Energy balance of turbulence in the upper atmosphere

Turbulent winds obtained from chemical release studies and turbulent diffusion observations of globule expansion can be used to obtain estimates of the terms in the energy balance equation εs = εg + εd, where εs is the rate per unit mass at which energy is supplied by wind shears, and εg and εd are the rates per unit mass at which energy is dissipated by buoyancy and viscous effects. Both εs and εg are found to vary slowly with altitude, having values of about 0.3 and 0.1 watt kg−1, respectively, in the altitude range 90 to 110 km. However, εd increases rapidly with altitude. This rapid increase in εd is responsible for the globule cutoff observed at an average altitude of 106 km. Globule growth analysis indicates that extremely rapid anomalous diffusion takes place during the period approximately 100 to 150 seconds after release. As globule diameters increase beyond the largest scale of the anomalous growth region they expand at a rate comparable to that of molecular diffusion for a period of approximately 50 seconds, after which a transition to d2 ∼ εd t3 turbulent diffusion occurs.