Numerical simulation of the evolution of a jet zonal wind flow Using combined dissipation

A.B. Fedotov

Institute of Natural and Technical Systems,

RF, Sevastopol, Lenin St., 28

DOI: 10.33075/2220-5861-2023-4-19-24

UDC 551.465.553                                                      



Within the framework of a numerical model of a two-layer ocean with a depth of layers, corresponding to average oceanic conditions, a study of the wind evolution of large-scale circulation is carried out with the simultaneous use of two mechanisms of vorticity dissipation on subgrid spatial scales: spectral filtration of higher harmonics and ordinary viscosity with a very small coefficient under the action of a stationary inhomogeneous external vorticity flow, simulating the effect of wind on the ocean. With such parametrization, the dissipative operator affects only a small-scale part of the energy and enstrophy spectrum, while the rest of the spectral dynamic range is not affected in this way, unlike the use of biharmonic viscosity. Experiments are carried out for two values of wind intensity, time and energy parameters of changes in the intensity of circulation are analyzed separately, a particular emphasis is placed on the process of formation of intense vortex rings. The main time scales of energy fluctuations of the upper layer are highlighted. Compared to experiments with biharmonic viscosity, this work demonstrates the possibility of the formation of vortices with a vorticity modulus exceeding the vorticity modulus of the main flow, which confirms the purely nonlinear mechanism of amplification of such vortices because of the impossibility of amplifying them due to advection. In addition, the transition of planetary vorticity to relative vorticity will not give such an effect. Firstly, because of the lack of meridional transfer in the direction of the latitude of rest, and, secondly, simply because of the insignificant meridional gradient of planetary vorticity.

Keywords: synoptic variability, large-scale variability, wind-forced currents, vortices.

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