bluuebunny/crossref_metadata_2025 huggingface dataset:
Stepwise improvement of hydrological models using satellite-based evaporation and total water storage estimations
Authors: Hrachowitz Markus , Hulsman Petra , Savenije Hubert
Published: March 2021

Hydrological models are often calibrated with respect to flow observations at the basin outlet. As a result, flow predictions may seem reliable but this is not necessarily the case for the spatiotemporal variability of system-internal processes, especially in large river basins. Satellite observations contain valuable information not only for poorly gauged basins with limited ground observations and spatiotemporal model calibration, but also for stepwise model development. This study explored the value of satellite observations to improve our understanding of hydrological processes through stepwise model structure adaption and to calibrate models both temporally and spatially. More specifically, satellite-based evaporation and total water storage anomaly observations were used to diagnose model deficiencies and to subsequently improve the hydrological model structure and the selection of feasible parameter sets. A distributed, process based hydrological model was developed for the Luangwa river basin in Zambia and calibrated with respect to discharge as benchmark. This model was modified stepwise by testing five alternative hypotheses related to the process of upwelling groundwater in wetlands, which was assumed to be negligible in the benchmark model, and the spatial discretization of the groundwater reservoir. Each model hypothesis was calibrated with respect to 1) discharge and 2) multiple variables simultaneously including discharge and the spatiotemporal variability in the evaporation and total water storage anomalies. The benchmark model calibrated with respect to discharge reproduced this variable well, as also the basin-averaged evaporation and total water storage anomalies. However, the evaporation in wetland dominated areas and the spatial variability in the evaporation and total water storage anomalies were poorly modelled. The model improved the most when introducing upwelling groundwater flow from a distributed groundwater reservoir and calibrating it with respect to multiple variables simultaneously. This study showed satellite-based evaporation and total water storage anomaly observations provide valuable information for improved understanding of hydrological processes through stepwise model development and spatiotemporal model calibration.
VLBI-GNSS co-location survey at the Ishioka Geodetic Observing Station in 2018 and 2020
Authors: Takagi Yu , Ueshiba Haruka , Nakakuki Tomokazu , Matsumoto Saho , Hayashi Kyonosuke , Yutsudo Toru , Mori Katsuhiro , Kobayashi Tomokazu
Published: March 2021

Geospatial Information Authority of Japan has a VLBI antenna (ISHIOKA) and an IGS station (ISHI) at the Ishioka Geodetic Observing Station. The Ishioka VLBI antenna has participated in the IVS sessions and IGS station ISHI has continuously provided the GNSS data.

We conducted co-location surveys in November 2018 and September 2020 to determine a local tie vector between the Ishioka VLBI antenna and the IGS station ISHI. In the surveys, we determined the position of ISHI w.r.t. four surrounding reference pillars by angle/distance measurements and leveling. To determine the position of the VLBI antenna reference point w.r.t. the pillars, we adopted the “inside method” (Munekane, 2019), where the position of the VLBI reference point is determined by observing mirror installed inside the AZ cabin from the fixed point inside the cabin; its position is determined by angle/distance measurements from the pillars. We plan to finish the calculation early this year and submit the results to IERS ITRS Center so as to contribute to the ITRF2020.

In this presentation, we will outline the inside method and compare the results in 2018 and 2020.
Stability relations of monazite-(Ce), gadolinite-(Ce), gadolinite-(Y), britholite-(Ce) and bastnäsite-(Ce) during late- to post-magmatic processes in nepheline syenite (Čistá pluton, Czech Republic)
Authors: Jaranowski Maciej , Budzyń Bartosz , Kozub-Budzyń Gabriela A. , Sláma Jiří , Klomínský Josef
Published: March 2021

Stability relations of the REE-bearing accessory phases and alteration processes in the cancrinite-bearing nepheline syenite from the Čistá pluton (the center of the upper-crustal Tepla–Barrandian unit, Bohemian Massif, Czech Republic) were studied. Observations of rock microtextures, quantitative analyses of minerals and compositional X-ray mapping were performed using electron probe microanalysis (EPMA). The primary REE-bearing accessory minerals assemblage includes monazite-(Ce) associated with gadolinite-group minerals (i.e. gadolinite-(Ce) and gadolinite-(Y)), which were partially replaced by britholite-(Ce), bastnäsite-(Ce), aggregates of fine-grained REE-bearing phases (possibly fluorapatite and/or britholite-(Ce)) and, rarely, cerianite. K-feldspar and albite form intergrowths or symplectites with REE-phases in the investigated reaction microtextures. Furthermore, the zircon crystals demonstrate oscillatory zoning and/or extensive patchy zoning due to alteration processes. The alteration of accessory minerals are interpreted as driven by K- and Na-bearing alkali fluids with high CO2 activity during late- to post-magmatic processes.

Acknowledgements: This work was supported by the National Science Centre research grant no. 2017/27/B/ST10/00813.
A Statistical Model of the Global Carbon Budget
Authors: Hillebrand Eric , Bennedsen Mikkel , Koopman Siem Jan
Published: March 2021

We propose a dynamic statistical model of the Global Carbon Budget (GCB) as represented in the annual data set made available by the Global Carbon Project (Friedlingsstein et al., 2019, Earth System Science Data 11, 1783--1838), covering the sample period 1959--2018. The model connects four main objects of interest: atmospheric CO2 concentrations, anthropogenic CO2 emissions, the absorption of CO2 by the terrestrial biosphere (land sink) and by the ocean and marine biosphere (ocean sink).  The model captures the global carbon budget equation, which states that emissions not absorbed by either land or ocean sinks must remain in the atmosphere and constitute a flow to the stock of atmospheric concentrations. Emissions depend on global economic activity as measured by World gross domestic product (GDP), and sink activity depends on the level of atmospheric concentrations and the Southern Oscillation Index (SOI). We use the model to determine the time series dynamics of atmospheric concentrations, to assess parameter uncertainty, to compute key variables such as the airborne fraction and sink rate, to forecast the GCB components from forecasts of World-GDP and SOI, and to conduct scenario analysis based on different possible future paths of World-GDP.
Southeast tropical Atlantic changing from subtropical to tropical conditions
Authors: Roch Marisa , Brandt Peter , Schmidtko Sunke
Published: March 2021

A warming and freshening trend of the mixed layer in the upper southeast tropical Atlantic Ocean (SETA) is observed by the Argo observation array during the time period of 2006 to 2019. Thus, the ocean surface density is reducing. This has an impact on the upper-ocean stratification which intensified by more than 30 % in the SETA region since 2006. The initial typical subtropical stratification with a salinity maximum at the surface is shifted to more tropical conditions characterized by warmer and fresher surface waters and a subsurface salinity maximum.

A more detailed analysis of isopycnals shows a continuous upward displacement of isopycnal surfaces suggesting that wind stress curl-driven upwelling has to play an essential role. Therefore, ASCAT wind stress changes are examined, revealing that increased open ocean wind curl-driven upwelling but also partly counteracting reduced coastal upwelling due to weakened alongshore southerly winds are present. Changing alongshore winds might be a reason why tropical surface waters spread further southward reaching more into the SETA region. Besides, atmospheric fluxes could further impact upper ocean characteristics.

Changes in the upper-ocean stratification matter as they affect not only physical ocean dynamics such as ocean ventilation processes but also biogeochemical and ecological activities such as nutrient fluxes and fisheries. Nevertheless, the consequences of increased stratification for upwelling regions are not yet fully understood. The SETA upwelling system is a key region for enhanced nutrient supply to the euphotic zone and hence, a core nutrient source for high coastal primary productivity.

We aim to assess the recent change of upper-ocean stratification towards tropical conditions at the sea surface in the SETA region and explore its driving mechanisms as well as possible consequences for the primary productivity and fisheries off Angola and Namibia, in order to improve our understanding of what is happening as a result of intensified upper-ocean stratification in upwelling regions.
From the Landslide to the Mangrove; Coupling Sediment Supply Pulses and River Sediment Deposits in the context of Climate Change in Thailand.
Authors: Curoy Jerome , Ward Raymond , Barlow John
Published: March 2021

In Thailand landslides and flooding are two major natural disasters affecting more than 11 million people living in coastal provinces. Such events have significant human and economic impacts. For example, in 1988, landslides resulted in 373 deaths and caused up to US$80 million in damage (Tanavud, 2008); in 2011, floods and landslides affected more than two million people and killed 53 across Southern Thailand with a village of about 100 households being buried by one large slide (EarthObservatory, 2021). Landslides in the Krabi province in Thailand are predominantly shallow and rainfall-induced, they also represent the main source of sediment pulses for coastal environments such as mangroves and beaches. This study aims at investigating the link between sediment availability from 3 river catchments in the province of Krabi in Southern Thailand and sedimentation rate evolution in mangroves directly downstream in order to understand coastal the sediment shortages and therefore coastal erosion in that area.

Landslide inventories were evaluated using high resolution imagery (<10m) such as aerial photographs, Theos and EO-1 satellite imagery, Google Earth historical tool covering a time period from 2007 to present. Calculations of the surface areas and volumes of landslides was calculated in ArcMap using the formulae developed by Larsen et al. (2010). Landslide erosion was modelled using an approach based upon the negative power law scaling properties of rockfall magnitude–frequency distribution to establish total volumes of sediment for specific years or seasons.

Core samples taken in the mangroves near the river mouths were used to identify markers of landslide events and associated sediment cascades based on grain size distribution and 137Cs dating.

Preliminary results show sedimentation rates in the mangroves from 0.9 to 2 mm/year since 1963 and sediment volumes made available to transport from 0.3 to 68300 m3/year since 2007 across the 3 catchments.

Grain size analysis shows variations of the D50 and the sorting coefficient throughout the sediment recording indicators of landslides and high intensity rainfall events.
A diffusive description of Vertical Mixing in the Benthic Biolayer.
Authors: Monofy Ahmed , Boano Fulvio , B. Grant Stanley , A. Rippy Megan
Published: March 2021

In-stream environments, many biogeochemical processes occur in the benthic biolayer, i.e., within sediments at a very shallow depth close to the sediment-water interface (SWI). These processes are important for stream ecology and the overall environment.

Here, a 1D diffusive model is used to analyze the vertical exchange of solutes through the SWI and in the benthic biolayer. The model is applied to an extensive set of previously published laboratory experiments of solute exchange with different bed morphologies: flatbeds, dunes, and alternate bars. Although these different bed features induce mixing that is controlled by different physical processes at the SWI, overall mixing within the sediment is well represented by a parsimonious diffusive model, provided that the diffusivity profile declines exponentially with sediment depth.

For all morphology types, mixing is better simulated by an exponential diffusivity model than a constant diffusivity approach. Two parameters define the exponential diffusivity model; the effective diffusivity at the SWI, and a depth scale over which the exponential profile decays. Using a combination of classification and regression trees (CART) and multiple linear regression approaches, we demonstrate that a single predictive model captures measured variability in the effective diffusivity coefficient at the SWI across all morphological types. The best predictive model for the decay depth scale, on the other hand, is tailored to each morphological type separately.

The predictive framework developed here contributes to our understanding of the physical processes responsible for mixing across the SWI,  and therefore the in-bed processes that contribute to the biogeochemical processing of nutrients and other contaminants in streams.
Long-term ventilation changes of Subpolar Mode Waters in the North Atlantic Ocean and its impact on the oxygen distribution
Authors: Stendardo Ilaria , Buongiorno Nardelli Bruno , Durante Sara
Published: March 2021

In the subpolar North Atlantic Ocean, Subpolar Mode Waters (SPMWs) are formed during late winter convection following the cyclonic circulation of the subpolar gyre. SPMWs participate in the upper flow of the Atlantic overturning circulation (AMOC) and provide much of the water that is eventually transformed into several components of the North Atlantic deep water (NADW), the cold, deep part of the AMOC. In a warming climate, an increase in upper ocean stratification is expected to lead to a reduced ventilation and a loss of oxygen. Thus, understanding how mode waters are affected by ventilation changes will help us to better understand the variability in the AMOC. In particular, we would like to address how the volume occupied by SPMWs has varied over the last decades due to ventilation changes, and what are the aspects driving the subpolar mode water formation, their interannual variations as well as the impact of the variability in the mixing and subduction and vertical dynamics on ocean deoxygenation. For this purpose, we use two observation-based 3D products from Copernicus Marine Service (CMEMS), the ARMOR3D and the OMEGA3D datasets. The first consists of 3D temperature and salinity fields, from the surface to 1500 m depth, available weekly over a regular grid at 1/4° horizontal resolution from 1993 to present. The second consists of observation-based quasi-geostrophic vertical and horizontal ocean currents with the same temporal and spatial resolution as ARMOR3D.
EstSoil-EH - Developing a high-resolution eco-hydrological modelling parameters dataset for Estonia
Authors: Kmoch Alexander , Kanal Arno , Astover Alar , Kull Ain , Virro Holger , Helm Aveliina , Pärtel Meelis , Ostonen Ivika , Uuemaa Evelyn
Published: March 2021

To understand, model and predict landscape evolution, ecosystem services and hydrological processes the availability of detailed observation-based soil data is extremely valuable. Estonia has a national digitized soil map based on decades of Soviet era field mapping. It maps more than 750 000 soil units throughout Estonia at a scale of 1:10 000 - with 75% of mapped units smaller than 4.0 ha. However, due to the way it was recorded the data is not immediately useful for numerical modelling. We synthesized the EstSoil-EH dataset - more than 20 eco-hydrological variables on soil, topography and land use for Estonia as numerical and categorical values - using data fusion and machine learning.
As additional feature information we used a 5m DEM, the Estonian Topographic Database, and EU-SoilHydroGrids layers. For each soil unit, we analysed type, texture, and layer information from the originally recorded composite text-based soil information, which contains the actual texture class, classifiers for rock content, peat soils, distinct compositional layers, and their depths. Subsequently, we derived soil layering, clay, silt, and sand contents and coarse fragments of the soil layers. In addition, we aggregated and predicted physical variables related to water and carbon cycles (bulk density, hydraulic conductivity, organic carbon content, available water capacity). We validated our modelled data and achieved satisfying degrees of agreement depending on the variables type.
Elevation angles and attenuation of gravity waves in the ionosphere
Authors: Chum Jaroslav , Podolska Kateřina , Base Jiri , Rusz Jan
Published: March 2021

     Characteristics of gravity waves (GWs) are studied from multi-point and multi-frequency continuous Doppler sounding in the Czech Republic. Three dimensional (3D) phase velocities of GWs are determined from phase shifts between the signals reflecting from the ionosphere at different locations that are separated both vertically and horizontally; the reflection heights are determined by a nearby ionospheric sounder located in Průhonice. Wind-rest frame (intrinsic) velocities are calculated by subtracting the neutral wind velocities, obtained by HWM-14 wind model, from the observed GW velocities. In addition, attenuation of GWs with height was estimated from the amplitudes (Doppler shifts) observed at different altitudes. A statistical analysis was performed over two one-year periods: a) from July 2014 to June 2015 representing solar maximum b) from September 2018 to August 2019 representing solar minimum.   

     The results show that the distribution of elevation angles of wave vectors in the wind–rest frame is significantly narrower than in the Earth frame (observed elevations). Possible differences were also found between the wind–rest frame elevation angles obtained for the solar maximum (mean value (around -24°) and solar minimum (mean value round -37°). However, it is demonstrated that the elevation angles partly depended on the daytime and day of year. As the distribution of the time intervals suitable for the 3D analysis in the daytime–day of year plane was partly different for solar maximum and minimum, no reliable conclusion about the possible dependence of elevation angles on the solar activity can be drawn.

     It is shown that the attenuation of GWs in the ionosphere was in average smaller at the lower heights. This is consistent with the idea that mainly viscous damping and losses due to thermal conductivity are responsible for the attenuation.

  
ENSO and SAM influence on the generation of long episodes of Rossby Wave Packets during Southern Hemisphere Summer
Authors: Perez Iago , Barreiro Marcelo , Masoller Cristina
Published: March 2021

Rossby Wave Packets (RWPs) are key to the improvement of  long-range forecasting and for the prediction of sub-seasonal extremes. Several studies have focused on their properties, such as time duration, trajectory, areas of detection and dissipation as well as interannual variability in the northern hemisphere, but only a few of them have focused in the southern hemisphere. Here we study the influence of low-frequency climate modes on RWPs during southern hemisphere summer using NCEP DOE 2 Reanalysis data. Focusing on long-lived RWPs, which we define as RWPs with a lifespan above 8 days,  we determine how El Niño-Southern Oscillation (ENSO) and the Southern Annular Mode (SAM) modify their frequency of occurrence and their main areas of detection and dissipation. We found that during El Niño and negative SAM years, the number of long-lived RWPs is maximum. In addition, years with the highest amount of long-lived RWPs show a zonally symmetric and narrow upper level jet that is shifted northward from its climatological position. On the other hand, when the jet is shifted southward, particularly in the southeastern Pacific, during positive SAM phases, only a small number of long-lived RWPs is detected. Therefore, negative SAM conditions provide a background mean flow that favours the occurrence of long-lived RWPs while positive SAM conditions have the opposite effect. The dependence on ENSO phase is not as symmetric: while El Niño sets atmospheric conditions that favour the formation of long-lived RWPs, La Niña years present high interannual variability in the frequency of occurrence. Furthermore, in El Niño events the main formation area is between 61-120ºE and the main dissipation area between 300-359ºE. During La Niña events, the main formation area is located by 241-300ºE and no main dissipation area is identified. In the case of positive SAM two main formation areas appear at 61-120ºE and 241-300ºE and two main dissipation areas within 121-180 and 301-359ºE. Lastly in the case of negative SAM one main formation area at 241-300ºE is detected and no main dissipation area is detected. The robustness of the results was tested repeating the analysis using data from the ERA5 Reanalysis and supports the finding that the maximum number of long-lived RWPs occur during negative SAM and El Niño years
Formation and evolution of a magma reservoir at a slow-spreading center (Atlantis Bank, Southwest Indian Ridge)
Authors: Boulanger Marine , France Lydéric , Deans Jeremy , Ferrando Carlotta , Lissenberg Johan , von der Handt Anette
Published: March 2021

The heterogeneous presence of ephemeral magmatic systems below the ridge axis and their complexity mostly account for the heterogeneous character of the oceanic crust accreted at (ultra) slow-spreading ridges. In order to better understand the magmatic processes involved in slow-spreading lower oceanic crust formation, we studied a drilled section of an oceanic core complex (OCC) interpreted as an exhumed portion of lower crust close to the ridge axis. We focused on ODP Hole 735B which presents the most primitive lithologies sampled at Atlantis Bank OCC (Southwest Indian Ridge) in a ~250 m thick section previously interpreted as a single crustal intrusion.

We combined detailed structural and petrographic data with whole-rock and in situ mineral analyses to determine the processes of emplacement and differentiation of melts within this section. The lower half of the unit is comprised of alternating troctolites and olivine gabbros showing intrusive contacts, and both magmatic and crystal-plastic fabrics. Such features are lacking in the upper half, rather uniform, gabbroic sequence. Whole-rock compositions highlight the cumulative character of both lower and upper units, and a great compositional variability in the lower sequence, whereas the upper sequence is rather homogeneous and differentiates up-section. In situ analyses of mineral phases document magma emplacement processes and provide evidence for ubiquitous reactive porous flow during differentiation. Comparison between both units' geochemistry also led us to strongly favor a model of formation of the reservoir that genetically links melts from the lower and the upper unit.

We show that the whole section, and related geochemical units, likely constitutes a single magmatic reservoir, in which the lower unit formed by emplacement of primitive sills related to the continuous recharge of primitive melts. Recharge led to partial assimilation of the crystallizing primitive mush, and related hybridization with interstitial melts. Hybrid melts were progressively collected in the overlying mushy part of the reservoir (upper unit), whereas the sills' residual melt differentiated by reactive porous flow processes under a predominantly crystallization regime. Similarly, hybrid melts’ evolution in the upper unit was governed by upward reactive porous flow and progressive differentiation and accumulation of evolved melts at the top of the reservoir. Our results provide the first integrated model for magma reservoir formation in the lower slow-spreading oceanic crust, and have potential implications regarding the lower crust structure and the composition of MORBs.
Lightning‐Generated Whistler Amplitudes Measured by the Van Allen Probes
Authors: Farges Thomas , Ripoll Jean-Francois , Malaspina David , Lay Erin , Cunningham Gregory , Hospodarsky George , Kletzing Craig , Wygant John
Published: March 2021

This talk will show a statistical analysis of both electric and magnetic field wave amplitudes of very low frequency lightning‐generated whistlers (LGWs) based on the equivalent of 11.5 years of observations made by the Van Allen Probes. We complement this analysis with data from the ground‐based World Wide Lightning Location Network (WWLLN) to explore differences between satellite and ground‐based measurements. We will discuss how LGW mean amplitudes were generally found to be low compared with other whistler mode waves even though there exists extreme events (1 out of 5,000) that can reach 100 pT and contribute strongly to the mean power below L = 2. We will reveal a region of low wave amplitude existing below L=2 thanks to the denser dayside ionosphere, which prevents the intense equatorial lightning VLF waves from propagating through it. Below L = 1.5 at all MLT, LGW amplitudes are found to be weak while the ground‐level lightning activity is maximal. This suggests a difficulty of lightning VLF waves to penetrate / propagate / remain at low L‐shells, certainly due at least to the denser ionosphere during daytime. On the contrary, the mean LGW magnetic power (or RMS) remains nearly constant with respect to L‐shell. We will explain that this is due to strong to extreme LGWs that dominate the wave mean power to the point of compensating the decay of LGW occurrence at low L‐shell. Even though extreme LGW were found to be very powerful, particularly at low L and during night, the mean electric/magnetic power remains low compared with other whistler waves. This implies that LGW resonant effects on electrons are consequently long‐term effects that contribute to “age” trapped inner belt electron populations.
H2020 SINOPTICA (Satellite-borne and IN-situ Observations to Predict The Initiation of Convection for ATM) project: initial results
Authors: Parodi Antonio , Temme Marco , Gluchshenko Olga , Kerschbaum Markus , Surian Nicola , Biondi Riccardo , Realini Eugenio , Gatti Andrea , Tagliaferro Giulio , Llasat Maria Carmen , Rigo Tomeu , Esbri Laura , Milelli Massimo , Mazzarella Vincenzo , Lagasio Martina , Parodi Andrea
Published: March 2021

The H2020 SINOPTICA Project (2020-2022) aims at exploiting the untapped potential of assimilating remote sensing (EO-derived and ground-based radar) as well as GNSS-derived datasets (including radio occultation data) and in-situ weather stations data. Those data will be used for very high-resolution, very short-range numerical weather forecasts to improve the prediction of extreme weather events to the benefit of Air Traffic Management (ATM) operations. This will be done by setting up a continuously updated database of remote sensing-derived, GNSS-derived and in-situ weather stations variables, in combination with an automated assimilation system to feed an NWP model. SINOPTICA weather forecast results will be integrated into ATM decision-support tools, visualizing weather information on the controller's display, and generating new 4D trajectories to avoid severe weather areas. This contribution presents the initial results of the assimilation of aforementioned observations into the WRF model, operated at cloud-resolving grid spacing, for two case studies: a hailstorm event occured on 11 May 2019 nearby Malpensa airport and a severe convection episode occurred near Punta Raisi airport (Palermo) on 15 July 2020.
Hydrogen gas bubble nucleation from corrosion of steel in compacted bentonite
Authors: Papafotiou Alexandros , Li Chao , Diomidis Nikitas , Leupin Olivier
Published: March 2021

The reference concept for the deep geological disposal of spent fuel and high-level radioactive waste in Switzerland foresees carbon steel disposal canisters surrounded by compacted bentonite buffer material. In support of performance assessments, long-term in-situ corrosion experiments were conducted in Opalinus Clay at the Mont Terri Underground Research Laboratory (URL) in Switzerland, wherein carbon steel coupons were embedded in MX-80 bentonite. The preparation of the steel specimens and bentonite, the exposure in a sealed borehole in the URL, and the retrieval, dismantling and imaging of specimens were conducted under strictly anoxic conditions. Samples were removed for analysis after exposure durations of 372, 628, 1024, and 2008 days. A key finding was the development of visible reddish-brown corrosion fronts around the metal surfaces and along shrinkage cracks that extend up to approximately 0.5 cm into the bentonite. Iron that originated from the corroded surface was transported along the cracks and precipitated as Fe-hydroxides due to oxygen sorbed on bentonite.

The formation of shrinkage cracks is thought to result from a local desaturation of the bentonite near the steel surface. To test this hypothesis i.e., to test the likelihood of a separate gas phase forming in addition to hydrogen mass dissolved in liquid water, it is necessary to evaluate the fate of hydrogen in the bentonite adjacent to the steel surface. For this, a flow and transport numerical model of the steel coupon surface and surrounding bentonite was implemented for the simulation of hydrogen release with the simultaneous consumption of water at the steel surface. The effect of single- and (potentially) two-phase flow with the diffusive and advective transport of the hydrogen and water components in the gas and liquid phases were modelled in a fully coupled manner. The numerical simulations were performed probabilistically in a Monte Carlo framework to account for parametric uncertainty, comprising 1’000 perturbations of all flow and transport parameters used in the model for the bentonite.

Overall, the simulation results are consistent with the hypothesis of a link between cracks observed in the bentonite and a temporary formation of a gas phase that results in preferential pathways for the transport of iron corrosion products.  The probability of gas formation in the model lies between 89% and 94% at the steel-bentonite interface and decreases significantly at distance of 1 cm from the steel coupon. Peak gas saturation at the steel-bentonite interface ranges up to approximately 1% with a mean value of approximately 0.18%. In all simulations, any gas phase forming in the bentonite dissolves back into the liquid phase within 300 days.
Longitudinal Survey Data Call For Diversifying Temporal Dynamics In Modelling Human-Water Systems
Authors: Mondino Elena , Scolobig Anna , Borga Marco , Di Baldassarre Giuliano
Published: March 2021

Numerous scholars have unravelled the complexities and underlying uncertainties of coupled human and water systems in various fields and disciplines. These complexities, however, are not always reflected in the way in which the dynamics of human-water systems are modelled. One reason is the lack of social data times series, that may be provided by longitudinal surveys. Here, we show the value of collecting longitudinal survey data to enrich sociohydrological modelling of flood risk. To illustrate, we compare and contrast two different approaches (repeated cross-sectional and panel) for collecting longitudinal data, and explore changes in flood risk awareness and preparedness in a municipality hit by a flash flood in 2018. We found that risk awareness has not changed significantly in the timeframe under study (one year). Perceived preparedness also did not change, but we observed differences related to damage severity. More precisely, preparedness increased only among those respondents who suffered low damages during the flood event. We also found gender differences across both approaches for most of the variables explored. Lastly, we argue that results that are consistent across the two approaches constitute robust data that can be used for the parametrisation of sociohydrological models. Moreover, we posit that there is a need to improve socio-demographic heterogeneity in modelling human-water systems in order to better support risk management.
Elaborating Hungarian segment of the Global Map of Salt-Affected Soils (GSSmap)
Authors: Szatmári Gábor , Bakacsi Zsófia , Laborczi Annamária , Petrik Ottó , Pataki Róbert , Tóth Tibor , Pásztor László
Published: March 2021

Recently, FAO and Global Soil Partnership (GSP) launched the Global Map of Salt-affected Soils (GSSmap) international initiative, which pursued a country-driven approach and aimed to update the global and country-level information on salt-affected soils (SAS). The objective of our study is to present how Hungary contributed to this international initiative by preparing its own SAS maps according to the GSSmap specifications. For this purpose, we used not just a combination of advanced machine learning and multivariate geostatistical techniques for predicting the spatial distribution of the selected SAS indicators (i.e., pH, electrical conductivity and exchangeable sodium percentage) for the topsoil (0–30 cm) and for the subsoil (30–100 cm), but also a number of image indices exploiting a huge amount of relevant information contained in Sentinel-2 satellite images. The importance plots of random forests showed that in addition to climatic, geomorphometric parameters and legacy soil information, image indices were the most important covariates. The performance of spatial modelling of SAS indicators was checked by 10-fold cross validation showing that the accuracy of the SAS maps was acceptable. By this study and by the resulting maps of it, we not just contributed to GSSmap, but also renewed the SAS mapping methodology in Hungary, where we paid special attention to modelling and quantifying the prediction uncertainty that had not been quantified or even taken into consideration earlier.

 

Acknowledgment: Our research was supported by the Hungarian National Research, Development and Innovation Office (NKFIH; K-131820 and K-124290) and by the Premium Postdoctoral Scholarship of the Hungarian Academy of Sciences (PREMIUM-2019-390) (Gábor Szatmári).
Estimating Surface Melt on the Larsen Ice Shelf Using a Deep Neural Network: Opportunities and Challenges
Authors: Hu Zhongyang , Kuipers Munneke Peter , Lhermitte Stef , Izeboud Maaike , van den Broeke Michiel
Published: March 2021

Presently, surface melt over Antarctica is estimated using climate modeling or remote sensing. However, accurately estimating surface melt remains challenging. Both climate modeling and remote sensing have limitations, particularly in the most crucial areas with intense surface melt.  The motivation of our study is to investigate the opportunities and challenges in improving the accuracy of surface melt estimation using a deep neural network. The trained deep neural network uses meteorological observations from automatic weather stations (AWS) and surface albedo observations from satellite imagery to improve surface melt simulations from the regional atmospheric climate model version 2.3p2 (RACMO2). Based on observations from three AWS at the Larsen B and C Ice Shelves, cross-validation shows a high accuracy (root mean square error = 0.898 mm.w.e.d−1, mean absolute error = 0.429 mm.w.e.d−1, and coefficient of determination = 0.958). The deep neural network also outperforms conventional machine learning models (e.g., random forest regression, XGBoost) and a shallow neural network. To compute surface melt for the entire Larsen Ice Shelf, the deep neural network is applied to RACMO2 simulations. The resulting, corrected surface melt shows a better correlation with the AWS observations in AWS 14 and 17, but not in AWS 18. Also, the spatial pattern of the surface melt is improved compared to the original RACMO2 simulation. A possible explanation for the mismatch at AWS 18 is its complex geophysical setting. Even though our study shows an opportunity to improve surface melt simulations using a deep neural network, further study is needed to refine the method, especially for complicated, heterogeneous terrain.
Combining LIDAR-derived Digital Terrain Indices and Machine Learning, for High Resolution National-scale Soil Moisture Mapping of the Swedish Forest Landscape.
Authors: Ågren Anneli M. , Larson Johannes , Paul Siddhartho S. , Laudon Hjalmar , Lidberg William
Published: March 2021

To meet the sustainable development goals and enable protection of surface waters, there is a strong need to plan and align forest management with the needs of the environment. The number one tool to succeed in sustainable spatial planning is accurate and detailed maps. High resolution soil moisture mapping over spatial large extent remains a consistent challenge despite its substantial value in practical forestry and land management. Here we present a novel technique combining LIDAR-derived terrain indices and machine learning to model soil moisture at 2 m spatial resolution across the Swedish forest landscape with high accuracy. We used field data from about 20,000 sites across Sweden to train and evaluate multiple machine learning (ML) models. The predictor features included a suite of terrain indices generated from national LIDAR digital elevation model and other ancillary environmental features, including surficial geology, climate, land use information, allowing for adjustment of soil moisture maps to regional/local conditions. In our analysis, extreme gradient boosting (XGBoost) outperformed the other tested ML methods (Kappa = 0.69, MCC= 0.68), namely Artificial Neural Network, Random Forest, Support Vector Machine, and Naïve Bayes classification. The depth to water index, topographic wetness index, and wetlands derived from Swedish property maps were the most important predictors for all models. With the presented technique, it was possible to generate a multiclass model with 3 classes with Kappa and MCC of 0.58. Besides the classified moisture maps, we also investigated the potential of producing a continuous map from dry to wet soils. We argue that the probability of a pixel being classified as wet from the 2-class model can be used as an index of soil moisture from 0% – dry to 100% – wet and that such maps hold more valuable information for practical forest management than classified maps.

The soil moisture map was developed to support the need for land use management optimization by incorporating landscape sensitivity and hydrological connectivity into a framework that promotes the protection of soil and water quality. The soil moisture map can be used to address fundamental considerations, such as;

(i) locating areas where different land use practices can be conducted with minimal impacts on water quality;

(ii) guiding the construction of vital infrastructure in high flood risk areas;

(iii) designing riparian protection zones to optimize the protection of water quality and biodiversity.
Management of groundwater sustainability and contamination - a Mozambique case study
Authors: Antunes Isabel Margarida Horta , Bande Ameno
Published: March 2021

Groundwater is vulnerable to contamination from natural and anthropogenic activities. The agricultural and human activities associated with hydrological characteristics influence the quality of groundwater. The City of Tete is in the Nharthanda Valley (Zambezi River, Central Mozambique). The city faces a set of serious structural issues of access to water such as a precarious public water supply system, including a lack of network management, water rationing, and a poor sewerage system. Groundwater is collected from the aquifer for the public water supply system of the old city of Tete and a for a traditional agro-livestock farm, which is irrigated by artesian wells. Groundwater abstraction has increased in the last few decades, and it was identified as a risk for groundwater quality and quantity. Groundwater physic-chemical and microbiological parameters obtained from fifteen boreholes and eleven wells have been determined to assess water quality. The presence of potential contaminant activities throughout the Nhartanda Valley and adjacent areas associated with contamination of the Zambezi River contribute to the degradation of water quality. The high vulnerability index for most chemical and microbiological elements indicates that groundwater is easily reached by bacteria and viruses and other potentially toxic substances. Most of the water parameters, from wells and boreholes, exceed the water referenced values allowed for human consumption and agricultural use. The protection of the Nhartanda Valley aquifer system is necessary and urgent. The identification of the most vulnerable areas provides important information for groundwater management, such as the indication of protection measures in aquifer systems.
A regime perspective on jet and blocking dynamics in CMIP6
Authors: Dorrington Joshua
Published: March 2021

Weather over the Euro-Atlantic region during winter is highly variable, with rich and chaotic internal atmospheric dynamics. In particular, the non-linear breaking of Rossby waves irreversibly mixes potential vorticity contours and so triggers shifts in the latitude of the eddy driven jet and establishes persistent anticyclonic blocking events. The concept of atmospheric regimes captures the tendency for blocks – and for the jet – to persist in a small number of preferred locations. Regimes then provide a non-linear basis through which model deficiencies, interdecadal variability and forced trends in the Euro-Atlantic circulation can be studied.

A drawback of past regime approaches is that they were unable to easily capture both the dynamics of the jet and of blocking anticyclones simultaneously. In this work we apply a recently developed regime framework, which is able to capture both these important aspects while reducing sampling variability, to the CMIP6 climate model ensemble. We analyse both the historical variability and biases of blocking and jet structure in this latest generation of climate models, and make new estimates of the anthropogenic forced trend over the coming century.

 
Ecological Consequences of a Millennium of Introduced Dogs on Madagascar
Authors: Hixon Sean , Douglass Kristina , Godfrey Laurie , Eccles Laurie , Crowley Brooke , Rakotozafy Lucien , Clark Geoffrey , Haberle Simon , Anderson Atholl , Wright Henry , Kennett Douglas
Published: March 2021

Introduced predators currently threaten endemic animals on Madagascar through predation, facilitation of human-led hunts, competition, and disease transmission, but the antiquity and past consequences of these introductions are poorly known. We use radiocarbon and stable carbon and nitrogen isotope data from the bone collagen of introduced dogs (Canis familiaris) and endemic fosa (Cryptoprocta spp.) in central and southern Madagascar to test for competition between introduced and endemic predators. Isotopic evidence indicates little overlap in diet between ancient dogs and fosa in these regions but leaves open the possibility that dogs competitively exclude fosa. Radiocarbon dates confirm that dogs have been present on Madagascar for at least a millennium and suggest that they briefly co-occurred with the island’s extinct megafauna, which included giant lemurs, elephant birds, and pygmy hippopotamuses. Dogs share a mutualism with pastoralists who also at least occasionally hunt, and this is reflected in deposits at several Malagasy paleontological sites that contain dog and livestock bones along with butchered bones of extinct megafauna and extant lemurs. Dogs on Madagascar have had a wide range of diets during the past millennium, but relatively high stable carbon isotope values suggest few individuals relied primarily on forest bushmeat. The absence of distinct dietary differences between dogs from archaeological and paleontological sites may reflect the absence of discrete feral populations. Our data suggest that dogs were part of a suite of animal introductions beginning over a millennium ago that coincided with widespread landscape transformation and megafaunal extinction.
River Breezes in the Central Amazon: Cluster Analysis of Meteorological and Chemical Data Sets Collected by an Unmanned Aerial Vehicle
Authors: Zhao Tianning , Ye Jianhuai , Ribeiro Igor , Ma Yongjing , Hung Hui-Ming , Batista Carla , Stewart Matthew , dos Santos Silva Jessica , Godoi Ricardo , Vilà-Guerau de Arellano Jordi , de Souza Rodrigo , Martin Scot
Published: March 2021

Local atmospheric circulation induced by wide rivers in Amazonia can strongly affect the transport of urban, industrial, fire, and forest emissions. Herein, a copter-type unmanned aerial vehicle (UAV) operated from a boat was used to collect vertical profiles of meteorological parameters and chemical concentrations during Sep-Oct 2019 of the dry season. Sensor packages mounted on the UAV measured wind speed and direction together with concentrations of carbon monoxide (CO) and total oxidants (Ox, defined as O3 + NO2). Multivariate statistical analysis identified distinguishing patterns for meteorological variables. The occurrence of river breeze circulations was linked to meteorological conditions from in-situ measurement and satellite images. Vertical profiles of chemical concentrations both from in-situ measurements and large eddy simulations confirmed that under some conditions a river breeze can facilitate pollutant mixing perpendicular to the river orientation. The results of this study advance an urgent need to quantify the occurrence and the properties of river breeze circulations in respect to microscale chemical dispersion, air quality, and human health.
Implications of the urban heat island and global climate change and nutritional status on the human thermal comfort in Mexico City
Authors: Barradas Victor L , Ballinas Monica
Published: March 2021

The urban heat island (UHI) is mostly due to urbanization and it is considered as a nocturnal phenomenon, but it also appears during the day in Mexico City. The UHI in concert with the high temperatures caused by global climate change (CC) may profoundly affect human thermal comfort, which can influence human productivity and morbidity in the spring/summer period. Obesity is a disease manifested by the accumulation of excess body fat with implications for the health of people, and Mexico ranks first in overweight and obesity, where 30% of the population has obesity and near 40% is overweight. The main objective of this investigation was to determine the changes in the degree of thermal comfort of Mexico City inhabitants according to their nutritional status, because of the increase in temperatures due UHI and CC. A series of microclimatological measurements to estimate the physiologically equivalent temperature (PET) were made. Concomitantly, a series of surveys of thermal perception were applied to 1300 passersby. The results show that PET has increased from 1990 to 2010 from 0.0372 °C/year to 0.0887 °C/year in the study sites, besides overestimating the degree of thermal comfort of people with normal weight but underestimating that of overweight and obese people according to the stablished categories or classes. It is concluded that it is imperative that people with overweight and obesity reduce their weight but also should be investigated that influences the unbalanced consumption of food. It is also imperative to mitigate UHI and CC through urban architectural techniques.