Preprints
Filtering by Subject: Physics
Nonlinear stochastic dissipation in turbulent geophysical flows
Published: 2020-06-19
Subjects: Earth Sciences, Fluid Dynamics, Physical Sciences and Mathematics, Physics
The purpose of this study is to further investigate the assumption that geophysical flows can be described and simulated by direct sampling from a dynamically constrained probability distribution, with a reversible formulation of dissipation. This is done by making the probability of the flow decrease with the deviation of entropy with respect to local equilibrium, and by assuming that this [...]
Sampling geophysical flows from a dynamically constrained probability distribution
Published: 2020-06-19
Subjects: Earth Sciences, Fluid Dynamics, Physical Sciences and Mathematics, Physics
The purpose of this study is to further investigate the problem of explicitly simulating uncertainties in geophysical models. Rather than introducing stochastic processes in forward-in-time partial differential equations, this is done here by reformulating the dynamical equations governing the time evolution of the flow as a probability distribution. Flows can then be drawn directly from the [...]
Increasing economic drought impacts in Europe with anthropogenic warming
Published: 2020-05-13
Subjects: Climate, Earth Sciences, Environmental Sciences, Hydrology, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Physics
While climate change will alter the distribution in time and space of water, quantifications of drought risk in view of global warming remain little explored. Here, we show that in Europe drought damages could strongly increase with global warming and cause a strong regional imbalance in future drought impacts. In the absence of climate action (4°C in 2100 and no adaptation) annual drought losses [...]
Constraining global changes in temperature and precipitation from observable changes in surface radiative heating
Published: 2020-04-30
Subjects: Climate, Earth Sciences, Environmental Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Physics
Changes in the atmospheric composition alter the magnitude and partitioning between the downward propagating solar and atmospheric longwave radiative fluxes heating the Earths surface. These changes are computed by radiative transfer codes in Global Climate Models and measured with high precision at surface observation networks. Changes in radiative heating signify changes in the global surface [...]
Interferometry with ALOS-2 full-aperture ScanSAR data
Published: 2020-04-14
Subjects: Aerospace Engineering, Civil and Environmental Engineering, Earth Sciences, Electrical and Computer Engineering, Engineering, Geology, Geophysics and Seismology, Glaciology, Mining Engineering, Other Engineering, Physical Sciences and Mathematics, Physics, Tectonics and Structure, Volcanology
Advanced Land Observing Satellite-2 (ALOS-2) is designed to routinely acquire both scanning synthetic aperture radar (ScanSAR) and stripmap data. In this paper, we present a special multiband bandpass filter (MBF) to remove azimuth nonoverlap spectra for the interferometric processing of ALOS-2 full-aperture ScanSAR product. As required by the MBF, we estimate the important ScanSAR system [...]
Estimating Azimuth Offset With Double-Difference Interferometric Phase: The Effect of Azimuth FM Rate Error in Focusing
Published: 2020-04-06
Subjects: Aerospace Engineering, Civil and Environmental Engineering, Earth Sciences, Electrical and Computer Engineering, Engineering, Environmental Sciences, Geology, Geomorphology, Geophysics and Seismology, Glaciology, Hydrology, Mining Engineering, Other Earth Sciences, Physical Sciences and Mathematics, Physics, Tectonics and Structure, Volcanology
Estimating azimuth offset with double-difference interferometric (DDI) phase, which is called multiple-aperture interferometric synthetic aperture radar (InSAR) or spectral diversity, is increasingly used in recent years to measure azimuth deformation or to accurately coregister a pair of InSAR images. We analyze the effect of frequency modulation (FM) rate error in focusing on the DDI phase with [...]
Event-based contact angle measurements inside porous media using time-resolved micro-computed tomography
Published: 2020-01-28
Subjects: Earth Sciences, Fluid Dynamics, Hydrology, Physical Sciences and Mathematics, Physics
Hypothesis Capillary-dominated multiphase flow in porous materials is strongly affected by the pore walls’ wettability. Recent micro-computed tomography (mCT) studies found unexpectedly wide contact angle distributions measured on static fluid distributions inside the pores. We hypothesize that analysis on time-resolved mCT data of fluid invasion events may be more directly relevant to the fluid [...]
Dynamics of displacement in mixed-wet porous media
Published: 2020-01-22
Subjects: Earth Sciences, Engineering, Fluid Dynamics, Physical Sciences and Mathematics, Physics
We identify a distinct two-phase flow invasion pattern in a mixed-wet porous medium. Time-resolved high-resolution synchrotron X--ray imaging is used to study the invasion of water through a small rock sample filled with oil, characterized by a wide non-uniform distribution of local contact angles both above and below $90^{\circ}$. The water advances in a connected front, but throats are not [...]
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: 2019-05-15
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 [...]