scholarly journals Image-model coupling: a simple information theoretic perspective for image sequences

2009 ◽  
Vol 16 (2) ◽  
pp. 197-210
Author(s):  
N. D. Smith ◽  
C. N. Mitchell ◽  
C. J. Budd
Keyword(s):  
Channel Model ◽  
Coupling Model ◽  
Model Coupling ◽  
Model Output ◽  
Image Model ◽  
Physical Processes ◽  
Information Theoretic ◽  
Discrete Channel ◽  
History Of ◽  
Earth’S Climate

Abstract. Images are widely used to visualise physical processes. Models may be developed which attempt to replicate those processes and their effects. The technique of coupling model output to images, which is here called "image-model coupling", may be used to help understand the underlying physical processes, and better understand the limitations of the models. An information theoretic framework is presented for image-model coupling in the context of communication along a discrete channel. The physical process may be regarded as a transmitter of images and the model as part of a receiver which decodes or recognises those images. Image-model coupling may therefore be interpreted as image recognition. Of interest are physical processes which exhibit "memory". The response of such a system is not only dependent on the current values of driver variables, but also on the recent history of drivers and/or system description. Examples of such systems in geophysics include the ionosphere and Earth's climate. The discrete channel model is used to help derive expressions for matching images and model output, and help analyse the coupling.

scholarly journals Image-model coupling: application to an ionospheric storm

2010 ◽  
Vol 17 (4) ◽  
pp. 361-369 ◽  
Author(s):  
N. D. Smith ◽  
D. Pokhotelov ◽  
C. N. Mitchell ◽  
C. J. Budd
Keyword(s):  
Tomographic Reconstruction ◽  
Model Coupling ◽  
Electron Content ◽  
Ionospheric Model ◽  
Image Model ◽  
Ionospheric Storm ◽  
Physical Processes ◽  
Tomographic Images ◽  
Ensemble Technique ◽  
Statistical Relationships

Abstract. Techniques such as tomographic reconstruction may be used to provide images of electron content in the ionosphere. Models are also available which attempt to describe the dominant physical processes operating in the ionosphere, or the statistical relationships between ionospheric variables. It is sensible to try and couple model output to tomographic images with the aim of inferring the values of driver variables which best replicate some description of electron content imaged in the ionosphere, according to some criterion. This is a challenging task. The following describes an attempt to couple an ionospheric model to a tomographic reconstruction of the geomagnetic storm of 20 November 2003, along a latitudal line segment above north America. A simple model was chosen to reduce the number of input drivers that were varied. The investigation illustrates some of the issues involved in image-model coupling. The ability to make scientific deductions depends on the accuracy of the assumptions in the ionospheric model and the accuracy of the tomographic reconstruction. An ensemble technique was used to help assess confidence in the reconstruction.

scholarly journals Learning dominant physical processes with data-driven balance models

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jared L. Callaham ◽  
James V. Koch ◽  
Bingni W. Brunton ◽  
J. Nathan Kutz ◽  
Steven L. Brunton
Keyword(s):  
Nonlinear Optics ◽  
Unsupervised Learning ◽  
History Of Science ◽  
Traditional Approach ◽  
Data Driven ◽  
Mechanistic Models ◽  
Physical Processes ◽  
History Of ◽  
Separation Of Scales ◽  
Geophysical Fluids

AbstractThroughout the history of science, physics-based modeling has relied on judiciously approximating observed dynamics as a balance between a few dominant processes. However, this traditional approach is mathematically cumbersome and only applies in asymptotic regimes where there is a strict separation of scales in the physics. Here, we automate and generalize this approach to non-asymptotic regimes by introducing the idea of an equation space, in which different local balances appear as distinct subspace clusters. Unsupervised learning can then automatically identify regions where groups of terms may be neglected. We show that our data-driven balance models successfully delineate dominant balance physics in a much richer class of systems. In particular, this approach uncovers key mechanistic models in turbulence, combustion, nonlinear optics, geophysical fluids, and neuroscience.

Effects of Continents and Supercontinents on Climate

2004 ◽  
Author(s):  
John J. W. Rogers ◽  
M. Santosh
Keyword(s):  
Global Climate ◽  
Climatic Conditions ◽  
Polar Regions ◽  
The North ◽  
Rock Types ◽  
Control Climate ◽  
The Earth ◽  
History Of ◽  
Earth’S Climate ◽  
Geologic Record

Continents affect the earth’s climate because they modify global wind patterns, control the paths of ocean currents, and absorb less heat than seawater. Throughout earth history the constant movement of continents and the episodic assembly of supercontinents has influenced both global climate and the climates of individual continents. In this chapter we discuss both present climate and the history of climate as far back in the geologic record as we can draw inferences. We concentrate on longterm changes that are affected by continental movements and omit discussion of processes with periodicities less than about 20,000 years. We refer readers to Clark et al. (1999) and Cronin (1999) if they are interested in such short-term processes as El Nino, periodic variations in solar irradiance, and Heinrich events. The chapter is divided into three sections. The first section describes the processes that control climate on the earth and includes a discussion of possible causes of glaciation that occurred over much of the earth at more than one time in the past. The second section investigates the types of evidence that geologists use to infer past climates. They include specific rock types that can form only under restricted climatic conditions, varieties of individual fossils, diversity of fossil populations, and information that the 18O/16O isotopic system can provide about temperatures of formation of ancient sediments. The third section recounts the history of the earth’s climate and relates changes to the growth and movement of continents. This history takes us from the Archean, when climates are virtually unknown, through various stages in the evolution of organic life, and ultimately to the causes of the present glaciation in both the north and the south polar regions. The earth’s climate is controlled both by processes that would operate even if continents did not exist and also by the positions and topographies of continents. We begin with the general controls, then discuss the specific effects of continents, and close with a brief discussion of processes that cause glaciation. The general climate of the earth is determined by the variation in the amount of sunshine received at different latitudes, by the earth’s rotation, and by the amount of arriving solar energy that is retained in the atmosphere.

scholarly journals Physical Processes in Temperate Glaciers

1976 ◽  
Vol 16 (74) ◽  
pp. 151-158 ◽  
Author(s):  
L. Lliboutry
Keyword(s):  
Grain Size ◽  
Liquid Phase ◽  
Water Content ◽  
Past History ◽  
Salt Content ◽  
Physical Processes ◽  
The Past ◽  
Glacier Ice ◽  
History Of

AbstractIn a temperate glacier ice the water content results from the past history of the ice, and the temperature adjusts itself to the appropriate value. Results obtained by the Laboratoire de Glaciologie are summarized. Several facts seem to prove some migration of the liquid phase and a coalescence of liquid inclusions. The enthalpy flux is calculated, but it cannot be proved that a spontaneous gathering together of liquid inclusions could occur. The water-rich, small grain-size layers should come from the lowering of the viscosity when the water content increases, as discovered by Duval. The form of Weertman’s sliding law without cavitation can be derived from simple dimensional considerations. Numerically, it cannot account for high sliding velocities, for which subglacial cavitation must be introduced. The cavities are infilled with more stagnant regelation ice than water. Two subglacial hydraulic regimes are distinguished: autonomous and interconnected. The effect which the salt content may have on cavitation is estimated.

Topological Climate Change

2020 ◽  
Vol 30 (02) ◽  
pp. 2030005 ◽  
Author(s):  
Kolja L. Kypke ◽  
William F. Langford
Keyword(s):  
Past History ◽  
Balance Model ◽  
Physical Parameters ◽  
Qualitative Behavior ◽  
Early Eocene ◽  
Topological Change ◽  
The North ◽  
Equable Climate ◽  
History Of ◽  
Earth’S Climate

This article presents a bifurcation analysis of a simple Energy Balance Model (EBM) of the Earth’s climate, which suggests that topological change has occurred in the paleoclimate history of the Earth. In the theory of dynamical systems, two systems that are topologically equivalent have solutions with the same qualitative behavior. A change in the topological equivalence class, as parameters are varied, is called a bifurcation. Thus, a bifurcation demarcates a significant change in the behavior of the solutions of a dynamical system. If that system represents climate, then that topological change may represent an abrupt transformation of the climate, occurring even with a very small change in the forcing parameters. In this paper, the existence of a cusp bifurcation is proven in a climate EBM. The existence of this cusp bifurcation implies the co-existence of two distinct stable equilibrium climate states (bistability), as well as the existence of abrupt transitions between these two states (fold bifurcations) in the EBM. These transitions are dependent on the past history of the system (hysteresis). The two universal unfolding parameters for the cusp bifurcation have been determined as functions of the relevant physical parameters. These ideas lead to the proposal of a new explanation for the so-called warm equable climate problem of the mid-Cretaceous and early Eocene. The analysis presented here implies that the mid-Cretaceous and early Eocene climate systems are topologically equivalent to each other, but they are not topologically equivalent to the preindustrial modern climate. The transition from the warm, equable paleoclimate to today’s cooler nonequable climate occurs via fold (or saddle-node) bifurcations in the EBM, which correspond to the Eocene-Oligocene Transition (EOT) at the south pole and the Pliocene-Pleistocene Transition (PPT) at the north pole, in the paleoclimate record of Earth.

The Ocean Acidification Challenges Facing Science and Society

2011 ◽  
Author(s):  
Carol Turley ◽  
Kelvin Boot
Keyword(s):  
Climate Change ◽  
Ocean Acidification ◽  
Well Being ◽  
Montreal Protocol ◽  
Positive Gain ◽  
History Of ◽  
Negative Impacts ◽  
Mitigate Climate Change ◽  
Earth’S Climate ◽  
Over Exploitation

Human development, inspiration, invention, and aspiration have resulted in a rapidly growing population, with each generation aspiring to greater wealth and well-being, so having greater needs than the previous generation. Amongst the resulting negative impacts are over-exploitation of planetary resources and the build-up of gases in the atmosphere and oceans to the extent that they are changing earth’s climate and ocean chemistry (IPCC 2007). However, the history of humanity’s relationship to the environment has shown that, if threatened, society can respond rapidly to environmental risks, introducing better practices, controls, regulations, and even global protocols, for example the reduction of city smog, the move from leaded to unleaded petrol, and reduction of chlorofluorocarbon (CFC) production to reduce loss of the ozone layer. Nearly all of these changes have led to direct and obvious positive gain to human health and well-being which has been a driving force in the production, agreement and implementation of the policies and laws that have brought them about. The spatial scale or ‘ecological footprint’ of these risks has increased with time, such that international agreements and protocols, like the Montreal Protocol for CFCs, have been increasingly necessary for reducing them. Along with the globalization of agriculture, business, industry, and financial markets and the expansion of the human population goes the globalization of risk to the environment. Climate change and ocean acidification are global issues with solutions that are only possible through global agreements and action. Substantial proportions of nations’ gross domestic product (GDP) were used to secure the banks and major industries in the economic crises that have swept the world in the last few years, far greater than the 1 to 2% per annum estimated to be required to mitigate climate change (Stern 2006). However, the response to the economic crisis does show that global society can react rapidly when it believes it is necessary. The question is, when do society and governments deem it necessary to act, and to act together? One issue may be time, the perceived immediacy of the crisis.

Effects of Multiplicative Power Law Neural Noise in Visual Information Processing

2011 ◽  
Vol 23 (4) ◽  
pp. 1015-1046 ◽  
Author(s):  
José M. Medina
Keyword(s):  
Power Law ◽  
Visual Information ◽  
Information Transfer ◽  
Channel Model ◽  
Internal Noise ◽  
Minimum Information ◽  
Information Theoretic ◽  
Neural Noise ◽  
Weakly Coupled ◽  
Transfer Of Information

The human visual system is intrinsically noisy. The benefits of internal noise as part of visual code are controversial. Here the information-theoretic properties of multiplicative (i.e. signal-dependent) neural noise are investigated. A quasi-linear communication channel model is presented. The model shows that multiplicative power law neural noise promotes the minimum information transfer after efficient coding. It is demonstrated that Weber's law and the human contrast sensitivity function arise on the basis of minimum transfer of information and power law neural noise. The implications of minimum information transfer in self-organized neural networks and weakly coupled neurons are discussed.

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