stress using Kirchner’s force balance model, parameterised using our measurements of pivot angle, sheltering and z0. We find that z0 has the largest impact on the predicted median values of critical shear stress. Including the measured pivot angles reduces the lowest values of critical shear stress, with implications for the onset of sediment transport. Overall, our data represent the first attempt to quantify fully how bedrock topography influences the critical shear stress of sediment grains in bedrock-alluvial channels.
Anisotropy of magnetic susceptibility as strain indicator in a fold-and-thrust belt sandbox model above décollements with frictional contrast
Authors: Schöfisch Thorben , Koyi Hemin , Almqvist Bjarne
Published: March 2020

Magnetic fabric is used as strain indicator to provide further insights into different tectonic settings. Applying anisotropy of magnetic susceptibility (AMS) analysis on analogue models has shown to be a useful approach to understand details of deformation. Here we use this technique on shortened sandbox models to illustrate the relationship between rotation of grains and the influence of décollement friction in fold-and-thrust belts. Layers of sand were scraped to a thickness of 2.5 cm on top of high-friction sandpaper on one side and on low-friction fibreglass on the other side of the sandbox model. After shortening the model by 26%, samples were taken at the surface and at depth for measuring AMS. During shortening, above the high-friction décollement, a stack of imbricates was formed, which shows distinct clustering of the main principal magnetic susceptibility axes (k1 ≥ k2 ≥ k3) around the dip of the forethrusts. In contrast, AMS data above the low-friction décollement show a more heterogeneous AMS pattern due to complex structure development with box folds and fault bending. In general, the magnetic fabric can be differentiated between the initial model fabric in the foreland and a tectonic overprint within the hinterland. The AMS analysis show that strain increases with the development of structures towards the hinterland and additionally with depth, but differs between the two frictional décollements. At the transition zone between the two different frictional environments, a deflection zone developed where the trace of thrusts change trend causing additional rotation of sand grains within this zone perpendicular to main shortening direction, as reflected by the orientation of the k1 and k3 axes. Overall, the orientation of the AMS axes and shape of anisotropy depend on the structure geometry and movement, which are determined by the friction of the individual décollement beneath. Consequently, AMS in models indicates and describes the development of structures and reflects strain above different basal friction.
Hurricane Eye Morphology
Authors: Ni Weicheng , Stoffelen Ad , Ren Kaijun
Published: March 2020

Among all kinds of natural disasters, hurricanes are regarded as one of the most destructive, which can cause tremendous losses to the global economic system and ecosystem every year. However, until now, there remain many issues unknown about hurricane dynamics, while hurricanes undergo amplification, shearing, eyewall replacements, diurnal influences, and so forth. Precise morphology parameters, extracted from high-resolution spaceborne Synthetic Aperture Radar (SAR) image, can play an essential role in further exploring and monitoring the hurricane dynamics. Moreover, these morphology parameters may help to build guidelines for the wind calibration of the more plentiful, but lower resolution scatterometer wind field data in hurricane events in order to better link scatterometer wind fields to hurricane categories. In this paper, we have developed a new method for extracting the hurricane eyes from C-band SAR data by constructing Gray Level-Gradient Co-occurrence Matrix (GLGCM) for each image. The hurricane eyewall (HE) area is determined with a 2-dimensional vector, which is automatically generated by maximizing the conditional entropy of HE area in GLGCM. Subsequently, we select the HE pixels based on minimizing the variance of normalized radar cross-section (NRCS) values of the pixel set chosen. The texture information of HE can be adequately preserved in this process. The experimental results prove the effectiveness of our method. Notably, the HE extracted with this automatic method is still in line with the visually observed eyewall even when the hurricane is weak or the eyewall is unclosed. Compared with the morphological analysis and wavelet analysis methods proposed in other papers, the approach developed here is able to accomplish in a simpler way with equally satisfying results. In conclusion, this study can provide a new choice for hurricane eye morphology extraction.
Heme b distributions through the Atlantic Ocean: in situ identification of iron limited phytoplankton
Authors: Louropoulou Evangelia , Gledhill Martha , Achterberg Eric P. , Browning Thomas J. , Honey David J. , Schmitz Ruth A. , Tagliabue Alessandro
Published: March 2020

Heme b is an iron-containing cofactor in hemoproteins that participates in the fundamental processes of photosynthesis and respiration in phytoplankton. Heme b concentrations typically decline in waters with low iron concentrations but due to lack of field data, the distribution of heme b in particulate material in the ocean is poorly constrained. Within the framework of the Helmholtz Research School for Ocean System Science and Technology (HOSST) and the GEOTRACES programme, the authors compiled datasets and conducted multidisciplinary research (e.g. chemical oceanography, microbiology, biogeochemical modelling) in order to test heme b as an indicator of in situ iron-limited phytoplankton. This study was initiated in the North Atlantic Ocean and expanded to the under-sampled South Atlantic Ocean for comparison of the results considering the different phytoplankton populations. Here, we report particulate heme b distributions across the Atlantic Ocean (59.9°N to 34.6°S). Heme b concentrations in surface waters ranged from 0.10 to 33.7 pmol L-1 (median=1.47 pmol L-1, n=974) and were highest in regions with a high biomass. The ratio of heme b to particulate organic carbon (POC) exhibited a mean value of 0.44 μmol heme b mol-1 POC. We identified the ratio of 0.10 µmol heme b mol-1 POC as the cut-off between heme b replete and heme b deficient phytoplankton. By this definition, the ratio heme b relative to POC was consistently below 0.10 μmol mol-1 in areas characterized by low Fe supply; these were the Subtropical South Atlantic gyre and the seasonally iron limited Irminger Basin. Thus, the ratio heme b relative to POC gave a reliable indication of iron limited phytoplankton communities in situ. Furthermore, the comparison of observed and modelled heme b suggested that heme b could account for between 0.17-9.1% of biogenic iron. This range was comparable to previous culturing observations for species with low heme b content and species growing in low Fe (≤0.50 nmol L-1) or nitrate culturing media. Our large scale observations of heme b relative to organic matter suggest the impact of changes in iron supply on phytoplankton iron status.
Spatial and temporal variations of air temperature inversions over different surface types on Ammassalik Island (East Greenland)
Authors: Hansche Iris , Abermann Jakob , Shahi Sonika , Schöner Wolfgang
Published: March 2020

Air temperature inversion, a situation in which atmospheric temperature increases with height, is a common feature in the Arctic planetary boundary layer. This stable layer has multiple consequences for the Arctic environment. While vertical gradients of flora and fauna are impacted by them, they also have a direct consequence on physical characteristics such as permafrost thaw depths and snow cover. Therefore, a comprehensive knowledge about the spatial and temporal variability of temperature inversion parameters such as thickness, intensity, magnitude and frequency is crucial for the surface impact of Arctic climate change.

Here, we investigate the spatial and temporal variations of temperature inversions over different surface types on Ammassalik Island in East Greenland. During a field campaign in summer 2019, high temporal resolution profiles of atmospheric variables such as air temperature, humidity and pressure were collected using UAVs. We acquired 147 profiles in a period of 13 days (06/07/2019-18/07-2019) over different surface types (rock, gravel, snow, ice) and with varying distance to the ocean (between 0 and 6 km). We found a distinct air temperature inversion present in most of the profiles whereby height and thickness differ considerably. Both ocean and ice surface act as near-surface cooling agents, which favours the development of surface inversions. The ice-free area between ocean and glacier tends to warm up strongly during Arctic summer and those different drivers manifest in an intricate pattern of air temperature stratification along a valley axis.

Our high-frequency and high-resolution profiles are compared with longer time series from the nearby Tassiilaq radiosonde and with ERA-5 reanalysis data in order to bring our campaign data into a larger spatio-temporal context. We conclude that the radiosonde is able to resolve the general pattern well but it fails in adequately representing the stratification relevant for glacio-meteorological processes.
Whitecap coverage measurements in laboratory modeling of wind-wave interaction
Authors: Kandaurov Alexander , Troitskaya Yuliya , Sergeev Daniil , Kozlov Dmitry
Published: March 2020

Whitecap coverage were retrieved from high-speed video recordings of the water surface obtained on the unique laboratory faculty Heidelberg Small-Scale Air-Sea Interaction Facility, the Aeolotron (annular wind-wave facility, 60 cm width, 2.4 m height, circumference of 27.3 m at the inner wall; water depth during experiments 1.0 m, water volume 18.0 m³, air space volume 24 m³; wind was generated by two axial fans mounted into the ceiling).

Records were made in the vertical direction (from top to bottom) in a shadowgraph configuration with backlight located under the channel. On the annular channel, regimes with an abrupt start of wind under an unperturbed surface condition were implemented, including the case of butanol presence in water simulating salinity. At the same time, the wave parameters varying depending on the time elapsed after the wind was turned on, made it possible to study the characteristics of the generation of spray at various effective fetches.
As a result of semi-automatic processing of image sequences using specially developed software that allows marking the moment and position of the bag-breakup formation on the videos, the dependences of the frequency of occurrence of these phenomena per unit surface area versus time after turning on the wind were obtained. From the same images, using the developed software for automatic detection of areas of wave breaking, the values of the whitecap coverage area were obtained. In this case, automatic image processing was performed using morphological analysis in combination with manual processing of part of the frames for tweaking the algorithm parameters: for each mode (water characteristics and wind speed), manual processing of several frames was performed, based on the results of which automatic algorithm parameters were selected to ensure that the resulting whitecap coverage corresponded. Since the same high-speed surface images were used to study the statistics of occurrence of events leading to the spray generation and the dependences of the whitecap coverage on time after turning on the wind for each regime were obtained, we were able to estimate the average number of fragmentation events per unit area of the collapse area.

The work was supported by the RFBR grant 18-35-20068 (conducting an experiment), President grant for young scientists MK-3184.2019.5 (software development) and the RSF grant No. 18-77-00074 (data processing).
What balloon soundings can tell about surface heat flux partitioning
Authors: Denissen Jasper , Wouters Hendrik , Orth René , Miralles Diego , Teuling Ryan
Published: March 2020

The land surface can influence near-surface weather. This happens, amongst others, through the impact of soil moisture availability on surface heat fluxes: when soil moisture is unavailable in soil moisture-limited conditions, most of the available energy will be used for heating the air above the land surface (sensible heat flux). But as soil moisture increases, evapotranspiration (latent heat flux) increases, affecting the surface heat flux partitioning. At the point that ample soil moisture is available in energy-limited conditions, the surface heat flux partitioning remains unaffected by soil moisture. The atmospheric boundary layer (ABL) responds to changes in surface heat flux partitioning in particular in terms of its temperature and humidity. Based on these mechanisms, observations of boundary layer dynamics should allow to infer the large-scale land surface state.

The goal of this study is to use atmospheric measurements of temperature and humidity to estimate the surface heat flux partitioning. This is achieved by constraining an ABL model (CLASS4GL) with the vertical temperature and humidity profiles as observed by thousands of soundings of hot air balloons across the globe. In CLASS4GL, the initial soil moisture is adjusted to yield matching modelled versus observed vertical temperature and humidity profiles. By doing so, the resulting surface fluxes are inferred exclusively from atmospheric measurements.

We find that ABL’s tend to higher, warmer and drier in water-limited conditions. This largely results from changes in soil moisture availability, which mainly affects the sensible heat flux and consequently, the surface heat flux partitioning. We determine the critical soil moisture, which distinguishes between soil moisture- and energy- limited conditions, using the ratio between the sensible- and latent heat flux and independent satellite surface soil moisture.

This is the first time that balloon soundings are used globally to assess the critical soil moisture. This research will help to further improve our understanding of land-atmosphere feedbacks and foster a correct representation of land surface characteristics in Land Models and subsequently, Climate Models.
The 2019/20 eastern Australian mega forest fires - a global forest perspective
Authors: Boer Matthias , Resco De Dios Víctor , Bradstock Ross
Published: March 2020

The 2019/20 forest fires in eastern Australia burned over 5.8 million hectares of mainly temperate broadleaf forest between September 2019 and January 2020. This burned area figure is expected to rise over the remainder of the austral summer, but is already an order of magnitude larger than the mean annual burned area for Australian forest fires over the last 20 years, which is ~0.59 Mha per year. Here we show that this forest fire event is of a record-breaking scale, both nationally and globally, and was pre-conditioned by wide-spread prolonged drought and extreme heat.

We analysed global remotely sensed burned area data for 2000-2019 to estimate annual burned area fractions of all continental forest biomes. The annual burned area fraction, which is related to the length of fire intervals and other aspects of fire regimes, allows us to compare levels of fire activity across different forest biomes and continents.

Though very large fires occur in some forest biomes, such as the boreal forests of North-America and Asia, over the 20 years covered by our data set, annual burned area fractions have been very small (<0.03) for nearly all continental forest biomes including Australia’s temperate broadleaf forest biome. These findings provide a global historical reference for the interpretation of the scale of the 2019/20 eastern Australian mega forest fires.

With fire activity in all forest biomes strongly constrained by the moisture content of the fuels, explanations for the unconstrained burning of millions of hectares of temperate broadleaf forest in a single season must be sought in the extreme drought that has affected eastern Australia for the last two years. We use gridded daily soil moisture predictions for the continent to show how widespread and prolonged dryness set the stage for the unprecedented forest fire event of 2019/20.
Rainfall-type landslide prediction based on landslide mechanism
Authors: Lin Wei , Yin Kunlong , Li Yuanyao , Li Ye
Published: March 2020

In general the determination of landslide rainfall threshold is mainly based on the empirical statistics of historical landslide disaster and rainfall. However, which often results in unsound prediction accuracy of regional rainfall-type landslide due to neglecting the difference effect of rainfall on diverse types of landslide disaster. In order to obtain accurate critical threshold of rainfall inducing landslides, based on the influence of rainfall on landslide mechanism and hydrological, in this paper a precise geological model is established and the soil water, ground water level and slope position shift of the landslides are monitored in real-time. By coupling the simulation results with the relationship between rainfall process and slope deformation, the regulation of slope failure induced by rainfall is discussed. The results indicate that a cumulative rainfall of 150 mm can make the landslide fully saturated, and generate the overall landslide instability along the soil-rock interface. Moreover, when the cumulative rainfall reaches 90 millimeter and lasts for more than 3 days, the displacement of bedding rock landslide exceeds 10 cm. This may because of the deterioration of the mechanical properties and the increase of the pore water pressure caused by the rainfall infiltration. The prediction criteria for landslide instability established from mechanism analysis can provide a theoretical basis for accurate prediction of rain-sensitive landslides.
Overdeepenings modelled with gravimetry-based data
Authors: Bandou Dimitri , Schläfli Patrick , Schwenk Michael , Douillet Guilhem , Kissling Edi , Schlunegger Fritz
Published: March 2020

The processes and mechanisms resulting in overdeepenings, valleys carved deeper than today’s rivers base level during glaciations, are still a matter of debate. Whether or not these valleys formation is due to glacial or fluvio-glacial processes or through fluvial down cutting in the geological past is difficult to affirm, as the depressions are filled with sediment or host lakes (Cook and Swift, 2012). In order to bypass this limitation, we use precise gravimetric data, GNSS data and borehole data, which we combine within a 3D forward modelling code, Gravi3D. We particularly aim at reconstructing the geometry of overdeepened valleys’ walls, which bear information on the erosional mechanism leading to the formation of these troughs. We proceed through the building of models for a given geometry to reproduce the Bouguer gravity that we measured in the field along sections and on a grid of stations. We constrain our models by using precise density values, determined by gravimetry, along with borehole data.

We apply this technique to overdeepenings located in the Alpine foreland (Belpberg area, Central Switzerland) because this area hosts multiple overdeepenings from the past glaciations. The region is characterized by three hill ranges made up of Molasse bedrock with c. 300 m-deep and c. 1 km-wide valleys in-between, where overdeepenings with a Quaternary infill are expected. The results of gravity data collection, accomplished over a section with stations spaced between 100 and 300 m and after standard corrections yield a Bouguer anomaly for the Belpberg region that ranges from c. -99 to -106 mgal. We infer this large range to the regional trend (c. 2 mgal over 8 km) and to the effect of the overdeepening infill (2-4 mgal over 1 km), disclosing a sharp anomaly pattern over the inferred overdeeping. The subsequent three steps include: (i) the removal of the regional trend, (ii) the use of the Nettleton method for the quantification of an accurate density contrast between the Molasse bedrock and the Quaternary infill, and (iii) the configuration of Gravi3D for the Belpberg situation, will yield further information on the morphology of the overdeeping. We thus conclude that Gravi3D, within this framework, is a useful tool to determine the geometry of overdeepings in particular, and shallow subsurface bodies and structures in general.

Reference:

Cook, S.J., Swift, D.A., 2012. Subglacial basins: Their origin and importance in glacial systems and landscapes. Earth-Science Reviews 115, 332–372.
Trade-off, vulnerability and power asymmetry in the Senegal River basin
Authors: Tilmant Amaury , Pina Jasson , Salman Maher , Casarotto Claudia , Lebdi Fethi , Pek Eva
Published: March 2020

The development of Senegal River basin involves trading-off competing objectives in an uncertain environment. Through a stochastic analysis, the trade-off discovery can be enriched to identify vulnerabilities; that is, the sensitivity of those losses with respect to changing natural and anthropogenic factors. In the Senegal River basin, the availability of water at a particular point in space and time is directly linked to both the hydrologic processes and the level of development of the water resources system. Our analysis of the trade-off relationships reveals the existence of two coalitions of objectives: traditional food production (agriculture and floodplain fisheries) versus hydropower-navigation. In terms of vulnerability, the examination of probabilistic trade-offs also shows that of the two main coalitions of objectives, the one dealing with traditional food production is much more vulnerable to changes in both hydro-climatic conditions and allocation policies. Of interest is the fact that the first coalition mostly concerns downstream riparian countries while hydropower, and to a less extent, navigation concern upstream countries. The result is a reinforced power asymmetry where vulnerable downstream riverine communities compete for water with politically and/or economically more powerful upstream water users like power companies.
Progress in evaluating satellite soil moisture products in Great Britain against COSMOS-UK and in-situ soil moisture measurements
Authors: Quinn Nevil Wyndham , Newton Chris , Boorman David , Horswell Michael , West Harry
Published: March 2020

The resolution of satellite of satellite-derived soil moisture data products has matured, notably in recent years due to the Soil Moisture Active Passive mission (SMAP) launched in 2015. Whilst spatial resolutions still fall short of those suitable for field-scale monitoring, there are several ‘value-added’ RS soil moisture products available at the regional (e.g. SMAP: 36km) to meso-scale (e.g. SMAP: 9km) resolution. Although the intended 3km scale SMAP product did not materialise due to the failure of the L-Band radar, a potential substitute product has recently become available (Das et al. 2019). The SMAP-Sentinel1 product combines data from SMAP and C-Band Sentinel 1A/B SAR data to synthesise global soil moisture at a 3km and 1km resolution (~6 day revisit for Europe).

Evaluation of these products against ground-based measurements in the USA and elsewhere is encouraging, but only preliminary evaluation has been undertaken in the United Kingdom. Evaluation is always challenging because (i) rather than a direct measurement, satellite estimates are based on other measured properties (e.g. brightness temperature) with soil moisture algorithmically inferred, (ii) ground-based measurements are highly localised in comparison with the measurement averaged over the satellites much larger pixel resolution, and (iii) satellite sensors typically estimate only surface soil moisture (0-5cm).

The COSMOS-UK network, under development since 2013, provides high resolution soil moisture data at 51 sites in the UK, corresponding to a variety of climatic, soil and land cover settings. Sites typically contain soil moisture probes at a variety of depths (including 10cm) as well as a cosmic ray sensor. The latter integrates soil moisture over an area of ~12ha, and while not matching the spatial scale or soil depth of satellite measurements, it does avoid some of the field-scale heterogeneity issues associated with point-based measurements.

The 9km SMAP L3 product performs well against 10cm soil probe measurements at most sites (>70% at ubRMSE <0.04), and seasonal patterns in performance are evident. Satellite measurements performed less well in comparison with COSMOS-UK estimates (68% at ubRMSE <0.06). Downscaling the SMAP L3 product based on hydroclimatology improves performance in some cases but worsens it in others. The SMAP-Sentinel 1 product generally performs worse than the 9km SMAP L3 product.  Reasons for spatio-temporal variations in correlations and performance are proposed including reference to soil profile characteristics and properties at each site, as well as vegetation and climatic setting.
Spatial observations of large eddies and cross-canopy coupling with joint fiber-optic distributed sensing and eddy covariance flux measurements
Authors: Peltola Olli , Lapo Karl , Thomas Christoph , Vesala Timo
Published: March 2020

Air flows above forest canopies are typically governed by large coherent eddies generated mechanically by inflected mean wind velocity profile or thermally by buoyancy in the convective regime. A significant body of research have been devoted to the role of these eddies on ecosystem scalar (gases and heat) exchange since they are likely related to the energy balance closure problem observed at the eddy covariance (EC) stations and turbulent flux divergence under stable stratification. Here we utilize fiber-optic distributed sensing on a tall mast to observe the turbulent fluctuations of air temperature with high spatial (25 cm) and temporal resolution (1 Hz) from the forest floor up to 120 m above the ground. These unique measurements resolved the continuous vertical profile of scalar turbulence and hence enabled us to study the topology (height – time space) of the turbulent eddies in different stability regimes. For example, the inclination angle of the eddies changed with stability and the scalar ramps often observed in canopy flows were evident only close to the canopy top, whereas higher up thermal eddies dominated the flow. Furthermore, the measurements permitted the identification of coupled air layers and hence analysis on the dynamics of below-canopy decoupling. During stable conditions with wind shear large eddies and the related inverted ramps in the temperature time series were observed at the top of the decoupling layer, however when the wind shear decreased the flow switched to submeso regime with canopy waves. These analyses were then combined with concurrent turbulence measurements with 3D sonic anemometers at several heights and EC gas flux measurements at one height to gain new insights on the role of these eddies on gas (e.g. carbon dioxide) transport. The measurements were conducted during summer 2019 at the Hyytiälä SMEAR II station located in central Finland and the permanent ICOS measurements at the site were utilized to the fullest.
Testing the ideal ice-core record for past temperature reconstructions using combined isotope and impurity analyses
Authors: Münch Thomas , Hörhold Maria , Freitag Johannes , Behrens Melanie , Laepple Thomas
Published: March 2020

Ice cores represent one of the most important palaeoclimate archives, which record, among many other parameters, changes in stable oxygen and hydrogen isotopic composition and soluble ionic impurities. While impurities serve, for example, as proxies for sea ice, marine biological activity and volcanism, records of isotopic composition are the major proxy for the reconstruction of natural polar temperature variability. The latter is based on the temperature-dependent distillation and fractionation of the isotopic composition of water vapour along its atmospheric pathway and empirically determined relationships thereof.

However, temperature is by far not the only driver of isotopic composition changes. A single isotopic ice-core record will comprise variations caused by a multitude of processes, from variable atmospheric circulation and moisture pathways to the intermittency of precipitation and finally to the mixing and re-location of surface snow by wind drift (stratigraphic noise). Taken together, these additional processes constitute a large amount of noise in the single isotope record, which masks the true temperature-related variability. Averaging a sufficient number of records to reduce overall noise is one means to allow for quantitative reconstructions, but its effectiveness depends on the spatial scales of the involved processes. Here, we discuss an alternative approach. Assuming that major impurity species exhibit a seasonal cycle and are mainly also, along with the isotopic composition, deposited by precipitation and redistributed by wind, a large portion of their interannual variability should be linked, which would offer the possibility of using the impurities to correct the variability of the isotopic records.

In this contribution, we present the "ideal" dataset for testing this idea. We sampled and analysed isotopic composition and major impurity species on a four metre deep and 50 metre long trench at Kohnen Station, East Antarctica. This enables us to study the two-dimensional structure and relationship of both proxies to learn about their deposition mechanisms, their seasonality, and to test the ability of a combined isotope–impurity approach to reconstruct local temperatures by comparing so obtained temperature reconstructions with the local weather station data.

 
Impacts of different RCP scenarios on ALADIN-Climate regional climate model projections over Hungary
Authors: Bán Beatrix , Zsebeházi Gabriella
Published: March 2020

The KlimAdat national project was started in 2016 to create a complex database of detailed meteorological information aiming to support local climate change impact studies in different sectors, adaptation strategies and related decision making. Besides observation data its primary basis will be ALADIN-Climate and REMO regional climate model simulations achieved by the Hungarian Meteorological Service and this set of projections will be extended by members of the Euro-CORDEX ensemble in order to quantify the projection uncertainties. 
This study is focusing on analysis of the ALADIN-Climate model projections driven with RCP4.5 and RCP8.5 scenarios. Firstly, the CNRM-CM5 global model outputs were downscaled to 50 km horizontal resolution over the EURO-CORDEX domain with ALADIN-Climate Version 5.2. Then using these  results as lateral boundary conditions, 10 km experiments were prepared on a domain covering Central and South-Eastern Europe.
The presentation aims to introduce the behaviour of these simulations achieved by different scenarios and at different spatial resolution from the aspect of temperature and precipitation change over Hungary. Special attention will be put on the differences in extreme indices. Finally, our 10 km resolution simulations are compared with EURO-CORDEX results to specify their place in a larger ensemble.
Assessment of magnetic data for landfill characterization by means of a probabilistic approach
Authors: Isunza Manrique Itzel , Caterina David , Inauen Cornelia , Watlet Arnaud , Dashwood Ben , Debouny Tom , Hermans Thomas , Nguyen Frederic
Published: March 2020

The sustainable vision of the Dynamic Landfill Management (DLM) deals not only with present but also with long-term waste management. In this context, DLM enhances the environmental assessment of landfills after closure as well as the recovery of materials and energy resources, for which, a proper characterization is required. To this end, geophysical methods have demonstrated their suitability for landfill exploration, characterization and monitoring. Due to the complexity of these sites and challenges in data acquisition and/or processing, the use of multiple methods is the best approach for landfill investigations. In this work, we used multiple geophysical methods, co-located with several trial pits and boreholes, to estimate the structure of a waste disposal site located in a quarry, and to better delineate the underlying geology composed of limestone. We applied electrical resistivity tomography (ERT), time-domain induced polarization (IP), H/V spectral ratio from microtremor records and magnetometry. We made a structural joint interpretation using the different datasets and the ground truth data. First, the ERT and IP data were individually inverted, and a first structural model was derived. Afterwards, we followed a parametric analysis of the H/V data to corroborate the thickness of some layers at the position of the seismic stations. Then, this model was used to compute synthetic magnetic data and by comparing them with the observed total field magnetic anomalies, a refined model was produced. We evaluated the improvement of including magnetic modelling by using a probabilistic approach previously reported. This approach is based on the computation of conditional probabilities by comparing the inverted models with the co-located data from trial pits and boreholes. Overall, we delineated the lateral and vertical extension of the waste body, the distribution of ash and lime deposits and estimated the upper limit structure of the bedrock.
A “web-enabled” sociohydrological model on the system dynamics of a smallholder farmer
Authors: Diederen Dirk , Pande Saket
Published: March 2020

We present a “web-enabled” sociohydrological model that can help us to better understand the system dynamics of a smallholder farmer. It couples the dynamics of the six main assets of a typical smallholder farmer: water storage capacity, capital, livestock, soil fertility, grazing access, and labor. The hydroclimatic variability, which is a main driver and source of uncertainty of the smallholder system, is accounted for at subannual scale. The model incorporates rule-based adaptation mechanisms of smallholders (for example, adjusting expenditures on food and fertilizers and selling livestocks) when farmers face adverse sociohydrological conditions, such as low annual rainfall, occurrence of dry spells, or variability of input or commodity prices.

The novelty presented is that the model has been enabled with remote access to the relevant modelled information through the world wide web, making it accessible to anyone with access to the internet without dealing with the complexity of installing or running models on one’s own machine. We present the sociohydrological model along with a first set up of the webserver, which is written in python (Django), to demonstrate how we envision sociohydrology to be brought to the people - literally at their fingertips.
How useful are CORDEX products for the assessment of future agricultural drought propensity across the Indian subcontinent?
Authors: Das Prabal , Chanda Kironmala , Maity Rajib
Published: March 2020

Abstract

This study aims to evaluate the future evolution of agricultural drought propensity across the Indian subcontinent through Drought Management Index (DMI), a probabilistic measure based on the concept of Reliability-Resilience-Vulnerability (RRV) of soil moisture series at a location/region (Chanda et al., 2014; Chanda and Maity, 2017). In this study, monthly gridded soil moisture products from the Coordinated Regional Climate Downscaling Experiment (CORDEX) framework are used after suitable bias correction, if needed. In the realm of RRV analysis, the fall of soil moisture below a threshold (e.g., Permanent Wilting Point, PWP) is considered as the ‘failure state’. The joint distribution of resilience (the ability of the soil moisture system to recover from a failure state) and vulnerability (severity of the deficit in soil moisture during a failure state) of soil moisture series is modelled through copulas (Nelsen, 2006; Maity, 2018) to develop the DMI.  The results of this study help to assess the evolution of agricultural drought propensity, in terms of DMI, in the near (2011-2040), intermediate (2041-2070) and far future (2071-2099). The findings from multiple emission pathways, designated as Representative Concentration Pathways (RCPs), are compared against each other during the future period and also against the historical period. As an outcome of the study, specific regions across the Indian mainland are identified that need immediate attention for managing sustainable agricultural and allied activities in future.

Keywords: Drought Management Index (DMI), soil moisture, future drought propensity, Reliability-Resilience-Vulnerability (RRV), CORDEX

 

 

 

 

References

Chanda, K., Maity, R., Sharma, A., and Mehrotra, R. (2014). Spatiotemporal variation of long-term drought propensity through reliability-resilience-vulnerability based Drought Management Index, Water Resources Research, 50(10), 7662-7676.

Chanda, K., and Maity, R. (2017). Assessment of Trend in Global Drought Propensity in the Twenty-First Century Using Drought Management Index, Water Resources Management, 31(4), 1209-1225.

Maity, R. (2018). Statistical Methods in Hydrology and Hydroclimatology. Springer.

Nelsen, R. B. (2007). An introduction to copulas. Springer Science & Business Media.