Acoustic travel-time tomography

Acoustic tomography is a remote sensing method to completely describe the spatial (3D) and temporal variability of meterological quantities without influence of the measurement area itself. Thereby, the known fact is used, that the variability of the sound speed and acoustic travel-time, respectively, is dependent on the variability of characteristic quantities of the sensed medium, especially the temperature and flow velocity. Therefore, the measured travel-time values of sound signals between several transmitters and receivers were used as initial line-integrated values to derive spatially averaged meteorological quantities. As each measurement contains information on the properties of the air volume which the sound wave propagates through, a tomographic inverse algorithm provides a spatial mapping of meteorological quantities (temperature, wind vector).

The resulting spatially averaged meteorological data are valuable, among other purposes, to validate atmospheric models and to derive parameterizations for models. By means of acoustic tomography it is possible to derive information on the representativeness of conventional point measurements dependent upon the surface characteristics of measuring sites. Furthermore, the tomographic measurement and analysis method is scalable which results in a wide spectrum of applications, e.g. in wind tunnels and over lysimter surfaces (meter scale), for indoor and (atmospheric) chamber measurements (decametre scale), and for boundary-layer meteorology (up to kilometre scale, see the example below).

 

Measurement area Melpitz
Receiver
Transmitter
Tomogram: Horizontal slice through the temperature field (colors) and the wind field (arrows) at a height of 2 m above the ground surface at the 06.10.2001, 12:45 local time at the research station Melpitz over a grassland site(northern part) and bare soil (southern part).

Click on the picture for large view

 

Poster: Tomography