The RASS addition to the profiler

Immediately adjacent to the profiler are four special speakers that are part of the Radio Acoustic Sounding System (RASS) addition to the profiler. The speakers broadcast sounds around 2000 Hz in the vertical. When the frequency of the sound is such that the sound waves are separated by a distance of half the wavelength of the profiler (32.8 cm ÷ 2 = 16.4 cm), the profiler can detect the sound waves. From this information, the speed of the sound waves can be measured with height. Since the speed of sound is related to temperature, temperature profiles can be obtained.

At McGill, the RASS system is operated a few minutes every hour. Typically, profiles of temperature can be obtained only in the first kilometer of the atmosphere. Beyond that distance, the wind pushes the sound waves away from the region sampled by the profiler and turbulence destroys the fairly high frequency sound. The RASS system is used primarily for research.