Recent progress in acoustic travel-time tomography of the atmospheric surface layer

Abstract

Acoustic tomography of the atmospheric surface layer (ASL) is based on measurements of the travel times of sound propagation between sources and receivers which constitute a tomography array. Then, the temperature and wind velocity fields inside the tomographic volume or area are reconstructed using different inverse algorithms. Improved knowledge of these fields is important in many practical applications. Tomography has certain advantages in comparison with currently used instrumentation for measurement of the temperature and wind velocity. In this paper, a short historical overview of acoustic tomography of the atmosphere is presented. The main emphasis is on recent progress in acoustic tomography of the ASL. The tomography arrays that have been used so far are discussed. Inverse algorithms for reconstruction of the temperature and wind velocity fields from the travel times are reviewed. Some results in numerical simulations of acoustic tomography of the ASL and reconstruction of the turbulence fields in tomography experiments are presented and discussed. Zusammenfassung

Wind Energy Instrumentation Atlas

“…Originally used for measuring currents in the ocean on mesoscales, acoustic tomography has since been applied to the atmosphere and extended into multiple dimensions and different scales (Barth and Raabe 2011;Holstein et al 2004). Ostashev et al (2009) provides a useful summary of measurements in the atmospheric boundary layer and demonstrates the ability to measure winds in an 80-m square grid with errors of less than 10%, temporal resolution of 1.5 s, and horizontal resolution of a few meters, albeit it in a plane a few meters thick. Acoustic tomography in the atmosphere has not been commercialized and should be considered a TRL of 6.…”

Spatial-temporal coherence of acoustic signals propagating in a refractive, turbulent atmosphere

“…This geometry is pertinent, for example, for localization of elevated sources (helicopters and airplanes) with microphones located on the ground, or for localization of acoustic sources on the ground (gun and rifle shots, rocket launches, and explosions) with elevated acoustic sensor arrays such as those suspended below aerostats. Line-of-sight propagation also occurs in acoustic tomography of the atmosphere, 21 when acoustic sources and microphones are located several meters above the ground and short acoustic pulses are transmitted to separate a direct signal from that reflected from the ground.…”

“…Temporal coherence is also pertinent for signal design in acoustic remote sensing of the atmosphere with sodars 22,23 and tomography techniques. 21,24,25 Temporal coherence has been studied intensively in ocean acoustics [26][27][28] and electromagnetic propagation. 5,29,30 As far as we know, the present paper is the first detailed study of temporal coherence in atmospheric acoustics.…”

Online Time-Resolved Reconstruction Method for Acoustic Tomography System

“…Improved knowledge of the wind velocity field of the near surface atmosphere is of great importance in many applications, such as the boundary layer meteorology, theories of turbulence, visualization of different dynamic processes, studies of sound wave propagation through a turbulent atmosphere, etc [30]. In order to reconstruct the wind velocity field without disturbing these meteorological quantities, remote sensing techniques are required.…”