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A model of Turbulence Suppression in the Intensive Atmospheric Vortex


L. Kh. Ingel

It is well-known that rotation of the fluid medium can suppress a turbulence This effect, most likely, can be substantial in the central areas of intensive atmospheric vortices (tornadoes, tropical cyclones). Suppression of turbulence in tornadoes proves to be true by the fact of presence a very large horizontal gradients of velocity in them, known from observations: the area of rapid rotation can be separated from practically resting medium in vicinities of a tornado only by rather thin layer of air. Such gradients (jumps) seem to be incompatible with intensive turbulent mixing. In view of the known analogy between the effects of rotation and stratification, for the description of the rotation influence on turbulence it is meaningful to use the models approved under description of the stratification effects. In particular, for the description of rapid rotation effects, in this paper there is modified a corresponding semiempirical model of turbulence in the Kolmogorov-Monin form, which is in a good agreement with the theory of similarity at the enough steady stratification. There is presented a simple analytical model describing the turbulence adaptation to the changes of turbulent energy generation and medium rotation velocity. According to the model, characteristic time of turbulence suppression due to rotation is comparable with period of rotation. Let in the central part of tropical cyclone tangential velocity is of the order of 50 m/sec at radius about 20 km. Then time interval during that turbulence is reduced, may be only one half an hour. Tornadoes with the same velocity usually have the horizontal scales less on 2-3 orders. Therefore time of turbulence suppression appears to be on the order of some seconds or ten seconds.

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