Preprints

Filtering by Subject: Applied Mathematics

Urban Air Quality Modeling Using Low-Cost Sensor Network and Data Assimilation in the Aburra Valley, Colombia

Santiago Lopez-Restrepo, Andres Yarce, Nicolas Pinel, O. Lucia Quintero, Arjo Segers, Arnold W. Heemink

Published: 2020-10-29
Subjects: Applied Mathematics, Atmospheric Sciences, Environmental Monitoring

The use of low air quality networks has been increasing in recent years to study urban pollution dynamics. Here we show the evaluation of the operational Aburra Valley's low-cost network against the official monitoring network. The results show that the PM2.5 low-cost measurements are very close to those observed by the official network. Additionally, the low-cost allows a higher spatial [...]

On the use of mesh movement methods to help overcome the multi-scale challenges associated with hydro-morphodynamic modelling

Mariana C A Clare, Joseph Wallwork, Stephan C Kramer, Hilary Weller, Colin J Cotter, Matthew Piggott

Published: 2020-10-22
Subjects: Applied Mathematics, Geomorphology, Mathematics, Numerical Analysis and Computation, Partial Differential Equations

Hydro-morphodynamic models are an important tool that can be used in the protection of coastal zones. They can be required to resolve spatial scales ranging from sub-metre to hundreds of kilometres and are computationally expensive. In this work, we apply mesh movement methods to a depth-averaged hydro-morphodynamic model for the first time, in order to tackle both these issues. Mesh movement [...]

Dynamical analysis of a reduced model for the North Atlantic Oscillation

Courtney Quinn, Dylan Harries, Terence J. O'Kane

Published: 2020-10-21
Subjects: Applied Mathematics, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

We apply a regularized vector autoregressive clustering technique to identify recurrent and persistent states of atmospheric circulation patterns in theNorthAtlantic sector (110W-0E, 20N-90N) associated with the Atlantic Ridge (AR) and the North Atlantic Oscillation (NAO). The technique additionally provides the temporal behavior in terms of a time-dependent switching between the respective [...]

An analytical solution to the Navier–Stokes equation for incompressible flow around a solid sphere

Ahmad Talaei, Timothy J. Garrett

Published: 2020-08-25
Subjects: Applied Mathematics, Earth Sciences, Engineering, Fluid Dynamics, Mechanical Engineering, Other Mechanical Engineering, Partial Differential Equations, Physical Sciences and Mathematics, Physics, Special Functions

This paper is concerned with obtaining a formulation for the flow past a sphere in a viscous and incompressible fluid, building upon previously obtained well-known solutions that were limited to small Reynolds numbers. Using a method based on a summation of separation of variables, we develop a general analytical solution to the Navier--Stokes equation for the special case of axially symmetric [...]

Robust Q estimation using surface seismic data

Joakim Oscar Blanch

Published: 2020-07-30
Subjects: Applied Mathematics, Computational Engineering, Earth Sciences, Engineering, Geophysics and Seismology, Numerical Analysis and Computation, Physical Sciences and Mathematics

Direct wave arrivals are the most robust signals to determine velocity and consequently they have been used for almost a century in hydrocarbon exploration. The reason is simple as the arrivaltime is explicitly available and provide a direct measurement of the average velocity of the sub-surface ray-path. These signals have not been extensively used to estimate attenuation or Q. One reason may [...]

Modelling hydrodynamics in an energetic tidal strait with pronounced bathymetric features

Lucas Mackie, Paul Evans, Magnus Harrold, Tim O`Doherty, Matthew Piggott, Athanasios Angeloudis

Published: 2020-07-16
Subjects: Applied Mathematics, Civil and Environmental Engineering, Civil Engineering, Engineering, Numerical Analysis and Computation, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Characterising tidal hydrodynamics in the vicinity of submerged features can be demanding given the hostility of the marine environment. Logistical challenges in the measurement of such flows has promoted research on wake studies through physical and numerical modelling. In this study, site measurements and modelled data are combined to provide an insight into the regional hydrodynamics within a [...]

Adjoint-based sensitivity analysis for a numerical storm surge model

Simon Warder, Kevin Horsburgh, Matthew Piggott

Published: 2020-06-29
Subjects: Applied Mathematics, Numerical Analysis and Computation, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Numerical storm surge models are essential to forecasting coastal flood hazard and informing the design of coastal defences. However, such models rely on a variety of inputs, many of which will carry uncertainty, and an awareness and understanding of the sensitivity of the model outputs with respect to those uncertain inputs is necessary when interpreting model results. Here, we use an [...]

A comparison of Bayesian inference and gradient-based approaches for friction parameter estimation

Simon Warder, Athanasios Angeloudis, Stephan C. Kramer, Colin Cotter, Matthew Piggott

Published: 2020-06-29
Subjects: Applied Mathematics, Numerical Analysis and Computation, Oceanography, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

Numerical tidal models are essential to the study of a variety of coastal ocean processes, but typically rely on uncertain inputs, including a bottom friction parameter which can in principle be spatially varying. Here we employ an adjoint-capable numerical ocean model, Thetis, and apply it to the Bristol Channel and Severn Estuary, using a spatially varying Manning coefficient within the bottom [...]

Seasonal impact-based mapping of compound hazards

John Hillier, Richard Dixon

Published: 2020-06-17
Subjects: Applied Mathematics, Atmospheric Sciences, Climate, Earth Sciences, Environmental Sciences, Hydrology, Mathematics, Multivariate Analysis, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics, Statistics and Probability

Impact-based, seasonal mapping of compound hazards is proposed. It is pragmatic, identifies phenomena to drive the research agenda, produces outputs relevant to stakeholders, and could be applied to many hazards globally. Illustratively, flooding and wind damage can co-occur, worsening their joint impact, yet where wet and windy seasons combine has not yet been systematically mapped. Here, [...]

Description of the continuous nature of organic matter in models of soil carbon dynamics

Julien Sainte-Marie, Matthieu Barrandon, Laurent Sainte-André, Eric Gelhaye, Francis Martin, Delphine Derrien

Published: 2020-05-29
Subjects: Applied Mathematics, Earth Sciences, Environmental Microbiology and Microbial Ecology Life Sciences, Geochemistry, Life Sciences, Microbiology, Physical Sciences and Mathematics, Soil Science

The understanding of soil organic matter (SOM) dynamics has considerably advanced in recent years. It was previously assumed that most SOM consisted of recalcitrant compounds, whereas the emerging view considers SOM as a range of polymers continuously processed into smaller molecules by decomposer enzymes. Mainstreaming these new insights in current models is challenging because of their [...]

Stress Recovery for the Particle-in-cell Finite Element Method

Haibin Yang, Louis Moresi, John Mansour

Published: 2020-05-26
Subjects: Applied Mathematics, Computer Sciences, Earth Sciences, Geophysics and Seismology, Mathematics, Numerical Analysis and Computation, Numerical Analysis and Scientific Computing, Physical Sciences and Mathematics, Tectonics and Structure

The interelement stress in the Finite Element Method is not continuous in nature, and stress projections from quadrature points to mesh nodes often causes oscillations. The widely used particle-in-cell method cannot avoid this issue and produces worse results when there are mixing materials of large strength (e.g., viscosity in Stokes problems) contrast in one element. The post-processing methods [...]

Quantification and interpretation of the climate variability record

Anna S von der Heydt, Peter Ashwin, Charles D. Camp, Michel Crucifix, Henk A Dijkstra, Peter Ditlevsen, Timothy M Lenton

Published: 2020-05-25
Subjects: Applied Mathematics, Earth Sciences, Oceanography and Atmospheric Sciences and Meteorology, Physical Sciences and Mathematics

This paper is currently in review for Global and Planetary Change. \\ The spectral view of variability is a compelling and adaptable tool for understanding variability of the climate. In the Mitchell (1976) seminal paper, it was used to express, on one graph with log scales, a very wide range of climate variations from millions of years to days. The spectral approach is particularly useful for [...]

A mixed $RT_0 - P_0$ Raviart-Thomas finite element implementation of Darcy Equation in GNU Octave

Agah D. Garnadi, Corinna Bahriawati

Published: 2020-04-14
Subjects: Applied Mathematics, Bioresource and Agricultural Engineering, Chemical Engineering, Computational Engineering, Earth Sciences, Engineering, Environmental Sciences, Hydrology, Numerical Analysis and Computation, Partial Differential Equations, Physical Sciences and Mathematics, Water Resource Management

In this paper we shall describe mixed formulations -differential and variational- of Darcys flow equation, an important model of elliptic problem. We describe * Galerkin method with finite dimensional spaces; * Local matrices and assembling; * Raviart-Thomas $RT_0 - P_0$ elements; * Edge basis and local matrices for $RT_0 - P_0$ FEM; * Model problem with corresponding local matrices, right hand [...]

SymAE: an autoencoder with embedded physical symmetries for passive time-lapse monitoring

Pawan Bharadwaj, Matt Li, Laurent Demanet

Published: 2020-04-13
Subjects: Applied Mathematics, Computer Sciences, Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

We introduce SymAE, an auto-encoder architecture that learns to separate multichannel passive-seismic datasets into qualitatively interpretable components: one component corresponds to path-specific effects associated with subsurface properties while the other component corresponds to the spectral signature of the passive sources. This information is represented by two latent codes produced by [...]

Global Sensitivity Analysis to Optimize Basin-Scale Conductive Model Calibration - Insights on the Upper Rhine Graben

Denise Degen, Karen Veroy, Jessica Freymark, Magdalena Scheck-Wenderoth, Florian Wellmann

Published: 2020-04-01
Subjects: Applied Mathematics, Earth Sciences, Physical Sciences and Mathematics

Geothermal simulations are widely used in both scientific and applied industrial contexts. Typically, the temperature state is evaluated on the basis of the heat equation, with suitable parameterizations of the model domain and defined boundary conditions, which are calibrated to obtain a minimal misfit between measured and simulated temperature values. We demonstrate the essential need for [...]

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