Acoustic tomography of the atmosphere at the Boulder Atmospheric Observatory

An array for acoustic tomography of the atmosphere has been built at the NOAA Boulder Atmospheric Observatory. In this paper, a short description of the array and some acoustic tomography results are presented. The array consists of three speaker and five microphone towers located along the perimeter of a square with a side length of 80 m. The towers are 9.1 m high. The speakers and microphones can be located at different (multiple) levels on the towers to do three-dimensional tomography. The transducers are connected via cables with the central command and data acquisition computer. The array enables measurements of travel times of sound propagation between different pairs of speakers and microphones. The measurements are done repeatedly within a short time interval so that the information about the temporal change in the travel times can be employed in tomographic reconstruction. Then, these travel times are used as input data in a time-dependent stochastic inversion for reconstruction of temperature and wind velocity fields. Examples of the reconstructed turbulence fields are presented and discussed. [Work supported by the Army Research Office.]