ZephIR - how does it work?

An eye-safe infrared beam illuminates natural aerosols in the atmosphere (such as dust, pollen and droplets) and a small fraction of the light is backscattered into a receiver. Motion of the target particles along the beam direction leads to a change in the light’s frequency through Doppler shift which is then accurately measured. A conical scan pattern is used to move the beam and intercept the wind at different angles, building up a series of measurements around a disc of air from which the wind speed vector is obtained.

ZephIR obtains each measurement in just 20 milliseconds, and one second of data can be used to derive the horizontal and vertical wind speed components and wind direction. This can then be repeated up to a height of 200 metres, at five or more user-defined heights by focussing the transmitted beam. After the recommended three second scan at each height a total of 150 points of data are gathered which enhance the quality of measurement, providing additional information on turbulence essential for sites with complex terrain.