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Accurate prediction of heat transport in porous media is important for understanding geoscience processes and properties and to design applications, for example geothermal energy systems. While heat transport is generally modelled assuming of local thermal equilibrium (LTE), i.e., instantaneous heat transfer between the fluid and solid phases, previous studies have demonstrated presence of local thermal non-equilibrium (LTNE), i.e., delayed heat transfer, in natural porous materials. However, factors that influence the rate of heat transfer between the phases and their significance for inherently heterogeneous natural systems remain unknown and untested. We develop an open-source fully coupled, finite-element application to numerically simulate heat transfer between the fluid and solid phases. This is based on the Multiphysics Object-Oriented Simulation Environment (MOOSE) and allows massively parallel modelling of heat transport including customized transfer rates. We verify our model using an analytical solution considering LTNE and illustrate several applications. The model can be used to investigate processes that affect heat transport such as heat transfer mechanisms and their dependence on different hydrogeological conditions.

Freshwater lenses are an important water resource in coastal areas as well as on oceanic islands, and understanding the dynamic forces acting upon this resource is vital for their sustainable management. A key water-management objective is to understand and manage these freshwater lenses, which requires accurate estimates of drawdown and groundwater recharge. Groundwater levels in such systems, however, are dominated by multiple dynamic factors, such as tidally and meteorologically forced ocean level fluctuations, coastal morphology, aquifer properties, recharge, and groundwater extraction. Unfortunately, tidal influences often dominate groundwater levels in these systems, which confounds the quantification of aquifer recharge and extraction.This work uses regression deconvolution to quantify oceanic influences on groundwater levels by generating an “Ocean Response Function” (ORF) that is used to reveal groundwater recharge and extraction, once influences have been removed. We use groundwater levels from an unconfined and unconsolidated (mostly fine sand) aquifer on the island of Norderney located in the North Sea in Northwest Germany. Confounding tidal influences are removed from observed groundwater levels to reveal underlying processes. Most prominently, seasonal recharge patterns are now clearly visible, along with responses to daily groundwater extraction from a nearby water-supply well. The obtained ORF also constrains the aquifer hydraulic diffusivity, in that higher diffusivities induce faster responses. Overall, this work demonstrates how regression deconvolution leads to improved insight into groundwater processes and properties when applied to coastal and island groundwater observations.

Earth tides exert small gravitational variations in the subsurface which lead to pore pressure changes and water level fluctuations in groundwater monitoring wells. This groundwater response to Earth tides has been used to estimate subsurface hydraulic and geomechanical properties. However, existing approaches are based on simplifying assumptions and their reliability has not been tested for realistic conditions. To simulate how Earth tides affect the subsurface, we developed and verified a numerical model that couples hydraulic and geomechanical theories. We modelled the response of a semi-confined aquifer which exchange water with an observation well for the dominant M2 Earth tide component. We reveal that undrained (i.e., groundwater does not flow in response to stress) and confined (i.e., groundwater is under pressure) conditions are necessary for the analytical solution to be valid. For the M2 frequency we assess that this occurs at depths ≤ 50 m and requires specific storage at constant strain sε ≥ 10-6 m-1, hydraulic conductivity of the aquitard kl ≤ 5 • 10-5 ms-1 and aquifer kl ≥ 1 • 10-4 ms-1, respectively. Further, we illustrate that established analytical solutions are valid in unconsolidated systems, whereas consolidated systems require additional consideration of the compressibility ratio between the porous medium and the porous skeleton (i.e., inclusion of the Biot coefficient). Overall, we find that a priori knowledge of the subsurface system increases the reliability of the groundwater response interpretation. Our results improve understanding of the effect of Earth tides on groundwater systems and provide a framework for evaluating subsurface properties.

Aquifers contain the largest store of unfrozen freshwater, making groundwater critical for life on Earth. Groundwater temperatures infl uence stream thermal regimes, groundwater-dependent ecosystems, aquatic biogeochemical processes, water quality, and the geothermal potential. Yet little is known about how groundwater responds to surface warming across spatial and temporal scales. We simulate current and projected groundwater temperatures at the global scale and show that groundwater at the depth of the water table is projected to warm on average by 3.3 ° C between 2000 and 2099 (RCP 8.5). However, regional groundwater warming patterns vary substantially due to spatial variability in climate and water table depth. The highest warming rates are projected in Central Russia, Northern China, and parts of North America and the Amazon rainforest. Results also show that by 2099, 234 million people are projected to live in areas where groundwater exceeds the highest threshold for drinking water temperatures set by any country.

Heat-related mortality and flooding are pressing challenges for the >4 billion urban population worldwide, exacerbated by increasing urbanization and climate change. Urban greening, such as green roofs and parks, can potentially help address both problems, but the geographical variation of the relative hydrological and thermal performance benefits of such interventions are unknown. Here we quantify globally how climate driven trade-offs exist between modelled hydrological retention and cooling potential of urban greening. Water retention generally increases with aridity in water limited environments, while cooling potential favors lower aridity, energy limited, climates. Urban greening cannot yield high performance simultaneously for addressing both urban heat-island and urban flooding problems in most cities globally. However, in more arid locations, where sustainable, irrigation might be used to improve potential cooling benefits while maintaining retention performance. We demonstrate that as precipitation becomes increasingly variable with climate change, the hydrological and thermal performance of thinner substrates would both diminish more quickly compared to thicker and more deeply vegetated systems, presenting challenges for urban greening strategies. Our results provide a conceptual framework and geographically targeted quantitative guide for urban development, renewal and policymaking.(See further details in the forthcoming paper Cuthbert et al. (In Press) in the journal Nature Communications, which is a more developed version of the pre-print available here: https://eartharxiv.org/repository/view/2100/)

Realistic modelling of tightly coupled hydro-geomechanical processes is relevant for the assessment of many hydrological and geotechnical applications. Such processes occur in geologic formations and are influenced by natural heterogeneity. Current numerical libraries offer capabilities and physics couplings that have proven to be valuable in many geotechnical fields like gas storage, rock fracturing and Earth resources extraction. However, implementation and verification of full heterogeneity of subsurface properties using high resolution field data in coupled simulations has not been done before. We develop, verify and document RHEA (Real HEterogeneity App), an open-source, fully coupled, finite-element application capable of including element-resolution hydro-geomechanical properties in coupled simulations. We propose a simple, yet powerful workflow to allow the incorporation of fully distributed hydro-geomechanical properties. We then verify the code with analytical solutions in one and two dimensions, and propose a benchmark semi-analytical problem to verify heterogeneous systems with sharp gradients. Finally, we demonstrate RHEA's capabilities with a comprehensive example including realistic properties. With this we demonstrate that RHEA is a verified open-source application able to include complex geology to perform scalable, fully coupled, hydro-geomechanical simulations. Our work is a valuable tool to assess challenging real world hydro-geomechanical systems that may include different levels of complexity like heterogeneous geology with several time and spatial scales and sharp gradients produced by contrasting subsurface properties.

In situ quantification of subsurface hydro-geomechanical properties is challenging and requires significant effort. Evolving research illustrates that subtle harmonic components in groundwater head measurements caused by Earth and atmospheric tides can be utilised to explore groundwater systems with little effort compared to traditional investigations. One long standing problem has been that, for dominant tidal components, Earth and atmospheric tides occur at the same frequency which prevents the use of the groundwater response to their individual forcing to infer subsurface properties. While Acworth et al. (2016) offered a way forward, their approach has assumptions that limit the applicability. Here, we illustrate an extended method that disentangles the borehole water level response and attributes magnitude and phase to their individual drivers. As a result, we obtain individual changes in harmonic properties of the drivers and their groundwater response (amplitude ratio and phase shift) using borehole water level records from different locations. In conjunction with groundwater flow and poroelastic theory, these properties can be used to infer the state of confinement, quantify specific storage and hydraulic conductivity as well as barometric efficiency of the formation. Further, because the stresses imposed by Earth and atmospheric tides are volumetric and uniaxial, respectively, their individual responses can be used to reveal strain anisotropy. Our new approach is passive, i.e. it only requires the measurements of atmospheric and groundwater pressure records, and can provide further insight into subsurface processes and properties using information hidden in standard pressure records. Acworth, R. I., Halloran, L. J. S., Rau, G. C., Cuthbert, M. O., and Bernardi, T. L. ( 2016), An objective frequency domain method for quantifying confined aquifer compressible storage using Earth and atmospheric tides, Geophys. Res. Lett., 43, 11,671–11,678, doi:10.1002/2016GL071328.

The paper explores the threat posed by terrorism in aviation domain, especially surface-to-air missile attacks against transport aircraft. While the focus of this paper is the mitigation of security risks in the aviation domain, the proposed solution based on concerted countermeasure systems discussed here may be developed in the context of homeland security policy promoting the principle of flight safety. The reception and the processing of data through the detection of signals emitted by various sources are proceeding in the absence of users interest about the form of the wave of the message. The detection of the presence / absence of the signal or the identification of its value is proceed by identifying the signal associated to each value of the message, considered a discrete variable, hence triggering of the adequate defence mechanism.

Unmanned Aerial Vehicles have seen a rapid development due to increased miniaturisation of technology, and their multiple usages in both military and civilian fields, thus making this business very profitable. Although the small UAVs are high enabling capabilities, they are still single-role (one flight, one mission). The present paper will present a comparative analysis of the solutions on flexible wing concept and will analyze the possibilities to use the morphing concept at small UAVs.