摘要:

We consider the linearized stability of a barotropic coastal current flowing parallel to a straight coastline over a continental shelf and slope whose depth varies monotonically with distance from the coast. Some necessary conditions for stability and various semi-circle theorems are reviewed for general current profiles and bottom topography. A criterion for topography to be a destabilizing influence is derived. Some general results for stable waves are also described. Analytic solutions are obtained for a piece-wise linear current profile and the exponential depth profile (Buchwald and Adams, 1968). Dispersion diagrams are obtained for a monotonic current profile, where it is shown that the effect of topography is destabilizing, and for a triangular current profile. The dispersion diagrams generally contain a finite number (usually one or two) of unstable waves, and a set of stable waves, which may be infinite in number. The results are applied to some specific coastal regimes.

ISSN:0309-1929    

DOI:10.1080/03091928408248189

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The behavior of the flux Richardson numberRf, as a function of the overall Richardson numberRi0, was investigated for a stably stratified, grid-generated, turbulent flow evolving in a closed-loop water channel. The turbulent dissipation rate ε, the buoyancy or vertical mass fluxpwbar; and the rms density fluctuation ρ′ were obtained from simultaneous single-point measurements of the horizontal and vertical velocity components and density fluctuations. From these,RfandRi0were calculated at each point in the spatially evolving flow. The resulting curves ofRfvs.Ri0exhibit the full range of behavior found in the very different case studied by Linden (1980). The length scale arguments of Gibson (1980) and Stillingeret al.(1983b) provide an underlying mechanism which successfully accounts for the shape of theRfvs.Ri0curve.

ISSN:0309-1929    

DOI:10.1080/03091928408248190

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The flow of large natural ice masses under gravity is described by the mass, momentum, and energy balances of an incompressible, homogeneous, heat conducting, non-linearly viscous fluid in which the shear response includes a strongly temperature-dependent rate factor. Dimensionless analysis and co-ordinate stretching reflecting the long aspect ratio show that series expansions in a small parameter which determines the surface slope magnitude are uniformly valid even when temperature variation induces a strongly non-uniform mechanical response. The normalised energy balance shows that both horizontal and vertical advection are significant in thin and thick grounded sheets and in floating shelves, and that viscous dissipation can be significant in basal regions of a grounded sheet, and hence there is strong thermomechanical coupling. Moreover, though a thermal basal boundary layer may arise in a thick sheet, it would only give rise to significantly enhanced temperature and strain-rate gradients in extreme circumstances. The leading order relations for steady plane flow of a grounded sheet are reduced to a parabolic system for the temperature and two velocity components, which incorporates the unknown surface slope in coefficients and boundary conditions. This provides a useful starting point for numerical solution of the thermomechanically coupled problem. A fixed domain mapping is presented as an attractive alternative formulation when the bed topography is close to planar.

ISSN:0309-1929    

DOI:10.1080/03091928408248191

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

In the terrestrial atmosphere described as an unbounded medium with variable temperature, the equations of small Mach number airflows are written in the framework of an asymptotic Boussinesq's approximation. An equation is obtained which is a Helmholtz equation with slowly varying coefficients. This equation is then used to describe the stationary linearized flow over an obstacle of small height. It is shown under realistic conditions of the repartition of Scorer's parameter that the flow over the obstacle is divided in two regions: a lee wave system builds up in the lower layer while a progressive wave emerges in the upper layer. The two flows appear to be uncoupled in a first approximation, so that the classical representation of lee waves by confined flows is justified.

ISSN:0309-1929    

DOI:10.1080/03091928408248192

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The generation of stationary Rossby waves by sources of potential vorticity in a westerly flow is examined here in the context of a two-layer, quasi-geostrophic, β-plane model. The response in each layer consists of a combination of a barotropic Rossby wave disturbance that extends far downstream of the source, and a baroclinic disturbance which is evanescent or wave-like in character, depending on the shear and degree of stratification. Contributions from each of these modes in each layer are strongly dependent on the basic flows in each layer; the degree of stratification; and the depths of the two layers. The lower layer response is dominated by an evanescent baroclinic mode when the upper layer westerlies are much larger than those in the lower layer. In this case, weak stationary Rossby waves of large wavelengths are confined to the upper layer and the disturbance in the lower layer is confined to the source region.

ISSN:0309-1929    

DOI:10.1080/03091928408248193

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

For the purpose of deriving an analytical parametrization, oceanic mesoscale eddies are represented as a horizontally propagating wave field in a non-uniform environment. The mathematical analysis rests upon the assumption of scale disparity between a short eddy scale and a long mean-flow scale. The novelty resides in the treatment of finite-amplitude eddies, which, moreover, form either a band-like or a cell-like pattern. A barotropic ocean is chosen as a first step to illustrate the mathematical analysis, but dissipation is included. The main result is an analytical derivation of a mesoscale-eddy parametrization: the mean-flow equation contains Reynolds-stress terms which are computed from parameters of the eddy field, which, in turn, are predicted by separate evolution equations. Due to restrictive assumptions (barotropy, orthogonal waves,…), the parametrization established here should be viewed only as a first step toward the design of a more practical parameterization for large-scale modelling.

ISSN:0309-1929    

DOI:10.1080/03091928408248194

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

EDDIES IN MARINE SCIENCE (Edited by A. R. Robinson) Springer-Verlag, 1983, 268 figures, 625 pages. Price: DM 120 (U.S. $49.60). ISBN 3-540-12253-2

ISSN:0309-1929    

DOI:10.1080/03091928408248195

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor