Acoustic tomography as a method to identify small-scale land surface characteristics

Sound waves propagate through the atmosphere with different sound velocities according to the spatial distribution of virtual air temperature and wind vector caused, e.g., by the environmental conditions. Therefore, acoustic parameters are able to spatially describe the atmospheric conditions. In the present study, measured travel time values of sound signals between transmitters and receivers are used as initial line-integrated values to derive spatially averaged quantities inside the surface layer of the atmosphere. Because each single measurement includes information on the properties of the atmospheric layer through which the sound propagates, a tomographic inversion algorithm provides a spatial mapping of meteorological quantities, such as the air temperature, derived from the measured acoustic parameters. The resulting spatially averaged meteorological quantities can be used for the evaluation of micrometeorological test sites, among other purposes. Application of acoustic travel time tomography can provide information on the homogeneity of measuring sites, and therefore on the applicability of turbulence theories in data analysis and in atmospheric models.