Time scale analysis of long-period variability of oceanic circulation using a three-layer numerical model

by

A.B. Fedotov

 Institute of Natural and Technical Systems, RF, Sevastopol, Lenin St., 28

E–mail: fedotov57@mail.ru

DOI: 10.33075/2220-5861-2022-1-15-19

UDC 551.465.553

Abstract:

   A relatively simple three-layer model of oceanic circulation is used to describe the basic physical characteristics of the wind flow system. The paper describes numerical experiments for the case of a stationary wind homogeneous in space, the northern part of the studied water area is affected by cyclonic wind, while the southern part is affected by anticyclonic wind. The flow of vorticity from the wind load enters the upper layer. Calculations are performed for the water area with solid boundaries in the beta-plane approximation, such a model satisfactorily describes the structure of currents for the middle latitudes. The biharmonic viscosity operator is used as a dissipative factor in the model for each of the layers, bottom friction acts on the lowest layer, external factors do not act on the middle intermediate layer, the fluid movement in it is initiated due to the impact with the upper and lower layers. Numerical calculations were carried out with a spatial resolution of 513 x 513 grid nodes, which, with a linear size of the water area of 3840 kilometers, allowed calculations to be carried out with a horizontal step of 7.5 kilometers. The calculations used a model of the evolution of a potential vortex in a three-layer liquid for the case of depths of the upper layer 60 m, the lower layer – 3300 m and the intermediate layer 250 m. Taking into account the second baroclinic mode can significantly affect the assessment of the temporal and spatial characteristics of the long-term variability of oceanic circulation. The experiments were carried out using an explicit time integration scheme with constant dissipation parameters, the characteristic time scales of long-period oscillations of the flow energy were analyzed, the nature of the variability of the kinetic energy of the upper layer was revealed, the average values of the flow velocity in the upper layer were analyzed, the characteristic vorticity fields for each of the three layers were given.

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

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REFERENCES

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