摘要:

The theory of the index cycle presented here is based on the action of the turbulent Coriolis force. Unlike the ordinary Coriolis force this force does work at a rate equal to the energy exchange between the kinetic energy of the regular motions and that of the turbulent motions. It is shown that in a rotating, differentially-heated fluid the turbulent Coriolis force generates a particular type of instability which we call“gyroturbulent instability”. Gyroturbulent instability is associated with barotropic transfer within the kinetic energy spectrum of a rotating turbulent fluid, and is connected with the conversion of kinetic energy between eddy energy and energy of mean flow as a result of the action of the turbulent Coriolis force. Gyroturbulent instability generates specific oscillations in the general circulation of the atmosphere between the state of high index with weak turbulence and that of low index with strong turbulence (the index cycle). In laboratory rotating annulus experiments, the analogous oscillation is called “vacillation”. Gyroturbulent oscillations are oscillations in the shape of the energy spectrum, the total kinetic energy being constant. Using perturbation theory, an analytical expression for the period of the index cycle is obtained. A strong similarity between the index cycle and vacillation is found. A comparison of the theoretical results with observations seems rather promising.

ISSN:0309-1929    

DOI:10.1080/03091928008243646

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

We consider a linearized, two-dimensional flow of moist air over a ridge. The moisture is assumed to be in a layer adjacent to the mountain and the cloud that forms as a result of the wave induced motion is assumed to be next to the mountain. We model pseudo adiabatic effects as follows: Latent heat is released when vertical displacements exceed a fixed quantity, ζ and when the motion is upwards. In the let of the cloud warm and cold wakes are found to alternate with height. Although we do not consider Coriolis forces, the presence of these warm wakes might have important implications in cyclogenesis in the Ice of mountain chains.

ISSN:0309-1929    

DOI:10.1080/03091928008243647

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The modulation of a topographic planetary wave packet in a stratified Ocean is discussed. The evolution of the packet is described by a nonlinear Schrödinger equation. The equation is used to derive the stability criterion of the uniform wavetrain. The analysis shows that the long wave resonance occurs when the group velocity of the primary wave packet equals the phase speed of the induced long wave. The evolution equations which describe the resonance are obtained and used to discuss the stability of a plane wave solution.

ISSN:0309-1929    

DOI:10.1080/03091928008243648

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

It is examined how the variational principle of Chandrasekhar and Lebovitz for adiabatic non-radial oscillations of a spherical star. and the variational principle for wave motions in a horizontal atmospheric layer given by Tolstoy stem for Hamilton's principle. The known variational functionals are recovered from the Lagrangian that is defined as the difference between the change in kinetic energy and the sum of the changes in the internal and gravitational potential energies. Certain terms of the Lagrangian vanish because of the boundary conditions of the star's equilibrium. The implications for the canonical energy densities and the canonical energy fluxes that are derived from the various Lagrangians are considered.

ISSN:0309-1929    

DOI:10.1080/03091928008243649

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The pseudoscalar χu(flux helicity), which determines the number of linked flow lines in a simply-connected volume, and the scalarIHv, which is proportional to the number of linkages of flow lines with magnetic field lines, are introduced. By these quantities a topological formulation of an antidynamo theorem is given. The conditions required for slow dynamo action are clarified. The relation of the flux helicity to the usual vortex helicity is discussed.

ISSN:0309-1929    

DOI:10.1080/03091928008243650

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This is the second in a series of papers intended to develop a practical theory for the motion of an iron-alloy core containing a slurry. We have developed a simplified theory based upon the general theory developed in the first paper (Loper and Roberts, 1978) and have solved completely a relatively simple problem to verify that our theory is complete and solvable and o illustrate some of its basic features. These features include diffusion of material driven by the hydrostatic pressure gradient and solidification of material onto a moving boundary of unknown position. The solution includes a linear stability analysis for the onset of convection driven by compositional buoyancy and the resulting nonlinear steady state which occurs in the long wavelength limit. Two important ideas emerged from the analysis of the strongly nonlinear convective state which occurs far above critical. First, the motions mix the fluid vigorously, producing a state of nearly constant composition. Second, two distinct timescales occur: a long evolutionary time and a short convective time.

ISSN:0309-1929    

DOI:10.1080/03091928008243651

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The linear propagation properties of wave motions in a rapidly rotating stratified Boussinesq spherical shell, of outer radius 1 and inner radius η, are studied in the small Prandtl number limit. When η = 0, the various possible motions can be accommodated in two classes: F and D. The class F is closely related to the class of free oscillations of the inviscid unstratified fluid shell while D corresponds to diffusive inertial-gravity waves. Both F and D are subdivided into two infinite sets of modes one of which (E) is symmetric and the other (O) is anti-symmetric about the equatorial plane. The sets E and 0 for class F are further subdivided into two infinite subsets one of which propagates (in phase) eastward and the other westward. Waves of class D propagate eastward. The two classes F and D are decoupledexceptfor one mode which belongs to D on and in the immediate neighbourhood of the axis of rotation and transforms into F away from the axis. This mode provided the already known mode of convection of the linear stability of a fluid sphere containing a uniform distribution of heat sources. When an inner solid core is present (and η is non-zero) all the modes of classes F and D persist outside C, (whereC, is the coaxial cylinder whose generators touch the inner core at its equator) but the set E of modes (of both F and D) issuppressedwithinCc.

ISSN:0309-1929    

DOI:10.1080/03091928008243652

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

By E. N. Parker. Oxford University Press. xvii + 841 pp. Price £45 ISBN 0-19-851290-2, 1979.

ISSN:0309-1929    

DOI:10.1080/03091928008243653

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091928008243654

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091928008243655

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor