摘要:

The linear stability of a laterally sheared barotropic flow along a trench is analyzed. The depth and mean flow profiles used in the model are piecewise constant and piecewise linear, respectively. As a consequence the stream function and dispersion relation describing the perturbation field can be written in terms of elementary functions. The dispersion relation, being a quartic in the wave frequency, yields four neutral wave modes: two shear waves, a shelf wave and a trench wave. An instability arises when two shear wave dispersion curves coalesce or when one of the shear wave curves coalesces with either a shelf or a trench wave dispersion curve. Further, because of the quartic nature of the dispersion relation, the stability diagrams can have overlapping regions of instability in Rossby number—wavenumber space.

ISSN:0309-1929    

DOI:10.1080/03091928208208945

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A new model of convection and mixing is presented. The fluid is envisioned as being composed of two buoyant interacting fluids, calledthermalsandanti-thermals. In the context of the Boussinesq approximation, pairs of governing equations are derived for thermals and anti-thermals. Each pair meets an Invariance Principle as a consequence of the reciprocity in the roles played by thermals and anti-thermals. Each pair is transformed into an average equation for which interaction terms cancel and another very simple equation linking the two fluid properties. An important parameter of the model is the fraction,f, of area occupied by thermals to the total area. A dynamic saturation equilibrium between thermals and antithermals is assumed. This implies a constant values offthroughout the system. The set of equations is written in terms of mean values and root-mean-square fluctuations, in keeping with equations of turbulence theories. The final set consists of four coupled non-linear differential equations. The model neglects dissipation and can be applied to any convective situations where molecular viscosity and diffusivity may be neglected. Applications of the model to mixed-layer deepening and penetrative convection are presented in subsequent papers.

ISSN:0309-1929    

DOI:10.1080/03091928208208946

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A new non-linear model of mixing and convection based on a modelling of two buoyant interacting fluids is applied to penetrative convection in the upper ocean due to surface cooling. In view of simple algebra, the model is one-dimensional. Dissipation is included, but no mean shear is present. A non-similar analytical solution is found in the case of a well-mixed layer bounded below by a sharp thermocline treated as a boundary layer. This solution is valid if the Richardson number,Ri, defined as the ratio of the total mixed-layer buoyancy to a characteristic rms vertical velocity, is much greater than unity. The model predicts a deepening rate proportional toRi−3/4. The thermocline remains of constant thickness, and the ratio thermocline thickness to mixed-layer depth decreases asRi−3/4as the mixed layer deepens. If the surface flux is constant, the mixed-layer depth increases with time ast½. The vertical structure throughout the mixed layer and thermocline is given by the analytical solution, and vertical profiles of mean temperature and vertical fluxes are plotted. Computed profiles and available laboratory data agree remarkably well. Moreover, the accuracy of the simple analytical results presented here is comparable to that of sophisticated turbulence numerical models.

ISSN:0309-1929    

DOI:10.1080/03091928208208947

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The linear stability of certain two-dimensional disturbances in turbulent density-stratified shear flow is examined. The vertical, turbulent transports of momentum and buoyancy are modelled as gradient transports, and the interaction between velocity and momentum fields through the gradient Richardson number is included. It is argued that solutions should be stable, since the ensemble-averaged equations may no longer exhibit the small-scale instabilities related to turbulence. The stability conditions obtained constitute a generalization of those obtained by Kranenburg (1980a, b) for one-dimensional disturbances, and set certain bounds to the dependence of eddy viscosity and diffusivity on the Richardson number.

ISSN:0309-1929    

DOI:10.1080/03091928208208948

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The problem of the calculation of the pressure gradient force in sigma (terrain following) coordinate models is reviewed. It is pointed out that one of the well known schemes, the scheme of Corbyet al.(1972), does not result in a convergent difference analogue of the pressure gradient force. Some other schemes, such as the one of Burridge and Haseler (1977) used at the European Centre for Medium Range Weather Forecasts, have a convergence condition, requiring thickness of sigma layersgreaterthan (or equal to) a given threshold value. The two-term error problem of these analogues is reexamined. A numerical example is given, showing that, in accordance with the convergence condition, an increase in vertical resolution will generallynotresult in a reduction of the error.

ISSN:0309-1929    

DOI:10.1080/03091928208208949

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The shallow-water equations are supplemented by a moisture equation in order to model effects of latent heat release on the horizontal propagation of disturbances. Since latent heating in regions of upward motion compensates the reduction in perturbation temperature due to lifting, buoyancy effects are reduced and disturbances propagate more slowly. Analytic solutions are obtained to illustrate this effect, a good example being provided by the collapse of an initial horizontal temperature discontinuity. Another interesting example is provided by the case of disturbances propagating through a region from one side. Moist regions are found to have front and rear boundaries which both move faster than rainbands do inside the moist region. If random disturbances are passed through a region which is initially saturated, the relative humidity drops until it reaches a value which depends on the disturbance level.

ISSN:0309-1929    

DOI:10.1080/03091928208208950

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

By F. Krause and K.-H. Rädler. Pergamon, Oxford, 1981. 271 pp. (Cloth £15.00 ($36.00) (ISBN 0 08025 0416))

ISSN:0309-1929    

DOI:10.1080/03091928208208951

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Edited by Sir Harrie Massey. Gordon and Breach, New York, London, Paris, 1979. 354 pp. ($35.50 (ISBN 0 677 15970 6))

ISSN:0309-1929    

DOI:10.1080/03091928208208952

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Edited by D. Sugimoto, D. Q. Lamb and D. N. Schramm. IAU Symposium No. 93, Reidel, Dordrecht, 1981. 343 pp. (Cloth Dfl. 90 ($47.50) ISBN 90-277-1273-5; Paper Dfl. 40 ($21.00) ISBN 90-277-1274-3)

ISSN:0309-1929    

DOI:10.1080/03091928208208953

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor