Turbulent Characteristics of Some Canadian Cumulus Clouds

Abstract

The turbulent characteristics of 17 Canadian cumulus clouds have been documented using the measurements from a specially instrumented T-33 aircraft. Most of the 33 cloud penetrations were made through the tops of cumuli 1–4.5 km in depth. Turbulent energy spectra over a range of wavelengths from 15 to 2500 m have been obtained for the two horizontal and the vertical gust velocities. Mean flow characteristics, especially any expected updrafts, tended to be obscured by turbulent fluctuations. The modal root-mean-square gust velocity was 1.7 m s⁻¹ and the calculated modal turbulent energy dissipation rate was 160 cm² s⁻³. Based on measured accelerations, estimates were made of expected vertical forces on several aircraft with a wide range of wing loadings. Cumulus clouds similar to those studied do not pose a safety hazard to these aircraft, and crew and passengers can easily tolerate the turbulence levels.