bluuebunny/crossref_metadata_2025 huggingface dataset:
Tides on a Snowball
Authors: Green Mattias , Davies Hannah , Duarte Joao , Creveling Jessica , Scotese Chris
Published: March 2021

The severe “Snowball Earth” glaciations proposed to have existed during the Cryogenian period (720 to 635 million years ago) coincided with the breakup of one supercontinent (Rodinia) and assembly of another (Pannotia). The presence of extensive continental ice sheets should theoretically lead to a tidally energetic Snowball ocean due to the reduced ocean depth, as was the case during the last glaciations, but the theory of the supertidal cycle suggests that the supercontinent paleogeography should lead to weak tides because the surrounding ocean is too large to host tidal resonances. So which theory is correct? Using an established numerical global tidal model and 22 paleogeographic reconstructions spanning 750-600Ma, we show that the Cryogenian ocean hosted diminished tidal amplitudes and associated energy dissipation rates, reaching 10-50% of today’s rates, during the Snowball glaciations. In contrast, the tides were more energetic during the ice-free periods, and we propose that the near-absence of Cryogenian tidal processes may have been one contributor to the prolonged glaciations if these were near-global. These results also constrain lunar distance and orbital evolution throughout the Cryogenian and highlight that simulations of past oceans should include explicit tidally driven mixing processes.
Orogen scale shear zone development in partially Variscan molten crust. The critical role of water-present melting in metagranite inducing strain localization.
Authors: Vanardois Jonas , Trap Pierre , Marquer Didier
Published: March 2021

The causes for heterogeneous deformation with strain partitioning into kilometre-scale shear zone within the partially molten crust and the spatiotemporal feedback relationships between strain localization and melt organization still remain unclear. In order to tackle these questions and unravel the strain localization in a partially molten crustal scale shear zone, we used field observations and thermodynamic modelling in the Eastern Variscan Shear Zone (EVSZ) located in the Aiguille-Rouge massif (Western Alps). The EVSZ is an orogen scale, 10 km wide and 600 km long, transpressional high strain corridor recognized in the French External Crystalline Massifs. The EVSZ affected the partially-molten late Variscan crust during late Carboniferous times (340-300 Ma). In this contribution we present a detailed field-map survey of the mid- and lower crusts focussed on the partitioning and strain pattern in the Aiguille-Rouge EVSZ. Detailed mapping revealed that high-strain deformation domains and orthogneiss occurrences are spatially related. New petrological, thermobarometrical and LA-ICP-MS dating also better constrain the P-T-t-D evolution of the partially molten crust along the EVSZ. Field observations and P-T pseudosection calculations show that among the three dominant lithologies forming the mid- and lower-crusts, i.e. metapelite, metagreywacke and orthogneiss, the latter is the most fertile if considering H2O-fluid-saturated melting. During prograde evolution at pressure between-12-15 kbar, orthogneisses reached the solidus at lower temperature and produced higher melt fraction than the metasedimentary rocks.  The water-present melting in the orthogneisses may have initiate strain localization at the end of the prograde evolution. Thus, the favoured localization of the shear zone within the metagranites is explained by a higher melt fraction than in the metapelites and metagreywackes. PTDt path and thermobarometrical modelling suggest that these transpressional deformation conditions occurred under suprasolidus conditions from at least 12 kbar to 4 kbar during a near isothermal decompression. During this cooling path, while crystallization of anatectic melts might have provoked strain hardening in the orthogneisses, a strength decrease might be controlled by a higher proportion of micas in metapelites and metagreywackes as suggested by forward modelling of modal proportion of mica. This change in the nature of the weakest phase, starting with melt in metagranites and followed by micas in metasedimentary rocks, seems to control the progressive localization and broadening of the crustal scale shear zone during clockwise P-T-t path. Our results suggest that H2O-fluid-saturated melting of metagranites has a first order rheological impact on the birth and growth of the orogen scale shear zone in the lower continental crust.
An assessment of basal melting parameterisations for Antarctic ice shelves
Authors: Burgard Clara , Jourdain Nicolas
Published: March 2021

Ocean-induced melting at the base of ice shelves is one of the main drivers of the currently observed mass loss of the Antarctic Ice Sheet. A good understanding of the interaction between ice and ocean at the base of the ice shelves is therefore crucial to understand and project the Antarctic contribution to global sea-level rise. 

Due to the high difficulty to monitor these regions, our understanding of the processes at work beneath ice shelves is limited. Still, several parameterisations of varying complexity have been developed in past decades to describe the ocean-induced sub-shelf melting. These parameterisations can be implemented into standalone ice-sheet models, for example when conducting long-term projections forced with climate model output.

An assessment of the performance of these parameterisations was conducted in an idealised setup (Favier et al, 2019). However, the application of the better-performing parameterisations in a more realistic setup (e.g. Jourdain et al., 2020) has shown that individual adjustments and corrections are needed for each ice shelf.

In this study, we revisit the assessment of the parameterisations, this time in a more realistic setup than previous studies. To do so, we apply the different parameterisations on several ice shelves around Antarctica and compare the resulting melt rates to satellite and oceanographic estimates. Based on this comparison, we will refine the parameters and propose an approach to reduce uncertainties in long-term sub-shelf melting projections.

References
- Favier, L., Jourdain, N. C., Jenkins, A., Merino, N., Durand, G., Gagliardini, O., Gillet-Chaulet, F., and Mathiot, P.: Assessment of sub-shelf melting parameterisations using the ocean–ice-sheet coupled model NEMO(v3.6)–Elmer/Ice(v8.3) , Geosci. Model Dev., 12, 2255–2283, https://doi.org/10.5194/gmd-12-2255-2019, 2019. 
- Jourdain, N. C., Asay-Davis, X., Hattermann, T., Straneo, F., Seroussi, H., Little, C. M., and Nowicki, S.: A protocol for calculating basal melt rates in the ISMIP6 Antarctic ice sheet projections, The Cryosphere, 14, 3111–3134, https://doi.org/10.5194/tc-14-3111-2020, 2020. 
Using repeat oblique aerial photography and satellite imagery to detect glacial change in the Cordillera Vilcanota, Peru, since 1931
Authors: Kamp Ulrich , Yager Karina , Arnett Elise , Bowen Krysten , Truitt Kate , Seimon Anton , Seimon Tracie , Ivanoff Alvaro
Published: March 2021

Terrestrial and aerial image analysis has proven to be a valuable survey method for documenting terrestrial landscape change related to, for example, biodiversity, urbanization, and environmental services such as land vegetation or forest cover and use, glacier extent, and water resources. Historical oblique aerial photographs offer exceptional opportunities to extend the observational record beyond the period covered by traditional nadir aerial surveys and satellite imagery. Here we apply these methods in the Cordillera Vilcanota of Southern Peru, home to the largest high alpine lake, Sibinacocha, in the Andes, a primary source of the Amazon River. The Shippee-Johnson aerial expedition of 1931 produced oblique photographs of glaciated peaks of the Cordillera Vilcanota. To determine the extent of glacial loss, we compared the 1931 glacier extents with more recent ones derived from satellite imagery analyses using Agisoft Metashape and Pixcavator. The identification of the flight camera positions from 1931 proved to be challenging, since the original photographs come with only rudimentary information. For three test glaciers, the Metashape analysis showed a glacier recession of between 50% and 95% from 1931 to 2018. Preliminary Pixcavator analysis results demonstrated a area decrease of 62% at two glacier termini between 1931 and 2020. Future studies will include repeating the oblique aerial photographs across the Vilcanota and other Andean mountain ranges, and also include ground truth and UAS imagery analysis.
Impact of the choice of surface mass balance models and their calibration on large-scale glacier change projections
Authors: Schuster Lilian , Rounce David , Maussion Fabien
Published: March 2021

A recent large model intercomparison study (GlacierMIP) showed that differences between the glacier models is a dominant source of uncertainty for future glacier change projections, in particular in the first half of the century.  Each glacier model has their own unique set of process representations and climate forcing methodology, which makes it impossible to determine the model components that contribute most to the projection uncertainty. This study aims to improve our understanding of the sources of large scale glacier model uncertainty using the Open Global Glacier Model (OGGM), focussing on the surface mass balance (SMB) in a first step. We calibrate and run a set of interchangeable SMB model parameterizations (e.g. monthly vs. daily, constant vs. variable lapse rates, albedo, snowpack evolution and refreezing) under controlled boundary conditions. Based on ensemble approaches, we explore the influence of (i) the parameter calibration strategy and (ii) SMB model complexity on regional to global glacier change. These uncertainties are then put in relation to a qualitative selection of other model design choices, such as the forcing climate dataset and ice dynamics model parameters. 
The impact of global climate change on the characteristics of seasons in the Carpathian Basin
Authors: Dian Csenge , Pongrácz Rita , Bartholy Judit , Talamon Attila
Published: March 2021

Similarly to many other regions, warming and extreme weather conditions (e.g. related to temperature and precipitation) are expected to increase due to the effects of climate change in the Carpathian Basin during the 21st century. Consequently, as a result of the clearly detectable warming, the number of frost days in winter decreases and the summer heat waves become more frequent. The transition between winter and summer tends to become shorter and the inter-annual variability is likely to increase. The precise definition of the transition periods between the two extremes of the annual temperature course is very important for several disciplines, e.g. building energy design, where outdoor temperature is a key input to determine the beginning and end of heating and cooling periods. The aim of this research is to examine the possible transformation of the four seasons characteristics of the Carpathian Basin in details using various specific climate indexes (e.g. monthly percentiles, daily temperature fluctuation time series) based on the data of regional climate model simulations taking into account different future scenarios. For this purpose, RCP4.5 and RCP8.5 scenarios are compared to historical runs, and simulated temperature data series are analyzed for the middle and end of the century.
Soil salinity initiates a cascade of changes in soil biological communities and activities
Authors: Gasch Caley , Harmon Jason , DeSutter Thomas , Banerjee Samiran , Darby Brian , Tenuta Mario
Published: March 2021

Soils in the Northern Great Plains of North America can host high salt concentrations, resulting from geologic origin, and strongly tied to landscape climate and hydrology patterns. Salt concentrations in topsoil can be elevated with intensive management for row crop production. We know that high salt concentrations in topsoil directly impact plant productivity and crop yield; however, our investigations indicate that belowground communities and processes do not necessarily align with patterns of plant productivity. Multiple years of field surveys have revealed that communities and functions of saline soils are distinctly different than non-saline soils. As expected, soils within saline patches tend to have reduced structural development, higher water content, lower surface residues and organic matter incorporation, and elevated soil nutrient concentrations. Thus, the habitat for soil organisms is physically and chemically different than nearby non-saline soils. We have observed that these habitat changes are associated with shifts in soil biological communities (microbial groups, nematodes, arthropods, and earthworms) and their activities (greenhouse gas production and decomposition) in unexpected ways. While total microorganism abundance is fairly stable across the saline and non-saline soils, arthropod, nematode, and earthworm counts are reduced in saline soils. Due to the abundance of microbes, soil water, and labile nutrients in saline soils, we observed elevated greenhouse gas emissions in saline soils. Decomposition rates are stable across salinity levels, providing further evidence that saline soils are microbiologically active despite a paucity of plant production. Given that soil salinity occurs within a suite of soil conditions that influence soil functions, and that these shifts happen over short distances, salinity appears to be an important driver of spatial heterogeneity in soil properties. These observations have implications for intensive, targeted management for mitigating the agroecosystem impacts of salts.
Estimation of soil loss with RUSLE during a period of increasing rainfall erosivity (1997-2018) in two-contrasted Mediterranean watersheds (southern Spain).
Authors: Martinez-Murillo Juan F. , Sillero-Medina José A. , Ruiz-Sinoga José D.
Published: March 2021

During the last 25 years, an increasing rainfall erosivity occurred in South of Spain according to recent studies. This fact may rendered in an increment of the derived threatens from water erosion and, consequently, soil loss processes, one of the main geomorphic agent in that geographical area. This study deals with the application of RUSLE equation in two-contrasted Mediterranean mountainous watershed from 1997 to 2018. Both of them are characterised with very common ecogeomorphologic features from Mediterranean mountains but differs in the rainfall regime: one watershed shows an altitudinal gradient from dry-Mediterranean to subhumid Mediterranean climate, and the other one from semiarid to dry-Mediterranean climate.

From the methodological point of view, RULSE was applied but some modifications were introduced in its calculation: i) rainfall intensity calculated in 10-minutes instead of 30-minutes for Factor R; ii) vegetation cover estimated by means of NDVI for Factor C; and iii) validation using field inventory of soil surface components.

The results indicated differences between both watersheds given their different ecogeomorphologic conditions. The precision of using I10 let valuate better the soil loss estimation and its spatial and temporal variability. The validation with the soil surface components obtained better results in the rainiest watershed with more biotic ecogeomorphological conditions. This study is of great useful to detect priority areas to carry out revegetation plans to control erosion and floodings.
Evaluation of NO2, O3, PM10, and PM2.5 in the city of Buenos Aires, Argentina using WRF-Chem model
Authors: Lopez-Noreña Ana Isabel , Berná Lucas , Tames María Florencia , Millán Emmanuel , Puliafito Enrique , Fernandez Rafael Pedro
Published: March 2021

The online-coupled Weather Research and Forecasting model with Chemistry (WRF-Chem v4.0), was applied to evaluate the impact of using different anthropogenic emissions inventories on regional air quality in Argentina. For this purpose, we couple the Argentinian high-resolution emissions inventory (GEAA-AHRI) and the Emissions Database for Global Atmospheric Research – Hemispheric Transport of Air Pollution (EDGAR-HTAP) and introduce them into the model, with a local optimized configuration considering 3 nested domains with a horizontal grid size of 20 x 20 km, 4 x 4 km, and 1.3 x 1.3 km and the MOZART chemical scheme. The model output for NO2, PM10, PM2.5, and O3 concentrations over the innermost domain was compared against the existing surface and satellite-derived observations for the Buenos Aires Metropolitan Area (AMBA) during austral fall 2018. We found an overall good model performance for all simulations, and large discrepancies between the emission inventories, obtaining an improved urban-scale spatio-temporal representation when the high resolution GEAA-AHRI dataset is considered. Our results show that the daytime concentrations of air pollutants are strongly influenced by the shape and shift of the hourly emissions profile before sunrise and after sunset, especially for NO2 where the inclusion of the temporal profile decreased the mean bias by ~80%. Performance criteria for modeled PM10 and PM2.5 were in general satisfied, despite having an average underestimation of observations. When compared to NO2 tropospheric columns derived from TROPOMI, The general magnitude and spatial pattern of the NO2 tropospheric column is in agreement with the mean TROPOMI columns during the modeled period, obtaining correlation coefficients higher than 0.6 for all simulations. Our results highlight the benefits of using a time-dependent and high-resolution local inventory for addressing the background air quality in AMBA. The implementation and validation of local emissions and static fields with high spatial and temporal resolution carried out in this work, establishes a benchmark for forthcoming studies in other regions of South America where different modeling tools for air quality analysis are currently being used to complement the usually sparse and discontinuous air quality networks.
Class II post-peak behaviour of cementitious material in uniaxial compression
Authors: Wang Hongyu , Dyskin Arcady , Dight Phil , Paternak Elena
Published: March 2021

An experimental study of post-peak behaviour of rock models in uniaxial compression under different controlling methods is presented. A series of mortar samples with different compositions are firstly tested into post-peak stages using the axial strain control. In axial strain control, all types of mortar samples including pure cement samples have unavoidable sudden failure beyond the peak stress at different stages, and therefore only limited post-peak stress-strain curves can be captured. In order to capture the post-peak stress-strain curves beyond the sudden failure, a failure control method based on controlling the rate of lateral strain is proposed in this study. Using this method, post-peak stress-strain curves with positive modulus could be obtained for class II behaviour. The failure modes of the samples tested in both axial strain control and failure control show similarity. Also, the failure-controlled experiments indicate that despite the unstable fracture growth in the samples being considerable after peak stress, it may not lead to the uncontrolled sudden failure of the whole sample but could produce a class II stress-strain curve.
Effects of hydropeaking on groundwater mixing: from laboratory experiments to field scale observations
Authors: Basilio Hazas Mónica , Ziliotto Francesca , Marcolini Giorgia , Rolle Massimo , Chiogna Gabriele
Published: March 2021

Hydropeaking, an artificial flow regime consisting on strong and frequent river stage fluctuations, is known to have important effects on groundwater-surface water interaction. It influences the transient dynamics of water flow and also of solute and energy fluxes between aquifers and rivers. In this work, we focus on the effects of hydropeaking at multiple spatial and temporal scales. We start the investigation at the laboratory scale using quasi-two-dimensional flow-through experiments in which we can characterize  flow and transport mechanisms, as well as the topology of the flow field, at high spatial and temporal resolution. We measure and model the spatial moments, the dilution index and the Okubo-Weiss parameter of a transient plume, and find a correlation between changes in flow topology and mixing enhancement. We then investigate a two-dimensional field scale cross section representative of the Adige aquifer in North-East Italy, where two rivers differently affected by hydropeaking influence groundwater flow, and we investigate the system considering hourly and mean daily fluctuations in the river stage. We characterize the transient groundwater dynamics for this and for other aquifers affected by hydropeaking using the Townley number, analyzing the potentiality of such systems for chaotic advection. Finally, at regional scale we use a three-dimensional transient model to show how the Adige aquifer is differently affected by hydropeaking depending on dry and wet years. Moreover, we apply the continuous wavelet transform to identify the main temporal scales of variability detected in the groundwater fluctuations and how they change with time. Our work therefore highlights the relevance of the effect of hydropeaking on groundwater flow and transport processes, and its impact on flow topology and mixing enhancement at multiple spatial and temporal scales.
Characterizing and linking macropore structure characteristics to water infiltration in stony soils
Authors: Dai Cuiting , Zhou Yiwen , Li Zhaoxia , Wang Tianwei , Deng Jun
Published: March 2021

Macropores have been widely recognized as preferential pathways for the rapid movement of water into soils. The objectives of this study were to characterize soil macropore structures using X-ray computed tomography (CT) and to explore the relationships between macropore characteristics and hydraulic properties of stony soils. To achieve these, a total of 18 soil columns were sampled from six sites (three sites covered with grass and three sites with forest) with stony soils located in a mountain watershed in the Three Gorges Reservoir Area of Central China. Field infiltration experiments were carried out at the sampling sites under near-saturated conditions using a tension disc infiltrometer. The three-dimensional macropore structures were visualized from X-ray CT images, and total macroporosity, connected macroporosity, macropore density, specific surface area, degree of anisotropy, fractal dimension, and hydraulic radius were characterized. The results showed that the largest total macroporosity and connected macroporosity were observed at forest sites. The macropore structure with high connectivity could facilitate greater water infiltration into the soils. The near-saturated hydraulic conductivity Kh was significantly higher at the forest sites than at the grassland sites at four water pressure heads. The stony soils studied had heterogenous macropore systems with large and well-connected macropores. The macroporosity of macropores with equivalent diameters between 0.5 and 2 mm was found best to predict the near-saturated hydraulic conductivity. Our study provides a helpful technique for a better understanding of stony soil macropores and hydraulic properties by a combination of 3D visualization methods and traditional hydraulic analysis.
Fog forecasting for Schiphol airport at sub-kilometre scale.  
Authors: Steeneveld Gert-Jan , Knol Roosmarijn
Published: March 2021

Fog is a critical weather phenomenon for safety and operations in aviation. Unfortunately, the forecasting of radiation fog remains challenging due to the numerous physical processes that play a role and their complex interactions, in addition to the vertical and horizontal resolution of the numerical models. In this study we evaluate the performance of the Weather Research and Forecasting (WRF) model for a radiation fog event at Schiphol Amsterdam Airport (The Netherlands) and further develop the model towards a 100 m grid spacing. Hence we introduce high resolution land use and land elevation data. In addition we study the role of gravitational droplet settling, advection of TKE, top-down diffusion caused by strong radiative cooling at the fog top. Finally the impact of heat released by the terminal areas on the fog formation is studied. The model outcomes are evaluated against 1-min weather observations near multiple runways at the airport.

Overall we find the WRF model shows an reasonable timing of the fog onset and is well able to reproduce the visibility and meteorological conditions as observed during the case study. The model appears to be relatively insensitive to the activation of the individual physical processes. An increased spatial resolution to 100 m generally results in a better timing of the fog onset differences up to three hours, though not for all runways. The effect of the refined landuse dominates over the effect of refined elevation data. The modelled fog dissipation systematically occurs 3-4 h hours too early, regardless of physical processes or spatial resolution. Finally, the introduction of heat from terminal buildings delays the fog onset with a maximum of two hours, an overestimated visibility of 100-200 m and a decrease of the LWC with 0.10-0.15 g/kg compared to the reference.
Local-scale secondary water resources modulate seasonal water limitation across Africa
Authors: Küçük Çağlar , Koirala Sujan , Carvalhais Nuno , Miralles Diego G. , Reichstein Markus , Jung Martin
Published: March 2021

Drylands contribute strongly to global biogeochemical cycles and their variability. While precipitation is the main driver of plant water availability, secondary water resources like shallow groundwater and lateral convergence of soil moisture may play important roles in supporting ecosystems against water limitation at the local scale. Despite their strong relevance, the effects of secondary water resources are often ignored or highly uncertain in studies over large spatial domains. 

Here, we aimed to quantify the degree to which land properties control secondary water resources over water-limited regions in Africa. To do so, we first detected the seasonal decay periods of Fractional Vegetation Cover (FVC) time series from the changes in FVC over time at daily temporal resolution. FVC data is provided by the EUMETSAT from the image acquisitions from the geostationary satellite MSG. We then calculated the seasonal decay rate of FVC (λ) and used it with other climate, land and vegetation properties at 5 km spatial resolution. We hypothesized that any secondary water resource should slow down vegetation decays in drylands. We used gradient boosting machine learning to model λ and constrained the model according to the hypothesis. Finally, we used Shapley additive explanations in order to quantify the effects of land properties on spatial variation of the modelled λ.

Model output (NSE = 0.55) revealed that over drylands of Africa, ∼1/3 of spatial variation of λ is attributed to land properties, half of which is attributed to direct land effects while the rest is attributed to the land interactions with climate and vegetation. Though at local scales, this attribution gets much stronger over hotspots with strong secondary water resources, i.e., shallow groundwater. Spatially, land attributed variations of λ show that vegetation decays slower in regions with shallow groundwater and faster in regions where land surface is disconnected from the groundwater. Topographic complexity is another important factor, with slower vegetation decay in complex terrain, likely due to enhanced lateral moisture convergence. Moreover, these responses intensify with increasing climatological water limitation. 

We found strong effects of land parameters on seasonal vegetation decay rate, spatially structured but at local scales. This highlights the importance of local scale processes affecting water availability in drylands not only at local but also continental to global scales and shows the need of bridging processes across spatial scales in regional-to-global hydrological and vegetation models.
On thin ice: contrasting responses of woody NPP to permafrost thaw
Authors: Kulawska Aleksandra , MacKenzie Angus Robert , Kettridge Nicholas , Ullah Sami , A. M. Pugh Thomas
Published: March 2021

Boreal forests are located at latitudes that are predicted to experience some of the greatest warming on the planet. Forests growing on permafrost may be particularly vulnerable, with accelerated soil warming and permafrost degradation linked to changes in woody net primary productivity (NPPw). Recent evidence suggests that the responses of NPPw to permafrost thaw are mixed, with both increases and decreases in productivity observed following the onset of permafrost degradation. What determines these contrasting responses is currently poorly understood. This leads to uncertainties in predicting the future vegetation and carbon dynamics in permafrost regions, which propagate to climate projections in Earth System Models. Here, we propose a framework, and a set of hypotheses to explain the observed differences in the response of NPPw to permafrost thaw. We argue that the relationship between permafrost thaw and NPPw is non-linear and determined by a set of climatic and environmental variables. On this basis, we partition ecosystems into classes, and describe their relationships between permafrost thaw and NPPw.
Bayesian improvements to 210Pb dating
Authors: Blaauw Maarten , Aquino-Lopez Marco , Christen J. Andrés
Published: March 2021

Dating with 210Pb has been instrumental in providing chronologies for sedimentary deposits back to around 100-150 years ago — a key period for recent environmental events such as increased pollution caused by industry developments. However, currently available 210Pb age-models often disagree with and/or cannot incorporate other types of dates, depend highly on the correct estimation of background 210Pb, often underestimate uncertainties and are limited by unrealistic assumptions of sediment accumulation over time. Plum is open-source Bayesian age-modelling software that solves the above problems. It can integrate other dates, produce realistic uncertainty estimates, and extend 210Pb chronologies several decades further back in time. Our method thus enables much more robust chronologies for studies of recent environmental change.
Estimation of Bed Material Load using Artificial Intelligence Techniques
Authors: Rathod Laxman , Barman Bandita , Kumar Bimlesh
Published: March 2021

Estimation of sediment transport has significant implementation on water resources and hydraulic engineering. Transport of sediment is affected by flow and sediment properties and also climatic variation of the region. To examine the behaviour of sediment transport, wide range of experiments have been performed in laboratories. Most of the developed sediment transport formulations are empirical or semi empirical in nature. These days, the development of computer-aided programs such as MATLAB has opened the way for researchers to quickly study the generation mechanism. The “Artificial Neural Networks (ANN) and Adaptive Neuro-Fuzzy Inference System (ANFIS)” can be used widely for developing sediment model. In this research, Feed Forward Back Propagation (FFBP) sort of ANN and Hybrid type based on the Sugeno approach of ANFIS is used to develop a model for bed material load transport using parameters like “channel discharge, width of the channel, flow depth,  friction/energy slope, mean size of sediment, bed shear stress, critical shear stress, gradation coefficient of the sediment particles, specific gravity, and viscosity”. Subsequently, the relationship between the expected and observed values is presented. The proposed approach showed superior results based on various statistical parameters, like the coefficient of determination (R2), Nash-Sutcliffe coefficient (NSE), Root mean square error (RMSE) and Mean absolute error (MAE). Correlation (R2), higher than (~0.90) indicates that ANN and ANFIS are compatible and capable of measuring the total bed material load.

Keywords: Sediment transport, Bed material Load, ANFIS, ANN, FFBP
Microbial community structure and function prediction of two typical biocrusts in the Mu Us Sandland, Northwest China
Authors: Tian Chang , Xi Jiao , Ju Mengchen , Li Yahong , Guo Qi , Yao Le , Wang Chun , Lin Yanbin , Li Qiang , Williams Wendy J. , Bu Chongfeng
Published: March 2021

Biocrusts (Biological soil crusts) are a living ground cover widely distributed in arid and semi-arid regions worldwide and provide important ecological functions in ecosystems. As an important part of biocrusts, the microorganisms in the formation and succession of biocrusts should not be underestimated. However, the microbial processes among different types of biocrusts are poorly understood. We used high-throughput sequencing to identify soil bacteria and fungal community in two types of biocrusts, lichen crust and moss crust, in the Mu Us Sandland. The aims were to explore the composition, diversity, and ecological function of the microbial community in two types of biocrusts. Our study found that (1) The diversity of bacterial and fungal communities was significantly different between the two types of biocrusts. The Shannon index (6.18) of fungi in moss crust was higher than that (5.75) in lichen crust, and the operational taxonomic units of bacteria and fungi in moss crust were also higher than those in lichen crust by 3.22% and 30.61%, respectively. The bacteria and fungi community structure in two types of biocrusts were significantly different, while the differences were not significant. (2) In the microbiomes of lichen and moss biocrusts, Actinomycetes, Cyanobacteria, and Proteobacteria, the sum of which accounted for 68.01% in lichen crust and 59.88% in moss crust at operational taxonomic units level, were dominant phylum of bacteria, while the dominant phylum of fungi was mainly Ascomycota. Microcoleus (11.10%) and Exophiala (7.37%) were dominant genera in lichen crust, while the dominant genus in moss crust was RB41 (5.16%). (3) The pH, soil dissolved organic carbon, and soil organic carbon were the top three factors that correlated with both bacterial and fungal community structures. (4) The metabolic function of the bacterial community in two types of biocrusts was quite different. The relative abundances of metabolic pathways in moss crust, such as chemoheterotrophy, ureolysis, aromatic compound degradation, and nitrate reduction, were significantly higher than those in lichen crust, however, the relative abundances of cyanobacteria, oxygenic photoautotrophy, photoautotrophy, and phototrophy were significantly lower (ANOVA, P<0.05). Altogether, our study suggests that the biocrust types have significant effects on the pH, taxonomic, and metabolic diversity, providing a theoretical basis for improving the physicochemical properties of the surface soil in the desertification land ecosystem.
Investigation of the effect of stress states on hydro-mechanical behaviors of reservoir rock under fluid injection
Authors: Li Qi , He Miao , Kühn Michael , Li Xiaying , Xu Liang
Published: March 2021

Injecting fluid into the formation is an effective solution for improving the permeability and production of a target reservoir. The evaluation of economy and safety of injection process is a challenging issue faced in reservoir engineering [1-2]. As known, the relative magnitude and direction of the principal stresses significantly influence the hydro-mechanical behavior of reservoir rock during fluid injection. However, due to the limitations of current testing techniques, it is still difficult to comprehensively conduct laboratory injection tests under various stress conditions, e.g. triaxial extension stress states [3]. To this end, a series of numerical simulations were carried out on reservoir rock to study the hydro-mechanical changes under different stress states during fluid injection. In this modelling, the saturated rock is first loaded to the target stress state under drainage conditions, and then the stress state is maintained and water is injected from the top end to simulate the reservoir injection process. Particular attention is paid to the difference in hydro-mechanical changes under triaxial compression and extension stresses. This includes the difference of the pore pressure propagation, mean effective stress, volumetric strain, and stress-induced permeability. The numerical results demonstrate that the differential stress will significantly affect the hydro-mechanical behavior of target rock, but the degree of influence is different under the two triaxial stress states. The hydro-mechanical changes caused by the triaxial compression stress states are generally greater than that of extension, but the difference decreases with increasing differential stress, indicating that the increase of the differential stress will weaken the impact of the stress state on the hydro-mechanical response. This study can deepen our understanding of the stress-induced hydro-mechanical coupling process in reservoir injection engineering.

Keywords: Reservoir injection; Subsurface flow; Hydro-mechanical coupling; Stress state; Triaxial experiment modelling

[1] Li, X., Lei, X. & Li, Q. 2016. Injection-induced fracturing process in a tight sandstone under different saturation conditions. Environmental Earth Sciences, 75, 1466, http://doi.org/10.1007/s12665-016-6265-2

[2] Yang, D., Li, Q. & Zhang, L. 2016. Propagation of pore pressure diffusion waves in saturated dual-porosity media (II). Journal of Applied Physics, 119, 154901, http://doi.org/10.1063/1.4946832

[3] Xu, L., Li, Q., Myers, M., Tan, Y., He, M., Umeobi, H.I. & Li, X. 2021. The effects of porosity and permeability changes on simulated supercritical CO2 migration front in tight glutenite under different effective confining pressures from 1.5 MPa to 21.5 MPa. Greenhouse Gases: Science and Technology, http://doi.org/10.1002/ghg.2043
GOCE SGG filtering with FIR, IIR and wavelet MRA  
Authors: Pitenis Eleftherios A. , Mamagiannou Elisavet G. , Natsiopoulos Dimitrios A. , Vergos Georgios S. , Tziavos Ilias N.
Published: March 2021

GOCE Satellite Gravity Gradiometry (SGG) data have been widely used in gravity field research in order to provide improved representations of the gravity field spectrum either in the form of Global Geopotential Models (GGMs) or grids at satellite altitude. One of the key points in utilizing SGG observations is their proper filtering, in order to remove noise and long-wavelength correlated error, while the signals in the GOCE measurement bandwidth (MBW) should be preserved. Due to the gradiometer’s design, the GOCE satellite can achieve high accuracy and stable measurements in the MBW of 0.005 Hz to 0.1 Hz. The gravity gradient in MBW are at an equivalent accuracy level, while   are of lower accuracy. Outside of the MBW, systematic errors, colored noise, and noise with sharp peaks are observed, especially in the frequencies lower than 0.005 Hz. With that in mind, the present work focuses on the investigation of various filtering options ranging from Finite Impulse Response (FIR) filters, Infinite Impulse Response (IIR) filters, and filtering based on Wavelets. The latter are employed given their inherent characteristic of being localized both in frequency and space, meaning that the signal can be decomposed at different levels, thus allowing multi-resolution approximation (MRA). The analysis is performed with one month of GOCE SGG data in order to conclude on the method that provides the overall best results. SGG observations are reduced to a GGM in order to account for the long- and medium-wavelengths of the gravity field spectrum. Then, various filter orders are investigated for the FIR and IIR filters, while selective reconstruction is employed for the WL-MRA. Evaluation of the results is performed in terms of the smoothness of the filtered fields and the Power Spectral Density (PSD) functions of the entire GOCE tensor.
Future Scenarios of Modes of Euro-Atlantic Atmospheric Variability: A First Look at CMIP6 Multi-Model Ensemble Results
Authors: Cusinato Eleonora , Zanchettin Davide
Published: March 2021

Euro-Atlantic climate modes such as the North Atlantic Oscillation (NAO), the Eastern Atlantic pattern (EA), the Eastern Atlantic Western Russian pattern (EAWR) and the Scandinavian pattern (SCA) are known to significantly affect interannual-to-decadal climatic and hydroclimatic variability in the Euro-Mediterranean region. They are characterized by alternating positive and negative states of the associated index, each with specific climatic conditions that can last for several weeks or months and sometimes even years.

Knowing how these climate modes will be affected by future global warming conditions can help to constrain uncertainties in projections of Euro-Mediterranean regional climate variability.

In this contribution, we will present and discuss results from a CMIP6 multi-model analysis performed to investigate the presence of robust changes in these climate modes under the SSP585 future scenario of anthropogenic forcing  (fossil-fueled development with 8.5 W/m² forcing level). Toward this goal, we first search for a reliable box-based definition of an index for each of the abovementioned climate modes for the historical period and, then, perform a comparative assessment of the temporal, spectral and distributional properties of the so-defined indices during the historical (1850-2014) and future scenario (2014-2099) time periods, with a special focus on two interdecadal periods: 1960-1999 and 2060-2099. 

Early results show that there are significant changes in the future distributions of the climate modes with respect to the historical period, especially for what concerns the EA and the EAWR. 
TRACMASS 7.0 - A Lagrangian trajectory code for atmosphere and ocean sciences
Authors: Aldama Campino Aitor , Döös Kristofer , Berglund Sara , Dey Dipanjan , Kjellsson Joakim , Jönsson Bror
Published: March 2021

The latest version of the TRACMASS trajectory code, version 7.0 will be presented. The latest version includes several new features, e.g. water tracing in the atmosphere, generalisation of the tracer handling, and improvements to the numerical scheme. The code has also become more user friendly and easier to get started with. Previous versions of TRACMASS only allowed temperature, salinity and potential density to be calculated along the trajectories, but the new version allows any tracer to be followed e.g. biogeochemical tracers or chemical compounds in the atmosphere. 

TRACMASS calculates Lagrangian trajectories offline for both the ocean and atmosphere by using already stored velocity fields, and optionally tracer fields. The code supports most vertical coordinate systems, e.g. z-star, z-tilde, sigma, and hybrid sigma-pressure coordinates. Hence, TRACMASS supports a range of atmosphere and ocean models such as ECMWF IFS, NEMO, ROMS, MOM, as well as reanalysis products (e.g. ERA-5) or observations (e.g. geostrophic currents from AVISO satellite altimetry). The fact that the numerical scheme in TRACMASS is mass conserving allows us to associate each trajectory with a mass transport and calculate the Lagrangian mass transport between different regions as well as construct Lagrangian stream functions. 

A short course on how to set up, configure and run the TRACMASS code will be given separately, SC5.17.
Winter limnology: how do hydrodynamics and biogeochemistry shape ecosystems under ice?
Authors: Jansen Joachim , MacIntyre Sally , Barrett David , Chin Yu-Ping , Cortés Alicia , Forrest Alexander , Hrycik Allison , Martin Rosemary , McMeans Bailey , Rautio Milla , Schwefel Robert
Published: March 2021

The ice-covered period in lakes is increasingly recognized for its unique hydrodynamic and biogeochemical phenomena and ecological relevance yet it remains poorly studied compared to the ice-free season. Knowledge gaps exist where research areas – hydrodynamics, biogeochemistry and biology – intersect. For example, density-driven circulation under ice coincides with an expansion of the anoxic zone, but abiotic and biotic controls on oxygen depletion have not been disentangled. While heterotrophic microorganisms and migrating phytoplankton often thrive at the oxycline, the extent to which physical processes induce fluxes of heat and substrates that further support under-ice food webs is uncertain. Similarly, radiatively-driven convection under ice in spring can promote growth of motile phytoplankton or diatoms depending on flow velocity, water clarity and mixing depth, but links between functional trait selection, trophic transfer to zooplankton and fish and the prevalence of microbial versus classical food webs in seasonally ice-covered lakes remain unclear. Under-ice processes cascade into and from the ice-free season, and are relevant to annual cycling of energy and carbon through aquatic food webs. Understanding the coupling between state transitions and the reorganization of trophic hierarchies is essential for predicting complex ecosystem responses to climate change. In this presentation, we briefly review existing knowledge regarding physical processes in lakes in winter and the parallel developments in under-ice biogeochemistry and ecology. We then illustrate interactions between these processes, identify extant knowledge gaps whose solution requires interdisciplinary approaches, and present (novel) methods to address outstanding questions.
The urban fingerprint in the sea-breeze hodograph reveled by high resolution WRF simulations
Authors: Avisar David , Pelta Ran , Chudnovsky Alexandra , Rostkier-Edelstein Dorita
Published: March 2021

We implement and verify for the first time four Weather Research and Forecasting model urban configurations, focused on the coastal metropolitan area of Tel-Aviv (MTA) using updated land use and urban morphological maps. We analyze the mesoscale summertime flow and the urban canopy (UC) role in the occurrence of different hodograph dynamics observed within MTA at night. These events may be significant in air quality research. The four configurations – bulk (MM), single-layer (SLUCM), multi-layer (BEP), and BEP coupled with the building energy model (BEPBEM) – reproduce the observed diurnal temperature and wind cycles, with similar 10m wind direction bias and RMSE (15° and ~30°, respectively), with preference for MM and SLUCM at night. However, the SLUCM shows the lowest skill for the 10m wind speed (WS) (bias and RMSE 1ms-1), and the BEP shows the largest underestimation of the 2m temperature, ~-2.5°C. In the SLUCM, the WS increases over an UC and with increasing building heights. The simulations show that at night, a convergence line (CL) builds up with the urban heat island, downstream of the NW flow. West of the CL, the wind continues flowing from the sea, and rotates anti-clockwise to form a non-elliptical sea-breeze hodograph. Removing MTA UC restores an elliptical hodograph. East of the CL, the UC supports an elliptical hodograph with a clockwise rotation through the NE sector, previously reported as dynamically unstable. We expect such wind hodograph dynamics within similar coastal metropolitan areas.