It is an instrument that acquires at high frequency, usually 10-20 Hz, the three components of local wind speed and sonic temperature. The sonic anemometer measures the time it takes for a sound wave to propagate between pairs of transducers of which the instrument is composed; this time interval is linked to air velocity through known relationships. In CIRAS there are two sonic anemometers: Metek USA-1 and GILL HS-50. During special experimental campaigns, a fast open-path gas analyser (LI-COR, Li-7500) is connected to the sonic anemometer to measure the latent heat flow.
Measured quantities: point values of the three components of wind velocity, sonic temperature, turbulent heat flow and momentum.
Applications: studies of turbulent surface-atmosphere exchanges, also in relation to air quality and pollutant dispersion, characterization of the remixed boundary layer forcing agents and surface dynamics.
