Preprints
Filtering by Subject: Physics
Detection of VLF attenuation in the Earth-ionosphere waveguide caused by X-class solar flares using a global lightning location network
Published: 2020-01-09
Subjects: Astrophysics and Astronomy, Earth Sciences, Geophysics and Seismology, Other Physics, Physical Sciences and Mathematics, Physics, The Sun and the Solar System
Solar flares, energetic particles and Earth-impacting coronal mass ejections enhance ionization in the lower ionosphere, inhibiting radio wave propagation in the Earth-ionosphere waveguide (EIWG). This enhanced ionization is observed locally by ionosondes and GPS/GNSS receivers, but spatial coverage of these observations is limited by receiver location. VLF propagation studies have previously [...]
Deep learning to infer eddy heat fluxes from sea surface height patterns of mesoscale turbulence
Published: 2019-11-14
Subjects: Earth Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Physics, Planetary Sciences
Oceans play a major role in Earths climate by storing and transporting heat via turbulent currents called mesoscale eddies. However, direct monitoring of eddy-driven heat fluxes is currently impossible because it requires simultaneous surface and subsurface observations of velocity and heat content, while only surface properties of mesoscale eddies can be comprehensively measured by satellites in [...]
A bedform phase diagram for dense granular currents
Published: 2019-07-04
Subjects: Earth Sciences, Fluid Dynamics, Geology, Physical Sciences and Mathematics, Physics, Sedimentology, Volcanology
Pyroclastic density currents are a life-threatening volcanic hazard. Our understanding and hazard assessments of these flows primarily rely on interpretations of their deposits. The occurrence of stratified layers, cross-stratification, and dune bedforms in these deposits has been assumed as indicative of dilute, turbulent, flows causing traction-dominated deposition. Here we show, through [...]
Dynamical Systems Theory Sheds New Light on Compound Climate Extremes in Europe and Eastern North America
Published: 2019-06-27
Subjects: Applied Mathematics, Atmospheric Sciences, Climate, Dynamic Systems, Earth Sciences, Meteorology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Physics, Statistical, Nonlinear, and Soft Matter Physics
We propose a novel approach to the study of compound extremes, grounded in dynamical systems theory. Specifically, we present the co-recurrence ratio (α), which elucidates the dependence structure between variables by quantifying their joint recurrences. This approach is applied to daily climate extremes, derived from the ERA-Interim reanalysis over the 1979-2018 period. The analysis focuses on [...]
Data-driven prediction of a multi-scale Lorenz 96 chaotic system using deep learning methods: Reservoir computing, ANN, and RNN-LSTM
Published: 2019-06-20
Subjects: Applied Mathematics, Artificial Intelligence and Robotics, Atmospheric Sciences, Climate, Computer Sciences, Dynamic Systems, Earth Sciences, Fluid Dynamics, Non-linear Dynamics, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Physics
In this paper, the performance of three deep learning methods for predicting short-term evolution and for reproducing the long-term statistics of a multi-scale spatio-temporal Lorenz 96 system is examined. The methods are: echo state network (a type of reservoir computing, RC-ESN), deep feed-forward artificial neural network (ANN), and recurrent neural network with long short-term memory [...]
Distributed sensing of earthquakes and ocean-solid Earth interactions on seafloor telecom cables
Published: 2019-06-07
Subjects: Earth Sciences, Environmental Sciences, Geophysics and Seismology, Physical Sciences and Mathematics, Physics
Two thirds of the surface of our planet are covered by water and are still poorly instrumented, which has prevented the earth science community from addressing numerous key scientific questions. The potential to leverage the existing fiber optic seafloor telecom cables that criss-cross the oceans, by turning them into dense arrays of seismo-acoustic sensors, remains to be evaluated. Here, we [...]
Representation of European hydroclimatic patterns with Self-Organizing Maps
Published: 2019-05-14
Subjects: Climate, Earth Sciences, Environmental Sciences, Hydrology, Life Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Physics, Planetary Sciences
Self-Organizing Maps provide a powerful, non-linear technique of dimensionality reduction that can be used to identify clusters with similar attributes. Here, they were constructed from a 1000-year-long gridded palaeoclimatic dataset, namely the Old World Drought Atlas, to detect regions of homogeneous hydroclimatic variability across the European continent. A classification scheme of 10 regions [...]
Characterising strong force networks produced during granular shear using percolation methods: Revealing the bridge between local grain scale processes and macroscopic sliding
Published: 2019-04-08
Subjects: Earth Sciences, Geology, Geophysics and Seismology, Other Earth Sciences, Physical Sciences and Mathematics, Physics, Tectonics and Structure
Faults, landslides and subglacial till often contain accumulations of granular debris. Their macroscopic motion is at least to some extent determined by the processes operating in this sheared granular material. A valid question in these environments is how the local behaviour at the individual granular contacts actually sums up to influence macroscopic sliding. Laboratory experiments and [...]
A simplified seasonal forecasting strategy, applied to wind and solar power in Europe
Published: 2019-04-01
Subjects: Applied Statistics, Earth Sciences, Environmental Sciences, Physical Sciences and Mathematics, Physics, Probability, Statistics and Probability, Sustainability
We demonstrate levels of skill for forecasts of seasonal-mean wind speed and solar irradiance in Europe, using seasonal forecast systems available from the Copernicus Climate Change Service (C3S). While skill is patchy, there is potential for the development of climate services for the energy sector. Following previous studies, we show that, where there is skill, a simple linear regression-based [...]
Minimal surfaces in porous media: pore-scale imaging of multiphase flow in an altered-wettability Bentheimer sandstone
Published: 2019-03-28
Subjects: Earth Sciences, Fluid Dynamics, Physical Sciences and Mathematics, Physics
We observed features of pore scale fluid distributions during oil-brine displacement in a mixed-wet sandstone rock sample. High-resolution X-ray imaging was used in combination with differential pressure measurements to measure relative permeability and capillary pressure simultaneously during a steady-state waterflood experiment on a sample of Bentheimer sandstone 51.6 mm long and 6.1 mm in [...]
The Impact of Melting Ice Sheets on Future Global Climate
Published: 2019-03-22
Subjects: Climate, Earth Sciences, Hydrology, Oceanography and Atmospheric Sciences and Meteorology, Other Earth Sciences, Physical Sciences and Mathematics, Physics
That is a preprint of an article suubmitted at Applied Greography (20tf of March 19). Climate change studies in the last decades have been based on Global Climate Models (GCM), and the distribution of climatic regions over time extracted from these models can be represented using the Köppen climatic classification. The Köppen approach predicts the distribution of biomes worldwide on the basis of [...]
Poroelastic effects destabilize mildly rate-strengthening friction to generate stable slow slip pulses
Published: 2019-03-18
Subjects: Applied Mechanics, Earth Sciences, Engineering, Geology, Geophysics and Seismology, Mechanical Engineering, Physical Sciences and Mathematics, Physics, Statistical, Nonlinear, and Soft Matter Physics, Tribology
Slow slip events on tectonic faults, sliding instabilities that never accelerate to inertially limited ruptures or earthquakes, are one of the most enigmatic phenomena in frictional sliding. While observations of slow slip events continue to mount, a plausible mechanism that permits instability while simultaneously limiting slip speed remains elusive. Rate-and-state friction has been successful [...]
Hydrodynamic control of gas-exchange velocity in small streams
Published: 2019-03-02
Subjects: Civil and Environmental Engineering, Earth Sciences, Engineering, Environmental Sciences, Fluid Dynamics, Hydraulic Engineering, Physical Sciences and Mathematics, Physics, Planetary Sciences
Gas exchange is a critical component of any biogeochemical mass balance model of dissolved gases in aquatic systems, yet the magnitude and drivers of spatial and temporal variations of air-water exchange rates in shallow streams are poorly understood. We investigated the relationships between gas exchange velocity of carbon dioxide and methane and flow hydraulics at different sections along a [...]
High-resolution prediction of organic matter concentration with hyperspectral imaging on a sediment core
Published: 2019-02-21
Subjects: Analytical Chemistry, Chemistry, Earth Sciences, Environmental Chemistry, Environmental Monitoring, Environmental Sciences, Optics, Physical Sciences and Mathematics, Physics, Sedimentology, Statistical Models, Statistics and Probability
In the case of environmental samples, the use of a chemometrics-based prediction model is highly challenging because of the difficulty in experimentally creating a well-ranged reference sample set. In this study, we present a methodology using short wave infrared hyperspectral imaging to create a partial least squares regression model on a cored sediment sample. It was applied to a sediment core [...]
Calibration of astigmatic particle tracking velocimetry based on generalized Gaussian feature extraction
Published: 2018-11-20
Subjects: Artificial Intelligence and Robotics, Computer Sciences, Earth Sciences, Engineering, Fluid Dynamics, Hydrology, Life Sciences, Physical Sciences and Mathematics, Physics
Flow and transport in porous media are driven by pore scale processes. Particle tracking in transparent porous media allows for the observation of these processes at the time scale of ms. We demonstrate an application of defocusing particle tracking using brightfield illumination and a CMOS camera sensor. The resulting images have relatively high noise levels. To address this challenge, we [...]