摘要:

We study the formation of lenses of the ocean's intermediate water using a 2.5-layerβ-plane primitive equation model with localized injection of water mass. For the injecting rate of 1.0 Sv, we have observed that strong vortices are shed regularly. These vortices propagate westward much faster than the second baroclinic long Rossby wave. They are totally isolated from each other and show strong baroclinicity as well. Moreover, they remain stable over a sufficiently long period of time. Regular formation of such strong vortices in the intermediate layer has not been reported previously. The translation speed is explained using the Euler's momentum integral theorem for the nonlinear baroclinic vortex on the β-plane. We have demonstrated that coupling between the primary motion in the intermediate layer and the secondary motion in the upper layer with a meridional shift is crucial to the fast westward translation of the intense vortices. A simple dispersion formula relating the zonal translation speed with the vortex radius is also derived under the assumption of quasi-geostrophy. It has turned out that the analytical relation explains the numerical results surprisingly well despite the limitation of its derivation.

ISSN:0309-1929    

DOI:10.1080/03091920008203709

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Just as a stream function gives both a qualitative and quantitative description of the flow, a 'string function' can be constructed to describe the propagation in a rotating fluid of large-scale energy anomalies such as eddies and Rossby waves. To simply introduce the string function in this paper, we consider only a homogenous 1-layer fluid. In this case, the string function is inversely proportional to large-scale potential vorticity and the contours of both are aligned. The string function contains more information, however, because the propagation speeds are described by the contour spacing. We introduce the string function and use it to derive and reinterpret governing equations for linear and nonlinear shallow-water dynamics. The string function allows for simple evolution equations incorporating both beta and topographic effects.

ISSN:0309-1929    

DOI:10.1080/03091920008203710

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We use results from a primitive-equation ocean numerical model (SCRUM) to test a theoretical 'string function' formulation put forward by Tyler and Käse in another article in this issue. The string function acts as a stream function for the large-scale potential energy flow under the combined beta and topographic effects. The model results verify that large-scale anomalies propagate along the string function contours with a speed correctly given by the cross-string gradient. For anomalies having a scale similar to the Rossby radius, material rates of change in the layer mass following the string velocity are balanced by material rates of change in relative vorticity following the flow velocity. It is shown that large-amplitude anomalies can be generated when wind stress is resonant with the string function configuration.

ISSN:0309-1929    

DOI:10.1080/03091920008203711

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

spin-up and spin-down in a circular tank with a uniformly sloping bottom are studied experimentally and numerically for small values of the relative change in the angular velocity of the tank. Generally, the initial single-cell flow evolves into a number of smaller vortices. The evolution is compared with an analytical model based on an expansion of the flow field in linear Rossby waves (Pedlosky and Greenspan, 1967). Although it is possible to tune the experimental parameters in such a way that agreement with the theory is found, in most cases the experiments show shedding of vortices in the initial stage of the spin-up or spin-down, a phenomenon not described by the analytical model. Nonetheless, in such cases the analytical model still accounts for other observations: the alternating generation of cyclonic and anticyclonic vortices in the eastern part of the tank and their subsequent westward motion.

ISSN:0309-1929    

DOI:10.1080/03091920008203712

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The new instability condition can be useful in the search of unstable perturbations to a harmonic wave and on trials of numerical stability study algorithms. For a Legendre-polynomial flow, it complements Kuo's (1949) condition in the sense that while the latter is related to the basic flow structure; the former characterizes the structure of a growing perturbation.

ISSN:0309-1929    

DOI:10.1080/03091920008203713

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091920008203714

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor