The miniSODAR is a high-frequency Doppler sodar system that was designed to measure the atmospheric wind profile from 15 meters to 150/200 meters (data is often available to 250 meters) in 5-meter increments. It operates by generating a short tone burst (30 ms to 100 ms) in the frequency range of 4 kHz to 6 kHz. It monitors the low-level acoustic signal echoed by the atmosphere. The echo is processed with for its frequency content. The shift in the received frequency with respect to the transmitted frequency is called the Doppler shift, which is directly related to the radial motion of the echo volume with respect to the miniSODAR acoustic antenna (see Figure 1).
The miniSODAR samples the atmosphere in three independent directions. These data are combined using geometry to deduce the horizontal and vertical wind profile directly above the antenna.
- The miniSODAR system consists of three components:
- 32 element speaker antenna and fiberglass acoustic enclosure;
- Acoustic signal processor (ASP);
- Audio power amplifier;
The system is supplied with the SodarPro interface software package which is the user interface to the ASP, store the wind profile data produced by the miniSODAR, graphically display the miniSODAR data and provide an ASCII based remote user interface to the miniSODAR system. SodarPro, using its split screen display, is able to display the wind and turbulence data both graphically and in tabular form for quick review. The Digital Facsimile Data can also be displayed in one of its split screen windows. These data are viewed and plotted offline with the DFSview software package. The facsimile data are color encoded according to the received signal intensity (decibel scaling). They are corrected for the spherical spreading of the acoustic wave to present a relative picture of the atmospheric thermal turbulence intensity. Spectral data from a single altitude and beam are also available as part of SodarPro. The wind and spectral data are stored in ASCII format and the facsimile data in binary format.