The natural occurrence of turbulence

In order to make the scientific meaning of the word ‘turbulence’ clear, it is proposed that a fluid be called turbulent if each component of the vorticity is distributed irregularly and aperiodically in time and space, if the flow is characterized by a transfer of energy from larger to smaller scales of motion, and if the mean separation of neighboring fluid particles tends to increase with time. Whether or not a flow is turbulent is not simply a matter of Reynolds number, since the stability of the flow is a criterion of at least equal importance. From the results of experimental work in recent years of a number of people (Anderson, Frenkiel and Katz, Kellogg, Liller and Whipple, Malkus) it seems reasonable to infer that, with the exception of strong inversion layers, the atmosphere may be assumed to be turbulent everywhere, although the intensity of the turbulence varies widely in both time and space. If the Kolmogoroff similarity theory of locally isotropic turbulence is accepted, the most important parameter in the turbulent field is the energy dissipation ε.