摘要:

A perturbation theory is developed to describe modon propagation over slowly varying topography. The theory is developed from the rigid-lid shallow-water equations on an infinite β-plane. Nonlinear hyperbolic equations are derived, based on the conservation of energy, enstrophy and vorticity, to describe the evolution of the slowly varying modon radius, translation speed and wavenumber for arbitrary finite-amplitude topography. To leading order, the modon is unaffected by meridional gradients in topography. Analytical perturbation solutions for the modon radius, translation speed and wavenumber are obtained for small-amplitude topography. The perturbations take the form of hyperbolic transients and a stationary component proportional to the topography. The solution predicts that as the modon moves into a region of shallower (deeper) fluid the modon radius increases (decreases), the translation speed decreases (increases) and the modon wavenumber decreases (increases). In addition, as the modon propagates into a region of shallower (deeper) fluid there is an amplification (diminishing) of the extrema in the streamfunction and vorticity fields. These properties suggest that the modon may be able to be topographically-captured and amplified, and thus may have application to the onset of atmospheric blocking. The general solution is applied to mid-latitude scales and a ridge-like topographic feature.

ISSN:0309-1929    

DOI:10.1080/03091928608208798

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Inertia-gravity waves trapped by a constant depth gradient against a vertical barrier are studied in an asymptotic limit (high frequency, weak depth gradient) of the shallow water equations; anf-plane is assumed. Both a numerical solution and an approximate analytical solution, which are in broad agreement, are presented. The waves display properties different from channel Kelvin and Poincark waves and different from coastal waves. Implications of inertia-gravity wave trapping for geostrophic adjustment in a channel fluid model are explored.

ISSN:0309-1929    

DOI:10.1080/03091928608208799

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

We have studied the behavior of nonlinear waves in isothermal atmospheres using an improved beam scheme method. It is shown that although the magnitude of the mass leakage due to side beams is significant, nevertheless in a motion close to hydrostatic equilibrium it can be suppressed, if special density distributions and/or suitable mesh intervals are selected. We adopt as the parameters for our model of the atmospheresM=1 M⊙,R=50 R⊙ andT=4864 K. The time variation of the physical quantities in each cell is found for several oscillation periods. The critical frequency for the model atmosphere in the case of waves with a weak nonlinearity seems to be consistent with that in the linear theory.

ISSN:0309-1929    

DOI:10.1080/03091928608208800

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The effect of an imposed horizontal magnetic field on two-dimensional convection in a plane layer heated from below is studied in the presence of periodic boundary conditions in the horizontal. An amplitude equation describing the transitions between travelling and standing waves and steady convection near a particular multiple bifurcation is derived. When the first instability is oscillatory, two solution branches bifurcate simultaneously from the conduction solution, corresponding to travelling and standing waves. The branch of travelling waves is stable throughout and terminates on the steady state branch in a steady state bifurcation as the Rayleigh number is increased. Beyond this point stable overturning convection is found. Standing waves are unstable. The results are indicative of the larger amplitude behavior of the system.

ISSN:0309-1929    

DOI:10.1080/03091928608208801

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A method for measuring liquid-gas and liquid-liquid interface height fields is presented. The technique uses the optical rotation properties of certain liquids, and provides a simple way to obtain global data on interfacial waves. The sensitivity of one version of our instrument is better than 0.05mm. Data on the essential properties of candidate fluids are given, and an application involving the visualization of baroclinic waves in a two-layer system is described.

ISSN:0309-1929    

DOI:10.1080/03091928608208802

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor