Application

Doppler effect is the difference in frequency between the wave transmitted or wave that leaves a source and the wave received or wave that reach the receiver due to the relative motion of source and receiver, while sound reflection is the reflection of the sound when it hits the surface of an object. These two, the Doppler effect and sound reflection, are some of the concepts that the SODAR instrument used.

SODAR is an acronym for Sound Detection and Ranging which is an instrument that used sound waves to investigate the lower atmosphere. It is generally used as a wind profiler which measures the wind speed, the wind direction, and the vertical wind speed at various heights above the ground. It is also called acoustic echo sounders (AES), echo sounder, and acoustic radar.

SODAR produces sound waves directly above the atmosphere at different angles. As the sound wave travels, the sound wave attenuates by the temperature and humidity in the atmosphere. When the sound
wave hit wind turbulence in the atmosphere, the sound wave is reflected. The reflected sound wave, which now has different intensity and frequency, goes back to SODAR. 

The received sound wave is then compared to the transmitted sound wave and the following were acquired:

• Time delay or the time the sound wave travels
• Intensity difference or the difference in amplitude of the wave
• Doppler shift or the difference in wave frequency

Turbulent strength is acquired using the intensity difference, height using the time delay and sound speed, wind speed using the Doppler shift or the frequency difference, and wind direction using the sound
wave received in different angles.

SODAR used remote sensing for air observation. It is a much smaller instrument compared to meteorological towers, so it is easy to install and collect data. Although it is smaller, it shows a very good correlation both in wind speed and wind direction to the meteorological towers. It is now used in many applications such as:

1. .Meteorological Monitoring
2. Wind Power Generation
3. Airport Low Altitude Wind Monitoring
4. Wind Resource Assessment and Measurement
5. Meteorological Research

Piezo Source is the leading supplier to the lower atmosphere meteorology industry. Our speakers are used as both transmitters and receivers in SODAR instruments including echo sounders and acoustic
radar.

Links:

Sound https://www.britannica.com/science/sound-physics

Boundary Layer (Atmospheric) And Air Pollution: Observational Techniques
https://www.sciencedirect.com/science/article/pii/B978012382225300089X

Detection and Ranging (SODAR) Wind Profiler Instrument Handbook
www.arm.gov/publications/tech_reports/handbooks/sodar_handbook.pdf

Comparison of Second Wind Triton Data with Meteorological Tower Measurements
www.nrel.gov/docs/fy10osti/47429.pdf