Imaging Doppler interferometry and the measurement of atmospheric turbulence

Data taken by an imaging Doppler interferometer (IDI) 3.175-MHz radar during the Arecibo Initiative on Dynamics of the Atmosphere in 1989 is interpreted in terms of turbulence parameters. The rms random velocity determined from scatterers within 2° of the zenith for the interval 1200-1416AST on April 10, 1989, is used to calculate the rate of dissipation of turbulent energy using two formulations, one based on an estimate of the lifetime (∼100 s) of the intermittent scatterers identified by the IDI technique, and another based on the turbulent structure function. Both techniques yield upper limit values of 0.01–0.06 W kg⁻¹ for the rate of dissipation of turbulent energy, increasing with height over the range from 72 to 90 km. The energy-bearing eddy scale of turbulence, neglecting buoyancy, is found to vary with height, being a minimum at 75 km (200 m) and a maximum at 90 km (400 m). The effects of buoyancy are discussed in detail, and the buoyancy, or outer scale, is found to vary from 300 m at 75 km to a maximum of 900 m at 90 km. The Kolmogorov microscale, or inner scale, is found to increase from 1 m at 72 km to 10 m at 93 km. Estimates of the vertical eddy diffusion coefficient are also made, and the values obtained are shown to be highly dependent on the assumptions underlying the calculations.