Some specific features of atmospheric turbulence

The specific features of atmospheric turbulence can hardly be observed in the laboratory and should be studied in the atmosphere, where the range of scales of disturbances is very broad. Slow fluctuations in energy dissipation which are due to the change of largescale processes (weather in a general sense) can be taken into consideration approximately by ‘statistical mixing’ (by using superposition) of various regimes. The analysis of the simplest schemes shows that some numerical ‘constants’ in particular Kolmogoroff's 2/3 law coefficient for a mixed regime, are, in general, functions of the external parameters of a flux (e.g., Reynolds number). Thermal inhomogeneity of the atmosphere and the resulting buoyancy are of importance as factors initiating turbulence and often become the dominant ones. To describe the turbulent structure under fully developed convection, we may suggest the model of axisymmetric turbulence over an infinite plane involving only one ‘external parameter’ the turbulent heat flux. The influence of compressibility and of the delayed interaction of flow patterns propagating with sound velocity has not been studied sufficiently. We may assume that the conditions are more favorable for studies of acoustical noise accompanying the turbulence itself (vorticity component of the velocity field) in the atmosphere than in wind tunnels. Therefore, the study of the frequency spectrum of small oscillations of a compressible stably stratified atmosphere may be of some interest.