Determination of the turbulence intensity from sound propagation fluctuations in the surface layer (Dome C, Antarctica)

In the years 1940-1950, Krasilnikov and Obukhov found theoretically that the magnitude of the phase and amplitude fluctuations of an acoustic wave propagating through the turbulent atmosphere depends on the intensity of the temperature and wind speed fluctuations. In these pioneer works, an idea about the possibility to measure the atmospheric turbulence characteristics using the fluctuations of acoustic wave parameters was suggested. An experiment on the application of this approach to determine the turbulence intensity in the surface layer was carried out in November 2014 at the Concordia station at Dome C, Antarctica. The transmitter and receiver were separated by a distance of 400 m in the horizontal direction and 16 m in the vertical. According to Krasilnikov and Obukhov theory, the root mean square of the logarithm of the ratio of the standard deviation of the fluctuation of the amplitude of the signal to its mean value is proportional to the structure parameter of the sound refraction index that, in turn, is determined by the sum /4T2 + /c02, where is the temperature structure parameter, is the wind velocity structure parameter, T is the absolute temperature, c0 is the sound velocity. and were estimated with a sonic thermometer-anemometer USA-1 at a height of 3.5 m. The results of sodar observations were used for monitoring the vertical turbulent structure of the surface layer and proper interpretation of measurements. Variations of the acoustic wave amplitude show a certain frequency dependence (~ f -?) with ? between 2.6 and 3.1 in the range 0.1-5 Hz and between -0.1 and 0.1 in the range 0.01-0.1 Hz that close to theoretical prediction. We are interested in this method because it can provide additional information in atmospheric turbulence studies.