Abstract
An acoustic sounding system with a Doppler analyser is developed. The Doppler shift of the return sound echo is measured by counting a time duration for a certain number of sound waves. The outputs of the system, echo intensity and the vertical velocity, are visualized by a computer controlled dot-printer which gives more minute information than the facsimile record. The output of the Doppler shift analyser is calibrated by the echo from a balloon descending or ascending near the sounder. The case study for thermal plumes shows a reasonable vertical velocity field.
