bluuebunny/crossref_metadata_2025 huggingface dataset:
Youth-led Participatory Sensing (YPS) Model to enhance drinking water security: a case study of Pokhara Metropolitan City, Nepal
Authors: Gautam Amrita , Ribbe Lars , Schneider Karl , Panthi Sudan , Bhattarai Mahesh
Published: March 2022

Water supply for drinking purpose with adequate quality is a global challenge. Majority of the developing countries face serious problems in proper technology and management strategy to regulate drinking water quality, though there are numerous cases of adverse health impacts. Population growth, unsystematic urbanization and improper management of the resources are some of the pressing factors. In Nepal, about 80% of prevalent communicable diseases are due to poor sanitation and lack of access to quality water. The coverage and functionality of the water supply system is still crucial owing to the degraded quality of water. In fact, there is no data available on water quality. Despite huge investment in implementing Water Safety Plan (WSP) approach in developing regions, many countries still lack the baseline water quality data (information flow) in the water supply system. Nepal is one of the countries where WSP is implemented for a long time (more than a decade) but the regular drinking water monitoring mechanism is still a matter of question. Studies have mentioned Water, Sanitation and Hygiene (WASH) practices in schools and possibilities of involving schools in WSP programs as well but the systematic method and model to integrate Youth/ Students and Information and Communication Technologies (ICTs) in Drinking Water Quality Monitoring is yet unexplored. In addition, the data accuracy of Citizen Based Monitoring needs to be checked. Therefore, the first phase of this research has developed a suitable design of Youth-led Participatory Sensing (YPS) to improve water supply management facility, including the strategy to support Climate Resilient Water Safety Plan (CR-WSP) framework of the local water utilities and, this paper highlights on performance evaluation and accuracy of data acquired from YPS Model with paired experimental approach, and gamified techniques in designing the participation from training to field implementation, including the community awareness targets for the selected water supply schemes of Pokhara Metropolitan City (PMC), Nepal, which can be validated and replicated in similar urban or peri-urban settings of national, regional and the global context.

Keywords:

Youth-led Participatory Sensing (YPS), Drinking Water Security, Water Quality, ICTs, Water Supply Schemes, CR-WSPs

https://www.youtube.com/watch?v=kS71uqFnjF0&t=66s

A video link about a part of the on-going doctoral research work in Nepal
Machine Learning Methods with the Standardized VPD Drought Index to Identify and Assess Drought in the United States
Authors: Gamelin Brandi , Rao Vishwas , Bessac Julie , Altinakar Mustafa
Published: March 2022

Extreme drought has a strong socio-economic impact on the human environment, especially where surface and ground water supplies are significantly reduced due to reduced stream flow, reduced hydroelectric generation, and increased ground water pumping for agricultural and human consumption. This reduction will likely increase in the future as drought is expected to increase in the United States due to global warming and climate change. However, identifying drought is problematic due to the lack of standardized classification or reliable methods for drought prediction. Recently, machine learning techniques have been applied to drought indices to identify drought features and for risk assessment. For this work, we utilize unsupervised machine learning (ML) computational algorithms to identify drought characteristics with a new drought index based on vapor pressure deficit (VPD). The Standardized VPD Drought Index (SVDI) is used to cluster points with common features to characterize spatial and temporal drought characteristics. The SVDI is calculated with the NASA’s Land Surface Assimilation System (NLDAS) data from 1990-2010. Several ML cluster techniques (e.g. HMM, k_means, BIRCH, DBSCAN) are applied to the SVDI to identify known short and long term drought events. Optimized techniques will be applied to downscaled global climate models (e.g. CCSM4, GFDL-ESM2G, and HadGEM2-ES) based on the 8.5 Representative Concentration Pathway (RCP8.5). From the space-time clustering algorithm, we will extract the spatiotemporal information for each identified event as a means of determining the probability of each type of event under global warming in the future.
Pore characteristics and hydraulic properties of shale samples under long-term exposure to hydraulic fracturing fluids
Authors: Hu Chenger , Tan Jingqiang , Lyu Qiao , Dick Jeffrey , Wood David
Published: March 2022

Fluids-shale interactions during hydraulic fracturing alters the pore characteristics and hydraulic properties of shale, thus affecting the oil and gas recovery efficiency and the geological storage capacity of shale reservoirs.  Short-term (0-1 month) and long-term (1-12 months) experiments are conducted to investigate the fluids-shale interaction behaviour during fracturing fluid injection and retention periods. The effects of fluids-rock interaction on pore characteristics and hydraulic properties are determined by characterizing the shale's mineralogy, surface morphology, pore structure characteristics, and hydraulic properties before and after the experiments. The experimental results show variability during the fluid injection and retention periods. In the short-term experiments, pyrite dissolution caused a rapid decrease in fluid pH (decreased by 1.7-5.1). In long-term experiments, feldspar and clay mineral dissolution caused a slow increase in fluid pH (increased by 0.5). The dissolution of minerals enlarged the native pores of the shale, thereby increasing the porosity, raising the average pore diameter, and increasing the gas adsorption capacity of the shale (by 14.1%). Measurements of fractal dimension D1 indicate that the pore surfaces become rougher during the short-term experiments, whereas the pore surfaces become smoother during the long-term experiments. The change in pore structure affects the hydraulic properties of the shale. In particular, the absolute permeability of the shale increased (60.0-129.1%), while the pore tortuosity decreased (26.1%-57.8%). However, as the pH rises above 4, substantial gypsum and iron hydroxide precipitation occurs, blocking shale fractures and pores. Such precipitation reduces shale porosity, hydraulic properties, and sorption capacity. On the other hand, lower pH (below 3.5) can inhibit the formation of secondary precipitation. Monitoring pH changes is, therefore, the key to improving oil and gas recovery by enhancing reservoir geological storage capacity following hydraulic fracturing.
Xenolith-based thermal and compositional lithospheric mantle profile of the central Siberian craton
Authors: Ionov Dmitri , Liu Zhe , Nimis Paolo , Xu Yigang , Golowin Alexander V.
Published: March 2022

Many aspects of structure and thermal state of >200 km thick cratonic lithospheric mantle (CLM) remain unclear because of insufficient sampling and uncertainties of pressure (P) and temperature (T) estimates. An exceptionally detailed record of equilibration temperature and composition for the central Siberian craton in the 60–230 km depth range was obtained using new and published petrographic and in-situ chemical data for ~200 garnet peridotite xenoliths from the Udachnaya kimberlite. The thermal profile is complex with samples between 35 and 40 mW/m2 model conductive geotherms as well as hotter layers in the middle and at the base (190–230 km) of the CLM. A previously unknown mid-lithospheric zone includes rocks up to 150° hotter than ambient geotherm, with high modal garnet and cpx, low-Mg# and melt-equilibrated REE patterns. We posit that hot domains with enriched compositions may form at depths where ascending melts stall (e.g., due to loss of volatiles and/or redox change) and react with wall-rock harzburgites. By contrast, we find no rocks rich in volatile-rich metasomatic amphibole, mica or carbonate, nor layers composed of peridotites with distinct melt-extraction degrees. The CLM base contains both coarse and variably deformed rocks heated and re-worked (Mg#Ol down to 0.86) by localized interaction with asthenospheric melts.
Seasonality of the Mesoscale Inverse Cascade as Inferred from Global Scale-Dependent Eddy Energy Observations
Authors: Steinberg Jacob , Cole Sylvia , Drushka Kyla , Abernathey Ryan
Published: March 2022

Oceanic mesoscale motions including eddies, meanders, fronts, and filaments comprise a dominant fraction of oceanic kinetic energy and contribute to the redistribution of tracers in the ocean such as heat, salt, and nutrients. This reservoir of mesoscale energy is regulated by the conversion of potential energy and transfers of kinetic energy across spatial scales. Whether and under what circumstances mesoscale turbulence precipitates forward or inverse cascades, and the rates of these cascades, remain difficult to directly observe and quantify despite their impacts on physical and biological processes. Here we use global observations to investigate the seasonality of surface kinetic energy and upper ocean potential energy. We apply spatial filters to along-track satellite measurements of sea surface height to diagnose surface eddy kinetic energy across 60-300 km scales. A geographic and scale dependent seasonal cycle appears throughout much of the mid-latitudes, with eddy kinetic energy at scales less than 60 km peaking 1-4 months before that at 60-300 km scales. Spatial patterns in this lag align with geographic regions where the conversion of potential to kinetic energy are seasonally varying. In mid-latitudes, the conversion rate peaks 0-2 months prior to kinetic energy at scales less than 60 km. The consistent geographic patterns between the seasonality of potential energy conversion and kinetic energy across spatial scale provide observational evidence for the inverse cascade, and demonstrate that some component of it is seasonally modulated. Implications for mesoscale parameterizations and numerical modeling are discussed.
Differentiating the Ribbon and Globally Distributed ENA Flux in IBEX Observations
Authors: Zirnstein Eric
Published: March 2022

The heliosphere surrounding our solar system is formed by the interaction between the solar wind and the local interstellar medium as the Sun moves through interstellar space. With dimensions on the order of hundreds to potentially thousands of au, it is extremely difficult to pinpoint the 3D structure of the heliosphere and its boundaries, and the properties of the plasma within it. However, we can remotely measure the properties of the heliosphere with energetic neutral atoms (ENAs) which are created as a product of charge exchange between interstellar neutrals and ions within the solar wind plasma. ENAs can propagate hundreds of au before ionizing, allowing us to remotely view the distant boundaries of the heliosphere.

The Interstellar Boundary Explorer (IBEX) mission, a NASA smaller explorer mission which has been measuring ENA fluxes at ~0.5-6 keV for more than a solar cycle, has revealed at least two separate sources of ENAs: the “ribbon” of enhanced ENA fluxes forming a narrow, circular band across the sky, and the “globally distributed flux” (GDF) that forms lower intensity, broad features near the nose and tail of the heliosphere. While it is believed that the ribbon is formed from secondary ENAs from outside the heliopause, and ENAs from the inner heliosheath inside the heliopause are a major contributor to the GDF, it is not clear exactly how much of the GDF may originate outside the heliopause, and how much of the flux observed in the Ribbon is from the GDF itself. To help solve this issue, we present recent developments in our understanding of the ribbon vs. GDF sources from both IBEX data analysis and modeling perspectives. Moreover, with the upcoming IMAP mission set to launch in 2025, we provide insight into how IMAP’s enhanced capabilities may improve our current understanding of the heliosphere.
The impact of drought on urban green space
Authors: Chavoshi Borujeni Sattar , Nouri Hamideh , Nagler Pamela , Abassi Neda , Pradhan Biswajeet , Huete Alfredo
Published: March 2022

The role of water in shaping and developing cities has been known and referred to in numerous studies in the last two decades. Urban water management encounters compelling features, including rapid urban expansion and consequent demographic change, climate change, and environmental limitations. Urban green spaces bridge the relationship between humans and nature. As the major feature of green infrastructure, urban green space (UGS) has a crucial role in cities' human health and quality of life. UGS makes cities more habitable and promotes psychological and physical health by filtering air, enhancing water quality, reducing traffic noise, and adjusting wind speed, among other benefits. One of the most important features of urban greenery is its contribution to reducing urban heat islands and cooling the city. In order to attain a water-resilient city, we need to overcome challenges associated with water scarcity, such as drought events. While the impact of drought on forestry, agriculture, and riparian corridors has already been studied, this study is one of the first to assess the effect of drought on the UGS. The main objective of this study is to find a sustainable approach toward a green, livable city under climate change by optimizing the water footprint of UGS. As the third most liveable city in the world in 2021, Adelaide city was selected as the case study. The changes in greenness and water requirement of UGS in Greater Adelaide were studied to detect the impact of drought from 2000 to 2020. The optical remote sensing techniques were employed using Landsat, MODIS, and Sentinel images. The study area's greenness and ETa time series were simulated on the Google Earth Engine platform. Preliminary results show that the water footprint of Adelaide's urban green space is the highest in December with the highest rate of heat-wave and the lowest in June.
Seasonal forecasts for hydropower: downscaling of precipitation in South American basins
Authors: Torralba Verónica , Materia Stefano , Álvarez-Castro Carmen , Bonetti Paolo , Metelli Alberto Maria , Restelli Marcello , Gualdi Silvio
Published: March 2022

Hydropower is one of the industrial sectors more strongly affected by the timing and intensity of extreme climatic conditions, especially related to precipitation. Particularly, the recent expansion of the hydropower capacity in South American regions has raised the interest of this sector in seasonal forecasts that can be used to anticipate persistent precipitation anomalies (e.g. meteorological droughts) over specific basins. Some of the limitations for the generation of seasonal forecast products that can be integrated in hydropower decision-making processes are the coarse spatial resolution and the limited forecast quality (i.e. systematic errors, low skill) of the current operational seasonal forecast systems. To overcome this problem, we propose a methodology based on machine learning-informed analogs. Information-theoretic preprocessing has been used to identify the large-scale drivers of precipitation in a drainage basin located in southern Brazil, where hydroelectric energy is produced. This information allows us to exploit the ability of the dynamical seasonal forecast systems to predict these large-scale drivers in combination with the statistical link between these drivers and precipitation. We have employed the global CMCC-SPS35 seasonal forecasts at 1° spatial resolution and the CHIRPS-V2 precipitation dataset at 0.05° to produce dynamical-statistical seasonal forecasts of precipitation. The results show that downscaled forecasts exhibit higher skill and are affected by smaller biases than those obtained directly from the operational dynamical systems. This suggests that there is potential for the use of hybrid forecasts in the optimal management of South Brazilian hydropower production. 
Development of Chemistry-Weather Fully Interacted Model System GRAPES_Meso5.1/CUACE CW v1.0 and Its Application in Better Air Quality Forecasting in China
Authors: Wang Hong , Zhang Xiaoye
Published: March 2022

The updated Chinese Unified Atmospheric Chemistry Environment (CUACE) model is driven by the operational mesoscale version of Global/Regional Assimilation and PrEdiction System (GRAPES_Meso 5.1) developed by China Meteorological Administration (CMA) to build the single way online atmosphere chemical model GRAPES-Meso v5.1/CUACE. Based on this, the aerosol-cloud-radiation interaction and its’ feedback on numerical weather prediction (NWP) is achieved leading to chemistry-weather interaction in GRAPES-Meso v5.1/CUACE and the first version t(v 1.) of double way model GRAPES-Meso v5.1/CUACE CW v1 is established in this study, which is used in the in Better Air Quality Forecasting in China

 The cloud condensation nuclei (CCN) number concentration activated from aerosols is crucial for understanding aerosol indirect effects and characterizing these effects in models. Morrison two moment cloud microphysical scheme combine with a size-resolved CCN parameterization scheme based on situ measurements of aerosol activation properties in China in implemented in meso-scale atmospheric chemical model GRAPES_CUACE to study the aerosols effects on cloud macro, micro features and radiation process under heavy polluted condition in East China.
Toward real-time GPP estimation using geostationary satellites
Authors: Stoy Paul C. , Khan Anam M. , Waupochick Angela , Zhang Zhou , Otkin Jason , Desai Ankur R.
Published: March 2022

Atmospheric carbon dioxide uptake is a critical ecosystem service that is highly sensitive to extreme events with important consequences for the human and natural systems that rely on it. We often monitor carbon dioxide uptake via gross primary productivity (GPP) at the ecosystem scale using the eddy covariance method, typically over half-hourly intervals. These observations are often ‘upscaled’ to regional or global scales using satellite observations, typically on time scales of weeks to years. These relatively infrequent estimates are due in part to intermittent overpasses from the polar-orbiting satellites like Landsat and MODIS that are commonly used for GPP monitoring.

Geostationary satellites on the other hand have long observed the Earth’s surface and atmosphere on the order of minutes with a consistent viewing geometry. The new generation of imagers on many geostationary platforms like the Advanced Baseline Imager (ABI) onboard the GOES-R satellite series now have enhanced spectral resolution in the visible and near-infrared regions of the electromagnetic spectrum. This resolution is comparable to Landsat and MODIS and can now in principle estimate GPP using similar approaches. Therefore, geostationary satellites can now measure ecosystem carbon uptake in near-real time and radically improve our understanding of the interaction between the carbon cycle, climate, and extreme events.

Here, we demonstrate an approach to estimate GPP using geostationary satellite observations. After correcting for atmospheric attenuation and applying a bidirectional reflectance distribution function, a model that uses the near-infrared reflectance of vegetation (NIRv) as a saturating function of GOES-derived photosynthetic photon flux density (PPFD) with adjustment for atmospheric vapor pressure deficit outperformed other models for simulating the diurnal pattern of eddy-covariance estimated GPP in crop, grass, savanna, and forested ecosystems. This model also captured the seasonal trend in the diurnal centroid of maximum diurnal GPP as it responds to seasonal drought stress. We describe current progress in upscaling geostationary GPP including machine learning algorithms to maximize computational efficiency and predictive skill. We also describe approaches to respect the data sovereignty of Tribal Nations while working with Tribal land managers to understand the consequences of ecosystem disturbances on natural resources. International collaboration is required to provide near-real-time GPP estimates across the globe, and our approach is applicable to European satellite systems like SEVIRI and other geostationary satellite systems like Himawari-8&9.
Numerical Simulations for Preferential Finger Flow Using a Two-Dimensional Non-Equilibrium Richards’ Equation with Preisach Hysteresis
Authors: Roche Warren , Flynn Denis , Murphy Kieran
Published: March 2022

A thorough understanding of preferential finger flow through the vadose zone is critical to deepen our knowledge on the processes of infiltration, runoff, erosion, plant growth, and contaminant transport. The paths formed during this fingered flow can be “remembered” by the soil matrix during future infiltration, even after periods of desaturation.

 

It has been shown many times that the traditional porous media equation, Richards’ equation, is incapable of capturing this phenomenon [1]. However, recent studies demonstrate the process can be described by combining a non-equilibrium, relaxation version of Richards’ equation [2] with Preisach hysteresis (applied to the pressure-saturation relationship). In this work, the authors build upon their previously published one-dimensional work [3]. The first part of this study is to present a numerical scheme for the two-dimensional non-equilibrium Richards’ equation using operator splitting methods. The second part is a comparison to previously published experimental results that demonstrates the ability of the model to capture realistic fingering behaviour.

 

[1] Nieber, J., et al. “Non-equilibrium model for gravity-driven fingering in water repellent soils: Formulation and 2D simulations.” Soil water repellency: occurrence, consequences and amelioration (2003): 245-258.

[2] G C Sander et al 2008 J. Phys.: Conf. Ser. 138 012023

[3] Roche, Warren & Murphy, K. & Flynn, Denis. (2021). Modelling preferential flow through unsaturated porous media with the Preisach model and an extended Richards Equation to capture hysteresis and relaxation behaviour. Journal of Physics: Conference Series. 1730. 012002. 10.1088/1742-6596/1730/1/012002.
Testing a new hybrid runoff generation module in four typical watersheds across different hydrometeorological zones in China
Authors: Zhang Qinuo , Zhang Ke , Chao Linjun , Chen Xinyu , Wang Jiayi , Wu Nan
Published: March 2022

Runoff generation in semi-humid regions is always characterized by a complex nonlinear process influenced by both saturation excess mechanism and infiltration excess mechanism. A hybrid runoff generation module is proposed in this study to delineate the mixed rainfall-runoff process by integrating an infiltration module, based on a modified Horton equation, with the saturation excess runoff generation module of Xinanjiang model at grid scale. A new distributed hydrological model, termed grid-Xinanjiang-infiltration-excess (GXAJ-IE) model, is subsequently developed in the context of grid-Xinanjiang model. Not only in semi-humid regions, but GXAJ-IE model is also expected to achieve acceptable performance in other hydrometeorological zones due to its superimposed runoff generation structure. Thus GXAJ-IE model is tested in four watersheds across different hydrometeorological zones (humid, semi-humid, semi-arid and arid) of China, and two models with single runoff generation mode, grid-Xinanjiang (GXAJ) model and grid-infiltration-excess (GIE) model, are set as benchmarks for comparison purpose. The results indicate that compared with the two benchmark models, GXAJ-IE model has higher flexibility and robustness in reproducing the flood hydrographs, especially the flood peaks, driven by various rainfall patterns in the semi-humid Dongwan and Maduwang watersheds. Furthermore, GXAJ-IE model could well capture the spatiotemporal characteristic of the saturation and infiltration excess runoff components, and delineate the evolution of their contributing areas within a flood event. Yet rainfall input with low spatiotemporal resolution still remains a limitation to give full play to the advantage of GXAJ-IE model. None of the models performs well in the arid and semi-arid Suide watershed, even though, GXAJ-IE model shows comparable simulation accuracy with GIE model whereas GXAJ model absolutely loses its edge. In the humid Tunxi watershed, GXAJ-IE model produces comparably good performance with GXAJ model while GIE model is slightly inferior. Overall, GXAJ-IE model is fairly adaptable to different hydrometeorological regions in China and shows great potential for universal application, with an especially promising prospect in improving the flood forecasting accuracy for the semi-humid watersheds.
Kinetic-Alfvén-wave turbulence in the low beta limit: role of current sheets and electron Landau damping 
Authors: Zhou Muni , Liu Zhuo , Loureiro Nuno F.
Published: March 2022

We report analytical and numerical investigations of sub-ion scale turbulence in weakly collisional, low beta plasmas using a hybrid fluid-kinetic model. In the isothermal limit, the same scalings for the energy spectrum and for the eddy anisotropy can be obtained from two distinct approaches: (i) tearing-mediated energy cascade (Loureiro & Boldyrev 2017), and (ii) intermittency corrections, arising from magnetic and density fluctuations concentrated mostly in two-dimensional structures (Boldyrev & Perez 2012). Our numerical results indicate that the latter case is the more plausible in this regime. With the inclusion of electron kinetic physics, the energy spectrum is found to steepen due to electron Landau damping, which is enabled by the local weakening of nonlinearities in current sheets, and yields significant energy dissipation in the velocity space. The use of a Hermite formalism to express the velocity space dependence of the electron distribution function allows us to obtain an analytical, zeroth-order solution for the Hermite moments of the distribution, which is borne out by numerical simulations.
Modelling the wave-induced fragmentation of the sea ice cover
Authors: Mokus Nicolas , Montiel Fabien
Published: March 2022

Fragmentation of the sea ice cover by wind-generated waves is an
important mechanism impacting ice evolution.
Fractured ice is more sensitive to melt, leading to a local reduction in
concentration, facilitating wave propagation, hence introducing a
positive feedback loop accelerating sea ice retreat.
Although this process and the concept of floe size distribution (FSD)
have been incorporated in several sea ice components of global climate
models (GCM), the physics governing ice breakup under wave action
remains poorly understood, and its parametrisation highly simplified.
We propose a numerical model of wave-induced sea ice breakup to estimate
the FSD resulting from repeated fracture events.
This model, based on linear water wave theory and viscoelastic sea ice
rheology, solves for the scattering of an incoming wave spectrum by the
ice cover and derives the corresponding strain field. Fracture occurs
when the undergone strain exceeds a prescribed threshold.
We find that under realistic wave forcing, lognormal FSDs appear
consistently in a large variety of model configurations.
This result contrasts with the power-law FSD behaviour often assumed by
modellers.
We discuss the properties of these modelled distributions, and
investigate the stochastic processes affecting their emergence.
The combined assimilation of MIPAS carbonyl sulfide (COS) and NOAA surface observations in TM5-4DVAR: Consequences for the global COS budget.
Authors: Krol Maarten , Ma Jin , Myriokefalitakis Stelios , Glatthor Norbert , von Hobe Marc , Montzka Steve
Published: March 2022

The atmospheric budget of carbonyl sulfide (COS, lifetime ~2 years) is primarily determined by emissions from anthropogenic and oceanic sources and uptake by the biosphere. Once the budget of COS is adequately understood, COS could be a suitable tracer to estimate Gross Primary Productivity (GPP), since stomatal uptake by plants is basically a one-way process, unlike the assimilation of CO2. However, currently the global budget of COS is not closed. Here, we will report progress on the use of inverse modelling to better constrain the atmospheric COS budget. To that end, we assimilate data from the MIPAS instrument that flew onboard the ENVISAT satellite (2002–2012). MIPAS is a limb sounder that measures atmospheric emission profiles down to the upper troposphere. Tropospheric COS retrievals are assimilated together with NOAA COS surface observations, and a bias correction scheme is employed to correct for potential calibration differences. Using the 4DVAR-TM5 model, we derive a consistent global COS budget. However, evaluation with independent data reveals that TM5 remains biased low in the free troposphere. We will show that this underestimate may be resolved by accounting for an aqueous-phase oxidation process of the newly discovered HydroPeroxyMethylThioFormate (HPMTF) intermediate in the DMS oxidation chain.
Investigation Into Antarctic Slope Front Regimes Using an Idealised Isopycnal Model
Authors: Ong Qing Yee Ellie , England Matthew , Hogg Andrew , Constantinou Navid , Doddridge Edward
Published: March 2022

The Antarctic Slope Current is a current that flows westward around Antarctica and lies close to the coast on the continental shelf. The slope current region features steeply sloping isopycnals at the continental shelf, characterising the Antarctic Slope Front (ASF). The ASF serves as a barrier between warm Circumpolar Deep Water and the continental shelf. Depending on the local structure of the ASF, Circumpolar Deep Water can flood on to the continental shelf and induce basal melt, with implications for sea level rise globally. Observations in these regions of the ocean are scarce, or even non-existent, and eddy-resolving modelling studies of the ASF are also limited. We have developed a set of idealised configurations with an isopycnal model that can emulate the conditions in different ASF regimes. We investigate how the different ASF regimes are affected by variations in wind forcing, topography and stratification. This aims to identify the different dynamics and the sensitivity of forcings and boundary conditions that allow warm water to reach the shelf in different ASF regimes.
Mechanisms for decadal Subantarctic Mode Water variability
Authors: Cerovecki Ivana , Haumann Alexander
Published: March 2022

Subantarctic Mode Water (SAMW) is a voluminous water mass that forms on the equatorward side of the Antarctic Circumpolar Current. The subduction and export of SAMW plays an important role in the global redistribution of heat, freshwater, nutrients, and dissolved gases such as oxygen and carbon dioxide. Recently the global Argo program of profiling floats provided for the first time near-global coverage of temperature and salinity in the upper 2000 m, revealing basin-wide spatial patterns of strong interannual SAMW variability. The same observations also indicate variations on decadal time scales. Combined with the output from an ocean state estimate, we investigate the mechanisms that drive the regional distribution of decadal variability of the SAMW.  We show that the decadal variability of SAMW volume and formation rate is strongly correlated with the decadal variability in the atmospheric circulation, in particular the zonal sea-level pressure gradients, governing the meridional wind component and meridional heat and moisture redistribution. These findings imply that strong quasi-decadal variability of surface heat and freshwater fluxes also governs the regional uptake of anthropogenic heat and carbon dioxide by SAMW.
Evolution of pH induced by salt concentration change under flowthrough conditions
Authors: Lützenkirchen Johhannes , Hanna Khalil , Marsac Remi
Published: March 2022

Column experiments are more sensitive to surface reactions than batch studies due to the increased surface area to liquid volume ratio. Moreover, these dynamic set-ups allow for stringent tests concerning the validity of equilibrium models for surface protonation and adsorption of pollutants.  In the present study, column experiments were carried out at constant pH, where the concentration of background electrolyte consisting of monovalent electrolytes like NaCl at the inlet were varied. Due to the charging phenomena caused by ionic-strength dependent acid-base reaction, the pH at the outlet of column varied. On a positively charged surface (such as alumina at pH 5.8) the increase in salt concentration at the inlet caused a transient increase in pH due to enhanced protonation of surface hydroxyls. On a negatively charged surface (PTFE at pH 5.8) the increase in salt concentration caused a decrease in pH at the column outlet due to enhanced uptake of hydroxide ions at higher salt concentrations. The charging behavior of both surfaces was independently determined by streaming potential measurements. For PTFE column experiments at different pH values were carried out to further relate them to the streaming potential data. Indeed below the isoelectric point, the trend of the pH-jump at the outlet of the column was inversed which suggests pH dependent charging of this inert surface due to protons and hydroxide ions.

Overall, the experiments show the high sensitivity of column experiments to changes in solution composition and the kind of experiments may allow for determining points of zero charge in an elegant way.
Evaluating uncertainty in aerosol forcing of tropical precipitation shifts
Authors: Peace Amy , Booth Ben , Regayre Leighton , Carslaw Ken , Sexton David
Published: March 2022

Increasing anthropogenic aerosol emissions have been attributed as the main driver of an observed southward shift in tropical precipitation between the 1950s and 1980s. In the near-term future, anthropogenic aerosol emissions will decline which could drive a northward shift in tropical precipitation over the coming decades. We use a perturbed parameter ensemble (PPE) of transient coupled-ocean atmosphere simulations that span a range of aerosol radiative forcing to investigate the role of aerosol radiative forcing uncertainty on tropical precipitation shifts in the 20th and 21st centuries. We find no relationship between the strength of the hemispheric contrast in pre-industrial to 1975 anthropogenic aerosol radiative forcing and tropical precipitation shifts during the 20th century. This result is in contrary to that from CMIP5, and we suspect internal variability plays a large role in why we do not see the expected relationship in our PPE. Tropical precipitation shifts are associated with major volcanic eruptions over the 20th century. However, we do find a relationship between the hemispheric contrast in pre-industrial to 2005 anthropogenic aerosol radiative forcing and the magnitude of future tropical precipitation shifts over 2006 to 2060 under scenario RCP8.5. Overall, our results suggest that reduction in aerosol radiative forcing uncertainty would improve projections of future precipitation shifts, but any predictive gains would be offset if future major volcanic eruptions temporarily shift tropical precipitation.
Simulating seasonal dynamics of Jakobshavn Isbrae through advancing the Elmer/Ice calving model
Authors: Wheel Iain , Crawford Anna , Todd Joe , Benn Doug , Van Dongen Eef , Cowton Tom
Published: March 2022

Jakobshavn Isbrae, the largest outlet glacier in Greenland, accounts for over 20% of the mass loss from the Greenland Ice Sheet. The calving of such large, marine-terminating glaciers is an important yet largely unconstrained contributor to global sea level rise. Understanding the influence of changing environmental conditions on calving at influential glaciers is critical for projections of glacier retreat and sea level rise. This understanding remains poor, in part due to the inability of 3D calving models to robustly simulate calving dynamics and large-scale retreat at fast-flowing glaciers such as Jakobshavn Isbrae. It is important to overcome these modelling challenges, as modelling calving in 3D is necessary to understand the role of geometry and internal glacier dynamics on calving and identify the key environmental forcers at individual glaciers.

We present results from a new calving algorithm implemented in the 3D full-Stokes continuum model Elmer/Ice and applied at Jakobshavn Isbrae, West Greenland. Elmer/Ice fully resolves the glacier velocity and stress fields, whilst recent developments in the calving algorithm allow the modelled glacier to advance and retreat limitlessly along the fjord. A positional crevasse depth calving law is implemented within the calving algorithm, which we use to investigate the dominant processes behind large scale calving and retreat at Jakobshavn Isbrae. Furthermore, we investigate the robustness of the crevasse depth calving law to simulate terminus position. Preliminary results suggest the current incarnation of the crevasse depth law underestimates calving and the crevasse depth required to calve needs to be reduced to accurately simulate terminus change at Jakobshavn Isbrae. Additionally, the inclusion of an ice mélange backstress in winter simulations is key to seasonal terminus advance.
Subsurface basement topography in the Cenozoic Andean foreland basin of northern Argentina: manifestations of long-wavelength deformation vs. inherited structures related to earlier orogeny and extensional processes
Authors: Cortassa Valentina , Rossello Eduardo , Back Stefan , del Papa Cecilia , Ondrak Robert , Strecker Manfred
Published: March 2022

The distal Andean foreland basin (Chaco-Pampean Plain) is thought to have been tectonically inactive during the Cenozoic. However, re-interpreted industry seismic reflection data, borehole information and gravity surveys document a rich and complex history of tectonic activity. Our new data synopsis and re-analysis reveals two, regionally extensive and approximately N-S oriented, basement highs beneath the flat present-day surface. The Quirquincho (or Rincón Caburé) and Pampeano-Chaqueño highs have been observed by previous authors, but the mechanism that elevated these features and the timing has remained elusive. Here, we discuss several viable mechanisms of their formation. The morphology, wavelength and stratal terminations suggest that the Quirquincho high could represent a forebulge due to Paleogene orogenic processes. In contrast, the Pampeano Chaqueño high farther east might correspond to a Neogene forebulge, implying forebulge migration. Alternatively, both highs could have been caused by blind and associated with a major crustal detachment. In this case these processes may have been facilitated by vertical mechanical strength contrasts in the foreland crust that have been invoked to drive spatially and temporally disparate thick-skinned deformation during the Andean orogeny. The fact that the arches occur in the vicinity of Cretaceous normal faults and rift basins suggests that these highs could also have been linked with extensional processes; in this case basement uplift and erosion would have been followed by sedimentary processes that finally caused the onlap of the Paleogene strata on the arches. Finally, we also consider the possibility they are Paleozoic, inherited features with posterior reactivation.
Retrofitting communication antennas for astronomical and geodetic VLBI applications
Authors: Laha Arnab , Tiwari Ashutosh , Srivastava Saurabh , Singh Shivangi , Joshi Bhal Chandra , Balasubramanian Nagarajan , Kumar Ajith , Gupta Yashwant , Dikshit Onkar
Published: March 2022

Very Long Baseline Interferometry (VLBI) technique was developed in the 1960s by astronomers, for high angular resolution observations of celestial radio sources. In the late 1970s, it was adopted for high-precision geodetic applications, in a reverse manner. In this application, VLBI is used to monitor the kinematics of individual points on the Earth, and also of the Earth as a body in the space using the precisely known astronomical positions of radio sources. Despite differences between astronomical and geodetic applications, the instrumentation and analysis techniques employed in VLBI are broadly similar, allowing for antennas designed for VLBI to be usable for either application. In this presentation, we describe a proposal for upgradation of three existing communication antennas with 18-m, 30-m and 32-m diameter, located at Arvi, Pune, India, for astronomical and geodetic VLBI purposes. The main objective is to retrofit the antenna with new gearboxes and modern servo control systems to make them compatible for use in VLBI observations, as well as with suitable L, S, and C band receivers and digital recorders, in a short period of time. Each motor will be driven by a drive with close loop precision pointing system, making it suitable to point to and track celestial sources. The antennas will be fitted with suitable antenna feeds and receiver systems, after the analysis of the dish parameters and its mounting possibilities. A development of cooled S-band feed will also be initiated simultaneously. Further, the three antennas will be fitted with new front-end electronics, baseband converter and digital recorders. The observed bandpass with different feeds (S and C band) will be down converted to L-band. This signal will be transported over optical fibre to the Giant Meterwave Radio Telescope (GMRT) facility, which is located nearby, for data recording and correlation activities. The retrofitted instrument will provide a test bed for instrumentation, tuning analysis pipelines and software, while providing the capability to carry out both astronomical and geodetic VLBI experiments with other international facilities.
Analytical developments on 6C computation inspired by navigation algorithms
Authors: Pinot Baptiste , Guattari Frederic , Honthaas Joachin , Mimoun David
Published: March 2022

The deployment of portable broadband rotational ground motion sensors in the field marks the beginning of 6 degrees of freedom simultaneous and co-located measurements in seismology, after decades of ground motion instrumentation measuring only translations. Regarding the computation of this new kind of data-set, there are obviously some analysis technics to inherit from navigation.

Hence, now seismology has also to solve the 6 equations system with 6 unknowns of dynamic motion. In a navigation system, it is computed real-time in onboard electronics, taking into account centrifugal forces, non-commutativity of rotations, and compensation of projection of gravity in accelerometers frame and Earth rotation rate in gyroscopes frame. For the moment, attempts at handling the merging of 6 components in seismology has remained mostly empirical, using cross-correlation maximization and other optimization methods.

In this study, we developed the analytical framework for seismological 6-C computation methods, derived from navigation-inspired methods to establish a stronger link between these algorithm expertises.
Using an ensemble of high-resolution climate model simulations to detect, attribute, and project changes in extreme rainfall over the Northeast U.S.
Authors: Jong Bor-Ting , Delworth Thomas L.
Published: March 2022

Extreme precipitation, both the occurrence and intensity, over the Northeast United States has significantly increased since the 1990s, evidenced by observations. The most salient increase has happened in the fall season (September to November). Understanding the attribution and projection of long-term trends in regional extreme precipitation is essential to adaptationion planning such as infrastructure upgrade. However, such work is challenging due to uncertainties caused by internal climate variability and the requirement of medium-to-high model resolution as well as ensemble size. In this work, we leverage the newly-developed GFDL (Geophysical Fluid Dynamics Laboratory) SPEAR (Seamless System for Prediction and EArth System Research) models which generate 25-km high-resolution simulations (ten members; SPEAR-HI) and 50-km large-ensemble simulations (30 members; SPEAR-MED) for both historical simulations from 1921 to 2014 and projections for the Shared Socioeconomic Pathway 5-8.5 (SSP585) from 2014 to 2100. We aim to address two related scientific questions using GFDL-SPEAR: (1) what are the factors that have contributed to the increasing autumn extreme precipitation over the Northeast US since 1990s? How much of the increase could be attributed to anthropogenic forcing? (2) when would the increased extreme precipitation in response to forced climate change emerge from the noise of internal climate variability?

Our preliminary results first suggest that higher atmospheric resolution in climate models is critical to facilitate the simulations of regional extreme precipitation. For example, SPEAR-HI can simulate comparable frequency of extreme precipitation over the Northeast US (rain rate > 50 mm/day), compared to the observation; while SPEAR-MED underestimates the frequency. Second, the recent increasing Northeast US extreme precipitation is unlikely due to the warming North Atlantic sea surface temperature, even though the timing of the abrupt increase in extreme precipitation coincided with the timing when the Atlantic Multidecadal Oscillation shifted from a cold to warm phase in the mid-1990s. Our ongoing work focuses on evaluating the attributions from other factors including internal variability, aerosols, and greenhouse gas. Last, we analyze SPEAR-HI SSP585 projections and extended control simulations starting from the year 1850. We estimate that the anthropogenically forced increase in the Northeast US autumn extreme precipitation would emerge from the noise of internal climate variability around the 2040s. However, ongoing work will employ more systematic methods to estimate the time of emergence.