Abstract
A series of records, totalling over 120 hr showing the vertical fluctuations of high‐response wind‐vanes positioned on a captive balloon cable, are analysed to give statistical information on turbulence at heights between 500 and 5,000 ft, for an eddy frequency range 0·003‐12 cycles min^−1^. The use of specially designed filter and smoothing circuits facilitates the determination of the angular standard deviation of the inclination of the vane, as a function of run of wind, and of spectra, length‐scales and other parameters of turbulence. 18 spectra are given which show well‐defined peaks. Except in very stable conditions, the high wave‐number forms of the spectra are generally consistent with the existence of an inertial sub‐range. Estimates of the length‐scale, again excluding very stable conditions, do not apparently vary with height and average about 300 m. Intensity is found to depend on stability and to decrease in a very marked way with increasing wind speed, a result peculiar to these heights. This variation, applicable to specified meteorological conditions, is shown to have value in the determination of the spread of both continuous‐source plumes and clusters of particles according to recent treatments.