Sodar

Sodar, an acronym of sonic detection and ranging, is a meteorological instrument used as a wind profiler based on the scattering of sound waves by atmospheric turbulence.

Sodar equipment is used to measure wind speed at various heights above the ground, and the thermodynamic structure of the lower layer of the atmosphere.

[1] Commercial sodars operated to collect upper-air wind measurements consist of antennas that transmit and receive acoustic signals.

The multiple-axis systems generally use three individual antennas aimed in specific directions to steer the acoustic beam.

The horizontal components of the wind velocity are calculated from the radially measured Doppler shifts and the specified tilt angle from the vertical.

Due to the attenuation characteristics of the atmosphere, high power, lower frequency sodars will generally produce greater height coverage.

By providing a more compact beam angle, these sodars reduce the effect of any change in the wind vector.

Both sodars and Acoustic Doppler Current Profilers (ADCP) can use either separate transducers for each beam or use phased arrays.

The operating range of typical ADCPs is less than two hundred meters (this lowers as frequency increases, as in air).