bluuebunny/crossref_metadata_2025 huggingface dataset:
Unprecedented Expansion of the Azores High due to Anthropogenic Climate Change
Authors: Cresswell-Clay Nathaniel , Ummenhofer Caroline C. , Thatcher Diana L. , Wanamaker Alan D. , Denniston Rhawn F.
Published: March 2020

The Azores High is a subtropical high-pressure ridge in the North Atlantic. During boreal winters, anticyclonic winds rotate around the Azores High, transporting moisture to Western Europe. Variability in the size and intensity of the Azores High thus corresponds to variability in hydroclimate across Western Europe. We use the Last Millennium Ensemble (LME), which is run using the Community Earth System Model (CESM) and features thirteen transient simulations covering the period 850 to 2005 A.D. with prescribed external forcing (e.g. greenhouse gas, solar, volcanic, land use, orbital, and aerosol). The LME is shown to accurately simulate the variability and trends in the Azores High when compared to observational records from the 20th century. The Azores High has grown in size during the Industrial Era. This growth is most dramatic when observing the frequency of winters during which the Azores High is extremely large. The LME shows more winters with an extremely large Azores High in the past 100 years than any other 100-year period in the last millennium. Using LME as well as other simulations from the Paleoclimate Modelling Intercomparison Project Phase III, the recent expansion of the Azores High is shown to be well outside the range of natural variability since 850 A.D. Individual forcing simulations within the LME provide smaller ensembles in which only one external forcing is varied. These experiments attribute Azores High expansion to the recent increase in atmospheric greenhouse gas concentrations. Recent hydroclimatic signals across Western Europe consistent with the Azores High variability are also discussed.
Variational Probabilistic Tomography
Authors: Curtis Andrew , Zhang Xin
Published: March 2020

Seismic Tomography is a method to image the interior of solid media, and is often used to map properties in the subsurface of the Earth. In order to better interpret the resulting images it is important to assess imaging uncertainties. Since tomography is significantly nonlinear, Monte Carlo sampling methods are often used for this purpose but the ‘curse of dimensionality’ generally makes them computationally intractable for large data sets and high-dimensional parameter spaces. To extend uncertainty analysis to larger systems we introduce variational inference methods to conduct seismic tomography. In contrast to Monte Carlo stochastic sampling, variational methods solve the Bayesian inference problem as an optimization problem, yet still provide probabilistic results.

We apply variational inference to solve two types of tomographic problems using synthetic and real data: travel time tomography and full waveform inversion. We test two different variational methods: automatic differential variational inference (ADVI) and Stein variational gradient descent (SVGD). In each case we compare the results to solutions given by a variety of Monte Carlo methods.

In the travel time tomography example we show that ADVI provides a robust mean velocity model but biased uncertainties due to an implicit Gaussian approximation, and that it cannot be used to find multi-modal Bayesian posterior probability distributions. SVGD produces an accurate match to the fully probabilistic results of Markov chain Monte Carlo analysis, but at significantly reduced computational cost – provided that gradients of model parameters with respect to data can be calculated efficiently.

In our waveform inversion example, the SVGD method produces results of similar quality to published results from an efficient Hamiltonian Monte Carlo analysis, at around the same cost. However, that particular Monte Carlo method has significant ‘hidden’ costs: these are necessarily incurred by running a substantial number of pre-run tests to determine suitable settings of run-time parameters, and are not generally included in quoted cost estimates. By contrast, SVGD has relatively low pre-run costs. In addition, SVGD is significantly easier to parallelize, and for very large problems can be run in minibatch mode; this is impossible for Monte Carlo methods without incurring probabilistic errors as so-called ‘detailed balance’ can not be maintained in minibatch Hamiltonian Monte Carlo. We therefore contend that the variational method may have greater potential to extend probabilistic analysis to higher dimensional tomographic systems than current Monte Carlo methods.

 
Why should we care about Carrying Capacity? A novel screening tool for the health risk in recreational waters near estuary
Authors: Galešić Morena , Di Dato Mariaines , Andričević Roko
Published: March 2020

The present work proposes a novel screening tool to improve the quality of recreational coastal water. Indeed, the recreational potential of beach resort depends on its health status, which in marine cities may be threatened by increasing stress produced by anthropogenic activity. In particular, we focus on the beach near an estuary, which may be affected by a considerable load of contaminants, especially when the urban sewage system is combined and designed to spill untreated wastewater directly in the coastal water. In a few words, when the Combined Sewer Overflows (CSOs) are activated, the bacterial concentration in the estuary increases, thereby resulting in a potential hazard for the swimmers’ health. In the present work, the bacterial transport is modelled through a physically-based stochastic framework, whereas the human health risk is evaluated by means of the Quantitative Microbial Risk Assessment (QMRA). As the human health risk is quantified, it is used to evaluate the Carrying Capacity indicator of the recreational coastal water. This indicator is defined as the number of swimmers that can be sustained by coastal water with an acceptable risk threshold. The results indicate that the Carrying Capacity increases by dilution processes and by reduction of the source concentration. This indicator may be viewed as a screening tool for policy-makers and other stakeholders. For instance, it can help to balance the resources needed to improve the sewage-system and the benefits coming from tourism and sustainable environmental policies, given that the beach quality, in turn, depends on the improvements in the sewage system.
A general methodology for beached oil spill hazard mapping and its application to the Atlantic basin coasts
Authors: Pinardi Nadia , Sepp-Neves Augusto , Trotta Francesco , Navarra Antonio
Published: March 2020

The current lack of a standardized approach to compute the coastal oil spill hazard due to maritime traffic accidental releases has hindered an accurate estimate of its global impact, which is paramount to manage and intercompare the associated risks. We propose here a hazard estimation approach that is based on ensemble simulations and the extraction of the relevant frequency distributions. We demonstrate that both open ocean and beached oil concentration distributions fit a Weibull curve, a two-parameter fat-tail probability distribution function. The simulation experiments are carried out in all the coastal areas of the Atlantic ocean basin. An indicator that quantify the coastal oil spill hazard is proposed and applied to the study areas.
An analytical model concerning the possible initiation of subduction between the India and Africa plates, caused by the Morondova plume
Authors: Steinberger Bernhard , van Hinsbergen Douwe
Published: March 2020

Identifying the geodynamic processes that trigger the formation of new subduction zones is key to understand what keeps the plate tectonic cycle going, and how plate tectonics once started. Here we discuss the possibility of plume-induced subduction initiation. Previously, our numerical modeling revealed that mantle upwelling and radial push induced by plume rise may trigger plate motion change, and plate divergence as much as 15-20 My prior to LIP eruption. Here we show that, depending on the geometry of plates, the distribution of cratonic keels and where the plume rises, it may also cause a plate rotation around a pole that is located close to the same plate boundary where the plume head impinges: If that occurs near one end of the plate boundary, an Euler pole of the rotation may form along that plate boundary, with extension on one side, and convergence on the other.  This concept is applied to the India-Africa plate boundary and the Morondova plume, which erupted around 90 Ma, but may have influenced plate motions as early as 105-110 Ma. If there is negligible friction, i.e. there is a pre-existing weak plate boundary, we estimate that the total amount of convergence generated in the northern part of the India-Africa plate boundary can exceed 100 km, which is widely thought to be sufficient to initiate forced, self-sustaining subduction. This may especially occur if the India continental craton acts like an “anchor” causing a comparatively southern location of the rotation pole of the India plate. Geology and paleomagnetism-based reconstructions of subduction initiation below ophiolites from Pakistan, through Oman, to the eastern Mediterranean reveal that E-W convergence around 105 Ma caused forced subduction initiation, and we tentatively postulate that this is triggered by Morondova plume head rise. Whether the timing of this convergence is appropriate to match observations on subduction initiation as early as 105 Ma depends on the timing of plume head arrival, which may predate eruption of the earliest volcanics. It also depends on whether a plume head already can exert substantial torque on the plate while it is still rising – for example, if the plate is coupled to the induced mantle flow by a thick craton.
Sustainable management of groundwater for mitigation of declining water tables in the Mid-South United States: challenges and potential solutions
Authors: Feng Gary , Han Yiwen , Ouyang Ying , Jing Wei
Published: March 2020

Long-term unsustainable use or overexploitation of groundwater resource have led to different degree of water table declining from arid to even humid regions across the globe. The Lower Mississippi River alluvial plain (refers to MS Delta) in subtropical humid Mississippi state, is a watershed where groundwater level has declined the most in the United States. It is even worse than any states and watersheds in the arid and semiarid regions such as Mid-West and western USA. Approximately 35 million cubic meter per day of water from the alluvial aquifer in MS Delta are withdrawn for irrigation, as a result, groundwater level has declined > 6.5 m since 1970, which threaten the sustainability of irrigated agriculture in this region. Surface water as an alternative irrigation source must be taken for sustainability of irrigated agriculture in the region. The objectives of the study were to: 1) determine the total amount of available surface water resources and its temporal and spatial variation in MS Delta; 2) simulate groundwater recharge as affected by ET based and soil moisture based full irrigation schemes using all groundwater and different percentages of surface and ground water. The coupled SWAT (Soil and Water Assessment Tool)-MODFLOW (Finite Difference groundwater model) was employed. Mean annual rainfall is 1290 mm, only 31%, 40%, and 34% of annual rainfall occurred in growing season of soybean, corn and cotton, respectively. Irrigation was required in all but 12 out of 100 years in the humid region. It was estimated that each of the three major crops required irrigation of 200 mm every year over the 100-year period. 180 billion cubic meter of ground water is required each year if all of those croplands are irrigated. The average loss of groundwater was about 5 billion cubic meter every year from 1987 to 2014 in MS Delta. There is about 0.1 million ha of surface water in the MS Delta. If only 19% of those water is used for irrigation, at least 37% of groundwater can be saved in the region. Simulation estimated that the annual available stream and pond water is 11 billion cubic meter. The amounts of weekly groundwater use for irrigation that could be replaced by surface water were 46% in May, 23% in June, 21% in July, 35% in August, and 56% in September. Results revealed that the groundwater storage was decreased by 26 cm/month due to conventional irrigation in crop season. It is promising that the groundwater storage was increased by 23 cm/month, sometimes even 60 cm/month in the crop non-growing season by recharge from rainfall. The model’s simulated results suggest that using either ET or soil moisture based groundwater irrigation scheduling, along with the conjunctive use of surface water, could be a sustainable groundwater management practice in the MS Delta.
A Triassic-Jurassic westward scissor-like subduction history of the Mudanjiang Ocean and amalgamation of the Jiamusi Block in NE China: Constraints from whole-rock geochemistry and zircon U-Pb and Lu-Hf isotopes of the Zhangguangcai Range granitoids
Authors: Ge Maohui , Zhang Jinjiang , Li Long , Liu Kai
Published: March 2020

NE China recorded the key tectonic evolution history of the Eurasian Plate from the Paleozoic-Mesozoic
collisional formation of the Central Asian Orogenic Belt to the Mesozoic subduction of the Paleo-Pacific Ocean.
To better understand this tectonic transition, it is crucial to constrain the time and pattern of the initial subduc-
tion of the Paleo-Pacific Ocean. Recently, someresearchers proposed that theMudanjiang Ocean existed between
the Songnen and Jiamusi blockswas part of the Paleo-Pacific Ocean. Here, through geochemical and geochrono-
logical studies on the widespread granitoids in the Lesser Xing'an-Zhangguangcai Range in the eastern Songnen
Block, we verify that these magmatic rocks show volcanic arc affinity with increased mantle contribution from
east to thewest of the range, likely related to a flattening subduction of theMudanjiang Ocean. In addition, a uni-
versal westward younging trend for over 70 Myr can be observed for the granitoids throughout the Lesser
Xing'an-ZhangguangcaiRange, indicating a long-lastingsubductionof theMudanjiangOcean.More interestingly,
the oldest ages of the granitoids in the east display a northward younging trend from275Ma to 218Ma, suggest-
ing that the subduction of the Mudanjiang Ocean had been initiated at latest by 275 Ma in the south and then
progressively expanded to the north. Based on these observations, we proposed a new tectonic evolution
model for theMudanjiang Ocean, i.e., a Triassic-Jurassicwestward scissor-like subduction and closure, to contrib-
ute to the understanding of the early subduction of the Paleo-PacificOcean
Modelling sub-hourly rainfall extremes with short records - a comparison of MEV, Simplified MEV and point process methods
Authors: Wang Li-Pen , Marra Francesco , Onof Christian
Published: March 2020

Accurate information on extreme rainfall frequency at sub-hourly timescales is useful for many hydrological applications, such as urban drainage design and stormwater management. However, the availability of sub-hourly rainfall records with sufficient length and quality is generally limited in most countries. With these short datasets, the conventional rainfall frequency analysis methods (e.g. annual maxima (AM) series) are prone to systematic biases and large uncertainties. In this work, we take advantage of long sub-hourly rainfall archives to explore the potential of alternative methods that exploit a larger fraction of the available data (or features), thus promising accurate estimates from relatively short data records.

The first method is based upon the Metastatistical Extreme Value (MEV) framework, which relaxes the asymptotic assumption of traditional AM methods. MEV considers, year by year, the full distribution of the underlying ordinary events and their number of occurrences. The second method, the Simplified MEV (SMEV, a variant of MEV), in which inter-annual variability is neglected in favour of simpler parametrisation and more robust parameter estimation, is also tested. So far, these two methods were shown to outperform traditional methods for daily amounts, but were never used on sub-hourly data.

The third method is based upon point process theory, which represents the temporal rainfall process in a realistic yet simple way, such that the hierarchical structure of rainfall is explicitly incorporated, and several parameters have a physical interpretation. Models based upon point process theory were known to be incapable of preserving extreme rainfall statistics at hourly and sub‑hourly timescales. Nonetheless, a recent breakthrough has overcome this deficiency (Onof and Wang, 2019). In this work, a revised randomised Bartlett-Lewis rectangular pulse model (RBL) is employed.

Five-minute rainfall data from 5 long recording rain gauges in Germany – Bochum (69 years), Aplerbeck, Kruckel, Marten and Nettebach (49 years) – are used. The comparison is conducted by resembling the scenarios where sub-hourly rainfall time series data are available with various short lengths (i.e. 5/10/15/20 years). SMEV and RBL generally outperform the MEV and AM in preserving sub-hourly rainfall extremes and are both much less sensitive to the use of short data records. SMEV outperforms RBL in preserving rainfall extremes at short return periods (< 10-year return periods), while they perform similarly at long return periods. RBL however has the advantage of preserving rainfall extremes across multiple timescales (i.e. from sub-hourly, hourly to 1-day) at the same time. The unsatisfactory performance of MEV is related to the influence of the low-intensity tail of yearly distributions.
Wave and coastal sea ice interaction along the Arctic coast
Authors: Hosekova Lucia , Malila Mika , Thomson Jim , Kumar Nirnimesh , Rogers Erick W. , Roach Lettie , Eidam Emily
Published: March 2020

Rapid decline in seasonal sea ice has been linked to increased surface wave activity and shoreline erosion in the coastal Arctic. This trend poses a risk to communities vulnerable to flooding and storm surges. Here we focus on quantifying the relationship between coastal erosion, increasing wave activity and the role of sea ice in protecting the coast. 

In November 2019, we observed a three day wave event in the Chukchi Sea along the coastal barrier system near Icy Cape, Alaska. The wave event was sampled using multiple drifting SWIFT (Surface Wave Instrument Float with Tracking) buoys, a cross-shore mooring array, and ship-based CTD casts.  This provided datasets for different ice types in both Eulerian and Lagrangian reference frames. Pancake and frazil sea ice near the coast attenuated the incident wave field, such that the significant wave height reduced from 3 to 1.5 m over less than 5 kilometers. The wave data combined with in-situ ice observations and satellite imagery are used to calculate spectral attenuation of wave energy segregated by ice type. Furthermore, observed temperature, mean circulation and surface heat fluxes are used to address the evolution of sea ice throughout the event. 

 

Supported by the National Science Foundation and the Office of Naval Research. 
Variations in soil chemical and physical properties explain basin-wide Amazon forest soil carbon concentrations
Authors: Quesada Carlos Alberto , Paz Claudia , Oblitas Erick , Phillips Oliver , Saiz Gustavo , Lloyd Jon
Published: March 2020

We investigate the edaphic, mineralogical and climatic controls of soil organic carbon (SOC) concentration utilising data from 147 primary forest soils (0-30 cm depth) sampled in eight different countries across the Amazon Basin. Sampling across 14 different World Reference Base soil groups our data suggest that stabilisation mechanism varies with pedogenetic level. Specifically, although SOC concentrations in Ferralsols and Acrisols were best explained by simple variations in clay content – this presumably being due to their relatively uniform kaolinitic mineralogy – this was not the case for less weathered soils such as Alisols, Cambisols and Plinthosols for which interactions between Al species, soil pH and litter quality are argued to be much more important. Although for more strongly weathered soils the majority of SOC is located within the aggregate fraction, for the less weathered soils most of the SOC is located within the silt and clay fractions. It thus seems that for highly weathered soils SOC storage is mostly influenced by surface area variations arising from clay content, with physical protection inside aggregates rendering an additional level of protection against decomposition. On the other hand, most of SOC in less weathered soils are associated with the precipitation of aluminium-carbon complexes within the fine soil fraction, with this mechanism enhanced by the presence of high levels of aromatic, carboxyl-rich organic matter compounds. Also examined as part of this study were a relatively small number of arenic soils (viz. Arenosols and Podzols) for which there was a small but significant influence of clay and silt content variations on SOM storage and with fractionation studies showing that particulate organic matter may accounting for up to 0.60 of arenic soil SOC. In contrast to what were in all cases strong influences of soil and/or litter quality properties, after accounting for these effects neither wood productivity, above ground biomass nor precipitation/temperature variations were found to exert any significant influence on SOC stocks. These results have important implications for our understanding of how Amazon forest soils are likely to respond to ongoing and future climate changes.
Late Miocene deformation and surface uplift of the North Pamir
Authors: Li Lin , Dupont-Nivet Guillaume , Roperch Pierrick , Najman Yani , Kaya Mustafa , Meijer Niels , Aminov Jovid
Published: March 2020

The Pamir Plateau, as the west extension of the Tibetan Plateau, forms a prominent salient into central Asia. Previous studies have suggested that the Pamir indented northward, causing retreat of the proto-Paratethys Sea and aridification of Central Asia. However, its indentation and surface uplift history are poorly constrained, with existing studies focusing mainly on the eastern side of the Pamir salient. This study presents new multi-proxy data from the southeast Tajik Basin, located on the western side of the salient, to explore the tectonic evolution of the Pamir Plateau. In the southeast Tajik Basin, our magnetostratigraphic study indicates that the fluvial and alluvial strata were deposited between ~20-8 Ma, with thick conglomerates starting at ~15 Ma. Provenance data from sandstone detrital zircon U-Pb ages and mudstone eNd values indicate a pronounced shift in sediment source from the Central Pamir to the North Pamir around 12 Ma. This provenance change is corroborated by carbonate stable oxygen isotopes showing a gradual decreasing trend between 12-8 Ma, which most likely reflects surface uplift of the North Pamir. Collectively, our results indicate that the North Pamir was originally part of the broad Tarim-Tajik Basin, and has been gradually uplifted since ~12 Ma.
Carbon-concentration and carbon-climate feedbacks in CMIP6 models, and their comparison to CMIP5 models
Authors: Arora Vivek , Katavouta Anna , Williams Richard , Jones Chris , Brovkin Victor , Friedlingstein Pierre ,   rest of C4MIP carbon feedbacks analysis team
Published: March 2020

Results from the fully-, biogeochemically-, and radiatively-coupled simulations in which CO2 increases at a rate of 1% per year (1pctCO2) from its pre-industrial value are analyzed to quantify the magnitude of two feedback parameters which characterize the coupled carbon-climate system. These feedback parameters quantify the response of ocean and terrestrial carbon pools to changes in atmospheric CO2 concentration and the resulting change in global climate. The results are based on eight comprehensive Earth system models from the fifth Coupled Model Intercomparison Project (CMIP5) and eleven models from the sixth CMIP (CMIP6). The comparison of model results from two CMIP phases shows that, for both land and ocean, the model mean values of the feedback parameters and their multi-model spread has not changed significantly across the two CMIP phases. The absolute values of feedback parameters are lower for land with models that include a representation of nitrogen cycle. The sensitivity of feedback parameters to the three different ways in which they may be calculated is shown and, consistent with existing studies, the most relevant definition is that calculated using results from the fully- and biogeochemically-coupled configurations. Based on these two simulations simplified expressions for the feedback parameters are obtained when the small temperature change in the biogeochemically-coupled simulation is ignored. Decomposition of the terms of these simplified expressions for the feedback parameters allows identification of the reasons for differing responses among ocean and land carbon cycle models.
Anthropogenic water depletion in the Indo-Gangetic Plain
Authors: Liu Bingshi , Zou Xiancai , Li Jiancheng
Published: March 2020

The Indo-Gangetic Plain, feeding more than 9 billion people, are facing serious water scarcity due to expanding populations and development in agriculture and industry. Rainfall concentrated in monsoon season, about 70% of precipitation falls between June and September, causes the imbalance between water supply and demand. A large amount of groundwater is extracted for irrigation during dry season, causes the groundwater to decline. Increasing glacier meltwater under the ongoing warming of global climate from upstream high mountainous also modulates the variation of terrestrial water storage (TWS) in this region. Thus, estimating and evaluating anthropogenic water depletion are beneficial to water resources protection and management in the Indo-Gangetic Plain.

Here, we propose a method to remove the influence of climate variability and obtain human-driven TWS variability. Atmosphere-driven TWS variability is estimated by a relationship between change in TWS (GRACE data) and precipitation and temperature, which has been confirmed that these two variables (precipitation and temperature) already explain a substantial fraction of continental-scale run off dynamics in previous studies. Glacier melting recharge from upstream high mountainous is calculated by the proportion with the temperature.

Results show that the rate of anthropogenic depletion of water in Indus Plain increased from -5.5 km3/yr to -25.0 km3/yr during 2003 - 2011 due to the deficient precipitation, and remained stable from 2011 to 2016 at the rate of ~-26.0 km3/yr with increasing precipitation and enhancing glacier meltwater recharge. The rate of anthropogenic depletion of water in Ganges Plain (including the Brahmaputra River) slowed from -37.7 km3/yr to -12.0 km3/yr during 2003 -2011due to the increased glacier meltwater recharge, which reduced the pressure of irrigation water in northwest of the Plain. However, with the increasing temperature since 2014, The rate of anthropogenic depletion of water increased to -20.0 km3/yr in 2016.
How many particles do we need to measure aerosol mixing state?
Authors: Riemer Nicole , Gasparik Jessica , Ye Qing , West Matthew , Curtis Jeff , Sullivan Ryan , Presto Albert
Published: March 2020

Atmospheric aerosols are evolving mixtures of different chemical species.  The term “aerosol mixing state” is commonly used to describe how different chemical species are distributed throughout a particle population.  A population is “fully internally mixed” if each individual particle consists of same species mixtures, whereas it is fully externally mixed if each particle only contains one species. Mixing state matters for aerosol health impacts and for climate-relevant aerosol properties, such as the particles’ propensity to form cloud droplets or the aerosol optical properties.

The mixing state metric χ quantifies the degree of internal or external mixing and can be calculated based on the particles’ species mass fractions. Several field studies have used this metric to quantify mixing states for different ambient environments using sophisticated single-particle measurement techniques. Inherent to these methods is a finite number of particles, ranging from a few hundred to several thousand particles, used to estimate the mixing state metric. 

This study evaluates the error that is introduced in calculating χ due to a limited particle sample size.  We used the particle-resolved model PartMC-MOSAIC to generate a scenario library that encompasses a large number of reference particle populations and that represents a wide range of mixing states. We stochastically sub-sampled these particle populations using sample sizes of 10 to 10,000 particles and recalculated χ based on the sub-samples. This procedure mimics the impact of only having a limited sample size as it is common in real-world applications. The finite sample size leads to a consistent overestimation of χ, meaning that the populations appear more internally mixed than they are in reality. These findings are experimentally confirmed using single-particle SP-AMS measurement data from the Pittsburgh area. We also determined confidence intervals of χ for our sub-sampled populations. To determine χ within a range of  +/- 10 percentage points requires a sample size of at least 1000 particles.

 
Rhizosphere legacy: amelioration of MicroBioPhysical properties of compacted soil
Authors: Razavi Bahar S. , Rudolph-Mohr Nicole , Tebbe Christoph
Published: March 2020

Soil compaction is a multi-disciplinary problem in which soil, plant, and air operations play an important role and may have dramatic environmental consequences throughout the world. In compacted soils, the increase in bulk density, and the accompanying decrease in porosity hinders the exchange of oxygen, carbon dioxide and other gases, thereby causing hypoxic stress in plant roots. Hypoxic stress can effects root physiological functions, reduce soil enzyme activity, hence reducing soil fertility. For the first time we applied a unique combination of two imaging techniques, zymography and optodes sensors with molecular microbial community analysis to illuminate the rhizosphere self-regulation for amelioration of microbiophysical properties of compacted soil. To this end maize in compacted and uncompacted soil under control condition for 2 weeks was planted.

Soil oxygen map and β-glucosidase activity in compacted maize treatment overlaid with the extracted root system demonstrated more than 65% positive correlation between hotspots of enzymatic activity and localities with high oxygen concentration –which were mostly in association with root. Similarly, extend of rhizosphere for oxygen concentration and enzyme activity across the root of compacted soil was 1mm broader than the uncompacted.

Based on root morphology analysis, compacted maize reduced roots diameter and increased the distribution. Which resulted in 30% higher ratio of rhizosheath mass in compacted than uncompacted soil. Rhizosheath formation changed porosity and aggregation around the root, thus, improved oxygen exchange. Accordingly, bacterial abundance and alpha diversity in hotspots of compacted soils were higher than the one of uncompacted. Thus, microorganisms localized in hotspots (rhizosheath) respond to better aeration, new carbon inputs compared to those inhabiting in the bulk soil. This confirms the distinguished role of rhizosphere-self organization for enzymatic mobilization of nutrients, and point out on the importance of aeration for rhizospheric microbial functionality (such as, enzyme expression for nutrients mining).
Variabilities of sea level components over the South China Sea based on multi-sensor satellite observations
Authors: Sha Jin , Li Xiaoming
Published: March 2020

Seawater temperature and salinity are the two key parameters related to the regional sea level variability. In this study, the spatial-temporal variabilities of the thermal and halo steric height over the South China Sea (SCS) are investigated using multi-senor satellite remote sensing products, in-situ measurements and reanalysis. The sea surface temperature and salinity products are used to reconstruct the upper layer sea level components, and the relative contribution of these two components are quantified. It is revealed that the thermal and halo components vary in an out-of-phase pattern, and dominant different regions within SCS. Variabilities of the sea level components on different timescale are further analyzed, and the linkage with large scale processes, such as the indo-pacific warm pool, will be presented.
What is the future for our earthen heritage? Modelling the risk of environmentally-driven deterioration at sites located in dryland areas
Authors: Richards Jenny , Mayaud Jerome , Bailey Richard , Viles Heather
Published: March 2020

Earthen heritage forms ~10% of UNESCO’s World Heritage List, with sites generally concentrated in dryland environments. Many sites are exposed to environmental processes such as wind, sediment movement and rain, which can result in extensive deterioration of the earthen heritage. To improve the effectiveness of conservation strategies that aim to minimise deterioration, there is an urgent need to understand how multiple environmental processes interact and impact earthen heritage, particularly over longer (centennial) timescales. We therefore apply the ViSTA-HD model (Vegetation and Sediment TrAnsport model for Heritage Deterioration) to Suoyang Ancient City, an archaeological site in north-west China made of rammed earth. ViSTA-HD is a cellular automata model developed by the authors to model the risk of environmentally-driven deterioration at earthen heritage sites. It is comprised of two modules: (i) an environmental module that spatially resolves environmental processes across an earthen site, and (ii) a deterioration module that spatially resolves the risk of deterioration across a wall face. The risk of deterioration is simulated for three common deterioration features at Suoyang - polishing, pitting and slurry. We use ViSTA-HD to investigate variations in deterioration risk under future potential climate scenarios across the 21st century. We also use the model to robustly test the impact of potential nature-based conservation strategies.
The impact of large-scale atmospheric patterns on Heatwaves in summer Northern China based on Self-Organizing Map
Authors: Shi Chen , Kaicun Wang , Chunlüe Zhou
Published: March 2020

Heatwave is affected by large-scale atmospheric circulation on temperature-related climates in the context of global warming. Recently Northern China have experienced an increase in heatwaves which is partly due to the atmospheric circulation. This study aims to address the influence clearly. Northern China heatwaves are computed on excess hot factor (EHF) and the five EHF indexes are studied afterwards to get a picture of heatwaves in summer Northern China. China circulation patterns are classified into nine typical circulation patterns on self-organizing map (SOM) which then can be described quantitatively by pattern factors: frequency, persistence and maximum persistence. Pearson correlation analysis and stepwise regression analysis are applied for exploring the impact. Results show the spatial pattern of the times of individual heatwave event (HWN) and the days of the longest heatwave duration (HWD) are high value everywhere in Northern China. The overall EHF indexes all rising in time series (P<0.05) and the regional heatwave occurrence have trends of 0.79 day per year (P<0.05). However, the factors of the patterns show inconspicuous tendency. Two patterns with significant correlations (P<0.05) are proved to be suggestive of Okhotsk Sea high and West Pacific Subtropical High. It declares that the Okhotsk Sea high favors Northern China heatwave occurrence rather than subtropical high: the warm center over Okhotsk Sea transfer heat upper and west, generating the high temperature and persist high pressure system, causing heatwave happening in summer Northern China. The two related atmospheric circulation patterns explain 38% of the heatwave occurrence based on stepwise regression model, the Okhotsk Sea high gets the coefficient of 0.443 and the subtropical high is -0.347.  
Examining saturated and unsaturated hydraulic parameter changes as a result of geochemical reactions in tailings
Authors: Akesseh Raphael , Edraki Mansour , Baumgartl Thomas
Published: March 2020

Freshly deposited tailings define finely crushed rock rarely altered by weathering processes. In modelling water flow and solute transport for saturated and unsaturated conditions in deposited tailings, the hydraulic parameters are essential required parameters. It has been proposed that these parameters vary as the materials evolve through weathering processes which transform minerals and hence chemical and physical properties. Several methods, destructive and non-destructive, have been used to determine the change of these parameters. The evaporation method as a non-destructive method, for deriving hydraulic parameters of porous media can be employed to monitor the overall changes in the pores as the properties of the porous matrix changes. In order to test this hypothesis, 25% of pyrite, 25% of dolomite, 35% of quartz and 15% of chlorite, reflecting typical acid producing, acid neutralising and inert minerals were mixed to form artificial tailings. The mineral admixture was mixed at a water content of 10% and allowed to equilibrate for two weeks before the start of the experiment. The mineral admixture was packed to a bulk density of 1.4 g/cm3. The hydraulic parameters for the near saturation state were measured using the simultaneous measurement of water content and water potential as a consequence of evaporation. The mineral admixture was subjected to 9 drying and wetting cycles over a period of 9 months. The hydraulic parameters were estimated using RETC and HYDRUS 1D. After 9 months of drying and wetting, there was a slight change in the bulk density of the material. This change had an overall effect on the subsequent hydraulic parameters. This study implies that feedback effects should be considered in modelling ageing of mine tailings.
Geodetic determination of the gravitational potential difference for an optical lattice clock comparison in the Kanto region in Japan
Authors: Tanaka Yoshiyuki , Aoki Yosuke , Nishiyama Ryuichi
Published: March 2020

Recent advancements in atomic clocks have enabled us to measure gravitational potential differences with a precision which is applicable to geodetic uses, based on the gravitational red shift. In Europe, international fiber networks linking optical clocks have been developed for promoting the unification of height reference systems across countries, and 10 cm-level agreements in terms of the equivalent height difference to the gravitational potential have been achieved in the comparisons between chronometric and classical geodetic methods. In Japan, similar comparisons using two optical lattice clocks were carried out for i) a 15-km fiber connecting RIKEN in Wako city and the Hongo campus of the University of Tokyo and ii) a 450-m fiber link which vertically connected the observatory and the ground at the Tokyo Skytree. For the former comparison, agreement between chronometric and geodetic results was better than 10 cm, and for the latter, data are under analysis. A new clock site has been developed at the NTT Basic Research Laboratories in Atsugi City. Clocks in Wako, Hongo and Atsugi constitute an approximately 100-km-scale network. In this presentation, we report a preliminary result on the geodetic leveling survey to determine the gravitational potential difference between these three sites. To estimate uncertainties in the potential difference, we will compare the result partially with those determined from the geoid model and the GNSS ellipsoidal height. We will also consider the effects of crustal vertical motion, in addition to measurement errors.
Assessment of surface soil moisture distribution across small scale tomato fields using L band SAR data
Authors: Gururaj Punithraj , Umesh Pruthviraj , Shetty Amba
Published: March 2020

Soil moisture is very important in several disciplines such as agriculture, hydrology and meteorology. It can be mapped using active and passive microwave remote sensing techniques. From literature it is observed that quad polarized data acquired at L-band is sensitive to soil moisture and can map surface soil moisture at high spatial resolution. The main objective of this study is to analyze the potential use of L-band radar data for the retrieval of surface soil moisture over small scale agricultural areas under vegetation cover conditions. Study area selected for this study was Malavalli, village in Karnataka state India which falls in Tropical semi-arid region. Two radar images were acquired using the Phased Array Synthetic Aperture Radar/Advanced Land Observing Satellite (PALSAR/ALOS)-2 sensor over the study area between 23/07/2018 and 17/09/2018 which has spatial resolution of 5m. Ground Soil moisture over 30 sample sites were collected in synchronization with satellite pass over the study area. Acquired ALOS PALSAR-2 images were processed using PolSARpro (Polarimetric SAR data Processing and Education Toolbox). ALOS PALSAR-2 has been processed and lee speckle filter is applied with window size of 3*3. Surface soil moisture distribution over small scale tomato fields are mapped by adding incidence angle using Oh Model. Incidence angle map which is not available with PolSARpro (Polarimetric SAR data Processing and Education Toolbox) software was derived using the polynomial given in the leader file which was required for oh model inversion. Study site clearly shown increasing trend of soil moisture from July to September. It is interesting to note that vegetation and urban areas are clearly discriminated in the PauliRGB images. The retrieval of soil moisture using Oh model is validated using Ground truth samples. The accuracy of Oh model over small scale tomato fields with RMSE of 1.83 m3/m-3.
Efficient simulation of flood events using machine learning
Authors: Elyahyioui Jihane , Pauwels Valentijn , Daly Edoardo , Petitjean Francois , Prakash Mahesh
Published: March 2020

Flooding is one of the most common and costly natural hazards at global scale. Flood models are important in supporting flood management. This is a computationally expensive process, due to the high nonlinearity of the equations involved and the complexity of the surface topography. New modelling approaches based on deep learning algorithms have recently emerged for multiple applications.

This study aims to investigate the capacity of machine learning to achieve spatio-temporal flood modelling. The combination of spatial and temporal input data to obtain dynamic results of water levels and flows from a machine learning model on multiple domains for applications in flood risk assessments has not been achieved yet. Here, we develop increasingly complex architectures aimed at interpreting the raw input data of precipitation and terrain to generate essential spatio-temporal variables (water level and velocity fields) and derived products (flood maps) by training these based on hydrodynamic simulations.

An extensive training dataset is generated by solving the 2D shallow water equations on simplified topographies using Lisflood-FP.

As a first task, the machine learning model is trained to reproduce the maximum water depth, using as inputs the precipitation time series and the topographic grid. The models combine the spatial and temporal information through a combination of 1D and 2D convolutional layers, pooling, merging and upscaling. Multiple variations of this generic architecture are trained to determine the best one(s). Overall, the trained models return good results regarding performance indices (mean squared error, mean absolute error and classification accuracy) but fail at predicting the maximum water depths with sufficient precision for practical applications.

A major limitation of this approach is the availability of training examples. As a second task, models will be trained to bring the state of the system (spatially distributed water depth and velocity) from one time step to the next, based on the same inputs as previously, generating the full solution equivalent to that of a hydrodynamic solver. The training database becomes much larger as each pair of consecutive time steps constitutes one training example.

Assuming that a reliable model can be built and trained, such methodology could be applied to build models that are faster and less computationally demanding than hydrodynamic models. Indeed, in with the synthetic cases shown here, the simulation times of the machine learning models (< seconds) are far shorter than those of the hydrodynamic model (a few minutes at least). These data-driven models could be used for interpolation and forecasting. The potential for extrapolation beyond the range of training datasets will also be investigated (different topography and high intensity precipitation events). 
Improving scheduling, benchmarking and forecasting to boost irrigation productivity
Authors: Western Andrew , Guo Danlu , Parehkar Arash , Gao Zitian , Ryu Dongryeol , Wang Quan
Published: March 2020

Irrigation water is an expensive and limited resource, and optimized water use is beneficial to saving water while boosting productivity. This project aims to develop integrated irrigation scheduling, benchmarking and forecasting capabilities to inform optimal irrigation practices and the suitable tools and information required for this. To achieve this, we designed a three-year project which combines simulations and field-scale monitoring. One aspect of this project is to develop a comprehensive uncertainty framework to better understand the uncertainty in scheduling, which is informed by soil water models, along with multiple sources of information such as soil, crop, weather and field management. Besides, we are also conducting large-scale benchmarking study to identify better irrigation practices across multiple farms, fields, crop types and seasons. The project outcomes will be integrated with our partner, Rubicon’s water ordering portal and adopted by most Australian irrigation farmers, with significant long-term benefits expected in agricultural production and water conservation. 