Skip to main content

1987 | Buch

Topics in Geophysical Fluid Dynamics: Atmospheric Dynamics, Dynamo Theory, and Climate Dynamics

verfasst von: M. Ghil, S. Childress

Verlag: Springer New York

Buchreihe : Applied Mathematical Sciences

insite
SUCHEN

Über dieses Buch

The vigorous stirring of a cup of tea gives rise, as we all know, to interesting fluid dynamical phenomena, some of which are very hard to explain. In this book our "cup of tea" contains the currents of the Earth's atmosphere, oceans, mantle, and fluid core. Our goal is to under­ stand the basic physical processes which are most important in describing what we observe, directly or indirectly, in these complex systems. While in many respects our understanding is measured by the ability to predict, the focus here will be on relatively simple models which can aid our physical intuition by suggesting useful mathematical methods of investiga­ tion. These elementary models can be viewed as part of a hierarchy of models of increasing complexity, moving toward those which might be use­ fully predictive. The discussion in this book will deal primarily with the Earth. Interplanetary probes of Venus, Mars, Jupiter and Saturn have revealed many exciting phenomena which bear on geophysical fluid dynamics. They have also enabled us to see the effect of changing the values of certain parameters, such as gravity and rotation rate, on geophysical flows. On the other hand, satellite observations of our own planet on a daily and hourly basis have turned it into a unique laboratory for the study of fluid motions on a scale never dreamt of before: the motion of cyclones can be observed via satellite just as wing tip vortices are studied in a wind tunnel.

Inhaltsverzeichnis

Frontmatter

Fundamentals

Chapter 1. Effects of Rotation
Abstract
The rotation of the Earth has an important dynamical effect on the fluid environment and we begin our discussion by studying the role of large-scale rotation in simple cases. In this chapter, the Rossby number is defined as a nondimensional measure of the importance of rotation. The usefulness of a rotating frame of reference is outlined.
M. Ghil, S. Childress
Chapter 2. Effects of Shallowness
Abstract
The most important geometrical approximation in geophysical fluid dynamics stems from the effective shallowness of the fluid layers relative to global horizontal scales of atmospheric and oceanic flow. In the present chapter we shall study this approximation in the simplest setting of an incompressible inviscid fluid of constant density, with uniform body force (gravitation) acting vertically downwards. The resulting approximate description of motion in a frame which rotates about a vertical axis is usually referred to as rotating shallow-water theory.
M. Ghil, S. Childress
Chapter 3. The Quasi-Geostrophic Approximation
Abstract
Rossby waves are of geophysical interest because of their relatively long periods. These periods correspond to the slow time scale of the motions with large horizontal length scale in the atmosphere and oceans. The relevant dynamical balance is worthy of further study.
M. Ghil, S. Childress

Large-Scale Atmospheric Dynamics

Chapter 4. Effects of Stratification: Baroclinic Instability
Abstract
In Chapters 1 and 2, we have considered the influence of rotation and of shallowness on geophysical flows. The combined effects of the two led to the quasi-geostrophic shallow-water theory of Chapter 3. In this theory, the fluid has constant density and variations of the flow in the vertical are negligibly small. In spite of these idealizations, the theory was able to explain some features of atmospheric and oceanic flows with large horizontal scales, such as planetary waves in the atmosphere and western boundary currents in the ocean.
M. Ghil, S. Childress
Chapter 5. Changing Flow Patterns and Successive Bifurcations
Abstract
Out of Sections 4.2 through 4.4 emerges a certain view of midlatitude atmospheric circulation. It is dominated by essentially axisymmetric, zonal flow — the prevailing westerlies. They represent the climatological mean of daily flow patterns. The zonal mean flow is baroclinically unstable, and cyclone waves grow on it, reaching finite amplitude and then decaying, to be replaced by new growth of instabilities.
M. Ghil, S. Childress
Chapter 6. Persistent Anomalies, Blocking and Predictability
Abstract
The rotating annulus experiments presented in the last chapter reproduce some important qualitative features of the atmosphere’s highly complex general circulation. Sequences of daily weather charts show large-scale wave-like patterns retrogressing with respect to a westerly mean zonal flow. These traveling planetary waves have many similarities with the corresponding Rossby wave regime in a rotating annulus. The atmospheric traveling waves, however, are much less regular than the laboratory waves. They are superimposed, moreover, on standing waves forced by zonal asymmetries of the Earth’s surface, as discussed toward the end of Section 4.4, and in Section 4.6.
M. Ghil, S. Childress

Dynamo Theory

Chapter 7. Models of Geomagnetism: A Survey
Abstract
We turn now to a problem of internal geophysical fluid dynamics connected with the explanation of the geomagnetic field. In the present chapter we shall examine some basic facts concerning geomagnetism and outline the main approaches that have been used to model it. Many of the ideas are applicable to planetary magnetism generally, and also to the solar magnetic cycle.
M. Ghil, S. Childress
Chapter 8. Kinematic Dynamo Theory
Abstract
Kinematic dynamo theory is concerned with solutions of the induction equation (7.8), which we rewrite here in the form
$$ \frac{{\partial B}} {{\partial t}} - \eta \nabla ^2 B = B \cdot \nabla u - u \cdot \nabla B, $$
(8.1a)
for a given velocity field u(r,t). In its broadest sense, the theory seeks to discover, among some classes of admissible u, those functions which lead to “dynamo action”, as discussed in Section 7.3. The precise meaning of dynamo action will generally depend upon the nature of the admissible functions u.
M. Ghil, S. Childress
Chapter 9. The Hydrodynamic Basis for Geomagnetism
Abstract
We turn now to the study of those aspects of the hydrodynamics of rotating, electrically conducting fluids, which can be expected to play some role in establishing the geodynamo. Current thinking favors convection within the spherical fluid shell between mantle and inner core as a mechanism apt to create the appropriate flow field u on which the magnetic field B can grow andbe maintained against dissipative loss in u and B.
M. Ghil, S. Childress

Theoretical Climate Dynamics

Chapter 10. Radiation Balance and Equilibrium Models
Abstract
Climate dynamics is a relatively new member of the family of geophysical sciences. Descriptive climatology goes back, of course, at least to the ancient Greeks, who realized the importance of the Sun’s mean zenith angle in determining the climate of a given latitude belt, as well as that of land-sea distribution in determining the regional, zonally asymmetric characteristics of climate. The general human perception of climate change is also preserved in numerous written records throughout history, starting with the floods described in the epic of Gilgamesh and in the Bible.
M. Ghil, S. Childress
Chapter 11. Glaciation Cycles: Phenomenology and Slow Processes
Abstract
The previous chapter dealt with the climatic system’s radiation balance, which led to the formulation of equilibrium models. Slow changes of these equilibria due to external forcing,internal fluctuations about an equilibrium, and transitions from one possible equilibrium to another one were also studied.
M. Ghil, S. Childress
Chapter 12. Climatic Oscillators
Abstract
In Section 11.1 we reviewed some of the geological evidence for glaciation cycles during the Quaternary period. Large changes in global ice volume and changes of a few degrees in global mean temperature have occurred repeatedly over the last two million years. It is these changes we would like to investigate in the present chapter with the help of very simple models.
M. Ghil, S. Childress
Backmatter
Metadaten
Titel
Topics in Geophysical Fluid Dynamics: Atmospheric Dynamics, Dynamo Theory, and Climate Dynamics
verfasst von
M. Ghil
S. Childress
Copyright-Jahr
1987
Verlag
Springer New York
Electronic ISBN
978-1-4612-1052-8
Print ISBN
978-0-387-96475-1
DOI
https://doi.org/10.1007/978-1-4612-1052-8